AZ31镁合金连续强流变轧制成形过程温度场模拟与优化

SIMULATION AND OPTIMIZATION OF THERMAL FIELD DURING CONTINUOUS CONSTRAINED RHEOROLLING OF AZ31 ALLOY

采用数值模拟与实验相结合,对AZ31镁合金连续强流变轧制成形过程温度场进行了模拟与优化.结果表明,在倾斜板表面,合金温度从浇注口到出口逐渐趋于线性降低;在横断面上,接触倾斜板一侧合金温度比上侧低,当浇注温度大于690℃时,熔体在倾斜板出口温度高于AZ31合金液相线温度,容易发生制品断裂.在轧制变形区后滑区,主要发生半固态金属变形,合金从孔型入口到出口温度逐渐降低,半固态区间随着浇注温度的升高而增长,温度等值线发生两次弯曲,表层合金温度等值线向孔型出口凸出,而中心合金温度等值线向孔型入口凸出,其弯曲程度从中性面到孔型入口越来越明显;在轧制变形区的前滑区,主要发生固态金属的变形,温度等值线发生一次弯曲,且向孔型出口凸出.在本实验条件下,较合理的浇注温度范围在670—690℃之间.

Semisolid metal processing（SSP） is recognized as a new near-shape forming technology, which combines the merits of both the liquid and the solid metal processing.Compared with the traditional rolling process,this technology has the features of low energy consumption,low cost equipment and high yield.Perhaps inevitably,a problem is the solid and liquid phases tend to separate with each other during rheo-rolling process,especially when the semisolid slurry has a low solid fraction.This problem causes macrosegregation and reduces the quality of the strip.Using rectangular groove roller may solve this problem.In this paper,numerical simulation method and experiment were combined for simulation and optimization of thermal field during continuous constrained rheo-rolling of AZ31 alloy.The results show that on the sloping plate surface,alloy temperature decreases gradually from the casting mouth to the exit with a linear pattern,the alloy temperature near the sloping plate surface is lower than that on the above surface,when the casting temperature is higher than 690℃,the melt temperature at the exit of the plate is higher than the liquidus of AZ31 alloy,which will cause product fracture.In the backward slip zone,semisolid metal deformation mainly happens,alloy temperature decreases gradually from the entrance to the exit of the roll gap,semisolid zone length increases with the casting temperature,isothermal lines have twice buckling, the buckling direction on the surface of the alloy is toward the exit of the roll gap,while the buckling direction in the center is toward the entrance of the roll gap,and their bending degree increases gradually from neutral flow plane to the entrance of the roll gap.In the forward slip zone,solid metal deformation mainly takes place,isothermal lines have once buckling,and the buckling direction is toward the exit of the gap.Under the current experimental conditions,the proper casting temperature between 670 and 690℃is suggested.