Super-long life tension-compression fatigue properties of quenched and tempered 0.46% carbon steel

To investigate the effect of non-metallic inclusions on fatigue properties of quenched and tempered 0.46% carbon steel (HV congruent to 650) in super-long life fatigue range (10(7) less than or equal to N less than or equal to 5.0 x 10(8)), tension-compression fatigue tests were carried out. The fatigue strength was discussed based on the root area parameter model. The results obtained are: 1. Fatigue fracture origins were mostly at a non-metallic inclusion. 2. However, the location of the inclusion at fracture origin were not uniformly distributed over the specimen section due to the non-uniform distribution of residual stress induced by heat treatment. 3. The fatigue limit by the cycle N = 5.0 x 10(8) can be predicted by the root area parameter model, i.e. with three parameters, the Vickers hardness, HV, of the matrix, the square root of the projected area of inclusions, root area, and residual stress. 4. The expected value of inclusion size root area(max) of 0.46% carbon steel in a definite number of specimens can be estimated using the statistics of extreme values, The lower bound of the scatter of fatigue strength was predicted with the combination of the root area parameter model and the value of root area(max). (C) 1998 Published by Elsevier Science Ltd. All rights reserved.