The present invention relates to a compact plant 10 for rolling a seamless tube. The plant comprises a rotary piercer 20 which defines a rolling axis X.sub.PR and is designed to pierce a billet 11 pressed against a plug 22 mounted on a rod so as to obtain a pierced blank 12. The rod is connected to a thrust block 26 designed to oppose the axial thrust during piercing. The plant also comprises a longitudinal mill 30 which defines a rolling axis X.sub.LL and is designed to roll the pierced blank 12 on a mandrel 32 so as to obtain a semi-finished tube 13. The mandrel is connected to a retaining block 34 designed to impart to the mandrel a predetermined speed during rolling. In the plant 10 according to the invention the rolling axes X.sub.PR and X.sub.LL coincide. The invention also relates to a method for rolling a seamless tube.

The invention relates to a pipe rolling plant 10 comprising a rotary piercer 20, a treatment station 30 and a main rolling mill 40. The rotary piercer and the treatment station are arranged so that the pierced blank 51 leaving them is arranged with the irregular tail 511 facing the main rolling mill 40 and with the regular head 510 facing the mandrel 41. The invention also relates to a rolling mill 40 comprising a plurality of rolling stations 43, each station comprising a plurality of rolling rolls 42, the radial position h of which is adjustable. The rolling mill also comprises a control circuit for calculating and/or measuring the distance d between the axes of rotation r of the rolls and the trailing edge 520 of the pipe 52. The control circuit is also designed to displace the rolling rolls radially towards the outside of the pipe in each rolling station 43.sub.n when the distance d assumes a predetermined value d.sub.0.

The invention relates to a pipe rolling plant 10 comprising a rotary piercer 20, a treatment station 30 and a main rolling mill 40. The rotary piercer and the treatment station are arranged so that the pierced blank 51 leaving them is arranged with the irregular tail 511 facing the main rolling mill 40 and with the regular head 510 facing the mandrel 41. The invention also relates to a rolling mill 40 comprising a plurality of rolling stations 43, each station comprising a plurality of rolling rolls 42, the radial position h of which is adjustable. The rolling mill also comprises a control circuit for calculating and/or measuring the distance d between the axes of rotation r of the rolls and the trailing edge 520 of the pipe 52. The control circuit is also designed to displace the rolling rolls radially towards the outside of the pipe in each rolling station 43.sub.n when the distance d assumes a predetermined value d.sub.0.

The invention relates to a method for producing seamless steel tubes in a rolling mill train with one or more consecutively positioned longitudinal or cross-rolling units and an inside tool which is used as mandrel bar or piercing plug during the rolling process. The aim is to provide a method to reduce the eccentricity of the rolling stock considerably. To achieve this, the longitudinal axis of the inside tool is forced by means of an apparatus to a movement in a distance to the longitudinal axis of the rolling stock. Simultaneously the rotation of the tool around its axis is kept, driven by the rolling stock during rolling.

The invention relates to a method for producing seamless steel tubes in a rolling mill train with one or more consecutively positioned longitudinal or cross-rolling units and an inside tool which is used as mandrel bar or piercing plug during the rolling process. The aim is to provide a method to reduce the eccentricity of the rolling stock considerably. To achieve this, the longitudinal axis of the inside tool is forced by means of an apparatus to a movement in a distance to the longitudinal axis of the rolling stock. Simultaneously the rotation of the tool around its axis is kept, driven by the rolling stock during rolling.

A manufacturing method of a seamless metal pipe includes determining whether a preceding-stage stand group is used in outer diameter reduction or in thickness reduction of a hollow shell; and performing elongating on the hollow shell, into which a mandrel bar is inserted, based on the determination. In addition, in the elongating, when the preceding-stage stand group is used in the outer diameter reduction, the hollow shell is rolled in a state where an inner surface of the hollow shell does not come into contact with the mandrel bar in the preceding-stage stand group, and the hollow shell is rolled in a state where the inner surface of the hollow shell comes into contact with the mandrel bar in the succeeding-stage stand group.

A manufacturing method of a seamless metal pipe includes determining whether a preceding-stage stand group is used in outer diameter reduction or in thickness reduction of a hollow shell; and performing elongating on the hollow shell, into which a mandrel bar is inserted, based on the determination. In addition, in the elongating, when the preceding-stage stand group is used in the outer diameter reduction, the hollow shell is rolled in a state where an inner surface of the hollow shell does not come into contact with the mandrel bar in the preceding-stage stand group, and the hollow shell is rolled in a state where the inner surface of the hollow shell comes into contact with the mandrel bar in the succeeding-stage stand group.

An apparatus, method and composition for long length tubing includes continuous production of long length seamless aluminum tubing suitable for use as coiled tubing in hydrocarbon wells. A 2XXX aluminum alloy may be used in combination with a continuous casting/extrusion apparatus using aluminum from a melt. Other metals may be used, as well as continuously cast rod from a casting wheel and belt or conform extruder, which is processed to form a hollow and then sized by drawing.

There is provided a piercing apparatus in which the occurrence of an inner surface flaw in a hollow shell is suppressed. A piercing apparatus (10) according to an embodiment of the present invention is the piercing apparatus (10) which pierces a billet (18). The piercing apparatus (10) has a plug (14). The plug (14) has a through hole (30). The through hole (30) extends along the central axis, and allows the central portion of the billet (18) being pierced to pass therethrough.

There is provided a piercing apparatus in which the occurrence of an inner surface flaw in a hollow shell is suppressed. A piercing apparatus (10) according to an embodiment of the present invention is the piercing apparatus (10) which pierces a billet (18). The piercing apparatus (10) has a plug (14). The plug (14) has a through hole (30). The through hole (30) extends along the central axis, and allows the central portion of the billet (18) being pierced to pass therethrough.