A wire steel core material based on a coherent structure double-strengthening phase and a preparation method thereof

Abstract

This invention provides a conductor core material based on a coherent structure dual-reinforcing phase and its preparation method. By mass percentage, it comprises the following chemical elements: C: 0.55%~0.65%, Si: 0.15%~0.35%, Mn: 0.20%~0.40%, Cr: 0.10%~0.30%, P≤0.015%, S≤0.010%; reinforcing phase elements: Ni+Al: 0.10%~0.60%, V: 0.01%~0.15%; the balance being Fe and unavoidable impurities. This invention, through the addition of Ni, Al, and V reinforcing phase elements, forms NiAl and VC phases that are highly coherent with the iron matrix. This results in a pearlitic structure with refined grains and small interlamellar spacing within the material. Nanoscale carbides / intermetallic compounds act as heterogeneous nuclei, promoting alternating nucleation of ferrite and cementite, making the sorbite lamellae finer and more uniform, which can effectively improve the alloy strength. In addition, the NiAl and VC phases can act as hydrogen traps, inhibiting the generation of hydrogen-induced cracks and avoiding sudden brittle fracture of the steel core, thus achieving simultaneous optimization of the steel core's strength and plasticity.

Description

Technical Field

[0001] This invention belongs to the technical field of steel core materials for overhead power transmission conductors, specifically providing a conductor steel core material based on a coherent structure dual-reinforcing phase and its preparation method. Background Technology

[0002] Overhead transmission lines bear the critical tasks of conducting current and transmitting electrical energy, while also bearing normal operating loads as well as additional loads caused by environmental factors such as icing and strong winds. As the core load-bearing component of the conductor, the mechanical properties of the steel core material determine the conductor's load-bearing capacity, overall tensile strength, anti-sag performance, and service life.

[0003] Currently, the core wires of overhead conductors are generally made of galvanized steel, with a maximum tensile strength of only 1960MPa, and their mechanical properties still need to be improved. The tensile strength of carbon fiber composite core wires can reach more than 2100MPa, but they have problems such as low shear strength, poor high temperature resistance, and easy aging, making it difficult to guarantee durability. In addition, the engineering cost and construction requirements are high.

[0004] Currently, the high strength of carbon steel materials used for ultra-high-strength steel cores typically relies on increasing carbon content or refining grain size. However, increasing carbon content leads to a significant decrease in the plasticity of the steel core, making it prone to brittle fracture. Furthermore, during smelting, processing, and service, the accumulation of hydrogen atoms within the steel core weakens grain boundary bonding, initiating hydrogen-induced cracks. Especially under high-stress conditions, this can easily lead to sudden brittle fracture of the steel core, severely impacting the safety and stability of overhead transmission lines. This results in a dilemma for ultra-high-strength carbon steel materials: a difficulty in balancing strength and plasticity, and high sensitivity to hydrogen embrittlement.

[0005] Accordingly, there is a need in the field for a new conductor core material and its preparation method to solve the above problems. Summary of the Invention

[0006] The purpose of this invention is to solve the problem that existing high-carbon steel cores for overhead conductors are difficult to balance in terms of strength and plasticity, and are highly susceptible to hydrogen embrittlement.

[0007] The objective of this invention is achieved through the following technical solution: This invention provides a conductor core material based on a coherent structure dual-reinforcing phase, comprising the following chemical elements by mass percentage: C: 0.55%~0.65%, Si: 0.15%~0.35%, Mn: 0.20%~0.40%, Cr: 0.10%~0.30%, P≤0.015%, S≤0.010%; reinforcing phase elements Ni+Al: 0.10%~0.60%, V: 0.01%~0.15%; the balance being Fe and unavoidable impurities.

[0008] Preferably, the reinforcing phase elements Ni+Al: 0.35%~0.45%, V: 0.02%~0.05%.

[0009] Preferably, the reinforcing phase element forms a NiAl phase and a VC phase, both of which have a coherent structure with the iron matrix.

[0010] Based on the same inventive concept, this invention also provides a method for preparing the conductor steel core material based on the coherent structure dual-strengthened phase, comprising: a smelting process: adding raw materials to pretreated molten iron according to the chemical element ratio of the conductor steel core material and smelting to obtain molten steel; a refining process: transferring the molten steel to a refining furnace for high-purity refining and desulfurization treatment to obtain refined molten steel; a degassing and impurity removal process: transferring the refined molten steel to a vacuum furnace for vacuum degassing and inclusion removal treatment to obtain high-quality molten steel with uniform composition and qualified purity; a casting process: continuously casting the high-quality molten steel and cooling it to room temperature to obtain a steel billet; and a forming process: sequentially subjecting the steel billet to hot rolling, heat treatment, and drawing treatment to obtain a single-wire steel core.

