U.S. patent application number 12/701343 was filed with the patent office on 2010-06-03 for cold working lubricant and cold working method for steel pipe.
This patent application is currently assigned to SUMITOMO METAL INDUSTRIES, LTD.. Invention is credited to Masayoshi Akiyama, Tsutomu Arita.
Application Number | 20100132427 12/701343 |
Document ID | / |
Family ID | 38693941 |
Filed Date | 2010-06-03 |
United States Patent
Application |
20100132427 |
Kind Code |
A1 |
Akiyama; Masayoshi ; et
al. |
June 3, 2010 |
Cold Working Lubricant and Cold Working Method for Steel Pipe
Abstract
The present invention provides a lubricant comprising an alkali
soap and a cold working method, in which the lubricant layer can be
easily formed on the surface of a steel pipe prior to cold working
the reduces the work load during cold working of the steel pipe,
and whose layer can be easily removed by washing the surface of the
steel pipe after cold working. After that, an alkali soap aqueous
solution or aqueous pasty alkali soap is applied to the working
surface of the steel pipe, cold working of the steel pipe is
performed, and thereafter the alkali soap layer is removed by
washing with water. The alkali soap aqueous solution or aqueous
pasty alkali soap is preferably prepared within a vessel having an
inner surface consisting of a non-metal material.
Inventors: |
Akiyama; Masayoshi;
(Kobe-shi, JP) ; Arita; Tsutomu; (Wakayama-shi,
JP) |
Correspondence
Address: |
MARSHALL, GERSTEIN & BORUN LLP
233 SOUTH WACKER DRIVE, 6300 WILLIS TOWER
CHICAGO
IL
60606-6357
US
|
Assignee: |
SUMITOMO METAL INDUSTRIES,
LTD.
Osaka
JP
|
Family ID: |
38693941 |
Appl. No.: |
12/701343 |
Filed: |
February 5, 2010 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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12270595 |
Nov 13, 2008 |
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12701343 |
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PCT/JP2007/059966 |
May 15, 2007 |
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12270595 |
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Current U.S.
Class: |
72/342.2 |
Current CPC
Class: |
C10M 105/24 20130101;
C10M 2207/1253 20130101; C10N 2050/02 20130101; C10N 2040/243
20200501; C10N 2040/241 20200501; C10M 173/02 20130101; C10N
2030/06 20130101; C10M 2207/1253 20130101; C10N 2010/02 20130101;
C10M 2207/1253 20130101; C10N 2010/02 20130101 |
Class at
Publication: |
72/342.2 |
International
Class: |
B21D 37/16 20060101
B21D037/16 |
Foreign Application Data
Date |
Code |
Application Number |
May 15, 2006 |
JP |
2006-135154 |
Claims
1. A cold working method for a steel pipe, comprising cold working
after forming a solid alkali soap layer on the working surface of a
steel pipe by coating an alkali soap aqueous solution thereto.
2. A cold working method for a steel pipe, comprising cold working
after forming a solid alkali soap layer on the working surface of a
steel pipe by coating an alkali soap aqueous solution thereto
followed by drying.
3. The cold working method for a steel pipe according to claim 1,
wherein the alkali soap aqueous solution to be coated to the
working surface of the steel pipe is prepared by dissolving alkali
soap in water within a vessel having an inner surface consisting of
a non-metal material.
4. The cold working method for a steel pipe according to claim 2,
wherein the alkali soap aqueous solution to be coated to the
working surface of the steel pipe is prepared by dissolving alkali
soap in water within a vessel having an inner surface consisting of
a non-metal material.
5. A cold working method for a steel pipe, comprising cold working
after forming a solid alkali soap layer on the working surface of a
steel pipe by coating an aqueous pasty alkali soap thereto.
6. A cold working method for steel pipe, comprising cold working
after forming a solid alkali soap layer on a working surface of a
steel pipe by coating an aqueous pasty alkali soap thereto followed
by drying.
7. The cold working method for a steel pipe according to claim 5,
wherein the aqueous pasty alkali soap to be coated to the working
surface of the steel pipe is prepared by impregnating alkali soap
with water within a vessel having an inner surface consisting of a
non-metal material.
8. The cold working method for a steel pipe according to claim 6,
wherein the aqueous pasty alkali soap to be coated to the working
surface of the steel pipe is prepared by impregnating alkali soap
with water within a vessel having an inner surface consisting of a
non-metal material.
9. The cold working method for a steel pipe according to any one of
claims 1 to 8, wherein the cold working of the steel pipe is a pipe
expansion work of the steel pipe end using a plug.
10. The cold working method for a steel pipe according to any one
of claims 1 to 8, wherein the alkali soap is composed of either or
both of Na salt and K salt of one or more kinds of straight-chain
fatty acids having 10 to 18 carbon atoms.
11. The cold working method for a steel pipe according to any one
of claims 1 to 8, wherein the cold working of the steel pipe is a
pipe expansion work of the steel pipe end using a plug, and wherein
the alkali soap is composed of either or both of Na salt and K salt
of one or more kinds of straight-chain fatty acids having 10 to 18
carbon atoms.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to a cold working lubricant
and a cold working method for steel pipe. More specifically, the
present invention relates to a lubricant excellent in lubricating
property during cold working of a steel pipe and excellent in
washing removability from the steel pipe surface after cold
working, and a cold working method for steel pipe using the
same.
BACKGROUND OF THE INVENTION
[0002] In cold working of a steel pipe, lubricating treatment has
been executed for the purpose of reducing a working load and
preventing a seizure between the steel pipe and a working tool.
[0003] Three methods have been conventionally known for the
lubricating treatment in cold working of a metal material including
the steel pipe, namely, a chemical treatment method, an oil
lubricating method and a synthetic resin layer lubricating
method.
[0004] The chemical treatment method comprises a chemical treatment
process such as pickling for removing an oxide layer or a hydroxide
layer formed on a surface of a metal material, and a layer process
for forming a substrate layer such as a phosphate layer or an
oxalate layer, followed by a process for forming a metal soap layer
including a non-alkali metal such as Zn on the substrate layer. The
substrate layer and the metal soap layer are formed on a work piece
surface through these processes. The layer formed by the chemical
treatment has an excellent lubricating property. The chemical
treatment method is frequently used for a pretreatment, mainly for
the cold working of a steel wire rod or a steel bar.
