The invention concerns a cold-worked steel with high compressive strength and the use of such steel for parts and tools.
Tools and machine parts are made from cold-worked steels where such steels are used for processing materials at temperatures less than 250.degree. C., especially at room temperature. Such processing may be cutting or non-cutting, e.g., stamping, pressing or extruding, the parts or tools being simultaneously subjected to various stresses. As a rule the desired properties of the parts, such as compressive strength, hardness, toughness, wear resistance, cutting life and possibly erosion matching the predominant stresses, shall be achieved by a suitable selection of the composition of the cold-worked steel.
It is known to meet the requirement, for instance, of high wear-resistance to make use of Cr steels with contents of 1.5 to 2.5% C and 10 to 17% Cr, illustratively steels corresponding to DIN material No. 1.2379 or AISI type D7. While such steels in fact do have high wear resistance, on account of their high and coarse carbide proportion, which most of the time is arrayed in lines, its toughness is low, and accordingly the part may fracture or crack when subjected to bending or shearing stresses.
To make cold-worked steel tools of good toughness, it is known to use alloys with about 5% or about 8% Cr and a carbon content of about 1.0% or about 0.5% with additions of Mo, W and V, illustratively steels according to DIN material No. 1.2363 or No. 1.2345 or AISI type A2. In the event of advantageous alloy structure or carbide structure, these steels may have good toughness and adequate erosion and abrasion behavior, but their wear resistance and compressive strength are not satisfactory for some applications. Moreover the alloy variations, namely those with Cr contents of 10 to 17% and those with 5 to 8% Cr, also incur the drawback that upon additional surface hardening by nitridation and/or carbonitridation, or upon surface coating using the CVD or PVD methods at temperatures between 350.degree. and 600.degree. C., the previously achieved improved hardening of the base material shall be reduced.