Az31b Magnesium Alloy Twin-roll Casting Temperature Field Of Finite Element Simulation And Experimental Study

With good overwell performance, magnesium alloy has an extremely important application value and broad application prospects in electronic, and defense fields of military industry. But the existing productions of magnesium alloy plate requires several repeated round of hot rolling and intermediate annealing. Not only the processes of produce last for a long time, but also the finished product is in very low efficiency. All this leading to large energy consumption, high cost, and restricton to magnesium alloy strip's development and application. Using twin-roll casting technology, the magnesium alloy strip of near net shape can be prepared directly from the melt, meanwhile the produce process of magnesium alloy strip could be shorten, and the production costs could be reduced. In this paper, the finite element model of casting area has been built, and the FEM method was used to simulate the distribution of temperature in the casting area, then the effects of process parameters on solidification structure and properties of the twin-roll casting plate was studied by experiments. Research results obtained in this study are as follows:1)The basic theory of thermal simulation was discribed; the 3D finite element model of casting area for temperature field simulation was modeled, and the boundary conditions for FEM simulation was determined.2) The comercial software, ANSYS10.0, was adopted to simulate the distribution of temperature in the casting area. By simulating, the author obtained the different influences law of pouring temperature, casting speed, roll gap size, and heat transfer coefficient on temperature distribution in the casting area. The simulation results show that proper scale of parameters, such as casting temperature is 660～690℃, casting speed keeps 2.5～3.0m/min, roll gap of 2.5-4.5mm, the material of roll shell has some effects on the distribution of temperature.3) Some twin-roll casting experiments of magnesium were done in the labrory, then the production was hot-rolled by sevral times. Compared with traditional plate, the average grain size of the plate produced by twin-roll casting has decresed to 6～8μm from10～12μm,and the tensile strength and yield strength increased by 25.3% and 18.8%.4) Based on the results of FEM analysis, the author studied the effect of the parameters on the solidification of magnesium alloy strip,which produced by twin-roll casting, by changing experimental parameters. The results show that when casting temperature changed from 700℃to 660℃, the average grain size from 50～60μm down to 30～35μm; when the casting speed increased from 1.5m/min to 3.0m/min, the average grain size from 40～50μm reduced to 20～25μm; if roller is not cooled by water, the average grain size is about 60～70μm, but the average grain size of 40～50μm can be obtained by cooling the roller by water.5) Changing magnetic field was applied on the front of the casting zone and the magnesium strip was produced, then compared it with the ordinaral plate about their solidification and properties. Results show that twin-roll casting billet affected by the electromagnetic with a much fine grain size, and the mechanical properties was significantly improved.