Method for manufacturing flat rolled product and plant

Abstract

The present invention relates to a method and a plant for manufacturing flat rolled products to obtain a strip (S) having a multi-crown transverse profile and subsequently divided longitudinally into a plurality of strips of smaller width, said method comprising a rolling step carried out in a rolling mill comprising roughing stands (14a, 14b, 14c) and a plurality of finishing stands (16a, 16b, 16c, 16d, 16e) each equipped with work rolls (24a, 24b) to obtain a strip (S) having a predetermined width.

Description

Technical Field

[0001] The present invention relates to a method for manufacturing flat-rolled products such as strips and a corresponding manufacturing plant. In particular, the present invention relates to a method and a plant for obtaining a strip having an optimal geometric feature with respect to the profile and flatness of the strip, even when the strip is later divided into longitudinal portions, and having a final transverse profile with multiple crowns.

[0002] The present invention can be applied to both hot and cold rolling processes for manufacturing strips of any type of ferrous or non-ferrous material.

Background Art

[0003] Rolling plants are generally known to comprise a multi-stand rolling mill divided into a first roughing stand and a second finishing stand. There may be a temperature recovery system between the roughing stand and the finishing stand.

[0004] The rolling mill may or may not be arranged in line with a continuous casting machine for manufacturing thin slabs, a so-called "thin slab caster".

[0005] These plants can be designed and configured for a substantially continuous rolling process, a so-called "endless" process, and the cast product engages directly with the continuous casting machine and is rolled in a rolling mill located downstream of the continuous casting machine.

[0006] This process may be of the semi-endless type, which cuts the cast slab to form a plurality of coils, or the coil-to-coil type, which manufactures one coil at a time for each cut of the slab.

[0007] It is known that the width of the strip obtained in this type of plant can usually vary within the range of 600 mm to 2500 mm depending on the use of the rolled material.

[0008] However, in order to meet market requirements, there is always a need to produce coils with a width narrower than the barrel of the rolling roll, which results in a decrease in the productivity of the plant.

[0009] For example, in a rolling plant that can produce strips up to a maximum width of 2000 mm and can cast slabs with a width of 800 or 1000 mm, if it is desired to obtain a strip width of 800 or 1000 mm, the productivity of the plant is substantially halved, which is a drawback to be avoided.

[0010] Therefore, according to the examples of, for example, Japanese Patent Laid-Open No. 58-68405 and Japanese Patent Laid-Open No. 57-175003, it is known to process a strip of a standard width, for example 1600 mm, and then cut it longitudinally in the inter-stand space along the rolling mill to obtain, for example, two half-strips with a width of 800 mm that are subsequently wound around corresponding coils.

[0011] This solution is effective in maintaining productivity, but it has several drawbacks. The first drawback relates to the crowning or crown of the two half-strips. Hereinafter, as will be explained later, the terms "crowning" or "crown" will be used interchangeably with the same meaning.

[0012] The dimensional quality of the product emerging from the hot rolling process focuses on the control of the thickness distribution along the width of the rolled strip. The shape of the thickness in the width direction of the rolled product is called the profile. The main parameter analyzed to evaluate the profile of the rolled product is the crown. The crown represents the difference between the thickness at the center of the rolled product and the average thickness at the edges.

[0013] Generally, it is preferable to obtain a rolled product that is thicker at the center than at the edges. Therefore, as shown in Figure 2a, when viewed in cross-section, it is assumed to have a convex lens shape that is symmetric with respect to the center line.

[0014] According to possible changes, it is very important to generate an accurate profile during hot rolling because defects may occur in flatness or it may become difficult to execute subsequent steps of the production cycle, and the profile cannot be changed in downstream processes.

[0015] Conversely, the flatness of the rolled product is defined as the ability to follow the theoretical plane, and the non-flatness is the difference between the theoretical plane and the rolled product.

[0016] During rolling, a predetermined crown is given across the entire width of the strip by the rolling rolls. However, if the strip thus adapted is later split in half, as shown in Fig. 2b, each half-strip will not have a symmetrical crown. In fact, the profile of the half-strip is trapezoidal (wedge-shaped) with different thicknesses at the edges on both sides.

[0017] However, this asymmetric profile is not very suitable for subsequent processing of the half-strips, so downstream processing becomes unstable and problems such as drift and difficulty in winding may occur. Therefore, in Japanese Patent Application Laid-Open No. 58-68405, in order to obtain two finished half-strips each with a normal profile, it is proposed to perform an additional rolling step to restore the symmetry of the profile by tapering the cut edges in an additional stand.

[0018] Furthermore, in Japanese Patent Application Laid-Open No. 58-68405, there are problems with performing longitudinal cutting in the inter-stand space. Especially when dealing with a thin thickness, since high speeds are involved, there are further problems in controlling the two half-strips.

[0019] In the solution described in Japanese Patent Application Laid-Open No. 58-68405, within a single rolling stand, the profile of the half-strip is almost restored symmetrically only by the Hertz pressure generated at the edge, so in practice, controlling the crowns of the two half-strips is not allowed.

