US20220001442A1 - Method to produce a metal strip, and production plant implementing said method - Google Patents

Method to produce a metal strip, and production plant implementing said method Download PDF

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Publication number
US20220001442A1
US20220001442A1 US17/283,820 US201917283820A US2022001442A1 US 20220001442 A1 US20220001442 A1 US 20220001442A1 US 201917283820 A US201917283820 A US 201917283820A US 2022001442 A1 US2022001442 A1 US 2022001442A1
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Prior art keywords
thickness
cast product
strip
rolling
crystallizer
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US17/283,820
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Gianpietro Benedetti
Paolo Bobig
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Danieli and C Officine Meccaniche SpA
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Danieli and C Officine Meccaniche SpA
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21B—ROLLING OF METAL
    • B21B1/00—Metal-rolling methods or mills for making semi-finished products of solid or profiled cross-section; Sequence of operations in milling trains; Layout of rolling-mill plant, e.g. grouping of stands; Succession of passes or of sectional pass alternations
    • B21B1/22—Metal-rolling methods or mills for making semi-finished products of solid or profiled cross-section; Sequence of operations in milling trains; Layout of rolling-mill plant, e.g. grouping of stands; Succession of passes or of sectional pass alternations for rolling plates, strips, bands or sheets of indefinite length
    • B21B1/24—Metal-rolling methods or mills for making semi-finished products of solid or profiled cross-section; Sequence of operations in milling trains; Layout of rolling-mill plant, e.g. grouping of stands; Succession of passes or of sectional pass alternations for rolling plates, strips, bands or sheets of indefinite length in a continuous or semi-continuous process
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21B—ROLLING OF METAL
    • B21B1/00—Metal-rolling methods or mills for making semi-finished products of solid or profiled cross-section; Sequence of operations in milling trains; Layout of rolling-mill plant, e.g. grouping of stands; Succession of passes or of sectional pass alternations
    • B21B1/46—Metal-rolling methods or mills for making semi-finished products of solid or profiled cross-section; Sequence of operations in milling trains; Layout of rolling-mill plant, e.g. grouping of stands; Succession of passes or of sectional pass alternations for rolling metal immediately subsequent to continuous casting
    • B21B1/466—Metal-rolling methods or mills for making semi-finished products of solid or profiled cross-section; Sequence of operations in milling trains; Layout of rolling-mill plant, e.g. grouping of stands; Succession of passes or of sectional pass alternations for rolling metal immediately subsequent to continuous casting in a non-continuous process, i.e. the cast being cut before rolling
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
    • B22D11/00—Continuous casting of metals, i.e. casting in indefinite lengths
    • B22D11/12—Accessories for subsequent treating or working cast stock in situ
    • B22D11/1206—Accessories for subsequent treating or working cast stock in situ for plastic shaping of strands
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21B—ROLLING OF METAL
    • B21B1/00—Metal-rolling methods or mills for making semi-finished products of solid or profiled cross-section; Sequence of operations in milling trains; Layout of rolling-mill plant, e.g. grouping of stands; Succession of passes or of sectional pass alternations
    • B21B1/22—Metal-rolling methods or mills for making semi-finished products of solid or profiled cross-section; Sequence of operations in milling trains; Layout of rolling-mill plant, e.g. grouping of stands; Succession of passes or of sectional pass alternations for rolling plates, strips, bands or sheets of indefinite length
    • B21B1/24—Metal-rolling methods or mills for making semi-finished products of solid or profiled cross-section; Sequence of operations in milling trains; Layout of rolling-mill plant, e.g. grouping of stands; Succession of passes or of sectional pass alternations for rolling plates, strips, bands or sheets of indefinite length in a continuous or semi-continuous process
    • B21B1/26—Metal-rolling methods or mills for making semi-finished products of solid or profiled cross-section; Sequence of operations in milling trains; Layout of rolling-mill plant, e.g. grouping of stands; Succession of passes or of sectional pass alternations for rolling plates, strips, bands or sheets of indefinite length in a continuous or semi-continuous process by hot-rolling, e.g. Steckel hot mill
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21B—ROLLING OF METAL
    • B21B1/00—Metal-rolling methods or mills for making semi-finished products of solid or profiled cross-section; Sequence of operations in milling trains; Layout of rolling-mill plant, e.g. grouping of stands; Succession of passes or of sectional pass alternations
    • B21B1/46—Metal-rolling methods or mills for making semi-finished products of solid or profiled cross-section; Sequence of operations in milling trains; Layout of rolling-mill plant, e.g. grouping of stands; Succession of passes or of sectional pass alternations for rolling metal immediately subsequent to continuous casting
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
    • B22D11/00—Continuous casting of metals, i.e. casting in indefinite lengths
    • B22D11/06—Continuous casting of metals, i.e. casting in indefinite lengths into moulds with travelling walls, e.g. with rolls, plates, belts, caterpillars
    • B22D11/0628—Continuous casting of metals, i.e. casting in indefinite lengths into moulds with travelling walls, e.g. with rolls, plates, belts, caterpillars formed by more than two casting wheels
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
    • B22D11/00—Continuous casting of metals, i.e. casting in indefinite lengths
    • B22D11/16—Controlling or regulating processes or operations
    • B22D11/20—Controlling or regulating processes or operations for removing cast stock
    • B22D11/207—Controlling or regulating processes or operations for removing cast stock responsive to thickness of solidified shell
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips

Definitions

  • the present invention concerns a method to produce a metal strip and the production plant implementing said method.
