Ladle Refining Patents: Who Leads, Where the Gaps Are 2026
- Ownership is concentrated but not locked down. the top 5 assignees hold 37.2% of the 188 records in scope, and the top 10 hold 49.5% — leaving roughly half the field to a long tail of single- and few-filing entrants.
- Filing has plateaued rather than grown. activity rose from 2 records in 2017 to a peak of 13 in 2022, and the years since show no clear upward trend.
- Claims cluster overwhelmingly in one subclass. 95.2% of records sit in C21C (steelmaking), while adjacent casting, furnace-detail and temperature-measurement classes are each claimed in single-digit percentages of records.
What this landscape covers
This dataset tracks patent activity at the intersection of ladle refining and secondary metallurgy — the processes applied to molten steel after tapping and before casting, including desulfurization, inclusion control, argon stirring, temperature control before casting, and alloy yield. The scope is defined by title and abstract terms combined with IPC classes C21C7, C21C1 and B22D1, capturing 188 published records filed between 2015 and mid-2026.
Because publication typically lags filing by around 18 months, the most recent filing years in this dataset are understated and should be read as a floor, not a ceiling, on current activity.
Filing trend and technology composition
Two views of the same 188 records: how filing activity has moved year over year, and which IPC subclasses carry the claims.
Filing trend, 2017–2026
Filings moved from 2 records in 2017 to a peak of 13 in 2022, with 2026 (partial year) also at 2. The flat trajectory around the 2022 midpoint suggests filing has plateaued rather than accelerated, though the final one to two years are likely undercounted due to publication lag.
IPC subclass composition (share of 188 records)
C21C (steelmaking) dominates at 95.2% of records, consistent with the search scope. C22C (alloys) and B22D (metal casting) follow at 22.9% and 16.5%. Smaller shares in C22B, F27D, C21D, G01K and B21B indicate that extraction/refining, furnace hardware, heat treatment, temperature sensing and rolling are claimed only incidentally alongside the core ladle-refining process, not as primary subject matter.
Shares are the percentage of the 188 records in scope. A patent can carry several IPC classes, so the shares add up to more than 100%.
Go deeper on Ladle Refining and Secondary Metallurgy with Eureka
This page is one run against one query. Ask Eureka your own question about ladle refining and secondary metallurgy and every answer comes back with the patent numbers behind it.
Try EurekaMost-cited records in this dataset
Duplex melting: pressurized ladle refining + pressurized electroslag remelting for high-nitrogen steel
The present disclosure provides a method for producing a high nitrogen steel by a duplex melting process of a pressurized ladle refining and a pressurized electroslag remelting, which relates to the technical field of high nitrogen steel melting. In the present disclosure, the molten steel is subjected in sequence to a nitrogen alloying, a deep deoxidation and a deep desulfurization by adding a nickel-magnesium alloy and rare earth in the pressurized ladle furnace, and a combination of a blowing nitrogen from the bottom of the pressurized ladle and a pressurized nitriding at the interface of gas and the molten steel is used to achieve a high-efficiency nitrogen alloying, a uniform nitrogen distribution.Filed by Northeastern University, 2022-07-21 (US20220228243A1).
| # | Publication no. | Patent title | Citations |
|---|---|---|---|
| 1 | US5397379A | Process and additive for the ladle refining of steel | 108 |
| 2 | CN103205524A | 一种半钢冶炼低硫钢的方法 | 32 |
| 3 | JP2001040411A | Ladle for refining molten steel | 30 |
| 4 | CN101423879A | 低磷钢水冶炼方法 | 28 |
| 5 | JP2005232536A | Method for smelting high cleanliness steel | 26 |
| 6 | JP2012012648A | Method for applying desulfurize-treatment to molten steel | 25 |
| 7 | CN101245432A | 一种生产低碳拉丝用盘条的工艺 | 25 |
| 8 | JP1984074212A | Ladle refining method of molten steel to be used for producing non-directional electrical sheet having less i… | 24 |
| 9 | CN102766728A | 钢包精炼炉精炼过程钢水硫含量实时预测的方法及装置 | 21 |
| 10 | CN103233096A | LF炉低碳深脱硫精炼方法 | 19 |
Citation counts inside this searched corpus favour older filings that have had more time to accumulate citations — treat them as a signal of influence on the field's prior art, not of current commercial importance.
