Steel wire cord with 1 + N strand structure and preparation method thereof

Abstract

The invention discloses a steel wire cord with a 1 + N strand structure and a preparation method of the steel wire cord, and belongs to the technical field of steel wire cords, the steel wire cord comprises a core strand, and the core strand comprises a core strand inner layer steel wire located on the inner layer and a core strand outer layer steel wire located on the outer layer; the N sheath plied yarns are uniformly arranged around the core plied yarn, the sheath plied yarns and the core plied yarn are stranded to form a rope, and each sheath plied yarn comprises a sheath plied yarn center wire located on the inner layer and a sheath plied yarn outer-layer steel wire located on the outer layer; the outer wrapping wire is wound on the outer surface of the rope; according to the invention, the extraction force of the core strand of the steel wire cord is improved structurally, the problem of piercing caused by migration of the core strand can be effectively prevented, and the service life of a tire is greatly prolonged.

Description

Technical Field

[0001] The invention relates to a 1+N-strand structure steel cord and a preparation method thereof, belonging to the technical field of steel cords. Background Art

[0002] Steel cord is widely used in the rubber products industry. The 7×7×d+0.15HT steel cord commonly used in tires is twisted together by seven 7×d strands and a 0.15mm outer winding wire. The core strand structure is the same as the outer strand structure. This structure is prone to the following defects during use: 1) Due to the small binding force of the core strand, migration problems occur, and the tire is prone to puncture, which greatly reduces the service life of the tire; 2) Due to various factors, the cord strength deviates, and the breaking force of the 7×7×d+0.15HT structure cannot be truly reflected, which greatly reduces the load-bearing capacity of the tire.

[0003] In order to meet the current industry demand for the use of steel cord for tires, how to provide a cord that reduces core strand migration and has a higher breaking force is a problem we are studying. Summary of the invention

[0004] The purpose of the present invention is to overcome the deficiencies in the prior art and to provide a 1+N-strand steel cord structure and a preparation method thereof, which, on the one hand, solves the problem of migration caused by the small binding force of the core strands of the steel cord structure of the prior art 7×7×d+0.15HT; on the other hand, enhances the breaking force of the cord, thereby improving the load-bearing capacity of the tire.

[0005] To achieve the above object, the present invention is implemented by adopting the following technical solutions: In a first aspect, the present invention provides a 1+N-strand structural steel cord, comprising: A core strand, wherein the core strand comprises an inner-layer steel wire of the core strand and an outer-layer steel wire of the core strand; N sheath strands, the N sheath strands are evenly arranged around the core strand, the sheath strands and the core strands are twisted into a rope, and the sheath strands include a sheath strand center wire located in an inner layer and a sheath strand outer steel wire located in an outer layer; The outer winding wire is wound around the outer surface of the rope.

[0006] Furthermore, the twist direction of the core strand is SS or ZZ, the inner layer of the core strand is formed by three monofilaments with a diameter of d1 twisted together with a twist length of L1, and the outer layer of the core strand is formed by nine monofilaments with a diameter of d2 uniformly arranged around the inner layer with a twist length of L2.

[0007] Furthermore, the core strand meets the following conditions: 0.20 mm ≤ d2 ≤ d1 ≤ 0.50 mm, 5.0 mm ≤ L1 ≤ 12.5 mm, 6.0 mm ≤ L2 ≤ 22.0 mm.

[0008] Furthermore, the number of sheath strands N ≥ 7, the twist direction of the sheath strands is S or Z, the inner layer of the sheath strands is a sheath strand center wire with a distance of d3, the outer layer of the sheath strands is composed of six single wires with a diameter of d4 uniformly arranged around the center wire with a twist pitch of L3, and the sheath strands are uniformly arranged around the core strands with a twist pitch of L4.

[0009] Furthermore, the sheath strands satisfy the following conditions: 0.20 mm ≤ d4 ≤ d3 ≤ 0.50 mm, 6.0 mm ≤ L3 ≤ 22.0 mm, 12.5 mm ≤ L4 ≤ 65 mm.

[0010] Furthermore, the outer winding wire is a monofilament with a diameter of d5, and the outer winding wire is evenly wound around the rope with a twist length L5; the outer winding wire meets the following conditions: 0.15mm≤d5≤0.25mm.

[0011] Furthermore, the strength grade of the core strands, sheath strands and outer winding wires of the steel cord is any one of normal strength NT, high strength HT, ultra-high strength ST, extra-high strength UT and extremely high strength MT.

