In this study, the effects of pre-tempering on microstructure, hardness, impact toughness and fracture modes of weld metals in 2.25Cr–1Mo-0.25 V heat-resistant steel were investigated. Four weld metals with as-welded, three different post welding heat treatments were chosen as the investigated materials. Optical Microscopy (OM), Scanning Electron Microscope (SEM) were used to evaluate the microstructures of the weld metals. The mechanical properties of the weld metals were examined by hardness, and impact toughness experiments. The fracture surfaces of the weld metals were observed and analyzed by SEM. Results indicated that the impact toughness of as-welded metal is only 6 J, Post welding heat treatment (PWHT) of 705 °C + 8 h can increase the impact toughness of the weld metals to 16,18 and 119 J; 44, 80, 100, 169 and 177 J, respectively. The pre-tempering process with 650 °C with the heating rate of 55 °C/h and holding 40 h before 705 °C+8 h tempering process can increase the impact toughness to 126, 135, 136, 136, 167 J. The change of the impact toughness is directly related to the change of the microstructure. The microstructure of as-welded weld metal is mainly composed of granular bainite, which determined the lower impact toughness. The improvement of impact toughness for the weld metals after post welding heat treatment is attributed to the decomposed degree from Martensite-Austenite constituent into carbides.

在本研究中，研究了预回火对 2.25Cr-1Mo-0.25 V 耐热钢焊缝金属组织、硬度、冲击韧性和断裂模式的影响。四种焊接金属和三种不同的焊后热处理被选为研究材料。使用光学显微镜 (OM)、扫描电子显微镜 (SEM) 来评估焊缝金属的微观结构。通过硬度和冲击韧性试验来检验焊缝金属的机械性能。用扫描电镜观察和分析焊缝金属的断口。结果表明，焊后金属的冲击韧性仅为6J，705℃+8h的焊后热处理(PWHT)可使焊缝金属的冲击韧性提高到16,18和119 J；分别为 44、80、100、169 和 177 J。650℃、55℃/h升温速率、705℃+8h回火前保温40h的预回火工艺可将冲击韧性提高到126、135、136、136、167J。冲击韧性的变化与显微组织的变化直接相关。焊后焊缝金属的显微组织主要由粒状贝氏体组成，决定了较低的冲击韧性。焊后热处理后焊缝金属冲击韧性的提高归因于马氏体-奥氏体成分分解为碳化物的程度。冲击韧性的变化与显微组织的变化直接相关。焊后焊缝金属的显微组织主要由粒状贝氏体组成，决定了较低的冲击韧性。焊后热处理后焊缝金属冲击韧性的提高归因于马氏体-奥氏体成分分解为碳化物的程度。冲击韧性的变化与显微组织的变化直接相关。焊后焊缝金属的显微组织主要由粒状贝氏体组成，决定了较低的冲击韧性。焊后热处理后焊缝金属冲击韧性的提高归因于马氏体-奥氏体成分分解为碳化物的程度。