Abstract: A lower surface cooling box 12 is arranged between transfer rolls 11 on a runout table 3 and an upper cooling box 14 moving freely is arranged at a position corresponding to the cooling box 12 to eject cooling water to the steel strip symmetrically in the vertical direction. The steel strip passes the center of convergence of cooling water from upper and lower surfaces of the steel strip. A water breaking roll 16 is provided elevating freely at least at the outlet side rotating at the same peripheral speed as the transfer rolls and is rotated to lower concurrently with passing of the steel strip top at the cooling apparatus. The upper cooling box is also lowered concurrently to cool the steel strip.

Abstract: A material 1 to be shaped is reduced and formed by bringing dies with convex forming surfaces, when viewed from the side of the transfer line of the material 1, close to the transfer line from above and below the material 1, in synchronism with each other, while giving the dies a swinging motion in such a manner that the portions of the forming surfaces of the dies, in contact with the material 1, are transferred from the upstream to the downstream side in the direction of the transfer line.

Abstract: The method for manufacturing steel sheet comprises the steps of: forming a sheet bar; forming a steel strip; primary-cooling; air-cooling; secondary-cooling; and coiling. The sheet bar is finish-rolled at finish temperatures of (Ar3 transformation point−20° C.) or more. The primary cooling cools the finish-rolled steel strip at cooling speeds of more than 120° C./sec down to the temperatures ranging from 500 to 800° C.

Abstract: The present invention relates to a high strength steel sheet consisting essentially of 0.04 to 0.1% C, 0.5% or less Si, 0.5 to 2% Mn, 0.05% or less P, 0.005% or less 0, 0.005% or less S, by weight, having 10 &mgr;m or less of average ferritic grain size, and 20 mm/mm2 or less of generation frequency A, which generation frequency A is defined as the total length of a banded secondary phase structure observed per 1 mm2 of steel sheet cross section along the rolling direction thereof. The steel sheet is manufactured by, for example, a method comprising the steps of: hot-rolling a continuously cast slab having the composition described above at temperatures of Ar3 transformation point or above directly or after reheating thereof; and cooling the hot-rolled steel sheet within 2 seconds down to the temperatures of from 600 to 750° C. at cooling speeds of from 100 to 2,000° C. /sec, followed by coiling the cooled steel sheet at temperatures of from 450 to 650° C.

Abstract: The method for manufacturing steel sheet comprises the steps of: rough-rolling to form a sheet bar; finish-rolling the sheet bar to form a steel strip; applying primary cooling and secondary cooling to the finish-rolled steel strip; and coiling the secondary-cooled steel strip. The primary cooling is conducted at cooling speeds of 120° C./sec or more down to the temperatures of from 500 to 800° C. The secondary cooling is conducted at cooling speeds of less than 60° C./sec.

Abstract: The method for manufacturing cold-rolled steel sheet comprises the steps of: rough-rolling a slab using a rough-rolling unit; finish-rolling the sheet bar using a continuous hot finishing-rolling mill; cooling the hot-rolled steel strip on a runout table; coiling thus cooled hot-rolled steel strip; and applying picking, cold-rolling the hot-rolled steel strip, and final annealing to the cold-rolled steel strip.

Abstract: C-shaped inductors for induction heating a heated steel material that is carried via table rollers. Each C-shaped inductor includes a C-shaped iron core having a pair of legs facing each other by sandwiching a gap through which the heated steel material passes, and heating coils wound around the pair of legs of the C-shaped iron core. A ring-shaped iron core for restricting induced currents generated in the heated steel material is disposed near the C-shaped inductors, and the heated steel material passes through the gap of each C-shaped inductor.