A preparation method of a steel strand-FRP composite bar and a system for preparing a steel strand-FRP composite bar

Abstract

The present invention provides a preparation method of a steel strand - FRP composite bar and a system for preparing the steel strand - FRP composite bar, which relates to the technical field of composite material preparation. The preparation method of the steel strand - FRP composite bar provided by the present invention includes the following steps: stranding steel wires to obtain a steel strand; placing the steel strand in a resin solution for impregnation to obtain a resin - coated steel strand; wrapping an FRP fiber bundle on the surface of the resin - coated steel strand, and sequentially performing heat curing and cooling contraction to obtain the steel strand - FRP composite bar. The steel strand - FRP composite bar prepared by the present invention can prevent the steel strand from carbonization, oxidation, and acid corrosion, and has high heat - resistant performance and mechanical properties.

Description

Technical Field

[0001] The present invention relates to the technical field of composite material preparation, and in particular to a method for preparing a steel strand-FRP composite reinforcement and a system for preparing the steel strand-FRP composite reinforcement. Background Art

[0002] Steel strand refers to a steel product composed of multiple steel wires twisted together. Due to its high strength, large elastic modulus, good torsion resistance and anti-slip performance, and convenient transportation and installation, it is widely used in bridges, buildings, water conservancy, energy and geotechnical engineering. However, steel products are prone to oxidation, carbonization, acid corrosion and other damage during service, and steel strands are often used in prestressed structures, which do not allow cracks to occur.

[0003] Fiber reinforced plastics (FRP) are increasingly used in the construction industry due to their advantages of light weight, high strength and good corrosion resistance. The method of using FRP bars instead of steel bars as force-bearing bars has also been widely used. However, compared with traditional steel bars, FRP bars have no obvious yield phenomenon, are very brittle, and have no signs of damage, making it difficult to meet actual needs. Summary of the invention

[0004] The object of the present invention is to provide a method for preparing a steel strand-FRP composite reinforcement and a system for preparing a steel strand-FRP composite reinforcement. The steel strand-FRP composite reinforcement prepared by the present invention can prevent carbonization, oxidation, and acid corrosion of the steel strand, and has high high temperature resistance and mechanical properties.

[0005] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0006] The present invention provides a method for preparing a steel strand-FRP composite reinforcement, comprising the following steps:

[0007] The steel wires are twisted to obtain steel strands;

[0008] placing the steel strand in a resin solution for dipping to obtain a resin-coated steel strand;

[0009] The FRP fiber bundle is wrapped on the surface of the resin-coated steel strand, and heating and curing and cooling and shrinking are performed in sequence to obtain a steel strand-FRP composite reinforcement.

[0010] Preferably, the method for preparing the steel strand comprises: pre-treating and stabilizing the steel wire in sequence, cold-drawing the single wire, connecting it to a shaping drum, and stranding it by a stranding machine.

[0011] Preferably, the pretreatment is carried out in a hydrogen peroxide aqueous solution, and the mass fraction of the hydrogen peroxide aqueous solution is 10-20%.

[0012] Preferably, the stabilization treatment adopts a stepwise heating method; the stepwise heating method includes: first heating from room temperature to 430 - 470°C at a heating rate of 6 - 8°C / min, and then heating to 870 - 930°C at a heating rate of 12 - 14°C / min.

[0013] Preferably, the coating thickness of the resin on the resin-coated steel strand is 1.5 - 2.5 mm.

[0014] Preferably, the FRP fiber bundle includes one or more of a carbon fiber bundle, a basalt fiber bundle, and a glass fiber bundle.

[0015] Preferably, the FRP fiber bundle is wrapped around the surface of the resin-coated steel strand in a continuous unidirectional form.

[0016] Preferably, the heat curing includes pre-curing and curing carried out in sequence; the temperature of the pre-curing is 100 - 120°C, and the time of the pre-curing is 10 - 15 min; the temperature of the curing is 150 - 200°C, and the time of the curing is 1 - 1.5 min.

[0017] Preferably, the cooling rate of the cooling and compressing is 12 - 18°C / min.

[0018] The present invention also provides a system for preparing a steel strand - FRP composite bar, including a strander, a U-shaped sleeve, and a fiber braiding machine arranged in sequence.

[0019] The present invention provides a method for preparing a steel strand - FRP composite bar, including the following steps: stranding steel wires to obtain a steel strand; placing the steel strand in a resin solution for impregnation to obtain a resin-coated steel strand; wrapping an FRP fiber bundle on the surface of the resin-coated steel strand, and carrying out heat curing and cooling and compressing in sequence to obtain a steel strand - FRP composite bar. The present invention uses an FRP fiber bundle to wrap the steel strand, which can effectively prevent the steel strand from carbonization, oxidation, and acidic corrosion during production, storage, transportation, and use, and can also improve the strength of the steel strand, with a wider protection range compared to galvanized or copper-plated steel strands; the present invention uses a structure in which an FRP fiber bundle wraps the resin. After the resin melts, the FRP fiber bundle can prevent resin leakage. The stable use temperature of traditional epoxy resin steel strands is only 5 - 35°C, while the stable use temperature of the steel strand - FRP composite bar provided by the present invention can reach above 400°C, which can meet the high-temperature environment encountered in engineering practice. Description of the Drawings

