U.S. patent application number 14/686071 was filed with the patent office on 2016-10-20 for ultra-fine grained steels having corrosion-fatigue resistance.
The applicant listed for this patent is Tenaris Connections Limited. Invention is credited to Martin Buhler, Matias Gustavo Pereyra.
Application Number | 20160305192 14/686071 |
Document ID | / |
Family ID | 57122286 |
Filed Date | 2016-10-20 |
United States Patent
Application |
20160305192 |
Kind Code |
A1 |
Buhler; Martin ; et
al. |
October 20, 2016 |
ULTRA-FINE GRAINED STEELS HAVING CORROSION-FATIGUE RESISTANCE
Abstract
Embodiments of an ultra-fine-grained, medium carbon steel are
disclosed herein. In some embodiments, the ultra-fine grained steel
can have high corrosion fatigue resistance, as well as high
toughness and yield strength. The ultra-fine grained steels can be
advantageous for use as sucker rods in oil wells having corrosive
environments.
Inventors: |
Buhler; Martin; (Villa
Mercedes, AR) ; Pereyra; Matias Gustavo; (Villa
Mercedes, AR) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Tenaris Connections Limited |
Kingstown |
|
VC |
|
|
Family ID: |
57122286 |
Appl. No.: |
14/686071 |
Filed: |
April 14, 2015 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C21D 6/008 20130101;
C22C 38/26 20130101; C22C 38/54 20130101; C21D 6/004 20130101; C22C
38/001 20130101; C22C 38/02 20130101; C22C 38/46 20130101; C21D
6/005 20130101; C22C 38/24 20130101; C22C 38/28 20130101; C21D
9/0075 20130101; C21D 8/065 20130101; C22C 38/06 20130101; C22C
38/48 20130101; C22C 38/04 20130101; C22C 38/22 20130101; C22C
38/002 20130101; C22C 38/44 20130101; C21D 6/002 20130101; C22C
38/32 20130101; C22C 38/50 20130101 |
International
Class: |
E21B 17/00 20060101
E21B017/00; C21D 9/00 20060101 C21D009/00; C21D 6/00 20060101
C21D006/00; C22C 38/54 20060101 C22C038/54; C22C 38/50 20060101
C22C038/50; C22C 38/48 20060101 C22C038/48; C22C 38/46 20060101
C22C038/46; C22C 38/44 20060101 C22C038/44; C22C 38/32 20060101
C22C038/32; C22C 38/28 20060101 C22C038/28; C22C 38/26 20060101
C22C038/26; C22C 38/24 20060101 C22C038/24; C22C 38/22 20060101
C22C038/22; C22C 38/06 20060101 C22C038/06; C22C 38/04 20060101
C22C038/04; C22C 38/02 20060101 C22C038/02; C22C 38/00 20060101
C22C038/00; C21D 8/06 20060101 C21D008/06 |
Claims
1. A steel sucker rod formed from a steel composition comprising
iron and, by weight: 0.15-0.4% carbon; 0.1-1.0% manganese; 0.5-1.5%
chromium; 0.01-0.1% aluminum; 0.2-0.35% silicon; 0.1-1.0%
molybdenum; 0.01-0.05% niobium; 0.005-0.03% titanium; and
0.0001-0.005% boron; wherein the steel has a final microstructure
comprising tempered martensite; and wherein an average grain size
of the final microstructure is between about 2 and about 5
micrometers.
2. The steel sucker rod of claim 1, wherein the rod has
approximately twice the average life of conventional sucker rod
materials in corrosion fatigue under CO.sub.2 or H.sub.2S
environments.
3. The steel sucker rod of claim 1, wherein the steel composition
comprises, by weight: 0 to 0.05 wt. % vanadium; and 0 to 0.2 wt. %
nickel.
4. The steel sucker rod of claim 1, wherein the final
microstructure comprises at least 90 volume % tempered
martensite.
5. The steel sucker rod of claim 1, comprising: a yield strength
greater than about 100 ksi; an ultimate tensile strength between
about 115 and about 140 ksi; and a minimum absorbed energy in
Charpy V-notch impact test of 100 Joules at room temperature.
6. The steel sucker rod of claim 1, wherein the steel composition
comprises, by weight: less than 0.01% sulfur; less than 0.015%
nitrogen; and less than 0.02% phosphorus.
7. The steel sucker rod of claim 1, wherein the steel composition
comprises, by weight: 0.15-0.3% carbon; 0.3-0.7% manganese;
0.2-0.35% silicon; 0.01-0.05% niobium; less than 0.008% sulfur;
less than 0.018% phosphorus; less than 0.015% nitrogen; 0.5-1.2%
chromium; 0.2-0.8% molybdenum; 0.01-0.03% titanium; 0.0010 to
0.0025% boron; and 0.01 to 0.05% aluminum.
8. The steel sucker rod of claim 7, wherein the steel composition
comprises, by weight: 0.2-0.3% carbon; 0.4-0.7% manganese; 0.2-0.3%
silicon; 0.02-0.04% niobium; less than 0.005% sulfur; less than
0.015% phosphorus; less than 0.01 nitrogen; 0.8-1.2% chromium;
0.3-0.8% molybdenum; 0.01-0.02% titanium; 0.001 to 0.002% boron;
and 0.01 to 0.04% aluminum.
9. The steel sucker rod of claim 1, wherein the steel composition
satisfies the formula: (Al/27+Ti/48+V/51+Nb/93-N/14)*100 between
about 0.08 and about 0.15% by weight.
10. The steel sucker rod of claim 1, wherein the steel composition
satisfies the formulas: C+Mn/10 between about 0.1 and about 0.4% by
weight, and Ni/10+Cr/12+Mo/8+Nb/2+20*B+V between about 0.1 and
about 0.25% by weight.
11. The steel sucker rod of claim 10, wherein the steel composition
satisfies the formulas: C+Mn/10 between about 0.2 and about 0.3% by
weight, and Ni/10+Cr/12+Mo/8+Nb/2+20*B+V between about 0.15 and
about 0.25% by weight.
12. A method of manufacturing a steel sucker rod, the method
comprising: providing a steel composition comprising iron and:
0.15-0.4 wt. % carbon; 0.1-1.0 wt. % manganese; 0.5-1.5 wt. %
chromium; 0.2-0.35 wt. % silicon; 0.1-1.0 wt. % molybdenum;
0.01-0.05 wt. % niobium; 0.005-0.03 wt. % titanium; 0.0001 to
0.0025 wt. % boron; 0.01 to 0.1 wt. % aluminum; hot rolling the
steel composition at a forging ratio greater than about 15;
austenitizing the hot rolled steel composition at a temperature
between the critical temperature (Ac3) and a maximum temperature
that satisfies the formula Tmax=1025.degree. C.-210.degree.
