相变温度及时间对SCM435钢盘条组织和性能的影响

Effect of phase transformation temperature and time on the microstructure and properties of SCM435 steel wire rod

针对小规格SCM435冷镦钢盘条因抗拉强度较高而影响后续加工的问题,设计了3种工艺,即通过调整终轧温度和斯太尔摩风冷线辊道速度,进而控制盘条相变温度和相变时间,使相变充分进行得到所需的铁素体+珠光体均匀组织,从而达到降低抗拉强度、提高面缩率的目的。试验结果表明,降低终轧温度至750℃、减小辊道速度至0.08 m/s,可以促进铁素体组织和珠光体组织的形成,抑制贝氏体组织和马氏体组织的产生,使SCM435冷镦钢热轧盘条抗拉强度降低172 MPa,面缩率提高12%;可使搭接点相变温度提高至750℃左右,相变时间延长至252 s左右,促进铁素体相变充分进行,使非搭接点相变温度提高至690℃左右,相变时间延长至168 s,促进铁素体相变充分进行,使盘条同圈性能均匀。

Aiming at the problem that small gauge SCM435 cold heading steel wire rod affects subsequent processing due to its high tensile strength,three processes to control the phase transformation temperature and time of the wire rod were designed by adjusting the finishing rolling temperature and the speed of the Stelmore air-cooling roller table,which make the phasetransformation fully proceed,and then obtain the required uniformly distributed ferrite and pearlite structure,to achieve the purpose of reducing the tensile strength and increasing the area shrinkage rate.The test results show that reducing the finishing rolling temperature to 750℃and reducing the roller speed to 0.08 m/s can promote the formation of ferrite and pearlite structures,inhibit the formation of bainite and martensite structures,and make the tensile strength of SCM435 wire rod reduced by 172 MPa,and the area shrinkage rate increased by 12%.It can increase the phasetransformation temperature of the lap joint to about 750℃and the phasetransformation time to about 252 s,promote the full progress of the ferrite phasetransformation,and it also can increase the phase transformation temperature of the non-lap joint to about 690℃,and extend the phase transformation time to 168 s to promote the full progress of ferrite transformation and make the performance of the wire rod in the same circle uniform.