Note: Descriptions are shown in the official language in which they were submitted.
CA 02258638 1998-12-17
WO 97/48783 PCT/US97/10108
Description
WATERBORNE LUBRICANT FOR THE COLD PLASTIC WORKING OF METALS
FIELD OF THE INVENTION
This invention relates to a waterborne lubricant for use during the plastic
cold
working (e.g., forging, tube and pipe drawing, wire drawing, and the like) of
stock of a
metal such as iron, steel, titanium, titanium alloy, copper, copper alloy,
aluminum, slum-
s inum alloy, and the like. Below, this lubricant is referred to simply as the
"waterborne
lubricant".
REVIEW OF RELATED ART
Lubricants that form a liquid or solid film are used in the plastic working of
met
als, for example, in the cold drawing of steel tubing and pipe. These
lubricants facilitate
,o drawing by reducing the friction between the work piece and the tool, e.g.,
die, plug, or
the like, and thereby prevent scuffing and seizure.
Among lub~cants of this type, the so-called oil-based lubricants are typical
of the
liquid lubricants. The base oil in oil-based lubricants is a mineral oil,
animal or plant oil,
or a synthetic oil. Lubrication is generally carried out by flowing the oil-
based lubricant
,s directly onto the tool or work piece from a lubricating oil applicator
built into the process-
ing equipment. Oil-based lubricants are frequently used in the case of
relatively low de-
grees of.working. In the case of heavy working, the oil viscosity is increased
or a solid
lubricant or extreme-pressure additive is added. Typical of the solid films
are the so-call-
ed conversion coatings in which a carrier film that tenaciously adheres to the
substrate
zo is formed by a reaction with the work piece. Phosphate coating treatments
that form a
zinc phosphate-based film are used with carbon steels and low-alloy steels,
while oxa-
late coating treatments that form an iron oxalate-based film are used with
stainless steel.
A reactive soap lubrication treatment is generally performed after these
conversion
coating treatments. The combination of these two processes gives a lubrication
method
2s with a very high resistance to seizure, because of the combination of the
carrier function
of the conversion coating and the lubricating function of the reactive soap
lubricant. This
sequence of reactive soap lubrication treatment after a conversion coating
treatment is
generally carried out by immersing the work piece in various treatment baths
prior to
drawing. However, since reactive treatments are involved, the treatments are
carried
so out on batches of several tens of units in order to minimize variations in
lubricant add-on,
even though parts of the work pieces may be brought into lineal contact with
each other
to a greater or lesser degree.
CA 02258638 1998-12-17
WO 97/48783 PCTIUS97/10108
However, requirements for higher speeds and higher pressures in the working
operation as well as environmental and energy considerations have created
demand for
a lubricant which can solve the problems associated with conversion films
while still ex-
hibiting a lubricating function equal to or greater than that for the
combination of a con-
version coating treatment with a reactive soap lubrication treatment.
Conversion films
are associated, for example, with environmental and cost problems and with
problems
in removing the lubricant film after the working that utilized the film is
complete. The en-
vironmental problems include issues with waste management and issues concerned
with the working environment. For example, due to the use of an acidic
treatment bath
,o maintained at 80 °C to 90 °C, the treatment bath has a
disagreeable odor and its mist
degrades the immediate environment of the bath. The cost issues involve
shortening
the process and economizing on energy and space. Finally, the problems with
post-
working film removal have generally required alkaline degreasing plus an acid
treatment.
Within the realm of oil-based lubricants that address the problems described
,s above, Japanese Patent Publication [Kokoku] Number Hei 4-1798 [1,798/1992]
disclos-
es a "cold working lubricant in which a metal soap or solid lubricant is
blended into a lub-
ricating oil comprising the blend of a plant or animal oil, a copolymer of
isobutylene and
n-butene, and an extreme-pressure agent such as chlorinated paraffin or
phosphate es-
ter". However, even though this is a high-performance lubricating oil, its
pertormance
zo in working operations is somewhat poorer than that afforded by reactive
soap lubrication
treatment after a conversion coating treatment. Moreover, since large amounts
of ex-
treme-pressure agent (a term which is equivalent to "extreme-pressure
additive") are
used, undesirable odors are generated during the working operation and there
is a risk
of adverse effects such as work piece corrosion by chlorine or phosphorus in
the post-
zs working step of softening and annealing.
The waterborne lubricants include lubricants which are used wet and lubricants
which are used in the form of their dried films. Like the oil-based lubricants
discussed
above, the wet-use waterborne lubricants are used by direct application to the
tool or
work piece. The dry-use waterborne lubricants, like the conversion films
discussed
so above, provide a solid film by immersion in a treatment bath followed by
evaporation of
the water fraction in a drying process. An example of the wet-use waterborne
lubricants
is disclosed in Japanese Patent Publication [Kokoku] Number Sho 58-30358
[30,3581
1983]. This reference discloses a "lubricant for the cold or hot working of
metal tubing,
comprising a bicarbonate salt (solid) as the main component and small amounts
of dis-
35 persant, surfactant, and solid lubricant". This lubricant, however, has not
achieved wide
2
CA 02258638 1998-12-17
WO 97/48783 PCT/ITS97/10108
use in place of conversion coating treatments. With regard to dry-use
waterborne lubri-
cants, Japanese Patent Application Laid Open [Kokai or Unexamined] Number Sho
52-
20967 [20,967/1977] teaches a "lubricating coating composition comprising
water-solu-
ble polymer or a waterborne emulsion thereof as its base, which is blended
with solid
s lubricant and a conversion film-forming agent". In addition, Japanese Patent
Application
Laid Open [Kokai or Unexamined] Number Sho 50-147460 [147,460/1975] discloses
a
"method for drawing stainless steel wire using the combination of a borax-
based film and
lime soap or metal soap". However, when the dry film is produced by immersing
a large
number of workpieces at one time followed by forced drying, a nonuniform add-
on is in-
,o evitabiy produced by the partial contact that occurs among workpieces. As a
result,
these dry-use lubricants are unable to solve a major problem with nonreactive
lubricants,
i.e., a pronounced tendency for seizure to occur during drawing operations.
