| 摘要 |
Provided is a steel material serving as a material for a shock-absorbent member having high impact energy absorption and reduced fracture under impact load, having the chemical composition, expressed in percentage by mass, of C: 0.05-0.18%, Mn: 1-3%, Si+Al: at least 0.5% but less than 2.5%, and N: 0.001-0.015%, and in some cases, Cr: ≤0.5%, Mo: ≤0.2%, Ti: ≤0.05%, Nb ≤0.05%, V ≤0.2%, and B: ≤0.002%, with the remainder being Fe and impurities, the material having a steel texture in which the area ratio of bainite constituted of lath morphology having average spacing of 1 μm or smaller is 70% or above and the area ratio of martensite is 5-30%, and which satisfies the following formulas (1) and (2): (1) 1.2 ≤ HM0/HB0 ≤ 1.6, (2) 0.90 ≤ {(HM10/HM0)/(HB10/HB0) ≤ 1.3, wherein HM0 and HM10 represent average nano-hardness, in an initial state and after 10% tensile deformation, of the martensite, and HB0 and HB0 represent that of the bainite, respectively. |
