• Title, Summary, Keyword: low-carbon steel

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The Effect of Solution Treatment on Intergranular Corrosion Resistance of a New Type Ultra Low Carbon Stainless Steel

  • Julin, Wang;Nannan, Ni;Qingling, Yan;Lingli, Liu
    • Corrosion Science and Technology
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    • v.6 no.3
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    • pp.140-146
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    • 2007
  • In the paper, with corrosion velocity measurement and metallographic observation on specimens after sulfuric acid/ferric sulfate boiling experiment, intergranular corrosion tendency of the new type ultra low carbon stainless steel developed by ourselves which experienced solution treatment at different temperatures was evaluated. A VHX 500 super depth field tridimensional microscope was used to observe corrosion patterns on the sample surfaces. The depth and width of grain boundary corrosion groove were measured by the tridimensional microscope, which indicated that the corrosion degrees of the samples which received solution treatment at different temperatures are quite different. Transgranular corrosion at different degree occurred along with forged glide lines. After comparison it was proved that the stainless steel treated at $1100^{\circ}C$ performs very well against intergranular corrosion.

Ultrafine Grained Steels Processed by Equal Channel Angular Pressing

  • Shin, Dong Hyuk
    • Corrosion Science and Technology
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    • v.5 no.1
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    • pp.23-26
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    • 2006
  • Recent development of ultrafine grained (UFG) low carbon steels by using equal channel angular pressing (ECAP) and their room temperature tensile properties are reviewed, focusing on the strategies overcoming their inherent mechanical drawbacks. In addition to ferrite grain refinement, when proper post heat treatments are imposed, carbon atom dissolution from pearlitic cementite during ECAP can be utilized for microstructural modification such as uniform distribution of nano-sized cementite particles or microalloying element carbides inside UFG ferrite grains and fabrication of UFG ferrite/martensite dual phase steel. The utilization of nano-sized particles is effective on improving thermal stability of UFG low carbon ferrite/pearlite steel but less effective on improving its tensile properties. By contrast, UFG ferrite/martensite dual phase steel exhibits an excellent combination of ultrahigh strength, large uniform elongation and extensive strain hardenability.

Strength Change in Ultra Low Carbon Steel due to Carburizing Heat Treatment for Hot Press Forming (HPF 적용을 위한 극저탄소강의 강도에 미치는 침탄 열처리의 영향)

  • Kang, Soo Young
    • Korean Journal of Metals and Materials
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    • v.50 no.6
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    • pp.433-438
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    • 2012
  • Strength change in ultra low carbon steel carburized at $880^{\circ}C$ and $930^{\circ}C$ for 10, 30, 60 and 120 minutes was investigated. The results were analyzed by a tensile test, chemical composition analysis, optical microscopy and scanning electron microscopy. Stress in the 0.5% strain specimen in the tensile test increased as the time treated at $880^{\circ}C$ and $930^{\circ}C$ increased, because the carbon diffusion layer and the martensite of the specimen increased with increasing treatment time. Martensite was found in the ferrite region in the specimen treated at $880^{\circ}C$, which is attributed to grain boundary diffusion.

Effect of Mn and S Contents on Edge Cracking of Low Carbon Steels in Mini-Mill Process (미니밀공정 중 저탄소강의 에지크랙에 미치는 Mn 및 S의 영향)

  • 곽재현;정진환;조경목
    • Transactions of Materials Processing
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    • v.9 no.1
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    • pp.66-71
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    • 2000
  • The present study tackles the metallurgical subjects involving the thin slab-direct hot rolling process, i.e. mini-mill process. In order to clarify the effect of chemical composition of steel and MnS precipitation behaviors on the development of edge cracking during hot rolling, the content of manganese and sulfur in low carbon steel was varied and the isothermal treatment prior to roughing was applied. Edge cracking during roughing in the hot-rolling process of mini-mill was effectively prevented by means of the isothermal treatment at 115$0^{\circ}C$ for 5 minutes in the 0.4% manganese steel containing sulfur lower than 0.013%. With the increase in manganese content in low carbon steel, coarser MnS developed. The edge cracking index which denotes the total length of edge crack per unit edge-length of rolled specimens was proposed in this paper. It was found that the edge cracking index linearly decreased with the increase in the ratio of MnS.

