 The prototypes and early production of the class were designated HP (), being redesignated as FD () class during the Cultural Revolution, before becoming the QJ class in 1971.The class became the primary mainline freight locomotive on the Chinese rail network by the 1980s, and were then displaced by diesel locomotives in 2005.After the end of steam on the national Chinese railway network many QJ locomotives were used on industrial lines, as well as on the Jitong railway.