A nickel-chromium electrothermal alloy and its preparation method

Abstract

This invention provides a nickel-chromium electric heating alloy and its preparation method, belonging to the field of alloy preparation technology. The chemical composition of the nickel-chromium electric heating alloy is: C, Si, S, P, Cr, Ni, Al, Ti, Hf, and rare earth elements, with the balance being iron. The rare earth elements include at least one of the following: Ce, La, and, by mass fraction, C content is 0.01%–0.05%, Si content is 1.0%–3.0%, S content is ≤0.003%, P content is ≤0.020%, Cr content is 21%–24%, Ni content is 64%–69%, Al content is 0.1%–0.7%, Ti content is 0.01%–0.5%, Hf content is 0.01%–0.2%, and the rare earth element content is 0.01%–0.5%. This invention reduces the nickel content in the nickel-chromium alloy Cr20Ni80 by adding Ce, Hf, and Al elements and partially replacing nickel with iron. The nickel-chromium electric heating alloy obtained by the preparation method of the present invention has a maximum operating temperature of 1200℃ for Cr20Ni80, a rapid service life of ≥100h at 1200℃, and a resistance temperature correction coefficient of 1.0~1.1 at 1200℃, with a small variation in the resistance temperature correction coefficient.

Description

Technical Field

[0001] This application relates to the field of alloy preparation technology, and in particular to a nickel-chromium electrothermal alloy and its preparation method. Background Technology

[0002] Cr20Ni80 is a single-phase alloy in which chromium is replaced by a nickel matrix. It has an austenitic structure at both room temperature and high temperature and does not undergo solid-state phase transformation during cooling. The alloy structure is stable. Cr20Ni80 alloy has excellent mechanical properties at both high temperature and room temperature, a maximum operating temperature of 1200℃, stable resistivity, and long service life. Therefore, it is widely used in industrial furnaces, metallurgy, machinery and other fields. Especially in harsh service environments with high temperature or vibration, only Ni-Cr series electric heating alloys can be used normally.

[0003] Currently available nickel-chromium-iron heating alloys such as Cr20Ni40, Cr20Ni35, and Cr15Ni60 have low nickel content and excellent mechanical properties at both high and room temperatures. However, their resistance temperature correction coefficient is higher than that of nickel-chromium alloys, resulting in poor resistivity stability. Among them, Cr15Ni60 has the highest operating temperature of 1150℃, which cannot meet the requirement of 1200℃. Therefore, it is necessary to develop a nickel-saving nickel-chromium heating alloy with a maximum operating temperature of 1200℃ that can replace Cr20Ni80. Summary of the Invention

[0004] This application provides a nickel-chromium electric heating alloy and its preparation method, which, while meeting the requirements of a maximum operating temperature of 1200 ℃ and a stable resistance temperature correction coefficient for Cr20Ni80 alloy, improves the technical problem of excessive nickel content in existing Cr20Ni80 alloys.

[0005] In a first aspect, this application provides a nickel-chromium heating alloy, the chemical composition of which is: C, Si, S, P, Cr, Ni, Al, Ti, Hf, and rare earth elements, with the balance being iron. The rare earth elements include at least one of the following: Ce, La, and; by mass fraction,

[0006] The content of C is 0.01%~0.05%, the content of Si is 1.0%~3.0%, the content of S is ≤0.003%, the content of P is ≤0.020%, the content of Cr is 21%~24%, the content of Ni is 64%~69%, the content of Al is 0.1%~0.7%, the content of Ti is 0.01%~0.5%, the content of Hf is 0.01%~0.2%, and the content of the rare earth elements is 0.01%~0.5%.

[0007] Optionally, the microstructure of the nickel-chromium electrothermal alloy is austenitic.

[0008] Optionally, the nickel-chromium heating alloy meets at least one of the following properties: maximum operating temperature of 1200 ℃, rapid life at 1200 ℃ ≥ 100 h, and resistance temperature correction coefficient of 1~1.1 at 1200 ℃.

