单项选择题
A.ZG30CrMoB.ZGMn13-4C.ZG30CrMnSiMoD.GS-1
A.铁素体B.奥氏体C.珠光体D.渗碳体
A.ZCM13-1B.ZG40CrSi2C.ZG270-500D.ZG20Cr13