Research On Purification Process Of 5356 Aluminum Alloy Wire Blank Material

5356 aluminum alloy welding wire has excellent weldability and good processability.As a large amount and wide range of filler materials,it has been widely used in aerospace,national defense and military industry,rail vehicles,automobile industry and other fields.However,due to its high magnesium content,easy inhalation and oxidation in the preparation process,and high hydrogen content and slag content,it leads to poor welding processability and low weld performance in the welding process.At present,the conventional purification method is difficult to ensure the acquisition of aluminum alloy welding wire materials with low hydrogen content and slag content.Therefore,the purification treatment of 5356 aluminum alloy welding wire materials is of great significance and application value.In this paper,5356 aluminum alloy was prepared by melting casting+hot extrusion method.The effects of melting and casting process parameters,annealing process parameters and extrusion process parameters on the hydrogen content and slag content of 5356 aluminum alloy were studied.The melting and casting process,vacuum homogenization annealing process and extrusion process of 5356 aluminum alloy were optimized to prepare 5356 aluminum alloy wire blank with high purity;The mechanism of hydrogen and slag removal from 5356 aluminum alloy melt under vacuum melting and casting process was revealed.The main results of this paper are as follows:(1)The effect of melting and casting process on the hydrogen content of 5356 aluminum alloy was studied.The effects of non-vacuum melting and casting process and vacuum melting and casting process on the hydrogen content of 5356 aluminum alloy were compared and analyzed,and the vacuum melting and casting process parameters were optimized.The results show that compared with non-vacuum casting,the hydrogen content of melt during vacuum casting is lower.The hydrogen content of 5356 aluminum alloy during non-vacuum casting is 3.41?4.97 ml/100gAl,while the hydrogen content during vacuum casting is ?0.20 ml/100gAl.In the process of vacuum melting and casting,three parameters including vacuum degree,melt stirring and standing time have a great influence on the hydrogen content of aluminum alloy melt.The higher the vacuum degree,the longer the melt stirring time,the longer the melt static treatment time and the lower the hydrogen content of the melt.The optimized vacuum melting and casting process parameters are:vacuum degree 10-1 Pa,melt stirring time 15 min,melt standing time 20 min,and the hydrogen content of 5356 aluminum alloy ingot obtained is?0.10 ml/100gAl.(2)The effects of annealing process and extrusion process on the hydrogen content of 5356 aluminum alloy were studied.The effects of non-vacuum annealing and vacuum annealing process and extrusion process on the hydrogen content of 5356 aluminum alloy were compared and analyzed,and the vacuum annealing process parameters and extrusion process parameters were optimized.The results show that the hydrogen content of 5356 aluminum alloy ingot cast in vacuum reaches 0.14?0.16 ml/100gAl under non-vacuum annealing;When annealed in vacuum,the hydrogen content of 5356 aluminum alloy ingot cast in vacuum is?0.10 ml/100gAl.In the vacuum annealing state,the change of hydrogen content is not obvious with the increases of annealing temperature.In the process of hot extrusion,the hydrogen content in the billet increases with the increase of preheating time.The optimized vacuum annealing process parameters are as follows:annealing temperature 480?,holding time 10 h.The optimized extrusion process:the extrusion temperature of the blank is 500?,the blank is heated by induction,and the heating time is 0.3 h.(3)The effects of melting and casting process,annealing process and extrusion process on the slag content of 5356 aluminum alloy were studied.The results show that compared with non-vacuum melt purification,vacuum melt purification reduces the impurity phase content of large blocks from 6.11%to 0.44%,and the oxide inclusion content from 0.45%to 0.03%.Compared with non-vacuum annealing process,the surface of ingot after vacuum annealing is bright and reticular ? phase(Al8Mg5)dissolved and there were no obvious inclusions in the microstructure,and no obvious inclusions were found in the microstructure of extruded wire blank.(4)The mechanism of hydrogen and slag removal from 5356 aluminum alloy melt under vacuum melting and casting process is revealed from two aspects of kinetics and thermodynamics.From the perspective of thermodynamics,the partial pressure of hydrogen above the aluminum alloy melt is very low and approaches zero under vacuum environment.The differential pressure of hydrogen inside and outside the aluminum melt significantly increases the dehydrogenation tendency of the aluminum melt.From the perspective of dynamics,stirring melt under vacuum environment changes the dynamic conditions of hydrogen precipitation,improves the "effective nucleation rate" of bubbles,speeds up the diffusion coefficient and precipitation rate of hydrogen atoms,promotes the diffusion of hydrogen from pure diffusion precipitation to bubble precipitation,and significantly reduces the ultimate solubility of hydrogen.