日本金属学会誌

J. Japan Inst. Metals, Vol. 52, No. 3 (1988),
pp. 363-368

Effects of Small Casting Defects on the Fatigue Properties of Cast Steel

Toshinori Ohshima1, Tadao Hayashi1 and Tadayoshi Takahashi2

1Department of Mechanical Engineering, Tomakomai College of Technology, Tomakomai
2Department of Metallurgical Engineering, Faculty of Engineering, Hokkaido University, Sapporo

Abstract:

The effects of small casting defects on the fatigue properties of medium carbon cast steel are studied using sample block cut from continuously cast steel bloom.
A series of variously defective specimens cut and machined from the single block are subjected to tensile, fatigue and fatigue crack growth tests. Some other specimens cut and machined from another hexahedrally forged block are also tested, in which defects are pressure welded to be almost removed without change in dendritic morphology.
The results are summarized as follows.
(1)  Fatigue crack growth rate of defective cast steel is little affected by the defectivity and dendritic morphology.
(2)  Fatigue properties of defective cast steel are almost governed by the magnitude of initial stress intensity factor of the defect from which fatigue crack originates.
(3)  In defective cast steel, fatigue limit σ W is closely related with the tensile fracture strain ε f as well as the tensile strength σ B. Therefore, σ w is successfully correlated with the parameter σ B\sqrtε f.


(Received 1987/11/2)

Keywords:

continuously cast steel, small casting defect, defectivity, defect size, stress intensity factor, fatigue properties, tensile strength, tensile fracture strain, fatigue limit


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