Abstract: Taking as-cast 42CrMo steel as deformation material, hot processing maps at different strains are established by analyses stress-strain curves during hot compression and corresponding calculation. In the hot processing map of the smaller strain, dynamic recrystallization occurs in the temperature range of 1 100-1 150 ℃ and strain rate range of 0.1-1 s1, and dynamic recovery dominants in the temperature range of 950-1 050 ℃ and strain rate range of 1-10 s1. The temperature and strain rate range for dynamic recovery and recrystallization become lager when strain increases. The optimum temperature and strain rate ranges for hot ring rolling at different strain of the steel are determined according to the hot processing maps. Based on the hot ring-rolling process test of the as-cast ring blank of the steel, the influences of the deformation ratio, the rotational speed of the driving roll and the feet speed of the pressure roll on the quality of ring-rolled parts are analyzed. And the influence of ring-rolling parameters on microstructure evolution and grains in ring-rolled parts is also analyzed. The results both of analyses and the hot ring rolling test show that the ring rolling process with the as-cast ring-blank can not only produce ring parts with perfect shape and accurate size, but also make the as-cast ring-blank get deformation large enough improve cast structures and refine grains to meet microstructure and mechanical property requirements of ring parts.

Key words: as-cast 42CrMo steel;hot processing map;hot ring rolling;microstructure;process parameters