| 摘要 |
A non-heat refining steel having a high fatigue strength in addition to an excellent machinability, which consists essentially of 0.30-0.50 wt % of C, 0.35-0.70 wt % of Si, 0.80-1.40 wt % of Mn, 0.30-0.80 wt % of Cr, 0.05-0.35 wt % of V, not more than 0.15 wt % of S and not more than 0.35 wt % of Pb so that (S+Pb) is not less than 0.06 wt % and (S+Pb/4) is not more than 0.15 wt %, 0.0003 to 0.0050 wt % of Ca, not more than 0.010 wt % of Al, 0.0015-0.0030 wt % of O and the balance of being Fe and inevitable impurities, and has a micro-structure composed of 10 to 40% by area of ferrite and balanced pearlite after hot working and air cooling.
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