[0020] British Patent Application Publication No. 2114034 describes a process of cold finishing and / or stretch bending a hot-rolled and pickled strip using a work roll with a double central raised crown to obtain a strip with a narrow central part and central crowns on both corresponding side parts. However, in the strip obtained with a work roll of this shape, the width of the central narrowing zone is very limited, and extremely precise positioning in the shearing means is required to obtain two substantially symmetrical half-strips.

[0021] Japanese Patent Application Laid-Open No. 51-094453 describes a rolling method for forming a strip having a central narrowing part and two round zones on both sides of the narrowing part. The work roll used has two concave parts and a substantially pointed central protruding zone so as to be able to define a substantially accurate narrowing part. Also in this case, precise positioning in the shearing means is required to accurately divide the strip into two parts of the same shape.

[0022] Therefore, it can be understood that in the prior art, there is no solution regarding precise control of the crown when the rolled strip has to be divided into two half-strips longitudinally before, during, or after winding.

[0023] The above-mentioned conventional solutions not only do not guarantee that two half-strips with the desired crown characteristics and symmetry can be obtained, but also cannot even dynamically change or adapt the crown profile as required.

[0024] In this regard, it should be noted that in recent years, the market requirements for flat products, especially hot-rolled strips, have become increasingly strict in both metallurgical quality and dimensional quality.

[0025] Furthermore, plant manufacturers and steel manufacturers are always pursuing to reduce conversion costs while maintaining or even improving the mechanical properties and subsequent workability of hot-rolled products.

[0026] The following points are correlated with the importance of the dimensional quality of hot-rolled strips: In the production of some products, gradually replacing cold-rolled strips with hot-rolled strips. Simplification of the manufacturing process for converting hot-rolled strips into finished products. Improve the geometric characteristics in terms of thickness, profile, and flatness. In fact, when the geometric conditions are improved, not only does the quality of the final product improve, but also the reliability and automation of downstream processes are enhanced.

[0027] The above points lead to requirements for "extreme" geometric characteristics such as the following: · Depending on the product type, the target value of the strip crown can vary within the range of 70 μm to 10 μm. For some products (especially thin and extra-thin thicknesses), the crown must be within 1.0 - 1.2% of the nominal thickness of the strip. In other words, for a 1.0 mm thick strip, a 10 μm crown is required. · Flatness of strips less than 12 and 30 I-Units, depending on the strip thickness and width. · Reduction of the thickness reduction at the strip edge (edge drop).

[0028] Therefore, in the production process of supplying hot-rolled strips with thin and extra-thin thicknesses, in both the endless or semi-endless mode and the coil-to-coil mode, the rolling stands need to have sufficient ability to control the profile and flatness of the strips throughout the production mix.

[0029] Therefore, by using a shaped roll, that is, a roll with a contour or profile described by a mathematical function, and performing an axial shift of the roll in the opposite direction, the shape of the roll gap can be changed.

[0030] Regarding the crown, it must also be considered that the heating of the rolling rolls is one of the basic problems faced in both hot rolling and cold rolling. Due to the direct contact of the strip being rolled with the work rolls, heat flow, heat transfer to the rolls themselves, and heating of the rolls are determined. These are accompanied by variations in both the dimensions (diameter) and profile of the rolls themselves.

[0031] To limit the above heating to a value compatible with the properties of the material constituting the rolls and to keep the progressive deterioration of the roll surface within the allowable values, it is essential to use a cooling system.

[0032] A solution commonly adopted in hot rolling is of the inclined path ( to cool the work rolls from the outside by a series of nozzles attached to a (ramp). In a conventional four - stand rolling mill for hot strip rolling, usually a total of four cooling devices, two in the exit zone and two in the entrance zone, are used. Each cooling device consists of one or more cold Is it a decline inclined path? and so on. To prevent the heat transferred from the material being rolled to the rolls from penetrating from the surface layer into the roll interior and making the heat accumulated inside the roll difficult to remove, it is preferable to enhance the heat exchange between the roll and the cooling water from the roll gap in the exit zone. This increases the flow rate and, in some cases, also improves the heat exchange efficiency.

[0033] Thermal crown is generated by the heat transferred to the rolls. Inside the roll, heat flows from the central zone to the cooler sides that are not affected by the contact of the strip, resulting in an axial flow. The result is differential expansion. Generally, this differential expansion generates a parabolic roll profile in the central zone, while at the edge of the strip, the expansion decreases rapidly and remains at a lower value than in the central zone.

[0034] Variations in the "thermal profile" of the roll clearly affect the rolling process, particularly the control of thickness, profile, and flatness. Therefore, although the temperature of the roll needs to reach an average value within the range of 50 to 80 °C (depending on the material constituting the roll jacket) in order to optimize the duration and reduce surface wear caused by thermal fatigue and friction between the strip and the roll, the role of the roll cooling system is to minimize disturbances due to variations in the thermal profile.

[0035] These issues are already significant in the case of hot rolling by conventional processes, and are even more serious in an endless production process where rolling on a strip finishing mill can continue for up to 10 hours without interruption, compared to 2 to 3 minutes in a conventional coil-to-coil process.

[0036] The thermal crown of the work roll depends on the temperature distribution along the axis of the roll. This distribution changes continuously during rolling, causing both an increase and a decrease in the thermal crown in response to changes in the roll's machining profile. This phenomenon causes disturbances in the control of the profile and flatness of the strip being rolled: · When the roll is cold, for example, after roll change or after a long production stop, the thermal crown gradually increases and 5 to 10 coils are required to reach a stable value. · When stable conditions are reached during rolling, the thermal crown decreases during the waiting time between one coil and the next, and returns to the average value of the thermal crown in a relatively short time from the start of rolling of the new coil.

