JPH038880A - Bead wire having electroplated bronze layer and production thereof - Google Patents

Abstract

PURPOSE:To obtain the subject bead wire having high adhesivity and improved bonding stability to rubber by plating a specified amount of copper to the top layer of a bead wire material by electroplating. CONSTITUTION:A steel wire produced by drawing a bead wire is plated successively with copper and tin, heat treated to effect the thermal diffusion for forming an alloy of copper and tin and pickled to obtain the objective bead wire having electroplated bronze layer. The produced bead wire has a surface layer having copper content of 25-35atom%, exhibits improved adhesivity to rubber and is suitable as a bead wire for pneumatic tire.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a bead wire used in pneumatic tires, and more particularly to a bronze electroplated bead wire with improved adhesion to rubber.

(Prior Art) Tire bead wires are widely subjected to plating treatment in order to improve their adhesion to rubber without impairing their mechanical properties.

Conventional bead wire plating is mainly bronze, and the copper content of bronze plating is 7 to 17% by weight.
and 1 to 3% by weight, and plating methods include electroplating and chemical plating. For electroplating, a cyanizing bath, a silifluorizing bath, etc. are generally used, while for chemical plating, an acidic bath of sulfuric acid or hydrochloric acid containing copper ions and tin ions is used, and bronze plating can be achieved by passing a wire through such a bath. was applied.

(Problems to be Solved by the Invention) In conventional chemical plating methods, the metal ion components in the plating solution are consumed during the plating process and their concentration decreases over time. Because it is determined by the copper content, it is difficult to obtain a bronze-plated bead wire with a constant copper content, and the conventional electroplating method uses a bluing bath, which is not desirable from a safety and health perspective. There was a point.

Therefore, an object of the present invention is to solve the problems of the conventional chemical plating method and electroplating method described above, and to provide a bead wire for tires that has improved adhesion to rubber using an excellent bronze electroplating technique. .

(Means for Solving the Problems) In order to solve the above problems, the present inventors have analyzed the surface of the bead wire using an Auger electron spectrometer and have conducted intensive studies. Due to the content of copper in the outermost surface layer, the inventors have found that a material with a copper content of about 25 to 35 at % exhibits high adhesive strength and stability, and has completed the present invention.

That is, the present invention relates to a bronze electroplated bead wire having a surface layer with a copper content of 25 to 35 at % in the outermost layer as determined by Auger electron spectroscopy, and a method for manufacturing the same.

As the wire material of the bead wire of the present invention, for example, JIS
G3506 hard @ wire rod type code indicated as 5WRI+72A, carbon content 10.69-0.76% by weight, silicon content 0.15-0.35% by weight, manganese content 1
Examples include those containing 0.30 to 0.60% by weight, phosphorus content of 10.030% by weight or less, sulfur content of 10.030% by weight or less, and a diameter of 5.5 mm.

The outermost surface layer measured by Auger electron spectroscopy refers to the surface layer extending from the outermost surface to approximately ten or more angstroms. It was determined by analyzing eight elements: nitrogen, copper, oxygen, and tin.

The bead wire of the present invention can be obtained as follows.

That is, the process of drawing a bead wire wire to a predetermined diameter as a bead wire, electroplating the drawn steel wire with copper using a commonly used plating bath, and then electroplating with tin, and heat treatment to form a copper wire. The target copper content in the surface layer is obtained by sequentially passing through the process of alloying with tin and thermally diffusing it to increase the copper content in the surface layer, and the process of pickling with inorganic acid. Obtain a bronze electroplated bead wire with adhesive strength and adhesive stability.

Here, in the case of copper, the preferred plating method is one with a copper ion concentration of 15 g/1 or more (pyrophosphate ion concentration), which has excellent adhesion to steel wires and uniform electrodeposition, and is good in terms of safety and hygiene. / (copper ion concentration) contains pyrophosphate ions with a value of 7.0 to 8.0, and pl+ is 0 to 9.0.
Using a copper phosphate plating bath, the bath temperature is 45°C or higher,
There is a method of plating at a current density of 2 to 15 A/dm2,
In the case of tin plating, the tin ion concentration is 20g/1 or more, cresol sulfonic acid is 30g/1 or more to obtain a dense plating quality, and 40g/1 or more is used to suppress bath deterioration due to tin ion oxidation. Using a sulfuric acid acidic tin plating bath containing sulfuric acid, at room temperature, the current density L A
An example is a method of plating at a density of /dm2 or higher. A suitable heat treatment condition for alloying copper and tin is, for example, holding the alloy at 440°C for 5 to 10 seconds. Although the temperature and holding time can be changed within the range that the desired surface layer is obtained,
00°C or higher is not appropriate because the holding time must be shortened and the heat treatment variation increases;
If it is less than C, the holding time becomes longer and productivity decreases, which is not appropriate. In addition, by direct power supply by a power supply roller or indirect power supply by electromagnetic induction, electricity can be passed through the steel wire and the steel wire can be heated to a desired temperature rapidly and stably by electrical resistance heating. Appropriate conditions for pickling are, for example, 20g/l to 40g
1 to 2 seconds at room temperature. If it exceeds 40 g/1 and exceeds 2 seconds, the surface of the copper wire will be damaged due to corrosion and adhesiveness will decrease, which is not appropriate.

In the above plating process, the copper plating thickness is 0.05
to 0.5μ and the tin plating thickness is 0.5μ. Can be selected from o1 to 0.01μ. Further, the temperature and holding time in the thermal diffusion step may be selected so as to obtain a surface layer having a predetermined tin content.

