CN113026402B - Large-sized hot-dip galvanized prestressed steel strand and manufacturing method thereof - Google Patents
Large-sized hot-dip galvanized prestressed steel strand and manufacturing method thereof Download PDFInfo
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- D—TEXTILES; PAPER
- D07—ROPES; CABLES OTHER THAN ELECTRIC
- D07B—ROPES OR CABLES IN GENERAL
- D07B1/00—Constructional features of ropes or cables
- D07B1/06—Ropes or cables built-up from metal wires, e.g. of section wires around a hemp core
- D07B1/0693—Ropes or cables built-up from metal wires, e.g. of section wires around a hemp core having a strand configuration
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- D—TEXTILES; PAPER
- D07—ROPES; CABLES OTHER THAN ELECTRIC
- D07B—ROPES OR CABLES IN GENERAL
- D07B2201/00—Ropes or cables
- D07B2201/20—Rope or cable components
- D07B2201/2015—Strands
- D07B2201/2023—Strands with core
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- D—TEXTILES; PAPER
- D07—ROPES; CABLES OTHER THAN ELECTRIC
- D07B—ROPES OR CABLES IN GENERAL
- D07B2201/00—Ropes or cables
- D07B2201/20—Rope or cable components
- D07B2201/2015—Strands
- D07B2201/2036—Strands characterised by the use of different wires or filaments
- D07B2201/2037—Strands characterised by the use of different wires or filaments regarding the dimension of the wires or filaments
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- D—TEXTILES; PAPER
- D07—ROPES; CABLES OTHER THAN ELECTRIC
- D07B—ROPES OR CABLES IN GENERAL
- D07B2201/00—Ropes or cables
- D07B2201/20—Rope or cable components
- D07B2201/2015—Strands
- D07B2201/2038—Strands characterised by the number of wires or filaments
- D07B2201/204—Strands characterised by the number of wires or filaments nine or more wires or filaments respectively forming multiple layers
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- D—TEXTILES; PAPER
- D07—ROPES; CABLES OTHER THAN ELECTRIC
- D07B—ROPES OR CABLES IN GENERAL
- D07B2205/00—Rope or cable materials
- D07B2205/30—Inorganic materials
- D07B2205/3021—Metals
- D07B2205/3025—Steel
- D07B2205/3046—Steel characterised by the carbon content
- D07B2205/3057—Steel characterised by the carbon content having a high carbon content, e.g. greater than 0,8 percent respectively SHT or UHT wires
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- D—TEXTILES; PAPER
- D07—ROPES; CABLES OTHER THAN ELECTRIC
- D07B—ROPES OR CABLES IN GENERAL
- D07B2501/00—Application field
- D07B2501/20—Application field related to ropes or cables
- D07B2501/2015—Construction industries
- D07B2501/2023—Concrete enforcements
Abstract
The invention belongs to the technical field of steel strand for prestressed concrete, relates to a production technology of steel strand for wind power engineering, and particularly relates to a large-size hot-galvanized prestressed steel strand and a manufacturing method thereof. Including a central silk and six limit silks, its characterized in that: the nominal diameter range of the central wire is 7.45-7.55mm, the nominal diameter range of the side wire is 7.25-7.35mm, the nominal diameter after twisting is 21.6mm, the allowable deviation range is 21.45-22.20 mm, and the tensile strength in the process parameters of the galvanized steel strand is more than or equal to 2000MPa. The manufacturing method of the large-size hot-galvanized prestressed steel strand comprises the following steps of wire rod selection → inspection, test → acid washing, phosphating → drawing → inspection, test → hot galvanizing → drawing after plating → twisting → stabilizing treatment → layer winding → inspection, test → packaging → warehousing.
Description
Technical Field
The invention belongs to the technical field of steel strand for prestressed concrete, relates to a production technology of steel strand for wind power engineering, and particularly relates to a large-size hot-galvanized prestressed steel strand and a manufacturing method thereof.
Background
With the development of wind power in the middle, east and south areas of China, the low-wind-speed wind turbine generator becomes a new favorite in the industry. In the face of relatively poor wind energy resource conditions, a higher wind turbine tower is applied, the height of a hub is increased, and higher-quality wind energy resources are captured, so that the method is one of important means for improving the power generation benefits of the low-wind-speed wind turbine.
Based on the development background, the combined university of Tongji of Tian Si science and technology Limited in Qingdao develops a prestressed framework type wind turbine tower, and a better solution is brought to the development of a low-wind-speed wind power plant.
The steel tube tower of the prestressed anti-fatigue framework type wind turbine generator consists of four parts: the tower comprises an independent foundation, a framework type steel pipe tower frame, a transition section and a traditional tower barrel, wherein prestressed steel strands are arranged in a tower column of the framework type tower frame, the prestressed steel strands penetrate from the bottom to the top of the tower column, the top end of the prestressed steel strands is tensioned and fixed to the top of the tower column, and the bottom end of the prestressed steel strands is anchored in a foundation fixing device.
