MXPA01003379A - Process and relative productionline for the direct manufacture of finished pressed or deep drawn pieces from ultrathin hot rolled strip cast and rolled in-line - Google Patents

Abstract

A process for the production of cold rolled finished strip with thickness of 0.5-0.1 mm and a maximum width of 2000 mm for direct preparation of end products such as pressed and deep drawn pieces from thin slab casting with a thickness of the bar leaving the mould of 90-50 mm, with preparation of pressed pieces and transfer of the finished pieces to the end user and return of the processing scrap to the steel manufacturing cycle. Also a production line for carrying out such a process is described.

Description

PROCEDURE AND PRODUCTION LINE RELATIVE TO THE DIRECT MANUFACTURE OF COMPRESSED OR EMBEDDED PIECES FINISHED FROM THE FOUNDRY OF HOT LAMINATED STRIPS AND ROLLED IN LINE DESCRIPTIVE MEMORY The present invention relates to a process and a relative production line for the direct manufacture of compressed or stuffed pieces? finished from the casting of ultra-thin strips hot rolled and rolled in line. The world production of hot-rolled strip for the manufacture of cold-rolled strips accounts for 40% of the world's steel production, which is currently approximately 750 million tons per year. However, this part of the production of cold rolled steel in industrial countries amounts to approximately 50% of which it can be deduced that the growth potential of the production of hot or cold rolled strips is very high worldwide. At the same time, it should be remembered that the investment costs for traditional production lines is very high and, based on a comprehensive steel mill with a capacity of approximately 4 million per year, expressed in specific investment costs, amounts to approximately US $ 1,000 per unit. ton of cold rolled strips. A traditional process and production line for the manufacture of cold rolled strips with gauges of 0.6 to 0.1 mm, coated or uncoated, is composed for example, as shown in Figure 1 in relation to the prior art, of: - blast furnace production (1); - foundry workshop (2) converter; - continuous plate casting plant with thicknesses of 200-250 mm and width of 800-2600 mm (3); - hot rolling mill (4) consisting of a furnace (4.1), a preliminary mill (4.2) and a finishing mill (4.3) for the manufacture of hot strips with gauge between 4 and 2 mm and a maximum width 1800 mm for the manufacture of hot rolled strips; - continuous deoxidizing treatment (5); - cold rolling mill (6), for example as a continuous or reversible laminator for the manufacture of gauges between 0.6 and 0.3 mm; - annealing (7) of the continuous or bell type; - cold finishing laminator (hardening laminator) with temperature management and control (8). This cold rolled strip, controlled in terms of thickness, convexity and flatness, will be supplied at choice to: a tinning line (9) or a galvanizing line (10) or, without surface coating, a service center (11) ) directly where, depending on the customer's needs, it will be transformed into a strip or packs of sheets, depending on the orders, to leave the factory (12) by ground transportation, by train and / or water (13). This traditional way of selling the finished cold rolled strips also involves the transport of process residues (16) produced by those who perform subsequent procedures (14). These residues derive, for example, from compressing or stuffing (15) the finished parts such as, for example, assembly components (boxes, auto parts and tanks etc.). These process residues (16), which currently account for approximately 15% of the total world steel production, can be seen as "steel tare" which is transported uselessly from the steel manufacturer (12) to the customer (14) to return once again to the steel manufacturer (12) and consequently implies transport costs in the form of time, energy and environmental pollution. The customer (14) traditionally picks from the steelmaker sheets or rolls that are suitable for stuffing and compressing, preferably with a carbon content of less than 0.06%. The customer unwinds them and places them, for example, in a press (15) in order to obtain products (17) such as: - pieces processed by compression or - embossed pieces, such as, for example, external or internal parts for the construction of cars or trucks. The waste derived from the process (16), also defined as "new waste", produced by the understanding of the customer's or end user's sheets (14) and as a tare add up to approximately 30% of the total waste production, which currently corresponds to about 50% of the production of waste. steel, they must be transported back to the steel mill, such as an oxygen melting shop (2) or an electric mill (2.1), thus causing other costs. This means that the waste goes back to the steel manufacturer to recirculate. In addition, this production line is characterized by a longitudinal dimension of approximately 1500 to 200 meters and a transverse dimension of approximately 50 meters, calculated from the continuous casting plant (3) to the shipment (11) of the cold rolled product in the form of rolls (1.11) or packets of leaves (11.2). In addition, each manufacturing phase is generally equipped with an uncoiling and winding station which also causes labor costs, loss of energy and material, as well as possible operating anomalies, and also needs storage space and to move the rolls between a phase of production and the next. An initial reduction of the melting and rolling processes, and therefore a cost reduction in the price per ton of hot rolled strips of approximately 50%, can be achieved with the introduction of the thin plate technique together with the laminator of continuous finishing. With regard to this, the process called ISP (production of in-line strips) in particular, with the components of the melt-rolling technique, ie the reduction of the thickness of the plate during and immediately after the solidification phase will be cited. (DE 38 40 812, DE 38 18 077, DE 44 03 048 AND DE 44 03 049). This technology, compared with other thin-plate technologies that do not show reduction in thickness, lead to a reduction of up to 50% during the solidification phase and up to 80% directly after solidification, a better surface quality and, at the same time, a finer crystalline structure, improved internal quality and, therefore, considerably improved properties of the material in the final product. In the ISP process (23.4) for example, which is partially shown in FIG. 2, the thickness of the plate melt (18.3) in the thin plate melting plant (18) is reduced during solidification in the roll table (18.3). 