  • the method according to the present invention allows to define the modes to obtain a metal strip and a constructive layout of a plant for producing hot-rolled metal strip.
  • plants for producing metal strip which usually comprise a mold configured to cast slabs, extraction devices provided to extract the slabs from the mold, and a rolling line located downstream of the extraction devices, configured to reduce the overall thickness of the slab until a metal strip of the desired thickness is obtained.
  • the endless-type plants provide to supply the cast product, gripped directly, from the mold to the rolling line without cutting the product being worked except for before the final winding.
  • the semicontinuous-type plants provide that downstream of the casting machine or the roughing stands, the cast products are cut to size and disposed in a heating and/or maintenance furnace which also acts as an accumulation buffer for the cast products when it is necessary, for example, to interrupt the downstream rolling due to small accidents or programmed roll change.
  • the process is called coil to coil. If, on the other hand, the cast product is cut, downstream of the casting machine or of the roughing stands, to a length such as to obtain, at the end of the rolling process, a single coil, the process is called coil to coil. If, on the other hand, the cast product is cut, downstream of the casting machine or of the roughing stands, to a length such as to obtain, at the end of the rolling process, a plurality of coils, usually between two and five, the process is called semi-endless.
  • the choice of the type of plant to adopt, as well as the number of components required, for example the number of rolling stands, or the choice of how many roughing stands and how many finishing stands to adopt, is usually determined based on the experience of the technicians of the field.
  • This sizing that is, the preparation of the strip production plant, however, sometimes does not allow to reach an effective compromise between the investments required for the construction of the plant, also called Capex, and the operating transformation costs, also called Opex.
  • Capex the investments required for the construction of the plant
  • Opex the operating transformation costs
  • a further purpose of the present invention is to provide a plant and to perfect the corresponding method to produce a hot-rolled metal strip that can selectively vary the thickness of the cast slab in relation to the final thickness of the strip.
  • the Applicant has devised, tested and embodied the present invention to overcome the shortcomings of the state of the art and to obtain these and other purposes and advantages.
  • a method to produce metal strip comprises the casting of a cast product through a casting machine provided with a crystallizer to obtain a slab, and the hot rolling of the slab in a rolling station to obtain metal strip having different strip thicknesses.
  • the casting machine during the casting, exerts an action of reducing the thickness of the cast product exiting the crystallizer.
  • the method provides that the casting machine is selectively set, on each occasion, as the strip thicknesses vary, in order to exert a different action of reducing the thickness of the cast product.
  • the present method comprises, with the sizes of the crystallizer being equal, at least a first step of producing a first strip having a first thickness, wherein the casting machine exerts a first thickness reduction ratio of the cast product, and at least a second step of producing a second strip having a second thickness, less than the first thickness, wherein the casting machine exerts a second thickness reduction ratio of the cast product, different from the first thickness reduction ratio;
  • this thickness reduction ratio is defined as the difference between the thickness of the cast product exiting from the crystallizer and the slab thickness exiting from the casting machine, correlated to the thickness of the cast product exiting from the crystallizer.
  • This solution allows to modulate the thickness of the slab exiting the casting machine, as a function of the final strip thicknesses to increase the efficiency of the strip production plant and increase the quality of the strip produced.
  • the action of reducing the thickness induced on the strip, produced on each occasion, is divided partly in the casting machine and partly in the rolling station, improving efficiency and increasing the quality of the strip produced.
  • the number of rolling stands of the rolling station is substantially the same as that of a known plant, with the present invention it is in any case possible to reduce the number of rolling compressions, since part of the reduction in thickness is carried out directly by the casting machine and not only in the rolling station as occurs in the state of the art.
  • This expedient allows to obtain energy savings thanks to a reduction in the pressure of the compression on the slab being rolled, and to obtain a higher quality of the strip because, for example, the profile and the flatness thereof are improved, and the risk of scale impressed onto its surface is reduced.
  • FIGS. 1-9 show some of the possible embodiments of a plant for producing a metal strip which implements a method in accordance with the present invention
  • FIG. 10 graphically shows some curves, determined in relation to the thickness H of the cast product exiting from the crystallizer, showing the development of the thickness reduction ratio of the cast product exerted by the casting machine as a function of the thickness of the strip;
  • FIG. 11 shows curves, determined in relation to the thickness H of the cast product exiting from the crystallizer, which show the development of the thickness reduction ratio in the drawing unit as a function of the thickness of the strip;
  • FIG. 12 shows the criteria for choosing the rolling modes
  • FIG. 13 graphically shows a further criterion for choosing the rolling modes in relation to the strip thicknesses and to the capacity of a plant layout to adopt one and/or the other of the rolling modes;
  • FIGS. 14 and 15 are graphs that correlate the nominal slab thickness to the productivity of the plant and to the casting speed; both charts refer to a casting operation of 7,200 hours/year;
  • FIG. 16 is a graph which correlates the ratio of thicknesses to the number of rolling stands required
  • FIGS. 17-22 show two example embodiments of implementation of the teachings of the present invention.
