Cobalt-containing high-strength cable steel and preparation method thereof

Abstract

The invention relates to cobalt-containing high-strength cable steel and a preparation method thereof, and belongs to the technical field of steel and iron material processing. Comprising the following chemical components in percentage by mass: 0.77%-1.8% of C, 0.1%-1.2% of Si, 0.2%-1.5% of Mn, less than or equal to 0.02% of S and the balance of Fe. The steel comprises the following components in percentage by weight: less than or equal to 0.02% of P, 0.1-2.5% of Co, less than or equal to 0.03% of Al and the balance of iron and The cobalt element is used for inhibiting precipitation of secondary cementite and martensite, so that the carbon content can be increased to 1.8%, the secondary cementite, martensite and other structure defects do not exist, breakage during straightening and drawing is avoided, the tensile strength of a wire rod reaches 1,300 MPa, and the tensile strength of a drawn steel wire reaches 2,200 MPa.

Description

Technical Field

[0001] The present invention relates to the technical field of steel material processing, and in particular to a cobalt-containing high-strength cable steel and a preparation method thereof. Background Art

[0002] Cables are extremely high-load-bearing components, typically composed of high-strength steel wires arranged in parallel or twisted into strands. They are widely used in large bridges, airports, heavy machinery, and other projects and equipment. To improve the load-bearing capacity of cables, the strength of cable wires has been increasing. For example, the previously commonly used 1860 MPa cable wire has been gradually replaced by 1960 MPa or 2000 MPa wire, and 2100 MPa wire has also been demonstrated in applications.

[0003] Currently, methods for improving the strength of cable steel wire primarily involve increasing the carbon and silicon content of the steel, adding small or trace amounts of elements such as Cr and V, or reducing the interlamellar spacing of pearlite by controlling the cooling system. Patent application number 202411244782.3 discloses a green and environmentally friendly 2300 MPa-grade steel strand wire rod and its production method. By increasing the carbon content to 0.95–1.05% and employing 0.025% V microalloying, the wire rod achieves a strength exceeding 1400 MPa for 14 mm and a strength exceeding 2300 MPa for drawn 7 mm wire. Patent 202410494289.0 describes a method for manufacturing 2200 MPa-grade, fatigue-resistant, and long-life ultra-high-strength prestressed steel strand. The carbon and silicon contents are 0.87–0.91% and 0.70–0.80%, respectively. V alloying is also performed, with a content of 0.04–0.05%. Patent application number 202210237747.3 discloses a spring steel wire rod for ultra-high-strength steel wire and its manufacturing method. The carbon and silicon contents are 0.35-0.8% and 1-3%, respectively. V alloying is also performed, with a content of 0.03-0.35%. Patent application number 202010216248.7 discloses a 2400 MPa-strength prestressed steel strand and its production process. The carbon and silicon contents are 0.88-1.02% and 0.1-1.3%, respectively. V alloying is also performed, with a content of 0.01-0.1%. The patent application number 201910447651.8 discloses a high-strength and high-toughness bridge cable steel and its preparation method. The carbon content is 0.22~0.28%, the Si content is 1.60~1.68%, the Mn content is 2.10~2.30%, the Al content is 1.0~1.5%, the Co content is 0.31~0.38%, and the V content is 0.75~0.85%. After controlled cooling, a carbon-free bainite structure is obtained with a strength greater than 2400 MPa. Analysis of cable literature shows that when the strength of the cable steel wire is greater than 2000 MPa, if the microstructure is controlled to be sorbite, the carbon content is basically controlled at 0.85~1.05%, the silicon content is often greater than 0.6%, and V is used for microalloying; if the microstructure is controlled to be carbon-free bainite, the carbon content can be reduced to about 0.25%, but the use of a large amount of alloying elements, such as high content of Si, Mn, V, Co, etc., will greatly increase the cost.