18.2) with a thickness of 65 mm when leaving the mold (18.1) at a minimum thickness of 30 mm. Directly after solidification the thickness of the plate is reduced to 6 mm by means of a rolling process, for example by three small boxes (19) with an input speed of 0.066 to a maximum of 0.15 m / s. These melt-rolling technologies during and directly after solidification produce plates with very good surface characteristics and a central convexity symmetrical and controlled for example from 1.0 to 1.5% in a thickness of 6 to 25 mm, good flatness as well as a structure of uniform grain size with minimum grades of plate deformation of 30 mm at a minimum thickness of 6 mm or with an elongation of 5 times.The good production of the thin plate (18.3) and especially the intermediate strip (19.1) in its shape and structure should be traced to the laminate in the melt during solidification and especially to the rolling process after solidification which is characterized by a considerable transverse flow of the thin plate to be rolled in the passage between the rolls. This transverse flow is caused by the low deformation speed and the low resistance to rolling in the transverse direction of the material in thin plates. Furthermore, the good flow behavior of the rolling material (18.3) in the passage between the rollers of the rolling mills (19) is favored directly, after solidification, by the low deformation force at the high average temperature of 1350 ° C. in the cross section of the plate. In addition, the plate (18.3) with a surface temperature of about 1200 ° C on entering the first lamination point of the pre-elimination mill (19) still has a thermal gradient, ie an increase in temperature in the direction of the core of the plate . This external and internal temperature between the solidification point and the entrance to the first point is controllable by cooling and favoring a uniform mass flow in the cross section of the plate in the passage between the rolling cylinders: that is, it allows a uniform degree of deformation in the thickness of the plate or better in the thickness of the material to be laminated. This intermediate product (19.1), melted and rolled during and directly after solidification, has the following characteristics: - thickness from 6 to 25 mm; - width from 700 to 2000 mm; - central symmetric convexity between 1.0 and 1.5%; - central symmetry of the convexity > 95% (wedge) in the width of the material to be laminated; - high degree of flatness of the material to be laminated; - better surface quality, which satisfies the high demands for the sausage (05/05) of external parts of automobiles; - uniform, homogeneous and transversely fine crystalline structure that provides high strength and hardness as well as excellent ductility for good cold deformation. This intermediate laminated product (19.1) made in this way with its positive characteristics, which does not generally show a laminate produced according to the prior art, with a thickness of 25 to 6 m derived from the traditional plate between the points (3 ) and (4.6) having a thickness of 280 to 150 mm, or of a conventional thin plate with a thickness of 50 mm, is now heated, preferably by means of an induction furnace (21), at an optimum temperature in relation to with the form of rolling that is determined by: - the steel grade; - the thickness of the final laminate; - handling the temperature of the hot strip in the laminator (23) between the first point and point n as well as in the cooling line (23.1) and in the hot rolled strip coiler (23.2); - the recrystallization and formation of the structure with respect to the material and its behavior in the T.T.T. (time-temperature-transformation); - the convexity; the planarity to be carried directly or again wound on an intermediate roll (22) in the laminator (23) for example by means of a continuous rolling form without longitudinal cutting of the plate (18.3). In the laminator (23) the customer strip (23.3) with a thickness between 1.2 and 0.6 mm finally reaches the hot strip roller (23.2) for recrystallization, from which it is taken and taken to other process procedures in the laminator in cold (25) with or without subsequent surface coating. The task of the invention is now to considerably simplify the traditional hot strip production process described above and based on the traditional plate or even on a normal thin plate (Figure 1) with the help of the ISP procedure (23.4) and a rolling product with a thickness of 0.6 to 1.2 mm, saving stages in the process, reducing costs and having the possibility of directly preparing, after the rolling process, for example compressed or stuffed pieces finished as the details for the door of a car, pieces that are then offered as finished products (32). ) to the final user, that is, the car manufacturer for the final assembly. This technology would allow savings in the following sectors: - investment costs; - manufacturing costs; • Energy; • material; • salaries and wages; • transportation; - cost per piece as well as improvements in environmental pollution, supported by: - savings in the annealing process; - savings in transport energy and - better exploitation of the material (recirculation). From WO 98/00248 there is known a method and a plant for the manufacture of an embossed steel strip or sheet, characterized in that the plant as defined in the main claim 13, for carrying out the method, includes a cooling apparatus to cool the plate when leaving the oven.

