This paper reports the result of experiments made of the effect of grinding, lapping and barrelfinishing operations on the fatigue strength of quenched and tempered 13 Cr stainless steel used for compressor valve.The reversed plane-bending fatigue tests were carried out by means of Schenk-type fatigue testing machine of 10kgm at about 1500rpm.The results obtained can be summarized as follows (1) In longitudinal grinding the fatigue limit of roughly ground specimens was almost the same as finely ground ones, but in transverse grinding the latter was about 10% higher than the former.(2) In rough grinding the fatigue limit of transversely ground specimens was contrary to general expectations, nearly equal to that of longitudinally ground ones, but in fine grinding the former was about 20% higher than the latter.(3) The lapped specimens, when barrel-finished, get their surface roughness reduced by half, with but little increase in fatigue limit.(4) In the surface finishing operations under the conditions used in this experiment it was necessary that the residual stress both in the surface layer and the surface roughness should be taken into consideration as having influence on the fatigue strength.

(1) Austenite in the solution treatment could be transformed into martensite by intermediate and subzero treatments, so that tensile strength, yield strength, plane-bending fatigue limit and hardness increased, but elongation considerably decreased.(2) After subzero treatment, the mechanical properties of this steel increased a little with increasing intermediate temperature.(3) In the relation between aging conditions and hardness, the lower the aging temperature, the longer was the aging time that showed a maximum value of hardness, but its value rose high. yield strength, fatigue limit and hardness were remarkably increased in the early stage of aging and showed the maximum values in 2 hours.But these elongation was nearly constant up to 7 hours.(6) In the condition of subzero treatment or aging treatment the ratio of the fatigue limit to the tensile strength was about one-third.

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Hereunder is reported the investigation made of the effect of grinding conditions and aftertreatments, such as barrel-finishing and grit-blasting, on the reversed plane-bending fatigue strength of hardened 13Cr stainless steel.Two grinding conditions were considered, the gentle and the severe.The grinding direction was always in parallel to the length of the specimen. The results obtained are summarized as follow:(1) The fatigue limit of severely ground specimens has remained about 42% lower than that of gently ground ones.(2) The surface residual stresses in parallel to the length of the specimens, both those gentlyground and those severely ground, were of tensile sort.Severe grinding, in particular, induced exceedingly high tensile stresses on the surface layer.(3) The barrel-finishing and grit-blasting after grinding have greatly raised the fatigue limit. (4) The barrel-finishing induced compressive residual stress on the surface, while, the distribution of residual stress on the surface layers of grit-blasting specimens was almost even for the two grinding conditions, and the stress was of compressive sort of considerably high degree.