EP4628565A1

EP4628565A1 - Lubricant composition, and manufacturing method of seamless metal pipes using same

Info

Publication number: EP4628565A1
Application number: EP23897215.2A
Authority: EP
Inventors: Daiki Ito; Naka SAEKI; Kiyofumi Suzuki
Original assignee: Nippon Steel Corp
Current assignee: Nippon Steel Corp
Priority date: 2022-11-28
Filing date: 2023-09-19
Publication date: 2025-10-08
Also published as: JPWO2024116556A1; EP4628565A4; CN120265738A; WO2024116556A1

Abstract

Provided is a lubricant composition in which an excellent adhesive property and drying property are obtained, and with which excellent lubricity, carburization resistance, adhesiveness, and water resistance are obtained when a lubricating film is formed from the lubricant composition. A lubricant composition according to the present disclosure consists of, in mass%, an oxide-based laminar compound: 10.0 to 40.0%, a boron compound: 7.5 to 35.0%, a silane coupling agent: 0.3 to 5.0%, a water-soluble polymer: 0 to 7.0%, and impurities: 0 to 1.0%, with the balance being water. A total content of the oxide-based laminar compound and the boron compound is 17.5 to 65.0% by mass. A ratio of the content of the oxide-based laminar compound to the content of the silane coupling agent is 3.0 to 30.0.

Description

TECHNICAL FIELD

The present disclosure relates to a lubricant composition, and a method for producing a seamless metal pipe using the lubricant composition.

BACKGROUND ART

The Mannesmann-mandrel mill process is available as one method for producing a seamless metal pipe. In the Mannesmann-mandrel mill process, a seamless metal pipe is produced by the following process. First, a round billet (a billet in which a cross section perpendicular to the axial direction is a round shape) that will serve as a material for the seamless metal pipe is heated in a reheating furnace. The heated round billet is subjected to piercing-rolling using a piercing-rolling mill to produce a hollow shell. The hollow shell is subjected to elongating using a mandrel mill in which a plurality of roll stands are arranged in a row. The wall thickness of the hollow shell is adjusted by the elongating. In addition, as necessary, the hollow shell after elongating is reheated in a reheating furnace, and diameter adjusting rolling is performed using a stretch reducer or a sizer. The diameter adjusting rolling is an optional process. A seamless metal pipe is produced by the above process.
In the above process for producing a seamless metal pipe, when performing elongating using a mandrel mill, a mandrel bar is inserted into the hollow shell, and thereafter elongating is performed on the hollow shell with the mandrel bar inserted therein. The wall thickness of the hollow shell can be adjusted by using rolls of the roll stands constituting the mandrel mill to roll the outer surface of the hollow shell that has the mandrel bar inserted therein.
The temperature of the hollow shell before elongating is approximately 1050 to 1200°C. The mandrel bar is inserted into the hollow shell which is at such a high temperature. For this reason, scoring is liable to occur on the outer surface of the mandrel bar and on the inner surface of the hollow shell. If scoring occurs, flaws will easily occur on the inner surface of the hollow shell. Therefore, before inserting the mandrel bar into the hollow shell, a lubricant composition is applied to the surface of the mandrel bar. The lubricant composition dries to thereby form a lubricating film. The occurrence of scoring at a contact surface between the mandrel bar and the hollow shell is suppressed by the lubricating film. After elongating by the mandrel mill is completed, the mandrel bar is drawn from the hollow shell. A lubricating film constituted by the lubricant composition is required to have excellent lubricity in order to suppress the occurrence of the aforementioned scoring and also to ensure that the mandrel bar can be easily drawn from the hollow shell after elongating.
Further, during the elongating, rolling rolls of the roll stands of the mandrel bar are cooled by roll cooling water. In some cases the roll cooling water for cooling the rolling rolls may splash onto the lubricating film of the mandrel bar. Therefore, the lubricating film is required to also have excellent water resistance, and not just excellent lubricity. Here, the term "water resistance" means a property such that it is difficult for the lubricating film to be peeled off from the surface of the mandrel bar even when water adheres to the lubricating film.
Further, during the elongating, an external force from the rolling rolls is applied not only to the hollow shell, but also to the lubricating film formed on the mandrel bar. If the lubricating film is easily peeled off by the external force, it will not be able to sufficiently fulfill its role as a lubricating film. Therefore, the lubricating film is also required to have excellent adhesiveness. Here, the term "adhesiveness" means a property such that it is difficult for the lubricating film to be peeled off from the surface of the mandrel bar even when an external force is applied to the lubricating film.
As described above, the lubricating film is required to have excellent lubricity, excellent water resistance, and excellent adhesiveness.
In addition, when applying a lubricant composition to a mandrel bar, it is desirable for the lubricant composition to be uniformly applied. If unevenness arises in the film thickness of the applied lubricant composition, in some cases drying unevenness will occur and the lubricating film may partially peel off. Further, if the drying time until a lubricating film is formed from the lubricant composition is too long, productivity will be affected. Accordingly, the lubricant composition that serves as the raw material for the lubricating film is required to have an excellent adhesive property and an excellent drying property.
Techniques for improving the aforementioned properties of a lubricant composition and a lubricating film are proposed in Japanese Patent Publication No. S59-37317 (Patent Literature 1) and Japanese Patent Application Publication No. H02-51592 (Patent Literature 2). The lubricant compositions disclosed in these Patent Literatures are mainly composed of graphite and an organic binder.
Graphite and an organic binder actually enhance the lubricity of a lubricating film. However, when a mandrel bar coated with a lubricant composition mainly composed of graphite and an organic binder is inserted into a hollow shell and elongating is performed, in some cases carburizing occurs on the inner surface of the hollow shell and a carburized layer is formed. Even if a heat treatment is performed in a later process, in some cases a part of the carburized layer formed during elongating may remain. The carburized layer lowers properties of the seamless metal pipe, such as corrosion resistance. Therefore, in the case of a seamless metal pipe that is required to have excellent corrosion resistance, after the seamless metal pipe is produced it is necessary to perform a repair process to grind and remove some of the inner surface of the seamless metal pipe. Such a repair process increases the product cost and decreases productivity. In addition, in the case of a seamless metal pipe with a small inner diameter, the repair process cannot be performed because, to begin with, a grinding wheel for performing grinding cannot be inserted into the pipe. Therefore, the lubricant composition also needs to be capable of suppressing carburizing of the workpiece (seamless metal pipe). In the present description, the property of suppressing carburizing of a workpiece is also referred to as "carburization resistance".
A lubricant composition with enhanced carburization resistance is proposed in Japanese Patent Application Publication No. H09-78080 (Patent Literature 3).
The lubricant composition disclosed in Patent Literature 3 is obtained by mixing: one or more types of particulate oxide-based lamellar substance selected from potassium tetrasilicic mica, sodium tetrasilicic mica, natural phlogopite, bentonite, montmorillonite, and vermiculite; and one or more types of binder selected from boron oxide, boric acid, an alkali metallic borate, sodium carbonate, potassium carbonate, and sodium silicate or potassium silicate having a melting point of 1000°C or less, at a weight ratio of 1:4 to 1:1.
The lubricant composition disclosed in Patent Literature 3 does not contain graphite. Therefore, excellent carburization resistance is obtained.

CITATION LIST

PATENT LITERATURE

Patent Literature 1: Japanese Patent Publication No. S59-37317
Patent Literature 2: Japanese Patent Application Publication No. H02-51592
Patent Literature 3: Japanese Patent Application Publication No. H09-78080

SUMMARY OF INVENTION

TECHNICAL PROBLEM

However, in Patent Literature 3, there is no discussion regarding the adhesive property and drying property of the lubricant composition. Furthermore, there is also no discussion regarding the adhesiveness and water resistance of a lubricating film formed from the lubricant composition. Therefore, in Patent Literature 1 to Patent Literature 3, there is no discussion regarding a lubricant composition in which an excellent adhesive property and excellent drying property are obtained, and with which excellent lubricity, excellent carburization resistance, excellent adhesiveness, and excellent water resistance are obtained when a lubricating film is formed from the lubricant composition.
An objective of the present disclosure is to provide a lubricant composition in which an excellent adhesive property and excellent drying property are obtained, and with which excellent lubricity, carburization resistance, adhesiveness, and water resistance are obtained when a lubricating film is formed from the lubricant composition, and a method for producing a seamless metal pipe using the lubricant composition.

SOLUTION TO PROBLEM

A lubricant composition according to the present disclosure contains, in mass%,

an oxide-based laminar compound: 10.0 to 40.0%,
a boron compound: 7.5 to 35.0%,
a silane coupling agent: 0.3 to 5.0%,
a water-soluble polymer: 0 to 7.0%, and
impurities: 0 to 1.0%,
with the balance being water,
wherein:
- a total content of the oxide-based laminar compound and the boron compound is 17.5 to 65.0% by mass, and
- a ratio of a content of the oxide-based laminar compound to a content of the silane coupling agent is 3.0 to 30.0.

A method for producing a seamless metal pipe according to the present disclosure includes:

an application process of applying the lubricant composition described above to a surface of a mandrel bar having a surface temperature of 60 to 150°C,
a drying process of, after the application process, drying the lubricant composition to form a lubricating film on the surface of the mandrel bar,
an insertion process of, after the drying process, inserting the mandrel bar into a hollow shell after piercing-rolling,
a rolling process of, after the insertion process, performing elongating using a mandrel mill on the hollow shell in which the mandrel bar is inserted, and
a drawing process of, after the rolling process, drawing the mandrel bar from the hollow shell.

ADVANTAGEOUS EFFECTS OF INVENTION

According to the lubricant composition of the present disclosure, an excellent adhesive property and an excellent drying property are obtained, and when the lubricant composition becomes a lubricating film, excellent lubricity, excellent carburization resistance, excellent adhesiveness, and excellent water resistance are obtained. According to the method for producing a seamless metal pipe of the present disclosure, a seamless metal pipe in which the occurrence of carburizing and scoring has been suppressed can be produced.

