KR19980056780A - Manufacturing method of steel cord - Google Patents

Abstract

The present invention provides a method of manufacturing a steel cord of a fresh steel wire of the first diameter d1 to a smaller diameter df suitable for reinforcing rubber products in a parting state, the method comprising: a) a medium diameter of medium-hardened state of the steel wire using a lubricant; d2, wherein the lubricant comprises copper plating, b) degreased the copper plating, c) plated steel wire of medium diameter d2 in work hardening state with brass alloy, and d) steel wire of d2 in the medium work hardening state. Provided is a method of manufacturing a steel cord characterized by freshness with a final diameter df, thereby obtaining a steel cord having high tensile strength and good adhesion to rubber.

Description

Manufacturing method of steel cord

The present invention relates to a method of manufacturing a steel cord, in particular having a high tensile strength in the production of a very high strength steel cord, and to improving the adhesion between the steel cord and rubber.

Steel cord is alloy-plated with 1 to 4 elements selected from copper, zinc, nickel, cobalt and tin with a thickness of 0.1 to 0.4 μm on wire with 0.1 to 0.4 mm wire diameter made of carbon steel with carbon content of 0.6 to 0.85 wt%. After the wire is twisted into various structures (1 × 4, 1 × 3, 2 + 2, 2 + 7, 3 + 6, 3 + 9 + l5, etc.) depending on the application, it is used for strength, modulus and heat resistance. And fatigue resistance is superior to other types of inorganic fibers and organic fibers, and is used as rubber reinforcement materials such as tires.

In general, steel cords should be excellent in adhesion with rubber, which is a heterogeneous material because they are used as reinforcing materials for tires, and should be excellent in the harsh environment formed by automobiles. In the steel cord and tire manufacturing industry, much research has been conducted to improve such durability.

Typically, high strength steel cords have a tensile strength Rm greater than 2,250 to 1,130 Logd / mm ² (where d represents the diameter of the steel cord filament in mm). In contrast, the tensile strength of the ultra high strength steel cord is the same. It has a value of about 8% higher than the tensile strength of the high strength steel cord of diameter.

According to the conventional method for manufacturing steel cords, the diameter (ds) of the steel wire, which is a raw material, is between 5.0 and 5.5 mm, and is first washed with water by mechanical descaling and pickling by sulfuric acid solution or hydrochloric acid solution. And after drying, the final parting process of the rubber tire reinforcing steel wire through the one or more dry drawing process and the intermediate patting process is performed at an intermediate diameter d1 of about 0.8 to 2.0 mm.

After the wire is pickled and washed, the electroplating in a copper pyrophosphate electrolytic cell and a zinc sulfate electrolytic cell and heat diffusion at 400 to 650 ℃ for 1 to 8 seconds to thermal diffusion. The steel wire is generally wet drawn to a final diameter (df) of 0.15 to 0.40 mm in diameter d1 in a suitable liquid lubricant.

Steel cords are formed by twisting steel wires in wet strands into several strands.

However, the method according to the above technique has some disadvantages, and the rate of reduction of the cross sectional area (R) for the cross sectional area in wet drawing after the last parting process is limited to maintain a value of 95 to 97%. That is, it corresponds to a median diameter (d1) of 96% 1.5mm and a final diameter (df) of 0.33mm. These restrictions limit the tensile strength (Rm). One advantage of steel cords with high tensile strength (Rm) is that they require less steel cords to reinforce rubber products. The need for less steel wire means a reduction in the adhesion surface area between the steel cord and the rubber. As a result, taking advantage of high strength steel cords is a significant challenge unless the steel cord has improved adhesion to rubber.

The present invention is to produce a steel cord with a high tensile strength of the steel wire to form a wet draw and twist to reduce the number of breaks and to adhere to a rubber product, so that the initial diameter (d1) is the final diameter (df). In the treatment process, use a lubricant to make the steel wire an intermediate diameter (d2) of medium work hardening, but the lubricant includes copper plating (100%) again to degrease the surface of the copper plating, and the intermediate diameter (d2). Steel cord manufacturing method characterized in that the steel wire in the state of work hardening is plated with a brass alloy and drawn to the final diameter (df).

