Study on heat transfer behavior and process optimization in differential phase electromagnetic DC casting of extra-large AZ31B alloy flat ingot: numerical simulation and experimental verification

Abstract

Based on the heat transfer analysis in the primary cooling region of large-size magnesium alloy flat ingot Direct-chill (DC) casting, a novel crystallizer structure for flat ingot electromagnetic DC casting was put forward, in which the primary cooling can be controlled independently from the secondary cooling, and the circumferential control of the primary cooling can be realized synchronously. The design and optimization of the inner sleeve material and thickness and the distribution of the primary cooling were also carried out. For the AZ31B flat ingot with a cross-section size of 1200 × 400 mm, the copper inner sleeve material was selected, and it is beneficial to control temperature gradient and mushy zone shape in flat ingot DC casting. A uniform temperature distribution can be obtained when the cooling intensity ratio of the wide and narrow faces is 1:1/3. Furthermore, the influence of casting process parameters on the mushy zone characteristic of 1200 × 400 mm flat ingot was studied by orthogonal planning of process parameters and numerical simulation methods. Simultaneously, the casting process parameters of other flat ingot sizes were determined, and AZ31B alloy DC casting flat ingots with section sizes of 750 × 440 mm, 1200 × 400 mm, and 1600 × 400 mm under industrial conditions were carried out, and the crack-free preparation of the above billets was successfully achieved.