Gradient stress distribution drilling ultra-long life fatigue-resistant wire rope and its manufacturing process

Abstract

This invention relates to the field of wire rope material preparation technology, specifically to a long-life, fatigue-resistant drilling wire rope with gradient stress distribution and its manufacturing process. The wire rope comprises one independent steel core rope and six outer strands. The outer strands are composed of a main load-bearing strand P and a bending-resistant buffer strand F arranged alternately along the circumference. The process involves preparing two types of steel wires separately, differentiated strand formation, local pre-shaping of the bending-resistant buffer strands, alternating P-F strand joining, selective final shaping, and stabilization and lubrication treatments to construct a gradient stress system of the independent steel core rope, the main load-bearing strand P, and the bending-resistant buffer strand F. Compared with existing wire ropes of the same type, this invention achieves a division of labor between the load-bearing channel and the buffer contact channel, which can reduce outer layer contact stress and bending fatigue damage, and improve fatigue life, contact stability, and overall service reliability under drilling conditions.

Description

Technical Field

[0001] This invention relates to the field of steel wire rope material preparation technology, specifically to ultra-long life anti-fatigue steel wire rope for drilling with gradient stress distribution and its production process. Background Technology

[0002] Drilling wire ropes operate under complex conditions involving heavy loads, multi-layer winding drums, and alternating impact loads. Their performance depends not only on breaking strength but also on bending fatigue properties, surface contact condition, interlayer compressibility, and internal stress distribution. Existing drilling wire ropes typically employ an independent steel core rope structure with outer strands of the same type. Their load-bearing capacity and service life are primarily improved by increasing wire strength, optimizing lay length parameters, compaction or forging, and pre-tensioning. While this approach can improve overall rope strength and structural stability to some extent, the outer strands often share the same strand type and approximate stress path. This lack of clear division of labor among the outer strands in terms of axial load bearing, surface contact, bending follow-through, and compressive buffering makes it easy for the outer working area to simultaneously bear high tensile stress and significant alternating bending stress.

[0003] Furthermore, existing wire ropes, in pursuit of high metal fill rate and large contact area, often employ integral compaction or integral shaping methods, resulting in a dense and smooth outer profile of the strands. While this approach improves compressive strength and surface abrasion resistance, it can also reduce the flexibility of the outer working area, leading to insufficient stress relief in local contact zones and consequently, high contact stress concentration during contact with the sheave and drum. For multi-layer winding applications, existing monolithic strand structures can also result in a uniform outer contact profile and uneven load transfer between local strand valleys and crowns, making fatigue cracks prone to initiation and propagation at the outer contact points. Therefore, existing technologies still suffer from problems such as ineffective separation of load-bearing and buffering channels, insufficient control of the outer contact profile, unreasonable local stress distribution, and limited overall fatigue life. A new structure and manufacturing process for drilling fatigue-resistant wire ropes that can balance load-bearing capacity, bending adaptability, and contact buffering performance are needed. Summary of the Invention

[0004] To overcome the shortcomings of existing technologies, the present invention aims to provide a long-life, fatigue-resistant steel wire rope for drilling with gradient stress distribution and its manufacturing process. The steel wire rope comprises one independent steel core rope and six outer strands. The outer strands are composed of a main load-bearing strand (P) and a bending-resistant buffer strand (F) arranged alternately along the circumference. The process involves preparing two types of steel wires separately, differentiated strand formation, local pre-shaping of the bending-resistant buffer strands, alternating strand assembly of the P and F strands, selective final shaping, and stabilization and lubrication treatments to construct a gradient stress system consisting of the independent steel core rope, the main load-bearing strand (P), and the bending-resistant buffer strands (F). Compared with existing steel wire ropes of the same type, the present invention achieves a division of labor between the load-bearing channel and the buffer contact channel, which can reduce outer layer contact stress and bending fatigue damage, and improve fatigue life, contact stability, and overall service reliability under drilling conditions.

[0005] To achieve the above objectives, the present invention provides the following technical solution: The ultra-long life fatigue-resistant steel wire rope for drilling with gradient stress distribution includes one independent steel core rope and six outer strands twisted around the independent steel core rope. The six outer rope strands include three main load-bearing strands P and three bending-resistant buffer strands F. The main load-bearing strands P and the bending-resistant buffer strands F are arranged alternately along the circumference in the order PFPFPF. The main load-bearing strand P is a compacted dense load-bearing strand with a 1+6+12 structure; the bending-resistant buffer strand F is a fine-filament flexible buffer strand with a 1+6+18 structure. The average diameter of the steel wires in the main load-bearing strand P is greater than the average diameter of the steel wires in the bending-resistant buffer strand F; The outermost radial arc region of the bending buffer strand F has a partially widened contact arc surface, and the two sides of the partially widened contact arc surface are provided with arc transition surfaces connected to the unshaped outer contour. On a cross section perpendicular to the axis of the wire rope, the locally widened contact arc surface forms an outer contact profile that is wider than the contact arc surface of the crown of the adjacent main bearing strand P.

[0006] Preferably, the average diameter of the steel wires in the main load-bearing strand P is 1.75-2.10 mm, the average diameter of the steel wires in the bending buffer strand F is 1.20-1.60 mm, and the average diameter of the steel wires in the main load-bearing strand P is 1.10-1.45 times the average diameter of the steel wires in the bending buffer strand F; the tensile strength of the steel wires in the main load-bearing strand P is 2150-2300 MPa, and the tensile strength of the steel wires in the bending buffer strand F is 1950-2150 MPa.

[0007] Preferably, the main load-bearing strand P is a compacted load-bearing strand with a compaction rate of 8-14%; the local widening contact arc surface of the bending buffer strand F has a compression deformation rate of 1.0-5.0%.

[0008] Preferably, the circumferential width of the locally widened contact arc surface of the bending buffer strand F is 25-55% of the arc length of the corresponding bending buffer strand F surface, and its shaping deformation rate is 1.5-5.0%; a lubrication micro gap of 0.03-0.20 mm is retained between adjacent outer steel wires in the locally widened contact arc surface.

[0009] Preferably, the lay length of the independent steel core rope is 1.05-1.20 times the lay length of the main bearing strand P; the nominal diameter of the wire rope is 26-38 mm.

