JP2019167423A - Hot-rolling oil for aluminum, hot-rolling coolant for aluminum and manufacturing method of aluminum rolled sheet - Google Patents

Abstract

To provide the hot-rolling oil for aluminum, the hot-rolling coolant for aluminum containing the hot-rolling oil, and the manufacturing method of the aluminum rolled sheet using the coolant, wherein the hot-rolling oil for aluminum can suppress generation of surface defects even when a high-strength aluminum material is rolled, and can reduce an amount of aluminum powder generated.SOLUTION: The hot-rolling oil for aluminum has a kinematic viscosity at a temperature of 40°C of 30 cSt or more to 160 cSt or less, the coolant contains the hot-rolling oil, and the manufacturing method of the aluminum rolled sheet uses this coolant. The rolled oil contains a base oil, a fatty acid and an oily agent. The fatty acid has 12 to 20 carbon atoms and a concentration of 2 mass% or more. The oily agent contains at least one of a synthetic ester and a natural fat/oil. The synthetic ester has a number average molecular weight of 650 or more and one or more hydroxyl groups in a molecule, or has the number average molecular weight of 850 or more. The natural fat/oil has the amount of fatty acids having 18 or more carbon atoms of 55 mass% or more based on a total fatty acid composition.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a hot rolling oil for aluminum, a hot rolling coolant for aluminum, and a method for producing an aluminum rolled sheet using the coolant.

  In hot rolling of an aluminum material, a hot rolling coolant for aluminum is used for the purpose of ensuring lubricity between the rolling roll and the aluminum material, cooling the rolling roll and the aluminum material, and the like. In the present specification, “aluminum” is a concept including pure aluminum and an aluminum alloy. The coolant is usually an oil-in-water emulsion in which hot rolled oil for aluminum is dispersed in water. For this reason, hot rolled oil for aluminum includes oily agents such as higher fatty acids, natural fats and oils and synthetic esters for ensuring lubricity, an emulsifier for forming oil droplets of hot rolled oil in water, an aluminum material, Mineral oil that serves as a solvent for carrying the oil-based agent to the sliding portion with the rolling roll is included.

  In hot rolling of an aluminum material, a high-temperature aluminum material of 300 to 550 ° C. is usually rolled with a 70 to 120 ° C. roll. At this time, in addition to the temperature of the aluminum material itself, the surface of the aluminum material instantaneously becomes extremely high due to frictional heat generated by sliding between the rolling roll and the surface of the aluminum material. In such a high temperature environment, the kinematic viscosity of the hot rolling oil is remarkably reduced, and the hot rolling oil is evaporated by heat, so that the oil film between the rolling roll and the aluminum material becomes thin. As a result, surface defects are generated due to remarkable adhesion between the surface of the aluminum material and the rolling roll.

  Such a problem can be avoided by lowering the temperature of the aluminum material or reducing the amount of reduction during rolling. However, the temperature drop of the aluminum material makes it difficult to deform the aluminum material and overloads the rolling roll during rotation. On the other hand, if the reduction amount is reduced, the time required to extend the aluminum material to a predetermined thickness becomes longer, and productivity is impaired. Therefore, it is often impossible to adopt an avoidance measure by adjusting such hot rolling conditions.

  For the above reasons, in addition to the adjustment of hot rolling conditions, improvement of hot rolling oil has been studied. For example, measures are taken to increase the amount of hot rolling oil introduced between the rolling roll and the aluminum material by increasing the kinematic viscosity of the mineral oil. In addition, by adding oily agents such as natural fats and oils and synthetic esters and fatty acids in hot rolled oil, an adsorption film consisting of an oil film is formed on the surface of the aluminum material, improving lubricity even with a very thin oil film. However, it is taken as a measure to suppress adhesion between the aluminum material surface and the rolling roll.

  Specifically, Patent Document 1 describes a hot rolled oil containing 20 mass% to 70 mass% of a natural fat or oil as an oiliness agent in order to improve lubricity.

Japanese Patent No. 2899223

  However, when a hot rolled oil of Patent Document 1 is used to roll an aluminum material having a large deformation resistance such as an aluminum alloy to which magnesium is added, surface defects due to pickup grooves and pickup inclusions are observed on the surface of the rolled plate. There was a thing. The pickup groove means a streak pattern on the plate surface by the roll coating adhered to the rolling roll being peeled off and adhering to the aluminum material surface. The pickup inclusion means a streak pattern on the plate surface by stripping the surface of the aluminum material by a rolling roll.

  Moreover, in the conventional hot rolling oil, there are many aluminum powders generated at the time of hot rolling, and this cannot be held in the coolant, which causes the periphery of the rolling mill and the rolled plate to become dirty. Therefore, it has been desired to develop a hot rolling oil for aluminum that suppresses generation of surface defects even when a high-strength aluminum material is rolled, and generates a small amount of aluminum powder.

  The present invention has been made in view of such a background, and even when a high-strength aluminum material is rolled, the occurrence of surface defects is suppressed, and the hot-rolled oil for aluminum with a small amount of aluminum powder is produced. An object of the present invention is to provide a hot rolling coolant for aluminum containing oil, and a method for producing an aluminum rolled sheet using this coolant.

One aspect of the present invention is a hot rolled oil for aluminum having a kinematic viscosity at a temperature of 40 ° C. of 30 cSt or more and 160 cSt or less,
Base oil,
A fatty acid having 12 to 20 carbon atoms;
An oily agent comprising at least one of a synthetic ester and natural fats and oils,
The concentration of the fatty acid is 2% by mass or more and 16% by mass or less,
The synthetic ester has a number average molecular weight of 650 or more and one or more hydroxyl groups in the molecule, or a number average molecular weight of 850 or more,
The said natural fats and oils are in the hot rolling oil for aluminum whose amount of fatty acids having 18 or more carbon atoms is 55% by mass or more in the total fatty acid composition.

