Study On Heavy Reduction Rolling Of AZ31B Magnesium Alloy

Magnesium alloy slab is of great importance in promoting applications of magnesium alloys in deformation products. AZ31B is the major alloy for magnesium alloy rolling. However, because of the low magnesium alloy plasticity, the difficulty and low yield of rolling forming. The magnesium alloy slab manufacturing costs increases and the market competitiveness of magnesium alloy sheet reduces. So improving the formability and yield of magnesium alloy slab by mending the rolling process is a very important research subject.In this paper, in order to improve the production efficiency of magnesium alloy sheet, reduce the level of edge crack and improve the microstructure and properties uniformity of the sheet, the effect of the cogging temperature and rolling patterns with heavy reduction and the effect of the temperature and the occasion of side pressing in the processing on the microstructure and properties of the cogging sheet and finish rolling sheet are researched. Also aim to the actual industrial application, the hot rolling with pre-deformation using vertical roll is simulated by rolling with side pressing at the same temperature. Through the experiment and research, the conclusions are as follows:1. To the rolling pattern with heavy reduction, the cogging temperature has a significant influence on edge cracks and microstructure uniformity. When rolling at350℃, it will have the least edge cracks and the greatest microstructure uniformity. To the rolling pattern with super heavy reduction, when rolling at250℃, it has the greatest microstructure uniformity. The microstructure uniformity will decrease when cogging temperature increases. Contrast with the rolling pattern with heavy reduction, the microstructure of sheet, after cogging, rolled with the rolling pattern with super heavy reduction at250℃is more uniform. Its microstructure uniformity will be worse than the second one’s when cogging temperature increases.2. To two rolling patterns with heavy reduction, the cogging temperature have a significant influence on microstructure uniformity and mechanical properties uniformity of the finish rolling sheet. The finish rolling sheet has uniform microstructure, good plasticity and small mechanical anisotropy, when cogging at350℃for the first one and300℃for the second one. Contrast with the rolling pattern with heavy reduction, the microstructure of sheet, after finish rolling, rolled with the rolling pattern with super heavy reduction is less uniform. Its finish rolling sheet has larger strength, larger hardness, but less elongation. It has less anisotropy when cogging temperature at low temperature.3. Rolling with side pressing can improve the deformation uniformity of the sheet in the thickness and width direction and reduce edge cracks. Additionally reducing side pressing temperature properly can improve the deformation uniformity and reduce edge cracks. When warm side pressing cogging at100℃～250℃, it will have the greatest deformation uniformity in the thickness and width direction and the least edge cracks.4. Side pressing can obviously reduce the microstructure anisotropy and mechanical properties uniformity of the finish rolling sheet. Reducing side pressing temperature properly can reduce the microstructure uniformity and mechanical properties uniformity. When warm side pressing cogging at100℃～250℃, it will have the least mechanical properties anisotropy of finish rolling sheet. Additionally, when side pressing at250℃, it will have the least strength anisotropy. When side pressing at100℃, it will have the least elongation anisotropy.5. Compared with side pressing before rolling, cogging with side pressing among rolling can improve the uniformity of the deformation microstructure of the sheet in the thickness and width direction direction and reduce edge cracks. The strength and plasticity both increase.The research of pre-deformation cogging with vertical rolls in the hot rolling indicates:for side pressing-heavy reduction rolling-finish rolling, when deformation is at350℃, it will have the least edge crack, the beast of the deformation uniformity and the least anisotropy of the mechanical property.