LUBRICANT COMPOSITION FOR COLD WORKING AND COLD WORKING METHOD USING SAME

Abstract

 A lubricating composition for cold working which has good lubricating and anti-seizure properties and which is less flammable without addition of a chlorine compound and a method for cold working using the same are provided.
The lubricating composition for cold working comprises at least one carbonate selected from alkali metal carbonates and alkaline earth metal carbonates and at least one hydroxide selected from alkali metal hydroxides and alkaline earth metal hydroxides in a lubricating base oil and which is free of chlorine compounds, wherein the content of the carbonate in the composition is at least 10% by mass and less than 100% by mass and wherein the content of the hydroxide is greater than 0 parts by mass and at most 5 parts by mass per 100 parts by mass of the carbonate.

Description

Technical Field

[0001] The present invention relates to a lubricating composition for cold working and a method of cold working using such a composition. More particularly, it pertains to a lubricating composition which is free of chlorine compounds which may have problems with respect to carcinogenicity and generation of dioxin, which exhibits good lubricating and anti-seizure properties even in cold forging and cold pipe forming, both of which easily cause seizure and have severe lubricating requirements (such a type of working hereinafter referred to as "hard metalworking"), and which is compatible with the environment and less flammable, and a method of cold working using such a composition.

Background Art

[0002] Hitherto, an oilness agent such as a fat or fatty oil, a fatty acid, or an ester and/or an extreme pressure agent (EP agent) such as a sulfur-, chlorine-, or phosphorus-containing compound has been added to a lubricating oil for use in cold working such as cold forging in order to improve its lubricating action. Among various extreme pressure agents, chlorine-containing extreme pressure agents such as chlrorinated paraffins and chlorinated fatty acid esters are less expensive compared to other extreme pressure agents, have good lubricating properties, and are less flammable, so they are added to a lubricating composition which is used for hard metalworking such as cold forging.

[0003] However, chlorine compounds have the problems that they may be carcinogenic or generate dioxin.
Regarding carcinogenicity, some specific chlorinated paraffins, for example, are classified as Group 2B (possibly carcinogenic substances) by IARC (International Agency for Research on Cancer). In addition, the sale of a product for metalworking which contains specific chlorinated paraffins in a concentration greater than 1% is prohibited in the European Union from the viewpoint that special precautions are needed in order to limit the risk to aquatic organisms.

[0004] It has been noticed that when a waste lubricating oil containing a chlorine compound is disposed of by incineration, hydrogen chloride (HCl) which causes air pollution may be generated during burning or dioxin may be generated depending on the burning temperature during incineration, both leading to environmental pollution.

[0005] In view of these problems with respect to health and the global environment, use of a lubricating oil for metalworking which contains chlorine compound such as chlorinated paraffin is being increasingly disfavored in many countries.
On this account, lubricating compositions for cold working which are free of chlorine compounds such as chlorinated paraffins have been developed.

[0006] For example, a lubricant of the type for use in forging comprising an alkaline earth metal salt (a phenate, a carboxylate, or a sulfonate) with a high basicity dispersed in a base oil is proposed in JP H08-333594 A1. A lubricating oil comprising a base oil to which a petroleum sulfonate of high basicity and an extreme pressure agent such as a calcium salt of a phosphoric acid ester or a sulfurized fat or fatty oil are added is proposed in JP H08-34988 A1. A lubricating oil comprising a base oil in which a film strengthening agent such as a ZnDTP (zinc dialkyldithiophosphate) or sulfurized lard and a carbohydrate such as starch or its derivative are dispersed is proposed in JP H06-256784 A1.

Disclosure of Invention

[0007] Each of the lubricating compositions proposed in the above-described patent documents which do not contain an organic chlorine compound has the disadvantage that sufficient lubricating and anti-seizure properties are not achieved in hard metalworking. Accordingly, there is still a need of a lubricating composition for metalworking which can prevent environmental pollution caused by a chlorine compound, which can exhibit good anti-seizure property even in hard metalworking, and which is less flammable.

[0008] The present invention provides a lubricating composition for cold working and a method of cold working using such a composition in which the composition is free of chlorine compounds which may cause the problems of carcinogenicity and generation of dioxin, exhibits good lubricating and anti-seizure properties even in cold forging or cold pipe forming which easily cause seizure (namely, in hard metalworking), and is compatible with the environment and less flammable.

[0009] The present invention is based on the finding that a lubricating composition containing an alkali metal and/or alkaline earth metal carbonate (particularly one having a specific crystal structure) and an alkali metal and/or alkaline earth metal hydroxide in a certain proportion exhibits good anti-seizure and lubricating properties in the absence of a chlorine compound.

