• Title/Summary/Keyword: Hot- Dip Galvanizing

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A Study on Dimensional Change after Heat Treatment and Optimal Chemical Composition of Steels with 1200 MPa Tensile Strength for Automotive Subframe (인장강도 1200 MPa 급 자동차 서브 프레임의 합금성분 최적화 및 열변형 거동 연구)

  • Jeong, Woo Chang
    • Journal of the Korean Society for Heat Treatment
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    • v.33 no.3
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    • pp.107-116
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    • 2020
  • Four air hardening steels with carbon, silicon, manganese, chromium, and molybdenum variations have been used in this study to find out the optimal chemical compositions of steels with over 1200 MPa tensile strength for automotive subframe. The dimensional changes after heat treatment were determined for two automotive parts with open and closed cross sections using 3D scanner. When four steels were austenitized at 900℃ for 30 seconds, cooled at 3℃/s, reheated to 450℃ for 10 seconds followed by air cooling to simulate hot-dip galvanizing treatment showed ultra high tensile strength over 1200 MPa. Rear floor cross member with open cross section revealed much bigger dimensional changes than subframe with closed cross section after heat treatment at 900℃ for 20 minutes followed by air cooling.

Formation Behavior of Intermetallic Dross Particles in Hot Dip Galvanizing Bath (용융아연 도금욕 내 드로스 생성에 관한 실험적 고찰)

  • Park, Ju-Hyeon;Baek, Du-Jin;Lee, Seok-Gyu
    • Proceedings of the Korean Institute of Surface Engineering Conference
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    • 2015.11a
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    • pp.216-216
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    • 2015
  • 용융아연 도금 공정에서 강판이 도금욕에 침적되는 동안 강판으로부터 용출되는 Fe는 도금욕 내 Al, Zn와 반응하여 다양한 형태의 드로스를 형성시키는 원인이 된다. 이들 드로스는 강판 표면에 다양한 형태의 결함을 야기하므로, 실제 도금 공정에서 도금욕 내 발생하는 드로스의 생성거동에 관한 이해는 필수적이다. 따라서 본 연구에서는 도금욕 내 $Fe_xAl_yZn_z$계 드로스 생성에 미치는 도금욕 내 Al 및 Fe 함량의 영향에 대해 고찰하였으며, in-situ sampling 기법 및 finger rotating method를 이용하였다.

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Application of Coating Thickness Control System (도금 두께 제어시스템의 개발 적용)

  • Choi, Il-Seop;Yoo, Seung-Ryul;Park, Han-Ku;Kwak, Young-Woo;Kim, Sang-Jun
    • Proceedings of the KIEE Conference
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    • 1995.07b
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    • pp.892-894
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    • 1995
  • This paper deals with developmeant and application of coating thickness control system in hot dip galvanizing process. According to the line conditions, such as line speed, strip size and target coating weight, a predictive preset model sets the initial oprating conditions. Referring the zine coating informations from the gauge, mean coating value controller adjusts the chamber pressure and horizontal distance between strip and air knife, while coating deviation controller adjusts the lip gap profile of the air knife. All adaptive gains are interactively calculated by numeric models based on the theoretical analysis. The operating result with this system effectively reduces the coating deviation in transverse direction as well as in longitudinal direction.

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Effect of Nickel Addition in Hot Dip Galvanizing of Mini-mill Steels Containing Silicon (실리콘을 함유한 미니밀 소재의 용융아연도금성에 미치는 니켈첨가의 영향)

  • Lee, H.J.;Kim, J.S.;Chung, J.H.
    • Journal of the Korean institute of surface engineering
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    • v.32 no.2
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    • pp.157-164
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    • 1999
  • In this study the effect of nickel addition on the coating weight of mini-mill steels containing silicon has been studied. It is shown that the pure zinc accelerated growth of the alloy layers occurred by a rapid growth of the zeta phase at 0.06%Si. The addition of 0.06%Ni to a pure zinc bath was found to be very effective in reducing the coating weight and promoting preferential development of the delta phase. The coating obtained by immersion in the Zn-Ni bath shows the presence of a nickel-rich region between the zeta phase and the eta phase. It is suggested that nickel prevents the rapid growth of the zeta phase due to the formation of the Zn-Ni-Fe ternary compound, which may act as a barrier to inward diffusion of zinc or iron at the zeta-eta boundary.

