The thermal conductivity of the titanium alloy billet is low, and the temperature difference between the surface layer and the inner layer will be large during hot extrusion. When the temperature of the extrusion cylinder is 400°C, the temperature difference can reach 200~250°C. Under the combined influence of suction strengthening and the large temperature difference of the billet section, the metal on the surface and the center of the billet has completely different strength and plasticity, which will cause very uneven deformation during the extrusion process, and produce a large additional tensile force on the surface layer. Stress becomes the source of cracks and cracks on the surface of extruded products. The hot extrusion process of titanium rectangular rod and titanium alloy rod products is more complicated than that of aluminum alloy, copper alloy and even steel, which is determined by the special physical and chemical properties of titanium rod and titanium alloy rod.
The research on the metal flow dynamics of industrial titanium alloys shows that there are great differences in the metal flow behaviors of different alloys in different temperature regions. Therefore, one of the main factors affecting the extrusion flow characteristics of titanium rods and titanium alloy rods is the heating temperature of the billet that determines the state of mental transformation. Compared with the temperature extrusion of the P-phase region, the metal flow in the a-phase region or the P-phase region is more uniform. It is difficult to obtain extruded products with high surface quality. Until now, the extrusion of medical titanium rod had to use lubricants. The main reason is that titanium will form eutectic with iron-based or nickel-based alloy mold materials at 980 degrees and 1030 degrees, which will cause strong mold wear.
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