GB2118875A

GB2118875A - Rod or bar deceleration

Info

Publication number: GB2118875A
Application number: GB08300566A
Authority: GB
Inventors: Dennis Stubbs; Alexander Ian Wilson
Original assignee: Hille Engineering Co Ltd
Current assignee: Hille Engineering Co Ltd
Priority date: 1982-04-16
Filing date: 1983-01-10
Publication date: 1983-11-09
Also published as: GB8300566D0

Abstract

A method of rod or bar deceleration and a rod or bar deceleration line are described in which pinch rolls, or the rolls of a mill stand or stands acting as pinch rolls, engage rod or bar from a mill and the pinch rolls or the mill stand rolls are braked so that the rod or bar is decelerated to a speed lower than mill line speed. In one embodiment, Figure 1, the rod or bar 12 is supplied to one of lines A and B and is cut into lengths by a shear 14. The cut lengths of rod or bar are decelerated by pinch rolls or mill stand 17A or 17B. Once a length of rod or bar has been decelerated on one line by one of the pinch rolls 17A, 17B the pinch rolls are accelerated to mill line speed while the next length of rod or bar is decelerated on the other line. Additional pinch rolls 20A or 20B may be used in tandem with pinch rolls 17A or 17B, so that, for example, as pinch roll 17A is decelerating a rod or bar, pinch roll 20A may be accelerated to line speed to receive next rod or bar on line A. In other embodiments, Figures 2a and 2b, and Figure 3, the rod or bar is cut after part of the rod or bar has been decelerated and loop is allowed to form in the rod or bar so that the speed of the rod or bar coming from the mill is maintained. <IMAGE>

Description

SPECIFICATION Rod or bar deceleration This invention relates to the deceleration of rods and bars, for example to bring to a reduced speed cut lengths leaving a rolling mill prior to delivery to a cooling bed.

It has already been proposed to decelerate cut bars for the latter purpose, by engaging each bar with a pair of pinch rolls driven at a constant slow speed. While that arrangement operates satisfactorily in braking the bars, the slipping between the bars and the pinch rolls during braking can produce unacceptable marking of the bars.

In the present invention, the pinch rolls are initially driven at a speed corresponding approximately to the speed of the bar and are then decelerated gradually to a given lower speed which may be zero.

Thus, one aspect of the present invention resides in a method of decelerating rod or bar moving at a relatively high speed, in which driven pinch rolls are engaged with the rod or bar at a speed corresponding approximately with the speed of the rod or bar, and the pich rolls are thereafter braked to a relatively low speed.

A second aspect of the invention provides a rod or bar deceleration line which includes pinch rolls adapted to engage with a moving rod or bar, and driving and braking means for the pinch rolls arranged to decelerate the pinch rolls from a speed corresponding approximately to the speed of the rod or bar to a lower speed.

The invention will be more readily understood by way of example from the following description reference being made to the accompanying drawings wherein: Figure 1 schematically illustrates a plan view of a first embodiment.

Figure 2a schematically illustrates a plan view of a second embodiment.

Figure 2b illustrates an elevational view of the second embodiment; and Figure 3 schematically illustrates a plan view of a third embodiment.

In Figure 1, 1 2 represents the path of the bar from a rolling mill, 13 a switch line for directing the bar to either line A or line B, 14 a cut-to-length flying shear, 1 5 a cooling bed, and 1 6 and 17 opening tubes, which correspond to lines A and B respectively and which can be operated to deposit a braked bar length on to the cooling bed 1 5.

Lines A and B consist of guide tubes which start just beyond the shear 14.

Each line A and B includes, just before the bed 15, a pair of deceleration pinch rolls 1 7A or 1 7B respectively driven by its motor 1 8A or 1 8B. Each motor can be decelerated gradually at a preselected rate, and for that purpose is a DC motor with regenerative braking.

The switch 1 3 is operated just before shear 14 effects a cut, so that the bar is deflected sideways towards the guide tube of the line A or B which is not at that time in use, the shear being sufficiently wide to cut the bar in either position of the switch.

When cut, the newly formed front end of the rod passes into the unoccupied tube, while the backend of the cut length is drawn into the occupied tube. The cut bars travelling at high speed are thus directed alternately to the lines A and B. The motor 1 8 of the respective line is driven up to linespeed so that the bar enters the pinch rolls without slip. Then, at a selected time after the shear 14 has operated, the motor is put into the regenerative braking mode causing the rolls to decelerate at a preselected rate down to a slow exit speed.

As a result, the bar is braked gently over a considerable proportion of its length without slip or marking of the bar and without the need for heavy pinch rolls clamping force. On leaving the pinch rolls, the respective opening tube 1 6 or 1 7 is opened to transfer the now stationary rod to the cooling bed 1 5. The deceleration rate is varied according to the bar size by adjustment of the regenerative braking circuit.

When a bar has left the rolls 18, the rolls must be accelerated up to line speed again before the arrival of the next bar. Because the interval time between the arrival of successive bars in either line A or B is short, a second pair of pinch rolls 20A or 20B, with its own motor, may be provided in each line A or B. Then each pair of pinch rolls 17 or 20 is accelerated up to line speed while the other pair is braking a bar.

