Type of Document] SPECIFICATION
[Title of the Invention] COMPOSlTION FOR SOLID COATING FORMATION
AND TUBULAR THREADED JOINT
[Technical Field]
[OOOI]
The present irlvention relates to a conlposition for solid coating fornlation
used to fasten a tubular threaded joint which connects steel pipes such as oil well pipes,
and a tubular threaded joint having a solid coating forn~edb y using the cotnposition for
solid coating formation.
Priority is claimed on Japanese Patent Application No. 2012-200118, filed on
Septe~nber1 2,2012, and the content of which is incorporated hcrein by reference.
[Background Art]
[0002]
Oil well pipes such as tubing or casings are used for drilling an oil well to
mine crude oil or gas oil. The oil well pipes are connected (fastened) to each other
generally using a tubular threaded joint. The depth of an oil well according to the
related art mas 2000 111 to 3000 m. The depth of a deep oil well such as an undersea
oil well in recent years may reach 8000 111 to 10,000 111.
[0003]
On the tubular tl~eadedjo int for the oil well pipes, a load called an axial
tensile force caused by the masses of the oil well pipes and the joint then~selvesu nder
the use environment, a complex pressure such as internal and external surface
pressures, and geotl~er~nhaela t are exerted. Therefore, for the tubular threaded joint
for the oil well pipes, nlaintaining gastightness is required without breakage under such
severe enviro~mlents.
[0004]
A typical tubular threaded joint (called special threaded joint) used for
tightening tlie oil well pipes lias a pin-box structure. The pin-box structure is
constituted by a member called a pin wl~iclis formed at both end portions of the oil
\veil pipes, and a member called a box which is fornled on the ituler surfaces of both
sides of a threaded joint coniponent (coupling). The pin lias nlale threads. The box
has female threads. Seal portions are respectively formed at the outer peripheral
portion near the end surface on the tip end side of the pin from the male threads and at
the inner peripheral surface of the base portion of the feniale tlueads of the box,
Shoulder portions (also called torque shoulders) are respectively formed at tlie end
surface of tlie tip end of the pin and at the corresponding innermost portion of the box.
[OOOS]
One end (pin) of the oil well pipe is inserted into tlie threaded joint component
(box) and the tnale threads and the feriiale threads are fastened until the shoulder
portions of tlie pin and the box abut on each other and interfere with each other at an
opti~numto rque. Accordingly, the seal portions of the pin and tlie box come into
close contact with each other and fomi a metal-to-metal seal, thereby ensuring
gastightness of the threaded joint. The seal portions and tlie shoulder portions for111
unthreaded nletal contact portions of tlie tubular threaded joint. The untl~eadedm etal
contact portions and tlie threaded portions (the nlale threads and the female threads)
become surfaces (called contact surfaces of the tubular threaded joint) that come into
contact with each other during fastening. An examnple of tlie spccial tlueaded joint is
described in Patent Doculllent 1 and Patent Docunlent 2.
[0006]
During an operation of lowering the oil well pipe to an oil well, due to various
problems, the oil well pipe is temporarily pulled up fronl the oil well, and a threaded
joint which is fastened once is loosened to release the fastening of tl~etl ueaded joint.
There is a case that the oil well pipe in which the fastening of the threaded joint is
loosened is lowered after re-fastening the joint. API (The American Petroleum
Institnte) requires seizure resistance in such a sense that cvcn when fastening (make-
LIP) of a threaded joint and loosening (break-out) thereof are performed a plurality of
times, seizure called galling does not occur and gastightness is maintained. For
example, ten successful times are required for a tubing joint, and three successful times
are required for a casing joint.
[0007]
At the time of fastening, in order to achieve enl~ancenlenitn seizme resistance
and gastightness, a viscous liquid lubricant (grease lubricant), that is called a
"comnpound grease", containing a large amount of heavy metal powder is applied to the
contact surfaces of the tl~eadedjo int. Such a compound grease is specified in the
Standard API BUL 5A2.
[0008]
For tlle purpose of ethancing the n~aintenanceo f the conlpound grease and
improving lubricity, surface treatnlcnts for a single layer or two or more layers, such as
a nitriding treatment, various plating processes including zinc-based plating and
dispersion plating, and a phosphate cl~emicalc onversion treatment are performed on
the contact surfaces of the threaded joint. However, there is a problem with the use of
the compound grease in that there is concern about a hartnfi~el ffect on the environment
or human bodies as described below.
[0009]
The conlpound grease contains a large amount of heavy metal powder such as
zinc, lead, and copper. Particularl>: there is a possibility that harmfi~hl eavy nletals
such as lead that is contained in the eonlpound grease may have a hartnfi~el ffect on the
environment, marine organisms, and the like. Further, an operational environment is
worsened by an operation of applying the eonlpound grease, and therc is a concern
about a liannfi~el ffect on human bodies.
[OOl 01
In recent years, upon the opportunity that OSPAR Conventio~(lt he Oslo and
Paris Con\~entions, OSPAR) regarding the prevention of ocean pollution of the
northeast Atlantic Ocean has taken effect since 1998, environment restrictions have
strictly proceeded on a global scale. Accordingly, the use of the conlpound grease is
also restricted it1 some regions. Therefore, in the operation of drilling a gas \veil or
oil well, in order to avoid the hannfi~el ffect on the enviro~ltnenot r human bodies, a
threaded joint capable of exhibiting excellent seizure resistance \vitliout the use of the
eotnpound grease has been required.
too1 11
As a threaded joint which can be used for fastening oil well pipes without the
compound grease being applied, in Patent Docunlent 3, a threaded joint for an oil well
in \vhich a resin coating eontailling lubricating powder is fornled on the contact
surfaces thereof is suggested. In addition, the applicant suggested a tubular threaded
joint in which a solid coating is fortlied on each of a pin and a box in Patent Document
4.
[Prior Art Docutnent]
[Patent Document]
[0012]
[Patent Document 11 Japanese Unexa~nitiedP atent Application, First
Publication No. H05-87275
[Patent Document 21 Specification of US Patent No. 5,137,3 10
[Patent D o c u ~ ~ l3e1 ~ ~PtC T I~~ternationPalu blication No. W096110710
[Patent Document 41 PCT Internatio~lalP ublication No. W02009/072486
[Disclosure of the Inventiol~]
[Problem that the Inve~~tioisn t o solve]
[OO 1 31
In many cases, a period of time over one year froom sl~ipn~eins tn eeded for
transport to the field or storage of a tubular threaded joint until the tubular tlxeaded
joint is actually fastened in an oil well. In the nmea~lwl~ilteh, e tubular threaded joint
may be exposed to severe en\iro~nllentss uch as sea transport through the hot and
humid equator, temperature changes of about 90°C fro111 high temperatures (daj.time)
to below the freezing point (nighttime) in the Middle East area, and temperature
changes of from -60°C (winter) to 40°C (sununes) in the Arctic Circle.
[00 141
In a case where the tubular threaded joint according to the related art is
exposed to an e~lviro~unewr~itth an extremely severe hot and cold cycle, which is
repeatedly cxposcd to an extre~~lellopw temperature to a high temperature of about
10O0C, cracking may occur due to the deterioration of a solid coating or the solid
coating may peel off due to the degradation in the adhesiveness of the solid coating.
Therefore, there is concern that a proble~nin \vl~iclicfip erformance required by the solid
coating cannot be exhibited may occur.
[0015]
In the special threaded joint provided with the seal portions and the shoulder
portions, the seal portions of the pin and the box form the metal-to-metal seal during
fastening, thercby ensuring gastightness. However, when the solid coating partially
peels off, not only seizure rcsistancc but also gastightness is degraded.
[OOI 61
Further, an operational enviro~nnentin 1vhic11 the oil well pipes are fastened is
also affected by a very wide range of tenlperatures of from a high temperature
environment of 40°C or higher in the Middle East area and the like to a low
temperature environment of about -40°C in the Arctic Circle and the like. Therefore,
it is expected to exhibit sufficient seizure resistance even when the temperature at the
time of fastening is a severe tenlperaturc such as an cxtre~nelylo w temperature or an
extremely high temperature. Even fron~th is point, there is concern that the
perfomlance of the solid coating according to the related art may be insufficient.