DESCRIPTION OF EMBODIMENTS

The present inventors conducted studies regarding the composition of a lubricant composition in which an excellent adhesive property and excellent drying property are obtained, and with which excellent lubricity, excellent carburization resistance, excellent adhesiveness, and excellent water resistance are obtained when a lubricating film is formed from the lubricant composition.
The present inventors have considered that in order to obtain carburization resistance in a lubricating film, it is necessary to suppress the content of carbon as low as possible in the lubricant composition. In addition, the present inventors have considered that it is necessary to take into account the surface temperature (60 to 150°C) of the mandrel bar at the time of applying the lubricant composition when considering the composition of a lubricant composition in which an appropriate adhesive property and drying property are obtained in the aforementioned temperature range. Furthermore, the present inventors have considered that it is necessary to take into account the temperature (1050 to 1200°C) of the hollow shell into which the mandrel bar is inserted when considering the composition of a lubricant composition that enables lubricity, carburization resistance, adhesiveness, and water resistance to be obtained in a lubricating film in the aforementioned temperature range.
As a result of taking the above three matters into consideration, the present inventors have considered that if a lubricant composition consists of, in mass%, an oxide-based laminar compound: 10.0 to 40.0%, a boron compound: 7.5 to 35.0%, a silane coupling agent: 0.3 to 5.0%, a water-soluble polymer: 0 to 7.0%, and impurities: 0 to 1.0%, with the balance being water, there is a possibility of obtaining the aforementioned properties.
However, some cases occurred where the aforementioned properties were not sufficiently obtained with a lubricant composition having the composition described above. Therefore, the present inventors conducted further studies. As a result, the present inventors obtained the following findings.
The total content of the oxide-based laminar compound and the boron compound influence the adhesive property of the lubricant composition and the lubricity and adhesiveness of the lubricating film. On the precondition that the components of the lubricant composition are within the range described above, if the total content of the oxide-based laminar compound and the boron compound is 17.5 to 65.0% by mass, the adhesive property of the lubricant composition and the adhesiveness and lubricity of the lubricating film can be enhanced.
Furthermore, the ratio of the content of the oxide-based laminar compound to the content of the silane coupling agent influences the lubricity, water resistance, adhesiveness, and drying property of the lubricating film. On the precondition that the composition of the lubricant composition is within the range described above, if the ratio of the content of the oxide-based laminar compound to the content of the silane coupling agent is 3.0 to 30.0, the lubricity, water resistance, adhesiveness, and drying property of the lubricating film will be enhanced.
A lubricant composition of the present embodiment was completed based on the above findings, and is as follows.
A lubricant composition according to a first configuration of the present embodiment consists of, in mass%,

A lubricant composition according to a second configuration of the present embodiment is in accordance with the lubricant composition of the first configuration, wherein:

a total content of the oxide-based laminar compound and the boron compound is 25.0 to 50.0% by mass, and
a ratio of the content of the oxide-based laminar compound to the content of the silane coupling agent is 5.0 to 15.0.

A lubricant composition according to a third configuration of the present embodiment is in accordance with the lubricant composition of the first or second configuration, wherein:

the oxide-based laminar compound is a phyllosilicate mineral, and
the phyllosilicate mineral is composed of one kind or more selected from a group consisting of mica, vermiculite, and bentonite.

A lubricant composition according to a fourth configuration of the present embodiment is in accordance with the lubricant composition of the third configuration, wherein:
the mica is composed of one kind or more selected from a group consisting of sodium tetrasilicic mica, potassium tetrasilicic mica, natural phlogopite, and naturalmuscovite.
A lubricant composition according to a fifth configuration of the present embodiment is in accordance with the lubricant composition of any one of the first to fourth configurations, wherein:
the boron compound is composed of one kind or more selected from a group consisting of boron oxide, an alkali metal borate, and an amine borate.
A lubricant composition according to a sixth configuration of the present embodiment is in accordance with the lubricant composition of the fifth configuration, wherein:
the alkali metal borate is composed of one kind or more selected from a group consisting of lithium borate, sodium borate, and potassium borate.
A lubricant composition according to a seventh configuration of the present embodiment is in accordance with the lubricant composition of any one of the first to sixth configurations, wherein:
the silane coupling agent is R_a-Si(OR_b)₃, where R_a is composed of one kind or more selected from a group consisting of an alkyl group, a vinyl group, an epoxy group, a styryl group, a methacryl group, an acryl group, an amino group, an isocyanurate group, a ureido group, a mercapto group, and an isocyanate group, and R_b is composed of a methyl group or an ethyl group.
A lubricant composition according to an eighth configuration of the present embodiment is in accordance with the lubricant composition of the seventh configuration, wherein:
the silane coupling agent is composed of one kind or more selected from a group consisting of methyltrimethoxysilane and 3-glycidoxypropyltrimethoxysilane.
A lubricant composition according to a ninth configuration of the present embodiment is in accordance with the lubricant composition of any one of the first to eighth configurations, wherein:
the water-soluble polymer is composed of one kind or more selected from a group consisting of a biogum, a natural polysaccharide, a cellulose derivative, a polyacrylate, an alginate, and an organic polymer.
A lubricant composition according to a tenth configuration of the present embodiment is in accordance with the lubricant composition of the ninth configuration, wherein:

the biogum is composed of one kind or more selected from a group consisting of xanthan gum, welan gum, and rhamsan gum;
the natural polysaccharide is composed of one kind or more selected from a group consisting of guar gum, locust bean gum, and carageenan;
the cellulose derivative is composed of one kind or more selected from a group consisting of methyl cellulose, ethyl cellulose, hydroxyethyl cellulose, hydroxyethyl methyl cellulose, hydroxypropyl methylcellulose, carboxymethyl cellulose, and salts of these cellulose derivatives; and
the organic polymer is composed of one kind or more selected from a group consisting of acrylic resin, acrylic styrene resin, vinyl acetate resin, and polypropylene resin.

A method for producing a seamless metal pipe according to the present embodiment includes:

an application process of applying the lubricant composition according to any one of the first to tenth configurations to a surface of a mandrel bar having a surface temperature of 60 to 150°C;
a drying process of, after the application process, drying the lubricant composition to form a lubricating film on the surface of the mandrel bar;
an insertion process of, after the drying process, inserting the mandrel bar into a hollow shell after piercing-rolling;
a rolling process of, after the insertion process, performing elongating using a mandrel mill on the hollow shell in which the mandrel bar is inserted; and
a drawing process of, after the rolling process, drawing the mandrel bar from the hollow shell.

Hereunder, the lubricant composition of the present embodiment and the method for producing a seamless metal pipe using the lubricant composition of the present embodiment are described.

[Features of lubricant composition of present embodiment]

The lubricant composition of the present embodiment satisfies Feature 1 to Feature 3.

(Feature 1)

The lubricant composition consists of, in mass%,

an oxide-based laminar compound (A): 10.0 to 40.0%,
a boron compound (B): 7.5 to 35.0%,
a silane coupling agent (C): 0.3 to 5.0%,
a water-soluble polymer (D): 0 to 7.0%, and
impurities: 0 to 1.0%,
with the balance being water.

(Feature 2)

The total content (A + B) of the oxide-based laminar compound (A) and the boron compound (B) is 17.5 to 65.0% by mass.

(Feature 3)

A ratio (A/C) of the content of the oxide-based laminar compound (A) to the content of the silane coupling agent (C) is 3.0 to 30.0.
Hereunder, Feature 1 to Feature 3 are described.

[(Feature 1) Regarding lubricant composition]

The lubricant composition of the present embodiment contains the following compounds. Hereunder, the symbol "%" used when describing the content of a compound means "mass percent" unless otherwise noted.
Oxide-based laminar compound (A): 10.0 to 40.0%
The oxide-based laminar compound (A) is used as a base material for the lubricant composition. The oxide-based laminar compound (A) enhances the lubricity of a lubricating film formed from the lubricant composition, and suppresses the occurrence of scoring during elongating. The oxide-based laminar compound (A) also enhances a drying property of the lubricant composition. If the content of the oxide-based laminar compound (A) is less than 10.0%, the aforementioned advantageous effects will not be sufficiently obtained. On the other hand, if the content of the oxide-based laminar compound (A) is more than 40.0%, the viscosity of the lubricant composition will be excessively high. In such a case, even when mixed with other compounds of the lubricant composition, the respective compounds cannot be uniformly dispersed, and a lubricant composition that has flowability cannot be prepared. Therefore, the content of the oxide-based laminar compound (A) is 10.0 to 40.0%.
A preferable lower limit of the content of the oxide-based laminar compound (A) is 11.0%, more preferably is 12.0%, further preferably is 14.0%, and further preferably is 15.0%.
A preferable upper limit of the content of the oxide-based laminar compound (A) is 35.0%, more preferably is 30.0%, and further preferably is 25.0%.
A preferable range of the content of the oxide-based laminar compound (A) is, for example, 11.0 to 35.0%, more preferably is 12.0 to 30.0%, further preferably is 14.0 to 25.0%, and further preferably is 15.0 to 25.0%.
The oxide-based laminar compound (A) is, for example, a phyllosilicate mineral. A phyllosilicate mineral is a mineral having a structure in which layers of silicate tetrahedrons are stacked. The phyllosilicate mineral may be a natural mineral or an artificial mineral.
The phyllosilicate mineral is composed of, for example, one kind or more selected from a group consisting of mica, vermiculite, and bentonite.
The mica is, for example, one kind or more selected from a group consisting of sodium tetrasilicic mica (NaMg_2.5(Si₄O₁₀)F₂), potassium tetrasilicic mica (KMg_2.5(Si₄O₁₀)F₂), natural phlogopite (KMg₃(AlSi₃O₁₀)(OH₂)), and natural muscovite (KAl₂(AlSi₃O₁₀)(OH)₂).
Note that, if another similar inorganic oxide or laminar compound is used instead of the aforementioned oxide-based laminar compound (A), sufficient lubricity will not be obtained in the lubricant composition. For example, even if boron nitride (BN) or titanium oxide (TiO₂) or the like is used instead of the oxide-based laminar compound, sufficient lubricity will not be obtained. It is considered that this is because the interlayer bonding strength of the oxide-based laminar compound (A) is lower than that of other similar inorganic oxides and laminar compounds.
An average particle size of the oxide-based laminar compound (A) is not particularly limited. A preferable average particle size of the oxide-based laminar compound (A) is 1 to 40 µm. If the average particle size of the oxide-based laminar compound (A) is 40 µm or less, the oxide-based laminar compound (A) will be less likely to settle and less likely to accumulate when the oxide-based laminar compound (A) is mixed with water together with other compounds during the production of the lubricant composition. Therefore, when discharging the lubricant composition from a container that stores the lubricant composition before use, the lubricant composition can be smoothly discharged without the occurrence of clogging. If the average particle size of the oxide-based laminar compound (A) is 1 µm or more, the oxide-based laminar compound (A) will have flowability without excessive thickening occurring in a case where the oxide-based laminar compound (A) is mixed with water together with other compounds during the production of the lubricant composition. Therefore, the lubricant composition can be applied uniformly to a mandrel bar.
A more preferable lower limit of the average particle size of the oxide-based laminar compound (A) is 5 µm, further preferably is 10 µm, and further preferably is 15 µm.
A more preferable upper limit of the average particle size of the oxide-based laminar compound (A) is 30 µm, further preferably is 25 µm, and further preferably is 20 µm.
A more preferable range of the average particle size of the oxide-based laminar compound (A) is, for example, 5 to 30 µm, further preferably is 10 to 25 µm, and further preferably is 15 to 20 µm.
The average particle size of the oxide-based laminar compound (A) can be measured by the following method using a laser diffraction/scattering particle size distribution analyzer.
The volume-based particle size distribution of the oxide-based laminar compound (A) is obtained using a laser diffraction/scattering particle size distribution analyzer. From the obtained particle size distribution, the sum of values obtained by multiplying each particle size by the frequency (sum of the products of particle size and frequency) is calculated. The average particle size (µm) is determined by dividing the obtained sum of the products of particle size and frequency by the sum of the frequencies. Note that, the diameter of a sphere having the same volume as the volume of the respective oxide-based layered compounds (A) that are measured is taken as the particle size of the respective oxide-based laminar compounds (A).
The conditions for measuring the average particle size using the aforementioned laser diffraction/scattering particle size distribution analyzer are as follows.