C.*sqrt(wt % C)+50.degree. C.*wt % Mo; quenching the steel
composition below about 100.degree. C. at a rate to produce a
martensitic microstructure; and tempering at a temperature between
565.degree. C. and a lower critical temperature (Ac1) to form
tempered martensite; wherein a time between a maximum austenitizing
and quenching is between 1 second and 10 seconds; and wherein an
austenitic grain size prior to quenching is 5 microns or less.
13. The method of claim 12, wherein the austenitizing and tempering
treatments are characterized by temperature equivalent parameters P
A / T ( T , t ) = - B / ln [ .intg. 0 t exp ( - Q R T ) t ]
##EQU00003## where T is the absolute temperature in .degree. K, t
is the time in seconds, R is the gas constant (J/mol .degree. K), Q
is an activation energy (425,000 J/mol) and B is a constant
(14,000.degree. C.), P.sub.A is below 800.degree. C., P.sub.T is
above 700.degree. C., and the difference between P.sub.A and
P.sub.T is less than or equal to 200.degree. C.
14. The method of claim 13, wherein the steel composition
comprises, by weight: 0 to 0.05 wt. % vanadium; and 0 to 0.2 wt. %
nickel.
15. The method of claim 13, wherein the difference between P.sub.A
and P.sub.T is less than 100.degree. C.
16. The method of claim 12, wherein the austenitic grain size prior
to quenching is between 2 and 5 microns.
17. The method of claim 12, wherein the steel is quenched at a rate
greater than about 50.degree. C./sec.
18. The method of claim 17, wherein the steel composition
comprises, by weight: 0.15-0.3% carbon; 0.3-0.7% manganese;
0.2-0.35% silicon; 0.01-0.05% niobium; less than 0.008% sulfur;
less than 0.018% phosphorus; less than 0.015% nitrogen; 0.5-1.2%
chromium; 0.2-0.8% molybdenum; 0.01-0.03% titanium; 0.0010 to
0.0025% boron; and 0.01 to 0.05% aluminum.
19. The method of claim 18, wherein the steel composition
comprises, by weight: 0.2-0.3% carbon; 0.4-0.7% manganese; 0.2-0.3%
silicon; 0.02-0.04% niobium; less than 0.005% sulfur; less than
0.015% phosphorus; less than 0.01 nitrogen; 0.8-1.2% chromium;
0.3-0.8% molybdenum; 0.01-0.02% titanium; 0.001 to 0.002% boron;
and 0.01 to 0.04% aluminum.
20. A steel formed from a steel composition comprising iron and, by
weight: 0.15-0.4% carbon; 0.1-1.0% manganese; 0.5-1.5% chromium;
0.01-0.1% aluminum; 0.2-0.35% silicon; 0.1-1.0% molybdenum;
0.01-0.05% niobium; 0.005-0.03% titanium; and 0.0001-0.0025% boron;
wherein the steel has a final microstructure comprising tempered
martensite; and wherein an average grain size of the final
microstructure is between about 2 and about 5 micrometers.
Description
BACKGROUND
[0001] 1. Field
[0002] Embodiments of the present disclosure relate to ultra-fine
grained steels which can have excellent toughness and high fatigue
resistance in corrosive environments.
[0003] 2. Description of the Related Art
[0004] A sucker rod is a steel solid bar, typically between 25 and
30 feet in length, upset and threaded at both ends, used in the oil
and gas industry to connect components at the surface and the
bottom of a well. Sucker rods can be used in, for example,
reciprocating rod lifts and progressive cavity pumping systems. Due
to the alternating movement of the system, fatigue is a common
failure mechanism of sucker rods in service.
[0005] Typically, there can be a strong correlation between fatigue
strength and tensile strength for steels up to about 170 ksi.
However, under the effect of a harsh environment, which very
frequently occurs in oil wells, the correlation may no longer be
valid because the presence of hydrogen sulfide (H.sub.2S), carbon
dioxide (CO.sub.2), chlorides, and other compounds in aqueous
solutions, can considerably reduce the fatigue life of the
components.
[0006] Accordingly, corrosion is a major issue in the oil and gas
industry, requiring special considerations in the selection of
materials and well design. There are many factors influencing the
initiation of one or several corrosion processes. These factors
include pH, pressure, potential, temperature, fluid flow,
concentration (solution constituents), and water cut. Further,
increased volumes of injection water/gas for mature fields and
shale operations can increase the risk of failures related to
corrosion processes.
SUMMARY
[0007] Disclosed herein are embodiments of a steel sucker rod
formed from a steel composition comprising iron and, by weight:
[0008] 0.15-0.4% carbon;
[0009] 0.1-1.0% manganese;
[0010] 0.5-1.5% chromium;
[0011] 0.01-0.1% aluminum;
[0012] 0.2-0.35% silicon;
[0013] 0.1-1.0% molybdenum;
[0014] 0.01-0.05% niobium;
[0015] 0.005-0.03% titanium; and
[0016] 0.0001-0.005% boron;
[0017] wherein the steel has a final microstructure comprising
tempered martensite, and wherein an average grain size of the final
microstructure is between about 2 and about 5 micrometers.
[0018] In some embodiments, the rod can have approximately twice
the average life of conventional sucker rod materials in corrosion
fatigue under CO.sub.2 or H.sub.2S environments. In some
embodiments, the chemical composition can further comprise 0 to
0.05 wt. % vanadium, and 0 to 0.2 wt. % nickel. In some
embodiments, the final microstructure can comprise at least 90
volume % tempered martensite. In some embodiments, the steel sucker
rod can comprise a yield strength greater than about 100 ksi, an
ultimate tensile strength between about 115 and about 140 ksi, and
a minimum absorbed energy in Charpy V-notch impact test of 100
Joules at room temperature. In some embodiments, the steel
composition can further comprise by weight, less than 0.01% sulfur,
less than 0.015% nitrogen, and less than 0.02% phosphorus.
[0019] In some embodiments, the steel composition can comprise, by
weight:
[0020] 0.15-0.3% carbon;
[0021] 0.3-0.7% manganese;
[0022] 0.2-0.35% silicon;
[0023] 0.01-0.05% niobium;
[0024] less than 0.008% sulfur;
[0025] less than 0.018% phosphorus;
[0026] less than 0.015% nitrogen;
[0027] 0.5-1.2% chromium;
[0028] 0.2-0.8% molybdenum;
[0029] 0.01-0.03% titanium;
[0030] 0.0010 to 0.0025% boron; and
[0031] 0.01 to 0.05% aluminum.
[0032] In some embodiments, the steel composition can comprise, by
weight:
[0033] 0.2-0.3% carbon;
[0034] 0.4-0.7% manganese;
[0035] 0.2-0.3% silicon;
[0036] 0.02-0.04% niobium;
[0037] less than 0.005% sulfur;
[0038] less than 0.015% phosphorus;
[0039] less than 0.01 nitrogen;
[0040] 0.8-1.2% chromium;
[0041] 0.3-0.8% molybdenum;
[0042] 0.01-0.02% titanium;
[0043] 0.001 to 0.002% boron; and
[0044] 0.01 to 0.04% aluminum.
