Full-glue-permeation type steel cord and production method

Abstract

The invention discloses a full-glue-permeation type steel cord and a production method, and belongs to the technical field of steel cord production, the steel cord comprises a core strand composed of two steel wires with the diameter of d1 and N externally-wound steel wires with the diameter of d2 spirally wound on the core strand, wherein the two steel wires of the core strand in the steel cord have different torsional stresses before being wound by the N steel wires on the outer layer; the diameter of the core strand and the diameter of the externally-wound steel wire meet a set interval, so that the bending rigidity of the core strand meets 0.9-1.76 times of the bending rigidity of the externally-wound steel wire; the section metal filling rate D of the steel cord is greater than a set threshold value; a distance H is formed between every two externally-wound steel wires; according to the invention, the generation of core strand defects in the production process of the steel cord is avoided, and the generality of the cord in use is improved.

Description

Technical Field

[0001] The invention relates to a fully-penetrated steel cord and a production method thereof, belonging to the technical field of steel cord production. Background Art

[0002] Research has found that when a tire is punctured by a sharp object, oxygen or water vapor will penetrate into the cord through the damaged area. Due to the gaps inside the cord, these oxygen or water vapor will continue to diffuse along the cord direction to the entire cord, causing steel wire corrosion and bonding failure. In order to solve this problem, in 1978, patent US4258543A proposed designing the cord as an open or highly permeable type, so that rubber can easily penetrate into the cord to fill the gaps during the vulcanization process with the cord, thereby preventing oxygen or water vapor from diffusing inside the cord. There are many ways to increase the rubber penetration of the cord, including pre-deforming the steel wires that make up the cord, increasing the gaps between the steel wires, and thus increasing the rubber penetration rate; it also includes increasing the openness of the cord through specific steel wire diameter matching and structural design, reducing or eliminating the closed space in the cord, so that the cord has a higher rubber penetration rate during the vulcanization process. For example, the CN207091801 patent discloses a 2+7 fully open steel cord structure, which improves the cord openness through the design of the twist pitch of the center strand and the outer winding steel wire and the ratio of the inner and outer wire diameters, thereby improving the cord's rubber penetration rate. In the actual production process, while ensuring the cord openness, in order to prevent the metal filling rate of the unit cross section of the 2+7 structure cord from being too low, it will be achieved by reducing the diameter of the core strand steel wire, such as the 2'0.25+6'0.33 and 2'0.26+6'0.37 disclosed in the patent JP2012148644A, which can increase the metal filling rate by 9.65% and 12.55% compared to the 2'0.33+6'0.33 and 2'0.37+6'0.37 cords. However, in the actual production process, the thinner the core wire diameter is, the better. The thinner the core wire diameter is, the unexpected results will be brought about during production, especially for the layered 2+N cord, which will cause uneven twisting of the core wire. Summary of the invention

[0003] The purpose of the present invention is to overcome the deficiencies in the prior art, provide a fully-penetrated steel cord and a production method, avoid the generation of core strand defects in the steel cord production process, and increase the cord's smoothness in use.

[0004] 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 fully rubberized steel cord, comprising a core strand composed of two steel wires with a diameter of d1 and N outer steel wires with a diameter of d2 spirally wound on the core strand, wherein: The two steel wires of the core strand in the steel cord have different torsional stresses before being wound by the outer N steel wires; The diameters of the core strand and the outer wrapped steel wire meet a set range, so that the bending stiffness of the core strand meets the bending stiffness of 0.9 to 1.76 times that of the outer wrapped steel wire; The cross-sectional metal filling rate D of the steel cord is greater than a set threshold; There is a distance H between the outer wrapped steel wires.

[0005] Furthermore, the lay pitch of the core strand is p1, and the lay pitch of the outer wrapped steel wire is p2, wherein 0.5p2≤p1≤p2.

[0006] Furthermore, N≥7, and / or N=7 or N=8.

[0007] Furthermore, the diameters of the core strand and the outer wrapped steel wire satisfy the following relationship: 0.90(d2) 4 ≤2 (d1) 4 ≤1.76 (d2) 4 .

