In the present work, solidification structure and centre segregation in continuously cast bearing steel GCr15 blooms with 220mm×260 mm were obtained by different casting conditions (M-EMS, M + F-EMS, M + F-EMS + MSR), which were systematically optimized by numerical simulation and experiments. The relationship between centre segregation in continuously cast GCr15 bloom, heredity in hot-rolled steel and carbide inhomogeneity of hot-rolled steel with was investigated comprehensively. Results showed that compared with M-EMS, centre carbon segregation ratio in the bloom decreased from 1.1∼1.4 to 1.04∼1.22 by M + F-EMS, and could be reduced to 0.96∼1.08 by MSR in combination with M + F-EMS. Moreover, centre segregation in hot-rolled steel decreased with the decrease of centre segregation in bloom. Grade of network and banded carbide in hotrolled steel decreased accordingly, especially for centre carbon segregation ratio with 0.96∼1.08, grade of network and banded carbide could be significantly reduced to 1. It was important to control centre segregation in as-cast steel to improve the resulting carbide homogeneity of asrolled steel. According to the experimental results, higher casting speed in bloom with M + F-EMS and MSR integrated process was preferred to effectively reduce centre segregation ratio and further decreased the occurrence of network and banded carbide in as-rolled bearing steel GC15.
In this paper, an electromagnetic torque device based on the theoretical model was established to determine the optimum frequency accurately and conveniently in billet and bloom continuous casting with in-mould electromagnetic stirring (M-EMS). Magnetic characteristics with M-EMS was investigated by numerical simulation and physical experiment with the application of electromagnetic torque device and gauss meter. In addition, the effects of stirring frequency with M-EMS on macro segregation and equiaxed crystal ratio were compared and analysed for 55SiCr with 150 mm × 150 mm billet caster and BU with 310 × 360 mm bloom caster by a series of plant trials, respectively. The results showed that maximum magnetic flux density and maximum electromagnetic torque occurred with different frequency and same current in M-EMS, and central equiaxed crystal ratio and macro segregation has been significantly improved by optimum frequency with M-EMS.
The optimal combination of current intensity and frequency of mould electromagnetic stirring (M-EMS) in continuous casting billet was a crucial compromise for improving inner quality of cast billet such as reduction in center segregation and porosity of medium-high carbon steel. In the present study, a decoupled three-dimensional mathematic model of electromagnetic field, fluid flow and heat transfer in continue casting billet mould with EMS has been developed, and the effects of current intensity and frequency on the system were also discussed. In addition, the industrial trials were carried out to investigate the magnetic field characteristics in the mould with M-EMS and the influence of M-EMS on the solidification structure of 55SiCr. According to the calculations and analysis, the optimal combination range of current intensity and frequency was 300–320 A and 3–4 Hz, respectively. The results showed that inner quality in as-cast billet of 55SiCr has been improved significantly with optimal parameter of 320 A and 3 Hz. For instance, central equiaxed zone increased from 19% to 33%, the center carbon segregation ratio decreased from 1.13 to 1.05 as well as center porosity has nearly disappeared.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.