US20100322813A1 - SiMo DUCTILE IRON CASTINGS IN GAS TURBINE APPLICATIONS - Google Patents
SiMo DUCTILE IRON CASTINGS IN GAS TURBINE APPLICATIONS Download PDFInfo
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- US20100322813A1 US20100322813A1 US12/489,872 US48987209A US2010322813A1 US 20100322813 A1 US20100322813 A1 US 20100322813A1 US 48987209 A US48987209 A US 48987209A US 2010322813 A1 US2010322813 A1 US 2010322813A1
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- 229910001141 Ductile iron Inorganic materials 0.000 title claims abstract description 27
- 241001168730 Simo Species 0.000 title description 8
- RLQJEEJISHYWON-UHFFFAOYSA-N flonicamid Chemical compound FC(F)(F)C1=CC=NC=C1C(=O)NCC#N RLQJEEJISHYWON-UHFFFAOYSA-N 0.000 title 1
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 claims abstract description 28
- PXHVJJICTQNCMI-UHFFFAOYSA-N Nickel Chemical compound [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 claims abstract description 24
- 229910052750 molybdenum Inorganic materials 0.000 claims abstract description 18
- 229910052710 silicon Inorganic materials 0.000 claims abstract description 18
- ZOKXTWBITQBERF-UHFFFAOYSA-N Molybdenum Chemical compound [Mo] ZOKXTWBITQBERF-UHFFFAOYSA-N 0.000 claims abstract description 17
- 239000011733 molybdenum Substances 0.000 claims abstract description 17
- 239000010703 silicon Substances 0.000 claims abstract description 17
- 229910052742 iron Inorganic materials 0.000 claims abstract description 14
- 239000011777 magnesium Substances 0.000 claims abstract description 14
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims abstract description 13
- FYYHWMGAXLPEAU-UHFFFAOYSA-N Magnesium Chemical compound [Mg] FYYHWMGAXLPEAU-UHFFFAOYSA-N 0.000 claims abstract description 12
- 229910052749 magnesium Inorganic materials 0.000 claims abstract description 12
- 229910052759 nickel Inorganic materials 0.000 claims abstract description 12
- NINIDFKCEFEMDL-UHFFFAOYSA-N Sulfur Chemical compound [S] NINIDFKCEFEMDL-UHFFFAOYSA-N 0.000 claims abstract description 10
- 229910052799 carbon Inorganic materials 0.000 claims abstract description 10
- 239000011593 sulfur Substances 0.000 claims abstract description 10
- 229910052717 sulfur Inorganic materials 0.000 claims abstract description 10
- 238000004519 manufacturing process Methods 0.000 claims abstract description 7
- 238000000034 method Methods 0.000 claims description 18
- 239000000155 melt Substances 0.000 claims description 13
- 239000002054 inoculum Substances 0.000 claims description 10
- 229910045601 alloy Inorganic materials 0.000 claims description 9
- 239000000956 alloy Substances 0.000 claims description 9
- 238000005266 casting Methods 0.000 claims description 9
- VYZAMTAEIAYCRO-UHFFFAOYSA-N Chromium Chemical compound [Cr] VYZAMTAEIAYCRO-UHFFFAOYSA-N 0.000 claims description 5
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 claims description 5
- PWHULOQIROXLJO-UHFFFAOYSA-N Manganese Chemical compound [Mn] PWHULOQIROXLJO-UHFFFAOYSA-N 0.000 claims description 5
- ATJFFYVFTNAWJD-UHFFFAOYSA-N Tin Chemical compound [Sn] ATJFFYVFTNAWJD-UHFFFAOYSA-N 0.000 claims description 5
- RTAQQCXQSZGOHL-UHFFFAOYSA-N Titanium Chemical compound [Ti] RTAQQCXQSZGOHL-UHFFFAOYSA-N 0.000 claims description 5
- 229910052782 aluminium Inorganic materials 0.000 claims description 5
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 claims description 5
- 229910052804 chromium Inorganic materials 0.000 claims description 5
- 239000011651 chromium Substances 0.000 claims description 5
- 229910052802 copper Inorganic materials 0.000 claims description 5
- 239000010949 copper Substances 0.000 claims description 5
- BHEPBYXIRTUNPN-UHFFFAOYSA-N hydridophosphorus(.) (triplet) Chemical compound [PH] BHEPBYXIRTUNPN-UHFFFAOYSA-N 0.000 claims description 5
- 229910052748 manganese Inorganic materials 0.000 claims description 5
- 239000011572 manganese Substances 0.000 claims description 5
- 229910052718 tin Inorganic materials 0.000 claims description 5
- 239000010936 titanium Substances 0.000 claims description 5
- 229910052719 titanium Inorganic materials 0.000 claims description 5
- 229910052720 vanadium Inorganic materials 0.000 claims description 5
