High-strength fatigue-resistant stainless steel wire rope and preparation method thereof

Abstract

The invention discloses a high-strength fatigue-resistant stainless steel wire rope and a preparation method thereof, and belongs to the field of material engineering. The stainless steel wire rope is formed by spirally twisting a plurality of stainless steel filaments in a multi-layer mode, the stainless steel filaments are martensitic stainless steel materials subjected to nanocrystalline strengthening treatment, and the stainless steel filaments comprise, by mass, 0.04%-0.12% of carbon, 16.0%-18.0% of chromium, 6.0%-8.5% of nickel, 1.5%-2.5% of molybdenum, 0.1%-0.5% of vanadium, 0.02%-0.06% of nitrogen and the balance iron and inevitable impurities. The stainless steel filaments are alternately treated through multiple plastic deformation and heat treatment. The wire rope structure adopts a multi-strand spiral stranded structure of which the strand is not less than 7 and each strand is not less than 19 monofilaments, the diameter of each monofilament is 0.15-0.30 mm, constant tension control is adopted in the stranding process, and the inter-strand contact stress is controlled between 3 MPa and 6 MPa. The preparation method comprises the steps of vacuum melting, high-temperature homogenization, solution treatment, alternate drawing, plasma fine polishing, tension control twisting and the like. The invention has the beneficial effects of obviously improving the strength and fatigue life of the wire rope.

Description

Technical Field

[0001] This invention relates to the field of materials engineering, and more specifically, to a high-strength fatigue-resistant stainless steel wire rope and its preparation method. Background Technology

[0002] High-strength, fatigue-resistant stainless steel wire ropes are widely used in critical engineering fields such as aviation, marine, and bridges. With increasing load density and service complexity, traditional wire ropes based on austenitic or semi-martensitic stainless steel, while possessing certain corrosion resistance, are prone to fatigue damage under high-frequency cyclic stress, making it difficult to meet the demands of lightweight and high-reliability next-generation structures. In recent years, key processes such as nanocrystalline strengthening technology, surface micro / nano modification, and intelligent tension stranding control have been gradually applied to steel wire preparation, significantly improving the fatigue life and tensile strength of wire ropes, and driving the transformation of materials in this field from macroscopic structural design to microstructure control.

[0003] However, several technical bottlenecks remain: existing grain refinement technologies lack stability in batch production; the stranding process lacks precise control over inter-wire tension, easily leading to stress concentration; and surface treatment methods struggle to balance polishing precision with oxide film uniformity. Furthermore, traditional manufacturing processes have a rough control over the heat treatment rhythm, easily causing microstructure coarsening and affecting the consistency of mechanical properties. Summary of the Invention

[0004] The purpose of this invention is to provide a high-strength, fatigue-resistant stainless steel wire rope and its preparation method, in order to solve the problems mentioned in the background art: existing grain refinement technology lacks stability in batch production; the stranding process does not accurately control the tension between wires, which easily leads to stress concentration; and surface treatment methods cannot simultaneously achieve polishing precision and oxide film uniformity. In addition, traditional preparation processes have a rough control over the heat treatment rhythm, which easily causes microstructure coarsening and affects the consistency of mechanical properties.

[0005] Technical solution: A high-strength fatigue-resistant stainless steel wire rope is composed of multiple strands of stainless steel wires twisted together in multiple layers of spirals. The stainless steel wires are martensitic stainless steel materials that have undergone nanocrystalline strengthening treatment. The chemical composition of the martensitic stainless steel material, by mass percentage, is as follows: carbon content 0.04-0.12, chromium content 16.0-18.0, nickel content 6.0-8.5, molybdenum content 1.5-2.5, vanadium content 0.1-0.5, nitrogen content 0.02-0.06, with the balance being iron and unavoidable impurities. After undergoing multiple plastic deformation and heat treatment processes, the stainless steel wire has a final tensile strength of not less than 2100 MPa and a cyclic fatigue life of not less than 10,000,000 cycles under a loading stress amplitude of 600 MPa and a stress ratio of 0.1. The stainless steel wire rope structure is a multi-strand spiral twisted structure with no less than 7 strands. Each strand contains no less than 19 monofilaments with a diameter between 0.15 and 0.30 mm. The multi-strand spiral twisted structure is formed by a constant tension control mechanism during the twisting process to ensure that the monofilaments are evenly arranged and the structure is dense during the rope formation process, and the inter-strand contact stress is controlled between 3 and 6 MPa.

