KR20030040863A - Steel cord for reinforcing with a good rubber penetration properties and method for making the same - Google Patents

Abstract

PURPOSE: A steel cord is characterized by having excellent rubber penetrating property, improving fatigue resistance, preventing core migration, increasing rubber adhesive property, increasing workability and increasing durability of a tire. The manufacturing method thereof is characterized by reducing the production cost. CONSTITUTION: The steel cord is obtained by the steps of: preparing two pieces of core wire(10a) and 4-6 pieces of side wire(10b) thicker than the core wire, followed by braiding them; passing the braided wire through a pre-overtwister(24) rotating in a R.P.M ratio 2.5-4.5times of a R.P.M of a revolving screen(23) for twisting to secure a surplus length of the side wire(10b); passing the wire through a pair of two revolving screens(23) to form continuous torsional twist; and then passing the cord slipped from a braiding machine through a flattening roller(26) having square grooves to manufacture 2/(4-6) flattening cord.

Description

STEEL CORD FOR REINFORCING WITH A GOOD RUBBER PENETRATION PROPERTIES AND METHOD FOR MAKING THE SAME}

The present invention relates to a structural improvement of a steel cord used as a reinforcement material for various rubber products including tires and industrial belts of a vehicle, and more specifically, a flat open type in which four to six strands are twisted together in one process around a core of two strands. As a double-stranded structure, by forming the mold by controlling the rotation ratio of the pre over twister (pre OT) in the twisted pair stage, a gap is formed between the core wire and the side wire and adjacent side wires to improve rubber permeability and prevent movement of core wires. And it relates to a steel cord for a rubber reinforcing material and a method of manufacturing the same to improve the aging adhesiveness.

In general, among various kinds of reinforcing materials used to reinforce various rubber products including tires and industrial belts of vehicles, steel cords are used in rubber reinforcing materials such as strength, modulus, heat resistance, heat transfer rate, fatigue resistance and rubber adhesiveness. Since it is superior to other reinforcing materials made of inorganic fibers or organic fibers in terms of required properties, it has been widely used as a tire reinforcing material, especially, and its usage is increasing rapidly.

On the other hand, steel cords used for reinforcement of automobile radial tires or conveying belts have a structure in which a plurality of strands of twisted filament wires are twisted or a structure in which a plurality of strands of twisted filament wires are twisted. In order to use such steel cord as an effective rubber reinforcing material, the steel cord is required to have a strong physical and chemical bond with rubber, that is, rubber adhesiveness. In particular, in the case of automobile tires, the aging adhesiveness between the tire rubber and the steel cord is more important because the tire is exposed to moisture and high temperature atmosphere according to the high-speed driving of the vehicle.

The radial tire filled with air is composed of a radial carcass portion having a radiation shaped carcass cord and a belt layer for reinforcing a tread portion arranged radially outward of the radial carcass. Steel cords formed by stranding two to 40 ultra fine steel wires having a substantially circular cross section with a diameter of 0.12 to 0.40 mm are embedded in the belt and the carcass layer so that the belt layer and the carcass layer can be reinforced.

Such steel reinforcing steel cords have a structural characteristic in which fine voids are formed inside surrounded by stranded filament wires, which are infiltrated when water penetrates along a gap formed by tire rubber damage during tire driving. It acts as a passage to amplify the corrosion of the steel wire as the filament element wire and damages the adhesive layer between the rubber and the steel cord, thereby causing a fatal problem of separating the belt layer and the steel cord.

And, as a result of the repetitive flexing movement accompanying the rotation of the tire, if severe external pressure, which is repeated in tension and compression, is transmitted to the steel cord, freting occurs due to contact between the wires and freting. It is known that structural problems have been constantly present in steel cords, which are drastically lowered and thus the durability of tires is reduced.

Recently, as the driving speed of the vehicle increases, the demand for tires with higher levels of durability has emerged, and there is an urgent need for the emergence of a new structure of steel cords that can satisfy these requirements.

As such, some typical steel cord structures embedded in rubber products including tires and serving as reinforcement materials will be described with reference to FIGS. 1 to 3.

First, FIG. 1 is a cross-sectional view of a conventional 3 + 6 hermetic steel cord, in which six outer strands 2b are fed together around a lower edge 1, which combines three inner strands 1a as shown. It has a so-called double-layer lead 3 + 6 structure.

