气滑半连铸6061铝合金铸锭热裂产生原因分析

Hot Crack Analysis of 6061 Aluminum Alloy Ingot by Air-slip Semi-continuous Casting

采用气滑半连铸方法制备了φ254 mm的6061铝合金圆铸锭。利用光学显微镜、扫描电镜、万能试验机等手段研究了铸锭的合金成分、微观结构与力学性能等,并结合相图计算,分析了铸锭中心热裂产生的原因。结果表明,较高的Si含量使得铸锭中心晶粒粗大的同时聚集大量针状β-Al_(5)FeSi相,这会降低铸锭中心区域伸长率并造成局部应力集中,从而引起铸锭中心热裂。综上分析,建议在该规格6061铸锭气滑半连铸时,控制过剩的Si含量,以减少铸锭热裂的发生。

6061 aluminum alloy ingots with the diameter of φ254 mm were fabricated by air-slip semi-continuous casting.The composition,microstructure and mechanical properties of ingots were characterized by optical microscopy(OM),scanning electron microscopy(SEM),universal stretching machine,and the origination of hot crack was analyzed combined with phase diagram calculation software.The results indicate that the higher Si content contributes to coarser grain and aggregation of large amounts of β-Al_(5)FeSi phases in the center of the ingot,resulting in the poor elongation and local stress concentration,leading to hot crack.In conclusion,it is recommended that excess Si amount should be controlled during the semi-continuous casting to reduce the occurrence of hot crack.