Cold rolling method, method for manufacturing steel sheet, cold rolling facility, and method for controlling cold rolling facility

Abstract

The present invention involves performing a rolling process on a steel sheet while maintaining the temperature of the steel sheet within the range not lower than a ductile-brittle transition temperature but not higher than a non-uniform deformation occurrence temperature. This cold rolling method is for performing a rolling process on a steel sheet S by means of a plurality of rolling stands std arranged in the conveying direction of the steel sheet S while supplying a rolling oil to each of the plurality of rolling stands std. The method comprises supplying at least a portion of the rolling oil recovered from a rolling stand std disposed on a downstream side in the conveying direction of the steel sheet S among the plurality of rolling stands std, to a prescribed number of the rolling stands std including the rolling stand std disposed most stream in the conveying direction of the steel sheet S.

Description

Cold rolling method, steel sheet manufacturing method, cold rolling equipment, and cold rolling equipment control method

[0001] The present invention relates to a cold rolling method, a method for manufacturing a steel sheet, cold rolling equipment, and a method for controlling cold rolling equipment.

[0002] For example, in steel sheets containing silicon (Si), such as electrical steel sheets, the temperature at which the material loses its ductility and becomes significantly brittle (hereinafter referred to as the ductile-brittle transition temperature) tends to decrease as the silicon content increases. Therefore, when cold-rolling such steel sheets, it is desirable to set the temperature of the steel sheet to be equal to or higher than the ductile-brittle transition temperature.

[0003] Methods for raising the temperature of a steel plate to the ductile-brittle transition temperature or higher include, for example, Patent Document 1 and Patent Document 2. Patent Document 1 discloses heating a steel plate by ejecting steam at 100 to 160°C from the underside of a steel plate moving at a constant speed toward the steel plate. Furthermore, Patent Document 2 discloses heating a steel plate using a solenoid-type induction heating device.

[0004] JP 2006-169546 A JP 2005-169458 A

[0005] Incidentally, in order to efficiently heat a steel sheet, it is desirable to perform heat exchange with the steel sheet using a fluid (or gas) having large values ​​for density, specific heat, temperature, heat transfer coefficient, flow rate, etc. For example, the specific heat and density of steam are smaller than those of water or rolling oil (coolant liquid), and therefore a method of heating the steel sheet using steam requires a larger amount of steam than a method of heating the steel sheet with warm water or rolling oil. In addition, the faster the speed of the steel sheet moving toward between a pair of work rolls where rolling processing is performed (hereinafter referred to as the conveying speed), the less steam is sprayed onto the steel sheet, which creates the problem of making it difficult to heat the steel sheet to the target temperature.

[0006] Furthermore, the method of heating steel sheets using a solenoid-type induction heating device has the advantage that the steel sheets can be heated to the desired temperature, but has the problem that the heating device is large and therefore difficult to install in a rolling mill.

[0007] In a tandem cold rolling facility having multiple rolling stands arranged along the steel sheet transport direction, in addition to the steel sheet heating methods disclosed in Patent Documents 1 and 2, a method of heating a steel sheet before rolling using a coolant circulated through each of the multiple rolling stands is also known. It is known that when a steel sheet is rolled, the steel sheet generates heat due to its own plastic deformation. In a tandem cold rolling facility, the rolling process is repeated through multiple rolling stands, and the temperature of the steel sheet increases as it is transported downstream in the steel sheet transport direction. This temperature increase not only causes deformation of the work rolls that roll the steel sheet, but also causes deformation (non-uniform deformation) of the steel sheet. Therefore, it is desirable to maintain the temperature of the steel sheet during rolling below the temperature at which deformation of the work rolls and the steel sheet occurs (non-uniform deformation temperature). That is, there is an increasing demand for a new cold rolling method, a steel sheet manufacturing method, and cold rolling equipment that can perform rolling treatment on a steel sheet in a state where the temperature of the steel sheet is maintained in a range of not less than the ductile-brittle transition temperature and not more than the temperature at which non-uniform deformation occurs, in a tandem cold rolling equipment having a plurality of mills.

[0008] The present invention has been made in view of the above-mentioned problems, and aims to provide a new cold rolling method, a steel sheet manufacturing method, cold rolling equipment, and a method for controlling cold rolling equipment, which are capable of performing a rolling process on a steel sheet while maintaining the temperature of the steel sheet in a range of not less than the ductile-brittle transition temperature and not more than the temperature at which non-uniform deformation occurs.

[0009] One aspect of the cold rolling method is a cold rolling method that performs rolling processing of a steel plate using a plurality of rolling stands while supplying rolling oil to each of the plurality of rolling stands arranged along the conveying direction of the steel plate, and is characterized in that at least a portion of the rolling oil recovered from a rolling stand arranged downstream in the conveying direction of the steel plate among the plurality of rolling stands is supplied to a predetermined number of rolling stands, including the rolling stand arranged most upstream in the conveying direction of the steel plate.

[0010] Furthermore, it is preferable that a rolling oil spraying device is provided which is arranged upstream of at least the most upstream rolling stand in the conveying direction of the steel plate and sprays rolling oil toward the steel plate, and that the rolling oil used in the rolling stand arranged downstream in the conveying direction of the steel plate is supplied to a predetermined number of rolling stands and, if necessary, to the rolling oil spraying device.

[0011] Furthermore, the temperature of the rolling oil supplied to the predetermined number of rolling stands is preferably 80°C or higher.

[0012] It is also preferable to supply rolling oil recovered from a predetermined number of rolling stands to rolling stands other than the predetermined number of rolling stands, thereby circulating the rolling oil among a plurality of rolling stands.

[0013] Further, a method for manufacturing a steel sheet according to one aspect includes a cold rolling step using the cold rolling method described above, and a finish annealing step of, as necessary, performing finish annealing on the steel sheet that has been subjected to the cold rolling step.

[0014] In addition, one aspect of cold rolling equipment is a cold rolling equipment that performs rolling processing of a steel plate using a plurality of rolling stands while supplying rolling oil to each of the plurality of rolling stands arranged along the conveying direction of the steel plate, and is characterized in that it comprises a supply system capable of supplying rolling oil to each of the plurality of rolling stands, a recovery system capable of recovering rolling oil from the plurality of rolling stands, a plurality of control valves arranged in each of the supply system and the recovery system, and a control device that switches the open / close state of each of the plurality of control valves, so that the recovery system forms a first recovery path that recovers rolling oil from the rolling stand arranged downstream in the conveying direction of the steel plate, and the supply system forms a first supply path that supplies a portion of the rolling oil recovered by the first recovery path to a predetermined number of rolling stands including the rolling stand arranged most upstream in the conveying direction of the steel plate.

[0015] It is also preferable to provide a rolling oil spraying device that is arranged upstream of at least the most upstream rolling stand in the conveying direction of the steel plate and is arranged downstream in the conveying direction of the steel plate, and that is capable of spraying a portion of the rolling oil recovered from at least one or more rolling stands toward the steel plate.

[0016] Furthermore, it is preferable that the recovery system forms a second recovery path that recovers rolling oil used in a predetermined number of rolling stands when the first recovery path is formed, and that the supply system forms a second supply path that supplies rolling oil recovered by the second recovery path to rolling stands excluding the predetermined number of rolling stands when the first supply path is formed.

[0017] Further, one aspect of the control method for cold rolling equipment is a control method for cold rolling equipment that performs a rolling process on a steel plate using a plurality of rolling stands while supplying rolling oil to each of the plurality of rolling stands arranged along the conveying direction of the steel plate, the cold rolling equipment having a supply system capable of supplying rolling oil to the plurality of rolling stands, a recovery system capable of recovering the rolling oil used in the plurality of rolling stands, a plurality of control valves arranged in each of the supply system and the recovery system, and a control device that switches the open / close state of each of the plurality of control valves, based on the temperature of the rolling oil supplied to the plurality of rolling stands and the temperature of the steel plate, thereby forming a first recovery path in the recovery system that recovers rolling oil from a rolling stand arranged downstream in the conveying direction of the steel plate, and forming a first supply path in the supply system that supplies a portion of the rolling oil recovered by the first recovery path to a predetermined number of rolling stands including the rolling stand arranged most upstream in the conveying direction of the steel plate.

