High-temperature iron-chromium-aluminum electrothermal alloy and preparation method thereof

Abstract

This application relates to a high-temperature iron-chromium-aluminum electric heating alloy and its preparation method, belonging to the field of high-temperature alloy materials and metallurgical processing technology. The chemical composition of the iron-chromium-aluminum electric heating alloy, by mass fraction, is: Cr: 21%~25%, Al: 4%~6%, Si≤0.50%, Mn≤0.50%, C≤0.015%, Ti: 0.02%~0.10%, Zr: 0.02%~0.15%, rare earth: 0.01%~0.20%, Mg: 0.001%~0.010%, with the remainder being Fe and unavoidable impurities; the rare earth is at least one of Y, La, Ce, and Hf. By optimizing the alloy composition and adding trace elements such as titanium, zirconium, rare earth, and magnesium, combined with a complete process including vacuum induction smelting, electroslag remelting, two-stage forging, hot rolling, annealing, multi-pass cold drawing, and heat treatment, the ferrite structure can be uniformly refined, thereby obtaining an iron-chromium-aluminum electric heating alloy with high strength and good ductility. This iron-chromium-aluminum heating alloy utilizes the ability to form chromium-aluminum oxide films and the grain boundary strengthening effect of rare earth elements to significantly improve high-temperature oxidation resistance and service life, making it suitable for high-temperature heating elements above 1300℃.

Description

Technical Field

[0001] This application relates to the fields of high-temperature alloy materials and metallurgical processing technology, and in particular to a high-temperature iron-chromium-aluminum electrothermal alloy and its preparation method. Background Technology

[0002] Iron-chromium-aluminum (ICAT) aluminum heating alloy is a high-resistance heating alloy material with iron as the base material and chromium and aluminum added to form a dense α-Al₂O₃ oxide film. This alloy has significant advantages such as high resistivity, high operating temperature, good oxidation resistance, low density, and no nickel content. Its operating temperature can reach over 1400℃, and it is widely used in heating elements for industrial furnaces and kilns in industries such as metallurgy, chemicals, ceramics, glass, and electronics. Compared with traditional nickel-chromium alloys, ICAT aluminum heating alloys not only significantly reduce raw material costs but also have a superior high-temperature service life. The dense Al₂O₃ oxide film formed on the surface of the ICAT aluminum alloy has good adhesion to the alloy substrate, effectively preventing oxygen from corroding into the alloy substrate at higher temperatures, thus significantly improving high-temperature oxidation resistance.

[0003] With the increasing demands on the operating temperature and lifespan of heating elements in industrial furnaces, traditional iron-chromium-aluminum (Fe-Chromium-Aluminum) heating alloys are no longer sufficient to meet the requirements for long-term service above 1400℃. The existing technology has the following four main defects: (1) The alloy composition design is not precise enough. The existing technology has not done enough research on the synergistic effect of titanium, zirconium, rare earth elements and trace elements such as magnesium, and has failed to give full play to the positive role of these elements in improving the purity of the alloy and improving the adhesion of the oxide film. (2) The yield of the forging process from large cross-section electroslag ingot to small cross-section billet is low. Due to the large total deformation of forging, this process is prone to causing cracks inside the Fe-Chromium-Aluminum heating alloy, thus wasting high-value materials. (3) The uniformity of grain structure is poor. The intermediate structure cannot be restored during the one-fire forging process, resulting in significant differences in grain size in different areas of the forged billet cross-section, which in turn affects the consistency of the subsequent processing performance and service performance of the Fe-Chromium-Aluminum heating alloy. (4) The high-temperature oxidation resistance life of the Fe-Chromium-Aluminum heating alloy above 1400℃ is limited, which is difficult to meet the requirements of high-end industrial furnaces for long-life heating elements.

[0004] Existing manufacturing processes for iron-chromium-aluminum electrothermal alloys typically employ a complete production route including vacuum induction smelting, electroslag remelting, forging, hot rolling, annealing, cold drawing, and finished product heat treatment. In the forging process, most schemes utilize a one-fire forming process, heating the electroslag remelted ingot to 1100℃~1180℃ and then directly forging it from a round ingot to a square billet of the target size. Additionally, some existing technologies employ a powder metallurgy route, first preparing pre-alloyed powders and then combining them with electroslag remelting and forging processes. However, this approach suffers from high equipment investment, low production efficiency, and the need to add expensive elements such as cobalt and niobium, leading to a significant increase in costs and making it unsuitable for large-scale industrial production. Summary of the Invention

[0005] This application provides a high-temperature iron-chromium-aluminum electrothermal alloy and its preparation method to solve the following technical problem: how to synergistically achieve high yield and uniform microstructure of the iron-chromium-aluminum electrothermal alloy. In a first aspect, embodiments of this application provide a high-temperature iron-chromium-aluminum electric heating alloy, characterized in that, by mass fraction, the chemical composition of the iron-chromium-aluminum electric heating alloy is: Cr: 21%~25%, Al: 4%~6%, Si≤0.50%, Mn≤0.50%, C≤0.015%, Ti: 0.02%~0.10%, Zr: 0.02%~0.15%, rare earth: 0.01%~0.20%, Mg: 0.001%~0.010%, with the remainder being Fe and unavoidable impurities; the rare earth is at least one selected from Y, La, Ce, and Hf; The microstructure of the iron-chromium-aluminum electrothermal alloy is ferrite, and the grain size of the ferrite is ≥8.0.

[0006] Optionally, the iron-chromium-aluminum electrothermal alloy satisfies at least one of the following properties: tensile strength ≥650MPa, elongation ≥25%.

[0007] Secondly, embodiments of this application provide a method for preparing the iron-chromium-aluminum electrothermal alloy described in the first aspect, the method comprising: The resulting masterbatch has the following chemical composition: Cr: 21%~25%, Al: 4%~6%, Si≤0.50%, Mn≤0.50%, C≤0.015%, Ti: 0.02%~0.10%, Zr: 0.02%~0.15%, rare earth: 0.01%~0.20%, Mg: 0.001%~0.010%, with the remainder being Fe and unavoidable impurities; The mother ingot was electroslag remelted using a CaF2-Al2O3-CaO-MgO quaternary slag system to obtain a cast ingot; The ingot is kept at 600°C or cooled to room temperature to obtain a heat-insulated ingot. The heat-insulated ingot is subjected to a first-stage forging process, a first-stage annealing process, and a second-stage forging process in sequence to obtain a square billet of 40mm×40mm~60mm×60mm. The billet is hot-rolled to obtain hot-rolled wire rods with a diameter of 8mm~12mm; The hot-rolled wire rod is subjected to a second annealing treatment to obtain annealed wire rod; The annealed wire rod is subjected to multiple cold drawing passes, and a third annealing treatment is performed between the cold drawing passes to obtain cold-drawn wire with a diameter of 2mm to 5mm. The cold-drawn wire is heat-treated to obtain an iron-chromium-aluminum electrothermal alloy.

[0008] Optionally, the master ingot is obtained by vacuum induction smelting, wherein the ultimate vacuum degree of the vacuum induction smelting is ≤5Pa.

[0009] Optionally, the refining vacuum degree of the vacuum induction smelting is ≤10Pa, the refining temperature of the vacuum induction smelting is 1550℃~1600℃, and the refining time of the vacuum induction smelting is 20min~30min.

[0010] Optionally, the argon-filling pressure in the vacuum induction smelting is 0.05 MPa to 0.10 MPa.

[0011] Optionally, the casting temperature of the vacuum induction smelting is 1600℃~1650℃.

[0012] Optionally, the amount of slag in the quaternary slag system is 3% to 5% of the mass of the mother ingot.

[0013] Optionally, the current of the electroslag remelting is 2000A~4500A, the voltage of the electroslag remelting is 35V~50V, and the melting rate of the electroslag remelting is 1.0kg / min~2.5kg / min.