[0010] A manufacturing process for a gradient stress distribution drilling ultra-long life fatigue-resistant steel wire rope, used to prepare the gradient stress distribution drilling ultra-long life fatigue-resistant steel wire rope, includes the following steps: S1. Prepare independent steel core ropes; S2. Prepare a first type of steel wire for forming the main load-bearing strand P and a second type of steel wire for forming the bending buffer strand F. Both the first and second types of steel wire are obtained by rough drawing, heat treatment, phosphating, and final drawing in sequence. S3. Pre-form the first type of steel wire and twist it into a main load-bearing strand P with a 1+6+12 structure. Compact the main load-bearing strand P to form a dense load-bearing outer contour. S4. Pre-form the second type of steel wire and twist it into a bending buffer strand F with a 1+6+18 structure. Perform local pre-shaping on the outermost radial arc area of ​​the bending buffer strand F to form a locally widened contact arc surface. Form arc transition surfaces on both sides of the locally widened contact arc surface that connect with the unshaped outer contour. S5. Wrap the three main load-bearing strands P and the three bending buffer strands F together around the independent steel core rope in the order PFPFPF. S6. During the rope assembly process, control the input tension of the independent steel core rope, the main load-bearing strand P, and the bending buffer strand F to form a gradient relationship; S7. After rope assembly, selectively finalize only the locally widened contact arc surface of the bending buffer strand F, so that on the cross-section perpendicular to the wire rope axis, the locally widened contact arc surface forms an outer contact profile wider than the crown contact arc surface of the adjacent main load-bearing strand P; S8. After rope assembly, perform stabilization and lubrication treatments on the wire rope to obtain the ultra-long life anti-fatigue wire rope with the gradient stress distribution.

[0011] Preferably, in step S2, the total compression rate of the first type of steel wire is 86-90%, and the total compression rate of the second type of steel wire is 80-88%; the heat treatment in step S2 is either lead bath heat treatment or isothermal transformation heat treatment; the tensile strength of the first type of steel wire is controlled at 2150-2300 MPa, and the tensile strength of the second type of steel wire is controlled at 1950-2150 MPa.

[0012] Preferably, in step S3, the twisting tension of the main bearing strand P is greater than the twisting tension of the bending buffer strand F; in step S6, the input tensions of the independent steel core rope, the main bearing strand P, and the bending buffer strand F form a gradient relationship, and the input tension of the independent steel core rope is greater than the input tension of the main bearing strand P, and the input tension of the main bearing strand P is greater than the input tension of the bending buffer strand F; the input tension ratio of the independent steel core rope, the main bearing strand P, and the bending buffer strand F is 1.30-1.45:1.10-1.20:1; and the lay length of the main bearing strand P is greater than the lay length of the bending buffer strand F.

[0013] Preferably, the local pre-shaping in step S4 is performed using a local pressing wheel or a strip pressing die, so that the circumferential width of the locally widened contact arc surface is 25-55% of the arc length of the outer contour surface of the corresponding bending buffer strand F; in step S7, the selective final shaping is performed using a local pressing wheel or a strip pressing die, so that the final shaping deformation rate of the locally widened contact arc surface is 1.5-5.0%; the selective final shaping is only applied to the locally widened contact arc surface of the bending buffer strand F, and the crown and valleys of the main bearing strand P are not subjected to the same degree of pressing; on the cross section perpendicular to the wire rope axis, the radial dimension change from the outer contour of each valley to the geometric center of the wire rope is less than 40% of the radial dimension change at the locally widened contact arc surface.

[0014] Preferably, in step S8, the stabilization treatment involves performing 2-4 loading-unloading cycles under a load of 15-30% of the minimum breaking strength of the wire rope. In step S8, the lubrication treatment involves filling the micro-gap of the outer steel wires, the contact interface between the outer strands, and the contact interface between the independent steel core rope and the outer strands at the locally widened contact arc surface of the bending buffer strand F with a lubricating medium.

[0015] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. This invention constructs a gradient force system of independent steel core rope—main load-bearing strand P—bending buffer strand F by dividing the outer layer of rope strands into two categories: main load-bearing strand P and bending buffer strand F, and arranging them alternately along the circumference in the order PFPFPF. Compared with existing outer layer rope strand structures of the same type, this scheme enables the axial load-bearing function to be divided with the surface contact and bending buffer functions, which helps to reduce the adverse effects caused by the outer working area simultaneously bearing high tensile stress and high bending alternating stress, thereby improving the fatigue resistance of the wire rope under drilling conditions. 2. The main load-bearing strand P of this invention adopts a compacted, dense structure, while the bending-resistant buffer strand F adopts a fine, flexible structure, with a locally widened contact arc surface formed on its outermost radial side. This gives the bending-resistant buffer strand F superior surface contact adaptability and buffering capacity. This structure, combined with the gradient tension relationship and differentiated lay length design of the steel core rope, main load-bearing strand P, and bending-resistant buffer strand F, facilitates a more rational load transfer path, improving the overall structural and contact stability of the rope. Simultaneously, through local pre-shaping, selective final shaping, stabilization treatment, and lubrication treatment, the outer contact profile and interface working condition are improved. Therefore, the wire rope produced by this invention has significant comprehensive technical advantages in terms of load-bearing capacity, fatigue resistance, contact wear resistance, and adaptability to drilling conditions. Attached Figure Description

[0016] Figure 1 This is a process flow diagram of the preparation process of the ultra-long life anti-fatigue steel wire rope for drilling with gradient stress distribution as described in this invention. Detailed Implementation

[0017] The present invention will now be clearly and completely described in conjunction with embodiments thereof. Obviously, the described embodiments are merely some, not all, of the embodiments of the present invention. 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.

[0018] Please see Figure 1 The present invention provides a technical solution: Example 1 This embodiment provides a long-life, fatigue-resistant drilling wire rope with gradient stress distribution. The nominal diameter of the finished wire rope is 30 mm, and its structure consists of one independent steel core rope and six outer strands. The six outer strands include three main load-bearing strands (P) and three bending-resistant buffer strands (F), arranged alternately along the circumference in the order PFPFPF. The main load-bearing strands (P) adopt a 1+6+12 structure, and the bending-resistant buffer strands (F) adopt a 1+6+18 structure. The independent steel core rope has an independent core rope structure, and its finished diameter is controlled at 9.8 mm. The finished diameter of the main load-bearing strands (P) is controlled at 9.9 mm, and the finished diameter of the bending-resistant buffer strands (F) is controlled at 9.7 mm. The overall finished diameter of the rope is controlled at 30.0 ± 0.3 mm.

[0019] In this embodiment, the steel wire used for the main load-bearing strand P is made of 82A high-carbon wire rod with an original diameter of 5.5 mm. The P strand is stranded in a 1+6+12 layered configuration, with a center wire diameter of 2.00 mm, six wires in the second layer with a diameter of 1.95 mm, and twelve wires in the third layer with a diameter of 1.90 mm. The calculated average wire diameter is 1.93 mm. The tensile strength of the P strand wire is controlled at 2220 MPa. After compaction, the compaction rate of the P strand is controlled at 10.5%, forming a dense load-bearing outer contour.

