航空用高品质7050铝合金大规格扁锭熔铸技术研究

Research on Smelting and Casting Technology of High-Quality 7050 Aluminum Alloy Large-Sized Slab for Aerospace Applications

7050铝合金具有密度低、强度高、热加工性能优异等优点,在航空航天结构件上应用广泛。但在7050铝合金大规格铸锭半连续铸造过程中,存在热裂、成形困难、严重显微疏松和氧化夹杂等问题。本研究开发了大规格扁锭半连续铸造过程中合金熔体冶金质量控制技术,系统考察了精炼工艺、晶粒细化技术对大规格扁锭品质的影响规律,确定了大规格扁锭铸造工艺。结果表明,优化工艺制度能严控熔体内氢和夹杂物含量,采用Al-Ti-C晶粒细化工艺制度将晶粒度控制在1~1.5级,高质量的熔体质量缓解了合金凝固收缩应变,极高比例地解决了扁锭开裂问题。最终,形成了一套适用于大规格7050合金扁锭的熔铸工艺制度。

7050 aluminum alloy is widely used in aerospace structural parts because of its low density,high strength and excellent thermal processing performance.However,the problems of hot tearing,difficult forming,severe microporosities and oxidation inclusions within slabs have been existed in the semi-continuous direct-chill casting(DC)process of large-sized 7050 aluminum alloy slabs.In this study,the metallurgical quality control technology of alloy melt in the DC casting process of large-sized slabs was investigated,and the influence of melt refining process and grain refinement technologies on the quality of large-sized slabs were systematically explored,and the casting process of large-sized slab was also confirmed.The results show that,applying the optimized processes,the hydrogen and inclusion contents of the melt can be strictly controlled,and the grain sizes can be controlled at 1-1.5 grades when the grain refinement process with Al-Ti-C refiner was used for the alloy.High-quality melt alleviated the solidification shrinkage strain of the alloy,which solved the hot tearing behaviors of the cast slab ingots in a large proportion.Finally,a set of melting and casting process suitable for large-sized 7050 alloy slab ingot had been established.