JPH11179419A - Manufacture of rubber reinforcing wire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacturing method for a rubber reinforcing wire having an excellent wire drawing property and moreover capable of obtaining a sufficient initial rubber adhesive property. SOLUTION: A brass plating layer is formed on the surface of a high carbon steel wire incorporating carbon of >=0.70% by a diffusion plating method, and a copper plating layer of 0.02-0.12 μm in thickness is formed on the brass plateing layer. Thereafter, the wire is drawn through a die and drawn at the reduction of area of >=90% to <98%, and a coated layer obtained by mechanically alloying brass plating and copper plating is formed, whereby the rubber reinforcing wire is manufactured.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a rubber reinforcing wire used for a steel radial tire, a high-pressure hose, a belt conveyor and the like.

[0002]

2. Description of the Related Art Steel radial tires, high-pressure hoses,
A steel wire used as a rubber reinforcing material in a belt conveyor or the like generally has a coating layer made of brass (brass) formed in order to obtain good adhesion to rubber. As a method of forming a brass layer, a diffusion plating method in which Cu and Zn are sequentially plated and then a heat diffusion treatment is performed is mainly used.

[0003] In order to enhance the strength and the reinforcing effect of rubber, the rubber reinforcing wire is subjected to cold working, in particular, wire drawing by drawing from a die. This wire drawing is performed under very severe conditions. For this reason, when the deformability of the brass plating is low, the wire drawing resistance increases, and when the deformability is remarkable, a problem occurs in the wire drawing workability such as breakage of the wire during drawing. At this time, if the surface of the wire is oxidized by frictional heat, the reactivity with rubber may be insufficient. In addition, there is a problem that the life of the die is shortened.

[0004] In order to improve the drawability, it is preferable that the ratio of the β phase in the brass plating is small. This is because the α phase has a better ductility than the β phase. In the diffusion plating method, the higher the heating temperature and the longer the heating time, the easier the fusion diffusion occurs, and the less the β phase.

On the other hand, characteristics such as lubricating adhesion to rubber are as follows.
The lower the Cu content of the brass plating layer, the better. However, when the Cu content in the brass plating is low, the β phase tends to increase. For example, when the Cu content in brass plating is 6
If it is 2% or less, the β phase increases and practical wire drawing becomes difficult.

From the above viewpoints, recently, the Cu content in the brass plating is controlled to be about 63%, and a considerable amount of β phase is generated in the brass plating.
In addition, when the amount of brass plating adhered to the wire before drawing is large, diffusion fusion by wire drawing is unlikely to occur, and the ratio of β phase tends to increase.

[0007] Therefore, there is a need for a technique that has good wire drawing workability and can obtain sufficient initial rubber adhesion. Japanese Patent Publication No. 60-57520 discloses that copper plating and zinc plating are alternately repeated twice or more, and then the outermost layer is plated with copper, and then the wire is drawn to diffuse copper and zinc. A method for brass plating is described. In this method, no heat diffusion treatment is performed.
The multi-layer plating is performed by this method because the diffusion distance between copper and zinc by wire drawing is short. According to this method, the β brass phase is not generated on the surface of the wire, and the adhesion to rubber is also improved.

However, in this method, a large-scale modification of plating equipment is required for a complicated multi-layer plating process,
Not practical. For this reason, the advantage that the heat diffusion process can be omitted is offset.

[0009]

SUMMARY OF THE INVENTION It is an object of the present inventors to provide a method for producing a rubber reinforcing wire which has a good drawability and a sufficient initial rubber adhesion.

