What Are The Main Measures To Prevent Pollution During The Titanium Tube Forming Process?

Titanium is a highly active metal, and its activity increases with increasing temperature.
Titanium and its alloys react with oxygen when heated in air or oxygen-containing atmospheres. When heated below 428 ℃, a protective oxide film is formed. As the temperature increases, the thickness of the oxide film increases. When the temperature exceeds 538 ℃, the oxide film begins to lose its protective effect, and oxygen diffuses into the metal through the film, forming a clear gas permeation layer. If it exceeds 815c, a loose oxide layer forms on the surface of titanium.
In order to prevent oxidation, hydrogen absorption, and contamination of other trace elements in titanium alloy during superforming, technical measures need to be taken to ensure that the formed titanium alloy components have good performance.
The main measures are coating protection, vacuum heating, and inert gas (argon) protection.
1. Coating Protection Law
After cleaning, apply a certain thickness of protective coating on the surface of the formed blank. After demolding the parts, remove the coating using alkaline washing, acid washing, or sand blowing methods.
The coating should have the following main properties:
a. High temperature resistance, able to be used at high temperatures of 750-1050 ℃;
b. It should have a certain lubricating effect to prevent scratches on the blank during the forming process;
c. The coating can firmly adhere to the surface of the billet at working temperature;
d. Easy to remove after heating;
e. No harmful substances, no pollution to the environment, and no hindrance to human health.
The coatings that have been identified as suitable for superplastic forming of titanium pipes and titanium alloys include: Ti-2 alcohol soluble formulations that can be used in conjunction with Ti-3 graphite lubricants, suitable for hot forming at 750-1050 ℃; KBC-12 water-soluble preparation, can be used in conjunction with graphite water agents.
2. Vacuum forming
Titanium tubes have high requirements for component wall thickness, surface brightness, and strong sensitivity to hydrogen embrittlement β Titanium alloy, vacuum formed.
Vacuum forming does not necessarily require expensive vacuum heating equipment. As long as a sealed space is formed between the upper and lower cavities of the billet and the mold, during the heating process, especially from above 400 ℃ to the forming temperature, the air in the upper and lower cavities is gradually extracted by the vacuum unit. The intersection degree between the upper and lower cavities of the mold reaches more than 10 (-3) torches, and the forming purpose can be achieved by cutting off the pipe and filling argon gas during the forming process. This method has been applied to the forming of titanium foil corrugated plates and achieved satisfactory results. When the vacuum degree is controlled at 10 ^ (-3) torr, the hydrogen content is lower than the standard requirement. When the vacuum degree reaches 10 ^ (-5) torr, a bright surface of the part can be obtained.
In addition, for parts with medium thickness and low requirements for surface roughness and brightness, vacuum argon filling protection method can also be used to test this aspect during the forming process of spherical gas cylinders, and the effect is also good.