Powder high-speed steel · ProterialHAP40 HAP40
Also called: HAP-40 · HAP 40
HAP40 is a non-stainless powder high-speed steel made by powder metallurgy from Proterial (formerly Hitachi Metals): 1.27–1.37% carbon, 3.70–4.70% chromium, and a maker hardening hardness of HRC 64–66 or 66–68, depending on quench temperature.
Composition
| C | Cr | Mo | W | V | Co |
|---|---|---|---|---|---|
| 1.27–1.37 | 3.70–4.70 | 4.60–5.40 | 5.60–6.40 | 2.80–3.30 | 7.50–8.50 |
Mass %. As published by the steelmaker (typical or representative values). Hardness: 64–66 or 66–68, depending on quench temperature.
What the data says
HAP40 is a Proterial high-speed tool steel in the JIS SKH40 class: 1.27–1.37% carbon, 3.70–4.70% chromium, 4.60–5.40% molybdenum, 5.60–6.40% tungsten, 2.80–3.30% vanadium and 7.50–8.50% cobalt in the maker’s range. Proterial calls it its most standard grade, with a good balance of hardness, toughness and wear resistance.
Its hardness depends on the quench: 66–68 HRC from 1,180–1,210 °C, or 64–66 HRC from a lower quench temperature, according to the maker. With only about 4% chromium, it is not a stainless steel and should be kept dry.
Retailers describe it as a powder-metallurgy steel; Proterial’s own grade page does not state this, so we mark it as a retailer claim.
HAP40 compared with similar steels
| Steel | Type | C % | Cr % | Maker HRC | CATRA mm |
|---|---|---|---|---|---|
| HAP40 | Powder high-speed · PM | 1.27–1.37 | 3.70–4.70 | 64–66 or 66–68, depending on quench temperature | — |
| ZDP-189 | Powder stainless · PM | 3.00 | 20.00 | ≥65 | 718 @ 65.1 |
| SG2 (Super Gold 2) | Powder stainless · PM | 1.25–1.45 † | 14.0–16.0 † | ≥62 | 522 @ 61.2 |
| SLD (≈ D2 / SKD11) | Semi-stainless | 1.50 | 12.00 | ≥58 | 486 @ 60.5 |
See all 15 steels in the Japanese knife steel chart, or compare up to three at once in the steel explorer.
Care
HAP40 is not stainless. Wipe the blade dry after use; a grey or blue patina is normal, but orange spots are rust and should be removed early.
Buying a HAP40 knife from a shop in Japan? Japanese kitchen knives currently pay about 31% US import duty — use the import duty calculator to compare with a US retailer.
Frequently asked questions
- Is HAP40 stainless?
- No. HAP40 contains only 3.70–4.70% chromium, while a stainless steel needs roughly 10.5% or more, so it can rust if left wet.
- How hard is HAP40?
- Proterial publishes a hardening hardness of HRC 64–66 or 66–68, depending on quench temperature. The hardness of a finished knife depends on the knifemaker’s heat treatment.
- Who makes HAP40?
- HAP40 is made by Proterial (formerly Hitachi Metals). It is a powder-metallurgy steel.
- HAP40 vs ZDP-189: what is the difference?
- HAP40: C 1.27–1.37%, Cr 3.70–4.70%, maker hardness HRC 64–66 or 66–68, depending on quench temperature. ZDP-189: C 3.00%, Cr 20.00%, maker hardness ≥65 HRC.
Sources
Checked 2026-10-21. Found a better source or an error? Tell us.