[0011] Preferably, the smelting process uses an electric arc furnace for smelting, with a smelting temperature of 1320℃~1580℃ and a smelting holding time of 20min~30min.

[0012] Preferably, the pretreated molten iron involves adding a CaO-based flux to the molten iron, performing dephosphorization treatment under an oxidizing atmosphere, with the molten iron temperature at 1300℃~1380℃, the stirring speed at 110r / min~150r / min, and finally performing desulfurization treatment to control the sulfur content of the molten iron to ≤0.006% and the total amount of unavoidable impurities to ≤0.015%.

[0013] Preferably, the refining process involves transferring the smelted molten steel into a refining furnace, adding high-purity CaO-Al2O3-based refining slag, controlling the slag basicity to 3.5~4.5, using argon gas to assist desulfurization with stirring intensity of 80r / min~120r / min, controlling the refining temperature to 1580℃~1620℃, and holding the refining temperature for 45min~60min to obtain refined molten steel.

[0014] Preferably, a vacuum furnace is used in the degassing and impurity removal process, with a vacuum degree of 66.7 Pa to 133.3 Pa and a vacuum holding time of 25 min to 35 min; After the vacuum treatment is completed and the vacuum is broken, argon blowing is used for stirring at a speed of 30 r / min to 50 r / min for 15 min to 20 min.

[0015] Preferably, the cooling rate is controlled at 5℃ / min to 8℃ / min during the continuous casting process of the casting procedure.

[0016] Preferably, in the forming process, the hot rolling treatment involves heating the steel billet to a hot rolling start temperature of 950℃~1050℃, holding it at the hot rolling temperature for 30 minutes, and then hot rolling is performed. The final hot rolling temperature is controlled at 800℃~850℃, and the hot-rolled wire rod is obtained by air cooling after rolling.

[0017] Preferably, in the forming process, the heat treatment is to perform isothermal quenching on the hot-rolled wire rod in a lead bath furnace, with the quenching temperature controlled at 550℃~600℃ and the quenching holding time at 60min.

[0018] Preferably, in the forming process, the drawing process involves drawing the hot-rolled wire rod in multiple passes to obtain a steel core single wire, with the total drawing deformation controlled at 60% to 75%, and the deformation per pass controlled not to exceed 15% during the drawing process.

[0019] Compared with the prior art, the beneficial effects of the present invention are as follows: This invention provides a conductor core material based on a coherent structure dual-reinforcing phase, comprising the following chemical elements by mass percentage: C: 0.55%~0.65%, Si: 0.15%~0.35%, Mn: 0.20%~0.40%, Cr: 0.10%~0.30%, P≤0.015%, S≤0.010%; reinforcing phase elements Ni+Al: 0.10%~0.60%, V: 0.01%~0.15%; the balance being Fe and unavoidable impurities. This invention, through the addition of Ni, Al, and V reinforcing phase elements, forms NiAl and VC phases that are highly coherent with the iron matrix. This results in a pearlitic structure with refined grains and small interlamellar spacing within the material. The nano-carbide VC / intermetallic compound NiAl acts as a heterogeneous nucleus, promoting alternating nucleation of ferrite and cementite, making the sorbite lamellae finer and more uniform, which can effectively improve the alloy strength. In addition, the NiAl and VC phases can act as hydrogen traps, inhibiting the generation of hydrogen-induced cracks and avoiding sudden brittle fracture of the steel core, thus achieving simultaneous optimization of the steel core's strength and plasticity. Detailed Implementation

[0020] The following embodiments are provided to better understand the present invention and are not limited to the preferred embodiments described. They do not constitute a limitation on the content and scope of protection of the present invention. Any product that is the same as or similar to the present invention, derived by any person under the guidance of the present invention or by combining the features of the present invention with other prior art, falls within the protection scope of the present invention.

[0021] For any experimental steps or conditions not specified in this invention, the conventional experimental steps or conditions described in the literature in this field can be followed.

[0022] This invention provides a conductor core material based on a coherent structure dual-reinforcing phase, comprising the following chemical elements by mass percentage: C: 0.55%~0.65%, Si: 0.15%~0.35%, Mn: 0.20%~0.40%, Cr: 0.10%~0.30%, P≤0.015%, S≤0.010%; reinforcing phase elements Ni+Al: 0.10%~0.60%, V: 0.01%~0.15%; the balance being Fe and unavoidable impurities.

