单项选择题
A.0.06% B.0.6% C.6% D.2%
A.优质碳素结构钢 B.优质碳素工具钢 C.优质低碳合金钢 D.优质高碳合金钢
A.0.50% B.0.60% C.0.70% D.0.80%
A.025%~0.025% B.0.25%~0.6% C.0.025%~0.06% D.2.5%~6%
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