Preparation method of steel core wire rod for steel-based alternating current composite conductor

Abstract

The invention discloses a preparation method of a steel core wire rod for a steel-based alternating current composite conductor, and the steel core wire rod with good toughness, tensile strength stabilized in a range of 500-550MPa, good mechanical property and excellent physical bonding property with a middle aluminum coating layer is produced by means of molten steel component control, continuous casting pulling speed, casting blank heating control and controlled rolling, the interlayer potential difference is further reduced, and the service life of the steel core wire rod is prolonged. A core material with relatively high cost performance is provided for the composite conductor, and the steel-based composite conductor has high strength, high modulus and low relaxation of steel and good conductivity and atmospheric corrosion resistance of copper, so that the purposes of excellent performance and low cost are achieved. The cable can be widely applied to the fields of power transmission, electronic equipment, communication systems, new energy automobiles, photovoltaic power generation and the like.

Description

A method for preparing steel core wire rod for steel-based AC composite conductors Technical Field

[0001] This invention belongs to the category of composite conductors, and relates to the field of AC composite conductors, and more particularly to a method for preparing steel core wire rods for steel-based AC composite conductors. Background Technology

[0002] Copper conductors possess excellent electrical conductivity and are widely used in power transmission, electronic equipment, communication systems, new energy vehicles, and photovoltaic power generation. They are also widely used in refractory layers, insulation layers, sheaths, and filler materials, playing a dominant role in ultra-high voltage projects. Due to the increasing imbalance between copper supply and demand and persistently high copper prices, copper has become the second most important resource after oil, forcing companies and researchers to seek new low-cost conductor materials to replace pure copper. Furthermore, steel possesses high mechanical strength, strong load-bearing capacity, making it more suitable for long-span power transmission projects, and is also inexpensive. Since the current density of alternating current is highest near the conductor surface and decreases exponentially with increasing conductor depth, using steel as the conductor base material and aluminum and copper as the conductive layers can achieve a combination of excellent conductivity (copper), lightweight aluminum, and high mechanical strength and load-bearing capacity (steel), resulting in superior performance at a low cost. However, when using traditional steel as the core of a composite conductor, the transition between the core and the intermediate aluminum cladding layer is not ideal, leading to adverse factors such as potential differences. Summary of the Invention

[0003] This invention discloses a method for preparing steel core wire rods for steel-based AC composite conductors, which addresses the shortcomings of existing technologies. By strictly controlling the Si content, alloying Nb and Ti, and rationally matching the temperature during hot rolling, a steel core wire rod for AC composite conductors with a uniform and fine ferrite + bainite structure is produced.

[0004] The technical solution provided by this invention is: a steel core wire rod for steel-based AC composite conductors, the chemical composition (mass percentage) of which is: C: 0.06-0.09%, Si≤0.03%, Mn: 1.40-2.0%, P≤0.015%, S≤0.008%, Nb: 0.04-0.05%, Ti: 0.010-0.030%, and Mn / Si>60, with the remainder being Fe and unavoidable inclusions.

[0005] To achieve the objective of this invention, a method for producing steel core wire rod for steel-based AC composite conductors includes the following steps: Step 1: Hot metal pretreatment, requiring slag removal before and after treatment, and ensuring S ≤ 0.002% after desulfurization; Step 2: Converter blowing, deoxidation and alloying at tapping, employing efficient slag-blocking operation, with slag thickness ≤ 40mm; Step 3: Ladle refining and calcium treatment, rapidly adding lime and fluorite upon arrival at the ladle to create white slag with high alkalinity, low oxidation, and good fluidity, adjusting key elements to target values, controlling the morphology, quantity, and size of non-metallic inclusions in the hot metal through dehydrogenation and oxygenation, reducing the formation of non-metallic inclusions, improving the purity of the hot metal, and controlling the SiO2 content in the slag to < 3% in the later stages of refining. Step 4: Continuous casting, with a casting speed control target of 2.2-2.4 m / min; continuous casting should be carried out at a constant casting speed; Step 5: Billet heating, with the billet heating temperature controlled at 1050℃~1100℃ and the heating time controlled at 1h20min-1h30min; the soaking zone temperature is 1060℃-1100℃ and the soaking time is maintained at 35min-40min; Step 6: Temperature-controlled rolling, with the roughing rolling temperature controlled at 980±30℃, the finishing rolling inlet temperature at 920±20℃, and the wire drawing temperature at 880-920℃; the initial roller speed is 0.42m / s.

