Fe-BASED HEAT-RESISTANT ALLOY

Abstract

To provide a novel Fe-based heat-resistant alloy that allows processing or manufacturing into components by general methods such as melting, casting, forging, or rolling, and that exhibits sufficient ductility at room temperature along with sufficiently high strength at high temperature.SOLUTION: An Fe-based heat-resistant alloy contains the following elements, expressed in atomic%, Al: 13-23%, Ti: 1.5-3.5%, Ni: 10-16%, Nb: 2.0-4.0%, W: 1.0-3.0%, C: 0.010% or less, N: 0.010% or less, S: 0.0020% or less, Si: 0.010% or less, Mn: 0.10% or less, and O: 0.010% or less, with the remainder consisting of Fe and inevitable impurities excluding the above elements.SELECTED DRAWING: Figure 4

Description

Technical Field

[0001] The present invention relates to an iron-based heat-resistant alloy suitable for use in various heat-resistant high-temperature parts, having good high-temperature strength, room-temperature ductility, and hot workability.

Background Art

[0002] In recent years, in heat-resistant high-temperature parts such as engines and turbines of various transportation equipment, due to the demands for reducing fuel consumption and carbon dioxide emissions, further high-temperature and high-speed rotation of the operating temperature have been required. Also, in heat-resistant high-temperature parts in various plants and industrial machines, for efficiency improvement, further high-temperature and high-pressure of the operating temperature have been required. Thus, since these heat-resistant high-temperature parts are placed in a severe environment where they are exposed to high stress at high temperature during use, a stable material that can function sufficiently even at high temperature and high stress is required.

[0003] Conventionally, Ni-based superalloys have been generally used as materials used at high temperature and high stress. As an example, general-purpose Ni-based superalloys such as Inconel 625 are used, and their usage amount is overwhelmingly larger than that of special Ni-based superalloys such as single-crystal superalloys. As a method of using general-purpose Ni-based superalloys, casting materials and rolled materials are often used. Therefore, in addition to high-temperature strength, hot workability is also required, and excellent room-temperature ductility is also required to ensure reliability in use. However, Ni is a rare element and is expensive. Also, since the production areas are limited, the supply is unstable. Therefore, a heat-resistant alloy based on Fe, which is significantly cheaper and has no limited production areas and is stably supplied, is desired for various applications.

[0004] As a conventional Fe-based heat-resistant alloy, for example, Patent Document 1 (Japanese Unexamined Patent Application Publication No. 2001-011583) discloses an austenitic heat-resistant alloy characterized by containing, by weight ratio, C: 0.01 to 0.10%, Si: ≤1.50%, Mn: ≤1.50%, P: ≤0.030%, S: ≤0.015%, Ni: 25.00 to 35.00%, Cr: 19.00 to 29.00%, Mo + W: ≤3.0%, V: ≤0.5%, Co: ≤5.0%, Al: ≤0.15%, Ti: ≤0.15%, Nb + Ta: ≤1.0%, N: 0.1 to 0.35%, with the balance being Fe and unavoidable impurities.

[0005] Patent Document 2 (Japanese Unexamined Patent Application Publication No. 2003-041347) discloses an austenitic heat-resistant steel characterized by containing, by weight%, Cr: 12 to 15%, Ni: 20 to 30%, Ti: 0.20 to 0.50%, Nb: 0.10 to 0.30%, P: 0.025 to 0.08%, V: 0.2 to 0.4%, and the balance being Fe.

[0006] Patent Document 3 (Japanese Unexamined Patent Application Publication No. 2012-001749) discloses an austenitic heat-resistant steel characterized by containing, by mass%, C: 0.01 to 0.12%, Si: 0.2 to 1.0%, Mn: 1.0 to 2.5%, Ni: 10.0 to 28.0%, Cr: 18.0 to 26.0%, Al: 0.001 to 0.050%, P: 0.040% or less, S: 0.010% or less, N: 0.09 to 0.30%, Nb + V: 0.25 to 0.70%, Mo + 0.5W: 1.5 to 4.0%, W / Mo: 3 to 16, with the balance being Fe and unavoidable impurities, and being solution-treated at 1180 to 1250°C.

[0007] However, any of the heat-resistant steels described in the above-mentioned documents still have room for further improvement in high-temperature strength, and it is not always clear whether they have other required properties near room temperature, such as room-temperature ductility, and there is also room for further improvement in hot workability. In addition, any of the heat-resistant steels described in the above-mentioned documents have Cr and Ni as main components, but no special consideration has been given to many impurity concentrations.

Prior Art Documents

Patent Documents

[0008]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0009] The present invention has been made to solve the conventional problems described in the above background art section. An ingot is produced by melting and casting, and it can be processed and manufactured as a member by subjecting it to general-purpose hot working methods such as forging and rolling. The purpose is to provide a novel Fe-based heat-resistant alloy that has sufficiently high strength at high temperatures, has sufficient ductility at room temperature, and is also excellent in hot workability.