[0012] In a second aspect, the present invention provides a method for preparing a 1+N-strand structural steel cord according to any one of the above items, comprising: The steel wire is wet drawn into single wires d1, d2, d3, d4 and d5 of corresponding specifications; The double twisting machine is used to produce strands of different specifications, and the monofilaments are twisted into core strands 3×d1+9×d2 and sheath strands d3+6×d4; The core strands and sheath strands are twisted into ropes using a single twist tubular machine; The rope is passed through a single-twist outer winding machine and evenly wound with an outer winding wire with a diameter of d5 to form the final 1+N strands of structural steel cord.

[0013] Furthermore, the steel wire is galvanized steel wire or brass-plated steel wire.

[0014] Furthermore, in the process of producing strands of different specifications using a double twisting machine, the residual stress torsion value of the 6m core strand is controlled to be 0 to 6 turns, and the residual stress torsion value of the 6m sheath strand is controlled to be 10 to 20 turns.

[0015] Compared with the prior art, the present invention has the following beneficial effects: The present invention provides a 1+N-strand steel cord structure and a preparation method thereof, which improves the extraction force of the core strands of the steel cord from the perspective of structure, can effectively prevent the core strands from migrating and causing puncture problems, and greatly improves the service life of the tire; compared with the existing 7×7+1 structure, the cord of this structure has a higher breaking force under the condition of the same diameter, and greatly improves the load-bearing capacity of the tire. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is a cross-sectional schematic diagram of a steel cord commonly used in the prior art; Figure 2 It is a cross-sectional schematic diagram of a 1+N-strand structural steel cord of the present invention; Figure 3 It is a schematic diagram of a method for preparing a 1+N-strand structural steel cord according to the present invention.

[0017] In the figure: 1, core strand; 2, sheath strand; 3, inner steel wire of core strand; 4, outer steel wire of core strand; 5, central wire of sheath strand; 6, outer steel wire of sheath strand; 7, outer winding wire. DETAILED DESCRIPTION

[0018] The present invention will be further described below in conjunction with the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present invention, and cannot be used to limit the protection scope of the present invention.

[0019] Embodiment 1, as Figure 1 , Figure 2 As shown, this embodiment introduces a 1+N strand structural steel cord, which is mainly divided into a core strand 1, N sheath strands 2 and an outer winding wire 7 (N≥7); the core strand 1 includes a core strand inner layer steel wire 3 located in an inner layer and a core strand outer layer steel wire 4 located in an outer layer; the N sheath strands 2 are evenly arranged around the core strand 1, the sheath strands 2 and the core strand 1 are twisted into a rope, the sheath strand 2 includes a sheath strand center wire 5 located in an inner layer and a sheath strand outer layer steel wire 6 located in an outer layer; the outer winding wire 7 is wound around the outer surface of the rope.

[0020] The core strand 1 is a 3+9 structure, with a twist direction of SS or ZZ, an inner layer of three monofilaments with a diameter of d1 twisted with a twist pitch of L1, and an outer layer of nine monofilaments with a diameter of d2 evenly arranged around the inner layer with a twist pitch of L2 (0.20mm≤d2≤d1≤0.50mm, 5.0mm≤L1≤12.5mm, 6.0≤L2≤22.0mm); The sheath strand 2 is a 1+6 structure, the twist direction is S or Z, the center wire diameter is d3, and the outer layer is composed of six monofilaments with a diameter of d4 and uniformly arranged around the center wire with a twist distance L3 (0.20≤d4≤d3≤0.50, 6.0≤L3≤22.0); The N sheath strands 2 are at least 7 strands, with a twist direction of S or Z, and are evenly arranged around the core strand 1 at a twist pitch L4 (N ≥ 7, 12.5 mm ≤ L4 ≤ 65 mm); The outer winding wire 7 has a diameter of d5 and is evenly wound around the cord at a twist pitch of L5 to form a final 1+7-strand structural steel cord (0.15 mm ≤ d5 ≤ 0.25 mm).

[0021] The strength grade of the core strands 1, sheath strands 2 and outer winding wires 7 of the steel cord is any one of normal strength NT, high strength HT, ultra-high strength ST, extra-high strength UT and extremely high strength MT.

