Autos, steel, semiconductors, sure. But heavy-duty staples? Canape machines? Trolly wheels? Old-line smokestack industries and high-technology firms aren't the only sectors of the US economy tussling with imports. As more types of foreign products march relentlessly on the United States, a wide spectrum of domestic companies is complaining to Washington about import problems.
For example: Until four years ago, American makers of heavy-duty carton staples had the domestic market pretty much to themselves. Then Sweden decided to become the Japan of the industry. The Swedish flooded the United States with low-priced carton staples, grabbing about 20 percent of the market by 1982, according to US competitors.
''We sell staples for about $1.13 per thousand,'' says Alberto Merchiroi, a vice-president of International Staple Inc of Butler, Pa. ''The Swedes sell them for about 76 cents. That's substantially under the price (they charge in Sweden).''
Earlier this year, International Staple filed suit with the Commerce Department, charging Sweden with unfair trade practices. Commerce agreed, and slapped a temporary tariff on carton-closing Swedish staples and staplers.
Another example: floating down a lazy river in an inner tube on an August afternoon is as American as Norman Rockwell or the World Series. Today, however, the inner tube itself is likely to be Korean. As late as 1979, few Korean tubes were sold here. Then began ''an extraordinary import surge,'' claims a domestic industry source who asked not to be identified. Korean tube imports (excluding bicycle tubes) tripled in one year, 1981, then jumped another 22 percent last year.
US rubber companies believe their Asian competitors are selling their products at less than fair value. They've asked the Commerce Department to conduct an investigation; a preliminary decision is expected by December.
In addition, the Commerce Department and the International Trade Commission (a US agency) are currently investigating cases dealing with trolley wheel assemblies, canape makers, small plastic screw anchors, poultry cut-up machines, spun acrylic yarn from Italy, canned tuna from the Philippines, portland cement from the Dominican Republic, and Canadian potatoes.
Overall, the number of trade complaints filed is generally heading upward, says David Binder, acting director of the Commerce Department's office of investigations. ''We're seeing 65 to 70 cases annually. There are so many things changing in the economy.''
Some industries - such as the staple-makers - are really being hurt by unfair foreign competition. But others, economists note, are trying to avoid a fair fight by hiding behind the US government's skirts.
''Never again will US firms enjoy freedoms of the past; they will forever be looking over their shoulders at foreign prices and products,'' says respected economic columnist Robert Samuelson in a recent National Journal article.
The result, Mr. Samuelson says, will be more and more firms pressing the US government for an ''activist'' trade policy.
Reagan administration officials, of course, say government should take as passive a role as possible when it comes to trade - though it has taken many ''activist'' actions, such as slapping quotas on sugar imports.
Democrats, meanwhile, are forging ahead with plans to capitalize on the issue of trade and economic planning in the 1984 election. A House subcommittee headed by Rep. John J. LaFalce (D) of New York expects to produce a broad ''industrial policy'' bill by fall.
At the very least, the bill will call for establishment of an Economic Cooperation Council, which would analyze the problems and prospects of various industries. The legislation may also suggest some sort of national bank to make low-cost loans to key industries.