Heat treatment oil

Abstract

Provided is a heat treatment oil comprising a poly-α-olefin as a base oil, wherein the poly-α-olefin has a kinematic viscosity at 40 °C of 5.0-12.0 mm2 / s, thereby making it possible to achieve both a cooling property and an evaporation property.

Description

Heat Treatment Oil

[0001] The present invention relates to a heat treatment oil.

[0002] Heat treatment processes such as quenching of metal materials are usually performed using a heat treatment liquid to impart a desired hardness to the metal material. Therefore, the heat treatment liquid must have excellent cooling performance to increase the hardness of the metal material. Water is a liquid with extremely excellent cooling capacity, but water-based heat treatment liquids have an excessively high cooling performance, which can cause quench cracking in the metal material and significant quench distortion. For this reason, oil-based heat treatment liquids, i.e., heat treatment oils, are generally used in heat treatment processes such as quenching of metal materials.

[0003] As an index showing the cooling property of heat treatment oil, the quench intensity (H value) calculated from the cooling time from 800°C to 300°C in the cooling curve specified in JIS K2242:2012 is widely used.

[0004] Furthermore, when quenching a heated metal material, if it is immersed in heat treatment oil, the cooling rate is not constant. It typically cools through the following three stages: (1) the first stage (vapor film stage), in which the metal material is enveloped in the vapor of the heat treatment oil; (2) the second stage (boiling stage), in which the vapor film breaks and boiling occurs; and (3) the third stage (convection stage), in which the temperature of the metal material drops below the boiling point of the heat treatment oil and heat is removed by convection. Of these three stages, the second stage (boiling stage) has the greatest cooling rate. Furthermore, if the time until the first stage (the "characteristic number of seconds" in the cooling test in accordance with JIS K2242:2012) is long, the resulting metal material, for example, carbon steel, is likely to have insufficient hardness.

[0005] On the other hand, quenching metal materials improves their hardness, but tempering, in which they are reheated, can further enhance their toughness. In this process, quenching oil adheres to the quenched metal material, and the material is typically washed to remove the oil before tempering. However, from the perspective of improving productivity, efforts have been made to reduce or eliminate the washing process. For example, Patent Document 1 discloses an invention related to a heat treatment oil containing multiple types of metal soaps, which has good aqueous cleanability after quenching. Patent Document 2 discloses a gas quenching method that uses gas as a coolant instead of heat treatment oil, thereby eliminating the need for a washing process. Patent Document 3 also discloses an invention related to an apparatus equipped with a reduced-pressure drying chamber for vaporizing the heat treatment oil. Furthermore, Patent Document 4 discloses a heat treatment oil containing a specific α-olefin oligomer compound.

[0006] Japanese Patent Application Laid-Open No. 9-176728 Japanese Patent No. 5817173 International Publication No. 2021 / 240718 Japanese Patent Application Laid-Open No. 2008-69321

[0007] However, even if the heat treatment oil described in Patent Document 1 is used, the cleaning process cannot be completely eliminated, leaving productivity issues. Next, with the gas quenching method described in Patent Document 2, depending on the cooling gas spray pressure, the H value may be insufficient, resulting in insufficient hardness of the resulting metal material. Furthermore, there is a risk of uneven cooling performance between areas with high and low cooling gas pressure. Furthermore, when using a quenching method using heat treatment oil, switching to a gas quenching method requires the complete replacement of the existing heat treatment equipment. The device described in Patent Document 3 also requires the replacement of the existing heat treatment equipment, and depending on the heat treatment oil used, there is a risk of insufficient volatility. Furthermore, Patent Document 4 does not consider base oils that allow the elimination of the cleaning process after heat treatment.

[0008] Therefore, the object of the present invention is to provide a heat treatment oil that can achieve both cooling properties and evaporativity, from the viewpoint of utilizing existing heat treatment equipment while eliminating the need for cleaning treatment after heat treatment.

[0009] The present inventors have found that a heat-treated oil containing a specific poly-α-olefin as a base oil can solve the above problems, and have completed the present invention.