[0006] Preferably, the nanocrystalline strengthening treatment includes the following process: controlling the austenitic transformation by alternately performing cold working and short-time isothermal heat treatment, so that the deformation exceeds 80% and the compression ratio between passes is not less than 25%, and in the final heat treatment, the material is heated to -800-850 degrees Celsius and held for 1-5 minutes and then rapidly cooled to form a martensitic nanostructure with an average grain size of less than 100 nanometers.

[0007] Preferably, the stainless steel filaments undergo a medium-temperature stabilization treatment before final plastic processing. The heat treatment temperature is controlled at 450-550 degrees Celsius, and the holding time is 10-30 minutes, in order to release residual stress and promote the homogenization of subgrain domains.

[0008] Preferably, the outer surface of the monofilament is subjected to high-frequency plasma polishing to control the surface roughness to below 0.10 micrometers.

[0009] Preferably, the stainless steel wire undergoes grain boundary stabilization treatment during processing, including a process sequence combining low-temperature annealing and medium-temperature stabilization treatment after multiple deformations, which induces grain boundary dislocation cell refinement and promotes the dispersion of precipitated particles within the 200-300 nanometer scale. The precipitated phase is mainly composed of carbides and intermetallic compounds.

[0010] Preferably, the stainless steel wire is drawn using a pulsed magnetic field assisted by a pulsed magnetic field with a frequency of 5-50 Hz and a magnetic induction intensity of 0.3-0.5 Tesla.

[0011] Preferably, the method for preparing a high-strength fatigue-resistant stainless steel wire rope includes the following steps: S1. Martensitic stainless steel ingots are prepared by vacuum induction melting. The chemical composition of the molten steel ingots, by mass percentage, is as follows: carbon content 0.04-0.12, chromium content 16.0-18.0, nickel content 6.0-8.5, molybdenum content 1.5-2.5, vanadium content 0.1-0.5, nitrogen content 0.02-0.06, with the balance being iron and unavoidable impurities. S2. The martensitic stainless steel ingot is subjected to high-temperature homogenization treatment at 1150-1200 degrees Celsius, and the holding time is 2-5 hours, followed by furnace cooling to room temperature. S3. The homogenized ingot is hot-rolled into wire with a diameter of 8-12 mm, and solution-treated at 1050-1100 degrees Celsius, held for 30-60 minutes and then water-cooled. S4. The drawing process is carried out by alternating cold deformation and isothermal heat treatment. The total compression ratio of the cold deformation passes is not less than 85%. The heat treatment temperature is controlled at 800-850 degrees Celsius. After holding at the temperature for 1-3 minutes, the wire is cooled to obtain a diameter of 0.15-0.30 mm. S5. Perform a medium-temperature stabilization treatment on the final filament at 450-550 degrees Celsius, hold for 10-30 minutes, and then cool to room temperature; S6. Perform plasma polishing on the final filament. The plasma atmosphere consists of argon and hydrogen, the pressure is controlled between 10-30 kPa, and the processing time is not less than 10 minutes. S7. The obtained stainless steel wires are twisted together in a 7-strand 19-wire structure under tension control. During the twisting process, the tension fluctuation of each strand is monitored to be no more than 3%, and finally a high-strength fatigue-resistant stainless steel wire rope is obtained.

[0012] Preferably, the interval between the completion of one heat deformation process and the next heat treatment process in the S4 heat treatment is controlled within 60 seconds, so as to avoid the coarsening of the nanostructure due to high temperature exposure during the processing of the martensitic stainless steel ingot.

[0013] Preferably, the S7 tension control twisting process adjusts the tension and winding angle of each strand in real time through a closed-loop servo system to ensure that the axial load of the wire rope is evenly distributed after final twisting and to avoid local stress concentration.

[0014] Preferably, the surface of the stainless steel wire rope undergoes low-temperature gas passivation treatment after stranding. The passivation atmosphere contains hydrogen with a volume fraction of not less than 5%, the treatment temperature is 200-300 degrees Celsius, and the treatment time is controlled at 30-60 minutes.

