The reaction of titanium alloy materials such as titanium rods and titanium tubes in the air usually reacts with non-metallic elements such as oxygen, nitrogen, and hydrogen. The reaction process is closely related to temperature.
Titanium reacts very slowly with oxygen below 100 degrees in the air and only oxidizes when the surface is at 500 degrees. As the temperature increases, the oxide film on the surface begins to dissolve, and oxygen begins to diffuse into the metal. However, at 700°C, oxygen does not enter the inner lattice of the metal. Above 700°C, the diffusion of oxygen on the metal is accelerated, and the surface oxide film loses its protective effect at high temperatures.
"The reaction of titanium to oxygen depends on the shape and temperature of titanium. Powdered titanium powder will burn or explode violently under the action of static sparks and friction in the air at room temperature. However, titanium is stable in air at room temperature. After being heated in the air, the dense titanium begins to react with oxygen. First, oxygen enters the titanium surface through the crystal lattice to form a dense oxide film. The surface of the oxide film can prevent oxygen from diffusing inward and play a protective role. As a result, titanium remains stable in the air below 500°C. The color of the surface oxide film is related to the formation temperature.
less than 200 degrees is silvery-white, 300 degrees is light yellow, 400 degrees is golden yellow, blue is 500 degrees, 600 degrees is purple, 700-800 degrees is red-gray, 800-900 degrees is gray. Under pure oxygen conditions, the initial temperature ratio of titanium to oxygen is lower than the initial temperature ratio in air. Titanium burns in oxygen at about 500-600°C. Titanium does not react with nitrogen at room temperature, but titanium is one of the few metal elements that can burn in nitrogen at high temperatures. When the combustion temperature of titanium in nitrogen exceeds 800°C, the reaction between titanium and nitrogen is very strong. The reaction of titanium with nitrogen can not only generate titanium (ti3n, TiN) but also form a Ti-N solid solution. At 500~550℃, titanium starts to absorb nitrogen and form an interstitial solid solution; when it exceeds 600℃, the nitrogen absorption rate of titanium increases. Nitrogen in the Ti-N solid solution enters the titanium lattice in the form of titanium nitride, the phase transition temperature of titanium increases, and nitrogen is also a stabilizer of titanium. The solubility (mass fraction) of nitrogen in the air is 7% at 1050°C and 2% at 2020°C. However, the absorption of nitrogen by titanium is much slower than the absorption of oxygen. Therefore, titanium mainly absorbs oxygen in the air, while the absorption of nitrogen is secondary.