[0009] Secondly, this application provides a method for preparing a nickel-chromium heating alloy, used to prepare the nickel-chromium heating alloy described in any embodiment of the first aspect, the method comprising:

[0010] The raw materials of the nickel-chromium electrothermal alloy are smelted to obtain an alloy rod containing the chemical composition.

[0011] The alloy rod is purified to obtain an alloy ingot;

[0012] The alloy ingot is heated, rolled, and wired to obtain alloy wire rod;

[0013] The alloy wire rod is subjected to a first annealing, cooling, surface treatment and drawing to obtain a drawn cold finished product;

[0014] The drawn cold-state product is subjected to a second annealing to obtain a nickel-chromium electrothermal alloy.

[0015] Optionally, the slag used in the smelting includes CaF2, CaO, and Al2O3, and the mass ratio of the slag satisfies: CaF2:CaO:Al2O3=(3~5):(2~4):(2~4), and the amount of slag used in the smelting is 50 Kg / t·steel to 60 Kg / t·steel.

[0016] Optionally, the tapping temperature of the smelting is 1620 ℃~1650 ℃, the smelting adopts bottom blowing argon, and the stirring time of the bottom blowing argon is 2 min~3 min.

[0017] Optionally, the purification method includes electroslag remelting and vacuum consumables. The purification slag includes CeO2, CaO and CaF2. The mass ratio of the purification slag satisfies CeO2:CaO:CaF2=(10~20):(3~5):(70~80). The amount of purification slag used is 3 Kg / t·steel to 5 Kg / t·steel.

[0018] Optionally, the heating temperature is 1100 ℃~1200 ℃, the heating time is 90 min~400 min, and the initial rolling temperature is 1150 ℃~1190 ℃.

[0019] Optionally, the temperature of the first annealing is 950 ℃~1050 ℃, and the time of the first annealing is 120 min~240 min.

[0020] Optionally, the temperature of the second annealing is 1000 ℃ to 1150 ℃.

[0021] The technical solutions provided in this application have the following advantages compared with the prior art:

[0022] This invention reduces the nickel content in the nickel-chromium alloy Cr20Ni80 by adding Ce, Hf, and Al elements and partially replacing nickel with iron. The nickel-chromium heating alloy obtained by the preparation method of this invention achieves a maximum operating temperature of 1200 ℃, the same as Cr20Ni80, with a rapid life of ≥100 h at 1200 ℃ and a resistance temperature correction coefficient of 1.0~1.1 at 1200 ℃, exhibiting minimal variation in the resistance temperature correction coefficient. Attached Figure Description

[0023] 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.

[0024] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0025] Figure 1 This is a schematic diagram of a method for preparing a nickel-chromium electrothermal alloy, provided in an embodiment of this application. Detailed Implementation

[0026] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0027] Various embodiments of this application may exist in the form of a range; it should be understood that the description in the form of a range is merely for convenience and brevity and should not be construed as a hard limitation on the scope of this application; therefore, it should be considered that the range description has specifically disclosed all possible sub-ranges and single numerical values ​​within that range. For example, it should be considered that the range description from 1 to 6 has specifically disclosed sub-ranges such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., and single numbers within the range, such as 1, 2, 3, 4, 5, and 6, regardless of the range. Furthermore, whenever a numerical range is referred to herein, it means including any referenced number (fraction or integer) within the referred range.

[0028] In the description of this application, the terms "comprising," "including," etc., mean "including but not limited to." In this document, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. In this document, "and / or" describes the relationship between related objects, indicating that three relationships may exist; for example, A and / or B can represent: A alone, A and B simultaneously, or B alone. A and B can be singular or plural. In this document, "at least one" means one or more, and "more than" means two or more. "At least one," "at least one of the following," or similar expressions refer to any combination of these items, including any combination of single or plural items. For example, "at least one of a, b, or c", or "at least one of a, b, and c", can both mean: a, b, c, a~b (i.e., a and b), a~c, b~c, or a~b~c, where a, b, and c can be a single or multiple.

[0029] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this application can be purchased from the market or prepared by existing methods.

