JP4042141B2 - Cold rolled steel sheet manufacturing method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for producing a cold rolled steel sheet using a tandem rolling mill having a circulating rolling oil supply system, and more particularly, in high speed rolling, by preventing chattering of the rolling mill, The present invention relates to a method for producing a cold-rolled steel sheet without a sheet.
[0002]
[Prior art]
In a cold rolling mill that performs high-speed rolling of a thin steel plate, one of the phenomena that hinders stable rolling is an abnormal vibration phenomenon accompanied by noise called chattering. When this chattering occurs, fluctuations in sheet thickness and tension between rolling stands occur, and in some cases, the steel sheet may be broken. As a result, quality and yield decrease due to fluctuations in sheet thickness, roll unit intensity deteriorates due to sheet breakage, and equipment operation rate decreases.
[0003]
The chattering phenomenon is a self-excited vibration phenomenon of a roll system of a rolling mill. Therefore, it is known that the vibration frequency coincides with the natural frequency of the rolling mill. This frequency is usually several tens to several hundreds Hz.
[0004]
One of the causes (trigger) of chattering (self-excited vibration) is that as rolling progresses, the work roll roughness decreases, and the coefficient of friction between the work roll and the rolled material decreases. It has been said that a state of excessive lubrication occurs, and accordingly, the advance rate becomes negative (that is, the neutral point jumps out of the roll bite) and the rolling becomes unstable (for example, , Iron and Steel, 73 (1987) No. 10, p.1358).
[0005]
On the other hand, with the recent trend toward tin and hard gauge, which is the product trend of tinplate materials, the rolling speed has been further increased in order to improve productivity, and high-speed rolling exceeding 1800 m / min is being carried out. And in the production process of such a product, chattering due to insufficient lubrication occurs, which is an impediment to high-speed rolling.
As can be seen from the above, the chattering phenomenon is greatly affected by the rolling lubricity, and the occurrence of chattering due to insufficient lubrication becomes a problem particularly in the high-speed rolling region.
[0006]
To date, as a technique for preventing chattering, a technique described in Japanese Patent Publication No. 3-50602 has been known. In this technology, a vibration meter is installed in the housing of the rolling mill to detect the housing vibration, and only the frequency that characterizes the chattering phenomenon, that is, the natural frequency of the rolling mill is extracted by a filter, and the vibration speed after passing through the filter ( When the value used in ISO 2372 and the like exceeds a certain value, sheet thickness variation and sheet breakage due to chattering are prevented by adjusting the rolling conditions. Specific methods for adjusting the rolling conditions include a method of reducing the rolling speed, a method of changing the rolling schedule of the tandem rolling mill, and a method of changing the spray flow rate of the emulsion rolling oil.
[0007]
[Problems to be solved by the invention]
However, any of the methods for adjusting rolling conditions described in Japanese Patent Publication No. 3-50602 has a problem that sufficient effects cannot be exhibited under high-speed rolling conditions.
That is, the method of reducing the rolling speed can prevent chattering, but cannot achieve a high rolling speed. Also, in the method of changing the rolling schedule, the rolling schedule is changed by changing the roll peripheral speed ratio of each stand. This causes rapid fluctuations in the tension, destabilizes the rolling, and in some cases causes sheet breakage.
[0008]
Moreover, there existed the following problems regarding the method of adjusting the spray flow rate of emulsion rolling oil. That is, in a cold tandem rolling mill having a circulating rolling oil supply system, an emulsion rolling oil prepared by previously mixing and stirring rolling oil with cooling water is used for the purpose of lubrication and cooling. Spraying from the nozzle on the surface ("Theory and practice of plate rolling", Japan Iron and Steel Institute, p. 208). In such an emulsion rolling oil spray system, the method of adjusting the flow rate of the emulsion rolling oil supplied to the work roll (hereinafter referred to as the roll coolant flow rate) is as high as 1800 m / min. A sufficient effect could not be obtained under high speed rolling conditions.
[0009]
The present invention has been made in view of such circumstances, and even when high-speed rolling exceeding 1800 m / min is performed in a cold tandem rolling mill having a circulating rolling oil supply system, abnormal sheet thickness is generated due to chattering. It is another object of the present invention to provide a method for producing a cold-rolled steel sheet that is free from defects and prevents the occurrence of sheet breakage.
[0010]
[Means for solving problems]
The first means for solving the problem is a method of manufacturing a cold rolled steel sheet by a cold continuous rolling mill, and when the chattering of the stand of the cold continuous rolling mill is detected, the stand or the stand Spraying the rolling mill oil supply system emulsion rolling oil onto the upstream steel plate away from the upstream stand roll bite and adjusting the flow rate to perform cold rolling while preventing chattering It is a manufacturing method (Claim 1) of the cold-rolled steel plate characterized by having.
[0011]
In order to achieve the above-mentioned problems, the present inventors have made extensive studies on a chattering prevention method by adjusting the spray flow rate of emulsion rolling oil in a tandem rolling mill. The reason for paying attention to this method is that the method of controlling the rolling lubricity is considered to be most effective in preventing chattering due to the fact that the occurrence of chattering is greatly affected by the rolling lubricity.
[0012]
In order to prevent chattering, chattering occurs when the vibration of the housing is detected, only the same frequency as the rolling mill's natural frequency is extracted by a filter, and the vibration speed after passing the filter exceeds a certain value. It is necessary to detect the occurrence of chattering by the above-described method for determining that the rolling lubrication has been performed, and to greatly control the rolling lubricity by adjusting the spray flow rate of the emulsion rolling oil. In order to confirm this point, the relationship between the roll coolant flow rate and the friction coefficient was investigated.
[0013]
FIG. 5 shows the arrangement of the emulsion and spray headers in the circulating rolling oil supply system in a tandem rolling mill with 5 stands. The roll coolant is installed on the entry side and the exit side of the stand. The entry side roll coolant serves both as lubrication and cooling, and the exit side roll coolant is for roll cooling.