[0018] Furthermore, it is preferable that the recovery system forms a second recovery path that recovers rolling oil from a predetermined number of rolling stands when the first recovery path is formed, and that the supply system forms a second supply path that supplies a portion of the rolling oil recovered by the second recovery path to rolling stands excluding the predetermined number of rolling stands when the first supply path is formed.

[0019] According to the present disclosure, it is possible to prevent brittle fracture of the steel sheet, deformation of the work roll, and deformation of the steel sheet associated with the deformation of the work roll that occur during the rolling process.

[0020] Fig. 1 is a schematic diagram showing the configuration of a cold rolling facility according to one embodiment of the present invention. Fig. 2 is a schematic diagram showing the configuration of the vicinity of the first and second rolling stands of a rolling mill. Fig. 3 is a schematic diagram showing the configuration of the vicinity of the third to fifth rolling stands of a rolling mill. Fig. 4 is a schematic flow chart showing the flow of a process for producing a cold-rolled coil from a hot-rolled coil. Fig. 5(a) is a schematic diagram showing the flow of rolling oil during operation of a conventional cold rolling facility, and Fig. 5(b) is a graph showing the temperature change of a steel sheet in the cold rolling facility shown in Fig. 5(a).

[0021] The configuration of a cold rolling facility according to one embodiment of the present invention will be described with reference to Figures 1 to 3. Figure 1 is a schematic diagram showing the configuration of a cold rolling facility according to one embodiment of the present invention. Figure 2 is a schematic diagram showing the configuration of the first rolling stand and the vicinity of the second rolling stand of a rolling mill, and Figure 3 is a schematic diagram showing the configuration of the vicinity of the third to fifth rolling stands.

[0022] The following description will be given taking a steel sheet S such as an electromagnetic steel sheet as an example of the material to be rolled, but the material to be rolled may also be an aluminum sheet or other metal sheet.

[0023] In the cold rolling facility 1 shown in Fig. 1, a steel sheet S is transported from the right side to the left side in Fig. 1. As shown in Fig. 1, the cold rolling facility 1 includes a cold tandem rolling mill 2. Hereinafter, the cold tandem rolling mill 2 will be simply referred to as the rolling mill 2. The rolling mill 2 includes a plurality of rolling stands (std) arranged along the transport direction of the steel sheet S. Although not shown in the figure, the rolling mill 2 also includes tension rolls and diff rolls, a thickness gauge, a shape gauge, and the like between adjacent rolling stands (std).

[0024] Hereinafter, a case will be described in which the rolling mill 2 is equipped with five rolling stands std. Of the five rolling stands std, the rolling stand std arranged most upstream in the conveyance direction of the steel sheet S will be referred to as the first rolling stand std1, and the rolling stand std arranged most downstream in the conveyance direction of the steel sheet S will be referred to as the fifth rolling stand std5. Note that, in this embodiment, a rolling mill 2 equipped with five rolling stands std will be exemplified, but the number of rolling stands std provided in the rolling mill 2 does not need to be limited to five, and is preferably two or more.

[0025] As an example, the first rolling stand std1, the second rolling stand std2, the third rolling stand std3, the fourth rolling stand std4 and the fifth rolling stand std5 each have a pair of upper and lower work rolls 11 that roll the steel plate S, a pair of upper and lower backup rolls 12 that support these work rolls 11, and a pair of upper and lower intermediate rolls 13 that are arranged between the work rolls 11 and the backup rolls 12.

[0026] Furthermore, the cold rolling equipment 1 includes, in addition to the rolling mill 2 described above, a lubrication coolant header 21 and a cooling coolant header 22. The lubrication coolant header 21 and the cooling coolant header 22 are provided corresponding to each of the multiple rolling stands std of the rolling mill 2. In the conveying direction of the steel sheet S, the lubrication coolant header 21 is disposed upstream of each rolling stand std, and the cooling coolant header 22 is disposed downstream of each rolling stand std.

[0027] In this embodiment, the lubrication coolant header 21 and the cooling coolant header 22 are configured separately from the rolling mill 2, but these headers 21, 22 may also be configured as part of the rolling mill 2.

[0028] Here, the lubrication coolant headers 21 and cooling coolant headers 22 provided for each rolling stand standard have the same configuration. Therefore, in Figure 1, only the configurations of the lubrication coolant header 21 and cooling coolant header 22 corresponding to the first rolling stand standard 1 are denoted by reference numerals.

[0029] The rolling oil sprayed from the lubricating coolant header 21 reduces the frictional force between the work rolls 11 and the steel sheet S, and cools the work rolls 11, the backup rolls 12, and the intermediate rolls 13. The lubricating coolant header 21 is equipped with spray nozzles 23 a, 23 b, and 23 c.

[0030] The jet nozzle 23a is disposed above the conveying plane L (see FIG. 2 or 3) of the steel sheet S. The jet nozzle 23a jets rolling oil (coolant liquid) toward each of the work rolls 11, backup rolls 12, and intermediate rolls 13, which are disposed above the conveying plane L.

[0031] The ejection nozzle 23b is disposed above the conveying plane L of the steel sheet S and below the ejection nozzle 23a. The ejection nozzle 23b ejects rolling oil toward the work rolls 11 and the upper surface of the steel sheet S, which are disposed above the conveying plane L.

[0032] The ejection nozzle 23c is disposed below the conveying plane L. The ejection nozzle 23c ejects rolling oil toward the lower surfaces of the work rolls 11 and the steel sheet S, which are disposed below the conveying plane L.

[0033] The rolling oil ejected from the cooling coolant header 22 cools the work rolls 11, the backup rolls 12, and the intermediate rolls 13. The cooling coolant header 22 is equipped with ejection nozzles 24a and 24b.

[0034] The ejection nozzle 24a is disposed above the conveying plane L of the steel sheet S. The ejection nozzle 24a ejects rolling oil toward each of the work rolls 11, backup rolls 12, and intermediate rolls 13, which are disposed above the conveying plane L.

[0035] The ejection nozzle 24b is disposed below the conveying plane L of the steel sheet S. The ejection nozzle 24b ejects rolling oil toward the work rolls 11 and intermediate rolls 13, which are disposed below the conveying plane L.

[0036] Hereinafter, the lubricating coolant header corresponding to the first rolling stand std1 will be referred to as lubricating coolant header 21a, the lubricating coolant header corresponding to the second rolling stand std2 will be referred to as lubricating coolant header 21b, and the lubricating coolant header corresponding to the third rolling stand std3 will be referred to as lubricating coolant header 21c. Also, the lubricating coolant header corresponding to the fourth rolling stand std4 will be referred to as lubricating coolant header 21d, and the lubricating coolant header corresponding to the fifth rolling stand std5 will be referred to as lubricating coolant header 21e.

[0037] Similarly, the cooling coolant header corresponding to the first rolling stand std1 will be referred to as cooling coolant header 22a, the cooling coolant header corresponding to the second rolling stand std2 as cooling coolant header 22b, and the cooling coolant header corresponding to the third rolling stand std3 as cooling coolant header 22c. Furthermore, the cooling coolant header corresponding to the fourth rolling stand std4 will be referred to as cooling coolant header 22d, and the cooling coolant header corresponding to the fifth rolling stand std5 as cooling coolant header 22e.

[0038] The heating device 25 is provided upstream of the lubricating coolant header 21 a and between the cooling coolant header 22 a and the lubricating coolant header 21 b in the conveying direction of the steel sheet S. The heating device 25 corresponds to a rolling oil injection device recited in the claims.

[0039] The heating device 25 is equipped with a plurality of jet nozzles provided below the conveying plane L of the steel sheet S. Here, the number of jet nozzles that the heating device 25 has is five, for example. The plurality of jet nozzles that the heating device 25 has jets rolling oil toward the steel sheet S from below the steel sheet S. Note that, although the rolling oil is jetted toward the steel sheet S from below the steel sheet S, the rolling oil may be jetted toward the steel sheet S from above and below the steel sheet S, or the rolling oil may be jetted toward the steel sheet S from above the steel sheet S.

