CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the priority of Korean Patent Application No. 10-2014-0190236 filed on December 26, 2014, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein by reference.

BACKGROUND OF THE INVENTION
Field of the Invention
[0002] The present invention relates to a method of managing final strip exit(strip metal out) from a finishing mill, and more particularly, to a method of managing final strip exit from a finishing mill during a Compact Endless cast-rolling Mill (CEM) process, in which a continuous casting process and a rolling process are directly connected, for stably rolling the final coils in a batch process of rolling thin materials using endless rolling.

Description of the Related Art
[0003] Related art rolling methods have limitations in that in a mill for rolling thin materials, a strip may not move in a perfectly straight line but may move in a meandering manner during a final strip exit event, and thus, strip twisting and the adhesion of a burnt portion of a strip to a roll occur. Thus, the operation may be stopped or a roll crack may be generated, leading to a decrease in productivity and a rise in manufacturing costs.
[0004] In particular, there may be a limitation that a work roll having low wear resistance and high twist resistance should be used in an endless rolling process, thereby leading to a decrease in the number of endless rolled sheets that may be rolled, due to wearing of the work roll.
[0005] ?Prior Art Documents?
[0006] (Patent Document 1) Korean Patent Application Laid-open Publication No. 10-1999-0059961

SUMMARY OF THE INVENTION
[0007] An aspect of the present invention provides a method of managing final strip exit from a finishing mill, the method being used in a Compact Endless cast-rolling Mill (CEM) process, in which a continuous casting process and a rolling process are directly connected, for stably rolling the final coils in a batch process of rolling thin materials using endless rolling.
[0008] Another aspect of the present invention provides a method of managing final strip exit from a finishing mill in order to minimize a defective portion of a steel strip, inevitably caused by rapidly increasing a rolling thickness, in the thickness of a final product
[0009] According to an aspect of the present invention, there is provided a method of managing final strip exit from a finishing mill, the method including increasing a rolling thickness of a tail-end portion of a strip by sequentially increasing roll gaps of a plurality of stands in a running direction of the strip immediately prior to a final strip exit event of the tail-end portion of the strip occurs at a following-stage stand.
[0010] According to another aspect of the present invention, when the final strip exit event of the tail-end portion of the strip occurs, set values for changing a rolling thickness may be calculated, and a rolling speed of each stand may be adjusted according to the set values
[0011] According to another aspect of the present invention, a rolling speed of each stand may be individually controlled.

