Study On The Recycling Of Valuable Metals In Waste Magnesium Alloys By Vacuum Sublimation

So far,the magnesium alloy is the lightest metal structure material on engineering application,which is not only behaving many excellent physical properties including low density,high specific strength and stiffness,damping and noise reduction capability good,but also is recyclable.So the Mg alloy is lower harmful to environmental,and it is known as the "21st century green engineering materials".However its application is limited by one reason of the magnesium alloy products qualified ratio is lower,the recycling cost for waste magnesium alloy is higher,and produce more waste residue or smelting loss during traditional melting method.Moreover when its melting in high temperature,it not only need adding expensive refining agent/covering agent,wasting a great deal of manpower and material resources,but also pollute the environment.Recycling waste magnesium alloys as a core link in magnesium dustry,its status is very import to the development of environmental protection and efficient waste magnesium alloy recovery technology.In this article,the vacuum sublimation-desublimation method has been used to refine industrial crude magnesium firstly.According to vacuum sublimation-desublimation theory analysis,discussed the effects of the refining process,from theoretical to experimental,and find out the optimum process conditions of the experiment:vacuum 1?10Pa,sublimation source and a condensation plate distance 16.4cm,constant temperature to 650?,insulation time depending on the weight of primary magnesium.By the theory,we have calculated condensation cylindrical crystal size of a disc of radius 1.41cm,while the existing condensation cylindrical crystal disc radius 2.5cm,taking into account the vacuum tank wall radius of 3.9 cm,we believe that the crystallization plate size is reasonable.On the basis of the above research,this paper also studied the vacuum sublimation-desublimation method,depending on the size of the saturated vapor pressure and the waste magnesium alloy AZ91D have valence metal aluminum,magnesium and zinc were isolated and make the AZ91D magnesium alloy has valence metal recycled.Using the theory of separation factor criterion in the analysis of the scrap magnesium alloy AZ91D in the Zn-Mg,Al-Mg,Cu-Mg,Ni-Mg,Mn-Mg,Fe-Mg,Si-Mg separation feasibility.In addition,we design a two factors five levels orthogonal experiment L25(52)to find out the influence degree of temperature and time.The results show that the temperature affects greater than the time,so the temperature occupies dominant position.In order to find the best process conditions,we also explored the influence of distance between the sublimation source and the condensation crystallization disc on the test.To summary,the optimization control factor is the constant temperature is 700? and constant temperature was positively correlated with the amount of material for the recovery waste magnesium alloy material,and the best distance of the sublimation source and the condensation crystal is 11.4cm.The results showed that the purity of magnesium on crystalline plate reached about 99%,and the zinc content is about 1%;the magnesium purity on water jacket of the crystallization is 94%,and the zinc content is nearly 6%,low content of other elements can be ignored.The purity of the detected aluminum was 82.1%by inductively coupled plasma(ICP)analysis.