[0005] The oil lubricating method comprises coating lubricating oil
such as mineral oil to a working surface of metal material. The
cold working is performed after coating the lubricating oil. The
oil lubricating method among the lubricating treatment methods is
extensively used for cold working because the lubricating oil that
forms a lubricant layer can be easily coated. The oil lubricating
method is applied mainly to pipe expansion work, diameter reducing
work, cold drawing work, cold rolling and the like of steel
pipe.
[0006] The synthetic resin layer lubricating method comprises
forming a synthetic resin layer on a working surface. This
synthetic resin layer functions as a lubricant during cold working.
The synthetic resin layer lubricating method is applied mainly to
press working of the steel sheet or the like.
[0007] However, all these lubricating treatment methods have
problems as described below. Particularly, the application to
lubricating treatments in the cold working of a steel pipe is
problematic.
[0008] The chemical treatment method cannot be adopted except for
cold working of a steel wire rod or a steel bar, because it
includes many processes for forming a substrate layer and thus
requires large-scaled facilities and troublesome works. In the
synthetic resin layer lubricating method, in order to prevent
peeling of the synthetic resin layer during cold working, the
synthetic resin layer is needed to be firmly adhered to the surface
of the metal material, which results in an increased cost caused by
an enlarged scale of facilities and a troublesome work. Therefore,
this method would not be adopted except for cold working of a steel
sheet.
[0009] On the other hand, the oil lubricating method requires
neither a troublesome work nor an enlarged scale of facilities,
compared with the chemical treatment method and the synthetic resin
layer lubricating method. However, the oil lubricating method does
not reduce the working load more than the chemical treatment method
or the synthetic resin layer lubricating method. In the oil
lubricating method, because the lubricating oil is simply coated to
the working surface of the metal material, the lubricating oil such
as mineral oil that is applied to the surface of the metal material
is low in the adhesiveness, and may not adhere to the part of the
surface of the metal material. It results in seizing on this
part.
[0010] In all theses lubricating treatment methods, it is difficult
to remove the lubricant or the lubricating oil from the surface of
the metal material after cold working. Accordingly, some lubricant
or lubricating oil is apt to remain on the surface of the resulting
metal product after removal treatment thereof. The remaining
lubricant or lubricating oil may cause various problems in a heat
treatment process or the like after the cold working.
[0011] When a metal material with a chemical treatment layer
consisting of a phosphate remaining on the surface is heat-treated,
for example, a phosphorization to the metal material may
deteriorate the material strength. Remaining lubricating oil on
stainless steel material, consisting of mineral oil, causes
carburization to the stainless steel product during heat treatment.
When a metal soap layer containing a non-alkali metal salt of Zn,
Mn or the like remains on the surface, the same problem is caused
during heat treatment. Namely, the lubricant remaining on the
surface may deteriorate the mechanical characteristics of the
surface of the metal product during heat treatment. Further, since
the lubricating oil or synthetic resin layer is regarded as dirt,
the product with remaining on the surface cannot be sold
thereafter. Because of this problem, the lubricant layer or
lubricating oil formed by the lubricating treatment must be removed
after cold working. It is preferable that the lubricant or
lubricating oil for cold working of a metal material can be easily
removed from the surface of the metal material after cold working,
in addition to the excellent lubricating property in the cold
working of the metal material.
[0012] Besides the three lubricating treatment methods described
above, a method, which is related to the press working of an
aluminum plate, is disclosed in Patent document 1. This method
comprises a liquid lubricant consisting of a mixture of fine
lubricant particles such as molybdenum disulfide and graphite with
metal soap applied to the working surface of an aluminum plate,
prior to press working However, this method aims at press working
of a sheet metal such as the aluminum plate with extremely low cold
deformation resistance, and is scarcely applicable to the
lubricating treatment for cold working of a pipe-shaped metal,
which involves harsh plastic deformation in addition to high cold
deformation resistance, such as a cold working of steel pipe
including pipe expansion work or cold drawing work. Furthermore,
the lubricant disclosed in Patent document 1 is difficult to be
removed, and when it is applied to the lubricating treatment during
the cold working of a steel pipe, particularly, the fine lubricant
particles such as molybdenum disulfide and graphite are scarcely
removed from the steel pipe surface. Because, when the oxide or a
hydroxide layer is formed on the surface of the steel pipe, a
minute unevenness or crack is apt to occur on the oxide or
hydroxide layer, which would trap fine particles of the lubricant
such as molybdenum disulfide and graphite cannot be removed.
[0013] In relation to the working of the aluminum plate, a solid
lubricant method is disclosed in Patent Document 2. This method
requires a solid lubricant consisting of 3-18% surfactant, 0.03-4.0
wt % rust preventive agent, and the balance of a water-soluble or
water-dispersible film forming component such as an
.alpha.-olefin/maleic monoester/maleic acid monoester salt
terpolymer that is a polymeric synthetic wax having a molecular
weight of 6000 or more, a carboxylated organic polymer compound
having a molecular weight of 1000 or more and a salt thereof.
However, this costly solid lubricant, although used for warm press
working of a sheet metal such as an aluminum plate with an
extremely low cold deformation resistance, cannot be applied to the
lubricating treatment for cold working of a pipe-shaped metal such
as pipe expansion work or cold drawing work with a high cold
deformation resistance, which requires a harsh plastic
deformation.
[0014] Patent Document 1: Japanese Patent Unexamined Publication
No. H6-277766. Patent Document 2: Japanese Patent Unexamined
Publication No. 6-264086
DISCLOSURE OF THE INVENTION
Problems to be Solved by the Invention
[0015] Due to these circumstances, one objective of the present
invention is to provide a cold working lubricant for a steel pipe,
which much reduces the work load on the cold working of a steel
pipe, which can easily form a lubricant layer on the surface of the
steel pipe prior to cold working, and is excellent in washing
removability thereof from the steel pipe surface after cold
working.
[0016] Another objective of the present invention is to provide a
cold working method for the steel pipe using this lubricant.
