A study on the characteristics of corrosion-fatigue-crack propagation in the welded parts of high tensile steels under sea water

J. Ocean Eng. Technol. 1987;1(2):113-122.

고장력강 용접부의 해수중 부식피로균열 성장특성에 관한 연구

김영식,박무창

한국해양대학 선박기계공학과,한국선급 기술연구소

Keywords: corrosion fatigue crack, crack growth rate, active path corrosion, hydrogen embrittlement

핵심용어: 부식피로균열, 균열성장속도, 활성경로부식, 수소철화

Abstract

Ships and offshore strrctures are exposed to the corrosive surroundings, and the extablishment of the design criteria and the elucidation on the influence by this environment are requested to maintain the safety and to demonstrate the function of the structure. In this paper, the fatigue-crack-growth behavior on the compact tension specimens of quenched, tempered HT80 grade steels and RA36 high tensile steels having a single edge fatigue cracked notch respectively, were investigated under the repeated tensile stress with constant stroke in sea water for the welded parts by shielded metal arc welding. Main results obtained are summerized as follows; 1. The fatigue-crack-growth rates da/dN in sea water appeared to be greater behavior than those in air environment at the same stress intensisy factor range $DeltaK$. 2. The correlation data of da/dN$DeltaK$ of the two kinds of high tensile steels in sea water showed no great difference, however, the correlation data of da/dN$DeltaK/sigma_y$($sigma_y$ stands for yield strength of the material) showed that the fatigue-crack-growth behavior of RA36 plate is affected by active path corrosion(APC) mechanism, while that of HT80 grade plate is mainly affected by hydrogen embrittlement mechanism.