When the hydrogen content in titanium tubing is too much, the impact toughness and notched tensile strength will be sharply reduced because of brittleness, so the hydrogen content in titanium tubing is generally specified to be no more than 0.015%. In order to reduce the amount of hydrogen absorption, parts in the heat treatment should be removed before fingerprints, rolling mill marks, grease and other residues, no water vapor in the atmosphere of the heat treatment furnace. If the hydrogen content of the titanium tube exceeds the allowable value, it must be removed by vacuum annealing. Dehydrogenation of the vacuum annealing is generally in the 538-760 ℃, less than 0.066 Pa pressure to maintain 2-4 hours.
When the temperature does not exceed 540 ° C, the oxide film on the surface of the titanium tube will not be significantly thickened, and at higher heat treatment temperatures (760 ° C or more), the oxidation rate will be rapidly accelerated, at the same time, the oxygen to the internal expansion of the material to form a diffusion layer - pollution layer. Oxygen contamination layer has a high brittle ratio leading to cracks and damage to the surface of the part.
Remove the oxygen contamination layer has mechanical processing methods (such as sandblasting, room chipping, etc.), or pickling, chemical milling and other chemical methods, in the heat treatment, the heating time should be shortened as much as possible under the premise of ensuring that the heat treatment meteoric rise, but also in the vacuum furnace or inert gases (argon, nitrogen, etc.) in the heating furnace. Appropriate application can also avoid or mitigate the pollution generated by the titanium tube parts heated in the air furnace.
