U.S. patent application number 15/129231 was filed with the patent office on 2018-07-05 for steel wire rod having coating film that has excellent corrosion resistance and workability, and method for producing same.
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 | 20180187119 15/129231 |
Document ID | / |
Family ID | 54194997 |
Filed Date | 2018-07-05 |
United States Patent
Application |
20180187119 |
Kind Code |
A1 |
ITO; Hirotaka ; et
al. |
July 5, 2018 |
STEEL WIRE ROD HAVING COATING FILM THAT HAS EXCELLENT CORROSION
RESISTANCE AND WORKABILITY, AND METHOD FOR PRODUCING SAME
Abstract
The present invention provides a steel wire rod having a
lubricating coating film, which can achieve both workabilities such
as wire drawability, spike property and ball ironing property, and
corrosion resistance such as long-term rust prevention property;
and a method for producing the same. Disclosed are a steel wire rod
having a coating film containing no phosphorus, wherein the coating
film includes a lower layer coating film composed of oxide and/or
hydroxide of zirconium and having a film thickness of 1.0 to 200
nm, and an upper layer coating film containing silicon and
tungsten, in order from a steel wire rod side, a mass ratio of
tungsten/silicon being in a range of 1.3 to 18; and a method for
producing the above steel wire rod, which includes bringing an
aqueous chemical conversion treatment solution, which has a pH in a
range of 2.5 to 5.0 and contains a water-soluble zirconium compound
dissolved therein, into contact with a surface of a steel wire rod
to form a lower layer coating film.
Inventors: |
ITO; Hirotaka; (KOBE-SHI,
JP) ; YANAGISAWA; Kasumi; (KOBE-SHI, JP) ;
OZAWA; Takahiro; (KOBE-SHI, JP) ; SHIIHASHI;
Keita; (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 |
|
JP
JP |
|
|
Assignee: |
Kabushiki Kaisha Kobe Seiko Sho
(Kobe Steel, Ltd.)
Kobe-shi
JP
NIHON PARKERIZING CO., LTD.
Chuo-ku
JP
|
Family ID: |
54194997 |
Appl. No.: |
15/129231 |
Filed: |
February 26, 2015 |
PCT Filed: |
February 26, 2015 |
PCT NO: |
PCT/JP15/55679 |
371 Date: |
September 26, 2016 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C10M 2201/0413 20130101;
C10M 163/00 20130101; C23C 22/83 20130101; C10M 107/24 20130101;
C10M 159/06 20130101; C10M 2207/1253 20130101; C10M 133/56
20130101; C10M 111/04 20130101; C10M 2205/18 20130101; C10M
2201/066 20130101; C10M 2215/2225 20130101; C10M 2201/0663
20130101; C23C 28/042 20130101; C10M 169/045 20130101; C10M 107/38
20130101; C10M 2201/041 20130101; C10M 2215/28 20130101; C10M
105/70 20130101; C10M 2201/0653 20130101; C10M 2213/0623 20130101;
C10M 2201/065 20130101; C10N 2030/06 20130101; C10M 105/68
20130101; C10M 105/24 20130101; C10M 2209/043 20130101; C10M 103/02
20130101; C10N 2050/025 20200501; C10N 2040/32 20130101; C10M
103/06 20130101; C10M 2213/062 20130101; C10M 2201/0623 20130101;
C10M 2201/1023 20130101; C10M 2215/0806 20130101; C10N 2030/12
20130101 |
International
Class: |
C10M 111/04 20060101
C10M111/04; C10M 103/06 20060101 C10M103/06; C10M 107/24 20060101
C10M107/24; C10M 159/06 20060101 C10M159/06; C10M 133/56 20060101
C10M133/56; C10M 163/00 20060101 C10M163/00; C10M 169/04 20060101
C10M169/04 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 28, 2014 |
JP |
2014-070445 |
Claims
1. A steel wire rod comprising a coating film comprising no
phosphorus, wherein the coating film comprises a lower layer
coating film comprising an oxide and/or hydroxide of zirconium and
having a film thickness of 1.0 to 200 nm, and an upper layer
coating film comprising silicon and tungsten, in order from a steel
wire rod side, wherein a mass ratio of tungsten/silicon is in a
range of 1.3 to 18.
2. The steel wire rod according to claim 1, wherein the silicon is
derived from a water-soluble silicate, and the tungsten is derived
from a water-soluble tungstate.
3. The steel wire rod according to claim 1, wherein the silicon is
derived from at least one selected from the group consisting of
lithium silicate, sodium silicate and potassium silicate, and the
tungsten is derived from at least one selected from the group
consisting of lithium tungstate, sodium tungstate, potassium
tungstate and ammonium tungstate.
4. The steel wire rod according to claim 1, wherein the upper layer
coating film further comprises a resin, and a mass ratio of
resin/(silicon+tungsten) is in a range of 0.01 to 3.2.
5. The steel wire rod according to claim 4, wherein the resin is at
least one selected from the group consisting of 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.
6. The steel wire rod according to claim 1, wherein the upper layer
coating film further comprises a lubricant, and a mass ratio of
lubricant/(silicon+tungsten) is in a range of 0.01 to 3.2.
7. The steel wire rod according to claim 6, wherein the lubricant
is at least one selected from the group consisting of a wax,
polytetrafluoroethylene, a fatty acid soap, a fatty acid metal
soap, a fatty acid amide, molybdenum disulfide, tungsten disulfide,
graphite and melamine cyanurate.
8. The steel wire rod according to claim 1, wherein a mass of the
coating film per unit area of the upper layer coating film is in a
range from 1.0 to 20 g/m.sup.2.
9. A method for producing the steel wire rod according to claim 1,
which comprises bringing an aqueous chemical conversion treatment
solution, which has a pH in a range of 2.5 to 5.0 and contains
comprises a water-soluble zirconium compound dissolved therein,
into contact with a surface of a steel wire rod to form a lower
layer coating film.
Description
TECHNICAL FIELD
[0001] The present invention relates to a steel wire rod having a
coating film containing no phosphorus on a surface, and a method
for producing the same.
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 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. 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 non-phosphorus based
water-soluble lubricant for 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%.
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), a lubricant (B)
which is at least one 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. 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 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 four
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 in 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] The aqueous lubricating coating film is inferior to the
chemical conversion coating film in nonuniformity of the coating
film. For example, if there are some positions where wire rods are
laid one upon another or binding positions, when a wire rod coil is
treated in a batchwise manner, a film treatment solution does not
spread to the positions, leading to formation of a thin coating
film. Particularly, since the thickness of the coating film exerts
a significant influence on corrosion resistance, for example, there
is recognized a phenomenon in which rusting starts from the binding
position of the coil. Degradation of corrosion resistance due to
nonuniformity of this film was a great problem for a conventional
aqueous lubricating coating film.
[0018] 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.
[0019] 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.
[0020] 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 metal 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.
[0021] The aqueous lubricating coating agents containing an aqueous
water-soluble inorganic salt mentioned in Patent Documents 1 to 3
are commonly 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.
[0022] 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.
[0023] 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.
[0024] As mentioned above, it was impossible for the aqueous
lubricating coating film to form a coating film that can achieve
both high corrosion resistance over a long term of about four or
more months comparable to that of the chemical conversion coating
film even in a service environment, and workability during severe
working. Particularly, with respect to corrosion resistance,
rusting from the position of the thin coating film becomes a
problem since the coating film is likely to become nonuniform. When
a silicate is contained in the aqueous lubricating coating agent,
insufficient film removal becomes a problem.
[0025] Thus, it is an object of the present invention to provide a
steel wire rod having a lubricating coating film that can achieve
both workabilities such as wire drawability, spike property and
hall ironing property, and corrosion resistance such as long-term
rust prevention property; and a method for producing the same.
Means for Solving the Problems
[0026] The inventors of the present invention have intensively
studied so as to solve the above problems and found that it is
possible to achieve both workability and corrosion resistance when
the below-mentioned upper layer coating film and lower layer
coating film are formed on/over a steel wire rod as a lubricating
coating film. Specifically, they have found that it is possible to
obtain high corrosion resistance and workability that have never
been achieved by each component mentioned below alone, by forming,
as a lower layer coating film, a film made of oxide and/or
hydroxide of zirconium, and adjustment of a ratio of a silicate to
a tungstate to a certain specific ratio, namely, adjustment of a
mass ratio of tungsten/silicon to a predetermined ratio to form a
composite upper layer coating film, and thus the present invention
has been completed.
