PlainPatent

CPC technology class · C21

C21C - Processing OF Pig-iron

Processing of pig-iron, e.g. refining, manufacture of wrought-iron or steel; treatment in molten state of ferrous alloys. 716 US utility patents granted 2015–2025, with the leading assignees and year-by-year filing trajectory.

716
US patents granted
C21
Parent CPC class
20
Active assignees
+9%
5-yr velocity

The verdict

Processing OF Pig-iron ranks #496 of 670 CPC technology areas - 716 US patents granted since 2015, with filing up 9% over five years.

#496
of 670 CPC technology areas
716
US patents granted, 2015–2025
Jfe Steel
leading assignee (37)
+9%
filing velocity, last 5 yrs
Top assignee: JFE Steel Corporation (37 patents)

CPC subclass C21C - PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS - covers 716 US utility patents granted between 2015 and 2025 according to USPTO PatentsView records, within the broader CPC class C21 (METALLURGY OF IRON). See our CPC classification guide for how the system works.

The competitive landscape in C21C is shaped by 20 distinct companies actively filing in this space. JFE Steel Corporation leads with 37 patents, followed by Danieli & C. Officine Meccaniche S.p.a. at 21 grants and University Of Science And Technology Beijing at 13.

Filing activity in C21C is up 9% over the past five years versus 2015-2019, a relatively steady filing pace. All counts come directly from USPTO PatentsView and reflect US granted utility patents only.

Is C21C innovation accelerating?

US utility-patent grants per year in C21C, 2015–2025 - recent five years are up 9% versus 2015–2019.

4050607080 20152016201720182019202020212022202320242025 63

Who leads C21C?

The 12 most active assignees in PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS - wider bars mean more grants

patents

What this shows Jfe Steel is the most active filer in C21C, holding 37 of the 716 patents in this class. Concentration at the top signals how contestable this technology area is for new entrants.

Source USPTO PatentsView, granted utility patents As of 2015–2025 grant years
View data table
Top patent holders in CPC subclass C21C
Rank Company Patents in C21C
#1 Carbon Technology Holdings, Llc 23
#2 Danieli & C. Officine Meccaniche S.p.a. 21
#3 University Of Science And Technology Beijing 13
#4 Refractory Intellectual Property Gmbh & Co. KG 12
#5 SMS Group Gmbh 11
#6 Heraeus Electro-nite International N.v. 11
#7 Elkem ASA 11
#8 Primetals Technologies Austria Gmbh 10
#9 Tata Steel Limited 10
#10 Arcelormittal 9
#11 Technological Resources PTY Limited 9
#12 PAUL Wurth S.a. 9
#13 KW Associates Llc 8
#14 Novelis Inc. 7
#15 Outotec (finland) OY 7
#16 Baoshan IRON & Steel Co., Ltd. 6
#17 Suncoke Technology AND Development Llc 6
#18 Outotec Oyj 6
#19 Tenova S.p.a. 6
#20 Berry Metal Company 6

About This Class

CPC subclass C21C belongs to class C21.

716 patents were granted in this class between 2015 and 2025.

20 companies actively patent in this space.

Classification System

Cooperative Patent Classification (CPC) is a hierarchical patent classification system used by the USPTO and EPO.

← All Technology Classes Technology Rankings →

Footprint here vs. claim strategy

Each dot is a leading C21C 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 C21C assignees by class footprint. Bubble size = patents in C21C. Source: USPTO PatentsView (claim depth is company-wide across all classes).

Top 14 C21C assignees by class footprint. Bubble size = patents in C21C. Source: USPTO PatentsView (claim depth is company-wide across all classes). Scatter plot of 14 data points (bubble-sized by third dimension). 51015202530 510152025 Patents in C21C Avg claims / patent (company-wide) Carbon Technology Hol…Danieli & C Officine…University of Science…Refractory Intellectu…Sms groupHeraeus Electro-nite…Elkem AsaPrimetals AustriaTata SteelArcelormittalTechnological Resourc…Paul WurthKw AssociatesNovelis
Top 14 C21C assignees by class footprint. Bubble size = patents in C21C. Source: USPTO PatentsView (claim depth is company-wide across all classes).

Frequently Asked Questions

What is CPC class C21C?
CPC subclass C21C covers PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS. It belongs to CPC class C21 (METALLURGY OF IRON), with 716 US utility patents granted since 2015.
How many patents have been filed in C21C?
716 US utility patents were granted in CPC subclass C21C between 2015 and 2025, based on USPTO PatentsView data.
Which company holds the most patents in C21C?
JFE Steel Corporation leads C21C with 37 patents, making it the most active assignee in this technology area.
How is patent data for C21C collected?
Patent data comes from USPTO PatentsView, a public research dataset maintained by the United States Patent and Trademark Office. It covers all US granted utility patents and assigns CPC codes based on the technology described in each patent.
What is the difference between CPC class and subclass?
A CPC class (e.g., C21) is a broad technology category. Subclasses like C21C provide finer granularity within that category. PlainPatent organizes data at the subclass level (4-character codes) for the most useful view of technology domains.

Read our methodology - how this data is sourced, computed, and verified.

Data sourced from USPTO PatentsView - official U.S. government patent data. See our methodology for computation details. Retrieved and formatted by PlainPatent Editorial

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.