Which metals often require leading and tailing shielding gases?

Titanium alloys often require leading and tailing shielding gases during welding due to their high reactivity with atmospheric gases, particularly oxygen and nitrogen. When welded, titanium can easily absorb these gases, leading to embrittlement and defects in the weld. This is especially critical at the start and end of the weld, where the molten weld pool is most exposed to the atmosphere. By using leading and tailing shielding gases, the welder can provide a protective atmosphere that prevents contamination during these vulnerable stages of the welding process, helping to ensure the quality and integrity of the weld.

In contrast, while other metals like aluminum alloys and copper alloys also require shielding gases, they might not be as sensitive to atmospheric contamination at the leading and tailing stages as titanium. Steel alloys generally require shielding gases primarily for penetration and to prevent oxidation, but the need for trailing shielding might not be as critical as it is for titanium. Thus, titanium stands out as the metal that most commonly necessitates the use of leading and tailing shielding gases to maintain weld quality.