焊后热处理时间对SA-508Gr.3Cl.2钢焊缝力学性能影响的研究

Study on Influence of PWHT Holding Time on SA-508Gr.3Cl.2 Weld Mechanical Properties

在三代非能动压水堆核电设备上,大量地使用到了SA-508Gr.3Cl.2钢,该材料具有较高的强度和低温冲击韧性。由于核电部件材料厚度大,SA-508Gr.3Cl.2钢焊接完成后需要进行较长时间的热处理,以消除残余应力。针对SA-508Gr.3Cl.2焊缝,选取了国内外不同牌号的四种埋弧焊焊丝焊剂进行焊接试验,并分别进行了不同焊后热处理保温时间下的焊缝金属拉伸和冲击试验。通过对试验结果的分析表明:焊后热处理后,SA-508 Gr.3Cl.2钢焊缝拉伸性能有较大程度的降低,随着焊后热处理时间的增长,焊缝强度降低的趋势逐渐减缓;焊后热处理对SA-508Gr.3Cl.2钢焊缝冲击性能影响无明显规律;随着焊后热处理时间的延长,焊缝基体组织未发生显著变化,晶间析出物有所增加并长大。焊缝的性能,特别是其低温冲击性能,更大程度取决于焊接参数,尤其是焊接热输入量。为获取理想的焊缝力学性能,需采用合适的焊接参数,控制热输入量。

SA-508 Gr.3 Cl.2 with high strength and low-temperature impact toughness is widely used in Generation-III passive PWR components. As nuclear power components are often with great thickness, long-time PWHT is often needed to reduce residual stress. The tensile strength and impact toughness tests of the weld welded with four kinds of SAW wires and fluxes for SA-508Gr.3Cl.2 under different PWHT holding time were carried out. The test results show that after PWHT, the tensile strength of the weld metal decreases considerably. As the PWHT holding time extends, the strength decreasing rate slows down. There is no clear regularity for the influence of PWHT on impact properties of SA-508 Gr.3 Cl.2 weld metal. As the PWHT holding time extends, the base structure of the weld metal does not change a lot, except that more intergranular precipitation appeares and grows. The weld metal properties, the low-temperature impact properties in particular, are more affected by welding parameters, especially the heat input. In order to obtain ideal weld mechanical properties, proper welding parameters should be used, and heat input should be controlled.