GB2096935A - Methods of, and apparatus for, dividing metal slabs or ingots into sections - Google Patents

Abstract

A metal slab or ingot 1 is divided longitudinally into sections of predetermined width during the course of its conveyance on the rollers 2 of a conveying table. For this purpose, the slab 1 is stopped on the table and is raised therefrom by lifting means 4a, 15. While in its raised position, the slab 1 is divided lengthwise thereof into sections by a gas cutting torch 8 mounted on a truck 6. The sections are then lowered on to the rollers 2 again one after the other and are then moved individually by the rollers to a device 18 which removes slag deposits formed on the bottom edges of the cut surfaces of the sections. The raising of the slab 1 before it is cut prevents the cutting torch from damaging the rollers 2 and the automatic removal of the slag deposits ensures that these do not harm the sections during subsequent rolling operations. <IMAGE>

Description

SPECIFICATION Methods of, and apparatus for, dividing metal slabs or ingots into sections The present invention relates to methods of and apparatus for dividing metal slabs or ingots into sections of predetermined widths.

In recent years it has become frequently necessary to divide ingots produced by continuous casting equipment or slabs produced by blooming mills lengthwise into sections of predetermined widths. If, in order to obtain ingots or slabs of small widths, it is necessary to cast these individually in continuous casting equipment or in small ingot casting moulds their production is low and thus uneconomical.

For this reason, it has become customary to manufacture, by continuous casting equipment or by large ingot casting moulds ingots which have a width which is an integral multiple of a predetermined ingot or slab width and then to divide, by means of gas cutting, the slab lengthwise into at least two sections, thus obtaining slabs of the desired width.

Nevertheless, such division, instead of being made on a slab conveying table, has been carried out after shifting the undivided ingot or slab elsewhere; so its shifting is very troublesome.

For instance, a slab having a width which is an integral multiple of the required dimension is manufactured by continuous casting or large ingot casting equipment (hereinafter referred to simply as continuous casting equipment) and is then shifted by a conveying table for specified treatment but additionally the slab has to be removed by a crane with a lifting magnet or the like from the conveying table to another location, for example, to an earth floor where the slab is divided lengthwise by means of gas cutting. After the dividing operation, the individual slabs each have to be moved again by a crane or the like from the earth floor to the conveying table or elsewhere for the next treatment. Consequently, such slab shifting operations involve much difficulty which affects the productivity of the slab manufacture.

To avoid this, a slab dividing device has been proposed which divides the slab into a number of sections of smaller widths by gas cutting on the conveying table. However, even this proposed device is attended with the possible danger of cutting rollers of the conveying table when the slab is divided by gas cutting while it is being carried by the table. To avoid this danger, the slab may be cut while it is being moved by the conveying table, and the gas cutting torch of the cutting device is held as fixed in relation to the conveying table and is located so that it does not interfere with the conveying rollers of the table.

With a slab dividing device arranged in this way, however, since the slab is cut while it is being moved relative to a stationary cutting torch, it is necessary to center the slab precisely on the table to ensure that it is cut in the correct position, but this centring is extremely difficult. The centring of the slab is performed by moving the slab along a guide. In this case, the slab movement must not be allowed to stop by being interfered with by the guide.

There are however unevennesses on the side surface of the slab, which, although invisible to the naked eye, are liable to catch the guide, causing the slab to stop. To eliminate such interruptions in movement of the slab, the guide has to be a largescale device. Further, as the guide is so constructed as to be detachable after the centring operation, errors can occur in the centring of the slab during its movement, owing to warping of the slab in its lengthwise direction, and these errors prevent high-precision dividing of the slab.

In addition, since along the bottom edges of the cut surfaces of each cut section of the slab there are slag deposits formed by the gas cutting torch, if the slab is rolled with the slag deposits remaining, the deposits cut deeply into the slab and remain there as permanent impurities. It is therefore necessary to eliminate such slag deposits before rolling. Nevertheless, in practicethe elimination of such slag deposits is at present carried out manually after turning over the slab following the dividing operation.

