Head Grade, material, Nominal Proof Yield Tensile Core marking and condition size range strength strength, strength, hardness (mm) (MPa/ksi) min. min. () (MPa/ksi) (MPa/ksi) Class 3.6 1.6–36 180/26 190/28 330/48 B52–95 Class 4.6 5–100 225/32.6 240/35 400/58 B67–95 Low or medium carbon steel Class 4.8 1.6–16 310/45 340/49 420/61 B71–95 Low or medium carbon steel; fully or partially annealed Class 5.8 5–24 380/55 420/61 520/75 B82–95 Low or medium carbon steel; cold worked Class 8.8 Under 16 580/84 640/93 800/120 Medium carbon (inc.) steel; quench and 17–72 600/87 660/96 830/120 C23–34 tempered Class 8.8 low carbon Low carbon boron steel; quench and tempered Class 8.8.3 Atmospheric corrosion resistant steel; quench and tempered - Type 1 12–36 Medium carbon steel; quench and tempered ASTM A325M - Type 3 Atmospheric corrosion resistant steel; quench and tempered
Head marking Grade, material, and condition Nominal size range (mm) Proof strength (MPa/ksi) Yield strength, min. (MPa/ksi) Tensile strength, min. (MPa/ksi) Core hardness () Class 3.6 1.6–36 180/26 190/28 330/48 B52–95 Class 4.6 Low or medium carbon steel 5–100 225/32.6 240/35 400/58 B67–95 Class 4.8 Low or medium carbon steel; fully or partially annealed 1.6–16 310/45 340/49 420/61 B71–95 Class 5.8 Low or medium carbon steel; cold worked 5–24 380/55 420/61 520/75 B82–95 Class 8.8 Medium carbon steel; quench and tempered Under 16 (inc.) 580/84 640/93 800/120 17–72 600/87 660/96 830/120 C23–34 Class 8.8 low carbon Low carbon boron steel; quench and tempered Class 8.8.3 Atmospheric corrosion resistant steel; quench and tempered - Type 1 Medium carbon steel; quench and tempered 12–36 ASTM A325M - Type 3 Atmospheric corrosion resistant steel; quench and tempered
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