Sewickley-based Esmark is the winner of a bid for a Serbian steel works plant once owned by United States Steel Corp. The Serbian government will now negotiate with Esmark and its European firm Esmark Europe BV on the terms of a deal to acquire an 80.1 percent stake in the A1 2elezara Smederevo Steel Works, which includes two blast furnaces, a tin-plate fabrication facility and a processing plant. A purchase price hasn't been announced, although Esmark expects to spend $400 million over five years to upgrade the facility and $28 million right away.