SJ Littera B

The B class of the Swedish State Railways (SJ) was a type of steam locomotive for mixed traffic, introduced in 1909. 96 locomotives were built for SJ by between 1909 and 1919. The 4-6-0 B class was part of the development of modern superheatedlocomotives that had begun with the A class in 1906. Intended for fast freight trains and heavy stopping passenger trains, they proved to be highly useful in all types of traffic, and remained in use until the end of steam operations in Sweden.

Eleven B class locomotives were sold to private railways during the 1930s, but all but one returned to SJ after the railway companies had been nationalized in the 1940s. One of the private operators, Stockholm–Västerås–Bergslagens Järnväg, had three more locomotives of the same type built, the last one in 1944. Most B class locomotives were eventually rebuilt with fully enclosed cabs, and some were equipped for oil-firing after the Second World War.

When the locomotives became unnecessary in the daily traffic they were placed in the strategic reserve. Some locomotives from the reserve were reactivated during the winter of 1965–1966 due to a temporary shortage of electric locomotives. Most survived into the 1990s, and several have been preserved by the Swedish Railway Museum and preservation societies in Sweden, while sales to heritage railways abroad failed to reach the expected numbers.