Big Steel's bid for import quotas - as seen from Sparrows Point

At Bethlehem Steel Corporation's huge Sparrows Point steel plant outside Baltimore, you can see why major United States steel producers are seeking protection from imports.

While the 1,500-acre plant is far from empty, the impact of rising steel imports is clearly visible. Where 30,000 workers once toiled in the heat and dust of the mill, now only 11,000 pick up paychecks.

Five huge buildings in one corner of the plant sit empty because Bethlehem decided last year that it could not meet the lower prices foreign steelmakers were charging for steel pipe.

''We are going to do what we think we can do best,'' says plant senior manager Leon Harbold. That means making steel plates, sheets, and rods and seeking protection while the plant is modernized.

The industry's battle for protection heated up this week when the International Trade Commission (ITC) began hearings on a petition from Bethlehem and the United Steelworkers of America. They are seeking a five-year cap on imported steel at 15 percent of the US market. A presidential decision on the ITC's recommendations, and action on a parallel bid for a 15 percent import ceiling the industry is pursuing in Congress, are scheduled to come around election day.

The process is likely to force a major debate over how much help the nation can afford to give its ailing ''smokestack'' industries and what form the aid should take. One result of the deliberations is likely to be considerable pressure on elected officials to provide some shelter from imported steel. So far this year, foreign steelmakers have grabbed an estimated 25 percent share of the United States market.

Another major reason for the decline of the US steel industry can be glimpsed just north of Sparrows Point on Baltimore Harbor, where thousands of imported cars, containing Japanese steel, are being unloaded at a freight terminal.

It is not all grim news at the Sparrows Point plant. Amid a waterfall of sparks from two modern basic-oxygen furnaces, Bethlehem is installing a $250 million continuous caster, a device that produces steel slabs more efficiently. It is part of a $450 million plant modernization plan. More investment is needed to make the facility fully competitive. But additional spending hinges on getting the five years of protection the industry is seeking, company officials say.

''It would stabilize our work force and operation . . . and mean we can plan on what we need in order to modernize and train,'' Mr. Harbold says.

In steelmaking areas of the US there is strong support for some protection. Sen. John H. Heinz III (R) of Pennsylvania told the ITC Wednesday, ''I can assure you that anyone representing steel-producing communities in an elected capacity has to be painfully aware of the devastating impact of the relentless surge of foreign steel imports on our domestic steel industry, its workers, and their communities.''

He claims that in the last two years, the industry has lost $6 billion and 200,000 jobs because of imports.

Despite its obvious woes, at the moment the steel industry faces an uphill fight in securing the kind of protection it wants. Reagan administration officials - and their allies in the GOP-controlled Senate - strongly oppose sweeping curbs on steel imports. President Reagan also makes the final decision on whether to provide ITC-recommended assistance to an industry. Meanwhile, the fair-trade-in-steel bill, which embodies the kind of protection the steel industry seeks, is given a good chance of clearing the House by election day.

Quotas on all steel imports, rather than curbs only on countries proved to be trading unfairly in a specific product, would be ''counterproductive to the industry's efforts to further improve its competitiveness by providing a false sense of security . . . ,'' US Trade Representative William Brock told the House Ways and Means Committee last week. The quotas are also troublesome, he says, because they ''would undermine the competitiveness of a great many industries highly dependent on steel as a raw material.''

Last week the Federal Trade Commission announced its opposition to any ITC quotas, noting that such a step would add $768 million annually to the US consumer's bill for durable goods like refrigerators. Across-the-board quotas would also subject some $6 billion in US exports to retaliation from unhappy US trading partners, Mr. Brock says. Sir Roy Denman, head of the European Economic Community mission to the US, says the quota bill makes the European Community ''very unhappy.''

Critics say the industry caused its own problems to a large degree by failing to modernize soon enough and letting wages escalate out of control. The poor performance of US firms ''can ultimately be traced to the lack of a well-conceived and well-coordinated strategy,'' according to a new book, ''Steel: Upheaval in a Basic Industry,'' by Donald F. Barnett, former chief economist at the American Iron and Steel Institute, the industry trade group.

But supporters argue that becoming competitive is essential if the US industry is to survive. The rising tide of imports ''is depriving the (US) industry of . . . the cash flow necessary to modernize,'' says Stanley Nehmer, president of Economic Consulting Services Inc., who testified before the ITC on behalf of the industry.