The Mills Behind the Steel

Who actually smelts the steel

Ask where a Japanese knife comes from and you will hear about Seki factories, Sakai smiths, and Echizen forges. All true, and all downstream. Almost no knife workshop in Japan melts its own steel. The smith buys bar stock, sheet, or pre-laminated billet from a specialty mill, and everything the smith does afterward, forging, hardening, grinding, happens within the limits that mill chemistry set. Our guide to how Japanese knives are made calls the mill the first stop on the journey; this page is the full profile of the companies standing at that stop.

The structure of the industry is simple to state. A mill makes steel. A smith or factory forges and grinds it into a blade. A brand puts a name on the handle and sells it. Sometimes two of those roles live under one roof, but the mill role almost never does. That is why the same steel names, VG-10, AUS-8, Shirogami, repeat across hundreds of competing brands: they are all shopping from the same short list of suppliers.

Our steel guide compares the alloys themselves. Here we go one level deeper, to the Japanese mills that matter for kitchen knives and the foreign mills whose steel arrives by ship.

The mills, side by side

"Documented users" means brands whose steel sourcing we have covered on their own pages here, based on maker-published specifications. Every mill above sells to far more workshops than we list.

Yasugi: the furnace with a tatara in its family tree

If Japanese knife steel has a spiritual home, it is a mill town on the Sea of Japan coast. The Yasugi works sits in Shimane Prefecture at the edge of the old Izumo iron country, where tatara furnaces smelted iron sand for centuries and fed Japan's sword tradition. A modern steelworks was established there in the late 1890s to carry that lineage into industry, branding its output Yasuki Hagane (安来鋼, Yasugi steel). Hitachi Metals later took over the plant, and in 2023 the company was renamed Proterial. Enthusiasts still say Hitachi, the datasheets now say Proterial, and the steel is the same. The full furnace story, including the revived Nittoho tatara that Proterial's Yasugi operation has long helped sustain, is on our tamahagane and the tatara page.

The knife world knows Yasugi through its YSS cutlery grades, and through a naming system that started as warehouse logistics. Billets of different grades were wrapped in colored paper so wholesalers and smiths could tell them apart: white paper for the purest simple carbon steel, blue for the tungsten-alloyed grade, yellow for the standard grade, silver for the stainless family. The wrapping paper is long gone; the entire industry still sorts traditional Japanese steel by its colors.

What Yasugi makes for knives

• Shirogami (white paper steel): pure high-carbon steel in three grades, the cleanest sharpening feel in kitchen cutlery and the choice of traditional Sakai smiths. Typically 62 to 65 HRC.
• Aogami (blue paper steel): Shirogami plus tungsten and chromium for longer edge retention. The enthusiast carbon workhorse.
• Aogami Super: the highest-alloy carbon grade, adding molybdenum and vanadium and hardening to roughly 64 to 66 HRC in skilled hands. The steel Moritaka built its reputation on.
• Ginsan (Silver 3): the fine-grained stainless that sharpens like carbon, beloved of Sakai single-bevel makers such as Sakai Takayuki and Sakai Kikumori.
• ZDP-189: the roughly 3 percent carbon powder-metallurgy experiment from the mid-1990s, capable of 64 to 67 HRC. Its production status is murky; we found no official discontinuation notice, but its most visible users have moved on, and we say so plainly on its page.
• HAP40 and YXR7: powder-metallurgy high-speed tool steels that crossed over into kitchen knives through specialists like Sukenari in Toyama.

The through-line is purity. The low-phosphorus, low-sulfur discipline that defines white and blue paper steel is a direct descendant of the tatara habit of starting from unusually clean iron sand. When a Sakai smith says the steel "moves honestly" under the hammer, that cleanliness is a large part of what they are feeling.

Who uses it: essentially every traditional carbon-steel workshop we have profiled touches Yasugi metal somewhere. Sakai's forges run White and Blue for single-bevel work, Tosa's free-forgers favor the Aogami grades, Sanjo smiths like Hinoura work Aogami, and Tokyo's Teruyasu Fujiwara is known for both White #1 and Aogami Super. On the stainless side, Ginsan is the quiet standard for professional single-bevel knives that cannot be allowed to rust mid-service.

Takefu: the small mill that rewired stainless

Takefu Special Steel Co., Ltd. (武生特殊鋼材) is a small specialty mill in Echizen City, Fukui, founded in 1954 inside one of Japan's oldest blade regions. Echizen has forged knives and farm tools for roughly 700 years, and Takefu began as a steel supplier to those local smiths before its alloys went national, then global. For a company of its size, its influence on what is in your knife block is out of all proportion.

Takefu's signature is the V Gold series of cutlery stainless steels. VG-1 and VG-2 came first; VG-10, with its signature cobalt addition, became the flagship and then the default steel of the entire mid-premium Japanese knife category. The cobalt, roughly 1.3 to 1.5 percent per Takefu's published ranges, is the unusual ingredient: it strengthens the steel matrix and supports high hardness, and it is a large part of why VG-10 at 60 to 62 HRC still sharpens like a civilized steel. Exactly when VG-10 was developed is debated; Takefu's own materials point to the company's early decades, and the steel rose to worldwide prominence in the 1990s when Seki's production houses adopted it at scale. We flag that uncertainty here the same way we do on the VG-10 page.

