Difficulty analysis of hot forming of titanium alloy rod
The geometric accuracy deviation of titanium alloy rods is mainly caused by the elasticity of the material. Hot forming of titanium alloy rods has plasticity inside and under, large deformation resistance and serious springback, so forming problems are difficult and geometric accuracy is low.
Hot forming of titanium alloy rods, the effect of high temperature on the softness of the material greatly reduces the distortion and springback of the parts after forming, but the springback cannot be completely eliminated. Such as the resistance heating of titanium alloy rods, drop forming or stroke forming. Tian parts still have a small amount of springback after thermoforming, and the geometric accuracy reaches the quality requirements, and heavy manual trimming is necessary.
TC4 titanium alloy has a series of advantages such as excellent corrosion resistance, low density, high specific strength, better toughness and weldability, etc., and has been successfully applied in the aerospace, petrochemical, shipbuilding, automotive and pharmaceutical sectors. During the hot forming process of TC4 titanium alloy, a layer of oxide scale will be formed on the surface, and the color of the obtained oxide scale will be different at different hot forming temperatures. Among them, when the thermoforming temperature is about 600°C, the oxide scale is blue; when the thermoforming temperature is about 850°C, the oxide scale is gray to reddish; and when the thermoforming temperature is 900°C, the oxide scale is gray. With the increase of temperature, the difficulty of removing oxide scale gradually increases. The removal of titanium alloy scale at home and abroad mostly adopts a two-step method, that is, first molten alkali washing and then acid washing; however, the temperature of molten alkali washing medium is higher, which can reach about 450 ℃, and it is easy to cause semi-finished products of α + β and β titanium alloys. The premature aging strengthening of sulphate brings difficulties to further processing. In addition, washing with nitric acid and hydrofluoric acid after hot alkaline washing may also cause hydrogen embrittlement corrosion on the surface of the titanium alloy.