An aluminum-containing heat-resistant alloy with excellent comprehensive performance and a preparation method thereof

Abstract

The application discloses an aluminum-containing heat-resistant alloy with excellent comprehensive performance and a preparation method thereof, and belongs to the technical field of aluminum-containing austenitic heat-resistant alloy materials. The application solves the problem that the good oxidation resistance and high-temperature durability, and the high room-temperature strength and good elongation after fracture of the existing alloy cannot be compatible. The aluminum-containing heat-resistant alloy of the application contains the following components in percentage by mass: C: 0.3% to 0.6%, P: ≤0.02%, S: ≤0.01%, Cr: 24% to 30%, Ni: 46% to 60%, Al: 3% to 5.5%, W: 0.3% to 2.5%, Co: 0.1% to 1.0%, Nb: 0.1% to 2.0%, Zr: 0.01% to 0.2%, Ti: 0.01% to 0.2%, RE: 0.005% to 0.5%, and the balance of Fe and inevitable impurities.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of aluminum austenitic heat-resistant alloy materials, and particularly relates to an aluminum-containing heat-resistant alloy with excellent comprehensive performance and a preparation method thereof. BACKGROUND

[0002] Due to the strong affinity of Al and O, the addition of aluminum in the austenitic heat-resistant alloy can improve the oxidation resistance of the alloy, but since Al is a ferrite-forming element, the addition of a certain amount of aluminum can greatly reduce the microstructure stability of the alloy, and further reduce the high-temperature durability of the alloy; in order to improve the durability, a solid solution strengthening element needs to be added for strengthening, and the addition of the solid solution strengthening element reduces the solid solubility of the second phase particle forming element, promotes the precipitation of a large amount of second phase particles, greatly increases the room temperature strength of the alloy, and significantly reduces the elongation after fracture, which is even lower than 2%, increases the difficulty of processing and welding forming, and reduces the toughness, and the alloy is prone to precipitate NiAl phase during long-term service, and reduces the durability of the alloy.

[0003] Therefore, there is an urgent need for an alloy with excellent comprehensive performance, which has good oxidation resistance and high-temperature durability, high room temperature strength and good elongation after fracture. SUMMARY

[0004] In view of the above, the present application aims to provide an aluminum-containing heat-resistant alloy with excellent comprehensive performance and a preparation method thereof, to solve the problem that the good oxidation resistance and high-temperature durability, high room temperature strength and good elongation after fracture of the existing alloy cannot be achieved at the same time.

[0005] The purpose of the present application is mainly achieved by the following technical solutions:

[0006] In a first aspect, the present application provides an aluminum-containing heat-resistant alloy with excellent comprehensive performance, which comprises, in terms of mass percentage: C: 0.3%-0.6%, P: ≤0.02%, S: ≤0.01%, Cr: 24%-30%, Ni: 46%-60%, Al: 3%-5.5%, W: 0.3%-2.5%, Co: 0.1%-1.0%, Nb: 0.1%-2.0%, Zr: 0.01%-0.2%, Ti: 0.01%-0.2%, RE: 0.005%-0.5%, and the balance being Fe and inevitable impurities.

[0007] Optionally, the heat-resistant alloy comprises, in mass percentage: C: 0.40%-0.55%, P: ≤0.02%, S: ≤0.01%, Cr: 25%-28%, Ni: 50%-60%, Al: 3%-5%, W: 0.5%-2.0%, Co: 0.1%-1.0%, Nb: 0.1%-1.5%, Zr: 0.01%-0.1%, Ti: 0.01%-0.2%, RE: 0.01%-0.3%, and the balance being Fe and inevitable impurities.

[0008] Optionally, the RE comprises one or a combination of several of La, Ce and Y.

[0009] In a second aspect, the present application provides a preparation method of an aluminum-containing heat-resistant alloy, for preparing the heat-resistant alloy described above, comprising the following steps:

[0010] S1: weighing raw materials according to the alloy composition ratio;

[0011] S2: melting the active element raw materials in vacuum to obtain an intermediate alloy, and then placing the intermediate alloy in a ladle; refining the non-active element to obtain refined molten steel;

[0012] S3: adjusting the temperature of the refined molten steel, tapping, introducing into the ladle containing the intermediate alloy to obtain molten steel to be cast, cooling, casting, and obtaining the alloy.

[0013] Optionally, the active elements comprise aluminum, yttrium, titanium, zirconium, lanthanum and cerium, and the non-active elements comprise chromium, nickel, tungsten, cobalt, niobium and iron.

[0014] Optionally, in step S2, part of the aluminum is melted into the intermediate alloy, and the other part of the aluminum is refined into the refined molten steel.

[0015] Optionally, the proportion of the aluminum refined into the refined molten steel is ≤20%.

[0016] Optionally, in step S3, the casting temperature is 1550-1690℃.

