Low-relaxation prestressed special stainless steel wire for cable stay and its production method

Abstract

The present application relates to the field of steel wire production, and more particularly to a low-relaxation pre-stressed special stainless steel wire for hoisting cable and a production method thereof, comprising the following steps: S1, wire rod surface treatment: pickling the wire rod to remove the scale and other impurities; S2, offline film lubrication: applying pressure-resistant coating to the surface of the wire rod; S3, online water-based lubrication: paying off and straightening the wire rod, and applying and drying an epoxy-based lubricating coating; S4, online dry lubrication: lubricating the wire rod with dry lubricating powder; S5, online temperature compensation: heating, holding and cooling the wire rod; S6, continuous drawing: drawing the metal wire rod to the required diameter or size; S7, finished product take-up: winding or coiling the metal wire rod; the stainless steel wire produced through these processes has high strength, good ductility, anti-relaxation performance and good corrosion resistance, and has wide potential in various high-performance applications.

Description

Technical Field

[0001] This invention relates to the field of steel wire production technology, and in particular to a low-relaxation prestressed special stainless steel wire for slings and its production method. Background Technology

[0002] Current prestressed low-relaxation suspenders generally use epoxy resin-coated steel strands and hot-dip galvanized steel strands as the main load-bearing structure. These steel strands are typically made of high-strength carbon steel wire or galvanized high-carbon steel wire. These materials simply add an anti-corrosion coating to the surface of easily corroded high-carbon steel wire, which only temporarily alleviates the overall corrosion resistance of the suspender. Furthermore, the anchorage requires hard contact between the anchorage and the strand, which damages the surface coating, leading to more severe corrosion of the steel wire in the anchorage section. This limits the service life of the entire suspender to the service life of the anchorage section. The performance indicators of the steel wire in suspenders produced using existing technology... Often, the requirements cannot be met. For example, the produced steel wire has poor ductility and cannot withstand long-term corrosion. These problems ultimately lead to insufficient strength and poor corrosion resistance in the manufactured steel cables. Furthermore, the existing high-carbon steel wire drawing equipment, drawing dies, and drawing reduction processes cannot meet the production needs of current special stainless steel wire. Since stainless steel and high-carbon steel are two materials with completely different alloy ratios and belong to different metal categories, their strengthening methods and phase transformation mechanisms are quite different. Therefore, the current high-carbon steel wire drawing process is completely unsuitable for the drawing production of this stainless steel wire. Summary of the Invention

[0003] (a) Technical problems to be solved To address the shortcomings of existing technologies, the present invention aims to provide a stainless steel wire for low-relaxation prestressed special stainless steel slings and its production method, thereby solving the problems existing in the prior art. The stainless steel wire for low-relaxation prestressed special stainless steel slings manufactured by this method has the following mechanical properties: tensile strength ≥1960MPa, plastic elongation Rp0.2 ≥1750MPa, elongation after fracture ≥4.0%, relaxation performance ≤2.5%, torsional performance ≥14 cycles, and winding performance ≥8 turns. It has high strength, good ductility, relaxation resistance, and good corrosion resistance, making it highly promising for various high-performance applications.

[0004] (II) Technical Solution To achieve the above objectives, the present invention provides the following technical solution: a stainless steel wire for low-relaxation prestressed special stainless steel slings and its production method, characterized by comprising the following steps: S1 wire rod surface treatment, S2 offline film lubrication, S3 online water-based lubrication, S4 online dry lubrication, S5 online temperature compensation, S6 continuous drawing, and S7 finished wire winding, wherein steps S4, S5, and S6 are performed cyclically for a total of ten times, and an online water-based lubrication step is introduced in the 8th to 10th steps, which is located before the online dry lubrication in S4.

