Cold rolled TC4 titanium alloy titanium tube technology

TC4 Titanium alloy is one of the most widely used titanium alloys at present. It has high strength and good corrosion resistance. However, it is difficult to see TC4 seamless titanium tubes in the domestic and foreign Titanium Tubing market.

TC4 titanium material is mainly plate, and TC4 titanium pipe in the market is mainly high-strength thick-wall tube produced by hot extrusion or oblique perforation, etc. The warm rolling process needs to improve the traditional roll, that is, install induction heating device on the pipe mill. This kind of processing equipment has a complex structure, complicated process and high production costs.

The main reason for the present situation is the extreme strength of TC4 titanium alloy and the difficulty of cold rolling forming. In order to solve the key technology of TC4 seamless tube cold rolling forming, a series of research has been carried out jointly by the university and enterprise. If the direct cold rolling process is used to produce superior strength titanium alloy pipe, it can not only considerably reduce the production cost, but also meet the requirements of high performance applications of titanium alloy.

The billet was rolled into the tube with the total deformation of 70% by two passes and three passes, respectively. Vacuum annealing was performed at 800℃×1h between passes. The cooling method was that the furnace cooled to 500℃ and then the air cooled to room temperature. The changes of microstructure and properties were observed. The conclusions are as follows:

Under the condition of slight deformation, the wall thickness deviation is tiny and the surface roughness is gradually reduced. Large deformation and large wall thickness deviation will affect the wall thickness deviation of the tube obtained by subsequent passes rolling.

When the total deformation is the same, the more rolling passes, the greater the elongation and hardness of the pipe, the higher the strength. ​Excellent comprehensive performance.

In the case of large deformation rolling, the material flow is banded, while in the case of tiny deformation rolling, the material flow is bunched. In the case of the same inter-pass heat treatment conditions and the subsequent rolling process, the microstructure distortion of the pipe with large deformation is more serious.

The tiny deformation of the blank has minor effect on the anisotropy of the pipe. The anisotropy of mechanical properties fluctuates in multi - pass rolling.