[00 1 71
An object of the present invention is to provide a co~npositionfo r solid
coating fornlation of a tubular joint capable of forming a solid coating capable of
maintaining and exhibiting seizure resistance, gastightness, and antirust properties
without including harntfi~lh eavy nietals such as lead which imposes a burden on the
earth enviromnent even in a hot and cold cycle of from an estre~uelylo w teniperat~~re
to a high tenlperaturc during a period of titile of over one year for transport or storage
until actual fastening and even when the tenlperature at the timc of fastening is an
cxtrernely high temperature or an extremely low temperature, and a tnbular threaded
joint having excellent hot and cold cycle perfor~nanceb y using the satne.
[00 181
Another object of the present invention is to provide a conlposition for solid
coating for~nationo f a tubular joint capable of forming a solid coating by only using
nlaterials wit11 a stnall environmental burden without the use of an organic solvent
having a har~nfe~f~felc t on biotic environment, and a tubular tlxeaded joint using the
same.
[Means for Solving the Problems]
[O019]
The present invention employs the following means in order to accomplish
the objects to solve the problems. That is,
(1) A composition for solid coating fonnation according to an aspect of the
present inve~ltioni,n cludes: a conlposition made by containing, in a mixed solvent
including water and a dipolar aprotic solve~lta, powdery organic resin which is
partially soluble at least in tlie dipolar aprotic solvent, in which tlie powdery organic
resin is present in a state of being dissolved or dispersed in the mixed solvent.
[OO2O]
(2) The composition for solid coating fonnation described in (1) tnay further
include lubricating particles.
[O021]
(3) In the composition for solid coating fomlation described in (1) or (2), the
powdery organic resin may be one or more types selected from a polyanlide-imide
resin, an epoxy rcsin, and a fluororesin.
[OO22]
(4) In the composition for solid coating formation described in any one of (1)
to (3), the dipolar aprotic solvent may be one or more types selected from Nmethylpyrrolido~
ied, imetllj~laceta~niddei,m ethylforma~nided, in~ctli~~lsulfoxiadned, ybutyrolactone.
[0023]
(5) A tubular threaded joint according to another aspect of tlie present
invention includes: a pin and a box each of u~l~iics lp~ro vided wit11 a contact surface
including a threaded portion and a unthreaded metal contact portion, in which the
colitact surface of at least one member of the pin and the box has a solid coating
formed from tlie composition described in any one of ( 1 ) to (4).
[0024]
(6) In the tubular threaded joint described in (5), the solid coatitig may have a
first layer whicli does not contain lubricating particles and a scco~ld layer formed
thereon, wllich contains lubricating particles.
[0025]
(7) The tubular theaded joint described in (5) or (6), a thickness of the solid
coating (a total thickness in a case of a coating having two or more layers) may be 5
pm to 100 pm.
[0026]
In the present invention, the "dipolar aprotic solvent" is an organic solvent
made fiom polar niolecules having an electric dipole moment in the tnolecules and
means a solvent that does not substantially have a proton donating property.
100271
In the present invention, "be partially soluble at least in the dipolar aprotic
solvent" means "be dissolved in the dipolar aprotic solvent at a concentration of 5
mass% or higher at room temperature or during heating".
[Advantage of the Inventio~l]
[0028]
Accordir~g to the aspects, not only tlie solid coating itself, which is fornled on
the contact surfaces of the tubular threaded joint, but also the composition for solid
coating formation for for~nirlgt he solid coating contains o111pt he comnponents whicli
have 110 or a low environtnental burden. The solid coating does not contain harnlful
heavy metals which are contained in a cotnpound grease according to the related art.
Therefore, the nlanufacturing environment of the tubular threaded joint is properly
maintained, and environtnental (for example, ocean) pollution during fastening is
prevented.
[0029]
Moreover, the solid coating has excellent lot and cold cycle performance,
properly nlaintains the adhesiveness of the coating even in a hot and cold cycle of fron~
an extrenlely low tcnlperature (-60°C) to a high temperature (90°C). Furthermore,
the solid coating exhibits seizure resistance even when a tenlperature during fastening
is an extremely low tenlperature of -40°C. Therefore, the tubular tlneaded joint does
not significantly deteriorate in seizure resistance and antirust performance even in such
a hot and cold cycle, and continuously exhibits a lubricating function even when
fastening and loosening are repeated, thereby ensuring gastightness after fastening.
Furthermore, even when the tubular threaded joint is exposed to a high temperature
close to 300°C in a high-temperature well, fastening can be released at the time of
pulling an oil well pipe without seizure.
[0030]
As described in Comparative Examples, wltich will be described later, even
the conlpound grease, ~v11ichh as been generally regarded as a nlaterial having higher
seizure resistance than a solid lubricating coating, is significantly degraded in seizure
resistance when the fastening tenlperature is a low tetnperature of -20°C. The solid
coating formed by using thc conlposition for solid coating fomlation according to the
aspects of the present invention exhibits higher performance than the contpound grease
under a hot and cold cycle envirolunent and at a low temperature of -20°C or less even
tl~ooughh eavy metals particles are not contained.
[Brief Description of the Drawing]
[003 11
FIG. I is a diagratn scliematically illustrating an assembled configuration of a
steel pipe and a threaded joint component during shipment of the steel pipe.
FIG. 2 is a diagram schematically illustrating fastening portions of a tlxeaded
joint.
FIG. 3A is a diagram illustrating an example of a coating configuration of a
tnbular threaded joint according to an embodiment of the present invention.
FIG. 3B is a diagram illustrating another exatilple of a coating co~~figuration
of a tubular threaded joint according to the embodiment of the present invention.
[Best Mode for Carrying Out the Invention]
[0032]
Hereinafter, an embodiment of the present invention will be described in
detail.
[0033]
FIG. 1 is a diagratn schen~aticallyil lustrating a state of a steel pipe for an oil
well pipe and a threaded joint component during shipment.
Both ends of a steel pipe A are provided nlith pins 1 fomied to have male
threaded portio~ls3 a. The male tlxeaded portions 3a are formed on the outer surface
of the pin 1. Both sides of a threaded joint component (coupling) B are provided with
boxes 2 fornied to have female threaded portions 3b. The female threaded portions
3b are fornied on the i~uiesru rface of the box 2. The pin 1 is a threaded joint metllber
having the male threaded portion 3a. The box 2 is a tlxeaded joint rneniber having
the female thcaded portion 3b. The tubular tllreaded joint is constituted by the pin 1
and the box 2.
[0034]
The coupling B is fastened to one end of the steel pipe A in advance.
Although not illustrated, to the pin 1 of tlie steel pipe A and the box 2 of the coupli~lgB
which are not fastened, protectors for protcctitlg the tl~seadedp ol-tions 3a and 3b are
respectively nlounted before shipment, and the protectors are taken off before the use
of the tubular threaded joint.
[0035]
In the tubular threaded joint, as illustrated, the pins 1 are fornied 011 the outer
surfaces of both ends of the steel pipe A, and the boxes 2 are formed on the inner
surfaces of the coupling B which is a separate mne~nber. Hoxvevel; although not
illustrated, there is also an integral type tubular threaded joint in w11ich one end of tlie
steel pipe A is a pin and the other end thereof is a box without the use of the coupling B.
The present invention can be applied to a tubular threaded joint in any of tlie above
types.
[0036]
FIG. 2 is a diagram scheniatically illustrating the configuration of the tubular
threaded joint (hereinafter, simply refcrrcd to as a "tlxeaded joint"). The tlxeaded
joint is constituted by the pin 1 fornied 011 the outer surface of the end portion of the
steel pipe A and the bas 2 forlned on tlie inner surface of the coupling B. The pin 1
includes the male tlreaded portion 3a, a seal portion 4a positioned on tlle tip end side
of the steel pipe A fro111 the nlale threaded pol-tion 3a, and a shoulder portion 5a
positioned on the end side fsotn the seal portion 4a. According to this, the box 2
i~lclndesth e female threaded portion 3b, and a seal portion 4b positioned on tlie base
end side from the female threaded portion 3b, and a shoulder portion 5b for~iledo n the
base end side fro111 the seal portion 4b.
[0037]
In any of the pi11 1 and the box 2, the seal portions 4a and 4b and the shoulder
portions 5a and 5b constitute unthreaded ~netacl ontact portions. The untllreaded
metal contact pol-tions and the threaded portions 3a and 3b are contact surfaces of the
threaded joirit. The contact surfaces require seizure resistance, gastightness, and
corrosion resistance. For this, in the rclated art, a compound grease contailling heavy
~netapl owder is applied, or a viscous liquid, a semisolid, or a solid lubricating coating
is forined on contact surfaces. However, as described above, the fanner has a
harmful effect 011 human bodies and the en\rironnlent. The latter has proble~nsi n that
gastightness is degraded during a hot and cold cycle of from an extremely low
temperature to a high tenlperature or results in deterioration in lubricity and antirust
properties are deteriorated.
