JP5239694B2 - Cold rolling mill row, cold rolling line, cold rolling method for metal sheet, and manufacturing method for cold rolled metal sheet - Google Patents

Description

  The present invention relates to a cold rolling mill train, a cold rolling line, a method for cold rolling a metal plate, and a method for producing a cold rolled metal plate.

  With increasing awareness of environmental issues, especially global warming, reducing carbon dioxide emissions has become a social issue. One method for suppressing carbon dioxide emissions is to reduce the weight of automobiles. In order to reduce the weight of automobiles, the use of aluminum or magnesium alloys having a low specific gravity or steel sheets (high-tensile steel sheets) with higher strength than conventional steel sheets is directed.

  By the way, there are some problems in cold rolling a metal plate such as this high-tensile steel plate.

  Since a high-tensile steel plate has a large deformation resistance, a large force is required when it is processed or deformed, and a rolling load, which is a reaction force, increases accordingly when cold-rolling. Moreover, when a rolling load becomes large, the bending of the roll which receives reaction force will become large, and the shape of the steel plate during rolling will deteriorate easily.

  For the purpose of reducing the rolling load when rolling a high-tensile steel plate, Patent Document 1 describes a method for reducing the diameter of a work roll of a rolling mill (the one shown in FIG. 5 is also included in this). )

  Further, in Patent Document 2, the upper and lower work rolls are crossed in the opposite directions in a plan view in an intermediate rolling mill in a group of rolling mills constituting a cold tandem rolling mill (cold rolling mill row). Is described.

  Furthermore, although not in cold rolling but in hot rolling, Patent Document 3 uses a work roll having different upper and lower diameters in a subsequent rolling mill constituting the finish rolling mill, and only one side of the upper and lower work rolls. A method of driving is described (this includes the one shown in FIG. 6 later. In the figure, a black and white divided into quadrants means a motor of a driving work roll. ).

In the method of Patent Document 1, at least one rolling mill having a diameter difference between the upper and lower work rolls is arranged upstream of the final rolling mill. In a conventional tandem rolling mill, a desired rolling is performed by one rolling. It is also described that a high-strength steel sheet that could not obtain a reduction ratio can be rolled once, contributing to an improvement in productivity and a reduction in running cost. The method of Patent Document 2 describes the work of an intermediate rolling mill. It is also described that by crossing the roll, the surface gloss of the steel sheet can be improved and surface defects can be reduced.
JP 57-019106 A JP 2000-202502 A JP 60-141303 A

  By the way, when cold-rolling a high-tensile steel sheet by the method of Patent Document 1, due to the effect of a small-diameter work roll, rolling at a higher pressure reduction than before is possible, but rolling at a high speed is difficult. was there.

  In the cold tandem rolling mill (cold rolling mill row), the peripheral speed of the work roll becomes higher as the downstream rolling mill is used. As the speed increases, the amount of rolling oil drawn between the small-diameter work roll and the steel plate increases.

  For this reason, as shown in FIG. 7, the neutral point in the roll bite (the point at which the roll speed and the plate speed in the roll bit match) is increased more than the roll bite due to the increased amount of drawn rolling oil. In other words, the steel plate speed becomes higher than the peripheral speed of the work roll and slips, and problems such as chattering due to the slip and an increase in thickness deviation may occur.

  When a small-diameter work roll is used, the peripheral speed of the work roll is increased correspondingly, and the above-described problem is easily realized.

  Therefore, when a small-diameter work roll is used, it is necessary to perform rolling while suppressing the rolling speed (the peripheral speed of the work roll of the final rolling mill) to 300 m / min or less, and when rolling twice with a conventional large-diameter work roll. Compared to that, we cannot expect much improvement in efficiency.

  On the other hand, as in Patent Document 2, when rolling a high-tensile steel sheet with a cold tandem rolling mill (cold rolling mill row) using a large-diameter work roll, there is a problem that the rolling reduction cannot be sufficiently secured. It was difficult to roll a high-strength steel sheet at a high pressure and a high rate at high speed by either method of Documents 1 and 2.

