Method for continuous casting of nichrome alloy wire blanks

Abstract

The application provides a continuous casting method for a nickel-chromium-aluminum current resistance alloy wire blank, adopts an online "melt argon-blowing atomization + slag pool filtration" technology and a boron nitride-graphite composite crystallizer, realizes continuous casting of a nickel-chromium-aluminum alloy atmosphere and secondary refining, and not only guarantees product quality, but also greatly improves raw material utilization and production efficiency.

Description

Technical Field

[0001] This invention relates to the field of alloy material processing technology, specifically to a method for continuous casting of nickel-chromium-aluminum current-sensing resistance alloy wire rods. Background Technology

[0002] Nickel-chromium-aluminum current sensing elements possess advantages such as high precision, high resistivity, good electrical stability, and a wide operating temperature range. They are widely used in new energy vehicles, consumer electronics, 5G communications, aerospace, communication satellites, and global positioning systems, serving as indispensable key components in control circuits. However, compared to copper-manganese based current sensing materials, nickel-based current sensing materials suffer from disadvantages such as poor processing performance and high raw material costs.

[0003] The current processing flow for nickel-chromium-aluminum alloy wires and profiles is as follows: atmospheric or vacuum casting → electroslag remelting → forging into square billets → hot rolling into round wires → cold drawing into thin wires → rolling into strips → finishing drawing → final heat treatment. Its fatal drawbacks are low material utilization, low production efficiency and continuity; after the initial alloy melting, it can only be cast into... The large ingots require a pointed tip to be machined at the front end, and after electroslag remelting, a tail ingot remains, greatly reducing the material utilization rate. Before forging, the remelted ingots need to be sawn off, peeled, and the head and tail removed, further affecting the material utilization rate.

[0004] Nickel is a scarce strategic resource in my country, with a huge domestic supply-demand gap. my country's dependence on imported nickel raw materials has been rising year by year, currently exceeding 80%. Domestic nickel raw material prices have soared in recent years, approaching 200 yuan per kilogram. However, the current nickel raw material utilization rate in my country's nickel-chromium-aluminum alloy wire processing is less than 50%, which is highly inconsistent with my country's scarce nickel resources. Therefore, developing a short-process near-net-shape forming technology for nickel alloys is of practical urgency.

[0005] Continuous casting of nickel alloys presents numerous technical challenges. One challenge is the refining and purification of the nickel melt, specifically how to control oxide inclusions and impurities such as sulfur (S) and phosphorus (P) within technically required ranges while ensuring production efficiency. Another challenge is the high-temperature sticking and wear issues of the continuous casting mold. Developing a mold with a long service life and high surface finish for the cast billet has been a persistent problem for nickel alloy producers both domestically and internationally. Some institutions at home and abroad have attempted to develop vacuum continuous casting technology for nickel alloys. While the oxygen and nitrogen content in the melt has been effectively controlled, the purification of impurities such as S and P remains a challenge. Furthermore, vacuum continuous casting suffers from high equipment maintenance costs, high energy consumption, and low production efficiency. Summary of the Invention

[0006] This invention addresses the technical problems existing in the continuous casting production of nickel-chromium-aluminum alloys by introducing secondary refining technology into the continuous casting process and optimizing the crystallizer structure, thus successfully realizing the atmospheric continuous casting of nickel-chromium-aluminum alloy wire.

[0007] To solve the above technical problems, the present invention provides a method for continuous casting of nickel-chromium-aluminum current-sensing resistance alloy wire rods, comprising:

[0008] The first step, initial smelting;

[0009] The second step is a second online refinement;

[0010] The third step is continuous casting.

[0011] The first step is further specified as follows: initial smelting is carried out in a magnesia-lined induction furnace, with the melt temperature maintained within the range of 1460–1500℃. 70–80% anhydrous sodium tetraborate (Na₂B₄O₇) + 20–30% glass is used as a surface covering agent. First, 0.1–0.3% of a 30% magnesium-nickel master alloy is added to deoxidize the melt, with a refining time of 10–15 minutes. After deoxidation, 0.05–0.1% of rare earth Ce is added for dehydrogenation, and the melt is allowed to stand for 15–20 minutes after dehydrogenation.