Another aspect of the present invention contains water and oil droplets made of the hot rolled oil for aluminum dispersed in the water,
The concentration of the hot rolling oil for aluminum is 3 to 10% by volume,
In the hot rolling coolant for aluminum, the median diameter of the oil droplets is 1 to 7 μm.

  Still another embodiment of the present invention lies in a method for producing an aluminum rolled sheet, wherein hot rolling of an aluminum material is performed using the hot rolling coolant for aluminum.

  In the following description, the hot rolling oil for aluminum is called “hot rolling oil”, the hot rolling coolant for aluminum is called “coolant”, and the aluminum rolled plate is called “rolled plate”. . The hot rolling oil having the above-described configuration can reduce friction between the rolling roll and the aluminum material. Therefore, even when an aluminum material made of a high-strength alloy having a 0.2% proof stress at room temperature of 90 MPa or more is rolled using hot rolling oil, the occurrence of surface defects can be suppressed. Furthermore, the amount of aluminum powder generated can be reduced. In addition, in this specification, room temperature means the temperature of 10-35 degreeC. The hot rolling oil can also be used for rolling an aluminum material having a 0.2% proof stress at room temperature of less than 90 MPa.

  The coolant contains water and oil droplets made of the hot rolling oil dispersed therein. That is, the coolant is an emulsion in which hot rolling oil is dispersed in water. In the coolant, the concentration of the hot rolling oil in the coolant and the median diameter of the oil droplets of the hot rolling oil are within the specific ranges. The coolant having such a configuration is suitable for hot rolling of an aluminum material, and even when a high-strength aluminum material is rolled, the generation of surface defects can be suppressed and the amount of aluminum powder generated can be reduced.

  Moreover, the said coolant can suppress coalescence of the oil droplets in coolant, for example, when the temperature of coolant rises in the tank of a hot rolling mill etc. As a result, it is possible to suppress a decrease in the concentration of the hot rolling oil in the coolant before reaching the rolling roll, thereby suppressing a decrease in the plate-out amount. Plate-out means that hot rolling oil adheres to the surface of the rolling roll after the rolling roll and coolant come into contact with each other, and the plate-out amount means the amount of adhesion. Further, the coolant in which the hot rolling oil is dispersed is easily demulsified by contact with the rolling roll. Therefore, the emulsion stability of the coolant can be increased moderately.

  The coolant is an emulsion in which the hot rolling oil is dispersed. By using such a coolant, even when a high-strength aluminum material is rolled in hot rolling, the generation of surface defects can be suppressed and the amount of aluminum powder generated can be reduced. Therefore, it is possible to produce a rolled plate having a good surface property.

It is a side view which shows the principal part of the hot rolling implemented for lubricity evaluation in an Example. It is a scanning electron micrograph of the surface of the rolling plate which has a pickup inclusion surface defect in a comparative example. It is sectional drawing of the rolled sheet in an Example.

  Embodiments of hot rolling oil, coolant, and rolled plate will be described. In addition, when using the expression “to” in the present specification, it is used in the meaning including numerical values or physical values described before and after.

[Hot rolling oil]
The hot rolling oil is suitable for an aluminum material made of a high strength alloy having a 0.2% proof stress at room temperature of 90 MPa or more. When hot rolling is performed on an aluminum material made of such a high-strength alloy using conventional hot rolling oil, surface defects tend to occur, and the amount of aluminum powder generated tends to increase. By using the hot rolling oil having the above-described configuration, it is possible to suppress the occurrence of surface defects during the rolling of a high-strength aluminum material and to suppress the generation of aluminum powder.

  The hot rolled oil has a kinematic viscosity at a temperature of 40 ° C. of 30 cSt or more and 160 cSt or less, a base oil, a fatty acid having 12 to 20 carbon atoms, and an oily agent composed of at least one of a synthetic ester and natural fats and oils. contains. The synthetic ester has a number average molecular weight of 650 or more and one or more hydroxyl groups in the molecule or a number average molecular weight of 850 or more. Natural fats and oils have a fatty acid content of 18 or more carbon atoms of 55% by mass or more in the total fatty acid composition.

<Base oil>
The base oil is not particularly limited, and various mineral oils can be used. A refined mineral oil is preferable. Refined mineral oil has a lower pour point than unrefined mineral oil and is hard to solidify in a low temperature environment. Therefore, for example, when storing hot rolled oil in a low temperature environment such as an outdoor tank in winter, freezing of the hot rolled oil in the tank can be suppressed, and the handleability of the hot rolled oil can be further improved. .

  Examples of the refined mineral oil include naphthenic refined mineral oil, paraffin refined mineral oil, and aromatic refined mineral oil. More specifically, as the refined mineral oil, for example, SUN40N, SUN100N, SUN500N, SUN2300N, SUNPAR (registered trademark) 110, SUNPAR115, SUNPAR150 (and above, Nippon Sun Oil Co., Ltd.); SNH-95 and SNH-220 (and above) Sankyo Oil Chemical Co., Ltd.), NCL-100, NCL-210 (above, Taniguchi Oil Co., Ltd.); EPX-1 (Fuji Kosan Co., Ltd.), and the like can be used.

<Fatty acid>
As the fatty acid, one having 12 to 20 carbon atoms is used. By using a fatty acid having 12 or more carbon atoms, boundary lubricity is improved, the adsorption film formed on the surface of the aluminum material becomes tough, and the occurrence of surface defects in the aluminum material can be further suppressed. Further, by using a fatty acid having 20 or less carbon atoms, the fatty acid is easily dissolved in the hot rolling oil, and the effect of suppressing surface defects due to the addition of the fatty acid is easily obtained.

  The fatty acid may be a saturated fatty acid or an unsaturated fatty acid. Moreover, the structure of the hydrocarbon chain in these fatty acids may be any of a straight chain structure, a branched chain structure, or a cyclic structure. More specifically, lauric acid, myristic acid, palmitic acid, palmitoleic acid, stearic acid, oleic acid, linoleic acid, linolenic acid, eicosenoic acid and the like can be used as the fatty acid.