[0027] To solve the above problems, the present invention was
structured as mentioned below.
[0028] A gist of the steel wire rod of the present invention lies
in a steel wire rod having a coating film containing no phosphorus,
wherein the coating film includes a lower layer coating film
composed of oxide and/or hydroxide of zirconium and having a film
thickness of 1.0 to 200 nm, and an upper layer coating film
containing silicon and tungsten, in order from a steel wire rod
side, a mass ratio of tungsten/silicon being in a range of 1.3 to
18.
[0029] It is preferred that the silicon is derived from
water-soluble silicate, and the tungsten is derived from
water-soluble tungstate.
[0030] It is preferred that the silicon is derived from at least
one selected from lithium silicate, sodium silicate and potassium
silicate, and the tungsten is derived from at least one selected
from lithium tungstate, sodium tungstate, potassium tungstate and
ammonium tungstate.
[0031] It is preferred that a resin is contained in the upper layer
coating film, and a mass ratio of resin/(silicon+tungsten) is in a
range of 0.01 to 3.2.
[0032] 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.
[0033] It is preferred that a lubricant is contained in the upper
layer coating film, and a mass ratio of
lubricant/(silicon+tungsten) is in a range of 0.01 to 3.2.
[0034] 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.
[0035] The mass of the coating film per unit area of the upper
layer coating film is preferably in a range of 1.0 to 20
g/m.sup.2.
[0036] A gist of the method for producing a steel wire rod of the
present invention lies in a method which includes bringing an
aqueous chemical conversion treatment solution, which has a pH in a
range of 2.5 to 5.0 and contains a water-soluble zirconium compound
dissolved therein, into contact with a surface of a steel wire rod
to form a lower layer coating film.
Effects of the Invention
[0037] Since a lubricating coating film including an upper layer
coating film and a lower layer coating film was structured as
mentioned above in the steel wire rod of the present invention, it
is possible to obtain a steel wire rod that is excellent in
workabilities such as wire drawability, spike property and ball
ironing property, as well as corrosion resistance such as long-term
rust prevention property. The steel wire rod of the present
invention is excellent as compared with a conventional aqueous
lubricating coating film in that all of these performances are
equal to or better than those of a steel wire rod including a
chemical conversion coating film. It is a feature that did not
exist in a conventional aqueous lubricating coating film that it is
possible to obtain high corrosion resistance even when an aqueous
lubricating coating film became thin due to external factors such
as overlapping and binding between materials.
MODE FOR CARRYING OUT THE INVENTION
[0038] The present invention is directed to a steel wire rod having
a coating film containing no phosphorus, wherein the coating film
includes a lower layer coating film composed of oxide and/or
hydroxide of zirconium and having a film thickness of 1.0 to 200
nm, and an upper layer coating film containing silicon and
tungsten, in order from a steel wire rod side, a mass ratio of
tungsten/silicon being in a range of 1.3 to 18.
[0039] 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
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.
[0040] The steel wire rod of the present invention includes a
lubricating coating film composed of at least two layers, namely, a
lower layer coating film and an upper layer coating film in order
from a surface of a steel wire rod. Each of the upper layer coating
film and the lower layer coating film may be a single layer, or a
layer composed of two or more layers. If necessary, a layer may be
further formed on the upper layer coating film, between the upper
layer coating film and the lower layer coating film, or between the
steel wire rod and the lower layer coating film.
[0041] Both of the coating films contain no phosphorus, and a
composition 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.
[0042] A description will be made in order from each component,
each composition, and the like of a lubricating coating film in a
steel wire rod according to the present invention.
[0043] There is a need that the upper layer coating film is a film
that contains silicon and tungsten, a mass ratio of
tungsten/silicon being in a range of 1.3 to 18. Inclusion of
silicon and tungsten in this range enables formation of a film
having high corrosion resistance, workability and sufficient
adhesion that have never been realized by the below-mentioned
silicate or tungstate alone, or the other aqueous inorganic
salt.
[0044] For example, when the below-mentioned water-soluble silicate
and water-soluble tungstate are composited to form a coating film,
the tungstate is incorporated into a network structure formed of
the silicate. As mentioned above, drawbacks of the tungstate depend
heavily on formation of a crystalline coating film and it becomes
possible for the tungstate to exist uniformly and finely by
incorporating into the network structure of the silicate. Whereby,
it is possible to achieve both property of being less likely to
transmit moisture of the silicate and a passive film having a
self-repair function of the tungstate, leading to a remarkable
improvement in corrosion resistance.
[0045] Examples of the influence of the tungstate on the include an
improvement in film removability. As mentioned above, the silicate
is inferior in workability and film removability since a firm
continuous film is formed by polymerization of the silicate. The
composited tungstate exists in the network structure of the
silicate, whereby, formation of a firm network structure is
appropriately suppressed, thus enabling an improvement in
workability and film removability.
[0046] A mass ratio tungsten/silicon is 1.3 or more, preferably 1.8
or more, and still more preferably 2.0 or more. The mass ratio is
18 or less, preferably 10 or less, and more preferably 5.4 or
less.
[0047] 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 preferably 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 the ratio
can be calculated as mentioned later.
[0048] The lower layer coating film is made of oxide and/or
hydroxide of zirconium, and preferably oxide of zirconium. In the
present invention, the lower layer coating film is sometimes a
zirconium coating film.
[0049] The film thickness of the lower layer coating film is 1.0 nm
or more, preferably 5 nm or more, and more preferably 20 nm or
more. The film thickness is 200 nm or less, preferably 150 nm or
less, and more preferably 130 nm or less. The film thickness of
less than 1.0 nm leads to too thin zirconium coating film, thus
failing to exhibit sufficient corrosion resistance. Whereas, the
film thickness of more than 200 nm exerts no influence on corrosion
resistance, but poor adhesion to the coating films is exhibited,
thus degrading workability.
[0050] Formation of a zirconium coating film in such a manner
enables an improvement in corrosion resistance. This is because
further formation of a zirconium coating film as a lower layer
coating film leads to a change of a network structure of the
silicate, whereby, not only binding is enhanced, but also corrosion
resistance of the binding enhancement part is further improved
because of having moisture blocking capability. The zirconium
coating film is a very thin film as compared with the upper layer
coating film and is therefore likely to form a uniform film even at
a point where a conventional aqueous lubricating coating film is
likely to become a thin film, and this leads to an improvement in
corrosion resistance even at such a point. As mentioned above,
since the network structure of the upper layer coating film and the
binding enhancement portion of a zirconium coating film are
important for an improvement in corrosion resistance, an influence
of a film thickness of the entire upper layer coating film is less
likely to be exerted. Therefore, corrosion resistance can be
sufficiently exhibited even in the point where the above-mentioned
aqueous lubricating coating film is likely to become a thin film.
When using the zirconium coating film alone, defects occur in the
film and serve as a starting point of corrosion and workability is
not obtained, leading to poor corrosion resistance.
[0051] As mentioned above, it is possible to realize high
workability and high corrosion resistance in a service environment,
which have never been achieved by the prior art, by using a coating
film of the silicate and the tungstate in combination with a
zirconium coating film.
[0052] In the present invention, it is suitable that the silicon is
derived from a water-soluble silicate, and the tungsten is derived
from a water-soluble tungstate.
[0053] The water-soluble silicate includes, for example, sodium
silicate, potassium silicate, lithium silicate and ammonium
silicate. These water-soluble silicates may be used alone, or two
or more water-soluble silicates may be used in combination.
[0054] The water-soluble tungstate includes, for example, sodium
tungstate, potassium tungstate, lithium tungstate and ammonium
tungstate. These water-soluble tungstates may be used alone, or two
or more water-soluble tungstates may be used in combination.