[0020] Figure 1Schematic diagram of the system for preparing steel strand - FRP composite bars in the embodiments of the present invention, where 1 is a single - wire steel wire rod, 2 is a sizing plate, 3 is a stranding machine, 4 is a U - shaped casing, 5 is a fiber braiding machine, 6 is the first oven, and 7 is the second oven;

[0021] Figure 2 Process flow chart for preparing steel strand - FRP composite bars in the embodiments of the present invention;

[0022] Figure 3 Schematic diagram of a sizing plate with 2 through - holes;

[0023] Figure 4 Schematic diagram of a sizing plate with 3 through - holes;

[0024] Figure 5 Schematic diagram of a sizing plate with 7 through - holes;

[0025] Figure 6 Schematic diagram of a sizing plate with 19 through - holes;

[0026] Figures 3 to 6 In it, d represents the diameter of a single steel wire, and D represents the nominal diameter of the steel strand. Detailed implementation manners

[0027] The present invention provides a method for preparing steel strand - FRP composite bars, including the following steps:

[0028] Strand the steel wires to obtain a steel strand;

[0029] Place the steel strand in a resin solution for impregnation to obtain a resin - coated steel strand;

[0030] Wrap an FRP fiber bundle on the surface of the resin - coated steel strand, and sequentially perform heat curing and cooling contraction to obtain steel strand - FRP composite bars.

[0031] In the present invention, if there are no special requirements, the raw materials used are all commercially available products well - known to those skilled in the art.

[0032] The present invention strands the steel wires to obtain a steel strand. In the present invention, the steel wires are preferably indented steel wires. In the present invention, the diameter of the steel wires is preferably 2.5 - 6 mm; the strength is preferably 1570 MPa or above.

[0033] In the present invention, the preparation method of the steel strand preferably includes: sequentially pre-treating and stabilizing the steel wire, then cold-drawing the single wire, connecting it to a shaping disc, and stranding it by a stranding machine. In the present invention, the pre-treatment is preferably carried out in an aqueous hydrogen peroxide solution, and the mass fraction of the aqueous hydrogen peroxide solution is preferably 10-20%, more preferably 15%. The present invention preferably immerses the steel wire in the aqueous hydrogen peroxide solution. In the present invention, the temperature of the immersion is preferably room temperature, and the time of the immersion is preferably 30-60 min, more preferably 45 min. During the immersion process in the present invention, stirring is preferably carried out, and the stirring speed is preferably 15-25 r / min. In a specific embodiment of the present invention, when no bubbles are generated in the system, the immersion ends. The present invention preferably dries the steel wire naturally at room temperature until there is no moisture on the surface after the immersion to obtain the pre-treated steel wire.

[0034] The present invention pre-treats the steel wire. The aqueous hydrogen peroxide solution can effectively remove the oil stain on the surface of the steel wire, reduce the impurities in the steel wire core, and increase the effective friction force. The present invention can ensure that there is no moisture on the surface of the steel wire through natural drying, which is beneficial to the combination with the resin, and at the same time, natural drying will not affect the mechanical properties of the steel wire.

[0035] The present invention preferably subjects the pre-treated steel wire to a stabilization treatment to obtain stabilized steel wire. In the present invention, the stabilization treatment is preferably carried out in a muffle furnace. In the present invention, the stabilization treatment preferably adopts a staged heating method; the staged heating method preferably includes: first heating from room temperature to 430-470 °C at a heating rate of 6-8 °C / min, and then heating to 930-870 °C at a heating rate of 12-14 °C / min. In a specific embodiment of the present invention, first heat from room temperature to 450 °C at a heating rate of 6-8 °C / min, and then heat to 850 °C at a heating rate of 12 °C / min. The present invention preferably keeps the temperature at 930-870 °C for heat preservation after heating to 930-870 °C; the heat preservation time is preferably 50-70 s, more preferably 60 s. During the process of heating from room temperature to 430-470 °C in the present invention, a slow heating rate can avoid defects such as cracks caused by uneven local heating; during the process of heating from 430-470 °C to 930-870 °C, Cr 23 C 6 is fully dissolved into austenite, and at this time, titanium and niobium fully form very stable titanium carbide and niobium carbide.

[0036] The present invention preferably naturally cools the obtained steel wire to room temperature after the stabilization treatment to obtain stabilized steel wire. The stabilized steel wire prepared by the present invention has no Cr even when passing through the sensitization temperature (450-850 °C). 23 C 6Precipitate at the grain boundaries. The austenitic stainless steel after stabilization treatment in the present invention can greatly reduce the possibility of intergranular corrosion.

[0037] In the present invention, it is preferred to cold-draw the stabilized steel wire into single wires to obtain the cold-drawn steel wire. In the present invention, the wire drawing speed of the cold-drawn single wire is preferably 50 - 70 mm / min, more preferably 60 mm / min; the cold-drawing rate of the cold-drawn single wire is preferably controlled at 1%.