  The concentration of the fatty acid in the hot rolling oil is preferably 2% by mass to 16% by mass. By making the concentration of the fatty acid 2% by mass or more, the aluminum powder generated during hot rolling is easily held inside the oil droplets in the coolant. As a result, it is possible to further prevent the periphery of the rolling mill, the aluminum material surface, and the rolled plate surface after rolling from being soiled. Moreover, generation | occurrence | production of the lower acid which generate | occur | produces by oxidative degradation when using hot rolling oil for a long period of time can be suppressed by making the density | concentration of a fatty acid 16 mass% or less.

<Oil agent>
The oily agent consists of at least one of natural fats and oils and synthetic esters. That is, as the oily agent, natural fats and oils or synthetic esters can be used, or both natural fats and oils and synthetic esters can be used.

  The concentration of the oiliness agent in the hot rolling oil is preferably 15% by mass to 35% by mass. By setting the concentration of the oily agent to 15% by mass or more, occurrence of surface defects of the aluminum material can be more sufficiently suppressed. By setting it as 35 mass% or less, the increase in the manufacturing cost of hot rolling oil accompanying the increase in the usage-amount of an oiliness agent can be prevented. That is, the hot rolling oil becomes more suitable for industrial use.

  The oil-based agent can form a multilayer adsorbing film mainly on the surface of the aluminum material at the sliding portion between the rolling roll and the aluminum material during hot rolling, thereby suppressing direct contact between the rolling roll and the aluminum material. Thereby, the surface defect of an aluminum material can be suppressed. The multilayer adsorbed film is considered to desorb when heat energy corresponding to the evaporation enthalpy of the adsorbed molecule is applied. For this reason, it is possible to form a thick adsorption film by using an oily agent that is difficult to evaporate and has a large amount of heating residue. Therefore, the lubricity between the rolling roll and the aluminum material can be improved, and surface defects of the aluminum material can be suppressed. In particular, when an aluminum material having a large frictional heat generation during hot rolling and a large deformation resistance is hot rolled, it is preferable to use an oily agent having the above characteristics.

  The hot rolling oil contains the oily agent and fatty acid described above, so that not only oil remains on the aluminum material, but also a multilayer adsorbing film having boundary lubricity due to synthetic ester, natural fat and fatty acid and fatty acid in the oil. Therefore, it is possible to manufacture a rolled sheet in which generation of surface defects is more sufficiently suppressed.

(Synthetic ester)
As the synthetic ester, those having a number average molecular weight of 650 or more and having one or more hydroxyl groups in the molecule can be used. As the synthetic ester, those having a number average molecular weight of 850 or more can be used. When the number average molecular weight of the synthetic ester is 850 or more, it is not always necessary to use one having a hydroxyl group, but one having a hydroxyl group may be used.

  Synthetic esters having a number average molecular weight of 650 or more and having one or more hydroxyl groups in the molecule are not only large in molecular weight, but also form hydrogen bonds between the molecules by the hydroxyl groups, so that they are difficult to evaporate synergistically. . Thereby, the heating residue of an oily agent increases. As a result, lubricity is improved and the occurrence of surface defects in the aluminum material can be further suppressed.

  A synthetic ester having a number average molecular weight of 850 or more is difficult to evaporate because the molecular weight is sufficiently large. Thereby, the heating residue of an oily agent increases. As a result, lubricity is improved and the occurrence of surface defects in the aluminum material can be further suppressed. As the synthetic ester, for example, a carboxylic acid ester obtained by a condensation reaction between an alcohol and a carboxylic acid can be used.

-Component derived from carboxylic acid in synthetic ester As carboxylic acid to be subjected to the condensation reaction, at least one of a saturated fatty acid and an unsaturated fatty acid can be used. As these saturated fatty acids and unsaturated fatty acids, one type of compound may be used, or two or more types of compounds may be used in combination. The structure of the hydrocarbon chain in these compounds may be a straight chain structure, a branched chain structure, or a cyclic structure. The carboxylic acid may be a monobasic acid or a dibasic acid and a polybasic acid having more ionizable protons.

  In the synthetic ester, the structural unit derived from the carboxylic acid preferably has 12 or more and 23 or less carbon atoms. By setting the carbon number of the structural unit derived from carboxylic acid to 12 or more, the friction between the rolling roll and the aluminum material can be further reduced. Moreover, the increase in the viscosity of hot rolling oil can be suppressed by making carbon number of the structural unit derived from carboxylic acid into 23 or less. Therefore, by making the carbon number of the structural unit derived from the carboxylic acid within the specific range, while avoiding the deterioration of the handleability associated with the increase in the viscosity of the hot rolling oil, between the rolling roll and the aluminum material. The friction can be further reduced.

  More specifically, the carboxylic acid constituting the synthetic ester is capric acid, lauric acid, myristic acid, palmitic acid, palmitoleic acid, stearic acid, oleic acid, linoleic acid, linolenic acid, arachidic acid, eicosenoic acid, behen. Acid, erucic acid and the like can be used.

-Alcohol-derived component in synthetic ester Moreover, polyhydric alcohol can be used as alcohol used for a condensation reaction. As the polyhydric alcohol, for example, ethylene glycol, neopentyl glycol, glycerin, trimethylolpropane, pentaerythritol, dipentaerythritol and the like can be used. From the viewpoint of further reducing the friction between the rolling roll and the aluminum material, it is preferable to use at least one selected from the group consisting of neopentyl glycol, trimethylolpropane, and pentaerythritol as the polyhydric alcohol.

  When a polyhydric alcohol is used as the alcohol, the synthetic ester may be a full ester in which all the hydroxyl groups of the polyhydric alcohol are esterified, or a partial ester in which some of the hydroxyl groups of the polyhydric alcohol are esterified. May be.