[0010] That is, the present invention provides the following [1] to

[10] . [1] A heat-treated oil containing a poly-α-olefin as a base oil, wherein the kinematic viscosity of the poly-α-olefin at 40°C is 5.0 to 12.0 mm ２ [2] The kinematic viscosity of the poly-α-olefin at 100°C is 1.5 to 3.0 mm / s. ２

[0023] The heat-treated oil according to [1] above, wherein the poly-α-olefin content is 50% by mass or more, based on the total amount of the heat-treated oil. [3] The heat-treated oil according to [1] or [2] above, wherein the poly-α-olefin content is 50% by mass or more, based on the total amount of the heat-treated oil. [4] The heat-treated oil according to any one of [1] to [3] above, wherein the flash point measured by the Cleveland Open Method is 150°C or more. [5] The heat-treated oil according to any one of [1] to [4] above, wherein the residual oil amount measured under the following measurement conditions for the poly-α-olefin is 1.0% by mass or less. [Measurement Conditions] Using a Tg-DTA apparatus according to JIS K0129:2005, 5.0 mg of sample oil was weighed out and placed in the sample measurement position of a heating furnace. The heating furnace was closed, and the temperature was raised to 200°C at 25°C / min while flowing nitrogen at 200 mL / min. After reaching 200°C, the oil was held for 2 hours, and the mass of the residual oil after the hold was measured, and the mass ratio to the mass before the hold was measured. [6] The heat treatment oil according to any one of [1] to [5] above, which is used as a quenching oil. [7] A method for producing a metal component, comprising a quenching step of immersing a heated metal component in the heat treatment oil according to any one of [1] to [6] above and cooling it. [8] A method for producing a metal component according to [7] above, in which the quenching temperature in the quenching step is 600 to 1400°C. [9] A method for producing a metal component according to [7] or [8] above, in which a tempering step is performed in which the metal component is reheated without being washed after the quenching step.

[10] A method for producing a metal component according to [9] above, in which the heating temperature in the tempering step is 150 to 600°C.

[0011] According to the present invention, it is possible to provide a heat treatment oil that has both cooling properties and evaporative properties.

[0012] The upper and lower limit values ​​of the numerical ranges described in this specification can be combined in any way. For example, when "A to B" and "C to D" are described as numerical ranges, the numerical ranges "A to D" and "C to B" are also included in the scope of the present invention. Furthermore, the numerical range "lower limit to upper limit" described in this specification means that the range is equal to or greater than the lower limit and equal to or less than the upper limit, unless otherwise specified. Furthermore, in this specification, the numerical values ​​in the examples are numerical values ​​that can be used as upper or lower limit values.

[0013] [Heat Treatment Oil] The heat treatment oil of this embodiment is a heat treatment oil containing a poly-α-olefin as a base oil, and the kinematic viscosity of the poly-α-olefin at 40° C. is 5.0 to 12.0 mm ２ / s.

[0014] As a result of extensive research conducted by the present inventors to solve the above problems, they have found that when a heat treatment oil contains the above specific poly-α-olefin (hereinafter, sometimes referred to as "PAO") as a base oil, it ensures cooling properties when performing heat treatments such as quenching, while exhibiting volatility to the extent that it can be evaporated during tempering without washing after the heat treatment, making washing after the heat treatment unnecessary.

[0015] The heat-treated oil of this embodiment may consist solely of the PAO, but may also contain other components besides the PAO as long as the effects of the present invention are not impaired. When the heat-treated oil of this embodiment contains additives, the total content of the PAO and additives is preferably 60% by mass or more, more preferably 70% by mass or more, even more preferably 80% by mass or more, and even more preferably 90% by mass or more, based on the total amount (100% by mass) of the heat-treated oil. Furthermore, it is usually 100% by mass or less, preferably less than 100% by mass, more preferably 99% by mass or less, and even more preferably 98% by mass or less.

