Effect of the change of second phase hardness on corrosion fatigue behavior of dual phase steel in 3% nacl solution

J. Ocean Eng. Technol. 1992;6(2):85-93.

3% NaCl 수용액중에서 복합조직강의 부식피로거동에 미치는 제2상 속도변화의 영향

오세욱,김웅집

동아대학교 기계공학과,동아대학교 기계공학과

Keywords: Dual Phase Steel, Corrosion Fatigue, Fatigue Strength, Initial Fatigue Crack, Crack Propagation Rate, Stress Intensity Factor, Corrosion Pit

핵심용어: 복합조직강, 부식피로, 피로강도, 초기피로크랙, 크랙전파속도, 응력확대계수, 부식피트

Abstract

The only hardness of 2nd phase of martensite in dual phase steel which was composed of the martensite and ferrite was changed. Fatigue test was conducted by cantilever type of self-made rotated bending fatigue testing machine. The corrosion fatigue fracture behaviors of dual phase steel were investigated in 3% NaCl solution at $N_f$ = $1.5 imes$$10^5$ $N_f$=1.0 $ imes$ $10^6$ cycles. The fatigue strength was increased with increasing the hardness of 2nd phase. The size and number of corrsion pits were influenced by the 2nd phase hardness and pits remain constant in size just after they were transited into cracks. The life of crack initiation was effected by stress level. The shape of relation of $Delta$K and da/dn has smaller scattering in it in 3% NaCl solution than that in air. The higher the 2nd phase hardness is, the higher the corrosion fatigue life becomes. Corrosion fatigue fracture behavior was effected by mechanics in case of $N_f$=1.5$ imes$10$^5$$N_f$=1.5$ imes$10$^6$ cycles.