U.S. patent application number 10/543627 was filed with the patent office on 2006-04-27 for oil tempered steel wire excellent in coiling workability and method for production thereof.
Invention is credited to Tadayoshi Fujiwara, Tetsuo Jinbo, Fumio Yamamoto.
Application Number | 20060088710 10/543627 |
Document ID | / |
Family ID | 32820749 |
Filed Date | 2006-04-27 |
United States Patent
Application |
20060088710 |
Kind Code |
A1 |
Fujiwara; Tadayoshi ; et
al. |
April 27, 2006 |
Oil tempered steel wire excellent in coiling workability and method
for production thereof
Abstract
An oil tempered wire, characterized in that it comprises a wire
material and, formed on the surface thereof, a coating film
comprising one or more inorganic salts selected from the group
consisting of a sulfate, a silicate and a borate. The coating film
optionally further comprises fats and oils and/or a soap exhibiting
lubricity. The oil tempered wire has a coating film exhibiting
satisfactory heat resistance and good lubricity and thus can secure
good coiling workability even in the case of a high strength wire
or a wire having a heteromorphic section.
Inventors: |
Fujiwara; Tadayoshi;
(Amagasaki-shi, JP) ; Jinbo; Tetsuo;
(Amagasaki-shi, JP) ; Yamamoto; Fumio;
(Miyada-mura, JP) |
Correspondence
Address: |
WENDEROTH, LIND & PONACK, L.L.P.
2033 K STREET N. W.
SUITE 800
WASHINGTON
DC
20006-1021
US
|
Family ID: |
32820749 |
Appl. No.: |
10/543627 |
Filed: |
December 26, 2003 |
PCT Filed: |
December 26, 2003 |
PCT NO: |
PCT/JP03/16915 |
371 Date: |
July 28, 2005 |
Current U.S.
Class: |
428/364 |
Current CPC
Class: |
C23C 30/00 20130101;
C23C 22/62 20130101; C23C 28/00 20130101; Y10T 428/2913 20150115;
B21C 37/04 20130101 |
Class at
Publication: |
428/364 |
International
Class: |
D02G 3/00 20060101
D02G003/00 |
Foreign Application Data
Date |
Code |
Application Number |
Jan 31, 2003 |
JP |
2003-023980 |
Claims
1. An oil tempered wire excellent in coiling workability, wherein a
coating film comprising one or more inorganic salts selected from a
group consisting of a sulfate, a silicate and a borate is formed on
a surface of a wire material
2. The oil tempered wire according to claim 1, wherein the
inorganic salt is one or more inorganic salts selected from a group
consisting of sodium silicate, potassium silicate, magnesium
silicate, sodium sulfate, potassium sulfate, sodium borate and
potassium borate.
3. The oil tempered wire according to claim 1, wherein the coating
film layer comprising the inorganic salt further contains a fat and
oil and/or a soap having lubricity.
4. The oil tempered wire according to claim 3, wherein the fat and
oil is a wax, and the soap is one or more salts selected from
sodium salts or potassium salts of stearic acid, palmitic acid,
oleic acid, linoleic acid and linolenic acid.
5. The oil tempered wire according to claim 3, wherein the coating
film contains the fat and oil and/or the soap in a content of 5 to
50% by mass.
6. The oil tempered wire according to claim 1, wherein a rust
preventing oil is further applied to the surface of the coating
film.
7. A production method of the oil tempered wire excellent in
coiling workability according to claim 1, comprising immersing an
oil tempered wire in an aqueous solution containing one or more
inorganic salts selected from a group consisting of a sulfate, a
silicate and a borate for forming a coating of the aqueous solution
on the wire material surface, and then drying and removing water
from the coating of the aqueous solution.
8. A production method of the oil tempered wire excellent in
coiling workability according to claim 2, comprising immersing an
oil tempered wire in an aqueous solution containing one or more
inorganic salts selected from a group consisting of a sulfate, a
silicate and a borate as well as a fat and oil and/or a soap having
lubricity for forming a coating of the aqueous solution on the wire
material surface, and then drying and removing water from the
coating of the aqueous solution.
