text:
(12) EUROPEAN PATENT APPLICATION
published in accordance with Art. 153(4) EPC
(43) Date of publication:
C21D 9/46(2006.01)
C22C 38/06(2006.01)
C22C 38/00; C21D 9/46; C22C 38/06; C22C 38/60
(86) International application number:
PCT/JP2021/010938
(87) International publication number:
WO 2021/193310 (30.09.2021 Gazette 2021/39)
Designated Extension States:
Designated Validation States:
KH MA MD TN
(30) Priority: 25.03.2020 JP 2020053545
(71) Applicant: JFE Steel Corporation
Tokyo 100-0011 (JP)
HASEGAWA, Hiroshi
KIMURA, Hideyuki
MORIYASU, Noriaki
GOTO, Sota
(74) Representative: Hoffmann Eitle
Patent- und Rechtsanwälte PartmbB Arabellastraße 30
(54) HIGH-STRENGTH HOT-ROLLED STEEL SHEET AND METHOD FOR PRODUCING SAME
(57) After low-temperature finish rolling has been performed as hot rolling on a steel material having a chemical composition containing, by mass%, C: 0.07% to 0.20%, Si: 1.50% or less, Mn: 1.0% to 4.0%, P: 0.030% or less, S: 0.0030% or less, Al: 0.010% to 1.000%, cooling is performed at an average cooling rate of 10°C/s or higher to a temperature of 500°C, rapid cooling is further performed in a temperature range from a Ms temperature to a temperature of (Ms temperature - 200°C), coiling is thereafter performed in a low temperature range of 250°C or lower, and the coiled steel sheet is uncoiled and further subjected to rolling with a certain amount or more of rolling load per unit width and the like. Consequently, it is possible to obtain a high-strength hot-rolled steel sheet excellent in terms of delayed fracture resistance having a microstructure including, in terms of area fraction, 95% or more of a martensite phase at a position located at 1/4 of the thickness of the steel sheet, in which an average aspect ratio of prior austenite grains is 3.0 or more, an amount of stress relaxation after a lapse of 5 min of 20 MPa or lower in a stress relaxation test with an applied stress of 400 MPa, and a tensile strength of 1180 MPa or higher.
[0001] The present invention relates to a high-strength hot-rolled steel sheet which can preferably be used as a material for automotive parts and a method for manufacturing the steel sheet. Here, the meaning of "steel sheet" includes a steel strip.
[0002] Nowadays, from the viewpoint of improving the crashworthiness and fuel efficiency of automobiles, there is a demand for increasing the strength of a steel sheet used for automotive parts. On the other hand, in the case of a steel sheet having increased strength, since there is an increased risk of the occurrence of delayed fracture, improving delayed fracture resistance is important. In particular, since a hot-rolled steel sheet which is used for the chassis of automobiles and the like is exposed to a harsh corrosive environment, such a steel sheet is required to have excellent delayed fracture resistance.
[0003] In response to such requirements, for example, Patent Literature 1 proposes "HIGH-STRENGTH HOT-ROLLED STEEL SHEET AND METHOD FOR MANUFACTURING THE SAME". Patent Literature 1 describes the technique in which, as a result of a steel sheet having a chemical composition containing, by mass%, C: 0.08% or more and less than 0.16%, Si: 0.01% to 1.0%, Mn: 0.8% to 2.0%, Al: 0.005% to 0.10%, and N: 0.002% to 0.006% with Nb, Ti, Cr, and B and a microstructure including a martensite phase or a tempered martensite phase as a main phase, in which, in a cross section parallel to the rolling direction, the average grain size and aspect ratio of prior austenite grains are 20 µm or less and 18 or less, respectively, it is possible to easily manufacture a high-strength hot-rolled steel sheet having a yield strength of 960 MPa or higher which is excellent in terms of toughness and delayed fracture resistance and which is also excellent in terms of abrasion resistance.
[0004] In addition, Patent Literature 2 proposes "HIGH-STRENGTH STEEL SHEET AND METHOD FOR MANUFACTURING THE SAME". Patent Literature 2 describes the technique in which, a steel sheet having a chemical composition containing, by mass%, C: 0.12% to 0.40%, Si: 0.6% or less, Mn: 1.5% or less, Al: 0.15% or less, and N: 0.01% or less is subjected to an annealing treatment where the steel sheet is heated to and held in a temperature range equal to or higher than the Ac3 transformation temperature and 950°C or lower, is quenched from a temperature range of 600°C or higher, and is tempered at a temperature of 350°C or lower, and is then subjected to correction utilizing a leveler. Consequently, Patent Literature 2 states that it is possible to manufacture a high-strength steel sheet having a martensite single-phase microstructure including a region having a KAM value of 1° or more in an amount of 50% or more, having the maximum tensile residual stress controlled to be 80 MPa or lower in a surface region from the surface to a position located at 1/4 of the thickness, and having excellent delayed fracture resistance in the cut end surface and base steel thereof.
[0005] In addition, Patent Literature 3 proposes "HIGH-STRENGTH STEEL SHEET WITH LOW YIELD RATIO EXCELLENT IN TERMS OF HYDROGEN-INDUCED CRACKING RESISTANCE AND BENDABILITY". Patent Literature 3 describes the technique in which it is possible to manufacture a high-strength steel sheet with a low yield ratio excellent in terms of both hydrogen-induced cracking resistance and bendability by controlling a chemical composition to contain, by mass%, C: more than 0.01% and 0.1% or less, Si: 0.05% to 0.45%, Mn: 0.5% to 1.6%, Al: 0.01% to 0.06%, N: 0.012% or less, and Ca: 0.0005% to 0.006% with at least one of V, Nb, and Ti in a total amount of 0.15% or less and controlling a microstructure in which when the steel sheet is divided into a surface layer, a center segregation portion, and a remaining ordinary portion, the ordinary portion includes 50% to 80% of ferrite and a balance including at least one of bainite, pearlite, and martensite-austenite constituent (MA), the center segregation portion includes 70% or more of bainite and a balance including at least one of ferrite, pearlite, and MA, in the center segregation portion the average grain size of bainite being 5 µm or less and the maximum length in the rolling direction and the maximum length in a direction perpendicular to the rolling direction and perpendicular to the thickness direction of pearlite grains and MA grains being both 10 µm or less, and a specified relationship is satisfied between the area fraction of ferrite in the surface layer and the area fraction of ferrite in the ordinary portion.
Citation List
Patent Literature
PTL 1: Japanese Unexamined Patent Application Publication No. 2016-211073
Summary of Invention
Technical Problem
[0007] However, in the technique according to Patent Literature 1, since it is not possible to sufficiently inhibit local concentration of hydrogen, delayed fracture resistance is low, which results in a problem in that it is not possible to achieve satisfactory delayed fracture resistance required in a harsh corrosive environment.
[0008] In addition, since the technique according to Patent Literature 2 is mainly intended for a cold-rolled steel sheet and requires complex processes such as an annealing treatment, correction utilizing a leveler, and the like, problems remain when the technique is used for a hot-rolled steel sheet. Moreover, in the technique according to Patent Literature 2, since it is not possible to sufficiently inhibit the local concentration of hydrogen, there is a problem in that it is not possible to achieve excellent delayed fracture resistance such that the requirements in a harsh corrosive environment are satisfied.
[0009] In addition, the technique according to Patent Literature 3 is intended for a steel sheet having a microstructure including 50% to 80% of ferrite and a strength level represented by a tensile strength TS of 590 MPa class, and only the effect for such steel sheet is clarified. In Patent Literature 3, there is no suggestion of a steel sheet having a strength level represented by a tensile strength of more than 590 MPa class, and, in particular, there is no suggestion of an improvement in the delayed fracture resistance of a high-strength steel sheet having a tensile strength of 1180 MPa or higher.
[0010] The present invention is intended to solve the problems of the techniques of the related art described above, and an object of the present invention is to provide a high-strength hot-rolled steel sheet excellent in terms of delayed fracture resistance which can preferably be used as a material for automotive parts and a method for manufacturing the steel sheet. Here, the expression "high strength" denotes a case of a tensile strength of 1180 MPa or higher and preferably 1700 MPa or lower. In addition, here, the expression "excellent in terms of delayed fracture resistance" denotes a case where, when an SSRT test (at a strain rate of 0.0000056 s-1) is performed with hydrogen charged under the hydrogen charge condition in which the amount of diffusible hydrogen is 1.0 mass ppm at the time of breaking, the fracture stress is 90% or more of the tensile strength TS.
Solution to Problem
[0011] To achieve the object described above, the present inventors diligently conducted investigations regarding various factors having effects on delayed fracture resistance and, as a result, conceived improving delayed fracture resistance by forming a microstructure including mainly a martensite phase whose grains have a large aspect ratio and by forming a dislocation structure in which the number of movable dislocations is as small as possible. Since it is difficult to directly determine the number of movable dislocations, the present inventors devised a method in which the index of the number of movable dislocations in a steel sheet is defined as the amount of stress relaxation that is determined by performing a stress relaxation test in which, after a test specimen (steel sheet) has been subjected to constant tensile stress (a low stress of 400 MPa or lower), strain increase is stopped, and the amount of stress relaxation is thereafter determined after a lapse of a predetermined time. Specifically, the present inventors found that in order to improve delayed fracture resistance, it is effective that after the test specimen has been subjected to a tensile stress of 400 MPa, strain increase is stopped and the amount of stress relaxation is determined after a lapse of 5 min, and such an amount of stress relaxation is decreased to a predetermined value (20 MPa) or lower. It is considered that, since movable dislocations, which move when being subjected to a low stress of 400 MPa or lower, do not contribute to increasing strength, and since such movable dislocations tend to draw hydrogen, thereby contributing to hydrogen transport, such movable dislocations cause a decrease in delayed fracture resistance.
[0012] In addition, the present inventors found that it is possible to form a microstructure including mainly a martensite phase having a high dislocation density by performing finish rolling in a hot rolling process with a low finishing temperature, by cooling the hot-rolled steel sheet at a cooling rate of 10°C/s or higher to a temperature of 500°C, by further rapidly cooling the cooled steel sheet in a temperature range from the Ms temperature to a temperature of (Ms temperature - 200°C), and by coiling the cooled steel sheet in a low temperature range of 250°C or lower and that it is possible to control the above-described amount of stress relaxation to be equal to or lower than a certain value by performing rolling on the formed microstructure with a rolling load equal to or higher than a certain value to form a dislocation structure in which dislocations tangle with each other, resulting in the completion of the present invention. The subject matter of the present invention is as follows.