[0045] In some embodiments, the steel composition can satisfy the
formula: (Al/27+Ti/48+V/51+Nb/93-N/14)*100 between about 0.08 and
about 0.15% by weight. In some embodiments, the steel composition
can satisfy the formulas: C+Mn/10 between about 0.1 and about 0.4%
by weight, and Ni/10+Cr/12+Mo/8+Nb/2+20*B+V between about 0.1 and
about 0.25% by weight. In some embodiments, the steel composition
can satisfy the formulas: C+Mn/10 between about 0.2 and about 0.3%
by weight, and Ni/10+Cr/12+Mo/8+Nb/2+20*B+V between about 0.15 and
about 0.25% by weight.
[0046] Also disclosed herein are embodiments of a method of
manufacturing a steel sucker rod, the method comprising providing a
steel composition comprising iron and:
[0047] 0.15-0.4 wt. % carbon;
[0048] 0.1-1.0 wt. % manganese;
[0049] 0.5-1.5 wt. % chromium;
[0050] 0.2-0.35 wt. % silicon;
[0051] 0.1-1.0 wt. % molybdenum;
[0052] 0.01-0.05 wt. % niobium;
[0053] 0.005-0.03 wt. % titanium;
[0054] 0.0001 to 0.0025 wt. % boron;
[0055] 0.01 to 0.1 wt. % aluminum;
[0056] hot rolling the steel composition at a forging ratio greater
than about 15, austenitizing the hot rolled steel composition at a
temperature between the critical temperature (Ac3) and a maximum
temperature that satisfies the formula Tmax=1025.degree.
C.-210.degree. C.*sqrt(wt % C)+50.degree. C.*wt % Mo; quenching the
steel composition below about 100.degree. C. at a rate to produce a
martensitic microstructure, and tempering at a temperature between
565.degree. C. and a lower critical temperature (Ac1) to form
tempered martensite, wherein a time between a maximum austenitizing
and quenching is between 1 second and 10 seconds, and wherein an
austenitic grain size prior to quenching is 5 microns or less.
[0057] In some embodiments, the austenitizing and tempering
treatments are characterized by temperature equivalent
parameters
P A / T ( T , t ) = - B / ln [ .intg. 0 t exp ( - Q R T ) t ] ,
##EQU00001##
where T is the absolute temperature in .degree. K, t is the time in
seconds, R is the gas constant (J/mol .degree. K), Q is an
activation energy (425,000 J/mol) and B is a constant
(14,000.degree. C.), P.sub.A is below 800.degree. C., P.sub.T is
above 700.degree. C., and the difference between P.sub.A and
P.sub.T is less than or equal to 200.degree. C.
[0058] In some embodiments, the steel composition can comprise 0 to
0.05 wt. % vanadium, and 0 to 0.2 wt. % nickel. In some
embodiments, the difference between P.sub.A and P.sub.T can be less
than 100.degree. C. In some embodiments, the austenitic grain size
prior to quenching can be between 2 and 5 microns. In some
embodiments, the steel can be quenched at a rate greater than about
50.degree. C./sec.
[0059] In some embodiments, the steel composition can comprise, by
weight:
[0060] 0.15-0.3% carbon;
[0061] 0.3-0.7% manganese;
[0062] 0.2-0.35% silicon;
[0063] 0.01-0.05% niobium;
[0064] less than 0.008% sulfur;
[0065] less than 0.018% phosphorus;
[0066] less than 0.015% nitrogen;
[0067] 0.5-1.2% chromium;
[0068] 0.2-0.8% molybdenum;
[0069] 0.01-0.03% titanium;
[0070] 0.0010 to 0.0025% boron; and
[0071] 0.01 to 0.05% aluminum.
[0072] In some embodiments, the steel composition can comprise, by
weight:
[0073] 0.2-0.3% carbon;
[0074] 0.4-0.7% manganese;
[0075] 0.2-0.3% silicon;
[0076] 0.02-0.04% niobium;
[0077] less than 0.005% sulfur;
[0078] less than 0.015% phosphorus;
[0079] less than 0.01 nitrogen;
[0080] 0.8-1.2% chromium;
[0081] 0.3-0.8% molybdenum;
[0082] 0.01-0.02% titanium;
[0083] 0.001 to 0.002% boron; and
[0084] 0.01 to 0.04% aluminum.
[0085] Also disclosed herein are embodiments of a steel formed from
a steel composition comprising iron and, by weight:
[0086] 0.15-0.4% carbon;
[0087] 0.1-1.0% manganese;
[0088] 0.5-1.5% chromium;
[0089] 0.01-0.1% aluminum;
[0090] 0.2-0.35% silicon;
[0091] 0.1-1.0% molybdenum;
[0092] 0.01-0.05% niobium;
[0093] 0.005-0.03% titanium; and
[0094] 0.0001-0.0025% boron;
[0095] wherein the steel has a final microstructure comprising
tempered martensite, and wherein an average grain size of the final
microstructure is between about 2 and about 5 micrometers.
BRIEF DESCRIPTION OF THE DRAWINGS
[0096] FIG. 1 illustrates testing results showing a correlation
between corrosion-fatigue life in harsh environments and impact
toughness for embodiments of an ultra-fined-grained steel as
compared to steels of the prior art.
[0097] FIG. 2 illustrates testing results showing the effect of
composition and heat treatment on toughness for embodiments of an
ultra-fined-grained steel as compared to steels of the prior
art.
[0098] FIG. 3 illustrates the effect of heat treatment on grain
size for some embodiments of a steel composition. Both steels shown
have the same composition and the same magnification but (left)
underwent fast heating and (right) underwent conventional
heating.
[0099] FIG. 4 illustrates testing results showing the effect of
composition and heat treatment on grain size of embodiments of the
disclosed steel.
[0100] FIG. 5 illustrates testing results showing the effect of
composition and heat treatment on fatigue life of embodiments of
the disclosed steel.
[0101] FIG. 6 illustrates testing results showing the effect of
composition and heat treatment on SSC performance of embodiments of
the disclosed steel.
[0102] FIG. 7 illustrates an embodiment of a heat treatment of the
disclosure.
DETAILED DESCRIPTION
[0103] Embodiments of the present disclosure are directed to
ultra-fine-grained steels (UFGSs), and methods of manufacturing
such steels. In general, the term ultra-fine-grain is used for
average grain sizes of 5 .mu.m and below (or about 5 .mu.m and
below), below 5 .mu.m (or below about 5 .mu.m), preferably between
1 .mu.m and 2 .mu.m (or between about 1 .mu.m and about 2 .mu.m) in
diameter. Embodiments of the disclosed steels can have advantageous
properties for use in an oil well. For example, embodiments of the
disclosed steel can be used to form sucker rods having excellent
toughness and a high fatigue resistance in corrosive environments
(e.g., carbon dioxide and/or seawater). These improved properties
can be achieved by, in some embodiments, combining a specific steel
composition with a specific microstructure. Further, in some
embodiments good process control, such as for hot rolling and heat
treatment, can be further used to adjust the properties of a
steel.