  More specifically, as the synthetic ester, pentaerythritol dioleate, trimethylolpropane dioleate, trimethylolpropane tripalmitate, trimethylolpropane tristearate, trimethylolpropane trioleate, Pentaerythritol tetralaurate, pentaerythritol tetramyristate, pentaerythritol tetrapalmitate, pentaerythritol tetrastearate, pentaerythritol tetraoleate, pentaerythritol tristearate, pentaerythritol trioleate Can be used. These synthetic esters may be used as a single compound or in combination of two or more compounds.

(Natural oil)
As the natural fats and oils, it is preferable to use fatty acids having 18 or more carbon atoms, the total amount of which is 55% or more of the fatty acid composition. In this case, since the molecular weight of the natural fat becomes sufficiently large, it is difficult to evaporate. Thereby, the heating residue of an oily agent increases. As a result, the lubricity can be improved and the occurrence of surface defects in the aluminum material can be further suppressed.

  As natural fats and oils, specifically, pork fat, beef tallow, rapeseed oil and palm oil can be suitably used. One type of natural fat / oil may be used, or two or more types may be used in combination.

<Nonionic emulsifier>
The hot rolling oil can further contain a nonionic emulsifier. The content of the nonionic emulsifier in the hot rolling oil is preferably 0.70 to 5.0% by mass. By setting the content of the nonionic emulsifier to 0.70% by mass or more, the emulsion stability of the coolant can be appropriately increased and the surface tension of the coolant can be appropriately decreased. From the viewpoint of making the emulsion stability and surface tension of the coolant more suitable ranges, the content of the nonionic emulsifier is preferably 0.90% by mass or more. By setting the content of the nonionic emulsifier to 5.0% by mass or less, the particle size of the oil droplet is not excessively reduced, so that the plate-out property can be improved.

  Nonionic emulsifiers include, for example, polyoxyalkylene branched decyl ether, polyoxyethylene tridecyl ether, polyoxyalkylene tridecyl ether, polyoxyethylene styrenated phenyl ether, polyoxyethylene isodecyl ether, polyoxyethylene lauryl ether , Polyoxyalkylene lauryl ether, polyoxyethylene alkyl ether, polyalkylene alkyl ether, polyoxyalkylene oleyl cetyl ether, polyoxyethylene polyoxypropylene block polymer, sorbitan fatty acid ester, polyoxyethylene sorbitan fatty acid ester, polyoxyethylene glycol, Polyoxyethylene fatty acid esters and the like can be used. These compounds may be used alone or in combination of two or more.

<Anionic emulsifier>
The hot rolling oil can further contain an anionic emulsifier. Alkanolamine can be used as the anionic emulsifier. The content of the anionic emulsifier in the hot rolling oil can be, for example, 0.10 to 1.0% by mass. In this case, the emulsion stability of the coolant can be adjusted to increase the plate-out amount, and the unevenness in the thickness of the oil film formed between the rolling roll and the aluminum material can be further reduced. As a result, the friction between the rolling roll and the aluminum material can be further reduced.

  As the alkanolamine, for example, triethanolamine, diethanolamine, methyldiethanolamine, ethyldiethanolamine, propyldiethanolamine, butyldiethanolamine, ethanolamine, dimethylethanolamine, diethylethanolamine, dipropylethanolamine, dibutylethanolamine can be used. it can. These compounds may be used alone or in combination of two or more.

<Other additives>
The hot rolling oil further includes an antioxidant for suppressing the oxidation of the hot rolling oil, an antiseptic for suppressing the decay of the hot rolling oil, and an electrode for improving the lubricity during rolling. A pressure agent or the like may be included. As the antioxidant, for example, sulfur compounds such as alkylphenols, aromatic amines, sulfurized fats and oils and sulfurized olefins can be used. As preservatives, for example, phenol compounds, formaldehyde donor compounds, saltyl anilide compounds and the like can be used. Examples of the extreme pressure agent include phosphorus compounds such as tricresyl phosphate and dilauryl hydrogenated phosphite, sulfur compounds such as sulfurized fats and oils and sulfurized olefins, and the like.

<Kinematic viscosity>
The kinematic viscosity at a temperature of 40 ° C. of the hot rolling oil is 30 cSt or more and 160 cSt or less. Since the kinematic viscosity is in this range, the required amount of hot rolling oil can be introduced into the sliding part when the aluminum material is caught in the rolling roll, ensuring lubricity and suppressing the occurrence of surface defects. Therefore, it is easy to feed the liquid from the tank storing the hot-rolled oil necessary for the preparation to the reserve tank for preparing the emulsion. That is, productivity is further improved.

[Coolant]
A coolant can be prepared by mixing hot rolling oil and water and dispersing oil droplets of the hot rolling oil in water. The content of hot rolling oil in the coolant is 3 to 10% by volume. Thereby, the lubricity at the time of hot rolling can be maintained in an appropriate range. When the content of hot rolling oil is less than 3% by volume, the amount of hot rolling oil adhering to the surface of the rolling roll is insufficient, which may increase friction between the rolling roll and the aluminum material. There is. On the other hand, when the content of the hot rolling oil exceeds 10% by volume, the amount of water is relatively insufficient, so that the cooling efficiency of the rolling roll may be reduced. From the viewpoint of further improving the cooling efficiency of the rolling roll, the content of hot rolling oil is preferably 8% by volume or less.

  The median diameter of the hot-rolled oil droplets dispersed in the coolant is 1 to 7 μm. Thereby, while improving lubricity at the time of hot rolling moderately, an emulsion can be stabilized. When the median diameter of the oil droplets is less than 1 μm, a boiling film is likely to form between the oil droplets in the coolant and the surface of the rolling roll during hot rolling. Therefore, the amount of hot rolling oil supplied to the rolling roll is insufficient, and there is a possibility that the lubricity is lowered. On the other hand, when the median diameter of the oil droplets exceeds 7 μm, the oil droplets in the emulsion easily float due to buoyancy, and in some cases, the hot rolling oil and water may be separated.