In the present invention, the use of the lubricant constituting the copper plating can be carried out by electroplating the steel wire of the first diameter (d1) in an electrolytic cell such as pyrophosphate, copper plating is brass plating after surface degreasing at the middle diameter (d2) Will be done.

In the present invention, the brass plating may include not only copper and zinc, but also nickel, tin, cobalt, iron, cadmium, antimony, and the like, and alloy elements that enable high deformation in drawing are preferred. Plating with brass is done by electroplating by thermal diffusion. Brass plating contains at least 65% atomic concentration with respect to copper, and preferably α-brass is preferred because of its good workability during drawing of α-brass. However, full α-brass plating is not suitable for wet drawing, so a maximum of about 20% β-brass (at least 63% atomic copper concentration) is allowed. The plating amount of the brass alloy is less than 2.2 g per Kg of steel wire, which corresponds to a mass less than 4.3 g per m ^{2 of} steel surface area for a median diameter (d 2) of 1.0 mm. In addition, when thermal diffusion is applied, the thermal diffusion time should be carefully adjusted to about 1 to 20 seconds to avoid substantial changes in the state of work hardening of steel wires.

In the process according to the present invention, the reduction rate of the cross-sectional area of the steel wire may be greater than 97% or 98%, and the final tensile strength (Rm) of the steel wire is at least 3,500 N / mm ² at a final diameter of about 0.2 mm, preferably 3,700. The value is larger than N / mm ² .

In the present invention, in the case of the final diameter (df) of 0.15 to 0.3mm in providing a steel alloy plating of the average thickness delta (δ) and rubber products having a high tensile strength (Rm) and a final diameter (df) The average thickness δ is less than 0.16 μm and the final diameter df greater than 0.4 mm is less than the average thickness of 0.25 μm, and the final thickness df greater than 0.3 to 0.4 mm is less than the average thickness δ 1.7 μm. It is done.

The average thickness δ of the brass alloy plating can be determined by measuring the mass rn of the brass alloy, and the mass of the brass alloy is a mixture of ammonia (10 to 90%) and hydrogen peroxide (10 to 90%) which does not affect iron. The solution is dissolved in solution and measured by peeling the brass plating from the steel wire. The plating mass corresponds to the mass difference between the plated steel and the stripped steel wire. Further, the thickness δ of the brass plating in relation to the mass of the brass alloy m is given by the following equation.

δ (μm) = m (g / Kg) × d (mn) × 0.235

Since the present invention does not plate the steel wire for the entire wet drawing process, the variation in thickness δ is limited, and the sulfuric acid pickling process of removing the plating layer is unnecessary by performing brass plating after degreasing without removing the copper plating layer after drawing. In addition, the plating of brass alloy is done at the middle diameter d2, and the surface is copper plated and wet drawn. Therefore, the surface of the first diameter d1 or wet drawn after galvanizing. It is less rough than the surface from which the galvanized layer was removed.

Therefore, the initial brass plating layer at the middle diameter d2 has a more uniform and thinner thickness δ compared to the conventional brass alloy plating d2. This indicates that it can have a high strength steel wire having a thickness smaller than the existing plating thickness.

According to the present invention, firstly, a high strength steel wire is obtained having an average thickness of plating smaller than 0.16 mu m, having a diameter df between 0.15 and 0.3 mm.

Secondly, a high strength steel wire having a diameter df of between 0.30 and 0.40 mm in average plating thickness smaller than 0.25 [mu] m is obtained.

Thus, the steel wire obtained in the present invention has a thin brass plated layer has a relatively small amount of copper that can diffuse into the rubber or contaminate the rubber compared to the conventional thick cloth has the effect of increasing the adhesion to the rubber.

Hereinafter, the present invention will be described in detail with reference to Examples and Comparative Examples.

