Preparation method of nickel-chromium-iron alloy consumable electrode, consumable electrode and alloy ingot

Abstract

The invention relates to a preparation method of a nickel-chromium-iron alloy consumable electrode, the consumable electrode and an alloy ingot. The method comprises the steps that an electrolytic nickel plate is subjected to vacuum melting under the condition that the vacuum degree is smaller than or equal to 0.67 Pa, after the electrolytic nickel plate is melted down, the vacuum degree is kept to be smaller than 2 Pa and lasts for 5 min to 10 min, and a nickel melt with the lead removal rate larger than or equal to 60% is obtained; pouring the nickel melt into a pure nickel electrode under a vacuum condition; combining the pure nickel electrode with industrial pure iron to form an iron-nickel composite electrode; with the iron-nickel composite electrode as a consumable electrode, ferrochrome is added into a lined electroslag furnace for smelting, and a high-temperature metal melt is obtained; the high-temperature metal melt is tapped to a steel ladle, and argon is blown to the bottom of the high-temperature metal melt in the steel ladle for 3-5 min; and the high-temperature metal melt obtained after bottom argon blowing is poured into the consumable electrode. According to the method, five types of fusible elements including Pb, Bi, Sn, As and Sb are systematically and gradually reduced to be extremely trace by coupling three steps of vacuum volatilization, deep electroslag separation and secondary ladle refining.

Description

Technical Field

[0001] This application belongs to the field of nickel-chromium-iron electrothermal alloy smelting technology, and particularly relates to a method for preparing a nickel-chromium-iron alloy consumable electrode, the consumable electrode and the alloy ingot. Background Technology

[0002] Nickel-chromium-iron (NiCrFe) heating alloys are widely used as electric heating elements for applications ranging from 500℃ to 1400℃ due to their stable resistance and excellent high-temperature strength. Currently, the mainstream process employs a dual-smelting method of "induction furnace + electroslag remelting." However, easily fusible elements such as Pb, Bi, Sn, As, and Sb in the raw materials accumulate at grain boundaries during solidification, forming a low-melting-point compound network. This leads to brittleness during hot working, rolling cracking, and a decrease in yield. Existing technologies rely solely on raw material screening, which cannot stably control Pb below 0.0005wt%, and lack a systematic solution for deep removal of easily fusible elements during the smelting process. This severely restricts the quality improvement and stable mass production of high-end heating alloys. Summary of the Invention

[0003] This application provides a method for preparing a nickel-chromium-iron alloy consumable electrode, the consumable electrode and the alloy ingot, to solve the following technical problem: how to systematically remove Pb, Bi, Sn, As and Sb and prepare a consumable electrode with low fusible elements.

[0004] In a first aspect, embodiments of this application provide a method for preparing a nickel-chromium-iron alloy consumable electrode, the method comprising: Electrolytic nickel plates are vacuum melted under a vacuum degree ≤ 0.67 Pa. After the electrolytic nickel plates are melted clean, the vacuum degree is maintained at < 2 Pa for 5 min to 10 min to obtain a nickel melt with a lead removal rate ≥ 60%. The nickel melt was cast into a pure nickel electrode under vacuum conditions; The pure nickel electrode is combined with industrial pure iron to form an iron-nickel composite electrode; The iron-nickel composite electrode was used as a consumable electrode and ferrochrome was added in a lined electroslag furnace for smelting to obtain a high-temperature metal melt. The high-temperature molten metal is tapped into a ladle, and argon gas is blown into the ladle for 3 to 5 minutes. The high-temperature molten metal after bottom blowing argon is cast into a consumable electrode, wherein the consumable electrode has a Pb content ≤0.0004wt%, a Sn content ≤0.0002wt%, an As content ≤0.0005wt%, an Sb content <0.0001wt%, and a Bi content ≤0.0002wt%.

[0005] Optionally, the weight ratio of iron in the iron-nickel composite electrode meets the iron content requirements of the target nickel-chromium-iron alloy, and the insufficient nickel content is compensated in real time by adding electrolytic nickel plates into the electroslag furnace.

[0006] Optionally, the slag system used in the electroslag remelting is a CaF2-Al2O3-CaO ternary slag, wherein the mass fraction of CaF2 is 60%–70%, the mass fraction of Al2O3 is 15%–25%, and the mass fraction of CaO is 10%–20%.

[0007] Optionally, the argon flow rate of the bottom-blown argon gas is 0.3 Nm³. 3 / t·min~0.5Nm 3 / t·min, the temperature of the melt in the ladle during the bottom blowing argon process is controlled at 1500℃~1550℃.

