特厚EH47止裂钢板及焊接热影响区的组织性能  

Microstructures and mechanical properties in ultra-thick EH47 steel plates and heat affected zones

作　　者：刘东升 程丙贵 罗咪 曲锦波 LIU Dong-sheng;CHENG Bing-gui;LUO Mi;QU Jin-bo(Institute of Research of Iron and Steel,Jiangsu Shagang Group Co.,Ltd.,Zhangjiagang 215625,Jiangsu,China)

机构地区：[1]江苏省(沙钢)钢铁研究院,江苏张家港215625

出　　处：《钢铁》2021年第3期92-102,共11页Iron and Steel

摘　　要：为开发大型集装箱船用特厚EH47止裂钢板,提出了一种低碳微合金MnCrNiCu钢,研究了其变形奥氏体连续冷却相变规律,使用控轧控冷工艺(TMCP)试制出最大厚度为85mm特厚EH47级钢板,使用埋弧焊(SMA)和药芯焊丝气保焊(FCAW)技术对最厚钢板进行焊接试验,研究钢板和焊接接头的显微组织和性能。通过系列V缺口Charpy(CVN)示波冲击试验研究钢板的韧脆转变行为,获得各部位的韧脆转变温度(DBTT)及其解理断裂强度σf;测试了钢板及热影响区粗晶区(CGHAZ)全厚度截面的组织和CVN韧性,测试了-10℃的裂纹张开位移(CTOD)及其启裂韧性(Kc);通过系列温度梯度宽板双重拉伸(DT)试验,获得了钢板的止裂韧性(Kca)与温度之间的关系。结果表明,钢板的显微组织由铁素体(PF)、针状铁素体(AF)和弥散分布的马氏体奥氏体(MA)组成;随着精轧压下率和冷却速率逐渐提高,大角度晶界分数逐渐增大,DBTT随之降低;CVN试样和DT试样具有相同的解理断裂临界事件;FCAW CGHAZ由粒状贝氏体(GB)+MA组元为主,SMA CGHAZ由AF+准多边形铁素体(QPF)+MA组元为主,前者K_(c)低于后者,更容易萌生解理断裂;钢板-10℃的K_(ca)为7 140N/mm^(3/2),具备止裂性能。A microalloyed low carbon MnCrNiCu steel has been proposed to develop EH47 steel plates via thermomechanical controlled processing(TMCP)route.The effect of hot deformation of austenite or cooling rate on phase transformation in the steel was investigated.Heavy steel plates with maximum thickness of 85 mm were rolled.Submerged arc welding(SMA)and flux-cored arc welding(FCAW)processes were employed in welding trials,respectively,to evaluate the weldability of the thickest plate.Microstructures in the plates and the coarse-grained heat affected zone(CGHAZ)were characterized.Ductile-to-brittle transition temperatures(DBTTs)in the plates were measured based on a series of instrumented Charpy V notch(CVN)impact tests,followed by the determination of the local cleavage fracture stresses(σf).Microhardness and CVN impact toughness in the heat affected zone(HAZ)produced by either SMA or FCAW were also tested.Full thickness crack tip open displacement(CTOD)in the mother plate or the weld joints was tested at -10℃leading to evaluation on the crack-initiation toughness(Kc)in the ultra-thick plate or the weld joints.A temperature dependency of crack-arrest toughness(Kca)in the ultra-thick plate was determined based on a series of large scale double tension(DT)tests across the entire thickness of the ultrathick plate.The results show that:a mixture of polygonal ferrite(PF)+acicular ferrite(AF)associated with dispersed martensite-austenite constituents was produced in the plates.An increase inσfleads to a decrease in DBTT.The critical events of cleavage fracture during the CVN testing and DT crack arrest testing are identical being grain-sized cracks.In comparison with the CGHAZ where quasi-polygonal(QPF)+AF are produced by SMA,cleavage crack can be initiated more easily in the CGHAZ by FCAW due to the formation of brittle GB.As a result,K_(c)associated with the latter CGHAZ is lower than the former.K_(ca)at -10℃is determined being 7 140 N/mm^(3/2 )indicating satisfactory crack arrestability in the mother plate.

关 键 词：控轧控冷工艺 特厚钢板 解理断裂应力 起裂韧性 止裂韧性 

分 类 号：TG142.1[一般工业技术—材料科学与工程]