KR100717150B1 - A high tensile steel cord and manufacturing method thereof - Google Patents

Abstract

The present invention is to control the carbon content and the number of draw times according to the material selection without changing the physical properties, to impart plastic deformation to the filament and stranded the filaments in an open structure, to improve the tensile strength and penetration of the rubber A high strength steel cord and a method of manufacturing the same.

The manufacturing method is a wire rod having a diameter of 5.5 mm and a carbon content of 0.8 to 0.9% after primary drawing processing to have a diameter of 1.0 to 2.5 mm, and then the structure inside the metal that has been deformed during the primary drawing processing To recover, austenitic by heating at a temperature of 900 to 1100 ℃, and then quenched and subjected to a patented heat treatment to incubate with a fine pearlite in the temperature range of approximately 500 to 650 ℃, and to coat the heat treated outer peripheral surface with brass Plated wire rod, and the plated wire rod was drawn and redrawn at least once to have a tensile strength of 360 to 420 kg / mm 2, and the diameter was reduced to a diameter of 0.35 to 0.40 mm, and then 3 to 4 manufactured through such a process. The filament of the strands is an open dog structure, which is twisted apart from each other and twisted.

According to the present invention, since the present invention can satisfy the sufficient rigidity in a small amount compared to the existing steel cord, it is possible to not only improve the weight and rolling resistance of the tire, but also reduce the cost and improve the fuel efficiency. Have

In addition, since the filament diameter is thicker than the conventional one, the stiffness is improved and the tire handling characteristics are excellent. In particular, the filament has a very useful advantage of excellent rubber permeability and improved rubber adhesion rate because the open structure is spaced between the filaments.

Description

High-strength steel cord and manufacturing method thereof

1 is a flowchart schematically illustrating a method of manufacturing a conventional high strength steel cord.

Figure 2 is a flow chart sequentially showing a method of manufacturing a high strength steel cord according to the present invention.

Figure 3a and Figure 3b is an illustration showing examples of imparting plastic deformation by using a molding machine to manufacture a high strength steel cord according to the present invention, respectively.

4 is a front view showing that the three filaments are plastically deformed and stranded by the mold swelling of FIG. 3.

5 is a cross-sectional view taken along the line A-A of FIG.

6 is an exemplary view showing another example of imparting plastic deformation to produce a high strength steel cord according to the present invention.

7 is a front view showing that the three filaments are plastically deformed and stranded by the preform device of FIG. 6.

8 is a cross-sectional view of FIG.

9 is a cross-sectional view showing the plastic strained and stranded state when the filament is four strands.

Description of the main parts of the drawing

20: mold book 30: preform device

F: Filament S: Steel Cord

ℓ₁: spacing between filaments in the process of stranded wire with 3 ~ 4 strands of filaments excessively plastically deformed by mold swelling

ℓ₂: spacing between filaments generated in the process of twisting three to four strands of filaments plastically deformed by a preform device

The present invention relates to a high-strength steel cord and a method of manufacturing the same, in particular, by controlling the carbon content and the number of fresh processing according to the material selection without changing the physical properties, by imparting plastic deformation to the filament and stranded the filaments in an open structure, It relates to a high-strength steel cord and its manufacturing method to improve the tensile strength and penetration of rubber.

In general, a radial tire belt layer for a passenger car is provided between the tread and the carcass, and has a function of increasing the tread rigidity by tightening the carcass like a ring in a circumferential direction.

The function of the belt layer is to allow the tire to support the load of the vehicle and at the same time to exert power in cornering.

Conventional tire belt layer is usually used by using a steel cord of twisted wire rods of a plurality of strands, the stranded steel cord has a high rigidity, while on the unpaved roads with poor road surface There was a disadvantage that the ride resistance is not good because the repulsive force of the tire is too strong.

In addition, when the tire is deformed or vibrated, there is a problem in that the cord wire is fatigue-deteriorated by generating a so-called fretting wear in which the twisted wires are rubbed and worn together.

On the other hand, steel wire for steel cord is generally manufactured through the process of manufacturing, drawing, heat treatment (patenting), drawing, heat treatment, coating (plating), drawing, etc., in consideration of the above problems. The manufacturing process will be described in detail below.