[0014] Optionally, the diameter of the master ingot is 150mm~160mm; the oxygen content of the master ingot is ≤10ppm, and the nitrogen content of the master ingot is ≤20ppm.

[0015] Optionally, the diameter of the ingot is 150mm~160mm; the oxygen content of the ingot is ≤10ppm, and the sulfur content of the ingot is ≤10ppm.

[0016] Optionally, when the ingot is at 600°C after heat preservation, the furnace loading temperature of the first stage forging process is ≤600°C; when the ingot has cooled to room temperature after heat preservation, the furnace loading temperature of the first stage forging process is ≤400°C.

[0017] Optionally, the heating temperature of the first stage forging process is 1050℃~1080℃, the heating time of the first stage forging process is 90min~120min, and the holding time of the first stage forging process is 30min~40min.

[0018] Optionally, the initial forging temperature of the first stage forging process is ≥1050℃, and the final forging temperature of the first stage forging process is ≥800℃.

[0019] Optionally, the temperature of the first annealing treatment is 740℃~830℃, and the time of the first annealing treatment is 1h~2h.

[0020] Optionally, the furnace loading temperature for the second stage forging process is ≤400℃.

[0021] Optionally, the heating temperature of the second stage forging treatment is 1100℃~1140℃, the heating time of the second stage forging treatment is 60min~90min, and the holding time of the second stage forging treatment is 25min~35min.

[0022] Optionally, the initial forging temperature of the second stage forging process is ≥1100℃, and the final forging temperature of the second stage forging process is ≥800℃.

[0023] Optionally, the furnace loading temperature of the hot-rolled material is ≤400℃.

[0024] Optionally, the heating temperature of the hot rolling is 1030℃~1070℃, and the holding time of the hot rolling is 60min~90min.

[0025] Optionally, the final rolling temperature of the hot rolling is ≥850℃.

[0026] Optionally, the total deformation ratio of the hot rolling is ≥15:1.

[0027] Optionally, the cooling method for the second annealing is at least one of slow cooling in the furnace and controlled-rate cooling; The temperature of the second annealing treatment is 750℃~800℃, and the holding time of the second annealing treatment is 1h~2h.

[0028] Optionally, the surface shrinkage rate of each pass in the multi-pass cold drawing is 15% to 25%, and the total surface shrinkage rate of the multi-pass cold drawing is 60% to 80%.

[0029] Optionally, the temperature of the third annealing treatment is 750℃~800℃, and the holding time of the third annealing treatment is 1h~2h.

[0030] Optionally, the heat treatment temperature is 850℃~950℃, and the heat treatment holding time is 1h~2h.

[0031] The technical solutions provided in this application have the following advantages compared with the prior art: This application provides a high-temperature iron-chromium-aluminum (ICH) heating alloy and its preparation method. The ICH heating alloy has the following chemical composition by mass fraction: Cr: 21%~25%, Al: 4%~6%, Si≤0.50%, Mn≤0.50%, C≤0.015%, Ti: 0.02%~0.10%, Zr: 0.02%~0.15%, rare earth elements: 0.01%~0.20%, Mg: 0.001%~0.010%, with the remainder being Fe and unavoidable impurities. The rare earth elements are at least one of Y, La, Ce, and Hf. The microstructure of the ICH heating alloy is ferrite, with a grain size grade ≥8.0. In the alloy design of the ICH heating alloy, chromium and aluminum are the core constituent elements. Chromium and aluminum, through the formation of a dense Al2O3-Cr2O3 composite oxide film, endow the ICH heating alloy with excellent high-temperature oxidation resistance. Meanwhile, strictly controlling the mass fractions of carbon, silicon, and manganese can significantly reduce the adverse effects of impurity elements on grain boundary brittleness, avoiding cracks caused by grain boundary weakening during high-temperature forging. The addition of titanium and zirconium can form high-temperature stable carbonitrides, which effectively pin grain boundaries and inhibit grain coarsening, thus providing a fine-grained initial structure for subsequent large deformation forging. The microalloying of rare earth elements with magnesium further purifies grain boundaries, improves oxide film adhesion, and promotes dynamic recrystallization during deformation, thereby improving microstructure uniformity. High mass fractions of chromium and aluminum ensure the stability of the oxide film at high temperatures, while the synergistic effect of titanium, zirconium, and rare earth elements can refine the as-cast microstructure, reduce the initial grain size of the ingot, and reduce the deformation resistance of subsequent forging. The composite oxide formed by trace amounts of magnesium and rare earth elements can effectively capture harmful elements such as oxygen and sulfur, improve the purity of the iron-chromium-aluminum heating alloy, and avoid grain boundary cracks caused by impurity segregation. The combined effect of high purity and fine grain formation allows the iron-chromium-aluminum electrothermal alloy to withstand large deformations without cracking during the staged forging process, while also achieving grain homogenization through intermediate annealing, ultimately resulting in high yield and a fine and uniform grain structure across the entire cross-section.

[0032] In summary, this application fundamentally reconciles the contradiction between the high-temperature plastic deformation capacity and the microstructure stability of iron-chromium-aluminum electrothermal alloys by optimizing both the elemental functional allocation and purity control in the composition design. Attached Figure Description

[0033] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application.

[0034] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the accompanying drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, those skilled in the art can obtain other drawings based on these drawings without any creative effort.

[0035] Figure 1 A flowchart illustrating a method for preparing a high-temperature iron-chromium-aluminum electrothermal alloy, as provided in this application embodiment. Detailed Implementation

[0036] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions in the embodiments of this application will be clearly and completely described below. Obviously, the described embodiments are only some, not all, of the embodiments of this application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of this application.

[0037] The range descriptions used herein, such as numerical ranges and proportional ranges, include all possible sub-ranges and single numerical values ​​within that range. For example, the range descriptions of "1 to 6" or "1~6" cover all sub-ranges between 1 and 6 (such as 1 to 3, 2 to 5, etc.) and single numbers (such as 1, 2, 3, 4, 5, 6). Unless otherwise specified, the terms "including" and "contains" used herein mean "including but not limited to"; relational terms such as "first" and "second" are used only to distinguish different entities or operations and do not imply an actual order or relationship. "And / or" indicates that multiple situations can exist individually or simultaneously. Expressions such as "at least one," "multiple," and "at least one" refer to any combination of the corresponding objects, including combinations of single or multiple objects. The proportional relationships mentioned herein, such as mass ratios and molar ratios, should be understood as the correspondence between the first and second terms of a proportional formula, according to the order of description. The raw materials, reagents, instruments, and equipment used herein can all be obtained through commercial purchase or prepared using existing methods.

[0038] In a first aspect, embodiments of this application provide a high-temperature iron-chromium-aluminum electric heating alloy, characterized in that, by mass fraction, the chemical composition of the iron-chromium-aluminum electric heating alloy is: Cr: 21%~25%, Al: 4%~6%, Si≤0.50%, Mn≤0.50%, C≤0.015%, Ti: 0.02%~0.10%, Zr: 0.02%~0.15%, rare earth: 0.01%~0.20%, Mg: 0.001%~0.010%, with the remainder being Fe and unavoidable impurities; the rare earth is at least one of Y, La, Ce and Hf.

[0039] The positive effects of limiting the Cr mass fraction to 21%~25%: Chromium is the core element for achieving high-temperature oxidation resistance in iron-chromium-aluminum heating alloys. Strictly controlling the Cr mass fraction between 21% and 25% ensures that a dense and continuous Cr2O3 anti-oxidation film preferentially forms on the surface of the iron-chromium-aluminum heating alloy under high-temperature service conditions. This oxide film acts as a barrier, effectively preventing oxygen from further penetrating into the alloy matrix, thereby significantly slowing down the oxidation process and enabling the iron-chromium-aluminum heating alloy to operate stably for a long time in high-temperature environments. For example, the Cr mass fraction can be 21%, 22%, 23%, 24%, 25%, etc.