  Moreover, the method of driving only one side of the upper and lower work rolls by using the upper and lower different diameter work rolls in the latter-stage rolling mill constituting the finishing mill in hot rolling as in Patent Document 3 is also applied to cold rolling. In this case, as a result of trying to bear a large torque with only one of the work rolls, there is a problem that slipping easily occurs.

  These problems can be said not only in the case of a high-tensile steel plate but also in the case of directing high-speed rolling at a high pressure reduction rate in general for cold rolling of a metal plate.

  The present invention has been made to solve such problems as in the prior art, prevents slipping between a metal plate such as a high-strength steel plate and a work roll, and can cool the metal plate at a high pressure reduction rate and at a high speed. An object of the present invention is to provide a cold rolling mill row, a cold rolling line, a cold rolling method for a metal plate, and a method for producing a cold rolled metal plate.

That is, the present invention is as follows.
[1] In a cold rolling mill row in which a plurality of rolling mills are arranged, the first rolling mill is composed of five rolls, all of them are non-driven, and the second and subsequent rolls are composed of four rolls. A cold rolling mill train comprising two work rolls configured to directly roll a metal plate among the four rolls.
[2] Of the rolls of the first rolling mill, about two work rolls for directly rolling a metal plate, one work roll is a small diameter work roll having a smaller diameter than the remaining one work roll, The cold rolling mill according to the above [1], wherein the diameter of the small diameter work roll is 50 to 80% of the diameter of the remaining one work roll.
[3] A cold rolling line provided with the cold rolling mill row of [1] or [2].
[4] A method for cold rolling a metal plate, comprising cold rolling a metal plate using the cold rolling mill according to [1] or [2].
[5] A method for producing a cold-rolled metal plate, comprising producing a cold-rolled metal plate by the cold rolling method of [4].
[6] The method for producing a cold-rolled metal plate according to [5], wherein the metal plate is a high-tensile steel plate.

  According to the present invention, a slip between a metal plate and a work roll is prevented, a cold rolling mill row capable of rolling the metal plate at a high pressure reduction rate, a high speed, a cold rolling line, a method for cold rolling a metal plate, and The manufacturing method of a cold-rolled metal plate can be provided.

  FIG. 1 shows a cold rolling mill row 1 comprising five rolls of a first rolling mill and a cold rolling line 100 including the cold rolling mill 100 according to the present invention. Here, in FIG. 1, the F1 small-diameter work roll 12 that is the first rolling mill is disposed on the upper side, but may be disposed on the lower side.

  S is a steel plate (also called a strip). In the cold rolling line 100, 2 is a payoff reel, and the scale generated on the surface of the steel sheet S during the hot rolling is removed from the payoff reel 2 by pickling or a mechanical method. After that, the coil 3 wound in a coil shape (the steel sheet S wound in the coil shape is often simply referred to as a coil) is loaded.

  And in the cold rolling line 100, while the steel plate S is passed between the upper and lower work rolls 12 and 13 of each rolling mill constituting the cold rolling mill row 1, the upper and lower work rolls 12, By rotating 13, the steel sheet S is rolled and the plate thickness is reduced.

  The rolled steel sheet S is wound into a coil shape by the tension reel 5 and becomes a coil 6 after cold rolling.

  The cold rolling mill row 1 is composed of first, second to sixth rolling mills (F1, F2 to F6) in order from the payoff reel 2 side, and the second to sixth rolling mills (F2 to F6). The roll is composed of four upper backup rolls 7, upper work roll 8, lower work roll 9, and lower backup roll 10.

  Here, the cold rolling mill row 1 is composed of six rolling mills, but may be five or fewer rolling mills.

  In the present invention, the roll of the first rolling mill is composed of five. Specifically, in the example of the present embodiment shown in FIG. 1, the backup rolls 7 and 10, the intermediate roll 11, the small diameter work roll 12, and the small diameter work. It consists of five work rolls 13 that make a pair with the roll 12.

  Although only the roll group is illustrated in FIG. 1, the rolling mill is configured by a housing or the like (not illustrated), and the roll group is supported by a chock or the like and is further moved up and down by a reduction device (not illustrated).

  The emulsion is sprayed from the emulsion upper header 14 and the emulsion lower header 15, and lubrication between the work rolls 12 and 13 and the steel plate is performed.

