U.S. patent application number 12/087797 was filed with the patent office on 2010-07-15 for cast iron comprising cobalt and component.
This patent application is currently assigned to SIEMENS AKTIENGESELLSCHAFT. Invention is credited to Stefan Janssen, Shilun Sheng.
Application Number | 20100178192 12/087797 |
Document ID | / |
Family ID | 36384290 |
Filed Date | 2010-07-15 |
United States Patent
Application |
20100178192 |
Kind Code |
A1 |
Janssen; Stefan ; et
al. |
July 15, 2010 |
Cast Iron Comprising Cobalt and Component
Abstract
Cast iron alloys have application limits with regard to
temperature. By means of the use of cobalt an optimal ferritic
structure can be achieved such that with an alloy containing
silicon 2.0-4.5 wt. %, cobalt 0.5-5 wt. %, carbon 2.5-4 wt. %,
molybdenum.ltoreq.1 wt. %, manganese.ltoreq.0.25 wt. %,
nickel.ltoreq.0.3 wt. %, the remainder iron where the proportion of
silicon cobalt and molybdenum is less than 7.5 wt. % the
application limits are shifted to higher temperatures.
Inventors: |
Janssen; Stefan; (Essen,
DE) ; Sheng; Shilun; (Oberhausen, DE) |
Correspondence
Address: |
SIEMENS CORPORATION;INTELLECTUAL PROPERTY DEPARTMENT
170 WOOD AVENUE SOUTH
ISELIN
NJ
08830
US
|
Assignee: |
SIEMENS AKTIENGESELLSCHAFT
Munchen
DE
|
Family ID: |
36384290 |
Appl. No.: |
12/087797 |
Filed: |
January 3, 2007 |
PCT Filed: |
January 3, 2007 |
PCT NO: |
PCT/EP2006/050057 |
371 Date: |
July 15, 2008 |
Current U.S.
Class: |
420/27 ; 420/13;
420/9 |
Current CPC
Class: |
C22C 37/10 20130101;
C22C 37/04 20130101 |
Class at
Publication: |
420/27 ; 420/9;
420/13 |
International
Class: |
C22C 37/00 20060101
C22C037/00; C22C 37/10 20060101 C22C037/10 |
Foreign Application Data
Date |
Code |
Application Number |
Jan 16, 2006 |
EP |
06000851.3 |
Claims
1-35. (canceled)
36. An alloy comprising in wt %: TABLE-US-00006 silicon 2.0%-4.5%;
cobalt 0.5%-5%; carbon 2.0%-4.5%; molybdenum .ltoreq.1.5%;
manganese .ltoreq.0.25%; nickel .ltoreq.0.5%; and iron.
37. The alloy as claimed in claim 36, wherein the proportion of
silicon, cobalt and molybdenum is less than 7.5 wt %.
38. The alloy as claimed in claim 36, comprising from 1.0 wt % to
2.0 wt % cobalt.
39. The alloy as claimed in claim 36, further comprising
molybdenum.
40. The alloy as claimed in claim 36, free of molybdenum.
41. The alloy as claimed in claim 36, further comprising
manganese.
42. The alloy as claimed in claim 41, wherein the manganese content
is .ltoreq.0.07 wt %.
43. The alloy as claimed in claim 36, free of manganese.
44. The alloy as claimed in claim 36, further comprising
nickel.
45. The alloy as claimed in claim 36, free of nickel.
46. The alloy as claimed in claim 36, further comprising 2.0 wt
%-3.0 wt % silicon.
47. The alloy as claimed in claim 36, further comprising from 3.5
wt % to 4.0 wt % carbon.
48. The alloy as claimed in claim 36, further comprising at most
0.07 wt % phosphorus.
49. The alloy as claimed in claim 36, further comprising at most
0.008 wt % sulfur.
50. The alloy as claimed in claim 36, further comprising at most
0.05 wt % magnesium.
51. The alloy as claimed in claim 36, free of chromium.
52. The alloy as claimed in claim 36, free of magnesium.
53. The alloy as claimed in claim 36, consisting of iron, silicon,
cobalt and carbon.
54. The alloy as claimed in claim 36, consisting of iron, silicon,
cobalt, carbon and manganese.
