Steel rope for rubber reinforcement

Abstract

The invention relates to a steel rope for rubber reinforcement. The steel rope has a configuration comprising an outer layer and inner strands surrounded by and adjacent to the outer layer, the inner strands comprising at least one steel wire having a number N1 and an average diameter d1 expressed in mm, the outer layer comprising steel wires having a number N2 and an average diameter d2 expressed in mm, the torque of the inner strands being T1, the torque of the outer layer being T2, the relationship between T1 and T2 being defined. In this way, the tip upwarp problem of the rubber cord fabric reinforced by the steel rope is reduced.

Description

[0001] This application is a divisional application of the international application entering the Chinese national phase, with the application date of November 30, 2021, the international application number: PCT / EP2021 / 083627, the national application number: 202180082948.4, and the name "Steel Rope for Rubber Reinforcement". Technical Field

[0002] The present invention relates to a steel cord for rubber reinforcement and a tire reinforced with the steel cord of the present invention. Background Art

[0003] Steel cords are widely used to reinforce rubber products, such as rubber belts, rubber tires, or rubber tubes, because the steel cords can provide sufficient strength to the rubber products and have good adhesion to the rubber.

[0004] A radial tire (a type of tire) consists of at least one belt, at least one carcass, at least one tread, and a pair of bead sections. Depending on the tire's application, radial tires have various designs for the belt, carcass, or tread. Steel cords are applied to the belt, carcass, and / or chafers to provide the desired strength. Depending on the tire section to which they are applied, the cords are designed with different constructions and performance parameters.

[0005] A rubber ply with embedded steel cords is a component used to manufacture the belt, carcass, and / or chafer. The rubber ply is processed by cutting it into small pieces of specific length, width, and thickness. The rubberized steel cord ply is cut at an angle to the longitudinal axis of the rubberized steel cord ply, or perpendicular to it. A machine then joins all the identically shaped pieces of rubber ply to the desired length for a tire.

[0006] After cutting, one or more of the four corners of a small piece of rubberized steel cord ply may sometimes warp out of plane. If the corners warp above a certain height, for example, ten millimeters or more, automated machines cannot splice the pieces, forcing manual splicing, which reduces efficiency. This is known as the "tip warp problem." This problem is more common when the steel cord has a layered structure.

[0007] US2017073888 discloses a steel cord comprising a core group and a sheath group to form an m+n configuration. By ensuring that the ratio of the absolute value of the difference in residual torsion between the core group and the sheath group to the absolute value of the difference in saturation level between the core group and the sheath group is within a specific range, the steel cord has no residual torsion, and thus, the tip of a rubber cord reinforced with the steel cord has low or no curling. Summary of the Invention

[0008] The main purpose of the present invention is to solve the problems of the prior art.

[0009] Another object of the present invention is to provide a steel cord for reducing the tip lift problem of the rubber ply.

[0010] Another object of the present invention is to provide a tire having improved operating efficiency.

[0011] According to one aspect of the present invention, there is provided a steel rope having a construction comprising an outer layer and an inner strand surrounded by and adjacent to the outer layer, the inner strand comprising at least one steel wire having a number N1 and an average diameter d1 expressed in mm, the outer layer comprising a number N2 of steel wires having an average diameter d2 expressed in mm, the torque of the inner strand being T1 and the torque of the outer layer being T2, T1 and T2 satisfying the following formula:

[0012] T1=G×RT1×π 2 ×D1 2 ×d1 2 ×N1 / 16000,

[0013] T2=G×RT2×π 2 ×(D1 2 +D2 2 )×d2 2 ×N2 / 16000,

[0014] │T1+T2│<60,

[0015] Where D1 is the theoretical diameter of the inner strand, D2 is the theoretical diameter of the steel rope, both D1 and D2 are expressed in mm, RT1 is the residual torsion of the inner strand, RT2 is the residual torsion of the outer layer, RT1 and RT2 are expressed in turns per meter in the clockwise direction "+" or counterclockwise direction "-", and G is 80000N / mm 2 , the absolute value of RT1 is not less than 0.05 circles per meter, and the absolute value of RT2 is less than 2 circles per meter.

[0016] By limiting the torque of the inner and outer layers to meet the above formula, the occurrence of tip curling in the rubber ply embedded with steel cords is reduced. The torque of the inner and outer layers of the steel cords is both related to the occurrence of tip curling in the rubber ply. The smaller the sum of the torque of the inner and outer layers, the less likely the rubber ply tip curling will occur.

