单项选择题
A.Cr B.Mn C.Ti D.V
A.3% B.4% C.5% D.6%
A.低碳钢 B.中碳钢 C.高碳钢 D.不加限制
A.<0.25% B.0.25%～0.3% C.0.3%～0.6% D.>0.6%
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