JP2007144472A - Method for cold-rolling metallic sheet and cold tandem mill - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for cold-rolling a metallic sheet and a cold tandem mill by which the high reduction rolling of a high-strength steel sheet is made possible by reducing rolling load by stably improving the lubricity of a rolling stand in the cold tandem rolling of the high-strength steel sheet even when it is in the low-speed rolling state without increasing the cost of equipment and the running cost. <P>SOLUTION: This method is a method for cold-rolling the metallic sheet for rolling the metallic sheet whose 0.2% proof stress before the cold-rolling is ≥220 MPa with the cold tandem mill The cold tandem mill, the work rolls of at least one rolling stand of which are 0.2-1.0 μm in the average roughness Ra of the surface, is used and the surface roughness is imparted by shot blasting using spherical particles of ≤200 μm in average particle size. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a cold rolling method of a metal plate when rolling a metal plate such as a steel plate using a cold tandem rolling mill, and in particular, high pressure of a high strength steel plate having a 0.2% proof stress before cold rolling of 220 MPa or more. The present invention relates to a cold rolling method and a cold tandem rolling mill for a metal plate that can be rolled under.

  When cold-rolling steel sheets, as a lubricant for reducing the friction generated between the steel sheet being rolled and the roll, and for the rolls and steel sheets heated to high temperatures due to frictional heat and work heat generated during rolling. Lubricating oil is used as a coolant for cooling. Here, in normal cold rolling, emulsion rolling oil is used as the lubricating oil. The emulsion refers to a mixed liquid in which rolling oil particles are stably suspended in water. Emulsions are characterized by concentration and average particle size. The emulsion concentration is the ratio of the oil volume in the entire emulsion volume. The average particle diameter is the average diameter of the rolling oil particles in the emulsion.

  FIG. 2 is a diagram showing an example of a schematic configuration of a circulating oil supply type cold tandem rolling mill having five stands according to the prior art. The cold tandem rolling mill shown in FIG. 2 continuously reduces the steel sheet 1 from the entry side by first to fifth five-stand rolling mills (2a to 2e from the entry side of the steel sheet).

  The circulating oil supply system refers to a system in which rolled rolling oil is diluted to a concentration of 1 to 5% by mass, and emulsion rolling oil made into an O / W emulsion in which oil is dispersed in water using a surfactant is used. In the circulating lubrication system, a spray nozzle for lubrication is usually provided on the roll bite entry side of each stand, and a spray nozzle for cooling is usually provided on the rolling roll. The lubrication spray and the cooling spray are the same. It is performed by emulsion rolling oil. The emulsion rolling oil clean tank 20 shown in FIG. 2 stores the emulsion rolling oil 10 to be circulated and supplied to each stand through the piping 8 of the circulation system.

  At this time, as the rolling emulsion oil 10 to be circulated, those having various emulsion concentrations and average particle diameters can be used, but as typical examples, those having an emulsion concentration of 1.5% and an average particle diameter of about 8 μm are used. be able to. This emulsion rolling oil contains 2% by mass of a nonionic surfactant and is circulated and used as a stable O / W emulsion by shearing in a pump or spray nozzle disposed in the pipe 8.

  The arrangement position of the spray nozzle for supplying the emulsion rolling oil to be circulated varies depending on the type of the target material, the rolling speed, etc., but in the example shown in FIG. The spray nozzles 3a to 3e of the emulsion rolling oil 10 are arranged so that the emulsion rolling oil 10 is supplied toward the roll bite. The same emulsion rolling oil 10 is spray nozzles 4b to 4d arranged on the second, third and fourth stand outlet side, and spray nozzles 5d and 5e arranged on the fourth and fifth stand inlet side. Is supplied to cool each rolling roll.

  The work roll of the cold tandem rolling mill is processed to an appropriate surface roughness for each stand by a normal polishing finish. For example, the work roll of the first stand is finished with an average surface roughness Ra of about 0.8 to 1.5 μm with a # 60 to # 80 grindstone, and the average roughness of the surface as it goes to the subsequent stage stand. Is made smaller. In addition, a dull roll by shot blasting is often used for the final stand, and the average roughness Ra of the surface is 1.5 by shot blasting using grit having a size of about 0.8 to 1.2 mm. A work roll (dull roll) finished to about ~ 3.0 μm is used. As the shape of the grit at that time, one having an angular shape in order to sharpen the roll surface is used.

  On the other hand, in recent years, high-strength steel sheets have been actively adopted to reduce the weight of automobile bodies and improve collision safety. However, since a high-strength steel plate has a larger deformation resistance than ordinary steel, an increase in rolling load in cold rolling may cause a disorder in the shape of the steel plate, which may cause problems such as plate breakage due to drawing.

  In order to reduce the rolling load in cold rolling, it is necessary to reduce the total rolling reduction in the cold tandem rolling mill by reducing the thickness of the steel sheet before cold rolling. While the rolling load in the hot rolling process which is a process increases, the coil length of a hot-rolled steel plate becomes long, and the problem that productivity in a pickling process falls arises. Furthermore, if the total rolling reduction in the cold tandem rolling mill is kept low, there is a problem that the product's Rankford value decreases and the formability in press forming decreases.

