A 2300MPa grade high-strength steel strand with good corrosion resistance and a production method thereof, and a 2300MPa grade high-strength steel strand with good corrosion resistance

Abstract

The present invention discloses a 2300MPa grade high-strength steel strand with good corrosion resistance, a production method thereof, and a 2300MPa grade high-strength steel strand with good corrosion resistance. The main chemical components and weight percentages of the steel strand are: C 0.85% to 0.95%, Mn 0.56% to 0.66%, Cr 0.10% to 0.18%, Nb 0.01% to 0.05%, Ni 0.01% to 0.03%, Cu 0.01% to 0.03%, Si 0.90%~1.03%; among them, 1.10≤Si+10*Nb≤1.45; 0.28≤1.2*[Cr]+1.8*[Ni]+5.0*[Cu]+2.0*[Nb]≤0.58, it has high strength, high toughness and corrosion resistance. The tensile strength of the steel strand produced by it is ≥2330MPa, and the stress corrosion performance is ≥5h.

Description

Technical Field

[0001] The present invention belongs to the technical field of steel strands, and in particular relates to a 2300MPa grade high-strength steel strand with good corrosion resistance, a production method thereof, and a 2300MPa grade high-strength steel strand with good corrosion resistance. Background Art

[0002] High-strength prestressed steel strand is a type of product widely used in the metal products industry. It has the characteristics of high tensile strength, good elongation, low relaxation value, small stress loss and excellent fatigue resistance. Due to its unique properties, so far no more ideal product has been found to completely or in one field to replace high-strength prestressed steel strand. It has become an indispensable component or material and is widely used in railways, highways, cross-sea bridges, large buildings, water conservancy and other fields.

[0003] my country is currently in a critical period of rapid construction, and the demand for high-strength prestressed steel strand is rapidly increasing. Demand for public facilities such as highways and railways is increasing, and is gradually expanding into remote mountainous areas. Complex geological conditions in some areas urgently require the construction of longer-span railways and bridges, and these areas also place higher demands on high strength and lightweight construction. As a key raw material used in these large-scale construction projects, the cost and quality of steel strand are directly related to the construction cost and safety of the buildings.

[0004] Currently, the prestressed concrete steel strand commonly used in domestic railway and bridge construction is 1860MPa grade steel strand. The highest strength grade specified in this standard is only 1960MPa. Improving the strength of steel strands can significantly reduce costs. For example, replacing 1860MPa grade steel strands with 1960MPa grade high-strength steel strands can save approximately 20% of strand usage. Therefore, larger spans, lighter weight, higher strength, and safer bridges will become an inevitable trend in future industry development. Existing steel strands all use a C-Si-Mn composition system. Increasing the C, Si, and Mn content can improve strength, but this can easily lead to the formation of network cementite and core martensite, which severely degrades the material's performance. In particular, the plasticity and toughness decrease dramatically, making it unable to withstand repeated bending and torsion during processing. Furthermore, the fatigue strength also fails to meet user requirements.

[0005] Chinese patent CN115160929A discloses a corrosion-resistant steel strand and its preparation method. The steel strand is made by pickling and drawing high-carbon steel, then plating it, then treating it with an anti-corrosion coating, and finally twisting and insulating it. When the anti-corrosion coating is applied to the surface of the pretreated carbon steel wire, the siloxy groups on the side chains of the anti-corrosion coating molecules can be grafted with the hydroxyl groups on the surface of the nickel-phosphorus coating, and then cooperate with the side chain chitosan molecules to greatly enhance the adsorption capacity of the coating. At the same time, the side chain reinforcing particles can form a dense shielding layer on the surface of the coating, so that the coating forms a three-layer protection of chitosan layer-resin layer-shielding layer, which effectively prevents corrosive substances from contacting the steel strand. At the same time, the anti-corrosion coating does not use graphene or carbon nanotube materials as fillers, which reduces the preparation cost of the coating. However, this method improves corrosion resistance by coating during the stranding process, which is costly and has limited improvement in corrosion resistance.

