Steel ropes for rubber reinforcement

Abstract

The present 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 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, the torque of the inner strand being T1, the torque of the outer layer being T2, the relationship between T1 and T2 being defined. By doing so, the tip lift problem of the rubber cord layer reinforced by the steel cord is reduced.

Description

Technical Field

[0001] The present invention relates to a steel cord for reinforcing rubber. The present invention also relates to a tire reinforced with the steel cord of the present invention. Background Art

[0002] Steel cords are widely used for reinforcing rubber products, such as rubber belts, rubber tires or rubber hoses, because steel cords can provide sufficient strength for rubber products and have good adhesion to rubber.

[0003] A radial tire (a type of tire) includes at least one belt layer, at least one carcass layer, at least one tread layer and a pair of bead portions. Depending on the application of the tire, the radial tire has various structures with different designs on the belt layer, the carcass layer or the tread layer. Steel cords are applied in the belt layer, the carcass layer and / or the chafer to provide the desired strength for the tire. Depending on the different tire parts where the steel cords are applied, the steel cords are designed to have different structures and performance parameters.

[0004] A rubber ply having embedded steel cords is a component for manufacturing the belt layer, the carcass layer and / or the chafer. The rubber ply is processed by cutting it into small pieces having a specific length, width and thickness. The rubberized steel cord ply is cut at an angle inclined to the longitudinal axis of the rubberized steel cord ply, or perpendicular to the longitudinal axis of the rubberized steel cord ply. Subsequently, all the small pieces of the rubber ply having the same shape are spliced by a machine into the required length for one tire.

[0005] After cutting, sometimes one or some of the four corners of the small pieces of the rubberized steel cord ply warp out of the plane. If the corner warps above a specific height, for example, ten millimeters or more, this will prevent the automatic machine from splicing, and then splicing can only be performed manually, which will result in a reduction in work efficiency. This is regarded as the occurrence of the "tip warping problem". This problem occurs relatively more when the steel cord has a layered structure.

[0006] US2017073888 discloses a steel cord which includes a core group and a sheath group to form an m + n structure. By making the ratio of the absolute value of the difference in residual twist 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 within a specific value range, the steel cord does not have residual twist. Therefore, the tips of the rubber ply reinforced with this steel cord warp low or do not warp. Summary of the Invention

[0007] The main object of the present invention is to solve the problems of the prior art.

[0008] Another object of the present invention is to provide a steel cord for reducing the problem of tip warping of a rubber ply.

[0009] Another object of the present invention is to provide a tire with improved working efficiency.

[0010] According to one aspect of the present invention, there is provided a steel cord having a structure including an outer layer and an inner strand surrounded by and adjacent to the outer layer. The inner strand includes at least one steel wire having a number of N1 and an average diameter of d1 expressed in mm. The outer layer includes steel wires having a number of N2 and an average diameter of d2 expressed in mm. The torque of the inner strand is T1, and the torque of the outer layer is T2. T1 and T2 satisfy the following formula:

[0011] T1 = G × RT1 × π 2 × D1 2 × d1 2 × N1 / 16000,

[0012] T2 = G × RT2 × π 2 × (D1 2 + D2 2 ) × d2 2 × N2 / 16000,

[0013] |T1 + T2| < 60,

[0014] wherein, D1 is the theoretical diameter of the inner strand, D2 is the theoretical diameter of the steel cord, 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, both RT1 and RT2 are expressed in turns per meter in the clockwise direction "+", or the counterclockwise direction "-", G is 80000 N / mm 2 , the absolute value of RT1 is not less than 0.05 turns per meter, and the absolute value of RT2 is less than 2 turns per meter.

[0015] By limiting the torque of the inner strand and the torque of the outer layer that satisfy the above formula, the occurrence of the tip warping problem of the rubber ply embedded with the steel cord is reduced. The torque of the inner strand and the torque of the outer layer of the steel cord are both related to the occurrence of the tip warping problem of the rubber ply. The smaller the sum of the torque of the inner strand and the torque of the outer layer, the less the occurrence of the tip warping problem of the rubber ply.

[0016] Different from the prior art that limits the residual torsion of different layers and / or the residual torsion of the cord, the present invention limits 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 to reduce the occurrence of the tip warping problem of the rubber ply.

[0017] Preferably, |T1 + T2| < 50. Most preferably, |T1 + T2| < 40.

