• Title, Summary, Keyword: low-carbon steel

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A Study on J-Resistance Curve of Low-Carbon Steel Using Center Cracked Tension Specimen (CCT 시험편을 이용한 저탄소강의 J 저항곡선에 관한 연구)

  • 고성위
    • Journal of the Korean Society of Fisheries and Ocean Technology
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    • v.22 no.2
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    • pp.40-45
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    • 1986
  • In this paper, the I-resistance curve of low-carbon steel with 3 mm thickness was investigated for various crack ratios. The experiments were carried out for the center cracked tension (CCT) specimen with about 50 mm width on an instron machine. The plane stress fracture toughness obtained by the Simpson's formula was Ii. = 24.96 kgffmm. Simpson's formula which considers crack growth in obtaining J integral showed more conservative lin than Rice's and Sumpter's. For materials that may be approximated by the Ramberg and Osgood stress strain law, the relevant crack parameters like the J integral, load line displacement are approximately normalized. Crack driving forces in terms of the I integral are computed for low-carbon steel CCT specimen using the above estimation scheme. Comparison of the prediction with actual experimental measurements by Simpson's formula showed good agreement for several different sized specimen.

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Weldability of boron containing low carbon quenched and tempered 60kg/mm$^{2}$ steel with low cold cracking susceptibility (저탄소 B 첨가 60kg/mm$^{2}$급 저균열감수성 조질고강력강의 용접성)

  • 장웅성;김태웅;장래웅;엄기원
    • Journal of Welding and Joining
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    • v.7 no.1
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    • pp.59-66
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    • 1989
  • The weldability and joint performance were evaluated for newly developed 60kg/mm$\^$2/ steel which had low cold cracking susceptibility. The main results obtained were as follows; In case of quenched and tempered 60kg/mm$\^$2/ steels, it was very effective to improve weldability and joint performance by lowering carbon and Pcm level. Very small addition of about 0.001 to 0.002wt% boron exhibited an appreciable compensation effect on strength which was decreased by lowering carbon and Pcm level. As a result, the newly developed steel was able to be welded without preheating and exhibited superior joint performance to conventional steels.

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Laser cladding of Ni-base superalloy on low carbon steel (저탄소강에 대한 Ni기 초합금의 레이저 클래딩)

  • 이제훈;서무홍;김정오;한유희
    • Journal of Korean Society of Laser Processing
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    • v.2 no.2
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    • pp.34-41
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    • 1999
  • A RS840 $CO_2$laser and a powder auto-feeding apparatus have been used to deposit single tracks of Ni-base superalloy on low carbon steel. In this paper, the effects of laser cladding parameters on clad geometry, dilution and microhardness are studied. As a results, the w/h ratio of the clad layer increases with decreasing powder feed rate and increasing laser scan speed. Increase of powder density and decrease of specific energy have little effect on dilution. It was found that the clad layer of the highest hardness has a structure in which fine and leaf like phases are dispersed in ${\gamma}$Ni matrix.

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Development of Low-Velocity Impact Analysis Model of Carbon-Steel Laminates through Finite Element Analysis (유한요소해석을 통한 탄소섬유-연강 적층판의 저속 충격 해석 모델 개발)

  • Park, Byung-Jin;Lee, Dong-Woo;Song, Jung-Il
    • Composites Research
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    • v.31 no.5
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    • pp.215-220
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    • 2018
  • In this study, finite element analysis of Carbon-Steel Laminates with different layup pattern was conducted to verify similarity to the results of previous studies and to develop the effective model for low-velocity impact analysis. As in the experiment, Finite element analysis of the Fiber metal laminates (FMLs) with five different lamination patterns was carried out, and the impact resistance of the FMLs was confirmed by comparing the energy absorption ratio. The FMLs showed the higher energy absorption ratio than the mild steel having the same thickness, and it was confirmed that all the FMLs had the high energy absorption ratio over than 96%. In addition, the low-velocity impact analysis model proposed in this study can be effectively used to study composite forms and automotive structures.