[0006] Chinese patent CN110819899A discloses a 2100MPa grade marine steel wire rope steel and a production method. The 2100MPa grade marine steel wire rope steel includes the following chemical components in weight percentage: C 0.95% to 1.10%, Si 0.10% to 0.50%, Mn 0.60% to 1.20%, Cr 0.10% to 0.50%, Nb 0.02% to 0.10%, Ni 0.01% to 0.50%, Al≤0.005%, P≤0.015%, S≤0.015%, O≤0.0015%, N≤0.006%, and the rest are Fe and unavoidable impurity elements. The invention utilizes a specific chemical composition and wire rod production process to produce hot-rolled wire rod with excellent mechanical properties and a high sorbitization rate. The resulting steel wire rope achieves strength exceeding 2100 MPa, along with good torsional and bending properties, making it suitable for producing 2100 MPa-grade high-strength marine steel wire rope. However, this material can only be used to produce 2100 MPa-grade high-strength steel wire rope products and lacks corrosion resistance, failing to meet the requirements for corrosion resistance in corrosive environments.

[0007] Chinese patent CN 113897544 A discloses a rare earth high-strength and high-toughness prestressed steel strand wire rod and its smelting and rolling production method. The chemical composition by mass percentage is: C: 0.70% to 0.90%, Si: 0.10% to 0.30%, Mn: 0.60% to 0.90%, P≤0.025%, S≤0.025%, V: 0.01% to 0.07%, Cr: 0.15% to 0.35%, Re: 0.0020% to 0.0040%, and the remainder is Fe and unavoidable impurities. The wire rod of this invention boasts a strength level exceeding 1570 MPa. The addition of rare earth elements La and Ce, combined with a high-carbon drawing process, optimizes and improves the centerline segregation of the ingot. The hot-rolled wire rod exhibits excellent initial performance, with improved plasticity indicators such as elongation and reduction of area. This eliminates a distinct ductile-brittle transition temperature range for high-carbon steel, enhancing the overall performance of steel strands. However, this invention requires the addition of rare earth elements to enhance strength and toughness, which is costly and challenging. Summary of the Invention

[0008] In order to solve the above technical problems, the present invention provides a 2300MPa grade high-strength steel strand with good corrosion resistance and a production method thereof. The steel strand is mainly micro-alloyed with Cr, Nb, Ni, Cu, etc., without the need to add precious alloy elements, with low cost, high strength, high toughness and corrosion resistance. The steel strand produced by the steel strand has a tensile strength of ≥2330MPa, good corrosion resistance, and stress corrosion resistance of ≥5h.

[0009] The present invention also provides a 2300MPa grade ultra-high strength steel strand, which is obtained by drawing and stranding the steel for the 2300MPa grade high strength steel strand with good corrosion resistance described in the present invention.

[0010] The technical solution adopted by the present invention is as follows:

[0011] The present invention provides a 2300MPa grade high-strength steel strand with good corrosion resistance. The chemical composition and weight percentage of the 2300MPa grade high-strength steel strand with good corrosion resistance are as follows: C 0.85%-0.95%, Mn 0.56%-0.66%, Cr 0.10%-0.18%, Nb 0.01%-0.05%, Ni 0.01%-0.03%, Cu 0.01%-0.03%, Si 0.90%-1.03%, Alt≤0.005%, P≤0.010%, S≤0.010%, O≤0.0020%, N≤0.0065%, and the remainder is Fe and other inevitable impurities; the remainder is Fe and inevitable impurity elements;

[0012] Wherein, X=Si+10*Nb, 1.10≤X≤1.45;

[0013] Y=1.2*[Cr]+1.8*[Ni]+5.0*[Cu]+2.0*[Nb], 0.28≤Y≤0.58; in the formula, the value of each chemical component is calculated according to the content of each chemical component in the steel × 100.

