New Processing Technology of Twin Roll Strip Casting of AZ31B Magnesium Strip

摘要

In order to improve the poor workability and solve the problem of difficult roughing rolling of magnesium billet, the twin roll strip castor (TRSC) was used for the manufacture of magnesium thin strip directly from its molten metal. Since the cooling rates achieved by TRSC casting process are in the range of five hundred to several thousands of degrees per second and the strip is formed under the pressure, therefore, this near- rapid solidification process can leads to homogeneity of microstructures, refined grain size and increased solid solubility. The experiments were carried out on the existing equipments at State Key Laboratory of Rolling and Automation (RAL), Northeastern University. Strip samples 200～350 mm wide and 1.5～3.5 mm thick have been successfully cast in standard AZ31B alloy. The surface of the as cast magnesium strip was smooth and the edge was tidy. The microstructure analysis of the as cast magnesium strip showed that the gain size was much refined compared to that of ingot samples, and there was no segregation in the strip. The tensile strength of the strip in the cast state was about 220 MPa. The as cast magnesium strips were cold rolled directly on a two-high rolling mill, the total reduction up to 40% can be reached. X- ray diffraction result showed that the main phase in the as cast state AZ31B magnesium strip was α (Mg), the γ (Mg_(17)Al_(12)) phase existing in the conventional wrought magnesium AZ31B sheet was vanished, therefore, the ductility of the strip increased.