氮对钒微合金钢粗晶热影响区(CGHAZ)的组织和性能的影响

用热模拟方法研究了氮含量对钒微合金钢粗晶热影响区(CGHAZ)的组织和性能的影响。结果表明，氮含量为0.0031%或0.021%时，CGHAZ的韧性较差。氮含量0.0031%时CGHAZ中有少量的Ti(C,N)，晶界铁素体(GBF)较少，晶内有大量尺寸较大的侧板条铁素体(FSP)，解理裂纹沿FSP的直线扩展使其韧性较差。氮含量0.021%时在CGHAZ中生成了较为粗大的(Ti, V)(C, N)和GBF，解理裂纹沿GBF扩展使其韧性较差。氮含量为0.012%时低温韧性较好，在CGHAZ中生成了大量细小的(Ti, V)(C, N)粒子，且GBF尺寸相对较小，晶内有大量的针状铁素体(AF)。这些因素都有利于阻止裂纹扩展，使其低温韧性显著提高。

Effect of Nitrogen on Microstructure and Mechanical Properties for Simulated CGHAZ of Normalized Vanadium Micro-alloyed Steel

The effect of N-content on the microstructure and mechanical properties for the simulated coarse-grain heat-affected zone (CGHAZ) of normalized vanadium micro-alloyed steel was investigated by thermal simulation method. The results show that N-content has significant effect on the low-temperature toughness, precipitates, impact fracture morphology and the ultimate microstructure. The steel containing 0.0031% N or 0.021% N has poor CGHAZ toughness. The steel with 0.012% N has optimal CGHAZ toughness. There is slight Ti-enriched carbonitride and grain boundary ferrite in the steel of 0.0031% N, the large-sized ferrite side-plate in the major microstructure can be as the channel of crack resulting the poor CGHAZ toughness. CGHAZ of 0.021% N contains coarse (Ti, V)CN and coarse grain boundary ferrite, the crack can extend along the coarse grain boundary ferrite resulting in poor toughness. CGHAZ of 0.012% N contains thin (Ti, V)CN, the fine grain boundary ferrite and abundant acicular ferrite, which can act as an obstacle to the crack extension, resulting in preferable CGHAZ toughness.