Improve The Performance Of Hot Work Die With H13 Steel Research

H13 steel with high hardenability,strength and toughness, thermal fatigue behavior is widely used in and abroad,which can be used in the manufacture of hot extrusion die,aluminium alloy die-casting die, hot forging die,etc.In nowadays,H13 steel is one of the most widely used hot die steel in worldwide.H13 steel will suffer from strong impact force, friction, abrasion, plastic distortion, thermal fatigue, mechanical deterioration while being used,therefore,the properties that resist the above phenomena of H13 steel is required.Compared with import H13 steel, Domestic H13 steel still have some deficiencies,especially with serious banding microsegregation,and also the heat checking appears early, with short service life,and the transverse orientation impact toughness is much lower while being used,there fore,the research on the isotropy of H13 steel is significative.The heat treatment process is the most effective method to change the microstructure of steels while the chemical composition is invariable.The microstructure development of H13 steel from original cast-microstructure dendritic segregation to uniform nodularization pearlitic structure is a complicated process.The chemical composition segregation in the microstructure of H13 steels can be improved through high temperature diffusion,and also the pore-cave defect existing in H13 ingot can relieve high temperature deffusion effect.Some pretreatments are done on H13 steel by high temperature diffusion pre-forging technology,which can elimate pore-cave defect,furthermore,the high temperture diffusion effect can be reinforced. Refine grain through ultrafining process after high temperature diffusion and also prepare well microstructure for the isothermal nodularization process,well nodularization microstructure can improve toughness of quenched-tempered of H13 steel.In this paper,the effect of high temperature diffusion on chemical composition segregation, nodularization microstructure of H13 steel was researched by the method of optical Metallurgical Microscopy,SEM,TEM, energy spectrum analysis and phase analysis,etc,so to investigate the effect of high diffusion on the impact toughness of the final quenched-tempered of H13 steel.With the help of Thermo-calc computation software,the precipitated and growth law of quenched and tempered carbide was probed in order to optimize the annealing heat treatment process for H13 steel,then the practical production can be realized.H13 steel ingot produced by non-vacuum induction furnace and ESR is used as experimantal material in this paper,through analyzing, the following results are concluded:1. The microstructure of as-cast H13 steel is granular pearlite, so the core dendritic segregation is much serious,also with more eutectic carbide and high element segregation,at the same time, some pore-cave defects exist.Through high temperature treatment at 1260℃for 8h,the element segregation is removed basically and the banding segregation is relieved,well prepared for the isothermal annealing.2. H13 steel forged before high temperature diffusion can reinforce high temperature diffusion effect and elimate the pore-cave defect of ingot before high temperature diffusion,so to reduce the annealed hardness of H13 steel dramaticlly and enhance the impact toughness of annealed,quenched-tempered of H13 steel.3. When the ultrafining temperature of H13 steel is at 1000℃, the same heat treatment followed shows well properties.