The prestressed frame tower has the advantages of strong fatigue resistance and corrosion resistance, good durability, steel saving, low manufacturing cost, good stability and convenient field construction. The prestressed steel strands are arranged in the tower column, so that the influence on the service life of the tower after the height of the tower is increased can be effectively avoided.
At present, the application of a steel pipe tower of a domestic framework type wind turbine generator system belongs to a starting stage, prototype trial operation and small-batch demonstration application are carried out on the tower, and meanwhile, the wind turbine generator system towers of 140 meters, 160 meters, 180 meters and even higher are successively pushed out in the wind turbine industry, so that higher benefits are created for the wind turbine industry by a better solution.
Through understanding, the high tower frame is erect in the coastal region, and the steel strand wires can expose and carry out the stretch-draw use in the coastal humid environment, in order to prevent the corrosion of steel strand wires, need improve the corrosion resisting property of steel strand wires to 160 meters high tower need possess the wind-resistance, will improve the bearing capacity of steel strand wires, thereby improves the life of wind tower.
The galvanizing protection is an internationally recognized effective anticorrosion form at present, the prestressed hot-dip galvanized steel strand is a structural material with excellent anticorrosion performance, and in the current national standard GB/T5224-2014 steel strand for prestressed concrete, the maximum specification of the steel strand is phi 21.6mm, but no regulation is made on the hot-dip galvanized steel strand in the standard. In the national standard GB/T33363-2016 (prestressed hot-dip galvanized steel strand) and the authoritative standard French NF A35-035-2001 standard of international prestressed galvanized steel strands, the maximum specifications of the galvanized steel strands with the 1 × 7 structure are 17.80 mm and 15.70mm respectively, so that the current domestic and foreign standards do not provide for the product requirements of the hot-dip galvanized steel strands with the 1 × 7-phi 21.6 mm. And no product meeting the relevant performance requirements is available in the market. Based on the technical blank and the application prospect, a 1860MPa phi 21.6mm large-specification high-strength prestressed hot-dip galvanized steel strand product is designed.
Disclosure of Invention
The invention aims to overcome the defects of the prior art and provides a large-size hot-dip galvanized prestressed steel strand and a manufacturing method thereof.
The technical problem to be solved by the invention is realized by adopting the following technical scheme:
a large-specification hot galvanizing prestress steel strand comprises a center wire and six side wires and is characterized in that: the nominal diameter range of the central yarn is 7.45-7.55mm, the nominal diameter range of the side yarn is 7.25-7.35mm, the nominal diameter after twisting is 21.6mm, and the allowable deviation range is 21.45-22.20 mm.
Moreover, the tensile strength in the process parameters of the galvanized steel strand is more than or equal to 1860MPa.
The manufacturing method of the large-size hot galvanizing prestress steel strand comprises the following steps of wire rod selection → inspection, test → acid washing, phosphating → drawing → inspection, test → hot galvanizing → drawing after plating → twisting → stabilizing treatment → layer winding → inspection, test → packaging → warehousing, and is characterized in that: the wire rod with the diameter of 14.0mm is used as the raw material of the central wire and the outer layer wire, the initial strength is not less than 1400MPa, and the reduction of area is not less than 28%.
Further, in the wire rod selecting procedure, the wire rod with the diameter of 14.0mm is specially developed, and the mass components of the wire rod are C%:0.90 to 0.98; si%:0.30 to 0.50; mn%:0.60 to 0.90; p%: less than or equal to 0.025; s%: less than or equal to 0.025; cr%: less than or equal to 0.35; n i%: less than or equal to 0.20; cu%: less than or equal to 0.20; v% is less than or equal to 0.10; al%: less than or equal to 0.035; ti%: less than or equal to 0.025; w%: less than or equal to 0.025.
Further, in the acid washing and phosphating working procedures, the phosphating processThe time adjustment of (2) is: 1.5-2 min, wherein the quality of the obtained phosphating film is as follows: 3 to 7g/m 2 。
Furthermore, in the hot galvanizing and drawing processes, the diameter of the drawn steel wire before galvanization, after galvanization and after galvanization needs to be designed and matched, wherein the diameter of the steel wire before galvanization of the central wire is 7.58mm, the allowable deviation range is 7.58-7.60mm, the diameter of the steel wire of the central wire after galvanization is more than or equal to 7.65mm, the diameter of the steel wire of the central wire after galvanization and drawing is 7.50mm, and the allowable deviation range is 7.48-7.55 mm; the diameter of the steel wire before galvanizing the side wire is 7.38mm, the allowable deviation range is 7.38-7.40mm, the diameter of the steel wire after galvanizing is more than or equal to 7.45mm, the diameter of the steel wire after galvanizing and drawing is 7.30mm, and the allowable deviation range is 7.28-7.35 mm.