[0004] When cable steel wire is designed with high carbon, high silicon, and microalloyed components and controlled to have a troostite microstructure, the high carbon content and its segregation make secondary cementite and martensite more likely to appear in the microstructure. This can cause problems such as wire breakage during wire rod straightening and drawing, directly affecting the production process and product quality. The appearance of secondary cementite also limits the ability to further increase the carbon content of cable steel wire to improve the strength of wire rod and steel wire, restricting the development of higher-grade cable steel wire. In view of this, the present invention provides a cobalt-containing high-strength cable steel and a method for preparing the same. Summary of the Invention

[0005] When ultra-high-strength cable steel wire is designed with a high carbon content, undesirable structures such as secondary cementite and martensite are easily present in the microstructure, which can easily cause the wire rod to break during straightening and drawing, and also limit the improvement of steel wire strength by increasing the carbon content. The present invention provides a cobalt-containing high-strength cable steel and a preparation method thereof, which utilizes the cobalt element to inhibit the precipitation of secondary cementite and martensite, thereby increasing the carbon mass content to 1.8% without structural defects such as secondary cementite and martensite.

[0006] The technical solution of the present invention to solve the above technical problems is as follows: In a first aspect, a cobalt-containing high-strength cable steel comprises the following chemical composition by mass fraction: C: 0.77%-1.8%, Si: 0.1%-1.2%, Mn: 0.2%-1.5%, S≤0.02%; P≤0.02%, Co: 0.1-2.5%, Al≤0.03%, and the remainder being iron and unavoidable impurity elements.

[0007] The beneficial effects of the present invention are as follows: the present invention utilizes the cobalt element to inhibit the precipitation of secondary cementite and martensite, thereby increasing the carbon content to 1.8% without structural defects such as secondary cementite and martensite, thereby avoiding fracture during straightening and drawing, and the tensile strength of the steel wire after drawing reaches 2200 MPa.

[0008] On the basis of the above technical solution, the present invention can also be improved as follows.

[0009] Furthermore, the chemical composition includes the following mass fractions: C: 0.87%~1.2%, Si: 0.8%~1.0%, Mn: 0.7%~1.5%, S≤0.02%; P≤0.02%, Co: 0.2~1.0%, Al≤0.03%, and the rest are iron and unavoidable impurity elements.

[0010] Furthermore, the present invention also includes the following chemical composition in mass fraction: Cr: 0.1%~0.5%, Mo: 0.001%~0.5%, Ni≤0.3%, Cu≤0.3%, Re≤1.0%, B≤0.005%, and micro-alloying elements≤0.4%; the micro-alloying elements include Nb, V and Ti.

[0011] The beneficial effects of adopting the above further scheme are: by adding a small amount of Cr, the strength and corrosion resistance can be improved, a small amount of Mo and Co have a good synergistic strengthening effect, Ni, Cu and rare earth can improve the corrosion resistance, B is beneficial to improve the high temperature strength, and the microalloying elements Nb, V and Ti can play a second phase strengthening role.

[0012] Furthermore, the chemical composition includes the following by mass fraction: C: 1.8%, Si: 0.8%, Mn: 0.7%, S≤0.02%; P≤0.02%, Co: 1.0%, Al: 0.015%, and the rest are iron and inevitable impurity elements.

[0013] In a second aspect, a method for preparing cobalt-containing high-strength cable steel comprises the following steps: (1) The chemical components of the cobalt-containing high-strength cable steel are sequentially smelted, refined, continuously cast, and hot rolled to obtain a wire rod, wherein the sorbite content of the wire rod is ≥90%; (2) Drawing the wire rod into a steel wire; and performing a peeling process on the wire rod and / or the steel wire.

[0014] The beneficial effects of adopting the above scheme are: compared with the existing technology, the preparation process of the cobalt-containing high-strength cable steel described in the present invention has a wire rod tensile strength greater than 1250MPa, and no secondary cementite and martensite structure appear in the core of the wire rod during ordinary hot rolling, which simplifies the controlled cooling process; the added Co is also beneficial to improving the high-temperature strength of the steel. During the processing, the peeling operation is carried out, which can thin or eliminate the decarburized layer on the surface of the wire rod or steel wire, greatly improving the strength of the steel wire, and the strength increment can reach 80-100MPa, providing a method for the development of 2200MPa cable steel wire.

[0015] Furthermore, the diameter of the wire rod in step (1) is 5.0 mm to 16.0 mm.

[0016] Furthermore, in step (2), when the steel wire is used as a steel strand, the diameter of the steel wire is 0.5 mm to 5 mm; when the steel wire is used as a cable wire, the diameter of the steel wire is 4 mm to 8 mm; The specific method of the peeling treatment in step (2) is: first adopting a mechanical peeling method, and then adopting an electrolytic polishing method.

