Steel cord for rubber reinforcement

Abstract

The invention relates to a steel cord for rubber reinforcement. The steel cord has 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 filament in a number N1 and having an average diameter d1 expressed in mm, the outer layer comprising steel filaments in a number N2 and having an average diameter d2 expressed in mm, the inner strand having a torque T1 and the outer layer having a torque T2, the relationship between T1 and T2 being limited. By doing so, the problem of sharp end lifting of the rubber plies reinforced by the steel cord is reduced.

Description

[0001] This application is a divisional application of the international application filed on November 30, 2021, with international application number PCT / EP2021 / 083627, national application number 202180082948.4, entitled "Steel rope for rubber reinforcement", which has entered the Chinese national phase. Technical Field

[0002] This invention relates to a steel rope for rubber reinforcement. It also relates to tires reinforced with the steel rope of this invention. Background Technology

[0003] Steel ropes are widely used to reinforce rubber products, such as rubber belts, rubber tires, or rubber hoses, because they provide sufficient strength and have good adhesion to rubber.

[0004] A radial tire (a type of tire) comprises at least one belt ply, at least one carcass ply, at least one tread ply, and a pair of bead portions. Depending on the application, radial tires have various structures with different designs on the belt ply, carcass ply, or tread ply. Steel cords are applied to the belt ply, carcass ply, and / or bead wrapping to provide the tire with the desired strength. Depending on the different tire portions to which the steel cords are applied, the steel cords are designed with different construction and performance parameters.

[0005] A rubber ply with embedded steel cords is a component used in the manufacture of belt layers, carcass layers, and / or bead wraps. The rubber ply is processed by cutting it into small pieces with specific lengths, widths, and thicknesses. The rubber ply is cut at an angle inclined to the longitudinal axis of the coated steel cord, or perpendicular to the longitudinal axis of the coated steel cord. Subsequently, a machine splices all the small pieces of the rubber ply with the same shape together to the required length for a tire.

[0006] After cutting, sometimes one or more corners of the small pieces of adhesive-coated steel cord fabric may protrude beyond the plane. If the corner protrudes above a certain height, such as ten millimeters or more, this prevents automated machines from splicing the cord, requiring manual splicing and reducing work efficiency. This is known as the "tip protrusion problem." This problem occurs relatively more frequently when the steel cord has a layered structure.

[0007] US2017073888 discloses a steel rope comprising a core assembly and a sheath assembly to form an m+n configuration. By keeping the ratio of the absolute value of the difference in residual torsion between the core assembly and the sheath assembly to the absolute value of the difference in the saturation level between the core assembly and the sheath assembly within a specific range, the steel rope has no residual torsion; therefore, the tips of the rubber cord layer reinforced with this steel rope are low-curved or not curled at all. Summary of the Invention

[0008] The main objective of this invention is to solve the problems of the prior art.

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

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

[0011] According to one aspect of the invention, a steel rope is provided, the steel rope having a structure comprising an outer layer and an inner strand surrounding and adjacent to the outer layer, the inner strand comprising at least one steel wire of number N1 and average diameter d1 expressed in mm, the outer layer comprising steel wire of number N2 and 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 expressed in mm; RT1 is the residual torsion of the inner strand, RT2 is the residual torsion of the outer layer, both expressed as the number of turns per meter in either a clockwise "+" or counterclockwise "-" direction; and G is 80000 N / mm. 2 The absolute value of RT1 is not less than 0.05 revolutions per meter, and the absolute value of RT2 is less than 2 revolutions per meter.

[0016] By limiting the torque of the inner strand and the torque of the outer layer to satisfy the above formula, the occurrence of tip warping in the rubber cord layer with embedded steel rope is reduced. Both the torque of the inner strand and the torque of the outer layer of the steel rope are related to the occurrence of tip warping in the rubber cord layer. The smaller the sum of the torque of the inner strand and the torque of the outer layer, the less tip warping occurs in the rubber cord layer.

[0017] Unlike existing technologies that define the residual torsion of different layers and / or the residual torsion of the rope, the present invention defines the torque of the inner strand 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 strand, so as to reduce the occurrence of tip warping problem of 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 range, the present invention makes a significant contribution.

[0021] To reduce the problem of the rubber cord layer's tip curling, preferably, |RT1+RT2| < 4. More preferably, |RT1+RT2| < 2. This greatly reduces the occurrence of the rubber cord layer's tip curling problem.