[0005] S1. Surface Treatment of Wire Rod: In this step, the surface of the metal wire rod is pickled to remove or reduce impurities, dirt, oxides, and other impurities, thereby improving the surface quality of the metal. S2. Offline Film Lubrication: A pressure-resistant coating is added to the surface of the wire rod from step S1 to reduce friction between the wire and the drawing die. S3. Online Water-Based Lubrication: After unwinding and straightening, an epoxy-based lubricating coating is applied online, followed by online drying before the first drawing pass. S4. Online Dry Lubrication: Dry lubricating powder is used to lubricate the wire rod. S5. Online Temperature Compensation: The metal wire rod from step S4 is heated to a specific temperature range to soften the metal for subsequent processing. S6. Continuous Drawing: The metal wire rod from step S5 is passed through a series of drawing dies, gradually reducing its cross-sectional area and increasing its length. S7. Finished Wire Winding: After nine drawing passes, the steel wire produced in step S6 is wound.

[0006] Preferably, step S3, online water-based lubrication, includes: the wire rod to be treated passes through a wire feeding device to make the wire rod straight, and an epoxy-based lubricating coating is applied to the wire rod by a water-based lubrication coating device at a coating speed of 1-5 m / min. Then, it enters an online drying device with a drying temperature of 100℃-200℃ and a drying time of 1-5 min.

[0007] Preferably, the online dry lubrication method in step S4 is hydrodynamic lubrication, wherein GB227 sodium-based dry lubricating powder is used for passes 1-5 with a linear velocity of 30m / min-50m / min, and calcium-based dry lubricating powder is used for passes 5-10 with a linear velocity of 40m / min-60m / min.

[0008] Preferably, the online temperature for step S5 is as follows: the temperature of the first 3 wire drawing passes is controlled at 40-55℃ when entering the mold and at 120-160℃ when exiting the mold; the temperature of the last 7 wire drawing passes is controlled at 50-60℃ when entering the mold and at 100-130℃ when exiting the mold.

[0009] Preferably, in step S6, the pulling force is controlled at 40KN-45KN for the first 3 pulls, 20KN-35KN for the 4th to 6th pulls, and 10KN-18KN for the 7th to 10th pulls.

[0010] Preferably, the speed control in step S6, continuous pulling, adopts PID closed-loop control.

[0011] Preferably, the area reduction rate of the stainless steel wire in the ten consecutive drawing passes in step S6 is as follows: the first 3 passes: 20-24%, the 4th to 6th passes: 15-22%, and the 7th to 10th passes: 10-15%.

[0012] Preferably, the working area angle range of the drawing die in the nine consecutive drawing passes in step S6 is: 1-2 passes: 12°, 3-4 passes: 11.5°, 5-6 passes: 10°, 7th pass: 9°, 8-10 passes: 8°.

[0013] Preferably, the actual working area length range of the drawing die in the nine consecutive drawing passes in step S6 is as follows: passes 1-3: 9.5±0.4mm, passes 4-5: 13±1mm, passes 6-9: 10.0±0.3mm, and the 10th pass: 7.5±0.3mm.

[0014] (III) Beneficial Effects The stainless steel wire for low-relaxation prestressed special stainless steel slings produced by this method has the following mechanical properties: tensile strength ≥1960MPa, ductile elongation Rp0.2 ≥1750MPa, elongation after fracture ≥4.0%, relaxation performance ≤2.5%, torsional performance ≥14 cycles, and winding performance ≥8 turns. It has high strength, good ductility, relaxation resistance, and good corrosion resistance, making it highly promising for various high-performance applications. Moreover, it is cost-effective and suitable for large-scale applications. Detailed Implementation

[0015] This invention provides a technical solution: a stainless steel wire for low-relaxation prestressed special stainless steel slings and its production method, characterized by the following steps: S1, wire rod surface treatment: In this step, the surface of the metal wire rod is pickled to remove or reduce impurities, dirt, oxides and other impurities on the surface to improve the surface quality of the metal; S2, offline film lubrication: a pressure-resistant coating is applied to the surface of the wire rod; S3, online water-based lubrication: the wire rod is unwound, straightened, coated with an epoxy-based lubricating coating and then dried; S4, online dry lubrication: the wire rod is lubricated using dry lubricating powder; S5, online temperature compensation: the metal wire rod from step S4 is heated to a specific temperature range for subsequent processing; S6, continuous drawing: the metal wire rod from step S5 is drawn through a series of drawing dies, gradually reducing its cross-sectional area and increasing its length; S7, finished product winding: the metal wire or wire is wound or coiled.