[0030] In a first aspect, this application provides a nickel-chromium heating alloy, the chemical composition of which is: C, Si, S, P, Cr, Ni, Al, Ti, Hf, and rare earth elements, with the balance being iron. The rare earth elements include at least one of the following: Ce, La, and; by mass fraction,

[0031] The content of C is 0.01%~0.05%, the content of Si is 1.0%~3.0%, the content of S is ≤0.003%, the content of P is ≤0.020%, the content of Cr is 21%~24%, the content of Ni is 64%~69%, the content of Al is 0.1%~0.7%, the content of Ti is 0.01%~0.5%, the content of Hf is 0.01%~0.2%, and the content of the rare earth elements is 0.01%~0.5%.

[0032] In the embodiments of this application, the positive effects of controlling the C content to be 0.01% to 0.05% are as follows: if the C content is too high, it will lead to the formation of large-sized chromium carbides to a certain extent, accelerating the oxidation of the material; if the C content is too low, it will increase the raw material and production costs. Specifically, the C content can be 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, etc.

[0033] The positive effects of controlling the Si content to 1.0%–3.0% include: Si reacts with air to form SiO2, which, located between the alloy matrix and the oxide film, acts as an oxygen barrier, playing a crucial role in the anti-oxidation mechanism and reducing the alloy's oxidation rate, thus extending its service life. Simultaneously, Si increases resistivity; maintaining a stable Si content is beneficial for the alloy's resistivity stability. However, excessive Si content can easily lead to segregation during use, affecting the material's microstructure stability, creep performance, and overall oxidation resistance, resistivity, and high-temperature microstructure stability. Specifically, the Si content can be 1.0%, 1.5%, 2.0%, 2.5%, or 3.0%, etc.

[0034] The positive effects of controlling the sulfur (S) content to ≤0.003% and the phosphorus (P) content to ≤0.020% are as follows: S and P elements are detrimental to the high-temperature oxidation resistance of materials, so low-limit control is adopted. Specifically, the S content can be 0.001%, 0.002%, 0.003%, etc., and the P content can be 0.005%, 0.010%, 0.015%, 0.020%, etc.

[0035] The positive effects of controlling the Cr content to 21%~24% include: Chromium improves the corrosion resistance of the alloy; when the Cr content is 20%-50%, the oxidation resistance reaches a plateau. After the Cr content reaches 20%, the anti-sulfurization effect of chromium also enters a relatively stable state. When the Cr content exceeds 20%, the effect of chromium content on resistivity tends to stabilize; controlling the Cr content above 20% helps maintain the stability of the alloy's resistivity. To obtain good corrosion resistance, high-temperature oxidation resistance, and sulfurization resistance, thereby improving the alloy's service life, the Cr content is designed to be in the range of 21-24%. Specifically, the Cr content can be 21%, 22%, 23%, 24%, etc.

[0036] The positive effects of controlling the Ni content to 64%~69% include: Ni is the main austenite-forming element, ensuring the material maintains a stable austenitic structure from high to low temperatures, reducing the tendency for brittle σ phase precipitation, guaranteeing the material's high-temperature mechanical properties, and improving oxide film stability. However, excessively high Ni content can increase costs to some extent, while excessively low Ni content can affect microstructure stability, lower the material's maximum service temperature, and cause brittle σ phase precipitation, leading to deterioration in processing performance. Specifically, the Ni content can be 64%, 65%, 66%, 67%, 68%, 69%, etc.

[0037] The positive effects of controlling the Al content to 0.1%~0.7% include: Al improving the adhesion of the oxide film and enhancing the alloy's oxidation and sulfidation resistance. Furthermore, Al can form grain boundary strengthening phases with Ni, improving the alloy's creep resistance. However, excessively high Al content reduces the alloy's strength and plasticity, affecting its processing performance. Specifically, the Al content can be 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, etc.

[0038] The positive effects of controlling the Ti content to 0.01%~0.5% include: Ti can prevent internal oxidation of the material, ensuring that SiO2 forms only on the surface; and it, in combination with Al, helps reduce the formation of aluminum nitrides and promotes the formation of the Ni3Al strengthening phase. Specifically, the Ti content can be 0.01%, 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, etc.