[0015] Compared with the prior art, the advantages of this invention are: (1) Using martensitic stainless steel material with a specific mass percentage, the trace elements such as carbon, nitrogen, and vanadium are precisely controlled, which improves the stability of the structure and fatigue resistance.

[0016] (2) By alternating cold working and short-time isothermal heat treatment, the grains are refined to below 100 nanometers, which significantly enhances the strength and fatigue resistance of the material.

[0017] (3) Using a pulsed magnetic field of 5 to 50 Hz and 0.3 to 0.5 Tesla, the grain boundary behavior is controlled, the microstructure uniformity is improved and the strain hardening effect is reduced.

[0018] (4) The strands are twisted together by tension control. A closed-loop servo system is used to dynamically adjust the tension and winding angle to suppress local stress concentration and ensure uniform axial load distribution.

[0019] (5) High-frequency plasma polishing is performed on the surface of the single wire, and low-temperature gas passivation is performed after twisting the stainless steel wire rope, which effectively reduces surface defects and corrosion sensitivity and increases the crack initiation threshold.

[0020] (6) Introducing a strategy of combining medium-temperature stabilization treatment with low-temperature annealing to induce dislocation cell refinement and dispersed precipitate distribution, thereby enhancing the ability to resist microcrack propagation.

[0021] (7) The interval between hot deformation and heat treatment is controlled within 60 seconds to prevent coarsening of nanostructure and ensure the uniformity and stability of the microstructure in the martensitic matrix.

[0022] (8) The tensile strength of stainless steel wire reaches more than 2100 MPa and the fatigue life reaches 10,000,000 times under a stress amplitude of 600 MPa, which is significantly better than traditional austenitic or semi-martensitic steel wire rope. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the overall process of a method for preparing a high-strength fatigue-resistant stainless steel wire rope according to the present invention. Detailed Implementation Example

[0024] Examples 1-4 Example 1. A high-strength fatigue-resistant stainless steel wire rope is composed of multiple strands of stainless steel wires twisted together in multiple layers of spirals. The stainless steel wires are martensitic stainless steel materials that have undergone nanocrystalline strengthening treatment. The chemical composition of the martensitic stainless steel material, by mass percentage, is as follows: carbon content 0.04-0.12, chromium content 16.0-18.0, nickel content 6.0-8.5, molybdenum content 1.5-2.5, vanadium content 0.1-0.5, nitrogen content 0.02-0.06, with the balance being iron and unavoidable impurities. After undergoing multiple plastic deformation and heat treatment processes, the stainless steel wire has a final tensile strength of not less than 2100 MPa and a cyclic fatigue life of not less than 10,000,000 cycles under a loading stress amplitude of 600 MPa and a stress ratio of 0.1. The stainless steel wire rope structure is a multi-strand spiral twisted structure with no less than 7 strands. Each strand contains no less than 19 monofilaments with a diameter between 0.15 and 0.30 mm. The multi-strand spiral twisted structure is formed by a constant tension control mechanism during the twisting process to ensure that the monofilaments are evenly arranged and the structure is dense during the rope formation process, and the inter-strand contact stress is controlled between 3 and 6 MPa.

[0025] The nanocrystalline strengthening treatment includes the following process: controlling the austenitic structure transformation by alternately implementing cold working and short-time isothermal heat treatment, so that the deformation exceeds 80% and the compression ratio between passes is not less than 25%, and in the final heat treatment, the material is heated to -800-850 degrees Celsius and held for 1-5 minutes and then rapidly cooled to form a martensitic nanostructure with an average grain size of less than 100 nanometers.

[0026] Before the final plastic processing, the stainless steel filaments undergo a medium-temperature stabilization treatment. The heat treatment temperature is controlled at 450-550 degrees Celsius, and the holding time is 10-30 minutes, in order to release residual stress and promote the homogenization of subgrain domains.

[0027] The outer surface of the monofilament is treated with high-frequency plasma polishing to control the surface roughness to below 0.10 micrometers.