Means for Solving the Problems
[0017] As a result of examinations and experiments for various
lubricants from the viewpoint of an easy formation of a lubricant
layer onto a surface of a steel pipe prior to cold working and easy
removal, the present inventors obtained the following knowledge,
focusing in alkali soap.
[0018] The alkali soap means a water-soluble alkali metal salt (Na
salt or K salt) of long-chain fatty acid. The alkali soap can be
easily coated to the working surface of a steel pipe by making it
into an alkali soap aqueous solution because it is water-soluble.
The layer formed on the working surface of the steel pipe exists as
a lubricant layer on the surface of the steel pipe as it is or in a
dried state, while the lubricant layer after cold working can be
easily removed by washing the surface of the steel pipe with water
or hot water after cold working, because it forms the water-soluble
alkali soap.
[0019] Otherwise, instead of the alkali soap in the state of an
alkali soap aqueous solution, an aqueous pasty alkali soap that has
some flowability can be coated to the working surface of the steel
pipe. Impregnating the alkali soap with water makes this aqueous
pasty alkali soap. This is, due to the pasty, conveniently used
when the coating is performed to only a part of the working place
that requires a lubricant layer. The aqueous pasty alkali soap
layer after drying is the same as the alkali soap aqueous solution
layer after drying.
[0020] The alkali soap is a water-soluble alkali metal salt (Na
salt or K salt) of long-chain fatty acid as described above, and
any straight chain fatty acid is adoptable thereto regardless of
whether the saturated fatty acid or unsaturated fatty acid.
Preferably, the alkali soap is composed of either or both of Na
salt and K salt of one or more kinds of straight-chain fatty acids
having 10 to 18 carbon atoms. Specific examples thereof include
such as capric acid (C.sub.9H.sub.19COOH), lauric acid
(C.sub.11H.sub.23COOH), myristic acid (C.sub.13H.sub.27COOH),
palmitic acid (C.sub.15H.sub.31COOH), palmitoleic acid
(C.sub.15H.sub.29COOH), margalinic acid (C.sub.16H.sub.33COOH),
stearic acid (C.sub.17H.sub.35COOH), oleic acid
(C.sub.17H.sub.33COOH), and linoleic acid
(C.sub.17H.sub.31COOH).
[0021] With respect to coating the alkali soaps having various
chemical compositions on a surface of a steel pipe, lubricating
property and washing removability thereof were examined. The result
is shown blow.
[0022] The alkali soaps, having chemical compositions shown in
Table 1, were prepared.
TABLE-US-00001 TABLE 1 Sample Sample Sample Sample Sample Sample
Alkali soap No. 1 No. 2 No. 3 No. 4 No. 5 No. 6 Na caprate -- 3 --
-- -- -- Na laurate 30 23 -- -- -- -- Na myristirate 10 35 2 -- --
2 Na palmitate 30 38 38 2 5 18 Na palmitoleate -- -- 4 7 6 4 Na
stearate -- 1 15 -- 7 35 Na oleate 30 -- 37 75 68 37 Na linorate --
-- 4 16 14 4
[0023] For each of the alkali soap layers, a pendulum friction test
was performed and the lubricating property concerned was evaluated
by measuring the frictional coefficient. The test conditions are as
follows.
[0024] Each of various alkali soaps having chemical compositions
shown in Table 1 was dissolved in water to prepare an alkali soap
aqueous solution with concentration of 11 mass %. A specimen ball
was covered with this aqueous solution and dried with cold air to
form a layer, and a frictional coefficient (.mu.) thereof was
measured. The measurements were 30 times performed for each
specimen at a room temperature (25.degree. C.). Table 2 shows the
friction coefficient in the first measurement and the friction
coefficient as a stabilized value for each sample. For a sample
whose friction coefficient exceeded 0.3.mu. before the final
measurement, the number of times of measurement until the friction
coefficient exceeded 0.3.mu. was shown.
TABLE-US-00002 TABLE 2 Friction Friction Number of times of
coefficient (.mu.) coefficient measurement until in 1.sup.st (.mu.)
as stabilized the friction coefficient measurement value exceeded
0.3.mu. Sample No. 1 0.089 0.448 11 Sample No. 2 0.158 0.387 19
Sample No. 3 0.097 0.100 -- Sample No. 4 0.101 0.104 -- Sample No.
5 0.110 0.300 13 Sample No. 6 0.102 0.105 --
[0025] Regarding the washing removability of each layer, a specimen
having each layer in a dried state was washed in water with
slightly stirring, and the adhesion amount of the layer was
measured before and after washing, whereby the degree of washing
removal was evaluated. The forming condition and test condition of
the specimen are as follows.
[0026] Each of various alkali soaps having chemical compositions
shown in Table 1 was dissolved in water to prepare an alkali soap
aqueous solution with concentration of 11 mass %. This aqueous
solution was coated by spraying onto one side of a SUS thin plate
specimen (80 mm.times.60 mm.times.1 mm) with a layer thickness of
about 30 g/m.sup.2 (in dried state), followed by drying for 24
hours by use of a dryer of 50.degree. C., whereby a dry layer was
formed on the specimen. The specimen with the dry layer was dunked
in a water bath (1000-mL beaker) of 50.degree. C. under stirring
(just to whirl), and the time (sec) for the removal of the layer by
washing was measured. The washing removal time of each specimen is
shown in Table 3.
TABLE-US-00003 TABLE 3 Washing time (sec) Sample No. 1 10-15 Sample
No. 2 15-20 Sample No. 3 30-40 Sample No. 4 20-30 Sample No. 5
20-25 Sample No. 6 40-50
[0027] Consequently, it was found that a layer can be easily formed
on a working surface by coating water-soluble alkali soap thereto,
and the resulting layer is excellent in lubricating properties with
a low friction coefficient. Further, when such a layer is formed,
it is also easy to remove the layer by washing after cold
working.
[0028] The present invention has been achieved based on the new
knowledge above. The cold working lubricants for a steel pipe
according to the present invention are shown in the following (1)
to (3). The cold working methods for a steel pipe according to the
present invention are shown in the following (4) to (12).
Hereinafter each one will be referred to as the present invention
(1) to (12), respectively. These may collectively be referred to as
the present invention.