[0017] Among them, mechanical peeling is first performed using a peeling machine with a feed speed of 20 m / min~150 m / min, a tool material of cemented carbide, a tool pressure of 50 N~200 N, and cooling using emulsion or oil-based coolant; then electrolytic polishing is performed with a phosphoric acid-sulfuric acid system as the electrolyte, an electrolysis temperature of 50℃~80℃, a current density of 5 A / dm²~45 A / dm², and a wire rod moving speed of 1 m / min~4 m / min.

[0018] Furthermore, when the wire rod is subjected to a peeling process, the peeling depth is 20 μm to 150 μm; When the steel wire is subjected to a peeling process, the peeling depth is 20 μm to 100 μm.

[0019] The beneficial effect of adopting the above further solution is that after peeling, the decarburized layer of the wire rod and the steel wire can be completely or partially removed, thereby increasing the strength by 30 to 100 MPa.

[0020] Furthermore, the method further comprises the following steps: (3) hot-dip treating the steel wire to obtain a steel wire with a coating; the coating is a zinc coating, a zinc-aluminum coating or a zinc-aluminum-magnesium coating, and the thickness of the coating is 50 μm to 350 μm; (4) The coated steel wire is subjected to a stabilization treatment at a temperature of 360° C. to 390° C. for a treatment time of ≤5 min.

[0021] Furthermore, the method further comprises the following steps: (5) Aging treatment: The steel wire after hot-dip treatment or stabilization treatment is subjected to aging treatment to further improve the strength. The conditions of the aging treatment are: heating temperature of 120℃~300℃, and holding time of 30 min~120 min.

[0022] A method for preparing cobalt-containing high-strength cable steel comprises the following specific steps: Smelting: The blast furnace molten iron is pre-desulfurized by KR and then smelted in the converter. The slag is blocked and the steel is tapped when the temperature of the molten steel is 1600℃~1650℃. Argon blowing is used after tapping. Refining: The molten steel is first subjected to LF refining, followed by further degassing refining using RH or VD to reduce the N content of the molten steel to less than 50 ppm, the O content to less than 15 ppm, and the H content to less than 6 ppm; Continuous casting: The molten steel is sent to the continuous casting machine for protected continuous casting. During the process, electromagnetic stirring and dynamic reduction are used to reduce segregation. The billet is square or rectangular. If there are no defects during flaw detection, it will wait for subsequent rolling. If there are surface defects, the billet can be ground. Hot Rolling: Defect-free ingots are heated in a furnace and subsequently subjected to rough rolling, intermediate rolling, finishing rolling, and sheathing rolling to produce wire rod. The ingots are heated in three stages: preheating at 650-850°C, heating at 1000-1150°C, and soaking at 1050-1200°C. The total furnace heating time is 90-400 minutes. After the ingots are removed from the furnace, high-pressure water is used to remove phosphorus and surface scale. The starting rolling temperature is 980-1100°C, the finishing rolling temperature is ≥900°C, and the sheathing temperature is 750-900°C.

[0023] Cooling: After spinning, the wire rod is cooled by controlled cooling, which is achieved by air cooling or water mist cooling. After cooling, the wire rod is gathered to obtain a wire rod with a diameter of 5.0 mm to 16.0 mm. The wire rod can also be subjected to offline heat treatment, that is, the wire rod is reheated to austenitize and then quenched into lead liquid, molten salt liquid or aqueous solution.

[0024] Wire rod peeling: The purpose of peeling is to remove part of the decarburized layer, and the peeling depth is 20μm~150μm; Drawing: After degreasing, degreasing and phosphating, the wire rod is drawn into steel wire. The diameter of the steel wire depends on the final product. When used as steel strand, the diameter of the steel wire is 0.5 mm to 5 mm. When used as cable wire, the diameter of the steel wire is 4 mm to 8 mm. Wire peeling: The purpose of peeling is to remove part of the decarburized layer, with a peeling depth of 20μm~100μm; when the wire rod peeling can completely remove the decarburized layer, this step can be omitted.

