• Title, Summary, Keyword: Dual Phase Steel

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Influence of pH in 3.5% NaCl aqueous solution on corrosion fatigue-fracture of dual phase steel (3.5% NaCl 수용액의 pH변화가 복합조직강의 부식피로파괴에 미치는 영향)

  • 오세욱;안호민;도영문
    • Journal of Ocean Engineering and Technology
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    • v.1 no.2
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    • pp.123-129
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    • 1987
  • Corrosion fatigue fracture of dual phase steel(SS41) and raw material steel(SS41) were investigated in 3.5% NaCl aqueous solution at PH 4,6,9 and 11. The fatigue limit of dual phase steel is increased approximately 1.8 times larger than that of raw material in air. The corrosion fatigue life of dual phase steel is about 5-10 times larger than that of raw material in 3.5% NaCl aqueous solution. The reduction of fatigue life is larger for the acidsalt solution than for the alkali salt solution. The reduction of stress level on the reduction ratio of corrosion fatigue life is large as pH 6-11. The reduction ratio of corrosion fatigue life of dual phase steel and raw material is nearly coincided at pH 2. While at pH4-2 the reduction ratio of corrosion fatigue life only depends on the corrosion effect. It has been found that the corrosion resistance effect of dual phase steel is smaller than that of raw material in corrosion fatigue crack propagation rate. As pH below 6 is changed, it can be clearly observed from raw material that the brittle intergranular fracture is characterized, and from the above result, the influence of corrosion of dual phase steel is small.

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Dry sliding wear behavior of plain low carbon dual phase steel by strain hardening and oxidation (가공경화와 산화층 형성에 의한 이상조직 저탄소강의 건식 미끄럼 마멸 거동)

  • Yu, H.S.;Kim, Y.S.
    • Proceedings of the Korean Society for Technology of Plasticity Conference
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    • pp.149-152
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    • 2006
  • Dry sliding wear behavior of low carbon dual phase steel, of which microstructure consists of hard martensite in a ductile ferrite matrix, has been investigated. The wear characteristics of the dual phase steel was compared with that of a plain carbon steel which was normalized at $950^{\circ}C$ for 30min and then air-cooled. Dry sliding wear tests were carried out using a pin-on-disk type tester at various loads of 1N to 10N under a constant sliding speed condition of 0.2m/sec against an AISI 52100 bearing steel ball at room temperature. The sliding distance was fixed as 1000m for all wear tests. The wear rate was calculated by dividing the weight loss measured to the accuracy of $10^{-5}g$ by the specific gravity and sliding distance. The worn surfaces and wear debris were analyzed by SEM, EDS and a profilomter. Micro vickers hardness values of the cross section of worn surface were measured to analyze strain hardening behavior underneath the wearing surfaces. The were rate of the dual phase steel was lower than the plain carbon steel. Oxidation on the sliding surface and strain hardening were attributed for the higher wear resistance of the dual phase steel.

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Influence of Notch Change on Corrosion Fatigue Fracture in F.E.M. Dual phase Steel of SS41 Steel (SS41강의 F.E.M.복합조직강에서 노치변화가 부식피로파괴에 미치는 영향)

  • 도영민;이규천
    • Journal of the Korean Society of Safety
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    • v.16 no.2
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    • pp.44-50
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    • 2001
  • The rotated bending fatigue test was conducted in air md in 3.5% NaCl salt solution to investigate the fatigue fracture behaviour of raw material and F.E.M dual phase steel made from raw material(SS41) by a suitable heat treatment. This study has compared the initial microcrack creation of material by tensile test with that by fatigue test. And the rotated bending test of cantilever type under the condition of 3.5% NaCl salt solution and air has investigated the corrosion fatigue fracture behaviour with the variation of stress concentration factor determined by each of notch shapes. The initial microcrack have been developed in fragile grainboundary with general corrosion occurring in raw material : in the pits built up by corrosion in F.E.M. dual phase steel because pits bring out stress concentration. It is small that the degree of decrease in corrosion fatigue life for F.E.M. dual phase steel compared with raw material because the notch sensitivity of F.E.M. dual phase steel is lower than raw material in reason of characteristics with two-phase construction.

