Study On The Manufacturing Processes Of New Style Steel For Large Die Casting Die

It was very important to study manufacturing processes for making the properties of materials well and obtaining ideal service life of die. Thus, the paper studied manufacturing processes of HHD steel in three areas those were improving purity, dismissing eutectic carbides, fining grain sizes. The microcosmic analysis and performance tests of HHD steel were carried out by spectrum analyzer, metalloscope, scanning electron microscope (SEM), energy dispersive spectroscopy (EDS), X-ray diffractomer (XRD), impact tester, and so on.Results indicated that twice electroslag remelting was necessary for getting the die steel with purity. Under this condition, the content of sulfur was decreased enormously that was controlled at around 0.0020%. Accordingly, the quantity of sulphide inclusion was decreased greatly. The grade of nonmetallic inclusion in raw steel was at above level 5, but now it was raised to level 1.5. Thus, the tiny particles of inclusion that evenly distributed took the place of those which were coarse particles, and the micro structure was clean relatively. Thereby, non breach impact toughness of HHD steel was stable.It was concluded that it was more suitable to choice 1230℃×14h as high temperature diffusion process parameters of HHD steel ingot for dismissing eutectic carbides. Results indicated that the oxidation rate of HHD steel at 1230℃×14h was the lowest, compared with that of 1210℃×30h,1190℃×40h and 1170℃×45h, but the crystal grains grew up so quickly that the crystal degree reached above 1 degree. So, it needed normalizing process for fine grain size. The results showed that normalizing at 1080℃could reduce grain size of HHD steel which reached degree 6.Consequently, the reasonable manufacturing processes of new style steel HHD were medium frequency smelting, out-of-furnace refining, secondary electroslag remelting, high temperature diffusion (1230℃×14h), multiple forging and then normalizing at 1080℃.