CN214219194U - Steel wire cord for engineering tire - Google Patents

Abstract

The utility model discloses a steel cord for engineering child, including cord and outer steel wire that twines, the cord includes core strand steel wire and a plurality of outer strand steel wire, and wherein the outside of core strand steel wire is located along the circumferencial direction to outer strand steel wire, twines the outside that the cord was located along the circumferencial direction to the steel wire outward. The utility model discloses a clearance between the outer strand steel wire is great, is favorable to rubber fully to permeate core strand steel wire, avoids leading to the point contact friction between each layer steel wire because of not permeating sufficient rubber, and then can solve the problem that steel cord bearing capacity became invalid because of wearing and tearing.

Description

Steel wire cord for engineering tire

Technical Field

The utility model relates to a steel cord for engineering child belongs to steel cord technical field.

Background

The steel cord is an important component in an engineering radial tire framework material, the steel cord is a steel cord of a 7 x (3 +9+ 15) x d1+ d2HT structure commonly used in engineering radial tires, and is formed by weaving and twisting one core strand, six outer layer strands and one outer winding steel wire, wherein the core strand and the outer layer strands are of the same structure, the steel wire d1 has the same diameter, the (3 +9+ 15) x d1 structure is SSS or ZZZ, the lay length is 5.0/10.0/16.0mm or 6.3/12.5/18.0mm, the six outer layer strands are S, the lay length is 38.0-56.0 mm, the outer winding steel wire is Z, the lay length is 5.0mm, the strands are arranged compactly, gaps among the outer layer strands are small, rubber cannot effectively permeate the core strand, and the air content in the steel cord is high.

During the use of the radial tire, the problem of the failure of the bearing capacity of the cord is easily caused by the insufficient strength of the steel wire cord or the corrosion and abrasion of the steel wire. The structure of the steel cord and the strength, bending stiffness and adhesive property with rubber thereof have direct influence on the tire, and the defects caused by unreasonable structural design cannot be completely compensated only by controlling the production process of the steel cord.

Disclosure of Invention

An object of the utility model is to overcome not enough among the prior art, provide a steel cord for engineering child, it is not enough to solve steel cord intensity, and the clearance is little between the outer thigh, and rubber can not effectively permeate core strand steel wire and cause the high defect of cord inside air content.

In order to achieve the above purpose, the utility model adopts the technical proposal that:

providing a steel cord for engineering tire, which comprises a cord and an outer winding steel wire, wherein the outer winding steel wire is wound on the periphery of the cord;

the cord comprises a core strand steel filament and a plurality of outer layer strand steel filaments; the outer layer strand steel wires are arranged along the circumferential direction and are arranged on the periphery of the core strand steel wires;

the core strand steel wire is formed by braiding and twisting at least three core strand first layer steel wires, at least nine core strand second layer steel wires and at least fifteen core strand third layer steel wires which are arranged layer by layer from inside to outside;

the outer layer strand wire steel wire is formed by braiding at least three outer layer strand first layer steel wires, at least nine outer layer strand second layer steel wires and at least fifteen outer layer strand third layer steel wires which are arranged layer by layer from inside to outside;

the diameter of the first layer of core strand steel wires, the diameter of the second layer of core strand steel wires and the diameter of the third layer of core strand steel wires are the diameter of the first steel wires, the diameter of the first layer of outer strand steel wires, the diameter of the second layer of outer strand steel wires and the diameter of the third layer of outer strand steel wires are the diameter of the second steel wires, and the diameter of the first steel wires is larger than the diameter of the second steel wires.

Furthermore, the diameter range of the first steel wire is 0.19-0.26 mm, and the diameter range of the second steel wire is 0.17-0.24 mm.

Further, the difference between the diameter of the first steel wire and the diameter of the second steel wire is not less than 0.02 mm.

Further, the gap distance between the steel wires of the outer layer strand is not less than 0.04 mm.

Furthermore, the diameter range of the externally-wound steel wire is 0.20-0.25 mm.

Further, the cord is provided with at least six outer strand steel wires.

