| 摘要 |
<p>If an area that is formed concentrically inward from a surface of a wire rod and whose cross section ratio with respect to the cross sectional area of a cross section of the wire rod is between 13% and 56% is defined as area I, an area that widens concentrically about the central axis of the wire rod and whose cross section ratio with respect to the cross sectional area of the wire rod is between 3% and 11% is defined as area III, and an area between area I and area III is defined as area II, then area I is a first negative segregation portion where the degree of C segregation with respect to the average C concentration of the wire rod is between 0.75 and 0.95, area II is a positive segregation portion where the degree of C segregation is between 1.00 and 1.10, area III is a second negative segregation portion where the degree of C segregation is between 0.80 and 0.95; and the wire rod has a sandwich structure in which the first negative segregation portion, the positive segregation portion, and the second negative segregation portion are placed in order from the surface.</p> |