In view of the above-mentioned shortcomings of the prior art, it is an object of the present invention to provide a method of dividing a slab into sections of predetermined widths and to provide apparatus for carrying out the method, wherein a slab is divided into sections by means of gas cutting on a conveying table in a manner which avoids causing damage to conveying rollers of the table and, further, slag deposits incidental to the gas cutting operation are automatically removed from the divided slab without turning the sections over.

Thus, according to one aspect of the present invention, we provide a method of dividing a metal slab or ingot into two or more sections of predetermined widths, the method comprising: (a) stopping a slab being conveyed by conveyance rollers; (b) raising the slab from the conveyance rollers; (c) dividing the slab lengthwise, while it is raised from the conveyance rollers, by gas cutting into the two or more sections; (d) returning the divided sections on to the conveyance rollers one after the other; (e) continuing the conveyance of the divided sections in the direction of conveyance of the slab or ingot; and (f) removing slag deposits formed during the gas cuttting from the bottom edges of the cut surfaces of the sections.

Since the slab is divided lengthwise into at least two sections while it is held in a raised position, such procedures as moving the slab from the conveyance rollers to another location to be divided and to be returned thereto after the dividing operation are avoided. In addition to this, the raising of the slab from the conveyance rollers eliminates the possibility of the rollers being damaged by the gas cutting operation.

According to another aspect of the invention, apparatus for carrying out the method in accordance with the invention comprises:~ (a) a slab conveyance table comprising conveyance rollers disposed flush with one another and spaced apart at intervals; (b) slab lift means associated with the conveyance table for raising a slab being conveyed by the table from the conveyance table and subsequently returning sections of the slab after it has been divided one after the other on to the rollers; (c) gas cutting means provided above the slab lift means for dividing a slab which has been lifted by the lift means, lengthwise thereof, into sections by gas cutting; and, (d) slag removing means provided downstream in the direction of conveyance of the conveyance rollers of the gas cutting means for removing slag deposits from the bottom edges of the surfaces of the sections cut by the gas cutting means.

Preferably, the slab is held stationary in a position into which it is raised from the conveyance rollers and a gas cutting torch is moved in the lengthwise direction of the slab to cut it into the sections.

Accordingly if centring is effected of a gas cutting torch forming part of the gas cutting means, the slab in the stationary state does not itself have to be centred so that the centring operation can be performed very easily and the slab can be divided with great accuracy.

Some example of apparatus and of methods in accordance with the invention will now be described with reference to the accompanying drawings in which:~ Figure 1 is a front view illustrating one example of the apparatus; Figure 2 is a plan view of the apparatus shown in Figure 1; Figures 3(a) to 3(f) show a sequence of steps involved in dividing a slab into sections and removing deposits from the divided sections in accordance with any example of the method of the present invention; Figure 4 is a plan view of a second example of the apparatus; Figures 5 and 6 are sectional views as seen in the direction of the arrows on the lines A-A and B-B respectively in Figure 4; Figure 7 is a section as viewed in the direction of the arrows on the line C-C in Figure 4;; Figure 8 is a view of a detail showing a slab cutting operation; Figure 9 is a side view illustrating a slag removing device forming part of the apparatus; Figure 10 is a front view showing an example of a device for detecting and following the profile of the cut surface of the divided slab; Figure 11 shows on an enlarged scale a portion of Figure 9; and Figure 12 is a plan view of the slag removing device shown in Figure 9.

