Aluminum-containing heat-resistant alloy with excellent comprehensive performance and preparation method of aluminum-containing heat-resistant alloy

Abstract

The invention discloses an aluminum-containing heat-resisting alloy with excellent comprehensive performance and a preparation method of the aluminum-containing heat-resisting alloy, and belongs to the technical field of aluminum-containing austenite heat-resisting alloy materials. The problem that good oxidation resistance and high-temperature durability, high room-temperature strength and good percentage elongation after fracture of an existing alloy cannot be achieved at the same time is solved. The aluminum-containing heat-resistant alloy comprises the following components in percentage by mass: 0.3%-0.6% of C, less than or equal to 0.02% of P, less than or equal to 0.01% of S, 24%-30% of Cr, 46%-60% of Ni, 3%-5.5% of Al, 0.3%-2.5% of W, 0.1%-1.0% of Co and the balance of Al. 0.1% to 2.0% of Nb; the alloy comprises the following components in percentage by weight: 0.01%-0.2% of Zr, 0.01%-0.2% of Ti, 0.005%-0.5% of RE and the balance of Fe and inevitable impurities.

Description

Technical Field

[0001] This invention relates to the field of aluminum austenitic heat-resistant alloy materials technology, and in particular to an aluminum-containing heat-resistant alloy with excellent comprehensive performance and its preparation method. Background Technology

[0002] Due to the strong affinity between Al and O, adding aluminum to austenitic heat-resistant alloys can improve their oxidation resistance. However, since Al is a ferrite-forming element, the addition of a certain amount of aluminum will greatly reduce the structural stability of the alloy, thereby reducing its high-temperature creep resistance. In order to improve creep resistance, solid solution strengthening elements need to be added. However, the addition of solid solution strengthening elements reduces the solid solubility of the second-phase particle-forming elements, promotes the precipitation of a large number of second-phase particles, and causes a significant increase in the room temperature strength of the alloy, a significant decrease in the elongation after fracture, and in some cases even less than 2%. This increases the difficulty of processing and welding, reduces toughness, and NiAl phase is prone to precipitate during long-term service, resulting in a decrease in the creep resistance of the alloy.

[0003] Therefore, there is an urgent need for an alloy with excellent comprehensive properties, including good oxidation resistance, high-temperature creep resistance, high room temperature strength, and good elongation after fracture. Summary of the Invention

[0004] In view of the above, the present invention aims to provide an aluminum-containing heat-resistant alloy with excellent comprehensive performance and its preparation method, so as to solve the problem that existing alloys cannot simultaneously achieve good oxidation resistance and high-temperature creep resistance, as well as high room temperature strength and good elongation after fracture.

[0005] The objective of this invention is mainly achieved through the following technical solutions:

[0006] In a first aspect, the present invention provides an aluminum-containing heat-resistant alloy with excellent comprehensive performance. The heat-resistant alloy comprises, by 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%, with the balance being Fe and unavoidable impurities.

[0007] Optionally, the heat-resistant alloy, by weight percentage, comprises: 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%, with the balance being Fe and unavoidable impurities.

[0008] Optionally, RE includes one or more of La, Ce, and Y.

[0009] Secondly, the present invention provides a method for preparing an aluminum-containing heat-resistant alloy, which includes the following steps:

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

[0011] S2: The active element raw material is melted in a vacuum to obtain an intermediate alloy, which is then placed in a ladle; the inactive element is refined to obtain refined steel.

[0012] 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, cast it, and obtain the alloy.

[0013] Alternatively, reactive elements include aluminum, yttrium, titanium, zirconium, lanthanum, and cerium, while inactive elements include chromium, nickel, tungsten, cobalt, niobium, and iron.

[0014] Optionally, in step S2, a portion of the aluminum is smelted into an intermediate alloy, and another portion of the aluminum is refined into refined steel.

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

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

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

[0018] Thirdly, the present invention also provides a pipe or ring casting that can operate in a high-temperature oxidizing, coking, or carburizing environment, wherein the casting is composed of the heat-resistant alloy described above or the heat-resistant alloy obtained by the preparation method described above.

