| 摘要 |
PROBLEM TO BE SOLVED: To provide hot-rolled bar steel or a wire material, which can prevent austenite grains from coarsening when heated in carburization or carbonitriding even when heated at various temperatures of 900-1200°C and hot forged.SOLUTION: The hot-rolled bar steel or the wire material includes: 0.1-0.3% C, 0.05-1.5% Si, 0.4-2.0% Mn, 0.003-0.05% S, 0.5-3.0% Cr, 0.020-0.060% sol.Al, 0.010-0.025% N and the balance Fe with impurities. In the impurities, P, Ti and O have chemical compositions of P≤0.025%, Ti≤0.003% and O≤0.002%, respectively. The amount of Al deposited as AlN is 0.030% or less. When eight regions in the cross section divided at every 45° of a center angle on the basis of a center position of the cross section to a position at the depth of 1 mm from the surface are subjected to line analysis, DI which is expressed by a specific expression has the minimum value of 2.0 or more and the maximum value of 5.0 or less. A specific amount of Cu or the like may be included. |
