U.S. patent application number 15/129321 was filed with the patent office on 2017-06-22 for steel wire rod having lubricating coating film that has excellent corrosion resistance and workability.
This patent application is currently assigned to Kabushiki Kaisha Kobe Seiko Sho (Kobe Steel, Ltd.). The applicant listed for this patent is Kabushiki Kaisha Kobe Seiko Sho (Kobe Steel, Ltd.), NIHON PARKERIZING CO., LTD. Invention is credited to Tsuyoshi HATAKEYAMA, Hirotaka ITO, Shinobu KOMIYAMA, Takahiro OZAWA, Keita SHIIHASHI, Kasumi YANAGISAWA.
Application Number | 20170175021 15/129321 |
Document ID | / |
Family ID | 54195365 |
Filed Date | 2017-06-22 |
United States Patent
Application |
20170175021 |
Kind Code |
A1 |
SHIIHASHI; Keita ; et
al. |
June 22, 2017 |
STEEL WIRE ROD HAVING LUBRICATING COATING FILM THAT HAS EXCELLENT
CORROSION RESISTANCE AND WORKABILITY
Abstract
The present invention provides a steel wire rod including a
lubricating coating film, which can reconcile workabilities such as
wire drawability, spike property, ball ironing property and film
removability, and corrosion resistance such as long-term rust
prevention property. The steel wire rod includes a lubricating
coating film on a surface, wherein the lubricating coating film
contains a water-soluble silicate and a water-soluble tungstate, a
mass ratio of water-soluble tungstate/water-soluble silicate being
in a range of 0.7 to 10, and contains no phosphorus
Inventors: |
SHIIHASHI; Keita; (Kobe-shi,
JP) ; YANAGISAWA; Kasumi; (Kobe-shi, JP) ;
ITO; Hirotaka; (Kobe-shi, JP) ; OZAWA; Takahiro;
(Kobe-shi, JP) ; KOMIYAMA; Shinobu; (Tokyo,
JP) ; HATAKEYAMA; Tsuyoshi; (Tokyo, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Kabushiki Kaisha Kobe Seiko Sho (Kobe Steel, Ltd.)
NIHON PARKERIZING CO., LTD |
Kobe-shi
chuo-ku, Toyko |
|
JP
JP |
|
|
Assignee: |
Kabushiki Kaisha Kobe Seiko Sho
(Kobe Steel, Ltd.)
Kobe-shi
JP
NIHON PARKERIZING CO., LTD
chuo-ku, Tokyo
JP
|
Family ID: |
54195365 |
Appl. No.: |
15/129321 |
Filed: |
March 20, 2015 |
PCT Filed: |
March 20, 2015 |
PCT NO: |
PCT/JP2015/058556 |
371 Date: |
September 26, 2016 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C10M 103/06 20130101;
C10M 145/12 20130101; C10N 2040/32 20130101; C10M 2201/0623
20130101; C10N 2050/02 20130101; C10M 133/16 20130101; B21C 9/00
20130101; C10N 2010/12 20130101; C10N 2030/12 20130101; C10N
2010/02 20130101; C10M 2209/12 20130101; B21C 9/02 20130101; C10M
2205/14 20130101; C10M 2209/043 20130101; C10M 2213/062 20130101;
C10M 2201/08 20130101; C10M 143/02 20130101; C10M 2215/08 20130101;
C10M 125/10 20130101; C10M 2205/0225 20130101; C10M 2201/0803
20130101; C10M 2201/102 20130101; C10N 2040/24 20130101; C10M
129/40 20130101; C10M 2207/126 20130101; C10M 2217/045 20130101;
C10M 145/40 20130101; C10M 2201/1023 20130101; C23C 22/82 20130101;
C10M 125/26 20130101; C10N 2010/04 20130101; C10M 147/02 20130101;
C10M 2209/086 20130101; C10M 2209/0863 20130101; C10M 145/04
20130101; C10M 2209/04 20130101; C10M 149/20 20130101 |
International
Class: |
C10M 103/06 20060101
C10M103/06; C10M 133/16 20060101 C10M133/16; C10M 129/40 20060101
C10M129/40; C10M 145/40 20060101 C10M145/40; C10M 143/02 20060101
C10M143/02; C10M 145/12 20060101 C10M145/12; C10M 147/02 20060101
C10M147/02; C10M 125/26 20060101 C10M125/26; C10M 125/10 20060101
C10M125/10; C10M 149/20 20060101 C10M149/20; B21C 9/02 20060101
B21C009/02; C10M 145/04 20060101 C10M145/04 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 28, 2014 |
JP |
2014-070446 |
Claims
1. A steel wire rod including a lubricating coating film on a
surface, wherein the lubricating coating film contains a
water-soluble silicate and a water-soluble tungstate, a mass ratio
of water-soluble tungstate/water-soluble silicate in the
lubricating coating film being in a range of 0.7 to 10, and
contains no phosphorus.
2. A steel wire rod including a lubricating coating film containing
no phosphorus, wherein the lubricating coating film is formed using
a composition prepared by mixing a water-soluble silicate and a
water-soluble tungstate so as to adjust a mass ratio of
water-soluble tungstate/water-soluble silicate in the lubricating
coating film in a range of 0.7 to 10.
3. The steel wire rod according to claim 1, wherein the lubricating
coating film contains a resin, and a mass ratio of
resin/(water-soluble silicate+water-soluble tungstate) is in a
range of 0.01 to 1.5.
4. The steel wire rod according to claim 3, wherein the resin is at
least one selected from a vinyl resin, an acrylic resin, an epoxy
resin, a urethane resin, a phenol resin, a cellulose derivative, a
polymaleic acid and a polyester resin.
5. The steel wire rod according to claim 1, wherein the lubricating
coating film contains a lubricant, and a mass ratio of
lubricant/(water-soluble silicate+water-soluble tungstate) is in a
range of 0.01 to 1.5.
6. The steel wire rod according to claim 5, wherein the lubricant
is at least one selected from wax, polytetrafluoroethylene, fatty
acid soap, fatty acid metal soap, fatty acid amide, molybdenum
disulfide, tungsten disulfide, graphite and melamine cyanurate.
7. The steel wire rod according to claim 1, wherein the mass of the
coating film per unit area of the lubricating coating film is in a
range of 1.0 to 20 g/m.sup.2.
8. The steel wire rod according to claim 2, wherein the lubricating
coating film contains a resin, and a mass ratio of
resin/(water-soluble silicate+water-soluble tungstate) is in a
range of 0.01 to 1.5.
9. The steel wire rod according to claim 2, wherein the lubricating
coating film contains a lubricant, and a mass ratio of
lubricant/(water-soluble silicate+water-soluble tungstate) is in a
range of 0.01 to 1.5.
10. The steel wire rod according to claim 2, wherein the mass of
the coating film per unit area of the lubricating coating film is
in a range of 1.0 to 20 g/m.sup.2.
Description
TECHNICAL FIELD
[0001] The present invention relates to a steel wire rod having a
lubricating coating film containing no phosphorus on a surface.
BACKGROUND ART
[0002] In plastic working of a steel wire and a steel wire rod,
since friction generated when surfaces of metals (particularly a
die and a workpiece) are violently rubbed against each other may
cause an increase in working energy, heat generation, seizure
phenomenon, and the like, there have been used various lubricants
which aim to reduce a friction force. Oils, soaps, and the like
have been used as the lubricant for a long time, and the friction
force has been reduced by supplying them to a friction surface to
form a fluid lubricating coating film. In plastic working in which
sliding occurs under high surface pressure involving significant
heat generation due to an increase in surface area, a seizure
phenomenon is likely to generate due to shortage of lubrication,
lubricating coating film disruption, and the like. Therefore, there
has been popularized technology in which a surface of a metal
material is coated in advance with a solid coating film, for
example, an inorganic coating film such as a borate coating film or
a phosphate crystal coating film, which has sufficient coating film
strength and exists at an interface between a die and a workpiece
and is therefore less likely to cause lubricating coating film
disruption even under high surface pressure, thus making it
possible to avoid direct contact between metals. In particular, a
composite coating film composed of a zinc phosphate coating film
and a soap layer (hereinafter sometimes referred to as a chemical
conversion coating film) has widely been employed because of having
high workability and corrosion resistance.
[0003] In recent years, there have been surging a wide range of
requirements for a solid coating film, for example, further
reduction in working energy and increase in working degree, coping
with a hard-to-work material, environmental protection of a coating
film process (for example, a phosphatizing treatment has an
environmental conservation problem because of generation of
numerous industrial wastes such as sludge), taking measures to
phosphorizing of a bolt (if phosphorus in a coating film component
remains during a heat treatment after heading of a high strength
bolt, phosphorus enters into a steel, thus causing brittle
fracture), and the like. While global environment conservation is
taken into consideration to these requirements, a solid coating
film having high lubricity has been developing. This technology
enables formation of a coating film having high lubricity by a
simple step of only applying an aqueous plastic working lubricant
to a surface of a workpiece, followed by drying.
[0004] Patent Document 1 discloses an aqueous lubricating coating
agent for plastic working of a metal material, which is a
composition comprising an aqueous inorganic salt (A) and a wax (B)
dissolved or dispersed in water, wherein a solid component weight
ratio (B)/(A) is in a range of 0.3 to 1.5; and a coating film
forming method thereof.
[0005] Patent Document 2 discloses an aqueous lubricating coating
agent for plastic working of a metal material, comprising an alkali
metal borate (A), wherein the alkali metal borate (A) contains
lithium borate, a molar ratio of lithium to the entire alkali metal
in the alkali metal borate (A) is in a range of 0.1 to 1.0, and
also a molar ratio (B/M) of boric acid B to an alkali metal M of
the alkali metal borate (A) is in a range of 1.5 to 4.0; and a
coating film forming method thereof. It is considered that this
technology suppresses crystallization of a coating film caused by
moisture absorption of the coating film, thus enabling formation of
a coating film having not only workability but also high corrosion
resistance.
