A material for a dc grounding electrode feeding element and a manufacturing process thereof
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- STATE GRID JIANGXI ELECTRIC POWER CO LTD RES INST
- Filing Date
- 2026-03-27
- Publication Date
- 2026-06-30
AI Technical Summary
Existing DC grounding electrode feeder components are prone to brittle fracture during construction and service, have insufficient mechanical and corrosion resistance, and have defects such as porosity and cracks in the casting process, which affect the stable operation of the equipment.
DC grounding electrode feeder components are prepared by mixing high-silicon ferrochrome material with alloying element powders and using vacuum melting and controlled cooling processes. The alloying elements include RE, Cu, Mo and Ni. The material composition and microstructure are optimized to suppress casting defects and improve material performance.
Through the synergistic effect of alloying elements, the corrosion resistance and mechanical properties of the material are improved, the corrosion rate is reduced, the density and mechanical properties of the material are increased, casting defects are reduced, and stable equipment operation is ensured.
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Abstract
Description
Technical Field
[0001] This invention relates to the field of power supply element materials, specifically to a DC grounding electrode power supply element material and its preparation process. Background Technology
[0002] DC grounding electrodes are a crucial component of DC transmission projects, responsible for safely guiding the load current of the healthy pole during unipolar operation and unipolar blocking, as well as the unbalanced current during bipolar operation, to the ground. They also act as a clamping device for the neutral point potential of the converter valve. Some of my country's early DC grounding electrodes have been in operation for two or three decades. With increasing ampere-hours of unipolar operation, environmental factors such as coke aging, corrosion of feeder components, and uneven current distribution in feeder cables have led to equipment damage, resulting in a decline in the electrical performance of the grounding electrodes and even major accidents such as grounding electrode burnout and DC power outages. The corrosion characteristics and material formulation of feeder components, as well as the current distribution and temperature rise characteristics of feeder cables during arc-reversal operation, significantly impact the stable operation of grounding electrodes. Improving the performance of grounding electrode feeder components from a materials perspective and conducting research on grounding electrode arc-reversal operation technology are of great significance for ensuring the safe and stable operation of high-voltage DC transmission systems. Regarding the materials used in DC grounding electrode feeder components, the following main problems exist: DC grounding electrode feeder components are prone to brittle fracture during construction and service; their mechanical properties, corrosion resistance, and current discharge capacity need further improvement. The sand casting process for feeder components suffers from defects such as porosity and cracks, and the stress generated during casting leads to relatively high brittleness, making them susceptible to breakage or damage. These problems seriously affect the service performance of DC grounding electrode feeder components and the safe operation of DC transmission projects. Therefore, improvements to the feeder component materials are necessary. Summary of the Invention
[0003] The purpose of this invention is to at least solve one of the technical problems existing in the prior art, and to provide a DC grounding electrode feed element material and its preparation process.
[0004] The technical solution of the present invention is as follows: A preparation process for a DC grounding electrode feeder material involves uniformly mixing high-silicon ferrochrome material with alloy element powder, and then melting the mixture in a vacuum melting furnace to obtain the desired material. The alloying element includes at least one of RE, Cu, Mo and Ni; The high-silicon ferrochrome material comprises 14-16 wt% Si, 4-5 wt% Cr, and the balance Fe.
[0005] Preferably, the RE content is 0.02-0.1 wt% of the high-silicon ferrochrome material; The Cu content of the high-silicon chromium iron material is 1-9 wt%; The Mo content in the high-silicon ferrochrome material is 0.2-2.0 wt%; The Ni content of the high-silicon ferrochrome material is 2-10 wt%.
[0006] Preferably, it includes the following steps: S1: Dry the high-silicon ferrochrome material and alloy element powder at 70-80℃ until the water content is <0.1% to avoid the generation of pores during smelting, and obtain a mixed powder; S2: The mixed powder is placed in a medium-frequency vacuum induction furnace for melting to obtain a molten liquid; during melting, the vacuum degree is ≤10. - 3 Pa, reducing oxidizing and impurity gases; First, heat to 1200℃ (melting point of high silicon chromium iron) at a heating rate of 3-8℃ / min, hold for 10-30min, then heat to 1600-1800℃ at a heating rate of 9-15℃ / min, hold for 10-20min. S3: The molten liquid is poured into a container and cooled under an inert atmosphere to obtain the product.