[0014] The metallographic structure of the 2300MPa grade high-strength steel strand hot-rolled wire rod with good corrosion resistance is sorbite, and the sorbitization rate is ≥95%. After the hot-rolled wire rod is treated in a salt bath, the sorbite lamella spacing is ≤70um, the tensile strength Rm is ≥1450MPa, and the cross-sectional shrinkage Z is ≥42%.

[0015] The finished steel strand made of the 2300MPa grade high-strength steel strand with good corrosion resistance has a tensile strength of ≥2330MPa and a stress corrosion resistance of ≥5h.

[0016] The present invention also provides a method for producing the 2300MPa grade high-strength steel strand with good corrosion resistance, which comprises the following steps: smelting → refining → continuous casting → high-strength wire rolling → controlled cooling → wire rod production.

[0017] In the continuous casting step, electromagnetic stirring of the crystallizer and electromagnetic stirring of the end are adopted, and soft reduction is performed, with a reduction amount of 13 to 17 mm, superheating is controlled at 20 to 40° C., and a casting speed of 1.9 to 2.6 mm / min.

[0018] Continuously cast into 160mm*160mm or 150mm*150mm small square billets.

[0019] In the high-speed wire rolling step, first, soaking is carried out at 1200-1250°C for 80-120 minutes, and then rolling is carried out, with the starting rolling temperature being 950-1000°C, the finishing rolling temperature being 870-900°C, and the spinning temperature being 850-890°C.

[0020] In the controlled cooling step, the wire rod is first cooled to 650-680°C at a cooling rate of 7-11°C / s, and a microstructure with a fine lamellar spacing and a high sorbite ratio is obtained through rapid cooling. The wire rod is then cooled to 580-620°C at a cooling rate of 7-9°C / s, and is held for 10-15 seconds to undergo an isothermal phase transformation. Finally, the wire rod is cooled to room temperature at a cooling rate of ≤3°C / s to avoid the formation of central martensite structure. That is, after the phase transformation, the fan is turned off and the cover is opened to cool the wire rod to room temperature at a cooling rate of ≤3°C / s. The three-stage cooling method effectively controls the transformation speed of the wire rod from the austenite region to the phase transformation point and the entire phase transformation range, making the phase transformation process smooth and the phase transformation time increased, which is beneficial to increasing the sorbite content of the wire rod and reducing the formation of abnormal structures. It is also beneficial to control the final cooling temperature and final cooling rate, reducing or eliminating the formation of abnormal structures.

[0021] The present invention also provides a 2300MPa grade high-strength steel strand with good corrosion resistance, which is obtained by salt bath treatment, drawing, and stranding the 2300MPa grade high-strength steel strand with good corrosion resistance described in the present invention.

[0022] Furthermore, the specific process of the salt bath treatment is: uncoiling → straightening → induction quenching → salt bath → water washing → drying; wherein the induction quenching is divided into three stages, first preheating at 740-760°C, austenitizing treatment at 930-950°C for 25-35s, and the salt bath isothermal temperature is 540-560°C for 35-45s; the wire rod travel speed is 10-14m / min.

[0023] The central steel wire diameter of the steel strand is Φ5.10-5.25 mm, the side wire diameter is Φ5.04-5.06 mm, and the finished steel strand is 15.40-15.15 mm thick.

[0024] The chemical composition control and function of the 2300MPa grade high-strength steel strand with good corrosion resistance provided by the present invention are as follows:

[0025] C: The C element is essential for achieving high strength and hardness. To achieve the high strength required for high-strength steel strand, the C content must be above 0.85%. However, excessive C content increases carbon segregation, which can lead to the formation of abnormal structures such as central martensite and network cementite, which is detrimental to drawing performance. Therefore, the C content should be controlled between 0.85% and 0.95%.

