Red scale defect is known to be mainly caused by net-like Fe2SiO4-FeO. In the present study, the morphology of Fe2SiO4-FeO in a Si-containing steel was investigated by simultaneous thermal analysis, high-temperature laser scanning confocal microscopy, scanning electron microscopy, and energy dispersive spectroscopy. Only liquid Fe2SiO4-FeO can form a net-like morphology. Liquid Fe2SiO4-FeO is classified into two types in this work. Type-1 liquid Fe2SiO4-FeO is formed by melting pre-existing solid Fe2SiO4-FeO that already exists before the melting point of Fe2SiO4-FeO. Type-2 liquid Fe2SiO4-FeO is formed at a temperature higher than the melting point of Fe2SiO4-FeO. The results show that type-1 liquid Fe2SiO4-FeO is more likely to form a net-like morphology than is type-2 liquid Fe2SiO4-FeO. The penetration depth of type-1 liquid Fe2SiO4-FeO is also larger at the same oxidation degree. Therefore, type-1 liquid Fe2SiO4-FeO should be avoided in order to eliminate red scale defect. Net-like Fe2SiO4-FeO may be alleviated by two methods: decreasing the oxygen concentration in the heating furnace before the melting point of Fe2SiO4-FeO is reached and increasing the reheating rate before the melting point. In addition, FeO is distributed with a punctiform or lamellar morphology on Fe2SiO4.
CITATION STYLE
Zhou, M., Xu, G., Hu, H., Yuan, Q., & Tian, J. (2017). The morphologies of different types of Fe2SiO4-FeO in Si-containing steel. Metals, 7(1). https://doi.org/10.3390/met7010008
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