This paper proposes a new technology of superimposed billet extrusion-forming for thin-walled magnesium alloy tubes. This process represents an improvement over the current technology, which suffers from low production efficiency, poor forming accuracy, and low material utilization. We developed a detailed forming process and mold structure, in which the excess material of the front billet is extruded out of the mold as the rear billet pushes on the front one. Through continuous extrusion, online direct water cooling, and cutting, the automated continuous production of thin-walled tubules is achieved. The optimization of the mandrel structure and its hovering action is also included, with the aim of improving the lifespan of the mandrel and the accuracy of tube size. The numerical simulation method evaluates the effect of the die angle (α) on the tube, formed using FORGE NXT 1.1. The results show that for an angle of less than 70°, the defect length of the tube decreases as the die angle decreases, forming an ordered flow of superimposed billets. If the angle is less than 50°, the two adjacently formed tubes separate automatically, with no need for the subsequent cutting process. The best choice of die angle is about 50°, which takes into account the effect of the change in extrusion force.
Keywords: continuous forming; extrusion mold; magnesium alloy; superimposed billet extrusion method; thin-walled tubule.