Abstract
Uniaxial tension-compression fatigue tests of Ni-Cr-Mo steel "SNCM439" tempered at different temperatures were conducted in air environment. Effects of tempering temperature on fatigue properties were investigated. As a result, the following conclusions were obtained; (1)Fatigue limit of surface fracture was proportional to Vickers hardness, and the relation was in good agreement with the expression 6 z 1.6HV. (2) In very high cycle region, the fatigue strength of the material tempered at 433K was lower than that tempered at 573K and 773K. In other words, the harder material showed lower fatigue strength. (3)The kinds of inclusions, which can be interior fracture origins, probably change between different tempering temperatures.
