Pipeline welding method

Abstract

The invention provides a pipeline welding method which comprises the following steps: carrying out pre-welding preparation, namely pairing all pipes according to a gap requirement and machining pipe grooves according to a groove angle requirement; choosing welding rods and electric currents, namely choosing proper welding rods and electric currents according to the diameters of the pipes, the thicknesses of pipe walls and welding skill proficiencies; carrying out backing welding by using argon arc welding; filling and welding cover surface by using electric covering surface large current interruption welding method. As the current interruption welding method controls welding sequences, welding current, welding rod angles, arc-starting points and arc-stopping points, the qualification rate of pipeline welding can be effectively increased.

Description

technical field [0001] The present invention relates to a welding method, more specifically, to a pipeline welding method. Background technique [0002] Heating is an indispensable part in winter. Boilers are widely used for heating in cities now. Welding is an important part of boiler quality. The quality of welding is directly related to the service life of the heating surface of boiler tubes. In the prior art, the continuous welding method of argon arc welding as the base and electric welding cover is often used, that is, the welding method of each electrode is continuously arced by means of lateral swinging, figure 1 It is a schematic diagram of the continuous welding welding method in the prior art. The welding sequence is from the overhead welding position Y1 to a certain vertical welding position L2 to reach the flat welding position P1, and then from the overhead welding position Y1 to another vertical welding position L1. After reaching the flat welding position P1...

AI Technical Summary

Problems solved by technology

[0003] First, the weldment needs arc preheating during continuous welding; at each arc starting point, the weldment is at normal temperature, and the arc needs to be re-used to preheat the weldment. When the weldment is preheated, the air easily invades the weld and slag inclusions occur and pores and other defects;

[0004] Second, in figure 1 The vertical climbing position at the center of the arc segment between the upward welding position Y1 and the vertical welding position L1 or L2 shown, and the vertical climbing position at the center of the arc segment between the vertical welding position P1 and the flat welding position P1 In the vicinity of the position, as the temperature of the weld rises, it is easy to appear concave or sag or even form weld bead

[0005] third, in figure 1 Near the flat welding position P1 shown, the weld seam temperature is rising continuously, the weld seam temperature is not easy to control, and the weld seam width is prone to inconsistency

[0006] Fourth, when the arc is closed and jointed at the vertical welding positions L1 and L2, the angle of the electrode changes quickly, the temperature of the weld is too concentrated, and the molten pool and the coating are prone to detachment. Over-standard defects such as point slag inclusion, line slag inclusion, air hole, needle shape, columnar shape, dense air hole, etc.

[0007] Fifth, in the above-mentioned continuous welding process, since the fusion width of continuous welding is about 1.5mm, and the reinforcement height is about 0.7-1.5mm, more electrodes are needed, so welding joints are increased, and welding appearance defects are prone to occur

[0008] Due to the above-mentioned shortcomings of the continuous welding method, the internal defects of the welded joints of the boiler body pipes are inspected by X-rays, such as welding slips, pores, slag inclusions, etc., and the pass rate of low-alloy weld joints is 50%. Carbon steel Welding joints are 25 percent, and carbon steel welding joints account for more than three quarters of the total welding joints of the boiler. Therefore, with the above-mentioned welding method, the pass rate of boiler body pipe welding is very low, resulting in waste of materials, low work efficiency, Slow welding speed and increased labor costs

Images