[0017] Optionally, the tapping temperature is 1650-1750℃.

[0018] In a third aspect, the present application further provides a pipe or ring casting serving in an environment of high-temperature oxidation, coking or carburization, wherein the composition of the casting is the heat-resistant alloy described above or obtained by the preparation method described above.

[0019] Compared with the prior art, the present application has the following beneficial effects:

[0020] a) The present application adjusts the microstructure of the alloy by preferably alloying elements and their component proportions. Specifically, by increasing the content of Ni, reducing the content of W, and by increasing the Co and Nb elements, the Co content is controlled to be 0.1%-1.0%, and the Nb content is controlled to be 0.1%-2.0%, so that the microstructure of the alloy is composed of austenite phase (about 92% in volume percentage) and carbide phase, and the volume fraction of the carbide phase is relatively small, about 8%. Specifically, the carbide phase is divided into two types: one is a Cr element-based carbide, and the other is a Nb-based carbide. And the Cr element-based carbide is distributed in a fishbone shape, and the Nb-based carbide is distributed in a dot strip shape.

[0021] b) In the preparation method of the present application, by placing part of the aluminum in a vacuum induction furnace to smelt into an intermediate alloy, and placing another part of the aluminum in a medium-frequency induction furnace to refine into a refined molten steel, both the purity of the molten steel in the medium-frequency induction furnace can be improved, and the burning loss of aluminum elements in the ladle can be reduced.

[0022] c) In the preparation method of the present application, by controlling the proportion of aluminum refined into a refined molten steel ≤20% (i.e. the mass percentage of aluminum placed in the medium-frequency induction furnace accounts for the total aluminum), both the purity of the molten steel in the medium-frequency induction furnace can be ensured, and the formed oxidation slag can be avoided from adhering to the furnace wall, thereby reducing the service life of the furnace lining.

[0023] d) The alloy of the present application has excellent comprehensive performance: the density ≤8.0 g / cm 3 (For example, 7.84-7.90 g / cm 3 ), the room temperature yield strength ≥600 MPa (for example, 655-702 MPa), the room temperature tensile strength ≥800 MPa (for example, 880-953 MPa), the elongation after fracture ≥5% (for example, 5%-7%), the average oxidation weight gain rate ≤0.1 g / m 2 ·h after exposure in air at 1100℃ for 100 hours, and the average oxide scale spalling amount ≤1.0 g / m 2 ; and the stress rupture life at 1100℃ / 17MPa ≥150 hours (for example, 152-212h), the long-term microstructure stability is excellent, and it is suitable for making pipe or ring castings serving in an environment up to 1150℃ high temperature oxidation, coking or carburizing.

[0024] Other features and advantages of the present application will be set forth in the following description, and in part will become apparent to those skilled in the art from the description, or can be learned by practice of the present application. The objects and other advantages of the present application can be realized and attained by particularly pointed out in the written description and the accompanying drawings. BRIEF DESCRIPTION OF DRAWINGS

[0025] The accompanying drawings, which are included to provide a further understanding of the application and are incorporated in and constitute a part of this application, illustrate embodiments of the application and together with the description serve to explain the principles of the application. In the drawings:

[0026] Figure 1 Microstructure of Example 2 of the present application;

[0027] Figure 2 Microstructure of Example 3 of the present application;

[0028] Figure 3 Microstructure of Comparative Example 1 of the present application;

[0029] Figure 4(a) is the oxidation weight gain curve of the examples and comparative examples of the present application at 1100℃ (tested according to the standard of HB5258-2000);

[0030] Figure 4(b) is the oxidation spalling curve of the examples and comparative examples of the present application at 1100℃ (tested according to the standard of HB5258-2000). DETAILED DESCRIPTION

[0031] The preferred embodiments of the present application will be described in detail below with reference to the drawings, in which the same reference numerals are used to represent the same elements throughout the several views, and the principles of the present application are illustrated by the embodiments of the present application.

[0032] The present application provides an aluminum-containing heat-resistant alloy with excellent comprehensive performance, which comprises, in mass percentage: C: 0.3%-0.6%, P: ≤0.02%, S: ≤0.01%, Cr: 24%-30%, Ni: 46%-60%, Al: 3%-5.5%, W: 0.3%-2.5%, Co: 0.1%-1.0%, Nb: 0.1%-2.0%, Zr: 0.01%-0.2%, Ti: 0.01%-0.2%, RE: 0.005%-0.5%, and the balance being Fe and inevitable impurities.

[0033] RE is one or a combination of several of La, Ce and Y.

[0034] The functions and dosage selection of the components contained in the present application are described in detail as follows:

[0035] C: C is an important precipitation strengthening element, which can form carbides with Cr, Nb and other elements, and is an important strengthening phase in the heat-resistant alloy. However, too much carbon content will reduce the welding performance, and too low carbon content will cause insufficient strength, so the content of C in the present application is controlled at 0.3%-0.6%.