[0006] Step 7: Fine finishing and collection. The collection temperature is controlled at 500-550℃. The beneficial effects of this invention are: good toughness, stable tensile strength within the range of 500MPa-550MPa, good mechanical properties, and excellent physical bonding with the intermediate aluminum cladding layer, further reducing the interlayer potential difference. This provides a cost-effective core material for composite conductors, satisfying the requirements of steel-based composite conductors to combine the high strength, high modulus, and low relaxation of steel with the good conductivity and atmospheric corrosion resistance of copper, thus achieving excellent performance and low cost. Attached Figure Description

[0007] Figure 1 is a flowchart of the processing steps of the present invention. Detailed Implementation

[0008] The technical solutions of this application will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this application. 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.

[0009] In the description of this application, it should be understood that the terms "center," "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "positive," "negative," "vertical," "horizontal," "top," "bottom," "inner," "outer," "one side," "one end," and "one side," etc., indicating the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation on this application. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this application, unless otherwise stated, "a plurality of" means two or more.

[0010] In the description of this application, it should be noted that, unless otherwise expressly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly; they can refer to mechanical connections or electrical connections; they can be direct connections or indirect connections through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances.

[0011] It should be understood that, when used in this specification and the appended claims, the terms "comprising" and "including" indicate the presence of the described features, integrals, steps, operations, elements and / or components, but do not exclude the presence or addition of one or more other features, integrals, steps, operations, elements, components and / or collections thereof.

[0012] It should also be understood that the terminology used in this specification is for the purpose of describing particular embodiments only and is not intended to limit the application. As used in this specification and the appended claims, the singular forms “a,” “an,” and “the” are intended to include the plural forms unless the context clearly indicates otherwise.

[0013] It should also be further understood that the term “and / or” as used in this specification and the appended claims means any combination of one or more of the associated listed items and all possible combinations, and includes such combinations.

[0014] The accompanying drawings illustrate various structural schematics according to embodiments disclosed in this application. These drawings are not to scale, and some details have been enlarged for clarity, and some details may have been omitted. The shapes of the various regions and layers shown in the drawings, as well as their relative sizes and positional relationships, are merely exemplary and may deviate from reality due to manufacturing tolerances or technical limitations. Furthermore, those skilled in the art can design regions / layers with different shapes, sizes, and relative positions as needed.

[0015] Referring to the accompanying drawings, the present invention discloses a method for preparing a steel core wire rod for a steel-based AC composite conductor. The technical solution is as follows: A steel core wire rod for a steel-based AC composite conductor has the following chemical composition (mass percentage): C: 0.06-0.09%, Si≤0.03%, Mn: 1.40-2.00%, P≤0.015%, S≤0.008%, Nb: 0.04-0.05%, Ti: 0.010-0.030%, and Mn / Si>60, with the remainder being Fe and unavoidable inclusions.

[0016] To achieve the objective of this invention, a method for producing steel core wire rod for steel-based AC composite conductors includes the following steps: Step 1: Hot metal pretreatment, requiring slag removal before and after treatment, and ensuring S ≤ 0.002% after desulfurization; Step 2: Converter blowing, deoxidation and alloying at tapping, while employing efficient slag-blocking operations, with slag thickness ≤ 40mm; Step 3: Ladle refining and calcium treatment, rapidly adding lime and fluorite upon arrival at the ladle to create white slag with high alkalinity, low oxidation, and good fluidity, adjusting key elements to target values, controlling the morphology, quantity, and size of non-metallic inclusions in the hot metal through dehydrogenation and oxygenation, reducing the formation of non-metallic inclusions, improving the purity of the hot metal, and controlling the SiO2 content in the slag to < 3% in the later stages of refining. %; tapping temperature T≥1620℃, liquidus temperature TL=1513±10℃; Step 4: continuous casting, casting speed control target 2.2-2.4m / min; continuous casting ensures constant casting speed operation; Step 5: billet heating, billet heating temperature controlled at 1050℃~1100℃, heating time controlled at 1h20min-1h30min; soaking zone temperature is 1060℃-1100℃, soaking time is maintained at 35min-40min; Step 6: temperature controlled rolling, roughing rolling temperature controlled at 980±30℃, finishing rolling inlet temperature is 920±20℃, wire drawing temperature is 880-920℃; initial roller speed is 0.42m / s.

