The　decarbonization　behavior　of　various　refractories　which　have　reacted with　molten　steel　at 1560℃ under argon　atmosphere　was　investigated．The　Al203－C　decarbonization　occurred　only　onthe　hot　face　and　is　cconcluded　to　be　caused　by　the　dissolution　of　graphite　into　the　molten　steel． In　the　case　of　MgO－C，a　dense　MgO　layer was　produced　on　the　hot　face　and　the　grains　of　original　graphite　and　MgO　became　samller　or　disappeared　in　the interior　side． The　decarbonization　was　causedby　the　reaction between graphite　and　MgO　and　further　decarbonization　was　prevented　after　the　dense　MgO　layer　was　produced　by　the　reaction　Mg（g）and　O　or　CO（g）． In　the case　of　 ZrO2－C　or　CaO－ZrO2－C，a　thick　decarbonization　zone　was　formed　and　a　few　large　metal　skulls　including many　graphite　strips　existed　in　the　zone．The　decarbonization　mechanism　can　be　explained　by　the　dissolution of　graphite　into　metal　skulls　which　were　the　molten　steel　penetrated　into　the　pores　in　the　refractory． The penetration　may　be　caused　by　the　good　wettability　of　ZrC　around　the　ZrO2 or　CaO・ZrO2 particles　in　the refractory　with　the　molten　steeL　The　ZrC　was　formed　by　the　reaction　between　graphite　and　ZrO2．

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