Microstructure And Property Of Friction Stir Processing Zone Of Backup Rolling Steel

In this study,two kinds of support roller steel Cr3 and Cr5 as the object,using friction processing methods to carry out the steel surface deformation heat treatment feasibility study.The phase diagrams of Fe-Cr were calculated by Thermo-Cale software and the CCT curve of Cr3 steel and Cr5 steel were calculated by Jmat-Pro software and the phase transmission point temperature of backup rolling steel were measured by using DSC.With using of the optical microscope analysis(OM),scanning electron microscope analysis,X-ray diffraction analysis(XRD),transmission electron microscope(TEM)analysis and Electron Backscattered Diffraction analysis(EBSD),the organizational structure and its evolution mechanism of the two kinds of steel before and after the friction stir processing were studied.At the same time,the mechanical properties and wear resistance of the processing zone were measured.The results show that : Cr3 steel is martensite in the condition of low heat input(rotation speed 800 r/min,traveling speed 50 mm/min),and its tensile behavior shows high brittle fracture characteristics.But its abrasion resistance has improved significantly,friction and wear to adhesive wear as the main form.After 550 ? high temperature tempering heat treatment,the strength of the processing zone is equal to that of the quenched and tempered matrix,but the elongation rate is obviously improved.The bainite microstructures in the processing zone were dominated by high heat input conditions(rotational speed 800 r/min,traveling speed 30 mm/min).The tensile strength of the untreated zone was improved by 23.7% and the elongation was improved.Due to the increase of Cr elements,Cr5 steel improve the hardenability,and thus in the two heat input conditions have access to a high hardness of martensite.And its processing area is characterized by high hardness,high strength,low plasticity.