Example 1

Wire rods with a carbon content of 0.82% by weight (ds) of 5.50mm are dry-drawn to make steel wire with an initial diameter (d1) of 1.50mm, pickled with sulfuric acid, washed with water and copper in an electrolytic cell in pyrophosphoric acid. After electroplating, the wires were drawn from the initial diameter (d1) 1.50mm to the middle diameter (d2) of 1.0mm. The steel wire of medium diameter (d2) is immersed in a solution of 40 g / L% sodium hydroxide for copper plating, washed with water, electroplated in a pyrophosphate electrolyzer (Cu ₂ P ₂ O ₇ 120 g / L%), and washed again. . Then, thermal diffusion was performed to plate the brass alloy.

Through this process, the wire was drawn from an intermediate diameter (d2) of 1.0 mm to an intermediate diameter (df ') of 0.20 mm and a final diameter (df) of 0.175 mm.

The test results showed that the tensile strengths Rm at d1, d2, df and df were 1,280, 1,700, 3,930 and 4,100 N / mm ²祉, respectively. .

Comparative Example 1

Dry wire drawn from the initial diameter (ds) of 5.5mm to 1.5mm of the median diameter (d1) of the wire rod with a carbon content of 0.82% by weight and then subjected to the intermediate parting process (austenitic at about l00 ° C and 560 for 8 seconds). Constant temperature transformation at 0 ° C.) at a rate of about 47 g / min.

Medium diameter (d1) 1.50mm is pickled in sulfuric acid solution, washed with water, electroplated in electrolytic cell such as pyrophosphate, washed with water, electroplated again in zinc sulfate electrolytic cell, washed with water and then brass alloy plated (67.5% atomic copper) Thermal diffusion is performed. Wet freshness from the initial diameter (d1) to the diameter of 0.2mm to the intermediate stage diameter (df) and finally the final diameter (df) of 0.175mm was tried.

As a result of the test, the final diameter (df) of 0.175 mm was not possible due to fracture, and the tensile strength Rm at d1 and df 'was 1,280 and 3,955 N / mm ^2, respectively.

Comparative Example 2

The wire rod having a carbon content of 0.82% by weight is dry-drawn and washed with an initial diameter (ds) of 5.5mm to 1.5mm of an intermediate diameter (d1), electroplated with zinc in a zinc zinc electrolytic cell, and washed with a medium diameter of 1.00mm. Fresh as (d2). In order to remove the zinc plating, it was pickled with sulfuric acid, washed with water, electroplated in pyrophosphate electrolyzer, and again washed with zinc sulfate electrolyzed and washed with zinc sulfate. Thermal diffusion was then performed to plate the brass alloy. Wet wire was used as a steel wire with a final diameter (df) of 0.175 mm from a middle diameter (d2) of 1.0 mm to a middle diameter (df) of 0.20 mm. The test results showed that the tensile strengths Rm at d1, d2, df and df were 1,280, 1,687, 3,836 and 4,100 N / mm ² , respectively.

Claims (8)

A method of manufacturing a steel cord of a fresh steel wire having an initial diameter d1 to a smaller diameter df suitable for reinforcement of a rubber product in a parting state, the method comprising: a) using a lubricant to wire the steel wire to a medium diameter d2 of an intermediate work hardening state. Wherein the lubricant comprises copper plating b) degreasing the copper plating and c) plating the steel wire of the medium diameter d2 of the work hardening state with a brass alloy d) the steel wire of d2 of the medium work hardening state of the final diameter df Steel cord manufacturing method characterized by the freshness. The method of manufacturing a steel cord according to claim 1, wherein the reduction ratio R of the steel wire is greater than 98% from the initial diameter d1 to the final diameter df. The method of manufacturing a steel cord according to claim 1 or 2, wherein the diameter d1 of the steel wire is larger than 0.9 mm and the final diameter df is smaller than 0.35 mm. The method according to claim 1, wherein the tensile strength Rm of the steel wire in the final diameter df step is greater than 3,500 N / mm ² . The method of manufacturing a steel cord according to claim 1, wherein the plating of the brass alloy is performed by electroplating followed by thermal diffusion. 6. The method of claim 1 or 5, wherein the brass alloy comprises at least 65% atomic concentration copper. 2. The method of claim 1, wherein the brass alloy is α-brass alloy. The method of manufacturing a steel cord according to claim 1, wherein the steel wire is formed by twisting multiple strands.