U.S. patent application number 10/855501 was filed with the patent office on 2004-12-02 for hard-carbon coated machine tool and cutting oil composition therefor.
This patent application is currently assigned to NISSAN MOTOR CO., LTD.. Invention is credited to Kondo, Tomohiro, Mabuchi, Yutaka, Nishimura, Kimio.
Application Number | 20040242435 10/855501 |
Document ID | / |
Family ID | 32599353 |
Filed Date | 2004-12-02 |
United States Patent
Application |
20040242435 |
Kind Code |
A1 |
Nishimura, Kimio ; et
al. |
December 2, 2004 |
Hard-carbon coated machine tool and cutting oil composition
therefor
Abstract
A machine tool is used for machining a workpiece in the presence
of a cutting oil composition. The machine tool includes a tool base
and a hard carbon coating formed on the tool base. The hard carbon
coating has 1 atomic % or less of hydrogen. The cutting oil
composition contains a base oil and at least one of an ashless
fatty-ester friction modifier and an ashless aliphatic-amine
friction modifier.
Inventors: |
Nishimura, Kimio; (Yokohama,
JP) ; Mabuchi, Yutaka; (Yokohama, JP) ; Kondo,
Tomohiro; (Shizuoka, JP) |
Correspondence
Address: |
FOLEY AND LARDNER
SUITE 500
3000 K STREET NW
WASHINGTON
DC
20007
US
|
Assignee: |
NISSAN MOTOR CO., LTD.
|
Family ID: |
32599353 |
Appl. No.: |
10/855501 |
Filed: |
May 28, 2004 |
Current U.S.
Class: |
508/291 ;
508/371; 508/375; 508/378 |
Current CPC
Class: |
C10M 2201/085 20130101;
C10M 2215/02 20130101; C10M 2219/044 20130101; C10M 2209/104
20130101; C10N 2040/243 20200501; C10N 2050/02 20130101; C10N
2060/06 20130101; C10M 2201/087 20130101; C10M 2201/084 20130101;
C10M 173/02 20130101; C10M 2201/062 20130101; C10N 2010/02
20130101; C10M 2215/223 20130101; C10M 2207/126 20130101; C10M
2219/09 20130101 |
Class at
Publication: |
508/291 ;
508/371; 508/375; 508/378 |
International
Class: |
C10M 141/06; C10M
129/68; C10M 133/00 |
Foreign Application Data
Date |
Code |
Application Number |
May 29, 2003 |
JP |
2003-151855 |
Dec 9, 2003 |
JP |
2003-409856 |
Claims
What is claimed is:
1. A cutting oil composition for a hard-carbon coated machine tool,
comprising: a base oil and at least one of an ashless fatty-ester
friction modifier and an ashless aliphatic-amine friction
modifier.
2. A cutting oil composition according to claim 1, wherein said at
lease one of the ashless fatty-ester friction modifier and the
ashless aliphatic-amine friction modifier has a C.sub.6-C.sub.30
hydrocarbon group, and is contained in an amount of 0.05 to 3.0% by
mass based on the total mass of the cutting oil composition.
3. A cutting oil composition according to claim 1, further
comprising a polybutenyl succinimide and/or a derivative
thereof.
4. A cutting oil composition according to claim 3, wherein the
polybutenyl succinimide and/or the derivative thereof is contained
in an amount of 0.1 to 15% by mass based on the total mass of the
cutting oil composition.
5. A cutting oil composition according to claim 1, further
comprising 0.1% or less by mass of zinc dithiophosphate in terms of
phosphorus based on the total mass of the cutting oil
composition.
6. A cutting oil composition according to claim 1, wherein the oil
is supplied in mist form.
7. A machine tool for machining a workpiece in the presence of a
cutting oil composition, the cutting oil composition containing at
least one of an ashless fatty-ester friction modifier and an
ashless aliphatic-amine friction modifier, the machine tool
comprising: a tool base; and a hard carbon coating formed on the
tool base, the hard carbon coating having 1 atomic % or less of
hydrogen.
8. A machine tool according to claim 7, wherein the hard carbon
coating has 0.5 atomic % or less of hydrogen.
9. A machine tool according to claim 7, wherein the hard carbon
coating is formed by physical vapor deposition.
10. A machine tool according to claim 7, wherein the tool base has
a surface roughness Ra of 0.03 .mu.m or lower.
11. A machine tool unit, comprising: a machine tool including a
tool base and a hard carbon coating formed on the tool base, the
hard carbon coating having 1 atomic % or less of hydrogen; and a
cutting oil composition to lubricate the machine tool, the cutting
oil composition containing at least one of an ashless fatty-ester
friction modifier and an ashless aliphatic-amine friction
modifier.
12. A machine tool unit according to claim 11, wherein the hard
carbon coating has 0.5 atomic % or less of hydrogen.
13. A machine tool unit according to claim 11, wherein the hard
carbon coating is formed by physical vapor deposition.
14. A machine tool unit according to claim 11, wherein the tool
base has a surface roughness Ra of 0.03 .mu.m or lower.
15. A machine tool unit according to claim 11, wherein said at
lease one of the ashless fatty-ester friction modifier and the
ashless aliphatic-amine friction modifier has a C.sub.6-C.sub.30
hydrocarbon group, and is contained in an amount of 0.05 to 3.0% by
mass based on the total mass of the cutting oil composition.
16. A machine tool unit according to claim 11, wherein the cutting
oil composition further contains a polybutenyl succinimide and/or a
derivative thereof.
17. A machine tool unit according to claim 16, wherein the
polybutenyl succinimide and/or the derivative thereof is contained
in an amount of 0.1 to 15% by mass based on the total mass of the
cutting oil composition.
18. A machine tool unit according to claim 11, wherein the cutting
oil composition further contains 0.1% or less by mass of zinc
dithiophosphate in terms of phosphorus based on the total mass of
the cutting oil composition.
