When the news hit here last week that the Bethlehem Steel Corp. plans to close its ship repair yard Dec. 31 unless a buyer can be found, there were few workers left to worry about its passing.

The Bethlehem yard on Key Highway is one of three port of Baltimore shipyards, all of which have been severely hurt in the current recession. As many as 80 percent of the city's 6,100 or more shipyard workers already have been laid off. And, if the Key Highway yard is shut down, nearly nine out of 10 of the city's shipyard workers could be unemployed.

Morale at the yard, which stretches along the waterfront, was "not too good today," reported C. W. Roberts, a 62-year-old steel burner, during an afternoon shift change. "People are saying: 'What are we going to do? Where do we find jobs?' "

Even now, only a trickle of workers emerge from two gates at the foot of newly fashionable Federal Hill in South Baltimore, just across the water from the massive redevelopment at Harborplace. Once, thousands of workers poured in and out of five gates to the 35-acre repair yard that dates back to 1853. But the bottom has fallen out of the American shipbuilding industry.

Nationwide, the country's major coastal yards repaired only 1,266 vessels in 1979, compared with 2,533 in 1960. At Bethlehem's Key Highway yard, the number of ships undergoing repair work dropped from 680 in 1972 to 236 last year. This year, just 100 vessels had put in for repairs through July.

"Worldwide shipping has become severely depressed due, in large part, to low levels of national economies," said a Bethelehem corporate spokesman.

In addition, union officials and others blame Reagan administration policies and congressional action that eliminated federal ship construction subsidies last year. Also scuttled was a rule that maritime firms receiving separate operating subsidies use only ships built and repaired in U.S. yards.

"Since Reagan's been in office, all the ships are going overseas to be built and repaired," complained Robert Pemberton, business agent for Local 24 of the Shipbuilders Union, which represents the workers at the Key Highway yard. "It's incredible."

Only 567 of the local's 1,355 members at Key Highway are still working, and union officials expect that number steadily to decline as the year winds down.

The workers represent a range of crafts: welders, pipe fitters, steel shapers and plate riggers. Pat Arnold, an analyst with the state's Employment Security Administration, said some of them could find other jobs in defense-related contracting or in commercial construction.

If there are no such job opportunities, Arnold said, "I would think the prospects for reemployment of these people are not good or, if they are, I'm unaware of where these opportunities are."

Local 24's Pemberton said that the union has offered to meet with the company to discuss employe ownership of the shipyard as one alternative to closure. "Industrial Relations said no," he said.

The Bethlehem spokesman asserted, however, that the corporation "has not been informed of such a proposal."

Although rumors of the shipyard's closure had circulated for months, official word of the impending action came through the news media.

"For our members to find out what the future is, they have to look in the newspaper each day," said George Morris, Local 24's vice president. "And all there is, is speculation."

For laid-off workers, the speculation offers little solace. The day after the news broke, a pipe fitter who had worked a total of two weeks this year told Pemberton he was losing his house through foreclosure.

"I get them all the time," the union official said. "It's nothing unusual. It happens every day."

"It's rough," said Jack Cole, 28, who was laid off from his $10.06-an-hour job as a steel shaper. "After you pay your bills, there's not enough left to go out and look for a job."

Cole, stopping by the union hall on his way to the yard to clean out his locker, added: "When it was moving, it looked like a good trade. I thought that I'd have a future with the company and security in life, work steady, and have a family. Now I'm skeptical of even getting married because of this. I can't afford to take care of myself. How can I handle a wife and kids?"

The future looks "pretty bleak," agreed 23-year-old Jack Lanier, another laid-off shaper. "Most likely, if I don't find anything in Maryland, I'd probably move to Florida, Houston or California and look for something," Lanier said.

Back at Gate Four, shipfitter Jeff Cox, 36, laid off, but waiting for a friend, allowed himself a grim recession joke: "I told my wife to buy me a .44 for Christmas so I can go out and [relieve] people [of] their money, because by Christmas time that's what it's gonna come to."

Nearby, three workers with a total of 94 years of seniority pondered their fate.

"Let's say we're gonna be out of a job," said Charles Lycett, 61, who first went to work for Bethlehem in 1941, building Liberty Ships for World War II. "Back then," he said, "we had 16 building ways and we built one ship a day."

A younger worker, born long after the shipyard's heyday, hopped on a motor scooter and said with a shrug: "Nine years down the tube. I hate to be on the street, but if you've got to go, you've got to go."

Moments after the afternoon shift change, the area around the gate was empty except for a vending van.

"You wait for the second shift," said Steve Arikos, owner of "Andy's Diner," the truck that has been feeding Bethlehem ship repair yard workers since the 1940s. "You have X amount of people working and all of a sudden . . . . It's bad. Business is dropping off.

"If it's tough here, it's tough all over," he said. "It's just like a chain."

So, instead of trying to relocate now, Arikos plans to stay put.

"I'm going to stay around and go down with them," he said.