[0104] Specifically, embodiments of the present disclosure can have
an ultra-fine grain martensitic microstructure, achieved through a
fast induction heating to austenitizing temperature followed by a
fast water quenching, combined with a selected chemical composition
with a proper combination of C, Mn, Cr, Mo and other microalloying
elements. Additionally, a fine carbide dispersion and a low
dislocation density can be achieved with a high tempering
temperature, while still maintaining high strength. In some
embodiments, the microstructure right before quenching, after
quenching, and after tempering can be identical or substantially
identical.
[0105] From the point of view of the materials, some parameters for
achieving advantageous corrosion-fatigue resistance can include the
steel chemistry, such as alloy additions and steel cleanliness,
microstructure, mechanical properties and toughness. While the
effect of steel chemical composition, structure and properties in
corrosion and stress cracking has been extensively investigated,
the mechanism of corrosion fatigue has not well been
understood.
[0106] However, it has been experimentally found that toughness can
have a direct relationship with corrosion-fatigue resistance in
different harsh environments. In some embodiments, an advantageous
material can be moderately corrosion resistant, with good sulfide
stress cracking performance, good fatigue strength and excellent
toughness. These conditions can be achieved with an ultra-fine
grain martensitic microstructure, combined with the proper chemical
composition (in terms of microalloying elements and steel
cleanliness), fine carbide dispersion and a low dislocations
density (achieved with a high tempering temperature), such as those
described herein. Particularly, it has been observed that reducing
the austenite grain size can notably increase toughness at a given
strength level. Moreover, control of carbides precipitation, in
terms of distribution and size, can also be advantageous in
achieving corrosion-fatigue resistance.
[0107] In view of the many factors mentioned above, several tests
and analyses were performed for different materials. Various
chemical compositions and different heat treatments were also
investigated. The behavior of the materials was analyzed using
several techniques and tests, in aggressive environments, looking
for stronger steels. Particularly, the corrosion fatigue resistance
was measured using time-to-failure tests: cycling tensile loads
were applied in different harsh environments like those encountered
in the oil and gas industry, at selected pressure and temperature.
Specifically, corrosion fatigue is the conjoint action of a cyclic
stress and a corrosive environment to decrease the number of cycles
to failure in comparison to the life when no corrosion is
present.
[0108] An advantageous combination of chemical composition and heat
treatment was achieved that can improve the performance of certain
steels under corrosion fatigue conditions. Furthermore, it was
found that there is a good correlation between corrosion fatigue
performance and material toughness that allows better understanding
of the behavior.
[0109] Moreover, the selection of a proper chemical composition (in
terms of microalloying elements and steel cleanliness) combined
with certain heat treatments, can lead to a better microstructure
to reach improved toughness. Particularly, it has been observed
that reducing the austenite grain size can noticeably increase
toughness at a given strength level. FIG. 3 depicts the effect of
heat treatment on grain size of steels formed having a composition
in the last row of Table 1 below. The steel shown in the left
figure was heated to an austenitizing temperature at a rate of
100.degree. C./s, while the heat rate for the right figure is below
1.degree. C./s. The photographs shown in FIG. 3 were taken in the
as-quenched condition for better accuracy, and it should be noted
that tempering does not modify the prior austenitic grain size.
[0110] As shown, a fast heating leads to a very much thinner grain,
and thus smaller subunits of the grain such as, for example,
packets and lathes, compared with conventional heating, in the same
steel composition. As explained, this reduction in grain size
notably increases the toughness of the material.
[0111] Steel, such as in the form of a sucker rod, can be
fabricated from a low alloy steel (medium C, Mn--Cr--Mo--Nb--Ti),
hot rolled bar, with a tight chemical composition, heat treated by
induction heating, water quenching and tempering. A high forging
ratio, determined as the area ratio before and after hot rolling,
and the tight control of the austenitizing process, can provide an
ultra-fine grained martensitic microstructure.
Composition
[0112] The steel composition of certain embodiments of the present
disclosure can be a steel alloy comprising carbon (C) and other
alloying elements such as manganese (Mn), silicon (Si), chromium
(Cr), boron (B), molybdenum (Mo), niobium (Nb), aluminum (Al) and
titanium (Ti). Additionally, one or more of the following elements
may be optionally present and/or added as well: vanadium (V) and
Nickel (Ni). The remainder of the composition can comprise iron
(Fe) and impurities. In certain embodiments, the concentration of
impurities may be reduced to as low as an amount as possible.
Embodiments of impurities may include, but are not limited to,
sulfur (S), phosphorous (P) and nitrogen (N). Residuals of lead
(Pb), tin (Sn) antimony (Sb), arsenic (As), and bismuth (Bi) may be
found in a combined maximum of 0.05% by weight (or about 0.05% by
weight).
[0113] In some embodiments, a steel rod can comprise a composition
of, by weight 0.15-0.4% (or about 0.15-0.4%) carbon (C), 0.1-1.0%
(or about 0.1-1.0%) manganese (Mn), 0.5-1.5% (or about 0.5-1.5%)
chromium (Cr), 0.2-0.35% (or about 0.2-0.35%) silicon (Si),
0.1-1.0% (or about 0.1-1.0%) molybdenum (Mo), 0.01-0.05% (or about
0.01-0.05%) niobium (Nb), 0.005-0.03% (or about 0.005-0.03%)
titanium (Ti), 0.0001 to 0.0050% (or about 0.0001-0.0050%) boron
(B) and 0.01 to 0.1% (or about 0.01-0.1%) aluminum (Al).
Additionally, one or more of the following elements may be
optionally present and/or added as well: 0 to 0.05% (or about
0-0.05%) vanadium (V) and 0 to 0.2% (or about 0-0.2%) nickel (Ni),
and the remainder being iron and unavoidable impurities. In some
embodiments, the steel rod can further comprise less than 0.01% (or
less than about 0.01%) sulfur, less than 0.02% (or less than about
0.02%) phosphorus and less than 0.02% (or less than about 0.02%)
nitrogen.
