The limit expansion joint must be placed in the center of the plate. The length of the limit expansion joint weld is 10 to 15mm and spot welded inside the pipe wall. It must be spot welded firmly to prevent cracking. The starting point is opposite the positioning weld, and the arc is ignited on the side of the tube 10 to 15 mm in front of the starting point, and the limit expansion joint is immediately depressed and operated with a short arc afterwards, and then led to the starting point for use classification.
This can avoid the production of porosity at the starting point of the weld, but also by melting the arc initiation point again, the arc will be led when the porosity is given to eliminate. The use of limit expansion joints, classification process always maintain a short arc operation. Use the sawtooth or straight line to carry the bar method. Swinging amplitude should be maintained at about 6mm, swinging to the side of the pipe when a slight pause to ensure root weld through. Limit expansion joint uses, classification to keep the welding rod angle basically the same, uses, classification speed should be uniform.
