6-K

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 January 9, 2018

Commission File Number 1-14878

GERDAU S.A.

(Exact Name as Specified in its Charter)

N/A

(Translation of Registrant’s Name)

Av. Farrapos 1811

Porto Alegre, Rio Grande do Sul - Brazil CEP 90220-005

(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:  January 9, 2018

GERDAU S.A.
By:	/s/ Harley Lorentz Scardoelli
Name:		Harley Lorentz Scardoelli
Title:		Investor Relations Director

2

EXHIBIT INDEX

Exhibit	Description of Exhibit
99.1	Material Fact, January 9, 2018

3

EX-99.1

Exhibit 99.1

GERDAU S.A. Corporate Taxpayer ID (CNPJ/MF): 33.611.500/0001-19 Company Registry (NIRE): 33300032266 MATERIAL FACT We announce that in the Board of Directors Meeting of GERDAU S.A. held on January 8th, 2018, in accordance with its bylaws and CVM Instructions 10/80 and 268/97, decided to authorize the Company to acquire shares of its own issue. Purposes: (i) to meet the needs of the Long-Term Incentive Program of the Company and its subsidiaries, (ii) held in treasury, (iii) cancellation or (iv) subsequent sale on the market. The acquisitions will be carried out supported from its existing profit reserves, with the Executive Committee responsible for establishing the number of shares and the opportune moment for each transaction. Number of shares to be acquired: up to 10,000,000 preferred shares (GGBR4) or American Depositary Receipts – ADRs (GGB), representing in aggregate approximately 0.96% of the preferred shares comprising the free-float, which on November 30th, 2017 totaled 1,040,867,403 shares. Acquisition period: from January 9th, 2018, for a maximum period of three months, until April 9th, 2018. The transactions will be carried out on the stock exchanges of São Paulo and New York, at market prices, through the intermediation of the following brokerages: - Itaú Corretora de Valores S.A. Avenida Faria Lima, 3.500, 3º andar, Itaim Bibi, São Paulo, SP; - Bradesco S.A. Corretora de Títulos e Valores Mobiliários Avenida Paulista, 1.450, 7°andar, Bela Vista, São Paulo, SP; and - Merrill Lynch, Pierce, Fenner & Smith Inc Bank of America Tower One, Bryant Park 8th Floor, New York, NY, 10036. Rio de Janeiro, January 9th, 2018. Harley Lorentz Scardoelli Executive Vice President Investor Relations Director