[0037] Taking all of the above into account, one object of the present invention is to provide a method and a corresponding plant for manufacturing finished thin strips, and even ultra-thin strips, which are later longitudinally split, in such a way as to obtain two, three, four, and more strips having optimal quality with respect to the profile, flatness, and thickness of each cross-section.

[0038] The object of the present invention is to maintain the productivity of the rolling mill unchanged whether a strip having a width equal to the maximum width is produced or a strip having a width smaller than the maximum width is produced.

[0039] The applicant has invented, tested, and embodied the present invention to overcome the drawbacks of the prior art and obtain these and other objects and advantages.

Summary of the Invention

[0040] The present invention is described and characterized in the independent claims. The dependent claims explain variations of the main inventive idea or define embodiments.

[0041] According to one embodiment of the present invention, the slab is cast with a width defined by the design parameters of the plant itself, such as the width of the mold, the dimensions of the line, and the required productivity, and is sent to a hot strip rolling mill to obtain the finally required thickness.

[0042] According to another embodiment of the present invention, the hot-rolled strip is further rolled in a cold rolling mill to obtain a thinner thickness.

[0043] In both of these embodiments, the work rolls of the stands of the rolling mill are configured to impart to the strip a transverse profile having a number of positive crowns that correlates with the number of portions in the longitudinal direction that need to be split later.

[0044] In the following description, the following terms are used: · A "positive" crown indicates a symmetric convex lens-shaped profile that is thicker in the center, as in the example shown in Figure 2a. · A "negative" crown indicates a symmetric profile with both concave surfaces, which is mating or complementary to the convex lens-shaped profile described above and is thinner in the center than at the edge portions.

[0045] According to the present invention, the object is to form by using a work roll having a profile with two or more positive crowns on a rolling strip and having a shape with two or more corresponding negative crowns.

[0046] According to another aspect of the present invention, the work roll comprises a profile in which negative crowns and connecting segments formed in an arch shape having a positive curvature are alternately arranged.

[0047] Correspondingly, the resulting rolling strip also respectively comprises alternately arranged positive crowns and intermediate portions formed in an arcuate shape having a negative curvature.

[0048] In the following description, the expression "positive curvature" means a convex profile with a thick center and a thin side portion, and the expression "negative curvature" means a concave profile with a thinner center than the side portions.

[0049] Therefore, the present invention provides a method of using a work roll having a single negative crown when the finished strip is used with the width of the initial product fed to the rolling mill. On the other hand, when it is necessary to divide the rolled strip into two, three, four, or generally a certain number of longitudinal portions of the strip in the longitudinal direction later, a work roll having double, triple, quadruple, or any number of multiple negative crowns is used.

[0050] The division in the longitudinal direction of the strip can be performed along the entire length of the strip from head to tail at a position between the exit from the last stand and each corresponding coiling unit where individual coils of each portion of the strip are formed. Alternatively, it can also occur along the entire length except for the head and tail portions of the strip immediately before winding into a single coil. Further, it can also be performed, for example, at the destination of the coil itself after removing the coil from the coiling unit.

[0051] According to the present invention, at least the last stand of the rolling mill, for example, the last stand of the finishing rolling mill, or the last two or three stands of the finishing rolling mill, is provided with work rolls having a profile that correlates with and depends on each part of the strip whose contact surface with the strip will later be obtained by a longitudinal cut.

[0052] According to some embodiments, the work roll has a number of multiple negative crown profiles that correlates with the number of parts into which the produced rolled strip will later be longitudinally divided.

[0053] In other words, the profile of the work roll has a double negative crown when the strip is longitudinally divided into two half-strips, and a triple negative crown when the strip is longitudinally divided into three parts, and so on for the following cases.

[0054] Consistently, in the case of a double negative crown, there is only one connecting segment with a positive curvature, in the case of a triple negative crown, there are two connecting segments with a positive curvature, and so on for the following cases.

[0055] According to some embodiments, in the profile of the work roll, the negative crown and the connecting segment with a positive curvature have substantially equal widths with respect to each other. In other words, since the width of the negative crown is substantially equal to the width of the connecting segment, on the strip, an intermediate portion with a negative curvature having a width and depth that correlate with the crown width and height of the corresponding positive crown portion is defined between the corresponding positive crown portions.

[0056] Thereby, a larger operating space for positioning the longitudinal cutting means can be ensured, and furthermore, the minimum deviation from the longitudinal center line can be ignored.

[0057] It is known from the literature that the profile of the work roll can be defined by a curve consisting of an antisymmetric trigonometric function and a cubic polynomial function.

[0058] The equation of the profile curve is shown as follows.

Number

[0059] The value of the crown can also be changed by changing the Value δ s to axial movement (shift) of the work roll. Also, by changing the parameters α and C in the above formula, the crown function of the gap between the rolls determines a group of different curves.