[0038]
According to this embodiment, the contact surface of at least one nlember of
the pin 1 and tlie box 2 of tlie theaded joint has a specific solid coating, wl~iclwi ill be
described later in detail, thereby solving the above-described probletns. The solid
coating is preferably for~nedo n the entire surface of the contact surface of the pin 1
andlor the box 2, but nlay also be formed on only a part of the contact surface, for
example, the unthreaded ~netacl ontact portions (that is, tlie seal portions 4a and 4b and
the shoulder portions 5a and 5b). In this case, a different coating may be for~nedo n
the residual part of the contact surface.
[0039]
Furthel; in a case where the solid coating described above is forined on only
the contact surface of one member of the pin 1 and the box 2, a different surface
treatnlent may also be performed on the contact surface of the other member. For
example, a solid anticorrosive coating or a liquid lubricating coating may also be
fornled 011 the contact surface of the other member.
[0040]
[Solid Coating]
I11 this embodiment, on tlie contact surfaces at least including the unthreaded
rnetal contact portions (tlie seal portions 4a and 4b and the shoulder portions 5a and
5b) of at least one inember of the pin 1 and the box 2 of the threaded joint, a solid
coating is formed by using a cornposition for solid coating fannation wl~ictis a
coniposition containing, in a mixed solvent of water and a dipolar aprotic solvent, a
powdery organic resin that is partially soluble at least in the dipolar aprotic solvent, the
powdery organic resin being present in a state of being dissolved or dispersed in the
mixed solvent.
[0041]
Tlie cotnposition for solid coating formation may further contain lubricating
particles. Accordingly, the lubricity of the solid coating is e~ltlanced. Tlierefore, the
seizure resistance of the threaded joint is enhanced.
[0042]
As tlie powdery organic resin, a resin having heat resistance at a temperature
of higher than 100°C is preferably used. As such a resin, a polyatnide-irnide resin, an
epoxy resin, a fluororesin, and the like, which are con~nierciallya vailable in a powdery
or dispersed liquid state, can be exemplified, and a tnixture including two or more
types thereof may also be used.
[0043]
Anlong these, the polyamide-iniide (PAI) resin is preferable as the powdery
organic resin because it has particularly excelle~litn heat resistance, call maintain the
coating strength and tougluless at a temperature of 300°C without the sig~lifica~lt
degradation therein, and also has excellent wear resistance and chemical resistance.
roo441
As the powdery polyamide-imide resin, Torlon (registered trademark) 4000T
and 4000TF made by SOLVAY can be exe~nplified. The Torlon polyamide-hide
resin is conmercially available in a powdery form having a particle size of about 30
pm to 40 p na~nd is completely soluble in the dipolar aprotic solveat.
[0045]
As ailother example of the powdery organic resin, there are an epoxy resin
and a fluororesin wllich are reformed so that the surfaces thereof partially increase
hydrophilicity, There may be cases where such a resin is commercially available in a
watcr-dispersed liquid state. Even in this case, a treatlilellt for changing a solvent to
the above-mentioned mixed solvent is necessary.
[0046]
In tliis embodime~ltt,h e powdery organic resin (hereinafter, simply referred to
as an "organic resin") is dispersed ia the 111ixed solvcnt i~lcludi~wlga ter and the dipolar
aprotic solve~a~ntd is mixed, thereby preparing a composition. Accordingl>: the
powdery organic resin is present ill the mixed solvent in a dispersed state or a
dissolved state depending on the solubility thereof. Both water and the dipolar
aprotic solvent are used as the solvent because eve11 when the organic resin is dissolved
or is not dissolved in the dipolar aprotic solvent, the surfaces of the particles of the
organic resin are reformed to be hydrophilic and thus dispersibility in water is
enhanced.
[0047]
As the mixed solvent, instead of a dipolar protic solvent represented by
alcol~ool r anline, a dipolar aprotic solvent such as dimethylfonnamide is preferably
used. Since the dipolar protic solvent snch as alcohol has too high an affinity to water,
there may be cases where it is difficult to achieve the effect intended by the present
invention and there rnay be cases where the dissolving power of the organic resin is
low.
to0481
As examples of the dipolar aprotic solvent, N-~netl~ylpyrrolido(~NleM P),
di~nethylacetamide( DMAC), dimethylfor~l~amid(De MF), dimethylsulfoxide (DMSO),
y-butyrolactone (GBL), and the likc may be used, and the dipolar aprotic solvent is not
limited thereto. Among these, di~llethylsulfoxidea nd y-butyrolactone are preferable.
Further, Torion 4000T and 4000TF which are the polyan~ide-imidere sin described
above are soluble in the dipolar aprotic solvent. In a case wllere tile anlount of the
dipolar aprotic solvent in the co~npositionis a certain degree or higher and in a case
where a tenlperature is high, the resin rnay be present in a state of being dissolved in
the composition. Other~visef,o r example, in a case where the ratio of water is high or
a ten~peratureis low, the resin is present in a dispersed state in the comnposition. Even
in any of the fonns being present, a hoinogeneous solid coating can be forllled.
[0049]
In a case where the powdery organic resin is another resin such as an epoxy
resin and a fluororesin, or is a nlixture of such a resin and the polyamide-imide resin,
there is a small possibility of the po~vderyo rganic resin being dissolved in the mixed
solvent. However, the surfaces of the powdery resin particles are reformed to be
hydropl~ilica s described above. In addition, depending on the case, the surfaces of
the resin particles are partially dissolved.
In a case \&ere the solid coating contains lubricating particles, as the
lubricating particles tliat can be used, although not limited, for example, there are
molybdenum disulfide, tungsten disulfide, graphite, graphite fluoride, an
organomolybdenu~c~ot~li pound (fore xample, molybdenutn dialkylthiophosphate and
molybdenum dialk~~lthiocarbamatPe)T,F E (polytetrafluoroetliylene), BN (boron
nitride), and the like. PTFE is a type of fluororesin, but is not soluble in the dipolar
aprotic solvent. Therefore, PTFE tilay not be used as the organic resin of the coating
fortilation components. One type or t\vo or more types may be used as the lubricating
particles. As the lubricating particles, graphite is preferable, and among the types
thereof, earthy graphite and PTFE are particularly preferable.
[005 11
Regarding tlie anloutlts of tlie conlponellts in the composition for solid coating
formation, it is preferable that when the total amount of the components excluding the
lubricating particles is 100 tilass%, the amount of water be in a range of 10 mass% to
50 inass%, tlie amount of the dipolar aprotic solvent be in a range of 25 mass% to 55
mass%, and the amount of tlie organic resin be in a range of 5 mass% to 25 mass%.
Regarding the ratios of tlie water and the dipolar aprotic solvent, it is preferable that
water occupy 12 mass% to 60 mass% of the entire solvent. The ratios of the water
and tlie dipolar aprotic solvent may be set so that the obtained cotnposition has an
appropriate viscosity for application and a solid coating having a desired thicluless can
be formed by a single application operation.
[0052]
In a case of fornling a solid coating containing the lubricating particles, it is
preferable that the lubricating pa~ticlcs be coiltained in the solid coating at a ratio of 2
mass% to 20 mass%.
[0053]
The conlposition for solid coating formation may contain other addition
conlponents that can be contained ia the solid coating. As an example of the
components, there is an antirust agent. The antirust agent reinforces an inorganic
powder for adjusting the lubricity of the solid coating arid the solid coating.
Examples of the inorganic powder include titanium dioxide and bismuth oxide.
Preferable examples of the antirust agent include calciun~io n-exchanged silica.
Furthernlore, a coln~ilerciallya vailable reaction water repellent agent can also be
contained in the solid coating. The inorganic powder, the antirust agent, and the other
addition components may be contained in the solid coating at a total amount of up to
20 mass%.
[0054]
Tlle solid coating may contain, in addition to the above-mentioned
components, a small amount of addition conlponents of at least one type or two or
more types selected from a surfactant, a colorant, an antioxidant, a defoaniing agent,
and the like at an atllount of, for exanlplc, 5 mass% or less. Moreover, the solid
coating may also contain an extreme pressure agent, a liquid oil agent, and the like at a
very snlall amount of 2 mass% or less.
