Grade 5 titanium alloy is one of the most widely used titanium alloys. It has high strength and good corrosion resistance. However, it is difficult to see seamless titanium tubes made of Grade 5 material on the market for seamless titanium tubes at home and abroad.
Grade 5 titanium is mainly based on sheet metal. Grade 5 titanium tubes on the market are mainly high-strength thick-walled tubes produced by hot extrusion or oblique perforation. The warm rolling process requires improvement of the traditional rolls, ie rolling. The induction heating device is installed on the tube machine, and the processing equipment has a complicated structure, a complicated process, and a high production cost. The main reason for the current status quo is the high strength of Grade 5 titanium alloys, which makes cold forming difficult. In order to solve the key technology of Grade 5 seamless cold-rolled forming, the school and enterprise jointly conducted a series of studies. If the direct cold rolling forming process is used to produce high-strength titanium alloy pipes, not only the production cost is greatly reduced, but also the requirements for the high-performance applications of titanium alloys can be met.
Using the method of different deformation amount, the tube blanks were rolled into two tubes with a total deformation of 70% through two passes and three passes respectively. After vacuum annealing at 800°C×1h between passes, the cooling method is to cool the furnace to 500°C and cool it to room temperature. Observe the change of its microstructure and properties. Concluded:
In the case of a small amount of deformation, the wall thickness deviation is small, and the surface roughness is gradually reduced; large deformations are opened and the wall thickness deviation is large, which will affect the wall thickness deviation of the pipe obtained by subsequent passes.
When the total deformation is the same, the more rolling passes, the greater the elongation and hardness of the pipe and the higher the strength. Comprehensive performance is good.
The flow of material in the large deformation rolling is in the form of a strip, and the flow of the material in the small deformation amount is bundled. In the case that the heat treatment conditions between passes and the subsequent rolling process are the same, the large deformation amount is obtained by the blanking of the obtained tube. The distortion of the organization is even more serious.
The anisotropic effect of a small deformation amount on the pipe material is not significant; the anisotropy of the mechanical properties in the multi-pass rolling has a certain fluctuation.
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