GB1573018A - Roll pass design - Google Patents

Description

(54) A ROLL PASS DESIGN (71 We, MANNESMANN AKTENGESELL SCHAFT, a German Body Corporate of 2 Mannesmannufer, 4 Dusseldorf 1, Federal Republic of Germany, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: The invention relates to a roll pass design for a skew-rolling mill for the finishrolling of seamless tubes, having cambered driven rolls, guides arranged between the rolls and a mandrel arranged inside the tube.

It is known from skew-rolling mills that it is difficult to produce thin-walled tubes and/or tubes having high surface quality on these mills. Consequently, it is the established practice to follow the skewrolling mill by gauging or calibrating rolling mills having roll shafts disposed perpendicular to the tube axis, the equipping of said mills with tools being complicated.

Despite several proposals to the contrary, this opinion held in practice has so far not been overcome. Thus, it has already been proposed to calibrate and to smooth tubes by mandrel-free diagonal rolling with at least three rolls and so-called "shoulder gauges" (German Patent Specification No.

936 322, Assel), but with this arrangement only acceptable results are produced with thick-walled, e.g. ball-bearing tubes. It has also been proposed in other publications to work without a mandrel and with shoulder gauges. Moreover, the smoothing is to be affected solely by a reduction in diameter or by using guide discs with an increased drawing action.

It is the aim of the invention to manufacture normal-walled seamless tubes by skew-rolling with a surface quality and uniformity sufficient to produce finished tubes.

Accordingly the present invention provides a roll pass design for a skew-rolling mill for the finish-rolling of seamless tubes, comprising driven rolls, elongate guides arranged between the rolls, and a mandrel adapted in use to be located inside the tube, wherein each roll comprises a conical entry portion for producing an initial reduction of the internal and external diameters of the tube, a cylindrical portion of greater diameter than the entry diameter of the roll and a conical exit portion of reducing diameter towards the exit to ensure roundness of the tube and substantial restoration of the external diameter of the tube.

The invention is capable of being used with two or three skew rolls in a frame, preference being given to the skew-rolling mill having two rolls, because of the more simple arrangement of the guiding straight edges or arms. The small angle between roll axis and tube axis may amount preferably to 2" to 80, so that the axial feed of the rolls onto the tube with each revolution of the tube is smaller than the effective width of the smoothing portion of the skew rolls. The mandrel disposed in the tube is held in known manner by a mandrel rod supported in a counter-support. The tube is at hot-shaping temperature.

The invention is employed for tubes which are produced in known manner by piercing a solid block and drawing on a skew-rolling mill having a roll pass design in accordance with the invention, the tubes are not subjected to any further heat deformation, i.e. are not subsequently treated by continuous rolling or reduction by drawing. It follows from this that the diameter of the finished tube amounts to more than 150 up to about 450 mm, with suitable wall thickness. Such tubes are used, for example, as cylinder tubes or, in a heat-resistant quality, as conduction tubes in boiler construction.

A reduction in diameter of the skew rolls towards the exit portion may be provided within the cylindrical smoothing portion with a corresponding portion on the mandrel having an increase in diameter.

By this additional feature, the method of operation of the invention, differing from the prior art, becomes particularly apparent, since no shoulder gauge is needed, the smooth rolling occurring in conjunction with a tube widening.

The elongate guides extended in all cases over the entire width of the rolls. The contour thereof is smooth in the direction of the tube axis and extends at least approximately parallel to the said axis. Perpendicularly thereof, the contour is adapted to the tube diameter. The elongate guides are arranged with small clearance from the largest tube diameter in the smoothing portion of the skew rolls.

The invention will now be described, by way of example, with reference to the accompanying diagrammatic drawings, in which: Fig. 1 shows one embodiment of a roll pass design, and Fig. 2 shows another embodiment of a roll pass design.

The bottom halves of the Figures show the arrangement of the elongate guides.

The representation is turned through 90" in relation to the tube axis, as compared with the upper half of the Figure.

In Figure 1, skew roll 1 takes up the tube 2 at the conical entry portion 3 and forces the tube, with a reduction in wall thickness up to 35%, on to the mandrel 4. Following said portion is a cylindrical smoothing portion 5, the length of which may be 1 to 5 times that of the entry portion 3, and an exit portion 6. Another skew roll is arranged opposite thereto.

Both rolls are mounted in a certain position and driven. The position of the skew rolls determines the diameter of the finished tube and, in association with the mandrel 4, the thickness of the wall.

Elongate guides 7 are arranged in pairs on the circumference of the tube between the skew rolls, the spacing of the guides from one another being somewhat larger than the spacing from one another of the skew rolls 1 with their smoothing portion 5. Since the tube becomes larger because of the reduction in the wall thickness, it bears against the guiding arms. The exit portion 6 causes a rounding of the finished tube 8, so that it is lifted all round from the mandrel 4.

