CN116716749A - Layered structure steel cord and preparation method thereof - Google Patents

Abstract

The invention discloses a layered structure steel cord and a preparation method thereof in the technical field of steel cord production. It aims to solve the problem of warping of steel cords caused by the large difference between the average tensile strength of core strand steel wires and the outer steel wires in the prior art. The first problem is that it includes a core strand steel wire group and an outer layer steel wire group. The core strand steel wire group is braided and twisted from two core strand steel wires. The outer layer steel wire group is located on the periphery of the core strand steel wire group and is composed of five core strand steel wire groups. An outer layer of steel wire is braided and twisted around a core strand of steel wire, and the diameter of the core strand of steel wire is smaller than the diameter of the outer layer of steel wire. The invention can effectively solve the warping of steel cord cloth caused by the inability to eliminate the residual torsion of the inner strands of the steel cord after braiding and twisting due to the large difference between the average tensile strength of the core strand steel wires and the average tensile strength of the outer steel wires.

Description

A layered structure steel cord and its preparation method

Technical field

The invention relates to a layered structure steel cord and a preparation method thereof, and belongs to the technical field of steel cord production.

Background technique

Steel cord has the advantages of high strength, good toughness and fatigue resistance. It is an important skeleton material of radial tires and plays an important role in promoting the development of green, low rolling resistance and lightweight tires.

The m+n structure steel cord is composed of a first group with m core strand steel wires and a second group with n outer steel wires. Since the average tensile strength of the first group of core strand steel wires is the same as that of the second group The average tensile strength of the outer steel wires has a large range, which causes the residual twist of the inner strands of the steel cord after twisting and forming cannot be eliminated under the existing twisting process, which can easily cause the steel cord to be cut and warped.

Contents of the invention

The purpose of the present invention is to overcome the deficiencies in the prior art and provide a layered structural steel cord and a preparation method thereof, which can effectively solve the problem caused by the large difference between the average tensile strength of the core strand steel wires and the average tensile strength of the outer layer steel wires. The residual torsion of the inner strands of the steel cord after braiding and forming cannot be eliminated, causing warping of the steel cord during cutting.

In order to achieve the above objects, the present invention is achieved by adopting the following technical solutions:

On the one hand, the present invention provides a layered structure steel cord, including a core strand steel wire group and an outer layer steel wire group. The core strand steel wire group is made of two core strand steel wires twisted clockwise, and the outer layer steel wire The assembly is arranged on the outer periphery of the core strand steel wire group, and is composed of five outer steel wires twisted around the core strand steel wire group. The diameter of the core strand steel wire is smaller than the diameter of the outer layer steel wire.

Optionally, the core strand steel wire group and the outer layer steel wire group have the same twisting direction.

Optionally, the braiding pitch of the core strand steel wire group is smaller than the braiding pitch of the outer layer steel wire group.

Optionally, the twisting direction of the core strand steel wire is clockwise.

Optionally, the diameter dm of the core steel wire ranges from 0.175mm≤dm≤0.300mm, and the diameter dn of the outer steel wire ranges from 0.250mm≤dn≤0.380mm.

Optionally, the average tensile strength Tm of the core steel wire is less than the average tensile strength Tn of the outer steel wire, and Tn≤4350-2000*dn Mpa.

On the other hand, the present invention also provides a method for preparing a layered structural steel cord, which is used to prepare the layered structural steel cord described in any one of the above, which includes the following steps:

Prepare the core strand steel wire group.

The core strand steel wires are arranged outside the rotating part of the double twisting machine, and the five outer steel wires are arranged inside the rotating part of the double twisting machine.

The core strand steel wire group is released from the I-shaped wheel a' point and is guided through the guide wheel b' point and the guide wheel c' point in sequence to the convergence point d'. At the same time, the five outer steel wires are released by the two I-shaped wheel e' The points are released separately, and are bundled together with the core strand steel wire group at the gathering point d′ to form steel cords.

The steel cords are twisted at point f' and point g' in turn, and then are collected on the I-shaped wheel after passing through the stress relief section.

Further, preparing the core strand steel wire group includes the following steps:

The two core strand steel wires are respectively released from point a of the two I-shaped wheels and bundled into a core strand steel wire group at the gathering point b.

The core strand steel wire group is twisted at point c of the guide wheel and point d of the guide wheel in turn, and then is collected on the I-shaped wheel after passing through the stress relief part.

Further, the double twisting machine includes a rotating part and a stress relief part. The rotating part can rotate around the axis of the double twisting machine, and is arranged symmetrically with respect to the axis of the double twisting machine.