[0010]

The method for producing a rubber reinforcing wire according to the present invention comprises a step of forming a brass plating layer on a surface of a high carbon steel wire containing 0.70% or more of carbon by a diffusion plating method. , 0.02-thick on brass plating layer
A step of forming a copper plating layer of 0.12 μm, a wire being pulled out through a die, and wire drawing with a reduction in area of 90% or more and less than 98% to form a coating in which brass plating and copper plating are mechanically alloyed. Forming a layer.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In a wire in which a brass plating layer and a copper plating layer are laminated, since the outermost layer is made of copper, a large amount of sulfide is generated at the wire-rubber interface under ordinary rubber vulcanization conditions. Does not provide good rubber adhesion. However, when such a wire is drawn through a die, the two plating layers are mechanically mixed and alloyed, and rubber adhesion is exhibited. It is considered that the reason why good adhesion to rubber is obtained is that moderate sulfides are generated at the wire-rubber interface in the rubber vulcanization step. Also,
Since copper has high deformability, the slipperiness is improved by copper on the surface during drawing. When copper and brass are mixed on the wire surface, the surface has a profile with more copper along the depth direction. The copper content profile becomes more homogenous as the degree of wire drawing increases. At this time, even if the β brass phase is generated in the heating diffusion step, diffusion mixing of the copper plating and the β brass phase is promoted during wire drawing, and the α phase is formed.
Therefore, the effect of improving the drawability can be obtained even in the latter half of the drawing.

In the present invention, in order to obtain good surface characteristics with good adhesion to rubber, the degree of wire drawing is increased and the reduction in area is 9%.
It is preferable to be 0 or more and less than 98%. In the present invention, the thickness of the copper plating layer formed on the brass plating layer,
It needs to be 0.02 to 0.12 μm. When the thickness of the copper plating layer is less than 0.02 μm, improvement in wire drawing workability and improvement in primary adhesion to rubber after wire drawing are not recognized. When the thickness of the copper plating layer exceeds 0.12 μm, the diffusion and mixing of copper does not proceed sufficiently during the wire drawing, so that poor adhesion to rubber occurs.

[0013]

Embodiments of the present invention will be described below. 0.82
% Of carbon (C), a brass layer was formed on the surface of a 1.37 mm diameter high carbon steel wire by diffusion plating. Specifically, the wire is treated in a copper pyrophosphate bath to form Cu plating, then treated in a zinc sulfate bath to form Zn plating, and then subjected to a heat diffusion treatment in a fluidized furnace to obtain a brass. A plating layer was formed. This wire was immersed in dilute sulfuric acid to etch the oxide layer on the surface. The brass plating layer of this plating wire has a Cu content of 63% and an adhesion amount of 4.0 g.
/ Kg, β brass phase was 30%.

In Examples 1 to 4, the above-mentioned wire was treated in a copper pyrophosphate bath so that a thickness of 0.02 to 0.02 mm was formed on the brass plating layer.
A copper plating layer of 0.12 μm was formed. In Comparative Example 1, no copper plating layer was formed. Comparative Example 2 is a copper plating layer having a thickness of 0.01 μm, and Comparative Example 3 is a copper plating layer having a thickness of 0.13 μm.
m of the copper plating layer. In Comparative Example 4, multi-layer plating of Cu and Zn was performed according to a conventional technique.

These wires were drawn to a diameter of 0.28 mm using a cemented carbide die. At this time, the normal drawing dose per die was determined, and the wire drawing workability was evaluated. In addition, a 1 × 2 steel cord was manufactured by performing stranded wire processing using the obtained wire. These steel cords were embedded in a rubber compound, and vulcanized and bonded in an optimum time. And the primary adhesion with rubber,
The evaluation was based on the pull-out force per 12.7 mm and the ratio of the rubber-attached score to the cord. Table 1 shows the results.

From Table 1, it can be seen that in the wires of Examples 1 to 4, by forming a copper plating layer having an appropriate thickness, the wire drawing workability can be improved by 5% or more compared to a normal brass plating wire. It can be seen that the primary adhesion to rubber is good.

[0017]

[Table 1]

[0018]

As described in detail above, according to the present invention, it is possible to produce a rubber reinforcing wire having good drawability and sufficient initial rubber adhesion.

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Claims (1)

[Claims] 1. A step of forming a brass plating layer on a surface of a high carbon steel wire containing 0.70% or more of carbon by a diffusion plating method, and a step of forming a brass plating layer having a thickness of 0.02 to
A step of forming a copper plating layer of 0.12 μm, a wire being pulled out through a die, and wire drawing with a reduction in area of 90% or more and less than 98% to form a coating in which brass plating and copper plating are mechanically alloyed. Forming a layer, the method for producing a rubber reinforcing wire.