U.S. patent application number 11/486335 was filed with the patent office on 2007-01-18 for electrolytic phosphating treatment method and warm or hot forging method.
This patent application is currently assigned to DENSO Corporation. Invention is credited to Shigeki Matsuda.
Application Number | 20070012381 11/486335 |
Document ID | / |
Family ID | 37660594 |
Filed Date | 2007-01-18 |
United States Patent
Application |
20070012381 |
Kind Code |
A1 |
Matsuda; Shigeki |
January 18, 2007 |
Electrolytic phosphating treatment method and warm or hot forging
method
Abstract
The invention provides an electrolytic phosphating treatment
method that forms a film by causing a large current to flow at a
voltage as low as possible and can improve efficiency. Namely, the
invention provides an electrolytic phosphating treatment method for
forming a film containing a metal precipitating from a nitrate, and
a phosphate, by executing electrolysis between a metal that is the
same as a metal of a nitrate of a treatment bath as an electrode
and a work by using a D.C. power source, the treatment bath
comprising phosphoric acid, zinc, iron or manganese as a metal
capable of dissociating phosphoric acid and dissolving in
phosphoric acid, and a solution dissolving a nitrate of a metal to
become a film component, wherein anions other than nitrate ions and
metal ions other than the metal ions to become the film component
are present at not greater than 0.5 g/L, the metal ion dissolving
from the nitrate is present at greater than 10 g/L and phosphoric
acid and phosphate ion are present at not greater than 1/2 of the
metal ion dissolving from the nitrate.
Inventors: |
Matsuda; Shigeki;
(Okazaki-city, JP) |
Correspondence
Address: |
HARNESS, DICKEY & PIERCE, P.L.C.
P.O. BOX 828
BLOOMFIELD HILLS
MI
48303
US
|
Assignee: |
DENSO Corporation
Kariya-city
JP
|
Family ID: |
37660594 |
Appl. No.: |
11/486335 |
Filed: |
July 13, 2006 |
Current U.S.
Class: |
148/241 |
Current CPC
Class: |
C25D 11/36 20130101;
B21J 3/00 20130101 |
Class at
Publication: |
148/241 |
International
Class: |
C23C 22/73 20070101
C23C022/73 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 15, 2005 |
JP |
2005-206921 |
Feb 7, 2006 |
JP |
2006-030084 |
Claims
1. An electrolytic phosphating treatment method for forming a film,
containing a metal precipitating from a nitrate and a phosphate by
executing electrolysis of a metal that is the same as a metal of a
nitrate of a treatment bath as an electrode and a work by using a
D.C. power source, the treatment bath comprising phosphoric acid;
zinc, iron or manganese as a metal capable of dissolving in a
phosphoric acid solution and dissociating phosphoric acid; and a
solution dissolving therein a nitrate of a metal to become a film
component, wherein anions other than nitrate ions and metal ions
other than the metal ions to become the film component are present
at not greater than 0.5 g/L, the metal ion dissolving from the
nitrate is present at greater than 10 g/L and phosphoric acid and
phosphate ion are present at not greater than 1/2 of the metal ion
dissolving from the nitrate.
2. An electrolytic phosphating treatment method for forming a film
containing a metal precipitating from a nitrate and a phosphate by
executing electrolysis between a metal that is the same as a metal
of a nitrate of a treatment bath as an electrode and a work by
using a D.C. power source, the treatment bath comprising a
phosphate solution prepared by dissolving zinc in a phosphoric acid
solution; phosphoric acid and phosphate ions; zinc ions as a metal
capable of dissociating, and dissolving in, phosphoric acid; and a
solution dissolving a nitrate of nickel, cobalt, manganese, copper
or zinc; wherein anions other than nitrate ions and phosphate ions
and metal ions other than the metal ions to become the film
component are not greater than 0.5 g/L, respectively, the metal ion
dissolving from the nitrate is greater than 10 g/L and phosphoric
acid and phosphate ion are not greater than 1/2 of the metal.
3. The electrolytic phosphating treatment method according to claim
1, wherein the metal ions dissolved from the nitrate are present at
at least 20 g/L and phosphoric acid and the phosphate ion are
present at 1/2 of the amount of the metal ions dissolved from the
nitrate.
4. The electrolytic phosphating treatment method according to claim
1, wherein an oxidation reduction potential (ORP: hydrogen standard
electrode potential) of the phosphating treatment bath is at least
770 mV.
5. The electrolytic phosphating treatment method according to claim
1, wherein an electrolytic voltage is 6 V or below and an
electrolytic current is at least 2 A/dm.sup.2.
6. The electrolytic phosphating treatment method according to claim
1, wherein an electrolytic voltage is 15 V or below and an
electrolytic current is at least 20 A/dm.sup.2.
7. A lubrication treatment method for warm or hot forging of a
metal, characterized by using a work, the work having a film having
a lubrication function and being formed by the steps of: forming a
formation film formed of a phosphate plus a metal constituted by a
metal having a melting point higher than the temperature applied to
the work during warm or hot forging of a metal and a phosphate on a
surface of the work; and supporting a lubricant on the formation
film.
8. The lubrication treatment method for warm or hot forging,
wherein a phosphating treatment film to be formed on a surface of a
work and constituted by a phosphate plus a metal is a phosphating
treatment film according to claim 1.
9. The lubrication treatment method for warm or hot forging
according to claim 7, wherein the lubricant is an organic compound
containing an organic fatty acid salt or an inorganic high
molecular weight compound having a multi-layered structure.
10. The lubrication treatment method for warm or hot forging
according to claim 9, wherein the lubricant is a stearate, a
graphite, molybdenum sulfide or a mica.
11. A warm or hot forging method comprising the steps of: forming a
phosphate+metal film constituted by a metal having a melting point
not lower than a temperature applied to a work during warm or hot
forging of a metal and a phosphate; supporting a lubricant on the
film to form the work having the film having a lubrication function
in warm or hot forging; and conducting warm or hot forging.
12. The warm or hot forging method according to claim 11, wherein
the phosphate+metal film contains a phosphate that does not contain
water of crystallization by differential thermal analysis.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] This invention relates to a treatment bath for forming a
film containing a phosphate and a metal on a metal surface by an
electrolytic treatment, a method for this treatment, and a
lubrication treatment for plastic working in which a work is heated
to a high temperature and to above a temperature for warm or hot
forging.
[0003] 2. Description of the Related Art Japanese Unexamined Patent
Publication (Kokai) No. 2000-234200 (JP-A-2000-234200) is a basic
patent application regarding an electrolytic phosphating treatment
and was filed by a present inventor. The feature of this patent
application resides in that a treatment bath does not substantially
contain metal ions other than film forming components (below 0.4
g/L). The feature of the treatment bath composition is that it
contains 6 to 140 g/L of nitrate ion, 0.5 to 60 g/L of phosphoric
acid and phosphate ion, 0.5 to 70 g/L of those ions which form a
complex with the phosphate ion inside the treatment bath and
dissolve therein (such as zinc ion) and 0 to 40 g/L of metal ions
that precipitate when dissolved ions are reduced and
precipitate.
[0004] In Examples 1, 3 and 4 of the patent JP-A-2000-234200, an
electrolytic voltage is 9.6 V or above when a current of at least 1
A/dm.sup.2 is caused to flow (one work is calculated at 2 dm.sup.2)
and as far as a cathodic treatment is concerned, it is at least
17.7 V.
[0005] Japanese Unexamined Patent Publication (Kokai) No.
2002-322593 (JP-A-2002-322593) is a patent application, also filed
by the present inventors, regarding an electrolytic phosphating
treatment. Whereas JP-A-2000-2343200, described above, has a
feature that reaction impeding substances (that is, metal ions
other than film forming components) are not allowed to be contained
from outside into the phosphating treatment bath, JP-A-2002-322593
relates to a invention in which the formation of the impeding
substance ions (N.sub.2O.sub.4 gas, excessive Fe ion), inside the
reaction system, is controlled.
[0006] The qualitative composition dissolved in the treatment bath
in JP-A-2002-322593 is the same as that of JP-A-2000-234200. The
treatment bath compositions of all Examples restrict the reduced
and precipitating metal ions to a range of 4.7 to 7.3 g/L which is
below 10 g/L. In all Examples, the electrolysis is executed at a
voltage of at least 8 V.
[0007] Japanese Unexamined Patent Publication (Kokai) No.
2004-52085 (JP-A-2004-52085) also relates to a invention regarding
an electrolytic phosphating treatment filed by the present
inventors. In JP-A-2004-52085, washing water, used after the
phosphating treatment, is subjected to electro-dialysis and the
concentrated portion is again returned to the treatment bath, and
findings about the electrolysis of the treatment bath components
are acquired.
[0008] FIG. 3 of JP-A-2004-52085 indicates that the electrolysis in
the electro-dialysis bath containing the electrolytic treatment
bath components is observed in two forms. In other words,
electro-dialysis at an impressed voltage of 6 V or below is ion
migration of only solute components but involves electrolysis of
water as a solvent at a voltage of 6 V or above. The reference
points it out that the electrolysis at 6 V or above may form sludge
with the decomposition of water.
[0009] The illustration shown in FIG. 3 indicates that 10
electrolytic baths are stacked and two electrolytic systems exist
with 0.6 V as the boundary per electrolytic bath.
[0010] Namely, JP-A-2004-52085 indicates that the electrolytic
phosphating treatment is constituted by two electrolytic systems
with respect to a change of the voltage. FIG. 3 demonstrates that a
current (X axis)--voltage (Y axis) relation of a lower electrolytic
voltage system has a smaller gradient than that of a higher
electrolytic voltage system and has higher electrolytic
efficiency.