Furthermore, in the hot galvanizing procedure, the galvanized steel wire needs to be inspected, and the galvanized steel wire is required to be tightly wound on a mandrel with the diameter being 4 times that of the galvanized steel wire for 6 circles, so that a galvanized layer is firmly attached to the steel wire and does not crack, or the galvanized layer is rubbed by fingers and does not fall off and peel; the zinc loading of the semi-finished steel wire is more than or equal to 270g/m 2 (ii) a The galvanized steel wire should have smooth surface, no zinc lumps, uniform zinc layer, and no allowance for local dezincification and iron exposure.
Furthermore, a single-pass drawing forming process is adopted for the galvanized steel wire, the compression rate of the single-pass drawing forming process is 2% -4%, the size of a sizing belt of the drawing die is smaller than that of the smooth steel wire, and the working cone angle is larger than that of the smooth steel wire.
Further, in the twisting step, the lay length of the steel strand is set to 300mm, which is about 14 times of the nominal diameter, and the allowable range is as follows: 290-345 mm.
Further, in the stabilizing treatment process, the tempering temperature range of the steel strand is as follows: 380 +/-10 ℃, the tension is set to be 235kN, the vehicle speed is set to be 25m/min, and the tempering elongation is 1.0-1.5 percent.
The invention has the advantages and positive effects that:
the hot-dip galvanized steel strand for the wind power engineering adopts a 1 x 7 structure, has the specification of 21.60mm and the tensile strength of 1860MPa.
In the manufacturing process of the steel strand, the wire matching design, the selection of wire rods, the hot galvanizing process, the drawing process, the twisting process and the stabilizing treatment process are redesigned. In order to achieve 1860MPa high strength level, the diameter of the steel strand should be properly enlarged when a development target is set, and specifications of the side wire, the center wire and the steel strand are designed.
The steel strand in the invention requires large specification and high strength, and the large specification raw material wire rod with the diameter of more than 13mm which can be purchased in the market at present has the defects of mature technology and large performance fluctuation. In addition, the mechanical properties of the steel wire are greatly influenced in the hot galvanizing process by adopting the hot galvanizing process, and the tensile strength of the steel wire is lost after hot galvanizing, so that the 1860MPa level of the hot galvanized steel strand with the diameter of 21.6mm is more difficult to realize, and in conclusion, the raw material wire rod needs to be researched and developed again. In the wire rod used by the invention, a micro-alloying means is utilized to seek the breakthrough of a large-specification high-strength raw material wire rod, and a micro-alloying steel wire rod special for a large-specification hot-dip galvanized prestressed steel strand is jointly developed through cooperation. In the chemical components of the wire rod, the content of C, si element is improved, a proper amount of trace elements such as Cr, ni and V is increased, the trace elements such as Al, ti and W are increased, the strength is improved, the effect of refining grains is achieved, the stability of raw materials is improved, and excessive loss of tensile strength and toughness of the steel strand after galvanization is avoided. And the phenomena of fracture and the like caused by large total compression ratio, high strength and severe deformation strengthening in the drawing process of the large-size raw material wire rod are considered, so that strict requirements are provided for the content of harmful elements such as S, P, cu in the steel.
On the basis of controlling the raw material components, the specification of the raw material is designed to be phi 14.0mm according to an empirical formula R n ＝kR 0 (d 0 /d n ) 1/2, and determining the parameter requirements that the initial strength of the wire rod is not less than 1400MPa and the reduction of area is not less than 28% by combining the specific condition of the strengthening coefficient k of wire drawing equipment of the company.
In the invention, in the hot galvanizing procedure, in order to ensure the firmness and uniformity of the galvanized layer, the surface pickling phosphating process of the wire rod is extremely important. On one hand, the technological parameters such as pickling concentration, pickling time and the like are determined to ensure that the scale of the large-size wire rod is cleaned. On the other hand, in the phosphating treatment process, the thickness of the phosphating film needs to be considered. The thickness of the phosphating film not only ensures the smoothness of the drawing process, but also is beneficial to cleaning before galvanization. Based on the reasons, the time of the phosphating process is finally determined through repeated demonstration of a plurality of experiments, so that the quality of the obtained phosphating film is slightly lower than that of the phosphating film for producing the common steel strand.
In the drawing process, the diameters of the drawn steel wires before, after and after galvanizing are designed according to the thickness of the galvanizing layer. And corresponding indexes are set after the galvanizing process so as to verify that the galvanized steel wire meets the corresponding production requirements.