Further, the six strands of outer strand steel wires are uniformly twisted along the periphery of the core strand steel wire, and the outer winding steel wires are uniformly twisted along the periphery of the cord thread and are distributed on the outer strand steel wires.

Further, the core strand steel wires and the outer layer strand steel wires have the same twisting direction, the cord has the same twisting direction as the core strand steel wires, and the outer winding steel wires have the opposite twisting direction to the cord.

Furthermore, the lay length of the first layer of steel wires of the core strand is 0.5 times of that of the second layer of steel wires of the core strand, and the lay length of the third layer of steel wires of the core strand is 1.44-1.6 times of that of the second layer of steel wires of the core strand; the first layer of steel wire lay length of the outer layer strand is 0.5 times of the second layer of steel wire lay length of the outer layer strand, and the third layer of steel wire lay length of the outer layer strand is 1.44-1.60 times of the second layer of steel wire lay length of the outer layer strand; the cord thread lay length is 42.0-70.0 mm, and the outer winding steel wire lay length is 5.0 mm.

Further, the strength grades of the first layer steel wire of the core strand, the second layer steel wire of the core strand and the third layer steel wire of the core strand and the first layer steel wire of the outer layer strand, the second layer steel wire of the outer layer strand and the third layer steel wire of the outer layer strand are any one of normal strength NT, high strength HT, ultrahigh strength ST, ultrahigh strength UT or ultrahigh strength MT.

Compared with the prior art, the utility model discloses the beneficial effect who reaches:

(1) the utility model discloses set up first steel wire diameter d1 and be greater than second steel wire diameter d2, be favorable to rubber infiltration to core strand steel wire, avoid because not permeating enough rubber and leading to the point contact friction between each layer steel wire, and then avoided the problem that steel cord bearing capacity became invalid because of wearing and tearing;

(2) the utility model provides a pair of steel cord for engineering child twists with fingers to structure can improve anticorrosive, fatigue-resisting, shock resistance and the bonding retentivity of tire, improves the life of tire.

Drawings

FIG. 1 is a schematic cross-sectional view of a steel cord for a construction tire according to an embodiment of the present invention;

FIG. 2 is a cross-sectional schematic view of a steel cord of the prior art;

in the figure: 1. a core strand first layer of steel filaments; 2. a core strand second layer of steel filaments; 3. a third layer of steel wires of the core strand; 10. core strand steel wire; 20. outer ply strand wire; 30. a cord; 4. the outer layer strands form first layer steel wires; 5. the outer layer strand is a second layer of steel wire; 6. the outer layer strand third layer steel wire; d1, first wire diameter; d2, second wire diameter; d3, first wrap wire diameter; d4, fourth wire diameter; d5, second wrap wire diameter; l, gap distance.

Detailed Description

The present invention will be further described with reference to the accompanying drawings. The following examples are only for illustrating the technical solutions of the present invention more clearly, and the protection scope of the present invention is not limited thereby.

In the description of the present invention, it is to be understood that the terms "center", "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", and the like, indicate orientations or positional relationships based on the orientations or positional relationships shown in the drawings, and are used merely for convenience of description and for simplicity of description, and do not indicate or imply that the device or element being referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore, should not be construed as limiting the present invention. Furthermore, the terms "first", "second", etc. are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first," "second," etc. may explicitly or implicitly include one or more of that feature. In the description of the present invention, "a plurality" means two or more unless otherwise specified.

In the description of the present invention, it is to be noted that, unless otherwise explicitly specified or limited, the terms "mounted," "connected," and "connected" are to be construed broadly, and may be, for example, fixedly connected, detachably connected, or integrally connected; can be mechanically or electrically connected; they may be connected directly or indirectly through intervening media, or they may be interconnected between two elements. The specific meaning of the above terms in the present invention can be understood by those of ordinary skill in the art through specific situations.

