Note: Descriptions are shown in the official language in which they were submitted.
CA 02343779 2001-03-12
WO 00/15879 PCT/US99/21117
Descril t~ ion
METHOD FOR FORMING A LUBRICATIVE FILM FOR COLD WORKING
BACKGROUND OF THE INVENTION
The present invention relates to a method for forming a lubricative film for
the
cold working of metal materials, which is used for the purpose of reducing the
friction that
occurs between a tool and a work piece, thereby preventing seizure during the
cold
s working of metal.
A method widely employed in the past in the field of the cold plastic working
of
metal materials involved forming a chemical conversion film as a lubrication
undercoating
on the surface of a metal material, and forming a lubricative film over this
by a lubrication
treatment featuring a water- or oil-based lubricant. For example: a phosphate
treatment
,o using zinc phosphate, zinc-iron phosphate, zinc-calcium phosphate,
manganese phos-
phate, iron phosphate, or the like has been performed on carbon steel or low-
alloy steel;
an oxalate treatment has been performed on stainless steel; a chemical
conversion film
treatment in which the main component of the film is an aluminum fluoride has
been
performed on aluminum; a chemical conversion film treatment in which the main
,s component is copper oxide has been performed on copper; and a conversion
film
treatment in which the main component is titanium fluoride has been performed
on ti-
tanium. (Process Tribology, edited by the Japanese Plastic Working Society,
pp. 56 -
62 (Corona, 1993)).
After the formation of a chemical conversion film, the general practice is to
form
2o a lubricative film using a water- or oil-based lubricant. In particular,
when a phosphate
treated material is brought into contact with a weakly alkaline aqueous
solution of a fatty
acid alkali metal salt, a lubricative film with a three-layer structure
composed of a
phosphate film, a metal soap, and a soap (this three layer structure being
hereinafter
referred to as a reaction type soap film) is formed on the material surface,
and this
2s method is called a reaction type soap treatment. The reaction is expressed
by the
following chemical equation (1 ):
Zn3(P04)2 ~ 4H20 + 6C,7H35COONa ~ 3(C"H35C00)2Zn + 2Na3P04 + 4H20 ... (1 )
Reaction type soap films are the most commonly used lubricative films because
they provide good lubrication performance even under harsh cold forging
conditions.
3o The process steps or operations generally entailed by a reaction type soap
treatment are
as follows:
1. Descaling (acid pickling with sulfuric acid, hydrochloric acid, or the
like, or
mechanical descaling by shot blasting or the like combined with acid pickling
with
1
CA 02343779 2001-03-12
WO 00/15879 PCT/US99/21117
sulfuric acid, hydrochloric acid, or the tike);
2. Rinsing with water;
3. Chemical conversion film treatment;
4. Rinsing with water;
s 5. Reaction type soap treatment;
6. Drying.
Nevertheless, the lubricative film formation methods used in the past had
several
drawbacks in terms of performance and their environmental impact. These are
described below.
,o The first problem is the generation of sludge. For example, in the
phosphate
treatment of an iron-based material, the ferrous ions that are dissolved into
the treatment
liquid by etching are turned into ferric ions through the action of an
oxidation promoter,
and this product is generally removed from the system as iron phosphate
sludge, which
is the source of the above-mentioned sludge generation. Similarly, large
amounts of
,5 sludge are generated in oxalate treatments, fluoride treatments, and oxide
treatments,
and people involved in the field of industrial waste are currently dealing
with the disposal
of this sludge.
Sludge management is disclosed in Japanese Laid-Open Patent Application
2-197581, for example, which deals with a method for reducing the amount of
sludge by
20 lowering the treatment temperature by using a treatment liquid to which a
water-soluble
aromatic compound having nitro groups and sulfone groups has been added. While
this
is indeed an effective method, the reduction in sludge generation is still
only about half
that in the past, and further reductions are needed.
A second problem is waste liquid treatment. Over time, the liquids used in the
2s oxalate treatment of stainless steel or in the chemical conversion
treatment of aluminum,
copper, or titanium lose their strength, so that the resulting film no longer
performs the
same as it did at first, and therefore the treatment liquid has to be
discarded and
replaced every so often. This waste liquid is processed with wastewater
equipment, or,
for production lines not having such equipment, industrial waste treatment
specialists
3o take over. Because the waste liquids contain various substances, including
the
components contained in the treated metal materials and the liquid components
from
pre-treatments such as degreasing and acid pickling, this wastewater treatment
is
tremendously expensive. Furthermore, as of now no practical way to regenerate
these
liquids has been implemented.
s5 A third problem is that the lubrication undercoating that can be formed is
limited
by the material intended for chemical conversion treatment. For example,
because the
2
CA 02343779 2001-03-12
WO 00/15879 PCT/US99/21117
above-mentioned reaction type soap film is not formed on a copper oxide film
or a titani-
um fluoride film, a lubricative film is formed by coating the surface of the
material in
question with a metallic soap or an oil-based lubricant whose lubricity has
been
enhanced by the addition of an extreme-pressure additive. However, the
performance
a of these lubricants is inherently inferior to that of reaction type soap
films, and the cross-
section reduction ratio per drawing pass cannot be increased in plastic
working, so this
inevitably requires more working passes, including the lubricative film
treatment step.
The result is a higher production cost.
Conversely, with an oxalate film or an aluminum fluoride film, the reactive
soap
,o tends to react excessively, and changes in the treatment time or liquid
temperature
cause undesirable and large changes in the amount of metallic soap generated.
