A potential connection between the residual stresses generated by a cladding operation, the thermal stresses generated during post weld heat treatment (PWHT), and the propensity for underclad cracking was investigated. As-deposited residual stresses were measured at ambient temperature, using the contour method and neutron diffraction. Measurements were performed in 20 mm thick steel substrates that were partially clad with AISI grade 309 (layer 1) and grade 308 (layer 2) stainless steels, using the submerged-arc welding process. Neutron diffraction measurements were also performed after heating the clad samples to 200 and 325  °C. The mechanical properties in each region within the steel heat affected zone (HAZ) were determined, at those same temperatures, by subjecting coupons to simulated cladding thermal cycles and then to tension tests. Substantial tensile residual stresses in the HAZ were measured after cladding. These persisted during subsequent heating to 325  °C: a temperature that is approximately at the mid-point of the heating ramp in a typical PWHT cycle. The tensile results, however, indicated that each microstructural zone within the HAZ is likely to retain sufficient ductility to prevent fracture, and that underclad cracking is unlikely to occur during the early stages of the PWHT ramp.

研究了包层操作产生的残余应力、焊后热处理 (PWHT) 期间产生的热应力和包层下裂纹倾向之间的潜在联系。沉积态残余应力在环境温度下使用等高线法和中子衍射进行测量。 使用埋弧焊工艺在 20毫米厚的钢基材上进行测量，这些钢基材部分包覆有 AISI 309 级（第 1 层）和 308 级（第 2 层）不锈钢。在将包层样品加热到 200 和 325 之后，还进行了中子衍射测量  ℃。钢热影响区 (HAZ) 内每个区域的机械性能是在相同温度下通过对试样进行模拟包层热循环然后进行拉伸试验来确定的。熔覆后测量了热影响区中的大量拉伸残余应力。这些在随后加热到 325   °C期间持续存在：该温度大约在典型 PWHT 循环中加热斜坡的中点。然而，拉伸结果表明，HAZ 内的每个显微结构区域都可能保留足够的延展性以防止断裂，并且在 PWHT 坡道的早期阶段不太可能发生包层下裂纹。