Metal pipe welding method and metal pipe welding assembly

Abstract

The invention discloses a metal pipe welding method and a metal pipe welding assembly. The method comprises the steps of: (1) inserting one end of a liner tube into the pipe cavity at the welded end of a pipe to be welded in such a manner that the other end of the liner tube protrudes out of the welded end of the pipe to be welded; (2) inserting the portion of the liner tube protruding out of the welded end of the pipe to be welded into the pipe cavity of the welded end of another pipe to be welded, and butt-connecting the welded ends of the two pipes to be welded to form a seam to be welded; and (3) welding the pipes at the seam to be welded to form a fusion region so as to connect the welded ends of the two pipes to be welded. The metal pipe welding assembly comprises two pipes to be welded and a liner tube, wherein both ends of the liner tube are respectively inserted in the pipe cavity of one pipe to be welded; and a fusion region is formed by welding at the joint of the welded ends of the two pipes to be welded. During conducting gas shielded welding, the metal pipe welding method can ensure the final welding seam strength equal to the strength of the two pipes at both ends without filling the inner side of the welding seam with a protective gas, and can effectively prevent occurrence of hanging accretions.

Description

technical field [0001] The invention belongs to the technical field of metal pipe welding connection, and in particular relates to a metal pipe welding method and a metal pipe welding assembly made by the method. Background technique [0002] The safest and most reliable connection method among metal pipe connection methods is undoubtedly the welding connection. However, several existing connection methods such as socket welding connection or butt welding connection have certain defects, especially for the welding of thin-walled stainless steel pipes. [0003] The socket welding connection method is to insert the welding end of a pipe fitting to be welded into the lumen of the welding end of another pipe fitting to be welded and then weld it. See figure 1 As shown, it has the following disadvantages: (1) The connection strength is low; the socket welding connection is a lap connection, and its weld seam is a fillet weld seam, and the working stress is shear stress. Accordin...

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Problems solved by technology

[0003] The socket welding connection method is to insert the welding end of a pipe fitting to be welded into the lumen of the welding end of another pipe fitting to be welded and then weld it. See figure 1 As shown, it has the following disadvantages: (1) The connection strength is low; the socket welding connection is a lap connection, and its weld seam is a fillet weld seam, and the working stress is shear stress. According to the allowable strength The calculation method, and the effective load-bearing area of ​​the fillet weld is 0.707 times the effective area of ​​the fillet weld. Therefore, when designing the lap weld, double-sided welding is required to make the weld strength and the component (generally pipe A and joint fitting B) equal intensity

For the socket connection between pipes and pipe fittings, in actual construction, only one side welding can be carried out on one side of the pipe fittings, and the end of the pipe inserted into the pipe fittings cannot be welded, so the weld strength of the socket connection joint can only reach the strength of the pipe 50% of

(2) Welding is difficult, and it is easy to weld through the pipe wall. The pipe must be inflated for protection and socket welding. Because the pipe inserted into the pipe fitting has a thin wall, when welding, the pipe fitting port must be melted to form an effective joint. Fillet welds, and the pipe fitting end is affected by the heat dissipation of the inserted pipe, so a large heat input is required to form a molten pool. The pipe wall is thin, and it is easy to overheat and burn through. If the heat input is small, the pipe fitting end will fuse Bad, so the operation is more difficult

If air-filled protection is applied to each welding joint, the construction site conditions are limited, it is very difficult, the work intensity is high, and the work efficiency is very low

[0004] The butt welding connection method directly welds two pipe fittings to be welded, see figure 2 As shown, it has the following disadvantages: the outer diameter of the butt welded pipe A port is the same as that of the pipe fitting B, and the welding is additionally welded with filler material. The temperature is overheated and the "hanging tumor" (melting tumor) appears at the weld seam in the pipe, which affects the service life

If the temperature is too low and there is no penetration, the pipe walls on both sides of the weld joint will not be completely connected, which will affect the quality of use

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