Patent titles are shown in the language they were filed in, not translated, so that each record stays verifiable against the original filing — a translated title will not match in Eureka or in any national register. Each row carries its publication number; clicking a row searches Eureka by that number.
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Three patterns stand out once filing volume, concentration and technology composition are read together.
Ownership is top-heavy but not closed
The top 5 assignees account for 37.2% of the 188 records in scope, rising to 49.5% for the top 10. That leaves just over half the field spread across 82 further ranked entities, most with only a handful of filings — a structure typical of an established process technology where a handful of integrated steelmakers hold the deepest portfolios but regional producers and research institutes keep filing around the edges.
Activity has plateaued since its 2022 peak
Filings grew from 2 records in 2017 to 13 in 2022, then did not sustain that pace into subsequent years. Combined with the recent-year momentum data — several of the historically active assignees show zero filings in the latest year — this points to a maturing rather than expanding claim landscape, though publication lag means the last one to two years understate true activity.
Claims are concentrated in core steelmaking, not casting or measurement
Nearly all records (95.2%) carry a C21C steelmaking classification, with C22C alloys and B22D casting as the next largest at 22.9% and 16.5%. Furnace detail (F27D), heat treatment (C21D) and temperature measurement (G01K) each appear in fewer than 7% of records, suggesting these adjacent process steps are claimed as secondary elements rather than as standalone inventions.
Eureka can read the same corpus for gaps instead of for coverage: under-claimed branches adjacent to ladle refining and secondary metallurgy, with the prior art for and against each one.
| Assignee | Co-assignee | Shared families |
|---|---|---|
| Sanyo Special Steel Co., Ltd. | SATO ICHIRO | 2 |
| Sanyo Special Steel Co., Ltd. | MORI TOMOMI | 2 |
| Sanyo Special Steel Co., Ltd. | KODAMA KAZUYA | 2 |
| Sanyo Special Steel Co., Ltd. | KITANO SHUHEI | 2 |
| Sanyo Special Steel Co., Ltd. | KAWAKAMI KIYOSHI | 2 |
| Sanyo Special Steel Co., Ltd. | ISHIDO KAICHIRO | 2 |
| Sanyo Special Steel Co., Ltd. | IRIE TOSHIHIRO | 2 |
| Northeastern University (China) | Pangang Group Research Institute Co., Ltd. | 2 |
Only 8 co-assignee pairs appear in the dataset, the strongest being repeated inventor pairings within a single Japanese steelmaker's filings — indicating most work here is filed by a single corporate assignee rather than through joint ventures or cross-licensing arrangements.
Who is filing, and where the field is open
Filing offices and assignee concentration point to where competitive pressure is real, and the gate chips below flag sub-areas that show up in the scope but carry little claim density.
A single leader holds the deepest portfolio
The top-ranked assignee holds 29 of the 188 records in scope, well ahead of fifth place at 7 and tenth place at 4. That gap between first and fifth is the clearest sign of a genuine leader rather than a cluster of near-equal filers.
China and Japan dominate filing venues
China and Japan each account for 72 records, far ahead of the United States (16), EPO (8), India (8) and Canada (6). Any freedom-to-operate review for this process needs to prioritise Chinese and Japanese national filings before broader jurisdictions.
A long tail of research institutes and regional mills
Beyond the top 10 assignees (who together hold 49.5% of records), the remaining ranked entities are mostly research institutes, regional steel groups and equipment makers with a handful of filings each — a pattern consistent with incremental process patents rather than platform-defining inventions.
| Assignee | Recent year | YoY |
|---|---|---|
| JFE Steel Corporation | 0 | — |
| Nippon Kokan KK | 0 | — |
| Kawasaki Steel Corporation | 0 | — |
| Nippon Steel Corporation | 0 | — |
| Kobe Steel, Ltd. | 0 | — |
| Sanyo Special Steel Co., Ltd. | 0 | — |
| Northeastern University (China) | 0 | — |
| Pangang Group Panzhihua Iron & Steel Research Institute Co., Ltd. | 0 | — |
Where to take this analysis
The dataset points to a mature, top-heavy field with specific gaps rather than open territory — the next step is turning that into a filing or freedom-to-operate decision.