[0016] Step S1, the surface treatment of the wire rod, includes: immersing the metal wire rod in an acid pickling tank, using a mixture of three acids to chemically react with oxides, dirt, and other impurities on the metal surface, dissolving or converting them into forms soluble in the solution. This process helps remove surface oxide scale, rust, grease, and other contaminants. The pickled metal wire rod is then removed from the acid tank and thoroughly rinsed to completely remove any remaining acid and impurities from the metal surface. Finally, the metal wire rod is sent to a drying device to ensure the surface is fully dry, preparing it for subsequent processing steps.

[0017] Step S2 offline film lubrication includes: applying an epoxy-based lubricating coating to the metal wire rod from step S1 using a coating device. The purpose of this step is to form a pressure-resistant coating on the wire surface, which mainly aims to reduce the friction between the wire and the drawing die, thereby improving metal flow during the drawing process and reducing die wear. Afterwards, the coating is cured and firmly adhered to the wire surface at a high temperature by using a drying device with the temperature controlled at 100-150℃. This process helps to improve the adhesion and durability of the coating.

[0018] The S3 step of online water-based lubrication includes: the wire rod to be treated first passes through a wire feeding device, a process designed to straighten the wire rod so that the subsequent coating unit can apply a lubricating coating evenly and consistently. Then, an online water-based lubrication coating unit applies an epoxy-based lubricating coating, a water-based epoxy material. The main function of this coating is to provide effective lubrication, reduce friction during the drawing process, thereby reducing surface wear and improving the surface quality of the metal. The coating speed is controlled within the range of 1-5 m / min to ensure uniformity and consistency. Appropriate adjustment of the coating speed helps ensure that the coating forms a uniform film on the wire rod surface. After the epoxy-based lubricating coating is applied, the wire rod enters an online drying unit. This unit evaporates the moisture in the water-based coating by raising the temperature, while simultaneously curing the epoxy material to form a robust lubricating film. The drying temperature is controlled between 100℃ and 200℃, and the drying time is 1-5 minutes. The lubricating coating successfully formed through step S3 will play a lubricating role in the subsequent drawing process, which helps to improve the ductility of the metal, reduce friction loss, and maintain the surface smoothness of the product.

[0019] The following steps S4, S5, and S6 are executed cyclically for a total of ten passes. In passes 8 to 10, an online water-based lubrication step is introduced, which is located before the online dry lubrication in S4. The principle is to apply water-based lubricant to the surface of the steel wire after demolding, so that a pressure-resistant coating is formed on the surface of the steel wire after the seventh pass. Then, after the subsequent three drawing passes, it helps to form a more uniform and fine lubricating film on the surface of the metal wire rod, thereby improving the quality of the metal surface.

[0020] In the S4 step of online dry lubrication, hydrodynamic lubrication is adopted. By applying dry lubricating powder, a lubricating film is formed, which reduces the friction between the metal material and the die during continuous drawing and improves the drawing efficiency. The S4 step of online dry lubrication consists of ten passes. Passes 1-5 use GB227 sodium-based dry lubricating powder, and passes 5-10 use calcium-based dry lubricating powder. The linear speed of sodium-based dry lubricating powder is 30m / min-50m / min, while the linear speed of calcium-based dry lubricating powder is 40m / min-60m / min. When the steel wire passes through the pressure lubrication die in each subsequent pass, the solid lubricating powder can be fully introduced into the forming die cavity, which can ensure sufficient lubrication in the subsequent drawing processes. This production process can ensure that there are no scratches or bamboo-like defects on the surface of the final finished steel wire.