First, one time of heat-treatment and one to two fresh processing are made by using hot rolled wire having a certain diameter (for example, a diameter of 5.5 mm, which is a common standard for wire rod) made of carbon steel having a carbon content of 0.6 to 0.95 wt%. The steel wire which is 0.8-2.0 mm in diameter is manufactured by carrying out (伸 線 加工).

Then, to recover the internal structure of the deformed metal, after another one of the petenting heat treatment, copper plating of 0.5 to 1.5 μm thick is performed, and zinc plating of 0.3 to 1.0 μm is sequentially applied thereto. After the thermal diffusion process of the method to obtain a brass plating layer is drawn to a diameter of 0.1 to 0.6 mm to produce a steel wire for reinforcement into rubber products.

Wire rods manufactured in this way are used by twisting them into various structures (1x3, 1x4, 2 + 2, 2 + 7, 3 + 6, 3 + 9 + 15, etc.), depending on the purpose of use, and the strength, modulus, heat resistance, fatigue resistance Compared with other kinds of inorganic fibers and organic fibers, it is useful for reinforcing rubber products such as tires and conveyor belts.

In the case of tire steel cord steel wire, the tensile strength of the wire should have a strength characteristic of at least 280 Kg / mm2 or more, and in general, the strength of the wire tensile strength of 280 to 300 Kg / mm2 is classified as a normal tensile steel cord. , Tensile tensile strength of 320 to 340 Kg / ㎜ is used to classify high tensile steel cord.

Hot rolled wire used in the manufacture of normal tensile steel cords has a carbon content of 0.69∼0.74 wt% and a tensile strength of 100 ~ 110 Kg / mm2, and hot rolled wire used in high tensile steel cords Usually, carbon content of 0.80 to 0.84 wt% and tensile strength of 110 to 120 Kg / mm 2 are used.

A general manufacturing process of high strength (high-tensile) steel cord is illustrated in FIG. 1.

Steel wire having a diameter of 3.0 to 3.4 mm was produced by primary drawing by using a hot rolled wire rod 10 having a constant diameter (for example, a diameter of 5.5 mm) made of carbon steel having a carbon content of 0.80 to 0.84 wt%. (S10). Then, the steel wire produced through the primary drawing is austenitized by heating at a temperature of 900 to 1100 ° C. in order to recover the structure inside the metal that is deformed during the primary drawing.

Next, after quenching and performing a pattening heat treatment for constant temperature transformation with fine pearlite in a temperature range of 500 to 650 ° C., secondary drawing is performed with a diameter of 0.8 to 2.0 mm (S12 and S14).

After that, once again the heat-treating heat treatment, the copper plating of 0.5 to 1.5 ㎛ thickness, and then the zinc plating of 0.3 to 1.0 ㎛ is sequentially performed thereon and the thermal diffusion process of various methods to perform a brass plating layer (S16).

Subsequently, drawing is performed with a diameter of 0.10 to 0.30 mm to finally produce an ultrafine steel wire for high strength (high-tensile) steel cord (S18).

The wire rod thus produced is twisted into various structures and used for reinforcement of a tire, depending on the application.

Summarizing the manufacturing process of the general high strength (high tenacity) steel cord described above, the hot-rolled wire rod 10 is used to perform 60 to 80% of the wire drawing, and the heat treatment is performed to obtain a pearlite structure without the effect of machining. After repeating the obtained process twice, brass plating is carried out, and final drawing is performed at 0.10 to 0.30 mm to produce ultrafine steel wire.

At this time, the intermediate heat treatment process (patterning), which is usually performed during drawing, is performed to control the deformed structure formed after the drawing is carried out to some extent so that drawing can be done to the final product diameter, and in the case of requiring high drawing processing It is an essential manufacturing process. This is because the degradation of freshness during drawing is caused by cracking during processing, and this cracking occurs due to cracking of cementite in the pearlite structure composed of ferrite / cementite.

As a method of increasing the strength of the steel cord, US Patent No. 5061557 produces a filament of 0.34 mm or less having a strength of up to 360 kg / mm2 with a wire rod of carbon content of 0.7 to 0.9%, and has a 1 × 2 structure as the filament produced. It is proposed to manufacture steel cords of the present invention, but since the filament is not an open structure, plating wear may occur between the filaments and the penetrability of the rubber penetrating into the steel cord side is reduced. By limiting to 0.34 mm or less, the material properties (ie, rigidity) of steel cords are limited.

