Like a public official touring a disaster scene, AFL-CIO President Lane Kirkland visited the Monongahela Valley today, observing the wreckage of the steel industry and endorsing one community's unique effort to reverse the decline by taking over a giant steel mill.

The tour by Kirkland, accompanied by Lynn Williams, president of the United Steelworkers of America, was intended to dramatize the union's struggle to save what is left of the industry here, where U.S. Steel Corp. alone has cut 20,000 jobs in five years.

"Pittsburgh looks beautiful. But I'd like to see it a little dirtier. A little more smoke," Kirkland said as his tour bus rolled past the rusted hulks of vacated riverfront mills and factories. "The most environmentally offensive thing I see is the shutdown mills.

"No nation can survive the disappearance of its basic industries without terrible consequences," he told 100 unemployed steelworkers outside a vacant mill.

Kirkland said the 13 million-member labor federation would continue pushing for stronger action against "dumping" of foreign steel and for other protections for domestic steel makers.

But he also accused some U.S. firms of unnecessarily closing profitable mills in the search for still-higher profit. "We have closed plants that represent the irresponsibility of the corporate structure of America, and the political leadership that allows this to happen," he said.

Kirkland heard from local politicians and union officials about unemployment rates as high as 50 percent in some "Mon Valley" towns, doubled rates of suicide, a rising toll of alcoholism and divorce and other measures of the painful decline of communities.

But a potentially brighter side of the picture emerged in visits to the giant "Dorothy Six" blast furnace in Duquesne and to the Rainbow Kitchen in Homestead, both representing novel grass-roots efforts to fight the decline.

Kirkland's tour stopped outside Dorothy, a million-ton-capacity furnace that is the largest in the region and one of only two "hot-end" furnaces in the valley capable of supporting full-scale steel production. In May 1984, U.S. Steel shut the furnace, calling it insufficiently profitable; five months later it announced plans to demolish Dorothy.

But the union and a broad-based coalition of church, political, academic and community activists drafted a plan to have Mon Valley cities and towns take over the abandoned steel mill.

By forming a "Steel Valley Authority" and using the power of eminent domain, if necessary, the group plans to find a new buyer for Dorothy or turn it into a worker-owned enterprise.

Nine municipalities, including Pittsburgh, have voted to join the authority, and U.S. Steel has agreed to postpone demolition pending the outcome of financial studies.

"We know this mill can be profitable. Our preliminary studies have shown it," said Bob Macey, a fourth-generation steelworker whose family has worked more than 100 years for U.S. Steel. "We're not letting our jobs go down the tube . . . . These mills don't just belong to U.S. Steel. They belong to the community."

"You are performing a great service here by dramatizing your determination," Kirkland told the steelworkers.

Union members are maintaining an around-the-clock vigil in a trailer to make sure that U.S. Steel does not begin dismantling Dorothy. Supporters of the "Save Dorothy" movement do a brisk business in bumper stickers, T-shirts and coffee mugs that immortalize the original Dorothy, the wife of a former company president, who gave her name to the plant in accord with corporate custom.

The storefront Rainbow Kitchen in Homestead, inspired by the 1984 "Rainbow Coalition" presidential campaign of Jesse L. Jackson, is run by laid-off steelworkers. The storefront's job bank, soup kitchen, emergency food pantry and community center serve hundreds of families, using private donations and volunteer labor, without any government money.

"We are just people who pitched in, because the need was there . . . and nobody else was doing it," said Dolores Patrick, who was laid off after eight years at U.S. Steel's Homestead Works.