Titanium Pipe Fittings Processing: Precautions & Characteristic Analysis When The Hydrogen Content Is Too High

In the processing process of titanium pipe fittings, the hydrogen content is a key factor that needs to be strictly controlled. When the hydrogen content in titanium pipe fittings is too high, it will have a significant adverse impact on its performance, which in turn affects the entire processing process and the quality of the final product.

Hazards & Standards Of Excessive Hydrogen Content

When the hydrogen content in titanium pipe fittings exceeds a reasonable range, its impact toughness and notch tensile strength will decrease due to increased brittleness. This is because the presence of hydrogen atoms in the titanium lattice will interfere with the binding force between the titanium atoms, resulting in a decrease in the toughness of the material, and it is more prone to brittle fracture when subjected to external forces. In order to ensure the performance and quality of titanium pipe fittings, it is generally stipulated that the hydrogen content in titanium pipe fittings should not be higher than 0.015%.This standard has been verified by a large number of experiments and practices, and is an important basis for ensuring the safe and reliable operation of titanium pipe fittings under various working conditions.

Measures To Reduce Hydrogen Absorption

1. Cleaning work before heat treatment

In order to reduce the absorption of hydrogen by titanium pipe fittings during processing, cleaning before heat treatment is essential. Fingerprints, wear marks, grease, and other residues may contain hydrogen or provide conditions for the absorption of hydrogen. Therefore, before heat treatment, the titanium pipe fittings must be thoroughly cleaned to remove impurities such as fingerprints, wear marks, grease, etc. on the surface. Organic solvent cleaning, ultrasonic cleaning and other methods can be used to ensure that the surface of the titanium pipe fittings is clean and pollution-free.

2. Ensure the environment in the heat treatment furnace

The environment in the heat treatment furnace also has a great impact on the hydrogen content of titanium pipe fittings. Water vapor is one of the important sources of hydrogen. If there is water vapor in the heat treatment furnace, the titanium pipe fittings will absorb hydrogen during the heating process, resulting in an increase in hydrogen content. Therefore, before heat treatment, make sure that the anhydrous vapor in the heat treatment furnace is dry. The moisture and air in the furnace can be eliminated by preheating the furnace and introducing dry inert gas, so as to create a good environment for the heat treatment of titanium pipe fittings.

3. Treatment method for excessive hydrogen content

When the hydrogen content of titanium pipe fittings is higher than the allowable value, the method of vacuum annealing needs to be used for cleaning. Vacuum annealing is the heating treatment of titanium pipe fittings in a vacuum environment to cause hydrogen to escape from the titanium pipe fittings. In a vacuum environment, the partial pressure of hydrogen is extremely low, which is conducive to the diffusion and discharge of hydrogen. At the same time, the appropriate heating temperature can promote the mobility of hydrogen atoms and accelerate the escape process of hydrogen. The temperature and time of vacuum annealing need to be determined according to the specific conditions and hydrogen content of titanium pipe fittings. It generally needs to be maintained at a higher temperature for a certain period of time to ensure that the hydrogen can be fully discharged.

Oxidation & Deoxygenation Problems During Heat Treatment

1. Generation of oxidation problems

During the heat treatment process, titanium pipe fittings are prone to oxidation. When the temperature is not higher than 540 degrees, the oxide film of the titanium pipe fittings will not thicken much, and the impact on the material properties is relatively small. However, at higher heat treatment temperatures, the oxidation rate will be accelerated, and the inner diffusion layer of the oxidized material will become a layer of pollution. The oxygen-contaminated layer has a high brittleness ratio, which can cause cracks and damage to the surface of the parts, which seriously affects the quality and service life of titanium pipe fittings.