[0036] Cr: Cr is a key element in heat-resistant alloy, which can improve the oxidation resistance of heat-resistant alloy, and can form carbide to strengthen the alloy, but Cr is also a ferrite forming element, and excessive addition is not conducive to the organizational stability of the alloy, therefore, the content of Cr in the application is limited to 24%~30%.

[0037] Ni: Ni is a key element to improve the high temperature thermal strength of heat-resistant alloy, but excessive Ni content will increase the solubility of C, reduce the content of carbide, and thus affect the strength of the alloy, and also increase the production cost of heat-resistant alloy, therefore, the content of Ni in the application is limited to 46%~60%.

[0038] Al: Al and O can form dense and stable Al2O3 oxide, prevent the alloy from being further oxidized, and improve the oxidation resistance of the alloy, but excessive addition of Al element is not conducive to the high temperature durability of the alloy, therefore, the content of Al is limited to 3%~5.5%.

[0039] W: W is an important solid solution strengthening element, which can improve the high temperature stability of heat-resistant alloy, but excessive W will significantly reduce the plasticity of the alloy and the solid solubility of the second phase particle forming element, promote the precipitation of a large number of second phase particles, and cause the room temperature strength of the alloy to increase significantly and the elongation after fracture to decrease obviously, therefore, the content of W in the application is limited to 0.3%~2.5%.

[0040] Co: Co can reduce the stacking fault energy of the alloy, thereby strengthening the alloy, and the content of Co in the application is limited to 0.1%~1.0%.

[0041] Nb: A small amount of Nb and C can form carbide to strengthen the alloy, and the content of Nb in the application is limited to 0.1~2.0%.

[0042] Ti, Zr: Ti and Zr are carbide forming elements, and also have strong affinity with O, which can purify the molten steel during melting and form carbide particles to strengthen the alloy, and the content of Ti and Zr in the application is limited to Ti: 0.01%~0.2%, Zr: 0.01%~0.2%.

[0043] RE: RE can purify the molten steel, improve the morphology of carbide, and improve the high temperature oxidation resistance of the alloy, but excessive RE will reduce the high temperature durability and melting point of the alloy, therefore, the content of RE in the application is limited to 0.005%~0.5%.

[0044] P, S: Phosphorus and sulfur are impurity elements, which reduce the toughness and high temperature durability strength of heat-resistant alloy, and need to be controlled, therefore, according to the current smelting process, the content of P is limited to ≤0.02%, and the content of S is limited to ≤0.01%.

[0045] To further improve the comprehensive performance of the above-mentioned aluminum-containing heat-resistant alloy, the components of the aluminum-containing heat-resistant alloy can be as follows in terms of mass percentage: C: 0.40%-0.55%, P: ≤0.02%, S: ≤0.01%, Cr: 25%-28%, Ni: 50%-60%, Al: 3%-5%, W: 0.5%-2.0%, Co: 0.1%-1.0%, Nb: 0.1%-1.5%, Zr: 0.01%-0.1%, Ti: 0.01%-0.2%, RE: 0.01%-0.3%, and the balance of Fe and inevitable impurities.

[0046] Specifically, the microstructure of the above-mentioned aluminum-containing heat-resistant alloy includes austenite phase and carbide phase; the volume percentage of the austenite is about 92%, specifically 90%-94%, and the volume percentage of the carbide phase is about 8%, specifically 6%-10%. Compared with Comparative Example 1, the carbide structure morphology of the aluminum-containing heat-resistant alloy of the present application is quite different. In the present application, the black Cr element-based carbide is mostly long and narrow in morphology, with a width of 2-6 µm and a length of 10-200 µm; the white Nb element-based carbide is mostly punctiform or massive, with a diameter size of 1-15 µm. In Comparative Example 1, the morphology of the carbide is mainly large net-shaped.

[0047] The design idea of the aluminum-containing heat-resistant alloy of the present application is as follows: by increasing the content of Ni, reducing the content of W, and increasing the contents of Co and Nb, the content of Co is controlled to be 0.1-1.0% and the content of Nb is controlled to be 0.1-2.0%, so that the microstructure of the alloy is composed of austenite phase and carbide phase, and the volume fraction of the carbide phase is relatively small. The carbide phase is divided into two types: the Cr element-based carbide is distributed in a fishbone shape, and the Nb-based carbide is distributed in a point strip shape.