Means for Solving the Problems

[0010] The inventors of the present invention have conducted intensive studies while constructing a hypothesis focusing particularly on B2-type intermetallic compounds for alloys with a composition ratio different from that of the conventional austenitic Fe-based heat-resistant alloys described in the above documents. As a result, unexpectedly, by setting the Al content ratio within a specific composition range containing a larger amount of Al than the above prior art documents and containing Ti, Nb, and W within a specific composition range without containing Cr, it has been found that the strength at high temperatures can be sufficiently increased. Furthermore, by containing Ni, the austenite phase is stabilized, and in addition, by reducing the concentration of a specific plurality of impurities to below a certain content ratio, it has also been found that an alloy with sufficiently high ductility at room temperature and excellent hot workability can be obtained, and the present invention has been completed as a means for solving the above problems.

[0011] That is, the gist of the present invention is as follows. [1] The content of each of the following elements is in atomic %, Al: 12.5 to 23.0%, Ti: 1.4 to 3.6%, Ni: 9.5 to 16.5%, Nb: 2.0 to 4.0%, W: 1.0 to 3.0%, C: 0.010% or less, N: 0.010% or less, S: 0.0020% or less, Si: 0.010% or less, Mn: 0.10% or less, O: 0.010% or less, and the balance consists of Fe and unavoidable impurities excluding the above elements, an Fe-based heat-resistant alloy. [2] The Fe-based heat-resistant alloy according to [1], having a ductility with an elongation of 5.0% or more in a tensile test at room temperature. [3] The Fe-based heat-resistant alloy according to [2], having a high-temperature strength with a tensile strength of 700 MPa or more in a tensile test at 700 °C. [4] The Fe-based heat-resistant alloy according to [3], which does not crack even when groove roll rolling is repeated with a heating temperature of 1100 °C when processed into an ingot of φ40 mm × 90 mm.

Advantages of the Invention

[0012] The Fe-based heat-resistant alloy of the present invention can be processed and manufactured as a member by a general method such as melting, casting, and / or rolling method, and has sufficient ductility at room temperature, sufficiently high strength at high temperature, and excellent hot workability, and can simultaneously have a plurality of excellent effects.

Brief Description of the Drawings

[0013]

Figure 1

Figure 2

Figure 3

Figure 4

Embodiments for Carrying Out the Invention

[0014] Hereinafter, an example of a preferred embodiment for carrying out the present invention will be described. However, the following embodiments are examples for explaining the present invention, and the present invention is not limited to the following embodiments at all.

[0015] [Components of Fe-based Alloy] Each component of the Fe-based alloy of the present invention will be described.

[0016] <al> The Fe-based alloy of the present invention contains Al as an essential component. Al is a component that can react with iron (Fe), which is a basic constituent element of the alloy, to form a B2-type intermetallic compound based on FeAl. It is considered that when the B2 phase is appropriately precipitated in the Fe-based alloy of the present invention, it has the effect of improving the high-temperature strength of the alloy. The effect is enhanced by containing Ti, which will be described later, and this point is one of the important features of the present invention. The mixing ratio of Al during alloy production is preferably 12.5% or more, more preferably 13.0% or more, still more preferably 13.5% or more, and preferably 23.0% or less, more preferably 22.5% or less in atomic percentage. If it is less than the above lower limit, the effect of Al may be insufficient. If it exceeds the upper limit, the ductility of the alloy at room temperature decreases, and the hot workability also decreases. It is considered that the cause is that the precipitation amount of the B2 phase is too large.

[0017] <ti> The Fe-based alloy of the present invention contains a small amount of Ti as an essential component. By containing Ti, the formation of the B2-type intermetallic compound based on FeAl described above is enhanced, and the B2 phase is appropriately precipitated in the Fe-based alloy, thereby showing the effect of improving the strength of the alloy at high temperatures. The mixing ratio of Ti during alloy production is preferably 1.4% or more, more preferably 1.5% or more, still more preferably 1.7% or more, and preferably 3.6% or less, more preferably 3.5% or less, still more preferably 3.3% or less, in atomic percentage. If it is below the above lower limit, the effect of Ti may be insufficient, and if it exceeds the upper limit, the ductility of the alloy at room temperature decreases and the hot workability decreases. It is considered that the cause is that the precipitation amount of the B2 phase is too large.

[0018] <ni> The Fe-based alloy of the present invention contains Ni as an essential component. Ni is a component that contributes to the stabilization of the austenite phase of the alloy, thereby enhancing the ductility of the alloy at room temperature and showing the effect of enhancing the hot workability. The mixing ratio of Ni during alloy production is preferably 9.5% or more, more preferably 10.0% or more, still more preferably 10.5% or more, and preferably 16.5% or less, more preferably 16.0% or less, still more preferably 15.5% or less in atomic percentage. If it is below the above lower limit, the effect of Ni may be insufficient, and if it exceeds the upper limit, the high-temperature strength of the alloy will decrease.

