Introduction to superplastic forming methods for titanium alloy sheets!
The superplastic forming methods of titanium alloy sheets can be roughly divided into the following three types: (1) vacuum forming; (2) Air pressure forming (blow molding); (3) Die forming (coupled die forming). The first two are commonly used methods for forming plastic (or glass) products. The superplastic forming of titanium plates can utilize low-pressure forming due to their viscous or semi viscous flow deformation. Pneumatic forming can also be combined with vacuum forming for application.
1. Vacuum forming method
Vacuum forming method can be divided into two types: punch method and concave method.
The punch method is a forming method that adsorbs the heated raw material onto a punch with internal shape of the part, used to form parts that require high internal dimensional accuracy. The concave die rule is a forming method of adsorbing heated raw materials onto a concave die with a part shape, used for forming parts that require high dimensional accuracy. Generally speaking, the former is used for the formation of deeper containers, while the latter is used for the formation of shallower containers.
Vacuum forming is also a type of pneumatic forming, but the forming pressure can only be one atmosphere. Therefore, for titanium plates, they can only form parts with thin thickness, simple shape, gentle curvature, and are not suitable for forming parts with thick thickness, complex shape, and severe deformation.
2. Pneumatic forming method
This is a special bulging process.
The traditional bulging process is achieved by mechanical, hydraulic or explosive bulging methods, which use high pressure and energy. Moreover, due to the limitations of material plasticity, the deformation is generally not too large. Blow forming is a sheet metal forming technology that uses low energy and low pressure to achieve large deformation, which is different from traditional process concepts. Due to the fact that metals are free during deformation, almost all of their power is consumed in deformation work, resulting in minimal friction loss (for free blow molding, there is no friction loss), which is fundamentally different from other stamping processes.
Blow molding can be divided into two types: free blow molding and mold blow molding. The characteristic of mold blow molding is semi mold forming, which is similar to vacuum forming and can be divided into two types: convex mold forming and concave mold forming; The difference is that the forming pressure can be greater than one atmospheric pressure, and the pressure can be adjusted through the air source system, making it possible to manufacture parts with complex shapes and large curvature changes.
(1) Free blow molding method
This is a simple blow molding process for Z. Its characteristic is that there is no need for molds, and the typical blown parts are spherical parts.
(2) Punch forming method
This method is to create a closed pressure space on the outer side of the titanium plate blank. After the titanium plate is heated to the superplastic temperature, under the pressure of compressed gas, the blank undergoes superplastic deformation and gradually approaches the mold surface until it fully fits with the mold, creating parts that match the mold surface. The internal surface of formed parts has high dimensional accuracy, accurate shape, large ratio of depth to width, and easy mold processing, but demolding is more difficult and raw materials are also more expensive. The bottom of the part formed by this method is thicker than the surrounding area.
(3) Concave die forming method
Unlike the punch forming method, a closed pressure space is formed on the inner side of the titanium plate blank during the forming process. The outer surface of formed parts has high dimensional accuracy, accurate shape, easy demolding of parts, less raw materials, but the depth and width are relatively small, and mold processing is also more difficult. The bottom of the part formed by this method is thinner than the surrounding area.
3. Molding method
Adopting coupling mode. Unlike ordinary molding, the higher the temperature, the slower the molding speed.
Due to the difficulty in manufacturing metal coupling molds with superplastic temperature for titanium plates, and the difficulty in ensuring matching accuracy (especially for molds with complex shapes), superplastic forming of titanium plates is rarely used.
