[0001] This invention relates to lubricating compositions for plastic working used in manufacturing
machine parts by a method which comprises placing a steel stock or the like in a mold
and pressing it with a hydraulic press, a machinery press or the like. More particularly,
the present invention is concerned with lubricating compositions for plastic working
suitable particularly for use in backward extrusion working and composite extrusion
working which cause a large area of a surface to be newly produced, leading to an
increase in the surface area, and articles worked by using said oils.
[0002] As opposed to lubricating oils for bearings, lubricating oils for plastic working
should exhibit lubricating capacities sufficient to withstand temperature rise attributable
to heat generation accompanying deformation, friction, etc. during working, a pressure
applied on a frictional surface and an increase in the area of a newly produced surface.
In other words, mold life is directly influenced by lubricating capacities of a lubricating
oil used.
[0003] The use of a lubricating oil which is not satisfactory in lubricating capacities
brings a material into direct contact with a mold, leading to seizing. If the seizing
takes place over a large area, working pressure is increased to cause a local damage
to or crack of the mold, which leads to not only a remarkable shortening in mold life
but also occurrence of defective moldings and further makes it impossible to conduct
working.
[0004] Conventional lubricating oils for cold working of steel stocks include a mineral,
synthetic oil, a mixture thereof (hereinafter referred to as "base oil") or a water-mixed
base oil obtained by adding water to a base oil, each incorporating therein, for example,
an oleaginous matter such as fatty acid or tallow, sulfur, phosphorus, chlorine-based
extreme-pressure additive, an organometal-based extreme-pressure additive such as
zinc dithiophosphate (Zn-DTP) or a solid lubricant such as graphite or molybdenum
disulfide as described in "SEKIYU SEIHIN TENKAZAI (additives for oil products)" (edited
by Toshio Sakurai, published on May 15, 1973 by Saiwai Shobo, Japan). These lubricating
oils for plastic working can be used for deep draw working and roll working which
are low in both degree of working and deformation of the material. However, the use
of the lubricating oils in working which is high in degree of working and brings about
a high temperature and high pressure on the worked surface, or working for complex
shapes causes seizing, because they are insufficient in capacity for forming a lubricating
coating having a satisfactory thermal resistance and loading resistance as well as
for forming a lubricating coating on a newly produced surface.
[0005] Conventional methods of lubrication for working which is high in degree of working
include a method in which a lubricant prepared by dispersing a solid lubricant in
a solution obtained by diluting or dissolving a synthetic resin in a solvent is applied
on the surface of a material to form a lubricating coating and a method which comprises
subjecting the surface of a material for plastic working to phosphate coating treatment,
treating the surface of the resulting coating with a treating solution composed mainly
of sodium stearate for forming a metal soap coating and subjecting the material to
plastic working. There is also known a method of lubrication in which the surface
of the material is subjected to oxalate coating treatment in place of the phosphate
coating treatment and the surface of the resulting coating is further subjected to
metal soap coating treatment. These chemical coating treatments are excellent in prevention
of seizing as compared with the lubrication by means of the above-mentioned lubricating
oils for plastic working. Therefore, in general, the chemical coating treatment is
practically used for lubrication in cold working for steel stocks. However, the chemical
coating treatment method in which a lubricating coating is formed on a material by
synthetic resin coating or a combination of phosphate coating or oxalate coating treatment
with metal soap coating treatment require a sufficient pretreatment and a strict process
control. For example, when metal soap coating treatment is conducted after phosphate
coating treatment, a material such as steel stock is degreased before immersed in
a phosphate bath having a predetermined phosphate concentration to form a coating.
Thereafter, the material is washed with water, neutralized, immersed in a metal soap
bath having a predetermined metal soap, concentration and then dried. In other words,
the above method requires complicated steps. Further, when the treating solutions
are deteriorated, there arises difficulties related to disposal of the resulting wastes.
As is apparent from the foregoing, the above-mentioned prior-art methods have some
advantages but involve problems more or less.
[0006] Lubricating oils for plastic working are extremely advantageous in that their use
contributes to simplification of processing steps, because lubrication can be conducted
by simply applying it to a material or a mold according to the customary method such
as spraying or dropping. However, conventional lubricating oils for plastic working
have not been used for a high degree of working which is conducted under severe working
conditions, because they are unsatisfactory in formation of a lubricating coating
and, therefore, tend to cause seizing.
[0007] In order to hold a large amount of a lubricant on the frictional surface for eliminating
the above-mentioned drawbacks of the lubricating oils, there has been proposed the
use of highly viscous liquid lubricants or greases having an excellent heat resistance,
e.g., greases as described in U.S. Patent Nos. 4,065,395, 4,100,081 and 4,113,640,
i.e., greases containing, as a thickener, a diurea or a polyurea obtained by reacting
a monoamine or a diamine with an isocyanate in a base oil. When such greases are used
for cold forging involving a high degree of working, a seizing preventing ability
thereof is slightly improved compared to liquid lubricants but is considerably inferior
to that of lubrication by the chemical coating treatment method.
