Optimization of non-isothermal hot extrusion process for 2A12 aluminum alloy pull rod

Abstract:

To reduce the risk of instability and wrinkling in the reducing and thickening extrusion process for aluminum alloy pull rod, and improve the production efficiency of the pull rod, a non-isothermal hot extrusion forming process was proposed, in which the fixture clamps the non-deformation zone of the tube blank, with only the extrusion die preheated and no cooling required for the tube blank. Firstly, the non-isothermal hot extrusion forming process of 2A12 aluminum alloy pull rod with diameter of  65 mm, thickness of 5 mm and target thickening ratio of 1.6 was analyzed based on finite element simulation, and then the effects of extrusion process parameters on forming quality were investigated. Secondly, under the optimized process parameters determined by simulation, the non-isothermal hot extrusion experiment of the pull rod was conducted, validating the effectiveness of the numerical simulation. The study demonstrated excellent agreement between simulation results and experimental data. The non-isothermal hot extrusion process eliminated bending deformation at the tube ends. Furthermore, the gradient-decreasing temperature distribution at the leading end of the tube along the extrusion direction helped maintain the material strength in the non-deformation zone, thereby reducing the risk of instability and wrinkling. Under the extrusion process parameters of friction coefficient of 0.05~0.3, extrusion speed of 1.6~7.6 mm/s and die temperature of 410~470 ℃, the friction coefficient exhibited a significant influence on the forming quality of the pull rod, while the extrusion speed and die temperature had relatively minor effects. However, none of these parameters showed a notable impact on the wall thickness uniformity in the thickened zone of the pull rod. As the friction coefficient decreased, the risk of wrinkling of the pull rod decreased, and the wall thickness of the thickened zone increased with a maximum increase of 56.5%. The findings of the study offer an innovative methodology for enhancing the extrusion forming quality of aluminum alloy pull rod.