For such a problem, for example, in Japanese Patent Application Laid-Open No. 2005-95928 (Patent Document 1), the surface roughness of the work roll of the first stand is lowered than usual, and the first stand entrance side A countermeasure for reducing the rolling load by reducing the coefficient of friction by spraying or applying Teflon powder (registered trademark) is disclosed.
JP 2005-95928 A

  However, as disclosed in Patent Document 1, the mechanical oil film is weakened simply by reducing the surface roughness of the rolling roll, particularly the surface roughness of the rolling roll of the first stand. Therefore, improvement in lubricity is not sufficient.

  In addition, in order to spray or apply Teflon powder on the entrance side of the first stand, it is necessary to install a chamber for preventing the Teflon powder from scattering around and to install a drying device, which increases the equipment cost. There is a problem of inviting. Furthermore, there is a possibility that the Teflon powder is scattered due to the deterioration of the seal portion of the chamber, or the Teflon powder dried by the drying apparatus falls and moves around. In this case, Teflon powder scattered around is not necessary to spray or apply Teflon powder because it is not necessary to improve lubrication performance as in the case of rolling ordinary steel other than high-strength steel plates. In some cases, it adheres to the surface of the ordinary steel and partially adheres to the surface of the ordinary steel, thereby causing meandering of the steel plate and disorder of the shape.

  Further, the stability of the emulsion may be hindered by mixing in the rolling emulsion oil in which the Teflon powder peeled from the steel plate during the rolling is circulating. Furthermore, the filter of the circulation system is clogged by the Teflon powder, and the filter function of removing the metal powder from the rolling oil cannot be sufficiently exhibited, and there is a problem that surface flaws are generated on the steel plate. Furthermore, when the amount of Teflon powder used is increased, there is a problem that the running cost is increased.

  Therefore, the present invention can stably improve the lubricity of the rolling stand in the cold tandem rolling of high-strength steel sheets and reduce the rolling load without increasing the equipment cost and running cost. Then, it aims at providing the cold rolling method and cold tandem rolling mill of a metal plate which enable high pressure rolling of a high strength steel plate.

In order to solve the above problems, the present invention has the following features.
[1] A cold rolling method of a metal plate, in which a 0.2% proof stress before cold rolling is 220 MPa or more by a cold tandem rolling mill,
The work roll of at least one rolling stand has an average surface roughness Ra of 0.2 μm or more and 1.0 μm or less, and the surface roughness is a shot using spherical particles having an average particle diameter of 200 μm or less. A cold rolling method for a metal sheet, characterized by using a cold tandem rolling mill provided by blasting.
[2] In the above [1], shot blasting using spherical particles having an average surface roughness Ra of 0.2 μm or more and 1.0 μm or less, and having a surface roughness of 200 μm or less in average particle diameter The entrance side of a rolling stand that uses a work roll provided by processing contains the same kind of rolling oil as the first emulsion rolling oil that is circulated, and is an emulsion as compared with the first emulsion rolling oil. The second emulsion rolling oil having a high concentration and / or a large average particle diameter, or the neat oil of the rolling oil contained in the first emulsion rolling oil is separated from the first emulsion rolling oil. A method for cold rolling a metal plate, characterized by comprising:
[3] Work rolls of at least one rolling stand have an average surface roughness Ra of 0.2 μm or more and 1.0 μm or less, and the surface roughness is spherical particles having an average particle diameter of 200 μm or less. A cold tandem rolling mill for metal sheets, which is provided by shot blasting used.
[4] In the above [3], shot blasting using spherical particles having an average surface roughness Ra of 0.2 μm or more and 1.0 μm or less, and having a surface roughness of 200 μm or less in average particle diameter Contained in the second emulsion rolling oil of the system different from the first emulsion rolling oil used in circulation or the first emulsion rolling oil on the entrance side of the rolling stand using the work roll provided by the processing A cold tandem rolling mill for a metal plate, characterized by comprising supply means for supplying neat oil of the rolled oil.

  According to the present invention, not only when the rolling speed is high, but also in the low-speed rolling state, by improving the lubricity in cold tandem rolling of the high-strength steel sheet and reducing the rolling load, Provided are a cold rolling method and a cold tandem rolling mill for a metal sheet that can be rolled under high pressure.

  Hereinafter, an example of the best mode for carrying out the present invention will be described.

  FIG. 1 is a diagram showing an example of a schematic configuration of a circulating tandem cold tandem rolling mill having a plurality of stands to which the present invention is applied. In addition, FIG. 1 has shown the case of the cold tandem rolling mill which has the 1st-5th 5 stand rolling mill (2a-2e from the entrance side of a steel plate) from the entrance side of a steel plate.

