The Knowledge Base · A Drawn First
鋼の系図

The Steel Family Tree

Japanese knife steels are not a list, they are a genealogy: three mills, a handful of family lines, and a century of one grade answering another. The lineage has been written about in prose for years. As far as we can find, nobody ever drew it. Click any steel for its full reference page.

How to read the tree
Arrows point from parent to descendant. The line style is the claim strength: red is a documented derivation, gray is only family membership, gold never claims a parent at all.
Documented derivative. Our sources state one steel was developed from, or as the next grade of, the other. Example: VG-MAX, "a proprietary Takefu derivative" of VG-10.
Family line. Same mill, same named series (V Gold, the paper colors, AUS), with no published claim about which grade begot which.
Siblings, no arrow. Steels our pages describe as behaving like relatives (ZA-18 and VG-10, Ginsan and Shirogami) without a documented parent between them.
Pre-industrial ancestry. The tatara sword-steel tradition the Yasugi works was founded to industrialize.
The highlights, five colored stripes, our editorial calls:
Most popular: VG-10, the steel hundreds of Seki brands build on The hardest: ZDP-189, 64 to 67 HRC Best all-rounder: SG2 / R2, powder edge life without carbon upkeep Sharpeners' favorite: Shirogami, the purest feel on the stones The cult favorite: Aogami Super, the steel of the unobtainable gyutos
† = phased out (its story is in the registry). Year chips mark documented introductions; a starred year (1950s*, 1996*) is reported or claimed but not mill-documented, and a steel with no year chip has no published date at all. The AUS series, VG-1, ZA-18, Ginsan, Aogami Super: none of their mills has ever published one, which is itself worth knowing. Hover any steel for sources; click for its full reference page.
PROTERIAL YASUGI WORKS · 安来 TAKEFU SPECIAL STEEL · 武生 AICHI STEEL AND OTHERS The tatara traditioniron-sand smelting, ShimaneYasugi sits in the historic heart of Japanese steelmaking, the region whose tatara iron-sand smelting fed centuries of sword production. Yasuki Hagane 安来鋼the Yasugi works, Shimaneest. 1899A modern steelworks was established in the late 1890s to carry the tatara lineage into industry, branding its output Yasuki Hagane. Kigamiyellow paper, standardpre-WWIIBillets were wrapped in colored paper: yellow for the standard carbon grade. Shirogamiwhite paper · #3 #2 #1pre-WWIIWhite paper for the purest simple carbon steel. The low-phosphorus discipline is a direct descendant of the tatara habit of starting from unusually clean iron sand. [Sharpeners' favorite, our editorial call: the purest feel on the stones.] Aogamiblue paper · #2 #1pre-WWIIBlue paper for the tungsten-alloyed grade: Hitachi's enhanced carbon-steel family, white steel's sharpening feel with longer working edges. Aogami Superthe flagshipDeveloped later than Blue #1 and #2 as the flagship of the line: how far can a forge-weldable carbon steel be pushed before it stops behaving like one? [The cult favorite, our editorial call: the steel of the unobtainable workhorse gyutos.] Ginsansilver paper · stainlessSilver paper for the stainless family, from the same Yasugi works. SLDtool steel branchHitachi's cold-work die steel, adopted by Sanjo knife houses like Yoshikane. ZDP-189 †powder · phased out1996*Extreme powder stainless developed by Hitachi Metals; quietly phased out circa 2020-2022. The dagger is earned: see the registry. [The hardest, our editorial call: 64 to 67 HRC, the category's hardness ceiling.] [Year: The 1996 development year is reported by retail and industry sources, not by a Hitachi document; Spyderco first heard of the steel around 2000.] V Gold stainless familyTakefu Special Steel, Echizenmill est. 1954Takefu Special Steel's named stainless line; when a new V Gold grade appears, its first users are smiths in the mill's own orbit. VG-1the early gradeThe early V Gold grade; Masutani still works VG-1 in Echizen. VG-10the workhorse1950s*High-carbon, high-chromium stainless with cobalt, developed by Takefu; rose to worldwide prominence in the 1990s when Seki adopted it at scale. [Most popular, our editorial call: the steel hundreds of Seki brands build on.] [Year: The development date is debated: Takefu's own materials imply the late 1950s, no patent or trademark evidence is cited by anyone, and the steel only became famous in the 1990s.] VG-MAXmade for Kai2013A proprietary Takefu derivative made for Kai, with small adjustments to carbon, chromium, vanadium, and added tungsten. Shun Classic moved from VG-10 to VG-MAX. VG-XEOSthe 2023 rethink2023Takefu's rethink of the VG-10 formula: keep the cutting performance, raise corrosion resistance and hardness. A next step in the conventional V Gold lineage, not a powder steel. Super Gold powder familyTakefu powder metallurgyTakefu's powder-metallurgy line, the SG mark. SG2 / R2one steel, two logospat. 1991Published compositions match and the knives behave identically, so we treat SG2 and R2 as one steel family with two logos; R2 is the mark associated with powder production inside the Kobe Steel group. [Best all-rounder, our editorial call: powder-steel edge life without carbon-steel upkeep.] [Year: Japanese Patent 2764659, filed 1991, issued June 11, 1998.] SPG STRIXthe sharpening fix2023Takefu's answer to the classic powder-steel complaint: SG2-class performance that fights you on the stones. The SPG mark ties it to the Super Gold family. AUS familyAichi Steel, NagoyaAichi Steel's stainless cutlery line: AUS-6, AUS-8, AUS-10. AUS-6entry gradeThe entry member of the AUS family. AUS-8the middle memberThe middle member of Aichi Steel's AUS family; the good first guess when a Japanese-made knife under $100 says only 'Japanese stainless'. AUS-10more carbon, 60-61 HRCSame mill, same family, one meaningful difference: AUS-10 raises carbon to roughly 1.0-1.1%, buying 60-61 HRC and clearly better edge retention. The steel of the Okami Premium. ZA-18attributed to Osaka CladCobalt-bearing stainless; importer documentation attributes development to Osaka Clad Co., a detail we can attribute but not independently confirm. In daily use, a sibling of VG-10.
How to Read It

