A steel cord, its manufacturing process and its use

Abstract

The application discloses a cord and a manufacturing method and application thereof in the technical field of steel cord product manufacturing, and the cord comprises an outer layer, a middle layer and a core layer, the core layer is one filament with a diameter of D1, the middle layer uniformly distributes n filaments with a diameter of D2, and the outer layer uniformly distributes n filaments with a diameter of D3; the cord is in a 1+n+n structure from the core layer to the outer layer, wherein the value range of n is 7-9, the filaments in different layers are in linear contact, uniform space gaps exist between adjacent filaments in the outer layer, the rubber fluid is more conducive to permeation, and thus the solidification of the cord and the rubber is facilitated, and the durability of the cord ply of the tire is improved. The manufacturing method of the cord provided by the application adopts a double-separating-die single-time forming device, and compared with a plurality of existing step-formed strand-shaped carcass cords, the forming 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, its manufacturing method, and its application. Background Technology

[0002] As the main skeleton material and core component of a tire, the ply is the primary load-bearing element. It must withstand external loads and impacts, as well as maintain the internal air pressure, especially crucial for heavy-duty tires. This necessitates superior fatigue resistance, impact resistance, and durability in the tire ply to maintain a long-term balance between the internal and external factors and the environment, ensuring tire lifespan and safety. The ply is composed of rubber and steel cords. Its performance largely depends on the material properties of the bonded cords and rubber compound. Therefore, after the cords possess relevant physical properties, the crucial factor is their ability to cure effectively with the rubber compound and maintain that curing ability.

[0003] Existing tire ply structures, especially those for heavy-duty truck tires, primarily use tightly packed, layered steel cords with virtually no gaps between adjacent filaments. This means that even after the cords are vulcanized with the tire carcass rubber under pressure, the rubber still struggles to penetrate the cord layers. Consequently, under cyclical stress and deformation during tire use, micro-movements may occur within the cords, leading to a gradual weakening of the bond between the cords and the rubber over time. Furthermore, when localized cracks appear in the tire rubber material, moisture, salt, and other corrosive media can continuously penetrate the tire's interior as the cracks extend. Since rubber has difficulty flowing between the cord layers, these corrosive media pose a direct risk of acting on the cord interior, accelerating detachment from the rubber. Therefore, designing a suitable ply structure to strengthen and maintain the bond between the cords and rubber, thereby improving the durability of the tire ply, 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, its manufacturing method and application. The cord includes an outer layer, a middle layer and a core layer. From the core layer to the outer layer, the cord has a 1+n+n structure, where n ranges from 7 to 9. The filaments in each layer are in linear contact, and there is a uniform 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, and helping to improve the durability of the tire ply.

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

[0006] In a first aspect, the present invention provides a cord, wherein the steel cord is made of multiple strands of layered filaments twisted together, including an outer layer, a middle layer and a core layer, wherein the core layer is a single filament with a diameter of D1, the middle layer has n filaments with a diameter of D2 evenly distributed, and the outer layer has n filaments with a diameter of D3 evenly distributed, wherein the value of n ranges from 7 to 9.

[0007] The filaments in each layer are in linear contact; the range of D1 and D3 is 0.30~0.40mm; the range of D2 is 0.18~0.22mm.

[0008] Furthermore, when n=7, the range of D1 and D3 is 0.30~0.40mm;

[0009] When n=8, the range of D1 and D3 is 0.35~0.38mm;

[0010] When n=9, the range of D1 and D3 is 0.30~0.40mm.

[0011] Furthermore, when n=7, the range of D2 is 0.20~0.22mm;

[0012] When n=8, the range of D2 is 0.18~0.22mm;

[0013] When n=9, the range of D2 is 0.18~0.20mm.

[0014] Furthermore, when n=7, the relationship between D1 and D2 is D1 / D2=1.36~1.50;

[0015] When n=8, the relationship between D1 and D2 is D1 / D2=1.82~2.05;

[0016] When n=9, the relationship between D1 and D2 is D1 / D2=2.00~2.12.

[0017] Furthermore, when n=7, D1 and D3 satisfy the relationship D1 / D3=0.75~0.79;

[0018] When n=8, D1 and D3 satisfy the relationship D1 / D3=1.05~1.00;

[0019] When n=9, the relationship between D1 and D3 is D1 / D3=1.26~1.33.

[0020] Furthermore, 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.

[0021] Furthermore, there is a gap L between adjacent filaments in the outer layer, and L ranges from 0.03 to 0.06 mm.

[0022] Secondly, the present invention provides a method for manufacturing the aforementioned cord, comprising the following steps:

[0023] 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;

[0024] To coat the steel wire before plating, a coating is applied to obtain coated steel wire;

[0025] Coated steel wire is compressed to a preset wire size under liquid lubrication to obtain wires of different diameters;

[0026] 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.

