The thermal conductivity of the titanium rod 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 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 metal 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 titanium alloy bars 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.
The main factors affecting metal flow during extrusion:
(1) Extrusion method. The metal flow of reverse extrusion is more uniform than forward extrusion, cold extrusion is more uniform than hot extrusion, and lubricated extrusion is more uniform than non-lubricated extrusion. The effect of the extrusion method is achieved by changing the friction conditions.
(2) Extrusion speed. The inhomogeneity of metal flow intensifies with the increase of extrusion speed.
(3) Extrusion temperature. When the extrusion temperature increases and the deformation resistance of the billet decreases, the uneven flow of the metal intensifies. During the extrusion process, if the heating temperature of the extrusion barrel and the die is too low, the temperature difference between the outer layer and the center layer is large, and the non-uniformity of metal flow will increase. The better the thermal conductivity of the metal, the more uniform the temperature distribution on the end face of the ingot.
(4) Metal strength. When other things are equal, the stronger the metal, the more uniform the metal flow.
(5) Die angle. The larger the die angle (ie the angle between the die end face and the central axis), the more uneven the metal flow. When extruding with a porous die, the die holes are arranged reasonably and the metal flow tends to be uniform.
(6) Degree of deformation. If the degree of deformation is too large or too small, the metal flows unevenly.
Contact us for more information. Thank you
Nicole
Company: Baoji Jimiyun Dynamic Co., Ltd
Cuntry:China
Add:Baoti road,Jintai,Baoji city,Shaanxi,China
Cel:+86 13369210920
Gmail:nicole@jmyunti.com
Website:www.jm-titanium.com