The steel cord of the conventional double-layered structure has a large number of strands (9 total strands) constituting the cord, and the complexity of the structure itself is not avoided, and in the manufacturing process, a one-step strand stranding process for forming the lower lead 1 Subsequently, the twisted wire process is required in two steps of stranding the outer element wire 2a thereon, resulting in a complicated manufacturing process and thus an increase in manufacturing cost.

When the steel cord of the 3 + 6 structure is embedded in rubber and vulcanized and manufactured by rubber reinforcement, the steel cord has a central space portion B surrounded by three inner strands 1a constituting the lower strand 1. The rubber is not filled and air remains.

When the rubber reinforcement with air remaining inside is used for the belt of the tire, the deterioration of the rubber is promoted due to the heat generation of the tire and the synergy of the remaining air while driving, resulting in the separation of the adhesive interface layer between the steel cord and the rubber. When the tire tread is damaged by stones or nails on the road surface, water penetrates into the capillary phenomenon through the damaged part and reaches the central space B of the steel cord. As the steel cord spreads in the longitudinal direction of the steel cord, the application of the steel cord proceeds rapidly.

Moisture permeated into the steel cord center space (B) inside the tire not only causes the steel cord itself to rust, but also destroys the adhesive interface layer between the rubber and the cord, which in turn causes peeling between the two members. On the other hand, the feed field causes physical and human losses.

In addition, the steel cord of the 3 + 6 structure is a lot of weight per unit length of its own, and the diameter of the cord is thick, the situation that does not meet the recent trend that the weight of the tire is required to improve the fuel efficiency of the vehicle.

Accordingly, there has been proposed a steel cord structure in which a cord can be manufactured in a single step with a small cord diameter and omitting the lower edge step, and JP-A-6-65877 is one of them.

Fig. 2 is a cross-sectional view of a steel cord of a 1 × 6 flat open structure of the structure shown in the Japanese Laid Open Patent Application. As shown, the 1x6 flat open steel cord is provided with a gap between the adjacent element wires by forming a gap (c) between adjacent element wires by flattening the entire cord by applying an external force to each element wire 3a and then applying an excessive mold. It is shaped.

Since the flat open steel cord is manufactured only by one twisted wire process, the steel cord is manufactured, and thus, compared to the 3 + 6 structure as described above, it is economical and has loosened association between wires due to excessive mold. A gap (c) is formed between the gaps to allow the rubber to enter the center space so that the rubber can easily enter the center space. Also, the cord is embedded in the rubber because the flat surface of the cord maintains the same direction over the entire length of the cord. It is also known that it has the advantage of being able to take a thin thickness of the rubber rubber, which is advantageous for the weight reduction of the tire.

On the other hand, in the case of conventional open steel cords, when the mold rates of the individual wires are uniform with each other, in particular, the gap between the wires is lost due to the tensile force acting on the cord during the rolling process, and the rubber permeability is rapidly lost. Steel cord is relatively advantageous in terms of rubber permeability in the longitudinal direction in the longitudinal direction due to the structural flattening.

However, the conventional flat open steel cord has an excessive shape and each wire is loosely twisted, so the structural shape is unstable, and the elongation at break is very high, which not only handles the tire during manufacturing, but also provides a predetermined amount of wire to each wire. In order to give a certain shape to the range, mechanical bending deformation is applied by using a special tool such as a hard plate molding machine. At this time, severe friction occurs at the contact part between the wire and the mold period, and thus, the rubber wire and the corrosion resistance can be improved. It is pointed out that the brass plating layer plated on the surface is damaged by the chipping, resulting in the deterioration of the adhesive and fatigue properties.

In particular, the flat open steel cord has a very low elongation at low load, which is extremely poor in handling, and it is difficult to arrange a uniform length in the top sheet due to the slight difference in elongation at each code. Along with the problem that the steel cord is used in the belt portion, there is a problem that the steel cord is easily stretched during driving and the possibility of collapsing of the shape is high, so that the steering responsiveness is deteriorated.

As such, the basic reason why the flat open steel cord is structurally unstable is that there is no core wire inside, and therefore, the necessity of placing the core wire in the center of the flat cord is considered.

Next, FIG. 3 shows a cross-sectional view of a steel cord having a conventional 1 + 6 structure, which shows three inner strands constituting a lower strand in a steel cord having a 3 + 6 structure shown in FIG. It replaces with core 4a, and the structure which couple | bonded six stranded outer element wire 4b around it.

As shown, the steel cord of the 1 + 6 structure can improve the stability of the cord structure by the core wire 4a located at the center thereof, and to reduce the elongation at low elongation during extension of the cord. Since 4b) is in continuous line contact with the core wire 4a, it is difficult to intrude rubber into the space between the core wire and the outer element wire.

