Parameter Optimization of Horizontal Direct Chill Casting Process for 6082 Aluminum Alloy Based on Finite Element Simulation

Abstract

Horizontal direct chill (HDC) casting technology has become a research hotspot in the field of aluminum alloy forming due to its continuous production characteristics, high safety and low cost advantages. As a key process parameter, casting speed significantly affects the solidification microstructure evolution and defect formation mechanism of ingot by adjusting the solidification thermodynamic conditions. In this study, the effects of casting speed (170 mm/min–250 mm/min) on the solidification behavior and microstructure properties of horizontally continuously cast 6082 aluminum alloy were systematically explored by combining numerical simulation and experimental verification. Based on the Ansys platform, a thermal-flow coupling model was constructed, and the temperature field distribution, cavity morphology evolution, billet shell thickness and liquid phase rate variation characteristics under different casting speeds were analyzed. Multiple control experiments were carried out to reveal the relationship between casting speed and microstructure, secondary phase distribution and mechanical properties. The results show that under the condition of low speed (180 mm/min), the thickness of the billet shell increases to 11.5 mm due to the slow advancement of the solidification interface, but the long melt residence time causes the cold insulation defect in the upper area (width 2.01 mm), and the proportion of coarse β-Al(Fe,Mn)Si phase at the bottom reaches 1.8%, which seriously affects the mechanical properties. When the velocity is increased to 210 mm/min, the melt shrinkage capacity and solidification rate form a dynamic equilibrium, the ingot presents a uniform equiaxed crystal structure (average grain size 108.9–117.8 µm), the second phase dispersion distribution (volume fraction 1.0%–1.1%), and the tensile strength is stable in the range of 248.3 MPa–267.2 MPa. When the speed is further increased to 240 mm/min, the intensification of coagulation shrinkage leads to a significant solute retention effect, and the coarsening of the bottom β-Fe phase (accounting for 1.8%), which induces a significant performance gradient of 48.1 MPa between the strength of the heart and the bottom.