Cold rolling equipment, cold rolling method, and method for manufacturing cold-rolled metal sheet

Abstract

The present invention provides a cold rolling technology capable of suppressing chattering. The cold rolling equipment comprises a cold tandem rolling mill equipped with multiple rolling stands, a rolling oil supply system that supplies rolling oil to the cold tandem rolling mill, multiple strip thermometers that measure the strip temperature of the rolled material on the entry or exit side of each rolling stand, and a control unit that controls rolling conditions including the rolling oil to be supplied to the entry side of each rolling stand, wherein the rolling oil supply system has a first rolling oil supply system that supplies a first emulsion rolling oil and a second rolling oil supply system that supplies a second emulsion rolling oil having a higher oil concentration than the first emulsion rolling oil, and the control unit is configured to adjust the mixing ratio of the first emulsion rolling oil and the second emulsion rolling oil at the entry side of a specific stand based on the measurement results of the strip thermometers on the entry or exit side of the specific stand, and supply the mixed rolling oil to the specific stand.

Description

[Technical Field]

[0001] The present invention relates to cold rolling equipment, a cold rolling method, and a method for producing a cold-rolled metal sheet.In this specification, "x to y" representing a range of numerical values ​​means not less than x and not more than y, and includes the boundary value. [Background technology]

[0002] Generally, when a material to be rolled, such as a steel plate, is cold-rolled using rolls, rolling oil is supplied to the rolls. Rolling oil serves as a lubricant that reduces friction between the material to be rolled and the rolls, that is, as a lubricant. In addition, rolling oil also serves as a coolant that cools the material to be rolled and the rolls to prevent excessive temperature rise due to frictional heat and processing heat generated during rolling. Known methods for supplying rolling oil during cold rolling include a direct oil supply method, in which rolling oil is not circulated, and a circulating oil supply method, in which rolling oil is circulated. The direct oil supply method is also called the direct method, and the circulating oil supply method is also called the recirculation method.

[0003] Recently, there has been an increasing need for thin, high-strength, thin-gauge hard materials, with the aim of reducing fuel consumption through weight reduction in automobiles and other vehicles. However, when rolling oil is supplied using the conventional circulating oil supply method during high-load cold rolling, insufficient lubrication can occur, resulting in vertical mill vibration known as chattering. Chattering often occurs at frequencies of around 100 to 200 Hz. When chattering occurs, the thickness of the material being rolled tends to fluctuate periodically. Therefore, chattering can hinder the productivity of high-value-added products.

[0004] In light of this background, Patent Document 1 aims to improve lubricity by supplying two types of emulsion rolling oil with different concentrations based on horizontal mill vibrations occurring at a frequency of several tens of Hz (approximately 30 to 100 Hz). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2022-071919 Summary of the Invention [Problem to be solved by the invention]

[0006] However, the conventional technology has the following problems. In the technology disclosed in Patent Document 1, two types of emulsion rolling oil with different concentrations are supplied, taking horizontal vibration into consideration. Incidentally, as shown in FIG. 3, the adhesion efficiency of the oil in the emulsion to the rolled material increases as the temperature of the rolled material increases at low temperatures, but then decreases after peaking at the temperature at which film boiling occurs. It is generally desirable to increase the mixing ratio of emulsion rolling oil with a high oil concentration when supplying the rolled material. As the oil concentration of the emulsion increases, the strip temperature during rolling is more likely to rise. As a result, when the rolled material exceeds the above-mentioned peak temperature, the adhesion efficiency of the emulsion oil to the rolled material decreases. Therefore, it is desirable to also consider the strip temperature when determining the mixing ratio of emulsions with different oil concentrations. However, this is not particularly taken into consideration in Patent Document 1.