In the steel cord of the 1 + 6 structure, the inner space without the intrusion of rubber is surrounded by the core wire and the outer wire, and the core wire becomes free without being bonded to the rubber. There is a problem that the so-called core migration phenomenon is caused to move to the end of the belt.

Accordingly, the present invention is advantageous in terms of productivity in terms of unit weight and structural stability compared to conventional cord structures in view of various problems of conventional steel cords, and is advantageous in terms of productivity. And to provide a new steel cord structure as a tire reinforcement material which can improve fatigue resistance and prevent core wire movement.

The present invention is to take a flat oval cross-sectional structure in the cross-sectional shape of the steel cord to enable a lighter weight of the tire, while in particular by suppressing damage to the surface brass plating layer of the wire to maintain a high level of adhesiveness with the rubber air injection Another object is to provide a steel cord suitable for reinforcing materials such as radial tires and a method of manufacturing the same.

1 is a cross-sectional view of a conventional 3 + 6 hermetic steel cord.

Figure 2 is a cross-sectional view of a conventional 1x6 flat open steel cord.

Figure 3 is a cross-sectional view of a conventional 1 + 6 hermetic steel cord.

4 is a cross-sectional view of a flat continuous steel cord according to the present invention;

(A) is 2/5 structure,

(B) is 2/4 structure.

Figure 5 is a schematic structural diagram of a twisted pair apparatus showing a steel cord manufacturing process of the present invention.

FIG. 6 is a partial cross-sectional view showing an extract of the flattening roller of the twisted pair device of FIG. 5; FIG.

Figure 7 is a cross-sectional view of the initial state of the union point of the steel cord produced according to the method of the present invention.

8 is a cross-sectional view of a wire showing a brass plated layer damaged by a mold-shaping machine;

((Description of the reference sign for the main part of the drawing))

10a. Core wire 10b. siding

20. Core feeder 21. Side feeder

22. Poise 23. Twisting rotor

24. All Over Twister 25. Smokers

26. Flat Straightening Roller

The above object of the present invention is a 2 / (4-6) two-layered flat twisted structure in which a strand of 4 to 6 strands having a relatively thick wire diameter is twisted and bonded in one process, compared to two strands and a core. It is composed of an element wire without damage to the surface brass plating layer by the rotation ratio control of the whole over twister, and the long diameter part ratio of the side line is different from the other side line, and the core line has uneven natural shape in the cord length direction. By means of wire contact between the cores, and achieved by a steel cord for rubber reinforcement having a flat cross section.

In the flat steel cord of the present invention having the above structure, the flatness ratio is appropriately in the range of 105 to 150%, wherein the long diameter is 1.0 to 2.0 mm, the short diameter is 0.8 to 1.5 mm, and the pitch of the flat continuous cord is 5 to 50 times that of the long diameter. proper.

The reason why the flatness is limited to 105 to 150% in the steel cord of the present invention having a substantially elliptical cross section is that when the flatness is less than 105%, the effect that the cord cross section is expected to be flattened cannot be obtained and exceeds 150%. This is because the long diameter is relatively increased, and the number of cord inputs (EPI) per unit area of the top sheet decreases, which reduces the strength of the rubber product.

In relation to the long diameter, the maximum diameter of the flat cord cannot satisfy sufficient tensile strength as a reinforcement material if it is too small, less than 1.0 mm. On the contrary, if the thickness is too thick over 2.0 mm, the rubber thickness of the belt layer of the tire increases. Therefore, it is preferable to limit the long diameter to the range of 1.0 to 2.0 mm since the tire is reversed to weight reduction and disadvantageous in riding comfort during driving.

If the shorter diameter of the cord is less than 0.8mm, the shape becomes too flat in relation to the range of the long diameter, and the structural shape stability is lowered. On the contrary, if the length of the cord exceeds 1.5mm, the thickness of the topsheet is inevitably increased. Since it will adversely affect the range of the short diameter is appropriate 0.8 ~ 1.5mm.

The reason why the soft pitch of the cord is limited to 5 to 50 times in comparison to the long diameter is that, if it is less than 5 times, it is disadvantageous in terms of productivity. On the contrary, if the pitch is made larger than 50 times, the strand form becomes unstable. Because.