[0028] The stainless steel wire undergoes grain boundary stabilization treatment during processing, including a process sequence combining low-temperature annealing and medium-temperature stabilization after multiple deformations. This process induces grain boundary dislocation cell refinement and promotes the dispersion of precipitated particles within a 200-300 nanometer scale. The precipitated phase is mainly composed of carbides and intermetallic compounds.

[0029] The stainless steel wire is drawn using a pulsed magnetic field with a frequency of 5-50 Hz and a magnetic induction intensity of 0.3-0.5 Tesla.

[0030] The method for preparing a high-strength, fatigue-resistant stainless steel wire rope includes the following steps: S1. Martensitic stainless steel ingots are prepared by vacuum induction melting. The chemical composition of the molten steel ingots, by mass percentage, is as follows: carbon content 0.04-0.12, chromium content 16.0-18.0, nickel content 6.0-8.5, molybdenum content 1.5-2.5, vanadium content 0.1-0.5, nitrogen content 0.02-0.06, with the balance being iron and unavoidable impurities. S2. The martensitic stainless steel ingot is subjected to high-temperature homogenization treatment at 1150-1200 degrees Celsius, and the holding time is 2-5 hours, followed by furnace cooling to room temperature. S3. The homogenized ingot is hot-rolled into wire with a diameter of 8-12 mm, and solution-treated at 1050-1100 degrees Celsius, held for 30-60 minutes and then water-cooled. S4. The drawing process is carried out by alternating cold deformation and isothermal heat treatment. The total compression ratio of the cold deformation passes is not less than 85%. The heat treatment temperature is controlled at 800-850 degrees Celsius. After holding at the temperature for 1-3 minutes, the wire is cooled to obtain a diameter of 0.15-0.30 mm. S5. Perform a medium-temperature stabilization treatment on the final filament at 450-550 degrees Celsius, hold for 10-30 minutes, and then cool to room temperature; S6. Perform plasma polishing on the final filament. The plasma atmosphere consists of argon and hydrogen, the pressure is controlled between 10-30 kPa, and the processing time is not less than 10 minutes. S7. The obtained stainless steel wires are twisted together in a 7-strand 19-wire structure under tension control. During the twisting process, the tension fluctuation of each strand is monitored to be no more than 3%, and finally a high-strength fatigue-resistant stainless steel wire rope is obtained.

[0031] The interval between the completion of one heat deformation process and the next heat treatment process in the S4 heat treatment is controlled within 60 seconds to avoid coarsening of the nanostructure due to high temperature exposure during the processing of the martensitic stainless steel ingot.

[0032] The S7 tension control stranding process uses a closed-loop servo system to adjust the tension and winding angle of each strand in real time, ensuring that the axial load of the wire rope is evenly distributed after final stranding and avoiding local stress concentration.

[0033] The surface of the stainless steel wire rope is subjected to low-temperature gas passivation treatment after stranding. The passivation atmosphere contains hydrogen with a volume fraction of not less than 5%, the treatment temperature is 200-300 degrees Celsius, and the time is controlled at 30-60 minutes.

[0034] Example 2. Martensitic stainless steel ingots were prepared by vacuum induction melting. The chemical composition (mass percentage) was: C 0.06, Cr 17.0, Ni 6.8, Mo 2.0, V 0.2, N 0.04, with the balance being Fe and impurities.

[0035] The ingot was homogenized at 1180°C for 4 hours, then furnace cooled, hot rolled into 10mm wire, and subsequently solution treated at 1080°C for 50 minutes and water cooled.

[0036] By employing alternating drawing with a cold deformation pass compression ratio of 90% and a heat treatment temperature of 840°C for 2 minutes, a single filament diameter of 0.20 mm and an average grain size of 85 nm were finally obtained.

[0037] Medium-temperature stabilization treatment was performed: the temperature was kept at 480°C for 20 minutes; then plasma polishing was carried out to achieve a surface roughness of Ra0.08μm.

[0038] The stranded structure uses 7 strands and 19 wires, with tension fluctuation controlled within ±3% and inter-strand contact stress controlled within 5MPa.

[0039] The finished stainless steel wire rope has a tensile strength of 2160 MPa and a cyclic fatigue life of 1.2 × 10⁻⁶ under a loading stress amplitude of 600 MPa and a stress ratio of 0.1.7 Second-rate.

