Machinists at Bath Iron Works would get a signing bonus, raises and pension gains under a tentative four-year contract, the union said on Friday.

The International Association of Machinists and Aerospace Workers, which represents about 3,200 mechanics, fitters, welders, painters and electricians, will vote on the tentative deal on Sunday at the Augusta Civic Center.

Pending ratification of the contract, union members would get a $3,000 signing bonus, according to John Carr, a union spokesman said. Starting in the second full-year of the contract, union workers would see annual wage hikes of 2.25 percent to 2.75 percent, he said.

Meanwhile, the union “held the line on health care costs and maintains the levels below the national norms,” Carr said. There would be no change to current health care coverage, and there would be no  deductibles or co-pays until 2014, he said.

Bath Iron Works also increased the amount it contributes to the union employees’ pension plan, Carr said.

The company, a unit of General Dynamics Corp., declined to comment. Bath Iron Works employs 5,400 workers.

The company, one of Maine’s largest employers, depends on defense contracts from the Navy. The Navy is expected to decide later this year on contracts for nine destroyers. BIW, which is a unit of General Dynamics Corp., is competing against Huntington Ingalls Industries for the DDG-51 destroyers the Navy will buy through fiscal 2017.