Buck Buchanan, a defensive lineman whose combination of size, strength and quickness carried him to the Pro Football Hall of Fame, died of lung cancer today at his home here. He was 51 years old.

Mr. Buchanan, one of the dominant players from 1963 to 1975 for the Kansas City Chiefs, had battled the illness for two years. But he never mentioned his illness during his acceptance speech at the Hall of Fame ceremony in 1990, so as not to sour the moment for others being inducted that day.

The son of a steelworker, Mr. Buchanan was born on Sept. 10, 1940, in Birmingham, Ala., and almost followed his father into the mills, despite a brilliant multisport career in high school. Few college scholarships were available to black young people in the late 1950's, but a relative of Mr. Buchanan contacted Coach Eddie Robinson of Grambling, a small, predominantly black college, and Mr. Robinson had a scholarship to offer. Drafted in First Round

The Chiefs, then the Dallas Texans, selected the 6-foot-8-inch, 300-pound lineman in the first round of the 1963 American Football League draft. The team then moved to Kansas City in time for the 1963 season.

"At that time, I was the first player from a small black school drafted in the first round," Mr. Buchanan once recalled. "It said a lot for a player from the Gramblings, the Prairie Views. That was important to me."

The New York Giants of the rival National Football League also drafted Buchanan, but he went with the Chiefs, where he was selected as an All-Pro player six times, played in 181 of 182 regular-season games and set the standard for modern defensive tackles.

"A big guy will be strong, and he might be quick, but he is rarely fast," said Hank Stram, Mr. Buchanan's coach with the Chiefs. "Or sometimes he's strong and fast, but not quick. But Buck had it all: plus he had a great attitude." Talented Supporting Cast

From 1966 to 1971, the Chiefs surrounded Mr. Buchanan with a host of talented teammates, including the quarterback Len Dawson and the linebacker Willie Lanier, and Kansas City reached the Super Bowl twice, winning in 1970 against Minnesota. Last Wednesday, the Chiefs announced that on Aug. 24 they would retire the jersey numbers of Mr. Buchanan, Mr. Lanier and the place-kicker Jan Stenerud.

After Mr. Buchanan retired, he became a defensive-line coach with Mr. Stram and the New Orleans Saints in 1976. After Mr. Stram was dismissed by the Saints, Mr. Buchanan moved to the Cleveland Browns as a coach in 1978, but he quit after one season and returned to Kansas City to operate a restaurant.

He went on to become one of Kansas City's most respected businessmen and civic leaders. He opened a construction and advertising business in the early 1980's, served as president of the Black Chamber of Commerce, and, in 1989, was appointed to the Kansas City Board of Election Commissioners.

Mr. Buchanan is survived by his wife, Georgia; two sons, Eric and Dwaine, and a daughter, Nicole.

Junious Buchanan