Friction
increases if a smaller amount of metallic soap is generated, but on the other
hand, if the
metallic soap is generated excessively, beyond the proper amount, then it will
tend to
clog the tool. Moreover, excessive reactivity leads to a need to replace the
reactive soap
,s treatment liquid more often. Working is sometimes performed using a
lubricative film
formed by a lubricant whose principal component is molybdenum disulfide and
using an
oxalate film as a lubrication undercoating in the hot forging of stainless
steel, but a prob-
lem with this method is that the iron oxalate that is the main component of
the oxalate
film decomposes in the course of the preheating of the material. These
problems occur
2o because the chemical conversion treatment is material-selective, and there
is a need for
a lubricative film formation method that is unrelated to the type of metal
material being
used, and which therefore does not have these problems.
A fourth problem is that it is difficult to produce the amount of lubricative
film
required by a chemical conversion treatment. Specifically, when a chemical
conversion
2s film is used as a lubrication undercoating, the formation of the chemical
conversion film
proceeds through the corrosion of the metal, so that a passivation layer is
produced,
which covers the metal surface and stops the production of the film. fn view
of this, the
concentration of the chemical conversion treatment liquid, the treatment
temperature, the
acid ratio, and other conditions are generally set with an eye toward
controlling the
ao amount of film. With these methods, however, precise control of the film
amount can not
be achieved just by setting general treatment conditions, and if an attempt is
made to set
the treatment conditions for every metal material to be treated, there will be
a marked
drop in production efficiency. In view of this, the actual practice is for the
working condi-
tions to be set up for the material that is the most difficult to work, which
is done as a
ss safety factor in real production.
Another method for forming a phosphate film is an electrolysis treatment that
3
CA 02343779 2001-03-12
WO 00/15879 PCT/US99/21117
makes use of an external power source. Japanese Laid-Open Patent Application
6-322592, for example, discloses a method in which a phosphate film is formed
by a
pulse current using a steel material as the anode, after which a sodium
stearate treat-
ment is performed to produce a reaction type soap film. This method, however,
gener-
s ates sludge because the phosphate film production proceeds while the steel
material is
dissolved.
The present invention is a method for forming a lubricative film for cold
working
on a metal material, and an object thereof is to provide a novel method for
forming a lub-
ricative film with which at least some, and most preferably all, of the above-
mentioned
problems encountered in the past can be solved.
BRIEF SUMMARY OF THE INVENTION
The inventors have learned that it is desirable for the chemical conversion
film
to have a thickness corresponding to a mass per unit area of 6 to 20 grams of
film per
square meter of surface coated, this unit of areal density or "coating weight"
as it is
~s usually called being hereinafter usually abbreviated as "g/m2. With
conventional
methods, more sludge was produced if such a thick chemical conversion film was
formed. A subordinate object of the present invention is accordingly to form a
thick
phosphate conversion film without producing so much sludge. Also, with
conventional
methods, a long contact time with the chemical conversion treatment liquid was
required
2o to form a thick conversion film; this diminished productivity. An
additional subordinate
object of the present invention is to form a thick phosphate conversion film
at a high level
of productivity. Further, with conventional methods, it was not easy to form a
thick
phosphate conversion film on stainless steel or the like, for example. A third
subordinate
object of the present invention accordingly is to provide a method with which
a thick
2s phosphate conversion film can be formed even on stainless steel or the
like.
One major embodiment of the present invention is a process for forming a lub-
ricative film for cold working, said process comprising the following
operations:
(I) bringing said metal substrate into contact with an aqueous electrolyte
solution
comprising, preferably consisting essentially of, or more preferably
consisting of
so water and:
(A) dissolved zinc cations;
(B) dissolved phosphate anions; and
(C) at least one dissolved auxiliary acid other than phosphoric acid, said
auxiliary acid having at least a first ionization constant that is greater
than
35 the third ionization constant for phosphoric acid; and, optionally, other
constituents as detailed further below,
4
CA 02343779 2001-03-12
WO 00/15879 PCT/US99/21117
this aqueous electrolyte also being in contact with a counter-electrode that
is not
said metal substrate to be cold worked, so that an electric current can pass
through the counter-electrode as anode, the aqueous electrolyte solution by
ionic
conduction, and said metal substrate as cathode;
s (II) passing through said metal substrate while it remains in contact with
said
aqueous electrolyte solution an electric current that has a net cathodizing
charac-
ter at said metal substrate for a sufficient time to form an adherent solid
phos-
phate conversion coating over said metal substrate;
(III) discontinuing contact between said aqueous electrolyte solution and said
metal
,o substrate bearing said adherent solid phosphate conversion coating; and
(IV) applying to the exterior surface of said solid phosphate conversion
coating, when
it is not in contact with said aqueous electrolyte solution, a water- or oil-
based
lubricant coating.
BRIEF DESCRIPTION OF THE DRAWINGS
,s Figure 1 is a cross-sectional view of apparatus used in a backward punch
test
that was run to test the efficacy of lubricant compositions and processes
according to the
present invention. Figures 2a through 2d are projection views of test
substrates used
in this test before being tested, while Figures 3a through 3d are projection
views of the
same test substrates after being punched.
2o DETAILED DESCRIPTION OF THE INVENTION AND !TS PREFERRED
EMBODIMENTS
Metal substrate materials that can be used in the present invention include
any
electrically conductive materials, including ferrous materials such as carbon
steel,
chromium steel, chromium-molybdenum steel, nickel-chromium steel, nickel-
chromium-
25 molybdenum steel, stainless steel, boron steel, and manganese steel, and
non-ferrous
materials such as aluminum, magnesium, titanium, and copper.