Next, the side wires of the strands constituting the steel cord of the present invention have a long diameter part ratio of 100 to 140%, and at least one strand of the side lines has a different ratio of 10% or more, more preferably 15% or more, and the sections in the lengthwise direction in the same wire. It is advantageous that the mold rate differs very much. At this time, when the long diameter mold rate of the side line is less than 100%, the rubber permeability through the side line is lowered, and if it exceeds 140%, there is a lack of structural stability of the strand according to the excessive mold.

In addition, when at least one strand of the side lines exhibits a difference of 10% or more from the other side lines, a structure having a relatively uniform mold rate is first subjected to a load having the lowest mold rate first in a particularly low load section. Elongation is lowered compared to It is more preferable that the side lines showing different mold percentages show a difference in mold percentage of 15% or more as compared to the other side lines.

The diameter of the core wire of the wire constituting the steel cord of the present invention is 0.1 ~ 0.25mm, the diameter of the side wire is 0.28 ~ 0.40mm is appropriate, if the core wire diameter is less than 0.1mm can not obtain sufficient cord cutting force and fresh plastic working It is disadvantageous in terms of cost due to the relatively high number of maneuvers, and larger than 0.25 mm has a disadvantage in that the cord diameter becomes large and the cord flexibility decreases.

If the side diameter is less than 0.28 mm, the cutting strength is lowered and the number of side strands is increased. If the side diameter is more than 0.4 mm, the fatigue resistance is decreased, the fatigue resistance is decreased, and the gap between the side lines is reduced. It is disadvantageous.

On the other hand, the core wire and the side wire constituting the steel cord have a tensile strength of 330 kgf / mm 2 or more, more preferably 330 to 450 kgf / mm 2, and an elongation at break of 2.0 to 3.5% is appropriate. Steel wires with the above mechanical properties are either JIS wire piano wire SWRS 82A (C = 0.82%), or increase the total throughput in the final wet drawing process to obtain higher strength, or over-steel steel wire wire (C≥0.9%). It is obtained by repeating cold drawing and parting heat treatment using raw materials as a raw material, followed by a wet-wetting drawing process, and finishing in the final drawing process.

Steel cord manufacturing method of the present invention having the structure as described above is as follows.

In manufacturing the steel cord of 2 / (4 to 6) flat continuous structure according to the present invention, the twisted pair coupling between the strands is carried out in a state in which a strand of the strands is attached using a mold stiffener in a conventional manner. Although the process of flattening by applying pressure to the pressure may be considered, in this method, the surface plating layer is damaged in the course of the wire passing through the mold swelling, so that the adhesiveness with the rubber is lowered. Through the repeated trial and error on the method that can be applied to the appropriate shape to the wire without this, the method of obtaining the steel cord structure according to the present invention without damaging the wire has been completed.

The method of manufacturing steel cord for rubber reinforcement of the present invention is a method for preventing the phenomenon that the brass plating layer formed on the surface of the wire is cut off by applying the wire of the wire using a mold machine. By controlling the rotation ratio of all over-twisters which are installed immediately after the resultant coalescing point, there is a technical feature to ensure that the appropriate shape is given to the element wire, especially the outer line, and that the gap as a rubber penetration path is secured between adjacent side lines.

According to the method of the present invention, the cores and sidelines are provided immediately after the joint point where the cores and the sidelines are associated with each other in supplying two to four strands having a diameter larger than the cores and the cores so as to be stranded together in one step at a time. Rotation ratio of over twister is rotated at 2.5 to 4.5 times the rotational speed of twisting rotor to ensure the excess supply length of the side line required in the flat twist structure and at the same time give the mold to the side line within the desired range. It is configured to be.

In general, in order to manufacture a conventional multilayer lead steel cord structure having a circular cross section as a flat multilayer lead structure, the wire length required per unit length of the outer layer lead is gradually supplied to the outermost layer gradually.

In other words, the stranded wire that passes through the twisting rotor and the over twister in the state where the stranded wire is connected between each strand and finally toward the winding bobbin is intended to inflate the shape of the cord before passing the flat straightening roller installed just before the winding bobbin. The larger the trend, the better the flattening.

If not, it is difficult to flatten the cord due to the lack of excess length of the side line when passing through the flat straightener, but rather the shape defect that the strands of the inner layer protrudes to the outermost layer and distorts the stranded form.

For the same reason as above, in order to supply the wire length of wires to each floor relatively differently, an additional mold is installed just before the federation point, and the wire wires are supplied in surplus due to the difference in mold rate. The method is mainly used.

In other words, the larger the shaping rate of the wire after passing through the federation point, the larger the amount of wire feeding, so that the wire forming the outer layer of the steel cord has a relatively large shaping rate so that the flattening as a subsequent process can be easily performed. do.