  • Embodiments of the present invention concern a method to produce a metal strip N in a production plant 10 .
  • FIGS. 2-9 show possible layouts of plants 10 for producing strip that implement the principles of the present invention.
  • FIG. 1 shows a plurality of operative components reciprocally disposed along a work line.
  • These operative components shown in FIG. 1 can be combined with each other to obtain one or more layouts for producing strip, then shown in FIGS. 2-9 .
  • the variant embodiments of the production plant 10 shown in FIGS. 2-9 refer to components of a plant described with reference to FIG. 1 .
  • the plant 10 for producing strip N comprises at least one casting machine 11 in which the liquid metal is cast to be solidified and to obtain a slab B.
  • the production plant 10 also comprises a rolling station 19 located downstream of the casting machine 11 and configured to hot roll the slab B and obtain strip N
  • the casting machine 11 comprises at least one mold 15 provided with a crystallizer 15 a in which the formation of a cast product P occurs, which passes through the entire casting machine 11 .
  • the crystallizer 15 a can comprise at least two wide plates facing each other and distanced, at least in the terminal segment, by a determinate value that substantially corresponds to the thickness H of the cast product P exiting from the crystallizer 15 a.
  • the plates of the crystallizer 15 a have a width which is determined in relation to the width of the strip N that is to be obtained.
  • the cast product P has a solidified external shell, or skin, which allows to contain the liquid metal even outside the crystallizer 15 a.
  • the casting machine 11 can be provided with thickness reduction means located downstream of the crystallizer and which can be selectively set, on each occasion, as the strip thicknesses vary, in order to exert a different action of reducing the thickness of the cast product P exiting from the crystallizer 15 a.
  • the thickness reduction means can comprise a pre-rolling device with rollers and/or a roller unit, for example of the drawing type as described below.
  • the casting machine 11 comprises a pre-rolling device 16 with rollers, also referred to as roller unit hereafter, located downstream of the mold 15 and configured to perform a reduction in the thickness of the cast product P exiting from the crystallizer 15 a while its core is still liquid or partially liquid.
  • a pre-rolling device 16 with rollers also referred to as roller unit hereafter, located downstream of the mold 15 and configured to perform a reduction in the thickness of the cast product P exiting from the crystallizer 15 a while its core is still liquid or partially liquid.
  • the roller unit 16 is provided with a plurality of rollers grouped into segments which are opposite each other and aligned along the casting axis.
  • the rollers are selectively moved toward/away from each other to exert a selective action of reducing the thickness of the cast product.
  • Regulating devices 17 of a known type for example hydraulic cylinders, are associated with the segments in order to move the rollers of the roller unit 16 toward/away from each other and perform the reduction of the thickness of the cast product P exiting from the crystallizer 15 a.
  • the overall reduction of the thickness which the cast product P exiting the crystallizer 15 a undergoes inside the roller unit 16 is a liquid core reduction, therefore it does not generate a lengthening of the material.
  • the slab thickness SB 1 which is obtained at the end of the liquid core pre-rolling determines the productivity of the casting machine 11 and therefore of the entire plant.
  • the compression carried out by the roller unit 16 allows to join the two half-skins in a joining point, also called “Kissing Point” (KP), in which there is the complete solidification of the cast product.
  • KP is also seen as the terminal vertex of the liquid cone which originates from the meniscus of the liquid metal in the crystallizer 15 a.
  • the position of the KP can be varied along the longitudinal extension of the roller unit 16 , intervening on the intensity of the liquid core thickness reduction obtained with the adjustment of the segments of the roller unit 16 and on the secondary cooling intensity.
  • the position of the KP is also a function of the casting speed.
  • the thickness of the cast product in correspondence with the KP is equal to the slab thickness SB 1 exiting from the roller unit 16 .
  • the slab thickness SB 1 is selectively set as a function of the final thicknesses of the strip N, in particular as a function of the product mix to be produced by the plant, as will be better explained below.
  • cooling device also called secondary cooling
  • Cooling devices can comprise nozzles to deliver nebulized water or water mixed with air (“air-mist”). The action of the cooling devices also has an influence on the position of the KP.
  • the casting machine 11 comprises a drawing unit 18 located downstream of the roller unit 16 and configured to draw the slab B toward the rolling station 19 .
  • the drawing unit 18 comprises a number of pairs of drawing rollers comprised between one and six.
  • the rollers of each pair are disposed on opposite sides of the slab B to be drawn.
  • the drawing unit 18 can also be configured to roll the slab B which passes through it.
  • the rollers of each pair can be associated with movement devices, for example hydraulic cylinders of the known type (not shown), to move the rollers toward/away from each other and also determine a predefined compression action on the completely solidified slab B, as described below.
  • movement devices for example hydraulic cylinders of the known type (not shown)
  • the drawing unit 18 can comprise a first drawing device 18 a located directly downstream of the roller unit 16 , that is, in the vertical segment of the casting machine 11 .
