含Ti复合第二相粒子对微合金钢焊接热影响区组织和性能的影响

来源期刊：金属学报2010年第8期

论文作者：舒玮 王学敏 李书瑞 贺信莱

文章页码：997 - 1003

关键词：含Ti第二相粒子； 焊接热影响区(WHAZ)； 晶内针状铁素体(IAF)； 相变冷却时间(t_8/5)

Key words：Ti-contianing second-phase particle； weld heat affected zone(WHAZ)； intragranular acicular ferrite(IAF)； phase change cooling time(t_8/5)

摘    要：系统分析了含Ti的复合第二相粒子对微合金钢模拟焊接热影响区(WHAZ)组织和性能的影响.研究发现,即使在较长的相变冷却时间t_8/5=120 s下(对应焊接线能量为100 kJ/cm),Ti脱氧实验钢的模拟WHAZ低温冲击韧性也明显好于Al脱氧对比钢.含Ti的第二相粒子对WHAZ性能的改善作用主要表现在以下两个方面:首先,钢中弥散分布着大量尺寸在几百纳米的含Nb的TiO_x-MnS粒子以及尺寸小于50 nm的含TiO_x的NbC粒子,这两类小尺寸的第二相粒子有效地阻碍了焊接热循环过程中原奥氏体晶粒的长大,细化了焊接热影响区的微观组织;此外,尺寸在1—3μm范围内的TiO_x-MnS型复合粒子能够有效地诱导晶内针状铁素体(IAF)在其表面形核,这些形核长大的IAF分割了原奥氏体晶粒,从而进一步细化了微观组织.在以上两种因素的共同作用下,Ti脱氧实验钢经过不同模拟焊接热循环后,组织得到明显细化,WHAZ的低温冲击韧性明显好于Al脱氧对比钢.

Abstract: The effects of Ti-containing second-phase particles on the microstructure and properties of simulated welding heat affected zone (WHAZ) in a microalloy steel have been systematically investigated.The results show that the Ti deoxidized steel has a better low temperature impact toughness of simulated WHAZ than the Al deoxidized steel even in a longer phase change cooling time (t_8/5=120 s,correspond to a welding heat input of 100 kJ/cm).The role of Ti-containing second-phase particles on improving the properties of WHAZ is mainly manifested in the following two aspects.First, there is a large number of Nb-containing TiO_x-MnS particles with the size about several hundreds nanometers and Ti oxide containing NbC particles with the size less than 50 nm dispersed in the Ti deoxidized steel,these two kinds of small second-phase particles restrain the growth of austenite grain and refine the microstructure of WHAZ.Second,TiO_x-MnS composite particles with the size between 1μm to 3μm can induce the nucleation of intragranular acicular ferrite (IAF) which could divide the prior austenite grain and refine the microstructure effectively.As a result of the above two effects,the low temperature toughness of HAZ in Ti deoxidized steel is significantly improved compared with the Al deoxidized steel.