[0014]
The mechanism by which the entry side roll coolant functions as lubrication is as follows. That is, some emulsion particles (oil particles) that directly collide with the upper work roll surface adhere to the work roll surface as an oil film, and the emulsion rolling oil that did not adhere on the upper surface side of the steel sheet stays on the steel sheet surface. Oil also adheres to the upper surface side of the steel plate. And the emulsion rolling oil which did not plate out a water | moisture content falls from the board end. On the other hand, among the emulsion rolling oil sprayed on the lower work roll, a part of the emulsion particles that directly collide with the roll surface simply adheres as an oil film to the roll surface and immediately falls without staying on the steel plate. The phenomenon that the oil particles in this emulsion rolling oil adhere to the steel plate and the roll surface is called plate-out. The work roll and the plate-out layer on the surface of the steel sheet are introduced into the roll bite and function as a lubricating oil film.
[0015]
FIG. 6 shows the final stand (No. 5 stand) having a high occurrence frequency of chattering in the tandem rolling mill shown in FIG. 5 when the final stand has a low speed rolling condition of 1000 m / min and a high speed rolling condition of 1800 m / min. This is the result of investigating the relationship between the inlet side roll coolant flow rate and the friction coefficient. The roll coolant flow rate is the total flow rate of the upper and lower spray headers.
[0016]
According to this, when the speed is 1000 m / min, the friction coefficient is greatly decreased as the roll coolant flow rate is increased, and the friction coefficient, that is, the rolling lubricity can be largely controlled by adjusting the roll coolant flow rate. On the other hand, when the speed is 1800 m / min, the friction coefficient is higher than the speed of 1000 m / min, and it is understood that the lubrication state is deteriorated. Also, at a speed of 1800 m / min, when the roll coolant flow rate exceeds a certain value, the friction coefficient hardly changes, and the adjustment of the roll coolant flow rate cannot reduce the friction coefficient below a certain value, that is, rolling. It can be seen that the lubricity cannot be improved. This suggests that a sufficient effect cannot be obtained by adjusting the flow rate of the roll coolant to prevent chattering due to insufficient lubrication, which is a problem under high-speed rolling conditions.
[0017]
One of the reasons why the friction coefficient at a speed of 1800 m / min is high is that when the rolling speed is high, the amount of emulsion rolling oil supplied per unit area of the steel sheet decreases due to the decrease in spray time, and the plate-out amount decreases. Is mentioned. As another reason, as described in detail below, there is an influence of a phenomenon depending on the time after the plate-out of the emulsion rolling oil reaches the spray surface of the steel plate.
[0018]
In addition, when the flow rate exceeds 1800 m / min and exceeds a certain roll coolant flow rate, the phenomenon that the friction coefficient cannot be lowered below a certain friction coefficient is the time after the plate-out of emulsion rolling oil reaches the spray surface of the steel sheet. It is related to the phenomenon that depends on.
[0019]
The phenomenon that depends on the time after the plate-out of the emulsion rolling oil reaches the spray surface of the steel sheet will be described in detail below. When emulsion rolling oil is sprayed onto steel plates and rolls, the oil component separates from the water and forms an oil film (plate-out layer). This is because a so-called O / W emulsion (oil droplets dispersed in water) in which oil droplets are dispersed in water is phase-shifted into a W / O emulsion (water droplets dispersed in oil) or an oil monolayer, and the oil content is reduced. It is a phenomenon that spreads on the spray surface. Since this process does not occur instantaneously when sprayed, but is caused by a transition process (reaction) such as phase inversion, it is considered to be a time-dependent process. The time required for this may be short, but it goes without saying that a certain time is required anyway. The inventors considered that the time for phase inversion (hereinafter referred to as phase inversion time) has a great influence on the plate-out property.
[0020]
The inventors investigated the relationship between the plate-out property of the emulsion rolling oil and the phase inversion time by the plate-out test method shown in FIG. 7 in order to confirm the influence of the phase inversion time on the plate-out property. In this plate-out test method, a steel plate sample (sample plate) heated to a predetermined temperature is given a predetermined speed by free fall, and emulsion rolling oil is sprayed on the surface of the steel plate sample in the middle of dropping, and only a predetermined distance below it. An air blow nozzle is provided at a distant position, the unphased emulsion on the sample is blown off, and only the plate-out layer (oil film) phase-shifted to the steel plate sample is evaluated. The plate-out amount is measured by a method of measuring the weight of the steel sheet sample before and after degreasing with an electronic balance or the like.
[0021]
FIG. 8 shows the plate-out test results. According to this, the plate-out amount greatly depends on the phase inversion time, and the plate-out amount decreases as the phase inversion time becomes shorter. This result shows that in actual rolling, when the roll peripheral speed and the steel plate speed are increased, the time from the supply of the emulsion rolling oil to the arrival of the roll bite, that is, the effect of shortening the phase inversion time, the plate out amount This suggests that the amount of oil introduced into the roll bite will decrease.
[0022]
Based on the results of the plate-out test described above, the interpretation of the relationship between the roll coolant flow rate and the friction coefficient shown in FIG.
The overall friction coefficient when rolled at a speed of 1800 m / min rather than a speed of 1000 m / min is the effect that the supply amount per unit area of steel sheet of emulsion rolling oil decreases due to a decrease in spray time, This is because the plate-out amount decreases due to the effect of shortening the phase inversion time, and the amount of oil introduced into the roll bite decreases.
[0023]
When using a spray header for roll coolant, under high-speed rolling conditions of 1800 m / min, the time from spraying the emulsion rolling oil on the roll surface to biting into the roll bite is very short, and the phase inversion of the emulsion It is thought that sufficient time cannot be secured. Thus, since it becomes difficult to plate out in a situation where a sufficient phase inversion time cannot be secured, it is considered that even if the spray flow rate of the emulsion rolling oil is increased, a phenomenon in which the plate out amount does not increase occurs.