[0029] (1) A cold working lubricant for a steel pipe, comprising
alkali soap.
[0030] (2) The cold working lubricant for a steel pipe according to
(1) above, wherein the cold working of a steel pipe is a pipe
expansion work of a steel pipe end using a plug.
[0031] (3) The cold working lubricant for a steel pipe according to
(1) or (2) above, wherein the alkali soap is composed of either or
both of Na salt and K salt of one or more kinds of straight-chain
fatty acids having 10 to 18 carbon atoms.
[0032] (4) A cold working method for a steel pipe, comprising cold
working after forming a solid alkali soap layer on the working
surface of a steel pipe by coating an alkali soap aqueous solution
thereto.
[0033] (5) A cold working method for a steel pipe, comprising cold
working after forming a solid alkali soap layer on the working
surface of a steel pipe by coating an alkali soap aqueous solution
thereto followed by drying.
[0034] (6) The cold working method for a steel pipe according to
(4) or (5), wherein the alkali soap aqueous solution to be coated
to the working surface of the steel pipe is prepared by dissolving
alkali soap in water within a vessel having an inner surface
consisting of a non-metal material.
[0035] (7) A cold working method for a steel pipe, comprising cold
working after forming a solid alkali soap layer on the working
surface of a steel pipe by coating an aqueous pasty alkali soap
thereto.
[0036] (8) A cold working method for a steel pipe, comprising cold
working after forming a solid alkali soap layer on the working
surface of a steel pipe by coating an aqueous pasty alkali soap
thereto followed by drying.
[0037] (9) The cold working method for a steel pipe according to
(7) or (8), wherein the aqueous pasty alkali soap to be coated to
the working surface of the steel pipe is prepared by impregnating
alkali soap with water within a vessel having an inner surface
consisting of a non-metal material.
[0038] (10) The cold working method for a steel pipe according to
any one of (4) to (9) above, wherein the solid alkali soap layer on
the working surface is removed after cold working of the steel
pipe, by washing the working surface with water or hot water.
[0039] (11) The cold working method for a steel pipe according to
any one of (4) to (10) above, wherein the cold working of the steel
pipe is a pipe expansion work of the steel pipe end using a
plug.
[0040] (12) The cold working method for a steel pipe according to
any one of (4) to (11) above, wherein the alkali soap is composed
of either or both of Na salt and K salt of one or more kinds of
straight-chain fatty acids having 10 to 18 carbon atoms.
[0041] The alkali soap referred to herein means alkali metal salt
(Na salt or K salt) of water-soluble long-chain fatty acid as
described above. Any straight-chain fatty acid can be used thereto
regardless of whether a saturated fatty acid or an unsaturated
fatty acid. Particularly, the alkali soap is preferably composed of
either or both of Na salt and K salt of one or more kinds of
straight-chain fatty acids having 10 to 18 carbon atoms.
Specifically, Na or K salts of capric acid (C.sub.9H.sub.19COOH),
lauric acid (C.sub.11H.sub.23COOH), myristic acid
(C.sub.13H.sub.27COOH), palmitic acid (C.sub.15H.sub.31COOH),
palmitoleic acid (C.sub.15H.sub.29COOH), margalinic acid
(C.sub.16H.sub.33COOH), stearic acid (C.sub.17H.sub.35COOH), oleic
acid (C.sub.17H.sub.33COOH), and linoleic acid
(C.sub.17H.sub.31COOH) are preferably used. The alkali soap such as
the Na salt and K salt of the water-soluble long-chain fatty acid
can be used independently or in combination as well. The cold
working lubricant such as alkali metal salts of straight-chain
fatty acid having 10 to 18 carbon atoms of the alkali soaps are
preferably used, and the alkali metal salts of straight-chain fatty
acid can be used independently or in combination of two or more
kinds thereof.
[0042] The cold working lubricant such as the alkali soap may be
coated to the surface of a working tool, but it is preferably
coated to the working surface of the steel pipe. The cold working
can be performed as the layer formed to the working surface of the
steel pipe or to the wet surface of the working tool, or after
drying it.
[0043] The steel pipe for cold working includes a stainless steel
pipe. The steel pipe can be not only a seamless steel pipe
manufactured by Mannesmann process or Ugine-Sejournet process, but
also a hot-forged steel pipe or a welded steel pipe.
[0044] The cold working method includes pipe expansion work of a
steel pipe end using a plug and drawing work of the steel pipe.
[0045] In one cold working method according to the present
invention, an alkali soap aqueous solution is used for a lubricant
layer by coating it to the working surface of a metal material that
is not subjected to substrate treatment in order to form a solid
alkali soap layer thereon. Although the cold working may be
performed as it is, the lubricant layer is preferably dried prior
to the cold working. Thus, the lubricant layer can be easily formed
without executing a substrate treatment process in the chemical
treatment. Further, the lubricating treatment method by an alkali
soap layer reduces workload more than the oil lubricating method or
synthetic resin layer lubricating method. The working surface of
the steel pipe may be in a surface-exposed state by executing
descaling by shot blasting or pickling after shaping the metal
material by rolling or the like, or in a state remaining on the
surface after rolling with a scale layer that is an oxide or with a
rust layer that is a hydroxide.
[0046] The alkali soap aqueous solution to be coated to the working
surface of the steel pipe is preferably prepared by dissolving the
alkali soap in water within a vessel that has an inner surface
consisting of a non-metal material. The non-metal material
includes, for example, resin, glass, and ceramics. Instead that the
vessel itself is made of a non-metal material, only the inner
surface of the vessel may be lined with or coated with the
non-metal material. When the alkali soap is dissolved in water
within a vessel whose inner surface is in contact with the alkali
soap aqueous solution and consists of a metal material such as zinc
(Zn) or tin (Sn), the alkali soap aqueous solution becomes
semi-solidified. This semi-solidified alkali soap aqueous solution
has the property of scarcely adhering to the working surface of the
steel pipe. Therefore, it is difficult to coat the working surface
with the alkali soap in a uniform thickness, and even if it is
dried, a layer all over the whole working surface is scarcely
formed. Consequently, the lubricating characteristic is
deteriorated, and a seizure may be caused during working on the
surface having no layer. The alkali soap aqueous solution should be
prepared within the vessel whose inner surface is covered with a
non-metal material, whereby the semi-solidification of the alkali
soap aqueous solution can be prevented, and the adhesiveness of the
alkali soap aqueous solution to the working surface is extremely
enhanced. Consequently, the alkali soap can be uniformly coated to
the working surface, and after drying it, a uniform solid alkali
soap layer can be formed over the whole working surface.
