Improving the Solidified Structure by Optimization of Coil Configuration in Pulsed Magneto-Oscillation

Abstract

Using both numerical and experimental methods, we studied the effect of coil configuration of pulsed magneto-oscillation (PMO) on distribution of electromagnetic field, flow field and solidification structure with the same pulse current parameters in Al ingots. We designed and constructed three types of coils: surface pulsed magneto-oscillation, hot-top pulsed magneto-oscillation (HPMO) and combined pulsed magneto-oscillation (CPMO). PMO treatment refined the solidification structure in all the ingots. The configuration of the PMO, however, introduced differences in magnetic field intensity, electromagnetic force, Joule heat, flow field, equiaxed grain zone, grain size and growth direction of columnar grains. The largest equiaxed grain zone was found in CPMO treated ingot, and the smallest grain size was found in both HPMO and CPMO treated ingots. Numerical simulation indicated that difference in electromagnetic field and flow field resulted in differences in solidification structure. HPMO is more advantageous over others for large ingot production.

Effect of Coil Configuration Design on Al Solidified Structure Refinement

“…We believe this difference has marginal impact on the simulated results. The current profile in the coil was similar to what we used before [27] ( Figure A1 in Appendix A). The relationship between the current and time was described as:…”

“…One parameter was the coil configuration. We modified SPMO [27] by SPMO-H (the coil was put on the top) and CPMO [27] by CPMO-H (the coil was put on and around the hot-top) ( Figure 1). We also changed the distance between the coil and melt surface.…”

“…Specimens were mechanically polished by vibration polisher (VibroMet2, Buehler, IL, American) for 3 h and then electronically polished with a mixture of distilled water and fluorotic acid at 0.3-0.5 A/cm 2 for 20-40 s. The microstructure of etched samples was examined in a Zeiss optical microscope (Axio Imager A2m, ZEISS, Oberkochen, Germany). The procedure for this experiment was the same as reported before [27]. The current profile in the coil was similar to what we used before [27] ( Figure A1 in Appendix A).…”

“…Refinement effect was better with higher peak current and lower frequency [19,[21][22][23][24][25][26]. PMO treatment shows great promise in the production of heavy steel ingots on an industrial scale [27].…”

“…We have previously studied the effect of PMO coil configuration on the distribution of electromagnetic field, flow field, and solidification structure [27]. In this study, we expanded our studies from three to five configurations with SPMO (plate coil on the top of mold), SPMO-H (ring coil on the top of mold), CPMO (plate coil on and around hot-top) and CPMO-H (ring coil on and around hot-top) included.…”