Gigacycle Fatigue Properties of Double-Melted SCM440 Steel and Size Effects

Abstract

Gigacycle fatigue tests were conducted on double-melted SCM440 low-alloy steel using larger and conventional specimens and comparing the results with those of single-melted steel. Although all specimens experienced internal fractures, size effects were minor in the double-melted steel, unlike in the single-melted steel: specifically, for the double-melted steel, differences in fatigue strength and inclusion size were minimal between the larger and conventional specimens. These results mean that the double-melted steel showed superior gigacycle fatigue properties to the single-melted steel when the larger specimens were used in the fatigue tests, whereas this superiority was doubtful when conventional specimens were used. When the inclusion sizes were estimated using the results for the larger specimens, the inclusion size for 150 kg of the double-melted steel was a maximum of 47 μm, one-third of that for the single-melted steel. The use of larger specimens is thus highly advisable for evaluating the gigacycle fatigue properties and the inclusion size of high-strength steels.