FIELD OF THE INVENTION
[0001] In recent years, important parts for transportation machineries are often manufactured
by applying cold forging of more than 70% of reduction area at one stroke to a steel
of having the tensile strength of more than 300 N/mm
2. This cold forging process is usually called as "high efficient cold forging". The
present invention is related to a process to form a lubricative coating layer having
excellent performance as lubricant onto the surface of a metallic material to be subjected
to the high efficient cold forging without any previous chemical treatment. The present
invention is related also to an aqueous lubricant of one process type used for high
efficient cold forging, which facilitates to simplify the conventional lubricant layer
forming processes, that is, to minimize space area required for forming the lubricative
coating layer and not to increase industrial waste products.
PRIOR ART
[0002] Generally, in cold forging of metallic material, such as steel and stainless steel,
coating layer is formed onto the surface of a metallic material. The coating layer
may prevent a direct contact of the metallic material with a forging tool, and may
decrease a surface defects of burning and biting of the metallic material which may
arise by direct contact with the forging tool.
[0003] There are two types of the coated layers to be formed onto the surface of a metallic
material, one of which is the type that a lubricant is being adhered directly onto
the surface of the metallic material and the other is the type that a lubricant is
being used onto the chemical layer being formed previously over the surface of the
metallic material.
[0004] The lubricative coating formed by being adhered directly onto the surface of a metallic
material has less adhesive performance than the lubricative coating by being used
lubricant on to the chemical layer formed previously over the surface of the metallic
material, and therefore, the former type is generally used for the cold forging with
less amount of deformation.
[0005] In case of the latter type, the chemical layer is firstly formed on the surface of
a metallic material through a chemical process such as phosphate layer forming process
and oxalate layer forming process, which generally form chemical layer suitable as
a carrier of a lubricant, and the lubricant having high lubricative property is used
on to the chemical layer. In this type, the formed film has a bilayer structure consisting
of a chemical layer as a carrier and a lubricant layer, which has high resistant property
against surface defects.
[0006] From this reason, this type has been widely employed in the field such as wire drawing,
tube drawing and cold forging. Particularly, in the cold forging where severe deformation
is required, a process firstly forming the chemical layer comprising phosphate or
oxalate and then using a lubricant onto the chemical layer is popularly employed.
[0007] The lubricant applied onto the chemical layer may be divided into major two groups
in terms of the usage. The first group includes a lubricant to be mechanically adhered
onto the chemical layer and the second group includes a lubricant which reacts with
the chemical layer.
[0008] The first group of lubricant includes one prepared by using mineral oil, vegetable
oil or synthetic oil as base oil and containing an extreme pressure additive in the
base oil and one prepared by dissolving a solid lubricant, such as graphite and molybdenum
disulfide, together with a binder component into the water. These lubricants may have
advantage of easy for controlling the solution since they can be used simply by means
of spray coating and dipping coating, however, as they have just a low lubricative
properties, they tend to be used for a case where less amount of deformation of metallic
material is required.
[0009] On the other hand, in the second group of lubricant, a reactive soap such as sodium
stearate is used for a cold forging where particularly high lubricative property is
required. The reactive soap reacts with the chemical layer and provides a layer of
high lubricative property.
[0010] However, since the reactive soap gives a chemical reaction, control of the composition
of the solution, temperature control for the chemical reaction and renewal control
of the deteriorated solution, etc. are very important during the process. Further,
for example, in the reaction of the phosphate layer with reactive soap, insoluble
matter are produced in the solution along with the formation of lubricative layer.
These insoluble matter are called as sludge, which is troublesome since it is required
to be regularly excluded from the solution.
[0011] Further, the waste water arising in the formation process of the phosphate layer
is containing the phosphate compounds. Such waste water should be appropriately treated
in order to remove its contained phosphate compounds. In most case, such waste water
containing phosphate compounds is subjected to neutralization with slaked lime to
precipitate the phosphate. The precipitated phosphate compounds is separated from
water and is discarded as industrial waste together with the sludge described above.
[0012] Recently, it is a big issue to reduce waste products from the industries for global
environmental protection, and industrial waste containing phosphate compounds has
been considered as serious problem in view of environmental protection. And therefore,
new processes which do not produce waste products are highly desired.