[0024]
The reason why the friction coefficient does not change when the roll coolant flow rate is exceeded at a speed of 1800 m / min is presumed to be because the sufficient phase inversion time cannot be obtained as described above. On the other hand, when the speed is 1000 m / min, the roll coolant flow rate can be changed to a lower friction coefficient because of the low speed, so the phase inversion time can be secured, and the plate-out amount can be adjusted according to the roll coolant flow rate. This is considered to be possible to change.
[0025]
The above results show that under high-speed rolling conditions where the final stand speed exceeds 1800 m / min, even if the roll coolant flow rate is changed to prevent chattering, the rolling lubricity cannot be controlled, so that a sufficient effect can be obtained. Suggests not.
[0026]
Based on the above findings, the present inventors have intensively studied a method that can greatly change the rolling lubricity even under high-speed rolling conditions of 1800 m / min or higher, and as a result, the upstream stand as far as possible from the roll bite entry side. We found a method of adjusting the flow rate by installing a coolant header at the steel plate position close to the side and spraying the emulsion rolling oil of the circulating rolling oil supply system. This method will be described in detail below.
[0027]
Fig. 9 shows the case where the installation position of the spray header for roll coolant of No. 5 stand (final stand) is moved to the position on the upstream stand side away from the roll bite entry side and sprayed toward the steel plate surface. The arrangement of the spray header is shown. The spray header A is a conventional spray header for roll coolant, and the spray headers B, C and D are installed at positions 0.5 m, 1.5 m and 2.5 m away from the roll bite entry side, respectively.
[0028]
The distance between the stands is 4.5m, but tension rolls and deflector rolls (deflores) are installed between the stands. Even if the emulsion rolling oil is sprayed upstream from this, In order to squeeze, the position of the spray header that is farthest from the roll bite entry side is actually immediately after the tension roll or defloor between the stands. The spray header D in FIG. 9 corresponds to this.
[0029]
FIG. 10 shows the flow rate of the spray toward the steel plate surface (hereinafter referred to as the strip coolant flow rate) and the friction of the final stand when rolling at the final stand speed of 1800 mpm in the tandem rolling mill shown in FIG. It is the result of investigating the relationship between the coefficients. The farther the spray header mounting position is from the roll bite and the closer to the upstream stand side, the wider the range of friction coefficient change by changing the strip coolant flow rate, and the lower the friction coefficient at the same strip coolant flow rate. In addition, when the constant spray flow rate exceeds a certain value, the phenomenon of saturation with a constant friction coefficient tends to be eliminated.
[0030]
FIG. 11 shows the results of investigation on the amount of oil adhering to the surface of the rolled material. The reason why the amount of oil adhering to the steel sheet has a certain value when the strip coolant flow rate is zero is that the rolling oil remains on the steel sheet after rolling in the upstream stand. According to this, the amount of oil adhering to the steel plate corresponds to the coefficient of friction, and increases as the spray header mounting position is moved away from the roll bite and closer to the upstream stand side.
[0031]
The reason is as follows. That is, even under high-speed rolling conditions exceeding 1800 m / min, the plate-out phase inversion time can be secured and the plate-out phase can be secured as the position where the emulsion rolling oil is sprayed onto the steel sheet is closer to the upstream stand side away from the roll bite. It becomes easy to form a layer. That is, even with the same strip coolant flow rate, the longer the phase inversion time is, the greater the plate-out amount becomes. Therefore, the change in the plate-out amount with respect to the change in the strip coolant flow rate also increases. As a result, the change in the coefficient of friction also increases.
[0032]
It is effective that the rolling stand for controlling the flow rate of the strip coolant is a chattering stand, or a chattering stand and a stand on the upstream side thereof. It is desirable to use the last stand or the last stand and one stand upstream of it.
[0033]
In addition, in this means, the “upstream side away from the roll bite” means that it is upstream from the position of the conventional strip coolant, but as described above, the distance from the roll bite is separated. The farther away, the greater the effect. Also, “adjusting the flow rate of the emulsion rolling oil” means that when chattering occurs, for example, the flow rate is changed depending on the degree of chattering (if the chattering is large, the flow rate is increased) or until chattering is resolved. Various methods such as increasing the flow rate sequentially can be considered.
[0034]
In addition, “in the actual process, spraying the emulsion rolling oil of the circulating rolling oil supply system on the steel plate on the upstream side away from the stand or the roll bite of the stand and the upstream stand” In this rolling mill, a pipe for spraying the emulsion rolling oil of the circulating rolling oil supply system is provided on the upstream side away from the roll bite position, and spraying is performed from this pipe even when chattering does not occur. This also includes a method of changing the flow rate when chattering occurs. Of course, if chattering does not occur, the emulsion rolling oil is sprayed from a pipe near the roll bite (prior art pipe), and only when chattering occurs, the emulsion rolling oil is switched from the spray away from the roll bite position. Alternatively, spraying may be repeated, but it is preferable to spray from the same pipe from the viewpoint of facility and control stability.
[0035]
The second means for solving the above-mentioned problem is a method for producing a cold rolled steel sheet by a cold continuous rolling mill, wherein a rolling oil supply system is provided separately from the circulating rolling oil supply system, When chattering of the stand of the rolling mill is detected, the emulsion rolling oil adjusted to have a larger average particle size than the circulating rolling oil supply system is sent from the separate rolling oil supply system to the stand or the stand and its stand. Cold rolling characterized by comprising a step of performing cold rolling while preventing chattering by spraying on the upstream steel plate away from the roll bit of the upstream stand and adjusting the flow rate thereof It is a manufacturing method (claim 2) of a steel plate.
[0036]
Moreover, the 3rd means for solving the said subject is said 2nd means, Comprising: The average particle diameter of emulsion rolling oil is 20 micrometers or more (Claim 3), It is characterized by the above-mentioned.