In addition, in another embodiment, as disclosed in Korean Patent Publication No. 10-276014 "High Strength Steel Cord for Pneumatic Tire", after drawing carbon steel, the surface of the brass is plated and drawn and stranded. In the pneumatic tire steel cord consisting of a plurality of filaments, the steel cord is composed of two strands of twisted filament has a structure of 1 × 2, the diameter of each filament is 0.15 ~ 0.40, the twisting cycle is filament It is in the range of 10 to 70 times the diameter, and the carbon content of the carbon steel for steel cord is 0.92 to 2.0%.

However, this is not a steel cord of open structure with open filament of steel cord, but a high carbon steel wire with 0.91 ~ 2.0% of carbon content. there was.

The present invention has been proposed in view of the above-mentioned problems, and an object thereof is to produce an open open structure having at least one drawing operation and plastic deformation, thereby improving the properties of the material without deteriorating material properties. The present invention relates to a high-strength steel cord and a method for manufacturing the same, which can be improved as much as possible to increase penetration into rubber and satisfy rigidity.

The present invention for achieving the above object is a wire rod which is carbon steel is drawn at least one or more times to be filamentized to reduce the diameter, the plurality of filaments are twisted so as to periodically twist each other,

The wire rod has a carbon content of 0.8 to 0.9%,

The filament is drawn a plurality of times to have a tensile strength of 360 ~ 420kg / ㎜,

The fresh processing is characterized in that the strand is stranded in an open structure so that the 3 to 4 strands of the filament having a diameter of 0.35 ~ 0.40mm is formed to be separated from each other.

In addition, the filaments are plastically deformed to be bent in the form of wrinkles.

In addition, the pitch interval of the filaments are twisted is 5 ~ 30mm.

In another aspect of the present invention, the primary wire processing to the wire rod of carbon content of 0.80 ~ 0.90%, carbon diameter of 5.5mm to have a diameter of 1.0 ~ 2.5mm,

Plating the primary fresh wire rod with a patented heat treatment and coating its outer circumferential surface with brass;

At least one more wire drawing is performed so that the tensile strength of the plated wire rod becomes a filament having a diameter of 0.35 to 0.40 mm of 360 to 420 kg / mm 2,

The final drawn filament 3 to 4 strands are twisted to have an open structure by twisting them to have portions spaced apart from each other.

The present invention further includes a step of processing the plastic filament to be plastically deformed in the form of curved wrinkles in the process of stranding the filament 3 to 4 strands.

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

High strength steel cord and a method of manufacturing the same according to the present invention will be described in detail with reference to the accompanying drawings.

The high strength steel cord according to the present invention, as shown in Figures 3 to 9, the structure is a carbon content of 0.8 ~ 0.9%, a plurality of draw processing so that the tensile strength is 360 ~ 420kg / mm2, plastic deformation The filament (F) 3 to 4 strands bent in a corrugated form has a structure of a steel cord (S) twisted to have a pitch (P) by twisted pair processing in a 1 × 3 or 1 × 4 structure.

In addition, the 3 to 4 filaments (F) is formed in a structure that is open so that the remaining portions are spaced apart from each other except the portion where the interval between each other.

In addition, the method of imparting plastic deformation to the filament (F) itself is a pattern in which the gear protruding by the preform device 30 is repeatedly formed, or is wound in a zigzag shape by the molding machine 20 to bend in a pleated form It is preferable to form a forge.

At this time, the spacing (l₁) between the filaments (F) plastically deformed by the mold-keeping machine 20 is spaced apart at a larger interval than the spacing (ℓ₂) between the filaments (F) plastically deformed by the preform device 30 This is because the plastic deformation caused by the mold-keeping machine 20 is excessively imparted.

More preferably, the cord outer diameter of the filament (F) is 0.6 ~ 0.8mm, but the actual diameter of the filament (F) is increased as the number of draw operations (within 2 ~ 10 times) to match the tensile strength Considering the reduction range of the diameter is preferably about 0.35mm or more, and the cord outer diameter is preferably about 0.7 as described below.

This is because the tensile strength is proportional as the number of drawing is increased, but too many draws increase the number of drawing machines (not shown) required for drawing, thereby increasing production cost and making workability difficult.