[0022] Embodiment 2, as Figure 3 As shown, this embodiment provides a method for preparing the 1+N-strand structural steel cord as described in any one of Embodiment 1, comprising the following steps: The steel wire is wet drawn into single wires of corresponding specifications d1, d2, d3, d4 and d5, and the steel wire is galvanized steel wire or brass-plated steel wire; According to the requirements, a double-twisting machine is used to produce strands of different specifications, and the monofilaments are twisted into core strands 3×d1+9×d2 and sheath strands d3+6×d4, wherein the core strands 3×d1+9×d2 represent 3 inner steel wires of the core strands with a diameter of d1 and 9 outer steel wires of the core strands with a diameter of d2; the sheath strands d3+6×d4 represent 3 central wires of the sheath strands with a diameter of d3 and 6 outer steel wires of the sheath strands with a diameter of d4; during the production process, the residual stress torsion value of the core strands of 6m is controlled to be 0 to 6 turns; at the same time, prestress needs to be applied to the sheath strands to control the residual stress torsion value of the 6m sheath strands to be 10 to 20 turns; The core strands and sheath strands are twisted by single-twist tubular machines to form a rope. The rope is evenly wound with the outer winding wire d5 by a single-twist outer winding machine to form the final 1+N strands of structural steel cord (N≥7).

[0023] The present embodiment provides a 1+N-strand structural steel cord and a preparation method thereof, which structurally improves the extraction force of the core strands of the steel cord, can effectively prevent the core strands from migrating and causing puncture problems, and greatly improves the service life of the tire; compared with the existing 7×7+1 structure, the structural cord has a higher breaking force at the same diameter, greatly improving the load-bearing capacity of the tire.

[0024] The contents involved in the above embodiment are described below in conjunction with a preferred embodiment.

[0025] Taking (3+9×0.205)+7×7×0.205+0.15ST as an example, d1=d2=d3=d4=0.205mm, d5=0.15mm, L1=6.3mm, L2=12.5mm, L3=12.5mm, L4=22.0mm, L5=5.0mm, the core strand twist direction is SS, the sheath strand twist direction is S, the combined rope twist direction is S, and the outer winding twist direction is Z.

[0026] Preparation method: The diameter of the semi-finished brass wire produced by 0.205 is 1.40mm, the carbon content is 0.82%, and the single wire strength is ST; the diameter of the semi-finished brass wire produced by 0.15 is 0.94mm, the carbon content is 0.72%, and the single wire strength is HT; Double twisting machine is used to produce 39205ST core strand (twisting direction SS) and 07205ST sheath strand (twisting direction S); 3. Use single twist machine to produce (3+9×0.205)+7×7×0.205+0.15ST, such as Figure 3 shown.

[0027] Table 1 is a comparison table of performance indicators of 7×7×0.22+0.15HT structural steel cord commonly used in radial tires in the prior art and Example 1 of the present invention.

[0028] Table 1

[0029] From the above comparison, it can be seen that the preparation method of a 1+N-strand structural steel cord of the present invention is used to make a 1+7-strand structural steel cord. Compared with the steel cord for a radial tire made by the prior art: without increasing the cord diameter, the cord breaking force is increased by 16.95%, and the core strand extraction force is increased by 38.2%. After being applied to tires, the service life and load-bearing capacity of the tires are greatly improved.

[0030] The contents involved in the above embodiments are described below in conjunction with the second preferred embodiment.

[0031] Taking (3+9×0.255)+8×7×0.215+0.15ST as an example, d1=d2=0.255mm, d3=d4=0.215mm, d5=0.15mm, L1=6.76mm, L2=13.5mm, L3=13.5mm, L4=33.33mm, L5=5.0mm, the core strand twist direction is SS, the sheath strand twist direction is Z, the combined rope twist direction is Z, and the outer winding twist direction is S.

[0032] Preparation method: 1. The diameter of the semi-finished brass wire produced by 0.215 is 1.40mm, the carbon content is 0.86%, and the single wire strength is ST; the diameter of the semi-finished brass wire produced by 0.255 is 1.65mm, the carbon content is 0.82%, and the single wire strength is ST; the diameter of the semi-finished brass wire produced by 0.15 is 0.94mm, the carbon content is 0.72%, and the single wire strength is HT; 2. Use double twisting machine to produce 39255ST core strand (twist direction SS) and 07215ST sheath strand (twist direction Z); 3. Use single twist machine to produce (3+9×0.255)+8×7×0.215+0.15ST, such as Figure 3 shown.