[0040] Example 3. The chemical composition of the martensitic stainless steel is: C 0.04, Cr 16.5, Ni 8.0, Mo 1.8, V 0.3, N 0.03.

[0041] The ingot homogenization temperature is 1200°C, held for 2 hours, and then hot rolled and solution treated at 1050°C for 60 minutes.

[0042] A pulsed magnetic field with a frequency of 30 Hz and a magnetic induction intensity of 0.4 T is applied during the drawing process; the cold deformation compression ratio is 88%, the heat treatment temperature is 820°C, and the grain size is controlled at 92 nm.

[0043] The medium-temperature stabilization treatment parameters were 500°C for 30 minutes, and the stranding tension was maintained stable through a closed-loop servo control system. The resulting wire rope achieved a tensile strength of 2210 MPa and a fatigue life of 1.4 × 10⁻⁶ MPa. 7 Second-rate.

[0044] Example 4. Composition of molten steel: C 0.08, Cr 17.5, Ni 6.2, Mo 2.4, V 0.5, N 0.06.

[0045] After homogenization at 1150°C for 3 hours, it is hot-rolled and then solution-treated at 1100°C.

[0046] In the alternating cold deformation and heat treatment process, the heat treatment is set at 850°C and held for 1 minute; the final filament diameter is 0.15 mm and the grain size is about 80 nm.

[0047] The medium-temperature stabilization treatment was set at 470°C for 15 minutes. After the stranding was completed, the surface was subjected to low-temperature gas passivation treatment at 200°C for 45 minutes. The hydrogen gas content in the passivation atmosphere was 5%.

[0048] The wire rope has a tensile strength of 2150 MPa and a fatigue life of 1.1 × 10⁻⁶ MPa. 7 Second-rate.

[0049] Comparative Example Comparative Examples 1-3 Comparative Example 1. (Without nanocrystalline strengthening treatment) Martensitic stainless steel of the same composition was used, without alternating cold working and short-time heat treatment, and was only cold drawn to 0.20 mm using conventional methods. The final grain size is approximately 500 nm.

[0050] The tensile strength is 1760 MPa, and the fatigue life is approximately 3.8 × 10⁻⁶ MPa. 6 This is significantly lower than in the previous example.

[0051] Comparative Example 2. (Uncontrolled hot deformation interval time) During the alternating deformation and heat treatment process, the post-deformation placement time exceeded 5 minutes (>300 seconds), resulting in partial grain growth to approximately 180 nm; Ultimately, the tensile strength of the wire rope decreased to 1980 MPa, and its fatigue life was only 7.2 × 10⁻⁶. 6 Second-rate.

[0052] Comparative Example 3. (Without plasma polishing) All treatments were the same as in Example 2, but plasma polishing was not performed. The surface roughness Ra of the monofilament was 0.21 μm, and there was an oxide layer and inclusions and scratches. The tensile strength of the wire rope decreased slightly to 2120 MPa, but the fatigue life decreased significantly to 5.9 × 10⁻⁶ MPa. 6 Secondly, cracks mainly originate from surface defects.

[0053] To determine the differences in fatigue life performance between the examples and the comparative examples, the following comparative experiment was designed, and the experimental steps are as follows: By comparing the cyclic fatigue life of Examples 2 and 3 of the present invention with Comparative Examples 1 and 3 under a loading stress amplitude of 600 MPa and a stress ratio of 0.1, the effect of nanocrystalline strengthening treatment and plasma polishing technology on improving fatigue performance is verified.

[0054] The experimental materials are prepared as follows: Experimental materials: a. Stainless steel wire rope sample prepared in Example 2, with a diameter of 0.20 mm and a structure of 7 strands and 19 wires; b. The stainless steel wire rope sample prepared in Example 3 has a diameter of 0.18 mm and a structure of 7 strands and 19 wires; c. The stainless steel wire rope sample prepared in Comparative Example 1 was not subjected to nanocrystalline strengthening treatment; d. The stainless steel wire rope sample prepared in Comparative Example 3 was not subjected to plasma polishing.

