Method for manufacturing galvanized steel strands

Abstract

The present application relates to the technical field of metal material, and more particularly to a manufacturing method of galvanized steel strand, comprising the following steps: S1, using converter to smelt molten steel by double-slag method; S2, using ladle furnace to refine the molten steel; before the end of refining, soft stirring the molten steel for more than 20 minutes; S3, continuously casting the molten steel to form castings; the continuous casting is carried out by using cross-section of 160*160mm2, horizontal pulling speed casting, and superheating temperature is 20-30℃; S4, using step-by-step heat accumulating heating furnace to hot roll the castings to form wire rod, and using fan with air volume of 260000m3 / h to cool the hot rolled wire rod; S5, using pressure die to draw the wire rod; S6, immersing the wire rod into zinc liquid to galvanize, the galvanizing speed is 13-25m / min, and the temperature of zinc liquid is 445-460℃; S7, drawing the galvanized wire rod; S8, twisting the galvanized wire rod to form the galvanized steel strand.

Description

Technical Field

[0001] This invention relates to the field of metal materials technology, and in particular to a method for manufacturing galvanized steel strand. Background Technology

[0002] As a crucial component of cable-stayed bridges, stay cables connect the main towers and the main girder, transferring the load borne by the main girder to the main towers. Fatigue in stay cables has always been a key concern in cable-stayed bridge design. Using galvanized steel strands with higher tensile strength can reduce the number of strands used and the weight of the cables. However, under the same load, a reduction in the cable's cross-sectional area leads to an increase in the stress amplitude.

[0003] The commonly used strength grade for prestressed galvanized steel strand is 1860 MPa. The commonly used steel grade is SWRS82B, with a C content of 0.80–0.85 wt%, a Si content of 0.12–0.32 wt%, a Mn content of 0.60–0.90 wt%, a P and S content below 0.020 wt%, and a Cr content of 0.13–0.25 wt%. Ultra-high strength galvanized steel strand commonly uses steel grades such as 92Si, with a C content of 0.90–0.95 wt%, a Si content of 0.80–1.10 wt%, a Mn content of 0.40–0.50 wt%, and a Cr content of 0.20–0.30 wt%. If the number of fatigue tests is less than 2 million cycles when the fatigue stress amplitude is 350 MPa–400 MPa, it is considered unqualified.

[0004] The highest strength grade of prestressed galvanized steel strand in GB / T 33363-2016 is 1960MPa, the fatigue stress amplitude is 300MPa, and it can withstand 2 million fatigue tests without breaking.

[0005] The patent document with announcement number CN110924202A discloses a production method for 2160MPa high-strength galvanized steel strands for cable stays. In this patent document, the C mass fraction is increased and the contents of elements such as P, S and Cu are strictly controlled. Only harmful elements are controlled, and no measures are taken to address high stress amplitude fatigue performance.

[0006] Patent document CN113897544A discloses a rare earth high-strength, high-toughness prestressed steel strand wire rod and its smelting and rolling production method. The steel contains 0.70–0.90 wt% C, 0.10–0.30 wt% Si, 0.60–0.90 wt% Mn, ≤0.025 wt% P, ≤0.025 wt% S, 0.01%–0.07 wt% V, 0.15–0.35 wt% Cr, and 0.0020–0.0040 wt% Re, with the remainder being Fe and unavoidable impurities. The produced wire rod has a tensile strength below 2100 MPa and no measures are taken to address high-stress amplitude fatigue performance.

[0007] Therefore, how to improve the fatigue resistance of galvanized steel strands while ensuring that they have ultra-high tensile strength has become a technical problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0008] To address the issue that galvanized steel strands, despite possessing ultra-high tensile strength, fail to meet fatigue resistance standards, this invention provides a method for manufacturing galvanized steel strands.

[0009] To achieve the objective of this invention, a method for manufacturing galvanized steel strand is provided, characterized by comprising the following steps:

[0010] S1. Steel is refined in a converter using the double-slag method;

[0011] S2. Use a ladle refining furnace to refine the molten steel; before the refining is completed, gently stir the molten steel for more than 20 minutes;

[0012] S3. Continuous casting of molten steel to form castings; continuous casting uses 160×160mm... 2 The cross section is subjected to horizontal casting at high speed, with an overheating temperature of 20-30℃.