[0012] The second step further involves the melt obtained from the initial smelting flowing into a secondary purification holding furnace via a pipette. Argon is blown at the pipette outlet to atomize the melt, with the argon pressure maintained at 1.50–2.50 atm. The atomized melt droplets, after secondary purification by the slag pool layer on the surface of the melt in the holding furnace, penetrate into the melt. The slag pool composition is 50–60% CaF₂ + 20–30% CaO + 10–20% MgO + 10–20% Ce₂O₃. The melt temperature in the holding furnace is maintained at 1450–1480℃. Simultaneously, the gap between the upper inlet of the holding furnace and the periphery of the pipette is 5.0–8.0 mm, and the argon flow rate is adjusted to maintain the argon pressure in the holding furnace within the range of 1.2–1.3 atm.

[0013] The third step is further specified as follows: the melt, after secondary refining, is continuously cast in a boron nitride-graphite composite crystallizer. The left and right sides are made of nickel-chromium-aluminum wire, and the hot end of the crystallizer is made of boron nitride ceramic material with an inner diameter of [missing information]. outer diameter is The length is 25.0 to 35.0 mm, the cold end material is conventional high-purity graphite, the outer jacket is water-cooled, and the casting speed is 1.5 to 2.3 m.

[0014] Beneficial effects of the present invention

[0015] Traditional nickel-chromium-aluminum alloy wire rod production requires casting into master ingots for electroslag remelting and secondary refining, which prevents continuous casting, resulting in low material utilization, low processing efficiency, and a significant increase in production costs. This invention employs "melt argon blowing atomization + slag pool filtration" technology and a boron nitride-graphite composite crystallizer in the nickel-chromium-aluminum alloy wire rod preparation process, enabling atmospheric continuous casting and secondary refining of nickel-chromium-aluminum alloys. This not only ensures product quality but also significantly improves raw material utilization and production efficiency.

[0016] Compared with traditional nickel-chromium-aluminum alloy wire rod preparation technology, this invention not only increases the utilization rate of nickel alloy from less than 50% to about 90%, but also eliminates the need for electroslag remelting and forging, resulting in a shorter process flow, significantly improved production efficiency and continuity, and a reduction in the wire rod processing cycle from the original 4 days to about 1 day. Attached Figure Description

[0017] Figure 1 Schematic diagram of a nickel-chromium-aluminum alloy wire casting equipment. Detailed Implementation

[0018] The following embodiments and accompanying drawings are used to describe in detail the implementation of the present invention, so that the process of how the present invention uses technical means to solve technical problems and achieve technical effects can be fully understood and implemented accordingly.

[0019] like Figure 1 As shown, the nickel-chromium-aluminum alloy wire continuous casting equipment used in this invention consists of a melting furnace 1 (medium frequency furnace), a pipette 2 (with valve), a secondary refining and holding furnace 3 (medium frequency furnace or industrial frequency furnace), a crystallizer 4, and a continuous casting mechanism.

[0020] The alloying and primary refining of nickel-chromium-aluminum alloys are carried out in a melting furnace, mainly to purify oxide inclusions and hydrogen and sulfur impurities in the melt. The main thermodynamic processes are: Mg + XO = X + MgO (where X is Ni, Cr, or Al), 2Ce(s) + 6H2O(g) → 2Ce(OH)3(aq) + 3H2(g), Ce + [S] Ni =CeS;

[0021] Secondary refining is carried out in a holding furnace, mainly to further purify sulfur and oxide particles in the melt. The nickel-chromium-aluminum melt is atomized into small droplets by argon gas at the outlet of a pipette, with the argon pressure maintained at 1.50–2.50 atm. The atomized melt droplets flow through the slag pool layer on the melt surface, fully contacting and purifying the slag. The slag pool composition is 50–60% CaF₂ + 20–30% CaO + 10–20% MgO + 10–20% Ce₂O₃, and its thermodynamic process is: 2Ce₂O₃ + [O] Ni→4CeO2, 3CaO + 2[Al] Ni +3[S] Ni = 3CaS + Al2O3.

[0022] The continuous casting of nickel-chromium-aluminum alloy wire is carried out in a boron nitride-graphite composite crystallizer. The hot end of the crystallizer is made of boron nitride ceramic material, and the inner diameter is [missing information]. outer diameter is The length is 25.0–35.0 mm, the cold end material is conventional high-purity graphite, it is fitted with a water-cooling jacket, and the casting speed is 1.5–2.3 m / s. This crystallizer structure... The large temperature gradient formed at the liquid-solid interface of the nickel-chromium-aluminum wire rod effectively ensures the smooth progress of continuous casting and the surface finish of the wire rod.