Apparatus name: Laser diffraction/scattering particle size distribution analyzer
Model number: LA-960 (manufactured by Horiba Ltd.)
Particle size measurement principle: Mie scattering theory
Light source: Semiconductor laser, light emitting diode
Detector: Ring-shaped 64-segment silicon photodiode, four-channel array detector, silicon photodetector
Measurement range: 0.01 to 5000 µm
Measurement temperature: 25°C
Solvent: Water
Measurement method: Flow cell method

Boron compound (B): 7.5 to 35.0%

The boron compound (B) enhances the adhesive property of the lubricant composition. The boron compound (B) also enhances the adhesive strength of the lubricating film by evaporation of moisture in the lubricant composition. This allows the oxide-based laminar compound (A) to be uniformly dispersed on the surface of the mandrel bar, thereby enhancing the adhesiveness of the lubricating film. In addition, the boron compound (B) enhances the lubricity of the lubricating film. Specifically, when the mandrel bar having the lubricating film which is formed as a result of the lubricant composition drying is inserted into a hollow shell having a high temperature (1050 to 1200°C), the boron compound (B) appropriately melts and provides a lubricating action. The fluid boron compound (B) also smoothly supplies the oxide-based laminar compound (A) to the entire interface between the surface of the mandrel bar and the inner surface of the hollow shell. As a result, the boron compound (B) enhances the lubricity of the lubricating film. If the content of the boron compound (B) is less than 7.5%, the aforementioned advantageous effects will not be sufficiently obtained.
On the other hand, if the content of the boron compound (B) is more than 35.0%, the boron compound (B) will impair the lubricity of the oxide-based laminar compound (A). As a result, the coefficient of friction of the lubricant composition will increase, and the lubricity of the lubricating film will, on the contrary, decrease. If the content of the boron compound (B) is more than 35.0%, furthermore, the drying property of the lubricant composition will decrease. Therefore, the content of the boron compound (B) is 7.5 to 35.0%.
A preferable lower limit of the content of the boron compound (B) is 10.0%, more preferably is 12.0%, and further preferably is 15.0%.
A preferable upper limit of the content of the boron compound (B) is 32.0%, more preferably is 30.0%, further preferably is 28.0%, and further preferably is 25.0%.
A preferable range of the content of the boron compound (B) is, for example, 10.0 to 32.0%, more preferably is 12.0 to 30.0%, further preferably is 15.0 to 28.0%, and further preferably is 15.0 to 25.0%.
The boron compound (B) is a compound in which boron and another element are chemically bonded. The boron compound (B) is, for example, one kind or more selected from the group consisting of boron oxide, an alkali metal borate, and an amine borate.
The alkali metal borate is a salt of boric acid and an alkali metal. The alkali metal borate is, for example, one kind or more selected from the group consisting of lithium borate, sodium borate, and potassium borate. Preferably, the alkali metal borate is potassium borate. In this case, the lubricity of the lubricant composition is more effectively enhanced. The amine borate is a salt of boric acid and an amine.
Preferably, the boron compound (B) is composed of one kind or more selected from boron oxide, lithium borate, sodium borate, potassium borate, and amine borate. When two or more types are contained, the mixing ratio thereof is not particularly limited.

Silane coupling agent (C): 0.3 to 5.0%

The silane coupling agent (C) enhances the dispersibility of each compound in the lubricant composition, thereby enhancing the adhesive property of the lubricant composition. The silane coupling agent (C) also enhances the drying property of the lubricant composition. In addition, the silane coupling agent (C) enhances the water resistance and adhesiveness of the lubricating film. Therefore, a strong lubricating film is formed from the lubricant composition. As a result, the lubricity of the lubricant composition is also enhanced. If the content of silane coupling agent (C) is less than 0.3%, the aforementioned advantageous effects will not be sufficiently obtained. Consequently, in some cases the lubricating film may peel off from the mandrel bar due to external forces and water during elongating. In such a case, the lubricity will decrease due to peeling of the lubricating film.
On the other hand, if the content of the silane coupling agent (C) is more than 5.0%, the excess silane coupling agent (C) will react with itself and form water-insoluble matter. The adhesive property of the lubricant composition will be reduced by the water-insoluble matter. In addition, the water resistance and adhesiveness of the lubricating film will decrease. As a result, lubricity will decrease due to peeling of the lubricating film. Further, the water-insoluble matter tends to precipitate, which reduces storage stability and causes clogging of a spray nozzle during an application process. Therefore, the content of the silane coupling agent (C) is 0.3 to 5.0%.
A preferable lower limit of the content of the silane coupling agent (C) is 0.4%, more preferably is 0.5%, and further preferably is 0.6%.
A preferable upper limit of the content of the silane coupling agent (C) is 4.0%, more preferably is 3.0%, and further preferably is 2.0%.
A preferable range of the content of the silane coupling agent (C) is, for example, 0.4 to 4.0%, more preferably is 0.5 to 3.0%, and further preferably is 0.6 to 2.0%.
The silane coupling agent (C) is represented by the chemical formula R_a-Si(OR_b)₃. R_a is, for example, one kind or more selected from the group consisting of an alkyl group, a vinyl group, an epoxy group, a styryl group, a methacryl group, an acryl group, an amino group, an isocyanurate group, a ureido group, a mercapto group, and an isocyanate group. Preferably, R_a is a methyl group or a 3-glycidoxypropyl group. In this case, the aforementioned advantageous effects of the silane coupling agent (C) are further enhanced. R_b is a methyl group or an ethyl group. Preferably, R_b is a methyl group, which increases the hydrolysis rate of the silane coupling agent (C). A preferable silane coupling agent (C) is composed of, for example, one kind or more selected from the group consisting of methyltrimethoxysilane and 3-glycidoxypropyltrimethoxysilane.

Water-soluble polymer (D): 0 to 7.0%

The water-soluble polymer (D) is a compound which can be optionally contained in the lubricant composition, and which does not have to be contained. That is, the content of the water-soluble polymer (D) may be 0%. When contained, the water-soluble polymer (D) adjusts the viscosity of the lubricant composition and enhances the adhesive property of the lubricant composition. The water-soluble polymer (D) also contributes to shortening the drying time of the lubricant composition, thereby enhancing the drying property. If even a small amount of the water-soluble polymer (D) is contained, the aforementioned advantageous effects will be obtained to a certain extent.
However, if the content of the water-soluble polymer (D) is more than 7.0%, the organic matter content in the lubricant composition will be excessively high. In such a case, in some cases carburizing may occur in the hollow shell during the process of producing a seamless metal pipe. In other words, the carburization resistance of the lubricant composition will decrease. Therefore, the content of the water-soluble polymer (D) is 0 to 7.0%.
A preferable lower limit of the content of the water-soluble polymer (D) is more than 0%, more preferably is 0.1%, further preferably is 0.2%, and further preferably is 0.3%.
A preferable upper limit of the content of the water-soluble polymer (D) is 6.5%, more preferably is 6.0%, and further preferably is 5.5%.
A preferable range of the content of the water-soluble polymer (D) is, for example, more than 0 to 6.5%, more preferably is 0.1 to 6.0%, further preferably is 0.2 to 5.5%, and further preferably is 0.3 to 5.5%.
The water-soluble polymer (D) is composed of one kind or more selected from the group consisting of natural, semi-natural, and synthetic water-soluble polymers. A single kind of water-soluble polymer may be used as the water-soluble polymer (D), or a plurality of kinds may be mixed and used.
The water-soluble polymer (D) is composed of, for example, one kind or more selected from a group consisting of a biogum, a natural polysaccharide, a cellulose derivative, a polyacrylate, an alginate, and an organic polymer.
The biogum is, for example, one kind or more selected from the group consisting of xanthan gum, welan gum, and rhamsan gum.
The natural polysaccharide is, for example, one kind or more selected from the group consisting of guar gum, locust bean gum, and carrageenan.
The cellulose derivative is, for example, one kind or more selected from the group consisting of methyl cellulose, ethyl cellulose, hydroxyethyl cellulose, hydroxyethyl methyl cellulose, hydroxypropyl methylcellulose, carboxymethyl cellulose and salts of these cellulose derivatives.
The organic polymer is, for example, one kind or more selected from the group consisting of acrylic resin, acrylic styrene resin, vinyl acetate resin, and polypropylene resin.

Impurities: 0 to 1.0%

Impurities do not have to be contained. That is the content of impurities may be 0%. Impurities are substances which are mixed in from raw materials or the like or which are unintentionally contained during the process of producing the lubricant composition. The impurities are, for example, one kind or more selected from the group consisting of graphite, iron oxide, silicon dioxide, calcium carbonate, titanium oxide, and molybdenum disulfide. Note that, compounds and the like other than the aforementioned compounds may also be contained as impurities.

[Balance of lubricant composition]

The lubricant composition contains the oxide-based laminar compound (A), the boron compound (B), and the silane coupling agent (C) that are described above, and may optionally contain the water-soluble polymer (D) and impurities, and the balance is water.