[0048] The aluminum-containing heat-resistant alloy of the present application has a density of ≤8.0 g / cm 3 , a room temperature yield strength of ≥600 MPa, a tensile strength of ≥800 MPa, and an elongation after fracture of ≥5%; after being exposed to air at 1100°C for 100 hours, the average oxidation weight gain rate is ≤0.1 g / m 2 ·h, and the average oxide scale spalling amount is ≤1.0 g / m 2 ; and the stress rupture life at 1100°C / 17 MPa is ≥150 hours, the long-term microstructure stability is excellent, and the alloy is suitable for manufacturing pipe or ring castings serving in high-temperature oxidation, coking or carburizing environments.

[0049] The present application also provides a preparation method of the above-mentioned aluminum-containing heat-resistant alloy, which is melted in air by a medium-frequency induction furnace and formed by centrifugal casting, and includes the following steps:

[0050] S1: weighing raw materials according to the component proportioning of the heat-resistant alloy;

[0051] S2: The active element raw material is melted in a vacuum induction furnace to obtain an intermediate alloy, and then the intermediate alloy is placed in a ladle; the inactive element raw material is refined in a medium-frequency induction furnace to obtain refined molten steel;

[0052] S3: Adjust the temperature of the refined molten steel, tap it out, and pour it into a ladle containing the intermediate alloy to obtain the molten steel to be cast. Cool it, and pour the molten steel into a high-speed rotating mold for centrifugal casting and solidification to obtain the alloy.

[0053] In step S1, the raw materials include pure metal ingots and / or alloy ingots. The pure metal ingots include chromium, tungsten, nickel plates, cobalt, niobium, aluminum, pure iron, yttrium, sponge titanium, and zirconium; the alloy ingots include ferrochrome carbide, ferrotungsten, ferroniobium, lanthanum, cerium rare earth elements, aluminum, titanium, zirconium, lanthanum, and cerium.

[0054] In step S2, the active elements are aluminum, yttrium, titanium, zirconium, lanthanum, and cerium. The inactive elements are chromium, nickel, tungsten, cobalt, niobium, and iron.

[0055] In a preferred embodiment, aluminum is smelted into a master alloy and refined into refined steel in a certain proportion. That is, in step S2, a portion of the aluminum is smelted into a master alloy in a vacuum induction furnace, and the other portion is refined into refined steel in a medium-frequency induction furnace. The advantage of doing this is that it can improve the purity of the molten steel in the medium-frequency induction furnace and reduce the loss of aluminum elements in the ladle.

[0056] Specifically, the proportion of aluminum in the refined steel should be ≤20% (i.e., the mass percentage of aluminum in the medium-frequency induction furnace). This has the advantage of ensuring the purity of the steel in the medium-frequency induction furnace and preventing the oxide slag from adhering to the furnace wall and reducing the service life of the furnace lining.

[0057] In step S2, the melting temperature is 1000℃-1500℃, for example, 1000℃, 1050℃, 1100℃, 1150℃, 1200℃, 1250℃, 1300℃, 1350℃, 1400℃, 1450℃, 1500℃.

[0058] The refining temperature is 1600℃-1700℃, for example, 1600℃, 1620℃, 1640℃, 1650℃, 1670℃, 1680℃, 1690℃, and 1700℃.

[0059] Specifically, in step S3, the tapping temperature is 1650-1750℃, for example, 1650℃, 1660℃, 1670℃, 1680℃, 1690℃, 1700℃, 1710℃, 1720℃, 1730℃, 1740℃, and 1750℃.

[0060] In step S3, the casting temperature is 1550-1690℃, for example, 1550℃, 1570℃, 1580℃, 1590℃, 1600℃, 1610℃, 1620℃, 1630℃, 1640℃, 1650℃, 1690℃.

[0061] In step S3, the rotational speed of the mold cylinder is not less than 1500 rpm, for example, 1600 rpm, 1800 rpm, 2000 rpm, 3000 rpm, 4000 rpm, 5000 rpm, 6000 rpm, 8000 rpm, or 10000 rpm.

[0062] The present invention will now be described in detail with reference to specific embodiments.

[0063] Example 1

[0064] An aluminum-containing austenitic heat-resistant alloy material smelted in the atmosphere is composed of the following elements by weight percentage: C: 0.35%, P: 0.015%, S: 0.001%, Cr: 24.5%, Ni: 46.0%, Al: 3.0%, W: 0.8%, Co: 0.5%, Nb: 0.3%, Zr: 0.02%, Ti: 0.015%, La: 0.020%, Ce: 0.015%, with the balance being Fe and unavoidable impurities.

[0065] The preparation method of the aluminum-containing austenitic heat-resistant alloy smelted in the atmosphere in this embodiment includes the following steps:

[0066] S1: Prepare raw materials such as ferrochrome carbide (or metallic chromium), nickel plate, ferrotungsten (or metallic tungsten), metallic cobalt, metallic niobium (or ferroniobium), pure iron, metallic aluminum, sponge titanium, metallic zirconium, lanthanum, cerium, and rare earth elements according to the above composition.

