KR100763761B1 - high tensile steel cord of 2 layer twisted in the same direction - Google Patents

Abstract

The high-strength steel cord of the two-layer lead structure having the same twisting direction according to the present invention is a two-layer lead 3 + 8 structure having three inner layers and eight outer layers, which are used for tires, and each filament has a diameter of 0.1 to 0.4 mm. The twisting period is the same between 5 and 40mm, and the twisting directions of the inner three wires and the outer eight wires are the same, thus reducing the cost of steel cords without reducing the strength and improving the tire rolling resistance. It can reduce fuel consumption and reduce the production cost of steel cord.

Description

High tensile steel cord of 2 layer twisted in the same direction}

1 is a plan view of a high strength steel cord of a two-layer lead structure according to the present invention,

2 is a cross-sectional view of FIG.

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

12: inner layer 14: outer layer

F1: inner layer filament F2: outer layer filament

The present invention relates to a high strength steel cord having a two-layered lead structure having the same twisting direction used for reinforcing rubber products of tires.

Steel cord is especially good for tire reinforcement because it has 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-drilled from 5.0 to 5.5 mm in diameter from carbon steel with carbon content of 0.6 to 0.95% by weight to primary wire drawing to 1.0 to 2.5 mm in diameter, followed by heat treatment and brass plating. Fresh, multi-filament strands with a diameter of 0.1 to 0.4 mm and a strength of 280 to 320 kgf / mm2, depending on the application (1x2, 1x3, 2 + 2, 2 + 7, 3 + 6, 3 + 8, 3 + 9, 3 + 9 + 15, 1 + 18, 3/8 + 13 etc.)

Double-structured steel cords, in which filaments form two or three layers, have been mainly used as steel cords for trucks and buses. Representative standards of the above-described double-structure steel cord are 3 + 6, 3 + 9, 3 + 9 + 15 steel cord.

Among the double-layered steel cords, a 3 + 9 steel cord having a two-layered lead structure includes a core, a filament located in the inner layer, in which three filaments are twisted in a predetermined direction, and an outer layer surrounding the core has nine filaments. As a structure in close contact with the core layer, there may be additionally a spiral wrap that is a single filament surrounding the outer layer. The three filaments constituting the inner layer are twisted with each other, the outer layer is twisted so that the inner layer and the filament diameter and the twist direction is the same, but the twist length is different, the spiral wrap is twisted in the opposite direction to the twist direction of the outer layer.

However, this steel cord is a normal tensile product with a strength of 280 ~ 300 kgf / mm2 of filament, and its strength is low, so the amount of steel cord used is increased when tires are applied. Since the process of the steel cord has a problem that the unit price of the expensive.

In addition, when the cut section is produced after the production of the steel cord, there is almost no gap between the filament of the outer layer and the inner layer, and the rubber adhesion force is reduced because the rubber penetration into the steel cord is difficult during the rubber topping. The voids between the filaments that are hardly penetrated become their moving passages, and the corrosion of the steel cords is promoted by the repeated bending of the tires, resulting in a 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 moisture due to incomplete line contact or point contact between the filaments forming the steel cord ( Fretting fatigue caused a problem of inferior tire durability. In other words, 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 motion of the tire.

Various attempts have been made to solve this problem. Japanese Patent No. Hei 7-109685 proposes a steel cord with a 3 + 8 structure, which removes one of the outer 9 wires to make a gap, and then again changes the wire diameter of the inner 3 wires and the outer 8 wires to the gap. The rubber permeability was improved, and thus the tire durability was improved. In addition, Japanese Patent No. Hei 10-131065 discloses a method in which the mold of the three inner layers is made larger than the outer 9 lines (or 8 lines) to make a gap to improve rubber penetration into the inner layer. Japanese Patent Laid-Open No. 10-292277 proposes a method of improving rubber penetration by giving a preform to three inner layers.

By the way, the steel cords proposed to improve the rubber permeability of the prior art, the normal tensile of the filament of 280 ~ 300 kgf / mm 2 and the high tensile steel of 300 ~ 320 kgf / mm 2 As the cord has a low strength, there is a risk that the tire may lead to a decrease in durability during manufacture of the tire or a decrease in rolling resistance due to an increase in the amount of steel cord used. In addition, because the twist length of the inner layer and the outer layer is different, the twisted wire must be carried out in two steps, resulting in an increase in steel cord production cost.

 Therefore, the present invention has been made to solve the above problems, an object of the present invention is to reduce the amount of steel cord without reducing the strength and to reduce the cost while improving the rolling resistance characteristics of the tire to reduce fuel consumption and steel To provide a high-strength steel cord with a two-layer lead structure for tires that reduces the production cost of the cord.

The high strength steel cord of the two-layer lead structure having the same twisting direction according to the present invention is a two-layer lead 3 + 8 structure having three inner layers and eight outer layers, which are used for tires, and each filament has a diameter of 0.1 to 0.4 mm. The twist period is the same as 5 to 40mm, and the twisting direction of the three inner wires and the twisting direction of the outer eight wires are the same.

Carbon content of the filament is 0.85 ~ 0.95% by weight and tensile strength after final drawing is 340 ~ 380 kgf / mm2, or 0.85 ~ 0.95% by weight of carbon content of the filament and tensile strength after final drawing is 380 ~ It is 420 kgf / mm <2>.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

1 is a plan view of a steel cord according to the present invention, Figure 2 is a cross-sectional view of FIG. As shown, the present invention is a steel cord having a two-layer lead 3 + 8 structure of three inner layers and eight outer layers, each filament F1 (F2) diameter is 0.1 ~ 0.4mm, the twist length (cycle) of the inner layer 12 ) A and the twist length B of the outer layer 14 are the same 5 ~ 40mm. The twisting directions of the inner and outer layers are also the same.