[0055] Test equipment: a. Miniature axial fatigue testing machine, with an adjustable frequency range of 5~50Hz and automatic stress amplitude control function; b. High-precision digital microscope for observing surface defects; c. Surface profilometer, used to determine the surface roughness Ra value of the wire; d. Constant temperature laboratory, with the ambient temperature controlled at 22±1°C.

[0056] The specific experimental steps are as follows: Sample pretreatment: Take 5 samples from each group of stainless steel wire ropes, clean the surface with anhydrous ethanol in a clean and dust-free environment, dry them, and then number and record the batch and structural parameters to ensure structural consistency.

[0057] Surface inspection: The surface roughness of the sample was measured using a profilometer, and the Ra value was recorded to compare the effects of different treatment methods on surface quality.

[0058] Fatigue loading settings: Install each sample into the fatigue testing machine fixture, set the loading stress amplitude to 600MPa, stress ratio R=0.1, and frequency to 20Hz.

[0059] The test conditions were kept at constant temperature and humidity to avoid environmental fluctuations interfering with the fatigue process.

[0060] Test process record: The testing machine monitors the load and number of cycles in real time, and records the number of cycles when each sample breaks as fatigue life data.

[0061] If the sample is at 1.5×10 7 If no breakage occurs after the first cycle, it is considered "no breakage" and the test is stopped.

[0062] Test repeatability verification: Each group of samples was tested 5 times, and the average value was taken as the representative fatigue life to improve the stability and representativeness of the data.

[0063] Fracture and defect analysis: The fracture surface of the fractured sample is observed under a microscope to determine the location of crack initiation and propagation path, and to assess the impact of surface defects on the crack initiation site.

[0064] The experimental data are shown in Table 1: Sample number Is it nanocrystalline reinforced? Whether plasma polishing Tensile strength (MPa) Surface roughness Ra (μm) <![CDATA[Fatigue life (×10 6 times)]]> Example 2 yes yes 2160 0.08 12 Example 3 yes yes 2210 0.07 14 Comparative Example 1 no yes 1760 0.09 3.8 Comparative Example 3 yes no 2120 0.21 5.9 Table 1 Experimental conclusion analysis: Nanocrystalline strengthening treatment has a significant effect: Compared with Example 1, Example 2 and Example 3, under the same material composition and stranding structure, showed that fatigue life was increased by more than 3 times, indicating that the refinement of microcrystalline structure significantly inhibited the initiation and propagation of fatigue cracks.

[0065] Key aspects of plasma polishing: Although Comparative Example 3 exhibits nanostructure, its surface roughness is higher than that of the Example, and its fatigue life is only 5.9 × 10⁻⁶. 6 The number of times was significantly lower than the 12.0 × 10⁻⁶ in Example 2. 6 This indicates that a high-quality surface condition is an important guarantee for delaying fatigue damage.

[0066] The sample with the best overall performance is Example 3: it combines superior mechanical strength and surface quality, and its fatigue life reaches 14.0 × 10⁻⁶. 6 This invention demonstrates the comprehensive technical advantages of the present invention in the fields of high strength and high fatigue performance.

[0067] To determine the effects of drawing deformation mode on microstructure uniformity and tensile strength in the examples and comparative examples, the following comparative experiment was designed, and the experimental steps are as follows: The effects of pulsed magnetic field assisted drawing in Example 4 and conventional drawing process in Comparative Example 2 on the microstructure uniformity and tensile strength of martensitic stainless steel wire were compared to evaluate the process advantages of magnetic field induced effect in high-strength processing.

[0068] The experimental materials are prepared as follows: Experimental materials: a. Stainless steel wire samples prepared in Example 4, which were drawn using a pulsed magnetic field assisted by a frequency of 20 Hz and a magnetic induction intensity of 0.4 T, resulting in a final diameter of 0.20 mm; b. The stainless steel wire sample prepared in Comparative Example 2 was not assisted by a magnetic field, and other drawing parameters remained consistent. c. Both groups of samples came from the same batch of martensitic stainless steel base material, and their chemical composition and initial structure were consistent.

[0069] Experimental equipment: a. Pulsed magnetic field assisted pulling device, frequency adjustable range 550Hz, magnetic induction intensity range 0-0.5T; b. Scanning electron microscopy (SEM) and EBSD system, used to analyze grain orientation and microstructure distribution; c. Tensile testing machine, accuracy 0.5%, maximum load 10kN; d. Metallographic sample preparation equipment and etching solution formulations are adapted to martensitic stainless steel.

