A high-strength weather-resistant bainitic wire rod and its preparation method

Abstract

Embodiments of the present application disclose a high-strength weather-resistant bainitic wire rod and a preparation method thereof, relating to the technical field of wire rod production, and capable of effectively improving the strength and weather resistance of the wire rod. The high-strength weather-resistant bainitic wire rod comprises the following components by mass percentage: C: 0.10 - 0.25%, Mn: 0.20 - 0.50%, Si: 0.20 - 0.50%, Cr: 2.00 - 2.80%, Ni: 0.15 - 0.40%, Cu: 0.15 - 0.40%, Al: 0.02 - 0.04%, Nb ≤ 0.06%, Mo ≤ 0.20%, P ≤ 0.03%; S ≤ 0.03%, and satisfying: Cr / (0.54Mo + 1.5Al) ≥ 1.5, and the balance is Fe and inevitable impurities. The present application is applicable to the production and manufacturing scenarios of wire rods or wire coils.

Description

Technical Field

[0001] This application relates to the technical field of wire production, and particularly relates to a high-strength weather-resistant bainite wire rod and a preparation method thereof. Background Art

[0002] At present, the variety structure of industrial wire rods for cold drawing is solidified, and it is difficult to break through the performance. Its matrix structure is generally ferrite, pearlite + ferrite, and all pearlite. Bainite and martensite are often strictly controlled as "abnormal structures" harmful to drawing.

[0003] However, on the one hand, although ferrite wire rods have certain weather resistance, their strength is far from sufficient and they cannot be widely used in major projects such as bridges and buildings. For example, Chinese Patent CN116770167B discloses a high-strength weather-resistant wire rod and production method for a photovoltaic bracket tie rod. By optimizing the design of the composition and the controlled cooling process, the strength and weather resistance of the wire rod are improved. However, its structure is mainly ferrite, and the tensile strength of the produced wire rod is less than 600 MPa, which cannot meet the production requirements of high-strength steel strands.

[0004] On the other hand, for all-pearlite wire rods, the strength is high. After drawing, the strength of the wire rod can be above 1860 MPa, and even can reach 2300 MPa. They are widely used in major projects such as bridges and large buildings, and high-end equipment such as automobiles and high-speed rails. However, their weather resistance and corrosion resistance are insufficient. For complex environments that require certain weather resistance and corrosion resistance, such as flexible photovoltaic brackets, prestressed steel wires for bridge cables, and steel ropes, the wire rods often need to be galvanized. Among them, the annual demand for steel ropes in China reaches 6 million tons, and about 1 / 3 of the steel ropes need to be galvanized. Due to the particularity of the galvanizing process, the galvanizing process often reduces the tensile strength of the steel wire by about 100 MPa. Therefore, the steel wire is required to have higher strength and plastic toughness. In addition, the galvanizing process also greatly increases the production cost of enterprises, generally increasing several thousand yuan per ton, and also increases the carbon emissions during the production process.

[0005] Therefore, it is urgent to break through the existing system composition of industrial wire rods and develop a new type of high-strength weather-resistant wire rod, so as to achieve performance breakthrough and cost reduction for wire rods applied in complex environments. At present, the production of domestic wire rods is still mainly carried out through the Stelmor air-cooling line. However, with the continuous improvement of the performance requirements for wire rods, for some high-carbon wire rods, the Stelmor air-cooling line has gradually been unable to meet the production requirements. Therefore, many domestic steel mills have started to seek the replacement and development of equipment. Among them, Angang, Xingcheng Special Steel, etc. have developed on-line water bath technology, which has greatly improved the cooling rate during controlled cooling; steel mills such as Qingdao Steel and Jinan Steel have developed off-line salt bath technology, and Qingdao Steel has also developed on-line salt bath technology, realizing the isothermal phase transformation of wire rods on-line. The advanced domestic on-line / off-line isothermal heat treatment technology and equipment for wire rods provide a basis for developing high-strength and weather-resistant bainite wire rods.

