The United Steelworkers union has reached a tentative contract agreement with U.S. Steel Canada Inc. that covers workers in Hamilton, marking the first time the steel company has not locked out workers at one of its two major Canadian mills. Since the 2007 purchase by United States Steel Corp. of what was then Stelco Inc., the company locked out workers once after failing to reach an agreement covering its Hamilton workers, and twice at its Lake Erie operations in Nanticoke, Ont.