[0007] The present invention has been made in consideration of the above circumstances, and has an object to provide a cold rolling facility and a cold rolling method that can suppress the occurrence of horizontal chattering while taking into consideration the sheet temperature of the rolled material. Another object of the present invention is to provide a cold rolled metal sheet manufacturing method that can manufacture cold rolled metal sheets with a high yield. [Means for solving the problem]

[0008] The cold rolling equipment of the present invention, which advantageously solves the above-mentioned problems, comprises: a cold tandem rolling mill equipped with a plurality of rolling stands; a rolling oil supply system which supplies rolling oil to the cold tandem rolling mill; a plurality of strip thermometers which measure the strip temperature of the rolled material at the entry or exit of each rolling stand; and a control unit which controls rolling conditions including the rolling oil to be supplied to the entry of each rolling stand, wherein the rolling oil supply system has a first rolling oil supply system which supplies a first emulsion rolling oil, and a second rolling oil supply system which supplies a second emulsion rolling oil having a higher oil concentration than the first emulsion rolling oil, and the control unit is configured to adjust the mixing ratio of the first emulsion rolling oil and the second emulsion rolling oil at the entry of a specific stand based on the measurement results of the strip thermometers at the entry or exit of the specific stand, and supply mixed rolling oil to the specific stand.

[0009] Furthermore, a more preferable solution is that the cold rolling equipment of the present invention is equipped with a coolant supply system that supplies coolant to the cold tandem rolling mill, and the control unit is further configured to control the flow rate of the coolant supplied to the rolled material on the inlet side of the specific stand based on the measurement results of the plate temperature gauge.

[0010] The cold rolling method of the present invention, which advantageously solves the above problem, is characterized in that when cold rolling a material to be rolled using the cold rolling equipment, if the plate temperature measured by a specific plate thermometer is equal to or higher than a predetermined value, the mixing ratio of the mixed rolling oil or the flow rate of the coolant is changed to adjust the plate temperature of the specific plate thermometer to be below the predetermined value.

[0011] The method for producing a cold-rolled metal sheet according to the present invention, which advantageously solves the above-mentioned problems, is characterized in that a cold-rolled metal sheet is produced by cold-rolling a metal plate as a rolling target material using the above-mentioned cold rolling method. [Effects of the Invention]

[0012] According to the cold rolling equipment and the cold rolling method of the present invention, it is possible to suppress the occurrence of vibration during cold rolling. Furthermore, according to the cold rolled metal sheet manufacturing method of the present invention, it is possible to manufacture the cold rolled metal sheet with a high yield. [Brief explanation of the drawings]

[0013] [Figure 1] 1 is a schematic diagram showing the configuration of a cold rolling facility according to an embodiment of the present invention. [Figure 2] FIG. 2 is a schematic diagram showing the configuration of a rolling oil supply control unit according to one embodiment of the present invention. [Figure 3] 1 is a graph showing the relationship between the adhesion efficiency of oil to a material being rolled during cold rolling and the temperature of the material being rolled. DETAILED DESCRIPTION OF THE INVENTION

[0014] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. The following embodiments are merely examples of devices and methods for embodying the technical concept of the present invention, and are not intended to limit the configuration to the following. In other words, the technical concept of the present invention can be modified in various ways within the technical scope defined in the claims.

[0015] A cold rolling facility, a cold rolling method, and a method for manufacturing a cold-rolled metal sheet according to one embodiment of the present invention will be described. The rolling oil used in this embodiment may be either a petroleum-based or emulsion-based rolling oil. However, since cold rolling oils in the steel industry generally require high cooling performance, emulsion-based rolling oils, i.e., emulsion rolling oils, are often used as rolling oils. Therefore, in the following embodiment, emulsion rolling oils (hereinafter simply referred to as "emulsion") will be used as an example of the rolling oil.

[0016] An emulsion is a liquid mixture in which rolling oil particles are stably suspended in water. The properties of an emulsion are characterized by the oil concentration and the average particle size of the oil droplets. The concentration of an emulsion is the ratio of the oil mass to the total mass of the emulsion. The average particle size of an emulsion is the average particle size of the rolling oil droplets in the emulsion. To produce an emulsion, a surfactant must be added to emulsify the oil in water. The amount of surfactant added is a predetermined amount expressed as the mass concentration relative to the amount of rolling oil (oil concentration). After adding the surfactant, the average particle size of the emulsion is adjusted by applying shear using a mixer and a pump. An example of an emulsion rolling oil is an O / W emulsion in which rolling oil is diluted with warm water or the like to a concentration of about 1 to 5% by mass and dispersed in water using a surfactant, i.e., an oil-in-water type rolling oil.