[0018] According to the present invention, the absolute value of RT1 is preferably not less than 0.1 revolutions per meter.

[0019] Preferably, the absolute value of RT2 is not less than 0.05 turns per meter. More preferably, the absolute value of RT2 is not less than 0.1 turns per meter. When RT2 is within this value range, the present invention contributes greatly.

[0020] In order to reduce the tip warping problem of the rubber cord layer, preferably, |RT1+RT2|<4. More preferably, |RT1+RT2|<2. Thus, the tip warping problem of the rubber cord layer is greatly reduced.

[0021] The present invention is applicable to steel ropes having a construction of two, three or more layers.

[0022] 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.

[0023] 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:

[0024] When N1 is 1, D1 = d1, or

[0025] When N1 is 2, D1 = 2 × d1, or

[0026] When N1 is 3, D1 = 2.155 × d1, or

[0027] When N1 is 4, D1=2.414×d1.

[0028] When the steel rope has a three-layer construction, this means that the inner strand includes 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 The average diameter is d c The middle layer includes at least one steel wire having an average diameter d m The calculation formula of D2 is: D2 = D1 + 2 × d2; and the calculation formula of D1 is:

[0029] When N c When it is 1, D1=d c +2×d m ,or

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

[0031] When N c is 3, D1 = 2.155 × d c + 2 × d m , or

[0032] When N c is 4, D1 = 2.414 × d c + 2 × d m .

[0033] According to the present invention, the steel wire 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.

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

[0035] 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 greater than 300 mm, and the outer layer has a twist pitch of less than 40 mm.

[0036] According to a second aspect of the present invention, there is provided a tire. 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 wire rope having a structure including an outer layer and an inner strand surrounded by and adjacent to the outer layer. The inner strand includes at least one steel wire having a number N1 and an average diameter d1, the outer layer includes steel wires having a number N2 and an average diameter d2, the torque of the inner strand is T1, and the torque of the outer layer is T2, and T1 and T2 satisfy the following formula:

[0037] T1 = G × RT1 × π 2 × D1 2 × d1 2 × N1 / 16000,

[0038] T2 = G × RT2 × π 2 × (D1 2 + D2 2 ) × d22 ×N2 / 16000,

[0039] │T1+T2│<60,

[0040] 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 the number of turns per meter in the clockwise direction "+" or counterclockwise direction "-", G is 80000N / mm 2 , the absolute value of RT1 is not less than 0.05 turns per meter, and the absolute value of RT2 is less than 2 turns per meter. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 Describes the measurement of tip lift of a rubber ply.

[0042] Figure 2a - Figure 2b The measurement of residual torsion is described. DETAILED DESCRIPTION

[0043] The steel wire used for steel rope is made of wire rod.

[0044] The wire is first cleaned by mechanical descaling and / or by chemical pickling 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.

[0045] At this first intermediate diameter, for example at about 3.0 to 3.5 mm, the dry-drawn wire is subjected to a first intermediate heat treatment known as lead quenching. Lead quenching means first austenitizing, up 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.

[0046] Thereafter, in a second diameter reduction step, the wire is further dry drawn from the first intermediate diameter to a second intermediate diameter, which is typically in the range of 1.0 mm to 2.5 mm.

[0047] 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.

[0048] 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.

[0049] After this second patenting treatment, the steel wire is usually provided with a brass coating: copper is plated on the steel wire and zinc is plated on the copper. A heat 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.

[0050] Then, the brass-coated or ternary alloy-coated steel wire is subjected to a final series of cross-sectional reductions by a wet drawing machine. The final product is a steel wire having 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) usually higher than 3000 MPa and suitable for reinforcing rubber products.

[0051] Steel wires suitable for tire reinforcement usually have a final diameter in the range 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, 0.40 mm. The diameter of the steel wire is preferably in the range from 0.10 mm to 0.50 mm.

[0052] A number of steel wires are twisted by an existing steel cord manufacturing process (i.e., cabling or bunching process) to form a steel cord having a structure including an outer layer and inner strands surrounded by and adjacent to the outer layer.

[0053] Based on the structure of the steel cord, the torque of the inner strands, the torque of the outer layer, the residual torsion of the inner strands, 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 strands 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 a straightener after twisting.

[0054] Table 1 summarizes the properties of the present invention and the reference.

[0055] Table 1

[0056]

[0057] All the steel wires of the steel cord in the above table have TS≥4100-2000×d, where d is the diameter of a single steel wire.