[0011] The electrolytic treatment at the lower voltage suppresses
the decomposition of water as the solvent and preferentially moves
the solute components, thereby improving film formation
efficiency.
[0012] On the other hand, a working technology called "warm or hot
forging" is known that heats a metal material to 200.degree. C. or
above and subjects it to plastic working. This working technology
has widely been employed for a variety of metal materials such as
iron and steel, aluminum and its alloys, magnesium and its alloys,
and so forth.
[0013] Japanese Unexamined Patent Publication (Kokai) No. 6-1994
(JP-A-6-1994) relates to a lubrication treatment for cold forging
of steel materials. As problems in the prior art technologies, this
reference describes that warm forging is carried out by heating a
work to 400 to 1,000.degree. C. and conducting forging but that a
suitable lubricant and treatment method are not known.
[0014] In cold forging, a method of forming a lubrication film that
forms a phosphating treatment film on a work, immerses the work
into an organic fatty acid salt bath (such as sodium stearate) and
forms a lubrication film has been established as the lubrication
treatment. In other words, a method that subjects the work to a
lubrication treatment using a phosphating treatment film has been
established.
[0015] In contrast, in warm or hot forging according to the prior
art, the method that forms the phosphating treatment film on the
work and forms a film using a lubricant on the former has not been
carried out for the following reasons. Namely, the phosphating
treatment film formed by a non-electrolytic system according to the
prior art cannot secure adhesion to a foundation metal within the
temperature range (about 400 to 1,000.degree. C.) for warm forging.
The lubrication film is destroyed and does not operate as the
lubrication treatment. The role of the lubrication treatment is to
interpose a lubricant between a die and a work and to prevent
direct contact between the mold and the work. However, it is
difficult to secure such a function unless adhesion of the
phosphating treatment film is secured at the temperature of warm
forging.
[0016] Therefore, warm or hot forging according to the prior art
employs the following steps. A work is first heated to about 250 to
300.degree. C. and is immersed immediately thereafter into a liquid
having dispersed therein a solid -lubricant such as graphite, or is
sprayed with a liquid containing graphite powder, to form a
graphite film on the surface of the work. The work is subsequently
heated to about 800.degree. C. and (warm forging) pressing is
successively conducted. In this case, another lubricant is
separately sprayed to the surface of the mold for mold lubrication.
Other methods have also been conducted that do not apply the
lubricant to the work and simply spray the lubricant into the
mold.
[0017] According to the method that applies only the lubricant to
the work, the lubricant merely adheres physically to the work.
Because the lubricant does not adhere to the work with a chemical
reaction, the lubricant is easily removed, at a machining portion,
when the mold and the work undergo strong friction or squeezing at
the working portion during machining. In this case, seizure occurs
at that portion.
[0018] In JP-A-6-1994, the work is immersed in a solution
consisting of water-soluble inorganic salts (K.sub.2SO.sub.4,
Na.sub.2B.sub.4O.sub.4, etc) and molybdenum disulfide and/or
graphite to uniformly apply the lubricant on the surface of the
work, then the work is dried, and a lubrication film consisting of
the inorganic salt, molybdenum disulfide and/or graphite is formed
on the surface of the work. The method of this reference requires
the step of washing the work with hydrofluoric acid and nitric acid
in the production steps of the lubrication film. This pickling is
directed to form a firm film on the surface. The specification
describes that the lubrication film so formed exhibits a
lubrication function for warm forging. However, the film is not
formed by allowing it to react with the surface of the work but
merely causes the solid components in the treatment bath to
physically adhere to the chemically active surface.
[0019] JP-A-2000-234200 filed by the present inventors describes an
invention relating to a phosphating treatment film as a foundation
film to be formed on various kinds of works for forging. However,
the reference discloses only a phosphate+metal film that is applied
to a coating foundation and improves coating corrosion resistance
and a formation example of a phosphating treatment film consisting
only of a phosphate that is applied to cold forging. The reference
does not describe or suggest the application of the phosphate+metal
film to warm or hot forging.
[0020] In other words, the basic element of the electrolytic
phosphating treatment technology described in JP-A-2000-234200 is
that the treatment bath substantially does not contain metal ions
that do not become the film component (below 400 ppm). The
reference describes that the forms of the film include the case
where metals that do not become the phosphate are contained (claim
36, Examples 1, 4 and 5) and the case where metals that do not
become the phosphate are not contained (claim 8, Example 2).
[0021] When the treatment bath contains the metal that does not
become the phosphate, the film is the film constituted as a
phosphate+metal. The metal contained in the film is the metal that
has existed as the cation in the solution is reduced and
precipitated. The reference discloses that when the film
constituted by a phosphate+metal is employed for the coating
foundation treatment, the coating corrosion resistance can be
improved. The reference clearly states that precipitation of the
metal is made as the metal ion dissolved in the solution is reduced
and precipitated. The reference further describes that to reduce
and precipitate the metal, it is necessary for the treatment bath
to not contain metal ions that do not become the film components
(such as sodium ion). This also indicates that the formation of the
film constituted by phosphate+metal is not possible from a
non-electrolytic treatment bath containing those metal ions which
do not operate as the film components. The reference represents
that the difference of such a foundation film invites a difference
of corrosion resistance in the coat.
[0022] JP-A-2000-234200 has an Example (Example 2) used for cold
forging. The reference indicates that the treatment bath
composition, as well as the film composition, are drastically
different between an Example for cold forging and Example for
coating. The reference further represents that the metal components
other than the phosphate are contained for coating foundation but
the metal components other than the phosphate are contained only
slightly for cold forging foundation.
[0023] Table 1 shows the comparison about the treatment method, the
application, the treatment bath composition and the film
composition in the Examples and the Comparative Examples of the
patent reference described above. TABLE-US-00001 TABLE 1 treatment
method, treatment film electrolytic bath composition or non-
composition ratio electrolytic application Ni/H.sub.3PO.sub.4:(g/L)
Ni/P: Wt % remarks Example 1 electrolytic coating 5.5/7.6 = 0.72
1.9-2.1 corrosion foundation resistance: Comparative electrolytic
coating 0.5/7 = 0.07 0.01-0.12 Example 1 > Example 1 foundation
Comparative Example 1 Example 2 electrolytic cold forging 0.25/21.2
= 0.01 0 foundation Comparative non- cold forging -- 0 Example 2
electrolytic foundation Example 4 electrolytic coating 3.8/2.8 =
1.36 0.51-0.75 foundation Example 5 electrolytic coating 3.9/2.8 =
1.39 0.77-0.94 foundation
[0024] The following can be confirmed from the comparison tabulated
above.
[0025] i. The film for cold forging is a film that does not contain
a metal component (Ni) that does not becomes a phosphate.
[0026] ii. Coating corrosion resistance is higher in the film
containing the metal component (Ni) that does not become the
phosphate.
[0027] In other words, the film not containing the metal component
that does not become the phosphate is suitable for the lubrication
treatment for cold forging (at a low temperature) but a film
containing the metal component is suitable for the coating
corrosion resistance. This difference corresponds to the fact that
the function of the phosphating treatment film is different between
the coating foundation and lubrication for cold forging.
[0028] Next, the reason why the phosphating treatment film not
containing Ni of the prior art has been used for the lubrication
treatment for cold forging will be clarified. The lubrication
function for cold forging is exhibited when a lubrication film
(foundation film: phosphate+lubricant (sodium stearate, etc))
covering the surface of the work is melted and starts fluidizing to
thereby prevent direct contact between the work and a mold in cold
forging where the mold and the work for forging (steel) come into
mutual contact within a temperature range (150 to 250.degree. C.)
for cold forging and the work undergoes plastic change. Therefore,
performance items required for the foundation film are a. a
chemical property capable of uniformly retaining the lubricant,
that is, to secure chemical affinity with the lubricant: and b. the
film starts fluidizing in such a fashion as to correspond to the
change of the work within the temperature range (150 to 250.degree.
C.) of cold forging. The requirement (a) described above can be
secured by the phosphate treatment film "not containing metals
reduced and precipitating" of the prior art. The requirement (b)
can be secured by the phosphate film that does not contain Ni.
[0029] In the film formed by the non-electrolytic treatment system,
the treatment bath is limited so as to secure the performances (a)
and (b). In other words, the "reduced and precipitating metal"
(generally, Ni) is limited to 0.5 g/L or below. The phosphating
treatment film for cold forging formed by the non-electrolytic
system of the prior art is the film that does not basically contain
Ni or the film that does not allow the activity of Ni, and
satisfies the performances (a) and (b) described above inside the
cold forging temperature range. In the non-electrolytic system, it
is basically impossible to precipitate the "reduced and
precipitating metal". In the non-electrolytic treatment system,
therefore, a thick film containing Ni and suitable for forging
(having a deposition amount of at least 5 g/m.sup.2, for example)
cannot be formed because the electrolytic reaction voltage is lower
than the decomposition voltage of water.
[0030] On the other hand, the film formed by the electrolytic
treatment method can precipitate the "reduced and precipitating
metal". That is, the film can contain, or does not contain, the
metal Ni having a high melting point (melting point: 1,453.degree.
C.) in the form of a chemical reaction in the work. However, when a
large amount of the "reduced and precipitating metal" such as Ni is
contained, the phosphate treatment film does not satisfy the
performances (a) and (b) required for cold forging of the steel.
Therefore, such a film is not applied to cold forging.
[0031] In Examples tabulated in Table 1, those examples in which
the coating corrosion resistance is improved (Examples 1, 4 and 5)
are all contain a large amount of the metal Ni. This represents
that the coating foundation film is preferably the one that
contains a large mount of the metal Ni precipitating with the
change of the charge and is strongly bonded to the foundation
support metal.