Preferably, a process according to the invention is applied to a metal
substrate
which has, if it has been normally soiled by any working oil or other foreign
matter used
in some previous working operation or has any scale formed in a previous
operation,
3o been cleaned and pickled before being contacted with the aqueous
electrolyte solution
in operation (I) of a process according to the invention as described above. A
commer-
cially available alkali-based cleaning and degreasing agent preferably is used
for the ini-
tial cleaning treatment when any oil or similar lubricant has been applied to
the metal sur-
face in a previous processing operation.
35 If any visible scale remains after cleaning, mechanical descaling is often
preferred as the next preparatory operation for the substrate surface
eventually to be
CA 02343779 2001-03-12
WO 00/15879 PCT/US99/21117
cold worked. Mechanical descaling includes the use of a bending roll, shot
blasting, air
blasting, and liquid honing. After mechanical descaling, any remaining scale
preferably
is removed by a high-pressure water jet or brushing.
Acid pickling may alternatively be used alone or in combination with
mechanical
s descaling to remove any scale present on the surface of the metal substrate
to be cold
worked. Sulfuric acid, hydrochloric acid, nitric acid, hydrofluoric acid,
hexafluorozirconic
acid, or the like can be used for the acid pickling liquid. The acid pickling
can also
include the use of electrolysis with the metal substrate as anode and/or
cathode. After
this acid pickling, the pickled surface preferably is thoroughly rinsed with
water so that
the acid pickling liquid is not admixed into the surface conditioning
treatment liquid and/or
the phosphate treatment liquid used later. It is preferable for acid pickling
to be
performed after mechanical descaling, if the latter is used, and it is
preferable for acid
pickling to be used even on substrates with no visible scale on the surface,
because the
pickling facilitates the formation of a good phosphate conversion coating
later.
,5 In order to raise the phosphate film production rate and produce finer
crystals in
the phosphate film, the substrate normally preferably is brought into contact
with a pre-
treatment liquid containing colloidal titanium, or with a pre-treatment liquid
in which a
metal phosphate including particles whose diameter is 5 micrometres,
hereinafter usually
abbreviated as "gym", or less has been dispersed, before beginning operation
(I) of a
2o process according to the invention as described above, but after any
chemical cleaning,
descaling, and/or pickling as described above. It is also effective to heat
the treated
material immediately prior to the phosphate treatment, in which case the rate
at which
the phosphate film is produced will increase.
As already noted, the aqueous electrolyte solution utilized in operation (I)
of a
2s process according to the invention as described above must contain
dissolved zinc ions.
Preferably, these ions are supplied from a source, such as a water soluble
salt of zinc,
in which zinc is already present in cationic form and is expected to remain in
cationic
form when dissolved, or from a source such as zinc metal or zinc oxide, that
is expected
to react with acid already present in a precursor solution made during the
course of pre-
so paring the final aqueous electrolyte solution to be used in a process
according to the
invention. Any zinc present in these sources that are mixed to make up the
final
aqueous electrolyte solution used in a process according to the invention is
to be
presumed for purposes of this description as present in cationic form to the
full extent
stoichiometrically possible from the amount of zinc contained in the sources)
used in
ss making the aqueous electrolyte solution, irrespective of any incomplete
dissociation,
complex formation, or the like that may occur in this electrolyte solution.
6
CA 02343779 2001-03-12
WO 00/15879 PCT/US99/21117
The dissolved phosphate anions required for the aqueous electrolyte solution
used in operation (I) of a process according to the invention as described
above may be
sourced to this solution by any water soluble salts, including only partially
neutralized
salts, of orthophosphoric or condensed phosphoric acids and/or by these acids
them-
s selves. The full stoichiometric equivalent as PO4 3 anions of all such
substances mixed
to make the aqueous electrolyte solution are to be understood for purposes of
this
description as constituting dissolved phosphate anions therein, irrespective
of the actual
degree of dissociation, complex formation, condensation to make polyphosphoric
acids
or their anions and the like that may occur in the actual electrolyte
solution. At least for
,o economy, orthophosphoric acid itself and/or its water soluble zinc salts
are preferred as
sources over any other substances.
The third necessary component of the aqueous electrolyte solution used in a
process according to this invention as described above is an auxiliary acid.
It is
preferred for this auxiliary acid to have at least a first ionization constant
that is at least,
~s with increasing preference in the order given, 10-5, 10-°, 10-3, 10-
2, or 0.10. Nitric acid
is particularly preferred as the auxiliary acid, but any other sufficiently
strong acid that
does not interfere with the intended operation of a process according to the
invention
may also be used. Quantitative preferences will be given below in terms of
nitric acid,
but amounts of any other strong acid that does not produce a noxious product
of anodi-
2o zation, precipitate any desired constituents of the electrolyte solution,
cause metallic zinc
instead of zinc phosphate to be coated on the cathodized substrate, or in any
other
manner damage or severely frustrate the process as described for nitric acid
and that
results in an electrolyte solution with the same pH value as those of
solutions containing
preferred amounts of other constituents along with the preferred amounts of
nitric acid
2s specified below can also be used in a process according to the invention.
The aqueous electrolyte solution used in a process according to the invention
preferably contains, independently for each constituent stated and
independently for the
lower and upper limits of preferred concentrations stated:
- 20 to 50 grams of zinc ions per liter of electrolyte solution, this
concentration unit
so of grams of a constituent per liter of any composition being hereinafter
usually
abbreviated as "g/I";
- 20 to 70 g/I of phosphate ions; and
- 30 to 80 g/I of nitric acid.