Thus, as discussed above, no lubricant has appeared that can meet all of the
de
mands elaborated above (single step, working pertormance, environmental
issues,
,5 waste management, energy savings, film removal, etc.) and is able to
replace the com
bined lubrication system of conversion coating treatment (phosphate treatment,
oxalate
treatment, etc.) + reactive soap treatment.
PROBLEMS TO BE SOLVED BY THE INVENTION
The present invention was developed in order to meet the requirements outlined
20 above. Th,e object of the present invention is to provide a one-step,
highly lubricating
waterborne lubricant for use in the cold plastic working of metals, that can
replace the
conversion coating treatment + reactive soap treatment combined lubrication
system,
is free of the environmental issues described above, provides for facile film
removal,
andlor is not subject to the decline in seizure resistance caused by
nonuniform add-on
zs when large numbers of individual workpieces are treated by immersion.
SUMMARY OF THE INVENTION
It has been found that the above stated object of the invention can be
achieved
by a waterborne lubricant comprising, preferably consisting essentially of, or
more
preferably consisting of, in addition to water:
ao (A} as its base, a water soluble inorganic salt that strongly adheres to
the substrate,
and that can introduce the lubricating components) to the tool surface and
main-
tain the lubricating components) in place during the cold working operation;
(B) as lubricating component, a solid lubricant;
(C) as lubricating component and/or lubrication auxiliary component, at least
one
35 ~~ substance selected from the group consisting of mineral oils, animal and
plant
3
CA 02258638 1998-12-17
WO 97/48783 PCT/i1S97/10108
oils and fats, and synthetic oils; and
(D) surfactant,
in which the solid lubricant:water-soluble inorganic salt weight ratio (B)/(A)
is from 0.05:1
to 2:1, the oil component/(water-soluble inorganic salt + solid lubricant)
weight ratio
s (C)/(A)+( B) is from 0.05/1 to 1/1, the solid lubricant is homogeneously
dispersed, and
the oily component (C) is homogeneously emulsified.
When this waterborne lubricant is used in the cold plastic working of metals,
which constitutes another embodiment of the invention, the drying process that
follows
treatment, e.g., by immersion, leads to the formation on the metal surface of
a solid inor-
,o ganic salt coating containing the solid lubricant in dispersed form and to
the formation
of an oily outer surface of the coating due to bleed by oily component (C)
onto the outer
surtaces of the film. This oily surface provides for a major improvement in
seizure resist-
ance by contributing to the initial lubrication during the working operation
and by com-
pensating for the nonuniform add-on of solid lubricant in any regions of the
workpieces
,s that have come into contact with each other during treatment and as a
result have less
treatment coating thickness than most parts of the workpieces.
In addition, the lubricating component remaining on the metal after plastic
work-
ing can as a rule be removed by treatment with alkaline degreaser alone.
BRIEF DESCRIPTION OF THE DRAWINGS
2o Figure 1 is a sectional view of the die, punch, and test substrate for the
backward
punching test of carbon steel that was run using the waterborne lubricant.
Figures
2.1.1, 2.x.1, 2.y.1, 2.13.1, 2.1.2, 2.x.2, 2.y.2, and 2.13.2 are projection
views of various
sized substrates for this test before and after punching has occurred.
DETAILED DESCRIPTION OF THE INVENTION
zs Water soluble inorganic salt component (A) constitutes the firm, solid, and
highly
metal-adherent coating formed by the waterborne lubricant according to the
present in-
vention. The chemical nature of this salt is not critical; it can be any water-
soluble inor-
ganic salt that forms the requisite type of coating, including those salts
typically or gener-
ally used in prior art as a carrier in the cold plastic working of metals.
This component
so is exemplified by borates such as sodium tetraborate (borax), potassium
tetraborate,
ammonium tetraborate, and the like; sulfates such as sodium sulfate, potassium
sulfate,
ammonium sulfate, and the like; silicates such as sodium silicate, potassium
silicate, and
the like; and nitrates such as sodium nitrate, potassium nitrate, and the
like. Borax, po-
tassium tetraborate, and sodium sulfate are preferred among the preceding. The
water-
as soluble inorganic salt may be a single selection or a combination of two or
more selec-
4
CA 02258638 1998-12-17
WO 97/48783 PCT/US97/10108
tions.
The solid lubricant (B) is homogeneously dispersed in the waterborne lubricant
according to the present invention. It is taken up when the waterborne
lubricant is coat-
ed on the workpiece and will be present mainly in the coating of water-soluble
inorganic
salt that is produced when the water fraction is evaporated during the drying
process.
The solid lubricant (B) contributes to preventing scuffing and seizure. The
chemical na-
ture of the solid lubricant is not critical; it can be any solid lubricant
with the requisite
physical properties, including those generally used for the cold plastic
working of metals.
Solid lubricant (B) is exemplified by metal soaps, micas, calcium compounds,
metal sul-
fides, nitrides, metal oxides, and solid polymers. Metal soaps are metal salts
of fatty
acids. The fatty acids are exemplified by lauric acid, myristic acid, palmitic
acid, stearic
acid, behenic acid, and hydroxystearic acid, with stearic acid being
preferred. The met-
als are exemplified by calcium, aluminum, magnesium, barium, zinc, lead,
lithium, and
potassium. The subject metal soap is preferably calcium stearate. Micas are
exemp-
15 lified by sericite, muscovite, and synthetic micas; the calcium compounds
are exempli-
fied by calcium hydroxide, calcium carbonate, and the like; the metal sulfides
are ex-
emplified by molybdenum disulfide, tungsten disulfide, selenium disulfide, and
the like;
the nitrides are exemplified by boron nitride and the like; the metal oxides
are exempli-
fied by titanium oxide, zinc oxide, silica, and the like; and the solid
polymers are exemp-
zo lified by poly(tetrafluoroethene), hereinafter usually abbreviated as
"PTFE", nylon, pol-
yethylene, and the like. Other examples of the solid lubricant are graphite,
talc, and
metals. The solid lubricant generally takes the form of a powder. Among the
preceding,
micas and the metal soaps and specifically calcium stearate are preferred.
