Abstract
Effects of the carbon content and heat treatment on fatigue properties of 18Cr-12Ni steels have been studied by the rotating-bending fatigue test at 600°C and 3000rpm. The results obtained are as follows.
(1) The fatigue strength of the steel increases roughly twofold as the carbon content of the steel increases from 0.06 to 0.29% in weight.
(2) As the carbon content of the steel increases, the effect of solution temperature on the fatigue strength becomes conspicuous.
(3) The optimum solution temperature is the lowest one that gives a complete solution of carbide.
(4) Slightly aged specimens give a higher fatigue strength than that of completely aged (maximum hardness) or unaged specimens.
(5) Coaxing behaviors are also influenced by heat treatments, and the treatment to give the highest fatigue strength results in the greatest coaxing effect.
(6) A coaxing process, which is interrupted before failure, can be utilized as a pre-treatment to improve the fatigue strength.
(7) Grain sizes, amounts of undissolved or dissolved carbides, and the precipitation during fatigue are influenced by carbon contents of the steel and heat treatments, and from these aspects the fatigue properties described above can be explained qualitatively.
