JP4797730B2 - Cold rolling method - Google Patents

Description

  The present invention relates to a cold rolling method effective for supplying emulsion rolling oil to a strip (metal strip) when performing cold rolling using a circulating rolling oil supply method.

  In general, when a strip is rolled by a cold rolling mill, rolling oil is supplied to the strip in order to improve rollability. As a general rolling oil supply method used at that time, a system in which coolant in an emulsion state in which water and rolling oil are mixed is sprayed from a nozzle onto a strip. In order to prepare an emulsion, a predetermined amount of oil is added to water, and stirring and shearing by a pump are added to obtain an emulsion liquid. In addition, the emulsion rolling oil supply method in cold rolling includes a direct method (direct method) and a circulation method (recirculation method).

  The direct rolling oil supply system (direct system) is excellent in lubricity and cooling properties because high-concentration emulsion rolling oil is sprayed on the steel sheet for the purpose of lubrication and water is sprayed on the roll for the purpose of cooling. However, unlike the circulation system, since the emulsion rolling oil is not circulated, the rolling oil intensity is high. On the other hand, the circulating rolling oil supply method (recirculation method) is a steel plate and roll for the purpose of lubrication and cooling while circulating low-concentration emulsion rolling oil prepared by mixing and stirring rolling oil and cooling water in advance. The basic unit of rolling oil is low. However, it cannot be denied that the lubricity and the cooling performance are inferior compared with the direct rolling oil supply system. Therefore, in the conventional circulation system, especially when a thin material having a finished sheet thickness of 0.2 mm or less is rolled at high speed, lubrication becomes insufficient, and rolling mill vibration called chattering and surface flaws called heat scratch occur, so the rolling speed There was a problem that could not be raised. In particular, when heat scratches are generated, surface defects are generated in the rolled material, so that not only the yield is lowered, but also a rolling mill in which heat scratches are generated has a problem that productivity is remarkably lowered because work rolls need to be replaced.

  In order to solve such a problem, various inventions have been made so far to solve the problem by eliminating insufficient lubrication that causes chattering and heat scratching. Among them, the following methods are known as methods for solving the lack of lubrication in the circulating oil supply system.

(1) A method of limiting the pressure of the lubricating and cleaning coolant to a low pressure (see Patent Document 1).
(2) A method of providing a second rolling oil supply system (see Patent Document 2).
Further, the following methods are known as methods for eliminating the temperature rise of the strip that causes heat scratch.

(3) A method of controlling the rolling reduction so as not to exceed the heat scratch control target temperature (see Patent Document 3).
(4) A method of controlling the work roll speed so as not to exceed the heat scratch control target temperature (see Patent Document 4).
Japanese Patent No. 2871392, claims, etc. JP 2003-266116 A, Claims, etc. JP 2000-202505 A, claims, etc. JP 2000-167614 A, claims, etc.

  However, since the prior art presented in Patent Document 1 limits the coolant pressure of the emulsion rolling oil to a low pressure, the amount of emulsion supplied to the strip is also limited at the same time. When the supply amount is limited, it becomes difficult to uniformly spray the strip, the rolling state in the width direction of the plate changes, and the shape of the plate may be defective.

  The prior art presented in Patent Document 2 improves lubricity and prevents chattering by injecting an emulsion with high adhesion efficiency from the second rolling oil supply system. However, regarding heat scratches, it is known that heat scratches are likely to occur when the interface temperature between the work roll and the rolled material or the exit-side rolled material temperature exceeds a certain value, regardless of the amount of oil film in the roll bite. Ori (Japan Iron and Steel Institute “Approaching Mechanism of Seizure Phenomenon”, (1999) p83), the frequency of heat scratching could not be reduced sufficiently only by increasing the amount of oil introduced into the roll bite.

  The conventional techniques presented in Patent Document 3 and Patent Document 4 are effective in preventing heat scratching because the rolling conditions are relaxed. However, not only the production efficiency is lowered, but when a rapid rolling condition change such as deformation resistance change during rolling due to the base plate factor occurs, when the rolling reduction (rolling load) or tension is changed to follow, There is a problem that the plate thickness fluctuates.