[0007] Preferably, in step S3, the cooling rate is controlled to be ≤10℃ / min.
[0008] Preferably, in step S2, Sn powder is first added to the bottom of the medium-frequency vacuum induction furnace, accounting for 0.2-1 wt% of the mixed powder, and then the mixed powder is added for melting.
[0009] Preferably, in step S1, the particle size of the high-silicon ferrochrome material is 0.25-6 mm, and the alloy powder is sieved to 200 mesh.
[0010] Preferably, a deoxidizer is added during smelting to remove oxides from the melt.
[0011] Preferably, the deoxidizer accounts for 0.5-1 wt% of the mixed powder.
[0012] The present invention also discloses a DC grounding feeder material, which is prepared by the preparation process described above.
[0013] The beneficial effects of this invention are: by introducing alloying elements to regulate the material composition and microstructure, and by studying the casting production process, it suppresses undesirable phenomena such as porosity and cold shuts caused by casting, thereby improving the overall performance of the grounding electrode material.
[0014] Alloying elements optimize the corrosion resistance and mechanical properties of cast iron through their own corrosion resistance and synergistic effects with other elements in the cast iron composition. Adding appropriate alloying elements can increase the corrosion potential of the material, reduce the anodic current, and slow down the corrosion rate of the matrix. Alloying elements can also promote the formation of amorphous substances in corrosion products, leading to the formation of a dense and stable rust layer on the steel surface.
[0015] Rare earth elements (Re): Rare earth elements can reduce harmful elements such as sulfur (S) and oxygen (O) in steel. They can also improve the inclusion situation in the microstructure, reducing the type and size of harmful inclusions. Adding a small amount of rare earth elements to high-silicon ferrochrome can reduce porosity and shrinkage tendency in castings, which is beneficial for obtaining dense castings. It can also improve mechanical properties and corrosion resistance. Cu and rare earth elements can change the morphology of graphite from long flakes to curved, discontinuous short flakes and dots, and make the distribution of silicon more uniform, resulting in a denser microstructure and significantly finer grains, thus improving mechanical properties and corrosion resistance.
[0016] Copper (Cu): Cu effectively reduces the dissolution rate of Fe and, in specific environments, promotes anodic passivation in cast iron, enhancing the corrosion resistance of the matrix. In pits, the insoluble salts formed by Cu help repair pores and cracks in the rust layer, improving the material's resistance to pitting corrosion. For high-silicon ferrochrome, adding copper improves its resistance to hot sulfuric acid because copper precipitates at grain boundaries, promoting anodic passivation of ferrite grains. Due to Cu's high electrode potential, adding a certain amount of Cu to high-silicon cast iron increases the alloy's total electrode potential. During corrosion, it promotes cathodic activation and, under certain conditions, can also promote matrix (anodic) passivation, thereby reducing the corrosion rate. In addition, Cu strengthens the matrix, improves graphite morphology, and refines the microstructure with more uniform composition. Adding Cu to high-silicon ferrochrome improves machinability, increasing its strength and toughness while reducing hardness, thus improving cutting performance.
[0017] Molybdenum (Mo): Mo is an effective element for improving the corrosion resistance of iron-based materials. Adding an appropriate amount of Mo to steel can effectively inhibit the corrosion of Cl. - Competitive adsorption of corrosive anions; the formation of an amorphous oxide film on the material surface can improve the purification performance of the matrix; in addition, MoO in the corrosion products of Mo-containing steel 42 - Both have good corrosion inhibition properties, which are beneficial to improving the corrosion resistance of materials.
[0018] Tin (Sn): It forms a stable Cu6Sn5 interface compound with Cu, reducing interface defects and inhibiting the precipitation of other brittle or harmful phases, thus potentially enhancing the hardness and wear resistance of the material. Detailed Implementation
[0019] The embodiments of the present invention are described in detail below. These embodiments are exemplary and are only used to explain the present invention, and should not be construed as limiting the invention. Where specific techniques or conditions are not specified in the embodiments, they are performed according to the techniques or conditions described in the literature in the art or according to the product instructions. Reagents or instruments used, unless otherwise specified, are all commercially available conventional products.