[0060] In other words, the axial movement operation of the work roll is performed to correct the position of the negative crown of the work roll with respect to the position of the strip, thereby dynamically modifying the range of the crown on the strip, that is, it is possible to emphasize or flatten the peaks and valleys of the profile of the strip.

[0061] Therefore, according to the present invention, by assigning appropriate values to the parameters α and C in the above formula, when the manufactured strip is divided into two half-strips, a "double crown" profile can be obtained. Further, when the strip is divided into several parts in the longitudinal direction, a general multi-crown profile such as a triple or quadruple crown can be obtained.

[0062] As described above, especially when the thickness of the strip is thin, the operation of imparting a double (or triple, or quadruple,...) crown to the strip is performed at the last stand of the finishing mill, for example, the last or the last two or three stands.

[0063] It should be noted that in a finishing mill having five, six, or seven finishing stands, the last three stands usually have work rolls of the same diameter and the same profile. Therefore, according to the present invention, it is convenient to form a multi-crown at the last three stands of the finishing mill.

[0064] Therefore, the present invention provides a method for manufacturing a finished strip having a multi-crown, which is then longitudinally divided into a plurality of separate strip parts each having its own crown as if each strip part had been rolled individually.

[0065] Thus, each part of the strip has an appropriate crown that provides desirable geometric and dimensional characteristics in terms of thickness, profile, and flatness.

[0066] According to the present invention, in order to more accurately control the multi-crown, in addition to the mechanical crown of the work roll, an intervention is also performed on the thermal crown of these work rolls using a cooling method described later.

[0067] According to the present invention, in the case of double crown rolling, it is advantageous to have the minimum cooling efficiency around the central zone of the work roll. As a result, the thermal crown in this zone where the strip is to be split increases. On the other hand, in the central zone of half of the strip, the thermal crown has the maximum cooling efficiency corresponding to the central parts of the two halves of the strip so as to decrease. In other words, the thermal crown of the work roll is controlled to follow the tendency of the mechanical crown and improve. In the case of other numbers of crowns such as triple and quadruple, the cooling of the work roll is adjusted in a similar manner, with less cooling in the parts where the strip is to be split and more cooling in the central zones of each multi-strip.

[0068] Basically, the control of the cooling system is realized through an online model that processes a series of information regarding the state of the process (such as strip temperature, rolling force, thickness reduction, rolling speed, etc.) at time intervals to determine the thermal profile.

[0069] According to the present invention, since the cooling efficiency in the width direction can be changed, it is possible to define an optimal thermal crown so as to maximize the control capacity for the profile / flatness of each part of the strip that is to be split later in a double or generally multi-crown rolling campaign.

[0070] Here, with reference to several specific embodiments given as non-limiting examples with reference to the accompanying drawings below, the features of the present invention will be described in detail.

Brief Description of the Drawings

[0071]

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Figure 18

Embodiments for Carrying out the Invention

[0072] Referring to FIG. 1, an example is shown in a co - rolling plant 10 for manufacturing a strip S, where a machine 11 for casting a thin slab feeds into a hot strip rolling mill 12.

[0073] It should be noted that the examples shown here should in no way be considered as limiting the applicability of the present invention. The reason is that the concepts shown here are applicable to many other types of plants, for example, in any of all cases where a casting machine separated from a rolling mill with a different number of stands, where slabs are manufactured at another location, and where it is necessary to longitudinally divide a metal strip having a predetermined nominal width at the end of rolling into several parts to obtain strip parts with a smaller width.

[0074] The illustrated embodiment shows a hot rolling mill installed in the same production line as the casting machine, but the present invention is also applicable to a cold rolling mill that rolls a strip obtained in a preliminary process of hot working.

[0075] In the case of the hot rolling process, as described above, the semi-finished product at the start is represented by a slab that can be cast in-line in the same plant (as disclosed in the embodiment of FIG. 1), or is produced offline or in another plant.

[0076] In the case of the cold rolling process, the semi-finished product at the start is represented by a coil of a rolled strip pre-manufactured by a hot rolling mill.

[0077] According to the present invention, in cold rolling, in order to be able to form multiple crowns on a strip having a single crown and pre-hot rolled, the thickness of the strip is preferably at least 2.5 mm. If it is less than this value, the strip to be cold rolled does not have a single crown profile, and it is preferable that the number of final crowns obtained at the end of cold rolling is already possessed. In this case, in the cold process, the rolling rolls are shaped to follow the multiple crown profile already imparted to the strip in the previous hot rolling process.

[0078] Furthermore, the present invention is applicable to the manufacture of both ferrous strip products such as steel and non-ferrous strip products such as aluminum.

[0079] In the specific example shown in FIG. 1, the rolling mill 12 includes a roughing unit 13 (or also referred to as a roughing mill) including, in this case, three stands 14a, 14b, and 14c, and a finishing unit 15 (or also referred to as a finishing rolling mill) including, in this case, five stands 16a, 16b, 16c, 16d, and 16e.

[0080] Between the roughing unit 13 and the finishing unit 15, there is a temperature recovery system, for example, an induction furnace 20, which returns the slab at the outlet from the roughing unit 13 to the correct rolling temperature.

[0081] Between the casting machine 11 and the roughing unit 13, there is a tunnel furnace 17 having a length sufficient to accommodate at least 2 to 5 slabs. This tunnel furnace 17 allows, in a known manner, to function as a buffer and to operate in a semi-endless mode in the event that the rolling mill is interrupted, even temporarily, due to an accident or a work roll change plan.