[0006] Patent Document 3 discloses a water-soluble lubricant for
non-phosphorus based plastic working, comprising an inorganic solid
lubricant as a component A, a wax as a component B, and a
water-soluble inorganic metal salt as a component C, wherein a
solid component mass ratio of the component A to the component B
(component A/component B) is in a range of 0.1 to 5, and a solid
component mass ratio of the component C to the total amount of the
component A, the component B, and the component C (component
C/(component A+component B+component C)) is in a range of 1 to
30.degree.. It is considered that this technology is directed to a
lubricant containing no phosphorus and enables realization of
corrosion resistance equal to that of a chemical conversion coating
film.
[0007] Patent Document 4 discloses an aqueous lubricating coating
agent comprising an aqueous inorganic salt (A), at least one
lubricant (B) selected from molybdenum disulfide and graphite, and
a wax (C), these components being dissolved or dispersed in water,
wherein (B)/(A) is in a range of 1.0 to 5.0 in terms of a solid
component weight ratio, and (C)/(A) is in a range of 0.1 to 1.0 in
terms of a solid component weight ratio; and a coating film forming
method thereof. It is considered that this technology enables
realization of high workability having the same level as that of a
chemical conversion coating film by mixing a conventional aqueous
lubricating coating agent with molybdenum disulfide or
graphite.
[0008] Patent Document 5 discloses a coating film forming agent
comprising a silicate (A), a polycarboxylate (B), a hydrophilic
polymer and/or a hydrophilic organic lamellar structure (C), and a
molybdate and/or a tungstate (D), a mass ratio of each component
being a predetermined ratio.
[0009] As mentioned in Patent Documents 1 to 5, the aqueous
inorganic salt is an essential component in the solid coating film
of the aqueous lubricating coating agent. The reason is that the
lubricating coating film composed of the aqueous inorganic salt has
sufficient coating film strength and, as mentioned above, the
lubricating coating film exists at an interface between a die and a
workpiece and is therefore less likely to cause lubricating coating
film disruption even under high surface pressure, thus making it
possible to avoid direct contact between metals. Therefore, in the
aqueous lubricating coating agent, it is possible to maintain a
satisfactory lubricated state during plastic working by using a
solid coating film composed of an aqueous inorganic salt or a
water-soluble resin in combination with an appropriate lubricant
capable of reducing a friction coefficient.
[0010] A description will be made of coating film formation
mechanism of the aqueous lubricating coating agent composed of a
water-soluble component. An aqueous inorganic salt of a
water-soluble component is in a state of being dissolved in water
in a lubricating treatment solution and, when a lubricant is
applied on a surface of a metal material and then dried, water as a
solvent is vaporized to form a lubricating coating film. In that
case, the aqueous inorganic salt is precipitated as a solid
substance on the surface of the metal material to form a solid
coating film. The solid coating film thus formed has a coating film
strength capable of enduring plastic working, and exhibits
satisfactory lubricity during plastic working by mixing with an
appropriate lubricant capable of reducing a friction
coefficient.
PRIOR ART DOCUMENT
Patent Document
[0011] Patent Document 1: WO 02/012420 A
[0012] Patent Document 2: JP 2011-246684 A
[0013] Patent Document 3: JP 2013-209625 A
[0014] Patent Document 4: WO 02/012419 A
[0015] Patent Document 5: JP 2002-363593 A
DISCLOSURE OF THE INVENTION
Problems to be Solved by the Invention
[0016] However, in the lubricating coating films of Patent
Documents 1 to 5, rust prevention property over a long term of two
or more months is drastically inferior as compared with the
above-mentioned chemical conversion coating films, thus failing to
enhance to a practical level. This is because a main component of
the coating film is a water-soluble component and therefore easily
absorbs or transmits moisture ip the atmosphere, leading to easy
contact between a steel material and moisture. In Patent Document
2, corrosion resistance is improved by suppressing crystallization
of the coating film due to moisture absorption, however, moisture
absorption itself is not suppressed, thus failing to obtain
sufficient corrosion resistance. It was mentioned that the aqueous
lubricating coating film mentioned in Patent Document 3 exhibited
corrosion resistance, which is equal to or better than that of the
chemical conversion coating film, in a corrosion resistance test in
a laboratory in which rusting is accelerated using a
thermo-hygrostat. Commonly, the lubricating coating film is
actually used in the environment where dusts and powders, and mists
of a picking agent are adhesible. In such severe environment,
corrosion resistance is actually inferior as compared with the
chemical conversion coating film. As mentioned above, there has
never been an aqueous lubricating coating film containing no
phosphorus, having rust prevention property which is equal to or
better than that of the chemical conversion coating film.
[0017] Examples of the aqueous inorganic salt capable of obtaining
comparatively high corrosion resistance include an alkali metal
salt of a silicate (hereinafter sometimes referred to as a
silicate) and an alkali metal salt and/or an ammonium salt of a
tungstate (hereinafter sometimes referred to as a tungstate). These
aqueous inorganic salts are also mentioned in Patent Document 1,
Patent Document 4, and Patent Document 5. However, they are far
inferior in practical corrosion resistance as compared with the
chemical conversion coating film.
[0018] The water-soluble silicate has a property that is less
likely to transmit moisture among the water-soluble aqueous
inorganic salts and also has very high adhesion to a material.
Because of this property, it is a material that can exhibit
comparatively high corrosion resistance, but not as much as the
chemical conversion coating film. This is because the water-soluble
silicate is crosslinked to from a network structure in a coating
film formation process in which water as a solvent of a lubricant
is vaporized. However, because of this network structure, the
coating film of the water-soluble silicate is too brittle as a
lubricating coating film. Therefore, when a base material is
worked, it is sometimes impossible to sufficiently conform because
of cracks of the coating film. Too high adhesion due to the network
structure may cause insufficient film removal, thus resulting in
various defects in the subsequent step. For example, when plating
is performed in the subsequent step, inclusion of a coating film
component may cause not only contamination of a plating solution,
but also poor plating in the portion where the coating film
component remains.
[0019] The water-soluble tungstate is less likely to absorb
moisture from external air when a coating film is formed. This is
because granular crystals are formed when the water-soluble
tungstate forms a coating film. Further, the water-soluble
tungstate has a property that forms a passive coating film having a
self-repair function on a surface of a steel material, and use of
the water-soluble tungstate as the coating film component enables
expectation of formation of a coating film having high corrosion
resistance. Because of its high water solubility, it is possible to
easily perform film removal with an aqueous solution. However, the
water-soluble tungstate is crystalline and is therefore inferior in
adhesion to a material and cannot form a uniform coating film, thus
failing to obtain corrosion resistance and workability as expected.
For example, it is possible to enhance adhesion and uniformity of a
coating film by adding a synthetic resin component in a lubricant,
but the corrosion resistance is drastically inferior as compared
with a chemical conversion coating film.
[0020] Both of the aqueous lubricating coating agents containing an
aqueous water-soluble inorganic salt mentioned in Patent Documents
1 to 3 were inferior in workability as compared with a chemical
conversion coating film. This tendency is particularly notable in
severe working wherein a surface area expansion ratio becomes at
least several tens of times (hereinafter sometimes referred to as
severe working), thus causing insufficient deformation of a
material, decrease in die life, occurrence of seizure, and the
like.
[0021] In the aqueous lubricating coating agent mentioned in Patent
Document 4, it is possible to obtain workability, which is equal to
or better than that of a chemical conversion coating film, even
during severe working by inclusion of molybdenum disulfide and
graphite. However, inclusion of these components colors a
lubricating liquid black, leading to extreme contamination of an
apparatus and peripheral parts, and operators. Molybdenum disulfide
and graphite are likely to be sedimented and may be sometimes
coagulated with the lapse of time on the bottom of a treatment
tank, thus making it difficult to disperse again. Therefore, it is
difficult to perform a stable operation. Further, these two
components may cause significant degradation of corrosion
resistance, so that the resulting coating film is inferior in
corrosion resistance as compared with the lubricating coating films
of Patent Documents 1 to 3, to say nothing of the chemical
conversion coating film.
[0022] In Patent Document 5, a coating film treatment agent
containing a silicate (A) as a main component and containing
excessively large amount of an anti-corrosive agent (D) is inferior
in lubricity since seizure occurs under high extrusion load.
Therefore, it becomes difficult to perform stable operation, thus
failing to obtain sufficient long-term rust prevention
property.
[0023] As mentioned above, the aqueous lubricating coating agent
could not form a coating film having both of high corrosion
resistance over a long term of about two or more months and
workability during severe working, that are comparable to those of
a chemical conversion coating film, even under service environment.
If a silicate is included in the aqueous lubricating coating agent,
there may arise a problem such as insufficient film removal.
[0024] Thus, it is an object of the present invention to provide a
steel wire rod including a lubricating coating film, which can
reconcile workabilities such as wire drawability, spike property,
ball ironing property and film removability, and corrosion
resistance such as long-term rust prevention property.
Means for Solving the Problems
[0025] The inventors of the present invention have intensively been
studied so as to solve the above problems and found that it is
possible to obtain high corrosion resistance and workability as
well as sufficient adhesion and film removability that have never
been achieved by each component alone, by adjustment of a ratio of
a silicate to a tungstate are adjusted to a certain specific ratio,
namely, adjustment of a mass ratio of water-soluble
tungstate/water-soluble silicate to a predetermined ratio to form a
composited lubricating coating film, and thus the present invention
has been completed.
[0026] The present invention was structured in the following manner
so as to solve the above problems.
[0027] The gist of the present invention lies in a steel wire rod
including a lubricating coating film on a surface, wherein the
lubricating coating film contains a water-soluble silicate and a
water-soluble tungstate, a mass ratio of water-soluble
tungstate/water-soluble silicate being in a range of 0.7 to 10, and
contains no phosphorus.
[0028] The lubricating coating film is preferably formed using a
composition prepared by mixing a water-soluble silicate and a
water-soluble tungstate so as to adjust a mass ratio of
water-soluble tungstate/water-soluble silicate in the lubricating
coating film in a range of 0.7 to 10.
[0029] The lubricating coating film preferably contains a resin,
and a mass ratio of resin/(water-soluble silicate+water-soluble
tungstate) is preferably in a range of 0.01 to 1.5.
