Method and apparatus for applying oil to steel strip

Abstract

To provide a method and an apparatus for applying oil to a steel strip, which can appropriately cope with a change in a target application amount of oil or a change in kinematic viscosity of rust-preventive oil, in an application technique of applying oil to the surface of the steel strip by using a brush roll.SOLUTION: In the oil coating method where the rust preventive oil 9 stored in an oil pan 6 is wound up by a pickup roll 5, and the rust preventive oil 9 stuck to the surface of the pickup roll 5 is scattered to a steel strip 12 by a brush roll 4, the adjustment of the rotating speed of the brush roll 4 is performed according to the target coating amount of the rust preventive oil 9 and the passing speed of the steel strip 12.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a method and apparatus for oiling a steel strip, and more particularly to a method and apparatus for oiling a steel strip using a brush roll to apply rust preventive oil to the steel strip. [Background technology]

[0002] A method using a brush roll is known for applying rust-preventive oil to a steel strip (Patent Documents 1 and 2). In this method, rust-preventive oil stored in an oil pan is wound up by a pickup roll (also called a "dip roll"), and the rust-preventive oil adhering to the surface of the pickup roll is scattered by the rotating brush roll to apply the oil to the steel strip.

[0003] For example, Patent Document 1 discloses equipment that allows the movement of an oil droplet receiver that receives oil droplets scattered from a brush roll above an unoiled product in order to prevent oil droplets from adhering to the unoiled product that is temporarily passed through an equipment line in which a brush roll is installed. However, it does not disclose a method for controlling the amount of oil applied to the oiled product.

[0004] On the other hand, for example, Patent Document 2 describes a method for controlling the amount of oil applied. This describes controlling the rotation speed of the pickup roll so that it is proportional to an exponential function of the strip threading speed, rather than the previous method of making it directly proportional to the strip threading speed. This makes it possible to maintain a constant amount of oil applied to the surface of the steel strip, regardless of the strip threading speed. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Utility Model Application Publication No. 61-125349 [Patent Document 2] Japanese Patent Application Publication No. 8-57407 Summary of the Invention [Problem to be solved by the invention]

[0006] However, in the conventional control in which the rotational speed of the pickup roll is directly proportional to the strip threading speed, the rotational speed of the brush roll is not taken into consideration, and therefore, when the strip threading speed changes, the amount of oil applied fluctuates.Furthermore, the control method described in Patent Document 2 has the problem that it does not take into consideration the case where the target oil application amount of the steel strip is changed, or further, the case where the kinematic viscosity of the rust preventive oil is changed.

[0007] In view of the above-mentioned problems, the present invention aims to provide a method and apparatus for applying rust-preventive oil to a steel strip in an oil application technique that uses a brush roll to apply rust-preventive oil to the surface of the steel strip, which can appropriately respond even if the target oil application amount or the dynamic viscosity of the rust-preventive oil changes. [Means for solving the problem]

[0008] The present inventors conducted extensive research to solve the above problems and found that by adjusting the rotation speed of the brush roll according to the target oil amount and the strip threading speed, it is possible to respond to changes in the target oil amount and control the oil amount as desired even when the strip threading speed changes. Furthermore, they discovered that adjusting the rotation speed of the brush roll according to the kinematic viscosity of the rust-preventive oil can improve the accuracy of oil amount control. They also discovered that by taking into account the temperature dependency of the kinematic viscosity, the accuracy of oil amount control can be further improved, and that by incorporating bubbles into the rust-preventive oil, the accuracy of oil amount control can be maintained even when the kinematic viscosity is significantly high.

[0009] The present invention was completed based on these findings and through further investigation, and the gist of the present invention is as follows. [1] A method for applying rust-preventive oil 9 stored in an oil pan 6 is wound up by a pickup roll 5, and the rust-preventive oil 9 adhering to the surface of the pickup roll 5 is scattered onto a steel strip 12 by a brush roll 4, characterized in that the rotational speed of the brush roll 4 is adjusted according to the target amount of rust-preventive oil 9 to be applied and the threading speed of the steel strip 12. [2] The method for oiling a steel strip according to [1] above, further characterized in that the rotational speed of the brush roll 4 is adjusted taking into consideration the dynamic viscosity of the rust preventive oil 9. [3] The method for oiling a steel strip according to [2] above, characterized in that the rust preventive oil 9 contains bubbles 10. [4] The method for oiling a steel strip according to [3], characterized in that the content of the bubbles 10 relative to the rust preventive oil 9 is 0.01 to 20.00% by volume. [5] The method for oiling a steel strip according to [3] or [4], characterized in that the gas in the bubbles 10 is nitrogen. [6] An oil application device for a steel strip, comprising an oil pan 6 storing rust-preventive oil 9, a pickup roll 5 that scoops up the rust-preventive oil 9 in the oil pan 6, and a brush roll 4 that scatters the rust-preventive oil 9 adhering to the surface of the pickup roll 5 onto a steel strip 12 as it rotates, characterized in that the oil application device for a steel strip is provided with a means for adjusting the rotational speed of the brush roll 4 in accordance with the target application amount of the rust-preventive oil 9 and the threading speed of the steel strip 12. [7] In the above [6], the oil application device for a steel strip is further characterized in that the means for adjusting the rotational speed of the brush roll 4 is a means for adjusting the rotational speed of the brush roll 4 taking into account the dynamic viscosity of the rust preventive oil 9. [8] The oil application device for a steel strip according to [7], further comprising a means for making the rust preventive oil 9 contain bubbles 10. [9] The oil application device for a steel strip according to [8], characterized in that the gas in the bubbles 10 is nitrogen. [Effects of the Invention]

