核岛堆芯补水箱筒体堆焊层下横向裂纹产生原因分析及对策

Analysis and treatment of transverse cracks under-cladding on nuclear island core makeup tank shell

对AP1000核岛设备堆芯补水箱简体内壁不锈钢堆焊层下大量横向缺陷的产生原因进行深入分析,结果表明,由于施焊时预热温度偏低导致焊接热影响区组织淬硬程度较大及该区域扩散氢含量较高,在焊接应力的作用下从焊接热影响区的锻件母材表面或近表面的组织疏松或夹杂物等薄弱区域启裂,向简体锻件母材的厚度方向扩展形成的冷裂纹。针对裂纹产生的原因,提出了防止措施。

A detailed analysis of the reason of transverse imperfections under the deposited metal layer of stainless steel in inner shell of API000 nuclear island equipment core makeup tank was carried out.It was found that the quenching degree and the diffusion hydrogen content in HAZ(heat- affected zone) are high because of the low preheat temperature before welding,so that the crack initiation occurs from the weak zone of forging metal near HAZ or near surface with loose structure or inclusion under the welding stress,and the cracks extend to the thickness of forging metal of shell.The prevention measures were proposed based on the analysis of the reasons of crack.