Santoku Corporation

Rare-earth alloy and metal producer, not a magnet maker: pioneer of the strip-cast NdFeB alloy process (introduced 1991) and a supplier of NdFeB and SmCo alloys, powders, and recycled rare-earth metal to magnet manufacturers.

At a glance

Founded: 1949 — Predecessor operations date to 1937. Wholly owned by Hitachi Metals (renamed Proterial in 2023 under a Bain Capital-led consortium) since November 2017.
Headquarters: Kobe, Japan, with plants in Kobe, Miki, Akashi, and Tsuruga
Ownership: Wholly owned subsidiary of Proterial, Ltd. (formerly Hitachi Metals), under a Bain Capital-led consortium since 2023. Santoku's own Japanese-language corporate history page states that in 2026, through organizational restructuring, it will become a subsidiary of Proterial Magnetics Co., Ltd.; this split is independently corroborated by Japan Metal Daily's trade reporting and by a Japanese government corporate-number registry entry for Proterial Magnetics Co., Ltd., though the exact effective date is not settled (see Conflicts).
Stage: Mature. A long-established supplier of strip-cast NdFeB alloy, SmCo alloy and rare earth metals; its separation plant is a new, grant-funded build.
Listing: Private. Subsidiary of Proterial (private).
Revenue: Not publicly disclosed. This company does not publish revenue and no named third party has published an estimate of it.
Private subsidiary; no revenue breakout found.

Capacity

Each date below links to the document the figure came from. A capacity figure with no source is not on this page.

What	Figure	Status	As of
NdFeB strip-cast alloy	Not disclosed	Operating	2026
SmCo alloy and powder	Not disclosed	Operating	2026
Rare-earth metal recycling — a standing Recycling Division that recovers neodymium magnet grinding and polishing powder from users or from the open market and returns it to rare-earth alloy feedstock	Not disclosed	Operating	Sep 2026
New rare-earth smelting/refining capacity, Japan — METI-certified supply-assurance plan under the critical-minerals track (2026重要鉱物第2号-1)	subsidy of approximately JPY 800 million; no production tonnage disclosed	Announced	2026-07-29
Certified permanent-magnet supply-assurance plan, Japan — METI's separate permanent-magnet track, administered through NEDO (2024永久磁石第3号-1)	amount not published in METI's index; the underlying plan document was not accessible	Announced	2024-07-24

Narrative

Santoku Corporation is a Japanese rare-earth alloy and metal producer headquartered in Kobe, with additional plants in Miki, Akashi, and Tsuruga. It has been a wholly owned subsidiary of Hitachi Metals, renamed Proterial in 2023 following its acquisition by a Bain Capital-led consortium, since November 2017. Santoku does not make finished magnets; it supplies strip-cast NdFeB alloy, SmCo alloy and powder, and recycled rare-earth metal to magnet manufacturers, and is credited with introducing the strip-cast NdFeB alloy process in 1991, a role comparable to that of Less Common Metals in the European supply chain. Santoku's own corporate history states that in 2026, through organizational restructuring, it will become a subsidiary of a newly separated entity, Proterial Magnetics Co., Ltd. — a split independently corroborated by Japanese trade press and a government corporate registry entry, though the exact effective date is unsettled. No public production-capacity figures in tons per year were located for any of Santoku's three main product lines, each of which is disclosed only qualitatively as an active business line. Japan's METI has certified two separate supply-assurance plans naming Santoku — a JPY 800 million critical-minerals grant for new rare-earth refining capacity (July 2026) and an earlier, separate permanent-magnet-track certification (July 2024) — though neither discloses a tonnage figure.

Where public sources disagree

Santoku's own Japanese-language corporate history page (santoku-corp.co.jp) confirms it will become a subsidiary of Proterial Magnetics Co., Ltd. as part of Proterial's 2026 corporate reorganization — the split itself is no longer sourced to the company alone: Japan Metal Daily's trade reporting on the reorganization and a Japanese government corporate-number registry entry for Proterial Magnetics Co., Ltd. both independently corroborate it. The exact effective date remains unsettled: Japan Metal Daily gives 1 April 2026, two other trade-press pieces give 1 April 2026 and 1 July 2026 for the same underlying split, and the corporate registry shows Proterial Magnetics newly registered on 28 May 2026. No single date is confirmed as authoritative.
No public capacity figures (tons per year or equivalent) were found for NdFeB strip-cast alloy, SmCo alloy/powder, or rare-earth metal recycling.
The previously unconfirmed government grant for refining-equipment investment is now traced directly to METI's own certified supply-assurance plan list: 2026重要鉱物第2号-1, approximately JPY 800 million, certified 29 July 2026, for new rare-earth smelting/refining capacity in Japan. Santoku also holds a separate, earlier certification on METI's permanent-magnet track (2024永久磁石第3号-1, 24 July 2024), whose funding amount is not published in METI's index and whose underlying plan document could not be retrieved. Neither certification discloses a production tonnage.

Sources

Company website — Santoku Corporation (2026-09)
Corporate history — Santoku Corporation (Japanese) (2026-09)
Proterial reorganization report — Japan Metal Daily (2026)
Corporate-number registry entry, Proterial Magnetics Co., Ltd. — Japan National Tax Agency (via GVA Houjin Bangou Search) (2026-05-28)
Certified critical-minerals supply-assurance plans — Ministry of Economy, Trade and Industry (METI) (2026-09)
Certified permanent-magnet supply-assurance plans — Ministry of Economy, Trade and Industry (METI) (2026-09)

How this page is sourced

Everything here comes from public sources — company filings, annual reports, exchange announcements, government releases and trade press. Every figure is linked to the document it came from and carries the date that document was published, because a capacity number without a date is not a fact, it is a rumor with a decimal point.

What is deliberately absent: material nonpublic information. I have spent more than two decades in this industry and a good deal of what I know about these companies I learned under NDA. Those obligations do not expire and they do not bend for a website. Nothing I have been told in confidence appears here in any form, and nothing on this page — or missing from it — should be read as a signal about what I know privately. I hold NDAs absolutely. It is the reason clients tell me things.

Judgment is the other thing left out on purpose. This page reports what has been published and who published it. Whether a target is credible, whether a ramp will hold, whether a capacity figure survives contact with the plant behind it — that is the work I do for clients, and it does not belong in a free reference page.

Where public sources disagree, I say so rather than picking a winner. Where a figure has not been published, the field says so rather than carrying an estimate. An empty field is information too.

Public filings tell you what a company has said. Whether it holds up is a different question, and the one I get hired to answer.

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