[0040] The positive effects of limiting the Al mass fraction to 4%–6%: Aluminum is a key element determining the maximum operating temperature of iron-chromium-aluminum heating alloys. Controlling the aluminum mass fraction within this range is both a necessary condition for achieving high-temperature performance and a core strategy for maintaining workability. Within this mass fraction range, aluminum preferentially oxidizes at high temperatures compared to chromium, forming a dense α-Al₂O₃ protective layer with an extremely high melting point. Compared to the chromium oxide film, the α-Al₂O₃ protective layer exhibits better thermodynamic stability and a lower oxygen diffusion rate under higher temperature service conditions. For example, the Al mass fraction can be 4%, 5%, 6%, etc.

[0041] The positive effects of limiting the Si mass fraction to ≤0.50%: The addition of appropriate amounts of silicon can enhance the density and stability of the oxide film by forming SiO2 or composite oxides, thereby further improving the oxidation resistance of the iron-chromium-aluminum heating alloy. However, when the silicon mass fraction exceeds 0.50%, it significantly weakens the high-temperature strength of the iron-chromium-aluminum heating alloy, causing it to become brittle due to grain coarsening after long-term high-temperature service. Keeping the silicon mass fraction no higher than 0.50% allows for the full utilization of silicon's role in promoting oxide film repair without compromising high-temperature strength, ensuring stable oxidation resistance of the iron-chromium-aluminum heating alloy during the heating and cooling cycles of staged forging. For example, the Si mass fraction can be 0.10%, 0.20%, 0.30%, 0.40%, 0.50%, etc.

[0042] The positive effects of limiting the mass fraction of manganese (Mn) to ≤0.50%: As a deoxidizing element, controlling the mass fraction of manganese within a specified range can effectively improve the hot working properties of iron-chromium-aluminum heating alloys. During steelmaking, manganese purifies the melt through deoxidation and desulfurization, reducing the adverse effects of non-metallic inclusions on plasticity. The addition of appropriate amounts of manganese can refine grains and inhibit recrystallization; however, excessive manganese can form hard compounds with elements such as aluminum and silicon. These compounds can lead to localized stress concentration and decreased thermal conductivity, thereby increasing the risk of forging cracks. Therefore, strictly limiting the mass fraction of manganese can balance the deoxidation effect with processing performance, providing a uniform deformation basis for subsequent staged forging. For example, the mass fraction of Mn can be 0.10%, 0.20%, 0.30%, 0.40%, 0.50%, etc.

[0043] The positive effects of limiting the carbon mass fraction to ≤0.015% are as follows: Excessive carbon can form carbides with chromium and iron. These carbides, after precipitating along grain boundaries, weaken grain boundary strength, leading to increased susceptibility to cracking during forging. Simultaneously, carbide formation consumes chromium in the alloy matrix, reducing the continuity and protective effect of the Cr2O3 oxide film. Furthermore, the presence of carbides hinders grain boundary migration, exacerbating stress concentration during deformation and thus impairing microstructure uniformity. Strictly controlling the carbon mass fraction within a defined range avoids the dual harm of carbides to the high-temperature performance of iron-chromium-aluminum heating alloys, ensuring that the alloy possesses both good plastic deformation capacity and oxide film stability during staged forging, thereby synergistically improving yield and microstructure uniformity. For example, the carbon mass fraction can be 0.005%, 0.010%, 0.015%, etc.

[0044] The positive effects of limiting the Ti mass fraction to 0.02%~0.10%: As a strong carbide and nitride forming element, controlling the titanium mass fraction within this range aims to achieve matrix purification and grain refinement through microalloying. Titanium preferentially combines with residual carbon and nitrogen to form Ti(C,N) compounds. The formation of these compounds can, on the one hand, fix harmful interstitial atoms, reducing the adverse effects of carbides on plasticity; on the other hand, it can inhibit high-temperature grain growth by pinning grain boundaries, providing a fine-grained initial microstructure for forging. Furthermore, the addition of titanium can improve the adhesion between the oxide film and the alloy matrix, reducing oxide film peeling during high-temperature service. For example, the Ti mass fraction can be 0.02%, 0.04%, 0.06%, 0.08%, 0.10%, etc.

[0045] The positive effects of limiting the Zr mass fraction to 0.02%~0.15%: As a strong carbonitride forming element, controlling the Zr mass fraction within this range can significantly refine the grains and improve high-temperature strength. Zr preferentially combines with carbon and nitrogen in the alloy to form stable Zr(C,N) compounds. These compounds can pin grain boundaries and inhibit high-temperature grain coarsening, providing a uniform and fine initial microstructure for subsequent large deformation forging. Simultaneously, the addition of Zr can increase the recrystallization temperature of the iron-chromium-aluminum heating alloy and delay grain growth during high-temperature service. For example, the Zr mass fraction can be 0.02%, 0.05%, 0.08%, 0.11%, 0.14%, etc.

[0046] The positive effects of limiting the mass fraction of rare earth elements to 0.01%~0.20% include: The addition of rare earth elements enhances alloy performance through a dual mechanism. On one hand, rare earth elements preferentially combine with impurities such as oxygen and sulfur, purifying grain boundaries and reducing non-metallic inclusions, significantly reducing high-temperature crack susceptibility. On the other hand, rare earth elements can optimize the interfacial bonding between the Al2O3-Cr2O3 composite oxide film and the alloy matrix, enhancing the oxide film's resistance to spalling, enabling the iron-chromium-aluminum heating alloy to maintain a dense protective layer even at high temperatures. For example, the mass fraction of rare earth elements can be 0.05%, 0.10%, 0.15%, 0.20%, etc.

[0047] The positive effects of limiting the mass fraction of Mg to 0.001%~0.010% include: the addition of magnesium purifies the alloy matrix through deep deoxidation and desulfurization. Magnesium forms high-melting-point compounds with oxygen and sulfur; these compounds effectively remove impurity elements segregating at grain boundaries, thereby improving grain boundary strength and high-temperature creep performance. Controlling the mass fraction of magnesium within this range avoids grain boundary embrittlement caused by excessive magnesium, and also reduces the risk of crack initiation during forging through grain boundary purification. For example, the mass fraction of Mg can be 0.002%, 0.004%, 0.006%, 0.008%, 0.010%, etc.

[0048] Fe is a matrix element, and the specific content / range of Fe can be obtained through the upper and lower limit formulas of the component, that is: The sum of the percentages of all components in a composition should equal 100%, and the content ranges of several components should meet the following conditions: the upper limit of a certain component + the lower limit of other components ≤ 100; the lower limit of a certain component + the upper limit of other components ≥ 100. Furthermore, the specific content of Fe is made up to 100% by the actual detected values ​​of the other chemical components mentioned above, together with any unlisted active elements and / or impurity elements, and Fe must constitute the absolute proportion as a matrix element.

[0049] The microstructure of the iron-chromium-aluminum electrothermal alloy is ferrite, and the grain size of the ferrite is ≥8.0.

[0050] The microstructure of the iron-chromium-aluminum heating alloy is ferrite, with a ferrite grain size grade ≥8.0, indicating a fine and uniform equiaxed grain structure. Fine grains can improve the room-temperature plasticity and toughness of the iron-chromium-aluminum heating alloy by increasing the total grain boundary area, effectively suppressing or delaying the inherent room-temperature and intermediate-temperature brittleness tendencies of the iron-chromium-aluminum heating alloy. This significantly reduces the risk of crack initiation due to stress concentration during forging and subsequent processing, thereby directly ensuring and improving the yield of the iron-chromium-aluminum heating alloy. For example, the ferrite grain size grade can be 8.0, 9.0, 9.5, etc.

[0051] In some embodiments, the iron-chromium-aluminum electrothermal alloy satisfies at least one of the following properties: tensile strength ≥650MPa, elongation ≥25%.

