t_(8/5)对含Zr钢热模拟焊接热影响区组织与性能的影响

Effects of t_(8/5) on microstructure and properties of thermal simulated heat affected zone of Zr-bearing steel

采用Gleeble热模拟方法研究了在峰值温度1400℃保温3 s条件下,不同t8/5时间对一种Zr处理钢热模拟粗晶区的组织与力学性能的影响。结果表明,t8/5时间为13-700 s时,试验钢热模拟粗晶区随t8/5的延长,奥氏体晶粒尺寸由50μm增加到接近520μm,相转变组织由贝氏体逐渐转变为晶界铁素体＋晶内针状铁素体＋晶内多边形铁素体,硬度值由220 HV0.5降低到145 HV0.5,热模拟粗晶区的-20℃冲击吸收能量≥200 J。经扫描电镜分析,晶内铁素体的形核得益于试验钢中大量弥散分布的0.5-2μm的Zr-Ti-O复合夹杂物;断口分析结果表明t8/5时间为80 s和〉300 s时,热模拟粗晶区冲击性能降低,与组织中的上贝氏体和粗大的晶界铁素体有关。

Effects of t8 /5on microstructure and mechanical properties of coarsen grain heat affected zones（ CGHAZ） of a Zr-bearing steel were analyzed by Gleeble simulation experiments under a peak temperature of 1400 ℃ for 3 s. The results show that when the t8 /5is within13-700 s,the grain size of austenite in CGHAZ increase from 50 μm to nearly 520 μm with the increasing of t8 /5,and results in microstructure change from bainite to grain boundary ferrite ＋ intragranular acicular ferrite ＋ intra granular polygonal ferrite,and thus leads to hardness decreases from 220 HV0. 5 to 145 HV0. 5,and CGHAZ with impact absorbed energy ≥200 J at- 20 ℃. Scanning electron microscope（ SEM） analysis result shows that the nucleation of intragranular ferrite originates from those dispersed Zr-Ti-O composite inclusions with a size range of 0. 5-2 μm. The fracture and microstructure analysis indicate that the decreasing of impact toughness of samples for which the t8 /5is 80 s or 300 s is related to the upper bainite and coarse grain boundary ferrite.