Stainless steel alloy, turbocharger component formed of the stainless steel alloy, and method for manufacturing the same

Abstract

The present invention relates to a stainless steel alloy, a turbocharger component formed from the stainless steel alloy, and a method for manufacturing the same. An austenitic stainless steel alloy is disclosed, which comprises or consists of the following components by weight: about 20.0% to about 21.5% chromium, about 8.5% to about 10.0% nickel, about 4.0% to about 5.0% manganese, about 0.5% to about 2.0% silicon, about 0.4% to about 0.5% carbon, about 0.2% to about 0.3% nitrogen, and the balance iron containing inevitable / unavoidable impurities. Niobium, tungsten and molybdenum elements are excluded from the impurity level. A turbocharger turbine housing made of the stainless steel alloy and a method for manufacturing the same are also disclosed. The stainless steel alloy is suitable for turbocharger turbine applications at temperatures up to about 1020°C.

Description

Technical Field

[0001] The present disclosure relates generally to stainless steel alloys. More particularly, the present disclosure relates to stainless steel alloys for casting applications, such as turbine and turbocharger housings, exhaust manifolds, and combustion chambers, which exhibit oxidation resistance at high temperatures, and methods for making the same. Background Art

[0002] During operation, automotive or aircraft turbocharger components are subject to high operating temperatures. These components must be able to accommodate turbine wheels that generate very high rotational speeds. At high temperatures, the exhaust gas from the automotive or aircraft engine initially contacts the turbocharger in metal sections such as the intake area of ​​the turbocharger. As high-speed performance is improved by increasing exhaust gas temperatures, attempts have been made to gradually increase the exhaust gas temperature of the engine. Due to these high temperatures, the thermal loads on parts such as the exhaust manifold and turbine housing become very large.

[0003] Various problems have been encountered with these elevated exhaust temperatures contacting the metallic sections of the turbocharger. For example, one problem caused by elevated exhaust temperatures is that of corrosion or oxidation. For example, at temperatures above about 800°C, and depending on the specific alloy used, oxygen may begin to attack the metallic elements of the alloy, causing them to oxidize or corrode, and thus lose their beneficial physical and material properties. Over repeated cycles of operation, corrosion or oxidation may eventually lead to complete failure of the part.

[0004] In order to overcome the challenges associated with higher operating temperatures, the prior art alloys used in turbocharger applications have included stainless steel alloys with higher chromium and nickel contents, such as commercially available high chromium and / or nickel ductile iron casting alloys. As used herein, the term operating temperature refers to the maximum temperature of the exhaust gas designed to be experienced by the turbine housing and blade components of the turbocharger (except for occasional higher transient temperatures). These higher chromium and nickel stainless steels are mainly austenitic, having a stable austenite phase that exists at much higher than the operating temperature, and a delta ferrite phase that promotes corrosion / oxidation to a minimum of none. Stainless steel alloys of the 1.48XX series such as stainless steel 1.4848 are well known in the art. With chromium specifications between 23% and 27% and nickel specifications between 19% and 22% (both by weight), they are exemplary prior art materials for turbine housing applications between 1000°C and 1020°C. Although the high temperature property requirements of the turbocharger housing are met, stainless steel 1.4848 is quite expensive due to its high chromium and nickel content. Since the turbocharger housing is typically the most expensive part of a turbocharger, the overall cost of the machine is greatly affected by the choice of material used for this component.

[0005] Alternatively, K273 with lower chromium and nickel content can be used for shell temperatures up to 1020°C. However, due to the higher carbon content, K273 causes manufacturing problems in terms of machinability. In addition, laboratory oxidation tests have shown that K273 has a lower oxidation resistance than other stainless steels recommended for such high temperature applications. Table 1 listed below provides the specifications of stainless steel 1.4848 and K273 in weight percentage:

[0006] Table 1 Composition of K273 and 1.4848 stainless steel

[0007] .