  The median diameter of the oil droplets described above is the cumulative median diameter in the volume-based particle size distribution obtained by the laser diffraction / scattering method. A laser diffraction / scattering particle size distribution measuring device (for example, “LA-950” manufactured by Horiba, Ltd.) can be used to measure the median diameter of oil droplets.

  The hot rolling oil and coolant are preferably used for rolling an aluminum alloy in which the 0.2% proof stress at room temperature of the annealed material is 90 MPa or more. In this case, even when an aluminum alloy made of a high-strength alloy is rolled, the effect of suppressing the generation of surface defects and reducing the amount of aluminum powder generated can be obtained.

  It is known that the deformation resistance during rolling is generally 2 / √3 times the yield stress, but aluminum usually does not show a clear yield and is replaced by 0.2% yield strength. The 0.2% yield strength is given as a function of the equivalent strain, strain rate, and temperature, but a material having a high 0.2% yield strength at room temperature exhibits a high value even at the hot rolling temperature.

  An example of an aluminum material having a 0.2% proof stress at room temperature of 90 MPa or more is JIS A5182. On the other hand, examples of the aluminum material having a 0.2% proof stress at room temperature of less than 90 MPa include JIS A3104 and A1050. Any of JIS A5182 and JIS A3104, JIS A5182 and JIS A1050 can cause a difference of 300 MPa or more in rolling load when rolling at a material temperature of 400 ° C. and a reduction ratio of 50%.

  When the rolling load is high, the amount of hot rolling oil introduced into the hot rolling mill roll and the sliding portion of the aluminum material decreases, and the lubrication conditions become severe. Therefore, it becomes easy to take the value with a high friction coefficient and advanced rate during a process. For this reason, the frictional heat generation of the sliding part between the rolling roll and the aluminum material calculated from the product of the sliding speed between the rolling roll and the aluminum material calculated at the advanced rate, the dynamic friction coefficient during rolling and the rolling load is calculated. It becomes larger (see formula (1)).

  Actually, when comparing the aluminum material surface temperature rise due to frictional heat generation calculated by the theoretical formula (see formula (2)), JIS A5182 having a 0.2% proof stress of 90 MPa or more has a 0.2% proof stress of less than 90 MPa. Compared with JIS A3104 and A1050, the temperature is higher by 30 ° C. or more, resulting in very severe rolling conditions.

  An increase in the surface temperature of the aluminum material during hot rolling causes the oily agent adsorbed on the surface of the aluminum material to be desorbed, resulting in a decrease in lubricity and, in turn, the occurrence of surface defects in the aluminum material. In general, an oily agent contained in the hot rolled oil for aluminum is an ester called natural fat or polyol ester. This ester is multilayer adsorbed on the aluminum material to form a strong adsorbed film, thereby preventing direct contact between the aluminum material and the rolling roll, thereby improving lubricity and suppressing surface defects of the aluminum material.

  An aluminum material having a 0.2% proof stress of less than 90 MPa has a small frictional heat generation, so that an adsorbed film can be maintained even with an ester having a low molecular weight and relatively easy evaporation, but the 0.2% proof stress is 90 MPa or more. Such an aluminum material has a large frictional heat generation, and it is difficult to maintain an adsorbed film with an ester having a small molecular weight and relatively easy evaporation.

  In order to maintain a hot rolling oil film between the rolling roll and the aluminum material at such a local high temperature on the surface of the aluminum material having a 0.2% proof stress of 90 MPa or more, the rolling roll and the aluminum material are slid. It is necessary to increase the amount of hot-rolled oil introduced into the moving part and to have a property that is difficult to evaporate at high temperatures. With the hot rolling oil having the above-described configuration, it is possible to increase the amount of hot rolling oil and suppress evaporation even when rolling an aluminum material having a 0.2% proof stress of 90 MPa or more.

[Aluminum rolled sheet]
By performing hot rolling using the hot rolling oil having the above configuration, an aluminum rolled plate having an aluminum plate and an oil component attached to the surface thereof is obtained. The adhesion amount (that is, the remaining amount) of oil in this aluminum plate is preferably ²⁰ to 100 mg / m ² . By performing the hot rolling using the hot rolling oil, the oil content is 20 to 100 mg / min on the surface of the material after hot rolling of the high strength alloy whose 0.2% proof stress at room temperature of the annealed material is 90 Mpa or more. m ² can remain. Therefore, lubrication can be maintained by the lubricating film. In addition, since the oil film thickness is maintained, the dynamic friction coefficient, the advanced rate, and the load during hot rolling are reduced, so that the frictional heat generation is reduced and the generation of surface defects can be suppressed synergistically.

By setting the amount of adhesion to the oil on the surface of the material after hot rolling to 20 mg / m ² or more, adhesion between the aluminum material and the rolling roll can be sufficiently suppressed during hot rolling. Surface defects can be further suppressed. By making the adhesion amount of the oil content 100 mg / m ² or less, it is possible to prevent the oil content on the rolled plate from being burnt and discoloring the surface of the rolled plate.

  Examples of the hot rolling oil and the coolant containing the hot rolling oil will be described. In addition, the hot rolling oil, coolant, aluminum rolled sheet, and manufacturing method thereof according to the present invention are not limited to the following modes, and the configuration can be changed as appropriate without departing from the scope of the invention.

  In this example, first, each component was mixed by the ratio shown in Table 1-Table 5, and hot-rolled oil (Examples 1-23, Comparative Examples 1-12) was prepared. Specific contents of the components described in Tables 1 to 5 are as follows.

