Engineering Transactions, 61, 2, pp. 87–98, 2013

Mechanical Characterization of Pre-Fatigued Free-Cutting Steels under Dynamic Tension

Masaaki ITABASHI
Tokyo University of Science, Suwa Department of Mechanical Systems Engineering

Heikichi KOSEKI
Tokyo University of Science, Suwa Department of Mechanical Systems Engineering

In the near future, toxic Pb will be prohibited to add to free-cutting steels. So far, many
types of free-cutting steels without Pb have appeared. In order to compare dynamic mechanical
properties of Pb added SUM24L steel (refer to JIS G 4804:2008, equivalent to AISI 12L14
steel) with those for Pb free SUM23 (equivalent to AISI 1215), high velocity tensile tests are
carried out at a strain rate of 1×103 s−1, at room temperature. A half of the specimens are
pre-fatigued before the dynamic tensile test. This loading combination, fatigue and impact,
simulates a certain service condition, normal operational loadings and an accidental dynamic
loading. Tensile strength of the pre-fatigued specimens is less than that of the virgin specimens,
to some extent, for both steels. Where the degradation is of almost the same level, replacement
of the Pb added free-cutting steel with the Pb free steel may be possible.
Keywords: dynamic tension; pre-fatigue; Pb free; free-cutting steel; degradation
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