服役劣化HP40Nb炉管模拟焊接热影响区的显微组织和拉伸性能

Microstructure and Tensile Properties of Heat Affected Zone by Simulation Welding of Service-Degraded HP40Nb Furnace Tube

通过焊接热模拟,研究了服役劣化HP40Nb制氢转化炉管热影响区的显微组织和拉伸性能。结果表明:服役劣化炉管的奥氏体晶界上存在粗大、连续的G相和富铬M_(23)C_(6)碳化物;在峰值温度(11001200℃)下热循环后,析出相仍主要为G相和M_(23)C_(6)碳化物,二者含量随峰值温度升高而减少;当峰值温度升至1250℃时,析出相主要为M_(23)C_(6)和NbC相;在较低峰值温度(9501050℃)下所得热影响区试样的抗拉强度和断后伸长率均较低;峰值温度高于1100℃时,抗拉强度和断后伸长率总体上均随温度的升高而增大,且在1150℃及以上时,抗拉强度满足未服役HP40Nb合金的强度要求,但伸长率远小于标准要求。

The microstructure and tensile properties of the heat affected zone of a service-degraded HP40Nb hydrogen production convert furnace tube were studied by the welding thermal simulation.The results show that coarse and continuous G phase and chromium-rich M_(23)C_(6) carbides existed on austenite grain boundaries in the service-degraded furnace tube.After thermal cycling at peak temperature of 1100-1200℃,the precipitates still consisted of G phase and M23 C6 carbides,and both decreased in content with increasing peak temperature.When the peak temperature was 1250℃,the precipitates were composed of M_(23)C_(6) and NbC phases.The tensile strength and elongation of the heat affected zone samples obtained at lower peak temperatures(950-1050℃)were lower.When the peak temperature was higher than 1100℃,the tensile strength and elongation increased with increasing temperature.When the peak temperature increased to 1150℃and above,the tensile strength reached the requirements of the unserviced HP40Nb alloy,while the elongation was smaller than the standard requirement.