JPH05255833A - Production of brass diffusion coated steel wire excellent in wiredrawability - Google Patents

Abstract

(57) [Summary] [Purpose] To manufacture brass diffusion plated steel wire with good wire drawing workability after brass diffusion plating. [Structure] In a method for producing a brass-plated steel wire by subjecting a steel wire to copper plating and zinc plating sequentially to a total thickness of 0.5 to 5 μm and then heating and alloying by diffusion of a metal, 770-193 log ( t) ≦ T ≦ 700-138
The diffusion is performed at log (t) (T: diffusion temperature (° C.), t: diffusion time (s)). [Effect] β brass ratio and surface oxide are reduced,
Drawability is improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a steel wire for reinforcing rubber articles such as tires, hoses and conveyor belts, and a method for producing a plated steel wire used for a steel cord.

[0002]

2. Description of the Related Art The strength of rubber by embedding a steel wire in the rubber,
Many techniques for improving durability have been implemented, but among them, composites of rubber and steel reinforcement are applied to automobile tires, high-pressure rubber hoses, conveyor belts, and the like.

[0003] The tire cords for automobiles are brass-plated on the surface in order to impart adhesiveness to rubber, but the conventional cyan plating bath for simultaneous precipitation of Cu and Zn is used because of serious toxicity and pollution of waste liquid treatment. Gone, instead of C
A diffusion plating method in which u and Zn are individually plated and then alloyed by thermal diffusion has become mainstream. However, in the case of diffusion, even if Cu: Zn = 7: 3 is plated, if Cu and Zn do not form a solid solution completely, an α structure having good workability cannot be obtained, and a β structure having poor workability is mixed. Further, in order to form a complete solid solution, high temperature or long-time diffusion is required, but in that case, ZnO having poor workability is likely to be generated because the oxidation of Zn on the surface is also promoted. This β texture and Zn
If there is a large amount of O, wire drawing workability performed after plating is hindered, which causes wire breakage and deterioration of the properties of the wire drawn material. The most common method for suppressing ZnO in the thermal diffusion is to reduce the amount of oxygen by controlling the atmosphere, but there is a problem that the cost such as N ₂ and Ar gas sealing becomes high.

In JP-A-62-243756, C
Cu such that u / (Cu + Zn) = 55 to 63%,
After the Zn is plated in a layered form, the surface reduction rate is 20 to 40% / pass for 8 or more passes, and the β-brass ratio is set to 10 to 50% by diffusing by utilizing the wire drawing heat. But 2
When 8 passes are drawn at 0-40% / pass, the load for each pass required to pull it out from the die is large, so heat generation during processing and aging deterioration are also large, so the types of steel that can be drawn are extremely easy to process. It is limited to mild steel equivalent material, and the harder the steel wire becomes, such as high strength material, the more difficult it is to draw wire. Therefore, although the plating can be diffused, the mechanical properties of the base material are likely to deteriorate and disconnection is likely to occur. That is, there is a problem in that the diffusion method utilizing heat generation of 20 to 40% / pass wire drawing limits the steel type.

In Japanese Patent Laid-Open No. 58-58297, C
Alternately repeat u and Zn plating twice or more, and use C as the outermost layer.
After being set to u, heat diffusion is performed. Furthermore, JP-A-58-612
In JP 97, similarly, Cu and Zn plating are alternately repeated and then diffused by working heat during wire drawing. Since these plating layers are thin, they are easily diffused and can be diffused at a lower temperature and in a shorter time. Further, since the outermost layer is Cu, Zn can be prevented from falling off and being oxidized. However, if Cu and Zn plating is repeated many times, there is a problem that the Cu and Zn plating baths and the water washing bath equipment between them increase in number and the equipment becomes complicated. No mention is made of brass rate control.

[0006]

The present invention solves the problems of the prior art and suppresses the β brass ratio and the surface oxide ZnO during plating in order to improve the wire drawing workability after brass diffusion plating. Provided is a method for producing a brass diffusion-plated steel wire that can be manufactured.