Map claims against the C21C core
Run a claim-by-claim comparison against the leader's 29-record portfolio before drafting anything touching desulfurization or inclusion control, since that is where prior art is thickest.
Explore ladle refining claims in EurekaCheck the under-claimed branches
Furnace-detail accessories, temperature sensing and heat-treatment integration each show low claim density relative to the core — worth a deeper prior-art pull before assuming they are open.
Run a white space search in EurekaTrack the China and Japan filing offices
With 72 records each, these two offices carry the bulk of relevant prior art and should be the first stop for any freedom-to-operate check.
Search assignees by office in EurekaCommon questions on ladle refining patents
The dataset ranks 92 companies by patent family count, and the top-ranked assignee holds 29 of the 188 records in scope — well ahead of the fifth-place holder at 7 and the tenth-place holder at 4. The top 5 assignees combined hold 37.2% of all records, and the top 10 combined hold 49.5%, meaning roughly half the field is spread across a long tail of smaller filers. This concentration pattern suggests one or two integrated steelmakers have built durable portfolios while the rest of the field files incrementally.
Filing activity rose from 2 records in 2017 to a peak of 13 in 2022, but has not sustained that growth since. Several historically active assignees show zero filings in the most recent year of data, which points to a plateau rather than continued expansion. That said, publication typically lags filing by around 18 months, so the last one to two years in any dataset understate real activity and should not be read as a hard decline.
Almost all records (95.2% of the 188 in scope) carry a C21C steelmaking classification, confirming the core subject matter is the ladle refining process itself — desulfurization, inclusion control, argon stirring and related steps. Secondary classifications in C22C alloys (22.9%) and B22D metal casting (16.5%) show up frequently as adjacent claim elements. Furnace accessories, heat treatment, temperature measurement and rolling appear in single-digit shares, meaning they are rarely the primary invention.
The under-claimed areas sit in the adjacent classes with low record shares: furnace-detail accessories (F27D, 6.4% of records), heat treatment integration following secondary metallurgy (C21D, 4.3%), and temperature measurement tied to casting readiness (G01K, 2.1%). These branches appear in the search scope but carry thin claim density compared to the core C21C cluster, which is where a first claim focused on integration — rather than the refining chemistry itself — is more likely to find open space.
China and Japan are the leading receiving offices, each with 72 of the 188 records in scope, far ahead of the United States (16), the European Patent Office (8), India (8) and Canada (6). Any competitive or freedom-to-operate review of this space should prioritise Chinese and Japanese national filings first, since together they account for the large majority of documented activity. The gap to other offices is wide enough that it reflects where the underlying steel production and R&D activity is concentrated, not just where applicants chose to file defensively.
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Disclaimer. This page is generated from Patsnap Eureka data drawn from a limited snapshot of global patent and scientific-literature records, and is provided for general information and reference only.
Patent data carries inherent limitations: recent filings (typically the most recent 18–24 months) are under-counted due to standard publication lag; counts may be reported at either a patent-family or a patent-record basis and are not always directly comparable; classification, applicant-name, and citation data may contain errors, duplicates, or omissions; and the underlying search query defines and constrains the scope shown. As a result, the analysis may be incomplete or inaccurate and may not reflect the full technology landscape.
Nothing on this page constitutes an exhaustive prior-art, novelty, freedom-to-operate, or validity search, nor does it constitute legal, financial, investment, or professional advice, and it should not be relied upon as such. Any patent, commercial, or strategic decision should be verified independently and reviewed with qualified patent, legal, and domain professionals. Patsnap makes no warranties, express or implied, as to the accuracy, completeness, or fitness for any particular purpose of the information presented.
Machine translation. Assignee and organisation names originally recorded in Chinese, Japanese or Korean have been rendered into English by an AI translation step so that the tables stay readable. These renderings are best-effort and may not match a company’s registered English name; the original name is what the underlying patent record carries, and it is what any Eureka query launched from this page uses.