Three mills, three philosophies

Yasugi reads bottom-up from the sword era. The works was founded in the late 1890s to carry the tatara iron-sand tradition into industry, and its billets were wrapped in colored paper so wholesalers could tell the grades apart: white for the purest carbon steel, blue for the tungsten-alloyed evolution, silver for the stainless family, yellow for the standard grade. Aogami Super was developed after Blue #1 and #2 as the flagship: the question it answers is how far a traditional forge-weldable steel can be pushed before it stops behaving like one. ZDP-189, the powder-metallurgy extreme of the same house, earned its dagger: it has been quietly phased out, a story told in full in the registry of discontinued knives.

Takefu reads sideways from one workhorse. VG-10 rose to world fame in the 1990s through Seki's production houses, and its descendants answer specific complaints about it: VG-MAX is the proprietary derivative Takefu made for Kai with adjusted carbon, chromium, vanadium and added tungsten; VG-XEOS is the mill's own 2023 rethink, more corrosion resistance and hardness in the conventional V Gold lineage. On the powder side, SG2 and R2 are one steel family with two logos, and SPG STRIX is Takefu's answer to the complaint that SG2-class steel fights you on the sharpening stones.

Aichi reads straight down. AUS-6, AUS-8, AUS-10: same mill, same family, each step buying carbon, hardness, and edge retention. AUS-8 is the good first guess whenever a Japanese-made knife under $100 says only "Japanese stainless"; AUS-10 is the steel of our own Premium Damascus knife, and we say so here rather than pretending otherwise.

Methodology

Where the lines come from

Every arrow encodes a statement already published on our steel reference pages, which are themselves built from mill documentation (Takefu Special Steel, Proterial's Yasugi Specialty Steel materials, Aichi Steel), maker documentation, and the metallurgy literature, with Knife Steel Nerds' published analyses as a repeated cross-check, cited by name here as everywhere on this site.

  • Solid red arrows mark documented derivations: statements like "a proprietary Takefu derivative made for Kai" or "a next step in the conventional V Gold lineage."
  • Gray arrows mark family membership within one mill's named line, without a claim about which grade begot which.
  • Dashed gold links mark siblings and counterparts: steels our pages describe as behaving like relatives without sharing a documented parent, like ZA-18 and VG-10.
  • What is absent is absent on purpose. Exact development dates for VG-10 are debated, so the tree does not print one. ZA-18's development is attributed to Osaka Clad by importer documentation we can attribute but not confirm, and the node says so. Where a lineage claim would be a guess, there is no line.

Last updated August 20, 2026. Hover any node for the underlying statement; click through for the full reference page with composition tables and sources.

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