GB2078579A

GB2078579A - A Method for Preparing a Polygonal Billet or Ingot for Processing in a Skew-roller Piercing Mill

Info

Publication number: GB2078579A
Application number: GB8029443A
Authority: GB
Original assignee: Benteler Deustchland GmbH
Current assignee: Benteler Deustchland GmbH
Priority date: 1980-06-21
Filing date: 1980-09-11
Publication date: 1982-01-13
Also published as: IT1145414B; BE884959A; FR2484872B1; FR2484872A1; JPS5714401A; DE3023284A1; IT8049629A0; GB2078579B

Abstract

In order to prepare a blank (3), in the form of a rolled or cast polygonal billet or cast polygonal ingot, for processing in a skew-roller piercing mill, the longitudinal edges of the blank are cylindrically deformed to approximately circular cross section. The blank (3) is deformed in a roll stand (11) comprising grooved rolls (13 to 16) defining a substantially circular pass, the blank being pushed through a guide (10) to the rolls, by means of a ram. The stand may have two sets of rolls arranged in tandem. <IMAGE>

Description

SPECIFICATION A Method and Apparatus for Preparing a Polygonal Billet or Block for Processing in a Skew-roller Piercing Mill This invention relates to a method and apparatus for preparing a rolled or cast polygonal billet or cast polygonal ingot for processing in a skew-roller piercing mill.

In the manufacture of seamless tubes, it is necessary during a first manufacturing stage to pierce the blanks, i.e. rolled or continuously cast billets or ingots produced by conventional casting.

The holes are formed in the blanks either in a punching press or a skew-roller piercing mill.

The advantage of using a punching press for piercing is that the blanks used can be round (circular), square, hexagonal, octagonal or twelve sided in cross-section, the polygonal blanks being cheaper to produce than round blanks. In order, however, to obtain a well-perforated blank with a bore having minimum eccentricity, it is found in practice that the ratio of the blank length to the hole diameter in the punching press must not exceed about 7:1 to 10:1. This of course limits the maximum weight of a blank which can be placed in a punching press.

This disadvantage of using a punching press for piercing is admittedly absent when a skew roller piercing mill is used, where the blank length/diameter ratio can be much greater than for the maximum weight of a blank which can be accommodated in a punching press. However, blanks for processing in a skew-roller piercing mill have to be made round in cross-section. Round ingots or round billets have the disadvantage that they are more expensive to make than polygonal ingots or billets and also pose greater problems regarding quality. This applies both to stationary casting and continuous casting.

The invention therefore is based on the problem of providing a method and apparatus which can make use of the qualitative and ecomomic advantage of polygonal ingots or billets for processing in skew-roller piercing mills.

The method of the invention is based on the discovery that a billet or ingot can be efficiently engaged and conveyed through a skew-roller piercingmill even if the cross-section of the billet or ingot is only approximately round.

In accordance with the invention, there is provided a method of preparing a blank, in the form of a rolled or cast polygonal cross-section billet or cast polygonal cross-section ingot, for processing in a skew-roller piercing mill, which method includes cylindrically deforming the longitudinal edges of the polygonal blank so that the diameter of the circle circumscribing the thus deformed edge regions and having its centre on the longitudinal axis of the polygonal blank is approximately equal to the diameter of the circle to whirh the straight side surfaces connecting the longitudinal edges of the polygonal blank before deformation are tangential.

The result of such deformation is a blank crosssection which has sufficiently large peripheral cylindrical surface regions for the blank to be efficiently engaged and pulled through a skewroller piercing mill.

A significant advantage of the method according to the invention is that the positive features of rolling or casting odpolygonal billets or ingots (these relate mainly to quality and low cost) can now be combined with the advantages resulting mainly from the considerably higher weight blanks which can be perforated in a skewroller piercing mill compared to a punching press.

In order further to increase the profitabiltiy, according to another feature of the invention in this connection, the billet or block having deformed longitudinal edges is supplied to a skew-roller piercing mill at approximately the same temperature.

Apparatus in accordance with the invention, comprises apparatus for preparing a blank, in the form of a rolled or cast polygonal cross-section billet or cast polygonal cross-section ingot, for processing in a skew-roller piercing mill, which apparatus includes a roll stand comprising a plurality of grooved rolls having axes in the same plane and cross-sections having double or multiple corners and combining to form an approximately round pass.

With regard to the shape of the round-pass cross-sections cut peripherally in the grooved rolls, it is important that the relatively sharp or slightly rounded longitudinal edges of a polygonal section blank can be cylindrically deformed until there is a minimum difference between the diameter of the circle circumscribing the deformed edge regions and the diameter of the circle to whictthe straight peripheral surfaces connecting the longitudinal edges of the polygonal blank before deformation are tangential. This ensures that the rollers in the skew-roller piercing mill can reliably grip the ingot or billet and convey it through the mill.

In a preferred embodiment of the apparatus according to the invention, the roll stand has four grooved rolls having axes at 90 intervals and disposed in the same vertical plane. A set of rolls of the aforementioned kind ensures e.g. that an octagonal block can be efficiently deformed until its cross-section is approximately round.

According to another embodiment of the invention, however, the roll stand contains two sets of grooved rolls one set being behind the other. This embodiment is of use when the blanks for producing seamless pipes are square section ingots. In such cases the four longitudinal edges of the polygonal ingot are first compressed in a first set of grooved rolls so aeto produce an octagonal section. In the second set of rolls, the last-mentioned section is deformed until it is approximately round, when thediameter of the circle circumscribing the cross-section is approximately equal to the diameter of the circle inscribe in the cross-section.

