AHSS Heat Treatment Patents: Who Leads, Where the Gaps Are 2026
- Filings peaked in 2017 at 200 and have declined since, with 2026 tracking at only 19 (partial year) — the claim space opened early and has not reopened.
- Steelmakers cluster tightly around C21D and C22C, while adjacent coating (C23C) and electroplating (C25D) subclasses carry a fraction of the filing volume.
- Momentum has gone flat across the named leaders, with several major Japanese and Korean assignees showing 0 filings or -100% YoY in the latest year.
What this patent landscape covers
This landscape tracks patent families filed against quenching and partitioning, intercritical annealing, continuous annealing and heat treatment claims applied to advanced high-strength steel and high-strength steel, classified under C21D8, C21D1 and C21D9. The corpus spans 2015 through the 2026-07-31 cut-off and totals 3,030 published families.
Filing activity is concentrated in the core heat-treatment subclass but extends into alloy composition, coating and rolling art, which is where cross-licensing and freedom-to-operate questions typically surface. Because publication lags filing by roughly 18 months, the last one to two years in any trend chart will read lower than the true filing rate once those applications publish.
Filing trend and technology composition
The chart below traces annual filings against the IPC subclasses this dataset actually touches, giving a sense of where the claim density sits relative to the core heat-treatment classification.
Filings rose to a 2017 peak, then eased back
Annual filings climbed to 200 in 2017, sat near the midpoint at 167 in 2022, and have since fallen — 2026 shows 19 filings, though that figure is partial and will revise upward as later applications publish.
Heat treatment and alloy classes dominate
C21D (heat treatment of metals) and C22C (alloys) cover almost the entire corpus at 3,027 and 2,696 records respectively; coating (C23C), rolling (B21B) and electroplating (C25D) subclasses trail well behind, with C21C (steelmaking) the thinnest at 99.
Shares are the percentage of the 3,030 records in scope. A patent can carry several IPC classes, so the shares add up to more than 100%.
Go deeper on Advanced High-Strength Steel Heat Treatment with Eureka
This page is one run against one query. Ask Eureka your own question about advanced high-strength steel heat treatment and every answer comes back with the patent numbers behind it.
Try EurekaMost-cited records and a representative filing
US10358691B2 — Apparatus for continuous annealing of strip and method for continuous annealing of same
The patent describes a continuous annealing apparatus that cools after heating and then reheats, rather than heating once and cooling or overaging as prior equipment did. POSCO frames this reheat step as a way to pre-set or control the steel's texture ahead of final processing, aimed at producing cold-rolled sheet with both high strength and ductility.Filed by POSCO CO., LTD; granted 2019-07-23.
| # | Publication no. | Patent title | Citations |
|---|---|---|---|
| 1 | JP1986157625A | Manufacture of high-strength steel sheet | 329 |
| 2 | EP2325346A1 | High-strength steel plate and manufacturing method thereof | 177 |
| 3 | US20110146852A1 | High strength steel sheet and method for manufacturing the same | 95 |
| 4 | EP0969112A1 | Dual-phase high-strength steel sheet having excellent dynamic deformation properties and process for preparin… | 92 |
| 5 | CN102747303A | 一种屈服强度1100MPa级高强度钢板及其制造方法 | 82 |
| 6 | US20090010793A1 | Method For Producing High Strength Steel Strips or Sheets With Twip Properties, Method For Producing a Compon… | 71 |
| 7 | US20110048589A1 | High-strength steel sheet and method for manufacturing the same | 68 |
| 8 | EP2765212A1 | High-strength steel sheet and method for manufacturing same | 67 |
| 9 | CN103352167A | 一种低屈强比高强度桥梁用钢及其制造方法 | 65 |
| 10 | US20120312433A1 | High-strength steel sheet excellent in workability and cold brittleness resistance, and manufacturing method … | 63 |
Citation counts inside a searched corpus favour older filings — treat the ranking as a signal of influence on later work, not of current commercial relevance.
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 structural features of this dataset matter more than any single ranking: where filings are geographically anchored, how concentrated the technology classes are, and how filing volume has moved over time.
Filing is spread across three major offices, not one
Europe, China and the United States each host a substantial share of filings, with India, Japan and Canada trailing. A freedom-to-operate review for this technology cannot rely on a single jurisdiction's register.
Almost every filing touches the core heat-treatment class
C21D and C22C together account for the overwhelming majority of records; the remaining subclasses — coating, rolling, extrusion, electroplating, steelmaking — are present but far thinner, suggesting most competitive activity sits on the core process claims rather than adjacent processing steps.
Volume peaked in 2017 and has not recovered
The midpoint year, 2022, sat at 167 filings — already below peak — and the trend has continued downward since. Read the final one to two years with the publication lag in mind, but the multi-year decline predates that effect.