[0016] <Poly-α-olefin> The heat treatment oil of this embodiment contains a PAO as a base oil. In this embodiment, the PAO has a kinematic viscosity at 40° C. (hereinafter, sometimes referred to as “40° C. kinematic viscosity”) of 5.0 to 12.0 mm ２ The kinematic viscosity of the PAO at 40°C is 5.0 mm / s.２ When the kinematic viscosity is 12.0 mm / s or more, the cooling property during heat treatment is good. ２ When the viscosity is 1 / s or less, the evaporation of the heat treatment oil is favorable, and the cleaning treatment after the heat treatment can be omitted, resulting in excellent productivity. Note that the kinematic viscosity at 40°C and the kinematic viscosity at 100°C in this specification refer to values ​​measured in accordance with JIS K2283:2000.

[0017] The method for producing the PAO is not particularly limited, and any method may be used as long as it can produce a PAO that satisfies the kinematic viscosity at 40°C. However, an α-olefin oligomer obtained by oligomerizing an α-olefin having 2 to 20 carbon atoms is preferred.

[0018] Examples of the α-olefin having 2 to 20 carbon atoms used as the raw material include ethylene, propylene, 1-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene, 1-nonene, 1-decene, 1-undecene, 1-dodecene, 1-tridecene, 1-tetradecene, 1-pentadecene, 1-hexadecene, 1-heptadecene, 1-octadecene, 1-nonadecene, and 1-icosene. These α-olefins may be linear or branched, and one type of α-olefin may be used alone, or two or more types of α-olefins may be used in combination. In the production of the PAO, the catalyst used for oligomerization of the α-olefin is not particularly limited, but a metallocene catalyst, for example, may be used.

[0019] In the heat-treated oil of this embodiment, the PAO functions as a base oil. In the heat-treated oil of this embodiment, the content of the PAO is preferably 50% by mass or more, more preferably 70% by mass or more, even more preferably 80% by mass or more, still more preferably 90% by mass or more, and even more preferably 95% by mass or more, based on the total amount (100% by mass) of the heat-treated oil. The content of the PAO is preferably 100% by mass or less, based on the total amount (100% by mass) of the heat-treated oil.

[0020] (Kinematic Viscosity of PAO) The kinematic viscosity of the PAO at 40°C is preferably 5.2 mmHg from the viewpoint of achieving both cooling properties and evaporation properties.２ / s or more 11.0mm ２ / s or less, and more preferably 5.3 mm ２ / s or more 10.0mm ２ The kinematic viscosity at 100°C of the PAO is preferably 1.5 mm / s or less from the viewpoint of achieving both cooling properties and evaporation properties. ２ / s or more 3.0mm ２ / s or less, and more preferably 1.7 mm ２ / s or more 2.8mm ２ / s or less.

[0021] <Base Oil Other Than PAO> The heat-treated oil of the present embodiment may or may not further contain a base oil other than PAO. Examples of the base oil other than PAO include one or more selected from the group consisting of synthetic oils that do not fall under the category of PAO and mineral oils.

[0022] Examples of synthetic oils that do not fall under the category of PAO include polyvinyl ethers, polyalkylene glycols, copolymers of polyalkylene glycols or their monoethers with polyvinyl ethers, polyol esters, polyesters, polycarbonates, alicyclic hydrocarbon compounds, alkylated aromatic hydrocarbon compounds, GTL base oils produced by isomerizing GTL wax (gas-to-liquid wax) produced by the Fischer-Tropsch process, etc. One type of synthetic oil may be used alone, or two or more types may be used in combination.

[0023] From the viewpoint of making it easier to exert the effects of the present invention, the content of synthetic oils other than PAOs is preferably small. Specifically, the content of synthetic oils other than PAOs is preferably less than 3 parts by mass, more preferably less than 1 part by mass, even more preferably less than 0.1 parts by mass, and even more preferably no synthetic oils other than PAOs, per 100 parts by mass of PAO.

[0024] Examples of mineral oils include atmospheric residues obtained by atmospheric distillation of crude oils such as paraffinic crude oil, intermediate crude oil, and naphthenic crude oil; distillates obtained by vacuum distillation of these atmospheric residues; mineral oils obtained by subjecting the distillates to one or more treatments such as solvent deasphalting, solvent extraction, hydrocracking, solvent dewaxing, catalytic dewaxing, and hydrorefining; wax isomerized mineral oil, etc. Note that one mineral oil may be used alone, or two or more mineral oils may be used in combination.