[0013] S4. Using a walking beam regenerative heating furnace, the castings are hot-rolled to form wire rods with a cross-sectional diameter of 13mm or 14mm, using an air volume of 260,000 m³ / h. 3 A fan with a capacity of / h cools the hot-rolled wire rod;

[0014] S5. Use pressure dies to draw the wire rod;

[0015] S6. Immerse the wire rod in the zinc bath for galvanizing at a speed of 13-25 m / min and at a temperature of 445-460℃.

[0016] S7. Draft the galvanized wire rod at a speed of less than 2 m / s;

[0017] S8. Twist the galvanized wire rod to form galvanized steel strand;

[0018] S5 includes the following steps:

[0019] The wire rods were pickled with hydrochloric acid at a concentration of 100–280 g / L for a duration of 25 min or longer.

[0020] The pickled wire rods are phosphated at a temperature of 60-70℃ for a duration of 7 minutes or more.

[0021] The required heating temperature for twisting is 360–380℃, the required tension is 0.40–0.50 Fm, the twisting speed is 40–80 m / min, and the twist pitch is 228–243 mm.

[0022] Wire rod, by weight percentage, includes the following elements:

[0023] C: 0.87–1.00 wt%; Si: 0.85–1.40 wt%; Mn: 0.30–0.90 wt%; Cr: 0.10–0.50 wt%; V: 0.01–0.10 wt%; Ni: 0.01–0.05 wt%; Re: 0.0005–0.008 wt%; Al: 0.01–0.08 wt%; balance Fe and unavoidable impurities.

[0024] In some specific embodiments, the wire rod also includes the following elements:

[0025] P and S, and the total content of P+S is ≤0.025wt%.

[0026] In some specific embodiments, the wire rod has a sorbite content of more than 85%, a lamellar spacing of less than 130 nm, a tensile strength of 1360~1450 MPa, and a shrinkage of area of ​​≥22%.

[0027] In some specific embodiments, the tensile strength of the galvanized steel strand is 2100-2200 MPa.

[0028] In some specific embodiments, the fatigue stress amplitude of the galvanized steel strand is 350-400 MPa, and it undergoes 2 million fatigue tests without breaking.

[0029] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0030] (1) Compared with the wire rod used for galvanized steel strand with a strength grade of 1860MPa, the content of C and Si elements in the wire rod is increased, thereby increasing the tensile strength of the wire rod and ensuring that the twisted galvanized steel strand has an ultra-high tensile strength of 2100MPa~2200MPa. Moreover, the Si element reduces the strength loss during galvanizing of the wire rod.

[0031] (2) By adding Ni and Re elements, the toughness of the wire rod used for galvanized steel strand is effectively increased, thereby improving the fatigue resistance of galvanized steel strand.

[0032] (3) The low-damage drawing process is adopted to reduce the damage to the surface of the wire rod during the drawing process, thereby improving the fatigue resistance of the galvanized steel strand.

[0033] (4) By optimizing the chemical composition elements and their content of wire rod, and combining them with low-damage drawing process, the galvanized steel strand produced has an ultra-high tensile strength of 2100MPa~2200MPa. When the fatigue stress amplitude is 350MPa~400MPa, the number of fatigue tests is 2 million and it does not break. Attached Figure Description

[0034] Figure 1 These are microstructure images of some specific embodiments of a galvanized steel strand wire rod according to the present invention;

[0035] Figure 2 These are microstructure images of some other specific embodiments of a galvanized steel strand wire rod according to the present invention;

[0036] Figure 3 These are microstructure images of some specific embodiments of a galvanized steel strand wire rod according to the present invention. Detailed Implementation

[0037] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention are described clearly and completely below. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0038] As described in the background section, galvanized steel strand has low tensile strength. Even if the tensile strength of galvanized steel strand can reach 2100~2200MPa, it cannot meet the fatigue test requirements of 350~400MPa fatigue stress amplitude.

[0039] To improve the above problems, refer to Figure 1 , Figure 2 and Figure 3In one aspect of this application, a galvanized steel strand wire rod is provided, comprising, by weight percentage, the following elements:

[0040] C: 0.87–1.00 wt%, Si: 0.85–1.40 wt%, Mn: 0.30–0.90 wt%, Cr: 0.10–0.50 wt%, V: 0.01–0.10 wt%, Ni: 0.01–0.05 wt%, Re: 0.0005–0.008 wt%, total P ≤ 0.015 wt%, total S ≤ 0.01 wt%, Al: 0.01–0.08 wt%, balance being Fe and unavoidable impurities.