  The cold tandem rolling mill shown in FIG. 1 has an average surface roughness Ra of 0.1 as the work roll of the first stand and the second stand in the cold tandem rolling mill according to the prior art shown in FIG. The surface roughness is given by shot blasting using spherical particles having an average particle diameter of 2 to 1.0 μm and an average particle diameter of 200 μm or less (hereinafter, this work roll is referred to as “work roll according to the present invention”). .) Is used. Specifically, the work roll of the first stand uses, for example, spherical high-speed particles having an average particle diameter of 55 μm manufactured by gas atomization as shot particles, and an average roughness Ra of the surface is set to 0. 0 by a pneumatic shot device. What finished to 7 micrometers can be used. Further, the work roll of the second stand uses the same shot particles as those of the work roll of the first stand, and adjusts the air pressure of the pneumatic shot device, so that the average roughness Ra is 0.35 μm. Can be used.

  In the present embodiment, the third stand and the fourth stand have the conditions that the rolling speed is high and a sufficient oil film can be formed, so that the surface roughness of the work roll is kept as before. Further, a dull roll by shot blasting is used for the final fifth stand, and the dull roll is transferred to the steel sheet surface by light reduction with a reduction rate of 5% or less. The work roll according to the present invention No application was made.

  As described above, surface roughness is imparted to the work roll according to the present invention by shot blasting using spherical particles having an average particle size of 200 μm or less as shot particles. The reason why the spherical particles are used as the shot particles is to provide dimple-shaped recesses on the roll surface when the spherical particles collide with the roll surface by shot blasting. Such dimple-shaped recesses have the effect of drawing an oil film inside the roll bite at the roll bite entrance of the cold rolling, so that the effect of reducing the rolling load by reducing the friction inside the roll bite can be obtained. .

  As the spherical particles, for example, various kinds of particles such as steel beads, high speed beads, SUS beads, cemented carbide beads, ceramic beads produced by a gas atomization method can be used. Note that the shape of the particles does not have to be a perfect sphere, and may be a sphere that forms a hollow in a circular shape when viewed from the roll surface.

  In addition, the average particle diameter of the spherical particles is set to 200 μm or less. When large particles having an average particle diameter exceeding 200 μm are used, a circular concave portion formed on the roll surface becomes large, and as a result, into the roll bite. This is because a rolling oil escape path occurs when the oil film is drawn, and the oil film drawing effect is reduced. Moreover, as a result of increasing the roughness of the roll surface, the effect of the increase in frictional resistance due to the convex portion is greater than the effect of reducing the friction due to the increase in the oil film thickness, thereby increasing the friction coefficient.

  Therefore, the smaller the spherical particles used for shot blasting, the better. However, if the particle diameter is made too small, it is difficult to increase the kinetic energy when the particles collide with the roll surface, and sufficient recesses are formed. Becomes difficult. Therefore, for practical use, it is preferable to use spherical particles having an average particle diameter of about 40 to 80 μm.

  On the other hand, when the roll surface is finished with spherical particles as described above, the average surface roughness Ra is 0.2 to 1.0 μm. When the average roughness Ra exceeds 1.0 μm, the unevenness of the roll surface becomes large, and the influence of the increase in the frictional resistance due to the convex portion is greater than the effect of drawing the oil film due to the dimple-like concave portion, and the friction coefficient as a whole Will increase. When the average roughness Ra is less than 0.2 μm, the dimple-like recesses are small and a sufficient oil film drawing effect cannot be obtained.

  In addition, in the said patent document 1, although it describes that surface roughness Ra of the work roll of a 1st stand shall be 0.20 micrometer or more and 0.50 micrometer or less, there is no description about the processing method. Further, the surface of the work roll of the first stand is usually finished by grinding with a grindstone, and in Patent Document 1 in which the surface roughness is lower than that of the work roll of the normal first stand, naturally, the polishing finish with a fine grindstone is performed. It seems that this is done, and the method of imparting surface roughness is fundamentally different from the present invention.

  Here, the work roll according to the present invention may be applied to at least one rolling stand of a cold tandem rolling mill, but is particularly effective when applied to a rolling stand where a high reduction ratio of a high-strength steel sheet is desired. It is. In the example shown in FIG. 1, the work roll according to the present invention is applied to the first and second stands because the rolling reduction or rolling amount of the first and second stands is larger than the others. The first stand has a lower rolling speed than the second stand, and a normal polishing finish work roll has a small oil film drawing effect, and it is difficult to increase the thickness of the oil film in the roll bite. Therefore, it is most effective to apply the work roll according to the present invention to the first stand.

  Moreover, in this invention, for supplying the 2nd emulsion rolling oil of a different system | strain to the entrance side of the rolling stand which uses the work roll which concerns on the said invention from the 1st emulsion rolling oil used cyclically. It is preferable to provide a supply means.

