---
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  Welding — process types, safety, materials, joint design, and quality control.
  Sources: USDA, OSHA, trade association guidelines, professional kitchen standards.
---

# Welding

## Welding processes

### MIG (GMAW — Gas Metal Arc Welding)

Most beginner-friendly. Wire electrode feeds automatically. Shielding gas protects weld pool.
**Good for:** Most steel and aluminum. Production welding. Thin to medium thickness.
**Shielding gas:** 75% Argon / 25% CO₂ (C25) for steel. 100% Argon for aluminum.
**Parameters:** Voltage, wire feed speed, travel speed, work angle. All affect bead.

### TIG (GTAW — Gas Tungsten Arc Welding)

Most precise. Separate filler rod fed by hand. Non-consumable tungsten electrode.
**Good for:** Stainless steel, aluminum, thin materials, critical welds, visible work.
**Shielding gas:** 100% Argon.
Requires more skill; both hands occupied plus foot pedal for amperage control.

### Stick (SMAW — Shielded Metal Arc Welding)

Flux-coated electrode. Flux provides shielding gas when it burns. No external gas needed.
**Good for:** Outdoors, wind, field work, thick materials, dirty/rusty metal.
**Electrodes:** E6011 (all positions, AC/DC), E6013 (clean metal, smooth bead), E7018 (strong, low hydrogen, good for structural).

### Flux-core (FCAW)

Similar to MIG but wire has flux core. Can be used without shielding gas (self-shielded).
**Good for:** Outdoor work, thick materials, production.

## Safety — non-negotiable

**Eye protection:** Welding arc emits UV and IR radiation. Arc eye (photokeratitis) is extremely painful.
Auto-darkening helmet: Shade 10-13 depending on process/amperage. Always wear; never look at arc without proper protection.
**Fire hazard:** Spatter can travel 35+ feet. Clear area of flammables. Have fire extinguisher accessible.
**Fumes:** Welding fumes are hazardous. Ventilate adequately. Local exhaust ventilation preferred. Never weld galvanized metal (zinc fumes = metal fume fever; cadmium = toxic).
**Electrical:** Keep cables, connectors, and electrode holder in good condition. Never stand in water while welding.
**Hot metal:** Weld metal stays hot long after arc stops. Mark with chalk "HOT." Use pliers/gloves.

## Joint types

**Butt joint:** Two pieces end to end. Most common.
**T-joint:** One piece perpendicular to another.
**Lap joint:** Two pieces overlapping.
**Corner joint:** Two pieces at a right angle (corner).
**Edge joint:** Two pieces side by side, welded at edge.

**Groove vs. fillet weld:**
Groove weld: In a groove/gap between two pieces (butt welds).
Fillet weld: Triangle cross-section, filling inside corner (T-joint, lap joint).

## Weld quality

**Good weld appearance:** Uniform width and height, consistent ripple pattern, no porosity, good fusion to base metal, no undercut at edges.
**Common defects:**
Porosity: Gas pockets in weld. Causes: moisture, contamination, wrong gas coverage.
Undercut: Groove melted into base metal at weld edge. Too much heat or wrong angle.
Overlap: Weld metal rolls over without fusing to base. Too slow, too cold.
Cracking: Hot cracks during cooling; cold cracks later. Serious structural defect.

## Materials

**Carbon steel:** Most commonly welded. Low carbon (mild steel) welds easily.
**Stainless steel:** Use 308 or 316 filler rod to match alloy. Purge back side for high-purity work.
**Aluminum:** AC TIG or MIG with aluminum wire and 100% Argon. Oxide layer must be cleaned. Preheating helps for thick sections.

Sources: AWS (American Welding Society — aws.org, free standards summaries), Lincoln Electric welding education (lincolnelectric.com/en/education), Miller Electric (millerwelds.com/resources), OSHA welding safety standards (29 CFR 1910.252)