[0006] Based on this, it is necessary to develop a new type of high-strength weather-resistant wire rod and its production method, so that the wire rod not only has high strength and plasticity, but also has good weather resistance, so as to effectively solve the problems such as insufficient corrosion resistance of existing pearlite wire rods and realize the integration of structure and function and greening of wire rods. Summary of the Invention

[0007] In view of this, the present application provides a high-strength weather-resistant bainite wire rod and its preparation method, which can effectively improve the strength and weather resistance of the wire rod.

[0008] In the first aspect, an embodiment of the present application provides a high-strength weather-resistant bainite wire rod, which includes the following components by mass percentage: C: 0.10 - 0.25%, Mn: 0.20 - 0.50%, Si: 0.20 - 0.50%, Cr: 2.00 - 2.80%, Ni: 0.15 - 0.40%, Cu: 0.15 - 0.40%, Al: 0.02 - 0.04%, Nb ≤ 0.06%, Mo ≤ 0.20%, P ≤ 0.03%; S ≤ 0.03%, and it satisfies: Cr / (0.54Mo + 1.5Al) ≥ 1.5, and the rest are Fe and inevitable impurities.

[0009] In a specific implementation scheme, the high-strength weather-resistant bainite wire rod includes the following components by mass percentage: C: 0.12 - 0.20%, Mn: 0.20 - 0.30%, Si: 0.20 - 0.30%, Cr: 2.00 - 2.60%, Ni: 0.20 - 0.35%, Cu: 0.20 - 0.35%, Nb: 0.02 - 0.04%, Mo: 0.05 - 0.15%, Al: 0.02 - 0.03%.

[0010] In a specific embodiment, the tensile strength of the high-strength weather-resistant bainitic wire rod is 1100 MPa or more; and / or the reduction of area of the high-strength weather-resistant bainitic wire rod is 45% or more; and / or the tensile strength of the high-strength weather-resistant bainitic wire rod after drawing is 1900 MPa or more; and / or the weather resistance index of the high-strength weather-resistant bainitic wire rod is 7.5 or more.

[0011] In a specific embodiment, the microstructure of the high-strength weather-resistant bainitic wire rod comprises bainite and martensite, wherein the content of the bainite is 90% or more.

[0012] In a second aspect, an embodiment of the present application further provides a method for preparing a high-strength weather-resistant bainitic wire rod for preparing any one of the high-strength weather-resistant bainitic wire rods in the embodiments of the present application. The method for preparing the high-strength weather-resistant bainitic wire rod comprises the following steps:

[0013] S1. Melting and refining the raw materials, and continuously casting the raw materials by using a continuous caster to obtain a steel billet; wherein the raw materials comprise the following components by mass percentage: C: 0.10-0.25%, Mn: 0.20-0.50%, Si: 0.20-0.50%, Cr: 2.00-2.80%, Ni: 0.15-0.40%, Cu: 0.15-0.40%, Al: 0.02-0.04%, Nb≤0.06%, Mo≤0.20%, P≤0.03%; S≤0.03%, and satisfying: Cr / (0.54Mo + 1.5Al)≥1.5, and the rest are Fe and inevitable impurities;

[0014] S2. Feeding the steel billet into a heating furnace for heating;

[0015] S3. Removing phosphorus from the heated steel billet;

[0016] S4. Performing wire rod rolling on the dephosphorized steel billet by using a rough rolling mill, a medium rolling mill and a finishing rolling mill, and then performing wire laying by using a wire laying machine to obtain an initial wire rod;

[0017] S5. Performing isothermal heat treatment on the initial wire rod to obtain the high-strength weather-resistant bainitic wire rod.

[0018] In a specific embodiment, in the step S1, the casting speed of the continuous caster is 1.0-1.8 m / min.

[0019] In a specific embodiment, in the step S4, the temperature of the steel billet before rough rolling is controlled at 950°C-1050°C, and the temperature before finishing rolling is controlled at 850°C-950°C.

[0020] In a specific embodiment, in the step S4, the wire drawing temperature is controlled at 860°C to 950°C.

[0021] In a specific embodiment, in the isothermal heat treatment, the phase transformation temperature of austenite to bainite in the initial wire rod is controlled at 350 to 480°C, and the time of the isothermal heat treatment is less than or equal to 10 minutes.

