U.S. patent application number 12/488514 was filed with the patent office on 2009-12-31 for protecting an element from excessive surface wear by localized hardening.
Invention is credited to Homer A. Milliken, Kevin J. Wyble.
Application Number | 20090321144 12/488514 |
Document ID | / |
Family ID | 41446044 |
Filed Date | 2009-12-31 |
United States Patent
Application |
20090321144 |
Kind Code |
A1 |
Wyble; Kevin J. ; et
al. |
December 31, 2009 |
PROTECTING AN ELEMENT FROM EXCESSIVE SURFACE WEAR BY LOCALIZED
HARDENING
Abstract
A method of protecting an element from excessive surface wear is
provided. In this method, a localized area of the element that will
be subjected to excessive surface wear is exposed to induction
heating for a period sufficient to heat the localized area to an
elevated temperature at which the localized area undergoes
austenitic transformation. The localized area is quenched, followed
by tempering, and then cooling. A result of the method is a
localized hardened area formed monolithically with the element and
having a localized hardness that is greater than a base hardness of
the element.
Inventors: |
Wyble; Kevin J.; (Spring,
TX) ; Milliken; Homer A.; (Village Mills,
TX) |
Correspondence
Address: |
JEFFREY E. DALY;National Oilwell Varco
7909 Parkwood Circle Drive
HOUSTON
TX
77036
US
|
Family ID: |
41446044 |
Appl. No.: |
12/488514 |
Filed: |
June 19, 2009 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61076836 |
Jun 30, 2008 |
|
|
|
Current U.S.
Class: |
175/320 ;
148/567 |
Current CPC
Class: |
Y02P 10/25 20151101;
C21D 9/08 20130101; E21B 17/10 20130101; C21D 1/10 20130101; C21D
2221/00 20130101; Y02P 10/253 20151101 |
Class at
Publication: |
175/320 ;
148/567 |
International
Class: |
C21D 1/10 20060101
C21D001/10; E21B 17/00 20060101 E21B017/00; E21B 17/10 20060101
E21B017/10; C21D 1/42 20060101 C21D001/42; C21D 1/78 20060101
C21D001/78 |
Claims
1. A method of protecting an element from excessive surface wear,
comprising: exposing a localized area of the element that will be
subjected to the excessive surface wear to induction heating for a
period sufficient to heat the localized area to an elevated
temperature at which the localized area undergoes austenitic
transformation; quenching the localized area; tempering the
localized area; and cooling the localized area; wherein a result of
the method is a localized hardened area formed monolithically with
the element and having a localized hardness that is greater than a
base hardness of the element.
2. The method of claim 1, wherein the induction heating is at a
frequency in a range from 1 kHz to 10 kHz and a power density of
0.5 kW/in.sup.2 to 10 kW/in.sup.2.
3. The method of claim 1, wherein the element is made of low-alloy
steel.
4. The method of claim 1, wherein a depth of the localized hardened
area is at least 0.25 in. (0.635 cm).
5. The method of claim 1, wherein the tempering step occurs at a
temperature in a range from 250.degree. F. to 295.degree. F.
6. The method of claim 1, wherein the localized hardness, expressed
as Rockwell hardness, is in a range from 56 to 63 HRC.
7. The method of claim 6, wherein the base hardness, expressed as
Rockwell hardness, is in a range from 30 to 36 HRC.
8. The method of claim 1, wherein the localized hardness is at
least 40% greater than the base hardness.
9. The method of claim 1, wherein quenching is in an aqueous
polymer medium.
10. The method of claim 9, wherein the aqueous polymer medium
comprises a polymer selected from polyalkylene glycol and
polyethylene glycol.
11. A downhole tool protected from excessive surface wear,
comprising: a tool body made of a material having a base hardness;
and a localized hardened area formed monolithically with the tool
body, the localized hardened area having a localized hardness that
is greater than the base hardness.
12. The downhole tool of claim 11, wherein the localized hardness,
expressed as Rockwell hardness, is in a range from 56 to 63
HRC.
