Study On Microstructure And Properties Of 4Cr13 Corrosion Resistant Plastic Mold Steel

With the development of plastic products gradually large-scale and species diversity, the demand of large module products represented by 4Cr13 steel Cr13 type martensitic plastic mould stainless gradually increased. In the past, more research had been done for 4Cr13 steel bars, but less for 4Cr13 steel large modules, especially the detailed studies about the difference and influence of microstructure and properties were less for large modules.Used herein high quality 4Cr13 corrosion resistant plastic mold steel modules with a large section was produced by a domestic steel plant. Microstructure, mechanical properties in different positions of the module, the corrosion resistance and polished performance were studied by metallographic, scanning electronic microscope (SEM), hardness and impact toughness tests. The results show that:(1) The annealing microstructure of the module was uniform and compact in different positions of the module, carbides slightly segregation in the center; carbide spheroidization has a slight difference in different positions, more closer to the center, more large size carbides, more inhomogeneous about carbides diameter, the spheroidization less and less;(2) Grain size level as quenching temperature is gradually lowered, at 1020℃, the quench grain size can reach 8.5, combined quenching microstructure, hardness, grain size, etc., test steel suitable quenching temperature is 1020 ℃;(3) Combined with tempering temperature - hardness curves and performance required of steel 4Cr13, selected test steel tempering temperature of 280℃;(4) Impact toughness, tensile strength is is gradually decreased from the edge to the center. The main reason is the degree of carbide spherical and diameter of edge are superior than 1/4 and center, small amounts large-sized carbide in the center are not completely crushed will also be significantly deteriorated mechanical properties of steel.(5) S-136 test steel corrosion rate faster than the test 4Cr13 steel, reasons include differences in the alloy composition and too many small non-metallic inclusions; Tested steel has good polishing performance, the roughness parameter gradually decreases from the edge to the center;(6) In order to improve some defects in annealing state like the chain microstructure and carbides uneven distribution, comparison of different annealing process, the most suitable annealing process is 1050℃×3h Oil-cooledâ†'780℃×8h air-cooled, It can significantly improve the annealing microstructure, chain carbides almost entirely, carbide distribution becomes more uniform, and has reasonable annealing hardness.