Forming Process Of Ti 6242 Titanium Rods Under Hot Extrusion

Ti 6242 titanium rods and titanium alloy rods billet thermal conductivity is low, in the hot extrusion will make the surface layer and the inner layer of the great temperature difference, when the temperature of the extrusion cylinder is 400 degrees, the temperature difference can reach 200 ~ 250 degrees. In the suction strengthening and billet section has a large temperature difference under the joint influence of the billet surface and the center of the metal to produce very different strength properties and plastic properties, in the extrusion process will cause very uneven deformation, in the surface layer of the large additional tensile stresses, to become in the extrusion of the surface of the product to form cracks and cracks at the root cause. Titanium rods and titanium alloy bar products hot extrusion process than aluminum alloys, copper alloys, and even steel extrusion process is more complex, which is determined by the titanium rods and titanium alloy bar special physical and chemical properties.

Industrial titanium alloy metal flow dynamics studies show that in the temperature zone corresponding to the different phase states of each alloy, the flow behavior of the metal appears to be very different. Therefore, one of the main factors affecting the extrusion flow characteristics of titanium rods and titanium alloy rods is the billet heating temperature that determines the phase state of the metal. Extrusion at a or a+P phase zone temperature results in more uniform metal flow compared to extrusion at p phase zone temperature. The difficulty of obtaining high surface quality of extruded products is great. Until now, the extrusion of titanium alloy rods has required the use of lubricants. The main reason for this is that titanium forms fusible eutectic crystals with iron-based or nickel-based alloy die materials at temperatures of 980° and 1030° C. This results in strong die wear.

The main factors affecting metal flow during extrusion.
(1) Extrusion method. Reverse extrusion than forward extrusion metal flow uniformity, cold extrusion than hot extrusion metal flow uniformity, lubricated extrusion than non-lubricated extrusion metal flow uniformity. The effect of extrusion method is realized through the change of friction conditions.
(2) Extrusion speed. The inhomogeneity of metal flow increases as the extrusion speed increases.
(3) Extrusion temperature. The uneven flow of metal increases when the extrusion temperature increases and the deformation resistance of the billet decreases. In the extrusion process, if the heating temperature of the extrusion barrel and die is too low, and the temperature difference between the outer layer and the metal in the center layer is large, the unevenness of metal flow increases. The better the thermal conductivity of the metal, the more uniform the temperature distribution on the end face of the ingot billet.
(4) Metal strength. All other conditions being equal, the higher the metal strength, the more uniform the metal flow.
(5) Die angle. The larger the die angle (i.e. the angle between the die end face and the center axis), the more uneven the metal flow. When using multi-hole die extrusion, die hole arrangement is reasonable, the metal flow tends to be uniform.
(6) Deformation degree. If the degree of deformation is too large or too small, the metal flow is not uniform. Forming process of titanium rods and titanium alloy bars under hot extrusion