[0038] The treatment of cold-drawing single wires in the present invention makes the steel wire more convenient to be installed in the through holes of the sizing plate. Cold-drawing can ensure that the steel wire will not have defects due to heat, and the cold-drawn steel wire can operate better on the production line.

[0039] In the present invention, it is preferred to connect the cold-drawn steel wire to the sizing plate and twist it by a stranding machine. In the present invention, a plurality of through holes are uniformly arranged inside the sizing plate, and the diameter of the through holes is preferably 4 - 6 mm, more preferably 5 mm, for uniformly arranging the steel wires. In a specific embodiment of the present invention, the steel wires arranged on the sizing plate are connected to the stranding machine through a restraining port, and the stranding machine is used to rotate the steel wires into a spiral shape.

[0040] In the present invention, the number of steel wires in the steel strand is preferably 2 - 19, more preferably 3 - 7; the steel wires in the steel strand are arranged in a spiral shape.

[0041] After obtaining the steel strand, the present invention places the steel strand in a resin solution for impregnation to obtain a resin-coated steel strand. In the present invention, the resin solution is preferably a polyurethane resin solution or a vinyl resin solution, more preferably a vinyl resin solution. In the present invention, the solid content of the resin solution is preferably 59 - 63%, the viscosity (25°C) is preferably 350 - 450 mPa·s, and the gel time is preferably 11 - 17 min. Using the above resin in the present invention can effectively improve the peel resistance and impact resistance of the composite bars.

[0042] In the present invention, the impregnation is preferably carried out in a U-shaped sleeve. The bilateral height of the resin solution in the U-shaped sleeve is preferably 25 - 35 cm, more preferably 30 cm; the diameter of the U-shaped sleeve is preferably 22 - 26 mm, more preferably 24 mm. The present invention uses a U-shaped sleeve to hold the resin solution. After the steel strand passes through the U-shaped sleeve, it can ensure that the entire steel strand is impregnated with the resin solution, and the resin solution can flow back into the U-shaped sleeve, which is suitable for flow operation.

[0043] In the present invention, the impregnation is preferably carried out at room temperature, and the impregnation time is preferably 10 - 12 min, more preferably 11 min.

[0044] In a specific embodiment of the present invention, the impregnation is an on-line impregnation, and the speed of the steel strand passing through the U-shaped sleeve is preferably 1.5 to 2 mm / s.

[0045] In the present invention, the coating thickness of the resin on the resin-coated steel strand is preferably 1.5 to 2.5 mm, more preferably 2 mm. By adopting the above coating thickness, the present invention can not only play a protective role, but also will not be too thick to affect the adhesion effect. In specific embodiments of the present invention, it can be appropriately adjusted according to actual production needs. The specific adjustment method can be to change the overall traveling speed of the production line or adjust the depth of the resin solution in the U-shaped sleeve.

[0046] After obtaining the resin-coated steel strand, the present invention wraps the FRP fiber bundle on the surface of the resin-coated steel strand, and successively performs heat curing and cooling contraction to obtain a steel strand-FRP composite bar. In the present invention, the FRP fiber bundle preferably includes one or more of a carbon fiber bundle, a basalt fiber bundle, and a glass fiber bundle. In the present invention, the FRP fiber bundle is preferably wrapped on the surface of the resin-coated steel strand in a continuous unidirectional form, which can improve the durability of the composite bar. In the present invention, the included angle between the direction of the unidirectional FRP fiber bundle and the direction of the steel strand is preferably 0° to 45°. In specific embodiments of the present invention, an epoxy resin sealing method is adopted to ensure that the fiber bundle is continuously and unidirectionally wrapped on the surface of the steel strand.

[0047] In the present invention, the wrapping of the FRP fiber bundle is preferably carried out in a fiber braiding machine.

[0048] In the present invention, the wrapping thickness of the FRP fiber bundle is preferably 3 to 8 mm, more preferably 5 mm.

[0049] In the present invention, the diameter of the FRP fiber bundle is preferably 3 to 5 mm, more preferably 4 mm. The present invention can increase the roughness of the surface of the composite bar by setting the diameters of each group of fiber bundles to different sizes, thereby increasing the mechanical biting force when the composite bar is used. In specific embodiments of the present invention, the specific setting method is: set the diameter of one group of fiber bundles to 5 mm, and the diameters of other fiber bundles to 3 mm. After the braiding is completed, a fiber bundle forms a structure similar to a thread.

[0050] In the present invention, the heat curing is preferably carried out in a molding die. The present invention preferably places the steel strand wrapped with the FRP fiber bundle in the molding die, then uses a nozzle to supplement resin into the molding die until the die is full, and then places the molding die in an oven for heat curing.

[0051] In the present invention, the heat curing preferably includes pre-curing and curing which are carried out in sequence; the temperature of the pre-curing is preferably 100-120 °C, the time of the pre-curing is preferably 10-15 min; the pressure of the pre-curing is preferably 5-10 MPa; the temperature of the curing is preferably 150-200 °C, and the time of the curing is preferably 1-1.5 min.