[0019] <nb> The Fe-based alloy of the present invention contains a small amount of Nb as an essential component. Nb is a component that contributes to precipitation strengthening, and thereby exhibits the effect of improving the strength of the alloy at high temperatures. The mixing ratio of Nb during alloy production is preferably 2.0% or more, more preferably 2.5% or more, and preferably 4.0% or less, more preferably 3.8% or less in atomic percentage. If it is below the above lower limit, the effect of Nb may be insufficient, and if it exceeds the upper limit, the ductility of the alloy at room temperature decreases and the hot workability also decreases.

[0020] <w> The Fe-based alloy of the present invention contains a small amount of Nb as an essential component. Similar to Nb, W is a component that contributes to precipitation strengthening, and thereby exhibits the effect of improving the strength of the alloy at high temperatures. The mixing ratio of W during alloy production is preferably 1.0% or more, more preferably 1.2% or more, and preferably 3.0% or less, more preferably 2.8% or less in atomic percentage. If it is below the above lower limit, the effect of W may be insufficient, and if it exceeds the upper limit, the ductility of the alloy at room temperature decreases, and the hot workability also decreases.

[0021] <Impurity elements: C, N, S, Si, Mn, O> The Fe-based alloy of the present invention may contain C, N, S, Si, Mn, and O as impurity elements, but each needs to be below a predetermined mixing ratio. By reducing the content in this way, it exhibits the effect of enhancing the ductility of the alloy at room temperature and enhancing the hot workability. The mixing ratios of these impurity elements during alloy production are respectively C: 0.010% or less, N: 0.010% or less, S: 0.0020% or less, Si: 0.010% or less, Mn: 0.10% or less, O: 0.010% or less, It is necessary to be. If it exceeds each of the above upper limits for the respective impurity elements, the effect of reducing the respective impurity elements is impaired.

[0022] [Properties of Fe-based alloy] The properties of the Fe-based alloy of the present invention will be described.

[0023] <Hot workability> The Fe-based alloy of the present invention does not crack in the groove roll rolling described later. Therefore, the Fe-based alloy of the present invention is expected not to crack in normal hot working methods such as casting and groove roll rolling, and has excellent hot workability.

[0024] <Room-temperature ductility> The Fe-based alloy of the present invention preferably has a ductility with an elongation of 5.0% or more, more preferably an elongation of 5.5% or more, in a tensile test at room temperature described below. The lower limit value of the above ductility can be set as a standard for ensuring stability during use.

[0025] <High-temperature strength> The Fe-based alloy of the present invention preferably has a high-temperature strength with a tensile strength of 700 MPa or more, more preferably a tensile strength of 720 MPa or more, in a tensile test at 700°C. The lower limit value of the tensile strength at 700°C can be set with reference to a specific strength equal to or higher than that of general-purpose Ni-based superalloys such as Inconel 625. Note that the specific strength is strength / density, which is the strength required for rotating parts used in engines and the like.

[0026] [Manufacturing method of Fe-based alloy] The Fe-based alloy of the present invention can be manufactured using general methods such as melting, casting or forging, and rolling of high-purity raw materials of each component element. Alternatively, techniques related to known and well-known methods in the technical field can be appropriately combined for manufacturing. Also, along the procedure of the examples described below, ingot production by high-frequency melting using a calcia crucible, groove roll rolling using heating at 1100°C, and / or heat treatment at 1000°C for 1 hour may be sequentially performed. In order to dissolve the essential element components Al, Ti, Ni, Nb, and W of the present invention in the Fe-based alloy and achieve solid-solution strengthening and precipitation strengthening of the Fe-based alloy, the heat treatment temperature is preferably 750 to 1200°C, more preferably 800 to 1100°C, most preferably 830 to 1030°C. Also, the heat treatment time is preferably 0.5 to 3 hours, more preferably 0.75 to 2 hours, most preferably 1 to 1.5 hours. The manufacturing conditions of the Fe-based alloy of the present invention can be appropriately selected from the perspective of preventing oxidation loss of the steel material in heat treatment and reducing the cost of heat treatment as long as the alloy can exhibit the effects of the present invention.