[0039] The positive effects of controlling the Hf content to 0.01%~0.2% include: Hf can improve the mechanical and processing properties of the alloy, improve the morphology of carbides in the material, form Hf-rich (Ti,Hf)C, and slow down M. 23 C6 formation improves service life. Hf can form intermetallic compounds with Ni, such as Ni7(Hf,Ti)2 and Ni3(Hf,Ti), which improves the material's service temperature and high-temperature creep strength. Specifically, the Hf content can be 0.01%, 0.05%, 0.10%, 0.15%, 0.20%, etc.

[0040] The positive effects of controlling the rare earth element content to 0.01%~0.5% include: Rare earth elements such as La, Ce, and Y can form rare earth compounds with elements such as N, O, and S in the alloy, effectively reducing the content of inclusions and ensuring their uniform dispersion throughout the alloy. Simultaneously, the addition of rare earth elements can inhibit grain growth, leading to finer grains, reducing crack formation, and improving the alloy's high-temperature and room-temperature plasticity and strength. Rare earth elements also improve the adhesion and density of the oxide film, thereby enhancing the alloy's high-temperature oxidation resistance. Specifically, the rare earth element content can be 0.01%, 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, etc.

[0041] In some embodiments, the microstructure of the nickel-chromium heating alloy is austenitic.

[0042] In some embodiments, the nickel-chromium heating alloy satisfies at least one of the following properties: a maximum operating temperature of 1200 ℃, a rapid life of ≥100 h at 1200 ℃, and a resistance temperature correction factor of 1.0~1.1 at 1200 ℃.

[0043] The nickel-saving nickel-chromium electric heating alloy in this application has excellent mechanical properties at high and room temperature, a maximum operating temperature of 1200℃, stable resistivity, and long service life, and can replace Cr20Ni80.

[0044] Secondly, this application provides a method for preparing a nickel-chromium heating alloy, used to prepare the nickel-chromium heating alloy described in any embodiment of the first aspect, the method comprising:

[0045] S1. The raw materials of the nickel-chromium electrothermal alloy are smelted to obtain an alloy rod containing the chemical composition.

[0046] In some embodiments, the raw materials may include crystalline silicon, micro-carbon ferrochrome, electrolytic nickel, metallic aluminum, sponge titanium, metallic hafnium, metallic cerium, metallic lanthanum, metallic yttrium, and pig iron.

[0047] In some embodiments, the smelting apparatus includes a three-phase lined electroslag furnace, a vacuum induction furnace, and a medium-frequency induction furnace. The slag used in the smelting includes CaF2, CaO, and Al2O3, and the mass ratio of the slag satisfies: CaF2:CaO:Al2O3=(3~5):(2~4):(2~4). The amount of slag used in the smelting is 50 kg / t steel to 60 kg / t steel. Aluminum powder deoxidation can be used in the smelting process.

[0048] In the embodiments of this application, the positive effects of controlling the CaF2:CaO:Al2O3 ratio to (3~5):(2~4):(2~4) are: ensuring stable resistivity of the smelting slag, good slag fluidity, and good adsorption capacity for inclusions. The mass ratio of CaF2, CaO, and Al2O3 can be 3:2:2, 4:2:2, 3.5:3:3.5, 4.5:3:2.5, 4:3:3, 5:3:4, 5:3:2, 4:3:4, 4:4:4, etc. The slag usage in this smelting process can be 50 kg / t steel, 52 kg / t steel, 54 kg / t steel, 56 kg / t steel, 58 kg / t steel, or 60 kg / t steel.

[0049] In some embodiments, the tapping temperature of the smelting can be 1620 ℃~1650 ℃, and the smelting can be carried out by inserting rare earth elements into the ladle and bottom blowing argon, with the bottom blowing argon stirring time being 2 min~3 min.

[0050] In this embodiment, controlling the tapping temperature of the smelting process to 1620℃~1650℃ has the following positive effects: ensuring smooth casting while reducing alloy loss. If the tapping temperature is too high, it will accelerate the oxidation and loss of alloying elements to some extent. If the tapping temperature is too low, it will cause the molten steel to solidify during casting, clogging the slurry and affecting the quality of the steel bar. The tapping temperature can be 1620℃, 1630℃, 1640℃, 1650℃, etc. Controlling the bottom-blowing argon stirring time to 2 min~3 min has the following positive effects: ensuring compositional uniformity. The bottom-blowing argon stirring time can be 2 min, 2.5 min, 3 min, etc.