13. The downhole tool of claim 11, wherein the base hardness,
expressed as Rockwell hardness, is in a range from 30 to 36
HRC.
14. The downhole tool of claim 11, wherein the localized hardness
is at least 40% greater than the base hardness.
15. The downhole tool of claim 11, wherein the material of the tool
body is comprised of a low-alloy steel.
16. The downhole tool of claim 11, wherein a depth of the localized
hardened area is at least 0.25 in. (0.635 cm).
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims benefit of Provisional Application
No. 61/076836, filed Jun. 30, 2008, the disclosure of which is
ENTIRELY incorporated herein by reference.
FIELD
[0002] The invention relates generally to methods for hardening
elements that are subjected to excessive surface wear during use.
The methods are particularly suitable for use with elements such as
downhole tools, e.g., drill bits, tool joints, stabilizers, and
drill collars, and other elements that require protection against
excessive surface wear.
BACKGROUND
[0003] FIG. 1 shows a conventional downhole tool string 31
suspended in a wellbore by a derrick 32. The downhole tool string
31 is coupled to a data swivel 34 that connects to surface
equipment 33, such as a computer. The data swivel 34 is adapted to
transmit data to and from a transmission network integrated with
the downhole tool string 31 while the downhole tool string 31 is
rotating. The integrated transmission network comprises the
transmission systems of the individual downhole components (e.g.,
components 36, 57, 35) of the downhole tool string 31. Preferably,
the downhole component is a drill pipe 57 or a tool 35. One or more
tools 35 may be located in the bottom hole assembly 37 or along the
length of the downhole tool string 31. Examples of tools 35 in a
bottom hole assembly 37 comprise sensors, drill bits, motors,
hammers, and steering elements. Examples of tools 35 located along
the downhole tool string 31 are links, jars, seismic sources,
seismic receivers, sensors, and other tools that aid in the
operations of the downhole tool string 31. Different sensors are
useful downhole, such as pressure sensors, temperature sensors,
inclinometers, thermocouples, accelerometers, and imaging devices.
Downhole tools 35 consisting of tubulars configured with sources
and sensors are commonly referred to as drill collars. The
illustrated downhole tool string 31 is a drill string.
[0004] During operation, the downhole tool string 31 often
encounters extreme conditions, such as high heat, high pressure,
torsion and tension-compression stress, vibration, and impact. The
components of the downhole tool string 31 are also subjected to
contact with abrasive formations, erosive fluids, frictional
contact with other tool elements, and sources of wear. To protect
against these conditions, particularly excessive wear, various
elements of the downhole tool string 31 are typically provided with
a welded metal hardfacing or hardface coating. These hardfacing
coatings provide hardness to the exterior of the string elements,
particularly the surfaces that will come in contact with the
abrasive formations. The required hardness is often accomplished by
providing a coating composed of tungsten carbide particles, which
are cemented in place by a metal binder. The matrix formed by the
carbide particles and the binder is applied as a coating to the
various surfaces.
[0005] Although conventional hardfacing techniques have proven
useful in the industry, a need remains for improved techniques to
harden tool and element surfaces, particularly for subsurface
applications.
SUMMARY
[0006] Aspects of the invention include a method of protecting an
element from excessive surface wear. The method comprises exposing
a localized area of the element that will be subjected to the
excessive surface wear to induction heating for a period sufficient
to heat the localized area to an elevated temperature at which the
localized area undergoes austenitic transformation. The localized
area is quenched after the exposure, followed by tempering, and
then cooling. A result of the method is a localized hardened area
formed monolithically with the element and having a localized
hardness that is greater than a base hardness of the element.
[0007] Aspects of the invention include a downhole tool protected
from excessive surface wear. The downhole tool comprises a tool
body made of a material having a base hardness and a localized
hardened area formed monolithically with the tool body. The
localized hardened area has a localized hardness that is greater
than the base hardness.
[0008] Other aspects and advantages of the invention will be
apparent from the following description and the appended
claims.