[0067] S2: The above-mentioned metallic aluminum, sponge titanium, metallic zirconium, lanthanum, cerium and rare earth are smelted into an intermediate alloy in a vacuum induction furnace at a melting temperature of 1000℃, and the smelted intermediate alloy is placed in a steel ladle.

[0068] S3: Place raw materials such as ferrochrome carbide (or metallic chromium), nickel plate, ferrotungsten (or metallic tungsten), metallic cobalt, metallic niobium (or ferroniobium), and pure iron in a crucible of a medium-frequency induction furnace for refining at a refining temperature of 1600℃; after refining in the medium-frequency induction furnace, refined molten steel is obtained.

[0069] S4: Adjust the temperature of the refined molten steel to 1670℃, pour the refined molten steel into a ladle containing the intermediate alloy to obtain the molten steel to be cast, cool it to 1590℃, pour the molten steel to be cast into a high-speed rotating mold to solidify and form the alloy.

[0070] Example 2

[0071] An aluminum-containing austenitic heat-resistant alloy material smelted in the atmosphere is composed of the following elements by weight percentage: C: 0.4%, P: 0.016%, S: 0.001%, Cr: 25.3%, Ni: 50.6%, Al: 3.5%, W: 1.5%, Co: 0.8%, Nb: 0.8%, Zr: 0.04%, Ti: 0.03%, Y: 0.05%, with the balance being Fe and unavoidable impurities.

[0072] The preparation method of the aluminum-containing austenitic heat-resistant alloy smelted in the atmosphere in this embodiment includes the following steps:

[0073] S1: Prepare raw materials such as ferrochrome carbide (or metallic chromium), nickel plate, ferrotungsten (or metallic tungsten), metallic cobalt, metallic niobium (or ferroniobium), pure iron, metallic aluminum, sponge titanium, metallic zirconium, and metallic yttrium according to the above composition;

[0074] S2: 90% of the above-mentioned sponge titanium, metallic zirconium, metallic yttrium and metallic aluminum are melted in a vacuum induction furnace to form an intermediate alloy at a melting temperature of 1500°C, and the melted intermediate alloy is placed in a ladle.

[0075] S3: Place ferrochrome carbide (or metallic chromium), nickel plate, ferrotungsten (or metallic tungsten), metallic cobalt, metallic niobium (or ferroniobium), pure iron, and 10% of the above-mentioned metallic aluminum in a crucible of a medium-frequency induction furnace for refining at a refining temperature of 1700℃; after refining in the medium-frequency induction furnace, refined molten steel is obtained.

[0076] S4: Adjust the temperature of the refined molten steel to 1700℃, pour the refined molten steel into a ladle containing the intermediate alloy to obtain the molten steel to be cast, cool it to 1630℃, pour the molten steel to be cast into a high-speed rotating mold to solidify and form the alloy.

[0077] Example 3

[0078] An aluminum-containing austenitic heat-resistant alloy material smelted in the atmosphere is composed of the following elements by weight percentage: C: 0.45%, P: 0.018%, S: 0.001%, Cr: 26.8%, Ni: 54.9%, Al: 3.8%, W: 1.0%, Co: 0.6%, Nb: 1.2%, Zr: 0.1%, Ti: 0.06%, Y: 0.09%, with the balance being Fe and unavoidable impurities.

[0079] The preparation method of the aluminum-containing austenitic heat-resistant alloy smelted in the atmosphere in this embodiment includes the following steps:

[0080] S1: Prepare raw materials such as ferrochrome carbide (or metallic chromium), nickel plate, ferrotungsten (or metallic tungsten), metallic cobalt, metallic niobium (or ferroniobium), pure iron, metallic aluminum, sponge titanium, metallic zirconium, and metallic yttrium according to the above composition;

[0081] S2: 80% of the above-mentioned sponge titanium, metallic zirconium, metallic yttrium and metallic aluminum are melted in a vacuum induction furnace to form an intermediate alloy at a melting temperature of 1200°C, and the melted intermediate alloy is placed in a ladle.

[0082] S3: Place ferrochrome carbide (or metallic chromium), nickel plate, ferrotungsten (or metallic tungsten), metallic cobalt, metallic niobium (or ferroniobium), pure iron, and 20% of the above-mentioned metallic aluminum in a crucible of a medium-frequency induction furnace for refining at a refining temperature of 1620℃; after refining in the medium-frequency induction furnace, refined molten steel is obtained.

[0083] S4: Adjust the temperature of the refined molten steel to 1730℃, pour the refined molten steel into a ladle containing the intermediate alloy to obtain the molten steel to be cast, cool it to 1650℃, pour the molten steel to be cast into a high-speed rotating mold to solidify and form the alloy.