Even in the case of the flat-rolled steel cord structure of the present invention, it is possible to achieve flattening of the cord by using a molding machine, but in consideration of damage to the brass plating layer of the wire due to the use of the molding machine and deterioration of physical properties of the wire due to mechanical bending plastic deformation. Instead of using the machine, all over twister's rotation ratio control method is adopted.

In the steel cord structure of the present invention, all the wires have the same soft direction and soft pitch because the wires are twisted together in one process. In the same longitudinal direction, the increase in the relative surplus feed length of the outer layer can be achieved by changing the operating range of the entire overtwist tool.

In general, the all-over twister is used in a two-degree twisted twister is set to approximately two times the rotation ratio on the basis of the number of rotation of the twisted body in the manufacture of a multi-layer lead structure having a conventional circular cross-section.

In this regard, in the manufacturing of the flat continuous steel cord structure according to the present invention, the main technical feature of the manufacturing process is to give a rotation ratio of 2.5 to 4.5 times larger than 2 times in order to secure the excess supply length of the side line.

Further details of the steel cord for rubber reinforcement excellent in the rubber permeability of the present invention and its manufacturing method will be clearly understood by the following description with reference to the drawings showing preferred embodiments of the present invention.

First, Figure 4 is a cross-sectional structural view of the steel cord structure according to the present invention, (a) is 2/5 structure, (b) is 2/4 structure.

As shown in Fig. 4A, the five strands 10b having a larger wire diameter than the core are adjacent to each other around the two strands of the core 10a which maintain approximately line contact with each other along the longitudinal direction. 4B is a structure in which four strands 10b are twisted and joined around two core strands 10a.

The steel cords of the 2/5 structure and the 2/4 structure according to the present invention all take an oval cross-sectional structure as a whole, and the core wire 10a located inside the side lines 10b is formed in the gap. It has an open structure that communicates with the outside through the gap. The open gap between the side lines 10b serves as a rubber inflow passage allowing the rubber to be filled around the core wire 10a when the rubber is bonded with the rubber.

The flat continuous steel cord according to the present invention has a long diameter (a) having a maximum diameter in the width direction and a short diameter (b) having a minimum diameter in the thickness direction as its cross section is generally oval in shape, wherein the long diameter with respect to the short diameter (b) The ratio of (a), that is, the flatness ratio (a / b) is 105 to 150%, the size of the long diameter a is 1.0 to 2.0 mm, the short diameter is 0.8 to 1.5 mm, and the cord soft pitch is larger than the diameter of the long diameter. It is the range of 5 to 50 times, and either or S is possible in the longitudinal direction.

The wire diameter of the core wire 10a is preferably in the range of 0.1 to 0.25 mm, and the wire diameter of the side wire is preferably 0.28 to 0.40 mm larger than that.

Core wires and side wires constituting the steel cord of the present invention is used in that the brass plating layer is formed on the surface of the steel cord for the tire reinforcement for ordinary tires, the brass plating layer is formed on the surface in order to improve the adhesiveness with the rubber, At this time, the thickness of the plating layer is preferably in the range of 0.07 ~ 1.5㎛, the copper content in the brass plating layer is suitable 55-70%. More preferably, brass plating is performed with a ternary alloy containing 0.1 to 5.0% of the third element Co, Fe, Ni, etc. to further improve the corrosion resistance of the steel wire and to improve rubber adhesiveness, particularly aging adhesiveness. You can also make it work.

On the other hand, Figure 5 schematically shows the overall structure of a two-degree twisted twisted pair machine for producing a flat twisted steel cord of the present invention, the steel cord manufacturing method of the present invention based on this.

First, 5 strands of side wires supplied from two core wires 10a released from two core wire feeders 20 mounted on a cradle inside a stranded wire and five side feeders 21 ( 10b) is formed at the entrance of the poise 22 for the first time to form a union of these seven strands in a twisted pair form a pass through the poise 22.

Subsequently, the stranded wire exiting the poise 22 passes through the entire twister 24 which rotates in the same direction as the twisting rotor 23 but rotates at a rotation ratio of 2.5 to 4.5 times that of the twisting rotor 23. . At this time, since the previous over twister 24 rotates at a relatively high rotation ratio, the supply length of the side line 10b is increased compared to the core line 10a, that is, the side line maintains the excess supply length.

Next, the stranded wire that has passed through the over twister 24 passes through the two sets of twisting rotors 23 and exits out of the twisted pair as two twisting twists are formed.