[0008] Secondly, embodiments of this application provide a nickel-chromium-iron alloy consumable electrode with low fusibility and harmful elements, wherein the consumable electrode is directly obtained by the preparation method described in any one of the first aspects; The chemical composition of the consumable electrode, by weight percentage, is: Pb≤0.0004%, Sn≤0.0002%, As≤0.0005%, Sb<0.0001%, Bi≤0.0002%, Ni20%~80%, Cr15%~25%, Fe balance; and there is no continuous low-melting-point compound network at the grain boundaries of the consumable electrode.

[0009] Optionally, the consumable electrode is forged in a hot forging test after being held at 1150℃ for 30 minutes, with no visible cracks on the surface and a forging qualification rate of ≥98%.

[0010] Optionally, the consumable electrode has a diameter of Φ200mm~Φ400mm, a length of ≥2000mm, and a chemical composition Pb content difference of ≤0.00005wt% at any position on the same electrode.

[0011] Optionally, the microstructure of the consumable electrode is single-phase austenite with an austenite grain size ≥ 5 and the total amount of Pb, Bi, Sn, As and Sb at the grain boundaries ≤ 0.001 wt%.

[0012] Thirdly, embodiments of this application provide an electroslag remelted nickel-chromium-iron alloy ingot, which is obtained by secondary electroslag remelting using the consumable electrode described in any of the second aspects as raw material. The Pb content of the electroslag remelted nickel-chromium-iron alloy ingot is ≤0.0003wt%, and the electroslag remelted nickel-chromium-iron alloy ingot has no edge cracking during hot rolling at 1200℃, with a yield of ≥95%.

[0013] Optionally, the electroslag remelted nickel-chromium-iron alloy ingot has a room temperature elongation ≥35%, a creep strength ≥100MPa at 750℃ and 100h, and a creep ductile elongation ≥25%.

[0014] The technical solutions provided in this application have the following advantages compared with the prior art: Since the saturated vapor pressure of Pb is 3 to 4 orders of magnitude higher than that of Ni, in this embodiment, the electrolytic nickel plate is first melted separately under a deep vacuum of ≤0.67 Pa. After melting, it is maintained at <2 Pa for 5–10 min, so that Pb and Bi preferentially volatilize and are discharged in the vacuum pump group, forming a "pre-purified" nickel melt with a lead removal rate of ≥60%. Since the molten pool at this time contains only Ni and a small amount of Co and Cu, and there is no interference from oxygen-affinity elements such as Fe and Cr, the vacuum volatilization interface is clean. As a result, the metal-vapor partition coefficients of Sn, As, and Sb remain high and are simultaneously reduced in their initial concentrations. The aforementioned "low-fusible" nickel melt is cast into a pure nickel electrode under vacuum, thereby "locking" the removed Pb, Bi, Sn, As, and Sb in the solidified structure and avoiding secondary contamination. Since industrial pure iron (≈30% Fe) needs to be introduced later, and Fe will significantly reduce the activity coefficients of As and Sb, the embodiments of this application combine "purified nickel" with industrial pure iron to form an iron-nickel composite electrode, thereby physically isolating the volatile stage from the alloying stage and preventing the trace amounts of As and Sb brought in by Fe from being "masked" during the volatilization period. Since the composite electrode itself may still contain 0.5–1 ppm of low-melting-point elements, this embodiment uses the electrode as a consumable electrode for secondary smelting in a CaF2–Al2O3–CaO lined electroslag furnace, thereby utilizing the slag-metal interface reaction: Pb and Sn enter the slag phase to form PbO and SnO2; As and Sb are adsorbed by (CaO) to form Ca3(AsO4)2 and Ca3(SbO4)2; Bi is complexed with fluoride and enters the slag; thus achieving deep removal by "slag washing"; Since the molten metal droplets pass through the slag pool in a thin film state during the electroslag process, with a large specific surface area and short residence time, the embodiments of this application add argon bottom blowing to the ladle for 3-5 minutes after tapping, thereby using argon bubbles to float residual oxide inclusions and further vaporize trace amounts of Pb and Bi, thus completing the "endpoint cleaning". The final cast consumable electrode contains Pb≤0.0004wt%, Sn≤0.0002wt%, As≤0.0005wt%, Sb<0.0001wt%, and Bi≤0.0002wt%, with the total amount of the five low-melting-point elements <1ppm. This completely eliminates the source of low-melting-point eutectic network film formation during subsequent VAR or service, and solves the problems of thermal cracking and grain boundary embrittlement.

[0015] Existing technologies either rely solely on vacuum volatilization (which can only remove Pb and Bi) or solely on electroslag remelting (which has low partition coefficients for As and Sb), failing to simultaneously reduce the total amount of the five low-melting elements to <1 ppm. This application's embodiments link "deep vacuum volatilization – solidification locking – iron-nickel composite – electroslag washing – argon flotation" into a relay removal chain of "gas phase – slag phase – gas phase." Spatial segmentation avoids interference from element activity, and time segmentation achieves step-by-step purification. Thus, for the first time on an industrial scale, the total amount of the five low-melting elements is controlled to sub-ppm levels, breaking through the bottleneck of the inability to simultaneously achieve "ultra-high purity + low melting" in nickel-chromium-iron alloy consumable electrodes. Detailed Implementation

[0016] 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 in conjunction with the embodiments of this application. 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.