Fig. 1 shows a schematic cross-sectional view of a steel cord for an engineering tire according to an embodiment of the present invention, which is a steel cord for an engineering tire (3 +9+15 × d1+ 6 × (3 +9+15 × d2 + d 3), and table 1 shows data parameters of steel cord embodiments 1 to 6 of the present invention, which is formed by twisting a core strand steel wire 10, six outer strand steel wires 20, and an outer twisted steel wire having a first outer twisted steel wire diameter d 3. The cross section of the cord 30 is circular, and the outer layer strand steel wires 20 are twisted around the core strand steel wires 10 to form a structure in which six outer layer strand steel wires 20 are uniformly twisted around one core strand steel wire 10. The core strand steel wire 10 is formed by three core strand first layer steel wires 1, nine core strand second layer steel wires 2 and fifteen core strand third layer steel wires 3 in a twisting mode. Nine core strand second layer steel wires 2 are twisted around the three core strand first layer steel wires 1, fifteen core strand third layer steel wires 3 are twisted around the nine core strand second layer steel wires 2. Wherein the diameters of the first layer of core strand steel wires 1, the second layer of core strand steel wires 2 and the third layer of core strand steel wires 3 are the same, and the diameter range is 0.19-0.26 mm.

The outer layer strand wire 20 is formed by three outer layer strand first layer steel wires 4, nine outer layer strand second layer steel wires 5 and fifteen outer layer strand third layer steel wires 6, the nine outer layer strand second layer steel wires 5 are twisted around the three outer layer strand first layer steel wires 4, and the fifteen outer layer strand third layer steel wires 6 are twisted around the nine outer layer strand second layer steel wires 5. Wherein the diameters of the outer layer strand first layer steel wire 4, the outer layer strand second layer steel wire 5 and the outer layer strand third layer steel wire 6 are the same, and the diameter range is 0.17-0.24 mm.

The core strand steel wires 10 are twisted in the same direction as the steel wires of the outer layer strand steel wires 20, the cord 30 is twisted in the same direction as the core strand 10, the outer wrap steel wires of the first outer wrap steel wire diameter d3 are twisted in the opposite direction to the cord 30, and the distance L between the outer layer strand steel wires 20 is at least greater than 0.04 mm.

The utility model discloses a change outer steel cord's structure, improve steel cord's intensity and ooze gluey performance, shock resistance and fatigue resistance ability, reduce the air content between tire steel cord strand and the thigh, compensate the unreasonable defect of bringing because of steel cord structural design, improve the life of tire cord fabric intensity level and tire.

In the embodiment of the present invention, the strength grade of the steel wire in the core strand steel wire 10 and the outer layer strand steel wire 20 is general strength NT, high strength HT, ultra-high strength ST, ultra-high strength UT, or ultra-high strength MT; the utility model is suitable for a steel wire to the different intensity grades of normal strength NT, high strength HT, superhigh strength ST, extra-high strength UT or high strength MT is compiled and is twisted with fingers, can improve the intensity requirement, the glue permeability performance and shock resistance, the fatigue resistance ability of compiling the steel cord that twists with fingers the formation.

TABLE 1

The first embodiment is as follows:

in this embodiment, the diameter d1 of the first steel wire in the core strand 10 is at least greater than the diameter d2 of the second steel wire in the outer layer strand 20 and has 0.02mm, the diameters of the first layer steel wire 1 of the core strand in the core strand steel wire 10, the second layer steel wire 2 of the core strand and the third layer steel wire 3 of the core strand are 0.26mm, and the diameter of the first layer steel wire 4 of the outer layer strand in the outer layer strand steel wire 20, the diameter of the second layer steel wire 5 of the outer layer strand and the diameter of the third layer steel wire 6 of the outer layer strand are 0.24 mm. The twisting pitch of the first layer of steel wires 1 of the core strand steel wire 10 is 6.3mm, the twisting pitch of the second layer of steel wires 2 of the core strand is 12.5mm, and the twisting pitch of the third layer of steel wires 3 of the core strand is 18.0 mm; the lay length of the first layer of outer layer strand steel wires 4 of the outer layer strand steel wires 20 is 6.3mm, the lay length of the second layer of outer layer strand steel wires 5 is 12.5mm, and the lay length of the third layer of outer layer strand steel wires 6 is 18.0 mm.

