STEEL AND PART

The purpose of the present invention is to provide steel having improved hardenability, toughness, surface originated exfoliation life, and bending fatigue strength, and a component manufactured using that steel. Provided is steel having prescribed components, wherein Fn1 as defined by the following equation (1) is 0.20 - 0.65 and Fn2 as defined by the following equation (2) is 0.50 - 1.00. Fn1 = 4.2 × [Cr]/(7.0 × [Si] + 16.0 × [Mn]) ... (1) [Elements]: percent by mass of elements Fn2 = A1/A2 ... (2) A1: total surface area (µm2) of included sulfides, which have a circle equivalent diameter of 1.0 µm or greater and include 1.0 mol% or greater Ca of the total number of moles included in the sulfides, in an observed region with a total surface area of 4.0 mm2 A2: total surface area (µm2) of included sulfides, which have a circle equivalent diameter of 1.0 µm, in an observed region with a total surface area of 4.0 mm2