JP2008006486A - Cold rolling method for metal plate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain excellent lubricity in cold rolling for a metal plate, and also, to obtain excellent effects in cooling property and washing property of a metal plate and a rolling roll by a coolant, and in separability of solid matter powder in the coolant or the like. <P>SOLUTION: A water solution having a cloud point is used as the coolant, and a metal plate is made to enter a roll bite at a temperature more than the cloud point of the coolant so as to be rolled. The coolant at a temperature less than the cloud point exhibits properties of a solution type, and is excellent in the cooling property and washing property of the metal plate and a rolling roll, and the separability of solid matter powder in the coolant. Further, in the coolant fed to the metal plate at a temperature more than the cloud point of the coolant, adhesiveness of lubricant components to the surface of the metal plate remarkably increases, and lubricity equal to that of the coolant of an emulsion type or above can be obtained. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a method for cold rolling a metal plate, while ensuring excellent lubricity equivalent to or better than that when using a conventional emulsion type coolant, the cooling performance of the metal plate and rolling roll by the coolant. It is an object of the present invention to provide a cold rolling method capable of obtaining excellent effects in terms of detergency and separability of solid powder in the coolant.

In cold rolling, two functions of lubrication and cooling of a rolling roll and a metal plate are important. Lubrication lowers the rolling load by lowering the coefficient of friction between the work roll and the metal plate (roll bite), and cooling reduces the friction of the rolling roll and metal plate due to frictional heat generated by the roll bite and heat generated by processing. This is necessary to prevent the temperature from rising excessively.
In order to exert such a lubricating function and a cooling function, in cold rolling of a metal plate such as a steel plate, a water-insoluble oil agent (rolling oil) such as mineral oil, natural oil or synthetic ester is turned into water with a surfactant. Dispersed and diluted emulsion is used as coolant. This emulsion is of the O / W type (oil-in-water type) in which the rolling oil is contained as oil droplets having a concentration of about 1 to 5 mass% and an average particle size of about 5 to 15 μm. It can be used as a coolant that has both.

Such emulsion-type coolant (hereinafter mainly referred to as “emulsion rolling oil”) is supplied from the coolant tank to the rolling section (metal plate or rolling roll), but the amount of rolling oil used is reduced and the amount of waste liquid is reduced. For reduction, it is usually used in a circulating manner, and this is called a circulating oil supply method (recirculation method).
When emulsion rolling oil is spray-supplied to a metal plate or a rolling roll, an oil film is formed while water is excluded on the surface of the metal plate or the roll bite inlet (this phenomenon is referred to as plate-out). The oil film formed in this way improves the lubricity of the roll bite. That is, the thicker the oil film introduced into the roll bite, the better the lubricity, and even a hard metal plate can be rolled under high pressure.
As a technique for improving lubrication performance when using such emulsion rolling oil, for example, Patent Document 1 discloses a method for improving plate-out performance by supplying rolling oil at a predetermined temperature or higher. Yes.

On the other hand, in order to prevent defects such as heat scratches as the speed of cold rolling increases, it is necessary to improve the cooling performance. In Patent Document 2, the amount of coolant and the temperature of cooling water are controlled. Thus, a method for lowering the metal plate and roll temperature is disclosed. Patent Document 3 discloses a method for enhancing the cooling effect by controlling the coolant flow rate in accordance with the rolling speed.
Further, regarding the hybrid lubrication system, Patent Document 4 discloses a method for increasing the effect of roll cooling by making the temperature of the roll coolant liquid lower than the temperature of the hybrid liquid used for lubrication.
JP 2000-218305 A JP 56-1111505 A JP 2002-66622 A JP-A-9-122733

With the recent increase in awareness of environmental issues, there is an increasing need for a longer life of lubricants and a reduction in the amount of waste liquid. From this point of view, recirculation systems that use coolant in a circulating manner play an important role. It is thought to be fulfilled.
However, all of the methods of circulating the coolant use emulsion rolling oil, and thus various problems as described below have occurred.

The first problem is that when emulsion rolling oil is used, filter loss, scum out, fume loss, and the like increase the amount of lubricant consumed.
The filter loss occurs because solid powder such as wear powder generated by cold rolling is taken into the emulsion, and when this is separated and removed by the filter, oil droplets in the emulsion are also captured by the filter. Scum-out is a loss of oil that occurs when solid powder such as wear powder is embraced in the oil droplets of the emulsion and scum that is a mixture with deteriorated rolling oil is generated. In addition, when using natural fats and oils with a high pour point, the fume loss is circulated by heating the entire coolant to about 50-60 ° C, and the resulting fumes contain oil. This is a loss caused by
These are problems that are fundamentally difficult to solve when using emulsion rolling oil, and measures such as selection of the type and viscosity of the base oil and optimization of the type and addition amount of the surfactant are taken. However, it has not yet reached a fundamental solution.

  The second problem is that emulsion rolling oil tends to change the emulsion stability depending on factors such as iron content, temperature, pH, etc. contained in the coolant. This is a point that requires a great deal of labor to manage the emulsion rolling oil. For example, the concentration, temperature, saponification value, acid value, pH, etc. of emulsion rolling oil are regularly analyzed using coolant sampled during circulation use, and the state of emulsion rolling oil is constant according to the results. Need to manage to keep. In addition, filter equipment such as an iron powder removing device and various measuring instruments for managing the state of the coolant are also required, and a great deal of labor is required for their maintenance and management.

