The QJ (Chinese: 前进; pinyin: Qián Jìn; lit. 'To go forward" or "to advance') was a type of heavy freight steam locomotive introduced in 1956 by the China Railway. The majority were built by Datong Locomotive Factory. The prototypes and early production of the class were designated HP (Chinese: 和平; pinyin: Hé Píng; lit. 'peace'), being redesignated as FD (Chinese: 反帝; pinyin: Fǎn Dì; lit. 'Anti-Imperialism') 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. Manufactured until 1988, they were displaced by diesel locomotives in 2005. A total of 4,717 were produced. 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. Several members of the class have been preserved.

42 prototypes were built by Dalian locomotive works, Tangshan locomotive works, and Shenyang, Mudanjiang, Changchun and Datong locomotive factories between 1956 and 1960. Originally the locomotives were designated as the HP (Heping meaning 'peace') class.^[1] The design is thought to be based in part on the Russian LV class.^[1][2] (see Паровоз ЛВ Russian).

The main tranche of production took place at Datong, beginning in 1964 starting with locomotive HP 101.^[2] A number of modifications were made to the locomotive, including a new design of boiler for the production version.^[6] The 500th QJ was built in 1968, the 1,000th in 1970, the 2,000th in 1974 and the 3,000th in 1979,^[7] with production rates varying from 150 to over 300 per year between 1966 and 1985.^[2] Production ended in 1988 with 4,717 produced.^[1][8]

During the Cultural Revolution of 1966, the locomotives were given the class FD (反帝 Fandi meaning 'anti-imperialism'), after 1971 the class was renamed again becoming the QJ class (Qian Jin, meaning 'march forward' or 'progress').^[1][9]

The prototypes used 8 wheel tenders, while later production models used 12 wheel tenders.^[1] QJs were equipped with mechanical stokers, feedwater heaters, electric lights, and air horns. Various modifications were used on some engines, including an ejector similar to the giesl type and smoke deflectors. One unit was used as a test bed for a 'Gas Producer Combustion System' (GPCS)^{[n 1]} in the 1980s.^[1]

A small number of locomotives were built to broad (Russian) 1,520 mm gauge.^[1][9]

The class became the primary freight locomotive on both the primary and secondary lines of the Chinese railway network by the 1980s, having displaced both JF and FD classes. From the late 1980s and through the 1990s the class were replaced by diesel locomotives. Steam traction officially ended on the Chinese national rail network in 2002, but a few units remained in use up to 2003 on minor lines.^[1]

The locomotives were also used on large passenger trains, when their high tractive power was advantageous.^[11]

After withdrawal from the Chinese national network many units were acquired by industrial railways as well as the regional Jitong Railway in Inner Mongolia which operated ~100 units.^[1] By 2005 the Jitong Railway had also replaced the QJ locomotives with diesel engines.^[12] Some remained in use on industrial lines in China in 2010.^[1]