[0055] A zirconium supply source in a film treatment agent for
formation of a zirconium coating film according to the present
invention includes, for example, zirconium sulfate, zirconium
oxysulfate, ammonium zirconium sulfate, zirconium nitrate,
zirconium oxynitrate, ammonium zirconium nitrate, zirconium
acetate, zirconium lactate, zirconium chloride, fluoroziroconic
acid, fluorozirconium complex salt and the like. These zirconium
supply sources may be used alone, or two or more zirconium supply
sources may be used in combination.
[0056] A resin will be described below. The resin is mixed in the
upper layer 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.
[0057] 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.
[0058] In the present invention, the upper layer coating film
contains a resin and a mass ratio of resin/(silicon+tungstate) is
preferably 0.01 or more, and more preferably 0.1 or more. The mass
ratio is preferably 3.2 or less, and more preferably 2.1 or less.
If the mass ratio is less than 0.01, the above effects are not
sufficiently exerted. Meanwhile, if the mass ratio exceeds 3.2, the
amounts of silicon and tungsten relatively decrease, thus failing
to exhibit high corrosion resistance and workability which are
features of the present invention.
[0059] 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 occurs. If the lubricant is included in an upper layer coating
of the steel wiring rod of 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.
[0060] 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.
[0061] In the present invention, when the lubricant is contained in
the upper layer coating film, the mass ratio of
lubricant/(silicon+tungsten) is preferably 0.01 or more, and more
preferably 0.1 or more, and the mass ratio is preferably 3.2 or
less, and more preferably 2.1 or less. Here, if the mass ratio of
lubricant/(silicon+tungsten) is less than 0.01, it is impossible to
exhibit performances because of too small amount of the lubricant.
If the mass ratio exceeds 3.2, the amounts of silicon+tungsten
relatively decrease, thus failing to exhibit high corrosion
resistance and workability which are features of the present
invention.
[0062] The upper layer coating film of the steel wire rod of the
present invention can be mixed with a viscosity modifier, in
addition to silicon, tungsten, 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. 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.
[0063] The upper layer 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.
[0064] 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.
[0065] The 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.
[0066] The upper layer coating agent used in the present invention
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.
[0067] 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 upper layer
coating agent.
[0068] 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 upper layer
coating agent.
[0069] 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.
[0070] In the lower layer of the steel wire rod of the present
invention, the lubricating coating film can be used 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.
[0071] In the present invention, a liquid medium (solvent,
dispersion medium) in an upper layer coating agent and a zirconium
coating agent is water. To shorten the drying time of the lubricant
in the drying step, it is possible to mix the upper layer coating
agent with an alcohol having a boiling point lower than that of
water.
[0072] To enhance stability of the solution, the upper layer
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.
[0073] 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 production step
of an upper layer coating agent and a lower layer coating agent
(aqueous chemical conversion treatment agent) as aqueous
lubricating coating agents, and a drying step. Each step will be
described below.
<Cleaning Step (Pretreatment Step)>
[0074] Before formation of a 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 the like,
and various contaminations (oils, etc.).
<Formation Step of Zirconium Coating Film>
[0075] The lower layer coating film is formed by bringing an
aqueous chemical conversion treatment solution, which has a pH in a
range of 2.5 to 5.0 and contains a water-soluble zirconium compound
dissolved therein, into contact with a surface of a steel wire rod
to form a lower layer coating film. The aqueous chemical conversion
treatment solution may be a solution containing the zirconium
supply source. The pH is preferably in a range of 2.8 to 4.8, more
preferably 3.1 to 4.6, and still more preferably 3.4 to 4.4. The pH
of lower than 2.5 leads to excessive etching, thus causing not only
degradation of precipitation efficiency of the coating film, but
also disturbing of uniform formation of the coating film. The off
of higher than 5.0 leads to degradation of liquid stability and
precipitation of a large amount of a zirconium compound or sludge,
thus exerting an adverse influence on formation of the coating
film.
[0076] The aqueous chemical conversion treatment solution may be a
commercially available zirconium chemical conversion treatment
agent, and the zirconium concentration (on a mass basis) is
preferably 10 ppm or more, and more preferably 30 ppm or more, and
is also preferably 500 ppm or less, and more preferably 300 ppm or
less.
[0077] In the present invention, the contact method for forming a
zirconium coating film is not particularly limited and includes,
for example, a spray treatment, an immersion treatment, pouring
treatment, and the like. To promote formation of the coating film,
the temperature of the aqueous chemical conversion treatment
solution in the case of contacting, namely, the treatment
temperature is preferably in a range of 20 to 60.degree. C., and
more preferably 30 to 50.degree. C. The contacting time varies
depending on the material and structure of a steel wire rod, the
concentration of a chemical conversion treatment solution, and the
treatment temperature, and is preferably in a rage of approximately
2 to 600 seconds, and can be appropriately adjusted according to
the amount of the coating film. After the chemical conversion
treatment, a water rinsing step is preferably provided so as not to
incorporate the aqueous chemical conversion treatment solution
adhered to a steel material into the upper layer coating
solution.
<Formation Step of Upper Layer Coating Film>
[0078] Next, an upper layer coating film is formed on the zirconium
coating film obtained as mentioned above. There no particular
limitation on the step of applying the upper layer 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. A
surface of the steel wire rod is sufficiently coated with an upper
layer coating agent as an aqueous lubricating coating agent, 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 aqueous 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 aqueous
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>
[0079] There is a need to dry the upper layer 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.
[0080] The mass of an upper layer coating film formed over a steel
wire rod is appropriately controlled depending on 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 lubricity. 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 lubricity. 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
aqueous 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>
[0081] In the present invention, film removal can be performed by
immersing the upper layer coating film 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 upper layer coating
film, the upper layer coating film dissolves in the cleaning
solution, thus making it possible to easily perform film removal.
The coating film thus obtained easily falls off by a heat treatment
after working. Therefore, alkali cleaning enables prevention of
contamination and poor plating in the subsequent step caused by
insufficient film removal.
[0082] A method for analysis of the composition of a coating film
will be described below.
[0083] Examples of the method for analysis of a zirconium coating
film include a method of observation using a cross-sectional
scanning electron microscope (SEM), or a method in which a film
thickness is directly observed in observation using a
cross-sectional transmission electron microscope (TEM). At this
time, it is effective to expose a cross-section by working using a
cross-section polisher (CP) or working using focused ion beams
(FIB) so as to perform cross-sectional observation without damaging
a coating film. A simple method includes a method in which a
thickness of a zirconium coating film on a surface of a steel
material is analyzed by fluorescent X-ray spectroscopy (X-ray
fluorescence (XRF)). At this time, an upper layer coating film is
preferably peeled with an aqueous alkali solution. A film thickness
of the lower layer coating film in the following manner: three
regions where a film thickness is measured are selected at random
on a surface of a steel material after peeling the upper layer
coating film, and then the film thickness is measured in all of
selected regions. An average of thicknesses measured in three
regions is regarded as a film thickness of an undercoating film of
the steel material.
[0084] The method for analysis of the composition of the upper
layer coating film includes, for example, a method using
inductively coupled plasma (ICP). In this case, the coating film on
the steel material is dissolved in an aqueous strong alkali
solution and the amounts of silicon and tungsten dissolved are
measured by ICP, thus enabling analysis of the composition of the
coating film.
[0085] When it is difficult to dissolve the upper layer coating
film, it is also possible to analyze the composition of the coating
film by using a method in which the amounts of silicon and tungsten
on a surface of a steel wire rod by fluorescent X-ray spectroscopy
(X-ray fluorescence (XRF)).
EXAMPLES
[0086] 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 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 Upper Layer Coating Agent as Aqueous
Lubricating Coating Agent and Lower Layer Coating Agent
[0087] In accordance with the combination and proportion shown in
Table 1, upper layer coating agents as aqueous lubricating coating
agents and lower layer coating agents of Examples 1 to 12 and
Comparative Examples 2 to 17 were prepared using the respective
components shown below. To upper layer coating agents of Examples 1
to 12 and Comparative Examples 3 to 17, lithium hydroxide was added
in the concentration of 1% in the solution so as to enhance liquid
stability. Comparative Example 18 means the case subjected to a
phosphate/soap treatment, and a wire drawing powder was not
used.