[0032] The phenomenon associated with the coating corrosion
resistance and its evaluation is conducted under normal atmospheric
pressure and ambient temperature conditions. Cracking and
degradation of the coat, to which the foundation film contributes,
is less when the phosphating treatment film is not bonded
chemically strongly to the metal blank. The bonding strength
between the metal blank and the phosphating treatment film becomes
greater in association with the magnitude of activation energy
related with the film formation reaction. Precipitation of the
"reduced and precipitating metal" involves a change in the charge.
In contrast, "precipitation of the phosphate crystal" is formed by
the reaction that does not involve the change of the charge of the
metal ions. Activation energy of both reaction systems is different
and the precipitation reaction of the "reduced and precipitating
metal" is greater. This corresponds to the fact that the film
containing a greater amount of Ni as the "reduced and precipitating
metal" is strongly bonded to the foundation metal in the formation
of the phosphating treatment film. The result tabulated in Table 1
evidences this fact.
[0033] In the lubrication treatment associated with cold forging,
high adhesion between the phosphating treatment film and the
foundation metal is not advantageous. In the lubrication treatment,
the surface must involve fluidity with the plastic change of the
blank metal. The lubrication property is the operation that
prevents the metal (press mold) and the metal (blank) from coming
into direct contact with each other. The film firmly bonded to the
foundation metal is likely to undergo a plastic change while
integrated with the foundation metal blank. Consequently, fluidity
is lost and the lubrication property drops.
[0034] The concept of the lubrication treatment in cold forging can
be applied to warm forging, too. In other words, the phosphating
treatment film requiring the lubrication performance and used for
warm forging preferably has fluidity without being integrated with
the metal blank in its plastic working temperature and pressure
range. That is to say, adhesion with the foundation metal
preferably drops in the temperature and pressure range of warm
forging.
[0035] In the temperature range (150 to 250.degree. C.) of cold
forging, therefore, the film not containing and, basically, the
"reduced and precipitating metal" is suitable. As to the retention
of the lubrication performance in warm forging for plastic working
after the work is heated, however, the film containing the "reduced
and precipitating metal" can be employed.
[0036] As explained above, the phosphating treatment film
containing the precipitating metal and formed by the electrolytic
phosphating treatment does not have lubrication performance in the
temperature range of cold forging (150 to 250.degree. C.).
JP-A-2000-234200 illustrates the film to be applied to cold forging
but does not teach or suggest the possibility of the application to
warm or hot forging.
SUMMARY OF THE INVENTION
[0037] It is a main object of the present invention to level up the
electrolytic phosphating treatment technology.
[0038] That is,
[0039] (i) To clarify an efficient control method of the
electrolytic treatment technology and to improve reaction
efficiency; and
[0040] (ii) To make the electrolytic phosphating treatment
technology more efficient than the prior art technology into
practical application and to expand the application range.
[0041] In other words, the object of the invention is to apply the
technology to warm or hot forging lubrication treatment.
[0042] The first object, i.e. "to clarify an efficient control
method of the electrolytic treatment technology and to improve
reaction efficiency", will be explained.
[0043] The inventor of the present invention classifies the
phosphating treatment bath into a "treatment bath for forming a
film mainly formed of a phosphate" and a "treatment bath for
forming a film of a metal+a phosphate". This concept has already
been explained by the present inventor in the first patent document
described above.
[0044] The "treatment bath for forming a film mainly formed of a
phosphate" is composed of phosphoric acid and a solution that
contains "zinc, iron or manganese as a metal dissolved in a
phosphoric acid solution and capable of dissociating and dissolving
phosphoric acid" as main components and also contains a "nitrate of
a metal which is to become a film component".
[0045] The "treatment bath for forming a film of a metal+a
phosphate" is a treatment bath constituted by "phosphoric acid",
"zinc as a metal dissolved in a phosphoric acid solution and
capable of dissociating and dissolving phosphoric acid" and a
solution dissolving "a nitrate of a metal that is to become a film
component".
[0046] The former treatment bath is an ordinary treatment bath in
the non-electrolytic treatment according to the prior art. The
present invention is directed to the latter.
[0047] The object, i.e. "to clarify an efficient control method of
the electrolytic treatment technology and to improve reaction
efficiency", is to form a film by causing a large current to flow
at a voltage as low as possible. That is, it means the formation of
the film with small electric energy.
[0048] The object "to expand the application range, that is, to
apply the treatment to the lubrication treatment for warm forging",
means the application of the present technology to the lubrication
treatment for warm or hot forging that has scored no actual record
in the past.
[0049] Another object of the invention is to level up the
lubrication treatment in forging in which a work is heated from
room temperature to 200.degree. C. or more. More specifically, a
lubrication treatment film capable of withstanding heating to
200.degree. C. or above (that is, the lubrication film does not
peel off from the work even when the temperature reaches a
predetermined heating temperature) is formed on the surface of the
work and the lubrication treatment is carried out. Such a
lubrication treatment is carried out by "a foundation film having
adhesion with a foundation metal material and capable of retaining
a lubricant" and "a layer (film) of a lubricant exhibiting a
lubrication function to a mold and to the work at a heated
temperature".
[0050] A concrete method of such a lubrication treatment varies
depending on an individual metal material. For, physical and
chemical properties are different depending on the individual
material. However, the concept of the lubrication treatment
described above (formation of the lubrication film constituted by
the heat resistant foundation film and the lubrication layer) is
common irrespective of the difference of the materials.
[0051] Lubricants have been used in the past for warm forging.
Under such circumstances, the problem that the present invention is
to solve is the formation of a foundation film having a heat
resistance to various works to be forged.
[0052] Warm forging has been most widely applied to steel
materials. In the case of the application to steel, the object of
the invention is to provide an excellent lubrication treatment in a
warm forging temperature range of 400.degree. C. or above. This
object can be achieved by uniformly forming a phosphating treatment
film consisting of "phosphate+metal" on the surface of a work that
is to be heated to 400.degree. C. or above and further forming a
lubrication film formed of a lubricant having excellent lubrication
performance at 400.degree. C. or above on the phosphating treatment
film.
[0053] As described above, the problem that the invention is to
solve is to form the strong heat resistant film (treatment film)
bonding chemically strongly to the surface of the work and the
lubrication treatment film supporting thereon the lubricant and to
apply this film to the lubrication treatment for warm forging.
[0054] The object "to improve electrolytic reaction efficiency" is
to cause a large current to flow at a low voltage by decreasing an
electric resistance of an electrolytic treatment reaction
system.
[0055] The flows of current and ions in the electrolytic treatment
will be explained with reference to FIG. 1. It will be assumed
hereby that the electric resistance does not exist in between a
D.C. power source; and an electrode or a work.
[0056] The resistance occurs at the following three points in the
electrolytic treatment system described above. (i) conversion on
electrode surface (electrode and treatment bath): conversion of
current.fwdarw.ion migration, (ii) stability of a solution state
inside treatment bath and ion migration, and (iii) conversion on
work surface: conversion from solution (ion).fwdarw.solid (film) :
film formation.
[0057] These three points will be explained.
[0058] (i) Conversion on electrode surface: conversion of
current.fwdarw.ion migration
[0059] It is necessary that the current easily moves to the
dissolved ion from the electrode. The ion that is mainly to be
moved is preferably a film forming component. The film that the
invention is to form is a "phosphate film containing a metal".
Therefore, it is preferred that the electrode material is the same
as the main component of the treatment bath that precipitates from
the treatment bath and becomes a film. In other words, a metal that
becomes the film component is preferably used as the electrode. As
the metal that becomes the film component is a nitrate and is
contained in the treatment bath, the electrode material is a metal
composed of the nitrate contained in the treatment bath.
[0060] Incidentally, in the electrolytic phosphating treatment, all
the currents associated with the electrode are not always consumed
for dissolution. This is different from electro-plating. In the
electrolytic phosphating treatment, the same metal component as the
electrode material is separately supplied in the dissolved form
(metal ion) into the treatment bath. Therefore, the current
impressed is divided into a portion of "dissolution of electrode
material" and a "portion directly associated with migration of
treatment bath component and executing reaction of component
ion".
[0061] The technical meaning of "improvement of electrolytic
reaction efficiency" is to increase the proportion of the portion
that "directly participates in the movement of the treatment bath
components and executes the reaction of the component ion", and
controls the reaction. The use of the same metal as the metal
nitrate to be added to the treatment bath for the electrode
material is effective for the operation described above.
[0062] In electric plating, however, the case where such metal ions
are supplied as the chemical does not exist. Therefore, the
impressed current is fully consumed for dissolving the electrode
material.
[0063] (ii) Stability of a solution state inside treatment bath and
ion migration
[0064] The main anion components of the treatment bath of the
present invention are only the phosphate ion and the nitrate ion.
The relation of solubility between the phosphate ion and the
nitrate ion is nitrate ion>phosphate ion. Therefore, a solution
containing a greater amount of the nitrate ion is more advantageous
from the aspect of solubility.
[0065] In the present invention, the condition of the treatment
bath of the nitrate ion>phosphate ion is expressed by the
proportion by setting the metal ion from the nitrate to 10 g/L and
limiting phosphoric acid and phosphate ion to not greater than 1/2
of the former. In this way, the concentration of the nitrate ion
and the proportion of the nitrate ion to the phosphate ion are
clarified. The invention further represents that in the treatment
bath, the nitrate ion has a concentration exceeding a certain level
(at least about 20 g/L) and is about 4 times the concentration of
the phosphate ion.
[0066] (iii) Conversion on work surface: conversion from solution
(ion).fwdarw.sold (film) : Film components precipitating in the
film formation are "metal" and "phosphate".
