| 摘要 |
PURPOSE:To improve the quality of a product and to reduce the cost thereof by subjecting a billet sealed internally with a flux into the working hole at the center of the section to hot rolling with a diamond square pass then to finish rolling with an oval round pass. CONSTITUTION:The billet sealed with the flux into the working hole formed in the longitudinal direction at the center of the section is formed. The billet is first hot rolled with the diamond square pass. The billet is then rolled with the oval round pass. The elongation in the rolling by the oval round pass is made <=2.5 times regardless of the rolling reduction per pass and the number of passes. The billet is rolled by the diamond square pass in all the passes on the upper stream side of the oval square pass. The diameter D of the working hole or the size T on one side with respect t the size S on one side of the billet is made <=0.75 D/S and <=0.70 T/S, respectively. The inexpensive production of the product having the high quality is thus made possible.
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