The control method of welded seam joint of welded pipe

The control method of welded seam joint of welded pipe

Start of welding

The beginning of the weld refers to the weld at the beginning of welding, and the reinforcement of this part is easy to increase. This is because the temperature of the weldment is low at the beginning of welding, and the temperature cannot rise rapidly after arc striking, so the penetration is shallow and the reinforcement is large. In order to avoid this situation, the electric arc can be slightly lengthened after arc striking for preheating, and the arc can be properly lowered for normal welding.

Control method of weld joint

The joint between the post weld and the pre weld is called the weld joint. Due to the limitation of welding rod, the weld joint is inevitable, but the joint should be uniform, so as to avoid the defects such as too high weld joint, disjoint and inconsistent width.

There are four kinds of weld joints

1.Intermediate joint: starting from the tail of the first weld, start the arc about 10 mm in front of the crater, the arc length is slightly longer than the normal welding, and then move back to the crater, depress the arc, and then weld forward normally. It is suitable for surface joint of single-layer welding and multi-layer welding, and is a joint method widely used.

2.Opposite joint: the beginning of the two welds are connected, the starting point of the first weld is required to be slightly lower, and the latter weld should start the arc a little before the starting point of the previous weld, and then lengthen the arc slightly, so that the arc will gradually lead to the starting point of the previous weld and cover the end point of the previous weld, and then move to the welding direction after flat welding.

3.Opposite joint: the back welding seam is welded to the arc stop position, and the welding speed is slowed down. After the welding pit is filled, the forward welding section is welded, and then the arc is extinguished.

4.Segmented back welding joint: the back welding seam is close to the beginning end of the front welding seam, and the welding rod angle is changed to point to the back end of the front welding seam. After forming the molten pool, the arc is pressed down, and then it returns to the original molten pool to stop the arc. Whether the joint connection is smooth or not is related to the welder's operation technology and the temperature at the joint. The temperature is high and the connection is smooth, so the arc breaking time of the middle joint is required to be short, and the welding rod is changed quickly, The interlaminar joints of multi-layer welding should be staggered to increase the density of the weld.

When welding the middle joint, it is not necessary to clean the welding slag. Before other joints, it is necessary to clean the welding slag at the joint. Otherwise, if the welding joint is not well connected, the joint can be polished into an inclined plane first and then welded.