Table 3.13 High-speed steels - BS 4659: 1989. Details of composition and hardness
Designation C% Cfi Mo% W% V% Co% Hardness after Hardness after heat
annealing HB (mar) matment HV (min.)
BM1 0.75-0.85 3.75-4.5 8-9 1-2 1-1.25 1 max. 241 823
BM2 0.82-0.92 3.75-4.5 4.75-55 6-6.75 1.75-2.05 1 max. 248 836
BM4 1.25-1.4 3.75-4.5 4.25-5 5.75-6.5 3.75-4.25 1 max. 255 849
BM15 1.45-1.6 4.5-5 2.75-3.25 6.25-7 4.75-5.25 4.5-5.5 277 869
BM35 0.85-0.95 3.75-4.5 4.75-5.25 6-6.75 1.75-2.15 4.6-5.2 269 869
BM42 1-1.1 3.5-4.25 9-10 1-2 1-1.3 75-8.5 269 897
BT1 0.7-0.8 3.75-4.5 0.7 ma^. 17.5-18.5 1-1.25 1 max. 255 823
BT4 0.7-0.8 3.75-4.5 1 ma^. 175-18.5 1-1.25 4.5-5.5 277 849
BT5 0.75-0.85 3.75-4.5 1 ma^. 18.5-19.5 1.75-2.05 9- 10 290 869
BT6 0.75-0.85 3.75-4.5 1 ma^. 20-21 1.25-1.75 11.25-12.25 302 869
BT15 1.4-1.6 4.25-5^1 max. 12-13 4.75-5.25 4.5-5.5 290 890
BT21 0.6-0.7 3.5-4.25 0.7 ma^. 13.5-14.5 0.4-0.6 lmax. 255 798
BT42 1.25-1.4 3.75-4.5 2.75-3.5 8.5-9.5 2.75-3.25 9-10 277 912
After BS 4659 1989.