[0025] From the viewpoint of more easily achieving the effects of the present invention, the mineral oil content is preferably low. Mineral oil has a wider molecular weight distribution than the PAO used in the heat treatment oil of this embodiment, and therefore contains lower or higher molecular weight components. Low molecular weight components have high volatility, i.e., they evaporate easily, which increases the time (characteristic seconds) until the vapor film stage of the heat treatment oil ends, so a low content is preferable. Furthermore, high molecular weight components have low volatility, i.e., they are difficult to evaporate, so a low content is preferable from the viewpoint of improving the volatility of the heat treatment oil. From the above viewpoints, the mineral oil content is preferably less than 10 parts by mass, more preferably less than 1 part by mass, per 100 parts by mass of PAO.

[0026] <Additives> The heat treatment oil of this embodiment may optionally contain additives commonly used in heat treatment oils. Examples of additives include glitter improvers, antioxidants, cooling improvers, and vapor film breakers. One type of additive may be used alone, or two or more types may be used in combination.

[0027] (Brilliance improver) When the heat treatment oil of this embodiment contains a brilliance improver, the brilliance of the appearance can be improved. Examples of brilliance improvers include fats and oils; complete esters of alkyl succinic acid and alkyl succinimides and derivatives thereof; complete esters of alkenyl succinic acid, alkenyl succinimides and derivatives thereof; substituted hydroxyaromatic carboxylic acid esters (complete esters) and derivatives thereof. Specific examples include polybutenyl succinimide, polyisobutenyl succinimide, pentadecenyl succinic acid, etc. These brilliance improvers may be used alone or in combination of two or more. The content of the brilliance improver is preferably 0.1% by mass to 5.0% by mass, more preferably 0.3% by mass to 3.0% by mass, and even more preferably 0.4% by mass to 2.5% by mass, based on the total amount of the heat treatment oil.