A. Upper Layer Coating Agent
<Water-Soluble Silicate>
[0088] (A-1) Sodium metasilicate [0089] (A-2) JIS No. 3 sodium
silicate (Na.sub.2OnSiO.sub.2, n=3) [0090] (A-3) Lithium silicate
(Li.sub.2OnSiO.sub.2, n=3.5)
<Water-Soluble Tungstate>
[0090] [0091] (B-1) Ammonium tungstate [0092] (B-2) Sodium
tungstate [0093] (B-3) Potassium tungstate
<Resin>
[0093] [0094] (C-1) Polyvinyl alcohol (average molecular weight of
about 50,000) [0095] (C-2) Sodium neutralizing salt of
isobutylene-maleic anhydride copolymer (average molecular weight of
about 165,000)
<Lubricant>
[0095] [0096] (D-1) Polyethylene wax (average particle size of 5
.mu.m) [0097] (D-2) Ethylenebis-stearic acid amide
<Water-Soluble Salt>
[0097] [0098] (E-1) Sodium metaborate [0099] (E-2) Sodium tartrate
[0100] (E-3) Sodium sulfate [0101] (E-4) Sodium Pyrophosphate
B. Lower Layer Coating Agent
<Zirconium Lower Layer Coating Film>
[0101] [0102] (F) Zirconium chemical conversion treatment agent
(PALLUCID (registered trademark) 1500, manufactured by Nihon
Parkerizing Co., Ltd.) <Lower Layer Coating Film except for
Zirconium Lower Layer Coating Film> [0103] (G-1) JIS No. 2
sodium silicate (Na.sub.2OnSiO.sub.2, n=2.5) [0104] (G-2) Zinc
phosphate
TABLE-US-00001 [0104] TABLE 1 Water-soluble silicate Water-soluble
tungstate Zirconium Resin Lubricant Water-soluble salt Component
(A) Component (B) coating Component (C) Component (D) Component (E)
(A-1) (A-2) (A-3) (B-1) (B-2) (B-3) film (nm) (C-1) (C-2) (D-1)
(D-2) (E-1) (E-2) Example 1 20 20 0 30 30 0 55 0 0 0 0 0 0 Example
2 0 15 10 15 60 0 195 0 0 0 0 0 0 Example 3 0 10 0 59 0 20 65 11 0
0 0 0 0 Example 4 0 0 40 0 0 40 75 0 5 15 0 0 0 Example 5 30 0 0 50
0 0 1 0 10 0 10 0 0 Example 6 40 0 10 0 40 0 150 7 0 0 3 0 0
Example 7 0 40 0 0 25 30 10 0 0 5 0 0 0 Example 8 10 0 5 17 0 10 22
18 0 20 20 0 0 Example 9 10 5 0 0 20 0 33 0 15 45 5 0 0 Example 10
0 10 10 10 10 0 55 15 25 0 20 0 0 Example 11 11 0 0 0 10 12 80 7 40
15 5 0 0 Example 12 0 15 0 0 0 15 5 0 35 35 0 0 0 Comparative No
coating film (only dry lubricant) Example 1 Comparative 0 0 0 0 0 0
100 0 0 0 0 0 0 Example 2 Comparative 25 0 15 0 0 60 0.6 0 0 0 0 0
0 Example 3 Comparative 0 30 0 0 70 0 230 0 0 0 0 0 0 Example 4
Comparative 75 0 0 25 0 0 80 0 0 0 0 0 0 Example 5 Comparative 0 10
0 90 0 0 66 0 0 0 0 0 0 Example 6 Comparative 0 100 0 0 0 0 100 0 0
0 0 0 0 Example 7 Comparative 0 0 0 0 0 90 90 10 0 0 0 0 0 Example
8 Comparative 0 0 0 60 0 0 95 0 15 0 0 25 0 Example 9 Comparative 0
0 0 0 35 30 85 10 0 0 0 0 25 Example 10 Comparative 50 15 0 0 0 0
60 0 0 0 0 0 10 Example 11 Comparative 0 55 15 0 0 0 128 0 0 0 0 0
0 Example 12 Comparative 0 0 0 0 0 0 51 0 20 0 0 40 0 Example 13
Comparative 0 0 0 0 0 0 111 5 0 0 0 95 0 Example 14 Comparative 0 0
0 0 0 0 50 0 10 0 0 0 90 Example 15 Comparative 35 0 0 35 20 0 0 0
10 0 0 0 0 Example 16 Comparative 0 10 10 10 70 0 0 0 0 0 0 0 0
Example 17 Comparative Phosphate/soap treatment Example 18 Mass of
coating film per unit Mass ratio Mass ratio Water-soluble salt
Undercoating area of upper Mass ratio of resin/ of lubricant/
Component (E) film (mg/m.sup.2) layer coating of tungsten/ (silicon
+ (silicon + (E-3) (E-4) (G-1) (G-2) film (g/m.sup.2) silicon
tungsten) tungsten) Example 1 0 0 0 0 7.5 3.6 -- -- Example 2 0 0 0
0 4.1 5.2 -- -- Example 3 0 0 0 0 6.6 16.1 0.19 -- Example 4 0 0 0
0 7.7 1.4 0.13 0.39 Example 5 0 0 0 0 1.6 5.4 0.23 0.23 Example 6 0
0 0 0 14.0 1.9 0.18 0.08 Example 7 0 0 0 0 3.5 2.5 -- 0.11 Example
8 0 0 0 0 5.0 4.5 0.79 1.76 Example 9 0 0 0 0 3.0 2.7 0.91 3.02
Example 10 0 0 0 0 13.1 1.8 1.88 0.94 Example 11 0 0 0 0 18.9 5.0
3.02 1.29 Example 12 0 0 0 0 9.9 1.5 2.56 2.56 Comparative No
coating film (only dry lubricant) Example 1 Comparative 0 0 0 0 --
-- -- -- Example 2 Comparative 0 0 0 0 6.5 2.9 -- -- Example 3
Comparative 0 0 0 0 5.5 4.1 -- -- Example 4 Comparative 0 0 0 0 3.3
1.1 -- -- Example 5 Comparative 0 0 0 0 2.2 19.6 -- -- Example 6
Comparative 0 0 0 0 2.8 -- -- -- Example 7 Comparative 0 0 0 0 4.4
-- -- -- Example 8 Comparative 0 0 0 0 9.9 -- 0.34 -- Example 9
Comparative 0 0 0 0 10.1 -- 0.26 -- Example 10 Comparative 25 0 0 0
8.1 -- -- -- Example 11 Comparative 0 30 0 0 7.7 -- -- -- Example
12 Comparative 0 40 0 0 -- -- -- -- Example 13 Comparative 0 0 0 0
-- -- -- -- Example 14 Comparative 0 0 0 0 -- -- -- -- Example 15
Comparative 0 0 1.9 0 8.9 4.9 0.21 -- Example 16 Comparative 0 0 0
4.3 7.4 6.6 -- -- Example 17 Comparative Phosphate/soap treatment
Example 18 *Numerical in each of components (A) to (E) means an
addition amount in an upper layer coating agent (% by mass).
(1-2) Analysis of Coating Film
[0105] A test material in size of .phi.3.2 mm.times.1 m subjected
to a treatment for formation of a lower layer coating film and an
upper layer coating film was immersed in an aqueous 2% sodium
hydroxide solution heated at 60.degree. C. for 2 minutes and the
upper layer coating film was peeled. Thereafter, the amounts of
silicon and tungsten contained in the aqueous sodium hydroxide
solution used for peeling were measured by inductively coupled
plasma (ICP) and the value of a mass ratio of tungsten/silicon was
examined. After immersing in an aqueous 2% sodium hydroxide
solution heated at 60.degree. C. for 2 minutes, the excessive upper
layer coating film was peeled. A film thickness of a zirconium
coating film was measured by subjecting the test material whose
upper layer coating was peeled to fluorescent X-ray spectroscopy
(XRF). The measured value is shown in Table 1. By carrying out
cross-sectional SEM analysis, the thickness of the lower layer
coating film was measured and the film thickness was measured. In
the measurement of the film thickness, the film thickness of the
lower layer coating film (namely, zirconium coating film) was
measured in the following manner: three regions where a film
thickness is measured are selected at random on a surface of a
steel material after peeling the upper layer coating film, and then
the film thickness is measured in all of selected regions. An
average of thicknesses measured in three regions is regarded as a
film thickness of an undercoating film of the steel material.