  • the drawing unit 18 can comprise a second drawing device 18 b located directly downstream of the curved segment of the casting machine 11 .
  • the presence of the first drawing device 18 a is provided only in the case of vertical casting.
  • the presence of the second drawing device 18 b is provided in the case of vertical and vertical-curved casting.
  • the first drawing device 18 a and/or the second drawing device 18 b can comprise a number of pairs of rollers comprised between 1 and 3.
  • the rollers of the drawing unit 18 are configured to perform a slight liquid core thickness reduction on the slab B of thickness SB 1 and therefore a real rolling, albeit of a light magnitude, which determines an elongation of the material.
  • the rolling, albeit light, of the drawing unit 18 generates a further reduction of the thickness of the slab B which takes on a further thickness SB 2 , smaller than SB 1 , thus allowing the rolling station 19 located downstream to reach thinner thicknesses. Since the drawing unit 18 is located at the end of the casting machine 11 , the thickness SB 2 of the slab B exiting from the drawing unit 18 corresponds to the thickness of the slab B exiting the casting machine 11 .
  • the drawing unit 18 together with the roller unit 16 and the crystallizer 15 a, forms an integral part of the casting machine 11 which, thanks to the rolling action performed by the rollers, can be defined as a “Rolling Caster”.
  • Rolling Caster we mean a casting machine 11 able to carry out both the casting of the product and also its rolling, partly liquid core and partly solid core.
  • the reduction in overall thickness which the cast product P exiting from the crystallizer 15 a inside the casting machine 11 undergoes is performed partly liquid core and partly solid core.
  • the distribution of thickness reduction in the casting machine 11 can be advantageously modulated between liquid core and solid core, according to specific production requirements.
  • the rolling station 19 comprises a roughing unit 12 configured to roll the slab B.
  • the roughing unit 12 can be provided with one or more roughing stands 20 .
  • the rolling station 19 comprises a finishing unit 13 configured to roll the slab B and bring it to its final size, that is, define the metal strip N.
  • the finishing unit 13 is located downstream of the roughing unit 12 .
  • the finishing unit 13 can also comprise one or more finishing stands 21 , each of which is configured to roll and define the strip thickness SN.
  • a cutting shear 26 is provided, configured to cut the roughed slab B and define a bar, also called transfer bar in the sector, which will be subjected to subsequent rolling to obtain the strip N.
  • the plant 10 can comprise at least one induction heating device, in this case one, two, or three induction heating devices 22 , 23 , and 34 and configured to heat the slab B.
  • the plant 10 comprises a first induction heating device 22 located downstream of the casting machine 11 , in this case upstream of the roughing unit 12 , and configured to restore the temperature of the slab before its introduction into the rolling station 19 .
  • the plant 10 comprises a second induction heating device 23 located upstream of the finishing unit 13 , for example between the roughing unit 12 and the finishing unit 13 , and configured to increase the temperature of the bar before its introduction into the finishing unit 13 .
  • the second induction heating device 23 is located directly downstream of the roughing unit 12 .
  • the plant 10 comprises a third induction heating device 34 interposed between two of the finishing stands 21 and configured to restore the temperature of the bar during the finishing process.
  • the production plant 10 can comprise at least one heating and/or maintenance unit, in this case two heating and/or maintenance units 32 and 33 , configured to heat or maintain the temperature of the bar segments.
  • the heating and/or maintenance unit 32 and 33 can comprise a heating and/or maintenance tunnel type furnace which also acts as an accumulation buffer for the bars in the event the rolling process is interrupted, due to accidents or a programmed roll change, thus avoiding losses of material and energy and, above all, avoiding an interruption of the casting.
  • the production plant 10 comprises a first heating and/or maintenance unit 32 located directly upstream of the rolling station 19 .
  • the production plant 10 comprises a second heating and/or maintenance unit 33 located between the roughing unit 12 and the finishing unit 13 .
  • the production plant 10 is provided with a shear 35 interposed between the casting machine 11 and the rolling station 19 and configured to cut the slab B produced by the casting machine 11 into segments.
  • the segments can be subsequently stored and kept at temperature inside the first heating and/or maintenance unit 32 .
  • the production plant 10 comprises an intermediate winding/unwinding device 29 interposed between the cutting shear 26 and the finishing unit 13 and configured to wind the bar cut by the cutting shear 26 and to supply the previously wound and cut bar to the finishing unit 13 .
  • the plant 10 can comprise both the second heating and/or maintenance unit 33 and the intermediate winding/unwinding device 29 located downstream with respect to the heating unit 32 .
  • the intermediate winding/unwinding device 29 can be for example of the type described in the international application WO-A-2011/080300 in the name of the Applicant.
  • the intermediate winding/unwinding device 29 comprises a first unit 30 and a second unit 31 which alternate in the function of winding the bar received from the roughing unit 12 , and in the function of unwinding the previously wound bar, in order to feed it to the finishing unit 13 .