In Figures 1 and 2, reference numeral 1 indicates a slab or ingot produced by a blooming mill or by continuous casting equipment, the width of the slab 1 being an integral multiple of a width of individual slab section, which it is desired ultimately to obtain. The slab 1 is conveyed on a table which comprises rollers 2 disposed at equal intervals. The slab 1 is conveyed from the continuous casting equipment to the next disposition site, for instance, in the arrowindicated direction. On the way of conveyance, that is, on the way of the conveyance table there are set up at least two lift means 3a and 3b, by which to raise the slab 1 to be held at this position. Though these lift means 3a and 3b are placed in parallel as shown, they are identical in construction with each other.The lift means 3a and 3b respectively consist of a plurality of cylinders 4a and 4b and a support beam 5 supported by such cylinders in a manner to be movable up and down, the support beam 5 having mounted thereon slab receptacles 1 5. For this reason, the slab 1 delivered from the continuous casting equipment is raised from the solid line position to the broken line position in Fig. 1 and is held at such a raised position.

A gas cutting device is provided above the conveyance table in opposing relation to the lift means 3a and 36. The gas cutting device has a pair of parallel rails 7a and 7b and a movable truck 6 which has wheels 6a fixed thereto to run on the parallel rails 7a and 7b. And, on this movable truck 6, there is disposed a table 9 movable along a guide rail 12 which perpendicularly crosses the rails 7a and 7b for the movable truck 6, and there is installed a gas cutting torch 8. Further, the moving table 9 has attached thereto a guide roller 10 which makes rotary contact with one side surface of the slab 1 during the slab dividing operation so that the cutting torch 8 is guided by the guide roller 10 when the former moves in the lengthwise direction of the slab 1 for cutting it.

That is to say, the guide roller 10 is rotatably supported as by an arm-like slide member 11, which is adapted so that its slide section 1 a may slide along the abovesaid guide rail 12. Further, the slide member 11 is connected with a coupling rod 14, which carries at one end press means 13, such as an air cylinder or the like, for urging the guide roller 10 against one side surface of the slab 1. Accordingly, at the time of the gas cutting operation, the truck 6 moves lengthwise of the slab 1 while being guided by the guide roller 10 pressed against the side surface of the slab 1 by dint of the press means 13, so the cutting torch 8 is guided along the center dividing line 1 a, whereby the slab 1 can be divided accurately.

Incidentally, the movable truck 9 has a retaining piece 9a to retain the coupling rod 14.

With such a slab dividing equipment, the slab 1 can be easily and precisely divided as shown in Figs. 3(a) to (d) while being transit from the continuous casting equipment by means of the conveyance table.

In the first place, the slab 1 of a two-fold width, for instance, is turned out by the continuous casting equipment and conveyed by the rollers 2.

At the time of division, the slab 1 is stopped temporarily at the lift means 3a and 3b (see Fig.

3(a)), after which the cylinders 4a and 4b of the lift means 3a and 3b are activated, thereby lifting the slab 1 up to the height of cut and then holding it at that elevation as shown in Fig. 3(b). Following it, the truck 6 is moved along rails 7a and 7b, and the slab 1 is divided along its center dividing line 18 by means of the gas cutting torch 8 mounted on the moving table 9. In this case, the guide roller 10 is set at a position spaced the one-half of the slab width apart from the position of the cutting torch 8; and the guide roller 10 moves in contact with one side surface of the slab 1 while being pressed thereagainst by the press means 13. With gas cutting flames emitting from the cutting torch 8, it advances along the line 18 to divide the slab 1 into two (see Fig. 3(c)).

If the space between cutting torch 8 and the guide roller 10 is initially set by adjusting the position of the moving table 9, to 1/2 of the slab breadth, for instance, it is always possible to cut the slab 1 as the guide roller 10 is being pressed by the force of the press means 13, even though the roller 10 moves breadthwise of the slab 1 due to its undulations. Thus it is always possible to cut the slab 1 to 1/2 breadth. After finish of the dividing operation, one of the two divided slabs is set down on the conveyance rollers 2 and then the other slab onto the conveyance roller 2 as shown in Fig. 3(d). As for the lifting device and the gas cutting device, even though they are not constituted as abovesaid, they can also be constituted in association with the conveyance table as illustrated in Figs. 4 to 7 if the slab on the conveyance table is given precentering.