[0021] The S5 process involves ten online temperature adjustments. In the first three adjustments, the entry temperature is controlled between 40-55℃, and the exit temperature between 120-160℃. The first purpose is to ensure the material reaches the appropriate temperature before entering the mold, which helps lubricate the material, reduce friction, minimize frictional losses within the mold, and prevent material from getting stuck or adhering to the mold. The second purpose is to shape and maintain the form: controlling the exit temperature ensures the material maintains appropriate fluidity and formability as it enters and exits the mold; a higher exit temperature helps ensure the integrity of the molding and surface quality. The third purpose is to control material properties: temperature control affects material properties such as hardness, strength, and toughness; adjusting the entry and exit temperatures controls the physical and mechanical properties of the final product. In the last seven adjustments, the entry temperature is controlled between 50-60℃, and the exit temperature between 100-130℃. This is to avoid deformation and defects. This design helps prevent unnecessary deformation and defects when the material enters and leaves the mold, contributing to maintaining product accuracy and quality.

[0022] The S6 continuous drawing process consists of ten passes. The drawing equipment is equipped with a rectifier control unit and an inverter to control the drawing motors for each pass. It also includes an inverter feedback unit. All motors use encoder closed-loop control to ensure torque control accuracy up to 1%. During the drawing process, the drawing force can be precisely controlled. Speed ​​control in continuous drawing uses PID closed-loop control, which offers the following advantages: Product quality control: It ensures that the drawing force in each pass remains within a specified range, helping to maintain product consistency and quality, and avoiding product defects or non-conforming products due to variations in drawing force; Process stability: PID closed-loop control can monitor and adjust the drawing force in real time to ensure it fluctuates within an acceptable range. This helps maintain production process stability and reduces instability factors; Avoiding excessive stress: Controlling the range of drawing force for different passes prevents excessive stress on the material, preventing damage or deformation, which is crucial for producing high-quality products; Increased production efficiency: By automatically controlling the drawing force, the need for manual operation can be reduced, improving production efficiency and consistency, which helps reduce labor costs and operational errors. The drawing force for the first three passes is controlled at 40KN-45KN, and the area reduction rate is controlled at 20-24%. The purpose of this setting is: In the initial stages of drawing, a higher drawing force and a relatively large reduction ratio help achieve initial plastic deformation, which facilitates rapid plastic processing, making it easier for the metal material to enter the desired shape. It also helps form a uniform initial structure. In the first few passes, by controlling the drawing force and reduction ratio, a more uniform and finer grain structure can be formed in the metal material, thereby improving the performance of subsequent processing stages.

[0023] The drawing force for the 4th to 6th passes is controlled between 20KN and 35KN, and the reduction ratio is controlled between 15% and 22%. At this stage, this setting of drawing force and reduction ratio helps to further deform the metal and enhance its mechanical properties, which involves more grain refinement and grain boundary strengthening. Furthermore, by adjusting the drawing force and reduction ratio, the size and shape of the product can be more precisely controlled to ensure that it meets specifications.

[0024] The drawing force for 7 to 10 passes is controlled between 10 kN and 18 kN, and the reduction rate is controlled between 10% and 15%. In the later stages of drawing, reducing the drawing force and reduction rate helps with final plastic processing, which includes further grain adjustment and material strengthening, while ensuring that excessive deformation is not achieved. Lower drawing forces and moderate reduction rates can selectively reduce grain size, thereby improving the final properties of the material. This setup allows for flexible control of the metal's deformation process at different stages, ultimately achieving the performance and structure required by the product design. This differentiated control helps maximize the utilization of the metal's properties while improving production efficiency and product quality.

[0025] The working area angle range of the drawing die for ten consecutive drawing passes is as follows: Passes 1-2: 12°, Passes 3-4: 11.5°, Passes 5-6: 10°, Pass 7: 9°, Passes 8-10: 8°. The actual working area length range of the drawing die is as follows: Passes 1-3: 9.5±0.4mm, Passes 4-5: 13±1mm, Passes 6-9: 10.0±0.3mm, Pass 10: 7.5±0.3mm. By adjusting the combination of working area angle and length, precise control of the shape and size of the stainless steel wire can be achieved simultaneously. The working area angle affects the shape, while the working area length affects the size. A reasonable combination of the two helps to meet product design requirements at different drawing stages and balances temperature and stress distribution during the drawing process. A reasonable design helps reduce temperature and stress concentration, slows wear on the die and stainless steel wire, and improves the stability of the entire production process. Finally, a reasonable combination of working area angle and length helps to improve production efficiency. They can ensure that the predetermined shape and size are achieved at each drawing stage, thereby reducing the generation of defective products and improving the stability and efficiency of the production line.