- LEONUFNNVUYDNQ-UHFFFAOYSA-N vanadium atom Chemical compound [V] LEONUFNNVUYDNQ-UHFFFAOYSA-N 0.000 claims description 5
- WFKWXMTUELFFGS-UHFFFAOYSA-N tungsten Chemical compound [W] WFKWXMTUELFFGS-UHFFFAOYSA-N 0.000 claims description 4
- 229910052721 tungsten Inorganic materials 0.000 claims description 4
- 239000010937 tungsten Substances 0.000 claims description 4
- OYPRJOBELJOOCE-UHFFFAOYSA-N Calcium Chemical compound [Ca] OYPRJOBELJOOCE-UHFFFAOYSA-N 0.000 claims description 2
- 229910000519 Ferrosilicon Inorganic materials 0.000 claims description 2
- 229910052791 calcium Inorganic materials 0.000 claims description 2
- 239000011575 calcium Substances 0.000 claims description 2
- 229910052732 germanium Inorganic materials 0.000 claims description 2
- GNPVGFCGXDBREM-UHFFFAOYSA-N germanium atom Chemical compound [Ge] GNPVGFCGXDBREM-UHFFFAOYSA-N 0.000 claims description 2
- 230000008018 melting Effects 0.000 claims description 2
- 238000002844 melting Methods 0.000 claims description 2
- 229910052761 rare earth metal Inorganic materials 0.000 claims description 2
- 229910052712 strontium Inorganic materials 0.000 claims description 2
- CIOAGBVUUVVLOB-UHFFFAOYSA-N strontium atom Chemical compound [Sr] CIOAGBVUUVVLOB-UHFFFAOYSA-N 0.000 claims description 2
- 238000000137 annealing Methods 0.000 claims 3
- 238000001816 cooling Methods 0.000 claims 2
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 description 13
- 235000000396 iron Nutrition 0.000 description 10
- 239000000463 material Substances 0.000 description 5
- 229910000831 Steel Inorganic materials 0.000 description 4
- 230000007423 decrease Effects 0.000 description 4
- 239000010959 steel Substances 0.000 description 4
- 229910000851 Alloy steel Inorganic materials 0.000 description 3
- 238000007792 addition Methods 0.000 description 3
- 229910002804 graphite Inorganic materials 0.000 description 3
- 239000010439 graphite Substances 0.000 description 3
- 238000011081 inoculation Methods 0.000 description 3
- 229910052751 metal Inorganic materials 0.000 description 3
- 239000002184 metal Substances 0.000 description 3
- 230000015572 biosynthetic process Effects 0.000 description 2
- 230000005496 eutectics Effects 0.000 description 2
- 238000010438 heat treatment Methods 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 230000008569 process Effects 0.000 description 2
- 238000007711 solidification Methods 0.000 description 2
- 230000008023 solidification Effects 0.000 description 2
- 229910001018 Cast iron Inorganic materials 0.000 description 1
- 229910052684 Cerium Inorganic materials 0.000 description 1
- 229910001182 Mo alloy Inorganic materials 0.000 description 1
- 239000001996 bearing alloy Substances 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- GWXLDORMOJMVQZ-UHFFFAOYSA-N cerium Chemical compound [Ce] GWXLDORMOJMVQZ-UHFFFAOYSA-N 0.000 description 1
- 238000005336 cracking Methods 0.000 description 1
- 230000001351 cycling effect Effects 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 239000007788 liquid Substances 0.000 description 1
- 238000011068 loading method Methods 0.000 description 1
- 238000005259 measurement Methods 0.000 description 1
- 150000002739 metals Chemical class 0.000 description 1
- 239000003607 modifier Substances 0.000 description 1
- 210000003739 neck Anatomy 0.000 description 1
- 230000006911 nucleation Effects 0.000 description 1
- 238000010899 nucleation Methods 0.000 description 1
- 239000000843 powder Substances 0.000 description 1
- 238000000638 solvent extraction Methods 0.000 description 1
- 238000011272 standard treatment Methods 0.000 description 1
- 230000007704 transition Effects 0.000 description 1
Images
Classifications
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C37/00—Cast-iron alloys
- C22C37/10—Cast-iron alloys containing aluminium or silicon
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
- C21D1/26—Methods of annealing
- C21D1/32—Soft annealing, e.g. spheroidising
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D5/00—Heat treatments of cast-iron
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C33/00—Making ferrous alloys
- C22C33/08—Making cast-iron alloys
Definitions
- the invention relates to ductile iron for use in gas turbines that provides cost benefits and improved supplier choices.
