An innovative method for calibrating local cooling rate in electroslag remelting of M42 high-speed steel

The determination of the local cooling rate has a great significance in optimizing the parameters of electroslag remelting (ESR) and improving the quality of the ingots. An innovative method was proposed for calibrating the local cooling rate of M42 high-speed steel (HSS) in the ESR process. After resolidification at different cooling rates under high-temperature laser confocal microscopy, the carbide network spacing of the specimen was observed using a scanning electron microscope. A functional relationship between the cooling rate and average carbide network spacing was established. The average local cooling rate of the solidification process of the M42 HSS ingot was calibrated. The results show that the higher the cooling rate, the smaller the network spacing of the carbides. For the steel ingot with a diameter of 360 mm, the average local cooling rate was 0.562 °C/s at the surface, 0.057 °C/s at the position of 0.25 D (where D is the diameter of the ingot), and 0.046 °C/s at the center of the ingot.