BRIEF DESCRIPTION OF THE DRAWINGS
[0012] The above and other aspects, features and other advantages of the present invention will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings, in which:
FIGS. 1 to 4 are schematic side views illustrating a finish rolling process in a running sequence of a strip, according to an embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0013] Hereinafter, a method of strip metal out in a finishing mill for a directly connected continuous casting and rolling process according to an embodiment of the present invention will be described with reference to the attached drawings.
[0014] The present inventive concept may, however, be exemplified in many different forms and should not be construed as being limited to the specific embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art.
[0015] Throughout the specification, it will be understood that when an element, such as a layer, region or wafer (substrate), is referred to as being “on,” “connected to,” or “coupled to” another element, it can be directly “on,” “connected to,” or “coupled to” the other element or other elements intervening therebetween may be present. In contrast, when an element is referred to as being “directly on,” “directly connected to,” or “directly coupled to” another element, there may be no elements or layers intervening therebetween. Like numerals refer to like elements throughout. As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items.
[0016] It will be apparent that though the terms first, second, third, etc. may be used herein to describe various members, components, regions, layers and/or sections, these members, components, regions, layers and/or sections should not be limited by these terms. These terms are only used to distinguish one member, component, region, layer or section from another region, layer or section. Thus, a first member, component, region, layer or section discussed below could be termed a second member, component, region, layer or section without departing from the teachings of the exemplary embodiments.
[0017] Spatially relative terms, such as “above,” “upper,” “below,” and “lower” and the like, may be used herein for ease of description to describe one element’s relationship to another element(s) as shown in the figures. It will be understood that the spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. For example, if the device in the figures is turned over, elements described as “above,” or “upper” other elements would then be oriented “below,” or “lower” the other elements or features. Thus, the term “above” can encompass both the above and below orientations depending on a particular direction of the figures. The device may be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein may be interpreted accordingly.
[0018] The terminology used herein is for describing particular embodiments only and is not intended to be limiting of the present inventive concept. As used herein, the singular forms “a,” “an,” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises,” and/or “comprising” when used in this specification, specify the presence of stated features, integers, steps, operations, members, elements, and/or groups thereof, but do not preclude the presence or addition of one or more other features, integers, steps, operations, members, elements, and/or groups thereof.
[0019] Hereinafter, embodiments of the present inventive concept will be described with reference to schematic views illustrating embodiments of the present inventive concept. In the drawings, for example, due to manufacturing techniques and/or tolerances, modifications of the shape shown may be estimated. Thus, embodiments of the present inventive concept should not be construed as being limited to the particular shapes of regions shown herein, for example, to include a change in shape results in manufacturing. The following embodiments may also be constituted by one or a combination thereof.
[0020] The contents of the present inventive concept described below may have a variety of configurations and propose only a required configuration herein, but are not limited thereto.
[0021] Referring to FIGS. 1 to 4, a finishing mill includes first to fifth stands 1 to 5, and a strip is supplied from the first stand 1 toward the fifth stand 5 and is continuously outputted.
[0022] In this embodiment, although five stands are described, the present invention is not limited thereto, and the number of stands may be four or less, or may be six or more.
[0023] Here, the strip 100 may first undergo a process for removing scale from the surface of the strip before finish rolling by installing a finishing mill scale breaker (FSB) 30 upstream of the first stand 1.
[0024] Also, a crop shearing device 40 may be installed to cut front and tail-end portions of the strip 100 upstream of the scale breaker 30.
[0025] Also, a leveler 10 for correcting the smoothness of the strip 100 may be installed upstream of the crop shearing device 40.
[0026] In this embodiment, a controller of the finishing mill includes a process control system (PCS) of a level 2 region, and a programmable logic controller (PLC) of a level 1 region.
[0027] The PCS calculates the output side thickness at each stand in the finishing mill on the basis of rolling result information collected in real time, and functions to calculate and set the roll gap, rolling speed, rolling load, draft percentage, forward slip, stand speed rheostat (SSRH), ramp-up time, required count of auto position control (APC), and the like.
[0028] APC means that the position of an apparatus is controlled by set values for the apparatus in an upper level computer at a stage of factory automation, and also in this embodiment, means that the position of the finishing mill is controlled by set values.
[0029] Also, the required count of APC means that a reference signal is dividedly sent several times.
[0030] The SSRH means that, in a finishing mill which is a tandem rolling mill, in order to balance the mass flow of a rolling material, the speeds of all stands are not controlled while being synchronized, and the speeds of the respective stands are independently controlled.
[0031] That is, in this embodiment, since the mass flows at the respective stands 1 to 5 are different from each other at the same time point, the speed of each stand should be individually controlled to maintain a predetermined tension between the stands, which means that such control is sequentially performed.
