During the 1950s SJ saw the need for a new universal locomotive, since the D-series was aging. In 1955 the Ra-series had proved successful with bogie wheels. At the same time there was interest to make a locomotive that could be exported abroad. The result was an agreement between ASEA and SJ where six test engines were delivered. The testing of the Rb was successful and based on this exports were made to the Yugoslav Railways (JŽ class 441) and Căile Ferate Române of Romania (CFR classes 43 and 44). The result of the testing was the Rc locomotive that was produced in 360 copies for SJ, in addition to export to Amtrak, Norges Statsbaner and Österreichische Bundesbahnen. The Rb-series was in use on passenger and freight trains until the mid-1970s.