[0052] Tensile strength: The maximum stress a material can withstand before fracture. A tensile strength ≥ 650 MPa ensures sufficient strength reserve while maintaining workability, allowing the iron-chromium-aluminum heating alloy to maintain a stable geometry at high temperatures and preventing deformation failure due to insufficient strength. Examples of tensile strength values ​​include 650 MPa, 660 MPa, 670 MPa, and 680 MPa. Elongation: The percentage of total elongation within the gauge length after tensile fracture relative to the original gauge length. An elongation ≥ 25% ensures sufficient plasticity reserve during staged large deformation forging of the iron-chromium-aluminum heating alloy, allowing for uniform deformation without localized fracture due to concentrated deformation. Examples of elongation values ​​include 25%, 26%, 27%, 28%, 29%, and 30%.

[0053] Figure 1 A flowchart illustrating a method for preparing a high-temperature iron-chromium-aluminum electrothermal alloy, as provided in this application embodiment.

[0054] Please see Figure 1 Secondly, this application provides a method for preparing the iron-chromium-aluminum electrothermal alloy described in the first aspect, the method comprising: S1. Obtain a masterbatch with the following chemical composition: Cr: 21%~25%, Al: 4%~6%, Si≤0.50%, Mn≤0.50%, C≤0.015%, Ti: 0.02%~0.10%, Zr: 0.02%~0.15%, rare earth: 0.01%~0.20%, Mg: 0.001%~0.010%, with the remainder being Fe and unavoidable impurities; S2. Using a CaF2-Al2O3-CaO-MgO quaternary slag system, the mother ingot is electroslag remelted to obtain a cast ingot; S3. The ingot is kept at 600°C or cooled to room temperature to obtain a heat-insulated ingot. S4. The heat-insulated ingot is subjected to a first-stage forging process, a first-stage annealing process, and a second-stage forging process in sequence to obtain a square billet of 40mm×40mm~60mm×60mm. S5. The billet is hot-rolled to obtain a hot-rolled wire rod with a diameter of 8mm~12mm; S6. Perform a second annealing treatment on the hot-rolled wire rod to obtain annealed wire rod; S7. The annealed wire rod is subjected to multiple cold drawing passes, and a third annealing treatment is performed between the cold drawing passes to obtain cold-drawn wire with a diameter of 2mm~5mm. S8. The cold-drawn wire is heat-treated to obtain an iron-chromium-aluminum electrothermal alloy.

[0055] In some embodiments, the master ingot is obtained by vacuum induction smelting, wherein the ultimate vacuum degree of the vacuum induction smelting is ≤5Pa.

[0056] The ultimate vacuum requirement in vacuum induction smelting is a fundamental condition for creating a high-purity environment for alloy melting. In a vacuum induction furnace, the ultimate vacuum refers to the lowest pressure achievable inside the furnace after complete evacuation. When the ultimate vacuum in vacuum induction smelting is ≤5 Pa, the partial pressures of harmful gases such as oxygen, nitrogen, and water vapor are significantly reduced. This low-pressure environment effectively inhibits the oxidation and burn-off of alloying elements during high-temperature melting. For example, the ultimate vacuum in vacuum induction smelting can be 1 Pa, 3 Pa, 5 Pa, etc.

[0057] In some embodiments, the refining vacuum degree of the vacuum induction smelting is ≤10Pa, the refining temperature of the vacuum induction smelting is 1550℃~1600℃, and the refining time of the vacuum induction smelting is 20min~30min.

[0058] The refining vacuum degree in vacuum induction smelting is ≤10Pa, ensuring the melt remains in a low oxygen partial pressure environment. This environment is conducive to the carbon deoxidation reaction, allowing carbon to combine with oxygen to generate carbon monoxide gas, which is then released, further reducing the oxygen content in the melt. The refining temperature in vacuum induction smelting is controlled between 1550℃ and 1600℃. This temperature is higher than the melting point of the iron-chromium-aluminum electrothermal alloy, ensuring good melt fluidity and facilitating impurity flotation and gas escape. It also avoids alloy element volatilization loss and furnace lining erosion caused by excessively high temperatures. The refining time in vacuum induction smelting is controlled between 20min and 30min. This time allows for sufficient degassing, deoxidation, and composition homogenization while avoiding alloy element volatilization or reduced equipment efficiency due to excessive time, and also avoids incomplete refining due to insufficient time. For example, the refining vacuum degree of vacuum induction smelting can be 2Pa, 4Pa, 6Pa, 8Pa, 10Pa, etc.; the refining temperature of vacuum induction smelting can be 1550℃, 1560℃, 1570℃, 1580℃, 1590℃, 1600℃, etc.; and the refining time of vacuum induction smelting can be 20min, 25min, 30min, etc.

[0059] In some embodiments, the argon pressure during vacuum induction smelting is 0.05 MPa to 0.10 MPa.

[0060] In vacuum induction smelting, the argon charging pressure is controlled between 0.05 MPa and 0.08 MPa, a key control method for achieving alloying operations under inert gas protection. Argon, as an inert gas, can form a protective atmosphere on the melt surface under slightly positive pressure, effectively isolating the residual air in the furnace from contact with the melt and preventing the oxidation and burn-off of easily oxidized elements during the addition process. Furthermore, the slightly positive pressure argon environment promotes the uniform diffusion of added trace elements in the melt. Strong carbonitride-forming elements such as titanium and zirconium need to be uniformly distributed in the melt after addition; the slightly positive pressure environment under argon protection provides favorable conditions for the uniform distribution of these elements, thus laying the foundation for the formation of fine grains during subsequent solidification. For example, the argon charging pressure in vacuum induction smelting can be 0.05 MPa, 0.06 MPa, 0.07 MPa, 0.08 MPa, 0.09 MPa, 0.10 MPa, etc.

[0061] In some embodiments, the casting temperature of the vacuum induction smelting is 1600℃~1650℃.

[0062] When the casting temperature exceeds 1650℃, the low viscosity of the melt will scour the inner wall of the ingot, causing surface defects. Simultaneously, an excessively high temperature gradient will exacerbate dendritic segregation and microstructural inhomogeneity in the ingot. When the casting temperature is below 1600℃, the melt fluidity decreases, easily leading to defects such as cold shuts and incomplete filling, and causing inclusions to remain trapped inside the ingot due to insufficient flotation. Controlling the casting temperature within the range of 1600℃ to 1650℃, combined with the bottom-pouring method, can yield a master ingot with a smooth surface and uniform internal structure. For example, the casting temperature for vacuum induction smelting can be 1600℃, 1610℃, 1620℃, 1630℃, 1640℃, 1650℃, etc.

[0063] In some embodiments, the amount of quaternary slag system is 3% to 5% of the mass of the mother ingot.

[0064] Using a quaternary slag system of CaF2-Al2O3-CaO-MgO, and controlling the slag content between 3% and 5% of the mother ingot mass, this process setting balances refining effectiveness and operational feasibility. An appropriate slag content ensures the slag pool has sufficient heat capacity and refining capability, providing favorable conditions for the molten metal droplets to fully contact the slag as they pass through the pool, thereby effectively removing sulfur, oxygen, and non-metallic inclusions. Simultaneously, this slag content range avoids increased power consumption and process control difficulties caused by excessive slag content. For example, the slag content of the quaternary slag system can be 3%, 4%, or 5% of the mother ingot mass.

[0065] In some embodiments, the current of the electroslag remelting is 2000A~4500A, the voltage of the electroslag remelting is 35V~50V, and the melting rate of the electroslag remelting is 1.0kg / min~2.5kg / min.

