U.S. patent application number 13/898720 was filed with the patent office on 2014-11-27 for martensitic alloy component and process of forming a martensitic alloy component.
This patent application is currently assigned to GENERAL ELECTRIC COMPANY. The applicant listed for this patent is GENERAL ELECTRIC COMPANY. Invention is credited to Ted F. MAJKA, Jeremy RIDGE, John Randolph WOOD.
Application Number | 20140345756 13/898720 |
Document ID | / |
Family ID | 50828698 |
Filed Date | 2014-11-27 |
United States Patent
Application |
20140345756 |
Kind Code |
A1 |
RIDGE; Jeremy ; et
al. |
November 27, 2014 |
MARTENSITIC ALLOY COMPONENT AND PROCESS OF FORMING A MARTENSITIC
ALLOY COMPONENT
Abstract
A reduced nickel-chromium alloy component having by weight about
0.38% to about 0.43% C, about 0.15% to about 0.30% Si, about 1.00%
to about 1.25% Mn, about 0.75% to about 0.90% Ni, about 1.00% to
about 1.30% Cr, about 0.25% to about 0.35% Mo, about 0.05% to about
0.12% V, up to about 0.015% S, up to about 0.015% P, up to about
0.15% Cu, and balance iron and incidental impurities. The component
has a hardenability corresponding to an ideal diameter of greater
than about 10 inches.
Inventors: |
RIDGE; Jeremy; (Greenville,
SC) ; MAJKA; Ted F.; (Greenville, SC) ; WOOD;
John Randolph; (Greer, SC) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
GENERAL ELECTRIC COMPANY |
Schenectady |
NY |
US |
|
|
Assignee: |
GENERAL ELECTRIC COMPANY
Schenectady
NY
|
Family ID: |
50828698 |
Appl. No.: |
13/898720 |
Filed: |
May 21, 2013 |
Current U.S.
Class: |
148/598 ;
148/332; 148/335; 148/649 |
Current CPC
Class: |
C22C 38/00 20130101;
C22C 38/04 20130101; C22C 38/44 20130101; C21D 8/065 20130101; C22C
38/42 20130101; Y02E 10/72 20130101; C22C 38/02 20130101; C21D 1/55
20130101; C22C 38/46 20130101 |
Class at
Publication: |
148/598 ;
148/649; 148/335; 148/332 |
International
Class: |
C22C 38/46 20060101
C22C038/46; C22C 38/02 20060101 C22C038/02; C22C 38/42 20060101
C22C038/42; C22C 38/04 20060101 C22C038/04; C21D 8/06 20060101
C21D008/06; C22C 38/44 20060101 C22C038/44 |
Claims
1. A martensitic alloy component, comprising by weight: about 0.38%
to about 0.43% C; about 0.15% to about 0.30% Si; about 1.00% to
about 1.25% Mn; about 0.75% to about 0.90% Ni; about 1.00% to about
1.30% Cr; about 0.25% to about 0.35% Mo; about 0.05% to about 0.12%
V; up to about 0.015% S; up to about 0.015% P; up to about 0.15%
Cu; and balance iron and incidental impurities; wherein the
component has a hardenability corresponding to an ideal diameter of
greater than about 10 inches.
2. The martensitic alloy component of claim 1, wherein the
component comprises about 1.05 to about 1.25% Mn.
3. The martensitic alloy component of claim 1, wherein the
component comprises about 1.15% Mn.
4. The martensitic alloy component of claim 1, wherein the
component has a hardenability corresponding to an ideal diameter of
from about 10 inches to about 18 inches.
5. The martensitic alloy component of claim 2, wherein the
component has a hardenability corresponding to an ideal diameter of
from about 11 inches to about 12 inches.
6. The martensitic alloy component of claim 3, wherein the
component has a hardenability corresponding to an ideal diameter of
about 11.4 inches.
7. The martensitic alloy component of claim 2, wherein the
component has a hardenability corresponding to an ideal diameter of
from about 13 inches to about 14 inches.
8. The martensitic alloy component of claim 5, wherein the
component has a hardenability corresponding to an ideal diameter of
about 13.3 inches.
9. The martensitic alloy component of claim 1, further comprising a
fracture apparent transition temperature at a surface of the
component of less than -40.degree. C.
10. The martensitic alloy component of claim 1, further comprising
a fracture apparent transition temperature at a maximum thickness
of the component of less than 30 .degree. C.