If the zinc ions content is less than 20 g/I, the phosphate ions content is
less than 20 g/I,
ss or the nitric acid content is less than 30 g/I, it will often take an
undesirably long time to
form a chemical conversion film of the desired thickness, so that productivity
of the
7
CA 02343779 2001-03-12
WO 00/15879 PCT/US99/21117
process will be suboptimal. If the amount of nitric acid is less than 30 g/I,
good coverage
of the surface with a phosphate film can not normally be achieved because
metallic zinc
will co-deposit preferentially, so that good lubricity will not be obtained.
However, it is
sufficient for the zinc ions content to be no more than 50 g/I, the phosphate
ions content
s to be no more than 70 g/I, and the nitric acid content to be no more than 80
g/I. No
particular benefit in productivity will normally be obtained by raising these
concentrations
any higher and more of the ingredients of the phosphate treatment liquid will
be wasted
by dragout, so that the cost of the process will be increased without any
compensating
economic benefit.
~o In the phosphate treatment liquid, it is independently preferable for the
molar ratio
of metal ions to phosphate ions to be from 0.3 to 2, and for the molar ratio
of nitric acid
to phosphate ions to be from 0.1 to 3. If the molar ratio of metal ions to
phosphate ions
is less than 0.3, it will be difficult to produce a phosphate film at an
economically attract-
ive rate. if this ratio exceeds 2, a film will still be readily produced, but
the electrolyte
,s solution will be more costly without any offsetting economic benefit. If
the molar ratio of
nitric acid to phosphate ions is below 0.3, there is a danger that zinc
plating will occur
preferentially, but if this ratio exceeds 3, the crystals in the phosphate
coating formed will
be undesirably coarser.
It is preferable for the electrolyte solution used in operation (I) of a
process
2o according to the invention as described above to contain, in addition to
zinc, at least one
type of divalent ar trivalent metal ions selected from among magnesium,
aluminum,
calcium, manganese, chromium, iron, nickel, and copper. It is especially
preferable for
the metal ions in the phosphate treatment to comprise, or more preferably to
consist
essentially of, zinc and calcium. If these ions comprise zinc and calcium,
then it is
2s preferable for the molar ratio of calcium ions to zinc ions to be between
0.1 and 2. A
cathodic electrolysis treatment conducted in this treatment liquid will yield
a zinc phos-
phate film that contains both Zn3(P04)2 ~ 4H20 and Zn2Ca(P04)2 ~ 2H20. The
higher the
molar ratio of calcium to zinc, the higher will be the content of calcium zinc
phosphate.
Only a zinc phosphate film will be produced if the molar ratio is less than
0.1, but if 2 is
3o exceeded, little or no calcium zinc phosphate will be produced, and instead
a calcium
monohydrogenphosphate dehydrate (CaHP04 ~ 2H20) coating will be produced.
The phosphate treatment is conducted using the metal substrate as the cathode.
The type of electrolysis may be either direct current, sine wave, or square
wave, and it
is also possible to use a method in which a direct current waveform is used as
a bias,
ss and a sine wave or square wave is superposed over this. The electrolysis
may be con-
trolled by means of the current or the voltage. Counter-electrodes that can be
used for
8
CA 02343779 2001-03-12
WO 00/15879 PCT/US99/21I 17
the electrolysis treatment include electrodes made of carbon, stainless steel,
platinum,
titanium alloy, and titanium-platinum-covered alloy.
With the present invention, because the phosphate film is formed while the sub-
strate metal is kept cathodic, metallic components of the substrate are not
eluted into the
treatment liquid. Therefore, there is normally no sludge production
whatsoever, nor is
there necessarily any decrease in the performance of the treatment liquid, and
no need
whatsoever to discard and replace the treatment liquid, provided that the
constituents of
the electrolyte solution that are incorporated into the phosphate coating
formed are
replenished in the electrolyte solution. (The metal ions incorporated into the
phosphate
,o coating formed can be replenished continuously if the same type of metal as
that of the
metal ions contained in the treatment liquid is used for the anode, but in
this case the
liquid must be managed so that the amount of metal ions is kept constant in
the treat-
ment liquid. The metal ions, alternatively, and the phosphate ions
incorporated into the
phosphate coating formed can be replenished by addition of one or more
replenishers
15 that contain them. Any adverse change in the electrolyte solution that
occurs as a result
of anodic reactions at the counter-electrode can also be corrected by suitable
replenish-
ment.)
Also, in a process according to the invention, the temperature of the
treatment
liquid can be much lower than in the past, and treatment at normal ambient
human com
zo fort temperature is possible, so that there is a significant savings in the
thermal energy
entailed by the treatment. Further, because a phosphate film can be formed
regardless
of the type of metal substrate with the present invention, high cold working
forces can be
used, even on substrates with which this was difficult with conventional
methods. For
instance, copper or stainless steel can be subjected to a phosphoric acid
treatment and
2s then to a reaction type soap treatment.
In addition, because the amount of phosphate film can be set as desired, it is
possible to obtain a lubricative film in the required amount that is suited to
the cold
working subsequently performed. The film amount can be controlled by means of
the
treatment liquid concentration, the treatment liquid temperature, the current
density, and
the treatment duration.