[0008] The above-mentioned prior-art methods have some advantages but also involve problems.
Specifically, with respect to liquid lubricants, there arose a problem related to
seizing resistance under working conditions which produce a large amount of heat due
to deformation as well as a large area of a new surface and which apply a high pressure
on the surface. On the other hand, the chemical coating treatment method had drawbacks
that it involved complicated treating steps and required much labor and cost because
of occurrence of a number of accompanying operations such as waste water disposal.
[0009] US patent 3 454 495 discloses lubricant compositions based on water, oil or an emulsion
and containing a solid phase comprising porous capillary active inorganic pigment
optionally impregnated with a thermoplastic. One example of the thermoplastic is polyurea.
The compositions are useful in cold forming of metals.
[0010] An article "Non-Soap Lubricating Greases", L.C. Brunstrum, NLGI Spokesman, October
1960, pages 279-283, provides background information on the thickeners used in greases,
of which one example mentioned is arylurea. The particle sizes mentioned for arylurea
thickeners are 0.5 µm and 0.7 µm.
[0011] An object of the present invention is to provide a lubricating composition for plastic
working which does not require any chemical coating treatment, but requires simply
to be fed to the surface of a material or a mold according to the customary method
by making use of an advantage of lubricating oils and exhibits a seizing resistance
which may be comparable to that of the lubrication by the chemical coating treatment.
[0012] Conventional lubricating oils of this kind comprise a mineral oil or a synthetic
oil as a base oil and, incorporated therein, an extreme-pressure additive comprising
a sulfur-, chlorine- or phosphorus-containing organic compound and a solid lubricant
such as graphite or molybdenum disulfide. However, such lubricating oils cannot be
used for a high degree of working and complicated working, because mere application
of such lubricating oils on a material etc. gives only a thin oil coating which easily
leads to seizing as compared with chemical coating and synthetic resin coating. The
present invention has at least partly eliminated such drawbacks.
[0013] The present inventors have made extensive and intensive studies to attain the above-mentioned
object. As a result, the present inventors have found that a liquid lubricating composition
comprising a base oil and a compound having a urea moiety (hereinafter referred to
as "urea lubricant") incorporated therein in dispersed form exhibits a remarkably
improved resistance to seizing and makes it possible to obtain highly worked moldings
and moldings having complex shapes by means of cold forging by merely applying it
on the surface of a metal stock or a mold.
[0014] According to the present invention, there is provided a lubricating composition as
set out in claim 1. The composition may have incorporated therein, as well as the
component A comprising a compound having a urea bond, a component B comprising at
least one extreme pressure additive selected from the group consisting of organic
compounds containing phosphorus, sulfur or chlorine (hereinafter referred to as "phosphorus-,
sulfur- or chlorine-based extreme-pressure additive") and condensed phosphoric acid.
The invention also provides a plastic working method using such a lubricating oil.
[0015] The lubricating composition for plastic working according to the present invention
forms a thick lubricating coating having excellent thermal resistance, lubricity and
loading resistance between a material and a mold by simply applying it on the surface
of a material or a mold by a customary method such as spraying, brushing or dropping
and, therefore, exhibits a remarkably improved resistance to seizing even in manufacture
of plastic working products having a high degree of working or complex shapes.
[0016] The urea lubricants, i.e., components A in the present invention include diurea,
tetraurea and polyurea. These urea lubricants can easily be produced by reacting an
amine with an isocyanate, which are starting materials, in an inert organic solvent,
e.g., toluene. Examples of monoamines which may be used in the reaction include pentylamine,
hexylamine, heptylamine, octylamine, decylamine, dodecylamine, tetradecylamine, hexadecylamine,
octadecylamine, eicosylamine, dodecinylamine, hexadecinylamine, octadecinylamine,
octadecanylamine, abietylamine, aniline, toluidine, naphthylamine, cumylamine, bornylamine,
butylamine, benzylamine, phenethylamine, laurylamine, palmitylamine, methylamine,
isoamylamine, cyclohexylamine, and 2-methyl-6-ethylaniline. Examples of diamines which
may be used in the reaction include ethylenediamine, propanediamine, butanediamine,
hexanediamine, dodecanediamine, octanediamine, hexadecanediamine, cyclohexanediamine,
cyclooctanediamine, phenylenediamine, tolylenediamine, xylylenediamine, dianilinomethane,
ditoluidinomethane, bisaniline, bistoluidine, diaminoheptane, diaminononane, diaminodecane,
diaminopentane, benzidine, diaminodiphenylmethane and methylenebis(2-chloroaniline).
