The Study On Heat Treatment Process And Mechanical Properties Of The New Patternhot Work Die Steel ZWT4

The hot work die steel plays an irreplaceable role in modern industrial production.Although traditional hot work die steel such as5CrNiMo?4Cr5MoSiV?4Cr5MoSiV1?3Cr2MoWVNiare domestic common hot work die steel at present,especially the dosage of 4cr5mosiv1 steel is the most.The investigation of this paper is based on 4 cr5mosiv1 steel,reduced the content of such elements as Mo,Si,Cr and V in the steel,and increased the content of Mn,combined with the micro-alloying of Ni at the same time,which can reduce the Cr and V of the carbide,increase the carbides of Mn and Carbon can more fully with V,Mn,and Mo combined into high hardness carbides.Mn can eliminate or reduce the brittleness of steel caused by sulfur,thus improve the thermal performance of steel.Ni can significantly increase the harden ability of steel and can improve the strength,toughness and plasticity,reduce the brittle transition temperature.It took strengthening and toughening theories of metal material as a basis,utilized modern analyzing and testing technology of material science,tested the effect of composition segregation inhomogeneity of ZWT4 on hardness of the material,and the effect of heat treatment process on the improving of the condition of the composition segregation.Through the microstructure of ZWT4 we can find that the carbide segregation in existence in the positive segregation,which leads to considerable differences in their hardness between the two segregation areas.The hardness difference is as high as 10 HRC in positive and negative segregation.The best way of improved the segregation is to choose proper pouring temperature and casting speed in smelting casting process,and adopt the appropriate high temperature diffusion treatment before ingot forging.After 880 ? quenching water,and 540 ? tempering,the hardness of the head of ZWT4 bar riser to 45.7HRC,and the cushion of ZWT4 bar was 45.0HRC;After 560 ? tempering,the hardness of the head of ZWT4 bar was 43.1HRC,and the cushion of ZWT4 bar was 42.9HRC,compared with the540 ? tempering,the drop of the hardness is about 2HRC.The rise of tempering temperature,provided the energy for the decomposition of martensite,but because of the increase is not much,the hardness of ZWT4 was improved less;After 580 ? tempering treatment,ZWT4 hardness value than the second 560 ? tempering treatment hardness value decreased,and the hardness of ingot riser and bottom cushion is relatively uniform,and the secondary tempering heat treatment of the tensile strength,yield strength,tensile strength by 1.5%,the yield strength was reduced by 4.6%.But transverse longitudinal impact energy increases,transverse U notch impact energy rose 9.4%,the longitudinal U notch impact energy of 3.9%.