(1-3) Coating Treatment
[0106] A coating treatment method is shown below. The material to
be treated is a .phi.3.2 mm steel wire rod. To reproduce thinning
of a lubricating coating film in the binding portion, the treatment
was performed in a state of being bundled with a binding band made
of a plastic.
Pretreatment and Coating Treatment of Examples 1 to 12 and
Comparative Examples 3 to 15
[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 [0108] (b) Water rinsing: tap
water, normal temperature, immersion: 30 seconds [0109] (c)
Pickling: hydrochloric acid, concentration: 17.5%, normal
temperature, immersion: 10 minutes [0110] (d) Water rinsing: tap
water, normal temperature, immersion: 30 seconds [0111] (e) Lower
layer coating 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., pH 4.0, immersion treatment:
immersion time is appropriately adjusted according to the amount of
the coating film. [0112] (f) Water rinsing: tap water, normal
temperature, immersion: 30 seconds [0113] (g) Upper layer coating
treatment: upper layer coating agent prepared in (1-1),
temperature: 60.degree. C., immersion: 1 minute [0114] (h) Drying:
100.degree. C., 10 minutes
Pretreatment and Coating Treatment of Comparative Example 1
[0114] [0115] (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 [0116] (b) Water rinsing: tap
water, normal temperature, immersion: 30 seconds [0117] (c)
Pickling: hydrochloric acid, concentration: 17.5%, normal
temperature, immersion: 10 minutes [0118] (d) Water rinsing: tap
water, normal temperature, immersion: 30 seconds [0119] (e) Pure
water rinsing: deionized water, normal temperature, immersion:
30.degree. C. [0120] (f) Drying: 100.degree. C., 10 minutes
Pretreatment and Coating Treatment of Comparative Example 2
[0120] [0121] (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 [0122] (b) Water rinsing: tap
water, normal temperature, immersion: 30 seconds [0123] (c)
Pickling: hydrochloric acid, concentration: 17.5%, normal
temperature, immersion: 10 minutes [0124] (d) Water rinsing: tap
water, normal temperature, immersion: 30 seconds [0125] (e) Lower
layer coating treatment: commercially available zirconium chemical
conversion treatment agent (PAILUCID (registered trademark) 1500,
manufactured by Nihon Parkerizing Co., Ltd.), concentration: 50
g/L, temperature: 45.degree. C., pH 4.0, immersion treatment:
immersion time is appropriately adjusted according to the amount of
the coating film. [0126] (f) Water rinsing: tap water, normal
temperature, immersion: 30.degree. C. [0127] (g) Pure water
rinsing: deionized water, normal temperature, immersion: 30.degree.
C. [0128] (h) Drying: 100.degree. C., 10 minutes
Comparative Example 16 (Silicate Lower Layer Coating Film, Upper
Layer Coating Treatment)
[0128] [0129] (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 [0130] (b) Water rinsing: tap
water, normal temperature, immersion: 30 seconds [0131] (c)
Pickling: hydrochloric acid, concentration: 17.5%, normal
temperature, immersion: 10 minutes [0132] (d) Water rinsing: tap
water, normal temperature, immersion: 30 seconds [0133] (e) Lower
layer coating treatment: commercially available surface treatment
agent (PREPALENE (registered trademark) 5557, manufactured by Nihon
Parkerizing Co., Ltd.), concentration 2.5 g/L, temperature
70.degree. C., immersion: 1 minute [0134] (f) Rough drying: normal
temperature, 60 seconds [0135] (g) Upper layer coating treatment:
upper layer coating agent prepared in (1-1), temperature:
60.degree. C., immersion: 1 minute [0136] (h) Drying: 100.degree.
C., 10 minutes
Pretreatment and Coating Treatment of Comparative Example 17 (Zinc
Phosphate Lower Layer Coating Film, Upper Layer Coating
Treatment)
[0136] [0137] (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 [0138] (b) Water rinsing: tap
water, normal temperature, immersion: 30 seconds [0139] (c)
Pickling: hydrochloric acid, concentration: 17.5%, normal
temperature, immersion: 10 minutes [0140] (d) Water rinsing: tap
water, normal temperature, immersion: 30 seconds [0141] (e) Lower
layer coating 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 [0142] (f)
Water rinsing: tap water, normal temperature, immersion: 30 seconds
[0143] (g) Upper layer coating treatment: upper layer coating agent
prepared in (1-1), temperature: 60.degree. C., immersion: 1 minute
[0144] (h) Drying: 100.degree. C., 10 minutes
Pretreatment and Coating Treatment of Comparative Example 18
(Phosphate/Soap Treatment)
[0144] [0145] (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 [0146] (b) Water rinsing: tap
water, normal temperature, immersion: 30 seconds [0147] (c)
Pickling: hydrochloric acid, concentration: 17.5%, normal
temperature, immersion: 10 minutes [0148] (d) Water rinsing: tap
water, normal temperature, immersion: 30 seconds [0149] (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: 10 minutes [0150] (f)
Water rinsing: tap water, normal temperature, immersion: 30 seconds
[0151] (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 [0152] (h) Drying: 100.degree.
C., 10 minutes [0153] (i) Amount of dry coating film: 10
g/m.sup.2
(1-4) Evaluation Test
(1-4-1) Workability (Wire Drawability) Test
[0154] 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.
At the position immediately before drawing a material, a die box
with the dry lubricant was provided 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.
Evaluation Criteria
[0155] A: No seizure occurs and no metal gloss is recognized and,
on the whole, a film remains in a large amount. [0156] B: No
seizure occurs and no metal gloss is recognized, and a film remains
in an amount which slightly smaller than that in A. [0157] C: No
seizure occurs and a film retention amount is slightly small, and
metal gloss is partially recognized. [0158] D: No seizure occurs
and metal gloss is recognized at numerous sites. [0159] E: Seizure
occurred.
(1-4-2) Corrosion Resistance (Long-Term Rust Prevention Property)
Test
[0160] 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 four 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
[0161] A: Extremely excellent as compared with a phosphate/soap
coating film (rust area of less than 5%) [0162] B: Excellent as
compared with a phosphate/soap coating film (rust area of 5% or
more and less than 15%) [0163] C: Equivalent to a phosphate/soap
coating film (rust area of 15% or more and less than 25%) [0164] D:
Inferior as compared with a phosphate/soap coating film (rust area
of 25% or more and less than 35%) [0165] E: Drastically inferior as
compared with a phosphate/soap coating film (rust area of 35% or
more)
[0166] The test results are shown in Table 2. In all Examples, a
coating film remains in a large amount, resulting in satisfactory
workability and satisfactory corrosion resistance. In Comparative
Example 1 in which the same upper and lower layer coating films as
those in the present invention are not used, seizure occurred
during wire drawing. In Comparative Example 2 in which a test was
performed using only a zirconium coating film, workability was
insufficient since seizure occurred, like Comparative Example 1,
and corrosion resistance was also insufficient. In Comparative
Examples 3 and 4, a film thickness of a zirconium coating film used
deviates from the scope of the present invention. In Comparative
Example 3 in which a film thickness of a zirconium coating film is
too small, corrosion resistance degraded, whereas, workability
tends to be degraded in Comparative Example 4 in which a film
thickness of a zirconium coating film is too large. In Comparative
Examples 5 to 12, a mass ratio of silicon to tungsten was set at a
value deviating from the scope of the present invention, and
workability was inferior and also corrosion resistance was inferior
because of small film retention amount after wire drawing. In
Comparative Examples 13 to 15 in which components other than a
water-soluble silicate and a water-soluble tungstate are included
as an aqueous inorganic salt, workability was inferior and also
corrosion resistance was inferior because of a small film retention
amount after wire drawing. In Comparative Example 16 in which a
coating film of a water-soluble silicate was formed as a lower
layer coating film, it was impossible to obtain high corrosion
resistance comparable to Examples. In Comparative Example 17, a
coating film of a phosphate was formed as a lower layer coating
film. Although workability and corrosion resistance are in the same
level as in Examples, this film is not preferred since it contains
phosphorus to cause the above-mentioned problem such as
phosphorizing of a bolt. In Comparative Example 18 in which a
phosphate coating film was subjected to a reactive soap treatment,
like Comparative Example 17, a phosphate coating film is not
preferred because of a problem such as phosphorizing of a bolt.
