JPS62148531A - Production of steel cord with high adhesivity to rubber - Google Patents

Abstract

PURPOSE:To obtain the titled steel cord for radial tire reinforcement, by drawing steel wire provided with brass plating through diffusion process, followed by heat treatment and by twisting specified number of the resultant wires. CONSTITUTION:The objective steel cord can be obtained by drawing steel wires provided with brass plating through diffusion process, followed by heat treatment under the condition satisfying the equations I and II [T is heating temperature ( deg.C); t is heat treatment time (sec)] and by twisting two or more wires heat- treated as above.

Description

DETAILED DESCRIPTION OF THE INVENTION <Field of Application in Industry> The present invention relates to a method for manufacturing steel cord used for reinforcing radial tires.

<Prior art and its problems> In recent years, steel radial tires using steel cords as reinforcement materials have been used in hot and humid regions and in cold regions where roads are coated with a lot of rock salt to prevent freezing. In some cases, due to corrosion of the steel cord, the adhesion between the cord and rubber deteriorates, causing tire separation, which significantly reduces the tire's life and weight. It is hoped that the water resistant adhesion will be defeated.

Conventionally, methods for making steel cords have water-resistant adhesion properties include changing the rubber composition, adding adhesion property V to steel cord table I+']i, and twisting the steel cord. There are attempts being made to change this. In order to improve the rubber or adhesive for water-resistant adhesive properties 1-, the inventors are working on improving the brass plating itself.

For improving brass plating, a method of adding or coating a third element such as Co (for example, Japanese Patent Laid-Open No. 55-7
1887) has also been proposed, or by changing the plating composition to 3
Making a base alloy complicates the manufacturing process and makes it difficult to control the plating composition. There is also the problem of increasing the cost of the product.

On the other hand, it is known that water-resistant adhesion can be improved by reducing the copper content of positive steel compositions, but with low copper compositions, β-positive properties appear, making wire drawing extremely difficult. Ru.

As a method to solve this problem, there are methods of adding elements that reduce the amount of β-plus phase, such as CO (see Japanese Patent Laid-Open No. 54-89940), and adding B to reduce the processability of the β-plus phase itself. How to improve (Japanese Patent Application Laid-Open No. 58-8499
However, such ternary plating composition has the problems mentioned above.

<Object of the Invention> Therefore, the present invention has been made in view of the above-mentioned current situation, and an object thereof is to provide a method for manufacturing steel cord that can significantly improve water-resistant adhesion through a simple process. shall be.

<Structure of the invention> The method of applying brass plating to the m-wire for steel cord includes the following steps:
There is a method in which copper and zinc are electrodeposited simultaneously using a cyanide bath (hereinafter referred to as the alloy method), and a method in which copper and then zinc are electrodeposited individually in sequence.
There is a method of thermally diffusing the material to make it positive (hereinafter referred to as the "diffusion method"). Since the alloy method uses a cyanide bath, it has disadvantages in terms of pollution and environmental hygiene, so the diffusion method is becoming more popular.

The present inventors conducted a detailed study on the relationship between the plating surface composition of steel cord and water-resistant adhesion performance using the diffusion method using surface analysis instruments such as AES and ESCA. We found that it is effective to increase the amount of zinc oxide.

That is, in the present invention, after drawing a steel wire that has been brass-plated by the diffusion method, the following formula % formula % (1) [In the above formula, T is the heating temperature (°C) and t is the heat treatment time (seconds)]
The present invention provides a method for producing steel cords with excellent rubber adhesion, which is characterized in that the steel cords are heat-treated under the conditions shown in the following range, and two or more cords are twisted together.

In addition, the present invention applies the following formula % formula % (1) [In the above formula, T is the heating temperature (℃)] , t is heat treatment time (seconds)
It is. ] Provides a method for producing a steel cord with excellent rubber adhesion, which is characterized by carrying out heat treatment under the conditions shown in the following.

The present invention will now be described in detail.

FIG. 1 is obtained by analyzing the surface χno: 1i; (at, %) and water resistant adhesion performance using ESCA. It can be seen from this diagram that increasing the amount of ZnO on the plating surface is extremely effective in improving water-resistant adhesion.

Next, the reason for limiting the upper and lower limits of the heat treatment temperature of the present invention as expressed by mf formula (1) will be described.

The reason for setting the upper limit temperature to 500℃ or less is that at temperatures exceeding 500℃, copper and zinc elements during plating will re-diffuse even for a short period of time, increasing the surface steel composition and causing damage to the wire material. This is because mechanical properties, especially strength, decrease.