Eureka can read the same corpus for gaps instead of for coverage: under-claimed branches adjacent to advanced high-strength steel heat treatment, with the prior art for and against each one.
Who is filing, and where they are not
Assignee activity in this corpus is dominated by a small set of large steelmakers with long co-filing histories between parent and subsidiary entities. Recent-year momentum has cooled sharply across nearly all of them.
Filings often pair a parent with a subsidiary or research arm
The strongest co-assignee relationship in this dataset links a major Japanese steelmaker with its former joint-venture entity, and similar parent-subsidiary or parent-research-institute pairs recur among Chinese steelmakers — a sign that internal group filing strategy, not open collaboration, drives most co-assignment here.
Recent-year activity has gone flat across the leaders
Multiple large steelmakers that filed steadily in earlier years show zero filings or year-over-year declines approaching -100% in the most recent year. Some of this reflects the publication lag rather than a genuine stop in R&D, but the direction is consistent across nearly every named assignee.
A large corpus with concentration at the top
The ranking runs across the full 3,030-family set, with volume concentrated among a handful of steelmakers and a long tail of single- or few-filing entrants — typical of a mature, heavily claimed process area rather than an emerging one.
| Assignee | Recent year | YoY |
|---|---|---|
| Angang Steel Company Limited | 1 | -90% |
| JFE Steel Corporation | 0 | -100% |
| Nippon Steel Corporation | 0 | — |
| POSCO Co., Ltd. | 0 | -100% |
| Kobe Steel, Ltd. | 0 | -100% |
| NIPPON STEEL & SUMITOMO METAL CORP | 0 | — |
| Baoshan Iron & Steel Co., Ltd. (Baosteel) | 0 | -100% |
| CONSOLIDATED METAL PRODUCTS INC | 0 | — |
Where to take this next
The data points to a mature, concentrated claim landscape with a few specific gaps. The next steps depend on whether you are clearing a product or looking for filing room.
Run a freedom-to-operate check across all three major offices
With filings split roughly evenly across EPO, China and the US, a single-jurisdiction search will miss live claims. Cross-reference the receiving-office split against your target markets before committing to a process route.
Explore assignee-level filings in EurekaMap the co-assignee network before approaching a licensing partner
The strongest co-filing pairs are internal group relationships, not open industry collaborations — useful context if you are trying to identify who actually controls a given claim family versus who is listed on it.
Trace co-assignee relationships in EurekaTest claim scope in the thinner IPC subclasses
Electroplating-integrated annealing and steelmaking-stage strength control carry far fewer filings than the core heat-treatment classes, which may leave room for narrower, well-drafted claims.
Search white space in EurekaFrequently asked questions
Quenching and partitioning (Q&P) is a heat-treatment route that quenches steel to an intermediate temperature to form martensite, then holds it to let carbon migrate into retained austenite, stabilising that austenite at room temperature. It is one of the main routes used to reach high strength without sacrificing ductility in advanced high-strength steel, which is why it appears repeatedly in the search terms and claim language across this corpus. Because it is a well-established route, expect dense prior art around specific temperature-hold combinations and alloy compositions rather than around the general concept.
This dataset shows filings rising to 200 in 2017, sitting at 167 by the 2022 midpoint, and falling further toward 19 by 2026 (a partial year). A decline like this typically reflects a technology area where the core process claims — continuous annealing, intercritical annealing, Q&P — were staked out early, leaving less open ground for new filings. Some of the most recent drop is an artefact of publication lag, since patents filed in the last 18 months have not all published yet, but the multi-year downward trend predates that effect and looks structural.
Filing activity in this corpus concentrates among major integrated steelmakers with long operating histories in flat-rolled steel, several of which co-file with subsidiary or research-institute entities within the same corporate group. Recent-year data shows momentum cooling sharply across nearly all of these assignees, with several posting zero filings or year-over-year declines near -100% in the latest tracked year. Rather than naming a single leader, treat the ranking as showing concentration at the top with a long tail of lighter filers — the assignee table on this page carries the specific counts.
The core heat-treatment and alloy classes, C21D and C22C, are saturated, covering nearly all 3,030 records in this corpus. Adjacent subclasses carry far fewer filings: electroplating-integrated processing (C25D, 111 records), steelmaking-stage strength control (C21C, 99 records), and extrusion or drawing post-treatment (B21C, 121 records) all sit well below the core. These thinner subclasses are the more realistic places to draft narrow, defensible claims than the crowded core annealing process art.
Not necessarily. Citation counts accumulate over time within a searched corpus, so older patents such as the highest-cited record in this dataset, filed in 1986, naturally collect more citations simply by having been available longer for later filings to reference. A high citation count is better read as a signal of historical influence on how the field's claims were shaped than as a marker that the specific patent still controls current commercial practice — for that, check the assignee's recent filing activity and the patent's legal status directly.
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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.