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

Abstract

To provide a cold rolling technology that can suppress chatter, the cold rolling equipment includes: a tandem cold rolling mill having a plurality of mill stands, a rolling oil supply system for supplying rolling oil to the tandem cold rolling mill, a plurality of plate thermometers for measuring the plate temperature of the rolled material at the entrance or exit side of each mill stand, and a control unit for controlling the rolling conditions including the rolling oil supplied to the entrance side of each mill stand. The rolling oil supply system includes: a first rolling oil supply system for supplying a first emulsion rolling oil, and a second rolling oil supply system for supplying a second emulsion rolling oil with a higher oil component 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 entrance side of a specific mill stand based on the measurement results of the plate thermometers at the entrance or exit side of that specific mill stand, thereby supplying mixed rolling oil to that specific mill stand.

Description

[Technical Field]

[0001] This invention relates to cold rolling equipment, cold rolling method, and method for manufacturing cold-rolled metal sheets. In this specification, "x~y" refers to values ​​above x and below y, including boundary values. [Previous Technology]

[0002] Typically, rolling oil is supplied to the rolls during cold rolling of steel plates and other rolling materials using rolling rolls. The function of rolling oil is to act as a lubricant, reducing friction between the rolling material and the rolls. Additionally, rolling oil also functions as a coolant to prevent excessive temperature rise in the rolling material and rolls due to frictional and processing heat generated during rolling. Known methods for supplying rolling oil during cold rolling include direct oil supply (where the rolling oil is not recycled) and recirculating oil supply (where the rolling oil is recycled). Direct oil supply is also called the direct method, and recirculating oil supply is also called the recirculation method.

[0003] Furthermore, in recent years, the demand for high-strength, thin-gauge, and rigid materials has been increasing in order to reduce fuel consumption through lightweighting of automobiles and other products. However, during high-load cold rolling, if the conventional circulating oil supply method is used to supply oil to the rolls, insufficient lubrication can sometimes occur, resulting in mill vibrations known as chattering, which occurs in the vertical direction. Chattering mostly occurs at frequencies of around 100-200 Hz. When chattering occurs, periodic variations in the thickness of the rolled material are likely to appear. Therefore, chattering has become a factor hindering the productivity of high-value-added products.

[0004] Against this background, Patent Document 1 describes a method for improving lubricity by supplying two types of emulsion rolling oil of different concentrations based on mill vibrations occurring at frequencies of tens of Hz (around 30-100 Hz) in the horizontal direction. [Prior Art Documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 2022-071919 [Summary of the Invention]

[0006] [Problem to be Solved by the Invention] However, the prior art has the following problems to be solved. In the technology disclosed in Patent Document 1, two emulsion rolling oils of different concentrations are supplied considering horizontal vibration. However, as shown in Figure 3, the adhesion efficiency of the oil component in the emulsion to the rolled material increases with the increase of the temperature of the rolled material at low temperatures, and decreases after reaching a peak 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 component concentration when supplying emulsion rolling oil to the rolled material. When the oil component concentration of the emulsion increases, the plate temperature during rolling is more likely to rise. As a result, when the rolled material exceeds the aforementioned peak temperature, the adhesion efficiency of the oil component in the emulsion to the rolled material decreases. Therefore, it is desirable to also consider the plate temperature when determining the mixing ratio of emulsions with different oil component concentrations. However, Patent Document 1 does not take this into consideration.

[0007] This invention was developed in view of the above-mentioned issues, and its object is to provide a cold rolling apparatus and cold rolling method capable of suppressing the generation of horizontal chatter by taking into account the sheet temperature of the rolled material. Another object of this invention is to provide a method for manufacturing cold-rolled metal sheets capable of producing cold-rolled metal sheets with high yield. [Technical Means for Solving the Problem]

[0008] The cold rolling equipment of the present invention, which is beneficial to solving the above-mentioned problems, comprises: a tandem cold rolling mill having a plurality of rolling stands; a rolling oil supply system for supplying rolling oil to the tandem cold rolling mill; a plurality of plate thermometers for measuring the plate temperature of the rolled material at the inlet or outlet side of each rolling stand; and a control unit for controlling rolling conditions including the rolling oil supplied to the inlet side of each rolling stand. The rolling oil supply system comprises: a first rolling oil supply system for supplying a first emulsion rolling oil; and a second rolling oil supply system for supplying a second emulsion rolling oil with a higher oil component 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 inlet side of a specific rolling stand according to the measurement results of the plate thermometers at the inlet or outlet side of that specific rolling stand, and supply mixed rolling oil to that specific rolling stand.