These pro-
vide excellent lubricity while being free of substances that disturb
annealing. The solid
zs lubricant may be a single selection or a combination of two or more
selections.
The oily component (C) is at least one selection from mineral oils, animal and
plant oils and fats, and synthetic oils. This oily component (C) forms an oily
surface on
the dried coating of water-soluble inorganic salt afforded by application of
the water-
borne lubricant according to the present invention to the metal and thereafter
drying.
ao Oily component (C) compensates for the reduced lubricating performance of
the solid
lubricant in those regions of the workpieces that are characterized by
nonuniform add-on
of the solid lubricant.
The flash point, melting point, and viscosity of the oily component used in
the
present invention preferably fall within specific ranges. The flash point
preferably falls
ss in the range from 150 °C to 300 °C. In the case of heavy cold
plastic working, the aver
CA 02258638 1998-12-17
WO 97/48783 PCT/US97/10108
age post-working temperature of the metal stock can reach up to 150 °C
and above.
When the flash point of the oily component is below 150 °C, large
amounts of gas may
be generated post-working, which would create an ignition risk. A flash point
in excess
of 300 °C is undesirable because the associated viscosity and melting
point will gener-
s ally be high. The preferred range for the melting point is -20 °C to
20 °C. A melting
point in excess of 20 °C leads to a diminished emulsifiability and re-
emulsifiability by the
oil in the waterborne lubricant and thus to a tendency for the treatment bath
stability to
be reduced. An oily component with a melting point below -20 °C will
typically have a
reduced flash point. The viscosity of the oily component is preferably 5 to
100 centi-
,o stokes at 40 °C. A viscosity below 5 centistokes is typically
associated with a low flash
point, which leads to the post-working generation of large amounts of gas and
hence an
ignition risk. Moreover, when the viscosity is below 5 centistokes, the slip
between the
solid lubricant particles is diminished and the lubrication pertormance tends
to decline.
A viscosity in excess of 100 centistokes usually leads to a diminished
emulsifiability and
,s re-emulsifiability of the oily component in the waterborne lubricant and
thus to a tenden-
cy for the treatment bath stability to be reduced.
Mineral oils are exemplified by machine oils, turbine oils, spindle oils, and
the
like; animal and plant oils and fats are exemplified by palm oil, rapeseed
oil, coconut oil,
castor oil, beef tallow, lard, whale oil, and fish oils; and the synthetic
oils are exemplified
2o by ester oils and silicone oils. The ester oils are exemplified by the
esters between a
fatty acid such as stearic acid or oleic acid and a polyhydric alcohol such as
ethylene
glycol or trimethylofpropane. The silicone oils are exemplified by
poly(dimethylsiloxane)
and poly(diphenylsiloxane).
An oily component used by the present invention may be a single selection or
xs a combination of two or more selections from the above-described mineral
oils, animal
and plant oils and fats, and synthetic oils. Regardless of the particular
selection, the oily
component preferably satisfies the above-described ranges for the flash point,
melting
point, and viscosity.
The oily component also has a secondary activity. When the waterborne lubri-
ao cant according to the present invention is coated at elevated temperature
on the metal
workpiece(s), the waterborne lubricant is typically heated by steam tubes
prior to its ap-
plication. The presence of the oily component inhibits adhesion by the solid
lubricant
to the heating tubes during this process.
Surfactant component (D) functions in a waterborne lubricant according to the
35 present invention to emulsify the oily component homogeneously in the water
and also
6
CA 02258638 1998-12-17
WO 97/48783 PCT/US97/10108
to disperse the solid lubricant homogeneously in the water. This surfactant
can be a
nonionic, anionic, amphoteric, or cationic surtactant. The chemical nature of
the noni-
onic surtactant is not critical and is exemplified by polyoxyethylene alkyl
ethers, polyoxy-
ethylene alkylphenyl ethers, polyoxyethylene alkyl esters derived from
polyethylene gly-
s col and higher fatty acids (e.g., C~2 - C~8 fatty acids), and
polyoxyethylene sorbitan alkyl
esters deriving from higher fatty acids (e.g., C~2 - C~8 fatty acids),
sorbitan, and polyeth-
ylene glycol (or ethylene oxide). The chemical nature of the anionic
surtactant is not crit-
ical and is exemplified by fatty acid salts, the salts of sulfate esters,
sulfonates, the salts
of phosphate esters, and the salts of dithiophosphate esters. The chemical
nature of
,o the amphoteric surfactant is not critical and is exemplified by amino acid-
type and be-
taine-type carboxylates, sulfate ester salts, sulfonate salts, and phosphate
ester salts.
The chemical nature of the cationic surfactant is not critical and is
exemplified by fatty
amine salts and quaternary ammonium salts. A surtactant component can be a
single
selection or a combination of two or more selections.
Water functions as a dispersion medium for the solid lubricant, as a medium
for
the homogeneous emulsification of the oily component through the action of the
surfact-
ant, and as a solvent for the water-soluble inorganic salt.
