焊接热输入对Nb-Ti钢CGHAZ组织韧性影响  

Effect of welding heat input on CGHAZ microstructures and toughness of Nb-Ti steel

作　　者：刘健 侯振伟 师仲然 LIU Jian;HOU Zhen-wei;SHI Zhong-ran(Synthesis Department, Suqian Jinxin Steel Rolling Co. , Ltd. of Nisco, Suqian 223800, Jiangsu, China;Department of Structural Steels, Central Iron and Steel Research Institute, Beijing 100081, China)

机构地区：[1]宿迁南钢金鑫轧钢有限公司综合部,江苏宿迁223800 [2]钢铁研究总院工程用钢研究所,北京100081

出　　处：《中国冶金》2019年第7期32-38,共7页China Metallurgy

摘　　要：为了探究Nb-Ti钢合适的焊接热输入范围并指导实际焊接工艺过程,利用Formastor-FⅡ型自动相变测量仪和Gleeble-3800热模拟试验机研究了焊接热输入对Nb-Ti钢相变温度、组织和韧性的影响规律。结果发现,当冷却速度大于6℃/s时,Nb-Ti钢模拟CGHAZ的组织为粒状贝氏体和板条贝氏体,且随着冷却速度降低,板条贝氏体含量下降,粒状贝氏体含量增加;当冷却速度为6℃/s时,出现晶界铁素体组织,且随着冷却速度继续下降,晶界铁素体含量增加;当冷却速度不大于0.6℃/s时,组织为完全的铁素体和珠光体。随t8/5时间的增加,M-A含量先增加后减少,在t8/5为178s时,M-A面积百分数达到最大值,为5.1%。当t8/5时间为144~178s时,M-A组元的含量是控制Nb-Ti钢模拟CGHAZ区韧性的主要因素;当t8/5为256s时,M-A组元含量下降,粗大的晶界铁素体是控制Nb-Ti钢模拟CGHAZ韧性的因素。For the purpose of exploring the welding suitable heat input and formulating the actual welding procedures,the effect of welding heat input on the phase transformation,microstructure and toughness of coarse heat affected zone(CGHAZ)of Nb-Ti micro-alloyed steel had been studied by using Formastor-F Ⅱfull automatic transformation measuring apparatus and Gleeble-3800 thermal simulator.The results showed that the microstructure of CGHAZ was granular bainite and lath bainite,when the cooling rate was larger than 6 ℃/s.With the decrease of cooling rate,the proportion of lath bainite decreased and the proportion of granular bainite increased.At the cooling rate of 6 ℃/s,the grain boundary ferrite formed and the proportion increased as the cooling rate furtherly decreased.When the cooling rate was no more than 0.6 ℃/s,the microstructure was composed by ferrite and pearlite.With the increase of t8/5,the M-A constitution increased firstly and then decreased.At the t8/5 of 178 s,the content of M-A reached a maximum of 5.1%.When the welding heat input range was 144-178 s,the content of M-A component was the main factor controlling the toughness of Nb-Ti steel in simulating CGHAZ zone.As the t8/5 was equal to 256 s,the content of M-A decreased,and the coarsening grain boundary ferrite was the main factor influencing the CGHAZ toughness.

关 键 词：NB-TI微合金钢 焊接热输入 低温韧性 晶界铁素体 M-A组元 

分 类 号：TG457.11[金属学及工艺—焊接]