A.球罐組裝完畢后,應(yīng)按先縱縫后環(huán)縫的原則安排焊接順序 B.縱縫焊接時,焊機布置應(yīng)對稱均勻,并同步焊接 C.縱縫焊接時,焊機布置應(yīng)對稱均勻,不應(yīng)同步焊接 D.環(huán)縫焊接時,焊機布置應(yīng)對稱,并沿同一旋轉(zhuǎn)方向焊接
A.20mg/L B.25mg/L C.30mg/L D.50mg/L