[0028] (Antioxidant) Examples of the antioxidant include phenol-based antioxidants, sulfur-based antioxidants, and amine-based antioxidants. Examples of the phenol-based antioxidant include 2,6-di-tert-butyl-paracresol, 2,6-di-tert-butyl-4-ethylphenol, 2,4,6-tri-tert-butylphenol, 2,6-di-tert-butyl-4-hydroxymethylphenol, 2,6-di-tert-butylphenol, 2,4-dimethyl-6-tert-butylphenol, 2,6-di-tert-butyl-4-(N,N-dimethylaminomethyl)phenol, 2,6-di-tert-amyl-4-methylphenol, n-octadecyl-3-(4 monocyclic phenols such as 4,4'-methylenebis(2,6-di-tert-butylphenol), 4,4'-isopropylidenebis(2,6-di-tert-butylphenol), 2,2'-methylenebis(4-methyl-6-tert-butylphenol), 4,4'-bis(2,6-di-tert-butylphenol), 4,4'-bis(2-methyl-6-tert-butylphenol), 2,2'-methylenebis(4-ethyl-6-tert-butylphenol), 4,Polycyclic phenols such as 4'-butylidenebis(3-methyl-6-tert-butylphenol); etc. Examples of sulfur-based antioxidants include alkyl sulfide compounds, thiadiazole compounds, and thiocarbamate compounds. Examples of alkyl sulfide-based sulfur-based antioxidants include didodecyl sulfide, didodecyl disulfide, dioctadecyl sulfide, dioctadecyl disulfide, didodecyl thiodipropionate, didodecyl dithiodipropionate, dioctadecyl thiodipropionate, dioctadecyl dithiodipropionate, dilauryl thiodipropionate, dilauryl dithiodipropionate, and distearyl thiodipropionate, distearyl dithiodipropionate, dimyristyl thiodipropionate, dimyristyl dithiodipropionate, dodecyl octadecyl thiodipropionate, dodecyl octadecyl dithiodipropionate, pentaerythritol-tetrakis-(3-lauryl thiopropionate), and pentaerythritol-tetrakis-(3-lauryl dithiopropionate). Examples of thiadiazole-based sulfur-based antioxidants include 2,5-bis(t-nonylthio)-1,3,4-thiadiazole, 2,5-bis(dimethylhexylthio)-1,3,4-thiadiazole, 2,5-bis(octadecenylthio)-1,3,4-thiadiazole, 2,5-bis(methylhexadecenylthio)-1,3,4-thiadiazole, 2,5-bis(2-hydroxyoctadecylthio)-1,3,4-thiadiazole, 2,5-bis(n-octoxycarbonylmethylthio)-1,3,4-thiadiazole, 2-mercapto-5-(2-ethylhexylthio)-1,3,4-thiadiazole, and 2-methyl-5-(2-ethylhexylthio)-1,3,4-thiadiazole. 2,5-bis(dimethylhexyldithio)-1,3,4-thiadiazole, 2,5-bis(octadecenyldithio)-1,3,4-thiadiazole, 2,5-bis(methylhexadecenyldithio)-1,3,4-thiadiazole, 2,5-bis(2-hydroxyoctadecyldithio)-1,3,4-thiadiazole, 2,5-bis(2-hydroxyoctadecyldithio)-1,3,4-thiadiazole, 2,5-bis(n-octoxycarbonylmethyldithio)-1,3,4-thiadiazole, 2-mercapto-5-(2-ethylhexyldithio)-1,3,4-thiadiazole, 2-mercapto-5-(t-nonyldithio)-1,3,4-thiadiazole, 2,5-bis(t-nonylamino)-1,3,4-thiadiazole, 2,5-bis(dimethylhexylamino)-1,3,4-thiadiazole, 2,5-bis(octadecenylamino)-1,3,4-thiadiazole, 2,5-bis(methylhexadecenylamino)-1,3,4-thiadiazole, 2,5-bis(2-hydroxyoctadecylamino)-1,3,4-thiadiazole, 2,5-bis(n-octoxycarbonylmethylamino)-1,3,4-thiadiazole, 2-amino- Examples of the thiadiazole include 5-(2-ethylhexylamino)-1,3,4-thiadiazole, 2-amino-5-(t-norylamino)-1,3,4-thiadiazole, 2,5-bis(t-noryl)-1,3,4-thiadiazole, 2,5-bis(dimethylhexyl)-1,3,4-thiadiazole, 2,5-bis(octadecenyl)-1,3,4-thiadiazole, 2,5-bis(methylhexadecenyl)-1,3,4-thiadiazole, 2-octyl-thiazoline, 2,5-bis(2-hydroxyoctadecyl)-1,3,4-thiadiazole, 2,5-bis(n-octoxycarbonylmethyl)-1,3,4-thiadiazole, 2-(2-ethylhexyl)-1,3,4-thiadiazole, and 2-(t-noryl)-1,3,4-thiadiazole. Examples of thiocarbamate-based sulfur-based antioxidants include bis(dimethylthiocarbamoyl) monosulfide, bis(dibutylthiocarbamoyl) monosulfide, bis(dimethylthiocarbamoyl) monosulfide, bis(dibutylthiocarbamoyl) monosulfide, bis(diamylthiocarbamoyl) monosulfide, bis(dioctylthiocarbamoyl) monosulfide, and methylenebis(dibutyldithiocarbamate). Other sulfur-based antioxidants include, for example, phenothiazine, 2,6-di-t-butyl-4-(4,6-bis(octylthio)-1,3,Also included are compounds containing sulfur atoms and nitrogen atoms, such as bis(3,5-di-t-butyl-4-hydroxybenzyl)sulfide, 2,2'-thiobis(4-methyl-6-t-butylphenol), and 4,4'-thiobis(3-methyl-6-t-butylphenol). Examples of the amine-based antioxidant include diphenylamine-based antioxidants and naphthylamine-based antioxidants. Examples of diphenylamine antioxidants include alkylated diphenylamines having an alkyl group having 3 to 20 carbon atoms, and specific examples thereof include diphenylamine, monooctyldiphenylamine, monononyldiphenylamine, 4,4'-dibutyldiphenylamine, 4,4'-dihexyldiphenylamine, 4,4'-dioctyldiphenylamine, 4,4'-dinonyldiphenylamine, tetrabutyldiphenylamine, tetrahexyldiphenylamine, tetraoctyldiphenylamine, tetranonyldiphenylamine, etc. Examples of naphthylamine antioxidants include alkyl-substituted phenyl-α-naphthylamines having 3 to 20 carbon atoms, and specific examples thereof include α-naphthylamine, phenyl-α-naphthylamine, butylphenyl-α-naphthylamine, hexylphenyl-α-naphthylamine, octylphenyl-α-naphthylamine, nonylphenyl-α-naphthylamine, etc. These antioxidants may be used alone or in combination of two or more. The content of the antioxidant is preferably 0.01% by mass to 5.0% by mass, more preferably 0.02% by mass to 3.0% by mass, and even more preferably 0.05% by mass to 2.0% by mass, based on the total amount of the heat-treated oil.

