Bending Forming: A Common Process Combining Plasticity and Elasticity. Bending forming is a processing technology that combines plastic and elastic deformation, and it is one of the most common forming methods in the manufacture of titanium equipment. During bending deformation, springback is a crucial factor that must be considered.
The bending angle of titanium materials can typically be greater than 90°, but a minimum bending radius must be met to ensure bending quality. For titanium tubes with a diameter less than 50mm, cold bending can be used. Cold bending is relatively simple, but stress-relieving annealing is recommended afterward. This is because residual stress is generated inside the titanium tube during cold bending, and if not eliminated in time, it may affect the performance and lifespan of the titanium tube. Hot bending of titanium tubes is divided into tension bending and push bending depending on the stress conditions. During hot bending, the heating temperature is generally controlled between 177-350℃ (titanium alloys can be heated to 427℃). Within this temperature range, the yield strength of titanium materials decreases by 25%-50%, while plasticity is improved, the springback angle is very small, and gas pollution is also less. These characteristics allow for better control of bending precision during hot bending, meeting the requirements of titanium equipment manufacturing.
Stamping Forming: Diverse Methods to Address the Unique Characteristics of Titanium Stamping titanium plates and alloys is relatively difficult, as their bending radii are larger than those of commonly used steel and non-ferrous metals. To achieve effective stamping forming of titanium plates and alloys, we employ various methods, primarily including cold forming, hot forming, and pre-forming followed by hot straightening. Cold forming is mainly used for workpieces with thin walls, small deformation, large bending radii, and low dimensional accuracy requirements. When the deformation during cold forming is significant, a combination of cold stamping and inter-process annealing can be used. After cold stamping, final annealing is required to eliminate residual stress and ensure workpiece stability. For titanium plates and alloys with complex shapes and large deformation, hot stamping is a more suitable choice. Hot stamping can be divided into lower-temperature forming and higher-temperature forming depending on the heating temperature. Lower-temperature forming involves heating at 200-350℃, where the deformation can reach 40%. Higher-temperature forming involves heating at 600-800℃, suitable for forming thicker plates, larger deformation, and larger finished workpieces. There are three main heating methods for thermoforming: heating the mold, heating the blank, and simultaneously heating both the mold and the blank. After thermoforming, titanium workpieces require surface treatments such as sandblasting and pickling to remove oxide scale and contaminant layers, improving the surface quality. Hot straightening after preforming involves first creating a preform using conventional stamping, and then heating and straightening it on a specialized machine tool or device. This method effectively eliminates residual stress and springback, ensuring the workpiece achieves the required shape and size, thus improving its precision and quality.
Spin forming: Combining the advantages of multiple processes, spin forming integrates the characteristics of forging, extrusion, stretching, bending, ring rolling, and cross rolling. This process has many advantages. First, it has good deformation conditions, allowing control of the material deformation process over a wide range. Second, it has high material utilization, saving 20%-50% of material and effectively reducing production costs. Furthermore, the finished products have high surface finish and small dimensional differences, meeting the manufacturing requirements of high-precision titanium equipment. These characteristics of the spin forming process have led to its widespread application in titanium equipment manufacturing.
Expansion joint: Titanium tube-to-titanium plate bonding is a mechanical connection method that relies on the deformation of the tube and tube sheet to achieve sealing and fastening. It is also an important process in the manufacture of shell-and-tube heat exchangers. When connecting titanium tubes to titanium tube sheets, the expansion degree (inner diameter expansion rate) should ideally be 1%-6%. If the expansion degree is expressed as the tube wall thinning rate, it can reach 5%. Expansion joint methods are mainly divided into three types: mechanical expansion joint, flexible expansion joint, and explosive expansion joint. Mechanical expansion joints are simple to operate and widely used; flexible expansion joints can better adapt to the deformation of pipes and tube sheets, improving the connection quality; explosive expansion joints utilize the energy generated by an explosion to achieve expansion joints, and have advantages such as high efficiency and strong connection, but have higher operation requirements.
The bending, stamping, spinning, and expansion processes in titanium equipment manufacturing each have their own characteristics and applicable scope. In actual production, it is necessary to rationally select and combine these processing processes based on the specific requirements of the titanium equipment, the properties of the titanium material, and production conditions to ensure the quality and performance of the titanium equipment and promote the continuous development of the titanium equipment manufacturing industry.