[0067] The "metal" is reduced and precipitated from the condition
under which the nitrate is dissolved. When the amount of the
nitrate component (nitrate ion+metal ion) is small, the dissolved
ion concentration is lower, so that current efficiency drops and
precipitation efficiency drops, as well. Therefore, the treatment
bath must have a predetermined concentration of the nitrate
component. This is also represented in (ii) as described above.
[0068] Precipitation of the phosphate occurs as the phosphoric acid
component (H.sub.3PO.sub.4 or H.sub.2PO.sub.4.sup.-) dissociates
and changes to PO.sub.4.sup.3-, thereby forming phosphate
(Zn.sub.3(PO.sub.4).sub.2, etc) crystals as the film. It is
therefore obvious that the precipitation process (level of
necessary energy, etc) is different depending on whether the
condition of phosphoric acid inside the treatment bath is
H.sub.3PO.sub.4 or H.sub.2PO.sub.4.sup.-. In other words, it is
easier to dissociate from H.sub.2PO.sub.4.sup.- to PO.sub.4.sup.3-
than from H.sub.3PO.sub.4 to PO.sub.4.sup.3-. To improve the
electrolytic reaction efficiency, it is therefore effective to
bring the treatment bath into the condition under which phosphoric
acid contains H.sub.2PO.sub.4.sup.- as much as possible. In other
words, the precipitation efficiency of the phosphate can be
improved by using the treatment bath in which dissociation of
H.sub.3PO.sub.4 .fwdarw.H.sub.2PO.sub.4.sup.- is promoted by
dissolving ZnO (zinc oxide), etc, in H.sub.3PO.sub.4 in the
solution state to dissolve the zinc ion (Zn.sup.2+).
[0069] Other means for improving electrolytic reaction efficiency
will be explained.
[0070] The existence of metal ions dissolved from the nitrate in an
amount of at least 20 g/L is directed to improving the electrolytic
reaction efficiency by increasing the concentration of the
electrolytic component of the treatment bath.
[0071] The oxidation reaction potential (ORP: hydrogen standard
electrode potential) of at least 770 mV in the phosphating
treatment bath represents a control item associated with the
electrochemical reaction of the iron expressed by:
Fe.sup.2+Fe.sup.3++e:0.77 V (1)
[0072] The case where ORP of the treatment bath is at least 770 mV
indicates that the condition of the iron ion inside the treatment
bath is fully in the state of Fe.sup.3+ from the formula (1). This
indicates also that the iron ions inside the treatment bath do not
change. To improve reaction efficiency, it is necessary to control
the condition of the chemical components of the treatment bath.
[0073] The current of at least 2 A/dm.sup.2 at the electrolytic
voltage of 6 V or below represents a feature of the present
invention in comparison with the prior art (JP-A-2000-234200 and
JP-A-2002-322593). The prior art technologies have no actual
records of requiring a current of at least 2 A/dm.sup.2 at 6 V or
below.
[0074] Similarly, a current of at least 20 A/dm.sup.2 at the
electrolytic voltage of 15 V or below represents a feature of the
present invention in comparison with the prior art
(JP-A-2000-234200 and JP-A-2002-322593). The prior art technologies
have no actual records of requiring a current of at least 20
A/dm.sup.2 at 15 V or below.
[0075] A further object of the invention is to apply afresh the
phosphating treatment to warm or hot forging lubrication treatment.
Namely, the invention provides the following as means for achieving
the object.
[0076] (1) An electrolytic phosphating treatment method for forming
a film containing a metal precipitating from a nitrate and a
phosphate by executing electrolysis of a metal, that is the same as
a metal of a nitrate of a treatment bath, as an electrode and a
work by using a D.C. power source, the treatment bath comprising
phosphoric acid; zinc, iron or manganese as a metal capable of
dissolving in a phosphoric acid solution and dissociating
phosphoric acid; and a solution dissolving therein a nitrate of a
metal to become a film component, wherein aninons other than
nitrate ions and metal ions other than the metal ions to become the
film component are present at not greater than 0.5 g/L, the metal
ions dissolved from the nitrate are present at greater than 10 g/L
and the phosphoric acid content and the phosphate ion content are
not greater than 1/2 of the metal ion dissolved from the
nitrate.
[0077] (2) An electrolytic phosphating treatment method for forming
a film containing a metal precipitating from a nitrate and a
phosphate by executing electrolysis between a metal, that is the
same as a metal of a nitrate of a treatment bath as an electrode,
and a work by using a D.C. power source, the treatment bath
comprising a phosphate solution prepared by dissolving zinc in a
phosphoric acid solution; phosphoric acid and phosphate ions; zinc
ions as a metal capable of dissociating, and dissolving in,
phosphoric acid; and a solution containing a nitrate of nickel,
cobalt, manganese, copper or zinc; wherein anions other than
nitrate ions and phosphate ions and metal ions other than the metal
ions to become the film component are not greater than 0.5 g/L,
respectively, the content of metal ions dissolved from the nitrate
is greater than 10 g/L and the phosphoric acid and the phosphate
ion contents are not greater than 1/2 of the metal.
[0078] (3) The electrolytic phosphating treatment method according
to (1) or (2), wherein the metal ion dissolving from the nitrate is
at least 20 g/L and phosphoric acid and the phosphate ion are 1/2
of the metal ion dissolving from the nitrate.
[0079] (4) The electrolytic phosphating treatment method according
to (1) or (2), wherein an oxidation reduction potential (ORP:
hydrogen standard electrode potential) of the phosphating treatment
bath is at least 770 mV.
[0080] (5) The electrolytic phosphating treatment method according
to (1) or (2), wherein an electrolytic voltage is 6 V or below and
an electrolytic current is at least 2 A/dm.sup.2.
[0081] (6) The electrolytic phosphating treatment method according
to (1) or (2), wherein an electrolytic voltage is 15 V or below and
an electrolytic current is at least 20 A/dm.sup.2.
[0082] (7) A lubrication treatment method for warm or hot forging
of a metal, characterized by using a work, the work having a film
having a lubrication function, and being formed by the steps
of:
[0083] forming a film formed of a phosphate plus a metal
constituted by a metal having a melting point higher than the
temperature applied to the work during warm or hot forging of a
metal and a phosphate on a surface of the work; and
[0084] supporting a lubricant on the formation film.
[0085] (8) The lubrication treatment method for warm or hot
forging, wherein a phosphating treatment film to be formed on a
surface of a work and constituted by a phosphate plus a metal is a
phosphating treatment film according to item (1) or (2).
[0086] (9) The lubrication treatment method for warm or hot forging
according to (7) or (8), wherein the lubricant is an organic
compound containing an organic fatty acid salt or an inorganic high
molecular weight compound having a multi-layered structure.
[0087] (10) The lubrication treatment method for warm or hot
forging according to (9), wherein the lubricant is a stearate,
graphite, molybdenum sulfide or mica.
[0088] (11) A warm or hot forging method comprising the steps
of:
[0089] forming a phosphate+metal film constituted by a metal having
a melting point not lower than a temperature applied to a work
during warm or hot forging of a metal and a phosphate;
[0090] supporting a lubricant on the film to form the work having
the film having a lubrication function in warm or hot forging;
and
[0091] conducting warm or hot forging.
[0092] (12) The warm or hot forging method according to (11),
wherein the phosphate+metal film contains a phosphate that does not
contain water of crystallization by differential thermal
analysis.
[0093] The effect of the present invention is, in the first place,
the provision of an efficient method when the metal+phosphate film
is formed by the electrolytic treatment method. In other words, the
method of the invention can cause a greater quantity of current to
flow than the treatment methods of the prior art and can therefore
shorten the treatment time.
[0094] The second effect of the present invention is that when the
"metal+phosphate" formation film is formed by the electrolytic
treatment method, the method of the invention can form the film at
a lower impressed voltage than in the prior art methods. The
phosphating treatment film according to the present invention can
be formed at an impressed voltage of 1.5 to 6 V for which no actual
records have been found. Lowering of the impressed voltage leads to
suppression of the decomposition of the treatment bath.
Consequently, stability of the treatment bath can be drastically
improved; hence, the formation of sludge can be efficiently
suppressed. Lowering of the impressed voltage can reduce the
diameter of the crystal grains of the film to be formed. A smaller
crystal grain will contribute to the improvement of the corrosion
resistance when used for coating foundation.
[0095] The third effect is to expand the application to a new field
by making the most of the features of the metal+phosphate treatment
film. The phosphating treatment film formed by the present
invention has heat resistance. Therefore, the phosphating treatment
film can be applied to the field of the lubrication treatment for
warm or hot forging to which films, obtained from the
non-electrolytic treatment of the prior art, have not been applied
in the past.
[0096] This new lubrication treatment uses the phosphating
treatment film which chemically reacts with the surface of the work
in the same way as in the lubrication treatment for cold forging,
and covers the surface with a lubricant to form the film.
Consequently, a material such as an organic fatty acid salt (e.g.
sodium stearate) that has not been applicable in the past can be
used as the lubricant for warm forging.
[0097] After the work is heated to about 250.degree. C., coating
can be done without heating for the lubricant, such as graphite,
that has been physically applied to the work. Adhesion to the work
can be improved because the lubricant, such as graphite, adheres to
the phosphating treatment film but not to the surface of heated
iron. This is a desirable lubrication property.
BRIEF DESCRIPTION OF THE DRAWINGS
[0098] FIG. 1 shows the flows of a current and ions in an
electrolytic treatment.
[0099] FIG. 2 is an SEM photograph of a film formed in Example 1
(1000 times).