  As a means for achieving the above method, in the example shown in FIG. 1, emulsion rolling oil 13 (second) is applied to the steel sheet surfaces on the entry side of the first and second stands with respect to the conventional cold tandem rolling mill shown in FIG. 2. The spray nozzles 9a and 9b, which are nozzles for supplying (emulsion rolling oil), are arranged. The spray nozzles 9a and 9b are supplied with the emulsion rolling oil 13 of a system different from the supply system of the emulsion rolling oil 10 (first emulsion rolling oil) that is circulated and used.

  The emulsion rolling oil 13 is stored in the storage tank 11, and the average particle diameter of the emulsion rolling oil 13 can be adjusted by adjusting the stirring rotation speed of the agitator 12 that is a stirrer provided in the storage tank 11. Done. Emulsion rolling oil 13 stored in the storage tank 11 is extracted by a pump 15 and supplied to the surface of the steel sheet 1 from the spray nozzles 9a and 9b through a pipe 14.

  Here, the storage tank 11, the agitator 12, the pipe 14, the pump 15, and the spray nozzles 9a and 9b constitute supply means for the emulsion rolling oil 13.

  Moreover, as shown in FIG. 1, the said emulsion rolling oil 10 stored in the clean tank 20 is extracted by the pump 23, and from the spray nozzles 3a-3e arrange | positioned through the piping 8 at all stand entrance sides. Spray nozzles 4b, 4c and 4d which are respectively supplied toward the roll bite and are arranged on the second, third and fourth stand outlet side, and spray nozzles which are arranged on the fourth and fifth stand inlet side In order to cool each rolling roll from 5d, 5e, it supplies in a rolling mill.

  The emulsion rolling oil 13 supplied from the spray nozzles 9a, 9b and the emulsion rolling oil 10 supplied from the spray nozzles 3a-3e, 4b, 4c, 4d, 5d, 5e are taken out of the system by a steel plate, It is recovered by the oil pan 6 except for what is lost by evaporation. The recovered emulsion rolling oil is temporarily stored in the dirty tank 21 by the recovery pipe 7, and foreign matter in the rolling oil is removed by the filter device 22, and then sent to the clean tank 20 by the pump 24.

  The clean tank 20, the pump 23, the pipe 8, the spray nozzles 3a to 3e, 4b, 4c, 4d, 5d, 5e, the oil pan 6, the recovery pipe 7, the dirty tank 21, the pump 24, and the filter device 22 are supplied. A circulation system for collecting and circulating the emulsion rolling oils 10 and 13 is configured.

  Further, in the cold tandem rolling mill according to the present invention, it is preferable to include means 25 for additionally adding a surfactant in the middle of a circulation system for recovering and circulating the supplied emulsion rolling oil. This is because it is possible to adjust the oil concentration of the surfactant contained in the emulsion rolling oil used in circulation.

  If the concentration of the surfactant contained in the emulsion rolling oil used in circulation decreases with time, the stability of the emulsion rolling oil used in circulation is reduced. Therefore, the means 25 for additionally adding the surfactant is connected to a pipe between the filter device 22 and the clean tank 20 provided in the middle of the circulation system, for example, the circulation system of the emulsion rolling oil, and circulated. A surfactant which is insufficient in the emulsion rolling oil used is additionally added. Here, the means 25 for additionally adding the surfactant can be constituted by, for example, a surfactant storage tank, a regulating valve for adjusting the flow rate of the surfactant to be added, and the emulsion used for circulation. The additional amount of the surfactant can be determined according to the concentration of the surfactant in the rolling oil, the change in the particle size distribution of the emulsion, and the like.

  Further, in the cold tandem rolling mill according to the present invention, the supply time of the emulsion rolling oil 13 is set to 0.1 seconds until the rolling oil attached to the steel sheet surface reaches the roll bite of the downstream rolling stand. It is preferable to arrange in the above position. Here, spray nozzles 9a and 9b constituting supply means for supplying the emulsion rolling oil 13 to the surface of the steel sheet are supplied from the nozzles to the surface of the steel sheet, and the attached emulsion rolling oil 13 is respectively a downstream rolling stand. It is arranged at a position where the time until it reaches the roll byte is 0.1 seconds or more. In a normal cold tandem rolling mill, the maximum rolling speed is about 1300 mpm. Even in this case, if the distance from the spray nozzles 9a to 9e to each subsequent roll bite is 2.2 m or more, Good.

  As described above, in the embodiment of the cold tandem rolling mill according to the present invention shown in FIG. 1, the cold tandem rolling mill having the five-stand rolling mill has been shown. can do.

  In the cold tandem rolling mill configured as described above, one embodiment of the cold tandem rolling method according to the present invention uses the work roll according to the present invention as at least one rolling stand of the cold tandem rolling mill. It is characterized by this. Thereby, not only when the rolling speed is high, but also in the low-speed rolling state, the lubricity in cold tandem rolling of the high-strength steel sheet is improved, and as a result, the rolling load can be reduced. High pressure rolling is possible.

