Hot processing, mainly forging, rolling and extruding, is the basic production method of titanium flange semi-finished products and products. In view of the strong sensitivity of the titanium flange structure to the hot processing process, the correct selection and mastering of process parameters are not only important for ensuring the shape and size accuracy of the product, but also the key factor for the internal quality of the product.
Compared with general metal structural materials, the thermal processing feature of titanium flanges is that the deformation resistance is large and the deformation temperature range is narrow. Titanium with a hexagonal crystal structure is not easy to deform. In order to improve the plasticity, it is necessary to heat the metal to the b-phase region above the transformation point, so-called b-processing. However, due to the large tendency of titanium flanges to overheat, high-temperature heating will cause b grains to grow rapidly, but if the amount of deformation is insufficient, the formation of a coarse Weiss structure after cooling will significantly reduce the periodicity and fatigue strength of the alloy. The organization is difficult to eliminate in the subsequent heat treatment, so the current production of the finished product or the thermal processing starting temperature before the finished product is not required to pass the critical point Tb. Because the deformation resistance of the titanium flange is very sensitive to the reduction of the deformation temperature or the increase of the deformation rate, the temperature of the forging stop cannot be too low. The constraints of these two factors limit the processing temperature range of most titanium flanges to 800-950°C, which is not easy to grasp. However, for the opening of the ingot, the temperature range can be expanded to 850-1150 ℃, in the subsequent processing of the fire, the temperature is gradually reduced.
Titanium flange alloy has poor thermal conductivity. During rapid deformation, the temperature of the core of the workpiece rises quickly. It is easy to cause overheating due to slow heat transfer, and the surface temperature of the workpiece is low, and surface cracks are easy to form. Therefore, it is necessary to pay attention to the deformation during processing Rate and deformation.
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