[0030] The resin is preferably at least one selected from a vinyl
resin, an acrylic resin, an epoxy resin, a urethane resin, a phenol
resin, a cellulose derivative, a polymaleic acid and a polyester
resin.
[0031] The lubricating coating film preferably contains a
lubricant, and a mass ratio of lubricant/(water-soluble
silicate+water-soluble tungstate) is preferably in a range of 0.01
to 1.5.
[0032] The lubricant is preferably at least one selected from wax,
polytetrafluoroethylene, fatty acid soap, fatty acid metal soap,
fatty acid amide, molybdenum disulfide, tungsten disulfide,
graphite and melamine cyanurate.
[0033] The mass of the coating film per unit area of the
lubricating coating film is preferably in a range of 1.0 to 20
g/m.sup.2.
Effects of the Invention
[0034] In the steel wire rod of the present invention, a
lubricating coating film is structured in the manner mentioned
above, thus obtaining a steel wire rod that has excellent
workabilities such as wire drawability, spike property, ball
ironing property and film removability, and corrosion resistance
such as long-term rust prevention property. The lubricating coating
film in the present invention is far better than a conventional
aqueous lubricating coating film in that all of these performances
are equal to or better than those of steel wire rods having a
chemical conversion coating film.
BRIEF DESCRIPTION OF THE DRAWINGS
[0035] FIG. 1 shows evaluation criteria for seizure when ball
ironing property is evaluated.
MODE FOR CARRYING OUT THE INVENTION
[0036] The present invention is directed to a steel wire rod
including a lubricating coating film on a surface, wherein the
lubricating coating film contains a water-soluble silicate and a
water-soluble tungstate, a mass ratio of water-soluble
tungstate/water-soluble silicate being in a range of 0.7 to 10, and
contains no phosphorus.
[0037] In the present invention, a steel used in the steel wire rod
also includes a carbon steel, an alloy steel, a special steel, and
the like. Examples of such steel include a mild steel having a
carbon content of 0.2% by mass or less (not including 0% by mass),
a carbon steel having a carbon content of exceeding 0.2% by mass
and 1.5% by mass or less, and an alloy or special steel containing
at least one selected from silicon, manganese, phosphorus, sulfur,
nickel, chromium, copper, aluminum, molybdenum, vanadium, cobalt,
titanium, zircon, and the like according to the application of the
mild steel or carbon steel. In the present invention, the steel
wire rod generally refers to those obtained by forming a steel into
a wire rod through hot working. The steel wire is included in the
steel wire rod of the present invention. The steel wire refers to
those obtained by further subjecting a steel wire rod to a working
treatment, such as those obtained by drawing a steel wire rod into
a wire having a specified size (wire diameter, circularity, etc.)
and those obtained by subjecting a steel wire rod or a steel wire
drawn into a wire to a plating treatment.
[0038] The steel wire rod of the present invention is not
particularly limited as long as it is excellent in corrosion
resistance and workability because of having the below-mentioned
lubricating coating film, and a film, namely, an undercoating film
may be further formed between a surface of the steel wire rod and
the lubricating coating film. Both of these films may be a single
layer, or a layer composed of two or more layers.
[0039] The lubricating coating film and the undercoating film
contain no phosphorus, and a lubricating coating agent used for
formation of the film does not contain a component containing
phosphorus. However, in the present invention, it is not excluded
that a component containing phosphorus is inevitably included in a
coating film of a surface of the steel wire rod in the operation
process. Namely, even if phosphorus as inevitable impurities may
cause contamination in the actual operation, there is little
possibility that phosphorus causes brittle fracture of a steel wire
rod when the content of phosphorus is about 1% by mass or less, and
thus it is possible to consider that phosphorizing does not
occur.
[0040] A description will be made in order below from each
component and composition of the lubricating coating film in the
steel wire rod according to the present invention.
[0041] There is a need for the steel wire rod of the present
invention to have a lubricating coating film on a surface, the
lubricating coating film containing a water-soluble silicate and a
water-soluble tungstate, and a mass ratio of water-soluble
tungstate/water-soluble silicate being in a range of 0.7 to 10.
When containing the water-soluble silicate and the water-soluble
tungstate within the above range, it is possible to form a
lubricating coating film having high corrosion resistance and
workability as well as sufficient adhesion and film removability
that have never been achieved by the water-soluble silicate or the
water-soluble tungstate alone, or the other aqueous inorganic
salt.
[0042] For example, the below-mentioned water-soluble silicate and
water-soluble tungstate are composited to form a lubricating
coating film, the water-soluble tungstate is incorporated into a
network structure formed of the water-soluble silicate. As
mentioned above, drawbacks of the water-soluble tungstate depend
heavily on formation of a crystalline coating film and it becomes
possible for the water-soluble tungstate to exist uniformly and
finely by incorporating into the network structure of the
water-soluble silicate. Whereby, it is possible to reconcile a
property of being less likely to transmit moisture of the
water-soluble silicate and a passive film having a self-repair
function of the water-soluble tungstate, leading to a remarkable
improvement in corrosion resistance.
[0043] Examples of the influence of the water-soluble tungstate on
the water-soluble silicate include an improvement in workability
and film removability. As mentioned above, the water-soluble
silicate is inferior in workability and film removability since a
firm continuous film is formed by polymerization of the
water-soluble silicate. The composited water-soluble tungstate
exists in the network structure of the water-soluble silicate,
whereby, formation of a firm network structure is appropriately
suppressed, thus enabling an improvement in workability and film
removability.
[0044] To exhibit the performances mentioned above, a ratio of the
amount of the water-soluble tungstate to that of the water-soluble
silicate is important. A mass ratio of water-soluble
tungstate/water-soluble silicate in the lubricating coating film is
0.7 or more, preferably 0.9 or more, and more preferably 1.1 or
more. The mass ratio is 10 or less, preferably 6.0 or less, and
more preferably 3.0 or less. If the mass ratio of water-soluble
tungstate/water-soluble silicate is less than 0.7, the obtained
film can achieve neither sufficient corrosion resistance nor
workability, and is also inferior in film removability. This is
because the amount of tungsten relatively decreases, thus failing
to sufficiently form a passive film, while the amount of silicate
relatively increases to form a firm network structure. If the mass
ratio of water-soluble tungstate/water-soluble silicate is more
than 10, the obtained film can achieve neither sufficient corrosion
resistance nor workability. This is because the amount of the
water-soluble silicate relatively decreases, thus making it easier
to transmit moisture, while crystals of tungsten are precipitated,
thus degrading adhesion and uniformity of the coating film.
[0045] As mentioned above, when a water-soluble silicate and a
water-soluble tungstate are composited at an appropriate ratio, the
synergy effect thereof enables realization of high workability and
high corrosion resistance in the service environment, that has
never been realized by the prior art, and formation of the
lubricating coating film having sufficient film removability. When
the lubricating coating film is formed, a lubricating coating agent
containing a water-soluble silicate and a water-soluble tungstate
may be prepared, followed by application to a surface of a steel
wire rod. After application of the lubricating coating agent
(namely, after a lubricating coating treatment), a mass ratio of
water-soluble tungstate/water-soluble silicate in the lubricating
coating film is the same as that of water-soluble
tungstate/water-soluble silicate in the lubricating coating
agent.
[0046] In the present invention, the lubricating coating film may
be formed using a composition prepared by mixing a water-soluble
silicate and a water-soluble tungstate so as to adjust a mass ratio
of water-soluble tungstate/water-soluble silicate in the
lubricating coating film in a range of 0.7 to 10.
[0047] In the lubricating coating film, a mass ratio
tungsten/silicon is preferably 1.3 or more, more preferably 1.8 or
more, and still more preferably 2.0 or more. The mass ratio is
preferably 18 or less, more preferably 10 or less, and still more
preferably 5.4 or less.
[0048] If the mass ratio of tungsten/silicon is less than 1.3, the
obtained film can achieve neither sufficient corrosion resistance
nor workability, and is also inferior in film removability. This is
because the amount of the tungstate relatively decreases, thus
failing to sufficiently form a passive film, while the amount of
the silicate relatively increases to form a firm network structure.
If the mass ratio of tungsten/silicon is more than 18, the obtained
film can achieve neither sufficient corrosion resistance nor
workability. This is because the amount of the silicate relatively
decreases, thus making it easier to transmit moisture, while
crystals of tungsten are precipitated, thus degrading adhesion and
uniformity of the film. In the present invention, the mass ratio of
tungsten/silicon is based on a ratio of tungsten element derived
from the water-soluble tungstate to a silicon element derived from
the water-soluble silicate in the film and can be calculated, for
example, using inductively coupled plasma or fluorescent X-ray
spectroscopy.
[0049] Examples of the water-soluble silicate used in the
lubricating coating agent include lithium silicate, sodium silicate
and potassium silicate. These water-soluble silicates may be used
alone, or two or more water-soluble silicates may be used.
[0050] Examples of the water-soluble tungstate used in the
lubricating coating agent include lithium tungstate, sodium
tungstate, potassium tungstate, and ammonium tungstate. These
water-soluble tungstates may be used alone, or two or more
water-soluble tungstates may be used.
[0051] A resin will be described below. The resin is mixed in the
coating film for the purpose of the binder effect, an improvement
in adhesion between a base material and a film, imparting of
leveling property by the thickening effect, and stabilization of a
dispersion component. Examples of the resin having such function
and property include a vinyl resin, an acrylic resin, an epoxy
resin, a urethane resin, a phenol resin, a cellulose derivative, a
polymaleic acid and a polyester resin. These resins may be used
alone, or two or more resins may be used in combination.
[0052] In the present invention, the lubricating coating film
contains a resin and a mass ratio of resin/(water-soluble silicate
and water-soluble tungstate) is preferably 0.01 or more, and more
preferably 0.05 or more. The mass ratio is preferably 1.5 or less,
and more preferably 1.0 or less. If the mass ratio is less than
0.01, the above effects are not sufficiently exerted. Meanwhile, if
the mass ratio exceeds 1.5, the amounts of the water-soluble
silicate and the water-soluble tungstate relatively decrease, thus
failing to realize sufficient workability and corrosion
resistance.