[0027] [Function of the Fe-based alloy of the present invention] In the embodiments described below, various Fe-based alloys of the present invention are actually manufactured, and a plurality of excellent effects of the alloys are demonstrated. Although not all the detailed reasons are necessarily strictly clear, they are presumed as follows. It is considered that there are three major points in the Fe-based alloy of the present invention. The first point is to add a large amount of Al and further Ti compared to ordinary austenitic Fe-based heat-resistant alloys, and by precipitating a large amount of B2-type intermetallic compounds based on FeAl, the high-temperature strength of the alloy is improved while ensuring sufficient room-temperature ductility of the alloy by its action. The second point is to add Nb and W to form fine precipitates such as the Laves phase to further improve the high-temperature strength. The third point is to reduce the concentrations of specific impurity elements (C, N, S, Si, Mn, O) to below a certain content ratio so as not to cause brittleness in the alloy, thereby improving the ductility at room temperature and the hot workability. Since conventional austenitic Fe-based heat-resistant alloys are solid-solution alloys, the mechanism of structure strengthening is basically solid-solution strengthening of the matrix phase by the added elements, and further precipitation strengthening of fine precipitates by the added components is intended. However, it is considered that there is a limit to the improvement of high-temperature strength only by such a method. In contrast, the Fe-based heat-resistant alloy of the present invention is characterized in that, in addition to solid-solution strengthening and precipitation strengthening by fine precipitates, precipitation strengthening by a B2-type intermetallic compound based on FeAl is also possible. By adopting such a composite structure strengthening method, the heat-resistant alloy of the present invention is expected to be used as an inexpensive heat-resistant material to replace the general-purpose Ni-based superalloy in the parts where the general-purpose Ni-based superalloy was conventionally used in various devices and the like. In the present invention, the B2-type intermetallic compound itself based on FeAl is utilized for its characteristic of being difficult to deform at high temperatures, and the strengthening mechanism due to the interface effect is also exhibited at the interface between the intermetallic compound and the matrix phase. In addition, the effect of the fine extraction part is also utilized for the characteristic of further enhancing the strength. Further, the Fe-based heat-resistant alloy of the present invention is also characterized in that, unlike the conventional Fe-based heat-resistant alloys, excellent room-temperature ductility and hot workability can be achieved simultaneously by reducing the concentrations of specific impurity elements (C, N, S, Si, Mn, O) to below a certain content ratio. An Fe-based alloy having these characteristics simultaneously is neither described nor suggested in the above-mentioned prior art documents, and was first discovered by the intensive studies of the present inventors.

Example

[0028] Hereinafter, based on the examples, the production and characteristics of the Fe-based heat-resistant alloy of the present invention will be described in more detail. Note that these descriptions are examples of the embodiments of the present invention, and the present invention is not limited to these examples.

[0029] [Procedure 1: Ingot production] Figure 1 is a photograph showing the appearance of the ingot produced in this example. As will be described later, in order to produce an ingot having the composition (component ratio) shown in Table 1 below, the raw materials of the ingot were put into a calcia crucible and produced by high-frequency melting. As the raw materials of the ingot, ultra-high-purity granular electrolytic iron was used as Fe, ultra-high-purity granular raw materials were used as Ni and Al, and raw materials of general purity were used as Ti, Nb, and W. Since the addition amounts of Ti, Nb, and W are relatively small, the increase in impurity elements is not significant. Also, when these raw materials are used, since the above-mentioned impurity elements are hardly contained in the alloy, C, N, S, Si, Mn, and O were intentionally added as impurity elements as appropriate, either as iron and the master alloy or as elemental raw materials. Specifically, as methods for intentionally adding the impurity elements C, N, S, Si, Mn, and O, C, Fe4N, FeS, Si, Mn, and FeO were used, respectively. The total weight of the raw materials of the ingot was set to about 1.5 kg. The melting atmosphere was in argon gas, and an atmosphere in which it was evacuated and then partially replaced with argon was used. Casting was performed in a cast iron mold with an inner diameter of φ40 mm, cutting was performed at the position indicated by the dotted line in Figure 1, and the lower side (length about 90 mm) was used for the groove roll rolling described later.

[0030] [Procedure 2: Component Analysis] In order to confirm the components of the ingot, elemental analysis was performed on Al, Ti, Ni, Nb, and W, and specific impurity elements (C, N, S, Si, Mn, and O), and it was confirmed that the content of each element was the desired component content in atomic %. The analysis results are shown in Table 1. Alloys within the range of the composition (component ratio) of the present invention are designated as "invention alloys" in the classification column, and alloys outside the range of the composition (component ratio) of the present invention are designated as "comparison alloys".