[0017] 〔composition〕 First, the configuration of a cold rolling facility according to one embodiment of the present invention will be described with reference to Fig. 1. Fig. 1 is a schematic diagram showing the configuration of a cold rolling facility according to one embodiment of the present invention. In the following description, a steel sheet S will be used as an example of a material to be rolled by the cold rolling facility, i.e., a material to be rolled. However, the material to be rolled may also be an aluminum sheet or other metal sheet.

[0018] As shown in FIG. 1, the cold rolling equipment 100 according to this embodiment includes a cold tandem rolling mill 200. The cold tandem rolling mill 200 has five rolling stands, numbered from a first rolling stand (#1STD) to a fifth rolling stand (#5STD), arranged in order from the entry side where the steel sheet S enters to the exit side. The entry side of the cold tandem rolling mill 200 is on the left side of the paper in FIG. 1, and the exit side of the cold tandem rolling mill 200 is on the right side of the paper in FIG. 1. While FIG. 1 shows a configuration with five stands, the present invention is not limited to this. In this cold tandem rolling mill 200, tension rolls, diff-rolls, thickness gauges, and shape gauges (not shown) are appropriately installed between adjacent rolling stands. The configuration of the cold tandem rolling mill 200 and the conveying device for the steel sheet S are not particularly limited, and known techniques may be applied as appropriate.

[0019] Emulsified rolling oil (hereinafter, "emulsified rolling oil" may be simply referred to as "rolling oil") is supplied to each rolling stand of the cold tandem rolling mill 200. In this embodiment, a first rolling oil supply system 2 and a second rolling oil supply system 14 are provided as rolling oil supply systems that supply rolling oil to each rolling stand.

[0020] The cold rolling facility 100 is equipped with a dirty tank 5 and a clean tank 7 as rolling oil storage tanks, which serve as recovery tanks. The rolling oil stored in these rolling oil storage tanks is supplied to each rolling stand through a first rolling oil supply system 2 and a second rolling oil supply system 14. Rolling oil recovered by an oil pan 10 located below each rolling stand, i.e., rolling oil used in cold rolling, flows into the dirty tank 5 through a return pipe 11.

[0021] The rolling oil stored in the clean tank 7 is clean rolling oil formed by mixing hot water (dilution water) with a rolling oil stock solution containing surfactants. The mixture of hot water and rolling oil stock solution is converted into a rolling oil having the desired average particle size and concentration range by adjusting the rotation speed of the agitator blades of the agitator 12, i.e., by adjusting the degree of agitation. Rolling oil stock solutions used in conventional cold rolling can be used. For example, those based on natural fats and oils, fatty acid esters, or hydrocarbon-based synthetic lubricants can be used. Furthermore, these rolling oils may contain additives commonly used in conventional cold rolling oils, such as oiliness improvers, extreme-pressure additives, and antioxidants. Surfactants added to the rolling oil may be either ionic or nonionic, and any surfactant used in a conventional circulating oil supply system may be used. The rolling oil stock solution is then diluted to an oil content of preferably 2.0 to 8.0% by mass, more preferably 3.0 to 6.0% by mass. Alternatively, the rolling oil may be an O / W emulsion in which oil is dispersed in water using a surfactant as described above. The average particle size of the oil droplets in the emulsion is preferably 15 μm or less, more preferably in the range of 3 to 10 μm.

[0022] After the start of operation, the rolling oil recovered in the dirty tank 5 is supplied to the clean tank 7 via an iron particle removal device 6, which includes an iron particle amount control device and the like. The rolling oil recovered in the dirty tank 5 contains wear particles such as iron particles generated by friction between the rolling rolls and the steel sheet S. The iron particle removal device 6 removes the wear particles so that the dissolved iron content in the recovered rolling oil becomes acceptable for the rolling oil stored in the clean tank 7. The transfer of emulsion rolling oil from the dirty tank 5 to the clean tank 7 via the iron particle removal device 6 may be continuous or intermittent. The iron particle removal device 6 is preferably a magnetic filter, such as an electromagnetic filter or a magnetic separator, that adsorbs and removes iron particles, but is not limited to this. The iron particle removal device 6 may also be a known device that uses a method such as centrifugation.