[0040] Hereinafter, the heating device 25 disposed upstream of the first rolling stand std1 will be referred to as the heating device 25a. Also, the heating device 25 disposed between the cooling coolant header 22a and the lubrication coolant header 21b will be referred to as the heating device 25b.

[0041] In this embodiment, the case where the heating devices 25 a and 25 b are provided is described. However, if the temperature of the steel sheet S is kept within a range of not less than the brittle transition temperature and not more than the non-uniform deformation temperature by spraying the rolling oil ejected from the lubricating coolant header 21 onto the steel sheet S, the configuration of the heating devices 25 a and 25 b can be omitted.

[0042] An oil pan 26 is provided below each rolling stand standard provided in the above-mentioned rolling mill 2. The oil pan 26 receives rolling oil sprayed from the lubrication coolant header 21 and the cooling coolant header 22 arranged corresponding to the rolling stand standard.

[0043] The cold rolling equipment 1 is equipped with a first storage tank 31, a second storage tank 32, and a third storage tank 33 as storage tanks for rolling oil. The first storage tank 31 stores rolling oil to be supplied to the above-mentioned lubrication coolant header 21 and cooling coolant header 22. Rolling oil from the third storage tank 33 flows into the first storage tank 31.

[0044] The first storage tank 31 is provided with a heating device 34. The heating device 34 is a device that heats the rolling oil, for example, by injecting steam into the rolling oil. The heating device 34 operates so that the temperature of the rolling oil stored in the first storage tank 31 becomes a predetermined temperature as measured by the liquid thermometer 111. Here, the temperature of the rolling oil stored in the first storage tank 31 is, for example, 50 to 60°C.

[0045] The second storage tank 32 stores the rolling oil to be supplied to the above-mentioned lubrication coolant header 21 and the cooling coolant header 22. A portion of the rolling oil recovered from the rolling mill 2 flows into the second storage tank 32.

[0046] The second storage tank 32 is provided with a heating device 35. Similar to the heating device 34, the heating device 35 is a device that heats the rolling oil, for example, by injecting steam into the rolling oil. The heating device 35 operates so that the temperature of the rolling oil stored in the second storage tank 32 becomes a predetermined temperature as measured by the liquid thermometer 112. Here, the temperature of the rolling oil stored in the second storage tank 32 is, for example, 90°C.

[0047] A portion of the rolling oil recovered from the rolling mill 2 flows into the third storage tank 33. The third storage tank 33 is connected to the first storage tank 31 by a delivery line 41. A pump 42 is disposed in the delivery line 41. The pump 42 delivers the rolling oil stored in the third storage tank 33 toward the first storage tank 31.

[0048] In this embodiment, three storage tanks, namely, the first storage tank 31, the second storage tank 32, and the third storage tank 33, are provided as storage tanks for rolling oil. However, it is also possible to omit the configuration of the third storage tank 33 shown in FIG. 1 and allow a portion of the rolling oil recovered from the rolling mill 2 to flow into the first storage tank 31.

[0049] The cold rolling equipment 1 has a first supply system Sr1 (shown by a thick line in FIG. 1 ) and a second supply system Sr2 (shown by a dotted line in FIG. 1 ) as supply systems that supply rolling oil to each rolling stand (standard). The cold rolling equipment 1 also has a recovery system C1 (shown by a dashed dotted line in FIG. 1 ) that recovers rolling oil received in an oil pan 26 provided for each rolling stand (standard). The cold rolling equipment 1 is provided with two supply systems Sr1, Sr2 and the recovery system C1, which allows rolling oil to circulate within the cold rolling equipment 1.

[0050] The first supply system Sr1 has a supply path 45 connected to the first storage tank 31, a lubrication supply path 46 branching from the supply path 45 and connected to the lubrication coolant header 21, and a cooling supply path 47 branching from the supply path 45 and connected to the cooling coolant header 22. The lubrication supply path 46 and the cooling supply path 47 are provided corresponding to the lubrication coolant header 21 and the cooling coolant header 22 provided in the rolling mill 2, respectively.

[0051] A pump 51 and a heat exchanger 52 are disposed in the supply path 45. The pump 51 sends out the rolling oil stored in the first storage tank 31 toward the downstream side of the supply path 45. The heat exchanger 52 exchanges heat between the rolling oil sent out by the pump 51 to the downstream side of the supply path 45 and a heat transfer medium, as necessary, to cool the rolling oil.

[0052] A plurality of control valves 48 are arranged in the supply path 45. Here, the control valves 48 are arranged in the supply path 45 between the connection portion of the cooling supply path 47 to the cooling coolant header 22 corresponding to the rolling stand std arranged on the upstream side of adjacent rolling stands std, and the connection portion of the lubrication supply path 46 to the lubrication coolant header 21 corresponding to the rolling stand std located on the downstream side. Hereinafter, of the control valves 48 provided in the first supply path 45, those on the downstream side in the delivery direction of the rolling oil in the first supply path 45, i.e., those on the upstream side in the transport direction of the steel sheet S, will be referred to as control valves 48a, 48b, 48c, and 48d.

[0053] During operation of the cold rolling facility 1, one of these control valves 48a, 48b, 48c, and 48d is held in a closed state, and the remaining control valves are held in an open state. As a result, the rolling stands std of the rolling mill 2 are grouped into rolling stands std to which rolling oil is supplied by the first supply system Sr1 and rolling stands std to which rolling oil is supplied by the second supply system Sr2.

[0054] The lubrication supply path 46 is connected to a first branch path 56, a second branch path 57, and a third branch path 58 of the lubrication coolant header 21. A control valve 61 is disposed in the lubrication supply path 46. A control valve 62 is disposed in the first branch path 56 of the lubrication coolant header 21. A control valve 63 is disposed in the second branch path 57 of the lubrication coolant header 21. A control valve 64 is disposed in the third branch path 58 of the lubrication coolant header 21. Here, the first branch path 56 of the lubrication coolant header 21 is connected to the jet nozzle 23a, the second branch path 57 is connected to the jet nozzle 23b, and the third branch path 58 is connected to the jet nozzle 23c.

[0055] A lubricant supply line 82 branching off from the branch line 77a of the second supply system Sr2 is connected to the lubricant supply line 46 provided corresponding to the first rolling stand std1 on the downstream side of the control valve 61. Similarly, a lubricant supply line 82 branching off from the branch line 77b of the second supply system Sr2 is connected to the lubricant supply line 46 provided corresponding to the second rolling stand std2 on the downstream side of the control valve 61.

[0056] The cooling supply path 47 is connected to a first branch path 65 and a second branch path 66 of the cooling coolant header 22. A control valve 68 is disposed in the cooling supply path 47. A control valve 69 is disposed in the first branch path 65 of the cooling coolant header 22. A control valve 70 is disposed in the second branch path 66 of the cooling coolant header 22. The first branch path 65 of the cooling coolant header 22 is connected to the jet nozzle 24a, and the second branch path 66 is connected to the jet nozzle 24b.

[0057] The second supply system Sr2 has a supply line 76 connected to the second storage tank 32, and two branch lines 77a, 77b branching off from the downstream end of the supply line 76. A pump 79 is disposed in the supply line 76 near the second storage tank 32. The pump 79 delivers the rolling oil stored in the second storage tank 32 to the downstream side of the supply line 76. Since the configuration downstream of the branch line 77a and the configuration downstream of the branch line 77b are the same, the following description will be given of the configuration downstream of the branch line 77a, and a description of the configuration downstream of the branch line 77b will be omitted.

[0058] At its downstream end, branch path 77a branches into a heating supply path 81 and a lubricating supply path 82. A control valve 83 is disposed in heating supply path 81. A control valve 84 is disposed in lubricating supply path 82. Here, heating supply path 81 is connected to heating device 25, and lubricating supply path 82 is connected to lubricating supply path 46.

[0059] The recovery system C1 has discharge passages 91a, 91b, 91c, 91d, and 91e connected to an oil pan 26 arranged below each rolling stand std, a recovery passage 92 to which these discharge passages 91a, 91b, 91c, 91d, and 91e are connected, and return flow paths 93 and 94 branching off from the recovery passage 92.