[0010] In cold working under severe working conditions, the temperature of the lubricating oil which is used may reach 150° C or higher. By increasing the proportion of an alkali metal and/or alkaline earth metal carbonate in the composition, the proportion of a flammable material can be decreased, thereby causing the composition to be less flammable.

[0011] A lubricating composition for cold working according to the present invention contains at least one carbonate selected from alkali metal carbonates and alkaline earth metal carbonates and at least one hydroxide selected from alkali metal hydroxides and alkaline earth metal hydroxides in a lubricating base oil and is free of chlorine compounds. The lubricating composition for cold working is characterized in that the content of the carbonate in the composition is at least 10% by mass and less than 100% by mass while the content of the hydroxide is greater than 0 parts by mass and at most 5 parts by mass per 100 parts by mass of the carbonate.

[0012] The lubricating composition for cold working can exhibit good lubricating and anti-seizure properties even in cold forging and cold pipe forming which have severe lubricating requirements and which tend to easily cause seizure (such as cold pilger mill rolling, for example). In addition, the composition has low flammability. Furthermore, the composition exhibits good lubricating performance without aid of a chlorine compound which is problematic with respect to carcinogenicity and generation of dioxin, so it is compatible with the environment.

[0013] The lubricating composition for cold working according to the present invention encompasses the following preferred embodiment.

• The composition further contains at least one metal salt selected from alkali metal or alkaline earth metal sulfonates, salicylates, phenates, and carboxylates. This makes it possible to provide the lubricating composition with detergent dispersant activity. The content of this metal salt is preferably from 1 to 50 parts by mass per 100 parts by mass of the carbonate.

[0014] 

• The composition further contains an organosulfur compound having a carbon atom to which a sulfur atom and a nitrogen or oxygen atom are bonded, and the content of the organosulfur compound in the composition is from 0.1 % to 50% by mass. It is possible to attain further improved lubricity in this manner.

[0015] 

• The carbonate has an amorphous crystal structure, whereby further improved anti-seizure property can be attained.
• The carbonate has a mean particle diameter of not greater than 0.5 micrometers. Again, further improved anti-seizure property can be thereby attained.

[0016] 

• The alkali metal is sodium, and the alkaline earth metal is calcium. It leads to decreased material costs, and makes it possible to stably provide the lubricating composition.
• The composition has a flash point of 150° C or higher, thereby making it possible to use the lubricating composition safely even for cold working under severe conditions which leads to an increased temperature of the composition.

[0017] The organosulfur compound is preferably at least one selected from the compounds having formulas (1) to (12):

[0018] where x₁ is an integer from 2 to 4.

[0019] 

[0020] where R₁ and R₂ are each -CH₃ or -C₂H₅ and may be the same or different from each other.

[0021] 

[0022] where x₂ is 1 or 2.

[0023] where R₃ is -C(CH₃)₃ or -C₆H₁₁.

[0024] where x₃ and x₄ are each an integer from 2 to 4 and may be the same or different from each other, and R₄ and R₅ are each -C₈H₁₇, -C₁₂H₂₅ or -C(S)N(C₂H₅)₂ and may be the same or different from each other.

[0025] where R₆ and R₇ are each -CH₃, -C₂H₅, -C₃H₇, -C₄H₉, -C₆H₅, or -CH₂C₆H₅ and may be the same or different from each other, and M is Na, K, or 1/2Ca.

[0026] where R₈ is H or -CH₃, and R₉ is -C₅H₁₀NH₂ or -CH(CH₃)C₄H₈NH₂.

[0027] where R₁₀, R₁₁, R₁₂, and R₁₃ are each -CH₃, -C₂H₅, -C₃H₇, -C₄H₉, or -CH₂CH(C₂H₅)C₄H₉ and may be the same or different from each other, and x₅ is an integer from 1 to 4.

[0028]  where x₆ is an integer from 1 to 4.

[0029] where R₁₄ and R₁₆ are each H, -CH₃, or -C₂H₅ and may be the same or different from each other, and R₁₅ and R₁₇ are each -CH₃, -C₂H₅, or -C₆H₅ and may be the same or different from each other.

[0030] According to the present invention, a method of cold working characterized by subjecting a material to be worked to cold working using the above-described lubricating composition for cold working is also provided. This method makes it possible to perform cold working satisfactorily on the material to be worked due to good anti-seizure and lubricating properties of the lubricating composition for cold working which is used.

[0031] A method of cold working according to the present invention can perform cold working satisfactorily on a material to be worked which is a stainless steel, a high alloy steel, aluminum, copper, titanium, nickel, or an alloy thereof.