[0013] Further, in the conventional process that produces a phosphate layer and uses a reactive
soap on the phosphate layer, simplification and improvement of the process is required,
since it requires wide area for the processing plant, greater time and complex control
of the process. For example, in the process of producing the phosphate layer, frequent
analysis of the phosphating solution on its free acidity, total acidity and concentration
of accelerator has to be carried out by means of titration and the like. Further,
in the reactive soap application process, analysis of free acidity and concentration
of its constituent are regularly and manually carried out.
[0014] In order to solve the problems as described above, JP52-20967A, wherein a lubricant
composition containing water soluble polymer or its aqueous emulsion as the base component,
a solid lubricant and a film-forming agent is disclosed. However, no composition which
has the same effect as the conventional process of using a chemical layer and a reactive
soap has been obtained.
[0015] In order to solve the problems described above, another prior art of "Aqueous lubricant
used for cold working of metallic material" disclosed in JP10-8085A can be cited.
This prior art relates to an aqueous lubricant used cold forging of metallic material
in which (A) water soluble inorganic salt, (B) solid lubricant, (C) at least one oil
selected from a group consisting of chemical oil, animal oil, vegetable oil and synthetic
oil, (D) surface active agent and (E) water are well dispersed and emulsified homogenously.
[0016] This prior art is related to an aqueous non-reactive type lubricant, and is aiming
at simplifying the conventional three processes of phosphate layer formation, water
rinsing and reactive soap application. That is, in this process, the lubricant film
is formed directly on the surface of the metallic material by contacting the metallic
material with the aqueous lubricant of one process type by means of dipping or the
like, without forming any chemical layer previously on the surface of the metallic
material. This type of lubricant is generally called as lubricant of one process type.
[0017] However, the lubricant according to this prior art is too unstable to use in an industrial
scale since it contains emulsified oil component, and it is not steady to show a high
lubricative properties in high efficient cold forging.
[0018] As another prior art, an invention of "A lubricant composition used for cold working
of metallic materials" shown in JP2000-63380A can be cited. This prior art is directed
to a lubricant comprising (A) synthetic resin, (B) water soluble inorganic salt and
water, wherein the ratio of (B) / (A) by weight in solid state is in a range from
0.25/1 to 9/1 and the synthetic resin is either dissolved or dispersed in the composition.
However, this composition is also not steady to show a high lubricative properties
in high efficient cold forging.
DISCLOSURE OF THE INVENTION
[0019] Therefore, it is an object of the present invention to solve the problems of the
conventional art as described above and to provide a new aqueous lubricant of one
process type used for high efficient cold forging, which is being suitable for manufacturing
of an important parts of transportation machineries, which is being simplified the
operation without requiring any previous chemical treatment to form a coating layer
and is favorable for keeping of good global environment.
[0020] The invention of the present invention have been made by investigation for solving
the problems described above and have found that a suitable aqueous lubricant of one
process type is obtainable by combining an water soluble inorganic salt, wax and metal
salt of a fatty acid in an aqueous solution at a specific combining rate.
[0021] The aqueous lubricant of the present invention requires only one step of applying
the lubricant and does not require 3 steps consisting of chemical reaction for phosphate
layer formation, water rinsing and application with a reactive soap. These 3 steps
are required in the conventional process. Also, the aqueous lubricant of the invention
is a simplified process and may decrease to produce industrial waste than the conventional
processes.
[0022] namely, the present invention is an aqueous lubricant of one process type used for
high efficient cold forging characterized in that the aqueous lubricant comprises
(A) a water soluble inorganic salt, (B) wax and (C) a metal salt of a fatty acid,
wherein these component are dissolved or dispersed in an aqueous solution and the
ratio by weight in solid state of (B) / (A) is in a range of 0.60 ∼ 0.70 and the ratio
by weight in solid state of (C) / (A) is in a range of 0.1 ∼ 0.3. And the lubricant
of the present invention is suitable for manufacturing an important parts of transportation
machineries.