[0031] [Procedure 3: Groove Roll Rolling] An ingot with a diameter of φ40mm and a length of 90mm obtained by cutting off the hot water was heated to 1100°C and subjected to grooved roll rolling. The shape of the groove was square, and the cross-sectional area was gradually reduced by passing the ingot through grooves with different sizes in sequence. Also, after approximately three rollings, reheating was performed. The heating holding time was set to about 10 minutes. An example of the grooved roll rolling process is shown below using arrow symbols (the numbers are the side lengths (mm) of the groove): <Start> → Heating and holding → 38.2 → 35.0 → 31.7 → Reheating → 28.7 → 25.9 → 23.5 → Reheating → 21.3 → 19.3 → 17.5 → Reheating → 15.8 → 14.3 → 12.9 → <End> In this example, a grooved roll rolled material shown in Fig. 2 was obtained by the above process. As shown in Table 1, among the "comparative alloys" outside the range of the composition (component ratio) of the present invention, there were also alloys that cracked and broke during grooved roll rolling. Therefore, the presence or absence of cracks during grooved roll rolling was indicated in the left column of the measurement results.

[0032] [Procedure 4: Heat treatment] The grooved roll rolled material that did not crack and break during grooved roll rolling was heat treated at 1000°C for 1 hour. Among them, for Alloy 3, after heat treatment, microstructure observation was performed by a backscattered electron image. A photograph of the backscattered electron image microstructure of Alloy 3 is shown in Fig. 4. The matrix showing a dark contrast is the austenite phase. Also, the relatively large white contrast precipitates are B2-type intermetallic compound phases formed by the addition of Al and Ti. Also, the small white contrast precipitates are precipitates such as Laves phases formed by the addition of Nb and W.

[0033] [Procedure 5: Property evaluation] Test pieces shown in Fig. 3 were processed from the grooved roll rolled material after heat treatment, and a tensile test at room temperature and a tensile test at 700°C were performed. In the tensile test at room temperature, elongation was measured as an evaluation of room temperature ductility, and in the tensile test at 700°C, tensile strength was measured as an evaluation of high temperature strength. The measurement results are shown in Table 1 below.

Table 1

[0034] From Table 1, the following was found for the groove roll-rolled materials of each ingot produced with a specific composition (component ratio).

[0035] (1) Regarding the preferred component ratio of Al Alloys 1 to 5 are a group in which the Al component ratio varies significantly. In this group, the component ratios excluding irreversible impurities excluding Al, Fe, and the above-specified impurity elements, that is, Ti, Ni, Nb, and W, and the respective specified impurity elements (C, N, S, Si, Mn, and O) are, in atomic %, Ti (2.3 - 2.7%): Ni (12.6 - 13.9%): Nb (2.7 - 3.2%): W (1.5 - 2.1%): C (0.004 - 0.006%): N (0.005 - 0.007%): S (0.0012 - 0.0015%): Si (0.004 - 0.007%): Mn (0.04 - 0.06%): O (0.006 - 0.007%). When Al is 13.5%, 18.2%, and 22.4% (alloys 2, 3, and 4 respectively), the hot workability, room-temperature ductility, and high-temperature strength are all good (◎). However, when Al is relatively low at 12.3% (alloy 1, comparative alloy), the high-temperature strength is poor (×), and when Al is relatively high at 23.6% (alloy 5, comparative alloy), it was found that the hot workability and room-temperature ductility are poor (×). In alloy 1, which is a comparative alloy, the Al component ratio is below the range of 12.5 - 23.0%, and since the amount of the B2 phase is small, it is considered that the effect of improving the high-temperature strength by adding Al was not observed. On the other hand, in alloy 5, which is a comparative alloy, the Al component exceeds the range of 12.5 - 23.0%, and since the precipitation amount of the B2 phase is too large, this is considered to be the cause of the reduction in hot workability and the low and poor room-temperature ductility.

[0036] (2) Regarding the preferred component ratio of Ti Alloys 6 to 10 are a group in which the Ti component ratio is varied significantly. In this group, the component ratios excluding irreversible impurities excluding Ti, Fe, and the specific impurity elements, that is, Al, Ni, Nb, and W, and the specific individual impurity elements (C, N, S, Si, Mn, and O) are, in atomic %, within the range of Al (16.9 to 20.1%): Ni (13.1 to 14.2%): Nb (2.6 to 3.4%): W (1.5 to 1.9%): C (0.004 to 0.006%): N (0.005 to 0.007%): S (0.0010 to 0.0016%): Si (0.004 to 0.006%): Mn (0.05 to 0.07%): O (0.004 to 0.007%). When Ti is 1.7%, 2.5%, and 3.3% (alloys 7, 8, and 9 respectively), the hot workability, room temperature ductility, and high temperature strength are all good (◎). However, when Ti is relatively low at 1.2% (alloy 6, comparative alloy), the high temperature strength is poor (×), and when Ti is relatively high at 3.8% (alloy 10, comparative alloy), the hot workability and room temperature ductility are poor (×). In alloy 6, which is a comparative alloy, the Ti component ratio is below the range of 1.4 to 3.6%, and the amount of the B2 phase is small. Therefore, it is considered that the effect of improving the high temperature strength by Ti addition was not observed. On the other hand, in alloy 10, which is a comparative alloy, the Ti component exceeds the range of 1.4 to 3.6%, and the precipitation amount of the B2 phase is too large. It is considered that this caused the reduction of hot workability and poor room temperature ductility.

