Study On The Carbides In Cast Strip Of M2 High Speed Steel By Twin-roll Casting

The twin-roll continous casting is one of the newest technologies in the field of ferrous metallurgy and materials processing, it can not only refine grain of cast strip and improve the quality of cast strip, but also short the process and save the energy and reduce the cost, with the advantage of near net shape processing. It is the development trend of the thin sheet and strip steel production and one of the key technologies to make the iron and steel.The microstructure of the high speed steel (HSS) produced by the twin-roll caster in an industrial scale is analysized by means of optical microscopy, quantitative metallography, SEM and XRD. Through comparasion with the electroslag remelting ingot, the effects of the different conditions on solidification microstructure of HSS are studied. The results show that rapid solidification can not only refine the size and interval spacing of eutectic carbides improve their distribution, and inhibit the segregation of carbon and alloy elements,but also obtain more metastable phase M2C, which can benefit the subsequent treatment of M2 HSS strip.The effects of the different heat-treatments on the eutectic carbides in HSS cast strip are studied. The results show that the heat treatment can make M2C metastable phase decompose. Due to the fine eutectic carbides resulted from rapid solidification of the caster, the decomposition of M2C is easier and then after heat treatment, the eutectic carbides of HSS cast strip become finer and uniformer with the better distrubiton. The optimized heat treatment processing of HSS cast strip is at 1150℃for 40 min, under which the fine and uniform carbides can be obtained.Microstructure of M2 HSS strip after being hot rolled is investigated. The results show that heat-rolling can make the eutectic carbides particles decompose,but decompose not entirely; the optimized hot rolling processing of HSS cast strip is at 1150℃for 40 min ,which can produce the better microstruture comparasion with the conventional processing.