METHOD OF AND APPARATUS FOR ROLLING DIRECTLY COUPLED WITH CONTINUOUS CASTING

Abstract: Disclosed are a method of and apparatus for effecting rolling directly coupled with continuous casting for rolling by a rolling machine (14, 60) a high-­ temperature slab (40) produced by a continuous casting machine (1 - 6) directly coupled with the rolling machine (14, 60). When the operation of machines, including the rolling machine (14, 60), disposed downstream of the continuous casting machine (1 - 6) is stopped, the slab (40) continuously being produced by the continuous casting machine (1 - 6) is sheared on the upstream side of the rolling machine (60); the sheared slab (30) is coiled to take up all the slab (40) being produced by the continuous casting machine (1 - 6); the coiled slab (30) is uncoiled after the restarting of the operation of the machines (60) shut down; the uncoiled slab (30) is supplied to the machines; and a rolling operation is effected with respect to the slab (30).

Description: The invention relates to an apparatus for continuous casting a slab and direct hot rolling the cast slab, comprising a continuous casting machine directly coupled with a downstream located rolling machine. Further the invention relates to a methode for casting a slab and hot rolling said slab by using such an apparatus. An apparatus according to the pre-characterising part of claim 1 is known from JP-A-60-87903. In the JP-A-60-87903 is disclosed a continuous casting machine and a rolling machine directly coupled with each other. Since the slab produced by the continuous casting machine is directly rolled without being sheared, large advantages in improving the production yield and energy saving take place. In this casting and rolling apparatus a large number of machines, including a width rolling machine, a reduction rolling machine constituted by a multiplicity of stands, a cooling apparatus for a strip after reduction, a shearing machine and a coiler for taking up final hot-rolled products are arranged downstream of the continuous casting machine. Frequently these machines have to be shut down during an operation due to failures, such as a shortage of slabs during rolling or a failure in coiling. In addition, if surface roughening occurs in a mill roll used in the rolling machine and rolling is continued with such a roll, harmful flaws are caused in the surface of the product which will be deprived of its commercial value, so that it is necessary to stop the rolling machine and replace the roll with a new one. In such a case, the casting cannot be continued, so that the molten metal prepared for casting by the continuous casting machine is wasted. In particular, with recent continuous casting machines, the amount of molten metal used in one cycle of casting is large at 100 to 200 tons, and an immense damage is incurred if such a large amount of molten metal is discarded due to the above-described reasons. The JP-A-56-144805 discloses a continuous casting machine and a directly coupled rolling machine in which, when trouble, such as damage to a roll, occurs in a group of rolling stands, the operation is backed up by other normal rolling stands and the normal operation is continued without using the faulty rolling stand. However, the group of the rolling machine stands disclosed therein are merely arranged as a group of rolling machines requiring a multiplicity of rolling machines, the arrangement being no different from a conventional one in which both a hot rolling machine and a cold rolling machine are disposed with a cooling apparatus interposed therebetween. As a result, they do not serve the originally intended purposes of the continuous casting-directly-coupled rolling facilities in which high-temperature slabs produced continuously are rolled into final products by a group of rolling machines on a small number of stands. The object of the invention is to provide an apparatus and a method for continuous casting slabs and direct rolling said slabs which are capable of effecting an operation without stopping the continuous casting machine even when a failure has occurred in a machine disposed downstream of the continuous casting machine and of minimizing an amount of wasting the slabs after the failure of the machine is rectified, thereby overcoming the above-described drawbacks of the prior art. This object will be solved by the featurs of claim 1 (apparatus) and claim 6 (method). When the operation of machines, including the rolling machine, disposed downstream of the continuous casting machine is stopped, the slab continuously produced from the continuous casting machine is sheared on the upstream side of the rolling machine, the sheared slab is coiled to take up all the slab produced from the continuous casting machine, the coiled slab is uncoiled after the restarting of the operation of the machines shut down, the uncoiled slab is supplied to the machines and a rolling operation is effected with respect to the slab thereby the continuous casting-directly-coupled rolling apparatus operates advantageously as described below. (1) When the surface of a roll of the rolling machine has become rough, and urgent replacement is necessary: In such a case, the slab is sheared by the shearing machine disposed immediately after the continuous casting machine. The slab located downstream of the shearing machine is supplied to the rolling machine. Even after shearing, production is continued without stopping the continuous casting machine, and this slab is taken up by the coiler. After it is taken up to a predetermined length, the slab is sheared by the shearing machine located immediately after the continuous casting machine. The coil taken up is promptly transferred to a furnace for heat-insulating and