Two more chapters followed. SG2, from Takefu's Super Gold powder-metallurgy line, defined the tier above VG-10 and became the benchmark for edge retention in the mid-premium market. And in late 2023 Takefu introduced SPG STRIX, a matrix-strengthened powder steel claimed at up to 65 HRC, whose composition the mill has not published; our STRIX page marks every unverified number accordingly.

The SG2 and R2 question, stated carefully

You will see the same powder steel labeled SG2 by some brands and R2 by others, and the mill attribution behind those marks is the most commonly garbled fact in Japanese knife retail. Our position, consistent across this site: SG2 is Takefu's steel, short for Super Gold 2 (Takefu's own mark is SPG2). The powder itself is widely reported to be produced within the Kobe Steel group and finished and distributed by Takefu, and R2 is the designation associated with that Kobelco powder production. Sources disagree on the fine print: some describe Kobelco as making the powder that Takefu finishes, others describe Kobelco as producing the same composition under its own R2 mark. The published compositions match, the knives behave identically, and no maker we know of claims otherwise, so we treat SG2 and R2 as one steel family with two logos and hold the supply-chain detail at "widely reported" rather than "confirmed."

The billet business

One under-appreciated part of Takefu's model: it does not just sell bar stock. It supplies pre-laminated billets, VG-10 or SG2 cores already clad in stainless or patterned suminagashi layers, which is how mid-size workshops offer Damascus lines without running their own forge-welding. Takefu also anchors its home region physically: the Takefu Knife Village cooperative keeps a cluster of independent Echizen smiths, several of whom we profile, working minutes from their steel supplier.

Who uses it: Tojiro's DP line is the famous value expression of VG-10; Shun ran VG-10 for years before moving to VG-MAX, the proprietary derivative Takefu developed for Kai; Kasumi builds its Damascus line on a VG-10 core; Masutani works VG-1 and VG-10 in Echizen; Takamura and Ryusen made their names in R2 and SG2 powder steel a short drive from the mill.

Kobelco: the giant behind one label

Kobe Steel, known internationally as Kobelco, is one of Japan's largest steelmakers, a heavy-industry group whose kitchen-knife relevance comes down to a single letter and number: R2. As covered above, R2 is the mark associated with powder production inside the Kobe Steel group for the steel family the knife world otherwise calls SG2. Brands that spec their blades as R2, Takamura, Ryusen, and Yu Kurosaki among the makers we cover, are using the same published composition as the SG2 crowd.

We will not pretend to more detail than exists in public. Neither Kobelco nor Takefu publishes a joint account of who does which production step, and the knife trade's understanding rests on consistent industry reporting rather than corporate documentation. What matters for a buyer is settled: SG2 and R2 knives are the same steel tier, and the maker's heat treatment, not the logo, decides which knife is better.

Aichi: the Toyota-group mill that feeds Seki

Aichi Steel Corporation (愛知製鋼) is the volume workhorse of Japanese knife steel. Headquartered in Tokai City, it is a member of the Toyota Group, incorporated in 1940 when Toyota's in-house steelmaking operations, begun in the mid-1930s to supply the young automobile business, were spun into their own company. Cutlery is a small, famous corner of a business that mostly serves forged automotive components, and that industrial scale is precisely the point: consistent chemistry, reliable supply, and pricing that keeps honest Japanese knives affordable.

The AUS family is Aichi's line of cutlery stainless steels, graded by carbon: AUS-4 and AUS-6 at the soft end, AUS-8 in the middle at roughly 0.75 percent carbon and 58 to 60 HRC, and AUS-10 at the top near 1 percent carbon and 60 to 61 HRC. On export knives the same alloys sometimes appear as 6A, 8A, and 10A. Geography did the rest: Seki, the production capital of Japanese kitchen knives, sits in the neighboring prefecture, and a large share of Seki's branded and OEM output runs on Aichi steel simply because it is the local, proven choice. If a Japanese-made knife under $100 says "Japanese stainless" without naming an alloy, an AUS grade is a good first guess.

One clarification worth repeating from our steel pages: Aichi's AUS series and Takefu's V Gold series are unrelated products from two different mills. VG-10 is not "AUS-8's big brother"; AUS-10 is. The two families simply compete in the same kitchens.

Who uses it: both of our own knives, which is why we know this supply chain firsthand. The Okami Classic runs AUS-8; the Okami Premium runs an AUS-10 core under 67-layer Damascus cladding. Beyond our shop, AUS grades appear across Seki production, from Kanetsune KC-series kitchen knives to Shizu Hamono's export Damascus lines and select Seki Magoroku models.

Daido: a brief, honest entry

Daido Steel (大同特殊鋼) is one of Japan's major specialty steel producers, based in Nagoya and serving mostly industrial and automotive customers. Its verified footprint in kitchen knives is narrow, so this section stays short. The grade you will actually meet is DSR1K6, a medium-carbon stainless in roughly the AUS-6 class, hardening to around 57 to 59 HRC, which appears in entry-tier Seki production including lines from Kanetsune and various house-brand knives. It is honest budget steel: easy to sharpen, rust-resistant, and modest in edge retention. Claims you may see attaching other famous grades to Daido are ones we could not verify, so we leave them out.

