KR20050050765A - Steel code for pneumatic radial tire - Google Patents

Abstract

The present invention relates to a steel cord for pneumatic radial tires, and more particularly, the steel cord for pneumatic radial tires for truck buses of the present invention is a core wire composed of two filaments having different diameters, and 5 to 7 strands. Fretting wear when steel cord of the present invention is used as a reinforcement for belts of pneumatic radial tires or rubber compositions of carcass plies as a steel cord consisting of a side line composed of filaments and an outermost side line composed of 10 to 14 strands of filaments. And provide excellent tensile properties.

Description

Steel Code for Pneumatic Radial Tires {Steel Code for Pneumatic Radial Tire}

The present invention relates to a steel cord for a pneumatic radial tire, and more particularly, to a pneumatic ring consisting of two cores composed of filaments having different diameters, five to seven strands, and 10 to 14 outermost strands. A steel cord for a radial tire.

The steel cord is a reinforcement of the belt of pneumatic radial tires or of the rubber composition of the carcass ply, the general structure of which is shown in FIG. 1. That is, it is a 3 + 9 + 15 + w structure which has 3 strands in a core wire, 9 strands in a side line, 15 strands in an outermost side line, and a wrapping filament. However, such steel cords have a densely arranged arrangement of 15 strands of the outermost layer and 9 strands of side lines, so that rubber penetration into the structure is not easy. Therefore, a fine flow of the core wire is generated by repeated deformation applied to the carcass while the tire is running, which leads to abrasion between the filament and the filament, resulting in fretting wear and a decrease in strength of the carcass cord. Occurs. Decreased carcass cord strength is a major cause of reduced tire life and reduced regeneration. In addition, the low permeability of the rubber becomes vulnerable to the occurrence of corrosion due to moisture and NaCl infiltration caused by the trauma occurring during driving or the infiltration of moisture present in the rubber composition. The occurrence of corrosion leads to a decrease in tensile strength of the steel cord, which reduces its lifespan. In particular, breakage of the adhesive interface due to galvanic corrosion or the like leads to sudden destruction of the tire while driving.

In order to improve this, a compact structure having a 1 + 18 structure as shown in FIG. 2 has been developed and used. The 1 + 18 structure enables one-step manufacturing, which reduces the manufacturing cost, and because the filament and the filament make line contact, the fret compared to the 3 + 9 + 15 + w structure having a point contact form It can improve the resistance to casting wear. However, due to the inherent low rubber permeability of the compact structure, the original solution to the fritting wear is not possible. In addition, the carcass cord corrosion caused by low rubber permeability and the reduction of tire life were not solved. In addition, since one strand of the core wire is stranded in a straight line without a mold part, the load and tension applied to the carcass cord are concentrated in the core wire, causing uneven stress distribution throughout the carcass cord and reducing the elongation at break. Its disadvantage is its poor properties.

Therefore, the present invention reduces the freting wear by increasing the rubber permeability to increase the life of the tire and to distribute the load and tension applied to the carcass cord to uniform the stress distribution to improve the cutting elongation structure To provide.

That is, one aspect of the present invention is to provide a steel cord for pneumatic radial tires consisting of two strands of cores composed of filaments of different diameters, 5 to 7 strands and 10 to 14 outermost strands.

Hereinafter, the present invention will be described in more detail.

Steel cord for pneumatic radial tire of the present invention is a core of two filaments of different diameters, the side line is made of 5 to 7 filament, the outermost side line is made of 10 to 14 filament, in Figure 3 Steel cords for pneumatic radial tires of the structure 1x2 + n + m (n: 5-7, m: 10-14) as shown.

That is, when the total diameter of the 1 × 2 structure having two core wire diameters different from each other is larger than the internal space formed by the side lines, a space is provided between the side line filaments to induce the opening of the entire structure. Therefore, it is possible to improve the permeability of the rubber composition. In addition, in the case of 1 × 2 structure, asymmetrical structures having different diameters of the core wires are formed, and thus the freting wear can be eliminated as it is difficult to move inside the sideline. This has the effect of weight reduction because the 1 × 2 structure has a smaller weight per unit length when compared to a single strand in a compact 1 + 18 structure or when both cores form the same core diameter. In addition, in the elongation at break, the elongation of the 1 × 2 structure having the mold part in each filament is larger than the elongation at one strand of the straight line, which shows excellent properties in terms of tensile properties.

In the steel cord of the present invention, the relationship between the diameter (d1) of the larger diameter filament and the diameter (d2) of the smaller diameter filament in the two strands of the core wire is D1 (= d1 / d2) value 1.2 <d1 / d2 <3.3 It is desirable to satisfy. If D1 is less than 1.2, it is difficult to give a regular wave to the side line by twisting of the core wire, and thus the problem of deterioration of rubber permeability may occur.If D1 is more than 3.3, it is difficult to twist the two strands. This is because a problem that may become very unstable may occur.

The relationship between the diameter (d3) of the side line and the outermost side line and the diameter (d1 and d2) of the core wire, D2 (= (d1 + d2) / d3) satisfies 1.0 ≤ (d1 + d2) / d3 ≤ 1.7 desirable. If D2 is less than 1.0, it may not induce an open in the sideline, and if it exceeds 1.7, it may cause a problem that the sideline becomes unstable.

It is preferable that the length L1 of the twist of the two filaments and the length L2 of the twist of the side line satisfy the relationship of 1≤L2 / L1≤2.5 in the core wire. When the value of L2 / L1 is less than 1, when tension is applied to the steel cord, a stress concentration phenomenon may occur in the core and a breakage of the core due to stress may occur. As in the case, flare (cord loosening, flare) may occur during the early breakage and cutting of the side line due to tension, which may cause the cord to become unstable and reduce workability in the tire manufacturing process. In addition, it is preferable that the length L3 of the twist of the outermost side line is (d1 + d2) ≦ L3 / 5π ≦ (d1 + d2 + d3). If L3 / 5π is less than (d1 + d2), premature breakage of core and side lines may occur due to stress concentration, and if it is larger than (d1 + d2 + d3), flare of outermost side line may occur. to be.

