55SiCr盘条表面异常组织原因分析  

Causeanalysis of 55SiCr wire rod surface abnormal structure

作　　者：王小忠 朱文凯 黄春成 安鹏达 WANG Xiaozhong;ZHU Wenkai;HUANG Chuncheng;AN Pengda(Zenith Steel Group Company Limited,Changzhou213011,Jiangsu,China)

机构地区：[1]中天钢铁集团有限公司,江苏常州213011

出　　处：《四川冶金》2022年第4期57-62,共6页Sichuan Metallurgy

摘　　要：55SiCr弹簧钢热轧盘条在拉拔、矫直、淬回火后的卷簧中发生异常断裂。为查明断裂原因,采用了化学分析、断口分析、金相检验等方法,并利用X射线能谱仪对拉拔矫直断裂源处的组织区域特征相进行了微区成分面分析。结果表明,55SiCr钢热轧盘条表面存在局部增碳,使盘条表面层产生沿纵向的带状异常组织区域,生产含有大量条块状碳化物的异常组织,拉拔变形过程中块状碳化物聚集处容易出现应力集中形成细小裂纹,进而在矫直受力过程中产生以细小裂纹为源头的断裂。弹簧钢棒表面异常组织区域经淬火回火后的组织为回火马氏体+回火屈氏体+残余奥氏体及少量碳化物,其硬度高、脆性大,在卷簧过程中,若表面异常组织区域正好处于弹簧外圆表面,受到较大拉应力作用,此处容易生成横向裂纹,最终导致弹簧断裂。55SiCr spring steel hot-rolled coils break abnormally in the coiled spring after drawing,straightening andquenching tempering.In order to find out the cause of fracture,chemical analysis,fracture analysis,metallographic testing and other methods were used,and X-ray energy spectrometer was used to analyze the characteristic phases of the tissue region at the source of the pull-straightening fracture.The results show that there is local carbonization on the surface of the 55SiCr steel hot-rolled wire rod,so that the surface layer of the coil produces a strip-like ab-normal tissue area along the longitudinal direction,and produces an abnormal tissue containing a large number of strips of carbide,and the stress concentration of the block carbide in the process of pulling deformation is prone to stress concentration to form small cracks,and then the fracture with small cracks as the source is generated in theprocess of straightening and stress.The abnormal tissue area on the surface of the spring steel rod is quenched and tempered after the organization is tempered martensitic+tempered traversite+residual austenite and a small a-mount of carbide,its hardness is high,brittle,in the process of spring winding,if the surface abnormal tissue area is just in the spring outer circular surface,subject to a large tensile stress,here it is easy to generate transverse cracks,eventually leading to spring rupture.

关 键 词：55SiCr 拉拔矫直 表面增碳 异常组织 

分 类 号：TG142.1[一般工业技术—材料科学与工程]