热输入对Q500qE钢模拟CGHAZ微观组织和冲击韧性的影响  

Effect of Welding Heat Input on Microstructure and Impact Toughness of the Simulated CGHAZ in Q500qE Steel

作　　者：朱东明 何江里 史根豪 王青峰[2,3] ZHU Dongming;HE Jiangli;SHI Genhao;WANG Qingfeng(China Railway Jiujiang Bridge Engineering Co.,Ltd.,Jiujiang 332004,China;College of Materials Science and Engineering,Yanshan University,Qinhuangdao 066004,China;StateKey Laboratory of Metastable Materials Science and Technology,Yanshan University,Qinhuangdao 066004,China)

机构地区：[1]中铁九桥工程有限公司,九江332004 [2]燕山大学材料科学与工程学院,秦皇岛066004 [3]燕山大学亚稳材料制备技术与科学国家重点实验室,秦皇岛066004

出　　处：《金属学报》2022年第12期1581-1588,共8页Acta Metallurgica Sinica

基　　金：国家自然科学基金项目No.51671165。

摘　　要：采用Gleeble-3500热模拟试验机模拟了Q500qE钢在不同热输入(E_(j)=15~30 kJ/cm)下的焊接热循环过程,结合OM、SEM以及EBSD等手段探讨了热输入对粗晶热影响区(CGHAZ)微观组织和冲击韧性的影响规律及其作用机理。结果表明,随着焊接热输入的降低,板条贝氏体(LB)增多,粒状贝氏体(GB)减少,相变温度A_(r3)降低,贝氏体块(packet)和贝氏体束(block)明显细化;CGHAZ的冲击功KV_(2)(-40℃)随着热输入的降低而提高,冲击断口均表现出明显的解理断裂特征,其解理面尺寸D_(f)随着热输入的降低而减小;贝氏体packet是Q500qE钢中控制CGHAZ冲击韧性最有效的结构单元。As China’s economy enters a stage of high-quality development, it is important to study high-performance bridge steels with high strength, high toughness, high efficiency, and easy welding.Presently, coarse-grained heat-affected zones(CGHAZs) of high-performance bridge steels are prone to coarse-grain embrittlement, which reduces its impact toughness. To improve their low-temperature toughness, the relationship between their microstructure and impact toughness has been extensively researched and discussed. However, the control connection and internal mechanism between the bainite microstructure and impact toughness have not been clarified. In this study, the simulated samples of CGHAZs in Q500qE steel with varying heat inputs, from 15 to 30 kJ/cm, were reproduced in Gleeble3500 thermal simulation-testing machine. The effect of different heat inputs on the microstructure, impact toughness of CGHAZs, and their inherent mechanism was discussed and analyzed in-depth using OM,SEM, and EBSD. The results indicate that the microstructure of each simulated sample of CGHAZs in Q500qE steel was composed of lath-like bainite(LB) and granular-like bainite(GB). The LB increased,the GB reduced, phase-transition temperature(A_(r3)) declined, and the bainitic packet/block substructure refined as the welding heat input decreased. In addition, with the decreased heat inputs, the Charpy impact energy(KV_(2)) at-40oC of CGHAZs is enhanced because of the refined microstructure. The impact fracture of all samples showed cleavage fracture characteristics, and the cleavage face size of the simulated samples of CGHAZs decreased due to the reduced heat inputs. Compared with prior austenite grain boundary and bainite block, the bainite packet is the most effective microstructural unit for controlling the impact toughness of CGHAZs in Q500qE steel, and its boundary effectively facilitates the prevention of further propagation of a secondary crack.

关 键 词：Q500qE钢 CGHAZ 焊接热模拟 冲击韧性 贝氏体 

分 类 号：TG401[金属学及工艺—焊接]