[0009] As a better solution, the cold rolling equipment of the present invention includes: a coolant supply system for supplying coolant to the aforementioned tandem cold rolling mill, wherein the aforementioned control unit is configured to further control the flow rate of the aforementioned coolant supplied to the rolled material at the inlet side of the aforementioned specific rolling mill stand based on the measurement results of the aforementioned plate temperature gauge.

[0010] The cold rolling method of the present invention, which is beneficial to solving the above-mentioned problems, when the material to be rolled is cold rolled by the above-mentioned cold rolling equipment, when the plate temperature measured by a specific plate temperature gauge is above a predetermined value, the mixing ratio of the mixing roller oil or the flow rate of the coolant is changed, and the plate temperature of the specific plate temperature gauge is adjusted to be below the predetermined value.

[0011] The cold-rolled metal sheet manufacturing method of the present invention, which is beneficial to solving the above-mentioned problems, manufactures a cold-rolled metal sheet by cold rolling a material to be rolled into a metal sheet using the above-mentioned cold rolling method. [Effects of the Invention]

[0012] According to the cold rolling equipment and cold rolling method of the present invention, vibrations generated during cold rolling can be suppressed. Furthermore, according to the method for manufacturing cold-rolled metal sheets of the present invention, cold-rolled metal sheets can be manufactured with high productivity.

Implementation Method

[0014] Hereinafter, embodiments of the present invention will be specifically described with reference to drawings. These embodiments are examples of apparatuses and methods for embodying the technical concept of the present invention, but are not limited to the following configurations. That is, the technical concept of the present invention can be modified in various ways within the scope of the technology described in the claims.

[0015] A method for manufacturing cold-rolled metal sheets according to one embodiment of the present invention will be described. Here, the rolling oil used in this embodiment can be either petroleum-based or emulsion-based. However, cold-rolling oils in the steel industry typically require high cooling performance, therefore emulsion-based rolling oils, i.e., emulsion rolling oils, are mostly used. Therefore, in the following embodiment, emulsion rolling oil (hereinafter also simply referred to as "emulsion") will be used as an example for explanation.

[0016] An emulsion is a mixed liquid in which rolling oil particles are stably suspended in water. The properties of an emulsion depend on the concentration of the oil component and the average particle size of the oil droplets. The concentration of an emulsion refers to the ratio of the mass of the oil component to the total mass of the emulsion. The average particle size of an emulsion refers to the average particle size of the oil droplets of the rolling oil in the emulsion. In addition, a surfactant needs to be added to emulsify the oil in water in order to manufacture an emulsion. The amount of surfactant added is a fixed amount expressed as a mass concentration (relative to oil concentration) relative to the amount of rolling oil. Moreover, after adding the surfactant, the average particle size of the emulsion is adjusted by applying shear force using a mixer and a pump. Examples of emulsion rolling oil include: rolling oil diluted with hot water to a concentration of about 1 to 5% by mass and then dispersed in water with a surfactant to form an O / W emulsion, i.e., water-droplet type rolling oil.

[0017] [Structure] First, referring to FIG1, the structure of a cold rolling mill according to an embodiment of the present invention will be described. FIG1 is a schematic diagram showing the structure of a cold rolling mill according to an embodiment of the present invention. In the following description, steel plate S is used as an example as the material to be rolled by the cold rolling mill. However, aluminum plate or other metal plates can also be used as the material to be rolled.

[0018] As shown in FIG1, the cold rolling mill 100 of this embodiment includes a tandem cold rolling mill 200. The tandem cold rolling mill 200 has five mill stands in sequence, from the inlet side where the steel plate S enters to the outlet side, numbered from the first mill stand (#1STD) to the fifth mill stand (#5STD). The left side facing FIG1 is the inlet side of the tandem cold rolling mill 200, and the right side facing FIG1 is the outlet side of the tandem cold rolling mill 200. Although FIG1 shows five mill stands, it is not limited to this. In this tandem cold rolling mill 200, tension rolls, deflector rolls, plate thickness gauges, and shape gauges (not shown) are suitably provided between adjacent mill stands. The structure of the tandem cold rolling mill 200 and the conveying device for the steel plate S are not particularly limited, and known technologies can be suitably applied.