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The Effect of Microstructure and Mechanical Property with Heat Treatment Condition in Boron-Treated Low Carbon Low Alloy Steel (저탄소.저합금 보론 첨가강의 열처리 조건에 따른 미세조직과 기계적 성질의 영향)

  • Son, J.Y.;Park, B.C.;Sung, H.;Kim, Y.S.
    • Proceedings of the Korean Society for Technology of Plasticity Conference
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    • pp.146-149
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    • 2007
  • The effects of boron additions in steels have long been recognized as very important, mainly with respect to hardnability of heat treatable steels. The systematics of structure and properties of boron steels will then be illustrated in the context of low-alloy steels with carbon contents raging from 0.05 to 0.25% and boron contents 0-130 ppm. we investigated the effect of the microstructure and mechanical properties with heat treatment condition of the boron-treated(0.0013 ppm) low carbon(0.2 %C) low alloy steel. The specimens were austenitised for 5 and 10, 15 min at $880{\sim}940^{\circ}C$(with/without tempered at 150, 180 and $210^{\circ}C$ for the various periods of time from 60 min to 120 min) After heat treatment, mechanical properties were measured by tensile test and hardness test. For analysis of microstructure, Optical/SEM analysis and XRD were carried out.

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Welding Characteristics of Low Carbon Steel with Al Coating Condition by Nd:YAG Laser (저탄소강의 알루미늄코팅조건에 따른 Nd:YAG 레이저 용접특성)

  • Kim, Jong-Do;Lee, Jung-Han;Kim, Sook-Hwan;Kim, Ki-Chol
    • Proceedings of the KSME Conference
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    • pp.1317-1321
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    • 2007
  • Aluminized steel sheet that Al coated on low carbon steel has a excellent heat resistance, thermal reflection and corrosion resistance. It has applied to fuel tank, automotive exhaust systems, etc. Laser weldability of the aluminized steel for the full penetration welding will be described in this paper. We focused on the effect of Al coating conditions on weld strength. For these objectives, aluminized steel sheets that has various thickness and coating weight were prepared for laser welding. And then, tensile-shear and hardness test were carried out. At that same time, Al content mixed in weld after laser welding was evaluated and investigated a correlation between the mixed Al and mechanical properties. Besides, as removing partially coating layer, weldability has been investigated according to position of coating layer. As a result of this study, as increasing Al content in weld, tensile-shear strength was decreased. Also it was identified that Al of coating layer caused grain growth.

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A Development of Connection Piece Steel Casting for the Offshore Structures Using High Impact Value with Low Temperature & High Strength Casting Steel Material (고강도 및 저온 고충격 주강소재를 이용한 해양플렌트용 커넥트 주강부품 개발)

  • Kim, Tae-Eon;Park, Sang-Sik;Kang, Chung-Gil
    • Journal of Korea Foundry Society
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    • v.30 no.4
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    • pp.151-156
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    • 2010
  • The high-strength low-alloy (HSLA) steels have low carbon contents (0.05~0.25% C) in order to produce adequate formability and weldability, and they have manganese contents up to 1.7%. Small quantities of silicon, chromium, nickel, copper, aluminum, molybdenum are used in various combinations. The results contained in this paper can provide the valuable information on the development of $-40^{\circ}C$ low temperature HSLA. Furthermore, the present experimental data will provide important database for casting steel materials of the offshore structure.