In Figs. 4 to 7, the conveyance table is constituted by parallel rollers 2 disposed horizontally at substantially equal intervals as in Figs. 1 and 2. The rollers 2 are rotatably supported at one end by a line shaft table 3c and at the other end by bearings 3d. Above the conveyance table is set the gas cutting device as shown in Fig. 7 and the gas cutting device is equipped with the gas cutting torch 8 thai emits flames 8a downwardly for cutting the slab 1. The cutting torch 8 is set on the moving truck 6 almost centrally thereof, with the wheels 6a rolling on the pair of rails 7a and 7b.

The gas cutting device shown in Fig. 7 is not equipped with the waving table 9, the guide-roller 10 and the guide roller pressurizing mechanism composed of the slide member 11, the coupling rod 14 and the press means 13 which are employed in Figs. 1 and 2. Even with such an arrangement, however, the slab 1 can be divided along the central dividing line 18 without much hindrance.

Under the rollers 2 of the conveyance table are installed the lift means of the same number as divided slabs desired to obtain; for instance, in the case of the slab from the continuous casting equipment being divided into two, there are provided two lift means 3a and 3b as is the case with Figs. 1 and 2. The lift means 3a is constituted by disposing two pairs of support frames 1 6a and 1 6b breadthwise of the slab 1, that is, in parallel with the conveyance rollers 2 and bridging a support beam 5a between a pair of support frames 1 6a and 1 6b and then setting the slab receptacle 1 5a on the support beam 5a.The other lift means 3b also has a support beam 5b bridged between the other pair of support frames 1 6b and 1 6b and a slab receptacle 1 5b mounted on the support beam Sb. Thus, by constituting the support frames 1 6a and 1 6b of each pair so that they may freely move up and down independently of the other pair, divided slabs can be successively aligned to be transferred by the conveyance rollers 2. For instance, with the lift means 3a, each support frame 1 6a is suspended at both ends by the cylinders 4a in a manner to be driven up and down.

Likewise, with the other lift means 3b, too, both ends of each support frame 1 6b are suspended by the cylinders 4b so that the support frame 1 6b is thereby moved up and down. Besides, the cylinders 4a and 4b are each installed on a support stand (as shown in Fig. 6 showing only the support stand 17 of each cylinder 4a) on the floor, and their lower ends are connected to the support frames 1 6a and 1 6b of the respective pairs. On the other hand, the support beam 5a is mounted on the support frame 1 6a with a spacer 17 disposed therebetween (see Fig. 6) so that the lift means 3a may not be interfered with by the other lift means 36. By installing the support beams 5a and Sb at different levels as described above, the lift means 3a and 3b can function without any interference with each other.

With such an arrangement, the slab 1 conveyed by the conveyance rollers 2 from the continuous casting equipment is once stopped on the way of conveyance and, in this case, since the guide roller 10 is not orovided unlike in the case of Figs. 1 and 2, centering of the slab 1 is effected first and then the both lift means 3a and 3b are simultaneously operated to elevate the slab 1 on the conveyance rollers 2 and to hold it at its elevated position. In other words, by activating the cylinders 4a and 4b simultaneously to lift the support frames 1 6a and 1 6b concurrently, together with the support beams 5a and 5b and the slab receptacles 1 5a and 1 5b thereon, thus bringing up the slab 1 which is held horizontally over the conveyance table.At the position where the slab 1 is held, the moving truck 6 of the gas cutting device is brought, dividing the slab 1 by the cutting torch 8 along the central dividing line 1 a. At this time, the truck 6 moves lengthwise of the slab 1 which has already undergone precentering, so that the cutting torch 8 can precisely divide the slab 1 along the preset central dividing line 18 as shown in Fig. 8. During this dividing operation, too, as the slab 1 is being held by the two lift means 3a and 3b above the conveyance rollers 2, there is no possibility of the rollers being damaged by the flames of the cutting torch 8. And, as the slab 1 is held by the slab receptacles 1 5a and 1 Sb of the lift means 3a and 3b in alignment with the central dividing line 1 a, the cutting operation of the cutting torch 8 cannot be obstructed by the receptacles 1 5a and 1 sub. Incidentally, after completion of the cutting operation, the first means 3a and 3b are lowered one after the other by operations reverse to those for raising them, whereby the divided slabs are redelivered onto the conveyance rollers 2 and then subjected to the next process.