[0010] According to the present invention, by adjusting the rotation speed of the brush roll according to the target oil amount and the strip passing speed, it is possible to respond to changes in the target oil amount and to control the oil amount as desired regardless of changes in the strip passing speed. Furthermore, by adjusting the rotation speed of the brush roll according to the kinematic viscosity of the rust-preventive oil, it is possible to improve the accuracy of oil amount control. Furthermore, by incorporating air bubbles into the rust-preventive oil, it is possible to maintain high accuracy in oil amount control even when the kinematic viscosity is extremely high. [Brief explanation of the drawings]

[0011] [Figure 1] 1A and 1B are explanatory views showing an example of an oil application method and an oil application device of the present invention, in which (a) is a side cross-sectional view, and (b) is a front cross-sectional view and a control block diagram. [Figure 2] 3A and 3B are explanatory views showing another example of the oil application method and oil application device of the present invention, in which (a) is a side cross-sectional view, and (b) is a front cross-sectional view and a control block diagram. [Figure 3] 4A and 4B are explanatory views showing another example of the oil application method and oil application device of the present invention, in which (a) is a side cross-sectional view, and (b) is a front cross-sectional view and a control block diagram. [Figure 4] 10A and 10B are explanatory views showing another example of an oil application method and an oil application device according to the fourth embodiment of the present invention, in which (a) is a side cross-sectional view, and (b) is a front cross-sectional view and a control block diagram. [Figure 5] 10A and 10B are explanatory views showing another example of an oil application method and an oil application device according to the fifth embodiment of the present invention, in which (a) is a side cross-sectional view, and (b) is a front cross-sectional view and a control block diagram. DETAILED DESCRIPTION OF THE INVENTION

[0012] Hereinafter, embodiments of the present invention will be described with reference to the drawings. In these drawings, the same or corresponding components as those in the previous drawings are designated by the same reference numerals, and their description may be omitted.

[0013] As shown in Figure 1, the oil application method of the present invention comprises the steps of winding up rust-preventive oil 9 stored in an oil pan 6 with a pickup roll 5 and scattering the rust-preventive oil 9 adhering to the surface of the pickup roll 5 onto a steel strip 12 with a brush roll 4. The method further comprises the step of adjusting the rotational speed of the brush roll 4 in accordance with the target amount of rust-preventive oil 9 to be applied and the threading speed of the steel strip 12.

[0014] Here, the rust preventive oil 9 is supplied at a volumetric flow rate that allows a predetermined amount of oil to be stored in the oil pan 6.

[0015] The oil application device 1 of the present invention also includes an oil pan 6 that stores rust-preventive oil 9, and a pickup roll 5 that scoops up the rust-preventive oil 9 in the oil pan 6. The oil application device 1 further includes a brush roll 4 that scatters the rust-preventive oil 9 adhering to the surface of the pickup roll 5 onto the steel strip 12 while rotating. The oil application device 1 further includes a means for adjusting the rotational speed of the brush roll 4 in accordance with the target application amount of the rust-preventive oil 9 and the threading speed of the steel strip 12.

[0016] In the following, the brush roll and pickup roll will be abbreviated as "BR" and "PR," respectively, and their rotational speeds will also be referred to as "BR rotational speed" and "PR rotational speed." Also, in Figure 1(b), "AO" is the target oil application amount, "VS" is the strip threading speed, and "VBR" is the target value of the BR rotational speed, and will also be abbreviated as "AO," "VS," and "VBR," respectively.

[0017] The oil application device 1 of the present invention shown in Figure 1(a) is preferably equipped with a leveling roll 2, a pinch roll 3, a mist cover 7, and a scraper 8, each of which plays the following role: The leveling roll 2 compresses the rust-preventive oil 9 sprayed on the surface of the steel strip 12 to make it a uniform thickness, and the pinch roll 3 pinches and rotates the steel strip 12, sending it out to the left in Figure 1(a). The mist cover 7 prevents contamination due to the atomized rust-preventive oil 9 diffusing into the air, and the scraper 8 scrapes off excess rust-preventive oil 9 adhering to the surface of the PR5.

[0018] The oiling device 1 includes a means for adjusting the rotational speed of the brush roll 4 to a target value (VBR) in accordance with a target oil amount (AO) of the rust preventive oil 9 and a threading speed (VS) of the steel strip 12. Specific examples of this adjusting means include a motor (M) 13, a tachometer (PG) 15, a regulator 16, and a computer 17. The motor 13 drives the rotation of the brush roll 4. The tachometer 15 measures the rotational speed of the motor 13 and transmits the obtained rotation measurement value to the regulator 16. The computer 17 calculates the VBR from the inputted AO and VS by a method described below and transmits the derived VBR to the regulator 16. The regulator 16 adjusts the driving force of the motor 13 so that the rotation measurement value received from the tachometer 15 matches the VBR received from the calculator 17, and transmits the signal to the motor 13.

[0019] According to the present invention, as described above, by adjusting the BR rotation speed in accordance with the target oil application amount and the strip threading speed, it is possible to respond to changes in the target oil application amount and to control the oil application amount as desired even if the strip threading speed changes.