[0020] In the following examples, cerium (Ce) is used as the rare earth element; aluminum deoxidizer is aluminum powder with a purity of ≥98%.
[0021] Example 1 A fabrication process for a DC grounding electrode feeder material includes the following steps: S1: Dry the high-silicon ferrochrome material and alloy element powder at 75°C until the water content is <0.1% to obtain a mixed powder; The alloying elements include RE, Cu, Mo, and Ni; The high-silicon ferrochrome material comprises 15.5 wt% Si, 4.5 wt% Cr, and the balance Fe.
[0022] The RE content is 0.02 wt% of the high-silicon chromium iron material; The Cu content is 5 wt% of the high-silicon chromium iron material. The Mo content is 0.3 wt% of the high-silicon ferrochrome material; The Ni content is 4 wt% of the high-silicon chromium iron material.
[0023] S2: The mixed powder is placed in a medium-frequency vacuum induction furnace for melting to obtain a molten liquid; during melting, the vacuum degree is ≤10. - 3 Pa; First, heat to 1200℃ at a heating rate of 5℃ / min and hold for 20min, then heat to 1700℃ at a heating rate of 15℃ / min and hold for 15min. S3: The molten liquid is poured into a container and cooled under an inert atmosphere to obtain the product.
[0024] In step S3, the cooling rate is controlled to be ≤10℃ / min.
[0025] In step S2, Sn powder is first added to the bottom of the medium-frequency vacuum induction furnace, accounting for 0.6 wt% of the mixed powder, and then the mixed powder is added for melting.
[0026] In step S1, the particle size of the high-silicon ferrochrome material is 0.4 mm, and the alloy powder is sieved to 200 mesh.
[0027] An aluminum deoxidizer is also added during smelting to remove oxides from the melt. The deoxidizer accounts for 0.5 wt% of the mixed powder.
[0028] Example 2 A fabrication process for a DC grounding electrode feeder material includes the following steps: S1: Dry the high-silicon ferrochrome material and alloy element powder at 75°C until the water content is <0.1% to obtain a mixed powder; The alloying elements include RE, Cu, Mo, and Ni; The high-silicon ferrochrome material comprises 15.5 wt% Si, 4.5 wt% Cr, and the balance Fe.
[0029] The RE content is 0.05 wt% of the high-silicon chromium iron material; The Cu content is 7 wt% of the high-silicon chromium iron material. The Mo content is 0.2 wt% of the high-silicon ferrochrome material; The Ni content is 6 wt% of the high-silicon chromium iron material.
[0030] S2: The mixed powder is placed in a medium-frequency vacuum induction furnace for melting to obtain a molten liquid; during melting, the vacuum degree is ≤10. - 3 Pa; First, heat to 1200℃ at a heating rate of 5℃ / min and hold for 20min, then heat to 1700℃ at a heating rate of 15℃ / min and hold for 15min. S3: The molten liquid is poured into a container and cooled under an inert atmosphere to obtain the product.
[0031] In step S3, the cooling rate is controlled to be ≤10℃ / min.
[0032] In step S2, Sn powder is first added to the bottom of the medium-frequency vacuum induction furnace, accounting for 0.6 wt% of the mixed powder, and then the mixed powder is added for melting.
[0033] In step S1, the particle size of the high-silicon ferrochrome material is 0.4 mm, and the alloy powder is sieved to 200 mesh.
[0034] An aluminum deoxidizer is also added during smelting to remove oxides from the melt. The deoxidizer accounts for 0.5 wt% of the mixed powder.
[0035] Example 3 A fabrication process for a DC grounding electrode feeder material includes the following steps: S1: Dry the high-silicon ferrochrome material and alloy element powder at 75°C until the water content is <0.1% to obtain a mixed powder; The alloying elements include RE, Cu, Mo, and Ni; The high-silicon ferrochrome material comprises 15.5 wt% Si, 4.5 wt% Cr, and the balance Fe.
[0036] The RE content is 0.1 wt% of the high-silicon ferrochrome material; The Cu content is 3 wt% of the high-silicon chromium iron material; The Mo content is 1 wt% of the high-silicon ferrochrome material. The Ni content is 8 wt% of the high-silicon chromium iron material.