Further, the stress relief part includes a twister and a straightener, and the twister and straightener are both located on the axis of the double twister.

Compared with the prior art, the beneficial effects achieved by the present invention are:

The layered structure steel cord provided by the present invention on the one hand solves the problem of large residual stress in the core strands after the outer layer of steel wires are removed from the steel cord. By making the average tensile strength of the inner layer of steel wires lower than that of the outer layer of steel wires, The average tensile strength, in addition, to maintain the breaking force of the steel cord without increasing the cost of the steel cord, the low tensile strength of the inner strand steel wire can resist the higher internal stress caused by multiple twists;

On the other hand, by adjusting the twist of the 2×dm core strands from counterclockwise to clockwise, the internal stress of the inner strands after secondary twisting is offset and the warping of the steel cord is improved;

This layered structure steel cord is used in the carcass or belt layer of radial tires, which can greatly improve the fatigue resistance of the tire, reduce the usage of steel cord and rubber, reduce rolling resistance, improve the overall performance of the tire, and reduce the wear and tear of the tire. Reduce manufacturing costs and reduce tire weight.

Description of the drawings

Figure 1 is a schematic structural diagram of a layered structure steel cord in an embodiment of the present invention;

Figure 2 is a schematic structural diagram of preparing a core strand steel wire group in an embodiment of the present invention;

Figure 3 is a schematic structural diagram of preparing layered structural steel cords in an embodiment of the present invention;

In the picture: 1 core strand steel wire, 2 outer steel wire, 3 stress relief part.

Detailed ways

The present invention will be further described below in conjunction with the accompanying drawings. The following examples are only used to more clearly illustrate the technical solutions of the present invention, but cannot be used to limit the scope of the present invention.

In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "upper", "lower", "front", "rear", "left", "right", " The orientations or positional relationships indicated by "vertical", "horizontal", "top", "bottom", "inner", "outer", etc. are based on the orientations or positional relationships shown in the drawings, and are only for the convenience of describing the present invention and The simplified description is not intended to indicate or imply that the device or element referred to must have a specific orientation, be constructed and operate in a specific orientation, and therefore should not be construed as a limitation of the present invention. In the description of the present invention, unless otherwise specified, "plurality" means two or more.

In the description of the present invention, it should be noted that, unless otherwise clearly stated and limited, the terms "installation", "connection" and "connection" should be understood in a broad sense. For example, it can be a fixed connection or a detachable connection. Connection, or integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium; it can be an internal connection between two components. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood through specific situations.

Example 1:

As shown in Figure 1, the layered structural steel cord provided by the embodiment of the present invention includes a core strand steel wire group and an outer layer steel wire group. The core strand steel wire group is located in the center of the outer layer steel wire group. The spiral directions of the core strand steel wire group and the outer layer steel wire group are the same, and the twist pitch and diameter of the core strand steel wire group are smaller than those of the outer layer steel wire group.

The core strand steel wire group is composed of two core strand steel wires 1 twisted clockwise, and the diameter dm range of the core strand steel wire 1 is 0.175mm≤dm≤0.300mm. The outer steel wire group is formed by braiding and twisting five outer steel wires 2 around the core strand steel wire group, and the diameter dn of the outer steel wires 2 ranges from 0.250mm≤dn≤0.380mm.

The average tensile strength Tm of the core steel wire 1 is less than the average tensile strength Tn of the outer steel wire 2, and Tm<Tn, Tn≤4350-2000*dn Mpa.

The core strand steel wire 1 has a diameter of 0.25mm, and the outer steel wire 2 has a diameter of 0.35mm to prepare a layered structural steel cord of 2×0.25+5×0.35UT as a sample.

Comparing the sample obtained in this example with the existing conventional structure 3×0.20+6×0.35HT steel cord, the specific parameter comparison is shown in Table 1:

Table 1: Parameter comparison between the sample of this embodiment and the steel cord of the prior art

steel cord structure 2×0.25+5×0.35UT 3×0.20+6×0.35HT Diameter(mm) 1.13 1.13 Linear density (g/m) 4.60 5.34 Twist length (mm) 7.0/14.0 10.0/18.0 twist S/S Z/S Breaking force(N) 1870 1850 Calendering density (root/dm) 55 55 Cord strength (N/dm) 93500 92500 Cord weight index (%) 90.9% 100%

Among them, the twist length refers to the length of the steel cord when the rotating part of the double twisting machine rotates once; the twist direction refers to the direction in which the rotating part of the double twisting machine rotates (S means counterclockwise, Z means clockwise); UT means ultra-high strength; HT is high intensity.

