Method to transform a rolling plant

Abstract: Method to transform a rolling mill in order to revamp an old-type rolling line (10) fed by slabs with a thickness greater than 160 mm and arriving from an accumulation store (12) and to insert a segment of new line comprising at least a continuous casting machine (19) to produce thin and medium slabs, with attached relative operating assemblies such as extraction, straightening, shearing devices etc., the old line (10) comprising a roughing unit with one or more stands and a terminal segment (21) with a finishing train (15), a cooling area (17), systems to collect the product (18a, 18b) etc., the segment of new line (110) being achieved and installed in a position near the old line (10) while the old line (10) continues working, the segment of new line (110) being equipped substantially at the terminal end with a movable element (120) in order to be at least temporarily connected to the terminal end (21) of the old line (10).

Description: FIELD OF APPLICATION This invention concerns a method to transform a rolling plant as set forth in the main claim. The invention is applied to revamp rolling lines employed in plants of the old type, principally operating semi-continuously, where slabs pre-sheared to size are fed from store areas in hot or cold loading, with lines adopting more modern technologies which produce thin slabs from a continuous casting machine located directly in line with the rolling train. STATE OF THE ART In recent years the technologies used in continuous casting and rolling have been the subject of intense and exhaustive studies and experimentation in order to find ever more advanced technological solutions which can combine great productivity, cost-effectiveness and a high inner and surface quality of the product. These studies and experiments have brought about particular technological developments, specifically in the field of medium and thin slabs continuously cast from an ingot mold, so that it has become possible to hypothesise and achieve a continuous casting line where the rolling train is directly connected to the ingot mold. This transformation of the plants has been motivated by the need to improve the quality of the product, to reduce production costs, to increase production, and to extend the range of products, particularly with regard to thinner widths. This solution has however entailed the problem that a great number of old plants, which employ rolling lines arranged to roll slabs starting from a thickness of around 160÷350 mm and fed from store areas, need to be transformed into more advanced plants which adopt the new technologies. The necessary transformation, which involves or will involve within a short time substantially a large majority of the old-type rolling plants, necessarily causes a long downtime in the plant, of about 5÷6 months, in order to carry out the necessary work, including foundation work, to replace and install the new assemblies; in actual fact, this causes a considerable economic loss for the steel works which can only be recouped when the new plant has been active for a long period. JP-A-61-056705, which represents the most relevant state of the art, discloses a rolling mill equipment in which a roughing mill line and a finishing mill line are located in an off-axis arrangement and wherein a coil box is provided on the exit side of the roughing mill line. The coil box and the finishing mill line are connected by a conveying machine which comprises a heat isolation device or soaking-pit furnace. In the event that a strip continuous casting machine is to be connected to the finishing mill line, such strip continuous casting machine is connected to the heat isolation furnace. In this manner the roughing mill line can be removed and the line of the strip continuous casting machine and the finishing mill line are arranged on a line. This equipment only allows the substitution of a roughing mill line with a strip continuous casting machine, or a strip caster. Moreover, in order to allow-this substitution, the equipment is provided with a coil box and a heat isolation furnace which normally connects the roughing mill line to the finishing mill line. The provision of the coil box to wind the strips coming from the roughing mill line, and the conveying machine to transport the bobbin so formed through the heat isolation furnace, before starting the finishing thereof, creates an unnecessary complication of the rolling line, when it normally works, solely in view to set the equipment to arrange the strip continuous casting machine in lieu of the roughing mill line. The present Applicant has designed and tested this invention to solve this serious operating problem with a solution which is relatively simple and such as will make it substantially painless to revamp an old plant so as to install more advanced technology, and also to obtain further advantages as will be shown hereinafter. DISCLOSURE OF THE INVENTION The invention is set forth and characterised in the main claim, while the dependent claims describe variants of the idea of the main embodiment. The purpose of the invention is to adopt a procedure which can be adopted in the transformation of an old-type semi-continuous plant, where rolling is carried out starting from slabs of 160÷350 mm thick arriving from a store area, into a plant with a continuous casting machine for thin slabs arranged directly in line with the rolling train which will minimise the economic impact caused by the transformation. According to the invention, the new segment of line, comprising the continuous casting machine for thin slabs and the operating assemblies placed downstream thereof, for example the heating and temperature equalisation furnace, is achieved in a position adjacent to (or at least near, depending on the configuration of the plant) the already existing line which continues to work. The operating assemblies associated with the continuous casting machine may comprise an extraction assembly, a straightening assembly, a shearing assembly, possibly heating assemblies, possibly descaling assemblies, and possibly other assemblies functional to the working and processing of