[0052] In a specific embodiment of the present invention, the pre-curing is carried out in a first oven, and the curing is carried out in a second oven.

[0053] In the present invention, the cooling and compressing is preferably carried out in a low-temperature box, and the temperature of the low-temperature box is preferably -5 °C. The present invention preferably immediately puts the cured composite tendon into the low-temperature box. In the present invention, the cooling rate of the cooling and compressing is preferably 12-18 °C / min, more preferably 14-16 °C / min. The present invention preferably reduces the temperature of the composite tendon below -5 °C through cooling and compressing. The present invention quickly and uniformly cools the composite tendon, which can cause the resin to contract and stabilize the structure, preventing the steel strand from being oxidized due to residual high temperature and preventing defects caused by uneven temperature at the overlapping part and inside the steel strand at room temperature.

[0054] Compared with the prior art, the present invention uses steel wires to prepare steel strand-FRP composite tendons, and can prepare composite tendons with different shapes and sizes according to needs. At the same time, since FRP fiber bundles are laid on the surface of the steel strand, the corrosion resistance and temperature stability of the steel strand are improved.

[0055] The present invention provides a system for preparing steel strand-FRP composite tendons, as Figure 1 shown, including a stranding machine, a U-shaped sleeve and a fiber braiding machine which are arranged in sequence. The present invention has no special requirements for the specific structures of the stranding machine, the U-shaped sleeve and the fiber braiding machine, and the equipment well-known to those skilled in the art can be adopted. In the present invention, the outlet of the stranding machine, the two ends of the U-shaped sleeve and the inlet of the fiber braiding machine are preferably on the same horizontal line.

[0056] As an embodiment of the present invention, with one end close to the U-shaped sleeve being the rear end of the stranding machine, the system provided by the present invention further includes a sizing plate arranged at the front end of the stranding machine. In the present invention, a plurality of through holes are preferably uniformly arranged inside the sizing plate, more preferably 2-19, and further preferably 3-7. The present invention uses the sizing plate to uniformly arrange the steel wires to obtain steel strands with different structures.

[0057] In a specific embodiment of the present invention, according to actual production needs, the shape and size of the steel strand can be adjusted by changing the position of the steel wire in the sizing plate, and four standard steel strands of 1×2, 1×3, 1×7, and 1×19 can be produced; steel strands with other shapes and sizes can also be produced according to special needs.

[0058] As an embodiment of the present invention, the system provided by the present invention further includes a traction wheel disc arranged at the front end of the sizing plate, and a plurality of single-wire steel wire coils are fixed on the traction wheel disc. In the present invention, the single-wire steel wire coils are used to place steel wires. In the present invention, the traction wheel disc can adjust the single-wire steel wire coils through a chute, thereby changing the number and form of the arranged steel wires, and thus changing the steel wire arrangement of the composite bar or the diameter of the composite bar.

[0059] As an embodiment of the present invention, the system provided by the present invention further includes a drying oven; the drying oven is arranged at the rear end of the fiber braiding machine. In the present invention, the drying oven preferably includes a first drying oven and a second drying oven arranged in sequence; the first drying oven is close to the fiber braiding machine. In the present invention, the heating section length of the first drying oven is preferably 1.0 - 1.4 m, more preferably 1.2 m; the heating section length of the second drying oven is preferably 0.1 - 0.14 m, more preferably 0.12 m.

[0060] Next, the technical solutions in the present invention will be clearly and completely described in conjunction with the embodiments in the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments in the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative efforts shall fall within the protection scope of the present invention.

[0061] Example 1

[0062] Adopt the process flow chart as Figure 2 shown to prepare the steel strand - FRP composite bar:

[0063] Select notched steel wires with a diameter of 5 mm, soak the untreated steel wires in a hydrogen peroxide aqueous solution with a mass fraction of 15%, control the temperature at 25°C, slowly stir during soaking, and the soaking time is 45 min. Stop soaking when no more bubbles are observed in the solution. After soaking, naturally dry the steel wires at room temperature until there is no moisture on the surface to obtain the pretreated steel wires;

[0064] Place the pretreated steel wires in a muffle furnace, raise the temperature from room temperature to 450°C at a heating rate of 8°C / min, and then raise the temperature to 850°C at a heating rate of 12°C / min, and keep warm for 1 min; after treatment, cool to room temperature to obtain stabilized steel wires;

[0065] Cold draw the stabilized steel wire into single wires to obtain the cold-drawn steel wire; the drawing speed of the cold-drawn single wire is 50 mm / min, and the cold-drawing rate is 1%;

[0066] Arrange two of the cold-drawn steel wires as Figure 3 shown on the sizing plate, connect them to a stranding machine through the restraint ports, and use the stranding machine to rotate the steel wires into a spiral shape to obtain a stranded steel wire;

[0067] Immerse the stranded steel wire through a U-shaped sleeve filled with a vinyl resin solution with a solid content of 60% to obtain a resin-coated stranded steel wire; the speed of the stranded steel wire passing through the U-shaped sleeve is 2 mm / s;