The higher the treatment liquid concentration, the greater is the possible
phos-
phate film amount, but a concentration that is too high will be economically
disadvan-
tageous because more of the phosphate treatment liquid will cling to the
treated material
and be taken out.
as Also, the higher the treatment liquid temperature, the greater the
phosphate film
amount tends to be, but a range of room temperature to 80 °C is
preferred. A phosphate
9
CA 02343779 2001-03-12
WO 00/15879 PCT/US99/21117
film will be produced even at temperatures over 80 °C, but this is
undesirable because
of the higher cost of the energy needed for heating and because of higher
water evapor-
ation costs. The higher the current density, the greater is the amount of
adhered film
possibly obtained in a given treatment time, and a current density of at least
20 amps per
s square decimeter of surface treated, this unit of current density being
hereinafter usually
abbreviated as "A/dm2", is preferred. A phosphate film can be formed even at
less than
20 A/dm2, but it will take a long time to form a chemical conversion film of 6
to 20 g/m2,
so that productivity will be low. 100 A/dm2 or less is adequate, however, and
no particu-
lar benefit will be accrued by raising the current density any higher, while
energy costs
,o will be increased. At any given current density, the longer the treatment
duration, the
larger the possible amount of phosphate film.
Normally, the most preferred method for controlling the amount of phosphate
film
is by controlling the current density and time of electrolysis. Controlling
the concentra-
tion, temperature, and treatment duration is possible with conventional
chemical conver-
~s sion treatment methods, but it is difficult to set these according to the
treated material on
an actual production line. The lubricative film formation method of the
present invention,
however, allows the specified phosphate film amount to be achieved merely by
varying
the setting of the current density in the cathodic electrolysis treatment, and
the preferred
amount of phosphate coating can be obtained within a few seconds of
electrolysis at the
2o preferred values of current density specified above.
After the phosphate treatment, the treated material preferably is rinsed with
water
to remove any phosphate treatment liquid that may be adhering. With the
present
invention, a phosphate film is formed, and then a lubricative film is formed.
(This makes
it possible to form a good lubricative film even on metal substrates with
which this was
zs impossible with conventional chemical conversion treatment methods
involving no
electrolysis. Specifically, it is possible to form a reaction type soap film
after phosphate
treatment on the surface of titanium or stainless steel, on which the
production of a
phosphate film used to be impossible, and this allows a large amount of
deformation to
be obtained in a single pass.) The lubrication treatment is formed by applying
either a
so water- or oil-based lubricant-containing liquid to the outer surface of the
phosphate film.
The lubrication liquid is normally prepared in a treatment tank, and either
the phosphate
coated substrate is dipped in this tank, or the lubricant is sprayed onto the
treated materi-
al, which forms a lubricative film. However, there are no particular
restrictions on the
contact method.
35 It is preferable for any water-based lubricant used to contain either an
alkali metal
salt of a fatty acid, a metallic soap, or a solid lubricant.
CA 02343779 2001-03-12
WO 00/15879 PCT/US99/21117
A sodium, potassium, lithium, or other such salt of a saturated or unsaturated
fatty acid can be used as the alkali metal salt of a fatty acid. An
unsaturated fatty acid
dimeric acid, trimeric acid, or the like having at least one double bond can
also be used.
The alkali metal salt of a fatty acid is made into a water-based treatment
liquid with a
content of 1 to 20 percent by weight (hereinafter usually abbreviated as
"wt°/p').
Any metallic soap and solid lubricant desired can be used after being
dispersed
in water using a surfactant, and the specific treatment method for bringing
about contact
is the same as that used for the alkali metal salt of a fatty acid. A metal
salt of a higher
fatty acid can be used as an aqueous metallic soap. Examples of higher fatty
acids
,o include lauric acid, myristic acid, palmitic acid, stearic acid, and
behenic acid, while
examples of metals include calcium, aluminum, magnesium, barium, zinc, and
lead, etc.
Of these, calcium stearate can be used to best advantage. The solid lubricant
can be
molybdenum disulfide, graphite, tungsten disulfide, fluorinated graphite,
boron nitride,
talc, mica, or PTFE (polytetrafluoroethylene). Since the alkali metal salt of
a fatty acid,
,s the metallic soap, and the solid lubricant are all water-based, a mixture
of these can also
be used.
When a water-based lubricant is used in a process according to the invention,
the liquid lubricant preferably is brought into contact at a treatment
temperature of 60 to
90 °C with a metal substrate that has undergone prior phosphate
treatment, and,
zo independently, any cold working preferably is performed only after the
water in the water-
based lubricant has been evaporated by a suitable drying apparatus, leaving
the other
constituents of the water-based lubricant to constitute a lubricative film.
It is preferable for any oil-based lubricant used according to the invention
to
comprise, or more preferably to consist essentially of, at least one type of
component
zs selected from among mineral oils, animal and vegetable oils, and synthetic
ester oils.
Machine oil, turbine oil, or spindle oil can be used as a mineral oil, while
palm oil,
rapeseed oil, coconut oil, castor oil, lard, beef ta8ow, fish oil, and the
like can be used
as animal and vegetable oils. A fatty acid ester of a polyhydric alcohol with
a neopentyl-
polyol ester structure can be used, for example, as a synthetic ester oil. A
chlorine-,
0o sulfur-, or phosphorus-based extreme-pressure additive may be added to
these oil-based
lubricants.
The lubricative film formation method of the present invention can be applied
to
a batch process in which the treated material is successively treated in the
order of the
separate process operations, or a continuous process, such as an in-line
process in
35 which a wire is drawn out and continuously treated. Batch processes include
barrel
treatment processes, which are generally performed for the treatment of forged
parts.