[0022] In a specific embodiment, the isothermal heat treatment includes at least one of the following: on-line water bath, on-line salt bath, off-line salt bath, off-line lead bath.

[0023] The high-strength weather-resistant bainite wire rod and its preparation method provided by the embodiments of the present application, the high-strength weather-resistant bainite wire rod comprises the following components by mass percentage: C: 0.10 - 0.25%, Mn: 0.20 - 0.50%, Si: 0.20 - 0.50%, Cr: 2.00 - 2.80%, Ni: 0.15 - 0.40%, Cu: 0.15 - 0.40%, Al: 0.02 - 0.04%, Nb≤0.06%, Mo≤0.20%, P≤0.03%; S≤0.03%, and satisfy: Cr / (0.54Mo + 1.5Al)≥1.5, the rest are Fe and inevitable impurities, which can effectively improve the strength and weather resistance of the wire rod. Description of the Drawings

[0024] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments of the present application. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained according to these drawings.

[0025] Figure 1 It is a schematic scanning electron microscope diagram of the microstructure of the high-strength weather-resistant bainite wire rod prepared in Experimental Example 1 in the embodiment of the present application;

[0026] Figure 2 It is a schematic scanning electron microscope diagram of the microstructure of the high-strength weather-resistant bainite wire rod prepared in Experimental Example 2 in the embodiment of the present application;

[0027] Figure 3 It is a schematic scanning electron microscope diagram of the microstructure of the high-strength weather-resistant bainite wire rod prepared in Experimental Example 3 in the embodiment of the present application;

[0028] Figure 4 It is a schematic scanning electron microscope diagram of the microstructure of the high-strength weather-resistant bainite wire rod prepared in Experimental Example 4 in the embodiment of the present application;

[0029] Figure 5 Schematic SEM diagram of the microstructure of the high-strength weather-resistant bainitic wire rod prepared in Experimental Example 5 of this application embodiment;

[0030] Figure 6 Schematic SEM diagram of the microstructure of the high-strength weather-resistant bainitic wire rod prepared in Experimental Example 6 of this application embodiment;

[0031] Figure 7 Schematic SEM diagram of the microstructure of the high-strength weather-resistant bainitic wire rod prepared in Experimental Example 7 of this application embodiment;

[0032] Figure 8 Schematic SEM diagram of the microstructure of the high-strength weather-resistant bainitic wire rod prepared in Experimental Example 8 of this application embodiment;

[0033] Figure 9 Schematic SEM diagram of the microstructure of the high-strength weather-resistant bainitic wire rod prepared in Experimental Example 9 of this application embodiment;

[0034] Figure 10 Schematic diagram of the tensile curve of the high-strength weather-resistant bainitic wire rod prepared in Experimental Example 1 of this application embodiment;

[0035] Figure 11 Schematic diagram of the tensile curve of the high-strength weather-resistant bainitic wire rod after drawing prepared in Experimental Example 1 of this application embodiment;

[0036] Figure 12 Schematic SEM diagram of the microstructure of the high-strength weather-resistant bainitic wire rod after drawing prepared in Experimental Example 1 of this application embodiment. Detailed implementation manners

[0037] The embodiments of this application will be described in detail below with reference to the accompanying drawings.

[0038] It should be clear that the described embodiments are only a part of the embodiments of this application, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in this application without making creative efforts belong to the scope protected by this application.

[0039] At present, the variety structure of industrial wire rods for cold drawing is solidified and it is difficult to break through their performance. For example, although ferritic wire rods have certain weather resistance, their strength is far from sufficient; while fully pearlitic wire rods have high strength, but their weather resistance and corrosion resistance are insufficient, making it difficult to be applied in complex environments. To solve the above problems, on the one hand, embodiments of the present application provide a high-strength weather-resistant bainitic wire rod. The high-strength weather-resistant bainitic wire rod comprises the following components by mass percentage: C: 0.10 - 0.25%, Mn: 0.20 - 0.50%, Si: 0.20 - 0.50%, Cr: 2.00 - 2.80%, Ni: 0.15 - 0.40%, Cu: 0.15 - 0.40%, Al: 0.02 - 0.04%, Nb ≤ 0.06%, Mo ≤ 0.20%, P ≤ 0.03%; S ≤ 0.03%, and it satisfies: Cr / (0.54Mo + 1.5Al) ≥ 1.5, and the rest is Fe and inevitable impurities.

