A.引燃電弧后將電弧拉長(zhǎng),對(duì)起焊端部進(jìn)行必要的預(yù)熱,然后壓短電弧長(zhǎng)度B.引燃電弧后即C.在離焊縫起焊處30mm 左右引燃電弧后拉向焊縫端部D.采用引弧板引燃電弧后即
A.結(jié)構(gòu)安全B.力學(xué)性能C.經(jīng)濟(jì)效益D.焊接電流