Titanium is a metallic chemical element with the chemical symbol Ti and an atomic number of 22. Titanium alloy is also an important metal material, widely used in aerospace, medical equipment, chemical industry and other fields due to its lightweight, high strength and good corrosion resistance. However, due to the unique properties of titanium alloys, there are some challenges and potential welding defects during the welding process.

Welding titanium alloys is relatively difficult. The difficulties and potential defects of its welding are mainly reflected in the following aspects:

Brittle phenomenon: Titanium alloys are prone to react with impurities such as oxygen, nitrogen, and hydrogen in the atmosphere at high temperatures, resulting in embrittlement and reducing the plasticity and toughness of welded joints. To avoid embrittlement, the atmosphere during the welding process and the purity of the processed material should be controlled.

Welding cracks: The occurrence of welding cracks in titanium alloys is related to stress and hydrogen content, so it is necessary to control stress during the welding process, avoid overheating and rapid cooling of the material, and ensure that the welding area is dry and clean.

Welding porosity: During the welding process, due to the reaction between titanium alloy and oxides, welding porosity is easily generated, which reduces the strength and sealing of the welded joint. Pay attention to controlling the argon gas protection and oxygen content of welding materials, while ensuring the dryness and cleanliness of the welding area.

To prevent the above problems in welding, relevant defect prevention measures should be taken.

1. Choose the appropriate welding process and wire, and select the appropriate welding method based on the material and impurities of the titanium alloy base material.

2. Use high-quality protective gas to ensure a purity of not less than 99.99%.

3. Thoroughly clean and treat the base metal and welding wire before welding to avoid cracks and interlayers.

4. During the welding process, appropriate argon protection measures should be taken for the molten pool and the heat affected zone of the weld to ensure welding quality.

Preparation before welding:

Surface treatment: Physical treatment of the surface of titanium alloy, including sandblasting, shot blasting, and polishing, to remove dirt and oxide layers from the surface. This can improve the quality and reliability of welding.

Chemical treatment: Dissolve and remove dirt and oxides on the surface of titanium alloys using acidic and alkaline chemicals. Chemical treatment helps improve the quality and characteristics of welded joints.

Cleaning and Drying: Ensure the welding area is dry and clean to avoid the formation of pores and other defects. Properly use drying ovens or heating equipment to ensure appropriate temperature and humidity in the welding environment.

Common welding methods:

Plasma arc welding: Heating and melting titanium alloys through high-energy plasma arc, often using direct current arc. Plasma arc welding has high energy density and welding speed, suitable for thick titanium alloy plates and large welded parts.

Gas tungsten arc welding (GTAW welding): an arc welding method that uses a non melting tungsten electrode for welding. When performing GTAW welding, the welding area is shielded with gas to prevent atmospheric pollution (inert gases such as argon are commonly used), and solder (filler metal) is usually used in combination.

Melting electrode argon arc welding (MIG welding): a semi-automatic or fully automatic welding method that uses argon gas to protect the welding area. MIG welding is easy to operate and suitable for welding thick titanium alloy plates and large structural components.

Tungsten inert gas welding (TIG welding): using a tungsten electrode to generate an arc to heat and melt titanium alloy, and protecting the welding area with argon gas. TIG welding has high welding quality and control ability, suitable for thin plate and precision welding.

Vacuum electron beam welding: Heating and melting of titanium alloys using an electron beam under vacuum conditions. Vacuum electron beam welding has high welding speed and weld quality, and is suitable for thicker titanium alloy structural components.