Beatrice M. McPherson, 75, one of the most prominent women in the welding trade and the operator of her own welding and construction firm, died Saturday at her summer home on Cobb Island, Md., after a long illness.

Mrs. McPherson, a 4-foot-11-inch woman who became fascinated by weding as a child on her family's ranch in Southern California, was a former chairman of the Washington Section of the American Welding Society.

Officials of the 30,000 member society said Mrs. McPherson is believed to be the only woman to head one of the group's 134 sections.

During World War II, when Mrs. McPherson worked as a welder at a plant in Silver Spring that was doing defense work, she developed a welding process for weapons sights that led to great reductions in production costs.

The Navy issued an award to Mrs. McPherson's employer in recognition of the new process.

After the war, 1946, Mrs. McPherson and her husband, Maynard E., founded that B&M Welding Works in Gaithersburg.

The firm, which began as a small workshop in a garage grew to employ 30 persons on major building projects. Mrs. McPherson served as president.

Instead of confining herself to office duties, however, Mrs. McPherson, who had put in 54-hour weeks with a welding torch in her hand during the war, continued to wield the tools of her trade at numerous construction sites.

She was born in 1901 in Carlsbad, Calif., where her father was in the construction business and maintained a ranch.

Although fascinated by welding as a child while watching and helping a blacksmith employed by her family, she embarked as a young woman on a nursing career.

After a time, however, she decided to switch to welding, and practiced with family facilities until she qualified for work in a general repair shop.

"I always preferred to work with men," she was quoted as saying in one newspaper report. "They're so much easier to get along with."

By the time she arrived in the Washington area in the early 1940s, she had been welding for years.

"I wouldn't swap places with any white collar job," she told an interviewer in 1943, while she was working in a defense plant.

"I am happy and glad I had the opportunity earlier in life to learn this work so I can be of service to my country without three or four years of learning," she added.

At that time, Mrs. McPherson was the only woman member of the Washington section of the American Welding Society.

In 1970, the section awarded her the A.G. Bissell Memorial award.

She had lived in Gaithersburg since 1941.

In addition to her husband, survivors include a daughter. June Marie McKiernan; a brother, Robert Culver; a sister, Dorthia Billings, and* five grandchildren and six great grandchilldren.