19. A machine tool unit according to claim 11, wherein the cutting
oil composition is supplied in mist form.
Description
BACKGROUND OF THE INVENTION
[0001] The prevent invention relates to a hard-carbon coated
machine tool and a cutting oil composition therefor.
[0002] It is desired that a machine tool (such as a drill or an end
mill) be able to machine a workpiece with high precision, to reduce
cutting resistance for improvement in machining efficiency and to
maintain a high-precision high-efficiency machining capability over
an extended time period. In order to respond to these desires,
Japanese Laid-Open Patent Publication No. 2003-25117 and No.
2001-62605 propose forming a high-hardness, wear-resistant coating
on the machine tool by chemical vapor deposition (CVD) or physical
vapor deposition (PVD).
SUMMARY OF THE INVENTION
[0003] With the recent awareness of environmental issues, the use
of a cutting oil in the machining process has become limited. In
such a semi-dry machining process, however, the cutting point where
the machine tool cuts a workpiece is not cooled sufficiently. As a
result, there arises a problem that, in the case of the machine
tool having a carbide base and a ceramic coating formed thereon,
the machine tool is susceptible to adhesion with the workpiece. In
addition, it is difficult to remove swarf from the cutting point.
In the case of another diamond machine tool, there arises a problem
that the machine tool is susceptible to chipping. The tool life of
the machine tool is then shortened due to these problems.
[0004] It is therefore an object of the present invention to
provide a hard-carbon coated machine tool and a cutting oil
composition therefor, wherein the machine tool is, when lubricated
with the cutting oil composition, capable of machining a workpiece
with high accuracy and efficiency while attaining a long tool life
even in a semi-dry machining process.
[0005] As a result of extensive researches, it was found by the
present inventors that a hard-carbon coated machine tool shows
excellent low-friction characteristics in the presence of a cutting
oil composition that contains a specific ashless friction modifier
or modifiers. The present invention has been accomplished based on
the above finding.
[0006] According to a first aspect of the invention, there is
provided a cutting oil composition for a hard-carbon coated machine
tool, comprising: a base oil and at least one of an ashless
fatty-ester friction modifier and an ashless aliphatic-amine
friction modifier.
[0007] According to a second aspect of the invention, there is
provided a machine tool for machining a workpiece in the presence
of a cutting oil composition, the cutting oil composition
containing at least one of an ashless fatty-ester friction modifier
and an ashless aliphatic-amine friction modifier, the machine tool
comprising: a tool base; and a hard carbon coating formed on the
tool base, the hard carbon coating having 1 atomic % or less of
hydrogen.
[0008] According to a third aspect of the invention, there is
provided a machine tool unit, comprising: a machine tool having a
tool base and a hard carbon coating formed on the tool base, the
hard carbon coating having 1 atomic % or less of hydrogen; and a
cutting oil composition to lubricate the machine tool, the cutting
oil composition containing at least one of an ashless fatty-ester
friction modifier and an ashless aliphatic-amine friction
modifier.
[0009] The other objects and features of the invention will also
become understood from the following description.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] FIG. 1A is an end view of a machine tool according to a
first embodiment of the present invention.
[0011] FIG. 1B is a side view of the machine tool of FIG. 1A.
[0012] FIG. 2A is an end view of a machine tool according to a
second embodiment of the present invention.
[0013] FIG. 2B is a side view of the machine tool of FIG. 2A.
[0014] FIG. 3A is an end view of a machine tool according to a
third embodiment of the present invention.
[0015] FIG. 3B is a side view of the machine tool of FIG. 3A.
[0016] FIG. 4 is a schematic view showing a unit for friction
test.
[0017] FIG. 5 is a graph showing a comparison of the tool life of a
machine tool according to an exemplary embodiment of the present
invention to that of a machine tool according to the earlier
technology.
[0018] FIG. 6 is a graph showing a comparison of the machining
accuracy and efficiency of a machine tool according to an exemplary
embodiment of the present invention to those of a machine tool
according to the earlier technology.
DESCRIPTION OF THE EMBODIMENTS
[0019] The present invention will be described below in detail. In
the following description, all percentages (%) are by mass unless
otherwise specified.
[0020] In the present invention, a hard-carbon coated machine tool
is used for machining a workpiece under a condition that the
machine tool and workpiece are lubricated with the cutting oil
composition.
[0021] The hard-carbon coated machine tool of the present invention
is not particularly restricted, and can be formed into a drill
(such as a gun drill), a reamer or an end mill.
[0022] For example, the hard-carbon coated machine tool may be
embodied as a drill 1, as shown in FIGS. 1A and 1B, and be used for
creating a hole in the workpiece in the presence of the cutting oil
composition. The drill 1 has a tool base made of a steel or carbide
material and a hard carbon coating 3 formed on the tool base to
cover the whole of the drill 1 including a cutting edge 2 (although
it may seem as if the hard carbon coating 3 covers only the shaded
areas in FIGS. 1A and 1B).
[0023] As shown in FIGS. 2A and 2B, the hard-carbon coated machine
tool may be embodied as another type of drill (called a gun drill)
21 and be used for creating a deeper hole in the workpiece in the
presence of the cutting oil composition. The gun drill 21 has a
tool base made of a steel or carbide material and a hard carbon
coating 23 formed on the tool base to cover a body portion 24 of
the gun drill 21 including a cutting edge 22, a groove 26 and a
core 27 (although it may seem as if the hard carbon coating 23
covers only the shaded areas in FIGS. 2A and 2B). An oil hole 25 is
formed through the drill body portion 24 for supplying the cutting
oil composition.