The reason why the lower limit temperature was set at 50°C or higher is that at temperatures below 50°C, long-term processing is required in order to obtain sufficient effects, and copper oxidation, which deteriorates water-resistant adhesion, is required. This is because substances (Cu20.CuO) are likely to appear.

Next, the heat treatment conditions of the present invention represented by the above equation (2) will be described.

T < 200-: In looIogt, an effective amount of Zn
O amount is not formed, water resistant adhesion is not improved, and T
>500-2001ogt is because copper oxide appears simultaneously with the formation of /nu and deteriorates water-resistant adhesion.

In addition, in the present invention, 7. Since O impairs wire drawability, it is preferable to remove it by a chemical treatment such as phosphoric acid treatment as disclosed in JP-A No. 57-4750.

<Example> The surface of a steel wire having a wire diameter of 1.23 ma+ was plated with copper by an electroplating method, and then plated with zinc, and then diffusion alloyed by heating with electricity. Two types of bus bars were produced in separate strips. One was chemically treated with 25% by volume phosphoric acid (hereinafter referred to as treated N[') line), and the other was not chemically treated (hereinafter referred to as untreated H1).
line). X&! both bus lines! d with i1 diffraction! As a result, the β plus rate was 20% for both. (β plus rate = Iβx100/(Iα+■β), Iα and Iβ are the X-ray diffraction peak heights of α plus (II+) and β plus (110))], and 7, n Ohk, is not detected at all in the processing bus line. It wasn't done.

Both busbars were drawn in a wet lubricant using tungsten carbide ties to a diameter of 0.25 mm. As a result of the fluorescent X-ray analysis of the wire after wire drawing, the steel composition was approximately 65%, and the plating thickness was approximately 0.025 mm, with no difference in score.

The strands thus obtained were then twisted into a 1×5 configuration using a wire twisting machine to form a coat. Thereafter, the steel cords produced from the treated I-wire were heat-treated at various temperatures and times using a heating device that passed air adjusted to a humidity of 50%. In order to check the water-resistant adhesion properties of these obtained steel cords, they were embedded in a tire rubber compound and vulcanized in accordance with STM D2229. The vulcanization conditions were a temperature of 160° C. and a time of 20 minutes.

After leaving the rubber vulcanized in this way for one day, the temperature was 70°C.
, placed in a constant temperature and humidity chamber with a humidity of 96% for 3 weeks, and then each sample was pulled out using a tensile tester at a speed of 50 [11111/min. It has been decided. The measurement results are shown in Figure 2.

From this measurement result, the heat treatment conditions for improving the water-resistant adhesion of the sample prepared from the treated nI line compared to the sample not subjected to heat treatment are 200-300 log, assuming heating temperature T (℃) and treatment time t (seconds). t≦T≦500-2001o
)<t.

<Effects of the Invention> The steel cord of the present invention does not require major changes to the conventional manufacturing process, and can significantly improve the water-resistant adhesive performance of products through short-time heat treatment without reducing productivity. Therefore, it is inexpensive, and at the same time, it has great social and economic effects because it improves the rubber adhesion performance during use in tires, increasing the tire life and ensuring greater safety.

[Brief explanation of drawings]

FIG. 1 is a graph showing the relationship between zinc oxide II7 on the steel cord plating surface and water-resistant adhesion performance. FIG. 2 is a graph showing the relationship between the heat treatment temperature and time and the water-resistant adhesion of the steel cord at that time. The circle mark indicates a condition where the rubber adhesion rate was improved compared to the non-heat treated material, and the X mark indicates a condition where the rubber adhesion rate was lower than that of the non-heat treated material or there was no difference. Moreover, the numerical value in parentheses indicates the rubber adhesion rate.

Claims (2)

[Claims] (1) After drawing a steel wire that has been brass plated using the diffusion method, use the following formula: 50≦T≦500 200-300logt≦T≦500-200logt
[In the above formula, T is heating temperature (℃), t is heat treatment time (seconds)
] A method for producing a steel cord with excellent rubber adhesion, which comprises heat-treating under the conditions shown in the following and twisting two or more cords together. (2) After drawing and twisting two or more steel wires that have been brass-plated using the diffusion method, the following formula is applied: 50≦T≦500 200-300logt≦T≦500-200logt
[In the above formula, T is heating temperature (℃), t is heat treatment time (seconds)
It is. ] A method for producing a steel cord with excellent rubber adhesion, characterized by heat treatment under the conditions shown in the following.