[0047] In another cold working method according to the present
invention, aqueous pasty alkali soap is coated to a working surface
of a metal material not subjected to substrate treatment in order
to form a solid alkali soap layer, whereby it is used as the
lubricant layer. Although the cold working may be performed as it
is, the lubricant layer is preferably dried after the coating prior
to the cold working. Thus, the lubricating layer can be easily
formed without executing a substrate treatment process in chemical
treatment. Further, the lubricating treatment method by alkali soap
layer shows better load reducing effect than the oil lubricating
method or synthetic resin layer lubricating method. The working
surface of the steel pipe may be in a surface-exposed state by
executing descaling by shot blasting or pickling after shaping the
metal material by rolling or the like, or in a state remaining on
the surface after rolling with scale layer that is an oxide or with
rust layer that is a hydroxide.
[0048] The aqueous pasty alkali soap can be prepared by
impregnating the alkali soap with warm water and cooling it to room
temperature, then into a pasty state, while maintaining the
softness to some degree. The preferable temperature of the warm
water used for the preparation of the aqueous pasty alkali soap is
60.degree. C. or higher. The aqueous pasty alkali soap to be coated
to the working surface of the steel pipe is preferably obtained by
impregnating the alkali soap with water within a vessel that has an
inner surface consisting of a non-metal material. The non-metal
material includes, for example, resin, glass and ceramics. Instead
that the vessel is entirely formed of the non-metal material, only
the inner surface of the vessel may be lined with or coated with
the non-metal material.
[0049] When the inner surface is in contact with the aqueous pasty
alkali soap and consists of a metal material such as zinc (Zn) or
tin (Sn), the aqueous pasty alkali soap has the property of
scarcely adhering to the working surface of the steel pipe.
Therefore, it is difficult to coat the working surface with the
alkali soap in a uniform thickness, and even if it is dried, a
layer all over the working surface is scarcely formed.
Consequently, the lubricating characteristic is deteriorated, and
seizure may be caused during working on the surface having no
layer. The aqueous pasty alkali soap should be prepared within a
vessel whose inner surface is coated with the non-metal material,
whereby the adhesiveness of the aqueous pasty alkali soap to the
working surface is extremely enhanced. Consequently, the alkali
soap layer can be uniformly formed on the whole working
surface.
[0050] In the present invention, the aqueous pasty alkali soap to
be coated to the working surface of the steel pipe is preferably
obtained by impregnating the alkali soap with water within a vessel
having an inner surface consisting of a non-metal material. The
non-metal material includes, for example, resin, glass and
ceramics.
[0051] When the alkali soap is impregnated with water within a
vessel whose inner surface in contact with the aqueous pasty alkali
soap consisting of a metal material, for example, such as zinc (Zn)
or tin (Sn), the aqueous pasty alkali soap is scarcely adhered to
the working surface of the steel pipe. Naturally, the lubricating
characteristic is deteriorated, and seizure is caused during
working on the surface having no layer. The aqueous pasty alkali
soap is prepared within the vessel whose inner surface is covered
with the non-metal material, whereby the adhesiveness of the alkali
soap aqueous solution to the working surface is extremely
enhanced.
[0052] Since the alkali soap is easily dissolved in water, the
working surface is washed with water or hot water after cold
working, whereby the solid alkali soap layer remaining on the
working surface can be easily removed. Consequently, the remaining
lubricant layer can be suppressed or solved.
[0053] The steel pipe to which the cold working lubricant
comprising alkali soap is coated includes a stainless steel pipe.
The steel pipe can be not only a seamless steel pipe manufactured
by Mannesmann process or Ugine-Sejournet process but also a
hot-forged steel pipe or a welded steel pipe.
[0054] The cold working method for the steel pipe includes pipe
expansion work of a steel pipe end using a plug, drawing work of
steel pipe and the like.
EFFECT OF THE INVENTION
[0055] According to the present invention, a layer of lubricant can
be easily formed on the surface of a steel pipe prior to cold
working with a high load reduction effect in cold working of the
steel pipe, and the layer can be easily removed by washing of the
steel pipe surface after cold working.
BEST MODE FOR CARRYING OUT THE INVENTION
[0056] Embodiments of the present invention will be described in
detail in reference to the attached drawings. In the drawings,
descriptions for identical or corresponding parts are omitted by
assigning the identical reference number thereto.
[0057] The cold working lubricant and cold working method for the
steel pipe will be described below. The cold working of the steel
pipe is a pipe expansion work of a steel pipe end using a plug.
[0058] In FIG. 1, an alkali soap aqueous solution of a lubricant is
prepared (S1). Specifically, the alkali soap of Na salt and/or K
salt of straight-chain fatty acid are prepared. A preferable main
component of the alkali soap is Na stearate. The content of the Na
stearate in the alkali soap may be such that the effect of the
present invention can be shown. Preferably, the alkali soap
contains 95 mass % or more of Na stearate.
[0059] The above-mentioned alkali soap is dissolved in water within
a vessel that has an inner surface coated with a non-metal material
in order to prepare the alkali soap aqueous solution. The non-metal
material means, for example, resin such as plastics, glass or
ceramics. When the alkali soap is dissolved in water within a
vessel that has an inner surface consisting of a metal material
such as a metal vessel, the alkali soap aqueous solution becomes
semi-solidified. Such an alkali soap aqueous solution scarcely
adheres to the working surface (inner surface or outer surface) of
a steel pipe, and even if it could adhere to the working surface,
the resulting layer is not uniform but uneven. Therefore, it is
extremely difficult to uniformly coat the alkali soap onto the
whole working surface. Although the cause of this is not
necessarily certain, the following explanation should be
considered. When solid alkali soap is dissolved in water within a
vessel that has an inner surface consisting of a metal material,
the metal element constituting the vessel inner surface is
dissolved in the alkali soap aqueous solution. During this time,
the dissolved metal element is bonded with long-chain fatty acid of
the alkali soap to produce a metal soap (non-alkali metal salt of
the long-chain fatty acid). This generation of metal soap causes
considerably deterioration of the adhesiveness to the working
surface.