[0017] Unlike the prior art that limits the residual torsion of different layers and / or the residual torsion of ropes, the present invention limits the torque of the inner strands and the torque of the outer layer based on the specific residual torsion of the outer layer and the specific residual torsion of the inner strands to reduce the occurrence of the tip lift problem of the rubber cord layer.

[0018] Preferably, |T1+T2|<50. Most preferably, |T1+T2|<40.

[0019] According to the present invention, the absolute value of RT1 is preferably not less than 0.1 revolutions per meter.

[0020] Preferably, the absolute value of RT2 is not less than 0.05 revolutions per meter. More preferably, the absolute value of RT2 is not less than 0.1 revolutions per meter. When RT2 is within this value range, the present invention contributes greatly.

[0021] In order to reduce the tip warping problem of the rubber cord layer, preferably, |RT1+RT2|<4. More preferably, |RT1+RT2|<2. This greatly reduces the occurrence of the tip warping problem of the rubber cord layer.

[0022] The present invention is applicable to steel ropes having a construction of two, three or more layers.

[0023] D1 is the theoretical diameter of the inner strand, while D2 is the theoretical diameter of the rope, i.e. the theoretical diameter of the outer layer. The theoretical diameter is the diameter calculated based on the rope construction, wire diameter and number of wires when assuming that the layers or strands of the rope are circular.

[0024] When the steel rope has a two-layer structure, N1 is 1, 2, 3 or 4. The calculation formula of D2 is: D2 = D1 + 2 × d2; and the calculation formula of D1 is:

[0025] When N1 is 1, D1 = d1, or

[0026] When N1 is 2, D1 = 2 × d1, or

[0027] When N1 is 3, D1 = 2.155 × d1, or

[0028] When N1 is 4, D1 = 2.414 × d1.

[0029] When the steel rope has a three-layer construction, this means that the inner strands include an intermediate layer and a core layer surrounded by the intermediate layer, the intermediate layer is surrounded by and adjacent to the outer layer, and the core layer includes a number N c And the average diameter is d c At least one steel wire, the middle layer includes an average diameter d m The calculation formula of D2 is: D2 = D1 + 2 × d2; and the calculation formula of D1 is:

[0030] When N c When it is 1, D1=d c +2×d m ,or

[0031] When N c When D1 is 2, D1 = 2 × d c +2×d m ,or

[0032] When N c When it is 3, D1=2.155×d c +2×d m ,or

[0033] When N c When it is 4, D1=2.414×d c +2×d m .

[0034] According to the present invention, the steel rope has a configuration of 1+3, 1+4, 1+5, 1+6, 1+7, 2+2, 2+3, 2+4, 2+5, 2+5cc, 2+6, 2+7, 2+7cc, 2+8, 3+2, 3+3, 3+6, 3+8, 3+8cc, 3+9, 3+9cc, 4+3, 4+6, 1+3+8, 1+4+8cc, 1+4+9, 1+5+10, 1+5+10cc, 1+6+11, 1+6+12, 1+6+12cc, 2+5+10, 2+6+12, 3+8+13, 3+9+15 or 4+10+16.

[0035] The present invention is beneficial for steel ropes having very high tensile strength steel wires. Preferably, each steel wire of the steel rope has a tensile strength TS satisfying TS≥4000-2000×d, where d is the diameter of a single steel wire, more preferably satisfying TS≥4100-2000×d.

[0036] The inner strands and outer layer each have a twist pitch of less than 40 mm, alternatively, the inner strands have a twist pitch greater than 300 mm and the outer layer has a twist pitch less than 40 mm.