The present invention will now be described in more detail with respect to an example of the embodiment based on the accompanying drawings in which: Figure 1 shows a method of the traditional process and relative production line for the manufacture of cold rolled products and products finished derivatives of them, as already described exhaustively, which describes the present state of the technique; and Figure 2 shows an inventive combination of the process and production line for the manufacture of cold-rolled finished products based on the melting of thin plates with the melt-rolling technique during and after solidification. The tests carried out in an ISP plant representing the bases of the process and production lines according to the invention are described with the help of figure 2. The newly invented process and production line presuppose the melting of the steel in a foundry oxygen BOF (converter) (2) or electric (2.1) and are based on a thin plate plant (18) with a thickness when leaving the mold (18.1) for example between 50 and 90 mm and for example with a reduction of thickness during solidification of at least 30 mm. A small preliminary mill (19) is connected to the continuous casting plant directly in line and passes the thin plate (18.3) with a casting speed of approximately 4 to 8m / min thus producing a high cross flow of the rolling stock (18.3) ) in the passage between the rolling cylinders. By means of this transverse flow, and not least by means of the controlled thermal gradient between the surface of the plate and the core of the plate, a very good and symmetrical convexity is obtained in the rough strip (19.1) equal to 1.0 to 1.5 % as well as a fine and uniform structure of the material in the cross section of the strip. The intermediate strip (19.1) at the end of the preliminary laminator (19) has a thickness of 25 to 6 mm and can be cut with a shear (20) in rolls with a specific weight of 15 to 25 kg / mm in width. After the preliminary laminator the intermediate strip (19.1) preferably flows in an induction furnace (21) with which it is brought to an optimum temperature for the final product depending on the grade of the steel, the thickness of the strip and the desired structure of the material or the desired properties of the material. Following the temperature control the strip with laminated structure rolls ur. intermediate winding (22), called a winding box, where the specific temperature of the roll can be rebalanced during the time the strip remains on the furler. It is also possible to achieve a continuous lamination (21.1) so that the strip (19.1), without intermediate winding, is brought directly to the dehuller (22.1) and the finishing laminator (23). The intermediate strip (19.1) leaves the continuous rolling table (23) as a hot strip (23.3) with a thickness of 1.2 to 0.6 mm and a width of 700 to 2000 mm, passes through the cooling area (23.1) with the purpose of controlling the structure in accordance with the TTT diagram and passes through a shear (20.1) to be wound on a hot roll by means of a furler (23.2). this hot strip (23.3) is carried and maintained at a controlled temperature along the entire lamination line between the induction furnace (21) and the furler (23.2) so as to maintain a recrystallized and uniform structure as in the TTT diagram: By controlling this hot strip (23.3), it is possible, after a deoxidizing treatment (24) to send directly (24.2) or by means of an intermediate winding (24.3) to the cold rolling mill (25). In addition, the hot strip (23.3) can also be sent directly (23.5) to a deoxidizing treatment without coiling on the furler (23.2). In the cold rolling mill (25) the hot strip is rolled down to a thickness of 0.5 to 0.1 mm. After the cold rolling step the strip (25.1) is taken to a finishing laminator (27) with temperature management (26). After passing through the finishing laminator (hardening laminator) (27) the strip is controlled in terms of: - thickness - convexity - flatness - structure and is carried directly to a surface coating line as, for example, a tinning line (28), a galvanizing line (29), an organic coating line (28.1) or without a coating directly to a press (30). Here the finished products (32) are prepared directly in the place of the steel manufacturer, or better yet the manufacturer of cold rolled steel; products such as: - compressed elements - embedded elements and the process residue (31) produced in the compression process can be sent directly and therefore recirculated to the steel casting process (2) or (2.1) with savings in transport costs and transport energy. When leaving through the factory door of the steel manufacturer (33) the products are finished products, finished pieces (32) without "steel tare" (31) and can be taken directly with the customer (35) for final assembly ( 36). If the traditional production method is compared with the new inventive solution, it can be seen that by means of the production of very thin, recrystallized hot-rolled strips, (27.1) and in calibers of between 1.2 and 0.6 mm, for example with ISP technology (23.4), very thin strips (25.1) can be produced in the cold rolling mill (25) in calibers of 0.5-0.1 mm. This cold and thin strip (25.1) is processed directly in the cold finishing laminator (27) with a temperature management (26) in order to obtain the finished product (27.1) without having to use a traditional continuous annealing furnace with long times of control of the temperature of the material.