[0020] The following describes the conditions that are preferable in the present invention.

[0021] [Steel strip and plate threading speed] Examples of the steel strip 12 include hot-rolled pickled steel strips, cold-rolled steel strips, cold-rolled annealed steel strips, and surface-treated steel strips. The width (plate width) of the steel strip 12 is 700 to 1800 mm. The threading speed commonly used in the oiling operation of these steel strips is, for example, 30 to 230 m / min.

[0022] [Oil pan] The width of the oil pan 6 is, for example, 100 to 200 mm larger on each side than the plate width. The capacity of the oil pan 6 is preferably in the range of 10 to 100 L. If the capacity is below this lower limit, it may be difficult to ensure the immersion depth of the PR5 (described below) required to obtain a sufficient amount of adhesion. If the capacity of the oil pan 6 exceeds 100 L, it may be excessive and economically disadvantageous.

[0023] [Characteristics of anti-rust oil] The rust preventive oil 9 can be a commonly used one. Its density is 0.80 to 0.90 g / cm 3 The viscosity is, for example, 100 to 700 g / m s. The kinematic viscosity (viscosity / density) is temperature dependent, for example, 70 to 80 mm at 10°C. 2 / s, 15-20mm at 40℃ 2 / s are mentioned.

[0024] [Supply flow rate of anti-rust oil 9] The supply flow rate of the rust preventive oil 9 (hereinafter also referred to as "oil supply flow rate") is expressed as a volumetric flow rate per unit time, and may be, for example, 0.5 to 50 L / h.

[0025] [Target amount of oil applied] The amount of oil applied is expressed as the weight of rust preventive oil per unit area of ​​the steel strip. The target amount of oil applied is 1.0 to 3.0 g / m 2 The target oil application amount is 1.0 g / m 2 If the coating is less than 3.0 g / m, the rust prevention effect is insufficient. 2 If the amount exceeds 1.3 to 1.5 g / m, the amount of rust preventive oil 9 that seeps out from the side due to contact between the front and back surfaces after winding the steel strip will be excessive. 2 is.

[0026] [Method for measuring oil application amount] The method for measuring the amount of oil applied can be, for example, a gravimetric method in which a part of a steel sheet sample to which oil has been applied is cut out, its mass is measured, the same sample is then degreased, and its mass is measured again, and the amount of oil applied to the steel sheet is calculated from the difference in mass.

[0027] [Pickup Roll (PR)] (Materials and Structure of Pickup Roll) An example of PR4 is a roll having a structure in which a steel core is provided with a rubber outer layer.

[0028] (Diameter of Pickup Roll) The PR diameter, which is the diameter of PR4, is preferably 100 to 1200 mm. If the PR diameter is less than 100 mm, the amount of rust-preventive oil 9 attached may become excessive, making it difficult to adjust with the scraper 8. On the other hand, if the PR diameter is more than 1200 mm, the distance that the attached rust-preventive oil 9 travels before reaching BR4 may be too long, and the oil may fall due to gravity or the like during this movement, resulting in an insufficient amount of attached oil.

[0029] (Immersion Depth of Pickup Roll) The immersion depth of PR4 (the depth from the oil surface of the rust-preventive oil 9 to the lower end position of PR4) is preferably 1 / 4 to 1 / 2 of the PR diameter. If the immersion depth of PR4 is less than 1 / 4 of the PR diameter, the amount of rust-preventive oil 9 adhering to PR4 may be insufficient. If the immersion depth of PR4 is more than 1 / 2 of the PR diameter, the contact point between PR4 and BR5 may be above the oil pan 6, and the amount of rust-preventive oil 9 splashed onto the steel strip 12 may be insufficient.

[0030] (Rotational Speed ​​of Pickup Roll) The rotational speed of the PR, which is the rotational speed of the PR 4, is preferably 10 to 100 rpm. If the PR rotational speed is less than 10 rpm, the oil may not be applied uniformly, resulting in unevenness, while if it exceeds 100 rpm, it may become difficult to control the amount of oil applied. In the present invention, from the viewpoint of improving the accuracy of controlling the amount of oil applied, it is preferable that the PR rotational speed be directly proportional to the sheet threading speed, as in the conventional case described above.

[0031] Brush Roll (Brush roll material, structure, etc.) BR4 is, for example, a resin base with 0.1 to 0.5 mm diameter nylon brushes at 1,000 to 10,000 brushes / m. 2 Examples of such rolls include those with a structure in which the fibers are planted at a density of 1000 times.

[0032] (Diameter of Brush Roll) The BR diameter, which is the diameter of BR4, is preferably 100 to 1500 mm. If the BR diameter is less than 100 mm, uniform oil application is difficult, while if it exceeds 1500 mm, an unnecessary increase in the load on the motor 13 occurs. In addition, the BR diameter is preferably equal to or greater than the PR diameter. If the BR diameter is less than the PR diameter, the BR rotation speed may exceed the upper limit of the preferred range described below.

[0033] (Rotational speed of brush roll) The rotational speed of the BR, which is the rotational speed of the BR4, is preferably 10 to 50 rpm. When the rotational speed of the BR is less than 10 rpm, the amount of oil applied falls within the preferred range of the target amount of oil applied (1.0 to 3.0 g / m 2 ), whereas if the rotational speed exceeds 50 rpm, the amount of oil applied may exceed the preferable range of the target amount of oil applied.