9. The oil tempered wire according to claim 2, wherein the coating
film layer comprising the inorganic salt further contains a fat and
oil and/or a soap having lubricity.
10. The oil tempered wire according to claim 4, wherein the coating
film contains the fat and oil and/or the soap in a content of 5 to
50% by mass.
11. The oil tempered wire according to claim 2, wherein a rust
preventing oil is further applied to the surface of the coating
film.
12. The oil tempered wire according to claim 3, wherein a rust
preventing oil is further applied to the surface of the coating
film.
13. The oil tempered wire according to claim 4, wherein a rust
preventing oil is further applied to the surface of the coating
film.
14. The oil tempered wire according to claim 5, wherein a rust
preventing oil is further applied to the surface of the coating
film.
15. A production method of the oil tempered wire excellent in
coiling workability according to claim 3, comprising immersing an
oil tempered wire in an aqueous solution containing one or more
inorganic salts selected from a group consisting of a sulfate, a
silicate and a borate as well as a fat and oil and/or a soap having
lubricity for forming a coating of the aqueous solution on the wire
material surface, and then drying and removing water from the
coating of the aqueous solution.
16. A production method of the oil tempered wire excellent in
coiling workability according to claim 4, comprising immersing an
oil tempered wire in an aqueous solution containing one or more
inorganic salts selected from a group consisting of a sulfate, a
silicate and a borate as well as a fat and oil and/or a soap having
lubricity for forming a coating of the aqueous solution on the wire
material surface, and then drying and removing water from the
coating of the aqueous solution.
17. A production method of the oil tempered wire excellent in
coiling workability according to claim 5, comprising immersing an
oil tempered wire in an aqueous solution containing one or more
inorganic salts selected from a group consisting of a sulfate, a
silicate and a borate as well as a fat and oil and/or a soap having
lubricity for forming a coating of the aqueous solution on the wire
material surface, and then drying and removing water from the
coating of the aqueous solution.
Description
FIELD OF THE INVENTION
[0001] The invention relates to an oil tempered wire to be used as
a material of valve springs of internal-combustion engines and a
material of bridging springs. Furthermore, the invention relates to
a production method for the oil tempered wire which enables
lubricity between a material and a tool to be improved remarkably
in spring working so that the productivity and precision of the
springs can be improved.
BACKGROUND ART
[0002] With respect to a wire material to be used as a material for
the above-mentioned various kinds of the spring, it is common to
produce the wire by heat treatment of quenching and tempering,
so-called oil tempering, to improve the properties, after
wire-drawing process. The wire material produced in such a manner
is to be formed into a spring by coiling and in such process, in
terms of improvement of the productivity, good lubricity between
the wire material and the spring forming tool is very
important.
[0003] Various techniques to improve the lubricity in the case of
coiling oil tempered wires have been proposed so far and the
following (1) to (3) are representative examples: (1) a method of
controlling components, the thickness and the adhesion property of
an oxide scale formed on the surface of an oil tempered wire to be
proper values to produce an oxide coating with good workability
(e.g. Japanese Patent Application Publication No. 5-14771); (2) a
method of applying a lubricating oil having an anti-rust property
to an oil tempered wire in place of a rust-preventing oil; and (3)
a method of controlling the thickness of an oxide scale formed on
the surface of an oil tempered wire to be a prescribed thickness or
thinner and forming a coating film of an alkyd resin, a resin
mainly containing an amino acid, or the like as means for assisting
the coiling property (e.g. Japanese Patent No. 3,003,831).