[1] A high-strength hot-rolled steel sheet having a chemical composition containing, by mass%, C: 0.07% to 0.20%, Si: 1.50% or less, Mn: 1.0% to 4.0%, P: 0.030% or less, S: 0.0030% or less, Al: 0.010% to 1.000%, and a balance of Fe and incidental impurities, a microstructure including, in terms of area fraction, 95% or more of a martensite phase at a position located at 1/4 of a thickness of the steel sheet, in which an average aspect ratio of prior austenite grains is 3.0 or more, an amount of stress relaxation after a lapse of 5 min of 20 MPa or lower in a stress relaxation test with an applied stress of 400 MPa, and a tensile strength of 1180 MPa or higher.
[2] The high-strength hot-rolled steel sheet according to item [1], in which the chemical composition further contains one, two, or more selected from Group A to Group E below.
Group A: by mass%, one, two, or more selected from Mo: 0.005% to 2.0%, V: 0.005% to 2.0%, Nb: 0.005% to 0.20%, and Ti: 0.005% to 0.20%
Group B: by mass%, one, two, or more selected from Cr: 0.005% to 2.0%, Ni: 0.005% to 2.0%, and Cu: 0.005% to 2.0%
Group C: by mass%, B: 0.0001% to 0.0050%
Group D: by mass%, one or two selected from Ca: 0.0001% to 0.0050% and REM: 0.0001% to 0.0050%
Group E: by mass%, one or two selected from Sb: 0.0010% to 0.10% and Sn: 0.0010% to 0.50%.
[3] The high-strength hot-rolled steel sheet according to item [1] or [2], in which the microstructure further includes, in terms of area fraction, 5% or less of a retained austenite phase.
[4] A method for manufacturing a high-strength hot-rolled steel sheet, the method including performing heating, rough rolling, and finish rolling on a steel material, in which the steel material is a steel material having the chemical composition according to item [1] or [2], in which the finish rolling is performed with a finishing delivery temperature of 890°C or lower, and in which, after the finish rolling performed, cooling is performed at an average cooling rate of 10°C/s or higher to a temperature of 500°C and at an average cooling rate of 100°C/s or higher in a temperature range from a Ms temperature to a temperature of (Ms temperature - 200°C), coiling is thereafter performed at a coiling temperature of 250°C or lower, and the coiled steel sheet is subjected to at least one rolling pass with a rolling load per unit width of 0.20 ton/mm or more, or alternatively, after the finish rolling performed, the cooling is performed to a temperature of 250°C or lower, and the cooled steel sheet, before being subjected to coiling, is subjected to at least one rolling pass with a rolling load per unit width of 0.20 ton/mm or more and then coiled. Advantageous Effects of Invention
[0013] According to the present invention, since there is a marked improvement in delayed fracture resistance while high strength represented by a tensile strength TS of 1180 MPa or higher is achieved, it is possible to manufacture a high-strength hot-rolled steel sheet excellent in terms of delayed fracture resistance which can preferably be used as a material for automotive parts, which has a significant effect on the industry. In addition, according to the present invention, there is also an effect of easily manufacturing products such as high-strength automotive parts and the like in which delayed fracture is less likely to occur.
Brief Description of Drawings
[0014] [Fig. 1] Fig. 1 is a schematic diagram illustrating a preferable cooling pattern after finish rolling has been performed.
Description of Embodiments
[0015] The high-strength hot-rolled steel sheet according to the present invention is a hot-rolled steel sheet having a tensile strength TS of 1180 MPa or higher and includes a non-pickled, so-called black surface, hot-rolled steel sheet and a pickled after hot rolling, so-called white surface, hot-rolled steel sheet. In addition, it is preferable that the high-strength hot-rolled steel sheet according to the present invention have a thickness of 0.6 mm or more and 10.0 mm or less, and, in the case where the steel sheet is used as a material for automotive parts, it is more preferable that the thickness be 1.0 mm or more and 6.0 mm or less, even more preferably 3.0 mm or less, or even much more preferably 2.0 mm or less. In addition, it is preferable that the steel sheet have a width of 500 mm or more and 1800 mm or less or more preferably 700 mm or more and 1400 mm or less.
[0016] Hereafter, the reasons for the limitations on the chemical composition of the high-strength hot-rolled steel sheet according to the present invention will be described. Hereafter, "%" related to a chemical composition denotes "mass%".
[0017] The high-strength hot-rolled steel sheet according to the present invention has a base chemical composition containing C: 0.07% to 0.20%, Si: 1.50% or less, Mn: 1.0% to 4.0%, P: 0.030% or less, S: 0.0030% or less, Al: 0.010% to 1.000%, and a balance of Fe and incidental impurities.
C: 0.07% to 0.20%
[0018] C is an element effective for contributing to the formation of martensite and increasing strength (tensile strength TS) by strengthening martensite. In the case where the C content is less than 0.07%, since it is not possible to expect such effects to be sufficiently realized, it is not possible to achieve high strength represented by a tensile strength of 1180 MPa or higher. On the other hand, in the case where the C content is more than 0.20%, since there is a marked increase in the hardness of martensite, it is not possible to achieve the desired delayed fracture resistance. Therefore, the C content is set to be 0.07% to 0.20%. Here, it is preferable that the C content be 0.08% or more from the viewpoint of stably achieving a high strength represented by a tensile strength of 1180 MPa or higher, and it is preferable that the C content be 0.19% or less from the viewpoint of stabilizing delayed fracture resistance. Here, it is more preferable that the C content be 0.17% or less, or even more preferably 0.16% or less.
Si: 1.50% or less
[0019] Si is an element effective for increasing strength (tensile strength TS) through solid solution strengthening or inhibiting temper softening of martensite. Such an effect becomes marked in the case where the Si content is 0.10% or more. From the viewpoint of more stably achieving high strength represented by a tensile strength of 1180 MPa or higher, it is preferable that the Si content be 0.10% or more. Here, it is more preferable that the Si content be 0.30% or more. On the other hand, in the case where the Si content is more than 1.50%, since an excessive amount of polygonal ferrite is formed, it is not possible to form the desired microstructure. Therefore, the Si content is set to be 1.50% or less. Here, it is preferable that the Si content be 1.30% or less or more preferably 0.90% or less.
Mn: 1.0% to 4.0%
[0020] Mn is an element effective for increasing tensile strength TS by forming martensite and lower bainite. In addition, Mn effectively contributes to achieving austenite grains having a large aspect ratio by inhibiting recrystallization of austenite. To realize such effects, it is necessary that the Mn content be 1.0% or more. In the case where the Mn content is less than 1.0%, since polygonal ferrite and the like are formed, and since austenite grains having a small aspect ratio are formed, there is a decrease in tensile strength TS and a decrease in delayed fracture resistance. From the viewpoint of more stably achieving high strength represented by a tensile strength of 1180 MPa or higher, it is preferable that the Mn content be 1.2% or more. On the other hand, in the case where the Mn content is more than 4.0%, since an excessive amount of retained austenite is formed, it is not possible to form the desired steel sheet microstructure. Therefore, the Mn content is set to be 1.0% to 4.0%. Here, from the viewpoint of improving delayed fracture resistance, it is preferable that the Mn content be 3.6% or less, more preferably 3.1% or less, or even more preferably 2.7% or less.
P: 0.030% or less
[0021] P is an element which is contained as an incidental impurity and which causes a decrease in delayed fracture resistance. Therefore, in the present invention, it is preferable that the P content be as small as possible. However, it is acceptable that the P content be 0.030% or less. Therefore, the P content is set to be 0.030% or less. Here, it is preferable that the P content be 0.010% or less or more preferably 0.008% or less. However, in the case where an attempt is made to decrease the P content excessively, since there is a decrease in production efficiency, there is an increase in refining costs. Therefore, it is preferable that the P content be 0.001% or more.
S: 0.0030% or less
[0022] S is an element which is contained as an incidental impurity and which causes a decrease in delayed fracture resistance. Therefore, in the present invention, it is preferable that the S content be as small as possible. However, it is acceptable that the S content be 0.0030% or less. Therefore, the S content is set to be 0.0030% or less. Here, it is preferable that the S content be 0.0020% or less or more preferably 0.0010% or less. However, in the case where an attempt is made to decrease the S content excessively, since there is a decrease in production efficiency, there is an increase in refining costs. Therefore, it is preferable that the S content be 0.0002% or more.
Al: 0.010% to 1.000%
[0023] Al is an element which functions as a deoxidizing agent, and it is necessary that the Al content be 0.010% or more from the viewpoint of using Al as a deoxidizing agent. On the other hand, in the case where the Al content is much more than 1.000%, since an excessive amount of polygonal ferrite is formed, it is not possible to form the desired steel sheet microstructure. Therefore, in the present invention, the Al content is set to be 0.010% to 1.000%. Here, it is preferable that the Al content be 0.50% or less or more preferably 0.300% or less.
[0024] The constituents described above are the base constituents, and, in the present invention, one, two, or more selected from Group A to Group E below may be added as needed as optional elements in addition to the base chemical composition described above:
Group A: one, two, or more selected from Mo: 0.005% to 2.0%, V: 0.005% to 2.0%, Nb: 0.005% to 0.20%, and Ti: 0.005% to 0.20%,
Group B: one, two, or more selected from Cr: 0.005% to 2.0%, Ni: 0.005% to 2.0%, and Cu: 0.005% to 2.0%,
Group C: B: 0.0001% to 0.0050%,
Group D: one or two selected from Ca: 0.0001% to 0.0050% and REM: 0.0001% to 0.0050%, and
Group E: one or two selected from Sb: 0.0010% to 0.10% and Sn: 0.0010% to 0.50%
Group A: one, two, or more selected from Mo: 0.005% to 2.0%, V: 0.005% to 2.0%, Nb: 0.005% to 0.20%, and Ti: 0.005% to 0.20%
[0025] Since Mo, V, Nb, and Ti constituting Group A are elements which are all effective for improving delayed fracture resistance by forming carbides, one, two, or more selected from these elements may be added as needed. To realize such an effect, it is preferable that the Mo content be 0.005% or more, the V content be 0.005% or more, the Nb content be 0.005% or more, or the Ti content be 0.005% or more. On the other hand, in the case where the Mo content is more than 2.0%, the V content is more than 2.0%, the Nb content is more than 0.20%, or the Ti content is more than 0.20%, since there is an increase in the grain size of the carbides, there is a decrease in hardenability, which may result in the desired steel sheet microstructure not being formed. Therefore, in the case where these elements are added, it is preferable that the Mo content be 0.005% to 2.0%, the V content be 0.005% to 2.0%, the Nb content be 0.005% to 0.20%, and the Ti content be 0.005% to 0.20%. Here, it is more preferable that the Mo content be 0.05% or more and 0.6% or less, the V content be 0.05% or more and 0.3% or less, the Nb content be 0.01% or more and 0.1% or less, and the Ti content be 0.01% or more and 0.2% or less.
