近液相线保温法制备低合金钢半固态熔体

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

为解决钢铁材料半固态熔体制备难题,研究了中频感应炉近液相线保温制备低合金钢半固态熔体的方法.结果表明,该方法简单可行.通过研究不同保温条件下的水淬组织和空冷组织,掌握了保温温度、保温时间及加热方式对组织的影响规律.在大过冷和大过热温度下,熔体内不易形成晶胚（准固相原子团簇）和游离晶,水淬组织粗大.而在近液相线温度（1 508 ℃）下,熔体内易形成大量晶胚并演化为游离晶均匀分布于熔体内,它们能在凝固时显著细化、匀化晶粒,使水淬组织细小、均匀,即使在空冷条件下,这种细化机制也起作用.由于中频感应炉的电磁搅拌作用,在近液相线温度短时保温就可孕育出相当数目的游离晶,并能在随后的保温过程中保持游离晶的形态和数目,保温时间为5～50 min的水淬组织没有显著变化.

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.