[0020] In this embodiment, the steel wire used for the bending buffer strand F is also made of 82A high-carbon wire rod with an original diameter of 5.5mm. The F strand adopts a 1+6+18 layered stranding method, where the diameter of the center wire is 1.55mm, the diameter of the second layer of 6 steel wires is 1.45mm, and the diameter of the third layer of 18 steel wires is 1.30mm. The calculated average wire diameter is 1.36mm. The tensile strength of the F strand steel wire is controlled at 2050MPa. The outermost radial arc area of ​​the F strand's outer contour is locally compressed to form a locally widened contact arc surface, with a compression deformation rate controlled at 2.8%. The circumferential width of this locally widened contact arc surface is 38% of the corresponding arc length of the F strand surface. Circular transition surfaces connecting to the unshaped outer contour are formed on both sides of the locally widened contact arc surface. A lubrication micro-gap of 0.06-0.10mm is maintained between adjacent outer layer steel wires in the locally widened contact arc surface.

[0021] In this embodiment, the independent steel core rope adopts a 7×7 independent steel core rope structure, formed by twisting 7 small strands together. Each strand adopts a 1+6 structure, with the center wire diameter being 1.10mm and the outer 6 steel wires having a diameter of 0.95mm. The tensile strength of the independent steel core rope wire is controlled at 2180MPa. The lay pitch of the independent steel core rope is controlled at 160mm. The lay pitch of the main load-bearing strand P is controlled at 145mm, and the lay pitch of the bending buffer strand F is controlled at 128mm. This forms a gradient structure where the lay pitch of the independent steel core rope is greater than that of the main load-bearing strand P, and the lay pitch of the main load-bearing strand P is greater than that of the bending buffer strand F. This allows the independent steel core rope and the main load-bearing strand P to preferentially bear the axial load, while the bending buffer strand F preferentially participates in surface contact and bending follow-through. Because the main load-bearing strand P adopts a compacted, dense structure with a large wire diameter, while the bending-resistant buffer strand F uses more fine filaments and has a locally widened contact arc surface, the resulting wire rope can effectively separate its load-bearing function from its buffering contact function, reducing local contact stress and bending fatigue damage in the outer layer. Simultaneously, the locally widened contact arc surface and its two side arc transition surfaces help to increase the contact width, improve contact profile stability, and, combined with lubricating micro-gap, reduce interface wear. This allows the resulting wire rope to balance load-bearing capacity, contact stability, and fatigue resistance under drilling conditions.

[0022] This embodiment also provides a manufacturing process for a gradient stress distribution drilling ultra-long life fatigue-resistant steel wire rope, including the following steps: S1. First, the independent steel core rope is prepared. The 82A wire rod used for preparing the steel core rope is sequentially pickled, washed, borated, and dried, followed by rough drawing. The diameter of the steel wire after rough drawing is controlled at 2.20 mm. Subsequently, lead bath heat treatment is performed, with the austenitizing temperature controlled at 980℃, the holding time controlled at 68s, and the lead bath temperature controlled at 540℃. After heat treatment, phosphating is performed, with the phosphating film weight controlled at 8 g / m². 2 Then, the final tension is performed, with the center wire pulled to 1.10 mm and the outer wires pulled to 0.95 mm. The center wire is then twisted together with the six outer wires into a single strand, and the seven single strands are then twisted together into an independent steel core rope. The twist direction is right-handed, and the twist pitch is controlled at 160 mm, resulting in an independent steel core rope with a diameter of 9.8 mm.

[0023] S2. Preparation of Type I and Type II steel wires The first type of steel wire used for the main load-bearing strand P and the second type of steel wire used for the bending buffer strand F are prepared separately. Both types of steel wire are made of 82A high-carbon wire rod with an original diameter of 5.5 mm. The first type of steel wire is obtained by pickling, washing, boronizing, drying, rough drawing, lead bath heat treatment, phosphating, and final drawing. The diameter of the first type of steel wire after rough drawing is controlled at 2.60 mm, the austenitizing temperature is controlled at 970℃, the holding time is 70 s, the lead bath temperature is 545℃, the total compression ratio is controlled at 88%, the diameter of the center wire after final drawing is 2.00 mm, the diameter of the second layer of steel wire is 1.95 mm, the diameter of the third layer of steel wire is 1.90 mm, and the tensile strength is controlled at 2220 MPa. The second type of steel wire was prepared using the same process route. After rough drawing, the diameter was controlled at 2.20 mm, the austenitizing temperature was controlled at 960℃, the holding time was 66 s, the lead bath temperature was 535℃, the total compression ratio was controlled at 84%, the diameter of the center wire after final drawing was 1.55 mm, the diameter of the second layer of steel wire was 1.45 mm, the diameter of the third layer of steel wire was 1.30 mm, and the tensile strength was controlled at 2050 MPa.

[0024] S3. Preparation of the main bearing strand P The first type of steel wire is pre-formed into a 1+6+12 structure and then twisted into the main load-bearing strand P. During pre-forming, the center wire is not significantly pre-bent, and the second and third layers of steel wires are pre-formed using the same twist direction, resulting in a naturally rounded strand after pre-forming. During strand formation, the single-wire tension of the main load-bearing strand P is controlled at 55 N / strand, and the strand twist pitch is controlled at 145 mm. After strand formation, the P strand is subjected to overall compaction treatment using a rounded transition compaction mold. After compaction, the diameter of the P strand is controlled at 9.9 mm, and the compaction rate is controlled at 10.5%, forming a dense load-bearing outer contour.

[0025] S4. Prepare the bending-resistant buffer strand F and perform local pre-shaping. The second type of steel wire is pre-formed into a 1+6+18 structure and then twisted into a bending-resistant buffer strand F. During strand formation, the tension of each F strand filament is controlled at 40 N / strand, and the strand pitch is controlled at 128 mm. After strand formation, the outermost radially curved area of ​​the F strand's outer contour is partially pre-shaped. This partial pre-shaping is accomplished using a set of pressing and supporting rollers, with a circular arc support roller at the bottom and a strip-shaped pressing roller at the top. The working surface width of the pressing roller is 3.5 mm, and the gap between the pressing roller and the support roller is reduced by 0.22 mm compared to the original outer diameter of the F strand. This creates a locally widened contact arc surface in the outermost radially curved area of ​​the F strand's outer contour, and circular arc transition surfaces connecting to the unshaped outer contour are formed on both sides of this contact arc surface. After pre-shaping, the circumferential width of the locally widened contact arc surface is approximately 36% of the corresponding arc length of the F strand's outer contour surface.