[0082] Upstream of the tunnel furnace 17, there is a first pendulum shearing machine 18 that cuts the slab to a predetermined size when the plant 10 operates in a coil-to-coil mode or a semi-endless mode.

[0083] Downstream of the finishing rolling mill 15, there are a cooling unit 22 and a second flying shear 19 that intervenes in the case of endless or semi-endless rolling to separate the strip gripped by one of the two downcoilers 21 or reels.

[0084] According to one aspect of the present invention, the obtained strip is subsequently longitudinally split (slitting) so that a divisor of the width of the cast slab, or in any case a portion of the strip having a width smaller than the width of the cast slab, is obtained.

[0085] In this way, for slabs and strips having a width close to the maximum width provided by the plant itself, strips of a narrower width can be obtained from a single rolled strip without restricting the overall productivity of the plant such that it can always be operated, under any circumstances.

[0086] The splitting with respect to the width of the finished rolled strip can be carried out directly inline at the outlet of the rolling mill or, in a step following the removal of the coil, for example, in another target plant where the strip is used.

[0087] In the first case, downstream of the finishing rolling mill 15, for example, for splitting into two parts, the following items can be considered:

[0088] Two different half strips S1, S2 are wound around the corresponding reels 21 respectively and split along the entire length from the head part to the tail part of the strip S. In this way, two separate coils are obtained.

[0089] To facilitate the insertion of the head part into a single reel and the winding of the last tail end turn, the strip S is split along the entire length of the strip S excluding the head part and the tail part. In this way, a single coil is split into two parts over almost the entire length.

[0090] For this purpose, a dedicated cutting device can be provided for longitudinally separating the strip S into two or more strip parts S1, S2 having the same or different widths. Advantageously, these devices can be inserted into or removed from the production line according to demand.

[0091] According to the present invention, a method is provided for creating the profiles of at least some of the work rolls 24a, 24b of the last finishing stands 16a - 16e so as to determine the exact crown in each part into which the strip is split, according to the number of width parts into which the strip S is split.

[0092] As an example, for instance, FIGS. 3a and 3b respectively show the cross-section of strip S on the downstream side of rolling mill 12 and the cross-sections of two half-strips S1, S2 obtained by longitudinally cutting strip S along the center line. In this example, strip S has a "double positive crown" PC that is substantially symmetric with respect to the symmetry plane passing through center line M, while the two half-strips S1, S2 each have their own single positive crown PC.

[0093] As can be seen in the figures, strip S has an intermediate portion 40 that connects between the two positive crown PC zones. Intermediate portion 40 has a negative curvature and has a width and depth that respectively match the width and height of the positive crown PC zones.

[0094] Therefore, when the strip is split into two half-strips in the width direction, the profiles of work rolls 24a, 24b are shown as double negative crowns NC, one for each half-strip obtained or that can be obtained downstream. The same applies when the strip is split into three, four, or more parts.

[0095] In particular, each of work rolls 24a, 24b has a multi-negative crown, and the number of negative crowns NC corresponds to the number of parts into which strip S is planned to be split.

[0096] Advantageously, negative crown NC is alternately arranged with connection segments 50 having a positive curvature.

[0097] Preferably, as can be observed by comparing the curves shown above and below the abscissa in FIGS. 4-5, FIGS. 7-8, FIGS. 10-11, and FIGS. 13-14, negative crown NC and connection segment 50 having a positive curvature have corresponding widths and depths / heights that are substantially equal to each other.

[0098] The profiles of the respective work rolls 24a and 24b can be defined by curves composed of an antisymmetric trigonometric function and a cubic polynomial function.

[0099] The equation of the curve of the profile is shown as follows.

Equation

[0100] According to the present invention, by assigning appropriate values to the parameters α and C in the above equation, when the manufactured strip is divided into two half strips, it becomes possible to obtain a "double crown" profile. Further, when the strip is divided into a plurality of parts in the longitudinal direction, it also becomes possible to obtain triple, quadruple, and generally multiple crown profiles.

[0101] As shown in FIGS. 6, 9, 12, and 15, when the profiles (mechanical crowns) of the work rolls 24a and 24b are determined, the range of the crown on the strip can be corrected by changing the value δ s of the axial movement (shift) of the work rolls 24a and 24b.

[0102] This has become possible due to the specific consistency in the profiles of the work rolls 24a and 24b.

[0103] Referring to the examples shown in FIGS. 4 to 6, a strip S having a width of 2000 mm corresponding to the width of the casting slab is rolled into a double crown by work rolls 24a, 24b having a barrel length equal to 2450 mm so as to be later divided into two 1000 mm half strips in the longitudinal direction. As shown in FIG. 3b, these figures represent the case where the strip is divided into two half strips of the same width, but it should be understood that they do not exclude the possibility that the two parts of the strip have different widths.

[0104] As an example, the last finishing stand 16e (although it may be the last two, three, or more) includes an upper work roll 24a and a lower work roll 24b, and an upper support roll 25a and a lower support roll 25b, as shown in FIGS. 4a and 5a.