In Figure 2, the diagonal roll 1, has a conical entry portion 3 and a conical exit portion 6, and between them two smoothing portions 9 and 10 by means of a portion 11 of reducing diameter. A corresponding portion 12 of increasing diameter is formed on the mandrel 4. The portion 11 of the skew roll 1 produces a more effective improvement in the internal surface of the tube 2.

WHAT WE CLAIM IS: 1. A roll pass design for a skew-rolling mill for the finish-rolling of seamless tubes, comprising driven rolls, elongate guides arranged between the rolls, and a mandrel adapted in use to be located inside the tube, wherein each roll com- prises a conical entry portion for producing an initial reduction of the intenal and external diameters of the tube, a cylindrical portion of greater diameter than the entry diameter of the roll and a conical exit portion of reducing diameter towards the exit to ensure roundness of the tube and substantial restoration of the external diameter of the tube.

2. A roll pass design according to Claim 1, wherein a reduction in diameter of the rolls towards the exit portion is provided within the cylindrical smoothing portion, opposite to which is located an enlargement in diameter of the mandrel.

3. A roll pass design according to Claim 1 or 2, wherein the elongate guides extend over the entire width of the roll and are arranged with small clearance from the largest tube diameter in the smoothing portion of the rolls.

4. A roll pass design substantially as herein described with reference to Figure 1 or Figure 2 of the accompanying drawings.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (4)

**WARNING** start of CLMS field may overlap end of DESC **. A reduction in diameter of the skew rolls towards the exit portion may be provided within the cylindrical smoothing portion with a corresponding portion on the mandrel having an increase in diameter. By this additional feature, the method of operation of the invention, differing from the prior art, becomes particularly apparent, since no shoulder gauge is needed, the smooth rolling occurring in conjunction with a tube widening. The elongate guides extended in all cases over the entire width of the rolls. The contour thereof is smooth in the direction of the tube axis and extends at least approximately parallel to the said axis. Perpendicularly thereof, the contour is adapted to the tube diameter. The elongate guides are arranged with small clearance from the largest tube diameter in the smoothing portion of the skew rolls. The invention will now be described, by way of example, with reference to the accompanying diagrammatic drawings, in which: Fig. 1 shows one embodiment of a roll pass design, and Fig. 2 shows another embodiment of a roll pass design. The bottom halves of the Figures show the arrangement of the elongate guides. The representation is turned through 90" in relation to the tube axis, as compared with the upper half of the Figure. In Figure 1, skew roll 1 takes up the tube 2 at the conical entry portion 3 and forces the tube, with a reduction in wall thickness up to 35%, on to the mandrel 4. Following said portion is a cylindrical smoothing portion 5, the length of which may be 1 to 5 times that of the entry portion 3, and an exit portion 6. Another skew roll is arranged opposite thereto. Both rolls are mounted in a certain position and driven. The position of the skew rolls determines the diameter of the finished tube and, in association with the mandrel 4, the thickness of the wall. Elongate guides 7 are arranged in pairs on the circumference of the tube between the skew rolls, the spacing of the guides from one another being somewhat larger than the spacing from one another of the skew rolls 1 with their smoothing portion 5. Since the tube becomes larger because of the reduction in the wall thickness, it bears against the guiding arms. The exit portion 6 causes a rounding of the finished tube 8, so that it is lifted all round from the mandrel 4. In Figure 2, the diagonal roll 1, has a conical entry portion 3 and a conical exit portion 6, and between them two smoothing portions 9 and 10 by means of a portion 11 of reducing diameter. A corresponding portion 12 of increasing diameter is formed on the mandrel 4. The portion 11 of the skew roll 1 produces a more effective improvement in the internal surface of the tube 2. WHAT WE CLAIM IS:

1. A roll pass design for a skew-rolling mill for the finish-rolling of seamless tubes, comprising driven rolls, elongate guides arranged between the rolls, and a mandrel adapted in use to be located inside the tube, wherein each roll com- prises a conical entry portion for producing an initial reduction of the intenal and external diameters of the tube, a cylindrical portion of greater diameter than the entry diameter of the roll and a conical exit portion of reducing diameter towards the exit to ensure roundness of the tube and substantial restoration of the external diameter of the tube.

2. A roll pass design according to Claim 1, wherein a reduction in diameter of the rolls towards the exit portion is provided within the cylindrical smoothing portion, opposite to which is located an enlargement in diameter of the mandrel.

3. A roll pass design according to Claim 1 or 2, wherein the elongate guides extend over the entire width of the roll and are arranged with small clearance from the largest tube diameter in the smoothing portion of the rolls.

4. A roll pass design substantially as herein described with reference to Figure 1 or Figure 2 of the accompanying drawings.