• Title/Summary/Keyword: Dual Phase(DP)

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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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    • 2008.05a
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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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Microstructural and Mechanical Analysis of a Friction Stir Welded Joint of Dissimilar Advanced High-Strength Steels (초고강도 합금강의 이종마찰교반 접합부에서의 미세조직 특성 및 기계적 물성 연구)

  • Lee, J.W.;Cho, H.H.;Mondal, Mounarik;Das, Hrishikesh;Hong, S.T.
    • Transactions of Materials Processing
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    • v.29 no.1
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    • pp.11-19
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    • 2020
  • For microstructural analysis of a friction stir welded (FSWed) joint of advanced high-strength steels, dual phase (DP) and complex phase (CP) steels, are studied. FSWed joints are successfully fabricated in the following four cases: (i) DP/DP; (ii) CP/CP; (iii) DP/CP, where the advancing side is DP and the retreating side is CP; (iv) CP/DP, where the advancing side is CP and the retreating side is DP. The stir zone (SZ) of (i) the DP/DP joint mainly consists of lath martensite, while the stir zone of (ii) the CP/CP joint consists not only of lath martensite but also of bainite. In the case of (iii) DP/CP and (iv) CP/DP, they exhibit a similar microstructure including acicular-shaped phases in the joints; however, cross-sections of the joints show differences in material mixing in each case. In (iv) the CP/DP joint, temperature towards the CP steel is sufficient to cause softening, thus leading to better mixing than that in (iii) DP/CP. The phases of the SZ in each of the four cases are formed by phase transformation during the FSWed process; however, the transformed phase volume fraction of CP steel is lower than that of DP steel, indicating that dynamic recrystallization occurs mainly in CP steel. The hardness values of the SZ are significantly higher than those of the base materials, especially, the SZ of (iii) the DP/CP joint has the highest value due to highest fraction of lath martensite.

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.

Nanoindenter Test of 680MPa Dual Phase Steel Charged with Hydrogen (수소주입시킨 680MPa DP강의 나노인덴터 시험)

  • Choi, Jong-Woon;Park, Jae-Woo;Kang, Kae-Myung
    • Journal of the Korean institute of surface engineering
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    • v.47 no.1
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    • pp.33-38
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    • 2014
  • Nanoindentater tests were conducted to conducted nanoindentation microhardness of the individual phase of ferrite and martensite of 680MPa dual-phase (DP) steel charged with hydrogen. Hydrogen was charged by electrochemical method with current densities of 150, $200mA/cm^2$ for charging times of 5, 10, 25, 50 hours, respectively. Nanoindenter test results showed that the nanoindentation microhardnesses of ferrite phase of DP steel were varied from min. 1.58 GPa to max. 2.82 GPa, and the nanoindentation microhardnesses of martensite phase varied from min. 3.19 GPa to max. 5.16 GPa with the variation of hydrogen charging conditions. It was observed that the variations of the nanoindention microhardnesses of martenstie phase were higher than those of ferrite phases. It was thought that martensite phase in the 680MPa DP steel was more sensitive than ferrite phase to hydrogen embrittlement.

The Effect of Mo and Cr addition on the Deep Drawability of Dual Phase Steel Sheets (이상조직강판의 성형특성에 미치는 Mo와 Cr첨가의 영향)

  • Han, Seong Ho;Ahn, Yeon Sang;Chin, Kwang Geun;Kim, In Bae
    • Korean Journal of Metals and Materials
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    • v.46 no.11
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    • pp.713-724
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    • 2008
  • The need to lower the weights of automotive vehicle and to improve the safety of cars has resulted in the development of high strength steels such as TRIP(Transformation Induced Plasticity) and DP (Dual Phase) steel. It is well known that the higher strength of steel shows the poorer press formability. Among the high strength steels, DP steel shows several good characteristics such as low yield ratio, high initial n value, high elongation, high bake hardenability and anti-aging property. However, there's a certain limit in application of DP steels to the automotive panel parts because their poor deep drawbility caused by martensite. In this study, the effect of alloying elements on the deep drawability and recrystallization texture in TS 440MPa grade DP steel with 0.015~0.02% carbon has been investigated on the base of SEM, TEM, XRD and EBSD analysis.

Effect of Si content on Nugget Diameter of Electric Resistance Spot Welded Dual Phase Steel (DP강의 전기저항점용접부 너깃직경에 미치는 Si 함량의 영향)

  • Kong, Jong-Pan;Kang, Gil-Mo;Han, Tae-Kyo;Chin, Kwang-Geun;Kang, Chung-Yun
    • Journal of Welding and Joining
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    • v.29 no.5
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    • pp.99-105
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    • 2011
  • In this study, effect of Si content on nugget diameter in electric resistance spot welded dual-phase(DP) steel was investigated. The cold rolled DP steels with different Si content (0.5, 1.0, 1.5, 2.0 wt.%) were used and thickness of those sheet was 1.2mm. With increasing Si content, nugget diameter was increased at the same welding current. This is attributed to increase of heat input result from high resistivity. Also, nugget diameter was increased with an increase in Si content for the same heat input. For this reason, the melting point of DP steel is lowered with an increase in the Si content. And solid DP steel can easily be transformed to a liquid phase because the low melting point. Finally, a prediction formula for the nugget diameter(N.D.) could be obtained in terms of heat input(Q) and melting point(M.P) as follows: N.D.(mm) = 0.11Q(J) - 0.0031 M.P.($^{\circ}C$) + 0.32.