The same twist direction is adopted for the core strand steel wire 10 and the outer layer strand steel wire 20, the twist direction of the core strand steel wire 10 is ZZZ twist, the twist direction of the outer layer strand steel wire 20 is ZZZ twist, the twist direction of the cord 30 is Z twist, the diameter of the outer-wound steel wire d3 is 0.20mm, and the twist direction of the outer-wound steel wire is S twist, in this embodiment, the steel cord structure of (3 +9+15 × 0.26) plus 6 × (3 +9+15 × 0.24) plus 0.20 is used for the steel cord for reinforcing the giant radial tire of the engineering vehicle.

As shown in fig. 2, which is a schematic cross-sectional view of a steel cord in the prior art, is a schematic cross-sectional view of a commonly used 7 × (3 +9+15 × 0.245) +0.245HT structural steel cord, the diameter of the 7 × (3 +9+15 × 0.245) +0.245HT structural steel cord is 4.84mm, the diameter of each of the core strand steel wires 10 and the outer layer strand steel wires 20 is 0.245mm, both the core strand steel wires 10 and the outer layer strand steel wires 20 are ZZZ-twisted, the cord 30 is S-twisted, the diameter of the second outer-wound steel wire d5 is 0.245mm, and the outer-wound steel wire direction is Z-twisted. The lay length of the first layer of steel wire 1 of the core strand in the core strand steel wire 10 and the outer layer strand steel wire 20 is 6.3mm, the lay length of the second layer of steel wire 2 of the core strand is 12.5mm, the lay length of the third layer of steel wire 3 of the core strand is 18.0mm, the lay length of the cord thread 30 is 56.0mm, and the lay length of the outer winding steel wire is 5.0 mm.

Table 2 is a performance index comparison table of a (3 +9+15 × 0.26 +6 × (3 +9+15 × 0.24) +0.20 structural steel cord in the embodiment of the present invention and a 7 × (3 +9+15 × 0.245) +0.245HT structural steel cord commonly used in radial tires in the related art:

TABLE 2

As can be seen from FIG. 2 and Table 2, the breaking force of the 7 × (3 +9+15 × 0.245) +0.245HT structural steel cord was not less than 22385N, the breaking force/linear density was 302.9N/(/ g/m), and the adhesion was not less than 2600N/25 mm.

The diameter of the steel cord of the first embodiment of the present invention is 4.65mm, the twist direction of the core strand steel wire (10) is ZZZ twist, the lay length is 6.3/12.5/18.0mm, the twist direction of the outer strand steel wire (20) is ZZZ twist, the lay length is 6.3/12.5/18.0mm, the lay length of the cord (30) is 65.0mm, the breaking force is not less than 23000N, the breaking force/linear density is 325.7N/(mm), the adhesive force is not less than 2800N/25 mm. Compared with the prior art, the embodiment of the utility model provides an adopt the steel wire strand of the same high strength grade, through increasing core strand diameter, change the cord twist to and increase steel wire cord lay length, can effectively promote cord intensity, glue permeation rate and fatigue resistance ability.

Example two:

the second embodiment of the present invention is (3 +9+15 × 0.24 +6 x (3 +9+15 × 0.215 + 0.20) structural steel cord, the diameter of the steel wire d1 in the core strand 10 in the embodiment is at least greater than the diameter of the second steel wire d2 in the outer strand 20 and is 0.025mm, the diameters of the core strand first layer steel wire 1 and the core strand second layer steel wire 2 and the core strand third layer steel wire 3 in the core strand steel wire 10 are 0.24mm, and the diameters of the outer strand first layer steel wire 4 in the outer strand steel wire 20 and the diameters of the outer strand second layer steel wire 5 and the outer strand third layer steel wire 6 are 0.215 mm. The lay length of 1 of the first layer steel wire of core thigh strand wire 10 plaiting twist is 6.3mm, the lay length of 2 plaiting twists of core thigh second layer steel wire is 12.5mm, the lay length of 3 plaiting twists of core thigh third layer steel wire is 18.0mm, the lay length of 4 plaiting twists of outer layer thigh first layer steel wire in outer layer thigh strand steel wire 20 is 6.3mm, the lay length of 5 plaiting twists of outer layer thigh second layer steel wire is 12.5mm, the lay length of 6 plaiting twists of outer layer thigh third layer steel wire is 18.0 mm. The same twist direction is adopted for the core strand steel wire 10 and the outer strand steel wire 20, the twist direction of the core strand steel wire 10 is ZZZ twist, the twist direction of the outer strand steel wire 20 is ZZZ twist, the twist direction of the cord 30 is Z twist, the diameter d3 of the first externally-wound steel wire is 0.20mm, and the twist direction of the externally-wound steel wire is S twist, in this embodiment, the structural steel cord of (3 +9+15 × 0.24) +6 × (3 +9+15 × 0.215) +0.20 is used for the reinforcing steel cord of the giant radial tire of the engineering vehicle.