  An emulsion is a rolling oil diluted with water. As shown in FIG. 2, the oil droplets are dissolved and dispersed in water by the action of the hydrophilic group through the surfactant. The diameter per particle of the emulsion is 1-30 μm.

  Here, the emulsion is supplied by an emulsion oil supply system as shown in FIG. The emulsion diluted to a certain concentration is stored in the tank 16, and via the pump 17, the work rolls 12 and 13 and the steel sheet S that is not shown here but actually exists in the same manner as in FIG. 1. Sprayed in between.

  More specifically, the emulsion sprayed with the target at the exit point of the roll bite (C in FIG. 7) and supplied in such a manner is recovered by the oil pan 18 and supplied to the tank 16 by the pump 19. Returned.

  FIG. 3 shows only the emulsion oil supply system of the first rolling mill, but the same applies to the second and subsequent rolling mills.

  FIG. 4 is a front view of the first rolling mill and includes the above-described roll group. Here, all the rolls are not driven.

  In cold rolling of high-tensile steel sheets, when the rolling reduction is increased, the rolling load increases, and there are cases where rolling exceeding the upper limit of the normal load on the specifications of the rolling mill is forced. In particular, when the plate width is wide, the rolling load is proportional to the plate width, and therefore rolling is performed at a high rolling load.

For cold rolling, the work roll radius R, effect on the rolling load p per unit width, there is Piarufaaru ^alpha relationship, alpha, although varies depending plate thickness and coefficient of friction, 1.0 to 1. Become 6.

  If the diameter of the work roll is small, the length of the roll bite, which is the part where the steel sheet to be rolled is in contact with the work roll, becomes short, and the rolling load decreases.

  Therefore, in order to reduce the rolling load, it is only necessary to reduce the diameter of the work roll. However, the length of the roll bite is shortened, and the neutral point is easily moved to the exit side of the roll bite. In some cases, slipping and chattering resulting from the occurrence of slipping may cause rolling failure.

  In particular, as the rolling speed increases, the amount of rolling oil drawn into the roll bite increases, and the coefficient of friction between the work roll and the steel sheet decreases, so slipping easily occurs.

  As a result of earnestly studying slip prevention in the first rolling mill that constitutes the cold rolling mill row 1, the inventors configure five rolls of the first rolling mill and make them all non-driven. As a result, the present invention has been conceived.

  Furthermore, about two work rolls that directly roll a steel plate among the rolls of the first rolling mill, by making one work roll a small diameter work roll having a smaller diameter than the remaining one work roll, The rolling load can be reduced and rolling can be performed at a high pressure reduction rate.

  In addition, the roll after a 2nd rolling mill is comprised with four, and let two work rolls which roll a steel plate directly among these four rolls be a drive type.

  The reason why all the roll groups of the first rolling mill should be non-driven is that the driving torque to be applied to the side of the work roll so that a force is applied to the steel sheet from the work roll by non-driving, It can be zero.

  That is, the work roll is rotated in a driven manner by the frictional force between the work roll and the steel plate. As a result, the work roll rotates in a state where the drive torque to be applied to the work roll side is zero so that a force is applied from the work roll side to the steel plate side.

  For this reason, a neutral point always exists in the roll bite, and even if the rolling conditions such as the lubrication state fluctuate somewhat, the advanced rate remains constant and almost no slip or the like occurs.

  In this way, when all the roll groups are rolled without being driven, rolling is performed in a so-called drawing state.

  That is, rolling in the first rolling mill is performed by the tension acting on the steel plate from the second rolling mill side. In such a state, even if the friction coefficient varies somewhat due to some variation in rolling conditions such as the lubrication state, the neutral point will be present in the roll bite and will not slip.

  By the way, the roll of a 1st rolling mill is comprised by five, and it is preferable to make one work roll into a thing smaller in diameter than the remaining one work roll about two work rolls which roll a steel plate directly. However, there are suitable diameter ratio ranges.