[0037] According to a second aspect of the present invention, a tire is provided. The tire comprises at least one belt layer, at least one carcass layer, at least one tread layer, and a pair of bead portions, wherein the belt layer and / or the carcass layer comprises at least one steel cord, the steel cord having a configuration comprising an outer layer and an inner strand surrounded by and adjacent to the outer layer, the inner strand comprising at least one steel wire having a number N1 and an average diameter d1, the outer layer comprising a number N2 of steel wires having an average diameter d2, the torque of the inner strand being T1, and the torque of the outer layer being T2, and T1 and T2 satisfying the following formula:

[0038] T1=G×RT1×π 2 ×D1 2 ×d1 2 ×N1 / 16000,

[0039] T2=G×RT2×π 2 ×(D1 2 +D2 2 )×d2 2 ×N2 / 16000,

[0040] │T1+T2│<60,

[0041] Where D1 is the theoretical diameter of the inner strand, D2 is the theoretical diameter of the steel rope, both D1 and D2 are expressed in mm, RT1 is the residual torsion of the inner strand, RT2 is the residual torsion of the outer layer, RT1 and RT2 are expressed in turns per meter in the clockwise direction "+" or counterclockwise direction "-", and G is 80000N / mm 2 , the absolute value of RT1 is not less than 0.05 circles per meter, and the absolute value of RT2 is less than 2 circles per meter. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 Describes the measurement of tip lift of a rubber ply.

[0043] Figure 2a - Figure 2b The measurement of residual torsion is described. DETAILED DESCRIPTION

[0044] The steel wire used for steel rope is made of wire rod.

[0045] The wire is first cleaned by mechanical descaling and / or chemical pickling in H2SO4 or HCl solution to remove any surface oxides. The wire is then rinsed in water and dried. The dried wire is then subjected to a first series of dry drawing operations to reduce the diameter until it reaches a first intermediate diameter.

[0046] At this first intermediate diameter, for example, about 3.0 to 3.5 mm, the dry-drawn wire undergoes a first intermediate heat treatment known as lead quenching. Lead quenching involves first austenitizing to a temperature of about 1000°C and then a phase transformation from austenite to pearlite at a temperature of about 600 to 650°C. The wire is then ready for further mechanical deformation.

[0047] Thereafter, in a second diameter reduction step, the wire is further dry-drawn from the first intermediate diameter to a second intermediate diameter, typically in the range of 1.0 mm to 2.5 mm.

[0048] At this second intermediate diameter, the wire is subjected to a second lead hardening treatment, ie it is austenitized again at a temperature of about 1000° C. and then quenched at a temperature of 600° C. to 650° C. to allow transformation into pearlite.

[0049] If the total reduction in the first dry drawing step and the second dry drawing step is not too large, a direct drawing operation from the wire to the second intermediate diameter may be performed.

[0050] After this second lead hardening treatment, the steel wire is typically provided with a brass coating: copper is plated on the steel wire, and zinc is plated on the copper. A thermal diffusion treatment is applied to form the brass coating. Alternatively, the steel wire can be provided with a ternary alloy coating comprising copper, zinc, and a third alloy of cobalt, titanium, nickel, iron, or other known metals.

[0051] The brass-coated or ternary alloy-coated wire then undergoes a final series of cross-sectional reductions in a wet drawing machine. The final product is a steel wire with a carbon content greater than 0.70 wt%, or not less than 0.80 wt%, or even greater than 0.90 wt%, with a tensile strength (TS) typically greater than 3000 MPa and suitable for reinforcement of rubber products.

[0052] Steel wire suitable for tire reinforcement typically has a final diameter ranging from 0.05 mm to 0.60 mm, for example, from 0.10 mm to 0.40 mm. Examples of wire diameters are 0.10 mm, 0.12 mm, 0.15 mm, 0.175 mm, 0.18 mm, 0.20 mm, 0.22 mm, 0.245 mm, 0.28 mm, 0.30 mm, 0.32 mm, 0.35 mm, 0.38 mm, and 0.40 mm. Preferably, the wire diameter is in the range of 0.10 mm to 0.50 mm.

[0053] A plurality of steel wires are twisted by conventional steel rope manufacturing processes (ie, cabling or bundling processes) to form a steel rope having a configuration including an outer layer and inner strands surrounded by and adjacent to the outer layer.

[0054] Based on the configuration of the steel rope, the torque of the inner strand, the torque of the outer layer, the residual twist of the inner strand, and the residual twist of the outer layer are set according to the formula of the present invention. The predetermined residual twist of the inner strand and the predetermined residual twist of the outer layer can be achieved by existing methods for residual twist control, such as using a false twister or a straightener after twisting.

[0055] Table 1 summarizes the properties of the invention and the reference.

[0056] Table 1

[0057]

[0058]

[0059] All the steel wires of the steel rope in the above table have TS≥4100-2000×d, where d is the diameter of a single steel wire.

