Some 2,200 United Steelworkers have begun returning to work one day before the seven-month anniversary of being locked out in a contract dispute with Allegheny Technologies. The union voted earlier this month to approve a four-year contract with the Pittsburgh-based speciality steelmaker, which has 12 plants in Pennsylvania and five other states. The company locked out the workers on August 15 after contract talks had stalled. About 1,500 of those locked out work at six plants in the Pittsburgh suburbs, including two plants the company says will remain idled until they can turn a profit. The National Labor Relations Board had to approve the contract because if filed unfair labor practice allegations against the company during the lockout. The workers today began returning to work gradually as production ramps up.