[0023] The preferable water soluble inorganic salt may be selected from a group consisting
of sulfate, silicate, borate, molybdate and tungstate, and the wax is preferably a
synthetic wax being dispersed in water and having a melting point in a range of 70
∼ 150°C. Further, the metal salt of a fatty acid is preferably a compound obtained
by reacting saturated fatty acid of C12 ∼ C26 with at least one metal selected from
a group consisting of zinc, calcium, barium, aluminum, magnesium and lithium.
BRIEF DESCRIPTION OF DRAWINGS
[0024]
Fig. 1 is a view showing the dimensional accuracy in cold forging process 2 shown
later in the embodiment.
MODES FOR CARRYING OUT THE INVENTION
[0025] Now, the present invention is explained further in detail. The water soluble inorganic
salt (A) used in the aqueous lubricant of the present invention is contained in order
to give hardness and strength to the lubricative coating layer formed on the surface
of the metallic material. The water soluble inorganic salt having such performance
is required to have a property to be homogeneously dissolved in the aqueous lubricant
and to form a strong lubricative coating layer when drying. As the inorganic salt
giving such property, it is preferable to use at least one selected from a group consisting
of sulfate, silicate, borate, molybdate and tungstate.
[0026] As the examples for the water soluble inorganic salt described above, sodium sulfate,
potassium sulfate, potassium silicate, sodium borate (sodium tetraborate), potassium
borate (potassium tetraborate), ammonium borate (ammonium tetraborate), ammonium molybdate,
sodium molybdate and sodium tungstate may be given. Any of these salts may be used
either alone or in combination of 2 or more salts.
[0027] As the wax (B), it is preferable to use a synthetic wax, though there is no specific
limitation in the structure and the type. The wax may melt by a heat generated during
the plastic deformation in cold forging, thereby improving the lubricative property
of the lubricative coating layer. From this reason, it is preferable having a melting
point in a range of 70 to 150°C and being stable in aqueous lubricant so as to perform
the preferable lubrication at the initial stage of the cold forging.
[0028] The practical examples for the wax may include microcrystalline wax, polyethylene
wax, polypropylene wax and the like. These waxes are preferably contained in a form
of water dispersion or water emulsion to the aqueous lubricant. The (B) / (A), namely
the ratio by weight in solid state of the wax (B) relative to the water soluble inorganic
salt (A) is preferably in a range of 0.6 ∼ 0.7. In high efficient cold forging, which
is a hard process, there is possibility that the lubricative performance of the lubricative
coating layer may be insufficient when the ratio described above is less than 0.6,
while the adhesive performance of the lubricative coating layer may be insufficient
when said ratio is more than 0.7.
[0029] The metal salt of a fatty acid (C) used in the present invention is for providing
lubricative performance, and as the metal salt of a fatty acid, though there is no
specific limitation in the type, it is preferable to use a product obtained by reacting
saturated fatty acids of C12 ∼ C26 with at least one metal selected from a group consisting
of zinc, calcium, barium, aluminum, magnesium and lithium.
[0030] However, it is more preferable to use any of calcium stearate, zinc stearate, barium
stearate, magnesium stearate and lithium stearate. The metal salt of a fatty acid
used in the present invention exists in an aqueous lubricant in dispersed from, and
a known surface active agent may be used when required.
[0031] The (C) / (A), namely the ratio of the aqueous inorganic salt (A) and the metal salt
of a fatty acid (C) is set at a rate ranging from 0.1 to 0.3 by weight as the solid
state. Under a severe working condition like the high efficient cold forging, the
knockout property of the processed parts may be insufficient when said ratio is less
than 0. 1. However, under a severe working condition like high efficient cold forging,
the accuracy of dimension of the obtained cold forged parts could be insufficient
when said ratio is more than 0.3.
[0032] When a surface active agent is required for dispersing the metal salt of fatty acid
and the wax in the aqueous lubricant, any surface active agent of nonionic, anionic,
amphoteric and cationic type may be used. The nonionic surface active agent includes,
but not specifically limited to, polyoxyethylene alkyl ester, polyoxyalkylene (ethylene
or propylene) alkyl phenyl ether, polyoxyethylene alkyl ester comprising polyethylene
glycol (or ethylene oxide) and higher fatty acid (C12 ∼ C18, for example), polyoxyethylene
sorbitan alkyl ester comprising sorbitan, polyethylene glycol and higher fatty acid
(C12 ∼ C18, for example).