[0024] As shown in FIGS. 3A and 3B, the hard-carbon coated machine
tool may be embodied as a reamer 31 and be used for enlarging,
shaping, smoothing, or otherwise fining a hole in the workpiece in
the presence of the cutting oil composition. The reamer 31 has a
tool base made of a steel or carbide material and a hard carbon
coating 33 formed on the tool base to cover a body portion 34 of
the reamer 31 including a cutting edge 32 (although it may seem as
if the hard carbon coating 33 covers only the shaded areas in FIGS.
3A and 3B).
[0025] The hard carbon coatings 3, 23 and 33 can be formed by
various physical vapor deposition (PVD) processes, and each of the
hard carbon coatings 3, 23 and 33 is preferably a diamond-like
carbon (DLC) coating formed by arc ion plating. The DLC coating is
a coating of amorphous carbon, such as hydrogen-free amorphous
carbon (a-C), hydrogen-containing amorphous carbon (a-C:H) and
metal-containing carbon or metal carbide (MeC) that contains metal
elements of e.g. titanium (Ti) or molybdenum (Mo). In order to
obtain a larger friction reducing effect, it is desirable to
minimize the amount of hydrogen in the DLC coating. The amount of
hydrogen in the DLC coating is preferably 1 atomic % or less, more
preferably 0.5 atomic % or less, still more preferably
substantially zero.
[0026] Further, the hard carbon coatings 3, 23 and 33 reflect the
surface roughness of the tool bases, respectively. When the tool
bases of the drill 1, the gun drill 2 and the reamer 3 have an
arithmetic mean surface roughness Ra exceeding 0.3 .mu.m, the hard
carbon coatings 3, 23 and 33 become susceptible to cracking due to
increased local contact of their surface roughness peaks with the
workpieces. It is thus preferable to control the surface roughness
Ra of the tool bases to be covered with the respective hard carbon
coatings 3, 23 and 33 to 0.03 .mu.m or lower.
[0027] The cutting oil composition of the present invention
contains a base oil and at least one of an ashless fatty-ester
friction modifier and an ashless aliphatic-amine friction modifier,
and may be supplied in mist form to limit the amount of the cutting
oil composition supplied effectively.
[0028] The base oil is not particularly limited, and can be
selected from any base oil compounds commonly used for cutting
oils, such as mineral oils, synthetic oils, and fats.
[0029] Specific examples of the mineral oils include normal
paraffins and paraffin or naphthene oils each prepared by
extracting cutting oil fractions from petroleum by atmospheric or
reduced-pressure distillation, and then, purifying the obtained
cutting oil fractions with at least one of the following
treatments: solvent deasphalting, solvent extraction,
hydrocracking, solvent dewaxing, hydro-refining, wax isomerization,
surfuric acid treatment and clay refining. Although a
solvent-refined or hydro-refined mineral oil is often used as the
base oil, it is more desirable to use a mineral oil prepared by
Gas-To-Liquids (GTL) wax isomerization or by deep hydrocraking for
reduction of an aromatics content in the oil.
[0030] Specific examples of the synthetic oils include:
poly-.alpha.-olefins, such as 1-octene oligomer, 1-decene oligomer
and ethylene-propylene oligomer, and hydrides thereof; isobutene
oligomer and a hydride thereof; isoparaffines; alkylbenzenes;
alkylnaphthalenes; diesters, such as ditridecyl glutarate, dioctyl
adipate, diisodecyl adipate, ditridecyl adipate and dioctyl
sebacate; polyol esters, such as trimethylolpropane esters (e.g.
trimethylolpropane caprylate, trimetylolpropane pelargonate and
trimethylolpropane isostearate) and pentaerythritol esters (e.g.
pentaerythritol-2-ethyl hexanoate and pentaerythritol pelargonate);
polyoxyalkylene glycols; dialkyl diphenyl ethers; and polyphenyl
ethers. Among others, preferred are poly-.alpha.-olefins, such as
1-octene oligomer and 1-decene oligomer, and hydrides thereof.
[0031] The above-mentioned base oil compounds may be used alone or
in combination thereof. It the case of using as the base oil a
mixture of two or more of the above base oil compounds, there is no
particular limitation to the mixing ratio of the base oil
compounds.
[0032] The sulfur content of the base oil is not particularly
restricted, and is preferably 0.2% or less, more preferably 0.1% or
less, still more preferably 0.05% or lower, based on the total mass
of the base oil. It is desirable to use the hydro-refined mineral
oil or the synthetic oil because the hydro-refined mineral oil and
the synthetic oil have a sulfur content of not more than 0.005% or
substantially zero (lower than a detection limit of e.g. 5
ppm).
[0033] The aromatics content of the base oil is also not
particularly restricted. Herein, the aromatics content is defined
as the amount of an aromatics fraction determined according to ASTM
D2549. In order for the cutting oil composition to maintain its
low-friction characteristics over time, the aromatics content of
the base oil is preferably 15% or less, more preferably 10% or
less, still more preferably 5% or less, based on the total mass of
the base oil. The cutting oil composition undesirably deteriorates
in oxidation stability when the aromatics content of the base oil
exceeds 15%.
[0034] The kinematic viscosity of the base oil is not particularly
restricted. The kinematic viscosity of the base oil is preferably 2
mm.sup.2/s or higher, more preferably 3 mm.sup.2/S, as measured at
100.degree. C. At the same time, the kinematic viscosity of the
base oil is preferably 20 mm.sup.2/s or lower, more preferably 10
mm.sup.2/s or lower, most preferably 8 mm.sup.2/s or lower, as
measured at 100.degree. C. When the kinematic viscosity of the base
oil is less than 2 mm.sup.2/s at 100.degree. C., there is a
possibility that the cutting oil composition fails to provide
sufficient wear resistance and causes a considerable evaporation
loss. When the kinematic viscosity of the base oil exceeds 20
mm.sup.2/s at 100.degree. C., there is a possibility that the
cutting oil composition fails to exhibit low-friction
characteristics and deteriorates in low-temperature performance. In
the case of using two or more of the above-mentioned base oil
compounds in combination, it is not necessary to limit the
kinematic viscosity of each base oil compound to within such a
specific range so long as the kinematic viscosity of the mixture of
the base oil compounds at 100.degree. C. is in the specified
range.