[0105] FIGS. 4b to 4c and FIGS. 5b to 5c respectively show the profiles of the upper work roll 24a and the lower work roll 24b under two different operating conditions.

[0106] In FIGS. 4b and 4c, the profile of the upper work roll 24a over the entire length of the barrel and the profile of the lower work roll 24b over the entire length of the barrel are respectively shown by line L(T) and line L(B) under the condition of no axial shift.

[0107] In FIGS. 5b and 5c, the dashed lines L(T) and L(B) indicate the profiles of the work rolls 24a, 24b over the entire length of the barrel, while the solid lines L(Tu) and L(Bu) indicate the useful portions in the profiles of the work rolls acting on the strip S under the condition of axial shift shown by arrow F1 and arrow F2 in FIG. 5a.

[0108] Finally, FIG. 5d shows the resulting profile P(S) of the strip S as the sum of the profiles L(Tu) and L(Bu). The vertical end lines indicate the lateral edges of the strip, while the central vertical line 26 simultaneously indicates the center point where the strip S will later be divided.

[0109] As can be observed from the graph, the profiles of the work rolls 24a, 24b, and the resulting profile P(S) of the strip clearly have two bumps and two corresponding valleys, and in this particular example, have a "double crown shape" NC that forms the desired crown in the resulting profiles of the two half-strips into which the strip S is divided.

[0110] In particular, the crown on the work rolls 24a, 24b has a "negative", i.e., concave shape, but a "positive" crown, i.e., a convex shape, is obtained on the rolled strip S.

[0111] Similarly, the connecting segment 50 between the negative crowns NC on the work rolls 24a, 24b has a positive curvature, while the corresponding intermediate part 40 obtained on the rolled strip S has a negative curvature corresponding to the central vertical line 26 where the strip S is divided.

[0112] As can also be observed by comparing the curves above and below the horizontal axis in FIGS. 5d, 8d, 11d, and 14d, the positive crown PC and the intermediate part 40 having a negative curvature on the strip S each have a substantially equal width and depth / height.

[0113] Thus, the strip S can be longitudinally divided corresponding to its center line, and it is also possible to remove a small central band to make the crowns of the two half-strips "completely" symmetric.

[0114] It should be considered that the range of the crown of a single "bump" is a function of the axial shift of the work rolls 24a, 24b.

[0115] This is the advantage that the adjustment of the profile can be of a dynamic type rather than a static type, and the degree of shift of the work rolls 24a, 24b changes in relation to the operating conditions of the work rolls 24a, 24b.

[0116] Furthermore, in order to maintain the uniformity of the cross-section of the strip S in the last rolling stand, the same profile of the work rolls 24a, 24b can be applied to several stands and operated in different shift fields. This is because it does not impair the planarity of the strip S itself.

[0117] The graph in Fig. 6 shows how the crown of the strip S can be corrected by acting on the shift, i.e., the axial displacement, of the two work rolls 24a, 24b in order to change the surface portion of each roll acting directly on the strip S.

[0118] Thanks to the axial shift of the work rolls 24a, 24b, it is possible to emphasize or flatten the peaks and valleys of the profile of the strip S, which means increasing or decreasing the crown of the S strip.

[0119] The shift of the work rolls 24a, 24b is symmetric, i.e., the rolls are translated in opposite directions by equal values with respect to the center line M.

[0120] In the graphs of Figs. 5a to 5d, a shift equal to 50 mm was considered.

[0121] Figs. 7 and 8 represent the case where the strip S needs to be divided into three parts in the longitudinal direction. In this case, each of the three parts has a width equal to 1 / 3 of the width of the strip S.

[0122] Figs. 7a and 8a show the respective upper work roll 24a and lower work roll 24b having a triple negative crown profile.

[0123] Also in this case, FIGS. 7b and 7c represent the profiles over the entire barrel length of the work rolls 24a, 24b under the reciprocating non-shift condition. FIGS. 8b and 8c represent the effective working portions L(Bu), L(Tu) with the work rolls 24a, 24b reciprocated by 50 mm.

[0124] Reference numeral 26 in FIG. 8d represents two sections from which three parts can be obtained from the manufactured strip S.

[0125] As can be seen from FIG. 8d, in this case, in order to determine the resulting profile having a triple positive crown PC that is substantially symmetric with respect to the center line of each of the (three) parts where the strip S is divided corresponding to section 26, it can be seen how the profiles of the work rolls 24a, 24b are formed into a negative crown NC so that a profile of a strip having triple bumps is obtained.

[0126] FIG. 9 correspondingly shows the control range of the crown obtained by axially shifting the work rolls 24a, 24b formed in the shapes shown in FIGS. 7b and 7c.

[0127] Finally, in a manner substantially equivalent to the above-described case, FIGS. 10 to 11 consider the case where the manufactured strip S needs to be divided into four parts. In this particular case, all parts have substantially equal widths.

[0128] It should be pointed out how the profiles of the work rolls 24a, 24b are formed into a quadruple negative crown. In FIG. 10, this point is represented under the non-shift condition. FIG. 11 represents the shift states of the two work rolls 24a, 24b having the effective profiles L(Tu) and L(Bu) corresponding to the upper work roll 24a (FIG. 11b) and the lower work roll 24b (FIG. 11c) shown by solid lines, respectively. In this case, the two work rolls 24a, 24b are shifted by 80 mm.