[(Feature 2) Regarding total content of oxide-based laminar compound (A) and boron compound (B)]

In the lubricant composition of the present embodiment, on the precondition that Feature 1 and Feature 3 are satisfied, in addition, the total content (A + B) of the oxide-based laminar compound (A) and the boron compound (B) is 17.5 to 65.0% by mass.
The total content (A + B) of the oxide-based laminar compound (A) and the boron compound (B) influences the adhesive property of the lubricant composition, and the lubricity and adhesiveness of the lubricating film.
If the total content (A + B) of the oxide-based laminar compound (A) and the boron compound (B) is less than 17.5%, a sufficient adhesive property will not be obtained in the lubricant composition and it will be difficult to cause the lubricant composition to sufficiently adhere to the mandrel bar. Furthermore, sufficient lubricity and sufficient adhesiveness will not be obtained in the lubricating film.
On the other hand, if the total content (A + B) of the oxide-based laminar compound (A) and the boron compound (B) is more than 65.0%, the flowability of the lubricant composition as a liquid will excessively decrease. In such a case, even when mixed with other compounds of the lubricant composition, it will not be possible to cause the respective compounds to uniformly disperse, and consequently the flowability of the lubricant composition will decrease.
Note that, if the flowability of the lubricant composition is low, even if spray application is possible, the lubricant composition will not be uniformly applied to the surface of the mandrel bar. In a case where the surface temperature of the mandrel bar is less than 100°C, and in particular is 80°C or less, the thickness of the lubricating film which is formed on the mandrel bar surface will be uneven, and the lubricating film will be partially thick. A thick portion of the lubricating film will not dry sufficiently, and will contain moisture. In this case, moisture in the thick portion of the lubricating film will bump during elongating, and the lubricating film will peel off. Consequently, the lubricity of the lubricating film will decrease. Further, in the lubricant composition applied by spray application, a thickly applied portion will have a large moisture content. Therefore, if the surface temperature of the mandrel bar is 100°C or more, bumping will occur at a thickly applied portion. In such a case, the lubricant film after drying will be porous. As a result, the water resistance and lubricity of the lubricating film will be reduced.
Therefore, the total content (A + B) of the oxide-based laminar compound (A) and the boron compound (B) is 17.5 to 65.0%.
A preferable lower limit of the total content (A + B) of the oxide-based laminar compound (A) and the boron compound (B) is 20.0%, more preferably is 25.0%, and further preferably is 30.0%.
A preferable upper limit of the total content (A + B) of the oxide-based laminar compound (A) and the boron compound (B) is 60.0%, more preferably is 55.0%, further preferably is 50.0%, further preferably is 45.0%, and further preferably is 40.0%.
A preferable range of the total content (A + B) of the oxide-based laminar compound (A) and the boron compound (B) is, for example, 20.0 to 60.0%, more preferably is 25.0 to 55.0%, further preferably is 30.0 to 50.0%, further preferably is 30.0 to 45.0%, and further preferably is 30.0 to 40.0%.

[(Feature 3) Regarding ratio (A/C) of content of oxide-based laminar compound (A) to content of silane coupling agent (C)]

In the lubricant composition of the present embodiment, on the precondition that Feature 1 and Feature 2 are satisfied, in addition, a ratio (A/C) of the content of the oxide-based laminar compound (A) to the content of the silane coupling agent (C) is 3.0 to 30.0.
The ratio (A/C) of the content of the oxide-based laminar compound (A) to the content of the silane coupling agent (C) influences the lubricity, water resistance, adhesiveness, and drying property of the lubricant composition. If the ratio (A/C) is less than 3.0, the content of the silane coupling agent (C) will be excessively large relative to the content of the oxide-based laminar compound (A). In such a case, the excess silane coupling agent (C) will react with itself and form water-insoluble matter. In this case, the action of the silane coupling agent (C) which causes the oxide-based laminar compound (A) to adhere to the mandrel bar will decrease, and water-insoluble matter will adhere to the mandrel bar. Consequently, the adhesiveness of the lubricating film containing the oxide-based laminar compound (A) will decrease and, as a result, the lubricity will also decrease.
On the other hand, if the ratio (A/C) is more than 30.0, the content of the silane coupling agent (C) will be excessively small relative to the content of the oxide-based laminar compound (A). In this case, the oxide-based laminar compound (A) will not sufficiently disperse in the lubricant composition. Consequently, when the lubricant composition is applied by spray application, the lubricant composition will not be uniformly applied to the surface of the mandrel bar. Therefore, in a case where the surface temperature of the mandrel bar is less than 100°C, and in particular is 80°C or less, the drying property of the lubricant composition will decrease. Further, if the surface temperature of the mandrel bar is 100°C or more, the adhesiveness of the lubricating film will decrease, and as a result, the lubricity will decrease. Therefore, the ratio (A/C) of the content of the oxide-based laminar compound (A) to the content of the silane coupling agent (C) is 3.0 to 30.0.
A preferable lower limit of the ratio (A/C) is 3.5, more preferably is 4.0, further preferably is 4.5, and further preferably is 5.0.
A preferable upper limit of the ratio (A/C) is 25.0, more preferably is 20.0, further preferably is 15.0, and further preferably is 12.5.
A preferable range of the ratio (A/C) is, for example, 3.5 to 25.0, more preferably is 4.0 to 20.0, further preferably is 4.5 to 15.0, and further preferably is 5.0 to 12.5.

[Advantageous effects of lubricant composition of present embodiment]

In the lubricant composition of the present embodiment, the organic matter content is very small. Therefore, the occurrence of carburizing that is attributable to organic matter during elongating using a mandrel mill can be sufficiently suppressed. In other words, sufficient carburization resistance is obtained in a lubricating film that is formed when the lubricant composition dries. Further, an excellent adhesive property and drying property are obtained in the lubricant composition. Therefore, in a case where the lubricant composition is applied to the surface of the mandrel bar at a temperature within the range of 60 to 150°C, a dense lubricating film with little variation in the film thickness can be formed in a short time. In addition, excellent lubricity, excellent adhesiveness, and excellent water resistance are obtained in the lubricating film.
When the lubricant composition of the present embodiment is used, carburizing is suppressed on the inner surface of the hollow shell, and furthermore, the occurrence of flaws attributable to scoring is suppressed. Therefore, it is not necessary to perform a repair process on a carburized layer or a flaw in the produced seamless metal pipe, and thus the care man-hours is significantly reduced.
As described above, in the lubricant composition of the present embodiment, an excellent adhesive property and an excellent drying property are obtained, and in a lubricating film formed when the lubricant composition dries, excellent carburization resistance, excellent lubricity, excellent adhesiveness, and excellent water resistance are obtained.

[Preferable viscosity of lubricant composition of present embodiment]

The viscosity of the lubricant composition of the present embodiment is not particularly limited. A preferable viscosity of the lubricant composition of the present embodiment is 500 to 2500 mPa·s.
If the viscosity of the lubricant composition is 500 mPa·s or more, in the lubricant composition that is stored in a container before use, acceleration of the settling velocity of the oxide-based laminar compound (A) can be sufficiently suppressed. Therefore, in the lubricant composition that is being stored, the oxide-based laminar compound (A) is less likely to settle, and the oxide-based laminar compound (A) is less likely to deposit at the bottom of the container.
Consequently, the lubricant composition can be smoothly discharged from the container when the lubricant composition is used. In addition, when the lubricant composition is applied by spraying onto the surface of a mandrel bar, the lubricant composition does not easily run off from the surface of the mandrel bar, and a markedly excellent adhesive property is obtained.
Further, if the viscosity of the lubricant composition is 2500 mPa·s or less, the lubricant composition will be easy to transfer and workability will be markedly enhanced. In addition, when applying the lubricant composition by spraying, the lubricant composition can be applied with an appropriate spray width. In other words, the adhesive property is markedly enhanced. Further, since an appropriate amount of the lubricant composition can be applied to the surface of the mandrel bar, the drying property is also markedly enhanced. In addition, even if the lubricant composition is splashed with roll cooling water from the mandrel mill or the like while drying, the lubricant composition does not easily run off from the surface of the mandrel bar, and thus water resistance is markedly enhanced. Furthermore, since the lubricant composition can be applied uniformly to the surface of the mandrel bar, the adhesiveness, water resistance, and lubricity of the lubricating film formed when the lubricant composition dries are markedly enhanced. Therefore, the preferable viscosity of the lubricant composition is 500 to 2500 mPa·s.
The viscosity of the lubricant composition can be adjusted by adjusting the content of each compound described above. Note that, the viscosity of the lubricant composition is measured using a B-type viscometer under conditions of a rotation speed of 60 rpm and a liquid temperature of 25°C. The value one minute after the start of measurement is regarded as the viscosity of the lubricant composition.

[Uses of lubricant composition of present embodiment]

The lubricant composition of the present embodiment is widely applicable to tools that come in contact with a workpiece during hot working. The lubricant composition of the present embodiment is also particularly suitable for application to tools used in hot working of a workpiece for which it is required to suppress the occurrence of carburizing. A workpiece for which it is required to suppress carburizing is a metallic material. Examples of the metallic material include a stainless steel material and an alloy material. For example, the metallic material is an austenitic stainless steel material or an Ni-based alloy.
The lubricant composition of the present embodiment is, in particular, suitable for production of a metal pipe (a steel pipe or an alloy pipe) using a Mannesmann-mandrel mill process. Note that, naturally, the lubricant composition of the present embodiment can also be used for hot working applications other than the Mannesmann-mandrel mill process for steel pipes made of low alloy steel or carbon steel for which it is required to suppress carburizing.

[Method for producing lubricant composition of present embodiment]

The lubricant composition of the present embodiment can be produced by the following method.
The oxide-based laminar compound (A), the boron compound (B), the silane coupling agent (C), and as required, the water-soluble polymer (D) are added to water in a manner so as to satisfy Feature 1 to Feature 3, and these components are mixed together. A slurry-like lubricant composition is produced by the above process.

[Method for producing seamless metal pipe of present embodiment]

A method for producing a seamless metal pipe using the lubricant composition of the present embodiment will now be described.
The method for producing a seamless metal pipe according to the present embodiment produces a seamless metal pipe by the Mannesmann-mandrel mill process. The method for producing a seamless metal pipe according to the present embodiment includes the following processes.

(Process 1) Application process
(Process 2) Drying process
(Process 3) Insertion process
(Process 4) Rolling process
(Process 5) Drawing process

Hereunder, each process is described.