[0037] S2: The mixed powder is placed in a medium-frequency vacuum induction furnace for melting to obtain a molten liquid; during melting, the vacuum degree is ≤10. - 3 Pa; First, heat to 1200℃ at a heating rate of 5℃ / min and hold for 20min, then heat to 1700℃ at a heating rate of 15℃ / min and hold for 15min. S3: The molten liquid is poured into a container and cooled under an inert atmosphere to obtain the product.
[0038] In step S3, the cooling rate is controlled to be ≤10℃ / min.
[0039] In step S2, Sn powder is first added to the bottom of the medium-frequency vacuum induction furnace, accounting for 0.6 wt% of the mixed powder, and then the mixed powder is added for melting.
[0040] In step S1, the particle size of the high-silicon ferrochrome material is 0.4 mm, and the alloy powder is sieved to 200 mesh.
[0041] An aluminum deoxidizer is also added during smelting to remove oxides from the melt. The deoxidizer accounts for 0.5 wt% of the mixed powder.
[0042] Example 4 A fabrication process for a DC grounding electrode feeder material includes the following steps: S1: Dry the high-silicon ferrochrome material and alloy element powder at 75°C until the water content is <0.1% to obtain a mixed powder; The alloying elements include RE, Cu, Mo, and Ni; The high-silicon ferrochrome material comprises 15.5 wt% Si, 4.5 wt% Cr, and the balance Fe.
[0043] The RE content is 0.05 wt% of the high-silicon chromium iron material; The Cu content is 7 wt% of the high-silicon chromium iron material. The Mo content is 0.2 wt% of the high-silicon ferrochrome material; The Ni content in the high-silicon chromium iron material is 6 wt%. S2: The mixed powder is placed in a medium-frequency vacuum induction furnace for melting to obtain a molten liquid; during melting, the vacuum degree is ≤10. - 3 Pa; First, heat to 1200℃ at a heating rate of 6℃ / min and hold for 20min, then heat to 1700℃ at a heating rate of 12℃ / min and hold for 15min. S3: The molten liquid is poured into a container and cooled under an inert atmosphere to obtain the product.
[0044] In step S3, the cooling rate is controlled to be ≤10℃ / min.
[0045] In step S2, Sn powder is first added to the bottom of the medium-frequency vacuum induction furnace, accounting for 0.6 wt% of the mixed powder, and then the mixed powder is added for melting.
[0046] In step S1, the particle size of the high-silicon ferrochrome material is 0.4 mm, and the alloy powder is sieved to 200 mesh.
[0047] An aluminum deoxidizer is also added during smelting to remove oxides from the melt. The deoxidizer accounts for 0.5 wt% of the mixed powder.
[0048] Example 5 A fabrication process for a DC grounding electrode feeder material includes the following steps: S1: Dry the high-silicon ferrochrome material and alloy element powder at 75°C until the water content is <0.1% to obtain a mixed powder; The alloying elements include RE, Cu, Mo, and Ni; The high-silicon ferrochrome material comprises 15.5 wt% Si, 4.5 wt% Cr, and the balance Fe.
[0049] The RE content is 0.05 wt% of the high-silicon chromium iron material; The Cu content is 7 wt% of the high-silicon chromium iron material. The Mo content is 0.2 wt% of the high-silicon ferrochrome material; The Ni content of the high-silicon chromium iron material is 6 wt%; S2: The mixed powder is placed in a medium-frequency vacuum induction furnace for melting to obtain a molten liquid; during melting, the vacuum degree is ≤10. - 3 Pa; First, heat to 1200℃ at a heating rate of 5℃ / min and hold for 20min, then heat to 1700℃ at a heating rate of 15℃ / min and hold for 15min. S3: The molten liquid is poured into a container and cooled under an inert atmosphere to obtain the product.
[0050] In step S3, the cooling rate is controlled to be ≤10℃ / min.
[0051] In step S2, Sn powder is first added to the bottom of the medium-frequency vacuum induction furnace, accounting for 1 wt% of the mixed powder, and then the mixed powder is added for melting.
[0052] In step S1, the particle size of the high-silicon ferrochrome material is 0.4 mm, and the alloy powder is sieved to 200 mesh.