[0037]
In the case of ultra-high speed rolling exceeding 2500 m / min, it is difficult to ensure sufficient phase inversion time even if the installation position of the strip / coolant spray header is as close as possible from the roll bite entry side to the upstream stand side. In the control of the flow rate of the strip coolant of the emulsion rolling oil of the circulation system by means 1, the sufficient effect may not be obtained.
[0038]
The inventors have intensively studied a method that can greatly change the rolling lubricity by adjusting the strip coolant flow rate even under ultra-high speed rolling conditions of 2500 m / min or more, which makes it difficult to ensure sufficient phase inversion time. The emulsion rolling oil adjusted so that it may become an average particle diameter larger than a type rolling oil supply system was sprayed in the steel plate position of the upstream stand side away from the roll bite, and the method of adjusting the flow volume was discovered. This method will be described in detail below.
[0039]
In general, since the emulsion rolling oil used in the circulating rolling oil supply system is recycled, emulsification dispersibility is emphasized, and the emulsion rolling oil having a small average particle diameter is used. The reason for this is that when emulsion rolling oil with a large average particle size is used, emulsion particles easily disintegrate due to the mixing of wear powder generated by rolling or iron powder brought into the steel sheet, and the emulsion dispersibility changes over time. This is because it becomes easy to cause problems such as instability of rolling and change in gloss of the steel sheet surface.
[0040]
On the other hand, FIG. 12 shows that when a cationic surfactant is added to beef tallow rolling oil and the average particle size of the circulating emulsion rolling oil is 10 μm, the average particle size of 20 μm emulsion is larger than this. 9 shows the relationship between the strip coolant flow rate at the rolling speed of 2500 m / min and the friction coefficient of the No. 5 stand when the steel sheet surface is sprayed from the spray header D shown in FIG. For comparison, the coefficient of friction when spraying the same emulsion rolling oil with an average particle size of 10 μm as the circulation system is also shown.
[0041]
As can be seen from FIG. 12, the coefficient of friction is lower when the average particle size is 20 μm. Further, when the average particle size is 10 μm, a phenomenon that the friction coefficient is saturated at a certain strip coolant flow rate or more is observed, but when the average particle size is 20 μm, this phenomenon is not observed.
FIG. 13 shows the measurement result of the amount of oil adhering to the surface of the rolled material. The emulsion having an average particle size of 20 μm has a larger amount of oil adhering and corresponds to the friction coefficient.
[0042]
FIG. 14 shows the amount of change in friction coefficient and emulsion when the average particle diameter of the emulsion rolling oil is changed in the range of 5 to 30 μm and the flow rate is changed in the range of 0 to 4000 L / min at a rolling speed of 2500 m / min. This shows the relationship of average particle diameter. According to this, the amount of change in the friction coefficient increases as the average particle diameter increases, and in particular, the amount of change in the friction coefficient rapidly increases when the average particle diameter is 20 μm or more.
[0043]
The above-described results are because the plate-out amount increases as the average particle size of the emulsion rolling oil increases, so that the change in the friction coefficient with respect to the change in the emulsion supply amount increases.
[0044]
As mentioned above, rolling lubricity is improved even at a rolling speed of 2500 m / min by spraying emulsion rolling oil with a larger average particle size than the circulation system at the steel plate position on the upstream stand side away from the roll bite and adjusting the flow rate. It can be seen that it can be controlled.
Further, as described above, by setting the average particle size of the emulsion rolling oil to be sprayed to 20 μm or more, the friction coefficient in high-speed rolling can be rapidly reduced.
[0045]
In addition, since the emulsion rolling oil having a large average particle size is not suitable for the emulsion rolling oil of the circulating rolling oil supply system, the emulsion rolling oil adjusted to have a larger average particle size than the circulating rolling oil supply system, Even in the case of spraying from the separate rolling oil supply system, in the upstream side stand (for example, No. 1 to No. 3 stand in the case of all 5 stand rolling mills), the normal (conventional) circulation type is not performed. From the rolling oil supply system, emulsion rolling oil having an average particle diameter similar to that of the conventional one is supplied.
[0046]
In addition, “spray on the steel plate on the upstream side away from the stand or the roll bite of the stand and the upstream side stand” means that chattering does not occur in the rolling mill that performs such a thing in the actual process. In this case, spraying of the emulsion rolling oil adjusted to have a larger average particle diameter than that of the circulating rolling oil supply system from the separate rolling oil supply system is performed, and when chattering occurs, the flow rate is reduced. It also includes a method of changing.
[0047]
Of course, even in such a stand, if the rolling oil of the conventional circulating rolling oil supply system is provided near the roll bite and chattering does not occur, the circulating rolling oil from the pipe near the roll bite (prior art piping). Emulsion that is sprayed from the rolling rolling oil supply system by switching the emulsion rolling oil with a large average particle size from the spraying of the separate rolling oil supply system or only when chattering occurs when spraying the emulsion rolling oil of the supply system It may be possible to spray the rolling oil redundantly, but from the viewpoint of facility and control stability, even if chattering does not occur, the average of the rolling oil supply system larger than the circulating rolling oil supply system than the piping of the separate rolling oil supply system It is more preferable to spray the emulsion rolling oil adjusted to have a particle size.
[0048]
The 4th means for solving the above-mentioned subject is the above-mentioned 2nd means or the 3rd means, Comprising: The emulsion rolling oil adjusted so that it may become an average particle size larger than a circulation type rolling oil supply system The same type and the same oil content concentration as the circulating rolling oil supply system, and the emulsion rolling oil of another rolling oil supply system that did not adhere to the steel plate surface is changed to the emulsion rolling oil of the circulating rolling oil supply system. It is what makes it merge (Claim 4).
