HRB500E高强度抗震钢筋焊接性能

国内某厂通过铌微合金化和控冷工艺开发试制HRB500E高强度抗震钢筋,采用金相显微镜、维氏硬度计、闪光焊接、疲劳试验机及力学性能测试,对HRB500E钢筋焊接样力学性能、HV5硬度、金相显微组织、焊接接头强度及疲劳强度进行了试验研究。结果表明:焊接前后焊件和母材强度变化小于5 MPa,强度变化不大,焊件拉伸断口远离焊缝,为延性断口,焊接性能良好;在焊接热循环作用下,焊接接头焊缝、热影响粗晶区、热影响细晶区的表层和芯部经历奥氏体化后再结晶,其组织和硬度变化不大;混晶区至母材表层和芯部则经历不完全奥氏体化后的再结晶,母材芯部组织为F+P+B、表层组织为S,表层硬度HV5高于芯部硬度30 HV5,其组织和硬度变化较大;焊接接头的抗拉断负荷从焊缝到混晶区逐渐减小,焊缝和热影响粗晶区的抗拉断负荷比母材的高;采用国际焊接学会推荐的FAT75疲劳设计曲线对钢筋焊接接头疲劳强度设计是安全的。

Welding properties for HRB500E high-strength and seismic steel bars

HRB500E high-strength and seismic steel bars with Nb-microalloyed and controlled cooling process were produced in domestic steel plant.The mechanical properties,HV5 hardness,microstructure for weldment,strength and fatigue strength of welding joint were researched by using metallographic microscopy,vickers hardness tester,flash-butt welding,fatigue testing machine and mechanical properties testing.The results show that strength changes between weldment and base metal are less than 5 MPa before and after welding,strength change of steel bars is little;fracture of weldment is away from welded joints with ductile fracture,welding properties is better;in the welding thermal cycles,core and outer layer of welding gap of joint,heat affected zone with coarse grain,heat-affected zone with fine grain are experienced austenite recrystallization,changes of microstructure and hardness are little;core and outer layer of mixed grain zone,base metal are experienced incomplete austenite recrystallization,core and outer microstructure of base metal is F+P+B and S,hardness of outer layer is 30 HV5 higher than that of core,changes of microstructure and hardness are little;tensile breaking load of welded joints decreases from weld seam to mixed grain zone,tensile breaking load of welding seam and heat affected zone with coarse grain is higher than that of base metal;fatigue strength design of welded joint for rebars which adopts FAT75 fatigue design curve recommended by the International Institute of welding is safe.