  Specifically, the diameter of one work roll (small work roll) is preferably 50 to 80% of the diameter of the remaining one work roll, and if it exceeds 80%, the load reducing effect is small. Thus, rolling becomes impossible at a high pressure ratio of 25% or more. Although there is no upper limit to the rolling reduction, in the case of rolling a high-tensile steel plate, it is practically 30% or less so that the rolling mill specification does not become excessive.

  Further, when the diameter of one work roll (small work roll) is less than 50% of the diameter of the remaining one work roll, the Hertz stress between the intermediate roll and the work roll is increased, and Since the amount of oil drawn into the roll bite is reduced, heat streak (soot due to seizure generated between the work roll and the steel plate) occurs, and the surface quality of the steel plate is significantly impaired.

  Next, preferable lubrication conditions between the work roll and the steel plate in the present invention will be described. As shown in FIG. 3, an emulsion obtained by diluting rolling oil with water is used for lubrication between the work roll and the steel plate.

The rolling oil is preferably based on a synthetic ester obtained by esterifying a fatty acid and an alcohol. Synthetic esters are generally difficult to thermally decompose and can maintain stable lubrication during rolling. Here, synthetic esters, as described above, usually, is synthesized from fatty acids and alcohols, the fatty acid is a monobasic acid or dibasic acid C ₁₂ -C _36, the alcohol, C ₁ -C ₁₈ Monohydric or polyhydric alcohols.

  Specific examples include ethyl hexyl palmitate, butyl oleate, butyl carbitol isostearate, pentaerythrole oleate and the like.

  An emulsifier that reduces the interfacial tension between the synthetic ester and water is added to this synthetic ester rolling oil.

  Moreover, you may add antioxidants and extreme pressure agents, such as phosphate ester, which have a lubrication effect in the contact part of a work roll and a steel plate.

  This rolling oil is diluted with water to make an emulsion. Antioxidants are useful for preventing deterioration of the emulsion.

  The temperature of the emulsion is preferably 40-60 ° C. If the temperature is lower than 40 ° C, there is a risk that the emulsion will spoil due to the generation of bacteria. On the other hand, when the temperature exceeds 60 ° C., the evaporation of water becomes remarkable, and the concentration of the rolling oil in the emulsion immediately increases, making it difficult to manage the concentration. Moreover, the steam for heating is also needed and the cost increases.

The viscosity of the rolling oil used in the cold rolling mill of the present invention is preferably 20 to 60 cSt (20 to 60 × 10 ⁻⁵ m ² / s) / 50 ° C. If it is less than 20 cSt (20 × 10 ^-5 m ² / s) / 50 ° C, the amount of emulsion drawn into the roll bite decreases, the rolling load increases and the above-mentioned heat streak (also simply called heat) occurs. It becomes easy to do. If it exceeds 60 cSt (60 × 10 ⁻⁵ m ² / s) / 50 ° C., slipping after the second rolling mill tends to occur.

  Furthermore, the concentration of the emulsion obtained by diluting the viscosity rolling oil with water is preferably 0.5 to 5% by mass. If it is less than 0.5%, the rolling load increases and heat streaks tend to occur. Moreover, when it exceeds 5 mass%, it becomes easy to generate | occur | produce the slip after a 2nd rolling mill. Further, it is preferable to spray the emulsion at a flow rate of 200 L / min or more per rolling mill. If it is less than 200 L / min, the temperature of the work roll rises and heat streaks are likely to occur on the steel sheet surface.

(Rolling conditions)
In order to confirm the effect of the present invention, a high-tensile steel plate was cold-rolled using the cold rolling mill train of the present invention. The rolling conditions are shown below. The rolled material (steel plate) was an 880 MPa steel plate. The 880 MPa steel plate has a tensile stress of 880 MPa or more in a tensile test (test piece conforming to JIS Z2201) after cold rolling and annealing. The deformation resistance at the time of rolling is as follows, and has a deformation resistance twice or more that of a general low carbon steel plate.

Rolled material (steel plate): 880 MPa Kf = 946 (0.02 + ε) ^0.12
here,
Kf: Deformation resistance (MPa)
ε: Cumulative strain. Other rolling conditions are as follows.