[0049]
Further, a fifth means for solving the above-mentioned problem is the fourth means, wherein the method of adjusting the emulsion rolling oil to have a larger average particle size than the circulating rolling oil supply system is Add the surfactant of the same type and the same oil concentration as the circulating rolling oil supply system to the rolling oil of the same type and the same oil concentration as the rolling oil supply system to adjust the rotation speed of the stirrer A method (claim 5).
[0050]
As described above, spraying emulsion rolling oil having a large average particle diameter is effective in reducing the friction coefficient in high-speed rolling, but as described above, emulsion rolling oil having a large average particle diameter is There is a problem that it is not suitable for emulsion rolling oil in a circulating rolling oil supply system. In contrast, a rolling oil supply system is provided separately from the circulating rolling oil supply system, and the rolling oil crude oil, surfactant, and dilution water are newly prepared to create an emulsion rolling oil with a large average particle size, and a steel plate A method of spraying on the surface is also conceivable. However, after spraying on the steel plate surface, the portion that does not plate out on the steel plate surface is merged with the emulsion rolling oil of the circulation system, so it is necessary to minimize the influence on the emulsion dispersibility of the emulsion rolling oil of the circulation system. is there.
[0051]
As a result of intensive studies on the above-mentioned problems, the surfactant for emulsification and dispersion added to the emulsion rolling oil of another rolling oil supply system should be the same type and the same oil concentration as the circulating rolling oil supply system. Furthermore, it has been found that the average particle diameter is adjusted by adjusting the mechanical stirring conditions based on the rotational speed of the stirrer installed in the tank.
[0052]
FIG. 15 shows the relationship between the stirring rotation speed and the average particle diameter in the stirrer. According to this, the emulsion rolling oil having a large average particle diameter is adjusted by adjusting the rotation speed of the stirrer of the emulsion tank of another system. You can see that you can build a bath.
[0053]
Of the emulsion rolling oil supplied to the steel plate surface from another rolling oil supply system, the emulsion rolling oil that did not plate out to the steel plate surface merges into the circulating rolling oil supply tank. When repeatedly subjected to strong stirring in the emulsion tank and strong shearing by pumps and nozzles in the circulation system, an emulsion having the same average particle size as the emulsion rolling oil of the circulation system is obtained. For this reason, the emulsification dispersion stability of the circulating rolling oil supply system can be maintained.
[0054]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is an example of equipment for carrying out the present invention in a tandem rolling mill with 5 stands. FIG. 1 shows an embodiment in which the invention according to claim 1 is applied to a final stand having a high chattering frequency.
[0055]
In the following drawings, 1 is a work roll, 2 is a backup roll, 3 is a strip, 4a is a conventional coolant coolant header, 4b is a coolant coolant header, 5 is a coolant coolant header according to the present invention, and 6 is a cyclic rolling. An oil supply tank, 7 is an emulsion supply pump, 8 is a rolling oil supply line, 9a and 9b are flow control valves, 10 is a flow control valve, 11 is a recovered oil pan, 12 is a return pipe, 13 is an agitator, and 14 is a mill. Housing, 15 is a vibration meter, 16 is a calculator, 17 is a strip coolant flow control device, 18 is a storage tank for emulsion rolling oil having a large average particle size, 19 is a hot water tank, 20 is a rolling oil crude oil tank, and 21 is an interface. Activator tank, 22a, 22b, 22c are pumps, 23a, 23b, 23c are valves, 24 is an agitator, 25 Emulsion supply pump, 26 denotes a rolling oil supply line. The structure of the rolling mill, the configuration of the strip / coolant system, and the like are well known and will not be described.
[0056]
According to the present invention, when the spray header for the strip coolant on the No. 5 stand entrance side is immediately after the exit roll bite of the No. 4 stand, the emulsion phase inversion time can be maximized. However, tension rolls and deflores are installed between the stands, and even if the emulsion rolling oil is sprayed on the upstream side of the stands, it is squeezed by the tension rolls or deflores, so that a sufficient plate-out amount cannot be obtained. In order to avoid this, in this embodiment, the coolant coolant header 5 is installed immediately after the tension roll and the defloor between the stands. The position from the roll bite is about L = 2.6 m.
[0057]
The apparatus 6 is a storage tank for emulsion rolling oil in a circulating rolling oil supply system. The emulsion rolling oil is adjusted to a desired average particle size by adjusting the rotation speed of the stirrer 16. For example, when a cationic surfactant is used, the average particle size is 9 to 15 μm, but in the case of other emulsifying surfactants, it may be 9 μm or less. And it supplies to each stand by the pump 7 via the rolling oil supply line 8, the spray coolant 5 for strip coolant in the No. 5 stand entrance side, the roll coolant in the entrance side of the No. 1-4 stands. Spray header 4a for rolls, and roll / coolant spray header 4b for roll cooling installed on the outlet side of No. 1-5 stand. In each stand, the flow rate of the emulsion is controlled by the flow rate control valves 9a and 9b. For the No. 5 stand entry side strip / coolant spray header 5, a flow rate adjusting valve 10 is provided. The rolled emulsion oil supplied to each stand is recovered by the recovery oil pan 11 and returned to the tank 6 via the return pipe 12 for circulation.
[0058]
A vibration meter 15 is installed in the housing 14 of the final stand. The signal output from the vibrometer 15 is input to the calculator 16, where only the same frequency as the natural frequency of the rolling mill is extracted by the filter, and the vibration speed after passing through the filter is calculated. Then, a constant vibration speed is set as a threshold value for chattering occurrence, a comparison calculation with the actual vibration speed is performed, and when the threshold value is exceeded, a control signal is output to the strip coolant flow control device 17.
[0059]
Upon receiving this control signal, the strip coolant flow control device 17 controls the opening degree of the flow rate adjusting valve 10 so as to increase the strip coolant flow rate by a certain amount. This process is repeated until the vibration speed falls below the threshold for chattering, and the strip coolant flow rate is corrected to an appropriate value. The strip coolant flow rate that is changed in a single process is determined to be the maximum flow rate that does not cause the problem of plate vibration accompanying the flow rate change, and is determined in advance by investigation.