[0033] The anionic surface active agent includes, but not specifically limited to, fatty
acid salts, sulfuric esters, sulfonates, phosphoric esters and dithiophosphoric esters.
The amphoteric surface active agent includes, but not specifically limited to, carboxylates
either in amino acid configuration or betaine configuration, sulfuric esters, sulfonates,
phosphoric esters. The cationic surface active agent includes, but not specifically
limited to, amine salts of fatty acids, quaternary ammonium salts and the like. Each
of these surface active agent may be used either alone or in combination of two or
more of them.
[0034] The aqueous lubricant of one process type of the present invention is used for high
efficient cold forging for metallic materials where more than 70% of section area
reduction rate are given at one stroke. The important parts for transportation machineries
used for automobiles and motorcycles, such as power train and chassis may be produced
preferably by applying the aqueous lubricant of the present invention. The shape of
the cold forging products is not particularly limited to cylindrical shape and is
also applicable foe processing of more complicated configuration, such as gears and
gear shafts.
[0035] Regarding the process to apply the aqueous lubricant of the present invention to
the metallic material, though it is not specifically limited to, dipping method can
be employed. The aqueous lubricant may satisfactorily be applied when the surface
of the metallic material is fully covered with the aqueous lubricant by any method.
After the coating, it is required to dry the coated aqueous lubricate.
[0036] The preferred coating operation can be given as below.
1) Shot blasting
2) Rinsing with hot water(Removal of soiled matter such as iron powder and heating
the metallic material) : 70 ∼ 90°C, 1 ∼ 3 minutes
3) Application of the aqueous lubricant : 50 ∼ 70°C, dipping for 1 ∼ 3 seconds
4) Drying: By air blowing under ambient temperature, 1∼2 minutes
5) Cold forging
[0037] The weight of the formed lubricative coating layer (the amount of the coating) onto
the surface of the metallic material is an important factor since it greatly affects
the processing performance, such as lubricative performance and resistance to burning
and biting. The weight of the formed coating layer may be calculated based on the
weight difference between before and after the formation of the coating layer and
the coated area of the metallic material.
[0038] Weight of the lubricative coating layer =(Weight after the formation of the coating
layer - Weight before the formation of the coating layer)/(Area of the metallic material)
[0039] The weight of the formed lubricative coating layer suitable for the following cold
forging process, it is preferable to be in a range of 5 ∼15 g/cm
2.
[0040] When the weight of the formed coating layer is less than 5 g/cm
2, sufficient lubricative performance cannot be provided, and causing burning defects
during the high efficient cold forging. Whereas, when the weight of the formed coating
layer exceeds 15 g/cm
2, exfoliated lubricant film(dregs) may tend to remain in the cold forging mold, and
the dregs in the cold forging mold may adversely affect the dimension accuracy of
the cold forged products by forming a partial underfill portion of the forged products.
The concentration of the constituent of the aqueous lubricant can be controlled so
as to adjust the weight of the formed lubricative coating layer to be in the range
described above.
EMBODIMENT EXAMPLES AND COMPARATIVE EXAMPLES [I]
[0041] Now, the present invention is further explained with referring Embodiment Examples
and Comparative Examples given in the following.
<Metallic materials>
[0042] 60, 000 pieces of steel bar for counter shaft : Diameter 50 mm, length 140 mm.
Grade of steel : JIS G 4105 SCM420.
Surface pretreatment : Shot blasted aiming at removing scales for 14 minutes by using
shot balls of 0.5mm diameter.
<Lubrication process A : One process type>
[0043]
1) Washing with hot water of 80°C : For removal of shot blast powder and preliminary
heating
2) Lubrication process : Dipping for 1 min. into a lubricant of 60°C.
3) Drying : Air blowing under room temperature for 1 min.
