A2
A2 is the tool steel that refuses to go out of style: an air-hardening workhorse that has spent decades as the steel behind Bark River’s hard-use knives and Lie-Nielsen’s plane irons. Its pitch is simple — noticeably tougher than D2, far easier to grind and finish than the PM steels, and capable of a keen, fine edge — in exchange for moderate wear resistance and carbon-steel-style rust care. For makers, it has one more quiet gift: it hardens in air, which makes it one of the friendliest tool steels to heat treat flat.
A2 FAQ
Is A2 stainless?
No. A2 carries about 5% chromium — enough to slow rust slightly and support air hardening, nowhere near the ~13%+ that stainless requires. Treat it like carbon steel: keep it oiled, expect a patina, and consider a forced patina for protection.
What hardness should A2 be heat treated to?
58–62 HRC is the working range. Austenitize at 1750–1800°F with a 30–45 minute soak, quench in air or between aluminum plates, and double temper — around 400°F lands near 60–62 HRC, 450–500°F trades a point of hardness for extra toughness. Lie-Nielsen runs its cryo-treated A2 irons at 60–62.
Is A2 good for knives?
Genuinely, yes — especially hard-use blades. Its toughness-to-hardness balance made it Bark River’s signature steel for years of choppers and survival knives, and it takes a finer edge than its coarser tool-steel cousins. The tradeoffs: it needs rust care, and steels like CPM 3V now beat it on paper (at a price).
A2 vs D2 — which should I pick?
A2 for toughness, ease of grinding, and a cleaner fine edge; D2 for wear resistance and slightly better stain resistance. Full breakdown in our A2 vs D2 comparison.
Also known as: AISI A2, DIN 1.2363, ~SKD-12
Composition
Carbon 1.00%, Chromium 4.75–5.50%, Molybdenum 0.90–1.40%, Vanadium 0.15–0.50%, Manganese 0.60–1.00%, Silicon ~0.50%
Properties
| Property | Rating | Notes |
|---|---|---|
| Toughness | ★★★★☆ | The reason makers pick A2: clearly tougher than D2 and other high-carbide tool steels at working hardness — the classic choice for choppers and hard-use blades that must not chip. Modern PM steels like CPM 3V exceed it, at a price. |
| Edge Retention | ★★★☆☆ | Moderate carbide volume holds a solid working edge — above simple carbon steels, clearly below D2 and the CPM class. Takes a notably fine, keen edge for a tool steel thanks to its restrained carbide structure. |
| Corrosion Resistance | ★★☆☆☆ | About 5% chromium: slows rust slightly versus 1084/1095 but this is tool steel, not stainless. It patinas and will rust if neglected — oil it, dry it, and consider a forced patina on users. |
| Machinability / Grinding | ★★★★☆ | One of the friendlier tool steels on the grinder and under files when annealed; finishes and hand-sands more cleanly than D2 or the PM steels. |
Heat Treatment
Air hardening — kiln territory (or a heat-treat service). Foil-wrap, austenitize 1750–1800°F, soak 30–45 minutes, then quench in still air or between aluminum plates (plates keep thin blades dead flat — see our plate quenching guide). Cool below ~150°F, then double temper 2 hours each: ~400°F for 60–62 HRC, 450–500°F for 58–60 with extra toughness. Cryo treatment is a worthwhile optional step (Lie-Nielsen cryo-treats its A2).
Best Uses
Hard-use outdoor knives: camp blades, choppers, survival and bushcraft knives where edge stability under abuse beats maximum wear resistance. Also excellent in tough-duty kitchen knives (with rust care), and the classic steel for woodworking plane irons and chisels. A strong first tool steel for stock-removal makers with kiln access.
Sources: Knife Steel Nerds — A2 Steel History and Properties (knifesteelnerds.com); Hudson Tool Steel — A2 technical data; Lie-Nielsen Toolworks — A2 blade specifications