This dataset counts 569 published patent families filed between 2015 and mid-2026 that combine AHSS or dual-phase steel terminology with process claims around hot rolling, annealing, martensite formation, formability or hydrogen embrittlement. That figure is a fair proxy for real filing activity because families neutralise repeat filings of the same invention across jurisdictions. The true current total is likely somewhat higher, since publication typically lags filing by around 18 months, so the most recent one to two years are undercounted.

The corpus is dominated by integrated steelmakers and their research subsidiaries, several of which also appear paired together in joint filings rather than filing solely on their own. Recent-year momentum data shows every tracked leading assignee at zero filings in the latest year, which most likely reflects publication delay rather than an actual pullback. A full ranking by family count is provided in the assignee table above rather than summarised here, since the exact order shifts as later filings publish.

Filing volume rose from 14 families in 2017 to a peak of 22 in 2022 and has not exceeded that level since. A flat-to-declining curve after a peak typically means the core claim space around a technology has become occupied, pushing new filers toward narrower or adjacent claims rather than broad composition-and-process patents. It does not necessarily mean R&D activity has slowed, since manufacturing process improvements are not always patented and the most recent years are still underreported due to publication lag.

Heat treatment (C21D) and alloy composition (C22C) are heavily claimed, appearing in 493 and 460 of the 569 records respectively, so a filing that only restates that combination faces dense prior art. Subclasses tied to metal rolling, extrusion and drawing, sheet-metal working and welding each carry far fewer records, roughly a tenth of the core classes, suggesting narrower and more specific claims there face less crowded prior art. Hydrogen-embrittlement-resistant coating and resistance-weld joint microstructure are two specific branches worth checking first.

US9593399B2, assigned to ThyssenKrupp Steel USA, claims a specific cold-rolled dual-phase steel process defined by exact soaking, hot-rolling reduction, intercritical annealing and rapid-cooling temperature ranges, plus a resulting ferrite-plus-martensite microstructure with defined yield and tensile strength minimums. Anyone developing a similar cold-rolled dual-phase route needs to check whether their process parameters and resulting mechanical properties fall inside those claimed ranges. Because the corpus also contains earlier, more heavily cited dual-phase steel patents from the 1990s, a full freedom-to-operate check should not stop at this one filing.