- gas turbine casings operating at elevated temperatures are restricted to alloy steel castings or fabrications. Gas turbines must endure unsteady operation to cover peak loads. This places thermal and mechanical stresses on the gas turbine components. Therefore, gas turbine casings must be able to withstand high temperature environments and repeated temperature cycling. The strength of the gas turbine casing material at high temperatures must be high.
- alloy steel castings for gas turbine casings meet these requirements; however, gas turbine casings of alloy steel are expensive to manufacture and there are a limited number of suppliers.
- Embodiments of the invention include a ductile iron gas turbine casing wherein the ductile iron includes carbon from about 2.8 to 3.7 w/o, silicon from about 3.0 to 3.5 w/o, molybdenum from about 0.8 to 1.5 w/o, magnesium from about 0.025 to 0.60 w/o, sulfur less than about 0.01 w/o and nickel from about 0.0 to 1.3 w/o, the remaining content being iron.
- Embodiments of the present invention also include a ductile iron gas turbine casing wherein the ductile iron includes carbon from about 2.8 to 3.7 w/o, silicon from about 3.0 to 3.5 w/o, molybdenum from about 0.8 to 1.5 w/o, magnesium from about 0.025 to 0.60 w/o, sulfur less than 0.01 w/o, nickel from about 0.0 to 1.3 w/o, phosphorous less than 0.05 w/o, titanium less than 0.05 w/o, vanadium less than about 0.05 w/o, tin less than 0.05 w/o, aluminum less than about 0.10 w/o, copper less than about 0.10 w/o, chromium less than about 0.10 w/o and manganese at less than about 0.15 w/o, the remaining content being iron.
- the ductile iron includes carbon from about 2.8 to 3.7 w/o, silicon from about 3.0 to 3.5 w/o, molybdenum from about 0.8 to
- Embodiments of the present invention also include a method of manufacturing a component.
- the method includes melting ductile iron that includes carbon, silicon, magnesium, sulfur and nickel, the remaining content being iron to form a melt.
- Inoculants and treatment alloys are added to the melt.
- Molybdenum is added to the melt.
- the melt is cast to form the component.
- the component includes carbon from about 2.8 to 3.7 weight percent, silicon from about 3.0 to 3.5 weight percent, molybdenum from about 0.8 to 1.5 weight percent, magnesium from about 0.025 to 0.60 weight percent, sulfur less than about 0.01 weight percent and nickel from about 0.0 to 1.3 weight percent, the remaining content being iron
- FIG. 1 shows a block diagram of an illustrative method for implementing one embodiment of the invention.
- High temperature strength, fatigue and creep behavior of ductile iron can be improved with large alloy additions of silicon and molybdenum.
- These irons are commonly classified as SiMo irons and have been used extensively in automotive applications such as turbocharger housings and exhaust manifolds.
- Ductile irons typically fail to meet design requirements for high temperature gas turbine casing applications such as compressor discharge casings or turbine shells.
- Generally alloyed steels are used for gas turbine casings.
- Ductile iron with improved high-temperature performance over conventional ferritic ductile iron by alloy additions of molybdenum and silicon is presented.
- the silicon and molybdenum additions are balanced to achieve adequate high temperature properties while retaining sufficient low temperature toughness.
- Standard silicon levels in heavy-section ductile iron are typically between 2.0 and 2.2 weight percent (w/o). It has been found that increasing silicon content to between 2.8 and 3.5 w/o substantially increases tensile strength between room temperature and about 400° C. Isothermal creep performance for a 0.5 w/o molybdenum ductile iron is substantially better than conventional ductile iron. High temperature strength is an indication of creep resistance. Improvements in creep resistance performance is maximized as the Mo content is increased from 0.8 to 1.5 weight percent (w/o). By using Si and Mo in the weight percentages shown a ductile iron with properties suitable for gas turbine casings is provided.
- the ductile iron used in embodiments of the present invention includes carbon from about 2.8 to 3.7 w/o, silicon from about 3.0 to 3.5 w/o, molybdenum from about 0.8 to 1.5 w/o, nickel from about 0.0 to 1.3 w/o, the remaining content being iron.