[0100] FIG. 3 is an SEM photograph of a film formed in Example 2
(1000 times)
[0101] FIG. 4 is an SEM photograph of a film formed in Example 3
(1000 times).
[0102] FIG. 5 is an SEM photograph of a film formed in Example 4
(1000 times).
[0103] FIG. 6 is an SEM photograph of a film formed in Example 5
(1000 times).
[0104] FIG. 7 is an SEM photograph of a film formed in Comparative
Example 1 (1000 times).
[0105] FIG. 8 shows an appearance after the passage of 2,000 hours
after a brine spray test conducted after a formation treatment and
electro-deposition coating (film thickness of 15 .mu.).
[0106] FIG. 9 is a schematic view of a work for forging (lower
body).
[0107] FIG. 10 shows the conditions before and after hot forging of
the work (lower body).
[0108] FIG. 11 is a differential thermal analysis diagram of
phosphating treatment films used in Examples 6 to 8 of the present
invention.
[0109] FIG. 12 is a differential thermal analysis diagram of the
phosphating treatment film of Comparative Example 4.
[0110] FIG. 13 is SEM photographs of phosphating treatment films of
Examples 6 to 7.
[0111] FIG. 14 is an SEM photograph of a phosphating treatment film
of Comparative Example 4.
[0112] FIG. 15 shows the appearance before warm forging (NB
cylinder) in Example 9 and Comparative Example 5.
[0113] FIG. 16 shows the appearance after warm forging (NB
cylinder) in Example 5 and Comparative Example 5.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0114] The film to be formed by the electrolytic treatment
according to the present invention is a metal+phosphate film.
[0115] The metal is dissolved and supplied in the form of a nitrate
in a treatment bath. The metal is reduced by electrolysis and
precipitates. In other words, it precipitates in the following
formula: M.sup.2++2e.fwdarw.M.degree. (2)
[0116] The phosphate precipitates as a metal salt as phosphoric
acid dissociates. The metal salt precipitating thereby is limited
to the kind of metals that can dissociate phosphoric acid and can
be dissolved. The kind of metals is limited to zinc, iron or
manganese. In the present invention, however, the metal that can
dissociate phosphoric acid and can be dissolved is suitably zinc
from the aspect of safety of the treatment bath.
[0117] First, the composition of the phosphate treatment bath will
be described.
[0118] The components that constitute the phosphating treatment
bath include phosphoric acid, a portion in which zinc is dissolved
while dissociating phosphoric acid and is dissolved while
associating with phosphate ion and a portion in which nitrates of
nickel, cobalt, manganese, copper and zinc are dissolved. When
these components are classified by the kind of anions, they can be
classified into a portion of the phosphate ion system and a portion
of nitrate ion system. The other kinds of ions are miscellaneous
ions and their amount is limited to 0.5 g/L or below.
[0119] When the components constituting the treatment bath are
expressed by the proportion of the kind of the anions described
above in the phosphating treatment bath according to the present
invention, the relation becomes nitrate ion system>phosphate ion
system, the metal nitrate is at least 10 g/L and the sum of the
phosphoric acid and the phosphate ion is not greater than 1/2 of
the metal nitrate.
[0120] In the phosphating treatment bath according to the
invention, the metal nitrate is more preferably at least 20 g/L and
the sum of phosphoric acid and the phosphate ion is not greater 1/2
of the metal nitrate.
[0121] Incidentally, in the electrolytic treatment of aluminum
materials, a necessary amount of F (fluorine) ions such as 1 g/L or
below is permissible for preventing the formation of an oxide film
on the surface of aluminum.
[0122] Next, the electrode materials will be explained. The
electrode material uses a metal that is to be precipitated. The
metal that is to be reduced and precipitated is the same as the
metal that is supplied as the nitrate to the treatment bath.
Therefore, the material of the metal electrode is nickel, cobalt,
manganese, copper and zinc or their alloys.
[0123] Next, the electrolytic treatment method will be described.
The electrolytic treatment is carried out by constituting an
electrolytic treatment system shown in FIG. 1 by using the
treatment bath and electrode materials described above and a D.C.
power source. The electrolytic treatment generally includes anodic
electrolytic treatment by using the work as a anode and an iron
electrode as a cathode and then cathodic electrolytic treatment by
using a metal of the nitrate of the treatment bath as the anode and
the work as the cathode. The anodic treatment may be omitted.
Generally, the electrode material is different between the anodic
treatment and the cathodic treatment and a plurality of materials
can be used. The electrolytic phosphating treatment bath generally
includes an electrolytic treatment bath and a tank in which the
treatment is not carried out so that the solution can be circulated
between them. In this instance, the treatment bath must have a
construction capable of removing molecular nitrogen oxides (NOx)
that are formed by the reduction of the nitrate ions generated in
the treatment bath.
[0124] Next, other contrivances will be explained. It is preferred
to measure the ORP (oxidation-reduction potential) of the treatment
bath and to keep it at 770 mV or more. This is necessary for
preventing the iron ions dissolving from the electrode and the work
and into the treatment bath. A bath having ORP of 770 mV or more
does not contain, in principle, Fe.sup.2+ from the formula (1). In
other words, when the treatment bath according to the invention
mainly containing the nitrate ion contains Fe.sup.2+ (that is, when
ORP is lower than 770 mV), oxidation to Fe 3+ occurs inside the
treatment bath and solubility of the Fe ions drops in the treatment
bath, so that sludge is formed.
[0125] Therefore, the ORP of the treatment bath at 770 mV or more
is important for controlling Fe2+ inside the treatment bath, that
is, the quantity of the iron ions dissolving from the electrode and
the work as represented by the formula (3): Fe.fwdarw.Fe.sup.2++2e
(3)
[0126] Consequently, ORP control of the treatment bath is
preferably carried out.
[0127] The electrolytic treatment is substantially carried out at a
voltage of 15 V or below and more preferably, 6 V or below.
[0128] Next, the application of the electrolytic phosphating
treatment according to the invention includes the application to
warm (or hot) forging/lubrication treatment. A best mode will be
explained.
[0129] According to the lubrication treatment for warm forging in
the present invention, there is formed a work in which a
phosphate+metal film, including a metal having a melting point
higher than the temperature applied to the work during warm forging
of the metal and the phosphate, is formed on the surface of the
work and the lubricant is supported on the coat, and the film of
which has the lubrication function in warm forging. The formation
of the phosphating treatment film consisting of the
"phosphate+metal" and formed on the surface of the work is carried
out by the electrolytic system.
[0130] The lubrication function in the forging of the metal has the
following mechanism. When the mold and the work (metal) come into
mutual contact and the work undergoes plastic deformation, the
lubrication film (foundation film+lubrication film) covering the
surface of the work is molten and fluidized in a temperature range
of forging and so changes as to follow up the plastic deformation
of the work, thereby preventing the direct contact of the work and
the mold. The foundation film constituting the lubrication film is
generally an inorganic compound containing a phosphate, and the
lubricant is preferably an organic compound generally softened
between 200 to 1,000.degree. C. or an inorganic compound having a
laminar structure. Suitable examples include organic fatty acid
salts such as sodium stearate, fluorocarbon resins, molybdenum
disulfide and graphite.
[0131] The reason why the phosphate compound is selected as the
foundation film for the lubrication treatment for cold forging is
as follows. When the mold and the work (metal) come into contact
and the work undergoes plastic deformation within the temperature
range of cold forging, the lubrication film (foundation
film+lubrication film) covering the surface of the work is molten
and fluidized in the temperature range of cold forging and can
change in such a fashion as to follow the plastic deformation of
the work. Therefore, the function required for the phosphating
treatment film in cold forging is to secure suitable adhesion with
the work (metal) and to uniformly distribute, and to maintain the
distribution of, the lubricant such as sodium stearate.
[0132] When the mold and the work (metal) come into mutual contact
and the work undergoes plastic deformation in the temperature range
of forging, the lubricant does not react with the mold as the
counter-part but exists stably. Because the lubricant has fluidity,
it can follow the plastic deformation (elongation) of the work, can
prevent the direct contact between the mold and the work and can
also prevent deterioration of the mold.
[0133] Next, the foundation treatment film of the
forging/lubrication treatment will be further explained. The
requirements for the foundation film are retention of adhesion with
blank metal and uniform retention of lubricant. The foundation
treatment film is not necessary if the lubricant can retain
adhesion with the blank metal through a chemical reaction. As such
a lubricant does not exist, however, the foundation treatment is
necessary.
[0134] Adhesion with the blank metal required for the foundation
treatment is an adhesion such that when the mold and the work
(metal) come into mutual contact and the work undergoes plastic
deformation in the temperature range of forging, the lubrication
film (foundation film+lubrication film) covering the surface of the
work is softened and fluidized in the temperature range of forging,
follows the plastic deformation of the work and changes.
[0135] Therefore, excessive adhesion of the foundation treatment
film with the blank metal is not suitable and suitable adhesion is
required.
[0136] The foundation treatment film is also required to uniformly
retain the lubricant. Lubricants in general are organic fatty acid
salts and inorganic high molecular weight compounds having
multi-layered structures (graphite, for example) and do not have
chemical affinity with the metal surface. (Therefore, the lubricant
cannot be formed directly on the metal). In contrast, as the
phosphate has chemical affinity with the lubricant described above,
it can retain the lubricant.
[0137] As described above, the lubrication foundation treatment
film exists between the blank metal and the lubricant having
mutually different properties and plays the role of combining them
together. This is an important function.
[0138] It is the temperature range that is to be taken into
consideration in the lubrication treatment of forging. The forging
temperatures are different among cold forging, warm forging and hot
forging. The forging temperature is also different in warm forging
depending on the kind of metals. Therefore, the classification of
lubrication property and fluidity in the temperature range of
forging is substantially as follows: Forging:
[0139] (i) cold forging: forging temperature 100 to 250.degree.