[0027] Furthermore, the carbon content of the wire rod is between 0.77% and 0.86% wt.

[0028] And / or, the coated steel wire is compressed to a preset filament size under liquid lubrication, with a diameter compression ratio of 0.932 to 0.985.

[0029] Furthermore, the equipment used for the single stranding forming application is a double-disc stranding machine.

[0030] Thirdly, the present invention provides an application of the aforementioned cord in the ply layer of a tire.

[0031] Compared with the prior art, the beneficial effects achieved by the present invention are as follows:

[0032] The cord provided by this invention includes an outer layer, a middle layer, and a core layer. The core layer consists of one filament, the middle layer has n filaments evenly distributed, and the outer layer has n filaments evenly distributed. From the core layer to the outer layer, the cord has a 1+n+n structure, where n ranges from 7 to 9. The filaments in each layer are in linear contact, and there is a uniform spatial gap between adjacent filaments in the outer layer, which is more conducive to the penetration of rubber fluid. This helps to enhance and maintain the curing effect of the cord and rubber, thereby improving the durability of the tire cord layer.

[0033] 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

[0034] Figure 1 This is a schematic cross-sectional view of the cord provided in an embodiment of the present invention;

[0035] Figure 2This is a schematic cross-sectional view of the cord provided in an embodiment of the present invention;

[0036] Figure 3 This is a schematic cross-sectional view of the cord provided in an embodiment of the present invention;

[0037] Figure 4 This is a schematic diagram of the single stranding and forming process of the cord provided in an embodiment of the present invention;

[0038] Figure 5 This is a cross-sectional schematic diagram of a conventional cord provided as a comparative example of the present invention.

[0039] In the diagram: 1. Outer layer fine wire feeding frame; 2. Core layer fine wire feeding frame; 3. Middle layer fine wire feeding frame; 4. First dividing reel; 5. Second dividing reel; 6. Take-up reel; 7. Main unit. Detailed Implementation

[0040] The present invention will be further described below with reference to the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present invention, and should not be used to limit the scope of protection of the present invention.

[0041] Example 1

[0042] This embodiment provides a cord and its preparation method. The cord has a multi-strand filament layered structure, including an outer layer, a middle layer, and a core layer. The core layer consists of a single filament with a diameter of 0.30 mm. The middle layer has seven filaments with a diameter of 0.22 mm evenly distributed, and the outer layer has seven filaments with a diameter of 0.38 mm evenly distributed. The filaments in each layer are in linear contact. A schematic diagram of the cord structure is shown below. Figure 1 ;

[0043] The method for preparing the cord provided in this embodiment is as follows:

[0044] Qualified wire rods with a carbon content of 0.831% were compressed into pre-plating steel wires of 2.05mm, 1.40mm, and 2.20mm diameters under dry powder lubrication. The three coils of steel wire were then sequentially plated with copper and zinc layers, and copper-zinc alloy coated steel wires were obtained through thermal diffusion. Three coils of alloy-coated steel wire with diameters of 2.05mm, 1.40mm, and 2.20mm were drawn to fine filaments of 0.30mm (1 pull), 0.22mm (7 pulls), and 0.38mm (7 pulls) respectively under liquid lubrication conditions, with compression ratios of 0.979, 0.975, and 0.970. The 0.30mm filament from the 1 pull was used for the core layer, the 0.22mm filament from the 7 pulls was used for the middle layer, and the 0.38mm filament from the 7 pulls was used for the outer layer. The required layers of fine 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 wire in a single pass to obtain the cord provided in this embodiment, denoted as 0.30+7×0.22+7×0.38 cord.

[0045] like Figure 4 As shown, during preparation, the core layer filaments are placed at the core layer filament pay-off frame 2; the middle layer filaments are placed at the middle layer filament pay-off frame 3; and the outer layer filaments are placed at the outer layer filament pay-off frame 1. The core layer filaments are passed through the first splitter 4 and the second splitter 5 respectively. The middle layer filaments are placed around the first splitter 4, and the outer layer filaments are placed around the second splitter 5. The main unit 7 is started, and the double splitter filament stranding machine performs a single stranding to form the cord. The prepared cord is then stored in the take-up reel 6.

[0046] Comparative Example 1

[0047] This comparative example provides an existing cord and its preparation method. The cord also has a three-layer structure, including an outer layer, a middle layer, and a core layer. Unlike Example 1, the core layer has 3 filaments, the middle layer has 9 filaments evenly distributed, and the outer layer has 15 filaments evenly distributed. The filaments in the outer, middle, and core layers all have the same diameter of 0.22 mm. The preparation method of the cord provided in the comparative example involves a two-step twisting process. First, the core and middle layer filaments are twisted to produce a semi-finished cord. Then, they are twisted again with the 15 single filaments of the outer layer to form the cord provided in the comparative example, denoted as 3+9+15×0.22 cord. A cross-sectional schematic diagram of the cord is shown below. Figure 5 .

