Abstract: A method for straightening a tube by using an asymmetric roll, which has different diameters D1 (exit side), D2 (entry side) at relative maximum diameter portions, left and right roll shoulder portions, as a straightening roll of a straightener, wherein the roll shoulder having a smaller diameter is disposed to be located on the tube entry side. The straightening roll used therefor comprises roll shoulders 3a and 3b and a roll barrel portion 4, in which D1>D2 and 0.004?(D1?D2)/d?0.2 (d: outer diameter of tube to be straightened) are satisfied. Further, an aspect of the invention may define radii of curvatures of entry-side and exit-side shoulder potions in a section of the roll cut along a plane including the roll central axis, or a curve representing an outer surface of the roll barrel portion.

Abstract: A method for straightening a tube by using an asymmetric roll, which has different diameters D1 (exit side), D2 (entry side) at relative maximum diameter portions, left and right roll shoulder portions, as a straightening roll of a straightener, wherein the roll shoulder having a smaller diameter is disposed to be located on the tube entry side. The straightening roll used therefor comprises roll shoulders 3a and 3b and a roll barrel portion 4, in which D1>D2 and 0.004?(D1?D2)/d?0.2 (d: outer diameter of tube to be straightened) are satisfied. Further, an aspect of the invention may define radii of curvatures of entry-side and exit-side shoulder potions in a section of the roll cut along a plane including the roll central axis, or a curve representing an outer surface of the roll barrel portion.

Abstract: The present invention provides a method for producing a threaded joint capable of improving the life of an O.D. turning tool and consequently improving the life of a chaser. The method for producing a threaded joint, which includes O.D. turning the surface of a joint followed by threading, wherein, before the O.D. turning, the surface of the joint is descaled by shot blasting.

Abstract: A blasting device for blasting steel pipe inner surface includes a tubular carrier fluid inflow unit connected to one end of a horizontal steel pipe, and a negative pressure suction unit connected to the other end of the steel pipe. A polishing material or a wiping material is injected horizontally into the carrier fluid inflow unit along with a carrier fluid from a hole formed in the edge face of the tubular carrier inflow unit. The device provides improved blast performance as well as the capability to blast the inner surface from beginning portion to an end portion to provide an excellent inner surface texture.

Abstract: A scale removing apparatus 7 in accordance with the present invention subjects the internal surface of the steel pipe 3 to a blasting process wherein abrasive particles (not shown) are ejected through a high-pressure jet nozzle 2 and collide with the internal surface of the steel pipe 3. The scale removing apparatus 7 has the high-pressure jet nozzle 2 for ejecting the abrasive particle, a dust collector 4 for collecting dust particles after blasting, and restraining means 6 for restraining air from flowing into the steel pipe 3 from an end part of the steel pipe 3 along with the transfer of abrasive particle ejected through the high-pressure jet nozzle 2. Therefore, the scale can be removed without scattering of dust particles into the atmosphere even with a low-capacity dust collector.

Abstract: [Problem] To provide a blasting device for steel pipe inner surface with improved blast performance as well as the capability to sufficiently blast the inner surface of the steel pipe from the beginning portion to the end portion; a blasting method for steel pipe inner surface; and a method for producing a steel pipe with excellent inner surface texture. [Solution] A blasting device for blasting steel pipe inner surface includes a tubular carrier fluid inflow unit 21 connected to one end of a horizontal steel pipe 6, and a negative-pressure suction unit connected to the other end of the steel pipe 6, and is characterized in that a polishing material or a wiping material 5 is injected horizontally into the carrier fluid inflow unit along with a carrier fluid 20 from a hole 19 formed in the edge face of the tubular carrier fluid inflow unit 21.