  • This intermediate winding/unwinding device 29 also allows to define a temporary accumulation buffer to compensate for the different work speeds of the casting machine 11 and of the finishing unit 13 . In this way, the intermediate winding/unwinding device 29 allows to absorb the shutdown times of the rolling mill for small maintenance or for the programmed roll change or for small accidents/blockages, without needing to interrupt the casting process, and therefore without loss of production and without penalizing the steelworks upstream.
  • the intermediate winding/unwinding device 29 can comprise heating devices, not shown, for heating or maintaining at temperature the bar contained inside.
  • the plant 10 can comprise a cutting member 28 disposed between the roughing unit 12 and the finishing unit 13 and configured to cut the head end or the tail end of the bar supplied by the roughing unit 12 , in this case by the intermediate winding/unwinding device 29 , and to be fed to the finishing unit 13 .
  • a cooling unit 24 is provided between the rolling station 19 and the final winding unit 14 , configured to cool the strip N exiting from the rolling station 19 and allow it to be collected in the final winding unit 14 .
  • the plant 10 comprises a final winding unit 14 of the strip N.
  • the final winding unit 14 can comprise a winding member 25 suitable to wind the strip N into coils.
  • the plant 10 comprises a cutting device 27 located upstream of the final winding unit 14 and configured to cut the strip N to size, once a predetermined weight of the coil of strip N has been reached.
  • the cutting device 27 can be positioned between the cooling unit 24 and the final winding unit 14 .
  • this shows a variant embodiment of a production plant 10 which comprises, disposed in sequence, the casting machine 11 as defined above, the shear 35 , the first induction heating device 22 and/or the first heating and/or maintenance unit 32 , the finishing unit 13 , the cooling unit 24 and the final winding unit 14 .
  • this shows a further variant embodiment of the production plant 10 which, in addition to the components provided in the production plant 10 of FIG. 2 , provides that the rolling station 19 comprises the roughing unit 12 , the second induction heating device 23 , the second heating and/or maintenance unit 33 , and the cutting member 28 located upstream of the finishing unit 13 .
  • this shows a variant embodiment of a production plant 10 which comprises, disposed in sequence, the casting machine 11 as defined above, the roughing unit 12 , the cutting shear 26 , the second induction heating device 23 , the intermediate winding/unwinding device 29 , the cutting member 28 , the finishing unit 13 , the cooling unit 24 and the final winding unit 14 .
  • the production plant 10 comprises, disposed in sequence, the casting machine 11 as defined above, the rolling station 19 provided with the roughing unit 12 , the cutting shear 26 , the second induction heating device 23 , the second heating and/or maintenance unit 33 , the finishing unit 13 , the cooling unit 24 and the final winding unit 14 .
  • the production plants 10 described with reference to FIGS. 2-5 can be selectively set to work in coil to coil mode.
  • the production plant 10 comprises disposed in sequence, the casting machine 11 as defined above, the rolling station 19 provided with the shear 35 , the second induction heating device 23 , the second heating and/or maintenance unit 33 , the finishing unit 13 , the cooling unit 24 , the cutting device 27 and the final winding unit 14 .
  • the production plant 10 described with reference to FIG. 6 can be configured to work in coil to coil or semi-endless mode.
  • the production plant 10 comprises disposed in sequence, the casting machine 11 as defined above, the rolling station 19 provided with the roughing unit 12 , the cutting shear 26 , the second induction heating device 23 , the finishing unit 13 , the third induction heating device 34 interposed between the finishing stands 21 , the cooling unit 24 , the cutting device 27 and the final winding unit 14 .
  • the production plant 10 described with reference to FIG. 7 can be configured to work in endless mode.
  • the production plant 10 comprises disposed in sequence, the casting machine 11 as defined above, the rolling station 19 provided with the roughing unit 12 , the cutting shear 26 , the second induction heating device 23 , the intermediate winding/unwinding device 29 , the cutting member 28 , the finishing unit 13 , the third induction heating device 34 interposed between the finishing stands 21 , the cooling unit 24 , the cutting device 27 and the final winding unit 14 .
  • the production plant 10 described with reference to FIG. 8 can be configured to work in coil to coil or endless mode.
  • the production plant 10 comprises disposed in sequence, the casting machine 11 as defined above, the rolling station 19 provided with the shear 35 , the first induction heating device 22 , the first heating and/or maintenance unit 32 , the roughing unit 12 , the cutting shear 26 , the second induction heating device 23 , the finishing unit 13 , the third induction heating device 34 interposed between the finishing stands 21 , the cooling unit 24 , the cutting device 27 and the final winding unit 14 .
  • the production plant 10 described with reference to FIG. 9 can be configured to work in coil to coil, semi-endless, or endless mode.
  • the embodiments of plants 10 described with reference to FIGS. 2-9 define examples of families of production plant layouts that the end user can choose in an optimized manner as a function of productivity, product mix, and types of steel, also called “steel grades”, which are to be produced.
  • a method to produce metal strip N comprises at least the casting of a cast product P through the casting machine 11 to obtain a slab B, and the hot rolling of the slab B in the rolling station 19 to obtain metal strip N.
  • the casting machine 11 during the casting, exerts an action of reducing the thickness of the cast product P exiting from the crystallizer 15 a.
  • the casting machine 11 for each thickness size of the strip N that is produced, is selectively set to exert a different action of reducing the thickness of the cast product P exiting from the crystallizer 15 a.
