Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
~ f~ 3~ ase P30,077
PRCCESS FOR PREPARING A METAL FOR COLD FORMING
Background of the Invention
This invention concerns a lubrication treatment method
for the cold working of metal materials such as steel, iron alloys
such as stainless steel, titanium, aluminum, magnesium, zirconium
and alloys of these metals which are suitable for use in wire
drawing, cold forging, spinning, tube drawlng etc.
Conventionally a phosphate film is formed on ~he base
surface and this is subjected to a lubricating treatment when cold
working iron and steel materials and it is well known that the
phosphate film doe s not fail in cold working even when the extent
of working is considerable.
In recent years materials other than iron and steel, for
example stainless steel, hastalloy, incalloy, titanium, aluminum,
magnesium, zirconium and alloys of these materials have found
increasing application and the development of lubrication treat-
ments to enable these materials to be cold worked to a consider-
able extent in line with the development of the applications for
these materials has become desirable. However, it is difficult to
form a phosphate film on these metal materials in order to improve
their potential for cold working and so they have been worked
under conditions where no such film has been used. In the case of
stainless steels an oxalate film has been used in place of a
phosphate film but baking scmetimes occurs when a high degree of
working is involved. Resin films have also been used as
lubricating films in cases where the use of a formed film such as
a phosphate film for example cannot be used. Hcwever these films
are unsuitable for high degrees of cold working because of their
poor adhesion to the metal materials, their Fcor heat resistance
and their Foor lubricating properties.
A problem with the chemically formed films that are used
as lubricating films at the present time is that, as mentionec
earlier, it is difficult to form such films chemically with some
--1--
~ 284930
materials and from the point of view of operability the treatment
time for the phosphate treatment of a steel material is quite long
as some 10-30 minutes while a similarly long period of time is
required for the formation of an oxalate film on stainless steel
where a temperature of at least 90C is also required and so these
processes are disadvantageous in terms of both efficiency and
cost.
The objective of this invention is to form a metal film
of zinc or zinc alloy on which a phosphate film can be formed
easily while simultaneously physically removing the oxide film
from the surface of the metal material, thus overcoming the prior
problems of operability and cost.
Summary of the Invention
The inventors have discovered a method of overcoming
these difficulties in which, by blasting fine particles of zinc or
zinc alloy or metal particles which are coated with zinc or zinc
alloy onto the metal surfaoe using a shot blasting system, simul-
taneously removing the surface oxide film from the surface of the
metal, a film of zinc or zinc alloy is formed on the metal surface
at the same time due to the impact of the said fine particles on
the surface following which a zinc phosphate based film can be
chemically formed easily and then a lubrication treatment applied.
The method of this invention can also be applied to the surfaces
of metals on which there is no oxide film.
Detailed Description of the Invention
Metals to which the invention can be applied include
steel and stainless steel, any iron alloys including bearing
steel, spring steel, high speed steel, and titanium, zirconium,
nickel, cobalt, lybdenum and their alloys.
The fine particles of zinc or zinc alloy or the fine
metal particles which have been coated with zinc or zinc alloy
have a diameter of 0.2-1.1 mm for example and since a high level
of hardness is preferred for removing the oxide film from the
surface of the metal material the material known as Z-Iron Aloyed
~ ~X4'3~'3(1
Shot (trade m~r~)of hardness Hv ~- 350-450, made by the Sanpo Company
by coating fine iron based particles with zinc, heating them and
alloying the zinc film with the iron of the iron based particles
and which are available commercially is suitable for this purpose.
The formation of a film of some 0.1-50 g/m of zinc or zinc alloy
on the surface of the metal material is ideal in consideration of
the economics of the process. m e shot blasting period has to be
lengthened to increase the amount of zinc or zinc alloy filming.
Furthermore if a short time is employed for forming the said metal
film the amount of shot blasted must be increased. me amount of
shot blasted is generally of the order of a thickness of 10-150
mm over the surface of the material which is being shot blasted.