[0023] Research has revealed that NiAl intermetallic compounds possess high strength, high hardness, and good thermal stability, and their crystal structure is highly coherent with the iron matrix. The VC (vanadium carbide) phase exhibits extremely high hardness and stability, effectively refining grains and hindering dislocation movement, while also acting as a hydrogen trap to capture diffusible hydrogen. Simultaneously introducing strengthening phase elements Ni, Al, and V into the material forms both NiAl and VC phases. Both NiAl and VC phases possess coherent structures with the iron matrix, achieving a synergistic effect. This allows for the enhancement of strength and plasticity through the coherent distortion strengthening effect of the NiAl phase with the iron matrix, while the refining and hydrogen trapping effects of the VC phase further improve strength and refine the microstructure. Simultaneously, it synergistically inhibits the initiation and propagation of hydrogen-induced cracks, doubly enhancing resistance to hydrogen embrittlement and fundamentally solving the performance bottleneck of existing high-carbon steel cores.

[0024] Based on the same inventive concept, this invention also provides a method for preparing a conductor steel core material based on a coherent structure dual-reinforcing phase, comprising: S1. Smelting process: Raw materials are added to the pretreated molten iron according to the chemical element ratio of the conductor steel core material and smelted to obtain molten steel. Specifically, the smelting process uses an electric arc furnace. The pretreatment of the molten iron involves dephosphorization under an oxidizing atmosphere. By adding CaO-based flux, the phosphorus in the molten iron reacts chemically with the flux to form a stable slag phase that separates. Finally, desulfurization is performed to control the sulfur content of the molten iron to ≤0.006%, while removing residual impurities such as Cu, As, Sn, and Sb from the molten iron. This ensures that the total amount of residual impurities in the molten iron after pretreatment is ≤0.015%. During the pretreatment process, the temperature of the molten iron is controlled at 1300℃~1380℃, and the stirring speed is 110r / min~150r / min to ensure that impurities and residual elements are fully separated and removed, thus achieving the purification of the molten iron.

[0025] During smelting, raw materials C, Si, Mn, Cr, P, and S are added to an electric arc furnace according to the chemical element ratios mentioned above. The smelting temperature is controlled at 1320℃~1580℃. After the raw materials are completely melted, strengthening phase elements Ni, Al, and V are added and stirred evenly. The holding time is 20min~30min to ensure that Ni and Al react fully to form NiAl phase and V and C react fully to form VC phase. At the same time, the impurity content is reduced and the two strengthening phases are uniformly dispersed. The slag is removed to obtain molten steel. S2, Refining process: The molten steel is transferred to a refining furnace for high-purity refining and desulfurization treatment to obtain refined molten steel; Specifically, the molten steel is transferred to an LF refining furnace, high-purity CaO-Al2O3-based refining slag is added, the slag basicity is controlled at 3.5~4.5, argon gas is used for assisted desulfurization with stirring intensity of 80r / min~120r / min, the refining temperature is controlled at 1580℃~1620℃, and the refining holding time is 45min~60min to obtain refined molten steel.

[0026] S3. Degassing and impurity removal process: The refined molten steel is transferred to a vacuum furnace for vacuum degassing and inclusion removal to obtain high-quality molten steel with uniform composition and high purity. Specifically, after refining, the molten steel is transferred to a VD vacuum furnace, and the vacuum degree of the vacuum furnace is controlled at 66.7 Pa to 133.3 Pa. The vacuum is maintained for 25 min to 35 min. Under vacuum, argon gas is used to stir the molten steel to promote the floating and separation of gases (H, O) and fine inclusions, effectively removing hydrogen (controlling the hydrogen content of the molten steel to ≤1.5 ppm), oxygen and various non-metallic inclusions from the molten steel. After the vacuum treatment is completed and the vacuum is broken, argon blowing and stirring are used. The argon blowing intensity is controlled at 30 r / min to 50 r / min, and the stirring time is 15 min to 20 min. This avoids secondary oxidation of the molten steel and re-entry of inclusions, ensuring that the molten steel has uniform composition and meets the purity standards, so as to provide high-quality molten steel for subsequent casting and molding.

[0027] S4. Casting process: High-quality molten steel is continuously cast and cooled to room temperature to obtain steel billets; Specifically, the molten steel is continuously cast after smelting. During the continuous casting process, the cooling rate is controlled at 5~8℃ / min to ensure that the NiAl phase and VC phase are evenly distributed and to avoid uneven microstructure caused by excessive cooling rate.

