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Glossary

2. Steel Types (Hitachi Carbon, Stainless & Powder Super-Steels)

From pure White & Blue paper steels to modern Takefu powder metallurgy (SG2, ZDP-189, SPG STRIX) and semi-stainless tool steels (SLD, SKD).

Written by Knife Fit from the sources listed under each entry; not the result of testing. Reviewed 29 Oct 2026. Report a correction

Carbon Steel Family (Overview)

Traditional reactive steels prized for razor keenness

Traditional Japanese high-carbon steels (Shirogami, Aogami) with virtually no chromium. Valued by many smiths and cooks for a fine grain, easy sharpening on a whetstone and a very keen edge.

Beginner Tip: Will oxidize and develop a blue/gray patina. Wipe it dry during cooking and do not leave it wet in the sink. Stainless-clad carbon knives keep the carbon-steel edge but expose less carbon steel to water, so the sides of the blade need less care; the edge itself still can rust.

Sources: Wikipedia: Japanese kitchen knife

Stainless Steel Family (Overview)

Corrosion-resistant kitchen steels (high chromium)

Contains enough chromium (by the usual definition, over about 10.5%) to form a thin oxide film that resists rust and discoloration. Modern Japanese stainless steels such as Ginsan, VG-10 and SG2 can take a very keen edge, though many cooks still find carbon steel easier to sharpen.

Beginner Tip: The stress-free choice for home cooks who prep tomatoes, citrus, and onions without wanting to wipe the blade every two minutes.

Sources: Wikipedia: Japanese kitchen knife

Semi-Stainless & Tool Steels (Overview)

High wear resistance with partial corrosion defense

Steels with a moderate amount of chromium (like SLD, SKD11, SKD12, HAP40). They hold an edge for a long time and resist rust better than carbon steel, but less than stainless; they can still stain or form a patina.

Beginner Tip: A step up in edge life from White steel, with some chromium added; many makers use it for the cutting edge of clad knives. It still needs drying after use, but it tolerates brief contact with acidic food better than White steel.

Sources: Wikipedia: Japanese kitchen knife

Shirogami #1 (White Paper Steel #1)

Highest carbon purity; maximum achievable keenness (62–65 HRC)

Produced by Hitachi Metals (Proterial). A high-carbon steel with very few alloying elements. Among the purest of the traditional carbon steels and capable of a very keen, clean edge. It is hard to heat-treat well, so it is mostly found in knives from experienced smiths.

Beginner Tip: The purist's steel. Sharpening on a quality whetstone feels like butter, but it is extremely reactive and will rust quickly if neglected.

Sources: Wikipedia: Japanese kitchen knife

Shirogami #2 (White Paper Steel #2)

The beloved classic Japanese carbon steel (60–63 HRC)

The most widespread and traditional carbon steel in Japanese cutlery. Slightly less brittle and more forgiving than White #1 while retaining the same fine-grain sharpness and effortless whetstone response.

Beginner Tip: A common first carbon steel: it sharpens readily on a medium whetstone and is less brittle than White #1.

Sources: Wikipedia: Japanese kitchen knife

Aogami #1 (Blue Paper Steel #1)

High carbon with tungsten for extended edge retention (63–65 HRC)

White #1 with added chromium and tungsten. The tungsten forms hard carbides, which improve wear resistance and edge life compared with White steel.

Beginner Tip: Maintains its biting edge noticeably longer than White steel on dense produce, while remaining very rewarding to sharpen.

Sources: Wikipedia: Japanese kitchen knife

Aogami #2 (Blue Paper Steel #2)

Aogami Super: very fine edge with long edge life, hardness typically 61–64 HRC

White #2 with added chromium and tungsten. It is a popular choice for a balance of hardness, toughness, edge life and ease of sharpening.

Beginner Tip: One of the safest and most satisfying high-carbon investments you can make (e.g., Moritaka, Masashi, Yoshikane).

Sources: Wikipedia: Japanese kitchen knife

Aogami Super (Super Blue / AS)

Apex carbon performance: immense edge longevity (64–66 HRC)

The most alloyed steel of the Hitachi paper-steel series, with extra tungsten and vanadium. Hardened high (often 63–65 HRC), it keeps an edge longer than the other paper steels but is harder to sharpen and more brittle.

Beginner Tip: Frequently paired with soft stainless cladding (San Mai). This keeps the Aogami Super cutting edge while the stainless sides protect most of the blade from rust.

Sources: Wikipedia: Japanese kitchen knife

Ginsan (Silver #3 / Gin-3)

The stainless steel that sharpens and cuts like carbon (60–62 HRC)

A fine-grained Hitachi stainless steel. Many sharpeners say it behaves on a whetstone much like White #2 while resisting rust far better; that is a matter of experience, not a measurement.

Beginner Tip: A stainless steel that many cooks pick for a carbon-like feel and easy whetstone sharpening; it resists rust better than carbon steel.