[0029] (Cooling Improver) Examples of the cooling improver include imide-based dispersants such as boron-containing alkenyl succinimides, and mono- or di-carboxylic acid amides such as fatty acids or succinic acid. These cooling improvers may be used alone or in combination of two or more. The content of the cooling improver is preferably 0.05% by mass to 5.0% by mass, more preferably 0.1% by mass to 3.0% by mass, and even more preferably 0.3% by mass to 2.0% by mass, based on the total amount of the heat treatment oil.

[0030] Furthermore, from the viewpoint of the volatility of the heat treatment oil, the content of the vapor film breaker in the heat treatment oil of this embodiment is preferably less than 3 mass%, more preferably less than 1 mass%, even more preferably less than 0.1 mass%, even more preferably less than 0.01 mass%, and even more preferably no vapor film breaker is contained, based on the total amount of the heat treatment oil.

[0031] [Physical properties of heat-treated oil] <Flash point> The heat-treated oil of this embodiment is not particularly limited in terms of its properties, but preferably has a flash point of 130°C or higher, more preferably 140°C or higher, even more preferably 150°C or higher, and particularly preferably 160°C or higher. In this specification, the flash point of the monoester (A) refers to the value measured by the Cleveland Open Cup method (C.O.C. method) in accordance with JIS K2265-4:2007. <Kinematic viscosity> The 40°C kinematic viscosity of the heat-treated oil of this embodiment is preferably 5.0 mm from the viewpoint of achieving both cooling properties and evaporability. ２ / s or more 12.0mm ２ / s or less, more preferably 5.2 mm ２ / s or more 11.0mm ２ / s or less, more preferably 5.3 mm ２ / s or more 10.0mm ２ / s or less.

[0032] <Coolability> The coolability of the heat treatment oil of this embodiment can be evaluated by using the quench intensity (H value) according to the method described in the examples below. The H value can be calculated from the cooling time from 800°C to 300°C in the cooling curve specified in JIS K2242:2012. The H value of the heat treatment oil of this embodiment is preferably 0.100 cm －１ More preferably, 0.105 cm －１ More preferably, 0.110 cm －１ More preferably, 0.120 cm or more －１ That's all.

[0033] <Characteristic seconds> The heat treatment oil of this embodiment can be evaluated for its characteristic seconds by the method described in the Examples below. From the viewpoint of shortening the time in the vapor film stage and suppressing quenching distortion, the characteristic seconds is preferably 10 seconds or less, more preferably 9.0 seconds or less, even more preferably 8.0 seconds or less, still more preferably 7.0 seconds or less, and most preferably 6.5 seconds or less.

[0034] <Residual Oil Amount> The volatility of the heat-treated oil of this embodiment can be evaluated based on the residual oil amount measured under the following measurement conditions. [Measurement Conditions] Using a Tg-DTA apparatus according to JIS K0129:2005, 5.0 mg of sample oil was weighed out and placed at the sample measurement location in the heating furnace, the heating furnace was closed, and the temperature was raised to 200°C at 25°C / min while flowing nitrogen at 200 mL / min. After reaching 200°C, the temperature was held for 2 hours, and the mass of the residual oil after holding was measured, and the mass ratio to the mass before holding was measured.