[0026] Mn: Mn is an effective element for deoxidation and desulfurization, and can also improve the hardenability and strength of steel. However, excessive Mn content can easily cause segregation, resulting in the formation of harmful structures such as central martensite and network cementite, which deteriorates the toughness of the steel. Therefore, the Mn content is controlled between 0.56% and 0.66%.

[0027] Cr: It is a strong carbide-forming element and exists in the cementite lamellae to form alloy cementite, thereby improving the strength. At the same time, the addition of Cr shifts the continuous cooling transformation curve of steel to the right, thereby refining the interlamellar spacing. At the same time, Cr can also reduce the activity of C and reduce the decarburization tendency of the steel surface during heating, rolling and heat treatment. It is useful for obtaining high fatigue resistance and improving corrosion resistance. Therefore, the Cr content is controlled at 0.10% to 0.18%.

[0028] Nb: Nb significantly refines grains, which not only increases the strength and toughness of steel but also improves its low-temperature properties. Nb is also a strong carbide-forming element. Its precipitation at austenite grain boundaries during the initial phase transformation can reduce the carbon content at the grain boundaries, effectively inhibiting the formation of network cementite. Furthermore, Nb (C, N) precipitated in ferrite can act as precipitation strengthening. Furthermore, due to the finer grains, it can also improve corrosion resistance. Excessive V content increases costs, so the Nb content can be controlled within the range of 0.01% to 0.05%.

[0029] Ni: Ni stabilizes austenite, enhances the hardenability of steel, improves low-temperature toughness, and reduces the notch sensitivity of fasteners. The addition of Ni also improves the rust layer structure, increasing density and adhesion to the steel surface, enhancing the steel's corrosion resistance, and inhibiting hydrogen adsorption, which in turn improves delayed fracture resistance. The Ni content should be controlled between 0.01% and 0.03%.

[0030] Cu: The element Cu significantly improves the corrosion resistance of steel. The cathodic contact between the steel and the secondary Cu deposited on the surface promotes anodization and the formation of a highly protective rust layer. Copper also alters the hygroscopicity of the rust layer, thereby increasing the critical humidity. However, excessive Cu content can reduce the steel's high-temperature plasticity and increase the risk of cracking during hot working. Therefore, the Cu content should be controlled between 0.01% and 0.03%.

[0031] Si: As a solid solution hardening element, Si can significantly increase the strength of high carbon steel. Increasing the Si content in high carbon steel wire rods helps reduce the segregation of carbon atoms in the ferrite lamellae, reducing the formation of central martensite and network cementite. Si can also significantly delay the exothermic peak of the steel wire to a higher temperature range, thereby improving the thermal stability of the steel wire. Therefore, the Si content should be controlled between 0.90% and 1.03%.

[0032] Alt: As a strong deoxidizing element, Alt easily forms immutable Al2O3-type brittle inclusions with oxygen. Higher Alt content leads to larger and more brittle inclusions. Larger brittle inclusions, in particular, can cause drawing fractures, impacting serviceability, and significantly reducing fatigue life. Therefore, to control inclusion morphology and size, the Alt content is strictly controlled to ≤0.005%.

[0033] S and P: Impurity elements such as S and P segregate at grain boundaries, significantly reducing delayed fracture resistance. P can form microsegregations during solidification and subsequently segregate at grain boundaries during austenitization, significantly increasing the steel's brittleness and delayed fracture sensitivity. S forms MnS inclusions and segregates at grain boundaries, further increasing the steel's delayed fracture sensitivity. Therefore, the P and S contents should be controlled within the range of P ≤ 0.010% and S ≤ 0.010%.

[0034] Oxygen and nitrogen: Oxygen forms various oxide inclusions in steel. Under stress, these inclusions easily cause stress concentration, leading to the initiation of microcracks and deteriorating the steel's mechanical properties, especially toughness and fatigue resistance. Therefore, measures must be taken in metallurgical production to minimize its content, controlling it to 0.0020% or less. Nitrogen precipitates as Fe₄N in steel, which diffuses slowly, causing aging. Nitrogen also reduces the steel's cold working properties, so the nitrogen content should be controlled to 0.0065% or less.