[0084] Example 4

[0085] An aluminum-containing austenitic heat-resistant alloy material smelted in the atmosphere is composed of the following elements by weight percentage: C: 0.55%, P: 0.013%, S: 0.001%, Cr: 28.2%, Ni: 58.2%, Al: 4.5%, W: 2.0%, Co: 0.3%, Nb: 1.8%, Zr: 0.15%, Ti: 0.16%, La: 0.07%, Ce: 0.12%, with the balance being Fe and unavoidable impurities.

[0086] The preparation method of the aluminum-containing austenitic heat-resistant alloy smelted in the atmosphere in this embodiment includes the following steps:

[0087] S1: Prepare raw materials such as ferrochrome carbide (or metallic chromium), nickel plate, ferrotungsten (or metallic tungsten), metallic cobalt, metallic niobium (or ferroniobium), pure iron, metallic aluminum, sponge titanium, metallic zirconium, lanthanum, cerium, and rare earth elements according to the above composition.

[0088] S2: The above-mentioned metallic aluminum, sponge titanium, metallic zirconium, lanthanum, cerium and rare earth are smelted into an intermediate alloy in a vacuum induction furnace at a melting temperature of 1400℃, and the smelted intermediate alloy is placed in a steel ladle.

[0089] S3: Place raw materials such as ferrochrome carbide (or metallic chromium), nickel plate, ferrotungsten (or metallic tungsten), metallic cobalt, metallic niobium (or ferroniobium), and pure iron in a crucible of a medium-frequency induction furnace for refining at a refining temperature of 1680℃; after refining in the medium-frequency induction furnace, refined molten steel is obtained.

[0090] S4: Adjust the temperature of the refined molten steel to 1720℃, pour the refined molten steel into a ladle containing the intermediate alloy to obtain the molten steel to be cast, cool it to 1640℃, pour the molten steel to be cast into a high-speed rotating mold to solidify and form the alloy.

[0091] Example 5

[0092] An aluminum-containing austenitic heat-resistant alloy material smelted in the atmosphere is composed of the following elements by weight percentage: C: 0.50%, P: 0.012%, S: 0.001%, Cr: 29.5%, Ni: 59.1%, Al: 5.0%, W: 2.2%, Co: 0.2%, Nb: 0.8%, Zr: 0.05%, Ti: 0.06%, La: 0.17%, Ce: 0.22%, with the balance being Fe and unavoidable impurities.

[0093] The preparation method of the aluminum-containing austenitic heat-resistant alloy smelted in the atmosphere in this embodiment includes the following steps:

[0094] S1: Prepare raw materials such as ferrochrome carbide (or metallic chromium), nickel plate, ferrotungsten (or metallic tungsten), metallic cobalt, metallic niobium (or ferroniobium), pure iron, metallic aluminum, sponge titanium, metallic zirconium, lanthanum, cerium, and rare earth elements according to the above composition.

[0095] S2: The above-mentioned metallic aluminum, sponge titanium, metallic zirconium, lanthanum, cerium and rare earth are smelted into an intermediate alloy in a vacuum induction furnace at a melting temperature of 1300℃, and the smelted intermediate alloy is placed in a steel ladle.

[0096] S3: Place raw materials such as ferrochrome carbide (or metallic chromium), nickel plate, ferrotungsten (or metallic tungsten), metallic cobalt, metallic niobium (or ferroniobium), and pure iron in a crucible of a medium-frequency induction furnace for refining at a refining temperature of 1650℃; after refining in the medium-frequency induction furnace, refined molten steel is obtained.

[0097] S4: Adjust the temperature of the refined molten steel to 1700℃, pour the refined molten steel into a ladle containing the intermediate alloy to obtain the molten steel to be cast, cool it to 1630℃, pour the molten steel to be cast into a high-speed rotating mold to solidify and form the alloy.

[0098] Comparative Example 1

[0099] This comparative example of an aluminum-containing austenitic heat-resistant alloy is composed of the following elements by weight percentage: C: 0.50%, P: 0.012%, S: 0.001%, Cr: 27.5%, Ni: 50.1%, Al: 3.6%, W: 4.2%, Zr: 0.02%, Ti: 0.05%, La: 0.17%, Ce: 0.22%, with the balance being Fe and unavoidable impurities.

[0100] The preparation method of this comparative example aluminum-containing austenitic heat-resistant alloy includes the following steps:

[0101] S1: Prepare raw materials such as ferrochrome carbide (or metallic chromium), nickel plate, ferrotungsten (or metallic tungsten), pure iron, metallic aluminum, sponge titanium, metallic zirconium, lanthanum, cerium and rare earth according to the above composition;

[0102] S2: The above-mentioned metallic aluminum, sponge titanium, metallic zirconium, lanthanum, cerium and rare earth are smelted into an intermediate alloy in a vacuum induction furnace at a melting temperature of 1300℃, and the smelted intermediate alloy is placed in a steel ladle.