[0060] Therefore, the alkali soap aqueous solution should be
prepared within a non-metal vessel. The alkali soap aqueous
solution can be uniformly adhered to the entire working surface
with good adhesiveness. Increasing the amount of alkali soap added
to the water results in increasing the viscosity of the alkali soap
aqueous solution, and improves the adhesiveness to the working
surface. When the alkali soap concentration in the alkali soap
aqueous solution is set at 100 g/L (liter) to 450 g/L, the
resulting alkali soap aqueous solution shows satisfactory
adhesiveness. Even out of this concentrated range, the alkali metal
soap aqueous solution is adhered to the entire working surface so
that the effect of the present invention is displayed to certain
degree.
[0061] The alkali soap aqueous solution prepared within the
non-metal vessel is applied to the working surface that is not
subjected to chemical treatment (S2). Specifically, the alkali soap
aqueous solution is directly applied to an inner or outer surface
of a steel pipe with a scale layer that is an oxide or rust layer,
which is a hydroxide adhered thereto after rolling, or an inner or
outer surface of a steel pipe free from scale or rust (or base
metal surface) which is subjected to descaling or derusting
treatment.
[0062] A chemical treatment layer formed by a chemical treatment
(phosphate layer, oxalate layer, and metal soap layer) is scarcely
removed after cold working since it is adhered to the steel pipe
surface by chemical bonding. If the chemical treatment layer is
left on the steel pipe inner or outer surface, mechanical
characteristics of the steel pipe can deteriorate. For example,
when a steel pipe's remaining zinc phosphate layer on the inner or
outer surface is heat-treated or welded to another steel pipe,
phosphorization can be caused and this may reduce the strength of
the steel pipe. If oil of the oil lubrication method remains, the
non-fitting of paint may cause a line pipe which connects steel
pipes with the steel pipe inner or outer surface, from being
painted. Therefore, in this situation, it is preferable to use a
steel pipe that has not been subjected to chemical treatment or to
oil lubrication.
[0063] The alkali soap solution is coated to a working surface of a
steel pipe, for example, by the following methods. A worker such as
an operator of a pipe expansion apparatus coats the alkali soap
aqueous solution to the working surface by use of a brush or the
like. Otherwise, the alkali soap aqueous solution may be coated to
the working surface by dunking the steel pipe itself in the alkali
soap aqueous solution within a non-metal vessel.
[0064] After the alkali soap aqueous solution is coated to the
steel pipe's inner surface, the alkali soap aqueous solution is
dried to form a solid alkali soap layer (S3). Since the alkali soap
is applied closely to all of the working surface and results in a
solid layer when dried, drying is preferably performed. The drying
can be performed, for example, by use of a blower or the like for
quick drying or by natural drying in the atmosphere.
[0065] After the solid alkali soap layer is formed, the resulting
steel pipe is expanded (S4). At this time, the steel pipe whose
inner surface has the solid alkali soap layer formed thereon is
expanded in contact with a plug that is a working tool. The solid
alkali soap layer has a higher adhesiveness to the working surface
than the lubricating oil used in the conventional oil lubrication.
Further, the oil escapes toward the lower pressure side when
working pressure is applied because it is a fluid, resulting in
deterioration of the lubricating performance. The solid alkali soap
layer has poor flowability because it is solid and stays there even
if the working pressure is applied. Therefore, the solid alkali
soap layer can prevent direct contact to the steel pipe with the
tool, which is more satisfactory in both lubricating property and
seizure resistance, than in the oil lubrication. Consequently,
flawing in the working surface can be prevented. Further, the
lubricating by a solid alkali soap layer can reduce the workload
more than the oil lubrication.
[0066] After the cold working, the working surface is washed with
water to remove the solid alkali soap layer (S5). Since the alkali
soap easily dissolves in water, the solid alkali soap layer adhered
to the working surface can be easily removed by washing with water.
Therefore, compared with the conventional lubricating treatment,
the lubricant layer is mostly removed. Since the dissolution degree
of alkali soap increases by raising the temperature of the water
for washing, and even though the water temperature may be normal,
the time necessary for removal can be also shortened. Namely, the
alkali soap can be removed in a short time by washing with hot
water.
[0067] In the cold working method according to the present
invention, using alkali soap for the lubricant can easily form a
lubricant layer. Therefore, the use of a plurality of different
processes is not needed for forming the lubricant layer (chemical
treatment layer) in comparison with the chemical treatment method,
and is not needed for facilities for producing a substrate layer
such as phosphate layer. The present invention reduces the workload
more than the conventional oil lubrication or synthetic resin layer
lubrication.
[0068] Further, the solid alkali soap layer that is the lubricant
layer in the present invention can be easily removed by washing
with water. Therefore, the lubricant layer can be removed more
easily than in the conventional lubricating treatments (chemical
treatment, oil lubrication and synthetic resin layer lubrication),
and the remaining lubricant layer on the working surface of a metal
product can be considerably removed.
[0069] Comparing the lubricant layers (chemical treatment layer,
lubricating oil and synthetic resin layers) formed in the
conventional lubricating treatments, the lubricant layer coated by
the alkali soap in the present invention has a small environmental
problem. Also the detergent used for removing the chemical
treatment layer or lubricating oil has not only a large
environmental problem, but also harmfully influences the human
body. The lubricant layer according to the present invention can be
easily removed with water, so that the environment and human body
problems can be significantly reduced.
[0070] Instead of the alkali soap aqueous solution that is coated
on the working surface mentioned above, the aqueous pasty alkali
soap can be applied. Impregnating solid alkali soap with warm water
and cooling to room temperature can be used to prepare the aqueous
pasty alkali soap. The temperature of warm water is preferably
60.degree. C. or higher and, more preferably, 80.degree. C. or
higher. The aqueous pasty alkali soap is preferably prepared within
a vessel having an inner surface consisting of a non-metal
material. The hardness of the aqueous pasty alkali soap is lower
than general solid alkali soap, and substantially equal to, for
example, the hardness of lipstick.
