The thermal extrusion of titanium rods and titanium alloy rod billets poses challenges due to their low thermal conductivity, resulting in significant temperature differences between the surface layer and the inner layer. At a temperature of 400 degrees in the extrusion cylinder, the temperature difference can reach 200-250 degrees. This temperature differential, combined with the suction reinforcement and billet section, leads to varying strength and plastic properties between the billet surface and the center. Consequently, the extrusion process results in uneven deformation, additional tensile stress cracks, and surface cracks on the extrusion products.
Compared to aluminum alloys, copper alloys, and even steel, the thermal extrusion process of titanium rods and titanium alloy rods is more complex due to the unique physical and chemical properties of titanium.
The flow dynamics study of industrial titanium alloy metals reveals significant variations in metal flow behavior across different phase states of each alloy at corresponding temperatures. Therefore, the billet heating temperature during extrusion significantly affects the flow characteristics of titanium rods and titanium alloy rods. Temperature extrusion in the α or α+P phase region exhibits more uniform flow compared to temperature extrusion in the β-phase region. Achieving high surface quality for extruded products is challenging. Currently, lubricants are necessary in the extrusion process of titanium alloy rods. This is primarily due to titanium forming a molten co-crystal with iron-based or nickel-based alloy mold materials at temperatures between 980 and 1030 degrees, leading to significant die wear.
The main factors influencing metal flow during extrusion are as follows:
1. Extrusion method: Reverse extrusion provides more uniform metal flow compared to forward extrusion. Cold extrusion yields more uniform flow than hot extrusion, while lubricated extrusion surpasses unlubricated extrusion. The extrusion method affects metal flow through changes in friction conditions.
2. Extrusion speed: Increasing extrusion velocity results in increased inhomogeneity of metal flow.
3. Extrusion temperature: Higher extrusion temperatures lead to increased nonuniformity of metal flow and decreased billet deformation resistance. Insufficient heating of the extrusion cylinder and mold, causing a large temperature difference between the outer layer and central layer of the metal, exacerbates nonuniform metal flow. Metals with higher thermal conductivity exhibit more uniform temperature distribution on the ingot end surface.
4. Metal strength: Under similar conditions, higher metal strength results in more uniform metal flow.
5. Die angle: Larger die angles (the angle between the die end surface and the central axis) contribute to greater unevenness in metal fluidity. When using porous mold extrusion, proper arrangement of mold holes promotes more uniform metal flow.
6. Deformation degree: Excessive or insufficient deformation degrees lead to nonuniform metal flow.
If you are interested in porous titanium sheets, filters, or other related products, TopTi Tech, as a professional manufacturer and supplier from China, can provide you with high-quality titanium, nickel, porous titanium plates or sheets, sintered titanium rod filters, and more. Please don't hesitate to contact us for further information.
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