Examples of triamines which may be used in the reaction include diethylenetriamine,
dipropylenetriamine and N-methyldiethylenetriamine. Examples of other polyamines which
may be used in the reaction include triethylenetriamine, tetraethylenepentaamine and
pentaethylenehexaamine. Examples of monoisocyanates which may be used in the reaction
include hexyl isocyanate, decyl isocyanate, dodecyl isocyanate, tetradecyl isocyanate,
hexadecyl isocyanate, phenyl isocyanate, cyclohexyl isocyanate, tolyl isocyanate,
xylylisocyanate, cumenyl isocyanate, cyclooctyl isocyanate, butyl isocyanate, methyl
isocyanate, ethyl isocyanate, isopropyl isocyanate, chloroethyl isocyanate, chlorophenyl
isocyanate, dichlorophenyl isocyanate, naphthyl isocyanate, octadecyl isocyanate,
phenyl isocyanate and tolylisocyanate. Examples of diisocyanates which may be used
in the reaction include xylylene diisocyanate, hexylene diisocyanate, decylene diisocyanate,
octadecylene diisocyanate, phenylene diisocyanate, tolidine diisocyanate, tolylene
diisocyanate, methylenebisphenylene isocyanate, naphthylene diiscyanate and polymethylenepolyphenyl
isocyanate.
[0017] The reaction product obtained by reacting the above-mentioned raw materials in an
organic solvent is filtered, dried and pulverized to obtain a urea lubricant powder.
The particle diameter of the powder may arbitrarily be selected within the range of
the invention taking into consideration working conditions, dispersion stability of
the powder, etc., and is generally in the range of 35 to 800 µm, preferably 35 to
500 µm. This is advantageous for backward extrusion working, composite extrusion working
or manufacture of articles having complex shapes or a high degree of working which
produces a large area of a new surface.
[0018] When a further improvement in lubricity of the urea lubricant is required, a powder
comprising a urea lubricant powder of which the surface is coated with, e.g., a synthetic
wax may also be used.
[0019] Examples of phosphorus-based extreme-pressure additive which is one choice for the
component B include phosphites, e.g., tertiary phosphites such as triphenyl phosphite,
tris(nonylphenyl) phosphite, triisooctyl phosphite, diphenyl isodecyl phosphite, phenyl
diisodecyl phosphite, tristearyl phosphite, trioleyl phosphite and trilauryl trithiophosphite
and secondary phosphites such as di-2-ethylhexyl hydrogen phosphite, dilauryl hydrogen
phosphite and dioleyl hydrogen phosphite and phosphates such as trimethyl phosphate,
tributyl phosphate, triphenyl phosphate, tricresyl phosphate, octyl diphenyl phosphate,
trilauryl phosphate, tristearyl phosphate, trioleyl phosphate, monobutyl phosphate,
dibutyl phosphate, monoisodecyl phosphate, trichloroethyl phosphate, methyl acid phosphate,
isopropyl acid phosphate, butyl acid phosphate, 2-ethylhexyl acid phosphate, lauryl
acid phosphate, stearyl acid phosphate and oleyl acid phosphate. Examples of sulfur-based
extreme-pressure additive which is another choice for the component B include sulfurized
fat and oil, dibenzyl sulfide disulfide, polysulfide, di-tert-butyl sulfide, di-n-butyl
disulfide and polyoxyethylene polysulfide. Examples of chlorine-based extreme-pressure
additive which is yet another choice for the component B include chlorinated paraffin,
chlorinated fat and oil and pentachlorinated fatty acid. Examples of condensed phosphoric
acid which is one of the component B include pyrophosphoric acid and polyphosphoric
acid.
[0020] Examples of the base oil to which the components A and B are added include mineral
oil, dibasic acid diester oil, neopentyl polyol ester oil, α-olefin oil, fluoro ester,
silicate ester oil, polyglycol oil, silicone oil, polyphenyl ether oil and polybutene
oil. The properties of the above-mentioned base oils may properly be determined taking
into consideration working conditions and operating conditions. In general, a preferred
viscosity of the base oil is in the range of about 10 to 500 mm²/s (cSt) at 40°C.
[0021] Although the amount of the urea lubricant powder or coated urea lubricant powder
to be incorporated should properly be determined taking into consideration the degree
of working of the intended molded parts and working conditions, said amount is 1 to
25 wt% in the case of ordinary extrusion working. However, a preferred amount of incorporation
in the case of backward extrusion working and composite extrusion working which bring
about a large area of a new born surface (nascent surface) and, therefore, brings
about an increase in the surface area is 1.5 to 25 wt%. Therefore, the amount of the
component A to be incorporated in the base oil may properly be determined taking into
consideration the kind of material, degree of working, shapes of intended worked articles,
method of feeding the lubricating oil, etc. However, a preferred amout of the component
A is generally in the range of 1.5 to 25 wt%.
[0022] When the amount of the component A is below the above-mentioned range, the effect
attained by its addition is small, leading to seizing. On the other hand, even if
the component is excessively added, an effect exceeding a certain limit cannot be
attained. Therefore, it is preferred that the component A be used in an amount in
the above-mentioned range.
[0023] The urea lubricant which is incorporated in the base oil is in powdery form, and
the diameter of the powder particles should properly be determined taking into consideration
the degree of working, method of working, dispersion stability, etc. However, the
particle diameter of the powder used in backward extrusion working and composite extrusion
working which bring about a large area of a new surface and, therefore, brings about
an increase in the surface area is 35 to 500 µm. In general, it is preferred that
the larger the increase in the surface area of the moldings, the larger the particle
diameter of the powder to be incorporated.