Sources: Wikipedia: Japanese kitchen knife

VG-10 (Takefu Special Steel)

The world's most famous Japanese stainless cutlery steel (60–61 HRC)

Takefu's iconic stainless blend containing Cobalt, Molybdenum, and Vanadium. Known worldwide through brands like Tojiro, Sakai Takayuki, and Shun. Highly corrosion resistant with solid edge life.

Beginner Tip: Great everyday stainless. Can be slightly gummy to deburr on whetstones compared to Ginsan or SG2, but maintains a keen working edge reliably.

Sources: Wikipedia: VG-10

VG-7 / VG-XEOS / VG-Max

Advanced refined-carbide Takefu stainless variants (60–62 HRC)

Modern metallurgical evolutions from Takefu Special Steel designed to overcome VG-10's coarser carbide structure. Refined chemistries improve toughness, micro-chip resistance, and edge stability.

Beginner Tip: Found in premium lines from Ryusen and specialized artisan workshops. Offers a cleaner polish and crisper sharpening feedback than standard VG-10.

Sources: Wikipedia: Japanese kitchen knife

AUS-8 / AUS-10 (Aichi Steel)

Tough, forgiving Japanese stainless (57–60 HRC)

Reliable stainless steels produced by Aichi Techno Metal Fukaumi. AUS-8 (~58 HRC) is extremely ductile and chip-resistant; AUS-10 (~60 HRC) contains more carbon and vanadium for heightened edge retention.

Beginner Tip: Outstanding for high-volume commercial prep kitchens, culinary students, or beginners who want a knife that won't chip if accidentally bumped.

Sources: Wikipedia: Japanese kitchen knife

SG2 / R2 (Super Gold 2 — Powder Stainless)

Top-tier powder metallurgy stainless: extreme sharpness & longevity (62–64 HRC)

High-speed powder metallurgy steel by Takefu Special Steel. Rapid gas-atomization creates an ultra-fine, uniform carbide dispersion impossible in conventionally melted steels. Delivers astronomical wear resistance alongside buttery whetstone feedback.

Beginner Tip: Used in thin "laser" knives from makers such as Shibata, Kei Kobayashi and Takamura. Stainless, very hard and long-lasting on the edge, but it needs care on the stone and is less tolerant of chipping than softer steels.

Sources: Wikipedia: Japanese kitchen knife

ZDP-189 (Hitachi Micro-Carbide Super Steel)

Ultra-high carbon hyper-steel (65–67 HRC)

A powder-metallurgy stainless steel with very high carbon and chromium, hardened very high. It keeps an edge for a long time but is brittle and hard to sharpen, so it suits careful use.

Beginner Tip: Due to extreme hardness, it requires diamond or high-end ceramic whetstones (like Shapton Glass) when sharpening or repairing chips. Not for beginners with poor board habits.

Sources: Wikipedia: Japanese kitchen knife

HAP40 (Hitachi High-Speed Powder Tool Steel)

Semi-stainless powder powerhouse (64–66 HRC)

Originally engineered for industrial high-speed metal-milling tools. Hardened up to 66 HRC with exceptional toughness and abrasion resistance. Highly rust-resistant though technically semi-stainless.

Beginner Tip: Famously utilized by Kohetsu and Gihei. Takes a wicked, toothy edge that refuses to dull during endless prep shifts.

Sources: Wikipedia: Japanese kitchen knife

SPG STRIX (Takefu Next-Gen Powder Steel)

Cutting-edge Takefu powder steel with balanced toughness (64–65 HRC)

Takefu Special Steel's latest powder metallurgy innovation. Specifically designed to optimize both high corrosion resistance and superior impact toughness at high hardness (64–65 HRC), reducing micro-chipping.

Beginner Tip: Rapidly gaining acclaim among modern artisan blacksmiths (like Yu Kurosaki and Nigara Hamono) as a premium upgrade over SG2.

Sources: Wikipedia: Japanese kitchen knife

SLD / SKD11 (Semi-Stainless Tool Steel)

High wear resistance, biting edge, semi-stainless (62–64 HRC)

A cold-work tool steel from the D2 family, originally made for industrial dies. It is not stainless, but resists rust better than carbon steel, and it holds an edge for a long time.

Beginner Tip: Made famous in kitchen cutlery by Sanjo masters like Tadafusa and Masashi Yamamoto. Very forgiving with moisture: only forms a faint patina over months of use.

Sources: Wikipedia: Japanese kitchen knife

SKD12 (A2 Die Steel)

Tough, highly stable Japanese tool steel (63–64 HRC)

A Japanese tool steel comparable to the A2 air-hardening tool steel; it is valued for toughness and fine grain.

Beginner Tip: The steel used in Yoshikane's SKD knives, a tool steel that is not stainless but is more rust-resistant than the traditional paper steels.

Sources: Wikipedia: Japanese kitchen knife

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