A device for handling mandrel rods in a rolling plant for rolling seamless tubes comprises an inserter. The inserter moves a mandrel rod in a rolling direction such that the mandrel rod, starting from an initial state, is pushed into a tube blank situated upstream of the mandrel rod. A retaining device has a fixing unit that is movable along the rolling line and is designed to temporarily hold the mandrel rod at an action point at a rear end of the mandrel rod and to carry out a working stroke. The mandrel rod can be inserted into the rolling mill in the rolling direction and pulled out of the rolling mill counter to the rolling direction by the retaining device. The retaining device is designed such that the starting position of the fixing unit lies between the two ends of the mandrel rod in the initial state.

A device for handling mandrel rods in a rolling plant for rolling seamless tubes comprises an inserter. The inserter moves a mandrel rod in a rolling direction such that the mandrel rod, starting from an initial state, is pushed into a tube blank situated upstream of the mandrel rod. A retaining device has a fixing unit that is movable along the rolling line and is designed to temporarily hold the mandrel rod at an action point at a rear end of the mandrel rod and to carry out a working stroke. The mandrel rod can be inserted into the rolling mill in the rolling direction and pulled out of the rolling mill counter to the rolling direction by the retaining device. The retaining device is designed such that the starting position of the fixing unit lies between the two ends of the mandrel rod in the initial state.

In order to improve the quality of pipe-like work pieces, a rolling mill has at least two successive consecutive rolling stages that have mandrel rods. A threading line for the mandrel rod of the second rolling stage can lie on an extraction line for the mandrel rod of the first rolling stage. The same advantage can be achieved in a rolling method for the production of pipe-like work pieces, comprising at least two successive consecutive rolling stages, wherein the two rolling stages perform the rolling with the use of mandrel rods. The work piece is brought from the mandrel rod of the first rolling stage onto the mandrel rod of the second rolling stage, without entirely emptying an interior of the work piece and/or without changing the direction of movement of the work piece or braking the work piece in the meantime and accelerating it once again.

A method for producing hot-rolled, seamless pipes having at least one wall thickening which can be arranged at any positions over the length of the pipe, wherein by means of a multiple-stand mandrel bar rolling mill, the rolls roll a hollow shell on a mandrel bar as an inner tool to a required nominal wall thickness and produce at specified positions over the length of the pipe a required wall thickening on the outer side of the pipe by opening the rolls in the rolling stands. The thickened wall is produced and finish-rolled by two rolling stands that are consecutive as seen in the rolling direction, in which the deviations of the finished contour of the thickening from an ideal circular cross-section are minimised, wherein the rolling stands located upstream are likewise opened as to avoid any contact of the rolls of these rolling stands with the previously produced thickening.

A method for producing hot-rolled, seamless pipes having at least one wall thickening which can be arranged at any positions over the length of the pipe, wherein by means of a multiple-stand mandrel bar rolling mill, the rolls roll a hollow shell on a mandrel bar as an inner tool to a required nominal wall thickness and produce at specified positions over the length of the pipe a required wall thickening on the outer side of the pipe by opening the rolls in the rolling stands. The thickened wall is produced and finish-rolled by two rolling stands that are consecutive as seen in the rolling direction, in which the deviations of the finished contour of the thickening from an ideal circular cross-section are minimised, wherein the rolling stands located upstream are likewise opened as to avoid any contact of the rolls of these rolling stands with the previously produced thickening.

A rolling mill stand for rolling rod-shaped bodies, in particular tubular bodies, said stand comprising at least three rolls (10) mutually arranged to define a rolling pass line for said rod-shaped and/or tubular bodies, wherein at least one of said three rolls (10) is rigidly mounted on a roll holder shaft (20), freely fixed in turn in a rotational manner to said stand by means of a first hollow support (40) and a second hollow support (30) arranged on opposite sides of said at least one roll (10), respectively, wherein a first portion (21) and a second portion (22) of said roll holder shaft (20) are housed in said first hollow support (40) and in said second hollow support (30), respectively, where the constraint between at least said first hollow support and said first portion (21) of the roll holder shaft is of elastic type.

A stretch reducing rolling mill for rolling pipes has a plurality of roll stands arranged in series in a conveying direction of a pipe. A wall thickness measuring device determines a wall thickness progression of the pipe prior to rolling. A control unit controls respective rotational speeds of the roll stands. A pipe position measuring device is arranged in front of the roll stands and continuously measures a current longitudinal coordinate of the pipe. The measured values of the longitudinal coordinate of the pipe are transmitted to the control unit. The control unit controls the rotational speeds of the roll stands based on both the determined wall thickness progression and the transmitted measured values of the current longitudinal coordinate of the pipe, in order to compensate for wall thickness variations of the pipe. A stretch reducing rolling mill is designed to carry out the method.

A stretch reducing rolling mill for rolling pipes has a plurality of roll stands arranged in series in a conveying direction of a pipe. A wall thickness measuring device determines a wall thickness progression of the pipe prior to rolling. A control unit controls respective rotational speeds of the roll stands. A pipe position measuring device is arranged in front of the roll stands and continuously measures a current longitudinal coordinate of the pipe. The measured values of the longitudinal coordinate of the pipe are transmitted to the control unit. The control unit controls the rotational speeds of the roll stands based on both the determined wall thickness progression and the transmitted measured values of the current longitudinal coordinate of the pipe, in order to compensate for wall thickness variations of the pipe. A stretch reducing rolling mill is designed to carry out the method.

The present invention relates to a device for guiding a movable element, in particular a driving bar of a mandrel or a mandrel, in a rolling mill with mandrel. The device according to the invention comprises a support structure for the advancement of the movable element along an advancement direction. The device comprises a first slide and a second slide which are carried by said support structure and are slidable along a transverse direction which is substantially orthogonal to said advancement direction, in which each slide carries two abutment surfaces for guiding the movable element and in which each slide is movable along said transverse direction between at least a first operating position, upon reaching which said abutment surfaces are susceptible to coming into contact with a movable element of a first predefined diameter, and at least a second operating position, upon reaching which said abutment surfaces are susceptible to coming into contact with a movable element of a second predefined diameter. According to the invention, the device comprises actuating means which move the slides along the transverse direction between the operating positions and lock the slides themselves when one of said operating positions is reached.

The present invention relates to a device for guiding a movable element, in particular a driving bar of a mandrel or a mandrel, in a rolling mill with mandrel. The device according to the invention comprises a support structure for the advancement of the movable element along an advancement direction. The device comprises a first slide and a second slide which are carried by said support structure and are slidable along a transverse direction which is substantially orthogonal to said advancement direction, in which each slide carries two abutment surfaces for guiding the movable element and in which each slide is movable along said transverse direction between at least a first operating position, upon reaching which said abutment surfaces are susceptible to coming into contact with a movable element of a first predefined diameter, and at least a second operating position, upon reaching which said abutment surfaces are susceptible to coming into contact with a movable element of a second predefined diameter. According to the invention, the device comprises actuating means which move the slides along the transverse direction between the operating positions and lock the slides themselves when one of said operating positions is reached.