[0040] The high strength in this application means that the tensile strength is above 1100 MPa.

[0041] Carbon (C) element, as the most important element in steel, is also the most effective element to improve the strength of steel. Increasing the carbon content within a certain range can greatly improve the strength of steel: theoretically, for high-carbon steel, when the mass fraction of carbon increases by 0.1%, its tensile strength increases by about 30 - 40 MPa. When the carbon content is relatively high, austenite is more stable and atomic diffusion is difficult, which will lead to a slowdown in the bainite transformation rate, thereby inhibiting the growth of bainite. Therefore, in this embodiment, the mass percentage of C element is controlled at C: 0.10 - 0.25%.

[0042] Manganese (Mn) element can form fine carbides or nitrides precipitates with other alloying elements (such as Nb, V, Ti). These precipitates are dispersed in the bainite structure and play a pinning role on dislocations, further improving the strength of the steel. The Mn element can refine the bainite structure, thereby improving the toughness of the steel. However, with the increase of Mn element, the bainite transformation temperature will be reduced and the bainite phase transformation time will be prolonged. Therefore, in this embodiment, the mass percentage of Mn element is controlled at Mn: 0.20 - 0.50%.

[0043] Silicon (Si) element can cooperate with other alloying elements (such as Mn, Cr, etc.) to improve the strength of steel. For example, when used together with Mn, Si can enhance the solid solution strengthening effect of Mn. At the same time, Si can prevent the aggregation of impurity elements at grain boundaries, purify the grain boundaries, and improve the bonding strength of grain boundaries, thereby maintaining the toughness of the steel during the tempering process. However, a relatively high Si element will delay the bainite transformation. Therefore, in this embodiment, the mass percentage of Si element is controlled at Si: 0.20 - 0.50%.

[0044] The chromium (Cr) element has a solid solution strengthening effect in bainitic steel. For every 1% increase in the Cr content, the yield strength of bainitic steel can be increased by 40 - 60 MPa, and the Cr element can help refine the bainite structure. In addition, the addition of the Cr element can improve the weather resistance of bainitic steel. During the bainite transformation process, Cr combines with carbon elements, slowing down the diffusion rate of carbon in austenite. At the same time, the segregation of Cr atoms at the austenite grain boundaries also hinders the nucleation of bainite ferrite, thus prolonging the incubation period of bainite transformation and reducing the pearlite transformation temperature. Therefore, the mass percentage of the Cr element in this embodiment is controlled at Cr: 2.00 - 2.80%.

[0045] The nickel (Ni) element can act as a heterogeneous nucleation core during the bainitic steel process, thus increasing the nucleation rate. The addition of nickel element can effectively improve the morphology of bainitic steel and can increase the strength of bainitic steel through the solid solution strengthening mechanism. In addition, the nickel element can improve the corrosion resistance of bainitic steel. In a corrosive environment, nickel can form a dense oxide film on the surface of the steel. However, due to the high price of nickel element, excessive addition will lead to a high cost of bainitic steel. Therefore, the mass percentage of the Ni element in this embodiment is controlled at Ni: 0.15 - 0.40%.

[0046] During the cooling process of the copper (Cu) element in bainitic steel, copper atoms will precipitate in the form of fine and dispersed particles, which can effectively hinder the movement of dislocations and play a certain dispersion strengthening role. The copper element affects the nucleation and growth process of bainite. During the bainite transformation process, it promotes the formation of crystal nuclei and refines the bainite structure. In addition, the copper element can form a dense protective film on the surface of bainitic steel, increasing the weather resistance of bainitic steel. Therefore, the mass percentage of the Cu element in this embodiment is controlled at Cu: 0.15 - 0.40%.

[0047] The aluminum (Al) element can participate in the formation of a protective film on the surface of bainitic steel. In humid air, aluminum reacts with oxygen to form an aluminum oxide protective film, which can effectively improve the weather resistance of bainitic steel. However, a high aluminum content will form a large number of aluminum oxide inclusions in the steel, seriously affecting the mechanical properties of bainitic steel. Therefore, the mass percentage of the Al element in this embodiment is controlled at Al: 0.02 - 0.04%.