Mother board thickness: 2.4mm, board width: 1200mm
Finish thickness: 1.0mm
Coil weight: 25ton
The rolling oil used for lubrication is based on synthetic ester (butyl oleate) with a viscosity of 30 cSt (30 × 10 ^-5 m ² / s) / 50 ° C, and nonionic emulsifier (polyoxyethylene fatty acid ester) as the base oil. 0.5% by weight with respect to the base oil, 0.2% by weight with respect to the base oil, 0.4% by weight with respect to the base oil, diluted with warm water at 50 ° C. It heated and sprayed at the flow volume of 300 L / min between the work roll and the steel plate from the entrance side of each rolling mill.

  Under the above conditions, the present invention example and the conventional example were compared as follows.

[Example 1]
The experiment was conducted with the mass of rolling oil in the total mass of the emulsion being 1% by mass.
(Example of the present invention)
In Invention Examples 1-1, 1-2, and 1-3, the above-described 880 MPa steel plate was cold-rolled by the cold rolling mill shown in FIG. The rolling conditions were as follows: the base plate thickness of the steel sheet was 2.4 mm, the rolling reduction rate in the first rolling mill was 25%, the total rolling reduction rate was 58.3%, and finished to 1.0 mm. In rolling mills other than the first rolling mill, the rolling reduction was made equal.

  In Examples 2-1 and 2-2 of the present invention, the diameter of the small-diameter work roll is excluded from the preferred range, that is, the range of 50 to 80% of the diameter of the other work roll. Rolling was carried out in the same manner as in Examples 1-1, 1-2 and 1-3.

  Here, the work roll diameter of the second to sixth rolling mills was 500 mm and the backup roll diameter was 1000 mm, and the intermediate roll diameter of the first rolling mill was 500 mm and the backup roll diameter was 1000 mm.

  The small diameter work rolls of the first rolling mills of Invention Examples 1-1, 1-2, and 1-3 were changed in various diameters, and the diameter of the work rolls paired with the small diameter work rolls was 500 mm.

  In all of Examples 1-1, 1-2, 1-3, 2-1, and 2-2 of the present invention, all rolls of the first rolling mill were not driven. In addition, the length of all work rolls was 1800 mm.

(Conventional example 1)
In Conventional Example 3-1, the above-described 880 MPa steel plate was cold-rolled by the cold rolling mill shown in FIG. The rolling reduction in the third and fourth rolling mills was 20%. Here, for the first, second and fifth rolling mills, the work roll diameter was 500 mm and the backup roll diameter was 1000 mm. In the third and fourth rolling mills, small-diameter work rolls were arranged, and the diameters of the work rolls, intermediate rolls, and backup rolls were 150 mm. In addition, the length of all work rolls was 1800 mm. Other conditions are the same as the above 1-1, 1-2, 1-3, 2-1, 2-2.

(Conventional example 2)
In Conventional Example 3-2, the above-described 880 MPa steel plate was cold-rolled by the cold rolling mill shown in FIG. Other conditions are the same as the above 1-1, 1-2, 1-3, 2-1, 2-2. Here, in Conventional Example 2, the same work roll diameter as that of Invention Example 1-1 (small diameter work roll diameter: 380 mm) was used, but the other work roll paired with the small diameter work roll was driven.

[Example 2]
The experiment was performed by setting the mass of the rolling oil in the total mass of the emulsion to 4% by mass. Other conditions are the same as those in the first embodiment.

(Experimental result)
The experimental results are shown in Tables 1 and 2.

In the case of the emulsion concentration of 1% by mass shown in Table 1, in Examples 1-1, 1-2, and 1-3 of the present invention, the peripheral speed of the work roll of the final rolling mill can be increased to a maximum value of 1000 m / min. It was possible to roll with high efficiency without any problems such as slip during rolling.

  On the other hand, in Example 2-1 of the present invention, the peripheral speed of the work roll of the final rolling mill was 660 m / min or more, and a minute heat streak that was thought to be due to insufficient lubrication occurred. Therefore, rolling at a higher speed was not possible. There wasn't. However, no slip occurred.

  In Inventive Example 2-2, since the diameter of the work roll was large, rolling at a high pressure reduction rate was not possible, and it was not possible to roll to the target plate thickness with the first rolling mill. The rolling reduction ratio at the first rolling mill was changed to 21%, and the rolling reduction distribution at the rear rolling mill was changed. As a result, the peripheral speed of the work roll of the final rolling mill could be increased up to 1000 m / min, and no slip occurred.

