The wettability between molten iron and MgAl2O4 substrate containing SiO2 has been investigated by a sessile drop method. Two kind of iron containing 0.008 and 0.030 mass％ oxygen were used. There were a lot of pores at the surface of pure MgAl2O4 substrate and substrate containing 1.0 mass％ SiO2. These pores gradually disappeared with holding time because of reaction between molten iron and substrate, resulting in decreasing contact angle. In contrast, the contact angle on dense MgAl2O4 substrate containing 2.5 and 5.0 mass％ SiO2 was independent of holding time. Even if the addition of SiO2 changed, there was no effect of contact angle. It was proved that the oxygen concentration of molten iron decreased with decreasing contact angle.

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