2. Method of deoxygenating the contaminated layer

In order to remove the oxygen pollution layer, machining, pickling, chemical grinding and other methods can be used. Machining is to remove the oxygen-contaminated layer on the surface by cutting, grinding, etc. This method is suitable for situations where the oxygen-contaminated layer is thicker. Pickling is the use of an acid solution to react chemically with the oxygen contaminated layer to dissolve and remove it. Commonly used acid solutions include hydrofluoric acid, nitric acid, etc., But during the pickling process, care should be taken to control the concentration, temperature and time of the acid solution to avoid excessive corrosion of titanium pipe fittings. Chemical grinding is the use of chemicals to react chemically with the surface of titanium pipe fittings, and at the same time cooperate with mechanical friction to remove the oxygen pollution layer and make the surface smoother and smoother.

3. Measures to reduce oxidation

During heat treatment, in order to reduce the impact of oxidation on titanium pipe fittings, the heating time should be shortened as much as possible under the premise of ensuring the heat treatment effect. Too long heating time will increase the time for titanium pipe fittings to come into contact with oxygen, thereby increasing the degree of oxidation. In addition, the heat treatment can be carried out in a vacuum furnace or an inert gas furnace. There is almost no oxygen in the vacuum furnace, which can effectively avoid the oxidation of titanium pipe fittings; the introduction of inert gases such as argon into the inert gas furnace can isolate the air and reduce the occurrence of oxidation. The heating of titanium pipe fittings in the air furnace should be avoided as much as possible. If it must be heated in the air furnace, appropriate protective measures should be taken, such as the use of protective coatings, etc., to reduce the oxidative pollution of titanium pipe fittings by the air.

Characteristics Of Titanium Pipe Fittings

1. Corrosion Resistance

Titanium is a highly active metal with a low equilibrium potential and a strong tendency to thermodynamic corrosion in the medium. However, titanium has good stability in various media such as oxidation, neutral, and weak reduction, and exhibits excellent corrosion resistance. This is because titanium will quickly form a dense oxide film in the air or in an oxygen-containing medium. This oxide film can prevent oxygen and other corrosive media from further contacting the titanium matrix, thereby playing a protective role.

2. Heat Resistance

Titanium pipe fittings have good heat resistance, and it can be used for a long time at a temperature of 600 degrees or higher. In a high temperature environment, titanium pipe fittings can still maintain good mechanical properties and chemical stability, without significant creep and relaxation, and can meet the requirements of use under high temperature conditions.

3. Non-Magnetic And Non-toxic

Titanium alloy pipe fittings are a kind of non-magnetic metal that will not be magnetized in a large magnetic field. This characteristic makes it widely used in some fields with special requirements for magnetism, such as electronics, medical and other industries. At the same time, titanium alloy pipe fittings are non-toxic and will not have harmful effects on the human body. They can be used in the manufacture of medical devices and food processing equipment in direct contact with the human body.

4. Low Elastic Modulus

The elastic modulus of titanium pipe fittings is low, about 57% of that of steel. The lower elastic modulus makes titanium pipe fittings more prone to elastic deformation when subjected to force, and has good flexibility and shock absorption properties. In some occasions with high requirements for shock absorption and flexibility, such as aerospace, automobile manufacturing and other fields, this characteristic of titanium pipe fittings has important application value.

5. Inhalation Performance

Titanium pipe fittings are a kind of active metal that can react with a variety of elements and compounds at high temperatures. This inhalation performance makes titanium pipe fittings need to pay attention to contact with other substances during processing to avoid unnecessary chemical reactions. At the same time, this characteristic can also be used to improve the performance of titanium pipe fittings through alloying and other methods to meet different needs.

In the processing process of titanium pipe fittings, great attention should be paid to the issue of hydrogen content, and effective measures should be taken to reduce the absorption of hydrogen and deal with situations where the hydrogen content exceeds the standard. At the same time, it is necessary to fully understand the characteristics of titanium pipe fittings, and reasonably select the processing technology and use environment according to their characteristics to ensure the quality and performance of titanium pipe fittings and promote the wide application of titanium pipe fittings in various fields.