Group B: one, two, or more selected from Cr: 0.005% to 2.0%, Ni: 0.005% to 2.0%, and Cu: 0.005% to 2.0%
[0026] Since Cr, Ni, and Cu constituting Group B are elements all effective for increasing strength by forming martensite, one, two, or more selected from these elements may be added as needed. To realize such an effect, it is preferable that the Cr content be 0.005% or more, the Ni content be 0.005% or more, or the Cu content be 0.005% or more. On the other hand, in the case where the Cr content is more than 2.0%, the Ni content is more than 2.0%, or the Cu content is more than 2.0%, since an excessive amount of retained austenite is formed, it is not possible to form the desired steel sheet microstructure. Therefore, in the case where these elements are added, it is preferable that the Cr content be 0.005% to 2.0%, the Ni content be 0.005% to 2.0%, and the Cu content be 0.005% to 2.0%. Here, it is more preferable that the Cr content be 0.1% or more and 0.6% or less, the Ni content be 0.1% or more and 0.6% or less, and the Cu content be 0.1% or more and 0.6% or less.
Group C: B: 0.0001% to 0.0050%
[0027] Since B constituting Group C is an element effective for increasing strength by increasing the hardenability of a steel sheet and thereby forming martensite, B may be added as needed. To realize such an effect, it is preferable that the B content be 0.0001% or more. On the other hand, in the case where the B content is more than 0.0050%, since there is an increase in the amount of B compounds (boron compounds), there is a decrease in hardenability, which may result in the desired steel sheet microstructure not being formed. Therefore, in the case where B is added, it is preferable that the B content be 0.0001% to 0.0050%. Here, it is more preferable that the B content be 0.0005% or more and 0.0040% or less or even more preferably 0.0010% or more and 0.0035% or less.
Group D: one or two selected from Ca: 0.0001% to 0.0050% and REM: 0.0001% to 0.0050%
[0028] Since Ca and REM constituting Group D are both elements effective for contributing to improving workability through the morphological control of inclusions, one or two selected from these elements may be added as needed. To realize such an effect, it is preferable that the Ca content be 0.0001% or more or the REM content be 0.0001% or more. On the other hand, in the case where the Ca content is more than 0.0050% or the REM content is more than 0.0050%, since there is an increase in the amounts of inclusions, there may be a deterioration in workability. Therefore, in the case where these elements are added, it is preferable that the Ca content be 0.0001% to 0.0050% and the REM content be 0.0001% to 0.0050%. Here, it is more preferable that the Ca content be 0.0005% or more and 0.0030% or less and the REM content be 0.0005% or more and 0.0030% or less.
[0029] Since Sb and Sn constituting Group E are both elements effective for contributing to inhibiting a decrease in the strength of steel, one or two selected from these elements may be added as needed. Sb contributes to inhibiting a decrease in the strength of steel by inhibiting denitrification, deboronization, and the like, and Sn contributes to inhibiting a decrease in the strength of steel by inhibiting the formation of pearlite. To realize such effects, it is preferable that the Sb content be 0.0010% or more or the Sn content be 0.0010% or more. On the other hand, in the case where the Sb content is more than 0.10% or the Sn content is more than 0.50%, embrittlement may occur in a steel sheet. Therefore, in the case where these elements are added, it is preferable that the Sb content be 0.0010% to 0.10% and the Sn content be 0.0010% to 0.50%. Here, it is more preferable that the Sb content be 0.0050% or more and 0.050% or less and the Sn content be 0.0050% to 0.050%.
[0030] The remainder other than the constituents described above is Fe and incidental impurities.
[0031] Although N is contained as an incidental impurity, it is preferable that the N content be as small as possible from the viewpoint of inhibiting the formation of nitrides. However, in the present invention, it is acceptable that the N content be 0.010% or less. In addition, as incidental impurities, Zr and Mg may be contained in a total amount of 0.002% or less. In the case where the total amount of Zr and Mg is more than 0.002%, since there is an increase in the amount of inclusions, there is a tendency for workability to be decreased. In addition, Cr, Ni, Cu, Mo, V, Nb, Ti, B, Ca, REM, Sb, and Sn, which are optional elements, may be contained as incidental impurities as long as the contents of these elements are less than the respective lower limits described above, because this causes no decrease in the effects of the present invention.
[0032] Hereafter, the microstructure of the high-strength hot-rolled steel sheet according to the present invention will be described.
[0033] The high-strength hot-rolled steel sheet according to the present invention has a microstructure including, in terms of area fraction, 95% or more of a martensite phase at a position located at 1/4 of the thickness of the steel sheet, in which an average aspect ratio of prior austenite grains is 3.0 or more. Here, the expression a "position located at 1/4 of the thickness of the steel sheet" denotes not only an exact position located at 1/4 of the thickness of the steel sheet but also a region, when the thickness of the steel sheet is defined as t, from a position located (t/4 - 100 µm) from the steel sheet surface to a position located (t/4 + 100 µm) from the steel sheet surface.
Martensite phase: 95% or more in terms of area fraction
[0034] In the present invention, to achieve both high strength (high tensile strength TS) and excellent delayed fracture resistance, it is necessary that the microstructure at a position located at 1/4 of the thickness of the steel sheet include a martensite phase in an amount of 95% or more in terms of area fraction. In the case where the area fraction of a martensite phase is less than 95%, it is not possible to achieve the desired high strength, or it is not possible to achieve the desired delayed fracture resistance. Therefore, the microstructure at a position located at 1/4 of the thickness of the steel sheet should include a martensite phase in an amount of 95% or more in terms of area fraction. Here, it is preferable that the area fraction be 97% to 100% or more preferably 98% to 100%. Regarding phases other than a martensite phase, it is acceptable that a bainite phase and the like be included in a total amount of less than 5% in terms of area fraction.
[0035] Average aspect ratio of prior austenite grains: 3.0 or more
[0036] A martensite phase formed from austenite grains having a large aspect ratio is a phase which has a high dislocation density and which is thereby effective for increasing both tensile strength TS and delayed fracture resistance. To realize such effects, it is necessary that the average aspect ratio of prior austenite grains be 3.0 or more. In the case where the average aspect ratio of prior austenite grains is less than 3.0, it is not possible to achieve the desired delayed fracture resistance. Therefore, the average aspect ratio of prior austenite grains is set to be 3.0 or more. Here, it is preferable that the average aspect ratio be 4.0 or more or more preferably 5.0 or more. In addition, although there is no particular limitation on the upper limit of the average aspect ratio, the aspect ratio is about 20.0 or less as long as the steel sheet is manufactured by using the method within the range of the present invention.
[0037] The above-described microstructure of the high-strength hot-rolled steel sheet according to the present invention may further include a retained austenite phase in an amount of 5% or less in terms of area fraction.
Retained austenite phase: 5% or less in terms of area fraction
[0038] Since a retained austenite phase causes a decrease in delayed fracture resistance, in the present invention, it is preferable that a retained austenite phase not be included (that is, have an area fraction of 0%) or that the area fraction be as small as possible, even in the case where a retained austenite phase is included. In addition, it is acceptable that the area fraction of a retained austenite phase be 5% or less. Therefore, in the case where a retained austenite phase is included, it is preferable that the area fraction of a retained austenite phase be 5% or less. Here, it is more preferable that the area fraction be 3% or less or more preferably 2% or less.
[0039] Moreover, the high-strength hot-rolled steel sheet according to the present invention has a microstructure in which the amount of stress relaxation after a lapse of 5 min is 20 MPa or lower in a stress relaxation test with an applied stress of 400 MPa.
[0040] Amount of stress relaxation after a lapse of 5 min in a stress relaxation test with an applied stress of 400 MPa: 20 MPa or lower
[0041] Movable dislocations, which move when being subjected to a tensile stress of 400 MPa or lower, do not contribute to increasing tensile strength TS, and such movable dislocations draw hydrogen, thereby contributing to hydrogen transport. In the case where there is an increase in the number of such movable dislocations, there is a decrease in delayed fracture resistance. In the case where the amount of stress relaxation after a lapse of 5 min in a stress relaxation test with an applied stress of 400 MPa is more than 20 MPa, since there is an increase in the number of movable dislocations contributing to hydrogen transport in the microstructure, there is a marked decrease in delayed fracture resistance, which results in the desired delayed fracture resistance not being achieved. Therefore, in the present invention, the amount of stress relaxation after a lapse of 5 min in a stress relaxation test with an applied stress of 400 MPa is set to be 20 MPa or lower. Here, it is preferable that the amount of stress relaxation be 18 MPa or lower or more preferably 16 MPa or lower.
[0042] Hereafter, the preferable method for manufacturing the high-strength hot-rolled steel sheet according to the present invention will be described.
[0043] A steel material (slab) having the chemical composition described above is charged into a heating furnace and heated. Although there is no particular limitation on the heating temperature, it is preferable that the heating temperature be 1100°C or higher from the viewpoint of removing segregation, dissolving precipitates, and the like and that the heating temperature be 1300°C or lower from the viewpoint of energy efficiency and the like.
[0044] Subsequently, the heated steel material is subjected to hot rolling including rough rolling and finish rolling. In the present invention, there is no particular limitation on the conditions applied for rough rolling. After rough rolling has been performed, finish rolling is performed with a rolling finish temperature (finishing delivery temperature) of 890°C or lower. Here, it is preferable that at least four rolling passes be performed as finish rolling from the viewpoint of reducing coarse grains, which cause a decrease in workability, and the like.