[0070] The specific experimental steps are as follows: Sample preparation and numbering: Take 10 filament samples from each of Example 4 and Comparative Example 2, ensuring that the final diameter is 0.20 mm. After cleaning, number the samples and record the drawing parameters and base material batch number for each group.

[0071] Microstructure analysis: Longitudinal sections of each sample were cut, and metallographic samples were prepared by mechanical grinding and electrolytic polishing. EBSD was used to determine the grain size distribution, orientation differences, and microstructure uniformity.

[0072] Tensile strength test: Under standard tensile test conditions (room temperature, loading rate 1 mm / min), the tensile strength of each group of samples was tested, and the average value of 5 tests was taken as the final result.

[0073] Data recording and fracture behavior observation: Record the fracture location and cross-sectional morphology of each sample to assess whether there is stress concentration induced by processing defects.

[0074] The experimental data are shown in Table 2: Sample number Should pulsed magnetic field assistance be used? Average grain size (nm) Grain orientation difference (°) Tensile strength (MPa) Tissue homogeneity score (1-10) Example 4 yes 82 5.1 2155 9 Comparative Example 2 no 121 12.4 1935 6 Table 2 Experimental Conclusions and Analysis: In Example 4, under the action of a pulsed magnetic field, the average grain size was significantly smaller than that in Comparative Example 2, indicating that the magnetic field effectively induced grain boundary slip and substructure refinement. The grain orientation difference in Example 4 was controlled within 5.1°, which was better than the 12.4° in Comparative Example 2, showing that magnetic field treatment promoted the homogenization of microstructure orientation and was beneficial to improving mechanical uniformity. The tensile strength of the filament in Example 4, which was drawn using magnetic field assistance, increased by more than 200 MPa, demonstrating its advantages in the preparation of high-strength wires. This comparison verifies the outstanding role of magnetic field-assisted plastic deformation in microstructure control and provides an effective process path for further development of high-strength, fatigue-resistant wire ropes.

[0075] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely preferred examples of the present invention and are not intended to limit the present invention. Various changes and modifications can be made to the present invention without departing from the spirit and scope thereof, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of the present invention is defined by the appended claims and their equivalents.

Claims

1. A high-strength, fatigue-resistant stainless steel wire rope, characterized in that, The high-strength fatigue-resistant stainless steel wire rope is composed of multiple strands of stainless steel wire twisted together in multiple layers. The stainless steel wire is a martensitic stainless steel material that has undergone nanocrystalline strengthening treatment. The chemical composition of the martensitic stainless steel material, by mass percentage, is as follows: carbon content 0.04-0.12, chromium content 16.0-18.0, nickel content 6.0-8.5, molybdenum content 1.5-2.5, vanadium content 0.1-0.5, nitrogen content 0.02-0.06, with the balance being iron and unavoidable impurities. After undergoing multiple plastic deformation and heat treatment processes, the stainless steel wire has a final tensile strength of not less than 2100 MPa and a cyclic fatigue life of not less than 10,000,000 cycles under a loading stress amplitude of 600 MPa and a stress ratio of 0.

1. The stainless steel wire rope structure is a multi-strand spiral twisted structure with no less than 7 strands. Each strand contains no less than 19 monofilaments with a diameter between 0.15 and 0.30 mm. The multi-strand spiral twisted structure is formed by a constant tension control mechanism during the twisting process to ensure that the monofilaments are evenly arranged and the structure is dense during the rope formation process, and the inter-strand contact stress is controlled between 3 and 6 MPa.

2. The high-strength fatigue-resistant stainless steel wire rope according to claim 1, characterized in that, The nanocrystalline strengthening treatment includes the following process: controlling the austenitic structure transformation by alternately implementing cold working and short-time isothermal heat treatment, so that the deformation exceeds 80% and the compression ratio between passes is not less than 25%, and in the final heat treatment, the material is heated to -800-850 degrees Celsius and held for 1-5 minutes and then rapidly cooled to form a martensitic nanostructure with an average grain size of less than 100 nanometers.

