Tube Material Cheat Sheet: Mild Steel, DOM, Chromoly, Stainless, Aluminum
Most fabrication work happens in five tubing materials: mild steel, DOM, chromoly 4130, 304 stainless, and 6061 aluminum. Each has a personality at the bender, the welding table, and on the scale. This is the one-page cheat sheet — what each material is good at, what it’s bad at, and when to reach for it.
Mild Steel (ERW, Mechanical Tube)
Yield strength: ~30,000–50,000 psi
Weldability: Excellent with any process.
Bending behavior: Forgiving. Bends cleanly without mandrel at moderate CLRs.
Springback: 1°–2° per 90°.
Cost: Cheapest. ~$2.50–$4.00/ft for 1.5″ tubing.
Best for: Practice tubing, light structural, brackets, conduit. Not for safety-critical structures.
DOM (Drawn Over Mandrel) Steel
Yield strength: ~70,000 psi (significantly higher than plain mild steel).
Weldability: Excellent.
Bending behavior: Predictable. Most chassis-grade bending tooling is calibrated to DOM.
Springback: 1°–2° per 90°.
Cost: Moderate. ~$5–$8/ft for 1.75″ × .120″.
Best for: Roll cages, suspension links, chassis tubing, structural fabrication. The workhorse of chassis work.
Chromoly 4130
Yield strength: ~75,000–95,000 psi annealed; higher when heat-treated.
Weldability: Good but demands attention. Heat-affected zone is brittle without normalization.
Bending behavior: Work-hardens fast; demands a mandrel at thin walls.
Springback: 2°–3° per 90°.
Cost: Expensive. ~$12–$18/ft for 1.75″ × .083″.
Best for: Race chassis where weight matters, aerospace structures, premium roll cages. Avoid for daily-driver chassis unless rulebook requires.
304 Stainless
Yield strength: ~30,000–40,000 psi annealed (work-hardens significantly during bending).
Weldability: Good with TIG and proper shielding. Poor without back-purge.
Bending behavior: Work-hardens aggressively; almost always needs a mandrel for tight bends.
Springback: 2.5°–4° per 90°.
Cost: Expensive. ~$15–$25/ft for 2.5″ × .065″.
Best for: Premium exhaust systems, food/pharma piping, marine fabrication, anywhere corrosion is the enemy.
6061-T6 Aluminum
Yield strength: ~40,000 psi.
Weldability: Demands TIG with high-frequency AC. MIG works for thicker sections.
Bending behavior: Cracks if bent at room temperature in tight CLRs without annealing first.
Springback: 1°–2° per 90° (after annealing).
Cost: Moderate. ~$8–$15/ft for 2″ × .065″.
Best for: Lightweight chassis, race car structures where weight is critical, custom intercooler piping, marine fabrication.
Quick Comparison Table
| Material | Yield (psi) | Cost (relative) | Weld difficulty | Mandrel required? |
|---|---|---|---|---|
| Mild steel | 30k–50k | 1.0× | Easy | Rarely |
| DOM | ~70k | 1.5× | Easy | Tight bends only |
| Chromoly 4130 | 75k–95k | 4× | Moderate | Thin walls |
| 304 stainless | 30k–40k* | 5× | Hard | Almost always |
| 6061-T6 aluminum | ~40k | 3× | Hard | Tight bends |
*Stainless yield is misleading — it work-hardens during cold working, so effective strength is much higher in service.
How to Pick the Material
- What rulebook applies? Sanctioning bodies often dictate material.
- What climate? Salt belt or marine demands stainless or aluminum.
- What budget? Material can be 30%+ of build cost.
- What welding capability do you have? Don’t spec stainless if you only have MIG without gas.
- What weight target? Aluminum or chromoly for serious weight reduction.
Material-Bending Pairings
Each material has a different relationship with the bender. Plug your specific material, OD, wall, and CLR into our Bend Radius Calculator to get a stress and wrinkle prediction tailored to that combination.
Sourcing Materials
For pre-cut tubing and material samples to test, tubing for fabrication on Amazon covers most common ODs and walls.
Final Word
Material choice is one of the most consequential decisions in fabrication. Match it to the application, the budget, and your welding capability — and your build is half-done before the first bend.