Title

OTIMIZAÇÃO DO SISTEMA FE-SI-SN-ZN A 450°C E UTILIZAÇÃO PARA A GALVANIZAÇÃO A FOGO

ASSESSMENT OF THE FE-SI-SN-ZN SYSTEM AT 450°C: ITS USE IN THE FIELD OF BATCH GALVANIZING

Authorship

Avettand-Fènoël, Marie-Noëlle; Reumont, Guy; Perrot, Pierre

DOI

10.5151/2594-5327-0166

Downloads

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Abstract

Tin added to the zinc bath has a beneficial effect by minimizing spangling and its role in decreasing the thickness of coating grown on hyper-Sandelin steels has also been pointed out. The work presents an assessment of the Fe-Sn-Zn system which is used for an experimental approach of the Fe-Si-Sn-Zn system. The microstructure of galvanized coatings (Fe-Si alloys dipped in Fe-Sn-Zn baths) is characterized by metallography, scanning electron microscopy (S.E.M.) coupled with X-ray energy dispersive spectroscopy (E.D.S.). Solidification phenomena and coating growth mechanisms during galvanizing are explained by means of equilibria in the ternary and quaternary systems at 450°C. Phase equilibria in the zinc rich corner of the Fe- Si-Sn-Zn system, unknown up to now, are presented together with an optimization at 450°C of the Fe-Sn-Zn diagram. Coherence of the quaternary diagram with the already known Fe-Si-Zn and Fe-Sn-Zn systems was carefully checked. A clear insight into the mechanism of galvanization is thus available. From a more fundamental point of view, tin present in tiny amounts in a zinc bath plays an important role of tracer and corroborates mechanisms previously developed to explain the overthickness of layers observed when galvanizing silicon steels around 0.07 % Si.

 

Tin added to the zinc bath has a beneficial effect by minimizing spangling and its role in decreasing the thickness of coating grown on hyper-Sandelin steels has also been pointed out. The work presents an assessment of the Fe-Sn-Zn system which is used for an experimental approach of the Fe-Si-Sn-Zn system. The microstructure of galvanized coatings (Fe-Si alloys dipped in Fe-Sn-Zn baths) is characterized by metallography, scanning electron microscopy (S.E.M.) coupled with X-ray energy dispersive spectroscopy (E.D.S.). Solidification phenomena and coating growth mechanisms during galvanizing are explained by means of equilibria in the ternary and quaternary systems at 450°C. Phase equilibria in the zinc rich corner of the Fe- Si-Sn-Zn system, unknown up to now, are presented together with an optimization at 450°C of the Fe-Sn-Zn diagram. Coherence of the quaternary diagram with the already known Fe-Si-Zn and Fe-Sn-Zn systems was carefully checked. A clear insight into the mechanism of galvanization is thus available. From a more fundamental point of view, tin present in tiny amounts in a zinc bath plays an important role of tracer and corroborates mechanisms previously developed to explain the overthickness of layers observed when galvanizing silicon steels around 0.07 % Si.

Keywords

Termodinâmica; Galvanização; Sistema Fe-Si-Sn-Zn

Galvanization; Thermodynamics; Fe-Si-Sn-Zn diagram.