[0028] S5. Forming process: The steel billet is successively subjected to hot rolling, heat treatment and drawing to obtain steel core single wire.

[0029] Specifically, hot rolling involves heating the steel billet to an initial hot rolling temperature of 950℃~1050℃, holding it at that temperature for 30 minutes, and then hot rolling it at a final temperature of 800℃~850℃. After rolling, the billet is air-cooled to obtain hot-rolled wire rod. Hot rolling refines the grains, promotes the formation of a stable coherent structure between the NiAl phase and the iron matrix, and simultaneously promotes the uniform dispersion of the VC phase, strengthening their synergistic effect.

[0030] The heat treatment involves isothermal quenching of the hot-rolled wire rod in a lead bath furnace, with the quenching temperature controlled at 550℃~600℃ and the holding time at that temperature being 60 minutes. Through isothermal quenching transformation, the material obtains a uniform and fine pearlitic structure, further optimizing the distribution of the NiAl and VC phases, improving the stability of the coherent structure and the dispersion of the VC phase, enhancing the synergistic strengthening and resistance to hydrogen embrittlement, and reducing hydrogen embrittlement sensitivity.

[0031] The drawing process involves drawing hot-rolled wire rods in multiple passes to obtain steel core single wires. The total drawing deformation is controlled at 60% to 75%, and the deformation per pass is controlled to not exceed 15% during the drawing process to avoid excessive drawing that could lead to cracks. After drawing, steel core material single wires are obtained.

[0032] The conductor steel core material of the present invention improves the alloy purity by adding Ni, Al, and V alloying elements, and by using molten iron pretreatment, refining, degassing and impurity removal, combined with isothermal quenching, to obtain coherent NiAl phase, VC phase and sorbite alloy structure that are highly coherent with the iron matrix, which greatly improves the tensile strength and elongation properties of the material.

[0033] The following examples were obtained by preparing samples using different proportions of the component elements and preparation process parameters of the above-mentioned steel core material.

[0034] Examples 1-8 and Comparative Example 1 Table 1 is a comparison table of the chemical element ratios of the steel core materials in Examples 1-8 and Comparative Example 1, as follows: Table 1

[0035] Note: In Table 1, the balance of steel core material proportions in Examples 1-8 and Comparative Example 1 is iron and unavoidable impurities.

[0036] Table 2 is a comparison table of the main process parameters for the preparation methods of the conductor steel core materials of Examples 1-8 and Comparative Example 1, as follows: Table 2

[0037] It should be noted that Table 2 above mainly lists the key preparation parameters. For preparation parameters not listed, those skilled in the art can use the defined parameter range or conventional values.

[0038] Test Results Mechanical property tests were conducted on Examples 1-8, and the results are as follows: As shown in Table 3, Table 3 is a comparison table of tensile strength and elongation performance of Examples 1-8.

[0039] Table 3

[0040] A comparison of Tables 1, 2, and 3 shows that the high-strength steel core composition of this invention, based on the addition of Ni, Al, and V alloying elements, promotes alternating nucleation of ferrite / cementite through the highly coherent NiAl and VC phases with the iron matrix. This results in finer and more uniform sorbite lamellars, forming hydrogen traps, reducing hydrogen embrittlement sensitivity, and achieving a synergistic improvement in strength and plasticity. Compared to Comparative Example 1, which did not add Ni, Al, and V alloying elements, the composition of this invention achieves peak performance of 2270 MPa tensile strength and 3.5% through multi-dimensional synergy of coherent dual-phase nucleation, mechanical properties, and resistance to hydrogen embrittlement. As shown in Example 8 compared to Comparative Example 1, although the strengthening phase elements Ni+Al and V are used at their maximum values, the tensile strength is significantly improved, but the balance between tensile strength and elongation is not ideal.

[0041] In the preferred embodiment, the reinforcing phase elements Ni+Al: 0.35%~0.45%, V: 0.02%~0.05%. The NiAl and VC phases are in an optimal coherent structural state, greatly improving the material's strength and plasticity. For example, the tensile strength and elongation of Examples 6 and 7 are in an optimal balance. Among them, Example 7 exhibits the best performance balance between a tensile strength of 2251 MPa and an elongation of 3.5%.

[0042] The above are merely embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention are included within the scope of the claims of the present invention pending approval.