Regarding phosphorizing, like Comparative Examples 12 and 13, the
same applies to the case of containing a phosphate as a
water-soluble salt.
[0167] It is possible to impart high corrosion resistance even when
an aqueous lubricating coating film became thinner at the bundled
portion as a result of bundling materials using a binding band.
TABLE-US-00002 TABLE 2 Corrosion Corrosion Workability resistance
resistance Phosphatizing (Wire drawability) (two weeks) (four
months) property*1 Example 1 A A A B Example 2 A A A B Example 3 B
A B B Example 4 A A B B Example 5 A A A B Example 6 A A A B Example
7 A A B B Example 8 A A A B Example 9 B A B B Example 10 B A A B
Example 11 B A B B Example 12 B A B B Comparative Example 1 E E E B
Comparative Example 2 E E E B Comparative Example 3 A D D B
Comparative Example 4 C A A B Comparative Example 5 C B C B
Comparative Example 6 D B C B Comparative Example 7 D D D B
Comparative Example 8 D D D B Comparative Example 9 D D D B
Comparative Example 10 D D D B Comparative Example 11 C E E B
Comparative Example 12 C E E E Comparative Example 13 D E E E
Comparative Example 14 D E E B Comparative Example 15 E E E B
Comparative Example 16 B C C B Comparative Example 17 A B B E
Comparative Example 18 B B B E *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.
[0168] 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 Upper Layer Coating Agent and Lower Layer
Coating Agent as Aqueous Lubricating Coating Agent
[0169] In accordance with the combination and proportion shown in
Table 3, upper layer coating agents and lower layer coating agents
of Examples 13 to 29 and Comparative Examples 19 to 35 were
prepared using the respective components shown below. Comparative
Example 36 means the case subjected to a phosphate/soap
treatment.
A. Upper Layer Coating Agent
<Water-Soluble Silicate>
[0170] (A-1) Sodium metasilicate [0171] (A-2) JIS No. 3 sodium
silicate (Na.sub.2OnSiO.sub.2, n=3) [0172] (A-3) Lithium silicate
(Li.sub.2OnSiO.sub.2, n=3.5)
<Water-Soluble Tungstate>
[0172] [0173] (B-1) Ammonium tungstate [0174] (B-2) Sodium
tungstate [0175] (B-3) Potassium tungstate
<Resin>
[0175] [0176] (C-1) Polyvinyl alcohol (average molecular weight of
about 50, 000) [0177] (C-2) Sodium neutralizing salt of
isobutylene-maleic anhydride copolymer (average molecular weight of
about 165,000) [0178] (C-3) Carboxymethylcellullose sodium (average
molecular weight of about 30,000) [0179] (C-4) Aqueous nonionic
urethane resin emulsion
<Lubricant>
[0179] [0180] (D-1) Anionic polyethylene wax (average particle size
of 5 .mu.m) [0181] (D-2) Ethylenebis-stearic acid amide [0182]
(D-3) Calcium stearate [0183] (D-4) Polytetrafluoroethylene
dispersion (average particle size of 0.2 .mu.m)
<Water-Soluble Salt>
[0183] [0184] (E-1) Sodium metaborate [0185] (E-2) Sodium tartrate
[0186] (E-3) Sodium sulfate [0187] (E-4) Sodium pyrophosphate
B. Lower Layer Coating Agent
<Zirconium Lower Layer Coating Film>
[0187] [0188] (F) Zirconium chemical conversion treatment agent
(PALLUCID (registered trademark) 1500, manufactured by Nihon
Parkerizing Co., Ltd.) <Lower Layer Coating Film other than
Zirconium Lower Layer Coating Film> [0189] (G-1) No. 2 sodium
silicate (Na.sub.2OnSiO.sub.2, n=2.5) [0190] (G-2) Zinc
phosphate
TABLE-US-00003 [0190] TABLE 3 Water-soluble silicate Water-soluble
tungstate Zirconium Resin Lubricant Component (A) Component (B)
coating Component (C) Component (D) (A-1) (A-2) (A-3) (B-1) (B-2)
(B-3) film (nm) (C-1) (C-2) (C-3) (C-4) (D-1) (D-2) (D-3) (D-4)
Example 13 0 20 0 40 0 0 99 0 20 0 0 20 0 0 0 Example 14 30 0 0 20
0 0 75 0 40 0 0 10 0 0 0 Example 15 0 8 0 15 51 0 30 13 0 0 0 0 0
13 0 Example 16 10 20 10 20 15 0 87 0 0 0 10 5 10 0 0 Example 17 10
10 0 0 40 10 123 0 0 10 0 0 10 0 10 Example 18 0 30 0 0 0 25 50 0
25 0 0 5 5 0 10 Example 19 0 15 10 0 0 50 150 0 0 0 10 0 0 15 0
Example 20 0 0 22 0 0 55 10 8 0 0 0 10 0 0 5 Example 21 10 0 20 0
20 20 1 0 0 0 15 5 0 0 10 Example 22 0 20 0 10 40 0 200 0 15 0 0 0
0 15 0 Example 23 0 0 12 63 0 0 112 0 0 0 0 0 0 0 25 Example 24 0
40 0 0 38 0 91 15 0 0 0 7 0 0 0 Example 25 0 10 10 0 10 10 80 0 25
0 5 20 10 0 0 Example 26 17 0 0 0 0 21 66 0 37 0 10 10 5 0 0
Example 27 0 20 0 10 5 0 54 13 0 0 0 25 10 0 15 Example 28 10 32 0
15 20 0 22 10 0 0 0 10 0 0 0 Example 29 0 10 0 0 30 0 35 0 20 0 0
25 0 10 5 Comparative 0 0 0 0 0 0 100 0 0 0 0 0 0 0 0 Example 19
Comparative 0 20 0 40 0 0 0.7 0 20 0 0 20 0 0 0 Example 20
Comparative 30 0 0 10 0 40 250 0 0 10 0 0 10 0 0 Example 21
Comparative 50 0 0 0 0 0 82 0 10 20 0 0 0 20 0 Example 22
Comparative 0 0 0 60 0 0 73 20 0 0 0 0 20 0 0 Example 23
Comparative 0 0 30 0 0 20 51 0 0 0 15 35 0 0 0 Example 24
Comparative 6 0 0 15 30 0 30 0 19 0 15 0 0 0 15 Example 25
Comparative 45 0 0 0 0 0 120 0 0 15 0 0 0 15 0 Example 26
Comparative 0 20 20 0 0 0 31 10 0 0 20 0 0 10 10 Example 27
Comparative 0 0 0 40 0 0 20 0 15 0 0 20 0 0 0 Example 28
Comparative 0 0 0 0 50 0 77 10 0 5 0 5 0 10 0 Example 29
Comparative 0 0 0 0 0 0 111 0 5 0 0 0 10 0 25 Example 30
Comparative 0 0 0 0 0 0 93 10 0 0 10 0 20 0 0 Example 31
Comparative 0 0 0 0 0 0 91 0 0 25 0 0 25 0 0 Example 32 Comparative
0 0 0 0 0 0 88 0 25 0 0 15 0 20 0 Example 33 Comparative 0 10 10 0
0 45 0 15 0 0 0 15 0 0 5 Example 34 Comparative 30 0 0 0 50 0 0 0 0
10 0 10 0 0 0 Example 35 Comparative Phosphate/soap treatment
Example 36 Mass of coating film per unit Mass ratio Mass ratio
Water-soluble alt Undercoating area of upper Mass ratio of resin/
of lubricant/ Component (E) film (mg/m.sup.2) layer coating of
tungsten/ (silicon + (silicon + (E-1) (E-2) (E-3) (E-4) (G-1) (G-2)
film (g/m.sup.2) silicon tungsten) tungsten) Example 13 0 0 0 0 0 0
10.1 4.4 0.54 0.54 Example 14 0 0 0 0 0 0 13.1 2.5 1.83 0.46
Example 15 0 0 0 0 0 0 12.2 16.0 0.28 0.28 Example 16 0 0 0 0 0 0
1.4 1.9 0.27 0.40 Example 17 0 0 0 0 0 0 8.1 5.3 0.27 0.55 Example
18 0 0 0 0 0 0 5.2 1.5 1.02 0.82 Example 19 0 0 0 0 0 0 4.1 3.0
0.27 0.40 Example 20 0 0 0 0 0 0 7.7 3.4 0.20 0.37 Example 21 0 0 0
0 0 0 13.8 2.2 0.44 0.44 Example 22 0 0 0 0 0 0 7.6 4.7 0.38 0.38
Example 23 0 0 0 0 0 0 6.6 9.6 -- 0.48 Example 24 0 0 0 0 0 0 9.0
1.7 0.40 0.19 Example 25 0 0 0 0 0 0 9.0 1.8 1.54 1.54 Example 26 0
0 0 0 0 0 8.1 2.7 2.98 0.95 Example 27 2 0 0 0 0 0 4.4 1.5 0.74
