KR20000055075A - Steel cords - Google Patents

Abstract

PURPOSE: A steel cords is provided which decreases rolling resistance given to a tire by reducing a number of filaments constituting the cords and has improved durability. CONSTITUTION: A steel cords is prepared by: (i) plating line materials which is made of carbon steel having a carbon content of 0.70-0.90 wt.% and has a diameter of 0.10-0.40 millimeter with brass in a thickness of 0.1-0.4 micrometer; (ii) freshly processing the step (i); and (iii) twisting the obtained two main filaments as 1 & times 2 structure.

Description

Steel Cords {Steel Cords}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a steel cord for reinforcing rubber products used for reinforcing belts in radial and bias tires, and more specifically, two filaments after wet drawing of carbon steel. The steel cord for reinforcing rubber products that can further improve the fuel economy performance when driving by reducing rolling resistance of the tire by twisting the two to 1 × 2 structure.

Steel cords are used to reinforce rubber products such as tires, high pressure hoses, conveyor belts, etc. because they have superior strength, modulus, heat resistance, and fatigue resistance compared to other types of inorganic and organic fibers. In general, steel belts used for tires are manufactured by coating a rubber layer on steel cords made by twisting a plurality of metal wires, and steel cords are usually coated on a wire surface of carbon steel having a carbon content of 0.6 to 0.95% by weight. To 0.4μm-thick brass plating, followed by wire drawing, and the obtained wire rods have various structures (1 × 3, 1 × 4, 2 + 2, 2 + 7, 3 + 6, 3 + 9 + 15, etc.). Prepared by twisting).

As the global environmental pollution problem has emerged as an important issue around the world, research is being actively conducted to improve fuel efficiency of automobiles in the automobile industry. In order to improve the fuel efficiency of a vehicle, it is required to reduce the weight of the tire and to increase the strength and weight of the tire reinforcement. When the vehicle is driven, the tire is subjected to repeated up and down torsional change as the load increases and decreases, and energy loss occurs due to the hysteriesis between the load and the torsion, which causes rolling resistance. The higher the rolling resistance, the worse the fuel economy performance when driving a car. Therefore, in order to improve fuel efficiency, it is necessary to reduce rolling resistance that hinders the progress of the tire when driving a vehicle, and a method of reducing rolling resistance is to lighten the tread portion of the tire.

Conventionally, steel cords used for reinforcement of tires have a structure made by twisting at least three filaments with each other (2 + 2, 2 + 7, etc.), and steel belts using such steel cords have a large weight per unit area Since the resistance is relatively large and many filaments are manufactured by twisting the filaments, the contact point between the filaments has a problem of causing a fretting phenomenon in which wear occurs easily.

The present invention overcomes the problems of the prior art described above, rolling resistance applied to the tire by reducing the number of filaments constituting the cord compared to three or more steel cords used as reinforcement of the existing tire steel belt portion It is possible to reduce the resistance and to provide a steel cord with improved durability.

That is, according to the present invention, two filaments obtained by drawing a wire after brazing the wire with a diameter of 0.10 to 0.40 mm made of carbon steel having a carbon content of 0.70 to 0.90% by weight are twisted into a 1 × 2 structure. It is to provide a steel cord characterized by.

1 is a schematic cross-sectional view of a typical tire,

2 is a view for explaining the concept of a 1 × 2 steel cord according to the present invention.

Hereinafter, the present invention will be described in more detail with reference to the accompanying drawings.

The steel cord of the present invention can be used for reinforcement in steel belt portions inside radial and bias tires, as shown in FIG.

The rolling resistance (R) acting on the tire when driving a car depends on the flexibility of the steel cord. It may be represented by Equation 1 of E. Dorr.

R = μW

In the above formula, μ is the rolling resistance coefficient of the following equation (2), W is the load acting on the tire (Ref .: New Automotive Engineering, p207, the same company).

In Equation 2, p is the tire internal pressure, v is the rotational speed of the tire and ω means the tire load.

The present invention is the above. It was conceived from the equation of rolling resistance of D'Or, and the number of filaments constituting the cord is reduced to 2 (1 × 2 structure) as compared to the steel cords of 3 or more used for reinforcement of steel belts. Therefore, when applied to tires, the steel cord can reduce the rolling resistance coefficient (μ) by reducing the weight and tire load per unit area of the tread part, thereby ultimately reducing the rolling resistance and improving fuel efficiency when driving a car. .

Specifically, the steel cord of the present invention is wet drawn to a filament diameter of 0.1 to 0.4mm in diameter using carbon steel having a carbon content of 0.70 to 0.90% by weight and twisted two filaments to each other as shown in FIG. It is manufactured in two structures. In the present invention, when the filament diameter exceeds 0.4mm, the critical load is excellent but the fatigue life is lowered, which is due to the decrease in fatigue life as the filament diameter increases and the contact point between the filaments increases.