  • the thickness of the slab B produced by the casting machine 11 will, on each occasion, be regulated as a function at least of the final thicknesses of the strip N to be obtained and possibly of the variety of products, or product mix, to be obtained.
  • This solution allows to reduce the compression action that has to be exerted in the rolling station 19 , to reduce the rolling powers required, to reduce the wear to which the rolling rolls are subjected and in some cases to also reduce, by at least one, the number of rolling stands with respect to known plants that have the same overall productivity.
  • the method comprises a first step of producing a first strip having a first strip thickness SN′ wherein the casting machine 11 exerts a first thickness reduction ratio TAU A′ of the cast product P exiting from the crystallizer 15 a, and a second step of producing a second strip having a second strip thickness SN′′, less than the first thickness, wherein the casting machine 11 exerts a second thickness reduction ratio TAU A′′ of the cast product P exiting from the crystallizer 15 a, and wherein the first thickness reduction ratio TAU A′ is different to the second thickness reduction ratio TAU A′′.
  • the first thickness reduction ratio TAU A′ is less than the second thickness reduction ratio TAU A′′.
  • the thickness reduction ratio TAU A is defined as the difference between the thickness H of the cast product P exiting from the crystallizer 15 a and the slab thickness SB 2 exiting from the casting machine 11 , correlated to the thickness H of the cast product P exiting from the crystallizer 15 a.
  • the Applicant has determined that the casting machine 11 is selectively set to exert an action of reducing the thickness of the cast product P, defined by the formula:
  • TAU A K ⁇ A ⁇ H ⁇ 1 ⁇ e a ⁇ SN
  • K is a variable parameter between 0.8 and 1.1
  • A is a coefficient equal to about 4689
  • H is the thickness of the cast product P exiting from the crystallizer 15 a, that is the thickness of the crystallizer 15 a;
  • a is a coefficient equal to ⁇ 0.37;
  • SN is the thickness of the strip N to be obtained at the end of rolling.
  • the TAU A which derives from the formula is a percentage value and, by way of example only, can be a value normally comprised between 2% and 75%.
  • FIG. 10 shows some examples of curves, determined in relation to the thickness H of the cast product P, which show the development of the TAU A as a function of the strip thickness SN.
  • This formula allows to optimize the setting of the casting machine 11 , as a function of the thickness of the crystallizer 15 a and of the strip thickness SN to be obtained for an efficient functioning of the entire production plant, as defined above.
  • the casting machine 11 is configured to exert:
  • the thickness reduction by means of the drawing unit 18 can be optional.
  • the thickness reduction ratio TAU A is therefore given by the combination of the reductions TAU 1 and TAU 2 .
  • the thickness reduction ratio in the roller unit TAU 1 is defined by the difference between the thickness H of the cast product P exiting from the crystallizer 15 a and the slab thickness SB 1 exiting from the roller unit 16 , correlated to the thickness H of the cast product P exiting from the crystallizer 15 a.
  • the thickness reduction ratio in the drawing unit TAU 2 is defined as the difference between the slab thickness SB 1 exiting from the roller unit 16 and the slab thickness SB 2 exiting from the drawing unit 18 , correlated to the slab thickness SB 1 exiting from roller unit 16 .
  • the Applicant has determined that the drawing unit 18 is selectively set to exert an action of reducing the thickness SB 1 of the solid core cast product P, defined by the formula:
  • TAU 2 Q ⁇ ( ⁇ B ⁇ H b ⁇ ln SN+C ⁇ H c )
  • Q is a variable parameter between 0.8 and 1.1
  • B is a first coefficient equal to 10928
  • H is the thickness of the cast product P exiting from the crystallizer 15 a as defined above;
  • b is a second coefficient equal to ⁇ 1.659;
  • SN is the thickness of the strip
  • C is a third coefficient equal to 10648
  • c is a fourth coefficient equal to ⁇ 1.596.
  • the solid core reduction of the thickness of the cast product P is applied for strip thicknesses SN comprised between 0.6 mm and 3.5 mm.
  • the action of liquid core reduction is relatively high in order to reduce, right from the start, the starting slab to the maximum, and therefore it is advantageous to also couple, with the action of liquid core reduction, a further action of solid core reduction of the thickness exerted with the drawing unit 18 .
  • FIG. 11 shows some examples of curves, determined in relation to the thickness H of the cast product P exiting from the crystallizer, which show the development of the TAU 2 as a function of the strip thickness SN.
  • TAU 3 The reduction ratio in the roughing unit 12 is called TAU 3 and is defined as the difference between the thickness SB 2 of the slab B upstream of the roughing unit 12 and the thickness of the slab B downstream of the roughing unit 12 , correlated to the thickness SB 2 of the slab B upstream of the roughing unit 12 .
  • TAU 4 The reduction ratio in the finishing unit 21 is called TAU 4 and is defined as the difference between the thickness of the slab B upstream of the finishing unit 21 and the strip thickness SN obtained, correlated to the thickness of the slab B upstream of the finishing unit 21 .