11. The martensitic alloy component of claim 1, wherein the
martensitic alloy component has a average grain size of less than
about 62 .mu.m.
12. The martensitic alloy component of claim 1, wherein the
martensitic alloy component has a yield strength at a surface of
the component of greater than about 650 MPa.
13. The martensitic alloy component of claim 1, wherein the
martensitic alloy component has a tensile strength at a surface of
the component of between about 800 and about 1,000 MPa.
14. The martensitic alloy component of claim 1, wherein the
component has a thickness of greater than 20 inches.
15. The martensitic alloy component of claim 1, wherein the
component is a wind turbine shaft.
16. The martensitic alloy component of claim 13, wherein the wind
turbine shaft has at least one solid segment.
17. The martensitic alloy component of claim 13, wherein the wind
turbine shaft has at least one hollow segment.
18. A process of forming a martensitic alloy component, the process
comprising: forging an alloy comprising by weight: about 0.38% to
about 0.43% C; about 0.15% to about 0.30% Si; about 1.00% to about
1.25% Mn; about 0.75% to about 0.90% Ni; about 1.00% to about 1.30%
Cr; about 0.25% to about 0.35% Mo; about 0.05% to about 0.12% V; up
to about 0.015% S; up to about 0.015% P; up to about 0.15% Cu; and
balance iron and incidental impurities; austenitizing the forged
alloy; quenching the austenitized alloy; and tempering the quenched
alloy; wherein the component has a hardenability corresponding to
an ideal diameter of greater than about 10 inches.
19. The process of claim 18, wherein the component has a thickness
of greater than 20 inches.
20. The process of claim 18, wherein the component is a wind
turbine shaft.
Description
FIELD OF THE INVENTION
[0001] The present invention is directed to martensitic alloys,
articles including martensitic alloys, and processes of forming
alloys. More specifically, the present invention is directed to a
reduced nickel-chromium martensitic alloy and a process of forming
a reduced nickel-chromium martensitic alloy.
BACKGROUND OF THE INVENTION
[0002] Wind turbines are exposed to significant operational
stresses from wind, rotational forces and the weight of a plurality
of blades. The operational stresses are often amplified by
environmental temperatures with extremes depending on geographical
location. The materials used for the components of the wind
turbines must be able to withstand operating stresses and strains
throughout the range of temperatures.
[0003] Wind turbines have a main shaft that transmits power from a
rotor to a generator. As wind turbines increase their outputs from
1.5 and 2.5 megawatts (MW) to 3, 4, 5, and 6 MW, the size and
required properties of the wind turbine drive shaft increases. In
addition, the loads from gearbox components, such as planet gear
carriers, are typically too high for conventional ductile iron
grades (ferritic/pearlitic grades). Forged/hardened steel is the
material of choice for gearbox components and drive shafts having
sizes greater than 3 tons. This shaft is typically machined out of
a steel forging. The material of the shaft is usually
quenched-tempered high-strength low-alloy steel with critical
fatigue properties. A common alloy currently used for these large
wind turbine components is 34CrNiMo6 steel. The nickel and chromium
provide a desirable hardenability of the alloy. Although 34CrNiMo6
steel provides desired hardenability and fracture appearance
transition temperature (FATT), the nickel and chromium used in
34CrNiMo6 steel is expensive, increasing the price of wind turbines
and replacement shafts.
[0004] A desired feature for wind turbine components is a FATT of
-40.degree. C. (-40.degree. F.). The FATT is the temperature at
which the fracture surface of a material is 50% low energy brittle
cleavage and 50% high energy ductile fibrous. Both a composition of
the material as well as the processes for forming and heat treating
the material affect FATT. FATT is important because it represents
the temperature above which brittle fracture will not occur. The
lower the FATT, the greater the toughness of the material.
[0005] Martensitic stainless steels, such as 34 CrNiMo6 steel,
having excellent strength, low brittle to ductile transition
temperature, and good hardening characteristics in thick sections
have long been used as turbine shaft materials. Decreasing the
amount of Ni and Cr in the alloy decreases the hardenability, which
reduces the amount of martensite that forms in the material.
Reducing the amount of martensite has the undesirable consequence
of increasing the FATT of the material.
[0006] A martensitic alloy and a method of forming an inexpensive
martensitic alloy having reduced amounts of nickel and chromium and
not suffering from the above drawbacks would be desirable in the
art.