It can be seen from Table 1 that the strength level of the steel cord in this embodiment is ultra-high strength. When its diameter, linear density, lay length and other parameters are the same as those of the existing steel cord, the breaking force and cord strength are both higher than those of the existing steel cord. The technical steel cord is larger, indicating that the mechanical strength of the steel cord of this embodiment is superior to that of the prior art steel cord. Moreover, the calendered density and cord weight index of the sample of this embodiment are lower than those of the prior art steel cord, indicating that the steel cord of this embodiment achieves superior mechanical strength while also reducing the weight of the cord, effectively reducing tire manufacturing costs. , achieving lightweight tires.

Example 2:

This embodiment provides a preparation method for preparing the layered structural steel cord of Example 1, which includes the following steps:

First, the core steel wire 1 and the outer steel wire 2 are both made of wire rods. The preparation steps include:

The oxides present on the surface of the wire rod are removed by mechanical rust removal, followed by pickling and cleaning of the wire rod using chemical acid, and then the wire rod is washed in water and dried.

A one-time dry drawing operation is performed on the dried wire rod, and the wire rod with a diameter of 5.5mm is dry-drawn into a steel wire with a diameter d1 (d1 ranges from 1.00 to 2.50mm).

The wire is subjected to an annealing process, which is to austenitize again at a temperature of about 1000°C, and then quenched at a temperature of 600°C to 650°C to allow the transformation to pearlite. After the annealing treatment, copper is plated on the steel wire and zinc is plated on the copper, and thermal diffusion treatment is applied to form a brass coating.

Through the adjustment of the wet drawing mode and the compression rate of different passes, the final cross-section reduction process of the brass-plated steel wire is performed, so that the final diameter ranges from 0.175mm to 0.380mm single wire.

The monofilament prepared through the above steps has a final monofilament carbon content higher than 0.82% (weight), a tensile strength usually higher than 2000MPa, and is suitable for the manufacture of ultra-high-strength steel cords for radial tire carcass or belts. layer, it can greatly improve the tire's fatigue resistance and reduce the usage of steel cords and rubber.

Next, the steel cord is prepared through a double twister. The double twister includes a rotating part and a stress relief part 3. The stress relief part 3 is arranged on the axis of the double twister and includes a twister and a straightener. The rotating part is about the double twister. The axis of the twisting machine is symmetrically arranged, and it can rotate around the axis of the double twisting machine.

For the core strand steel wire 1, a monofilament with a diameter dm of 0.250mm is selected, and for the outer steel wire 2, a monofilament with a diameter dn of 0.350mm is selected to prepare the steel cord. The preparation steps are as follows:

As shown in Figure 2, two monofilaments are braided and twisted counterclockwise into a 2×0.25 core strand steel wire group. The braiding pitch of the core strands is L1=7.0mm. The specific operation is as follows:

The two single wires are respectively released from point a of the two I-shaped wheels and bundled into a core strand steel wire group at point b (aggregation point); the core strand steel wire group is twisted at points c and d of the guide wheel in turn, Then it is collected on the I-shaped wheel after passing through the stress relief part 3.

As shown in Figure 3, the core strand steel wire group is located at the center of the outer steel wire 2. The outer steel wire 2 is composed of five single wires and twisted clockwise around the core strand steel wire group into a 5×0.35 outer steel wire group. The outer steel wire 2 The twisting distance of the braiding is L2 = 14.0mm, thereby braiding and twisting into 2×0.25+5×0.35UT layered structure steel cord. The specific operation is as follows:

The core strand steel wire group is arranged outside the rotating part of the double twisting machine, and the five outer steel wires 2 are arranged inside the rotating part of the double twisting machine; the core strand steel wire group is released from the I-shaped wheel a' point and is guided through it in sequence Point b′ of the guide wheel and point c′ of the guide wheel reach point d′. At the same time, the five outer steel wires 2 are respectively released from the points e′ of the two I-shaped wheels and are bundled with the core strand steel wire group at point d′ (aggregation point). The steel cord is formed into a steel cord; the steel cord is twisted at points f' and g' in turn, and then is collected on the I-wheel after passing through the stress relief part 3.

