As a new type of light alloy material, titanium and titanium alloys have been widely used because of their excellent properties such as high specific strength, non-magnetic, and corrosion resistance. In recent years, the advantages of titanium alloys in the fields of energy, chemical industry, and ships due to their high strength and corrosion resistance have become more and more obvious, and the application of titanium alloys in the above fields is mostly thick plate materials with a thickness of more than 20 mm. Higher requirements are put forward for welding processing, and the research on the welding of thick titanium alloys plate is also more urgent.
Strict protective measures should be taken when welding titanium alloys. Titanium alloys are active metals that absorb hydrogen above 300°C, oxygen above 600°C, and nitrogen above 700°C. These gases will cause embrittlement of welded joints. At the same time, thick plate materials will inevitably produce great stress and deformation during the welding process.
Therefore, it is proposed to use the narrow gap TIG method to weld thick plate titanium alloy. TIG welding is especially suitable for welding non-ferrous metals. The argon gas emitted during the welding process can continuously protect the weld area, and the welding stress and deformation can be reduced. Narrow gap groove reduces the amount of deposited metal and improves the quality of welded joints.
The study of the temperature field in the narrow gap TIG welding process of titanium alloy can determine the protection degree of titanium alloy and further improve the welding process, deepen the understanding of the welding process, and establish the relationship between temperature change and microstructure transformation during the welding process. Although the finite element analysis method has achieved some results, the full-scale model and the actual welding process are still needed to guide the welding process.
1) By welding the 52 mm thick unilateral U-shaped narrow gap groove titanium alloy test plate, the temperature field under the narrow gap TIG welding condition of the thick plate was measured. With the increase of weld thickness, the heating and cooling rate of the temperature field gradually decreases, and the time of the peak temperature of the temperature field is particularly obvious because of the poor thermal conductivity of titanium alloy.
2) The temperature field measurement test determined that during the narrow-gap TIG multi-layer welding of thick titanium alloy, when the thickness of the filler metal reaches 37 mm, the protection measures on the back side of the titanium alloy test plate can be removed.
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