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Current Status of Zinc Smelting and Recycling (아연의 제련 및 리사이클링 현황)

  • Sohn, Ho-Sang
    • Resources Recycling
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    • v.28 no.5
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    • pp.30-41
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    • 2019
  • Global production of zinc is about 13 million tons and zinc is the fourth-most widely used primary metal in the world following iron, aluminum and copper. When zinc is recycled to produce secondary zinc, it can save about 75 % of the total energy that is needed to produce the primary zinc from ore, and in therms of $CO_2$ emissions reduced by about 40 %. However, since zinc is mainly used for galvanizing of steel, the recycling rate of zinc is about 25 %, which is lower than other metals. The raw materials for recycling of zinc include dusts generated in the production of steel and brass, sludge in the production process of non-ferrous metals, dross in the melting of zinc ingots or hot dip galvanizing, waste batteries, and metallic scrap. Among them, steelmaking dust and waste batteries are most actively recycled up to now. Most of the recycling process uses pyrometallurgical methods. Recently, however, much attention has been given to a combined process of pyrometallurgical and hydrometallurgical processes.

Development of High Erosion Resistant Fe-based Alloy for Continuous Hot Dipping Line (연속용융 도금라인 용 고내침식 Fe계 합금 개발)

  • Baek, Min-Sook;Kim, Yong-Cheol;Baek, Kyeong-Cheol;Kwak, Joon-Seop;Yoon, Dong-Joo
    • Journal of the Korean institute of surface engineering
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    • v.53 no.3
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    • pp.95-103
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    • 2020
  • In this study, the material used in the hot dip galvanizing equipment was poorly corrosion-resistant, so it was performed to solve the cost and time problems caused by equipment replacement. The theoretical calculation was performed using the DV-Xα method(Discrete Variational Local-density approximation method). The alloy (STS4XX series) of the equipment currently used has a martensite phase. Therefore, the theoretical calculation was performed by applying P4 / mmm, which is a tetragonal structure. The new alloy was chosen by designing theoretical values close to existing materials. Considering elements that contribute to corrosion, most have high prices. Therefore, the design was completed by adjusting the content using only the components of the reference material in the theoretical design. The final design alloys were chosen as D6 and D9. Designed D6 and D9 were dissolved and prepared using an induction furnace. After the heat treatment process was completed, the corrosion rate of the alloys was confirmed by using the potentiodynamic polarization test. The surface of the prepared alloys were processed horizontally and then polished to # 1200 using sand paper to perform potentiodynamic polarization test. Domestic products: 4.735 mpy (mils / year), D6: 0.9166 mpy, D9: 0.3372 mpy, alloys designed than domestic products had a lower corrosion rate. Therefore, the designed alloy was expected to have better erosion resistance.

Effects of Galvannealing Temperatures on Iron-Zn Intermetallic Compounds and Friction Characteristic of Galvannealed Coatings (갈바어닐링온도변화가 합금화용융아연코팅의 합금상과 마찰특성에 미치는 영향)

  • Lee, Jung-Min;Kim, Dong-Hwan;Lee, Seon-Bong;Kim, Dong-Jin;Kim, Byung-Min
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.32 no.12
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    • pp.1107-1114
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    • 2008
  • This paper is aimed to understand the effect of different galvannealing temperatures on the frictional properties and Fe-Zn intermetallic phases of the galvannealed (GA) coatings on steel sheets. Their galvannealing treatments were conducted at 465, 505, 515 and $540^{\circ}C$ for about 10s in the additional heating furnace of an industrial continuous hot-dip galvanizing line. The mechanical and the frictional properties of the coatings were estimated using nanoindentation, nanoscratch, micro vickers hardness tests and flat friction tests, which were performed at contact pressures of 4, 20 and 80MPa. Also, the correlation between the microstructure and the frictional properties of the GA coatings were investigated by SEM observation for the cross-section of the GA coating after and before flat friction tests. The results showed that the mechanical and the frictional properties of the coatings are strongly dependent on their phase distributions and microstructure. Especially, in low contact pressure of 4MPa the frictional properties of the coatings were dependent on the surface phases and morphology, while in high contact pressure of 80MPa it was influenced by their mechanical properties based on the dominant phase distributions.