BRIEF DESCRIPTION OF DRAWINGS
[0009] The accompanying drawings, described below, are referenced
in the background and detailed description. The figures are not
necessarily to scale, and certain features and certain views of the
figures may be shown exaggerated in scale or in schematic in the
interest of clarity and conciseness.
[0010] FIG. 1 is a schematic of a conventional drill rig showing a
drill string and a system for drilling a well bore in a subsurface
formation and obtaining formation measurements.
[0011] FIG. 2 is a schematic of a downhole tool tubular implemented
with a hardened segment in accordance with aspects of the
invention.
[0012] FIG. 3 is a cross-section of a pin-end tool joint including
a localized hardened area.
[0013] FIG. 4 is a schematic of induction heating of an
element.
[0014] FIG. 5 is a cooling curve analysis comparing cooling rates
of different quenchants.
DETAILED DESCRIPTION
[0015] Aspects of the invention entail processes to produce an
induction hardened surface or area on a desired element. For
purposes of this disclosure it will be clearly understood that the
word "element" means any type of tool, machine, apparatus, or
component that may be subjected to excessive wear during operation.
According to aspects of the invention, an element, e.g., a downhole
tool joint, is hardened by a process entailing exposure to a
surface heat treatment, followed by polymer quenching,
low-temperature tempering, and air cooling.
[0016] FIG. 2 shows a drill pipe 57 including a tubular 55, a
pin-end tool joint 14, and a box-end tool joint 15. Typically, the
drill pipe 57 is made of metal, e.g., low-alloy steel. The pin-end
tool joint 14 and box-end tool joint 15 are attached to either ends
of the tubular by a method such as friction/inertia welding. The
tool joints 14, 15 have thickened walls in comparison to the
tubular 55 in order to accommodate mechanical and hydraulic tools
used to connect and disconnect the drill pipe 57 from a tool
string, such as the downhole tool string 31 shown in FIG. 1.
Similar tool joints are found on other downhole components that
make up a downhole tool string. The tool joints 14, 15 may have a
smaller inside diameter and a larger outside diameter in order to
achieve the thicker walls. Therefore, it is typically necessary to
forge, or "upset", the ends of the tubular 55 in order to increase
the wall thickness of the tubular 55 prior to attachment of the
tool joints 14, 15. The upset end portions 19, 20 of the tubular 55
provides a transition region between the tubular 55 and the tool
joint 14, 15, respectively, where there is a change in the inside
and outside diameter of the drill pipe 57. High torque threads 16
on the pin-end 16 and on the box-end 17 (the threads are internal
at the box-end 17) provide for mechanical attachment of the drill
pipe 57 in a downhole tool string.
[0017] Aspects of the invention include forming a localized
hardened area 62 on the drill pipe 57. In the embodiment shown in
FIG. 2, the localized hardened area 62 is formed on the pin-end
tool joint 14 of the drill pipe 57. By "localized," it is meant
that the hardening is confined to the area 62 shown and that the
base hardness of the material of the pin-end tool joint 14 (or
element in general) is not significantly affected by the forming of
the hardened area 62 on the pin-end tool joint 14 (or element in
general). The localized hardened area 62 is monolithic with the
pin-end tool joint 14. By "monolithic" it is meant that the
localized hardened area 62 is formed in-situ on the pin-end tool
joint 14 by manipulating the material of the pin-end tool joint 14
rather than by applying an external hardened or hardening material
on the pin-end tool joint 14. By "localized hardened," it is meant
that the area 62 has a localized hardness that is greater than the
base hardness of the material in which it is formed.
[0018] FIG. 3 shows a cross-section of the pin-end tool joint 14.
The depth of the localized hardened area 62 into the wall of the
pin-end tool joint 14 is indicated at "d." In certain aspects of
the invention, d is at least 0.25 in. (0.635 cm). In other aspects
of the invention, d is in a range from 0.25 in. (0.635 cm) to 0.375
in. (0.9525 cm). Although the localized hardened area 62 is formed
on the pin-end tool joint 14 in the embodiment shown in FIGS. 2 and
3, it should be clear that this is not intended to limit the
invention as such. The localized hardened area 62 can be formed on
any element deserving of protection from excessive surface wear.
