Patent ID: 12247352

10: steel core wire;20: sheath-layer steel wire;30: steel cord.

DETAILED DESCRIPTION

In order to make the objectives, technical solutions and advantages of the present invention clearer, the present invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments escribed herein are merely used to explain the present invention, and are not intended to limit the present invention.

The application principle of the present invention will be described in detail below with reference to the accompanying drawings.

According to the structure of a steel cord manufactured by the present invention shown inFIG.1, the steel cord30includes a steel core wire10located in the center, and M sheath-layer steel wires20arranged around the steel core wire10in the center and tangent to the outer peripheral surface of the steel core wire10. There are at least two gaps L between the M sheath-layer steel wires. The diameter d of the steel core wire10is less than the diameter d1 of the sheath-layer steel wires20.

Specifically, the steel cord30used by a radial tire meets the requirement of the tire cord strength, and also further improves the performance of the tire and facilitates prolonging of the service life of the tire.

The width dimension of the gaps L is adjusted by adjusting the ratio of d to d1. In the present invention, the ratio of d to d1 is 0.420-0.640, so as to avoid aggregation of the gaps L caused by sliding of the outer sheath-layer steel wires20, which causes the total dimension of the aggregated gaps L to be greater than the dimension of the steel core wire10, and may cause the central steel core wire10to slide to the outer layer to form a tight structure.

On this basis, in order to enable rubber to be fully penetrated into the gaps L, the dimension of the gaps L is controlled by adjusting the diameter d1 of the sheath-layer steel wires. The diameter d1 of the sheath-layer steel wires is between 0.20 mm and 0.44 mm, and the average width of the obtained gaps L is not less than 0.0008 mm.

More preferably, the ratio of d to d1 is 0.462-0.640, so that the average width of the obtained gaps L is not less than 0.006 mm.

Specifically, adjustment may be made in the following two situations.

When the diameter d1 of the sheath-layer steel wires is between 0.20 mm and 0.30 mm, the dimension of the gaps L needs to be increased to improve the success rate of the rubber penetration. Therefore, 0.521<(d/d1)<0.640. L is controlled to be at least 0.015 mm.

When the diameter d1 of the sheath-layer steel wires is between 0.30 mm and 0.44 mm, the dimension of the gaps L may be appropriately reduced to ensure complete penetration of the rubber. Therefore, 0.462<(d/d1)<0.640. The dimension of the gaps L is only required to be controlled at 0.010 mm or above.

The steel cord30of the structure has the following advantages.

(1) A double-layer 1+M structure is used, and the middle steel core wire10has a diameter less than that of the sheath-layer steel wires20, so that the central single steel wire is prevented from serving as a main part for bearing mechanical impact, and the possibility of breakage of the steel cord30is reduced.

(2) The ratio of d to d1 is adjusted. Therefore, on one hand, a quadrilateral cross-section having a stable structure can be obtained, as shown inFIG.4a, thereby avoiding the displacement of the sheath-layer steel wires20, which causes the central steel core wire10to be exposed to the outer layer to form a pentagon with poor rubber penetration and irregular structure, as shown inFIG.4b; on the other hand, two connected sheath-layer steel wires20are not in contact with each other, so that the gap L reserved between the two sheath-layer steel wires20facilitates rubber penetration.

(3) By means of the adjustment, while the structure of the steel cord30is ensured to be stable, the width of the gaps L can also be adjusted. Since the width position at the gaps L is the narrowest position for a rubber body wrapped in the steel cord30, it is not just the position of a penetration port of the rubber, but also a position similar to a bottleneck, as shown in the E position ofFIG.5b. Due to large viscosity and poor fluidity of the rubber fluid, the rubber fluid is easily blocked at the bottleneck in the process of the rubber penetration process, so that an internal cavity between the bottleneck and the middle steel core wire10is formed, as shown in the F position ofFIG.5c. Therefore, the structure of the tire cord layer of the tire is not uniform, and the occurrence of steel wire corrosion caused by penetration of moisture in the later period is also avoided. Moreover, the diameters of the steel core wire10and the sheath-layer steel wires20also affect penetration of the rubber fluid, in particular, the diameter of the sheath-layer steel wires20. When the rubber fluid is penetrated into the steel cord30, an ideal flow condition of the fluid is that, firstly, the rubber fluid flows inwardly to the surface of the steel core wire10along the surfaces of the sheath-layer steel wires20, which is followed by opposite filling from the bottom. Since the surface curvatures of the steel core wire10and the sheath-layer steel wires20are different, the fluid ductility on the respective surfaces is also different. In the present invention, the diameter of the sheath-layer steel wires20is greater than the diameter of the steel core wire10, so that the rubber fluid may flow to positions of vertex angles where the steel core wire10makes contact with the sheath-layer steel wires20, and the gaps of the vertex angles are completely filled. Moreover, the ratio of d to d1 is adjusted according to the diameter of the sheath-layer steel wires20, so as to adjust the dimension of the gaps L at the bottleneck positions, so that a steel cord having a more stable structure is obtained while effective penetration of the rubber fluid is satisfied.

The steel cord30having a 1+4 structure is constructed. The steel cord30is manufactured according to the following process.

The process flow is:raw material→coarse drawing→central wire thermal treatment→medium drawing→thermal treatment electroplating→wet drawing→twisting→finished product.