BRIEF DESCRIPTION OF THE INVENTION
[0007] In an exemplary embodiment of the present disclosure, a
martensitic alloy component includes by weight: [0008] about 0.38%
to about 0.43% C; [0009] about 0.15% to about 0.30% Si; [0010]
about 1.00% to about 1.25% Mn; [0011] about 0.75% to about 0.90%
Ni; [0012] about 1.00% to about 1.30% Cr; [0013] about 0.25% to
about 0.35% Mo; [0014] about 0.05% to about 0.12% V; [0015] up to
about 0.015% S; [0016] up to about 0.015% P; [0017] up to about
0.15% Cu; and [0018] balance iron and incidental impurities. The
component has a hardenability corresponding to an ideal diameter of
greater than about 10 inches (25.4 cm).
[0019] In another embodiment of the present disclosure, a process
of forming a reduced nickel-chromium martensitic alloy component
includes forging the reduced nickel-chromium alloy component
including by weight: [0020] about 0.38% to about 0.43% C; [0021]
about 0.15% to about 0.30% Si; [0022] about 1.00% to about 1.25%
Mn; [0023] about 0.75% to about 0.90% Ni; [0024] about 1.00% to
about 1.30% Cr; [0025] about 0.25% to about 0.35% Mo; [0026] about
0.05% to about 0.12% V; [0027] up to about 0.015% S; [0028] up to
about 0.015% P; [0029] up to about 0.15% Cu; and [0030] balance
iron and incidental impurities. After forging, the reduced
nickel-chromium martensitic alloy component is austenitized,
quenched and tempered. The tempered forged alloy has a
hardenability corresponding to an ideal diameter of greater than
about 10 inches (25.4 cm).
[0031] Other features and advantages of the present invention will
be apparent from the following more detailed description of the
preferred embodiment, taken in conjunction with the accompanying
drawings which illustrate, by way of example, the principles of the
invention.
DETAILED DESCRIPTION OF THE INVENTION
[0032] Provided is an exemplary reduced nickel-chromium alloy
component having a plurality of predetermined properties and a
process of forming the reduced nickel-chromium alloy component
having a plurality of predetermined properties. Embodiments of the
present disclosure, in comparison to methods and products not
utilizing one or more features disclosed herein, decrease nickel
percentage, decrease chromium percentage, increase carbon
percentage, increase manganese percentage, decrease material cost,
maintain or increase martensite percentage, maintain or decrease
fracture appearance transition temperature (FATT), or a combination
thereof.
[0033] In one embodiment, the disclosure includes a process for
producing the main shaft for a wind turbine from a martensitic
alloy, though it should be understood that the invention is also
well suited for the production of a wide variety of components from
martensitic alloy compositions. Other non-limiting examples include
automotive components, such as turbine shafts, axles, and various
other components used in the energy, automotive, railroad,
construction, mining and agricultural industries. Such components
are well known in the art and therefore require no further
description.
[0034] With reference to FIG. 1, the shaft 100 is represented as
having a tubular shape with a flange formed at one end, though it
can be appreciated that FIG. 1 is merely a schematic representation
and different configurations for the shaft 100 are also within the
scope of the invention. Although the shaft 100 shown in FIG. 1
includes a plurality of segments, the shaft 100 may also be formed
of a unitary piece. The shaft 100 may be solid or hollow or a
combination of solid and hollow components. The shaft 100 has an
axisymmetric geometry with respect to the longitudinal axis of
rotation of the shaft 100. For use in the wind turbine 10, the main
shaft 100 will have an outer diameter well in excess of 20 inches
(about 50 cm), and more typically in excess of 24 inches (about 60
cm), with a typical range being about 25 to 60 inches (about 63 to
about 152 cm), though lesser and greater diameters are also
foreseeable. Other aspects of the shaft 100, including its
installation in wind turbines and the operation of the wind
turbines, are otherwise known in the art, and therefore will not be
discussed here in any detail.
[0035] The martensitic alloy, according to the present disclosure,
includes the composition shown in Table 1.