- These four components are critical to providing a ductile iron that meets the requirements for gas turbine casings. At elevated temperatures, tensile strength as well as low cycle fatigue (LCF) capability is determined by the occurrence of elevated temperature brittleness. Magnesium must be kept from 0.025 to 0.60 w/o to provide a SiMo ductile iron with the proper characteristics with sulfur less than 0.01 w/o.
- tungsten content of the SiMo ductile iron is less than 0.05 w/o.
- Molybdenum-rich eutectic phases can lead to poor mechanical properties, specifically elongation and toughness.
- the strong partitioning of molybdenum to cell boundaries in the form of eutectic, intermetallic or metallic carbide phases is unavoidable. However, these phases can be reduced to acceptable levels by proper inoculation and chilling as well as implementing of other standard foundry practices.
- FIG. 1 A method of producing SiMo ductile iron is shown in FIG. 1 .
- step 10 the iron and other components are melted.
- Specified product chemistry is not identical to melt chemistry.
- the final melt chemistry is different than the initial melt chemistry.
- step 11 standard inoculants and treatment alloys are added to the melt.
- a molybdenum alloy is added to the melt in step 12 .
- the melt is cast to form the part in step 13 . Higher dross levels are associated with SiMo iron chemistry so these levels need to be accounted for in the foundry. Additionally, higher shrinkage and reduced feeding characteristics of the parts are typical.
- a heat treatment or ferritizing anneal in step 14 is generally required to improve toughness and prevent cracking during handling at the foundry.
- a typical heat treatment or ferritizing anneal process for the cast material is as follows. Hold cast part at 900° C. for at least 7 hours. Allow part cool to 720° C. and hold for at least 2 hours. Allow part cool to 690° C. and hold for at least 8 hours.
- a stress relief anneal can be performed on cast parts.
- the stress relief anneal is from about 650 to 750° C. for 1 hour per inch thickness of the section with the greatest thickness.
- Inoculation is required to promote the formation of graphite instead of metastable carbide.
- Inoculants provide heterogeneous nucleation sites (seeds) for graphite to form.
- the primary component of the inoculant is silicon.
- Foundry grade ferrosilicon (75 w/o Si) is often used for inoculation.
- Typical commercial inoculants contain high levels of silicon plus various levels of calcium, germanium, strontium, and rare earth elements (cerium is most common due to other beneficial characteristics in heavy section iron). Inoculants are often added multiple times in the production of large ductile iron castings. Suitable inoculants are available from many sources.
- Standard treatment alloys are added to the melt in step 11 of FIG. 1 .
- Treatment (sometimes referred to as modification) is necessary to force the formation of graphite spheroids instead of flakes.
- Treatment can be in the form of nearly pure Mg in powder form (George Fischer converter) or most cases in the form of a Mg-bearing alloy (often with Nickel).
- Shrinkage occurs during solidification. Chilling (strategic placement of large cast iron blocks to remove heat) is used to promote directional solidification to limit macroscopic shrinkage porosity in critical areas of the casting. The size, type, number and placement of these chills becomes more important in SiMo irons due to reduced feeding and shrinkage levels associated with these irons.
- Risers are needed to supply molten metal to prevent large shrinkage porosity in critical locations. These risers are often placed in regions susceptible to shrinkage (hard to feed thick-to-thin geometry transitions, for example). General foundry practice requires the distance between risers to decrease as the castability decreases. Additionally, larger risers and riser necks are often used as the castability decreases. Adjustments in pouring temperature are also common as the castability of the alloy decreases.
- first,” “second,” and the like, herein do not denote any order, quantity, or importance, but rather are used to distinguish one element from another, and the terms “a” and “an” herein do not denote a limitation of quantity, but rather denote the presence of at least one of the referenced item.
- the modifier “about” used in connection with a quantity is inclusive of the stated value and has the meaning dictated by the context, (e.g., includes the degree of error associated with measurement of the particular quantity).
- the suffix “(s)” as used herein is intended to include both the singular and the plural of the term that it modifies, thereby including one or more of that term (e.g., the metal(s) includes one or more metals).
- Ranges disclosed herein are inclusive and independently combinable (e.g., ranges of “up to about 25 w/o, or, more specifically, about 5 w/o to about 20 w/o”, are inclusive of the endpoints and all intermediate values of the ranges of “about 5 w/o to about 25 w/o,” etc.).