[0068] Pass the resin-coated stranded steel wire through a fiber braiding machine. The fiber bundle selects a glass fiber bundle (GFRP fiber bundle) with a diameter of 4 mm. The fiber bundle is continuously wound around the stranded steel wire unidirectionally at 45°, and the thickness of the fiber bundle wrapping is 4 mm;

[0069] Place the stranded steel wire wrapped with the FRP fiber bundle in a molding die, then use a nozzle to supplement resin into the molding die until the die is full, and then place the molding die in a first oven and a second oven for heating and curing in sequence. The first oven is heated and pressurized to 10 MPa, heated to 120 °C, and preheated and maintained for 10 min; the second oven is heated to 200 °C and maintained for 1 min to complete the curing;

[0070] Immediately place the cured composite bar into a low-temperature box with the temperature set at -5 °C, and cool it to -5 °C at a cooling rate of 18 °C / min to obtain a 1×2 stranded steel wire-FRP composite bar.

[0071] Perform performance testing on the 1×2 stranded steel wire-FRP composite bar prepared in this example, and the test results are shown in Table 1.

[0072] Table 1 Performance test results of Example 1

[0073]

[0074] As can be seen from Table 1, all the indicators of the stranded steel wire-FRP composite bar prepared by the present invention meet the requirements of the national standard GB8919-2006 "Steel Wire Rope Standard".

[0075] Example 2

[0076] Select a grooved steel wire with a diameter of 5 mm, immerse the untreated steel wire in an aqueous hydrogen peroxide solution with a mass fraction of 15%, control the temperature at 25 °C, slowly stir during the immersion, and stop the immersion when no more bubbles are observed in the solution. After immersion, naturally dry the steel wire at room temperature until there is no moisture on the surface to obtain the pretreated steel wire;

[0077] Place the pre-treated steel wire in a muffle furnace, heat it from room temperature to 430°C at a heating rate of 6°C / min, then heat it to 830°C at a heating rate of 12°C / min, and hold for 1 min; after treatment, cool it to room temperature to obtain stabilized steel wire;

[0078] Cold draw the stabilized steel wire into single wires to obtain cold-drawn steel wire; the drawing speed of cold drawing single wires is 60 mm / min, and the cold drawing rate is 1%;

[0079] Arrange three of the cold-drawn steel wires as shown in Figure 4 on a sizing plate, connect them to a stranding machine through a restraint port, and use the stranding machine to rotate the steel wires into a spiral shape to obtain a steel strand;

[0080] Immerse the steel strand through a U-shaped sleeve filled with a vinyl resin solution with a solid content of 60% to obtain a resin-coated steel strand; the speed of the steel strand passing through the U-shaped sleeve is 1.5 mm / min;

[0081] Pass the resin-coated steel strand through a fiber braiding machine. The fiber bundles are glass fiber bundles (GFRP fiber bundles) with diameters of 3 mm and 4 mm. The fiber bundles are continuously wound around the steel strand unidirectionally at 45°, and the thickness of the fiber bundle wrapping is 4 mm;

[0082] Place the steel strand wrapped with FRP fiber bundles in a molding die, then use a nozzle to supplement resin into the molding die until the die is full, and then place the molding die in a first oven and a second oven for heating and curing in sequence. The first oven is heated and pressurized to 10 MPa, heated to 120°C, and preheated and held for 10 min; the second oven is heated to 200°C and held for 1 min to complete curing;

[0083] Immediately place the cured composite bars into a low-temperature box, set the temperature at -5°C, and cool them to -5°C at a cooling rate of 16°C / min to obtain 1×3 steel strand - FRP composite bars.

[0084] Perform performance testing on the 1×3 steel strand - FRP composite bars prepared in this example, and the test results are shown in Table 2.

[0085] Table 2 Performance test results of Example 2

[0086]

[0087]

[0088] As can be seen from Table 2, all the indicators of the steel strand - FRP composite bars prepared by the present invention meet the requirements of the national standard GB8919 - 2006 "Steel Wire Rope Standard".

[0089] Example 3

[0090] Select a notched steel wire with a diameter of 5 mm, immerse the untreated steel wire in an aqueous hydrogen peroxide solution with a mass fraction of 15%, control the temperature at 25 °C, slowly stir during immersion, and the immersion time is 45 min. Stop immersion when no more bubbles are observed in the solution. After immersion, naturally dry the steel wire at room temperature until there is no moisture on the surface to obtain the pretreated steel wire;

[0091] Place the pretreated steel wire in a muffle furnace, heat it from room temperature to 450 °C at a heating rate of 7 °C / min, and then heat it to 850 °C at a heating rate of 12 °C / min, and hold for 1 min; after treatment, cool it to room temperature to obtain stabilized steel wire;

[0092] Cold draw the stabilized steel wire into single wires to obtain cold-drawn steel wires; the drawing speed of cold drawing single wires is 70 mm / min, and the cold drawing ratio is 1%;

[0093] Arrange seven of the cold-drawn steel wires as shown in Figure 5 on a sizing plate, connect them to a stranding machine through a restraint port, and use the stranding machine to rotate the steel wires into a spiral shape to obtain a steel strand;