[0055]
The composition for solid coating fortilation can be prepared by adding the
powdery organic resin that is soluble in the dipolar aprotic solvent as the coating
fom~atioac onlponent to the ~ilixeds olvent including the water and the water-miscible
organic solvent, and stirring and mixing the resultant at an appropriate temperature to
cause the organic resin to be dispersed or dissolved in the solvent. In a case where
the solid coating contains the lubricating particles or the other addition components,
tl~ercaftert,h e addition co~nponentsm ay be gradually added to form a uniform
con~position. It is preferable that the composition for solid coating formation be
adjusted to an appropriate viscosity for stirring and application by setting the
temperature to be in a range of 20°C to 60°C although it also depends on the properties
of the dipolar aprotic solvent.
[OO56]
The composition for solid coating formation is applied to the contact surfaces
of the threaded joint to be coated by an appropriate method, and is heated as necessary
to dry and cure the coating, thereby forming the solid coating on the contact surfaces.
Application can be performed by, for example, spraying the composition while rotating
the tlreaded joint at a predeternlined speed. In addition, application methods such as
brushing or ininlersion can also be enlployed. The heating temperature is set so that
the solvent is completely volatilized and the resin is cured.
[0057]
The solid coating wl~ichu ses the composition for solid coating forillation can
be formed as a single layer or two or more layers. I11 a case of the single layel; in
order to enhance lubricity, it is preferable that solid coating be a coating containing the
lubricating particles. However, depending on the type of water-dispersed resin, a
solid coating without lubricating particles being contained may also impart sufficient
seizure resistance to the tlreaded joint.
[0058]
In a case of fortiling two or more layers of the solid coating, it is preferable
that the first layer as the lower layer be a solid coating which is made of the organic
resin and does not contain the lubricating particles in order to ellhance coating
adliesivc~iessa tid antirust properties. It is preferable that tlie second layer for~iied
tliereon be a solid coating which is made of the organic resin containing the lubricating
particles in order to c~lha~iclueb ricity (seizure resistance). Both the first layer atid the
second layer may contain the other addition compone~itsd escribed above. Further, as
tlie uppermost layer of the solid coating, a top coating layer (third layer) having
antirust properties liiay also be provided.
[0059]
In addition, in a case where the solid coating is for~iiedin multiple layers, on a
first layer that does not contain lubricating particles, a plurality of second layers
co~itai~lil~ubigri cating particles tilay also be provided. I11 this case, it is preferable
that the plurality of second layers be formed so tliat the ratio of tlie lubricating particles
is increased fro111 the lower layer to the upper layer. Accordingly, tlie solid coating
having excellent coating adliesive~lessa nd lubricity (seizure resistance) can be
obtained.
[0060]
In the case wliere tlie organic resin is the Torlor1 polyatiiide-imide resin, a
preferable heating temperature after applyiag the co~ilpositionfo r solid coating
formation is as follows.
[0061]
In the case where tlie solid coatinig is the single-layer coating, first, the
coniiposition for solid coating formation is applied onto the contact surfaces of the
threaded joint. Thereafter, the composition is heated and maintained at 80 to 100°C
for 5 to 20 minutes for predrying. Next, tlie resultant is heated and maintained at 180
to 280°C for 10 to 30 niinutes for main heating for curing. . In a case of another
organic resin, a heating temperature or a heating time riiay be appropriately depending
on the type of the used organic resin, and any of predrying or main heating tnay be
omitted.
[0062]
In the case of forming the solid coating having two or more layers, predrying
and main heating as described above may be perfornted on each layer for forn~ingth e
coating. In addition, after the first layer is applied and heated and maintained at 80 to
100°C for 5 to 20 minutes for predrying, main heating may be not perfortned thereon,
and the second layer may be applied and be subjected to main heating after the
predrying. That is, main heating may be collectively perfomled on the first layer and
the second layer.
[0063]
In addition, the temperature or the holding time is a temperature measured at
the contact surfaces of the threaded joint and is not the setting temperature or the
holding time of a heating furnace.
[0064]
It is preferable that the temperature of the contact surfaces of the threaded
joint during application be atmosphere (about 20°C). 111 addition, in order to reduce
an operation time, the contact surfaces to be applied rnay be heated by setting the main
heating temperature as the upper limit. In this case, it is preferable that the heating
temperature be a temperature lower than the boiling points of the water and the dipolar
aprotic solvent.
[0065]
It is preferable that the tl~icknesso ft he solid coating be 5 p111 to 100 bun from
the viewpoint of adhesiveness, seizure resistance, and antirust properties. 111 the case
where the solid coating is two or more layers, the total thickness thereof is the
thickness of tlie solid coating. Wllen tlie thickness of the solid coating is less than 5
pm, the lubricity of the tubular threaded joint is insufficient, and seizure is likely to
occur at the time of fastening and loosening. Further, altl~oougtlh~c solid coating lias a
certain degree of antirust properties, wvl~ent lie tliickness thereof is too small, antilust
properties become insufficient, resulting in degradation in corrosion resistance of tlie
contact surfaces. When the thickness of the solid coating is too large, it is difficult to
sufficiently remove volatile ~naterialss uch as ~noisturea nd the volatile materials are
rapidly volatilized during the drying, heating, and curing treatments, and thus a coating
\&it11g ood sti~ootlmesisn tlie surfaces thereof is not obtained. For this reason, the
upper limit of tlie thickness of the solid coating is 100 pm. Considering the
viewpoint of adhesiveness, a preferable upper liinit of the thickness of tlie solid coating
is 50 prn.
[0066]
[Base Treatment]
Regarding the tlu.eaded joint having the solid coating formed on the contact
surfaces of the pin 1 and/or the box 2, when a base treatment for roughening the
co~ltacst urfaces is perfonned thereon before forming the solid coating on the contact
surfaces to incrcase the surface roughness to be higlxr than 3 prn to 5 pm which is the
surface roughness after a ct~ttingp rocess, seizure resistance is etlhanced in many cases.
Therefore, it is preferable that the contact surfaces be roughened by tlic base treatment
before forming tlie solid coating.
[0067]
Particularly, in the case \vliere the solid coating is the single-layer coating
containing the lubricating particles, there is a tendency to reduce coating adl~esiveness
compared to a coating without lubricating particles being contained. Therefore, it is
preferable that the contact surfaces be roughened in advance. As a matter of course,
even in the case where the solid coating is the laminated coating described above,
~vllenth e contact surfaces are roughened by the base treatment, enhancement in seiznre
resistance is obtained in lnany cases.
[0068]
As the subsurface treatment, for example, there is a blasting treatment of
projecting a blast ~natcrials uch as a sl~omt aterial hawing a spl~ericaslh ape and a grid
material having an angular shape. In addition, as the sttbsurface treatment, for
example, there is pickling which damages the skin due to immersion in a strong acid
liquid such as sulfuric acid, hydrochloric acid, nitric acid, and hydrofluoric acid. In
addition, as the subsurface treatment, for example, there are a chemical conversion
treatment such as a phosphatizing treatment, an oxalate treatment, or a borate treatment
(the rougl~nesso f crystal surfaces increases as the generated crystals grow), electro
plating of metals such as Cu, Fe, SII, or Zn or an alloy thereof (since convex portions
are preferentially plated, surfaces are slightly roughened), and impact plating in which
a porous plated coating can be for~ned. In addition, as a type of electro plating,
co~npositep lating in which a plated coating is for~ncdb y dispersing solid fine particles
in a nletal is possible as a method of imparting rouglmess to surfaces because the solid
fine particles protrude from the plated coating.
[0069]
Even when tl~esu bsurface treatment for the contact surfaces is any of the
methods, it is preferable that the surface rougl~nessh nax after roughening by the
subsurface treatment be 5 Fun to 40 ~um When Rmax is less than 5 pm, adhesiveness
to the solid coating and maintenance of the coating may become insufficient. On the
other hand, when Rnlax exceeds 40 pni, frictio~lalf orce is increased, and thus the
coating tilay not bear shear stre~lgtlai nd compressive force at a high surface pressure
and may be easily broken or pccl off. As the subsurface treatment for roughetling,
two or more treatments may be used in combination, and the treatment method may
use well-known metl~ods.
[0070]
Frotii the viewpoint of the adl~esivenesso f tlic solid coating, the subsurface
treatment capable of forming a porous coating, that is, the chemical conversio11
treatment and tl~cim pact plating are preferable. In this case, in order for Rmax of tlie
porous coating to be 5 ~utn or greater, it is preferable that the thickness thereof be 5 pm
or greater. Although the upper limit of the tliickaess is not particularly specified,
typically, a thickness of 50 pm or less, and preferably, a thickness of 40 11111 or less is
sufficient. When the solid coating is formed on the porous coating forrned by tlie
subsurface treatment, the adhesiveness thereof to the solid coating is illcreased due to
the so-called "anclior effect". As a result, even when fastening and looseni~iga re
repeated, peeling of thc solid coating is less likely to occur. Accordiagly, metal-tometal
contact is effectively prevented, and thus seizure resistance, gastightness, and
corrosion resistance are further enhanced.
