Heat treatment oil

Abstract

To provide heat treatment oil that can achieve both coolability and evaporability.SOLUTION: The heat treatment oil contains poly-α-olefin as base oil, and the kinematic viscosity of the poly-α-olefin at 40°C is 5.0-12.0 mm2 / s.SELECTED DRAWING: None

Description

[Technical Field]

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

[0002] Heat treatment processes such as quenching of metal materials are usually carried out using a heat treatment liquid to impart a desired hardness to the metal material, and therefore the heat treatment liquid must have excellent cooling performance to increase the hardness of the metal material. Water is a liquid with excellent cooling capacity, but water-based heat treatment liquids have the risk of causing quenching cracks in metal materials due to their excessive cooling capacity, and they also cause significant quenching 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 of the cooling ability 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] Regarding quenching of metal materials, when heated metal materials are immersed in heat treatment oil, the cooling rate is not constant, and they are usually cooled through the following three stages (1) to (3). (1) The first stage (vapor film stage) in which the metal material is enveloped in heat treatment oil vapor. (2) The second stage (boiling stage) occurs when the vapor film breaks and boiling occurs. (3) The third stage (convection stage) occurs when the temperature of the metal material drops below the boiling point of the heat treatment oil and heat is removed by convection. Of the three stages, the cooling rate is greatest in the second stage (boiling stage). If the time until the first stage (vapor film stage) ends (the "characteristic seconds" in the cooling test according to JIS K2242:2012) is long, the hardness of the resulting metal material may be insufficient, depending on the material, such as carbon steel.

[0005] On the other hand, although quenching metal materials improves their hardness, they may be subjected to a tempering process in which they are reheated to further impart toughness. In this case, since quenching oil adheres to the metal material after quenching, it is common to perform a cleaning process to remove this before performing the tempering process. However, from the perspective of improving productivity, studies are being conducted to reduce or omit the cleaning process. For example, Patent Document 1 discloses an invention relating to a heat treatment oil using 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 cleaning. Patent Document 3 discloses an invention relating to an apparatus equipped with a reduced-pressure drying chamber for vaporizing heat treatment oil. Furthermore, Patent Document 4 discloses a heat treatment oil containing a specific α-olefin oligomer compound. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Publication No. 9-176728 [Patent Document 2] Patent No. 5817173 [Patent Document 3] International Publication No. 2021 / 240718 [Patent Document 4] Japanese Patent Application Laid-Open No. 2008-69321 Summary of the Invention [Problem to be solved by the invention]

[0007] However, even if the heat treatment oil described in Patent Document 1 is used, the cleaning treatment cannot be completely omitted, and problems remain from the viewpoint of productivity. Next, with the gas quenching method described in Patent Document 2, depending on the cooling gas blowing pressure, the H value may be insufficient, resulting in an insufficient hardness of the resulting metal material. Also, 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 a complete replacement of the existing heat treatment equipment. The device described in Patent Document 3 also requires replacement of the existing heat treatment device, and there is a risk that the evaporation rate may be insufficient depending on the heat treatment oil used. Furthermore, Patent Document 4 does not consider a base oil that allows the omission of a washing treatment 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. [Means for solving the problem]

[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 / s heat treatment oil. [2] The kinematic viscosity of the polyα-olefin at 100°C is 1.5 to 3.0 mm 2 The heat treatment oil according to [1] above, wherein [3] The heat treatment oil according to [1] or [2] above, wherein the content of the poly-α-olefin is 50 mass% or more based on the total amount of the heat treatment oil. [4] The heat-treated oil according to any one of [1] to [3] above, 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 [1] to [4] above, wherein the poly-α-olefin has a residual oil content of 1.0 mass % or less as measured under the following measurement conditions: [Measurement conditions] Using a Tg-DTA device conforming to JIS K0129:2005, 5.0 mg of sample oil was weighed out and placed in the sample measurement location of the heating furnace. The heating furnace was then closed, and the temperature was raised to 200°C at 25°C / min while nitrogen was flowing at 200 mL / min. After reaching 200°C, the temperature was maintained for 2 hours. The mass of the residual oil after the temperature maintenance was measured, and the mass ratio to the mass before the maintenance was measured. [6] The heat treatment oil according to any one of the above [1] to [5], 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 the component. [8] The method for producing a metal member according to the above [7], wherein the quenching temperature in the quenching step is 600 to 1400°C. [9] The method for manufacturing a metal component according to the above [7] or [8], wherein after the quenching step, a tempering step of reheating the metal component is carried out without cleaning the metal component.

