Research On Electromagnetic Semi-continuous Casting Of 7050 Aluminium Alloy Slab

7050 and 7055 aluminium alloy which have high strength and high toughness are used as principal structural materials in carrier rocket,space vehicle and space base industry et al.So the researches and application of 7050 and 7055 aluminium alloy are atteached more attentions.Because of high element content of 7050 and 7055 aluminium alloy,cracks and element segregation exist in conventional semi-continuous casting,which badly affect the yield and mechanical properties.In recent years,special technics are used such as powder metallurgy,adding minor element Ag,Mg and Zr,and new technics are applied such as high intensity spraying deposit and hot extrusion to produce higher element content,higher strength and higher toughness aluminium alloy which always increase the cost.In this thesis,according to the cracks and element segregation defects,effects of current intensity and electromagnetic frequency on magnetic distribution of electromagnetic coil of one circle,five circles and one hundred circles are tested.Static pouring experiments are done to investigate the effects of electromagnetic parameters on solidification structure and element distribution of 7050 and 7055 aluminium alloy.The result shows that the average grain sizes are refined obviously and element segregation are restrained effectively with electromagnetic field.Electromagnetic frequency has a great effect on the shaping property of the melt.The height of meniscus increases with the electromagnetic frequency enhances.By increasing the circles of electromagnetic coil,the current intensity can be reduced and the intensity of electromagnetic field can be enhanced to increase the electromagnetic stirring force and constraining force.Effects of casting parameters such as casting speed,casting temperature,cooling water intensity,element content and casting liquid level on the quality of semi-continuous casting of 7050 aluminium alloy slab are studied.Electromagnetic semi-continuous casting technics are explored to get high quality 7050 aluminium alloy slabs.The result shows that,when the current intensity is 2500A,electromagnetic frequency is 1700Hz,casting speed is 85 mm/min, casting temperature is 710℃,cooling water intensity is 3 m~3/h and casting liquid level is in the half height of the graphite mould,7050 aluminium alloy slab whose size is 420mm×130mm×1000mm is cast successfully.The casting defects such as crack,element segregation,cold shut,remelt and surface segregation knots are restrained effectively by electromagnetic field.The average grain size is refined from 71.4μm to 62.9μm with the application of electromagnetic field.The tensile strength is increased by 15.6%and the elongation is improved by 76.8%compared to those without electromagnetic field.The action mechanism of electromagnetic field on semi-continuous casting of 7050 aluminiurn alloy slab is discussed.