[0045] Cooling following finish rolling is performed at an average cooling rate of 10°C/s or higher to a temperature of 500°C and at an average cooling rate of 100°C/s or higher in a temperature range from the Ms temperature to a temperature of (Ms temperature - 200°C), and coiling is thereafter performed at a coiling temperature of 250°C or lower.
[0046] In the present invention, although the cooling conditions to a temperature of 500°C and in a temperature range from the Ms temperature to a temperature of (Ms temperature - 200°C) are specified as described above, it is not necessary to put a particular limitation on the cooling conditions in a temperature range from a temperature of 500°C to the Ms temperature. As illustrated in Fig. 1, cooling to a temperature of 500°C may be continued to the Ms temperature, or cooling to a temperature of 500°C may be stopped first to perform cooling to the Ms temperature at another cooling rate, because this causes no problem.
[0047] Subsequently, in the present invention, coiling is first performed, the coiled steel sheet is uncoiled, and the uncoiled steel sheet is subjected to at least one rolling pass with a rolling load per unit width of 0.20 ton/mm or more. Alternatively, after the cooling following the above-described finish rolling has been performed to a temperature of 250°C or lower, the cooled steel sheet, which has not been subjected to coiling, may be subjected to at least one rolling pass with a rolling load per unit width of 0.20 ton/mm or more online and then coiled.
[0048] The temperature described above denotes the temperature (surface temperature) at the central position in the width direction of the steel sheet, and the average cooling rate described above denotes the cooling rate at the central position (surface) in the width direction of the steel sheet.
[0049] Hereafter, the reasons for the limitations on the conditions applied for finish rolling and cooling will be described.
[0050] Finishing delivery temperature: 890°C or lower
[0051] In the present invention, to promote the formation of austenite grains having a large aspect ratio, the rolling finish temperature of finish rolling (finishing delivery temperature) is set to be 890°C or lower. In the case where the finishing delivery temperature is higher than 890°C, since recrystallization of austenite grains markedly occurs and since it is not possible to form prior austenite grains having a large aspect ratio, it is not possible to form the desired steel sheet microstructure. Therefore, the finishing delivery temperature is set to be 890°C or lower. Here, it is preferable that the finishing delivery temperature be 870°C or lower, more preferably 850°C or lower, or even more preferably 830°C or lower. Although there is no particular limitation on the lower limit of the steel sheet temperature at which cooling following finish rolling starts, it is preferable that the cooling start temperature be 700°C or higher from the viewpoint of the shape stability of a steel sheet.
Cooling to a temperature of 500°C: an average cooling rate of 10°C/s or higher
[0052] After finish rolling has been performed, in the case where the average cooling rate in cooling to a temperature of 500°C is lower than 10°C/s, since a ferrite phase, a bainite phase, and the like are formed in large amounts, it is not possible to form the desired steel sheet microstructure. Therefore, the average cooling rate in cooling to a temperature of 500°C is set to be 10°C/s or higher. Here, it is preferable that the average cooling rate be 20°C/s or higher or more preferably 30°C/s or higher. In addition, although there is no particular limitation on the upper limit of the average cooling rate, it is preferable that the average cooling rate be 1000°C/s or lower from the viewpoint of the shape stability and the like of a steel sheet.
[0053] Cooling in a temperature range from the Ms temperature to a temperature of (Ms temperature - 200°C): an average cooling rate of 100°C/s or higher
[0054] In the case where the average cooling rate in cooling in a temperature range from the Ms temperature to a temperature of (Ms temperature - 200°C) is lower than 100°C/s, since a bainite phase is formed, it is not possible to form the desired steel sheet microstructure. Therefore, the average cooling rate in cooling in a temperature range from the Ms temperature to a temperature of (Ms temperature - 200°C) is set to be 100°C/s or higher. Here, it is preferable that the average cooling rate be 200°C/s or higher or more preferably 300°C/s or higher. Although there is no particular limitation on the upper limit of the average cooling rate, it is preferable that the average cooling rate be 1000°C/s or lower from the viewpoint of the shape stability and the like of a steel sheet. However, in the case where a temperature of (Ms temperature - 200°C) is equal to or lower than the coiling temperature, the average cooling rate is defined as an average cooling rate in a temperature range from the Ms temperature to the coiling temperature. Here, the Ms temperature is a temperature at which martensite transformation starts. The transformation temperature (Ms temperature) is derived from a thermal expansion-contraction curve which is obtained by performing a predetermined heating-cooling cycle test with a thermo-dilatometer (Formaster testing machine: trade name).
Coiling temperature: 250°C or lower
[0055] In the case where the coiling temperature is higher than 250°C, since a bainite phase and the like are formed, it is not possible to form the desired steel sheet microstructure including a martensite phase in an amount of 95% or more in terms of area fraction. Therefore, the coiling temperature is set to be 250°C or lower. Here, it is preferable that the coiling temperature be 200°C or lower or more preferably 180°C or lower.
Rolling load per unit width: 0.20 ton/mm or more
[0056] In the present invention, at least one rolling pass (cold rolling or warm rolling) is performed after coiling has been performed, or alternatively, online before coiling is performed. The purpose of such rolling is to form a dislocation structure in which dislocations tangle with each other, thereby reducing the number of movable dislocations as much as possible so that a decrease in delayed fracture resistance is inhibited. In the case where the rolling load per unit width is less than 0.20 ton/mm, since the movable dislocations do not sufficiently tangle with each other, it is not possible to achieve the desired delayed fracture resistance. Therefore, the rolling load per unit width in rolling, which is performed after uncoiling following coiling has been performed, or alternatively, online before coiling is performed, is set to be 0.20 ton/mm or more. Here, it is preferable that the rolling load per unit width be 0.30 ton/mm or more or more preferably 0.40 ton/mm or more.
[0057] Molten steels having the chemical compositions given in Table 1, which had been prepared by using a vacuum melting furnace, were made into steel ingots, and the ingots were subjected to rough rolling so as to be made into slabs. The obtained slabs were heated to a temperature of 1250°C and the heated slabs were subjected to finish hot rolling consisting of seven rolling passes with the finishing delivery temperatures given in Table 2. Subsequently, after cooling following finish rolling had been performed under the conditions given in Table 2, the cooled steel sheets were subjected to a treatment simulating coiling, in which the cooled steel sheets were charged into a furnace (the furnace temperatures were set to be equal to the respective coiling temperatures given in Table 2), held for one hour, and thereafter cooled in the furnace to room temperature, so as to be made into hot-rolled steel sheets (having a thickness of 3.0 mm). After the treatment simulating coiling had been performed, cold rolling was performed with the rolling loads per unit width given in Table 2. Here, one of the steel sheets (steel sheet No. 20) was cooled to a temperature of 250°C or lower before the treatment simulating coiling was performed, the cooled steel sheet was subjected to rolling online with the rolling load per unit width given in Table 2, and the rolled steel sheet was subjected to a treatment simulating coiling, in which the rolled steel sheet was charged into a furnace (the furnace temperature was set to be equal to the coiling temperature given in Table 2), held for one hour, and thereafter cooled in the furnace to room temperature.
[0058] After pickling had been performed on the obtained hot-rolled steel sheets to remove oxide layers, microstructure observation, a tensile test, a stress relaxation test, and a delayed fracture test were performed. The test methods were as follows.
(1) Microstructure observation (area fractions of respective phases)
[0059] A sample (test specimen for microstructure observation) was taken from the obtained hot-rolled steel sheet, a cross section in the thickness direction parallel to the rolling direction was polished and etched in an etching solution (3% nital), and a microstructure at a position located at 1/4 of the thickness was observed by using a scanning electron microscope SEM (at a magnification of 1500 times) to take microstructure photographs in three fields of view for each sample. From the obtained secondary electron image data, the area fractions of respective phases were determined by using Image-Pro produced by Media Cybernetics, Inc., and the average area fraction in the three fields of view of each of the respective phases was defined as the area fraction of each of the respective phases. The expression "area fraction of each of respective phases" denotes the proportion of the area of each of the respective phases with respect to the total area of a field of view observed. In the image data, a polygonal ferrite phase is identified as a black region, a lower bainite phase is identified as a gray or light-gray region containing uniformly oriented carbides, a martensite phase is identified as a gray or light-gray region containing carbides having plural orientations or a white or light-gray region containing no carbide, and a retained austenite phase is identified as a white or light-gray region containing no carbide. Since there was a case where it was not possible to distinguish between a martensite phase and a retained austenite phase, the retained austenite phase was determined by using X-ray diffractometry, and the area fraction of a martensite phase was calculated by subtracting the obtained area fraction of a retained austenite phase from the total area fraction of a martensite phase and a retained austenite phase obtained from the SEM image. Here, in the present invention, the meaning of "martensite phase" may include auto-tempered martensite and tempered martensite. Carbides have a white linear or point-like shape.
[0060] The area fraction of a retained austenite phase was determined by using X-ray diffractometry. The determination method was as follows.
[0061] A test specimen for determination was taken from the obtained hot-rolled steel sheet, the surface layer of the obtained test specimen was removed by grinding up to a thickness of 1/4 + 0.1 mm of the thickness of the test specimen, and a layer having a thickness of 0.1 mm was further removed by chemical polishing. The chemically polished surface was used as an observation surface, and an X-ray diffractometer with the Kα1-ray of Mo was used to determine the integrated reflection intensities from the (200)-plane, (220)-plane, and (311)-plane of fcc-iron (austenite) and from the (200)-plane, (211)-plane, and (220)-plane of bcc-iron (ferrite). By calculating a volume fraction from the ratio of the integrated reflection intensity from the planes of fcc-iron to the integrated reflection intensity from the planes of bcc-iron, the volume fraction was defined as the area fraction of a retained austenite phase.
[0062] The obtained area fractions of the respective phases are given in Table 3. Here, the area fractions of phases other than a martensite phase and a retained austenite phase were summed up and given in the column "Total Area Fraction of Other Phases (%)".