[0008] Therefore, materials that are cheaper, have fewer machining issues, and better oxidation resistance would be suitable alternatives to the available options. These materials should have a stable austenite phase that exists above the operating temperature and have minimal to no delta ferrite phase. Therefore, there is a need for stainless steel alloys useful in turbocharger applications that can withstand the higher operating temperatures generated by modern engines, but minimize the expensive nickel content. In addition, other desirable features and characteristics of the inventive subject matter will become apparent from the subsequent detailed description of the inventive subject matter and the appended claims, taken in conjunction with the accompanying drawings and this background of the inventive subject matter. Summary of the invention

[0009] Stainless steel alloys, turbocharger turbine components, and methods of making turbocharger turbine components are provided.

[0010] In one embodiment, by way of example only, the austenitic stainless steel alloy comprises or consists of the following components by weight: about 20.0% to about 21.5% chromium, about 8.5% to about 10.0% nickel, about 4.0% to about 5.0% manganese, about 0.5% to about 2.0% silicon, about 0.4% to about 0.5% carbon, about 0.2% to about 0.3% nitrogen, and the balance iron containing unavoidable / unavoidable impurities. Niobium, tungsten, and molybdenum elements exceeding the impurity level are not included. As a variation of the aforementioned embodiment, the alloy may include or consist of chromium in an amount of about 20.3% to about 21.2%, or about 20.5% to about 21.0%. As a variation of any of the aforementioned embodiments, the alloy may include or consist of nickel in an amount of about 8.8% to about 9.7%, or about 9.0% to about 9.5%. As a variation of any of the foregoing embodiments, the alloy may include or consist of manganese in an amount of about 4.1% to about 4.9%, or about 4.2% to about 4.8%. As a variation of any of the foregoing embodiments, the alloy may include or consist of silicon in an amount of about 0.6% to about 0.9%. As a variation of any of the foregoing embodiments, the alloy may include or consist of carbon in an amount of about 0.42% to about 0.48%. As a variation of any of the foregoing embodiments, the alloy may include or consist of nitrogen in an amount of about 0.22% to about 0.28%.

[0011] In another embodiment, by way of example only, the turbocharger turbine housing comprises an austenitic stainless steel alloy comprising or consisting of the following components by weight: about 20.0% to about 21.5% chromium, about 8.5% to about 10.0% nickel, about 4.0% to about 5.0% manganese, about 0.5% to about 2.0% silicon, about 0.4% to about 0.5% carbon, about 0.2% to about 0.3% nitrogen, and the balance iron containing unavoidable / unavoidable impurities. Niobium, tungsten, and molybdenum elements exceeding the impurity level are not included. As a variation of the aforementioned embodiment, the alloy may include or consist of chromium in an amount of about 20.3% to about 21.2%, or about 20.5% to about 21.0%. As a variation of any of the aforementioned embodiments, the alloy may include or consist of nickel in an amount of about 8.8% to about 9.7%, or about 9.0% to about 9.5%. As a variation of any of the foregoing embodiments, the alloy may include or consist of manganese in an amount of about 4.1% to about 4.9%, or about 4.2% to about 4.8%. As a variation of any of the foregoing embodiments, the alloy may include or consist of silicon in an amount of about 0.6% to about 0.9%. As a variation of any of the foregoing embodiments, the alloy may include or consist of carbon in an amount of about 0.42% to about 0.48%. As a variation of any of the foregoing embodiments, the alloy may include or consist of nitrogen in an amount of about 0.22% to about 0.28%.

[0012] In yet another embodiment, a method for manufacturing a turbocharger turbine housing includes forming a turbocharger turbine housing from an austenitic stainless steel alloy, the alloy comprising or consisting of the following components by weight: about 20.0% to about 21.5% chromium, about 8.5% to about 10.0% nickel, about 4.0% to about 5.0% manganese, about 0.5% to about 2.0% silicon, about 0.4% to about 0.5% carbon, about 0.2% to about 0.3% nitrogen, and the balance iron containing unavoidable / unavoidable impurities. Niobium, tungsten, and molybdenum elements exceeding the impurity level are not included. As a variation of the aforementioned embodiment, the alloy may include or consist of chromium with a content of about 20.3% to about 21.2%, or about 20.5% to about 21.0%. As a variation of any of the aforementioned embodiments, the alloy may include or consist of nickel with a content of about 8.8% to about 9.7%, or about 9.0% to about 9.5%. As a variation of any of the foregoing embodiments, the alloy may include or consist of manganese in an amount of about 4.1% to about 4.9%, or about 4.2% to about 4.8%. As a variation of any of the foregoing embodiments, the alloy may include or consist of silicon in an amount of about 0.6% to about 0.9%. As a variation of any of the foregoing embodiments, the alloy may include or consist of carbon in an amount of about 0.42% to about 0.48%. As a variation of any of the foregoing embodiments, the alloy may include or consist of nitrogen in an amount of about 0.22% to about 0.28%.