[0035] The residual oil amount measured under the above measurement conditions serves as an indicator of volatility, and from the viewpoint of making it possible to omit the cleaning process after heat treatment, the residual oil amount of the heat-treated oil of this embodiment is preferably 1.0 mass% or less, more preferably 0.5 mass% or less, and even more preferably 0.1 mass% or less.

[0036] [Method for Manufacturing Metal Components] The method for manufacturing a metal component of this embodiment includes a quenching step in which a heated metal component is immersed in the heat treatment oil and cooled. The quenching temperature in the quenching step is preferably 400 to 1500°C, more preferably 500 to 1400°C, and even more preferably 600 to 1400°C. Furthermore, the method for manufacturing a metal component of this embodiment preferably includes a tempering step in which the metal component is reheated after the quenching step without being cleaned. By subjecting the quenched metal component to the tempering step as is in this manner, the cleaning step can be omitted, improving productivity. Furthermore, the heat treatment oil of this embodiment has excellent volatility, particularly under the temperature conditions of the tempering step, and can therefore evaporate from the metal component during the tempering step. The heating temperature in the tempering step can be appropriately set depending on the desired hardness and toughness of the metal component, but is, for example, approximately 150 to 600°C.

[0037] [Uses of Heat Treatment Oil] The heat treatment oil of this embodiment can be used for heat treatments such as quenching, tempering, annealing, and normalizing. Furthermore, since the heat treatment oil of this embodiment has excellent cooling properties and evaporativity, the heat treatment oil of this embodiment can be suitably used in heat treatments that do not require cleaning after the heat treatment, and can be particularly suitably used as a cleansing-less quenching oil that does not require cleaning after quenching.

[0038] The present invention will be specifically described with reference to the following examples, but the present invention is not limited to these examples.

[0039] [Methods for Measuring Physical Properties] The methods for measuring physical properties were as follows: (1) Kinematic viscosity at 40°C: Measured in accordance with JIS K2283:2000.

[0040] <Measurement of Flash Point> The flash point was measured by the Cleveland Open Cup method (C.O.C. method) in accordance with JIS K2265-4:2007.

[0041] [Examples 1 to 4 and Comparative Examples 1 to 6] Using heat-treated oils containing the following components in the amounts shown in Table 1, the flash point and kinematic viscosity at 40°C were measured, and the volatility, characteristic seconds, and H value were also evaluated.

[0042] <Base oil, air> α-olefin: a mixture mainly consisting of C16 olefin and C18 olefin, kinematic viscosity at 40°C: 2.971 mm ２ / s PAO1: 1-decene oligomer, kinematic viscosity at 40°C: 5.575 mm ２ / s PAO2: 1-decene oligomer, kinematic viscosity at 40°C: 6.459 mm ２ / s PAO3: 1-decene oligomer, kinematic viscosity at 40°C: 7.709 mm ２ / s PAO4: α-olefin oligomer, kinematic viscosity at 40°C: 9.545 mm ２ / s PAO5: α-olefin oligomer, kinematic viscosity at 40 ° C: 13.47 mm ２ / s PAO6: 1-decene oligomer, kinematic viscosity at 40°C: 17.32 mm ２ / s PAO7: 1-decene oligomer, kinematic viscosity at 40°C: 30.46 mm ２ / s Air: 5 kg / cm instead of heat treatment oil ２ Air is injected at

[0043] <Additives> Ca salicylate: calcium salicylate (calcium atom content: 8.0 mass%, base number (perchloric acid method): 225 mg KOH / g, density: 1.051 g / cm ３ Na sulfonate: sodium sulfonate (sodium atom content: 3.4 mass%, density: 1.02 g / cm ３ )

[0044] [Evaluation of Volatility] Evaluation was performed using a Tg-DTA apparatus according to JIS K0129:2005. 5.0 mg of sample oil was weighed and placed in the sample measurement location of the heating furnace. The heating furnace was closed, and while flowing nitrogen at 200 mL / min, the temperature was raised to 200°C at 25°C / min, and after reaching 200°C, the temperature was maintained for 2 hours. Thereafter, the mass of the residual oil after the maintenance was measured, and the ratio (mass%) to the mass before the maintenance was calculated.

