Development of an experimental system for the study of the effects of electromagnetic stirring on mold heat transfer
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I. INTRODUCTION
IN high-speed, continuous casting, while the importance of the application of mold–electromagnetic stirring (M-EMS) is re-emphasized for high productivity and good product quality, the behavior of mold heat transfer plays an important role in this application. Many studies have been done to investigate the benefits of M-EMS on the quality of steel billets in continuous casting, through improving the uniformity of shell solidification, enlarging equiaxed zones, and reducing centerline segregation and bridging.[1,2] However, very few studies[3,4] have been reported on the effects of M-EMS on thermal response and mold heat transfer in continuous casting of billets or slabs. In one of them,[4] the effect of M-EMS in billet molds was measured and an increase of the heat-transfer amount of the cooling water by 5 to 8 pct was reported. However, a more recent investigation[5] found that the application of M-EMS had decreased the mold heat transfer. These conflicting results show that the effect of M-EMS on the mold thermal behavior (mold heat flux and temperature) is not fully understood. Furthermore, no successful instrumented mold studies using embedded thermocouples have been conducted with M-EMS, since, under low-frequency M-EMS with high current, it is difficult to collect a real temperature signal due to strong electromagnetic interference. In this article, a specially designed heat flux sensor is adopted to measure the mold heat fluxes together with the mold temperatures. An on-line monitoring system is also developed to collect temperature and heat flux data of the continuous casting mold within a high electromagnetic field. To ensure the validity of the data measurement, a series of anti-interference methods have been taken including appropriate hardware suppression and software filtration. The analysis of the influence of electromagnetic current and frequency on the mold heat transfer (heat fluxes and temperatures) is also carried out. MAN YAO and DA-CHENG FANG, Professors, and HE-BI YIN, Graduate Student, Department of Materials Engineering, and JIN-CHENG WANG, Department of Automation, are with Dalian University of Technology, Dalian 116024, Liaoning Province, P.R. China. Contact e-mail: [email protected] or [email protected] XIAO LIU, YAN YU, Ph.D.s, and JUN-JIANG LIU, Senior Engineer, are with Shanghai Baosteel Co., Baoshan District, Shanghai 201900, P.R. China. Manuscript submitted September 21, 2004. METALLURGICAL AND MATERIALS TRANSACTIONS B
II. EXPERIMENT A. Caster The monitoring of heat flux was undertaken in a six-strand, curved caster machine installed with M-EMS. The diameter of a round billet is 178 mm. The magnetic flux density, B, mainly centralizes in the region of coil and iron core that produces magnetic field (Figure 1). B. Monitoring System In the cross sections of the six transverse faces of the mold and the six longitudinal faces, with an angle of 60 deg between any two of them, 36 monitoring points are designated (Figure 1). One specially designed heat flux sensor[6] is inst
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