[0022] This invention is used for steel ropes having a structure with two, three or more layers.

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

[0024] When the steel rope has a two-layer construction, N1 is 1, 2, 3, or 4. The formula for calculating D2 is: D2 = D1 + 2 × d2; and the formula for calculating 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 a 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 being surrounded by and adjacent to the outer layer, and the core layer comprising N layers. c And the average diameter is d c At least one steel wire, the intermediate layer including an average diameter of d m For the steel wire, the formula for calculating D2 is: D2 = D1 + 2 × d2; and the formula for calculating D1 is:

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

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

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

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

[0034] According to the present invention, the steel rope has a structure 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] This invention is beneficial for steel ropes with steel wires having very high tensile strength. Preferably, each steel wire of the steel rope has a tensile strength TS that satisfies TS≥4000-2000×d, where d is the diameter of a single steel wire; more preferably, it satisfies TS≥4100-2000×d.

[0036] The inner strand and the outer layer each have a twist pitch of less than 40 mm. Alternatively, the inner strand has a twist pitch of more than 300 mm, while the outer layer has a twist pitch of less than 40 mm.

[0037] According to a second aspect of the invention, a tire is provided. The tire includes 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 includes at least one steel cord, the steel cord having a configuration including an outer layer and an inner strand surrounded by and adjacent to the outer layer, the inner strand comprising at least one wire of number N1 and average diameter d1, the outer layer comprising wire of number N2 and average diameter d2, the torque of the inner strand being T1, and the torque of the outer layer being T2, 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 expressed in mm; RT1 is the residual torsion of the inner strand, RT2 is the residual torsion of the outer layer, both expressed as the number of turns per meter in either a clockwise "+" or counterclockwise "-" direction; and G is 80000 N / mm. 2 The absolute value of RT1 is not less than 0.05 revolutions per meter, and the absolute value of RT2 is less than 2 revolutions per meter. Attached Figure Description

[0042] Figure 1 The measurement of the tip curling of the rubber cord layer is described.

[0043] Figure 2a - Figure 2b Measurements of residual torsion are described. Detailed Implementation

[0044] The steel wire used in steel ropes is made of wire.

[0045] First, the wire is cleaned by mechanical descaling and / or by chemical acid washing in H2SO4 or HCl solution to remove oxides present on the surface. 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 a first intermediate diameter is reached.

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

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

[0048] At this second intermediate diameter, the steel wire undergoes a second lead hardening treatment, namely, austenitization at a temperature of about 1000°C, followed by quenching 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 can be performed from the wire to the second intermediate diameter.

[0050] Following this second lead quenching treatment, the steel wire is typically coated with a brass layer: copper is plated onto the wire, and zinc is plated onto the copper. A heat diffusion treatment is applied to form the brass coating. Alternatively, the steel wire may be coated with a ternary alloy, comprising a third alloy of copper, zinc, and cobalt, titanium, nickel, iron, or other known metals.

[0051] Then, the brass-coated or ternary alloy-coated steel wires undergo a final series of cross-sectional reductions using a wet drawing machine. The final product is a steel wire with a carbon content higher than 0.70 wt%, or not less than 0.80 wt%, or even higher than 0.90 wt%, with a tensile strength (TS) typically higher than 3000 MPa, suitable for reinforcing rubber products.

[0052] Steel wires used for tire reinforcement typically have 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. The wire diameter is preferably in the range of 0.10 mm to 0.50 mm.

[0053] A steel rope is formed by twisting many steel wires using existing steel rope manufacturing processes (i.e., cabling or bundling processes) to have a structure that includes an outer layer and inner strands that surround and are adjacent to the outer layer.

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

[0055] Table 1 summarizes the performance of the present invention and the reference object.

[0056] Table 1

[0057]

[0058]

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

[0060] Figure 1 The measurement of the tip lift value is shown. A small piece 100, cut from a rubber cord layer embedded with steel rope 110, has a defined length, width, and thickness. The thickness of the rubber cord layer can be set according to the way the steel rope is applied in the tire; for example, the thickness of the rubber cord layer is the diameter of the steel rope plus 1.1 mm, while the width and length of the rubber cord layer are both 1 meter. Two of the four corners 105 of the small piece 100 lift. A value T is measured in the thickness direction 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 cord layer. If the tip lift value is greater than 10 mm, a tip lift problem is considered to have occurred.

