Inflation and production problems have hit U.S. high technology so hard in the last two years that federal contractors have been forced to buy major components from foreign suppliers for the first time in decades.

In each case, the purchase was made at the end of a process that began with requests for bids from suppliers and ended with the selection of a foreign supplier whose bid was so far below the lowest U.S. proposal that the "buy America" rule on federal projects was waived. The "buy America" policy states that a foreign bid must be at least 6 percent below the U.S. bid to considered

Among the high-technology components bought abroad were $470,000 worth of quick-acting Swiss vacuum valves for the Positron-Electron colliding beam project near completion at the Stanford Linear Accelerator Center; $100,000 worth of special Japanese steel for the Nova laser project at Lawrence Livermore Laboratory outside San Francisco; and $3.9 million worth of pumps, seals and low-temperature controls from the Swiss, West Germans and French for the Tokomak Fusion Test Reactor being built at Princeton N.J.

"These are the sort of things we've never had to buy outside the U.S.," said one official of the Department of Energy, which is financing all three projects. "Times have changed in the last few years."

The foreign purchases that have raised the most concern are a pair of orders placed with West Germany and Japan for the fusion project at Princeton. One is a $1.5 million order for special steel from Japan, the other a $1.6 million order for long billets of specially extruded copper from West Germany.

Both will be used in fabricating the largest magnets ever built. No fewer than 20 of theses magnets will be placed in the doughnut-shaped Tokomak being built at Princeton to confine the deuterium plasma expected to reach heats of 100 million degrees and demonstrate the scientific feasibility of fusion.

The order placed to a West German firm called Kabble Metal is for 500,000 pounds of copper extruded into shapes 50 feet long, 6.5 inches wide and five-eights of an inch thick. Each 50-foot extrusion has an elliptical hole through its center.

Many of these copper stris already have been shipped to Westinghouse Electric Corp. in the United States, where 44 are welded together and wound to form the coil that will generate the magnetic field in the fusion machine. There will be 20 coils in the machine, each weighing 25,000 pounds.

The thing that most concerned Princeton project officials when bids came in for this job is that the two lowest bids were from West Germany and Finland. Only Phelps-Dodge and Anaconda in this country bid on the job.Neither one was close to the German and Finnish bids, according to DOE officials.

At each end of each of the 20 magnetic coils in the Princeton Tokomak, enormous steel rings will hold the copper coils rigidly in place. Each ring weight 15,000 pounds and is being forged out of a supertough and superhard steel called "nitronic" steel. All the rings are being forged by the Japan Steel Co.

"These rings have a six-foot radius and they're six inches thick," one Energy Department official said. "The Japanese were not only the lowest bidder, they were the only suppliers who could deliver these very special rings on the schedule at which we needed them."

Carter administration officials point out that the orders to West Germany and Japan represent only 25 percent of the $12 million in orders placed for the 20 magnets that will be the heart of the Princeton fusion machine.

"I do not see this as a worrisome trend," said R. Robert Russell, director of the Council on Wage and Price Stability. "The whole idea of international trading is that trading countries are better off by trading. High technology should be no exception to this."

One Energy Department official said that West Germany and Japan are the only countries with extrusion presses and forging furnaces large enough to make major magnet components. At least two U.S. suppliers said they could have developed such a capability if they'd been given time enough to do so.

There is no question that U.S. suppliers see it differently. One suggested that the Germans and Japanese deliberately may have shaved their bid price to get in on the ground floor of fusion development, which promises to take off in the next 20 years.

"One objective of this program was to train U.S. industry in the fabrication of major components," one potential supplier complained. "But when you go out of the country for these components, you defeat that objective All you're really doing is exporting the know-how."

Dr. Melvin B. Gottlieb, director f Princeton University's Plasma Physics Laboratory and builder of the Princeton fusion machine, summed up this viewpoint:

"It raises by hackles to find out we have to go abroad for these things. It's all American money in this project, but it's sure not all American suppliers."