| 6xxx series aluminum alloy is a heat-treated strengthened aluminum alloy with appropriate strength,excellent formability and processability,and good corrosion resistance.In the economic development trend of low carbon and environmental protection,it is considered to be a good exterior Plate with aluminum alloy material.Twin-roller casting and rolling technology is a typical short process,high yield,low-carbon environmental protection,energy-saving and efficient process technology.It is the choice of the most quality and cost advantages for the production of 6xxx series aluminum alloy automotive sheet.However,one of the main problems of this technology is that when producing alloys with high alloy grades and wide solidification intervals,it is easy to form a macrosegregation zone near the centerline of the plate,which significantly reduces the quality of the plate,so it limits the production of high-quality aluminum by this technology and widely using in the field of alloy plate and strip.Based on the traditional cast-rolled 6016 aluminum alloy sheet,this paper uses Ansys simulation and experimentation to study the influence by applying a single pulse current field,a single DC magnetic field,and a composite field(combined field of pulse current field and DC magnetic field),that physical field on the morphology,velocity field,electromagnetic force distribution,microstructure,and mechanical properties of cast-rolled aluminum alloys,revealing the mechanism of mitigating segregation defects under different process conditions,and exploring the best process technology solutions to reduce 6016 Segregation defects of aluminum alloy casting and rolling provide a certain theoretical basis for improving the subsequent processing performance of aluminum casting and rolling sheet.The main conclusions are as follows:(1)In the simulation of aluminum alloy casting and rolling,as the pouring temperature increases,the liquid cavity becomes deeper,the kiss point moves toward the exit of the casting and rolling zone,and the speed of the two-phase zone also increases with the increase of the pouring temperature;In the composite field,the electromagnetic force is distributed across the entire central symmetry plane,and the electromagnetic force at the upper and lower boundaries is the largest.The maximum electromagnetic force generated by the 20 Hz-15%-400 A+300 A composite electromagnetic field can reach 10.5 N/m3.(2)The structure distribution of traditional cast-rolled sheet is uneven,and the center segregation is serious.After applying a pulse current field of a certain current intensity or frequency,the shock wave effect and pinch effect of the pulse current can reduce the temperature gradient of the melt,eliminate the condition of dendrite growth,increase the nucleation rate of the melt,and reduce the solute cluster bias.Aggregation,promote the refinement of microstructure,and effectively reduce the segregation defects of the macro center of the castrolled alloy.(3)Comparing with traditional casting and rolling,the influence of DC magnetic field with different current strength on microstructure is different.When the current intensity is 100A and below,there is no significant change;with the increase of the current intensity,the microstructure and macro hardness of the cast and rolled plate are significantly improved,and the macrosegregation defects are also reduced to a certain extent.(4)The addition of a composite electromagnetic field during the casting and rolling process can generate electromagnetic oscillations in the melt,reduce the temperature gradient inside the melt,eliminate dendrite growth conditions,increase the nucleation rate,and improve segregation defects.The greater the strength of the magnetic field current,the stronger the ability of the composite electromagnetic field to improve segregation,the more uniform the microstructure of the cast-rolled specimen,and the better the macro hardness.Different pulse current frequencies have different effects on improving segregation.(5)Comparing the microstructure and properties of cast-rolled specimens under different external physical fields,it is found that the application of external fields can optimize the structure to different degrees and improve segregation defects.The single DC magnetic field and pulse current field cast-rolled specimens are better than the traditional cast-rolled specimens,while the composite electromagnetic field cast-rolled specimens have better performance than the single electromagnetic field cast-rolled specimens,showing more obvious advantages.(6)The optimal process plan for this experiment is that:on the basis of casting and rolling conditions such as roll diameter of 500 mm,width of 500 mm,casting and rolling slab thickness of 5 mm,pouring temperature of 690? and rolling speed of 1.2 m/min.A composite electromagnetic field in which a pulsed current field with a frequency of 20 Hz,a duty cycle of 15%,and a peak current of 400 A is coupled to a direct current magnetic field of 300 A. |
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