[0004] On the other hand, it has been said in recent years that an
oil tempered wire to be used for valve springs and the like of
automotives are required to satisfy the following requirements: (1)
to meet the lightweight requirement for automobiles, a wire is
required to have a further improved strength and a thinner diameter
and tends to be used under high design stress: and (2) a wire with
a modified cross-section, for example an oval shape, tends to be
used more increasingly to install a spring in a narrower space and
at the same time assure a needed stroke. In a coiling work of the
wire with a modified cross-section, to secure needed spring
precision, it is required to strictly suppress rotation of the
wiring material during the coiling.
[0005] Particularly, in recent years, in conformity to the
requirements for high performance and lightweight, designs of
spring forms have to be proper to be used under high load stress
and materials with higher strength and hardness tend to be used
often for producing springs with a large amount of plastic
deformation degree in spring machining.
[0006] A spring is required to have satisfactorily small diameters
and wide spring pitches so as to have a ratio (D/d) of an average
diameter of spring (D) to the wire diameter (d) smaller than 3.5 as
a practical evaluation standard.
[0007] At the time of coiling for obtaining such a spring, because
of wear of a material against a tool and heat generation by
working, the temperature in the interface of the material and the
tool is increased. At the time of coiling, although good
workability is assured by an oxide coating formed on the wire
material surface and application of a rust preventing oil, the heat
resistance of the lubricating coating cannot necessarily be
sufficient in such a lubricating method to result in occurrence of
adhesive wear between the wire material and the tool, and
difficulty of efficient production of a spring with a prescribed
shape.
[0008] Also, in the case of producing a spring from a wire material
with a modified cross section, in order to keep the precision high,
it is required to carry out coiling the material by fixing the
material by several guides and pins with small clearance. Springs
produced from high strength wire materials with modified
cross-sections tend to be used increasingly.
[0009] Under the above-mentioned situation, it possibly leads to
the following undesirable consequences that only a conventional
oxide coating on the oil tempered wire surface and a rust
preventing oil are used because the lubricating effect of the rust
preventing oil is not so significant: 1: owing to insufficient
lubricity between a coiling tool such as a coiling pin and a guide
and the wire surface, seizure easily occurs to shorten the tool
life and therefore, the operation of the machine has to be stopped
and the tool has to be replaced or repaired to result in decrease
of productivity: 2: in the case the seizure occurs, dispersion of
the diameter and the free length (the length of the spring without
any load) of a product spring tends to be wide and the precision of
the product is worsened and the yield of the product tends to be
decreased as well: and 3: further, the seizure as described causes
harmful linear scratches on the spring surface and causes adverse
effects on the spring life in some cases.
[0010] In view of the above-mentioned state of the art, it is an
object of the present invention to provide a lubricating coating
with sufficient heat resistance and accordingly secure good
lubricity and to provide an oil tempered wire having secured good
coiling workability even if the wire is a high strength wire or an
oil tempered wire with a modified cross-section.
DISCLOSURE OF THE INVENTION
[0011] An oil tempered wire of the present invention achieving the
above-mentioned object is characterized in that a coating film
layer comprising one or more inorganic salts selected from a group
consisting of a sulfate, a silicate and a borate is formed on a
surface of a wire material.
[0012] As the inorganic salt of the coating film, one or more
compounds selected from a group consisting of sodium silicate,
potassium silicate, magnesium silicate, sodium sulfate, potassium
sulfate, sodium borate and potassium borate can be used.
[0013] With respect to the oil tempered wire of the invention, the
coating film layer comprising the inorganic salt is preferable to
further contain a fat and oil and/or a soap having lubricity if
necessary. As the fat and oil to be added to the coating film,
waxes such as petroleum waxes can be used, and as the soap, one or
more salts selected from sodium salts or potassium salts of stearic
acid, palmitic acid, oleic acid, linoleic acid and linolenic acid
can be used. In the case of adding a fat and oil and/or a soap, the
content of them in the coating film is preferably adjusted to be 5
to 50% by mass.
[0014] In the oil tempered wire of the invention, it is also
preferable to further apply a rust preventing oil on the coating
film surface if necessary and accordingly the anti-rust property of
the oil tempered wire can further be improved.