[0060] Control valves 96, 97, 98, and 99 are provided in the flow paths 92a, 92b, 92c, and 92d that constitute the recovery path 92, respectively. The control valves 96, 97, 98, and 99 are controlled by a control device 110 to open and close.

[0061] Of the flow paths 92a, 92b, 92c, and 92d that constitute the recovery path 92 described above, the flow path 92a is connected to an upstream end of a return flow path 94 between the discharge path 91a and a control valve 96. Furthermore, of the flow paths 92a, 92b, 92c, and 92d, the flow path 92d is connected to an upstream end of a return flow path 93 between the discharge path 91e and a control valve 99. A control valve 100 is provided upstream of the return flow path 93 (on the recovery path 92 side).

[0062] The control device 110 outputs the necessary signals (control signals) to each part of the cold rolling equipment 1 based on signals (measurement signals) from each measurement location (thickness gauge, shape gauge, thermometer, etc.) installed in each part of the cold rolling equipment 1.

[0063] Next, a process for manufacturing a cold-rolled coil from a hot-rolled coil will be described. As shown in Fig. 4, an apparatus for manufacturing a cold-rolled coil from a hot-rolled coil includes, as an example, a pickling process, a cold rolling process, and a finish annealing process. Although not shown, the hot-rolled coil is produced by rolling (hot rolling) a heated slab using a rolling mill such as a roughing mill or a finishing mill, and winding the steel sheet S produced by the hot rolling using a winder.

[0064] The pickling process is a process of removing an oxide film covering the surface of the steel sheet S. Although not shown, the pickling process is carried out in a pickling facility having a pickling tank in which a strong acid such as sulfuric acid is stored, a water washing tank in which washing water is stored, and a dryer. That is, the pickling process includes a process of transporting the steel sheet S while immersing it in the pickling tank, a process of transporting the steel sheet S while immersing it in a washing tank, and a process of drying the surface of the steel sheet S.

[0065] The cold rolling process is a process in which the steel sheet S from which the oxide film has been removed by the pickling process is subjected to rolling treatment using the above-mentioned cold rolling equipment 1 to produce a steel sheet S of the desired thickness.

[0066] The finish annealing process is a process in which the steel sheet S rolled in the cold rolling process is annealed. By performing the finish annealing process, it is possible to soften the steel sheet S hardened in the cold rolling process to a target hardness. The steel sheet S that has been subjected to the finish annealing process is wound up by a winder.

[0067] In the finish annealing step, annealing is performed while the steel sheet S is being transported. However, it is also possible to perform annealing on a wound coil obtained by winding up the steel sheet that has been subjected to the cold rolling step.

[0068] Furthermore, the process of manufacturing a cold-rolled coil from a hot-rolled coil shown in FIG. 4 includes a finish annealing step, but depending on the type of material to be rolled, the finish annealing step may be omitted.

[0069] Next, the cold rolling process will be described. When producing a cold-rolled coil from a hot-rolled coil, the steel sheet S is transported in this order through the pickling facility and then through the cold rolling facility 1. When producing a cold-rolled coil from a hot-rolled coil, the control device 110 starts the operation of the cold rolling facility 1. That is, the control device 1 operates the rolling mill 2 of the cold rolling facility 1 to rotate each of the pair of work rolls 11 of the rolling stand standard of the rolling mill 2. At the same time, the control device 110 switches the open / closed state of the control valves provided in the cold rolling facility 1 as necessary. Furthermore, the control device 110 drives the pumps 42, 51, and 79.

[0070] First, an example of switching the open / closed state of the control valve provided in the cold rolling equipment 1 will be described.

[0071] (1) Regarding the control valve 48a The control device 110 calculates the temperature of the steel sheet S to be rolled in the first rolling stand std1 from the temperature of the rolling oil supplied to the lubricating coolant header 21a, the amount of rolling oil sprayed to the lubricating coolant header 21a, the temperature of the steel sheet S being transported, and the transport speed of the steel sheet S. The temperature of the steel sheet S being transported is measured by a thermometer 114. The temperature of the rolling oil is measured by a liquid thermometer 112. The transport speed is the speed at which the steel sheet S enters each rolling stand.

[0072] When the calculated temperature of the steel sheet S becomes equal to or higher than the ductile-brittle transition temperature, the control device 110 switches the control valve 48a provided in the supply path 45 from a closed state to an open state. Note that if the control valve 48a provided in the supply path 45 is in an open state, the control device 110 does not perform switching control on the control valve 48a, and maintains the state of the control valve 48a.

[0073] On the other hand, when the calculated temperature of the steel sheet S becomes lower than the ductile-brittle transition temperature, the control device 110 switches the control valve 48a provided in the supply path 45 from the open state to the closed state. Note that if the control valve 48a provided in the supply path 45 is in the closed state, the control device 110 does not perform switching control on the control valve 48a, and maintains the state of the control valve 48a.

[0074] (2) Regarding the control valve 48b The control device 110 calculates the temperature of the steel sheet S to be rolled in the second rolling stand std2 from the temperature of the rolling oil supplied to the lubrication coolant header 21b, the amount of rolling oil sprayed to the lubrication coolant header 21b, the temperature of the steel sheet S being transported, and the transport speed of the steel sheet S. The temperature of the steel sheet S being transported is measured by a thermometer 115. The temperature of the rolling oil is measured by a liquid thermometer 112.

[0075] When the calculated temperature of the steel sheet S becomes equal to or higher than the ductile-brittle transition temperature, the control device 110 switches the control valve 48b provided in the supply path 45 from a closed state to an open state. Note that if the control valve 48b provided in the supply path 45 is in an open state, the control device 110 does not perform switching control on the control valve 48b, and maintains the state of the control valve 48b.

[0076] On the other hand, when the calculated temperature of the steel sheet S becomes lower than the ductile-brittle transition temperature, the control device 110 switches the control valve 48b provided in the supply path 45 from the open state to the closed state. Note that, if the control valve 48a provided in the supply path 45 is in the closed state, the control device 110 does not perform switching control on the control valve 48a, and maintains the state of the control valve 48a.

[0077] (3) Regarding the control valves 48c and 48d: For example, if either the control valve 48c or the control valve 48d provided in the supply path 45 is in a closed state, the control device 110 switches the closed control valve to an open state. On the other hand, if both the control valves 48c and 48d provided in the supply path 45 are in an open state, the control device 110 does not perform switching control on the control valves 48c and 48d, and maintains the states of the control valves 48c and 48d.

[0078] (4) Regarding the control valve 61 When the control valve 48a is closed, the control device 110 switches the control valve 61 of the lubrication supply passage 46 corresponding to the first rolling stand std1 from an open state to a closed state. Note that if the control valve 61 is closed, the control device 110 does not perform switching control on the control valve 61, and maintains the state of the control valve 61.

[0079] On the other hand, when the control valve 48a is in the open state, the control device 110 switches the control valve 61 provided in the lubrication supply passage 46 corresponding to the rolling stand std2 from the closed state to the open state. Note that if the control valve 61 is in the open state, the control device 110 does not perform switching control on the control valve 61, and maintains the state of the control valve 61.

[0080] Furthermore, when the control valve 48b is closed, the control device 110 switches the control valve 61 of the lubricant supply passage 46 corresponding to the second rolling stand std2 from an open state to a closed state. If the control valve 61 is closed, the control device 110 does not perform switching control on the control valve 61, and maintains the state of the control valve 61. If the control valve 48b is open, the control device 110 switches the control valve 61 provided in the lubricant supply passage 46 corresponding to the second rolling stand std2 from a closed state to an open state. If the control valve 61 is open, the control device 110 does not perform switching control on the control valve 61, and maintains the state of the control valve 61.

[0081] Furthermore, the control device 110 switches the control valves 61 provided in the lubrication supply passages 46 corresponding to the third rolling stand std3, the fourth rolling stand std4, and the fifth rolling stand std5 from a closed state to an open state. If these control valves 61 are in an open state, the control device 110 does not perform switching control on the control valves 61, and maintains the state of the control valves 61.

