Research on Preparation Bof Semi-solid Slurry of Low Alloy Steel by Near Liquidus Holding Method

The preparation of semi-solid slurry is a troublesome problem for ferrous alloys.In order solve it,the preparation of semi-solid slurry of low alloy steel by near liquidus holding method was investigated with medium-frequency induction furnace.The results show this method is simple and feasible.The influence of holding time,holding temperature and heating methods on the microstructure of water quenched and air quenched samples was investigated.At a temperature with large superheat or supercooling,it is difficult to form free nuclei and free crystals and coarse grains were found in water quenched samples.However,at near liquidus(1 508 ℃) a large number of free nuclei were formed and gradually evolved into free crystals which were distributed uniformly in the melt These fine grains can refine and homogenize grains significantly during solidification and make water-quenched structure finely and homogeneously;the mechanism can also play a role even at the air cool condition.Due to electromagnetic stirring brought by medium-frequency induction,a quite large number of free nuclei could be formed if holding at near liquidus for a short time,and can keep original morphology and the number of those free crystals during the later holding process.The microstructure of water quenched samples holding for 5 to 50 mins at liquidus.has not significant difference.