[0017] 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 (such as 1 to 3, 2 to 5, etc.) and single numbers (such as 1, 2, 3, 4, 5, 6) between 1 and 6. Unless otherwise specified, the terms "including" and "contains" as 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.

[0018] In a first aspect, embodiments of this application provide a method for preparing a nickel-chromium-iron alloy consumable electrode, the method comprising: S1. Vacuum melting of electrolytic nickel plate under vacuum degree ≤0.67Pa, and after the electrolytic nickel plate is melted, vacuum degree <2Pa is maintained for 5min to 10min to obtain nickel melt with lead removal rate ≥60%; S2. Cast the nickel melt into a pure nickel electrode under vacuum conditions; S3. Combine the pure nickel electrode with industrial pure iron to form an iron-nickel composite electrode; S4. Using the iron-nickel composite electrode as a consumable electrode, ferrochrome is added and smelted in a lined electroslag furnace to obtain an electroslag melt. S5. Tap the electroslag furnace melt into a ladle and blow argon gas into the high-temperature molten metal in the ladle for 3 to 5 minutes. S6. The high-temperature molten metal after bottom blowing argon is cast into a consumable electrode, wherein the consumable electrode has a Pb content ≤0.0004wt%, Sn content ≤0.0002wt%, As content ≤0.0005wt%, Sb content <0.0001wt%, and Bi content ≤0.0002wt%.

[0019] "Electrolytic nickel plate": refers to the cathode nickel plate, a solid nickel raw material used in the vacuum smelting process. "Iron-nickel composite electrode": refers to a binary consumable electrode formed by mechanically combining a "pure nickel electrode" and "industrial pure iron," used in lined electroslag furnace smelting. "Clear molten state": refers to the instantaneous state in which the "electrolytic nickel plate" is completely melted into a liquid state with no solid floating matter on the surface.

[0020] Since the saturated vapor pressures of Pb and Bi are much higher than those of Ni, this embodiment first performs vacuum melting on the "electrolytic nickel plate" under a vacuum degree ≤0.67 Pa to establish a high escape gradient at the metal-gas interface. Then, after the "electrolytic nickel plate" is completely melted, the vacuum degree is maintained at <2 Pa for 5 to 10 minutes, allowing Pb, Bi, Sn, As, and Sb to continuously volatilize into the gas phase and be discharged by the vacuum system, resulting in a lead removal rate ≥60%. The process involves: 1% nickel melt; 2) casting the nickel melt into a pure nickel electrode under vacuum conditions, thereby locking the reduced fusible element content into the solidified structure; 3) combining the "pure nickel electrode" with "industrial pure iron" to form an iron-nickel composite electrode, thus physically isolating the volatile purification stage from the iron alloying stage; 4) using the "iron-nickel composite electrode" as a consumable electrode in a lined electroslag furnace for smelting, thereby utilizing the slag-metal reaction and the thin-film interface of the molten droplets to allow residual Pb, Sn, As, Sb, and Bi to further enter the slag phase or volatilize; 5) tapping the high-temperature molten metal into a ladle and bottom-blowing argon gas into the ladle for 3-5 minutes, allowing the argon bubbles to rise, carrying inclusions and assisting in the vaporization of trace fusible elements; 6) casting the bottom-blown high-temperature molten metal into a consumable electrode, resulting in a consumable electrode with Pb content ≤0.0004 wt%, Sn content ≤0.0002 wt%, and As content ≤0.0005 wt%. With Sb content <0.0001 wt% and Bi content ≤0.0002 wt%, the system achieves the removal of Pb, Bi, Sn, As, and Sb, and prepares a consumable electrode with low fusible element content. Existing technologies using vacuum or electroslag alone cannot simultaneously compress the five fusible elements to sub-ppm levels. This application, through a four-step process of "deep vacuum volatilization - solidification locking - electroslag washing - argon flotation," achieves for the first time on an industrial scale a consumable electrode with a total content of the five elements <1 ppm.

[0021] Vacuum degree ≤ 0.67 Pa: including but not limited to 0.60 Pa, 0.50 Pa, 0.40 Pa, 0.30 Pa, 0.20 Pa, 0.10 Pa, etc. Vacuum degree < 2 Pa: including but not limited to 1.9 Pa, 1.5 Pa, 1.0 Pa, 0.8 Pa, 0.5 Pa, 0.3 Pa, etc. Duration 5 min to 10 min: including but not limited to 5 min, 6 min, 7 min, 8 min, 9 min, 10 min, etc. Bottom blowing argon gas 3 min to 5 min: including but not limited to 3.0 min, 3.5 min, 4.0 min, 4.5 min, 5.0 min, etc.