In the 1 × 2 steel cord of the present invention, the twist pitch is 3 mm to 20 mm, the cord diameter is preferably 0.20 mm to 0.80 mm, and the tensile strength of the filaments constituting the steel cord is 280 to 360 kg / mm 2. need.

For example, when the structure of the 1 × 2 steel cord structure of the present invention is 0.82 wt% of carbon content, 0.3 mm of filament diameter and 9.5 mm of twisted pitch, it is used in reinforcement of existing tire belt parts. Compared to the steel cord of 2 + 2 × 0.25 structure disclosed in 57-193253, the critical load at which the steel cord embedded in the end of the tire belt and rubber begins to separate increases by 20% and weight by 12%. Thus, the steel cord of the present invention has a rolling resistance of 10% less than the steel cord of 2 + 2 × 0.25 structure embedded in the tire in the same way.

In addition, when the flexibility of the 1 × 2 steel cord of the present invention was measured by a tabor stiffness tester, the flexibility was found to be 60 g or less, the critical load was 108 kg / mm 2, and the critical strain at this time did not exceed 11%.

Furthermore, since the steel cord of the present invention is manufactured by twisting two filaments, it is possible to reduce the production cost compared to the existing cord composed of three or more filaments, and to make the thickness of the reinforcing material thin, and to be lightweight and simple in structure to provide flexibility ( flexibility has an advantage. When opening two filaments of the 1 × 2 steel cord of the present invention can improve the rubber penetration.

Table 1 below compares the 1 × 2 steel cord of the present invention with 2 + 2 × 0.25, and 2 + 7 × 0.22 steel cords used to reinforce conventional tire steel belts.

2 + 7x0.22 2 + 2x0.25 2x0.3 SHT Burial number of steel cord per 1cm of rubber 6.30 7.87 9.45 Cord diameter (mm) 0.838 0.686 0.610 Critical load (kg / mm ² ) 90 90 108 Critical strain (%) - 10.7 10.9 Tensile Strength of Filament (kg / mm ² ) 300 300 320

The through Table 1, the critical load of the steel cords of 1x2 structure of the present invention may determine the 20% increased than the steel cord of 2 + 2x0.25 structure 90kg / mm ² as 108kg / mm ^2. In addition, 1x2 steel cord has 9.45 pieces of steel cord embedded per 1cm of rubber, so it has excellent adhesion.

Table 2 below is a result of comparing the fatigue resistance of the steel cord of the present invention when the filament diameter is 0.3mm and the steel cord of the conventional 2 + 2 x 0.25 structure. Fatigue resistance was conducted at 90kg / mm ² load using a Rotating Beam Tester (Beaker) fatigue tester.

2 + 2x0.25 2x0.3 Number of buried steel cords per rubber 1 cm 7.87 9.45 Test load (kg / mm ² ) 90 90 Fatigue life cycle 185.910 2,000,000 or more

As disclosed in Table 2, the 1x2 steel cord of the present invention did not cause fatigue failure even at 5,000,000 cycles, which is 0.05mm larger than the conventional 2 + 2x0.25 steel cord but has a smaller contact point between the filaments. Therefore, the fatigue life is due to improved.

Table 3 below is a comparison of the relative weight of the steel cord of the present invention and the existing 2 + 2 structure, the weight of each steel cord was expressed in terms of the weight of 2 + 2 × 0.25 as 100.

rescue Relative weight 2x0.3 88 2x0.32 90 2 x 0.34 92 2 + 2x0.25 100

The 2 × 0.3 steel cord of the present invention has a 20% weight reduction compared to 2 + 2 × 0.25. When used as a tire reinforcement, the 2x0.3 steel cord reduces the weight of the tire, thereby reducing rolling resistance, thereby greatly improving fuel efficiency. Therefore, the 2x0.3 steel cord of the present invention is mainly applicable for reinforcing the steel belt portion of a tire for a passenger car.

Steel cord of the present invention has a structure of two filaments compared to a steel cord consisting of three or more filaments, so light and simple structure improves flexibility, and the contact point is small, thus reducing fritting Its durability is improved and its weight is light, so when used for reinforcement of the steel belt part of the tire, it reduces the rolling resistance of the tire and provides a remarkable effect to improve the fuel efficiency of the vehicle.

Claims (3)

The two filaments manufactured by drawing steel after 0.1 ~ 0.4μm thick brass plating were applied to wires of 0.10 to 0.40mm in diameter made of carbon steel with carbon content of 0.70 to 0.90% by weight. Steel cord, characterized in that. The steel cord according to claim 1, wherein the filament has a twist pitch of 3 mm to 20 mm and a cord diameter of 0.20 mm to 0.80 mm. The steel cord according to claim 1, wherein the tensile strength of the filament is 280 to 360 kg / mm 2.