That is to say, during the gas cutting operation by the cutting torch 8 slags are apt to be formed on the lower edges of the cut surfaces of the divided slabs and must be removed. Accordingly, the divided slabs have to be conveyed separately.

Forthis reason, the support frame 1 6a of the one lift means 3a is lowered first by extending the cylinders 4a, whereby only the divided slab supported by the first means 38 is brought down onto the conveyance rollers 2. Following this, the support frame 1 6b of the other lift means 3b is set down to deliver the divided slab to the conveyance rollers 2.

For removing the slags attached to the lower edges of the cut surfaces of the divided slabs, a skimmer is provided downstream of the gas cutting device. With the-skimmer, the divided slabs conveyed thereto by the conveyance rollers 2 are automatically removed of slags formed on the lower edges of their cut surfaces, without being turned over. As shown in Figs. 1 and 2, the skimmer comprises a travelling truck 19 which is mounted on a stand 18 and moves in the direction of conveyance of each divided slab, an alignment truck 20 which is mounted on the travelling truck 19 and moves perpendicularly to the direction of conveyance of the divided slab, and a skimming nozzle 21 which is mounted on the alignment truck 20. The skimming nozzle 21 is disposed slantingly upward, unlike the cutting torch 8 of the gas cutting device.

When each divided slab conveyed by the conveyance rollers 2 has reached the skimmer, flames are slantly emitted up from the skimming nozzle 21 of the skimmer to remove slags 22 deposited on the lower end edge of the cut surface of the slab 1, as shown in Fig. 3(f). It is preferable that when once stopping the divided slab 1 just before the skimming nozzle 21, the leading end of the slag 22 be preheated momentarily, after which, by driving the rollers 2, the slab 1 is moved forward to be subjected to the slagging off operation. Such operations of stop and advance may be carried out by the means of signals which are produced by a timer, photoelectric tube, numerical controller or the like.After the finish of the slagging off of the one divided slab 1, the other divided slab is lowered onto the conveyance roller 2 as shown in Fig. 3(f) and is similarly brought to the skimmer, where it is removed of slags attached thereto. Incidentally, to actuate the skimming nozzle 21,the position of the cut surface of the divided slab 1 is shifted correspondingly. Consequently, when to the slags attached to the one divided slab after the slagging off of the other divided slab, the skimming nozzle 21 is set by slightly moving it perpendicularly to the direction of conveyance of the slab. To this end, the alignment truck 20 having mounted thereon the nozzle 21 is constituted in the manner of its center being movable by adjustment in the truck 19 by means of a fine control mechanism such as a rail feeder, or screw feeder.

It is also possible to mount means on the alignment truck 20 for detecting the cut surface and the underside of the divided slab by tracing them.

In Fig. 9, the divided slab 1 is carried by the conveyance rollers 2 driven in the direction indicated by the arrows. Reference numeral 22a designates a dust collecting hood which collects dust in smoke or the like during the slagging off operation. On the lower end edge of the cut surface of the slab 1 are formed slags. Under the conveyance rollers 2 are disposed the truck 19 and the alignment truck 20, the latter being constituted in a manner to be movable by a cylinder 23 in a direction perpendicular to the direction of conveyance of the slab 1 (see Fig. 12).

