| 摘要 |
PROBLEM TO BE SOLVED: To lighten the load at boring time of a seamless steel pipe with skew rolling, by that linear segregation except the central part in a bloom with a continuous casting is lightened to form only the center segregation and easily perform the boring of the central part, and micro-porosity at the peripheral part is reduced and the development of scab and bulging flaw caused by oxidation is reduced. SOLUTION: In a multi-steps type light rolling-reduction facility composed of multi-steps of drawing-out strand in the continuous casting, the linear segregation in the cross sectional face in the thickness direction of the bloom except the central part, is restrained by applying the rolling-reduction of the bloom at 1.0-1.5 mm/step in each step of the rolling-reduction rolls disposed at the downstream of the mold in the range of 0.2-0.6 center solid-phase ratio of the bloom. Further, in each step of the rolling-reduction rolls at the rolling-reduction end stage zone of the drawing-out strand, the rolling-reduction action in the central part at the solidified end stage, is eliminated by opening the rolls, so as to develop the intense segregation only to the central part. COPYRIGHT: (C)2005,JPO&NCIPI
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