[0023] Incidentally, a portion of the rolling oil supplied to the cold rolling equipment 100 is carried out of the system by the steel sheet S or is lost due to evaporation. For this reason, the system is configured such that undiluted rolling oil is appropriately replenished (supplied) from a concentrate tank (not shown) so that the storage level and concentration of the rolling oil in the clean tank 7 are within a predetermined range. In addition, hot water for dilution is also appropriately replenished (supplied) to the clean tank 7. The storage level and concentration of the first emulsion rolling oil 13 in the clean tank 7 can be measured by a sensor (not shown).

[0024] The emulsion tank 19 is connected to a rolling oil crude oil tank 22 and a hot water tank 23. The rolling oil crude oil stored in the rolling oil crude oil tank 22 and the hot water stored in the hot water tank 23 are fed into the emulsion tank 19 via a pump and a flow control valve 21 (not shown). At the same time, they are mixed in the emulsion tank 19 by an agitator 20. The conditions of the rolling oil in the emulsion tank 19 do not need to be the same as those of the rolling oil in the clean tank 7. The average particle size of the oil droplets of the second emulsion rolling oil 15 in the emulsion tank 19 is adjusted to 10 to 30 μm by adjusting the rotation speed of the agitator blades of the agitator 20, and the oil concentration is adjusted to a range of 3 to 20 mass%.

[0025] Next, the first rolling oil supply system 2 and the second rolling oil supply system 14 will be described in detail. Both the first rolling oil supply system 2 and the second rolling oil supply system 14 have a dirty tank 5, an iron powder removal device 6, a clean tank 7, and a pump 8 that sucks up rolling oil from the clean tank 7. The first rolling oil supply system 2 and the second rolling oil supply system 14 branch off downstream of the pump 8. The following description will focus on the configuration after the branching point. A strainer for removing foreign matter may be placed between the clean tank 7 and the pump 8.

[0026] [1st rolling oil supply system] The first rolling oil supply system 2 includes a first rolling oil pipeline 9 connected at one end to a clean tank 7 as a first rolling oil supply line. The other end of the first rolling oil pipeline 9 branches off on the rolling mill side. The first rolling oil supply system 2 includes five sets of lubricating coolant headers 3 and five sets of cooling coolant headers 4, each of which is located at a position corresponding to each rolling stand. Each lubricating coolant header 3 is located on the entry side of the rolling stand and sprays rolling oil as lubricating oil toward the roll bite from spray nozzles provided on each header. This supplies rolling oil to the roll bite and work rolls. The cooling coolant headers 4 are located on the exit side of the rolling stand and spray rolling oil toward the rolls from spray nozzles provided on each header. This cools the rolls.

[0027] With this configuration, in the first rolling oil supply system 2, rolling oil in the clean tank 7 is pumped by a pump 8 to a first rolling oil pipe 9. Hereinafter, the rolling oil pumped to the first rolling oil pipe 9 and supplied to each rolling stand will also be referred to as a first emulsified rolling oil 13. The first emulsified rolling oil 13 is supplied through the first rolling oil pipe 9 to a lubrication coolant header 3 and a cooling coolant header 4 arranged in each rolling stand, and is sprayed from spray nozzles provided in each. The first emulsified rolling oil 13 supplied to the rolling rolls is recovered in an oil pan 10 and returned to the dirty tank 5 through a return pipe 11, except for the oil that has been carried out of the system by the steel sheet S or lost due to evaporation. Thereafter, a part of the emulsion rolling oil stored in the dirty tank 5 is returned to the clean tank 7 via the iron powder removal device 6 in order to remove a certain amount of dissolved iron in the emulsion rolling oil generated by cold rolling, as described above.