A 7 × (3 +9+15 × 0.22) +0.20HT structural steel cord commonly used in the prior art, the diameter of the cord is 4.35mm, the diameters of the core strand steel wires 10 and the outer strand steel wires 20 are both 0.22mm, the twisting directions of the core strand steel wires 10 and the outer strand steel wires 20 are both ZZZ twisting, the cord 30 is S twisting, the diameter of the second outer winding steel wires d5 is 0.20mm, the twisting directions of the outer winding steel wires are Z twisting, the twisting pitches of the core strand steel wires 1 and the first layer steel wires 1 of the core strand steel wires 20 are both 6.3mm, the twisting pitches of the second layer steel wires 2 of the core strand are both 12.5mm, the twisting pitches of the third layer steel wires 3 of the core strand are both 18.0mm, the twisting pitch of the cord 30 is 48.0mm, and the twisting pitch of the outer winding steel wires is 5.0 mm.

Table 3 is a performance index comparison table between the second (3 +9+15 × 0.24 +6 x (3 +9+15 × 0.215) +0.20 structural steel cord of the embodiment of the present invention and the 7 x (3 +9+15 × 0.22) +0.20HT structural steel cord commonly used in radial tires in the related art:

TABLE 2

As can be seen from FIG. 2 and Table 3, the breaking strength of the 7X (3 +9+ 15X 0.22) +0.20HT structural steel cord was not less than 17955N, the breaking strength/linear density was 303.5N/(g/m), and the adhesive strength was not less than 2600N/25 mm. The diameter of the steel cord of the second embodiment of the utility model is 4.25mm, the 10 steel wire twist directions of the core strand steel wire are ZZZ twist, the twist pitch is 6.3/12.5/18.0mm, the 20 steel wire twist directions of the outer strand steel wire are ZZZ twist, the twist pitch is 6.3/12.5/18.0mm, the twist pitch of the cord 30 is 60.0mm, the breaking force is not less than 19300N, the breaking force/linear density is 331.6N/(mm), the adhesive force is not less than 2800N/25 mm; compared with the two, the embodiment of the utility model provides a two adopt the steel wire strand of the same high strength grade, through increasing core strand diameter, change the cord twist to and increase steel wire cord lay length, effectively promote cord intensity, glue permeation rate and fatigue resistance ability.

Example three:

the third embodiment of the present invention is (3 +9+15 × 0.19 +6 x (3 +9+15 × 0.17 + 0.20) structural steel cord, the diameter of the steel wire d1 in the core strand 10 in the embodiment is at least greater than the diameter of the second steel wire d2 in the outer strand 20 and is 0.025mm, the diameters of the core strand first layer steel wire 1 and the core strand second layer steel wire 2 and the core strand third layer steel wire 3 in the core strand steel wire 10 are 0.19mm, and the diameters of the outer strand first layer steel wire 4 in the outer strand steel wire 20 and the diameters of the outer strand second layer steel wire 5 and the outer strand third layer steel wire 6 are 0.17 mm. The lay length of 1 of the first layer of steel wire of core thigh strand wire 10 plaiting twist is 6.3mm, the lay length of 2 plaiting twists of core thigh second layer steel wire is 12.5mm, the lay length of 3 plaiting twists of core thigh third layer steel wire is 18.0mm, the lay length of 4 plaiting twists of outer layer thigh first layer steel wire in outer layer thigh strand steel wire 20 is 5.0mm, the lay length of 5 plaiting twists of outer layer thigh second layer steel wire is 10.0mm, the lay length of 6 plaiting twists of outer layer thigh third layer steel wire is 16.0 mm. The same twist direction is adopted for the core strand steel wire 10 and the outer strand steel wire 20, the twist direction of the core strand steel wire 10 is ZZZ twist, the twist direction of the outer strand steel wire 20 is ZZZ twist, the twist direction of the cord 30 is Z twist, the diameter d3 of the first externally-wound steel wire is 0.20mm, and the twist direction of the externally-wound steel wire is S twist, in this embodiment, the structural steel cord of (3 +9+15 × 0.19) +6 × (3 +9+15 × 0.17) +0.20 is used for the reinforcing steel cord of the giant radial tire of the engineering vehicle.

A 7 × (3 +9+15 × 0.175) +0.20HT structural steel cord commonly used in the prior art, the diameter of the cord is 3.42mm, the diameters of the core strand steel wires 10 and the outer strand steel wires 20 are both 0.175mm, the twisting directions of the core strand steel wires 10 SSS and the outer strand steel wires 20 are both ZZZ twisting, the cord 30 is S twisting, the diameter of the second outer winding steel wires d5 is 0.20mm, the twisting directions of the outer winding steel wires are Z twisting, the twisting pitches of the core strand first layer steel wires 1 in the core strand steel wires 1 and the outer strand steel wires 20 are both 5.0mm, the twisting pitches of the core strand second layer steel wires 2 are both 10.0mm, the twisting pitches of the core strand third layer steel wires 3 are both 16.0mm, the twisting pitch of the cord 30 is 38.0mm, and the twisting pitch of the outer winding steel wires is 5.0 mm.

Table 4 is a performance index comparison table between a third (3 +9+15 × 0.24 +6 x (3 +9+15 × 0.215) +0.20 structural steel cord of the embodiment of the present invention and a 7 x (3 +9+15 × 0.22) +0.20HT structural steel cord commonly used in radial tires of the related art:

TABLE 4

As can be seen from FIG. 2 and Table 4, the breaking strength of the 7 × (3 +9+15 × 0.175) +0.20HT structural steel cord is not less than 11470N, the breaking strength/linear density is 305.8N/(g/m), and the adhesive strength is not less than 2200N/25 mm. The diameter of the steel cord of the third embodiment of the utility model is 3.42mm, the 10 steel wire twist directions of the core strand steel wire are ZZZ twist, the twist pitch is 6.3/12.5/18.0mm, the 20 steel wire twist directions of the outer strand steel wire are ZZZ twist, the twist pitch is 5.0/10.0/16.0mm, the twist pitch of the cord 30 is 45.0mm, the breaking force is not less than 12000N, the breaking force/linear density is 330.5N/(mm), the adhesive force is not less than 2200N/25 mm; compared with the two, the embodiment of the utility model provides a three steel wire strand wires that adopt the same intensity level through increasing core strand diameter, change the cord twist to and increase steel cord thread pitch, effectively promote cord strength, glue permeation rate and fatigue resistance ability.

It can be seen through the comparison of above embodiment, when the radial tire of the equal density of preparation, adopt the utility model discloses the radial tire intensity of preparation compares with the radial tire intensity that adopts the prior art preparation, can improve radial tire intensity 8% to and cord oozes gluey performance and fatigue resistance ability. Just the utility model discloses can effectively reduce the manufacturing cost of engineering vehicle radial tire, prolong engineering vehicle radial tire's life.

The embodiment of the present invention is only an example, and according to different applications, the present invention (3 +9+15 × d1+ 6 × (3 +9+15 × d 2) + d3 structure, the core strand steel wire in the core strand steel wire 10 and the outer strand steel wire in the outer strand steel wire 20 can be proportioned using different wire diameters and strengths, and the twist direction is zz Z/S or SSS/S/Z.

