一、填空(40分) 1.焊条牌号最末尾的数字中的“2”表示_______;“6”表示_____;“7”表示_____;“8”表示_____。(4分) 2.为确保旋转式直流弧焊机的使用安全,应在______状态下起动;调节焊接电流须在_______情况下进行。焊接回路中,短路的时间一般不应超过____。(3分) 3.在BX3型焊机的调节焊接电流方法中,改变_____作为粗调;改变_____作为细调。(2分) First, fill in the blanks (40 points) 1 electrode at the end of the number of “2” said _______; “6” said _____; “7” said _____; “8” said _____. (4 points) 2. In order to ensure the safety of rotary DC arc welding machine, it should start in ______ state; adjust the welding current to be carried out under _______. Welding circuit, the short circuit time should generally not exceed ____. (3 points) 3. In the method of adjusting welding current of BX3 welder, change _____ as coarse adjustment; change _____ as fine adjustment. (2 minutes)