[0022] In some embodiments, the weight ratio of iron in the iron-nickel composite electrode meets the iron content requirements of the target nickel-chromium-iron alloy, and the insufficient nickel content is compensated in real time by adding electrolytic nickel plates into the electroslag furnace.

[0023] Since the target nickel-chromium-iron alloy has a fixed requirement for iron content, this application embodiment ensures that the iron weight ratio meets this requirement before assembling the iron-nickel composite electrode, thereby avoiding excessive or insufficient iron content later. Furthermore, any insufficient nickel is compensated in real-time by adding electrolytic nickel plates into the electroslag furnace, ensuring that the molten pool composition remains within the target range. This guarantees the final consumable electrode has a qualified chemical composition while maintaining low levels of easily fusible elements, achieving the systematic removal of Pb, Bi, Sn, As, and Sb to prepare a low-fusible-element consumable electrode. This application embodiment embeds "one-time iron addition and dynamic nickel compensation" into the electroslag process, solving the dual control problem of iron-nickel ratio and low-fusible-element content. Iron weight ratio: For Cr20Ni80, the iron content is 0%; for Cr20Ni30, the iron content is approximately 47%; intermediate grades have iron contents of 10%, 20%, 30%, and 40%, etc.

[0024] In some embodiments, the slag system used in the electroslag remelting is a CaF2-Al2O3-CaO ternary slag, wherein the mass fraction of CaF2 is 60% to 70%, the mass fraction of Al2O3 is 15% to 25%, and the mass fraction of CaO is 10% to 20%.

[0025] "CaF2-Al2O3-CaO ternary slag": In the embodiments of this application, it refers to a liquid metallurgical slag composed of calcium fluoride, alumina and calcium oxide, which is used in the smelting process of a lined electroslag furnace.

[0026] Because the F provided by CaF2 has a mass fraction of 60% to 70%, - Ions can form volatile fluorides with Bi and Sn; the Al2O3 network provided by 15%–25% mass fraction of Al2O3 can adsorb As and Sb oxides; and the O2O network provided by 10%–20% mass fraction of CaO can adsorb O2 and Sb oxides. 2- This method can improve the PbO partition coefficient. In this embodiment, a ternary slag system is used, allowing Pb, Bi, Sn, As, and Sb to migrate simultaneously into the slag phase. Consequently, the fusible element content is further reduced after the high-temperature molten metal passes through the slag pool, achieving the systematic removal of Pb, Bi, Sn, As, and Sb, and preparing a low-fusible-element consumable electrode. This embodiment integrates "fluorination volatilization-network adsorption-alkaline absorption" into a single slag by fixing the slag system range, breaking through the single-mechanism removal limit.

[0027] CaF2 mass fraction 60%–70%: including but not limited to 60%, 62%, 65%, 68%, 70%, etc. Al2O3 mass fraction 15%–25%: including but not limited to 15%, 18%, 20%, 22%, 25%, etc. CaO mass fraction 10%–20%: including but not limited to 10%, 12%, 15%, 18%, 20%, etc.

[0028] In some embodiments, the argon flow rate of the bottom-blown argon gas is 0.3 Nm³. 3 / t·min~0.5Nm 3 / t·min, the temperature of the melt in the ladle during the bottom blowing argon process is controlled at 1500℃~1550℃.

[0029] Due to the argon flow rate of 0.3 Nm 3 / t·min~0.5 Nm 3 A uniform rising bubble flow can be formed within the ladle at a flow rate of / t·min. In this embodiment, argon gas is bottom-blown in the temperature range of 1500 ℃ to 1550 ℃, thereby capturing residual oxides in the bubbles and carrying trace amounts of fusible element vapors to float and be discharged. This further improves the purity of the high-temperature molten metal, enabling the system to remove Pb, Bi, Sn, As, and Sb, and to prepare a low-fusible-element consumable electrode. This embodiment couples "micro-flow argon gas" with "high-temperature range," which both prevents nickel oxidation and enhances flotation, avoiding the temperature drop and splashing caused by traditional high-flow rates.

[0030] Argon flow rate: including but not limited to 0.30 Nm3 / t·min, 0.35 Nm3 / t·min, 0.40 Nm3 / t·min, 0.45 Nm3 / t·min, 0.50 Nm3 / t·min, etc. Melt temperature: including but not limited to 1500 ℃, 1510 ℃, 1520 ℃, 1530 ℃, 1540 ℃, 1550 ℃, etc.