[0094] Immerse the steel strand through a U-shaped sleeve filled with a vinyl resin solution with a solid content of 60% to obtain a resin-coated steel strand; the speed of the steel strand passing through the U-shaped sleeve is 2 mm / s;

[0095] Pass the resin-coated steel strand through a fiber braiding machine. The fiber bundle selects a glass fiber bundle (GFRP fiber bundle) with a diameter of 4 mm. The fiber bundle is continuously wound around the steel strand unidirectionally at 45°, and the thickness of the fiber bundle wrapping is 4 mm;

[0096] Place the steel strand wrapped with FRP fiber bundles in a molding die, then use a nozzle to supplement resin into the molding die until the die is full, and then place the molding die in a first oven and a second oven for heating and curing. The first oven is heated and pressurized to 10 MPa, heated to 120 °C, and preheated and held for 10 min; the second oven is heated to 200 °C and held for 1 min to complete curing;

[0097] Immediately place the cured composite bars into a low-temperature box, set the temperature at -5 °C, and cool them to -5 °C at a cooling rate of 14 °C / min to obtain 1×7 steel strand - FRP composite bars.

[0098] Perform performance testing on the 1×7 steel strand - FRP composite bars prepared in this comparative example, and the test results are shown in Table 3.

[0099] Table 3 Performance test results of Example 3

[0100]

[0101] As can be seen from Table 3, all the indicators of the steel strand - FRP composite bars prepared by the present invention meet the requirements of the national standard GB8919 - 2006 "Steel Wire Rope Standard".

[0102] Example 4

[0103] Select grooved wires with a diameter of 5 mm. Immerse the untreated wires in an aqueous hydrogen peroxide solution with a mass fraction of 15%, control the temperature at 25°C, stir slowly during immersion, and the immersion time is 45 min. Stop immersion when no more bubbles are observed in the solution. After immersion, dry the wires naturally at room temperature until there is no moisture on the surface to obtain pretreated wires;

[0104] Place the pretreated wires in a muffle furnace, heat from room temperature to 430°C at a heating rate of 6°C / min, and then heat to 830°C at a heating rate of 12°C / min, and hold for 1 min; after treatment, cool to room temperature to obtain stabilized wires;

[0105] Cold - draw the stabilized wires into single wires to obtain cold - drawn wires; the drawing speed of cold - drawing single wires is 60 mm / min, and the cold - drawing rate is 1%;

[0106] Arrange 19 of the cold - drawn wires as shown in Figure 6 on a shaping plate, connect them to a stranding machine through a restraining port, and use the stranding machine to rotate the wires into a spiral shape to obtain steel strands;

[0107] Immerse the steel strands through a U - shaped sleeve filled with a vinyl resin solution with a solid content of 60% to obtain resin - coated steel strands; the speed of the steel strands passing through the U - shaped sleeve is 2 mm / s;

[0108] Pass the resin - coated steel strands through a fiber braiding machine. Select a glass fiber bundle (GFRP fiber bundle) with a diameter of 4 mm as the fiber bundle. The fiber bundle is continuously wound around the steel strands unidirectionally at 45°, and the thickness of the fiber bundle wrapping is 4 mm;

[0109] Place the steel strands wrapped with FRP fiber bundles in a molding die, then use a nozzle to supplement resin into the molding die until it is full, and then place the molding die in a first oven and a second oven for heating and curing in sequence. The first oven is heated and pressurized to 10 MPa, heated to 120°C, and pre - heated and held for 10 min; the second oven is heated to 200°C and held for 1 min to complete curing;

[0110] Immediately after the curing is completed, the composite bars are immediately placed in a low-temperature box with the temperature set at -5°C and cooled to -5°C at a cooling rate of 16°C / min to obtain 1×19 steel strand-FRP composite bars.

[0111] Perform performance tests on the 1×19 steel strand-FRP composite bars prepared in this example. The test results are shown in Table 4.

[0112] Table 4 Performance test results of Example 4

[0113]

[0114] As can be seen from Table 4, all the indicators of the steel strand-FRP composite bars prepared by the present invention meet the requirements of the national standard GB8919-2006 "Steel Wire Rope Standard".

[0115] Comparative Example 1

[0116] Select grooved wires with a diameter of 5 mm. Immerse the untreated wires in an aqueous hydrogen peroxide solution with a mass fraction of 15%, control the temperature at 25°C, stir slowly during immersion, and the immersion time is 45 min. Stop immersion when no more bubbles are observed in the solution. After immersion, dry the wires naturally at room temperature until the surface has no moisture to obtain pretreated wires;

[0117] Place the pretreated wires in a muffle furnace, raise the temperature from room temperature to 430°C at a heating rate of 6°C / min, and then raise the temperature to 830°C at a heating rate of 12°C / min, and hold for 1 min; after treatment, cool to room temperature to obtain stabilized wires;

[0118] Perform cold drawing on the stabilized wires to obtain cold-drawn wires; the drawing speed of the cold-drawn single wire is 60 mm / min, and the cold drawing rate is 1%;