The cord coming out of the twisted pair is passed through an overheater (25) called an over twister to correct the rotational force (torsion), and then through the straightening roller (26) for flat processing of the cord. Winding is performed on the winder 27 to obtain a steel cord having a flat bladder 2/5 structure according to the present invention.

At this time, the flat straightening roller 26 has a rectangular outer groove 26a on the surface of the roller as shown in the cross-sectional view of FIG. It is preferable that the cord be flattened while passing through the groove 26 to prevent the cord from being separated in the process of passing through the calibration roller 26. In the figure, reference numeral 28 denotes a drawing capstan as a feed driving source of the cord.

Although the drawing shows an example in which the flat straightening roller is installed at the rear of the rear overtwister, in some cases, the flat straightening roller is installed at the front of the rear overtwistor, or in the front and rear of the rear overtwister. Calibration rollers may be installed.

In the present invention, when the entire overtwisting tool is used instead of the molding machine, two strands of the core wire are formed in the final steel cord product by forming a so-called non-uniform natural shape that naturally gives the mold by the twisting method of the second degree twister. The five strands can produce a 2/5 flat twist structure in which at least one strand has a long diameter moldability different from each other.

The reason why the steel cord manufactured by the method of the present invention has the above structural characteristics is as follows based on the cross-section of the initial twisted-pair form of the 2/5 structural steel cord according to the present invention shown in FIG. .

As shown, since the 2/5 structure is not a geometrically dense filling structure due to its structural characteristics, at the time of the formation of the first stranded line at the junction, all five strands 10b are approximately symmetrically surrounded around the core 10a. The distance L1 between the center of the strand and the cord center point is different from the distance L2 between the other strand and the cord center point, that is, the length of the layer center radius is different (L1? L2).

In any element wire the layer center radius changes from time to time due to the 2/5 structure being asymmetrical. That is, it has a relatively nonuniform mold rate in the cord length direction.

Accordingly, at least one of the five strands has a different wire length per unit length, and thus shows a relatively different mold portion after the partial evaluation. In general, the smaller the core radius, the smaller the wire feed length.

At least one strand of each sideline differs by at least 10%, preferably at least 15%, i.e., low, especially in very low underload sections, the wire with the lowest moldability is loaded first and is relatively uniform. Compared with one structure, the elongation at low decreases.

The two strands of the core wire constituting the steel cord manufactured by the method of the present invention are composed of non-uniform natural dies in the cord length direction, so that the core wires are in the form of stranded wires with approximately linear contact with each other. Will be done.

Thus, the steel cord of the present invention additionally provides a lower lower elongation at break by the core wire. In other words, the structural features of the side lines and the core wires formed by the full overtwist method result in a 2/5 flat twist structure showing lower elongation at break.

In general, in the open type structure in which the element ratio of each wire is approximately uniform, it tends to easily increase even at a relatively low load, so it is easily converted into a closed type, and the rubber permeability decreases, and it is very sensitive to the slight change in supply tension applied to the cord in the tire rolling process. Handling is disadvantageous.

However, the present invention does not increase the elongation at low by adopting the all-over twister method as a method which is different from the conventional method of imparting excessive mold to the steel wire by using the mold machine or providing local unevenness (bending). There is a characteristic in the cord manufacturing method in that a 2 / (4-6) flat-duplex structure can be obtained.

That is, the present invention increases the rotation ratio of all over-twisters in comparison with the prior art so that the excess supply length of the side line is secured so that the stranded line of the core line and the side line is coupled, and then the individual side lines constituting the cord by flattening the side line. By providing a gap geometrically, the surface plating layer is prevented from being damaged by severe friction between the element wire and the mold forming device in the process of performing mechanical and plastic processing to impart the mold to the conventional element wire.

On the other hand, the wire for steel cords used for tire reinforcement is formed with a brass plated on the surface to improve the adhesiveness with the rubber, in the case of imparting the mold by using a mold-keeping machine according to the conventional general cord manufacturing method As a result of the frictional contact during the mold period, the brass plating layer 31 on the surface of the element wire 30 is damaged in the longitudinal direction as in the cross-sectional structure of the element wire passing through the mold machine shown in FIG. When the brass plating layer on the wire surface is damaged as a result, the damaged portion is inevitably deteriorated in rubber adhesiveness, in particular aging adhesiveness. However, in the steel cord of the present invention, the above-described problem is eliminated because the molding process is not performed by the molding machine which causes damage to the brass plating layer of the wire.

Embodiments of the present invention are as follows.