[0031] Secondly, embodiments of this application provide a nickel-chromium-iron alloy consumable electrode with low fusibility and harmful elements, wherein the consumable electrode is directly obtained by the preparation method described in any one of the first aspects; Since the consumable electrode has Pb≤0.0004%, Sn≤0.0002%, As≤0.0005%, Sb<0.0001%, and Bi≤0.0002%, and there is no continuous low-melting-point compound network at the grain boundaries, the embodiments of this application avoid grain boundary embrittlement during subsequent electroslag remelting or hot processing, thereby achieving the technical goal of systematically removing Pb, Bi, Sn, As, and Sb and preparing a consumable electrode with low fusible elements. This application embodiment is the first to simultaneously include "upper limit of composition + microstructure" in the product claims, upgrading the control of low fusible elements from a "result" to a "structural feature."

[0032] Ni 20%~80%: including but not limited to 20%, 30%, 40%, 50%, 60%, 70%, 80%, etc. Cr 15%~25%: including but not limited to 15%, 18%, 20%, 22%, 25%, etc.

[0033] In some embodiments, the consumable electrode is forged in a hot forging test after being held at 1150°C for 30 minutes, with no visible cracks on the surface and a forging pass rate of ≥98%.

[0034] "Hot forging test": refers to a laboratory procedure in which a consumable electrode is heated and held at a certain temperature to test its thermoplasticity.

[0035] Because the total amount of fusible elements in the consumable electrode is extremely low and there is no continuous network film at the grain boundaries, the grain boundary slip resistance is low when the embodiment of this application is forged after holding at 1150 ℃ for 30 min, so there are no visible cracks on the surface and the forging qualification rate is ≥98%, thereby verifying the effect of the system in removing Pb, Bi, Sn, As and Sb and preparing a consumable electrode with low fusible elements.

[0036] In some embodiments, the consumable electrode has a diameter of Φ200mm to Φ400mm, a length of ≥2000mm, and a chemical composition Pb content difference of ≤0.00005wt% at any position on the same electrode.

[0037] The specifications of Φ200 mm~Φ400 mm in diameter and ≥2000 mm in length ensure a moderate solidification rate of the molten metal pool, thereby suppressing the segregation of fusible elements; furthermore, the Pb content difference at any position on the same electrode is ≤0.00005 wt%, achieving the systematic removal of Pb, Bi, Sn, As and Sb and preparing a low-fusible-element consumable electrode.

[0038] Diameter: including but not limited to 200 mm, 250 mm, 300 mm, 350 mm, 400 mm, etc. Length: including but not limited to 2000 mm, 2100 mm, 2200 mm, 2300 mm, 2400 mm, 2500 mm, etc.

[0039] In some embodiments, the microstructure of the consumable electrode is single-phase austenite with an austenite grain size ≥5 and the total amount of Pb, Bi, Sn, As and Sb at the grain boundaries ≤0.001wt.

[0040] "Austenitic grain size ≥ 5" refers to the grain size grade as assessed by GB / T 6394.

[0041] Since the microstructure of the consumable electrode is single-phase austenite with a grain size ≥5, the total area of ​​the grain boundaries increases. In this embodiment, the residual fusible elements are further dispersed; thus, the total amount of Pb, Bi, Sn, As and Sb at the grain boundaries is ≤0.001 wt%, realizing the systematic removal of Pb, Bi, Sn, As and Sb and the preparation of a consumable electrode with low fusible elements.

[0042] Thirdly, embodiments of this application provide an electroslag remelted nickel-chromium-iron alloy ingot, which is obtained by secondary electroslag remelting using the consumable electrode described in any of the second aspects as raw material. The Pb content of the electroslag remelted nickel-chromium-iron alloy ingot is ≤0.0003wt%, and the electroslag remelted nickel-chromium-iron alloy ingot has no edge cracking during hot rolling at 1200℃, with a yield of ≥95%.

[0043] "Electroslag remelted nickel-chromium-iron alloy ingot": refers to the ingot obtained by secondary electroslag remelting using the first consumable electrode as raw material.

[0044] Since the consumable electrode has reduced the total amount of fusible elements to sub-ppm levels, this embodiment uses the consumable electrode as raw material for secondary electroslag remelting, resulting in Pb ≤ 0.0003 wt% in the ingot. Consequently, the ingot exhibits no edge cracking during hot rolling at 1200 ℃, achieving a yield ≥ 95%. This ultimately enables downstream verification of the system's removal of Pb, Bi, Sn, As, and Sb to prepare a low-fusible-element consumable electrode. This embodiment uses a combination of "low-fusible electrode + secondary electroslag remelting" to simultaneously improve both yield and creep strength, overcoming the bottleneck of hot cracking in traditional nickel-chromium-iron alloys.

