A 2230mpa steel strand for prestressed concrete and a method for manufacturing the same

Abstract

The application belongs to the technical field of steel strand preparation, and particularly relates to a 2230 MPa steel strand for prestressed concrete and a preparation method thereof. The 2230 MPa steel strand for concrete comprises the following raw materials in percentage by mass: C 0.90-0.95wt%, Mn 0.30-0.90wt%, Si 0.10-1.20wt%, Ta 0.15-0.28wt%, Sc 0.07-0.12wt%, Pr 0.04-0.08wt%, P≤0.020wt%, Cr≤0.40wt%, S≤0.020wt%, Ni≤0.10wt%, Cu≤0.20wt%, V≤0.15wt%, and the balance is Fe. The application can improve the mechanical properties and corrosion resistance of the steel strand by adding C, Mn, Cr, Ta, Sc, Pr and other elements for micro-alloying.

Description

Technical Field

[0001] This invention belongs to the field of steel strand preparation technology, specifically relating to a 2230MPa steel strand for prestressed concrete and its preparation method. Background Technology

[0002] With economic and technological development, my country's urbanization process has accelerated, leading to a gradual increase in high-rise buildings and large-span public buildings. These structures often bear heavy loads and have high requirements for functionality and construction quality. Prestressed concrete structures combine high-strength steel and high-strength concrete. By pre-applying forces to structural members, prestress is generated in the members to produce stress opposite to that of the external load. This allows the concrete structure to withstand greater loads, achieve larger spans, and delay the appearance and propagation of cracks. It also allows for smaller component cross-sectional dimensions, improving building utilization and achieving material savings and reduced project costs. Therefore, prestressed concrete structures have broad application prospects in the construction industry.

[0003] Steel strand is a steel product made of multiple strands of steel wire twisted together. As an important basic material for prestressed concrete, it needs to possess excellent comprehensive mechanical properties such as high tensile strength, high elongation, and high fatigue resistance, as well as good corrosion and weather resistance. Currently, high-grade steel strand with a tensile strength of 1860 MPa is commonly used in the market. Further increasing the strength of steel strand can reduce the amount of steel strand used, thus enabling the construction of higher-strength, larger-span, and lighter buildings. Existing steel strand strengthening methods typically involve alloying, which adds elements such as C, Si, Mn, or rare earth elements to change the internal microstructure of the alloy, thereby improving the material's strength. Alternatively, coatings or paints can be applied to the surface of the steel strand to improve its corrosion and weather resistance. However, these methods have limited strengthening effects on steel strands, and some are costly. Further improvements in strengthening methods are needed to obtain steel strands with higher strength. Summary of the Invention

[0004] The primary objective of this invention is to provide a 2230 MPa steel strand for prestressed concrete, which has excellent mechanical properties and superior corrosion resistance.

[0005] The second objective of this invention is to provide a method for preparing the above-mentioned 2230 MPa steel strand for prestressed concrete.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0007] A 2230MPa steel strand for prestressed concrete comprises the following raw materials by weight percentage: C 0.90-0.95wt%, Mn 0.30-0.90wt%, Si 0.10-1.20wt%, Ta 0.15-0.28wt%, Sc 0.07-0.12wt%, Pr 0.04-0.08wt%, P≤0.020wt%, Cr≤0.40wt%, S≤0.020wt%, Ni≤0.10wt%, Cu≤0.20wt%, V≤0.15wt%, with the balance being Fe.

[0008] Furthermore, the surface of the steel strand is also provided with a composite coating; the composite coating comprises the following raw materials in parts by weight: 10 parts of high entropy alloy, 1-2 parts of titanium carbonitride whiskers and 0.2-0.5 parts of polypropylene.

[0009] Furthermore, the titanium carbonitride crystals must be prepared by the following process:

[0010] Titanium dioxide, carbon powder, sodium chloride, and nickel chloride were ball-milled and mixed, and then sintered under a nitrogen atmosphere to obtain titanium carbonitride whiskers.

[0011] Furthermore, the mass ratio of titanium dioxide, carbon powder, sodium chloride, and nickel chloride is (20-21):(6-8):(23-27):1; the sintering temperature is 1300-1450℃, and the time is 80-120min.

[0012] Furthermore, the high-entropy alloy is prepared by the following process:

[0013] Fe, Ni, Mo, Ce and B are weighed and melted in an argon atmosphere. After atomization, a high-entropy alloy is obtained.

[0014] Further, the molar ratio of Fe, Ni, Mo, Ce to B is (6-7):(6-7):(2-3):(1-2):(2-4); the pressure of the gas atomization is 3-5 MPa, and the atmosphere is argon.