[0048] Performance tests were conducted on the 0.30+7×0.22+7×0.38 cord provided in Example 1 and the 3+9+15×0.22 cord provided in Comparative Example 1. The test items and results are shown in Table 1. The test method followed GB / T 33159-2016.

[0049] Table 1. Performance Comparison between 1+7+7 Structure Cord and Existing 3+9+15 Structure Cord

[0050]

[0051] As shown in Table 1, compared with the existing 3+9+15×0.22 cord provided in Comparative Example 1, the 0.30+7×0.22+7×0.38 cord provided in Example 1 has a smaller difference in overall cord thickness, but the 0.30+7×0.22+7×0.38 cord provided in Example 1 has higher breaking strength and stiffness, which are about 3.7% and 95.4% higher than the aforementioned existing cord specifications, respectively. Furthermore, the cord in Example 1 has significantly different interlayer gaps and rubber penetration rates compared with the cord in Comparative Example 1. The 0.30+7×0.22+7×0.38 cord prepared according to the present invention has a more effective interlayer gap to facilitate rubber penetration.

[0052] Example 2

[0053] This embodiment provides a cord and its preparation method. The cord has a multi-strand filament layered structure, including an outer layer, a middle layer, and a core layer. The core layer consists of a single filament with a diameter of 0.365 mm. The middle layer has eight filaments with a diameter of 0.200 mm evenly distributed, and the outer layer has eight filaments with a diameter of 0.350 mm evenly distributed. The filaments in each layer are in linear contact. The cross-sectional view of the cord is shown below. Figure 2 As shown.

[0054] The method for preparing the cord provided in this embodiment is as follows:

[0055] 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 and zinc layers, and copper-core alloy coated steel wires were obtained through thermal diffusion. Three coils of alloy-coated steel wire with diameters of 1.94mm, 1.40mm, and 2.10mm were drawn to fine filaments of 0.365mm (1 coil), 0.200mm (8 coils), and 0.350mm (8 coils) respectively under liquid lubrication conditions, with compression ratios of 0.965, 0.980, and 0.972 respectively. The 0.365mm filaments were used for the core layer, the 0.200mm filaments for the middle layer, and the 0.350mm 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+8×0.200+8×0.350 cord.

[0056] Comparative Example 2

[0057] This comparative example provides an existing cord and its preparation method. The cord also has a three-layer structure, including an outer layer, a middle layer, and a core layer. Unlike Example 2, the core layer has 3 filaments, the middle layer has 9 filaments evenly distributed, and the outer layer has 15 filaments evenly distributed. The filaments in the outer, middle, and core layers all have the same diameter of 0.225 mm. The preparation method of the cord provided in the comparative example involves a two-step twisting process. First, the core and middle layer filaments are twisted to produce a semi-finished cord. Then, they are twisted again with the 15 single filaments of the outer layer 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 .

[0058] Performance tests were conducted on the 0.365+8×0.200+8×0.350 cord provided in Example 2 and the 3+9+15×0.225 cord provided in Comparative Example 2. The test items and results are shown in Table 2. The test method followed GB / T 33159-2016.

[0059] Table 2. Performance Comparison between 1+8+8 Structure Cords and Existing 3+9+15 Structure Cords

[0060]

[0061] As shown in Table 2, compared with the existing 3+9+15×0.225 cord provided in Comparative Example 2, the 0.365+8×0.20+8×0.35 cord provided in Example 2 has a smaller difference in overall cord thickness. However, the 0.365+8×0.20+8×0.35 cord provided in Example 2 has higher breaking strength and stiffness, which are approximately 4.9% and 94.8% higher than the aforementioned existing cord specifications, respectively. Furthermore, the cord of Example 2 has significantly different interlayer gaps and rubber penetration rates compared with the cord in Comparative Example 2. The 0.365+8×0.20+8×0.35 cord of Example 2 prepared according to the present invention has a more effective interlayer gap to facilitate rubber penetration.

[0062] Example 3

[0063] This embodiment provides a cord and its preparation method. The cord has a multi-strand filament layered structure, including an outer layer, a middle layer, and a core layer. The core layer consists of a single filament with a diameter of 0.38 mm. The middle layer has nine filaments with a diameter of 0.18 mm evenly distributed, and the outer layer has nine filaments with a diameter of 0.30 mm evenly distributed. The filaments in each layer are in linear contact. A schematic diagram of the cord cross-section is shown below. Figure 3 ;

[0064] The method for preparing the cord provided in this embodiment is as follows:

[0065] Qualified wire rods with a carbon content of 0.819% were compressed into pre-plating steel wires of 2.20mm, 1.15mm, and 2.05mm diameter under dry powder lubrication. The three coils of steel wire were then sequentially plated with copper and zinc layers, and copper-core alloy-plated steel wires were obtained through thermal diffusion. Three coils of alloy-coated steel wire with diameters of 2.20mm, 1.15mm, and 2.05mm were drawn to fine filaments of 0.38mm (1 coil), 0.18mm (9 coils), and 0.30mm (9 coils) respectively under liquid lubrication conditions, with compression ratios of 0.970, 0.979, and 0.972 respectively. The 0.38mm filament from the 1 coil was used for the core layer, the 0.18mm filament from the 9 coils was used for the middle layer, and the 0.30mm filament from the 9 coils was used for the outer layer. The required layers of fine 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 0.38+9×0.18+9×0.30 cord.