[0051] S2. Purify the alloy rod to obtain an alloy ingot;

[0052] In some embodiments, the purification method includes electroslag remelting and vacuum consumables. The purification slag includes CeO2, CaO and CaF2. The mass ratio of the purification slag satisfies CeO2:CaO:CaF2=(10~20):(3~5):(70~80). The amount of purification slag used is 3 kg / t steel to 5 kg / t steel.

[0053] In the embodiments of this application, the positive effects of controlling CeO2:CaO:CaF2 = (10~20):(3~5):(70~80) are as follows: To ensure the rare earth recovery rate in the purified alloy, CeO2 is added to the purification slag. While ensuring that the resistivity, melting point, and adsorption capacity of the refining slag are not reduced, the loss of rare earth elements is reduced, and the recovery rate is improved. The mass ratio of CeO2, CaO, and CaF2 can be 20:3:77, 15:5:80, 20:4:76, 20:5:75, 15:3:72, 15:4:71, 15:5:70, etc. The amount of purification slag used in this purification process is 3 kg / t steel, 3.5 kg / t steel, 4 kg / t steel, 4.5 kg / t steel, and 5 kg / t steel.

[0054] S3. The alloy ingot is heated, rolled, and wired to obtain alloy wire rod;

[0055] In some embodiments, the heating temperature is 1100 ℃~1200 ℃, the heating time is 90 min~400 min, and the rolling start temperature is 1150 ℃~1190 ℃.

[0056] In this embodiment, the positive effect of controlling the heating temperature to 1100℃~1200℃ is that it ensures that the steel ingot reaches the initial rolling temperature both internally and externally. If the temperature is too high, it can lead to oxidation of the steel ingot surface, severe coarsening of the microstructure, and cracking during rolling due to overheating. If the temperature is too low, the steel ingot may not reach the initial rolling temperature, resulting in poor thermoplasticity of the material and cracking during deformation. The heating temperature can be 1100℃, 1120℃, 1140℃, 1160℃, 1180℃, 1200℃, etc.

[0057] The positive effects of controlling the heating time to 90-400 minutes include ensuring uniform heating of the steel ingot both inside and out. Excessive heating time can lead to microstructural growth and surface oxidation of the ingot; conversely, insufficient heating time can result in the internal temperature of the ingot not reaching the set temperature, causing core cracking during rolling. Suitable heating times include 90, 100, 150, 200, 250, 300, and 400 minutes.

[0058] The positive effects of controlling the initial rolling temperature to 1150℃-1190℃ include: good thermoplasticity within this temperature range, which is beneficial for hot working deformation. If the initial rolling temperature is too high, it can lead to surface oxidation, severe microstructure coarsening, and rolling cracking to some extent; if the initial rolling temperature is too low, it can result in poor thermoplasticity of the alloy, leading to cracking during deformation. Specifically, the initial rolling temperature can be 1150℃, 1160℃, 1170℃, 1180℃, 1190℃, etc.

[0059] S4. Anneal, cool, surface treat and draw the alloy wire rod to obtain a drawn cold-state finished product;

[0060] In some embodiments, the temperature of the first annealing is 950 ℃ to 1050 ℃, and the time of the first annealing is 120 min to 240 min.

[0061] The positive effects of controlling the first annealing temperature to 950℃-1050℃ and the first annealing time to 120 min-240 min are: within this controlled temperature and time range, it constitutes solution treatment, resulting in a uniform composition of the wire rod microstructure and eliminating work hardening. If the annealing temperature is too high, it can lead to a coarse wire rod microstructure and surface oxidation to some extent; if the annealing temperature is too low, it may not achieve the desired solution treatment effect to some extent. Specifically, the first annealing temperature can be 950℃, 970℃, 990℃, 1110℃, 1130℃, 1150℃, etc., and the first annealing time can be 120 min, 150 min, 180 min, 210 min, 240 min, etc.

