The deviation of geometric accuracy of titanium alloy bar is mainly caused by the action of elasticity problem of the material. Titanium alloy bar thermoforming, the inner and lower plasticity is poor, deformation resistance is large, rebound is serious, thus forming problems are difficult, geometric accuracy is low.
Titanium alloy bar thermoforming, due to high temperature on the material soft than the role of the material, greatly reducing the distortion and springback of the parts after forming, but springback can not be completely eliminated. Such as titanium alloy bar resistance heating pressure forming or punching distance forming. Field parts still have a small amount of springback after thermoforming, geometric accuracy is not listed in the quality requirements, must be heavy manual trimming.
TC4 titanium alloy has excellent corrosion resistance, small density, high specific strength and good toughness and weldability and a series of advantages, in aerospace, petrochemical, shipbuilding, automotive and pharmaceutical sectors have been successfully applied.TC4 titanium alloy in the process of thermoforming, the surface of a layer of oxide skin will be formed, the thermoforming temperature is different, the colour of the oxide skin is different. Among them, when the thermoforming temperature is about 600℃, the oxide skin is blue; when the thermoforming temperature is about 850℃, the oxide skin is grey and reddish; and when the thermoforming temperature is 900℃, the oxide skin is grey. As the temperature rises, the difficulty of removing the oxide skin gradually increases. Most of the removal of titanium alloy oxide skin at home and abroad adopts a two-step method, i.e., first melt alkali washing, and then pickling; however, the temperature of the melt alkali washing medium is high, about 450 ℃, and it is easy to cause premature aging and strengthening of α + β and β titanium alloy semi-finished products, which will bring difficulties to further processing. In addition, hot alkali cleaning followed by nitric acid and hydrofluoric acid cleaning may also lead to hydrogen embrittlement corrosion of the titanium alloy surface.
