A large-gap multi-layer step-by-step argon arc welding bottom sealing repair method for carbon steel pipes and containers

Abstract

The invention discloses a large-gap multi-layer step-by-step argon arc welding backsealing repair method for carbon steel pipes and containers, which comprises the following steps: welding defect positioning, defect excavation and repair, groove grinding, groove penetration flaw detection, weld seam fixing, Pre-weld preheating, argon arc welding bottom sealing, electrode arc welding filling, covering, post-weld heat treatment, non-destructive testing. The welding process of the present invention combines two different welding methods of argon arc welding and manual arc welding, and uses a special welding back sealing method. Even in the face of large gap welds at the root of pipes and containers due to assembly errors and weld repairs, through A reasonable welding process can also obtain high-quality welds. Due to the fine metallographic structure, the impact toughness of welds, fusion zones, and heat-affected zones is high, and the crack tendency is small, which improves the service life of welded joints.

Description

technical field [0001] The invention relates to the technical field of pipe container welding, in particular to a large-gap multi-layer step-by-step argon arc welding bottom sealing repair method for carbon steel pipes and containers. Background technique [0002] During the construction and installation of carbon steel pipes and containers, in order to ensure that the plate is welded through the thickness direction, it is often designed with grooves at different angles, and a gap of 2 to 5 mm is reserved, so that the arc can penetrate deep into the root of the weld to ensure Complete fusion of the weld section. Due to assembly errors, the phenomenon of super-wide gaps sometimes occurs, resulting in increased root gaps; carbon steel pipes and container welds are detected to have excessive defects in the roots after welding. The final groove is often wider, and sometimes the root gap of the groove in which the above-mentioned abnormal conditions occur reaches 10-20mm, or eve...

AI Technical Summary

Problems solved by technology

Due to assembly errors, the phenomenon of super-wide gaps sometimes occurs, resulting in increased root gaps; carbon steel pipes and container welds are detected to have excessive defects in the roots after welding. The final groove is often wider, and sometimes the groove root gap in the above-mentioned abnormal situation can reach 10-20mm, or even larger, which is very different from the design value.

[0003] For carbon steel and large-gap argon-arc welding bottom-sealing welding with penetrating defects in container pipes, the two sides of the root of the groove are generally used as the base point to perform zigzag or crescent-shaped swing welding. Larger, wide and thick molten pool, large volume, long time at high temperature, which is very unfavorable to the use of welded joints: (1). The mechanical properties of the weld metal are closely related to its microstructure. The grains in the affected area are coarse, and the plasticity and toughness are poor; (2). During welding, the weld seam is heated and expanded locally, and is restrained by the part far from the weld seam and cannot be freely elongated, so that the weld zone is compressed and produces plastic deformation; During the cooling process, the welding area shrinks shorter than other parts, and it cannot be freely shortened by the constraints of the part far from the welding area, so the residual tensile stress is generated by tension; (3). It is easy to form concave, and the sharp change of geometric shape increases the local stress, forms stress concentration, and easily produces fatigue cracks; (4). The flow of the internal medium causes resistance

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