[0034] [How to adjust the brush roll rotation speed: Calculating the target value (VBR) of the BR rotation speed] In the oil application method of the present invention shown in FIG. 1, the target oil application amount (g / m 2 The BR rotation speed is adjusted according to the AO and the strip threading speed (m / min) (VS). The adjustment is done by increasing or decreasing the BR rotation speed to increase or decrease the amount of oil applied. Also, the BR rotation speed is increased or decreased in response to an increase or decrease in VS.

[0035] An example of a method for calculating the target value (VBR) of the BR rotation speed to specifically accomplish this will be described below.

[0036] The ambient temperature near the oil pan 6 is defined as air temperature T. If the oil application amount is obtained experimentally in an environment where air temperature T is stable at, for example, 20°C, and the strip threading speed VS and BR rotation speed shown in Table 1, the oil application amount is directly proportional to the BR rotation speed, and the proportionality constant is a linear expression of VS, and the following equation (1) is obtained.

[0037] Oil amount (g / m 2 ) = (a × VS (m / min) + b) × BR rotation speed (rpm) ‥‥ (1) Here, a and b are coefficients at the temperature T=20° C., and in this case, a=−0.0005 and b=−0.055.

[0038] Therefore, in equation (1), the amount of oil applied (g / m 2 ) to the target oil application amount (g / m 2 ) (AO), and the BR rotation speed (rpm) is set to its target value (rpm) (VBR), and VBR is calculated using the following equation (2) which is a modification of equation (1).

[0039] VBR(rpm)=AO(g / m 2 ) / (a×VS(m / min)+b) ‥‥(2) In an environment where the temperature T (hereinafter simply referred to as "T") changes with the seasons, the following can be done: For example, when T=40°C, the following equation (3), which has the same format as equation (2), can be obtained by the same procedure as above.

[0040] VBR(rpm)=AO(g / m 2 ) / (a1×VS(m / min)+b1) ‥‥(3) Here, a1 and b1 are coefficients at T=40°C.

[0041] For temperatures T (°C) other than 20°C and 40°C, the value of equation (2) (assuming V20 (rpm)) and the value of equation (3) (assuming V40 (rpm)) at the same AO and VS are used to calculate VBR (rpm) at temperature T using the following equation (4) by linear interpolation.

[0042] VBR at temperature T = V20 + (V40 - V20) / 20 x (T - 20) ... (4) Next, as shown in Fig. 2, the oiling method of the present invention preferably further adjusts the rotation speed (BR rotation speed) of the brush roll 4 in consideration of the kinematic viscosity OKV of the rust-preventive oil 9. For this reason, the oiling device 1 of the present invention preferably further adjusts the rotation speed (BR rotation speed) of the brush roll 4 in consideration of the kinematic viscosity OKV of the rust-preventive oil 9. An example of such a means is a calculator 17A (Fig. 2(b)). The calculator 17A calculates VBR from the inputted and set AO, VS, and OKV by a method described below, and transmits the derived VBR to the adjuster 16.

[0043] In this way, adjusting the BR rotation speed according to the target oil application amount (AO), strip threading speed (VS), and kinematic viscosity (OKV) of the rust preventive oil 9 is preferable because it makes it easy to respond to changes in the specifications of the rust preventive oil 9.

[0044] [Calculation of target value (VBR) of brush roll rotation speed taking into account dynamic viscosity] One method for adjusting the BR rotation speed is to take into account the kinematic viscosity, which increases or decreases the amount of rust preventive oil 9 adhering to PR 5 and therefore the amount of splashing from BR 4 to steel strip 12, and therefore to increase or decrease VBR accordingly. Specifically, one method is to calculate VBR at temperature T using the following equation (5), which is obtained by multiplying equation (4) by a correction coefficient α that depends on the kinematic viscosity (OKV) that has been set and input.

[0045] VBR at temperature T = α × {V20 + (V40 - V20) / 20 × (T - 20)} (5) Here, α is expressed by the following equation (6). α = Coefficient K × (1 - kinematic viscosity at temperature T / reference kinematic viscosity) (6) In equation (6), the reference kinematic viscosity is the median value of the range of kinematic viscosity used. The kinematic viscosity at temperature T is calculated using the temperature dependency information of kinematic viscosity in the purchase specifications for the rust preventive oil 9, assuming that the temperature in the oil temperature dependency information is equal to temperature T. The coefficient K is used to obtain a VBR that maintains an appropriate oil application amount in response to changes in kinematic viscosity. This coefficient K can be determined in advance through experiments in which the kinematic viscosity is changed to multiple levels without changing any other conditions, and the oil application amount is calculated.

[0046] Next, when the oil application method of the present invention takes into consideration the kinematic viscosity (OKV), it is preferable to include a step of actually measuring the temperature (OT) of the rust preventive oil 9 and calculating the OKV from the measured value, as shown in Figure 3. For this purpose, it is preferable that the oil application device 1 of the present invention further includes a thermometer 20 and a kinematic viscosity calculator 18.

[0047] A thermometer 20 is installed, for example, in the oil pan 6, and measures the temperature (OT) of the rust preventive oil 9. A kinematic viscosity calculator 18 derives a kinematic viscosity (OKV) from the measured OT. Then, calculator 17A calculates a target value (VBR) of the BR rotation speed from the inputted and set AO, VS, and the derived kinematic viscosity (OKV) using a method described later, and transmits the derived VBR to adjuster 16.

