Abstract
Influences of chemical composition, heat treatment and microstructure on impact toughness of 15Cr ferritic steel have been investigated. Charpy impact values of the furnace cooled steels were lower than 15J/cm^2 at room temperature independent of chemical composition. Drastic improvement in impact toughness has been attained by controlling independent of chemical composition. Drastic improvement in cooling rate after annealing. However, effect of nickel on impact toughness strongly depends on carbon and nitrogen contents Improvement in impact toughness of the 15Cr ferritic steel has not been explained by individual microstructural factors of grain size, distribution of precipitates, volume fraction of martensitic phase. It has been supposed that the increase in Charpy impact toughness of the 15Cr ferritic steel was attained by improvement in toughness of ferrite matrix itself.