[0045] [Evaluation of Cooling Ability] In accordance with the cooling ability test method specified in JIS K 2242:2012, a cooling curve was created by recording the temperature change from 800°C for 60 seconds, and the characteristic number of seconds was determined from the time required to reach the characteristic temperature. In addition, the H value was determined by the Osaka University cooling capacity evaluation method using the time required to cool from 800°C to 300°C on the created cooling curve. However, in Comparative Example 6, in which air was used as the coolant, air at 25°C was blown at 5 kg / cm. ２ The cooling curve was created.

[0046] Table 1 shows the compositions and evaluation results of the heat treatment oils of Examples 1 to 4 and Comparative Examples 1 to 5, as well as the evaluation results of Comparative Example 6, in which air was used as the coolant.

[0047]

[0048] As shown in Table 1, the kinematic viscosity at 40°C is 5.0 to 12.0 mm ２ The heat-treated oils of Examples 1 to 4, which used PAO as the base oil with a kinematic viscosity of 12.0 mm / s, were excellent in volatility, had relatively short characteristic seconds, and had relatively high H values. In contrast, the heat-treated oil of Comparative Example 1, which used mineral oil as the base oil, and the heat-treated oil of Comparative Example 2, which used a mineral oil as the base oil and had a kinematic viscosity of 12.0 mm / s at 40°C, ２ The heat-treated oils of Comparative Examples 3 to 5, which used PAOs with a kinematic viscosity of more than 5.0 mm / s, had low volatility and required cleaning after heat treatment. ２ The heat-treated oil of Comparative Example 2, which used a base oil of less than 1 / s, had a long characteristic time, a low flash point, and a relatively low H value. In addition, the heat-treated oil of Comparative Example 6, which used air as a coolant, had a low H value.

Claims

1. A heat-treated oil containing poly-α-olefin as a base oil, wherein the kinematic viscosity of the poly-α-olefin at 40°C is 5.0 to 12.0 mm ２ / s. Heat-treated oil.

2. The kinematic viscosity of the poly-α-olefin at 100°C is 1.5 to 3.0 mm ２ The heat-treated oil according to claim 1, wherein the hydroxyl group is hydroxypropyl methylcellulose.

3. A heat treatment oil according to claim 1 or 2, wherein the content of the poly-alpha-olefin is 50 mass% or more based on the total amount of the heat treatment oil.

4. A heat-treated oil according to any one of claims 1 to 3, having a flash point of 150°C or higher as measured by the Cleveland Open Flame Method.

5. The heat-treated oil according to any one of claims 1 to 4, wherein the residual oil content of the poly-α-olefin measured under the following measurement conditions is 1.0 mass% or less: [Measurement conditions] Using a Tg-DTA apparatus according to JIS K0129:2005, 5.0 mg of sample oil was weighed out and placed at the sample measurement location in the heating furnace, the heating furnace was closed, and the temperature was raised to 200°C at 25°C / min while flowing nitrogen at 200 mL / min, and after reaching 200°C, the oil was held for 2 hours, and the mass of the residual oil after the hold was measured, and the mass ratio to the mass before the hold was measured.

6. The heat treatment oil according to any one of claims 1 to 5, which is used as a quenching oil.

7. A method for manufacturing a metal component, comprising a quenching step of immersing a heated metal component in the heat treatment oil according to any one of claims 1 to 6 and cooling it.

8. The method for producing a metal part according to claim 7, wherein the quenching temperature in the quenching step is 600 to 1400°C.

9. The method for manufacturing a metal component according to claim 7 or 8, wherein after the quenching step, a tempering step is carried out in which the metal component is reheated without being washed.

10. The method for manufacturing a metal part according to claim 9, wherein the heating temperature in the tempering step is 150 to 600°C.

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