基于SYSWELD的核电隔板焊接热力耦合分析

某核电直焊式隔板在装焊后,渗透检查发现叶片背弧进汽侧和出汽侧位置的热影响区出现大量裂纹。采用SYSWELD对该结构进行热力耦合计算,分析裂纹的萌生机理,阐明结构应力、相变应力和淬硬组织是造成叶片热影响区延迟裂纹的根本原因,并明确了手工修磨坡口过量易造成叶片厚度方向出现贯穿式裂纹。对多种焊接工艺优化方案进行模拟分析,结果表明,结构应力、相变应力和淬硬组织的状态均在一定程度上有所改善,提出采用中间热处理+预热及后热+四段交叉焊接顺序的焊接工艺,叶片热影响区表面应力可减少约260 MPa,极大地降低了后续隔板延迟裂纹倾向。

Thermal-mechanical coupling analysis of the nuclear power diaphragm welding based on SYSWELD

After assembling and welding of a nuclear power directly-welded diaphragm,a large number of cracks were found in the heat-affected zone (HAZ) at the steam inlet and exit sides of the blade convexity by penetration inspection. In this paper,the thermal-mechanical coupling calculation of this structure is carried out by SYSWELD,the crack initiation mechanism was analyzed,structural stress,transformation stress and hardened structure are the fundamental causes of delayed crack in the HAZ of the blade. It is clear that the excessive manual grinding of groove is likely to cause the penetrating crack along the thickness direction of the blade;vicarious optimized welding procedures are simulated,the results show that the structural stress,transformation stress and hardened structure are all improved to some extent,a special welding procedure adapting intermediate heat treatment,preheating,post-heating and four-stage cross welding sequence is proposed,the surface stress in the HAZ of the blade will be reduced by about 260 MPa,which will greatly lower the delayed crack tendency of the subsequent diaphragms.