[0026] It's important to note that the reduction ratio refers to the ratio between the initial cross-sectional area of ​​the metal billet and the final product cross-sectional area; the working zone angle refers to the taper of the die's conical bore or drawing die, usually expressed in angles. This angle determines the deformation speed and extent of the metal billet during the drawing process. A larger working zone angle means a steeper taper, allowing the metal billet to be drawn into wires or tubes more quickly. The choice of working zone angle depends on the required product specifications and the specific requirements of the drawing process; minimum working zone length: the minimum working zone length refers to the length of the metal billet subjected to tensile and plastic deformation in the drawing die. Minimum length: This parameter determines the length of the metal billet required during drawing to allow for appropriate plastic deformation in the die. The minimum working length is usually determined based on the material properties, the requirements of the drawing process, and the die design. Actual working length: The actual working length refers to the length of the metal billet that is actually stretched and deformed during the drawing process. It may be slightly longer than the minimum working length because some unavoidable elongation and deformation may occur during the drawing process. The actual working length is a key parameter that needs to be precisely controlled to ensure that the dimensions and shape of the final product meet the requirements.

[0027] The following will describe the technical solution of the present invention clearly and completely. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0028] Example 1: A stainless steel wire for low-relaxation prestressed special stainless steel suspension cable and its production method, comprising the following steps: S1. Surface treatment of wire rod: Pickling is used to remove or reduce impurities, dirt, oxides and other impurities on the surface.

[0029] S2, Offline film lubrication: Add a pressure-resistant coating to the surface of the wire rod from step S1 to reduce the friction between the wire and the drawing die.

[0030] S3. Online water-based lubrication: The wire rod to be processed passes through the wire feeding equipment to make the wire rod straight. Then, an epoxy-based lubricating coating is applied to the wire rod by the water-based lubrication coating device at a speed of 3m / min. After that, it enters the online drying device at a drying temperature of 150℃ for 3min before entering the first drawing stage.

[0031] S4. Online dry lubrication: The method of hydrodynamic lubrication is adopted. A lubricating film is formed by applying dry lubricating powder. Passes 1-5 use GB227 sodium-based dry lubricating powder with a linear velocity of 30m / min, and passes 5-10 use calcium-based dry lubricating powder with a linear velocity of 40m / min.

[0032] S5. Online temperature compensation: The temperature of the first 3 wire drawing passes is 40℃ when entering the mold and 120℃ when exiting the mold; the temperature of the last 7 wire drawing passes is 50℃ when entering the mold and 100℃ when exiting the mold. S6. Continuous drawing: The metal wire rod is drawn to the required diameter or size. The specific values ​​for each pass are shown in Table 1 below. Table 1 Example 2: The rest is the same as Example 1, except that in step S3, the temperature of the first 3 wire drawing passes is 45°C when entering the mold and 140°C when exiting the mold, and the temperature of the last 6 wire drawing passes is 55°C when entering the mold and 115°C when exiting the mold.

[0033] Example 3: The rest is the same as Example 1, except that in step S3, the temperature of the first 3 wire drawing passes is 55°C when entering the mold and 160°C when exiting the mold, while the temperature of the last 6 wire drawing passes is 60°C when entering the mold and 130°C when exiting the mold.

[0034] Example 4: The rest is the same as Example 2, except that the specific values ​​of the reduction rate for each pass are shown in Table 2 below.

[0035] Table 2 Comparative Example 1: The rest is the same as Example 2, except that there are 6 drawing passes, and the specific values ​​of the reduction rate for each pass are shown in Table 3 below.

[0036] Table 3 Comparative Example 2: The rest is the same as Example 2, except that there are 8 drawing passes, and the specific values ​​of the reduction rate for each pass are shown in Table 4 below.

[0037] Table 4 Comparative Example 3: The rest is the same as Example 2, except that there are 12 drawing passes, and the specific values ​​of the reduction rate for each pass are shown in Table 5 below.