Assume that the average tensile strength of the core strand steel wire group is Tm, and the average tensile strength of the outer steel wire group is Tn. When the strength grade ratios of Tm and Tn are different, the residual stress of the inner strands of the steel cord is as follows:

Tm>Tn, 2×dm+5×dn inner strand torsion value -10t/m;

Tm＜Tn, 2×dm+5×dn inner strand torsion value -6t/m;

Since the residual stress of the inner core strands of the steel cord rotates counterclockwise to a large value, which can easily cause the steel cord to warp when cut, the embodiment preferably has Tm<Tn, and satisfies Tn≤4350-2000*dn (dn is the diameter of the outer steel wire). .

Since the core strand torsion standard is It is clockwise (+), that is, +X±3t/6m.

Assuming that X=10, the residual stress of the inner strands of the steel cord is:

-X±3t/6m, that is, -10±3t/6m, 2×dm+5×dn inner strand torsion value -6t/m;

0±3t/6m, that is, 0±3t/6m, 2×dm+5×dn inner strand torsion value -2t/m;

+X±3t/6m, that is, +10±3t/6m, 2×dm+5×dn inner strand torsion value +0.5t/m;

When the value of Residual stress 0±2t/m control requirement.

Comparing the layered structural steel cord prepared in this embodiment with the steel cord prepared by the improved process, as shown in Table 2:

Table 2: Comparison between the layered structure steel cord of the present invention and the steel cord prepared by the improved process

As can be seen from Table 2, the present invention adjusts the twist of the 2×dm core strands from counterclockwise to clockwise, which offsets the internal stress of the inner strands after secondary twisting and improves the steel cord warping.

The above are only preferred embodiments of the present invention. It should be noted that those of ordinary skill in the art can also make several improvements and modifications without departing from the technical principles of the present invention. These improvements and modifications It should also be regarded as the protection scope of the present invention.

Claims (10)

1. A layered structure steel cord, characterized in that: the core strand steel wire group is formed by twisting two core strand steel wires, the outer layer steel wire group is arranged on the periphery of the core strand steel wire group and is formed by twisting five outer layer steel wires around the core strand steel wire group, and the diameter of the core strand steel wires is smaller than that of the outer layer steel wires.

2. A layered structure steel cord according to claim 1, characterized in that: the twisting directions of the core strand steel wire groups and the outer layer steel wire groups are the same.

3. A layered structure steel cord according to claim 1, characterized in that: the twisting lay length of the core strand steel wire group is smaller than that of the outer layer steel wire group.

4. A layered structure steel cord according to claim 1, characterized in that: the torsion direction of the core strand steel wire is clockwise.

5. A layered structure steel cord according to claim 1, characterized in that: the diameter dm of the core strand steel wire is in the range of 0.175 mm-dm-0.300 mm, the diameter dn of the outer layer steel wire is more than or equal to 0.250mm and less than or equal to 0.380mm.

6. A layered structure steel cord according to claim 5, characterized in that: the average tensile strength Tm of the core strand steel wire is smaller than the average tensile strength Tn of the outer layer steel wire, and Tn is less than or equal to 4350-2000 dn Mpa.

7. A preparation method of a layered structure steel cord is characterized by comprising the following steps: the preparation method is used for preparing the layered structure steel cord according to any one of claims 1 to 6, and comprises the following steps:

preparing a core strand steel wire group;

the core strand steel wires are assembled outside the rotating part of the double twisting machine, and the 5 outer layer steel wires are arranged inside the rotating part of the double twisting machine;

the core strand steel wire group is discharged from the spool a 'and is led to sequentially pass through the guide wheel b' and the guide wheel c 'to reach the aggregation point d', and meanwhile, 5 outer layer steel wires are respectively discharged from the two spools e 'and are clustered with the core strand steel wire group at the aggregation point d' to form a steel cord;

the steel cord is twisted by the point f 'and the point g' respectively, and then is collected on the spool after passing through the stress relief part.

8. The method of manufacturing a layered structure steel cord according to claim 7, characterized in that: preparing a core strand steel wire set, comprising the following steps:

2 core strand steel wires are respectively discharged from two spool points a and clustered into a core strand steel wire group at a polymerization point b;

the core strand steel wire group is twisted by the guide wheel point c and the guide wheel point d respectively in turn, and then is collected on the spool after passing through the stress relief part.

9. The method of producing a layered structure steel cord according to claim 7 or 8, characterized in that: the double twisting machine comprises a rotating part and a stress relieving part, wherein the rotating part can rotate around the axis of the double twisting machine and is symmetrically arranged around the axis of the double twisting machine.

10. The method of manufacturing a layered structure steel cord according to claim 9, characterized in that: the stress eliminating part comprises an over-twister and a straightener, and the over-twister and the straightener are both arranged on the axis of the double-twister.