[0032] The PLC functions to supply, to the mill, the information received from level 2 at an appropriate time as a reference for the APC.
[0033] The finishing mill of this embodiment configured as mentioned above is operated through the following method in a directly connected continuous casting rolling process.
[0034] When an off-event occurs in a finishing mill entry temperature (FET) thermometer 50, the finishing mill of this embodiment, as illustrated in FIG. 1, collects information related to the roll gap, rolling speed, and rolling load of each of the first to fifth stands 1 to 5, and calculates the current output side thickness of each of the first to fifth stands 1 to 5 on the basis of the collected information.
[0035] Here, the FET thermometer 50 also functions to detect the position of the tail-end portion of the strip 100 as well as to measure the temperature.
[0036] Then, on the basis of the calculated thicknesses, a target thickness to be changed for each of the first to fifth stands 1 to 5 is calculated, and then rolling set values (roll gaps, rolling speeds, draft percentages, forward slips) and set values (SSRH, ramp time, required APC count) for a thickness change during rolling are calculated to be sent to the PLC.
[0037] Next, as illustrated in FIG. 2, when a final strip exit event occurs at the second stand 2, the PLC performs the APC at a ramp starting point P1 such that the roll gap of the third stand 3 is changed to a set value for changed thickness through the received set values, and at the same time, the changed SSRH is applied to the rolling speed (B1). At this time, the speed of the second stand 2 is individually controlled such that only the speed of the second stand 2 is increased to maintain the tension between the second and third stands 2 and 3.
[0038] The reason for performing such control is because, when the tension is abruptly changed, the material width is decreased due to a decrease in the straight motion property of the material in the mill, and in severe cases, a rupture may occur.
[0039] Next, as illustrated in FIG. 3, when a ramp stating point P2, at which the APC is performed in the third stand 3, arrives at the fourth stand 4, the PLC performs the APC such that the roll gap of the fourth stand 4 is changed to a set value for a changed thickness (A2) and, at the same time, the changed SSRH is applied to the rolling speed (B2) of the fourth stand. Also, the APC is independently performed such that an SSRH changed to maintain the tension between the third and fourth stands 3 and 4 is applied to the rolling speed B1 of the third stand 3.
[0040] Next, as illustrated in FIG. 4, when a ramp stating point P3, at which the APC is performed in the fourth stand 4, arrives at the fifth stand 5, the PLC performs the APC such that the roll gap of the fifth stand 5 is changed to a set value for a changed thickness (A3) and, at the same time, the changed SSRH is also applied to the rolling speed (B3) of the fifth stand 5. Also, the APC is individually performed such that an SSRH changed to maintain the tension with respect to the fifth stand 5 is applied to the rolling speeds B1 and B2 of the third and fourth stands 3 and 4.
[0041] In this embodiment, all APCs may be dividedly performed step by step a number of times, the required count of APC set in the set values.
[0042] That is, level 1 PLC sends a reference signal for operating a motor or a cylinder of the finishing mill. Here, it is desirable that such operations are not performed at once but are dividedly performed several times. The dividedly sending of the reference signal several times is defined as the required count of the APC.
[0043] The purpose of dividedly spreading the sending of the reference signal several times is to individually control the speed to maintain the tension between the stands by equally matching start and end points in the operation times of each of the stands at one time point, because the APC amounts of the first to fifth stands 1 to 5 are different from one another, and through this, to match the mass flows between the stands which are different from one another.
[0044] Also, reference numbers 21, 23, 35, and 27 denote loopers for controlling the balance of the mass flows among the first to fifth stands 1 to 5, and the reference number 22, 24, 26, and 28 denote looper rollers installed at ends of the loopers.
[0045] According to the above-mentioned embodiment, by using the physical property that the degree of meandering movement is remarkably decreased in thick materials in comparison with thin materials, a strip is rolled with a quick increase in a rolling thickness immediately prior to the metal-out of the tail-end portion of the strip at a following-stage stand of the finish rolling, thereby providing a method for avoiding a strip twist, and ensuring passability through the stabilization of mass flows between the stands as well as the increase in the rolling thickness.
[0046] According to an embodiment of the present invention, there are effects in that roll accidents and quality defects are prevented by preventing strip twists and burnt strip adhesion which frequently occur during passing of the tail-end portion of a thin material, and accordingly the possibility of errors caused by a bar plate occurring in an irregular replacement change of a work roll is decreased.
[0047] While the present invention has been shown and described in connection with the exemplary embodiments, it will be apparent to those skilled in the art that modifications and variations can be made without departing from the scope of the present invention as defined by the appended claims.

Claims:We Claim:
1. A method of managing final strip exit from a finishing mill, the method comprising increasing a rolling thickness of a tail-end portion of a strip by sequentially increasing roll gaps of a plurality of stands along a running direction of the strip immediately prior to a final strip exit event of the tail-end portion of the strip occurs at a following-stage stand.

2. The method of claim 1, wherein when the final strip exit event of the tail-end portion of the strip occurs, set values for changing a rolling thickness are calculated, and a rolling speed of each stand is adjusted according to the set values.
3. The method of claim 1, wherein a rolling speed of each stand is individually controlled.