The pinch rolls may be constituted by, a mill stand or mill stands may be used to decelerate the bar. For example, the final stand of the rod or bar mill feeding the line 12 may roll the rod or bar to oval cross-section. The pairs or pinch rolls 1 7A and 1 7B are then constituted by the rolls of mill stands with the rolls designed to roll a round bar.

The operation of such an arrangement is then substantially the same as that already described using conventional pinch rolls, except that the rolls shape the rod or bar in addition to decelerating it.

An advantage of using mill stand which roll the section of the bar is that the danger of marking the bar is eliminated. Other cross-sections of rod or bar may be produced in this manner.

Instead of using a single mill stand to decelerate the bar, two mill stands may be used in tandem. For example a round bar could be delivered to a first stand 20A or 20B which would form an oval and then the second stand 1 7A or 1 7B would produce a finished round bar. Each pair of stand 17A and 20A, 1 7B and 20B would be decelerated together. Such an arrangement has the advantage that it is easier to guide a round bar into a mill stand than to do the same with an oval bar. Again, other bar cross-sections may be formed using an arrangement such as this, particularly those bar shapes which are difficult to feed down a line in the correct attitude.

Referring now to the embodiment of Figures 2a and 2b, 30 represents the path of the bar from a rolling mill of which the final stand is shown at 31, 32 a looper as hereinafter described, 36 a switch line for directing the bar into one of the lines 37 and 38, and 35 a cut-to-length flying shear; the cut bar is deposited onto a cooling bed 39 from the lines 37 and 38. Pinch rolls 33 and mill stand 34 are located after looper 32. The stand 31 is designed to produce an oval cross-section while the second mill stand 34 is designed to produce a round bar and be controllably decelerated. The pinch rolls 33 may be used to feed the bar into the second mill stand 34 as described later.

The looper 32 has a substantially U-shaped cross-section and can be rotated about its length.

The looper is used in two modes, in a first mode the "U"- looper is upright and carries the bar while in the second mode the "U"-looper is inverted, i.e.

rotated through 1 800 and the bar is allowed to loop downwards.

In use an oval section bar or rod is fed from stand 31 through the looper 32, which is in the first "upright" mode, and the pinch rolls 33 engage the bar to guide it into the second mill stand 34. Once the bar has been introduced into the second mill stand 34, the pinch rolls 33 are disengaged from the bar. The mill stands 31 and 34 now run at mill line speed to feed the final, round bar onto one of the lines 37, 38 of the cooling bed, as determined by the switch 36. Just before deceleration is initiated the looper is actuated to move into the second "inverted" mode. At this stage only a slight loop will form in the bar. When a substantial part, e.g. 75%, of the desired "bed length" of the bar has passed through the shear 35, the second mill stand 34 is decelerated to a suitable low speed, e.g. 25% of mill line speed.Since the bar from the stand 31 is still travelling at mill line speed, a loop of bar 40 forms under the looper. The shear 35 cuts the bar to produce the desired "bed-length" of bar and the switch 36 operates to send the new front end of the bar into the other of the lines 37, 38. Mill stand 34 is now accelerated to above line speed so that the loop 40 is substantially taken up, and the process of deceleration can then begin again as desired.

Each time the front end of a rod or bar is entered into a stand there is the danger of a cobble or of the rolls being damaged. In Figures 2 and 2b the rod or bar is sheared downstream of the final stand 34, so that it is necessary to enter a front end only once for each billet rolled, and the danger of a cobble is correspondingly reduced. It is also advantageous to shear the bar at low speeds.

Instead of one looper, two or more loopers may be used. These could then be actuated together or separately to produce or form a desired loop. Also, other forms of looper to the one described may be employed. One suitable form of looper would be a rectangular tube in which the bottom is operable to release the loop. The tube could be mounted at angle and a tray used to support the loop.

In Figure 3 another embodiment is illustrated, in which bar from a rolling mill, of which the final stands are shown at 45, is initially guided by a looper 46 to decelerating stands 47. A shear 48 cuts the bar downstream of the stand 47 and the cut lengths of bar are delivered to a cooling bed 49 by means of a kick off system or a drop-out tube system. When operated, the looper 46 allows a loop 50 to form laterally when the bar is decelerated by the stands 47.

This embodiment illustrates that the decelerating rolls or stands need not be in line with the mill train and an advantage of such an arrangement is that a lateral loop of the bar can be allowed to form.

Other cross-sections than oval to round may be rolled using the laterly described embodiments, and the stands may have vertical or horizontal rolls.

To improve the metallurgical quality of the finished bar it is desirable, in some circumstances, to finish roll at a lower temperature. The described embodiments may be readily adapted to facilitate such rolling, for example by providing cooling stations before the final mill stand. The cooling station may provide a spray for the bar either along the lines A and B of the first embodiment or the loop of the second embodiment.

Claims

1. A method of decelerating rod or bar moving at a relatively high speed, in which driven pinch rolls are engaged with the rod or bar at a speed corresponding approximately with the speed of the rod or bar, and the pinch rolls are thereafter braked to a lower speed.