(Function) In the present invention, the reason why the content of the copper component in the outermost surface layer is defined as 25 to 35 atomic % by Auger electron spectroscopy is that only within this range can high adhesive strength and stable adhesion be achieved with rubber. This is because the sex can be changed. That is, when the content exceeds 35 at %, excessive sulfide compounds are produced in the vulcanization adhesion reaction between the rubber and the bead wire, resulting in a decrease in adhesive strength.
On the other hand, if it is less than 25 atomic %, it is presumed that the copper component in the surface layer of the bead wire required for the vulcanization adhesion reaction is insufficient, resulting in a decrease in adhesive strength.

The method of the present invention, in which copper electroplating is followed by tin electroplating, is not affected by variations in the plating solution composition or plating current density, and the plating current value in copper and tin plating processes is kept constant. It can be done. As a result, bronze plating with a constant and stable bronze deposition amount and constant tin content can be continuously applied to the wire surface, and bead wires whose surface layer has the desired copper content can be continuously applied. Obtainable. Furthermore, in this electroplating method, by using copper and tin in the anode plate, metal ions can be replenished into the plating bath, and the addition and renewal of metal ions in the case of chemical plating can be omitted. Industrially advantageous.

Further, in the method of the present invention, after the thermal diffusion treatment, pickling with an inorganic acid is performed to remove oxides, and the reason for this is that high adhesive strength can be obtained by performing such treatment. That is,
It is presumed that the metal oxides generated during heat treatment inhibit adhesion to rubber, resulting in a decrease in adhesive strength.

(Example) The present invention will be explained below with reference to Examples.

A wire rod of type 5WRI+72A and a diameter of 5.5M was processed by patenting and wire drawing in the same manner as a normal bead wire manufacturing method to obtain a steel wire with a diameter of 1.55 mm. As shown in FIG. 1, this steel kjA 1 a is heated at a low temperature and for a heating time so as to obtain predetermined mechanical properties as a bead wire in a low-temperature heat treatment process consisting of a molten lead tank 2, a pickling tank 3, and a water washing tank 4. was selected and subjected to low-temperature heat treatment. However, this treatment step is not necessarily required in the present invention, and can be replaced by a thermal diffusion step.

On the steel wire lb which has undergone the low temperature heat treatment process, there is a brush plating tank 5,
In a plating process consisting of a tin plating bath 6 and a water washing bath 4, copper with a thickness of 0.1 μm is electrodeposited using a copper birophosphate alkaline plating bath at a temperature of 50°C, and then at room temperature,
A tin sulfate acidic plating bath containing 0g/l of cresol sulfonic acid was used to deposit tin to a thickness of 0.002μ.

Next, in the heat diffusion process, the temperature was 440°C for 5 seconds to 10 seconds.
This was held for seconds to diffuse the copper and tin on the steel wire 1c that had undergone the plating process.

Subsequently, the steel wire 1d that has undergone the thermal diffusion process is subjected to a pickling process consisting of a pickling tank 8 and a water washing tank 4, at room temperature of 30 g/l ~
After pickling by immersing in a 60 g/] phosphoric acid bath for 1 to 2 seconds, drying by blowing heated air higher than room temperature, iron, sulfur, chlorine, carbon, and nitrogen were analyzed using an Auger electron spectrometer. , the copper content in the surface layer within a few tens of angstroms from the surface was determined by analyzing the eight elements copper, oxygen, and tin.
Various bronze electroplated bead wires were obtained having surface layers ranging from 5 at.% to 35 at.%.

Rubber for normally used bead wires is pasted on both sides of the bead wire treated as in step 2, and 145
Vulcanization treatment was performed at °C for 40 minutes. A bead wire pullout test was conducted on the obtained rubber product, and the adhesiveness was evaluated based on the pullout force.

In addition, we evaluated the adhesion of bead wires that had been continuously bronze plated at the beginning and end of the plating process.
The variation in adhesive strength was evaluated. The results of these experiments are shown in Table 1 below. For comparison, the same procedure was applied to bead wires subjected to conventional treatment (conventional example) and bead wires in which the copper content of the bronze surface layer deviates from the scope of the present invention (comparative examples 1 and 2). Evaluations were conducted, and the experimental results are also shown in Table 1 below.

(Effects of the Invention) As explained above, in the bronze electroplated bead wire of the present invention, the copper content of the outermost layer is set to 25 to 35 at% by performing a prescribed treatment, so that the copper content between the rubber and the rubber is reduced. High adhesive strength and high adhesion stability can be obtained.

Furthermore, in the manufacturing method of the present invention, low-temperature heat treatment can be omitted,
It becomes possible to control the amount of plating deposited and the plating composition using the plating current, thereby improving productivity.

[Brief explanation of the drawing]

FIG. 1 is a process diagram showing an example of the method for manufacturing a bronze electroplated bead wire of the present invention. la, lb, lc, ld...steel wire 2...
Molten lead tank 3... Pickling tank 4... Washing tank 5... Copper plating tank 6... Tin plating tank 7
... Normal heating machine 8 ... Pickling tank procedure amendment document July 180, 1989

Claims (2)

[Claims] 1. A bronze electroplated bead wire having a surface layer with a copper content of 25 to 35 atomic % in the outermost layer. 2. A claim characterized in that tin is electroplated next to copper on a steel wire obtained by drawing a beat wire wire, and then copper and tin are alloyed and thermally diffused by heat treatment, and then pickled with an inorganic acid. Item 1. A method for producing a bronze electroplated bead wire according to item 1.