Process Study On Electromagnetic Two-Roll Casting And Subsequent Heat Treatment Of Al-1.3%Mn And Al-1.8%Mn Alloy

Al-Mn alloys are widely used in auto industry and packaging industry because of its many advantages,such as good plasticity,corrosion resistance and weldability.3003 aluminum alloy is one of the most common Al-Mn alloys.The traditional method for producing 3003 alloy sheet has multiple processes,including hot rolling ingot,intermediate annealing,cold rolling and so on,which has high equipment investment,long process flow,massive energy consumption and heavy production cost.Combining roll casting with cold rolling for producing aluminum alloy sheet can reduce equipment investment,energy consumption and lower dramatically production cost.However,because of the specific trait of Al-Mn alloys and technological characteristics of roll casting,sheet by cold rolling and recrystallization annealing has coarse grain.In this paper,in order to produce 3003 aluminum alloy sheet having a uniform and small grain,electromagnetic field is applied in the process of traditional two-roll casting and homogenizing annealing is studied,at the same time for roll casting instead of hot rolling to provide certain experimental and theoretical foundation.Effects of electromagnetic field on the microstructure of 3003 roll casting sheet are discussed in this paper.Besides,designing six kinds of homogenizing annealing system,transformation law of micro segregation under the influence of different homogenizing annealing system is researched and effects of different homogenizing annealing system on recrystallized grain of 3003 cold rolling sheet are discussed.At the same time,according to the solidification of Al-Mn alloy and recrystallization characteristic,to design a high manganese content in aluminum alloy,effects of electromagnetic field and homogenizing annealing on Al-1.8%Mn alloy organization are studied.A series of conclusions are obtained as follows:(1)The microstructure of 3003 sheet produced by traditional roll-casting has large dendrite and severely dendritic segregation.Impressed electromagnetic field can effectively improve the microstructure.(2)Electromagnetic field would induce 3003 to appear sheet edge of segregation,and stronger the electromagnetic field intensity is,more obvious and farther from edge the segregation is.The severity of element enrichment of segregation zone is Fe>Si>Mn.Impressed electromagnetic field makes iron-bearing phase to sustain larger electromagnetic force and easily to form segregation of edge.(3)Homogenization annealing can eliminate dendrite segregation of 3003 roll-casting sheet in different extent,make supersaturated solid solution to dissolve out,induce excess phase to gather and grew up.One-step homogenizations effect is not as good as two-step homogenizations,600?×15h+500?×15h of which is best.Under same homogenization system,the homogenization effect of electromagnetic roll-casting plate is superior to the traditional roll-casting plate.(4)For roll casting 3003 sheet by industrial production,recrystallization grain of cold sheet by secondary heat treatment(600?×15h+500?×15h)is small,equiaxed.For 3003 sheet by electromagnetic two-roll casting,field current and pulse current of which is respectively 250A and 200A,recrystallization grain of cold rolled sheet by secondary heat treatment(600?×15h+500?×15h)is also small,equiaxed,of small grain size gradient.(5)Al-1.8%Mn sheet microstructure by conventional roll casting includes bulky dendrite network and developed dendrite wall.Electromagnetic field can effectively reduce bulky dendrite network and refine the grain,and stronger the electromagnetic field intensity is,more remarkable the improving effect is.(6)For Al-1.8%Mn cast-rolling sheet,the precipitated phases of sample by different homogenization have differences in number,morphology and distribution.The precipitated phases of sample by the two-step homogenization(600?+500?)are dispersively distributed sphere,short rod,block and small particle;with the extension of time,Al6(MnFe)becomes gradually ?-Al(MnFe)Si phase.(7)For Al-1.8%Mn cold-rolled sheet,recrystallization organization of sample by two-step homogenization is coarse,long and narrow grain;recrystallization organization of sample by one-step homogenization is refined in some extent,but grain sizes isn't uniform and has large gradient.Six kinds of homogenization system didn't obtain good effect.