A steel cord and a method of manufacturing the same

Abstract

The application discloses a cord and a manufacturing method thereof in the technical field of steel cord product manufacturing, wherein the cord comprises an outer layer, a middle layer and a core layer, the core layer is one filament, the middle layer uniformly distributes eight filaments, the outer layer uniformly distributes eight filaments, the filaments in each layer are in linear contact, uniform and consistent space gaps exist between the adjacent filaments in the outer layer, the rubber fluid is more conducive to permeation, and the filament layer contains high corrosion resistance elements, so that the solidification of the cord and rubber is enhanced and maintained, and the manufacturing method of the cord adopts a double-separating disc type single molding equipment, compared with a plurality of step molding of a strand layer cord body cord, the molding time is shortened, and the production cost is reduced.

Description

Technical Field

[0001] This invention relates to the field of steel cord product manufacturing technology, specifically to a steel wire cord and its manufacturing method. Background Technology

[0002] The tire carcass is the main structural support component of the tire, bearing not only the load pressure and internal air pressure, but also flexural and shear forces from the sidewalls. Heavy-duty tires, in particular, require even higher load-bearing capacity. This necessitates that the reinforcing cords used in the carcass possess both tensile and compressive load-bearing capacity; that is, the cords themselves must have sufficient strength and stiffness. The material properties of the bonded cords and carcass rubber affect the tire's load-bearing performance; therefore, the cords and carcass rubber must have good curing ability and stability.

[0003] Existing tire carcass cords are mostly multi-layered structures, with each layer's individual cords in close contact. The gap between adjacent cords in the outermost layer after twisting is generally no more than 0.02mm, almost nonexistent. Therefore, even after the cords are vulcanized with the carcass rubber under pressure, the rubber still has difficulty penetrating between the cord layers. Consequently, during tire use, under cyclical stress, tire deformation causes micro-movements between the individual cords. Over time, this accumulation leads to the gradual weakening of the bond between the cords and the rubber. Simultaneously, when localized cracks appear in the tire rubber material, especially on the sidewall, as the cracks extend, corrosive media such as moisture and salt continuously penetrate the tire's interior. Since rubber has difficulty flowing between the cord layers, these corrosive media pose a risk of directly impacting the cord interior, causing the cords themselves to rust and accelerating their separation from the carcass rubber. Therefore, increasing the corrosion resistance of the cord steel wires and designing a reasonable interlayer structure to strengthen and maintain the bonding between the cords and rubber, thereby improving the tire carcass's service life, is urgently needed. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of the prior art and provide a steel cord and its manufacturing method, which includes an outer layer, a middle layer and a core layer. The filaments in each layer are in linear contact, and there is a uniform and consistent spatial gap between adjacent filaments in the outer layer, which is more conducive to the penetration of rubber fluid. In addition, the steel cord layer contains highly corrosion-resistant elements, which helps to enhance and maintain the curing effect of the cord and rubber, and helps to improve the tire carcass life.

[0005] To achieve the above objectives, the present invention is implemented using the following technical solution:

[0006] On one hand, the present invention provides a cord, wherein the steel wire cord is made of multi-strand layered filaments twisted together, including an outer layer, a middle layer and a core layer. The core layer consists of one filament with a diameter of D1, the middle layer has eight filaments with a diameter of D2 evenly distributed, and the outer layer has eight filaments with a diameter of D3 evenly distributed. The filaments in each layer are in linear contact. The range of D1 and D3 is 0.35~0.38mm, and the range of D2 is 0.18~0.22mm.

[0007] The filament is coated with a layer containing La, Sm or Mg.

[0008] Furthermore, the relationship between D1 and D2 is D1 / D2 = 1.82~2.05;

[0009] Furthermore, the relationship between D1 and D3 is D1 / D3 = 1.00~1.05.

[0010] Furthermore, the twist pitch of the middle and outer layer filaments is 14.5±2.5mm, and the middle and outer layer filaments are twisted in the same direction.

[0011] Furthermore, there is a gap L between adjacent filaments in the outer layer, and L ranges from 0.03 to 0.06 mm.

