研究了焊接热模拟工艺参数中，冷却时间t8/5对Ti-N和Ti-Nb-N两种成分系列钢热影响区（HAZ）显微组织和冲击韧性的影响。用光学显微镜和电子显微镜（SEM，TEM）观察了不同试样的HAZ中，铁素体（F）和粒贝组织的特征，特别是M－A组元的形态、数量和分布，分析了不同冷却速度产生的显微组织与冲击韧度的关系，探讨了微量合金元素Ti、Nb、N的添加对焊后试样HAZ组织和韧性所起的作用。结果表明，随t8/5趋缓，Ti-N系列钢中F数量增加，粒贝数量减少，M－A组元由长条状变为方块状，韧性相应大幅提高。而Nb的添加抑制了F的生成，有利于产生侧板条状粒贝，对韧性的改善不利。%Effects of cooling rate (t8/5) during simulated welding thermal cycle on the microstructures and toughness of HAZ in two series Ti—Nb steels were studied.The morphology,numbers and distribution of ferrite and granular bainite,especially M-A constituent in HAZ at different cooling rate (t8/5) were observed by optical and electron micro-scopes.The relation between microstructures and impact toughness in different cooling rates was analysised.The actions of added microalloying elements Ti,Nb and N on improving microstructures and toughness of HAZ in specimens was discussed.
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