[0024] The urea lubricant or coated urea lubricant is used in the form of a dispersion in
the above-mentioned base oil. Although the dispersant used varies depending on the
kinds of base oil and urea lubricant, examples of such dispersants are polymethacrylate,
ethylene-olefin copolymer and polyisobutylene. Another method for attaining effective
dispersion is to adjust the specific gravity of the base oil to that of the urea lubricant.
[0025] The lubricating composition for plastic working of the present invention may contain
known organic extreme-pressure additives containing chlorine, phosphorus or sulfur,
antioxidants and anticorrosive agents.
[0026] The lubricating composition for plastic working of the present invention is used
by applying it on the surface of a material for plastic working or a mold by known
methods such as spraying, dropping, immersion, roll coating, etc.
[0027] The article produced by plastic working according to the present invention has a
coating on its surface and, therefore, has anticorrosive properties. The powder of
the compound having a urea bond forms a coating on the worked article together with
the lubricating oil after working.
[0028] Prior to the description of the function of the components of the lubricating composition
for plastic working of the present invention, some description will be given of a
lubrication mechanism of liquid lubricants in deep draw working, roll working, etc.
With respect to the lubrication mechanism, reference may be made to Mitsugu Tokizawa,
Lubrication in the Plastic Working of Metals ("JUNKATSU", Vol. 18, No. 3, (1973) pp.
193 - 201) and Yasuo Kasuga, Lubrication Mechanism in Plastic Working ("SOSEI TO KAKO",
Vol. 9, No. 87, (1968) pp. 202 - 214). As is described in the above references, a
liquid lubricant which has been brought into the space between the face of a material
and a face of a mold is confined in the recessed portions present in the surface of
the material during working. In the process of plastic deformation, the protruded
portions on the surface are pressed down to cause the liquid lubricant remaining in
the recessed portions to be forcibly discharged therefrom, which causes the discharged
lubricant to be fed to the flat face formed by pressing to form a thin oil coating.
When the liquid lubricant contains a phosphorus-, chlorine- or sulfur-based extreme-pressure
additive, an extreme-pressure coating is formed on the surface of the material due
to the heat generated accompanying plastic deformation, which contributes to prevention
of seizing. Although lubrication is conducted based on the above-mentioned mechanism
also in the case of working which is high in degree of working and large in an increase
in the surface area, the formation of an extreme-pressure coating is insufficient
at the frictional surfaces exposed to high temperature and high pressure, which leads
to occurrence of seizing.
[0029] The lubrication mechanism of a liquid lubricant for plastic working containing a
urea lubricant powder dispersed therein according to the present invention is the
same as that described above. However, in the case of the liquid lubricant of the
present invention, the powdery urea lubricant is confined together with the base oil
in the recessed portions present on the surface of the material. Since the protruded
portions present on the surface of the material is pressed down at a high temperature
under a high pressure, the powdery urea lubricant is allowed to dissolve to form a
highly viscous oil or rolled and fed to the frictional surfaces in one form of a mixture
with the base oil, as the deformation of the material proceeds. A thick lubricating
coating is formed on the frictional surface to prevent direct contact of the material
with a mold. A coated urea lubricant for improving the lubricity of the urea lubricant
functions in the same manner as mentioned above.
[0030] When the urea lubricant and coated urea lubricant are incorporated in an amount below
the above-mentioned range or small in particle diameter, a satisfactory lubricating
coating cannot be formed. On the other hand, the incorporation thereof in excessive
amounts leads to an increase in the viscosity, which not only causes lowering in applicability
on the surface of a metal stock and a mold, but also gives no further improved effect.
Therefore, it is preferred that the amounts of the urea lubricant and coated urea
lubricant incorporated be in the above-mentioned range.
In the drawings:-
FIG. 1 is a graph showing the relationship between the particle diameter of a diurea
powder and the maximum allowable working temperature in a forward extrusion working;
FIG. 2 is a graph showing the relationship between the particle diameter of a diurea
powder and the maximum allowable working temperature in a backward extrusion working;
FIG. 3 is a graph showing the amount of a diurea powder incorporated and the maximum
allowable working temperature in a forward extrusion working and a backward extrusion
working;
FIG. 4 is an illustrative view of a forward extrusion working method, in which FIG.
4(a) is a cross-sectional view illustrating a state in which a workpiece coated with
a liquid lubricant has been inserted into a mold and FIG. 4(b) is a cross-sectional
view illustrating a state in which a punch has been pressed down to extrude the workpiece
from the mold;
FIG. 5 is an illustrative view of a backward extrusion working method, in which FIG.
5(a) is a cross-sectional view ilustrating a state in which a workpiece coated with
a liquid lubricant has been inserted into a mold and FIG. 5(b) is a cross-sectional
view illustrating a state in which a punch has been pressed down for working of the
workpiece;
Fig. 6 is a longitudinal sectional view of a workpiece used for forging;
FIG. 7 is a longitudinal sectional view of a cylinder for a video tape recorder produced
by forging;
FIG. 8 is a longitudinal sectional view of a photosensitive drum for electrophotography
produced by forging; and
FIG. 9 is a longitudinal sectional view of a pinion for automobiles produced by forging.