[0060]
In the above embodiment, the present invention is applied to the final stand. However, the present invention is not limited to this, and may be applied to the final stand and its upstream stand as shown in FIG. Good. Further, not only the stand where chattering is detected (for example, No. 5 stand) but also the front stand (for example, No. 4 stand) from the coolant header 5 for lubrication provided at a position away from the roll bite. The flow rate of the strip coolant may be adjusted.
[0061]
FIG. 3 is an example of equipment for carrying out another example of the embodiment of the present invention, and is applied to the final stand of all five tandem rolling mills. The arrangement of the spray header, the circulating rolling oil supply system, the vibrometer, the strip coolant control device, and the like are the same as the equipment shown in FIG.
[0062]
The apparatus 18 in FIG. 3 is a tank that stores emulsion rolling oil having an average particle size larger than that of the circulating rolling oil supply system. The hot water, the rolled oil crude oil, and the surfactant are supplied from the tanks 19, 20, and 21 through the supply pumps 22a, 22b, and 22c, and the flow rate adjusting valve 23a is adjusted to have a predetermined oil concentration and a concentration of the surfactant with respect to the oil. , 23b and 23c, the replenishment amount is adjusted and supplied to the emulsion storage tank 18. The emulsion concentration in the tank, the oil concentration of the surfactant, and the emulsion temperature are the same as those in the circulating rolling oil supply system. The average particle size in the tank is an emulsion having an average particle size larger than that of the circulating rolling oil supply system by adjusting the rotation speed of the agitator 24.
[0063]
For example, when the base oil is beef tallow and a cationic dispersion type surfactant is added to the emulsifying dispersant at an oil concentration of 0.6%, the average particle size of the emulsion built in the tank 6 of the circulating rolling oil supply system Is about 9-10 μm. In the case of other emulsifying surfactants, it may be 9 μm or less in the circulation system. On the other hand, the average particle size in the tank 18 of another system is adjusted to be 30 μm.
[0064]
The emulsion rolling oil having a large average particle diameter is supplied from the spray header 5 to the upper and lower surfaces of the strip via the rolling oil supply line 26 by the pump 25. The strip coolant flow rate is controlled based on the output of a vibrometer installed in the housing 14 via the calculator 16 and the strip coolant flow rate control device 17 so that the vibration speed falls below the threshold value for chattering.
[0065]
After spraying on the steel plate, the emulsion rolling oil that does not plate out on the steel plate is collected together with the circulation system emulsion in the recovery oil pan 11 and mixed into the circulating rolling oil supply tank 6 via the return line 12. After mixing, the mixture is agitated by the agitator 13 in the tank, and repeatedly subjected to strong shearing at the pump 7 in the circulation system and the nozzle part of the spray header, and is subdivided to the same particle size as the circulation system emulsion. Become.
[0066]
The above embodiment has been described as applying the present invention to the final stand, but the present invention is not limited to this, and may be applied to the final stand and its upstream side stand as shown in FIG. Further, not only the stand where chattering is detected (for example, No. 5 stand) but also the front stand (for example, No. 4 stand) from the coolant header 5 for lubrication provided at a position away from the roll bite. The flow rate of the strip coolant may be adjusted.
[0067]
【Example】
Example 1
Using a total of 5 cold tandem rolling mills shown in FIG. 1, a hard tin plate having a base material thickness of 1.8 mm and a plate width of 900 mm was rolled to a final thickness of 0.183 mm at a target speed of 1850 m / min. As a comparative example, the same material was rolled in the conventional method of spraying roll coolant on the No. 5 stand entrance side. The rolling oil used was a synthetic ester type (kinematic viscosity 53 cSt at 40 ° C.) with a concentration of 3.5%. Further, an emulsion type surfactant was added to an oil concentration of 0.3 wt%, and after sufficient stirring in the tank, an emulsion having an average particle size of 7 μm and a temperature of 60 ° C. was obtained.
[0068]
The natural frequency of the rolling mill is 220 Hz. When the vibration speed after extracting only the same frequency as the natural frequency of the rolling mill exceeds 0.4 mm / s, the plate thickness fluctuates, and when it exceeds 0.5 mm / s, the mill vibration reaches the audible range, Plate breakage or the like occurs. Therefore, the vibration speed threshold for chattering is set to 0.3 mm / s.
[0069]
FIG. 16 shows the relationship between the rolling speed, the vibration speed, the roll coolant flow rate, and the friction coefficient when the roll coolant flow rate on the final stand entrance side of the conventional method is controlled when chattering occurs. The vibration speed exceeded 0.3mm / s when the final stand speed exceeded 1500m / min. The coefficient of friction at this time also increases rapidly as the speed increases. After exceeding the vibration speed of 0.3 mm / s, the roll coolant flow rate was increased, but the friction coefficient of the No. 5 stand was not changed, and the vibration speed could not be reduced to 0.3 mm / s or less. For this reason, the subsequent rolling was performed with the rolling speed reduced to 1350 m / min in order to reduce the vibration speed to 0.3 mm / s or less.
[0070]
On the other hand, FIG. 17 shows the relationship between the rolling speed, the vibration speed, the friction coefficient, and the strip coolant flow rate when the present invention (Claim 1) is applied to the final stand. The friction coefficient is lower when the present invention is applied. This is because, according to the present invention, the spray header for strip coolant is positioned upstream from the roll bite, so that the phase inversion time of the emulsion can be secured, and the amount of plate-out is larger than when using conventional roll coolant. This is because of the rise. The vibration speed exceeded 0.3mm / s around the speed of 1700m / min, but the strip coolant flow rate was increased step by step, and the vibration speed gradually decreased. At this time, it can be seen that the coefficient of friction also decreases. The strip coolant flow rate was increased until the vibration speed was below 0.3 mm / s. Since then, the rolling speed has been gradually increased and the speed has been accelerated to 1850 m / min.
