A.3B.4C.5D.6
A.優(yōu)質(zhì)碳素結(jié)構(gòu)鋼 B.低合金高強(qiáng)度結(jié)構(gòu)鋼 C.合金鋼 D.45號(hào)鋼
A.0.07% B.0.12% C.0.01% D.0.005%