Study on Recrystallization Process of Industrial Pure Titanium TA2 Cold Rolled Sheet

Titanium and titanium alloys have a wide range of applications in aerospace and other fields because of their excellent performance, but they are also constrained by their processing efficiency and production cost. With the development of titanium alloys, the increase in the number of titanium materials, and the reduction in prices, the application of titanium in the civil industry will increase exponentially, especially in shipbuilding, automobile manufacturing, chemicals, electronics, marine development, biomedicine, desalination of seawater Civilian fields such as geothermal power generation, pollution discharge and corrosion protection will be widely used. At the same time, the market demand will also accelerate the development of titanium industry and titanium processing technology.

Industrial pure titanium is mostly used in the annealed state. After recrystallization annealing, pure titanium can be uniform in structure and properties, completely softened, and has appropriate plasticity and toughness. In the context of the current industrial pure titanium cold rolled strip of a large number of applications, the recrystallization temperature determined by cold rolling pure titanium sheet, the theoretical basis for the development of rational annealing process. The researchers used a Gleeble-3500 thermal simulation tester to vacuum-anneal the cold-rolled TA2 titanium plates, measured the hardness curves of TA2 at constant and constant temperatures, and calculated the recrystallization activation based on the recrystallization time corresponding to different recrystallization temperatures. can. The recrystallization law of industrial pure titanium was studied to provide basis for the formulation of annealing process.

The experimental material is industrial pure titanium TA2, cold rolling reduction rate is 75%, thickness of 0.8mm cold rolled titanium plate. The recrystallization process is not a constant temperature process but a process that starts at a certain temperature and ends at a certain temperature as the temperature rises. In order to determine the temperature of recrystallization of TA2 and the time of recrystallization, a temperature change test of 9 minutes at a time was performed under vacuum conditions on Gleeble-3500. The annealing temperatures were 520, 540, 560, 580, 600, 620, 640, 660, respectively. At 680, 700, and 720°C, the hardness difference between the original sample and the completely softened sample is defined as 100%. Then, when the hardness is reduced by 50%, the recrystallization condition (i.e., recrystallization temperature or recrystallization time) is defined. After confirming the recrystallization temperature of the timed test, a thermostatic time change test is again performed with a constant temperature of 700° C. and a holding time of 3, 6, 9, 12, 15, 18, 21, 24 min to determine the temperature conditions. Crystallization time.

On the cold-rolled sheet and the recrystallization annealing sheet, a metallographic specimen having a size of 12 mm×10 mm was cut out, and the side metallographic structure parallel to the rolling direction was observed. The mechanical performance testing equipment is MTS810 precision testing machine. The main test parameters are set as follows: experimental tensile force 98kN, collet displacement speed 2mm · min-1; axial extensometer gauge length 50mm, extensometer measurement error 0.3 %; test temperature is 25°C.

Under the experimental conditions, the recrystallization activation energy of TA2 can be calculated according to the Arrhenius formula according to the constant temperature variation test and the constant temperature variation test, and the recrystallization activation energy can be calculated as Q=5.6578×104kJ·mol-1.

Combining the hardness method and the metallographic method, the recrystallization temperature is between 520 and 600°C, the recrystallization time is within 9 minutes, the recrystallization annealing temperature is between 680 and 700°C, and the holding time is about 30 minutes, which can maintain the good mechanical properties of the titanium plate.