Recent Progress in New Functional Coating Technology (신기능성 표면처리강판 제조기술의 최근 진보)

  • Kim, Tae-Yeop
    • Proceedings of the Korean Institute of Surface Engineering Conference
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    • 2012.05a
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    • pp.37-37
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    • 2012
  • The coated steels, mainly with zinc by either hot-dip galvanizing or electroplating, are widely used for panels of automotive, electrical appliances and construction, whose size of world market have reached 130 million tons in 2008. Current issues for the coated steels can be integrated in terms of high functionality, low cost, environment-friend and available resource. The best solution can be provided if thin layer coating with higher quality is produced by an eco-friendly process, and PVD, physical vapor deposition, can be an alternative practice to existing coating processes. PVD technologies have been very common ones in electronic and semiconductor industries, but recognized as non-profitable processes for the coated steels due to low process speed and lack of continuous operation skills. Systematic researches from 1990s in Europe, even though discouraged by a shutdown of the first Japanese PVD coating plant in 1999, have realized several continuous PVD coating plants, and also enhanced launching of developments in steel industries. To be successful with PVD coating technologies over existing ones, productivity to meet economics should be created from a highly sophisticated process. Some PVD technologies fit for the high-speed process will be introduced together with experiences from industrial applications.

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Surface Characteristics of the Galvannealed Coating in Interstitial-Free High Strengthen Steels Containing Si and Mn (Si, Mn함유 IF 고강도 합금화 용융아연도금강판의 표면특성)

  • Jeon, Sun-Ho;Chin, Kwang-Geun;Kim, Dai-Ryong
    • Korean Journal of Metals and Materials
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    • v.46 no.2
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    • pp.58-64
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    • 2008
  • Surface-void defects observed on the galvannealed(GA) steel sheets in Interstitial-free high-strengthened steels containing Si and Mn have been investigated using the combination of the FIB(Focused Ion Beam) and FE-TEM(Field Emission-Transmission Electron Microscope) techniques. The scanning ion micrographs of cross-section microstructure of defects showed that these defects were identified as craters which were formed on the projecting part of the substrate surface. Also, those craters were formed on the Si or Mn-Si oxides film through the whole interface between galvannealed coating and steel substrate. Interface enrichments and oxidations of the active alloying elements such as Si and Mn during reduction annealing process for galvanizing were found to interrupt Zn and Fe interdiffusion during galvannealing process. During galvannealing, Zn and Fe interdiffusion is preferentially started on the clean substrate surface which have no oxide layer on. And then, during galvannealing, crater is developed with consumption of molten zinc on the oxide layer.

Electrochemical Hydrogen Permeation Behaviors of Pre-Strained Fe-Mn-C TWIP Steel With or Without Zn Coating (소성인장변형 몇 아연도금된 Fe-Mn-C계 TWIP 강의 전기화학적 수소투과거동)

  • Sung Jin Kim
    • Corrosion Science and Technology
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    • v.22 no.4
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    • pp.297-303
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    • 2023
  • This study aimed to evaluate hydrogen permeation behaviors of pre-strained twinning-induced plasticity steel with or without Zn coating using electrochemical permeation technique. In contrast to un-strained and 30% strained samples, permeation current density was measured in the 60% strained sample. Tensile pre-straining at 60% involved microstructural modifications, including a high level of dislocation density and stacking fault with a semi-coherent twin boundary, which might provide a high diffusion path for hydrogen atoms. However, reproducibility of measurements of hydrogen permeation current was low due to non-uniform deformation and localized stress concentration. On the other hand, the permeation current was not measured in pre-strained TWIP steel with Zn coating. Instead, numerous blisters with some cracks were observed on the surface of the coating layer. In locally damaged Zn coating under tensile straining, hydrogen atoms could relatively easily permeate through the coating layer. However, they were trapped at the interface between the coating layer and the substrate, which might delay hydrogen penetration into the steel substrate.