Claims

1. A conductor core material based on a coherent dual-reinforcing phase structure, characterized in that, By mass percentage, it includes the following chemical elements: C: 0.55%~0.65%, Si: 0.15%~0.35%, Mn: 0.20%~0.40%, Cr: 0.10%~0.30%, P≤0.015%, S≤0.010%; strengthening phase element Ni+Al: 0.10%~0.60%, V: 0.01%~0.15%; balance is Fe and unavoidable impurities.

2. The conductor core material based on a coherent dual-reinforcing phase structure according to claim 1, characterized in that, The reinforcing phase elements Ni+Al: 0.35%~0.45%, V: 0.02%~0.05%.

3. The conductor core material based on a coherent dual-reinforcing phase structure according to claim 1, characterized in that, The strengthening phase elements form NiAl and VC phases, both of which have a coherent structure with the iron matrix.

4. A method for preparing a conductor core material based on a coherent dual-reinforcing phase according to any one of claims 1-3, characterized in that, include: Smelting process: Raw materials are added to the pretreated molten iron according to the chemical element ratio of the conductor steel core material and smelted to obtain molten steel; Refining process: The molten steel is transferred to a refining furnace for high-purity refining and desulfurization treatment to obtain refined molten steel; Degassing and impurity removal process: The refined molten steel is transferred to a vacuum furnace for vacuum degassing and inclusion removal to obtain high-quality molten steel with uniform composition and qualified purity. Casting process: High-quality molten steel is continuously cast and cooled to room temperature to obtain steel billets; Forming process: The steel billet is successively subjected to hot rolling, heat treatment and drawing to obtain steel core single wire.

5. The method for preparing conductor core material based on coherent dual-reinforcing phase according to claim 4, characterized in that, The smelting process uses an electric arc furnace for smelting, with a smelting temperature of 1320℃~1580℃ and a smelting holding time of 20min~30min.

6. The method for preparing conductor core material based on coherent dual-reinforcing phase according to claim 4, characterized in that, The pretreated molten iron involves adding CaO-based flux to the molten iron, performing dephosphorization treatment under an oxidizing atmosphere, with the molten iron temperature at 1300℃~1380℃ and the stirring speed at 110r / min~150r / min, and finally performing desulfurization treatment to control the sulfur content of the molten iron to ≤0.006% and the total amount of unavoidable impurities to ≤0.015%.

7. The method for preparing conductor core material based on coherent dual-reinforcing phase according to claim 4, characterized in that, The refining process involves transferring the molten steel to a refining furnace, adding high-purity CaO-Al2O3-based refining slag, controlling the slag basicity to 3.5-4.5, using argon gas to assist in desulfurization with stirring intensity of 80-120 r / min, controlling the refining temperature to 1580-1620℃, and holding the refining temperature for 45-60 minutes to obtain refined molten steel.

8. The method for preparing conductor core material based on coherent dual-reinforcing phase according to claim 4, characterized in that, A vacuum furnace is used in the degassing and impurity removal process, with a vacuum degree of 66.7 Pa to 133.3 Pa and a vacuum holding time of 25 min to 35 min. After the vacuum treatment is completed and the vacuum is broken, argon blowing is used for stirring at a speed of 30 r / min to 50 r / min for 15 min to 20 min.

9. The method for preparing conductor core material based on coherent dual-reinforcing phase according to claim 4, characterized in that, During the continuous casting process of the aforementioned casting procedure, the cooling rate is controlled at 5℃ / min to 8℃ / min.

10. The method for preparing conductor core material based on coherent dual-reinforcing phase according to claim 4, characterized in that, In the forming process, the hot rolling process involves heating the steel billet to a hot rolling start temperature of 950℃~1050℃, holding it at the hot rolling temperature for 30 minutes, and then hot rolling is performed. The hot rolling finish temperature is controlled at 800℃~850℃, and the billet is air-cooled after rolling to obtain hot-rolled wire rod.

11. The method for preparing conductor core material based on coherent dual-reinforcing phase according to claim 4, characterized in that, In the forming process, the heat treatment involves isothermal quenching of the hot-rolled wire rod in a lead bath furnace, with the quenching temperature controlled at 550℃~600℃ and the quenching holding time at 60min.

12. The method for preparing conductor core material based on coherent dual-reinforcing phase according to claim 4, characterized in that, In the forming process, the drawing process involves drawing the hot-rolled wire rod in multiple passes to obtain a steel core single wire. The total drawing deformation is controlled at 60% to 75%, and the deformation per pass is controlled to not exceed 15% during the drawing process.

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