7005铝合金挤压管材开裂原因

Cause analysis of cracking of 7005 aluminum alloy extruded pipe

外径Φ180 mm、内径Φ60 mm的7005-T6铝合金管材在某公司机加工过程中,发现管材横截面沿径向出现多处裂纹。对裂纹处进行宏观组织、显微组织以及化学成分分析结果表明:裂纹是由于铸锭内部冷却不均匀而产生极大的应力不平衡,形成收缩应力,此应力如集中到铸锭的一些薄弱处,并超过了金属的强度或塑性极限而造成的,该裂纹为铸造裂纹。提出了预防铸造裂纹的措施。

In the machining process of 7005-T6 aluminum alloy pipes( OD = 180 mm and ID = 60 mm) in a company,many cracks were found in the cross section of pipes along the radial direction. The macrostructure,microstructure and chemical composition of cracks were analyzed. The analysis results show that the cooling unevenness in the ingot leads to a great imbalance of stress,and after that results in formation of shrinkage stress. The crack is a casting crack if the stress is concentrated at some weak spots in the ingot and exceeds the strength or plasticity limit of the metal. The measures to prevent casting crack are put forward.