[0048] The niobium (Nb) element, as a strong carbide-forming element, can form fine carbides in steel, which can serve as effective nucleation sites for bainite phase transformation. During the bainite transformation period, due to the presence of compounds, it will pin the grain boundaries, thereby refining the bainite structure. However, the niobium element has a high cost, and excessive addition of niobium element in steel will greatly increase the cost. Therefore, the mass percentage of the Nb element in this embodiment is controlled at Nb ≤ 0.06%.

[0049] The molybdenum (Mo) element forms carbides in steel, such as Mo2C, etc. These carbides are distributed in bainite in a fine and dispersed state, improving the strength of bainite steel. Some molybdenum atoms dissolve in the matrix, playing a certain solid-solution strengthening role. The molybdenum element can effectively refine the bainite microstructure and improve the plasticity and toughness of bainite steel. However, a higher content of molybdenum element will delay bainite transformation and reduce the bainite transformation rate. In addition, due to the high price of molybdenum, it is not easy to add a large amount in steel. Therefore, in this embodiment, the mass percentage of Mo element is controlled at Mo≤0.20%.

[0050] Based on the analysis of the performance of the above elements, in order to ensure that sufficient bainite can be formed in the microstructure of the high-strength weather-resistant bainite wire rod, and the structural distribution and mechanical properties of bainite can reach the expected effects, this embodiment specifically limits that the mass percentage ratio of Cr, Mo, and Al satisfies: Cr / (0.54Mo + 1.5Al)≥1.5, so that the finally produced high-strength weather-resistant bainite wire rod meets the strength and weather resistance requirements.

[0051] Optionally, in an embodiment of the present application, the high-strength weather-resistant bainite wire rod includes the following components by mass percentage: C: 0.12~0.20%, Mn: 0.20~0.30%, Si: 0.20~0.30%, Cr: 2.00~2.60%, Ni: 0.20~0.35%, Cu: 0.20~0.35%, Nb: 0.02~0.04%, Mo: 0.05~0.15%, Al: 0.02~0.03%.

[0052] Optionally, in an embodiment of the present application, the tensile strength of the high-strength weather-resistant bainite wire rod is above 1100 MPa; and / or the reduction of area of the high-strength weather-resistant bainite wire rod is above 45%; and / or the tensile strength of the high-strength weather-resistant bainite wire rod after drawing is above 1900 MPa; and / or the weather resistance index of the high-strength weather-resistant bainite wire rod is above 7.5. Weather resistance refers to the durability of materials and the ability to resist environmental changes. For example, the antioxidant and corrosion resistance of materials in different natural environments such as the atmosphere, soil, water, and ocean. The weather resistance index of this embodiment is obtained according to the calculation formula of GB / T 4171 "Weather-resistant Structural Steel". The calculation of the weather resistance index I can be calculated by the following formula:

[0053] I = 26.01(Cu%) + 3.88(Ni%) + 1.29(Cr%) + 1.49(Si%) + 17.28(P%) - 7.29(Cu%)(Ni%) - 9.10(Ni%)(P%) - 33.9(Cu%) 2

[0054] Optionally, in an embodiment of the present application, the microstructure of the high-strength weather-resistant bainitic wire rod includes bainite and martensite, wherein the content of bainite is more than 90%.

[0055] The high-strength weather-resistant bainitic wire rod provided by the embodiment of the present application comprises the following components by mass percentage: C: 0.10-0.25%, Mn: 0.20-0.50%, Si: 0.20-0.50%, Cr: 2.00-2.80%, Ni: 0.15-0.40%, Cu: 0.15-0.40%, Al: 0.02-0.04%, Nb≤0.06%, Mo≤0.20%, P≤0.03%; S≤0.03%, and it satisfies: Cr / (0.54Mo + 1.5Al)≥1.5, and the rest is Fe and inevitable impurities, which can effectively improve the strength and weather resistance of the wire rod.