[0032] Use of the above-described lubricating composition for cold working having good anti-seizure and lubricating properties affords the following benefits:

• It makes it possible to manufacture cold worked products such as metal pipes and tubes, metal wires, metal rods and bars, or billets; and
• It makes it possible to carry out cold working such as cold forging and cold 5 pipe forming in a stable manner.

Brief Description of the Drawing

[0033] Figure 1 is an explanatory view schematically showing a testing machine used in an ironing test.

Best Mode for Carrying Out the Invention

(1) Lubricating composition for cold working

[0034] A lubricating composition for cold working according to the present invention contains an alkali metal and/or alkaline earth metal carbonate (hereinafter referred to simply as a "carbonate") and an alkali metal and/or alkaline earth metal hydroxide (hereinafter referred to simply as a "hydroxide") in a lubricating base oil and is free of chlorine compounds. The carbonate and hydroxide are present in the base oil in dispersed state, but they may partly be dissolved therein.

[0035] The "lubricating base oil" is not limited to a particular type, and any known lubricating base oil can be used. The lubricating base oil includes mineral oils, fats and fatty oils, and synthetic lubricating oils, for example. The mineral oils include kerosene, light oil, spindle oil, machine oil, neutral oil, turbine oil, cylinder oil, and liquid paraffin. The fats and fatty oils include beef tallow, lard, rapeseed oil, coconut oil, palm oil, and rice bran oil, as well as hydrogenated oils of these. The synthetic oils include fatty acids derived from the above-described fats and fatty oils, esters of a fatty acid and an alcohol, poly(alpha-olefins) such as polybutene, polyols such as polyethylene glycol and polyol esters, polyethers or polyesters, and higher alcohols. The "lubricating base oil" may be constituted by one or more oils.

[0036] The content of the lubricating base oil in the lubricating composition for cold working is not limited, but it is preferably in the range of from 1% to 90%, more preferably from 5% to 80%, even more preferably from 10% to 70%, and most preferably from 10% to 60% by mass based on the mass of the composition (total mass of all the constituents constituting the composition).

[0037] For the carbonate, the "alkali metal" includes lithium, sodium, and potassium, and the "alkaline earth metal" includes magnesium, calcium, and barium. Specific examples of the carbonate include lithium carbonate, sodium carbonate, potassium carbonate, magnesium carbonate, calcium carbonate, and barium carbonate. Of these, from consideration as an alternative to a chlorine compound which is inexpensive, sodium carbonate and calcium carbonate are preferred since they are inexpensive and make it possible to stably provide a lubricating composition. One or more carbonates may be used.

[0038] The crystal structure of the carbonates is not limited to a specific form. For alkaline earth metal carbonates, possible crystal structures include vaterite, calcite, and amorphous. It is preferable to use a carbonate which is amorphous in crystal structure since a lubricating composition for cold working having improved anti-seizure property can be obtained. Two or more carbonates having different crystal structures may of course be used.

[0039] The mean particle diameter of the carbonates is not limited either, but it is preferably not greater than 0.5 micrometers (and usually at least 0.001 micrometers), and more preferably not greater than 0.3 micrometers and even more preferably not greater than 0.1 micrometers. The reason why the mean particle diameter is preferably not greater than 0.5 micrometers is that it is possible to obtain a lubricating composition for cold working having improved anti-seizure property.

[0040] The content of the carbonates is at least 10% and less than 100% (usually at most 95%) by mass based on the mass of the composition. It is preferably in the range of from 10% to 90%, more preferably from 10% to 80%, even more preferably from 10% to 70%, and most preferably from 15% to 65% by mass. If this content exceeds 10% by mass, a lubricating composition for cold working having both good lubricity and good anti-seizure property cannot be obtained. In addition, it is not possible for the lubricating composition to have a sufficiently increased flash point.

[0041] The "alkali metal" and "alkaline earth metal" in the above-described hydroxide include the same metal species as listed above for each of these classes with respect to the carbonates. The particular alkali metal and/or alkaline earth metal constituting the hydroxide may be the same as or different from the particular alkali metal and/or alkaline earth metal constituting the carbonate. Specific examples of the hydroxide include lithium hydroxide, sodium hydroxide, potassium hydroxide, magnesium hydroxide, calcium hydroxide, and barium hydroxide. One or more hydroxides may be used.

[0042] The content of the hydroxides, when expressed as parts by mass per 100 parts by mass of the carbonate, is greater than 0 parts by mass and not greater than 5 parts by mass (usually at least 0.01 parts by mass). It is preferably in the range of from 0.05 to 5 parts by mass, and more preferably from 0.05 to 4 parts by mass, and most preferably from 0.09 to 3.5 parts by mass. If the content of the hydroxides exceeds 5 parts by mass, sufficient anti-seizure property cannot be obtained. The content of the hydroxides can be determined by a common titration method such as neutralization titration with an acid.