[0019] Emulsion rolling oil is supplied to each mill stand of the tandem cold rolling mill 200 (in the following description, "emulsion rolling oil" is sometimes simply referred to as "rolling oil"). In this embodiment, as a rolling oil supply system for supplying rolling oil to each mill stand, a first rolling oil supply system 2 and a second rolling oil supply system 14 are provided.

[0020] The cold rolling equipment 100 is equipped with a sludge tank 5 (for recovery) and a clean oil tank 7 as rolling oil storage tanks. The rolling oil stored in these rolling oil storage tanks is supplied to each mill stand through the first rolling oil supply system 2 and the second rolling oil supply system 14. The rolling oil recovered by the oil pan 10 located below each mill stand, that is, the rolling oil used in cold rolling, flows into the sludge tank 5 through the return pipe 11.

[0021] The rolling oil stored in the clean oil tank 7 is a clean rolling oil formed by mixing hot water as dilution water and the original rolling oil containing surfactants. By adjusting the rotation speed, i.e., the degree of agitation, of the stirring blades of the mixer 12, the mixture of hot water and the original rolling oil is made into a rolling oil with a desired average particle size and concentration range. The original rolling oil can be used in general cold rolling applications. For example, it can be based on natural oils, fatty acid esters, or hydrocarbon synthetic lubricants. Furthermore, oiliness modifiers, extreme pressure additives, antioxidants, and other additives commonly used in general cold rolling oils can be added to such rolling oils. As for the surfactants added to the rolling oil, either ionic or nonionic surfactants can be used, as long as they are used in general circulating oil supply systems. Furthermore, it is preferable to dilute the stock rolling oil to an oil component concentration of 2.0 to 8.0% by mass, more preferably to an oil component concentration of 3.0 to 6.0% by mass. It is also acceptable to prepare an O / W emulsion rolling oil that disperses the oil in water using the aforementioned surfactants. 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 operation begins, the rolling oil recovered to the sludge tank 5 is supplied to the clean oil tank 7 via an iron powder removal device 6, which includes an iron powder quantity control device. The rolling oil recovered to the sludge tank 5 contains abrasive particles such as iron powder generated by friction between the rolls and the steel plate S. The iron powder removal device 6 removes these abrasive particles, resulting in an oil-soluble iron content in the recovered rolling oil that is acceptable for the rolling oil stored in the clean oil tank 7. The movement of the emulsion rolling oil from the sludge tank 5 to the clean oil tank 7 via the iron powder removal device 6 can be continuous or intermittent. Preferably, the iron powder removal device 6 uses a magnetic filter such as an electromagnetic filter or a magnetic separator to adsorb and remove the iron powder, but it is not limited to this. The iron powder removal device 6 can also be a known device using methods such as centrifugal separation.

[0023] However, a portion of the rolling oil supplied to the cold rolling equipment 100 is lost due to being carried out of the system by the steel plate S or evaporation. Therefore, the rolling oil is suitably replenished (supplied) from the raw material tank (not shown) to keep the storage level and concentration of the rolling oil in the clean oil tank 7 within a predetermined range. Hot water for dilution is also suitably replenished (supplied) to the clean oil tank 7. The storage level and concentration of the first emulsion rolling oil 13 in the clean oil tank 7 can be measured by a sensor (not shown).

[0024] The emulsion tank 19 is connected to the rolling oil crude oil tank 22 and the hot water tank 23. Furthermore, 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 supplied to the emulsion tank 19 via a pump (not shown) and a flow control valve 21. Simultaneously, the emulsion tank 19 is mixed by a mixer 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 oil tank 7. In addition, by adjusting the rotational speed of the mixing blades of the mixer 20, the average droplet size of the second emulsion rolling oil 15 in the emulsion tank 19 is adjusted to 10~30 μm, and the oil component concentration is adjusted to the range of 3~20% by mass.

[0025] Next, the first rolling oil supply system 2 and the second rolling oil supply system 14 will be described in detail. Furthermore, both the first rolling oil supply system 2 and the second rolling oil supply system 14 include: a sludge tank 5, an iron powder removal device 6, a clean oil tank 7, and a pump 8 for drawing rolling oil from the clean oil tank 7. Moreover, 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 structure after the branch point. A strainer for removing foreign matter may also be installed between the clean oil tank 7 and the pump 8.