[(Process 1) Application process]

In the application process, the lubricant composition of the present embodiment is applied to the surface of a mandrel bar whose surface temperature is 60 to 150°C. As described above, the lubricant composition of the present embodiment is excellent in an adhesive property. Therefore, the lubricant composition can be uniformly applied to the surface of the mandrel bar. The surface temperature of the mandrel bar may be 60 to 120°C. Note that, the mandrel bar is prepared as follows. The mandrel bar is drawn from a hollow shell after elongating. The surface temperature of the drawn mandrel bar is higher than 150°C. Therefore, the drawn mandrel bar is cooled with cooling water to lower the surface temperature to within the range of 60 to 150°C.
The method of applying the lubricant composition is not particularly limited, and a known method may be employed as appropriate. For example, the lubricant composition is applied by spraying. For example, an airless spray is used for the spray application. In the case of using an airless spray, for example, the discharge pressure is 0.1 to 10 MPa and the spray angle is 30 to 150°. The distance from the opening of the nozzle to the surface of the mandrel bar is, for example, 50 to 500 mm.
When applying the lubricant composition by spraying, the lubricant composition may be applied to the surface of the mandrel bar while the spray applicator or the mandrel bar moves relatively in the axial direction of the mandrel bar. In this case, the relative speed is, for example, 0.5 to 5.0 m/s. Preferably, the lubricant composition is applied to the surface of the mandrel bar by fixing the spray applicator and moving the mandrel bar.

[(Process 2) Drying process]

The drying process is performed after the application process. In the drying process, the lubricant composition applied to the surface of the mandrel bar in the application process is dried to form a lubricating film. Specifically, after applying the lubricant composition to the mandrel bar, the mandrel bar is left in place. The drying time is, for example, less than 60 seconds, and preferably is less than 40 seconds. A lower limit of the drying time is, for example, 30 seconds. The lubricant composition of the present embodiment is excellent in a drying property. Therefore, the lubricant composition dries in a short time and a lubricating film is formed.

[(Process 3) Insertion process]

The insertion process is performed after the drying process. In the insertion process, the mandrel bar on which the lubricating film is formed is inserted into a hollow shell. The hollow shell is a material for a seamless metal pipe, and the hollow shell is produced by the following well-known method.
A round billet that is a material for a hollow shell is heated in a reheating furnace. The heated round billet is subjected to piercing-rolling using a piercing-rolling mill. A hollow shell is produced by performing the piercing-rolling on the round billet. The hollow shell is a hollow shell that has a through-hole in the axial direction. At such time, the mandrel bar is inserted into the hollow shell until the front end of the mandrel bar projects out from the front end of the hollow shell.
The temperature of the hollow shell in the insertion process is 1050 to 1200°C. That is, the temperature of the hollow shell after the piercing-rolling and immediately before the mandrel bar is inserted is 1050 to 1200°C. When the mandrel bar is inserted into the through-hole of the hollow shell that is at the aforementioned high temperature, the temperature of the surface of the mandrel bar rapidly increases. If drying of the lubricant composition is insufficient at the time when the mandrel bar is inserted, in some cases a lubricant composition portion where the drying is insufficient may bump, and may peel off from the surface of the mandrel bar. However, the lubricant composition of the present embodiment is excellent in a drying property. Therefore, bumping of the lubricant composition is sufficiently suppressed in the insertion process.

[(Process 4) Rolling process]

The rolling process is performed after the insertion process. In the rolling process, the hollow shell in which the mandrel bar has been inserted is subjected to elongating using a mandrel mill. The mandrel mill includes a plurality of roll stands arranged in a row. The number of roll stands is not particularly limited. The number of roll stands is, for example, five to nine stands. Each roll stand includes a plurality of rolling rolls. At the plurality of roll stands of the mandrel mill, the hollow shell is subjected to rolling by the rolling rolls. At such time, the mandrel bar is already inserted inside the hollow shell. Therefore, the hollow shell is subjected to rolling by the rolling rolls in a state in which the hollow shell is sandwiched between the rolling rolls and the mandrel bar.
In the rolling process, in order to cool the rolling rolls of the mandrel mill, roll cooling water is sprayed onto the rolling rolls during elongating. In some cases the roll cooling water adheres to the surface of the mandrel bar. The lubricating film formed by the lubricant composition of the present embodiment is excellent in water resistance. Consequently, even if roll cooling water adheres to the lubricating film formed on the mandrel bar surface, the lubricating film does not easily fall off from the mandrel bar surface. Therefore, in the drawing process that is the next process, the mandrel bar can be easily drawn from the workpiece while retaining the lubricating film on the mandrel bar surface.

[(Process 5) Drawing process]

The drawing process is performed after the rolling process. In the drawing process, a well-known method is used to draw the mandrel bar from the hollow shell for which elongating has been completed. As described above, the lubricating film formed by the lubricant composition has excellent water resistance. Therefore, even if roll cooling water adheres to the lubricating film during the rolling process, the lubricating film will not easily peel off from the surface of the mandrel bar. Therefore, when drawing the mandrel bar from the hollow shell after elongating also, the lubricating film sufficiently remains on the surface of the mandrel bar. As mentioned above, the lubricating film is also excellent in lubricity. As a result, in the drawing process, the mandrel bar can be easily drawn from the hollow shell. Note that, the drawn mandrel bar is reused after being cooled with cooling water as described above.
A seamless metal pipe can be produced by performing the above processes. Note that, diameter adjusting rolling may be performed on the hollow shell after the drawing process to produce a seamless metal pipe. For example, a stretch reducer or a sizer is used to perform the diameter adjusting rolling. The seamless metal pipe may also be subjected to a surface treatment such as descaling. The produced seamless metal pipe may be cut to a desired length in accordance with the purpose.

[Advantageous effects of production method of present embodiment]

In the method for producing a seamless metal pipe of the present embodiment, the lubricant composition of the present embodiment described above is used. The lubricant composition of the present embodiment is excellent in an adhesive property and a drying property. Therefore, in the application process, it is possible to uniformly apply the lubricant composition to the surface of the mandrel bar, and in the drying process the lubricant composition dries in a short time to form a lubricating film. In addition, the lubricating film formed from the lubricant composition is excellent in adhesiveness, water resistance, and lubricity. Therefore, during the period from the insertion process to the drawing process, the lubricating film is sufficiently adhered to the surface of the mandrel bar and does not easily peel off. As a result, during the period from the insertion process to the drawing process, the occurrence of scoring due to contact between the mandrel bar surface and the inner surface of the hollow shell can be sufficiently suppressed.
Further, the content of organic matter in the lubricant composition of the present embodiment is small. Therefore, the lubricating film formed by the lubricant composition is excellent in carburization resistance. As a result, the occurrence of carburizing on the inner surface of the hollow shell during elongating can be sufficiently suppressed.
In addition, as described above, because the lubricating film is excellent in lubricity, the occurrence of flaws attributable to scoring on the inner surface of the hollow shell during elongating can be sufficiently suppressed. In a case where a carburized layer or a flaw attributable to scoring is formed on a seamless metal pipe, it is necessary to carry out a repair process to remove the carburized layer or scoring. However, in the production method of the present embodiment, the occurrence of a carburized layer or the occurrence of flaws attributable to scoring can be sufficiently suppressed. Therefore, the time required to perform the aforementioned repair process can be reduced or a repair process can be made unnecessary.

EXAMPLES

Various lubricant compositions were prepared, and the properties of the lubricant compositions were evaluated by the following methods.

[Preparation of lubricant compositions]

Lubricant compositions were prepared by mixing the compounds described in Examples 1 to 16 and Comparative Examples 1 to 21 that are described in Table 1 to Table 4. The respective compounds described in Table 1 to Table 4 were as follows. The unit of the numerical value of each compound described in Table 1 to Table 4 is mass percent.

[Oxide-based laminar compound (A)]

The following compounds were used as the oxide-based laminar compound (A).

Oxide-based laminar compound (a): sodium tetrasilicic mica
Oxide-based laminar compound (b): potassium tetrasilicic mica
Oxide-based laminar compound (c): natural muscovite
Oxide-based laminar compound (d): natural phlogopite

The average particle size of the oxide-based laminar compound (A) was 30 µm in each of (a) to (d).
Note that, in Comparative Example 2 and Comparative Example 5, graphite having an average particle size of 30 µm was used instead of the oxide-based laminar compound (A).

[Boron compound (B)]

The following compounds were used as the boron compound (B).

Boron compound (a): potassium borate
Boron compound (b): amine borate
Boron compound (c): boron oxide
Boron compound (d): sodium borate

[Silane coupling agent (C)]

Methyltrimethoxysilane was used as the silane coupling agent (C).

[Water-soluble polymer (D)]

The following compounds were used as the water-soluble polymer (D).

Water-soluble polymer (a): xanthan gum
Water-soluble polymer (b): sodium carboxymethyl cellulose
Water-soluble polymer (c): acrylic resin
Water-soluble polymer (d): acrylic styrene resin
Water-soluble polymer (e): vinyl acetate resin
Water-soluble polymer (f): polypropylene resin

[Solvent]

Water was used as the solvent.
In each Example and Comparative Example, the compounds described in Table 1 to Table 4 were mixed to prepare a lubricant composition. The aforementioned mixing was performed using a propeller stirrer.

[Regarding evaluation tests]

The following evaluation tests were performed in the lubricant composition of each Example and Comparative Example.

(Test 1) Test to evaluate whether it is possible to prepare lubricant composition
(Test 2) Lubricity evaluation test
(Test 3) Carburization resistance evaluation test
(Test 4) Adhesive property evaluation test
(Test 5) Water resistance evaluation test
(Test 6) Adhesiveness evaluation test
(Test 7) Drying property evaluation test

Hereunder, Test 1 to Test 7 are described.

[(Test 1) Test to evaluate whether it is possible to prepare lubricant composition]

In the aforementioned [Preparation of lubricant compositions], whether or not a lubricant composition could be successfully prepared was evaluated by determining whether or not the respective compounds could be mixed. If the respective compounds could be mixed, it was determined that the lubricant composition could be successfully prepared (indicated by "E (Excellent)" in the column "Preparation" in Table 1 to Table 4). On the other hand, in a case where the result of attempting to mix the respective compounds was that the compounds could not be mixed because the viscosity was too high, it was determined that the lubricant composition could not be prepared (indicated by "NA (Not Accepted)" in the column "Preparation" in Table 1 to Table 4). Note that, the tests from Test 2 onward were not conducted for those Comparative Examples in which it was determined that the lubricant composition could not be prepared.