The cold strip manufactured in this ready way (27.1) can optionally be inserted into surface coating lines (28), (28.1) and (29) and / or supplied directly to the press (30) for the production of finished parts (32). ). This preparation phase (30), directly connected to the cold rolling mill (25) and the cold finishing mill (27) for the production of finished parts (32), again leads to a reduction in energy, transportation costs and pollution environmental. The invention of a technical process with its production lines, compared with the traditional preparation line based on the traditional plate or the thin plate without the reduction of thickness during and after the solidification, leads to a very thin hot strip (23.3), precise in its geometric and recrystallized form, with a thickness of 1.2 and 0.6 mm and a convexity of between 1.0 and 1.5% or 10 to 15 microns which, after the deoxidizing treatment, allows the production of a finished strip and cold rolled finished (27.1) without a traditional annealing. This cold strip ready laminated in this way, which involves low costs, is coated or uncoated, directly to the press (30) for the production of finished products (32) where, with the recirculation of the process residue (31) In a nearby foundry shop, more costs are saved. The savings and / or advantages of the new inventive process with its production lines are: - annealing, bell annealing or continuous, after cold rolling; - transport costs for the process waste due to the production of the finished product (32) with the steel manufacturer instead of the end user (35), as is customary up to now; and - savings in the following fields: • investment costs • manufacturing costs - energy - material - wages and salaries - transportation - cost per piece.

Claims (4)

NOVELTY OF THE INVENTION CLAIMS

1. - A procedure for the manufacture of cold-rolled steel strips finished in calibers of 0.5 to 0.1 mm and a maximum width of 2000 mm for the direct preparation of final products such as compressed and pressed parts, which include the following steps: melting plates thin with a thickness of the bar coming out of the mold of 90 to 50 mm; reduce the thickness of the bar during solidification to a minimum of 30 mm; reduce the thickness of the plate directly after the solidification connected to the melting process to a minimum of 6 mm (preliminary stage), with a central symmetric convexity of 1.0 to 1.5%; regulate and control the temperature of the molten-laminated plate directly after the preliminary phase; produce a molten-laminated product controlled in terms of temperature, thickness, width, convexity and flatness; finish the laminate in order to obtain a recrystallized hot strip with a thickness of 1.2 to 0.6 mm and a convexity of 1.0 to 1.5%; a process of deoxidizing treatment with the subsequent cold rolling for the production of cold strips with a thickness between 0.5 to 0.1 mm; cold finishing (hardening) preferred by temperature management for the control of the structure of the material; characterized in that it comprises the additional step of in-line compression of finished parts, ready to be used with the return of the process residue to the steel making cycle; further characterized in that the intermediate strip is hot rolled directly in the finishing mill without an intermediate winding through a winding box and the hot strip is sent directly to a deoxidizing treatment without an intermediate winding in a furler.

2. A method according to claim 1, further characterized in that between the steps of cold finishing and compression a coating can be provided to the cold-rolled strip.

3. A production line for carrying out the process according to claim 1, including: a thin plate plant (18) with a hydraulically operated oscillating mold (18.1) and a mold leaving thickness of between 90 and 50 mm , a maximum width of 2000 mm and a maximum melting speed of 10m / min; a laminar table (18.2) composed exclusively of rolls that allow a reduction of the thickness of the sheet (18.3) during solidification to a minimum of 30 mm; a preliminary laminator (19) composed of at least one box, connected directly and in line with the continuous melting plant (18) for the reduction or roughing of the plate (18.3) to a thickness of the strip stripped (19.1) of 25 mm to a minimum of 6 mm; an oven; preferably an induction furnace 21, for controlling the temperature of the intermediate strip (19.1) directly after the preliminary mill (19); a finishing laminator (23) including at least 4 boxes, a cooling table (23.1) and a reel for the hot strip (23.2); a deoxidizing treatment unit (24) with a subject cold rolling mill (25) for the manufacture of cold rolled strips in a caliber of 0.5 to 0.1 mm; a finishing laminator (27) with temperature control (26); further characterized in that it comprises a press (30) directly connected to the finishing laminator (27) for the manufacture of finished products (32) ready to be used, characterized in that between the preliminary laminator (19) and the finishing laminator (23) the strip intermediate (19.1) is directly hot rolled (23.3) (21.1) in the finishing laminator (23) without going through an intermediate winding box (22) and the hot strip (23.3) is sent directly (23.5) to deoxidizing treatment (24) without being wound on a reel (23.2).

4. A production line according to claim 3, further characterized in that between the cold finishing laminator (27) the press (30) is provided a strip coating plant (28), (28.1) or (29) ).