As a third problem, the emulsion rolling oil is usually sprayed on a rolling roll or a metal plate for cooling, but the oil in the emulsion forms an oil film on the roll surface or the like. There is a problem that the effect is hindered.
On the other hand, in order to improve the cooling effect, it is effective to lower the temperature of the emulsion rolling oil as shown in Patent Document 2 and Patent Document 4, but the deterioration component of the rolling oil is such as wear powder. When forming a scum by forming a mixture with solid powder, clogging may occur in the piping, so it is necessary to maintain the emulsion rolling oil at a temperature above a certain level. Cooling by reducing the temperature of the emulsion rolling oil There are certain limits to improving performance.

Moreover, as shown in Patent Document 3, it is possible to enhance the cooling effect by controlling the flow rate of the cooling water according to the rolling speed, but for increasing the capacity of the circulation pump in order to increase the amount of water. Since it requires equipment costs and power costs for circulation, it is not necessarily an economical method.
Further, as shown in Patent Document 1, when the coolant is heated to improve the lubricity, the cooling performance is deteriorated, so it is not easy to achieve both lubricity and cooling performance.

The fourth problem is a problem that is difficult to solve when using emulsion rolling oil. During cold rolling, metal foreign matter adhering to the rolling roll due to peeling from the surface of the metal plate is between the work roll and the backup roll. It is mentioned that wrinkles are easily formed on the surface of the work roll by being bitten or jumping into a roll bite. When wrinkles are formed on the surface of the work roll in this way, it is transferred to the surface of the metal plate, which causes a significant decrease in yield as a surface defect.
As described above, the circulating oil supply method using emulsion rolling oil has various problems that cannot be solved by the prior art.

On the other hand, when rolling a softened steel sheet under light pressure like temper rolling, it is not necessary to have excellent lubricity, and conversely, a high coefficient of friction is required to obtain a stable elongation. The For this reason, in wet temper rolling, a solution type coolant (tempered rolling fluid) in which a water-soluble substance is dissolved in water is used.
Such a solution type coolant does not form large oil droplets like emulsion rolling oil because the lubricating component itself exhibits solubility in water. Therefore, it becomes very easy to separate from solid powder such as wear powder generated in cold rolling, and it is very easy to remove the solid powder from the coolant, and the filter equipment can be simplified. In addition, since solid powder is not embraced in the oil, there is very little loss due to scum formation, and furthermore, since it can be used at room temperature, there is little fume loss. Moreover, since it is excellent also in the washing | cleaning property, there are very few lubrication components which remain | survive on a metal plate after rolling, and the take-out loss by a steel plate can also be reduced.

However, conventional solution type coolants such as those used in temper rolling are extremely inferior in lubricity compared to emulsion rolling oils, so it is difficult to use them in cold rolling such as ordinary tandem rolling. It has been thought that there is. For this reason, conventionally, in cold rolling with a large rolling reduction such as a tandem rolling mill or levers rolling mill, emulsion rolling oil with excellent lubricity is used, and the elongation is 5% or less as in temper rolling. In the light pressure region, solution type coolant with a high friction coefficient is used, and both are clearly used according to the rolling conditions.
In addition, Patent Document 5 discloses a solution type tempered rolling liquid for performing a high pressure with a reduction ratio of about 20% even in temper rolling, but this tempered rolling liquid is a material after annealing. Even if it can be applied to 1-pass rolling of a softened steel sheet, sufficient lubricity cannot be obtained under severe rolling conditions in which work hardening occurs in multi-pass rolling such as tandem rolling or lever rolling.
JP 61-7395 A

  Accordingly, the object of the present invention is to solve the above-mentioned problems of the prior art and to obtain excellent lubricity equivalent to or higher than that obtained when a conventional emulsion type coolant is used in rolling a metal plate. An object of the present invention is to provide a cold rolling method for a metal plate that can provide excellent effects in terms of the cooling and cleaning properties of the plate and the rolling roll and the separability of the solid powder in the coolant.

  In order to solve the above-mentioned problems, the present inventors have studied the characteristics of an aqueous solution used as a solution type coolant, and the relationship between the characteristics and the temperature of a rolled metal sheet. When an aqueous solution having a cloud point by dissolving a functional lubricant is used as a coolant, the properties of the coolant change between a temperature range below the cloud point and a temperature range above the cloud point. By controlling the temperature of the rolled metal sheet while taking advantage of the properties of the material, the rolling lubricity is equivalent to or better than that of emulsion type coolant, and the excellent cooling and solid powder separation characteristics unique to solution type coolants. The present inventors have found that a cold rolling method for a metal plate can be performed while simultaneously satisfying cleaning properties and the like.

The present invention has been made on the basis of such findings and has the following gist.
[1] In a method of cold rolling a metal plate while supplying a coolant,
A solution having a cloud point by diluting a lubricant mainly composed of a water-soluble lubricant with water and dissolving the water-soluble lubricant is used as a coolant, and at least in some rolling stands or rolling passes, a metal plate Is a cold rolling method for a metal sheet, wherein the metal sheet enters and rolls at a temperature equal to or higher than the cloud point of the coolant.
[2] The cold rolling method according to [1], wherein a coolant having a temperature lower than the cloud point is supplied to the metal plate and / or the rolling roll.

[3] In the cold rolling method of [1] or [2] above, the coolant is circulated and used, and after being supplied to the metal plate and / or rolling roll, the coolant below the cloud point is recovered. A method for cold rolling a metal plate, characterized by subjecting solid matter in the liquid to a removal treatment at a temperature.
[4] In the cold rolling method according to any one of [1] to [3], the cloud point of the coolant is 30 to 80 ° C.
[5] In the cold rolling method according to any one of [1] to [4], at least a part of the water-soluble lubricant is a polyalkylene glycol having an average molecular weight of 500 to 5000. Hot rolling method.