holding coils. In the meantime, casting is continued, and the on-going slab is coiled again by the coiler. The size of the coil is approximately 15 to 40 tons. This operation is continued, and after all the molten metal prepared for the continuous casting machine is cast, the continuous casting machine is stopped. Subsequently, after the mill roll in question is recovered, the coils are removed from the furnace, the slabs are unwound by the uncoiler, and rolling is effected to produce rolled products. In the above-described operation, molten metal prepared for the continuous casting machine can be made into products without any waste. (2) When a machine disposed downstream of the continuous casting machine has broken down: In this case, the slab is sheared simultaneously by a shearing machine disposed upstream of the coiler and another disposed downstream of the uncoiler, and the sheared slab placed between the two shearing machines is sheared to predetermined lengths by the downstream shearing machine and is accommodated. In the meantime, the casting operation is continued, and coiling is performed in the same way as described in item (1). In addition, with respect to the method of uncoiling and rolling after rectification of the failure, the same processing as that described in item (1) above is performed. In this case, only the slabs sheared by the two shearing machines are not made into rolled products, and remain as slabs cut to a predetermined size. However, this results in only a small decline in production yield. The frequency of occurrence of failure such as those described in item (2) above is small. DESCRIPTION OF THE DRAWINGS: Fig. 1 is an overall schematic diagram of continuous casting-directly-coupled rolling facilities in accordance with an embodiment of the present invention; Fig. 2 is a schematic top plan view of an arrangement of a coiler, an uncoiler, and their peripheral equipment shown in Fig. 1; Fig. 3 is a front elevational view illustrating a section for transversely conveying coils in the coiler and the uncoiler; Fig. 4 is an overall schematic diagram of the continuous casting-directly-coupled rolling facilities in accordance with another embodiment of the present invention; and Fig. 5 is a schematic top plan view of the section for transversely conveying the coils in the coiler and the uncoiler shown in Fig. 4. Referring now to Fig. 1, description will be given to a preferred embodiment of the present invention. When rolling is effected directly without shearing a continuously cast slab using a continuous casting machine and a rolling machine, a high-speed thin-slab continuous casting machine is generally employed as the casting machine. As for dimensions of a section of a thin slab, the thickness is about 10 to 40 mm and the width is about 600 to 1,600 mm, while the casting speed is 10 to 25 m/min or thereabout. As for the types of continuous casting machine, various types of machine can be used, including a double drum system reported in JP-A-60-87903, a double belt-type bending continuous casting machine shown in JP-A-58-110161, and a throttling-type double-belt continuous casting machine shown in JP-A-58-218349. The embodiment shown in Fig. 1 illustrates a case in which an inclined-type double-belt continuous casting machine is used. In the double-belt continuous casting machine, a mold is formed by two belts 5, 7 respectively guided by two guide rollers 8, 9, 10, 11. Molten metal 5 is poured into this mold after a stopper 1 is opened and molten metal 3 is transferred to a turn ladle 6 through a nozzle 4. As the belts 5, 7 are rotated in the direction of the arrows A, a slab 40 is produced continuously. This slab 40 is bent into a horizontal shape by means of two bending rollers 12, 13, and is normally sent to a group of rolling machines 39 so as to be reduced and rolled into a predetermined thickness. A hot-rolled sheet product 70 is thereby obtained, and is taken up by a coiler 100. The thickness of this product is approximately 1.6 to 6 mm. The number of stands in the group of rolling machines is three to five, and surface roughening or surface defects of mill rolls 71, 72, 73 which directly roll a material 74 to be rolled is liable to occur in these rolling machines. When such trouble occurs in the roll, the surface quality of the product is impaired and cannot be sold as it is as a commercial product, so that it is necessary to stop the operation promptly and replace the roll with a new one. In such a case, while casting is being continued, the slab 40 is sheared by a shearing machine 14 provided immediately after the continuous casting machine. The leading slab sheared is rolled by the rolling machines at an accelerated speed, so that an interval will be secured between the leading slab and the following slab. The shearing of the slab is effected by blades 16, 17 which are installed on the rotational shafts 15, 18 housed inside a frame 14 as the rotational shafts 15, 18 are rotated in the directions of the arrows shown in Fig. 1. The following slab thus sheared is bent upwardly as a bending roller 21 installed on an arm 22 is moved upwardly to the position shown by an alternate long and two-short-dash line when the arm 22 is rotated with a fulcrum 23 as a center relative to two bending rollers 19, 20. Subsequently, this slab is guided by a guider 26, is bent by three bending rollers 24, 25, 27 and is taken up into a coil 30 indicated by the alternate long and two short dashes line. During the coiling, the coil 30 is supported by coil support rollers 28, 29. The machine which performs the above-described coiling operation is called as a coiler. After the slab is taken up into a predetermined coil length, while casting is being continued, the slab is sheared by