[0082] (5) Regarding the control valves 62, 63, 64 When the control valves 62, 63, 64 are held in an open state, the control device 110 does not perform switching control on the control valves 62, 63, 64, and maintains the states of the control valves 62, 63, 64. When at least one of the control valves 62, 63, 64 is in a closed state, the control device 110 switches that control valve from a closed state to an open state. Although the example shows a case where all of the control valves 62, 63, 64 are in an open state, one or two of the control valves 62, 63, 64 may be opened depending on the temperature and lubrication state of the steel sheet S. The temperature of the steel sheet S can be obtained from thermometers 114, 115, 116, 117, 118 arranged upstream of each rolling stand.

[0083] (6) Regarding the control valves 68 When cooling of the rolls of each rolling stand std is not required, the control device 110 switches the control valves 68 of the cooling supply passages 47 corresponding to each of the first to fifth rolling stands from the open state to the closed state. Furthermore, when the control valves 68 are in the closed state, the control device 110 does not perform switching control of the control valves 68, and maintains the state of the control valves 68.

[0084] On the other hand, when cooling of each roll of each rolling stand std is necessary, the control device 110 switches the control valve 68 of the cooling supply passage 47 corresponding to each of the first to fifth rolling stands std1 to std5 from the closed state to the open state. Furthermore, if the control valve 68 is in the open state, the control device 110 does not perform switching control of the control valve 68, but maintains the state of the control valve 68.

[0085] (7) Regarding the control valves 69 and 70: When cooling of each roll of each rolling stand (std) is required, the control device 110 switches the control valves 69 and 70 from a closed state to an open state. For example, when the control valves 69 and 70 are in an open state, the control device 110 maintains the states of the control valves 69 and 70.

[0086] (8) Regarding the control valve 83 As described above, the control device 110 calculates the temperature of the steel plate S undergoing rolling processing in the first rolling stand std1 from the temperature of the rolling oil supplied to the lubricating coolant header 21a, the amount of rolling oil sprayed to the lubricating coolant header 21a, the temperature of the steel plate S being transported, and the transport speed of the steel plate S.

[0087] When the calculated temperature of the steel sheet S becomes lower than the ductile-brittle transition temperature, the control device 110 switches the control valve 83 of the heating supply path 81 connected to the heating device 25a from a closed state to an open state. Note that if the control valve 83 is in an open state, the control device 110 does not perform switching control on the control valve 83, and maintains the state of the control valve 83. On the other hand, when the calculated temperature of the steel sheet S becomes equal to or higher than the ductile-brittle transition temperature, the control device 110 switches the control valve 83 of the heating supply path 81 connected to the heating device 25a from an open state to a closed state.

[0088] (9) Regarding the control valve 84 As described above, the control device 110 calculates the temperature of the steel plate S undergoing rolling processing in the second rolling stand std2 from the temperature of the rolling oil supplied to the lubricating coolant header 21b, the amount of rolling oil sprayed to the lubricating coolant header 21b, the temperature of the steel plate S being transported, and the transport speed of the steel plate S.

[0089] When the calculated temperature of the steel sheet S becomes less than the ductile-brittle transition temperature, the control device 110 switches the control valve 83 of the heating supply path 81 connected to the heating device 25b from a closed state to an open state. Note that if the control valve 83 is in an open state, the control device 110 does not perform switching control on the control valve 83, and maintains the state of the control valve 83. On the other hand, when the calculated temperature of the steel sheet S becomes equal to or higher than the ductile-brittle transition temperature, the control device 110 switches the control valve 83 of the heating supply path 81 connected to the heating device 25b from an open state to a closed state.

[0090] (10) Regarding control valves 96, 97, 98, and 99 When the control valve 48a is closed, the control device 110 switches the control valve 96 from an open state to a closed state. At the same time, the control device 110 switches the control valves 97, 98, and 99 from a closed state to an open state. Note that if the control valve 96 is closed, the control device 110 does not perform switching control on the control valve 96 and maintains the state of the control valve 96. Note that if the control valves 97, 98, and 99 are open, the control device 110 does not perform switching control on the control valves 97, 98, and 99 and maintains the states of the control valves 97, 98, and 99.

[0091] Furthermore, when control valve 48b is closed, control device 110 switches control valve 96 from a closed state to an open state and control valve 97 from an open state to a closed state. At the same time, control device 110 switches control valves 98 and 99 from a closed state to an open state. If control valve 96 is open, control device 110 does not perform switching control on control valve 96 and maintains the state of control valve 96. If control valve 97 is closed, control device 110 does not perform switching control on control valve 97 and maintains the state of control valve 97. If control valves 98 and 99 are open, control device 110 does not perform switching control on control valves 98 and 99 and maintains the states of control valves 98 and 99.

[0092] (11) Regarding the Control Valve 100: For example, when the second storage tank 32 is not used, the control device 110 switches the control valve 100 from an open state to a closed state. On the other hand, when the second storage tank 32 is used, the control device 110 keeps the control valve 100 in an open state.

[0093] As described above, when the cold rolling facility 1 starts operation, the control device 110 drives the pumps 42 , 51 , and 79 .

[0094] For example, when the control valve 48a is closed and the control valves 48b, 48c, and 48d are open, the pumps 42 and 51 are driven to supply the rolling oil stored in the first storage tank 31 to the lubrication coolant headers 21b, 21c, 21d, and 21e via the first supply system Sr1. That is, the rolling oil flows through the supply path 45 and the lubrication supply paths 46, and is then supplied to the lubrication coolant headers 21b, 21c, 21d, and 21e. Here, the supply path 45 and the lubrication supply paths 46 correspond to the second supply paths recited in the claims.

[0095] Furthermore, when the pump 79 is driven, the rolling oil stored in the second storage tank 32 is supplied to the lubrication coolant header 21a via the second supply system Sr2. That is, the rolling oil flows through the supply path 76, the branch path 77a, the lubrication supply path 82, and the lubrication supply path 46, and is then supplied to the lubrication coolant header 21a. Here, the supply path 76, the branch path 77a, the lubrication supply path 82, and the lubrication supply path 46 correspond to a first supply path recited in the claims.

[0096] At this time, when the control valve 83 provided in the heating supply path 81 connected to the branch path 77a is in an open state, the rolling oil flows through the heating supply path 81 and is supplied to the heating device 25a.

[0097] As described above, the temperature of the rolling oil stored in the second storage tank 32 is maintained at 90°C. Therefore, the rolling oil ejected from the lubrication coolant header 21a and the rolling oil ejected from the heating device 25a are sprayed onto the steel sheet S. As a result, the steel sheet S is heated. Therefore, the temperature of the steel sheet S becomes equal to or higher than the ductile-brittle transition temperature.

[0098] As described above, the rolling oil stored in the first storage tank 31 is supplied to the lubrication coolant headers 21b, 21c, 21d, and 21e via the first supply system Sr1. The temperature of the rolling oil stored in the first storage tank 31 is 50 to 60°C. Therefore, the steel sheet S undergoing rolling processing in each of the rolling stands from the second rolling stand std2 to the fifth rolling stand std5 is cooled by the rolling oil sprayed from the lubrication coolant headers 21b, 21c, 21d, and 21e. That is, in the second rolling stand std2 to the fifth rolling stand std5, the steel sheet S is cooled by the rolling oil, and therefore the rolling processing is performed in a state in which the temperature of the steel sheet S is equal to or higher than the ductile-brittle transition temperature and equal to or lower than the non-uniform deformation occurrence temperature.

[0099] Incidentally, rolling oil used in the rolling process of the steel sheet S in the rolling mill 2 is received in the oil pans 26 corresponding to each rolling stand. For example, when the control valve 96 is closed, rolling oil received in the oil pan 26 located below the first rolling stand std1 flows through the discharge path 91a, the recovery path 92, and the return path 94, in that order, and is recovered in the third storage tank 33. At this time, the control valves 97, 98, 99, and 100 are open, so that rolling oil received in the oil pans 26 located below the second rolling stand std2 to the fifth rolling stand std5 flows through the discharge paths 91b, 91c, 91d, and 91e connected to each oil pan 26, the recovery path 92, and the return path 93, in that order, and is recovered in the second storage tank 32. Here, the discharge path 91a, the recovery path 92, and the return path 94 correspond to the first recovery path recited in the claims. The discharge paths 91b, 91c, 91d, and 91e through the recovery path 92 and the return path 93 correspond to a second recovery path in the claims.