  The present invention was made to solve these problems of the prior art, and by adjusting the base oil component ratio of the emulsion rolling oil supplied according to the rolling conditions, the response of the lubricating oil supply control is improved. An object of the present invention is to provide a cold rolling method that is excellent and efficient in preventing chattering and heat scratching, improving productivity, and enabling improvement in oil intensity.

  Emulsion-type rolling oil used for cold rolling is based on simple oils or mixtures of animal and vegetable oils, mineral oils, synthetic esters, etc., as well as various surfactants, oiliness improvers, extreme pressure additives, antioxidants, etc. Additives are appropriately blended, and this is diluted with water to an emulsion of usually about 1 to 4% by volume, and supplied to the strip or roll.

  In addition, base oils based on natural fats and oils are low in cost, but have many problems such as high pour point and high scum accumulation and insufficient circulation stability. Therefore, although the rolling oil cost increases, a liquid synthetic ester that does not solidify at room temperature is blended to reduce the pour point of the rolling oil itself and improve workability.

  As a result of earnestly examining the means for preventing heat scratches in the high-speed rolling zone when the emulsion is supplied to the steel sheet, the present inventors have obtained the following conclusions.

  In general, it is well known that heat scratches are caused by metal contact between the steel sheet and the roll due to the breakage of the lubricating film to be interposed in the roll bite. To prevent heat scratching, the strip temperature is Even in a high region, it is necessary to keep the oil film strength of the lubricating film strong. However, in a circulating supply system that circulates and uses an emulsion, a decrease in oil film strength due to deterioration over time is unavoidable. Therefore, when the strip temperature reaches or approaches the limit temperature at which heat scratches occur, an emulsion with an increased base oil ratio of an ester having high heat resistance deterioration is injected from a lubrication header provided in another system. This maintains the oil film strength in the high-temperature strip region and prevents heat scratches.

  The emulsion of the second rolling oil supply system is prepared by newly blending rolling oil base oil and dilution water. Since the base oil component ratio of the rolling mill oil and the supply amount of the rolling oil are mixed just before the header, the adjustment response is very high. Moreover, in order to eliminate the influence when the emulsion of a 2nd rolling oil supply system mixes in a circulating rolling oil supply tank, it is set as the same kind of base oil as a circulating rolling oil supply system.

  In the high-speed rolling zone, the spraying time is shortened as the speed is increased, and the amount of rolling oil supplied per unit area of the steel sheet is reduced. Therefore, it is effective to use an emulsion with a high average particle size and high plate-out characteristics.

  Also, during high-speed rolling, heat scratches may occur not only on the lower surface side of the steel plate but also on the upper surface side, so it is necessary to improve the lubricity on the upper surface side of the steel plate, and the average grain size was increased on the upper surface side. It is necessary to supply an emulsion with high plate-out characteristics.

  Moreover, in this invention, it is preferable to make the position of the spray header for supplying the emulsion of a 2nd rolling oil supply system into the position as close as possible to the upstream stand away from the roll bite. This is due to the following reason. In order to form a stable plate-out layer, the time for phase inversion from a state of an O / W emulsion in which oil is dispersed in water to a W / O emulsion in which water is dispersed in oil or a single oil phase (hereinafter, It is preferable to ensure a phase inversion time). In the rolling mill, the time from when the emulsion is supplied to the steel sheet surface on the inlet side of the rolling mill until reaching the roll bite according to the sheet feeding speed corresponds to the phase inversion time. Therefore, it is assumed that the higher the rolling speed, the shorter the phase inversion time, and thus it becomes difficult to form the plate-out layer. On the other hand, the phase inversion time can be secured by setting the position of the spray nozzle as close as possible to the upstream stand far from the roll bite.

  In addition, since the emulsion of the second rolling oil supply system is effectively used to supplement the shortage of the circulating supply system, the basic unit of the rolling oil is the same as in the conventional circulating rolling oil supply system. Can be lowered.

  The present invention has been made based on the above findings, and includes the following steps.