[0035] To achieve high-strength steel strands with good ductility and toughness, controlling the formation of central martensite and network cementite is crucial. Therefore, Si and Nb are added. Si promotes the precipitation of niobium carbonitride in ferrite. The combined addition of Si and Nb reduces the network cementite in the core of the wire rod, ensuring a level of ≤1.0. It also alters the morphology of cementite precipitated at grain boundaries, preventing a networked distribution. Adding Si offers the advantage of lower cost compared to adding Nb, but adding large amounts of Si can lead to adverse consequences such as increased decarburization thickness and graphitization. Therefore, the chemical composition must satisfy the requirement of 1.10≤Si+10*Nb≤1.45.

[0036] To achieve good corrosion resistance, Cr, Ni, Cu, and Nb are micro-alloyed to form a dense oxide film on the surface. Cu, in particular, facilitates the conversion of γ-Fe2O3 / γ-FeOOH in the rust layer to α-FeOOH, making the rust layer denser. The chemical composition must meet the requirements of 0.28≤1.2*[Cr]+1.8*[Ni]+5.0*[Cu]+2.0*[Nb]≤0.58. A B value that is too small cannot guarantee corrosion resistance, while a value that is too large cannot guarantee strength and ductility.

[0037] In order to reduce the cost, the present invention adopts the "one-fire material" process, that is, after continuous casting, the billet is heated at 1200-1250℃ for 80-120 minutes and then high-speed wire rolling is carried out to achieve Wire rod is rolled to produce hot-rolled wire rod with excellent corrosion resistance, producing 2300MPa-grade high-strength steel strand. The sorbitization ratio of the hot-rolled wire rod is ≥95%. To ensure material uniformity, the hot-rolled wire rod is treated in an offline salt bath. After salt bath treatment, the sorbite interlamellar spacing of the hot-rolled wire rod is ≤70μm, the network cementite is grade 0, the central martensite is grade 0, the tensile strength Rm is ≥1450MPa, and the reduction of area Z is ≥42%. After drawing and stranding, this hot-rolled wire rod can be used to produce 2300MPa-grade ultra-high-strength steel strand, which also exhibits excellent corrosion resistance and stress corrosion corrosion resistance of ≥5h.

[0038] Compared with the prior art, the present invention has the following beneficial effects:

[0039] The present invention uses microalloying of Cr, Nb, Ni, Cu, etc., without adding precious alloy elements, with low cost, high strength and high toughness. The steel strand produced by the present invention has a tensile strength of ≥2330MPa, good corrosion resistance, and stress corrosion resistance of ≥5h.

[0040] The present invention adopts a three-stage cooling method after high-speed wire rolling, which effectively controls the transformation speed of the wire rod from the austenite region to the phase transformation point and the entire phase transformation range, making the phase transformation process smooth and the phase transformation time increased, which is beneficial to increasing the sorbite content of the wire rod and reducing the generation of abnormal tissues, and is beneficial to controlling the final cooling temperature and final cooling speed, reducing or eliminating the generation of abnormal tissues. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 This is a schematic diagram of the spacing between sorbite lamellae in the hot-rolled wire rod of the steel strand in Example 1.

[0042] The present invention provides a 2300MPa grade high-strength steel strand with good corrosion resistance. The chemical composition and weight percentage of the 2300MPa grade high-strength steel strand with good corrosion resistance are as follows: C 0.85%-0.95%, Mn 0.56%-0.66%, Cr 0.10%-0.18%, Nb 0.01%-0.05%, Ni 0.01%-0.03%, Cu 0.01%-0.03%, Si 0.90%-1.03%, Alt≤0.005%, P≤0.010%, S≤0.010%, O≤0.0020%, N≤0.0065%, and the remainder is Fe and other inevitable impurities; the remainder is Fe and inevitable impurity elements;

[0043] Wherein, X=Si+10*Nb, 1.10≤X≤1.45;

[0044] Y=1.2*[Cr]+1.8*[Ni]+5.0*[Cu]+2.0*[Nb], 0.28≤Y≤0.58. In the formula, the value of each chemical component is calculated according to the content of each chemical component in the steel × 100.

