A federal appeals court refused yesterday to overturn a representation election the United Steelworkers won at Newport News Shipbuilding and Dry Dock Co. but sent the case back to the National Labor Relations Board for a hearing on two contested vote-fraud issues.

The ruling will delay for at least several weeks resolution of all legal issues in the case and may prolong a strike the union called a lmonth ago to force the company to the bargaining table.

The company has claimed it has been able to continue essential work at the yard with about 60 percent of its work force, but has refused to bargain, citing numerous complaints of irregularities in the 1978 steelworkers election at the huge Newport News, Va., yard. Most of the complaints were rejected yesterday by a three-judge panel of the 4th U.S. Circuit Court of Appeals.

In a ruling issued in Richmond, the three judges found that two complaints merited further consideration and remanded the case to the NLRB "for the limited purpose of conducting a hearing" on them.

The complaints involved the availability of blank ballots in polling booths and allegations of "chain voting." That is a process by which a voter takes an unmarked ballot from a booth, a second person marks it, and a third person casts it, picking up another unmarked ballot to begin the cycle all over again.

"If either of these objections is proved." the court said in a unanimous ruling, "the board (NLRB) SHOULD SET ASIDE THE ELECTION."

Both the Steelworkers, one of the nation's largest industrial unions, and the company, Virginia's largest private employer, claimed vindication.

"I would consider, under the circumstances, (the ruling) to be a step forward, without question," Bruce Thrasher, dircctor of Steelworkers' District 35, was reported as telling 4,500 supporters at a rally near the shipyard. "We shall remain on strike until that one issue is resolved," he said, according to the Associated Press.

"We are delighted that the court had vindicated our position," said a company spokesman. "The court has recognized our complaint about the conduct of last year's representation election by finally giving us an opportunity to present our eyidence before the (NLRB), AS WE HAD ASKED IN OUR BRIEF."

A spokesman for the NLRB in Washington said a hearing will be expedited, adding that the process would take "a matter of weeks."

The vote in the Jan. 31, 1978, election was recorded by the NLRB as 9,093 for the Steelworkers and 7,548 for the Peninsula Shipbuilders Association, a rival independent union that had represented the yard's 15,500 blue-collar workers for years. The NLRB had earlier certified the Steelworkers as the winner.