[0058] Figure 1The measurement of the tip lift value is shown. A small piece 100 cut from a rubber cord layer with embedded steel cord 110 has a determined length, width and thickness. The thickness of the rubber cord layer can be set according to the application method of the steel cord in the tire, for example, the thickness of the rubber cord layer is the diameter of the steel cord plus 1.1 mm, and the width and length of the rubber cord layer are both 1 meter. Two of the four corners 105 of the small piece 100 are lifted. The value T is measured in the thickness direction of the small piece. The larger of the two T values ​​of 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, it is considered that the tip lift problem occurs.

[0059] GB / T 33159-2016 clearly describes the measurement method of the wire diameter and residual torsion of steel ropes.

[0060] The residual torsion of the inner strand and the residual torsion of the outer layer are measured as follows:

[0061] a) preparing a steel rope sample of about 1.2 m in length by fusion to ensure that both ends ("first end" and "second end") of the steel rope sample are not opened, and preparing a frame equipped with two clamps ("first clamp" and "second clamp"), which are laid on the same horizontal plane at a distance of 1 m;

[0062] b) clamping the steel rope sample by a first clamp and a second clamp, the first clamp being close to a first end of the steel rope sample, and the length from the first end of the steel rope sample to the first clamp being about 5 cm to 7 cm ("reversed length of the steel rope");

[0063] c) opening the first clamp to release the residual torsion of the steel rope sample, and then bending the steel rope sample upward from the portion to be clamped by the first clamp so that the reverse length of the steel rope is almost perpendicular to the horizontal plane (the "bent portion"); ensuring that the bending operation does not produce any torsion on the steel rope sample, otherwise the newly produced torsion is released;

[0064] d) cutting the first end and stripping the outer wires along the length of the curved portion until the portion of the steel rope sample that is clamped by the second clamp; when the stripping of the outer wires is sufficient to allow this operation, clamping the inner strands by the first clamp; ensuring that during the stripping operation, the curved portion of the outer layer and the curved portion of the inner strand as a single group are always perpendicular to the horizontal plane;

[0065] 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. The observation is made when facing the rotation of the bent portion in the direction toward the second clamp.

[0066] Figures 2a to 2b shows an example of residual torsion, Figure 2a Examples of residual twists of 0.05, 0.25, 0.5, 0.75, and 1.0 in the counterclockwise direction are shown, Figure 2b Examples of residual twists of 0.15, 0.25, 0.5, 0.75, and 1.0 in the clockwise direction are shown.

[0067] It can be clearly seen from Table 1 that the steel rope of the present invention does not have the tip lift problem and has a better performance in tip lift than the reference steel rope.

Claims

1. A steel rope, the structure of which includes an outer layer and an inner strand surrounded by and adjacent to the outer layer, the inner strand including at least one steel wire with a number of N1 and an average diameter of d1 expressed in mm, and the outer layer including steel wires with a number of N2 and an average diameter of d2 expressed in mm, characterized in that, The torque of the inner strands 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, where D1 is the theoretical diameter of the inner strands, 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 strands, and RT2 is the residual torsion of the outer layer. Both RT1 and RT2 are expressed in number of turns per meter in the clockwise direction "+", or the counterclockwise direction "-", G is 80000 N / 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.

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

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

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

6. The steel wire rope according to any one of claims 1 to 3, characterized in that, The absolute value of RT2 is not less than 0.1 turns 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 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 for D2 is: D2 = D1 + 2×d2; and the calculation formula for 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.

9. The steel rope according to any one of claims 1 to 3, characterized in that, The steel wire rope has a three-layer structure. Among them, the inner stranded wire includes an intermediate layer and a core layer surrounded by the intermediate layer. The core layer includes at least one steel wire with a quantity of N c and an average diameter of d c The intermediate layer includes steel wires with an average diameter of d m The calculation formula for D2 is: D2 = D1 + 2×d2; and the calculation formula for D1 is: When N c is 1, D1 = d c + 2×d m or When N c is 2, D1 = 2 × d c + 2 × d m or When N c is 3, D1 = 2.155 × d c + 2 × d m or When N c is 4, D1 = 2.414 × d c + 2 × d m .

10. The wire 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.

11. The steel wire 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.

12. The wire rope according to claim 11, characterized in that, TS ≥ 4100-2000×d MPa.

13. 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.

14. A tire, the 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 includes at least one steel rope according to any one of claims 1 to 13.

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