[0103] S3: Place raw materials such as ferrochrome carbide (or metallic chromium), nickel plate, ferrotungsten (or metallic tungsten), and pure iron in a crucible of a medium-frequency induction furnace for refining at a refining temperature of 1640℃; after refining in the medium-frequency induction furnace, refined molten steel is obtained;

[0104] S4: Adjust the temperature of the refined molten steel to 1690℃, pour the refined molten steel into a ladle containing the intermediate alloy to obtain the molten steel to be cast, cool it to 1620℃, pour the molten steel to be cast into a high-speed rotating mold to solidify and form the alloy.

[0105] Comparative Example 2

[0106] This comparative example of an aluminum-containing austenitic heat-resistant alloy material is composed of the following elements by weight percentage: C: 0.45%, P: 0.012%, S: 0.001%, Cr: 27.5%, Ni: 52.4%, Al: 3.2%, W: 1.2%, Co: 0.4%, Nb: 0.5%, Zr: 0.02%, Ti: 0.03%, Y: 0.03%, with the balance being Fe and unavoidable impurities.

[0107] The preparation method of this comparative example aluminum-containing austenitic heat-resistant alloy includes the following steps:

[0108] S1: Prepare raw materials such as ferrochrome carbide (or metallic chromium), nickel plate, ferrotungsten (or metallic tungsten), metallic cobalt, metallic niobium (or ferroniobium), pure iron, metallic aluminum, sponge titanium, metallic zirconium, and metallic yttrium according to the above composition;

[0109] S2: The above-mentioned aluminum, sponge titanium, zirconium and yttrium are smelted into an intermediate alloy in a vacuum induction furnace at a melting temperature of 1400°C, and the smelted intermediate alloy is placed in a ladle.

[0110] S3: Place raw materials such as ferrochrome carbide (or metallic chromium), nickel plate, ferrotungsten (or metallic tungsten), metallic cobalt, metallic niobium (or ferroniobium), and pure iron in a crucible of a medium-frequency induction furnace for refining at a refining temperature of 1620℃; after refining in the medium-frequency induction furnace, refined molten steel is obtained;

[0111] S4: Adjust the temperature of the refined molten steel to 1600℃, pour the refined molten steel into a ladle containing the intermediate alloy to obtain the molten steel to be cast, cool it to 1530℃, pour the molten steel to be cast into a high-speed rotating mold to solidify and form the alloy.

[0112] The main performance test results of the embodiments and comparative examples of the present invention are shown in Table 1 and Table 2.

[0113] Table 1. Density and tensile properties of the examples and comparative examples

[0114]

[0115] Table 2. High-temperature creep performance of the examples and comparative examples

[0116]

[0117] As can be seen from Table 1, the density of the alloy of the present invention is 7.84-7.90 g / cm³. 3 The density is comparable to that of the comparative alloy. The room temperature tensile strength R of the alloy of this invention is... m and room temperature yield strength Rp 0.2 The strengths are 880-953 MPa and 655-702 MPa, respectively, which are comparable to the comparative examples. However, the elongation after fracture of the alloy of this invention is >5%, specifically 5%-7%, which is significantly higher than the 2% and 3% of the comparative alloys.

[0118] As can be seen from Table 2, the crease life of the alloy of the present invention at 1100℃ is 152-212h, which is significantly better than that of the comparative alloy.

[0119] Tables 1 and 2 show that unsuitable alloy composition (Comparative Example 1) or casting temperature that is too low (Comparative Example 2) will affect the elongation after fracture and high-temperature creep life of the alloy, thus proving the importance of the present invention in controlling the alloy composition and content as well as process parameters.

[0120] Figure 1 and Figure 2 The microstructures of Examples 2 and 3 of this invention show that the alloy of this invention consists of austenite ( Figure 1 and Figure 2 Medium-dark gray phase), chromium carbide ( Figure 1 and Figure 2 The black phase) and the niobium carbide phase ( Figure 1 and Figure 2 It consists of a white phase. Furthermore, the chromium carbide phase, dominated by Cr, is distributed in a fishbone pattern, while the niobium carbide phase, dominated by Nb, is distributed in a dotted or striped pattern. The proportion of carbides (chromium carbide phase and niobium carbide phase) is relatively small, about 8%.

[0121] Figure 3The microstructure of Comparative Example 1 of this invention consists of austenite ( Figure 3 Medium-dark gray phase), chromium carbide (tungsten) phase ( Figure 3 It consists of clustered phases. Furthermore, the chromium carbide (tungsten) phase is clustered and constitutes a relatively large proportion, approximately 10%.

[0122] Figure 4(a) shows the oxidative weight gain curves of the embodiments and comparative examples of the present invention (tested according to HB5258-2000 standard).

[0123] Figure 4(b) shows the oxidation exfoliation curves of the embodiments and comparative examples of the present invention (tested according to HB5258-2000 standard).