[0017] Step 7: Fine collection. The collection temperature is controlled at 500-550℃.

[0018] This invention controls the carbon content (C) within the range of 0.06% to 0.09% to ensure the target steel possesses good tensile strength, toughness, and yield strength. Si in steel achieves strength enhancement through solid solution strengthening; however, during the formation of primary iron oxide scale in Si-containing steel, high-viscosity Fe2SiO4 forms at the iron oxide scale / matrix interface, penetrating deep into the FeO and steel matrix to form an "anchor-like structure," leading to "red scale" defects on the surface after hot rolling. Therefore, the Si content is controlled below 0.04%. Mn is one of the main and economical elements for improving strength in steel. Due to the strong affinity of added Ti for S, MnS is easily replaced by Ti4C2S2. Furthermore, due to the strict control of Si content, it is difficult to form (FeMn)2SiO4, which is detrimental to surface quality. From an economic perspective, the Mn content can be increased as much as possible, with Mn / Si > 60. However, excessively high Mn content can easily cause central segregation, which is detrimental to the uniform distribution of the steel's microstructure and properties. Therefore, Mn is controlled between 1.40% and 2.00%. P and S are harmful substances in steel and unavoidable residual elements. They are prone to segregation in steel, so P and S are controlled between P ≤ 0.015% and S ≤ 0.002%. Nb is one of the important alloying elements in high-strength steel. Nb has a significant grain-refining strengthening effect. Adding an appropriate amount of Nb at high temperature will precipitate carbonitrides, which not only prevents austenite grain growth but also effectively inhibits the recrystallization and growth of deformed austenite grains, thus improving the strength and toughness of steel. However, if the Nb content is too high, it may lead to coarse precipitates and reduced toughness. Therefore, Nb is controlled between 0.04% and 0.05%. Ti has a strong affinity for nitrogen, oxygen, and carbon. Its affinity for sulfur is stronger than that for iron. However, excessive Ti can easily cause coarsening and excessive precipitation of Ti carbonitrides, which is not conducive to improving strength and toughness. Therefore, Ti is controlled between 0.01% and 0.03%.

Claims

1. A method for producing steel core wire rod for steel-based AC composite conductors, characterized in that: The process includes the following steps: Step 1: Hot metal pretreatment, requiring slag removal before and after the process, and ensuring S ≤ 0.002% after desulfurization; Step 2: Converter blowing, deoxidation and alloying at tapping, while employing efficient slag-blocking operations; Step 3: Ladle refining and calcium treatment, producing high-basicity, low-oxidizing, and highly fluid white slag upon arrival at the station, adjusting key elements to target values, controlling the morphology, quantity, and size of non-metallic inclusions in the molten steel through dehydrogenation and oxygenation, reducing the formation of non-metallic inclusions, and improving the purity of the molten steel; tapping temperature T ≥ 1620℃, liquidus temperature TL = 1513 ± 10℃; Step 4: Continuous casting, with casting speed controlled to target 2. 2-2.4 m / min; Continuous casting ensures constant casting speed operation; Step 5: Billet heating, billet heating temperature controlled at 1050℃~1100℃, heating time controlled at 1h20min-1h30min; soaking zone temperature 1060℃-1100℃, soaking time maintained at 35min-40min; Step 6: Temperature controlled rolling, roughing rolling temperature controlled at 980±30℃, finishing rolling inlet temperature 920±20℃, wire drawing temperature 880-920℃; initial roller speed 0.42m / s; Step 7: Finishing collection. Collection temperature controlled at 500~550℃.

2. The steel core wire rod for a steel-based AC composite conductor according to claim 1, characterized in that: Its chemical composition (mass percentage) is as follows: C: 0.06-0.09%, Si ≤ 0.04%, Mn: 1.50-1.60%, P ≤ 0.015%, S ≤ 0.008%, Nb: 0.04-0.05%, Ti: 0.010-0.030%, with Mn / Si > 60, and the remainder being Fe and unavoidable inclusions.

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