(1) A first rolling oil supply step, which is composed of a mixture of two or more types of base oils, supplies emulsion rolling oil in cold rolling to the strip surface in a circulating manner; and a first rolling oil supply step The emulsion rolling oil, which is composed of a mixture of base oils having the same components as the emulsion and adjusted to have an average particle size larger than that of the emulsion in the first rolling oil supply step, is positioned at the upstream stand side away from the roll bite. A second rolling oil supply step for supplying the strip surface;
Recovering the emulsion that did not adhere to the steel sheet in the rolling oil supply step, and collecting and joining the emulsion in the first rolling oil supply step, a cold rolling method comprising :
The second rolling oil supply step includes a step of adjusting a base oil component ratio of the emulsion rolling oil to be supplied according to rolling conditions,
The step of adjusting the base oil component ratio of the emulsion rolling oil includes a step of measuring the strip temperature on the rolling stand exit side in real time or a step of calculating a predicted value of the strip temperature on the rolling stand exit side, and measurement. Alternatively, the strip temperature obtained by the calculation is supplied to the second rolling oil supply process based on the temperature difference between the strip temperature and the heat scratch generation limit temperature so as not to exceed the heat scratch generation limit temperature determined in advance. And a step of controlling the base oil component ratio of the emulsion rolling oil .

(2) The step of controlling the base oil component ratio of the emulsion rolling oil is such that the ester ratio is constant when the strip temperature obtained by measurement or calculation is less than the preliminarily determined heat scratch generation limit temperature, and the heat scratch generation limit temperature The cold rolling method according to (1), wherein the base oil component ratio of the emulsion rolling oil is changed at a certain point.

(3) The second rolling oil supply step includes a step of supplying emulsion rolling oil to the strip surface at the header where the mixer is arranged,
The step of adjusting the base oil component ratio of the emulsion rolling oil includes the step of adjusting the base oil component mixing ratio of the emulsion rolling oil using a mixer disposed immediately before or in the header ( The cold rolling method according to 1) or (2) .

  In the present invention, the base oil component ratio of the supplied emulsion rolling oil, specifically the ester ratio, is adjusted according to the rolling conditions so that the strip temperature does not exceed the heat scratch generation limit temperature determined in advance. In the case of rolling a thin material having a finishing plate thickness of 0.2 mm or less, the lack of lubrication that has occurred at the time of high-speed rolling in the conventional method is solved, and chattering and heat scratching can be prevented. As a result, since the rolling speed can be improved, the productivity can be greatly improved.

  Furthermore, when the strip temperature is low, the operation is performed with a constant ester ratio, the strip temperature becomes high, and the base oil component ratio of the emulsion rolling oil is changed at or near the heat scratch generation limit temperature, The influence on the emulsion of the entire circulation system can be extremely reduced.

  Next, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a schematic configuration diagram showing a rolling oil supply device according to the present embodiment, in which the emulsion rolling oil supply from the second rolling oil supply means is applied to the fifth stand of all five tandem mills. is there.

  The reason why it is applied to the fifth stand is that the rolling speed is higher in the latter stand, and the plate thickness becomes thinner, so that the rolling load becomes higher and the lubrication conditions become stricter. In this cold rolling mill, tension rolls and deflores (not shown) are installed between adjacent stands. In the present invention, the stand of the rolling mill is a single stand or all or any of a plurality of stands.

  The first rolling oil supply means as the circulating rolling oil supply means of the cold rolling mill in FIG. 1 includes a lubricating coolant header 4a, a cooling coolant header 4b, and a circulating rolling oil supply tank 5. A tank 5 is a tank for storing the emulsion rolling oil for lubrication, and a stirrer 11 is provided. The tank 5 is passed through the rolling oil supply line 7 with The coolant headers 4a and 4b of the stands 1 to 5 communicate with each other, and a pump 6 is interposed in the line 7. Here, a one-fluid nozzle is used as the lubricating coolant header 4a, but a two-fluid nozzle may be used in the same manner as the two-fluid nozzle header 28 described later.

  Hot water and rolling oil crude oil are accommodated in the circulating rolling oil supply tank 5 and mixed. The accommodated mixture is made into the 1st emulsion rolling oil which has a desired average particle diameter by adjusting the rotation speed of the stirring blade of the stirrer 11. FIG. The first emulsion rolling oil of the first rolling oil supply means is pumped by the emulsion supply pump 6, and the 1 to 5 is supplied to each stand, and spray is supplied from the spray header 4a on the entrance side of each stand and the spray header 4b on the exit side of each stand toward the roll tool and the work roll, respectively. Of the supplied first emulsion rolling oil, the emulsion rolling oil that has fallen from the strip 3 is recovered by a recovery oil pan 9 as rolling oil supply means, and returned to the tank 5 via a return pipe 10. . The spray supply of the first emulsion rolling oil is performed from the start of rolling.