In addition to the essential components described above, a waterborne
lubricant
according to the present invention may contain a conventional waterborne
lubricant for
zo the cold plastic working of metals. it may also contain an oiliness
improver such as a
fatty acid or higher alcohol, an extreme-pressure additive such as a chlorine-
based or
sulfur-based extreme-pressure additive, a defoamer, and a preservative. The
water-
borne lubricant according to the present invention may additionally contain a
colloidal
titanium compound for the purpose of improving the lubricity and rust
prevention. The
z5 subject colloidal titanium compound is exemplified by the turbid liquids
afforded by the
neutralization, with a strong alkali such as sodium hydroxide or the like, of
a compound
of sulfuric acid and titanium or a compound of phosphoric acid and titanium.
The solid lubricant/water-soluble inorganic salt weight ratio (B)/(A) in the
water
borne lubricant according to the present invention must be in the range from
0.05:1 to
so 2:1 and is preferably in the range from 0.1:1 to 1.5:1 and more preferably
is in the range
from 0.3:1 to 1.5:1. The particular value of this ratio is preferably selected
based on the
specific shape of the metal stock to be subjected to plastic working, the
working condi-
tions, the working device, and so forth. When this weight ratio has a value
below 0.05:1,
the resulting coating has reduced lubricating properties and scuffing and
seizure of the
35 metal workpiece will often occur. A weight ratio in excess of 2:1 results
in a reduced ad-
7
CA 02258638 1998-12-17
WO 97/48783 PCT/US97/10108
hesion between the substrate and the resulting coating and a reduced coating
hardness.
When the metal is introduced to the mouth of the tool under these
circumstances, the
dried coating formed on the surface is very prone to debonding, which results
in im-
paired lubricating properties.
s The weight ratio of oily component to the sum of the water-soluble inorganic
salt
and solid lubricant {(C)/(A)+(B)} must be in the range from 0.05:1 to 1.0:1
and preferably
is in the range from 0.1:1 to 0.8:1. A weight ratio below 0.05:1 results in a
diminished
bleed by the oily component onto the surface of the coating during drying.
This results
in a substantial impairment of a major feature of the present waterborne
lubricant, i.e.,
,o the supplementation or compensation, by the bled-out oily component, of the
lubricity
in regions that would otherwise suffer from a diminished seizure resistance
due to a non-
unifoml uptake of the solid lubricant. While bleed out by the oily component
onto the
coating surtace does not pose any problems at weight ratios in excess of
1.0:1, the cor-
responding coating is usually neither hard nor solid, and this reduces the
persistence
~s of the lubricant in place during the entire working time and thereby
impairs the lubricat-
ing properties.
The amount of surfactant (D) used in the waterborne lubricant according to the
present invention is not critical as long as at least the minimum amount is
used that is
capable of emulsifying the oily component in the water to homogeneity and
dispersing
2o the solid lubricant in the water to homogeneity. However, the use of too
much surtactant
facilitates foaming and is economically inefficient. The generally preferred
concentration
for the surfactant in the waterborne lubricant is 0.2 to 5 weight % of the
total composi-
tion.
The solids fraction, defined as {A + B + C + D + optional solids (i.e., any
solids
zs in optional components such as the oiliness improver referenced
above)}/(the total com-
position), in a waterborne lubricant according to the present invention is not
critical. The
preferred solids fraction is about 20 to 45 weight % during preparation,
transport, and
storage and about 5 to 45 weight % during application.
The method for preparing the waterborne lubricant according to the present in-
so vention is not critical and any method can be used that gives a waterborne
lubricant
meeting the conditions described above. In general, the waterborne lubricant
is prefer-
ably prepared by dissolving the water soluble inorganic salt (A) in water and
then disper-
sing the solid lubricant (B) to homogeneity into this solution; adding to this
a liquid in
which the oily component (C) is homogeneously emulsified in water using the
surfactant
ss (D); and agitating the combination in order to homogeneously disperse the
solid lubri-
8
CA 02258638 1998-12-17
WO 97/48783 PCT/US97/10108
cant and homogeneously emulsify the oily component. Dispersion of the solid
lubricant,
emulsification of the oily component, and the final agitation are preferably
effected by
strong agitation using a homogenizer, in order to obtain a uniform and
microfine emul-
sification and dispersion.
A waterborne lubricant according to the present invention can be diluted with
water at the point of application as a function of the type of metal, type of
cold plastic
working, degree of metal working, and the like. Waterborne lubricants prepared
by dilu-
tion are included within the scope of the present invention.
A process according to the invention for cold plastic working of a solid metal
sub
,o strate by mechanically forcing said solid metal substrate through an
opening bounded
by at least one solid surtace of at least one metal working tool comprises, at
a minimum,
steps of:
(I) coating, with a layer of a liquid waterborne lubricant according to the
invention,
any solid surface of said metal substrate that, if not coated, would contact a
solid
metal working tool surface during the process;
(II) drying the layer of liquid waterborne lubricant formed during step (I)
into place
over any solid surtace of said metal substrate that was coated with a layer of
li-
quid waterborne lubricant during step (I), so that the liquid layer is
converted to
a corresponding solid lubricant layer consisting of non-aqueous and non-
volatile
2o constituents of the liquid layer from which it was formed; and
(III) mechanically forcing the solid metal substrate, while any of its surface
that was
covered with a liquid lubricant layer in step (I) remains coated with the
corre
sponding solid lubricant layer formed in step (il), through said opening
bounded
by at least one metal working tool surface, so that the metal substrate is
cold
25 worked.
A waterborne lubricant according to the present invention can be used as lubri-
cant in cold plastic working, e.g., tube and pipe drawing, wire drawing,
forging, etc., of
substrates such as tube stock, wire stock, bar stock, etc., of a metal such as
iron, steel,
titanium, titanium alloy, copper, copper alloy, aluminum, or aluminum alloy.
It can be
ao used in particular as lubricant for the drawing of steel tubing and pipe.