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- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Materials Engineering (AREA)
- Mechanical Engineering (AREA)
- Metallurgy (AREA)
- Organic Chemistry (AREA)
- Physics & Mathematics (AREA)
- Thermal Sciences (AREA)
- Crystallography & Structural Chemistry (AREA)
- Refinement Of Pig-Iron, Manufacture Of Cast Iron, And Steel Manufacture Other Than In Revolving Furnaces (AREA)
- Turbine Rotor Nozzle Sealing (AREA)
- Molds, Cores, And Manufacturing Methods Thereof (AREA)
Abstract
A cast article of a ductile iron wherein the ductile iron includes carbon from about 2.8 to 3.7 w/o, silicon from about 3.0 to 3.5 w/o, molybdenum from 0.8 to 1.5 w/o, magnesium from about 0.025 to 0.60 w/o, sulfur less than 0.01 w/o and nickel from about 0.0 to 1.3 w/o, the remaining content being iron is provided. The cast article is suitable for a gas turbine casing. A method of manufacturing a cast article is also provided.
Description
- The invention relates to ductile iron for use in gas turbines that provides cost benefits and improved supplier choices.
- Currently, gas turbine casings operating at elevated temperatures (greater than 370° C.) are restricted to alloy steel castings or fabrications. Gas turbines must endure unsteady operation to cover peak loads. This places thermal and mechanical stresses on the gas turbine components. Therefore, gas turbine casings must be able to withstand high temperature environments and repeated temperature cycling. The strength of the gas turbine casing material at high temperatures must be high. Presently, alloy steel castings for gas turbine casings meet these requirements; however, gas turbine casings of alloy steel are expensive to manufacture and there are a limited number of suppliers.
- Traditional ferritic ductile irons are less costly than alloy steels but typically, have inadequate combination of properties, precluding their use in advanced gas turbine compressor discharge and turbine shell casings. Irons with higher silicon and molybdenum contents have found use in certain automotive applications, typically exhaust manifolds. These irons are referred to as SiMo irons. However, these irons are generally brittle at cold temperatures making them likely to crack. In addition, these materials do not possess the requisite toughness at elevated temperatures. Examples of such materials are found in US Pub. 2008/0092995, WO 2006/121826, U.S. Pat. No. 6,508,981 and EP 1724370 A1.
- With increasing casing size it becomes more costly to manufacture gas turbine casings from steel castings. In addition, the current supply base to produce such large steel castings is small.
- Embodiments of the invention include a ductile iron gas turbine casing wherein the ductile iron includes carbon from about 2.8 to 3.7 w/o, silicon from about 3.0 to 3.5 w/o, molybdenum from about 0.8 to 1.5 w/o, magnesium from about 0.025 to 0.60 w/o, sulfur less than about 0.01 w/o and nickel from about 0.0 to 1.3 w/o, the remaining content being iron.
- Embodiments of the present invention also include a ductile iron gas turbine casing wherein the ductile iron includes carbon from about 2.8 to 3.7 w/o, silicon from about 3.0 to 3.5 w/o, molybdenum from about 0.8 to 1.5 w/o, magnesium from about 0.025 to 0.60 w/o, sulfur less than 0.01 w/o, nickel from about 0.0 to 1.3 w/o, phosphorous less than 0.05 w/o, titanium less than 0.05 w/o, vanadium less than about 0.05 w/o, tin less than 0.05 w/o, aluminum less than about 0.10 w/o, copper less than about 0.10 w/o, chromium less than about 0.10 w/o and manganese at less than about 0.15 w/o, the remaining content being iron.
- Embodiments of the present invention also include a method of manufacturing a component. The method includes melting ductile iron that includes carbon, silicon, magnesium, sulfur and nickel, the remaining content being iron to form a melt. Inoculants and treatment alloys are added to the melt. Molybdenum is added to the melt. The melt is cast to form the component. The component includes carbon from about 2.8 to 3.7 weight percent, silicon from about 3.0 to 3.5 weight percent, molybdenum from about 0.8 to 1.5 weight percent, magnesium from about 0.025 to 0.60 weight percent, sulfur less than about 0.01 weight percent and nickel from about 0.0 to 1.3 weight percent, the remaining content being iron
- The above described and other features are exemplified by the following detailed description.
- These and other features of this invention will be more readily understood from the following detailed description of the various aspects of the invention taken in conjunction with the accompanying drawings that depict various embodiments of the invention, in which:
-
FIG. 1 shows a block diagram of an illustrative method for implementing one embodiment of the invention. - High temperature strength, fatigue and creep behavior of ductile iron can be improved with large alloy additions of silicon and molybdenum. These irons are commonly classified as SiMo irons and have been used extensively in automotive applications such as turbocharger housings and exhaust manifolds.