[0041] Carbon (C) is an essential chemical element for ensuring the strength of wire rod, and its content determines the volume fraction of cementite in the sorbitic structure. Increasing the C content in the wire rod promotes the formation of more cementite lamellae, refines the sorbitic lamellar structure, and thus improves the deformation and work hardening properties of the wire rod, which is beneficial for enhancing the strength of the wire rod during subsequent processing. Therefore, the C content should be controlled above 0.87 wt%. However, it should be noted that as the C content increases, segregation control becomes more difficult during the early stages of smelting and continuous casting, especially the formation of grain boundary precipitation of network cementite, which drastically reduces the material's ductility and toughness, thereby affecting the fatigue performance of the galvanized steel strand. Therefore, the C content should not be too high.

[0042] In smelting, silicon (Si) is often added to molten steel as a deoxidizer, existing in solid solution form. It refines the interlamellar spacing of pearlite, significantly improving the strength of wire rod. Furthermore, during the cooling phase transformation of the wire rod, Si accumulates at the interface between the ferrite and cementite phases. After high-reduction-area drawing, during hot-dip galvanizing, this Si accumulation at the phase interface slows down the decomposition of cementite lamellars during large deformation, reducing the strength loss of the wire. To ensure the strength of the wire twisted into galvanized steel strand after galvanizing, the Si content needs to be higher than 0.9 wt%. However, excessive Si will cause the wire rod to become brittle and reduce its plasticity.

[0043] Manganese (Mn) is used as a deoxidizer and desulfurizer, exhibiting good deoxidation and desulfurization performance. Mn combines with sulfur (S) in molten steel to form MnS, thus reducing its harmful effects. Furthermore, Mn is also a strength-enhancing element, primarily playing a role in solid solution strengthening, resulting in alloy cementite with higher strength. Therefore, the Mn content should be higher than 0.30 wt%. However, excessively high Mn content can lead to low-temperature microstructures and reduce the drawing performance of wire rods; therefore, the Mn content should be less than or equal to 0.90 wt%.

[0044] Cr can improve the hardenability of steel and refine the pearlite lamellar spacing, thereby effectively improving the strength and plasticity of wire rod. However, in order to prevent the formation of abnormal martensitic structures and reduce the difficulty of microstructure control, the Cr content should be less than or equal to 0.50 wt%.

[0045] V can refine grains, reduce element segregation at grain boundaries, and form submicron V compounds with C and N elements. These compounds precipitate during phase transformation, effectively improving the strength and toughness of wire rods. Secondly, V can suppress the precipitation of network cementite at grain boundaries in high-carbon steel. However, excessive V content will lead to coarsening of carbonitrides and increase material costs. Therefore, the V content should not be too high.

[0046] Ni primarily increases hardenability, expands the austenite region, refines grains, and improves the toughness and fatigue resistance of steel. However, excessive Ni content significantly increases the brittleness and overheating sensitivity of the steel. Therefore, the Ni content should not be too high.

[0047] Re is used as a deoxidizer and desulfurizer. It has good deoxidation and desulfurization performance, can eliminate or weaken the effects of many harmful elements in steel, improve the quality of steel, and enhance the plasticity and toughness of steel.

[0048] P and S elements are harmful elements, which reduce the plasticity and toughness of wire rods and ultimately affect the fatigue performance of galvanized steel strands. Therefore, the lower the content, the better.

[0049] Al primarily functions as a deoxidizer and controls grain size. However, excessive Al content can lead to inclusions with poor plasticity, thus reducing fatigue performance. Therefore, the Al content should not be too high.

[0050] Overall, compared to the wire rod used for galvanized steel strand with a strength grade of 1860 MPa, the increased content of carbon (C) and silicon (Si) in the wire rod enhances its tensile strength, ensuring that the twisted galvanized steel strand possesses an ultra-high tensile strength of 2100 MPa to 2200 MPa. Furthermore, the addition of silicon reduces strength loss during galvanizing. The addition of nitrogen (Ni) and retinylamine (Re) effectively increases the toughness of the wire rod used for galvanized steel strand, thereby improving its fatigue resistance.

