Research on process parameters of homogenised continuous casting for GCr15 bearing steel bloom

A solidification and heat transfer model was established to analyse quantitatively the influence of process parameters on solidification behaviour during bloom continuous casting (CC), and then the appropriate process parameters for homogenised CC were determined through systematically considering soft/heavy reduction (SR/HR), final electromagnetic stirring (F-EMS), shell thickness and temperature re-rising of secondary cooling zone (SCZ). Results indicate that solute element is prone to enrich towards the bloom's centre when liquid core is a slender conical shape. And casting speed needs to be controlled within 0.450 m/min < V < 0.478 m/min for making seven HR rollers be in liquid core reduction and the corresponding solidification rate of F-EMS is F S = 0.65∼0.69, namely, both key processes are in suitable operating ranges. Moreover, the shell thickness of mould outlet is about 13.51∼17.81 mm and the maximum re-rising temperature in the SCZ is 121°C, and consequently neither of them will affect the strand quality. Eventually, the appropriate control strategies of process parameters for homogenised CC are 0.46 m/min or 0.47 m/min in casting speed, superheat of 20∼30°C, 0.125 L/kg in water ratio and running one reduction rollers, and so corresponding solid fractions f s = 0.43∼1.0 (0.46 m/min) and f s = 0.41∼1.0 (0.47 m/min) in the SR/HR region are more reasonable. Finally, centre segregation was reduced from 1.18 to 1.09 in industrial production.