JPH02175984A - Production of bead wire with brass plating - Google Patents

Abstract

PURPOSE:To obtain a bead wire with brass plating and excellent adhesion without impairing mechanical properties by plating a steel wire drawn as the bead wire with copper, subsequently galvanizing the resultant plated wire and subjecting the galvanized wire to heat and acid washing treatment. CONSTITUTION:A steel wire drawn as a bead wire is plated with copper, subsequently galvanizd and then heat-treated to thermally diffuse copper and zinc and simultaneously correct drawing strain of the steel wire. The resultant wire is then subjected to acid washing treatment with an inorganic acid. The amount of zinc oxide on the surface of the bead wire with the brass plating is preferably <=30mg/m<2>.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to bead wires used in pneumatic tires, and more particularly to a method for manufacturing brass-plated bead wires that have improved adhesion to rubber. be.

(Prior Art) In recent years, there has been a remarkable development in the performance of pneumatic tires, and as a result, there has been a demand for further improvements in the feed used in tires. In the case of tire bead wires, there is a need to improve the adhesion to rubber without impairing mechanical properties so that the bead wires can cope with higher loads, longer lifespans, and higher speeds of tires.

The plating of conventional bead wires is mainly bronze, and the manufacturing method thereof is as follows.

First, a bead wire is subjected to a patenting treatment and drawn to a predetermined wire diameter as a bead wire. Next, low-temperature heat treatment is performed in a molten lead bath or the like in order to correct internal stress distortion caused by wire drawing and to impart necessary properties to the bead wire, such as mechanical properties and fatigue resistance. After that,
Bronze plating is applied to ensure adhesion with rubber.

(Problems to be Solved by the Invention) In order to improve the adhesion of the bronze-plated bead wire, which has been mainly used, with rubber, the composition of the plating,
Improvements have been made in the amount of plating deposited, the adhesion of plating, etc., but there is now a need for even greater improvement in adhesion, a level of improvement that cannot be achieved with bronze plating.

On the other hand, today, improvements in the rubber that covers bead wires have made it possible to use brass plating, which has higher adhesive strength than bronze plating, but brass plating using the cyan method is not desirable from an environmental hygiene perspective. Currently, brass plating using the thermal diffusion method is used, which eliminates this concern.

However, heat treatment to thermally diffuse copper and zinc may impair the mechanical properties of the bead wire, and conversely, if heat treatment is performed without impairing the mechanical properties, the desired adhesion force cannot be obtained and the mechanical properties are impaired. It was almost impossible to obtain high adhesion without damage.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a method for solving the above-mentioned problems and manufacturing a brass-plated bead wire having excellent adhesive properties without impairing mechanical properties.

(Means for Solving the Problems) As a result of intensive studies by the present inventors on a method for improving the adhesion with rubber without impairing the mechanical properties of bead wires, the above-mentioned problems can be solved by the following steps. The inventors have discovered that the problem can be solved, and have completed the present invention.

That is, the present invention includes a step of plating a steel wire drawn from a bead wire rod with copper and then zinc, and heat-diffusing the copper and zinc through heat treatment, and drawing the steel wire. The present invention relates to a method for manufacturing a brass-plated bead wire, which is characterized by sequentially passing through a step of correcting distortion and a step of pickling with an inorganic acid.

In the present invention, it is preferable to specify phosphoric acid as the inorganic acid in the step of pickling with an inorganic acid in order to obtain high adhesive strength and adhesive stability.

(Function) The reason why the plating of the bead wire in the present invention is limited to brass is because it makes it possible to obtain high adhesive strength that could not be obtained with bronze. The weight ratio of copper and zinc in such brass plating may be within the range normally applied for adhesion to rubber, and the
/Zn weight ratio in the range of 50,150 to 80/20, high adhesive strength can be obtained. Furthermore, high adhesive strength can be obtained without any particular limitation on the amount of brass plating deposited, but from the viewpoint of maintaining the corrosion resistance and mechanical properties of the bead wire, the plating thickness is preferably within the range of 0.2 to 0.5 μm.

In addition, the brass plating method is limited to a method in which copper is first plated, then zinc plated, and then both are thermally diffused through heat treatment.The reason why the cyanide method is limited to the method of applying heat to copper and zinc plating, and then heat-diffusing both is because the cyanide method can cause environmental pollution if waste liquid treatment and drainage are not thoroughly managed. Although there are some problems, with this method there is no risk of environmental pollution even if a problem occurs during plating work.

By the way, brass plating using the thermal diffusion method does not cause problems with environmental pollution, but the bead wire may undergo thermal history during thermal diffusion, which may impair desired mechanical properties such as strength, elongation, and twisting value. Furthermore, there is a problem in that when heat treatment conditions are selected to obtain desired mechanical properties, the adhesion strength decreases. In the present invention, as a means to solve this problem, a step of pickling with an inorganic acid is provided after the thermal diffusion step. By doing so, it has become possible to obtain high adhesive strength even under heat treatment conditions that allow for obtaining predetermined mechanical properties. The reason for this effect is not very clear, but
It is determined that one of the reasons is that zinc and copper oxides are generated during heat treatment and these oxides are removed by pickling. That is, when the amount of zinc oxide on the surface of the brass-plated bead wire was 30 mg/m'' or less, the brass structure exhibited high adhesive strength regardless of α or β.