[0053] A lubricant will be described below. The lubricant itself
has slipperiness, and has a function of reducing a friction force.
In general, if the friction force increases during plastic working,
an increase in working energy, heat generation, seizure, and the
like occur. It the lubricant is included in a lubricating coating
agent used in the present invention, the lubricant exists in a
lubricating coating film in the form of a solid, thus suppressing
an increase in friction force. Examples of the lubricant having
such function and property include wax, polytetrafluoroethylene,
fatty acid soap, fatty acid metal soap, fatty acid amide,
molybdenum disulfide, tungsten disulfide, graphite and melamine
cyanurate. These lubricants may be used alone, or two or more
lubricants may be used in combination.
[0054] Specific examples of the wax include polyethylene wax,
paraffin wax, microcrystalline wax, polypropylene wax, and carnauba
wax. Specific examples of the fatty acid soap include sodium
myristate, potassium myristate, sodium palmitate, potassium
palmitate, sodium stearate and potassium stearate. Specific
examples of the fatty acid metal soap include calcium stearate,
zinc stearate, barium stearate, magnesium stearate, and lithium
stearate. The fatty acid amide is, for example, an amide compound
having two fatty acids, and specific examples thereof include
ethylenebislauric acid amide, ethylenebisstearic acid amide,
ethylenebisbehenic acid amide, N,N'-distearyladipic acid amide,
ethylenebisoleic acid amide, ethylenebiserucic acid amide,
hexamethylenebisoleic acid amide, and N,N'-dioleyladipic acid
amide.
[0055] When the lubricating coating film is mixed with the
lubricant, the mass ratio of lubricant/(water-soluble silicate and
water-soluble tungstate) is preferably 0.01 or more, and more
preferably 0.05 or more, and the mass ratio is preferably 1.5 or
less, and more preferably 1.0 or less. Here, if the mass ratio of
lubricant/(water-soluble silicate+water-soluble tungstate) is less
than 0.01, it is impossible to perform performances because of too
small amount of the lubricant. If the mass ratio exceeds 1.5, the
amounts of the water-soluble silicate and the water-soluble
tungstate relatively decrease, thus failing to exhibit high
corrosion resistance and workability which are features of the
present invention.
[0056] The lubricating coating film of the steel wire rod of the
present invention can be mixed with a viscosity modifier, in
addition to the water-soluble silicate, the water-soluble
tungstate, the resin, and the lubricant, for the purpose of
imparting leveling property and thixotrophy so as to ensure a
uniform coating state when a lubricating treatment solution is
applied to a base material. The amount of the viscosity modifier is
preferably in a range of 0.1 to 30% by mass based on the mass of
total solid component. Specific examples of the viscosity modifier
include smectite-based clay minerals such as montmorillonite,
sauconite, beidellite, hectorite, nontronite, saponite, iron-rich
saponite, and stevensite; and inorganic thickeners such as
pulverized silica, bentonite, and kaolin.
[0057] The lubricating coating film may contain water-soluble
salts, for example, inorganic salts, such as sulfates and borates,
and organic salts so as to improve adhesion and workability.
Examples of the sulfate include sodium sulfate, potassium sulfate,
and the like. Examples of the borate include sodium metaborate,
potassium metaborate, ammonium metaborate, and the like.
[0058] Examples of the organic salt include salts of formic acid,
acetic acid, butyric acid, oxalic acid, succinic acid, lactic acid,
ascorbic acid, tartaric acid, citric acid, malic acid, malonic
acid, maleic acid, phthalic acid, and the like, with alkali metals,
alkali earth metals, and the like.
[0059] The lubricating coating film of the steel wire rod of the
present invention can be imparted with high corrosion resistance
before and after working, and may be mixed with other water-soluble
rust preventives and inhibitors for the purpose of further
improving corrosion resistance. Specifically, it is possible to use
known rust preventives and inhibitors, for example, various organic
acids such as oleic acid, dimer acid, tartaric acid, and citric
acid; various chelating agents such as EDTA, NTA, HEDTA, and DTPA;
mixed components of alkanolamine such as triethanolamine, and amine
salts of p-t-butylbenzoic acid; and combinations of a carboxylic
acid amine salt, a dibasic acid amine salt, an alkenylsuccinic
acid, and a water-soluble salt thereof with aminotetrazole and a
water-soluble salt thereof. These rust preventives and inhibitors
may be used alone, or two or more rust preventives and inhibitors
may be used in combination. The amount is preferably in a range of
0.1 to 30% by mass based on the mass of total solid component.
[0060] In the present invention, the lubricating coating agent
contains the water-soluble silicate and the water-soluble tungstate
as essential components, and optionally contains the
above-mentioned resin, lubricant, and water-soluble salts.
[0061] The amount of the water-soluble silicate preferably exceeds
5% by mass, more preferably 10% by mass or more, and still more
preferably 15% by mass or more, and is also preferably 58% by mass
or less, more preferably 52% by mass or less, and still more
preferably 45% by mass or less, in 100% by mass of the lubricating
coating agent.
[0062] The amount of the water-soluble tungstate is preferably 10%
by mass or more, more preferably 15% by mass or more, and still
more preferably 20% by mass or more, and is also preferably 91% by
mass or less, more preferably 85% by mass or less, and still more
preferably 80% by mass or less, in 100% by mass of the lubricating
coating agent.
[0063] If the amount of the water-soluble silicate is 5% by mass or
less and the amount of the water-soluble tungstate exceeds 91% by
mass, the obtained film cannot achieve sufficient long-term rust
prevention property, and is inferior in wire drawability and ball
ironing property. This is because the amount of the water-soluble
silicate relatively decreases, thus making it easier to transmit
moisture, while crystals of tungsten are precipitated, thus
degrading adhesion and uniformity of the coating film. If the
amount of the water-soluble silicate exceeds 58% by mass and the
amount of the water-soluble tungstate is less than 10% by mass, the
obtained film can achieve neither sufficient corrosion resistance
nor workability. This is because the amount of tungsten relatively
decreases, thus failing to sufficiently form a passive film, while
the amount of silicate relatively increases to form a firm network
structure.
[0064] In the present invention, the lubricating coating film may
also be formed as a lubricating undercoating film for dry
lubricant. Use as an undercoating film of a dry lubricant enables
leveling up of lubricity, seize resistance, and corrosion
resistance. There is no limitation on the dry lubricant and it is
possible to use, for example, a general lubricating powder or wire
drawing powder which contains, as main components, higher fatty
acid soap, borax, lime, molybdenum disulfide, and the like.
[0065] In the present invention, a liquid medium (solvent,
dispersion medium) for formation of a lubricating coating film in a
film treatment agent is water. To shorten the drying time of the
lubricant in the drying step, it is possible to mix with an alcohol
having a boiling point lower than that of water.
[0066] To enhance stability of the solution, the lubricating
coating agent may contain a water-soluble strong alkali component.
Specific examples thereof include lithium hydroxide, sodium
hydroxide and potassium hydroxide. These water-soluble strong
alkali components may be used alone, or two or more water-soluble
strong alkali components may be used in combination. The amount of
these water-soluble strong alkali components is preferably in a
range of 0.01 to 10% by mass based on the mass of total solid
component.
[0067] The lubricating coating agent used in the present invention
is produced by adding a water-soluble silicate and a water-soluble
tungstate, and a resin and a lubricant, and if necessary a
viscosity modifier to water as a liquid medium, followed by mixing.
The water-soluble silicate and the water-soluble tungstate used
herein are soluble in water, but some of the resin, the lubricant,
the viscosity modifier, and the like are insoluble or slightly
soluble in water, so that there is a need to disperse them in the
lubricating coating agent. They are dispersed by a method in which
a surfactant capable of serving as a dispersant is optionally added
to water and, after sufficiently maintaining the surfactant in
close association with water, stirring is continued until a
dispersed state becomes uniform. Stirring is performed by a general
method such as propeller stirring or stirring with a homogenizer.
To obtain a stable dispersed state, known surfactants can be
used.
[0068] A method for producing a steel wire rod according to the
present invention will be described below. The method according to
the present invention includes a cleaning step of a steel wire rod,
a production step of a film treatment agent, and a drying step.
Each step will be described below.
Cleaning Step (Pretreatment Step)
[0069] Before formation of a lubricating coating film on a steel
wire rod, at least one cleaning treatment selected from shot
blasting, sand blasting, wet blasting, peeling, alkali degreasing,
and pickling is preferably performed. Cleaning as used herein is
performed for the purpose of removing oxide scales grown by
annealing, and various contaminations (oils, etc.).
Production Step of Lubricating Coating Film
[0070] In the present invention, there is no particular limitation
on a production step of a lubricating coating film on a steel wire
rod, and it is possible to use coating methods such as an immersion
method, a flow coating method, and a spraying method. Coating is
not particularly limited as long as a surface of the steel wire rod
is sufficiently coated with a lubricating coating agent of the
present invention, and also the coating time is not particularly
limited. To enhance drying property in this case, the steel wire
rod may be brought into contact with the lubricating coating agent
after heating to a temperature in a range of 60 to 80.degree. C.
The steel wire rod may also be brought into contact with the
lubricating coating agent heated to a temperature in a range of 40
to 70.degree. C. Whereby, the drying property may be sometimes
improved significantly, thus enabling drying at a normal
temperature and reduction in thermal energy loss.
Drying Step
[0071] There is a need to dry the lubricating coating agent. Drying
may be performed by being left to stand at a normal temperature, or
may performed at 60 to 150.degree. C. for 1 to 30 minutes.
[0072] The mass of a lubricating coating film formed on a steel
wire rod is appropriately controlled by the degree of subsequent
working, and the mass of the coating film is preferably 1.0
g/m.sup.2 or more, more preferably 2.0 g/m.sup.2 or more, and is
also preferably 20 g/m.sup.2 or less, and more preferably 15
g/m.sup.2 or less. Low mass of the coating film leads to
insufficient workability. It is not preferred that the mass of the
coating film exceeds 20 g/m.sup.2 since clogging occurs in a die,
although there is no problem in workability. The mass of the
coating film can be calculated from a difference in mass between
steel wire rods before and after a treatment, and a surface area.