Total time (Time for processing + Time for transportation) for lubrication process
A : 2 minutes and 30 seconds
Total plant area necessary for lubrication process A : 9 m2
<Lubrication process B : Conventional type (phosphate layer + Reactive soap)>
[0044]
1) Degrease by alkali degreasing agent : (Trademark : Parclean 357, manufactured by
Nippon Parkerizing Co., Ltd), being diluted to 3% aqueous solution, 80°C, 10 minutes
2) Washing with water : tap water, room temperature, 5 minutes
3) Washing with acid : 10% aqueous solution of hydrochloric acid, room temperature,
5 minutes
4) Washing with water : tap water, room temperature, 5 minutes
5) Washing with water : tap water, room temperature, 5 minutes
6) Chemical treatment by dipping in the phosphate film forming solution : Trademark
: Palbond L3675XHM (manufactured by Nippon Parkerizing Co., Ltd), being diluted to
1% aqueous solution, 80°C, 10 minutes
7) Washing with water : tap water, room temperature, 5 minutes
8) Washing with water : tap water, room temperature, 5 minutes
9) Treatment with reactive soap : (Trademark : Paloob 236H, manufactured by Nippon
Parkerizing Co.,Ltd.), being diluted to 1% aqueous solution, 90°C, 10 minutes
10) Washing with hot water : tap water, 80°C, 5 minutes
11) Drying : Air blowing under room temperature, 10 minutes
Total time (Time for processing + Time for transportation) necessary for lubrication
process B : 60 minutes
Total plant area necessary for lubrication B : 90 m2
<Cold forging process 1 : Resistance to burning>
[0045]
Section area reduction rate by forward extrusion : 77%
Cold forging mold : ultrahard alloy, high speed steel (Heis)
Cold forging punch : high speed steel (Heis)
Cold forging speed : 0.078 m/sec
<Cold forging process 2 : Dimensional accuracy by resistance to under fill>
[0046] A shaft specimen having a diameter of 27 mm produced in the forging process 1 was
subjected to annealing and then cold forged by forward extrusion as shown in Fig.
1 and the diameter at A part of Fig. 1 was measured.
<Evaluation>
[0047]
· Resistance to burning in cold forging process 1 : Surface defects on the cold forging
tool and cold forged products were visually observed. If surface defects are observed,
it is not acceptable.
· Dimensional accuracy in cold forging process 2 : The diameter of the A part (Fig.
1) was measured. If cold forging is in good accuracy, the diameter of the A part is
27 mm. If the diameter is less than 27 mm, it is in a state so-called "non-accurate",
which is not acceptable. A diameter of 27 mm was expressed as "o mm", and for example,
a measured diameter of 26. 5 mm is expressed as "-0. 5 mm".
· Simplification of the lubrication process : Evaluation was made based on the number
of treatment steps in lubrication process and the total plant area necessary for lubrication
process. Less treatment step and less area are preferable.
· Environmental protection : Amount of waste products (drainage, sludge, etc) generated
in treatment of 6,000 pieces of specimen was measured. Less amount for the treatment
is preferable.
<Embodiment Example 1>
[0048] A lubricant 1 as below was used, and coating was carried out according to lubrication
process A (one process type).
Lubricant 1 :
[0049]
Aqueous inorganic salt : Sodium tetraborate
Wax : Polyethylene wax (1% by weight of nonionic surface active agent was added for
improving dispersion).
Metal salt of fatty acid : Calcium stearate
Solid component ratio : (B) / (A) 0.70
Solid component ratio : (C) / (A) 0. 1
Weight of formed coating layer, g/cm2 : 15
<Embodiment Example 2>
[0050] A lubricant 2 as below was used, and coating was carried out according to lubrication
process A (one process type).
Lubricant 2 :
[0051]
Aqueous inorganic salt : Potassium tetraborate
Wax : Microcrystalline wax (1% by weight of nonionic surface active agent was added
for improving dispersion).
Metal salt of fatty acid : Calcium stearate
Solid component ratio : (B) / (A) : 0.6
Solid component ratio : (C) / (A) : 0. 3
Weight of formed coating layer (g/cm2) : 15
<Embodiment Example 3>
[0052] A lubricant 3 as below was used, and coating was carried out according to lubrication
process A (one process type).