Effects of Silicon on Galvanizing Coating Characteristics in Dual Phase High Strength Steel (복합조직형 고강도 용융아연 도금강판의 도금특성에 미치는 강중 Si의 영향)

  • Jeon, Sun-Ho;Chin, Kwang-Geun;Shin, Kwang-Soo;Lee, Joon-Ho;Sohn, Ho-Sang
    • Korean Journal of Metals and Materials
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    • v.47 no.7
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    • pp.423-432
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    • 2009
  • In the galvanizing coating process, the effects of the silicon content on the coatability and wettability of molten zinc were investigated on Dual-Phase High Strength Steels (DP-HSS) with various Si contents using the galvanizing simulator and dynamic reactive wetting systems. DP-HSS showed good coatability and a well-developed inhibition layer in the range of Si content below 0.5 wt%. Good coatability was the results of the mixed oxide $Mn_{2}SiO_{4}$, being formed by the selective oxidation on the surface, with a low contact angle in molten zinc and a large fraction of oxide free surface that provided a sufficient site for the molten zinc to wet and react with the substrate. On the other hand, with more than 0.5 wt%, DP-HSS exhibited poor coatability and an irregularly developed inhibition layer. The poor coatability was due to the poor wettability that resulted from the development of network-type layers of amorphous ${SiO}_{2}$, leading to a high contact angle in molten zinc, on the surface.

Simulation of Texture Evolution and Anisotropy Behavior in Dual Phase Steels during Deep Drawing Process (DP강의 디프드로잉 시 집합조직 발달과 이방성 거동 시뮬레이션)

  • Song, Young-Sik;Kim, Dae-Wan;Yang, Hoe-Seok;Han, Sung-Ho;Chin, Kwang-Gun;Choi, Shi-Hoon
    • Korean Journal of Metals and Materials
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    • v.47 no.5
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    • pp.274-282
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    • 2009
  • To investigate the evolution of deformation texture in dual phase (DP) steels during deep-drawing deformation, deep-drawing experiments were performed. Microtexture measurements were conducted using electron backscattered diffraction (EBSD) to analyze texture evolution. A rate-sensitive polycrystal model was used to predict texture evolution during deep-drawing deformation. In order to evaluate the strain path during deep-drawing deformation, a steady state was assumed in the flange part of a deep-drawn cup. A ratesensitive polycrystal model successfully predicted the texture evolution in DP steels during deep-drawing deformation. The final stable orientations were found to be strongly dependent on the initial location in the blank. Texture analysis revealed that the deep drawability of DP steels decreases as the true strain in the radial direction of the deep-drawn cup increases during deep-drawing deformation.

Transmission Performance Comparison of Direction Detection-Based 100-Gb/s Modulation Formats for Metro Area Optical Networks

  • Chung, Hwan Seok;Chang, Sun Hyok;Lee, Jonghyun;Kim, Kwangjoon
    • ETRI Journal
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    • v.34 no.6
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    • pp.800-806
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    • 2012
  • Transmission performances of direct detection-based 100-Gb/s modulation formats are investigated and compared for metro area optical networks. The effects of optical signal-to-noise ratio sensitivity, chromatic dispersion, cross-channel nonlinearity, and transmission distance on the performance of differential 8-ary phase-shift keying (D8PSK), differential phase-shift keying plus three-level amplitude-shift keying (DPSK+3ASK), and dual-carrier differential quaternary phase-shift keying (DC-DQPSK) are evaluated. The performance of coherent dual-polarization quadrature phase-shift keying (DP-QPSK) with block phase estimation and coherent DP-QPSK with digital differential detection are also presented for reference. According to our analysis, all three direct detection modulation formats could transmit a 100-Gb/s signal over several hundred kilometers of a single-mode fiber link. The results also show that DC-DQPSK outperforms D8PSK and DPSK+3ASK, and the performance of DC-DQPSK is comparable to that of coherent DP-QPSK with digital differential detection. The maximum transmission distance of DC-DQPSK is over 1,000 km, which is enough distance for metro applications.

A Study of Automobile Product Design using Hole Expansion Testing of High Strength Steels (고장력강의 구멍 확장 실험을 이용한 자동차부품 설계연구)

  • Park, B.C.;Bae, K.U.;Gu, S.M.;Jang, S.H.;Hong, S.H.;Kim, Y.S.
    • Transactions of Materials Processing
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    • v.19 no.6
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    • pp.337-343
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    • 2010
  • Current need of weight reduction in automotive part increases the application for high strength steel (HSS). The various types of high strength steels have been used to produce chassis part, control arms and trailing arms for weight reduction and increasing of fatigue durability such as dual phase steel (DP) and ferrite bainite steel (FB). But, DP and FB steels have proven to show inferiority in durability as well as press formability. Edge cracking occurred often in flange forming and hole expansion processes is the major failure encountered. This paper discussed the behavior of edge stretchability of high strength steel of DP and FB steels. Experimental works have been conducted to study the effect of punch clearance and burr direction on hole expansion ratio (HER). Also finite element simulation (FEM) has been preformed to clarify the mechanism of flange crack and support the experimental results on HER of DP and FB steels. It was simulated the whole process of blanking process following by hole expansion process and ductile fracture criterion named the modified Cockcroft-Latham model which was used to capture the fracture initiation. From the hole expansion tests and FEM simulation studies it was concluded that ferrite bainite steel showed better stretch-flangeability than dual phase steel. It was attributed to the lower work hardening rate of ferrite bainite steel than dual phase steel at the sheared edge.