  As the base oil component of the first emulsion rolling oil, those conventionally used for cold rolling oil can be used. For example, animal and vegetable fats and oils such as beef tallow and palm oil and their refined products; synthetic esters with polyhydric fatty acids; mineral oils such as machine oil, spindle oil and turbine oil, and two or more selected from these groups (base Oil mixture). However, in order to prevent the formation of scum around the rolling mill due to the solidification of the rolling oil and the mixing of the rolling powder with the metal powder, which tends to occur particularly when the temperature is low, the pour point is 20 ° C. or lower. It is preferred to use oil. When using animal and vegetable fats and oils or synthetic esters having a pour point higher than 20 ° C., the pour point of the rolling oil itself is preferably 20 ° C. or lower, more preferably, in combination with another base oil having a low pour point. By making it 10 degrees C or less, the surface quality and working environment of a rolling material are improved.

  Next, the 2nd rolling oil supply means as a circulation type rolling oil supply means is demonstrated.

  As the base oil component of the second emulsion rolling oil, the same component as the base oil component of the first emulsion rolling oil is used. The base oil of the rolling oil used for the second rolling oil supply means is stored in the storage tank 15. The rolling oil supply line 19 is provided with a rolling oil pump 16 and a flow rate control valve 18 so that the supply flow rate of the base oil discharged to the rolling oil mixer 20 can be controlled. The flow rate of the flow rate control valve 18 is adjusted by a command from the base oil adjustment controller 17. A radiation thermometer 29 is disposed on the final stand exit side, and the radiation thermometer 29 outputs a detection signal to the base oil adjustment controller 17. The base oil adjustment controller 17 determines whether or not the output measurement value of the radiation thermometer 29 is within a range of a safe strip temperature (heat scratch generation limit temperature) that can prevent the occurrence of heat scratch that has been obtained in advance. If it is determined that the temperature reaches or is close to the heat scratch generation limit temperature, the ester in the base oil according to the relative value from the safety strip temperature based on the heat clutch generation limit temperature line (see FIG. 2). The ratio is calculated and output to the flow control valve 18.

  Here, the heat scratch generation limit temperature is obtained in advance as follows. As the range of the safety strip temperature, a region where heat scratches may occur when the range is exceeded is obtained in advance from experiments and operation data, and the safety strip temperature as shown in FIG. 2 for each steel type, size, and rolling cycle. Set the range. For example, as shown in FIG. 3, the ester ratio of the second emulsion rolling oil is kept constant below the heat scratch generation limit temperature, and when the strip temperature rises, the second temperature is set so as not to exceed the heat scratch generation limit temperature. Change the ester ratio of emulsion rolling oil. In the example of FIG. 3, the ester ratio is changed in proportion to the amount of displacement of the heat scratch generation limit temperature, but the present invention is not limited to this. For example, the displacement amount and the base oil ratio may be associated in a stepped manner.

  Here, it is preferable that the ester ratio of the second emulsion rolling oil below the heat scratch generation limit temperature is the same as the ester ratio of the first emulsion rolling oil. This is because the influence on the first emulsion rolling oil used in circulation can be extremely reduced. In addition, it is also possible to make it lower than the ester ratio of 1st emulsion rolling oil. In that case, since the effect of lowering the rolling oil intensity is obtained, the ester ratio of the second emulsion rolling oil can be appropriately set according to the purpose.

  In the above description regarding the present embodiment, the ester ratio of the base oil has been described as being controlled. However, the present invention is not limited to this, and the ratio of the animal or vegetable oil or mineral oil in the base oil may be controlled.

  Reference numeral 12 denotes a storage tank that stores hot water, and a hot water pump 13 is interposed in the hot water supply line 14. The supply flow rate at which the rolling oil base oil whose base oil ratio is adjusted by the hot water and the rolling oil mixer 20 is discharged to the mixer 22 by the flow rate adjusting valve 21 is controlled. The flow rate control valve 21 adjusts the supply oil amount according to a command from the supply oil amount adjustment controller 25. Then, the coolant in an emulsion state by the mixer 22 is sent out to the two-fluid nozzle header 28.