[0071]
Particularly preferable subsurface treatments for fortiiing a porous coating are
a pliospliate chemical conversio~tlr eatment (a treatment using manganese phosphate,
zinc phosphate, ferromanganese phosphate, or zinc calcium phosphate) and for~nation
(poro~m~se tal plating) of a coating of zinc or an alloy of zinc and iron by impact
plating. Atno~lgth ese, from tlie viewpoint of adhesiveness, a manganese phosphate
coating is Inore preferable. On the other hand, from tlie viewpoint of corrosion
resistance, a coating of zinc or an alloy of zinc and iron by which sacrificial corrosion
resistance can be expected due to zinc is more preferable.
[0072]
The phosphate chc~nicacl onversio~tlr eatmelit can be performed by irn~nersion
or spraying according to an ordinary method. As a chemical conversion treatment
liquid, an acidic phosphate treatment liquid for general zinc plating can be used. For
example, a zinc phosphate-based cl~e~niccaoln \~ersiontr eatment using 1 to 150 g/L of
phosphate ions, 3 to 70 g/L of zinc ions, 1 to 100 glL of nitric acid ions, 0 to 30 g/L of
nickel ions can be employed. In addition, a manganese phosphate-based clietnical
conversion treatment which is colnnlonly used for a threaded joint can also be used.
The temperature of the liquid niay be atmosphere (room temperature) to 100°C, and
the treatment time may be up to 15 mim~tesd epending on a desired thickness. In
order to accelerate the forlnation of the coating, before the phosphate treatment, an
aqueous solution for surface adjustment, w11ich contains a colloidal titanium may be
supplied for surfaces to be treated. After the phosphate treatment, drying is
preferably pcrfornled after water washing or hot-water washing.
[0073]
The impact plating can be performed by ~nechanicapl lating in which particles
and an object to be plated itnpact with each other in a rotating barrel or projection
plating in v~hic11p articles and an object to be plated iliipact with each other using a
blasting device. I11 the tlneaded joint, plating may be performed only on the contact
surfaces. Therefore, it is preferable to employ projection plating which enables local
plating.
[0074]
For example, a projection material made of particles obtained by coating the
surfaces of iron-based nuclei with zinc or a zinc alloy is projected onto the contact
surfaces to be coated. The content of zinc or the zinc alloy in the particles is
preferably in a range of 20 mass% to 60 mass%. The pa~ticled ianleters of the
particles are preferably in a range of 0.2 nlln to 1.5 ~mn. Through projection, only
zinc or the zinc alloy \vhich is the coating layer of the particle adheres to the contact
surfaces which are the base body, and a porous coating made of zinc or the zinc alloy is
fanned on the contact surfaces. The projection plating enables a porous metal plated
coating with good adhesiveness to be fornled on the surface of steel regardless of the
material of the steel.
[0075]
The thickness of zinc or the zinc alloy fornled by the impact plating is
preferably 5 pm to 40 bun in terms of both corrosion resistance and adhesiveness.
When the thickness is less than 5 pm, sufficient corrosion resistance cannot be ensured.
When the thickness exceeds 40 pn1, adhesiveness to the solid coating nlay be degraded.
[0076]
Two or nlore types of the above-described subsurface treatments may be
combined to be perfornled.
As another subsurface treatment, although there is a slight roughening cffect,
specific single-layer or multiple-layer electro plating is perfornled, adhesiveness
between the solid coating and the subsurface is increased, and the seizure resistance of
the tubular threaded joint nlay be improved.
[0077]
As the subsurface treat~uentf or the solid coating, for exanlple, electro plating
using metals suc11 as Cu, Sn, and Ni or an alloy thereof may be employed. Plating
may be single-layer plating or multiple-layer plating for hvo or more layers. As
specific exanlples of this type of electro plating, there are Cu plating, Sn plating, Ni
plating, Cu-Sn alloy plating fi~rtlledr escribed in Japanese Unexamined Patent
Application, First Publication No. 2003-74763, CLI-Sn-Zna lloy plating, two-layer
plating i~icludingC u plating and Sn plating, and thee-layer plating including Ni
plating, Cu plating, and Sn plating. Particularly, in a tubular threaded joint
manufactured from a steel type in which the Cr content exceeds 5%, seizure is very
likely to occur. Therefore, it is preferable that single-layer plating of a Cu-Sn alloy or
a Cu-Sn-Zn alloy, or multiple-layer metal plating using a combination of two or more
types of plating selected fro111 the alloy plating, Cu plating, St1 plating, and Ni plating
be perfornled as the subsurface treatment. As the multiple-layer metal plating, for
example, there are two-layer plating including Cu plating and Sn plating, two-layer
plating includirig Ni plating and Sii plating, two-layer plating iticludi~igN i plating atid
Cu-Sn-Zn alloy plating, and three-layer plating including Ni plating, Cu plating, and
Sn plating.
[0078]
Such plating Tilay be perfor~iieda ccording to a method described in Japanese
U~lexatiiinedP atent Application, First Publication No. 2003-74763. In tlie case of the
inultiple-layer plating, a plated coating (typically Ni plating) at tlie lowest layer is
preferably a plated layer called strike plating, wliicli has an extremely stilall thickness
of 1 111no r less. It is preferable that the thiclu~esso f the plating (the total thickness in
tlie case of the inultiple-layer plating) be in a range of 5 11111 to 15 ~1111.
[0079]
As still another subsurface treatment, a solid anticorrosive coating treatment is
also possible. The above-described solid coating is a viscous liquid or a se~iiisolida s
described above, and tlie surface thereof has slight stickiness. Pai-ticularly, the solid
coating of tlie viscous liquid has high stickiness. As a result, pai-ticnlarly at the time
of allowing the oil well pipe to stand upright, rust that re~llai~oins the inner surface or
abrasive grains for abrasive blasting injected to remove the rust fall, and they may
adhere to the solid coating and be buried into the solid coating. The foreign matter
buried into tlie coating is not completely re~llovcdb y air blowing or the like and causes
degradation in lubricity. In order to solve this problem, a thin dried solid coating may
also be for~nedo n the upper layer of the solid coating. The dried solid coating may
be a general resin coating (for example, an epoxy resin, a polyamide resin, a
polyaulide-itnide resin, or a vinyl resin), and the coating can be fornled from ally of a
water-based cotnposition and an organic solvent-based composition. Further, a small
amount of wax may be contained in tlie coating.
[0080]
FIG. 3A is a diagram scheniatically illustrating a coating structure in a case
where a subsurface treattnent layer (for exa~tlplea, phosphate chemical collvcrsioll
treattilent coating or a porous tnetal plated coating for~iledb y impact plating) 32 for
roughening is first formed on the contact surface of a base body 30 that forms the pin 1
andlor the box 2 of the tubular threaded joint and a solid coating 3 lb, which contains
the lubricating particles, is forlned thereon. As described above, roughening may also
be achieved by roughe~lirigth e contact surface itself tl~oughf,o r example, sandblastitig
instead of forming the base treatment layer 32. Fulthel; the solid coating may also
not contain the lubricating particles.
[0081]
FIG. 3B is a diagram schematically illustrating a coating structure in a case
where a solid coating 3 la, \vl~iclid oes not contain tlie lubricating particles, is formed
as a first layer on the contact surface of a base body 30 of the pin 1 andlor the box 2 of
the tubular threaded joint and a solid coating 3 1 b, which contains the lubricating
particles, is formlled thereon as a second layer. It is preferable that, on the contact
surface of the base body 30, the subsurface treatment coating for rougl~cningb e formed
as illustrated in FIG. 3A, or the two layers of solid coatings be formed after roughening
the contact surface itself.