[0033] Table 2 is a comparison table of performance indicators of 7×7×0.25+0.15HT structural steel cord commonly used in radial tires in the prior art and Example 2 of the present invention.

[0034] Table 2

[0035] From the above comparison, it can be seen that the preparation method of a 1+N-strand structural steel cord of the present invention is used to make a 1+8-strand structural steel cord. Compared with the steel cord for a radial tire made by the prior art: without increasing the cord diameter, the cord breaking force is increased by 13.39%, and the core strand extraction force is increased by 23.72%. After being applied to tires, the service life and load-bearing capacity of the tires are greatly improved.

[0036] Compared with the existing 7×7×d+0.15HT steel cord structure: 1) The present invention discloses a method for preparing a 1+N strand steel cord structure; 2) By redesigning the cord structure, the breaking force and core strand extraction force of the cord are greatly improved without changing the diameter, which can effectively improve the core strand migration problem; 3) After the 1+N strand steel cord structure is applied to tires, the service life and load-bearing capacity of the tires can be greatly improved.

[0037] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the technical principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A 1+N strand steel cord, characterized in that: include: A core strand, wherein the core strand comprises an inner-layer steel wire of the core strand and an outer-layer steel wire of the core strand; N sheath strands, the N sheath strands are evenly arranged around the core strand, the sheath strands and the core strands are twisted into a rope, and the sheath strands include a sheath strand center wire located in an inner layer and a sheath strand outer steel wire located in an outer layer; The outer winding wire is wound around the outer surface of the rope.

2. The 1+N strand structural steel cord according to claim 1, characterized in that: The core strands have a twist direction of SS or ZZ, an inner layer of the core strands is formed by three monofilaments with a diameter of d1 twisted together at a twist length of L1, and an outer layer of the core strands is formed by nine monofilaments with a diameter of d2 evenly arranged around the inner layer at a twist length of L2.

3. The 1+N strand structural steel cord according to claim 2, characterized in that: The core strand meets the following conditions: 0.20 mm ≤ d2 ≤ d1 ≤ 0.50 mm, 5.0 mm ≤ L1 ≤ 12.5 mm, 6.0 mm ≤ L2 ≤ 22.0 mm.

4. The 1+N strand structural steel cord according to claim 1, characterized in that: The number of sheath strands N≥7, the twist direction of the sheath strands is S or Z, the inner layer of the sheath strands is a sheath strand center wire with a distance of d3, the outer layer of the sheath strands is composed of six single wires with a diameter of d4 uniformly arranged around the center wire with a twist pitch of L3, and the sheath strands are uniformly arranged around the core strands with a twist pitch of L4.

5. The 1+N-strand structural steel cord according to claim 4, characterized in that: The sheath strands meet the following conditions: 0.20 mm ≤ d4 ≤ d3 ≤ 0.50 mm, 6.0 mm ≤ L3 ≤ 22.0 mm, and 12.5 mm ≤ L4 ≤ 65 mm.

6. The 1+N strand structural steel cord according to claim 1, characterized in that: The outer winding wire is a monofilament with a diameter of d5, and the outer winding wire is evenly wound around the rope with a twist length L5; the outer winding wire meets the following conditions: 0.15mm≤d5≤0.25mm.

7. The 1+N-strand structural steel cord according to claim 1, characterized in that: The strength grade of the core strands, sheath strands and outer winding wires of the steel cord is any one of ordinary strength NT, high strength HT, ultra-high strength ST, extra-high strength UT and extremely high strength MT.

8. The method for preparing the 1+N strand structural steel cord according to any one of claims 1 to 7, characterized in that: include: The steel wire is wet drawn into single wires d1, d2, d3, d4 and d5 of corresponding specifications; The double twisting machine is used to produce strands of different specifications, and the monofilaments are twisted into core strands 3×d1+9×d2 and sheath strands d3+6×d4; The core strands and sheath strands are twisted into ropes using a single twist tubular machine; The rope is passed through a single-twist outer winding machine and evenly wound with an outer winding wire with a diameter of d5 to form the final 1+N strands of structural steel cord.

9. The preparation method according to claim 8, characterized in that: The steel wire is a galvanized steel wire or a brass-plated steel wire.

10. The preparation method according to claim 8, characterized in that: In the process of producing strands of different specifications using a double-twisting machine, the residual stress torsion value of the 6m core strand is controlled to be 0 to 6 turns, and the residual stress torsion value of the 6m sheath strand is controlled to be 10 to 20 turns.

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