  • the overall reduction ratio of the rolling station 19 is defined as TAUB and is defined as the difference between the slab thickness SB 2 exiting from the casting machine 11 and the thickness of the strip N obtained, correlated to the slab thickness SB 2 supplied by the casting machine 11 .
  • the overall reduction ratio TAUB of the rolling station 19 can also be defined as the combination of the reduction ratios of the roughing unit 12 and of the finishing unit 13 , TAU 3 and TAU 4 .
  • the method to produce metal strip comprises the supply, by a client, of design data comprising at least:
  • the set of parameters above defines the so-called “product mix” of the plant, that is, the variety of products that the production plant 10 will have to produce and according to which it is sized in order to achieve the purposes of the present invention.
  • Supplying the range of thicknesses RS provides to determine a minimum thickness SMIN and a maximum thickness SMAX of strip obtainable.
  • the rolling method provides to determine the optimal type of rolling mode of the slab B in relation to the product mix requested by the client.
  • the rolling mode of the slab B is chosen from endless, semi-endless and coil to coil rolling modes.
  • FIG. 12 shows a graph showing the criteria for choosing one of the rolling modes as above, at least in relation to the strip thicknesses SN and to castable steel grades.
  • the rolling mode to be implemented on each occasion will be defined by optimizing the operating conditions of the plant, on the basis of economic assessments (energy consumption and yield of the process) and of the quality required for the final product (size tolerances and mechanical characteristics of the strip).
  • a coil to coil and semi-endless rolling mode is generally chosen, and therefore one of the plant layouts shown in FIGS. 6 and 9 can be chosen. Both the coil to coil and semi-endless modes allow to cast special steels at low speed, since the casting process is not constrained by the rolling process.
  • the semi-endless mode is preferred for thin and ultra-thin strip N thicknesses, for example comprised between 0.8 mm and 1.4 mm.
  • the coil to coil mode is preferred instead for strip thicknesses greater than 1.4 mm.
  • FIG. 13 graphically shows a further criterion for choosing the rolling modes in relation to the strip thickness and the capacity of the plant layout chosen to adopt one and/or the other of the rolling modes as above.
  • the constructive layouts of FIGS. 2-5 are chosen, it is provided to make the plants work in coil to coil mode for strip thicknesses comprised between about 1.2 mm and about 12 mm, while if the constructive layout of FIG. 9 is chosen, it is provided to make the plant work in endless mode for strip thicknesses comprised between about 0.6 mm and about 1 mm, in semi-endless mode for strip thicknesses comprised between about 1 mm and about 2 mm and in coil-to-mode for strip thicknesses comprised between about 2 mm and about 12 mm.
  • the production method provides to set a casting speed VC which is selected from a value comprised between 4.5 m/min and 6 m/min.
  • a lower casting speed is advantageously set, for example comprised between 4.5 and 5 m/min.
  • a higher casting speed is set, for example comprised between 5 m/min and 6 m/min.
  • the choice of casting speed VC can also be defined in relation to the rolling modes selected, that is, relatively low casting speeds for coil to coil and semi-endless modes, and higher casting speeds for endless modes.
  • the production method then provides to determine a nominal slab thickness SBN value which, in relation to the casting speed VC and to the average strip width LN, allows to reach the productivity PR.
  • the nominal slab thickness SBN can also be interpreted as the constant thickness of an equivalent slab which, for the same overall production for that given product mix, corresponds to the average of the (variable) slab thicknesses after the liquid core reduction weighted (the average) on the respective hourly productions.
  • the nominal slab thickness SBN is determined by the formula:
  • PS is the specific weight of steel which usually can be around 7.8 kg/dm 3 .
  • FIG. 14 refers to a width of the slab of about 1300 mm
  • FIG. 15 refers to a width of the slab of about 1400 mm.
  • the method comprises determining the thickness H of the cast product P exiting from the crystallizer 15 a, that is, determining the distance between the plates of the crystallizer 15 a in correspondence with the exit section of the latter.
  • This thickness H of cast product P is the one adopted for the entire product mix defined by the client.
  • the thickness H of the cast product P exiting from the crystallizer 15 a is a number comprised between 10 mm and 15 mm more than the nominal slab thickness SBN.
  • the method then provides to determine a ratio of thicknesses RSP applied by the rolling station 19 and which is calculated as the ratio between the value of the slab thickness SB 2 entering the rolling station 19 , when the strip N of minimum thickness SMIN is processed, and the minimum thickness SMIN of the strip N obtainable.
  • the value of the slab thickness SB 2 entering the rolling station 19 when the strip N of minimum thickness SMIN is processed is calculated as the thickness H of the cast product P exiting from the crystallizer 15 a minus the maximum thickness reduction imparted by the casting machine. According to a possible solution, this maximum thickness reduction induced by the casting machine 11 is at least equal to 31 mm, or more.
  • the method provides to determine the number of rolling stands of the rolling station 19 , in relation to the ratio of thicknesses.
  • the number of rolling stands of the rolling station 19 is intended as the sum of the number of finishing stands 21 and the number of roughing stands 20 .
  • the method provides to set a mode to distribute the liquid core reduction and the solid core reduction in the casting machine 11 , performed with the roller unit 16 and with the drawing unit 18 , on the slab B exiting from the crystallizer 15 a, in relation to the final thickness of the strip N.