[0062] In some embodiments, the surface treatment methods include: laser cleaning, mechanical polishing, plasma treatment, wire rod peeling, pickling, and molten alkali washing.

[0063] In this embodiment, the method for removing the surface oxide film is as follows: the alloy wire rod is immersed in molten sodium hydroxide at 700°C for 3-5 minutes, rinsed with water, then immersed in sulfuric acid with a concentration greater than 180g / L for 30-40 minutes, rinsed with water to remove surface residue, and then dried.

[0064] S5. Perform a second annealing on the drawn cold finished product to obtain a nickel-chromium electrothermal alloy.

[0065] In some embodiments, the temperature of the second annealing is 1000 °C to 1150 °C.

[0066] In this embodiment, controlling the second annealing temperature to be between 1000℃ and 1150℃ has the following positive effects: controlling it within this temperature range helps eliminate processing stress and dislocations, improving the mechanical properties of the finished product. If the annealing temperature is too high, it can lead to a coarse internal structure in the alloy to some extent; if the annealing temperature is too low, it can lead to excessively high material strength and poor material processing performance to some extent. The annealing temperature can be 1000℃, 1050℃, 1100℃, 1150℃, etc.

[0067] The nickel-chromium heating alloy is realized based on the above-described preparation method of the nickel-chromium heating alloy. The specific steps of the preparation method of the nickel-chromium heating alloy can be referred to the above embodiments. Since the nickel-chromium heating alloy adopts some or all of the technical solutions of the above embodiments, it has at least all the beneficial effects brought about by the technical solutions of the above embodiments, which will not be elaborated here.

[0068] The present application is further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the application. Experimental methods in the following embodiments that do not specify specific conditions are generally determined according to national standards. If there is no corresponding national standard, then general international standards, conventional conditions, or conditions recommended by the manufacturer are followed.

[0069] Example 1

[0070] A nickel-chromium heating alloy, the chemical composition of which, by mass fraction, is: C 0.025%, Si 2.28%, S 0.0018%, P 0.017%, Cr 22.65%, Ni 64.91%, Ce 0.027%, Hf 0.05%, Al 0.5%, with iron as the balance.

[0071] The preparation method of this nickel-chromium electric heating alloy is as follows:

[0072] S11 alloy steel bars are smelted in a three-phase lined electroslag furnace using pure iron, low-carbon ferrochrome, electrolytic nickel, crystalline silicon, metallic cerium, metallic hafnium, and aluminum blocks as raw materials. The slag and its mass ratio are CaF2:CaO:Al2O3 = 3.5:3.5:3, with a slag consumption of 120 kg / t. Aluminum powder is used for deoxidation during the smelting process. The tapping temperature is 1650℃. Argon stirring is performed at the bottom of the ladle for 3 minutes to ensure compositional homogeneity. The steel is cast into alloy bars.

[0073] S21. Using the above alloy rod as a consumable electrode, the alloy ingot is purified by a single-phase electroslag remelting furnace. The refining slag and its mass ratio are Al2O2:CaO:CaF2=15:5:80, with 5 kg of refining slag per furnace.

[0074] S31. The obtained alloy ingot is heated in a heating furnace at a temperature of 1200 ℃ for 400 min; then rolled at a rolling temperature of 1150 ℃; and then wire rod is produced to obtain alloy wire rod.

[0075] S41. Annealing is performed in a pit-type annealing furnace, held at 1050℃ for 180 min, then removed from the furnace and water-cooled. The surface oxide film is then removed by immersion in molten sodium hydroxide at 700℃ for 5 minutes, followed by rinsing with water. Next, the wire is immersed in 180g / L sulfuric acid for 40 minutes, rinsed with water to remove surface residue, and then air-dried. Finally, the cleaned wire is drawn to obtain the cold-drawn finished product.

[0076] S51. The drawn cold finished product is annealed in a continuous annealing furnace under atmosphere protection at an annealing temperature of 1100℃ to obtain a nickel-chromium electric heating alloy finished product, which can be used for the production of heating elements.

