JP2645457B2 - Method of manufacturing steel wire and steel cord for reinforcing rubber articles - Google Patents

Description

The present invention relates to a method for producing a steel wire and a steel cord for reinforcing rubber articles such as tires, hoses, and conveyor belts, and more particularly, to a method for producing a rubber and a steel wire and a steel cord. The present invention relates to a method which is effective for improving the adhesiveness of a sheet.

[Conventional technology and its problems]

Techniques for improving the strength and durability of rubber products by embedding various reinforcing materials in rubber are widely practiced. Among them, composites of rubber and steel reinforcement are applied to automobile tires, high-pressure rubber hoses, conveyor belts, etc., and the required quality performance is also diverse. Improving is a universal requirement.

In particular, in steel radial tires using a steel cord plated with a copper-zinc binary alloy as a reinforcing material, there is a strong demand for increasing the high-speed durability and high-speed stability of tires with the development of highways, Improving the adhesion between steel cord and rubber has become a very important issue in order to achieve this demand.

Regarding this adhesiveness, research on improvement of steel wires, steel cords and rubber has been carried out, and the adhesiveness at the time of rubber product production, so-called initial adhesiveness, is being improved, but it is actually used under severe conditions. And good initial adhesiveness gradually decrease, and the present situation is that the state is not sufficiently satisfactory.

For example, in steel radial tires, steel cords and rubber can be stored for a long time in a humid atmosphere before being mounted on a car, or when the rubber is scratched when used after being mounted on a car and water infiltrates, The problem is the so-called moisture-resistant adhesiveness, which lowers the adhesiveness of, and this improvement has been eagerly sought.

Conventional steel wire and steel cord for rubber articles, after copper-zinc binary alloy plating on the rope,
Draw wire and even twisted wire are generally used, and in order to improve moisture resistance adhesiveness, lower the copper content of copper-zinc binary alloy plating, or nickel to copper-zinc,
Ternary alloy plating to which one of cobalt, iron and tin is added, or reduction in the thickness of a plating layer has been performed. However, the copper content is 62%
If the temperature is lowered below, the β phase is precipitated, so that the wire drawing workability is deteriorated, and wire drawing troubles such as thinning and disconnection are liable to occur. Therefore, the limit value of the copper content is about 62%. On the other hand, in the case of ternary alloy plating in which one of nickel, cobalt, iron and tin is added to copper-zinc, a uniform alloying treatment by heat diffusion is necessary. Takes a long time to reduce productivity
It is desirable to make it as thin as possible. However, if the thickness of the plating layer is too small, the peeling of the plating during wire drawing increases, and the initial adhesion decreases.

There is such a problem during wire drawing, and it has not yet been possible to obtain a sufficiently satisfactory moisture resistance.

The present inventors, in order to elucidate the cause of increased plating peeling during wire drawing when the thickness of the plating is reduced, in order to elucidate the plating adhesion state to the wire rod for each wire drawing die in the wire drawing process. Upon microscopic observation, it was found that the smoothness of the wire surface before drawing affected the plating adhesion state, and that if the smoothness was poor, local plating peeling was likely to occur. FIG. 1 is a cross-sectional view showing the state of plating adhesion in the conventional method.
FIG. 3 shows an example examined by SEM (scanning electron microscope) observation. Wire 1 which is the plating base before wire drawing
Is very poor in smoothness as shown in (a) of the figure, and when this is drawn, the plating 2 on the surface convex portion is peeled off as shown in the figure (b). I have.

It was also found out that the wire had poor surface smoothness, that is, large irregularities had already occurred before the plating step. However, the conventional plating pre-treatment step was performed to remove scale or activate the surface. Surface roughness is little effective in improving surface roughness and the average surface roughness is 2 μm
Larger than above, 2 to 5 μm for wire rods with a wire diameter of 1.0 to 1.6 mm
This is the reason for the local peeling of the plating in the wire drawing process.

[Means for solving the problem]

The present inventors consider that it is effective to newly add a smoothing treatment of a wire surface by electrolytic polishing to a pretreatment step of plating in order to suppress plating peeling in a wire drawing step from the above circumstances. As a result of thinking and conducting it, it was found that even if the thickness of the plating was reduced, there was almost no peeling of the plating during wire drawing, and it was possible to improve the moisture resistance adhesion without lowering the initial adhesion, The present invention has been completed.

That is, in the method of the present invention, after removing the surface scale by acid washing or electrolytic washing using hydrochloric acid, sulfuric acid or the like,
Electropolishing is performed with an aqueous solution containing phosphoric acid as a main component and sulfuric acid or chromic acid mixed therein to reduce the average roughness of the wire surface to preferably 1 μm or less. Thereafter, on the surface of the smoothed member, copper-zinc binary alloy plating, so that the plating thickness in the final product is maintained at 0.05 to 0.20 μm, that is, the plating layer thickness represented by the following formula: Alternatively, ternary alloy plating in which one of nickel, cobalt, iron, and tin is added to copper-zinc is applied.

The method of the present invention is to form a steel wire obtained through a heat diffusion and wire drawing process and a steel cord obtained by twisting these wires.