[0066] Electroslag remelting (ESR) is controlled between 2000A and 4500A. An appropriate current value provides sufficient heat input to ensure stable electrode melting. The voltage for ESR is controlled between 35V and 50V. This reasonable voltage range maintains an appropriate slag pool depth and thermal field distribution. This distribution provides favorable conditions for the molten metal droplets to fully react with the slag as they pass through the slag pool, thereby completing refining processes such as desulfurization and removal of non-metallic inclusions. The melting rate for ESR is controlled between 1.0 kg / min and 2.5 kg / min. An appropriate melting rate directly determines the solidification rate and crystallization direction of the molten metal pool. This parameter is beneficial for obtaining a longitudinally oriented columnar crystal structure in the ingot and ensures that a uniform insulating and heat-insulating layer is formed between the ingot and the crystallizer, preventing electrical shunting and providing lubrication. For example, the current for electroslag remelting can be 2000A, 2500A, 3000A, 3500A, 4000A, 4500A, etc.; the voltage for electroslag remelting can be 35V, 40V, 45V, 50V, etc.; and the melting rate for electroslag remelting can be 1.0kg / min, 1.5kg / min, 2.0kg / min, 2.5kg / min, etc.

[0067] In some embodiments, the diameter of the master ingot is 150mm~160mm; the oxygen content of the master ingot is ≤10ppm, and the nitrogen content of the master ingot is ≤20ppm.

[0068] The diameter of the master ingot is controlled between 150mm and 160mm. This diameter range can form a reasonable matching gap with the electroslag remelting crystallizer, ensuring that the consumable electrode melts uniformly during the smelting process and avoiding problems such as molten pool fluctuations and arc instability caused by electrodes that are too thick or too thin. For example, the diameter of the master ingot can be 150mm, 155mm, 160mm, etc.

[0069] The oxygen content in the master ingot should be ≤10 ppm. This oxygen mass fraction requirement is to control the amount of oxide inclusions at the source. During electroslag remelting, oxide inclusions in the master ingot will react with the slag system at high temperatures. If the initial oxygen mass fraction is too high, even after slag refining, it will be difficult to completely remove the inclusions to the target level. The nitrogen content in the master ingot should be ≤20 ppm. This nitrogen mass fraction requirement is to prevent nitrogen from forming bubbles or precipitating nitrides during solidification. Nitrogen has limited solubility in the iron-chromium-aluminum matrix. An excessively high nitrogen mass fraction can lead to porosity or aluminum nitride inclusions inside the ingot, thereby impairing the density and high-temperature performance of the iron-chromium-aluminum heating alloy. For example, the oxygen content in the master ingot can be 5 ppm, 10 ppm, etc.; the nitrogen content in the master ingot can be 5 ppm, 10 ppm, 15 ppm, 20 ppm, etc.

[0070] In some embodiments, the diameter of the ingot is 150mm to 160mm; the oxygen content of the ingot is ≤10ppm, and the sulfur content of the ingot is ≤10ppm.

[0071] The diameter of the ingot is controlled between 150mm and 160mm, which not only matches the diameter of the master ingot to maintain a reasonable filling ratio, but more importantly, provides a suitable billet size for the subsequent two-stage forging: ensuring sufficient deformation to fully break up the as-cast structure, while avoiding forging difficulties and uneven microstructure caused by excessively large ingots. For example, the diameter of the ingot can be 150mm, 155mm, 160mm, etc.

[0072] The ingot's oxygen content is ≤10 ppm. This oxygen mass fraction requirement is to minimize oxide inclusions. Oxygen is a major source of non-metallic inclusions. Excessive oxygen content can lead to the formation of hard and brittle inclusions such as Al2O3 and SiO2 in the iron-chromium-aluminum heating alloy. These inclusions can become stress concentration points during subsequent forging and wire drawing, resulting in cracking and wire breakage. The ingot's sulfur content is ≤10 ppm. This sulfur mass fraction is set to eliminate the detrimental effects of sulfur on the hot working plasticity of the iron-chromium-aluminum heating alloy. Sulfur segregation at grain boundaries significantly reduces the high-temperature plasticity of the iron-chromium-aluminum heating alloy, leading to hot brittle cracking during forging and hot rolling. For example, the ingot's oxygen content can be 5 ppm, 10 ppm, etc.; the ingot's sulfur content can be 5 ppm, 10 ppm, etc.

[0073] In some embodiments, when the ingot is at 600°C after heat preservation, the furnace loading temperature of the first stage forging process is ≤600°C; when the ingot has cooled to room temperature after heat preservation, the furnace loading temperature of the first stage forging process is ≤400°C.

[0074] When the ingot is held at 600℃ after heat treatment, the furnace loading temperature for the first stage of forging should be ≤600℃. This effectively utilizes the residual heat accumulated during the immediate transfer of the ingot to a 600℃ heating furnace after demolding in the hot transfer process, allowing the ingot to directly enter the heating stage, thereby reducing energy consumption and shortening the process cycle. When the ingot has cooled to room temperature after heat treatment, the furnace loading temperature for the first stage of forging should be ≤400℃. This upper limit of the furnace loading temperature is set to avoid the severe thermal stress generated by directly charging the cold ingot into the furnace at high temperature. Iron-chromium-aluminum electrothermal alloys have poor plasticity at room temperature. If a cold ingot is directly charged into a high-temperature furnace, the large temperature difference between the cold ingot and the high temperature inside the furnace will lead to thermal stress concentration, increasing the risk of surface cracking. The upper limit of the furnace loading temperature of 400℃ provides a gentle preheating window for the cold ingot, reducing the internal temperature gradient and creating a safe stress environment for subsequent uniform heating, thus ensuring the yield rate during the forging process from the source. For example, when the ingot is at 600°C after heat preservation, the furnace loading temperature for the first stage of forging can be 500°C, 550°C, 600°C, etc.; when the ingot has cooled to room temperature after heat preservation, the furnace loading temperature for the first stage of forging can be 300°C, 350°C, 400°C, etc.

[0075] In some embodiments, the heating temperature of the first stage forging process is 1050℃~1080℃, the heating time of the first stage forging process is 90min~120min, and the holding time of the first stage forging process is 30min~40min.

[0076] The heating temperature for the first stage of forging is controlled between 1050℃ and 1080℃, lower than the traditional forging heating temperature of 1140℃ for iron-chromium-aluminum (FeChA) heating alloys. Its core purpose is to control the grain growth behavior of FeChA heating alloys at high temperatures. At high temperatures, the grains of FeChA heating alloys tend to coarsen, and coarse grains lead to a significant decrease in the plasticity of the FeChA heating alloy, making it highly susceptible to cracking defects during forging. Controlling the heating temperature of the first stage of forging within this range ensures that the FeChA heating alloy has sufficient plastic deformation capacity during forging while effectively suppressing excessive grain coarsening. For example, the heating temperature for the first stage of forging can be 1050℃, 1060℃, 1070℃, 1080℃, etc. The heating time for the first stage of forging is controlled between 90 and 120 minutes. This heating time range provides a slow and uniform heating rate, ensuring that the temperature of the ingot core and surface is consistent, thus avoiding thermal stress cracks caused by excessive internal and external temperature differences due to rapid heating. For example, the heating time for the first stage of forging can be 90, 100, 110, or 120 minutes. The holding time for the first stage of forging is controlled between 30 and 40 minutes. This holding time range ensures that the overall temperature of the ingot is sufficiently uniform, eliminating temperature lag in the ingot core and ensuring that the entire ingot has a consistent plastic state before forging. For example, the holding time for the first stage of forging can be 30, 35, or 40 minutes.

[0077] In some embodiments, the initial forging temperature of the first stage forging process is ≥1050℃, and the final forging temperature of the first stage forging process is ≥800℃.

[0078] The initial forging temperature of the first stage of forging is ≥1050℃. This initial forging temperature requirement means that when the ingot is forged immediately after exiting the furnace, it still possesses sufficient plasticity and deformation capacity in the ferrite state, capable of withstanding large deformations without cracking. The final forging temperature of the first stage of forging is ≥800℃. While the iron-chromium-aluminum (FeCrA) heating alloy exhibits good plasticity at high temperatures, this plasticity gradually decreases as the temperature drops. When the final forging temperature is below 800℃, the FeCrA heating alloy lacks sufficient plasticity reserves, making it prone to cracking in the later stages of forging. By controlling the final forging temperature above 800℃, the FeCrA heating alloy remains within its optimal plasticity range throughout the forging process, allowing the ingot to be successfully forged to the target size billet without cracking defects. For example, the initial forging temperature of the first stage forging process can be 1050, 1100, 1150, 1200, etc.; the final forging temperature of the first stage forging process can be 800, 850, 900, etc.