[0048] In the present invention, when taking into consideration the kinematic viscosity, as in the example of Figure 3, it is preferable to derive the kinematic viscosity from the actual measured value of the temperature OT of the rust preventive oil 9 rather than from the air temperature T, as this can improve the accuracy of oil application amount control compared to the example of Figure 2, which uses measurement of the air temperature T.

[0049] [Calculation of the target value (VBR) of the brush roll rotation speed taking into account the kinematic viscosity by measuring the temperature of the rust preventive oil 9] As a method for calculating VBR in the example of FIG. 3, for example, the VBR at the temperature OT of the rust preventive oil 9 can be calculated using the following equation (7), which is obtained by multiplying the equation (4) by a correction coefficient β that depends on the kinematic viscosity derived from the OT.

[0050] VBR at temperature OT of rust preventive oil 9 = β × {V20 + (V40 - V20) / 20 × (T - 20)} ‥‥(7) Here, β is expressed by the following equation (8) in which the "kinetic viscosity at temperature OT of the rust preventive oil 9" is substituted for the "kinetic viscosity at temperature T" in the above equation (6). β = Coefficient K × (1 - kinematic viscosity of rust preventive oil 9 at temperature OT / standard kinematic viscosity) ‥‥(8) In equation (8), the kinematic viscosity of the rust preventive oil 9 at temperature OT is the kinematic viscosity calculated using the temperature dependency information of the kinematic viscosity in the purchase specifications of the rust preventive oil 9.

[0051] Next, as shown in Fig. 4, the oil application method of the present invention preferably further comprises a step of incorporating air bubbles 10 into the rust preventive oil 9 in the above-mentioned oil application method (Fig. 2). For this purpose, the oil application device 1 of Fig. 4 is provided with a means for incorporating air bubbles 10 into the rust preventive oil 9.

[0052] In the present invention, which takes the kinematic viscosity into consideration, as shown in Fig. 3, for example, high precision oil application amount control can be achieved by adjusting the BR rotation speed in accordance with the target oil application amount (AO) and the strip threading speed (VS) and taking into consideration the kinematic viscosity (OKV) of the rust preventive oil 9. In particular, when the kinematic viscosity is low, it is easy to increase the BR rotation speed to bring the oil application amount closer to the target oil application amount (AO). However, when the kinematic viscosity is extremely high, reducing the BR rotation speed does not reduce the oil application amount sufficiently, and the oil application amount may end up being greater than the target oil application amount (AO). In such cases, it is difficult to maintain high precision oil application amount control by measuring the air temperature T. Note that an example of an extremely high kinematic viscosity is when the outside air temperature is extremely low (for example, below 0°C) and the kinematic viscosity is extremely high (for example, 100 mm 2 / s or more) or when using a highly lubricating and rust-preventive oil with an extremely high kinetic viscosity.

[0053] On the other hand, when the kinematic viscosity is extremely high, as shown in FIG. 4, by adding bubbles 10 to the rust-preventive oil 9, the density of the rust-preventive oil 9 is reduced, and the weight of the rust-preventive oil 9 per unit area on the surface of the steel strip 12, i.e., the amount of oil applied, is reduced by the same amount. Therefore, when the kinematic viscosity is abnormally high (for example, 100 mm 2 / s or more), the oil application amount can be brought close to the target oil application amount (AO) and high-precision oil application amount control can be maintained.

[0054] In the oil application device 1 of FIG. 4, the means for incorporating air bubbles 10 into the rust preventive oil 9 is exemplified by one equipped with a gas supply pipe (hereinafter also referred to as a “gas pipe”) 11 and a gas supply control unit 30.

[0055] The gas pipe 11 has a nozzle (not shown) at its tip, and is used to blow gas 19 into the rust-preventive oil 9 in the oil pan 6, for example, to incorporate air bubbles 10 into the rust-preventive oil 9. The gas supply control unit 30 controls the amount of gas 19 supplied depending on the kinematic viscosity (OKV). The means for performing this function will be described later.

[0056] [Bubble content] The content of bubbles 10 in the rust preventive oil 9 (hereinafter also referred to as "bubble content") is calculated by the following formula (9).

[0057] Air bubble content (volume %) = gas supply flow rate (L / h) / (gas supply flow rate (L / h) + oil supply flow rate (L / h)) × 100 (9) Here, the gas supply flow rate and the oil supply flow rate are volumetric flow rates when the gas 19 and the rust preventive oil 9 are supplied into the oil pan 6, respectively.

[0058] The range of the bubble content is preferably 0.01 to 20.00% by volume, because if the bubble content is less than 0.01% by volume, the effect of lowering the density of the rust preventive oil 9 is insufficient, and if the bubble content exceeds 20.00% by volume, the bubbles become saturated and escape from the oil, making it difficult to achieve and increasing the cost.

[0059] [Method for measuring bubble content] The air bubble content is determined by measuring the specific gravity of oil 9 that does not contain air bubbles 10 and the specific gravity of oil 9 that contains air bubbles 10, and designating them as A1 and A2, respectively, and calculating the value of (A1-A2) / A1 x 100. The calculated value of formula (9) is approximately the same as this measured value.

