The　lime-free　roasting　process　of　trivalent　chromium-containing　slag　was　investigated.　The　effect　of　Fe　and　liquid　phase　on　the　conversion　reaction　of　chromium　was　discussed.　The　oxidation　of　trivalent　chromium　depends　greatly　on　the　diffusion　of　Na+　and　O-2.　Both　the　raw　material　Na2CO3　and　the　intermediate　product　NaFeO2　serve　as　the　carriers　of　Na+.　The　Na+　diffusion　is　improved　by　the　binary　liquid　phase　of　Na2CrO4-Na2CO3,　whereas　excess　liquid　phase　results　in　a　low　conversion　rate　of　chromium　by　hindering　the　diffusion　of　oxygen　towards　the　reaction　interface.　With　the　increasing　of　liquid　volume,　the　controlled　step　of　chromium　oxidation　changes　from　Na+　diffusion　to　oxygen　diffusion.　The　mechanism　study　showed　that　the　volume　of　liquid　phase　increased　while　raising　the　reaction　temperature　or　prolonging　the　reaction　time.　Based　on　the　role　of　both　liquid　phase　and　Fe,　the　oxidation　process　of　chromium　was　summarized　as　a　three-stage　model:　the　Na+　diffusion-controlled　stage,　the　O-2　diffusion-controlled　stage,　and　the　oxidation　reaction　halted　stage.　(C)　The　Minerals,　Metals　&　Materials　Society　and　ASM　International　2015