[0053] An aluminum deoxidizer is also added during smelting to remove oxides from the melt. The deoxidizer accounts for 0.5 wt% of the mixed powder.
[0054] Comparative Example 1 Unlike Example 3, no rare earth elements were added to the alloy elements, but the rest remained the same.
[0055] Comparative Example 2 Unlike Example 3, Mo was not added to the alloy elements, but the rest remained the same.
[0056] Comparative Example 3 Unlike Example 3, Cu was not added to the alloy elements, but the rest remained the same.
[0057] Comparative Example 4 Unlike Example 3, Sn powder was not added to the bottom of the medium-frequency vacuum induction furnace, but everything else remained the same.
[0058] Comparative Example 5 Unlike Example 3, the temperature was increased to 1700°C at a rate of 15°C / min and held for 15 minutes; the rest remained unchanged.
[0059] The performance of the above embodiments and comparative examples was tested, and the test results are shown in Table 1.
[0060] The tensile and flexural strengths of the material samples were examined using a universal testing machine. The electrical conductivity of the material was measured using the four-probe method or an eddy current conductivity meter.
[0061] A sample with a diameter of 16 mm and a diameter of 5 cm was prepared and its corrosion rate was tested in a 15% NaCl / NaOH / HCl solution at room temperature for 480 h.
[0062] Table 1 Performance test results of the examples and comparative examples
[0063] As can be seen from the table above, the corrosion resistance of the embodiment is better than that of the comparative example. The main reason is that the addition of alloy powder has a synergistic effect with each other, which works together to improve the performance of the material. In addition, the influence of the smelting process makes the alloy elements more uniformly dispersed in the melt, reducing the agglomeration of alloy powder, thereby improving the performance of the material.
[0064] The embodiments described above are merely preferred embodiments of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various other corresponding changes and modifications based on the technical solutions and concepts described above, and all such changes and modifications should fall within the protection scope of the claims of the present invention.
Claims
1. A fabrication process for a DC grounding electrode feeder material, characterized in that, The high-silicon ferrochrome material is mixed evenly with alloy element powder and then melted in a vacuum melting furnace to obtain the product. The alloying element includes at least one of RE, Cu, Mo and Ni; The high-silicon ferrochrome material comprises 14-16 wt% Si, 4-5 wt% Cr, and the balance Fe.
2. The preparation process according to claim 1, characterized in that, The RE content is 0.02-0.1 wt% of the high-silicon ferrochrome material; The Cu content of the high-silicon chromium iron material is 1-9 wt%; The Mo content in the high-silicon ferrochrome material is 0.2-2.0 wt%; The Ni content of the high-silicon ferrochrome material is 2-10 wt%.
3. The preparation process according to claim 1, characterized in that, Includes the following steps: S1: Dry the high-silicon ferrochrome material and alloy element powder at 70-80℃ until the water content is <0.1% to obtain a mixed powder; S2: The mixed powder is placed in a medium-frequency vacuum induction furnace for melting to obtain a molten liquid; during melting, the vacuum degree is ≤10. -3 Pa; First, heat to 1200℃ at a heating rate of 3-8℃ / min and hold for 10-30min. Then, heat to 1600-1800℃ at a heating rate of 9-15℃ / min and hold for 10-20min. S3: The molten liquid is poured into a container and cooled under an inert atmosphere to obtain the product.
4. The preparation process according to claim 3, characterized in that, In step S3, the cooling rate is controlled to be ≤10℃ / min.
5. The preparation process according to claim 3, characterized in that, In step S2, Sn powder is first added to the bottom of the medium-frequency vacuum induction furnace, accounting for 0.2-1 wt% of the mixed powder, and then the mixed powder is added for melting.
6. The preparation process according to claim 3, characterized in that, In step S1, the particle size of the high-silicon ferrochrome material is 0.25-6 mm, and the alloy powder is sieved to 200 mesh.
7. The preparation process according to claim 3, characterized in that, In step S2, a deoxidizer is also added during smelting.
8. The preparation process according to claim 7, characterized in that, The deoxidizer accounts for 0.5-1 wt% of the mixed powder.
9. A material for a DC grounding feeder element, characterized in that, It is prepared using the preparation process described in any one of claims 1-8.