The characteristics of Near-thrshold fatigue crack propagation for welding zone in TMCP high strength steels

J. Ocean Eng. Technol. 1997;11(3):39-47.

TMCP 고장력강 용접부의 하한계 피로균열진전 특성평가

이택순,오대석,이휘원

영남대,영남대,영남대

Keywords: Accelerated cooling, Frequency, Stress Ratio, near-threshold stress intensity factor

핵심용어: 가속냉각, 반복 주파수, 응력비, 하한계응력확대계수

Abstract

Recently developed TMCP steels, which were manufactured by controlled rolling followed by accelerated cooling process, were examined to study their characteristics and weldability. Accelerated cooling type TMCP steel's hardness test result exhibited high value on weld zone. On the contrary, base metal and HAZ exhibited comparatively the similar value. On this experiment result Softening of HAZ is not occurred. in the-heat affected zone, grain size repression be caused by chemical composition properties which a small quantity Al-Ti-B-N. Changing stress ratio near-threshold fatigue crack propagation experiments were carried out. According to this result, crack propagation velocity of the HAZ exhibited slower than the base metal and near-threshold value had increased at the HAZ. Finally accelerated cooling type TMCP steels were exhibited excellent mechanical properties in both strength and toughness.