[0026] S5. Alternating rope joining The three main load-bearing strands P and the three bending-resistant buffer strands F are joined together around the independent steel core rope in the order PFPFPF, with a right-hand twist. During joining, each strand is evenly arranged on the outer circumference of the independent steel core rope in a predetermined order, ensuring that the three F strands are evenly distributed in the circumferential direction to form an alternating load-bearing-buffering structure.

[0027] S6. Control Gradient Tension During the rope assembly process, the input tensions of the independent steel core rope, the main load-bearing strand P, and the bending buffer strand F are controlled to form a gradient relationship. Taking the input tension of strand F as a baseline, the rope assembly input tension of strand F is controlled at 10.0 kN, the rope assembly input tension of strand P is controlled at 11.5 kN, and the rope assembly input tension of the independent steel core rope is controlled at 14.0 kN, i.e., the input tension ratio of the independent steel core rope, strand P, and strand F is 1.40:1.15:1. Under this tension relationship, the independent steel core rope and strand P preferentially form the load-bearing skeleton, while strand F maintains good outer layer compliance contact characteristics.

[0028] S7. Selective final plastic surgery After the rope is joined, selective final shaping is performed only on the locally widened contact arc surface of strand F. Final shaping is performed using a local pressing wheel, with the working surface width controlled at 3.8 mm. The forming gap between the pressing wheel and the support wheel is further reduced by 0.12 mm compared to the outer contour of strand F before rope joining, controlling the final shaping deformation rate of the locally widened contact arc surface to 3.1%. After final shaping, on a cross-section perpendicular to the wire rope axis, the locally widened contact arc surface of strand F forms an outer contact profile wider than the contact arc surface of the crown of the adjacent main bearing strand P. Final shaping is applied only to the locally widened contact arc surface of strand F, without applying the same degree of pressing to the crown of the main bearing strand P and the valleys of each strand. The measured radial dimension change from the outer contour of each strand valley to the geometric center of the wire rope is approximately 0.04 mm, while the radial dimension change at the locally widened contact arc surface is approximately 0.18 mm; the former is less than 40% of the latter.

[0029] S8. Stabilization and Lubrication Treatment After final shaping, the wire rope undergoes stabilization and lubrication treatment. The stabilization treatment is performed using a load-unload cycle. Based on the minimum breaking strength of 680 kN for this specification of wire rope, 22% of this strength is taken as the stabilization load, i.e., 150 kN. Three load-unload cycles are performed, each with a 60-second loading period followed by a 60-second interval after unloading before the next cycle. After stabilization, high-adhesion wire rope grease is applied to the micro-gap between the outer wires at the locally widened contact arc surface of the F-strand, the contact interface between the outer strands, and the contact interface between the independent steel core rope and the outer strands. The grease dosage is controlled at 18 g / m to ensure sufficient interface lubrication.

[0030] Example 2 Example 2 differs from Example 1 in the following way: In Example 2, the nominal diameter of the steel wire rope is 28 mm, the finished diameter of the independent steel core rope is controlled at 9.2 mm, the finished diameter of the main load-bearing strand P is controlled at 9.3 mm, the finished diameter of the bending buffer strand F is controlled at 9.1 mm, and the overall finished diameter of the rope is controlled at 28.0 ± 0.3 mm. In the steel wire used in the main load-bearing strand P, the diameter of the center wire is 1.90 mm, the diameter of the 6 wires in the second layer is 1.85 mm, the diameter of the 12 wires in the third layer is 1.80 mm, the average wire diameter is 1.83 mm, the tensile strength is controlled at 2190 MPa, and the compaction rate is controlled at 9.2%. In the bending buffer strand F, the diameter of the central wire is 1.45 mm, the diameter of the second layer of 6 wires is 1.35 mm, the diameter of the third layer of 18 wires is 1.25 mm, the average wire diameter is 1.31 mm, the tensile strength is controlled at 2000 MPa, the compression deformation rate of the locally widened contact arc surface is controlled at 2.2%, and its circumferential width is 34% of the corresponding arc length of the F strand surface. A lubrication micro-gap of 0.05-0.09 mm is maintained between adjacent outer layer wires in the locally widened contact arc surface. The independent steel core rope still adopts a 7×7 structure, with a central wire diameter of 1.05 mm per strand, a diameter of 0.90 mm for the outer 6 wires, a tensile strength of 2160 MPa for the steel core rope, a lay pitch of 150 mm for the independent steel core rope, a lay pitch of 138 mm for the main load-bearing strand P, and a lay pitch of 122 mm for the bending buffer strand F. In step S2, the diameter of the first type of steel wire after rough drawing is controlled at 2.45 mm, the austenitizing temperature is controlled at 965℃, the holding time is 68 s, the lead bath temperature is 540℃, and the total compression rate is controlled at 87%. The diameter of the second type of steel wire after rough drawing is controlled at 2.05 mm, the austenitizing temperature is controlled at 955℃, the holding time is 64 s, the lead bath temperature is 532℃, and the total compression rate is controlled at 83%. In step S3, the tension of the main bearing strand P single wire is controlled at 52 N / strand. In step S4, the tension of the bending buffer strand F single wire is controlled at 38 N / strand. During local pre-forming, the working surface width of the pressing wheel is 3.2 mm, and the gap between the pressing wheel and the support wheel is reduced by 0.18 mm compared to the original outer diameter of strand F. In step S6, with the input tension of the F-strand as the baseline, the input tension of the F-strand combined rope is controlled at 10.0 kN, the input tension of the P-strand combined rope is controlled at 11.2 kN, and the input tension of the independent steel core rope is controlled at 13.5 kN, with an input tension ratio of 1.35:1.12:1. In step S7, the final shaping deformation rate of the locally widened contact arc surface is controlled at 2.5%. In step S8, the stabilization load is taken as 20% of the minimum breaking tensile force, and two loading-unloading cycles are performed, with each loading held for 55 s, and the amount of lubricating grease is controlled at 17 g / m. The remaining steps are exactly the same in this embodiment and Embodiment 1.