55. A housing part, comprising an alloy having iron and in wt %:
TABLE-US-00007 silicon 2.0%-4.5%; cobalt 0.5%-5%; carbon 2.0%-4.5%;
molybdenum .ltoreq.1.5%; manganese .ltoreq.0.25%; nickel
.ltoreq.0.5%.
56. A component, comprising an alloy having iron and in wt %:
TABLE-US-00008 silicon 2.0%-4.5%; cobalt 0.5%-5%; carbon 2.0%-4.5%;
molybdenum .ltoreq.1.5%; manganese .ltoreq.0.25%; nickel
.ltoreq.0.5%,
wherein the component is a steam turbine or a gas turbine.
57. The component as claimed in claim 56, a substrate which is
iron-based or steel-based.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application is the US National Stage of International
Application No. PCT/EP2007/050057, filed Jan. 3, 2007 and claims
the benefit thereof. The International Application claims the
benefits of European Patent Office application No. 06000851.3 EP
filed Jan. 16, 2006, both of the applications are incorporated by
reference herein in their entirety.
FIELD OF INVENTION
[0002] The invention relates to an alloy, a cast iron comprising
cobalt and a component thereof.
BACKGROUND OF INVENTION
[0003] The known cast iron alloys now employed (so-called GJS
spherocast alloys) primarily use silicon and molybdenum to increase
the creep strength, scaling resistance and endurance strength. Over
time, however, these elements lead to a significant decrease in the
ductility.
[0004] Molybdenum furthermore exhibits a very high susceptibility
to segregation.
SUMMARY OF INVENTION
[0005] It is therefore an object of the invention to provide an
alloy and a component, which overcome the aforementioned
disadvantages and have better mechanical strengths over the service
life.
[0006] The object is achieved by an alloy as claimed in an
independent claim and e.g. by a component as claimed in a further
independent claim.
[0007] Further advantageous measures are listed in the dependent
claims, and these may advantageously be combined with one another
in any desired way.
[0008] The invention consists in cobalt partially or fully
replacing molybdenum. The working limitations presented by the
previous GJS alloy can therefore be overcome. The alloy according
to the invention has high elongations for the application field in
the temperature range of 450.degree. C.-550.degree. C., and has the
following composition (in wt %):
TABLE-US-00001 silicon 2.0%-4.5% cobalt 0.5%-5% carbon 2.0%-4.5%,
in particular 2.5%-4%, molybdenum <1.5%, in particular
.ltoreq.1.0%, manganese <0.5%, in particular .ltoreq.0.25%,
nickel <0.5%, in particular .ltoreq.0.3%, remainder iron.
[0009] Advantageously, the proportion of silicon, cobalt and
molybdenum is less than 7.5 wt %.
[0010] Preferably, the proportion of cobalt in the alloy lies
between 0.5 and 1.5 wt % cobalt.
[0011] Advantageous mechanical values are achieved for the alloy
respectively when the cobalt content is 0.5 wt %, with 1 wt %
cobalt, with 1.5 wt % cobalt and 2.0 wt % cobalt.
[0012] The alloy may contain further elements. Preferably, however,
the alloy consists of iron, silicon, cobalt and carbon.
[0013] Particular advantages are also achieved when the alloy
consists of iron, silicon, cobalt, carbon and manganese.
[0014] Further advantages are obtained with an alloy which consists
of iron, silicon, cobalt, carbon and optionally admixtures of
molybdenum, manganese and/or nickel.
[0015] The alloy may optionally contain undesired impurities of at
most
TABLE-US-00002 phosphorus 0.007 wt % sulfur 0.008 wt % magnesium
0.049 wt %.
[0016] Furthermore, there is preferably no chromium (Cr) in the
alloy except for the usual impurities.
[0017] Likewise, there is preferably no magnesium (Mg) in the alloy
except for the usual impurities.
BRIEF DESCRIPTION OF THE DRAWINGS
[0018] Embodiments of the invention will be explained in more
detail with the aid of the following figures, in which:
TABLE-US-00003 [0019] FIG. 1 shows a micrograph, FIG. 2 shows
mechanical characteristics, FIG. 3 shows a steam turbine, FIG. 4
shows a gas turbine.