[0015] On the other hand, to produce the oil tempered wire of the
invention, the lubricant coating film may be formed on the wire
material surface by immersing an oil tempered wire in an aqueous
solution containing one or more inorganic salts selected from a
group consisting of a sulfate, a silicate and a borate or in an
aqueous solution containing a fat and oil and/or a soap having
lubricity in addition to the inorganic salts, if necessary, for
forming a coating of the aqueous solution on the wire material
surface, and then drying and removing water from the coating of the
aqueous solution. To carry out the method, the solid matter
concentration in the aqueous solution coating is preferably 1.5 to
30% by mass.
BEST MODE FOR CARRYING OUT OF THE INVENTION
[0016] Inventors of the present invention have made various
investigations and experiments of means of preventing seizure from
a viewpoint of improving lubricity and heat resistance in coiling
of an oil tempered wire for a spring, have found the
above-mentioned object could be accomplished in the above-mentioned
manner, and have completed the present invention.
[0017] The lubrication mechanism of a wire and a tool in presently
carried out spring machining is attributed to an oxide film on the
wire surface formed during the production process of the oil
tempered wire and the lubricity of a rust preventing oil applied to
the surface of a wire product presently made available. On the
other hand, only improvement of the lubricity by the rust
preventing oil alone is insufficient in order to satisfy the
requirement for an oil tempered wire with high strength and a
modified cross-section, requirement for a product spring with a
high precision, requirement for improvement of the productivity by
high speed coiling.
[0018] Also, with respect to the oxide coating film on the wire
surface, it is required for the oxide coating film to maintain the
rust preventing oil and have a certain coating thickness to
moderate the direct contact between the wire material and a tool,
however if the thickness becomes so thick, the adhesion property of
the oxide coating film is deteriorated to result in undesirable
consequence that the coating is separated before a coiling pin.
Such an undesirable consequence leads to deterioration of the
coiling workability.
[0019] Accordingly, the oxide coating film has to be controlled to
have a proper thickness and a method of controlling the thickness
of an oxide coating film is proposed (e.g. in Japanese Patent
Publication No. 5-14771), but it is still insufficient to
satisfactorily meet the requirement of lubricity improvement, which
has become more and more demanded, in coiling machining.
[0020] To satisfy such a requirement, the inventors of the
invention have divided the functions which the oxide coating film
and the rust preventing oil in the coiling machining should carry
out as follows and have noted that the composition of a coating
film to be formed on the spring surface should properly be
controlled so as to execute the functions: (a) a function of
moderating the direct metal contact of a tool such as a pin with
the material (the wire surface); (b) a function of decreasing the
friction coefficient of the rust preventing oil as a lubricating
oil; and (c) a function as a rust preventing oil for the wire
material.
[0021] The above-mentioned function (a), it has been found that not
only the oxide coating film on the wire surface formed in the oil
tempering treatment but also deposition and retention of inorganic
fine hard particulates on the wire material surface can positively
reinforce the role as a buffering agent having heat resistance
between the tool and the material at the time of machining.
[0022] Also, it has been found that a sulfate, a silicate and a
borate are optimum as practical inorganic fine particulates. That
is, if a coating film layer containing the above-mentioned various
inorganic salts is formed on the oil tempered wire material
surface, the above-mentioned function (a) can efficiently be
exhibited. Further, as the means for reinforcing the
above-mentioned function (b), a lubricating component such as a fat
and oil and a soap is positively added to the coating film layer,
based on necessity, to further improve the lubricity. With respect
to the above-mentioned function (c), a rust preventing oil is
applied further to the surface of the coating film layer, based on
necessity, to exhibit the function. Additionally, it has been
confirmed that the respective components in the coating film layer
do not cause any adverse effect on the anti-rust property of the
rust preventing oil.