[0013] This summary is provided to introduce some concepts in a simplified form, which are further described in the detailed description below. This summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used as an aid in determining the scope of the claimed subject matter. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] The inventive subject matter will hereinafter be described in conjunction with the following drawings, wherein like numerals represent like elements, and wherein:

[0015] Figure 1 is a system view of an embodiment of a turbocharger for a turbocharged internal combustion engine according to the present disclosure;

[0016] Figure 2 is a simulated phase diagram of an alloy according to the present disclosure showing the phase composition (particularly austenite and delta ferrite) of the alloy at various temperatures as a function of carbon content; and

[0017] Figure 3A - 3D, Figure 4A - 4D, Figure 5A - 5D and Fig. 6A- 6D is a simulated phase diagram of various alloys according to the present disclosure, showing the phase composition (particularly austenite and delta ferrite) of the alloy at various temperatures as a function of nitrogen content. DETAILED DESCRIPTION

[0018] The following detailed description is merely exemplary in nature and is not intended to limit the invention or the application and use of the invention. As used herein, the word "exemplary" means "used as an example, instance or illustration". Therefore, any embodiment described herein as "exemplary" is not necessarily interpreted as being preferred or advantageous over other embodiments. In addition, as used herein, numerical ordinals such as "first", "second", "third", etc., such as first, second and third components, simply represent different single components in multiple components, unless specifically limited by language in the appended claims. Further, the term "about" is used herein to imply a change in the composition percentage, which is + / - 10% on a relative basis, or + / - 5% on a relative basis, or + / - 1% on a relative basis. Of course, in some embodiments, any composition percentage used with the term "about" can also be understood to include the precise (or substantially precise with respect to the precision of the decimal places) composition percentage described.

[0019] All embodiments and implementations of the stainless steel alloy, turbocharger turbine component and manufacturing method thereof described herein are exemplary embodiments, which are provided to enable those skilled in the art to make or use the invention, rather than to limit the scope of the invention, which is defined by the claims. In addition, it is not intended to be bound by any express or implied theory presented in the preceding technical field, background technology, summary of the invention or the following detailed description.

[0020] The present disclosure generally relates to austenitic stainless steel alloys suitable for various turbocharger turbine and exhaust applications. Exemplary turbocharger turbine components according to the present disclosure include turbine housing components and turbine exhaust components, which are subjected to operating temperatures of up to about 1020°C in some applications. The turbocharger turbine housing is typically cast stainless steel or cast iron and is often the most expensive component of the turbocharger. Reductions in housing costs will have a direct impact on the cost of the turbocharger. In order to withstand the high operating temperatures typically generated by the exhaust gas that strikes the turbine housing, turbine housing materials are typically alloyed with elements such as chromium and nickel, in addition to other carbide-forming elements, resulting in increased costs. Reducing the content and / or eliminating these expensive alloying elements will have a direct impact on the cost of the turbine housing.

[0021] Typical embodiments of the present disclosure reside in a vehicle, such as a vehicle operating on land, air, or water, equipped with a powered internal combustion engine ("ICE") and a turbocharger. The turbocharger is equipped with a unique combination of features that, in various embodiments, can provide efficiency benefits by relatively limiting the amount (and kinetic energy) of secondary flow in the turbine and / or compressor compared to comparable unmodified systems.

[0022] Reference Figure 1 , an exemplary embodiment of a turbocharger 101 having a radial turbine and a radial compressor includes a turbocharger housing and a rotor configured to rotate within the turbocharger housing about a rotor rotation axis 103 during turbocharger operation on thrust bearings and two sets of journal bearings (one for each corresponding rotor wheel), or alternatively, on other similar support bearings. The turbocharger housing includes a turbine housing 105, a compressor housing 107, and a bearing housing 109 (i.e., a center housing containing bearings) connecting the turbine housing to the compressor housing. The rotor includes a radial turbine impeller 111 substantially located within the turbine housing 105, a radial compressor impeller 113 substantially located within the compressor housing 107, and a shaft 115 extending through the bearing housing 109 along the rotor rotation axis 103 to connect the turbine impeller 111 to the compressor impeller 113.