[0100] In this case, the rolling oil stored in the first storage tank 31 is supplied to the second to fifth rolling stands std2, std3, std4, and std5. The rolling oil used in the second to fifth rolling stands std2, std3, std4, and std5 is recovered in the second storage tank 32 and then supplied to the first rolling stand std1. The rolling oil used in the first rolling stand std1 is recovered in the first storage tank 31. In other words, the rolling oil is circulated between the respective rolling stands of the rolling mill 2.

[0101] Furthermore, when the control valve 48b is closed and the control valve 48a is open, the control valves 96, 98, 99 and 100 are open, and the control valve 97 is closed. In this case, the rolling oil stored in the first storage tank 31 is supplied to the lubrication coolant headers 21c, 21d, and 21e via the first supply system Sr1. Meanwhile, the rolling oil stored in the second storage tank 32 is supplied to the lubrication coolant headers 21a and 21b via the second supply system Sr2. At this time, if the control valve 83 of the heating supply path 81 connected to the branch path 77a or the control valve 83 of the heating supply path 81 connected to the branch path 77b is open, the rolling oil is supplied to the heating devices 25a and 25b.

[0102] That is, the rolling oil stored in the first storage tank 31 is supplied to the third to fifth rolling stands std3, std4, and std5. Then, the rolling oil used in the third to fifth rolling stands std3, std4, and std5 is recovered in the second storage tank 32, and then supplied to the first and second rolling stands std1 and std2. Then, the rolling oil used in the first and second rolling stands std1 and std2 is recovered in the first storage tank 31. That is, in this case too, the rolling oil is circulated between the respective rolling stands of the rolling mill 2.

[0103] As described above, in the cold rolling equipment 1 of this embodiment, the control device 110 sets the rolling stand std that supplies the rolling oil used in the rolling stand std disposed downstream in the conveying direction of the steel sheet S, based on the temperature of the rolling oil and the steel sheet S. Then, the control device controls the opening and closing of each control valve based on the setting. This makes it possible to switch between heating and cooling of the steel sheet S at appropriate timing.

[0104] Incidentally, the temperature of the rolling oil recovered from each of the first rolling stand std1, second rolling stand std2, third rolling stand std3, fourth rolling stand std4 and fifth rolling stand std5 is the highest for the rolling oil recovered from the fifth rolling stand std5, which is located at the most downstream position.

[0105] Therefore, it is also possible to open the control valves 96, 97, and 98 and close the control valve 99. In this case, the rolling oil recovered from the first rolling stand std1, the second rolling stand std2, the third rolling stand std3, and the fourth rolling stand std4 is recovered in the third storage tank 33. On the other hand, the rolling oil recovered from the fifth rolling stand std5 is recovered in the second storage tank 32.

[0106] Furthermore, if the temperature of the rolling oil recovered from the fifth rolling stand std5 is low, it is also possible to open the control valve 99 and close the control valve 98, and recover the rolling oil recovered from the fourth rolling stand std4 and the fifth rolling stand std5 in the second storage tank 32.

[0107] For example, as shown in Fig. 5(a), in a conventional cold rolling facility 1', rolling oil stored in a first storage tank 31 is supplied to a lubrication coolant header 21 corresponding to each rolling stand (std). At this time, as shown in Fig. 5(b), the temperature of the steel sheet S that is rolled in the first rolling stand (std1) is lower than the ductile-brittle transition temperature. Therefore, the steel sheet S is prone to brittle fracture during the rolling process in the first rolling stand (std1).

[0108] The temperature of the steel sheet S after rolling by the first rolling stand std1 exceeds the non-uniform deformation temperature. At this time, in the rolling treatment by the second rolling stand std2 and onwards, the steel sheet S is cooled by the rolling oil sprayed from the lubricating coolant header 21, and the temperature of the steel sheet S becomes equal to or higher than the ductile-brittle transition temperature and equal to or lower than the non-uniform deformation temperature. Therefore, brittle fracture does not occur in the rolling treatment by the second rolling stand std2 and onwards.

[0109] Furthermore, in the rolling process from the second rolling stand std2 onwards, the steel sheet S is cooled by the rolling oil sprayed from the lubricating coolant header 21, and the temperature of the steel sheet S is kept below the temperature at which non-uniform deformation occurs, so deformation of the work roll 11 and deformation of the steel sheet S due to this do not occur.

[0110] However, if the temperature of the rolling oil sprayed from the lubrication coolant header 21 or the amount of rolling oil sprayed is insufficient, the rolling process from the second rolling stand std2 onwards may reach a temperature at which non-uniform deformation occurs.

[0111] On the other hand, in this embodiment, for example, in the rolling process in the first rolling stand std1, by supplying high-temperature rolling oil that has been used in the third to fifth rolling stands, the temperature of the steel sheet S being rolled in the first rolling stand std1 can be heated to a temperature equal to or higher than the ductile-brittle transition temperature and equal to or lower than the temperature at which non-uniform deformation occurs. As a result, the occurrence of brittle fracture during the rolling process of the steel sheet can be prevented.

[0112] In this embodiment, the rolling oil used in the rolling stand std on the downstream side in the conveying direction of the steel sheet S is supplied to the rolling stand std on the upstream side, and the rolling oil used in the rolling stand std on the upstream side is supplied to the rolling stand std on the downstream side. As a result, there is no need to cool the rolling oil by the heat exchanger 52 when supplying it from the first storage tank or the second storage tank to the rolling mill 2.

[0113] In this way, of the rolling stands std provided in the rolling mill 2, the rolling oil used in the rolling stand std arranged downstream in the conveying direction of the steel sheet S is supplied to the rolling stand std arranged upstream in the conveying direction. At this time, the temperature of the rolling oil used in the rolling stand std arranged downstream in the conveying direction of the steel sheet S is high due to heating by the steel sheet S which has been heated by multiple rolling processes. Therefore, by using such rolling oil in the rolling stand std arranged upstream in the conveying direction of the steel sheet S, it is possible to heat the steel sheet S without providing a new heating device.

[0114] Furthermore, rolling oil used in the rolling stand std arranged upstream in the conveying direction of the steel sheet S is supplied to the rolling stand std arranged downstream in the conveying direction. The temperature of the rolling oil used in the rolling stand std arranged upstream in the conveying direction of the steel sheet S is relatively low. Therefore, by using such rolling oil in the rolling stand std arranged downstream in the conveying direction of the steel sheet S, it is possible to cool the steel sheet S without providing a new cooling device.

[0115] In this way, by spraying rolling oil onto the steel sheet S before the rolling process in each standard rolling stand, the temperature of the steel sheet S immediately before the rolling process in each standard rolling stand can be kept within a range of not less than the ductile-brittle transition temperature and not more than the non-uniform deformation onset temperature. Here, the range of not less than the ductile-brittle transition temperature and not more than the non-uniform deformation onset temperature is a temperature range in which the rolling process can be carried out appropriately, and it is therefore possible to prevent brittle fracture of the steel sheet S being rolled, thermal deformation of the work rolls that perform the rolling process, and further the occurrence of defective shapes of the steel sheet S due to the thermally deformed work rolls.

[0116] Finally, the error temperature ΔT from the target temperature of the steel sheet S at the biting portion of the first rolling stand std1 and the fracture rate of the steel sheet were measured when the conveying speed of the steel sheet S was changed. The measurement results of the error temperature ΔT and the fracture rate of the steel sheet are shown in Table 1.

[0117]

[0118] In Table 1, measurement results No. 1 to No. 4 obtained using the cold rolling equipment of this embodiment are designated as invention examples, and measurement results No. 5 to No. 8 obtained using the cold rolling equipment using the steam heating device disclosed in Patent Document 1 are designated as comparative examples.