C.
[0140] (ii) warm forging:
[0141] (ii-1) steel: forging temperature 300 to 1,000.degree.
C.
[0142] (ii-2) non-ferrous metal: forging temperature 200 to
600.degree. C.
[0143] Therefore, the temperature for the lubrication treatment
(foundation film+lubrication film) is decided in consideration of
the temperatures listed above.
[0144] The reason why the phosphate compound is selected as the
foundation film of cold forging/lubrication treatment of the steel
is as follows. When the mold and the work (metal) come into mutual
contact in the temperature range of cold forging and the work
undergoes plastic deformation, the lubrication film (foundation
film+lubrication film) covering the surface of the work is softened
and fluidized in the temperature range of cold forging and can
exhibit the function of changing while following the plastic
deformation of the work. Therefore, the functions required for the
phosphating treatment film of the lubrication treatment for cold
forging are suitable adhesion with the work (metal), uniform
distribution of the lubricant and the retention of this
distribution.
[0145] The forging temperature must be taken into consideration
when the lubrication foundation film capable of being applied to
warm forging is considered. In other words, it is desired that the
foundation film does not fall off from the blank even when heated
to a temperature above 200.degree. C. but follows the plastic
deformation of the blank. Chemical affinity of the phosphating
treatment film with the lubricant has been confirmed in the past.
However, the film obtained by the conventional non-electrolytic
treatment has not been applied to the foundation treatment for warm
forging because, according to a conventional method, the
phosphating treatment film is decomposed and dissociates from the
work when the work is heated to a temperature of 200.degree. C. or
above.
[0146] The phosphating treatment film obtained by the
non-electrolytic treatment of the prior art has the form of crystal
grains containing water of crystallization such as
Zn.sub.3(PO.sub.4).sub.2-4H.sub.2O and having a size of about 50
.mu.m. It is presumed that water of crystallization dissociates
with the temperature rise and the chemical structure of the film of
the large crystal grains is destroyed. Therefore, the phosphating
treatment film formed by the non-electrolytic treatment does not
have heat resistance.
[0147] The phosphating treatment film applied to lubrication
treatment for warm forging desirably has heat resistance. The
phosphate+metal treatment film obtained by the electrolytic
treatment of the invention has the heat resistance that can be
applied to warm forging. This film contains large amounts of metals
that are reduced and precipitated, and also contains the
phosphate.
[0148] The film formed by the electrolytic treatment of the
invention has affinity with the lubricant because the film is the
phosphate+metal treatment film and contains the phosphate.
Therefore, the film according to the invention has the heat
resistance and affinity with the lubricant.
[0149] The formation of such a film can be conducted on the basis
of the use of the treatment bath not containing metal ions other
than the film components that is disclosed in JP-A-2000-234200.
[0150] In other words, the lubrication treatment for warm forging
according to the invention for forming the phosphating treatment
film consisting of the phosphate+metal on the surface of the work
is carried out by the method that electrolyzes on the surface of
the work inside the treatment bath constituted by phosphoric acid
and phosphate ion; zinc ion as a metal capable of dissociating and
dissolving in phosphoric acid; and a solution containing a nitrate
of nickel, cobalt, manganese, copper or zinc.
[0151] Suitably, the formation of the phosphating treatment film,
consisting of phosphate+metal and formed on the surface of the
work, is carried out in the treatment bath in which the metal ion
dissolving from the nitrate is at least 10 g/L and phosphoric acid
and phosphate ion are not greater than 1/2 of the metal ion.
Further suitably, the formation of the phosphating treatment film
consisting of the phosphate+metal and formed on the surface of the
work is carried out in the treatment bath in which the metal ion
dissolved from the nitrate is at least 20 g/L and phosphoric acid
and phosphate ion are not greater than 1/2 of the metal ion
dissolved from the nitrate.
[0152] Next, the application of the film described above to warm
forging will be explained. In the invention, the explanation will
be given mainly on the example of the steel as described above but
the invention can be applied to all the metal materials used for
executing warm forging.
[0153] The term "warm forging" means those kinds of forging which
execute forging after a metal material is heated to a temperature
higher than room temperature. The heating temperature varies
depending on the kind of the metals. Table 2 tabulates general warm
and hot forging temperatures of various metals subjected to warm
forging. TABLE-US-00002 TABLE 2 warm & hot melting point
forging of metal: .degree. C. temperatures: .degree. C. remarks
iron and 1535 300-1100 steel aluminum 660 200-450 and its alloy
magnesium 648 200-450 and its alloy copper and 1083 200-600 its
alloy
[0154] Next, the metal characteristics of the phosphate+metal film
formed on the work and the condition of the treatment bath will be
clarified. Table 3 tabulates those metals which can be contained in
the phosphating treatment film. TABLE-US-00003 TABLE 3
precipitation- divalent-trivalent melting point dissolution
reaction equilibrium of metal: .degree. potential: V potential: V
C. M M.sup.2++ 2e M.sup.2+ M.sup.3+ + e Ni 1453 -0.257 -- Mn 1244
-1.18 1.51 Co 1495 -0.277 1.92 Cu 1083 0.34 -- Zn 419 -0.77 --
[0155] The first necessary condition corresponding to the
phosphate+metal is the melting point of the metal. The metal
contained in the film must have a melting point higher than the
forging temperature of the work (refer to Table 2).
[0156] The second necessary condition is the behavior in the
treatment bath for forming the film. In order for the metal to be
taken into the film, the metal must be stably dissolved and exist
as the divalent metal ion in the phosphating treatment bath. For
this purpose, it is necessary that the charge of the metal does not
easily change within the range of the oxidation reduction potential
at which water, as the solvent, is not decomposed. In other words,
the equilibrium of M.sup.2+.revreaction.M.sup.3++e does not
exist.
[0157] (Solubility drops when the metal ions change to M.sup.3+ in
the relation M.sup.2+.fwdarw.M.sup.3++e. Consequently, the sludge
is formed in the treatment bath. The sludge impedes stability of
the treatment bath as the solution and is not permissible).
[0158] The third condition is that the metal is not affected by
hydrolysis of water as the solvent. The decomposition of water as
the electrochemical reaction occurs when the potential of the
treatment bath exceeds the oxidation reduction potential
represented by the following formulas (4) and (5):
[0159] Anodic reaction: H.sub.2+2OH.sup.-2H.sub.2O+2e: -0.83 V (4)
Cathodic reaction: O.sub.2+4H.sup.++4e2H.sub.2O: 1.23 V (5)
[0160] Therefore, as long as the equilibrium potential of the metal
component inside the treatment bath, that is, M.sup.2+M.sup.3++e,
is within the range of the potential represented by the formulas
(4) and (5), the metal component ion has the possibility of
changing from the condition M.sup.2+ to the condition M.sup.3+
inside the treatment bath. The occurrence of such a change is not
preferred.
[0161] The metals tabulated in Table 3 do not have the equilibrium
potential M.sup.2+M.sup.3++e within the range of -0.83 V to 1.23
V.
[0162] The fourth essential condition is that cathodic
precipitation can be conducted without being affected by the
electrolysis of water as the solvent. The relation
M.sup.2+M.sup.3++e tabulated in Table 3 must be taken into
consideration. In other words, when the cathodic precipitation of
the metal ion, i.e. M.sup.2++2e.fwdarw.M, is 0.83 V or below, the
reaction of the cathodic decomposition reaction formula (4) of
water as the solvent occurs preferentially and the cathodic
precipitation of the metal ion is not possible in principle.
Namely, when the precipitation-dissolution reaction potential of
the metal shown in Table 3 is by far lower than -0.83 V,
electrolytic precipitation from the aqueous solution is not
possible. The precipitation-dissolution reaction potentials of the
metals tabulated in Table 3 (Ni, Mn, Co, Cu, Zn) other than Mn are
higher than -0.83 V and precipitation is possible. The potential of
Mn is only slightly lower than -0.83 V and precipitation is
possible.
[0163] Therefore, as the metals tabulated in Table 3 satisfy the
three conditions described above, the phosphate+metal treatment
film can be formed by the electrolytic treatment. However, it is
necessary to suitably use the precipitation metal in accordance
with the kind of materials to be forged.
[0164] Next, the function of the lubricant and its best mode will
be described. The lubricant that is formed on the work and has been
used in the past for warm forging, such as graphite, can be used in
the invention. An organic fatty acid salt can be used as a novel
lubricant for warm forging. This is because the phosphating
treatment film having the heat resistance is used for the
foundation treatment.
[0165] The function of the lubricant is to prevent the direct
contact between the work and the mold during warm forging. In the
case of the iron and steel, graphite has been used as the lubricant
to be directly applied to the work after heating to about
250.degree. C. However, graphite only adheres physically to the
work and does not have reliable adhesion. Therefore, the work is
immediately heated to about 800.degree. C. and subjected to warm
forging.
[0166] The formation of the lubricant film on the work becomes easy
when the phosphating treatment film having the heat resistance is
formed as the foundation film. This is because the lubricant has
chemical affinity (analogous properties) to the phosphating
treatment film. Therefore, the lubricant can be dispersed, attached
and allowed to-adhere to the surface of the treatment film more
uniformly and more reliably than the surface of iron and steel
materials.
[0167] In the warm forging method according to the invention, the
phosphating treatment film having the heat resistance is formed and
the lubricant is applied onto the film. Therefore, the organic
fatty acid salt can be used as the novel lubricant. In other words,
the fatty acid salts such as sodium stearate that have been used in
the past for cold forging can be used for warm forging.
