Persistence of superficial contamination of rolled steel during successive treatments up to the formation of a galvannea
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Persistence of Superficial Contamination of Rolled Steel during Successive Treatments up to the Formation of a Galvanneal Coating S. FELIU, Jr., M.L. PÉREZ-REVENGA, and V. BARRANCO With the assistance of X-ray photoelectron spectroscopy (XPS) the outer surface (approx. 3 nm) of IF steels that have to react with zinc in order to produce the galvanneal coating has been characterized. In particular, attention has been focused on the nature and content of carbon-rich impurities on the surface of these steels, which have been cold rolled and annealed. The study has found a type of superficial contamination in which the elements C and Ca are associated and which persists throughout the annealing and galvannealing processes. In this case, the contamination surprisingly seemed to shift from the surface of the steel substrate to the outer surface of the galvanneal coating. The present communication is intended to report this unexpected fact.
In recent years, the growing importance of galvanneal coatings on automobile body work has led to studies of the mechanisms of their growth on interstitial-free (IF) steel substrates of high mechanical strength.[1] It is well known that the metallic alloying elements segregate toward the surface of IF steels in order to precipitate in the form of metallic oxides and hydroxides as a result of the annealing process; this segregation seems to inhibit the nucleation and growth of Fe-Zn intermetallic compounds.[2] Less attention has been focused on how the presence of carbonaceous residues on the steel surface affect the characteristics of the galvanneal coating that is formed. With the assistance of X-ray photoelectron spectroscopy (XPS), the outer surface (approximately 3 nm) of IF steels that have to react with zinc in order to produce the galvanneal coating has been characterized. [3] In particular, attention has been focused on the nature and content of carbon-rich impurities on the surface of these steels, which have been cold rolled and annealed. The study has found a type of superficial contamination in which the elements C and Ca are associated and which persists throughout the annealing and galvannealing processes. In this case, the
S. FELIU, Jr., Scientific Researcher, and M.L. PÉREZ-REVENGA and V. BARRANCO, Postoctoral Fellows, are with CENIM (CSIC), 28040 Madrid, Spain. Contact e-mail: [email protected] Manuscript submitted January 29, 2004. METALLURGICAL AND MATERIALS TRANSACTIONS A
contamination surprisingly seemed to shift from the surface of the steel substrate to the outer surface of the galvanneal coating. The present article intended to report this unexpected fact. The annealing process was performed in a laboratory-scale simulator (RHE
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