[0035] The viscosity index of the base oil is not particularly
restricted, and is preferably 80 or higher, more preferably 100 or
higher, most preferably 120 or higher, in order for the cutting oil
composition to attain improved oil-consumption performance and
low-temperature viscosity characteristics.
[0036] As the fatty-ester friction modifier and the aliphatic-amine
friction modifier, there may be used a fatty acid ester and an
aliphatic amine having C.sub.6-C.sub.30 straight or branched
hydrocarbon chains, preferably C.sub.8-C.sub.24 straight or
branched hydrocarbon chains, more preferably C.sub.10-C.sub.20
straight or branched hydrocarbon chains, respectively. When the
carbon number of the hydrocarbon chain of the friction modifier is
not within the range of 6 to 30, there arises a possibility of
failing to obtain a sufficient friction reducing effect. Specific
examples of the C.sub.6-C.sub.30 straight or branched hydrocarbon
chain include: alkyl groups, such as hexyl, heptyl, octyl, nonyl,
decyl, undecyl, dodecyl, tridecyl, tetradecyl, pentadecyl,
hexadecyl, heptadecyl, octadecyl, nonadecyl, icosyl, heneicosyl,
docosyl, tricosyl, tetracosyl, pentacosyl, hexacosyl, heptacosyl,
octacosyl, nonacosyl and triacontyl; and alkenyl groups, such as
hexenyl, heptenyl, octenyl, nonenyl, decenyl, undecenyl, dodecenyl,
tridecenyl, tetradecenyl, pentadecenyl, hexadecenyl, heptadecenyl,
octadecenyl, nonadecenyl, icosenyl, heneicosenyl, docosenyl,
tricosenyl, tetracosenyl, pentacosenyl, hexacosenyl, heptacosenyl,
octacosenyl, nonacosenyl and triacontenyl. The above alkyl and
alkenyl groups include all possible isomers.
[0037] The fatty acid ester is exemplified by esters of fatty acids
having the above hydrocarbon groups and monofunctional aliphatic
alcohols or aliphatic polyols. Specific examples of such fatty acid
esters include glycerol monolate, glycerol diolate, sorbitan
monolate and sorbitan diolate.
[0038] The aliphatic amine is exemplified by aliphatic monoamines
and alkylene oxide adducts thereof, aliphatic polyamines,
imidazolines and derivatives thereof each having the above
hydrocarbon groups. Specific examples of such aliphatic amines
include: aliphatic amine compounds, such as laurylamine,
lauryldiethylamine, lauryldiethanolamine, dodecyldipropanolamine,
palmitylamine, stearylamine, stearyltetraethylenepentamine,
oleylamine, oleylpropylenediamine, oleyldiethanolamine and
N-hydroxyethyloleylimidazolyne; alkylene oxide adducts of the above
aliphatic amine compounds (C.sub.6-C.sub.28 alkyl or alkenyl
amines), such as N,N-dipolyoxyalkylene-N-alkyl (or alkenyl) amines;
and acid-modified compounds prepared by reacting the above
aliphatic amine compounds with C.sub.2-C.sub.30 monocarboxylic
acids (such as fatty acids) or C.sub.2-C.sub.30 polycarboxylic
acids (such as oxalic acid, phthalic acid, trimellitic acid and
pyromellitic acid) so as to neutralize or amidate the whole or part
of the remaining amino and/or imino groups. Above all,
N,N-dipolyoxyethylene-N-oleylamine is preferably used.
[0039] The amount of the fatty-ester friction modifier and/or the
aliphatic-amine friction modifier contained in the cutting oil
composition is not particularly restricted, and is preferably 0.05
to 3.0%, more preferably 0.1 to 2.0%, and most preferably 0.5 to
1.4%, based on the total mass of the cutting oil composition. When
the amount of the fatty-ester friction modifier and/or the
aliphatic-amine friction modifier in the cutting oil composition is
less than 0.05%, there arises a possibility of failing to obtain a
sufficient friction reducing effect. When the amount of the
fatty-ester friction modifier and/or the aliphatic-amine friction
modifier in the cutting oil composition exceeds 3.0%, the
solubility of the friction modifier or modifiers in the base oil
becomes so low that the cutting oil composition deteriorates in
storage stability to cause precipitations.
[0040] The cutting oil composition preferably includes polybutenyl
succinimide and/or a derivative thereof as an ashless
dispersant.
[0041] As the polybutenyl succinimide, there may be used compounds
represented by the following general formulas (1) and (2). 1
[0042] In the formulas (1) and (2), PIB represents a polybutenyl
group derived from polybutene having a number-average molecular
weight of 900 to 3500, preferably 1000 to 2000, that can be
prepared by polymerizing high-purity isobutene or a mixture of
1-butene and isobutene in the presence of a boron fluoride catalyst
or aluminum chloride catalyst. When the number-average molecular
weight of the polybutene is less than 900, there is a possibility
of failing to obtain a sufficient detergent effect. When the
number-average molecular weight of the polybutene exceeds 3500, the
polybutenyl succinimide tends to deteriorate in low-temperature
fluidity. The polybutene may be purified, before used for the
production of the polybutenyl succinimide, by removing trace
amounts of fluorine and chlorine residues resulting from the above
polybutene production catalyst with any suitable treatment (such as
an adsorption or washing process) in such a way as to control the
amount of the fluorine and chlorine residues in the polybutene to
50 ppm or less, desirably 10 ppm or less, more desirably 1 ppm or
less.
[0043] Further, n represents an integer of 1 to 5, preferably 2 to
4, in the formulas (1) and (2) in view of the detergent effect.
