摘要
采用Formastor-FⅡ全自动相变仪、光学显微镜(OM)与维氏硬度计等设备,对比研究了800~500℃冷却时间(t_(8/5))对1 100、1 400 MPa级试验钢粗晶热影响区组织转变和性能变化的影响规律。结果表明:当LG1100QT钢t_(8/5)<30 s、LG1400QT钢t_(8/5)<60 s时,试验钢热影响区均为细小的板条马氏体组织;随着t_(8/5)(150→300→2 000 s)延长,热影响区组织由板条马氏体→板条马氏体/贝氏体+粒状贝氏体→粒状贝氏体+铁素体+珠光体构成演化,且晶粒尺寸逐渐增大,组织粗化。在相同冷速下,LG1100QT钢组织转变均比LG1400QT钢提前,即LG1100QT钢热影响区中先开始出现贝氏体、珠光体等组织转变,这与钢中合金元素的含量有关;LG1100QT钢、LG1400QT钢热影响区硬度随t_(8/5)的延长呈下降趋势,这是由于组织构成由板条马氏体向贝氏体类及铁素体/珠光体组织演化所致。当LG1100QT钢t_(8/5)时间超过75 s时、LG1400QT钢t_(8/5)时间超过30 s时,其热影响区硬度已低于试验钢母材硬度,即热影响区出现软化现象。由冷裂敏感性评价结果可知:LG1100QT钢碳当量为0.52%、冷裂纹敏感系数为0.27%;LG1400QT钢碳当量为0.66%、冷裂纹敏感系数为0.37%,表明试验钢具有较大的淬硬倾向及冷裂纹敏感性,为获得与母材相当性能的接头,焊接时LG1100QT钢和LG1400QT钢t_(8/5)时间分别控制在75和30 s以内,并采取焊前预热和焊后热处理等工艺措施,避免产生焊接冷裂纹等缺陷。
To provide theoretical and experimental basis for the proper selection of welding parameters in engineering application, the effect of cooling time from 800 to 500 ℃(t_(8/5)) on the microstructure transformation and properties variation of the coarse grained heat affected zone(CGHAZ) of the 1 100, 1 400 MPa grade steel was investigated by using the Formastor-FⅡ, optical microscope(OM) and vickers hardness tester. The results indicated that when the t_(8/5)of LG1100QT steel was less than 30 s or the t_(8/5)of LG1400QT steel was less than 60 s, the heat-affected zone was transformed from lath martensite/bainite→lath bainite+granular bainite→granular bainite→granular bainite+ferrite+pearlite, and the size of the grain and microstructure gradually increased. The microstructure transformation of LG1100QT steel was earlier than that of LG1400QT steel, and at the same cooling rate, the microstructure transformation such as bainite and pearlite first appeared in the heat affected zone of LG1100QT steel, which was related to the content of alloying elements in the steel. With the increase of t_(8/5)and transformation of its microstructure from lath martensite to bainite and ferrite/pearlite, the hardness of the heat affected zone decreased. When the t_(8/5)of LG1100QT steel exceeded 75 s and the t_(8/5)of LG1400QT steel exceeds 30 s, the hardness of the heat-affected zone was lower than that of the test steel. The carbon equivalent and cold cracking susceptibity coefficient of LG1100QT steel is 0.52% and 0.27%, the carbon equivalent and cold cracking susceptibity coefficient of LG1400QT steel is 0.66% and 0.37%, respectively, indicating that two test steels all had strong harden quenching tendency and cold cracking susceptibility. In order to avoid welding cold cracks and other defects and obtain joints with properties equivalent to the base metal, the t_(8/5)time of LG1100QT steel and LG1400QT steel should be controlled within 75 s and 30 s respectively, and preheating and post-weld heat treatment should be tak
作者
安同邦
郑庆
张永林
梁亮
朱彦洁
韩胜
AN Tongbang;ZHENG Qing;ZHANG Yonglin;LIANG Liang;ZHU Yanjie;HAN Sheng(Department of Welding,Central Iron and Steel Research Institute,Beijing 100081,China;Centre for Product and Technology Hunan Valin Lianyuan Iron and Steel Company,Loudi 417009,Hunan,China)
出处
《金属功能材料》
CAS
2023年第1期73-80,共8页
Metallic Functional Materials
基金
国家重点研发计划(2017YFB0305105)。