[0043] The content of the hydroxides, when expressed as % by mass based on the mass of the composition, is generally greater than 0% and less than 5%, preferably in the range of from 0.05% to 4%, and more preferably from 0.05% to 3%, even more preferably from 0.05% to 2%, and most preferably from 0.1% to 1% by mass.

[0044] By incorporating the hydroxide within the above-described content range, it is possible to obtain a lubricating composition for cold working having both good lubricity and good anti-seizure property.
The carbonates and the hydroxides may be obtained by a chemical reaction, or they may be commercially available products. Commercially available products of these compounds can be obtained in powder form. It is also possible to obtain these compounds in the form of a solution or dispersion containing an alkali metal and/or alkaline earth metal carbonate and hydroxide uniformly dissolved or dispersed in an appropriate medium (an inorganic solvent or an organic solvent, and particularly an oil for use as a lubricating base oil).

[0045] A lubricating composition for cold working according to the present invention is free of chlorine compounds. The expression "chlorine compound" indicates any inorganic or organic compound containing one or more chlorine atoms. Specific examples of such a compound include chlorine-containing extreme pressure agents such as chlorinated paraffin and chlorinated fats and fatty oils, chlorinated solvents such as carbon tetrachloride, trichloroethylene, and methylene chloride, chlorine-containing fluorinated solvents such as chlorofluorocarbons, and inorganic chlorine compounds such as ammonium chloride.

[0046] A lubricating composition for cold working according to the present invention which "is free of chlorine compounds" ideally has 0% content of chlorine-containing compounds. However, it encompasses a composition containing a slight amount of a chlorine-containing compound due to contamination by unavoidable impurities or similar reason. The present invention does not exclude a lubricating composition for cold working containing chlorine compounds in an amount of greater than 0% and not greater than 1% by mass based on the mass of the composition. In this case, the content of the chlorine compound is preferably at most 0.5%, more preferably at most 0.1 %, even more preferably at most 0.01%, and 5 most preferably at most 0.001% by mass.

[0047] A lubricating composition according to the present invention may further include at least one metal salt selected from alkali metal or alkaline earth metal sulfonates, salicylates, phenates, and carboxylates. As a result, it becomes possible to provide the lubricating composition with detergent dispersant activity.

[0048] The "alkali metal" and "alkaline earth metal" for the metal salt include the same metal species as listed above for each of these classes. The particular "alkali metal" and "alkaline earth metal" constituting the metal salt may be the same as or different from the particular alkali metal and/or alkaline earth metal constituting the carbonate and/or hydroxide.

[0049] The "sulfonates" include alkali metal salts and alkaline earth metal salts of a sulfonic acid such as petroleum sulfonate, an alkyl-aromatic sulfonic acid such as alkylbenzenesulfonic acid, an alkyl sulfonic acid, or polyisobutenylsulfonic acid. The "salicylates" include alkali metal salts and alkaline earth metal salts of a salicylic acid such as an alkylsalicylic acid. The "phenates" include alkali metal salts and alkaline earth metal salts of a phenol such as phenol or an alkylphenol. The "carboxylates" include alkali metal salts and alkaline earth metal salts of a carboxylic acid such as maleic polybutene, a fatty acid, or a carboxyl-modified acrylic resin. One or more metal salts may be used.

[0050] The metal salt such as an alkali metal and/or alkaline earth metal salt of a sulfonate, salicylate, phenate or carboxylate can be prepared by blowing carbon dioxide into a system which is a solution of the corresponding acid, i.e., a sulfonic acid, a salicylic acid, a phenol, or a carboxylic acid dissolved in a base oil and which contains an alkali metal and/or alkaline earth metal hydroxide (and/or oxide) added to the solution.

[0051] Usually, the alkali metal and/or alkaline earth metal hydroxide is used in an excess amount. In this case, the resulting metal salt contains an alkali metal and/or alkaline earth metal carbonate and in some cases unreacted alkali metal and/or alkaline earth metal hydroxide, so it becomes a basic salt. The base number of the metal salt depends on the amount of the alkali metal and/or alkaline earth metal hydroxide added to the system, and a metal salt having a high base number of 100 mg-KOH/g may be formed in some cases. The base number of the metal salt which is used in the present invention is not limited.

[0052] When a lubricating composition for cold working according to the present invention contains a metal salt such as a sulfonate and the metal salt contains an alkali metal and/or alkaline earth metal carbonate and/or hydroxide, the amount of the carbonate and/or hydroxide contained in the metal salt is included in the amount of the "carbonate" and/or "hydroxide" described above as essential constituents in the composition according to the present invention.

