某200 MW机组高压主蒸汽门阀体内壁裂纹的补焊修复技术

Repairing Welding Repair Technology of Inner Wall Crack of High-pressure Main Steam Valve in a 200 MW Unit

通过分析某200 MW机组ZG15Cr1Mo1V钢高压主汽阀裂纹产生的原因及其焊接性,研究不同焊材冷态手工电弧焊修复工艺特点.基于镍基焊条熔敷金属及耐热钢焊条熔敷金属性能特点,通过优化,最终确定裂纹挖补修复焊接方案:采用ENI6182镍铬铁类的ENiCrFe-3焊条焊接打底过渡层;选用E5515-B2-V(R317L)焊条焊接中间填充层;采取焊后锤击消除焊接应力、焊后消氢处理等工艺措施,改善焊缝组织状态和减小焊接残余应力;最后再用ENiCrFe-3镍基焊条焊接表面层.通过以上工艺,焊缝中镍基组织既可以抑制母材中的碳扩散问题,减轻因碳扩散而带来的不良后果,又可以避免因热膨胀系数与母材不一致而带来新的裂纹,进而解决大厚件铸造阀体缺陷修复焊接质量问题.研究成果具有较高的工程应用价值.

Through analyzing the crack cause of the high-pressure main steam valve of the ZG15Cr1Mo1V steel for a 200 MW unit and its weld ability,the characteristics of the cold-state shielded metal arc welding of different welding materials were studied.Based on the characteristics of the respective properties of the deposited metal of the nickel-based electrode and the deposited metal of the heat-resistant steel,the welding scheme for repairing the crack was finally determined by means of process optimization.The final determination of the repair and welding of the crack were as follow:using the ENI6182 nickel-chromium-iron-type ENiCrFe-3 welding rod as the base transition layer and using the E5515-B2-V(R317L)welding rod to weld the intermediate filling layer;adopting some measures such as the post-weld hammering for welding stress relief,and hydrogen removal after welding to improve the microstructure of the weld and reduce the welding residual stress;finally,the surface layer was welded with ENiCrFe-3 nickel base electrode.Through the above process,the nickel base structure in the weld can not only inhibit the carbon diffusion in the base metal,reduce the adverse consequences because of the carbon diffusion,but also avoid the new cracks caused by the inconsistency between the thermal expansion coefficient and the base metal,and solve the welding quality problem of defect repair for large thickness casting valve body.The research job exhibits the good engineering application value.