Research On The Heat Treatment And Structural Properties Of Casting Cold-working Die Steel

In recent years, the rapid development of the automobile and household appliancemanufacturing industry has brought tremendous opportunities for mold manufacturing in-dustry, but there are also a lot of challenges, which is the big gap between domestic and for-eign mold materials in variety, quality, and performance, this will severely restrict the fur-ther development of manufacturing industry. Therefore, we need to develop more new moldmaterials and improve the material process of existing mold material, and according to this,we conducted the research work about this project.The single factor analysis method was used for the composition optimization of casting5Cr5MoV testing steel, and carried out heat treatment process test of Cr12Mo1V1,Cr5Mo1V and new5Cr5MoV die steel, we attempted to change the network carbide mor-phology with high temperature treatment process. Developed different annealing, quenchingand tempering process according to transformation temperature and related technical data,compared and analyzed the changes of microstructure, hardness, strength and other proper-ties of test materials under different process conditions, and determined the rationality ofprocess and alloy composition by finding the best match of microstructure and properties,completed the composition optimization of5Cr5MoV test steel and the heat treatmentprocess test of the three die steels.The test results show that, the new5Cr5MoV cold-working die steel has a betterstrength-toughness combination, less alloying elements usage means significant reduction incost. Casting Cr12Mo1V1and Cr5Mo1V steel have achieved a high strength, but the brit-tleness is also very obvious. Although the testing steel obtains a more satisfactory annealingmicrostructure after isothermal spheroidizing annealing, and has the maximum hardnesswhen tempered at the secondary hardening temperature after quenching, the segregation andother defects that exist in the original as cast structure will still be retained after heat treat-ment, and this will have bad effect on strength and toughness of the testing material and limit its performance. High temperature treatment process of Cr12Mo1V1plays a signifi-cant role in changing the net carbide morphology, but its strength and toughness reduce dueto the coarsening of microstructure.The testing material with new composition and optimazition of heat treatment processachieves a more satisfactory property of strength and hardness, a big progress will be madein practical use for lowering the manufacturing cost and shortening the process cycle. Cer-tainly, more processing test is needed to realize a better strength-toughness combination ofthe testing material.