[0045] The production method of the 2300MPa grade high-strength steel strand with good corrosion resistance comprises the following steps: smelting→refining→continuous casting→high-strength wire rolling→controlled cooling→wire rod production.

[0046] The smelting adopts converter smelting, and the end point C is controlled at ≤0.10%, and P≤0.010%; slag is blocked for tapping, and refined slag and lime are added when about 1 / 5 of the molten steel is tapped. When about 1 / 3 of the molten steel is tapped, deoxidizer and alloy are added in the following order: silicon balls → silicon manganese → high carbon ferromanganese → high carbon ferrochrome → ferrovanadium → recarburizer → slag, and aluminum particles are not allowed to be thrown on the slag surface.

[0047] During the LF furnace refining process, argon is blown from the ladle bottom throughout the entire process, with the argon flow rate set to prevent molten steel from splashing out of the ladle. To ensure the absence of Al2O3-based hard inclusions, a Si deoxidation process is employed. The use of Al-containing alloys is strictly controlled, and a low-alkalinity slag system is employed. Silicon carbide is used as a deoxidizer, and lime and wollastonite are added to form the slag, with a basicity of 1.5 ≤ R ≤ 2.5. Alloys are added before and during refining to adjust the Si, Mn, Cr, Ni, Cu, and Nb contents based on component analysis results before entering the LF furnace.

[0048] In the continuous casting step, 160 mm*160 mm small square billets are continuously cast, and the casting is protected throughout the whole process. Electromagnetic stirring of the crystallizer and electromagnetic stirring at the end are adopted, and soft reduction is performed with a reduction of 15 mm. The superheat is controlled at 20-40° C. and the casting speed is 1.9-2.6 mm / min. In this way, low-segregation and defect-free billets can be obtained, and the billet carbon segregation index is ≤1.13.

[0049] Furthermore, the crystallizer electromagnetic stirring frequency is 20 Hz, and the current is 200 A; the end electromagnetic stirring frequency is 3.0 Hz, and the current is 250 A.

[0050] In the high-speed wire rolling step, first, soaking is carried out at 1200-1250°C for 80-120 minutes, and then rolling is carried out, with the starting rolling temperature being 950-1000°C, the finishing rolling temperature being 870-900°C, and the spinning temperature being 850-890°C.

[0051] In the controlled cooling step, the temperature is first cooled to 650-680° C. at a cooling rate of 7-11° C. / s, then cooled to 580-620° C. at a cooling rate of 7-9° C. / s, held for 10-15 seconds, and finally cooled to room temperature at a cooling rate of ≤3° C. / s.

[0052] The present invention also provides a 2300MPa grade high-strength steel strand with good corrosion resistance, which is obtained by salt bath treatment, drawing, and stranding the 2300MPa grade high-strength steel strand with good corrosion resistance described in the present invention.

[0053] The specific process of the salt bath treatment is: uncoiling → straightening → induction quenching → salt bath → water washing → drying; wherein the induction quenching is divided into three stages, first preheating at 740-760°C, austenitizing treatment at 930-950°C and holding for 25-35s, and the salt bath isothermal temperature is 540-560°C and held for 35-45s; the wire rod travel speed is 10-14m / min.

[0054] The central steel wire diameter of the steel strand is Φ5.10-5.25 mm, the side wire diameter is Φ5.04-5.06 mm, and the finished steel strand is 15.40-15.15 mm thick.

[0055] The present invention is described in detail below with reference to the embodiments.

[0056] The chemical composition and weight percentage of the steel used for the steel strands in the embodiments and comparative examples are shown in Table 1.