[0023] The turbine housing 105 and the turbine wheel 111 form a turbine that is configured to circumferentially receive a high-pressure and high-temperature exhaust gas flow 121 from an engine (e.g., from an exhaust manifold 123 of an internal combustion engine 125). The turbine wheel 111 (and thus the rotor) is driven to rotate about the rotor rotation axis 103 by the high-pressure and high-temperature exhaust gas flow, which becomes a low-pressure and low-temperature exhaust gas flow 127 and is axially released into an exhaust system (not shown).

[0024] The compressor housing 107 and the compressor wheel 113 form a compressor stage. The compressor wheel, driven to rotate by the exhaust-driven turbine wheel 111, is configured to compress axially received input air (e.g., ambient air 131, or already pressurized air from a previous stage in a multi-stage compressor) into a pressurized air flow 133 ejected circumferentially from the compressor. Due to the compression process, the pressurized air flow is characterized by an increase in temperature compared to the temperature of the input air.

[0025] Optionally, the pressurized air flow can be directed through a convection-cooled charge air cooler 135, which is configured to dissipate heat from the pressurized air flow, increasing its density. The resulting cooled and pressurized output air flow 137 is directed into an intake manifold 139 on the internal combustion engine, or alternatively into a subsequent stage tandem compressor. The operation of the system is controlled by an ECU 151 (engine control unit), which is connected to the rest of the system via a communication connection 153.

[0026] Embodiments of the present disclosure are directed to improvements to currently available stainless steel alloys for turbochargers operating at temperatures up to about 1020°C. In particular, embodiments of the present disclosure are directed to austenitic stainless steel alloys having chromium and nickel contents less than stainless steel 1.4848 for cost considerations and having better machinability than K273 for manufacturing considerations. The stainless steel alloys described herein include iron alloyed with various alloying elements, which will be described in more detail below in terms of weight percentages based on the total weight of the alloy. In addition, the discussion of the effects and inclusion of certain percentages of elements is specific to the inventive alloys described herein.

[0027] In one embodiment, the austenitic stainless steel alloy of the present disclosure includes or consists of chromium (Cr) from about 20.0% to about 21.5%, for example, about 20.3% to about 21.2% Cr, such as about 20.5% to about 21.0% Cr. For example, when operating at relatively high temperatures such as up to about 1020°C, chromium is provided to obtain a desired austenite phase for oxidation resistance / corrosion resistance in the alloy. However, as initially described, in order to reduce costs, it is desirable to minimize the Cr content. In addition, when the content of Cr increases, the content of Ni, which is also expensive, should also be increased to maintain the volume fraction, resulting in further cost increases. In addition, if Cr is added in excess, coarse primary carbides of Cr are formed, resulting in extreme brittleness. Therefore, it has been found herein that when Cr is provided within the above range (e.g., from about 20.0% to about 21.5%), a balance is achieved between sufficient austenite phase stability and prevention of delta ferrite phase formation (and cost reduction).

[0028] In one embodiment, the austenitic stainless steel alloy of the present disclosure includes or consists of nickel (Ni) from about 8.5% to about 10.0%, for example, about 8.8% to about 9.7% Ni, such as about 9.0% to about 9.5% Ni. Ni, together with manganese and nitrogen (as described in more detail below, which are included in the alloy of the present disclosure), is an element that stabilizes the austenite phase together with the aforementioned Cr, which is desirable for achieving oxidation resistance / corrosion resistance at high temperatures, as described above. In order to reduce production costs, if the content of relatively expensive Ni is reduced, the reduction of Ni can be replaced by increasing the content of manganese and nitrogen that form the austenite phase. However, it has been found that if the content of Ni is excessively reduced, manganese and nitrogen will be excessively required, so that corrosion resistance / oxidation resistance and hot formability characteristics deteriorate. Therefore, it has been found herein that when Ni is provided in the above range (e.g., from about 8.5% to about 10.0%), a balance is achieved between sufficient austenite phase stability and casting considerations (and cost reduction).