3. A high-strength fatigue-resistant stainless steel wire rope according to claim 1, characterized in that, Before the final plastic processing, the stainless steel filaments undergo a medium-temperature stabilization treatment. The heat treatment temperature is controlled at 450-550 degrees Celsius, and the holding time is 10-30 minutes, in order to release residual stress and promote the homogenization of subgrain domains.

4. The high-strength fatigue-resistant stainless steel wire rope according to claim 1, characterized in that, The outer surface of the monofilament is treated with high-frequency plasma polishing to control the surface roughness to below 0.10 micrometers.

5. The high-strength fatigue-resistant stainless steel wire rope according to claim 1, characterized in that, The stainless steel wire undergoes grain boundary stabilization treatment during processing, including a process sequence combining low-temperature annealing and medium-temperature stabilization after multiple deformations. This process induces grain boundary dislocation cell refinement and promotes the dispersion of precipitated particles within a 200-300 nanometer scale. The precipitated phase is mainly composed of carbides and intermetallic compounds.

6. The high-strength fatigue-resistant stainless steel wire rope according to claim 1, characterized in that, The stainless steel wire is drawn using a pulsed magnetic field with a frequency of 5-50 Hz and a magnetic induction intensity of 0.3-0.5 Tesla.

7. A method for preparing a high-strength, fatigue-resistant stainless steel wire rope, characterized in that, The method for preparing a high-strength, fatigue-resistant stainless steel wire rope includes the following steps: S1. Martensitic stainless steel ingots are prepared by vacuum induction melting. The chemical composition of the molten steel ingots, by mass percentage, is as follows: carbon content 0.04-0.12, chromium content 16.0-18.0, nickel content 6.0-8.5, molybdenum content 1.5-2.5, vanadium content 0.1-0.5, nitrogen content 0.02-0.06, with the balance being iron and unavoidable impurities. S2. The martensitic stainless steel ingot is subjected to high-temperature homogenization treatment at 1150-1200 degrees Celsius, and the holding time is 2-5 hours, followed by furnace cooling to room temperature. S3. The homogenized ingot is hot-rolled into wire with a diameter of 8-12 mm, and solution-treated at 1050-1100 degrees Celsius, held for 30-60 minutes and then water-cooled. S4. The drawing process is carried out by alternating cold deformation and isothermal heat treatment. The total compression ratio of the cold deformation passes is not less than 85%. The heat treatment temperature is controlled at 800-850 degrees Celsius. After holding at the temperature for 1-3 minutes, the wire is cooled to obtain a diameter of 0.15-0.30 mm. S5. Perform a medium-temperature stabilization treatment on the final filament at 450-550 degrees Celsius, hold for 10-30 minutes, and then cool to room temperature; S6. Perform plasma polishing on the final filament. The plasma atmosphere consists of argon and hydrogen, the pressure is controlled between 10-30 kPa, and the processing time is not less than 10 minutes. S7. The obtained stainless steel wires are twisted together in a 7-strand 19-wire structure under tension control. During the twisting process, the tension fluctuation of each strand is monitored to be no more than 3%, and finally a high-strength fatigue-resistant stainless steel wire rope is obtained.

8. The method for preparing a high-strength fatigue-resistant stainless steel wire rope according to claim 7, characterized in that, The interval between the completion of one heat deformation process and the next heat treatment process in the S4 heat treatment is controlled within 60 seconds to avoid coarsening of the nanostructure due to high temperature exposure during the processing of the martensitic stainless steel ingot.

9. The method for preparing a high-strength fatigue-resistant stainless steel wire rope according to claim 7, characterized in that, The S7 tension control stranding process uses a closed-loop servo system to adjust the tension and winding angle of each strand in real time, ensuring that the axial load of the wire rope is evenly distributed after final stranding and avoiding local stress concentration.

10. The method for preparing a high-strength fatigue-resistant stainless steel wire rope according to claim 9, characterized in that, The surface of the stainless steel wire rope is subjected to low-temperature gas passivation treatment after stranding. The passivation atmosphere contains hydrogen with a volume fraction of not less than 5%, the treatment temperature is 200-300 degrees Celsius, and the time is controlled at 30-60 minutes.

Images