[(Test 2) Lubricity evaluation test]

The following method for producing a seamless metal pipe was carried out using the lubricant composition of each Example and Comparative Example, and the lubricity of each lubricant composition was evaluated.
The material of the mandrel bar was SKD61 defined in the JIS Standard. The diameter of the mandrel bar was 140.5 mm, and the effective portion length was 18 m.
The aforementioned mandrel bar which used in elongating of a plurality of carbon steel pipes was allowed to cool until the surface temperature of the mandrel bar became 80 to 100°C. The lubricant composition was applied by spraying to the surface of the mandrel bar whose surface temperature was 80 to 100°C (application process). The coating mass of the lubricating film was adjusted so as to be 40 g/m². After the application process, the lubricant composition was dried for 40 seconds (drying process). Specifically, the mandrel bar to which the lubricant composition was applied was left in place in an air atmosphere for 40 seconds.
A hollow shell as the workpiece was prepared by the following method.
The material of the hollow shell was SUS304L defined in the JIS Standard. A round billet serving as a material for the hollow shell was subjected to piercing-rolling using a inclined roll piercing mill, and a hollow shell was obtained. The hollow shell after the piercing-rolling had an outer diameter of 181.0 mm, a wall thickness of 16.0 mm, and a length of 7000 mm.
The mandrel bar after the drying process was inserted into the prepared hollow shell (insertion process). The hollow shell with the mandrel bar inserted therein was subjected elongating using a mandrel mill composed of a roll stand with seven stands (rolling process). The hollow shell after the elongating had an outer diameter of 151.0 mm, a wall thickness of 5.0 mm, and a length of 25300 mm. Note that, the temperature of the hollow shell immediately before the rolling process was 1050 to 1200°C. The mandrel bar was drawn from the hollow shell after the elongating was completed (drawing process).
The total rolling load ΣPi of the seven stands of the mandrel mill in the aforementioned rolling process was determined. Further, a thrust force F of the mandrel bar relative to ΣPi was determined. A coefficient of friction F/ΣPi during elongating was calculated based on the rolling load ΣPi and the thrust force F. The lubricity was evaluated as follows based on the obtained coefficient of friction F/ΣPi.

E (Excellent): Coefficient of friction F/ΣPi is 0.045 or less.
G (Good): Coefficient of friction F/ΣPi is more than 0.045 and 0.060 or less.
NA (Not Accepted): Coefficient of friction F/ΣPi is more than 0.060.

The evaluation results are shown in the column "Lubricity" in Table 1 to Table 4.

[(Test 3) Carburization resistance evaluation test]

The carburization resistance of the lubricant composition of each Example and Comparative Example was evaluated by the following method.
The hollow shell after the elongating performed in the above [(Test 2) Lubricity evaluation test] was subjected to diameter adjusting rolling using a stretch reducer composed of 26 roll stands to produce a seamless metal pipe. The produced seamless metal pipe had an outer diameter of 63.5 mm, a wall thickness of 7.0 mm, and a length of 40000 mm. Note that, the temperature of the hollow shell during the diameter adjusting rolling was about 1000°C.
An arc-shaped plate material that included the inner surface of the pipe was taken from the produced seamless metal pipe. The taken plate material was subjected to hammering to process the plate material into a flat test specimen having a wall thickness of 5.0 mm, a width of 25 mm, and a length of 50 mm. A sulfuric acid-copper sulfate corrosion test defined in JIS G 0575: 2012 was conducted using the flat test specimen, and whether or not intergranular corrosion cracking occurred on a surface of the flat test specimen corresponding to the inner surface of the seamless metal pipe was inspected by visual observation. The carburization resistance was evaluated as follows based on whether intergranular corrosion cracking was present or absent.

E: No intergranular corrosion cracking present
NA: Intergranular corrosion cracking present

The evaluation results are shown in the column "Carburization Resistance" in Table 1 to Table 4.

[(Test 4) Adhesive property evaluation test]

The adhesive property of the lubricant composition of each Example and Comparative Example was evaluated by the following method.
Test specimens composed of SKD61 defined in the JIS Standard were prepared to simulate a mandrel bar. Each test specimen had a width of 65 mm, a length of 120 mm, and a thickness of 30 mm.
After the test specimens were heated to a temperature of 60°C, 80°C, 100°C, and 120°C, respectively, the test specimen at each temperature was subjected to the following adhesive property evaluation test.
The test specimen was set on a pendulum-type support rod. The test specimen was passed at a speed of 2 m/s through a region where the lubricant composition was being sprayed by a spray applicator. The spray conditions of the spray applicator used were as follows.

(Test conditions)

Spray method: Airless spray
Discharge pressure: 3.0 MPa
Spray angle: 90°
Spray distance (distance from nozzle to test specimen): 200 mm
Test specimen temperatures: 60°C, 80°C, 100°C, 120°C
Nozzle: 1/4MVVP5010 (manufactured by H. Ikeuchi & Co., Ltd.)

After the lubricant composition that was applied to the test specimen after passing through the spraying region had completely dried, a polypropylene sheet of 50 mm in width × 50 mm in length was overlaid at the center position of the surface (65 mm × 120 mm) of the test specimen on which the lubricant composition was applied. The polypropylene sheet was marked with 10 squares (5 mm × 5 mm per square) in the width direction and the longitudinal direction, respectively.
The region where the polypropylene sheet was overlaid was inspected by visual observation. Among the 100 squares, the number of squares in which the lubricating film was not formed over the entire area inside the square and the base metal of the test specimen was exposed even a little was counted. The ratio of the number of counted squares to the total number of square (100) was taken as a lubricating film non-formation ratio (%).
After determining the lubricating film non-formation ratio, all of the lubricating film formed on the test specimen was removed using a cutter. The mass of the entire lubricating film that was removed was determined. The coating mass (g/m²) of the lubricating film was determined by dividing the obtained mass of the lubricating film by the surface area (0.0078 m²) of the test specimen.
The adhesive property was evaluated as follows based on the lubricating film non-formation ratio and the coating mass.
E: At all of the temperature conditions 60°C, 80°C, 100°C, and 120°C, the lubricating film non-formation ratio was less than 5% and the coating mass was 40 g/m² or more.
G: At any of the temperature conditions, the lubricating film non-formation ratio was 5% or more and less than 15% and the coating mass was 40 g/m² or more.
NA: At any of the temperature conditions, the lubricating film non-formation ratio was 15% or more or the coating mass was less than 40 g/m².
The evaluation results are shown in the column "Adhesive Property" in Table 1 to Table 4.

[(Test 5) Water resistance evaluation test]

The water resistance of the lubricant composition of each Example and Comparative Example was evaluated by the following method.
Test specimens that were made of the same material and with the same dimensions as the test specimens used in the aforementioned [(Test 4) Adhesive property evaluation test] were prepared. The lubricant composition was applied to the surface of each test specimen by spraying under the same conditions as in [(Test 4) Adhesive property evaluation test], and thereafter the lubricant composition was completely dried to form a lubricating film.
After the lubricant composition was completely dried to form a lubricating film, the test specimens were reheated to a test specimen temperature at the time of the spray application (one of 60°C, 80°C, 100°C, and 120°C). The reheated test specimens were then passed at a speed of 2 m/s through a spraying region where water was sprayed under the test conditions shown below. Each of the test specimens was passed through the spraying region three times.

(Test conditions)

Spray method: Airless spray
Discharge pressure: 0.2 MPa
Spray angle: 90°
Spray distance (distance from nozzle to test specimen): 200 mm
Test specimen temperatures: 60°C, 80°C, 100°C, 120°C
Nozzle: 1/2MVVP501000 (manufactured by H. Ikeuchi & Co., Ltd.)

A polypropylene sheet that was the same as the polypropylene sheet used in [(Test 4) Adhesive property evaluation test] was overlaid at the center position of a surface of 65 mm in width × 120 mm in length of the test specimen before the test. The region where the polypropylene sheet was overlaid was inspected by visual observation. Among the 100 squares, squares in which the lubricating film was formed over the entire area inside the square were identified.
A polypropylene sheet that was the same as the polypropylene sheet used in [(Test 4) Adhesive property evaluation test] was overlaid at the center position of the surface of 65 mm in width × 120 mm in length of the test specimen after the test. At such time, the region where the polypropylene sheet was overlaid was the same as the region where the polypropylene sheet was overlaid before the test. The region where the polypropylene sheet was overlaid was inspected by visual observation. Among the 100 squares, with respect to the squares identified before the test, if one half or more of the lubricating film remained in the area inside the square, it was determined that the lubricating film remained. The squares where it was determined that the lubricating film remained were counted.
The ratio of the total number of squares where it was determined that the lubricating film remained after the test to the total number of squares where it was determined that the lubricating film was formed over the entire area inside the square before the test was defined as a lubricating film residual ratio (%).
The water resistance was evaluated as follows based on the obtained lubricating film residual ratio.
E: At all of the temperature conditions 60°C, 80°C, 100°C, and 120°C, the lubricating film residual ratio was 70% or more.
G: At any of the temperature conditions, the lubricating film residual ratio was 50% or more and less than 70%.
NA: At any of the temperature conditions, the lubricating film residual ratio was less than 50%.
The evaluation results are shown in the column "Water Resistance" in Table 1 to Table 4.