In the present invention, a certain zinc layer deposition occurs in the steel wire after the hot dip galvanizing treatment. In the twisting process of the steel strand, the size of the stranded forming and the abrasion and falling of the zinc coating on the surface of the steel wire can be influenced. In order to ensure the smooth completion of the twisting process, a single-pass galvanized steel wire drawing forming process is designed, the quality of a zinc layer is more uniform and compact through one-pass drawing of the galvanized steel wire, the uniform and consistent appearance size of the steel strand can also be ensured, and the surface finishing treatment is carried out on the galvanized steel wire. Because drawing after plating is bimetal drawing, the ductility of the zinc coating and the steel base is asynchronous. Therefore, the die tooling is designed in size and angle to achieve synchronous drawing of the bimetal. According to the size and angle design of the die, the surface defects such as zinc scraping and zinc layer non-uniform deformation do not occur in the actual production, and the obtained zinc coating is uniform and compact.
In the twisting process, the lay length of the 1 multiplied by 7 structure prestressed steel strand is 12 to 16 times of the nominal diameter of the steel strand according to the national standard, the comprehensive design requirement and the performance parameters are considered, the lay length is set to be 300mm (14 times of the nominal diameter), and the range of the lay length parameters is determined to be 290 to 345mm.
In the stabilizing treatment process, the temperature of stabilizing treatment is properly increased, the vehicle speed is reduced, and the tempering temperature range of the finally determined steel strand is as follows: 380 +/-10 ℃, the tension is set to be 235kN, the vehicle speed is set to be 25m/min, and the tempering elongation is 1.0-1.5 percent. The optimized optimal stabilization treatment process ensures that the performance indexes of the hot-dip galvanized steel strand, such as tensile strength, yield strength, elongation and the like, meet the requirements of development targets.
In the invention, the process optimization is realized based on the design and the matching of all working procedures, and the tensile strength of the steel strand manufactured by trial can reach more than 2000MPa. The steel strand is applied to the prestressed anti-fatigue framework type wind tower, and can meet the requirement on the service performance of the steel strand when the installation height of a fan is increased to 160 meters, so that the capacity of capturing wind resources is improved, and more electric energy is obtained. Compared with other towers with the same height, the wind tower directly reduces the comprehensive cost by 10-20%, but increases the power generation amount by 3-8%.
Description of the drawings:
fig. 1 is a schematic cross-sectional view of a steel strand according to the present invention.
Detailed Description
The present invention is further illustrated by the following specific examples, which are intended to be illustrative, not limiting and are not intended to limit the scope of the invention.
The invention discloses a large-specification hot-dip galvanized prestressed steel strand, which comprises a center wire and six side wires, and is characterized in that the nominal diameter range of the center wire is 7.45-7.55mm, the nominal diameter range of the side wires is 7.25-7.35mm, the nominal diameter after twisting is 21.60mm, and the allowable deviation range is 21.45-22.0 mm.
In the embodiment, the tensile strength of the galvanized steel strand is more than or equal to 1860MPa.
The manufacturing method of the large-size hot galvanizing prestress steel strand comprises the following steps of wire rod selection → inspection, test → acid washing, phosphating → drawing → inspection, test → hot galvanizing → drawing after plating → twisting → stabilizing treatment → layer winding → inspection, test → packaging → warehousing, and is characterized in that: the wire rod with the diameter of 14.0mm is used as the raw material of the central wire and the outer layer wire, the initial strength is not less than 1400MPa, and the reduction of area is not less than 28%.
On the basis of controlling the raw material components, the specification of the raw material is designed to be phi 14.0mm according to an empirical formula R n ＝kR 0 (d 0 /d n ) 1/2, and determining the parameter requirements that the initial strength of the wire rod is not less than 1400MPa and the reduction of area is not less than 28% by combining the specific condition of the strengthening coefficient k of wire drawing equipment of the company.
In the embodiment, in the wire rod selecting procedure, a wire rod with the diameter of 14.0mm is specially developed, and the wire rod comprises the following mass components: 0.90 to 0.98; si%:0.30 to 0.50; mn%:0.60 to 0.90; p%: less than or equal to 0.025; s%: less than or equal to 0.025; cr%: less than or equal to 0.35; ni%: less than or equal to 0.20; cu%: less than or equal to 0.20; v% is less than or equal to 0.10; al%: less than or equal to 0.035; ti%: less than or equal to 0.025; w%: less than or equal to 0.025. The quality component of the alloy improves the content of C, si element, properly increases the content of Cr, ni and V microelements, increases the microelements such as Al, ti and W, and strictly limits S, P, cu and other harmful elements.