In order to obtain good results, prior to application of the waterborne
lubricant ac-
cording to the present invention, a work piece is preferably pretreated, in
the order giv-
en, by degreasing (typically with an alkaline degreaser), washing with water,
pickling
(hydrochloric acid, for example, is used to remove oxide scale from the metal
work piece
ss and improve coating adherence), and washing with water. The pickling and
ensuing
9
CA 02258638 1998-12-17
WO 97/48783 PCT/US97/10108
water wash can be omitted when oxide scale is not present, as on most kinds of
stain-
less steel, for example. This pretreatment can be carried out by the usual
techniques.
A waterborne lubricant according to the present invention can be applied to
the
metal work piece by dipping, flow coating, and so forth. The temperature of
the water
s borne lubricant during application is not critical, but suitable
temperatures fall in the
range from ambient temperature to 90 °C. The dipping time is also not
critical, but dip-
ping is suitably continued until the temperature of the metal work piece has
reached the
bath temperature, for example, generally about 5 to 10 minutes. After
application and
drainage, the dried coating is obtained by drying the applied coating in a
drying oven,
etc. The drying temperature is not critical, but will generally preferably be
from 60 °G
to 150 °C.
The optimal thickness of the dried coating will vary as a function of the type
of
metal working, degree of working, and surtace roughness. The coating will
generally
have an average mass, per unit area of work piece coated with the coating,
that is from
1 to 50 grams per square meter, hereinafter usually abbreviated as "g/m2", and
prefer
ably is from 5 to 40 glm2. When the dried coating is too thin, strong contact
will occur
between the tool and metal work piece and seizure will then be prone to occur.
When
the dried coating is too thick, a large amount of the dried coating will not
be drawn into
the working intertace between workpiece and drawing tool, resulting in waste
of the wat
zo erborne lubricant.
The waterborne lubricant according to the present invention can be applied to
the plastic working of metals by the usual plastic working methods.
A solid coating according to the invention that remains on a work piece after
plastic working can be easily stripped off.
25 Metal is typically formed or molded by plastic working in a repetitive
sequence
of lubrication treatment and then plastic working in order to gradually form
the work
piece into the desired product shape. During this process, the metal work
piece is an-
nealed in order to soften it, since the direct transfer of the work-hardened
metal work
piece to the next plastic working step would eventually interfere with forming
due to the
so high working force required to further deform such work-hardened metal.
When the lub-
ricating coating remains present during annealing, the components in the
lubricant can
lead to infiltration of carbon, sulfur, phosphorus, etc., into the metal work
piece, which
can impair the corrosion resistance and mechanical strength of the metal
itself. More-
over, the adherence of the new coating will be usually be poor when an old
lubricating
35 coating is present during the next lubrication treatment after a plastic
working step.
CA 02258638 1998-12-17
WO 97/48783 PCT/LTS97/10108
As a result of these considerations, the residual coating is ordinarily
removed
after each cold working stage of a plastic working operation. However, the
prior-art
combined lubrication system of conversion coating treatment + reactive soap
treatment
at the very least requires alkaline degreasing and pickling (hydrochloric acid
cleaning
s or sulfuric acid cleaning) to remove the residual coating. In contrast, with
use of a wat-
erborne lubricant according to the present invention, the residual coating can
generally
be removed with an alkaline degreaser alone. This alkaline degreaser can be an
alka-
line degreaser in general use, for example, an alkaline degreaser containing
sodium
phosphate, sodium silicate, surtactant, etc. A specific example of a useable
alkaline de-
,o greaser is FINECLEANERT"" 4360 from Nihon Parkerizing Company, Limited,
Tokyo.
The function of the waterborne lubricant according to the present invention is
not
entirely clear. It is thought, however, that when the waterborne lubricant
according to
the present invention is coated on metal and then dried at elevated
temperature to give
the dried coating, the oily component, present as an emulsion, bleeds onto the
outside
,s of the coating, so that this bled-out oily component supplements the
lubricity in those
regions having a low dry coating add-on mass. In other words, due to the
drying pro
cess-induced bleed onto the outer surfaces of the coating by the so-called
lubrication
auxiliary present as one component of the waterborne lubricant, seizure
phenomena are
substantially reduced due to a reduction in friction between the work piece
and tool (e.g.,
zo die, plug, punch, etc.).
The reason why the residual coating can be so easily stripped off after the
cold
plastic working step is also not entirely clear. However, it is thought that
the coating of
water-soluble inorganic salt is itself easily removed by alkaline degreaser
and that the
solid lubricant and oily component taken up therein are also removed at the
same time.
Zs Waterborne lubricants according to the present invention will be
illustrated in the
following working examples, and their benefits may be further appreciated by
contrast
with the following comparison examples.
Examples 1 to 16
Preparation and application of waterborne lubricants and testing in steel pipe
drawing
ao Lubricants were prepared with the compositions reported in Tables 1 and 2.