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A Study on Strain-Void Growth Mechanism of Dual Phase Steel by Statistical Method (통계적 방법을 이용한 복합조직강의 변형률과 보이드 성장거동에 관한 연구)

  • 오경훈;유용석;오택열
    • Proceedings of the Korean Society of Precision Engineering Conference
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    • pp.533-538
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    • 2000
  • Ductile fracture of dual phase steel begins with void nucleation, at martensite-ferrite interface of deformed martensite particle. In this study, void nucleation, growth, and coalescence under various strain were studied in dual phase steel. Therefore, by means of the heat treatment of low carbon steel, the study deals with void nucleation and growth for ferrite grain size and martensite volume fraction of dual phase steel using statistical method. Void nucleation and growth with increasing strain are shown depend upon the ferrite grain size. Voids volume fraction generally increase as ferrite grain size decease.

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Sliding Wear Mechanism of Ultra-Fine Grained Low Carbon Dual Phase Steel as n Function of Applied Load (결정립 미세화에 따른 이상조직 탄소강의 하중에 따른 마멸 기구)

  • Yu, H.S.;Yi, S.K.;Shin, D.H.;Kim, Y.S.
    • Proceedings of the Korean Society for Technology of Plasticity Conference
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    • pp.421-424
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    • 2007
  • Dry sliding wear behavior of ultra-fine grained (UFG) plain low carbon dual phase steel, of which microstructure consists of hard martensite in a ductile ferrite matrix, has been investigated. The wear characteristics of the UFG dual phase steel was compared with that of a coarse grained dual phase steel under various applied load conditions. Dry sliding wear test were carried out using a pin-on-disk type tester at various loads of 1N to 100N under a constant sliding speed condition of 0.20m/s against an AISI 52100 bearing steel ball at room temperature. The sliding distance was fixed as 1000m for all wear tests. The wear rate was calculated by dividing the weight loss, measured to the accuracy of 10-5g by the specific gravity and sliding distance. The worn surfaces and wear debris were analyzed by SEM, EDS and profilometer. Micro-vickers hardness of the cross section of worn surfaces were conducted to analyze strain hardening underneath the contact surfaces. The wear mechanism of the UFG dual phase steel was investigated with emphasis on the unstable nature of the grain boundaries of the UFG microstructure.

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Sliding Wear Mechanism of Ultra-Fine Grained Low Carbon Dual Phase Steel as a Function of Applied Load (경정립 미세화에 따른 이상조직 탄소강의 하중에 따른 마멸기구)

  • Yu, H.S.;Yi, S.K.;Shin, D.H.;Kim, Y.S.
    • Transactions of Materials Processing
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    • v.16 no.4
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    • pp.299-303
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    • 2007
  • Dry sliding wear behavior of ultra-fine grained(UFG) plain low carbon dual phase steel, of which microstructure consists of hard martensite in a ductile ferrite matrix, has been investigated. The wear characteristics of the UFG dual phase steel was compared with that of a coarse grained dual phase steel under various applied load conditions. Dry sliding wear test were carried out using a pin-on-disk type tester at various loads of 1N to 100N under a constant sliding speed condition of 0.20m/s against an AISI 52100 bearing steel ball at room temperature. The sliding distance was fixed as 1000m for all wear tests. The wear rate was calculated by dividing the weight loss, measured to the accuracy of 10-5g by the specific gravity and sliding distance. The worn surfaces and wear debris were analyzed by SEM, EDS and profilometer. Micro-vickers hardness of the cross section of worn surfaces were conducted to analyze strain hardening underneath the contact surfaces. The wear mechanism of the UFG dual phase steel was investigated with emphasis on the unstable nature of the grain boundaries of the UFG microstructure.