The raw material is:a steel wire rod including the following components: a minimum carbon content of 0.60% (e.g., at least 0.72% or at least 0.80% or at least 0.86% or at least 0.92%); a manganese content ranging from 0.20% to 0.90%; a silicon content ranging from 0.15% to 0.90%; a maximum sulfur content of 0.03%; and a maximum phosphorus content of 0.30%. In order to reduce the amount of deformation required for a predetermined tensile strength, elements such as chromium (up to 0.1 to 0.4%) and boron can also be added. The remaining component is iron, and all percentages are weight percentages.

The steel wire rod is drawn to a steel wire having a required final diameter through the steps of coarse drawing, medium pulling, wet drawing and the like. The final diameter of the steel wire ranges from 0.10 mm to 0.44 mm. There may be one or two thermal treatment steps between the drawing steps such as coarse pulling, medium pulling, and wet drawing, for example, patenting treatment of the steel wire.

The steel wire is subjected to electroplating treatment before wet drawing, so that the steel wire has a coating layer for improving the rubber adhesion force. The coating layer is, for example, a composite body with different copper-zinc percentages, and the percentage is weight percentage.

The twisting can be performed by a tubular twisting machine or a double-twisting machine, preferably a double-twisting machine, as shown inFIG.3. The steel core wire10and the M sheath-layer steel wires20are simultaneously unwound, the unwinding tension of all the M sheath-layer steel wires20is equal, and the unwinding tension of the steel core wire10is greater than the average value of the unwinding tension of the M sheath-layer steel wires20. When all the steel wires pass through a wire dividing device a, the steel core wire10is located in the central position of a wire dividing disc, and the M sheath-layer steel wires20are uniformly distributed at 360° around the steel core wire10, and together pass through a bundling position b and a steel cord structure stabilizing device c and then are twisted in an S direction, with a lay length of 20 mm (d1 of the sheath-layer steel wires is 0.415 mm) or a lay length of 16 mm (d1 of the sheath-layer steel wires is 0.280 mm). The steel wire bundle passes through a stress relief device d and finally becomes the steel cord30.

Description of Results

Taking a 1+4 structure as an example

Embodiments 1-5 and 7-11: the steel cord30is manufactured by adjusting the structure of the steel cord30according to a parameter relationship corresponding to the various embodiments shown in Table 1.

TABLE 1Sheath-RubberRubberSteellayerpenetrationpenetrationcoresteeltesttestwire dwire d1Gap L(pressure(coating)(mm)(mm)d/d1(mm)drop) %%Control00.41500640group 1Embodiment0.2000.4150.4820.01990611Embodiment0.2100.4150.5060.02690752Embodiment0.2200.4150.5300.03400783Embodiment0.2600.4150.6270.06240944Embodiment0.3000.4150.7230.09067885Control00.28000430group 2Embodiment0,1300.2800.4640.009916387Embodiment0.1400.2800.5000.017015468Embodiment0.1500.2800.5360.02413789Embodiment0.1700.2800.6070.038208810Embodiment0.1900.2800.6790.0524106911

In Table 1, the lower the pressure drop of the rubber penetration test, the better the rubber penetration performance; 0% of pressure drop indicates complete rubber penetration. For a specific rubber penetration pressure drop method, please refer to Chinese Patent Application with a publication No. being CN 102666972A.

In Table 1, the larger the coating of the rubber penetration test, the better the rubber penetration performance; 100% of coating indicates complete rubber penetration. The specific coating method for the rubber penetration test is: intercepting a section of steel cord and placing same in a mold box in which rubber has been placed; then, also coating rubber on the other side of the placed steel cord; under a high temperature and a high pressure for a certain time, forming a steel cord sample cured in the rubber; intercepting a 25 mm sample, stripping the sheath-layer steel wire, and measuring the approximate length J and the width K of the uncoated part of the sheath-layer steel wire M; calculating the area of the uncoated steel wire, and causing the area to be divided by the total area of all steel wires obtained by multiplying the approximate width of the uncoated part by 25 mm, so as to obtain the percentage of the non-coated part; and obtaining a coating percentage by 1 minus this percentage. Please refer to formula 1 for details:
[1−(J1*K1+J2*K2+ . . . +JM*KM)/(K1+K2+ . . . +KM)*25]×100%

Table 1 clearly shows that the rubber penetration performance of the steel cord is greatly improved compared with existing products. Rubber of the existing products substantially cannot be penetrated, so that steel wire corrosion easily occurs inside the steel cord. Moreover, the steel cord in the present invention has an open structure, and the rubber can well be penetrated into the steel cord, so that corrosion of the steel wires is well avoided, and the service life of the tire is prolonged. The ratio of the diameter of the steel core wire to the diameter of the sheath-layer steel wires determines the width of the gaps L, and also determines the difference of the rubber penetration performance.

The basic principles, major features and advantages of the present invention are displayed and described above. Persons skilled in the art should understand that the present invention is not limited by the foregoing embodiments. The foregoing embodiments and the description are merely illustrative of the principles of the present invention. Various changes and modifications can be made in the present invention without departing from the spirit and scope of the present invention, and these variations and improvements fall within the scope of protection of the present invention. The scope of protection of the present invention is defined by the appended claims and equivalents thereof.