[0053] The content of the metal salt (an alkali metal and/or alkaline earth metal salt of a sulfonate, salicylate, phenate and/or carboxylate) is preferably from 1 to 50 parts, more preferably 1 to 40 parts, and even more preferably 5 to 30 parts by mass, expressed as the mass of the metal salt per 100 parts by mass of the carbonate. When the metal salt contains a carbonate and/or hydroxide, the mass of the carbonate and/or hydroxide in the salt is excluded from the mass as the metal salt itself.

[0054] A lubricating composition according to the present invention may further contain an organosulfur compound having a carbon atom to which a sulfur atom and a nitrogen or oxygen atom are bonded in order to further improve the lubricity of the composition. The organosulfur compound includes organic compounds having a moiety such as N=C-S, N-C=S, N-C-S, N=C=S, O=C-S, O-C=S, O-C-S or O=C=S, for example. Preferred examples of the organosulfur compounds are those of the preceding formulas (1) to (12), which make it possible to ensure that a lubricating composition having further improved lubricity is obtained. One or more organosulfur compounds may be used.

[0055] The content of the organosulfur compound is not limited, but it is preferably from 0.1 % to 50%, more preferably from 1% to 40%, and even more preferably from 5% to 30% by mass based on the mass of the composition. When the content is within the above-described range, it is possible to obtain a lubricating composition having further improved lubricity.

[0056] A lubricating composition for cold working according to the present invention may include, if necessary, various additives which are added to conventional oils for plastic working, in addition to the above-described constituents. Examples of such additives include oilness agents such as hindered esters and alkylamines; extreme pressure agents including organosulfur compounds such as polysulfides and sulfurized fats and fatty oils; organophosphorous compound such as phosphate and phosphite esters and acidic phosphate and phosphite esters; organometallic salts such as zinc dithiophosphate and molybdenum dithiocarbamate; solid lubricants such as graphite and molybdenum sulfide; antioxidants, antirust agents, and anticorrosive agents. Use of solid lubricants such as graphite and molybdenum sulfide is preferably avoided as much as possible since they may adversely affect the working environment.

[0057] Since a lubricating composition for cold working according to the present invention is free of chlorine compounds, optional additives when they are used should be other than chlorine compounds. However, as long as no disadvantageous effect is produced, the present invention does not exclude the use of a chlorine compound as an optional additive used in a slight amount.

[0058] A lubricating composition for cold working according to the present invention is in the form of a liquid or gel at room temperature (about 25° C). The composition preferably has a flash point of 150° C or higher, more preferably 170° C or higher, and even more preferably 200° C or higher. When its flash point is at least 150° C, the lubricating composition can be used safely even in cold working under severe conditions which cause the lubricating composition to have a high temperature.

(2) Method of cold working

[0059] When a lubricating composition for cold working according to the present invention is used to perform cold working of a material to be worked, the material to be worked is not limited. The material to be worked includes stainless steel, high alloy steel, aluminum, copper, titanium, nickel, and alloys of these. The shape of the material to be worked is not limited, and it may be a bar or rod or a block. Alternatively, it is conceivable to perform working on hot-forged shapes (such as gears and shafts). The product produced by cold working is also not limited. Some specific examples of cold worked products include metal tubes and pipes, metal wires, metal rods or bars, and billets.

[0060] Specific types of cold working include plate rolling, pipe or tube rolling, rolling of bar steels (shape steels, bars, and wire rods), drawing, forging, and the like. Particularly preferred cold working is cold forging or cold pipe forming. The conditions and method for cold working such as cold forging or cold pipe forming are not limited, and cold working can be carried out using a known apparatus under conditions which are appropriately set.

Examples

[0061] The present invention will be specifically described by the following examples, which are not intended to limit the invention thereto. In the description of the examples, "percent" and "parts" are "percent by mass" and "parts by mass", respectively.

[1]Preparation of lubricating compositions for cold working

[0062] Carbonate dispersions Nos. 1 to 5 shown in Table 1 were prepared by dispersing the indicated alkali metal or alkaline earth metal carbonate and hydroxide, and a metal sulfonate (calcium or sodium salt of an alkylbenzenesulfonic acid) in a mineral oil (purified mineral oil manufactured by Nippon Oil Corporation) such that each constituent had the indicated content. Table 1 also indicates the mean particle diameter and crystal structure of each alkali metal or alkaline earth metal carbonate which was used as well as the appearance of the dispersions. In each dispersion, the metals of the carbonate and hydroxide were the same.

