Slide 001: Metal Properties & Their Effect on Plasma Cutting¶
Slide Visual¶
Slide Overview¶
This slide explores how the physical and thermal properties of different metals affect plasma cutting parameters and results. Students will learn why the same plasma cutter behaves differently on different metals and how to adjust parameters accordingly.
Instruction Notes¶
Key Material Properties That Affect Plasma Cutting¶
Thermal Conductivity: How quickly a metal conducts heat away from the cut zone. - High thermal conductivity (aluminum, copper) = heat dissipates quickly = requires more energy input or slower speed - Low thermal conductivity (stainless steel) = heat concentrates in the cut zone = can cut faster relative to thickness but larger HAZ risk
Melting Point: The temperature at which the metal transitions to liquid.
| Metal | Melting Point | Thermal Conductivity (W/m·K) | Cutting Difficulty |
|---|---|---|---|
| Mild Steel | 2,750°F (1,510°C) | 50 | Easiest — baseline |
| Stainless Steel (304) | 2,550°F (1,400°C) | 16 | Moderate — low conductivity helps |
| Aluminum (6061) | 1,220°F (660°C) | 167 | Moderate — high conductivity offsets low melting point |
| Copper | 1,984°F (1,085°C) | 401 | Difficult — extremely high conductivity |
| Brass | 1,700°F (927°C) | 120 | Moderate-difficult — zinc fumes hazard |
Mild Steel — The Baseline Material¶
Mild steel (low-carbon steel, A36, 1018) is the most common plasma cutting material: - Cuts cleanly with compressed air as the cutting gas - Oxygen in the air creates an exothermic reaction with iron, adding cutting energy - Produces the cleanest cuts with the widest parameter window - Moderate dross that is typically easy to remove with a grinder or scraper
Stainless Steel Considerations¶
- Lower thermal conductivity means heat concentrates — produces a wider HAZ
- Nitrogen or nitrogen/hydrogen mix recommended for cleanest edges (air works but leaves oxidized edge)
- Cut speed is similar to mild steel of the same thickness
- Hexavalent chromium fumes — enhanced ventilation and respiratory protection required (OSHA PEL: 5 μg/m³)
Aluminum Considerations¶
- Low melting point but very high thermal conductivity — these partially cancel out
- Requires 10-20% more amperage than mild steel of the same thickness (or 15-25% slower speed)
- Produces more dross than steel — dross is harder to remove (aluminum oxide)
- Nitrogen gas preferred; air acceptable for non-critical cuts
- Reflective surface can fool some THC systems — may need THC sensitivity adjustment
Coatings and Surface Treatments¶
Always know what you are cutting: - Galvanized: Zinc fumes — toxic. Grind off coating at cut line if possible - Painted/powder-coated: May produce toxic fumes depending on paint type - Anodized aluminum: Cuts normally but anodize layer is non-conductive — ensure arc starts on bare metal
Key Talking Points¶
- Thermal conductivity is the most important material property for parameter selection
- Mild steel is the easiest and most forgiving material for plasma cutting
- Aluminum requires more energy than its low melting point suggests
- Always identify material type AND any coatings before cutting
- Stainless steel fumes require enhanced respiratory protection
Learning Objectives (Concept Check)¶
- [ ] Explain how thermal conductivity affects plasma cutting parameters
- [ ] Rank 4 common metals by cutting difficulty and justify the ranking
- [ ] Identify at least 2 hazardous coating/material combinations
Last Updated: 2026-03-19