[0037] (3) Regarding the suitable component ratio of Ni Alloys 11 to 15 are a group in which the Ni component ratio is greatly varied. In this group, the component ratios excluding Ni, Fe, and irreversible impurities other than the above-specified impurity elements, that is, Al, Ti, Nb, and W, and specific individual impurity elements (C, N, S, Si, Mn, and O) are, in atomic percentages, within the range of Al (16.6 to 18.9%): Ti (2.2 to 2.7%): Nb (2.7 to 3.2%): W (1.8 to 2.6%): C (0.003 to 0.006%): N (0.004 to 0.007%): S (0.0009 to 0.0014%): Si (0.004 to 0.006%): Mn (0.04 to 0.06%): O (0.004 to 0.007%). However, when Ni is 10.5%, 12.7%, and 15.4% (alloys 12, 13, and 14 respectively), the hot workability, room-temperature ductility, and high-temperature strength are all good (◎). When Ni is relatively low at 9.2% (alloy 11, comparative alloy), the room-temperature ductility is poor (×), and when Ni is relatively high at 16.7% (alloy 15, comparative alloy), the high-temperature strength is poor (×). In alloy 11, which is a comparative alloy, the Ni component ratio is below the range of 9.5 to 16.5%, and it is considered that the amount of the austenite phase has decreased, resulting in poor room-temperature ductility. On the other hand, in alloy 15, which is a comparative alloy, the Ni component exceeds the range of 9.5 to 16.5%, and it is considered that the amount of the B2 phase has decreased, resulting in a decrease in high-temperature strength.

[0038] (4) Regarding the suitable component ratio of Nb Alloys 16 to 20 are a group with a largely varying Nb component ratio. In this group, the component ratios excluding irreversible impurities excluding Nb, Fe, and the above-specified impurity elements, that is, Al, Ti, Ni, and W, as well as specific individual impurity elements (C, N, S, Si, Mn, and O), are, in atomic %, within the range of Al (16.8 to 19.7%): Ti (2.2 to 2.5%): Ni (12.6 to 13.4%): W (1.6 to 2.5%): C (0.003 to 0.006%): N (0.005 to 0.007%): S (0.0009 to 0.0016%): Si (0.004 to 0.007%): Mn (0.04 to 0.07%): O (0.004 to 0.007%). However, when Nb is 2.5%, 3.2%, and 3.7% (alloys 17, 18, and 19 respectively), the hot workability, room temperature ductility, and high temperature strength are all good (◎). When Nb is relatively low at 1.6% (alloy 16, comparative alloy), the high temperature strength is poor (×), and when Nb is relatively high at 4.3% (alloy 20, comparative alloy), the hot workability is poor (×). In alloy 16, which is a comparative alloy, the Nb component ratio is below the range of 2.0 to 4.0%, and it is considered that the high temperature strength decreased due to the reduced amount of precipitates. On the other hand, in alloy 20, which is a comparative alloy, the Nb component exceeds the range of 2.0 to 4.0%, and it is considered that the hot workability decreased due to the excessive amount of precipitates.

[0039] (5) Regarding the preferred component ratio of W Alloys 21 to 25 are a group with a significantly varied W component ratio. In this group, the component ratios excluding W, Fe, and irreversible impurities other than the specific impurity elements, that is, Al, Ti, Ni, and Nb, as well as the specific individual impurity elements (C, N, S, Si, Mn, and O), are, in atomic percentages, within the range of Al (16.8 - 20.0%): Ti (2.3% - 2.8%): Ni (12.5 - 14.2%): Nb (2.7 - 3.3%): C (0.003 - 0.007%): N (0.005 - 0.007%): S (0.0011 - 0.0015%): Si (0.005 - 0.007%): Mn (0.04 - 0.06%): O (0.005 - 0.007%). When W is 1.2%, 1.6%, and 2.7% (alloys 22, 23, and 24 respectively), the hot workability, room temperature ductility, and high temperature strength are all good (◎). However, when W is relatively low at 0.8% (alloy 21, comparative alloy), the high temperature strength is poor (×), and when W is relatively high at 3.3% (alloy 25, comparative alloy), the room temperature ductility is poor (×). In alloy 21, which is a comparative alloy, the W component ratio is below the range of 1.0 - 3.0%, and it is considered that the high temperature strength decreased due to the reduced amount of precipitates. On the other hand, in alloy 25, which is a comparative alloy, the W component exceeds the range of 1.0 - 3.0%, and it is considered that the room temperature ductility became poor due to the excessive amount of precipitates.