  A two-fluid nozzle is used for the two-fluid nozzle header 28 in FIG. Air used in the two-fluid nozzle header 28 is pumped by the gas supply line 27 through the compressor 26 and supplied to the two-fluid nozzle header 28. The two-fluid nozzle header 28 is branched and disposed so as to be located both above and below the strip 3. The second emulsion rolling oil whose supply oil amount is adjusted by the mixer 22 is mixed with air by the two-fluid nozzle header 28 and sprayed toward the front and back surfaces of the strip 3. In addition, the mixer 22 is preferably installed at a position close to the two-fluid nozzle header 28 in order to improve the response of adjusting the amount of oil supplied to the emulsion.

  In the two-fluid nozzle header 28, the emulsion particle size is adjusted by adjusting the air amount of the two-fluid nozzle, and the average particle size of the emulsion sprayed from the two-fluid nozzle header 28 is the circulating rolling oil supply system. An emulsion having an average particle size larger than that. For example, when the base oil is an animal and vegetable oil and a synthetic ester and an emulsifying surfactant is combined, the average particle size of the emulsion in the circulation system is about 7 to 10 μm. On the other hand, the average particle diameter of the emulsion sprayed from the two-fluid nozzle header 28 is adjusted to 15 to 30 μm. The temperatures in the hot water tank 12 and the rolling oil base oil tank 15 are the same as those in the circulating rolling oil supply system.

  The amount of oil supplied from the two-fluid nozzle header 28 is controlled based on an advanced rate that is closely related to the friction coefficient. The roll speed meter 23 and the plate speed meter 24 measure the roll peripheral speed and the plate speed. These measurement results are sent to the controller 25 for adjusting the supply oil amount, and the advanced rate is calculated. The supply oil amount adjustment controller 25 obtains a required supply oil amount based on the relationship between the friction coefficient and the advanced rate, and outputs an operation signal to the flow control valve 21. As a result, the amount of oil supplied to the strip 3 is controlled, and the oil film is maintained at a required thickness.

  In the rolling oil supply apparatus configured as described above, the required amount of supply oil is adjusted by mixing the necessary amount of rolling oil base oil and hot water just before the two-fluid nozzle header 28 and supplying it to the two-fluid nozzle header 28. Rolled oil is sprayed on the surface of the strip 3. Since the supply oil amount is adjusted immediately before the two-fluid nozzle header 28 as described above, the responsiveness of the supply oil amount adjustment of the rolling oil is very high.

  Moreover, since the mixing of the rolling oil base oil and the hot water is performed immediately before the two-fluid nozzle header 28, the shearing force applied to the emulsion is minimized, and the rolling oil having a large emulsion particle size with high adhesion efficiency is applied to the surface of the strip 3. Is injected into.

  In addition, even though the optimum supply amount of rolling oil is supplied with high response, since the emulsion with a large particle size is sprayed over a wide range by the two-fluid nozzle, the plate-out on the surface of the strip 3 becomes uniform, Stable lubricity can be obtained.

  Moreover, in order to make it possible to cope with all rolling conditions, the lower limit value of the emulsion concentration sprayed from the two-fluid nozzle header 28 may be the concentration of the first emulsion rolling oil of the first rolling oil supply means. preferable. The upper limit of the emulsion concentration sprayed from the two-fluid nozzle header 28 is 100% (crude oil concentration of rolling oil).

The flow rate of the jetting air from the two-fluid nozzle is preferably 0.5 to 10 Nm ³ / hr per nozzle. If it is less than 0.5 Nm ³ / hr, the interference between the droplets of the rolled emulsion oil increases, so that the adhesion efficiency decreases due to the influence of surrounding moisture during plate-out. On the other hand, if it exceeds 10 Nm ³ / hr, the amount of emulsion rolling oil scattered by excess air increases, and the adhesion efficiency decreases.

  The position of the two-fluid nozzle header 28 is as far as possible from the roll bite (indicated by L in FIG. 1), that is, as close as possible to the upstream stand. From the O / W emulsion to the W / O emulsion, The time for phase inversion to the phase, that is, the phase inversion time is secured.

