In titanium alloy plate and titanium plate, the recrystallization process is often accompanied by some other organizational changes. For example, near a alloy and a+ beta alloy with a relatively small content of beta stable elements, accompanied by the dissolution of phase a and the change of beta components; The recrystallization process in a heat-treated beta alloy is often performed simultaneously with the recrystallization process, or the subsequent aging effect is produced. In addition, different types of alloy are different at room temperature microstructure, and the process and characteristics of the recrystallization are different.

 

In addition to the recovery and recrystallization of the cold processing group, the solution of the compound and the polytypic change of a and beta are in addition to the recovery and recrystallization process of the titanium alloy plate and titanium plate. In order to improve the performance of titanium alloy and titanium plate, in addition to the necessary alloying, proper heat treatment is also required. The recovery process of titanium alloy and titanium plate is also the process of eliminating most of the second type of internal stress caused by the space and dislocation motion at certain temperature. Reply to process the temperature below the recrystallization temperature, is in commonly 500 ~ 500 ℃.

 

The effect of alloy elements on the crystallization temperature of pure titanium has been described in the previous section. In addition to niobium and cobalt, the commonly used alloy elements and impurity elements can improve the recrystallization temperature of titanium. The determination of recrystallization is mainly based on the combination of metallographic observation and X-ray diffraction. As the recrystallization occurs, small axial grains appear in the fibrous tissue of the transformed fibers, and the diffraction rings at the back of the x - ray back are turned into non-concatenated spots. For beta alloy heat treatment, can also to burn the whole ageing (500 ℃ / 4 ~ 8 hours, air cooling) method shows recrystallization organization, after incomplete limitation of recrystallization grain size not dull after corrosion. The mensuration, the beginning of pure titanium TA2 recrystallization temperature about 550 ℃, TA7 titanium alloy is about 600 ℃, TC4 titanium alloy is about 700 ℃, TB2 alloy is 750 ℃.

 

As with other metals, the recrystallization process of titanium alloy plates and titanium plates is also the process of growing the nucleation of crystalline grains after the deformation. The lattice type does not change at this time, but the dynamic performance changes. The process is influenced by the degree of cold deformation, heating temperature and thermal insulation time, and can be crystallized through the cold deformation rate, heating temperature and the three-dimensional recrystallization of the recrystallized grain size.

 

The shape of the titanium sheet must consider the following five factors:

 

1. Conditions of dangerous section strength. Titanium and titanium alloys due to the anisotropic index r a large, thick and dangerous section is circumferential strain of two-way tensile stress state, at this time of the bearing capacity of the dangerous section is a lot of steel to improve r = 1, the limit drawing coefficient k and r statistical relationship type.

 

2. Rational conditions. Usually mild steel or aluminum plate tensile don't need to consider this condition, because even if under the limit drawing coefficient of its plasticity is more than enough, but its deformation ability of titanium especially titanium alloy co., LTD. It cannot bear the deformation of the diameter of the material from the diameter of the wool to the diameter of the cylinder, so it is often the key to determine the success or failure of the drawing.

 

3. Accuracy problem. Especially for high strength titanium alloy titanium springback is steel plate to too many times, so sometimes parts while stretching out, but the precision is too low, when stretching box parts precision problem becomes more serious.

 

4. Bending conditions. This is also a special case of titanium, which is easy to understand from the data, such as the minimum bending radius of the TC3 titanium plate in a simple bending state of 5. 5-6 times the thickness of the sheet metal, if we use the tensile steel plate is usually appropriate radius of 5 times the thickness of mold to stretch TC3 titanium plate, obviously it will due to the bending rupture, this is a more dangerous tension bending, assuming that the corners of sheet metal and punch without relative sliding contact, can have the following relations: r > 2 rmin + t.

 

5. Wrinkles. This is also due to the properties of the titanium plate itself. The stability of the titanium plate when the pressure is only about half that of steel or aluminum, which is easy to wrinkle, thus difficult to when stretching through the die fillet of dangling part, combined with titanium plate bending and is not good, so easy to wrinkle and at the same time at the peak valley wrinkles happen bending crack, the so-called knit crack. In order to avoid wrinkles, special measures should be taken.

 

In summary, there are many factors to draw the titanium parts, so the data of many limit stretch coefficients vary widely.