The acid used for pickling may be any economically usable inorganic acid, but hydrochloric acid can cause hydrogen chloride to enter the atmosphere during the manufacturing process and corrode the bead wire, resulting in a decrease in adhesive strength and mechanical properties. This requires management to prevent the dissipation of hydrogen chloride, and if sulfuric acid is used, a small amount of residual sulfuric acid will cause hydrogen embrittlement and reduce fatigue resistance, so water washing equipment that can sufficiently remove the acid after pickling is required. do. From this point of view, a particularly preferred inorganic acid is phosphoric acid; phosphoric acid does not dissipate into the atmosphere, does not cause hydrogen embrittlement, and even if it remains in the bead wire after washing with water, it will not turn into phosphate. It has the advantage that it cannot affect adhesion.

(Example) Hereinafter, the present invention will be specifically explained with reference to Examples.

Wire rod (type: 5WR1172^, diameter: 5.5mm)
was made into a steel wire with a diameter of 0.96 mm by patenting and wire drawing, which are the same methods used for manufacturing ordinary bead wires. Next, as shown in FIG. 1, this steel wire 1 is subjected to a low-temperature heat treatment process consisting of a molten lead tank 2, a pickling tank 3, and a water washing tank 4, at a heating temperature and heating time so that predetermined mechanical properties can be obtained as a bead wire. was selected and subjected to low-temperature heat treatment. However, this step is not necessarily a necessary step in the present invention, and can be replaced by a thermal diffusion step.

In the bronze-plated bead wire, a steel wire that has undergone a low-temperature heat treatment process is passed through a sulfuric acid acid bath containing copper sulfate and tin sulfate, and bronze is deposited on the steel wire by chemical plating, but in this example, bronze is deposited on the steel wire by chemical plating. The steel wire 1 that has undergone a low-temperature heat treatment process (not necessarily a process) is passed through a plating process consisting of a copper plating tank 5, a galvanizing tank 6, and a water washing tank 4. In this process, copper pyrophosphate is applied onto the steel wire. Copper was electrodeposited in a bath followed by zinc in a zinc sulfate bath.

Thereafter, in a thermal diffusion step, the steel wire 1 was electrically heated to thermally diffuse copper and zinc. At this time, the heating temperature,
The heating time may be selected so that predetermined mechanical properties can be obtained for the bead wire, and the degree of thermal diffusion of the plating need not be taken into account.

Subsequently, the steel wire 1 was passed through a pickling process consisting of a pickling tank 8 and a water washing tank 4, and was dried by blowing heated air higher than room temperature to obtain a brass-plated bead wire.

The conditions and results of these experiments (1 to 15) are summarized in Table 1.

The method for measuring zinc oxide on the brass-plated bead wire and the adhesion test were conducted as follows.

A weighed bead wire was placed in 0.0 IN hydrochloric acid to dissolve the zinc oxide, and then inductively coupled high frequency plasma (Inducti) was added.
Zinc was measured by emission spectroscopic analysis using a very coupled plasma (very coupled plasma) as a light source, and expressed as the weight of zinc oxide (+ng) per 1 m'' of surface area of the bead wire.

The rubber composition used for the reinforcement test was 100 parts by weight of natural rubber,
Consisting of 50 parts by weight of carbon black, 5 parts by weight of zinc white, 1 part by weight of anti-aging agent, 2.5 parts by weight of cobalt naphthenate, 1.5 parts by weight of vulcanization accelerator, and 4 parts by weight of sulfur, ^STM
Evaluation was made according to the test method of D 2229-73.

(Effects of the Invention) As is clear from Table 1, in the method for producing a brass-plated bead wire of the present invention, the adhesive strength is significantly improved without impairing the tensile strength, elongation, torsion value, and elastic limit of the bead wire. It becomes possible to manufacture a bead wire with

In particular, bead wires that have been pickled with phosphoric acid in the pickling process exhibit less rust and stable high adhesive strength even during long-term storage.

[Brief explanation of the drawing]

FIG. 1 is a process diagram showing an example of the manufacturing method of the present invention.

Claims (1)

[Claims] 1. A process of plating a steel wire drawn as a bead wire with copper and then zinc, and thermally diffusing the copper and zinc through heat treatment, and drawing the steel wire. A method for manufacturing a brass-plated bead wire, characterized by sequentially passing through a process of correcting distortion and a process of pickling with an inorganic acid. 2. The method for producing a brass plated bead wire according to claim 1, wherein the amount of zinc oxide on the surface of the brass plated bead wire is 30 mg/m^2 or less.