To
prepare the lubricants, the water-soluble inorganic salt was dissolved in
water and the
solid lubricant was then uniformly dispersed in this solution. This was
followed by the
introduction of water in which the oily component was homogeneously emulsified
by the
surfactant. A homogenizer was used for preparing the separate dispersion and
emulsifi
es cation. The mixture of the dispersion and emulsion was stirred to give a
uniform
11
CA 02258638 1998-12-17
WO 97/48783 PCT/US97/10108
Table 1: COMPOSITION DATA FOR EXAMPLES 1 TO 16
Ex- Variable Ingredients
amp- in Lubricant
Composition (Percents
as Weight % of
Total
Composition)
le
Num- Water Soluble Solid Lubricant Oily Component
ber Inorganic Salt Component (C)
Component (A) (B)
Name % Name % Name
1 borax 10.0calcium stearate10.0 palm oil 5.0
2 borax 20.0calcium stearate10.0 ester oil 10.0
3 otassium tetraborate10.0calcium stearate5.0 alm oil 5.0
4 otassium tetraborate15.0mica 7.0 ahn oil 10.0
sodium sulfate 12.0calcium stearate12.0 machine oil 6.0
6 sodium sulfate 15.0calcium stearate15.0 ester oil 5.0
7 borax 10.0calcium stearate10.0 ester oil 5.0
8 borax 20.0mica 7.0 ester oil 15.0
9 otassium tetraborate10.0calcium stearate2.0 ester oil 5.0
otassium tetraborate10.0calcium stearate15.0 ester oil 5.0
11 otassium tetraborate10.0calcium stearate5.0 alm oil 12.0
12 otassium tetraborate15.0calcium stearate5.0 alm oil 15.0
13 otassium tetraborate15.0PTFE 1.0 ester oil 5.0
14 otassium tetraborate15.0mica 7.0 ester oil i5.0
sodium sulfate 12.0calcium stearate12.0 ester oil 5.0
16 sodium sulfate 15.0calcium stearate10.0 machine oil 5.0
Note for Table 1
In addition to the ingredients shown in Table 1, every example had 1 % by
weight of poly{oxyethyl-
ene}alkyl ether surfactant, with the balance not otherwise accounted for being
water.
dispersion of the solid lubricant and uniform emulsification of the oily
component.
The starting materials used to prepare the waterborne lubricants had the
follow-
ing properties. The water-soluble inorganic salts were in all cases reagent
first-grade
quality. The calcium stearate used was a waterborne dispersion with 30 %
solids. The
s PTFE used was a waterborne dispersion with 60 % solids. The machine oil had
a vis-
cosity of 46 millimeters squared per second, hereinafter usually abbreviated
as "mm2/s"
at 40 °C. The palm oil was a purified palm oil with a viscosity of 28
mm2/s at 50 °C. The
ester oil was the ester condensate of oleic acid dimer, lauric acid, and
trimethylolpro-
pane and had a viscosity of 64 mm2/s at 50 °C. The surfactant was a
polyoxyethylene
,o alkyl ether and was added at 1 weight % of the total quantity of lubricant.
The water-
borne lubricant prepared as described above was applied to carbon steel pipe
and stain-
less steel pipe (see below) and then dried, and the pipe carrying the
resulting dried
coating was subjected to a drawing test. The pertormance of the waterborne
lubricant
12
CA 02258638 1998-12-17
WO 97/48783 PCT/US97l10108
Table 2: Composition Ratios and Test Evaluation Results for Examples 1 - 16
Ex- Composition Dry SubstrateReductionDrawing
ample Ratios Coat- T R Test
e ti Ratings
i
yp a
o
n
Num- ~g~~~A~~C~~ ing Drawing pipe Coatin
ber {~A~..FB~}Add- Test, Surface Remova-
On % Condition
,
g~mz Outer Inner bility
1 1.00 0.25 23.8 STKM13A 46.0 +++ +++ +++
2 0.50 0.33 34.0 STICM13A46.0 +++ +++ +++
3 0.50 0.33 10.6 STKM13A 46.0 +++ +++ +++
4 0.47 0.45 18.1 STKM13A 46.0 ++ ++ +++
I.00 0.25 21.7 STKM13A 46.0 ++ ++ +++
6 1.00 0.17 29.9 STKM13A 46.0 +++ ++ +++
7 i.00 0.25 15.0 SUS304 43.0 +++ +++ +++
8 0.35 0.56 32.3 SUS304 43.0 ++ ++ +++
9 0.20 0.42 8.6 SUS304 43.0 ++ ++ +++
1.50 0.20 18.8 SUS304 43.0 +++ +++ +++
11 0.50 0.80 21.2 SUS304 43.0 +++ +++ +++
I2 0.33 0.75 24.5 SUS304 43.0 +++ +++ +++
13 0.07 0.31 16.7 SUS304 43.0 + + + + + +
14 0.47 0.68 24.8 SUS304 43.0 ++ ++ +++
1.00 0.21 20.1 SUS304 43.0 +++ ++ +++
16 0.67 0.20 19.9 SUS304 43.0 ++ ++ +++
was evaluated based on the extent of scratching on the inside and outside of
the pipes.
The drawing stock was STKM13A carbon steel pipe with an outside diameter of
25.4
millimeters, hereinafter usually abbreviated as "mm", and a wall thickness of
3.0 mm or
SUS304 stainless steel pipe with an outside diameter of 25.0 mm and a wall
thickness
s of 2.5 mm.
Prior to application of the waterborne lubricant, the pipe was subjected to
the
pretreatment described below. The carbon steel pipe was subjected to process
steps
(1) to (4) in the order given, while the stainless steel pipe was subjected to
process
steps (1) and (2) in the order given.
,o {1) Degreasing
alkaline degreaser: FINECLEANERT"~ 4360 from Nihon Parkerizing Company,
Ltd.
concentration: 20 grams per titer, hereinafter usually abbreviated as "gIL"
temperature: 60 °C
dipping time: 10 minutes
(2) Water wash: dipping in tap water at ambient temperature
13
CA 02258638 1998-12-17
WO 97/48783 PCT/US97110108
(3) Pickling
industrial hydrochloric acid
concentration: 17.5 weight
temperature: ambient
s dipping time: 10 minutes
(4) Water wash: dipping in tap water at ambient temperature
The waterborne lubricant was applied by immersion at a treatment bath tempera-
ture of 50 °C. After treatment, the treated work piece was dried by
placement in a
tunnel-shaped drying box and heating for 1 hour at 100 °C to 120
°C, using a kerosene-
,o fired jet heater.
