After the ingot was heated at a higher temperature above the phase change point, a 101MN hydraulic fast forging machine was used for upsetting and drawing forging with large deformation. Then, the blank was heated at a higher temperature above the phase change point in a tram type resistance furnace, and the ring blank was prepared by multiple rounds of free forging (upsetting and drawing). After surface grinding, the blank was heated above the phase change point. By upsetting, punching, reaming and drawing the mandrel, the ring billet with a specification of Φ1 350 mm/Φ800 mm×1 950 mm was prepared. After the billet was heated above the phase change point by the shield resistance furnace, the finished ring was rolled by the CMC10000 horizontal ring roller, and the large size ring of Φ3 384 mm/Φ3 300 mm×1 950 mm TC4ELI titanium alloy was prepared.
The sample ring was cut from the finished ring, and the heat treatment experiment was carried out in the resistance box furnace. The annealing process was 700, 750, 800, 850, 900 ℃ for 2 h, and then air cooling. Then, tensile specimens, impact specimens and metallographic specimens at room temperature were cut from the annulus after annealing at different temperatures. Metal pendulum type impact test machine to test room temperature impact performance.
Room temperature tensile properties of large size titanium alloy rings after annealing at different temperatures. It can be seen that when annealed below 800 ℃, the tensile strength at room temperature has little change with the gradual increase of annealing temperature. The average tensile strength at room temperature and yield strength in hot working state are 917.0 MPa and 812.5 MPa respectively. After annealing at 700 ~ 800 ℃, the average tensile strength at room temperature is 867.0 MPa, the maximum difference is 11.5 MPa, and the average yield strength is 770.0 MPa, the maximum difference is only 9.0 MPa. After annealing at 850 ℃ and 900 ℃, the tensile strength and yield strength are slightly increased, the average tensile strength is 902.5 MPa, the difference is 6.0 MPa, the average yield strength is 809.5 MPa, the difference is 2.0 MPa. The results show that the tensile strength fluctuation of large size TC4ELI titanium alloy rings is small at room temperature after annealing at 800 ~ 900 ℃. By observing the shrinkage rate of section, it can be seen that the shrinkage rate of section is basically unchanged when annealed below 800 ℃. When annealed at temperatures above 800 ℃, the section shrinkage increases significantly, and the section shrinkage is basically the same after annealing at 850 ℃ and 950 ℃.