  Between the stands, tension rolls and deflours are installed, and even if the emulsion rolling oil is sprayed on the upstream side of the stands, since it is squeezed by the tension rolls or defloors, a sufficient plate-out amount cannot be obtained. In order to avoid this, in this example, it was installed immediately after the tension roll and defloor between the stands. In order to secure the transfer time, the two-fluid nozzle header 28 is desirably located at a position 1 m or more, more preferably 2 m or more away from the roll bite.

  After spraying on the strip 3, the emulsion rolling oil that does not plate out to the strip 3 is collected in a collecting oil pan 9 as a rolling oil collecting means, collected together with the first emulsion rolling oil, and circulated through the return pipe 10. Returned to the type rolling oil supply tank 5. The recovered first and second emulsion rolling oils are stirred by the stirrer 11 in the tank 5 and then repeatedly subjected to strong shearing at the nozzles of the pump 6 and the coolant and cooling coolant headers 4a and 4b. It is subdivided to the same particle size as the circulatory system emulsion and becomes a tight emulsion. The concentration of the circulating emulsion is usually in the range of 1 to 4%.

  When the second rolling oil supply means is used, the flow rate from the lubricating coolant header 4a of the first rolling oil supply means need not be particularly adjusted. This is because the plate-out by the emulsion rolling oil from the two-fluid nozzle header 28 of the second rolling oil supply means is dominant for the oil film formation, and the influence of the plate-out from the lubricating coolant header 4a is small. It is.

  Spraying from the two-fluid nozzle header 28 is preferably performed on the front and back surfaces of the metal strip for the metal strip, but when lubrication failure is characteristic on one side, only the front side or only the back side only You may go to Further, the injection from the two-fluid nozzle header 28 may be stopped only for the soft material just before the low-speed rolling part or roll reassignment in which the rolling oil tends to be excessively supplied. Moreover, although the embodiment shown in FIG. 1 has been described that the base oil component ratio and the supply oil amount of the upper and lower two-fluid nozzle headers 28 are controlled by a single system mixer, a mixer is provided for each of the upper nozzle and the lower nozzle. You may change a base oil component ratio and supply oil amount with a nozzle. For example, when a lubricant with a high ester ratio is sprayed on the lower surface, which is considered to be relatively severely lubricated, and a lubricant with a low ester ratio is sprayed on the upper surface, it is mixed into the first rolling oil supply means. The impact can be minimized.

  In the present invention, the embodiment shown in FIG. 1 has been described as being applied to five stands, but the rolling oil supply from the second rolling oil supply means may be applied only to a single stand of a rolling mill, The present invention may be applied to all of a plurality of stands or a plurality of arbitrary stands. Examples of the strip include a steel strip, a stainless steel strip, an aluminum strip, and a copper strip.

  Further, the embodiment shown in FIG. 1 has been described on the assumption that a radiation thermometer is installed on the outlet stand. However, when there is no means for measuring the strip temperature, heat generation terms such as processing heat generation and friction heat generation, cooling coolant, The strip temperature may be predicted from a heat balance equation formed from a deprivation term such as air cooling.

  Using a cold tandem rolling mill with 5 stands in the embodiment shown in FIG. 1, a hard tin plate having a base material thickness of 2.3 mm and a plate width of 900 mm was rolled to a finish thickness of 0.200 mm at a target speed of 2400 m / min. Rolling oil is a mixed oil of synthetic ester and vegetable oil (ester ratio in base oil 30%, kinematic viscosity 43 cSt at 40 ° C), and emulsion rolling of circulating rolling oil supply means (first rolling oil supply means) The oil was added with an emulsion concentration of 3%, an emulsifying surfactant, and after sufficient stirring in the tank, an emulsion having an average particle size of 9 μm and a temperature of 60 ° C. was obtained. Moreover, the temperature of the emulsion rolling oil of the 2nd rolling oil supply means was made the same with a circulation system, and the rolling oil density | concentration was 10%.

  In Example 1, the supply flow rate of the second rolling oil supply means is adjusted to 50 liters / min, and the average particle size of the emulsion is adjusted to 20 μm, and the controller 17 for adjusting the base oil as shown in FIG. The base oil ratio was controlled according to the strip temperature at the stand exit side.