[0012] Furthermore, the diameter of the cord is in the range of 1.4 ± 0.06 mm.

[0013] Furthermore, the mass percentage of La, Sm, or Mg shall not exceed 1% of the total mass of the coating and shall not be less than 0.2% of the total mass of the coating.

[0014] On the other hand, the present invention provides a method for manufacturing the aforementioned cord, comprising the following steps:

[0015] The wire rod is compressed to the preset size of the steel wire before plating under dry powder lubrication to obtain the steel wire before plating;

[0016] To coat the steel wire before plating, a coating is applied to obtain coated steel wire;

[0017] Coated steel wire is compressed to a preset wire size under liquid lubrication to obtain wires of different diameters;

[0018] Fine filaments of different diameters are fixed in position according to the cord structure and twisted together in a single operation to form a cord.

[0019] Furthermore, the carbon content of the wire rod is between 0.78% and 0.85% wt.

[0020] And / or, the coated steel wire is compressed to a preset filament size under liquid lubrication, with a diameter compression ratio of 0.945 to 0.983;

[0021] Furthermore, the equipment used for the single stranding forming application is a double-disc stranding machine.

[0022] Compared with the prior art, the beneficial effects achieved by the present invention are as follows:

[0023] The cord provided by the present invention includes an outer layer, a middle layer and a core layer, wherein the core layer is a single filament, the middle layer has eight filaments evenly distributed, and the outer layer has eight filaments evenly distributed. The filaments in each layer are in linear contact, and there is a uniform and consistent spatial gap between adjacent filaments in the outer layer, which is more conducive to the penetration of rubber fluid, thereby helping to enhance and maintain the curing effect of the cord and rubber.

[0024] The cord provided by this invention uses fine filaments with corrosion-resistant elements introduced into the alloy coating, which significantly improves the corrosion resistance of the cord steel wire itself compared with the existing brass coating.

[0025] The cord provided by this invention uses a double-splitting disc type single-formation equipment, which shortens the forming time and reduces production costs compared to the existing multi-step forming of layered tire cords. Attached Figure Description

[0026] Figure 1 This is a schematic cross-sectional view of the cord provided in an embodiment of the present invention;

[0027] Figure 2 This is a schematic diagram of the disassembly of the cord provided in an embodiment of the present invention;

[0028] Figure 3 This is a schematic diagram of the single stranding and forming process of the cord provided in an embodiment of the present invention;

[0029] Figure 4 This is a cross-sectional schematic diagram of a conventional cord provided as a comparative example of the present invention;

[0030] Figure 5 This is a graph showing the corrosion resistance test results of the lanthanum alloy-coated steel wire used in the cord provided in this embodiment of the invention.

[0031] Figure 6 This is a graph showing the corrosion resistance test results of the brass-plated steel wire used in the conventional cord provided in the comparative example of this invention;

[0032] In the diagram: 1. Core filament; 2. Middle filament; 3. Outer filament; 4. Cable feeder; 5. First cable reel; 6. Second cable reel; 7. Main unit. Detailed Implementation

[0033] The present invention will be further described below with reference to the accompanying drawings. The following embodiments are merely representative examples of the technical solutions of the present invention, used to more clearly illustrate the technical solutions of the present invention, and should not be used to limit the scope of protection of the present invention.

[0034] Example

[0035] This embodiment provides a cord and its preparation method, the cross-sectional view of which is shown below. Figure 1 As shown, it is made of multi-strand layered filaments twisted together, including an outer layer, a middle layer and a core layer. The core layer is a single filament with a diameter of 0.365 mm. The middle layer has eight filaments with a diameter of 0.20 mm evenly distributed. The outer layer has eight filaments with a diameter of 0.35 mm evenly distributed. The filaments in each layer are in linear contact with each other. The filaments are coated with a coating containing La. Figure 2 This is a schematic diagram showing the separation of the outer layer, middle layer and core layer of the cord provided in this embodiment.