Microstructure and Mechanical Properties of High-Strength Low-Carbon Bainitic Steels with Enhanced Deformability (높은 변형능을 갖는 저탄소 베이나이트계 고강도강의 미세조직과 기계적 특성)

  • Hwang, Byoungchul
    • Korean Journal of Materials Research
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    • v.23 no.8
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    • pp.423-429
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    • 2013
  • Recently, steel structures have increasingly been required to have sufficient deformability because they are subjected to progressive or abrupt displacement arising from structure loading itself, earthquake, and ground movement in their service environment. In this study, high-strength low-carbon bainitic steel specimens with enhanced deformability were fabricated by varying thermo-mechanical control process conditions consisting of controlled rolling and accelerated cooling, and then tensile and Charpy V-notch impact tests were conducted to investigate the correlation between microstructure and mechanical properties such as strength, deformability, and low-temperature toughness. Low-temperature transformation phases, i.e. granular bainite (GB), degenerate upper bainite(DUB), lower bainite(LB) and lath martensite(LM), together with fine polygonal ferrite(PF) were well developed, and the microstructural evolution was more critically affected by start and finish cooling temperatures than by finish rolling temperature. The steel specimens start-cooled at higher temperature had the best combination of strength and deformability because of the appropriate mixture of fine PF and low-temperature transformation phases such as GB, DUB, and LB/LM. On the other hand, the steel specimens start-cooled at lower temperature and finish-cooled at higher temperature exhibited a good low-temperature toughness because the interphase boundaries between the low-temperature transformation phases and/or PF act as beneficial barriers to cleavage crack propagation.

Fatigue Crack Growth Behavior in Ultrafine Grained Low Carbon Steel

  • Kim, Ho-Kyung;Park, Myung-Il;Chung, Chin-Sung;Shin, Dong-Hyuk
    • Journal of Mechanical Science and Technology
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    • v.16 no.10
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    • pp.1246-1252
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    • 2002
  • Ultrafine grained (UFG) low carbon (0.15 wt.% C) steel produced by equal channel angula. pressing (ECAP) was tested for investigating the effect of load ratio on the fatigue crack growth rate. Fatigue crack growth resistance and threshold of UFG steel were lower than that of asreceived coarse grained steel. It was attributed to the less tortuous crack path. The UFG steel exhibited slightly higher crack growth rates and a lower △Kth with an increase of R ratio. The R ratio effect on crack growth rates and △Kth was basically indistinguishable at lower load ratio (R >0.3), compared to other alloys, which indicates that contribution of the crack closure vanishes. The crack growth rate curve for UFG steel exhibited a longer linear extension to the lower growth rate regime than that for the coarse grained as-received steel.

Effect of Carbon and Nickel on Microstructure and Low Temperature Charpy Impact Properties of HSLA Steels (HSLA 강의 미세조직과 저온 샤르피 충격 특성에 미치는 탄소와 니켈의 영향)

  • Eom, Haewon;Cho, Sung Kyu;Cho, Young Wook;Shin, Gunchul;Kwon, Yongjai;Lee, Jung Gu;Shin, Sang Yong
    • Korean Journal of Materials Research
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    • v.30 no.4
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    • pp.184-196
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    • 2020
  • In this study, effects of carbon and nickel on microstructure and low temperature Charpy impact properties of HSLA (high strength low alloy) steels are investigated. To understand the complex phase transformation behavior of HSLA steels with high strength and toughness before and after welding processes, three kinds of HSLA steels are fabricated by varying the carbon and nickel content. Microstructure analysis, low temperature Charpy impact test, and Vickers hardness test are performed for the base metals and CGHAZ (coarse-grain heat affected zone) specimens. The specimens with the lowest carbon and nickel content have the highest volume fraction of AF, the lowest volume fraction of GB, and the smallest GB packet size. So, the low temperature Charpy absorbed energy of the CGHAZ specimen is the highest. The specimens with increased carbon and nickel content have the lowest volume fraction of AF, the highest volume fraction of GB, and the largest GB packet size. So, the low temperature Charpy absorbed energy of the CGHAZ specimen is the lowest.

