2A12铝合金拉杆非等温热挤压成形工艺优化

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

关键词:  铝合金  拉杆  缩径增厚工艺  非等温热挤压  成形质量

Key words:  aluminum alloy  pull rod  necking and thickening process  non-isothermal hot extrusion  forming quality

摘要:

为降低铝合金拉杆缩径增厚挤压成形的失稳起皱风险、提高拉杆生产效率,提出一种“夹具夹持管坯非变形区、仅预热模具、无需冷却管坯”的非等温热挤压成形工艺。首先,采用有限元仿真分析直径 65 mm、厚度5 mm、目标增厚比1.6的2A12铝合金拉杆非等温热挤压成形工艺,研究挤压工艺参数对拉杆成形质量的影响规律；其次,在仿真确定的较佳工艺参数下进行拉杆非等温热挤压成形实验,验证模拟的有效性。研究表明,仿真与实验结果高度吻合,非等温热挤压工艺不仅避免了管坯尾端屈曲变形,而且管坯首端沿挤压方向梯度递减的温度分布,有利于维持管坯非变形区材料强度,降低管坯首端失稳起皱风险。在摩擦系数0.05～0.3、挤压速度1.6～7.6 mm/s、模具温度410～470 ℃的参数范围内,摩擦系数对拉杆成形质量影响显著,而挤压速度和模具温度影响较小。不过,这3类参数对拉杆增厚区壁厚均匀性均无显著影响。随着摩擦系数减小,拉杆失稳起皱风险降低,增厚区壁厚增加,最大壁厚增幅可达56.5%。研究成果为提高铝合金拉杆挤压成形质量提供了一种新思路。

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.