[0060] [Gas supply flow rate] To keep the bubble content within the above-mentioned preferred range (0.01 to 20.00% by volume), for example, when the supply flow rate of the rust preventive oil 9 is a maximum of 50 L / h, the gas supply flow rate can be set in proportion to the bubble content, within the range of 0.005 to 10 L / h. Note that the upper limit is preferably set lower than 10 L / h, for example, 8 L / h, to provide some leeway.

[0061] [Bubble size] The bubble diameter, which is the size of the bubbles 10, is expressed as the diameter of a sphere with the same volume and is preferably 5000 μm or less. If the bubble diameter exceeds 5000 μm, the bubbles 10 will burst due to buoyancy while rising before adhering to the PR5, making it difficult to obtain the desired bubble content.

[0062] The critical condition for generating bubbles 10 in the rust preventive oil 9 from the discharge port of the gas pipe 11 is expressed by, for example, the following formula (10).

[0063] Gas density / 2 x (gas flow rate / piping cross-sectional area) 2 + Gas density × Gravitational acceleration × Bubble volume = Pipe outlet diameter × Bubble surface tension ‥‥(10) Equation (10) expresses the critical condition under which the bubble will leave the outlet when the gas pressure plus buoyancy of the bubble connected to the outlet exceeds the bubble surface tension (i.e., the surface tension of the oil on the bubble interface). The bubble volume can be calculated from equation (10), and the bubble diameter can be calculated assuming the bubble is spherical. For example, if the gas density is 1145 g / m 3 , Gas flow rate = 40 L / h, Pipe cross-sectional area = 19.6 mm 2 , gravitational acceleration=9.8m / s 2 When the pipe outlet diameter is 5 mm and the bubble surface tension is 36 mN / m, the bubble diameter is 0.06 mm.

[0064] [Gas supply control means] The gas supply control unit 30 has the following means A to C (not shown) to control the supply amount of the gas 19 according to the kinematic viscosity (OKV).

[0065] (Means A) Means A compares the kinematic viscosity with a threshold value, and if it exceeds the threshold value, calculates the excess of the oil application amount from the target oil application amount based on the excess of the kinematic viscosity. This can be configured using a normal personal computer. Here, the threshold value is set to, for example, 80% of the upper limit of the preferred range of kinematic viscosity. The excess of the oil application amount is calculated by using information on the relationship between the kinematic viscosity and the oil application amount at the lower limit of the preferred range of the BR rotation speed, which has been determined in advance through experiments, to find the excess of the oil application amount corresponding to the excess of the kinematic viscosity.

[0066] (Means B) Means B calculates the bubble content to cancel out the excess amount of oil applied calculated in Means A, and calculates the gas supply flow rate to achieve that bubble content. This can be configured using a normal personal computer (which can also be used for Means A). Here, the bubble content is calculated by subtracting the excess amount of oil applied (g / m 2 ) corresponding to the oil weight increase per unit volume (g / m 3), it can be calculated using the following formula (11): 2 ) the oil weight increase per unit volume is x / d (g / m 3 )

[0067] Air bubble content (volume %) = oil weight increase per unit volume (g / m 3 ) / Oil density (g / m 3 ) × 100 ‥‥(11) The gas supply flow rate (L / h) can be calculated using the following formula (12), which is a modification of the formula (9).

[0068] Gas supply flow rate (L / h) = Air bubble content (volume %) × Oil supply flow rate (L / h) / (100 - Air bubble content (volume %)) (12)

[0069] (Means C) Means C controls the flow rate of gas 19 so that it coincides with the calculated value of equation (12). This means C can be configured with a normal gas supply source, a gas flow meter, a flow rate adjusting valve, and the like.

[0070] [Type of gas] The type of gas 19 to be used to form the bubbles 10 in the rust-preventive oil 9 is not particularly limited, and may be any of nitrogen, air, argon, helium, oxygen, hydrogen, etc., but nitrogen is preferred. Nitrogen is preferred because it is not only relatively inexpensive to obtain but also, being an inert gas, does not cause problems such as deterioration of the rust-preventive oil 9 or corrosion of the steel strip 12.

[0071] Next, as shown in Fig. 5, the oil application method of the present invention preferably measures the temperature OT of the rust-preventive oil 9 and incorporates air bubbles 10 into the rust-preventive oil 9. For this reason, the oil application device 1 in Fig. 5 is equipped with a thermometer 20 that measures the temperature of the rust-preventive oil 9, and a gas pipe 11 and a gas supply control unit 30 for incorporating air bubbles 10 into the rust-preventive oil 9. This allows for even more accurate control of the oil application amount than when the air temperature T is measured and air bubbles 10 are incorporated into the rust-preventive oil 9 (Fig. 4).

