Investigate The Edge Prefabricated Crown Rolling Process Of AZ31 Magnesium Alloy

Magnesium alloy,as the representative of the lightweight materials characteristics,has excellent comprehensive mechanical properties and can meet the basic requirements of aerospace,rail transportation and automotive industry.However,under the current actual situation of industrial production,magnesium alloy is easy to form edge crack and lower formability limits the wider application range of magnesium alloys.Edge crack greatly reduces the yield of rolling products of magnesium alloy.In this study,several numerical simulations of rolling process and experimental verifications were carried out at 450? of as-cast the AZ31 magnesium alloy sheet with initial thickness of 7mm.The results show that the edge crack was occurred when the single pass reduction came up to 20%.The edge crack depth has increased from 5240 ?m of 20% reduction to 14056 ?m of 45% in current rolling condition.According to numerical simulation results,the damage distribution along the width of the plate was obtained.The prediction model of edge crack depth was also established.For the edge crack depth,the average error between the actual measured data and the calculated value through the prediction model was 9.23%.At the same time,the finite element method was used to simulate the rolling process of pre-deformation by vertical roller.The mathematical model of edge contour of the plate with thickness of 10 mm,15 mm,20 mm was established,respectively.The results show that pre-deformation by vertical roll before flat rolling can significantly reduce maximum damage factor of rolled magnesium plate.After vertical rolling,the large reduction can be carried out for magnesium alloy plate.With the increase of vertical reduction,the maximum damage was decrease after large flat reduction.The value of vertical roll reduction was related to the initial thickness of magnesium plate.The influence of prefabricated crown on edge cracking of rolled AZ31 magnesium alloy plate was investigated.The rolling experiment has been carried out and initial thickness of the rolled sheet was 10 mm The prefabricated crowns were 0 mm,2.5 mm,3.3 mm,and 4.1 mm.Results show that using the prefabricated crown rolling process to produce AZ31 magnesium alloy slab can effectively control the generation of edge crack.Generation of edge crack of prefabricated crown samples during rolling was associated with the maximum differential reduction between the center and edge of the samples.The optimal value of differential reduction between the center and edge was 15.2% under the rolling temperature of 450 °C and rolling speed of 0.2 m/s.No edge crack was generated in the prefabricated crown sample of 4.1mm after five passes,with accumulated reduction coming up to 77%.