  In Comparative Example 1, the base oil ratio control is not performed, and the base oil ratio of the emulsion rolling oil in the second rolling oil supply means is the same as that of the emulsion rolling oil in the first rolling oil supply means. Similarly, cold rolling was performed.

  The rolling oil supply as described above was performed, rolling was performed while changing the speed, and the occurrence of chattering and heat scratching was investigated. The survey results are shown in Table 1 below.

  As shown in Table 1, when the present invention was used, acceleration was possible up to 2400 mpm without generating heat scratches. On the other hand, in the case of Comparative Example 1, mild heat scratches were generated at 2100 mpm, and remarkable heat scratches were generated at higher speeds. The reason for this is that the interface temperature between the work roll and the rolled material or the temperature of the rolled material is high in the high-speed rolling region, so that the oil film strength is insufficient at the current base oil ratio, and the oil film breaks in the roll bite.

As shown in the test results, when the fifth stand was lubricated by the rolling oil supply method of Comparative Example 1 as before, the rolling speed was limited to 1900 mpm due to the generation of heat scratch, and high speed rolling was hindered. However, by using the present invention, heat scratches in the high speed region are eliminated, so that heat scratches can be prevented and high speed rolling at 2400 mpm is possible.

The figure which shows the example applied to the tandem rolling mill in connection with embodiment of this invention. The figure which shows an example of the ester ratio in base oil required for prevention of a heat scratch. The figure which shows the target ester ratio according to the strip temperature used for the base oil ratio control of an Example.

Explanation of symbols

1 Work Roll 2 Backup Roll 3 Strip 4a Lubricating Coolant Header 4b Cooling Coolant Header 5 Circulating Rolling Oil Supply Tank 6 Emulsion Supply Pump 7 Rolling Oil Supply Line 8 Flow Control Valve 9 Recovery Oil Pan 10 Return Pipe 11 Agitator 12 Hot Water Tank 13 Hot water pump 14 Hot water supply line 15 Rolling oil base oil tank 16 Rolling oil pump 17 Base oil adjusting controller 18 Flow control valve 19 Rolling oil supply line 20 Rolling oil mixer 21 Flow control valve 22 Mixer 23 Roll speed meter 24 Plate speed Total 25 Controller for adjusting oil supply amount 26 Compressor 27 Gas supply line 28 Two-fluid nozzle header

Claims (3)

The same as the emulsion of the 1st rolling oil supply process which comprises the mixture of two or more types of base oils, and supplies the emulsion rolling oil in cold rolling to the strip surface in a circulating manner, and the 1st rolling oil supply process An emulsion rolling oil composed of a mixture of component base oils and adjusted to have an average particle size larger than that of the emulsion in the first rolling oil supply process is applied to the strip surface at a position on the upstream stand side away from the roll bite. A second rolling oil supply step to supply, and a recovery and merging step for recovering the emulsion that did not adhere to the steel plate in the second rolling oil supply step and merging with the emulsion in the first rolling oil supply step. Cold rolling method ,
The second rolling oil supply step includes a step of adjusting a base oil component ratio of the emulsion rolling oil to be supplied according to rolling conditions,
The step of adjusting the base oil component ratio of the emulsion rolling oil includes a step of measuring the strip temperature on the rolling stand exit side in real time or a step of calculating a predicted value of the strip temperature on the rolling stand exit side, and measurement. Alternatively, the strip temperature obtained by the calculation is supplied to the second rolling oil supply process based on the temperature difference between the strip temperature and the heat scratch generation limit temperature so as not to exceed the heat scratch generation limit temperature determined in advance. And a step of controlling the base oil component ratio of the emulsion rolling oil . The step of controlling the base oil component ratio of the emulsion rolling oil is performed at the time when the strip temperature obtained by measurement or calculation is less than the predetermined heat scratch generation limit temperature, the ester ratio is constant, and the heat scratch generation limit temperature is reached. cold rolling method according to claim 1, characterized in that the change of the base oil component ratio of the emulsion rolling oil. The second rolling oil supply step includes a step of supplying emulsion rolling oil to the strip surface at the header where the mixer is arranged,
The step of adjusting the base oil component ratio of the emulsion rolling oil includes the step of adjusting the base oil component mixing ratio of the emulsion rolling oil using a mixer disposed immediately before or within the header. Item 3. The cold rolling method according to Item 1 or 2 .

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