[0077] Example 2

[0078] A nickel-chromium heating alloy, the chemical composition of which, by mass fraction, is: C 0.012%, Si 2.28%, S 0.0016%, P 0.020%, Cr 22.36%, Ni 65.20%, Ce 0.015%, with iron as the balance.

[0079] The preparation method of this nickel-chromium electric heating alloy is as follows:

[0080] S11 alloy steel bars are smelted in a three-phase lined electroslag furnace using pure iron, low-carbon ferrochrome, electrolytic nickel, crystalline silicon, metallic cerium, and aluminum blocks as raw materials. The slag and its mass ratio are CaF2:CaO:Al2O3 = 4.5:3:2.5, with a slag consumption of 120 kg / t. Aluminum powder is used for deoxidation during the smelting process. The tapping temperature is 1650℃. Argon stirring is performed at the bottom of the ladle for 3 minutes to ensure compositional homogeneity. The steel is cast into alloy bars.

[0081] S21. Using the above alloy rod as a consumable electrode, the alloy ingot is purified by a single-phase electroslag remelting furnace. The refining slag and its mass ratio are Al2O2:CaO:CaF2=22:3:75, with 5 kg of refining slag per furnace.

[0082] S31. The obtained alloy ingot is heated in a heating furnace at a temperature of 1200 ℃ for 400 min; then rolled at a rolling temperature of 1150 ℃; and then wire rod is produced to obtain alloy wire rod.

[0083] S41. Annealing is performed in a pit-type annealing furnace, held at 1050℃ for 180 min, then removed from the furnace and water-cooled. The surface oxide film is then removed by immersion in molten sodium hydroxide at 700℃ for 5 minutes, followed by rinsing with water. Next, the wire is immersed in 180g / L sulfuric acid for 40 minutes, rinsed with water to remove surface residue, and then air-dried. Finally, the cleaned wire is drawn to obtain the cold-drawn finished product.

[0084] S51. The drawn cold finished product is annealed in a continuous annealing furnace under atmosphere protection at an annealing temperature of 1100℃ to obtain a nickel-chromium electric heating alloy finished product, which can be used for the production of heating elements.

[0085] Comparative Example 1

[0086] A nickel-chromium heating alloy, the chemical composition of which, by mass fraction, is: C 0.021%, Si 1.89%, S 0.0025%, P 0.020%, Cr 21.26%, Ni 65.37%, with iron as the balance.

[0087] The preparation method of this nickel-chromium electric heating alloy is as follows:

[0088] S11 alloy steel bars are smelted in a three-phase lined electroslag furnace using pure iron, low-carbon ferrochrome, electrolytic nickel, and crystalline silicon as raw materials. The slag and its mass ratio are CaF2:CaO:Al2O3 = 4:3:3, with a slag consumption of 120 kg / t. Aluminum powder is used for deoxidation during the smelting process. The tapping temperature is 1650℃. Argon stirring is performed at the bottom of the ladle for 3 minutes to ensure compositional homogeneity. The steel is cast into alloy bars.

[0089] S21. Using the above alloy rod as a consumable electrode, the alloy ingot is purified by a single-phase electroslag remelting furnace. The refining slag and its mass ratio are Al2O2:CaO:CaF2=20:5:75, with 5 kg of refining slag per furnace.

[0090] S31. The obtained alloy ingot is heated in a heating furnace at a temperature of 1200 ℃ for 400 min; then rolled at a rolling temperature of 1150 ℃; and then wire rod is produced to obtain alloy wire rod.

[0091] S41. Annealing is performed in a pit-type annealing furnace, held at 1050℃ for 180 min, then cooled with water. The surface oxide film is then removed by immersion in molten sodium hydroxide at 700℃ for 5 minutes, followed by rinsing with water. Next, the wire is immersed in 180g / L sulfuric acid for 40 minutes, rinsed with water to remove surface residue, and then air-dried. Finally, the cleaned wire is drawn to obtain the cold-drawn finished product.

[0092] S51. The drawn cold finished product is annealed in a continuous annealing furnace under atmosphere protection at an annealing temperature of 1100℃ to obtain a nickel-chromium electric heating alloy finished product, which can be used for the production of heating elements.