Because a large-size high-strength raw material wire rod is adopted, in the processing process, the power and the limitation of the drawing pass of the existing wire drawing machine can cause the influence of various adverse factors of subsequent drawing, such as insufficient drawing force, poor plasticity and toughness index of a steel wire, breakage in drawing and the like. For this reason, special requirements are required for controlled cooling of high-strength microalloyed wire rods. The process flow of the high-speed wire controlled rolling and cooling process is as follows:
billet heating, rough rolling, medium rolling, finish rolling, wire spinning, controlled cooling, wire rewinding and packaging
Heating a steel billet, wherein the tapping temperature is 980-1060 ℃, rough rolling, medium rolling and finish rolling are carried out, the final spinning temperature is 860-880 ℃, cooling is controlled on a Stelmor roller way, a wire rod is coiled and scattered on the roller way, a coil is blown by a fan arranged below the roller way to be cooled in the transportation process, the speed of the roller way and the air cooling capacity of the fan are adjustable, the adjustment is carried out according to different product steel numbers and specifications, and the cooling speed is controlled by the speed and the air cooling capacity of the roller way.
In addition, after controlled cooling on a Stelmor roller way, the method increases the sorbitizing isothermal treatment of the off-line salt bath of the wire rod, and uses the isothermal salt bath as a quenching medium to carry out the sorbitizing treatment, thereby realizing the approximate isothermal phase change of the wire rod. After the stelmor line air-cooled wire rod is subjected to sorbitizing treatment by an off-line salt bath, the sorbitizing rate is improved to 95 percent from 89 percent, bad tissues such as net carbides are eliminated, and the microstructure is more uniform; the high-strength wire rod and the high-sorbite-rate wire rod are obtained at the same time, and conditions are created for smooth follow-up drawing process of a company.
In this embodiment, in the acid washing and phosphating processes, the time of the phosphating process is adjusted to: 1.5-2 min, wherein the quality of the obtained phosphating film is as follows: 3 to 7g/m 2 。
In the example, the drawing before plating was performed by reducing the drawing speed and reducing the drawing stress as much as possible by adopting a multi-pass drawing process, and the strengthening coefficient K value of the drawing process was ensured to be 1.0 or less, and the strengthening coefficient K value of the drawing process was usually 1.02 to 1.03. According to the calculation of an empirical formula, if the K value is lower than 1.0, the tensile strength of the steel wire semi-finished product after drawing is slightly reduced, but under the condition that the initial strength of the raw materials is met, the deformation of the steel wire semi-finished product is small, the tensile strength performance is stable, the excessive loss of the tensile strength of the steel wire after hot galvanizing caused by the violent reaction of zinc liquid and iron due to the high content of C, si in the raw materials can be avoided, and the tensile strength level during smooth drawing can still be maintained.
In the formula: sigma b0 -initial strength of the wire rod; sigma b1 -tensile strength of the wire after drawing; d 0 -wire rod diameter; d 1 -wire diameter after drawing; k-strengthening factor.
In the embodiment, in the hot galvanizing and drawing processes, the diameter of the drawn steel wire before galvanization, after galvanization and after galvanization needs to be designed and matched, wherein the diameter of the steel wire before galvanization of the central wire is 7.58mm, the allowable deviation range is 7.58-7.60mm, the diameter of the steel wire of the central wire after galvanization is more than or equal to 7.65mm, the diameter of the steel wire of the central wire after galvanization and drawing is 7.50mm, and the allowable deviation range is 7.48-7.55 mm; the diameter of the steel wire before galvanizing the side wire is 7.38mm, the allowable deviation range is 7.38-7.40mm, the diameter of the steel wire after galvanizing is more than or equal to 7.45mm, the diameter of the steel wire after galvanizing and drawing is 7.30mm, and the allowable deviation range is 7.28-7.35 mm. The dimensions of the steel wire at each stage of the design are shown in table 1.
Diameter of steel wire before and after galvanizing table 1
| Steel wire diameter before galvanization (mm) | Galvanized steel wire diameter (mm) | Galvanized steel wire drawing back diameter (mm) | |
| Center wire | 7.58(0,+0.02) | ≥7.65 | 7.50(+0.05,-0.02) |
| Edge thread | 7.38(0,+0.02) | ≥7.45 | 7.30(+0.05,-0.02) |
In this example, in the hot dip galvanizing process, the galvanized steel wire needs to be inspected, and it is required that the galvanized steel wire is tightly wound on a mandrel with a diameter of 4 times that of the galvanized steel wire for 6 turns, and a galvanized layer is firmly attached to the steel wireThe zinc coating does not crack or fall off and peel when being rubbed by fingers; the zinc loading of the semi-finished steel wire is more than or equal to 270g/m 2 (ii) a The galvanized steel wire should have smooth surface, no zinc lumps, uniform zinc layer, and no allowance for local dezincification and iron exposure. The outsourcing galvanized steel wires are subjected to axis-by-axis acceptance, and the size and the zinc layer quality of the galvanized steel wires are shown in a table 2.
