| 摘要 |
A carburizing steel has a composition containing, in mass %, C: 0.1-0.35%; Si: 0.01-0.22%; Mn: 0.3-1.5%; Cr: 1.35-3.0%; P: 0.018% or less; S: 0.02% or less; Al: 0.015-0.05%; N: 0.008-0.015%; and O: 0.0015% or less, each being contained in an amount within a range satisfying formulas (1), (2) and (3) below, and the balance of the composition being Fe and incidental impurities, and the carburizing steel having microstructures before spheroidizing annealing such that a total microstructure proportion of ferrite and pearlite is 85% or more and an average ferrite grain size is 25 mum or less. 3.1>={([% Si]/2)+[% Mn]+[% Cr]}>=2.2 (1) [% C]-([% Si]/2)+([% Mn]/5)+2[% Cr]>=3.0 (2) 2.5>=[% Al]/[% N]>=1.7 (3) [% M] represents content (in mass %) of element M. |