[0040] (6)Regarding the component ratio of C Alloys 26 - 28 are a group with varying C component ratios. In this group, the component ratios excluding C, Fe, and irreversible impurities other than the above - specified impurity elements, i.e., Al, Ti, Ni, Nb, and W, and specific individual impurity elements (N, S, Si, Mn, and O) are, in atomic percentages, within the range of Al(18.8 - 19.9%):Ti(2.2 - 2.6%):Ni(12.6 - 13.9%):Nb(2.6 - 3.2%):W(1.6 - 2.0%):N(0.006%):S(0.0012 - 0.0016%):Si(0.004 - 0.005%):Mn(0.04 - 0.05%):O(0.005 - 0.007%). When C is 0.008% and 0.005% (alloys 27 and 28 respectively), the hot workability, room - temperature ductility, and high - temperature strength are all good (◎). However, when C is relatively high at 0.012% (alloy 26, the comparative alloy), it was found that the hot workability and room - temperature ductility are poor (×). In alloy 26, which is the comparative alloy, the C component exceeds the range of 0.010% or less. The amount of the specific impurity element C is too much, which embrittles the matrix phase. Therefore, it is considered that this is the reason for the decrease in hot workability and poor room - temperature ductility.

[0041] (7)Regarding the component ratio of N Alloys 29 - 31 are a group with varying N component ratios. In this group, the component ratios excluding N, Fe, and irreversible impurities other than the above - specified impurity elements, i.e., Al, Ti, Ni, Nb, and W, and specific individual impurity elements (C, S, Si, Mn, and O) are, in atomic percentages, within the range of Al(17.3 - 18.3%):Ti(2.4 - 2.6%):Ni(12.6 - 14.2%):Nb(2.9 - 3.3%):W(1.9 - 2.3%):C(0.004 - 0.007%):S(0.0008 - 0.0016%):Si(0.004 - 0.006%):Mn(0.04 - 0.07%):O(0.005 - 0.007%). When N is 0.009% and 0.006% (alloys 30 and 31 respectively), the hot workability, room - temperature ductility, and high - temperature strength are all good (◎). However, when N is relatively high at 0.013% (alloy 29, the comparative alloy), it was found that the hot workability and room - temperature ductility are poor (×). In alloy 29, which is a comparative alloy, the N component exceeds the range of 0.010% or less, and the amount of the specific impurity element N is too large, which is considered to cause embrittlement of the matrix phase, resulting in a decrease in hot workability and poor room temperature ductility.

[0042] (8) Regarding the component ratio of S Alloys 32 to 34 are a group in which the S component ratio is changed. In this group, the component ratios excluding S, Fe, and irreversible impurities excluding the above specific impurity elements, that is, Al, Ti, Ni, Nb, and W, and specific individual impurity elements (C, N, Si, Mn, and O) are, in atomic percentages, within the range of Al (18.9 to 19.8%): Ti (2.7 to 2.8%): Ni (12.6 to 13.4%): Nb (2.8 to 3.4%): W (1.7 to 2.3%): C (0.004 to 0.007%): N (0.006 to 0.007%): Si (0.005 to 0.006%): Mn (0.04 to 0.07%): O (0.005 to 0.007%). When S is 0.0018% and 0.0010% (alloys 33 and 34 respectively), the hot workability, room temperature ductility, and high temperature strength are all good (◎), but when S is relatively large at 0.0024% (alloy 32, comparative alloy), it was found that the hot workability is poor (×). In alloy 32, which is a comparative alloy, the S component exceeds the range of 0.0020% or less, and the amount of the specific impurity element S is too large, which is considered to cause embrittlement of the matrix phase, resulting in a decrease in hot workability.

[0043] (9) Regarding the component ratio of Si Alloys 35 to 37 are a group with varying Si component ratios. In this group, the component ratios excluding irreversible impurities excluding Si, Fe, and the above-specified impurity elements, that is, Al, Ti, Ni, Nb, and W, as well as specific individual impurity elements (C, N, S, Mn, and O), are, in atomic percentage, within the range of Al (17.3 to 19.6%): Ti (2.5 to 2.7%): Ni (12.9 to 14.3%): Nb (2.6 to 3.4%): W (2.4 to 2.6%): C (0.006%): N (0.004 to 0.006%): S (0.0010 to 0.0016%): Mn (0.05 to 0.07%): O (0.006 to 0.007%). However, when S is 0.009% and 0.005% (alloys 36 and 37 respectively), the hot workability, room-temperature ductility, and high-temperature strength are all good (◎), but when Si is relatively high at 0.013% (alloy 35, comparative alloy), it was found that the room-temperature ductility is poor (×). In alloy 35, which is a comparative alloy, the Si component exceeds the range of 0.010% or less, and the amount of the specific impurity element Si is too much, which embrittles the matrix phase. For this reason, it is considered that this causes poor room-temperature ductility.