[0051] In some specific embodiments, the sorbite content of the galvanized steel strand wire rod is greater than 85%, the lamellar spacing is less than 130nm, the tensile strength is 1360~1450MPa, and the area shrinkage is ≥22%.

[0052] In another aspect of this application, a galvanized steel strand is provided, which is twisted from the wire rod provided in any of the above-described specific embodiments. The tensile strength of the galvanized steel strand is 2100–2200 MPa. The fatigue stress amplitude of the galvanized steel strand is 350–400 MPa, and it can withstand 2 million fatigue tests without fracture.

[0053] In another aspect of this application, a method for manufacturing galvanized steel strand is provided, comprising the following steps:

[0054] S1. The steel is refined in a converter using the double-slag method. In this step, molten iron is mixed with clean scrap steel to form molten steel. Using the double-slag method in a converter effectively reduces the phosphorus content in the molten steel. The converter employs a sliding plate slag-blocking system to prevent slag from falling into the converter, reducing the amount of inclusions at the source, which in turn helps improve the fatigue resistance of the resulting galvanized steel strand.

[0055] S2. The molten steel is refined using a ladle refining furnace. To ensure the purity of the molten steel, it is gently stirred for more than 20 minutes before the refining is completed, which further reduces the amount of inclusions in the molten steel.

[0056] S3. Continuous casting of molten steel to form castings. Continuous casting uses 160×160mm... 2 The casting process is carried out across the cross-section, with full protection throughout, and horizontal casting at high speed. The overheating temperature is 20-30℃. A combination of electromagnetic stirring in the crystallizer and end-stage electromagnetic stirring, along with strong secondary cooling in continuous casting, reduces the columnar crystal zone and increases the equiaxed crystal zone, thereby mitigating component segregation during solidification.

[0057] S4. Using a walking beam regenerative heating furnace, the castings are hot-rolled to form wire rods with a cross-sectional diameter of 13mm or 14mm, using an air volume of 260,000 m³ / h. 3 A fan operating at / h cools the hot-rolled wire rod. During rolling, a combination of finishing and sizing mills is used, and the cross-sectional diameter of the wire rod is measured online using an online diameter gauge to ensure timely and accurate dimensional accuracy, achieving Class C precision. A high-temperature initial rolling process improves carbon diffusion efficiency at the core casting area, further mitigating segregation at the core. High-temperature wire drawing increases the cooling gradient and reduces the cooling rate. The cooling air volume is 260,000 m³ / h. 3 The / h fan ensures the strength and metallographic structure of the wire rod.

[0058] S5. Using pressure dies to draw the wire rod achieves low-damage drawing. In this step, before drawing, the wire rod is first opened, and its surface is pickled with hydrochloric acid at a concentration of 100–280 g / L for at least 25 minutes to thoroughly remove iron oxide from the surface. Next, the pickled wire rod is phosphated at 60–70°C for at least 7 minutes to obtain a good lubricating carrier. Compared to traditional methods of surface treatment, pickling avoids the problem of incomplete cleaning at the overlaps of the wire rod, thus preventing uneven phosphate film. Pickling also keeps the wire rod in a loose state, improving the uniformity of phosphate. The phosphate process mainly involves chemical and electrochemical reactions. Temperature is one of the most critical factors affecting the chemical reaction. The temperature of the phosphate solution is automatically detected and controlled by an automatic adjustment loop, with temperature fluctuations within ±5°C to ensure a phosphate film weight of 8 g / m³. 2 That's all. Next, pressure dies are used to draw the wire rod. Compared to the traditional method of drawing wire rod using ordinary dies, pressure lubrication improves the adhesion of the lubricating powder, reduces damage to the wire rod and the dies used in production, reduces frictional heat generation, and helps improve the toughness of the wire rod. Reasonable control of the compression rate in each pass ensures that the wire rod has a reasonable reduction in surface area in each pass, guaranteeing both the strength of the wire rod and reasonable heat generation during drawing.