[0124] As shown in Figure 4(a), from the start of oxidation up to 50 hours, the oxidation weight gain of the alloy of the present invention and the comparative alloy were similar. After 50 hours of oxidation, the oxidation weight gain of the alloy of the present invention was significantly lower than that of the comparative alloy. After exposure to air at 1100°C for 100 hours, the average oxidation weight gain rate was ≤0.1 g / m³. 2 ·h.

[0125] As shown in Figure 4(b), from the start of oxidation until 50 hours, the oxide peeling amount of the alloy of the present invention and the alloy of Comparative Example 1 were similar, while the oxide peeling amount of the alloy of Comparative Example 2 was significantly higher than that of the alloy of the present invention and the alloy of Comparative Example 1. After 50 hours of oxidation, the oxide peeling amount of the alloy of the present invention was significantly lower than that of the comparative alloy. After exposure to air at 1100°C for 100 hours, the average oxide scale peeling amount was ≤1.0 g / m². 2 .

[0126] This demonstrates that the oxidation resistance of the alloy of this invention is significantly superior to that of the comparative alloy. Furthermore, it shows that unsuitable alloy composition (comparative Example 1, W content too high) or casting temperature too low (comparative Example 2) will affect the oxidation resistance of the alloy, thus proving the importance of controlling the alloy composition and content, as well as process parameters, in this invention.

[0127] The microstructures of Examples 1-5 and the comparative examples are shown in Table 3 below.

[0128] Table 3 Microstructure of the alloy

[0129]

[0130] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. An aluminum-containing heat-resistant alloy having excellent comprehensive properties, characterized by comprising, in mass %, The heat-resistant alloy comprises, in mass percentage: C: 0.3%-0.6%, P: ≤0.02%, S: ≤0.01%, Cr: 24%-30%, Ni: 46%-60%, Al: 3%-5.5%, W: 0.3%-2.5%, Co: 0.1%-1.0%, Nb: 0.1%-2.0%, Zr: 0.01%-0.2%, Ti: 0.01%-0.2%, RE: 0.005%-0.5%, and the balance of Fe and inevitable impurities. The microstructure of the heat-resistant alloy is composed of austenite phase and carbide phase; the carbide phase is divided into two types: one is Cr-based carbide, and the other is Nb-based carbide; the Cr-based carbide is distributed in a fishbone shape, with a width of 2-6 µm and a length of 10-200 µm; the Nb-based carbide is distributed in a dot strip shape, with a diameter of 1-15 µm. The volume percentage of the austenite phase is 90%-94%, and the volume percentage of the carbide phase is 6%-10%.

2. The heat resistant alloy of claim 1, wherein, The heat-resistant alloy comprises, in mass percentage: C: 0.40%-0.55%, P: ≤0.02%, S: ≤0.01%, Cr: 25%-28%, Ni: 50%-60%, Al: 3%-5%, W: 0.5%-2.0%, Co: 0.1%-1.0%, Nb: 0.1%-1.5%, Zr: 0.01%-0.1%, Ti: 0.01%-0.2%, RE: 0.01%-0.3%, and the balance of Fe and inevitable impurities.

3. The heat resistant alloy according to claim 1 or 2, characterized in that, The RE comprises one or a combination of several of La, Ce, and Y.

4. A method of producing an aluminum-containing heat-resistant alloy, characterized by, The heat-resistant alloy of any one of claims 1-3 is prepared by the following steps: S1: weighing raw materials according to the alloy composition ratio; S2: melting active element raw materials in a vacuum to obtain an intermediate alloy, and then placing the intermediate alloy in a ladle; refining non-active element raw materials to obtain refined molten steel; S3: adjusting the temperature of the refined molten steel, tapping, and introducing into the ladle containing the intermediate alloy to obtain molten steel to be cast, cooling, and casting to obtain the alloy.

5. The production method according to claim 4, characterized by, The active elements include aluminum, yttrium, titanium, zirconium, lanthanum, and cerium, and the non-active elements include chromium, nickel, tungsten, cobalt, niobium, and iron.

6. The production method according to claim 5, wherein In step S2, part of the aluminum is melted into the intermediate alloy, and the other part of the aluminum is refined into the refined molten steel.

7. The production method according to claim 6, characterized by, The proportion of the aluminum refined into the refined molten steel is ≤20%.

8. The method of any one of claims 4-7, wherein, In step S3, the casting temperature is 1550-1690 ℃.

9. The preparation method according to claim 8, characterized in that, In step S3, the tapping temperature is 1650-1750 ℃.

10. A tubular or ring-shaped casting for service in an oxidizing, coking or carburizing environment, characterized in that The castings have the composition of the heat-resistant alloy of any one of claims 1-3 or the heat-resistant alloy prepared by the method of any one of claims 4-9.

Images