the shearing machine disposed immediately after the casting machine. After the shearing, the coiling speed of the coiler with respect to the leading slab increases so that an interval will be secured between the forward end of the following slab and the rear end of the leading slab. Before the forward end of the following slab reaches the three bending rollers 24, 25, 27, the coil 30 whose coiling has been completed is loaded on cradle rollers 32, 33 of a coil car by means of a crane (not shown) on standby, a coil coveying swing arm, or the like. It goes without saying that, during this operation, a slab 80 indicated by the solid lines has already been provided with rolling and is therefore no longer present in this portion. An operating method of conveying the coil 30 on the coil car to the heat insulating furnace will be described with reference to Fig. 3 which is a front elevational view of a coil conveying section. The coil car comprises the two cradle rollers 32, 33 as well as a car 34 detachably supporting these cradle rollers 32, 33 and supporting a liftable frame 36. This car 34 is movable back and forth in the direction of the arrows, using wheels 35. The coil car is moved in the direction of a heat insulation furnace 44, and the coil 30 is placed on a coil conveying beam 46. A wire crane 52 supported by a column 51 is operated to lift a door 50 located in front of a coil heat-insulating furnace 44. Subsequently, a cylinder 47 coupled with the coil conveying beam 46 by means of a pin 48 is retracted, and the coil 30 is stored in the heat insulating furnace 44. Incidentally, the coil conveying beam 46 is supported by a multiplicity of guide rollers 49 so as to facilitate its movement. The state of storage of the coils is shown in Fig. 2 which is a cross-sectional view. In terms of the state of storage of the coils inside the heat insulating furnace 44, the coil 30 which is closest to the side of the coil car is the one which has been delivered last. Incidentally, although, in Fig. 2, the number of coils in the heat insulating furnace is set to three, a greater number of coils can be stored if the heat insulating furnace is enlarged, as necessary. In addition, heating energy may be provided to the heat insulating furnace by means of such as a burner to compensate for a drop in the temperature of the coils. The above-described operation is continued until casting of all molten metal in the ladle 2 shown in Fig. 1 is completed. By the time when casting is completed, the replacement of a mill roll is usually completed. Namely, the roll replacement takes 10 minutes or thereabout, whereas 30 to 60 minutes is required in casting 100 tons. Upon completion of casting, the coil 30 is returned to the cradle rollers 32, 33 in the reverse order of that of the above-described coil storing operation. These cradle rollers are rotated, the coil 30 is uncoiled, and the slab is delivered to the group of rolling machines 39 to effect rolling. This uncoiling operation is effected by the coil car which also serves to convey the coil. When a machine disposed downstream of the continuous casting machine, particularly one disposed downstream of the rolling machines, breaks down, and the machines are to be stopped, a shearing machine 60 disposed downstream of the uncoiler and the shearing machine 14 disposed immediately after the continuous casting machine are operated simultaneously to shear the slab 80. Specifically, the slab length which is present between the two shearing machines is sheared to pieces of a predetermined length by blades 61, 64 installed on rotary shafts 62, 63 which are housed in a frame 60 when the rotary shafts 62, 63 are rotated. The slab sheared to the pieces of predetermined length is stored in a bucket 66 through a chute 65. Casting is continued during this time, and the rear end of the slab sheared by the shearing machine disposed immediately after the casting machine is taken up into a coil in the same way as during the above-described replacement of the mill roll and is stored in the heat insulating furnace 44. In addition, after the faulty machine is repaired, the slab is uncoiled and rolled. It should be noted that, in Fig. 1, the coils 30, 41, 42 accommodated in the heat insulation furnace 44 are sent to the uncoiler in the reverse order of that at the time of their accommodation, and the waiting time of each coil in the heat insulating furnace 44 is not uniform. For this reason, in another embodiment of the present invention shown in Fig. 4, an arrangement is provided to overcome the above-described drawback. Incidentally, with reference to Fig. 4, a description will be omitted with respect to arrangements that are identical with those shown in Fig. 1, and a description will be given only with respect to differences. Namely, as shown in Fig. 4, intermediate coil support rollers 93 are provided between the coiler and the uncoiler, and the coil for which coiling has been completed by the coiler is placed thereon, and is subsequently stored in a heat insulating furnace 90 shown in Fig. 5, thereby overcoming the above-described drawback. Namely, in the heat insulating furnace 90, the coils 30 are adapted to move in the direction of the arrow A, then in the direction of the arrow B, and further in the directoin of the arrow C, and are supplied to the uncoiler. As a result, the waiting time of the coils inside the heat insulating furnace 90 becomes substantially uniform. In accordance with the embodiments of the present invention, the following advantages can be obtained: In other words, in an arrangement in which a continuous casting machine and a rolling machine are arranged in series and a cast slab is normally rolled directly by the rolling machine without being sheared, even in