Continuous Annealing Line Patents: Who Leads, Filing Trends 2026
- 68.4% concentration. The top five assignees alone hold 1,898 of 2,776 records in scope — a field dominated by a small group of integrated steel producers.
- Filings down 39% since the last complete peak. From 77 filings in 2021 to 47 in 2024, momentum has cooled from the 2017 high of 118 filings a year.
- Heat treatment claims dominate at 82.2%. C21D covers the large majority of records; coating (C23C, 29.1%) and layered products (B32B, 9.7%) sit far behind and are less contested.
Filing growth compares 2021 (77 records) with 2024 (47) — a three-year span. 2024 is the most recent year we treat as complete: publication lags filing by roughly 18 months, so 2025 onwards are still filling in and any growth rate that ends there would understate the field. Top-5 share is the combined record count of the five largest assignees divided by all 2,776 records in scope (CR5), not by the ranked leaders only.
What continuous annealing line patents actually cover
Continuous annealing lines sit at the centre of modern cold-rolled steel production, controlling the heating, soaking and cooling cycles that set a strip’s final mechanical properties. The search set combines core process terms — continuous annealing line, strip rapid cooling, recrystallization annealing — with the equipment and control vocabulary that distinguishes production-grade claims: strip temperature profile, furnace roll buildup, overaging treatment, line speed, and soaking zone design. That pairing captures both the metallurgical outcome claims and the line-control claims that get filed around them.
2,776 published records sit in scope, spanning 2015 through the 2026 data cut-off. Because publication typically lags filing by around 18 months, the most recent one to two years of the trend are still filling in and should not be read as a decline in filing activity itself.
Filing trend and technology composition
Two views of the same 2,776-record set: how filing activity has moved year over year, and which IPC subclasses carry the claim volume today.
Filing trend, 2017–2026
Filings peaked at 118 in 2017 and had fallen to 47 by 2024, a 39% drop from the 77 filed in 2021 — the last three-year span that can be read as complete. Data past 2024 is still arriving as later applications publish.
Technology composition by IPC subclass
C21D (heat treatment of metals) appears on 82.2% of the 2,776 records, with C22C (alloys) close behind at 52.2%. Coating and surface deposition (C23C, 29.1%) and layered products (B32B, 9.7%) are present but far less saturated, and furnace hardware classes F27B and F27D each sit near 2%, marking the equipment side of the line as comparatively under-claimed relative to the metallurgical side.
Shares are the percentage of the 2,776 records in scope. A patent can carry several IPC classes, so the shares add up to more than 100%.
Go deeper on Continuous Annealing Lines with Eureka
This page is one run against one query. Ask Eureka your own question about continuous annealing lines and every answer comes back with the patent numbers behind it.
Try EurekaMost-cited records and a representative recent filing
Continuous annealing line, continuous annealing method, method of producing cold-rolled steel sheet, and method of producing coated or plated steel sheet
Filed by JFE Steel Corporation and published 2026-03-12, this application describes a continuous annealing line with heating, soaking and cooling zones in sequence, plus an induction heating device placed between the soaking and cooling zones. A control device sets operating conditions based on a predicted phase fraction of the steel sheet under high-temperature conditions, adjusting the annealing condition as that predicted fraction varies.Abstract condensed from the published filing; see the full record for complete claim language.
| # | Publication no. | Patent title | Citations |
|---|---|---|---|
| 1 | JP1981139654A | High-tensile cold-rolled steel plate with superior formability and its manufacture | 110 |
| 2 | JP1988293121A | Production of high-strength cold rolled steel sheet having excellent local ductility | 69 |
| 3 | EP0339474A1 | Process for preparation of grain-oriented electrical steel sheet having excellent magnetic and film character… | 66 |
| 4 | JP1984031827A | Production of quench hardenable steel plate for ultra deep drawing | 63 |
| 5 | US20100304183A1 | High strength hot dip galvanized steel sheet and high strength galvannealed steel sheet excellent in shapeabi… | 61 |
| 6 | US4750949A | Grain-oriented electrical steel sheet having stable magnetic properties resistant to stress-relief annealing,… | 60 |
| 7 | US4440583A | Method of controlled cooling for steel strip | 59 |
| 8 | JP1980122820A | Manufacture of alloyed zinccplated high tensile steel sheet with superior workability | 58 |
| 9 | US20080202639A1 | Hot-rolled steel sheet and cold-rolled steel sheet and manufacturing method thereof | 56 |
| 10 | JP1980122821A | Manufacture of alloyed zinccplated high tensile steel sheet with high workability | 55 |
Citation counts favour older documents simply because they have had longer to accumulate citations within the searched corpus; treat them as a signal of influence on the field's vocabulary rather than of current commercial relevance.
Each row carries its publication number; clicking a row searches Eureka by that number.
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Browse MCP servers →What the numbers mean for a filing decision
Three findings that shape where a new application is likely to compete against dense prior art, and where it is not.