[0056] In a second aspect, the embodiment of the present application further provides a preparation method of a high-strength weather-resistant bainitic wire rod, which is used to prepare any high-strength weather-resistant bainitic wire rod in the embodiment of the present application, and can effectively improve the strength and weather resistance of the wire rod.

[0057] The preparation method of the high-strength weather-resistant bainitic wire rod includes the following steps:

[0058] S1. Melting and refining the raw materials, and continuous casting with a continuous caster to obtain a steel billet; wherein, the raw materials comprise the following components by mass percentage: C: 0.10-0.25%, Mn: 0.20-0.50%, Si: 0.20-0.50%, Cr: 2.00-2.80%, Ni: 0.15-0.40%, Cu: 0.15-0.40%, Al: 0.02-0.04%, Nb≤0.06%, Mo≤0.20%, P≤0.03%; S≤0.03%, and it satisfies: Cr / (0.54Mo + 1.5Al)≥1.5, and the rest is Fe and inevitable impurities.

[0059] S2. Feeding the steel billet into a heating furnace for heating.

[0060] S3. Removing phosphorus from the heated steel billet. During the phosphorus removal process, high-pressure water phosphorus removal can be specifically adopted.

[0061] S4. Rolling the phosphorus-removed steel billet with rough rolling, medium rolling and finishing mills to produce wire rods, and then passing through a laying head to lay the wire rods into coils to obtain initial wire rods. The phosphorus-removed steel billet is rolled by rough rolling, medium rolling and finishing mills to produce wire rods that meet the cross-sectional dimension requirements, and then the laying head lays the rolled wire rods into coils to obtain initial wire rods for easy collection.

[0062] S5. Isothermally heat treat the initial wire rod to obtain a high-strength weather-resistant bainite wire rod. The qualified finished products can be stacked in a heat preservation warehouse and await delivery and transportation. A wire rod generally refers to a coiled small-diameter round steel, and the diameter of the wire rod ranges from 5 to 19 mm, usually 6 to 9 mm. In this embodiment, the initial wire rod produced by the wire laying machine is further isothermally heat treated to finally obtain a high-strength weather-resistant bainite wire rod.

[0063] Optionally, in an embodiment of the present application, in step S1, the casting speed of the continuous casting machine is 1.0 - 1.8 m / min. The casting speed (abbreviated as the drawing speed) is expressed by the length of the steel billet drawn per minute by each strand of the continuous casting machine. The drawing speed is one of the important parameters of the continuous casting machine. After the cross-section of the steel billet is determined, the drawing speed determines the production capacity of the continuous casting machine. The greater the drawing speed, the greater the production capacity of the continuous casting machine, but it has a certain limit because the solidification speed of the molten steel limits the thickness of the billet shell when the steel billet exits the mold. The higher the drawing speed, the thinner the billet shell, which is prone to excessive deformation or even breakout, and at the same time, it will cause porosity and shrinkage in the internal part of the steel billet, deteriorating the quality. Therefore, in this embodiment, based on on-site experimental verification, the casting speed of the continuous casting machine is controlled at 1.0 - 1.8 m / min.

[0064] Optionally, in an embodiment of the present application, in step S4, the temperature of the steel billet before rough rolling is controlled at 950°C - 1050°C, and the temperature before finish rolling is controlled at 850°C - 950°C. Optionally, in an embodiment of the present application, in step S4, the wire laying temperature is controlled at 860°C - 950°C.

[0065] Optionally, in an embodiment of the present application, during isothermal heat treatment, the phase transformation temperature of austenite to bainite in the initial wire rod is controlled at 350 - 480°C, and the time of isothermal heat treatment is less than or equal to 10 minutes. This isothermal heat treatment method can ensure that the microstructure of the obtained high-strength weather-resistant bainite wire rod contains more than 90% bainite and a small amount of martensite. Optionally, in an embodiment of the present application, the isothermal heat treatment includes at least one of the following: on-line water bath, on-line salt bath, off-line salt bath, off-line lead bath. Through isothermal heat treatment, the metallographic structure inside the initial wire rod can undergo corresponding transformation, and the strength, hardness, and corrosion resistance are significantly improved, thereby obtaining a high-strength weather-resistant bainite wire rod.