11
CA 02343779 2001-03-12
WO 00/15879 PCf/US99/2I I 17
The underlying metal substrate on which a lubricative film is formed by the
method of the present invention may be subjected directly as it is to cold
working, but it
may also be cold worked after undergoing cold drawing at a cross sectional
reduction
of 15 % or less.
s EXAMPLES AND COMPARISON EXAMPLES
METAL SUBSTRATES USED
Substrates of carbon steel (Type S45C), austenitic stainless steel (Type SUS
304), and aluminum (Type A6061 ), each with a diameter of 30 millimeters
(hereinafter
usually abbreviated as "mm"), were cut into pieces having a diameter of 30 mm
and a
,o height of one of each 2 mm increment from 18 to 40 mm. These were subjected
to an
electrolysis treatment and lubrication treatment by the procedures set forth
below, after
which performance tests were conducted.
PROCESS OPERATIONS - VARIATION 1:
(1 ) Degreasing: This consisted of a 10-minute dipping treatment at 60
°C in a 2
solution of FINECLEANER~ 4360, an alkali-based degreaser concentrate made by
Nikon Parkerizing.
(2) Water rinsing: The material was immersed in room-temperature tap water,
then
sprayed clean.
(3) Acid pickling: The material was immersed for 10 minutes in 10 %
hydrochloric
2o acid solution in water (for carbon steel), immersed for 10 minutes in 7 %
nitric acid and
3 % hydrofluoric acid solution in water (for stainless steel), or immersed for
30 seconds
in 10 % nitric acid solution in water (for aluminum).
(4) Water rinsing: The material was immersed in room-temperature tap water,
then
sprayed clean.
zs (5} Surface preparation: The surface was immersed for 1 minute at room
temperature in a 3 % solution of PREPALENE~ Z, a colloidal titanium-based
surface
preparation agent concentrate made by Nikon Parkerizing, or in a 0.3 %
solution of PL-
XT"", a metal phosphate-based surface preparation agent concentrate made by
Nikon
Parkerizing. (The particular treatment used is specified in one or more tables
below.)
30 (6) Electrolysis treatment: A treatment was conducted with the treatment
liquid
compositions and under the electrolysis conditions given in the tables below.
(7) Water rinsing: The material was immersed in room-temperature tap water,
then
sprayed clean.
(8) Lubrication treatment: A lubrication treatment was conducted as described
in the
3s tables below. PALUBE~ 234 and 235 (reaction type soap lubricants}, PALUBE~
4612
(a non-reaction type soap), and PALUBE~ 4649C (a molybdenum disulfide-based
lubri
12
CA 02343779 2001-03-12
WO 00/15879 PCT/US99/21117
cant), all made by Nihon Parkerizing, were used. A commercial palm oil product
was
used when that lubricant is shown in the tables.
PROCESS OPERAT10NS - VARIATION 2
(1 } Descaling: This consisted of 30 seconds of shot blasting.
s (2) Water rinsing: The substrate was immersed in room-temperature tap water,
then
sprayed clean.
(3) Film treatment: A treatment was conducted with the treatment liquid
composition
and under the conditions given in later tables. In the comparative examples,
PALBONDO 181 X (a zinc phosphate-based chemical conversion treatment agent)
and
,o FERRBOND~ A (an oxalate-based chemical conversion treatment agent), both
made
by Nihon Parkerizing, were used.
(4) Water rinsing: The material was immersed in room-temperature tap water,
then
sprayed clean.
(5) Lubrication treatment: A lubrication treatment was conducted as shown in
tables
,s below. PALUBE~ 234 (a reaction type soap lubricant), PALUBE~ 4612 (a non-
reaction
type soap), and PALUBE~ 4649C (a molybdenum disulfide-based lubricant), all
made
by Nihon Parkerizing, were used.
PERFORMANCE TESTS
(1 ) Measurement of the Amount of Lubricative Film Formation
2o W 1 = Film mass in g/m2 for the lubricated material.
W2 ---- Film mass in g/m2 after the lubricated material was immersed for 30
minutes in 90
to 95 °C distilled water, then dried in an oven, after which it was
immersed for 30
minutes in a mixed solvent (isopropyl alcohol, n-butane, and ethyl
CellosolveT"~,
mixed in a volumetric ratio of 6:3:1, respectively) that had been heated to 75
°C,
zs then cooled to normal temperature.
W3 = Film mass in g/m2 after the material treated as defined for W2 was
immersed for
15 minutes in an 80 °C, 5 % solution in water of Cr03, then rinsed with
water,
dried, and cooled.
The film amount and the lubrication amount were calculated from these
so measured values using the following equations:
Film amount = (W2-W3)
Lubrication amount = (W 1-W2),
except that when the lubrication was performed with palm oil, the lubrication
amount was
calculated from the increase in weight before and after the oil was applied.
ss (2) Lubrication Performance
The lubrication performance was checked by means of a backward punching test
13
CA 02343779 2001-03-12
WO 00/158'79 PCT/US99/21117
as illustrated in the drawing figures. In the backward punch test procedure,
the dies 2
in Figure 1 were set to bind the circumference of the cylindrical test
specimens 1 as
illustrated in Figure 1, and the specimen was then subjected to a downward
stroke from
a punch 3 also shown in Figure 1. The punch had a diameter designed to give a
50
s cross section reduction of the test specimens 1 and to produce a cup-like
molding as
shown in Figures 3a through 3b. The lower dead point of the press was adjusted
to give
a 10 mm residual margin at the bottom of the test specimen. In this test,
different test
specimens with a diameter of 30 mm and a height of 18 to 40 mm in 2 mm
increments
was were placed in the die 2, starting with the shortest test specimen. Each
test
specimen tested was punched from above with a punch corresponding to a cross
sectional reduction of 50 %, which formed a cup-shaped piece. The punch left
10 mm
at the bottom of the test piece, and the conditions were such that the taller
the test piece,
the greater was the working. The inner surface of the cup was observed after
this work-
ing, and the test was concluded at the point when scratches were noted. The
maximum
depth of the hole at which no scratches occurred was termed the good punching
depth.