[0114] In some embodiments, a steel rod can comprise a composition
of, by weight 0.15-0.3% (or about 0.15-0.3%) carbon (C), 0.3-0.7%
(or about 0.3-0.7%) manganese (Mn), 0.5-1.2% (or about 0.5-1.2%)
chromium (Cr), 0.2-0.35% (or about 0.2-0.35%) silicon (Si),
0.2-0.8% (or about 0.2-0.8%) molybdenum (Mo), 0.01-0.05% (or about
0.01-0.05%) niobium (Nb), 0.01-0.03% (or about 0.01-0.03%) titanium
(Ti), 0.0010 to 0.0025% (or about 0.0010-0.0025%) boron (B), 0.01
to 0.05% (or about 0.01-0.05%) aluminum (Al), and the remainder
being iron and unavoidable impurities. In some embodiments, the
steel rod can further comprise less than 0.008% (or less than about
0.008%) sulfur, less than 0.018% (or less than about 0.018%)
phosphorus and less than 0.015% (or less than about 0.015%)
nitrogen.
[0115] Cu is not needed in embodiments of the steel composition,
but may be present. In some embodiments, depending on the
manufacturing process, the presence of Cu may be unavoidable.
Thereafter, in an embodiment, the maximum Cu content may be 0.12%
(or about 0.12%) or less.
[0116] In some embodiments, a steel composition can be provided
comprising carbon (C), manganese (Mn), nickel (Ni), chromium (Cr),
molybdenum (Mo), niobium (Nb), boron (B) and vanadium (V). The
amount of each element is provided, in by weight of the total steel
composition, such that the steel composition satisfies the
formulas: C+Mn/10 between 0.1 and 0.4% (or about 0.1-0.4%) and
Ni/10+Cr/12+Mo/8+Nb/2+20*B+V between 0.1 and 0.25% (or about
0.1-0.25%).
[0117] Further, a balanced content of aluminum, titanium, vanadium,
niobium and nitrogen can be advantageous for optimal toughness. The
amount of each element, based on stoichiometric relations, by
weight of the total steel composition, can satisfy the formula:
(Al/27+Ti/48+V/51+Nb/93-N/14)*100 between 0.08 and 0.15% (or about
0.08-0.15%).
[0118] In certain embodiments, steel compositions can comprise
restricted ranges of C, Mn, Cr, Si, Mo, Nb, Ti, B, Al, V, Ni, S, P
and N. These compositions are listed in Table 1 together with
mentioned ranges, by weight of the total composition unless
otherwise noted. In some embodiments, the steel compositions
consist essentially of the restricted ranges of C, Mn, Cr, Si, Mo,
Nb, Ti, B, Al, V, Ni, S, P and N. These compositions are listed
below in Table 1, by weight of the total composition, unless
otherwise noted.
TABLE-US-00001 TABLE 1 Embodiments of steel compositions. C Mn Cr
Si Mo Nb Ti 0.15-0.4 0.1-1.0 0.5-1.5 0.2-0.35 0.1-1.0 0.01-0.05
0.005-0.03 0.15-0.3 0.3-0.7 0.5-1.2 0.20-0.35 0.2-0.8 0.01-0.05
0.01-0.03 0.2-0.3 0.4-0.7 0.8-1.2 0.20-0.30 0.3-0.8 0.02-0.04
0.01-0.02 B Al V Ni S P N 0-50 ppm 0.01-0.1 0-0.05 0-0.2 0-0.01
0-0.02 0-0.02 10-25 ppm 0.01-0.05 0-0.05 0-0.2 0-0.008 0-0.018
0-0.015 10-20 ppm 0.01-0.04 0-0.03 0-0.1 0-0.005 0-0.015 0-0.01
[0119] Carbon is an element which can improve the hardenability and
increase the strength of the steel. If C content is below 0.15% (or
about 0.15%), it may be difficult to achieve high levels of
hardenability and strength. But C content exceeding 0.4% (or about
0.4%) may reduce the toughness of the steels. Accordingly, in some
embodiments carbon content can be in the range of 0.15 to 0.4% (or
about 0.15-0.4%). In some embodiments, carbon content can be in the
range of 0.15 to 0.3% (or about 0.15-0.3%). In some embodiments,
carbon content can be in the range of 0.2 to 0.3% (or about
0.2-0.3%).
[0120] Manganese is an element which also can improve hardenability
and strength, but too high of Mn content can promote segregation of
impurities that can reduce the toughness and corrosion-fatigue
resistance of a steel. Accordingly, it can be advantageous to have
a balance between C and Mn content. In some embodiments, manganese
content can be in the range of, by weight 0.1 to 1.0% (or about
0.1-1.0%). In some embodiments, manganese content can be in the
range of 0.3 to 0.7% (or about 0.3-0.7%). In some embodiments,
manganese content can be in the range of 0.4 to 0.7% (or about
0.4-0.7%). %.
[0121] Chromium is an element which can improve hardenability,
increase strength and also increase the tempering resistance of the
steel. Further, Cr can increase corrosion resistance of a steel,
being in solid solution. In some embodiments, chromium content can
be in the range of 0.5 to 1.5% (or about 0.5-1.5%). In some
embodiments, chromium content can be in the range of 0.5 to 1.2%
(or about 0.5-1.2%). In some embodiments, chromium content can be
in the range of 0.8 to 1.2% (or about 0.8-1.2%).
[0122] Silicon is an element that can have a deoxidizing effect
during steel making process and can also raise the strength of a
steel. If the Si content is too low, a high level of
micro-inclusions due to oxidation can be present. Moreover, high Si
content may decrease toughness and also can modify the adherence of
oxides during rolling. In some embodiments, silicon content can be
in the range of 0.2 to 0.35% (or about 0.2-0.35%). In some
embodiments, silicon content can be in the range of 0.2 to 0.3% (or
about 0.2-0.3%).
[0123] Molybdenum is an element which can have a strong effect on
temperability. Mo also can improve hardenability and strength of a
steel. However, Mo is an expensive element, and has a saturation
level that can limit its desirable content. In some embodiments,
molybdenum content can be in the range of, by weight 0.1 to 1.0%
(or about 0.1-1.0%). In some embodiments, molybdenum content can be
in the range of 0.2 to 0.8% (or about 0.2-0.8%). In some
embodiments, molybdenum content can be in the range of 0.3 to 0.8%
(or about 0.3-0.8%).
[0124] Vanadium is an element which can improve both hardenability
and temperability of a steel, and its effect can be even stronger
than that of Mo. Accordingly, V and/or Mo can be used to control
dislocation density after tempering. However, vanadium can cause
cracking in steel during manufacturing and, therefore, its content
may be reduced. In some embodiments, vanadium content can be in the
range of 0 to 0.05% (or about 0-0.05%). In some embodiments,
vanadium content can be in the range of 0 to 0.03% (or about
0-0.03%).
[0125] Boron in small quantities can significantly increases
hardenability of a steel. In some embodiments, boron content can be
in the range of 0 to 50 ppm (or about 0-50 ppm). In some
embodiments, boron content can be in the range of 10 to 25 ppm (or
about 10-25 ppm). In some embodiments, boron content can be in the
range of 10 to 20 ppm (or about 10-20 ppm).
