Jfe Steel Corporation

Keigo Toishi

Norichika Aramaki

Yuji Miki

Naoki Kikuchi

Hiroyuki Ono

Hiroyuki Ohno

Yutaka Awajiya

Tomoya Odagaki

Shizuhiko Ikeno

Keisuke Sano

Toshinori Tawa

Toru Ikagawa

A continuous casting method of steel includes the step of bulging wide side surfaces of a slab having there inside an unsolidified layer with a total intentional bulging amount of 3 to 10 mm by increasing stepwise toward a downstream side in a casting direction a roller gap of a plurality of pairs of slab support rollers disposed in a continuous casting machine.

Continuous casting method of steel

In the continuous steel casting method of the present invention, a gap between strand support rolls with a strand in a rectangular shape interposed therebetween is increased toward a downstream side in a casting direction to thereby bulge the strand having an unsolidified layer thereinside such that the thickness between long-side surfaces of the strand increases within the range of 0.1% or more and 10% or less of the thickness of the strand inside a mold. A portion of the strand in which the solid phase fraction in a central portion of the strand is within the range of 0.2 or more and less than 0.9 satisfies a prescribed total rolling reduction and a prescribed reduction gradient, and a portion of the strand in which the solid phase fraction is within the range of 0.9 or more satisfies a prescribed total rolling reduction and a prescribed reduction gradient.

Continuous steel casting method

Conditions for soft reduction are determined in a method of continuous casting in accordance with a method utilizing the thickness of a slab strand to prevent center segregation from occurring in the strand due to an insufficient pressing rate or internal cracks from occurring in the strand due to an excessively high pressing rate.

Provided is a continuous casting method of steel that prevents a solidification completion position from being changed even when a drawing speed V of a cast slab is changed. The method includes drawing a cast slab by setting a drawing speed Vwhile spraying cooling water to the cast slab at a cooling water spray amount W[kg/ton-cast slab]. Then, changing the drawing speed to the speed Vwhile spraying cooling water to the cast slab at a cooling water spray amount W[kg/ton-cast slab]. The method further includes spraying cooling water to the cast slab at a cooling water spray amount Wt [kg/ton-cast slab] during a period of time t that is obtained by dividing a target length Lt by the drawing speed V. The water spray amount Wt satisfying either formula (1): Wt&#x3c;Wunder a condition of V&#x3c;V, or formula (2): Wt&#x3e;Wunder a condition of V&#x3e;V

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Tokyo, Japan

Keigo Toishi