[0026] [First Roll Oil Supply System] The first roll oil supply system 2 includes a first roll oil pipeline 9 connected at one end to the clean oil tank 7 as a first roll oil supply line. Furthermore, the other end of the first roll oil pipeline 9 of the first roll oil supply system 2 branches off at the mill side. The first roll oil supply system 2 includes five sets of lubricating coolant manifolds 3 and five sets of cooling coolant manifolds 4, each located at a position corresponding to the branch destination end of each mill stand. Each lubricating coolant manifold 3 is located at the inlet side of the mill stand, and roll oil, acting as lubricant, is sprayed from nozzles provided on each lubricating coolant manifold 3 toward the roll bite area. This supplies roll oil to the roll bite area and the work rolls. The cooling coolant manifolds 4 are located at the outlet side of the mill stand, and roll oil is sprayed from nozzles provided on each cooling coolant manifold 4 toward the rolls. This cools the rolls.

[0027] According to this configuration, in the first rolling oil supply system 2, the rolling oil in the clean oil tank 7 is pumped to the first rolling oil pipeline 9 by the pump 8. Hereinafter, the rolling oil pumped to the first rolling oil pipeline 9 and supplied to each mill stand is also referred to as the first emulsion rolling oil 13. The first emulsion rolling oil 13 is supplied through the first rolling oil pipeline 9 to the lubrication coolant manifold 3 and the cooling coolant manifold 4 arranged in each mill stand, and is sprayed from the nozzles provided in each manifold. In addition, the first emulsion rolling oil 13 supplied to the rolls, except for the portion lost due to being carried out of the system by the steel plate S or evaporation, is recovered to the oil receiving pan 10 and returned to the sludge tank 5 through the return pipe 11. Afterwards, as described above, in order to remove a certain amount of the oil-soluble iron component in the emulsion rolling oil produced by cold rolling, a portion of the emulsion rolling oil stored in the sludge tank 5 is returned to the clean oil tank 7 via the iron powder removal device 6.

[0028] Based on the above configuration of the first rolling oil supply system 2, the rolling oil after the abrasive powder removal treatment is performed is circulated and supplied to the rolls. That is, the first emulsion rolling oil 13 is recycled. Here, the clean oil tank 7 corresponds to the rolling oil tank used for recycling in the conventional circulating oil supply method, and the clean oil tank 7 is appropriately replenished (supplied) with the original rolling oil as described above.

[0029] [Second Roll Oil Supply System] The second roll oil supply system 14 includes: a second roll oil pipeline 16 with one end connected to the first roll oil pipeline 9, and a third roll oil pipeline 24 with one end connected to the emulsion tank 19. The other end of the second roll oil pipeline 16 of the second roll oil supply system 14 branches off at the mill side. The second roll oil supply system 14 includes: five flow control valves 17, each disposed at a position corresponding to each mill stand at the branch destination end and connected to the other end of the third roll oil pipeline 24. The second roll oil supply system 14 includes: a mixing roll oil pipeline 26 with one end connected to the flow control valves 17, and a lubricating coolant manifold 25 connected to the other end of the mixing roll oil pipeline 26.

[0030] The emulsion tank 19 is connected to the rolling oil crude oil tank 22 and the hot water tank 23. Furthermore, 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 supplied to the emulsion tank 19 via a pump (not shown) and a flow control valve 21. Simultaneously, the emulsion tank 19 is mixed by a mixer 20. In the following description, the rolling oil in the emulsion tank 19 is sometimes referred to as the second emulsion rolling oil 15.

[0031] Preferably, the temperature conditions of the second emulsion rolling oil 15 are the same as those of the first emulsion rolling oil 13. However, from the viewpoint of improving the cooling capacity of the steel plate S at the downstream mill stand, the temperature of the second emulsion rolling oil 15 can be made lower than that of the first emulsion rolling oil 13 via a cooling device not shown. Furthermore, the concentration and particle size conditions of the rolling oil in the second emulsion rolling oil 15 do not need to be the same as those in the first emulsion rolling oil 13.

