A.電機 B.進給 C.主軸 D.伺服
A.高級優(yōu)質(zhì)鋼 B.優(yōu)質(zhì)鋼 C.質(zhì)量等級 D.工具鋼
A.2.11% B.1.4% C.0.6% D.0.25%