A.低碳鋼 B.中碳鋼 C.高碳鋼 D.中低碳鋼
A.無(wú)效數(shù)據(jù) B.參考數(shù)據(jù) C.有效數(shù)據(jù)
A.10×10×55 B.7×10×55 C.5×10×55 D.6×10×55