DETAILED DESCRIPTION OF INVENTION
[0020] FIG. 1 shows an almost optimal ferritic structure (etched)
with spherical graphite made of an alloy with about 2 wt %
cobalt:
TABLE-US-00004 carbon 3.67 wt %, molybdenum 2.41 wt %, manganese
0.029 wt %, nickel 1.94 wt %, iron remainder.
[0021] FIG. 2 shows the influence of cobalt on the mechanical
properties of the alloys, which are listed in the following table
(data in wt %).
TABLE-US-00005 cobalt 0 0.54 1.04 1.94 carbon 3.63 3.61 3.68 3.67
silicon 2.45 2.44 2.47 2.41 manganese 0.067 0.036 0.03 0.029
phosphorus 0.007 0.006 0.007 0.007 Sulfur 0.009 0.006 0.008 0.008
Magnesium 0.044 0.04 0.05 0.049
[0022] The elongation at break R.sub.p02 increases from 271
N/mm.sup.2 to 284 N/mm.sup.2.
The tensile strength Rm increases from 403 N/mm.sup.2 to 412
N/mm.sup.2. The elongation at break A5 increases from 15.5% to
21.9%. Likewise, the necking at fracture Z increases from 13.8% to
29.5%.
[0023] Even small proportions of cobalt (0.5 wt % to 1.0 wt % or
1.0 wt % to 1.5 wt %) improve the mechanical characteristics.
[0024] FIG. 3 shows a steam turbine 300, 303 having a turbine shaft
309 extending along a rotation axis 306.
[0025] The steam turbine comprises a high-pressure turbine part 300
and a medium-pressure turbine part 303, each with an inner housing
312 and an outer housing 315 enclosing the latter. The
high-pressure turbine part 300 is, for example, configured in pot
design. The medium-pressure turbine part 303 is, for example,
configured to be twin-streamed. It is likewise possible for the
medium-pressure turbine part 303 to be configured to be
single-streamed.
[0026] A bearing 318 is arranged along the rotation axis 306
between the high-pressure turbine part 300 and the medium-pressure
turbine part 303, the turbine shaft 309 comprising a bearing region
321 in the bearing 318. The turbine shaft 309 is mounted on a
further bearing 324 beside the high-pressure turbine part 300. In
the region of this bearing 324, the high-pressure turbine part 300
comprises a shaft seal 345. The turbine shaft 309 is sealed
relative to the outer housing 315 of the medium-pressure turbine
part 303 by two further shaft seals 345. Between a high-pressure
steam intake region 348 and a steam outlet region 351, the turbine
shaft 309 in the high-pressure turbine part 300 comprises the
high-pressure rotor blading 357. With the associated rotor blades
(not represented in detail), this high-pressure rotor blading 357
constitutes a first blading region 360.
[0027] The medium-pressure turbine part 303 comprises a central
steam intake region 333. Associated with the steam intake region
333, the turbine shaft 309 comprises a radially symmetric shaft
shield 363, a cover plate, on the one hand to divide the steam flow
into the two streams of the medium-pressure turbine part 303 and
also to prevent direct contact of the hot steam with the turbine
shaft 309. In the medium-pressure turbine part 303, the turbine
shaft 309 comprises a second blading region 366 with the
medium-pressure rotor blades 354. The hot steam flowing through the
second blading region 366 flows from the medium-pressure turbine
part 303 out of a discharge port 369 to a low-pressure turbine part
(not shown) connected downstream.
[0028] The turbine shaft 309 is composed for example of two turbine
shaft parts 309a and 309b, which are connected firmly to one
another in the region of the bearing 318. Each turbine shaft part
309a and 309b comprises a cooling line 372 formed as a central bore
372a along the rotation axis 306. The cooling line 372 is connected
to the steam outlet region 351 via a feed line 375 comprising a
radial bore 375a. In the medium-pressure turbine part 303, the
coolant line 372 is connected to a cavity (not shown) below the
shaft shield. The feed lines 375 are configured as a radial bore
375a, so that "cold" steam from the high-pressure turbine part 300
can flow into the central bore 372a. Via the discharge line 372
also formed in particular as a radially directed bore 375a, the
steam passes through the bearing region 321 into the
medium-pressure turbine part 333 and there onto the lateral surface
330 of the turbine shaft 309 in the steam intake region 333. The
steam flowing through the cooling line is at a much lower
temperature than the temporarily superheated steam flowing into the
steam intake region 333, so as to ensure effective cooling of the
first rotor blade row 342 of the medium-pressure turbine part 303
and the lateral surface 330 in the region of this rotor blade row
342.