[0071] The aqueous pasty alkali soap prepared by the
above-mentioned method is applied to a working surface of a steel
pipe in the same manner as the alkali soap aqueous solution. The
aqueous pasty alkali soap is solid having no flowability.
Therefore, the aqueous pasty alkali soap can be easily applied to
the working surface, particularly only to a place that requires a
lubricant layer on the surface of the steel pipe. The aqueous pasty
alkali soap is easy to adhere to the working surface because of
it's low hardness, and thus can be easily uniformly coated.
[0072] The cold working is preferably carried out after drying the
aqueous pasty alkali soap applied to the working surface.
[0073] Although the cold working is carried out at a normal
temperature in the above-mentioned conditions, the present
invention is applicable to hot working which is carried out by
heating a steel pipe to a temperature of 150.degree. C. or lower,
which has the same effect as above.
Example 1
[0074] A seamless steel pipe was subjected to pipe expansion using
Na stearate as a lubricant, and the load applied in the pipe
expansion was examined.
[0075] A seamless steel pipe with a shape and a strength (grade)
shown in Table 4 (hereinafter simply referred to as steel pipe) was
prepared. In the table, the unit of outside diameter, inside
diameter, pipe thickness and length are shown by mm, and the grade
is based on the API standard. The material of the steel pipe is
carbon steel.
TABLE-US-00004 TABLE 4 Shape Outside Inside diameter Pipe thickness
Length diameter (mm) (mm) (mm) (mm) Grade 89.05 75.33 6.86 150
5CT3-P110
[0076] Three pipe expansion plugs 1 of a shape shown in FIG. 2 were
prepared. A layer of 3 mm thickness was formed respectively on the
surface 10 to contact with the inner surface of the steel pipe of
each plug 1, using the materials and formation method shown in
Table 5.
TABLE-US-00005 TABLE 5 Plug No. Layer material 1 Cemented carbide 2
SKD steel 3 CrN layer by ion plating
[0077] The plug of Plug No. 1 is a cemented carbide plug. The plug
of Plug No. 2 is made of cold working tool steel (SKD steel). The
plug layer of Plug No. 3 is CrN layer formed by ion plating. The
maximum value of the plug diameter of each plug 1 is 76.8 mm.
[0078] The pipe expansion work was executed by use of an apparatus
shown in FIG. 3 according to the following method. A steel pipe 2
was fixed between the plug 1 and a cylindrical pushing and pulling
tool 4. After fixing, the pushing and pulling tool 4 was pushed by
a press head 3 of a 150-t press machine arranged on the opposite
side of the steel pipe 2 across the pushing and pulling tool 4,
whereby the steel pipe 2 was pushed into the plug 1. At this time,
the steel pipe 2 was pushed until the plug 1 was passed through the
whole length of the steel pipe 2. The pipe expansion ratio was 2.0%
in each case.
[0079] The 150-t press machine is provided with a load cell, and
the working load in the pipe expansion was determined using the
load cell.
[0080] The pipe expansion work was performed while variously
changing the condition of lubricant. The test condition is shown in
Table 6.
TABLE-US-00006 TABLE 6 Test Lubricant condition Steel pipe inner
surface Plug surface 1 Non Non 2 Mineral oil Non 3 Water Non 4 Non
Na stearate (not dried) 5 Na stearate (not dried) Na stearate (not
dried) 6 Na stearate (dried) Non 7 Na stearate (not dried) Non
[0081] As shown in Table 6, in Test condition 1, the pipe expansion
was carried out without coating any lubricant to the steel inner
surface. In test condition 2, the pipe expansion was carried out
after coating mineral oil (manufactured by Idemitu Kosan, SD22) to
the whole steel pipe inner surface. In Test condition 3, the pipe
expansion was carried out after coating water as lubricant to the
whole steel pipe inner surface. In Test condition 4, the pipe
expansion was carried out after coating Na stearate aqueous
solution with concentration of 100 g/L (liter) as lubricant to the
plug surface and substantially perfectly drying and solidifying the
lubricant by air blowing for 10 minutes. No lubricant was coated to
the steel pipe inner surface in Test condition 4. In Test condition
5, the same Na stearate aqueous solution as in Test condition 4 was
coated to the whole steel pipe inner surface and to the whole plug
surface, thereafter the pipe expansion was performed before the
coated Na stearate aqueous solution was dried. In Test condition 6,
the pipe expansion was carried out after the same Na stearate
aqueous solution as in Test condition 4 was coated to the whole
steel pipe inner surface, and dried by air blowing for 10 minutes
to form a solid Na stearate layer. In Test condition 7, the same Na
stearate aqueous solution in Test condition 4 was coated to the
whole steel pipe inner surface, and the pipe expansion was carried
out before it is dried. The Na stearate aqueous solution of each
condition was prepared within a plastic vessel. In the conditions
other than Test conditions 4 and 5, no lubricant was coated to the
plug surface.
[0082] In each test condition, the pipe expansion was carried out
using part or all of the plugs of Plug Nos. 1 to 3.
[0083] The test result is shown in FIG. 4. In the drawing, each
black bar chart shows the load in pipe expansion using the plug of
Plug No. 1. Each white bar chart shows the load in use of the plug
of Plug No. 2. Each internally hatched bar chart shows the load in
use of the plug of Plug No. 3.
[0084] In use of each of the plugs of Plug Nos. 1 to 3, the load
was minimized in Test condition 6. Namely, the load in the pipe
expansion could be reduced more in Test condition 6, with the Na
stearate layer formed on the working surface, than in Test
condition 2 using mineral oil as in the conventional pipe expansion
work. The load was reduced more in Test condition 6, in which the
coated Na stearate was dried, than Test conditions 4 and 7, in
which the pipe expansion work was carried out before drying it.
This result is attributed to that, since the adhesiveness of Na
stearate to the working surface (inner surface) was higher in its
dried state, the function of the lubricant was further
expressed.