[0119] The nipping portion of the first rolling stand std1 is the location where the steel sheet is rolled by the pair of work rolls 11. In the following, the target temperature of the steel sheet at the nipping portion of the first rolling stand std1 is set to 80°C. In addition, measurements were taken at conveying speeds of the steel sheet of 15, 50, 100, and 150 mpm.

[0120] In the inventive example, when the conveying speed of the steel sheet S was set to 15, 50, 100, and 150 mpm, the temperature error ΔT from the target temperature of the steel sheet S was +18°C, +15°C, +10°C, and +5°C, respectively. In contrast, in the comparative example, the temperature error ΔT from the target temperature of the steel sheet S was +15°C, +8°C, -5°C, and -10°C. In other words, it was found that the inventive example was able to reliably heat the steel sheet even when the conveying speed of the steel sheet was increased.

[0121] Furthermore, since the temperature in the inventive examples is higher than the target temperature, the fracture rate during rolling is 0.15% or less, whereas in the comparative examples it is 0.25% or less. That is, the inventive examples allow the steel sheet to be heated more efficiently than the comparative examples. As a result, it was found that the inventive examples are less likely to suffer from brittle fracture during rolling than the comparative examples.

[0122] In this embodiment, the rolling process of the steel plate S is described without supplying rolling oil to the cooling coolant header 22, but the rolling process of the steel plate S may also be performed while supplying rolling oil not only to the lubrication coolant header 21 but also to the cooling coolant header 22.

[0123] In this embodiment, rolling oil used in the first rolling stand std1 or the second rolling stand std2 is collected in the first storage tank 31, and rolling oil used in the third rolling stand std3, the fourth rolling stand std4 and the fifth rolling stand std5 is collected in the second storage tank 32.

[0124] In a rolling process using a plurality of rolling stands arranged in the conveying direction of the steel sheet S, the temperature of the steel sheet S increases the further downstream in the conveying direction of the steel sheet S. Therefore, the amount of rolling oil ejected from the lubricating coolant header 21 corresponding to the rolling stand std located downstream is greater than the amount of rolling oil ejected from the lubricating coolant header 21 corresponding to the rolling stand std located upstream. As a result, the amount of rolling oil stored (recovered) in the second storage tank 32 is greater than the amount of rolling oil stored (recovered) in the first storage tank 31. That is, there is a risk that rolling oil will not be able to be supplied from the first storage tank 31 to the third rolling stand std3, the fourth rolling stand std4, and the fifth rolling stand std5. Therefore, it is possible to flow a portion of the rolling oil used in the third rolling stand std3, the fourth rolling stand std4, and the fifth rolling stand std5 toward the second storage tank 32, and the remainder toward the first storage tank 31.

[0125] In this embodiment, there is no particular limitation on the amount of rolling oil sprayed from the lubricating coolant header 21 corresponding to each rolling stand std, but the amount of rolling oil sprayed may be changed depending on the position of the lubricating coolant header 21.

[0126] In this embodiment, the rolling oil used in the rolling stand standard located downstream is supplied to the rolling stand located upstream, and the rolling oil used in these rolling stands is supplied to the rolling stand standard located downstream, thereby circulating the rolling oil. However, it is not necessary to circulate the rolling oil within the cold rolling equipment 1, and for example, it is not necessary to supply the rolling oil used in the rolling stand standard located upstream in the conveying direction of the steel sheet S to the rolling stand located downstream.

[0127] <Summary of Effects> The cold rolling method of the present invention is a cold rolling method for performing rolling processing of a steel sheet S by a plurality of rolling stands std while supplying rolling oil to each of the plurality of rolling stands std arranged along the conveying direction of the steel sheet S, and is characterized in that at least a portion of the rolling oil recovered from a rolling stand std arranged downstream in the conveying direction of the steel sheet S among the plurality of rolling stands std is supplied to a predetermined number of rolling stands std including the rolling stand std arranged most upstream in the conveying direction of the steel sheet S.

[0128] For example, in a rolling process using a plurality of standard rolling stands, the temperature of the steel sheet S increases as the number of rolling processes increases. That is, the temperature of the rolling oil used in the rolling process in the standard rolling stands arranged downstream in the conveying direction of the steel sheet S increases as the rolling process proceeds downstream. Therefore, by supplying rolling oil recovered from the standard rolling stands arranged downstream to a predetermined number of standard rolling stands, including the standard rolling stand arranged most upstream, the steel sheet S being rolled in the predetermined number of standard rolling stands is heated. As a result, in the rolling process in these standard rolling stands, it is possible to prevent the occurrence of brittle fracture in the steel sheet S.

[0129] In addition, a heating device 25 is provided which is arranged upstream of at least the rolling stand std arranged at the most upstream position in the conveying direction of the steel plate S and sprays rolling oil toward the steel plate S, and the rolling oil used in the rolling stand std arranged downstream in the conveying direction of the steel plate S is supplied to the heating device 25 as well as to a predetermined number of rolling stands std, as necessary.

[0130] According to this, the rolling oil used in the rolling stand std arranged downstream is not only supplied to a predetermined number of rolling stands std including the rolling stand std arranged most upstream, but also to the heating device 25, thereby increasing the amount of rolling oil sprayed onto the steel sheet S, and therefore the steel sheet S being rolled can be effectively heated.

[0131] The temperature of the rolling oil supplied to the predetermined number of rolling stands std is 80°C or higher.

[0132] This makes it possible to effectively heat the steel sheet S before the rolling process.

[0133] In addition, rolling oil recovered from a predetermined number of standard rolling stands is supplied to standard rolling stands excluding the predetermined number of standard rolling stands, thereby circulating the rolling oil among a plurality of standard rolling stands.

[0134] According to this, by supplying rolling oil heated in the downstream rolling stand std to the rolling stand std arranged upstream in the conveying direction of the steel sheet S, and supplying rolling oil cooled in the upstream rolling stand std to the rolling stand std arranged downstream in the conveying direction of the steel sheet S, it becomes possible to adjust the temperature of the steel sheet in the rolling process to be not less than the ductile-brittle transition temperature and not more than the temperature at which non-uniform deformation occurs, without providing a new heating device or cooling device.

[0135] In addition, the manufacturing method of the steel sheet S of the present invention includes a cold rolling process using the cold rolling method shown in the present invention, and a finish annealing process in which, if necessary, the steel sheet S that has been subjected to the cold rolling process is subjected to finish annealing.

[0136] This makes it possible to prevent brittle fracture of the steel plate, deformation of the work rolls, and deformation of the steel plate due to the deformation of the work rolls that occur during the rolling process, without the need to install new heating or cooling equipment.

[0137] The cold rolling equipment of the present invention is a cold rolling equipment for performing rolling processing of a steel sheet S by a plurality of rolling stands std while supplying rolling oil to each of the plurality of rolling stands std arranged along the conveying direction of the steel sheet S, and includes supply systems Sr1, Sr2 capable of supplying rolling oil to each of the plurality of rolling stands std, a recovery system C1 capable of recovering rolling oil from the plurality of rolling stands std, a plurality of control valves arranged in each of the supply systems Sr1, Sr2 and the recovery system C1, and a control valve in each of the plurality of control valves. and a control device 110 that switches the open / close state of each of the plurality of control valves, and by the control device 110 switching the open / close state of each of the plurality of control valves, the recovery system C1 forms a first recovery path that recovers rolling oil from the rolling stands std arranged downstream in the conveying direction of the steel plate S, and the supply systems Sr1 and Sr2 form a first supply path that supplies a portion of the rolling oil recovered by the first recovery path to a predetermined number of rolling stands std, including the rolling stand std arranged most upstream in the conveying direction of the steel plate S.

[0138] For example, in a rolling process using a plurality of standard rolling stands, the temperature of the steel sheet S increases as the number of rolling processes increases. That is, the temperature of the rolling oil used in the rolling process in the standard rolling stands arranged downstream in the conveying direction of the steel sheet S increases as the rolling process proceeds downstream. Therefore, by supplying rolling oil recovered from the standard rolling stands arranged downstream to a predetermined number of standard rolling stands, including the standard rolling stand arranged most upstream, the steel sheet S being rolled in the predetermined number of standard rolling stands is heated. As a result, in the rolling process in these standard rolling stands, it is possible to prevent the occurrence of brittle fracture in the steel sheet S.

