| 摘要 |
PROBLEM TO BE SOLVED: To prevent the development of pushing recessed flaw with a projecting roller in the formation of a channel preform produced by hot-rolling by forming the large radius of curvature of the recessed part in a recessed roller in the specific range. SOLUTION: A flange part 2 is formed so as to reduce the curve of a web part 1 by pushing with the projecting roller 4 and the recessed roller 5. In order to obtain this formation, at the time of using R for the radius of curvature of the recessed part in the recessed roller 5, R1 for the radius of curvature of the arch part in the projecting roller 4 and (t) for the thickness of the flange part 2, the radius R of curvature of the recessed part in the recessed roller 5 is to satisfy R=(R1+t)×α. In the equation,αis 1.2-1.8. In the case of forming the channel preform by using the recessed roller 5 having the relation of R>R1, a gap is developed between the recessed roller 5 surface and the web part 1 surface near both ends of the recessed roller 5, and since the channel material can be bend-formed by the gap size even in the case the pushing force is too large, the pushing recessed flaw on the web part 1 is not developed. |