Welding behavior between Zn-coated steel plate and free cutting carbon steel rod by Nd:YAG laser beam (Nd:YAG 레이저빔을 이용한 아연도금강판(SECC)과 쾌삭강봉(SUM24L)의 용접에 관한 연구)

  • 노영태;김병철;김도훈;윤갑식
    • Journal of Korean Society of Laser Processing
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    • v.4 no.3
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    • pp.30-39
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    • 2001
  • This work was tamed out to apply a laser welding technique in joining between a Zn coated low carbon steel plate(SECC) and a free cutting carbon steel shaft(SUM24L) with or without W coating. Experiments were carried out and analysed by applying the FD(factorial design)method to obtain the optimum Laser welding condition. Optical microscopy, SEM, TEM and XRD analyses were performed in order to observe the microstructures in the fusion zone and the HAZ. Mechanical properties of the welded specimens were examined by microhardness test, tensile test and twist test. There was no flawed Zn in the fusion zone by EDS analysis. This means that during the welding process, Zn gas could be eliminated by appropriate shielding gas flow rate and butt welding gap. Ni coating itself did not influence on the tensile strength and hardness. However, twist bending strength and the weld depth of the Ni-coated free cutting carbon steel were lower as compared with those of the uncoated free cutting carbon steel. It was attributed to a lower absorbance of laser beam to the shin Ni surface. According to the results of the factorial design tests, the twist bending strength of welded specimens was primarily affected by pulse width, laser power, frequency and speed.

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Effects of Carbon and Sulfur Content on Mechanical Properties of High Purity Steel (고순도강의 기계적 성질에 미치는 탄소 및 황 함량의 영향)

  • Yoon, Jeong-Bong;Kim, Sung-Il;Kim, In-Bea
    • Korean Journal of Metals and Materials
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    • v.47 no.6
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    • pp.331-337
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    • 2009
  • To lower the annealing temperature and the deviation of the mechanical properties of bake hardening steels, high purity steels were investigated. The steels were characterized by treating at low recrystallization temperature. It was confirmed that the strengthening originated from the solid solution of carbon and the ferrite grain refinement by fine MnS precipitates as carbon and sulfur contents increased in high purity steels. However, it was observed that there was no more increase of strength in steels containing over 40 ppm of carbon. It was considered that the excess carbon formed either the carbon cluster or the low temperature unstable carbides which had the negligible effect on the strengthening because they were reported to be highly coherent with the matrix. The carbon cluster and unstable carbides could be transformed to the stable cementite during bake hardening treatment. MnS was not observed in the high purity steel containing 5 ppm S, resulting in very coarse recrystallized grains and good ductility. As sulfur content increased, the recrystallized grain size decreased due to the formation of the fine MnS precipitates.

Microstructures and Mechanical Properties of Friction Stir Welded High Strength Steels far Shipbuilding (선급용 고장력강 FSW접합부의 미세조직 및 기계적 성질)

  • 장웅성;최기용
    • Journal of Welding and Joining
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    • v.20 no.3
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    • pp.67-73
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    • 2002
  • In an attempt to evaluate the feasibility of friction stir welding(FSW) for joining carbon steels, microstructures and mechanical properties of friction stir welded carbon steels with different grain structures were investigated. In comparison of O-type stir zone(SZ) appeared in various aluminium alloys, configuration of SZ in friction stir welded carbon steels displayed U-type. Plastically deformed pearlite band structure was identified to surround the SZ, indicating the existence of so-called thermo-mechanically affected zone(TMAZ). However, the TMAZ of carbon steels was much narrower than that of Al alloys. The microstructures of both stir zone and TMAZ revealed bainite matrix in a conventional carbon steel for shipbuilding, while, in the same region, ferrite matrix microstructures were formed in a low carbon fine grained steel. The conventional carbon steel showed superior stirring workability to that of the fine grained carbon steel. The yield and tensile strength of the friction stir welded joints were comparable to those of the base metals, and the elongation in welded joints demonstrated excellent ductility. Absorbed energy in SZ of the fine grained carbon steel was ten times higher than that obtained from conventional submerged arc weld metal of the same steel. Based on these results, the application FSW to carbon steels was found to be feasible.