Moreover, the invention relates to an integrated plant for the production of elongated metal products starting from the liquid steel upstream of the continuous caster and with an automatic and continuous proceed, obtaining a quality finished product, already treated thermally and in its surface. All the indispensable operations for arriving at the finished and packaged product are executed in line with benefits both as to material yield and as to the mill utilization factor.

Background of the Invention Various systems are known for the production of cast, hot rolled and heat treated products, such as bars or rods, and the like. However, such processes conventionally utilize off-line heat treating and metal processing facilities.

It has commonly been the practice to separate the caster and the rolling mill in order to enable product which has been prepared by a variety of preliminary processing procedures to be preliminarily processed and thereafter introduced to the rolling line. More recently, since the development of"hot charging"processes, it is known to provide transport means and storage devices for handling cut to length billets or blooms and to introduce them while hot to a heating furnace.

While this practice saves energy and reduces the need for billet storage, it suffers the drawbacks of reduced material output due to the need for cropping the cast product into short lengths, the presence of short bars in the bed, and the generation of scale in the furnace.

Although several of these defects have been overcome by the method for the continuous casting of long products as described in European Patent Application No. EP 0 761 327 of the same Applicant, the disclosed method suffers from its own drawbacks in that the rolling mill is essentially dedicated to a single caster and casting line, and is therefore restricted to rolling speeds which conform

substantially with the casting speed of product from the caster. Consequently not only may production output be reduced, but also limitations are imposed on the performance of the rolling mill.

It is to the amelioration of these drawbacks that the present invention is directed.

Summary of the Invention In accordance with the present invention there is provided apparatus for the production of elongated rolled product comprising continuous casting equipment operative to produce a plurality of parallel lines of elongated product, a rolling mill positioned downstream of the continuous casting equipment in alignment with one of the lines of product, and a tunnel furnace disposed intermediate the continuous casting equipment and the rolling mil long the one line of product. The tunnel furnace has a length at least equal to the length of the product received from the continuous caster and a width effective to enclose all of the plurality of parallel lines of product. Means are provided for sequentially transferring product within the tunnel furnace from a line other than the one line of product into the one line of product for delivery to the rolling mill.

It is accordingly an object of the invention to provide a production line which is adapted for the production of elongated product, particularly, in the form of bars or rods in which the yield of the plant is optimized.

It is a further object of the invention to provide a line for the production of elongated bar or rod product in which the size of the heat treating and metal processing facilities of the plant is minimized, thus to provide production efficiencies.

It is yet another object of the invention to provide a production facility in which the operating speed of the casting equipment may not dictate the operating speed of the rolling mill.

It is another object to provide a casting strand aligned with the rolling mill that can be used to continuously feed the mill without intermediate bar cuts. The plant therefore offers, on the one hand, the advantage of using a single strand thereby obtaining high performances, and on the other, the possibility of using two or more strands thus achieving greater operational flexibility.

It is a still further object of the invention to provide a facility in which production

output is increased through the use of plural casters.

For a better understanding of the invention, its operating advantages and the specific objectives obtained by its use, reference should be made to the accompanying drawings and description which relate to a preferred embodiment thereof.

Brief Description of the Drawings Fig. 1 is a schematic representation illustrating an overall plant layout incorporating the invention.

Fig. 2 is a somewhat enlarged schematic of the casting/mill area of the plant sncw"in Fig. 1.

Fig. 3 is a plan view of a tunnel furnace and outlet conveyor therefrom of the type suitable for use in the plant shown in Fig. 1.

Fig. 4 is a sectional view of one embodiment of the tunnel furnace taken along line A-A of Fig. 3.

Fig. 5 is a sectional view, similar to Fig. 4, of another embodiment of the tunnel furnace taken along line A-A of Fig. 3.

Fig. 6 is a sectional view of the tunnel furnace discharge conveyor taken along line B-B of Fig. 3.

Fig. 7 is schematic diagram consisting of steps A to H indicating the sequencing of billets within the tunnel furnace for transferring said billets from parallel conveyors into alignment on a single conveyor for conduct to the rolling mill in accordance with the present invention.

