Nippon Steel Corporation

Kichi Nakazawa

Osamu Akisue

Masafumi Okamoto

Kiyoshi Tanaka

Atsuhiro Wakako

Tadashi Sakazaki

Seiryo Hatae

Hiroaki Toki

In a method for producing a cold-rolled steel sheet by continuously casting, hot-rolling, cold-rolling, and continuously annealing Al-killed steel, it is known to coil a hot-rolled strip at a coiling temperature of 630.degree. C. to 710.degree. C. so as to attain satisfactory precipitation of AlN in the hot-rolling step. When the direct-rolling of a continuously cast strand (DR method) is employed to produce a cold-rolled strip, it is impossible to attain satisfactory precipitation of AlN even by carrying out the known coiling method. The present invention is characterized in that an extremely high coiling temperature of at least 780.degree. C. is used to essentially prevent aging due to the precipitation of AlN, and, further, the carbon content of a continuously cast slab is 0.005% at the highest so as to essentially prevent the occurrence of orange peel. Heat conservation due to use of the DR method and excellent properties of the cold-rolled steel strip are simultaneously attained.

Method for producing a cold-rolled steel sheet having excellent

A method for treating a steel slab containing 2.5 to 4% Si to a temperature not lower than 1260.degree. C. in a continuous heating furnace of the walking-beam type, comprising; charging the slabs into the continuous heating furnace through its charge inlet, transferring the slabs by means of walking-beams in the furnace with the rear end of a preceding slab substantially contacting a front end of a subsequent slab under the condition that the contact time of the slab with fixed beams is not more than three times longer than the contact time of the slab with the transfer beams, and separating the adjacent slabs with a space sufficient to permit remelting of solidified slag adhered between the adjacent slabs approaching the extraction outlet of the furnace.

Method for heating a silicon-containing steel slab in a walking-beam

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Himeji, Japan

Kichi Nakazawa