[0031] Example 3 Example 3 differs from Example 1 in the following way: In Example 3, the nominal diameter of the steel wire rope is 32 mm, the diameter of the independent steel core rope is controlled at 10.4 mm, the diameter of the main load-bearing strand P is controlled at 10.6 mm, the diameter of the bending buffer strand F is controlled at 10.3 mm, and the overall diameter of the rope is controlled at 32.0 ± 0.3 mm. In the main load-bearing strand P, the diameter of the center wire is 2.10 mm, the diameter of the six wires in the second layer is 2.00 mm, the diameter of the twelve wires in the third layer is 1.95 mm, the average wire diameter is 1.98 mm, the tensile strength is controlled at 2280 MPa, and the compaction rate is controlled at 12.0%. In the bending buffer strand F, the diameter of the central wire is 1.60 mm, the diameter of the second layer of 6 wires is 1.50 mm, the diameter of the third layer of 18 wires is 1.35 mm, the average wire diameter is 1.42 mm, the tensile strength is controlled at 2100 MPa, the compression deformation rate of the locally widened contact arc surface is controlled at 3.3%, and its circumferential width is 40% of the corresponding arc length of the F strand surface. A lubrication micro-gap of 0.07-0.12 mm is maintained between adjacent outer layer wires in the locally widened contact arc surface. The independent steel core rope still adopts a 7×7 structure, with a central wire diameter of 1.15 mm per strand, a diameter of 1.00 mm for the outer 6 wires, a tensile strength of 2200 MPa for the steel core rope, a lay pitch of 168 mm for the independent steel core rope, a lay pitch of 150 mm for the main load-bearing strand P, and a lay pitch of 132 mm for the bending buffer strand F. In step S2, the diameter of the first type of steel wire after rough drawing is controlled at 2.70 mm, the austenitizing temperature is controlled at 975℃, the holding time is 72 s, the lead bath temperature is 548℃, and the total compression rate is controlled at 89%. The diameter of the second type of steel wire after rough drawing is controlled at 2.30 mm, the austenitizing temperature is controlled at 965℃, the holding time is 68 s, the lead bath temperature is 538℃, and the total compression rate is controlled at 85%. In step S3, the tension of the main bearing strand P single wire is controlled at 60 N / strand. In step S4, the tension of the bending buffer strand F single wire is controlled at 43 N / strand. During local pre-forming, the working surface width of the pressing wheel is 3.8 mm, and the gap between the pressing wheel and the support wheel is reduced by 0.25 mm compared to the original outer diameter of strand F. In step S6, with the input tension of the F-strand as the baseline, the input tension of the F-strand combined rope is controlled at 10.0 kN, the input tension of the P-strand combined rope is controlled at 11.8 kN, and the input tension of the independent steel core rope is controlled at 14.5 kN, with an input tension ratio of 1.45:1.18:1. In step S7, the final shaping deformation rate of the locally widened contact arc surface is controlled at 3.6%. In step S8, the stabilization load is taken as 24% of the minimum breaking tensile force, and four loading-unloading cycles are performed, with each loading held for 60 s, and the amount of lubricating grease is controlled at 20 g / m. The remaining steps are exactly the same in this embodiment and Embodiment 1.

[0032] Example 4 Example 4 differs from Example 1 in the following way: the only difference is that in Example 4... The nominal diameter of the wire rope remains 30 mm, but in the main load-bearing strand P, the diameter of the center wire is 1.95 mm, the diameter of the second layer of 6 wires is 1.90 mm, the diameter of the third layer of 12 wires is 1.85 mm, the average wire diameter is 1.88 mm, the tensile strength is controlled at 2170 MPa, and the compaction rate is controlled at 8.8%. In the bending buffer strand F, the diameter of the center wire is 1.50 mm, the diameter of the second layer of 6 wires is 1.40 mm, the diameter of the third layer of 18 wires is 1.28 mm, the average wire diameter is 1.34 mm, and the tensile strength is controlled at 1980 MPa. The compression deformation rate of the locally widened contact arc surface of the bending buffer strand F is controlled at 2.5%, and its circumferential width is 42% of the corresponding arc length of the F strand surface. A lubrication micro-gap of 0.08-0.12 mm is maintained between adjacent outer layer wires in the locally widened contact arc surface. The independent steel core rope lay length is controlled at 158 ​​mm, the main load-bearing strand P lay length is controlled at 142 mm, and the bending buffer strand F lay length is controlled at 124 mm. In step S2, the total compression rate of the first type of steel wire is controlled at 87%, and the total compression rate of the second type of steel wire is controlled at 82%. In step S3, the single wire tension of the main load-bearing strand P is controlled at 53 N / strand. In step S4, the single wire tension of the bending buffer strand F is controlled at 39 N / strand, the working surface width of the pressing wheel is 3.7 mm, and the gap between the pressing wheel and the support wheel is reduced by 0.20 mm compared to the original outer diameter of strand F. In step S6, the input tension of strand F is controlled at 10.0 kN, the input tension of strand P is controlled at 11.0 kN, and the input tension of the independent steel core rope is controlled at 13.8 kN, with an input tension ratio of 1.38:1.10:1. In step S7, the final shaping deformation rate of the locally widened contact arc surface is controlled at 2.7%. In step S8, the stabilizing load is taken as 18% of the minimum breaking tensile force, and two loading-unloading cycles are performed, with each loading held for 50 seconds, and the amount of lubricating grease is controlled at 19 g / m. The remaining steps are exactly the same in this embodiment and Embodiment 1.

[0033] Comparative Example Comparative Example 1 The difference between this comparative example and Example 1 is that, in this comparative example, the steel wire rope still adopts the structure of 1 independent steel core rope + 6 outer strands, the nominal diameter of the steel wire rope is still 30 mm, the diameter of the finished rope is controlled at 30.0 ± 0.3 mm, and the diameter of the independent steel core rope is controlled at 9.8 mm. However, all 6 outer strands adopt the same structure of compacted dense load-bearing strands, and the main load-bearing strand P and the bending buffer strand F are no longer distinguished, nor are they arranged alternately in the PFPFPF sequence. The 6 outer strands all adopt a 1+6+12 structure, and the diameter of the finished product is controlled at 9.9 mm. The steel wires used in each outer layer of the rope strands all adopt the same wire parameters as the main load-bearing strand P in Example 1, wherein the diameter of the center wire is 2.00 mm, the diameter of the 6 wires in the second layer is 1.95 mm, the diameter of the 12 wires in the third layer is 1.90 mm, the average wire diameter is 1.93 mm, the tensile strength of the steel wire is controlled at 2220 MPa, and the compaction rate is controlled at 10.5%. The outer contour of each outer layer of the rope strand is a conventional rounded and compacted contour, without any locally widened contact arc surface, and there are no arc transition surfaces on both sides connecting with the unshaped outer contour. No deliberate lubrication micro-gaps are retained between the outer layer steel wires.

[0034] In this comparative example, the independent steel core rope still adopts a 7×7 independent steel core rope structure, formed by the twisting of 7 small strands. Each strand adopts a 1+6 structure, with the center wire diameter being 1.10 mm and the outer 6 steel wires having a diameter of 0.95 mm. The tensile strength of the independent steel core rope wire is controlled at 2180 MPa, and the lay pitch of the independent steel core rope is controlled at 160 mm. The lay pitch of the 6 outer strands is controlled at 145 mm, and the shorter lay pitch bending buffer strands are no longer included.