[0015] The above-mentioned method for preparing 2230MPa steel strand for prestressed concrete includes the following steps:

[0016] (1) The raw materials of the steel wire are mixed, melted, refined, slag removed, cast into shape, heat treated, rolled and cooled to form wire rods, and then drawn to obtain steel wire.

[0017] (2) The high-entropy alloy, titanium carbonitride whiskers and polypropylene are added to ethanol and ultrasonically dispersed, coated on the surface of steel wire, and heat-treated to obtain coated steel wire.

[0018] (3) The coated steel wire is twisted and stabilized to obtain 2230MPa steel strand for prestressed concrete.

[0019] Further, the temperature of the homogenization heat treatment in step (1) is 1150-1200℃ and the time is 50-80min; the initial rolling temperature is 920-960℃, the final rolling temperature is 840-880℃, and the wire drawing temperature is 820-850℃.

[0020] Furthermore, the coating thickness in step (2) is 20-50 μm; the heat treatment temperature is 1300-1350 °C, and the time is 1-3 h.

[0021] Furthermore, the stabilization treatment in step (3) is carried out at a temperature of 405-410℃ and a linear velocity of 40-45 m / min. The beneficial technical effects of this invention are as follows:

[0022] 1. This invention involves microalloying steel strands by adding elements such as C, Mn, Cr, Ta, Sc, and Pr. C and Mn can enhance the strength of the steel strands through solid solution strengthening; elements such as Cr and Ta can form carbides, creating a dispersion strengthening effect, which can pin grain boundaries and refine grains, thereby improving strength and hardness; and the combination of rare earth elements Pr and Sc can adsorb impurities, purify the alloy melt, and inhibit grain boundary corrosion, effectively improving the strength and corrosion resistance of the steel strands.

[0023] 2. This invention prepares a high-entropy alloy-titanium carbonitride whisker composite coating on the surface of steel wire, which can improve the strength and corrosion resistance of the steel strand. The high-entropy alloy possesses thermodynamic high-entropy effects and kinetic hysteresis diffusion effects, exhibiting excellent mechanical properties and chemical stability, and good adhesion to the metal matrix. Titanium carbonitride is a continuous solid solution formed from TiC and TiN, with whiskers exhibiting high orientation, extremely high tensile strength and elastic modulus, as well as excellent properties such as high-temperature resistance, oxidation resistance, and corrosion resistance. The high-entropy alloy mainly inhibits localized corrosion, while the titanium carbonitride whiskers mainly block the penetration of corrosive media. The combination of the two forms a denser coating, significantly improving the corrosion resistance of the steel strand. Attached Figure Description

[0024] Figure 1 This is a scanning electron microscope image of the titanium carbonitride whiskers prepared in Example 1 of the present invention. Detailed Implementation

[0025] The following is a further detailed description of the present invention in conjunction with specific preferred embodiments, and it should not be construed that the specific implementation of the present invention is limited to these descriptions. For those skilled in the art, various simple deductions or substitutions can be made without departing from the concept of the present invention, and all such modifications and substitutions should be considered within the scope of protection of the present invention. Specific conditions not specified in the embodiments are performed according to conventional conditions or conditions recommended by the manufacturer. Unless otherwise specified, all reagents or instruments used are conventional products obtained through commercial channels.

[0026] (I) Implementation Examples Example 1

[0027] Example 1 provides a 2230MPa steel strand for prestressed concrete, comprising steel wire and a composite coating on the surface of the steel wire; wherein the steel wire comprises the following raw materials by weight percentage: C 0.92wt%, Si 0.62wt%, Mn 0.71wt%, Ta 0.20wt%, Sc 0.10wt%, Pr 0.06wt%, P 0.012wt%, Cr 0.35wt%, S 0.005wt%, Ni 0.08wt%, Cu 0.06wt%, V 0.10wt%, with the balance being Fe; the composite coating comprises the following raw materials by weight: 10 parts high-entropy alloy, 1 part titanium carbonitride whiskers, and 0.4 parts polypropylene.

[0028] The titanium carbonitride crystals are prepared by the following process:

[0029] Titanium dioxide, carbon powder, sodium chloride, and nickel chloride were ball-milled and mixed uniformly according to a mass ratio of 20:7:25:1. The mixture was then placed in a sintering furnace and sintered at 1400℃ for 100 min under a nitrogen atmosphere to obtain titanium carbonitride whiskers. A scanning electron microscope image of the titanium carbonitride whiskers is shown below. Figure 1 As shown.