Aspects of the invention include forming the localized hardened
area 62 on elements or components of a downhole tool string, where
the localized hardened area 62 will be monolithic with the
respective downhole element or component on which it is formed.
[0019] Aspects of the invention include a process for forming a
localized hardened area on an element. The process includes
exposing a localized area of the element that will be subjected to
excessive surface wear to localized heat for a period sufficient to
heat the localized area to an elevated temperature at which the
localized area undergoes austenitic transformation. Preferably, the
elevated temperature is such that the localized area undergoes 100%
austenitic transformation. In a preferred embodiment, the localized
heat is provided by an electromagnetic induction heater.
[0020] Referring to FIG. 4, a localized area 70 of an element 72
(e.g., a tool joint) is disposed adjacent to an electromagnetic
heater 74. The induction heater 74 includes a susceptor 76 and
induction coil 78. A magnetic field is generated by running
alternating current through the induction coil 78. The magnetic
field induces eddy currents in the susceptor 76 to generate the
localized heat. Typically, the susceptor 76 is concentric with the
induction coil 78, and the induction heater 74 delivers heat
uniformly and locally to the localized area 70. The induction
heater 74 heats the localized area 70 to the elevated temperature
required for austenitic transformation. In certain aspects of the
invention, the induction heater 74 operates with frequency ranges
from 1 KHz to 10 KHz and power densities on the order of 0.5
KW/in.sup.2 to 10 KW/in.sup.2. In general, the operating parameters
of the induction heater 74 will be chosen to achieve the goal of
heating the localized area 70 to achieve austenitic transformation
in the localized area 70. To achieve austenitic transformation, the
element 72, at least in the vicinity of the localized area 70, is
made of an austenitizeable material. In certain aspects, the
austenitizeable material is a low-alloy steel.
[0021] The austenitizing temperature is determined based on the
chemistry of the austenitic material. For low-alloy steel, the
austenitizing temperature (T) can be determined according to the
following expression:
T = 910 - 203 .times. C + 44.7 .times. Si - 15.2 .times. Ni + 31.5
.times. Mo + 104 .times. V + 13.1 .times. W ( .degree. C . ) ( 1 )
##EQU00001##
where C represents percent weight (wt %) of carbon in the steel, Si
represents wt % of silicon in the steel, Ni represents wt % of
nickel in the steel, Mo represents wt % of molybdenum in the steel,
V represents wt % of Vanadium in the steel, and W represents wt %
of Tungsten in the steel.
[0022] The elevated temperature to which the localized area 70 is
heated for austenitic transformation may be the same as the
calculated austenitizing temperature or may be higher than the
calculated austenitizing temperature. In certain aspects, the
elevated temperature is the calculated austenitizing temperature
plus a safety margin to ensure 100% austenitic transformation. In
certain aspects, the austenitizing temperature is at least
1525.degree. F. (830.degree. C.). In certain aspects, the safety
margin may be, for example, about 37.8.degree. C. (100.degree. F.)
above the calculated austenitizing temperature. The advantage of
localized heating, preferably by use of electromagnetic induction,
is that the hardening can be confined to the localized area 70,
leaving the remainder of the element 72 substantially
unchanged.
[0023] After the austenitizing heat treatment, the localized area
70 is quenched in a liquid medium. The objective of quenching the
high strength low alloy (HSLA) steel in a liquid medium is to
remove the heat from the part as quickly as possible to change the
crystal structure from the austenitic state (FCC-face center cubic)
to a martensitic state (BCT-body center tetragonal). In a preferred
embodiment, the liquid medium is an aqueous polymer medium. In some
embodiments, the aqueous polymer medium is comprised of a low
concentration of a polymer and water. In some embodiments, the
polymer is selected from polyalkylene glycol and polyethylene
glycol. Quenching in a controlled aqueous polymer medium helps
reduce residual stress and prevent cracking. In certain aspects,
quench bath temperature is between 90.degree. F. (.about.32.degree.