[0168] In other words, in the warm forging lubrication treatment
according to the invention, the work having the lubrication
function in warm forging is formed in which the phosphate+metal
film constituted by the metal having a melting point equal to or
higher than the temperature applied to the work during warm forging
of the metal and the phosphate is formed, the lubricant as the
organic fatty acid salt and the inorganic high molecular weight
compound having the multi-layered structure is supported on the
coat, and warm forging is carried out by heating this work. Warm
forging itself is basically carried out in the same way as the
existing methods. A spray of the lubricant onto the warm or hot
forging mold has also the function of cooling the mold and is
necessary.
[0169] Examples 1 to 5:
I. Improvement of Efficiency of Electrolytic Phosphating
Treatment
[0170] Table 4 shows the treatment bath conditions in Examples 1 to
5 and Comparative Example 1. TABLE-US-00004 TABLE 4 bath of bath of
Examples 1 Comparative to 5 Example 1 bath phosphate ion: g/L 12 12
composition zinc ion: g/L 10 10 nitrate ion: g/L 150 60 nickel ion:
g/L 54 22 total acidity: pt. 200 45 electro- pH 0.8-1.0 1.6-1.8
chemical index ORP: shown by 670 mV 676 mV of treatment
silver/silver bath chloride electrode
[0171] In Comparative Example, the concentrations of phosphoric
acid and phosphate ion are higher than 1/2 of the metal ion (Ni).
In this point, the treatment bath is out of the range of the bath
of the present invention.
[0172] The electrolytic phosphating treatment is carried out in
these treatment baths. Table 5 shows an outline. TABLE-US-00005
TABLE 5 trial product/test condition test No. Comparative Examples
1-5 Example 1 1 2 3 4 5 1 test material cold rolled steel sheet:
SPCC material clutch (50 .times. 50 .times. 1 mm) component:
stator: spcc material treatment step degreasing .fwdarw. washing
with water .fwdarw. surface Table 6 conditioning .fwdarw.
electrolytic phosphating treatment .fwdarw. washing with water
.fwdarw. drying electrolytic phosphating bath of Example of Table 1
bath of treatment bath Comparative Example 1 of Table 1
electrolytic anodic immersed for 5 secs 3 V .times. 0.01 A/dm.sup.2
.times. 12 sec condition treatment cathodic 1.8 V .times. 3 V
.times. 4 V .times. 5 V .times. 6 V .times. 8 V .times. 1.5
A/dm.sup.2 .times. (9 sec.uparw., treatment 2.5 A .times. 5 A
.times. 3.4 A .times. 7 A .times. 7 A .times. 77 sec.fwdarw.)
(current: (5 sec.uparw., (5 sec.uparw., (5 sec.uparw., (5
sec.uparw., (5 sec.uparw., dm.sup.2 40 sec.fwdarw.) 40 sec.fwdarw.)
40 sec.fwdarw.) 40 sec.fwdarw.) 20 sec.fwdarw.) calculation value)
total 50 sec 30 sec 98 sec treatment time resulting film 1 5 3 7 5
2 film thickness: .mu.m appear- gray gray black ance SEM .times.
FIGS. 1-5 1,000 times
[0173] Incidentally, the film thickness is measured by using an
electromagnetic film thickness meter (LE-300J, K.K. Ketto Kagaku
Kenkyujo).
[0174] FIGS. 2 to 7 show the SEM photographs (1,000 times) of the
films formed in Examples 1 to 5 and Comparative Example 1,
respectively. Because the voltage is small in Example 1, a current
is small, too, and film formation is 10 not sufficient. Films are
formed in Examples 2 to 5.
[0175] Comparative Example 1 represents the result in mass
production equipment. Table 6 shows the process steps of
Comparative Examples. TABLE-US-00006 TABLE 6 step: time (sec)
transfer (sec) time total: sec. step content remarks 1 degreasing:
100 50 150 55.degree. C.: alkali degreasing 2 degreasing: 100 50
150 55.degree. C.: alkali degreasing 3 washing with 50 150 water:
100 4 washing with 50 150 water: 100 5 phosphating: 100 50 150
electrolytic (1.5 A/dm.sup.2) treatment: 8 V .times. 3 A/ piece 6
washing with 50 150 water: 100 7 pure water spray: 50 150 spray for
45 sec 45 and leave-standing for balance 8 electro-deposition 50
150 lead-free paint: voltage 200 V coating: 100 film thickness of
15 .mu. or more 9 washing with pure 50 150 water: 100 10 washing
with pure 50 150 water: 100 11 washing with pure 50 150 water: 100
12 pure water spray: 50 150 spray for 45 sec 100 and leave-standing
for balance time: sub-total 1800 13 temperature elevation: 1200 =
20 min. 1200 inclusive of transfer and replace 14 baking: 1500 = 25
min. 1500 200.degree. C. 15 cooling: 1500 = 25 min 1500 inclusive
of transfer and replace total: time = lead time 6000 = 100 min
--
[0176] In Comparative Example 1, the work is a clutch component
stator and FIG. 8 shows the appearance after the phosphating
treatment.fwdarw.electro-deposition film (film thickness: 15 .mu.)
and salt spray test for 2,000 hours. Peeling of the film from a
film cross-cut portion does not occur and the corrosion resistance
is fair.
[0177] Incidentally, the paint is electro-deposition paint
"Power-Nix" 110 black, lead-free cation electro-deposition paint of
Nippon Paint K. K.
[0178] Next, electro-deposition films of Examples 1 to 5 will be
described.
[0179] Coating condition: Power-Nix 110 Black (lead-free cation
electro-deposition)
[0180] Coating condition:
[0181] The following three kinds are used.
[0182] A: electro-deposition time: 45 sec (including 10 sec for
rise voltage control)
[0183] B: electro-deposition time: 60 sec (including 11 sec for
rise voltage control)
[0184] C: electro-deposition time: 90 sec (including 12 sec for
rise voltage control)
[0185] Coating temperature: 30.degree. C., baking-drying
temperature: 160.degree. C..times.10 min
[0186] Coating voltage: 150 V
[0187] The coat thickness of each Example after
coating.fwdarw.baking is shown in Table 7 (unit: .mu.m).
TABLE-US-00007 TABLE 7 formation treatment condition coating
condition Example 1 2 3 4 5 A 8 .mu.m 6 7 7 9 B 10 8 10 9 12 C 16
12 16 17 17
[0188] The thickness of the coat film greatly depends on the
electro-deposition coating time rather than on the formation
condition of the phosphating film.
[0189] Table 8 shows the result of the salt spray test of the
coating products described above. The numeral shown in FIG. 8
represents the peel width by mm from the line formed by cutting the
coat film. The smaller the value, the better the result.
[0190] The result shown in Table 8 represents that the corrosion
resistance of the film depends more greatly on the formation
treatment condition than on the coating film thickness. In Examples
of the electrolytic treatment products, the corrosion resistance of
the film remains at the existing level even when the film thickness
is small with the exception of a voltage of 1.8 V. TABLE-US-00008
TABLE 8 coating brine spray test condition: time 408H 1008H 1248H
1608H 2016H 45 sec Example 1 2 10 11 15 15 Example 2 0 0 0 0 0
Example 3 0 0 0 0 0 Example 4 0 0 0 0 0 Example 5 0 3 10 10 15 60
sec Example 1 0 5 5 15 15 Example 2 0 0 0 0 0 Example 3 0 0 0 0 0
Example 4 0 0 0 0 0 Example 5 0 0 0 0 0 90 sec Example 1 0 3 3 15
15 Example 2 0 0 0 0 0 Example 3 0 0 0 0 0 Example 4 0 0 0 0 0
Example 5 0 0 0 0 0
[0191] It can be understood that Examples according to the
invention can execute the treatment (formation treatment,
electro-deposition coating, baking) within 1/2 of the time of
Comparative Example. This can be achieved by the combination of the
coating condition A described above with Examples 1 to 5. According
to these combinations, the thickness of the film becomes 1/2 of the
thickness of Comparative Example but the corrosion resistance can
maintain the level of Comparative Example 1.
[0192] The electrolytic voltage is 3 to 6 V and the treatment at a
lower voltage than 8 V of Comparative Example 1 becomes possible.
Therefore, from the aspect of the electrolytic voltage,
decomposition of the treatment bath components is suppressed. In
other words, the formation of the sludge can be much more
suppressed.
[0193] Examples 6 to 8
II. Application to Warm Forging
[0194] A car engine component (lower body: material SCM415) is
used. FIG. 9 shows the condition before warm forging and FIG. 10
shows the condition before and after warm forging.
[0195] Table 9 shows the process steps of warm forging in Examples
6 to 8 and Comparative Example 2. However, washing with water and
washing with hot water are omitted. In warm forging press, a solid
lubricant (graphite) is sprayed to a press mold under the same
condition in Examples 6 to 8 and Comparative Example 2.
TABLE-US-00009 TABLE 9 Comparative step Example 6 Example 7 Example
8 Example 2 Pre-step Coil material having phosphating treatment
film + lubricant (stearate) formed as lubrication treatment is cold
forged. 1 shot blast .largecircle. .largecircle. .largecircle. -
(nil) 2 degreasing .largecircle. .largecircle. .largecircle. -
(nil) 3 electrolytic phosphating .largecircle. .largecircle.
.largecircle. - (nil) formation treatment: metal + phosphate 4
lubrication treatment .largecircle.: .largecircle.: .largecircle.:
- (nil) graphite "Moricoat" synthetic mica molybdenum disulfide 5
heating: 850.degree. C. .largecircle.: induction heating 6 warm
forging press .largecircle.: Nippon Atison K. K., "Aquaduck", 10%
aqueous solution is applied by spraying.