[0029] In one embodiment, the austenitic stainless steel alloy of the present disclosure includes or consists of from about 4.0% to about 5.0% manganese (Mn), for example, from about 4.1% to about 4.9% Mn, such as from about 4.2% to about 4.8% Mn. As initially described above, Mn provides stability for the austenite phase. In addition, Mn is effective as a deoxidizer for the melt along with Si (which is included in the alloy of the present disclosure as described in more detail below), and it has the benefit of improving fluidity during casting operations. However, when the content of Mn is excessive, Mn combines with sulfur in the steel and forms excessive levels of manganese sulfide, thereby reducing corrosion resistance and hot formability. Therefore, it has been found herein that when Mn is provided within the above range (e.g., from about 4.0% to about 5.0%), a balance is achieved between sufficient austenite phase stability, deoxidation properties, and casting considerations.

[0030] In one embodiment, the austenitic stainless steel alloy of the present disclosure includes or consists of silicon (Si) from about 0.5% to about 2.0%, for example, from about 0.6% to about 0.9%. Si has the effect of improving the stability of its metal structure and its oxidation resistance. In addition, it has the function of a deoxidizer and is also effective for improving castability and reducing pinholes in the resulting cast product. If the content of Si is excessive, Si degrades the mechanical properties of the alloy, such as the impact toughness of steel. Therefore, it has been found herein that when Si is provided in the above range (e.g., from about 0.5% to about 2.0%), a balance is achieved between sufficient mechanical properties, deoxidation properties, and casting considerations.

[0031] In one embodiment, the austenitic stainless steel alloy of the present disclosure includes or consists of carbon (C) from about 0.4% to about 0.5%, such as about 0.42% to about 0.48%. C generally provides hardness and strength to stainless steel, and can form carbides with metallic elements. In addition, C has the function of improving the fluidity and castability of the melt. However, when provided in excess, C can make stainless steel brittle, making it more likely to crack during use in turbocharger applications. Therefore, it has been found herein that when C is provided within the above range (e.g., about 0.4% to about 0.5%), a balance is achieved between sufficient mechanical properties and casting considerations.

[0032] In one embodiment, the austenitic stainless steel alloy of the present disclosure includes or consists of nitrogen (N) from about 0.2% to about 0.3%, such as N from about 22% to about 0.28%. N, together with Ni, is one of the elements that contribute to the stability of the austenite phase. As the content of N increases, corrosion resistance / oxidation resistance and high strength are obtained. However, when the content of N is too high, the hot formability of the steel deteriorates, thereby reducing its product yield. In addition, N is an element that can improve high temperature strength and thermal fatigue resistance like C. However, when the content of N is excessive, brittleness may occur due to the precipitation of chromium nitride. Therefore, it has been found herein that when N is provided within the above range (e.g., about 0.2% to about 0.3%), a balance is achieved between austenite phase stability and corrosion resistance / oxidation resistance, sufficient mechanical properties and casting considerations.

[0033] Certain unavoidable / inevitable impurities may also be present in the austenitic stainless steel alloys of the present disclosure. The amount of such impurities is minimized as much as possible. In one embodiment, phosphorus (P) may be present in the alloy, but is minimized to about 0.03% or less, and preferably minimized to about 0.02% or less. P species are in grain boundaries or interfaces, and are likely to deteriorate corrosion resistance and toughness. Therefore, the content of P is reduced as much as possible. In addition, sulfur (S) may be present in the alloy, but is minimized to about 0.03% or less, and preferably minimized to about 0.02% or less. S in steel deteriorates hot workability and can form sulfide inclusions (such as MnS), which negatively affect pitting resistance. Therefore, the content of S is reduced as much as possible.

[0034] In one embodiment, certain relatively expensive carbide forming elements exceeding the impurity level may not be included. These elements include, for example, niobium, tungsten, and molybdenum, and any combination of two or more thereof may not be included. It has been found that austenite phase stability, delta ferrite phase minimization, and adequate mechanical and casting properties can be achieved without including these elements exceeding levels that cannot be avoided as impurities, such as less than about 0.3%, less than about 0.1%, or less than about 0.05%. Additional specific elements (greater than the amount of impurities) that may be excluded from the alloy include one or more of aluminum, titanium, vanadium, cobalt, and / or copper, and any combination of two or more thereof may be excluded from levels that cannot be avoided as impurities, such as less than about 0.3%, less than about 0.1%, or less than about 0.05%, the percentage depending on the specific element under consideration.

