The proper heating temperature, holding time and forming pressure must be selected in order to make the forming work.Heat alignment on the parts of the pressure, as long as you can ensure that the parts pressed in the mold can be, and then large pressure on the branches of the role is not, but may lead to the mold and the work table.Therefore, temperature and time are the main factors that affect the effect of thermal alignment, and temperature is the decisive factor.In order to eliminate rebound satisfactorily, only at a certain temperature.The so-called thermal specification is mainly to determine the calibration temperature and time.Generally speaking, a suitable thermal specification for a certain type of titanium plate forming must ensure that the following basic requirements are met after the parts are shaped:
1. the parts of the paste die is good, basically do not need manual repair.Shape, size and surface quality meet the inspection requirements of titanium plate parts;
2. The mechanical properties of the materials are basically stable, and the main performance indexes at room temperature and service temperature are in line with the regulations;
3. The residual stress inside the parts is basically eliminated;
4. After thermal correction, the average hydrogen content of the material shall not exceed the allowable value of 150p.P.M;
5. The total thickness of oxide skin and gas permeable layer shall not exceed half of the allowable negative deviation of plate thickness;
6. The metallographic structure of the material did not change, and there was no obvious growth or overheating of the grain.
7. in the premise of meeting the above requirements, the temperature should be as low as possible time to be as short as possible, the pressure to ensure that the parts can be pressed paste.
Our calibration test is carried out on the domestic RX - 1 machine tool.The materials are TA2 and TC1, and the thickness is 0.5, 0.8 and 1.0 mm.Thermocouple is used to indicate the temperature of mold or working area, which can be controlled within ±10℃.Time is controlled by time relay, from the time when the specimen is put into the mold, closed the mold or put into the working cavity to the time when it is taken out
The problem of forming accuracy is emphasized.Forming accuracy is the most basic requirement of parts forming, and it is the main index to measure whether the temperature and time specification are suitable.The way to judge the forming accuracy is to measure the degree of non-sticking mold after the parts are cooled to room temperature, that is, the size of the remaining rebound.Take wide plate of circular arc as an example first.It can represent the aircraft on the curvature of a small, but accurate shape requirements of a class of parts.The relative bending radius of such parts is large (such as R/t = 200).If the elastic modulus E = 10500 kg/m2;Yield limit alpha 0.2, take 40 for TA2.5 kilograms per square millimeter, 60 for TC1.Five kilograms per square millimeter.
In conclusion, the specification of thermal alignment of titanium plate can be preliminarily determined on the premise of basic maintenance of forming accuracy.