Filing activity is concentrated among a small group of integrated steelmakers, with Nippon Steel, POSCO, ArcelorMittal, JFE Steel and Baoshan Iron & Steel all among the more active recent filers. However, momentum has diverged sharply: POSCO's latest-year filings grew 8% year-on-year while the others posted declines of 68% to 93%. A ranking by raw count and a ranking by recent momentum tell different stories, so both are worth checking before assuming any one company is currently the most active.

Annual filings peaked at 418 in 2020 and have eased since, down to 296 at the 2022 midpoint and 41 in the still-partial 2026 count. This pattern is consistent with a claim space where the core alloy compositions and heat-treatment routes under C21D and C22C are already densely covered by prior art, making broad new claims harder to clear. It is also worth remembering that publication lags filing by roughly 18 months, so the most recent one to two years are understated in any raw count.

Grain-oriented steel patents concentrate on texture control and coating chemistry that align magnetic domains along a preferred rolling direction, which is why filings like chromium-free surface treatment agents for grain-oriented sheet rank among the most-cited records in this dataset. Non-oriented steel patents, such as the representative Baoshan Iron & Steel filing in this set, instead focus on balancing silicon, aluminium and manganese content with annealing conditions to achieve low iron loss and high magnetic induction without directional grain alignment. Both share the same IPC backbone in C21D and C22C but target different end uses — transformers favour grain-oriented sheet, while motors typically use non-oriented sheet.

The IPC composition shows heavy concentration in heat treatment (4,733 records) and alloy composition (3,878), against much thinner coverage in coating chemistry (C23C, 1,031; C09D, 136), rolling process control (B21B, 289), joining methods (B23K, 182) and motor or generator integration (H02K, 150). These smaller clusters are not necessarily technically exhausted — they simply carry far fewer claims relative to the core metallurgical routes, which makes them worth checking first for a defensible first-filed position. Thin-gauge cold-rolling control and lamination integration for motors stand out as specific candidates.

Core loss claims typically combine a bounded chemical composition — controlling carbon, silicon, aluminium, manganese and titanium content within narrow ranges — with a specific process sequence covering hot rolling, pickling, cold rolling, annealing and final coating, as seen in the representative non-oriented steel filing in this dataset. Because core loss depends on both microstructure and surface treatment, many of the most-cited patents pair a composition claim with an insulation coating or surface-treatment claim rather than covering either alone. This dual structure is a large part of why C21D and C22C dominate the IPC distribution rather than any single narrower subclass.