[0023] The oil tempered wire of the invention is basically the wire
wherein the coating film containing the inorganic salt is formed on
the surface thereof and as the inorganic salt to be used in this
case, a sulfate such as potassium sulfate and sodium sulfate; a
silicate such as sodium silicate, potassium silicate, and magnesium
silicate; and a borate such as sodium borate and potassium borate
can be exemplified and one of them can be used, or two or more of
them can be used in combination. Among them, in terms of the heat
resistance and environmental affinity, particularly preferable
inorganic salts are a silicate such as sodium silicate, potassium
silicate, and magnesium silicate and a sulfate such as sodium
sulfate and potassium sulfate.
[0024] Besides the above-mentioned inorganic salt, the coating film
layer to be formed on the wire material surface of the invention
may contain a fat and oil and/or a soap if necessary and these
components have a function of providing lubricity to the coating
film [the above-mentioned function (b)].
[0025] As the above-mentioned fat and oil, waxes such as petroleum
waxes can be exemplified and as the above-mentioned soap, one or
more salts selected from sodium salts or potassium salts of stearic
acid, palmitic acid, oleic acid, linoleic acid and linolenic acid
can be used. The content of the fat and oil and/or the soap in the
coating film is preferably in a range of 5 to 50% by mass. That is,
if the content of the fat and oil and/or the soap in the coating
film is less than 5% by mass, the effect to provide the lubricity
is insufficient and if it exceeds 50% by mass, the ratio of the
inorganic salt is lowered to lead to insufficiency of the strength
and heat resistance of the coating film and difficulty to withstand
strong machining.
[0026] Formation of the lubricant coating film layer containing the
above-mentioned respective components on the oil tempered wire
provides sufficiently high heat resistance to the lubricant coating
film and secures the good lubricity and accordingly gives an oil
tempered wire having good coiling workability even in the case of
an oil tempered wire having high strength or a modified
cross-section. In such an oil tempered wire is also preferable to
be further coated with a rust preventing oil on the coating film
surface, based on the necessity. Accordingly, the oil tempered wire
is provided with the anti-rust property [the above-mentioned
function (c)]. As the rust preventing oil to be used for this case,
those which have been used conventionally may be used and mixtures
of petroleum type hydrocarbons and rust preventing additives can be
exemplified.
[0027] The oil tempered wire of the invention is the wire wherein
the coating film layer containing the above-mentioned components is
formed on the surface of the wire material and with respect to a
method of forming the coating film layer, the lubricant coating
film can be formed on the wire material surface, for example, by
immersing an oil tempered wire in an aqueous solution containing
the various inorganic salts or an aqueous solution further
containing, if necessary, a fat and oil and/or a soap having
lubricity at proper ratio other than the inorganic salts for
forming an aqueous solution coating on the wire material surface,
and then drying out the water in the aqueous solution coating.
[0028] In the case of carrying out the method, the solid matter
concentration (that is the concentration of the inorganic salts and
if necessary, the fat and oil and/or the soap) in the aqueous
solution is preferably 1.5 to 30% by mass. If the solid matter
concentration is lower than 1.5% by mass, the effect of the
lubricant coating film cannot be obtained and if it exceeds 30% by
mass, these components are oversaturated and unevenly distributed
in the coating film to result in a problem of uniformity of the
coating film.
[0029] The invention is effective in the case of application to a
spring having a spring diameter wherein a ratio (D/d) of the
average diameter (D) and the wire diameter (d) of the spring is
lower than 3.5 and having a large spring pitch; however the
invention should not be limited to such a spring and exerts the
objective effects also in application to springs having a ratio
(D/d) of 3.5 or higher.
EXAMPLES
[0030] Hereinafter, the features and advantages of the present
invention will be described more in detail along with Examples.
However, it is not intended that the invention be limited to the
Examples to be illustrated. Modifications and substitutions to
specific process conditions and structures can be made without
departing from the spirit and scope of the invention.