EXAMPLES
[0031] The examples of the present invention will now be described together with comparative
examples. The present invention should not be construed to be limited to these examples.
[0032] First, some description will be given with respect to criteria for evaluating working
performance.
[0033] Working performance of liquid lubricants was evaluated by the forward extrusion working
method as shown in FIG. 4 and the backward extrusion working method as shown in FIG.
5. Specifically, a mold 3 was equipped with a band heater 4. The temperature of the
mold 3 was stepwise raised by 5 to 10°C a time. At each temperature, a material 2
coated with a liquid lubricant was inserted into the mold 3, and 10 to 15 pieces of
the material were worked at the same temperature at a press-down rate of a punch 1
of 8 mm/s to determine a mold temperature at which the material could be worked without
causing any seizing (maximum allowable working temperature). The higher the maximum
allowable working temperature, the more excellent the thermal resistance and loading
resistance of the lubricating coating.
1. Working Conditions:
1.1 Forward Extrusion Working Method
[0034]
(a) Material and Dimensions
material |
outside dia. (mm) |
length (mm) |
surface roughness (µm) |
SCM415 |
9.9 |
30 |
Ra 1.5 |
Ra is average surface roughness.
(b) Principal Dimensions of Mold
material |
land inside dia. (mm) |
extrusion angle (°) |
drawing dia. (mm) |
degree of working (%) |
hard metal V₅ |
10 |
120 |
5 |
75 |
1.2 Backward Extrusion Working
[0035]
(a) Material and Dimensions
material |
outside dia. (mm) |
length (mm) |
surface roughness (µm) |
SCM415 |
20 |
30 |
Ra 2.0 |
(b) Principal Dimensions of Mold
material |
land inside dia. (mm) |
punch dia. (mm) |
depth of boring (mm) |
degree of working (%) |
hard metal V₅ |
20.1 |
16.1 |
48 |
64 |
EXAMPLE 1
[0036] 60 g (0.283 mol) of o-tolidine was added to 600 ml of dried toluene, and the mixture
was heated at 110 to 115°C to dissolve the o-tolidine in the toluene. To the resulting
solution was dropwise added 67.3 g (0.565 mol) of phenyl isocyanate at 106°C over
15 min. The mixture was stirred at 110 to 113°C for 4 hr, allowed to cool at room
temperature, filtered and dried to obtain 117.8 g of a white crystalline diurea [4,4'-(3,3'-dimethyldiphenylene)-diphenylurea].
The diurea thus obtained was pulverized and classified to obtain a diurea powder having
a particle diameter of 63 to 88 µm. 10% by weight of the diurea powder was incorporated
in a mineral oil (viscosity at 40°C: 150 mm²/s) at ordinary temperature, and the mixture
was stirred at 130 rpm for 10 min to obtain a liquid lubricant of the present invention
comprising a diurea powder dispersed in the oil. The results of evaluation on working
performance of the liquid lubricant thus obtained are shown in Table 1.
[0037] The compositions of the comparative lubricants are shown below.
COMPARATIVE EXAMPLE 1 (commercially available processing oil)
[0038] base oil: mineral oil the remainder (amount)
extreme-pressure additive: a fatty acid content of 43 wt%, a chlorine content of 12
wt%, and a sulfur content of 6 wt%.
COMPARATIVE EXAMPLE 2 (urea grease obtained by reacting amine with isocyanate in a
base oil)
[0039] base oil: mineral oil (88 wt%)
thickener: diurea (10 wt%)
additive: antioxidant (2 wt%)
The above grease is in the form of semi-solid to solid obtained by agglomeration of
the finely divided powder thickener in a colloidal form.
EXAMPLE 2
[0040] 90.8 g (0.84 mol) of p-phenylenediamine was added to 1400 ml of dried toluene. To
the resulting mixture was dropwise added 200 g (1.68 mol) of phenyl isocyanate at
100 to 110°C over 1 hr. The mixture was stirred at 110 to 112°C for 4 hr, allowed
to cool at room temperature, filtered and dried to obtain 283.8 g of a white crystalline
diurea [p-phenylenediphenylurea]. The diurea thus obtained was pulverized and classified
to obtain a diurea powder having a particle diameter of 63 to 88 µm. 10% by weight
of the diurea powder was incorporated in a mineral oil (viscosity at 40°C: 150 mm²/s)
at ordinary temperature, and the mixture was stirred at 130 rpm for 10 min to obtain
a liquid lubricant of the present invention comprising a diurea powder dispersed in
the oil. The results of evaluation on working performance of the liquid lubricant
thus obtained are shown in Table 1.
EXAMPLE 3
[0041] 13.9 g (0.080 mol) of tolylene diisocyanate was dissolved in dried toluene at 25
to 33°C. To the resultig solution was dropwise added 20.5 g (0.16 mol) of p-chloroaniline.