(3) Check for Sludge Generation
After treatment, the material was visually checked to see whether any sludge
had
been generated.
DETAILS OF SPECIFIC EXAMPLES AND COMPARISON EXAMPLES
2o Table 1 shows the concentrations of important constituents in electrolyte
solutions from which a phosphate conversion coating was deposited in at least
one
comparison example or example according to the invention.
Table 1
IdentifierConcentration
for Electro-in Grams
l per
i Liter
in the
Electrolyte
of:
yte
n Zn+Z Ca+z Al+3 Mg+a P~4 3 N~3
Later
Tables
ES 1 22 None None None 28 31
ES2 33 None None None 40 46
ES3 45 None None None 54 62
ES4 22 6 None None 28 50
ESS 33 None 1 None 40 51
ES6 33 None None 1 40 51
ES7 0.15 None None None 0.23 0.31
ES8 45 None None None 56 62
ES9 21 25 None None 66 72
14
CA 02343779 2001-03-12
WO 00/15879 PCT/US99/21117
Solutions of lubricants, primarily commercial products identified by trade
marks,
and of some surface treatment compositions used in comparison examples and
their
short identifiers used in later tables are listed in Table 2.
Further details of the specific examples and comparison examples and of the
,o evaluation results of them are given in Table 3. The following conditions
apply to all
entries in Table 3 unless otherwise noted to the contrary in the notes
thereto:
- For examples according to the invention:
-- A phosphate coating was deposited by simple direct current cathodic
electrolysis at 80 °C; and
,s -- A conventional colloidal titanium surface conditioning pretreatment was
used on the substrates after they were cleaned and before beginning the
electrolysis that deposited the phosphate coating.
Table 2
Description Identifier
Solution of 70 g/1 in water of PALUBE~ 235 ConcentrateL1
Solution of 200 g/1 in water of PALUBE~ 4612 L2
Concentrate
Palm oil L3
Solution of 700 g/1 in water of PALUBE 4649C L4
Concentrate
Solution of 100 g/1 in water of PALUBE~ 234 L5
Concentrate
Solution of 100 g/1 in water of PALUBE~ 4612 L6
Concentrate
Solution of 850 g/1 in water of PALUBE 4649C L7
Concentrate
Solution of 300 g/1 in water of PALUBE~ 4612 L8
Concentrate
Solution of 90 g/1 in water of PALBOND~ 181X P1
Concentrate
Solution in water of 35 g/1 of FERRBOND~ A # P2
1 and 17 g/1 of
FERRBOND~ A #2 Concentrates
Solution in water of 30 g/1 of ALBOND~ A ConcentrateP3
Solution in water of 400 g/1 of PALBOND~ 187A P4
Concentrate
- For comparison examples:
-- When there was no electrolysis (as indicated by the word "none" in the
current density column of Table 3}, the chemical phosphating was per-
formed at 80 °C; and
CA 02343779 2001-03-12
WO 00/15879 PCT/US99/21117
-- No surface conditioning pretreatment was used between cleaning the
substrates and forming the phosphate coating on them.
Also, the following abbreviations are used in Table 3:
- "E" preceding an integer means "Example " according to the invention;
,o - "CE" preceding an integer means "Comparison Example '; and
- In the column headed "Time", "min" means "minutes" and "sec" means
"seconds".
The results in Table 3 indicate that only the examples according to the
invention
were effective in accomplishing all of the objects of the invention. In
Comparison Ex-
,5 amples 1 through 7, 9, and 11 - 14, substantial amounts of sludge were
formed during
the phosphating operation. In Comparison Examples 7, 8, 10, 15, and 16, poor
to very
poor punching depth was obtainable with the lubricated film formed.
BENEFIT OF THE INVENTION
With the present invention, it is possible to form a thick chemical conversion
film
20 of a phosphate without generating sludge. A thick chemical conversion film
can also be
formed at a high level of productivity. Furthermore, a thick chemical
conversion film of
Table 3
Ex- Process Evaluation
Conditions Results
amp-
le
or
Com-Sub- Phos-Phosphating Lubrication Coating Good
Sludge
pari-strate phat-Conditions Conditions Weights, Punch-Forme
g/mz,
son Identi-ing for: ing d?
_
N
'
b fi Li
r
er - z Depth,
quid~dm Time Lu o MinutesPhos-Lubri-M;lli-
C
Iden bri- Expos- phatecant meters
tifier cant ure Coatin
g
E1 S45C ES1 20 10 L1 80 5 11.6 5.3 48 No
sec
E2 S45C ES2 25 5 L1 80 5 10.5 4.9 48 No
sec
E3 S45C ES3 35 3 L1 80 5 9.9 5.1 48 No
sec
E4 S45C ES 20 10 L2 80 5 13.4 2.3 44 No
1 sec
ES S45C ES2 25 5 L2 60 5 12.1 2.2 44 No
sec
E6 S45C ES3 35 3 L2 60 5 12.3 2.6 44 No
sec
E7 S45C ES 20 10 L2 60 0.5 13.8 5.7 44 No
1 sec
E8 S45C ES2 25 5 L3 40 0.5 12.9 5.4 44 No
sec
E9 S45C ES3 35 3 L3 40 0.5 13.6 5.8 44 No
sec
E10 S45C ES1 20 20 L3 80 5 7.4 5.4 44 No
sec
E11 S45C ES4 20 10 L1 80 5 7.7 4.2 52 No
sec
This table is contihued on the next page. ...