[0063] In addition, after the test specimen for microstructure observation described above had been etched by using an etching solution (picric acid saturated aqueous solution + surfactant + oxalic acid) to expose the grain boundaries of prior austenite (γ) at a position located at 1/4 of the thickness in a cross section in the thickness direction parallel to the rolling direction, the aspect ratio (length in the rolling direction/length in the thickness direction) of a prior austenite grain was determined. The number of grains observed was 500, and the average aspect ratio of the 500 grains was defined as the average aspect ratio of prior austenite grains of the relevant steel sheet.
(2) Tensile test
[0064] A JIS No. 5 tensile test specimen (refer to JIS Z 2201) was taken from the obtained hot-rolled steel sheet so that the tensile direction was perpendicular to the rolling direction, and a tensile test was performed in accordance with the prescription in JIS Z 2241 with a strain rate of 10-3/s to determine tensile strength TS. Here, the front and back surfaces of the test specimen were in the pickled state.
(3) Stress relaxation test
[0065] A JIS No. 5 tensile test specimen (refer to JIS Z 2201) was taken from the obtained hot-rolled steel sheet so that the tensile direction was perpendicular to the rolling direction, a tensile test was performed in accordance with the prescription in JIS Z 2241 with a strain rate of 10-3/s, in which strain increase was stopped when the stress reached 400 MPa and held for 5 min, to determine a decrease in stress from 400 MPa, and the obtained amount of decrease in stress was defined as the amount of stress relaxation after a lapse of 5 min. Here, the front and back surfaces of the test specimen were in the pickled state. As a tensile testing machine, Autograph AG-X produced by Shimadzu Corporation was used.
(4) Delayed fracture test
[0066] A tensile test specimen having a parallel portion length of 15 mm and a parallel portion width of 6 mm was taken from the obtained hot-rolled steel sheet so that the tensile direction was perpendicular to the rolling direction, an SSRT test (slow strain-rate tensile test) was performed at a cross head speed of 0.005 mm/min while hydrogen charge was performed in an electrolyte (3% NaCl + 0.3% NH4SCN aqueous solution) to determine fracture stress, and the ratio (SSRT fracture stress ratio) of the fracture stress to the tensile strength TS was calculated. Here, the amount of diffusible hydrogen at the time of fracture was determined by performing thermal desorption analysis (TDA) on the fractured sample by using gas chromatography. Here, the total amount of hydrogen desorbed in a temperature range from room temperature to a temperature of 210°C was defined as the amount of diffusible hydrogen. A case where the amount of diffusible hydrogen was 0.80 mass ppm to 1.20 mass ppm was judged as a case where a delayed fracture test was performed under satisfactory conditions. When the amount of diffusible hydrogen was out of the range described above, a delayed fracture test was performed again by changing hydrogen charge conditions so that the amount of diffusible hydrogen was within the range described above. Here, the front and back surface layers each having a thickness of 0.3 mm were removed from the test specimen by grinding before the test specimen was used in the test. A case where the determined fracture stress was 90% or more of the tensile strength TS (that is, the SSRT fracture stress ratio was 90% or more) was judged as a case of excellent delayed fracture resistance.
[0067] The obtained results are given in Table 3.
Steel No. Chemical Composition (mass%) Note
C Si Mn P S Al Group A (Mo, V, Nb, Ti) Group B (Cr, Ni, Cu) Group C (B) Group D (Ca, REM) Group E (Sb, Sn) N
A 0.08 0.50 3.1 0.015 0.0003 0.022 - - - - - 0.003 Example
B 0.07 0.50 1.7 0.022 0.0025 0.035 Mo: 0.1 Ni: 0.5 B: 0.0023 - - 0.004 Example
C 0.19 1.50 2.0 0.015 0.0019 0.030 - - - - - 0.005 Example
D 0.20 1.00 2.5 0.010 0.0021 0.031 - - B: 0.0035 - - 0.003 Example
E 0.11 0.10 2.0 0.005 0.0007 0.030 Mo: 0.1, Ti: 0.07 - B: 0.0018 - Sb: 0.01 0.004 Example
F 0.17 0.70 1.3 0.010 0.0015 0.038 - Cr: 0.9 - Ca: 0.0015 - 0.003 Example
G 0.15 0.20 3.0 0.015 0.0010 0.085 Nb: 0.02 Cu: 0.2 - REM: 0.001 Sn: 0.01 0.003 Example
H 0.06 0.30 2.5 0.010 0.0015 0.033 Mo: 0.2, Ti: 0.02 - B: 0.0020 - - 0.006 Comparative Example
I 0.23 0.50 3.0 0.011 0.0015 0.034 Ti: 0.01 - B: 0.0005 - - 0.002 Comparative Example
J 0.11 3.10 2.2 0.010 0.0015 0.030 Ti: 0.03 Ni: 0.3 - REM: 0.002 - 0.003 Comparative Example
K 0.15 0.50 0.9 0.012 0.0016 0.042 Mo: 0.2 Ni: 0.4, Cu: 0.2 - Ca: 0.0010 - 0.003 Comparative Example
L 0.15 1.00 4.5 0.010 0.0016 0.033 - - - - - 0.003 Comparative Example
M 0.15 0.10 2.6 0.011 0.0015 1.500 Mo: 0.2 - B: 0.0020 - - 0.003 Comparative Example
Steel Sheet No. Steel No. Finish Rolling Cooling after Rolling Coiling Rolling Transformation Temperature Note
Finishing Delivery Temperature (°C) Average Cooling Rate to 500°C (°C /s) Cooling Stop Temperature (°C) Average Cooling Rate from Ms to (Ms-200°C) (°C /s) Coiling Temperature (°C) Rolling Load per Unit Width (ton/mm) Number of Rolling Passes (times) Ms(°C)
1 A 830 30 500 500 80 1.00 1 400 Example
2 A 900 30 500 500 80 1.00 1 400 Comparative Example
3 A 830 30 500 500 80 - - 400 Comparative Example
4 B 850 50 450 300 25 0.80 1 449 Example
5 B 850 50 450 50 25 0.80 1 446 Comparative Example
6 B 850 50 450 300 270 0.80 1 441 Comparative Example
7 C 890 100 400 150 150 0.40 1 403 Example
8 C 890 100 400 150 150 0.15 1 403 Comparative Example
9 C 890 8 400 150 150 0.40 1 394 Comparative Example
10 D 850 15 450 100 200 0.25 2 379 Example
11 E 860 30 500 200 250 0.80 1 431 Example
12 F 880 15 500 200 150 0.60 1 430 Example
13 G 820 50 450 200 130 1.20 1 379 Example
14 H 870 15 500 200 200 0.50 1 431 Comparative Example
15 I 870 15 500 200 200 0.50 1 350 Comparative Example
16 J 870 15 500 200 200 0.50 1 398 Comparative Example
17 K 870 15 500 200 200 0.50 1 417 Comparative Example
18 L 870 15 500 200 100 0.50 1 320 Comparative Example
19 M 870 15 500 200 150 0.50 1 354 Comparative Example
20 A 830 30 500 500 *80 1.00 1 400 Example
*) Coiling was performed after rolling had been performed online.
Steel Sheet No. Steel No. Steel Sheet Microstructure Stress Relaxation Tensile Strength Delayed Fracture Resistance Note
Martensite Phase Area Fraction (%) Retained γ Phase Area Fraction (%) Total Area Fraction of Other Phases (%) Average Aspect Ratio of Prior γ Grains Amount of Stress Relaxation after a Lapse of 5 min* (MPa) Tensile Strength TS (MPa) SSRT Fracture Stress Ratio (%)
1 A 100 - - 7.7 7 1198 96 Example
2 A 100 - - 2.8 8 1203 86 Comparative Example
3 A 100 - - 7.5 21 1199 88 Comparative Example
4 B 100 - - 5.4 5 1188 99 Example
5 B 86 2 12 5.6 6 1156 99 Comparative Example
6 B 72 3 25 5.8 5 1142 100 Comparative Example
7 C 98 2 - 3.8 14 1565 93 Example
8 C 98 2 - 3.5 22 1560 85 Comparative Example
9 C 84 4 12 3.7 16 1591 83 Comparative Example
10 D 96 2 2 5.1 12 1534 95 Example
11 E 96 1 3 8.5 10 1326 99 Example
12 F 99 1 - 3.6 10 1467 94 Example
13 G 100 - - 11.3 6 1428 100 Example
14 H 99 1 - 4.4 6 1160 100 Comparative Example
15 I 98 2 - 3.9 10 1772 55 Comparative Example
16 J 57 6 37 4.1 19 1221 86 Comparative Example
17 K 55 4 41 6.9 23 1206 77 Comparative Example
18 L 97 3 - 8.9 16 1489 82 Comparative Example
19 M 52 5 43 5.4 15 1265 80 Comparative Example
20 A 100 - - 7.8 8 1200 96 Example
*) When a stress of 400 MPa was applied.
[0068] The examples of the present invention were all high-strength hot-rolled steel sheets having both high strength represented by a tensile strength TS of 1180 MPa or higher and excellent delayed fracture resistance represented by an SSRT fracture stress ratio of 90% or more. On the other hand, in the case of the comparative examples, which were out of the range of the present invention, the desired high strength was not achieved, or the excellent delayed fracture resistance was not achieved.
1. A high-strength hot-rolled steel sheet having
a chemical composition containing, by mass%,
C: 0.07% to 0.20%,
Si: 1.50% or less,
Mn: 1.0% to 4.0%,
P: 0.030% or less,
S: 0.0030% or less,
Al: 0.010% to 1.000%, and
a balance of Fe and incidental impurities,
a microstructure including, in terms of area fraction, 95% or more of a martensite phase at a position located at 1/4 of a thickness of the steel sheet, in which an average aspect ratio of prior austenite grains is 3.0 or more,
an amount of stress relaxation after a lapse of 5 min of 20 MPa or lower in a stress relaxation test with an applied stress of 400 MPa, and
a tensile strength of 1180 MPa or higher.
2. The high-strength hot-rolled steel sheet according to Claim 1, wherein the chemical composition further contains one, two, or more selected from Group A to Group E below:
3. The high-strength hot-rolled steel sheet according to Claim 1 or 2, wherein the microstructure further includes, in terms of area fraction, 5% or less of a retained austenite phase.