[0044] The production method of the polybutenyl succinimide is not
particularly restricted. For example, the polybutenyl succinimide
may be prepared by reacting a chlorinated product of the
polybutene, or the polybutene from which fluorine and chlorine
residues are sufficiently removed, with maleic anhydride at 100 to
200.degree. C. to form polybutenyl succinate, and then, reacting
the thus-formed polybutenyl succinate with polyamine (such as
diethylene triamine, triethylene tetramine, tetraethylene pentamine
or pentaethylene hexamine).
[0045] As the polybutenyl succinimide derivative, there may be used
boron- or acid-modified compounds obtained by reacting the
polybutenyl succinimides of the formula (1) or (2) with boron
compounds or oxygen-containing organic compounds so as to
neutralize or amidate the whole or part of the remaining amino
and/or imide groups. Among others, boron-containing polybutenyl
succinimides, especially boron-containing
bis(polybutenyl)succinimide, are preferably used. The content ratio
of nitrogen to boron (B/N) by mass in the boron-containing
polybutenyl succinimide is usually 0.1 to 3, preferably 0.2 to
1.
[0046] The boron compound used for producing the polybutenyl
succinimide derivative can be a boric acid, a borate or a boric
acid ester. Specific examples of the boric acid include orthoboric
acid, metaboric acid and tetraboric acid. Specific examples of the
borate include: ammonium salts such as ammonium borates (e.g.
ammonium metaborate, ammonium tetraborate, ammonium pentaborate and
ammonium octaborate). Specific examples of the boric acid ester
include: esters of boric acids and alkylalcohols (preferably
C.sub.1-C.sub.6 alkylalcohols), such as monomethyl borate, dimethyl
borate, trimethyl borate, monoethyl borate, diethyl borate,
triethyl borate, monopropyl borate, dipropyl borate, tripropyl
borate, monobutyl borate, dibutyl borate and tributyl borate.
[0047] The oxygen-containing organic compound used for producing
the polybutenyl succinimide derivative can be any of
C.sub.1-C.sub.30 monocarboxylic acids, such as formic acid, acetic
acid, glycolic acid, propionic acid, lactic acid, butyric acid,
valeric acid, caproic acid, enanthic acid, caprylic acid,
pelargonic acid, capric acid, undecylic acid, lauric acid,
tridecanoic acid, myristic acid, pentadecanoic acid, palmitic acid,
margaric acid, stearic acid, oleic acid, nonadecanoic acid and
eicosanoic acid; C.sub.2-C.sub.30 polycarboxylic acids, such as
oxalic acid, phthalic acid, trimellitic acid and pyromellitic acid,
and anhydrides and esters thereof; C.sub.2-C.sub.6 alkylene oxides;
and hydroxy(poly)oxyalkylene carbonates.
[0048] The amount of the polybutenyl succinimide and/or the
derivative thereof added in the cutting oil composition is not
particularly restricted, and is preferably 0.1 to 15%, more
preferably 1.0 to 12%, based on the total mass of the cutting oil
composition. When the amount of the polybutenyl succineimide and/or
the derivative thereof in the cutting oil composition is less than
0.1%, there is a possibility of failing to attain a sufficient
detergent effect. When the amount of the polybutenyl succineimide
and/or the derivative thereof in the cutting oil composition
exceeds 15%, the cutting oil composition may deteriorate in
demulsification ability. In addition, there is a possibility of
failing to obtain a detergent effect commensurate with the amount
of the polybutenyl succineimide and/or the derivative thereof
added.
[0049] Furthermore, the cutting oil composition preferably includes
zinc dithiophosphate of the following general formula (3) as an
antioxidant and as an anti-wear agent. 2
[0050] In the general formula (3), R.sup.4, R.sup.5, R.sup.6 and
R.sup.7 each represent C.sub.1-C.sub.24 hydrocarbon groups. The
C.sub.1-C.sub.24 hydrocarbon group is preferably a C.sub.1-C.sub.24
straight-chain or branched-chain alkyl group, a C.sub.3-C.sub.24
straight-chain or branched-chain alkenyl group, a C.sub.5-C.sub.13
cycloalkyl or straight- or branched-chain alkylcycloalkyl group, a
C.sub.6-C.sub.18 aryl or straight- or branched-chain alkylaryl
group, or a C.sub.7-C.sub.19 arylalkyl group. The above alkyl group
or alkenyl group can be primary, secondary or tertiary. Specific
examples of R.sup.4, R.sup.5, R.sup.6 and R.sup.7 include: alkyl
groups, such as methyl, ethyl, propyl, butyl, pentyl, hexyl,
heptyl, octyl, nonyl, decyl, undecyl, dodecyl, tridecyl,
tetradecyl, pentadecyl, hexadecyl, heptadecyl, octadecyl,
nonadecyl, icosyl, heneicosyl, docosyl, tricosyl and tetracosyl;
alkenyl groups, such as propenyl, isopropenyl, butenyl, butadienyl,
pentenyl, hexenyl, heptenyl, octenyl, nonenyl, decenyl, undecenyl,
dodecenyl, tridecenyl, tetradecenyl, pentadecenyl, hexadecenyl,
heptadecenyl, octadecenyl (oleyl), nonadecenyl, icosenyl,
heneicosenyl, docosenyl, tricosenyl and tetracosenyl; cycloalkyl
groups, such as cyclopentyl, cyclohexyl and cycloheptyl;
alkylcycloalkyl groups, such as methylcyclopentyl,
dimethylcyclopentyl, ethylcyclopentyl, propylcyclopentyl,
ethylmethylcyclopentyl, trimethylcyclopentyl, diethylcyclopentyl,
ethyldimethylcyclopentyl, propylmethylcyclopentyl,
propylethylcyclopentyl, di-propylcyclopentyl,
propylethylmethylcyclopenty- l, methylcyclohexyl,
dimethylcyclohexyl, ethylcyclohexyl, propylcyclohexyl,
ethylmethylcyclohexyl, trimethylcyclohexyl, diethylcyclohexyl,
ethyldimethylcyclohexyl, propylmethylcyclohexyl,
propylethylcyclohexyl, di-propylcyclohexyl,
propylethylmethylcyclohexyl, methylcycloheptyl,
dimethylcycloheptyl, ethylcycloheptyl, propylcycloheptyl,
ethylmethylcycloheptyl, trimethylcycloheptyl, diethylcycloheptyl,
ethyldimethylcycloheptyl, propylmethylcycloheptyl,
propylethylcycloheptyl, di-propylcycloheptyl and
propylethylmethylcyclohe- ptyl; aryl groups, such as phenyl and
naphthyl; alkylaryl groups, such as tolyl, xylyl, ethylphenyl,
propylphenyl, ethylmethylphenyl, trimethylphenyl, butylphenyl,
propylmethylphenyl, diethylphenyl, ethyldimethylphenyl,
tetramethylphenyl, pentylphenyl, hexylphenyl, heptylphenyl,
octylphenyl, nonylphenyl, decylphenyl, undecylphenyl and
dodecylphenyl; and arylalkyl groups, such as benzyl, methylbenzyl,
dimethylbenzyl, phenethyl, methylphenethyl and dimethylphenethyl.
