A.優(yōu)質(zhì)鋼 B.碳素鋼 C.合金鋼 D.普通鋼
A.≤0.25% B.0.25-0.6% C.>0.6% D.>0.8%
A.合金結(jié)構(gòu)鋼 B.低合金鋼 C.中合金鋼 D.高合金鋼