The drawing test was run using a 10-tonne chain-type drawbench and a die
(Model KD Superhard Die from Fuji Die Company, Limited) and plug (Model MB
Super-
hard Plug from Fuji Die Company, Limited) composed of superhard tooling. The
draw
rate was 17 meters per minute. The reduction ratio (= cross section reduction
ratio) was
,s set at 46 % for the STKM13A stock (outside diameter after drawing = 20 mm,
wall thick-
ness = 2 mm) and 43 % for the SUS304 stock (outside diameter after drawing =
20 mm,
wall thickness = 1.75 mm). The reduction ratio was calculated from the
equation:
reduction ratio (%) - {(Ao - A~)/Ao} x 100,
where Ao is the pre-working cross-sectional area of the pipe and A~ is the
post-working
2o cross-sectional area of the pipe.
Scratch development on the inner and outer surtaces of the pipe was evaluated
by visual inspection of the drawn pipe and was rated on the following 4-level
scale:
+ + + ; no scratching, no unevenness in the finish;
+ + : no scratching, but an uneven finish was observed;
is + : minor scratching was observed;
scratching was clearly observed.
In this evaluation, scratching denotes strip-like seizure scratching observed
on the inner
or outer surtace of the pipe, while an uneven finish refers to differences in
gloss caused
by a mixture of glossy regions and orange peel-like textured regions on the
surface after
3o drawing.
The post-working removability of the residual coating was evaluated using an
al-
kaline degreaser (FINECLEANERT"" 4360 from Nihon Parkerizing Co., Ltd.,
concentra-
tion = 20 g/L, temperature = 60 °C). The alkaline-degreased pipe was
visually inspected
and rated on the following 4-level scale:
14
CA 02258638 1998-12-17
WO 97/48783 PCT/US97/10108
+ + + a no residual coating could be observed after immersion for 5 min-
utes;
+ + : no residual coating could be observed after immersion for 10
minutes;
s + : coating remained even after immersion for 10 minutes;
coating remained even after immersion for 20 minutes.
The results of the drawing tests are reported in Table 2.
Comaarison Examples 1 to 10
Waterborne lubricants were prepared as in Examples 1 to 16, but in these in-
stances using the compositions reported in Tables 3 and 4. Testing was also
carried
out as in Examples 1 to 16. These results are reported in Table 4.
Problems occurred with all the lubricants outside the scope of the present
inven-
tion, e.g., scratching on the inner or outer wall of the test-drawn pipe, poor
removal by
alkaline degreasing of the residual post-working coating, etc.
's Comparison Examples 11 and 12
For Comparison Example 11, Type STKM13A Steel as used in Examples 1 to
16 was subjected to a zinc phosphate conversion treatment by immersion for 10
minutes
in a solution in water containing 90 g/L of a commercially available product,
PALBOND~
181X concentrate from Nihon Parkerizing Co., Ltd., Tokyo; the solution was
maintained
zo at 80 °C during the immersion. For Comparison Example 12, Type
SUS304 stainless
steel as used in Examples 1 to 16 was subjected to an oxalate conversion
coating by
immersion for 10 minutes at 95 °C in a solution in water containing 35
g/L of FERR-
BOND~ A Agent # 1 and 17 gIL of FERRBOND~ A Agent #2.
After completion of these conversion coatings, both types of pipe were
immersed
is for 5 minutes at 80 °C in a solution in water containing 70 g/L of
PALUBE~ 235 concen
trate. (All materials identified by trademarks in this description of
Comparison Examples
11 and 12 are commercially available from Nihon Parkerizing Co., Ltd., Tokyo.)
The re
sulting lubricated steel pipe was subjected to the same drawing test as
described for Ex
amples 1 to 16. The results of these tests and some additional characteristics
of the
so coatings are reported in Table 5. Neither seizure nor finish unevenness
occurred in
these comparison examples, but the post-draw removability of the residual
coating was
poor.
CA 02258638 1998-12-17
WO 97!48783 PCT/US97/10108
Table 3: COMPOSITION DATA FOR COMPARISON EXAMPLES 1 - 1 O
Com- Variable Ingredients
par- in Lubricant
i Composition
(Percents as
Weight % of
Total
Composition)
son
Ex- Water Soluble Solid Lubricant Oily Component
amp- Inorganic Salt Component (C)
Component (A) (B)
le
Num- Name % Name % Name
ber
1 borax 10.0 calcium stearate10.0palm oil 0.5
2 borax 20.0 calcium stearate0.5 ester oil 10.0
3 otassium tetraborate10.0 calcium stearate5.0 alm oil 0.5
4 sodium sulfate 12.0 calcium stearate12.0machine oil 30.0
S borax 10.0 calcium stearate25.0machine oil S.0
6 otassium tetraborate10.0 calcium stearate2.0 machine oil 15.0
7 otassium tetraborate10.0 PTFE 21.0alm oil 5.0
8 otassium tetraborate15.0 calcium stearate0.5 ester oil 5.0
9 otassium tetraborate10.0 mica 21.0ester oil 5.0
sodium sulfate 12.0 calcium stearate12.0ester oil 1.0
Note for Table 3
In addition to the ingredients shown in Table 3, each of comparison examples 1
through 10 had 1 % by
weight of poly{oxyethylene}alkyl ether surfactant, with the balance not
otherwise accounted for being
water.
