The thermodynamic equation for segregation in multicomponent steels is extended from that in ternary system and the segregation amounts of Cr, C and P in the intergranular phase in a Cr-steel are estimated. The thermodynamic equation for segregation in multicomponent steels is extended from that in ternary system and the segregation amounts of Cr, C and P in the intergranular phase in a Cr-steel are estimated.