[0060] Figure 1 The measurement of tip lift values ​​is shown. A small piece 100 cut from a rubber ply embedded with steel cord 110 has a defined length, width, and thickness. The thickness of the rubber ply can be set based on how the steel cord is applied in the tire. For example, the thickness of the rubber ply is the diameter of the steel cord plus 1.1 mm, while the width and length of the rubber ply are both 1 meter. Two of the four corners 105 of the small piece 100 are lifted. A value T is measured through the thickness of the small piece. The larger of the two T values ​​for the two lifted corners 105 is the tip lift value of the rubber ply. If the tip lift value is greater than 10 mm, it is considered a tip lift problem.

[0061] GB / T 33159-2016 clearly describes the measurement method of steel wire diameter and residual torsion of steel rope.

[0062] The residual torsion of the inner strand and the residual torsion of the outer layer are measured as follows:

[0063] a) Prepare a steel rope sample of about 1.2 m in length by fusion, ensuring that both ends ("first end" and "second end") of the steel rope sample are not opened, and prepare a frame equipped with two clamps ("first clamp" and "second clamp"), which are laid on the same horizontal surface with a distance of 1 m between them;

[0064] b) clamping the steel cord sample by a first clamp and a second clamp, the first clamp being proximate to a first end of the steel cord sample, and a length from the first end of the steel cord sample to the first clamp being approximately 5 cm to 7 cm ("reversed length of the steel cord");

[0065] c) opening the first clamp to release any residual torsion in the steel cord sample, and then bending the steel cord sample upward from the portion to be clamped by the first clamp so that the reverse length of the steel cord is almost perpendicular to the horizontal plane (the "bent portion"); ensuring that the bending operation does not induce any torsion in the steel cord sample, otherwise any newly induced torsion is released;

[0066] d) cutting the first end and peeling the outer wires along the length of the curved portion until the portion of the rope sample is clamped by the second clamp; when the outer wires have been peeled off sufficiently to allow this operation, the inner strands are clamped by the first clamp; ensuring that the curved portion of the outer layer and the curved portion of the inner strand, as a group, are always perpendicular to the horizontal plane during the peeling operation;

[0067] e) Release the bent portion of the outer layer, observe and record the number of turns of the bent portion of the outer layer, which is the residual torsion RT2 of the outer layer; then release the bent portion of the inner strand, observe and record the number of turns of the bent portion of the inner strand, which is the residual torsion RT1 of the inner strand. The residual torsion is recorded in units of 0.05 turns / meter (corresponding to a rotation angle of 18°), and is "+" if in the clockwise direction and "-" if in the counterclockwise direction, and is observed when facing the rotation of the bent portion in the direction toward the second clamp.

[0068] Figure 2a to Figure 2b shows an example of residual torsion, Figure 2a Examples are shown for residual twists of 0.05, 0.25, 0.5, 0.75, and 1.0 in the counterclockwise direction. Figure 2b Examples are shown where the residual twist in the clockwise direction is 0.15, 0.25, 0.5, 0.75, and 1.0.

[0069] It can be clearly seen from Table 1 that the steel rope of the present invention does not have the problem of tip lift and has a better performance in tip lift than the reference steel rope.

Claims

1. A steel rope having a construction comprising an outer layer and an inner strand surrounded by and adjacent to the outer layer, the inner strand comprising at least one steel wire having a number N1 and an average diameter d1 expressed in mm, the outer layer comprising a number N2 and an average diameter d2 expressed in mm, characterized in that The torque of the inner strand is T1, and the torque of the outer layer is T2. T1 and T2 satisfy the following formula: T1=G×RT1×π 2 ×D1 2 ×d1 2 ×N1 / 16000, <h2 style=";text-align:left;direction:ltr">T2=G×RT2×π<h2 style=";text-align:left;direction:ltr"> 2 <h2 style=";text-align:left;direction:ltr"> ×(D1<h2 style=";text-align:left;direction:ltr"> 2 <h2 style=";text-align:left;direction:ltr"> +D2<h2 style=";text-align:left;direction:ltr"> 2 <h2 style=";text-align:left;direction:ltr"> )×d2<h2 style=";text-align:left;direction:ltr"> 2 <h2 style=";text-align:left;direction:ltr"> ×N2 / 16000, │T1+T2│<60, in, D1 is the theoretical diameter of the inner strand, and D2 is the theoretical diameter of the steel rope. Both D1 and D2 are expressed in mm. RT1 is the residual torsion of the inner strand, and RT2 is the residual torsion of the outer layer. Both RT1 and RT2 are expressed as the number of turns per meter in the clockwise direction "+" or counterclockwise direction "-". G is 80000N / mm 2 , And the absolute value of RT2 is less than 2 turns per meter, and the absolute value of RT1 is not less than 0.05 turns per meter, The diameter of the steel wire of the steel rope ranges from 0.05 mm to 0.60 mm.

