ABSTRACT:

M.E.F. dual phase steel was made from structural steel (SS41), and corrosion fatigue tests With rotated bending test machine have been performed in 35% NaCl solution The variable was temperature (278, 288, 303 and 318°K). The effects of solution temperature on the corrosion fatigue strengths, corrosion fatigue crack propagation rates, fracture appearances and corrosion morphologies are described.

1 INTRODUCTION

Extensive studies on the corrosion fatigue have been performed for the purpose of safe designs and life predictions of the structures in the corrosive environments The structures, used particularly under the sea-water corrosive condition, can undergo the earlier fatigue crack initiation and the faster crack propagation to fracture by corrosion activity. The fracture of the steels can be influenced by the mechanical, metallurgical properties, and also the service conditions or environments. In aqueous solution, the environmental variables are purity, composition, pH, temperature, dissolved oxygen, and flow rate (Scott and Turnbull, 1985), which can significantly affect the stress corrosion cracking (SCC), the hydrogen embrittlement cracking (HEC), and corrosion fatigue behaviors of the structure. But It is inevitable to use the high tensile strength steel because of the increasing needs of design, cost and safety. Hence, in case that the dual phase steel should be used for the offshore structures, It IS necessary to investigate its corrosion fatigue characteristics m sea-water environment. Effects of pH(Oh et aI, 1987), solution concentration (Oh et al, 1988) and ferrite grain size(Oh et al, 1987) on the corrosion fatigue behavior of the dual phase steel In sea-water environment have been reported, but few on the effect of the solution temperature In this study, rotated bending corrosion fatigue tests have been carried out With structural steel (SS41) and dual phase steel that was produced from SS41 by a series of heat treatment.

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