4. A method for manufacturing a high-strength hot-rolled steel sheet, the method comprising performing heating, rough rolling, and finish rolling on a steel material,
wherein the steel material is a steel material having the chemical composition according to Claim 1 or 2,
wherein the finish rolling is performed with a finishing delivery temperature of 890°C or lower, and
wherein, after the finish rolling performed, cooling is performed at an average cooling rate of 10°C/s or higher to a temperature of 500°C and at an average cooling rate of 100°C/s or higher in a temperature range from a Ms temperature to a temperature of (Ms temperature - 200°C), coiling is thereafter performed at a coiling temperature of 250°C or lower, and the coiled steel sheet is subjected to at least one rolling pass with a rolling load per unit width of 0.20 ton/mm or more, or alternatively,
after the finish rolling performed, the cooling is performed to a temperature of 250°C or lower, and the cooled steel sheet, before being subjected to coiling, is subjected to at least one rolling pass with a rolling load per unit width of 0.20 ton/mm or more and then coiled.
Search report
JP2016211073A [0006]


text:
Being scary in my Onyx, and stealing a tower
A hauler is making its way back to the tower and is asking if an escort is available for the w-space journey. I have my new Onyx HIC, I think I can at least appear threatening for a while, so I agree. It will be a while before the hauler gets in to w-space, though. Another plea comes to rescue a pilot stuck in a hostile class 5 w-space system, where Tengu strategic cruisers are spotted on the directional scanner. I don't quite fancy that, personally. But he has only forgotten to bookmark the wormhole out and needs someone to pop in to the system to give him a point to warp to, so it's not quite as dangerous as rescuing him from the attentions of Tech III ships. He gets a volunteer willing to be the beacon.
I follow a colleague's Zealot heavy assault ship and jump in to the neighbouring system just to see what's happening, preparing for the hauler's entrance. Sitting on the other side of our connecting wormhole and punching d-scan shows signs of occupation, but a colleague mentions something about them not being dangerous. I think I'll buzz them in my Onyx. Using d-scan to find the moon they anchored their tower to, helped by my colleague's knowledge that it was around a planet with a single moon, I warp in. I don't quite know what I'll find. A warp disruption module is visible on the scan but there is no sign of hostile ships, and this is effectively my maiden flight in Ro-Jaws, even if I've already been shot at.
There they are. A Helios covert operations ship, an Iteron hauler, and a Viator transport ship, all close to a Caldari tower that is in the middle of being unanchored. What a target, made more alluring by only the Iteron being piloted. The warp disruption module must be elsewhere in the system. It looks like the hauler is waiting for the tower to un-anchor to scoop it in to its hold, but why there are two Tech II ships floating in space next to it is a mystery. At least they had the good sense to anchor the tower some distance from the moon, as they are quite out of range when I drop from warp. As my colleauge in the Zealot joins me, I hit the micro-warp drive and burn towards the ships, feeling quite aggressive in my pointy and mean-looking ship. I am not able to close the gap quickly enough, the sluggish Iteron able to turn and enter warp before I can lock down his drives. But we are left with some goodies.
The tower still has a few minutes before it unanchors, and we need to find pilots capable of flying the two hulls in front of us. The pilot rescued from the class 5 system next door is able to get the Helios back to the tower, and our hauler coming in from New Eden docks his ship to come and pilot the Viator, the only engineer who can. Meanwhile, Onyx and Zealot sit around looking suitably mean, expecting others to come looking for their possessions. But no one comes, and we are able to snatch the two ships and haul the tower away with no incident. I imagine the Iteron pilot is just happy to have got away cleanly, unaware that it was a carebear who trepidatiously warped in and closed the distance with him. But facing specialised combat ships in an unarmed industrial vessel is never going to end well.
I am a little disappointed in myself. I was surprisingly nervous at facing non-combat vessels, which probably delayed my actions a little. I also didn't interpret the overview quickly enough, failing to realise which ship was piloted and which weren't. But this only shows a lack of experience, and that can be rectified by throwing myself in to similar situations again. As a first attempt, the engagement has been suitably benign to let me recognise without consequence issues that I can correct. I still have a lot to learn and am probably a bit too attached to my ships. At least I know that I can give the impression of being a menacing pirate. And when you want to appear dangerous sometimes it is enough just to pretend.
Tags: eve online, helios, iteron, mmorpg, onyx, penny ibramovic, pvp, tengu, viator, w-space, zealot

redpajama_set_name: RedPajamaCommonCrawl


text:
Moby-Dick or the Whale - CHAPTER 3. The Spouter-Inn.
Entering that gable-ended Spouter-Inn, you found yourself in a wide, low, straggling entry with old-fashioned wainscots, reminding one of the bulwarks of some condemned old craft. On one side hung a very large oilpainting so thoroughly besmoked, and every way defaced, that in the unequal crosslights by which you viewed it, it was only by diligent study and a series of systematic visits to it, and careful inquiry of the neighbors, that you could any way arrive at an understanding of its purpose. Such unaccountable masses of shades and shadows, that at first you almost thought some ambitious young artist, in the time of the New England hags, had endeavored to delineate chaos bewitched. But by dint of much and earnest contemplation, and oft repeated ponderings, and especially by throwing open the little window towards the back of the entry, you at last come to the conclusion that such an idea, however wild, might not be altogether unwarranted.
But what most puzzled and confounded you was a long, limber, portentous, black mass of something hovering in the centre of the picture over three blue, dim, perpendicular lines floating in a nameless yeast. A boggy, soggy, squitchy picture truly, enough to drive a nervous man distracted. Yet was there a sort of indefinite, half-attained, unimaginable sublimity about it that fairly froze you to it, till you involuntarily took an oath with yourself to find out what that marvellous painting meant. Ever and anon a bright, but, alas, deceptive idea would dart you through.—It's the Black Sea in a midnight gale.—It's the unnatural combat of the four primal elements.—It's a blasted heath.—It's a Hyperborean winter scene.—It's the breaking-up of the icebound stream of Time. But at last all these fancies yielded to that one portentous something in the picture's midst. That once found out, and all the rest were plain. But stop; does it not bear a faint resemblance to a gigantic fish? even the great leviathan himself?
In fact, the artist's design seemed this: a final theory of my own, partly based upon the aggregated opinions of many aged persons with whom I conversed upon the subject. The picture represents a Cape-Horner in a great hurricane; the half-foundered ship weltering there with its three dismantled masts alone visible; and an exasperated whale, purposing to spring clean over the craft, is in the enormous act of impaling himself upon the three mast-heads.
The opposite wall of this entry was hung all over with a heathenish array of monstrous clubs and spears. Some were thickly set with glittering teeth resembling ivory saws; others were tufted with knots of human hair; and one was sickle-shaped, with a vast handle sweeping round like the segment made in the new-mown grass by a long-armed mower. You shuddered as you gazed, and wondered what monstrous cannibal and savage could ever have gone a death-harvesting with such a hacking, horrifying implement. Mixed with these were rusty old whaling lances and harpoons all broken and deformed. Some were storied weapons. With this once long lance, now wildly elbowed, fifty years ago did Nathan Swain kill fifteen whales between a sunrise and a sunset. And that harpoon—so like a corkscrew now—was flung in Javan seas, and run away with by a whale, years afterwards slain off the Cape of Blanco. The original iron entered nigh the tail, and, like a restless needle sojourning in the body of a man, travelled full forty feet, and at last was found imbedded in the hump.
Crossing this dusky entry, and on through yon low-arched way—cut through what in old times must have been a great central chimney with fireplaces all round—you enter the public room. A still duskier place is this, with such low ponderous beams above, and such old wrinkled planks beneath, that you would almost fancy you trod some old craft's cockpits, especially of such a howling night, when this corner-anchored old ark rocked so furiously. On one side stood a long, low, shelf-like table covered with cracked glass cases, filled with dusty rarities gathered from this wide world's remotest nooks. Projecting from the further angle of the room stands a dark-looking den—the bar—a rude attempt at a right whale's head. Be that how it may, there stands the vast arched bone of the whale's jaw, so wide, a coach might almost drive beneath it. Within are shabby shelves, ranged round with old decanters, bottles, flasks; and in those jaws of swift destruction, like another cursed Jonah (by which name indeed they called him), bustles a little withered old man, who, for their money, dearly sells the sailors deliriums and death.
Abominable are the tumblers into which he pours his poison. Though true cylinders without—within, the villanous green goggling glasses deceitfully tapered downwards to a cheating bottom. Parallel meridians rudely pecked into the glass, surround these footpads' goblets. Fill to this mark, and your charge is but a penny; to this a penny more; and so on to the full glass—the Cape Horn measure, which you may gulp down for a shilling.
Upon entering the place I found a number of young seamen gathered about a table, examining by a dim light divers specimens of skrimshander. I sought the landlord, and telling him I desired to be accommodated with a room, received for answer that his house was full—not a bed unoccupied. "But avast," he added, tapping his forehead, "you haint no objections to sharing a harpooneer's blanket, have ye? I s'pose you are goin' a-whalin', so you'd better get used to that sort of thing."
I told him that I never liked to sleep two in a bed; that if I should ever do so, it would depend upon who the harpooneer might be, and that if he (the landlord) really had no other place for me, and the harpooneer was not decidedly objectionable, why rather than wander further about a strange town on so bitter a night, I would put up with the half of any decent man's blanket.
"I thought so. All right; take a seat. Supper?—you want supper? Supper'll be ready directly."
I sat down on an old wooden settle, carved all over like a bench on the Battery. At one end a ruminating tar was still further adorning it with his jack-knife, stooping over and diligently working away at the space between his legs. He was trying his hand at a ship under full sail, but he didn't make much headway, I thought.
At last some four or five of us were summoned to our meal in an adjoining room. It was cold as Iceland—no fire at all—the landlord said he couldn't afford it. Nothing but two dismal tallow candles, each in a winding sheet. We were fain to button up our monkey jackets, and hold to our lips cups of scalding tea with our half frozen fingers. But the fare was of the most substantial kind—not only meat and potatoes, but dumplings; good heavens! dumplings for supper! One young fellow in a green box coat, addressed himself to these dumplings in a most direful manner.
"My boy," said the landlord, "you'll have the nightmare to a dead sartainty."
"Landlord," I whispered, "that aint the harpooneer is it?"
"Oh, no," said he, looking a sort of diabolically funny, "the harpooneer is a dark complexioned chap. He never eats dumplings, he don't—he eats nothing but steaks, and he likes 'em rare."
