TIG (GTAW) shielding gases In tungsten inert gas (TIG) arc welding, the weld zone is commonly shielded by:

Introduction / Context:
TIG (GTAW) welding requires an inert atmosphere around the tungsten electrode and molten pool to prevent oxidation and contamination. Selecting the proper shielding gas influences arc stability, heat input, and bead shape.

Given Data / Assumptions:

• Process uses a non-consumable tungsten electrode.
• Shielding must be inert for clean, high-quality welds.
• Common base metals: aluminum, stainless steel, magnesium, titanium.

Concept / Approach:
Argon and helium are the standard inert gases for TIG. Argon offers easy arc starts and stable arcs; helium provides higher heat input and deeper penetration, useful for thick sections and high-conductivity metals. Mixtures of Ar-He tune performance. Active gases like CO2 or N2 are avoided in TIG because they destabilize the arc and contaminate the weld.

Step-by-Step Solution:
List acceptable inert gases: argon, helium, or their mixtures.Exclude active gases that would react with the weld pool (CO2, N2).Therefore, the shielding is provided by either argon or helium.

Verification / Alternative check:
Manufacturer application notes for GTAW torches specify argon or helium flow rates; gas mixtures like Ar-He are widely used for aluminum and copper alloys.

Why Other Options Are Wrong:
CO2 is typical for GMAW/MAG on steels, not TIG; nitrogen is reactive and causes porosity/embrittlement in many alloys during TIG.

Common Pitfalls:
Insufficient gas flow leading to porosity; drafts blowing away shielding; using incorrect gas for thick aluminum leading to lack of fusion.

Final Answer:
either (a) or (b)