Description of the Preferred Embodiments of the Invention The disclosed invention is particularly directed to a plant for the production of"long products", i. e. billets or blooms from about forty meters or more in length, used in the production of bars, wire, rod, rebar, or shaped beams or angles, and the like, in which the production machinery utilized is typically smaller in size than that used in the production of sheet material from slabs. As used herein, the word,"billet", shall include blooms or slabs, or other strand forms produced by a continuous caster and useful in the production of the aforementioned intended product.

Fig. 1 of the drawings shows a schematic representation of an overall plant layout suitable for the practice of the present invention. The described plant comprises a

casting/mill entry area A according to the invention, a rolling mill/stands store area B, a finishing area C for the in-line heat treatment of product; and a finishing area D for the in-line heat treatment of wire rod and bars. A description of the respective areas of the plant is presented hereinafter.

As shown in the schematic representation of Fig. 1, the casting/mill entry area of the plant includes that area of the plant beginning with the continuous casting equipment 12 and extending essentially to the entrance to the roughing mill stand 16 of the rolling mill 14.

In Fig. 2 the production line is shown in somewhat more detail as containing continuous caster equipment 12 which may be operable ! u) producing a pair of billets 18. The caster equipment 12 comprises a mold 20 which, as is well known, receives molten metal from a tundish (not shown), or the like, and delivers a plurality (here shown as a pair) of billet strands 22 to a conveyor 24, typically a roll conveyor, suitable for conveying high temperature metal product. Depending upon the ultimate shape of the product to be produced, the caster strands may be billet strands, as embodied in the described line, or they may be of bloom or other dimensions. In either event, the plant 10, being intended for the production of rolled bar, wire product or other elongated shaped product, will produce strands of predetermined dimensions suitable for the ultimate production of the desired elongated product.

The illustrated production line contains a pair of in-line shears 26 which may be of the blade or flame-type. A quenching box 28, a cooling bed 30 and a reheat furnace 32 optionally may also be disposed in an"in-line"configuration in the production line. A tunnel furnace 34, whose principal function it is to heat up and to equalize the temperature of the billets and to bring them to a rolling temperature prior to their being passed to the rolling mill 14, as hereinafter more fully described, is provided upstream of the roughing mill stand 16. A dividing and cropping shear 26 is disposed in each of the lines for cutting the product strands to length, which is contemplated to be upwards of forty meters in length.

According to the invention, one of the conveyors, indicated as 24a in the drawings, and adapted to receive one of the billet strands 22 from the caster, extends the length of the production line in alignment with the entrance to the rolling mill 14, as

determined by the entrance end of the roughing mill stand 16. The adjacent conveyor, indicated as 24b in the drawings, extends parallel to the first conveyor 24a continuously from its position to receive a billet strand and convey it to a position spaced inwardly of the outlet of the tunnel furnace 34.

Advantageously, a descaling assembly 36, as shown in Fig. 2, can be disposed in conveyor line 24a intermediate the discharge end of the tunnel furnace 34 and the entrance to the roughing mill stand 16. The descaling assembly 36 may be of any well known type but preferably is of the water-operated type including rotary nozzles (not shown) providing a high pressure impact and a low overall rate of water flow so as to reduce tc a minimum the loss of temperature from the billet 18 passing to the rolling mill. Between the tunnel furnace 34 and mill inlet, in an advantageous position between the descaler 36 and the mill 14, an on-line conditioning device 35 can be provided which enables an efficacious elimination of surface defects before entering the mill. The device 35 may comprise in-line grinding systems or in-line scarfers using a special flame for eliminating the billet surface layer.

The tunnel furnace 34 may be heated by any of a number of available heating sources including free flame burners, radiating pipes, induction heaters, or any combination of these, either with or without a protective atmosphere. The tunnel furnace 34 is of a size to receive both conveyors 24a and 24b and is of a length to accommodate the product being conveyed along the respective conveyors.

Exiting the tunnel furnace 34, as illustrated, is the tunnel furnace discharge end of conveyor 24a which is aligned with the entrance to the roughing mill stand 16.