[0066] Comparative Example 3

[0067] This comparative example provides an existing cord and its preparation method. The cord also has a three-layer structure, including an outer layer, a middle layer, and a core layer. Unlike Example 3, the core layer has 3 filaments, the middle layer has 9 filaments evenly distributed, and the outer layer has 15 filaments evenly distributed. The filaments in the outer, middle, and core layers all have the same diameter of 0.21 mm. The preparation method of the cord provided in the comparative example involves a two-step twisting process. First, the core and middle layer filaments are twisted to produce a semi-finished cord. Then, they are twisted again with the 15 single filaments of the outer layer to form the cord provided in the comparative example, denoted as 3+9+15×0.21 mm cord. A cross-sectional schematic diagram of the cord is shown below. Figure 5 .

[0068] Performance tests were conducted on the 0.38+9×0.18+9×0.30 cord provided in Example 3 and the 3+9+15×0.21 cord provided in Comparative Example 3. The test items and results are shown in Table 3. The test method followed GB / T 33159-2016.

[0069] Table 3. Performance Comparison between 1+9+9 Structure Cord and Existing 3+9+15 Structure Cord

[0070]

[0071] As shown in Table 3, the 0.38+9×0.18+9×0.30 cord provided in Example 3 of the present invention has a smaller overall thickness compared to the existing 3+9+15×0.21 cord provided in Comparative Example 3. Furthermore, the 0.38+9×0.18+9×0.30 cord provided in Example 3 has higher breaking strength and stiffness, exceeding the aforementioned existing cord specifications by approximately 5.9% and 98.4%, respectively. Moreover, the cord in Example 3 shows significant differences in interlayer spacing and rubber penetration rate compared to the cord in Comparative Example 3. The 0.38+9×0.18+9×0.30 cord in Example 3 prepared according to the present invention has a more effective interlayer spacing to facilitate rubber penetration.

[0072] Example 4

[0073] This embodiment provides a tire ply layer, which is prepared from the cords provided in this embodiment.

[0074] In summary, the cord provided in this embodiment of the invention has a linear density no higher than that of existing cords, and the outer filaments have uniform interlayer spacing, making it easier for rubber fluid to penetrate into the cord strands. This means that the rubber penetration performance is much higher than that of existing cords, resulting in a more stable curing effect of rubber and cord. This also means that the cord provided in this invention, compared with existing cords, will give the tire ply a higher load-bearing capacity, resistance to deformation and corrosion, and can effectively improve the durability and lifespan of the tire ply.

[0075] 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.

[0076] 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.

[0077] 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 n fine filaments with a diameter of D2 evenly distributed, and the outer layer has n fine filaments with a diameter of D3 evenly distributed, where n ranges from 7 to 9. The fine filaments in each layer are in linear contact. The ranges of D1 and D3 are 0.30 to 0.40 mm, and the range of D2 is 0.18 to 0.22 mm. When n=7, the range of D1 and D3 is 0.30~0.40mm; When n=8, the range of D1 and D3 is 0.35~0.38mm; When n=9, the range of D1 and D3 is 0.30~0.40mm; When n=7, the range of D2 is 0.20~0.22mm; When n=8, the range of D2 is 0.18~0.22mm; When n=9, the range of D2 is 0.18~0.20mm; When n=7, the relationship between D1 and D2 is D1 / D2=1.36~1.50; When n=8, the relationship between D1 and D2 is D1 / D2=1.82~2.05; When n=9, the relationship between D1 and D2 is D1 / D2=2.00~2.12; When n=7, the relationship between D1 and D3 is D1 / D3=0.75~0.79; When n=8, the relationship between D1 and D3 is D1 / D3=1.00~1.05; When n=9, the relationship between D1 and D3 is D1 / D3=1.26~1.33; 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.

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 0.77 and 0.86 wt%. And / or, the coated steel wire is compressed to a preset filament size under liquid lubrication, with a diameter compression ratio of 0.932 to 0.985; And / or, the equipment used for the single stranding forming is a double-distributor stranding machine.

4. An application of the steel wire cord as described in claim 1, characterized in that: The cord layer used in tires.

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