[0196] The difference of Examples 6 to 8 is only the difference of
the lubricant. The difference of Examples 6 to 8 from Comparative
Example 2 is that Examples execute the "metal+phosphate" foundation
treatment and the lubrication treatment inclusive of shot blast
(executed by removing the pre-step phosphating formation treatment
film), whereas the Comparative Examples do not include such
treatments.
[0197] The detail of the electrolytic phosphating treatment is as
follows. The composition of the treatment bath contains phosphoric
acid and phosphate ion: 15 g/L, zinc ion: 10 g/L, Ni ion: 51 g/L
and nitrate ion: 157 g/L. The work (lower body) shown in FIG. 9 is
placed as the negative electrode into the treatment bath and a Ni
plate, as a positive plate. After the work is immersed for 10
seconds without the application of the voltage, a voltage is raised
to 13 V in the course of 5 seconds and a current is caused to flow
at 28 to 32 A for 25 seconds through one work (surface area of 1.2
dm.sup.2). The temperature at that time is 30 to 34.degree. C. A
film of phosphate+Ni having a black gray color is formed in this
way on the surface of the work.
[0198] The lubrication treatment is carried out by immersing the
work into an aqueous solution to form a film. The outline is shown
in Table 10. TABLE-US-00010 TABLE 10 Example 6 Example 7 Example 8
composition graphite: molybdenum synthetic Nippon Atison K. K.,
disulfide: mica: "Delta-forge", Nihon Corp Chemical F818 30%
Parkerizing K.K., Co. K.K., "Palub", "Somashiff", LUB4642 S1ME 30%
temperature 60-80.degree. C. 60-80.degree. C. 60-80.degree. C.
treatment immersion for immersion for immersion for time 30 sec 30
sec 30 sec
[0199] Table 11 shows the difference of the machining load in warm
forging press. TABLE-US-00011 TABLE 11 Comparative Example 6
Example 7 Example 8 Example 2 machining 40 40 40 70 load: 10 KN
[0200] The machining load is remarkably different between Examples
and Comparative Example. In examples, the 15 machining load is low
and excellent. This represents that lubrication performance is
greatly different between the case where the lubrication film is
formed on the work (Examples) and the case where the lubrication
film is not formed (Comparative Example). It is obvious that the
present invention is effective.
III. Comparison of Composition of Phosphating Treatment Film
[0201] The difference of Examples 6 to 8 of the present invention
from the electrolytic phosphating treatment film of the prior art
will be demonstrated. Examples 1 and 4 described in
JP-A-2000-234200 are cited as Comparative Example 3 to demonstrate
the film obtained by the electrolytic treatment of the prior art.
TABLE-US-00012 TABLE 12 Comparative Example 3 Example 1 of Example
4 of Exam- JP-A-2000- JP-A-2000- ples 232400 232400 6-8 treatment
phosphate ion 7.6 2.8 12.3 bath nitrate ion 12 10.1 150 composition
Ni ion 5.5 3.8 51 g/L Zn ion 0.4 0.4 9.1 (Ni + Zn)/ 0.78 1.5 4.9
phosphate ion film Ni 6.1 9.6 22.2 composition Zn 1.9 8.6 27.6 Wt %
P 2.9 19 5.9 Ni/P 2.1 0.5 3.8 (Ni + Zn)/P 2.8 0.96 8.4
[0202] The difference between Examples 6 to 8 and Comparative
Example 3 is the proportion of the metal component to phosphoric
acid or phosphorus (P) in both treatment bath composition and film
composition.
[0203] Examples of the present invention have greater proportion of
the metal component in the treatment bath composition and the film
composition than in Comparative Example 3. In other words, the film
of the present invention is a film having a large metal component.
In any case, the difference from the prior art example is
distinctive.
IV. Comparison of Heat Resistance of Phosphate Formation Coat
[0204] Next, the heat resistance of the film is represented by the
result of DSC: differential thermal analysis.
[0205] FIG. 11: diagram of differential thermal analysis of
Examples 6 to 8 (phosphating treatment film for warm forging from
electrolytic treatment)
[0206] FIG. 12: diagram of differential thermal analysis of
Comparative Example 4 (phosphating treatment film from
non-electrolytic treatment)
[0207] Comparative Example 4 represents the film produced by the
conventional non-electrolytic system. The phosphating formation
treatment bath is prepared by adjusting "Pal-bond" 3684X, a
formation treatment chemical from Nihon Pakerizing K. K., under
predetermined conditions. A cold rolled steel sheet is immersed in
the treatment bath (80.degree. C.) for 10 minutes to form a film.
FIG. 12 is a differential thermal analysis diagram of the film and
FIG. 14 is an SEM photograph of the film.
[0208] FIG. 11 is a differential thermal analysis diagram of a
phosphating film structure used in Examples 6 to 8 of the present
invention. In other words, it is a phosphating film produced by the
electrolytic treatment for warm forging of the steel materials.
[0209] FIG. 12 is a differential thermal analysis diagram of a
phosphating treatment film structure of the prior art used for cold
forging of iron and steel materials. In other words, it is a
differential thermal analysis diagram of a phosphate film produced
by the non-electrolytic treatment system.
[0210] The great difference between FIG. 11 and FIG. 12 is that
whereas a change of a differential scanning calorie curve exists in
a temperature range of 200.degree. C. or below in FIG. 12, such a
phenomenon cannot be observed in FIG. 11.
[0211] A large weight change (decrease) takes place during the
temperature rise of up to 200.degree. C. in the film of FIG. 12
produced by the non-electrolytic treatment. This large change of
the differential scanning calorie curve represents a large change
of the film structure. It is well known that the phosphating film
obtained by the non-electrolytic treatment of the prior art exists
in the form of the crystal containing the crystal of water
(moisture salt): Zn.sub.3(PO.sub.4).sub.24H.sub.2O. Therefore, the
large change of the film structure results from fall-off of the
crystal of water from the phosphate crystal owing to heat of up to
200.degree. C. It is clear, when FIGS. 13 and 14 are examined, that
the appearance of the film is different between the electrolytic
treatment and the non-electrolytic treatment. Presumably, this
difference of appearance is related to the film structure.
[0212] It is impossible from the observation described above to
apply the phosphating treatment film formed by the non-electrolytic
treatment of the prior art to the foundation film for warm forging
in which the film is heated to a temperature of 500.degree. C. or
above. Consequently, the phosphating treatment film of the prior
art has not been used for warm forging.
[0213] The result of the differential thermal analysis represents
the weight change of the coat due to heating. The film formed by
the non-electrolytic treatment (FIG. 12) exhibits a weight decrease
of 9.78/11.062=0.884 till the absorption of the differential
scanning calorie curve due to heating but the electrolytic
treatment film of the present invention (FIG. 11) exhibits a slight
change of 187.degree. C. and its weight change remains at
13.57/13.804=0.983. This represents that the phosphating treatment
film of the present invention is more effective in the heat
resistance than the coat of the prior art.
EXAMPLE 9
Example Using Organic Fatty Acid Salt for Lubricant
[0214] A car engine component (NB cylinder: material SUJ2:
Cr-containing alloy steel) is used. FIGS. 15 and 16 show the forms
of the NB cylinder before and after warm forging, respectively.
[0215] Table 13 shows the warm forging steps of Example 9 and
Comparative Example 5.
[0216] Incidentally, the lubricant is spray coated to the press
mold under the same conditions as in warm forging for Example 9 and
Comparative Example 5. TABLE-US-00013 TABLE 13 Comparative step
Example 9 Example 5 1 shot blast .smallcircle. -- (nil) 2
degreasing .smallcircle. -- (nil) 3 surface .smallcircle. -- (nil)
adjustment 4 electrolytic .smallcircle. -- (nil) phosphating
treatment: metal + phosphate 5 lubrication .smallcircle.: sodium
stearate -- (nil) treatment 3-6%: 85.degree. C. solution, 3 min. 6
heating: 850.degree. C. .smallcircle. .smallcircle. 7 warm forging
.smallcircle. .smallcircle. press
[0217] The difference between Example 9 and Comparative Example 5
is as follows. In Example 9, the foundation treatment of
metal+phosphate and immersion into the sodium stearate solution as
the lubrication treatment are carried out for the work after the
shot blast (executed by removing a pre-step phosphating film) is
conducted. In contrast, these treatments are not carried out in
Comparative Example 5.
[0218] The electrolytic phosphating treatment in Example 9 is the
same as that of Examples 6 to 8.
[0219] Table 14 shows the machining load in warm press forging.
TABLE-US-00014 TABLE 14 Comparative Example 9 Example 5 machining
load: 10 KN 120-150 130-160
[0220] The machining load of Example 9 is equal to that of
Comparative Example 5. Example 9 is an example that uses sodium
stearate as the lubricant of the work. This compound has no actual
performance record as the lubrication coat for work in the prior
art. The present invention demonstrates that sodium stearate can be
applied to the lubrication treatment.
[0221] The electrolytic phosphating treatment method according to
the invention can apply a greater current at a lower voltage than
in the electrolytic treatment of the prior art. In other words, the
method of the invention is an electrolytic phosphating treatment
technology that has higher efficiency than the prior art
technologies.
[0222] The present invention is effective for the lubrication
treatment for warm forging. It has not been possible to apply the
phosphating treatment film to the foundation treatment of the warm
forging lubricant but the invention has developed a novel warm
forging lubrication treatment system by developing the film capable
of being applied to warm forging by utilizing the method of the
invention that precipitates greater amounts of metals. It has been
confirmed that the lubrication treatment thus developed can
drastically lower the machining load during warm forging.
Therefore, the method of the invention is a technology that can
improve warm forging.
* * * * *