Carbide Spheroidizing Mechanics During the Annealing of TwinRoll Casting HighSpeed Steel Strips

?The experimental study on castrolling of W9 highspeed steel strip was carried out by using the horizontal twinroll strip caster. The effects of the main processing parameters on the microstructure of the strips were investigated,and the optimal processing parameters were obtained. Microstructure and eutectic carbide morphology of the strip in the castrolled state and subsequent annealled were examined. The microstructure of the strip in the castrolled state is mainly consiste of martensite, residual austenite and eutectic carbide. Fish bone ledeburite does not exist in the strip and the amount of residual austenite is just 10 per cent. The microstructure of the strip in the subsequent annealled state is mostly composed of sorbite and eutectic carbide. Carbide spheroidizing mechanics denpends on the casting operation which improved dynamics condition of eutectic carbide spheroidizing. The twinroll strip casting results in carbide layer tablets finer and easier to be spheroidizied. And at the same time twin roll strip casting process is favorable to formation of M2C type carbide due to the rapid cooling of the process.