[0019] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0020] a) This invention adjusts the microstructure of the alloy by optimizing the alloying elements and their composition ratios. Specifically, by increasing the Ni content and decreasing the W content, and by increasing Co and Nb elements, controlling the Co content to 0.1%-1.0% and the Nb content to 0.1%-2.0%, the microstructure of the alloy consists of austenite phase (volume percentage approximately 92%) and carbide phase, with the carbide phase having a relatively low volume fraction, approximately 8%. Specifically, the carbide phase is divided into two types: one is Cr-dominated carbide, and the other is Nb-dominated carbide. Furthermore, the Cr-dominated carbide exhibits a fishbone-like distribution, while the Nb-dominated carbide exhibits a dotted or striped distribution.

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

[0022] c) In the preparation method of the present invention, by controlling the proportion of aluminum in the refined steel to be ≤20% (that is, the mass percentage of aluminum placed in the medium frequency induction furnace), the purity of the steel in the medium frequency induction furnace can be guaranteed, and the oxide slag formed can be avoided from adhering to the furnace wall and reducing the service life of the furnace lining.

[0023] d) The alloy of this invention exhibits excellent overall properties: density ≤ 8.0 g / cm³. 3 (e.g., 7.84-7.90 g / cm³) 3 The room temperature yield strength is ≥600MPa (e.g., 655-702MPa), the room temperature tensile strength is ≥800MPa (e.g., 880-953MPa), and the elongation after fracture is ≥5% (e.g., 5%-7%); after being exposed to air at 1100℃ for 100 hours, the average oxidation weight gain rate is ≤0.1g / m³. 2 •h, and the average amount of oxide scale peeling is ≤1.0g / m 2 Furthermore, it has a creep life of ≥150 hours (e.g., 152-212h) at 1100℃ / 17MPa, exhibiting excellent long-term structural stability, making it suitable for manufacturing pipe or ring castings that operate in environments with high-temperature oxidation, coking, or carburizing up to 1150℃.

[0024] Other features and advantages of the invention will be set forth in the description which follows, and will be apparent in part from the description, or may be learned by practicing the invention. The objects and other advantages of the invention may be realized and obtained by means of what is particularly pointed out in the written description and the accompanying drawings. Attached Figure Description

[0025] The accompanying drawings are for illustrative purposes only and are not intended to limit the invention. Throughout the drawings, the same reference numerals denote the same parts.

[0026] Figure 1 The microstructure of this invention is shown in Example 2.

[0027] Figure 2 The microstructure of this invention is shown in Example 3.

[0028] Figure 3 This is the microstructure of Comparative Example 1 of the present invention;

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

[0030] Figure 4(b) shows the oxidation and peeling curves of the embodiments and comparative examples of the present invention at 1100°C (tested according to HB5258-2000 standard). Detailed Implementation

[0031] The preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings, which form part of the present invention and, together with the embodiments of the present invention, serve to illustrate the principles of the present invention.

[0032] This invention provides an aluminum-containing heat-resistant alloy with excellent comprehensive performance. The aluminum-containing heat-resistant alloy with excellent comprehensive performance comprises, by mass percentage: 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%, with the balance being Fe and unavoidable impurities.

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

[0034] The following details the function and dosage selection of the components contained in this invention:

[0035] C: C is an important precipitation strengthening element, which can form carbides with elements such as Cr and Nb, and is an important strengthening phase in heat-resistant alloys. However, too much carbon will reduce weldability, while too little will result in insufficient strength. Therefore, the C content in this invention is controlled at 0.3% to 0.6%.

[0036] Cr: Cr is a key element in heat-resistant alloys. It can improve the oxidation resistance of heat-resistant alloys and combine with carbon to form carbide-strengthening alloys. However, Cr is also a ferrite-forming element. Adding too much is not conducive to the structural stability of the alloy. Therefore, the Cr content in this invention is limited to 24% to 30%.