As shown in Fig. 3 the longitudinally parallel conveyors 24a and 24b, which each comprise a series of transversely parallel rollers 35 rotatably driven by motors 37, are arranged to convey billets 18 from the respective caster strands 22 to the tunnel furnace 34. In the tunnel furnace 34 the conveying rollers are enclose within walls having a thermal resistant lining. Openings are provided in the furnace walls to accommodate penetration of connecting shafts extending between the motors and the rollers 35. As shown best in Fig. 4 the rollers 35 defining the conveyors 24a= and 24b= may be mutually separated by conductor beams 39'whose temperature is maintained by a transfer of heat with respect to

fluid circulated through heat transfer line 41. In an alternative embodiment of the tunnel furnace 34 shown in Fig. 5, the conductor beams 39'and heat transfer line 41 are eliminated.

According to the invention, means are provided to insure the placement of the billets 18 in close end-to-end alignment at the time of delivery to the rolling mill 16 so that the rolling operation performed on billets from the respective strands 22 is conducted substantially continuously. Thus, as shown, the billet transfer device 38 comprises a series of movable structures 39 that penetrate the furnace wall on one lateral side along substantially the full length of the respective conveyors within the tunnel furnace 34. In operation, those segments of conveyors 24a and 24b within the tunnel furnace 34, identified as segments 24a'and 24b', respectively, produce a running velocity for the billets 18 variable in relation to the continuous feeding cycle phase of the billet to the rolling mill. An illustrative operating cycle is described hereafter.

Consequently, the operating procedure of the disclosed equipment can be appreciated from consideration of Steps (A) through (H) in Fig. 7 of the drawings.

In operation, with billet 18A on conveyor 24b and billet 18B on conveyor 24a and lagging billet 18A, billet 18A enters the tunnel furnace 34 and is received upon conveyor 24b' (Step A). Due to the increased velocity of conveyor 24b', billet 18A is moved at a greater velocity to the end of the conveyor and stopped (Step B). In the meantime, immediately prior to the entry of billet 18B on conveyor 24a into the tunnel furnace 34, billet 18A, by operation of the transfer apparatus 38, is transferred from conveyor 24b'to conveyor 24a'in forwardly spaced relation from billet 18B (Step C). Thereafter, billet 18A and billet 18B are both conducted on the conveyor 24a'with billet 18A being conducted from the tunnel furnace 34 through the descaling assembly 36 toward the entrance to the roughing mill stand 16 and billet 18B being simultaneously conducted into the tunnel furnace (Step D).

During this period, a following billet, designated in the drawings as billet 18A1, which is in lagging relation with respect to billet 18B on conveyor 24a, has been conveyed by conveyor 24b toward the entrance of the tunnel furnace 34 (Steps B to D). Billet 18Ai enters the tunnel furnace 34 on conveyor 24b to be received on conveyor 24b'as billet 18B is leaving the part of the roller table 24a which will then

be occupied by billet 18A1 (Step E). As indicated previously, the running speeds of the respective conveyors, 24a, 24b, 24a'and 24b', are controlled to be time- variable for performing the described working cycle.

As shown in Step (F) billet 18A is conducted through the roughing mill 16 at rated rolling speed to the position indicated in the drawing figure. While billet 18A is rolled, billet 18B is brought to a position immediately adjacent the rearward end of billet 18A wherein it is substantially contiguous therewith. This establishes sufficient space on conveyor 24a'rearwardly of billet 18B to permit billet 18A, to be transferred to conveyor 24a'from conveyor 24b'by the transfer device 38. As billets 18A and 18e are conveyed at rated rolling speed through the rolling mill and descaling assembly, respectively (Step G), billet 18A1 is transferred to conveyor 24b'and moved into close, substantially contiguous relation with the rear end of billet 18B (Step H). At this time billets 18B1, 18A1 and 18A2 are at locations corresponding to billets 18B, 18A and 18A1 shown in Step (D) whereupon the operating cycle continues in a repeating manner.