GB2104814A - Rolling mill entry guide - Google Patents

Abstract

An entry guide for a rod rolling mill guides the stock into the mill through a guide channel defined between opposed guide rollers (22, 23). The rollers accommodate changes in the stock thickness by means of inward or outward displacements, and are connected so that their displacements are coordinated and the axial location of the guide channel is thereby maintained substantially constant. Preferably the rollers are connected by a spring (36) and balls (38, 39, 40) which act upon levers 10, 20 carrying the rollers. The separation of the guide members may be monitored to give a direct read-out of the thickness or gauge of the stock to the mill operator. <IMAGE>

Description

SPECIFICATION Rolling mill entry guide This invention relates to an entry guide for a rolling mill and to a method of rolling elongate stock in a rolling mill. The invention is especially suited to use in rolling steel rod, bar or continuous sections. In a particular embodiment, the invention provides a roller entry guide for a rod mill.

Known rolling mill entry guides include a pair of spaced apart rollers carried in fixed guide leaves to define a guide channel. The guide is mounted on the entry side of the mill with the gap between the guide rollers set to the appropriate size and aligned with the roll pass in the mill. When the mill is operating, in the case for example of a steel rod mill, the rod may be passing through the guide at a speed of around 20,000 ftZmin and drive the rollers in the guide at speeds of up to 40,000 rpm.

In practice, the stock being rolled in the mill is of variable thickness, especially at the back end where, owing to reduced plasticity resulting from the lower rolling temperature, the stock tends not to be rolled down to the same thickness as the leading end. As a result it is necessary to set the roller gap in the guide a little wider than the nominal stock size. The guide rollers consequently give the stock only discontinuous support and the accuracy of the guide is reduced; furthermore, since wear in the miíl is likely to result in the stock size increasing over a period of time, back end overfill is still apt to occur and overload the rollers and damage their bearings.

The tendency to overfill the guide channel also means that very hard rollers, which tend to be brittle, cannot be used: it is necessary instead to use more ductile rollers, for example of stellite, but these wear relatively rapidly and typically the mill operator has to make allowance for the wear rate.

According to the present invention there is provided a mill entry guide for a rolling mill for rolling elongate stock, comprising opposed guide members, connected by coupling means, defining between them a stock guide channel, wherein each of the said guide members is displaceable outwardly of the guide channel against biassing means urging the guide member into the guide channel, and wherein the coupling means are adapted to coordinate the displacements of each of the said guide members and thereby maintain substantialiy constant the axial location of the guide channel.

The invention also provides a method of rolling elongate stock of irregular thickness along its length in a rolling mill, comprising guiding the stock into the mill through a guide channel defined between opposed guide members, holding each of the guide members in contact with the stock passing through the guide channel while accommodating changes in the stock thickness by means of inward or outward displacements of the guide members, and connecting the guide members so that their displacements are coordinated and the axial location of the guide channel is thereby maintained substantially constant.

The invention further provides a rolling mill including a mill entry guide as set forth above.

Use of the invention allows more continuous contact between the stock and the guide to give better support and more positive guidance to the stock as it enters the roli pass of the mill. The coordination of the guide member movements prevents lateral displacement of the guide channel and thereby further improves the accuracy of the entry guide. Since the guide members are enabled to move apart when the stock thickness increases it is possible to manufacture them of a more hardwearing but brittle material, such as sintered hard metal, tungsten carbide or titanium carbide, which wears as slowly as the rolls of the mill; in the case of a roller guide, the lives of both the rollers and their bearings may be extended with a concomitant improvement in the quality of the product rolled in the mill.

The guide members preferably comprise rollers, which may be provided with peripheral grooves of a suitable shape for the intended stock. The guide members may be mounted each on a displaceable support, such as a pivoted cantilever arm. In the case of a rod mill entry guide, two opposed rollers, each on its own pivoted guide leaf, are normally sufficient; however, more complex systems with a greater number of guide members can be used, for example two opposed pairs of guide rollers in which one pair is spaced upstream of the other pair to improve the alignment of the rod in the guide. Means are preferably provided for adjusting the position of each guide member independently of the other in order to set the location of the guide channel.