[0028] With the above-described configuration of the first rolling oil supply system 2, rolling oil from which abrasion powder has been removed is circulated and supplied to the rolling rolls. That is, the first emulsion rolling oil 13 is circulated and used. Here, the clean tank 7 corresponds to the rolling oil tank for circulation in the conventional circulating oil supply system, and undiluted rolling oil is replenished (supplied) to the clean tank 7 as needed, as described above.

[0029] [Second rolling oil supply system] The second rolling oil supply system 14 comprises a second rolling oil pipeline 16 having one end connected to the first rolling oil pipeline 9, and a third rolling oil pipeline 24 having one end connected to an emulsion tank 19. The second rolling oil supply system 14 has the other end of the second rolling oil pipeline 16 branched off on the rolling mill side. The second rolling oil supply system 14 has five flow control valves 17 whose branched ends are respectively arranged at positions corresponding to each rolling stand, and to which the other end of the third rolling oil pipeline 24 is connected. The second rolling oil supply system 14 comprises a mixed rolling oil pipeline 26 having one end connected to the flow control valve 17, and a lubrication coolant header 25 to which the other end of the mixed rolling oil pipeline 26 is connected.

[0030] The emulsion tank 19 is connected to a rolling crude oil tank 22 and a hot water tank 23. The rolling crude oil stored in the rolling crude oil tank 22 and the hot water stored in the hot water tank 23 are fed into the emulsion tank 19 via a pump (not shown) and a flow control valve 21. At the same time, they are mixed in the emulsion tank 19 by an agitator 20. In the following description, the rolling oil in the emulsion tank 19 may also be referred to as second emulsion rolling oil 15.

[0031] The temperature conditions of the second emulsion rolling oil 15 are preferably the same as those of the first emulsion rolling oil 13. However, from the viewpoint of improving the cooling capacity of the steel sheet S in the subsequent rolling stands, the temperature of the second emulsion rolling oil 15 may be set lower than that of the first emulsion rolling oil 13 via a cooling device (not shown). In addition, the concentration conditions and particle size conditions of the rolling oil in the second emulsion rolling oil 15 do not need to be the same as those of the first emulsion rolling oil 13.

[0032] The first emulsified rolling oil 13 stored in the clean tank 7 is supplied to the flow control valve 17 through the second rolling oil pipeline 16 by driving the pump 8. The second emulsified rolling oil 15 is supplied to the flow control valve 17 through the third rolling oil pipeline 24 by the pump 18. The second emulsified rolling oil 15 is then mixed with the first emulsified rolling oil 13 in the flow control valve 17 to form a mixed rolling oil containing the second emulsified rolling oil 15 having a predetermined emulsion concentration. This mixed rolling oil is sent to a lubricating coolant header 25 of each rolling stand through a mixed rolling oil pipeline 26. The lubricating coolant header 25 is arranged branching out to both the front and back sides of the steel sheet S. This makes it possible to spray mixed rolling oil of a desired concentration from multiple spray nozzles toward both the front and back sides of the steel sheet S. Subsequently, the rolling oil collected in the oil pan 10 is returned to the dirty tank 5 through a return pipe 11 and is recycled for reuse.

[0033] The flow control valve 17 may control the flow rate of the second emulsion rolling oil 15 relative to the flow rate of the first emulsion rolling oil 13. Alternatively, the second emulsion rolling oil 15 may be supplied directly to the steel sheet S without going through the flow control valve 17 constituting the mixing section. More preferably, a mixed rolling oil obtained by mixing the first emulsion rolling oil 13 and the second emulsion rolling oil 15 is supplied.

[0034] As described above, the flow control valve 17 constitutes a mixing section that mixes the first emulsion rolling oil 13 and the second emulsion rolling oil 15. The opening of the flow control valve 17 is adjusted in response to a command from the supply control section 38 shown in Fig. 2, and this adjustment adjusts the mixing ratio of the first emulsion rolling oil 13 and the second emulsion rolling oil 15. When the second emulsion rolling oil 15 is supplied directly to the steel sheet S without going through the flow control valve 17, the supply rate ratio of the first emulsion rolling oil 13 and the second emulsion rolling oil 15 can be read as the mixing ratio.

