Steel for separators of solid-oxide type fuel cells

Provided is a steel for separators of solid-oxide type fuel cells, which forms oxide films having good electrical conductivity at 700 to 950 DEG C or so, has good oxidation resistance and, in particular, resistance to exfoliation even in the case of long hours of use, is excellent in impact properties at room temperature, shows a small difference in thermal expansion from the electrolyte, and is inexpensive. This steel for separators of solid-oxide fuel cells includes, by mass %, not more than 0.2% C, not more than 1.0% Si, not more than 1.0 % Mn, not more than 2% Ni, 15 to 30% Cr, not more than 1% Al, one or more elements selected from the group of not more than 0.5% Y, not more than 0.2% REM and not more than 1% Zr, and the balance of Fe and unavoidable impurities. In this steel, amounts of S, O, N and B in the unavoidable impurities are restricted to not more than 0.015%, not more than 0.010%, not more than 0.050% and not more than 0.0050%, respectively, the following equation is satisfied: (0+2S)/(0.27Y+0.035Zr+0.16REM) ≤ 2.0, Furthermore, in this steel, the hardness is not more than 280 HV and the average ferrite grain size number is not less than ASTM No. 2, which provides fine grains.