[0085] After the pipe expansion work, the inner surface of each
steel pipe product, which was expanded in Test conditions 2 and 6,
was washed with water. Specifically, a water of normal temperature
was injected from a nozzle with an inside diameter of 3.6 mm at a
rate of 8 L (liter)/min to wash the steel pipe's inner surface.
Consequently, the mineral oil layer coated in Test condition 2 was
scarcely removed, while the Na stearate layer coated as the
lubricant in Test condition 6 was fully removed.
[0086] Table 7 is a result of water washing that was separately
carried out at a hydraulic pressure of 5 MPa to the Na stearate
layer coated as the lubricant in Test condition 6. The washing
removability of Na stearate layer after the pipe expansion work was
evaluated by variously changing the time from the pipe expansion
work of the steel pipe end using the plug at the start of washing.
At this time, the temperature (.degree. C.) of the washing water
and the washing time (sec) were varied. Consequently, it could be
confirmed that the Na stearate layer can be easily removed by water
washing regardless of the temperature of washing water
(10-80.degree. C.) and the washing time (20-30 sec) if the washing
is started within 1 hour after the pipe expansion work.
TABLE-US-00007 TABLE 7 Time to start of Temperature Washing washing
of washing Washing time condition after working water (.degree. C.)
(sec) Evaluation 1 5 min 10 20 .largecircle. 2 5 min 20 20
.largecircle. 3 5 min 30 20 .largecircle. 4 5 min 80 20
.largecircle. 5 1 hour 10 20 .largecircle. 6 1 hour 20 20
.largecircle. 7 1 hour 30 20 .largecircle. 8 1 hour 80 20
.largecircle. 9 3 hours 10 20 X 10 3 hours 20 20 .DELTA. 11 3 hours
20 30 .largecircle. 12 3 hours 30 20 .largecircle. 13 3 hours 80 20
.largecircle. (Note) Evaluation: .largecircle.: Layer was perfectly
removed by washing. .DELTA.: Layer was almost removed by washing,
but partially left. X: Layer was almost left after washing.
[0087] As an additional test, a plurality of alkali soap
lubricants, which differed in concentration of Na stearate, was
prepared. Specifically, three kinds of alkali soap lubricants of
(1) Na stearate aqueous solution having a concentration of 200 g/L,
(2) aqueous pasty Na stearate obtained by impregnating Na stearate
with hot water of about 80.degree. C. to a concentration of 350 g/L
followed by cooling to room temperature, and (3) aqueous pasty Na
stearate obtained by impregnating Na stearate with hot water of
about 80.degree. C. to a concentration of 450 g/L followed by
cooling to room temperature were prepared.
[0088] Each of the prepared alkali soap lubricants was coated to
the whole inner surface of the above-mentioned steel pipe and dried
by air blowing for 10 minutes to form Na stearate layer, thereafter
the pipe expansion was carried out. Consequently, in each alkali
soap lubricant, the load reducing effect of the same degree as in
the Na stearate aqueous solution, with concentration of 100 g/L
used in Test condition 6, was obtained.
Example 2
[0089] A pipe end of a stainless steel pipe was expanded using Na
stearate and conventional mineral oil as lubricants, respectively,
and the load applied in pipe expansion was examined for each
lubricant.
[0090] A super-13Cr steel pipe (hereinafter simply referred to as
stainless steel pipe) with an outside diameter 114.3 mm, a
thickness 8.56 mm and an inside diameter 97.18 mm was prepared as a
steel pipe material.
[0091] A plug used for the pipe expansion was made of cemented
carbide. This plug has a TD-treated surface and a shape similar to
that of FIG. 3. The maximum plug diameter of the plug is 98.15
mm.
[0092] The pipe expansion was carried out according to the
following method. Ten stainless steel pipes were prepared, in which
the inner surface was at least within the range of 50 mm from the
pipe end and was coated with Na stearate aqueous solution of 100
g/L (liter) uniformly, and substantially dried. The Na stearate
aqueous solution was prepared within a plastic vessel. In order to
compare the material, four stainless steel pipes were prepared, in
which the inner surface of the pipe end, within the same range as
above, was coated with conventional mineral oil.
[0093] The pipe end portion of 50 mm in length from the pipe end of
each steel pipe was expanded at normal temperature, using hydraulic
machining equipment mounted with the above-mentioned plug. The pipe
expansion rate was 1.0%. The maximum value and minimum value of the
original pressure of the hydraulic machining equipment in pipe
expansion were measured. Based on the measurement result, the
average values of the maximum value and minimum value of original
pressure were determined for each lubricant.
[0094] The examination result is shown in FIG. 5. In the drawing,
the vertical axis shows the original pressure (kgf/cm.sup.2). In
the drawing, each white bar chart shows the average of the maximum
value of original pressure, and each black bar chart shows the
average of the minimum value of original pressure. As is referred
from FIG. 5, the maximum value and minimum value of the original
pressure were lower in the Na stearate than in the mineral oil.
[0095] After the pipe expansion work, the inner surface of each
steel pipe was washed in the same condition as in Example 1.
Consequently, only a small amount of the mineral oil was removed,
while the Na stearate was easily removed without any remaining.
INDUSTRIAL APPLICABILITY
[0096] According to the present invention, a layer of the lubricant
can be easily formed on a surface of a steel pipe prior to cold
working, in which much reduces the workload during cold working of
the steel pipe. A layer of the lubricant can be also easily removed
by washing the steel pipe surface after cold working. The present
invention is applicable to cold working, particularly, pipe
expansion work of the steel pipe end using a plug.
BRIEF DESCRIPTION OF THE DRAWINGS
[0097] FIG. 1 is a flow chart showing each process of a cold
working method according to an embodiment of the present
invention.
[0098] FIG. 2 is a side view showing the shape of a plug used in
Example 1.
[0099] FIG. 3 is a schematic view of a pipe expansion apparatus
used in Example 1.
[0100] FIG. 4 is a view showing the pipe expansion load value in
each test condition determined in Example 1.
[0101] FIG. 5 is a view showing the original pressure value of
hydraulic machining equipment in each lubricating treatment
determined in Example 2.
EXPLANATION OF REFERENCE NUMERALS
[0102] 1. Plug [0103] 2. Steel pipe [0104] 3. Press head [0105] 4.
Pushing and pulling tool
* * * * *