Al-7Zn-3Mg直冷铸坯对刮水器的热力响应研究

Thermal-mechanical Response of Al-7Zn-3Mg Direct Chill Ingot to a Wiper

建立了工业熔铸Al-7Zn-3Mg变形铝合金扁锭的三维数值模型。模拟研究了刮水器安装位置对铸坯热场和应力场的影响,并应用Clyne-Davies热裂模型计算和评估了铸坯的热裂敏感性。结果表明,刮水器置于结晶结束面底部附近时,其对宏观偏析和热裂倾向的影响很小;当刮水器上移至液穴底部附近时,铸坯的宏观偏析和热裂倾向显著提高。为了抑制宏观偏析和热裂,应将刮水器置于液穴底部以下约10cm处。与此相反,铸坯热应力随刮水器安装位置的上升而降低。另外,还研究了一种新型的阶梯形刮水器。结果表明,与传统的平面刮水器相比,在不导致宏观偏析和热裂倾向的前提下,铸坯的最大主应力下降了4.5MPa。

A 3DFEM model of Al-7Zn-3Mg wrought aluminum alloy slab ingot with 450mm×1 620mm was established. Both thermal and stress fields of a slab billet were obtained via simulating casting conditions without wiper and with various wiper inserting positions,and the Clyne-Davies hot cracking model was used to calculate and evaluate the HCS(hot cracking susceptibility)of the ingots.The results reveal that the wiper has a little effect on both macrosegregation and HCSwhen it is placed at a height near the bottom of the solidifying end.The macrosegregation and HCSare increased greatly with the wiper setting position increases.When the wiper is inserted near the bottom of the sump,the macrosegregation and HCSof the billet are increased significantly.In order to suppress macrosegregation and hot cracking,it is suggested to insert the wiper at about 10cm below the bottom of the sump.In contrast,the thermal stress of the ingot is decreased with the wiper setting position increases.In addition,the effect of an innovative stepwise wiper has also been analyzed.The results show that the new wiper can decrease the thermal stress by 4.5MPa of the ingot than the conventional flat one and without negative effect on both macrosegregation and hot cracking tendency.