• Title/Summary/Keyword: Galvannealed Coating

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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.

Structure of Surface Oxide Formed on Zinc-Coated Steel Sheet During Hot Stamping

  • Shota Hayashida;Takuya Mitsunobu;Hiroshi Takebayashi
    • Corrosion Science and Technology
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    • v.23 no.3
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    • pp.221-227
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    • 2024
  • During hot stamping of hot-dip zinc-coated steel sheets such as hot-dip galvanized steel sheets and hot-dip galvannealed steel sheets, an oxide mainly composed of ZnO is formed on the sheet surface. However, excessive formation of ZnO can lead to a decrease in the amount of metal Zn in the coating layer, decreasing the corrosion resistance of hot-stamped members. Therefore, it is important to suppress excessive formation of ZnO. While the formation of Al oxides and Mn oxides along with ZnO layer during the hot stamping of hot-dip zinc-coated steel sheets can affect ZnO formation, crystal structures of such oxides have not been elucidated clearly. Thus, this study aimed to analyze structures of oxides formed during hot stamping of hot-dip galvannealed steel sheets using transmission electron microscopy. Results indicated the formation of an oxide layer comprising ZnAl2O4 at the interface between ZnO and the coating layer with Mn3O4 at the outermost of an oxide layer.

Effects of Substrate Texture on Galvannealing Behavior of High Tensile GA Sheet Steel (고장력 합금화용융아연도금 강판의 합금화 거동에 미치는 집합조직의 영향)

  • 문만빈;신철수;오현운;남궁성;박용범
    • Proceedings of the Korean Institute of Surface Engineering Conference
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    • 2003.05a
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    • pp.31-32
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    • 2003
  • In the Present study, the effect of galvannealing conditions on the phase distribution of the Zn-Fe intermetallic phases in the coating layer of the galvannealed steel sheets(GA) was investigated in an interstitial free steel and two kinds of high strength steels. The composition profiles of the coating layers were analyzed using AA and EDS analysis, and the distribution of the intermetallic phases was examined with the aids of X-ray diffraction. On the basis of the pole figure and OIM analyses, it was clarified that the preferred orientation of the $\zeta$ phase depended on the development of the $\gamma$-fibre texture in the substrate.

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Evaluation of Frictional Characteristic of Galvannealed sheet steel with different annealing temperatures at Lower Normal Loads (저면압 영역에서 합금화 온도에 따른 합금화용융아연도금 강판의 마찰특성 평가)

  • Lee Jung-Min;Jeon Seong-Jin;Kim Dong-Hwan;Kim Dong-Jin;Park Sung-Ho;Kim Byung-Min
    • Journal of the Korean Society for Precision Engineering
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    • v.23 no.4 s.181
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    • pp.109-115
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    • 2006
  • This paper is designed to estimate friction and powdering characteristic of coating layer on galvannealed sheet steel with different annealing temperature, which is 465, 505, 515 and $540^{\circ}C$, Estimations of powdering and friction were done using a $60^{\circ}$ bending test and one side friction test, respectively. In order to obviously understand the effect of coatings on friction cross-section of coatings before and after friction test was also observed by SEM. The results show that powdering of coatings is increased with increasing of annealing temperature and that friction characteristic greatly depends on powdering which leads to increase of real contact area between tools and coatings.

Development of 590MPa Grade Galvannealed TRIP Steel Sheets containing Low Silicon Contents for High Strength and Formability (차량구조용 고강도 고성형성 590MPa급 Si 저감형 변태유기소성 합금화 용융아연 도금강판의 개발)

  • Chi, Kwang-Sub;Kim, Yong-Hee;Kim, Byoung-Il
    • Transactions of the Korean Society of Automotive Engineers
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    • v.16 no.6
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    • pp.141-147
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    • 2008
  • Hot-dip galvannealed sheet (GA) with high strength of 590MPa grade in tensile strength, has developed for automotive applications. However, for a successful application, the microstructure and galvannealing behavior of galvannealed TRIP steel sheets must be strictly controlled. High silicon contents steel has problems with weld-ability, zinc coating and reduction of retained austenite volume fraction after galvannealing process. The main purpose of this study is to solve the problem as indicated above.

Development of 980MPa Grade Galvannealed Advance High Strength Steel Sheets for Automobile

  • Kim, Byoung-Jin;Kim, Young-Hee;Park, Jun-Young;Lee, Young-Soo;Moon, Man-Been
    • Corrosion Science and Technology
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    • v.10 no.2
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    • pp.47-51
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    • 2011
  • Main issues in the automotive industry are the reduction of vehicle body weight for energy savings and improvement of crashworthiness for passenger safety. In order to address both these issues, there has recently been increasing application of galvannealed advance high strength steel (GA AHSS) sheets for automobiles. However, GA AHSS sheets have some surface defects such as coating bare spots due to the addition of solid-solution strengthening elements, which result in the deterioration of the galvannealing reaction. In this study, the effects of galvannealed manufacturing conditions on surface and mechanical properties, resistance spot weldability on a laboratory scale, and GA 980 MPa steel sheets produced by commercial continuous galvannealing line (CGL) were investigated.

Development of Ultra-High Strength Galvannealed Steel Sheets

  • Fujita, Nobuhiro;Matsumura, Ken-Ichiro;Nonaka, Toshiki;Tomokiyo, Toshimasa
    • Corrosion Science and Technology
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    • v.9 no.1
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    • pp.16-19
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    • 2010
  • Application of ultra-high strength steel sheets is one of the most important methods to satisfy weight reduction and crash safety of a vehicle. Recently, there has been a trend to apply ultra-high strength steel sheets widely to underbody parts in which corrosion resistance is required. In this work, ultra-high strength galvannealed steel sheets with a tensile strength of 1180 MPa were developed. Newly developed ultra-high strength galvannealed steel sheets have comparable properties, such as mechanical properties, spot weldability, crashworthiness and adhesion of coatings, to conventional steel sheets.

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.