[0036] The method for preparing the cord provided in this embodiment is as follows:

[0037] Qualified wire rods with a carbon content of 0.827% were compressed into uncoated steel wires of 1.94mm, 1.40mm, and 2.10mm in diameter under dry powder lubrication. The three coils of steel wire were then sequentially coated with copper, lanthanum, and zinc layers, with the lanthanum layer accounting for 0.6% of the total mass of the three metal layers. The skin effect was generated through electromagnetic induction to obtain alloy-coated steel wires of the three metals. Three coils of alloy-coated steel wire with diameters of 1.94mm, 1.40mm, and 2.10mm were compressed to fine filaments of 0.365mm (1 coil), 0.20mm (8 coils), and 0.35mm (8 coils) respectively under liquid lubrication conditions. The 0.365mm filaments were used for the core layer, the 0.20mm filaments for the middle layer, and the 0.35mm filaments for the outer layer. The required filaments were placed in fixed positions on a double-splitter stranding machine, and the components controlling the parameters were adjusted to the desired state. The middle and outer layer strands had the same twist pitch and twist direction. The machine was started to strand the filaments in a single pass to obtain the cord provided in this embodiment, denoted as 0.365+8×0.20+8×0.35 cord.

[0038] Figure 3 This is a schematic diagram of the single stranding and forming process of the cord provided in this embodiment, as shown below. Figure 3 As shown, the fine filaments to be used are all stored on the wire feeding frame 4. During the single stranding and forming process, the core layer filament 1 and the middle layer filament 2 are first wound on the first wire separating plate 5, and the outer layer filament 3 is wound on the second wire separating plate 6. Then, the core layer, middle layer and outer layer filaments are transported together to the host machine 7 for stranding and forming, and finally the cord provided in this embodiment is obtained.

[0039] Comparative Example

[0040] This comparative example provides an existing cord and its preparation method, wherein the cord also has a three-layer structure, such as... Figure 4As shown, it includes an outer layer, a middle layer, and a core layer. The core layer consists of 3 filaments, the middle layer has 9 filaments evenly distributed, and the outer layer has 15 filaments evenly distributed. The filaments in the outer layer, middle layer, and core layer all have the same diameter of 0.225 mm.

[0041] The preparation method of the cord provided in this comparative example differs from that of the embodiment in the following ways: 1. After the steel wire is coated with a copper layer and a zinc layer, it undergoes electromagnetic induction to generate a skin effect, resulting in an alloy-coated steel wire of the two metals. The steel wire coating does not contain La, Sm, or Mg elements. 2. The cord stranding is a two-step forming process. First, the core layer and middle layer filaments are stranded to produce a semi-finished cord. Then, it is twisted again with the 15 outer single wires to form the cord provided in the comparative example, denoted as 3+9+15×0.225 cord. A cross-sectional schematic diagram of the cord is shown below. Figure 5 .

[0042] Performance tests were conducted on the 0.365+8×0.20+8×0.35 cord provided in the example and the 3+9+15×0.225 cord provided in the comparative example. The test items and results are shown in Table 1. The test method followed GB / T 33159-2016.

[0043] Table 1. Comparison of relevant performance characteristics between 0.365+8×0.20+8×0.35 cord and 3+9+15×0.225 cord.

[0044]

[0045] As shown in Table 1, the 0.365+8×0.20+8×0.35 cord provided in this embodiment of the invention has a similar overall thickness to the 3+9+15×0.225 cord provided in the comparative example. However, the 0.365+8×0.20+8×0.35 cord provided in this embodiment of the invention has higher breaking strength and stiffness, which are approximately 4.9% and 94.8% higher than those of the 3+9+15×0.225 cord provided in the comparative example, respectively. The linear density of the cord provided in this embodiment of the invention is not higher than that of existing cords, and the interlayer gaps between the outer filaments are uniform, making it easier for rubber fluid to penetrate into the outer layer of the cord. This means that the rubber penetration performance is much higher than that of existing cords. This also means that the cord provided in this invention has higher load-bearing capacity, resistance to deformation and environmental erosion, and more stable rubber and cord curing effect compared to existing cords, which can effectively improve the service life of the tire carcass.

