SCHEDULE 13D/A 0001742916 XXXXXXXX LIVE 1 Common Shares, without par value 09/10/2025 false 0001860805 015658107 Algoma Steel Group Inc.

105 WEST STREET, SAULT STE. MARIE, Ontario Z4 P6A 7B4

Michael P. McNamara (312) 275-1600 Zekelman Industries, Inc. 227 West Monroe Street, Suite 2600 Chicago IL 60606 0001742916 N Zekelman Industries, Inc. WC N DE 0 3229998 0 3229998 3229998 N 3.08 CO The percentage reported in Row 13 is based on 104,933,802 Common Shares outstanding as of July 17, 2025, as reported in the Issuer's registration statement on Form F-10 filed with the Commission on July 18, 2025. Y Atlas Tube Canada ULC WC N A0 0 3229998 0 3229998 3229998 N 3.08 OO The percentage reported in Row 13 is based on 104,933,802 Common Shares outstanding as of July 17, 2025, as reported in the Issuer's registration statement on Form F-10 filed with the Commission on July 18, 2025. Common Shares, without par value Algoma Steel Group Inc. 105 WEST STREET, SAULT STE. MARIE, Ontario Z4 P6A 7B4 This Amendment No. 1 ("Amendment") amends and supplements the Schedule 13D initially filed by the Reporting Persons on July 31, 2024 (the "Original Schedule 13D", and as amended by this Amendment, the "Schedule 13D"). Except as specifically modified hereby, the Original Schedule 13D remains unchanged. Capitalized terms but not otherwise defined herein shall have the meanings ascribed to them in the Original Schedule 13D. As a result of the transactions described herein, this Amendment represents the final amendment to the Schedule 13D and constitutes an "exit filing" for each of the Reporting Persons. Item 5(a) is hereby amended and supplemented as follows: The information required by this Item 5(a) is set forth in Rows (11) and (13) of the cover page (including the accompanying comments thereto) for each Reporting Person hereto and is incorporated herein by reference for each such Reporting Person. Item 5(b) is hereby amended and supplemented as follows: The information required by this Item 5(a) is set forth in Rows (7) through (10) of the cover page (including the accompanying comments thereto) for each Reporting Person hereto and is incorporated herein by reference for each such Reporting Person. Item 5(c) is hereby amended and supplemented as follows: The transactions in securities of the Issuer by the Reporting Persons during the past sixty days are set forth in Schedule B and are incorporated herein by reference. Each such transaction was effected directly by Atlas Tube. As a result of the transactions described herein, on September 10, 2025, each of the Reporting Persons ceased to be beneficial owners of more than five percent (5%) of the Issuer's Common Shares. Zekelman Industries, Inc. /s/ Michael P. McNamara 09/23/2025 Atlas Tube Canada ULC /s/ Michael P. McNamara 09/23/2025