[0071]
As the above results show, by using the present invention (Claim 1), rolling lubricity can be controlled by changing the strip coolant flow rate even under high-speed rolling conditions at a speed of 1800 m / min. High-speed rolling can be achieved while maintaining a level at which sheet thickness fluctuation and sheet breakage do not occur.
[0072]
FIG. 18 shows the results of summarizing examples of occurrence frequency of plate breakage and plate thickness variation due to chattering when the invention of claim 1 is applied. As can be seen from the figure, the application of the present invention greatly reduced the occurrence of abnormal plate thickness due to chattering and plate breakage.
[0073]
FIG. 19 shows the distribution of the average rolling speed of the embodiment of the present invention (Claim 1) and the conventional system. By using the present invention, the average rolling speed is 1320 m / min of the conventional system. It was improved to 1810m / min.
[0074]
(Example 2)
Using a total of 5 cold tandem rolling mills shown in FIG. 3, 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 2550 m / min. As a comparative example, the same material was rolled in the conventional method of spraying roll coolant on the No. 5 stand entrance side. The rolling oil was beef tallow (kinematic viscosity at 40 ° C. 43 cSt) with a concentration of 3.5%. Further, a cationic dispersion type surfactant was added to an oil content concentration of 0.6 wt%, 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. Further, according to the present invention (Claim 5), the concentration of the emulsion rolling oil in the separate rolling oil supply system, the concentration of the surfactant to the oil added, and the temperature are the same as those in the circulation system, and the average particle size is agitated in the tank. It was set to 20 μm by adjusting the rotation speed.
The natural frequency of the rolling mill is 220 Hz as in the first embodiment, and the threshold value of the vibration speed for chattering is the same as in the first embodiment.
[0075]
FIG. 20 shows the relationship among the rolling speed, vibration speed, roll coolant flow rate, and friction coefficient in the case of the conventional method. The vibration speed exceeded 0.3mm / s when the final stand speed exceeded 1650m / min. The friction coefficient at this time also increases rapidly with the increase in speed. On the other hand, the roll coolant flow rate was increased after exceeding the vibration speed of 0.3 mm / s, but the friction coefficient was not changed and the vibration speed could not be reduced to 0.3 mm / s or less. Therefore, in order to reduce the vibration speed to 0.3 mm / s or less, the subsequent rolling was performed at a speed of 1550 m / min.
[0076]
On the other hand, FIG. 21 shows an example of the relationship between the rolling speed, the vibration speed, the strip coolant flow rate, and the friction coefficient when the present invention (Claim 5) is applied to the final stand. Compared to the case of the conventional method, the strip coolant flow rate in this embodiment is lower. This is because the position of the spray header for the strip coolant of the present invention can secure the phase inversion time, and furthermore, the emulsion rolling oil having a large average particle size is used, so that the plate is used rather than the conventional roll coolant. This is because the amount of out increases.
[0077]
When the final stand speed exceeded 2000 m / min, the vibration speed exceeded 0.3 mm / s, but the strip coolant flow rate increased stepwise, and the vibration speed gradually decreased. The strip coolant flow rate was increased until the vibration speed was below 0.3 mm / s. It can also be seen that the coefficient of friction decreases as the strip coolant flow rate increases. Thereafter, the rolling speed was gradually increased, and the vibration speed exceeded 0.3 mm / sec even at a speed of 2350 m / min, but the same strip coolant flow rate control was performed, and the speed could eventually be increased to 2550 m / min. It was.
[0078]
FIG. 22 shows the results of investigating the particle size distribution of the emulsion rolling oil in the circulation system tank 6 when this embodiment is performed. For comparison, the particle size distribution when the conventional method is used is also shown. According to this, both are almost in agreement. Thus, according to the invention of claim 5, it is understood that the emulsification dispersibility of the emulsion rolling oil in the circulation system tank 6 can be maintained even when the emulsion rolling oil having an average particle size larger than that of the circulation system is used.
[0079]
As can be seen from the above results, by using the invention of claim 5, rolling lubricity can be controlled by changing the coolant flow rate even under ultra-high speed rolling conditions at a speed of 2500 m / min or more. High-speed rolling can be achieved while maintaining a level at which fluctuations and plate breakage do not occur. Moreover, even if emulsion rolling oil with a large average particle diameter is used, the emulsification dispersibility of the circulation system tank can be stably maintained.
[0080]
FIG. 23 summarizes the frequency of occurrence of plate breakage and plate thickness fluctuation due to chattering. From this, it can be seen that application of the present invention can greatly reduce the occurrence of abnormal plate thickness due to chattering and plate breakage. Further, FIG. 24 shows the distribution of the average rolling speed of the embodiment of the invention of claim 5 and the conventional method. As can be seen from this, by using the present invention, the average rolling speed is The conventional method was improved from 1510 m / min to 2520 m / min.
[0081]
【The invention's effect】
As described above, according to the first aspect of the present invention, when chattering occurs even in the high-speed rolling state, the friction coefficient can be changed by adjusting the strip coolant flow rate. This can eliminate chattering. Therefore, a cold-rolled steel sheet can be produced by high-speed rolling in a stable state.
[0082]
In the invention according to claim 2, when chattering occurs in a higher rolling speed region, the friction coefficient can be changed by adjusting the emulsion rolling oil flow rate, thereby eliminating chattering. it can. Therefore, a cold-rolled steel sheet can be produced by a higher speed rolling in a stable state.
[0083]
In the invention which concerns on Claim 3, a friction coefficient can be reduced more reliably and a cold-rolled steel plate can be manufactured in a stable state by high-speed rolling.
[0084]
In the invention which concerns on Claim 4, and the invention which concerns on Claim 5, the influence on the emulsification dispersibility of the emulsion rolling oil of a circulation system can be minimized.
[0085]
In any of the inventions, it is possible to significantly reduce quality defects due to plate breakage and plate thickness fluctuation by preventing chattering. In addition, high-speed rolling is possible, and productivity is greatly improved.
