起始铸造速度对AA7050合金半连续铸锭应力分布的影响

Effect of Start-up Casting Speed on Stress Field of AA7050 Aluminum Alloy Billets during Direct-Chill Casting

摘要:

通过温度场、流场和应力场的三场耦合，对某铝业公司AA7050铝合金铸锭在半连铸过程中3种不同起始铸造速度下的应力、应变分布进行了数值模拟研究。结果显示，铸锭心部呈现很大的三轴拉应力，表面则呈现明显的压应力。根据在糊状区环向和径向的应力、应变分量较大，而轴向应力、应变分量较小，可以预计热裂纹倾向平行于轴向分布，不太可能发生垂直于轴向的热裂纹。铸造时在起始铸造阶段有必要采用小的铸造速度，以降低糊状区的热应力、应变，减小开裂倾向。

Abstract:

The stress and strain fields of AA7050 aluminum alloy billets during direct-chilling (DC) casting process from an aluminum production company were simulated by directly coupling thermal, fluid and stress fields for three different start-up casting speeds. The results show that the center of the billet is subjected to large tri-axial tensile stress whereas the periphery demonstrates obvious compressive stress. According to the relatively higher circumferential and radial stress and strain combined with lower axial stress and strain in the mushy zone, it can be predicted that hot tears tend to propagate along the axial direction while hot tears perpendicular to axial direction are not likely to occur. It is necessary to apply a lower casting speed at start-up phase in the casting process to decrease thermal stress and strain in the mushy zone in order to reduce cracking tendency.