In the twisting direction of the filament, it is preferable that the twisting directions of the core line and the side line are the same direction while the twisting directions of the side line and the outermost side line are opposite directions.

Furthermore, it is more preferable that the filament diameter used for the said side line and said outermost side line is 0.10 mm-0.30 mm. In the case of wires of 0.10mm or less, it is difficult to produce wires with sufficient tensile strength, and application of wires of 0.10mm or less causes an increase in manufacturing cost.In the case of wires of 0.30mm or more, 0.30 at the final drawing stage This is because the processing amount is lower than that of wires of mm or less, which leads to a decrease in tensile strength. Therefore, when wire wires of 0.30 mm or more are applied, cutting strength is lowered, thereby reducing the weight.

The filaments of the core wire, the side wire and the outermost side wire used in the present invention are carbon steels, and the wire content of the carbon content is 0.7% to 0.95%, and the strength is preferably 2500 MPa to 4000 MPa. In addition, it is preferable that the relationship between the strength (s1) of the large diameter filament and the strength (s2) of the small diameter filament, S1 (= s2 / s1) is greater than 0.8 and less than 1 of the two strands of the core wire. This is because the smaller diameter of the filaments plays a greater role in imparting the wave form of the core than the strength of the stranded steel cord. Therefore, when S1 exceeds 1, the stranded core wire has a uniform shape rather than a wave shape, and as a result, rubber permeability can be reduced. If S1 is less than 0.8, the wave form becomes very irregular and the twisting of the lateral line becomes unstable.

Hereinafter, the present invention will be described in more detail with reference to examples, but these examples are only for illustrating the present invention and are not intended to limit the protection scope of the present invention.

Examples and Comparative Examples 1-2

Steel cords were prepared as shown in Table 1 below to compare the physical properties of each steel cord. The steel cord was manufactured using a conventional method, and cutting strength and elongation were measured by ASTM D 2969. The measuring instrument used Tensile Testing Apparatus from INSTRON. The steel cord for pneumatic radial tires produced in the examples was 250 mm long and the tensile speed was 50 mm / min. The strength and elongation at break were automatically recorded by the computer. Adhesive force was also measured by the ASTM D 2229 method using an INSTRON company. As a result, the steel cord according to the present invention showed excellent results in terms of unit weight, elongation, and aging adhesive strength compared to the steel cord having a 3 + 9 + 15 + w structure or a 1 + 18 compact cord. The results are shown in Table 1 below. The physical property of Table 1 shows the relative value which made the physical property of an Example 100%.

Item Example Comparative Example 1 Comparative Example 2 Structure (diameter of filament) 1 (0.13) X1 (0.11) + 6 + 12 (0.22) HT 1 (0.24) +18 (0.22) HT 3 + 9 + 15 (0.22) + w Twist Length (Twisting Direction) 10.0 / 18.0 / 30.0 (S / S / Z) -/ 30.0 (-/ Z) 6.5 / 0.43 / 0.55 / 3.5 (S / S / Z / S) Unit weight 100 102 142 Cutting strength 100 100 130 Elongation 100 90 100 Code 100 100 132 Aging Adhesion Salt aging 3 weeks 100 85 73 Heat Resistance Aging 3 Weeks 100 53 67

Steel cord of 1 × 2 + n + m structure having different diameters of two core wires according to the present invention has improved rubber permeability, thereby reducing freting wear and increasing tire life and applying to carcass cord. It distributes the load and tension to make the stress distribution uniform, providing the effect of improving the elongation at break.

Figure 1 shows a steel cord cross-sectional structure of a conventional 3 + 9 + 15 + w structure, Figure 2 is a cross-sectional structure of a compact steel cord of 1 + 18 structure, Figure 3 is a steel cord according to the present invention It is a cross-sectional structure.

(Description of the main parts of the drawing)

1 ...

2 ... side line

3.Outermost side line

Claims (6)

Steel cord for pneumatic radial tires consisting of two strands of different diameter filaments, 5 to 7 strands and 10 to 14 outermost strands. The diameter (d1) of the larger diameter filament and the diameter (d2) of the smaller diameter filament, the diameter (d3) of the filament used for the side line and the outermost side line of the two strands of the core wire is 1.1≤ A steel cord for a pneumatic radial tire, characterized by satisfying a relationship of d1 / d2 ≦ 3.3 and 1.0 ≦ (d1 + d2) /d3≦1.7. The steel cord for a pneumatic radial tire according to claim 1, wherein the filament diameter d3 used for the side line and the outermost side line is 0.10 mm to 0.30 mm. The filament of claim 1, wherein the filaments of the core wire and the side wire are carbon steels, the wire content of which is from 0.7% to 0.95% of carbon, and the strength of the filament has a value of 2500 MPa to 4000 MPa and the larger diameter of the two strands A steel cord for pneumatic radial tires, characterized in that the relationship between the filament strength s1 and the small diameter filament strength s2 satisfies 0.8 ≦ S1 (= s2 / s1) ≦ 1. The steel cord for pneumatic radial tires according to claim 1, wherein the twist length L1 of the two core wires and the twist length L2 of the side lines satisfy a relationship of 1≤L2 / L1≤2.5. The steel for pneumatic radial tires according to claim 1, wherein the twist length L3 of the outermost side line satisfies a relationship of (d1 + d2) ≤ L2 / 5π ≤ (d1 + d2 + d3). code.