[6] In the cold rolling method according to any one of [1] to [5], an aqueous solution containing 1 to 15% by mass of a water-soluble lubricant is used as a coolant. .
[7] In the cold rolling method according to any one of [1] to [6] above, the temperature of the coolant supplied to the metal plate and / or the rolling roll according to the plate temperature when the metal plate enters the roll bite And / or adjusting the flow rate.
[8] In the cold rolling method according to any one of [1] to [7] above, in some rolling stands or rolling passes, the metal plate enters and rolls at a temperature below the cloud point of the coolant. A cold rolling method for a metal sheet, wherein a coolant having a temperature equal to or higher than the cloud point is supplied to the roll bite.

  According to the present invention, the coolant is maintained in a state in which the lubricant component is dissolved in water at a liquid temperature below its cloud point, so that solid powder separability and deterioration resistance during circulation use, rolling rolls and metals The cleanability of the plate is extremely good, so the basic unit of the lubricant in the coolant can be greatly improved compared to conventional emulsion type coolant, and the surface defects of the rolling roll and the metal resulting therefrom Generation of surface defects on the plate can also be effectively reduced. Moreover, since coolant temperature can be made low, the cooling effect of a rolling roll or a metal plate can be acquired appropriately, and generation | occurrence | production of the heat scratch which is easy to occur by high-speed rolling can also be suppressed. On the other hand, the coolant supplied to the roll bite in which the metal plate enters and is rolled at a temperature higher than the cloud point of the coolant greatly improves the adhesion of the lubricant component to the metal plate. The metal plate can be cold-rolled while maintaining the same or better lubricity.

In the present invention, when cold rolling a metal plate while supplying a coolant, a solution having a cloud point by diluting a lubricant mainly composed of a water-soluble lubricant with water and dissolving the water-soluble lubricant Is used as a coolant, and at least in some rolling stands or rolling passes, the metal plate enters the roll bite and is rolled at a temperature equal to or higher than the cloud point of the coolant.
Here, a solution having a cloud point is a solution having the property that when the temperature is increased, the solubility of the dissolved component is suddenly lowered at a certain temperature to become cloudy, and the cloud point is so clouded. Refers to the liquid temperature. In this invention, when the temperature of the aqueous solution (coolant) which has a cloud point is changed, the temperature which confirmed the white turbidity visually is made into the cloud point of the aqueous solution. The photograph of FIG. 6 illustrates the difference in the appearance at a temperature lower than the cloud point and the appearance at a temperature higher than the cloud point for an aqueous solution having a cloud point of 40 ° C.

In the present invention, an aqueous solution having a cloud point is used as a coolant for cold rolling because the aqueous solution has a temperature range (liquid temperature) below the cloud point and a temperature range (liquid temperature) above the cloud point as a coolant. This is because the following characteristics and effects can be obtained.
Since the lubricant component dissolves in water in the temperature range below the cloud point, the coolant can be immediately separated from solid powder such as wear powder during circulation, and the wear powder is removed from the coolant. It becomes extremely easy to reduce the filter loss. Moreover, since wear powder is not embraced in the oil, the loss due to scum generation is extremely reduced. Therefore, fume loss can be reduced by using at normal temperature without the need to raise the temperature in order to cause the scum to flow. Furthermore, since it is excellent in cleaning properties, there are very few lubricant components remaining on the metal plate, and take-out loss due to the metal plate can be reduced. Furthermore, management of the coolant is simplified in that it does not require management of emulsification stability like emulsion rolling oil.

In addition, even when sprayed on a rolling roll for cooling, it has excellent cleaning properties, so even if the lubricant component adheres to the roll surface, it can be cooled while washing it down, so it is cooler than emulsion rolling oil. The performance can be improved. Furthermore, due to the excellent cleaning properties, the foreign metal adhering to the rolling roll can be easily washed away from the surface, and surface flaws are hardly generated on the roll surface.
On the other hand, in the temperature range above the cloud point, the coolant has a cloudy appearance due to a decrease in the solubility of the lubricant component in water, but the metal plate rolls at a temperature above the cloud point of the coolant. Even when the coolant is supplied to the surface of the metal plate (roll bite) at such a temperature, the lubricant component in the coolant and water are easily separated from each other, so that the lubricant is lubricated. Adhesiveness of the agent component to the surface of the metal plate is greatly enhanced, and lubricity in a roll bite equivalent to or higher than that of emulsion rolling oil can be ensured.
The adhesion performance of the coolant having a cloud point to the surface of the metal plate is such that the coolant is supplied to the surface of the metal plate having a temperature higher than the cloud point of the coolant, rather than heating the coolant to the cloud point or higher. It turns out that it is considerably better.

For the above reasons, in the present invention, a solution having a cloud point is used as a coolant, and the metal plate enters the roll bite and is rolled at a temperature equal to or higher than the cloud point of the coolant.
In the present invention, in order for the metal plate to enter the roll bite and be rolled at a temperature equal to or higher than the cloud point of the coolant, the metal plate may be positively heated, or heat generated by rolling The temperature may be higher than the cloud point of the coolant.
The metal plate enters the roll bite at a temperature above the cloud point of the coolant and is not necessarily rolled, but it is not necessarily a full rolling stand (eg, a full rolling stand of a tandem cold rolling mill) or a full rolling pass (eg, levers). It is not necessary to be a total rolling pass of rolling by a type cold rolling mill), and may be at least a part of a rolling stand or a rolling pass that requires lubricity. The lubricity required for rolling differs depending on the difference in the position of the front and rear stages of the rolling stand, the difference in the stage of the rolling pass, the type and size of the material to be rolled, the roll diameter, the roll roughness, the rolling speed, etc. This is because some rolling stands and rolling passes do not require much lubricity.