[0119] Arrange three of the cold-drawn wires as Figure 4 shown on the sizing plate, connect them to the stranding machine through the restraint port, and use the stranding machine to rotate the wires into a spiral shape to obtain steel strands;

[0120] Immerse the steel strands through a U-shaped sleeve filled with a vinyl resin solution with a solid content of 60% to obtain resin-coated steel strands; the speed of the steel strands passing through the U-shaped sleeve is 1.5 mm / min;

[0121] Pass the resin-coated steel strands through a fiber braiding machine. The fiber bundles are glass fiber bundles (GFRP fiber bundles) with diameters of 3 mm and 4 mm. The fiber bundles are continuously wound around the steel strands unidirectionally at 45°, and the thickness of the fiber bundle wrapping is 4 mm;

[0122] Place the steel strand wrapped with FRP fiber bundles in a molding die, then use a nozzle to supplement resin into the molding die until it is full, and then place the molding die in a first oven and a second oven in sequence for heating and curing. The first oven increases the temperature and pressure by 10 MPa, raises the temperature to 120 °C, and preheats and maintains for 10 minutes; the second oven raises the temperature to 200 °C and maintains for 1 minute to complete the curing;

[0123] Immediately place the composite bar after curing in a room temperature environment for natural cooling to obtain a 1×3 steel strand - FRP composite bar.

[0124] Conduct performance tests on the 1×3 steel strand - FRP composite bars prepared in this comparative example, and the test results are shown in Table 5.

[0125] Table 5 Performance test results of Comparative Example 1

[0126]

[0127] It can be seen from Table 5 that the mechanical properties of the steel strand - FRP composite bars without cooling and compressing have decreased significantly. Therefore, cooling and compressing play an important role in ensuring the quality of the steel strand.

[0128] Comparative Example 2

[0129] Select a grooved wire with a diameter of 5 mm, immerse the untreated wire in an aqueous hydrogen peroxide solution with a mass fraction of 15%, control the temperature at 25 °C, stir slowly during immersion, and the immersion time is 45 minutes. Stop immersion when no more bubbles are observed in the solution. After immersion, dry the wire naturally at room temperature until there is no moisture on the surface to obtain the pretreated wire;

[0130] Place the pretreated wire in a muffle furnace, raise the temperature from room temperature at a heating rate of 7 °C / min to 450 °C, and then raise the temperature at a heating rate of 12 °C / min to 850 °C, and hold for 1 minute; after treatment, cool to room temperature to obtain stabilized wire;

[0131] Cold draw the stabilized wire into single wires to obtain cold - drawn wires; the drawing speed of the cold - drawn single wires is 70 mm / min, and the cold - drawing rate is 1%;

[0132] Arrange seven of the cold - drawn wires as shown in Figure 5 on a sizing plate, connect them to a stranding machine through a restraint port, and use the stranding machine to rotate the wires into a spiral shape to obtain a steel strand;

[0133] Immerse the steel strand through a U - shaped sleeve filled with a vinyl resin solution with a solid content of 60% to obtain a resin - coated steel strand; the speed of the steel strand passing through the U - shaped sleeve is 2 mm / s;

[0134] Pass the resin-coated steel strand through a fiber braiding machine. The fiber bundle is a glass fiber bundle (GFRP fiber bundle) with a diameter of 4 mm. The fiber bundle is continuously wound around the steel strand unidirectionally at an angle of 45°, and the thickness of the fiber bundle wrapping is 4 mm.

[0135] Place the steel strand wrapped with FRP fiber bundles in a molding die, then use a nozzle to supplement resin into the molding die until it is full. Then place the molding die in a first oven and a second oven in sequence for heating and curing. The first oven is not pressurized, heated to 80 °C, and preheated and maintained for 4 min; the second oven is heated to 100 °C and maintained for 1 min to complete the curing.

[0136] Immediately place the cured composite bars into a low-temperature box with the temperature set at -5 °C and cool them to -5 °C at a cooling rate of 14 °C / min to obtain 1×7 steel strand - FRP composite bars.

[0137] Conduct performance tests on the 1×7 steel strand - FRP composite bars prepared in this comparative example. The test results are shown in Table 6.

[0138] Table 6 Test results of various performances of Comparative Example 2

[0139]

[0140] It can be seen from Table 6 that the mechanical properties of the steel strand - FRP composite bars prepared in this comparative example are much lower than those of the examples, but still meet the requirements; the temperature and pressure during the heating and curing stage do not meet the requirements. Therefore, the resin and fiber bundles on the surface of the composite bars show uneven consolidation, and there is a situation of local steel strand exposure, which will greatly reduce the durability of the composite bars during use.

[0141] Comparative Example 3

[0142] Select a grooved wire with a diameter of 5 mm, soak the untreated wire in an aqueous hydrogen peroxide solution with a mass fraction of 15%, control the temperature at 25 °C, stir slowly during soaking, and the soaking time is 45 min. Stop soaking when no more bubbles are observed in the solution. After soaking, dry the wire naturally at room temperature until there is no moisture on the surface to obtain the pretreated wire.

