When the hydrogen content in titanium pipes is too high, the impact toughness and notch tensile strength will sharply decrease due to embrittlement. Therefore, it is generally stipulated that the hydrogen content in titanium pipes should not exceed 0.015%. To reduce hydrogen absorption, fingerprints, mill marks, grease, and other residues should be removed from the parts before heat treatment, and there should be no water vapor in the atmosphere of the heat treatment furnace. If the hydrogen content of titanium tubes exceeds the allowable value, it must be removed through vacuum annealing. Vacuum annealing for dehydrogenation is generally carried out at a temperature of 538-760 ℃ and a pressure below 0.066Pa for 2-4 hours.
The titanium tube manufacturer stated that when the temperature does not exceed 540 ℃, the oxide film on the surface of the titanium tube will not significantly thicken. However, at higher heat treatment temperatures (above 760 ℃), the oxidation rate will rapidly accelerate, and oxygen will expand into the material to form a diffusion layer - pollution layer. The pollution layer of oxygen has a high brittleness ratio, which leads to cracks and damage on the surface of the parts.
There are mechanical processing methods (such as sand blasting, room cutting, etc.), or chemical methods such as acid cleaning, chemical milling, etc. to remove the oxygen from the contaminated layer. During the heat treatment, the heating time should be as short as possible on the premise of ensuring the heat treatment of meteorites, or it can be carried out in a Vacuum furnace or an inert gas (argon, nitrogen, etc.) heating furnace. Appropriate application can also avoid or reduce the pollution generated by titanium tube parts during heating in an air furnace.
