The unique properties of air-cooled bainitic steels have been described. A series of Mn containing air-cooled bainitic steels invented by authors is presented in this paper: including low carbon granular bainitic steels, low carbon grain-boundary allotriomorphic ferrite/granular bainite duplex steels, medium and medium high carbon bainite/martensite duplex steel, and low carbon carbide free bainite/martensite duplex steels. The development of ultra-low carbon bainitic steels in China is also introduced.