| abstract |
Disclosed is an automotive underbody part having excellent low cycle fatigue properties. The automotive underbody part is characterized by comprising a steel which comprises (in mass%) 0.02-0.10% of C, 0.05-1.0% of Si, 0.3-2.5% of Mn, 0.03% or less of P, 0.01% or less of S, 0.005-0.1% of Ti, 0.005-0.1% of Al, 0.0005-0.006% of N, 0.0001-0.01% of B and the remainder made up by Fe and unavoidable impurities, wherein 80% or more of the structure of the automotive underbody part is made up by a steel having a bainite structure. The automotive underbody part is also characterized in that the X-ray half value width of the face (211) of a part of the automotive underbody part which has a ratio of the thickness (t) to the curvature radius (R) of the outside surface (i.e., an R/t ratio) of 5 or less is 5 (deg) or less. |