H13 Die Steel Heat Treatment Process Optimization And Surface Nitriding Treatment

This article combines with practical production,for the purpose of improving the service life of extrution die,the failure modes of the nitrided layer of a H13 extrusion die were analysed,and a series basic research on heat treatment and nitriding of H13 tool treatment was carried out.The primary investigations of this paper include three main parts:heat treatment optimization of H13 tool steel,study on the effects of the nitriding on nitrided layer of H13 tool steel,and the effects of heat treatment conditions on nitrided layer of H13 tool steel.The main conclusions are as follows:1 Failure Analysis of H13 extrusion dieThe failure mode of the nitrided layer of the H13 hot extrusion die is wear which due to soften,break and plastic deformation.2 Heat treatment optimization of H13 tool steelThe hardness of H13 steel may reach the optimum use range(HRC48-52),after quenching at 1050℃and tempering for two times at the temperature ranging from 560℃to 600℃,this material may obtain improved plastic and toughness.3 Study on effects of the procedure of nitriding on nitrided layer of H13 tool steelThe thickness of the nitrided layer is 0.24mm,the compound layer is 10μm, hardness of the surface is 950HV(67HRC),and the compound layer is dense,when procedurel is used.When the H13 tool steel is nitrided by procedure2,the thickness of the nitrided layer is only 25μm,there isn't white layer,hardness of the surface is 52HRC,because of the shot time in the first step of the nitriding.And the thickness of the nitrided layer dosen't increase when the steel is nitrided two times by procedure2, but there has been formed a thin white nitrided layer,the thickness of which is 3μm, the hardness of the surface is 53.8HRC.4 Study on effects of heat treatment conditions on nitrided layer of H13 tool steelThe hardness of the steel before and after nitriding in the core become less,but the microstructure of the core after nitriding is more stady.The thickness of the nitrided layer is 0.24mm,the compound layer is 10μm,hardness of the surface is 950HV(67HRC),when the heat treatment conditions of H13 tool steel before nitriding are "quenching and twice tempering" and "quenching and three-times tempering",and the wear-resistance is good,the compound layer mainly incloudsε-phase (Fe2N),γ′-phase and Fe3O4,andα-Fe,ε-phase(Fe3N),γ′-phase and CrN are the major phase of diffusion layer,but the content is different in different heat treatment conditions,However,the heat treatment conditions before nitriding are "quenching" and "quenching and once tempering" couldn't hold the nitrided layer which has well comprehensive properties.By comparing the microstructures and properties under deferent heat temperature and tempering times,under deferent nitriding procedure,the thickness of the compound layer and the whole nitrided layer,the hardness of the nitriding layer and decreasation from the surface to the core,the dense and defacts of the nitrided layer, the stabilization of microstructure,the optimized heat treatment and nitriding procedure has been obtained,which is quenching at 1050℃(holding for 200 seconds, then cooling in warm water of 50-60℃)and tempering for 2 hours at the temperature ranging from 560℃to 600℃,tempering for two times(tempering for three times for more strict die),nitriding at 540～570℃for 12h,the resolve rate of NH₃ 30～40%...