[0035] As described herein, iron constitutes the balance of the alloy. The disclosed alloys may include the aforementioned elements, as other elements may be included in the alloy composition within the scope of the present disclosure. However, preferably, the disclosed alloys consist of the aforementioned elements, as no other elements (greater than unavoidable / unavoidable impurities) are included in the alloy.

[0036] Table 2 lists composition ranges (all elements in weight %) for exemplary austenitic stainless steel alloys of the present disclosure, according to the described examples provided above.

[0037] Table 2 Composition of the stainless steel alloy of the present invention

[0038] .

[0039] Illustrative examples

[0040] The present disclosure is now illustrated by the following non-limiting examples. It should be noted that various changes and modifications may be applied to the following examples and processes without departing from the scope of the present disclosure as defined by the appended claims. Therefore, it should be noted that the following examples should be interpreted as merely illustrative and not limiting in any sense.

[0041] Using the material simulation software Thermo-Calc® (available from ThermoCalc Software AB; Stockholm, Sweden), various alloy compositions within the above element ranges were tested for austenite and delta ferrite content. As mentioned above, it is desirable that the austenite phase remain stable at and above the expected design operating temperature of 1020°C, while the delta ferrite phase should be essentially absent, or at least minimized as much as possible, so that the stainless steel can avoid corrosion / oxidation.

[0042] In the first example, Figure 2is a simulated phase diagram of an alloy according to the present disclosure (20% Cr, 8.5% Ni, 4.5% Mn, 0.5% Si, 0.2% N, variable C from 0.0% to 1.0%, balance Fe), showing the phase constituents (particularly austenite and delta ferrite) of the alloy at various temperatures from about 400° C. to about 1600° C. as a function of carbon content. As shown, the austenite phase remains stable well above 1020° C., while the delta ferrite phase is substantially absent above 0.4% C. Therefore, the lower limit of 0.4% C is determined to be suitable for embodiments of the present disclosure.

[0043] In another example, Figure 3A - 3D, Figure 4A - 4D, Figures 5 A - 5D and Fig. 6A - 6D is a simulated phase diagram of various alloys according to the present disclosure, showing the phase composition (particularly austenite and delta ferrite) of the alloys at various temperatures as a function of nitrogen content. For each of the aforementioned figures, the Mn content is 4.5%. For each of the aforementioned "A" series figures, the Cr content is 20.0% and the Nickel content is 8.5%; for each of the aforementioned "B" series figures, the Cr content is 21.5% and the Ni content is 8.5%; for each of the aforementioned "C" series figures, the Cr content is 20.0% and the Ni content is 10.0%; and, for each of the aforementioned "D" series figures, the Cr content is 21.5% and the Ni content is 10.0%. About Figure 3A - 3D, C content is 0.4%, and Si content is 0.5%; Figure 4A - 4D, C content is 0.4%, and Si content is 1.0%; Figure 5A - 5D, C content is 0.5%, and Si content is 0.5%; and, with respect to Fig. 6A - 6D, the C content is 0.5%, and the Si content is 1.0%. For each of the aforementioned figures, the material phase content is shown as a function of the N content in various temperature ranges from about 400°C to about 1600°C. Therefore, according to embodiments of the present disclosure, the full range of each of Cr, Ni, Si, C and N is tested in various combinations for the purpose of determining the phase content, particularly with respect to the austenite phase and the delta ferrite phase. As shown, for each of the various combinations, the austenite phase remains stable well above 1020°C, while the delta ferrite phase is essentially absent above 0.2% N. Therefore, the lower limit of 0.2% N is determined to be suitable for embodiments of the present disclosure, and further, the ranges of Cr, Ni, Si, C and N are determined to be suitable for embodiments of the present disclosure.

[0044] Thus, embodiments of the present disclosure provide numerous benefits over the prior art, including minimizing expensive nickel content while maintaining desirable material properties for use as turbocharger turbine components, such as housing components or exhaust components. In addition, the disclosed alloys maintain a stable austenite material phase above expected operating temperatures, such as 1020°C, while substantially minimizing the delta ferrite material phase, which is susceptible to corrosion / oxidation. Thus, embodiments of the present disclosure are suitable for use as lower cost alloys for turbocharger turbine components, such as turbocharger turbine housings, for design operations up to about 1020°C.

