Production method of excellent steel in an inner quality

摘要

The present invention relates to when the round cross-section material by hot rolling round cross-section steel, there is provided a method of improving the internal quality due to strong pressure under application, the shape. As we A forms a round cross section steel product subjected to steel of round cross section material in the rolling three or more paths between the heat, the first pass using a pair of upper and lower flat roll, after the second pass up and down the same kind pair or up and down disparate using a pair of hole-type roll, and rolling the reduction rate of the first pass as in the range of material of less than the total area reduction rate of up to product. Reduction of area of ​​the first pass is preferably 50% or more of the total reduction of area after the second pass. .BACKGROUND