[Brief description of the drawings]
FIG. 1 is a diagram showing a first example of the configuration of a rolling mill for carrying out the present invention.
FIG. 2 is a diagram showing a second example of the configuration of a rolling mill for carrying out the present invention.
FIG. 3 is a diagram showing a third example of the configuration of a rolling mill for carrying out the present invention.
FIG. 4 is a diagram showing a fourth example of the configuration of a rolling mill for carrying out the present invention.
FIG. 5 is a diagram showing the arrangement position of a conventional spray header.
FIG. 6 is a graph showing a relationship between a conventional inlet-side roll coolant flow rate and a friction coefficient.
FIG. 7 is a diagram showing an outline of a plate-out test apparatus.
FIG. 8 is a graph showing a plate-out test result (relationship between phase inversion time and plate-out amount).
FIG. 9 is a view showing a mounting position of a spray coolant for strip coolant on the entrance side of the fifth stand.
FIG. 10 is a graph showing the relationship between the strip coolant flow rate and the friction coefficient.
FIG. 11 is a graph showing the relationship between the strip coolant flow rate and the amount of oil adhering to the steel plate.
FIG. 12 is a graph showing the relationship between the strip coolant flow rate and the friction coefficient.
FIG. 13 is a graph showing the relationship between the strip coolant flow rate and the amount of oil adhering to the steel plate.
FIG. 14 is a graph showing the relationship between the average emulsion particle size and the change range of the friction coefficient.
FIG. 15 is a graph showing the relationship between stirring rotation speed and average particle diameter.
FIG. 16 is a diagram illustrating an effect of preventing chattering by a conventional method. (Comparative example of Example 1)
FIG. 17 is a diagram illustrating the chattering preventing effect according to the first embodiment.
FIG. 18 is a view showing a comparison between the embodiment of the invention according to claim 1 and the frequency of occurrence of plate thickness fluctuation and plate breakage in the conventional rolling.
FIG. 19 is a diagram comparing the maximum rolling speed in the embodiment of the invention according to claim 1 and the conventional rolling method.
FIG. 20 is a diagram showing an effect of preventing chattering by a conventional method (comparative example of Example 2).
FIG. 21 is a diagram illustrating the chattering preventing effect according to the second embodiment.
22 is a graph showing a particle size distribution in the circulation system tank in Example 2. FIG.
FIG. 23 is a diagram showing a comparison between the embodiment of the invention according to claim 5 and the occurrence frequency of plate thickness fluctuation and plate breakage in rolling in the conventional method.
FIG. 24 is a diagram comparing the maximum rolling speed in the embodiment of the invention according to claim 5 and the conventional rolling method.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Work roll, 2 ... Backup roll, 3 ... Strip, 4a ... Conventional coolant header for lubrication, 4b ... Coolant header for cooling, 5 ... Coolant header for lubrication in this invention, 6 ... Circulating rolling oil supply tank, 7 ... Emulsion supply pump, 8 ... Rolling oil supply line, 9a, 9b ... Flow control valve, 10 ... Flow control valve, 11 ... Recovered oil pan, 12 ... Return pipe, 13 ... Agitator, 14 ... Mill housing, 15 ... Vibration 16 ... Calculator, 17 ... Strip / Coolant Flow Control Device, 18 ... Emulsion Rolled Oil Storage Tank with Large Average Particle Size, 19 ... Warm Water Tank, 20 ... Rolled Oil Crude Oil Tank, 21 ... Surfactant Tank, 22a , 22b, 22c ... pump, 23a, 23b, 23c ... valve, 24 ... agitator, 25 ... emulsion supply Pump, 26 ... rolling oil supply line

Claims (5)

A method of producing a cold rolled steel sheet by a cold continuous rolling mill, wherein when chattering of a stand of the cold continuous rolling mill is detected, the stand or an upstream away from the roll bit of the stand and the upstream side stand A step of performing cold rolling while spraying the emulsion rolling oil of the circulating rolling oil supply system on the steel plate on the side and preventing chattering by adjusting the flow rate thereof. A method for producing a rolled steel sheet. A method for producing a cold rolled steel sheet by a cold continuous rolling mill, wherein a rolling oil supply system is provided separately from the circulating rolling oil supply system, and when chattering of a stand of the cold continuous rolling mill is detected, circulation is performed. Emulsion rolling oil adjusted so as to have a larger average particle size than the rolling oil supply system, the upstream steel plate separated from the stand or the roll bite of the stand and the upstream stand from the separate rolling oil supply system A method for producing a cold-rolled steel sheet, characterized by comprising a step of performing cold rolling while preventing chattering by spraying and adjusting the flow rate. It is a manufacturing method of the cold rolled steel plate of Claim 2, Comprising: The average particle diameter of emulsion rolling oil is 20 micrometers or more, The manufacturing method of the cold rolled steel plate characterized by the above-mentioned. It is a manufacturing method of the cold rolled steel plate of Claim 2 or Claim 3, Comprising: The emulsion rolling oil adjusted so that it might become a larger average particle diameter than a circulating rolling oil supply system | strain is circulating rolling oil supply It is characterized by the same type and the same oil concentration as the system, and the emulsion rolling oil of another rolling oil supply system that did not adhere to the steel sheet surface is merged with the emulsion rolling oil of the circulating rolling oil supply system. A method for producing a cold rolled steel sheet. It is the manufacturing method of the cold rolled steel plate of Claim 4, Comprising: The method of adjusting emulsion rolling oil so that it may become a larger average particle diameter than a circulating rolling oil supply system is the same as a circulating rolling oil supply system It is a method of adjusting the rotation speed of the stirrer by adding a surfactant of the same type and the same oil concentration as the circulating rolling oil supply system to the rolling oil of the same type and the same oil concentration. A method for producing a cold rolled steel sheet.

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