"The devil he does," says I. "Where is that harpooneer? Is he here?"
"He'll be here afore long," was the answer.
I could not help it, but I began to feel suspicious of this "dark complexioned" harpooneer. At any rate, I made up my mind that if it so turned out that we should sleep together, he must undress and get into bed before I did.
Supper over, the company went back to the bar-room, when, knowing not what else to do with myself, I resolved to spend the rest of the evening as a looker on.
Presently a rioting noise was heard without. Starting up, the landlord cried, "That's the Grampus's crew. I seed her reported in the offing this morning; a three years' voyage, and a full ship. Hurrah, boys; now we'll have the latest news from the Feegees."
A tramping of sea boots was heard in the entry; the door was flung open, and in rolled a wild set of mariners enough. Enveloped in their shaggy watch coats, and with their heads muffled in woollen comforters, all bedarned and ragged, and their beards stiff with icicles, they seemed an eruption of bears from Labrador. They had just landed from their boat, and this was the first house they entered. No wonder, then, that they made a straight wake for the whale's mouth—the bar—when the wrinkled little old Jonah, there officiating, soon poured them out brimmers all round. One complained of a bad cold in his head, upon which Jonah mixed him a pitch-like potion of gin and molasses, which he swore was a sovereign cure for all colds and catarrhs whatsoever, never mind of how long standing, or whether caught off the coast of Labrador, or on the weather side of an ice-island.
The liquor soon mounted into their heads, as it generally does even with the arrantest topers newly landed from sea, and they began capering about most obstreperously.
I observed, however, that one of them held somewhat aloof, and though he seemed desirous not to spoil the hilarity of his shipmates by his own sober face, yet upon the whole he refrained from making as much noise as the rest. This man interested me at once; and since the sea-gods had ordained that he should soon become my shipmate (though but a sleeping-partner one, so far as this narrative is concerned), I will here venture upon a little description of him. He stood full six feet in height, with noble shoulders, and a chest like a coffer-dam. I have seldom seen such brawn in a man. His face was deeply brown and burnt, making his white teeth dazzling by the contrast; while in the deep shadows of his eyes floated some reminiscences that did not seem to give him much joy. His voice at once announced that he was a Southerner, and from his fine stature, I thought he must be one of those tall mountaineers from the Alleghanian Ridge in Virginia. When the revelry of his companions had mounted to its height, this man slipped away unobserved, and I saw no more of him till he became my comrade on the sea. In a few minutes, however, he was missed by his shipmates, and being, it seems, for some reason a huge favourite with them, they raised a cry of "Bulkington! Bulkington! where's Bulkington?" and darted out of the house in pursuit of him.
It was now about nine o'clock, and the room seeming almost supernaturally quiet after these orgies, I began to congratulate myself upon a little plan that had occurred to me just previous to the entrance of the seamen.
No man prefers to sleep two in a bed. In fact, you would a good deal rather not sleep with your own brother. I don't know how it is, but people like to be private when they are sleeping. And when it comes to sleeping with an unknown stranger, in a strange inn, in a strange town, and that stranger a harpooneer, then your objections indefinitely multiply. Nor was there any earthly reason why I as a sailor should sleep two in a bed, more than anybody else; for sailors no more sleep two in a bed at sea, than bachelor Kings do ashore. To be sure they all sleep together in one apartment, but you have your own hammock, and cover yourself with your own blanket, and sleep in your own skin.
The more I pondered over this harpooneer, the more I abominated the thought of sleeping with him. It was fair to presume that being a harpooneer, his linen or woollen, as the case might be, would not be of the tidiest, certainly none of the finest. I began to twitch all over. Besides, it was getting late, and my decent harpooneer ought to be home and going bedwards. Suppose now, he should tumble in upon me at midnight—how could I tell from what vile hole he had been coming?
"Landlord! I've changed my mind about that harpooneer.—I shan't sleep with him. I'll try the bench here."
"Just as you please; I'm sorry I can't spare ye a tablecloth for a mattress, and it's a plaguy rough board here"—feeling of the knots and notches. "But wait a bit, Skrimshander; I've got a carpenter's plane there in the bar—wait, I say, and I'll make ye snug enough." So saying he procured the plane; and with his old silk handkerchief first dusting the bench, vigorously set to planing away at my bed, the while grinning like an ape. The shavings flew right and left; till at last the plane-iron came bump against an indestructible knot. The landlord was near spraining his wrist, and I told him for heaven's sake to quit—the bed was soft enough to suit me, and I did not know how all the planing in the world could make eider down of a pine plank. So gathering up the shavings with another grin, and throwing them into the great stove in the middle of the room, he went about his business, and left me in a brown study.
I now took the measure of the bench, and found that it was a foot too short; but that could be mended with a chair. But it was a foot too narrow, and the other bench in the room was about four inches higher than the planed one—so there was no yoking them. I then placed the first bench lengthwise along the only clear space against the wall, leaving a little interval between, for my back to settle down in. But I soon found that there came such a draught of cold air over me from under the sill of the window, that this plan would never do at all, especially as another current from the rickety door met the one from the window, and both together formed a series of small whirlwinds in the immediate vicinity of the spot where I had thought to spend the night.
The devil fetch that harpooneer, thought I, but stop, couldn't I steal a march on him—bolt his door inside, and jump into his bed, not to be wakened by the most violent knockings? It seemed no bad idea; but upon second thoughts I dismissed it. For who could tell but what the next morning, so soon as I popped out of the room, the harpooneer might be standing in the entry, all ready to knock me down!
Still, looking round me again, and seeing no possible chance of spending a sufferable night unless in some other person's bed, I began to think that after all I might be cherishing unwarrantable prejudices against this unknown harpooneer. Thinks I, I'll wait awhile; he must be dropping in before long. I'll have a good look at him then, and perhaps we may become jolly good bedfellows after all—there's no telling.
But though the other boarders kept coming in by ones, twos, and threes, and going to bed, yet no sign of my harpooneer.
"Landlord!" said I, "what sort of a chap is he—does he always keep such late hours?" It was now hard upon twelve o'clock.
The landlord chuckled again with his lean chuckle, and seemed to be mightily tickled at something beyond my comprehension. "No," he answered, "generally he's an early bird—airley to bed and airley to rise—yes, he's the bird what catches the worm. But to-night he went out a peddling, you see, and I don't see what on airth keeps him so late, unless, may be, he can't sell his head."
"Can't sell his head?—What sort of a bamboozingly story is this you are telling me?" getting into a towering rage. "Do you pretend to say, landlord, that this harpooneer is actually engaged this blessed Saturday night, or rather Sunday morning, in peddling his head around this town?"
"That's precisely it," said the landlord, "and I told him he couldn't sell it here, the market's overstocked."
"With what?" shouted I.
"With heads to be sure; ain't there too many heads in the world?"
"I tell you what it is, landlord," said I quite calmly, "you'd better stop spinning that yarn to me—I'm not green."
"May be not," taking out a stick and whittling a toothpick, "but I rayther guess you'll be done brown if that ere harpooneer hears you a slanderin' his head."
"I'll break it for him," said I, now flying into a passion again at this unaccountable farrago of the landlord's.
"It's broke a'ready," said he.
"Broke," said I—"broke, do you mean?"
"Sartain, and that's the very reason he can't sell it, I guess."
"Landlord," said I, going up to him as cool as Mt. Hecla in a snow-storm—"landlord, stop whittling. You and I must understand one another, and that too without delay. I come to your house and want a bed; you tell me you can only give me half a one; that the other half belongs to a certain harpooneer. And about this harpooneer, whom I have not yet seen, you persist in telling me the most mystifying and exasperating stories tending to beget in me an uncomfortable feeling towards the man whom you design for my bedfellow—a sort of connexion, landlord, which is an intimate and confidential one in the highest degree. I now demand of you to speak out and tell me who and what this harpooneer is, and whether I shall be in all respects safe to spend the night with him. And in the first place, you will be so good as to unsay that story about selling his head, which if true I take to be good evidence that this harpooneer is stark mad, and I've no idea of sleeping with a madman; and you, sir, you I mean, landlord, you, sir, by trying to induce me to do so knowingly, would thereby render yourself liable to a criminal prosecution."
"Wall," said the landlord, fetching a long breath, "that's a purty long sarmon for a chap that rips a little now and then. But be easy, be easy, this here harpooneer I have been tellin' you of has just arrived from the south seas, where he bought up a lot of 'balmed New Zealand heads (great curios, you know), and he's sold all on 'em but one, and that one he's trying to sell to-night, cause to-morrow's Sunday, and it would not do to be sellin' human heads about the streets when folks is goin' to churches. He wanted to, last Sunday, but I stopped him just as he was goin' out of the door with four heads strung on a string, for all the airth like a string of inions."
This account cleared up the otherwise unaccountable mystery, and showed that the landlord, after all, had had no idea of fooling me—but at the same time what could I think of a harpooneer who stayed out of a Saturday night clean into the holy Sabbath, engaged in such a cannibal business as selling the heads of dead idolators?
"Depend upon it, landlord, that harpooneer is a dangerous man."
"He pays reg'lar," was the rejoinder. "But come, it's getting dreadful late, you had better be turning flukes—it's a nice bed; Sal and me slept in that ere bed the night we were spliced. There's plenty of room for two to kick about in that bed; it's an almighty big bed that. Why, afore we give it up, Sal used to put our Sam and little Johnny in the foot of it. But I got a dreaming and sprawling about one night, and somehow, Sam got pitched on the floor, and came near breaking his arm. Arter that, Sal said it wouldn't do. Come along here, I'll give ye a glim in a jiffy;" and so saying he lighted a candle and held it towards me, offering to lead the way. But I stood irresolute; when looking at a clock in the corner, he exclaimed "I vum it's Sunday—you won't see that harpooneer to-night; he's come to anchor somewhere—come along then; do come; won't ye come?"
I considered the matter a moment, and then up stairs we went, and I was ushered into a small room, cold as a clam, and furnished, sure enough, with a prodigious bed, almost big enough indeed for any four harpooneers to sleep abreast.
"There," said the landlord, placing the candle on a crazy old sea chest that did double duty as a wash-stand and centre table; "there, make yourself comfortable now, and good night to ye." I turned round from eyeing the bed, but he had disappeared.