[0059] S6. Immerse the wire rod in molten zinc for galvanizing at a speed of 13–25 m / min. The temperature of the molten zinc is 445–460℃. The zinc coating amount is 200–300 g / m. 2 Before galvanizing, the drawn wire rod undergoes a series of processes including alkaline degreasing, hydrochloric acid pickling, fluxing, and drying. After galvanizing, the wire rod is wound up.

[0060] S7. The galvanized wire rod is drawn at a speed of less than 2 m / s to achieve finishing of the galvanized wire rod. This results in wire rods with a more precise cross-sectional diameter and better galvanizing effect.

[0061] S8. The galvanized wire rod is twisted to form galvanized steel strand. The required heating temperature for twisting is 360–380℃, the required tension is 0.40–0.50 Fm, the twisting speed is 40–80 m / min, and the lay length is 228–243 mm. It should be noted that Fm is the nominal breaking strength of the steel strand. By controlling the lay length at 228–243 mm, the galvanized steel strand achieves better fatigue resistance.

[0062] The following examples are used to illustrate the present invention, but are not intended to limit the scope of the invention.

[0063] The chemical composition and content of the galvanized steel strand wire rods used in Examples 1-5 and Comparative Example 1 are shown in Table 1 below:

[0064]

[0065] Table 1

[0066] The mechanical property test results of the galvanized steel strand wire rods in Examples 1-5 and Comparative Example 1 are shown in Table 2 below:

[0067] Mechanical properties Tensile strength / MPa Shrinkage / % Comparative Example 1 1400~1450 18~22 Example 1 1300~1350 22~27 Example 2 1360~1400 24~28 Example 3 1400~1450 22~27 Example 4 1400~1450 22~27 Example 5 1450~1510 24~28

[0068] Table 2

[0069] Based on the data in Tables 1 and 2, it can be seen that the tensile strength gradually increases with the increase of C, Si, Cr, and V content, reaching a maximum of 1450~1510 MPa. Adding an appropriate amount of Re can reduce the surface shrinkage of the wire rod by ≥22%.

[0070] The galvanized steel strands used in Examples 1-5 and Comparative Example 1 were pickled and phosphated under the test conditions specified in Table 3:

[0071] project Before pickling, was the wire rod opened? Pickling time / min Phosphating time / min Phosphating temperature / °C Comparative Example 1 no 20 5 50~70 Example 1 yes 25 7 60~70 Example 2 yes 25 7 60~70 Example 3 yes 25 7 60~70 Example 4 yes 30 10 60~70 Example 5 yes 25 7 60~70

[0072] Table 3

[0073] After phosphating the galvanized steel strands in Examples 1-5 and Comparative Example 1 with wire rod, the weight of the phosphating film was tested. The test results are shown in Table 4 below:

[0074] project Membrane weight / g / m2 Comparative Example 1 7.3 Example 1 8.2 Example 2 8.9 Example 3 9.2 Example 4 9.1 Example 5 9.5

[0075] Table 4

[0076] Based on the data in Tables 3 and 4, it can be seen that opening the wire rod before pickling, pickling time ≥25min, phosphating time ≥7min, and phosphating temperature 60~70℃ can ensure that the weight of the phosphating film is above 8.0g / m2.

[0077] Use the dies in Table 5 below to draw the phosphated wire rod:

[0078] project Types of wire drawing dies Comparative Example 1 Ordinary mold Example 1 Pressure mold Example 2 Pressure mold Example 3 Pressure mold Example 4 Pressure mold Example 4 Pressure mold

[0079] Table 5

[0080] The galvanized wire rods are drawn at the speeds shown in Table 6 below:

[0081] project Drawing (finishing) speed (m / s) Comparative Example 1 3 Example 1 1 Example 2 1.5 Example 3 2 Example 4 1.5 Example 5 1.5

[0082] Table 6

[0083] The galvanized wire rod is twisted using the twist pitch shown in Table 7 below:

[0084] project Twist pitch / mm Comparative Example 1 213 Example 1 228 Example 2 233 Example 3 236 Example 4 236 Example 5 243

[0085] Table 7

[0086] The performance test results of the steel strands made from galvanized steel strands twisted from wire rods in Examples 1-5 and Comparative Example 1 are shown in Table 8 below:

[0087] Specifications (mm) 15.2 - 1 × 7 Tensile strength / MPa Total elongation at maximum force / % relaxation / % Comparative Example 1 2172 4.5 1.81 Example 1 2101 5.8 1.47 Example 2 2109 6.0 1.53 Example 3 2145 5.5 1.78 Example 4 2161 5.5 1.80 Example 5 2197 5.7 1.92

[0088] Table 8

[0089] The high-stress amplitude fatigue test results of the steel strands made from galvanized steel strands in Examples 1-5 and Comparative Example 1 by twisting wire rod are shown in Table 9 below:

[0090]

[0091] Table 9

[0092] As shown in Tables 1-9, compared to the galvanized steel strand with a strength grade of 1860 MPa, the increased content of C and Si elements in the wire rod improves the tensile strength of the wire rod, thus ensuring that the twisted galvanized steel strand has an ultra-high tensile strength of 2100 MPa to 2200 MPa. Furthermore, Si reduces the strength loss during galvanizing. The addition of Ni and Re elements effectively increases the toughness of the wire rod used for galvanized steel strand, thereby improving its fatigue resistance. The use of a low-damage drawing process reduces the degree of damage to the wire rod surface during drawing, further improving the fatigue resistance of the galvanized steel strand. By optimizing the chemical composition and content of the wire rod, combined with the low-damage drawing process, the resulting galvanized steel strand, with an ultra-high tensile strength of 2100 MPa to 2200 MPa, can withstand 2 million fatigue cycles without fracture at a fatigue stress amplitude of 350 MPa to 400 MPa.

[0093] It should be noted that, under the composition and formulation specified in this invention, galvanized steel strand wire rods with relatively superior performance can be obtained, simultaneously meeting the requirements for strength grade and high fatigue stress amplitude tests, thus offering greater practicality. Furthermore, the preparation method of this invention yields even better results, therefore the invention is not limited to the preparation method described herein.

[0094] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for manufacturing galvanized steel strand, characterized in that, Includes the following steps: S1. Steel is refined in a converter using the double-slag method; S2. Refine the molten steel using a ladle refining furnace; before the refining is completed, gently stir the molten steel for at least 20 minutes. S3. The molten steel is continuously cast to form a casting; the continuous casting uses a 160×160mm casting machine. 2 The cross section is subjected to horizontal casting at high speed, with an overheating temperature of 20-30℃. S4. The casting is hot-rolled in a walking beam regenerative furnace to form wire rods with a cross-sectional diameter of 13mm or 14mm, using an air volume of 260,000 m³ / h. 3 A fan with a capacity of / h cools the hot-rolled wire rod; S5. The wire rod is drawn using a pressure die; S6. The wire rod is immersed in zinc liquid for galvanizing at a galvanizing speed of 13-25 m / min and at a zinc liquid temperature of 445-460℃. S7. The galvanized wire rod is drawn at a drawing speed of less than 2 m / s; S8. Twist the galvanized wire rod to form the galvanized steel strand; S5 includes the following steps: The wire rods were pickled with hydrochloric acid at a concentration of 100–280 g / L for a duration of 25 min or longer. The pickled wire rods are phosphated at a temperature of 60-70℃ for a duration of 7 minutes or more. The required heating temperature for twisting is 360–380℃, the required tension is 0.40–0.50 Fm, the twisting speed is 40–80 m / min, and the twist pitch is 228–243 mm. The wire rod, by weight percentage, includes the following elements: C: 0.87–1.00 wt%; Si: 0.85–1.40 wt%; Mn: 0.30–0.90 wt%; Cr: 0.10–0.50 wt%; V: 0.01–0.10 wt%; Ni: 0.01–0.05 wt%; Re: 0.0005–0.008 wt%; Al: 0.01–0.08 wt%; balance Fe and unavoidable impurities. The wire rod has a sorbite content of more than 85%, a lamellar spacing of less than 130 nm, a tensile strength of 1360-1450 MPa, and a shrinkage of area of ​​≥22%. The fatigue stress amplitude of the galvanized steel strand is 350-400 MPa, and it does not break after 2 million fatigue tests.

2. The method for manufacturing galvanized steel strand according to claim 1, characterized in that, The wire rod also includes the following elements: P and S, and the total content of P+S is ≤0.025wt%.

3. The method for manufacturing galvanized steel strand according to claim 1, characterized in that, The tensile strength of the galvanized steel strand is 2100-2200 MPa.

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