[0063] 

Table 1

		Carbonate				Hydroxide		Sulfonate	Appearance
		Type	Crystal structure	Content (%)	Mean particle diameter (µm)	Type TyPe	Content (%)	Content (%)
Dispersion of carbonate	No.1	CaCO3	Amorphous	36.0	0.03	Ca(OH)2	0.04	20.0	brown liquid
	No.2	Na2CO	Amorphous	40.0	0.1	NaOH	0.1	19.0	brown liquid
	No.3	CaCO	Hexagonal (vatelite)	33.4	50	Ca(OH)2	0.03	20.0	brown liquid
	No.4	CaCO3	Trigonal (calcite)	25.9	0.1	Ca(OH)2	0.04	20.0	brown liquid
	No.5	CaCO3	Amorphous	36.0	0.03	Ca(OH)2	2.2	20.0	brown liquid

[0064] Each of the lubricating compositions for cold working of Examples 1 to 18 and Comparative Examples 1 and 2 were prepared by dispersing a carbonate dispersion selected from the above-described No.1 to No. 5 and an organosulfur compound selected from the following No. 1 to No. 12 in a mineral oil (purified mineral oil manufactured by Nippon Oil Corporation) such that each constituent had the content indicated in Table 2 or 3. Tables 2 and 3 include the content of the alkali metal or alkaline earth metal carbonate, its crystal structure and mean particle diameter, and the content of the alkali metal or alkaline earth metal hydroxide relative to the amount of the alkali metal or alkaline earth metal carbonate. The figures with an asterisk in Table 3 indicate that the figures are outside the scope of the present invention.

[0065] Organosulfur compounds which were used:

No. 1: the compound of the above-indicated formula (1);

No. 2: a compound of the above-indicated formula (2) (x₁ = 2);

No. 3: a compound of the above-indicated formula (3) (R₂ = R₂ = -C₂H₅);

No. 4: a compound of the above-indicated formula (4) (x₂ = 2);

No. 5: a compound of the above-indicated formula (5) (R₃ = -C(CH₃)₃);

No. 6: the compound of the above-indicated formula (6) ;

No. 7: a compound of the above-indicated formula (7) (x₃ = x₄ = 2, and R₄ = R₅ = -C₈H₁₇);

No. 8: a compound of the above-indicated formula (8) (R₆ = R₇ = -C₄H₉, and M = 1/2Ca);

No. 9: a compound of the above-indicated formula (9) (R₈ = H, and R₉ =-C₅H₁₀NH₂);

No. 10: a compound of the above-indicated formula (10) (x₅ = 2, and R₁₀ to R₁₃ = -CH₂CH(C₂H₅)C₄H₉);

No. 11: a compound of the above-indicated formula (11) (x₆ = 4);

No. 12: a compound of the above-indicated formula (12) (R₁₄ = R₁₆ = H, and R₁₅ = R₁₇ = -C₆H₅).

[0066] As Comparative Example 3, a water-insoluble type lubricating oil (primarily comprising 15% of fatty acid esters and 70% of a sulfurized fat and fatty oil) was used.

[2] Evaluation of performance of lubricating compositions

[0067] The performance of each of the lubricating compositions of Examples 1 to 18 and Comparative Examples 1 to 3 was evaluated by the following methods.

(1) Cold drawing test of a steel pipe with a laboratory drawing machine

[0068] A steel pipe having dimensions of 21.5 mm in outer diameter, 16.04 mm in inner diameter, and 750 mm in length (made of SUS 304) was used as a material to be worked. The pipe had previously been subjected to solution treatment and then surface roughening by pickling. The laboratory drawing machine had a drawing die with an inner diameter of 17.5 mm and a plug of the semi-floating type having an outer diameter of 13.2 mm in its straight portion. The reduction of area of a pipe which had been subjected to cold drawing with the laboratory drawing machine was 35.6%.

[0069] Cold pipe drawing was carried out after each of the lubricating compositions for cold working of Examples 1 to 18 and Comparative Examples 1 to 3 was applied to the outer and inner surfaces of a steel pipe as described above. In addition, the lubricating compositions for cold working of Examples 1 to 18 and Comparative Examples 1 to 3 were supplied to the outer and inner surfaces of the steel pipe immediately before drawing.

[0070] The surface of each steel pipe after drawing was observed visually to determine the presence or absence of seizure and evaluate the performance of the lubricating composition being tested. The results are shown in Table 2 or 3. In each table, the symbol "⊚" indicates no occurrence of seizure, "O" indicates the occurrence of slight seizure, "Δ" indicates the occurrence of mild seizure, and "X" indicates the occurrence of heavy seizure.

(2) Ironing test

[0071] An ironing test was carried out in the following manner using the testing machine shown in Figure 1 for evaluation of lubricity. The testing machine T had a die 1 (a female-shaped cemented carbide tool having a diameter of 20.85 mm) placed on a pedestal 7, a steel ball 4 (a male-shaped tool made of SUJ 2 (bearing steel) having a diameter of 19 mm), and a press 5 placed above the die 5 and capable of a vertical stroke.

