Discussion on thermal correction requirements of titanium plate
In order to make the heat calibration form work, it is necessary to select the appropriate heating temperature, holding time and forming pressure. The pressure applied to the part during the thermal shape correction process ensures that the part is pressed against the mold. However, no matter how much pressure, can lead to mold and workbench deformation. Therefore, temperature and time are the main factors affecting the thermal correction effect, and temperature is the decisive factor. In order to satisfactorily eliminate rebound, it must be carried out at a certain temperature. The so-called thermal specification mainly determines the temperature and time of shape correction. In general, the proper thermal specifications for forming titanium plates must ensure that the parts meet the following basic requirements after forming:
1. The parts are well bonded with the mold, and there is basically no need for manual trimming. The appearance, size and surface quality meet the inspection requirements of titanium plate parts;
2. The mechanical properties of the material are basically stable, and the main performance indicators meet the requirements at room temperature and use temperature;
3. The residual stress inside the parts is basically eliminated;
4. The average hydrogen content of the material after thermal correction does not exceed the allowable value of 150p.p.m.
5. The total thickness of the oxide and breathable layer shall not exceed half of the allowable negative deviation of the thickness of the metal plate;
6. The metallographic structure of the material has no change, no obvious grain growth, overheating and other phenomena;
7. Under the premise of meeting the above requirements, the temperature should be as low as possible and the time should be as short as possible. The pressure is appropriate to ensure that the parts can be pressed.
Discussion on forming accuracy:
Forming accuracy is the most basic requirement of parts pressing and forming, and it is also the main index to measure whether the temperature and time specifications are suitable. The method to judge the forming accuracy is to measure the degree of non-adhesion of the part after cooling to room temperature, that is, the residual rebound amount. First, take the curved part of the curved wide plate as an example. It can represent a class of aircraft parts with small curvature and accurate shape. The relative bending radius of such parts is large (for example, the relative bending radius before springback is r/t=200). If the elastic modulus E = 10500 kg/mm2; The yield limit, α0.2, is 40.5 kg/mm2 for TA2 and 60.5 kg/mm2 for TC1. In summary, under the premise of basically maintaining the forming accuracy, the specification of titanium plate thermal correction can be preliminarily determined.