采用统计设计的一系列钒和铌微合金化C-Mn高强度低合金钢，对焊后热处理（PWHT）多道焊的热影响区（HAZ）韧性进行了研究。钒添加量在0.005至0.097 Wt.%范围内，铌添加量在0.004至0.06 Wt.%范围内。采用焊接热输入为3kJ/mm和5kJ/mm的GMAW工艺，并在620°C下进行2小时和10小时的焊后热处理。在焊态和焊后热处理条件下，添加微合金元素V和Cb后，HAZ韧性降低。在所有焊接条件下，HAZ的50焦耳（37英尺-磅）转变温度（TT50J）与最大HAZ硬度相关。 观察到焊后热处理导致热影响区硬度和TT50J增加。因此，在某些情况下，PWHT可能对V/Cb微合金化HLSA钢不利。V和Cb碳化物（V，Cb）C的随机分布沉淀，包括位错沉淀和基体沉淀，粒度为5-15nm，是这些钢中主要的合金碳化物沉淀形态。在热影响区中很少观察到（V，Cb）C沉淀的带状形态。（V，Cb）C沉淀的体积分数随着实验加热中V和/或Cb含量的增加而增加。随着焊后热处理时间的增加，析出物的体积分数也增加。

A statistically designed series of vanadium and columbium microalloyed C-Mn HSLA steels was used for an investigation of heat-affected zone (HAZ) toughness in post weld heat treated (PWHT) multi-pass welds. The vanadium additions were in the range 0.005 to 0.097 Wt.% and the columbium additions were in the range 0.004 to 0.06 Wt.%. GMAW processes with welding heat inputs of 3kJ/mm and 5kJ/mm and post-weld heat treatments at 620°C for 2 and 10 hours were employed. A degradation of the HAZ toughness with additions of microalloy elements V and Cb in the as-welded and PWHT conditions was revealed. The 50 Joule (37 ft-lb) transition temperature (TT50J) for HAZs in all weld conditions correlated with maximum HAZ hardness. Increases in HAZ hardness and TT50J caused by PWHT were observed. Hence PWHT in some situations may not be beneficial for V/Cb microalloyed HLSA steels.The randomly distributed precipitation of V and Cb carbides (V, Cb)C, including dislocation precipitation and matrix precipitation with particle sizes of 5-15 nm, is the predominant alloy carbide precipitate morphology in these steels. Banded morphology of (V, Cb)C precipitation is rarely observed in the HAZ. The volume fraction of (V, Cb)C precipitates increases as increasing V and/or Cb contents in the experimental heats. The volume fraction of precipitates also increases with increasing the PWHT time.