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

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

[0063] a) Prepare a steel rope sample with a length of about 1.2 m by fusion to ensure that the two ends of the steel rope sample (“first end” and “second end”) do not open, and prepare a frame with two clamps (“first clamp” and “second clamp”) installed at a distance of 1 m on the same horizontal plane.

[0064] b) The steel rope sample is held by a first clamp and a second clamp, with the first clamp close to the first end of the steel rope sample. The length from the first end of the steel rope sample to the first clamp is about 5 cm to 7 cm (“reversed length of the steel rope”).

[0065] c) Open the first clamp to release any residual torsion in the steel rope sample, then bend the steel rope sample upward from the portion to be clamped at the first clamp so that the reverse length of the steel rope is almost perpendicular to the horizontal plane (“bent portion”); ensure that the bending operation does not introduce any torsion into the steel rope sample, or release any newly generated torsion.

[0066] d) Cut the first end and peel the outer steel wire along the length of the bend until the portion of the steel rope sample is held by the second clamp; when the peeling of the outer steel wire is sufficient to allow this operation, hold the inner stranded wire by the first clamp; ensure that during the peeling operation, the bend of the outer layer and the bend of the inner stranded wire, which are separate as a group, are always perpendicular to the horizontal plane.

[0067] e) Release the outer layer's bent portion, observe and record the number of turns of the outer layer's bent portion; this is the residual torsion RT2 of the outer layer. Then release the inner strand's bent portion, observe and record the number of turns of the inner strand's bent portion; this 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 marked "+" if it is in the clockwise direction and "-" if it is in the counterclockwise direction. Observe the rotation of the bent portion in the direction towards the second clamp.

[0068] Figures 2a to 2b An example of residual torsion is shown. Figure 2a Examples of residual torsion in the counterclockwise direction are shown, with values ​​of 0.05, 0.25, 0.5, 0.75, and 1.0. Figure 2b Examples of residual torsion in the clockwise direction are shown as 0.15, 0.25, 0.5, 0.75, and 1.0.

[0069] As can be clearly seen from Table 1, the steel rope of the present invention does not have the problem of tip curling and has better performance in terms of tip curling compared with the reference steel rope.

Claims

1. A steel rope comprising an outer layer and inner strands surrounding and adjacent to the outer layer, the inner strands comprising at least one wire of number N1 and average diameter d1 (in mm), the outer layer comprising wires of number N2 and average diameter d2 (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, T2=G×RT2×π 2 ×(D1 2 +D2 2 )×d2 2 ×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 represents the residual torsion of the inner strand, while RT2 represents the residual torsion of the outer layer. Both RT1 and RT2 are indicated by the number of turns per meter in either a clockwise "+" or a counterclockwise "-". G is 80000 N / mm 2 , Furthermore, the absolute value of RT2 is less than 2 revolutions per meter, and the absolute value of RT1 is not less than 0.05 revolutions per meter. The diameter of the steel wires in 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 is not 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 is not 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 satisfy: │RT1+RT2│<4.

8. The steel rope according to claim 7, characterized in that, RT1 and RT2 satisfy: │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 in 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 in 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, where N1 is 1, 2, 3, or 4, and D2 is calculated using the formula: D2 = D1 + 2 × d2; and D1 is calculated using the formula: 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 comprises N layers. c And the average diameter is d c At least one steel wire, the intermediate layer comprising an average diameter of d m For the steel wire, the formula for calculating D2 is: D2 = D1 + 2 × d2; and the formula for calculating D1 is: When N c When the value is 1, D1 = d c +2×d m ,or When N c When the value is 2, D1 = 2 × d c +2×d m ,or When N c When the value is 3, D1 = 2.155 × d c +2×d m ,or When N c When the value 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 strand and the outer layer each have a twist pitch of less than 40 mm.

14. The steel rope according to any one of claims 1 to 3, characterized in that, The inner strand has a twist pitch greater than 300 mm, and the outer strand has a twist pitch less than 40 mm.

15. The steel rope according to any one of claims 1 to 3, characterized in that, Each 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 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 structure 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 rope is used to reinforce the tire.

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 comprise at least one steel rope according to any one of claims 1 to 18.

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