In order to compare and evaluate the quality and mechanical properties required as a rubber reinforcement material between the flat open steel cord and the conventional steel cord according to the present invention, pickling, dry, drawing, After the sequential heat treatment and brass plating process, the specimens were fabricated under the conditions as shown in Table 1 below in the stranded wire process using steel wires with diameters of 0.2, 0.35, and 0.37 mm respectively obtained by final drawing in the three-wet wet process. Was measured.

division Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Example 1 Example 2 Structure Name 3 + 6 1 * 6 1 + 6 2/5 2/5 2/5 Shape features closeness Flat open Filling Flat open Flat open Flat open Wire diameter (mm) Core 0.20 X 0.37 0.20 0.20 0.20 siding 0.35 0.37 0.35 0.37 0.37 0.37 Yearwise S / Z S S S S S Cord Pitch (mm) 10/18 18 18 18 18 18 Cord diameter (mm) Long view 1.135 1.15 1.07 1.31 1.25 1.12 Short diameter 1.13 0.85 1.07 0.97 0.98 0.93 Number of stranded wires Episode 2 1 time 1 time 1 time 1 time 1 time Method Bookkeeping Bookkeeping All OT All OT % Flatness 100 135 100 135 128 120 Small linear float rate (%) Core 102 X 100 118 95 95 Sideline (long diameter) at least 98 128 98 124 105 108 maximum 101 137 102 133 128 131 Core rubber adhesive appearance (%) 30 X 21 82 80 84 * Fatigue Resistance 100 121 102 124 136 128 Aging rubber adhesiveness 100 138 106 135 158 162 Surface Fe Elution (g / ㎡) 0.23 0.54 0.27 0.51 0.21 0.24 Elongation at Break (%) 2.6 3.2 2.6 2.9 2.9 2.9 Lowered Elongation Rate (%) 0.045 0.243 0.032 0.088 0.075 0.078 * Handling workability ◎ X ◎ △ ○ ○

The fatigue fatigue and aging rubber adhesion and handling workability indicated by * in Table 1 are the results of relative evaluation in the relative ratio (%) for Comparative Example 1.

In Table 1, the core rubber adhesive appearance is a test method adopted as a means for comparing and evaluating rubber permeability by structure. After embedding steel cord in rubber and vulcanizing, the rubber is filled in the cord length direction of the core wire inside the cord. It was relatively evaluated in terms of the length of attachment. 100% means that 100% rubber is filled in the center of the steel cord core wire.

Next, the fatigue resistance was embedded in the center of the small rubber specimen mold having a rectangular shape of 5mm long and 2.5mm long steel cord specimens, and using the rubber compound having a 100% modulus of 35kgf / ㎠ to give three bends The frequency of reciprocating cycles until the pulley was moved from side to side until the steel cord specimen in the rubber broke due to abrasion fatigue or the like was measured and evaluated relative to Comparative Example 1.

Aging rubber adhesion was compared by US Standard Test Method (ASTM 2229) with rubber, in particular with harsh humidity (95% RH) and wet heat aging under high temperature (82 ° C).

The surface iron (Fe) elution amount is a test method for evaluating defects or damage of the surface brass plating layer of the steel cord. The iron elution method (sample; 0.5 N-HNO ₃ solution × 22 ° C × 1 min) The amount of iron eluted per square meter (m 2) of the surface of the specimen was expressed in g / m 2. That is, the greater the amount of iron elution per time, the greater the damage to the brass surface layer.

The elongation at break is expressed as a percentage of elongation at break of the cord, and the elongation at break is a percentage of the elongated length of the specimen at low loads, typically in the range 0.5 to 3 kgf. Indicates.

The handling workability is the convenience or ease in handling the steel cord in the tire forming process. The lower the elongation at break, especially due to the structural twist stability of the steel cord, the better. ), ○ (good), △ (normal), and X (bad).

According to the comparison result of the core rubber adhesive appearance, it can be seen that the rubber penetrated well into the cord in the flat open structure (Comparative Example 2, Comparative Example 4, Example 1 and Example 2).

Embodiment 1 and 2 steel cords of the present invention are very advantageous in terms of rubber adhesive side, in particular thermo-wet age adhesiveness, compared to Comparative Example 1 in the conventional steel cords, which form side-side gaps due to the flattened shape of the stranded structure. Due to the removal of the passage to diffuse the rust, it can be seen that the improved effect compared to the case of using the mold of the comparative example 4 due to the flattening while retaining the intact brass layer.

In Comparative Example 2, it is excellent in terms of rubber permeability, but it is understood that the elongation during deterioration increases, which is disadvantageous in terms of handling workability.

