Starting in sales as a contact man, Carlen was soon promoted to manager of inside sales. In 1955, he was elected Ryerson's vice president for operations. He became executive vice president in 1964 and president of Ryerson in 1968.
Named an Inland director in 1969, Carlen became senior vice president of the parent corporation in 1976. He was elected corporate vice chairman in 1978, serving until his retirement in 1982. As a result of Carlen's foresight and leadership in introducing new steelmaking technology, the Ryerson Company is the leading steel-service entity in the nation.
Carlen received his MBA from Chicago Booth in 1950 as a member of the sixth class to graduate from the Executive MBA Program. He devoted much of his time to Chicago Booth and was among the originators of the Executive MBA Program's management conferences. A member of the Council on Chicago Booth from 1959 to 1972, he served as president in 1962 – 63 and led the Alumni Fund Drive in 1971. As head of Chicago Booth's Associates Program, Carlen doubled its corporate membership.