[0035] [Coolant supply system] The coolant supply system 31 includes a coolant tank 29, a coolant line 32, a flow control valve 17, a coolant header 27, and a strip temperature measuring device 30. In the example of FIG. 1, the coolant tank 29 stores coolant 28, which is supplied between each rolling stand. Alternatively, rolling oil may be supplied as a coolant by branching off from the first rolling oil system or the second rolling oil system. In the example of FIG. 1, the strip temperature measuring device 30 is installed on the exit side of each rolling stand, but it may also be installed on the entry side. In the example of FIG. 1, the strip temperature measuring device 30 is a non-contact type, but it may also be a contact type. The coolant flow rate is adjusted according to commands from a supply control unit 38 shown in FIG. 2.

[0036] [Method for controlling supply of mixed rolling oil and coolant] Next, with reference to FIG. 2, a method for controlling the supply of mixed rolling oil (method for controlling the mixing ratio) and a method for controlling the supply of coolant (method for controlling the flow rate of coolant) by the supply control unit 38 will be described.

[0037] Fig. 2 is a schematic diagram showing the configuration of a supply control unit according to one embodiment of the present invention. The supply control unit 38 adjusts the strip temperature of any one of the five rolling stands to a set temperature to ensure optimal lubrication. While Fig. 2 shows a configuration of five rolling stands, the present invention is not limited to this.

[0038] [Method for controlling the supply of mixed rolling oil] 2, the supply control unit 38 includes a strip temperature acquisition unit 33, a rolling oil mixing ratio calculation unit 34, and a rolling oil mixing ratio control unit 36. The supply control unit 38 may be built into the cold tandem rolling mill 200, or may be built into an operation panel connected wirelessly or by wire to the cold tandem rolling mill 200. Here, the operation panel is an operation member used when an operator himself sets the rolling conditions, etc., for the cold tandem rolling mill 200.

[0039] In this mixed rolling oil supply control method, a strip temperature acquisition unit 33 acquires the strip temperature at the exit of each rolling stand and transmits a preset rotational speed to a rolling oil mixing ratio control unit 36 ​​in a rolling oil mixing ratio calculation unit 34 according to the difference in strip temperature from a preset strip temperature target. Then, in response to a command from the rolling oil mixing ratio control unit 36, the rotational speed of the motor for changing the rolling oil mixing ratio of the relevant rolling stand is changed. While the above example changes the motor rotational speed to a preset value, it is also possible to adjust the motor rotational speed by 1 rpm increments until the set temperature is reached. If the measured temperature is higher than the target temperature, the motor rotational speed is reduced to reduce the rolling oil mixing ratio and increase thermal conductivity, thereby lowering the steel strip temperature. While the rolling oil mixing ratio is changed by the motor rotational speed in the above example, it may also be changed by changing the valve opening.

[0040] [Coolant supply control method] As shown in FIG. 2, the supply control unit 38 includes a strip temperature acquisition unit 33, a coolant flow rate calculation unit 35, and a coolant flow rate control unit 37.

[0041] In the coolant supply control method, the strip temperature acquisition unit 33 acquires the strip temperature at the exit of each rolling stand, passes the valve opening preset in the coolant flow rate calculation unit 35 to the rolling oil mixing ratio control unit 36 ​​according to the strip temperature difference from a preset strip temperature target, and changes the opening of the coolant flow rate changing valve between the rolling stand in question and the preceding rolling stand according to a command from the coolant flow rate control unit 37.

[0042] In the above example, the coolant flow rate is changed by changing the valve opening, but this can also be done by changing the motor rotation speed. In the above example, the valve opening is changed to a preset value, but it is also possible to change the valve opening by 1% increments and adjust it until the set temperature is reached. If the measured temperature is higher than the target temperature, the valve opening can be increased to increase the coolant flow rate, increasing the amount of heat dissipation and reducing the steel plate temperature.

[0043] In the above, the supply of mixed rolling oil and the supply of coolant are carried out separately, but both may be controlled together. In the latter case, they may be controlled simultaneously without considering the interference between them. Alternatively, the rolling oil mixture ratio may be changed preferentially, and the coolant flow rate may be adjusted when the rolling oil mixture ratio reaches its lower limit. Furthermore, the coolant flow rate may be changed, and the rolling oil mixture ratio may be adjusted when the coolant flow rate reaches its upper limit.