[0079] In some embodiments, the temperature of the first annealing treatment is 740°C to 830°C, and the time of the first annealing treatment is 1 hour to 2 hours.

[0080] A first annealing treatment is performed after the first stage of forging. This annealing treatment is a key step in realizing the core innovation of the two-stage forging process. The first annealing treatment achieves three key functions: first, it eliminates the internal residual stress generated in the first stage of forging, preventing stress accumulation and crack propagation during the second stage of forging; second, it recrystallizes the deformed structure generated during the first stage of forging, obtaining a uniform and fine equiaxed grain structure; and third, it allows the alloying elements to fully diffuse through sufficient heat preservation, eliminating compositional segregation and achieving a homogenized structure. After the first annealing treatment, the iron-chromium-aluminum heating alloy has a more uniform initial structure and better plasticity, enabling it to successfully complete subsequent large deformation forging. At the same time, a high-quality forging billet with uniform grain size and a sufficiently refined structure is obtained after this stage of forging. For example, the temperature of the first annealing treatment can be 740℃, 770℃, 800℃, 830℃, etc.; the time of the first annealing treatment can be 1 hour, 2 hours, etc.

[0081] In some embodiments, the furnace loading temperature for the second stage forging process is ≤400°C.

[0082] The charging temperature for the second-stage forging process is ≤400℃. This upper limit provides a gentle preheating window for the billet, reducing the internal temperature gradient and creating a safe stress environment for subsequent uniform heating. This ensures the yield of the second-stage forging process from the outset. For example, the charging temperature for the second-stage forging process can be 300℃, 350℃, 400℃, etc.

[0083] In some embodiments, the heating temperature of the second stage forging process is 1100℃~1140℃, the heating time of the second stage forging process is 60min~90min, and the holding time of the second stage forging process is 25min~35min.

[0084] The heating temperature for the second stage of forging is controlled between 1100℃ and 1140℃, which is higher than the heating temperature for the first stage. This temperature setting is chosen because the cross-section of the billet after annealing in the first stage of forging is significantly reduced, resulting in a relatively small deformation required for subsequent forging. Appropriately increasing the heating temperature helps improve the forging plasticity of the iron-chromium-aluminum electrothermal alloy. For example, the heating temperature for the second stage of forging can be 1100℃, 1120℃, or 1140℃. The heating time for the second stage of forging is controlled between 60min and 90min, which is shorter than that for the first stage. The shorter heating time is because the heat conduction distance is shortened after the billet cross-section is reduced, thus increasing the heating efficiency of the billet. However, sufficient heating time is still necessary to avoid excessive temperature difference between the surface and core of the billet. For example, the heating time for the second stage of forging can be 60min, 70min, 80min, or 90min. The holding time for the second stage of forging is controlled between 25 and 35 minutes. This holding time range ensures that the overall temperature of the billet is sufficiently uniform, so that the billet has a consistent plastic state before being forged. For example, the holding time for the second stage of forging can be 25 minutes, 30 minutes, 35 minutes, etc.

[0085] In some embodiments, the initial forging temperature of the second stage forging process is ≥1100°C, and the final forging temperature of the second stage forging process is ≥800°C.

[0086] The second stage of forging involves an initial forging temperature ≥1100℃. This initial forging temperature means that the billet is still in a high-temperature plastic state when forging begins immediately after exiting the furnace. At this temperature, the iron-chromium-aluminum (FeCrA) heating alloy has good deformation capacity and can withstand the large deformation required to forge the billet to the target size without cracking. The final forging temperature in the second stage is ≥800℃. This final forging temperature ensures that the forging process is completed while the FeCrA heating alloy is still in a relatively high plastic state. While the FeCrA heating alloy exhibits good plasticity at high temperatures, this plasticity gradually decreases as the temperature drops. When the final forging temperature is below 800℃, the FeCrA heating alloy lacks sufficient plasticity reserves, making it prone to cracking in the later stages of forging. After forging, the billet is slowly cooled using sand cooling or a heat-insulating box. This slow cooling further eliminates forging stress and prevents rapid cooling from causing cracks, providing a process guarantee for obtaining a high-quality forged billet with a uniform microstructure and refined grains. For example, the initial forging temperature of the second-stage forging process can be 1100℃, 1200℃, 1300℃, etc.; the final forging temperature of the second-stage forging process can be 800℃, 900℃, 1000℃, etc.

[0087] In some embodiments, the furnace loading temperature of the hot-rolled material is ≤400°C.

[0088] The furnace charging temperature for hot rolling is ≤400℃. This upper limit provides a mild preheating window for the billet, reducing the internal temperature gradient and creating a safe stress environment for subsequent uniform heating, thus ensuring the yield of the hot rolling process from the source. For example, the furnace charging temperature for hot rolling can be 300℃, 350℃, 400℃, etc.

[0089] In some embodiments, the heating temperature of the hot rolling is 1030℃~1070℃, and the holding time of the hot rolling is 60min~90min.

[0090] The heating temperature for hot rolling is controlled between 1030℃ and 1070℃, placing the billet in the ferrite single-phase heating state. This temperature range ensures sufficient plastic deformation capacity of the iron-chromium-aluminum electrothermal alloy while effectively suppressing excessive grain coarsening. The holding time for hot rolling is controlled between 60 min and 90 min. This holding time range ensures that the overall temperature of the billet is sufficiently uniform, giving the billet a consistent plastic state before exiting the furnace for hot rolling. For example, the heating temperature for hot rolling can be 1030℃, 1050℃, 1070℃, etc.; the holding time for hot rolling can be 60 min, 70 min, 80 min, 90 min, etc.

[0091] In some embodiments, the final rolling temperature of the hot rolling is ≥850°C.

[0092] The final rolling temperature of hot rolling is ≥850℃. This final rolling temperature ensures that the iron-chromium-aluminum electrothermal alloy remains within a temperature range with good plasticity throughout the hot rolling process, allowing the billet to be deformed to the target size through multiple rolling passes without cracking defects. Simultaneously, the final rolling temperature provides a sufficient temperature environment for dynamic recrystallization, which is beneficial for obtaining a fine and uniform grain structure through deformation-induced recrystallization during hot rolling. Post-rolling air cooling or wind cooling can further refine the microstructure, providing a foundation for good mechanical properties and microstructure uniformity in the final product. For example, the final rolling temperature of hot rolling can be 850℃, 900℃, 950℃, 1000℃, etc.

[0093] In some embodiments, the total deformation ratio of the hot rolling is ≥15:1.

[0094] A total deformation ratio of ≥15:1 in hot rolling indicates that the iron-chromium-aluminum heating alloy has undergone significant plastic deformation during the hot rolling process. This large deformation effectively breaks up any residual cast dendritic structure that may remain from two-stage forging, resulting in a more uniform and dense microstructure. The substantial plastic deformation provides ample deformation storage energy for dynamic recrystallization, promoting the formation and uniform distribution of recrystallized grains, ultimately yielding a fine and uniform hot-rolled microstructure. Furthermore, a higher deformation ratio also helps eliminate micropores and porosity within the billet, improving the density and mechanical properties of the iron-chromium-aluminum heating alloy. For example, the total deformation ratio in hot rolling can be 15:1, 16:1, 17:1, etc.

[0095] In some embodiments, the cooling method for the second annealing is at least one of slow furnace cooling and controlled-rate cooling; The temperature of the second annealing treatment is 750℃~800℃, and the holding time of the second annealing treatment is 1h~2h.