[0066] The high-strength weather-resistant bainite wire rod obtained according to the above method has a strength of more than 1100 MPa, an area reduction of more than 45%, and a strength of up to 1900 MPa after drawing, meeting the production requirements for 1860 MPa grade steel strands, and having excellent weather resistance. According to the calculation formula in GB / T4171 - 2008 "Weather-resistant Structural Steel", its weather resistance index can reach more than 7.5.

[0067] To further illustrate the preparation method of the high-strength weather-resistant bainitic wire rod, the following specific comparative experiments are given in this embodiment. Among them, Experimental Examples 1-9 are high-strength weather-resistant bainitic wire rods prepared by the method of this application, and the comparative example is a wire rod prepared from 82B high-carbon steel material (carbon content is 0.82%).

[0068]

[0069] To further illustrate the performance of the high-strength weather-resistant bainitic wire rod prepared by this application through experimental comparison, a comparative experiment is carried out on Experimental Examples 1-9 and the comparative example. Experimental Examples 1-9 and the comparative example are isothermally heat-treated at the same temperature. The wire rods prepared in Experimental Examples 1-9 and the comparative example are made into metallographic samples with a height of 10 mm by wire cutting. After grinding, mechanical polishing, and vibration polishing of the surface of the metallographic samples, they are etched with 4% nitric acid alcohol, and then the microscopic tissue structure characteristic parameters are counted by a scanning electron microscope. The specific results are shown in Table 2. Among them, the microscopic structure of the wire rods prepared in Experimental Examples 1-9 contains bainite, and the microscopic structure of the wire rod prepared in the comparative example contains pearlite. The microstructural morphology of the wire rods prepared in Experimental Examples 1-9 is as Figures 1-9 shown.

[0070]

[0071] The wire rods prepared in Experimental Examples 1-9 and the comparative example are subjected to a tensile test using a hydraulic universal testing machine, and the tensile strength, yield strength, and reduction of area of the corresponding wire rods are recorded. The specific results are shown in Table 3. Among them, the tensile curve of Experimental Example 1 is as Figure 10 shown.

[0072]

[0073] The wire rods prepared in Experimental Examples 1-9 and the comparative example are used to calculate the corresponding weather resistance index I through the following weather resistance index formula:

[0074] I = 26.01(Cu%) + 3.88(Ni%) + 1.29(Cr%) + 1.49(Si%) + 17.28(P%) - 7.29(Cu%)(Ni%) - 9.10(Ni%)(P%) - 33.9(Cu%) 2

[0075] The specific results are shown in Table 4. Among them, the wire rods prepared in Experimental Examples 1-9 have excellent weather resistance, while the comparative example obviously does not have weather resistance.

[0076]

[0077] In addition, in this embodiment, taking Experimental Example 1 as an example, the Φ13mm wire rod prepared was drawn to Φ6.0mm, and standard tensile specimens were cut to detect the mechanical properties of the steel wire. The specific results are shown in Table 5, and its tensile curve is as Figure 11 shown.

[0078]

[0079] Taking Experimental Example 1 as an example, the Φ13mm wire rod was drawn to Φ6.0mm. Metallographic samples were cut by a wire cutting device. After grinding, mechanical polishing, and vibration polishing of the surface of the metallographic samples, 4% nitric acid alcohol was used for etching, and its microstructure is as Figure 12 shown. From the above experimental results, it can be seen that for the high-strength weather-resistant bainitic wire rod prepared in this embodiment, its microstructure and mechanical properties have achieved the expected effects and meet the use requirements of strength and weather resistance.

[0080] It should be noted that in this article, relational terms such as first and second are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variant thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements not only includes those elements, but also includes other elements not expressly listed, or also includes elements inherent to such process, method, article or device. Without further limitation, an element defined by the statement "including a..." does not exclude the existence of additional identical elements in the process, method, article or device including the said element.

[0081] Each embodiment in this specification is described in a related manner. The same or similar parts between each embodiment can be referred to each other, and the differences between each embodiment and other embodiments are emphasized.

