Research Of Edge Crack Characteristic On High Magnesium Aluminum Alloy Plate Rolling Process

5083 aluminum alloy is representative among deformable aluminum alloy which has been widely used in industrial equipment.This series alloy is used for all kinds of forming process,and has been widely adopted in vehicles,ships and other transportation industry on account of the excellent mechanical performance and machining performance.The edge crack in the rolling process of high magnesium aluminum sheets has been one of the main problems that restrict the product quality.In this paper,tests were performed to study the rolling process of 5083 aluminum alloy by combining thermal physical simulation,numerical simulation and rolling experiment.The hot compressive deformation behavior of as-cast 5083 aluminum alloy was studied by hot compression test in the range of temperature 250~450 ? and strain rates of 0.002~10s-1onGleeble-1500 thermal-mechanical simulator.Meanwhile the constitutive equation (?) and processing map were established.The above points provide the basis for rolling process parameters of 5083 aluminum alloy.In order to obtain the fracture threshold value C,the temperature of tensile deformation test was 25 ?,100 ?,200 ?,and the strain rate was 0.1 s-1,1 s-1,10 s-1,respectively.The as-cast 5083 aluminum alloy was simulated by Deform-3D finite element software,and the rolling crack initiation conditions of the alloy were predicted with rolling experiment validation.The errors between simulation and experiment results are within 5%.The rolling deformation,rolling pass,annealing temperature and the content of magnesium in alloy,as variables,were studied by rolling experiment in the rolling mill.The results showed that the length of rolling crack increases from 0.12 mm to 0.95 mm with the increase of rolling deformation from 49% to 75%.At the rolling deformation of 80%,the length of crack initiation of 5083 aluminum alloy is 0.97 mm after first pass of rolling,while it is 0.69 mm after five passes.The aluminum alloy plate with a rolling deformation of 40% was annealed at 150 ?,200 ?,250 ?,300 ?,350 ?,then there's another rolling deformation of 40%.The length of crack at 150 ?and300 ? are 1.96 mm and 0.4 mm,respectively.When temperature reaches 300 ?,the length of plate rolling crack no longer changes.Under the same rolling conditions,rolling crack length increases exponentially with the increase of magnesium content in the alloy.The equation of crack length with the change of magnesium content is y=0.00057x6.57 in rolling deformation of 60%.According to the parameters of the numerical model simulation and rolling experiments,the coefficient of friction and the roll diameter size,as the parameters in rolling experiments,were simulated.The change of the crack length,effective strain,effective strain rate and rolling force of rolling experiments were carried out at the conditions of different friction coefficients(0.3,0.4,0.5)and different roll diameters(150 mm,180 mm,240 mm).The results showed that under the same rolling conditions,the crack length decreases with the decrease of friction coefficient from 0.5to 0.3.There is no crack initiation when the friction coefficient is 0.3.The length of crack at roll diameter of 150 mm and 240 mm are 0.324 mm and 0,respectively.It would indicate that increasing the roll diameter could reduce work piece edge crack initiation.