[0037] Ni: Ni is a key element for improving the high-temperature thermal strength of heat-resistant alloys. However, if the Ni content is too high, it will increase the solubility of C, resulting in a decrease in carbide content, which will affect the strength of the alloy and also increase the production cost of the heat-resistant alloy. This invention limits the Ni content to 46% to 60%.

[0038] Al: Al and O can form a dense and stable Al2O3 oxide, which prevents the alloy from being further oxidized and improves the alloy's oxidation resistance. However, the addition of too much Al is not conducive to the alloy's high-temperature creep resistance. Therefore, the Al content is limited to 3% to 5.5%.

[0039] W: W is an important solid solution strengthening element that can improve the high-temperature stability of heat-resistant alloys. However, excessive W will significantly reduce the plasticity of the alloy, reduce 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 while the elongation after fracture decreases significantly. In this invention, the W content is limited to 0.3% to 2.5%.

[0040] Co: Co can reduce the stacking fault energy of the alloy, thereby strengthening the alloy. In this invention, the Co content is limited to 0.1% to 1.0%.

[0041] Nb: A small amount of Nb and C can form a carbide-reinforced alloy. In this invention, the Nb content is limited to 0.1-2.0%.

[0042] Ti and Zr: Ti and Zr are carbide-forming elements and have a strong affinity for O. They can purify molten steel during the smelting process and also form carbide particles to strengthen the alloy. In this invention, the content of Ti and Zr is limited to Ti: 0.01% to 0.2% and Zr: 0.01% to 0.2%, respectively.

[0043] RE: RE can purify molten steel, improve the morphology of carbides, and enhance the high-temperature oxidation resistance of alloys. However, excessive RE will reduce the high-temperature creep resistance and melting point of alloys. This invention limits the content of RE to 0.005% to 0.5%.

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

[0045] To further improve the overall performance of the above-mentioned aluminum-containing heat-resistant alloy, the composition of the above-mentioned aluminum-containing heat-resistant alloy, by mass percentage, can be as follows: 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%, with the balance being Fe and unavoidable impurities.

[0046] Specifically, the microstructure of the aforementioned aluminum-containing heat-resistant alloy includes an austenitic phase and a carbide phase; the volume percentage of austenite is approximately 92%, specifically 90%-94%, and the volume percentage of the carbide phase is approximately 8%, specifically 6%-10%. Compared with Comparative Example 1, the carbide structure morphology of the aluminum-containing heat-resistant alloy of the present invention is significantly different. In the present invention, the black carbides, mainly composed of Cr, are mostly elongated in shape, with a width of 2-6 μm and a length of 10-200 μm; the black carbides, mainly composed of Nb, are mostly dot-like or blocky, with a diameter ranging from 1-15 μm. In contrast, the morphology of the carbides in Comparative Example 1 is mainly a large network structure.

[0047] The design concept of the aluminum-containing heat-resistant alloy of this invention is as follows: by increasing the Ni content and decreasing the W content, and by increasing Co and Nb elements, controlling the Co content to 0.1-1.0% and the Nb content to 0.1-2.0%, the microstructure of the alloy is composed of austenite phase and carbide phase, with a relatively low volume fraction of carbide phase. The carbide phase is divided into two types: Cr-dominated carbides exhibit a fishbone-like distribution, while Nb-dominated carbides exhibit a dotted or striped distribution.

[0048] The aluminum-containing heat-resistant alloy of this invention has a density ≤8.0 g / cm³. 3 The room temperature yield strength is ≥600MPa, tensile strength is ≥800MPa, and elongation after fracture is ≥5%; after exposure to air at 1100℃ for 100 hours, the average oxidation weight gain rate is ≤0.1g / m³. 2 •h, and the average amount of oxide scale peeling is ≤1.0g / m 2 Furthermore, its service life at 1100℃ / 17MPa can reach ≥150 hours, exhibiting excellent long-term structural stability, making it suitable for manufacturing pipe or ring castings that operate in high-temperature oxidation, coking, or carburizing environments.