Any conventional acidic phosphate treatment solution for use with
zinc materials can be used. For example no accelerator such as
sodium nitrite is required when treatment is carried out using an
aqueous acidic phosphate solution consisting of 5-100 grams per
liter of phosphate ion, 3-50 grams per liter of zinc ion, 1-100
grams per liter of nitrate ion and 0-20 grams per liter of nickel
ion for example. m e phosphate treatment is typically carried out
by dipping or spraying for 5-10 minutes at a temperature in the
range from normal temperature and 80& . me surface of the metal
which is to be treated on which the film of zinc or zinc alloy has
been formed can be subjected to a preliminary adjustment process
with an aqueous adjusting solution which contains colloidal titanium
in order to speed up the film forming reaction. After the metal
which is being treated has been subjected to the phosphate forming
treatment and a phosphate film has been formed on the surface of
the said metal it may or may not be rinsed with water and it may
or may not be dried before carrying out the final lubrication treat-
ment.
m e lubrication treatment can take the form of
a treatment with an aqueous solution of an alkali soap, a treatment
with a solution which contains a metal soap, a treatment with a
lubricating oil or a treatment with a solid lubricant for example.
~ X(~49~30
An example of an alkali soap treatment involves an
immersion treatment lasting 1-10 minutes in an aqueous solution
containing 40-60 grams/liter of a fatty acid soap such as sodium
stearate at a temperature of 70-90C and then drying to form a
film of lubricant and an example of a metal soap treatment
involves treatment with a solvent dispersion of the metal salt of
a fatty acid such as calcium stearate, barium stearate or zinc
stearate etc. or with the metal salt of the fatty acid in powder
form. Oils and fats, synthetic oils and mineral oils can be used
as bases for a lubricating oil and these may be used in
conjunction with sulfides, phosphides and chlorides as extreme
pressure additives. Examples of solid lubricants other than metal
soaps include molybdenum disulfide, tungsten disulfide,
fluorinated resins, graphite and waxes in the form of powders or
solvent dispersions. Resins may also be incorporated in order to
improve the adhesion between the solid lubricant and the base
surface.
The oxide film on the surface of the metal material is
removed by shot blasting with fine particles of zinc or zinc alloy
or fine particles of metal which have been coated with zinc or
zinc alloy and at the same time a film of the zinc or zinc alloy
which is firmly attached to or impregnated into the fine particles
is formed on the surface of the metal material. A composite film
of metallic zinc-phosphate is then formed on the surface of the
metal material by subjecting the surface on which this film has
been formed to a phosphate treatment and so an excellent base film
is provided for the lubrication treatment. The phosphate film is
composed of fine crystal clusters and so the retention of the
lubricant is good and by subjecting this film to a lubrication
treatment it is possible to provide excellent lubrication
properties as a result of the synergistic action of the zinc or
zinc alloy film - phosphate film - lubricant film system.
--4--
4~'33~)
Examplç 1
Fine zinc particles of size 0.3 x 0.7 mm were used to
shot blast the surface of a pure titanium sheet measuring 50 x 100
x 0.55 mm and a 15 g/m2 metallic zinc film was formed on the sheet.
The sheet was then immersed for 10 minutes in a conventional zinc
phosphate based treatment solution for zinc at a temperature of
62-68C and a 9.8 g/m2 zinc phosphate based film was formed. The
sample was rinsed with water and then immersed for 5 minutes in
aqueous lubricant solution of which the principal component was
sodium stearate at a temperature of 72-88C and dried to form a
film with a 7 g/m2 stearic acid soap fraction.
The lubrication properties of the treated material were
evaluated using a Bowden type friction wear testing machine and
the results obtained are shcwn in Table 1.
Reference Ex~-,ple 1
For Reference Example 1 the treatment and tests of
Example 1 were repeated without using the shot blasting process
with the fine zinc particles. No phosphate film was formed in
this case and the results obtained on evaluating the lubrication
properties in the same way as in Example 1 are shown in Table 1.
It is clear from Table 1 that the sample treated in Example 1 had
a lower coefficient of friction at 0.08 than the sample from
Reference Example 1 and it was also superior in that it required
1200 rubbings to cause baking.
Table 1
'~
~ Item Coefficient Number of Rubbing
Example ~ of Friction Strokes to Cause Baking ¦
Example 1 0.08 1200
Reference Example 1 0.1 5
,
Bowden Test Conditions:
Load 5 Kg.
Stroke Length 10 mm.