To control so as to adjust in a range of the above-mentioned mass
of the coating film, the solid component mass (concentration) of
the lubricating coating agent is appropriately adjusted. In
practice, after diluting a high concentration lubricant with water,
the thus obtained treatment solution is often used. There is no
particular limitation on water used for dilution and adjustment,
and, for example, pure water, deionized water, tap water, ground
water, industrial water, and the like can be used.
Film Removal Method
[0073] In the present invention, film removal can be performed by
immersing the lubricating coating film formed of the lubricating
coating agent in an aqueous alkali cleaner, or spraying the aqueous
alkali cleaner. The alkali cleaner is a solution prepared by
dissolving a common alkali component such as sodium hydroxide or
potassium hydroxide in water and, when the alkali cleaner is
brought into contact with the lubricating coating film, the
lubricating coating film dissolves in the cleaning solution, thus
making it possible to easily perform film removal. It is also
possible to obtain a film capable of easily falling off by a heat
treatment after working. Therefore, alkali cleaning and heat
treatment enable prevention of contamination and poor plating in
the subsequent step caused by insufficient film removal.
EXAMPLES
[0074] The present invention will be described below in a more
specific manner by way of Examples and Comparative
[0075] Examples, together with effects thereof, with respect to a
steel wire rod. The present invention is not limited to these
Examples. In the following description, parts are by mass and
percentages are by mass, unless otherwise specified.
(1-1) Preparation of Lubricating Coating Agent
[0076] In accordance with the combination and proportion shown in
Table 1, lubricating coating agents of Examples 1 to 18 and
Comparative Examples 1 to 12 were prepared using the respective
components shown in Table 1. Comparative Example 13 means the case
subjected to a phosphate/soap treatment.
<Water-Soluble Silicate>
[0077] (A-1) Sodium metasilicate (A-2) JIS No. 3 sodium silicate
(Na.sub.2O.nSiO.sub.2, n=3) (A-3) Lithium silicate
(Li.sub.2O.nSiO.sub.2, n=3.5)
<Water-Soluble Tungstate>
[0078] (B-1) Ammonium tungstate (B-2) Sodium tungstate (B-3)
Lithium tungstate
<Resin>
[0079] (C-1) Polyvinyl alcohol (average molecular weight of about
50,000) (C-2) Sodium neutralizing salt of isobutylene-maleic
anhydride copolymer (average molecular weight of about 165,000)
<Lubricant>
[0080] (D-1) Anionic polyethylene wax (average particle size of 5
.mu.m) (D-2) Ethylenebis-stearic acid amide
<Water-Soluble Salt>
[0081] (E-1) Sodium metaborate (E-2) Sodium tartrate (E-3) Sodium
sulfate (E-4) Sodium pyrophosphate
<Undercoating Film>
[0082] (F-1) Zirconium chemical conversion treatment agent
(PALLUCID (registered trademark) 1500, manufactured by Nihon
Parkerizing Co., Ltd.)
TABLE-US-00001 TABLE 1 Water-soluble silicate Water-soluble
tungstate Resin Lubricant Undercoating Component (A) Component (B)
Component (C) Component (D) film (A-1) (A-2) (A-3) (B-1) (B-2)
(B-3) (C-1) (C-2) (D-1) (D-2) (F-1) Example 1 40 15 0 45 0 0 0 0 0
0 None Example 2 0 25 0 0 75 0 0 0 0 0 None Example 3 30 20 5 0 0
45 0 0 0 0 None Example 4 9 0 0 25 30 30 6 0 0 0 None Example 5 10
0 30 38 0 0 2 0 20 0 None Example 6 0 0 20 0 30 20 0 10 10 10 None
Example 7 40 0 0 0 50 0 7 0 0 3 None Example 8 0 45 0 0 20 30 0 0 5
0 None Example 9 10 0 5 17 0 10 18 0 20 20 None Example 10 15 15 0
0 23 0 0 0 24 23 None Example 11 0 10 10 10 10 0 15 25 0 20 None
Example 12 5 0 0 0 35 0 5 40 15 0 None Example 13 10 30 0 40 0 20 0
0 0 0 None Example 14 0 0 15 0 0 65 20 0 0 0 None Example 15 30 10
0 0 40 0 0 0 5 15 None Example 16 10 30 0 20 40 0 0 0 0 0 Exist
Example 17 30 10 10 0 0 50 0 0 0 0 Exist Example 18 15 0 0 60 25 0
0 0 0 0 Exist Comparative Example 1 No coating film (only dry
lubricant) Comparative Example 2 65 0 0 35 0 0 0 0 0 0 None
Comparative Example 3 0 7 0 93 0 0 0 0 0 0 None Comparative Example
4 0 100 0 0 0 0 0 0 0 0 None Comparative Example 5 0 0 0 0 0 90 10
0 0 0 None Comparative Example 6 0 0 0 60 0 0 0 15 0 0 None
Comparative Example 7 0 0 0 0 35 30 10 0 0 0 None Comparative
Examole 8 50 15 0 0 0 0 0 0 0 0 None Comparative Example 9 0 55 15
0 0 0 0 0 0 0 None Comparative Example 10 0 0 0 0 0 0 0 20 0 0 None
Comparative Example 11 0 0 0 0 0 0 5 0 0 0 None Comparative Example
12 0 0 0 0 0 0 0 10 0 0 None Comparative Example 13 Phosphate/soap
treatment Mass of Mass ratio of film per unit resin/(water- Mass
ratio of area of Mass ratio of soluble lubricant/(water-
Water-soluble salt lubricating water-soluble tungstate + soluble
tungstate + Component (E) coating film tungstate/water-
water-soluble water-soluble (E-1) (E-2) (E-3) (E-4) (g/m.sup.2)
soluble silicate) silicate) silicate) Example 1 0 0 0 0 15.0 0.82
-- -- Example 2 0 0 0 0 3.0 3.00 -- -- Example 3 0 0 0 0 1.2 0.82
-- -- Example 4 0 0 0 0 7.7 9.44 0.06 -- Example 5 0 0 0 0 6.6 0.95
0.03 0.26 Example 6 0 0 0 0 7.0 2.50 0.14 0.29 Example 7 0 0 0 0
20.0 1.25 0.08 0.03 Example 8 0 0 0 0 5.5 1.11 -- 0.05 Example 9 0
0 0 0 4.2 1.80 0.43 0.95 Example 10 0 0 0 0 3.8 0.77 -- 0.89
Example 11 0 0 0 0 3.9 1.00 1.00 0.50 Example 12 0 0 0 0 2.2 7.00
1.13 0.38 Example 13 0 0 0 0 7.1 1.50 -- -- Example 14 0 0 0 0 7.8
4.33 0.25 -- Example 15 0 0 0 0 5.9 1.00 -- 0.25 Example 16 0 0 0 0
6.5 1.50 -- -- Example 17 0 0 0 0 7.5 1.00 -- -- Example 18 0 0 0 0
8.5 5.67 -- -- Comparative Example 1 No coating film (only dry
lubricant) Comparative Example 2 0 0 0 0 3.0 0.54 -- -- Comparative
Example 3 0 0 0 0 1.8 13.29 -- -- Comparative Example 4 0 0 0 0 3.0
-- -- -- Comparative Example 5 0 0 0 0 5.1 -- 0.11 -- Comparative
Example 6 25 0 0 0 7.7 -- 0.25 -- Comparative Example 7 0 25 0 0
6.3 -- 0.15 -- Comparative Examole 8 0 10 25 0 5.5 -- -- --
Comparative Example 9 0 0 0 30 5.6 -- -- -- Comparative Example 10
40 0 0 40 -- -- -- -- Comparative Example 11 95 0 0 0 -- -- -- --
Comparative Example 12 0 90 0 0 -- -- -- -- Comparative Example 13
Phosphate/soap treatment *Numerical in each of components (A) to
(E) means an addition amount in a lubricating coating agent (% by
mass).
(1-2) Lubricating Coating Treatment
[0083] Each lubricating coating treatment was carried out by the
following steps, with respect to a surface of a .phi.3.2 mm sample
steel wire rod (steel type: S45C). After subjecting to the
lubricating coating treatment, a mass ratio of water-soluble
tungstate/water-soluble silicate in a lubricating coating film of a
sample steel wire rod is the same as a mass ratio of water-soluble
tungstate/water-soluble silicate in a lubricating coating agent
mentioned in Table 1.
Pretreatment and Lubricating Coating Treatment of Examples 1 to 15
and Comparative Examples 2 to 12
[0084] (a) Degreasing: commercially available degreasing agent
(FINECLEANER (registered trademark) E6400, manufactured by Nihon
Parkerizing Co., Ltd.), concentration: 20 g/L, temperature:
60.degree. C., immersion: 10 minutes (b) Water rinsing: tap water,
normal temperature, immersion: 20 seconds (c) Pickling: 17.5%
hydrochloric acid, normal temperature, immersion: 20 minutes (d)
Water rinsing: tap water, normal temperature, immersion: 20 seconds
(e) Neutralization: commercially available neutralizer (PREPALENE
(registered trademark) 27, manufactured by Nihon Parkerizing Co.,
Ltd.) (f) Lubricating coating treatment: lubricating coating agent
prepared in (1-1), temperature: 60.degree. C., immersion: 1 minute
(g) Drying: at 100.degree. C. for 10 minutes (h) The amount of a
lubricating coating film was appropriately adjusted by the
concentration of a treatment agent.
