In the forging process of titanium alloys, the original structure characteristics of the billet, encompassing chemical composition, impurity distribution, selection of thermal processing parameters, and subsequent heat treatment procedures, significantly influence the final microstructure and mechanical properties of the forgings.
The selection of rolling temperature stands as a pivotal determinant. Optimal rolling temperatures, ensuring substantial deformation of the billet during forging, effectively mitigate adverse effects on the original structure. However, achieving such high deformation rates poses challenges in industrial settings. As deformation rates decrease, the detrimental impacts of the original structure become more pronounced, posing a potential threat to forging quality.
For titanium and titanium alloy ingots, the original structure often exhibits coarse grains and limited process plasticity. The pre-forging heating process becomes crucial in ameliorating this condition. Heating the ingot above the transformation point and completing the primary deformation in the β phase has proven effective. In the β phase, material deformation resistance significantly diminishes while plasticity drastically increases, allowing for more thorough fragmentation of the cast structure, thereby enhancing production efficiency and reducing energy consumption.
Further research and practice demonstrate that when the total deformation of the ingot reaches 70% to 80%, a significant transformation occurs in the internal microstructure of the forging. The coarse grains are refined, forming a uniform and fine fibrous structure. This transition not only enhances the material's tensile strength but also significantly improves its ductility, rendering the forging more resilient and durable when subjected to external forces.
Additionally, the selection of rolling temperature must consider the specific composition and impurity content of the material. Different titanium alloy compositions and impurity levels have varying effects on rolling temperature selection and structural evolution during forging. Hence, practical operations necessitate the formulation of rational rolling temperature specifications and forging process parameters tailored to the specific titanium alloy material to ensure optimal forging quality and performance.
In conclusion, rolling temperature exerts a profound influence on the microstructure and properties of titanium forgings. Strict control of rolling temperature, optimization of the billet's original structure, and the establishment of rational forging process parameters and heat treatment procedures are essential to ensure forging quality at its peak.