[0057] Table 1

[0058]

[0059]

[0060] The steel strand steel in each embodiment and comparative example adopts the following production route: smelting → refining → continuous casting → high-speed wire rolling → controlled cooling → wire rod production.

[0061] The production process parameters of the steel strand steel in each embodiment and comparative example are shown in Table 2.

[0062] Table 2

[0063]

[0064]

[0065] The microstructures of the hot-rolled steel wire rods for steel strands in the embodiments and comparative examples are shown in Table 3.

[0066] Table 3

[0067]

[0068] Table 4 shows the mechanical properties of the hot-rolled wire rods for steel strands in the various examples and comparative examples after salt bath heat treatment. The salt bath treatment process is as follows: uncoiling → straightening → induction quenching → salt bath → water washing → drying. The induction quenching process consists of three stages: preheating at 750°C, austenitizing at 940°C for 30 seconds, and a salt bath at 550°C for 40 seconds. The salt bath contains 100% sodium nitrite. The wire rods are transported at a speed of 12 m / min.

[0069] Table 4

[0070]

[0071]

[0072] In Table 4, the tensile strength Rm and the post-fracture shrinkage Z were tested for mechanical properties according to the room temperature test method for metal materials in GB / T 228.1-2010 “Tensile tests on metallic materials - Part 1: Room temperature test methods”.

[0073] According to the methods of GB / T 19746-2018 "Corrosion of metals and alloys in salt solution cyclic immersion test" and GB / T10125-2012 "Salt spray test for corrosion test in artificial atmosphere", a 288h cyclic immersion corrosion test and a 72h salt spray corrosion test were carried out.

[0074] The hot-rolled steel wire rods treated with salt bath in each embodiment and comparative example were drawn and stranded to prepare steel strands with a center wire diameter of Φ5.25 mm, a side wire diameter of Φ5.06 mm, and a finished steel strand thickness of 15.2 mm. The properties of each steel strand are shown in Table 5.

[0075] Table 5

[0076]

[0077]

[0078] The test methods for various properties in Table 5 are as follows: Steel strand properties were tested in accordance with GB / T 21839-2019, "Test Methods for Steel for Prestressed Concrete." Mechanical properties (including Rm, elastic modulus, and yield strength ratio) were tested using tensile testing, fatigue strength was tested using axial fatigue testing, and stress corrosion performance was tested using a stress corrosion test in a thiocyanate solution.

[0079] From the above content, it can be seen that the Si content in Comparative Example 1 is not properly controlled, the X value is not controlled within the range of 1.10 to 1.45, and the strength of the finished steel strand cannot reach 2330 MPa; in Comparative Example 2, although the chemical components are controlled in accordance with the requirements of the present invention, the X value is not controlled within the range of 1.10 to 1.45, and the Y value is not controlled within the range of 0.28 to 0.58, resulting in the strength of the finished steel strand unable to reach 2330 MPa; in Comparative Example 3, due to the lack of addition of Nb, Ni, and Cu, the performance and corrosion resistance of the hot-rolled wire rod are poor, and ultimately a 2330 MPa steel strand product cannot be obtained; in Comparative Example 3, although the chemical composition is the same as in Example 1, due to the failure to perform cooling control in the three-stage manner required by the present invention, central martensite and network cementite are present in the structure, and the sorbitization rate is low.

[0080] From the above content, it can be seen that according to the solution provided by the present invention, a hot-rolled wire rod with a sorbite rate ≥ 95% can be obtained. After the hot-rolled wire rod is treated in a salt bath, the sorbite lamella spacing is ≤ 70 μm, the tensile strength Rm is ≥ 1450 MPa, and the cross-sectional shrinkage rate Z is ≥ 42%.

[0081] The hot-rolled wire rod can be drawn, stranded and twisted to produce a finished steel strand with a tensile strength of ≥2330 MPa and a stress corrosion resistance of ≥5h.