[0032] The first emulsion rolling oil 13 stored in the clean oil tank 7 is supplied to the flow control valve 17 through the second rolling oil pipeline 16 by the drive pump 8. Furthermore, the second emulsion rolling oil 15 is supplied to the flow control valve 17 through the third rolling oil pipeline 24 by the pump 18. The second emulsion rolling oil 15 mixes with the first emulsion rolling oil 13 within the flow control valve 17 to form a mixed rolling oil containing the second emulsion rolling oil 15 at a predetermined emulsion concentration. This mixed rolling oil is transported to the lubrication coolant manifold 25 of each mill stand through the mixed rolling oil pipeline 26. The lubrication coolant manifold 25 branches on the surface and back sides of the steel plate S. This configuration allows the mixed rolling oil of the desired concentration to be sprayed towards both the surface and back sides of the steel plate S from multiple nozzles. Subsequently, the rolling oil recovered to the oil receiving plate 10 is returned to the sludge tank 5 via the return pipe 11 for recycling.

[0033] Alternatively, the flow control valve 17 may also control the flow rate of the second emulsion rolling oil 15 relative to the flow rate of the first emulsion rolling oil 13. Furthermore, the second emulsion rolling oil 15 may be supplied directly to the steel plate S without passing through the flow control valve 17 constituting the mixing section. More preferably, a mixed rolling oil formed 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 for mixing the first emulsion rolling oil 13 and the second emulsion rolling oil 15. The opening degree of the flow control valve 17 is adjusted according to instructions from the supply control section 38 shown in FIG2, thereby adjusting the mixing ratio of the first emulsion rolling oil 13 and the second emulsion rolling oil 15. Furthermore, when the second emulsion rolling oil 15 is supplied directly to the steel plate S without being supplied through the flow control valve 17, the supply ratio of the first emulsion rolling oil 13 and the second emulsion rolling oil 15 can be referred to as the mixing ratio.

[0035] [Coolant Supply System] The coolant supply system 31 includes: a coolant tank 29, a coolant pipeline 32, a flow control valve 17, a coolant manifold 27, and a plate temperature measuring device 30. In the example of FIG1, coolant 28 is stored in the coolant tank 29 and supplied to each mill stand. Alternatively, rolling oil can be supplied as coolant from branches of the first or second rolling oil system. In the example of FIG1, the plate temperature measuring device 30 is located on the outlet side of each mill stand, but it can also be located on the inlet side. In the example of FIG1, the plate temperature measuring device 30 is non-contact, but it can also be contact. Adjustments are made according to instructions from the supply control unit 38 shown in FIG2, thereby adjusting the coolant flow rate.

[0036] [Method for controlling the supply of mixed rolling oil and coolant] Next, referring to FIG2, the method for controlling the supply of mixed rolling oil (method for controlling the mixing ratio) and the method for controlling the supply of coolant (method for controlling the coolant flow rate) based on the supply control unit 38 will be described.

[0037] Figure 2 is a schematic diagram showing the structure of a supply control unit according to one embodiment of the present invention. Furthermore, the supply control unit 38 adjusts the plate temperature of any of the five rolling mill stands to a set temperature to ensure optimal lubrication. Although Figure 2 is composed of five rolling mill stands, it is not limited to this.

[0038] [Method for Controlling the Supply of Mixed Rolling Oil] As shown in Figure 2, the supply control unit 38 includes: a plate temperature acquisition unit 33, a rolling oil mixing ratio calculation unit 34, and a rolling oil mixing ratio control unit 36. Furthermore, the supply control unit 38 can be integrated into the tandem cold rolling mill 200, or it can be integrated into an operating panel connected to the tandem cold rolling mill 200 wirelessly or wiredly. Here, the operating panel is an operating component used by the operator to set the rolling conditions, etc., of the tandem cold rolling mill 200.

[0039] In the method for supplying and controlling the mixed rolling oil, the plate temperature acquisition unit 33 acquires the plate temperature at the exit side of each mill stand, and provides the rolling oil mixing ratio control unit 36 ​​with a preset rotational speed relative to a pre-set plate temperature target based on the plate temperature difference. Then, according to the instruction from the rolling oil mixing ratio control unit 36, the rotational speed of the rolling oil mixing ratio changing motor for that mill stand is changed. Furthermore, although the above example changes to a preset motor speed, an adjustment method can also be used that gradually changes the motor speed in increments of 1 rpm until the set temperature is reached. When the measured temperature is higher than the target temperature, the motor speed is reduced, decreasing the rolling oil mixing ratio and increasing the heat transfer coefficient, thereby lowering the steel plate temperature. Although the above example uses motor speed to change the rolling oil mixing ratio, it can also be changed using valve opening.