Examples
[0031] High strength oil tempered wires for valve springs which
were made of various steels shown in Table 1 were produced by
conventional quenching and tempering treatment. Oxide coating films
with the same thickness as that of a conventional agent were found
formed on the surfaces of the respective oil tempered wires
(reference to Table 2). In this case, wires having oval
cross-sectional shapes and wires having round shapes were produced
and the tensile strength of them was measured. TABLE-US-00001 TABLE
1 Chemical component composition (% by mass) Steel type C Si Mn P S
Cu Ni Cr V Remarks A 0.54 1.43 0.69 0.013 0.008 0.01 -- 0.71 --
Silicon--chromium steel B 0.63 1.44 0.62 0.011 0.010 0.01 -- 0.67
0.092 High strength silicon--chromium steel C 0.59 2.00 0.89 0.012
0.009 0.01 0.26 0.99 0.095 High strength silicon--chromium
steel
[0032] Lubricant coating films were formed on the surfaces of the
above-mentioned respective oil tempered wires by the following
methods 1 to 5. In this case, to reinforce the anti-rust property,
as rust preventing oils for ferrous materials, commonly used
mixtures of petroleum type hydrocarbons and rust preventing
additives were used for applying to the coating films.
[Coating Film Formation Method 1]
[0033] The coating film was formed on the wire material surface by
immersing an oil tempered wire in an aqueous solution at 70.degree.
C. containing sodium silicate, potassium silicate, and potassium
sulfate and adjusted to have a solid matter concentration 11% by
mass and removing water from the formed solution coating by
drying.
[Coating Film Formation Method 2]
[0034] To an aqueous solution containing sodium silicate, potassium
silicate, and potassium sulfate was added a wax. The coating film
was formed on the wire material surface by immersing an oil
tempered wire in the aqueous solution at a room temperature
(25.degree. C.) with a solid matter concentration 11.5% by mass and
removing water from the formed solution coating by drying.
[Coating Film Formation Method 3]
[0035] To an aqueous solution containing sodium silicate and
potassium silicate was added a wax. The coating film was formed on
the wire material surface by immersing an oil tempered wire in the
aqueous solution at a room temperature (25.degree. C.) with a solid
matter concentration 8.5% by mass and removing water from the
formed solution coating by drying.
[Coating Film Formation Method 4]
[0036] To an aqueous solution containing sodium silicate and
potassium silicate was added sodium stearate as a soap component.
The coating film was formed on the wire material surface by
immersing an oil tempered wire in the aqueous solution at a room
temperature (25.degree. C.) with a solid matter concentration 10%
by mass and removing water from the formed solution coating by
drying.
[Coating Film Formation Method 5]
[0037] To an aqueous solution containing sodium silicate, potassium
silicate, and magnesium silicate was added a wax. The coating film
was formed on the wire material surface by immersing an oil
tempered wire in the aqueous solution at a room temperature
(25.degree. C.) with a solid matter concentration 8.5% by mass and
removing water from the formed solution coating by drying.
[0038] The obtained oil tempered wires were subjected to tensile
strength measurement and at the same time coiled to produce sprigs
having the various D/d ratios, and the dispersion .sigma.(D) of the
coil diameters and the dispersion .sigma.(H) of the free lengths of
the springs were investigated. The dispersion .sigma.(H) of the
lengths was shown as the dispersion per 1 mm free length
[dispersion .sigma.(H)/H] calculated by dividing the dispersion
.sigma.(H) by the free length H (mm). Also, an investigation was
carried out in which the number of coils is counted until a tool is
needed to be grinded or repaired due to occurrence of a linear
scratch (galling) caused by poor lubricity between the wire surface
and a tool during the spring machining, observing the spring
surfaces appropriately.
[0039] The results are collectively shown in the following Table 2.