The mixture was stirred at 110°C for 5 hr, allowed to cool at room temperature, filtered
and dried to obtain 33.6 g of a white crystalline diurea [1-methyl-2,4-bis(4-chlorophenylureido)benzene].
The diurea thus obtained was pulverized and classified to obtain a diurea powder having
a particle diameter of 63 to 88 µm. 10% by weight of the urea powder was incorporated
in a mineral oil (viscosity at 40°C: 150 mm²/s) at ordinary temperature, and the mixture
was stirred at 300 rpm for 10 min to obtain a liquid lubricant of the present invention
comprising a diurea powder dispersed in the oil. The results of evaluation on working
performance of the liquid lubricant thus obtained are shown in Table 1.
EXAMPLE 4
[0042] 17.4 g (0.1 mol) of tolylene diisocyanate was dissolved in 180 ml of dried toluene.
To the resulting solution was dropwise added 18.6 g (0.20 mol) of aniline at 27 to
34°C while stirring. The mixture was stirred at 75 to 80°C for 5 hr, allowed to cool
at room temperature, filtered and dried to obtain 35.5 g of a white crystalline diurea
[1-methyl-2,4-diphenylureidobenzene]. The diurea thus obtained was pulverized and
classified to obtain a diurea powder having a particle diameter of 63 to 88 µm. 10%
by weight of the urea powder was incorporated in a mineral oil (viscosity at 40°C:
150 mm²/s) at ordinary temperature, and the mixture was stirred at 130 rpm for 10
min to obtain a liquid lubricant of the present invention comprising a diurea powder
dispersed in the oil. The results of evaluation on working performance of the liquid
lubricant thus obtained are shown in Table 1.
EXAMPLE 5
[0043] 3 g (0.05 mol) of ethylenediamine and 26 g (0.10 mol) of oleylamine were added to
200 ml of dried toluene of 60 to 75°C. 50 ml of dried toluene containing 17.4 g (0.10
mol) of tolylene diisocyanate dissolved therein was dropwise added to the above-prepared
amine solution while stirring over 1 hr. Subsequently, the mixture was heated at 110°C
for 5 hr to obtain a print-like reaction product. The reaction product was vacuum
dried to obtain 40.2 g of a light yellow crystalline polyurea [1,2-ethylenebis(2-methyl-5'-octadecylureidophenyl)urea].
The polyurea thus obtained was pulverized and classified to obtain a polyurea powder
having a particle diameter of 63 to 88 µm. 10% by weight of the urea powder was incorporated
in a mineral oil (viscosity at 40°C: 150 mm²/s) at ordinary temperature, and the mixture
was stirred at 300 rpm for 10 min to obtain a liquid lubricant of the present invention
containing a polyurea powder dispersed therein. The results of evaluation on working
performance of the liquid lubricant thus obtained are shown in Table 1.
EXAMPLE 6
[0044] A mixture of 3.6 g (0.06 mol) of ethylenediamine with octadecylamine (0.10 mol) is
heated at 60°C to form a solution. Separately, 17.4 g of a mixture of 2,4-tolylene
diisocyanate with 2,6-tolylene diisocyanate in a ratio of 80 : 20 was added to dried
toluene. The mixture was subjected to dispersion at about 30°C. The resulting dispersion
was dropwise added to the above-prepared hot solution while stirring. The mixture
was stirred at 80°C for 5 hr, allowed to cool at room temperature, filtered and dried
to obtain 27.9 g of a white crystalline diurea. The diurea thus obtained was pulverized
and classified to obtain a diurea powder having a particle diameter of 63 to 88 µm.
10% by weight of the urea powder was incorporated in a mineral oil (viscosity at 40°C:
150 mm²/s) at ordinary temperature, and the mixture was stirred at 130 rpm for 10
min to obtain a liquid lubricant of the present invention containing a diurea dispersed
therein. The results of evaluation on working performance of the liquid lubricant
thus obtained are shown in Table 1.
[0045] As is apparent from Table 1, the liquid lubricants of the present invention are higher
in the temperature of a mold at which seizing occurs than those of comparative examples,
i.e., are superior in working performance to the comparative lubricants.
EXAMPLE 7
[0046] The diureas as obtained in EXAMPLES 1 and 3 are separately incorporated in an amount
of 10% by weight to a mineral oil having a viscosity of 150 mm²/s at 40°C. The relationship
between the particle diameter of the powder and the maximum allowable working temperature
was determined by the forward extrusion working method and the backward extrusion
working method using the above-prepared samples. FIG. 1 shows the results with respect
to a degree of working of 75% in the forward extrusion, while FIG. 2 shows the results
with respect to a degree of working of 64% in the backward extrusion. As is apparent
from Fig. 1, the maximum allowable working temperature increases rapidly when the
particle diameter of the powder exceeds about 0.5 µm. Further, as is apparent from
FIG. 2, the maximum allowable working temperature increases rapidly when the particle
diameter of the powder exceeds about 35 µm.