2.85 Example 28 0 3 0 0 0 0 6.6 1.8 0.27 0.27 Example 29 0 0 0 0 0
0 17.7 5.4 0.90 1.80 Comparative 0 0 0 0 0 0 -- -- -- -- Example 19
Comparative 0 0 0 0 0 0 8.2 4.3 0.54 0.54 Example 20 Comparative 0
0 0 0 0 0 6.6 4.3 0.27 0.27 Example 21 Comparative 0 0 0 0 0 0 11.1
-- 2.61 1.74 Example 22 Comparative 0 0 0 0 0 0 12.2 -- 0.45 0.45
Example 23 Comparative 0 0 0 0 0 0 4.2 0.9 0.64 1.49 Example 24
Comparative 0 0 0 0 0 0 5.1 21.7 1.08 0.48 Example 25 Comparative 0
0 25 0 0 0 9.9 -- 1.45 1.45 Example 26 Comparative 0 0 0 10 0 0
10.2 -- 1.98 1.32 Example 27 Comparative 25 0 0 0 0 0 8.8 -- 0.50
0.67 Example 28 Comparative 10 10 0 0 0 0 7.2 -- 0.48 0.48 Example
29 Comparative 30 0 0 30 0 0 -- -- -- -- Example 30 Comparative 0
40 20 0 0 0 -- -- -- -- Example 31 Comparative 50 0 0 0 0 0 -- --
-- -- Example 32 Comparative 0 40 0 0 0 0 -- -- -- -- Example 33
Comparative 0 0 0 0 1.5 0 4.6 3.4 0.46 0.61 Example 34 Comparative
0 0 0 0 0 4.4 5.8 4.5 0.26 0.26 Example 35 Comparative
Phosphate/soap treatment Example 36 *Numerical in each of
components (A) to (E) means an addition amount in an upper layer
coating agent (% by mass).
(2-2) Analysis of Coating Film
[0191] An SPCC-SD material was subjected to a treatment for
formation of a lower layer coating film and an upper layer coating
film, and then the amounts of silicon and tungsten on a surface
were directly measured by fluorescent X-ray spectroscopy (XRF) and
the value of a mass ratio of tungsten/silicon was examined. After
immersing in an aqueous 2% sodium hydroxide solution heated at
60.degree. C. for 2 minutes, the upper layer coating film was
peeled. A film thickness of a zirconium coating film was measured
by subjecting the test material whose upper layer coating was
peeled to fluorescent X-ray spectroscopy (XRF). The measured values
are shown in Table 3. The film thickness measured from XRF is
consistent with the results obtained by directly measuring the
thickness of a zirconium coating film by carrying out
cross-sectional SEM analysis.
(2-3) Coating Treatment
Pretreatment and Coating Treatment of Examples 13 to 29 and
Comparative Examples 20 to 33
[0192] (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 [0193] (b) Water rinsing: tap
water, normal temperature, immersion: 20 seconds [0194] (c)
Pickling: 17.5% hydrochloric acid, normal temperature, immersion:
20 minutes [0195] (d) Water rinsing: tap water, normal temperature,
immersion: 20 seconds [0196] (e) Lower layer coating 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., pH 4.0, immersion treatment: immersion time is
appropriately adjusted according to the amount of the coating film.
[0197] (f) Water rinsing: tap water, normal temperature, immersion:
20 seconds [0198] (g) Neutralization: commercially available
neutralizer (PREPALENE (registered trademark) 27, manufactured by
Nihon Parkerizing Co., Ltd.) [0199] (h) Upper layer coating film
treatment: upper layer coating agent prepared in (2-1),
temperature: 60.degree. C., immersion: 1 minute [0200] (i) Drying:
100.degree. C., 10 minutes
Pretreatment and Coating Treatment of Comparative Example 19
[0200] [0201] (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 [0202] (b) Water rinsing: tap
water, normal temperature, immersion: 30 seconds [0203] (c)
Pickling: hydrochloric acid concentration: 17.5%, normal
temperature, immersion: 10 minutes [0204] (d) Water rinsing: tap
water, normal temperature, immersion: 30 seconds [0205] (e) Lower
layer coating 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., pH 4.0, immersion treatment:
immersion time is appropriately adjusted according to the amount of
the coating film. [0206] (f) Water rinsing: tap water, normal
temperature, immersion: 30.degree. C. [0207] (g) Pure water
rinsing: deionized water, normal temperature, immersion: 30.degree.
C. [0208] (h) Drying: 100.degree. C., 10 minutes
Comparative Example 34 (Silicate lower Layer Coating Film, Upper
Layer Coating Film Treatment)
[0208] [0209] (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 [0210] (b) Water rinsing: tap
water, normal temperature, immersion: 30 seconds [0211] (c)
Pickling: hydrochloric acid, concentration: 17.5%, normal
temperature, immersion: 10 minutes [0212] (d) Water rinsing: tap
water, normal temperature, immersion: 30 seconds [0213] (e) Lower
layer coating treatment: commercially available surface treatment
agent (PREPALENE (registered trademark) 5557, manufactured by Nihon
Parkerizing Co., Ltd.), concentration 2.5 g/L, temperature
70.degree. C., immersion: 1 minute [0214] (f) Rough drying: normal
temperature, 60 seconds [0215] (g) Upper layer coating film
treatment: upper layer coating agent prepared in (2-1),
temperature: 60.degree. C., immersion: 1 minute [0216] (h) Drying:
100.degree. C., 10 minutes
Pretreatment and Coating Treatment of Comparative Example 35 (zinc
phosphate lower layer coating film, upper layer coating film
treatment)
[0216] [0217] (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 [0218] (b) Water rinsing: tap
water, normal temperature, immersion: 30 seconds [0219] (c)
Pickling: hydrochloric acid, concentration: 17.5%, normal
temperature, immersion: 10 minutes [0220] (d) Water rinsing: tap
water, normal temperature, immersion: 30 seconds [0221] (e) Lower
layer coating 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 [0222] (f)
Water rinsing: tap water, normal temperature, immersion: 30 seconds
[0223] (g) Upper layer coating treatment: upper layer coating agent
prepared in (2-1), temperature: 60.degree. C., immersion: 1 minute
[0224] (h) Drying: 100.degree. C., 10 minutes
Pretreatment and Coating Treatment of Comparative Example 36
(Phosphate/Soap Treatment)
[0224] [0225] (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 [0226] (b) Water rinsing: tap
water, normal temperature, irrunersion: 30 seconds [0227] (c)
Pickling: hydrochloric acid, concentration: 17.5%, normal
temperature, immersion: 10 minutes [0228] (d) Water rinsing: tap
water, normal temperature, immersion: 30 seconds [0229] (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 [0230] (f)
Water rinsing: tap water, normal temperature, immersion: 30 seconds
[0231] (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 [0232] (h) Drying: 100.degree.
