Arc welding processes — which one of the following uses a non-consumable tungsten electrode to sustain the arc while the filler (if any) is added separately?

Introduction / Context:
Identifying whether an electrode is consumable or non-consumable is fundamental to classifying arc welding processes and predicting bead characteristics, heat input, and metallurgical outcomes. Tungsten Inert Gas (TIG), also called Gas Tungsten Arc Welding (GTAW), is the canonical non-consumable electrode process.

Given Data / Assumptions:

• Electrode types: consumable (melts, supplies filler) vs non-consumable (does not melt).
• Shielding: inert gases like argon/helium commonly used in TIG/MIG.
• Process names: TIG (GTAW), MIG (GMAW), Manual Metal Arc (SMAW), Submerged Arc (SAW).

Concept / Approach:

In TIG/GTAW, a tungsten electrode sustains the arc but is not intended to melt into the weld pool. Filler, when needed, is added separately as a rod. MIG/GMAW, SMAW, and SAW all employ consumable electrodes: the wire (MIG/SAW) or the coated stick (SMAW) melts to become filler metal. Thus, the presence of a tungsten electrode that remains essentially intact is the distinguishing feature of TIG.

Step-by-Step Solution:

Verification / Alternative check:

Welding handbooks and training curricula define TIG/GTAW by its use of non-consumable tungsten electrodes, with shielding by inert gases to prevent tungsten oxidation and weld contamination.

Why Other Options Are Wrong:

MIG, Manual arc (SMAW), and SAW all melt the electrode to supply filler; none uses a non-consumable electrode.

Common Pitfalls:

Confusing tungsten (non-consumable) with “TIG wire”; in TIG, any added filler is a separate rod, not the electrode itself.

Final Answer:

TIG welding