Pretreatment and Lubricating Coating Treatment of Examples 16 to
18
[0085] (a) Degreasing: commercially available degreasing agent
(FINECLEANER (registered trademark) 6400, manufactured by Nihon
Parkerizing Co., Ltd.), concentration: 20 g/L, temperature:
60.degree. C., immersion: 10 minutes (b) Water rinsing: tap water,
normal temperature, immersion: 30 seconds (c) Pickling:
hydrochloric acid, concentration: 17.5%, normal temperature,
immersion: 10 minutes (d) Water rinsing: tap water, normal
temperature, immersion: 30 seconds (e) Zirconium treatment:
commercially available zirconium chemical conversion treatment
agent (PALLUCID (registered trademark) 1500, manufactured by Nihon
Parkerizing Co., Ltd.), concentration: 50 g/L, temperature:
45.degree. C., immersion: 2 minutes (f) Water rinsing: tap water,
normal temperature, immersion: 30 seconds (g) Lubricating coating
treatment: lubricating coating agent prepared in (1-1), temperature
60.degree. C., immersion: 1 minute (h) Drying: 100.degree. C., 10
minutes (i) Amount of undercoating film: zirconium undercoat: 50
mg/m.sup.2
[0086] The amount of a lubricating coating film was appropriately
adjusted by the concentration of a treatment agent.
Treatment of Comparative Example 1
[0087] (a) Degreasing: commercially available degreasing agent
(FINECLEANER (registered trademark) 6400, manufactured by Nihon
Parkerizing Co., Ltd.), concentration: 20 g/L, temperature:
60.degree. C., immersion: 10 minutes (b) Water rinsing: tap water,
normal temperature, immersion: 30 seconds (c) Pickling:
hydrochloric acid, concentration: 17.5%, normal temperature,
immersion: 10 minutes (d) Water rinsing: tap water, normal
temperature, immersion: 30 seconds (e) Pure water rinsing:
deionized water, normal temperature, immersion: 30.degree. C. (f)
Drying: at 100.degree. C. for 10 minutes
Pretreatment and Film Treatment of Comparative Example 13
(Phosphate/Soap Treatment)
[0088] (a) Degreasing: commercially available degreasing agent
(FINECLEANER (registered trademark) 6400, manufactured by Nihon
Parkerizing Co., Ltd.), concentration: 20 g/L, temperature:
60.degree. C., immersion: 10 minutes (b) Water rinsing: tap water,
normal temperature, immersion: 30 seconds (c) Pickling:
hydrochloric acid, concentration 17.5%, normal temperature,
immersion: 10 minutes (d) Water rinsing: tap water, normal
temperature, immersion: 30 seconds (e) Chemical conversion
treatment: commercially available zinc phosphate chemical
conversion treatment agent (PALBOND (registered trademark) 3696X,
manufactured by Nihon Parkerizing Co., Ltd.) concentration 75 g/L,
temperature 80.degree. C., immersion: 10 minutes (f) Water rinsing:
tap water, normal temperature, immersion: 30 seconds (g) Soap
treatment: commercially available reactive soap lubricant (PALUBE
(registered trademark) 235, manufactured by Nihon Parkerizing Co.,
Ltd.), concentration: 70 g/L, temperature 85.degree. C., immersion:
3 minutes (h) Drying: at 100.degree. C. for 10 minutes (i) Amount
of film: 10 g/m.sup.2
[0089] (1-3) Evaluation Test
[0090] (1-3-1) Workability (Wire Drawability) Test
Wire drawing was performed by drawing a sample wire rod in size of
.phi.3.2 mm.times.20 m through a .phi.2.76 die. Missile C40
available from Matsuura Kougyo K.K. was used as a dry lubricant.
Immediately before drawing a material, a die box was charged with
the dry lubricant so that the dry lubricant naturally adheres to
the material. Evaluation was made from seizure of the test material
and the remaining amount of the lubricating coating film after wire
drawing. In wire drawing of the phosphate/soap coating film of
Comparative Example 13, the dry lubricant is not used in accordance
with a normal usage manner.
Evaluation Criteria
[0091] A: No seizure occurs and no metal gloss is recognized and,
on the whole, a film remains in a large amount. B: No seizure
occurs and no metal gloss is recognized, and a film remains in an
amount which slightly smaller than that in A. C: No seizure occurs
and a film retention amount is slightly small, and metal gloss is
partially recognized. D: No seizure occurs and metal gloss is
recognized at numerous sites. E: Seizure occurred.
(1-3-2) Corrosion Resistance (Long-Term Rust Prevention Property)
Test
[0092] In summer season, a wire rod subjected to the
above-mentioned wire drawing test was exposed to an open air
atmosphere indoors for two weeks or two months, and then the degree
of rusting was observed. It was judged that the more the rust area
increases, the more corrosion resistance becomes inferior.
Evaluation Criteria
[0093] A: Extremely excellent as compared with a phosphate/soap
coating film (rust area of 3% or less) B: Excellent as compared
with a phosphate/soap coating film (rust area of exceeding 3% to
10% or less) C: Equivalent to a phosphate/soap coating film (rust
area of exceeding 10% to 20% or less) D: Inferior as compared with
a phosphate/soap coating film (rust area of exceeding 20% to 30% or
less) E: Drastically inferior as compared with a phosphate/soap
coating film (rust area of exceeding 30%)
[0094] The test results are shown in Table 2. In all Examples,
rusting is less likely to occur over a long term and satisfactory
corrosion resistance is exhibited, and also a lubricating coating
film remains in a large amount, resulting in satisfactory
workability. As a result of subjecting to a zirconium chemical
conversion treatment as a surface treatment, higher corrosion
resistance was exhibited. In Comparative Example 1 which is an
example in which a lubricating coating film used in Examples is not
formed, seizure occurred during wire drawing and rusting frequently
occurred in both cases where the wire rod was exposed to an open
air atmosphere for two weeks and two months, thus failing to reach
a practical level. In Comparative Examples 2 to 9 in which a ratio
of a water-soluble silicate to a water-soluble tungstate deviates
from the scope of the present invention, workability was inferior
and also corrosion resistance was inferior because of small film
retention amount after wire drawing. In Comparative Examples 10 to
12 in which components other than the silicate and tungstate were
included as aqueous inorganic salts, workability was inferior and
also corrosion resistance was inferior because of small film
retention amount after wire drawing. In Comparative Example 13 in
which the phosphate coating film was subjected to a reactive soap
treatment, comparatively excellent performances were exhibited.
However, because of containing phosphorus, when subjecting to a
heat treatment such as quenching and tempering while having the
lubricating coating film on a surface, there is a fear that the
steel wire rod becomes fragile as a result of the occurrence of
phosphorizing. Therefore, Comparative Example 13 deviates from the
object of the present invention. Similarly, Comparative Examples 9
and 10 deviate from the scope of the present invention because of
containing phosphorus.
TABLE-US-00002 TABLE 2 Corrosion resistance Workability (Rust
prevention property) (Wire Two Two Phosphatizing drawability) weeks
months property*1 Example 1 B A B B Example 2 A A A B Example 3 B A
B B Example 4 B A B B Example 5 B A A B Example 6 A A A B Example 7
A A A B Example 8 B A A B Example 9 A A A B Example 10 B A B B
Example 11 B A A B Example 12 B A B B Example 13 A A A B Example 14
A A B B Example 15 A A B B Example 16 A A A B Example 17 B A A B
Example 18 B A A B Comparative E E E B Example 1 Comparative C B D
B Example 2 Comparative D B C B Example 3 Comparative D C C B
Example 4 Comparative D D D B Example 5 Comparative D D D B Example
6 Comparative D D D B Example 7 Comparative C E E B Example 8
Comparative C E E E Example 9 Comparative D E E E Example 10
Comparative D E E B Example 11 Comparative E E E B Example 12
Comparative B B B E Example 13 *1B: There is no possibility of
brittle fracture of a steel wire rod due to phosphorus because of
containing no phosphorus. E: There is possibility of brittle
fracture of a steel wire rod due to phosphorus because of
containing phosphorus.
[0095] The present invention will be described below in a more
specific manner by way of Examples and Comparative Examples,
together with effects thereof, with respect to a steel wire. The
present invention is not limited to these Examples. In the
following description, parts are by mass and percentages are by
mass, unless otherwise specified.
(2-1) Preparation of Lubricating Coating Agent
[0096] In accordance with the combination and proportion shown in
Table 3, lubricating coating agents of Examples 19 to 38 and
Comparative Examples 14 to 25 were prepared using the respective
components shown below. Comparative Example 26 means the case
subjected to a phosphate/soap treatment.
<Water-Soluble Silicate>
[0097] (A-1) Sodium metasilicate (A-2) JIS No. 3 sodium silicate
(Na.sub.2O.nSiO.sub.2, n=3) (A-3) Lithium silicate (LiO.nSiO.sub.2,
n=3.5)
<Water-Soluble Tungstate>
[0098] (B-1) Ammonium tungstate (B-2) Sodium tungstate (B-3)
Lithium tungstate
<Resin>
[0099] (C-1) Polyvinyl alcohol (average molecular weight of about
50,000) (C-2) Sodium neutralizing salt of isobutylene-maleic
anhydride copolymer (average molecular weight of about 165,000)
(C-3) Carboxymethylcellullose sodium (average molecular weight of
about 30,000) (C-4) Aqueous nonionic urethane resin emulsion
<Lubricant>
[0100] (D-1) Anionic polyethylene wax (average particle size of 5
.mu.m) (D-2) Ethylenebis-stearic acid amide (D-3) Calcium stearate
(D-4) Polytetrafluoroethylene dispersion (average particle size of
0.2 .mu.m)
<Water-Soluble Salt>
[0101] (E-1) Sodium metaborate (E-2) Sodium tartrate (E-3) Sodium
sulfate (E-4) Sodium pyrophosphate
<Undercoating Film>
[0102] (F-1) Zirconium chemical conversion treatment agent
(PALLUCID (registered trademark) 1500, manufactured by Nihon
Parkerizing Co., Ltd.)
