KR20090099208A - Steel cord - Google Patents

Abstract

A steel cord is provided to improve durability of a tire by preventing moisture and salinity from permeating into an air gap between an inner layer and an outer layer. A steel cord is composed of an inner layer, a lapping layer, and an outer layer. The inner layer includes first filaments of n1 which are twisted with a first direction and a first length(P1). The lapping layer covers the inner layer, and includes second filaments(12) of n2 which are twisted with a second direction and a second length(P2). The outer layer includes third filaments(13) of n3 which are twisted with a third direction and a third length(P3). The n1 is the number of 1-3, the n2 is the number of 1-2, and the n3 is the number of 5-9. The first filament and third filament have carbon of 0.85-0.95% and tensile strength of 340-380kgf/mm^2.

Description

Steel cord

The present invention relates to a steel cord used as a tire reinforcing material and a manufacturing method thereof, and more particularly, to a steel cord further comprising a wrapping layer between an inner layer and an outer layer.

Steel cord is one of several kinds of reinforcing materials used for reinforcing various rubber products including vehicle tires and industrial belts. Among them, steel cords are widely used as tire reinforcement materials because of their excellent tensile strength, modulus, heat resistance, heat transfer rate, fatigue resistance, and rubber adhesiveness, and their usage is increasing day by day.

Among them, the double-structured steel cords are made of two or three layers of filaments, mainly developed for trucks and buses. Representative standards of the above-described double-structure steel cord are 3 + 6, 3 + 9, 3 + 9 + 15 steel cord. Looking at the structure of the 3 + 9 steel cord in more detail, first the core (core) filament is located in the inner layer (內層) is made of three filaments are twisted in a certain direction. In the outer layer surrounding the core, nine filaments are in close contact with the core layer, and thereafter, a spiral wrap, which is a single filament surrounding the outer layer, may additionally exist. Here, the three filaments constituting the inner layer are twisted with each other. The outer layer is stranded so that the inner layer and the filament diameter (also referred to as a wire diameter) and the twist direction are the same, but the twist length is different. In addition, the spiral wrap is stranded in a direction opposite to the twisting direction of the outer layer.

Hereinafter, the manufacturing method of the conventional steel cord is demonstrated.

First, a wire rod having a diameter of 5.0 to 5.5 mm consisting of carbon steel having a carbon content of 0.6 to 0.82 wt% is first drawn to a diameter of 1.0 to 2.5 mm. Thereafter, heat treatment and brass plating are performed, and final drawing is performed to prepare a filament having a diameter of 0.1 to 0.4 mm and a tensile strength of 280 to 320 kgf / mm 2. Various structures of the filament according to the use (1 × 2, 1 × 3, 2 + 2, 2 + 7, 3 + 6, 3 + 8, 3 + 9 + 15, 1 + 18, 3/8 + 13) Etc.) to finish the steel cord.

However, the steel cord is a normal tensile product having a tensile strength of 280 to 320 kgf / mm 2 of the filament, and the tensile strength is low. In addition, there is a problem that the cost of steel cord is expensive because the spiral wrap process must go through a three-step process. In addition, when the cut section is seen after manufacture, there is almost no gap between the filaments of the outer layer and the inner layer, and the rubber adhesion force is reduced due to the difficulty of infiltrating the rubber into the steel cord during the rubber topping. When water or salt penetrates, the voids between the filaments that are not penetrated into the rubber become a moving passage of water or salt, and the corrosion of the steel cord is promoted by repeated bending of the tire, resulting in tire durability. There is a big issue with this falling. In addition, when the steel cord is applied to a tire, wear and tear fatigue caused by addition of friction and moisture due to incomplete line contact or point contact between the filaments forming the steel cord ( 타이어; tire durability was deteriorated due to fretting fatigue. That is, if the inner layer and the outer layer, and the spiral wrap or the twist length of the spiral wrap is different to form an incomplete line contact, the wear progresses rapidly due to friction during the bending of the tire.

Several attempts have been made to remedy this problem.

First, Japanese Patent No. Hei 7-109685 proposed a steel cord having a 3 + 8 structure. This steel cord was designed to create a gap by removing one of the outer 9 wires and then to change the diameters of the inner 3 wires and the outer 8 wires to improve rubber permeability through the gap, thereby improving tire durability. In addition, Japanese Patent No. Hei 10-131065 discloses a method in which the mold of the three inner layers above is made larger than the outer nine lines (or eight lines) to form a gap to improve rubber penetration into the inner layer. Japanese Patent No. Hei 10-292277 has proposed a method of improving rubber permeability by preforming the inner three wires.

However, if you look at the patents proposed so far, the tensile strength of the wire is 280 ~ 320kgf / ㎜ normal tensile and High Tensile steel cords with low tensile strength, reducing the durability or increase the use of steel cords There is a risk of deterioration of rolling resistance, and the twisting length of the filament is different, or the steel cord is formed differently in the twisting direction, and there is a risk of rapid wear due to incomplete line contact or point contact.