[0044] (10) Regarding the component ratio of Mn Alloys 38 to 40 are a group with varying Mn component ratios. In this group, the component ratios excluding irreversible impurities excluding Mn, Fe, and the above-specified impurity elements, that is, Al, Ti, Ni, Nb, and W, as well as specific individual impurity elements (C, N, S, Si, and O), are, in atomic percentage, within the range of Al (16.8 to 18.1%): Ti (2.5 to 2.7%): Ni (13.1 to 13.4%): Nb (2.9 to 3.3%): W (1.6 to 2.4%): C (0.002 to 0.006%): N (0.002 to 0.006%): S (0.0002 to 0.0009%): Si (0.002 to 0.004%): O (0.002 to 0.005%). However, when Mn is 0.08% and 0.07% (alloys 39 and 40 respectively), the hot workability, room-temperature ductility, and high-temperature strength are all good (◎), but when Mn is relatively high at 0.013% (alloy 38, comparative alloy), it was found that the room-temperature ductility is poor (×). In alloy 38, which is a comparative alloy, the Mn component exceeds the range of 0.10% or less, and the amount of the specific impurity element Mn is too large, which embrittles the matrix phase. Therefore, it is considered that this causes poor room temperature ductility.

[0045] (11)Regarding the component ratio of O Alloys 41 to 43 are a group in which the O component ratio is changed. In this group, the component ratios excluding O, Fe, and irreversible impurities excluding the above specific impurity elements, that is, Al, Ti, Ni, Nb, and W, and specific individual impurity elements (C, N, S, Si, and Mn) are, in atomic%, Al (17.4 to 18.7%): Ti (2.4 to 2.8%): Ni (13.3 to 13.6%): Nb (2.9 to 3.1%): W (1.5 to 2.6%): C (0.002 to 0.003%): N (0.002 to 0.003%): S (0.0002 to 0.0003%): Si (0.002 to 0.003%): Mn (0.02 to 0.03%). When O is 0.007% and 0.004% (alloys 42 and 43 respectively), the hot workability, room temperature ductility, and high temperature strength are all good (◎), but when O is relatively large at 0.013% (alloy 41, comparative alloy), it was found that the room temperature ductility is poor (×). In alloy 41, which is a comparative alloy, the O component exceeds the range of 0.010% or less, and the amount of the specific impurity element O is too large, which embrittles the matrix phase. Therefore, it is considered that this causes poor room temperature ductility.

[0046] (12)Summary As described above, from the measurement results and evaluation results in Table 1, the component ratios excluding Fe and irreversible impurities excluding the following specific impurity elements, that is, Al, Ti, Ni, Nb, and W, and specific individual impurity elements (C, N, S, Si, Mn, and O) are, in atomic%, An Fe-based alloy within the range of Al(12.5~23.0%):Ti(1.4~3.6%):Ni(9.5~16.5%):Nb(2.0~4.0%):W(1.0~3.0%):C(less than 0.010%):N(less than 0.010%):S(less than 0.0020%):Si(less than 0.010%):Mn(less than 0.10%):O(less than 0.010%) has been shown to simultaneously possess a plurality of excellent effects compared to alloys outside the range of these composition ratios.

Industrial Applicability

[0047] The Fe-based heat-resistant alloy of the present invention has sufficient ductility at room temperature, sufficiently high strength at high temperatures, and excellent hot workability. Therefore, it is suitable for use as a material for heat-resistant high-temperature parts such as engines and turbines of various transportation equipment, as well as heat-resistant high-temperature parts in various plants and industrial machines. In addition, since the Fe-based heat-resistant alloy of the present invention can be processed and manufactured as a member by general methods such as melting, casting, forging, and rolling, it can be put into practical use while maintaining cost advantages in manufacturing.< / w> < / nb> < / ni> < / ti> < / al>

Claims

1. The content of each of the following elements is in atomic percentage: Al: 12.5 to 23.0%, Ti: 1.4 to 3.6%, Ni: 9.5 to 16.5%, Nb: 2.0 to 4.0%, W: 1.0 to 3.0%, C: 0.010% or less, N: 0.010% or less, S: 0.0020% or less, Si: 0.010% or less, Mn: 0.10% or less, O: 0.010% or less, and the balance consists of Fe and inevitable impurities excluding the above elements, an Fe-based heat-resistant alloy.

2. The Fe-based heat-resistant alloy according to Claim 1, having a ductility with an elongation of 5.0% or more in a tensile test at room temperature.

3. The Fe-based heat-resistant alloy according to Claim 2, having a high-temperature strength with a tensile strength of 700 MPa or more in a tensile test at 700 °C.

4. The Fe-based heat-resistant alloy according to Claim 3, which does not crack even when groove roll rolling is repeatedly performed with a heating temperature of 1100 °C when processed into an ingot of φ40 mm × 90 mm.

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