[10] The method for producing a metal member according to the above [9], wherein the heating temperature in the tempering step is 150 to 600°C. [Effects of the Invention]

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

[0012] The upper and lower limits of the ranges described herein can be combined in any way. For example, if the ranges are "A to B" and "C to D," the ranges "A to D" and "C to B" are also included in the scope of the present invention. Furthermore, unless otherwise specified, 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. 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] In order to solve the above problems, the inventors conducted extensive research and 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 heat treatment, making washing after heat treatment unnecessary.

[0015] The heat-treated oil of this embodiment may consist solely of the above-mentioned PAO, but may also contain components other than 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. Also, 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-treated oil of this embodiment contains 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 / s. The kinematic viscosity of the PAO at 40°C is 5.0 mm 2 When the kinematic viscosity is 12.0 mm / s or more, the cooling property during heat treatment is good. 2When the heat treatment oil is used at a temperature of 1000°C or less, the evaporation of the heat treatment oil is good, and the cleaning treatment after the heat treatment can be omitted, resulting in excellent productivity. In this specification, the 40°C kinematic viscosity and the 100°C kinematic viscosity refer to values ​​measured in accordance with JIS K2283:2000.

[0017] There are no particular limitations on the method for producing the PAO, and any method may be used as long as it 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 oligomerizing the α-olefin is not particularly limited, but for example, a metallocene catalyst can be used.

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

[0020] (Kinematic viscosity of PAO) The kinematic viscosity of the PAO at 40°C is preferably 5.2 mm 2 / s or more and 11.0 mm 2 / s or less, more preferably 5.3 mm 2 / s or more and 10.0 mm 2 / s or less. Also, the kinematic viscosity of the PAO at 100°C is preferably 1.5 mm 2 / s or more and 3.0 mm 2 / s or less, more preferably 1.7 mm 2 / s or more and 2.8 mm 2 / s or less.

[0021] <Other base oils other than PAO> The heat treatment oil of this embodiment may further contain other base oils other than PAO, or may not contain them. Examples of other base oils other than PAO include one or more selected from the group consisting of synthetic oils not corresponding to PAO and mineral oils.

[0022] Examples of synthetic oils not corresponding to PAO include polyvinyl ethers; polyalkylene glycols; copolymers of polyalkylene glycol or its monoether and polyvinyl ether; 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 processes such as the Fischer-Tropsch process; etc. Note that the synthetic oil may be used alone or in combination of two or more.

[0023] From the perspective of more easily exerting the effects of the present invention, the content of synthetic oil not corresponding to PAO is preferably low. Specifically, the content of synthetic oil not corresponding to PAO is preferably less than 3 parts by mass, more preferably less than 1 part by mass, still more preferably less than 0.1 part by mass, and even more preferably does not contain synthetic oil not corresponding to PAO, with respect to 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 processes such as solvent deasphalting, solvent extraction, hydrocracking, solvent dewaxing, catalytic dewaxing, and hydrorefining; and wax isomerized mineral oils. The mineral oils may be used alone or in combination of two or more.

[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 evaporate less easily, so a low content is preferable from the viewpoint of improving the volatility of the heat treatment oil. From the above viewpoint, the content of the mineral oil is preferably less than 10 parts by mass, more preferably less than 1 part by mass, per 100 parts by mass of the PAO.