The biassing means is preferably such as to act equally on each guide member, and may for example comprise one spring or other energy store acting in a similar way on each guide member. Stop means are preferably present to limit the inward movement of each guide member and thereby define a minimum guide channel width. Means may also be provided to adjust the force exerted by the biassing means on the guide members, and accordingly by the guide members on the stock in the guide channel, in order to allow for different stock sizes and physical properties.

In one embodiment of the invention the guide members are connected by coupling means which comprise a connector of variable length having an intermediate element which is positively located in relation to the guide whereby to ensure that both ends of the connector move upon a change in the length of the connector. The connector may in particular comprise a train of abutting elements, including an intermediate element, held in abutment by inwardly directed forces acting on either end of the train, the elements other than the said intermediate element being movable longitudinally of the train, and the said intermediate element being immovable longitudinally of the train but movable into and out of the train whereby to progressively and equally move the ends of the train in opposite directions longitudinally of the train.In such a connector the intermediate element acts as a wedge to drive the ends apart against the inward forces acting on the ends of the train, which may be provided by a spring in tension between the ends of the train, or, when the ends are driven together, to be driven laterally out of the train. The wedge surfaces may be provided on the intermediate element and/or on the adjacent elements of the train. The elements having the wedge surfaces may usefully be spherical, cylindrical with hemispherical ends or cylindrical with conical orfrustoconical ends.

According to a further important aspect of the invention, the mill entry guide may additionally comprise means, such as a position transducer, adapted to monitor the separation of the guide members and hence the thickness or gauge of the stock when passing through the guide, and the method of the invention may correspondingly further comprise the step of monitoring the separation of the guide members.

The thickness or gauge of the stock thereby obtained may be made available by means of a direct read-out to the mill operator. This information is valuable as a check on many aspects of the rolling operation, and in particular can give an advance warning of an impending cobble in a rod mill caused by an oversize back end to the rod being rolled.

One embodiment of the invention is shown by way of example in the accompanying drawings, in which: Figure 1 is a side elevation, partly in section, of an entry guide for a steel rod mill; Figure 2 is a plan view, partly in section, of the entry guide; and Figure 3 is an end elevation of the same guide.

The guide shown in the drawings has a body portion 10 which carries a static guide tube 11 and two pivoted guide leaves 20, 21. The guide tube 11 is held in the body 10 by clamping screws 12 and is provided with a bell mouth 13 through which the rod is led into the guide. After passing along the static guide tube within the body of the guide the rod emerges to pass between guide rollers 22, 23 supported by the respective guide leaves 20, 21 and then leaves the guide to enter the next roll pass of the rolling mill.

The guide body 10 has a base flange 1 5 which has its front and rear ends tapered to fit in a complementary transverse dovetail groove located in a table on the entry side of the next pair of rolls in the mill. By this means the entry guide can be clamped in position in approximate alignment with the next roll pass.

Guide leaf 20 is pivotally mounted on a vertical spindle 24 held in the guide body. Roller 22 is mounted by way of bearings 26 in the nose of the guide leaf, which is tapered to allow it to be positioned closely between the mill rolls. The position of the guide leaf on the spindle is adjusted to achieve correct vertical alignment with the roll pass.

Guide leaf 21 is similarly mounted on vertical spindle 25 and carries roller 23 in bearings 27.

Figure 2 shows guide leaf 20 carrying a small roller 22 pivoted inwardly towards the other roller 23 in full outline, and carrying a large roller 22 pivoted outwardly from the other roller 23 in chain dotted outline. Conversely, guide leaf 21 is shown carrying a large roller 23 and pivoted outwardly away from the other roller 22 in full outline, and carrying a small roller 23 and pivoted inwardly towards the roller 22 in chain dotted outline. In practice, the rollers 22 and 23 wili be of the same diameter at any one time and the guide leaves will be adjusted to be equally or nearly equally distant from the axis of the guide tube 11; the alternatives are illustrated merely to show the range of adjustment available. The rollers 22, 23 define between them a guide channel for the rod in front of the rolls of the rod mill.