[0030] The high-entropy alloy is prepared by the following process:

[0031] According to the molar ratio of Fe, Ni, Mo, Ce and B of 7:7:2:1:3, the raw materials were weighed, heated to melt under an argon atmosphere, transferred to the heat preservation bag of the gas atomization device, nitrogen was introduced, the gas atomization gas pressure was set to 4MPa, the gas atomization device was started, and the high entropy alloy was collected.

[0032] This embodiment also provides a method for preparing the above-mentioned 2230MPa steel strand for prestressed concrete, the specific steps of which are as follows:

[0033] (1) Weigh the above steel wire raw materials, melt, refine, remove slag, and cast to form a steel billet; heat treat the steel billet at 1180℃ for 60 minutes, and then roll it, wherein the initial rolling temperature is maintained at 950℃, the final rolling temperature is maintained at 860℃, and the wire drawing temperature is maintained at 830℃. After cooling, it forms a wire rod, which is then drawn to obtain steel wire.

[0034] (2) According to the mass ratio of high entropy alloy, titanium carbonitride whiskers, polypropylene and ethanol of 10:1:0.4:12, the high entropy alloy, titanium carbonitride whiskers and polypropylene are added to ethanol and ultrasonically dispersed evenly, and coated on the surface of the above steel wire with a coating thickness of 40μm. First, it is dried at 80℃, and then heat-treated at 1320℃ for 2h to obtain coated steel wire.

[0035] (3) The coated steel wire is twisted and stabilized at 405℃ and 42m / min to obtain 2230MPa steel strand for prestressed concrete. Example 2

[0036] Example 2 provides a 2230MPa steel strand for prestressed concrete, comprising steel wire and a composite coating on the surface of the steel wire; wherein the steel wire comprises the following raw materials by weight percentage: C 0.90wt%, Si 0.85wt%, Mn 0.62wt%, Ta 0.15wt%, Sc 0.07wt%, Pr 0.04wt%, P 0.010wt%, Cr 0.25wt%, S 0.011wt%, Ni 0.04wt%, Cu 0.08wt%, V 0.03wt%, with the balance being Fe; the composite coating comprises the following raw materials by weight: 10 parts high-entropy alloy, 1 part titanium carbonitride whiskers, and 0.2 parts polypropylene.

[0037] The titanium carbonitride crystals are prepared by the following process:

[0038] Titanium dioxide, carbon powder, sodium chloride, and nickel chloride were ball-milled and mixed evenly according to a mass ratio of 20:6:23:1. The mixture was then placed in a sintering furnace and sintered at 1300°C for 80 minutes under a nitrogen atmosphere to obtain titanium carbonitride whiskers.

[0039] The high-entropy alloy is prepared by the following process:

[0040] According to the molar ratio of Fe, Ni, Mo, Ce and B of 6:6:2:2:4, the raw materials were weighed, heated to melt in an argon atmosphere, transferred to the heat preservation bag of the gas atomization device, nitrogen was introduced, the gas atomization gas pressure was set to 3MPa, the gas atomization device was started, and the high entropy alloy was obtained after collection.

[0041] This embodiment also provides a method for preparing the above-mentioned 2230MPa steel strand for prestressed concrete, the specific steps of which are as follows:

[0042] (1) Weigh the above steel wire raw materials, melt, refine, remove slag, and cast to form a steel billet; heat-treat the steel billet at 1150℃ for 50 minutes, and then roll it, wherein the initial rolling temperature is maintained at 920℃, the final rolling temperature is maintained at 840℃, the wire drawing temperature is maintained at 820℃, and after cooling, it forms a wire rod, which is then drawn to obtain steel wire.

[0043] (2) According to the mass ratio of high entropy alloy, titanium carbonitride whiskers, polypropylene and ethanol of 10:1:0.2:8, the high entropy alloy, titanium carbonitride whiskers and polypropylene are added to ethanol and ultrasonically dispersed evenly, and coated on the surface of the above steel wire with a coating thickness of 20μm. First, it is dried at 80℃, and then heat-treated at 1300℃ for 1h to obtain coated steel wire.

[0044] (3) The coated steel wire is twisted and stabilized at 408℃ and 40m / min to obtain 2230MPa steel strand for prestressed concrete. Example 3

[0045] Example 3 provides a 2230MPa steel strand for prestressed concrete, comprising steel wire and a composite coating on the surface of the steel wire; wherein the steel wire comprises the following raw materials by weight percentage: C 0.92wt%, Si 1.02wt%, Mn 0.78wt%, Cr 0.35wt%, Ta 0.28wt%, Sc 0.12wt%, Pr 0.08wt%, P 0.008wt%, Cr 0.18wt%, S 0.016wt%, Ni 0.02wt%, Cu 0.13wt%, V 0.05wt%, with the balance being Fe; the composite coating comprises the following raw materials by weight: 10 parts high-entropy alloy, 2 parts titanium carbonitride whiskers, and 0.5 parts polypropylene.