Mineral oil VG22 mineral oil: naphthenic refined mineral oil (Nihon Sun Oil Co., Ltd., kinematic viscosity at 40 ° C. 20.6 mm ² / sec)
VG150 mineral oil: Aroma-based refined mineral oil (manufactured by Fuji Kosan Co., Ltd., kinematic viscosity at 40 ° C., 164 mm ² / sec)
VG450 mineral oil: refined paraffinic mineral oil (manufactured by Nippon San Oil Co., Ltd., kinematic viscosity at 40 ° C. 480.2 mm ² / sec)

・ Oil-based agent Natural fats and oils 1: Refined palm oil (made by Miyoshi Oil & Fat Co., Ltd., the total amount of fatty acids having 18 or more carbon atoms is 55% of the fatty acid composition)
Natural fat and oil 2: Refined rapeseed oil (manufactured by Miyoshi Oil & Fat Co., Ltd., the total amount of fatty acids having 18 or more carbon atoms is 92% of the fatty acid composition)
Natural fat and oil 3: Palm oil (manufactured by Kaneda Yushi Co., Ltd., the total amount of fatty acids having 18 or more carbon atoms is 12% of fatty acid composition)
Synthetic ester 1: Trimethylolpropane trioleate (manufactured by NOF Corporation, number average molecular weight 926, 0 hydroxyl group)
Synthetic ester 2: pentaerythritol trioleate (manufactured by NOF Chemical, number average molecular weight 928, one hydroxyl group)
Synthetic ester 3: Pentaerythritol dioleate (manufactured by NOF Chemical, number average molecular weight 665, two hydroxyl groups)
Synthetic ester 4: Trimethylolpropane trilaurate (manufactured by NOF Chemical, number average molecular weight 760, 0 hydroxyl groups)

・ Fatty acid oleic acid (Wako Pure Chemical Industries, Ltd., carbon number 18)
Lauric acid (Wako Pure Chemical Industries, Ltd., carbon number 12)
Arachidic acid (Wako Pure Chemical Industries, Ltd., carbon number 20)
Capric acid (Wako Pure Chemical Industries, Ltd., carbon number 10)
Behenic acid (Wako Pure Chemical Industries, Ltd., carbon number 22)

-Nonionic emulsifier polyethylene glycol lauryl ether (Daiichi Kogyo Seiyaku Co., Ltd., HLB13.8)
Polyethylene glycol monooleate (Daiichi Kogyo Seiyaku Co., Ltd., HLB11.5)
Polyethylene glycol diolate (Daiichi Kogyo Seiyaku Co., Ltd., HLB8.6)

・ Anionic emulsifier triethanolamine (Mitsui Chemicals)

<Evaluation of hot rolling oil>
For Examples 1 to 23 and Comparative Examples 1 to 12 prepared as described above, the kinematic viscosity at 40 ° C. was measured by a method based on JIS K2283 using a Canon-Fenske viscometer. The kinematic viscosity of each hot rolling oil at 40 ° C. was as shown in Tables 1 to 5.

<Evaluation of coolant>
First, deionization treatment was performed on tap water using an ion exchange resin, and deionized water having a conductivity of 10 μS / cm at 25 ° C. was produced. The deionized water thus obtained was used as a dispersion medium, and the hot rolling oils of Examples 1 to 23 and Comparative Examples 1 to 12 were dispersed in the dispersion medium at the concentrations shown in Tables 1 to 5 to provide a coolant. Was prepared. Subsequently, using this coolant, evaluation of emulsion stability, plate-out property, and lubricity was performed by the following methods. The coolant obtained in this example was an oil-in-water emulsion. The volume average particle diameters of the oil droplets in Examples and Comparative Examples are as shown in Tables 1-5.

-Emulsification stability The separatory funnel into which 400 mL of coolant was poured was placed in a thermostatic bath at 65 ° C, and left for 60 minutes with the cock facing downward. After 60 minutes, the cock of the separating funnel was opened, and among the coolant discharged from the legs of the separating funnel, 100 mL discharged first and 100 mL discharged last were collected. Then, the hot-rolled oil concentration Vi [volume%] in the first discharged 100 mL coolant and the hot-rolled oil concentration Vf [volume%] in the finally discharged 100 mL coolant were measured. The emulsification stability index ESI indicating the stability of the emulsified state of the coolant can be expressed by the following formula (3) using the concentrations Vi and Vf of these hot rolled oils.
ESI = Vi / Vf (3)

  The values of the emulsification stability index of the coolant containing each hot rolled oil in Examples and Comparative Examples were as shown in Tables 6 to 8. In addition, when the value of the emulsification stability index exceeds 0.8, the symbol “◎” appears in the “Evaluation” column of Tables 1 to 4, and when the value is 0.7 or more and 0.8 or less, the same column. The symbol “◯” is described in “”, and the symbol “X” is described in the same column when it is less than 0.7.

  In the evaluation of the emulsion stability, the closer the emulsion stability index value is to 1.0, the less likely the oil droplets coalesce and the oil droplets hardly settle. Therefore, the symbols "◎" and "○" with an emulsification stability index value of 0.7 or higher have excellent emulsification stability and can pass coalescence of oil droplets in the coolant. It was determined. Moreover, when the value of the emulsification stability index was less than 0.7, the symbol “x” was judged to be unacceptable because the emulsification stability was poor and coalescence of oil droplets in the coolant was likely to occur.

-Plate-out amount An aluminum block having a length of 80 mm, a width of 25 mm, and a thickness of 5 mm was prepared, and with the temperature of the aluminum block maintained at 100 ° C, coolant heated to 65 ° C was sprayed onto the aluminum block. The coolant spraying conditions were a discharge pressure of 0.3 MPa and a discharge time of 10 milliseconds. After cooling the aluminum block, the coolant was dried in a desiccator for 23 hours to remove moisture in the coolant. The mass (unit: g) of each hot rolling oil adhering to the aluminum block after drying was measured. And the value (unit: g / m < ² >) which converted the mass of this hot rolling oil into the mass per unit area was made into plate-out amount.