  Moreover, in the cold tandem rolling mill having the above-described configuration, another embodiment of the cold tandem rolling method according to the present invention is used for circulation on the entrance side of the rolling stand using the work roll according to the present invention. A second emulsion rolling oil containing the same type of rolling oil as the first emulsion rolling oil and having a larger average particle size and / or a higher emulsion concentration compared to the first emulsion rolling oil, The first emulsion rolling oil is supplied by a separate system.

  The emulsion rolling oil 10 (first emulsion rolling oil) that is circulated is mixed with wear powder generated during rolling, working oil of a rolling mill, and the like, and the stability of the emulsion decreases with time. Therefore, the circulation system is provided with a filter device 22, and the type and addition amount of the surfactant contained in the rolling emulsion oil are adjusted as appropriate, so that an emulsion that is stable against disturbance is formed. Rolling oil is selected. However, if the amount of surfactant added to form a stable emulsion against disturbance is increased, the emulsion rolling oil 10 supplied on the rolling stand entrance side for lubrication is stabilized by phase inversion. There is a problem that it becomes difficult to form an oil film.

  Therefore, in the present invention, the emulsion rolling oil 13 (second emulsion rolling oil) having a larger average particle diameter and / or higher emulsion concentration than the emulsion rolling oil 10 used in circulation is used as the workpiece according to the present invention. Supply to the entrance side of the stand that uses the roll. Thereby, phase inversion from the emulsion rolling oil 13 is facilitated, and an oil film is easily formed, so that the effect of drawing the oil film by the work roll according to the present invention is further increased. In addition, since a part of the supplied emulsion rolling oil 13 is mixed and collected in the emulsion rolling oil 10 being circulated, the emulsion rolling oil 13 containing the same type of rolling oil as the emulsion rolling oil 10 is collected. Supply.

  Here, as the rolling oil that constitutes the emulsion rolling oil, one that uses a base oil of any of natural fats and oils, fatty acid esters, and hydrocarbon-based synthetic lubricating oils is used as that used in ordinary cold rolling. Can do. For example, as said natural fats and oils, vegetable oils, such as mineral oil and palm oil, and animal oils, such as beef tallow, can be used. In addition, as the fatty acid ester, a diester that is an ester of a monohydric alcohol and a divalent fatty acid, a polyol ester that is a combination of a polyhydric alcohol such as neopentyl glycol, trimethylolpropane, pentaerythritol, and a monohydric fatty acid, or the like. Can be used. Moreover, as said hydrocarbon type synthetic lubricating oil, poly-alpha-olefin etc. which can obtain various viscosities can be used. Furthermore, you may add the additive used for normal cold rolling oil, such as an oil improvement agent, an extreme pressure additive, antioxidant, to these rolling oil.

  Moreover, as said surfactant, any of an ionic type and a nonionic type may be used, and what is used for a normal circulation type coolant system should just be used.

  As an example, for example, as the above-mentioned emulsion rolling oil 10 that is circulated, the rolling oil is diluted to a concentration of 1 to 5% by mass, and an O / W emulsion in which oil is dispersed in water using a surfactant is used. It is done. The average particle size may be about 5 μm to 12 μm, and the emulsion concentration may be about 1.2% to 2.0%.

  Further, as described above, the rolling emulsion oil 13 includes the same kind of rolling oil as the rolling emulsion oil 10 and has a larger average particle diameter and / or an emulsion concentration than the rolling emulsion oil 10. Higher ones are used. Specifically, the average particle diameter is 1.5 times or more and / or the emulsion concentration is 2 times or more as compared with the emulsion rolling oil 10 used for circulation.

  Here, even if emulsion rolling oil 13 having a larger average particle size than that of emulsion rolling oil 10 is supplied, if the surfactant type and oil concentration contained therein are the same, a circulation pump or spray The diameter can be easily reduced by the shearing work of the nozzle, and the emulsion rolling oil 10 can be used as it is for circulation. Moreover, even if the emulsion rolling oil 13 having a high emulsion concentration is supplied, the concentration of the emulsion rolling oil 10 during circulation hardly increases as long as the supply amount of the emulsion rolling oil 10 is approximately the same.

  The emulsion rolling oil 13 having an average particle size larger than that of the emulsion rolling oil 10 reduces the mechanical energy applied by the stirrer when mixing water and the rolling oil as compared with the adjustment of the emulsion rolling oil 10. Can be prepared. Moreover, the said emulsion density | concentration can be performed by adjusting the ratio of the oil content volume in the whole emulsion volume.

  Here, the emulsion rolling oil 13 having an average particle size larger and / or a higher emulsion concentration than the emulsion rolling oil 10 used for circulation is supplied to the entrance sides of the first and second stands. The oil content in the oil adheres to the surface of the steel sheet to form an oil film (hereinafter, this phenomenon is referred to as “plate-out”), and the oil film forming ability is improved. This is because by making it possible to form, the amount of rolling oil drawn into the roll bite is increased, and the lubricating performance during rolling is further improved.

