A steering rack bar rolled round steel, and a steering rack bar

A steering rack bar rolled round steel, which has the following chemical composition, C: 0.38 ~ 0.55%, Si≤1.0%, Mn: 0.20 ~ 2.0%, S: 0.005 ~ 0.10%, Cr: 0.01 ~ 2.0 %, Al: 0.003 ~ 0.10%, B: 0.0005 ~ 0.0030%, Ti≤0.047%, Cu: 0 ~ 1.0%, Ni: 0 ~ 3.0%, Mo: 0 ~ 0.50%, Nb: 0 ~ 0.10%, V : 0 ~ 0.30%, Ca: 0 ~ 0.005%, Pb: 0 ~ 0.30%, the balance being Fe and impurities, the impurities P≤0.030%, N≤0.008% satisfying [3.4N≤Ti≤3.4N + 0.02], microstructure comprising a ferrite (F), lamellar pearlite (LP) and cementite (C), in cross-section, an average particle diameter region from the surface to a position of 1/2 of a radius of ≤ F 10μm, the area ratio of the number of LP <20% and globular cementite (SC) within th C ≥4 × 105 / mm2, and thus the area ratio of the central portion LP of ≥20% and the number of SC <4 × 105 / mm2, and in a longitudinal section, from the position of 1/2 of the area of ​​the surface to a radius of the average aspect ratio ≥3 F. Even if the steel is quenched and tempered not have a high base metal toughness and good machinability.