- Ductile irons typically fail to meet design requirements for high temperature gas turbine casing applications such as compressor discharge casings or turbine shells. Generally alloyed steels are used for gas turbine casings.
- Ductile iron with improved high-temperature performance over conventional ferritic ductile iron by alloy additions of molybdenum and silicon is presented. The silicon and molybdenum additions are balanced to achieve adequate high temperature properties while retaining sufficient low temperature toughness.
- Standard silicon levels in heavy-section ductile iron are typically between 2.0 and 2.2 weight percent (w/o). It has been found that increasing silicon content to between 2.8 and 3.5 w/o substantially increases tensile strength between room temperature and about 400° C. Isothermal creep performance for a 0.5 w/o molybdenum ductile iron is substantially better than conventional ductile iron. High temperature strength is an indication of creep resistance. Improvements in creep resistance performance is maximized as the Mo content is increased from 0.8 to 1.5 weight percent (w/o). By using Si and Mo in the weight percentages shown a ductile iron with properties suitable for gas turbine casings is provided.
- The ductile iron used in embodiments of the present invention includes carbon from about 2.8 to 3.7 w/o, silicon from about 3.0 to 3.5 w/o, molybdenum from about 0.8 to 1.5 w/o, nickel from about 0.0 to 1.3 w/o, the remaining content being iron. These four components are critical to providing a ductile iron that meets the requirements for gas turbine casings. At elevated temperatures, tensile strength as well as low cycle fatigue (LCF) capability is determined by the occurrence of elevated temperature brittleness. Magnesium must be kept from 0.025 to 0.60 w/o to provide a SiMo ductile iron with the proper characteristics with sulfur less than 0.01 w/o. Magnesium loadings outside this range produce iron that generally has inadequate mechanical behavior. In addition to the components listed above, minor amounts of the following components are allowable. Phosphorous at less than 0.05 w/o, titanium at less than 0.05 w/o, vanadium at less than 0.05 w/o, tin at less than 0.05 w/o, aluminum at less than 0.10 w/o, copper at less than 0.10 w/o, chromium at less than 0.10 w/o and manganese at less than less than 0.15 w/o. In one embodiment, the tungsten content of the SiMo ductile iron is less than 0.05 w/o.
- Molybdenum-rich eutectic phases can lead to poor mechanical properties, specifically elongation and toughness. The strong partitioning of molybdenum to cell boundaries in the form of eutectic, intermetallic or metallic carbide phases is unavoidable. However, these phases can be reduced to acceptable levels by proper inoculation and chilling as well as implementing of other standard foundry practices.
- A method of producing SiMo ductile iron is shown in
FIG. 1 . Instep 10, the iron and other components are melted. Specified product chemistry is not identical to melt chemistry. As there are losses associated with the initial liquid melt, the final melt chemistry is different than the initial melt chemistry. Instep 11, standard inoculants and treatment alloys are added to the melt. A molybdenum alloy is added to the melt instep 12. The melt is cast to form the part instep 13. Higher dross levels are associated with SiMo iron chemistry so these levels need to be accounted for in the foundry. Additionally, higher shrinkage and reduced feeding characteristics of the parts are typical. A heat treatment or ferritizing anneal instep 14 is generally required to improve toughness and prevent cracking during handling at the foundry. - A typical heat treatment or ferritizing anneal process for the cast material is as follows. Hold cast part at 900° C. for at least 7 hours. Allow part cool to 720° C. and hold for at least 2 hours. Allow part cool to 690° C. and hold for at least 8 hours.
- Rather than a ferritizing anneal process, a stress relief anneal can be performed on cast parts. The stress relief anneal is from about 650 to 750° C. for 1 hour per inch thickness of the section with the greatest thickness.
- Inoculation is required to promote the formation of graphite instead of metastable carbide. Inoculants provide heterogeneous nucleation sites (seeds) for graphite to form. The primary component of the inoculant is silicon. Foundry grade ferrosilicon (75 w/o Si) is often used for inoculation. Typical commercial inoculants contain high levels of silicon plus various levels of calcium, germanium, strontium, and rare earth elements (cerium is most common due to other beneficial characteristics in heavy section iron). Inoculants are often added multiple times in the production of large ductile iron castings. Suitable inoculants are available from many sources.