Lubricant 3 :
[0053]
Aqueous inorganic salt : Sodium tetraborate
Wax : Polyethylene wax (1% by weight of nonionic surface active agent was added for
improving dispersion).
Metal salt of fatty acid : Calcium stearate
Solid component ratio : (B) / (A) : 0.6
Solid component ratio : (C) / (A) : 0.2
Weight of formed coating layer (g/cm2) : 10
<Embodimerit Example 4>
[0054] A lubricant 4 as below was used, and coating was carried out according to lubrication
process A (one process type).
Lubricant 4 :
[0055]
Aqueous inorganic salt : Sodium tetraborate
Wax : Paraffin wax (1% by weight of nonionic surface active agent was added for improving
dispersion).
Metal salt of fatty acid : zinc stearate
Solid component ratio : (B) / (A) : 0.7
Solid component ratio : (C) / (A) : 0.2
Weight of formed coating layer (g/cm2) : 12
<Comparative Example 1>
[0056] A lubricant 5 as below was used, and coating was carried' out according to lubrication
process A (one process type).
Lubricant 5 :
[0057]
Aqueous inorganic salt : Sodium tetraborate
Wax : Paraffin wax (1% by weight of nonionic surface active agent was added for improving
dispersion).
Metal salt of fatty acid : Calcium stearate
Solid component ratio : (B) / (A) : 1.0 (Out of the scope of
the present invention)
Solid component ratio : (C) / (A) : 0.2
Weight of coated film (g/cm2) : 10
<Comparative Example 2>
[0058] A lubricant 6 as below was used, and coating was carried out according to lubrication
process A (one process type).
Lubricant 6:
[0059]
Aueous inorganic salt : Sodium tetraborate
Wax ; Polyethylene wax (1% by weight of nonionic surface active agent was added for
improving dispersion).
Metal salt of fatty acid : Calcium stearate
Solid component ratio : (B) / (A) : 0.7
Solid component ratio : (C) / (A) : 0.5 (Out of the scope of the present invention)
Weight of coated film (g/cm2) : 5
<Comparative Example 3>
[0060] A lubricant 7 as below was used, and coating was carried out according to lubrication
process A (one process type).
Lubricant 7 :
[0061]
Aqueous inorganic salt : Potassium tetraborate
Wax : Polyethylene wax (1% by weight of nonionic surface active agent was added for
improving dispersion).
Metal salt of fatty acid : Calcium stearate
Solid component ratio : (B) / (A) : 0.80 (Out of the scope of the present invention)
Solid component ratio : (C) / (A) : 0.4 (Out of the scope of the present invention)
Weight of coated film (g/cm2) : 15
<Comparative Example 4>
[0062] Coating was carried out according to the lubrication process B (Phosphate layer +
Reactive soap).
<Results>
[0063] The results of the above described tests are shown in Table 1. As shown in Table
1, Embodiment Examples 1 to 4, where the aqueous lubricant of one process type of
the present invention was used for high efficient cold forging, can form a coating
layer with excellent -performance, and are less number of treatment steps and less
plant area for coating process. And, it is also understandable that the aqueous lubricant
of the present invention may not produce much industrial waste products, that is waste
drainage and waste sludge. In Comparative Example 1, where the ratio of (B) / (A)
is out of the scope of the present invention, and in Comparative Example 2, where
the ratio of (C) / (A) is higher than the scope of the present invention, burning
are observed and inferior process performance are shown. For the coating obtained
in Comparative Example 3, where both (B) / (A) and (C) / (A) are slightly different
from the scope of the present invention, the dimensional accuracy was insufficient.
Further, in Comparative Example 4, where (phosphate layer + reactive soap) were applied
as same as a conventional process, similar process performance with that obtainable
in the present invention are shown, however, this Comparative example requires more
treatment steps and requiring more plant area necessary for process, and furthermore,
it produces greater amount of waste products.