  In this invention, it is preferable to supply the coolant of the temperature below a cloud point to a metal plate and / or a rolling roll. As described above, when the metal plate enters the roll bite at a temperature equal to or higher than the cloud point of the coolant and is rolled, the adhesion of the lubricant component of the coolant to the surface of the metal plate is sufficiently high, and the lubricity can be ensured. On the other hand, if the temperature of the coolant itself is maintained at a low temperature below the cloud point, the cooling effect of the metal plate is high, and a high cooling effect can be obtained even if it is supplied to the rolling roll. In addition, by maintaining the coolant in a temperature range below the cloud point as a whole coolant circulation system, it is possible to secure advantages as a solution type coolant such as excellent solid powder separation during circulation.

  In the case where the coolant is circulated in the present invention, it is usually supplied to a metal plate and / or a rolling roll, and then recovered in the liquid at a liquid temperature lower than its cloud point with respect to the recovered coolant (mainly wear powder or the like). The solid powder) is removed. The coolant is maintained in a state where the lubricant component is dissolved in water in the temperature range below the cloud point, so that it has good separability from the solid powder and the loss of the lubricant component (system) Discharge to the outside) can be minimized. As a means for performing the removal process, a filter system (Hoffman filter, electromagnetic filter, etc.) is generally used. However, other appropriate systems such as a centrifugal separation system and a magnetic adsorption system can be adopted. The coolant recovered after being supplied to the metal plate and / or rolling roll may be at a liquid temperature higher than the cloud point, in which case the coolant is cooled and / or before the removal of solid matter in the liquid. Cool by natural cooling in the circulatory system and keep the liquid temperature below the cloud point.

  The coolant used in the present invention preferably has a cloud point of 30 to 80 ° C. When the cloud point of the coolant is less than 30 ° C, the temperature at which the water-soluble lubricant dissolves in water becomes low. Therefore, in order to enjoy the above advantages as a solution type lubricant, maintain the entire circulating coolant at a low temperature. Therefore, the equipment cost and running cost of the heat exchanger for that purpose increase. On the other hand, when the cloud point exceeds 80 ° C., it is necessary to keep the temperature of the metal plate high (for example, 90 ° C. or higher) in order for the normal temperature coolant to contact the metal plate and sufficiently adhere to the metal plate surface. ) If the rolling speed is low and the temperature of the metal plate is low, the method of the present invention cannot be applied, and the lubricity may be insufficient.

A solution (aqueous solution) having a cloud point by dissolving a water-soluble lubricant used as a coolant in the present invention is maintained in a state where the lubricant component is dissolved in water at a liquid temperature lower than the cloud point as described above. Therefore, it has a transparent or semi-transparent appearance, and can be distinguished from a milky white appearance caused by irregular reflection of light by emulsion particles of about 5 to 15 μm like emulsion rolling oil. On the other hand, when the solution reaches a liquid temperature equal to or higher than the cloud point, it does not have a transparent appearance and generally has an opaque appearance such as cloudiness (see FIG. 6).
The type of water-soluble lubricant contained in the coolant is not limited as long as the solution (aqueous solution) can have a cloud point, and among them, a chemically synthesized lubricant (hereinafter referred to as synthetic lubrication). (Referred to as agent) is particularly preferred. This synthetic lubricant is advantageous in that it is more resistant to spoilage than conventionally used rolling oil, and it is difficult to form a scum that is a mixture of solid powder such as wear powder and a deteriorated oil agent.

Further, the lubricant blended in the coolant may partially be a water-insoluble lubricant (for example, conventionally used rolling oil), but 80 mass% or more of the blended lubricant, preferably It is desirable that 95 mass% or more is a water-soluble lubricant (particularly preferably a water-soluble synthetic lubricant). If the proportion of water-soluble lubricant (particularly preferably water-soluble synthetic lubricant) is less than 95 mass%, the amount of water-insoluble lubricant increases, so solid powder separability, deterioration resistance, and washability as a solution type coolant. Etc., particularly when the content is less than 80 mass%, the characteristics are remarkably deteriorated.
As the water-insoluble lubricant blended with the water-soluble lubricant in the coolant, one or more kinds of rolling oils used in emulsion-type coolants such as fats and oils, fatty acid esters, mineral oils and the like can be used. Even if a small amount of non-water-soluble lubricant is used in this way, the characteristics as a solution-type coolant are not lost, and the basic unit of lubricant can be greatly improved compared to emulsion-type coolant. is there.

As the water-soluble synthetic lubricant used in the present invention, polyalkylene glycol is particularly preferable, and polyalkylene glycol having an average molecular weight of 500 to 5000 is particularly preferable. Therefore, it is preferable that at least a part, preferably all of the water-soluble lubricant is a polyalkylene glycol having a molecular weight of 500 to 5,000.
Polyalkylene glycol is also called polyglycol, polyether or polyalkylene oxide, and is obtained by ring-opening polymerization of alkylene oxide (AO) such as ethylene oxide (EO) or propylene oxide (PO) to a substance having active hydrogen. It is a polymer. This is a synthetic lubricant mainly used in brake fluids and flame retardant hydraulic fluids. By changing the degree of polymerization, alkyl groups, etc., water-soluble to water-insoluble ones with various viscosity grades It is a substance that can obtain a polymer having a wide range of characteristics.

In general, the polyalkylene glycol tends to increase in viscosity and increase in viscosity index as the molecular weight increases. For use in cold rolling, the polyalkylene glycol preferably has an average molecular weight of 500 to 5,000. This is because the larger the average molecular weight, the higher the viscosity and the better the adhesion to the metal plate. However, if the average molecular weight is too large, the pour point becomes high and there is a risk of hindering cleaning in the subsequent process.
As polyalkylene glycols, those having various chemical structures can be used, but those having a structure in which a block portion consisting of oxyethylene units is bonded to both ends of a block portion consisting of oxypropylene units are representative. It is. As a commercial item, Asahi Denka Co., Ltd. brand name "Adeka Pluronic L31", "Adeka Pluronic L62" etc. are mentioned, for example. Moreover, a reverse block type copolymer can be used as a block copolymer having a structure in which a block portion consisting of oxypropylene units is bonded to both ends of a block portion consisting of oxyethylene units. As a commercial item, Asahi Denka Co., Ltd. brand name "Adeka Pluronic 25R2", BASF Japan brand name "Pluronic 25R2" etc. can be mentioned, for example.