[0035] This comparative example also provides a wire rope manufacturing process, the only difference being that in step S2, only one type of steel wire for forming the outer strands is prepared. The raw materials, rough drawing, heat treatment, phosphating treatment, and final drawing parameters of this type of steel wire are the same as those of the first type of steel wire in Example 1. In step S3, this type of steel wire is twisted into 6 identical outer strands in a 1+6+12 structure, and each outer strand is subjected to overall compaction treatment to form a dense load-bearing outer contour. In step S4, local pre-shaping of the outermost radial arc area of ​​the bending buffer strand F is not performed. In step S5, the 6 identical outer strands are evenly wrapped around the independent steel core rope to form a rope. In step S6, the input tension of the independent steel core rope is controlled at 14.0 kN, and the input tension of each of the 6 outer strands is controlled at 11.5 kN. kN, there is no gradient tension relationship between the main load-bearing strand P and the bending buffer strand F; in step S7, selective final shaping is not performed only on the local contact arc surface of a certain type of outer layer strand, but only conventional sizing shaping is performed on the entire rope to keep the outer contour round; the stabilization and lubrication treatment parameters in step S8 are the same as in Example 1. The remaining steps are exactly the same in this comparative example and Example 1.

[0036] Comparative Example 2 In this comparative example, the wire rope still adopts the structure of 1 independent steel core rope + 6 outer strands. The outer strands still include 3 main load-bearing strands P and 3 bending buffer strands F, and are still arranged alternately along the circumference in the order PFPFPF. The material system, strand structure, nominal diameter, and basic dimensional parameters of the independent steel core rope, main load-bearing strand P, and bending buffer strand F are the same as in Example 1. The main load-bearing strand P still adopts a 1+6+12 structure, and the bending buffer strand F still adopts a 1+6+18 structure. The finished diameter of the independent steel core rope is controlled at 9.8 mm, the finished diameter of the main load-bearing strand P is controlled at 9.9 mm, the finished diameter of the bending buffer strand F is controlled at 9.7 mm, and the overall finished diameter of the rope is controlled at 30.0±0.3 mm. The wire parameters used for the main load-bearing strand P and the bending buffer strand F are the same as in Example 1.

[0037] The difference between this comparative example and Example 1 is that the outermost radial arc region of the bending buffer strand F is not subjected to local pre-shaping and selective final shaping, thus not forming a locally widened contact arc surface, nor forming a circular arc transition surface connecting it to its two sides. The bending buffer strand F maintains a conventional rounded outer contour, and the width of its outer surface contact arc surface is not locally widened, nor is a 0.03-0.20 mm lubrication micro-gap intentionally retained between the outer steel wires.

[0038] This comparative example also provides a wire rope manufacturing process, the only difference being that steps S1, S2, and S3 are exactly the same as in Example 1; in step S4, only the second type of steel wire is twisted into a bending-resistant buffer strand F according to a 1+6+18 structure, without performing local pre-shaping on the outermost radial arc area of ​​the outer contour of the bending-resistant buffer strand F; in step S5, the three main load-bearing strands P and the three bending-resistant buffer strands F are still wound around the independent steel core rope in the order PFPFPF; in step S6, the input tension of the independent steel core rope, the main load-bearing strand P, and the bending-resistant buffer strand F are still controlled at 14.0 kN, 11.5 kN, and 10.0 kN, respectively. kN, the input tension ratio is maintained at 1.40:1.15:1; in step S7, selective final shaping is no longer performed only on the locally widened contact arc surface of the bending buffer strand F, but only conventional sizing shaping is performed to keep the outer contour of the entire rope round; the stabilization and lubrication treatment parameters in step S8 are the same as in Example 1, but the grease is mainly distributed at the contact interface between the outer strands and the contact interface between the independent steel core rope and the outer strands, and the micro-gap grease storage lubrication structure of the locally contact arc surface described in Example 1 is not formed between the outer steel wires of the bending buffer strand F. The remaining steps are exactly the same in this comparative example and Example 1.

[0039] Performance testing To evaluate the comprehensive performance of the wire rope of this invention, wire ropes prepared in Examples 1-4, Comparative Examples 1 and 2 were selected as test samples. All samples were taken from stable sections of the same batch of finished wire ropes, avoiding cuts at least 3 m from the beginning and end of the rope to reduce the impact of structural fluctuations in the starting and winding sections on the test results. All samples underwent visual inspection before cutting, and samples with broken wires, local flattening, surface corrosion, abnormal scratches, or obvious kinking defects were rejected. After cutting, the surface of the samples was cleaned of oil and impurities, and the samples were allowed to stand at room temperature for 24 hours to allow the internal stress and surface condition to stabilize. The nominal diameter, actual diameter, mass per unit length, and sample length of each group of samples were measured before testing.

[0040] The breaking tensile strength test was conducted according to the method specified in GB / T 8358-2023 "Method for Determining Breaking Tensile Strength of Steel Wire Rope". The specimens used for the breaking tensile strength test were whole rope specimens, with no fewer than 3 specimens per group. The actual elastic modulus test was conducted according to the method specified in GB / T24191-2009 "Method for Determining Actual Elastic Modulus of Steel Wire Rope". The specimens used for this test were whole rope specimens, with no fewer than 3 specimens per group. The bending fatigue test was conducted according to the method specified in GB / T 12347-2008 "Method for Bending Fatigue Test of Steel Wire Rope". The specimens used for the bending fatigue test were relatively long whole rope specimens, with no fewer than 6 specimens per group. To further evaluate the effect of the locally widened contact arc surface and lubrication micro-gap of the bending buffer strand F of this invention on the improvement of the surface contact state and cross-sectional profile stability, supplementary tests for contact wear and cross-sectional profile stability were set up. This supplementary test used specimens from the same batch as the bending fatigue test. After completing the specified number of cycles, a section was taken from the stable working area in the middle of the specimen to measure the wear mark width, mass loss, outer diameter change, and radial dimension change from the outer contour of each strand's valley to the geometric center of the wire rope at the locally widened contact arc surface. The relevant test results are shown in Tables 1 and 2. Table 1. Structure and test results of steel wire ropes in different embodiments and comparative examples

[0041] Table 2. Test results of cross-sectional profile stability of steel wire ropes in different embodiments and comparative examples

[0042] As can be seen from Tables 1 and 2, the differences between Examples 1-4 and the two comparative examples are mainly reflected in bending fatigue life, contact wear, outer diameter retention, and cross-sectional profile stability, while no significant adverse losses were observed in breaking tensile strength and elastic modulus. This indicates that the present invention does not sacrifice overall load-bearing capacity for fatigue performance, but rather optimizes the force path and contact path by dividing the functions of the main load-bearing strand P and the bending buffer strand F while maintaining a high load-bearing level. The breaking tensile strength of Comparative Example 1 reached 689 kN, close to the 684 kN of Example 1, and the elastic modulus was also slightly higher, but its bending fatigue life was only 213,000 cycles, significantly lower than the 328,000 cycles of Example 1; at the same time, its mass loss, diameter change, and contact wear mark width after 100,000 cycles were significantly worse than those of Example 1. This indicates that although the traditional six identical compacted outer strands can maintain high overall stiffness and load-bearing capacity, the outer strands simultaneously bear the functions of load bearing, contact, and bending, making it easier for stress superposition and local wear concentration to occur in the working area of ​​the outer surface under the conditions of winding around the wheel and multi-layer winding, resulting in faster accumulation of fatigue damage.

