普通螺纹和梯形螺纹的代号分别为()、()。
参考答案:M;T
On my first night in New York, I decided that I had to learn to speak English.
采用钨极氩弧焊打底、焊条电弧焊盖面的焊接工艺,打完底后进行填充层电弧焊接时,应注意不得将打底层焊道烧穿,否则会产生凹坑或()等缺陷。
A.背面焊道强烈氧化
B.根部未熔
C.夹渣
D.未焊透