The foregoing is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, a plurality of modifications and variations can be made without departing from the technical principle of the present invention, and these modifications and variations should also be considered as the protection scope of the present invention.

Claims (10)

1. A steel cord for a construction tire, characterized by comprising a cord (30) and an outerwrap steel wire wound around the outer circumference of the cord (30);

said cord (30) comprising a core strand steel filament (10) and a plurality of outer layer strand steel filaments (20); the outer layer strand steel wires (20) are arranged along the circumferential direction and are arranged on the periphery of the core strand steel wire (10);

the core strand steel wire (10) is formed by braiding and twisting at least three core strand first layer steel wires (1), at least nine core strand second layer steel wires (2) and at least fifteen core strand third layer steel wires (3) which are arranged layer by layer from inside to outside;

the outer-layer strand steel wire (20) is formed by braiding and twisting at least three outer-layer strand first-layer steel wires (4), at least nine outer-layer strand second-layer steel wires (5) and at least fifteen outer-layer strand third-layer steel wires (6) which are arranged layer by layer from inside to outside;

the diameter of the core strand first layer steel wire (1), the core strand second layer steel wire (2) and the core strand third layer steel wire (3) is a first steel wire diameter (d 1), the diameter of the outer layer strand first layer steel wire (4), the outer layer strand second layer steel wire (5) and the outer layer strand third layer steel wire (6) is a second steel wire diameter (d 2), and the first steel wire diameter (d 1) is larger than the second steel wire diameter (d 2).

2. A steel cord for construction tires according to claim 1, characterized in that, the first steel wire diameter (d 1) ranges from 0.19 to 0.26mm, the second steel wire diameter (d 2) ranges from 0.17 to 0.24 mm.

3. A steel cord for construction tires according to claim 1 or 2, characterized in that, the difference of the first steel wire diameter (d 1) and the second steel wire diameter (d 2) is not less than 0.02 mm.

4. A steel cord for engineering tires according to claim 1, characterized in that, the gap distance (L) between the outer layer strand steel wires (20) is not less than 0.04 mm.

5. A steel cord for engineering tire according to claim 1, characterized in that the diameter of the steel filament is in the range of 0.20 to 0.25 mm.

6. A steel cord for construction tyres as claimed in claim 1, characterized in that said cord (30) is provided with at least six outer strand steel wires (20).

7. A steel cord for construction tires according to claim 6, characterized in that, the six outer strand steel wires (20) are uniformly twisted along the outer circumference of the core strand steel wire (10), and the outer wrap steel wires are uniformly twisted on the outer strand steel wires (20) along the outer circumference of the cord (30).

8. A steel cord for construction tires according to claim 1, characterized in that, the twist direction of the core strand steel wires (10) is the same as the twist direction of the steel wires in the outer layer strand steel wires (20), the twist direction of the cord (30) is the same as the twist direction of the core strand steel wires (10), and the twist direction of the outer wrap steel wires is opposite to the twist direction of the cord (30).

9. A steel cord for engineering tire according to claim 1, characterized in that the core strand first layer steel wires (1) have a lay length 0.5 times the lay length of the core strand second layer steel wires (2), and the core strand third layer steel wires (3) have a lay length 1.44 to 1.6 times the lay length of the core strand second layer steel wires (2); the lay length of the first layer of steel wires (4) of the outer layer strands is 0.5 times of that of the second layer of steel wires (5) of the outer layer strands, and the lay length of the third layer of steel wires (6) of the outer layer strands is 1.44-1.60 times of that of the second layer of steel wires (5) of the outer layer strands; the lay length of the cord thread (30) is 42.0-70.0 mm, and the lay length of the externally wound steel wire is 5.0 mm.

10. A steel cord for construction tires according to claim 1, characterized in that the strength grade of the core strand first layer steel wires (1), the core strand second layer steel wires (2) and the core strand third layer steel wires (3), and the outer strand first layer steel wires (4), the outer strand second layer steel wires (5) and the outer strand third layer steel wires (6) is any one of normal strength NT, high strength HT, ultra-high strength ST, ultra-high strength UT or ultra-high strength MT.

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