Titanium alloy hot stamping is an advanced manufacturing process, in which the heating rate plays an extremely critical role and profoundly affects the final forming effect.
First, the heating rate affects the microstructure change of titanium alloy. When the heating rate is slow, the titanium alloy has enough time to undergo uniform structural transformation, and the grains can grow relatively slowly to form a relatively coarse but uniform grain structure. This structure deforms more uniformly during the subsequent stamping process, which is beneficial to improve the overall stability of the formed part, but may lead to a slight decrease in strength and hardness. On the contrary, rapid heating will cause the titanium alloy to reach a higher temperature in a short time, inhibit the growth of grains, and form a fine grain structure. This makes the material have higher strength and hardness, but during stamping, it may increase the risk of cracking due to strong anisotropy and uneven local deformation.
Secondly, the heating rate plays an important role in the phase transformation of titanium alloy. Different heating rates will change the proportion and distribution of phases in titanium alloys. For example, for some titanium alloys, rapid heating may lead to incomplete phase transformation, leaving some phases that are not conducive to forming, reducing the plasticity of the material, making the fluidity of the material worse during stamping, and making it difficult to obtain complex-shaped molded parts; while the appropriate heating rate can ensure that the phase transformation is sufficient and uniform, and improve the comprehensive forming performance of the material.
Furthermore, the heating rate is closely related to the thermal stress of titanium alloys. Rapid heating will produce a large temperature gradient inside the titanium alloy, thereby inducing higher thermal stress. During the hot stamping process, this thermal stress is superimposed on the forming stress, which can easily cause cracks or uneven deformation of the material. Slow heating helps to reduce the temperature gradient and thermal stress, so that the material can better withstand external stress during stamping and improve the success rate of forming.
In addition, the heating rate will also affect the degree of oxidation on the surface of the titanium alloy. Rapid heating may cause the surface of the titanium alloy to react violently with oxygen in a short period of time, forming a thicker oxide layer. This will not only consume the material itself, but may also cause the oxide layer to fall off during stamping, affecting the surface quality of the molded part; a moderate heating rate can control the oxidation reaction to a certain extent, reduce the thickness of the oxide layer, and ensure the appearance and performance of the molded part.
From the perspective of energy consumption, a higher heating rate usually requires a greater power input, which will increase production costs in large-scale production. Reasonable selection of heating rate and reduction of energy consumption while meeting molding requirements are of great significance for improving the economic efficiency of the process.
In the titanium alloy hot stamping process, the heating rate comprehensively determines the molding effect by affecting microstructure, phase transformation, thermal stress, oxidation degree and cost. Therefore, precise control of heating rate is one of the key links to optimize the titanium alloy hot stamping process and obtain high-quality molded parts.
