The reaction of titanium alloy materials such as titanium rods and titanium tubes in the air is usually a reaction with oxygen, nitrogen and hydrogen, which are three non-metallic elements, and their reaction process is closely related to temperature.
Titanium reacts with oxygen in air, is very slow below 100 ° C, and only the surface is oxidized at 500 ° C. With the increase of temperature, the surface oxide film began to dissolve in titanium, and oxygen began to diffuse to the internal character of the metal, but oxygen did not enter the internal lattice of the metal in large quantities at 700℃. When the temperature exceeds 700℃, the diffusion of oxygen to the interior of the metal accelerates, and the surface oxide film loses its protective effect at high temperatures.
The reaction of titanium with oxygen depends on the form and temperature at which titanium is present. Powder titanium in the air at room temperature, due to static electricity, sparks, friction and other effects of intense combustion or explosion. However, dense titanium is very stable in air at room temperature. When dense titanium is heated in the air, it begins to react with oxygen, and initially oxygen enters the titanium surface lattice to form a dense oxide film, which prevents oxygen from spreading internally and has a protective effect, so titanium is stable in the air below 500 ° C. The color of the oxide film on the surface is related to the generation temperature, which is silver white below 200 ° C, light yellow at 300 ° C, golden yellow at 400 ° C, blue at 500 ° C, purple at 600 ° C, red-gray at 700 ~ 800 ° C, and gray at 800 ~ 900 ° C. In pure oxygen, the initial temperature of the violent reaction between titanium and oxygen is lower than that in air, and titanium burns in oxygen at about 500 ~ 600 ° C.