  In the present invention, a metal plate having a 0.2% proof stress before cold rolling of 220 MPa or more is mainly targeted. Any kind of metal is acceptable as long as the 0.2% proof stress before cold rolling is 220 MPa or more, but the high tensile strength is 390 MPa or more by cold rolling, annealing, or temper rolling. For strength steel plates. According to the present invention, even when such a high-strength metal plate is cold-rolled, the rolling load can be reduced and high-pressure rolling is possible.

  Further, in the cold tandem rolling method according to the present invention, the surfactant contained in the emulsion rolling oil 13 is the same kind and lower than the surfactant contained in the emulsion rolling oil 10 used in circulation. Adjusting the oil concentration of the surfactant contained in the emulsion rolling oil to be circulated by adding the surfactant to the emulsion rolling oil recovered from the cold tandem rolling mill as well as the oil concentration. It may be.

  When the emulsion rolling oil 13 supplied by a system different from the emulsion rolling oil 10 used for circulation is supplied to the surface of the steel sheet, the oil in the emulsion rolling oil 13 adheres to the surface of the steel sheet to form an oil film. . And the oil component in the emulsion rolling oil 13 which did not adhere to the steel plate surface is mixed with the other components of the emulsion rolling oil 13 and collected in the emulsion rolling oil 10 that is circulated and collected. At this time, if the type of surfactant contained in the mixed emulsion rolling oil 13 is different from the type of surfactant contained in the emulsion rolling oil 10 used for circulation, It may inhibit the stability of the emulsion. Therefore, in this embodiment, the surfactant contained in the emulsion rolling oil 13 supplied by another system is the same type as the surfactant of the emulsion rolling oil 10 that is circulated.

  Furthermore, the oil concentration of the surfactant contained in the emulsion rolling oil 13 supplied by the separate system is preferably lower than the oil concentration of the surfactant contained in the emulsion rolling oil 10 used in circulation. . By making the oil concentration of the surfactant contained in the emulsion rolling oil 13 lower than the oil concentration of the surfactant contained in the emulsion rolling oil 10, the average particle size in the emulsion rolling oil 13 is emulsion-rolled. This is because it becomes easy to make the diameter larger than the average particle diameter in the oil 10, and the plate-out property of the emulsion rolling oil 13 can be further enhanced.

  However, if the emulsion rolling oil 13 having a low surfactant concentration to the oil is continuously supplied from another system, the concentration of the surfactant contained in the emulsion rolling oil 10 that is circulated decreases over time and is used in a circulating manner. This will reduce the stability of the emulsion rolling oil 10 emulsion. Therefore, it is preferable to additionally add a surfactant in the middle of a circulation system for recovering and circulating the supplied emulsion rolling oil. This makes it possible to stabilize the concentration of the surfactant in the rolled emulsion oil 10 that is circulated and used over time and to stabilize the emulsion.

  If the oil concentration of the surfactant contained in the emulsion rolling oil 13 is the same as the oil concentration of the surfactant contained in the emulsion rolling oil 10 that is circulated, the emulsion rolling oil that is circulated and used. The concentration of the surfactant contained in 10 hardly changes with time, and it is not necessary to add an additional surfactant.

  Furthermore, in the cold tandem rolling method according to the present invention, the emulsion rolling oil 13 is the steel plate surface between the rolling stands, and the emulsion rolling oil 13 attached to the steel plate reaches the roll bite of the downstream rolling stand. It is preferable to supply to a position where the time until the time is 0.1 seconds or more.

  When the emulsion rolling oil 13 is supplied to the steel plate surface, an oil film is formed on the steel plate surface by plate-out. However, a certain amount of time is required before water is removed from the emulsion rolling oil 13 that is an O / W emulsion and an oil film is formed on the surface of the steel sheet. For example, for a high-strength steel sheet having a 0.2% proof stress of 220 MPa or more before cold rolling, the time from reaching the roll bite after the emulsion rolling oil 13 is supplied to the steel sheet surface is set to 0. By ensuring 1 second or more, a stable oil film can be formed on the steel plate surface, and the lubricity can be further improved.

  In addition, in the case shown in FIG. 1, the supply flow rate of the emulsion rolling oil 13 from the spray nozzles 9a and 9b is not more than 1/10 of the flow rate of the emulsion rolling oil 10 supplied from the spray nozzles 3a to 3e. In practical terms, each stand may be a spray nozzle that can supply about 100 L / min.

  Further, in the cold tandem rolling method according to the present invention, instead of the emulsion rolling oil 13, a neat oil of the rolling oil contained in the emulsion rolling oil 10 that is circulated is separated from the emulsion rolling oil 10. You may make it supply with a system | strain. Here, unlike the method of supplying the above-described emulsion rolling oil 13 to form an oil film on the surface of the steel sheet, neat oil is supplied to the surface of the steel sheet as it is without being made into an emulsion. However, when a portion of the neat oil that did not adhere to the surface of the steel sheet is mixed in the circulation system of the emulsion rolling oil 10 that is circulated and used, so as not to hinder the stability of the emulsion of the emulsion rolling oil 10, It is preferable to use the same type of rolling oil as that used for the emulsion rolling oil 10 as the neat oil.