[0026] <Additives> The heat treatment oil of this embodiment may contain additives commonly used in heat treatment oils, such as glitter improvers, antioxidants, cooling improvers, and vapor film breakers, if desired. The additives may be used alone or in combination of two or more.

[0027] (gloss improver) When the heat treatment oil of this embodiment contains a glitter improver, the glitter of the appearance can be improved. Examples of glitter improvers include fats and oils; complete esters of alkylsuccinic acid, alkylsuccinimides and derivatives thereof; complete esters of alkenylsuccinic acid, alkenylsuccinimides and derivatives thereof; substituted hydroxyaromatic carboxylic acid esters (complete esters) and derivatives thereof. Specific examples include polybutenyl succinimide, polyisobutenyl succinimide, and pentadecenyl succinic acid. These glitter improvers may be used alone or in combination of two or more. The content of the glitter improver is preferably 0.1 to 5.0 mass %, more preferably 0.3 to 3.0 mass %, and even more preferably 0.4 to 2.5 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 phenolic antioxidants include 2,6-di-tert-butyl-para-cresol, 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, and n-octadecyl-3-(4-hydroxy-3,5-di-tert-butylphenyl) monocyclic phenols such as propionate; and polycyclic 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), and 4,4'-butylidenebis(3-methyl-6-tert-butylphenol). Examples of sulfur-based antioxidants include alkyl sulfide-based, thiadiazole-based, and thiocarbamate-based 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-ethoxymethylthio)-1,3,4-thiadiazole, and 2-methyl-5-(2-ethoxymethylthio)-1,3,4-thiadiazole. 2,4-bis(2-ethylhexyldithio)thiazole, 2,5-bis(t-nonyldithio)-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(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-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,Examples include 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 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 compounds containing sulfur atoms and nitrogen atoms, such as phenothiazine, 2,6-di-t-butyl-4-(4,6-bis(octylthio)-1,3,5-triazin-2-ylamino)phenol, and 2-mercaptobenzimidazole. Further examples include phenolic compounds containing a sulfur atom, 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, and tetranonyldiphenylamine. Examples of naphthylamine antioxidants include alkyl-substituted phenyl-α-naphthylamines having 3 to 20 carbon atoms, and specific examples include α-naphthylamine, phenyl-α-naphthylamine, butylphenyl-α-naphthylamine, hexylphenyl-α-naphthylamine, octylphenyl-α-naphthylamine, and nonylphenyl-α-naphthylamine. These antioxidants may be used alone or in combination of two or more. The content of the antioxidant is preferably 0.01 to 5.0% by mass, more preferably 0.02 to 3.0% by mass, and even more preferably 0.05 to 2.0% by mass, based on the total amount of the heat-treated oil.

[0029] (cooling agent) Examples of the cooling improver include imide-based dispersants such as boron-containing alkenyl succinimides, and mono- or di-carboxylic acid amides typified by fatty acids or succinic acid. These cooling improvers may be used alone or in combination of two or more. The content of the coolability improver is preferably 0.05 to 5.0 mass %, more preferably 0.1 to 3.0 mass %, and even more preferably 0.3 to 2.0 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 treatment oil] <Flash point> The properties of the heat-treated oil of this embodiment are not particularly limited, but it is preferable that the flash point be 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 a value measured by the Cleveland Open Chamber method (COC method) in accordance with JIS K2265-4:2007. <Kinematic viscosity> The kinematic viscosity at 40°C of the heat treatment oil of this embodiment is preferably 5.0 mm from the viewpoint of achieving both cooling properties and evaporative properties. 2 / s or more 12.0mm 2 / s or less, 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] <Cooling property> The coolability of the heat treatment oil of this embodiment can be evaluated 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 than 0.105cm, preferably 0.105cm -1 More preferably, 0.110 cm -1 More than 0.120 cm, especially preferred -1 That's all.