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

[0041] In the coolant supply control method, the plate temperature acquisition unit 33 acquires the plate temperature at the outlet side of each mill stand, and provides the rolling oil mixing ratio control unit 36 ​​with the valve opening preset by the coolant flow calculation unit 35 based on the plate temperature difference relative to the pre-set plate temperature target. The opening of the coolant flow rate change valve between the mill stand and the front mill stand is changed according to the instruction of the coolant flow rate control unit 37.

[0042] In the above description, although the coolant flow rate is changed by using the valve opening, it can also be changed by using the motor speed. In the above description, although the valve opening is changed until a predetermined value is reached, an adjustment method can also be used to gradually change the valve opening by 1% until the set temperature is reached. When the measured temperature is higher than the target temperature, the valve opening is increased to increase the coolant flow rate and increase the heat dissipation, thereby lowering the temperature of the steel plate.

[0043] In the above description, although the supply of the mixed rolling oil and the supply of coolant are implemented separately, both can also be controlled together. In the latter case, interference between the two can be considered and they can be controlled simultaneously. Furthermore, the rolling oil mixing ratio can be changed preferentially, and the coolant flow rate can be adjusted when the lower limit of the rolling oil mixing ratio is reached. Alternatively, the coolant flow rate can be changed, and the rolling oil mixing ratio can be adjusted when the upper limit of the coolant flow rate is reached.

[0044] The supply method for the mixed rolling oil and the control method for the coolant can be controlled at all rolling mill stands, or at a single rolling mill stand or multiple rolling mill stands. Preferably, only the rolling mill stand where a plate temperature exceeding a preset temperature as a reference is controlled, or multiple rolling mill stands including the one before and after that rolling mill stand are controlled. [Example]

[0045] Hereinafter, the present invention will be described with reference to embodiments. The following embodiments are not intended to limit the present invention.

[0046] In this embodiment, a tandem cold rolling mill as shown in FIG1 is used. A base steel sheet containing 2.5% by mass Si and 3.0% by mass Si with a base thickness of 2.0 mm and a width of 1000 mm is used as the rolling material, and cold-rolled to a final thickness of 0.300 mm. The supply of rolling oil and coolant is controlled by a supply control unit configured as shown in FIG2. In this embodiment, the lower limit of the speed of the motor for changing the rolling oil mixing ratio is, for example, 500 rpm, and the upper limit of the opening of the coolant supply valve is 100%. The initial value of the valve opening is 50%, and the initial value of the speed of the motor for changing the rolling oil mixing ratio is 3000 rpm. Here, the base steel sheet for electromagnetic steel is hard, and it is known that chatter is easily generated under high-load rolling conditions such as low rolling speeds. The stock solution used as the rolling oil is a base oil made by adding vegetable oil to a synthetic ester oil base, with 1% by mass of oiliness agent and 1% by mass of antioxidant added, and a non-ionic surfactant added at 3% by mass of the oil concentration. The first emulsion rolling oil 13 supplied from the first rolling oil supply system 2 and recycled is an emulsion rolling oil prepared with a rolling oil concentration of 3.5% by mass, an average particle size of 5 μm, and a temperature of 55°C. Various test conditions and results are summarized in Table 1. In this embodiment, the peak temperature of film boiling shown in Figure 3 is 260°C.

[0047]

[0048] In Test No. 1, when controlling the front plate temperature, since the temperature reading of plate thermometer No. 3 reached the peak temperature at which film boiling occurs, the mixing ratio of the mixed rolling oil supplied from the second rolling oil supply system at the inlet side of the #3STD of the third mill stand was controlled. After controlling the supply of rolling oil, the temperature after plate thermometer No. 3 decreased, and no chattering was observed.

[0049] In Test No. 2, when controlling the front plate temperature, since the temperature reading of plate thermometer No. 3 exceeded the peak temperature at which film boiling occurs, the mixing ratio of the mixed rolling oil supplied from the second rolling oil supply system at the inlet side of the #3STD of the third mill stand and the flow rate of the coolant were controlled. After controlling the supply of rolling oil, the temperature reading of plate thermometer No. 3 decreased to below the peak temperature at which film boiling occurs, and the temperatures of plate thermometers No. 4 and thereafter also decreased, and no chattering was observed.

