| 摘要 |
PURPOSE:To produce a high tensile steel wire for a concrete pipe which is excellent in delayed cracking resistance having excellent tensile strength and relaxation value by subjecting the steel wire contg. P and S at a low ratio to a heat treatment under prescribed conditions. CONSTITUTION:The low phosphorus and low sulfur steel wire contg. <0.5% C, <0.015% P, <0.010% S as the deformed PC steel bar 1 used for the concrete pile is heated to the temp. above the Ac3 transformation point and is then quickly cooled at a cooling rate above the critical cooling rate, by which the steel wire is hardened. The steel wire is subjected to drawing at a room temp., as necessary, and is subjected to a temperating treatment by heating the same to a 100-700 deg.C range. While the steel wire is held at the temperating temp., the steel wire is subjected to plastic working or straightening at 3-90% strain quantity. The high tensile steel wire for the concrete pile having the excellent delayed cracking resistance of >=145kgf/mm<2> tensile strength and <=10% delayed cracking resistance characteristic is thus obtd.
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