TABLE-US-00001 TABLE 1 Broad Alternate Alternate wt % Range Range
Range C 0.38-0.43 0.38-0.43 0.39-0.41 Si 0.15-.030 0.15-.030
0.20-.025 Mn 1.00-1.25 1.05-1.25 1.10-1.17 Ni 0.75-0.90 0.75-0.90
0.78-0.85 Cr 1.00-1.30 1.00-1.30 1.10-1.20 Mo 0.25-0.35 0.25-0.35
0.27-0.32 V 0.05-0.12 0.05-0.12 0.07-0.11 S <0.015 <0.015
<0.015 P <0.015 <0.015 <0.015 Cu <0.15 <0.15
<0.15 Fe Bal Bal Bal
[0036] A component formed from the composition, according to the
present disclosure, includes a hardenability corresponding to an
ideal diameter of greater than about 10 inches (25.4 cm) or 10 to
18 inches (25.4 to 45.72 cm) or 11 to 12 inches (27.94 to 30.48 cm)
or 13 to 14 inches (33.02 to 35.56 cm) or any suitable combination,
sub-combination, range, or sub-range within. In one embodiment, the
component has a hardenability corresponding to an ideal diameter of
about 11.4 inches (28.96 cm). Hardenability corresponding to an
ideal diameter, as utilized herein, is the ability of material,
component, and heat treatment (e.g., after quench from an
austenitizing temperature), to form at least 50% martensite at the
center of a solid cylinder. While the above definition of
hardenability corresponding to an ideal diameter is based from a
solid component, one of ordinary skill in the art would understand
that the geometry is not limited to a solid cylinder and may
include other geometries and/or hollow components. For example, the
hardenability of hollow components corresponds to the corresponding
center depth within the material (e.g., the center of the wall) in
which at least 50% martensite forms after heat treatment.
[0037] The martensitic microstructure has increased material
toughness as compared to bainite and ferrite/pearlite
microstructures. Increasing the percentage of martensite in the
material microstructure will decrease the FATT of the material.
Increasing the ideal diameter of a material increases the amount of
martensite thus decreasing the FATT of the material in thicker
cross sections. A material at a temperature below the FATT will
have low fracture toughness and low damage tolerance. To form a
damage tolerant component, the operating temperature of the
component should be above the FATT.
[0038] In one embodiment, a component formed from the composition,
according to the present disclosure, includes a FATT at the surface
of less than -40.degree. F. (-40.degree. C.) or less than
-50.degree. F. (-45.6.degree. C.) or less than -60.degree. F.
(-51.1.degree. C.). In addition, the component includes a FATT of
less than 86.degree. F. (30.degree. C.) or less than 80.degree. F.
(26.7.degree. C.) or less than 75.degree. F. (23.9.degree. C.) at
the maximum thickness of the component.
[0039] In addition to increasing the ideal diameter, properties of
the material that decrease FATT include, but are not limited to,
increasing martensite percentage, decreasing grain size, decreasing
yield strength, or a combination thereof. In one embodiment, a
desired yield strength of the material is 650 MPa or greater or
about 650 MPa to about 1000 MPa and tensile strength between about
800 and about 1,000 MPa. In a further embodiment, the average grain
size of a material is formed during processing of the material, and
is maintained to about 62 .mu.m or less or about 50 .mu.m or less.
The FATT of the material having a defined yield strength range and
grain size range is adjusted through adjustments in microstructure.
In one embodiment, the microstructure is adjusted through increases
and/or decreases in concentrations of alloying elements. The
alloying elements include, but are not limited to, carbon, silicon,
manganese, nickel, chromium, molybdenum, vanadium, sulfur,
phosphorus, copper, or a combination thereof. In addition to
adjusting microstructure, increases and/or decreases in the
concentrations of the alloying elements adjust material strength,
toughness, ductility, grain size, or a combination thereof.
[0040] In one embodiment, the nickel concentration and the chromium
concentration are decreased and a carbon concentration and a
manganese concentration are increased. A hardenability of a
material is affected by the amount of each element present in the
material. The hardenability is the ease at which the material forms
a martensitic structure during quenching from an austenitizing
temperature. Increasing the carbon concentration and the manganese
concentration maintains or increases a hardenability of the
material. Increasing the hardenability of the material increases
the ideal diameter, which increases martensitic structure formation
and decreases the FATT in thick cross sections, thus providing for
increased damage tolerance.
[0041] An exemplary process for forming the component includes
forging of the component. After forging, the component is heat
treated through methods including, but not limited to,
austenitizing, quenching, tempering, or a combination thereof.
Austenitizing is the process of holding the martensitic alloy
forging above a critical temperature for a sufficient period of
time to ensure that the matrix is fully transformed to austenite.
