KR20080028558A - Super high tensile steel cord - Google Patents

Abstract

A high-strength steel cord is provided to prevent the penetration of moisture or salt into voids of inner and outer layers by increasing the adhesive strength of rubber and core rubber and to secure sufficient strength with a few steel cords. A high-strength steel cord for reinforcing rubber products of tires for a vehicle comprises steel filaments containing carbon of 0.85~0.95wt.% and having tensile strength of 340~380 kg/mm^2, and satisfies the following condition, dc=(1.05~1.10)xds and P1=P2. The twisting directions of filaments of the inner and outer layers are same. dc is a diameter(mm) of the filament of the inner layer. ds is a diameter(mm) of the filament of the outer layer. P1 is twisting length(mm) of the inner layer, and P2 is twisting length(mm) of the outer layer.

Description

Super high tensile steel cord {Super high tensile steel cord}

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

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

Steel cord is especially good for tire reinforcement because of its excellent strength, modulus, heat resistance, heat transfer rate, fatigue resistance and rubber adhesion among various kinds of reinforcement materials used for reinforcement of various rubber products including tires and industrial belts of vehicles. It is widely used, and its usage is increasing day by day.

Steel cords are usually wire drawn with a diameter of 5.0 to 5.5mm from carbon steel with carbon content of 0.6 ~ 0.82% by weight to primary diameter 1.0 ~ 2.5mm, followed by heat treatment, brass plating and final drawing. Various structures of filament with 0.1 ~ 0.4mm in diameter and strength of 280 ~ 320kg / mm2 (1 × 2, 1 × 3, 2 + 2, 2 + 7, 3 + 6, 3 + 8, 3 + 9) Produces stranded wire with +15, 1 + 18, 3/8 + 13, etc.).

Double-ply steel cords allow filaments to form two- or three-ply layers, primarily for trucks and buses.

Representative standards of the double-steel structure cord is 3 + 6, 3 + 9, 3 + 9 + 15 steel cord, of which the 3 + 9 steel cord in more detail, first located in the inner layer (內層) The filament core is composed of three filaments twisted in a certain direction, and the outer layer surrounding the core is a spiral filament that is a single filament in which nine filaments are in close contact with the core layer. (spiral wrap) may be additionally present.

Here, the three filaments constituting the inner layer are twisted with each other, and the outer layer is stranded so that the filament diameter and the twisting direction are the same, but the twist length is different, and the spiral wrap is twisted in the opposite direction to the twisting direction of the outer layer. do.

However, since the steel cord is a normal tensile product having a strength of 280 to 300 kgf / mm2 of the filament, the strength of the steel cord is increased when applied as a tire reinforcement due to its low strength, and three steps up to the spiral wrap process when the stranded wire is processed. Since the process of the steel cord has a problem that the unit price of the expensive.

In addition, the steel cord has little gap between the filament of the outer layer and the inner layer, and the rubber adhesion force is low due to the difficulty of infiltrating the rubber into the steel cord during rubber topping, and between the filaments that are not made to penetrate when water or salt penetrates. The pores become their movement paths, and the corrosion of the steel cords is promoted by repeated bending of the tires, resulting in a big problem that the durability of the tires is lowered.

In addition, when the steel cord is applied to a tire, wear and tear fatigue caused by addition of friction and water due to incomplete line contact or point contact between the filaments forming the steel cord ( Fretting fatigue caused a problem of inferior tire durability.

That is, if the inner layer and the outer layer, and the spiral wrap in the twist direction or the twist length is different to form an incomplete line contact, the wear progresses quickly due to friction during the bending motion of the tire.

Several attempts have been made to remedy this problem.

Japanese Patent Laid-Open No. 7-109685 proposed a steel cord having a structure of 3 + 8, which removes one wire from the outer 9 wires to form a gap, and then reinforces rubber penetration into the gap by varying the wire diameters of the inner 3 wires and the outer 8 wires. It was proposed to improve the tire durability in the end.

In addition, Japanese Patent Application Laid-open No. Hei 10-131065 discloses a method in which the shape of the inner three layers is larger than the outer nine lines (or eight lines) to make a gap to improve rubber penetration into the inner layer. Japanese Patent Laid-Open No. Hei 10-292277 has proposed a method of improving rubber penetration by giving a preform to three inner layers.

However, when looking at the inventions proposed so far, the normal tensile and the high tensile steel cords having a wire strength of 280 to 300 kg / mm2 are low in strength, resulting in deterioration in durability or increased use of steel cords. The rolling resistance may be lowered due to the lowering of rolling resistance, and the filament may have different twisting lengths or different twisting directions to form steel cords, which may cause rapid wear due to incomplete line contact or contact contact.

Accordingly, the present invention solves the above problems and at the same time improves the strength without causing any deterioration in physical properties as compared to conventional steel cords, and improves rubber adhesion and core rubber penetration and reduces the weight due to lighter tires. It is a technical task to provide a steel cord for tire reinforcement material with saving effect.

The present invention will be described in detail with reference to the drawings.

1 is a plan view of a high strength steel cord having a 3/8 structure according to the present invention, and FIG. 2 is a cross sectional view of a high strength steel cord having a 3/8 structure according to the present invention.