The plate-out amounts in Examples and Comparative Examples were as shown in Tables 6 to 8. Further, when the plate out amount exceeds 1.1 g / m ^2, the symbol "◎" to "evaluation" column of Table 1 to Table 4, in the case of 0.7~1.1g / m ² is The symbol “◯” is described in the same column, and the symbol “X” is described in the same column when it is less than 0.7 g / m ² .

In the evaluation of the plate-out property, the larger the plate-out amount, the easier the demulsification occurs when coming into contact with the rolling roll, indicating that a larger amount of hot rolling oil can be adhered to the surface of the rolling roll. Therefore, the case of the symbols “」 ”and“ ◯ ”having a plate-out amount of 0.7 g / m ² or more was judged as acceptable because the amount of hot rolling oil adhering to the surface of the rolling roll can be increased. Further, in the case of the symbol “x” where the plate-out amount is less than 0.7 g / m ² , the amount of hot rolling oil adhering to the surface of the rolling roll is likely to be insufficient, so that it was judged as rejected.

-Yield strength The proof strength of the aluminum material used for hot rolling is JIS A2202, A5082, and A5182 alloy aluminum plate with a thickness of 5.0 mm, and a JIS Z2201 No. 5 test piece is prepared. Evaluation was performed by a tensile test based on JIS Z2231. The yield strength used was a value indicating 0.2% permanent elongation. The results are shown in Tables 6-8.

・ Lubricity (Baking temperature)
An aluminum material 10 having a width of 40 mm, a length of 500 mm, and a thickness of 5.0 mm made of JIS A5052, A5082, and A5182 alloy was prepared and pre-rolled at a reduction rate of 20%. Next, a pair of rolling rolls 4 having an arithmetic average roughness Ra as measured in the sheet width direction of 0.3 to 0.4 μm and a maximum height Rz = 3.5 to 4.0 μm (see FIG. 1) was prepared. In addition, about the rolling roll 4, it adjusted to the said surface roughness by grind | polishing the roll surface in a rolling direction using abrasive paper.

The aluminum material 10 was hot-rolled with the rolling roll 4 while applying a coolant to the pair of rolling rolls 4 (4a, 4b) at 0.5 L / min. The material temperature at the start of hot rolling was increased from 300 ° C. by 25 ° C. until pick-up inclusion surface defects (see FIG. 2) occurred. The presence or absence of surface defects was determined by observing the material surface after hot rolling with a scanning electron microscope. As illustrated in FIG. 2, the surface defect exhibits a fastener-like configuration. As described above, the temperature was increased by 25 ° C., and the material temperature at the start of hot rolling at which surface defects first occurred was defined as the seizure temperature. The results are shown in Tables 6-8. In addition, the rolling conditions in hot rolling were as follows.
Rolling speed: 40 m / min
Reduction ratio: 50%

  As the seizure temperature is higher, even when the material surface temperature is higher, the oil film due to the hot rolling oil is not broken and surface defects can be suppressed. When the seizure temperature is less than 375 ° C., the symbol “x” because the seizure resistance is insufficient, and when the seizure temperature is 375 ° C. or more and less than 400 ° C., the symbol “O” is sufficiently provided. A seizure temperature of 400 ° C. or higher was evaluated as “記号” as having good seizure resistance. Therefore, it was determined that the symbols “◎” and “◯” were acceptable because surface defects could be suppressed. Moreover, since there was a possibility of causing a surface defect in the case of the symbol “x”, it was determined to be unacceptable.

Aluminum powder adhesion First, an aluminum material made of a JIS A5052 alloy having a width of 20 mm, a length of 100 mm, and a thickness of 2.0 mm was immersed in a coolant subjected to hot rolling for 10 seconds. Thereafter, the aluminum material was washed away with 100 mL of ethanol, and the ethanol used for cleaning the aluminum material was filtered through a membrane filter having a pore diameter of 0.2 μm. After the aluminum powder remaining on the membrane filter was acid-decomposed with aqua regia, the amount of aluminum powder was quantified with an inductively coupled plasma (ie, ICP) emission spectroscopic analyzer.

The amount of aluminum powder adhered in Examples and Comparative Examples was as shown in Tables 6-8. When the aluminum powder adheres to 0.3 g / m ² or less, the symbol “◎” in the “Evaluation” column of Tables 6 to 8 exceeds 0.3 g / m ² and is 0.5 g / m ² or less. In this case, the symbol “◯” was entered in the same column, and when it exceeded 0.5 g / m ² , the symbol “X” was entered in the same column.

In the evaluation of the aluminum powder adhesion, the larger the aluminum powder adhesion amount, the more aluminum powder is generated during hot rolling, and the aluminum powder is more likely to adhere to the surface of the aluminum material or around the hot rolling mill. Therefore, in the case of symbols “◯” and “◎” where the amount of aluminum powder adhering to 0.5 g / m ² or less, the amount of aluminum powder adhering to the surface aluminum material surface of the rolling roll and the hot rolling mill is reduced. It was judged as acceptable because it was possible. In addition, in the case of the symbol “x” where the amount of aluminum powder adhering exceeds 0.5 g / m ² , there is a risk of increasing the amount of aluminum powder adhering to the surface of the aluminum surface of the rolling roll or around the hot rolling mill. Judgment was rejected.

Measurement of residual oil content on plate surface As illustrated in FIG. 3, after hot rolling, a rolled plate 1 having an aluminum plate 2 and an oil component 3 attached to the surface is obtained. In measuring the residual oil content, first, in the rolling test described above, the material rolled at a material temperature of 400 ° C. was cut so that the length in the rolling direction was 100 mm. The cut piece was ultrasonically cleaned for 10 minutes in a beaker containing hexane. The washed hexane was suction filtered using a membrane filter having a pore diameter of 0.45 μm, and the filtrate was placed in a beaker and allowed to dry for 48 hours. Thereafter, the weight of the obtained residue was determined, and the result was defined as the residual oil content. The results are shown in Tables 1-5.

