Mandrel mill, operating method of the same and production method of seamless pipe
OwnerKenichi Sasakiinventor
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Abstract
The object of the present invention is to provide a mandrel mill capable of producing a seamless pipe without flaws such as necking. The mandrel mill of the present invention includes a plurality of consecutively provided grooved-roll stands and a mandrel bar 3 provided in a roll groove array formed by the grooved-roll stands so as to continuously elongate a hollow shell 2. Roll grooves 4 of at least a first stand and a second stand are arranged so as to satisfy conditions represented by the following formulas (1) to (4): b≦10a+1.5 (1) b≧10a−0.2 (2) b≦−a+1.5 (3) b≧−a+1.15 (4) wherein a=S/R1, b=C/(R1−S).
Claims3
A mandrel mill comprising a plurality of consecutively provided grooved-roll stands and a mandrel bar provided in a roll groove array formed by the grooved-roll stands so as to continuously elongate a hollow shell, characterized in that roll grooves of at least a first stand and a second stand are arranged so as to satisfy conditions represented by the following formulas (1) to (4):
- b≦10a+1.5 (1)
- b≧10a−0.2 (2)
- b≦−a+1.5 (3)
- b≧−a+1.15 (4)
- wherein “a” is a ratio of S/R1 between a groove bottom curvature radius R1 of each grooved-roll and a displacement-offset-amount S between a groove bottom curvature center and a mill center, and “b” is ellipticity.
An operating method of a mandrel mill including a plurality of consecutively provided grooved-roll stands and a mandrel bar provided in a roll groove array formed by the grooved-roll stands, characterized in that a hollow shell is continuously elongated when a groove bottom curvature radius R1, a displacement-offset-amount S, and ellipticity of each of grooved-rolls satisfy conditions represented by the following formulas (1) to (4) in at least a first stand and a second stand, whereby a hole occurrence and flaw generation are prevented:
- b≦10a+1.5 (1)
- b≧10a−0.2 (2)
- b≦−a+1.5 (3)
- b≧−a+1.15 (4)
- wherein “a” is a ratio of S/R1 between a groove bottom curvature radius R1 of each grooved-roll and a displacement-offset-amount S between a groove bottom curvature center and a mill center, and “b” is ellipticity.
A production method of a seamless pipe using a mandrel mill including a plurality of consecutively provided grooved-roll stands and a mandrel bar provided in a roll groove array formed by the grooved-roll stands, characterized in that a hollow shell is continuously elongated when a groove bottom curvature radius R1, a displacement-offset-amount S, and ellipticity of each of grooved-rolls satisfy conditions represented by the following formulas (1) to (4) in at least a first stand and a second stand:
- b≦10a+1.5 (1)
- b≧10a−0.2 (2)
- b≦−a+1.5 (3)
- b≧−a+1.15 (4)
- wherein “a” is a ratio of S/R1 between a groove bottom curvature radius R1 of each grooved-roll and a displacement-offset-amount S between a groove bottom curvature center and a mill center, and “b” is ellipticity.
Dependencies are inferred from the claim text.