In the present invention, the strength of the steel cord is improved by using a high-strength steel filament having a carbon content of 0,85 ~ 0.95% by weight and a tensile strength of 340 ~ 380 kg / mm2.

In addition, in the present invention, as shown in Fig. 1, the inner twist length (P1) and the outer twist length (P2) are the same, and the twist direction is the same, and as shown in Fig. 2, the diameter (dc) of the inner filament is the outer layer filament. It was 5 to 10% larger than the diameter (ds) of. {dc = (1.05 ~ 1.10) x ds}

The steel cord of the present invention has the same twisting length of the steel filaments between the inner and outer layers (P1 = P2) and the same twisting direction, so that the wear and tear of tires can proceed quickly because the preemption or point contact between the steel filaments between the inner and outer layers is complete. Can be prevented.

In addition, since the diameter (dc) of the inner layer filament is 5 to 10% thicker than the diameter (ds) of the outer layer filament, a space is naturally formed in the outer layer of the steel cord, and as a result, rubber easily penetrates through the space, thereby adhering to rubber. At the same time, moisture and salts, etc., penetrate into the tires between the voids in which rubber has not penetrated, thereby preventing the defect of deteriorating the durability of the tire by corroding the steel cord.

In the present invention, if the thickness of the inner layer filament (dc) is less than 5% thicker than the outer layer filament thickness (ds), it does not exhibit satisfactory rubber penetration, and if the thickness is greater than 10%, the present invention does not exhibit the desired strength.

Steel cord of the present invention is preferably dc = 0.21 ~ 0.40mm,

ds = 0.20-0.38mm and twist length is 5-40mm which falls within the range of general twist length.

Table 1 compares the steel cord according to the present invention and the prior art. The steel cord according to the present invention uses a high-strength carbon steel filament having a carbon content of 0.92%, and has a filament diameter of 0.35mm inner layer 0.32mm and inner layer 0.22 mm, outer layer 0.20mm is applied to show the physical properties of the brass plated steel cord.

In the following Examples, the present invention will be described in more detail, but the following examples are for the purpose of explanation and are not intended to limit the scope of the claims of the present invention.

1) Example 1

After heating the wire rod with the carbon content of 0.92% and the diameter of 5.5mm, the heat treatment and the brass plating are carried out, and the final filament is prepared by the final drawing up to the diameter of 0.22mm and 0.20mm, followed by three inner layers (0.22mm) and the outer layer (0.20mm). ) Was twisted in the direction of S (coincidence) with 12mm twist length to produce 3x0.22 / 8x0.20ST steel cord, and the results of the test were shown in [Table 1].

2) Example 2

After heating the wire rod with the carbon content of 0.92% and the diameter of 5.5mm, heat-treatment and brass plating are carried out, and final filaments are prepared by the final drawing up to 0.35mm and 0.32mm in diameter, and three inner layers (0.35mm) and the outer layer (0.32mm) are prepared. ) Was stranded in the direction of S (coincidence) with 18mm twist length to produce 3x0.35 / 8x0.32ST steel cord, and the results of the test were shown in [Table 1].

2) Comparative Example 1

After heating the wire rod with 0.82% of carbon and 5.5mm in diameter, heat-treating and brass plating, and final drawing to 0.35mm in diameter to prepare the filament.The inner three strands have 9mm twist length and the outer layer in the S (clockwise) direction. The eight strands were stranded in the direction of 18mm S (coincidence) to produce 3 + 8x0.35HT steel cords, and the results of the test were shown in [Table 1].

2) Comparative Example 2

After heating the wire rod with carbon content of 0.82% and diameter of 5.5mm, heat-treating and brass plating, final filament is prepared up to diameter of 0.22mm, and 3 inner strands and 8 outer strands are twisted with 12mm twisted length. 3 / 8x0.22HT steel cord was produced by stranded wire in the direction of) and the results of the test were shown in [Table 1].

※ S: coincidence

※ Deep rubber adhesive force (Kg / 1 ”)

: Cover the manufactured steel cord with rubber of 6mm thickness from the top and bottom, prepare a rubber block of 25.4mm length, and vortex it for 150 ℃ x30 minutes (same as mold in rubber adhesion test) to prepare all the outer layer filaments of the steel cord. After removal, the adhesion of the three seams was evaluated.

High-strength steel cord according to the present invention is improved in rubber adhesion and core rubber adhesion when applied to tires to prevent penetration of moisture or salts between the pores of the inner layer and the outer layer, thereby improving durability, and being sufficient in a small amount compared to existing steel cords. Since the strength can be maintained, the weight of the tire can be reduced, cost reduction and fuel efficiency can be improved.

Claims (2)

Steel cord for reinforcement of rubber products in 3/8 construction tires made of steel filaments with carbon content of 0.85 to 0.95% by weight and tensile strength of 340 to 380kg / mm2, satisfying the following conditions Steel cord.      --- below ---    Dc = (1.05 to 1.10) x ds    P1 = P2    ㆍ The twisting direction of inner filament is the same as the twisting direction of outer filament.      Dc; Diameter of inner layer filament (mm)          ds; Diameter of outer layer filament (mm)          P1; Inner layer twisting length (mm)          P2; Outer twisting length (mm) The high strength steel cord according to claim 1, wherein the inner and outer layers have a twist length of 5 to 40 mm.

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