Inspection data Table 2 of galvanized Steel wires
In the embodiment, the galvanized steel wire is subjected to a single-pass drawing forming process, the single-pass drawing forming compression rate is in a range of 2% -4%, the size of a sizing zone of the drawing die is smaller than that of the plain round steel wire, and the working cone angle is larger than that of the plain round steel wire. Through tests, the size and angle of the die are reasonably designed, the drawing is smooth, surface defects such as zinc scraping and zinc layer non-uniform deformation do not occur, and the obtained zinc coating is uniform and compact. The semi-finished steel wire drawn after plating was tested, and the test data are shown in Table 3.
Inspection data table 3 of the galvanized steel wire after single-pass forming
In the embodiment, the lay length of the prestressed steel strand with the 1 × 7 structure is regulated in the national standard GB/T5224-2014 steel strand for prestressed concrete, and is 12-16 times of the nominal diameter of the steel strand. Therefore, we consider both the twist loss and the compactness of the steel strand when designing the lay length, and set the lay length of the steel strand to 300mm (14 times of the nominal diameter), with the allowable range: 290-345 mm.
In this embodiment, in the stabilizing process, the tempering temperature range of the steel strand is as follows: 380 +/-10 ℃, the tension is set to be 235kN, the vehicle speed is set to be 25m/min, and the tempering elongation is 1.0-1.5 percent.
The steel strand inspection and test process described in the present patent application is as follows:
the company has advanced detection and test equipment such as a large-tonnage tensile testing machine, a stress corrosion testing machine, a Chuiss metallographic microscope, a Sipek direct-reading spectrometer and the like, and can realize the self-detection of all detection items of a new product from a raw material wire rod, a semi-finished product and a finished product.
The project detects the chemical components, the metallographic structure, the diameter, the tensile strength, the reduction of area, the surface quality and the like of the raw materials; detecting the diameter, tensile strength, zinc layer quality, winding and the like of the semi-finished product; and (4) detecting mechanical properties and corrosion resistance such as diameter, tensile strength, yield strength, relaxation performance, zinc layer quality and uniformity and the like of the finished steel strand. The test method is carried out according to GB/T5224-2014 steel strand for prestressed concrete and the test method according to GB/T21839-2019 steel test method for prestressed concrete and other current test standards and test operation rules formulated by the company.
Through the development of large-size raw materials and the technical research on the product manufacturing process, we successfully develop and develop a 1860MPa phi 21.6mm large-size high-strength hot-dip galvanized steel strand for wind power engineering in a low wind speed area. The galvanized steel strand is subjected to strand splitting, the zinc sheet is removed from the steel wire, a mechanical property test is performed, and the test data are shown in table 4.
Mechanical property data table 4 of steel wire after strand splitting
| Diameter mm | 7.23 | 7.21 | 7.20 | 7.23 | 7.22 | 7.23 | 7.37 | Resultant force |
| Force value kN | 85.4 | 87.0 | 84.6 | 87.0 | 85.0 | 86.6 | 90.2 | 605.8 |
The galvanized steel strand is self-checked, and the inspection data are shown in table 5.
Inspection data table 5 for galvanized steel strand of 1X 7-phi 21.6mm
The steel strand product is sent to a specified national building steel quality supervision and inspection center for outsourcing inspection in 2019, 12 months and 9 days, and the inspection data are shown in a table 6.
Data table 6 for outsourcing inspection of steel strands
The hot-dip galvanized steel strand for the wind power engineering adopts a 1 x 7 structure, has the specification of 21.60mm and the tensile strength of 1860MPa.
In the manufacturing process of the steel strand, the wire matching design, the selection of wire rods, the hot galvanizing process, the drawing process, the twisting process and the stabilizing treatment process are redesigned. In order to achieve 1860MPa high strength level, the diameter of the steel strand needs to be increased properly when a development target is determined, and the specifications of the side wire, the center wire and the steel strand are designed.