[0093] Example 1 Rapid life tests were conducted on the nickel-chromium heating alloys provided in Comparative Example 2 and Comparative Example 1, and the results are shown in Table 1.

[0094] Table 1: Example 1 Rapid life values ​​of the nickel-chromium heating alloys provided in Example 2 and Comparative Example 1 at 1200 °C

[0095]

[0096] As shown in the table above, the nickel-chromium heating alloy prepared using the method provided in this application can achieve a rapid lifespan of up to 105 hours at 1200°C. Furthermore, the resistance temperature correction coefficient of the nickel-chromium heating alloy prepared using the method provided in Example 1 is tested, and the coefficient at 1200°C is 1.09, indicating minimal change. Therefore, the nickel-saving nickel-chromium heating alloy of this application exhibits excellent high-temperature and room-temperature mechanical properties, a maximum operating temperature of 1200°C, stable resistivity, and a long service life, making it a viable alternative to Cr20Ni80.

[0097] 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 herein.

Claims

1. A nickel-chromium electrothermal alloy, characterized in that, The chemical composition of the nickel-chromium electrothermal alloy comprises C, Si, S, P, Cr, Ni, Al, Ti, Hf and rare earth elements, the balance being iron, and the rare earth elements comprise at least one of Ce, La and, in terms of mass fraction, The content of C is 0.01% to 0.05%, the content of Si is 1.0% to 3.0%, the content of S is ≤0.003%, the content of P is ≤0.020%, the content of Cr is 21% to 24%, the content of Ni is 64% to 69%, the content of Al is 0.5% to 0.7%, the content of Ti is 0.01% to 0.5%, the content of Hf is 0.01% to 0.2%, and the content of the rare earth elements is 0.01% to 0.2%. The microstructure of the nickel-chromium electrothermal alloy is austenite. The nickel-chromium electrothermal alloy satisfies at least one of the following properties: the maximum use temperature is 1200 ℃, the 1200 ℃ rapid life is ≥100 h, and the 1200 ℃ resistance temperature correction coefficient is 1 to 1.

1.

2. A method of producing a nickel-chromium electrothermal alloy, characterized by, A method for preparing the nickel-chromium electrothermal alloy of claim 1, the method comprising: Smelting raw materials of the nickel-chromium electrothermal alloy to obtain an alloy bar containing the chemical composition; Purifying the alloy bar to obtain an alloy ingot; Heating, rolling and wire bar of the alloy ingot to obtain an alloy wire bar; First annealing, cooling, surface treatment and drawing of the alloy wire bar to obtain a drawn cold finished product; Second annealing of the drawn cold finished product to obtain a nickel-chromium electrothermal alloy.

3. The method of claim 2, wherein, The smelting slag comprises CaF2, CaO and Al2O3, the mass ratio of the smelting slag satisfies CaF2:CaO:Al2O3=(3 to 5):(2 to 4):(2 to 4), and the smelting slag usage is 50 Kg / t·steel to 60 Kg / t·steel.

4. The preparation method according to claim 2, characterized in that, The smelting tapping temperature is 1620 ℃ to 1650 ℃, the smelting adopts bottom argon blowing, and the stirring time of the bottom argon blowing is 2 min to 3 min.

5. The preparation method according to claim 2, characterized in that, The purifying mode comprises electroslag remelting and vacuum consumable, the purifying slag of the purifying comprises CeO2, CaO and CaF2, the mass ratio of the purifying slag satisfies CeO2:CaO:CaF2=(10 to 20):(3 to 5):(70 to 80), and the purifying slag usage is 3 Kg / t·steel to 5 Kg / t·steel.

6. The preparation method according to claim 2, characterized in that, The heating temperature is 1100 ℃ to 1200 ℃, the heating time is 90 min to 400 min, and the rolling open rolling temperature is 1150 ℃ to 1190 ℃.

7. The preparation method according to claim 2, characterized in that, The first annealing temperature is 950 ℃ to 1050 ℃, and the first annealing time is 120 min to 240 min.

8. The preparation method according to claim 2, characterized in that, The second annealing temperature is 1000 ℃ to 1150 ℃.

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