C., 10 minutes [0233] (i) Amount of dry coating film: 10
g/m.sup.2
(2-4) Evaluation Test
(2-4-1) Workability (Spike Property) Test
[0234] A spike test was performed as a test for simulating forward
extrusion. 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. [0235]
Lubricity of the film was evaluated by measuring the load and the
spike height during working. [0236] Test piece for evaluation: S45C
spheroidizing-annealed material in size of 25 mm.phi..times.30
mm
Evaluation Criteria
[0236] [0237] A: Extremely excellent as compared with a
phosphate/soap coating film [0238] B: Excellent as compared with a
phosphate/soap coating film [0239] C: Equivalent to a
phosphate/soap coating film [0240] D: Inferior as compared with a
phosphate/soap coating film [0241] E: Drastically inferior as
compared with a phosphate/soap coating film
(2-4-2) Workability (Upsetting-Ball Ironing Property) Test
[0242] An upsetting-ball ironing test was performed as a test for
simulating forming of a bolt head. 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 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. [0243] Test piece for evaluation: S10C
spheroidizing-annealed material in size of 14 mm.phi..times.32 mm
[0244] Bearing ball: 10 mm.phi..times. SUJ2
Evaluation Criteria
[0245] Evaluation was made of the area where seizure occurred based
on the area of the entire ironing surface. [0246] A: Extremely
excellent as compared with a phosphate/soap coating film [0247] B:
Excellent as compared with a phosphate/soap coating film [0248] C:
Equivalent to a phosphate/soap coating film [0249] D: Inferior as
compared with a phosphate/soap coating film [0250] E: Drastically
inferior as compared with a phosphate/soap coating film
(2-4-3) Evaluation of Corrosion Resistance (Long-Term Rust
Prevention Property)
[0251] 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 four 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. [0252] Test piece: SPCC-SD in size of 75 mm.times.35
mm.times.0.8 mm Evaluation criteria: [0253] A: Extremely excellent
as compared with a phosphate/soap coating film (rust area of less
than 5%) [0254] B: Excellent as compared with a phosphate/soap
coating film (rust area of 5% or more and less than 15%) [0255] C:
Identical to a phosphate/soap coating film (rust area of 15% or
more and less than 25%) [0256] D: Inferior to a phosphate/soap
coating film (rust area of 25% or more and less than 35%) [0257] E:
Drastically inferior as compared with a phosphate/soap coating film
(rust area of 35% or more)
[0258] The test results are shown in Table 4. As is apparent from
Table 4, Examples exhibited satisfactory workability (spike test,
ball ironing test), and corrosion resistance (particularly
long-term rust prevention property). In Comparative Example 19 in
which a coating film is composed only of a zirconium coating film,
workability and corrosion resistance were drastically inferior. In
Comparative Examples 20 and 21, a film thickness of a zirconium
coating film was set at the value deviating from the scope of the
present invention. In Comparative Example 20 in which a film
thickness of a lower layer coating film was made to be too small,
corrosion resistance was inferior. In Comparative Example 21 in
which a film thickness of a lower layer coating film was made to be
too large, workability was inferior. In Comparative Examples 22 to
29, a mass ratio of silicon to tungsten was set at the value
deviating from the scope of the present invention, ball ironing
property and corrosion resistance tended to be inferior. In
Comparative Examples 30 to 33 in which components other than a
water-soluble silicate and a water-soluble tungstate were included
as an aqueous inorganic salt, ball ironing property and corrosion
resistance were inferior. In Comparative Example 34 in which a
coating film of a silicate was formed as a lower layer coating
film, it was impossible to obtain high corrosion resistance
comparable to Examples. In Comparative Example 35, a coating film
of a phosphate was formed as a lower layer coating film.
Workability and corrosion resistance are in the same level as in
Examples, but this film is not preferred since it contains
phosphorus to cause the above-mentioned problem such as
phosphorizing of a bolt. In Comparative Example 36 in which a
phosphate coating film was subjected to a reactive soap treatment,
corrosion resistance was inferior as compared with Examples. Like
Comparative Example 35, a phosphate film is not preferred because
of a problem such as phosphorizing of a bolt. Regarding
phosphorizing, like Comparative Examples 27 and 30, the same
applies to the case of containing a phosphate as a water-soluble
salt.
TABLE-US-00004 TABLE 4 Workability Workability Corrosion Corrosion
(Spike (Ball ironing resistance resistance Phosphatizing property)
property) (two weeks) (four months) property*1 Example 13 A A A A B
Example 14 A B A A B Example 15 A B A A B Example 16 B A A A B
Example 17 A A A A B Example 18 A B A A B Example 19 A A A A B
Example 20 A A A A B Example 21 A A A B B Example 22 B B A A B
Example 23 B A A A B Example 24 B A A A B Example 25 B B A A B
Example 26 B C A A B Example 27 B C A A B Example 28 A A A A B
Example 29 A B A A B Comparative Example 19 E E E E B Comparative
Example 20 A A C C B Comparative Example 21 D C A A B Comparative
Example 22 A D D D B Comparative Example 23 A D D D B Comparative
Example 24 A D B D B Comparative Example 25 A D B D B Comparative
Example 26 B D E E B Comparative Example 27 B D D D E Comparative
Example 28 A D D D B Comparative Example 29 B D D D B Comparative
Example 30 B D D D E Comparative Example 31 C D E E B Comparative
Example 32 A D D D B Comparative Example 33 B E D D B Comparative
Example 34 B B C C B Comparative Example 35 B B B B E Comparative
Example 36 B B C C 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.
[0259] As is apparent from the above description, when using a
steel wire rod having a lubricating coating film, which includes an
upper layer coating film and a lower layer coating film, of the
present invention, it is possible to achieve both high workability
and sufficient corrosion resistance in service environment.
Therefore, the present invention has extremely high industrial
value of utilization.
[0260] The present invention includes the following aspects.
Aspect 1:
[0261] A steel wire rod having a coating film containing no
phosphorus, wherein
[0262] the coating film includes a lower layer coating film
composed of hydroxide of zirconium and having a film thickness of
1.0 to 200 nm, and an upper layer coating film containing silicon
and tungsten, in order from a steel wire rod side, a mass ratio of
tungsten/silicon being in a range of 1.3 to 18.
Aspect 2:
[0263] The steel wire rod according to the aspect 1, wherein the
silicon is derived from water-soluble silicate, and the tungsten is
derived from water-soluble tungstate.
Aspect 3:
[0264] The steel wire rod according to the aspect 1 or 2, wherein
the silicon is derived from at least one selected from lithium
silicate, sodium silicate and potassium silicate, and the tungsten
is derived from at least one selected from lithium tungstate,
sodium tungstate, potassium tungstate and ammonium tungstate.
Aspect 4:
[0265] The steel wire rod according to any one of the aspects 1 to
3, wherein a resin is contained in the upper layer coating film,
and a mass ratio of resin/(silicon+tungsten) is in a range of 0.01
to 3.2.
Aspect 5:
[0266] The steel wire rod according to the aspect 4, 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 6:
[0267] The steel wire rod according to any one of the aspects 1 to
5, wherein a lubricant is contained in the upper layer coating
film, and a mass ratio of lubricant/(silicon+tungsten) is in a
range of 0.01 to 3.2.
7.
[0268] The steel wire rod according to the aspect 6, 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 8:
[0269] The steel wire rod according to any one of the aspects 1 to
7, wherein the mass of the coating film per unit area of the upper
layer coating film is in a range from 1.0 to 20 g/m.sup.2.
Aspect 9:
[0270] A method for producing the steel wire rod according to any
one of the aspects 1 to 8, which comprises bringing an aqueous
chemical conversion treatment solution, which has a pH in a range
of 2.5 to 5.0 and contains a water-soluble zirconium compound
dissolved therein, into contact with a surface of a steel wire rod
to form a lower layer coating film.
[0271] This application claims priority based on Japanese Patent
Application No. 2014-070445, filed on Mar. 28, 2014, the disclosure
of which is incorporated by reference herein
* * * * *