A Continuous Casting Device with Electromagnetic Stirring for Production of SSM Feedstock Using Al-Si Alloys

Abstract

This work describes the design, construction and testing of a continuous casting device coupled to an electromagnetic stirring system for the production of thixoforming feedstock using Al-Si alloys. The following processing and construction parameters were tested: pouring temperature (660-800 °C), mould cavity roughness (Ra = 0.17-1.06 µm), casting speed (2-4 mm/s), use of a combined (primary and secondary) cooling system and the intensity and radial penetration of electromagnetic stirring (0, 1500 and 3000 W stator power). The macro-appearance of the ingots and the longitudinal and radial microstructural parameters were then evaluated. The results indicate that the surface finish of the mould cavity was an important construction parameter as it had a strong influence on heat transfer and, consequently, feed speed; use of a secondary cooling system for the mould allowed greater grain refinement and microstructural homogeneity to be achieved for all the conditions tested; optimal electromagnetic stirring power was 1500 W (EMF max = 22 Gauss); this resulted in a grain size-todendritic arm spacing ratio of close to 1, which is suitable for subsequent SSM processing.

Distribution and Morphology of α-Al, Si and Fe-Rich Phases in Al–Si–Fe Alloys under an Electromagnetic Field

“…Flemings [4] discovered metallic alloys with special rheological properties caused by the formation of a non-dendritic structure in the semisolid state, e.g., in aluminum alloys, which leads to a transformation of the dendritic phase into the α-Al phase, shaped as rosettes or spheroids (globular) [5]. Non-dendritic structures exhibit rheological properties [6] that improve the mechanical properties of composites [7] and alloys [8], thereby allowing for the production of advanced engineering parts [9] in rheocasting [10], thixowelding [11], semisolid metal processing (SSM) [12,13], thixoforming [14], through the use of cooling slopes [15], by magnetohydrodynamics (MHD) [16] or simply by mechanical stirring [17]. Melt flow induced by rotating magnetic fields (RMF) in a technology called electromagnetic stirring (EMS) [18,19], transforms the microstructure [20] and improves the properties of billets [21].…”

“…Two main motivations spurred the current study. Firstly, due to the continuous development of forced-flow manufacturing technologies [5][6][7][8][9][10][11][12][13][14][16][17][18][19][20][21][22][23][24], the modification of the microstructure was investigated on the whole sample and in detail on individual Cylindrical samples were solidified with and without an induced rotating magnetic field (RMF) during the controlled slow cooling in insulated crucibles. Microstructures from optical metallography were measured using the ImageJ 1.51a software.…”

Morphology and Distribution of α-Al and Mn-rich Phases in Al-Si-Mn Alloys under an Electromagnetic Stirring

“…Started together with studies by Flemings on non-dendritic structures [4] with special rheological properties [5] developments allows: casting production with higher mechanical properties [6], semisolid metal processing (SSM) [7], by magnetohydrodynamics (MHD) [8] and by high shear melt conditioning (HSMC) [9]. In a technology called electromagnetic stirring (EMS) [10], flow of liquid driven by rotating magnetic fields (RMF) modify the alloys microstructure [11] and increases the properties.…”

“…Induced by forced convection, the whole microstructure and individual phases modification or separation was investigated, in aspect of the development in forced-flow technologies [5][6][7][8][9][10][11].…”

Effect of Rotating Magnetic Field on Microstructure in AlCuSi Alloys

“…In the presence of intensive melt stirring, non-dendritic structures may occur, with the primary α-Al phase shaped as spheroids (globular) or rosettes [5]. Non-dendritic structures exhibit rheological properties [6] improving the mechanical properties of alloys [7] and composites [8], making semisolid metal processing (SSM) [9], thixoforming [10], rheocasting [11] and thixowelding [12] unique for the production of advanced engineering parts [13]. Semisolid slurries [14] with globular solid particles may be produced by magnetohydrodynamic (MHD) [15] or mechanical stirring [16].…”