409, 409L, 410S, 420, 430, 440C and 444 Stainless Steel: Bright Annealed Coil Grades Compared
May 09, 2025
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Seven Grades, Two Metallurgical Families
The seven grades compared here fall into two groups. Ferritic grades - 409, 409L, 430 and 444 - are chromium-only stainless steels with a body-centred cubic structure; they are magnetic, cannot be hardened by heat treatment, and offer good corrosion resistance with excellent formability. Martensitic grades - 410S, 420 and 440C - are also chromium-based but can be hardened by quenching and tempering because of their higher carbon content. The single exception in behaviour is 410S, the low-carbon version of 410, which is supplied in the annealed condition with very low hardness and good weldability.
All seven grades can be produced as bright annealed coil, in which the strip is annealed in a protective hydrogen atmosphere so that no scale forms and the surface comes out bright and reflective without subsequent pickling or mechanical polishing.
Chemical Composition per ASTM A240 and A276
| Grade | C | Cr | Ni | Mo | Other | Standard |
|---|---|---|---|---|---|---|
| 409 (S40900) | ≤ 0.08 | 10.5–11.75 | ≤ 0.50 | – | Ti 6 × (C + N) min | A240 |
| 409L (S40910) | ≤ 0.030 | 10.5–11.75 | ≤ 0.50 | – | Ti 6 × (C + N) min | A240 |
| 410S (S41008) | ≤ 0.08 | 11.5–13.5 | ≤ 0.60 | – | – | A240 |
| 420 (S42000) | ≥ 0.15 | 12.0–14.0 | – | – | – | A276 |
| 430 (S43000) | ≤ 0.12 | 16.0–18.0 | ≤ 0.75 | – | – | A240 |
| 440C (S44004) | 0.95–1.20 | 16.0–18.0 | – | ≤ 0.75 | – | A276 |
| 444 (S44400) | ≤ 0.025 | 17.5–19.5 | ≤ 1.00 | 1.75–2.50 | Ti + Nb 8 × (C + N) min, N ≤ 0.035 | A240 |
Maximum values for Mn, Si, P and S in all seven grades are typically 1.00, 1.00, 0.040–0.045 and 0.030% respectively, per the applicable standard.
What Bright Annealing Does to the Coil
Bright annealing is a continuous process in which cold-rolled strip is heated to the full solution annealing temperature inside a furnace flooded with a protective atmosphere, then cooled in the same atmosphere. No oxygen reaches the surface, so no chromium-depleted oxide scale forms. The result is a smooth, lustrous finish with a low surface roughness that needs no pickling or grinding. For ferritic grades such as 430 and 444, bright annealing also develops the fully recrystallized, soft structure required for deep drawing and roll forming. Bright annealed coil is therefore preferred for decorative trim, kitchen appliances, food equipment and automotive components where surface quality and cleanliness matter.
Mechanical Behaviour and Hardenability
In the annealed condition the ferritic grades show moderate strength and very high ductility: 430 has a minimum tensile strength of about 450 MPa with elongation of 22% or more, while 444 develops higher strength from molybdenum and niobium-titanium stabilization and is used where both corrosion resistance and formability are required. Martensitic 420 and 440C are soft and easily machined in the annealed condition but reach 500–600 HB or higher after hardening and tempering, which is what makes 440C a classic bearing and knife steel. 410S stays soft and weldable because its low carbon content prevents air hardening on cooling.
Selecting the Right Grade
409 and 409L: automotive exhaust systems, mufflers, catalytic converter shells - good oxidation resistance and low cost
410S: annealing boxes, heat treatment fixtures and welded assemblies needing a soft, crack-resistant 12% Cr steel
420: cutlery, surgical instruments and shafts requiring hardenability with moderate corrosion resistance
430: kitchen equipment, appliance panels, architectural trim and washing machine drums
440C: ball bearings, valve seats, high-wear tools and premium knife blades
444: water heaters, heat exchangers and solar collectors, where molybdenum gives resistance approaching austenitic grades in chloride-bearing water
Frequently Asked Questions
What is the difference between 409 and 409L?
Both are 11% Cr ferritic grades stabilized with titanium. 409L has a lower carbon limit of 0.030% maximum against 0.08% for 409, which reduces hardening at weld heat-affected zones and improves toughness and ductility in welded exhaust systems.
Is 410S ferritic or martensitic?
410S is classified as a martensitic grade with restricted carbon, but because its carbon is held at 0.08% maximum it does not harden on air cooling. In the annealed condition it behaves like a soft, weldable 12% Cr steel, which is why it is often treated as a ferritic-type material in practice.
Can 430 stainless steel be hardened by heat treatment?
No. As a ferritic grade, 430 has a body-centred cubic structure that does not undergo the austenite-to-martensite transformation. It can be strengthened by cold working but not by quenching.
What is 440C used for?
440C is a high-carbon, high-chromium martensitic grade used for ball bearings, races, valve parts, nozzles and knife blades. After hardening it reaches hardness values around 58–60 HRC, giving outstanding wear resistance, though its corrosion resistance is lower than the ferritic grades in the same chromium range.
Why is 444 sometimes called a super ferritic grade?
Because it combines 17.5–19.5% chromium with 1.75–2.50% molybdenum and a very low carbon limit of 0.025%, 444 resists pitting and crevice corrosion in chloride-bearing water far better than 430, in some applications approaching the performance of 316 while remaining a lower-cost, magnetic ferritic material.
What does bright annealed mean for the surface?
It means the strip was annealed in a protective hydrogen atmosphere, so the surface remains bright and oxide-free after heat treatment. The finish is smooth and reflective with no pickling residue, and it is usually classified as a BA finish in JIS G4305 terminology.
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