[0043] A comparison between Example 1 and Comparative Example 2 further demonstrates that the technical advantages of this invention do not solely stem from the alternating arrangement of P / F strands. Comparative Example 2 retains the alternating arrangement of the main load-bearing strand P and the bending buffer strand F, as well as the same tension gradient. However, due to the elimination of the local pre-shaping and selective final shaping of the outermost radial arc region in the outer contour of the bending buffer strand F, it fails to form a locally widened contact arc surface or a corresponding micro-gap grease reservoir structure. Consequently, its bending fatigue life is only 256,000 cycles, significantly lower than the 328,000 cycles of Example 1, and the mass loss and diameter variation are also significantly greater. Therefore, the alternating arrangement addresses the functional zoning of load-bearing and buffering, while the locally widened contact arc surface and selective final shaping address the contact interface morphology and contact stress distribution. The combined effect of these two aspects constitutes the core technical advantage of this solution.

[0044] The differences between Examples 1-4 show a consistent overall performance trend, indicating that the scheme has a good parameter adaptability range. Example 3 achieved a breaking tensile force of 742 kN and a bending fatigue life of 356,000 cycles, ranking as the best among all groups. This is related to its increased nominal diameter, further improved average diameter and tensile strength of the main load-bearing strand P, increased compaction rate to 12.0%, and further optimized input tension ratio between the independent steel core rope and the P strand. Higher load-bearing skeleton strength allows the load to be more stably borne by the independent steel core rope and the main load-bearing strand P, while the bending buffer strand F maintains good outer compliance and a wider contact profile, thus achieving simultaneous improvement in load-bearing capacity and fatigue life. Example 2, due to its smaller overall size, had a breaking tensile force reduced to 612 kN and a bending fatigue life of 304,000 cycles, but its mass loss was only 4.8 g and diameter change was only 0.17 mm, indicating that even with smaller dimensions, this scheme can achieve good contact wear control through lighter local compaction and lower structural load. In Example 4, with a decrease in the compaction rate of the P-strand and an increase in the width of the contact arc surface of the F-strand to 42%, the breaking tensile force was slightly lower than in Example 1, but the fatigue life still reached 317,000 cycles, and the contact wear mark width increased to 6.5 mm. This indicates that a wider contact profile is beneficial for further dispersing contact stress. However, if the compaction rate and strength of the P-strand decrease slightly, the overall load-bearing capacity will be affected to some extent. This shows that the parameter design of this invention needs to balance the load-bearing skeleton capacity and the contact buffer capacity, rather than simply pursuing the maximization of a certain indicator.

[0045] In Table 1, the contact wear marks widths of Examples 1-4 are significantly larger than those of the two comparative examples, but their mass loss and diameter changes are smaller. This is because the outermost radial arc region of the bending buffer strand F, after local pre-shaping and selective final shaping, forms a locally widened contact arc surface and two circular arc transition surfaces, expanding the originally narrow outer contact arc surface into a wider and smoother contact profile, thus increasing the wear mark width. However, due to the increased contact area, the contact pressure per unit area decreases, reducing local plastic damage and interfacial wear. Therefore, mass loss, outer diameter change, and fatigue damage are effectively controlled. Although Comparative Examples 1 and 2 have smaller wear mark widths, their contact is closer to narrow arc contact or even local line contact, resulting in stronger stress concentration and thus more severe wear and dimensional decay.

[0046] Table 2 verifies the effectiveness of the selective final shaping of this invention. In Examples 1-4, the radial dimension changes at the locally widened contact arc surface are 0.18, 0.16, 0.19, and 0.17 mm, respectively, while the radial dimension changes at the trough are only 0.04-0.05 mm. The proportion of the trough change to the total contact arc surface change is less than 30%. This indicates that the final shaping mainly focuses on the locally widened contact arc surface of the bending buffer strand F, rather than compressing the entire wire rope into a highly rigid outer contour. In other words, this solution, through "local shaping and overall shape preservation," ensures that strand F forms a stable preferred contact contour while avoiding excessive deformation of the crown and trough of the main load-bearing strand P, thereby maintaining the functional separation between the load-bearing frame and the contact buffer structure. In contrast, Comparative Example 1 and Comparative Example 2 did not have locally widened contact arc surfaces, and the radial dimension changes of the valley section reached 0.12 mm and 0.10 mm, respectively. This indicates that under the same service conditions, their structural deformation is more manifested as overall profile attenuation and increased inter-strand interlocking, and the outer profile stability is significantly worse.

[0047] Based on the above data, it is clear that the performance improvement of this invention has a clear structural origin. The gradient tension relationship and lay pitch hierarchy formed by the independent steel core rope, the main load-bearing strand P, and the bending buffer strand F ensure that the main load-bearing channel is preferentially borne by the steel core rope and the P strand, reducing the load proportion of the bending buffer strand F under high tensile stress conditions. At the same time, the F strand uses thinner steel wire, lower strand tension, and a shorter lay pitch, and forms a locally widened contact arc surface and lubrication micro-gap in the radially outermost arc area of ​​its outer contour, making it easier to undertake contact buffering and bending following functions when in contact with the sheave and between layers. It is this functional division of "load-bearing strands bearing the load and buffer strands bearing the contact," coupled with the directional control of the outer contact contour by selective final shaping, that ultimately enables the steel wire rope of this invention to achieve higher bending fatigue life, lower wear mass loss, smaller outer diameter attenuation, and a more stable cross-sectional profile without significantly reducing the load-bearing capacity.