16
CA 02343779 2001-03-12
WO 00/15879 PCT/US99/21117
Ex- Process Evaluation
amp- Conditions Results
le
or
Com- Sub- Phos-Phosphating Lubrication Coating Good Sludge
pari-stratephat-Conditions Conditions Weights, Punch-Forme
son Identi-ing g/mz, in d?
Num- h Li for:
er - Depth,
ber quidA~dm2 TimeLu C MinutesPhos- Lubri-Milli-
Iden bri- Expos- phate cant meters
tifier cant ure Coatin
g
E12 A6061 ES2 25 5 L1 80 5 8.3 5.6 48 No
sec
EI3 A6061 ES5 25 5 L1 60 5 9.6 5.2 52 No
sec
E14 SUS304ES6 25 5 L2 30 5 8.3 2.4 48 No
sec
E15 SUS304ES2 25 5 L4 80 3 9.7 I7.4 36 No
sec
E16 SUS304ES2 25 5 Ll 80 5 8.6 6.8 32 No
sec
EI7 SUS304ES3 80 3 L4 80 3 10.2 18.0 36 No
sec
E18 S45C ES8 35 5 L5 80 10 14.3 3.8 48 No
sec
E19 S45C ES8 85 2 LS 80 10 10.5 2.1 48 No
sec
E20 S45C ES8 35 5 L6 60 3 16.9 3.6 44 No
sec
E21 S45C ES8 85 2 L6 60 3 11.3 3.7 44 No
sec
E22 S45C ES8 35 5 LS 80 10 9.2 3.0 44 No
sec
E23 S45C ES8 35 5 L5 80 10 8.4 3.2 52 No
sec
E24 SUS304ES8 35 5 L7 80 10 10.8 9.8 36 No
sec
E25 SUS304ES9 35 5 L7 80 10 9.8 10.1 36 No
sec
E26 SUS304ES8 35 5 L7 80 IO 12.3 10.4 36 No
sec
CE S45C P None 10 L 80 5 5.3 5.5 44 Yes
1 1 min 1
CE2 S45C P1 None 10 L2 30 1 6.2 3.5 40 Yes
min
CE3 S45C P1 None 10 L3 40 0.5 6.5 2.7 32 Yes
min
CE4 S45C P1 None 10 L1 80 5 1.3 1.5 32 Yes
min
CE5 S45C ES7 10 30 L1 80 5 4.5 1.6 32 Yes
sec
CE6 S45C ES7 10 45 L1 80 5 5.6 1.9 36 Yes
sec
CE7 SUS304P2 None 10 L4 80 3 11.0 17.2 16 Yes
min
CE8 SUS304P1 None 10 L4 80 3 0.3 10.2 0 No
min
CE9 A6061 P3 None 1 L1 80 3 10.2 4.4 52 Yes
min
CE10 A6061 P1 None IO L1 80 3 0.2 0.1 16 No
min
CEII S45C P4 None 5 L5 80 0.17 5.3 3.5 44 Yes
sec
CE12 S45C P4 None 5 L8 60 0.17 6.2 2.2 40 Yes
sec
CE13 S45C P4 None 5 L5 80 0.17 4.5 2.7 32 Yes
sec
CE14 S45C P4 None 5 L5 80 0.17 3.3 2.5 32 Yes
sec
CE15 SUS304P2 None 5 L7 80 0.17 0.9 2.7 16 Yes
sec
CE16 SUS304P4 None 5 L7 80 0.17 0.2 0.3 0 No
sec
17
CA 02343779 2001-03-12
WO 00/15879 PCT/US99/21117
Exception Notes for Table 3
E10: The electrolysis was pulsed rather than simple direct current.
E22: The electrolysis was at 40 °C instead of 80 °C.
E23: The surface conditioning treatment was the dispersed solid phosphate type
rather than the
conventional titanium type, and the electrolysis was at 40 °C instead
of 80 °C.
E26: The surface conditioning treatment was the dispersed solid phosphate type
rather than the
conventional titanium type.
CE4: The chemical conversion treatment was at 40 °C instead of 80
°C.
CES: Electrolysis of the substrate was anodic rather than cathodic.
CE6: Electrolysis of the substrate was anodic rather than cathodic and was
pulsed rather than simple DC.
CE7: The chemical conversion treatment was at 9S °C instead of 80
°C.
CE9: The chemical conversion treatment was at 90 °C instead of 80
°C.
CE11 through CE14: The chemical conversion treatment was at 8S °C
instead of 80 °C.
CE13: A conventional colloidal titanium surface conditioning treatment was
used on the substrates
between cleaning and phosphating.
CE14: A dispersed solid phosphate particle type surface conditioning treatment
was used on the substrates
between cleaning and phosphating.
CE1S: The chemical conversion treatment was at 9S °C instead of 80
°C.
CE16: The chemical conversion treatment was at 8S °C instead of 80
°C.
a phosphate can be formed even on materials other than carbon steel, namely,
stainless
steel or non-ferrous materials. If the thick chemical conversion film of a
phosphate
formed by the method of the present invention is coated with a conventional
water- or oil-
based lubricant, an excellent lubricative film for cold working can be
obtained.
18
