| 摘要 |
PURPOSE:To manufacture constantly wire rod having excellent cold workability, by cooling hot rolled steel wire rod under specific conditions, then by reheating it so as to transform the austenite to sorbite. CONSTITUTION:Steel wire rod having been hot rolled is cooled to a temp. not lower than Ms temp. at such a cooling rate that sorbite structure is formed. Then the wire rod is reheated to a temp. corresponding to the nose of its TTT curve and is kept at the temp. for sufficient time in order to complete transformation of untransformed austenite to sorbite. For example, stop of control cooling when the highest temp. portion of the wire crosses the nose of CCT curve and arrives at a point (a) allows to cross the TTT curve Pf shown by a curve A by reheating even when the lowest temp. portion is supercooled to a point (b), hereby sorbite transformation is completed. The rate of cooling is selected in accordance with the kind of steel, and the diameter of the wire. This treatment allows to uniformalize the temp. of the wire rod in cross sectional and longitudinal directions, and the heat treatment before working of the wire rod becomes useless. |