[0048] 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 variations 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 long-life, fatigue-resistant drilling wire rope with gradient stress distribution, characterized in that, It includes one independent steel core rope and six outer strands twisted together around the independent steel core rope; The six outer rope strands include three main load-bearing strands P and three bending-resistant buffer strands F. The main load-bearing strands P and the bending-resistant buffer strands F are arranged alternately along the circumference in the order PFPFPF. The main load-bearing strand P is a compacted dense load-bearing strand with a 1+6+12 structure; the bending-resistant buffer strand F is a fine-filament flexible buffer strand with a 1+6+18 structure. The average diameter of the steel wires in the main load-bearing strand P is greater than the average diameter of the steel wires in the bending-resistant buffer strand F; The outermost radial arc region of the bending buffer strand F has a partially widened contact arc surface, and the two sides of the partially widened contact arc surface are provided with arc transition surfaces connected to the unshaped outer contour. On a cross section perpendicular to the axis of the wire rope, the locally widened contact arc surface forms an outer contact profile that is wider than the contact arc surface of the crown of the adjacent main bearing strand P.

2. The ultra-long life fatigue-resistant steel wire rope for drilling with gradient stress distribution according to claim 1, characterized in that, The average diameter of the steel wires in the main load-bearing strand P is 1.75-2.10 mm, and the average diameter of the steel wires in the bending buffer strand F is 1.20-1.60 mm. The average diameter of the steel wires in the main load-bearing strand P is 1.10-1.45 times the average diameter of the steel wires in the bending buffer strand F. The tensile strength of the steel wires in the main load-bearing strand P is 2150-2300 MPa, and the tensile strength of the steel wires in the bending buffer strand F is 1950-2150 MPa.

3. The ultra-long life fatigue-resistant steel wire rope for drilling with gradient stress distribution according to claim 2, characterized in that, The main load-bearing strand P is a compacted load-bearing strand with a compaction rate of 8-14%; the local widening contact arc surface of the bending buffer strand F has a compression deformation rate of 1.0-5.0%.

4. The ultra-long life fatigue-resistant steel wire rope for drilling with gradient stress distribution according to claim 2, characterized in that, The circumferential width of the locally widened contact arc surface of the bending buffer strand F is 25-55% of the corresponding arc length of the bending buffer strand F surface, and its shaping deformation rate is 1.5-5.0%; a lubrication micro gap of 0.03-0.20 mm is retained between adjacent outer steel wires in the locally widened contact arc surface.

5. The ultra-long life fatigue-resistant steel wire rope for drilling with gradient stress distribution according to claim 1, characterized in that, The lay length of the independent steel core rope is 1.05-1.20 times the lay length of the main bearing strand P; the nominal diameter of the wire rope is 26-38 mm.

6. A manufacturing process for ultra-long life anti-fatigue steel wire rope with gradient stress distribution for drilling, used to prepare the ultra-long life anti-fatigue steel wire rope with gradient stress distribution as described in any one of claims 1-5, characterized in that, Includes the following steps: S1. Prepare independent steel core ropes; S2. Prepare a first type of steel wire for forming the main load-bearing strand P and a second type of steel wire for forming the bending buffer strand F. The first type of steel wire and the second type of steel wire are obtained by rough drawing, heat treatment, phosphating treatment and final drawing treatment in sequence; S3. After preforming the first type of steel wire, twist it into a main load-bearing strand P with a 1+6+12 structure, and compact the main load-bearing strand P to form a dense load-bearing outer contour; S4. After preforming the second type of steel wire, twist it into a bending buffer strand F with a 1+6+18 structure, and perform local pre-shaping on the outermost radial arc area of ​​the outer contour of the bending buffer strand F, so that the arc area forms a locally widened contact arc surface, and form arc transition surfaces on both sides of the locally widened contact arc surface that connect with the unshaped outer contour; S5. Join the three main load-bearing strands P and the three bending buffer strands F around the independent steel core rope in the order PFPFPF; S6. During the joining process, control the input tension of the independent steel core rope, the main load-bearing strand P and the bending buffer strand F to form a gradient relationship; S7. After joining, only perform selective final shaping on the locally widened contact arc surface of the bending buffer strand F, so that on the cross section perpendicular to the axis of the steel wire rope, the locally widened contact arc surface forms an outer contact contour wider than the crown contact arc surface of the adjacent main load-bearing strand P; S8. After the rope is assembled, the wire rope is stabilized and lubricated to obtain the ultra-long life anti-fatigue wire rope with the gradient stress distribution.

7. The manufacturing process of the gradient stress distribution drilling ultra-long life fatigue-resistant steel wire rope according to claim 6, characterized in that, In step S2, the total compression rate of the first type of steel wire is 86-90%, and the total compression rate of the second type of steel wire is 80-88%; the heat treatment in step S2 is either lead bath heat treatment or isothermal transformation heat treatment; the tensile strength of the first type of steel wire is controlled at 2150-2300 MPa, and the tensile strength of the second type of steel wire is controlled at 1950-2150 MPa.

8. The manufacturing process of the gradient stress distribution drilling ultra-long life fatigue-resistant steel wire rope according to claim 6, characterized in that, In step S3, the twisting tension of the main bearing strand P is greater than the twisting tension of the bending buffer strand F; in step S6, the input tensions of the independent steel core rope, the main bearing strand P, and the bending buffer strand F form a gradient relationship, and the input tension of the independent steel core rope is greater than the input tension of the main bearing strand P, and the input tension of the main bearing strand P is greater than the input tension of the bending buffer strand F; the input tension ratio of the independent steel core rope, the main bearing strand P, and the bending buffer strand F is 1.30-1.45:1.10-1.20:1; and the lay length of the main bearing strand P is greater than the lay length of the bending buffer strand F.

9. The manufacturing process of the gradient stress distribution drilling ultra-long life fatigue-resistant steel wire rope according to claim 6, characterized in that, In step S4, the local pre-shaping is performed using a local pressing wheel or a strip pressing die, so that the circumferential width of the locally widened contact arc surface is 25-55% of the arc length of the outer contour surface of the corresponding bending buffer strand F; In step S7, the selective final shaping is performed using a local pressing wheel or a strip pressing die, so that the final shaping deformation rate of the locally widened contact arc surface is 1.5-5.0%; The selective final shaping is only applied to the locally widened contact arc surface of the bending buffer strand F, and the crown and valleys of the main bearing strand P are not subjected to the same degree of pressing; On the cross-section perpendicular to the wire rope axis, the radial dimension change from the outer contour of each valley to the geometric center of the wire rope is less than 40% of the radial dimension change at the locally widened contact arc surface.

10. The manufacturing process of the gradient stress distribution drilling ultra-long life fatigue-resistant steel wire rope according to claim 6, characterized in that, In step S8, the stabilization treatment involves performing 2-4 loading-unloading cycles under a load of 15-30% of the minimum breaking strength of the wire rope. The lubrication treatment involves filling the micro-gap of the outer steel wires, the contact interface between the outer strands, and the contact interface between the independent steel core rope and the outer strands at the locally widened contact arc surface of the bending buffer strand F with a lubricating medium.

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