AZ31镁合金板材轧制过程边裂形成原因分析

Causes analysis on the edge crack formation of rolled AZ31 Mg alloy sheet

针对AZ31镁合金板材轧制过程中出现边部裂纹的问题,采用数值模拟方法研究了AZ31镁合金板材轧制过程中轧制温度对板材边裂的影响,利用实验室热轧试验方式研究了AZ31镁合金板坯宽厚比、轧制道次数以及工作辊直径等工艺参数对镁板边部裂纹的影响.研究表明,边裂的产生多数情况是由于几种因素共同作用的结果,其主要影响因素有轧制温度、道次加工率、轧辊直径以及板坯宽度和厚度等.在其他条件不变的情况下,减少板材宽厚比,可降低边部所受拉应力,有利于减少横向裂纹产生;当b>(R·△h)^(1/2)时,随着板材宽度增加,轧制力逐渐升高,边部产生横向裂纹的几率增加;对于相同规格板坯,随着辊径增大,轧制过程中板坯的宽展量和所受摩擦力逐渐增加,有利于发挥板材塑性从而减小边部裂纹产生的趋势.

To concern the edge cracks of AZ31 Mg alloy sheet during rolling, in this paper, we study the effect of rolling temperature on edge cracks of AZ31 Mg alloy by numerical simulation and the effect of width to thickness ratio, passes and work roll diameter on the edge cracks of Mg sheet by hot rolling on laboratory mill. The results showed that the apperace of edge cracks was due to several factors including rolling temperature, passes, roll diameter and width to thickness ratio. The theoretical research proved that if the others conditions keep constant, the decrease of Mg sheet＇s width to thickness ratio could reduce the edge tensile stress, thus reduce transverse cracks. With b〉 （R ·△h）^1/2, increasing sheet width could raise the rolling stress. For the same size slab, the friction of Mg plate increases with increasing roll diameter. This can release plasticity of Mg sheet and decrease the possibility of emerging edge cracks.