"Swedish steel": the imports Japan swears by

Not all the steel in Japanese knives is Japanese, and the makers who import are refreshingly open about it. "Swedish steel" has carried prestige in Japanese cutlery for generations, built on clean Scandinavian ore and low-impurity steelmaking, and a handful of professional lines are defined by it.

Misono in Seki is the flagship example. Its dragon-etched Swedish Steel line, labeled EU Carbon in Misono's own catalog, is hand-forged from a very pure Swedish high-carbon steel from the specialty-steel tradition associated with Sweden's Sandvik-family mills; the stainless flagship UX10 is likewise built on Swedish stainless. Misono does not publish the exact mill or grade, so neither do we. For reference, Sandvik's strip-steel business has traded under the Alleima name since 2022, which is why you now see both names attached to the same Swedish tradition.

In Sakai, Sakai Takayuki's Grand Chef line runs a low-impurity special stainless supplied through the Bohler-Uddeholm channel and marketed as Swedish steel, hardened to roughly 58 to 59 HRC, one of Japan's default professional knives. That is the one place a Bohler-Uddeholm connection is documented in our own brand research; we have not verified broader Bohler usage in Japanese kitchen knives and do not claim it.

The pattern to notice: foreign steel enters Japanese knives at the top of the purity ladder, not the bottom. When a Japanese maker names a Swedish source, it is bragging, not cost-cutting. The cheap end of the market works the other way around, with foreign blades borrowing Japanese words; our buying guides cover how to spot that.

Mill, forge, brand: one supply chain

Put the layers together and the industry stops being mysterious. The mill makes steel: Yasugi's carbon and fine stainless grades, Takefu's cobalt stainless and powder steels, Aichi's dependable AUS series, Kobelco's powder, Daido's budget stainless, Sweden's clean imports. The workshop turns that steel into a blade, and this is where the personality of a knife is really decided: the same VG-10 can become a modest workhorse or a superb cutter depending on the forging, heat treatment, and grinding it receives. The brand, finally, names and sells the result, sometimes from its own factory floor, sometimes from blades it commissioned three towns away.

This is why "what steel is it" is a necessary question but never a sufficient one. Steel names tell you the ceiling; the workshop decides how close a knife gets to it. Our page on how Japanese knives are made follows the full journey stage by stage, and every steel named above links to its own reference page with composition tables and care guidance.

The mills, quick answers

Who makes the steel in Japanese kitchen knives?

A short list of specialty mills supplies almost the entire industry: Proterial's Yasugi works in Shimane (Shirogami, Aogami, Ginsan, ZDP-189), Takefu Special Steel in Echizen (VG-10, SG2, SPG STRIX), and Aichi Steel near Seki (the AUS series), with Kobe Steel powder behind the R2 mark, Daido Steel at the entry tier, and Swedish steel imported by makers like Misono. Knife brands buy from these mills; they do not smelt their own steel.

Is Hitachi knife steel the same as Proterial steel?

Yes. Hitachi Metals was renamed Proterial in 2023, and its Yasugi Specialty Steel (YSS) grades, including Shirogami, Aogami, Aogami Super, and Ginsan, continue unchanged. When one knife listing says Hitachi White #2 and another says Proterial White #2, they mean the same steel from the same works.

Who makes VG-10 steel?

Takefu Special Steel Co., Ltd. of Echizen City, Fukui Prefecture, founded in 1954. Knife brands buy VG-10 from Takefu, often as pre-laminated blanks, and do their own grinding and heat treatment, which is why VG-10 knives from different brands can behave differently.

Are SG2 and R2 made by the same mill?

They are the same steel family wearing two marks. SG2 is Takefu Special Steel's steel, and the powder is widely reported to be produced within the Kobe Steel (Kobelco) group, whose production the R2 designation is associated with. Sources disagree on the exact division of labor between the two companies, but published compositions match and the knives are equivalent in practice.

Do any Japanese knife makers use foreign steel?

Yes, openly. Misono forges its dragon-etched carbon line from very pure Swedish steel and builds the UX10 on Swedish stainless, and Sakai Takayuki's Grand Chef line uses a low-impurity stainless supplied through the Bohler-Uddeholm channel and marketed as Swedish steel. In Japan, a named foreign source at the premium end is a point of pride, not a shortcut.

Sources

Proterial Ltd. (formerly Hitachi Metals) Yasugi Specialty Steel grade documentation; Takefu Special Steel published steel chart, V Gold and Super Gold product literature; Aichi Steel alloy datasheets for the AUS series; Kobe Steel (Kobelco) powder metallurgy materials data; Daido Steel DSR1K6 grade listings and retailer specifications; maker-published specifications from the brands referenced above; Larrin Thomas, "Knife Engineering" and the Knife Steel Nerds VG10 and SG2 history; zKnives steel composition database. Where a claim rests on industry reporting rather than mill documentation, the text says so.