The Fe–Cr–Zn System in Relation with the Galvanizing Process in Chromium-Added Zinc Bath

Abstract

The Fe-Cr-Zn system in relation with the galvanizing process in chromium-added zinc bathTaking into account new experimental measurements, the Fe -Zn -Cr ternary system is critically modified at 460°C. A continuous solid solution between f-FeZn 13 and CrZn 13 compounds is shown but is shared at 460°C by the stable CrZn 17 compound containing about 2 wt.% Fe. This ternary system is assessed with the CALPHAD method using the PARROT modulus of the Thermo-Calc software. The liquid and solid solution phases are modeled with Redlich -Kister -Muggianu equations. The intermetallic compounds f-(Fe,Cr)Zn 13 and CrZn 17 are treated as stoichiometric compounds in the binary systems. The experimental Fe and Cr solubilities at various temperatures modify the shape of the liquidus curve and are satisfying for industrial applications. A set of parameters consistent with most of the available experimental data on both phase diagram and solubility measurements is obtained by optimization. A comparison with previous experimental work is also presented and a reactional model between iron substrate and Zn -Cr bath is proposed. This optimization allows to interpret the growth of intermetallic layers and the formation of dross when galvanizing in Cr-added Zn bath.

Experimental investigation on the phase equilibria of the Mn–Ni–Zn system at 400 °C

“…It was reported that information on the Al-Fe-Zn system had been effectively applied to the galvanizing industry for the determination of effective Al content in the molten bath, the management of the dross generation and the prediction of the Al consumption [2]. Several galvanizing-related alloy systems, such as Fe-Ni-Zn [3], Fe-Sn-Zn [4], Fe-Ti-Zn [5], Al-Fe-Zn [6], Fe-Mn-Zn [7], Cr-Fe-Zn [8], Bi-Ni-Zn [9] and Al-Mo-Zn [10], were experimentally investigated. In addition, the phase equilibria in some quaternary systems, such as Zn-Fe-Ni-Ti [11] and Zn-Fe-Ni-Si [12], were also experimentally studied.…”

Experimental investigation and thermodynamic assessment of the Zn–Cr system

“…Reumont and Perrot [4] reassessed this partial phase diagram and included the CrZn13 phase as well. The partial phase diagram was subsequently accepted in the related higher order systems [14][15][16][17][18][19]. However, the stability of CrZn13 was questioned by Hansen [6] from the very beginning.…”

Reactions of FeCr alloys with liquid zinc in hot-dip galvanizing

“…Nevertheless, a few difficulties have been encountered while galvanizing such AHSS because of the high alloy chemistry of the substrate [2]. High silicon concentration in martensitic steel could modify the reactivity in the bath due to the Sandelin effect [3], Mn tends to form MnO at the external steel surface during continuous annealing prior hot-dipping [4], and Cr could also form specific intermetallic compounds (IMCs) [5][6][7][8][9]. The formation, transformation, and growth of IMCs in interfacial reaction and post-treatment process crucially determine the interfacial properties of coating and thus the mechanical reliability of galvanized AHSS products.…”

“…By dipping three starting materials, Fe, Cr, and Fe-77 wt.% Cr in a molten Zn bath containing 0.71 wt.% Cr at 460°C up to 16 h, Reumont et al [5] identified a ternary phase ζ′ having a Cr content of 2-5.5 wt.% and a Zn content of~93-95 wt.%, and it was in equilibrium with ζ-FeZn 13 , CrZn 17 , CrZn 13 and liquid phase in the Zn-rich corner. Tang et al [6] equilibrated Fe-Cr-Zn molted alloys in a ceramic crucible between 470 and 430°C at~10°C intervals.…”