An object of the present invention is to improve the rubber adhesive force and the core rubber adhesive force when the tire is applied, and to prevent the penetration of moisture or salts between the pores of the inner layer and the outer layer, thereby improving durability and maintaining sufficient tensile strength in a small amount. It is to provide a steel cord that can reduce weight, reduce cost and improve fuel economy.

In order to solve the above problems, the present invention has an inner layer comprising a twisted n ₁ of the first filament in a first direction and a first length; A wrapping layer surrounding the inner layer and including n ₂ second filaments twisted in a second direction and a second length; And an outer layer surrounding the lapping layer, the outer layer including n ₃ third filaments twisted in a third direction and a third length.

Steel cord of the present invention, the inner layer is naturally open by the wrapping of the filament of the inner layer to improve the rubber adhesive force and the core rubber adhesive force when applying the tire. In addition, penetration of moisture or salts is prevented between the pores of the inner layer and the outer layer, thereby improving durability. In addition, since the steel cord is manufactured from a filament made of high carbon steel having a carbon content of 0.85 to 0.95%, sufficient tensile strength can be maintained in a smaller amount than conventional steel cords, thereby reducing tire weight, reducing costs, and improving fuel efficiency. Can be.

Hereinafter, exemplary embodiments of the present invention will be described with reference to the accompanying drawings. In the accompanying drawings, the length, the diameter of the line, etc. may be exaggerated for convenience. Like numbers refer to like elements throughout.

1 is a plan view of a steel cord according to an embodiment of the present invention, Figure 2 is a cross-sectional view of FIG.

1 and 2, a steel cord includes an inner layer including n _one first filaments 11 twisted in a first direction and a first length P1, and surrounds the inner layer and has a second direction and a second length ( A lapping layer comprising n _two second filaments 12 twisted with P2), an outer layer surrounding the lapping layer and including n _three third filaments 13 twisted in a third direction and a third length P3; Include.

 The first and third filaments 11 and 13 are made of high carbon steel having a carbon content of 0.85 to 0.95%, a tensile strength of 340 to 380 kg / mm 2, and diameters d 1 and d 3 of 0.20 to 0.40 mm. . The second filament 12 is made of low carbon steel having a carbon content of 0.60 to 0.70, and has a tensile strength of 250 to 300 kgf / mm 2. The diameter d2 of the second filament 12 is 30 to 50% of the diameters of the first and third filaments d1 and d3, and when the above range is satisfied, the diameter and the structural stability of the cord are prevented from being lowered. can do.

Preferably, the first direction and the third direction are the same direction, and the first and third directions and the second direction are opposite to each other. Preferably, the first length P1 and the third length P3 are equal to each other, and the first and third lengths P1 and P3 are preferably 5 to 40 mm. When the above-mentioned range is satisfied, the structural stability can be prevented from deteriorating. The second length P2 is P1 × (0.2 to 1). If the above range is satisfied, there is an advantage that the rubber penetration force is improved. N ₁ is preferably 1 to 3, n ₂ is 1 to 2, and n ₃ is preferably 5 to 9. When satisfying the above-described range, there is an advantage that can implement a steel cord having a stable two-layer structure.

This concludes the description of the steel cord according to an embodiment of the present invention.

Steel cord of the present invention is naturally open by the wrapping of the filament of the inner layer to improve the rubber adhesive force and the core rubber adhesive force when the tire is applied. In addition, penetration of moisture or salts is prevented between the pores of the inner layer and the outer layer, thereby improving durability. In addition, since the steel cord is manufactured from a filament made of high carbon steel having a carbon content of 0.85 to 0.95%, sufficient tensile strength can be maintained in a smaller amount than that of a conventional steel cord, thereby reducing tire weight, reducing cost, and improving fuel efficiency. have.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the following Examples are for the purpose of explanation and are not intended to limit the present invention.

1) Example 1

After the wire rod having a carbon content of 0.92% and a diameter of 5.5 mm was fresh, heat treatment and brass plating were carried out, and finally drawn to a diameter of 0.32 mm to prepare first and third filaments having a tensile strength of 340 kgf / mm 2. Thereafter, three strands of the first filament were twisted in the S (clockwise) direction with an 18 mm twist length to form an inner layer. Subsequently, while wrapping the inner layer, a second filament having a carbon content of 0.70%, a tensile strength of 280 kgf / mm 2, and a diameter of 0.15 mm was twisted in a 9 mm twist length in the Z (counterclockwise) direction to form a lapping layer. While wrapping the lapping layer, the third filament was twisted in an S (clockwise) direction with an 18 mm twist length to form an outer layer. This produced (3 + W) /8×0.32ST steel cords. The results of testing the physical properties are shown in Table 1 below.

2) Example 2

After the wire rod having a carbon content of 0.92% and a diameter of 5.5 mm was fresh, heat treatment and brass plating were performed, and the wire was finally drawn to a diameter of 0.20 mm to prepare first and third filaments having a tensile strength of 340 kgf / mm 2. Thereafter, the first three filament strands were twisted in a S (clockwise) direction with a twist length of 12 mm to form an inner layer. Subsequently, while wrapping the inner layer, a second filament having a carbon content of 0.70%, a tensile strength of 280 kgf / mm 2, and a diameter of 0.10 mm was stranded in a twist length of 6 mm in the Z (counterclockwise) direction to form a lapping layer. While wrapping the lapping layer, eight strands of the third filament were twisted in a S (clockwise) direction with a length of 12 mm to form an outer layer. This completed the (3 + W) /8×0.20ST steel cord. The results of testing the physical properties are shown in Table 1 below.