[0045] In some embodiments, the electroslag remelted nickel-chromium-iron alloy ingot has a room temperature elongation ≥35%, a creep strength ≥100MPa at 750℃ and 100h, and a creep ductile elongation ≥25%.

[0046] Because the electroslag remelted nickel-chromium-iron alloy ingot has extremely low fusible elements and a uniform microstructure, the embodiments of this application showed no slip cracks at the grain boundaries during a 750℃, 100h creep test, resulting in a creep strength ≥100 MPa and a creep ductile elongation ≥25%, and a room temperature elongation ≥35%. Ultimately, this achieved the final performance verification of the system removing Pb, Bi, Sn, As and Sb and preparing a low fusible element consumable electrode.

[0047] Creep strength ≥100 MPa: including but not limited to 100 MPa, 105 MPa, 110 MPa, 115 MPa, 120 MPa, etc. Creep elongation ≥25%: including but not limited to 25%, 26%, 27%, 28%, 29%, 30%, etc. Room temperature elongation ≥35%: including but not limited to 35%, 36%, 37%, 38%, 39%, 40%, etc.

[0048] 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 industry standards. If there is no corresponding industry standard, then generally accepted international standards, conventional conditions, or conditions recommended by the manufacturer are followed.

[0049] Example 1 A method for preparing a nickel-chromium-iron alloy consumable electrode, the method comprising: Electrolytic nickel plates were vacuum melted at a vacuum degree of 0.67 Pa. After the electrolytic nickel plates were melted clean, the vacuum degree was maintained at 1.9 Pa for 5 minutes to obtain a nickel melt with a lead removal rate of 60%. The nickel melt was cast into a pure nickel electrode under vacuum conditions; The pure nickel electrode is combined with industrial pure iron to form an iron-nickel composite electrode, wherein the weight ratio of iron in the iron-nickel composite electrode is 20%. The iron-nickel composite electrode is used as a consumable electrode and ferrochrome is added for smelting in a lined electroslag furnace. The slag system used for electroslag remelting is CaF. 2- The Al2O3-CaO ternary slag system contains 60% CaF2, 25% Al2O3, and 15% CaO, yielding a high-temperature metal melt. The high-temperature molten metal is tapped into a ladle, and argon gas is bottom-blown into the ladle for 3 minutes at a flow rate of 0.3 Nm³. 3 / t·min, the temperature of the melt in the ladle is controlled at 1500℃; The high-temperature molten metal after bottom blowing argon gas is cast into a consumable electrode.

[0050] Example 2 A method for preparing a nickel-chromium-iron alloy consumable electrode, the method comprising: Electrolytic nickel plates were vacuum melted at a vacuum degree of 0.50 Pa. After the electrolytic nickel plates were melted clean, the vacuum degree was maintained at 1.5 Pa for 7 minutes to obtain a nickel melt with a lead removal rate of 70%. The nickel melt was cast into a pure nickel electrode under vacuum conditions; The pure nickel electrode is combined with industrial pure iron to form an iron-nickel composite electrode, wherein the weight ratio of iron in the iron-nickel composite electrode is 30%. The iron-nickel composite electrode is used as a consumable electrode and ferrochrome is added for smelting in a lined electroslag furnace. The slag system used for electroslag remelting is a CaF2-Al2O3-CaO ternary slag, in which the mass fraction of CaF2 is 65%, the mass fraction of Al2O3 is 20%, and the mass fraction of CaO is 15%, to obtain a high-temperature metal melt. The high-temperature molten metal is tapped into a ladle, and argon gas is bottom-blown into the ladle for 4 minutes at a flow rate of 0.4 Nm³. 3 / t·min, the temperature of the melt in the ladle is controlled at 1525℃; The high-temperature molten metal after bottom blowing argon gas is cast into a consumable electrode.

[0051] Example 3 A method for preparing a nickel-chromium-iron alloy consumable electrode, the method comprising: Electrolytic nickel plates were vacuum melted at a vacuum degree of 0.30 Pa. After the electrolytic nickel plates were melted clean, the vacuum degree was maintained at 1.0 Pa for 10 min to obtain a nickel melt with a lead removal rate of 80%. The nickel melt was cast into a pure nickel electrode under vacuum conditions; The pure nickel electrode is combined with industrial pure iron to form an iron-nickel composite electrode, wherein the weight ratio of iron in the iron-nickel composite electrode is 50%. The iron-nickel composite electrode is used as a consumable electrode and ferrochrome is added for smelting in a lined electroslag furnace. The slag system used for electroslag remelting is a CaF2-Al2O3-CaO ternary slag, in which the mass fraction of CaF2 is 70%, the mass fraction of Al2O3 is 15%, and the mass fraction of CaO is 15%, to obtain a high-temperature metal melt. The high-temperature molten metal is tapped into a ladle, and argon gas is bottom-blown into the ladle for 5 minutes at a flow rate of 0.5 Nm³. 3 / t·min, the temperature of the melt in the ladle is controlled at 1550℃; The high-temperature molten metal after bottom blowing argon gas is cast into a consumable electrode.

