| 摘要 |
PURPOSE:To make sure formation of a zinc phosphate film on the surface of a steel wire made of a silicon killed steel contg. high carbon and to prevent formation of surface roughening and flawing on the surface of the wire rod owing to drawing by controlling the size and amt. of the A1 inclusion on the surface of said wire rod. CONSTITUTION:The A1 inclusions such as MnS in the range within 1mm. from the surface of a wire rod consisting of a silicon killed steel of high carbon contg. 0.6-0.9wt% C, <0.5wt% Si and 0.3-0.9wt% Mn in the section of said wire are so controlled as to exist by >=100 pieces in each 0.2mm.<2> sectional area of the wire rod when observed with 1,000-times magnification by an optical microscope and that the inclusions having <=0.9mum<2> sectional area are >=75% of the number of the inclusions over the entire part in the stage of producing the above-described wire rod. If such wire rod is pickled and descaled, fine ruggedness is formed on the surface and the film of zinc phosphate is uniformly formed by the successive treatment by which the lubricity is improved and therefore the wire rod having the excellent surface layer free from surface roughening and flawing on the wire rod surface even if the wire rod is drawn to an extra-fine wire is obtd.
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