The steel strand in the invention requires large specification and high strength, and the large specification raw material wire rod with the diameter of more than 13mm which can be purchased in the market at present has the defects of immature technology and large performance fluctuation. In addition, the mechanical properties of the steel wire are greatly affected in the hot galvanizing process by adopting the hot galvanizing process, and the tensile strength of the steel wire is lost after hot galvanizing, so that the 1860MPa level of the hot galvanized steel strand with the diameter of 21.6mm is more difficult to realize, and in conclusion, the raw material wire rod needs to be researched and developed again. In the wire rod used by the invention, a micro-alloying means is utilized to seek the breakthrough of a large-specification high-strength raw material wire rod, and a micro-alloying steel wire rod special for a large-specification hot-dip galvanized prestressed steel strand is jointly developed through cooperation. In the chemical components of the wire rod, the content of C, si element is improved, the content of Cr, ni and V microelements is increased in a proper amount, al, ti, W and other microelements are increased, the strength is improved, the effect of refining grains is achieved, the stability of raw materials is improved, and the excessive loss of the tensile strength and the toughness of the steel strand after galvanization is avoided. And the phenomena of fracture and the like caused by large total compression ratio, high strength and severe deformation strengthening in the drawing process of the large-size raw material wire rod are considered, so that strict requirements are provided for the content of harmful elements such as S, P, cu in the steel.
On the basis of controlling the raw material components, the specification of the raw material is designed to be phi 14.0mm according to an empirical formula R n ＝kR 0 (d 0 /d n ) 1/2, and determining the parameter requirements that the initial strength of the wire rod is not less than 1400MPa and the reduction of area is not less than 28% by combining the specific condition of the strengthening coefficient k of wire drawing equipment of the company.
In the invention, in the hot galvanizing procedure, in order to ensure the firmness and uniformity of the galvanized layer, the surface pickling phosphating process of the wire rod is extremely important. On one hand, the technological parameters such as pickling concentration, pickling time and the like are determined to ensure that the scale of the large-size wire rod is cleaned. On the other hand, in the phosphating treatment process, the thickness of the phosphating film needs to be considered in an important way. The thickness of the phosphating film not only ensures the smoothness of the drawing process, but also is beneficial to cleaning before galvanization. Based on the reasons, the time of the phosphating process is finally determined through repeated demonstration of a plurality of experiments, so that the quality of the obtained phosphating film is slightly lower than that of the phosphating film for producing the common steel strand.
In the drawing process, the diameters of the drawn steel wires before, after and after galvanizing are designed according to the thickness of the galvanized layer. And corresponding indexes are set after the galvanizing process so as to verify that the galvanized steel wire meets the corresponding production requirements.
In the present invention, after the hot dip galvanizing treatment, the steel wire has a certain zinc layer deposition. In the twisting process of the steel strand, the size of the stranded forming and the abrasion and falling of the zinc coating on the surface of the steel wire can be influenced. The single-pass galvanized steel wire drawing forming process is designed for ensuring the smooth completion of the twisting process, the quality of a zinc layer is more uniform and compact through one-pass drawing of the galvanized steel wire, the uniform and consistent appearance size of the steel strand can also be ensured, and the surface finishing treatment is carried out on the hot-galvanized steel wire. Because drawing after plating is bimetal drawing, the ductility of the zinc coating and the steel base is asynchronous. Therefore, the die tooling is designed in size and angle to achieve synchronous drawing of the bimetal. According to the size and angle design of the die, the surface defects such as zinc scraping and zinc layer non-uniform deformation do not occur in the actual production, and the obtained zinc coating is uniform and compact.
In the twisting process, the lay length of the prestressed steel strand with the 1 × 7 structure is 12-16 times of the nominal diameter of the steel strand according to the national standard, the comprehensive design requirement and performance parameters are considered, the lay length is set to be 300mm (14 times of the nominal diameter), and the range of the lay length parameters is determined to be 290-345 mm.
In the stabilizing treatment process, the temperature of stabilizing treatment is properly increased, the speed of the vehicle is reduced, and the finally determined tempering temperature range of the steel strand is as follows: 380 +/-10 ℃, the tension is set to be 235kN, the vehicle speed is set to be 25m/min, and the tempering elongation is 1.0-1.5 percent. The optimized optimal stabilization treatment process ensures that the performance indexes of the hot-dip galvanized steel strand, such as tensile strength, yield strength, elongation and the like, meet the requirements of development targets.
In the invention, the process optimization is realized based on the design and the matching of all working procedures, and the tensile strength of the steel strand manufactured by trial can reach more than 2000MPa. The steel strand is applied to the prestressed anti-fatigue framework type wind tower, and can meet the requirement on the service performance of the steel strand when the installation height of a fan is increased to 160 m, so that the capacity of capturing wind resources is improved, and more electric energy is obtained. Compared with other towers with the same height, the wind tower directly reduces the comprehensive cost by 10-20%, but increases the power generation by 3-8%.
