Intergranular zinc embrittlement and its inhibition by phosphorus in 55 pct Al-Zn-coated sheet steel

Allegra, L.; Hart, R. G.; Townsend, H. E.

doi:10.1007/bf02644218

Cited by 36 publications

(17 citation statements)

References 3 publications

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“…[17][18][19] The strengthening effect and required microstructure can be obtained by addition of minor alloying elements such as C, Mn, Al and Si, [20][21][22] where Al plays a role to stabilize austenite and to substitute for Si in view of the detrimental effect of Si such as the formed Si-oxides on the surface do not wet with coating alloy resulting in the uncoated regions during galvanizing process. 23,24) The addition of Al in the steel, however, may cause great process control problems due to the chemical reactions between SiO2 in mold slag and dissolved Al in steel, 25,26) which results in a significant increase in the mass ratio between Al2O3 and SiO2 (mAl 2 O 3 / mSiO 2 ) ratio in the mold slag as continuous casting progresses.…”

Section: Introductionmentioning

confidence: 99%

Effect of Al2O3/SiO2 Ratio on the Viscosity and Structure of Slags

et al. 2012

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The present paper investigates how the mass ratio between Al2O3 and SiO2 (mAl 2 O 3 /mSiO 2 ) in slag compositions influences the structure, viscosity and crystallization of the slag melts. The objective is to study the variations in viscosity and structure of slags with increasing mAl 2 O 3 /mSiO 2 ratio. In practice the results of the study are relevant to the significant changes in slag property caused by the changes in chemical composition during continuous casting of steels containing high amounts of dissolved aluminum.The viscosity was found to decrease slightly with increasing mAl 2 O 3 /mSiO 2 ratio up to 0.56. The degree of polymerization for [SiO4]-tetrahedra was found to decrease with increasing mAl 2 O 3 /mSiO 2 ratio based on the Fourier Transformation-Infrared Spectra (FT-IR) and Raman spectra, which could explain the observed decrease in viscosity. AtmAl 2 O 3 /mSiO 2 ratios above 0.56, the viscosity was found to abruptly increase which could be caused by the presence of spinel crystals. The activity coefficient was computed and it was found that the activity coefficient of alumina presents negative deviation when mAl 2 O 3 /mSiO 2 ratio is less than 0.35, while it shows a positive deviation when mAl 2 O 3 /mSiO 2 ratio exceeds 0.35. This phenomenon may be related to the change of the primary phase region correlating to the phase diagram to the slag composition.

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Section: Introductionmentioning

confidence: 99%

Effect of Al2O3/SiO2 Ratio on the Viscosity and Structure of Slags

et al. 2012

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“…The delta phase was found to be present in the coatings on all grades of steel in three different compositions. The zeta phase, of same chemical composition (FeZn 15 ), was also identified © 2007 ISIJ Fig. 3(a).…”

Section: X-ray Diffraction Analysismentioning

confidence: 99%

“…The lower Fe-Zn reaction kinetics shown by rephosphorized steel is well known. 14,15) According to these literature, in this ultra low carbon steel, phosphorus (like carbon in steel S 1 ), segregates at the ferrite grain boundaries and hinders the path for iron diffusion leading to low iron dissolution. On the contrary, it is supposed that the higher iron dissolution shown by steel (S 4 ) is due to segregation free grain boundaries, which have no hindrance for iron diffusion.…”

Section: Iron Dissolutionmentioning

confidence: 99%

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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“…[2,[5][6][7][8] Mercer [7] found that phosphorus segregated to the grain boundaries, impeded Fe and Zn interdiffusion, and lowered the amount of Fe that was found in galvanized coatings. Therefore, phosphorous in steel actually acts as an inhibitor to Fe-Zn alloy formation.…”

Section: Introductionmentioning

confidence: 99%

Ternary Phase Equilibria at 450 °C in the Zn-Fe-P System

2007

J Phs Eqil and Diff

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The 450°C isothermal section of the Zn-Fe-P ternary phase diagram has been determined experimentally using optical microscopy, scanning electron microscopy (SEM) coupled with energy dispersive x-ray spectroscopy (EDS), and x-ray diffraction (XRD). The research of the work has concentrated on the Zn-rich corner, which is relevant to galvanizing. Experimental results indicate that P solubility in liquid zinc and all four Fe-Zn compounds, including f, d, U 1 , and U, is limited at 450°C. Fe 2 P is found to be in equilibrium with the f and d phases. Fe 3 P is found to be in equilibrium with d, U 1 , U, and aFe, respectively. Liquid Zn is in equilibrium with the Fe 2 P and FeP phases.

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Intergranular zinc embrittlement and its inhibition by phosphorus in 55 pct Al-Zn-coated sheet steel

Cited by 36 publications

References 3 publications

Effect of Al<sub>2</sub>O<sub>3</sub>/SiO<sub>2</sub> Ratio on the Viscosity and Structure of Slags

Effect of Al<sub>2</sub>O<sub>3</sub>/SiO<sub>2</sub> Ratio on the Viscosity and Structure of Slags

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

Ternary Phase Equilibria at 450 °C in the Zn-Fe-P System

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