| 摘要 |
A resulfurized and rephosphorized free-machining steel bar formed by cold drawing a hot rolled steel bar has the composition, by weight, C up to 0.08%; Mn 0.6% to 1.4%; Si up to 0.1%; P at least 0.03%; S 0.25% to 0/50%; Cb 0.02% to 0.10%; the sum of Ni, Cr, Mo and Cu up to 0.15%; balance iron. The ratio of %Mn/%S is from 1.6 to 4.0, and the ratio of [%Mn-(1.62x%S)]/%Cb is from 2 to 50. The yield strength of the steel bar is further determined by the draft in cold drawing the bar from the hot rolled state and the size and cross section of the bar after draft. The relationship between strength and ductility is further improved by heavy drafting in cold drawing the bar from the hot rolled state.
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