Claims (6)
1. The manufacturing method of the large-size hot galvanizing prestress steel strand comprises a center wire and six side wires, and is characterized in that: the nominal diameter range of the central wire is 7.45-7.55mm, the nominal diameter range of the side wire is 7.25-7.35mm, the nominal diameter after twisting is 21.6mm, the allowable deviation range is 21.45-22.20 mm, and the tensile strength in the process parameters of the galvanized steel strand is more than or equal to 1860MPa;
the manufacturing method of the steel strand comprises the following steps of wire rod selection → inspection, test → acid washing, phosphating → drawing → inspection, test → hot galvanizing → post-plating drawing → twisting → stabilizing treatment → layer winding → inspection, test → packaging → warehousing, and is characterized in that: adopting a wire rod with the diameter of 14.0mm as a raw material of a central wire and an outer layer wire, wherein the initial strength is not less than 1400MPa, and the reduction of area is not less than 28%;
in the wire rod selection procedure, a wire rod with the diameter of 14.0mm is specially developed, and the wire rod comprises the following mass components in percentage by mass: 0.90 to 0.98; si%:0.30 to 0.50; mn%:0.60 to 0.90; p%: less than or equal to 0.025; s%: less than or equal to 0.025; cr%: less than or equal to 0.35; ni%: less than or equal to 0.20; cu%: less than or equal to 0.20; v% is less than or equal to 0.10; al%: less than or equal to 0.035; ti%: less than or equal to 0.025; w%: less than or equal to 0.025 percent, and the rest elements are iron elements; in the hot galvanizing and drawing processes, the diameter of a drawn steel wire before galvanization, after galvanization and after galvanization needs to be designed and matched, wherein the diameter of the steel wire before galvanization of the central wire is 7.58mm, the allowable deviation range is 7.58-7.60mm, the diameter of the steel wire of the central wire after galvanization is more than or equal to 7.65mm, the diameter of the steel wire of the central wire after galvanization and drawing is 7.50mm, and the allowable deviation range is 7.48-7.55 mm; the diameter of the steel wire before galvanizing the side wire is 7.38mm, the allowable deviation range is 7.38-7.40mm, the diameter of the steel wire after galvanizing is more than or equal to 7.45mm, the diameter of the steel wire after galvanizing and drawing is 7.30mm, and the allowable deviation range is 7.28-7.35 mm.
2. The method for manufacturing the large-size hot-galvanized prestressed steel strand as claimed in claim 1, wherein the method comprises the following steps: in the acid washing and phosphating procedures, the time of the phosphating process is adjusted as follows: 1.5 to 2min, wherein the quality of the obtained phosphating film is as follows: 3 to 7g/m 2 。
3. The method for manufacturing the large-size hot-galvanized prestressed steel strand as claimed in claim 1, wherein the method comprises the following steps: in the hot galvanizing procedure, the galvanized steel wire needs to be inspected, and the galvanized steel wire is required to be tightly wound on a mandrel with the diameter being 4 times that of the galvanized steel wire for 6 circles, so that a galvanized layer is firmly attached to the steel wire and does not crack, or the galvanized layer is rubbed by fingers to avoid peeling; the zinc adding amount of the semi-finished steel wire is more than or equal to 270g/m 2 (ii) a The galvanized steel wire should have smooth surface, no zinc lumps, uniform zinc layer, and no allowance for local dezincification and iron exposure.
4. The method for manufacturing the large-size hot-galvanized prestressed steel strand as claimed in claim 1, wherein the method comprises the following steps: the galvanized steel wire is subjected to a single-pass drawing forming process, the single-pass drawing forming compression rate is in a range of 2% -4%, the size of a sizing belt of a drawing die is smaller than that of the plain round steel wire, and the working cone angle is larger than that of the plain round steel wire.
5. The method for manufacturing the large-size hot-galvanized prestressed steel strand as claimed in claim 1, wherein the method comprises the following steps: in the twisting process, the twist pitch of the steel strand is set to be 300mm, which is about 14 times of the nominal diameter, and the allowable range is as follows: 290 to 345mm.
6. The method for manufacturing the large-size hot-galvanized prestressed steel strand as claimed in claim 1, wherein the method comprises the following steps: in the stabilizing treatment procedure, the tempering temperature range of the steel strand is as follows: 380 +/-10 ℃, the tension is set to be 235kN, the vehicle speed is set to be 25m/min, and the tempering elongation is 1.0-1.5 percent.
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| CN113445338A (en) * | 2021-06-30 | 2021-09-28 | 新余新钢金属制品有限公司 | Aluminum-clad steel wire with high torsion performance |
| CN114653765B (en) * | 2022-03-31 | 2024-03-22 | 宣化钢铁集团有限责任公司 | Production method of 1860 Mpa-level steel strand |
| CN115627468A (en) * | 2022-10-14 | 2023-01-20 | 广东冀安筛网有限公司 | Preparation method of stainless steel wire mesh |
| CN115673010B (en) * | 2022-12-30 | 2023-03-31 | 天津市新天钢中兴盛达有限公司 | Manufacturing method of corrosion-resistant steel strand with thick zinc layer |
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