Although there is no special restriction | limiting in the content density | concentration of the water-soluble lubricant in a coolant, It is preferable to set it as about 1-15 mass% in the ratio in a solution. If the content concentration of the lubricant is less than 1 mass%, sufficient lubricity necessary for cold rolling cannot be obtained. On the other hand, if the content concentration exceeds 15 mass%, the consumption of the lubricant increases, which is economically disadvantageous. Become.
When a polyalkylene glycol, preferably a polyalkylene glycol having a molecular weight of 500 to 5000, is used as the water-soluble lubricant, the higher the proportion of polyalkylene glycol in the lubricant blended with the coolant, the better. Here, when the proportion of polyalkylene glycol in the blended lubricant is less than 50 mass%, the effect of improving the low-temperature fluidity and chemical stability of the coolant by using polyalkylene glycol as the lubricant is sufficiently obtained. Absent. Therefore, the proportion of polyalkylene glycol in the lubricant blended in the coolant is preferably 50 mass% or more, and more than 80 mass%, preferably 95 mass% or more of the other water-soluble lubricant. Is a water-soluble lubricant (preferably a water-soluble synthetic lubricant). As mentioned above, the coolant may contain other lubricants.
Further, also when polyalkylene glycol is used as part or all of the lubricant as described above, the concentration of the lubricant blended in the coolant, the cloud point of the coolant, and the like are as described above. Therefore, the most preferable form of the coolant used in the present invention is that the total amount of the water-soluble lubricant is polyalkylene glycol, preferably polyalkylene glycol having a molecular weight of 500 to 5000, and the concentration of the water-soluble lubricant is 1 to 3 in a solution. It is about 15 mass%.

In addition to the lubricant (polyalkylene glycol, etc.), one or more kinds of extreme pressure additives, rust preventives, antifoaming agents, various amines, preservatives, surfactants and the like are appropriately added to the coolant. Also good. Further, oils, fatty acid esters, and mineral oils may be added in a small amount together with a surfactant to prepare ones that assist lubricity. If additives other than lubricants are only included in the coolant with an average particle size of about 1 μm or less, the properties as a solution are maintained as a whole, and emulsion rolling as described above This is because it exhibits advantageous properties compared to oil. In that case, the cloud point of a coolant shall use the value measured about the aqueous solution which removed components other than a water-soluble lubricant. This is because the cloud point may not be clearly measured depending on the inclusion of the additive.
As the extreme pressure additive, for example, one or more kinds of chlorinated compounds such as chlorinated oils and fats, chlorinated fatty acid esters, synthetic sulfur compounds such as sulfurized oils and fats, alkyl polysulfides, phosphorus compounds, and organometallic salt compounds are used. be able to. Moreover, as a water-soluble rust preventive agent, what added alkanol aluminum etc. as a basic substance to fatty acids, such as aliphatic monocarponic acid, can also be used.

Examples of the cold rolling mill used in the present invention include those performing normal cold rolling, such as a tandem cold rolling mill and a levers cold rolling mill. Although not subject to light rolling of annealed materials such as temper rolling, the present invention may be applied to the case where rolling with a rolling reduction of 10% or more is performed using a temper rolling mill.
A typical example of the metal plate to be rolled in the method of the present invention is a thin steel plate, but is not limited to this, and various metal plates such as aluminum, aluminum alloy, copper, copper alloy, and alloy plates. Is the target. Moreover, in the case of a steel plate, steel types, such as normal steel, high carbon steel, and stainless steel, are not ask | required.
Moreover, there is no restriction | limiting in the thickness of a metal plate, Thin metal plates, such as metal foil, can also be made into object.

  In the present invention, it is preferable to adjust the temperature and / or flow rate of the coolant supplied to the metal plate and / or the rolling roll according to the plate temperature when the metal plate enters the roll bite. As described above, when the metal plate enters the roll bite at a temperature equal to or higher than the cloud point of the coolant and is rolled, the adhesion of the lubricant component of the coolant to the surface of the metal plate is sufficiently high, and the lubricity can be ensured. However, if the temperature of the metal plate becomes too high, heat scratches are likely to occur, so the temperature of the metal plate should be kept below the temperature at which heat scratches may occur while maintaining the temperature above the cloud point of the coolant. Is preferred. Therefore, the temperature and / or flow rate of the coolant supplied to the metal plate and / or the rolling roll is adjusted according to the plate temperature when the metal plate enters the roll bite so that the heat of the metal plate does not occur. It is preferable to control the temperature. Here, even if the temperature of the coolant is lowered, unlike the case of the emulsion rolling oil, there is no problem of scum formation or emulsification instability, while the temperature at which the metal plate enters the roll bite is the cloud point of the coolant. If it is above, lubricity can also be ensured.

