WASHINGTON (AP) _ Showa Denko Carbon, Inc., a U.S. subsidiary of a Japanese company, agreed today to pay a $29 million criminal fine and plead guilty to a worldwide scheme to fix prices for graphite electrodes used in steelmaking, the Justice Department said.

The fine is the fourth largest in antitrust history.

``This case is the first step by the Department of Justice in prosecuting and dismantling an international cartel that increased prices of a vital product used in American steelmaking,'' said Attorney General Janet Reno.

The department filed a one-count criminal information against the company in U.S. District Court in Philadelphia. A criminal information is used to bring charges when a defendant has waived the right to a grand jury indictment and agreed to plead guilty.

Showa Denko Carbon (SDC) and its affiliated companies agreed to cooperate in the investigation of what the Justice department called a wide-ranging international conspiracy to fix prices and allocate market shares worldwide for the electrodes.

Graphite electrodes are large carbon columns used in electric arc furnaces in steelmaking mini-mills to generate the heat necessary to melt and further refine steel. Nine electrodes, joined in columns of three each, are used in the average electric arc furnace to melt scrap steel. The electrodes are continuously consumed in the process.

Total sales of graphite electrodes in the United States were estimated at $500 million in 1996 and at more than $1.5 billion over the course of of the conspiracy, which the government alleges ran from 1993 until January 1997. The government alleged that during this period, customers were hit with significant price increases for graphite electrodes that far out-paced inflation.

``Today's case is likely only the first in the graphite electrode industry and represents a continuing expansion of the antitrust division's investigations into many international markets,'' said Deputy Assistant Attorney General Gary R. Spratling. ``In future months, we expect more prosecutions in this and other international industries.''

UCAR International Inc., of Danbury, Conn., and SGL Carbon AG, of Wiesbaden, Germany, are the two largest producers of graphite electrodes in the world.

UCAR International and SGL Carbon Corp., a Charlotte, N.C. subsidiary of SGL Carbon AG, previously announced that federal agents executed search warrants at their offices on June 5, 1997.

Another producer, The Carbide/Graphite Group of Pittsburgh, announced that it has been accepted into the antitrust division's corporate leniency program, under which a company may avoid criminal prosecution if it voluntarily reports its involvement in a crime before the government is aware of it.

The Justice Department said Showa Denko Carbon would enter its guilty plea soon in Philadelphia, where the investigation has been conducted by an antitrust division field office and the FBI.

SDC was charged with violating the Sherman Antitrust Act by conspiring with unnamed co-conspirators to suppress and eliminate competition by fixing prices and allocating market shares for the product in this country and abroad.

SDC, a subsidiary of the Japanese firm Showa Financing KK, manufactures graphite electrodes in the United States at its headquarters in Ridgeville, S.C. and has customers throughout the United States and elsewhere.

The government charged that the company and its co-conspirators held meetings in the Far East, Europe and the United States at which they agreed to raise prices, eliminate discounts and divide the world market among themselves.

Using code names for their corporate conspirators, the companies designated which conspirator would fix the price in each region of the world, agreed to restrict their capacity and to withhold technology from non-conspirator companies, the government said.