The above hydrocarbon groups include all possible isomers. Above
all, preferred are C.sub.1-C.sub.18 straight- or branched-chain
alkyl groups and C.sub.6-C.sub.18 aryl or straight- or
branched-chain alkylaryl groups.
[0051] The zinc dithiophosphate is exemplified by zinc
diisopropyldithiophosphate, zinc diisobutyldithiophosphate, zinc
di-sec-butyldithiophosphate, zinc di-sec-pentyldithiophosphate,
zinc di-n-hexyldithiophosphate, zinc di-sec-hexyldithiophosphate,
zinc di-octyldithiophosphate, zinc di-2-ethylhexyldithiophosphate,
zinc di-n-decyldithiophosphate, zinc di-n-dodecyldithiophosphate
and zinc diisotridecyldithiophosphate.
[0052] The amount of the zinc dithiophosphate contained in the
cutting oil composition is not particularly restricted. In order to
obtain a larger friction reducing effect, the amount of the zinc
dithiophosphate in the cutting oil composition is preferably 0.1%
or less, more preferably 0.06% or less, still more preferably a
minimum effective amount, in terms of the phosphorus element, based
on the total mass of the cutting oil composition. When the amount
of the zinc dithiophosphate in the cutting oil composition exceeds
0.1%, there is a possibility of inhibiting the effect of the
ashless fatty-ester friction modifier and/or the ashless
aliphatic-amine friction modifier.
[0053] The production method of the zinc dithiophosphate is not
particularly restricted, and the zinc dithiophosphate can be
prepared by any known method. For example, the zinc dithiophosphate
may be prepared by reacting alcohols or phenols having the above
R.sup.4, R.sup.5, R.sup.6 and R.sup.7 hydrocarbon groups with
phosphorous pentasulfide to form dithiophosphoric acid, and then,
neutralizing the thus-formed dithiophosphoric acid with zinc oxide.
It is noted that the molecular structure of zinc dithiophosphate
differs according to the alcohols or phenols used as raw materials
for the zinc dithiophosphate production.
[0054] The above-mentioned zinc dithiophosphate compounds may be
used alone or in the form of a mixture of two or more thereof. In
the case of using two or more of the above zinc dithiophosphate
compounds in combination, there is no particular limitation to the
mixing ratio of the zinc dithiophosphate compounds.
[0055] The cutting oil composition may further include any other
additive or additives, such as a metallic detergent, an
antioxidant, a viscosity index improver, a friction modifier other
than the above-mentioned fatty-ester friction modifier and the
aliphatic-amine friction modifier, an ashless dispersant other than
the above-mentioned polybutenyl succinimide and the derivative
thereof, an anti-wear agent or extreme-pressure agent, a rust
inhibitor, a nonionic surfactant, a demulsifier, a metal
deactivator and/or an anti-foaming agent, so as to meet the
performance required of the cutting oil composition.
[0056] The metallic detergent can be selected from any metallic
detergent compounds commonly used for cutting oils. Specific
examples of the metallic detergent include sulfonates, phenates and
salicylates of alkali metals, such as sodium (Na) and potassium
(K), or alkali-earth metals, such as calcium (Ca) and magnesium
(Mg); and a mixture of two or more thereof. Among others, sodium
and calcium sulfonates, sodium and calcium phenates, and sodium and
calcium salicylates are suitably used. The total base number and
amount of the metallic detergent can be determined in accordance
with the performance required of the cutting oil composition. The
total base number of the metallic detergent is usually 0 to 500
mgKOH/g, preferably 150 to 400 mgKOH/g, as measured by perchloric
acid method according to ISO 3771. The amount of the metallic
detergent is usually 0.1 to 10% based on the total mass of the
cutting oil composition.
[0057] The antioxidant can be selected from any antioxidant
compounds commonly used for cutting oils. Specific examples of the
antioxidant include: phenolic antioxidants, such as
4,4'-methylenebis(2,6-di-tert-but- ylphenol) and
octadecyl-3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate; amino
antioxidants, such as phenyl-.alpha.-naphthylamine,
alkylphenyl-.alpha.-naphthylamine and alkyldiphenylamine; and a
mixture of two or more thereof. The amount of the antioxidant is
usually 0.01 to 5% based on the total mass of the cutting oil
composition.
