The Rust Bowl's loss has been Connecticut's gain.

With imports of foreign steel and copper causing the loss of tens of thousands of jobs in other parts of the country in recent years, those same imports have created employment and brought new life to the ports of New Haven, Bridgeport and New London.

Now, the Rust Bowl is getting some measure of revenge: The announcement yesterday that the United States has negotiated limits on steel imports is likely to put something of a damper on the boom at the Connecticut ports.

But the three once-sleepy harbors have enjoyed a steady stream of traffic for the past two years from ships bearing foreign steel and copper, and the limits, which could cut steel imports by as much as 30 percent, are not likely to completely stall the ports' resurgence.

Over the past couple of years, Connecticut has won a large portion of the sharp increase in metal imports to the United States. Bound for construction sites, factories and finishing plants throughout New England, the shipments of steel and copper created a new bustle of activity in these harbors along Long Island Sound that their operators say was almost completely unexpected -- but certainly not unwelcome.

"It's like a positive catastrophe, or a positive disaster," says Joseph Crowley, president of New Haven Terminal Co., the family-owned company that owns the New Haven port and runs the state-owned New London port. "It's a lot better than coping with the recession."

Shipments of steel into New Haven harbor alone have tripled in the past two years, to 450,000 tons this year, roughly 5 percent of the national total. The increase in Bridgeport has not been so dramatic, but it will handle 650,000 tons of steel this year. New London's volumes are much smaller.

Even more strikingly, New Haven is now handling more than a third of the nation's copper imports -- about 150,000 tons of copper will pass through the port this year. A few years ago, almost no copper came into the state from abroad.

Connecticut's emergence as a major import center is the flip side of the upheaval that has ravaged the nation's steel and copper industries in recent years, as foreign producers have proven their ability to make higher quality finished steel and copper sheet, tubing and other products more cheaply than American makers. Manufacturers who once shopped the metals centers of Pittsburgh and Youngstown, Ohio, for raw ingredients now look overseas for metals.

"Even though it's bad that people lost their jobs in Youngstown to a mill in Brazil, the availability of high-quality, inexpensive steel keeps jobs in Connecticut," Crowley says.

The state's unemployment rate of 4.2 percent is one of the lowest in the nation. "We look at it as a job manufacturer at the ports and in several manufacturers in Connecticut who use copper and steel," Peter Burns, deputy commissioner of Connecticut's Department of Economic Development, says of the import boom.

State and local officials believe the revival of activity at the Connecticut ports -- which in recent years had been handling mostly petroleum, lumber and an occasional metals shipment -- will have a lightning-rod effect in bringing new businesses to the once-moribund waterfront areas in New Haven and Bridgeport. Already, New Haven is pushing a $250 million private commercial and residential development for the Long Wharf area across the harbor from New Haven Terminal.

At the same time, the business increase is straining Connecticut's already crowded highway system, because virtually all of the metal shipped into the ports is distributed by truck. Crowley and other port operators and local officials hope the state eventually will beef up the highway system, or repair crumbling rail lines that once made New Haven a major rail freight terminus.

The metals import boom appeared seemingly overnight at the Connecticut ports. "This place was like a graveyard," Crowley remembers.

Until January 1983, that is.

"The recession ended just like that," he says. Suddenly, New Haven and the other ports found themselves handling huge amounts of foreign steel. "At first we thought, well, it's just a cyclical recovery," Crowley says. "It was only with the recovery that it became clear to us the extent to which the domestic steel industry had been liquidated."

The port operators believe Connecticut got the bulk of the increase in metals shipments to the East Coast because the handling costs at the state ports are slightly lower than at neighboring ports in Boston and New York; because the ports are better able to handle bulky, unwieldy cargos like steel than, say, New York, which handles primarily containerized freight; and because there is more room for expansion at the previously underused Connecticut facilities.

The increase in business has already led to expansion at the ports, in the most ironic of fashions. New Haven Terminal has taken over a 34-acre abandoned United States Steel plant to use for storage, while Cilco Terminal Co., which operates the Bridgeport terminal, has appropriated an old Bridgeport Brass Co. warehouse to store imported metals.

Having turned imports into big business, the Connecticut ports would like to return the favor with some exports. But so far, they've been unable to drum up much export business. "When you get a steel ship in here and it drops its load, to some extent it's leaving empty," Burns says. "We want to give them some cargo." To accomplish that, there is some talk about starting a small container port operation as a low-cost alternative to New York and Boston, or of drumming up enough new industry around the port area to produce something that can be shipped by water.

The hopes are darkened by the newly announced limits on steel imports. Although President Reagan has declined to put a ceiling on copper imports, he allowed trade negotiators to hammer out restraining agreements with major steel-exporting countries that could cut steel imports by as much as 30 percent. Steel imports had been running at better than 25 percent of consumption so far this year.

Naturally, Connecticut officials have worried that any kind of limits on steel imports also will limit their newfound boom. Crowley argues that imports of metals are necessary, in New England at least, because land transportation problems, combined with the decline of the American steel and copper industries, make domestic metals harder to obtain in the region.

Still, Crowley has been fairly confident that the good fortune of New Haven and the other ports will last. "There seem to be pretty good reasons why steel is not going to be produced in the Midwest any more; it's going to be produced overseas," he said in an interview a few weeks ago. "And it's going to have to be shipped by water to the U.S."