[0007]

SUMMARY OF THE INVENTION The gist of the present invention is that a steel wire is sequentially plated with copper and zinc, and the total thickness is 0.5 to 5 μm.
m, then heated and alloyed by diffusion of metal to produce a brass-plated steel wire.
log (t) ≦ T ≦ 700-138 log (t) (T:
A method for producing a brass diffusion-plated steel wire excellent in wire drawing workability, which comprises diffusing at a diffusion temperature (° C) and t: diffusion time (s). Specifically, it diffuses in the region shown in FIG.

[0008]

The furnace for diffusing may be any furnace as long as temperature control is easy and the heat transfer coefficient is relatively high, but a fluidized bed is preferable, which does not require waste treatment and is polluted in terms of exhaust gas. This is because it has the advantages that it is a safe facility, that it can diffuse in a short time because of its high heat transfer coefficient, and that the oxidation of the surface layer can be suppressed because the amount of oxygen in the furnace during combustion is smaller than in the atmosphere.

The relational expression is brass plating thickness 0.5 to 5 μm.
It was obtained as a result of an experiment in which the temperature and the time were changed in the fluidized bed for the steel wire subjected to
(T) ≦ T is a region where the β brass ratio is 20% or less. When the relationship between the β brass ratio and the drawing after drawing was investigated, the β brass ratio was 20 as shown in FIG.
The boundary was set at 20% because it showed a sharp drop above%. Further, T ≦ 700-138 log (t) is the surface Zn
This is a region where the O layer thickness is 0.05 μm or less. Surface Z
As a result of investigating the relationship between the thickness of the nO layer and the drawing after wire drawing, 0.05 μm was set as the boundary because a sharp decrease was observed at 0.05 μm or more as shown in FIG. Also, FIG.
In the above, when the diffusion temperature is 300 ° C. or lower, the diffusion time becomes too long and it is not practical.

The reason why the brass plating thickness is limited to 0.5 to 5 μm is that if the plating thickness exceeds 5 μm, the applicable range of the above formula is exceeded and the diffusion becomes insufficient, so that the β brass ratio. Is difficult to reduce. The relationship is shown in FIG. Further, if the plating thickness is less than 0.5 μm, the lubrication effect at the time of wire drawing by plating is lost, die wear becomes severe, and the number of wire breakage increases. The relationship is shown in FIG.

Further, in the phase diagram of Cu and Zn, when Cu is about 6.5 or more, a Cu weight ratio is about 6.5 or more, preferably C because a 100% α structure is obtained if Cu is about 6.5 or more.
u: Zn = 7: 3. This is because if the Cu ratio is less than 6.5, the β structure remains even after complete diffusion, deteriorating the wire drawing workability.

[0012]

[Examples] SWRS82A steel having a wire diameter of 1.4 mm was subjected to lead patenting treatment, electrolytic pickling, alkali washing, Cu, Z
After performing n-plating and drying sequentially, Cu, Z in the fluidized bed furnace
A test for diffusing n was conducted. Here, lead patenting was performed at 950 ° C. (heating in an electric furnace, in Ar gas) at −550 ° C. (lead bath), and electrolytic pickling was performed in a 20 wt% sulfuric acid solution at a current density of 1
00A / dm ² bipolar type AC electrolysis, alkaline cleaning is AC electrolysis with current density of 10A / dm ² , and Cu plating is 10A / d with copper pyrophosphate plating bath.
In m ^2, Zn plating was performed at a current density of 20A / dm ² using a zinc sulfate plating bath. Further, each plating method is an overflow method, and the plating efficiency is 95%. C
u and Zn are Cu: Zn = in a weight ratio regardless of the plating thickness.
It was plated so as to be 7: 3. Fluidized bed furnace has a particle size of 150
Zircon sand of about μm was used as fluidized sand, propane gas was burned, and the amount of the gas was controlled to keep the temperature within ± 1 ° C. The diffusion time is the time in the fluidized bed, and the diffusion temperature is the fluidized bed set temperature. The evaluation is β brass rate measurement by X-ray diffraction (β / (α + β),
%), Thickness measurement of surface oxide ZnO by depth direction analysis using Auger electron spectroscopy, drawing measurement after wire drawing to 0.2 mm, number of wire breaks per 100,000 m long wire draw by. The number of passing average breaks is 1 time or less / 100,000 m. The wire drawing machine is a twin-screw 20-step wire drawing machine, and each step has a surface reduction rate of 14% and a wire drawing speed of 600 at 0.2 mm.
m / min, the lubricant used was a phosphoric acid ester sodium salt aqueous solution of a higher alcohol.

