Exhibit 99.1 Metallus Announces Fourth-Quarter and Full-Year 2023 Results • Net sales of $328.1 million in the fourth quarter and$1.4 billion for the full year • Fourth-quarter net income of $1.3 million and full-year net income of$69.4 million with adjusted EBITDA (1) of $35.7 million in the fourth quarter and$169.0 million for the full year • Operating cash flow of $74.1 million in the fourth quarter with$125.3 million for the full year • For the full year, the company deployed $51.6 million of cash f ...