C.) and 105.degree. F. (.about.41.degree. C.).
[0024] AQUA-QUENCH 245 is an advanced biostable polymer quenchant
suitable for induction heat treating. It is a polyalkylene glycol
based polymer quenchant formulation with a combination of
ingredients that provide greater stability to microbial intrusion
of the quenchant. AQUA-Quench 245 is specifically designed for use
in induction hardening and immersion quenching applications. FIG. 5
is a cooling curve analysis showing the cooling rates of a steel
quench in an aqueous polymer medium. The quenchant for Sample #1
was 20 vol % AQUA-QUENCH 365 and 80 vol % water. The quenchant for
Sample #2 was 20 vol % AQUA-QUENCH 245 and 80 vol % water. The
quenchant for Sample #3 was 17 vol % AQUA-QUENCH 245 and 83% water.
From FIG. 5, both AQUA-QUENCH 245 solutions (#2 and #3) are faster
than the AQUA-QUENCH 365 (#1) in cooling the steel parts at high
temperatures. Cooling rates for the different quenchants below
700.degree. F. (.about.371.degree. C.) are similar. Both
AQUA-QUENCH 245 solutions will provide deeper hardening of the
quenched part with the same level of distortion control as the
AQUA-QUENCH 365. AQUA-QUENCH 365 is a concentrated solution of
polyethylene glycol. In the examples shown in FIG. 5, the bath
temperature was held at 100.degree. F.
[0025] Although AQUA-QUENCH 245 and AQUA-QUENCH 365 have been
presented as examples of polymer quenchants, it should be clear
that aspects of the invention are not limited to these particular
polymer quenchants. Other types of polymer quenchants may be used.
In some cases, non-polymer quenchants may also be used provided
that the quenchant is capable of producing the desired hardness in
the material being hardened, preferably without cracking the
material.
[0026] After quenching, the localized area 70 is tempered at a low
temperature. In certain aspects, the low temperature is in a range
of 275.degree. F..+-.25.degree. F. Tempering time is selected to
attain a specified case hardness range for the localized area while
maintaining a desired base hardness for the element. As an example,
tempering time may be on the order of 2 hours. In certain aspects,
the minimum tempering time is 2 times the wall thickness of the
element. After tempering, the localized area 70 is cooled, e.g., by
air cooling.
[0027] The resultant product of the process described above is a
localized hardened area monolithically formed in an element, where
the localized hardened area has a localized hardness that is
greater than the base hardness of the element. In certain aspects,
the element 72 (which is not restricted to a pin-end tool joint)
has a base hardness, expressed as Rockwell hardness, in a range
from 30-36 HRC, and the localized area 70, after hardening by the
process described above, has a localized hardness, expressed as
Rockwell hardness, in a range from 56-63 HRC. In certain aspects,
the localized hardened area 70 has a localized hardness that is at
least 40% greater than the base hardness of the element 72. In
certain aspects, the depth of the localized hardened area 70 is in
a range from 0.25 in. (0.635 cm) to 0.375 in. (0.9525 cm).
[0028] Advantages provided by the disclosed techniques include,
without limitation, no welding requirement, shortened process time,
reduced machine time, energy competitiveness, lack of need for
additional costly filler metals, cracking reduction, distortion
reduction, elimination of need for arc gouging once the element is
worn, and ease of re-treatment of the element surface or area. It
will be appreciated by those skilled in the art that the techniques
disclosed herein can be fully automated using conventional
equipment configured with software code to perform the techniques
as described herein. Aspects of the invention may be implemented
with any conventional tools, tubulars, and equipment.
[0029] While the invention has been described with respect to a
limited number of embodiments, those skilled in the art, having
benefit of this disclosure, will appreciate that other embodiments
can be devised which do not depart from the scope of the invention
as disclosed herein. Accordingly, the scope of the invention should
be limited only by the attached claims.
* * * * *