On the alignment truck 20 is installed a guide frame 29 and a lift member 22b is provided to be movable up and down under the guide of the guide frame 29. The lift member 22b has at its top end a contact member 24, the tip of which makes contact with the underside 1 b of the slab 1 to trace it during the slag removal. In addition to the slab underside detecting-tracer means composed of the contact member 24, the lift member 22b has mounted thereon the skimming nozzle 21 and cut surface detecting-tracer means. The cut surface detecting-tracer means, as illustrated in Fig. 10, has a link mechanism around the lift member 22h - the link mechanism comprising a pair of trace member 25a and 256 and cylinders 26a and 26b.The trace members 25a and 25b have attached thereto guide rollers 27a and 27b in opposing relation. With such an arrangement, it is possible to effect the positioning of the skimming nozzle 21 with respect to the cut surface and the underside of the slab, making it possible to automatically clear the slag deposited continuously on the lower end edge of the cut surface of the slab.

The divided slab 1 is conveyed in from the direction indicated by the arrows in Figs. 9 and 12; in which case,-the entirety of the skimmer lies under the conveyance path line and the divided slab 1 is stopped as shown in Fig. 9 when its leading portion has reached right above the skimmer. In this case, the pair of trace members 25a and 256 are left open (as indicated by the broken lines in Fig. 10) by actuating the cylinders 26a and 266. In this state, the lift member 22b is raised by the cylinder 23a to bring the contact member 24 into contact with the underside 1 b of the divided slab 1, detecting its position.

Thereafter, the contact member 24 is lowered about 10 mm and then the alignment truck 20 is moved about 100 mm in the widthwise direction of the divided slab 1, while, on the other hand, the one trace member 256 is brought from the broken line position to the solid line one by the cylinder 26b and, in this state, the alignment truck 20 is moved to urge the guide roller 27b of the trace member 256 against the cut surface of the divided slab 1. This allows ease in determining the position of the cut surface of the divided slab 1 from which slags have to be removed. Further, the truck 19 is moved back so that the skimming nozzle 21 may be spaced a certain distance apart from the leading end face of the divided slab 1.

Then, the cylinder 26a is actuated to move the other trace member 25a from the broken line position to the full line position, after which the truck 19 is moved forward to bring the trace member 25a into contact with the leading portion of the divided slab 1. Following this, the truck 1 9 is retreated approximately 100 mm and then the trace member 25a is moved from the full line position to the broken line one, thus establishing the position of the skimming nozzle 21.

After determining the position of the cut surface of the divided slab 1 as described above, the skimming nozzle 21 is ignited and the divided slab 1 is moved, whereby the slags attached to the lower end edge of its cut surface can automatically be eliminated. At the start of this slagging off operation, the one trace member 25b does not trace the cut surface of the divided slab 1 until after the slab has advanced 100 mm or so but, thereafter, the trace member 25b makes contact with the slab cut surface. When the divided slab 1 has advanced about 100 mm, the contact member 24 is moved into contact with the underside 1 b of the slab 1 to trace it.

After completion of the slagging off operation, the one trace member 25b is moved to the broken line position and the lift member 22b is also lowered. In the case of removing slags from the other divided slab after the one divided slab, the operations of the trace members 25a and 256 are reversed. In the skimmer of the abovesaid arrangement, it is preferred to instal a pair of highpressure water nozzles 28a and 28b as depicted in Fig. 12. When the slags are being removed, there is the fear that they scatter before the skimming nozzle, thereby attaching to the dust collecting hood 22a and the rollers 2. In this respect, if high-pressure water is jetted out of the water nozzles 28a and 28b, the slags being removed are blown off laterally.As the contact member 24 is constituted to be movable up and down by the cylinder 23a, it is able to sufficiently trace the underside 1 b of the divided slab 1 even if it wraps lengthwise. Besides, in the case of removing slags from either one of the divided slabs, it is possible to prespecify one of them, so that it is preferable to displace the truck 19 about 100 mm to left or right from the center of the conveyance table. For instance, in the case of removing slags from the one divided slab, if the truck 19 is displaced about 100 mm, for example, to right from the center of the conveyance table, the contact member 24 does not contact the slag attaching portion. And, the leading end face of each divided slab is detected by contacting therewith any one of the trace members but a leading end face detector may also be provided instead of such trace member and the contact member can be formed by a roller. The alignment truck 20 can also be constituted to be movable along a guide rail. Also it is possible to constitute the truck 19 to be movable by a cylinder and to constitute the pair of trace members to freely raise and lower the alignment truck via a link mechanism, instead of arranging the pair of trace members to be freely moved up and down the cylinders.