[0072] 1 to 5 show the oil application method and oil application device of the present invention for applying oil to the top surface of a steel strip. While the present invention also allows for oil application to the bottom surface of a steel strip, it is preferable to use a BR rotation speed that is higher than that for the top surface in order to disperse the oil upward against gravity. However, even when oiling the top surface, if the steel strip is wound into a coil, the rust-preventive oil on the top surface is sandwiched between the top and bottom surfaces and transferred to the bottom surface, resulting in the bottom surface also being oiled, so this is not a particular problem. [Example]

[0073] Example 1 In Example 1 of the present invention, a cold-rolled annealed steel strip having a width of 1000 mm was subjected to oil application using the oil application method and oil application device of the present invention shown in Figure 1, while adjusting the BR rotation speed according to the target oil application amount and strip threading speed. The oil pan 6 has a width of 2000 mm and a capacity of 80 L. The rust preventive oil 9 has a kinematic viscosity of 80 mm at 10°C. 2 / s, 20 mm at 40°C 2 / s temperature dependency. The oil supply flow rate is 40 L / h, and the target oil application amount is 1.5 g / m 2 , 2.5g / m 2 The strip threading speed is adjusted appropriately within the range of 50 to 200 m / min. The PR diameter is 500 mm, the PR4 immersion depth is 200 mm, and the PR rotation speed is directly proportional to the strip threading speed within the range of 10 to 100 rpm. The BR diameter is 1000 mm. The BR rotation speed is adjusted to the value calculated by equation (4) within the aforementioned preferred range.

[0074] In Example 1, the oil application amount error was evaluated for 20 coils of steel strip using the following formula (13).

[0075] Oil amount error = |1 - actual oil amount / target oil amount| for each coil, total over the number of coils / number of coils (13) Here, the actual oil amount is calculated by cutting a cut sheet from the outermost winding of each coil, measuring the oil film thickness of the rust preventive oil 9 with an infrared absorption type film thickness meter, and using the following formula (14).

[0076] Actual oil amount (g / m 2) = Oil film thickness of anti-rust oil 9 (m) × Density of anti-rust oil 9 (g / m 3 ) ...(14) As a comparative example, instead of using the formula (4) in Example 1, the BR rotation speed was adjusted to 0.5 to 2 times the PR rotation speed, and other conditions were the same as in Example 1. The oil application amount error was evaluated for 20 coils of steel strip using the formula (13).

[0077] As a result, the oil application error in the comparative example was 0.29 g / m 2 In contrast, the oil application error in Example 1 was 0.21 g / m 2 This indicates that the accuracy of oil application amount control according to the present invention is improved.

[0078] Example 2 In Example 2, the same cold-rolled and annealed steel strip as in Example 1 was used, and oiling was carried out by the oiling method and oiling device of the present invention shown in Fig. 2 described above, while adjusting the BR rotation speed in Example 1 in consideration of the kinematic viscosity of the rust-preventive oil 9. The width and capacity of the oil pan 6, the rust-preventive oil 9, the oil supply flow rate, the strip threading speed, the PR diameter, the immersion depth of the PR 4, the PR rotation speed, and the BR diameter were the same as in Example 1.

[0079] In Example 2, when considering the kinematic viscosity of the rust preventive oil 9, the air temperature T is measured and used as the temperature related to the temperature dependency of the kinematic viscosity. The BR rotation speed is adjusted to be within the above-mentioned preferred range so as to obtain the calculated value of the above-mentioned equation (5). The coefficient K in the above-mentioned equation (6), which represents the correction coefficient α in the above-mentioned equation (5), is determined in advance through an experiment in which the kinematic viscosity is changed to multiple levels and the oil application amount is determined while keeping conditions other than the kinematic viscosity unchanged.

[0080] In Example 2, the oil application amount error was evaluated using the formula (13) for 20 coils of steel strip. As a result, in Example 2, the oil application amount error was 0.19 g / m 2 This was smaller than in Example 1, and the accuracy of oil application amount control was improved compared to Example 1.

[0081] Example 3 In Example 3, the same cold-rolled and annealed steel strip as in Example 1 was used, and oiling was carried out by the oiling method and oiling device of the present invention shown in Fig. 3 described above, while adjusting the BR rotation speed in Example 1 in consideration of the kinematic viscosity of the rust-preventive oil 9. The width and capacity of the oil pan 6, the rust-preventive oil 9, the oil supply flow rate, the strip threading speed, the PR diameter, the immersion depth of the PR 4, the PR rotation speed, and the BR diameter were the same as in Example 1.

[0082] In Example 3, when considering the kinematic viscosity of the rust-preventive oil 9, the temperature OT of the rust-preventive oil 9 is measured and used as the temperature related to the temperature dependency of the kinematic viscosity. The BR rotation speed is adjusted to be the value calculated by equation (7) above within the above-mentioned preferred range. β in equation (7) above is expressed by equation (8) above, and the coefficient K in equation (8) above is shared with equation (6) above.

[0083] In Example 3, the oil application amount error was evaluated for 20 coils of steel strip using the above formula (13). As a result, in Example 3, the oil application amount error was 0.17 g / m 2 This was smaller than in Example 2, and the accuracy of oil application amount control was improved compared to Example 2.

[0084] Example 4 In Example 4, the same cold-rolled and annealed steel strip as in Example 1 was used, and oiling was performed using the oiling method and oiling device of the present invention shown in FIG. 4 above, with the addition of a step of incorporating air bubbles 10 into the rust-preventive oil 9, as in Example 2. The width and capacity of the oil pan 6, the rust-preventive oil 9, the oil supply flow rate, the strip threading speed, the PR diameter, the immersion depth of the PR 4, the PR rotation speed, and the BR diameter were the same as in Example 2. As in Example 2, the BR rotation speed was adjusted so that it was within the above-mentioned preferred range and was the value calculated by the above-mentioned formula (5).

