Performance characteristics of titanium flanges and titanium alloy flanges, as well as relevant precautions for hot processing

Hot processing, mainly including forging, rolling and extrusion, is the basic production method for semi-finished products and finished products of titanium flanges. Given the strong sensitivity of the titanium flange's organizational structure to the hot processing technology, the correct selection and control of process parameters are not only very important for ensuring the dimensional accuracy of the products, but also crucial for the intrinsic quality of the products.

Compared with general metal structural materials, the hot processing characteristics of titanium flanges are high deformation resistance and a narrow temperature range for deformation. Titanium with a hexagonal crystal structure is difficult to deform. To improve plasticity, the metal needs to be heated to the b-phase region above the transformation point for so-called b processing. However, titanium flanges have a high tendency to overheat, and high-temperature heating will cause the b grains to grow rapidly. But if the deformation amount is insufficient, the coarse Widmanstätten structure formed after cooling will significantly reduce the homogeneity and fatigue strength of the alloy. And this overheated structure is difficult to eliminate in subsequent heat treatment. Therefore, in current production, the starting temperature for hot processing of finished products or the first heat treatment is not required to be at the critical point Tb. Due to the high sensitivity of the deformation resistance of titanium flanges to the reduction of deformation temperature or the increase of deformation rate, the stop forging temperature cannot be too low. The constraints of these two factors limit the processing temperature range of most titanium flanges' finished products to 800-950℃, which is very difficult to master. However, for the opening of ingots, the temperature range can be expanded to 850-1150℃, and the temperature can be gradually reduced in subsequent heat treatment processes.

Titanium flange alloys have poor heat conductivity. During rapid deformation, the core of the workpiece heats up quickly, and due to the slow heat transfer, it is prone to overheating, while the surface temperature is lower, which is prone to form surface cracks. Therefore, during the processing, it is necessary to pay attention to controlling the deformation rate and deformation amount.