Semi-Stainless
Semi-Stainless Steel
Semi-stainless steels sit between carbon and full stainless. They will rust if left wet or neglected, but under normal use they tend to develop a patina — a dark, protective layer — rather than forming aggressive surface rust. Rinse and wipe dry after use and you will rarely have issues. Much more forgiving than true carbon steel, while still offering excellent cutting performance. Hitachi Metals (now Proterial), Japan 🇯🇵
Semi-stainless steels sit between carbon and full stainless. They will rust if left wet or neglected, but under normal use they tend to develop a patina — a dark, protective layer — rather than forming aggressive surface rust. Rinse and wipe dry after use and you will rarely have issues. Much more forgiving than true carbon steel, while still offering excellent cutting performance. Hitachi Metals (now Proterial), Japan 🇯🇵
YXR7
Typical hardness
Rockwell C Hardness(HRC) measures how resistant a steel is to permanent deformation. For kitchen knives:
55–58 HRC — Soft. Easy to sharpen and forgiving of rough use, but dulls faster. Typical of most German knives.
59–61 HRC — Balanced. Good edge retention with manageable sharpening. Common in mid-range Japanese knives.
62–64 HRC — Hard. Excellent edge retention, holds a very fine edge. Requires more care and a fine stone to sharpen.
65+ HRC — Very hard. Exceptional edge longevity but more brittle — more prone to chipping if used roughly.
Higher is not always better — it depends on how you use and maintain your knife.
55–58 HRC — Soft. Easy to sharpen and forgiving of rough use, but dulls faster. Typical of most German knives.
59–61 HRC — Balanced. Good edge retention with manageable sharpening. Common in mid-range Japanese knives.
62–64 HRC — Hard. Excellent edge retention, holds a very fine edge. Requires more care and a fine stone to sharpen.
65+ HRC — Very hard. Exceptional edge longevity but more brittle — more prone to chipping if used roughly.
Higher is not always better — it depends on how you use and maintain your knife.
62 to 65 HRC
555759616365+
YXR-7 is a matrix high-speed steel made by Proterial. Proterial lists it for forging tools such as general dies, rolled dies and cold forging punches, and describes its strength and toughness as superior. Proterial gives 0.80% carbon, 4.70% chromium, 5.50% molybdenum, 1.30% tungsten and 1.30% vanadium, and a hardening hardness of over 62 HRC.
Proterial lists 4.70% chromium, below the Japan Stainless Steel Association's 10.5% line for stainless steel. Dry the knife after use.
We list a Sukenari YXR-7 petty.
Proterial lists 4.70% chromium, below the Japan Stainless Steel Association's 10.5% line for stainless steel. Dry the knife after use.
We list a Sukenari YXR-7 petty.
Composition
YXR7 Element Composition
Compare with
YXR7
—
5.0%
3.8%
2.5%
1.3%
0
C
0.8%
Cr
5.0%
V
1.1%
Mo
5.0%
W
1.1%
C — Carbon
Cr — Chromium
V — Vanadium
Mo — Molybdenum
W — Tungsten
Typical values from third-party sources.
Hardness
62–65 HRC
555759616365+
YXR7 Composition
What's in YXR7
What each element does in your knife.
| Element | Composition | What it does in your knife |
|---|---|---|
| CrChromium | 5.0% | Raises corrosion resistance; at roughly 13%+ free chromium the steel qualifies as stainless. Also improves hardenability and wear. |
| MoMolybdenum | 5.0% | Improves hardenability and toughness, boosts corrosion resistance, and helps the steel hold hardness under heat. |
| VVanadium | 1.1% | Forms extremely hard vanadium carbides for superior edge retention, and refines the grain for a finer, tougher edge. |
| WTungsten | 1.1% | Forms hard carbides for wear resistance and edge stability, and keeps the steel hard even at elevated temperatures. |
| CCarbon | 0.8% | The primary hardening element. More carbon means a harder edge that holds longer — but past a point it trades away toughness and rust resistance. |
Composition from zknives (K&S steel dataset) reference material. These ranges come from the K&S steel composition dataset, which is derived from zknives; maker figures are cited separately only when they are used on the page.
Frequently asked questions
Is YXR-7 stainless?
Published by K&S Education Desk; staff review pending