In the present invention, in some rolling stands or rolling passes, when a metal plate enters and rolls into a roll bite at a temperature lower than the cloud point of the coolant, coolant having a temperature higher than the cloud point is supplied to the roll bite. It is preferable to do so.
In the present invention, if the metal plate enters the roll bite and is rolled at a temperature equal to or higher than the cloud point of the coolant, the adhesion of the lubricant component of the coolant to the surface of the metal plate is sufficiently high, and lubricity can be ensured. If a heating device for positively heating the metal plate is not installed, depending on the cloud point of the coolant, the metal plate may not reach such a temperature in some rolling stands or rolling passes. obtain. Such a case is likely to occur particularly under conditions where the rolling speed is low. Generally, when the rolling speed is low, high lubricity as in high speed rolling is not required, but when the deformation resistance of the metal plate is high, lubricity may be necessary. Therefore, in such a case, it is preferable that the coolant having a temperature higher than the cloud point is supplied to the roll bite by heating the coolant as necessary. As a result, the solubility of the lubricant component of the coolant is lowered even when the temperature of the metal plate is low, and the adhesion to the surface of the metal plate is increased to some extent, so that the metal plate is rolled at a temperature above the cloud point of the coolant. Although it is not as much as when entering a bite and rolling, a certain degree of improvement in lubricity can be expected.

FIG. 1 shows one embodiment of rolling maintenance equipped with a tandem cold rolling mill used in the practice of the present invention, in which a metal plate 1 is discharged from a payoff reel 2 and five rolling stands 4a to 4e. Is continuously rolled by a cold rolling mill having a roll and wound by a tension reel 3.
Spray nozzles 5a to 5e for supplying coolant to the metal plate 1 are installed on the roll bite entry sides of the rolling stands 4a to 4e. In addition, roll cooling nozzles 6a to 6e for supplying coolant to the rolling rolls for cooling are provided on the exit sides of the rolling stands 4a to 4e.

This rolling equipment has a coolant circulation system for circulating the coolant. In this circulation system, the coolant supplied from the spray nozzles 5 a to 5 e and the roll cooling nozzles 6 a to 6 e is collected by the oil pan 8. Since solid powder such as wear powder is mixed in the coolant, the coolant is temporarily stored in the dirty tank 10. The coolant in the dirty tank 10 is transferred to the filtering equipments 9 and 11, where the solid powder in the coolant is separated and removed, and then transferred to the clean tank 12, where it is temporarily stored. The filtering equipments 9 and 11 may be provided with filtering means of the type normally used for emulsion rolling oil such as Hoffman filters, electromagnetic filters, etc., but considering the ease of separation of solid powder. And simpler equipment.
The coolant stored in the clean tank 12 is sent to the spray nozzles 5a to 5e and the roll cooling nozzles 6a to 6e by the supply pump and is circulated for use.

In this circulation system, a coolant cooler 13 is installed for maintaining the coolant temperature below the cloud point. Further, before the spray nozzles 5a to 5e for supplying the coolant to the metal plate 1 (in the middle of the supply branch pipes for supplying the coolant to the spray nozzles 5a to 5e), the coolant is heated to a cloud point or higher as necessary. There are cases where heating devices 7a to 7e are installed. In addition, the position which arrange | positions the coolant cooler 13 is not limited to embodiment of FIG. In other words, the coolant cooler 13 is preferably arranged as shown in FIG. 1 in order to reliably supply coolant having a temperature lower than the cloud point to the metal plate 1, but for separating and removing solid powder, the coolant is filtered. It is preferable that the temperature is lower than the cloud point before the equipment (upstream side). Therefore, the coolant cooler 13 may be installed in front of the dirty tank 10 (upstream side) from the viewpoint of separating and removing solid powder. . Further, for example, in addition to the coolant cooler 13 having the arrangement shown in FIG. 1, another coolant cooler may be provided in front of the dirty tank 10 (upstream side) or in the dirty tank 10.
Moreover, the thermometer 14 for measuring the temperature of the metal plate 1 is installed on the exit side of the final rolling stand 4e. The temperature of the metal plate 1 on the roll bite entry side of each of the rolling stands 4a to 4e (metal plate temperature when entering the roll bite) can be obtained by calculation from the rolling conditions in the plate temperature calculation device 15, but the temperature The metal plate temperature actually measured by the meter 14 can be used to correct an error in the calculation result. However, the installation of the thermometer 14 is not essential, and is not necessarily required if the metal plate temperature on the roll bite entry side of each of the rolling stands 4a to 4e can be calculated with a certain degree of accuracy.

In the above rolling equipment, for example, the implementation status of the present invention will be described on the assumption that an aqueous solution containing 3% by mass of polyalkylene glycol and having a cloud point of 50 ° C. is used as a coolant.
The coolant is adjusted to a temperature below 50 ° C. by the coolant cooler 13. Since the temperature of the metal plate differs depending on each rolling stand depending not only on the influence of the rolling speed but also on the deformation resistance, rolling reduction, lubrication state, etc. of the material to be rolled, The temperature of the metal plate 1 on the bite entry side (temperature when entering the roll bite) is calculated.

When the temperature of the metal plate 1 on the roll bite entry side in each of the rolling stands 4a to 4e determined by the plate temperature calculation device 15 is 50 ° C. or higher, the coolant adjusted to less than 50 ° C. by the coolant cooler 13 is used as a spray nozzle. It supplies to the metal plate surface of the roll bite entry side from 5a-5e. Moreover, a coolant is supplied to the rolling roll from the roll cooling nozzles 6a to 6e as necessary. In this case, adhesion of the lubricant component of the coolant to the surface of the metal plate is good, and sufficient lubricity is ensured.
On the other hand, among the temperatures of the metal plate 1 on the roll bite entry side in each of the rolling stands 4a to 4e obtained by the plate temperature calculation device 15, the temperature at some of the rolling stands 4 is less than 50 ° C. If necessary, the coolant supplied to the spray nozzle 5 of the rolling stand 4 is heated by the coolant heating device 7, and the coolant having a temperature not lower than the cloud point (50 ° C. or higher) is supplied from the spray nozzle 5 to the surface of the metal plate. To supply. In this case, the adhesion of the lubricant component of the coolant to the surface of the metal plate is increased to some extent, and as described above, the metal plate enters the roll bite at a temperature higher than the cloud point of the coolant and is rolled. There is no improvement in lubricity to some extent.