[0082]
[Surface Treatment of Counterpart Member]
In a case where the solid coating is formed on the contact surfaces of only one
member (for example, the box 2) of the pin 1 and the box 2 of the tubular threaded
joint, the contact surfaces of the other member (for example, the pin 1) that is not
coated with the solid coating may be untreated. However, preferably, the abovedescribed
subs~urfacetr eatment for roughening may be performed thereon to roughen
the contact surfaces. That is, the roughening can be performed by employing a
blasting treatment, pickling, a chemical con\~ersiontr eatment using phosphate, oxalate,
borate, or the like, electro plating, con~positep latiug in \vliich a plated coating
containing solid fine particles is formed, and a combination of two or Illore types
thereof. At the time of fastening a counterpart member whicll is coated with the solid
coating, the contact surfaces of the other membcr which does not have the solid
coatirlg exhibits good nlaintenance due to the anchor effect by the roughening.
Accordingly, the seizure resistance of the tubular threaded joint is increased.
[0083]
In addition, in order to impart antirust properties, a well-known waterproof
coating such as a ultraviolet curable resin or a thermosetting resin may also be
performed after the subsurface treatment, if desired. By blocking the contact with the
atlllospfiere by the antirust coating, even when contact with water occurs due to the
dew poi~ldt uring storage, generation of rust on the contact surfaces is prevented.
[0084]
Since the surface treatment of the contact surfaces of the counterpart member
is not particularly limited, the other surface treatments can also be perforrtled. For
example, various solid coatings (for example, a solid lubricating coating) whicli are
different from the solid coating of this elllbodi~nellct an be fornled on the contact
surface of the counterpart member.
[Examples]
[008S]
The effect of the present invention is cxe~nplifiedb y the following Exanlples
and Conlparative Examples. Further, hereinafter, the contact surface including the
threaded portion and the unthreaded rnetal contact portion of the pin is referred to as a
"pin surface" and the contact surface including the tlxeaded portion and the unthrcaded
rnetal contact portion of the box is referred to as a "box surface". Surface roughness
is Rnlax. "%" is "mass% unless otherwise designated.
[0086]
On the pin surface and the box surface of a coupling type prenliu~nth readed
joint VAM TOP (outside diameter: 17.78 cm (7 inches), thickness: 1.036 cnl(0.408
inches), including the threaded portion, the seal portion, and the shoulder portion)
made of any of a Cr-Mo steel A, a 13% Cr steel B, a 25% Cr steel C s11o~v1i1n Table 1,
the subsurface treatment shown in Table 3 was performed, and by using a co~tlposition
for solid coating formation having the chemical co~npositions hown in Table 2, a solid
coating was formed under the solid coating formati011 conditions shown in Table 3.
Regarding the average thickness of the obtained solid coating, the thickness of the
solid coating at the unthreaded rnetal contact portio~wl as nleasured by a connnercially
available thickness meter.
The colnpositioti for solid coating for~ilatiotiw as prepared by preparing a
mixed solvent by mixing a dipolar aprotic solvcnt and pure water at a predetermined
ratio, adding a powdery organic resin to tlie mixed solvent, and stirring the resultant at
a temperature of 60 to 80°C using a stirrer to cause the resin powder to be dissolved or
dispersed in the solvent. In a case where tlie composition contains the lubricating
particles, lubricating particles are added and fi~~flisetirr red to cause the particles to be
uliifortnly dispersed for the preparation. Further, in a case of a resin which is
obtained in a dispersed liquid state, the solvent is prepared to be the mixed solvent
according to the emboditnent of the present invention, and lubricating particles are
fi~rthera dded and stirred depending on the case, thereby forming tlie composition for
solid coating formation.
(Note) The content of each element is mass%, and the balance being Fe and itilpurities.
[Table 11
Symbol
A
B
C
C
0.25
0.19
0.02
Si
0.25
0.25
0.3
Mn
0.8
0.8
0.5
P
0.02
0.02
0.02
Cu
0.04
0.04
0.5
S
0.01
0.01
0.01
Ni
0.05
0.1
7
Cr
0.95
13
25
Mo
0.18
0.04
3.2
* The amount of amorphous graphite is an added amount with respect to 100 parts by mass of the total amount of resin? water. and organic
solvent.
No.
[Table 31
Constitution of composition for solid coating formation (mass%)
Water-dispersible resin Water I Aqueous organic solvent / Lubricating solid particles
Example 1 1 Polyamide-imide resin (15) I Pure water 1 NMP 1
treatment
Example 1 1. Grinding Polyamide-imide
finish (R=3) resin (F25)
2. Zinc
phosphate phosphate (R=10)
(R=8) (t-12)
Example 2 Sandblasting Polyamide-imide
(R= 1 0) resin with PTFE resin with PTFE
powder dispersed powder dispersed (t
plating+Cu plating =20)
amorphous gaphite
Steel
composition
No. Box
---/ -
Example 4 Grinding Mixture of Mixture of Mixture of A
Subsurface I First layer of solid Second layer of 1 Subsurface treatment First layer of solid Second layer of
Pin
finish (R=3)
1. Grinding finish
Example 1 finish (R=3) specified in the (R=3)
2. Zinc Standard API BUL 2. Manganese
phosphate (R=lO)
(R=8) (-1 2) (t= 15)
Comparative 1. Grinding Polyamide-imide 1. Grinding finish
Exampie 2 finish (R=3) resin with (R=3)
2. Zinc molybdenum 2. Manganese
phosphate disulfide dispersed phosphate (R=10)
(R=S) (-12) (t=25) (t=15)
polyamide-imide
resin and
fluororesin (F15)
R: Surface roughness (pm), t: Thickness (pm)
flubroresin (t=20)
Compound gease
specified in the
Standard API BUL
5A2
Polyamide-imide
resin with
molybdenum
disulfide dispersed
(-25)
A
A
polyamide-imide
resin with
amorphous gpahite
disoersed and
(R=3) polyamide-imide
resin and
fluororesin (t=15)
polyamide-imide
resin with
amorphous ,gpahite
dis~erseda nd
[0091]
For tlie evaluatioa, in a state where protectors for protecting a pin threaded
portiori and a threaded portion of a box inner surface of a couplitig of an oil well pipe
were tnou~itedb efore fastening, a weather resistance test in wliicli all climates were
sirilr~lated in tlie order from a frigid weather to a high temperature under tlie test
climate conditiotis (humidity is relative humidity) as described in Table 4 was
performed. Thereaftel; the coupling was taken off, tlie pin surface and the box
surface were visually observed, the external form of the solid coating (presence or
absence of peeling, discoloration, and tlie like) was examined, and tlie hardness of tlie
solid coating before and after the weather resistance test was measured by a pencil
hardness tester. Thereafter, a repeated fastening and loosening test, \vliich will be
described later, was ininiediately performed, and occurrence of seizure was exa~nitled.
I11 addition, in Table 4, under tlie ocean envirotlment exposure condition, a saturated
NaCl solution for a salt spray test according to tlie JIS standard was sprayed for the test
under the conditions of +4OoC and a humidity of 98%.
[0092]
In the rcpcatcd fastening and loosening test, the threaded joint was fastened at
a fastening speed of 10 rpm and a fastening torque of 20 kN.111,a nd the seiz~~srtea tuses
oft lie pin surface and tlie box surface were cxa~iii~leadft er loosening. Tlie first to
fourth fastening and loosening operations were performed in a warm e~ivirontnent
(about 2OoC). Tlie fifth and tlie rest fastening and looselling operations were
performed at -20°C by coolilig the periphery of tlie fastened part with dry ice. In a
case where seizure marks generated by fastening were small and re-fastening was
possible after repail; fastening and looselling were co~lti~iueadft er tlie repair. The
results oft he weather resista~icete st and the repeated fastening and loosening test
perfor~~iethde reafter are collectively sho~vnin Table 5.
[Table 41
Order
1
2
3
4
5
6
Climate conditions
Thermal deterioration
Exposure to low temperature
Temperature change
Hot and humid
Exposure to ocean environment
(salt spray)
Exposure to high-temperature steam
Temperature (OC)
+40
-60
+20
-20
+40
+40
-40
+lo0
Humidity (%I
Not designated
Not designated
98
Not designated
98
98
Test time
6 days
3 days
Total of 36 cycles of 4 hours per each temperature
5 days
2 days
Not designated
98
1 hour
1 minute

[0095]
(Example 1)
On the pin surface and the box surface of the pretiiium threaded joint made of
tlie Cr-Mo steel having tlie cotiiposition A showtl in Table 1, surface treatments were
performed to achieve the subsurface treattnent and tlie solid coating confignration
shown in Exarnple 1 of Table 3.
[0096]
The box surface was subjected to a niechanical grinding finish (a surface
roughness of 3 p i ) arid thereafter was inlniersed in a manganese phosphate chemical
conversion treattllent liquid at 80°C to 95°C for 10 minutes, thereby forming a
niatlgatlese phosphate coating (a surface roughness of 10 ptn) having a thickness of 15
ptn.