[0050] In Test No. 3, the temperature reading of plate thermometer No. 3 exceeded the peak temperature at which film boiling occurs, despite the control of the front plate temperature. The lack of control over the mixing ratio of the rolling oil and the flow rate of the coolant resulted in chattering.

[0051] In Test No.4, the temperature readings at all mill stands were below the peak temperature at which film boiling occurs, allowing rolling to continue without chattering.

[0052] In tests No. 5 to 8, the temperature readings of plate thermometers No. 2, 1, 4, and 5 were above the peak temperature at which film boiling occurs, respectively, while the control parameters were the mixing ratio of the rolling oil and the flow rate of the coolant. As a result, all the measured temperature readings were below the peak temperature at which film boiling occurs, and no flutter was observed.

[0053] In Test No. 9, when controlling the front plate temperature, the temperature reading of plate thermometer No. 3 exceeded the peak temperature at which film boiling occurs. The mixing ratio of the rolling oil and the flow rate of the coolant were adjusted at the third rolling mill stand #3STD and the adjacent second rolling mill stand #2STD. As a result, the temperature readings from plate thermometer No. 2 onwards decreased, and all readings became below the peak temperature at which film boiling occurs; no chattering was observed.

[0054] In Test No. 10, with the front plate temperature controlled, the temperature readings of plate thermometers No. 3 to No. 5 were above the peak temperature at which film boiling occurs. At rolling mill stands #3 to #5, the mixing ratio of the rolling oil and the flow rate of the coolant were adjusted. As a result, the temperature readings after plate thermometer No. 3 decreased, and all readings became below the peak temperature at which film boiling occurs; no chattering was observed.

[0055] The above description pertains to embodiments of the invention developed by the inventors of this case, but does not limit the invention by the description and drawings that constitute part of the disclosure of this invention based on these embodiments. That is, other embodiments, implementations, and techniques developed based on these embodiments by those skilled in the art are all included within the scope of this invention. [Simplified Explanation of the Diagram]

[0013] [Figure 1] is a schematic diagram showing the structure of a cold rolling apparatus according to an embodiment of the present invention. [Figure 2] is a schematic diagram showing the structure of a rolling oil supply control unit according to an embodiment of the present invention. [Figure 3] is a graph showing the relationship between the adhesion efficiency of oil components to the rolled material and the temperature of the rolled material during cold rolling.

Claims

1. A cold rolling apparatus comprising: a tandem cold rolling mill having a plurality of mill stands; a rolling oil supply system for supplying rolling oil to the tandem cold rolling mill; a plurality of plate thermometers for measuring the plate temperature of the rolled material at the inlet or outlet side of each mill stand; and a control unit for controlling rolling conditions including the rolling oil supplied to the inlet side of each mill stand; the rolling oil supply system comprising: a first rolling oil supply system for supplying a first emulsion rolling oil; and a second rolling oil supply system for supplying a second emulsion rolling oil with a higher oil component concentration than the first emulsion rolling oil; the control unit being configured to supply mixed rolling oil to the specific mill stand by adjusting the mixing ratio of the first emulsion rolling oil and the second emulsion rolling oil at the inlet side of the specific mill stand based on the measurement results of the plate thermometers at the inlet or outlet side of the specific mill stand.

2. The cold rolling equipment as requested in item 1, wherein, The control unit is configured to further control the flow rate of the aforementioned coolant supplied to the rolled material at the inlet side of the aforementioned specific mill stand based on the measurement results of the aforementioned plate temperature gauge.

3. A cold rolling method wherein, when cold rolling a material to be rolled using the cold rolling equipment of claim 1, when the plate temperature measured by a specific plate thermometer is above a predetermined value, the mixing ratio of the mixing roller oil is changed to adjust the plate temperature of the specific plate thermometer to be below the predetermined value.

4. A cold rolling method wherein, when cold rolling a material to be rolled using the cold rolling equipment of claim 2, when the plate temperature measured by a specific plate thermometer is above a predetermined value, the mixing ratio of the mixing roller 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.

5. A method for manufacturing a cold-rolled metal sheet, wherein the cold-rolled metal sheet is manufactured by cold rolling a material to be rolled into a metal sheet using the cold rolling method described in claim 3 or 4.

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