In addition, in the iron dissolution test, in the case of the flat open type of Comparative Examples 2 and 4, it was found that the brass plating layer was damaged due to the imparting of the steel wire by the mold deformation due to coercive plastic deformation. In the case of not using a mold swelling to maintain a good brass plated layer also worked in favor of adhesion with rubber, in particular in the heat-wetting age adhesiveness.

In comparison with Examples 1 and 2 and Comparative Example 4 of the present invention, the core portion has a natural mold by the method of twisting twisted twister with a 2 degree twisted wire contact, and at least one strand is 10 Since the long diameter moldability is different by more than%, it can be seen that the elongation at lower is relatively low compared to Comparative Example 4, which has a relatively uniform twist, and thus the handling workability is excellent in the tire manufacturing process. In the case of the flat open structure without the core wire of Comparative Example 2, it can be seen that the elongation at break is considerably high.

As described above, the steel cord of the present invention has a flat open structure, and a gap is formed in the vertical direction in the longitudinal direction between the strands of the side lines so that rubber can easily penetrate into the cord. Due to this, the problem of core movement is prevented, and in particular, the hot and wet aging adhesiveness is excellent, and the rubber acts as a buffer between the side lines and the core wires, thereby preventing direct contact between the wires.

In addition, since the steel cord of the present invention does not use a molding machine, the damage of the brass plating layer is minimized to further improve hot-humidity aging adhesiveness and fatigue resistance. Due to its properties, the rubber reinforcement and handling workability are improved by providing a gap between adjacent strands of the stranded structure without causing an increase in elongation during degradation as a material for reinforcing tires.

In addition, the steel cord of the present invention is advantageous in terms of manufacturing cost because the twisted pair coupling of the core wire and the side wire is performed in one step. Therefore, the steel cord of the present invention is expected to be usefully used as a new steel cord structure for tire reinforcement to increase the running performance and service life of the tire and ultimately improve the durability of the tire.

Claims (6)

In steel cord embedded in vulcanized rubber, 2 / (4 ~ 6) double-layered flat ablation, in which a strand of 4-6 strands with a relatively thick wire diameter is stranded in one step, compared to two strands and a core As a structure, the side line without damage of the surface brass plating layer is stranded by maintaining the clearance between adjacent side lines by using the rotation ratio control of all over-twisters without using mold-shaping machine, and the long diameter part ratio of the side line is different from other side lines. The core wire has a non-uniform natural shape in the cord longitudinal direction and is connected in line contact between the core wires, and the steel cord for rubber reinforcement having excellent rubber permeability, characterized in that the cross section of the cord is flat. The flat cord has a flattening ratio of 105 to 150%, a long diameter of 1.0 to 2.0 mm, a short diameter of 0.8 to 1.5 mm, and a pitch of the flat short cord of 5 to 50 times the long diameter of the cord. The steel cord for rubber reinforcement having excellent rubber penetration, characterized in that the direction of any one of S or Z. The rubber permeability of claim 1, wherein the long diameter moldability of the side line is 100 to 140%, at least one strand of the side line has a different ratio of 10% or more, and the mold penetration rate is different for each section in the longitudinal direction even in the same strand. Steel cord for superior rubber reinforcement. The steel cord for rubber reinforcement having excellent rubber permeability according to claim 1, wherein the side diameter of the side line is 100 to 140%, and at least one strand of the side line has a different ratio of 15% or more. The rubber reinforcing material having excellent rubber permeability according to claim 1, wherein the core wire has a diameter of 0.1 to 0.25 mm, the diameter of the ship's wire is 0.28 to 0.40 mm, and the core wire and the ship's wire have tensile strength of 330 to 450 kgf / mm 2. Steel cord. A method of manufacturing steel cord embedded in vulcanized rubber, comprising: stranding four to six strands having a relatively thicker wire diameter than a core and two strands without imparting a mold, and surrounding the core Passing the twisted pair of stranded strands connected to the stranded wires at a rotation ratio of 2.5 to 4.5 times the rotational speed of the twisted rotor to ensure that the excess supply length of the stranded vessels is secured compared to the cores, 2 Passing two sets of twisting twists while passing through the twisting rotor of the set, and the cord exiting the twisted pair passes through a flat straightening roller with a rectangular groove formed on the outer circumferential surface of the rear or front and rear of the twister. Rubber reinforcement for excellent rubber permeability, characterized in that the step consisting of 2 / (4 to 6) flat short cord The method of code.