cases where the machines disposed downstream of the continuous casting machine have to be stopped owing to the breakdown of a machine disposed downstream of the continuous casting machine or for another unavoidable reason, it is possible to cast all molten metal prepared for the continuous casting machine without stopping the continuous casting machine. The slab formed by casting is taken up into a coil and is reduced into a shape that gives a small surface area and, hence, a small amount of heat dissipation. This coil is stored in the heat insulating furnace in an isolated state. Therefore, the casting heat is practically not lost, and in conjunction with the restarting of the machines downstream of the continuous casting machine, these coils are uncoiled and can be made into products. In addition, since the large amount of molten metal remaining in the ladle can be made into products by applying the present invention, a substantial improvement can be made in the yield of production. In addition, such an arrangement is also advantageous when those steel types are handled that would be cracked if they are rolled immediately after casting, as in the case of special products including high alloy steel. In other words, ordinary products are directly rolled, whereas special products are temporarily coiled and are stored in a heat insulating furnace for a predetermined time, and are then taken out and rolled, thereby making it possible to effect the operation selectively. While the coils are held in the heat insulating furnace for a predetermined time, the alloy products undergo homogeneous diffusion, so that cracking will not occur even if they are rolled. In accordance with the present invention, there is an advantage in that it is possible to provide a continuous casting-directly-coupled rolling apparatus of practical use in which a continuous casting machine and a rolling machine are coupled with each other and a high-temperature slab produced continuously by the continuous casting machine is directly rolled, and which, even if a malfunctioning occurs in a machine disposed downstream of the continuous casting machine, is capable of effecting the operation without stopping the operation of the continuous casting machine. Even after the overcoming of the malfunctioning of said machine, it is possible to minimize the amount of the slab being wasted.

Claims: Apparatus for continuous casting a slab and direct hot rolling the cast slab, comprising a continuous casting machine ( 1 to 11) directly coupled with a downstream located rolling machine (39) characterized in that a shearing machine (14) is disposed between the casting machine (1 to 11) and the rolling machine (39), a coiler (20 to 29) and an uncoiler (32, 33, 34) are disposed between the shearing machine (14) and the rolling machine (39), the former being adapted to take up and coil a following high temperature slab (40) sheared by the shearing machine (14) and the latter being adapted to uncoil the coiled slab (30) and to feed the uncoiled slab (80) to the rolling machine (39), a second shearing machine (60) is disposed between the uncoiler (32, 33) and the rolling machine (39) and a bucket (66) is provided between the second shearing machine (60) and the rolling machine (39) for storing the sheared length of slab. Apparatus according to claim 1, characterized in that the coiler (20 to 29) includes a bending roller (21) installed on an upwardly movable arm (22), a guider (26) and bending rollers (24, 25, 27). Apparatus according to claims 1 and 2, characterized in that a coil car (34) is provided with a liftable frame (36) on which cradle rollers (32, 33) for supporting and uncoiling the coiled slab (30) are detachably mounted. Apparatus according to claims 1 to 3, characterized in that a heat insulating device (44; 90) is provided for maintaining the high-temperature state of the coiled slabs (30). Apparatus according to claims 1 to 4, characterized in that intermediate coil support means (93) are provided between the coiler (20 to 29) and the uncoiler (32, 33) and that the coils (30) are moved from said support means (93) in the storing furnace (90) first in their lengthwise direction A, then in their cross direction B and then backwards in their lengthwise direction C to the uncoiler (32, 33). Method for continuously casting a slab and direct rolling the cast slab by using an apparatus according to claims 1 to 5, characterized by the steps of: shearing the continuous cast slab (40) at two positions respectively located on the upstream side of said rolling machine (39), when the operation of machines including said rolling machine (39) disposed downstream of the casting machine is stopped; shearing the rear end portion of the sheared slab to pieces of predetermined length and storing said pieces outside of the passline; coiling the following portion of the continuous cast slab produced by the casting machine (1 to 11); uncoiling the coiled slab (30) after restarting the operation of said machines shut down; and rolling the uncoiled slab in the rolling machine (39). Method according to claim 6, characterized in that the coiled slab (30) will be warmed up and held in a high-temperature state until the subsequent uncoiling and rolling operation takes place. Method according to claim 6 or 7, characterized in that the rear end portion (80) of the sheared slab will be rolled with an accelerated speed before the rolling operation is interrupted or stopped. Method according to claims 6 to 8, characterized in that the interrupted rolling operation starts again after the casting of the whole ladle charge has been completed.

Inventors: KIMURA, TOMOAKI
Applicants: HITACHI, LTD.
Application year: 1988
Main classification: B21B1
IPC codes: B21B1, B21B15