[0025] Hot dip: hot dip process is used to complete the coating of galvanizing, galvanized aluminum or galvanized aluminum magnesium, with the coating thickness of 50μm~350μm; Stabilization treatment: Stabilization treatment is carried out in the range of 360℃~390℃, and the treatment time is ≤5min. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is a metallographic image of the Co-containing wire rod according to Example 6 of the present invention (surface decarburization); Figure 2 This is a metallographic image (core structure) of the Co-containing wire rod according to Example 6 of the present invention; Figure 3 This is the metallographic image of the Co steel wire of Example 6 (core structure); Figure 4 This is a diagram of the steel wire surface coating in Example 6 of the present invention. DETAILED DESCRIPTION

[0027] The principles and features of the present invention are described below. The examples are only used to explain the present invention and are not intended to limit the scope of the present invention. Where specific techniques or conditions are not specified in the examples, the techniques or conditions described in the literature in this field or the product instructions are used. Where the manufacturers of the reagents or instruments used are not specified, they are all conventional products that can be purchased through regular channels.

[0028] Example 1 A cobalt-containing high-strength cable steel includes the following chemical compositions expressed in mass fractions as shown in Table 1.

[0029] The method for preparing a cobalt-containing high-strength cable steel comprises the following specific steps: Smelting: The blast furnace molten iron is pre-desulfurized by KR and then smelted in the converter. The slag is blocked and the steel is tapped when the temperature of the molten steel is 1600℃~1650℃. Argon blowing is used after tapping. Refining: The molten steel is subjected to LF refining, and then further degassing refining is performed using RH or VD to reduce the N content of the molten steel to less than 50 ppm, the O content to less than 15 ppm, and the H content to less than 6 ppm; Continuous casting: The molten steel is sent to the continuous casting machine for protected continuous casting. During the process, electromagnetic stirring and dynamic reduction are used to reduce segregation. The billet is square or rectangular. If there are no defects during flaw detection, it will wait for subsequent rolling. If there are surface defects, the billet can be ground. Hot rolling: Defect-free ingots are heated in a heating furnace and then subjected to rough rolling, intermediate rolling, finishing rolling, and spinning rolling to obtain wire rods with a diameter of 5.0 mm to 16.0 mm. Wire rod peeling: The purpose of peeling is to remove part of the decarburized layer, and the peeling depth is 20μm~150μm; Drawing: After degreasing, degreasing and phosphating, the wire rod is drawn into steel wire. The diameter of the steel wire depends on the final product. When used as steel strand, the diameter of the steel wire is 0.5 mm to 5 mm. When used as cable wire, the diameter of the steel wire is 4 mm to 8 mm. Wire peeling: The purpose of peeling is to remove part of the decarburized layer, and the peeling depth is 20μm~100μm; Hot dip: The hot dip process is used to complete the coating of galvanizing, galvanized aluminum or galvanized aluminum magnesium, with a coating thickness of 50μm~350μm; Stabilization treatment: Stabilization treatment is carried out in the range of 360℃~390℃, and the treatment time is ≤5min.

[0030] Table 1 Chemical composition and mass content of cobalt-containing high-strength cable steel in Examples 1 to 6 Examples 2-4 The chemical compositions and mass fractions of Examples 2-4 are shown in Table 1, and the preparation methods are the same as those of Example 1.

[0031] Example 5 The chemical composition and mass fraction of Example 5 are shown in Table 1. The preparation method is the same as that of Example 1 except that only the wire rod is peeled and the steel wire is not peeled.

[0032] Example 6 The chemical composition and mass fraction of Example 6 are shown in Table 1. The preparation method is the same as that of Example 1 except that only the steel wire is peeled and the wire rod is not peeled. Figures 1 to 4 ).

[0033] Comparative Example 1 Compared with Example 6, except that Co is not contained, the rest is the same as Example 6.

[0034] Comparative Example 2 The chemical composition and mass fraction of Comparative Example 2 are the same as those of Example 6, and the preparation method is the same as that of Example 1 except that the steel wire is not peeled and the wire rod is not peeled.

[0035] Test example Testing standard adopted: YB / T 4264-2020.

[0036] Table 2 Strength of high strength steel wires of Examples 1 to 6 As shown in Table 2, compared with the comparative example, the steel wire obtained by the present invention has a higher troostite ratio, a higher number of torsions and a higher strength.

[0037] The steel wire obtained in Example 1 was subjected to aging treatment. The aging treatment conditions were as follows: heating temperature of 120° C. to 300° C., holding time of 30 min to 120 min. The results are shown in Table 3.