In this case, the carbon content of each filament is 0.85 ~ 0.95% by weight and the tensile strength after the final drawing is 340 ~ 380 kgf / mm2, or 0.85 ~ 0.95% by weight of the carbon content of the filament and the tensile strength after the final drawing It is 380-420 kgf / mm <2>. Tensile strength of the filament is determined according to the carbon content and the number of draw processing.

These filaments are subjected to well-known drawing, heat treatment, and brass plating using wire rods having the carbon content (0.85 to 0.95 wt%), followed by final fresh drawing to a predetermined diameter (0.1 to 0.4 mm), followed by stranded steel cord. Is molded into.

Example 1

After drawing, heat-treating and brass plating carbon steel wire with 0.92% by weight of carbon, and final drawing to 0.22mm in diameter, stranded wire was produced to produce 3 + 8 x 0.22 ST steel cord and tested its properties. It is shown in [Table 1].

Comparative Example 1

After drawing, heat-treating and brass plating carbon steel wire with carbon content of 0.82% by weight, final drawing to 0.22mm in diameter, followed by stranded wire to produce 3 + 8 x 0.22 HT steel cord and tested its properties. Is shown in [Table 1].

Comparative Example 2

After drawing, heat-treating and brass plating carbon steel wire with carbon content of 0.72% by weight, and final drawing to 0.22mm in diameter, stranded wire is processed to produce 3 + 9 x 0.22 + W NT steel cord and test its properties. One result is shown in [Table 1].

TABLE 1

Item unit Example 1 Comparative Example 1 Comparative Example 2 3 + 8x0.22ST 3 + 8x0.22HT 3 + 9x0.22NT + W Twist Length Inner layer mm 12 6 6 Outer layer mm 12 12 12 Wrapping mm - - 3 Twisting direction S / S S / S S / Z / S Small diameter mm 0.22 0.22 0.22 Code mm 0.9 0.9 1.2 Cutting load Kgf 143 132 51 Elongation at break % 2.6 2.4 2.4 Lowering elongation % 0.054 0.047 0.05 Unit weight g / m 3.35 3.35 3.63 Adhesion % 125 (95) 120 (90) 115 (95) RBT fatigue test 110 and above 100 or more over 90

Example 2

After drawing, heat-treating and brass plating the carbon steel wire with 0.92% of carbon content and final drawing again with diameter of 0.22mm, the inner and outer layers are clockwise and the twisted length is equal to 12.5mm. The result of producing 8 x 0.22 UT steel cord and testing its physical properties is shown in [Table 2].

Comparative Example 3

After drawing, heat-treating and brass plating the carbon steel wire with 0.82% of carbon content, and final drawing to 0.22mm in diameter, stranded wire with 6mm of inner layer and 12mm of twisted wire of outer layer is 3 + 8 x The result of producing 0.22 HT steel cord and testing its physical properties is shown in [Table 2].

TABLE 2

Item unit Example 2 Comparative Example 3 3 + 8x0.22UT 3 + 8x0.22HT Twist Length Inner layer mm 12.5 6 Outer layer mm 12.5 12 Twisting direction S / S S / S Small diameter mm 0.22 0.22 Code mm 0.9 0.9 Cutting load kgf 150 132 Elongation at break % 2.6 2.4 Lowering elongation % 0.054 0.047 Unit weight g / m 3.35 3.35 Adhesion % 125 (95) 120 (95) RBT fatigue test 120 or more 100 or more

The numerical values in () of the above [Table 1] and [Table 2] section on the adhesion force represent the rubber coverage of the specimens tested for rubber adhesion as a percentage.

As can be seen from the table, Example 1 and Example 2 can reduce the amount of steel cord used while maintaining the same strength as the existing steel cord through a steel cord made of high-strength carbon steel, The steel cord cost can be reduced while improving the tire rolling resistance to reduce fuel economy.

And according to this embodiment, since the twist length (cycle) of the inner layer and the outer layer is the same, when producing a high-strength steel cord, it is possible to produce a steel cord with one step stranded wire can reduce the production cost of steel cord.

According to the high-strength steel cord of the two-layer lead structure with the same twisting direction according to the present invention, it is possible to reduce fuel consumption by reducing the amount of steel cord without reducing the strength, and to improve fuel resistance by improving the rolling resistance characteristics of the tire and the steel cord It has the effect of reducing the cost of production.

Claims (3)

delete As a two-layer lead 3 + 8 structure with three inner layers and eight outer layers for tires, The diameter of each filament is 0.1 ~ 0.4mm and the twisting period of inner layer and outer layer is 5 ~ 40mm, and the twisting direction of 3 inner wires and 8 outer wires are the same. The carbon content of the filament is 0.85 ~ 0.95% by weight, and the tensile strength after the final wire processing is 340 ~ 380 kgf / ㎜ characterized in that the high-strength steel cord having the same twist direction of the two-layer structure. As a two-layer lead 3 + 8 structure with three inner layers and eight outer layers for tires, The diameter of each filament is 0.1 ~ 0.4mm and the twisting period of inner layer and outer layer is 5 ~ 40mm, and the twisting direction of 3 inner wires and 8 outer wires are the same. The carbon content of the filament is 0.85 ~ 0.95% by weight, the tensile strength after the final wire processing is 380 ~ 420 kgf / ㎜ characterized in that the high-strength steel cord having the same twist direction of the two-layered structure.

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