[0044] The method of supplying the mixed rolling oil and the method of controlling the coolant may be controlled for all rolling stands, or may be controlled for a single rolling stand or multiple rolling stands. As a criterion, it is preferable to control only the rolling stand that detects a strip temperature that is outside a preset temperature, or multiple rolling stands including those before and after it. [Example]

[0045] The present invention will be described below based on examples, but the following examples are not intended to limit the present invention.

[0046] In this example, a tandem cold rolling mill shown in FIG. 1 was used to cold roll a base steel sheet for electrical steel sheets containing 2.5 mass% Si and 3.0 mass% Si, with a base thickness of 2.0 mm and a width of 1000 mm, to a finished thickness of 0.300 mm. The supply of rolling oil and coolant was controlled by a supply control unit configured as shown in FIG. 2. In the rolling process according to this example, the lower limit of the rotational speed of the motor for changing the oil mixture ratio was set to, for example, 500 rpm, and the upper limit of the opening of the coolant supply valve was set to 100%. The initial valve opening was set to 50%, and the initial rotational speed of the motor for changing the oil mixture ratio was set to 3000 rpm. It is known that base steel sheets for electrical steel sheets are hard and prone to chattering when rolling at a low rolling speed or other high load. The rolling oil stock solution used was a synthetic ester oil-based base oil to which vegetable oil had been added, to which 1% by mass of an oiliness agent and antioxidant had been added, and a nonionic surfactant was also added at a concentration of 3% by mass relative to the oil. The first emulsion rolling oil 13 supplied from the first rolling oil supply system 2 and recycled was prepared to have a rolling oil concentration of 3.5% by mass, an average particle size of 5 μm, and a temperature of 55°C. Table 1 summarizes the various test conditions and results. In this example, the peak temperature at which film boiling occurred, as shown in Figure 3, was 260°C.

[0047] [Table 1]

[0048] In Test No. 1, the temperature reading of strip thermometer No. 3 reached the peak temperature at which film boiling occurs before control, so the mixing ratio of the mixed rolling oil supplied from the second rolling oil supply system on the inlet side of the third rolling stand #3STD was controlled. After controlling the supply of rolling oil, the temperature from strip thermometer No. 3 onwards decreased, and no chattering was observed.

[0049] In test No. 2, the temperature reading of strip thermometer No. 3 at the strip temperature before control exceeded the peak temperature at which film boiling occurs, so the mixing ratio of the mixed rolling oil supplied from the second rolling oil supply system on the inlet side of the third rolling stand #3STD and the flow rate of the coolant were controlled. After controlling the supply of rolling oil, the temperature reading of strip thermometer No. 3 fell below the peak temperature at which film boiling occurs, and the temperatures from strip thermometer No. 4 onwards also fell, with no chattering observed.

[0050] In test No. 3, the temperature measured by plate thermometer No. 3 exceeded the peak temperature at which film boiling occurs before control. Chattering occurred as a result of not controlling the mixing ratio of the rolling oil or the flow rate of the coolant.

[0051] In Test No. 4, the measured temperature was below the peak temperature at which film boiling occurred in all rolling stands, and rolling could be continued without chattering.

[0052] In tests Nos. 5 to 8, the measured temperature values ​​of plate thermometers Nos. 2, 1, 4, and 5 at the plate temperature before control were above the peak temperature at which film boiling occurs. The control procedures for each test were the rolling oil mixture ratio and coolant flow rate, the rolling oil mixture ratio and coolant flow rate, and the rolling oil mixture ratio and coolant flow rate. As a result, all measured temperature values ​​were below the peak temperature at which film boiling occurs, and no chattering occurred.

[0053] In test No. 9, the temperature reading from strip thermometer No. 3 exceeded the peak temperature at which film boiling occurs before control. The rolling oil mixture ratio and coolant flow rate were adjusted at the affected third rolling stand, #3STD, and the immediately preceding second rolling stand, #2STD. As a result, the temperature readings from strip thermometer No. 2 onwards decreased, and all temperature readings fell below the peak temperature at which film boiling occurs, preventing chattering.