Folding back the counterpane, I stooped over the bed. Though none of the most elegant, it yet stood the scrutiny tolerably well. I then glanced round the room; and besides the bedstead and centre table, could see no other furniture belonging to the place, but a rude shelf, the four walls, and a papered fireboard representing a man striking a whale. Of things not properly belonging to the room, there was a hammock lashed up, and thrown upon the floor in one corner; also a large seaman's bag, containing the harpooneer's wardrobe, no doubt in lieu of a land trunk. Likewise, there was a parcel of outlandish bone fish hooks on the shelf over the fire-place, and a tall harpoon standing at the head of the bed.
But what is this on the chest? I took it up, and held it close to the light, and felt it, and smelt it, and tried every way possible to arrive at some satisfactory conclusion concerning it. I can compare it to nothing but a large door mat, ornamented at the edges with little tinkling tags something like the stained porcupine quills round an Indian moccasin. There was a hole or slit in the middle of this mat, as you see the same in South American ponchos. But could it be possible that any sober harpooneer would get into a door mat, and parade the streets of any Christian town in that sort of guise? I put it on, to try it, and it weighed me down like a hamper, being uncommonly shaggy and thick, and I thought a little damp, as though this mysterious harpooneer had been wearing it of a rainy day. I went up in it to a bit of glass stuck against the wall, and I never saw such a sight in my life. I tore myself out of it in such a hurry that I gave myself a kink in the neck.
I sat down on the side of the bed, and commenced thinking about this head-peddling harpooneer, and his door mat. After thinking some time on the bed-side, I got up and took off my monkey jacket, and then stood in the middle of the room thinking. I then took off my coat, and thought a little more in my shirt sleeves. But beginning to feel very cold now, half undressed as I was, and remembering what the landlord said about the harpooneer's not coming home at all that night, it being so very late, I made no more ado, but jumped out of my pantaloons and boots, and then blowing out the light tumbled into bed, and commended myself to the care of heaven.
Whether that mattress was stuffed with corn-cobs or broken crockery, there is no telling, but I rolled about a good deal, and could not sleep for a long time. At last I slid off into a light doze, and had pretty nearly made a good offing towards the land of Nod, when I heard a heavy footfall in the passage, and saw a glimmer of light come into the room from under the door.
Lord save me, thinks I, that must be the harpooneer, the infernal head-peddler. But I lay perfectly still, and resolved not to say a word till spoken to. Holding a light in one hand, and that identical New Zealand head in the other, the stranger entered the room, and without looking towards the bed, placed his candle a good way off from me on the floor in one corner, and then began working away at the knotted cords of the large bag I before spoke of as being in the room. I was all eagerness to see his face, but he kept it averted for some time while employed in unlacing the bag's mouth. This accomplished, however, he turned round—when, good heavens! what a sight! Such a face! It was of a dark, purplish, yellow colour, here and there stuck over with large blackish looking squares. Yes, it's just as I thought, he's a terrible bedfellow; he's been in a fight, got dreadfully cut, and here he is, just from the surgeon. But at that moment he chanced to turn his face so towards the light, that I plainly saw they could not be sticking-plasters at all, those black squares on his cheeks. They were stains of some sort or other. At first I knew not what to make of this; but soon an inkling of the truth occurred to me. I remembered a story of a white man—a whaleman too—who, falling among the cannibals, had been tattooed by them. I concluded that this harpooneer, in the course of his distant voyages, must have met with a similar adventure. And what is it, thought I, after all! It's only his outside; a man can be honest in any sort of skin. But then, what to make of his unearthly complexion, that part of it, I mean, lying round about, and completely independent of the squares of tattooing. To be sure, it might be nothing but a good coat of tropical tanning; but I never heard of a hot sun's tanning a white man into a purplish yellow one. However, I had never been in the South Seas; and perhaps the sun there produced these extraordinary effects upon the skin. Now, while all these ideas were passing through me like lightning, this harpooneer never noticed me at all. But, after some difficulty having opened his bag, he commenced fumbling in it, and presently pulled out a sort of tomahawk, and a seal-skin wallet with the hair on. Placing these on the old chest in the middle of the room, he then took the New Zealand head—a ghastly thing enough—and crammed it down into the bag. He now took off his hat—a new beaver hat—when I came nigh singing out with fresh surprise. There was no hair on his head—none to speak of at least—nothing but a small scalp-knot twisted up on his forehead. His bald purplish head now looked for all the world like a mildewed skull. Had not the stranger stood between me and the door, I would have bolted out of it quicker than ever I bolted a dinner.
Even as it was, I thought something of slipping out of the window, but it was the second floor back. I am no coward, but what to make of this head-peddling purple rascal altogether passed my comprehension. Ignorance is the parent of fear, and being completely nonplussed and confounded about the stranger, I confess I was now as much afraid of him as if it was the devil himself who had thus broken into my room at the dead of night. In fact, I was so afraid of him that I was not game enough just then to address him, and demand a satisfactory answer concerning what seemed inexplicable in him.
Meanwhile, he continued the business of undressing, and at last showed his chest and arms. As I live, these covered parts of him were checkered with the same squares as his face; his back, too, was all over the same dark squares; he seemed to have been in a Thirty Years' War, and just escaped from it with a sticking-plaster shirt. Still more, his very legs were marked, as if a parcel of dark green frogs were running up the trunks of young palms. It was now quite plain that he must be some abominable savage or other shipped aboard of a whaleman in the South Seas, and so landed in this Christian country. I quaked to think of it. A peddler of heads too—perhaps the heads of his own brothers. He might take a fancy to mine—heavens! look at that tomahawk!
But there was no time for shuddering, for now the savage went about something that completely fascinated my attention, and convinced me that he must indeed be a heathen. Going to his heavy grego, or wrapall, or dreadnaught, which he had previously hung on a chair, he fumbled in the pockets, and produced at length a curious little deformed image with a hunch on its back, and exactly the colour of a three days' old Congo baby. Remembering the embalmed head, at first I almost thought that this black manikin was a real baby preserved in some similar manner. But seeing that it was not at all limber, and that it glistened a good deal like polished ebony, I concluded that it must be nothing but a wooden idol, which indeed it proved to be. For now the savage goes up to the empty fire-place, and removing the papered fire-board, sets up this little hunch-backed image, like a tenpin, between the andirons. The chimney jambs and all the bricks inside were very sooty, so that I thought this fire-place made a very appropriate little shrine or chapel for his Congo idol.
I now screwed my eyes hard towards the half hidden image, feeling but ill at ease meantime—to see what was next to follow. First he takes about a double handful of shavings out of his grego pocket, and places them carefully before the idol; then laying a bit of ship biscuit on top and applying the flame from the lamp, he kindled the shavings into a sacrificial blaze. Presently, after many hasty snatches into the fire, and still hastier withdrawals of his fingers (whereby he seemed to be scorching them badly), he at last succeeded in drawing out the biscuit; then blowing off the heat and ashes a little, he made a polite offer of it to the little negro. But the little devil did not seem to fancy such dry sort of fare at all; he never moved his lips. All these strange antics were accompanied by still stranger guttural noises from the devotee, who seemed to be praying in a sing-song or else singing some pagan psalmody or other, during which his face twitched about in the most unnatural manner. At last extinguishing the fire, he took the idol up very unceremoniously, and bagged it again in his grego pocket as carelessly as if he were a sportsman bagging a dead woodcock.
All these queer proceedings increased my uncomfortableness, and seeing him now exhibiting strong symptoms of concluding his business operations, and jumping into bed with me, I thought it was high time, now or never, before the light was put out, to break the spell in which I had so long been bound.
But the interval I spent in deliberating what to say, was a fatal one. Taking up his tomahawk from the table, he examined the head of it for an instant, and then holding it to the light, with his mouth at the handle, he puffed out great clouds of tobacco smoke. The next moment the light was extinguished, and this wild cannibal, tomahawk between his teeth, sprang into bed with me. I sang out, I could not help it now; and giving a sudden grunt of astonishment he began feeling me.
Stammering out something, I knew not what, I rolled away from him against the wall, and then conjured him, whoever or whatever he might be, to keep quiet, and let me get up and light the lamp again. But his guttural responses satisfied me at once that he but ill comprehended my meaning.
"Who-e debel you?"—he at last said—"you no speak-e, dam-me, I kill-e." And so saying the lighted tomahawk began flourishing about me in the dark.
"Landlord, for God's sake, Peter Coffin!" shouted I. "Landlord! Watch! Coffin! Angels! save me!"
"Speak-e! tell-ee me who-ee be, or dam-me, I kill-e!" again growled the cannibal, while his horrid flourishings of the tomahawk scattered the hot tobacco ashes about me till I thought my linen would get on fire. But thank heaven, at that moment the landlord came into the room light in hand, and leaping from the bed I ran up to him.
"Don't be afraid now," said he, grinning again, "Queequeg here wouldn't harm a hair of your head."
"Stop your grinning," shouted I, "and why didn't you tell me that that infernal harpooneer was a cannibal?"
"I thought ye know'd it;—didn't I tell ye, he was a peddlin' heads around town?—but turn flukes again and go to sleep. Queequeg, look here—you sabbee me, I sabbee—you this man sleepe you—you sabbee?"
"Me sabbee plenty"—grunted Queequeg, puffing away at his pipe and sitting up in bed.
"You gettee in," he added, motioning to me with his tomahawk, and throwing the clothes to one side. He really did this in not only a civil but a really kind and charitable way. I stood looking at him a moment. For all his tattooings he was on the whole a clean, comely looking cannibal. What's all this fuss I have been making about, thought I to myself—the man's a human being just as I am: he has just as much reason to fear me, as I have to be afraid of him. Better sleep with a sober cannibal than a drunken Christian.
"Landlord," said I, "tell him to stash his tomahawk there, or pipe, or whatever you call it; tell him to stop smoking, in short, and I will turn in with him. But I don't fancy having a man smoking in bed with me. It's dangerous. Besides, I ain't insured."
This being told to Queequeg, he at once complied, and again politely motioned me to get into bed—rolling over to one side as much as to say—"I won't touch a leg of ye."
"Good night, landlord," said I, "you may go."
I turned in, and never slept better in my life.