[0058] As the viscosity index improver, there may be used:
non-dispersion type polymethacrylate viscosity index improvers,
such as copolymers of one or more kinds of methacrylates and
hydrogenated products thereof; dispersion type polymethacrylate
viscosity index improvers, such as copolymers of metacrylates
further containing nitrogen compounds; and other viscosity index
improvers, such as copolymers of ethylene and .alpha.-olefin (e.g.
propylene, 1-butene or 1-pentene) and hydrogenated products
thereof, polyisobutylenes and hydrogenated products thereof,
styrene-diene hydrogenated copolymers, styrene-maleate anhydride
copolymers, and polyalkylstyrenes. The molecular weight of the
viscosity index improver needs to be determined in view of the
shear stability. For example, the number-average molecular weight
of the viscosity index improver is desirably in the range of 5000
to 1000000, more desirably 100000 to 800000, for the dispersion or
non-dispersion type polymethacrylate; in the range of 800 to 5000
for the polyisobutylene or hydrogenated product thereof; and in the
range of 800 to 300,000, more desirably 10,000 to 200,000 for the
ethylene/.alpha.-olefin copolymer or hydrogenated product thereof.
The above viscosity index improving compounds can be used alone or
in the form of a mixture of two or more thereof. The amount of the
viscosity index improver is preferably 0.1 to 40.0% based on the
total mass of the cutting oil composition.
[0059] The friction modifier other than the above-mentioned
fatty-ester and aliphatic-amine friction modifiers can be any of
ashless friction modifiers, such as boric acid esters, higher
alcohols or aliphatic ethers, and metallic friction modifiers, such
as molybdenum dithiophosphate, molybdenum dithiocarbamate and
molybdenum disulfide.
[0060] The ashless dispersant other than the above-mentioned
polybutenyl succinimide and derivative thereof can be any of
polybutenylbenzylamines and polybutenylamines each having
polybutenyl groups of which the number-average molecular weight is
900 to 3500, polybutenyl succinimides having polybutenyl groups of
which the number-average molecular weight is less than 900, and
derivatives thereof.
[0061] As the anti-friction agent or extreme-pressure agent, there
may be used: disulfides, sulfurized fats, olefin sulfides,
phosphate esters having one to three C.sub.2-C.sub.20 hydrocarbon
groups, thiophosphate esters, phosphite esters, thiophosphite
esters and amine salts of these esters.
[0062] As the rust inhibitor, there may be used: alkylbenzene
sulfonates, dinonylnaphthalene sulfonates, esters of
alkenylsuccinic acids and esters of polyalcohols.
[0063] As the nonionic surfactant and demulsifier, there may be
used: noionic polyalkylene glycol surfactants, such as
polyoxyethylene alkylethers, polyoxyethylene alkylphenylethers and
polyoxyethylene alkylnaphthylethers.
[0064] The metal deactivator can be any of imidazolines, pyrimidine
derivatives, thiazole and benzotriazole.
[0065] The anti-foaming agent can be any of silicones,
fluorosilicones and fluoroalkylethers.
[0066] Each of the friction modifier other than the fatty-ester and
aliphatic-amine friction modifiers, the ashless dispersant other
than the polybutenyl succinimide and derivative thereof, the
anti-wear agent or extreme-pressure agent, the rust inhibitor and
the demulsifier is usually contained in an amount of 0.01 to 5%
based on the total mass of the cutting oil composition, the metal
deactivator is usually contained in an amount of 0.005 to 1% based
on the total mass of the cutting oil composition, and the
anti-foaming agent is usually contained in an amount of 0.0005 to
1% based on the total mass of the cutting oil composition.
[0067] As described above, the hard-carbon coated machine tool
shows a considerably low friction coefficient in combination with
the cutting oil composition containing the ashless fatty-ester
friction modifier and/or the ashless aliphatic-amine friction
modifier so that the adhesion of the workpiece or swarf to the
machine tool does not occur. This makes it possible to increase
machining precision and efficiency and to avoid tool breakage. The
machine tool is thus able to machine a workpiece with high
precision and efficiency while attaining a longer tool life.
[0068] The present invention will be described in more detail by
reference to the following examples. It should be however noted
that the following examples are only illustrative and not intended
to limit the invention thereto.
EXAMPLE 1
[0069] A test unit was set up with a sliding member 10 (as a test
sample) and a counterpart member 11 as shown in FIG. 4. The sliding
member 10 was prepared by cutting a semi-cylindrical base piece
from S45C steel (compliant with JIS G4051), and then, forming a DLC
coating on the base piece by PVD arc ion plating to cover a curved
portion 10a of the sliding member 10. The sliding member 10 had a
size of 8.times.10.times.40 mm, and the DLC coating had a hydrogen
content of 0.5 atomic % or less, a Knoop hardness Hk of 2170
kg/mm.sup.2, a surface roughness Ry of 0.03 .mu.m and a thickness
of 0.5 .mu.m. On the other hand, the counterpart member 11 was
formed into a plate of ADC12 alloy (compliant with JIS H5302)
having a size of 40.times.60.times.7 mm. The sliding member 10 and
the counterpart member 11 were lubricated with a cutting oil
composition A. The chemical makeup of the cutting oil composition A
is shown in TABLE 1. In TABLE, the amount of each component in the
cutting oil composition A is indicated with respect to the total
mass of the cutting oil composition A.
[0070] The coefficient of friction of the sliding member 10 was
measured by sliding the curved portion 10a of the sliding member 10
over the counterpart member 11 in such a manner as to cause a
reciprocating motion of the sliding surface 10 in the direction of
arrows Q and R within a range A of the counterpart member 11 while
pressing the sliding member 10 against the counterpart member 11
under a load P. The test was conducted under the following test
conditions. The test result is shown in TABLE 2.