[0033] <Characteristic seconds> The heat-treated oil of this embodiment can be evaluated for its characteristic number of 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 number of 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 amount of residual oil measured under the following measurement conditions. [Measurement conditions] Using a Tg-DTA device conforming to JIS K0129:2005, 5.0 mg of sample oil was weighed out and placed in the sample measurement location of the heating furnace. The heating furnace was then closed, and the temperature was raised to 200°C at 25°C / min while nitrogen was flowing at 200 mL / min. After reaching 200°C, the temperature was maintained for 2 hours. The mass of the residual oil after the temperature maintenance was measured, and the mass ratio to the mass before the maintenance 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] [Metal component manufacturing method] 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 without being cleaned after the quenching step. By subjecting the quenched metal component to the tempering step as is in this way, 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 be evaporated 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 member, and is, for example, about 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. [Example]

[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] [Method of measuring physical properties] The physical properties were measured as follows. (1)Kinematic viscosity at 40℃ Measurements were made in accordance with JIS K2283:2000.

[0040] <Flash point measurement> Measurement was performed using the Cleveland Open Chamber (COC) 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 of C16 and C18 olefins, kinematic viscosity at 40°C: 2.971 mm 2 / s PAO1: 1-decene oligomer, kinematic viscosity at 40°C: 5.575mm 2 / s PAO2: 1-decene oligomer, kinematic viscosity at 40°C: 6.459mm 2 / s PAO3: 1-decene oligomer, kinematic viscosity at 40°C: 7.709mm 2 / s PAO4: α-olefin oligomer, kinematic viscosity at 40°C: 9.545mm 2 / s PAO5: α-olefin oligomer, kinematic viscosity at 40°C: 13.47mm 2 / s PAO6: 1-decene oligomer, kinematic viscosity at 40°C: 17.32mm 2 / s PAO7: 1-decene oligomer, kinematic viscosity at 40°C: 30.46mm 2 / s Air: 5kg / cm instead of heat treatment oil 2 Air is injected at

[0043] <Additives> Calcium salicylate: Calcium salicylate (calcium atom content: 8.0% by 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] The evaluation was carried out using a Tg-DTA device according to JIS K0129:2005. 5.0 mg of sample oil was weighed and placed in the sample measurement position 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, it was held for 2 hours. Thereafter, the mass of the residual oil after holding was measured, and the ratio (mass%) to the mass before holding was calculated.

[0045] [Cooling performance evaluation] In accordance with the cooling test method specified in JIS K 2242:2012, a cooling curve was created recording the temperature change from 800°C for 60 seconds, and the characteristic number of seconds was calculated from the time it took to reach the characteristic temperature. In addition, the H value was calculated using the time it took to reach 300°C from 800°C on the created cooling curve, using the Osaka University cooling capacity evaluation method. 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] [Table 1]

[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 with a viscosity of 1 / s as the base oil, were excellent in volatility, had a relatively short characteristic time, and also had a relatively high H value. In contrast, the heat-treated oil of Comparative Example 1, which uses mineral oil as the base oil, and the oil having a kinematic viscosity of 12.0 mm at 40°C 2 The heat-treated oils of Comparative Examples 3 to 5, which used PAO with a viscosity of more than 1 / s, had low volatility and required washing after the heat treatment. On the other hand, the kinematic viscosity at 40°C is 5.0mm 2 The heat-treated oil of Comparative Example 2, which used a base oil of less than 1 / s, had a long characteristic number of seconds, a low flash point, and a relatively low H value. Furthermore, in Comparative Example 6, in which air was used as the coolant, the H value was low.

Claims

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

4. The 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 Method.

5. The heat treatment oil according to any one of claims 1 to 4, wherein the poly-α-olefin has a residual oil amount of 1.0 mass% or less as 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 set at the sample measurement location in the heating furnace. The heating furnace was then 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 holding was measured, and the mass ratio to the mass before holding 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 member, comprising a quenching step of immersing a heated metal member in the heat treatment oil according to any one of claims 1 to 6 and cooling the metal member.

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

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

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

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