[0129] The resulting profile of strip S (Figure 11d) has four bumps or positive crowns PC in substantially symmetric positions. Thus, after separation into four parts longitudinally by means of section 26, each part has a precisely defined crown pre-established.

[0130] Similar to each of the above cases, crown control can be performed by using an axial shift, for example as in the example shown in Figure 12.

[0131] Referring to Figures 13 to 15, in the same rolling mill where the barrel length of the work roll is 2450 mm a strip S is manufactured, the strip S having a width of 1600 mm corresponding to the width of the cast slab and always being rolled with a double crown and then split longitudinally into two half-strips of 800 mm is shown as an example.

[0132] In the examples shown in Figures 13b and 13c, the work rolls 24a, 24b have a profiled profile with a double negative crown having straight edge segments (not formed) because the width of the strip to be rolled is smaller than in the above example.

[0133] Figures 13b and 13c show the overall profiles of the work rolls 24a, 24b under reciprocating non-shift conditions, and Figures 14b and 14c show the overall profiles of the two work rolls 24a, 24b under shift conditions. The effective profiles L(Tu) and L(Bu) corresponding to the upper work roll 24a (Figure 14b) and the lower work roll 24b (Figure 14c) respectively are represented by solid lines. In this case, the work rolls 24a, 24b are shifted by 50 mm.

[0134] The resulting profile of the strip S (Figure 14d) has two bumps or positive crowns in substantially symmetric positions. After being separated into two longitudinal parts by means of section 26, each part has the correct crown established in advance according to the required quality requirements.

[0135] Similar to the above cases, as shown in the example of Figure 15, by using an axial shift, the control of the crown can be achieved.

[0136] As described above, the operation of imparting a double (or triple, or quadruple, …) crown to the strip is carried out at the last stand of the finishing rolling mill 15, for example, the last stand, or the last two or three stands, especially when the thickness is thin.

[0137] Figure 16 shows how the amplitude of the angle α changes as a function of the total width of the rolled strip S. For example, in the case of the strip S having a double crown PC, it is when the width value is between 800 and 2000 mm inclusive.

[0138] As described above, multi-crown rolling can be selectively varied from the center to the periphery by requiring strict control over the cooling efficiency across the width of the work roll.

[0139] According to the present invention, as shown in Figure 17 as just an example, the cooling system 30 includes respective main feed pipes 31 and delivery nozzles 32 arranged across the entire width of the work rolls 24a, 24b, and one or more the inclined path 33 of for delivering the cooling fluid.

[0140] The delivery nozzles 32 are arranged adjacent to each other in two or three rows at a constant pitch and are connected to the pipes 31 in independent groups for each so as to define independently differentiated cooling zones in the width direction of the roll. In the example shown in Figure 17 , the inclined path is it is divided into 11 independent cooling zones.

[0141] Each feed pipe 31 is equipped with a unique proportional valve for adjusting the flow rate to the corresponding group of nozzles 32.

[0142] In this way, it becomes possible to manage the groups of nozzles 32 individually, and thus it becomes possible to vary the cooling of the corresponding surface zones of the work rolls 24a, 24b.

[0143] According to the present invention, based on the portion of the width obtained starting from a predetermined width of the strip, each delivery rise inclined path 3 3 can be divided into a plurality of, for example, independent zones between 7 and 17. Therefore, it becomes possible to define an appropriate variation in the cooling efficiency along the axes of the work rolls 24a, 24b, especially for individually controlling the cooling of two halves, or three, four, and more parts of the strip S that will be divided later.

[0144] For example, in the case of double crown processing, it is advantageous to have a minimum cooling efficiency around the central zone of the work rolls 24a, 24b, where the thermal crown increases in this zone, while having a maximum cooling efficiency in the zone of the rolls that operates corresponding to the central portions of the two halves of the strip, where the thermal crown decreases in this zone. In this way, the thermal crown can be controlled to follow the tendency of the mechanical crown.

[0145] For example, in the work rolls 24a, 24b for manufacturing a strip with a maximum width of 2000 mm, the width of each zone can vary from about 130 mm to about 220 mm.

[0146] According to some embodiments, for example, in the example described with reference to FIG. 18, the cooling system 30 can include four coolers arranged in pairs at the inlets and outlets to the upper work roll 24a and the lower work roll 24b for each of the multiple crown finishing stands 16a - 16e. decline inclined path 3 3 can be provided.

[0147] Cool decline inclined path 3 In 3, in order to change the incident angle of the coolant to the work rolls 24a, 24b, for each work roll 24a, 24b, the cold decline inclined path 3 3 is moved closer or farther away, or the cold decline inclined path 3 3 is provided with a drive device 34 configured to rotate it, which is advantageous.

[0148] According to some embodiments, the strip S can be longitudinally cut in a process downstream of the rolling mill 12 and then wound into a coil having an overall multi-crown profile.

[0149] According to some variations, the strip S is wound around an initial head segment having a multi-crown shape, and then a cutting disk located upstream of the reel 21 is driven to longitudinally divide the strip S during winding. In this case, the longitudinal cut can be interrupted in front of the final tail end, so that this tail end remains intact as a head with a multi-crown profile.