[0071] [Test Conditions]
[0072] Test unit: Reciprocating type friction/wear tester
[0073] Sliding member: 8.times.10.times.40 mm (JIS S45C base with
DLC coating)
[0074] Counterpart member: 40.times.60.times.7 mm (JIS ADC12
plate)
[0075] Reciprocating speed: 600 cpm (counts per minute)
[0076] Test temperature: 25.degree. C.
[0077] Load (P) applied: 10 kgf
[0078] Measuring time: 60 min. after the test start.
COMPARATIVE EXAMPLE 1
[0079] The same test unit as used in Example 1 was set up, except
that the sliding member 10 and the counterpart member 11 were
lubricated with a cutting oil composition B. The chemical makeup of
the cutting oil composition B is also indicated in TABLE 1. In
TABLE 1, the amount of each component in the cutting oil
composition B is indicated with respect to the total mass of the
cutting oil composition B. The coefficient of friction of the
sliding member 10 was measured under the same conditions as used in
Example 1. The test result is shown in TABLE 2.
COMPARATIVE EXAMPLE 2
[0080] The same test unit as used in Comparative Example 1 was set
up, except that the sliding member 10 was made of K10 carbide
(compliant with ISO 513) with no DLC coating. The coefficient of
friction of the sliding member 10 was measured under the same
conditions as used in Example 1 and Comparative Example 1. The test
result is shown in TABLE 2.
1 TABLE 1 Oil composition (mass %) A B Base oil 87 100 (mineral
oil) Fatty-ester friction modifier 1.0 -- (glycerol monolate)
Aliphatic-amine friction modifier -- -- Ashless dispersant 5.0 --
(polybutenyl succinimide) Other additives (including an 7.0 --
antioxidant and a rust inhibitor)
[0081]
2 TABLE 2 Friction coefficient Example 1 0.05 Comparative Example 1
0.08 Comparative Example 2 0.11
[0082] As is apparent from TABLE 2, the sliding member 10 of
Example 1 had a much lower friction coefficient than those of
Comparative Examples 1 and 2.
EXAMPLE 2
[0083] The same type of drill as shown in FIG. 1 was produced by
preparing a tool base of K10 carbide (compliant with ISO 513) and
forming a DLC coating on the tool base. The DLC coating had a
hydrogen content of 0.5 atomic % or less, a Knoop hardness Hk of
2170 kg/mm.sup.2, a surface roughness Ry of 0.03 .mu.m and a
thickness of 0.5 .mu.m. The thus-produced drill was set to a main
shaft of a machining center, thereby machining a workpiece while
supplying the above cutting oil composition A in mist form. The
machining conditions are indicated below. In the process of
machining, the drill was tested for cutting resistance (i.e., a
cutting force applied to the main shaft). The test result is shown
in FIG. 5.
[0084] [Machining Conditions]
[0085] Workpiece: ADC 12/AC2A alloy (JIS H53 02/H5202)
[0086] Cutting speed: 213.52 m/min.
[0087] Shaft rotation speed: 10000 rpm
[0088] Feed rate: 0.2 mm/rev.
[0089] Oil mist discharge rate: 5 cc/hr.
COMPARATIVE EXAMPLE 3
[0090] The same drill as used in Example 2 was produced, except
that no DLC coating was formed on the drill. The produced drill was
set to a machining center, thereby machining a workpiece while
supplying the above cutting oil composition B in mist form. The
machining conditions were the same as in Example 2. In the process
of machining, the drill was tested for cutting resistance. The test
result is shown in FIG. 5.
[0091] As is apparent from FIG. 5, the drill of Example 2 had much
lower cutting resistance than that of Comparative Example 3.
EXAMPLE 3
[0092] The same type of reamer as shown in FIG. 3 was produced by
preparing a tool base of K10 carbide (compliant with ISO 513) and
forming a DLC coating on the tool base. The DLC coating had a
hydrogen content of 0.5 atomic % or less, a Knoop hardness Hk of
2170 kg/mm.sup.2, a surface roughness Ry of 0.03 .mu.m and a
thickness of 0.5 .mu.m. The thus-produced reamer was set to a
machining center, thereby finishing holes in a workpiece while
supplying the cutting oil composition A in mist form. The machining
conditions are indicated below. The finished holes were tested for
surface roughness Ra. The test result is shown in FIG. 6. In FIG.
6, the degree of machining represents the number of holes finished
by the reamer.
[0093] [Test Conditions]
[0094] Workpiece: ADC 12/AC2A alloy (JIS H5302/H5202)
[0095] Cutting speed: 339.12 m/min.
[0096] Rotation speed: 6000 rpm
[0097] Feed rate: 0.24 mm/rev.
[0098] Oil mist discharge rate: 5 cc/hr.
COMPARATIVE EXAMPLE 4
[0099] The same reamer as used in Example 3 was produced, except
that no DLC coating was formed on the reamer. The produced reamer
was set to a machining center, thereby finishing holes in a
workpiece while supplying the above cutting oil composition B in
mist form. The machining conditions were the same as in Example 3.
The finished holes were tested for surface roughness Ra. The test
result is shown in FIG. 6.
[0100] As is apparent from FIG. 6, the surface roughness Ra of the
holes finished by the reamer of Example 3 was much lower than that
of Comparative Example 4.
[0101] It is thus proved by the test results of TABLE 2 and FIGS. 5
and 6 that the machine tool of the present invention has the
advantages of not only a longer tool life but also higher machining
precision and efficiency over the machine tool of the earlier
technology.
[0102] The entire contents of Japanese Patent Application Nos.
2003-151855 (filed on May 29, 2003) and 2003-409856 (filed on Dec.
9, 2003) are herein incorporated by reference.
[0103] Although the present invention has been described with
reference to a specific embodiment of the invention, the invention
is not limited to the above-described embodiment. Various
modifications and variations of the embodiment described above will
occur to those skilled in the art in light of the above teaching.
The scope of the invention is defined with reference to the
following claims.
* * * * *