2. The steel rope according to claim 1, characterized in that T1 and T2 satisfy │T1+T2│<50.

3. The steel rope according to claim 2, characterized in that T1 and T2 satisfy │T1+T2│<40.

4. The steel rope according to any one of claims 1 to 3, characterized in that The absolute value of RT1 is not less than 0.1 revolutions per meter.

5. The steel rope according to any one of claims 1 to 3, characterized in that The absolute value of RT2 shall not be less than 0.05 revolutions per meter.

6. The steel rope according to any one of claims 1 to 3, characterized in that The absolute value of RT2 shall not be less than 0.1 revolutions per meter.

7. The steel rope according to any one of claims 1 to 3, characterized in that RT1 and RT2 meet the following requirements: │RT1+RT2│<4.

8. The steel rope according to claim 7, characterized in that RT1 and RT2 meet the following requirements: │RT1+RT2│<2.

9. The steel rope according to any one of claims 1 to 3, characterized in that The diameter of the steel wire of the steel rope ranges from 0.10 mm to 0.50 mm.

10. The steel rope according to claim 9, characterized in that The diameter of the steel wire of the steel rope ranges from 0.10 mm to 0.40 mm.

11. The steel rope according to any one of claims 1 to 3, characterized in that The steel rope has a two-layer structure, N1 is 1, 2, 3 or 4, and the calculation formula of D2 is: D2=D1+2×d2; and the calculation formula of D1 is: When N1 is 1, D1 = d1, or When N1 is 2, D1 = 2 × d1, or When N1 is 3, D1 = 2.155 × d1, or When N1 is 4, D1 = 2.414 × d1.

12. The steel rope according to any one of claims 1 to 3, characterized in that The steel rope has a three-layer structure, wherein the inner strand includes an intermediate layer and a core layer surrounded by the intermediate layer, and the core layer includes N c And the average diameter is d c At least one steel wire, the intermediate layer comprises an average diameter d m The calculation formula of D2 is: D2 = D1 + 2 × d2; and the calculation formula of D1 is: When N c When it is 1, D1=d c +2×d m ,or When N c When D1 is 2, D1 = 2 × d c +2×d m ,or When N c When it is 3, D1=2.155×d c +2×d m ,or When N c When it is 4, D1=2.414×d c +2×d m .

13. The steel rope according to any one of claims 1 to 3, characterized in that The inner strands and the outer layer each have a lay length of less than 40 mm.

14. The steel rope according to any one of claims 1 to 3, characterized in that The lay length of the inner stranded wire is greater than 300 mm, and the lay length of the outer layer is less than 40 mm.

15. The steel rope according to any one of claims 1 to 3, characterized in that Each steel wire of the steel rope has a tensile strength TS that satisfies TS≥4000-2000×d MPa, where d is the diameter of a single steel wire.

16. The steel rope according to claim 15, characterized in that TS≥4100-2000×d MPa.

17. The steel rope according to claim 1, characterized in that The steel rope has a configuration of 1+3, 1+4, 1+5, 1+6, 1+7, 2+2, 2+3, 2+4, 2+5, 2+5cc, 2+6, 2+7, 2+7cc, 2+8, 3+2, 3+3, 3+6, 3+8, 3+8cc, 3+9, 3+9cc, 4+3, 4+6, 1+3+8, 1+4+8cc, 1+4+9, 1+5+10, 1+5+10cc, 1+6+11, 1+6+12, 1+6+12cc, 2+5+10, 2+6+12, 3+8+13, 3+9+15 or 4+10+16.

18. The steel rope according to any one of claims 1 to 3, characterized in that The steel cords are used to reinforce tires.

19. A tire comprising at least one belt layer, at least one carcass layer, at least one tread layer and a pair of bead portions, characterized in that: The belt layer and / or the carcass layer comprises at least one steel cord according to any one of claims 1 to 18.

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