1400 MPa级超高强钢SH-CCT曲线及其热影响区组织和性能  

SH-CCT diagram and microstructure and properties of heat-affected-zone of 1400 MPa ultra high strength steel

作　　者：曹志龙 朱浩[2] 安同邦[1] 王晨霁 马成勇[1] 彭云[1] CAO Zhilong;ZHU Hao;AN Tongbang;WANG Chenji;MA Chengyong;Peng Yun(Central Iron&Steel Research Institute,Beijing,100081,China;Shijiazhuang Tiedao University,Shijiazhuang,050043,China)

机构地区：[1]钢铁研究总院,北京100081 [2]石家庄铁道大学,石家庄050043

出　　处：《焊接学报》2023年第8期109-115,I0009,I0010,共9页Transactions of The China Welding Institution

基　　金：国家重点研发计划(2017YFB0305105)。

摘　　要：采用Formastor-FⅡ全自动相变仪,结合光学显微镜(OM)和维氏硬度测试,研究不同冷却速率对1400 MPa级超高强钢焊接热影响区(HAZ)粗晶区组织转变和性能的影响规律,绘制焊接连续冷却转变曲线(SH-CCT),结合焊接工艺试验,采用公式法确定最佳焊接工艺参数.结果表明,1400 MPa级超高强钢马氏体临界转变冷却速率约为5℃/s,当冷却速率大于5℃/s时,热影响区粗晶区组织为单一板条马氏体,硬度值为487~509 HV5,冷却速率小于5℃/s时,粗晶区组织中出现中高温相变产物,即板条贝氏体、粒状贝氏体和铁素体等组织,硬度值下降为487~260 HV5,同时组织中还出现M-A组元,其含量随冷却速率降低先增加后减少,形态也由弥散颗粒状变为断续长条状或块状分布;厚度8 mm的1400 MPa级超高强钢焊接时,热输入控制在20 kJ/cm以内,粗晶区组织为板条马氏体,硬度维持在500 HV5左右,粗晶区不发生软化现象,满足工程使用要求.The effects of different cooling rates on the microstructure transformation and properties of the coarse grained heat affected zone(HAZ)of the 1400 MPa ultra-high-strength steel were studied by using a Formastor-FⅡautomatic phase changer,combined with metallographic microscope(OM)and Vickers hardness test.According to the simulation results,the welding continuous cooling transformation curve(SH-CCT)is drawn,and the formula method is used to determine the optimal welding parameters combined with the welding process test.The results show that the critical transformation cooling rate of martensite in 1400 MPa ultra-high strength steel is about 5℃/s.When the cooling rate is greater than 5℃/s,the microstructure of the coarse grained zone in the heat-affected zone is single lath martensite,and the hardness value is 487~509 HV5.When the cooling rate is less than 5℃/s,medium and high temperature phase transformation products appear in the structure of the coarse-grained region,which are lath bainite,granular bainite and ferrite,and the hardness value drops to 487~260 HV5.At the same time,M-A component also appeared in the tissue,and its content increased first and then decreased with the decrease of cooling rate.and the shape also changed from dispersed granular to intermittent long strip or block distribution.When welding 1400 MPa ultra-high-strength steel with a thickness of 8 mm,the welding heat input is controlled within 20 kJ/cm,the microstructure of the coarse-grained zone is lath martensite,the hardness value is maintained at about 500 HV5,and no softening occurs in the coarse-grained region,which meets engineering requirements.

关 键 词：1400 MPa级超高强钢 冷却转变曲线 焊接热影响区组织 M-A组元 

分 类 号：TG406[金属学及工艺—焊接] TG142.1[一般工业技术—材料科学与工程]