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Hot processing, mainly forging, rolling, and extrusion, is the basic production method for titanium flange semi-finished products and products. Given the strong sensitivity of the titanium flange structure to hot working processes, the correct selection and mastery of process parameters are not only important for ensuring the dimensional accuracy of the product, but also a key factor in the internal quality of the product.
Compared with general metal structural materials, the hot working characteristics of titanium flanges are high deformation resistance and narrow deformation temperature range. Titanium with hexagonal crystal structure is not easily deformed. To improve plasticity, it is necessary to heat the metal to the b-phase zone above the phase transition point and perform so-called b-processing. However, due to the tendency of titanium flanges to overheat, high-temperature heating will cause rapid growth of b grains. However, if the deformation amount is insufficient, the formation of coarse Weinstein structure after cooling will significantly reduce the ductility and fatigue strength of the alloy. This type of overheated structure is difficult to eliminate in subsequent heat treatment. Therefore, the starting temperature of heat treatment for finished products or the previous heat treatment of finished products is not required to exceed the critical point Tb in current production. Due to the high sensitivity of the deformation resistance of titanium flanges to the decrease in deformation temperature or the increase in deformation rate, even the stopping forging temperature cannot be too low. The constraints of these two factors limit the processing temperature range of most titanium flanges to between 800 and 950 ℃, making it difficult to master. But for the opening of the ingot, the temperature range can be expanded to 850-1150 ℃, and the temperature can be gradually reduced during the subsequent processing.
Titanium flange alloy has poor thermal conductivity. During rapid deformation, the temperature at the center of the workpiece rises rapidly, which can easily cause overheating due to slow heat transfer. On the other hand, the surface temperature of the workpiece is lower, which can easily form surface cracks. Therefore, it is necessary to pay attention to controlling the deformation rate and amount during the processing.
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