Table 4: COMPOSITION RATIO AND TEST EVALUATION RESULTS FOR COMPARISON EXAMPLES
1 - 10
Com- Composition Dry SubstrateReductionDrawing
par- Ratios Coat- Type Ratio Test
in Ratings
icon ing Drawing
Ex- ~~/~''~~~C~/ Add- Test, Pipe Coating
ample {~A~B~}On, % Surface Remova-
Condition
Num- g/m2 bility
ber Outer Inner
1 1.00 0.03 28.3 STICM13A46.0 + ++ +++
2 0.03 0.49 15.5 STKM13A 46.0 x x +++
3 0.50 0.03 10.2 STICM13A46.0 + ++ +++
4 1.00 1.25 35.1 STICM13A46.0 + + +++
5 2.50 0.14 32.1 SUS304 43.0 + + +++
6 0.20 1.25 11.8 SUS304 43.0 ++ + +++
7 2.10 0.08 29.5 SUS304 43.0 +++ +++ x
8 0.03 0.32 15.8 SUS304 43.0 x x +++
9 2.10 0.08 19.4 SUS304 43.0 + + + + +
10 1.00 0.04 22.7 SUS304 43.0 ++ + +++
16
CA 02258638 1998-12-17
WO 97/48783 PCT/US97/10108
Table 5: COATING PARAMETERS AND EVALUATION TEST RESULTS, COMPARISON EXAMPLES
11 - 12
Com- Coating Results ReductionDrawing
Test
Ratings
pari9on Ratio
Eaamp- Coating ComponentAdd- in Pipe Coating
l On Drawing Surface
N Condition
e , Teat, Remova-
o. g/L % Outer Inner bility
Conversion coating8.2
mass
1 Quantity of metal6. 46.0 + + + + + + x
soap S
Quantity of hot 3.7
water
soluble soap
Conversion coating6.2
mass
2 Quantity of metal3.0 43.0 + + + + + +
soap
x
Quantity of hot 1.5
water
soluble soap
Examples 17 to 19
Preparation and application of the waterborne lubricants and for ing testing
The waterborne lubricants were prepared as described for Examples 1 to 16, but
using the compositions reported in Table 6. The resulting waterborne
lubricants were
s coated on carton steel followed by drying, and the dry-coating bearing
carbon steel was
then subjected to backward punching. The pertormance of the waterborne
lubricants
was evaluated based on the depth to which the samples could be satisfactorily
punched
in an apparatus partially illustrated in drawing Figure 1.
Table 6: COMPOSITION DATA FOR EXAMPLES 17 - 19
Corn-Variable Ingredients
par- in Lubricant
Composition (Percents
as Weight % of
Total
Composition)
ison
Ex- Water Soluble Solid Lubricant, Oily Component
amp- Inorganic Salt, Component (B) (C)
Component (A)
le
Num- Name % Name % Name
ber
17 otassium tetraborate10.0calcium stearate5.0 alm oil 5.0
18 otassium tetraborate20.0barium stearateS.0 ester oil 10.0
19 borax 15.0zinc stearate 10.0alm oil 10.0
Note for Table 6
In addition to the ingredients shown in Table 6, each of examples 17 through
19 had 1 % by weight of
poly{oxyethylene}alkyl ether surfactant, with the balance not otherwise
accounted for being water.
17
CA 02258638 1998-12-17
WO 97/48783 PCT/US97/10108
The substrate stock for the backward punching test was a commercial S45C nor-
malized carbon steel (hardness about Hv 180). All of the test specimens
depicted in
Figures 2.1.1, 2.x.1, etc. had a diameter of 30 mm, while the initial height
of the test
specimens varied from 16 mm to 40 mm at 2-mm intervals, resulting in 13
distinct initial
s height values, only four of which, including the smallest and the largest,
are depicted in
the drawing figure numbers beginning with "2". The final digit of these figure
numbers
is "1" for initial test specimens, while the final test specimens formed by
punching these
initial test specimens have a final digit of "2", with all preceding parts of
the figure num-
ber the same as for the corresponding initial test specimen.
to The waterborne lubricant was applied to the initial test specimens by
dipping at
a waterborne lubricant temperature of 80 °C. The liquid coating in
place on the sub-
strate was then dried for one hour using a forced convection drying oven at 90
°C to 100
°C.
The backward punching test was run using a 200-tonne crank press. The punch
~s 1 in drawing Figure 1 was driven from above onto the circular test specimen
2 set in the
die 3 with its circumference held to give a cup-shaped molding. The SKD11 die
had an
inside diameter of 30.4 mm for the test specimen insertion zone. The SKH53
punch had
an outside diameter of 21.21 mm on its lower end, which was driven into the
specimen,
after the latter was in place in the die, at an operating rate of 30
strokeslminute. The ter-
zo urinal point of the press was controlled so as to give a 10-mm residual
margin at the bot-
tom of the final test specimen in all the tests. As a result, the surface
enlargement ratio
of the worked part increased with test specimen height (deeper hole). The
shortest sub-
strate sample thus tested increased in length from 16 to 20 mm, corresponding
to a 10
mm hole depth, as a result of this punching, while the longest substrate
sample thus
25 tested increased in length from 40 to 70 mm, corresponding to a hole depth
of 60 mm.
Test substrate cylinders such as those depicted in Figures 2.x.1 and 2.y.1
with intermed-
iate initial heights had intermediate hole depths. The performance of the
waterborne lub-
ricant was evaluated based on the hole depth that could be worked without
seizure
("good-punch depth"). The results are reported in Table 7.
Benefits of the Invention
The waterborne lubricant according to the present invention provides, in a
single
step, the same lubrication performance in the cold plastic working of metals
as the prior-
art two or more step conversion coatinglreactive soap treatment. At the same
time,
treatment according to the invention provides substantial improvement in the
working
~s environment, treatment bath management, waste disposal, and so forth.
Moreover, use
18
CA 02258638 1998-12-17
WO 97/48783 PCT/US97/10108
Table 7: COMPONENT RATIOS AND TEST RESULTS FOR EXAMPLES 17 - 19
Example Component Dry Coating Good-Punch
N Ratios
b
um Add-On Mass, Depth, mm
er (B)/(A) (C)/~(A)+(B)~2
g/m
1 ~ 0.50 0.33 14.8 44
18 0.25 0.40 22.6 48
19 0.67 0.40 30.4 52
of the waterborne lubricant according to the present invention in the cold
plastic working
of metals provides an easier post-working removal of the residual coating than
in
conversion coating plus reactive soap treatment.
19