Temperature Room temperature
Pressing Probe Material SW -2 5~ steel ball
--5--
~ 2~4~
Example 2
Fine particles of zinc-iron alloy covered metal (trade
mark:Z-Iron Aloyed Shot, diameter 0.2-0.3 mm, made by the Sanpo
Co.) were blasted onto SUS 304 stainless steel wire which had an
oxide film of diameter 2.3 mm using a shot blasting system and the
stainless steel wire was coated with 10 g/mm2 of zinc-iron alloy.
miS wire was then subjected to a 5 minute immersion treatment in
a conventional zinc phosphate based treatment solution at 75-80C
and a 12 g/m2 film of a zinc phosphate system was formed. The
sample was then rinsed with water and dried. The lubrication
properties of the wire were then evaluated using a wire drawing
tester. Moreover calcium stearate in powder form was placed in
the die box before the drawing process and used as a lubricant.
The results obtained on drawing the wire under the conditions
shown in Table 2 were good in that there was no baking even after
the third pass.
Table 2
. ,
Drawing Rate 50 m/min.
Extent of Working First Pass: 27.4%
Second Pass: 20%
Third Pass: 20%
. .
Reference ExamPle 2
The results obtained on carrying out the same method of
treatment and tests as in Example 2 except for the exclusion of
the shot blasting process with the zinc-iron alloy coated
particles showed that no zinc phosphate based film was formed
under these conditions. The results of an evaluation of the
lubrication properties using the wire drawing type tester showed
that baking occurred on the first pass.
3~30
Reference Example 3
An oxalate film of 9 g/m2 was fonmed using the process
outlined in Table 3 using the same type of stainless steel wire as
in Example 2. m e lubrication properties were evaluated using the
wire drawing tester in the same way as in Example 2.
The results showed that baking occurred on the second
pass.
Table 3
Acid Wash L Water Rinse Chemlcal Forming ~Water Rinse ¦ Drying
HN03-HF Town's Water Ferubond A Town's Water Hot
Normal 35 grams per blcwer
temp. liter, 90C at 100C
10 minutes 15 minutes 30 min.
~ ~ ~ 4~3~()
Example 3
SCM-3 bar material of diameter 12mm was blasted for 10
minutes with zinc-iron alloy coated fine metal particles (trade
mar~ Z-Iron Aloyed Shot, particle size 0.2-0.3 mm, made by the
Sanpo Company) using a shot blasting system and a 15 g/m2 coating
of zinc-iron alloy was formed on the bar. The bar was then
treated for 5 minutes with a conventional zinc phosphate based
treatment solution at a temperature of 65C and a 10 g/m2 zinc
phosphate film was formed. The sample was then rinsed with water,
treated for 5 minutes with a sodium stearate solution at a
temperature of 75C and dried. A 7 g/m2 lubrication layer of
stearic acid soap was formed in this way.
Drawing tests were carried out using a draw bench in
order to evaluate the lubrication properties of this bar material.
The results obtained are shown in Table 5. When drawing under the
conditions shown in Table 4 there was no baking and the drawing
power was also low.
Table 4
.
Drawing Rate 17.8 m/min.
'
Extent of First Pass 12.0~-~10.0~ Extent of Working 30.0%
Working Second Pass 10.0~ > 8.5~ Extent of Working 27.7
_ m ird Pass 8.5~-~ 7.0~ Extent of Working 32.2%
Reference Example 3'
The weight of zinc phosphate based film formed as a
result of carrying out the same tests and treatment as in Example
3 except for the omission of the shot blasting process with the
zinc-iron alloy coated fine particles was 7 g/m2 and the film was
seen to be incomplete on examination with a microscope. The
chemical formation time was increased to 10 times that used in
Example 3 whereupon a film of weight 11 g/m2 was obtained.
--8--
3493~
The lubrication properties of the bar so obtained were
evaluated in the same way as in Example 3 and the results obtained
are shown in Table 5.
Table 5
\ Item Number of Draws Drawing Force
. Example \
Example 3 First Pass 3090
Second Pass 2369
. . Third Pass 2339
Reference ~ First Pass 3170
Example 3' Second Pass 2412
. Third Pass 2420
It is clear from Table 5 that the drawing force is lower in the
case of the bar prepared in Example 3 than in the case of the bar
from Reference Example 3', shcwing that the bar from Example 3 has
superior lubrication properties.