  • This mode to distribute the reduction in the thickness of the cast product P can be determined by means of the TAU A and TAU 2 formulae defined above.
  • the casting machine 11 can be set to perform a reduction in the thickness of the cast product P equal to 5 mm for a strip thickness equal to the maximum thickness SMAX, and a thickness reduction comprised between 25 mm and 31 mm for a strip thickness equal to the minimum thickness SMIN.
  • the roller unit 16 can perform a maximum liquid core reduction RCLMAX of about 25 mm. According to a possible solution, the roller unit 16 can perform a minimum liquid core reduction RCLMIN of about 5 mm. This reduction allows to confer greater quality to the cast metal product P.
  • the drawing unit 18 can perform a maximum solid core reduction of at least 7 mm, while the minimum reduction is zero.
  • each individual pair of rollers of the drawing unit 18 can achieve, when necessary, a compression comprised between 0.5 mm and 1.5 mm.
  • the number of the roughing stands 20 is determined so as to supply at entry to the winding/unwinding device 29 a bar with a thickness comprised between 8 mm and 25 mm. Bar thicknesses of less than 8 mm would entail problems with transport and introducing the bar into the winding/unwinding device, while bar thicknesses greater than 25 mm would lead to operating and/or sizing difficulties with possible generation of surface defects on the bar itself.
  • the number of the roughing stands 20 is determined so as to supply at entry to the heating unit a bar with a thickness greater than or equal to 30 mm. Sizes smaller than these thickness values would require the use of an extremely long heating unit, difficult to manage and uneconomical.
  • the number of finishing stands 21 is at least two.
  • a first case is shown in which a production PR of approximately 1.1 Mton/year, a range of thicknesses RS comprised between 1.2 mm and 8 mm and an average width LN of the strip of about 1300 mm are required.
  • a second case is shown in which a production PR of approximately 1.4 Mton/year, a range of thicknesses RS comprised between 0.8 mm and 3 mm and an average width LN of the strip of about 1400 mm are required.
  • the product mix and annual productivity values are parameters requested by the client and set according to how the client needs to use the plant.
  • the slab thickness SB 2 exiting from the casting machine 11 is not a constant value as the thickness of the strip varies, but it is a value that decreases as the thickness in the strip decreases.
  • the slab thickness SBN exiting from the casting machine is always the same as the thickness of the strip varies, as shown in the second column from the left. This consideration is also shown graphically in FIGS. 18 and 21 .
  • the tables also show the thickness reductions performed with the drawing unit 18 (fifth column), with the roughing unit 12 (seventh column), and with the finishing unit 13 (ninth column), and how these actions are distributed according to the final strip thicknesses to be obtained.
  • FIGS. 19 and 22 graphically show the distribution of the hourly productivities of the plant as a function of the strip thickness to be obtained, in the case of a known conventional casting, and of a casting with variable thickness reduction in accordance with the present invention.
  • the slab thickness SB 2 entering the rolling station 19 when the minimum thickness is processed is 24 mm.
  • a number of stands equal to 6 corresponds to this ratio of thicknesses. From this example it is possible to observe how, with the same annual productivity of the plant, it is possible, with respect to the conventional production mode, to reduce the number of rolling stands by one unit.
  • the slab thickness SB 2 entering the rolling station 19 when the minimum thickness is processed is 34 mm.
  • a number of stands equal to 7 corresponds to this ratio of thicknesses. From this example it is possible to observe how, with the same annual productivity of the plant, it is possible, compared with the conventional production mode, to reduce the number of rolling stands by one.

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US17/283,820 2018-10-08 2019-09-25 Method to produce a metal strip, and production plant implementing said method Abandoned US20220001442A1 (en)

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IT102018000009259A IT201800009259A1 (it) 2018-10-08 2018-10-08 Metodo di produzione di un nastro metallico, ed impianto di produzione che implementa detto metodo
IT102018000009259 2018-10-08
PCT/IT2019/050210 WO2020075205A1 (en) 2018-10-08 2019-09-25 Method to produce a metal strip, and production plant implementing said method

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US20110272116A1 (en) * 2010-05-10 2011-11-10 Danieli & C. Officine Meccaniche Spa Method and plant for the production of flat rolled products

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KR100298471B1 (ko) * 1998-07-20 2001-09-22 최중갑 복합염료 조성물을 이용한 폴리아크릴아미드 겔상의 단백질의 검출방법 및 복합염료 조성물
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AUPQ779900A0 (en) * 2000-05-26 2000-06-22 Bhp Steel (Jla) Pty Limited Hot rolling thin strip
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US20110272116A1 (en) * 2010-05-10 2011-11-10 Danieli & C. Officine Meccaniche Spa Method and plant for the production of flat rolled products

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US20230330740A1 (en) 2023-10-19
EP3863781A1 (en) 2021-08-18
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CN113272084A (zh) 2021-08-17
CN116511247A (zh) 2023-08-01
IT201800009259A1 (it) 2020-04-08
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KR20210102877A (ko) 2021-08-20
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