Babcock & Wilcox Co., U.S. Steel Corp. and three other makers of specialty steel filed antidumping complaints yesterday against three Japanese steel firms.

The domestic steel makers claimed in petitions filed with the Commerce Department and the International Trade Commission that the Japanese firms sold steel here at prices as much as 63 percent lower than the prices at which they sold it in Japan. Injuring the domestic industry by selling steel in the United States below its home market value is "dumping," a violation of the Trade Agreements Act of 1979.

"Our petition is not a spur-of-the-moment thing," said Thomas Krebs, senior vice president of the Babcock & Wilcox tubular products division. "We're not filing this because everyone else is," he added, referring to more than 100 complaints against foreign steel makers by U.S. producers of carbon steel. The complaints of the specialty steel industry, which makes steel alloyed with other elements, is unrelated to the carbon steel cases.

The specialty steel industry is about a $215 million business in the United States. Carbon steel products comprise about 90 percent of U.S. steel-making.

The domestic steel companies contend that the Japanese are taking market share from American firms in seamless alloy pressure pipes and tubes, used by the utility boiler industry, and in seamless heat-resistant pipes and tubes and seamless stainless pipes and tubes used in the petrochemical, chemical and refining industries.

Krebs, asked what means the Japanese were using to sell their steel here at allegedly low prices, said he didn't know. But he said he knew that the steel was being sold here at prices lower than those in Japan.

Babcock & Wilcox has no plans to file complaints against any European firms, Krebs said.

The company is not strong in exports, he noted. "We don't have good overseas sales. We haven't really gone after that."

All of the product areas are not losing money as a result of Japanese imports, but seamless alloy pressure products lost market share last year, and profits dropped for the seamless heat-resistant and seamless stainless goods, Krebbs said. He would not elaborate.

A few employes have been laid off, Krebs continued, and others were shifted to different areas of the company.

Other companies joining in the complaint were Al Tech Specialty Steel Corp., of Dunkirk, N.Y.; ITT Harper of Morton Grove, Ill., a subsidiary of International Telephone and Telegraph, and Quanex Corp., of Houston.

The targets of the complaints constitute the bulk of the Japanese specialty steel business, Krebs said. They are Sumitomo Metal Industries Ltd., Nippon Kokan KK and Sanyo Specialty Steel Co. Ltd.