Metallurgy of galvanized coatings

Mackowiak, J.; Short, N. R.

doi:10.1179/095066079790136327

Cited by 87 publications

(62 citation statements)

References 9 publications

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“…Any variation in manganese within about 1% has little effect on coating microstructure 1) and therefore its influence in the results can be ignored in the present study.…”

Section: Resultsmentioning

confidence: 99%

“…Due to a Si concentration gradient in liquid zinc from strip surface to the bulk and low solubility of Si, the z (zeta) crystals start forming away from the steel surface, and the formation of zinc pockets between z (zeta) crystallites takes place. 1,12,17) Similar coating structure with the presence of overly thick z (zeta) crystals embedded in zinc, a thin d (delta) layer and no G (gamma) layer in a 0.37 % Si steel was observed by Jintang et al18) for higher immersion time. In rephosphorized interstitial free steel (S 3 ), the coating consists of mainly z (zeta) phase and a thin d (delta) layer near the interface (Fig.…”

mentioning

confidence: 80%

“…At the galvanizing temperature, iron atoms have a strong affinity toward zinc and various Fe-Zn intermetallics may develop. 1,2) The Fe-Zn interface is not in equilibrium at the time of entry of the strip. Even if the bath is saturated with iron, dissolution of iron from the strip surface continues during the initial moments after immersion.…”

Section: Introductionmentioning

confidence: 99%

“…Although these results and analyses give a good knowledge about iron dissolution, its transient activity at the interface, formation of the intermetallics, and the effects of some process parameters on these, very few have discussed about the effect of steel composition. 1,9) The alloying elements present in steel may affect the iron diffusivity and thus the activation energy of Fe-Zn reactions and their kinetics. Higher amount of alloying additions are required to produce advanced high strength steels that show various difficulties in galvanizing.…”

Section: Introductionmentioning

confidence: 99%

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Effect of Steel Composition on Iron Dissolution in Molten Zinc and Development of Fe–Zn Phases on Steel Surface

Mishra

Dutta

2007

ISIJ Int.

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The effect of steel composition on iron solubility in molten zinc and coating microstructure was studied by immersing test coupons of four different steel grades in zinc bath for 20 min at 470°C. The amount of iron dissolved in the molten zinc depends upon the steel composition. The coating was characterized by energy dispersive spectroscopy, X-ray diffraction and galvanostatic methods. The coating consists of mainly z (zeta) and d (delta) phases along with zinc layer at the top, irrespective of the steel composition. The presence of a thin layer of gamma phase has also been confirmed by XRD and galvanostatic analysis. However, the proportion and distribution of the coating phases varies with the steel chemistry.KEY WORDS: iron dissolution; hot-dip galvanizing; iron zinc alloys. ExperimentalThe iron dissolution and galvanizing experiments were carried out in an alumina crucible. Four different steel compositions (namely S 1 , S 2 , S 3 and S 4 ) were selected so that the effect of different interstitial and substitutional alloying elements like C, Si, P etc. could be examined. The details of cold rolled and annealed steel strips used in the experiments are listed in Table 1.Commercially pure zinc (800 g. of 99.99 % purity) was melted in the alumina crucible and held at 470°C for 15 min prior to each experiment to avoid any thermal gradient within the bath. Small test coupons (45ϫ40 mm 2 ) of 1 mm thick steel strips were pickled in hot HCl (15 %) for about 1 min and immediately dipped in the molten zinc for 20 min. The liquid zinc bath was stirred by the immersed sample after every 5 min (i.e. after 5, 10 and 15 min). For the entire experiment, the liquid zinc was maintained at 470°C (Ϯ5°C) in a closed chamber furnace. The dipping time was decided based on the iron saturation limit in zinc and the time required to attain that. The saturation limit of iron in molten zinc can be calculated from the following equation where [Fe] is in wt% and T is in Kelvin.The saturation limit comes to be 0.053 wt% at 470°C. The time required for saturation of molten zinc is in hours.5) The dipping time was therefore chosen such that significant iron dissolution takes place without attaining saturation in order to reveal the effects of different steel compositions. At the end of dipping i.e. after 20 min, the zinc bath was again stirred, the top dross was removed and steel test coupon was taken out of the bath quickly and air cooled. The molten zinc was cast in a sand mould. Chemical analysis of the cast zinc was carried out. This analysis has given the amount of Fe dissolved during 20 min of dipping in the molten zinc for each sample, which has been discussed in Sec. 3.1. A mixture consisting of 1 % picric acid in amyl alcohol and 1% nitric acid in amyl alcohol was used as the etchant. The micro structural and energy dispersive spectroscopy (EDS) characterization of the transverse section was carried out under scanning electron microscope (SEM) for coated samples to examine the elemental distribution across the coating. The coati...

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“…Any variation in manganese within about 1% has little effect on coating microstructure 1) and therefore its influence in the results can be ignored in the present study.…”

Section: Resultsmentioning

confidence: 99%

mentioning

confidence: 80%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Effect of Steel Composition on Iron Dissolution in Molten Zinc and Development of Fe–Zn Phases on Steel Surface

Mishra

Dutta

2007

ISIJ Int.

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“…1,11) However, microscopic investigations confirmed that four layers have been formed and EDS analysis detected no aluminum within the layers. It is probably due to the fact that for Fe 2 Al 5 layer to be formed, in addition to the required amount of aluminum concentration in the bath (at least 0.1 wt%), 1,12) low temperature of the bath, 13) high difference between the strip-entry and the bath temperatures, 14) high silicon content of the steel, low iron content in the bath and agitation of the bath should be prepared.…”

Section: Discussionmentioning

confidence: 99%

The Role of Texture and Microstructure in Optimizing the Corrosion Behaviour of Zinc Hot-dip Coated Steel Sheets

2008

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Crystallization of Intermetallic Phases Fe‐Zn during Hot‐Dip Galvanizing Process

Kopyciński¹

2013

TMS2013 Supplemental Proceedings

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Metallurgy of galvanized coatings

Cited by 87 publications

References 9 publications

Effect of Steel Composition on Iron Dissolution in Molten Zinc and Development of Fe–Zn Phases on Steel Surface

Effect of Steel Composition on Iron Dissolution in Molten Zinc and Development of Fe–Zn Phases on Steel Surface

The Role of Texture and Microstructure in Optimizing the Corrosion Behaviour of Zinc Hot-dip Coated Steel Sheets

Crystallization of Intermetallic Phases Fe‐Zn during Hot‐Dip Galvanizing Process

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