- Standard treatment alloys are added to the melt in
step 11 ofFIG. 1 . Treatment (sometimes referred to as modification) is necessary to force the formation of graphite spheroids instead of flakes. Treatment can be in the form of nearly pure Mg in powder form (George Fischer converter) or most cases in the form of a Mg-bearing alloy (often with Nickel). - Shrinkage occurs during solidification. Chilling (strategic placement of large cast iron blocks to remove heat) is used to promote directional solidification to limit macroscopic shrinkage porosity in critical areas of the casting. The size, type, number and placement of these chills becomes more important in SiMo irons due to reduced feeding and shrinkage levels associated with these irons.
- Risers (or feeders) are needed to supply molten metal to prevent large shrinkage porosity in critical locations. These risers are often placed in regions susceptible to shrinkage (hard to feed thick-to-thin geometry transitions, for example). General foundry practice requires the distance between risers to decrease as the castability decreases. Additionally, larger risers and riser necks are often used as the castability decreases. Adjustments in pouring temperature are also common as the castability of the alloy decreases.
- The terms “first,” “second,” and the like, herein do not denote any order, quantity, or importance, but rather are used to distinguish one element from another, and the terms “a” and “an” herein do not denote a limitation of quantity, but rather denote the presence of at least one of the referenced item. The modifier “about” used in connection with a quantity is inclusive of the stated value and has the meaning dictated by the context, (e.g., includes the degree of error associated with measurement of the particular quantity). The suffix “(s)” as used herein is intended to include both the singular and the plural of the term that it modifies, thereby including one or more of that term (e.g., the metal(s) includes one or more metals). Ranges disclosed herein are inclusive and independently combinable (e.g., ranges of “up to about 25 w/o, or, more specifically, about 5 w/o to about 20 w/o”, are inclusive of the endpoints and all intermediate values of the ranges of “about 5 w/o to about 25 w/o,” etc.).
- While various embodiments are described herein, it will be appreciated from the specification that various combinations of elements, variations or improvements therein may be made by those skilled in the art, and are within 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 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.
Claims (19)
1. A gas turbine casing comprising:
a cast ductile iron wherein the ductile iron comprises: carbon from about 2.8 to 3.7 weight percent, silicon from about 3.0 to 3.5 weight percent, molybdenum from about 0.8 to 1.5 weight percent, magnesium from about 0.025 to 0.60 weight percent, sulfur less than about 0.01 weight percent and nickel from about 0.0 to 1.3 weight percent, the remaining content being iron.
2. The gas turbine casing of claim 1 , further comprising phosphorous, titanium, vanadium and tin each at weight percent of less than about 0.05.
3. The gas turbine casing of claim 1 , further comprising aluminum, copper and chromium each at weight percent of less than about 0.1.
4. The gas turbine casing of claim 1 , further comprising manganese at weight percent of less than about 0.15.
5. The gas turbine casing of claim 1 further comprising tungsten at a weight percent of less than about 0.05.
6. A gas turbine casing comprising:
a cast ductile iron wherein the ductile iron comprises: carbon from about 2.8 to 3.7 weight percent, silicon from about 3.0 to 3.5 weight percent, molybdenum from about 0.8 to 1.5 weight percent, magnesium from about 0.025 to 0.60 weight percent, sulfur less than 0.01 weight percent, nickel from about 0.0 to 1.3 weight percent, phosphorous less than about 0.05 weight percent, titanium less than about 0.05 weight percent, vanadium less than about 0.05 weight percent, tin less than about 0.05 weight percent, aluminum less than about 0.10 weight percent, copper less than about 0.10 weight percent, chromium less than about 0.10 weight percent, manganese less than about 0.15 weight percent, tungsten less than about 0.05 weight percent, the remaining content being iron.
7. A method of manufacturing a component, the method comprising:
melting ductile iron comprising carbon, magnesium, sulfur and nickel, the remaining content being iron to form a melt;
adding inoculants and treatment alloys to the melt;
adding molybdenum to the melt; and
casting the melt to form the component wherein the component comprises carbon from about 2.8 to 3.7 weight percent, silicon from about 3.0 to 3.5 weight percent, molybdenum from about 0.8 to 1.5 weight percent, magnesium from about 0.025 to 0.60 weight percent, sulfur less than 0.01 weight percent and nickel from about 0.0 to 1.3 weight percent, the remaining content being iron.
8. The method of claim 7 further comprising:
annealing the component after casting the melt.