The reason why the roughness is preferably 1 μm or less is that if the roughness is larger than 1 μm, a local plating peeling phenomenon easily occurs when wire drawing is performed with a reduction in area of 80% or more to obtain a predetermined tensile strength. This is because it is difficult to reduce the thickness to 0.20 μm or less. Also, set the thickness of plating after wire drawing to 0.
The reason for keeping at 0.05 to 0.20 μm is that if it is larger than 0.20 μm, almost no improvement in moisture resistance is seen, while if it is smaller than 0.05 μm, the amount of adhesion reaction with rubber is insufficient and initial adhesion is reduced. I do. Next, the calculation formula (1) for defining the plating thickness in the plating step is obtained by examining the change in the thickness of the plating layer accompanying the wire drawing after plating on the surface of the wire smoothed by electrolytic polishing. is there.

[Action]

As described above, when a wire surface smoothing process by electrolytic polishing is added as a pretreatment for plating, the flow of plating into concave portions in the drawing step after plating is reduced, and the state of plating adhesion on the entire surface is more uniform. It is maintained in a state. FIG. 2 shows an example in which the plating state in the method of the present invention is examined by SEM observation. After the wire drawing (b in the same drawing), the plating 2 is uniformly adhered to the surface of the wire 1 in the same manner as before the wire drawing (a in the same drawing), and the local portion according to the conventional method shown in FIG. No typical plating peeling phenomenon is observed.

For this reason, even if the thickness of the plating is reduced, unlike the conventional method, there is almost no peeling of the plating during the wire drawing, and the moisture resistance adhesion can be improved without impairing the initial adhesion.

 Hereinafter, more detailed embodiments of the present invention will be described.

〔Example〕

Using a rope having a wire diameter of 1.25 mm, the surface scale was removed by pickling in the plating pretreatment step, and then electropolishing was performed with a mixed aqueous solution of phosphoric acid and sulfuric acid to smooth the wire surface. Thereafter, copper-zinc binary alloy plating with a copper content of 63% and a plating layer thickness of 0.58 μm, and copper-zinc with a copper content of 63%, a nickel content of 5.5% and a plating layer thickness of 0.63 μm.
Nickel ternary alloy plating is performed. The wire diameter was reduced to 0.25 mm by wire drawing, and the obtained wires were twisted with a twisting machine to produce a 1 × 5 steel cord. The plating layer thickness of this final product is 0.
11μm, 0.12μm with copper-zinc-nickel ternary alloy plating
Met. These steel cords were examined for adhesion to rubber.

The adhesion was evaluated by bonding rubber having the composition shown in Table 1 from both sides of the steel cord and vulcanizing it at 150 ° C for 30 minutes. After leaving in the atmosphere shown in Table 2, a peeling test was carried out, and the steel cord was evaluated for rubber coverage on a scale of 5.0 out of 5.0.

For comparison, a 1 × 5 steel cord of a copper-zinc binary alloy plating with a wire surface smoothed by electrolytic polishing and having a copper content of 63% in the final product and a plating layer thickness of 0.25 μm, In addition, a copper-zinc binary alloy plating which does not perform a wire surface smoothing treatment by electrolytic polishing and has a copper content of 63% in the final product, a plating layer thickness of 0.25 μm (conventional), or 0.11 μm. The adhesion was also examined for a × 5 steel cord.

Table 2 shows the results. From this table, it can be seen that the steel cord according to the method of the present invention has slightly improved initial adhesion as compared with the conventional method, but in particular, has greatly improved moisture resistance.

[Effects of the Invention] According to the present invention, by performing a smoothing treatment of a wire surface by electrolytic polishing before plating, plating peeling in a wire drawing process is suppressed, so that a plating thickness is reduced. Became possible. Further, it was found that the plating amount in the plating step also had an appropriate range, and the deterioration of the moisture resistance and the initial adhesion due to the inappropriate amount of this amount was eliminated. As a result, the effect that the moisture resistance of the steel wire and the steel cord to the rubber can be greatly improved is obtained, which can greatly contribute to the improvement of the reliability and durability of the rubber article.

[Brief description of the drawings]

FIG. 1 is a SEM observation result of examining the state of plating adhesion according to the conventional method, and FIG. 2 is a view showing an SEM observation result of examining the adhesion state of plating according to the present invention. (B) before is a surface state after drawing at a surface reduction rate of 30%. 1 ... wire, 2 ... plating.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification number Agency reference number FI Technical display location C25D 7/06 D07B 1/06 A D07B 1/06 B29C 67/14 X

Claims (1)

(57) [Claims] In a pre-treatment step of wire drawing, a step of smoothing the surface of the wire by electrolytic polishing, a copper-zinc binary alloy plating on the smoothed wire surface, or nickel on copper-zinc, Cobalt, iron, including the step of applying one of the ternary alloy plating of tin, the amount of plating in the plating step, so that the plating layer thickness after drawing is 0.05 to 0.20 μm. A method for producing a steel wire and a steel cord for reinforcing rubber articles, wherein the plating layer has a thickness represented by the following formula.