Claims (10)

1. A method of dividing a metal slab or ingot into two or more sections of predetermined widths, the method comprising:~ (a) stopping a slab being conveyed by conveyance rollers; (b) raising the slab from the conveyance rollers; (c) dividing the slab lengthwise, while it is raised from the conveyance rollers, by gas cutting into the two or more sections; (d) returning the divided sections on to the conveyance rollers one after the other; (e) continuing the conveyance of the divided section in the direction of conveyance of the slab or ingot; and (f) removing slag deposits formed during the gas cutting from the bottom edges of the cut surfaces of the sections.

2. A method according to Claim 1, wherein the slab is held stationary in a position into which it is raised from the conveyance rollers and a gas cutting torch is moved in the lengthwise direction of the slab to cut it into the sections.

3. Apparatus for carrying out the method in accordance with Claim 1, the apparatus comprising:~ (a) a slab conveyance table comprising conveyance rollers disposed flush with one another and spaced apart at intervals; (b) slab lift means associated with the conveyance table for raising a slab being conveyed by the table from the conveyance rollers and subsequently returning sections of the slab after it has been divided one after the other on to the rollers; (c) gas cutting means provided above the slab lift means for dividing a slab which has been lifted by the lift means, lengthwise thereof into sections by gas cutting; and, (d) slag removing means provided downstream in the direction of conveyance of the conveyance rollers of the gas cutting means for removing slag deposits from the bottom edges of the surfaces of the sections cut by the gas cutting means.

4. Apparatus according to Claim 3, wherein the slab lift means comprises a pair of lift frames provided under the conveyance table, support beams bridging between the pair of lift frames, slab receptacles mounted on the support beams at positions such that they can pass between the conveyance rollers and means for moving the pair of lift frames upwards and downwards.

5. Apparatus according to Claim 3 or Claim 4, wherein the gas cutting means comprises a pair of parallel guide rails which are disposed one on each side of the position in which the slab is held by the lift means after it has been raised from the rollers, the rails extending in the direction of conveyance of the slab, a truck movable on the pair of guide rails, and a gas cutting torch mounted on and directed downwardly from the truck substantially centrally thereof.

6. Apparatus according to Claim 5, wherein the truck has mounted thereon a moving table which is movable transversely of the direction of conveyance of the slab; the gas cutting torch is mounted on the moving table; a coupling rod is provided extending from the moving table in a direction transversely to the direction of conveyance of the slab; the coupling rod has a slide member slidable thereon; a guide roller is supported by the slide member; and the guide roller is rotatable and is arranged to make rolling contact with one side surface of the slab to guide the torch along the slab.

7. Apparatus according to any one of Claims 3 to 6, wherein the slag removing means comprises a truck which reciprocates in the direction of conveyance of the slab: an alignment truck movable along a rail perpendicular to the direction of travel of the reciprocating truck, and a slag skimming gas flame cutting nozzle mounted on and directed upwardly from the alignment truck.

8. Apparatus according to Claim 7, wherein a lift member is mounted on the alignment truck and is movable upwards and downwards, the lift member having the skimming nozzle mounted thereon in an upwardly slanting position, a contact member for detecting the position of the skimming nozzle with respect to the underside of each section of the divided slab and following the underside when removing slag deposits formed on the bottom edge of the cut surface of the section, and a cut surface detecting-follower member, for making contact with the cut surface of the section and following it to set the position of the skimming nozzle with respect to the cut surface.

9. A method according to Claim 1, substantially as described with reference to Figures 1 to 3(f), or Figures 4 to 8, or Figures 9 to 12 of the accompanying drawings.

10. Apparatus according to Claim 3, substantially as described with reference to Figures 1 to 3(f), or Figures 4 to 8, or Figures 9 to 12 of the accompanying drawings.