Study On Microstructure And Properties Of 420 Series Typical Corrosion Resistant Plastic Die Steel

420 series corrosion-resistant plastic mold steel has become the best choice for small and medium high-end plastic molds due to its low cost,high strength and toughness,and excellent corrosion resistance.With the development of high and new technology,there are more and more precision moulds,so the dimensional stability of 420 series corrosion resistant plastic mould steel is required.However,there is no relevant literature to study its dimensional stability fluctuation and other characteristics after typical heat treatment,nor to compare the characteristics of similar steel grades at home and abroad.The manufacturer is not clear about the physical property difference of the same type of steel at home and abroad after typical heat treatment,so it is difficult to select,machine process,heat treatment and assembly on demand.Therefore,in this paper,three kinds of 420 series typical corrosion resistant plastic mold steels S136 and S136 SUP of ASSAB in Sweden and 2083 ESR of LKM in Hong Kong were analyzed by means of XRD,OM,SEM,carbide statistics,mechanical properties detection,salt spray corrosion test and dimensional stability test.The annealing microstructure and properties of 2083 ESR were analyzed,and a series of annealing processes were designed to improve the annealing microstructure of 2083 ESR by JMat Pro simulation and synchronous thermal analysis test verification.The reasons for differences in temper microstructure and properties,corrosion mechanism research and dimensional stability model establishment were carried out.The results show that:1.In addition to the annealing hardness of 2083 ESR is lower than THAT of S136 and S136 SUP,and it is easy to be cut,the quantity,size,distribution of carbide and the rating of non-metallic inclusion of 2083 ESR are far worse than that of S136 and S136 SUP.2083 ESR has a large number of carbides,large particle size,high inhomogeneity,poor spheroidization effect and obvious segregation of some carbides.The phase transition temperature of 2083 ESR was obtained by CCT and TTT curve simulation and synchronous thermal analysis test,and 12 groups of annealing processes were designed.The annealing process was 1000?×3h,oil cooling to 680?,680?×2h+880?×2h with furnace ?760?×4h furnace cooling ?500?,air cooling,the original annealing microstructure of 2083 ESR was improved most obviously.Compared with the original annealed microstructure,the grade of annealed microstructure changed from AS4 to AS1.The annealing hardness decreased by 14.5%,the impact toughness increased by55.38% after low temperature tempering at 280?,and 30.82% after high temperature tempering at 520?.2.After tempering at different temperatures(280? and 520?),the rod-like and irregular carbides of 2083 ESR were found to persist in the tempering structure,resulting in poor mechanical properties of the three corrosion-resistant plastic die steels.The impact toughness of S136 SUP is much higher than that of S136 and 2083 ESR.The main reason is that THE C content of S136 SUP is low and the carbide generated is small and small.High Ni content and high residual austenite content are beneficial to coordinate multi-grain deformation.The corrosion resistance of the three corrosion resistant plastic mold steels under low temperature tempering at 280? is better than that of high temperature tempering at 520?.The main reason is that the high tempering temperature(520?)will make the test steel produce chromium-poor zone,appear dedulating phenomenon,and reduce the corrosion resistance;Under low temperature tempering at 280?,the corrosion resistance of S136 and 2083 ESR is better than that of S136 SUP,because the nanoscale M23C6 of S136 SUP will reduce the intergranular corrosion resistance of S136 SUP.The changing process of its dimensional stability is as follows:first decrease,then increase,and finally become stable;After tempering at 520 ?,the size fluctuation of S136 and S136 SUP samples reaches 2.42?m and 1.16?m,respectively.After tempering at 280 ?,the size fluctuation of 2083 ESR reaches 3.52?m,and the dimensional stability of 2083 ESR in different time periods can be calculated by the established mathematical model.