thin slabs. The new segment of line according to the invention comprises at the end at least a movable connection element suitable to connect the new segment of line with the terminal end of the pre-existing line, which remains unchanged; the terminal segment comprises a possible descaling assembly, the finishing train, the cooling area, the assemblies to coil and discharge the product, conditioning, measuring, shearing and emergency assemblies, etc. According to a variant, the terminal segment comprises one or more roughing stands at the leading end. According to a further variant, the terminal segment comprises a reversible-type roughing stand, possibly associated with a coil box, at the leading end. According to one embodiment, the connection element can be translated in a direction parallel to itself. According to a variant, the connection element is movable in a pivoting manner. According to another variant, the connection element is moved on rails. According to yet another variant, the connection element is moved on a trolley or slider or translatable platform. When the new segment of line has been prepared, the conversion of the plant is carried out by connecting the new segment to the terminal segment which remains unchanged; according to the preferential embodiment, this occurs when the plant is given a periodical and pre-determined maintenance operation. During this pre-determined downtime, all the necessary connections can be made: the hydraulic and electrical connections, and all the other equipping and installation operations necessary to reconfigure the line. In this way, the downtimes when the plant is totally stopped are substantially eliminated and the economic impact caused by the transformation of the plant is minimised. According to another evolution of the invention, once the new line has been installed and has started working, the old line arranged on an axis with the rolling train is completely dismantled and replaced by a new line with a continuous casting machine. This operation can be carried out without interfering in any way with the already completed first line, which can operate under normal working conditions, and therefore without compromising the productivity of the newly transformed plant in any way. ILLUSTRATION OF THE DRAWINGS The attached Figures are given as a non-restrictive example and show some preferential embodiments of the invention as follows: Fig. 1 shows a first embodiment of the invention; Figs. 2 and 3 show variants of Fig. 1. Fig. 4 shows another variant of Fig. 1. DESCRIPTION OF THE DRAWINGS In Fig. 1, the reference number 10 denotes generally an old-type rolling line, comprising an initial segment with a rollerway 11 feeding the slabs fed from a store 12 through heating and temperature equalisation furnaces 13. The slabs supplied from the store 12 can arrive hot or cold, they are pre-sheared and normally have a thickness of between 160 and 350 mm. The slabs are progressively sent to a plurality of roughing stands arranged in sequence, in this case 14a, 14b, 14c, 14d and 14e, and are then sent to the finishing train 15 comprising in this case six finishing stands 16. It is the same, as in Fig. 4, if the line 10 includes only one roughing stand, for example 14e, of the reversible type, followed by a coil box 24 and preceded by a descaling assembly. For simplicity of illustration, obviously, no further description is given of the plurality of operating and functional assemblies - conditioning, measuring, auxiliary, emergency assemblies, etc. - which any person of skill in the art can identify as essential or at least important within the line 10. After the finishing train 15 there is the cooling area 17, for example a cooling bed or plane, which is followed in turn by the systems to collect the product, in this case comprising two downcoilers 18a and 18b. Such a line 10 as described is well-known to the state of the art. In this case, adjacent to this old-type line 10, or at least nearby, a segment of new line 110 is progressively achieved which adopts the most advanced and recent technology of continuous casting for slabs and comprising at least a continuous casting machine 19. In this case, the segment of new line 110 is parallel to the old line 10, but it is also possible for the new line 110 to be oblique thereto. According to a variant which is not shown here, there may be two or even more segments of new line 110 which can be connected, either temporarily or stably, to the old line 10. The slabs produced by the continuous casting machine 19 are advantageously around 50÷70 mm thick, but according to the invention they may also have other formats according to the possibilities offered by the continuous casting machine 19, the products which are to be obtained, the configuration of the finishing train 17, the inclusion of one or more roughing stands 14, etc. Only the components of the segment of new line 110 which are strictly essential have been shown here: any person of skill in the art can complete the line with the operating assemblies which are functionally suitable according to the requirements of the specific plant. The sizing of the new segment 110, both in terms of length and configuration, can be a function of the specific requirements of the plant and the products which are to be obtained. Downstream of the continuous casting machine 19, the new segment 110 comprises a rollerway 20 to feed the slabs whose terminal segment 120 is movable and has the function of connecting the rollerway 20 to the terminal segment, indicated in its entirety by the reference number 21, of the old line 10. The terminal segment 120, in a first embodiment, can be structured as a tunnel furnace. In another embodiment, the terminal segment 120 is structured as a tunnel furnace with burners. In yet another embodiment, the terminal segment 120 has heating and temperature equalisation means for the sections of slab contained inside. According to the embodiment shown in Fig. 1, the terminal end 120 can be moved in a direction parallel to itself so as to be inserted into the old line 10, either on rails 27 or a motorised trolley. In this embodiment, according to a variant, the rollers