[0126] Titanium can be added to increase the effectiveness of B in
the steel. The role of titanium can be to protect boron from
nitrogen by forming titanium nitride (TiN) particles. However, Ti
can produce coarse TiN particles, which can lead to deterioration
in toughness. In some embodiments, titanium content can be in the
range of, by weight 0.005 to 0.03% (or about 0.005-0.03%). In some
embodiments, titanium content can be in the range of 0.01 to 0.03%
(or about 0.01-0.03%). In some embodiments, titanium content can be
in the range of 0.01 to 0.02% (or about 0.01-0.02%).
[0127] Niobium is an element whose addition to the steel
composition can refine the austenitic grain size during hot
rolling, with the subsequent increase in both strength and
toughness. Nb may also precipitate during tempering, increasing the
steel strength by particle dispersion hardening. In some
embodiments, niobium content can be in the range of, by weight 0.01
to 0.05% (or about 0.01-0.05%). In some embodiments, niobium
content can be in the range of 0.02 to 0.04% (or about
0.02-0.04%).
[0128] Sulfur is an element that can cause the toughness of the
steel to decrease. Accordingly, in some embodiments sulfur content
is limited to a maximum of 0.01% (or about 0.01%). In some
embodiments, sulfur content is limited to a maximum of 0.008% (or
about 0.008%). In some embodiments, sulfur content is limited to a
maximum of 0.005% (or about 0.005%).
[0129] Phosphorous is an element that can cause the toughness of
the steel to decrease. Accordingly, in some embodiments phosphorous
content is limited to a maximum of 0.02% (or about 0.02%). In some
embodiments, phosphorous content is limited to a maximum of 0.018%
(or about 0.018%). In some embodiments, phosphorous content is
limited to a maximum of 0.015% (or about 0.015%).
[0130] Nitrogen is an element, if not fixed with Ti or Al, that can
interact with B, thereby forming BN. This can reduce the overall
amount of B in the alloy, which can reduce hardenability. Nickel
can reduce the SSC resistance while increasing the toughness of the
system. Aluminum can be used as a deoxidizing or killing agent.
[0131] In some embodiments, contents of unavoidable impurities
including, but not limited to, Pb, Sn, As, Sb, Bi and the like, can
be kept as low as possible. In some embodiments, each of the
impurities is limited to 0.08 wt. % (or about 0.08 wt. %) or less.
In some embodiments, each of the impurities is limited to 0.004 wt.
% (or about 0.004 wt. %) or less. In some embodiments, Ca is
limited to 0.004 wt. % (or about 0.004 wt. %) or less. In some
embodiments, W is limited to 0.08 wt. % (or about 0.08 wt. %) or
less. In some embodiments, the steel does not contain any Ni. In
some embodiments, the steel does not contain any Ca, which can
reduce the effectiveness of inclusion control. In some embodiments,
the steel does not contain any W. In some embodiments, the steel
does not contain any Ni.
Methods of Manufacturing
[0132] Also disclosed herein are embodiments of manufacturing
methods that can be used to achieve advantageous properties in
ultra-fine-grained steels.
[0133] In some embodiments, a steel composition, such as those
described above, can be melted, for example, in an electric arc
furnace (EAF), with an eccentric bottom tapping (EBT) system, or
through any other melting system. In some embodiments, aluminum
de-oxidation practice can be used to produce fine grain fully
killed steel. Further, liquid steel refining can be performed by
control of the slag and argon gas bubbling in the ladle furnace.
Ca--Si wire injection treatment can be performed for residual
non-metallic inclusion shape control. In some embodiments, none of
the method is performed in a carburizing atmosphere.
[0134] After melting the steel, the melted steel can then be formed
by hot rolling to a desired shapes, such as a steel rod or steel
sucker rod. In some embodiments, the forging ratio, determined as
the area ratio before and after hot rolling, can be at least 15:1
(or at least about 15:1). In some embodiments, a forging ratio of
34 (or about 34), 44.3 (or about 44.3), and 60.4 (or about 60.4)
can be used. This high forging ratio can improve material
homogeneity, thus improving the distribution of elements (e.g.,
reducing element segregation). Further, the high forging ratio can
reduce corrosion due to micro galvanic effects.
[0135] In some embodiments, the formed steel can be heat treated,
and an embodiment of the process is shown in FIG. 7. For example,
the steel can be rapidly heated to an austenitizing temperature in
a fast induction heating/hardening process, as shown as the first
peak in FIG. 7. The steel can remain at this high austenitizing
temperature and then quickly cooled below 100.degree. C. (or about
100.degree. C.). In some embodiments, the cooling rate can be
greater than 50.degree. C./s (or greater than about 50.degree.
C./s). In some embodiments, the steel can remain at the high
temperature for just a few seconds. Further, the quenching can last
only a few seconds as well. In some embodiments, the elapsed time
between maximum temperature and fast cooling can be no less than 1
second and no more than 10 seconds (or about 1-10 seconds).
Further, the austenitizing temperature in some embodiments can be
no lower than the higher critical temperature (Ac3) and no higher
than about a maximum that satisfies the formula
Tmax=1025.degree. C.-210.degree. C.*sqrt(wt % C)+50.degree. C.*wt %
Mo.
[0136] Since the heating transformation to austenite can be a
nucleation and growth process, the rapid heating (e.g., above
100.degree. C./c or above about 100.degree. C./s) up to the
austenitizing temperature can lead to the nucleation of several
small grains without having enough time for growth due to the fast
cooling stage. For this to occur, it can be advantageous to have an
adequate initial microstructure, homogeneous with an even carbon
distribution, avoiding coarse precipitates. This initial
microstructure of mainly bainite with a prior austentitic grain
size no higher than 30 .mu.m (or no higher than about 30 .mu.m) can
be achieved with the proper chemical composition and forging ratio,
as described above.
[0137] In addition to providing for advantageous physical
properties, the fast induction heating/hardening process can
provide considerable energy savings over conventional furnace
heating (up to 95% of energy savings), and can help to reduce
CO.sub.2 emissions.
[0138] After austenitizing and quenching, the steel can then be
tempered, shown as the second increase in FIG. 7. In some
embodiments, the steel can remain at the tempering temperature for
between 40 minutes (or about 40 minutes) to 1 hour (or about 1
hour). In some embodiments, the steel can be tempered at a
temperature higher than 565.degree. C. (or about 565.degree. C.),
such as 720.degree. C. (or about 720.degree. C.) and lower than the
lower critical temperature (Ac1).
[0139] The austenitizing and tempering treatments can be
characterized by temperature equivalent parameters, using integral
time-temperature equations:
P A / T ( T , t ) = - B / ln [ .intg. 0 t exp ( - Q R T ) t ] ( 1 )
##EQU00002##
where T is the absolute temperature in .degree. K, t is the time in
seconds, R is the gas constant (J/mol .degree. K), Q is an
activation energy (425,000 J/mol) and B is a constant
(14,000.degree. C.). As austenitizing and tempering treatments are
time and temperature dependent, the above formula can correlate
both parameters into one parameter, which can be advantageous in
providing the best combination of treatments.