The grooved rolls of the stand can be either driven or not. If the rolls are driven, according to an advantageous embodiment, the peripheral speed of the grooved rolls is adjusted to the advance speed of the billet or ingot which is moved relative to the rolls. The adjusting means can be mechanical or electronic. If the grooved rolls are not driven, there will of course be no need to connect the rolls by transmission means, e.g. gearwheels.

A pusher may be provided for pushing the billet or ingot towards the roll stand and may be actuated by a hydraulic or pneumatic cylinder or an electric motor. Preferably the pusher is reciprocated by a hydraulic cylinder.

In order that the invention may be readily understood, an embodiment thereof will now be described, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a plan view of an apparatus embodying the invention for deforming a polygonal ingot: Figure 2 shows the apparatus in vertical longitudinal section along line Il-Il of Figure 1; Figure 3 is a vertical section through the apparatus along line Ill-Ill in Figure 2; Figure 4 shows another vertical section through the apparatus along IV--IV in Figure 2; Figure 5 is an end view of an ingot having an octagonal transverse cross-section before its longitudinal edges have been deformed; and Figure 6 likewise is an end view of the octagonal ingot in Figure 5 after its longitudinal edges have been deformed.

Figures 1 and 2 show an apparatus 2 for deforming a polygonal ingot 3, the apparatus having a frame 1. At one end the device 2, which is shown only schematically, has a hydraulic cylinder 4 extending in the vertical central longitudinal plane. A pusher 6 is secured to the end face of the piston rod 5 of the cylinder 4. The cylinder 4 is supported on brackets 7 and 8 fixed to frame 1.

The pusher 6 can be used, for example, to push an octagonal ingot 3 sliding in a feed bed 9 (see Figure 4) into a centring sleeve 10 from where it is conveyed to a set 11 of grooved rolls (see Figure 3). After leaving roller set 11, and ingot 3 has been peripherally deformed and is supplied by a roller conveyor 12 to a skew-roller piercing mill (not shown).

Roller set, 11 comprises four grooved rolls 13, 14, 1 5 and 1 6 at 900 intervals and having axes 18, 19, 20, 21 in a common vertical plane in a roll stand 17. Rolls 13 to 1 6 all have cylindrical crosssections and, as shown more particularly in Figure 3, combine to form a substantially round pass 22.

Rolls 13 to 1 6 are rotatably driven and, to this end, the grooved rolls 13, 1 6 and 1 5 downstream of roll 14, which is secured to a drive shaft 23, are inter-connected by bevel gearing 24, 25 and 26.

Before being introduced into the centring sleeve 10, the polygonal ingot 3 sliding in bed 9 has approximately the cross-section shown in detail in Figure 5, the longitudinal edges 27 of ingot 3 being slighly rounded.

In the set of rolls 11, the longitudinal edges 27 of ingot 3 are cylindrically deformed (see Figure 3) so that the diameter D of the circle DK circumscribing the deformed edge regions 28 and having its centre on the longitudinal axis LA of ingot 3 is approximately equal to the diameter d of the circle dk to which the straight side surfaces 29 connecting the longitudinal edges 27 of ingot 3 before deformation are tangential.

Claims

1. A method of preparing a blank, in the form of a rolled or cast polygonal cross-section billet or cast polygonal cross-section ingot, for processing in a skew-roller piercing mill, which method includes cylindrically deforming the longitudinal edges of the polygonal blank so that the diameter of the circle circumscribing the thus deformed edge regions and having its centre on the longitudinal axis of the polygonal blank is approximately equal to the diameter of the circle to which the straight side surfaces connecting the longitudinal edges of the polygonal blank before deformation are tangential.

2. A method according to claim 1, wherein the blank having deformed longitudinal edges is supplied to a skew-roller piercing mill at approximately the same temperature.

3. Apparatus for preparing a blank, in the form of a rolled or cast polygonal cross-section billet or cast polygonal cross-section ingot for processing in a skew-roller piercing mill, which apparatus includes a roll stand comprising a plurality of grooved rolls having axes in the same plane and cross-sections having double or multiple corners and combining to form an approximately round pass.

4. Apparatus according to claim 3, wherein the roll stand has four grooved rolls having axes at 900 intervals and disposed in the same vertical plane.

5. Apparatus according to claim 3 or 4, wherein the roll stand contains two sets of grooved rolls, one set being behind the other.

6. Apparatus according to any one of claims 3 to 5, wherein the grooved rolls are driven.

7. Apparatus according to claim 6, wherein the peripheral speed of the grooved rolls is adjusted to the speed of advance of the blank which is moved relative to the rolls.

8. Apparatus according to claim 7, whereon a pusher is provided for pushing a blank forward to the roll stand and is actuated by a hydraulic br pneumatic cylinder or an electric motor.

9. A method of preparing a rolled or cast polygonal cross-section billet or ingot for processing in a skew-roller piercing mill substantially as hereinbefore described with reference to the accompanying drawings.

10. Apparatus for preparing a rolled or cast polygonal billet or ingot for processing in a skewroller piercing mill substantially as hereinbefore described with reference to, and as illustrated in, the accompanying drawings.

11. Any novel feature or combination of features herein described.