400-Series Stainless Steel for Strips and Tubes
overview
The stainless steel 400-series covers two families. Ferritic grades (409, 430, 439, 441) are chromium-based, magnetic, and nickel-lean, ideal for cost-efficient stainless steel strip and stainless steel tube in automotive and architectural uses. Martensitic grades (410, 420) can be heat-treated for higher hardness and wear resistance. This guide compares properties, uses, finishes, and standards, so international buyers can specify the right stainless steel material with confidence.
Quick Facts
Family: Ferritic and martensitic stainless steels with low or no nickel. Magnetic in most conditions.
Typical grades: 409, 430, 439, 441 (ferritic); 410, 420 (martensitic).
Where it fits: Cost-efficient choices for exhaust parts, appliance panels, trims, brackets, furniture, and architectural tubing.
Strength & hardening: Martensitic grades (410/420) can be heat-treated for higher hardness; ferritic grades gain strength by cold work.
Weldability: Ferritic grades weld with controlled heat input; martensitic grades typically need preheat and tempering to reduce cracking.
Common forms: A554 mechanical tube (round, square, rectangular) and A240/A480 precision strip for slitting programs.
Ferritic 400 Series
Common applications: automotive exhaust & thermal parts, architectural/mechanical tubing, appliance components, interior trim, heat-resistant liners.
Key features
- Chromium steels with little or no nickel are magnetic in all conditions
- Good oxidation resistance and moderate corrosion resistance
- Formable and weldable with sensible heat control
Common product forms
- Precision strip with ASTM A240/A480
- Mechanical tube with ASTM A554 (e.g., 430)
- Automotive tube with ASTM A268 (e.g., 409/439/441)
Grades
- 409: Workhorse for exhaust shells and pipes. Chosen for high-temperature oxidation resistance at a very competitive cost. Best for hot gas paths rather than decorative use.
- 430: The architectural favourite. Polishes well for No.4, hairline, and mirror finishes. Common in ASTM A554 round, square, and rectangular mechanical tubes, as well as appliance panels and interior trim.
- 439: Upgrades weldability and toughness compared with 430. Popular for exhaust and thermal shields. Good choice when forming and welding steps are demanding.
- 441: Higher strength and better high-temperature stability than 430. Used in more severe exhaust sections and hot zones that see repeated thermal cycles.
Martensitic 400 Series
Common applications
knife/edge parts, shafts, fasteners, clips, wear components, springs (select tempers).
Key features
Magnetic and heat-treatable to higher hardness than ferritics.
Higher strength / lower formability; weld with care.
Common forms
- precision strip to ASTM A240/A480
- tubing possible to ASTM A268 for specific designs.
Grades
410 – General-purpose martensitic; balance of strength, hardness, and corrosion resistance.
420 – Higher carbon for greater hardness and edge retention; used where abrasion resistance matters.
Chemical Compositions of Common 400 Stainless Steel
| Grade (UNS / EN) | C | Cr | Ni | Mo | N (max) | Ti / Nb (stabilizers) |
|---|---|---|---|---|---|---|
| 409 (S40900 / ~1.4512) | ≤ 0.08 | 10.5–11.75 | ≤ 0.50 | — | ≤ 0.03 | Ti ≥ 6×C to ≤ 0.75. |
| 430 (S43000 / 1.4016) | ≤ 0.12 | 16.0–18.0 | ≤ 0.75 | — | — | Not stabilized (Ti/Nb not required). |
| 439 (S43035 / 1.4510) | ≤ 0.03 | 17.0–19.0 | ≤ 0.50 | ≤ 0.50 | ≤ 0.04 | Ti 0.20 + 4(C+N) min, ≤ 1.10 (Nb may be present). |
| 441 (S43932/S43940 / 1.4509) | ≤ 0.03 | 17.5–18.5 | — | — | — | Ti 0.10–0.60 and Nb (3×C+0.3)–1.00. |
| 410 (S41000 / 1.4006) | 0.08–0.15 | 11.5–13.5 | ≤ 0.75 | — | — | Not stabilized (martensitic). |
| 420 (S42000 / 1.4021/1.4028) | 0.15–0.40* | 12.0–14.0 | — | — | — | Not stabilized (martensitic); C varies by subtype (A/B/C). |
FAQs
1. Are 400-series stainless steels magnetic?
Yes. Ferritic and martensitic grades are magnetic in typical conditions.
2. Do ferritic grades polish well for decorative work?
430 does. It is widely used in ASTM A554 mechanical tube with No.4, hairline, and mirror finishes. Protective film helps keep faces clean during fabrication.
3. How do 409, 439, and 441 differ in exhaust service?
409 is the cost-efficient baseline. 439 improves weldability and toughness. 441 (Ti+Nb stabilized) adds strength and high-temperature stability for more severe sections.
4. Can 410 and 420 be welded?
They can, but both require careful procedures. Many designs avoid welding and instead shape, harden, and mechanically join.