  Further, for the same reason as described above, it is preferable that the neat oil contains a surfactant of the same kind and the same oil concentration as the emulsion rolling oil 10 that is circulated and used. Even if the neat oil is mixed into the circulation system, the same emulsion as the emulsion rolling oil 10 that is circulated is formed by the shearing work of the circulation pump, and the stability of the emulsion rolling oil 10 is maintained even if the circulation use is continued. It is because it does not affect.

  In addition, since it is preferable to supply a small amount of rolling oil uniformly in supply of neat oil, it is preferable to supply on a steel plate by the system which sprays mist-like neat oil with many nozzles.

  Here, in order to realize the above method, in the cold tandem rolling mill shown in FIG. 1, neat oil is stored in the storage tank 11, and the stored neat oil is supplied from the spray nozzles 9a and 9b to the steel plate. What is necessary is just to set it as the structure supplied to the surface. However, in this case, the agitator 12 is not necessary, and the spray nozzles 9a and 9b are sprayed in a mist form so as to supply only the oil necessary for forming the necessary oil film on the surface of the steel plate. Preferably, a nozzle having a flow rate of about 10 L / min or less is sufficient.

  Moreover, in the cold tandem rolling method according to the present invention, in order to obtain higher lubrication performance, the emulsion rolling oil 13 supplied by a system different from the emulsion rolling oil 10 used for circulation or the circulation use. On the surface of the steel plate between the supply position of the neat oil supplied by a system different from the emulsion rolling oil 10 and the roll bite entrance side of the downstream rolling stand, the emulsion rolling oil 10 that is circulated is used. It is preferable not to supply. By supplying the emulsion rolling oil 13 or the neat oil, an oil film is formed on the surface of the steel sheet by plate-out. After the oil film is formed by the plate-out, the emulsion rolling oil 10 that is circulated is used as the surface of the steel sheet. This is because the formed oil film may be washed away and lubricity may be lowered.

  Further, only the spray nozzle for supplying the circulating rolled emulsion oil 10 toward the roll bite between the position where the rolled emulsion oil 13 or the neat oil is supplied and the position where the roll bite enters the next stand. In some cases, a spray for cooling the steel sheet is installed between the stands and the emulsion rolling oil 10 is supplied. Since such an emulsion rolling oil 10 is not supplied to the steel sheet, a sufficient oil film can be formed in the roll bite, so that it is not supplied in the stand that supplies the emulsion rolling oil 13 or the neat oil. It is preferable to make it.

  However, if the emulsion rolling oil 10 is not supplied between the position where the emulsion rolling oil 13 or the neat oil is supplied and the position where the roll bit enters the next stand, cooling of the steel sheet may be insufficient. In such a case, the emulsion rolling oil 10 may be supplied.

  Hereinafter, as an example of the present invention, results of rolling by a cold tandem rolling mill of a circulating oil supply system having the configuration shown in FIG. 1 will be described. The cold tandem rolling mill is a 5-stand 4Hi mill, each work roll diameter is 500 to 560 mm, and is driven by an electric motor through a spindle.

  The emulsion rolling oil 10 that is circulated is a nonionic surface active agent as a surfactant, in which 1% by mass of each of an oily agent and an antioxidant is added to a base oil to which vegetable oils and fats are added based on a synthetic ester. The agent was added in an amount of 3% by mass with respect to the oil concentration, and an agent having an emulsion concentration of 1.5% and an average particle size of 8 μm at a temperature of 50 ° C. was used.

  In addition, as an example of the present invention, the work roll according to the present invention was processed by using high-speed particles prepared by a gas atomization method and changing the particle diameter according to the roughness level of the surface finish. For shot blasting, a pneumatic shot device was used, and the finishing roughness was changed by adjusting the air pressure.

  In Invention Examples A-1 to A-5 and B-1 to B-4, only the work roll of the first stand uses the work roll according to the present invention, and the work rolls of the second to fifth stands are conventional. Work roll was used. The work roll of the first stand was processed so as to satisfy various surface roughness conditions shown in Table 1 below, and the influence on the rolling load of the first stand was evaluated.

  In Invention Examples A-1 to A-5, the emulsion rolling oil 13 was not supplied from the spray nozzles 9a and 9b, and the emulsion rolling oil 10 was supplied from the spray nozzles 3a to 3e by the conventional method. (Note that Table 1 below shows the concentration (%) and average particle diameter (μm) of the emulsion rolling oil 10). In Invention Examples B-1 to B-4, the emulsion rolling oil 13 having the emulsion concentration (%) and the average particle size (μm) shown in Table 1 below is supplied only from the spray nozzle 9a, and the spray nozzles 3a to 3a. From 3e, the emulsion rolling oil 10 was supplied by a conventional method.

