Materials
AISI 440A stainless
A higher-carbon, higher-chromium stainless used where a fine working edge must last.
A short history
440A belongs to the 440 family of high-carbon martensitic stainless steels in the AISI system. Compared with 440C it has a little less carbon, which makes it slightly tougher while still hardening well for fine edges.
Composition
- Chromium
- 16–18%
- Carbon
- 0.60–0.75%
- Molybdenum
- ≤ 0.75%
- Structure
- Martensitic, with chromium carbides
Steel counts as stainless when it carries at least about 10.5% chromium (the threshold used in the European standard EN 10088). The chromium reacts with oxygen to form an extremely thin, self-repairing chromium-oxide film on the surface. This passive layer is what stops rust. It re-forms on its own after light scratching, provided the surface is clean and exposed to air.
How it's hardened and tempered
Martensitic stainless steels are hardened in three steps: austenitizing (heating to roughly 950–1,050 °C so carbon dissolves into the steel), quenching (rapid cooling, which locks the structure into hard martensite) and tempering (reheating to a lower temperature to trade a little hardness for toughness, so edges and tips don't chip or snap). Exact temperatures depend on the grade and the part. The extra carbon allows higher hardness than 420, which helps thin scaler and curette blades keep their edge.
Why it lasts
- Higher hardness potential for working ends that stay sharp longer between sharpenings.
- Higher chromium than 410/420 for good corrosion resistance.
- Fine grain takes a precise edge.
Autoclave and sterilization
Like other surgical stainless steels, 440A is steam-sterilizable. Dry instruments thoroughly, avoid chloride residues, and keep sharp working ends protected in cassettes so they don't contact each other.
Care tips
- Sharpen regularly with a stone or send for sharpening — a dull scaler needs more force.
- Use cassettes or tip protectors during cleaning and sterilization.
- Dry fully; avoid leaving instruments in solutions.
Compared with cheaper alternatives
| Feature | 440A | 420 | Unbranded "stainless" |
|---|---|---|---|
| Hardness potential | Higher | High | Unknown |
| Edge life | Longer | Good | Unpredictable |
| Corrosion resistance | Good (16–18% Cr) | Good (12–14% Cr) | Unknown |
Where we use it
Ask us to confirm the grade used for a specific instrument or batch.
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