What Are The Main Measures To Prevent Contamination Caused By The Forming Process Of Titanium Square Tube?

Titanium is a highly reactive metal and its activity increases with temperature.

Titanium and its alloys act with oxygen when heated in air or in an oxygenated atmosphere. When heated below 428°C, a protective oxide film is formed. When the temperature increases, the thickness of the oxide film increases. When the temperature is higher than 538c, the oxide film begins to lose its protective effect and oxygen diffuses through the film into the metal, forming a distinct gas permeable layer. If it is higher than 815c, a loose oxide layer forms on the surface of titanium.

In order to prevent the oxidation of titanium alloys, hydrogen absorption and contamination with other trace elements during superforming, technical measures are needed to give good properties to the formed titanium alloy parts.

The main measures are coating protection, vacuum heating and inert gas (argon) protection.

1, coating protection method

After cleaning, the surface of the forming blank is coated with a certain thickness of protective coating, and after the parts are demolded, the coating is removed by alkaline washing, acid washing or sand blowing.

The coating should have the following main properties:

a. High temperature resistance, can be used at high temperature of 750-1050℃;

b. It should have certain lubrication to prevent the blank from being abraded in the molding process;

c. The coating can be firmly attached to the surface of the blank under the working temperature;

d. It is easy to remove after heating;

e, no harmful substances, does not pollute the environment, does not hinder human health.

After identification of titanium tubes and titanium alloys suitable for use in superplastic forming coatings are: Ti-2 alcohol-soluble preparations can be used in conjunction with Ti-3 graphite-based lubricants for use in 750-1050 ℃ thermoforming; KBC-12 water-soluble preparations can be used in conjunction with the graphite aqueous agent. KBC-12 water-soluble preparation, can be used with graphite water agent.

2,Vacuum forming

Titanium tube for parts with thin wall thickness, high surface brightness requirements, hydrogen embrittlement sensitivity of β-type titanium alloy, vacuum forming.

Vacuum forming does not necessarily require expensive vacuum heating equipment. As long as the upper and lower cavities in the billet and mold to form a sealed space between the heating process, especially from 400 ℃ above to the forming temperature during the upper and lower cavities in the air is gradually pumped out by the vacuum unit, the mold of the upper and lower cavities of the degree of intersection between the above and below 10 (-3) torr, and in the process of forming through the cut off the tube and filled with argon can be achieved for the purpose of forming. The method was used for forming titanium foil corrugated sheet and satisfactory results were achieved. The hydrogen content is lower than the standard requirement when the vacuum is controlled at 10^(-3) torr, and parts with bright surfaces can be obtained when the vacuum reaches 10^(-5) torr.

In addition, for parts with medium thickness and not high requirements for surface concavity and brightness, the vacuum argon filling protection method can also be used to carry out tests in this regard during the molding process of spherical cylinders, and the results are also better.