CPC technology class · C21

C21B - Manufacture Of Iron Or Steel

Manufacture of iron or steel. 713 US utility patents granted 2015–2025, with the leading assignees and year-by-year grant trajectory.

Compiled by PlainPatent · May 15, 2026

713
US patents granted: #3/3
in C21: 8.6%
C21 class share: -29%
5-yr velocity

The verdict

According to USPTO PatentsView, Manufacture Of Iron Or Steel ranks #497 of 670 CPC technology areas - 713 US patents granted since 2015, with recorded grant volume down 29% over five years.

#497
of 670 CPC technology areas: 713
US patents granted, 2015–2025: Paul Wurth
leading assignee (45): -29%
grant velocity, last 5 yrs

How C21B's grant cadence moved

Between 2020–2024, C21B recorded 246 grants versus 345 in 2015–2019 (-29% equal-window velocity). Across complete years, output peaked in 2015 at 83 grants and bottomed in 2021 at 39 (+113% peak-over-trough). Lead assignee Paul Wurth S.A. holds 6.3% of the class ; the top three share 14.4%.

Leaderboard read

C21B concentration, lead at 6.3%

Paul Wurth S.A. leads this historical grant record at 6.3% of C21B - foreign corporation assignees hold 68% of class grants (229 of 336). Figures describe granted US utility patents in this CPC subclass, not current investment or legal strength.

Leader's share: 6.3%
Top three share: 14.4%
Lead over #2: 15

Where C21B sits inside C21

Among 3 subclasses in C21 (Metallurgy OF Iron), C21B ranks #3 and holds 8.6% of the parent class's 8,280 recorded grants. Sibling chips below are the other subclasses in the same parent class, not the nationwide volume/lead-share peers further down.

C21D 6,851 C21C 716

Rising assignees active in C21B

Company-wide grant multiples (2022–2024 vs 2019–2021) among assignees with ≥5 patents in this subclass. Growth is company-wide; class patent counts are subclass-specific.

#1 Tata Steel Nederland Technology B.V. 5.33x 3 → 16 company-wide · 5 in C21B
#2 Carbon Technology Holdings, LLC 2.33x 12 → 28 company-wide · 25 in C21B
#3 Midrex Technologies, Inc. 1.43x 7 → 10 company-wide · 30 in C21B
#4 Tata Steel Limited 1.09x 11 → 12 company-wide · 13 in C21B
#5 Primetals Technologies Austria GmbH 1.05x 40 → 42 company-wide · 28 in C21B

C21B grants by year, peak 2015 (83)

US utility-patent grants per year in C21B, 2015–2025 - recent five years are down 29% versus 2015–2019.

Paul Wurth

45
Midrex

30
Primetals Austria

28
Carbon Technology…

25
Danieli & C Officine…

15
Tata Steel

13
Suncoke Technology…

11
Hyl De C V

10
Technological…

9
Siemens Vai Metals

7
Outotec (Finland) Oy

5
Tata Steel Nederland…

5

What this shows Paul Wurth is the most active filer in C21B, holding 45 of the 713 patents in this class. Concentration at the top signals how contestable this technology area is for new entrants.

View data table

Top patent holders in CPC subclass C21B
Rank	Company	Patents in C21B
#1	Paul Wurth S.A.	45
#2	Midrex Technologies, Inc.	30
#3	Primetals Technologies Austria GmbH	28
#4	Carbon Technology Holdings, LLC	25
#5	Danieli & C. Officine Meccaniche S.P.A.	15
#6	Tata Steel Limited	13
#7	Suncoke Technology AND Development LLC	11
#8	HYL Technologies, S.A. DE C.V.	10
#9	Technological Resources PTY Limited	9
#10	Siemens VAI Metals Technologies GMBH	7
#11	Outotec (FINLAND) OY	5
#12	Tata Steel Nederland Technology B.V.	5
#13	Tenova S.P.A.	5
#14	Berry Metal Company	5
#15	Orbite Technologies Inc.	5
#16	Techemet, LP	5
#17	Macrae Technologies, Inc.	5
#18	Nucor Corporation	4
#19	Nisshin Steel Co., Ltd.	4
#20	Refractory Intellectual Property GMBH & Co. KG	4

Footprint here vs. claim strategy

Each dot is a leading C21B assignee, placed by how many patents it holds in this class (horizontal) against its company-wide average claims per patent (vertical) - a read on whether the class is led by broad-but-shallow filers or focused deep-claim players.

Top 14 C21B assignees by class footprint. Bubble size = patents in C21B. Source: USPTO PatentsView (claim depth is company-wide across all classes).

Classes near C21B's 713-grant footprint

Nationwide nearest neighbors for C21B (#497 of 670 by volume ; lead share 6.3%) - not the C21 parent-class siblings above.

Nearest by grant volume

B09C 712 C21C 716 C05D 707 C23G 703

Nearest by lead-assignee share

G10L 6.3% A63H 6.4% A62D 6.4% B63J 6.3%

Questions about C21B

Which company holds the most patents in C21B?

Paul Wurth S.A. leads C21B with 45 patents (6.3% of the subclass). By PatentsView assignee type, foreign corporations account for 68% of class grants.

Which C21B assignees grew fastest recently?

Among assignees with ≥5 grants in C21B, Tata Steel Nederland Technology B.V. shows the highest company-wide grant multiple (5.33x: 3 grants in 2019–2021 → 16 in 2022–2024) while holding 5 patents in this subclass. Growth is company-wide, not class-only.

How does C21B compare inside parent class C21?

Inside C21 (Metallurgy OF Iron), C21B ranks #3 of 3 subclasses by grant volume and holds 8.6% of the parent class total. The largest sibling is C21D (6,851 grants).

What to do with this data

C21B in context - here's where to go next.

Paul Wurth S.A. leads C21B with 45 grants in this class. See full portfolio
C21B ranks #497 of 670 by grant volume among all tracked CPC technology areas. See the ranking
Inside parent class C21, the largest sibling subclass is C21D with 6,851 grants. Explore C21D

Figures reflect USPTO PatentsView grant data through 2026-05-15; pending applications not yet granted are not counted.

Methodology - C21B figures are USPTO PatentsView granted-utility totals for this subclass (713 grants in the tracked window).

Every figure on PlainPatent is rendered directly from USPTO source data, no number is typed in by an editor. This page draws directly on USPTO source data, no figure is typed in by an editor. See our editorial standards & corrections policy, the methodology behind these numbers, or report a data error.