A.自中間向四周打 B.自兩邊向中央打 C.又一側(cè)向另一側(cè)打 D.自中間向兩側(cè)打
A.50% B.70% C.90% D.100%
A.對(duì)焊 B.電弧焊 C.電阻點(diǎn)焊 D.埋弧壓力焊