Field welding repair method especially for larger and penetrating defects in steel casting with heavy wall thickness

A technology of on-site welding and repairing methods, applied in welding equipment, arc welding equipment, manufacturing tools, etc., can solve problems such as difficult completion, achieve good quality, eliminate welding residual stress, and prevent cracks from recurring

Inactive Publication Date: 2012-10-31
SUZHOU NUCLEAR POWER RES INST +4
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  • Abstract
  • Description
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Problems solved by technology

However, for larger (up to half of the wall thickness) and through-type defects, it is difficult to complete the heterogeneous cold welding process

Method used

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  • Field welding repair method especially for larger and penetrating defects in steel casting with heavy wall thickness
  • Field welding repair method especially for larger and penetrating defects in steel casting with heavy wall thickness
  • Field welding repair method especially for larger and penetrating defects in steel casting with heavy wall thickness

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Embodiment Construction

[0029] It is known that the main steam valve is the main thermal equipment of the thermal power plant. It not only bears the high temperature and high pressure load for a long time under the stable operation condition, but also is subjected to the alternating stress when it starts, stops and changes in compliance. Therefore, in the main Weak parts of steam valves or areas with internal manufacturing defects are prone to cracks and failure.

[0030] In April 2011, the No. 2 steam valve body of a Russian supercritical 500MW coal-fired unit of a power generation company (the material is ZG15Cr1Mo1V low-alloy heat-resistant steel) had penetrating cracks, causing steam leakage, and then the No. 1 main steam valve valve It is also found that there are multiple cracks and other defects in the body. Below is a crack with a length of about 100mm on the outer surface of No. 2 valve (see figure 1 , the crack opening width is 2-3 mm, corresponding to one inner wall crack, and the leakage...

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Abstract

The invention relates to a field welding repair method especially for larger and penetrating defects in a steel casting with heavy wall thickness. The method comprises a pre-welding preparation process, a welding repair process and a post-welding quality inspection process, wherein the welding repair process comprises the steps of (1) preheating; (2) carrying out 1 to 2 layers of backing weld for all positions of a groove by adopting TIG weld, and filling the whole bottom of the groove with solid wire materials; (3) warming up to 220 to 330 DEG C, carrying out constant thermal insulation for 3 to 8 hours, adopting manual arc welding to implement the filler welding for the groove, hammering the welded bead immediately with an air hammer, and ensuring the dense and uniform traces of the hammer; (4) carrying out dehydrogenation heat treatment; (5) carrying out post-welding treatment: carrying out stress annealing at the temperature of 500 to 550 DEG C, then carrying out high tempering at the temperature of 700 to 750 DEG C, and finally, cooling at the speed of 65 to 150 DEG C / h to the room temperature. After welding repair, a welding seam is tested to be good in quality, and have low possibility of cracking again.

Description

technical field [0001] The invention belongs to the technical field of casting welding repair, and in particular relates to a field welding repair method for thick-walled steel castings. Background technique [0002] There are many large-scale steel castings used in important components such as boilers, four major pipelines, and steam turbines in thermal power plants, and most of them are used in high-temperature and high-pressure working conditions. The harsh working conditions put forward very high requirements for their safety. Main steam valve, regulating valve, blocking valve and casting tee on the boiler header are often inhomogeneous in structure due to different cooling rates during the manufacturing process due to factors such as large volume and large changes in wall thickness at different parts. Often accompanied by casting defects, resulting in cracking failures that are prone to occur under operating conditions. [0003] In the prior art, since it is difficult ...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): B23P6/00B23K9/00
Inventor 王淦刚于程炜鲁立王宝臣赵建仓贺桂林成鹏梁军
Owner SUZHOU NUCLEAR POWER RES INST
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