短语词组短语backing g weld 用垫环的焊缝backing groove of weld 焊缝反面坡口weld backing 焊接衬垫;焊缝衬垫;焊缝垫;焊缝背衬垫nonfusible weld backing 非熔性焊接背垫weld with backing ring 背面垫环焊接weld with backing strip 背面垫板条焊接 返回 backing weld