[0140] In some embodiments, the P.sub.A parameter for austenitizing
treatment is as low as possible. For example, in some embodiments
P.sub.A can be below 800.degree. C. (or below about 800.degree.
C.). In some embodiments, the P.sub.T parameter for tempering
process can be as high as possible. For example, in some
embodiments P.sub.T can be above 700.degree. C. (or below about
700.degree. C.). Further, in some embodiments the difference
P.sub.A-P.sub.T can be as low as possible. For example, in some
embodiments the difference can be lower than 100.degree. C. (or
below about 100.degree. C.). In some embodiments, the difference
can be lower than 150.degree. C. (or below about 150.degree. C.).
In some embodiments, the difference can be less than or equal to
200.degree. C. (or below bout 200.degree. C.). The combination of
austenitizing and tempering conditions, in terms of time and
temperature, can ensure the formation of a microstructure having
fine grains with a fine well distributed carbide precipitates.
[0141] Embodiments of the disclosed ultra-fine grain steels using
embodiments of the disclosed methods can have numerous advantageous
physical characteristics. For example, in some embodiments the
steels can have characteristics that can make them advantageous for
use in sour service, or other corrosive environments. A discussion
of ultra-fine grain steels can be found at Structural Ultrafine
Grained Steels Obtained by Advanced Controlled Rolling, R. Gonzalez
et al, Journal of Iron and Steel Research, International, 2013, 20
(1), 62-70, herein disclosed by reference in its entirety.
[0142] In some embodiments, the average grain size of the steel
composition after heat treatment (e.g., after quenching or after
tempering as tempering may not affect grain size) can be less than
5 .mu.m (or less than about 5 .mu.m). Moreover, the average grain
size of the steel composition can be between 2 and 5 (or about 2
and about 5) micrometers after heat treatment. Such a reduction in
grain size (from values between 10 and 20 micrometers for
conventional treated steels) can increase the yield strength to
tensile strength ratio while also enhancing the Charpy V-notch
energy. In some embodiments, the structure can be full martensitic
(90% minimum) which can improve the corrosion-fatigue resistance of
the composition. In some embodiments, the final microstructure of
the steel, such as those described above, can comprise tempered
martensite with at least 90 (or at least about 90) volume % of
martensite. As mentioned, the ultra-fine grained homogeneous
structure notably improves the toughness of the steel.
[0143] In some embodiments, the steel can have a minimum yield
strength of about 100 ksi and a target tensile strength between 115
and 140 (or about 115-140) ksi. Further, in some embodiments the
steel can have a minimum absorbed energy in Charpy V-notch impact
test of 100 (or about 100) Joules at room temperature.
Examples
[0144] The below examples illustrate the fatigue corrosion
performance of a steel manufactured from embodiments of the above
disclosure as compared to other chemical compositions or
manufacturing routes.
[0145] Ultra-fine grain steels (UFGS), such as those described
above, were manufactured at industrial scale complying with the
following equations in order to investigate the effect of different
elements and the performance of each steel chemical composition
under different conditions (all UFGS steels and Set A):
0.2%<C+Mn/10<0.3%
0.15%<Ni/10+Cr/12+Mo/8+Nb/2+20*B+V<0.25%
[0146] Billets with an outside diameter of 148 mm were produced in
a vertical continuous casting machine. Billets were heated up to
1270.degree. C. and hot rolled to diameters ranging from 19 up to
32 mm.
[0147] Bars were then subjected to a fast induction heating
reaching a target temperature of about 900.degree. C. in about 4
seconds in the whole section, held at temperature for about 4
seconds and quenched in water down to below 100.degree. C. in about
6 seconds. Different maximum temperatures were also used to analyze
the effect of temperature on grain size for short time cycles. The
lowest temperature can be advantageous for energy savings.
[0148] The as quenched bars were then subjected to a tempering
process in a batch furnace, at about 710.degree. C. during a total
residence time of about 40 minutes. Ultimate tensile strengths
between about 120 and 140 ksi were reached. Lower temperatures were
also analyzed to reach different strengths.
[0149] Full size specimens were tensile tested as defined in ASTM
A370 standard, hereby incorporated by reference in its entirety.
Full size, 10.times.10, Charpy V-notch specimens were also obtained
and tested according ASTM A370. Austenitic grain size was measured
according ASTM E112, hereby incorporated by reference in its
entirety, in the as quenched condition.
[0150] Corrosion fatigue tests were performed in specially
dedicated machines. Other steels were also manufactured and tested
for comparison: [0151] Set A: Steels with the same chemical
composition as UFGS but with a different processing route: a lower
forging ratio of 8.5 during rolling and a conventional batch
quenching and tempering heat treatment (e.g., austenitization at an
average of 1.degree. C./s up to 900.degree. C., held for 15
minutes, and quenched at 30.degree. C./s. Tempering follows at
690.degree. C. for about 1 hour). As a result, the austenitic grain
size is about 10 microns. [0152] Set B: Quenched and tempered
steels (treated in with heat treatment as above with regards to Set
A) with composition, by weight 0.25% carbon, 1.20% manganese, 1.0%
chromium, 0.25% silicon, 0.03% niobium, 0.01% titanium, 0.001%
boron and 0.02% aluminum. [0153] Set C: Normalized and tempered
steels with several chemical compositions and strengths like those
typically found for steel sucker rod grades: [0154] Steel 4142M
with 0.42% carbon, 0.85% manganese, 1.0% chromium, 0.25% silicon,
0.2% molybdenum, and 0.02% aluminum. [0155] Steel 4330M with 0.30%
carbon, 0.80% manganese, 1.0% chromium, 0.25% silicon, 0.25%
molybdenum, 1.7% Ni, 0.05% V and 0.02% aluminum. [0156] Steel 4320M
with 0.20% carbon, 0.90% manganese, 0.8% chromium, 0.25% silicon,
0.25% molybdenum, 1.2% Ni, 0.05% V and 0.02% aluminum. [0157] Steel
4138M with 0.38% carbon, 1.20% manganese, 0.7% chromium, 0.25%
silicon, 0.3% molybdenum, 0.05% V and 0.02% aluminum.
[0158] FIG. 1 illustrates the correlation between corrosion-fatigue
resistance in harsh environments and impact toughness as determined
experimentally, and clearly shows the beneficial effect of material
toughness on corrosion-fatigue life. Furthermore, embodiments of
steel from this disclosure presents improved performance, both in
CO.sub.2 and H.sub.2S harsh environments. Advantageously, disclosed
herein are steels having a combination of an excellent toughness,
and a good corrosion and sulfide stress cracking resistance. In
fact, in some embodiments, steel rods of the present disclosure can
have approximately twice the average life of conventional sucker
rod materials in corrosion fatigue under CO.sub.2 or H.sub.2S
environments.