[0082] In particular, for the device embodiment, since it is basically similar to the method embodiment, the description is relatively simple, and the relevant parts can refer to the partial description of the method embodiment.

[0083] The above is only the specific implementation manner of this application, but the protection scope of this application is not limited thereto. Any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed in this application should be covered by the protection scope of this application. Therefore, the protection scope of this application should be subject to the protection scope of the claims.

Claims

1. A high-strength weather-resistant bainite wire rod, characterized in that: The following components are included by mass percentage: C: 0.10~0.25%, Mn: 0.20~0.50%, Si: 0.20~0.50%, Cr: 2.00~2.80%, Ni: 0.15~0.40%, Cu: 0.15~0.40%, Al: 0.02~0.04%, Nb≤0.06%, Mo≤0.20%, P≤0.03%; S≤0.03%, and meets the following requirements: Cr / (0.54Mo+1.5Al)≥1.5, the rest is Fe and unavoidable impurities; The tensile strength of the high-strength weather-resistant bainite wire rod is above 1100MPa; the cross-sectional shrinkage of the high-strength weather-resistant bainite wire rod is above 45%; the tensile strength of the high-strength weather-resistant bainite wire rod after drawing is above 1900MPa; the weather resistance index of the high-strength weather-resistant bainite wire rod is above 7.5; The microstructure of the high-strength weather-resistant bainite wire rod comprises bainite and martensite, wherein the content of the bainite is greater than 90%.

2. The high-strength weather-resistant bainite wire rod according to claim 1, characterized in that: The components by mass percentage are as follows: C: 0.12~0.20%, Mn: 0.20~0.30%, Si: 0.20~0.30%, Cr: 2.00~2.60%, Ni: 0.20~0.35%, Cu: 0.20~0.35%, Nb: 0.02~0.04%, Mo: 0.05~0.15%, Al: 0.02~0.03%.

3. A method for preparing a high-strength weather-resistant bainite wire rod, for preparing the high-strength weather-resistant bainite wire rod according to any one of claims 1 to 2, characterized in that: The following steps are involved: S1. Smelting and refining the raw materials, and continuously casting them by a continuous casting machine to obtain a steel billet; wherein the raw materials include the following components by mass percentage: C: 0.10-0.25%, Mn: 0.20-0.50%, Si: 0.20-0.50%, Cr: 2.00-2.80%, Ni: 0.15-0.40%, Cu: 0.15-0.40%, Al: 0.02-0.04%, Nb≤0.06%, Mo≤0.20%, P≤0.03%; S≤0.03%, and satisfying: Cr / (0.54Mo+1.5Al)≥1.5, and the rest is Fe and unavoidable impurities; S2, sending the steel billet into a heating furnace for heating; S3, dephosphorizing the heated steel billet; S4, the steel billet after dephosphorization is subjected to wire rolling by rough rolling, intermediate rolling and finishing rolling mills, and then subjected to wire laying by a wire laying machine to produce an initial wire rod; S5. Isothermally heat treating the initial wire rod to obtain the high-strength weather-resistant bainite wire rod.

4. The method for preparing the high-strength weather-resistant bainite wire rod according to claim 3, characterized in that: In the step S1, the casting speed of the continuous casting machine is 1.0-1.8 m / min.

5. The method for preparing the high-strength weather-resistant bainite wire rod according to claim 3, characterized in that: In the step S4, the temperature of the steel billet before the rough rolling is controlled at 950°C to 1050°C, and the temperature of the steel billet before the finish rolling is controlled at 850°C to 950°C.

6. The method for preparing high-strength weather-resistant bainite wire rod according to claim 3, characterized in that: In the step S4, the spinning temperature is controlled at 860°C to 950°C.

7. The method for preparing high-strength weather-resistant bainite wire rod according to claim 3, characterized in that: During the isothermal heat treatment, the phase transition temperature of the initial wire rod from austenite to bainite is controlled at 350-480° C., and the time of the isothermal heat treatment is less than or equal to 10 minutes.

8. The method for preparing high-strength weather-resistant bainite wire rod according to claim 3, characterized in that: The isothermal heat treatment comprises at least one of the following: an online water bath, an online salt bath, an offline salt bath, and an offline lead bath.

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