TABLE-US-00003 TABLE 3 Water-soluble silicate Water-soluble
tungstate Resin Lubricant Undercoating Component (A) Component (B)
Component (C) Component (D) film (A-1) (A-2) (A-3) (B-1) (B-2)
(B-3) (C-1) (C-2) (C-3) (C-4) (D-1) (D-2) (D-3) (D-4) (F-1) Example
19 0 20 0 40 0 0 0 25 0 0 15 0 0 0 None Example 20 25 0 0 20 0 0 0
40 0 5 10 0 0 0 None Example 21 5 20 0 0 0 35 20 0 0 0 0 0 20 0
None Example 22 21 10 5 18 21 0 0 0 0 5 10 10 0 0 None Example 23 0
15 0 0 0 45 0 0 10 0 0 10 0 20 None Example 24 20 0 10 0 50 0 10 0
0 0 10 0 0 0 None Example 25 0 25 0 0 0 21 0 25 12 0 0 0 7 10 None
Example 26 0 0 15 65 0 0 0 0 0 0 0 0 0 20 None Example 27 0 40 0 0
40 0 15 0 0 0 5 0 0 0 None Example 28 9 18 25 37 0 0 0 0 0 2 0 0 9
0 None Example 29 0 10 5 0 15 10 0 30 0 10 10 10 0 0 None Example
30 5 0 0 0 50 0 0 15 10 0 10 0 0 10 None Example 31 0 25 0 10 8 0 5
0 0 0 20 10 0 20 None Example 32 10 32 0 15 27 0 10 0 0 0 8 0 0 0
None Example 33 0 10 0 0 40 20 0 20 0 0 10 0 0 0 None Example 34 0
24 0 0 23 0 0 11 0 0 5 20 0 17 None Example 35 0 15 15 30 0 0 10 0
0 10 0 0 10 10 None Example 36 20 0 0 10 30 0 0 0 15 0 10 5 0 10
Exist Example 37 0 20 10 0 25 0 0 30 0 5 10 0 0 0 Exist Example 38
0 10 0 0 30 25 20 0 0 0 0 0 15 0 Exist Comparative Example 14 50 0
0 0 0 0 0 10 20 0 0 0 20 0 None Comparative Example 15 0 0 0 60 0 0
20 0 0 0 0 20 0 0 None Comparative Example 16 0 0 37 0 0 15 0 0 0
13 35 0 0 0 None Comparative Example 17 0 2 0 0 50 0 0 20 0 15 0 0
0 13 None Comparative Example 18 45 0 0 0 0 0 0 0 15 0 0 0 15 0
None Comparative Example 19 0 20 20 0 0 0 10 0 0 20 0 0 10 10 None
Comparative Example 20 0 0 0 40 0 0 0 15 0 0 20 0 0 0 None
Comparative Example 21 0 0 0 0 50 0 10 0 5 0 5 0 10 0 None
Comparative Example 22 0 0 0 0 0 0 0 5 0 0 0 10 0 25 None
Comparative Example 23 0 0 0 0 0 0 10 0 0 10 0 20 0 0 None
Comparative Example 24 0 0 0 0 0 0 0 0 25 0 0 25 0 0 None
Comparative Example 25 0 0 0 0 0 0 0 25 0 0 15 0 20 0 None
Comparative Example 26 Phosphate/soap treatment Mass of film Mass
ratio of Mass ratio of per unit area Mass ratio of resin/(water-
lubricant/(water- Water-soluble salt of lubricating water-soluble
soluble tungstate + soluble tungstate + Component (E) coating film
tungstate/water- water-soluble water-soluble (E-1) (E-2) (E-3)
(E-4) (g/m.sup.2) soluble silicate) silicate) silicate) Example 19
0 0 0 0 11.1 2.00 0.42 0.25 Example 20 0 0 0 0 12.5 0.80 1.00 0.22
Example 21 0 0 0 0 10.5 1.40 0.33 0.33 Example 22 0 0 0 0 1.0 1.08
0.07 0.27 Example 23 0 0 0 0 10.0 3.00 0.17 0.50 Example 24 0 0 0 0
2.2 1.67 0.13 0.13 Example 25 0 0 0 0 3.5 0.84 0.80 0.37 Example 26
0 0 0 0 7.7 4.33 -- 0.25 Example 27 0 0 0 0 9.7 1.00 0.19 0.06
Example 28 0 0 0 0 9.2 0.71 0.02 0.10 Example 29 0 0 0 0 8.9 1.67
1.00 0.50 Example 30 0 0 0 0 10.2 10.00 0.45 0.36 Example 31 2 0 0
0 5.5 0.72 0.12 1.16 Example 32 0 3 0 0 8.9 1.00 0.12 0.10 Example
33 0 0 0 0 19.5 6.00 0.29 0.14 Example 34 0 0 0 0 16.9 0.96 0.23
0.89 Example 35 0 0 0 0 19.9 1.00 0.33 0.33 Example 36 0 0 0 0 10.1
2.00 0.25 0.42 Example 37 0 0 0 0 6.6 0.83 0.64 0.18 Example 38 0 0
0 0 5.5 5.50 0.31 0.23 Comparative Example 14 0 0 0 0 12.8 -- 0.60
0.40 Comparative Example 15 0 0 0 0 13.3 -- 0.33 0.33 Comparative
Example 16 0 0 0 0 3.9 0.41 0.25 0.67 Comparative Example 17 0 0 0
0 3.9 25.00 0.67 0.25 Comparative Example 18 0 0 25 0 11.1 -- 0.33
0.33 Comparative Example 19 0 0 0 10 10.8 -- 0.75 0.50 Comparative
Example 20 25 0 0 0 9.2 -- 0.38 0.50 Comparative Example 21 10 10 0
0 6.2 -- 0.30 0.30 Comparative Example 22 30 0 0 30 -- -- -- --
Comparative Example 23 0 40 20 0 -- -- -- -- Comparative Example 24
50 0 0 0 -- -- -- -- Comparative Example 25 0 40 0 0 -- -- -- --
Comparative Example 26 Phosphate/soap treatment *Numerical in each
of components (A) to (E) means an addition amount in a lubricating
coating agent (% by mass). For a phosphate/soap treatment, a film
removal method is different from that for an aqueous lubricant,
film removability was not evaluated.
(2-2) Lubricating Coating Treatment
[0103] For evaluation on the hypothesis of a bolt production step
to be the object of working of a steel wire, various test pieces
were subjected to the following lubricating coating treatment.
After subjecting to the lubricating coating treatment, a mass ratio
of water-soluble tungstate/water-soluble silicate in a lubricating
coating film of a sample steel wire rod is the same as a mass ratio
of water-soluble tungstate/water-soluble silicate in a lubricating
coating agent mentioned in Table 3.
Pretreatment and Lubricating Coating Treatment of Examples 19 to 35
and Comparative Examples 14 to 25
[0104] (a) Degreasing: commercially available degreasing agent
(FINECLEANER (registered trademark) E6400, manufactured by Nihon
Parkerizing Co., Ltd.), concentration: 20 g/L, temperature:
60.degree. C., immersion: 10 minutes (b) Water rinsing: tap water,
normal temperature, immersion: 20 seconds (c) Pickling: 17.5%
hydrochloric acid, normal temperature, immersion: 20 minutes (d)
Water rinsing: tap water, normal temperature, immersion: 20 seconds
(e) Neutralization: commercially available neutralizer (PREPALENE
(registered trademark) 27, manufactured by Nihon Parkerizing Co.,
Ltd.) (f) Lubricating coating treatment: lubricating coating agent
prepared in (2-1), temperature: 60.degree. C., immersion: 1 minute
(g) Drying: at 100.degree. C. for 10 minutes (h) The amount of a
lubricating coating film was appropriately adjusted by the
concentration of a treatment agent.
Pretreatment and Lubricating Coating Treatment of Examples 36 to
38
[0105] (a) Degreasing: commercially available degreasing agent
(FINECLEANER (registered trademark) 6400, manufactured by Nihon
Parkerizing Co., Ltd.), concentration: 20 g/L, temperature:
60.degree. C., immersion: 10 minutes (b) Water rinsing: tap water,
normal temperature, immersion: 30 seconds (c) Pickling:
hydrochloric acid, concentration: 17.5%, normal temperature,
immersion: 10 minutes (d) Water rinsing: tap water, normal
temperature, immersion: 30 seconds (e) Zirconium treatment:
commercially available zirconium chemical conversion treatment
agent (PALLUCID (registered trademark) 1500, manufactured by Nihon
Parkerizing Co., Ltd.), concentration: 50 g/L, temperature:
45.degree. C., immersion: 2 minutes (f) Water rinsing: tap water,
normal temperature, immersion: 30 seconds (g) Lubricating coating
treatment: lubricating coating agent prepared in (2-1),
temperature: 60.degree. C., immersion: 1 minute (h) Drying: at
100.degree. C. for 10 minutes (i) Amount of undercoating film:
zirconium undercoat: 50 mg/m.sup.2
[0106] The amount of a lubricating coating film was appropriately
adjusted by the concentration of a treatment agent.
Pretreatment and Film Treatment of Comparative Example 26
(Phosphate/Soap Treatment)
[0107] (a) Degreasing: commercially available degreasing agent
(FINECLEANER (registered trademark) 6400, manufactured by Nihon
Parkerizing Co., Ltd.), concentration: 20 g/L, temperature
60.degree. C., immersion: 10 minutes (b) Water rinsing: tap water,
normal temperature, immersion: 30 seconds (c) Pickling:
hydrochloric acid, concentration: 17.5%, normal temperature,
immersion: 10 minutes (d) Water rinsing: tap water, normal
temperature, immersion: 30 seconds (e) Chemical conversion coating:
commercially available zinc phosphate chemical conversion treatment
agent (PALBOND (registered trademark) 3696X, manufactured by Nihon
Parkerizing Co., Ltd.), concentration: 75 g/L, temperature:
80.degree. C., immersion: 7 minutes (f) Water rinsing: tap water,
normal temperature, immersion: 30 seconds (g) Soap treatment:
commercially available reactive soap lubricant (PALUBE (registered
trademark) 235, manufactured by Nihon Parkerizing Co., Ltd.),
concentration: 70 g/L, temperature: 85.degree. C., immersion: 3
minutes (h) Drying: at 100.degree. C. for 10 minutes (i) Amount of
film: 10 g/m.sup.2
(2-3) Evaluation Test
(2-3-1) Workability (Spike Property) Test
[0108] A spike test was performed as a test on the hypothesis of
shank reducing when a steel wire is formed into a bolt.