The tail ends of the guide leaves are provided with adjustment screws 28, 29 above the level of the static guide tube 11 and with downwardiy projecting pins 30, 31 below the level of the static guide tube. The pins are connected together by means of a link spring 36 in tension between them, which accordingly tends to draw the tail ends of the guide leaves towards one another and to cpen up the guide channel between the rollers 22, 23. Such movement is resisted by a train of three adjacent spherical steel balls lying in abutment between the adjustment screws 28, 29 in a channel 37 passing transversely through the guide body 10 above the static guide tube.

These three balls comprise two outer balls 38, 39 in contact with the adjustment screws 28, 29 respectively, and an intermediate ball 40 keeping the outer balls separated. The two outer balls are free to move along the transverse channel 37, either inwardly or outwardly, but the intermediate bail is trapped in a forward channel 45 in the guide body !ying above and parallel to the static guide tube and intersecting the transverse channel 37.The intermediate ball is pressed between the two outer balls by a coil spring 46 in compression in the forward channel between the intermediate ball and a pressure adjusting screw 47 The location of the intermediate ball 40 in the end of the forward channel 45 at its junction with the transverse channel 37 ensures that the train of three balls in abutment between the adjustment screws 28, 29 in the tail ends of the guide leaves 20, 21 cannot move as a whole to either side of the guide. It is therefore possible to centralise the guide channel between the rollers 22, 23 by means of the adjustment screws.

When the entry guide has been set up at the entry side of the mill rolls with the guide channel centred and in approximate alignment with the roll pass, fine lateral adjustment can be carried out using the adjustment screws 28, 29 to shift the centre line or axis of the guide channel to one side or the other.

In use, when rod is passing through the guide along the static guide tube 11 and between the rollers 22. 23, the compression spring 46 drives the intermediate ball 40 between the outer balls 38, 39 which in turn press out on the tail ends of the two guide leaves 20, 21. The guide leaves then pivot on the spindles 24, 25 and the rollers 22, 23 move towards each other into the guide channel defined between them until they abut the rod passing through the guide.If the gauge of the rod increases, as normally happens at the tail end of the rod, the greater diameter of the rod presses the rollers apart; as the guide leaves pivot, the adjusters at their tail ends drive the outer balls 38, 39 further into the transverse channel 37, thereby forcing the ball 40 back into the forward channel 45 against the spring 46 and reducing the overall length of the train of abutting elements between the two guide leaves.

The total linkage between the guide rollers is such as to keep a constant location to the centre line of the guide channel between the rollers.

When an increase in the rod gauge occurs and one of the guide rollers moves outwardly, the corresponding outer ball, 38 say, pushes the intermediate ball 40 a short distance further into the forward channel 45. This movement relieves the pressure of the intermediate ball on the other outer ball 39, and would accordingly eliminate the resistance offered by the compression spring 46 to the outward movement of the other roller 23; however, since the rod presses virtually equally on the two rollers, the system functions so that the rollers open equally and both the outer balls 38, 39 are pressed with equal force against the ball 40. The link spring 36 serves to keep the adjustment screws in the guide leaves in contact with the outer balls, and them in turn in contact with the intermediate ball, when there is no rod present in the guide channel.A stop 50 is provided in the wall of the transverse channel 37 opposite the forward channel 45 to limit the extent to which the ball 40 can project into the transverse channel when it is not otherwise limited by the presence of rod in the guide channel between the rollers 22, 23.

The three balls 38, 39, 40 together make up a wedge system having spherical surfaces. One result of this geometry is that the force required to separate the guide rollers further decreases as the separation increases. This compensates for the increased force exerted by the spring 46 as it becomes more compressed and helps to prolong the life of the bearings 27.

The balls could be replaced by cylinders having hemispherical, conical or frustoconical noses.

Such cylinders could more easily be provided with circumferential bearings and/or sealing rings on which they would slide in the channels 37 and 45.

The stop 50 contains a position transducer 51, which comprises a spring loaded piston located in a bore 52 in the nose of the stop having a probe which abuts the surface of the intermediate ball 40. A linear transformer gives an output which is directly related to the position of the piston in the bore, hence to the position of the ball 40, and hence ultimately to the separation of the guide rollers 22 and 23. An armoured cable 55 conducts the signal from the transducer to the mill operator's control cabin, where it provides a direct read-out of the gauge of the rod as it passes through the guide.

