The Effect Of Heat Treatment Process On Microstructure And Properties Of H13 Steel

H13 steel with high heat resistance,red rigid,high toughness,wear resistance,thermal fatigue resistance and thermal cracking ability is widely used in and abroad,which can be used in the manufacture of hot extrusion die,hot forging die,aluminum alloy and copper alloy die-casting die,etc.H13 steel is one of the most widely used hot die steel in the world,which belongs to the cold hardening type hot die steel with high strength and toughness.In order to stabilize the production of high quality H13 steel,aiming at the problem of poor quality stability of H13 steel production in China.In this paper,H13 steel vacuum ingot and electroslag ingot are used as test materials.The CCT curve of the test steel is measured,and the influence of heat treatment process on the microstructure and properties of H13 steel is studied systematically.The H13 steel homogenization treatment,pretreatment process and quenching and tempering process were optimized through experiments,and the following conclusions were obtained:1)H13 steel vacuum ingots and electroslag ingots in the as-cast structure in the presence of severe dendrite segregation and liquid carbide.In order to eliminate the defects of the ingot,the homogenization treatment was carried out.After testing,the optimal homogenization process of the electroslag ingot and the vacuum ingot are 1 180℃×6 h,air cooling,1 280 ℃ ×8 h,air cooling.After homogenizing treatment,the composition segregation was improved,and the edge of the massive liquid-extraction carbides was dissolved and the shape of the carbide was increased,the dendrite segregation and structure homogeneity improved obviously.2)The CCT curves of H13 steel show that H13 steel has good hardenability,and the complete martensite structure can be obtained at the cooling rate of 1℃/s.Ms point decreases with increasing quenching temperature,and the Ms points at 980℃ and 1030℃ after austenitization are 360℃ and 330℃.3)Under the experimental conditions,the best preheating heat treatment process of H13 steel is solid solution + isothermal annealing,the process parameters are 1 080℃ × 1 h,air cooling,870℃ × 1 h,furnace cooling to 750℃ × 2 h,air cooling.The hardness of the specimen annealed was 175 HBW.After 1 040℃ × 1 h,air-cooled quenching,600℃ × 2 h,air-cooled secondary tempering treatment,the sample hardness of 44.38 HRC,transverse impact work 12.2 J,transverse longitudinal impact power ratio 0.82,the organization and performance to achieve high-quality H13 steel standards.4)After quenching and tempering treatment organization,the microstructure of H13 steel is tempering martensite,carbides and a small quantity of retained austenite.In the quench temperature range from 980℃ to 1 080℃,quench hardness and temper hardness,impact toughness and thermal stability of H13 steel increases with the increasing quench temperature.The secondary hardening peak increases and the temper temperature of the secondary hardening decreases with the increases of quenching temperature.980℃,1030℃ and 1 080℃ quenched samples,tempering secondary hardening occurred in the temperature range 550 ~ 570℃,530 ~ 550℃,510 ~ 530℃.H13 steel the best quenching and tempering process: 1 080 ℃ × 1 h,air-cooled quenching,600℃ × 2 h,air-cooled tempering twice.