[0139] The rolling mill further includes a heating device 25 that is arranged upstream of at least the most upstream rolling stand std in the conveying direction of the steel sheet S and is capable of spraying a portion of the rolling oil recovered from at least one rolling stand std arranged downstream in the conveying direction of the steel sheet S toward the steel sheet S.

[0140] According to this, the rolling oil used in the rolling stand std arranged downstream can be supplied not only to a predetermined number of rolling stands std including the rolling stand std arranged most upstream, but also from the heating device 25, so that the steel sheet S can be effectively heated before the rolling process.

[0141] In addition, the recovery system C1 forms a second recovery path that recovers rolling oil used in a predetermined number of rolling stands std when the first recovery path is formed, and the supply system forms a second supply path that supplies rolling oil recovered by the second recovery path to rolling stands std excluding the predetermined number of rolling stands std when the first supply path is formed.

[0142] For example, the temperature of the rolling oil used in a predetermined number of rolling stands std including the first rolling stand std1 is lower than the temperature of the rolling oil used in the rolling stands std arranged downstream of the predetermined number of rolling stands std. Therefore, by supplying such rolling oil to the rolling stands std arranged downstream, it is possible to effectively cool the steel sheet S.

[0143] Further, the control method of the cold rolling equipment of the present invention is a cold rolling method for performing rolling processing of a steel sheet S by a plurality of rolling stands std while supplying rolling oil to each of the plurality of rolling stands std arranged along the conveying direction of the steel sheet S, and the cold rolling equipment includes supply systems Sr1, Sr2 capable of supplying rolling oil to each of the plurality of rolling stands std, a recovery system C1 capable of recovering rolling oil from the plurality of rolling stands std, a plurality of control valves arranged in each of the supply systems Sr1, Sr2 and the recovery system C1, and a control system for switching the open / close state of each of the plurality of control valves. The control system has a control device 110, and by switching the open / close state of each of a plurality of control valves based on the temperature of the rolling oil supplied to the plurality of rolling stands std and the temperature of the steel sheet S due to the rolling process, a first recovery path is formed in the recovery system C1 for recovering rolling oil from the rolling stands std arranged downstream in the conveying direction of the steel sheet S, and first supply paths are formed in the supply systems Sr1 and Sr2 for supplying a portion of the rolling oil recovered by the first recovery path to a predetermined number of rolling stands std including the rolling stand std arranged most upstream in the conveying direction of the steel sheet S.

[0144] This makes it possible to easily set the rolling stand std that heats the steel sheet S during rolling processing by controlling the control valve.

[0145] In addition, the recovery system C1 forms a second recovery path that recovers rolling oil used in a predetermined number of rolling stands std when the first recovery path is formed, and the supply systems Sr1 and Sr2 form a second supply path that supplies a portion of the rolling oil recovered by the second recovery path to rolling stands std excluding the predetermined number of rolling stands std when the first supply path is formed.

[0146] According to this, by using the rolling oil circulated among the plurality of rolling stands, a rolling process can be performed in each rolling stand, with the temperature of the steel sheet S being in a range of not less than the ductile-brittle transition temperature and not more than the temperature at which non-uniform deformation occurs. As a result, it is possible to prevent the occurrence of brittle fracture during the rolling process, deformation of the work rolls, and deformation of the steel sheet S due to the deformation of the work rolls.

[0147] REFERENCE SIGNS LIST 1 Cold rolling equipment 2 Rolling mill 21 Lubrication coolant header 22 Cooling coolant header 25 Heating device 31 First storage tank 32 Second storage tank 33 Third storage tank S Steel plate std Rolling stand Sr1 First supply system Sr2 Second supply system C1 Recovery system

Claims

1. A cold rolling method for rolling a steel plate using a plurality of rolling stands arranged along the conveying direction of the steel plate while supplying rolling oil to each of the plurality of rolling stands, characterized in that at least a portion of the rolling oil recovered from a rolling stand arranged downstream in the conveying direction of the steel plate among the plurality of rolling stands is supplied to a predetermined number of rolling stands including the rolling stand arranged most upstream in the conveying direction of the steel plate.

2. A cold rolling method as described in claim 1, characterized in that it comprises a rolling oil spraying device that is arranged upstream of at least the rolling stand arranged at the most upstream position in the conveying direction of the steel plate and sprays the rolling oil toward the steel plate, and the rolling oil used in the rolling stand arranged downstream in the conveying direction of the steel plate is supplied to the predetermined number of rolling stands as well as to the rolling oil spraying device as necessary.

3. A cold rolling method according to claim 1, characterized in that the temperature of the rolling oil supplied to the predetermined number of rolling stands is 80°C or higher.

4. A cold rolling method as described in claim 1, characterized in that the rolling oil recovered from the predetermined number of rolling stands is supplied to rolling stands other than the predetermined number of rolling stands, and the rolling oil is circulated among the plurality of rolling stands.

5. A method for manufacturing a steel sheet, comprising: a cold rolling step using the cold rolling method according to any one of claims 1 to 4; and a finish annealing step of, as necessary, subjecting the steel sheet that has been subjected to the cold rolling step to finish annealing.

6. A cold rolling facility that performs rolling processing of a steel plate using a plurality of rolling stands while supplying rolling oil to each of the plurality of rolling stands arranged along the conveying direction of the steel plate, the cold rolling facility comprising: a supply system capable of supplying rolling oil to each of the plurality of rolling stands; a recovery system capable of recovering the rolling oil from the plurality of rolling stands; a plurality of control valves arranged in each of the supply system and the recovery system; and a control device that switches the open / close state of each of the plurality of control valves, wherein the control device switches the open / close state of each of the plurality of control valves, so that the recovery system forms a first recovery path that recovers the rolling oil from the rolling stand arranged downstream in the conveying direction of the steel plate, and the supply system forms a first supply path that supplies a portion of the rolling oil recovered by the first recovery path to a predetermined number of rolling stands including the rolling stand arranged most upstream in the conveying direction of the steel plate.

7. The cold rolling equipment according to claim 6, further comprising a rolling oil ejection device that is arranged upstream of at least the most upstream rolling stand in the conveying direction of the steel plate and that is arranged downstream in the conveying direction of the steel plate and is capable of ejecting a portion of the rolling oil recovered from at least one or more of the rolling stands toward the steel plate.

8. A cold rolling facility as described in claim 6 or claim 7, characterized in that the recovery system forms a second recovery path that recovers rolling oil used in the specified number of rolling stands when the first recovery path is formed, and the supply system forms a second supply path that supplies rolling oil recovered by the second recovery path to rolling stands excluding the specified number of rolling stands when the first supply path is formed.

9. A method for controlling cold rolling equipment that supplies rolling oil to each of a plurality of rolling stands arranged along a conveying direction of a steel plate while performing rolling processing on the steel plate using the plurality of rolling stands, wherein the cold rolling equipment comprises: a supply system capable of supplying rolling oil to the plurality of rolling stands; a recovery system capable of recovering rolling oil used in the plurality of rolling stands; a plurality of control valves arranged in each of the supply system and the recovery system; and a control device that switches the open / closed state of each of the plurality of control valves, a control device for controlling a cold rolling facility, the control device switching the open / close state of each of the plurality of control valves based on the temperature of the rolling oil supplied to the plurality of rolling stands and the temperature of the steel plate, thereby forming a first recovery path in the recovery system for recovering the rolling oil from a rolling stand arranged downstream in the conveying direction of the steel plate, and forming a first supply path in the supply system for supplying a portion of the rolling oil recovered by the first recovery path to a predetermined number of rolling stands including the rolling stand arranged most upstream in the conveying direction of the steel plate.

10. A method for controlling cold rolling equipment as described in claim 9, characterized in that the recovery system forms a second recovery path that recovers the rolling oil from the specified number of rolling stands when the first recovery path is formed, and the supply system forms a second supply path that supplies a portion of the rolling oil recovered by the second recovery path to rolling stands excluding the specified number of rolling stands when the first supply path is formed.

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