Study On Performance And Microstructure Of Surfacing Layer Of Cr5 Support Roller

Cr5 support roller is one of the important equipment of steel rolling,which works in the bad environment of large load and high temperature for a long time. Wearing and spalling phenomena caused by these shortens the construction’s life.Developing the material of flux-cored wire for repairing Cr5 support roller and studying on the microstructure and performance of surfacing layer metal are very important, which has larger engineering value to extend the service life of supporting roller.This paper selects the martensitic alloy of Cr5 support roller repairing as the research object and uses the several elements of Mo,Ni,V and Nb to alloy,which have developed the material of flux-cored wire for repairing Cr5 support roller and researched the submerged-arc surfacing process of material of flux-cored wire.Then the paper optimizes the parameters of welding process and researches the metal organization of surfacing welding layer under the different Nb content systematically.Following these,we discusses the impact of Nb carbide on the metal organization of surfacing welding layer during the heat-treatment at different temperature and the hardness and wearability of surfacing welding layer metal under the different Nb content and different heat-treatment temperature.The results are as follows:(1)The results make it clear that the weld metal with favorable slag detachability and molding has no air hole,crack and slag inclusion when the flux-cored wire for repairing Cr5 support roller matched with HJ107 flux on condition of submerged-arc surfacing that welding voltage is 35 V,welding current is 350 A and welding speed is13cm/min.(2)The metal microstructure of repairing Cr5 support roller surfacing welding is consisted of the martensite, retained austenite and the carbide of Nb.With more Nb content of surfacing welding,the grain size of martensite gets small and the content of carbide increases. After high temperature tempering,the metal microstructure of surfacing welding is consisted of tempered martensite, retained austenite and carbide.With increasingtempering temperature,the grain size of martensite gets small and the content of carbide increases. The tempered martensite turns into tempered sorbite when the tempering temperature is 600℃,and the carbide begins to dissolve.(3)With the increasing content of Nb, the hardness of surfacing welding metal increases and then the value of hardness decreases after it reaches the maximum.The hardness of surfacing welding metal reaches the maximum when joining 2%Nb into material of flux-cored wire.When the tempering temperature goes up at a range between 480℃ and600 ℃,the hardness of surfacing welding metal increases first and then decreases.The hardness of surfacing welding metal reaches the maximum when the tempering temperature reaches at 520℃.Under the conditions of joining 2%Nb into material of flux-cored wire and tempering temperature reaching at 520℃,the hardness of surfacing welding metal reaches the maximum.(4)With the increasing content of Nb, the wear resistance of surfacing welding metal increases and then the wear resistance decreases after it reaches the maximum.The wear resistance of surfacing welding metal reaches the maximum when joining 2%Nb into material of flux-cored wire and tempering temperature reaching at 520℃.