[0008] Furthermore, the diameters of the core strand and the outer wrapped steel wire satisfy the following relationship: (d2) 4 ≤2 (d1) 4 ≤1.76 (d2) 4 .

[0009] Furthermore, the cross-sectional metal filling rate D of the steel cord satisfies: D ≥ 60%, wherein the calculation formula of D is: .

[0010] Furthermore, the spacing H between the outer wrapped steel wires satisfies: H≥20 μm.

[0011] Furthermore, the twist direction of the core strands is the same as the twist direction of the outer wrapped steel wires.

[0012] In a second aspect, the present invention provides a method for producing a fully rubberized steel cord according to any one of the above items, comprising: One steel wire pay-off unit is placed inside the core strand twisting device, and another steel wire pay-off unit is placed outside the core strand twisting device; The steel wire placed outside the core strand twisting device is twisted and untwisted before being pulled to the twisting point; The steel wire placed in the core strand twisting device is only twisted before being pulled to the twisting point; Two core steel wires with different torsional stresses are obtained.

[0013] Furthermore, the production method also includes: placing both steel wires of the core strand inside a core strand twisting device, and selecting one of the steel wires for straightening or twisting.

[0014] Compared with the prior art, the present invention has the following beneficial effects: The present invention provides a fully-impregnated steel cord and a production method thereof. By designing the diameters of the core steel wire and the outer winding steel wire and designing the production process, the cord is ensured to have a high adhesive penetration rate while reducing the difference in bending stiffness between the core steel wire and the outer winding steel wire, thereby reducing the core strand twisting defects of the steel cord during the production process and increasing the smoothness of the calendering and cutting processes during the use of the product by the customer.

[0015] The core strands of the cord of the present invention are twisted evenly, and due to the differential design of the torsional stress of the two steel wires, the overall torsional stress of the core strands is smaller. After the tire customer produces the cord fabric, the obtained cord fabric is smoother and has a smaller warping effect when cutting. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is a schematic diagram of a 2+7 structure cord; Figure 2 It is a schematic diagram of a 2+8 structure cord; Figure 3 It is a schematic diagram of a 2+N cord with a core strand in a normal state; Figure 4 It is a schematic diagram of 2+N cord with abnormal core strand state; Figure 5 Schematic diagram of different torsional stresses of two core wires in 2+N structure cord; Figure 6 This is a schematic diagram of the production of 2+N structure cords, where 1 is the twisting point, 2 is the outer layer single wire pay-off unit, 3 is the take-up unit, and 4 is the two core wire pay-off unit; Figure 7 Schematic diagram of the second production of 2+N structure cord; 5 in the figure is a core wire pay-off unit that has been straightened or twisted in a wet drawing machine; Figure 8 The third production schematic diagram of 2+N structure cord. In the figure, 6 is a straightener installed in the core strand twisting device. DETAILED DESCRIPTION

[0017] 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.

[0018] Embodiment 1: This embodiment introduces a fully rubber-impregnated steel cord, which has a core strand composed of two steel wires with a diameter of d1 and N outer steel wires with a diameter of d2 spirally wound on the core strand, wherein N≥7, preferably N=7 and N=8.

[0019] The core strand lay pitch is p1, the outer wrapped steel wire lay pitch is p2, and the core strand lay direction is the same as the outer wrapped steel wire lay direction, wherein 0.5p2≤p1≤p2.

[0020] The main features of the cord are: (1) The relationship between the core strand and the outer wrapped wire needs to be 0.90 (d2) 4 ≤2 (d1) 4 ≤1.76 (d2) 4 , preferably, satisfying (d2) 4 ≤2 (d1) 4 ≤1.76 (d2) 4 ; (2) The steel cord meets the requirement of cross-sectional metal filling rate ≥ 60%, thereby ensuring that the product has sufficiently high specific strength; (3) The average spacing between the outer wrapped steel wires of the steel cord needs to satisfy H ≥ 20 μm; (4) The two steel wires in the core strand of the steel cord have different torsional stresses before being wound by the N outer steel wires, such as Figure 5 As shown in , two steel wires with different torsional stresses in the core strand are marked.