[0023] Example 1

[0024] This invention discloses a continuous casting method for nickel-chromium-aluminum current-sensing resistance alloy wire rods. The initial melting is carried out in a magnesia-lined medium-frequency furnace, with the melt temperature maintained at approximately 1480°C. A surface covering agent of 70% anhydrous sodium tetraborate (Na₂B₄O₇) + 30% glass is used. First, the melt is deoxidized using 0.1% magnesium-nickel master alloy for 15 minutes. After deoxidation, 0.1% rare earth element Ce is added for hydrogen removal, followed by a 15-minute settling period.

[0025] The primary purified melt flows into the secondary purified holding furnace via a pipette. Argon is blown at the pipette outlet for atomization, with the argon pressure maintained at 1.50 atm. The atomized melt droplets are then purified a second time by a slag pool layer on the surface of the melt in the holding furnace. The slag pool composition is 50% CaF2 + 20% CaO + 10% MgO + 20% Ce2O3. The melt temperature in the holding furnace is maintained at 1480℃. Simultaneously, the gap between the upper inlet of the holding furnace and the periphery of the pipette is 5.0 mm to maintain the argon pressure in the holding furnace at 1.3 atm. The melt is then continuously cast in a boron nitride-graphite composite crystallizer. The left and right sides are made of nickel-chromium-aluminum wire, and the hot end of the crystallizer is made of boron nitride ceramic material with an inner diameter of [missing information]. outer diameter is The length is 25.0mm, the cold end material is conventional high-purity graphite, the outer jacket is water-cooled, and the casting speed is 1.5m.

[0026] Under this process, the material utilization rate is 87.5%, the billet production cycle is about 15 hours, the O content in the material is 27 PPM (mass percentage), the N content is 18 PPM (mass percentage), the S content is 0.001%, and the P content is 0.0023%.

[0027] Example 2

[0028] The present invention provides a method for continuous casting of nickel-chromium-aluminum current-sensing resistance alloy wire rods. The primary smelting is carried out in a magnesia-lined medium-frequency furnace, with the melt temperature maintained at approximately 1480°C. Anhydrous sodium tetraborate (Na₂B₄O₇) + 20% glass is used as a surface covering agent. First, the melt is deoxidized using 30% magnesium-nickel master alloy (0.3% addition ratio) for 15 minutes. After deoxidation, 0.1% rare earth Ce is added for hydrogen removal, followed by a 20-minute settling period. The primary purified melt flows into a secondary purified holding furnace via a pipette. Argon is blown at the pipette outlet for atomization, with the argon pressure maintained at 2.50 atm. The atomized melt droplets are then purified a second time by a slag pool layer on the surface of the melt in the holding furnace. The slag pool composition is 60% CaF₂ + 10% CaO + 10% MgO + 20% Ce₂O₃. The melt temperature in the holding furnace is maintained at 1450°C. Meanwhile, the gap between the upper inlet of the holding furnace and the periphery of the pipette is 8.0 mm to maintain the argon pressure in the holding furnace at 1.2 atm; then, the melt is continuously cast into a boron nitride-graphite composite crystallizer. The left and right sides are made of nickel-chromium-aluminum wire, and the hot end of the crystallizer is made of boron nitride ceramic material with an inner diameter of [missing information]. outer diameter is The length is 35.0mm, the cold end material is conventional high-purity graphite, the outer jacket is water-cooled, and the casting speed is 2.3m.

[0029] Under this process, the material utilization rate is 89.0%, the billet production cycle is about 15 hours, the O content in the material is 25 PPM (mass percentage), the N content is 16 PPM (mass percentage), the S content is 0.002%, and the P content is 0.0025%.