Moreover, when the temperature of the metal plate 1 on the roll bite entry side obtained by the plate temperature calculation device 15 exceeds the heat scratch generation temperature, it is predicted that the coolant temperature is further lowered by the coolant cooler 13 or heat scratch is generated. The spray flow rate from the spray nozzle 5 of the rolling stand 4 is increased to enhance the cooling of the metal plate. In cold rolling of thin steel plates, the heat scratch generation temperature is usually about 150 to 200 ° C., so if the heat scratch generation limit temperature is preset for each target material while referring to the operation results, Good. In addition, a temperature lower than that is set as the control start temperature so as not to reach the heat scratch generation limit, and when the temperature is reached, the coolant temperature is lowered by the coolant cooler 13 in advance. It is also possible to prevent the heat scratch generation limit temperature from being reached.
In order to prevent heat scratching, it is effective not only to cool the metal plate as described above, but also to increase the coolant flow rate from the roll cooling nozzles 6a to 6e or to lower the coolant temperature.

[Example 1]
The result of investigating the relationship between the temperature of the metal plate and the lubricating performance of the coolant containing polyalkylene glycol is shown in comparison with the case where conventional emulsion rolling oil is used as the coolant.
In the present invention example, an aqueous solution containing 3% by mass of polyalkylene glycol was used as the coolant (= coolant A). This aqueous solution contains no components other than polyalkylene glycol. As the polyalkylene glycol, trade name “Adeka Pluronic L31” manufactured by Asahi Denka Co., Ltd. was used. This polyalkylene glycol has an average molecular weight of 1100, a cloud point at a concentration of 3% by mass of 40 ° C., and a kinematic viscosity at 25 ° C. of 196 mm ² / s.
In the comparative example, emulsion rolling oil used for normal cold rolling was used as the coolant (= coolant B). This emulsion rolling oil is composed of 60 mass% synthetic ester, 30 mass% natural fat and oil, 5 mass% higher fatty acid, 2 mass% nonionic surfactant and 3 mass% stock solution containing 3 mass% extreme pressure additive, etc. And diluted with water at 60 ° C. and adjusted with a stirrer so that the emulsion particle size becomes 8 μm.

First, a plate-out test was conducted in order to investigate the adhesion to the steel plate when the above coolants A and B were used. The plate-out test is a test for evaluating the adhesion performance to the steel plate by measuring the mass of the lubricant component adhering to the steel plate after spraying the coolant onto the surface of the steel plate. Here, the adhesion performance was evaluated while heating a steel plate as a sample and adjusting the temperature to various temperatures. The spray pressure of the coolant is 1.0 kgf / cm ² , and the air purge is performed immediately after spraying on the surface of the steel sheet for 0.1 seconds to remove the coolant not adhering to the steel sheet. Only the lubricant component adhering to the surface was measured. In addition, about the coolant A, the test which changed coolant temperature in the wide range including the cloud point vicinity was implemented. On the other hand, for the coolant B, the emulsion temperature became unstable when the coolant temperature was lowered, so the coolant temperature was kept constant at 60 ° C.

FIG. 2 shows the result of the plate-out test. According to this, it can be seen that for the coolant A which is an example of the present invention, the plate-out performance is improved in a range where the plate temperature is not lower than the cloud point (40 ° C.) of the coolant, particularly 50 ° C. or higher. In addition, when the temperature of the coolant A is changed to 20 ° C. below the cloud point, 50 ° C. above the cloud point, and 80 ° C., the plate-out property improves as the coolant temperature increases, but the plate temperature increases. It can be seen that the effect is relatively small compared to the effect. When the plate temperature is lower than the cloud point (40 ° C.) of the coolant, the amount of plate-out is reduced, but when the coolant temperature is higher than the cloud point (40 ° C.), the plate-out property is relatively improved. I understand that.
On the other hand, for the coolant B as a comparative example, although the plate-out property tends to improve as the plate temperature rises, the dependence on the plate temperature is small, and when the plate temperature is high, the coolant A is more plate-like. It can be seen that the out-out property has improved remarkably.

Next, the result of examining the lubricity by performing cold rolling using the coolants A and B is shown. As another comparative example, an aqueous solution containing 3% by mass of polyalkylene glycol having an average molecular weight of 3500, a cloud point of 82 ° C. at a concentration of 3% by mass, and a kinematic viscosity at 50 ° C. of 240 mm ² / s is used as a coolant (= Used as coolant C).
In order to obtain a sheet gauge material of normal steel with a thickness of 0.8 mm, cold rolling was performed under conditions of a work roll diameter of 500 mm and a rolling speed of 1200 mpm, and the coefficient of friction was calculated backward from the measured rolling load. The material to be rolled was heated to a predetermined temperature in advance, and then sprayed with a coolant so that rolling was performed immediately after. In addition, about the coolants A and C, the temperature was 20 degreeC and the coolant B which is emulsion rolling oil was 60 degreeC.