[0054] In test No. 10, the temperature readings from strip thermometers No. 3 to No. 5 exceeded the peak temperature at which film boiling occurs before control. The rolling oil mixture ratio and coolant flow rate were adjusted in the corresponding No. 3 to No. 5 rolling stands #3 to #5STD. As a result, the temperature readings from strip thermometer No. 3 onwards decreased, and all temperature readings were below the peak temperature at which film boiling occurs, preventing chattering.

[0055] Although the present invention has been described above as an embodiment, the present invention is not limited to the description and drawings that form part of the disclosure of the present invention. In other words, other embodiments, examples, and operational techniques that can be made by those skilled in the art based on the present invention are all included in the scope of the present invention. [Explanation of symbols]

[0056] S steel plate 2 (First) rolling oil supply system (first rolling oil supply means) 3 Lubrication coolant header 4 Coolant header 5. Dirty Tank 6. Iron powder removal device 7 Clean Tank 8. Pump 9. First rolling oil pipeline (supply line) 10 Oil pan 11 Return piping 12 Stirrer 13 First emulsion rolling oil 14 (Second) rolling oil supply system (second rolling oil supply means) 15 Second emulsion rolling oil 16 Second rolling oil pipeline (supply line) 17 Flow control valve 18 Pump 19 Emulsion Tank 20 Stirrer 21 Flow control valve 22 Rolled Crude Oil Tank 23 Hot water tank 24 Third rolling oil pipeline (supply line) 25 Lubrication coolant header 26 Mixed rolling oil pipeline 27 Coolant Header 28 Coolant 29 Coolant Tank 30 Plate temperature measuring device 31 Coolant supply system 32 Coolant pipe (supply line) 33 Board temperature acquisition section 34 Rolling oil mixing ratio calculation section 35 Coolant flow rate calculation unit 36 Rolling oil mixing ratio control unit 37 Coolant flow control section 38 Supply control section 100 Cold rolling equipment 200 Tandem Cold Rolling Mill #1STD~#5STD (1st~5th) rolling stands

Claims

1. a cold tandem rolling mill having a plurality of rolling stands; a rolling oil supply system for supplying rolling oil to the cold tandem rolling mill; a plurality of strip temperature meters for measuring the strip temperatures of the rolled material on the entry side or exit side of each rolling stand; a control unit for controlling rolling conditions including rolling oil supplied to the inlet side of each rolling stand, the rolling oil supply system includes a first rolling oil supply system that supplies a first emulsion rolling oil, and a second rolling oil supply system that supplies a second emulsion rolling oil having an oil content higher in concentration than the first emulsion rolling oil; the control unit is configured to adjust the mixing ratio of the first emulsion rolling oil and the second emulsion rolling oil at the entry side of a specific stand based on the measurement result of the strip temperature gauge at the entry side or the exit side of the specific stand so that the strip temperature becomes a target temperature that is lower than the peak temperature at which film boiling occurs, and supply the mixed rolling oil to the specific stand.

2. a coolant supply system for supplying a coolant to the cold tandem rolling mill; 2. The cold rolling facility according to claim 1, wherein the control unit is further configured to control the flow rate of the coolant supplied to the rolled material on the inlet side of the specific stand based on the measurement result of the plate temperature gauge so that the plate temperature becomes a target temperature that is lower than a peak temperature at which film boiling occurs.

3. When cold rolling a material to be rolled by the cold rolling equipment according to claim 1 or 2, A cold rolling method in which, when the strip temperature measured by a specific strip thermometer is equal to or higher than a predetermined value, the mixing ratio of the mixed rolling oil or the flow rate of the coolant is changed to adjust the strip temperature measured by the specific strip thermometer to be below the predetermined value.

4. A method for producing a cold-rolled metal sheet, comprising cold-rolling a metal sheet as a rolling target material by the cold rolling method according to claim 3 to produce a cold-rolled metal sheet.

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