[0096] The second annealing treatment is a crucial heat treatment step after hot rolling to fully soften and restore the plasticity of the iron-chromium-aluminum (Fe-Chromium-Aluminum) heating alloy. After hot rolling, the Fe-Chromium-Aluminum heating alloy contains numerous dislocation entanglements and work-hardened structures. By controlling the temperature of the second annealing treatment between 750℃ and 800℃, recrystallization of the deformed structure can be induced, forming uniform and fine equiaxed grains. This significantly reduces the hardness of the Fe-Chromium-Aluminum heating alloy and restores its plasticity. The holding time for the second annealing treatment is controlled between 1 and 2 hours to ensure uniform temperature throughout the billet, allowing the recrystallization process to be fully completed and preventing subsequent cold drawing cracks caused by localized lack of recrystallization. Slow furnace cooling after annealing further eliminates residual thermal stress, enabling the Fe-Chromium-Aluminum heating alloy to achieve a stable microstructure during cooling. For example, the temperature of the second annealing treatment can be 750℃, 760℃, 770℃, 780℃, 790℃, 800℃, etc.; the holding time of the second annealing treatment can be 1h, 2h, etc.

[0097] In some embodiments, the shrinkage rate of each pass in the multi-pass cold drawing is 15% to 25%, and the total shrinkage rate of the multi-pass cold drawing is 60% to 80%.

[0098] The reduction of area in each pass of multi-pass cold drawing is controlled between 15% and 25%, ensuring a moderate deformation amount in each pass. This guarantees sufficient deformation efficiency while avoiding cracking or wire breakage in the iron-chromium-aluminum heating alloy caused by excessive deformation in a single pass. Iron-chromium-aluminum heating alloys are high-resistance alloys with a rapid cold work hardening rate. Excessive deformation in a single pass will cause the material to quickly reach its hardening limit, making it difficult for the alloy to continue deforming in subsequent passes. The total reduction of area in multi-pass cold drawing is controlled between 60% and 80%, a reliable deformation range determined based on the intermediate annealing process. Performing multi-pass cold drawing within this total reduction of area range, combined with appropriate intermediate annealing at suitable temperatures, allows hot-rolled wire rods to be gradually drawn from a larger cross-section to the target wire diameter, simultaneously obtaining cold-drawn wire with precise dimensions and a smooth surface.

[0099] In some embodiments, the temperature of the third annealing treatment is 750℃~800℃, and the holding time of the third annealing treatment is 1h~2h.

[0100] In multi-pass cold drawing processes, when the cumulative deformation reaches a predetermined upper limit or the intermediate blank shows significant hardening, a third annealing treatment is required to restore plasticity and ensure that subsequent cold drawing can continue. The temperature of the third annealing treatment is controlled between 750℃ and 800℃, which effectively initiates the recrystallization process, causing the fibrous structure generated during cold drawing to revert to equiaxed grains, thereby eliminating the work hardening effect. The holding time for the third annealing treatment is controlled between 1 hour and 2 hours, ensuring sufficient recrystallization and allowing the intermediate blank to recover to a good plastic state before entering the next round of cold drawing. For example, the temperature of the third annealing treatment can be 750℃, 760℃, 770℃, 780℃, 790℃, 800℃, etc.; the holding time can be 1 hour, 2 hours, etc.

[0101] In some embodiments, the heat treatment temperature is 850℃~950℃, and the heat treatment holding time is 1h~2h.

[0102] The heat treatment temperature is controlled between 850℃ and 950℃. This temperature condition keeps the cold-drawn wire above the ferrite recrystallization temperature, allowing the fibrous structure generated after cold drawing to completely recrystallize into uniform equiaxed grains and eliminating residual stress generated during cold working. The holding time for heat treatment is controlled between 1 hour and 2 hours. This holding time range ensures uniform temperature throughout the cold-drawn wire, allowing the recrystallization and stress release processes to be fully completed. For example, the heat treatment temperature can be 850℃, 900℃, 950℃, etc.; the holding time can be 1 hour, 2 hours, etc.

[0103] The product prepared by the preparation method of the iron-chromium-aluminum electric heating alloy is the aforementioned iron-chromium-aluminum electric heating alloy. Since the preparation method of the iron-chromium-aluminum electric heating alloy adopts some or all of the technical solutions of the iron-chromium-aluminum electric heating alloy embodiments, it has at least all the beneficial effects brought about by the technical solutions of the aforementioned embodiments, which will not be elaborated here.

[0104] The present application is further illustrated below with reference to specific embodiments. Experimental methods in the following embodiments that do not specify specific conditions are generally determined according to national standards / industry standards / the disclosure herein; if there are no corresponding national standards / industry standards / the disclosure herein, they are performed according to generally accepted international standards, conventional conditions, or conditions recommended by the manufacturer.

[0105] The chemical composition (mass percentage / %) of the examples and comparative examples is shown in Table 1.

[0106] Table 1

[0107] Based on the chemical composition of the examples and comparative examples, this embodiment also provides a method for preparing a high-temperature iron-chromium-aluminum electric heating alloy, including the following steps: A masterbatch having the chemical composition described in Table 1 was obtained: Using a CaF2-Al2O3-CaO-MgO quaternary slag system, the mother ingot is electroslag remelted to obtain the cast ingot; The ingot is kept at 600℃ or cooled to room temperature to obtain a heat-insulated ingot. After heat preservation, the ingot is subjected to the first stage forging treatment, the first annealing treatment and the second stage forging treatment in sequence to obtain a square billet of 40mm×40mm~60mm×60mm. The billet is hot-rolled to obtain hot-rolled wire rods with a diameter of 8mm~12mm; The hot-rolled wire rod is subjected to a second annealing treatment to obtain annealed wire rod; Annealed wire rods are subjected to multiple cold drawing passes, and a third annealing treatment is performed between the cold drawing passes to obtain cold-drawn wire with a diameter of 2mm to 5mm. Cold-drawn wire was heat-treated to obtain an iron-chromium-aluminum heating alloy. The process parameters for preparation are shown in Tables 2 to 4.

[0108] The process parameters for the examples and comparative examples are shown in Tables 2 to 4.

[0109] Table 2

[0110] Table 3

[0111] Table 4

[0112] The overall performance of the embodiments and comparative examples is shown in Table 5.

[0113] Table 5

[0114] The data tables above provide a clear comparison of the differences between various embodiments and comparative examples. The following conclusions can be drawn: As can be seen from the data in Table 5, the iron-chromium-aluminum electric heating alloy provided in this application has a grain size of 8.0, a tensile strength of 652MPa~670MPa, an elongation of 28%~30%, a rapid life at 1400℃ of 85h~92h, and a forging yield of 91%~92%.

[0115] Examples 1-5 and Comparative Examples 1-2 demonstrate that Examples 1-5 employ optimized chemical composition design, combined with a synergistic process involving vacuum induction smelting, electroslag remelting, two-stage forging, hot rolling, multi-pass cold drawing, and annealing. This resulted in superior overall performance, characterized by stable high grain size, high tensile strength, excellent elongation, long high-temperature lifespan, and high forging yield. In contrast, Comparative Examples 1 and 2, under the same subsequent process conditions, exhibited insufficient mass fractions of the key alloying elements chromium and aluminum, leading to a grain size of only 6.5-7.0, a tensile strength reduced to 560-580 MPa, an elongation reduced to 20%-22%, a significantly reduced rapid lifespan at 1400℃ to 58-65 hours, and a lower forging yield. Therefore, controlling the mass fractions of chromium and aluminum within a suitable range is crucial for achieving high purity, fine grain structure, and excellent high-temperature performance. This composition design, combined with the refined process control of the entire process, including vacuum smelting, electroslag remelting, two-stage forging, and hot rolling, can synergistically achieve the comprehensive high-performance goals of fine-grained structure, high tensile strength, long high-temperature life, and high yield of iron-chromium-aluminum electrothermal alloys.