EXAMPLE 8
[0047] The same diurea as obtained in EXAMPLE 3 was incorporated in an amount of 0.6 to
12 wt% to a mineral oil having a viscosity of 150 mm²/s at 40°C. The relationship
between the amount of the powder incorporated and the maximum allowable working temperature
was determined by the forward extrusion working method and the backward extrusion
working method. The results are shown in FIG. 3, in that, curve 10 shows the relationship
with respect to the forward extrusion working method, curve 20 the backward extrusion
working method.
[0048] As is apparent from FIG. 3, the effect of addition is observed when the amount of
incorporation is 1 wt% or larger in the forward extrusion working method and 1.5 wt%
or larger in the backward extrusion working method.
EXAMPLE 9
[0049] The diurea and polyurea respectively obtained in EXAMPLES 4 and 5 and comprising
particles of which the diameters were adjusted to 63 to 88 µm were separately added
in an amount of 10 wt% to the synthetic oil as indicated in Table 2 and dispersed
therein under the same stirring conditions as in EXAMPLES 4 and 5 to obtain liquid
lubricants. Evaluations on the maximum allowable working temperature of the above-prepared
liquid lubricants were conducted by the forward extrusion working method and the backward
extrusion working method.
[0050] As is apparent from Table 2, the liquid lubricants of the present invention containing
a diurea or polyurea incorporated therein are higher in the maximum allowable working
temperature than those obtained in COMPARATIVE EXAMPLES 1 and 2 as indicated in Table
1, i.e., are superior in working performance to the comparative lubricants.
EXAMPLES 10 to 23
[0051] 60 g of o-tolidine was added to 600 ml of dried toluene, and the mixture was heated
at 110 to 115°C to dissolve the o-tolidine in the toluene. To the resulting solution
was dropwise added 67.3 g of phenyl isocyanate at 106°C. The mixture was stirred at
110 to 113°C for about 4 hr, allowed to cool at room temperature, filtered and dried
to obtain a white crystalline diurea. The diurea thus obtained was pulverized to obtain
a urea lubricant having an average particle diameter of 90 µm which is the component
A. In a mineral oil as a base oil having a viscosity of 150 mm²/s (cSt) at 40°C were
incorporated the above-obtained component A and phosphorus-, sulfur-or chlorine-based
extreme-pressure additives as the component B in amounts as indicated in Table 3 to
obtain lubricating oils for plastic working of the present invention. The lubricating
oils thus obtained were applied on the surface of a chromium-molybdenum steel (SCM415)
material 2 having a diameter of 10 mm or 20.1 mm and a length of 30 mm by dropping.
Thereafter, molds 3 (made of a hard metal, V₅) for the forward extrusion working method
as shown in FIG. 4 and for backward extrusion working method as shown in FIG. 5 were
equipped with a band heater 4. The temperature of the molds 3 was stepwise raised
by 5 to 10°C a time, and 10 pieces of the material 2 were worked with a punch 1 with
the same condition for evaluating maximum allowable working temperature.
[0052] The forward extrusion working was conducted under the following conditions:
material: a diameter of 10 mm and a length of 30 mm
extrusion angle: 120°
drawing diameter: 5 mm
degree of working (reduction of cross-sectional area): 75%
press-down rate of punch: 8 mm/s
The backward extrusion working was conducted under the following conditions:
material: a diameter of 20.1 mm and a length of 30 mm
punch diameter: 16.1 mm
degree of working: 64%
depth of bore in worked article: 48 mm
press-down rate of punch: 8 mm/s
The compositions of the processing oils which have conventionally been used are
shown in Table 4. The maximum allowable working temperature on these processing oils
were also determined under the above-mentioned conditions. The results are shown in
Table 5. As can be seen from Table 5, the lubricating oils for plastic working of
the present invention exhibit a high maximum allowable working temperature, i.e.,
exhibit an excellent resistance to seizing.
Table 5
group |
No. |
maximum allowable working temp.(°C) |
|
|
forward extrusion working (degree of working: 75%) |
backward extrusion working (degree of working: 64%) |
lubricating oil for plastic working of the present invention |
10 |
350 |
240 |
11 |
350 |
190 |
12 |
330 |
195 |
13 |
350 or higher |
210 |
14 |
350 or higher |
220 |
15 |
340 |
215 |
16 |
350 or higher |
180 |
17 |
340 |
200 |
18 |
345 |
200 |
19 |
350 or higher |
240 |
20 |
350 |
240 |
21 |
350 |
235 |
22 |
335 |
210 |
23 |
350 or higher |
245 |
conventional lubricating oil |
A |
80 |
30°C, seizing occurred in working of single piece |
B |
30 |
" |
C |
60 |
" |
EXAMPLES 24 to 39
[0053] With respect to lubricating oils for plastic working of the present invention prepared
by incorporating a urea lubricant powder as the component A and an extreme-pressure
additive as the component B in base oils, i.e., α-olefin oil, neopentyl polyol ester
oil, polyphenyl ether oil or fluorosilicone oil as indicated in Table 6, the maximum
allowable working temperature was determined by the forward extrusion working method
and the backward extrusion working method under the same conditions as in EXAMPLE
1. The results are shown in Table 7. The lubricating oils for plastic working containing
a urea lubricant powder as the component A and at least one member selected from among
phosphorus-, sulfur- and chlorine-based extreme-pressure additives as the component
B exhibits an excellent resistance to seizing, regardless of the kind of the base
oil.