[0049] This invention also provides a method for preparing the above-mentioned aluminum-containing heat-resistant alloy, which involves melting in an atmospheric medium-frequency induction furnace and forming by centrifugal casting, comprising the following steps:

[0050] S1: Weigh the raw materials according to the composition ratio 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 in 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 in 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 steel 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 in 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 steel 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 in 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 in 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℃. The smelted intermediate alloy is then placed in a 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℃. The smelted intermediate alloy is then placed in a 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]

[0116] Table 2 High-Temperature Duration Performance of Examples and Comparative Examples

[0117]

[0118] 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.

[0119] 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.

[0120] 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.

[0121] 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 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%.

[0122] Figure 3 The 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%.

[0123] 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).

[0124] Figure 4(b) shows the oxidation exfoliation curves of the embodiments and comparative examples of the present invention (tested according to HB5258-2000 standard).

[0125] As shown in Figure 4(a), from the start of oxidation up to 50 hours, the weight gain of the alloy of the present invention and the comparative alloy were similar. After 50 hours of oxidation, the 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 weight gain rate was ≤0.1 g / m³. 2 ·h.

[0126] 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 alloy of the comparative examples. After exposure to air at 1100°C for 100 hours, the average oxide scale peeling amount was ≤1.0 g / m². 2 .

[0127] 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) both affect the alloy's oxidation resistance, thus proving the importance of controlling the alloy composition and content, as well as process parameters, in this invention.

[0128] The microstructures of Examples 1-5 and the comparative examples are shown in Table 3 below.

[0129] Table 3 Microstructure of the alloy

[0130] serial number Microorganism Longest size of carbide phase Example 1 austenitic phase + chromium carbide phase + niobium carbide phase 150μm Example 2 austenitic phase + chromium carbide phase + niobium carbide phase 170μm Example 3 austenitic phase + chromium carbide phase + niobium carbide phase 130μm Example 4 austenitic phase + chromium carbide phase + niobium carbide phase 200μm Example 5 austenitic phase + chromium carbide phase + niobium carbide phase 180μm Comparative Example 1 austenitic phase + chromium carbide (tungsten) phase 30μm Comparative Example 2 austenitic phase + chromium carbide phase + niobium carbide phase 130μm

[0131] 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 with excellent comprehensive performance, characterized in that, The heat-resistant alloy comprises, by weight 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%, with the balance being Fe and unavoidable impurities.

2. The heat-resistant alloy according to claim 1, characterized in that, The heat-resistant alloy comprises, by weight 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%, with the balance being Fe and unavoidable impurities.

3. The heat-resistant alloy according to claim 1 or 2, characterized in that, RE includes one or more of La, Ce, and Y.

4. A method for preparing an aluminum-containing heat-resistant alloy, characterized in that, The method for preparing the heat-resistant alloy according to any one of claims 1-3 comprises the following steps: S1: Weigh the raw materials according to the alloy composition ratio; S2: The active element raw material is melted in a vacuum to obtain an intermediate alloy, which is then placed in a ladle; the inactive element is refined to obtain refined steel. 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, cast it, and obtain the alloy.

5. The preparation method according to claim 4, characterized in that, The reactive elements include aluminum, yttrium, titanium, zirconium, lanthanum, and cerium, while the inactive elements include chromium, nickel, tungsten, cobalt, niobium, and iron.

6. The preparation method according to claim 5, characterized in that, In step S2, a portion of the aluminum is smelted into an intermediate alloy, and the other portion is refined into refined steel.

7. The preparation method according to claim 6, characterized in that, The proportion of aluminum in refined steel is ≤20%.

8. The preparation method according to any one of claims 4-7, characterized in that, 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 pipe or ring casting for use in high-temperature oxidizing, coking, or carburizing environments, characterized in that, The composition of the casting is the heat-resistant alloy as described in any one of claims 1-3 or the heat-resistant alloy obtained by the preparation method described in any one of claims 4-9.

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