Mn-Mo系低合金焊丝盘条的试制及退火对组织性能的影响

Trial produce of Mn-Mo low alloy welding wire rod and effect of annealing on its microstructure and properties

利用Gleeble-3800热模拟仪研究了1.7Mn-0.5Mo气体保护焊丝钢的连续冷却相变行为,对其进行试轧制,并研究了退火工艺对热轧盘条组织与性能的影响。结果表明:0.3~0.8℃/s冷速形成多边形铁素体和块状马奥岛组织,1.5~2.5℃/s冷速形成多边形铁素体+块状马奥岛+粒状贝氏体,且粒状贝氏体比例随冷速增加而增加,3.4~5.0℃/s冷速形成粒状贝氏体+块状马奥岛。轧制过程中吐丝温度890~910℃,边部盘条为多边形铁素体+块状马奥岛组织,抗拉强度640 MPa,中部盘条为多边形铁素体+块状马奥岛+粒状贝氏体组织,抗拉强度672 MPa。经690℃保温6 h退火后,盘条抗拉强度低于500 MPa、断面收缩率高于78%、断后伸长率高于29%。

Continuous cooling transformation behavior of 1. 7Mn-0. 5Mo gas shielded welding wire steel was studied on thermal simulator Gleeble-3800,trial rolling of the wire was conducted,and then effect of annealing treatment on microstructure and properties of the wire was investigated. The results show that at cooling rate of 0. 3-0. 8 ℃ / s,polygonal ferrite and massive martensite-austenite is formed,while at cooling rate of 1. 5-2. 5 ℃ / s,polygonal ferrite,massive martensite-austenite and granular bainite is formed,and the volume fraction of granular bainite increases with the increase of cooling rate,and at cooling rate of 3. 4-5. 0 ℃ / s,granular bainite and massive martensiteaustenite is formed. During hot rolling,after spinning at 890-910 ℃,the wire in the edge of the control cooling line is with a microstructure of polygonal ferrite and massive martensite-austenite,the wire in the middle of the control cooling line is with a microstructure of polygonal ferrite,massive martensite-austenite and granular bainite,which correspond to the tensile strength of 640 and 672 MPa respectively.Annealing treatment at 690 ℃ for 6 h,the tensile strength of the wire is less than 500 MPa,the area reduction is above 78%,while the elongation is above 29%.