[0109] The spike test was performed in accordance with the method
defined in JP 05-7969 A. After the test, lubricity was evaluated by
a spike height and a forming load. The more the spike height
increases and the more the forming load decreases, the more
lubricity becomes excellent. As mentioned in the above document, an
area expansion ratio in the spike test is about 10 times. Lubricity
of the film was evaluated by measuring the load and the spike
height during working.
Test piece for evaluation: S45C spheroidizing-annealed material in
size of 25 mm.phi..times.30 mm
Evaluation Criteria
[0110] Spike performance: spike height (mm)/working load
(kNf).times.100
[0111] The more the value increases, the more spike property
becomes satisfactory.
A: Extremely excellent as compared with a phosphate/soap coating
film (0.96 or more) B: Excellent as compared with a phosphate/soap
coating film (0.94 or more and less than 0.96) C: Equivalent to a
phosphate/soap coating film (0.92 or more and less than 0.94) D:
Inferior as compared with a phosphate/soap coating film (0.90 or
more and less than 0.92) E: Drastically inferior as compared with a
phosphate/soap coating film (less than 0.90)
(2-3-2) Workability (Upsetting-Ball Ironing Property) Test
[0112] An upsetting-ball ironing test was performed as a test on
the hypothesis of forming of a bolt head when a steel wire is
formed into a flange bolt. The upsetting-ball ironing test was
performed in accordance with the method defined in JP 2013-215773
A. An area expansion ratio in the upsetting-ball ironing test was
adjusted to at most 150 or more times, and the area expansion ratio
is very large as compared with the above-mentioned spike test.
Therefore, it is a test capable of reproducing working that
requires high workability for formation of a head part of a hexagon
bolt with flange. Seizure resistance of the coating film was
evaluated by evaluating the amount of seizure of an ironing
surface. Test piece for evaluation: S10C spheroidizing-annealed
material in size of 14 mm.phi..times.32 mm
Bearing ball: 10 mm.phi. SUJ2 Evaluation criteria (Evaluation was
performed in accordance with the following criteria A to E based on
each seizure state shown in FIG. 1)
[0113] Evaluation was made of the area where seizure occurred based
on the area of the entire ironing surface.
A: Extremely excellent as compared with a phosphate/soap coating
film B: Excellent as compared with a phosphate/soap coating film C:
Equivalent to a phosphate/soap coating film D: Inferior as compared
with a phosphate/soap coating film E: Drastically inferior as
compared with a phosphate/soap coating film
(2-3-3) Film Removability Test
[0114] A film removability test was performed as follows. Using an
upper mold and a lower mold, each having a plane surface, a
columnar test piece was subjected to upsetting at a compression
ratio of 50%, and then immersed in an alkali cleaner mentioned
below. A film retention ratio was calculated by measuring the
weight of a coating film before and after a film removal
treatment.
Test piece for evaluation: S45C spheroidizing-annealed material in
size of 25 mm.phi..times.30 mm Alkali cleaner: aqueous 2% NaOH
solution Film removal conditions: liquid temperature: 60.degree.
C., immersion: time: 2 minutes
Treatment Procedure:
[0115] Measurement of the weight of a coating film before a film
removal treatment, a film removal treatment, water rinsing, drying,
and measurement of the weight of a coating film after a film
removal treatment were performed in this order.
Film retention ratio (%)=(film weight after film removal
treatment/film weight before film removal treatment).times.100
Evaluation Criteria:
[0116] The more a film retention ratio decreases, the more film
removability becomes satisfactory.
A: A film retention ratio is 0% B: A film retention ratio exceeds
0% and less than 8% C: A film retention ratio 8% or more and less
than 16% D: A film retention ratio is 16% or more and less than 25%
E: A film retention ratio is 25% or more
(2-3-4) Evaluation of Corrosion Resistance (Long-Term Rust
Prevention Property)
[0117] In summer season, a test piece subjected to the
above-mentioned coating film treatment was exposed to an open air
atmosphere indoors for two weeks or two months, and then the degree
of rusting was observed. It was judged that the more the rust area
increases, the more corrosion resistance becomes inferior.
Test piece: SPCC-SD in size of 75 mm.times.35 mm.times.0.8 mm
Evaluation criteria: A: Extremely excellent as compared with a
phosphate/soap coating film (rust area of 3% or less) B: Excellent
as compared with a phosphate/soap coating film (rust area of
exceeding 3% to 10% or less) C: Identical to a phosphate/soap
coating film (rust area of exceeding 10% to 20% or less) D:
Inferior to a phosphate/soap coating film (rust area of exceeding
20% to 30% or less) E: Drastically inferior as compared with a
phosphate/soap coating film (rust area of exceeding 30%)
[0118] The test results are shown in Table 4. As is apparent from
Table 4, in Examples, workabilities (spike property, ball ironing
property, film removability) and corrosion resistance (long-term
rust prevention property) were satisfactory. As a result of
subjecting to a zirconium chemical conversion treatment as a
surface treatment, higher corrosion resistance was exhibited. In
Comparative Examples 14 to 21 in which a ratio of a water-soluble
silicate to a water-soluble tungstate deviated from the scope of
the present invention, there was a tendency that the results of
ball ironing property and corrosion resistance are inferior. In
Comparative Examples 22 to 25 in which components other than the
silicate and tungstate were included as aqueous inorganic salts,
there was a tendency that the results of ball ironing property and
corrosion resistance are inferior. In Comparative Example 26 in
which the phosphate coating film was subjected to a reactive soap
treatment, comparatively excellent performances were exhibited.
However, because of containing phosphorus, when subjecting to a
heat treatment such as quenching and tempering while having the
lubricating coating film on a surface, there is a fear that the
steel wire rod becomes fragile as a result of the occurrence of
phosphorizing. Therefore, Comparative Example 26 deviates from the
object of the present invention. Similarly, Comparative Examples 19
and 22 deviate from the scope of the present invention because of
containing phosphorus.
[0119] Even if the lubricating coating film contains a
water-soluble silicate but contains no water-soluble tungstate,
insufficient film removability was exhibited.
TABLE-US-00004 TABLE 4 Workability Corrosion resistance Ball (Rust
prevention property) Spike ironing Film Two Two Phosphatizing
property property removability weeks months property*1 Example 19 A
A A A A B Example 20 B B B A B B Example 21 A A A A A B Example 22
C B A A B B Example 23 A A A A A B Example 24 A A A A A B Example
25 A A B A A B Example 26 A B A A A B Example 27 A A A A A B
Example 28 A B B A B B Example 29 A A A A A B Example 30 A B A A B
B Example 31 B C B A B B Example 32 C A A A A B Example 33 A B A A
A B Example 34 A B A A B B Example 35 A B A A A B Example 36 A A A
A A B Example 37 A B B A A B Example 38 A B A A A B Comparative
Example 14 A D E D D B Comparative Example 15 A D A D D B
Comparative Example 16 A D C B D B Comparative Example 17 A D A B D
B Comparative Example 18 B D B E E B Comparative Example 19 B D D D
D E Comparative Example 20 A D A D D B Comparative Example 21 B D A
D D B Comparative Example 22 B D A D D E Comparative Example 23 C D
A E E B Comparative Example 24 A D A D D B Comparative Example 25 B
E A D D B Comparative Example 26 B B -- B B E *1B: There is no
possibility of brittle fracture of steel wire rod due to phosphorus
because of containing no phosphorus. E: There is possibility of
brittle fracture of a steel wire rod due to phosphorus because of
containing phosphorus.
[0120] As is apparent from the above description, the steel wire
rod of the present invention does not exhibit phosphorizing
property during a heat treatment because of containing no
phosphorus, and also can reconcile high workability and corrosion
resistance which are equal to or better than those of the steel
wire rod subjected to conventional phosphate and soap treatments.
Because of satisfactory film removability of the lubricating
coating film due to a cleaner after working, the steel wire rod of
the present invention also contributes to an improvement in process
efficiency when the subsequent step such as a plating step is
performed after forming into a bolt. Therefore, the steel wire rod
of the present invention has an industrially high utilization
value.
[0121] The present invention includes the following aspects.
Aspect 1:
[0122] A steel wire rod including a lubricating coating film on a
surface, wherein the lubricating coating film contains a
water-soluble silicate and a water-soluble tungstate, a mass ratio
of water-soluble tungstate/water-soluble silicate being in a range
of 0.7 to 10, and contains no phosphorus.
Aspect 2:
[0123] A steel wire rod including a lubricating coating film
containing no phosphorus, wherein
[0124] the lubricating coating film is formed using a composition
prepared by mixing a water-soluble silicate and a water-soluble
tungstate so as to adjust a mass ratio of water-soluble
tungstate/water-soluble silicate in the lubricating coating film in
a range of 0.7 to 10.
[0125] Aspect 3:
[0126] The steel wire rod according to aspect 1 or 2, wherein the
lubricating coating film contains a resin, and a mass ratio of
resin/(water-soluble silicate+water-soluble tungstate) is in a
range of 0.01 to 1.5.
Aspect 4:
[0127] The steel wire rod according to aspect 3, wherein the resin
is at least one selected from a vinyl resin, an acrylic resin, an
epoxy resin, a urethane resin, a phenol resin, a cellulose
derivative, a polymaleic acid and a polyester resin.
Aspect 5:
[0128] The steel wire rod according to any one of aspects 1 to 4,
wherein the lubricating coating film contains a lubricant, and a
mass ratio of lubricant/(water-soluble silicate+water-soluble
tungstate) is in a range of 0.07 to 1.5.
Aspect 6:
[0129] The steel wire rod according to aspect 5, wherein the
lubricant is at least one selected from wax,
polytetrafluoroethylene, fatty acid soap, fatty acid metal soap,
fatty acid amide, molybdenum disulfide, tungsten disulfide,
graphite and melamine cyanurate.
Aspect 7:
[0130] The steel wire rod according to any one of aspects 1 to 6,
wherein the mass of the coating film per unit area of the
lubricating coating film is in a range of 1.0 to 20 g/m.sup.2.
[0131] This application claims priority based on Japanese Patent
Application No. 2014-070446, filed on Mar. 28, 2014, the disclosure
of which is incorporated by reference herein.
* * * * *