Table 1
|
Performance |
Simplification |
Enviroment |
|
(Resistance to burning)/(Dimensional accuracy) |
Number of treatment step |
Total plant area for process (m2) |
Drainage (t) |
Sludge (kg) |
Embodiment Example 1 |
Good/0 mm |
3 |
9 |
0 0 |
|
Embodiment Example 2 |
Good/0 mm |
3 |
9 |
0 0 |
|
Embodiment Example 3 |
Good/0 mm |
3 |
9 |
0 0 |
|
Embodiment Example 4 |
Good/0 mm |
3 |
9 |
0 0 |
|
Comparative Example 1 |
No good/-*1 |
3 |
9 |
-*1 |
-*1 |
Comparative Example 2 |
No good/-*1 |
3 |
9 |
-*1 |
-*1 |
Comparative Example 3 |
Good/-0.5 mm |
3 |
9 |
-*2 |
-*2 |
Comparative Example 4 |
Good/0 mm |
11 |
90 |
570 |
100 |
*1: No data due to inferior process performance. |
*2: No data due to occurrence of under fill. |
EMBODIMENT EXAMPLES AND COMPARATIVE EXAMPLES [II]
[0064]
<Metallic Materials> Steel bar of JIS G 4105 SCM420, Diameter : 50 mm, Length : 140
mm.
<Lubrication process> Same as Lubrication Process A (one process type) as in embodiment
example and comparative example [I].
<Usual cold forging> Section area reduction rate : 51%, Cold forging mold : High Speed
Steel, Cold forging punch : High Speed Steel.
<High efficient cold forging> Section area reduction rate 77%, Cold forging mold :
High Speed Steel, Cold forging punch : High Speed Steel.
<lubricant>
Using the (A), (B) and (C) as below, and aqueous lubricant of one process type was
prepared by adjusting (B) / (A) and (C) / (A) as Table 2 and tested.
Water soluble inorganic salt (A) : Sodium tetraborate
Wax (B) : Polyethylene wax
Metal salt of fatty acid (C) : Calcium stearate.
<Results>
As shown in Table 2, in the usual cold forging of which section area reduction rate
is 51%, good results are obtained in all of the lubricant, namely, good resistance
to burning as well as good dimensional accuracy can be obtained even though the ratio
of (B) / (A) is less than 0.60 or more than 0.70. On the other hand, in the high efficient
cold forging of which section area reduction rate of 77%, good lubricant performance
can be obtained only when the ratio of (B) / (A) is in a narrow range of 0.60 to 0.70.
Similarly, in usual cold forging, good results are obtained even though the ratio
of (C) / (A) is less than 0.1 or more than 0.3. However, in the high efficient cold
forging, good results can be obtained only when the ratio of (C) / (A) is in a narrow
range of 0. 1 to 0. 3.
Table 2
One process type lubricant |
Cold forging |
Resistance to burning |
Dimensional Accuracy |
(B) / (A) |
(C) / (A) |
|
|
|
0. 55 |
0. 2 |
Usual cold forging |
○ |
○ |
0. 55 |
0.2 |
High efficient cold forging |
Δ |
Δ |
0.65 |
0.2 |
Usual cold forging |
○ |
○ |
0.65 |
0.2 |
High efficient cold forging |
○ |
○ |
0.75 |
0.2 |
Usual cold forging |
○ |
○ |
0.75 |
0.2 |
High efficient cold forging |
Δ |
Δ |
0.65 |
0.05 |
Usual cold forging |
○ |
○ |
0.65 |
0.05 |
High efficient cold forging |
Δ |
Δ |
0.65 |
0.15 |
Usual cold forging |
○ |
○ |
0.65 |
0.15 |
High efficient cold forging |
○ |
○ |
0.65 |
0.35 |
Usual cold forging |
○ |
○ |
0.65 |
0.35 |
High efficient cold forging |
Δ |
Δ |
ADVANTAGE OF THE INVENTION
[0065] As described above, the aqueous lubricant of the present invention enables to form
a coating layer having high performance to the surface of metallic materials. And
less number of treatment steps and less plant area necessary for coating process are
required in the present invention. In addition, aqueous lubricant of the present invention
produces less industrial waste and is preferable for global environmental protection.
[0066] Further, the process of the present invention enables to improve the process by saving
the treatment time of coating, by increasing the efficiency of coating, by saving
the energy and by saving the production cost.