Table 2 also show the results of the evaluations carried out
similarly to wire materials coated with common rust preventing oils
alone (Nos. 1, 3, 6, and 11 in Table 2). TABLE-US-00002 TABLE 2
Dispersion Dispersion The number of Coating film Cross-section
Tensile Oxide film of of coils until formation Steel shape of wire
Wire diameter strength thickness diameter free length Occurrence
re-grinding of tool No. method type material (mm) (MPa) (.mu.m) D/d
.sigma.(D) .sigma.(H)/H of scratches (pieces) 1 -- A Oval Major
axis: 4.0 1920 1.6 3.0 0.042 0.0036 Found 2000 2 1 A Oval Major
axis: 4.0 1920 1.6 3.0 0.026 0.0022 None 10000 3 -- B Oval Major
axis: 4.4 2045 1.8 3.8 0.035 0.0022 Found 2000 4 1 B Oval Major
axis: 4.4 2045 1.8 3.8 0.023 0.0017 None 10000 5 3 B Oval Major
axis: 4.4 2045 1.8 3.8 0.021 0.0015 None 10000 6 -- C Round 5.0
2060 2.1 3.2 0.045 0.0049 Found 1500 7 1 C Round 5.0 2060 2.1 3.2
0.035 0.0023 None 10000 8 2 C Round 5.0 2060 2.1 3.2 0.038 0.0022
None 10000 9 3 C Round 5.0 2060 2.1 3.2 0.032 0.0022 None 10000 10
4 C Round 5.0 2060 2.1 3.2 0.039 0.0026 None 10000 11 -- C Round
3.2 2150 2.0 2.9 0.129 0.0096 Found 1000 12 3 C Round 3.2 2150 2.0
2.9 0.043 0.0028 None 10000 13 2 C Round 2.7 2200 1.8 7.6 0.022
0.0026 None 10000 14 3 C Round 6.1 2040 2.0 3.9 0.031 0.0012 None
10000 15 5 C Round 6.1 2040 2.0 3.9 0.027 0.0013 None 10000
[0040] According to the results, the following can be understood.
At first, as compared with those coated conventionally only with
the oxide coating film and the rust preventing oil (Nos. 1, 3, 6,
and 11), the coils (Nos. 2, 4, 5, 7 to 10, and 12 to 15) satisfying
the factors defined by the invention had narrow coil diameter
dispersion and free length dispersion and the number of coiling
times until the time of occurrence of scratches was high and no pin
grinding was needed until completion of the coiling of 1 lot
(10,000 coils). In other words, it was found that the oil tempered
wires of the invention gave springs as products excellent in the
precision at a high productivity, scarcely damaging the tool, which
requires wasteful preparatory time. According to the investigations
carried out by inventors of the invention, it was also confirmed
that the lubricating components to be employed in the invention did
not cause any adverse effects in the quality and working
environments in tempering treatment and shot-pinning in the spring
manufacturing process.
INDUSTRIAL APPLICABILITY
[0041] The invention is constituted as described above and in the
coiling of a spring, the heat resistance of a lubricating film
between a wire and a tool is improved and the lubricity itself is
also improved, so that in the case of manufacturing a coil with a
small D/d ratio from a high strength wire by severe machining, the
machining can be carried out easily and the invention practically
causes the following effects (a) to (c). (a) The dispersion of the
free lengths of springs as products and the dispersion of coil
diameters of the springs are narrowed to improve the machining
yield. (b) The lives of machining tools are prolonged and the time
taken to replace or repair the tools is shortened to improve the
productivity. (c) The scratches by galling of the surfaces of
springs are hardly formed to improve the reliability of the
products.
[0042] Further, the invention providing the above-mentioned oil
tempered wire is (1) optimum in the case of machining a wire with
modified cross-sections, e.g. an oval cross-sectional shape,
requiring to have better lubricity; (2) suitable in the case of
coiling a wire with large diameter and having high plane pressure
to tool surfaces; and (3) applicable to coiling at an increased
coiling speed owing to the high heat resistance of the coating film
and thus contributes to improvement of the productivity.
* * * * *