-Color tone of rolled plate The color tone of the rolled plate after hot rolling at a material temperature of 400 ° C was visually observed. As a result, when there was no yellowing on the surface, the symbol A was marked in the column of “color tone of rolled sheet” in Tables 6 to 8, and when the surface was slightly yellowed, the symbol B was markedly yellowed. In this case, the symbol C is described. And the case of the symbol A and the symbol B was determined to be acceptable because yellowing on the surface of the rolled plate could be sufficiently suppressed.

-Oxidation resistance 100 g of cast iron chips were added to 600 ml of coolant. The air was blown into the coolant and kept at a temperature of 80 ° C. for 100 hours, and then the amount of formic acid generated in the coolant was measured. The amount of formic acid produced in the coolants of the examples and comparative examples was as shown in Tables 6-8. Moreover, in the “judgment” column in Tables 1 to 3, the symbol “A” is described when the amount of formic acid is less than 100 mass ppm, and the symbol “C” is described when the amount is 100 mass ppm or more.

  In the evaluation of oxidation resistance, it is considered that radicals generated by the oxidation of the oily agent decompose each component in the hot rolling oil to produce lower fatty acids such as formic acid. Therefore, in the evaluation of oxidation resistance, the case of the symbol “A” in which the amount of formic acid generated was 100 mass ppm or less was judged acceptable because the oxidation of the oily agent could be sufficiently suppressed. Further, the case of the symbol “C” in which the amount of formic acid generated exceeded 100 mass ppm was determined to be rejected because the oxidation of the oily agent was insufficiently suppressed.

  As shown in Tables 1-3, Table 6, and Table 7, Examples 1-23 were excellent in emulsification stability and plate-out property, and suppressed the surface defect of the aluminum material after hot rolling. Furthermore, in an Example, the adhesion amount of aluminum powder is also low.

On the other hand, as shown in Table 2, in Comparative Example 1, the 40 ° C. kinematic viscosity was lower than the specific range, and the oil film thickness between the rolling roll and the aluminum material was insufficient. Therefore, the seizure temperature was lower than in Examples 1-23.
In Comparative Example 2, the kinematic viscosity at 40 ° C. was higher than the specific range, so that the liquid could not be pumped. In Comparative Example 4, the carbon number of the fatty acid was higher than the specific range. It could not be dissolved in oil and could not be dispersed in water.

In Comparative Example 3, since the carbon number of the fatty acid was smaller than the specific range, the boundary lubricity was insufficient. Therefore, the seizure temperature was lower than in Examples 1-23.
In Comparative Example 5, since the fatty acid concentration was lower than the specific range, the dispersibility of the aluminum powder of the hot rolling coolant was insufficient. Therefore, aluminum powder adhesiveness deteriorated compared with Examples 1-23.

In Comparative Example 6, since the fatty acid concentration was higher than the specific range, the oxidation resistance of the hot rolling coolant was insufficient.
In Comparative Example 7, the oil concentration of the hot-rolled coolant was low, and in Comparative Example 9, the volume average particle size of the oil droplets of the hot-rolled coolant was lower than the specific range. Furthermore, the oil film thickness between the rolling roll and the aluminum material was insufficient due to insufficient plate-out amount. Therefore, the seizure temperature was lower than in Examples 1-23.

In Comparative Example 8, since the oil concentration of the hot-rolled coolant was higher than the specific range, the emulsification stability was insufficient, and the oil on the plate surface increased and the plate surface turned yellow.
In Comparative Example 10, the oil concentration of the hot-rolled coolant was higher than the specific range, so that the oil droplets in the hot-rolled coolant were easy to coalesce. Therefore, the emulsion stability was lower than in Examples 1-23.

In Comparative Example 11, the total amount of fatty acids having 18 or more carbon atoms of natural fats and oils added as an oily agent was lower than the specific range, and as a result, the heating residue was lower than the specific range. The oil film thickness between aluminum materials was insufficient. Therefore, the seizure temperature was lower than in Examples 1-23.
In Comparative Example 12, the molecular weight of the synthetic ester added as the oiliness agent was lower than the specific range, and as a result, the heating residue was lower than the specific range, so the oil film thickness between the rolling roll and the aluminum material was I was short. Therefore, the seizure temperature was lower than in Examples 1-23.

1 Aluminum rolled plate 2 Aluminum plate 3 Oil

Claims (5)

A hot rolling oil for aluminum having a kinematic viscosity at a temperature of 40 ° C. of 30 cSt or more and 160 cSt or less,
Base oil,
A fatty acid having 12 to 20 carbon atoms;
An oily agent comprising at least one of a synthetic ester and natural fats and oils,
The concentration of the fatty acid is 2% by mass or more and 16% by mass or less,
The synthetic ester has a number average molecular weight of 650 or more and one or more hydroxyl groups in the molecule, or a number average molecular weight of 850 or more,
The natural fat / oil is a hot rolled oil for aluminum in which the amount of fatty acid having 18 or more carbon atoms is 55% by mass or more in the total fatty acid composition.   The hot rolling oil for aluminum according to claim 1, wherein the content of the oily agent is 15% by mass or more and 35% by mass or less. Water and oil droplets made of hot rolled oil for aluminum according to claim 1 or 2, dispersed in the water,
The concentration of the hot rolling oil for aluminum is 3 to 10% by volume,
The hot rolling coolant for aluminum whose median diameter of the said oil droplet is 1-7 micrometers.   The hot-rolling coolant for aluminum according to claim 3, which is used for rolling an aluminum alloy in which the 0.2% proof stress at room temperature of the annealed material is 90 MPa or more.   The manufacturing method of an aluminum rolled sheet which performs hot rolling of the aluminum material using the hot rolling coolant for aluminum of Claim 3 or 4.