[0021] In the present invention, the cross-sectional metal filling rate of the steel cord product refers to the ratio of the sum of the area of ​​the two core wires and the area of ​​the N outer wrapped steel wires on the cross section of the cord to the nominal cross-sectional circular area of ​​the steel cord. The calculation formula is: ; In the present invention, the core strand composed of two core wires is regarded as a unit, and the overall bending stiffness of the core strand unit cannot be too different from the bending stiffness of the outer wrapped steel wire, especially the overall bending stiffness of the core strand cannot be too small, so that when the outer wrapped steel wire is wound on the core strand during the twisting process, the core strand is hindered from being formed. Therefore, in the present invention, the bending stiffness of the core strand cannot be less than 0.9 times the bending stiffness of the outer wrapped steel wire, that is: ; ; After simplification, we can get: 2´(d1) 4 ≥0.90(d2) 4 ; Where: E is the elastic modulus of the material; I1 is the moment of inertia of the core strand, and I2 is the moment of inertia of the outer wrapped steel wire.

[0022] In addition, the overall bending stiffness of the core strands cannot be too high compared to the outer steel wires. For example, when 0.37+6´0.32 cords are used as belt layers in tires, the core wires are prone to piercing. According to the applicant's calculations, when the overall bending stiffness of the core strands does not exceed 1.76 times the bending stiffness of the outer steel wires, the friction between the core strands and the outer steel wires when the cords are bent as a whole can restrain the bending stress difference between the core strands and the outer steel wires during the bending process, thereby avoiding relative sliding and causing the core strand piercing problem.

[0023] The steel cord product of the present invention reduces the difference in bending stiffness between the core strands and the outer winding steel wires while ensuring a high adhesive penetration rate of the cord through diameter design of the core strand steel wire and the outer winding steel wire and production process design, reduces the core strand twisting defects of the steel cord during the production process, and increases the smoothness of the calendering and cutting processes during customer use of the product.

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

[0025] Table 1 discloses the product parameter characteristics, glue penetration rate and production process monitoring of the embodiments and comparative examples of the present invention.

[0026] Table 1

[0027] As shown in Table 1, the design lay length of the core wire is 9.0 mm for 2´0.20+5´0.37 in Comparative Example 1 and 2´0.22+6´0.33 in Comparative Example 2. However, the lay length of the core wire is uneven during the production process. Figure 4 As shown in the figure, for the same lay length, L2 is obviously larger than L1. This is caused by the large difference in diameter between the center wire d1 and the outer layer winding wire d2, especially in the production process of double-twist machines, this phenomenon is more obvious.

[0028] In comparative example 3, the cross-sectional metal filling rate of the 2´0.35+7´0.35 cord is only 56.2%. In comparative example 4, the cross-sectional metal filling area of ​​the 2´0.30+8´0.36 cord is 69.8%. However, since the gap H between the outer steel wires is too small, the glue penetration rate is insufficient, only 30%.

[0029] In comparative example 5, 2´0.36+8´0.34 cords, two 0.36 steel wires are used as core wires, and the overall bending stiffness of the core strands is higher than that of the outer steel wires. According to calculations, the overall bending stiffness of the core strands is 2.5 times that of the outer steel wires. When the steel cords are used in tires, the core strands are prone to piercing.

[0030] Examples 1 to 4 are several steel cords produced by the inventor according to the design method described in the present application document. When N=7, the cord structure is 2'0.30+7'0.36 and 2'0.25+7'0.30. The cord structure diagram is shown in FIG. Figure 1 As shown in; when N=8, the cord structure is 2´0.33+8´0.36 and 2´0.28+7´0.30, the cord structure diagram is as shown in Figure 2 The twist length of the core strands of the cords in Examples 1 to 4 is as shown in Figure 3 As shown in , uniform and consistent.

[0031] In the production process of the cord, the two steel wires in the core wire are arranged in the following way: Figure 6 As shown in the figure, one core wire pay-off unit is placed in the core strand twisting device, and the other core wire pay-off unit is placed outside the core strand twisting device. The core wire placed outside the core strand twisting device is twisted and untwisted before being pulled to the twisting point, while the core wire placed in the core strand twisting device is only twisted before being pulled to the twisting point, so that the two steel wires in the core strand have different torsional stresses before being wrapped by the outer steel wire.

