Study On The Melt Purification And Structure And Properties Of Semi-continuous Casting Process Of 6063 Recycled Aluminum Alloy

Recycled aluminum alloy not only has the same characteristics as primary aluminum,such as low density,corrosion resistance,good thermal conductivity,electrical conductivity and good ductility.In practical application,it can also save resources,reduce the emission of solid waste and polluting gas and reduce the cost.Therefore,it is of great significance to develop recycled aluminum industry.Recycled aluminum is the main raw material of aluminum alloy profiles.Usually semi-continuous casting is used to prepare hot extruded billet.Due to the fast cooling rate and high casting speed of semi-continuous casting,impurities(gas,inclusions,etc.)in recycled aluminum have a significant effect on ingot performance,and the quality(strength,plasticity,etc.)of liquid aluminum must be improved by refining.In this paper,the purification process of 6063 recycled aluminum alloy was optimized,and the effect of flux content on the microstructure and properties of semi-continuous casting ingot was studied.firstly,the gas content,microstructure and properties of 6063 recycled aluminum alloy with different flux contents(0 wt.%,0.2 wt.%,0.3 wt.%,0.4 wt.%,0.5 wt.% and0.6 wt.%)were studied by experiments.The results show that with the increase of flux content,the melt purification effect increases first and then decreases.When the flux content is 0.4 wt.%,the degassing efficiency is the highest,which is 25.6%.The inclusions and hydrogen in the melt are significantly reduced,and the strength and plasticity of the alloy are significantly improved.Secondly,the effects of different refining temperatures(730?,740?,750?and 760?)on the gas content,microstructure and properties of the castings were studied.With the increase of refining temperature,the fluidity of the melt increases,and the wettability of slag and aluminum melt decreases,which is beneficial to improve the purification effect.At the same time,hydrogen absorption and oxidation of aluminum melt increased.The best purification effect is obtained at 740?750?,and the mechanical properties of the material are also good.Finally,the recycled 6063 aluminum alloy melt was refined at 750? by semi-continuous casting with different flux contents(0.16 wt.% and 0.20 wt.%),and the microstructure and properties of the ingots were analyzed.The results show that the microstructure and properties of ingot are different with different flux contents in length direction,the number of porosity and holes at both ends of ingot is obviously higher than that in the middle,and the mechanical properties are lower.When the flux content is higher(0.20 wt.%),the porosity and holes in the whole length direction of the ingot(both ends and middle)are reduced and the performance is better.Radially(from center to surface),the casting strength decreases gradually,but the elongation increases first and then decreases.The grain size decreases from the center to the surface in the radial direction,and more ?-Fe phase and higher alloying element content(reverse segregation)and pores are found at the surface edges.This is mainly due to the uneven cooling rate in the radial direction of semi-continuous casting and the solidification shrinkage of the casting.When the flux content is higher(0.2wt.%),the surface segregation(reverse segregation)of ingot is more obvious,but the content of gas and inclusions is less,and the performance is better.