[0150] It is obvious that modifications and / or additions of components can be made to the plants and methods described so far without departing from the field and scope of the present invention.

Claims

1. A method for manufacturing a flat-rolled product for obtaining a strip (S) having a lateral profile of a multi-positive crown, comprising: The manufacturing method includes a rolling step performed on a rolling mill (12) including a plurality of finishing stands (16a, 16b, 16c, 16d, 16e) each provided with work rolls (24a, 24b) so as to provide a strip (S) having a predetermined width. The work rolls (24a, 24b) of at least the last finishing stand (16e) have a profile of a multi-negative crown. The number of negative crowns (NC) in the profile of the work rolls (24a, 24b) is associated with the number of longitudinally divided portions of the strip (S) to be rolled downstream of the plurality of finishing stands (16a, 16b, 16c, 16d, 16e). The negative crowns (NC) and the connecting segments (50) having a positive curvature are alternately arranged. The work rolls (24a, 24b) are configured to have an axial movement, and the axial movement is performed to correct the position of the negative crowns (NC) of the work rolls (24a, 24b) with respect to the position of the strip (S) and the range of the positive crowns (PC) in the strip (S). In order to control the thermal crown so as to follow the tendency of the mechanical crown of the work rolls (24a, 24b), differential cooling is provided for the work rolls (24a, 24b), which has a maximum cooling intensity corresponding to the negative crowns (NC) and a minimum cooling intensity corresponding to the connecting segments (50) having a positive curvature. The manufacturing method is characterized by this.

2. The manufacturing method according to claim 1, wherein each width of the negative crowns (NC) and the connecting segments (50) having a positive curvature in the work rolls (24a, 24b) is substantially equal to each other.

3. Among the last three of the finishing stands (16a, 16b, 16c, 16d, 16e), the last three finishing stands (16c, 16d, 16e) are provided with work rolls (24a, 24b) having the same diameter and the same profile. The profile of the work roll (24a, 24b) having a multiple negative crown is applied to the last three of the finishing stands, the manufacturing method according to claim 1 or claim 2.

4. The equation of the curve of the forming profile of the work roll (24a, 24b) is as follows: 【Number 1】 Here, D ｔ (y) is the diameter of the upper work roll, D ｂ (y) is the diameter of the lower work roll, D is the nominal diameter of the work roll, α is the angle of the modifiable shape of the curve of the gap between the work rolls, b is the barrel length of the work roll, C is the amplitude of the sine curve, δ ０ is the value of the primary displacement of the formed curve of the work roll, δ ｓ is the value of the relative movement from the first position, a １ is the first coefficient, a ３ is the second coefficient, By determining the parameters α and C, the profile of the multiple positive crown related to the number of parts into which the strip (S) is divided is determined, the manufacturing method according to any one of claims 1 to 3.

5. In the case of a strip (S) having a profile of a double positive crown, the maximum cooling intensity is provided at the periphery of the central zone of the work roll (24a, 24b) and at the zone of the work roll (24a, 24b) operating corresponding to the central portions of the two halves of the rolled strip (S), providing differential cooling, the manufacturing method according to any one of claims 1 to 4.

6. A plant for manufacturing a flat rolled product in order to obtain a strip (S) having a lateral profile of a multiple positive crown, The plant has at least one unit (15) comprising finishing stands (16a to 16e) having work rolls (24a, 24b), At the end of rolling and in the next step, in order to obtain a strip (S) divided into a plurality of parts in the longitudinal direction, at least the last finishing stand (16e) of the finishing unit (15) has the work roll (24a, 24b) having a profile of a multiple negative crown, The number of negative crowns (NC) in the profile of the work roll (24a, 24b) is associated with the number of parts into which the strip (S) to be rolled is later divided in the longitudinal direction, The negative crowns (NC) and the connecting segments (50) having a positive curvature are arranged alternately, At least the work roll (24a, 24b) is configured to have an axial movement, and the magnitude and direction of the axial movement are associated with the desired profile obtained on the strip (S), The plant has an adjustable cooling intensity as a function of the profile of the formed multi-negative crown of the work rolls (24a, 24b), and further comprises a differentiated cooling system (30) for the work rolls (24a, 24b). The cooling system (30) comprises a plurality of cooling ramps (33), each having a plurality of delivery nozzles (32), so as to define differentiated cooling zones independently in the width direction of the work rolls (24a, 24b). The plurality of delivery nozzles (32) are arranged adjacent to each other in two or three rows at a constant pitch, and each group is connected to a corresponding plurality of feed pipes (31) that are independent of each other. Each feed pipe (31) is provided with a proportional valve for adjusting the flow rate of the corresponding nozzle (32) by providing differentiated cooling for the work rolls (24a, 24b) to control the thermal crown so as to follow the tendency of the mechanical crown of the work rolls (24a, 24b), including a minimum cooling intensity corresponding to the negative crown (NC) and a maximum cooling intensity corresponding to the connection segment (50) having a positive curvature. A plant characterized by this.

7. The plant according to claim 6, wherein at least the last three stands (16a to 16e) of the finishing unit (15) are provided with work rolls (24a, 24b) having a profile of a multi-negative crown.

8. The plant according to claim 6 or claim 7, configured to operate in any one of an endless mode, a semi-endless mode, and a coil-to-coil mode.

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