A. M. Castle & Co. (CTAM) SC 13D CASTLE A M & CO / RYERSON ownership change

Exhibit 99.1

JOINT FILING AGREEMENT

PURSUANT TO RULE 13d-1(k)

The undersigned acknowledge and agree that the foregoing statement on Schedule 13D is filed on behalf of each of the undersigned and that all subsequent amendments to this statement on Schedule 13D may be filed on behalf of each of the undersigned without the necessity of filing additional joint filing agreements.  The undersigned acknowledge that each shall be responsible for the timely filing of such amendments, and for the completeness and accuracy of the information concerning him or it contained herein or therein, but shall not be responsible for the completeness and accuracy of the information concerning the others, except to the extent that he or it knows or has reason to believe that such information is inaccurate.

Dated: August 20, 2012	EPE, LLC
	By:	/s/ Edward J. Lehner
		Name:	Edward J. Lehner
		Title:	Executive Vice President and Chief Financial Officer
	RYERSON INC.
	By:	/s/ Edward J. Lehner
		Name:	Edward J. Lehner
		Title:	Executive Vice President and Chief Financial Officer
	RYERSON HOLDING CORPORATION
	By:	/s/ Edward J. Lehner
		Name:	Edward J. Lehner
		Title:	Executive Vice President and Chief Financial Officer

[Signature Page to Joint Filing Agreement]

PLATINUM EQUITY CAPITAL PARTNERS-PF, L.P.
By:	Platinum Equity Partners, LLC, its general partner
	By:	Platinum Equity Investment Holdings, LLC, its senior managing member
		By: /s/ Mary Ann Sigler
			Name:	Mary Ann Sigler
			Title:	Vice President

PLATINUM EQUITY CAPITAL PARTNERS, L.P.
By:	Platinum Equity Partners, LLC, its general partner
	By:	Platinum Equity Investment Holdings, LLC, its senior managing member
		By: /s/ Mary Ann Sigler
			Name:	Mary Ann Sigler
			Title:	Vice President
PLATINUM EQUITY CAPITAL PARTNERS-A, L.P.
By:	Platinum Equity Partners, LLC, its general partner
	By:	Platinum Equity Investment Holdings, LLC, its senior managing member
		By: /s/ Mary Ann Sigler
			Name:	Mary Ann Sigler
			Title:	Vice President
PLATINUM EQUITY CAPITAL PARTNERS-PF II, L.P.
By:	Platinum Equity Partners II, LLC, its general partner
	By:	Platinum Equity Investment Holdings II, LLC, its senior managing member
		By: /s/ Mary Ann Sigler
			Name:	Mary Ann Sigler
			Title:	Vice President

[Signature Page to Joint Filing Agreement]

PLATINUM EQUITY CAPITAL PARTNERS II, L.P.
By:	Platinum Equity Partners II, LLC, its general partner
	By:	Platinum Equity Investment Holdings II, LLC, its senior managing member
		By: /s/ Mary Ann Sigler
			Name:	Mary Ann Sigler
			Title:	Vice President

PLATINUM EQUITY CAPITAL PARTNERS-A II, L.P.
By:	Platinum Equity Partners II, LLC, its general partner
	By:	Platinum Equity Investment Holdings II, LLC, its senior managing member
		By: /s/ Mary Ann Sigler
			Name:	Mary Ann Sigler
			Title:	Vice President
PLATINUM RHOMBUS PRINCIPALS, LLC
By:	Platinum Equity Investment Holdings, LLC, its senior managing member
		By: /s/ Mary Ann Sigler
			Name:	Mary Ann Sigler
			Title:	Vice President
By:	PLATINUM EQUITY PARTNERS, LLC
	By:	Platinum Equity Investment Holdings, LLC, its senior managing member
		By: /s/ Mary Ann Sigler
			Name:	Mary Ann Sigler
			Title:	Vice President
PLATINUM EQUITY INVESTMENT HOLDINGS, LLC
		By: /s/ Mary Ann Sigler
			Name:	Mary Ann Sigler
			Title:	Vice President

[Signature Page to Joint Filing Agreement]

PLATINUM EQUITY PARTNERS II, LLC
By:	Platinum Equity Investment Holdings II, LLC, its senior managing member
		By: /s/ Mary Ann Sigler
			Name:	Mary Ann Sigler
			Title:	Vice President
PLATINUM EQUITY INVESTMENT HOLDINGS II, LLC
		By: /s/ Mary Ann Sigler
			Name:	Mary Ann Sigler
			Title:	Vice President

PLATINUM EQUITY LLC
By:	/s/ Mary Ann Sigler
	Name:	Mary Ann Sigler
	Title:	Title: Executive Vice President and Chief Financial Officer

By:	/s/ Mary Ann Sigler
	Name:	Tom T. Gores, by Mary Ann Sigler, attorney-in-fact

[Signature Page to Joint Filing Agreement]