FIG. 3 shows the friction coefficient calculated backward from the rolling load. According to this, for the coolant A, it can be seen that the coefficient of friction is greatly reduced when the plate temperature is in the range of the coolant cloud point (40 ° C.) or higher, particularly in the range of 50 ° C. or higher. This is consistent with the results of the plate-out test in FIG. On the other hand, for the coolant B as a comparative example, the change in lubricity due to the plate temperature is small, and when the plate temperature is 50 ° C. or higher, the result is the same as the coolant A or slightly inferior in lubricity. Furthermore, as for the coolant C as a comparative example, the cloud point is as high as 85 ° C., so that the lubricity is not improved unless the plate temperature is higher than that. From a practical point of view, when a coolant having such a high cloud point is used, for example, when the rolling speed is relatively low, the plate temperature does not reach the cloud point of the coolant, and the necessary lubricity cannot be obtained. Is likely to occur.
The coolant A has a very good plate-out property as compared to the coolant B when the plate temperature is 50 ° C. or higher, but the friction coefficient is not so different from that of the coolant B. This is because the extreme pressure additive or the like is not added to the coolant A, and therefore, even if a thick fluid lubricating film is formed in the roll bite, the friction coefficient at the boundary contact portion is high. Conceivable. Therefore, if an extreme pressure additive is added to the coolant A, the lubricity can be further improved.

[Example 2]
The result of having compared the cooling effect by the coolant A and the coolant B using the 5-stand tandem rolling mill shown in FIG. 1 is shown.
The material to be rolled was a plain steel plate with a thickness of 3.2 mm. Cold rolling was performed at a rolling speed of 1300 mpm up to a thickness of 0.8 mm, and the cooling performance was compared according to the steel plate temperature on the delivery side of the rolling mill. In addition, about the coolant A, the case where the temperature was set to 30 degreeC lower than a cloud point, and the case where it was set to 60 degreeC higher than a cloud point were evaluated.
FIG. 4 shows a comparison result of the plate temperatures. When the coolant A which is an example of the present invention is used at a coolant temperature of 30 ° C., the plate temperature is lowered by 20 ° C. or more compared to the coolant B by emulsion rolling oil which is a comparative example. It can be seen that high cooling performance is exhibited while maintaining the properties. In addition, when the coolant A is used at 60 ° C., although not so much cooling performance can be obtained, better cooling performance is obtained as compared with the coolant B. In the case of the coolant B, the oil and fat component in the emulsion adheres to the roll surface to inhibit the cooling performance, whereas the cooling performance is improved by the excellent cleaning effect of the coolant A. This is probably because

[Example 3]
The result of having carried out the cold rolling of the hard material in the same tandem-type rolling mill as Example 2 is shown.
In Invention Example 1, the coolant A was set to 30 ° C. lower than the cloud point, and the coolant flow rate and temperature were kept constant even when the rolling speed was changed. In the comparative example, the coolant B was used at 60 ° C., and in this case, the same coolant flow rate was supplied.
FIG. 5 shows changes in the plate temperature with respect to the rolling speed. In Example 1 of the present invention, the cooling effect was higher than that of the comparative example and the plate temperature was lowered. However, when the rolling speed was high, there were cases in which the heat scratch generation temperature exceeded 160 ° C.
Therefore, in Example 2 of the present invention, when the plate temperature reaches 140 ° C., which is 20 ° C. lower than the heat scratch generation temperature, the temperature of the coolant A is adjusted to a range of 20 to 25 ° C. and the flow rate of the coolant A is 15 % Increase. In this case, even when the rolling speed was high, the heat scratch generation temperature was not reached. The lubricity in these cases is almost the same level, and all have sufficient lubricity.

Explanatory drawing which shows an example of the tandem type cold rolling mill used for implementation of this invention The graph which shows the plate-out characteristic of the coolant in Example 1 The graph which shows the friction coefficient at the time of rolling in Example 1 The graph which shows the cooling effect by the coolant in Example 2 The graph which shows the heat-scratch prevention effect in Example 3 Photo showing the appearance of coolants with different liquid temperatures used in Example 1

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Metal plate 2 Pay-off reel 3 Tension reel 4a, 4b, 4c, 4d, 4e Rolling stand 5a, 5b, 5c, 5d, 5e Spray nozzle 6a, 6b, 6c, 6d, 6e Roll cooling nozzle 7a, 7b, 7c, 7d 7e Coolant heating device 8 Oil pan 9, 11 Filtering equipment 10 Dirty tank 12 Clean tank 13 Coolant cooler 14 Thermometer 15 Plate temperature calculation device

Claims (8)

In a method of cold rolling a metal plate while supplying a coolant,
A solution having a cloud point by diluting a lubricant mainly composed of a water-soluble lubricant with water and dissolving the water-soluble lubricant is used as a coolant, and at least in some rolling stands or rolling passes, a metal plate Is a cold rolling method for a metal sheet, wherein the metal sheet enters and rolls at a temperature equal to or higher than the cloud point of the coolant.   The method of cold rolling a metal sheet according to claim 1, wherein a coolant having a temperature lower than the cloud point is supplied to the metal sheet and / or the rolling roll.   The coolant is used in a circulating manner, and after being supplied to the metal plate and / or rolling roll, the recovered coolant is subjected to a removal process of solid matter in the liquid at a liquid temperature lower than the cloud point. The cold rolling method of the metal plate of 1 or 2.   The cloud point of a coolant is 30-80 degreeC, The cold rolling method of the metal plate in any one of Claims 1-3 characterized by the above-mentioned.   The method for cold rolling a metal sheet according to any one of claims 1 to 4, wherein at least a part of the water-soluble lubricant is a polyalkylene glycol having an average molecular weight of 500 to 5,000.   The method for cold rolling a metal sheet according to any one of claims 1 to 5, wherein an aqueous solution containing 1 to 15% by mass of a water-soluble lubricant is used as a coolant.   The temperature and / or flow rate of the coolant supplied to the metal plate and / or the rolling roll is adjusted according to the plate temperature when the metal plate enters the roll bite. The cold rolling method of the metal plate as described.   In some rolling stands or rolling passes, when a metal plate enters and rolls into a roll bite at a temperature below the cloud point of the coolant, the coolant at a temperature higher than the cloud point is supplied to the roll bite. A cold rolling method for a metal plate according to any one of claims 1 to 7, wherein the method is a cold rolling method.