[0143] Place the pretreated wire in a muffle furnace, raise the temperature from room temperature to 830 °C at a heating rate of 12 °C / min, and keep it warm for 1 min; after treatment, cool it to room temperature to obtain stabilized wire.

[0144] Cold draw the stabilized wire into single wires to obtain cold-drawn wires; the drawing speed of the cold-drawn single wire is 60 mm / min, and the cold-drawing rate is 1%.

[0145] Arrange 19 of the cold-drawn wires asFigure 6 The arrangement shown is on the sizing plate and is connected to the stranding machine through the restraint opening. The stranding machine is used to rotate the steel wire into a spiral shape to obtain a stranded steel wire;

[0146] The stranded steel wire is impregnated through a U-shaped sleeve filled with a vinyl resin solution with a solid content of 60% to obtain a resin-coated stranded steel wire; the speed of the stranded steel wire passing through the U-shaped sleeve is 2 mm / s;

[0147] The resin-coated stranded steel wire is passed through a fiber braiding machine. The fiber bundle selected is a glass fiber bundle (GFRP fiber bundle) with a diameter of 4 mm. The fiber bundle is continuously wound around the stranded steel wire unidirectionally at 45°, and the thickness of the fiber bundle wrapping is 4 mm;

[0148] The stranded steel wire wrapped with the FRP fiber bundle is placed in a molding die. Then, resin is supplemented into the molding die using a nozzle until the die is full. Then, the molding die is placed in a first oven and a second oven in sequence for heating and curing. The first oven is heated and pressurized to 10 MPa, heated to 120 °C, and preheated and maintained for 10 min; the second oven is heated to 200 °C and maintained for 1 min, and the curing is completed;

[0149] Immediately after that, the cured composite bars are put into a low-temperature box, the temperature is set at -5 °C, and the temperature is decreased to -5 °C at a cooling rate of 16 °C / min to obtain 1×19 stranded steel wire - FRP composite bars.

[0150] The properties of the 1×19 stranded steel wire - FRP composite bars prepared in this comparative example are detected, and the detection results are shown in Table 7.

[0151] Table 7 Detection results of various properties of Comparative Example 3

[0152]

[0153]

[0154] As can be seen from Table 7, in this comparative example, the stabilization treatment was not carried out by the segmented heating method, but directly heated rapidly to the forming stage. All the mechanical properties of the stranded steel wire decreased significantly. The reason is that the heating rate was too fast in the initial stage of heating, and the local heating of the steel wire was uneven, resulting in initial cracks; in the later stage of heating, Cr 23 C 6 in the steel could not be fully dissolved. Therefore, the stabilization treatment needs to be carried out according to the segmented heating method of the present invention.

[0155] The present invention is applicable to steel strand - FRP composite bars prepared with steel wire cores in various forms, and can solve the problems of poor corrosion resistance of existing steel strands, low elastic modulus and high brittleness of FRP materials, enabling the performance of the composite bars to meet the standard requirements. At the same time, steel wire cores with different shapes and sizes can be designed according to requirements. Therefore, the present invention effectively overcomes the defects of the prior art and has high utilization value.

[0156] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. A preparation method of a steel strand - FRP composite bar, characterized in that, it comprises the following steps: Strand the steel wires to obtain a steel strand; Place the steel strand in a resin solution for impregnation to obtain a steel strand coated with resin; Wrap an FRP fiber bundle on the surface of the resin - coated steel strand, and sequentially carry out heat curing and cooling contraction to obtain a steel strand - FRP composite bar; The coating thickness of the resin in the resin - coated steel strand is 1.5 - 2.5 mm; The preparation method of the steel strand includes: sequentially pre - treating and stabilizing the steel wires, then cold - drawing single wires, connecting them to a shaping disc, and stranding them by a stranding machine; The stabilizing treatment adopts a staged heating method; the staged heating method includes: first heating from room temperature to 430 - 470 °C at a heating rate of 6 - 8 °C / min, and then heating to 930 - 870 °C at a heating rate of 12 - 14 °C / min; The heat curing includes pre - curing and curing carried out sequentially; the temperature of the pre - curing is 100 - 120 °C, the time of the pre - curing is 10 - 15 min; the pressure of the pre - curing is 5 - 10 MPa; the temperature of the curing is 150 - 200 °C, and the time of the curing is 1 - 1.5 min; The cooling rate of the cooling contraction is 12 - 18 °C / min.

2. The preparation method according to claim 1, characterized in that, The pre - treatment is carried out in an aqueous hydrogen peroxide solution, and the mass fraction of the aqueous hydrogen peroxide solution is 10 - 20%.

3. The preparation method according to claim 1, characterized in that, The FRP fiber bundle includes one or more of a carbon fiber bundle, a basalt fiber bundle, and a glass fiber bundle.

4. The preparation method according to claim 1 or 3, characterized in that, The FRP fiber bundle is wrapped on the surface of the resin - coated steel strand in a continuous unidirectional form.

5. A system adopting the preparation method according to any one of claims 1 - 4, characterized in that, it includes a stranding machine, a U - shaped sleeve, and a fiber braiding machine arranged in sequence.

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