[0072] A material (blank) to be worked which was used was a test plate 2 (made of SUS 304, thickness of 2.0 mm, disk shaped) having a hole 6 with a diameter of 10 mm formed at the center. Each of the lubricating compositions for cold working of Examples 1 to 18 and Comparative Examples 1 to 3 was applied in an adequate amount to both surfaces of such a test plate 2. The test plate 2 was then secured at the center of the die 1 with a blank holder 3. The steel ball 4 was then placed on the center hole 6 of the test plate 2. This placement was carried out such that the axes of the die 1, the test plate 2, the ball 4, and a cylinder rod 8 of the press 5 were in alignment. Then, the bottom end 81 of cylinder rod 8 of the press 5 was lowered to rest against the steel ball 4, and a hydraulic cylinder was extended downward to perform ironing of the test plate so as to form a boss. The reduction ratio of the test plate 2 achieved in a single stroke of working was 45%. Prior to the test, the die 1 and steel ball 4 were preheated to 100° C using an electric furnace.

[0073] After the ironing, the resulting boss was observed visually to determine the presence or absence of seizure to evaluate the performance of the lubricating composition. The result is shown in Table 2 or 3. In each table, the symbol "O" indicates no occurrence of seizure, "○" indicates the occurrence of slight seizure, " Δ" indicates the occurrence of seizure on half of the surface area, and "X" indicates the occurrence of heavy seizure.

(3) Evaluation of flammability

[0074] The flash point of each of the lubricating compositions for cold working of Examples 1 to 18 and Comparative Examples 1 to 3 was measured with a Cleveland open-cup flash point tester in accordance with JIS K2265. The result is also shown in Table 2 or 3.

[0075] 

Table 2

		EXAMPLE
		1	2	3	4	5	6	7	8	9	10
Dispersion of carbonate	No.	1	1	1	2	3	4	1	1	1	1
	Content (%)	41.7	80	41.5	80	80	80	80	80	80	80
	No.	---		5	---
	Content (%)			38.5
Organo-sulfur compound	No.	---						1	2	3	4
	Content (%)							10	10	10	10
Mineral oil	Content (%)	58.3	20	20	20	20	20	10	10	10	10
Total		100	100	100	100	100	100	100	100	100	100
Content of carbonate (%)		15.0	28.8	28.8	32.0	26.7	20.7	28.8	28.8	28.8	28.8
Crystal structure of carbonate		amorphous	amorphous	amorphous	amorphous	Hexagonal (vatelite)	Trigonal (calcite)	amorphous	amorphous	amorphous	amorphous
Mean particle diameter of carbonate (µm)		0,03	0.03	0.03	0.1	50	0.1	0.03	0.03	0.03	0.03
% Hydroxide based on carbonate		0.11	0.11	3.00	0.13	0.09	0.15	0.11	0.11	0.11	0.11
Cold drawing test		O	⊚	O	⊚	O	O	⊚	⊚	⊚	⊚
lroning test		O	⊚	O	O	O	O	O	O	O	O
Flash point (° C)		154	220	230	210	248	232	198	202	218	220

[0076] 

Table 3

		EXAMPLE								COMPARATIVE EXAMPLE
		11	12	13	14	15	16	17	18	1	2	3
Dispersion of carbonate	No.	1	1	1	1	1	1	1	1	1	5	Water-insoluble type lubricating oil
	Content (%)	80	80	80	80	80	80	80	80	33.2	80
Organo-sulfur compound	No.	5	6	7	8	9	10	11	12	---
	Content (%)	10	10	10	10	10	10	10	10
Mineral oil	Content (%)	10	10	10	10	10	10	10	10	66.8	20
Total		100	100	100	100	100	100	100	100	100	100
Content of carbonate (%)		28.8	28.8	28.8	28.8	28.8	28.8	28.8	28.8	12.0*	28.8
Crystal structure of carbonate		amorphous	amorphous	amorphous	amorphous	amorphous	amorphous	amorphous	amorphous	amorphous	amorphous
Mean particle diameter of carbonate (µm)		0.03	0.03	0.03	0.03	0.03	0.03	0.03	0.03	0.03	0.03
% Hydroxide based on carbonate		0.11	0.11	0.11	0.11	0.11	0.11	0.11	0.11	0.11	6.1*
Cold drawing test		⊚	⊚	⊚	⊚	⊚	⊚	⊚	⊚	Δ	×	×
Ironing test		⊚	⊚	⊚	⊚	⊚	⊚	⊚	⊚	Δ	Δ	×
Flash point (°C)		170	224	230	230	178	220	200	218	140	250	224

[0077] As can be seen from Table 3, in Comparative Examples 1 to 3 having conditions outside the scope of the present invention, heavy seizure occurred on the surface of the pipe which had been subjected to cold drawing. In addition, in the above-described ironing test, flaws due to seizure were observed on the boss.
In contrast, as can be seen from Tables 2 and 3, in each of Examples 1 to 18 having conditions within the scope of the present invention, it was confirmed that pipe drawing could be performed without occurrence of surface flaws such as seizure and that no surface flaws such as seizure occurred on the boss in the ironing test.