On the other hand, the method of manufacturing a high strength steel cord according to the present invention, when described with reference to Figure 2, first, the diameter of the wire rod 5.5 mm (common standard of wire rod) and the carbon content of 0.8 ~ 0.9% (carbon steel) diameter After primary drawing processing to 1.0-2.5 mm, the austenite was heated by heating at a temperature of 900 to 1100 ° C. in order to recover the structure inside the metal that was processed and deformed during the primary drawing. In the temperature range of approximately 500 to 650 ° C, a patterning heat treatment for constant temperature transformation with fine pearlite, plating the heat treated outer circumferential surface to be coated with brass, and the plated wire rod were subjected to tensile strength of 360 to 420 kg / mm2. After drawing a plurality of times to reduce the diameter of the filament (F) having a diameter of 0.35 ~ 0.40mmm, and then open the three to four strands of filament (F) manufactured through this process to each other open It made the process of standing stranded prices to be twisted.

In addition, the process of plastic deformation of the filaments (F) (S4), as shown in Figure 3a and 3b, by winding the outer circumferential surface of the molding machine 20 having a plurality of rod-shaped bars in a zigzag shape, excessive plastic deformation It is preferable that the distance between each filament (F) is provided by giving.

In addition, the process of plastic deformation of the filaments (F) (S4), as shown in Figure 6, by the preform device (30) of the gear shape is plastically deformed in a shape corresponding to the gear tooth is repeatedly in the form of curved wrinkles It may be further provided to form a process.

The two plastic deformation methods are to secure more space to penetrate the rubber in order to further improve the penetration force with the rubber before the stranding process of the open filament (F).

In more detail, the process of manufacturing so that the tensile strength of the filament (F) corresponds to 360 ~ 420kg / ㎜ depends on the material properties (variable according to the carbon content), heat treatment, the number of times of drawing In addition, since it is also variable depending on the performance of the drawing machine, the tensile strength can be adjusted by varying the number of drawing operations under the same material properties and heat treatment conditions.

At this time, as the number of drawing operations during the manufacture of the filament (F) has a semi-proportional relationship in which the diameter is reduced, the tensile strength has a correlation that increases to be proportional thereto.

Therefore, as described above, there are various examples of satisfying the tensile strength (360 to 420 kg / mm 2) according to the change of various conditions, among which the filament F is fired under the same conditions in the twisted pair process. Although two things that can be varied according to the modification is described in the first and second embodiments below, the following embodiments are not intended to be limited to the purpose of the present invention in detail.

First Embodiment

Wire rods with a carbon content of 0.90% and a diameter of 5.5 mm are first drawn to a diameter of 2.0 mm, and the surface is plated with brass while the plated heat treatment is performed at a temperature of at least 900 ° C, and then at least 1 up to 0.35 mm in diameter. After drawing the filament (F) by redrawing it more than once, the zigzag shape is formed on the outer circumferential surface side of the filament (F) by using the mold-keeping machine (20) in the process of strand drawing the final fresh filament (F). By providing a plastic deformation of, the gap between the filaments F is largely formed.

Second Embodiment

Wire rods with a carbon content of 0.90% and a diameter of 5.5 mm are first drawn to a diameter of 2.0 mm, and the surface is plated with brass while the plated heat treatment is performed at a temperature of at least 900 ° C, and then at least 1 up to 0.35 mm in diameter. After drawing the filament (F) by re-processing it more than once, in the process of twisting the final filament (F) of the final drawn three-fiber, the gear is pre-curved in the form of curved wrinkles by using the preform device (30). After molding, the strands were to be stranded.

Comparative Examples 1 and 2 produced by the existing method can be compared as follows.

Comparative Example 1

Wire rods with a carbon content of 0.90% and a diameter of 5.5mm were drawn to a diameter of 1.80mm, followed by patenting heat treatment and brass plating, and final drawing to a diameter of 0.30mm to prepare filaments. It is produced by processing three strands of filament by conventional stranded method without plastic deformation.

Comparative Example 2-

After the wire rods with a carbon content of 0.80% and a diameter of 5.5mm are fresh to a diameter of 1.80mm, the plated heat treatment and brass plating are carried out, and the final drawing is carried out to 0.30mm in diameter to prepare the filaments. Filament is produced by processing with conventional stranded method without plastic deformation.

The results of evaluating the physical properties of Examples 1 and 2 and Comparative Examples 1 and 2 are shown in Table 1 below.