[0097]
The pin surface was subjected to a n~echanicalg rinding finish (a surface
roughness of 3 pm) and thereafter was irnlllerscd in a zinc phosphate chemical
cotlversion treattnent liquid at 75 to 8S°C for 10 minutes, thereby forniing a zinc
pl~osphatec oating (a surface roughness of 8 pm) liavillg a thickuess of 12 pm.
[0098]
Next, onto the pin surface and the box surface subjected to the subsurface
treatment, a compositiorl for solid coating fortliation tilade by mixing a polyatnideimide
resin ( ~ o r l o t4l0~00~T F made by SOLVAY) as an organic resin that is soluble in
a dipolar aprotic solvent, pure water, and NMP (N-methylpyrrolidone) as the dipolar
aprotic solvetit to have the cotnpositiotl of Exatllple 1 of Table 2 was applied through
spraying. Thereafter, resultatlt was subjected to predrying (at 80°C for 10 nlinutes)
and tilain heating (at 230°C for 30 minutes), thereby forniing a solid coating having an
average thickness of 25 pm.
[0099]
After mounting the protectors nlade of resin to the pin and thc box having the
solid coatings formed thereon, the weather resistance test shown in Table 4 was
perfonned. As shown in Table 5, deterioration such as peeling, discoloration, and
hardness degradation of the solid coatings of the pin surface and the box surface was
not confirmed after tlie test. Subsequently, tlie repeated fastening and loosening test
was perfornled. After the ninth loosening, slight seizure had occurred in tlie threaded
portion of the pin surface. However, the tlxcaded portion was repaired and
continuously subjected to the test as it was, and tenth fastening and loosening could be
perfonned.
[Ol 001
(Example 2)
On the pin surface and the box surface of the premium threaded joint made of
the 13% Cr steel having the conlposition B shown in Table 1, surface treatments were
perfornled to achieve the subsurface treatment and the solid coating configuration
shown in Example 2 of Table 3.
[OlOl]
The box surface was subjected to a mcclianical grinding finish (a surface
roughness of 3 pm) shown in Table 3 and thereafter was subjected to, first, Ni strike
plating, and next, Cu plating througl~e lectro plating, thereby fornling a plated coating
(a surface rouglmess of 5 ~111h) aving a total thickness of 10 pn~. The pin surface was
subjected to sandblasti~lgin which sand is blasted 80 times to have a surface roughness
of 10 pm.
[O 1021
Next, onto thc pin surface and the box surface subjected to the subsurface
treatment, a compositio~flo r solid coating forlnation made by mixing a polyatnideiniide
resin (the same as that of Example 1) as an organic resin that is soluble in a
dipolar aprotic solvc~~ptu,r e water, DMSO (ditnethylsulfoxide) as the dipolar aprotic
solvent, and PTFE particles as lubricating particles at the ratio shown in Example 2 of
Table 2 was applied through spraying. Thereafter, the resultant was subjected to
predrying (at 8S°C for 10 minutes) and main heating (at 280°C for 30 minutes),
thereby forming a solid coating having an average thickness of 20 pm.
[0 1031
After mounting the protectors made of resin to the pin and the box having the
solid coatings formed thereon, the weather resistance test shown in Table 4 was
performed. As sho~+min Table 5, deterioration sucli as peeling, discoloration, and
hardness degradation of the solid coatings of the pin surface and the box surface was
not confirmed after the test. Subsequently, the repeated fastening and loosening test
was performed, and fastening and loosening could be performed 10 times without the
occurrence of seizure.
[0104]
(Example 3)
On the pin surface and the box surface of the prernium threaded joint made of
the 25% Cr steel having the con~positioC~i s liom~nin Table 1, surface treatments were
performed to achieve the subsurface treatment and the solid coating co~~figuration
shown in Exanlple 3 of Table 3.
[O 1051
The box surface was subjected to a nlechanical grinding finish (a surface
roughness of 3 pm) and thereafter was subjected to, first, Ni strike plating, and next,
Cu-Sn-Zn alloy plating through electro plating, thereby forming a plated coating (a
surface roughness of 5 pm) having a total thickness of about 7 pm. The pin surface
was subjected to sandblasting in which 80th sand is blasted to have a surface roughness
of 10 blnl.
[0 1061
Next, otlto the pin surface and the box surface subjected to the subsurface
treatment, a composition for solid coating formation made by mixing a co~nn~ercially
available water-dispersible epoxy resin (MODEPICS301 (registered trademark) made
by Arakawa Chenlical Iadustries, Ltd., obtained in a water-dispersed liquid state) as an
organic resin that is partially soluble at least in a dipolar aprotic solvent, GBL (ybutyrolactone)
as the dipolar aprotic solvent, and amorphous graphite as lubricating
particles at the ratio sholvn in Example 3 of Table 2 was applied though spraying.
Thereafter, the resultant was subjected to predrying (at 80°C for 10 mi~lutcsa)n d ~nain
heating (at 230°C for 30 tnitlutes), thereby forming a solid coating having at1 average
thickness of 20 ~un.
[0 1071
After mounting the protectors made of resin to the pin and the box having the
solid coatings formed thereon, the weather resistance test shown in Table 4 was
perfor~ned. As show11 in Table 5, deterioration such as peeling, discoloration, and
hardness degradation of the solid coatings of the pin surface and the box surface was
not confirmed after the test. Subsequently, the fastening and loosening test was
performed, and fastening and loose~lillgc ould be performed 10 times without the
occurrence of seizure.
[0108]
(Exa~nple4 )
On the pin surface and the box surface of t he prclniu~nth readed joint made of
the Cr-Mo steel having the con~positionA shown in Table 1, surface treatments were
performed to achieve the subsurface treatment and the solid coating configuration
shown in Example 4 of Table 3.
[0109]
The pin surface and the box surface were subjected to a mechanical grinding
finish (a surface roughness of 3 pm). Onto the pin surface and the box surface, first,
as a first layer, a colnposition for solid coating formation made by mixing a mixture
(the mass ratio of polyatnide-imide resin/fluororesin = 70130 in terms of solid content)
of a polyamide-imide resin (the same as that of Example 1) as an organic resin that is
soluble in a dipolar aprotic solvent and a conlmercially available water-dispersible
fluororesin (POLYFLON (registered trademark) PTFE D-210C made by DAIKIN
INDUSTRIES, Itd., obtained in a water-dispersed liquid state), and as the balance, pure
water and DMSO as the dipolar aprotic solvent at the ratio shown in the first layer of
Example 4 of Table 4 was applied through spraying. Thereafter, the resultant was
subjected to predrying (at 80°C for 10 minutes). Next, as a second lapel; a
colnposition for solid coating fornlation made by further adding and dispersing 17
pal-ts by mass of a~norphousg raphite in 100 parts by mass of the composition for solid
coating formation for the first layer was applied through spraying. Thereafter, the
resultant was subjected to predrying (at 80°C for 10 minutes) and tnain heating (at
230°C for 30 minutes). Accordingl~: a solid coating in which the first layer and the
second layer have a total average thickness of 35 bun was formed. As shown in Table
3, the thickness of the first layer that did not contain lubricating particles was about 15
pnl, and the thickness of the second layer that contained the lubricating particles
(amorphous graphite) was about 20 pm.
[OllO]
After nlounting the protectors nlade of resin to thc pin and the box having the
solid coatings forn~edth ereon, the weather resistance test sho\nl in Table 4 was
performed. As shown in Table 5, deterioration such as peeling, discoloration, and
hardness degradation of the solid coatings of the pin surface and the box surface was
not confimied after the tcst. Subsequently, the repeated fastening and loosening test
was perforn~ed. Fastening and loosening could be perfo~iied 10 times without the
occurrence of seizure.
[Olll]
(Con~parativeE xample 1)
On the premium threaded joint made of the Cr-Mo steel of the composition A
shown in Table 1, the subsurface treatment of Co~uparativeE xanlple 1 of Table 2 was
performed, and a grease (a con~poundg rease in a viscous liquid for111 specified in the
Standard API BUL 5A2) that contained heavy metals such as lead was applied thereto.
