FORM 6-K

U.S. SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

REPORT OF FOREIGN PRIVATE ISSUER

PURSUANT TO RULE 13a-16 OR 15d-16 UNDER THE

SECURITIES EXCHANGE ACT OF 1934

Dated August 7, 2019

Commission File Number 1-14878

GERDAU S.A.

(Exact Name as Specified in its Charter)

N/A

(Translation of Registrant’s Name)

Av. das Nações Unidas, 8,501 — 8° andar

São Paulo, São Paulo - Brazil CEP 05425-070

(Address of principal executive offices)

Indicate by check mark whether the registrant files or will file annual reports under cover Form 20-F or Form 40-F.

Form 20-F x

Form 40-F o

Indicate by check mark if the registrant is submitting the Form 6-K in paper as permitted by Regulation S-T Rule 101(b)(1): o

Indicate by check mark if the registrant is submitting the Form 6-K in paper as permitted by Regulation S-T Rule 101(b)(7): o

Indicate by check mark whether by furnishing the information contained in this Form, the registrant is also thereby furnishing the information to the Commission pursuant to Rule 12g3-2(b) under the Securities Exchange Act of 1934.

Yes o

No x

If “Yes” is marked, indicate below the file number assigned to the registrant in connection with Rule 12g3-2(b): Not applicable.

SIGNATURES

Pursuant to the requirements of the Securities Exchange Act of 1934, the registrant has duly caused the Report to be signed on its behalf by the undersigned, thereunto duly authorized.

Date: August 7, 2019

	GERDAU S.A.


	By:	/s/ Harley Lorentz Scardoelli
	Name:	Harley Lorentz Scardoelli
	Title:	Investor Relations Director

EXHIBIT INDEX

Exhibit		Description of Exhibit

99.1		Material Fact, August 7, 2019

Exhibit 99.1

GERDAU S.A. Corporate Taxpayer ID (CNPJ/MF): 33.611.500/0001-19 MATERIAL FACT In accordance with CVM Instructions 358/02 and 480/09, Gerdau S.A. (“Company”) hereby informs that, on August 6, it approved its investment plan for fiscal year 2019. In view of the current pace of investments, the capital expenditure estimate for 2019 was revised downwards from R$ 2.2 billion to R$ 1.8 billion. However, the capital expenditure estimate for the period 2019-21 remains unchanged, at R$ 7.1 billion. 2,637 2,599 2019E* 2020E* 2021E* General maintenanc e Ouro Branco Maintenance Technological expansion and updating *Estimated Information Gerdau S.A. informs that it will present the restated version of item 11 of its Reference Form in a timely manner, within the period envisaged in CVM Instruction 480, of December 7, 2009, as amended. The Company further clarifies that the data disclosed in this document are merely estimates, in other words, hypothetical information that in no way should be construed as a promise of performance. The projections presented are subject to market factors that are beyond the control of the Company, and as such may suffer further revisions. São Paulo, August 7, 2019 Harley Lorentz Scardoelli Executive Vice-President Investor Relations Officer 1,840 874 912 635 562 593 441 1,163 1,132 764