[0038] Table 5 Mechanical property tests were conducted on the above embodiments and comparative examples, and the data are shown in Table 6 below: Mechanical Property Test Table Table 6 As can be seen from the data in Table 2, the stainless steel wire rods processed by the present invention have significant advantages over the stainless steel wire rods of the prior art in terms of yield strength, tensile strength, elongation and corrosion resistance. In particular, the advantages of the stainless steel wire rods produced in Example 2 and Comparative Example 3 are more obvious. Considering the overall production cost, the chemical composition ratio and processing technology of the stainless steel wire rods in Example 2 are the preferred solutions.

[0039] Through numerous experiments, the applicant has discovered that the processing technology with this reduced surface area design is the most effective. The special stainless steel wire drawn with this reduced surface area design can achieve a torsional performance of 14 turns, a relaxation performance of ≤2.5% after 1000 hours, a winding performance of 10 turns without cracks, and a uniform distribution of residual stress on the wire surface without any residual stress release.

[0040] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for producing stainless steel wire for low-relaxation prestressed special stainless steel suspension cables, characterized in that, Includes the following steps: S1. Surface treatment of wire rod: Pickling of wire rod to remove impurities such as oxide scale; S2, Offline film lubrication: Applying an epoxy-based lubricating coating to the surface of the wire rod; S3. Online water-based lubrication: The wire rod is laid out, straightened, coated with an epoxy-based lubricating coating, and then dried. S4. Online dry lubrication: Dry lubricating powder is used to lubricate the wire rods; S5. Online temperature compensation: Heat the metal strip from step S4 to a specific temperature range; S6. Continuous drawing: The metal wire rod from step S5 is passed through a series of drawing dies, gradually reducing its cross-sectional area and increasing its length; S7. Finished wire winding: Winding or reeling the metal wire or wire into a coil; S4, S5, and S6 are executed in a cycle for a total of ten times. In step S5, the temperature range is as follows: for the first three times, the wire drawing temperature is controlled between 40-55℃ when entering the mold and between 120-160℃ when exiting the mold; for the last seven times, the wire drawing temperature is controlled between 50-60℃ when entering the mold and between 100-130℃ when exiting the mold.

2. The method for producing stainless steel wire for low-relaxation prestressed special stainless steel suspension cables according to claim 1, characterized in that, In passes 8 through 10, an online water-based lubrication step is introduced, preceding the online dry lubrication in S4.

3. The method for producing stainless steel wire for low-relaxation prestressed special stainless steel suspension cables according to claim 1, characterized in that, The S3 online water-based lubrication process includes: the wire rod to be processed passes through a wire feeding device to make the wire rod straight, and an epoxy-based lubricating coating is applied to the wire rod by a water-based lubrication coating device at a coating speed of 1-5 m / min. Then, it enters an online drying device with a drying temperature of 100℃-200℃ and a drying time of 1-5 min.

4. The method for producing stainless steel wire for low-relaxation prestressed special stainless steel suspension cables according to claim 1, characterized in that, In the S6 continuous drawing process, the drawing force is controlled at 40KN-45KN for the first three passes, 20KN-35KN for the fourth to sixth passes, and 10KN-18KN for the seventh to tenth passes.

5. The method for producing stainless steel wire for low-relaxation prestressed special stainless steel suspension cables according to claim 1, characterized in that, The speed control in the continuous drawing process of S6 adopts PID closed-loop control.

6. The method for producing stainless steel wire for low-relaxation prestressed special stainless steel suspension cables according to claim 1, characterized in that, The area reduction rate of the stainless steel wire in the ten consecutive drawing passes of S6 is as follows: the first 3 passes: 20-24%, the 4th to 6th passes: 15-22%, and the 7th to 10th passes: 10-15%.

7. The method for producing stainless steel wire for low-relaxation prestressed special stainless steel suspension cables according to claim 1, characterized in that, The working area angle range of the drawing die in the ten consecutive drawing passes of S6 is as follows: Passes 1-2: 12°, Passes 3-4: 11.5°, Passes 5-6: 10°, Pass 7: 9°, Passes 8-10: 8°.

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