The company on Monday announced that Millett will take on the additional role, effective immediately. He succeeds Keith E. Busse, who will remain a board member.   

"Mark has done a tremendous job leading the company," Busse said. "He has a clear strategic vision for Steel Dynamics and has demonstrated effective execution of this strategy. I believe Mark and the Steel Dynamics team will propel the company forward through the next stage of growth.”

Busse and Millett, along with Dick Teets Jr., who retired in 2016 but continues to serve on the board, founded Steel Dynamics in 1993. Busse has served as the board chairman since the company’s inception.

"His expertise in the industry, multitude of business relationships and wise judgment have been instrumental in guiding Steel Dynamics through many business and developmental milestones,” Millett said in a statement. “I look forward to continuing to work closely with Keith as a director of our board."