[0052] Comparative Example 1 A method for preparing a nickel-chromium-iron alloy consumable electrode, the method comprising: Electrolytic nickel plates are induction melted under normal pressure. After the electrolytic nickel plates are completely melted, the pressure is maintained at normal pressure for 5 minutes to obtain nickel melt. The nickel melt was cast into a pure nickel electrode under normal pressure. The pure nickel electrode is combined with industrial pure iron to form an iron-nickel composite electrode, wherein the weight ratio of iron in the iron-nickel composite electrode is 20%. The iron-nickel composite electrode is used as a consumable electrode and ferrochrome is added for smelting in a lined electroslag furnace. The slag system used for electroslag remelting is a CaF2-Al2O3-CaO ternary slag, in which the mass fraction of CaF2 is 60%, the mass fraction of Al2O3 is 25%, and the mass fraction of CaO is 15%, to obtain a high-temperature metal melt. The high-temperature molten metal is tapped into a ladle, and argon gas is bottom-blown into the ladle for 3 minutes at a flow rate of 0.3 Nm³. 3 / t·min, the temperature of the melt in the ladle is controlled at 1500℃; The high-temperature molten metal after bottom blowing argon gas is cast into a consumable electrode.

[0053] Comparative Example 2 A method for preparing a nickel-chromium-iron alloy consumable electrode, the method comprising: Electrolytic nickel plates were vacuum melted at a vacuum degree of 0.67 Pa. After the electrolytic nickel plates were melted clean, the vacuum degree was maintained at 1.9 Pa for 5 minutes to obtain a nickel melt with a lead removal rate of 60%. The nickel melt was cast into a pure nickel electrode under vacuum conditions; The pure nickel electrode is combined with industrial pure iron to form an iron-nickel composite electrode, wherein the weight ratio of iron in the iron-nickel composite electrode is 20%. The iron-nickel composite electrode is used as a consumable electrode and ferrochrome is added for smelting in a lined electroslag furnace. The slag system used for electroslag remelting is a CaF2-Al2O3-CaO ternary slag, in which the mass fraction of CaF2 is 50%, the mass fraction of Al2O3 is 30%, and the mass fraction of CaO is 20%, to obtain a high-temperature metal melt. The high-temperature molten metal is tapped into a ladle, and argon gas is bottom-blown into the ladle for 3 minutes at a flow rate of 0.3 Nm³. 3 / t·min, the temperature of the melt in the ladle is controlled at 1500℃; The high-temperature molten metal after bottom blowing argon gas is cast into a consumable electrode.

[0054] Experimental methods for evaluating results: Determination of fusible element content: Sampling was performed according to the GB / T223 series, and the average value of five points at 1 / 2 radius of the consumable electrode cross section was determined by inductively coupled plasma mass spectrometry.

[0055] 1150℃ Hot Forging Crack Rate: A Φ80mm×120mm sample was cut from the consumable electrode and forged into a Φ40mm sample along the height direction after being held at 1150℃ for 30min. The proportion of visible crack length to perimeter was statistically analyzed.

[0056] 1200℃ hot rolling yield: Φ200mm ingots are obtained by secondary electroslag remelting using consumable electrodes as raw materials, heated to 1200℃ and hot rolled to Φ20mm wire rods, and the ratio of qualified wire rod weight to ingot weight is measured.

[0057] Table 1. Results data for both the examples and comparative examples.

[0058] As shown in Table 1, the technological advancements of this application's technical solution include: 1. The Pb content was reduced from 0.00080 wt% in Comparative Example 1 to 0.00015 wt% in Example 3, a reduction of ≥81%, thereby eliminating the continuous low-melting-point lead phase at the grain boundaries and reducing the hot forging crack rate at 1150℃ from 15% to 0%.

[0059] 2. The Sn content was reduced from 0.00030 wt% in Comparative Example 1 to <0.00010 wt% in Example 3, a reduction of ≥67%, thereby inhibiting the precipitation of low-melting-point Sn-Ni compounds at grain boundaries and improving hot working plasticity.

[0060] 3. The As content was reduced from 0.00070 wt% in Comparative Example 1 to 0.00020 wt% in Example 3, a reduction of ≥71%, thereby avoiding high-temperature embrittlement caused by As grain boundary segregation and ensuring a creep strength of ≥100 MPa at 750°C.

[0061] 4. The Sb content was reduced from 0.00020 wt% in Comparative Example 1 to <0.00010 wt% in Example 3, a reduction of ≥50%, thereby eliminating liquid film cracking caused by Sb enrichment at grain boundaries and increasing the yield of hot-rolled material at 1200℃ from 85% to 99%.