In order to produce a single phase matrix microstructure
(austenite) with a uniform carbon distribution, austenitizing
includes holding the forging at temperatures greater than about
870.degree. C. (1598.degree. F.) for a time period that is
sufficient to fully convert the matrix of the thickest section to
austenite. Quenching from the austenitizing temperature forms a
martensite microstructure and may be accomplished with any suitable
quenching method known in the art. The rate of quench has to be
high enough to reduce or eliminate ferrite/pearlite formation.
Tempering is provided to increase the toughness and reduce the
brittleness of the component. Suitable tempering temperatures
include, but are not limited to, between about 550.degree. C.
(1022.degree. F.) and about 650.degree. C. (1202.degree. F.),
between about 580.degree. C. (1076.degree. F.) and about
620.degree. C. (1048.degree. F.), or about 600.degree. C.
(1112.degree. F.), or any combination, sub-combination, range, or
sub-range thereof.
EXAMPLES
Comparative Example 1
[0042] Comparative Example 1: The known composition of 34CrNiMo6
steel, a material known for use in wind turbine main shaft
manufacture, is shown below:
Comparative Ex. 1--34CrNiMo6
TABLE-US-00002 [0043] wt % Carbon 0.34 Silicon 0.2 Manganese 0.65
Nickel 1.5 Chromium 1.5 Molybdenum 0.23 Vanadium -- Iron
Balance
[0044] The nominal composition of Comparative Example 1 corresponds
to a hardenability corresponding to an ideal diameter of 7.4
inches.
Comparative Example 2
[0045] Comparative Example 2: A steel alloy composition having the
following composition:
Comparative Ex. 2
TABLE-US-00003 [0046] wt % wt % Carbon 0.26 Silicon 0.23 Manganese
1.00 Nickel 0.70 Chromium 1.10 Molybdenum 0.25 Vanadium 0.09 Sulfur
<0.015 Phosphorus <0.015 Copper <0.25 Iron Balance
[0047] The nominal composition of Comparative Example 2 has a
hardenability corresponding to an ideal diameter of 6.1 inches.
Example 1
[0048] Example 1: A martensitic alloy composition having the
following composition:
Example 1
TABLE-US-00004 [0049] Element wt % Carbon 0.35 Silicon 0.31
Manganese 1.12 Nickel 0.94 Chromium 1.31 Molybdenum 0.35 Vanadium
0.092 Sulfur 0.002 Phosphorus 0.014 Copper 0.06 Aluminum 0.004 Tin
0.004 Antimony 0.001 Arsenic 0.003 Iron Balance
[0050] A component, shown as Example 1, is formed from an exemplary
composition according to the present disclosure. The final product
includes a hardenability corresponding to an ideal diameter of 13.3
inches (33.78 cm).
Example 2
[0051] Example 2: A martensitic alloy composition having the
following composition:
Example 2
TABLE-US-00005 [0052] Element wt % Carbon 0.40 Silicon 0.23
Manganese 1.10 Nickel 0.80 Chromium 1.15 Molybdenum 0.30 Vanadium
0.09 Sulfur -- Phosphorus -- Copper -- Iron Balance
[0053] A component, shown as Example 2, is formed from an exemplary
composition according to the present disclosure. The final product
includes a hardenability corresponding to an ideal diameter of 12.4
inches (31.50 cm).
Example 3
[0054] Example 3: A martensitic alloy composition having the
following composition:
Example 3
TABLE-US-00006 [0055] Element wt % Carbon 0.43 Silicon 0.30
Manganese 1.25 Nickel 0.90 Chromium 1.30 Molybdenum 0.35 Vanadium
0.12 Iron Balance
[0056] A component, shown as Example 3, is formed from an exemplary
composition, according to the present disclosure. The final product
includes a hardenability corresponding to an ideal diameter of 17.3
inches (43.94 cm).
[0057] While the invention has been described with reference to a
preferred embodiment, it will be understood by those skilled in the
art that various changes may be made and equivalents may be
substituted for elements thereof without departing from the scope
of the invention. In addition, many modifications may be made to
adapt a particular situation or material to the teachings of the
invention without departing from the essential scope thereof.
Therefore, it is intended that the invention not be limited to the
particular embodiment disclosed as the best mode contemplated for
carrying out this invention, but that the invention will include
all embodiments falling within the scope of the appended
claims.
* * * * *