The field is a small-group contest, not an open race
Five assignees hold 1,898 of the 2,776 records in scope, with the leader alone at 759. Filing into the core annealing-cycle claim space means filing against a small set of long-established integrated steel producers, not a fragmented field.
Activity has cooled from the 2017 peak
118 filings in 2017 marked the high point for the field; by 2024, the last year that can be treated as a complete filing year, annual volume had fallen to 47. Several of the largest historical filers show sharp year-on-year drops in the most recent complete data.
Heat treatment claims are the densest ground
C21D appears on the large majority of records, with C22C alloy claims close behind. Furnace hardware classes (F27B, F27D) sit near 2% each, a much thinner layer that points to equipment-level claims as comparatively open relative to process and metallurgy claims.
Eureka can read the same corpus for gaps instead of for coverage: under-claimed branches adjacent to continuous annealing lines, with the prior art for and against each one.
Who holds the ground, and where activity is slowing
The ranked leaders in this dataset are almost entirely integrated steel producers with decades of continuous-annealing filing history; recent-year momentum for several of them has turned sharply negative in the latest complete data.
A single assignee anchors the field
The leading assignee holds 759 of the 2,776 records in scope, well ahead of fifth place at 144 and tenth place at 48. That gap defines the field's shape: one dominant filer, a handful of strong followers, then a long tail.
Recent-year activity has dropped sharply for long-time leaders
Several of the historically largest assignees show steep year-on-year declines in the latest tracked year, including drops of -86%, -67% and -100% among named leaders. This is consistent with the broader 2021-to-2024 slowdown, not isolated to one company.
Cross-filing is limited and concentrated
Only 10 co-assignee pairs appear in the dataset, and the strongest of them links a steel producer with a heavy-industry equipment maker at 30 shared filings. Most assignees in this field file independently rather than jointly.
| Assignee | Recent year | YoY |
|---|---|---|
| JFE Steel Corporation | 2 | -86% |
| POSCO | 1 | -67% |
| Nippon Steel Corporation | 0 | -100% |
| Kawasaki Steel Corporation | 0 | — |
| ArcelorMittal | 0 | — |
| Nippon Kokan K.K. | 0 | — |
| Sumitomo Metal Industries, Ltd. | 0 | — |
| Tata Steel IJmuiden B.V. | 0 | -100% |
Where to take this analysis
The dataset points to specific next steps depending on whether the goal is freedom-to-operate, white-space filing, or tracking a competitor.
Check freedom-to-operate against the top holders
With 68.4% of records held by five assignees, any new filing in the core annealing-cycle claim space should be checked against their granted claims before drafting.
Explore assignee portfolios in EurekaScope claims toward under-claimed equipment classes
Furnace hardware classes sit near 2% of records each, well below the metallurgical classes, suggesting more room to claim novel equipment configurations than novel alloy or process combinations.
Run a white-space search in EurekaTrack momentum shifts among leading filers
Several long-time leaders show sharp year-on-year drops in the latest complete data, which can signal a shift in R&D priority or a move toward trade secrecy rather than patenting.
Set up assignee monitoring in EurekaCommon questions about continuous annealing line patents
Filing in this field is concentrated among a small number of integrated steel producers, with the leading assignee alone holding 759 of the 2,776 records in scope. The top five assignees combined hold 1,898 records, or 68.4% of the total, and the top ten reach 84.1%. This means any new entrant is filing against a small, well-established set of incumbents rather than a fragmented competitive field.
Filing peaked at 118 records in 2017 and has since cooled; from 2021 (77 filings) to 2024 (47 filings) volume fell 39%, and 2024 is the most recent year that can be read as complete. Because publication lags filing by roughly 18 months, the 2025 and 2026 figures in any trend chart are still filling in and should not be read as a further decline. The honest read is a maturing field with reduced but ongoing activity, not a field in collapse.
The large majority, 82.2% of the 2,776 records, carry a C21D heat-treatment classification, with C22C alloy claims close behind at 52.2%. Coating and surface deposition (C23C) and layered products (B32B) appear on meaningfully smaller shares, and furnace hardware classes F27B and F27D each sit near 2%. Since a single record can carry several IPC classes, these shares overlap and add to more than 100%.
IPC composition points to furnace hardware and equipment-level claims as comparatively thin relative to the dense metallurgical and process literature: F27B and F27D each cover only about 2% of records versus 82.2% for C21D. Specific under-claimed areas include furnace roll buildup mitigation, induction heating zone control, and line-speed adaptive cooling control. These are areas where a first mover can still stake out clear claim territory rather than competing directly against decades of process patents.
US20260071291A1, filed by JFE Steel Corporation and published 2026-03-12, describes a continuous annealing line with heating, soaking and cooling zones in sequence, an induction heating device placed between the soaking and cooling zones, and a control device that adjusts annealing conditions based on a predicted phase fraction of the steel sheet under high-temperature conditions. It is a control-and-configuration claim rather than a pure metallurgy claim, so it is most relevant to anyone building or licensing line-control systems with predictive phase-fraction adjustment. Anyone working near this configuration should review the full claim set rather than the abstract alone before designing a similar control loop.
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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.