[0082] The above-mentioned reference embodiments provide a detailed description of a steel for a 2300MPa grade high-strength steel strand with good corrosion resistance, a production method thereof, and a 2300MPa grade high-strength steel strand with good corrosion resistance. This is illustrative rather than restrictive, and several embodiments may be listed within the limited scope. Therefore, changes and modifications without departing from the overall concept of the present invention should fall within the scope of protection of the present invention.

Claims

1. A 2300MPa grade high strength steel strand with good corrosion resistance, characterized in that: The chemical composition and weight percentage of the 2300MPa grade high-strength steel strand steel with good corrosion resistance are as follows: C 0.85%-0.95%, Mn 0.56%-0.66%, Cr 0.10%-0.18%, Nb 0.01%-0.05%, Ni 0.01%-0.03%, Cu 0.01%-0.03%, Si 0.90%-1.03%, Alt ≤0.005%, P ≤0.010%, S ≤0.010%, O ≤0.0020%, N ≤0.0065%, and the rest are Fe and other unavoidable impurities; Where, X=Si+10*Nb, 1.10≤X≤1.45; Y=1.2*[Cr]+1.8*[Ni]+5.0*[Cu]+2.0*[Nb], 0.28≤Y≤0.

58.

2. The 2300MPa grade high strength steel strand steel with good corrosion resistance according to claim 1, characterized in that: The metallographic structure of the 2300MPa grade high-strength steel strand hot-rolled wire rod with good corrosion resistance is sorbite, and the sorbitization rate is ≥95%; after the hot-rolled wire rod is treated by a salt bath, the sorbite lamellar spacing is ≤70um, the tensile strength Rm is ≥1450MPa, and the cross-sectional shrinkage rate Z is ≥42%.

3. The 2300 MPa grade high strength steel strand steel with good corrosion resistance according to claim 1, characterized in that: The tensile strength of the finished steel strand made of the 2300MPa grade high-strength steel strand with good corrosion resistance is ≥2330MPa.

4. A method for producing 2300 MPa grade high strength steel strand with good corrosion resistance according to any one of claims 1 to 3, characterized in that: The production method comprises the following steps: smelting→refining→continuous casting→high-speed wire rolling→controlled cooling→wire rod production.

5. The production method according to claim 4, characterized in that In the continuous casting step, electromagnetic stirring of the crystallizer and electromagnetic stirring of the end are adopted, and soft reduction is performed, with a reduction of 13-17 mm, superheating controlled at 20-40° C., and a casting speed of 1.9-2.6 mm / min.

6. The production method according to claim 4 or 5, characterized in that Continuously cast into 160mm*160mm small square billets.

7. The production method according to claim 4, characterized in that In the high-speed wire rolling step, first, soaking is performed at 1200-1250°C for 80-120 minutes, and then rolling is performed, with the starting rolling temperature being 950-1000°C, the finishing rolling temperature being 870-900°C, and the spinning temperature being 850-890°C.

8. The production method according to claim 4, characterized in that In the controlled cooling step, the temperature is first cooled to 650-680°C at a cooling rate of 7-11°C / s, then cooled to 580-620°C at a cooling rate of 7-9°C / s, held for 10-15 seconds, and finally cooled to room temperature at a cooling rate of ≤3°C / s.

9. A 2300MPa grade high strength steel strand with good corrosion resistance, characterized in that: The 2300MPa grade high-strength steel strand with good corrosion resistance as claimed in any one of claims 1 to 3 is obtained by salt bath treatment, drawing, and stranding.

10. The 2300 MPa grade high strength steel strand with good corrosion resistance according to claim 9, characterized in that: The specific process of the salt bath treatment is: uncoiling → straightening → induction quenching → salt bath → water washing → drying; wherein the induction quenching is divided into three stages, first preheating at 740-760°C, austenitizing treatment at 930-950°C for 25-35s, and the salt bath isothermal temperature is 540-560°C for 35-45s; the wire rod travel speed is 10-14m / min.

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