An acceptable rod product from the mill may cause the rollers to move in and out of the guide channel by up to 0.1 mm, but the increased thickness at the back end may cause movements up to 0.25 mm. Such movements can readily be accommodated by the entry guide as particularly described above. It is even possible in a single guide to allow for such extensive guide leaf movement that a range of different rod gauges and roller diameters can be tolerated.

Provision is made in the guide for the supply of lubricating and cooling fluids where necessary.

Claims (20)

1. A mill entry guide for a rolling mill for rolling elongate stock, comprising opposed guide members, connected by coupling means, defining between them a stock guide channel, wherein each of the said guide members is displaceable outwardly of the guide channel against biassing means urging the guide member into the guide channel, and wherein the coupling means are adapted to coordinate the displacements of each of the said guide members and thereby maintain substantially constant the axial location of the guide channel.

2. A mill entry guide according to claim 1, wherein the guide members comprise rollers of a material selected from sintered hard metal, tungsten carbide and titanium carbide, provided with peripheral grooves of a suitable shape for the stock.

3. A mill entry guide according to claim 1 or claim 2, further comprising means for adjusting the position of each guide member independently of the other in order to set the location of the guide channel.

4. A mill entry guide according to any one of the preceding claims, wherein the guide members are mounted each on a pivoted cantilever arm.

5. A mill entry guide according to any one of the preceding claims, further comprising stop means to limit the inward movement of each guide member and thereby define a minimum guide channel width.

6. A mill entry guide according to any one of the preceding claims, wherein the biassing means is such as to act equally on each guide member.

7. A mill entry guide according to any one of the preceding claims, comprising means to adjust the force exerted by the biassing means on the guide members, and accordingly by the guide members of the stock when in the guide channel.

8. A mill entry guide according to any one of the preceding claims, wherein the guide members are connected by coupling means which comprise a connector of variable length having an intermediate element which is positively located in relation to the guide whereby to ensure that both ends of the connector move upon a change in the length of the connector.

9. A mill entry guide according to claim 8, wherein the connector comprises a train of abutting elements, including an intermediate element, held in abutment by inwardly directed forces acting on either end of the train, the elements other than the said intermediate element being movable longitudinally of the train, and the said intermediate element being immovable longitudinally of the train but movable into and out of the train whereby to progressively and equally move the ends of the train in opposite directions longitudinally of the train.

10. A mill entry guide according to claim 9, wherein the inward forces acting on the ends of the train are provided by a spring in tension between the ends of the train.

11. A mill entry guide according to any one of the preceding claims, further comprising means, such as a position transducer, adapted to monitor the separation of the guide members and hence the thickness or gauge of the stock when passing through the guide.

12. A mill entry guide for a rolling mill for rolling elongate stock substantially as herein described with reference to and as illustrated in the accompanying drawings.

13. A rolling mill provided with an entry guide according to any one of the preceding claims.

14. A method of rolling elongate stock of irregular thickness along its length in a rolling mill, comprising guiding the stock into the mill through a guide channel defined between opposed guide members, holding each of the guide members in contact with the stock passing through the guide channel while accommodating changes in the stock thickness by means of inward or outward displacements of the guide members, and connecting the guide members so that their displacements are coordinated and the axial location of the guide channel is thereby maintained substantially constant.

1 5. A method according to claim 14, wherein the guide members are held in contact with the stock by biassing means acting equally on each guide member.

16. A method according to claim 14 or claim 15, wherein the guide members are connected by coupling means which comprise a connector of variable length having an intermediate element which is positively located in relation to the guide channel, both ends of the connector moving upon a change in the length of the connector.

1 7. A method according to any one of claims 14 to 16, further comprising monitoring the separation of the guide members.

1 8. A method according to claim 17, wherein the thickness or gauge of the stock thereby obtained is made available by means of a direct read-out to the mill operator.

1 9. A method according to any one of claims 14 to 18, wherein the elongate stock is steel rod stock.

20. A method of rolling elongate stock of irregular thickness along its length in a rolling mill substantially as herein described with reference to the accompanying drawings.