EXAMPLES 40 to 70
EXAMPLES 71 to 78
[0055] A mineral oil having a viscosity of 150 mm²/s (cSt) at 40°C was used as the base
oil. A urea lubricant powder, i.e., component A, produced by using the same raw materials
as in EXAMPLE 1, i.e., o-tolidine and phenyl isocyanate was incorporated in the base
oil in varied average particle diameter in the range of 0.2 to 800 µm as indicated
in Table 10. The maximum allowable working temperature of the resulting lubricating
oil for plastic working was evaluated. The results are shown in Table 10. Examples
71 to 74 are comparative examples.
EXAMPLE 79
[0056] The lubricating oil as obtained in EXAMPLE 1 was applied on the surface of JIS A2218
aluminum alloy material having a shape as shown in FIG. 6 by spraying. The material
was inserted into a mold and subjected to cold forging in such a state that the temperature
of both the alloy and the mold were ordinary one to form 500 cylinders for a video
tape recorder having a shape as shown in FIG. 7. A coating, i.e., a product of a reaction
of the lubricant oil with the substrate, is formed on the surface of the material
after working, and the surface was like a mirror.
[0057] In the present example, one or both of the internal and external peripheral surfaces
11, 12 on which a tape is traveled is often cut and polished. Alternatively, the cylinder
may be used as it is without removing the coating formed by a reaction between the
lubricating oil for plastic working and the substrate. When an oval through-hole is
provided at the bottom of the internal peripheral surface 14, the external peripheral
surface is cut and polished to attain roundness of the external peripheral surface.
When a groove is provided at the step portion 13, the entire portion of the step is
cut and polished.
[0058] However, the cylinder may be used as it is without removing the coating formed by
a reaction between the lubricating oil for plastic working and the substrate. The
worked material itself has a mirror surface.
EXAMPLE 80
[0059] The lubricating oil as obtained in EXAMPLE 1 was applied on the surface of A3003
aluminum alloy material having a diameter of 50 mm and a length of 45 mm. The material
was inserted into a mold and subjected to cold forging in such a state that the temperature
of both the alloy and the mold were ordinary one to form a vessel as shown in FIG.
8 having an external diameter of 50 mm, an internal diameter of 40 mm and a length
of 100 mm. A coating i.e., a product of a reaction of the lubricant oil with the substrate,
is formed on the surface of the material after working, and the surface was like a
mirror.
[0060] In the present invention, a cup-like article as shown in FIG. 8 was formed from a
block. The article having the worked internal and external peripheral surfaces can
be used as it is. Both of the internal and external peripheral surfaces were like
a mirror. The bottom was cut to form a cylinder. A coating, i.e., a reaction product,
is formed on the surface of the material after working. Only the external periperal
surface may be cut and polished.
[0061] Further, it is possible to directly form a cylinder by subjecting a pipe shaped material
to plastic working. Therefore, the formed product is used as it is after cutting only
the edge face. The article can be formed by a single-step working or two-step working
in which a further working is conducted in the smaller degree of working than that
in the first step. The two-step working leads to a further improved mirror surface.
The second working is conducted without addition of the lubricating oil.
EXAMPLE 81
[0062] The lubricating oil as obtained in EXAMPLE 1 was applied on the surface of A2218
aluminum alloy material having a diameter of 40.4 mm and a length of 20 mm by the
immersion method. The material was inserted into a mold and subjected to cold forging
in such a state that the temperature of both the alloy and the mold was ordinary one
to form a pinion having a shape as shown in FIG. 9. A coating, i.e., a product of
a reaction of the lubricant oil with the substrate, is formed on the surface of the
material after working, and the surface was like a mirror.
[0063] In the present example, the coating which has been formed during the working of the
curved portions of the teeth 22 remains on the article. However, the top of the teeth
22 may be cut and polished. The internal peripheral surface 21 is left intact. Numeral
24 designates a through-hole portion formed by cutting. The surface designated by
numeral 25 may be left intact or may be subjected to cutting treatment. The bottom
surface 23 is left as it is.
[0064] As is apparent from the foregoing, the lubricating oil of the present invention comprising
a base oil such as a mineral oil or synthetic oil or a mixture thereof and a diurea
or polyurea incorporated therein forms a lubricating coating having excellent thermal
resistance and loading resistance on the frictional surface during working by simply
applying it on the surface of a material or a mold and, therefore, not only effectively
prevent occurrence of seizing but also greatly contributes to an improvement in the
service life of tools such as a mold, enhancement of productivity and reduction in
production cost.
[0065] Further, the plastic working product of the present invention has a coating comprising
the above-mentioned lubricating oil on its surface which particularly exhibits an
excellent anticorrosive effect for steel stocks, so that a plastic working product
having excellent corrosion resistance is advantageously provided.