Nucor Corporation, the largest steel producer in the United States, announced its Chairman and CEO John Ferriola will retire at year end.

Leon Topalian will succeed Ferriola as CEO on Jan. 1. He was named as president and COO effective immediately.

Ferriola has been with Nucor for almost three decades, joining in 1991 as an engineering manager at Nucor Steel-Texas. He also served as COO and president in his time at the company.

“John Ferriola has been a thought leader in the steel industry and helped position Nucor at the forefront of its peers,” said John H. Walker, Nucor’s lead independent director.

Topalian, who has been with the company in various capacities since 1996, has served as an executive vice president since 2017.

Nucor shares were trading at $50.15 on Friday, down 19 cents.