Valve crack cold welding process

Abstract

The invention discloses a valve crack cold welding process which comprises the following steps that before preheating before welding, the periphery of a groove is covered with a thermal insulation material for thermal insulation, and base metal of a to-be-welded part is uniformly heated; the preheating temperature is kept, a plurality of weld bead layers are continuously welded, a heat insulation material is immediately used for covering for heat insulation after all the weld bead layers are welded, and slow cooling is carried out to decrease the temperature of the welded part to the room temperature; and cold welding of a filling layer and a cover surface layer is conducted on the groove, the temperature of surrounding matrix metal in the whole cold welding process is not higher than 70 DEG C, and after cold welding is finished, an angle grinder is used for grinding, so that the periphery of a repair welding area is flush with the surface of the base metal. According to the valve crack cold welding process, on the premise of ensuring the strength and toughness of the repair welding area, a post-weld heat treatment process is omitted, and the problems that the strength and toughness of the repair welding part cannot meet the requirements and the welding residual stress is large due to the fact that post-weld heat treatment cannot be carried out or the heat treatment uniform temperature range is insufficient are solved.

Description

technical field [0001] The invention relates to welding technology, in particular to a valve crack cold welding process. Background technique [0002] There are many large high-pressure valves installed in thermal power plants. The valve structure is complex, the wall thickness is uneven, and the material is mostly low-medium alloy steel, such as main valve, regulating valve, plug valve, etc. During the long-term operation of these valves, due to manufacturing defects, stress, structure and other reasons, it is easy to cause cracks in the shoulder of the shell, the joint between the valve seat and the shell. [0003] Conventional crack repair welding requires post-weld heat treatment. Due to the complex shape and structure of large valves and uneven wall thickness, some parts cannot be subjected to post-weld heat treatment or the uniform temperature range of heat treatment is insufficient, resulting in the strength and toughness of the weld repaired parts not meeting the req...

AI Technical Summary

Problems solved by technology

[0004] The present invention overcomes the deficiencies of the prior art, and provides a valve crack cold welding process. On the premise of ensuring the strength and toughness of the welding repair area, the post-weld heat treatment process is omitted, and the post-weld heat treatment cannot be performed or the heat treatment is uneven. Insufficient temperature range, resulting in problems such as the strength and toughness of the welded parts cannot meet the requirements, and the welding residual stress is large