[0029] FIG. 4 shows a gas turbine 100 by way of example in a
partial longitudinal section.
[0030] The gas turbine 100 internally comprises a rotor 103, which
will also be referred to as the turbine rotor, mounted so as to
rotate about a rotation axis 102 and having a shaft 101.
[0031] Successively along the rotor 103, there are an intake
manifold 104, a compressor 105, an e.g. toroidal combustion chamber
110, in particular a ring combustion chamber, having a plurality of
burners 107 arranged coaxially, a turbine 108 and the exhaust
manifold 109.
[0032] The ring combustion chamber 110 communicates with an e.g.
annular hot gas channel 111. There, for example, four successively
connected turbine stages 112 form the turbine 108.
[0033] Each turbine stage 112 is formed for example by two blade
rings. As seen in the flow direction of a working medium 113, a
guide vane row 115 is followed in the hot gas channel 111 by a row
125 formed by rotor blades 120.
[0034] The guide vanes 130 are fastened on an inner housing 138 of
a stator 143 while the rotor blades 120 of a row 125 are fastened
on the rotor 103, for example by means of a turbine disk 133.
[0035] Coupled to the rotor 103, there is a generator or a work
engine (not shown).
[0036] During operation of the gas turbine 100, air 135 is taken in
and compressed by the compressor 105 through the intake manifold
104. The compressed air provided at the end of the compressor 105
on the turbine side is delivered to the burners 107 and mixed there
with a fuel. The mixture is then burnt to form the working medium
113 in the combustion chamber 110. From there, the working medium
113 flows along the hot gas channel 111 past the guide vanes 130
and the rotor blades 120. At the rotor blades 120, the working
medium 113 expands by imparting momentum, so that the rotor blades
120 drive the rotor 103 and the work engine coupled to it.
[0037] During operation of the gas turbine 100, the components
exposed to the hot working medium 113 experience thermal loads.
Apart from the heat shield elements lining the ring combustion
chamber 110, the guide vanes 130 and rotor blades 120 of the first
turbine stage 112, as seen in the flow direction of the working
medium 113, are heated the most.
[0038] In order to withstand the temperatures prevailing there,
they may be cooled by means of a coolant.
[0039] Substrates of the components may likewise comprise a
directional structure, i.e. they are monocrystalline (SX structure)
or comprise only longitudinally directed grains (DS structure).
[0040] Iron-, nickel- or cobalt-based superalloys are for example
used as material for the components, in particular for the turbine
blades 120, 130 and components of the combustion chamber 110.
[0041] Such superalloys are known for example from EP 1 204 776 B1,
EP 1 306 454, EP 1 319 729 A1, WO 99/67435 or WO 00/44949; with
respect to the chemical composition of the alloys, these documents
are part of the disclosure.
[0042] The blades 120, 130 may likewise have coatings against
corrosion (MCrAlX; M is at least one element from the group iron
(Fe), cobalt (Co), nickel (Ni), X is an active element and stands
for yttrium (Y) and/or silicon, scandium (Sc) and/or at least one
rare earth element, or hafnium). Such alloys are known from EP 0
486 489 B1, EP 0 786 017 B1, EP 0 412 397 B1 or EP 1 306 454 A1
which, with respect to the chemical composition, are intended to be
part of this disclosure.
[0043] On the MCrAlX, there may furthermore be a thermal barrier
layer which consists for example of ZrO.sub.2,
Y.sub.2O.sub.3--ZrO.sub.2, i.e. it is not stabilized or is
partially or fully stabilized by yttrium oxide and/or calcium oxide
and/or magnesium oxide.
[0044] Rod-shaped grains are produced in the thermal barrier layer
by suitable coating methods, for example electron beam deposition
(EB-PVD).
[0045] The guide vane 130 comprises a guide vane root (not shown
here) facing the inner housing 138 of the turbine 108, and a guide
vane head lying opposite the guide vane root. The guide vane head
faces the rotor 103 and is fixed on a fastening ring 140 of the
stator 143.
* * * * *