1. Reactivity: Titanium is highly reactive with oxygen, nitrogen, and hydrogen at elevated temperatures. This means that during welding, it can easily absorb these gases from the air, leading to contamination and resulting in brittle welds. Special precautions, such as inert gas shielding (typically with argon) and a clean welding environment, are necessary.
2. Thermal Conductivity: Titanium has low thermal conductivity, which can cause uneven heating and cooling during welding. This can lead to distortion and internal stresses in the welded joint.
3. Oxidation: Titanium forms a stable oxide layer on its surface, which must be removed before welding. If the oxide layer is not properly removed, it can lead to poor weld quality and defects.
4. Maintenance of Temperature: Maintaining a consistent temperature is crucial when welding titanium. Rapid temperature changes can cause cracking and other defects in the weld.
5. Equipment and Techniques: Specialized equipment and techniques are often required to weld titanium effectively. Welders need to be highly skilled and experienced in working with this metal.

Despite these challenges, titanium is highly valued in various industries, such as aerospace and medical applications, due to its excellent strength-to-weight ratio and corrosion resistance.