Titanium alloy TC18 (BT22) is a crucial material characterized by a martensite transformation temperature close to room temperature and a higher content of alloying elements, approximately Kβ≈1.1. Its welding properties are commendable, suitable for various methods such as fusion welding, contact welding (roller welding and spot welding), and electron beam welding. Although annealing the joint is necessary to achieve good plasticity, heat treatment for strengthening purposes is not advisable. This alloy finds extensive application in aerospace manufacturing, including load-bearing landing gear, engine fans, low-pressure compressor leaf discs and blades, and engine fixed support structures.

When butt welding titanium alloy TC18 with a thickness of 18 mm or less, a titanium alloy TA20 wire with a diameter of 2.0 mm is recommended. Typically, the weldment groove is in the form of a UV composite groove, and manual argon arc welding is carried out in a vacuum argon protection box. Controlling welding speed and minimizing welding line energy are crucial to reduce heat input, prevent accumulation of multiple heat inputs, and thus, avoid compromising joint performance. Welding stability, concentrated heat source, uniform droplet transfer, and well-formed front and back surfaces after multiple welds are essential for quality control during the welding process.

To ensure weld internal quality, strict surface cleaning of the weldment and welding wire is essential before welding. X-ray inspection is performed on the bottom welding and between the 2nd and 3rd layers to identify and eliminate welding defects promptly, reducing the impact of repair welding on joint microstructure. Welding only proceeds when meeting the stringent quality requirements for first-grade welds of the navigation mark.