[0116] One or more technical solutions in the embodiments of the present invention have at least the following technical effects or advantages: (1) Significantly improved forging yield: By adopting a two-stage forging process, the large deformation is rationally distributed across two forging stages. The deformation in each stage is controlled within the plastic bearing capacity of the iron-chromium-aluminum heating alloy, and the annealing treatment between stages effectively eliminates accumulated stress. This improvement increases the forging yield from 60% in traditional one-fire forging to over 90%, effectively reducing the waste of iron-chromium-aluminum heating alloy and lowering production costs.

[0117] (2) Fully homogenized and refined grain structure: The heating temperature in the first stage is controlled at 1040℃~1080℃, which effectively suppresses grain growth behavior at high temperatures. Intermediate annealing at 750℃ for 2 hours between stages achieves recrystallization and composition homogenization. Based on the homogenized structure, the second stage forging completes the final forming process. The grain size grade of the final product reaches 8.0 or above, which is significantly better than similar foreign products. The grain size uniformity coefficient (the ratio of the maximum grain size to the average grain size) is ≤1.5, and the uniformity of the structure and the fine grain strengthening effect are excellent.

[0118] (3) Precise alloy composition and excellent high-temperature life: Through the synergistic ratio of trace elements such as titanium, zirconium, rare earth and magnesium, the bonding force between the alloy oxide film and the substrate is significantly enhanced, resulting in a rapid life test result of >80h for the iron-chromium-aluminum heating alloy at 1400℃. The above performance is more than 30% higher than that of traditional iron-chromium-aluminum heating alloys, which can meet the requirements of high-end industrial furnaces for long-life heating elements.

[0119] (4) Excellent mechanical properties of the product: The iron-chromium-aluminum heating alloy has high tensile strength and good elongation. This combination of high strength and good plasticity makes the iron-chromium-aluminum heating alloy have excellent cold drawing and winding properties, which can fully meet the various processing requirements in the manufacturing process of heating elements.

[0120] (5) Complete and adaptable process route: This process route covers the complete production process from vacuum induction smelting to heat treatment. The process route adopts a two-stage forging process combined with a hot transfer process, forming a highly efficient and energy-saving production mode, while avoiding high-cost technical paths such as powder metallurgy, making it suitable for large-scale industrial production. In addition, the two-stage forging process concept can be extended to the processing and preparation of other ferritic alloy materials with a tendency to embrittle at high temperatures.

[0121] (6) Not dependent on scarce elements: The alloy composition does not contain scarce and expensive elements such as cobalt and niobium. The main constituent elements are common elements with abundant resources such as iron, chromium and aluminum. The low cost advantage brought about by the alloy composition design makes the iron-chromium-aluminum electric heating alloy highly competitive in the market.

[0122] The above description is merely a specific embodiment of this application, enabling those skilled in the art to understand or implement this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features claimed in this application.

Claims

1. A high-temperature iron-chromium-aluminum electric heating alloy, characterized in that, The chemical composition of the iron-chromium-aluminum heating alloy, by mass fraction, is as follows: Cr: 21%~25%, Al: 4%~6%, Si≤0.50%, Mn≤0.50%, C≤0.015%, Ti: 0.02%~0.10%, Zr: 0.02%~0.15%, rare earth elements: 0.01%~0.20%, Mg: 0.001%~0.010%, with the remainder being Fe and unavoidable impurities; the rare earth elements are at least one of Y, La, Ce and Hf; The microstructure of the iron-chromium-aluminum electrothermal alloy is ferrite, and the grain size of the ferrite is ≥8.

0.

2. The iron-chromium-aluminum electrothermal alloy according to claim 1, characterized in that, The iron-chromium-aluminum electrothermal alloy meets at least one of the following properties: tensile strength ≥650MPa, elongation ≥25%.

3. A method for preparing the iron-chromium-aluminum electrothermal alloy according to any one of claims 1 or 2, characterized in that, The method includes: A masterbatch having the chemical composition described in any one of claims 1 to 2 is obtained; The mother ingot was electroslag remelted using a CaF2-Al2O3-CaO-MgO quaternary slag system to obtain a cast ingot; The ingot is kept at 600°C or cooled to room temperature to obtain a heat-insulated ingot. The heat-insulated ingot is subjected to a first-stage forging process, a first-stage annealing process, and a second-stage forging process in sequence to obtain a square billet of 40mm×40mm~60mm×60mm. The billet is hot-rolled to obtain hot-rolled wire rods with a diameter of 8mm~12mm; The hot-rolled wire rod is subjected to a second annealing treatment to obtain annealed wire rod; The annealed wire rod is subjected to multiple cold drawing passes, and a third annealing treatment is performed between the cold drawing passes to obtain cold-drawn wire with a diameter of 2mm to 5mm. The cold-drawn wire is heat-treated to obtain an iron-chromium-aluminum electrothermal alloy.

4. The method according to claim 3, characterized in that, The master ingot is obtained by vacuum induction smelting, wherein the ultimate vacuum degree of the vacuum induction smelting is ≤5Pa; The refining vacuum degree of the vacuum induction smelting is ≤10Pa, the refining temperature of the vacuum induction smelting is 1550℃~1600℃, and the refining time of the vacuum induction smelting is 20min~30min. The argon-filling pressure for the vacuum induction smelting is 0.05 MPa to 0.10 MPa; The casting temperature for vacuum induction smelting is 1600℃~1650℃.

5. The method according to claim 3, characterized in that, The amount of slag in the quaternary slag system is 3% to 5% of the mass of the mother ingot; The current for electroslag remelting is 2000A~4500A, the voltage for electroslag remelting is 35V~50V, and the melting rate for electroslag remelting is 1.0kg / min~2.5kg / min.

6. The method according to claim 3, characterized in that, The diameter of the mother ingot is 150mm~160mm; the oxygen content of the mother ingot is ≤10ppm, and the nitrogen content of the mother ingot is ≤20ppm; and / or, The diameter of the ingot is 150mm~160mm; the oxygen content of the ingot is ≤10ppm, and the sulfur content of the ingot is ≤10ppm.

7. The method according to claim 3, characterized in that, When the ingot is heated to 600°C, the furnace loading temperature of the first stage forging process is ≤600°C; when the ingot has cooled to room temperature, the furnace loading temperature of the first stage forging process is ≤400°C. The heating temperature of the first stage forging process is 1050℃~1080℃, the heating time of the first stage forging process is 90min~120min, and the holding time of the first stage forging process is 30min~40min. The initial forging temperature of the first stage forging process is ≥1050℃, and the final forging temperature of the first stage forging process is ≥800℃. The temperature of the first annealing treatment is 740℃~830℃, and the time of the first annealing treatment is 1h~2h.

8. The method according to claim 3, characterized in that, The furnace loading temperature for the second stage of forging treatment is ≤400℃; The heating temperature for the second stage forging process is 1100℃~1140℃, the heating time for the second stage forging process is 60min~90min, and the holding time for the second stage forging process is 25min~35min. The initial forging temperature of the second stage forging process is ≥1100℃, and the final forging temperature of the second stage forging process is ≥800℃.

9. The method according to claim 3, characterized in that, The furnace charging temperature of the hot-rolled product is ≤400℃; The heating temperature of the hot rolling is 1030℃~1070℃, and the holding time of the hot rolling is 60min~90min; The final rolling temperature of the hot rolling is ≥850℃; The total deformation ratio of the hot rolling is ≥15:

1.

10. The method according to claim 3, characterized in that, The cooling method for the second annealing is at least one of slow furnace cooling and controlled-rate cooling; The temperature of the second annealing treatment is 750℃~800℃, and the holding time of the second annealing treatment is 1h~2h; and / or, The shrinkage rate of each pass in the multi-pass cold drawing is 15%~25%, and the total shrinkage rate of the multi-pass cold drawing is 60%~80%; and / or, The temperature of the third annealing treatment is 750℃~800℃, and the holding time of the third annealing treatment is 1h~2h; and / or, The heat treatment temperature is 850℃~950℃, and the heat treatment holding time is 1h~2h.

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