of the terminal segment 120 are interpenetrating with the rollers of the corresponding element 26 of the old line 10 so that modifications to the element 26, in order to achieve the transfer of the slabs from the old line 10 to the new line 110, can be limited to a minimum. According to a variant, there is a translating platform on which the element 120 of the new line 110 and the element 26 of the old line 10 are mounted. In Fig. 4, if no descaling assembly is already included, then a descaling assembly 25 is installed immediately upstream of the reversible roughing stand 14e. According to a variant shown in Figs. 2 and 3, there is at least a terminal segment 120 movable in a pivoting manner around its rear end (Fig. 2) or its front end (Fig. 3), cooperating with a connection element 22, which is also movable in a pivoting manner, of the old line 10 so as to align with the segment 120 and transfer the slabs. In this case, the terminal segment referenced by 21, which remains unchanged even after the plant has been transformed with the new segment of line 110, has a roughing stand 14e which acts on the thin slabs produced by the continuous casting machine 19 even after conversion has been completed. In the case of Fig. 2, in the new line 110 the slabs pass into the roughing stand 14e. In Fig. 3, on the contrary, the slabs produced by the new line 110 do not pass through the roughing stand 14e, inasmuch as they emerge from the continuous casting machine with a shape which allows them to be sent directly to the finishing train 15. According to another variant, the terminal segment 120 can oscillate in a pivoting manner around its forward or rear end according to whether the roughing stand 14e needs to be included or not. In the variant shown in Figs. 2 and 3, there is a rollerway 23 to discharge the discarded slabs downstream of the movable terminal segment 120. According to a variant, there are two or more roughing stands which remain in the line after conversion. According to a further variant, the roughing stand 14e is of the reversible type. According to the invention, the necessary connections, for example hydraulic and electrical, to make the new segment of line 110 operational - since these connections derive from the old line - are carried out during a pre-determined maintenance of the old line 10, so as to make the conversion economically painless. Once the new segment of line 110 has been connected to the terminal segment 21, which remains unchanged, the segment of old line 10 which has been replaced can be either maintained so as to work in alternation with the new line 110, or dismantled and/or reconverted. For example, as shown in Fig. 4, a second continuous casting machine 19 and a relative second new line 210 can be inserted, with the relative assemblies, while the continuous casting plant consisting of the new line 110 is working normally, so that productivity is not prejudiced in any way, thus achieving, in the end, two continuous casting lines 110 and 210, with a shared finishing train 15, with transformation times reduced to a minimum.

Claims: Method to transform a rolling mill in order to revamp an old-type rolling line (10) fed by slabs with a thickness greater than 160 mm and arriving from an accumulation store (12) and to insert a segment of new line (110) comprising at least a continuous casting machine (19) to produce thin and medium slabs, with attached relative operating assemblies, the old line (10) comprising a roughing train with one or more stands and a terminal segment (21) with a finishing train (15), a cooling area (17) and systems to collect the product (18a, 18b), the method comprising the step of installing a segment of new line (110) in a position next to the old line (10) while the old line (10) continues working, characterised in providing the segment of new line (110) being equipped substantially at the terminal end with a connection terminal segment (120) movable in a pivoting manner or transversely between two parallel position, and connecting at least temporarily the connection terminal segment (120) of the new line (110) to the terminal segment (21) of the old line (10). Method as in Claim 1, in which the step of connecting the connection terminal segment to the existing terminal segment (21) of the old line (10) is performed during a pre-determined maintenance procedure of the old line (10). Method as in claim 1, in which the new segment of line (110) is installed parallel and adjacent to the old line (10). Method as in claim 1, in which the new segment of line (110) is installed obliquely to the old line (10). Method as in any claim hereinbefore, in which the connection terminal segment (120) of the new line (110) is movable parallelly to said old line (10). Method as in claim 1, in which rollers of the connection terminal segment (120) are made interpenetrating with rollers of the corresponding element (26) of the old line (10). Method as in claim 1, in which the connection terminal segment (120) of the new line (110) is movable in a pivoting manner and cooperates with a mating element (22) of the old line (10), also movable in a pivoting manner. Method as in claim 1, in which the connection terminal segment (120) moves on rails. Method as in claim 1, in which the connection terminal segment (120) moves on a trolley or slider or motorised platform. Method as in any claim hereinbefore, in which the connection terminal segment (120) is connected upstream of at least a roughing stand (14e). Method as in claim 10, in which the roughing stand (14e) is of the reversible type and cooperates with a coil box (24). Method as in any claim hereinbefore, in which downstream of the movable connection terminal segment (120) there is an element (23) to discharge discarded slabs. Method as in any claim hereinbefore, in which, after the new line (110) has started normal functioning, the old line (10) is replaced by a second new line (210) of continuous casting.

Inventors: BENEDETTI GIANPIETRO, COASSIN GIOVANNI, BENEDETTI, GIANPIETRO, COASSIN, GIOVANNI
Applicants: DANIELI OFF MECC, DANIELI & C. OFFICINE MECCANICHE S.P.A.
Application year: 1998
Main classification: B21B1
IPC codes: B21B1