焊后热处理温度对P92钢焊缝显微组织和力学性能的影响

Effect of Postweld Heat Treatment Temperature on Microstructure and Mechanical Properties of P92 Weld Metal

采用光学金相显微镜、透射电子显微镜、扫描电子显微镜和力学性能测试等方法,研究了焊后热处理温度对P92钢焊缝显微组织和力学性能的影响.结果表明:热处理前P92钢焊缝硬度高、脆性大;随着焊后热处理温度的提高,P92钢焊缝的硬度降低、缺口冲击韧性升高;采用目前的常规热处理恒温时间、焊后热处理恒温温度达到746℃后,焊缝硬度和缺口冲击韧性可以达到母材的力学性能要求;造成P92钢焊缝硬度降低、缺口冲击性能提高的原因是由于板条马氏体基体向等轴亚晶转变、M23C6及MX相的脱溶析出及M23C6的聚集球化和缓慢长大造成的.

Effect of post weld heat treatment（PWHT） temperature on microstructure and mechanical properties of P92 weld metal was studied by optical microscopy（OM）,transmission electron microscopey（TEM）,scanning electron microscopey（SEM） and mechanical property tests.Results show that the hardness of P92 weld metal is relatively high and its Charpy impact toughness is relatively low before PWHT.With the rise of PWHT temperature,the hardness reduces gradually while the impact toughness increases.The mechanical propeties of P92 weld metal are equivalent to that of the base metal when the PWHT temperature gets above 746 ℃ at a conventionally applied holding time.The hardness decreasing and toughness increasing of P92 weld metal are caused by the microstructure transformation of matrix from lath martensite to subgrain,the precipitation of phases M23C6 and MX,and the M23C6＇s congregation,spheroidization and growth.