[0112]
The box surface was subjected to a ~nechanicalg rinding finish (a surface
roughness of 3 pm) and thereafter was inu~~erseind a iilanganese phosphate chemical
conversion trcatnlent liquid at 80 to 95'C for 10 minutcs, thereby forming a
nlariganese phosphate coating (a surface roughness of 10 11n1) having a thickness of 15
LIIII. Nest, the compound grease was applied onto the surface subjected to the
subsurface treatment, thereby fornling a lubricating coating (a total amount of the
compound grease applied onto the pin and the box was 50 g, and the application area
thereof is approximately 1400 cm2 in total)
[0113]
Tlie pin surface was subjected to a mechanical grinding finish (a surface
rouglu~esso f 3 pni) and thereafter was i~iunersedi n a zinc phosphate chemical
co~ivcrsiontr eatment liquid at 75 to 85°C for 10 miiiotes, thereby forming a zinc
phosphate coating (a surface roughness of 8 pm) liaving a thickness of 12 Inn. The
compound grease as such was applied onto tlie surface thereof.
[0114]
After mou~itingth e protectors made of resin to the pin and the box, the
weather resistance test shown in Table 4 was perfoniied. As show11 in Table 5, no
significant changes in the lubricating coatirig grease on the pin surface and the box
surface were confirmed after the test. In the fastening and looseiiirig test performed
subsequently, during the first to fourth fastening and loosening operations perfo~med in
a warm environment (about 20°C), seizure had not occurred. However, in tlie fifth
and tlie rest fastening and loosening operations at about -20°C, seizure had occurred in
the threaded portion of the pi11 from the sixth fastening and loosening operation, and
seizure in the eighth fastening and loosening operation was at such a level that could
not bc repaired. Therefore, tlie test was stopped.
[0115]
From tlie results, it was determined that even though the cotnpound grease
containing heavy tnetal powder, which had been used froin the past, was considered to
have excellent seizure resistance, satisfactory perfor~nancec ould not be exhibited
during fastening in a low temperature environment after an exposure to a hot and cold
cycle of from an extremely low temperature to a high temperature.
[0116]
(Comparative Example 2)
On the pin surface and tlie box surface of the premium threaded joint lnade of
tlie Cr-Mo steel having the composition A shown in Table 1, surface treatments were
performed to achieve the subsurface treatment and the solid coating configuration
slio\m in Comparative Exanlple 2 of Table 3.
[0117]
Tl~beo x s~urfacew as subjected to a n~ecliatticalg rinding finish (a surface
roughness of 3 ~111a) nd tliereafter was inlmersed in a manganese phosphate chemical
conversion treatment liquid at 80.to 95OC for 10 minutes, tliereby forniing a
manganese phosphate coating (a surface rougliness of 10 ptn) having a thickness of 15
pm.
[0118]
The pin surface was subjected to a mechanical grinding finish (a surface
rougliness of 3 pm) and tliereafter was immersed in a zinc phosphate chemical
conversion treatment liquid at 75 to 85'C for 10 minutes, thereby forming a zinc
phosphate coating (a surface roughness of 8 pm) havilig a thickness of 12 p i .
[0119]
Next, onto tl~epi n ssuface and the box surface subjected to the subsurface
treatment as such, a composition for solid coating for~nation(c orresponding to the
composition described in Patent Docunient 1) made by nlixing a polyamide-imide
resin (VYLOMAX (registered tradeniark) HR-BNX tilade by TOYOBO CO., LTD.)
that is soluble in a non-dipolar (lion-polar) organic solvent, a nlixed solvent including
xylene and NMP at a mass ratio of 33 and 67 as an organic solvent, and ~nolybdenum
disulfide as lubricating particles at the ratio shown in Comparative Exaniple 2 of Table
2 was applied though spraying. Thereafter, the resultant was subjected to predrying
(at 80°C for 10 mi~iutesa) nd ~ilaillii eating (at 230°C for 30 minutes), thereby forming
a solid coating having an average thichiess of 25 Fun.
[0120]
After mounting the protectors made of resin to the pin and the box having the
solid coatings fornled thereon, the weather resistance test shown in Table 4 was
perfomled. As shown in Table 5, partial peeling and blisters were obsewed from the
solid coatings of the pin surface and the box surface after the test. In the repeated
fastening and loosening test perfomled subsequently, during the first to fout-th
fastening and loosening operations perfortned i11 a warn1 environment (about 20°C),
seizure had started to occur in the threaded portion of the pin fiom the third fastening
and loosening operation. Thereafter, the tlxeaded portion was repaired to continue
the test. Howcver, in the fifth fastening and loosening operation which was the
fastening and loosening test performed at about -2OoC, and seizure was at st~cha level
that could not be repaired. Therefore, the test was stopped.
[0121]
From the results, even in the tubular threaded joints having the solid coatings
made of the similar polyamide-imide resins as such, it was apparently seen that the
solid coating formed fiom the con~positiond issolved in the organic solvent of
Cotnparative Example 2 and the solid coatings fornted from the compositions
dispersed in water in Exanlples 1 to 4 were different in the perfornlance in the hot and
cold cycle of from an extremely lo\\' temperature to a high tenlperature and in the
seizure resistance performance in the fastening and loosening test at a low tenlperature.
[O 1221
The antirust propel-tics of the ttubular tlxeaded joints of Exaunples 1 to 4 and
Conlparative Examples 1 and 2 were exanlined by perfornling the same subsurface
treatments as those of the pin surfaces and the box surfaces of Table 3 on additionally
prepared coupon specinlens (70 1nrnxl50 mmxl.0 mtll thick) and foin~ingth e same
solid coatings. Tllc specinlens \\?ere provided for a salt spray test (based on JIS
22371 (corresponditlg to IS0 9227), a tenlperature of 35"C, 1000 hours) and a
humidity test (based on JIS K5600-7-2 (corresponding to IS0 6270), a temperature of
50°C, a h~~midiotyf 98%, 200 hours) to exatnine presence or absence of rust being
generated. As a result, it was confirmed that there was no rust being generated in all
the Exatnples I to 4.
[0123]
While the present invention has been described according to the elnbodi~ne~its
which are considered to be preferable at this point in time, the present invention is not
limited to the embodiments discloscd above. Modifications can be added in a range
that does not depart from the technical idea of the present illvelltion that call be read
froln the appended clai~nsa nd the entire specification, and it should be u~~derstoothda t
threaded joints according to such lnodifications are included in the technical scope of
the present invention.
[Description of Reference Nutnerals and Signs]
[0124]
A: STEELPIPE
B: COUPLING
1: Pm'
2: BOX
3a: MALE THREADED PORTION
3b: FEMALE THREADED PORTION
4a, 4b: UNTHREADED METAL CONTACT PORTION
5a, 5b: SI-IOULDER PORTION
30: STEEL SURFACE
3 la: SOLID COATING (FIRST LAYER IN TWO-LAYER
CONFIGURATION)
3 1 b: SOLID COATING (IN SINGLE-LAYER CONFIGURATION OR
SECOND LAYER IN TWO-LAYER CONFIGURATION)
32: SUBSURFACE TREATMENT LAYER

[Type of Docutnent] CLAIMS
[Claim 1]
A composition for solid coating fornlation, conlprising
a colnposition tnade by containing, in a mixed solvent including water and a
dipolar aprotic solvent, a powdery organic resin which is partially soluble at least in
the dipolar aprotic solvent,
wherein the powdery organic resin is present in a state of being dissolved or
dispersed in the mixed solvent.
[Claim 2]
The composition for solid coating formation according to Claitn 1, furtllei
comprising lubricating particles.
[Claim 3]
The composition for solid coating formation according to Claim 1 or 2,
wherein tlie powdely organic resin is one or Inore types selected from a
polyamide-imide resin, an epoxy resin, and a fluororesin.
[Claim 4]
The composition for solid coating formation according to any one of Claims 1
to 3,
wherein tlie dipolar aprotic solvent is one or rnore types selected fro111 Nn~
etli~~lpyrrolidodaiem, ethylacetamide, di~lletl~~~lformarndiidne~,e tliyls~~lfoxiadned, ybutyrolactone.
[Claim 5]
A tubular theaded joint co~nprising
a pin and a box each of 1~11ich is provided with a contact surface including a
threaded portion and a untl~readedm etal contact portion,
wherein the contact surface of at least one menlber of the pin and the box lias
a solid coating formed from thc compositio~fl or solid coating formation according to
any one of Claims 1 to 4.
[Claim 6]
The tubular readed joint according to Claim 5,
wllerein the solid coating has: a first layer w11ich does not contain lubricating
particles; and a second layer fornied thereon, m41ich contains lubricating particles.
[Claim 71]
The tubular threaded joint according to Claim 5 or 6,
wherein a thickness of the solid coating is 5 pm to 100 µm.