  Further, as a comparative example, the work roll of the first stand was adjusted to have the surface roughness adjusted to the conditions shown in Table 1 below by polishing finishing (Comparative Examples C-1 to C-3), normal The effect on the rolling load of the first stand for the steel sheets used for shot blasting, the surface roughness of which was adjusted to satisfy the conditions shown in Table 1 below (Comparative Examples D-1 and D-2) Evaluated. The emulsion rolling oil 10 was supplied from the spray nozzles 3a to 3e by a conventional method.

  Both the present invention example and the comparative example are hot-rolled and pickled coils having a sheet thickness of 2.8 mm and a sheet width of 1650 mm, and are cold-rolled to a high-strength steel sheet having a 0.2% proof stress of 240 MPa before cold-rolling. Was given. This hot-rolled / pickled coil was cold-rolled to a thickness of 0.65 mm, and the rolling load of the first stand when the rolling speed of the final stand was as low as 300 mpm was examined.

  At that time, as a conventional rolling condition, the work roll of the first stand was subjected to polishing load and the average surface roughness Ra was set to 0.9 μm, based on the rolling load (in the case of Comparative Example C-2). The load ratio under each condition was used as an evaluation index. That is, as the load ratio is smaller, the lubricity is improved and high pressure is possible. The evaluation results (load ratio) are shown in Table 1 below.

  From Table 1 above, it can be seen that the load reduction effect of 10% or more is obtained by the present invention example as compared with the case of the comparative example which is a conventional rolling condition. Thereby, the total rolling reduction in a cold tandem rolling mill can be improved. In addition, by reducing the rolling load at a specific stand by changing the pass schedule, it becomes possible to increase the rolling reduction rate of the stand, and as a result, the rolling reduction rate of other stands can be reduced to reduce the overall rolling load. It can also be seen that the plate shape can be stabilized.

  Furthermore, also for the second stand, by applying the work roll according to the present invention by the same method as the first stand of the above-described example of the present invention, a mother for producing the same plate width and thickness as a high-strength steel plate. When the work roll according to the present invention is applied only to the first stand, the material thickness can be increased from 2.8 mm to 3.1 mm, and the efficiency of the entire production process can be further expanded. I knew it was possible.

  In addition, although a present Example is a result in the low speed | velocity | rate area | region where the rolling speed of a final stand is 300 mpm, since the drawing effect of the oil film to a roll bite becomes remarkable, so that the rolling speed is large, the rolling speed of a final stand is quick. In this case, the load reduction effect is expanded.

It is the figure which showed an example of schematic structure of the cold tandem rolling mill of the circulating oil supply system which has several stands with which this invention is applied. It is the figure which showed an example of schematic structure of the cold tandem rolling mill of the circulating oil supply system which has 5 stands concerning a prior art.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Steel plate 2a, 2b, 2c, 2d, 2e Rolling mill 3a-3e, 4b-4d, 5d, 5e, 9a-9e Spray nozzle 6 Oil pan 7 Recovery piping 8, 14 Piping 10, 13 Emulsion rolling oil 11 Storage tank 12 Agitator 15, 23, 24 Pump 20 Clean tank 21 Dirty tank 22 Filter device 25 Means for additionally adding surfactant

Claims (4)

A cold rolling method of a metal plate, in which a 0.2% proof stress before cold rolling is rolled by a cold tandem rolling mill with a metal plate of 220 MPa or more,
The work roll of at least one rolling stand has an average surface roughness Ra of 0.2 μm or more and 1.0 μm or less, and the surface roughness is a shot using spherical particles having an average particle diameter of 200 μm or less. A cold rolling method for a metal sheet, characterized by using a cold tandem rolling mill provided by blasting. Use a work roll having an average surface roughness Ra of 0.2 μm or more and 1.0 μm or less, and the surface roughness is provided by shot blasting using spherical particles having an average particle diameter of 200 μm or less. On the entrance side of the rolling stand
The second emulsion rolling oil containing the same type of rolling oil as the first emulsion rolling oil used in circulation and having a larger average particle diameter and / or a higher emulsion concentration compared to the first emulsion rolling oil 2. The metal plate cooling according to claim 1, wherein the neat oil of the rolling oil contained in the first emulsion rolling oil is supplied by a system different from the first emulsion rolling oil. Hot rolling method.   The work roll of at least one rolling stand has an average surface roughness Ra of 0.2 μm or more and 1.0 μm or less, and the surface roughness is a shot using spherical particles having an average particle diameter of 200 μm or less. A cold tandem rolling mill for metal sheets, which is provided by blasting. Use a work roll having an average surface roughness Ra of 0.2 μm or more and 1.0 μm or less, and the surface roughness is provided by shot blasting using spherical particles having an average particle diameter of 200 μm or less. On the entrance side of the rolling stand
A supply means for supplying a second emulsion rolling oil of a different system from the first emulsion rolling oil used for circulation or a neat oil of the rolling oil contained in the first emulsion rolling oil; The cold tandem rolling mill for metal sheets according to claim 3.

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