Table 1 shows the test conditions and results, together with examples of the present invention and comparative examples.

[0014]

[Table 1]

In Comparative Example 1, since the plating thickness is 0.5 μm or less, even if the β brass ratio and ZnO are suppressed by diffusing in the region satisfying the conditional expression, the plating thickness is too thin and the plating lubrication effect is obtained. It was not possible to show it, and the number of disconnections increased.

In Comparative Example 2, since the plating thickness is 5 μm or more, the diffusion conditions in the formula of the present invention cannot be applied, and the diffusion cannot be sufficiently performed, so that the β brass ratio is increased and the ductility is deteriorated, so There was a decrease in the diaphragm and an increase in the number of wire breaks.

In Comparative Example 3, the temperature was lower than the diffusion temperature calculated from the diffusion time, the diffusion was insufficient, and the β brass ratio was 2.
Since the content exceeds 0%, the ductility deteriorates and the drawing after drawing deteriorates.

In Comparative Example 4, the temperature was higher than the diffusion temperature calculated from the diffusion time, and the surface oxide ZnO had a thickness of 0.0.
Since the diameter exceeds 5 μm, the ductility deteriorates and the draw after drawing deteriorates.

On the other hand, all of the examples of the present invention show good results without deterioration of ductility, and it can be seen that a brass diffusion plated steel wire excellent in wire drawability can be manufactured.

[0020]

The present invention makes it possible to control the β brass ratio and surface oxide in brass diffusion plating.
By reducing the β brass ratio and the surface oxide, the wire drawing workability can be significantly improved, which leads to the improvement of high quality and productivity, which is a great industrial advantage.

[Brief description of drawings]

FIG. 1 is a diffusion condition 770-193 log (t) of the present invention.
It is a figure which shows <= T <= 700-138 log (t) (T: diffusion temperature (degreeC), t: diffusion time (s)).

[Fig. 2] β before drawing of a SWRS82A steel brass diffusion-plated wire having a wire diameter of 1.4 mm up to 0.2 mm
It is a figure which shows the relationship between the brass rate and the diaphragm after drawing.

FIG. 3 is a diagram showing the relationship between the thickness of the surface oxide ZnO before drawing and the drawing after drawing when a SWRS82A steel brass diffusion plated wire having a wire diameter of 1.4 mm is drawn to 0.2 mm.

FIG. 4 is a diagram showing a β brass ratio when diffused under the optimum diffusion conditions of the present invention in each plating thickness.

FIG. 5 is a diagram showing a relationship between a plating thickness and an average number of wire breakages when a wire having a length of 100,000 m is drawn in Examples.

[Explanation of symbols]

1 straight line showing T = 700-138 log (t) 2 straight line showing T = 770-193 log (t) 3 770-193 log (t) ≦ T ≦ 700-138
Area showing log (t)

Claims (1)

[Claims] 1. A method for producing a brass-plated steel wire, wherein a steel wire is sequentially plated with copper and zinc to a total thickness of 0.5 to 5 μm, and then heated to alloy by diffusion of a metal to produce a brass-plated steel wire. 193 log (t) ≦ T ≦ 700-13
A method for producing a brass diffusion-plated steel wire excellent in wire drawing workability, which comprises diffusing at 8 log (t) (T: diffusion temperature (° C), t: diffusion time (s)).