Mechanical Property and Ductile-Brittle Transition Behavior of Ti-Nb-P Added Extra Low Carbon High Strength Steel Sheets (Ti-Nb-P 첨가 극저탄소 고강도 강판의 기계적 성질과 연성-취 천이거동)

  • Park J. J.;Lee O. Y.;Park Y. K.;Han S. H.;Chin K. G.
    • Korean Journal of Materials Research
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    • v.14 no.12
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    • pp.863-869
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    • 2004
  • The purpose of this research is to investigate the mechanical property and ductile-brittle transition temperature of Ti-Nb-P added extra low carbon interstitial free steel having a tensile strength of 440 MPa. The mechanical property and transition temperature of hot rolled steel sheets were more influenced by the coiling temperature rather than by the small amount of alloying element. Further, at the same composition, the property of the specimen coiled at low temperature was superior to that obtained at higher coiling temperature. The fracture surface of 0.005C-0.2Si-1.43Mn steel coiled at $630^{\circ}C$ showed a ductile fracture mode at $-100^{\circ}C$, but coiling at $670^{\circ}C$ showed a transgranular brittle fracture mode at $-90^{\circ}C$. The galvannealed 0.006C-0.07Si-1.33Mn steel sheet annealed at $810^{\circ}C$ has tensile strength and elongation of 442.8 MPa and $36.6\%$, respectively. The transition temperature of galvannealed 0.006C-0.07Si-1.33Mn steel sheet was increased with a drawing ratio, and the transition temperature of the galvannealed 0.006C-0.07Si-1.33Mn steel was $-60^{\circ}C$ at a drawing ratio of 1.8

Constitutive Relation of Alloy Steels at High Temperatures

  • Lee, Young-Seog
    • International Journal of Precision Engineering and Manufacturing
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    • v.6 no.4
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    • pp.55-59
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    • 2005
  • This paper presents a feasibility study whether Shida's constitutive equation being widely used for plain carbon steel in steel manufacturing industry can be extended to alloy steels with a due carbon equivalent model. T,he constitutive relation of the alloy steels (SAE9254, AISI52100 and AISI4140) is measured using hot deformation simulator (GLEEBLE 3500C) at high temperatures ($800^{\circ}C{\~}1000^{\circ}C$) within strain rates of $0.05{\~}40\;s^{-1}$. It has been found the predicted flow stress behavior (constitutive relation) of AISI52100 steel is in agreement with the measured one. On the other hand, the measured flow stress behavior of SAE9254 and AISI4140 steel partly concords with the predicted one when material experiences relatively high strain rate ($10{\~}40\;s^{-1}$) deformation at low temperature ($800^{\circ}C$). It can be deduced that, for AISI52100 steel, Shida's equation with the carbon equivalent model can be applicable directly to the roughing and intermediate finishing stand in hot rolling process for calculating the roll force and torque.

Effect of Carbon on Microstructure and Texture in Low Carbon Steels (저탄소강의 미세조직과 집합조직에 대한 탄소의 영향)

  • Jeong, Woo Chang
    • Journal of the Korean Society for Heat Treatment
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    • v.27 no.2
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    • pp.79-89
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    • 2014
  • The effect of carbon on the microstructure and texture of low carbon steels was investigated in a series of 1.6 Mn-0.3Cr-0.2Mo-0.001B steels with carbon ranging from 0.021 to 0.048%. Intensity of {111} orientation increased with decreasing the carbon content, resulting in the increase in $r_m$ value. The highest $r_m$ value of 1.30 was obtained in 0.021%C steel annealed at $820{\sim}850^{\circ}C$ according to the typical galvannealing heat cycle. Martensite volume fraction was not substantially affected by the annealing temperature. It was found that the fine and uniformly distributed martensite particles which were present in amounts of about 5% volume fraction were desirable for the highest $r_m$ value. The other factor affecting the high $r_m$ value was the preferred epitaxial growth of retained ferrite with {111} orientation into austenite during cooling.