[(Test 6) Adhesiveness evaluation test]

The adhesiveness of the lubricant composition of each Example and Comparative Example was evaluated by the following method.
Test specimens that were made of the same material and with the same dimensions as the test specimens used in the aforementioned [(Test 4) Adhesive property evaluation test] were prepared. The lubricant composition was applied to the surface of each test specimen by spraying under the same conditions as in [(Test 4) Adhesive property evaluation test], and thereafter the lubricant composition was completely dried to form a lubricating film.
A polypropylene sheet that was the same as the polypropylene sheet used in [(Test 4) Adhesive property evaluation test] was overlaid at the center position of a surface of 65 mm in width × 120 mm in length of the test specimen before the test. The region where the polypropylene sheet was overlaid was inspected by visual observation. Among the 100 squares, squares in which the lubricating film was formed over the entire area inside the square were identified.
The blade surface of a cutter was pressed with a constant load against the formed lubricating film, and the entire area from one end to the other end in the longitudinal direction of the test specimen was rubbed one time. This operation was performed on the entire surface of the lubricating film. The load applied to the cutter was the same in each Example and Comparative Example.
After rubbing the blade surface of the cutter over the entire surface of the lubricating film, a polypropylene sheet that was the same as the polypropylene sheet used in [(Test 4) Adhesive property evaluation test] was overlaid at the center position of a surface of 65 mm in width × 120 mm in length of the test specimen. At such time, the region where the polypropylene sheet was overlaid was the same as the region where the polypropylene sheet was overlaid before the test. The region where the polypropylene sheet was overlaid was inspected by visual observation. Among the squares identified before the test, if even a small amount of the lubricating film was peeled off within a square, it was determined that the lubricating film had peeled off. The squares where it was determined that the lubricating film had peeled off were counted. The ratio of the number of squares that was counted to the total number of squares where it was determined that the lubricating film was formed over the entire area inside the square before the test was defined as a lubricating film peeling ratio (%).
The adhesiveness was evaluated as follows based on the obtained lubricating film peeling ratio.
E: At all of the temperature conditions 60°C, 80°C, 100°C, and 120°C, the lubricating film peeling ratio was 0%.
G: At any of the temperature conditions, the lubricating film peeling ratio was more than 0% and less than 5%.
NA: At any of the temperature conditions, the lubricating film peeling ratio was 5% or more.
The evaluation results are shown in the column "Adhesiveness" in Table 1 to Table 4.

[(Test 7) Drying property evaluation test]

The drying property of the lubricant composition of each Example and Comparative Example was evaluated by the following method.
Test specimens that were made of the same material and with the same dimensions as the test specimens used in the aforementioned [(Test 4) Adhesive property evaluation test] were prepared. The lubricant composition was applied to the surface of each test specimen by spraying under the same conditions as in [(Test 4) Adhesive property evaluation test], and thereafter the lubricant composition was completely dried to form a lubricating film. Note that, in the present test, the temperature of the test specimen was made 80°C.
In the above test, the drying time taken until the entire area of the lubricant composition completely dried to become a lubricating film after the lubricant composition was applied by spraying was determined. Here, the completion of drying was confirmed by visual inspection. The drying property was evaluated as follows based on the obtained drying time.

E: Drying time was less than 40 seconds
G: 40 seconds or more and less than 60 seconds
NA: 60 seconds or more

The evaluation results are shown in the column "Drying Property" in Table 1 to Table 4.

[Table 1]

TABLE 1

Components (Unit Is Mass%)		Comparati ve Example 1	Comparati ve Example 2	Comparati ve Example 3	Comparati ve Example 4	Comparati ve Example 5	Comparati ve Example 6	Comparati ve Example 7	Comparati ve Example 8	Comparati ve Example 9
Oxide-Based Laminar Compou nd (A)	Oxide-Based Laminar Compou nd (a)	10.0	-	10.0	20.0	-	25.0	-	-	20.0
Graphite		-	30.0	-	-	25.0	-	-	-	-
Boron Compou nd (B)	Boron Compou nd (a)	-	-	-	5.0	2.0	-	20.0	-	-
Boron Compou nd (B)	Boron Compou	3.0	-	1.0	15.0	-	-	-	-	-
	nd (b)
	Boron Compou nd (c)	-	-	3.0	-	-	-	-	-	-
	Boron Compou nd (d)	-	-	3.0	-	-	-	-	-	-
Silane Coupling Agent (C)		-	-	-	-	-	-	-	2.0	2.0
Water-Soluble Polymer (D)	Water-Soluble Polymer (a)		-	-	0.1	0.1	-	-	-	-
	Water-Soluble Polymer (b)		-	-	1.0	1.0	-	-	-	-
	Water-Soluble Polymer (c)	-	5.4	-	-	-	-	-	-	-
	Water-Soluble Polymer (d)
	Water-Soluble Polymer (e)	-	-	-	-	10.0	-	-	-	-
	Water-Soluble Polymer (f)	-	1.3	-	-	-	-	-	-	-
Water		87.0	63.3	83.0	58.9	61.9	75.0	80.0	98.0	78.0
(A)+(B)		13.0	0	17.0	40.0	2.0	25.0	20.0	0	20.0
(A)/(C)		0	0	0	0	0	0	0	0	10.0
Preparation		E	E	E	E	E	E	E	E	E
Lubricity		NA	NA	NA	NA	NA	NA	NA	NA	NA
Carburization Resistance		E	NA	E	E	NA	E	E	E	E
Adhesive Property		NA	G	NA	NA	E	NA	G	NA	NA
Water Resistance		NA	G	NA	NA	E	NA	NA	E	E
Adhesiveness		NA	NA	NA	NA	NA	NA	E	NA	NA
Drying Property		NA	NA	NA	NA	NA	E	NA	G	E

[Table 2]

TABLE 2

Components (Unit Is Mass%)		Compar ative Exampl e 10	Compar ative Exampl e 11	Compar ative Exampl e 12	Compar ative Exampl e 13	Compar ative Exampl e 14	Compar ative Exampl e 15	Compar ative Exampl e 16	Compar ative Exampl e 17	Compar ative Exampl e 18	Compar ative Exampl e 19	Compar ative Exampl e 20	Compar ative Exampl e 21
Oxide-Based Lamin ar Comp ound	Oxide-Based Lamin ar Comp ound	15.0	-	50.0	10.0	15.0	15.0	40.0	15.0	10.0	35.0	10.0	20.0
(A)	(a)
Graphite		-	-	-	-	-	-	-	-	-	-	-	-
Boron Comp ound (B)	Boron Comp ound (a)	15.0	20.0	20.0	5.0	15.0	8.0	35.0	8.0	45.0	35.0	10.0	20.0
	Boron Comp ound (b)	-	-	-	-	-	8.0	-	8.0	-	-	-	-
	Boron Comp ound (c)
	Boron Comp ound (d)
Silane Coupling Agent (C)		-	2.0	2.0	2.0	2.0	10.0	2.0	0.1	2.0	2.0	5.0	0.5
Water-Solubl e Polym er (D)	Water-Solubl e Polym er (a)	0.1	-	-	-	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1
	Water-Solubl e Polym er (b)	1.0	-	-	-	1.0	1.0	1.0	1.0	1.0	-	1.0	1.0
	Water-Solubl e Polym er (c)	-	-	-	-	-	-	-	-	-	-	-	-
	Water-Solubl e Polym er (d)	-	-	-	-	15.0	-	-	-	-	-	-	-
	Water-Solubl e Polym er (e)	-	-	-	-	-	-	-	-	-	-	-	-
	Water-Solubl e Polym er (f)	-	-	-	-	-	-	-	-	-	-	-	-
Water		68.9	78.0	28.0	83.0	51.9	57.9	21.9	67.8	41.9	27.9	73.9	58.4
(A)+(B)		30.0	20.0	70.0	15.0	30.0	31.0	75.0	31.0	55.0	70.0	20.0	40.0
(A)/(C)		0	0	25.0	5.0	7.5	1.5	20.0	150.0	5.0	17.5	2.0	40.0
Preparation		E	E	NA	E	E	E	NA	E	E	E	E	E
Lubricity		NA	NA	-	NA	E	NA	-	NA	NA	NA	NA	NA
Carburization Resistance		E	E	-	E	NA	E	-	E	E	E	E	E
Adhesive Property		NA	G	-	NA	E	NA	-	NA	E	G	G	E
Water Resistance		NA	NA	-	G	E	NA	-	NA	G	NA	G	G
Adhesiveness		NA	E	-	NA	E	NA	-	NA	E	G	NA	NA
Drying		NA	NA	-	G	E	E	-	NA	NA	G	G	NA
Property

[Table 3]

TABLE 3

Components (Unit Is Mass%)		Example 1	Example 2	Example 3	Example 4	Example 5	Example 6	Example 7
Oxide-Based Laminar Compound (A)	Oxide-Based Laminar Compound (a)	10.0	15.0	-	-	-	30.0	40.0
	Oxide-Based Laminar Compound (b)	-	-	15.0	-	-	-	-
	Oxide-Based Laminar Compound (c)		-	-	15.0	-	-	-
	Oxide-Based Laminar Compound (d)	-	-	-	-	15.0	-	-
Graphite		-	-	-	-	-	-	-
Boron Compound (B)	Boron Compound (a)	7.5	8.0	8.0	8.0	8.0	35.0	25.0
Boron Compound (B)	Boron Compound (b)	-	8.0	8.0	8.0	8.0	-	-
Silane Coupling Agent (C)		2.0	2.0	2.0	2.0	2.0	2.0	2.0
Water-Soluble Polymer (D)	Water-Soluble Polymer (a)	0.1	0.1	0.1	0.1	0.1	0.1	0.1
	Water-Soluble Polymer (b)	1.0	1.0	1.0	1.0	1.0	0.5	0.5
	Water-Soluble Polymer (d)	-	-	-	-	-	-	-
Water		79.4	65.9	65.9	65.9	65.9	32.4	32.4
(A)+(B)		17.5	31.0	31.0	31.0	31.0	65.0	65.0
(A)/(C)		5.0	7.5	7.5	7.5	7.5	15.0	20.0
Preparation		E	E	E	E	E	E	E
Lubricity		G	E	E	G	E	G	G
Carburization Resistance		E	E	E	E	E	E	E
Adhesive Property		E	E	E	E	E	G	G
Water Resistance		G	E	E	E	E	G	G
Adhesiveness		G	E	E	E	E	G	G
Drying Property		E	E	E	E	E	G	G

[Table 4]