[0062] 5. The Bi content was reduced from 0.00030 wt% in Comparative Example 1 to <0.00010 wt% in Example 3, a reduction of ≥67%, thereby completely removing the low-melting-point network film formed by Bi at the grain boundaries, and increasing the hot forging qualification rate from 85% to 100%.

[0063] 6. The total amount of fusible elements was reduced from 0.00230 wt% in Comparative Example 1 to ≤0.00065 wt% in Example 3, a reduction of ≥72%. As a result, the yield was increased from 85% to 99% under the same heat treatment regime, reaching the industrial preparation level of high-purity nickel-chromium-iron alloy consumable electrodes.

[0064] 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 method for preparing a nickel-chromium-iron alloy consumable electrode, characterized in that, The method includes: Electrolytic nickel plates are vacuum melted under a vacuum degree ≤ 0.67 Pa. After the electrolytic nickel plates are melted clean, the vacuum degree is maintained at < 2 Pa for 5 min to 10 min to obtain a nickel melt with a lead removal rate ≥ 60%. The nickel melt was cast into a pure nickel electrode under vacuum conditions; The pure nickel electrode is combined with industrial pure iron to form an iron-nickel composite electrode; The iron-nickel composite electrode was used as a consumable electrode and ferrochrome was added in a lined electroslag furnace for smelting to obtain a high-temperature metal melt. The high-temperature molten metal is tapped into a ladle, and argon gas is blown into the ladle for 3 to 5 minutes. The high-temperature molten metal after bottom blowing argon is cast into a consumable electrode, wherein the consumable electrode has a Pb content ≤0.0004wt%, a Sn content ≤0.0002wt%, an As content ≤0.0005wt%, an Sb content <0.0001wt%, and a Bi content ≤0.0002wt%.

2. The preparation method according to claim 1, characterized in that, The iron-nickel composite electrode contains iron in proportions that meet the iron content requirements of the target nickel-chromium-iron alloy. Any nickel deficiency is compensated in real time by adding electrolytic nickel plates into the electroslag furnace.

3. The preparation method according to claim 1, characterized in that, The slag system used in the electroslag remelting is a CaF2-Al2O3-CaO ternary slag, wherein the mass fraction of CaF2 is 60% to 70%, the mass fraction of Al2O3 is 15% to 25%, and the mass fraction of CaO is 10% to 20%.

4. The preparation method according to claim 1, characterized in that, The argon flow rate of the bottom-blown argon gas is 0.3 Nm. 3 / t·min~0.5Nm 3 / t·min, the temperature of the melt in the ladle during the bottom blowing argon process is controlled at 1500℃~1550℃.

5. A consumable electrode made of nickel-chromium-iron alloy with low fusibility and harmful elements, characterized in that, The consumable electrode is directly obtained by the preparation method according to any one of claims 1 to 4; The chemical composition of the consumable electrode, by weight percentage, is: Pb≤0.0004%, Sn≤0.0002%, As≤0.0005%, Sb<0.0001%, Bi≤0.0002%, Ni20%~80%, Cr15%~25%, Fe balance; and there is no continuous low-melting-point compound network at the grain boundaries of the consumable electrode.

6. The consumable electrode according to claim 5, characterized in that, The consumable electrode was forged in a hot forging test after being held at 1150℃ for 30 minutes. There were no visible cracks on the surface, and the forging qualification rate was ≥98%.

7. The consumable electrode according to claim 5, characterized in that, The consumable electrode has a diameter of Φ200mm~Φ400mm, a length of ≥2000mm, and a chemical composition Pb content difference of ≤0.00005wt% at any position on the same electrode.

8. The consumable electrode according to claim 5, characterized in that, The microstructure of the consumable electrode is single-phase austenite with an austenite grain size ≥ 5 and the total amount of Pb, Bi, Sn, As and Sb at the grain boundaries ≤ 0.001 wt%.

9. An electroslag remelted nickel-chromium-ferroalloy ingot, characterized in that, The electroslag remelted nickel-chromium-iron alloy ingot is obtained by secondary electroslag remelting using the consumable electrode described in any one of claims 5 to 8 as raw material. The Pb content of the electroslag remelted nickel-chromium-iron alloy ingot is ≤0.0003wt%, and the electroslag remelted nickel-chromium-iron alloy ingot has no edge cracking during hot rolling at 1200℃, with a yield of ≥95%.

10. The electroslag remelted nickel-chromium-ferroalloy ingot according to claim 9, characterized in that, The electroslag remelted nickel-chromium-iron alloy ingot has a room temperature elongation of ≥35%, a creep strength of ≥100MPa at 750℃ and 100h, and a creep ductile elongation of ≥25%.

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