[0030] Example 3

[0031] The present invention provides a method for continuous casting of nickel-chromium-aluminum current-detecting resistance alloy wire rods. The primary melting is carried out in a magnesia-lined medium-frequency furnace, with the melt temperature maintained at approximately 1480°C. Anhydrous sodium tetraborate (Na₂B₄O₇) + 20% glass is used as a surface covering agent. First, 30% magnesium-nickel master alloy is added to deoxidize the melt (0.3% addition ratio), and the refining time is 15 minutes. After deoxidation, 0.1% rare earth Ce is added for hydrogen removal, and the mixture is allowed to stand for 20 minutes after hydrogen removal. Then, the casting is completed. The large ingots undergo electroslag remelting at the leading edge, resulting in a slag pool composition of 60% CaF2 + 10% CaO + 10% MgO + 20% Ce2O3. After electroslag remelting, the ingots are sawn in half, peeled, and have their ends removed. They are then forged into 50mm square bars, which are further hot-rolled into... The wire rod is rolled at a temperature of 980℃.

[0032] Under this process, the material utilization rate is 48.2%, the billet production cycle is about 96 hours, the O content in the material is 26 PPM (mass percentage), the N content is 16 PPM (mass percentage), the S content is 0.002%, and the P content is 0.0025%.

[0033] All of the foregoing primary implementations of this intellectual property right do not limit other forms of implementation of this new product and / or new method. Those skilled in the art will utilize this important information to modify the foregoing to achieve similar implementations. However, all modifications or alterations based on this new product invention are reserved rights.

[0034] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention in any other way. Any person skilled in the art may make changes or modifications to the above-disclosed technical content to create equivalent embodiments. However, any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the protection scope of the present invention.

Claims

1. A method of continuous casting of a nickel-chromium-aluminium resistance wire alloy strand, characterized in that, The application relates to a method for preparing a rare earth permanent magnet material, which comprises the following steps: The first step is primary smelting; The second step is secondary on-line refining; Specifically, the melt obtained through primary smelting is flowed into a secondary refining holding furnace through a pipette, argon is blown at the outlet of the pipette to realize atomization, the atomized melt small droplets flow through the slag pool layer on the surface of the melt, sufficiently contact with the smelting slag and are purified; the slag pool composition is 50-60% CaF2+20-30% CaO+10-20% MgO+10-20% Ce2O3; The third step is continuous casting.

2. The method of continuously casting a nickel-chromium-aluminum resistance alloy wire blank of claim 1 wherein: The first step is further specifically primary smelting in a magnesia lining medium frequency furnace, 30% magnesium-nickel intermediate alloy is used to deoxidize the melt, and then hydrogen is removed after the deoxidization is completed.

3. The method of continuous casting of nickel-chromium-aluminum resistance alloy wire blanks according to claim 1 or 2, characterized in that: The melt temperature in the first step is kept at 1460-1500 DEG C.

4. The method of claim 1 or 2, wherein the nickel-chromium-aluminum resistance alloy wire blank is continuously cast by: 70-80% anhydrous sodium tetraborate (Na2B4O7) +20-30% glass is added as a surface covering agent in the first step.

5. The process of claim 2 wherein the nickel-chromium-aluminum resistance wire alloy is cast in a continuous process. The proportion of the intermediate alloy 30% magnesium-nickel added for deoxidization in the first step is 0.1-0.3%, and the refining time is 10-15 min.

6. The process of claim 2 wherein the nickel-chromium-aluminum resistance wire alloy is cast in a continuous process. 0.05-0.1% rare earth Ce is added for hydrogen removal in the first step, and the hydrogen removal is completed after 15-20 min.

7. The process of claim 1 or 2, wherein the nickel-chromium-aluminum resistance alloy wire blank is continuously cast by a method comprising: The temperature of the secondary refining holding furnace in the second step is kept at 1450-1480 DEG C.

8. The process of claim 1 or 2, wherein the nickel-chromium-aluminum resistance wire alloy is cast in a continuous casting process. The pressure of the argon during atomization in the second step is kept at 1.50-2.50 atm.

9. The process of claim 1 or 2, wherein the nickel-chromium-aluminum resistance wire alloy is cast in a continuous process. The third step is further specified as the secondary refining melt is continuously cast by a boron nitride-graphite composite crystallizer Nickel-chromium-aluminum wires on the left and right, the hot end of the crystallizer is boron nitride ceramic material, the inner diameter is The outer diameter is The length is 25.0-35.0mm, the cold end material is conventional high purity graphite, the outer sleeve is water cooled, and the drawing and casting speed is 1.5-2.3m.

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