Physical property measurement method used in the present invention is as follows.

1) Cord diameter, wire diameter: measured with micro meta

2) Twisting length (pitch): The average value was obtained by dividing the length of the twist occurring 10 times in steel cord (S) by 10.

* Pitch (P) = length where 10 twists occurred / 10

3) Lowered elongation rate: It shows the change in length when the steel cord (S) is loaded in% (load load 0.25 ~ 1.6kgf).

4) Unit weight: Measure the weight of steel cord (S) 1m with balance

5) Adhesion and rubber adhesion rate: The mold is manufactured by the method of American Material Testing Association (ASTM), drawn out by a tensile tester, and the load is made into adhesive force. The rubber adhesion rate is determined by visually determining the degree of rubber adhesion on the surface of the cord. Marked and represented by%

6) Fatigue resistance: After coating the steel cord (S) with rubber, measure the number of times until fatigue failure occurs by applying repeated tensile and compressive stress using a 3 roll tester.

7) Stiffness: Measured by the Taber Stiffness Tester and evaluated by kg-mm2

Item unit Example 1 Example 2 Comparative Example 1 Comparative Example 2     Mechanical properties Sir Code mm 0.765 0.765 0.654 0.654 Twist Length mm 18.0 18.0 16.0 16.0 Cutting load kgf 108 108 70 64 Filament Tensile Strength  kg / mm2  380  380  340  320 Lowered elongation rate % 0.05 0.04 0.04 0.04 Unit weight g / m 2.29 2.29 1.68 1.68 Stiffness kg-mm2 47 46 26 26 Adhesion kgf 92 92 57 56 Rubber adhesion rate % 95 95 90 90 Fatigue Characteristics 3 roll with inner skin Sashimi 2200 2200 1900 1850

According to the table, Examples 1 and 2 not only have a high strength excellent fatigue resistance significantly different from Comparative Examples 1, 2, it can be seen that the performance is improved also in the adhesion and rubber adhesion rate.

As described above, the present invention relates to a high strength steel cord and a method of manufacturing the same, which provide plastic deformation without deteriorating existing physical properties and satisfy tensile strength only by drawing a plurality of times. Since sufficient rigidity can be satisfied in a small amount compared to the cord, it can not only improve the weight and rolling resistance of the tire, but also have a useful effect of reducing the cost and improving fuel economy.

In addition, since the filament diameter is thicker than the conventional one, the stiffness is improved and the tire handling characteristics are improved, and in particular, the open structure with the space between the filaments is spaced apart, thereby minimizing the contact area between each other and suppressing the wear of the rubber. It has a very useful advantage of excellent permeability and improved rubber adhesion rate.

Claims (5)

In the high-strength steel cord is a wire rod of carbon steel is drawn at least one or more times to form a filament (F) to reduce the diameter, and the plurality of filaments (F) are twisted to periodically twist each other, The wire rod has a carbon content of 0.8 to 0.9%, The filament (F) is drawn a plurality of times to have a tensile strength of 360 ~ 420kg / ㎜, The wire is stranded in an open structure to form a portion in which 3 to 4 strands of filament (F) having a diameter of 0.35 to 0.40 mm are separated from each other. The high strength steel cord, characterized in that the filaments (F) are plastically deformed to be bent in a pleated form. delete The method of claim 1, High-strength steel cord, characterized in that the interval of the pitch in which the filaments (F) are twisted 5 ~ 30mm. Firstly, wire rods made of carbon steel with a carbon content of 0.80 to 0.90% and a diameter of 5.5 mm are first drawn to have a diameter of 1.0 to 2.5 mm, Plating the primary fresh wire rod with a patented heat treatment and coating its outer circumferential surface with brass; At least one more wire drawing is performed so that the tensile strength of the plated wire rod becomes a filament (F) having a diameter of 0.35 to 0.40 mm of 360 to 420 kg / mm 2, Method for producing a high-strength steel cord, characterized in that the twisted filament (F) 3 to 4 strands of the final wire is twisted to have an area spaced apart from each other. The method of claim 4, wherein In the process of twisting the filament (F) 3 to 4 strands, the method of manufacturing a high strength steel cord, characterized in that the filament (F) further comprises the step of processing to plastic deformation in the form of curved wrinkles.

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