METHOD FOR MANUFACTURING STEEL EXCELLENT IN INNER QUALITY

摘要

PROBLEM TO BE SOLVED: To provide a method for improving inner quality and a shape of a round cross section steel material by applying strong pressure, when forming a round cross section raw material into the round cross section steel material by hot rolling.SOLUTION: When forming a round cross section steel product by performing three or more passes of hot rolling to a round cross section raw material of steel, a pair of upper and lower flat rolls are used in the first pass; a pair of the same or different upper and lower grooved rolls are used in the second and subsequent passes; and rolling is performed such that an area reduction rate in the first pass is controlled to be within a range less than a total area reduction rate from the raw material to the product. The area reduction rate of the first pass is preferably 50% or more of the total area reduction rate of the second and subsequent passes.