[0159] Specifically, the tests performed for FIG. 1 were carried
out in simulated production environments, at 10 bar of partial
pressure of CO.sub.2. A simulated formation water composition used
was 124 g/lt NaCl and 1.315 g/lt NaHCO.sub.3, with predicted pH at
test conditions of 5. The solution temperature was of 60.degree. C.
and the total pressure was 31 bar (reached using N.sub.2 high
purity) in all tests.
[0160] The tests in H.sub.2S were carried out in a buffering
solution (adjusted by addition of HCl or NaOH) with a pH of 4.5, at
1 bar of pressure of (1 bar of total pressure) and at room
temperature.
[0161] The maximum and minimum applied stresses were 47 Ksi and 12
Ksi respectively. The frequency of cycling was 20 cycles/min.
[0162] Further, it can be advantageous to improve the toughness of
the material, for example by means of a fine grained homogeneous
microstructure. FIG. 2 shows the effect of composition and heat
treatment on impact toughness measured as Charpy V-notch energy at
room temperature. As shown in FIG. 2, embodiments of the ultra-fine
grained steels of the present disclosure clearly show the better
performance at all the yield strengths.
[0163] Results showed a good correlation between toughness as
evaluated by Charpy V-notch energy at room temperature and
corrosion fatigue life in two different environments: a buffered
solution saturated with CO.sub.2 at high pressure and 60.degree.
C., and another buffered solution saturated with H.sub.2S at 1 bar
and room temperature (see FIG. 1). UFGS showed at least
approximately twice the average life of conventional sucker rod
materials (set C) in corrosion fatigue under CO.sub.2 or H.sub.2S
environments.
[0164] A remarkable improvement in toughness was achieved with the
proper heat treatment, i.e., with the UFGS as compared with the
other sets of steels. The chemical composition proves to have the
desirable hardenability, necessary to attain a martensitic
transformation. Furthermore, the alloy addition also was adequate
to hit a high tempering temperature, reducing the dislocation
density while keeping a high tensile strength. UFGS presented at
least 10% more absorbed energy for the same strength (FIG. 2) than
conventionally batch treated steels (set A), at least 20% more
compared with other quenched and tempered steels (set B) and huge
differences as compared with normalized and tempered steels (set
C).
[0165] FIG. 4 presents the effect of austenitizing temperature on
grain size for different steel compositions and heat treatment
methods. As shown, the UFGS is stable within a wide range of
temperatures. This behavior is very advantageous from the point of
view of manufacturing process, allowing a better control. Further,
as can be observed in FIG. 4, there is not a big influence of
temperature on grain size within the range 880-960.degree. C.
[0166] FIG. 5 shows the effect of composition and heat treatment on
fatigue life in air. The steels of the embodiments of the present
disclosure have a better performance than conventional sucker rod
steels. Accordingly, even in the absence of harsh environments,
embodiments of the disclosed steel can have better, or at least the
same, performance than a conventional sucker rod.
[0167] FIG. 6 presents the effect of composition and heat treatment
on sulfide stress cracking (SSC) performance. The steels of the
embodiments of the present disclosure have an excellent behavior in
static tests under wet hydrogen sulfide environments. This is again
a consequence of the proper microstructure in terms of martensite
content, grain size, carbide size, shape and distribution, and
dislocation density.
[0168] From the foregoing description, it will be appreciated that
an inventive corrosion resistant steels are disclosed. While
several components, techniques and aspects have been described with
a certain degree of particularity, it is manifest that many changes
can be made in the specific designs, constructions and methodology
herein above described without departing from the spirit and scope
of this disclosure.
[0169] Certain features that are described in this disclosure in
the context of separate implementations can also be implemented in
combination in a single implementation. Conversely, various
features that are described in the context of a single
implementation can also be implemented in multiple implementations
separately or in any suitable subcombination. Moreover, although
features may be described above as acting in certain combinations,
one or more features from a claimed combination can, in some cases,
be excised from the combination, and the combination may be claimed
as any subcombination or variation of any subcombination.
[0170] Moreover, while methods may be depicted in the drawings or
described in the specification in a particular order, such methods
need not be performed in the particular order shown or in
sequential order, and that all methods need not be performed, to
achieve desirable results. Other methods that are not depicted or
described can be incorporated in the example methods and processes.
For example, one or more additional methods can be performed
before, after, simultaneously, or between any of the described
methods. Further, the methods may be rearranged or reordered in
other implementations. Also, the separation of various system
components in the implementations described above should not be
understood as requiring such separation in all implementations, and
it should be understood that the described components and systems
can generally be integrated together in a single product or
packaged into multiple products. Additionally, other
implementations are within the scope of this disclosure.
[0171] Conditional language, such as "can," "could," "might," or
"may," unless specifically stated otherwise, or otherwise
understood within the context as used, is generally intended to
convey that certain embodiments include or do not include, certain
features, elements, and/or steps. Thus, such conditional language
is not generally intended to imply that features, elements, and/or
steps are in any way required for one or more embodiments.
[0172] Conjunctive language such as the phrase "at least one of X,
Y, and Z," unless specifically stated otherwise, is otherwise
understood with the context as used in general to convey that an
item, term, etc. may be either X, Y, or Z. Thus, such conjunctive
language is not generally intended to imply that certain
embodiments require the presence of at least one of X, at least one
of Y, and at least one of Z.
[0173] Language of degree used herein, such as the terms
"approximately," "about," "generally," and "substantially" as used
herein represent a value, amount, or characteristic close to the
stated value, amount, or characteristic that still performs a
desired function or achieves a desired result. For example, the
terms "approximately", "about", "generally," and "substantially"
may refer to an amount that is within less than or equal to 10% of,
within less than or equal to 5% of, within less than or equal to 1%
of, within less than or equal to 0.1% of, and within less than or
equal to 0.01% of the stated amount.
[0174] Some embodiments have been described in connection with the
accompanying drawings. The figures are drawn to scale, but such
scale should not be limiting, since dimensions and proportions
other than what are shown are contemplated and are within the scope
of the disclosed inventions. Distances, angles, etc. are merely
illustrative and do not necessarily bear an exact relationship to
actual dimensions and layout of the devices illustrated. Components
can be added, removed, and/or rearranged. Further, the disclosure
herein of any particular feature, aspect, method, property,
characteristic, quality, attribute, element, or the like in
connection with various embodiments can be used in all other
embodiments set forth herein. Additionally, it will be recognized
that any methods described herein may be practiced using any device
suitable for performing the recited steps.
[0175] While a number of embodiments and variations thereof have
been described in detail, other modifications and methods of using
the same will be apparent to those of skill in the art.
Accordingly, it should be understood that various applications,
modifications, materials, and substitutions can be made of
equivalents without departing from the unique and inventive
disclosure herein or the scope of the claims.
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