3) Comparative Example 1

After the wire rod having a carbon content of 0.82% and a diameter of 5.5 mm was fresh, heat treatment and brass plating were performed, and a final filament having a tensile strength of 300 kgf / mm 2 was prepared by final drawing to a diameter of 0.35 mm. Thereafter, three filament strands were twisted in a S (clockwise) direction with a 9 mm twist length to form an inner layer. Subsequently, the eight layers of the filament were twisted in the S (clockwise) direction with an 18 mm twist length while surrounding the inner layer to form an outer layer. This completed a 3 + 8 × 0.35HT steel cord. The results of testing the physical properties are shown in Table 1 below.

4) Comparative Example 2

After the wire rod having a carbon content of 0.82% and a diameter of 5.5 mm was fresh, heat treatment and brass plating were performed, and a final filament having a tensile strength of 300 kgf / mm 2 was prepared by final drawing to a diameter of 0.22 mm. Thereafter, three filament strands were twisted in a S (clockwise) direction with a twist length of 12 mm to form an inner layer. Subsequently, while wrapping the inner layer, eight filament strands were twisted in a S (clockwise) direction with a twist length of 12 mm to form an outer layer. This completed the 3/8 × 0.22HT steel cord. The results of testing the physical properties are shown in Table 1 below.

Item unit Example 1 Example 2 Comparative Example 1 Comparative Example 2 (3 + W) /8×0.32ST (3 + W) / 8 x 0.20 ST 3 + 8 × 0.35HT 3 + 8 × 0.22HT Twist length and direction Inner layer Mm 18 mm S 9 mm S 12 mm S 6 mm S Outer layer Mm 18 mm S 18 mm S 12 mm S 12 mm S First and third filament diameter Mm 0.32 0.20 0.35 0.22 Twist Length and Direction of Second Filament Mm 9 mm Z 6 mm Z - - 2nd filament diameter Mm 0.15 0.10 - - Steel cord diameter Mm 1.48 0.91 1.47 0.90 Cutting load Kgf 323 130 296 126 Unit weight g / m 7.32 2.80 8.43 3.35 Rubber Penetration Test Time / 30mm 83 sec. 89 sec. 18sec. 20sec Deep Rubber Adhesion Kg / 1in 37 25 20 13

In the present invention, the concept of the deep rubber adhesive force, rubber penetration force is as follows.

* Evaluation method of deep rubber adhesive force (㎏ / 1in)

The steel cord was coated with 6 mm thick rubber from the top and bottom to prepare a rubber block having a length of 25.4 mm, and then vulcanized for 150 ° C. × 30 minutes (same as the mold in the rubber adhesion test) to the outer layer of the steel cord. After removing all the filaments located, the adhesive force of the three filament strands was evaluated.

* Rubber penetration (Time / 30㎜)

Prepare the sample by coating the prepared steel cord with rubber of 6mm thickness from the top and bottom and cutting the rubber cord inserted part of the mold which was vulcanized for 150 ℃ × 30 minutes in parallel with the rubber mold after manufacturing the rubber block of 12.7mm length. . Nitrogen gas was blown into the steel cord injected part of the sample at a constant pressure, and the amount of nitrogen gas from the opposite side was measured at the water level to evaluate the rubber penetration force. The better the rubber penetration, the longer it takes to raise the 30mm water level.

1 is a plan view of a steel cord according to an embodiment of the present invention.

2 is a cross-sectional view of a steel cord according to an embodiment of the present invention.

<Description of the symbols for the main parts of the drawings>

11: first filament 12: second filament

13: third filament d1: diameter of first filament

d2: diameter of second filament d3: diameter of third filament

P1: first length P2: second length

P3: 3rd length

Claims (6)

The inner layer comprises a twisted n ₁ of the first filament in a first direction and a first length; A wrapping layer surrounding the inner layer and including n ₂ second filaments twisted in a second direction and a second length; And And an outer layer surrounding the wrapping layer, the outer layer including n ₃ third filaments twisted in the first direction and the first length. The method according to claim 1, N ₁ is 1 to 3, n ₂ is 1 to 2, and n ₃ is a steel cord, characterized in that 5 to 9. The method according to claim 1, The first filament and the third filament each have a carbon content of 0.85 to 0.95%, a tensile strength of 340 to 380 kgf / mm2, and a diameter of 0.2 to 0.4 mm. The method according to claim 1, The second filament has a carbon content of 0.60 to 0.70%, a tensile strength of 200 to 300 kgf / mm 2, and a diameter of 30 to 50% of the diameter of the first filament and the third filament. The method according to claim 1, The first direction is a direction opposite to the second direction, the steel cord, characterized in that the same direction as the third direction. The method according to claim 1, The first length and the third length are 5 to 40 mm, and the second length is 0.2 to 1 times the first length and the third length.

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