[0085] In Example 4, when the air bubbles 10 are contained in the rust preventive oil 9, the gas of the air bubbles 10 is nitrogen gas, and when the kinematic viscosity exceeds a threshold value, the air bubbles 10 are contained in the rust preventive oil 9 by the above-mentioned means A to C. The threshold value of the kinematic viscosity is 40 mm 2 / s.

[0086] In Example 4, the oil application amount error was evaluated using the above formula (13) for 20 coils of steel strips whose kinematic viscosity exceeded the threshold. As a result, the oil application amount error was 0.22 g / m 2 In Example 2, the kinematic viscosity was below the threshold value. In Example 2, the oil application amount error was evaluated in the same manner for 20 coils of steel strips whose kinematic viscosity exceeded the threshold value. As a result, the oil application amount error was 0.27 g / m 2 That is, when the kinematic viscosity was extremely high (above the threshold value), the accuracy of the oil application amount control decreased in Example 2, but the accuracy of the oil application amount control could be maintained in Example 4.

[0087] Example 5 In Example 5, the same cold-rolled and annealed steel strip as in Example 1 was used, and oiling was performed using the oiling method and oiling device of the present invention shown in Figure 5 above, with the addition of a step of incorporating air bubbles 10 into the rust-preventive oil 9 in Example 3. The width and capacity of the oil pan 6, the rust-preventive oil 9, the oil supply flow rate, the strip threading speed, the PR diameter, the immersion depth of the PR 4, the PR rotation speed, and the BR diameter were the same as in Example 3. The BR rotation speed was adjusted to be the value calculated by the above formula (7) within the above-mentioned preferred range.

[0088] In Example 5, when the air bubbles 10 are contained in the rust preventive oil 9, the gas of the air bubbles is nitrogen gas, as in Example 4, and the air bubbles 10 are contained in the rust preventive oil 9 by the above-mentioned means A to C when the kinematic viscosity exceeds the threshold value. The threshold value of the kinematic viscosity is 40 mm 2 / s.

[0089] In Example 5, the oil application amount error was evaluated using the above formula (13) for 20 coils of steel strips whose kinematic viscosity exceeded the threshold. As a result, the oil application amount error was 0.18 g / m 2 In Example 3, the kinematic viscosity was below the threshold value. In Example 3, the oil application amount error was evaluated in the same manner for 20 coils of steel strips whose kinematic viscosity exceeded the threshold value. As a result, the oil application amount error was 0.21 g / m 2 That is, when the kinematic viscosity was extremely high (above the threshold value), the accuracy of the oil application amount control decreased in Example 3, but the accuracy of the oil application amount control could be maintained in Example 5.

[0090] [Table 1] [Explanation of symbols]

[0091] 1. Oil application device of the present invention 2 Leveling roll 3 Pinch Roll 4 Brush Roll (BR) 5 Pickup Roll (PR) 6 Oil pan 7 Mist Cover 8. Scraper 9. Rust prevention oil 10 bubbles 11 Gas piping (gas supply piping) 12 Steel strips 13 Motor (for brush roll) 14 Motor (for pickup roll) 15 Tachometer 16 Regulator 17, 17A computing unit 18 Kinematic viscosity calculator 19 Gases 20 thermometer 30 Gas supply control unit AO target oil amount OKV kinematic viscosity OT Temperature of rust preventive oil 9 T Air temperature (ambient temperature around oil pan 6) VBR Brush Roll 4 rotation speed (BR rotation speed) target value VS Threading speed

Claims

1. A method for applying rust-preventive oil to a steel strip, in which rust-preventive oil 9 stored in an oil pan 6 is wound up by a pickup roll 5 and the rust-preventive oil 9 adhering to the surface of the pickup roll 5 is scattered onto a steel strip 12 by a brush roll 4, characterized in that the rotational speed of the brush roll 4 is adjusted according to the target amount of rust-preventive oil 9 to be applied and the passing speed of the steel strip 12.

2. 2. The method for oiling a steel strip according to claim 1, wherein the rotational speed of said brush roll is adjusted in consideration of the kinetic viscosity of said rust preventive oil.

3. 3. The method for oiling a steel strip according to claim 2, wherein the rust preventive oil (9) contains air bubbles (10).

4. 4. The method for oiling a steel strip according to claim 3, wherein the content of the bubbles in the rust-preventive oil is 0.01 to 20.00 volume %.

5. 5. A method for oiling a steel strip according to claim 3 or 4, characterized in that the gas in the bubbles (10) is nitrogen.

6. An oil application device comprising an oil pan (6) storing anti-rust oil (9), a pickup roll (5) for picking up the anti-rust oil (9) in the oil pan (6), and a brush roll (4) for scattering the anti-rust oil (9) adhering to the surface of the pickup roll (5) onto a steel strip (12) while rotating, A means for adjusting the rotation speed of the brush roll 4 in accordance with the target oil application amount of the rust preventive oil 9 and the threading speed of the steel strip 12 is provided. An oil application device for steel strips.

7. The oil application device for a steel strip as described in claim 6, characterized in that the means for adjusting the rotational speed of the brush roll (4) is a means for adjusting the rotational speed of the brush roll (4) taking into account the dynamic viscosity of the rust-preventive oil (9).

8. 8. The oil application device for a steel strip according to claim 7, further comprising means for making the rust preventive oil (9) contain air bubbles (10).

9. 9. An oiling device for a steel strip according to claim 8, wherein the gas in the bubbles is nitrogen.

Images