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M₂₃C₆碳化物；在峰值温度（1 100~1 200℃）下热循环后，析出相仍主要为G相和M₂₃C₆碳化物，二者含量随峰值温度升高而减少；当峰值温度升至1 250℃时，析出相主要为M₂₃C₆和NbC相；在较低峰值温度（950~1 050℃）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1 100℃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1 150℃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 M₂₃C₆ carbides existed on austenite grain boundaries in the service-degraded furnace tube. After thermal cycling at peak temperature of 1 100-1 200 ℃, the precipitates still consisted of G phase and M₂₃C₆ carbides, and both decreased in content with increasing peak temperature. When the peak temperature was 1 250 ℃, the precipitates were composed of M₂₃C₆ and NbC phases. The tensile strength and elongation of the heat affected zone samples obtained at lower peak temperatures (950-1 050 ℃) were lower. When the peak temperature was higher than 1 100 ℃, the tensile strength and elongation increased with increasing temperature. When the peak temperature increased to 1 150 ℃ and above, the tensile strength reached the requirements of the unserviced HP40Nb alloy, while the elongation was smaller than the standard requirement.