[0046] In terms of molding process comparison, the 0.365+8×0.20+8×0.35 cord provided in this embodiment of the invention adopts a double-splitter single-stranding process, while the existing 0.365+8×0.20+8×0.35 cord adopts a step-by-step molding process. Compared with the two, single-step molding can avoid the transfer of products in the intermediate process, reduce the frequency of errors, and increase production efficiency, thereby reducing costs.

[0047] The corrosion resistance of the lanthanum-containing alloy-plated steel wire used in the 0.365+8×0.20+8×0.35 cord provided in this embodiment of the invention was tested against that of the brass-plated steel wire used in the existing 0.365+8×0.20+8×0.35 cord. Both were placed in salt water of the same concentration for corrosion experiments. The results are shown in […]. Figure 5 and Figure 6 .

[0048] Figure 5 This is the result of etching a lanthanum alloy-coated steel wire in salt water for 12 hours. Figure 6 The figure shows the results of 4 hours of corrosion of brass-plated steel wire in salt water. No rust was found in the lanthanum alloy-plated steel wire, while corrosion spots appeared in the brass-plated steel wire. This indicates that the lanthanum alloy-plated steel wire used in the cord provided in this embodiment of the invention has a better resistance to corrosion than the existing brass-plated steel wire.

[0049] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only used to explain the relative positional relationship and movement between components in a specific posture. If the specific posture changes, the directional indication will also change accordingly. They are used only for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. Furthermore, the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, features defined with "first," "second," etc., may explicitly or implicitly include one or more of that feature. In the description of this invention, unless otherwise stated, "a plurality of" means two or more.

[0050] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art will understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0051] The embodiments of the present invention have been described above with reference to the accompanying drawings. However, the present invention is not limited to the specific embodiments described above. The specific embodiments described above are merely illustrative and not restrictive. Those skilled in the art can make many other forms under the guidance of the present invention without departing from the spirit and scope of the claims. All of these forms are within the protection scope of the present invention.

Claims

1. A steel wire cord, characterized in that: The steel wire cord has a multi-strand layered structure, made of fine filaments twisted together, including an outer layer, a middle layer, and a core layer. The core layer consists of one fine filament with a diameter of D1. The middle layer has eight fine filaments with a diameter of D2 evenly distributed, and the outer layer has eight fine filaments with a diameter of D3 evenly distributed. The fine filaments in each layer are in linear contact. The diameters of D1 and D3 range from 0.35 to 0.38 mm, and the diameter of D2 ranges from 0.18 to 0.22 mm. Each layer of filaments is coated with a layer containing La, Sm or Mg; The relationship between D1 and D2 is D1 / D2 = 1.82~2.05; The relationship between D1 and D3 is D1 / D3 = 1.00~1.05; The twist pitch of the middle and outer layer filaments is 14.5±2.5mm; the middle and outer layer filaments are twisted in the same direction. There is a gap L between adjacent filaments in the outer layer, and the range of L is 0.03~0.06mm; The diameter of the steel wire cord is 1.4 ± 0.06 mm; The mass percentage of La, Sm, or Mg shall not exceed 1% of the total mass of the coating and shall not be less than 0.2% of the total mass of the coating.

2. A method for manufacturing steel wire cord as described in claim 1, characterized in that, Includes the following steps: The wire rod is compressed to the preset size of the steel wire before plating under dry powder lubrication to obtain the steel wire before plating; To coat the steel wire before plating, a coating is applied to obtain coated steel wire; Coated steel wire is compressed to a preset wire size under liquid lubrication to obtain wires of different diameters; Thin filaments of different diameters are fixed in position according to the structure of steel wire cord and twisted together in a single operation to form steel wire cord.

3. The method for manufacturing steel wire cord according to claim 2, characterized in that: The carbon content of the wire rod is between 0.78% and 0.85 wt%. And / or, the coated steel wire is compressed to a preset filament size under liquid lubrication, with a diameter compression ratio of 0.945 to 0.

983.

4. The method for manufacturing steel wire cord according to claim 2, characterized in that: The equipment used for the single stranding forming is a double-distributor type stranding machine.

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