TABLE 4

Components (Unit Is Mass%)		Example 8	Example 9	Example 10	Example 11	Example 12	Example 13	Example 14	Example 15	Example 16
Oxide-Based Laminar Compound (A)	Oxide-Based Laminar Compound (a)	15.0	15.0	15.0	25.0	15.0	15.0	15.0	15.0	15.0
	Oxide-Based Laminar Compound (b)	-	-	-	-	-	-	-	-	-
	Oxide-Based Laminar
	Compound (c)
	Oxide-Based Laminar Compound (d)	-	-	-	-	-	-	-	-	-
Graphite		-	-	-	-	-	-	-	-	1.0
Boron Compound (B)	Boron Compound (a)	8.0	8.0	5.0	20.0	8.0	8.0	8.0	8.0	8.0
Boron Compound (B)	Boron Compound (b)	8.0	8.0	5.0	5.0	8.0	8.0	8.0	8.0	8.0
Silane Coupling Agent (C)		5.0	3.0	2.0	2.0	1.0	0.5	0.5	2.0	2.0
Water-Soluble Polymer (D)	Water-Soluble Polymer (a)	0.1	0.1	0.1	0.1	0.1	0.1	-	-	0.1
	Water-Soluble Polymer (b)	1.0	1.0	1.0	1.0	1.0	1.0	1.0	-	1.0
	Water-Soluble Polymer (d)	-	-	-	-	-	-	6.0	-	-
Water		62.9	64.9	71.9	46.9	66.9	67.4	61.5	67.0	64.9
(A)+(B)		31.0	31.0	25.0	50.0	31.0	31.0	31.0	31.0	31.0
(A)/(C)		3.0	5.0	7.5	12.5	15.0	30.0	30.0	7.5	7.5
Preparation		E	E	E	E	E	E	E	E	E
Lubricity		G	E	E	E	E	G	G	E	E
Carburization Resistance		E	E	E	E	E	E	E	E	E
Adhesive Property		E	E	E	E	E	G	G	G	E
Water Resistance		G	E	E	E	E	G	G	E	E
Adhesiveness		G	E	E	E	E	G	G	E	G
Drying Property		E	E	E	E	G	G	G	G	E

[Regarding evaluation results of Test 1 to Test 7]

In Table 1 to Table 4, the symbol "-" indicates that the corresponding compound was not contained, or that the evaluation tests from Test 2 onward were not carried out because the result of [(Test 1) Test to evaluate whether it is possible to prepare lubricant composition] was "NA".
Referring to Table 1 to Table 4, the lubricant compositions of Examples 1 to 15 satisfied Feature 1 to Feature 3. Therefore, the lubricant compositions of these examples sufficiently suppressed carburizing on the hollow shell. It is considered that the reason is that these examples did not contain graphite and the content of organic matter was extremely small. Furthermore, these examples achieved excellent lubricity, adhesive property, adhesiveness, water resistance, and drying property.
In addition, although the lubricant composition of Example 16 contained graphite as an impurity, the lubricant composition satisfied Feature 1 to Feature 3. Therefore, the lubricant composition of Example 16 sufficiently suppressed carburizing on the hollow shell. Furthermore, Example 16 achieved excellent lubricity, adhesive property, adhesiveness, water resistance, and drying property.
In particular, in Examples 2 to 5, 9 to 12, 15, and 16, the total content (A + B) of the oxide-based laminar compound (A) and the boron compound (B) was 25.0 to 50.0, and furthermore, the ratio (A/C) of the content of the oxide-based laminar compound (A) to the content of the silane coupling agent (C) was 5.0 to 15.0. Therefore, in these examples the evaluation "E" was determined for four or more among lubricity, carburization resistance, adhesive property, adhesiveness, water resistance, and drying property, which was superior in comparison to the other examples (Example 1, 6 to 8, 13, and 14).
Note that, in Examples 1 to 16, the viscosity of the lubricant composition was 500 to 2500 mPa·s.
On the other hand, in Comparative Examples 1, 3, and 6, the content of the boron compound (B) and the content of the silane coupling agent (C) were too low. Therefore, the result was "NA" for at least one evaluation among the evaluation items, and sufficient properties were not obtained.
Comparative Example 2 did not contain the oxide-based laminar compound (A), and instead contained graphite. Consequently, sufficient carburization resistance was not obtained. In addition, the contents of the boron compound (B) and the silane coupling agent (C) were too low. Therefore, at least one evaluation among the evaluation items was "NA".
In Comparative Examples 4, 10, and 17, the content of the silane coupling agent (C) was too low. Consequently, a sufficient adhesive property and a sufficient drying property were not obtained in the lubricant compositions, and sufficient water resistance and adhesiveness were also not obtained in the lubricating film. As a result, sufficient lubricity was also not obtained.
Comparative Example 5 did not contain the oxide-based laminar compound (A), and instead contained graphite. Consequently, sufficient carburization resistance was not obtained. In addition, the contents of the boron compound (B) and the silane coupling agent (C) were too low. Furthermore, the content of the water-soluble polymer (D) was too high. Therefore, at least one evaluation among the evaluation items was "NA".
In Comparative Example 7, the content of the oxide-based laminar compound (A) and the content of the silane coupling agent (C) were too low. Therefore, at least one evaluation among the evaluation items was "NA".
In Comparative Example 8, the contents of the oxide-based laminar compound (A) and the boron compound (B) were too low. Therefore, sufficient lubricity, a sufficient adhesive property, and sufficient adhesiveness were not obtained.
In Comparative Examples 9 and 13, the content of the boron compound (B) was too low. Therefore, sufficient lubricity, a sufficient adhesive property, and sufficient adhesiveness were not obtained.
In Comparative Example 11 the content of the oxide-based laminar compound (A) was too low. Therefore, sufficient lubricity and a sufficient drying property were not obtained. In addition, because the lubricant composition was composed of the boron compound (B) and the silane coupling agent (C), water resistance was not obtained.
In Comparative Example 12, the content of the oxide-based laminar compound (A) was too high. Therefore, a lubricant composition could not be prepared as a liquid having sufficient flowability.
In Comparative Example 14, the content of the water-soluble polymer (D) was too high. Therefore, sufficient carburization resistance was not obtained.
In Comparative Example 15, the content of the silane coupling agent (C) was too high. Therefore, a sufficient adhesive property, sufficient water resistance, and sufficient adhesiveness were not obtained. As a result, sufficient lubricity was also not obtained.
In Comparative Example 16, the total content (A + B) of the oxide-based laminar compound (A) and the boron compound (B) was too high. Therefore, a lubricant composition could not be prepared as a liquid having sufficient flowability.
In Comparative Example 18, the content of the boron compound (B) was too high. Therefore, sufficient lubricity and a sufficient drying property were not obtained.
In Comparative Example 19, the total content (A + B) of the oxide-based laminar compound (A) and the boron compound (B) was too high. Therefore, although sufficient flowability of the lubricant composition was obtained, sufficient lubricity and water resistance were not obtained.
In Comparative Example 20, the ratio (A/C) of the content of the oxide-based laminar compound (A) to the content of the silane coupling agent (C) was too low. Therefore, sufficient lubricity and adhesiveness were not obtained.
In Comparative Example 21, the ratio (A/C) of the content of the oxide-based laminar compound (A) to the content of the silane coupling agent (C) was too high. Therefore, sufficient lubricity, sufficient adhesiveness, and a sufficient drying property were not obtained.
An embodiment of the present disclosure has been described above. However, the embodiment described above is merely an example for carrying out the present disclosure. Therefore, the present disclosure is not limited to the above-described embodiment, and can be implemented by appropriately modifying the above-described embodiment within a range not departing from the gist thereof.

Claims

A lubricant composition comprising, in mass%,
an oxide-based laminar compound: 10.0 to 40.0%,

a boron compound: 7.5 to 35.0%,

a silane coupling agent: 0.3 to 5.0%,

a water-soluble polymer: 0 to 7.0%, and

impurities: 0 to 1.0%,

with the balance being water,

wherein:
a total content of the oxide-based laminar compound and the boron compound is 17.5 to 65.0% by mass, and

a ratio of a content of the oxide-based laminar compound to a content of the silane coupling agent is 3.0 to 30.0.
The lubricant composition according to claim 1, wherein:
the total content of the oxide-based laminar compound and the boron compound is 25.0 to 50.0% by mass, and

the ratio of the content of the oxide-based laminar compound to the content of the silane coupling agent is 5.0 to 15.0.
The lubricant composition according to claim 1 or claim 2, wherein:
the oxide-based laminar compound is a phyllosilicate mineral, and

the phyllosilicate mineral is composed of one kind or more selected from a group consisting of mica, vermiculite, and bentonite.
The lubricant composition according to claim 3, wherein:
the mica is composed of one kind or more selected from a group consisting of sodium tetrasilicic mica, potassium tetrasilicic mica, natural phlogopite, and natural muscovite.
The lubricant composition according to claim 1 or claim 2, wherein:
the boron compound is composed of one kind or more selected from a group consisting of boron oxide, an alkali metal borate, and an amine borate.
The lubricant composition according to claim 5, wherein:
the alkali metal borate is composed of one kind or more selected from a group consisting of lithium borate, sodium borate, and potassium borate.
The lubricant composition according to claim 1 or claim 2, wherein:
the silane coupling agent is R_a-Si(OR_b)₃, where R_a is composed of one kind or more selected from a group consisting of an alkyl group, a vinyl group, an epoxy group, a styryl group, a methacryl group, an acryl group, an amino group, an isocyanurate group, a ureido group, a mercapto group, and an isocyanate group, and R_b is composed of a methyl group or an ethyl group.
The lubricant composition according to claim 7, wherein:
the silane coupling agent is composed of one kind or more selected from a group consisting of methyltrimethoxysilane and 3-glycidoxypropyltrimethoxysilane.
The lubricant composition according to claim 1 or claim 2, wherein:
the water-soluble polymer is composed of one kind or more selected from a group consisting of a biogum, a natural polysaccharide, a cellulose derivative, a polyacrylate, an alginate, and an organic polymer.
The lubricant composition according to claim 9, wherein:
the biogum is composed of one kind or more selected from a group consisting of xanthan gum, welan gum, and rhamsan gum;

the natural polysaccharide is composed of one kind or more selected from a group consisting of guar gum, locust bean gum, and carageenan;

the cellulose derivative is composed of one kind or more selected from a group consisting of methyl cellulose, ethyl cellulose, hydroxyethyl cellulose, hydroxyethyl methyl cellulose, hydroxypropyl methylcellulose, carboxymethyl cellulose, and salts of these cellulose derivatives; and

the organic polymer is composed of one kind or more selected from a group consisting of acrylic resin, acrylic styrene resin, vinyl acetate resin, and polypropylene resin.
A method for producing a seamless metal pipe, comprising:
an application process of applying the lubricant composition according to claim 1 to a surface of a mandrel bar having a surface temperature of 60 to 150°C;

a drying process of, after the application process, drying the lubricant composition to form a lubricating film on the surface of the mandrel bar;

an insertion process of, after the drying process, inserting the mandrel bar into a hollow shell after piercing-rolling;

a rolling process of, after the insertion process, performing elongating using a mandrel mill on the hollow shell in which the mandrel bar is inserted; and

a drawing process of, after the rolling process, drawing the mandrel bar from the hollow shell.