9. The method of claim 8 , wherein the annealing comprises:
holding the component at 900° C. for at least 7 hours;
cooling the component to 720° C. and holding for at least 2 hours;
cooling the component to 690° C. and holding for at least 8 hours.
10. The method of claim 7 wherein the component comprises a gas turbine casing.
11. The method of claim 7 , wherein the component comprises phosphorous, titanium, vanadium, and tin each at weight percent of less than about 0.05.
12. The method of claim 7 , wherein the component comprises aluminum, copper and chromium each at weight percent of less than about 0.1.
13. The method of claim 7 , wherein the component comprises manganese at weight percent of less than about 0.15.
14. The method of claim 7 wherein the component comprises tungsten at a weight percent of less than about 0.05.
15. The method of claim 7 wherein the inoculants comprise ferrosilicon.
16. The method of claim 15 wherein the inoculants further comprise calcium, germanium, strontium and rare earth elements.
17. The method of claim 7 wherein the treatment alloys comprises magnesium and nickel.
18. The method of claim 7 further comprising;
stress relief annealing at about 650 to 750° C. for 1 hour per inch thickness of the component.
19. The method of claim 7 wherein the casting comprises placement of large cast blocks to remove heat.
Priority Applications (4)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US12/489,872 US20100322813A1 (en) | 2009-06-23 | 2009-06-23 | SiMo DUCTILE IRON CASTINGS IN GAS TURBINE APPLICATIONS |
EP10165664A EP2267174A3 (en) | 2009-06-23 | 2010-06-11 | Simo ductile iron castings for gas turbine applications |
JP2010138951A JP2011007182A (en) | 2009-06-23 | 2010-06-18 | SiMo DUCTILE CAST IRON FOR GAS TURBINE |
RU2010125395/02A RU2010125395A (en) | 2009-06-23 | 2010-06-22 | CASTINGS FROM SIMO HIGH-STRENGTH IRON IN APPLICATIONS RELATED TO GAS TURBINES |
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US12/489,872 US20100322813A1 (en) | 2009-06-23 | 2009-06-23 | SiMo DUCTILE IRON CASTINGS IN GAS TURBINE APPLICATIONS |
Publications (1)
Publication Number | Publication Date |
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US20100322813A1 true US20100322813A1 (en) | 2010-12-23 |
Family
ID=42983747
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
US12/489,872 Abandoned US20100322813A1 (en) | 2009-06-23 | 2009-06-23 | SiMo DUCTILE IRON CASTINGS IN GAS TURBINE APPLICATIONS |
Country Status (4)
Country | Link |
---|---|
US (1) | US20100322813A1 (en) |
EP (1) | EP2267174A3 (en) |
JP (1) | JP2011007182A (en) |
RU (1) | RU2010125395A (en) |
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CN102691535A (en) * | 2011-03-23 | 2012-09-26 | 通用电气公司 | Cast turbine casing and nozzle diaphragm preforms |
CN104911458A (en) * | 2015-04-27 | 2015-09-16 | 苏州劲元油压机械有限公司 | Hydraulic pump body casting process |
CN108103392A (en) * | 2018-01-12 | 2018-06-01 | 湖北星源科技有限公司 | A kind of high-strength ductile cast iron production method |
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US10975718B2 (en) | 2013-02-12 | 2021-04-13 | Garrett Transportation I Inc | Stainless steel alloys, turbocharger turbine housings formed from the stainless steel alloys, and methods for manufacturing the same |
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US10975718B2 (en) | 2013-02-12 | 2021-04-13 | Garrett Transportation I Inc | Stainless steel alloys, turbocharger turbine housings formed from the stainless steel alloys, and methods for manufacturing the same |
CN104911458A (en) * | 2015-04-27 | 2015-09-16 | 苏州劲元油压机械有限公司 | Hydraulic pump body casting process |
CN108103392A (en) * | 2018-01-12 | 2018-06-01 | 湖北星源科技有限公司 | A kind of high-strength ductile cast iron production method |
CN109943767A (en) * | 2019-03-29 | 2019-06-28 | 浙江欧冶达机械制造股份有限公司 | Elevator traction sheave casting technique |
CN113088804A (en) * | 2021-05-19 | 2021-07-09 | 太原市三高能源发展有限公司 | Cast high-strength ductile iron and manufacturing method thereof |
Also Published As
Publication number | Publication date |
---|---|
EP2267174A2 (en) | 2010-12-29 |
EP2267174A3 (en) | 2012-05-02 |
JP2011007182A (en) | 2011-01-13 |
RU2010125395A (en) | 2011-12-27 |
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