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 June 13, 2018

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:  June 13, 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, June 13, 2018

3

EX-99.1

Exhibit 99.1

GERDAU S.A.

CNPJ/MF n.º 33.611.500/0001-19

Company Registry (NIRE) pending due to change of registered office

MATERIAL FACT

Gerdau S.A. informs that, on June 12, 2018, the 5th Panel of the Regional Federal Appellate Court of the 1st Region issued a decision in the second instance, against the Company in lawsuits filed by two civil construction unions in São Paulo claiming that Gerdau S.A. and other long steel producers in Brazil violated antitrust laws.

In the first instance, the trial court ordered the Company to pay a fine equivalent to 7% of gross revenue for the year prior to the filing of the Administrative Proceeding, which occurred in fiscal year 2000, excluding taxes, which amount, according to the last restatement by the Court Accountant, corresponded to R$417,819,805.95 on August 1, 2013. This amount must be updated again by the Court Accountant.

Note that the decision issued on said date has not been formalized by the competent appellate decision and, after said decision is handed down, the Company will continue to seek all applicable legal remedies to defend its rights.

Lastly, Gerdau clarifies that its business practices are grounded in the principles of transparency and free competition, which it has upheld over its 117 years history in Brazil, during which it has built a business culture guided by ethics and respect for all stakeholders.

São Paulo, June 13, 2018.

Harley Lorentz Scardoelli

Executive Vice-President

Investor Relations Officer