Industrial pure titanium is a dry and difficult to forge material. It is easy to produce cracks in the process of forging industrial titanium rings, and has strong oxidizing property. Cracks can only be removed by grinding after cooling to room temperature in one day. In order to meet the requirements for the geometric size and surface quality of the finished titanium ring, the ring blank is roughed, the surface defects are cleaned, and chamfering and beveling are carried out in special cases.
The surface layer of the titanium ring blank after rough turning is coated with anti-oxidation paint and heated. The rolling process is a continuous line contact process, the forming speed is fast, and the deformation energy will increase the temperature of the titanium ring forging. The thermal conductivity of the titanium ring is poor, and the temperature rises beyond the phase transition region. In combination with the phase transition temperature of pure titanium and the high temperature of the ring during rolling, dynamic recrystallization will occur. Therefore, in order to ensure that titanium is not rolled in the β phase region, The heating temperature should be lower than the phase transition temperature, the temperature of the heating soaking section should be set at 880~900℃, and the forging temperature should be controlled at 850~900℃.
The higher speed in the rolling process can refine the grains, but it also generates a lot of deformation heat, which makes the billet temperature too high and increases the possibility of dynamic recrystallization behavior. If the temperature of the ring is too high, it is easy to coarse grain, and if it is too low, it is easy to cause cracks. Therefore, it is necessary to reasonably set the rolling process parameters, and the focus of the rolling process parameters is the design of the rolling curve. The ring is a typical thin-walled cylindrical ring, and the rolling curve of the cylindrical ring is selected.
In the blooming stage, the feed is slow, which mainly eliminates the bad ellipse of the ring and the difference in wall thickness, and the rolling force and growth rate increase slowly. In the main rolling stage, rapid and stable rolling is realized. The rolling speed is set at (5~7 mm/s and the centering force is 10%~15%. The rolling force decreases correspondingly with the decrease of ring rigidity. The centering force finally decreases in the deceleration and rounding stage. As small as 5% or less, to ensure the elimination of defects such as ellipses and waves. The surface of the rolled product is uniform and smooth, with no visible defects to the naked eye, and the roundness is good. After the rolling is completed, the shrinkage of the forgings is within the predetermined 1.007, showing an ellipse of 5 mm, fulfil requirements.