2. A method as claimed in claim 1 wherein the pinch rolls are the rolls of a mill stand and those rolls shape the rod or bar.

3. A method as claimed in claim 1 or 2 wherein the rod or bar is cut into lengths by a shear before being decelerated by the pinch rolls.

4. A method as claimed in claim 3 wherein the cut lengths of rod or bar are supplied alternately to two sets of pinch rolls, so that while one length of the rod or bar is being decelerated by one of the sets of pinch rolls the next cut length of rod or bar can be fed to the other set of pinch rolls for deceleration.

5. A method as claimed in claim 3 or 4 wherein one of two sets of aligned pinch rolls is used to decelerate the cut length of rod or bar and the other set of aligned pinch rolls is disengaged from that length of rod or bar and is accelerated to or is approximately at the speed of the next incoming length of rod or bar.

6. A method as claimed in claim 1 or 2 wherein the rod or bar is cut into lengths after at least part of the rod or bar has been decelerated.

7. A method as claimed in claim 6 wherein the rod or bar is shaped by a mill stand before passing through the pinch rolls or mill stand or stands used to decelerate the rod or bar.

8. A method as claimed in claim 7 wherein the rod or bar from the last stand of the mill has one section and the rod or bar is rolled to a different section by the mill stand or group of stands which decelerates the rod or bar.

9. A method as claimed in claim 8 wherein the rod or bar from the last stand of the mill has an oval section and the rod or bar is rolled to a round section by the decelerating mill stand.

10. A method as claimed in claim 7, 8 or 9 wherein the speed of the rod or bar upstream of the deceleration pinch rolls or mill stand is maintained, so that a loop is formed in the rod or bar when the pinch rolls or mill stand are/is decelerated.

11. A method as claimed in any one of claims 6 to 10 wherein the leading end of the rod or bar is initially guided into the pinch rolls or mill stand which will decelerate the rod or bar by other pinch rolls.

12. A method as claimed in any preceding claim wherein the rod or bar is cooled prior to a final finishing rolling or between the last stand of the mill line and the deceleration stand or stands.

1 3. A method of decelerating rod or bar substantially as herein described, with reference to Figure 1 or with reference to Figures 2a and 2b of the drawings.

14. A rod or bar deceleration line which includes pinch rolls which engage with the rod or bar, and brake means associated with the pinch rolls for braking the rod or bar to a lower speed.

1 5. A rod or bar deceleration line as claimed in claim 14 wherein the pinch rolls are constituted by the rolls of a mill stand or stands, while rolls are adapted to shape the rod or bar.

1 6. A rod or bar deceleration line as claimed in claim 14 or 15 wherein the line includes a shear before the pinch rolls or mill stand, so that in use the shear can cut the rod or bar into lengths which are then decelerated by the pinch rolls or mill stand.

1 7. A rod or bar decelerStion line as claimed in claim 1 6 wherein the cut lengths are supplied to one or other of two lines by a switch line, and each of the two lines has pinch rolls or a mill stand for decelerating the cut length of rod or bar.

18. A rod or bar deceleration line as claimed in claim 1 6 or 17 wherein the another set of pinch rolls is aligned with the already mentioned pinch rolls, so that while a length of rod or bar is being decelerated by one of the aligned sets of pinch rolls the other set of the pinch rolls can be disengaged from the rod or bar being decelerated and be being accelerated to or is approximately at the speed of the next incoming length of rod or bar.

1 9. A rod or bar deceleration line as claimed in claim 14 or 1 5 wherein the line includes a shear downstream of the decelerating pinch rolls or mill stand for cutting the decelerated rod or bar into lengths.

20. A rod or bar deceleration line as claimed in claim 19 wherein a mill stand upstream of the decelerating pinch rolls or mill stand or stands is used to shape the rod or bar.

21. A rod or bar deceleration line as claimed in claim 20 wherein the upstream mill stand is adapted to roll the rod or bar to one section and the decelerating mill stand is adapted to roll the rod or bar to another section.

22. A rod or bar deceleration line as claimed in claim 21 wherein the upstream mill stand is adapted to roll the rod or bar to an oval section and the decelerating mill stand is adapted to roll the rod or bar to a round section.

23. A rod or bar deceleration line as claimed in any one of claims 19 to 22 wherein the line includes a looper upstream of the decelerating pinch rolls or mill stand or stands, and the looper is operable in two modes such that in one mode the rod or bar is guided by the looper and in the other mode the rod or bar can form a loop or loops when the rod or bar is decelerated by the pinch rolls or mill stand or stands.

24. A rod or bar deceleration line as claimed in any of claims 1 9 to 23 wherein the line includes pinch rolls for guiding the leading end of the rod or bar into the pinch rolls or mill stand which will decelerate the rod or bar.

25. A rod or bar deceleration line as claimed in any preceding claim wherein the line includes a cooling station for cooling the rod or bar prior to a final finishing rolling.

26. A rod or bar deceleration line substantially as herein described, with reference to Figure 1, or with reference to Figures 2a and 2b, or with reference to Figure 3 of the drawings.