Microstructure and deformation behavior of nanostructured dual-phase steel (나노 결정립 이상 조직강의 미세조직 및 변형거동)

  • Ko, Y.G.;Lee, K.M.;Lee, C.W.;Kum, D.H.;Shin, D.H.
    • Proceedings of the Korean Society for Technology of Plasticity Conference
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    • pp.445-448
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    • 2009
  • The present work deals with microstructure and tensile deformation of nanostructured dual-phase steel consisting of ferrite and martensite phases. Prior to deformation, a fully martensite phase is prepared and then processed by equal channel angular pressing (ECAP) and subsequent annealing. Room-temperature tensile properties are examined and compared to those of dual-phase steels with coarse grains. Due to the combined effects coming from the grain refinement of both phases and their uniform distributions, the nanostructured dual-phase steel exhibits better strength and ductility than coarse grained counterpart, achieving ${\sim}1\;GPa$ and ${\sim}20%$ for tensile strength and elongation, respectively.

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Effect of Prior Deformation on the Sliding Wear of Ultra-fine Grained Ferrite-Martensite Dual Phase Steel (초기 소성변형이 초미세 결정립 페라이트-마르텐사이트 이상조직 탄소강의 건식 미끄럼마멸 특성에 미치는 영향)

  • Park, J.K.;Yi, S.K.;Shin, D.H.;Kim, Y.S.
    • Proceedings of the Korean Society for Technology of Plasticity Conference
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    • pp.521-524
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    • 2008
  • Effect of prior deformation on the sliding wear of the ultra-fine grained (UFG) ferrite-martensite dual phase (DP) steel was investigated. The UFG DP steel was fabricated by the ECAP and subsequent intercritical annealing. The steel was cold rolled before the wear test, and the effect of the prior deformation on the wear was examined. The wear tests were carried out at various loads against a bearing steel ball. The wear rate of the UFG DP steel that did not experience the prior deformation was higher than that of the coarse-grained (CG) DP steel, because of more severe surface shear deformation. The wear rate of the specimens with prior deformation was much higher than that of the specimen without prior deformation. The deformed CG DP specimen showed higher rate than the deformed UFG DP specimen, and the rate-variation of the CG DP steel was much bigger under the same test condition.

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Development of Al-added High Strength Galvannealed Daul Phase Steel Sheets

  • Kim, Dong-Eun;Han, Young-Chul;Ko, Heung Seok;Kim, Jong-Gi;Moon, Man-Been
    • Corrosion Science and Technology
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    • v.10 no.5
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    • pp.162-166
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    • 2011
  • Effects of chemical compositions and manufacturing conditions on mechanical properties and microstructures were investigated in order to obtain galvannealed high strength dual phase steel sheets with superior mechanical properties and coating properties. An intercritical annealing between Ac1 and Ac3 was conducted to produce the DP (dual phase) steel sheets, followed by quenching to room temperature. The purposes of Al addition are to reduce the iron oxidation with chemical composition (Si, Mn etc.) and to improve the wettability by liquid zinc. The present study will focus on the characterization for making dual phase steel sheets and enhancing the galvanizability of Al added DP steel sheets about continuous annealing line in CGL.

Effect of the change of second phase hardness on corrosion fatigue behavior of dual phase steel in 3% nacl solution (3% NaCl 수용액중에서 복합조직강의 부식피로거동에 미치는 제2상 속도변화의 영향)

  • 오세욱;김웅집
    • Journal of Ocean Engineering and Technology
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    • v.6 no.2
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    • pp.85-93
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    • 1992
  • 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\times$$10^5$ $N_f$=1.0 $\times$ $10^6$ cycles. The fatigue strength was increased with increasing the hardness of 2nd phase. The size and number of corrsion pits were influenced by the 2nd phase hardness and pits remain constant in size just after they were transited into cracks. The life of crack initiation was effected by stress level. The shape of relation of $\Delta$K and da/dn has smaller scattering in it in 3% NaCl solution than that in air. The higher the 2nd phase hardness is, the higher the corrosion fatigue life becomes. Corrosion fatigue fracture behavior was effected by mechanics in case of $N_f$=1.5$\times$10$^5$$N_f$=1.5$\times$10$^6$ cycles.

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