[0046] The titanium carbonitride crystals are prepared by the following process:

[0047] Titanium dioxide, carbon powder, sodium chloride, and nickel chloride were ball-milled and mixed evenly according to a mass ratio of 21:8:27:1. The mixture was then placed in a sintering furnace and sintered at 1450°C for 120 minutes under a nitrogen atmosphere to obtain titanium carbonitride whiskers.

[0048] The high-entropy alloy is prepared by the following process:

[0049] According to the molar ratio of Fe, Ni, Mo, Ce and B of 7:7:3:1:2, the raw materials were weighed, heated to melt under an argon atmosphere, transferred to the heat preservation bag of the gas atomization device, nitrogen was introduced, the gas atomization gas pressure was set to 5MPa, the gas atomization device was started, and the high entropy alloy was obtained after collection.

[0050] This embodiment also provides a method for preparing the above-mentioned 2230MPa steel strand for prestressed concrete, the specific steps of which are as follows:

[0051] (1) Weigh the above steel wire raw materials, melt, refine, remove slag, and cast to form a steel billet; heat treat the steel billet at 1200℃ for 80 minutes, and then roll it, wherein the initial rolling temperature is maintained at 960℃, the final rolling temperature is maintained at 880℃, the wire drawing temperature is maintained at 850℃, and after cooling, it forms a wire rod, which is then drawn to obtain steel wire.

[0052] (2) According to the mass ratio of high entropy alloy, titanium carbonitride whiskers, polypropylene and ethanol of 10:2:0.5:18, the high entropy alloy, titanium carbonitride whiskers and polypropylene are added to ethanol and ultrasonically dispersed evenly, and coated on the surface of the above steel wire with a coating thickness of 20μm. First, it is dried at 80℃, and then heat-treated at 1350℃ for 3h to obtain coated steel wire.

[0053] (3) The coated steel wire is twisted and stabilized at 410℃ and 45m / min to obtain 2230MPa steel strand for prestressed concrete.

[0054] (ii) Comparative Example

[0055] Comparative Example 1

[0056] Comparative Example 1 is basically the same as Example 1, except that the raw materials Ta, Sc and Pr of the steel wire in Example 1 are omitted.

[0057] Comparative Example 2

[0058] Comparative Example 2 is basically the same as Example 1, except that the high-entropy alloy of the composite coating in Example 1 is omitted.

[0059] Comparative Example 3

[0060] Comparative Example 3 is basically the same as Example 1, except that the titanium carbonitride whiskers of the composite coating in Example 1 are omitted.

[0061] (III) Test Examples

[0062] The steel strands prepared in Examples 1-3 and Comparative Examples 1-3 were subjected to performance tests.

[0063] Mechanical property testing: The mechanical properties of the steel strands in Examples 1-3 and Comparative Examples 1-3 were tested according to GB / T 21839-2019 "Test methods for steel for prestressed concrete". The results are shown in Table 1.

[0064] Corrosion resistance test: The mass loss rate of the steel strands of Examples 1-3 and Comparative Examples 1-3 after 24 h was tested according to GB / T 10125-2021 "Artificial Atmosphere Corrosion Test Salt Spray Test". The results are shown in Table 1.

[0065] Table 1. Test results of mechanical properties and corrosion resistance of steel strand.

[0066] Group Tensile strength (MPa) 24-hour mass loss rate (%) Example 1 2326 0.017 Example 2 2275 0.021 Example 3 2238 0.025 Comparative Example 1 2017 0.042 Comparative Example 2 2108 0.068 Comparative Example 3 2156 0.072

[0067] As shown in Table 1, the 2230MPa steel strands for prestressed concrete prepared in Examples 1-3 of the present invention have excellent mechanical properties and superior corrosion resistance.

