| 摘要 |
PROBLEM TO BE SOLVED: To obtain the severer accuracy of an outer diameter in case of a thick-walled tube having t/d of 8% or more. SOLUTION: Sizing is carried out by using the similar stands having the number of N or more which are provided with 2 to 4 pieces of grooved rolls in the vertical plane thereof. When the ellipticity of a rolling stand before a final one is determined asβN<SB>-1</SB>and the working rate of the outer diameter of a last rolling stand is determined asρN, hot rolling is carried out by satisfying the conditions represented by three formulas 0.99≤βN<SB>-1</SB>≤1.00,ρN≤1.0,βN<SB>-1</SB>≥-0.05ρN+1.0. Accordingly, the hot rolling of a metal pipe can be carried out by using the line of rolling mills having the same configurations without causing flaws at the edge of a reduction roll in case of the thick-walled tube having t/d of 8% or more. Further, the hot rolling can be carried out thus obtaining severer accuracy of an outer diameter such as roundness of 1.0 mm or less. COPYRIGHT: (C)2003,JPO
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