[0045] Although at least one exemplary embodiment has been presented in the foregoing detailed description of the subject matter of the present invention, it should be understood that there are a large number of variations. It should also be understood that one or more exemplary embodiments are merely examples and are not intended to limit the scope, applicability, or configuration of the subject matter of the present invention in any way. On the contrary, the foregoing detailed description will provide a convenient roadmap for those skilled in the art to implement the exemplary embodiments of the subject matter of the present invention. It should be understood that various changes may be made to the functions and arrangements of the elements described in the exemplary embodiments without departing from the scope of the subject matter of the present invention set forth in the appended claims.

Claims

1. An austenitic stainless steel alloy comprising, by weight: 20.0% to 21.5% chromium; 8.5% to 9.7% nickel; 4.1% to 4.9% manganese; 0.5% to 2.0% silicon; 0.4% to 0.5% carbon; 0.22% to 0.3% nitrogen; and The balance of iron containing inevitable / unavoidable impurities, Among them, niobium, molybdenum and tungsten exceeding the impurity level are excluded from the alloy.

2. Austenitic stainless steel alloy according to claim 1, comprising 20.3% to 21.2% chromium.

3. The austenitic stainless steel alloy of claim 1 comprising 8.8% to 9.7% nickel.

4. The austenitic stainless steel alloy of claim 1 comprising 4.6% to 4.9% manganese.

5. The austenitic stainless steel alloy of claim 1 comprising 0.6% to 0.9% silicon.

6. The austenitic stainless steel alloy of claim 1 comprising 0.42% to 0.48% carbon.

7. The austenitic stainless steel alloy of claim 1 comprising 0.22% to 0.28% nitrogen.

8. The austenitic stainless steel alloy according to claim 1, consisting of the following components by weight: 20.0% to 21.5% chromium; 8.5% to 9.7% nickel; 4.1% to 4.9% manganese; 0.5% to 1.0% silicon; 0.4% to 0.5% carbon; 0.22% to 0.3% nitrogen; and Balance iron containing inevitable / unavoidable impurities.

9. A turbocharger turbine component, comprising: Austenitic stainless steel alloy, wherein the austenitic stainless steel alloy comprises by weight: 20.0% to 21.5% chromium; 8.5% to 9.7% nickel; 4.10% to 4.9% manganese; 0.5% to 2.0% silicon; 0.4% to 0.5% carbon; 0.22% to 0.3% nitrogen; and The balance of iron containing inevitable / unavoidable impurities, Niobium, molybdenum and tungsten above impurity levels are excluded from the alloy.

10. The turbocharger turbine component according to claim 9, wherein: The austenitic stainless steel comprises 20.3% to 21.2% chromium.

11. The turbocharger turbine component according to claim 9, wherein: The austenitic stainless steel alloy comprises 8.8% to 9.7% nickel.

12. The turbocharger turbine component according to claim 9, wherein: The austenitic stainless steel alloy includes 4.6% to 4.9% manganese.

13. The turbocharger turbine component according to claim 9, wherein: The austenitic stainless steel alloy includes 0.6% to 0.9% silicon.

14. The turbocharger turbine component according to claim 9, wherein: The austenitic stainless steel alloy includes 0.42% to 0.48% carbon.

15. The turbocharger turbine component according to claim 9, wherein: The austenitic stainless steel alloy includes 0.22% to 0.28% nitrogen.

16. The turbocharger turbine component according to claim 9, wherein: The austenitic stainless steel alloy consists of the following components by weight: 20.0% to 21.5% chromium; 8.5% to 9.7% nickel; 4.1% to 4.9% manganese; 0.5% to 2.0% silicon; 0.4% to 0.5% carbon; 0.22% to 0.3% nitrogen; and Balance iron containing inevitable / unavoidable impurities.

17. The turbocharger turbine component according to claim 9, wherein: The turbocharger turbine component includes a turbocharger turbine housing.

18. A vehicle comprising a turbocharger turbine component according to claim 9.

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