[0068] Compared to Example 1, Comparative Example 1 omits the Ta, Sc, and Pr raw materials of the steel strand in Example 1; Comparative Example 2 omits the high-entropy alloy of the composite coating in Example 1; and Comparative Example 3 omits the titanium carbonitride whiskers of the composite coating in Example 1. The tensile strength, elastic modulus, and corrosion resistance of Comparative Examples 1-3 all decrease to varying degrees. Specific analysis reveals that: on the one hand, the addition of elements such as C, Mn, Cr, Ta, Sc, and Pr to the steel strand in this invention for microalloying allows C and Mn to enhance the strength of the steel strand through solid solution strengthening; elements such as Cr and Ta can form carbides, creating a dispersion strengthening effect that pins grain boundaries and refines grains, thereby improving strength and hardness; and the composite of rare earth elements Pr and Sc can adsorb impurities, purify the alloy melt, and inhibit grain boundary corrosion, effectively improving the strength and corrosion resistance of the steel strand. On the other hand, the high-entropy alloy-titanium carbonitride whisker composite coating prepared on the surface of the steel wire in this invention can improve the strength and corrosion resistance of the steel strand. High-entropy alloys possess thermodynamic high-entropy effects and kinetic hysteresis diffusion effects, exhibiting excellent mechanical properties and chemical stability, and demonstrating good adhesion to the metal matrix. Titanium carbonitride, a continuous solid solution formed from TiC and TiN, has whiskers with high orientation, exhibiting ultra-high tensile strength and elastic modulus, as well as excellent properties such as high temperature resistance, oxidation resistance, and corrosion resistance. High-entropy alloys primarily inhibit localized corrosion, while titanium carbonitride whiskers primarily block the penetration of corrosive media. The combination of the two can form a denser coating, significantly improving the corrosion resistance of the steel strand.

[0069] 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. The basic principles and main features of the present invention have been described above with specific implementation schemes. Based on the present invention, some modifications or substitutions can be made, but these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of protection claimed by the present invention.

Claims

1. A 2230MPa steel strand for prestressed concrete, characterized in that, The product comprises steel wire and a composite coating applied to the surface of the steel wire; the steel wire comprises the following raw materials in weight percentages: C 0.90-0.95wt%, Mn 0.30-0.90wt%, Si 0.10-1.20wt%, Ta 0.15-0.28wt%, Sc 0.07-0.12wt%, Pr 0.04-0.08wt%, P≤0.020wt%, Cr≤0.40wt%, S≤0.020wt%, Ni≤0.10wt%, Cu≤0.20wt%, V≤0.15wt%, with the balance being Fe; The composite coating comprises the following raw materials in parts by weight: 10 parts high-entropy alloy, 1-2 parts titanium carbonitride whiskers, and 0.2-0.5 parts polypropylene.

2. The 2230MPa steel strand for prestressed concrete according to claim 1, characterized in that, The titanium carbonitride crystals are prepared by the following process: Titanium dioxide, carbon powder, sodium chloride, and nickel chloride were ball-milled and mixed, and then sintered under a nitrogen atmosphere to obtain titanium carbonitride whiskers.

3. The 2230MPa steel strand for prestressed concrete according to claim 2, characterized in that, The mass ratio of titanium dioxide, carbon powder, sodium chloride and nickel chloride is (20-21):(6-8):(23-27):1; the sintering temperature is 1300-1450℃ and the time is 80-120min.

4. The 2230MPa steel strand for prestressed concrete according to claim 1, characterized in that, The high-entropy alloy is prepared by the following process: Fe, Ni, Mo, Ce and B are weighed and melted in an argon atmosphere. After atomization, a high-entropy alloy is obtained.

5. The 2230MPa steel strand for prestressed concrete according to claim 4, characterized in that, The molar ratio of Fe, Ni, Mo, Ce to B is (6-7):(6-7):(2-3):(1-2):(2-4); the pressure of the gas atomization is 3-5 MPa, and the atmosphere is argon.

6. A method for preparing 2230MPa steel strand for prestressed concrete according to any one of claims 1-5, characterized in that, Includes the following steps: (1) The raw materials of the steel wire are mixed, melted, refined, slag removed, cast into shape, heat treated, rolled and cooled to form wire rods, and then drawn to obtain steel wire. (2) The high-entropy alloy, titanium carbonitride whiskers and polypropylene are added to ethanol and ultrasonically dispersed, coated on the surface of steel wire, and heat-treated to obtain coated steel wire. (3) The coated steel wire is twisted and stabilized to obtain 2230MPa steel strand for prestressed concrete.

7. The method for preparing 2230MPa steel strand for prestressed concrete according to claim 6, characterized in that, The temperature of the homogenization heat treatment in step (1) is 1150-1200℃ and the time is 50-80min; the initial rolling temperature is 920-960℃, the final rolling temperature is 840-880℃, and the wire drawing temperature is 820-850℃.

8. The method for preparing 2230MPa steel strand for prestressed concrete according to claim 6, characterized in that, The coating thickness in step (2) is 20-50 μm; the heat treatment temperature is 1300-1350℃ and the time is 1-3 h.

9. The method for preparing 2230MPa steel strand for prestressed concrete according to claim 6, characterized in that, The stabilization treatment in step (3) is performed at a temperature of 405-410℃ and a linear velocity of 40-45m / min.

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