Analysis of Defects and Welding Repair Technology for High-Pressure Main Steam Valves in Nuclear Power Plant Turbines

XU Baoping; ZHANG Hanzhong; KONG Xian; ZHANG Xiaodong; WANG Dengxing

doi:10.7512/j.issn.1001-2303.2025.11.15

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Analysis of Defects and Welding Repair Technology for High-Pressure Main Steam Valves in Nuclear Power Plant Turbines
Vol. 55, Issue 11, Pages: 113-119(2025)
Received：22 November 2024，

Revised：2025-01-13，

Published：20 November 2025
DOI： 10.7512/j.issn.1001-2303.2025.11.15
稿件说明：

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徐宝坪，张瀚中，孔铣，等.核电厂汽轮机高压主汽阀缺陷分析与焊接修复技术［J］.电焊机，2025，55（11）：113-119. DOI： 10.7512/j.issn.1001-2303.2025.11.15.

XU Baoping, ZHANG Hanzhong, KONG Xian, et al.Analysis of Defects and Welding Repair Technology for High-Pressure Main Steam Valves in Nuclear Power Plant Turbines[J].Electric Welding Machine, 2025, 55(11): 113-119. DOI： 10.7512/j.issn.1001-2303.2025.11.15.

摘要

核电厂汽轮机高压主汽阀（铸钢）因结构形式复杂、刚性拘束度大和铸造材质等多方面因素的影响，导致焊接难度特别是现场焊接修复难度大。某核电厂5号机组大修期间，高压主汽阀阀座内表面及密封面因人为操作失误造成损伤，直接威胁主汽阀安全可靠运行。为彻底消除主汽阀阀座缺陷并恢复部件服役性能，结合国内外铸钢部件修复经验，针对主汽阀G20Mo5铸钢母材的焊接性特点，提出基于钨极氩弧焊的异质镍基焊材修复方案。通过专项焊接试验系统优化工艺参数，选用ERNiCr-3镍基焊丝，重点研究焊接接头的微观组织演化与力学性能。在不进行焊后热处理的情况下，通过控制预热温度、层间温度及焊接线能量，避免热影响区硬化与裂纹萌生。采用无损检测（液体渗透、射线检测）、金相分析及力学性能测试（拉伸、弯曲、冲击）对修复接头进行全面评估，验证工艺可行性后，成功完成主汽阀损伤区域的现场焊接修复。结果表明，修复后的焊接接头焊缝区以奥氏体组织为主，无裂纹、未熔合等缺陷，接头硬度分布均匀（无明显硬化/软化区），抗拉强度、弯曲性能及低温冲击韧性均满足相关标准要求。该修复技术有效解决了G20Mo5铸钢高压主汽阀现场修复的技术瓶颈，为核电厂同类关键部件的应急修复提供了可靠的工艺参考，对保障机组大修工期与长期安全运行具有重要工程价值。

Abstract

The high pressure main steam valve (cast steel) of the steam turbine of a nuclear power plant is difficult to be welded

especially on-site welded and repaired

due to the influence of various factors such as complex structural type

rigidity constraints and casting materials. During the overhaul of a power plant

the high-pressure main steam valve of the No. 5 unit turbine was completely disassembled and overhauled

and the inner surface and sealing surface of the main steam valve seat were damaged due to the human factor when the spool of the high-pressure main steam valve was being reassembled

which had a serious impact on the safe and reliable operation of the main steam valve. In order to completely eliminate the main steam valve seat defects and restore its original appearance

combined with domestic and foreign experience in repairing cast steel parts

using tungsten argon arc welding method

the choice of heterogeneous nickel-based welding consumables

targeted to carry out a special welding test

and a systematic study on the organization and performance of welded joints. On the basis of the experimental research

combined with the structure

material

damage characteristics and on-site welding conditions of the high-pressure main steam valve

the on-site welding repair of the damaged area of the steam turbine's high-pressure main steam valve made of G20Mo5 cast steel was successfully realized without post-welding heat treatment

which in turn ensured the reliability of the unit's key equipment operation.

关键词

Keywords

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