[0078] In addition, the lubricating compositions of Examples 1 to 18 had a high flash point in the range of 150 - 260° C, so it could be confirmed that these lubricating compositions could be used safely even for cold working under severe working conditions in which the temperatures of the compositions became high.

[0079] The present invention is not limited to the above-described specific examples, and various modifications can be made depending on the purpose and application of the lubricating composition without departing from the scope of the invention.

Claims

1. A lubricating composition for cold working which comprises at least one carbonate selected from alkali metal carbonates and alkaline earth metal carbonates and at least one hydroxide selected from alkali metal hydroxides and alkaline earth metal hydroxides in a lubricating base oil and which is free of chlorine compounds, characterized in that the content of the carbonate in the composition is at least 10% by mass and less than 100% by mass and in that the content of the hydroxide is greater than 0 parts by mass and at most 5 parts by mass per 100 parts by mass of the carbonate.

2. A lubricating composition for cold working as set forth in claim 1 which further contains at least one metal salt selected from alkali metal or alkaline earth metal sulfonates, salicylates, phenates, and carboxylates.

3. A lubricating composition for cold working as set forth in claim 1 or 2 which further contains an organosulfur compound having a carbon atom to which a sulfur atom and a nitrogen or oxygen atom are bonded, the content of the organosulfur compound in the composition being from 0.1 % to 50% by mass.

4. A lubricating composition for cold working as set forth in any of claims 1 to 3 wherein the carbonate has an amorphous crystal structure.

5. A lubricating composition for cold working as set forth in any of claims 1 to 4 wherein the carbonate has a mean particle diameter of not greater than 0.5 micrometers.

6. A lubricating composition for cold working as set forth in any of claims 1 to 5 wherein the alkali metal is sodium and the alkaline earth metal is calcium.

7. A lubricating composition for cold working as set forth in any of claims 1 to 6 wherein the composition has a flash point of 150° C or higher.

8. A lubricating composition for cold working as set forth in claim 2 wherein the content of the metal salt is from 1 to 50 parts by mass per 100 parts by mass of the carbonate.

9. A lubricating composition for cold working as set forth in claim 3 wherein the organosulfur compound is at least one selected from the compounds having formulas (1) to (12):



where x₁ is an integer from 2 to 4;

where R₁ and R₂ are each -CH₃ or -C₂H₅ and may be the same or different from each other;



where x₂ is 1 or 2;

where R₃ is -C(CH₃)₃ or -C₆H₁₁;



where x₃ and x₄ are each an integer from 2 to 4 and may be the same or different from each other, and R₄ and R₅ are each -C₈H₁₇, -C₁₂H₂₅ or -C(S)N(C₂H₅)₂ and may be the same or different from each other;

where R₆ and R₇ are each -CH₃, -C₂H₅, -C₃H₇, -C₄H₉, -C₆H₅, or -CH₂C₆H₅ and may be the same or different from each other, and M is Na, K, or 1/2Ca;

where R₈ is H or -CH₃, and R₉ is -C₅H₁₀NH₂ or -CH(CH₃)C₄H₈NH₂;

where R₁₀, R₁₁, R₁₂, and R₁₃ are each -CH₃, -C₂H₅, -C₃H₇, -C₄H₉, or -CH₂CH(C₂H₅)C₄H₉ and may be the same or different from each other, and x₅ is an integer from 1 to 4;

where x₆ is an integer from 1 to 4; and

where R₁₄ and R₁₆ are each H, -CH₃, or -C₂H₅ and may be the same or different from each other, and R₁₅ and R₁ are each -CH₃, -C₂H₅, or -C₆H₅ and may be the same or different from each other.

10. A method of cold working characterized by subjecting a material to be worked to cold working using a lubricating composition for cold working as set forth in any of claims 1 to 9.

11. A method of cold working as set forth in claim 10 wherein the material to be worked is a stainless steel, a high alloy steel, aluminum, copper, titanium, nickel, or an alloy thereof.

12. A method of cold working as set forth in claim 10 or 11 wherein a metal pipe or tube, a metal wire, a metal rod or bar, or billet is produced by cold working.

13. A method of cold working as set forth in any of claims 10 to 12 wherein the cold working is cold forging or cold pipe forming.

Drawing