[0038] Table 3 Effect of aging treatment It can be seen from Table 3 that when the steel wire is heated in the range of 120~300℃ and kept warm for 30~120min, the strength increment of the steel wire is about 50~100MPa.

[0039] In summary, adding a small amount of Cr can improve strength and corrosion resistance, a small amount of Mo and Co has a good synergistic strengthening effect, Ni, Cu and rare earth can improve corrosion resistance, B is beneficial to improve high temperature strength, and microalloying elements Nb, V and Ti can play a second phase strengthening role.

[0040] Although the embodiments of the present invention have been shown and described above, it will be understood that the above embodiments are illustrative and are not to be construed as limitations on the present invention. A person skilled in the art may change, modify, replace and modify the above embodiments within the scope of the present invention.

Claims

1. A cobalt-containing high-strength cable steel, characterized in that: The chemical composition includes the following mass fractions: C: 0.77%~1.80%, Si: 0.1%~1.2%, Mn: 0.2%~1.5%, S≤0.02%; P≤0.02%, Co: 0.1~2.5%, Al≤0.03%, and the rest are iron and unavoidable impurity elements.

2. The cobalt-containing high-strength cable steel according to claim 1, characterized in that: Including the following chemical composition in mass fraction: C: 0.87%~1.2%, Si: 0.8%~1.0%, Mn: 0.7%~1.5%, S≤0.02%; P≤0.02%, Co: 0.2~1.0%, Al≤0.03%, and the rest are iron and unavoidable impurity elements.

3. The cobalt-containing high-strength cable steel according to claim 1, characterized in that: It also includes the following chemical composition in mass fraction: Cr: 0.1%~0.5%, Mo: 0.001%~0.5%, Ni≤0.3%, Cu≤0.3%, Re≤1.0%, B≤0.005%, micro-alloying elements≤0.4%; the micro-alloying elements include Nb, V and Ti.

4. The cobalt-containing high-strength cable steel according to claim 1, characterized in that: The chemical composition includes the following mass fractions: C: 1.8%, Si: 0.8%, Mn: 0.7%, S≤0.02%; P≤0.02%, Co: 1.0%, Al: 0.015%, and the rest are iron and unavoidable impurity elements.

5. A method for preparing a cobalt-containing high-strength cable steel according to any one of claims 1 to 4, characterized in that: The steps include: (1) The chemical components of the cobalt-containing high-strength cable steel are sequentially smelted, refined, continuously cast, and hot rolled to obtain a wire rod, wherein the sorbite content of the wire rod is ≥90%; (2) Drawing the wire rod into a steel wire; and performing a peeling process on the wire rod and / or the steel wire.

6. The method for preparing a cobalt-containing high-strength cable steel according to claim 5, characterized in that: The diameter of the wire rod in step (1) is 5.0 mm to 16.0 mm.

7. The method for preparing a cobalt-containing high-strength cable steel according to claim 5, characterized in that: In step (2), when the steel wire is used as a steel strand, the diameter of the steel wire is 0.5 mm to 5 mm; when the steel wire is used as a cable wire, the diameter of the steel wire is 4 mm to 8 mm; The specific method of the peeling treatment in step (2) is: first adopting a mechanical peeling method, and then adopting an electrolytic polishing method.

8. The method for preparing a cobalt-containing high-strength cable steel according to claim 7, characterized in that: When the wire rod is subjected to a peeling process, the peeling depth is 20 μm to 150 μm; When the steel wire is subjected to a peeling process, the peeling depth is 20 μm to 100 μm.

9. The method for preparing cobalt-containing high-strength cable steel according to claim 5, characterized in that: The following steps are also included: (3) hot-dip treating the steel wire to obtain a steel wire with a coating; the coating is a zinc coating, a zinc-aluminum coating or a zinc-aluminum-magnesium coating, and the thickness of the coating is 50 μm to 350 μm; (4) The coated steel wire is subjected to a stabilization treatment at a temperature of 360° C. to 390° C. for a treatment time of ≤5 min.

10. The method for preparing cobalt-containing high-strength cable steel according to claim 9, characterized in that: The following steps are also included: (5) Aging treatment: The steel wire after hot-dip treatment or stabilization treatment is subjected to aging treatment. The aging treatment conditions are: heating temperature of 120°C to 300°C, and holding time of 30 min to 120 min.

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