[0032] In addition, when the two steel wires of the core strand are placed inside the core strand twisting device, Figure 7 As shown in , one of the steel wires can be selected for straightening or twisting. Preferably, when straightening and twisting are performed, the straightener and the twister are both installed on the wet drawing machine. At the same time, it is not excluded that when there is enough space inside the core strand twisting device, the straightener or the twister is installed in the core strand twisting device, such as Figure 8 shown.

[0033] The core strands of the cord of the present invention are twisted evenly, and due to the differential design of the torsional stress of the two steel wires, the overall torsional stress of the core strands is smaller. After the tire customer produces the cord fabric, the obtained cord fabric is smoother and has a smaller warping effect when cutting.

[0034] Embodiment 2: This embodiment provides a method for producing a fully rubber-impregnated steel cord according to any one of Embodiment 1, comprising: One steel wire pay-off unit is placed inside the core strand twisting device, and another steel wire pay-off unit is placed outside the core strand twisting device; The steel wire placed outside the core strand twisting device is twisted and untwisted before being pulled to the twisting point; The steel wire placed in the core strand twisting device is only twisted before being pulled to the twisting point; Two core steel wires with different torsional stresses are obtained.

[0035] The production method further comprises: placing both the two steel wires of the core strand inside the core strand twisting device, and selecting one of the steel wires for straightening treatment or twisting treatment.

[0036] 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 fully rubberized steel cord, characterized in that: It comprises a core strand composed of two steel wires with a diameter of d1 and N outer winding steel wires with a diameter of d2 spirally wound on the core strand, wherein: The two steel wires of the core strand in the steel cord have different torsional stresses before being wound by the outer N steel wires; The diameters of the core strand and the outer wrapped steel wire meet a set range, so that the bending stiffness of the core strand meets the bending stiffness of 0.9 to 1.76 times that of the outer wrapped steel wire; The cross-sectional metal filling rate D of the steel cord is greater than a set threshold; There is a distance H between the outer wrapped steel wires.

2. The fully rubberized steel cord according to claim 1, characterized in that: The core strand lay pitch is p1, and the outer wrapped steel wire lay pitch is p2, wherein 0.5p2≤p1≤p2.

3. The fully rubberized steel cord according to claim 1, characterized in that: Said N≥7, and / or, N=7 or N=8.

4. The fully rubberized steel cord according to claim 1, characterized in that: The diameters of the core strand and the outer wrapped steel wire satisfy the following relationship: 0.90(d2) 4 ≤2(d1) 4 ≤1.76(d2) 4 。 5. The fully rubberized steel cord according to claim 1, characterized in that: The diameters of the core strand and the outer wrapped steel wire satisfy the following relationship: (d2) 4 ≤2(d1) 4 ≤1.76(d2) 4 。 6. The fully rubberized steel cord according to claim 1, characterized in that: The cross-sectional metal filling rate D of the steel cord satisfies: D ≥ 60%, wherein the calculation formula of D is: 。 7. The fully rubberized steel cord according to claim 1, characterized in that: The spacing H between the outer wrapped steel wires satisfies: H≥20 μm.

8. The fully rubberized steel cord according to claim 1, characterized in that: The twist direction of the core strands is the same as that of the outer wrapped steel wires.

9. A method for producing a fully rubberized steel cord according to any one of claims 1 to 8, characterized in that: include: One steel wire pay-off unit is placed inside the core strand twisting device, and another steel wire pay-off unit is placed outside the core strand twisting device; The steel wire placed outside the core strand twisting device is twisted and untwisted before being pulled to the twisting point; The steel wire placed in the core strand twisting device is only twisted before being pulled to the twisting point; Two core steel wires with different torsional stresses are obtained.

10. The production method according to claim 9, characterized in that: The production method further comprises: placing both the two steel wires of the core strand inside the core strand twisting device, and selecting one of the steel wires for straightening treatment or twisting treatment.

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