  In Conventional Example 1, slips occurred in the third and fourth rolling mills, and the peripheral speed of the work roll of the final rolling mill could not be increased above 300 m / min.

  In Conventional Example 2, since it is a one-side drive, slip occurred in the first rolling mill, and the peripheral speed of the work roll of the final rolling mill could not be increased above 450 m / min.

  In the case of the emulsion concentration of 4% by mass shown in Table 2, in Examples 1-1, 1-2 and 1-3 of the present invention, slip does not occur, and the peripheral speed of the work roll of the final rolling mill is a maximum value of 1000 m / min. I was able to raise it.

  In the case of the comparatively high emulsion concentration of 4% by mass, in Example 2-1 of the present invention, the peripheral speed of the work roll of the final rolling mill could be increased to 750 m / min. There has occurred.

  In Inventive Example 2-2, since the diameter of the work roll was large, rolling at a high pressure reduction rate was not possible, and it was not possible to roll to the target plate thickness with the first rolling mill. The rolling reduction at the first rolling mill was changed to 23%, and the distribution of rolling reduction at the rear rolling mill was changed. As a result, the peripheral speed of the work roll of the final rolling mill could be increased up to 1000 m / min, and no slip occurred.

  In the case of high lubrication with an emulsion concentration of 4% by mass, in the conventional example 1, slip occurs in the third and fourth rolling mills, and the peripheral speed of the work roll of the final rolling mill is higher than 120 m / min. I couldn't. In Conventional Example 2, since it is a one-side drive, slip occurred in the first rolling mill, and the peripheral speed of the work roll of the final rolling mill could not be increased beyond 280 m / min.

  As described above. In the above description, the case of cold-rolling a high-tensile steel sheet has been described. However, the cold rolling mill according to the present invention can be used for cold rolling of not only a high-strength steel sheet but also any metal sheet. .

  By cold rolling a metal plate using the cold rolling mill of the present invention to produce a cold-rolled metal plate, slip between the metal plate and the work roll is prevented, and the metal plate is reduced at a high pressure and at a high speed. Can be rolled with.

Diagram for explaining an embodiment of the present invention Diagram for explaining emulsion Diagram for explaining an embodiment of the present invention Diagram for explaining an embodiment of the present invention Diagram for explaining the prior art Diagram for explaining the prior art Diagram for explaining roll bite and neutral point

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Cold rolling mill line 2 Pay-off reel 3 Coil 4 Small diameter roll group 5 Tension reel 6 Coil after cold rolling 7 Upper backup roll 8 Upper work roll 9 Lower work roll 10 Lower backup roll 11 Intermediate roll 12 Work roll, small diameter work Roll 13 Work roll paired with small diameter work roll 14 Emulsion upper header 15 Emulsion lower header 16 Tank 17 Pump 18 Oil pan 19 Pump 100 Cold rolling line A Conveying direction C Roll bite exit point S Steel plate

Claims (6)

  In the cold rolling mill row in which a plurality of rolling mills are arranged, the rolls of the first rolling mill are configured with 5 rolls, all are non-driven, and the rolls after the second rolling mill are configured with 4 rolls, A cold rolling mill row, wherein two of the four rolls that directly roll a metal plate are driven.   Among the rolls of the first rolling mill, one work roll is a small-diameter work roll having a smaller diameter than the remaining one work roll, and the small-diameter work roll. The cold rolling mill according to claim 1, wherein the roll has a diameter of 50 to 80% of the diameter of the remaining one work roll.   The cold rolling line provided with the cold rolling mill row | line | column of Claim 1 or Claim 2.   A cold rolling method for a metal plate, comprising cold rolling a metal plate using the cold rolling mill train according to claim 1 or 2.   A method for producing a cold-rolled metal plate, comprising producing a cold-rolled metal plate by the cold rolling method according to claim 4.   The method for manufacturing a cold-rolled metal plate according to claim 5, wherein the metal plate is a high-tensile steel plate.

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