JPS5871391A - Method for electroplating steel wire for welding in copper sulfate bath - Google Patents

Abstract

PURPOSE:To form copper plating with uniformity in electrodeposition and high adhesive strength equal to those of copper plating obtd. by plating in a cyanide bath by plating the surface of a steel wire with copper in a plating bath having a specified composition contg. copper sulfate. CONSTITUTION:In the manufacture of a copper plated steel wire for welding, a steel wire is electroplated as a cathode at >=150 A/dm<2> current density while passing the wire through a plating bath having 10-300g/lCuSO4.5H2O concn. and 10-100g/l H2SO4 concn. at 55-80 deg.C bath temp. by 250m/min rate. Copper plating with uniformity in elctrodeposition and superior adhesive strength to the base equal to those of copper plating obtd. by plating in a cyanide bath can be formed without causing environmental pollution.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for forming a copper plating film with good uniform electrodeposition and adhesion.

Steel wires for welding are coated with copper for electrical conductivity and rust prevention, but conventional copper plating mainly utilizes a V annealing bath, and there are many problems with MA liquid treatment terminals. Ta. On the other hand, with copper sulfate bath plating, the waste liquid is less toxic;
In recent years, copper sulfate bath plating has been adopted because it is desirable from the perspective of environmental pollution and also has the advantage of allowing highly efficient plating operations. The drawback is that it is inferior to Y-An bath in terms of uniform electrodeposition and layer density to the base.

The present invention was made in view of this situation #IcWI, and is a method of sulfuric acid steel bath electroplating for forming a plating film having the same level of uniform electrodeposition and adhesion as that of %V bath plating. The purpose is to establish a method.

However, the electroplating method of the present invention has copper sulfate concentration: 1
0-800g/1. The gist is that a steel wire for welding is immersed in a copper sulfate bath with a sulfuric acid concentration of 10 to 100 g/l and a bath temperature of 56 to 80°C, and electroplated at a current density of 150 A/dXxP or more. The reasons for selecting these plating conditions will be explained below.

In order to form a uniform plating film in electroplating, it is said that it is necessary to increase the uniform current density throwing force (throwing power) 2T shown by equation (1) as much as possible. te^ru.

To bring the throwing power T closer to 100, 11
) in the formula, set R as small as possible, and set the cathode polarization ΔE
It is desirable to increase /ΔI.

First, basically, the concentration of copper sulfate must be above a certain level, but it is required to be at least 10 g/l. That is, when it is less than 10 g//, the steel ion concentration is low, so that the bath resistance R increases and the 9° throwing power T decreases. In other words, the bath resistance is high, the conductivity is poor, and the limiting current density is low, making it impossible to obtain a practically satisfactory plating speed.

In the electrolytic reaction of a sulfuric acid steel bath, the diffusion of copper ions into the cathode is rate-determining, so it is necessary to increase the copper ion concentration in order to easily reduce the diffusion into the wire (cathode).

However, the saturation concentration of sulfuric acid steel at room temperature is 800 g/
1. Therefore, in the present invention, 800 g/l is also set as the upper limit. The temperature during the plating operation is 55-8 as described below.
Since the temperature is 0°C, it is possible to achieve an even higher concentration by considering only during operation, but if the temperature drops when plating operation is interrupted, excess sulfuric acid steel will precipitate and cause damage to the plating equipment. High concentrations of more than 800 g// are not preferred because of adverse effects. Therefore, the copper sulfate concentration is 10-8
00g// range.

Next, the sulfuric acid concentration was determined to be 10 g/1 or more for the following reasons. In other words, when the concentration is higher than log//, the alkaline substances in the wire drawing moisturizer brought into the plating bath from the gloss are neutralized, so the pH of the plating bath is kept constant and a uniform plating film is formed. becomes possible. Furthermore, as shown in FIG. 1, when the sulfuric acid concentration exceeds 10 g/e, the bath voltage required to obtain the same current density decreases. That is, as the sulfuric acid concentration increases, the bath resistance R decreases, so that the throwing power T approaches 100 IC@, making it easier to form a uniform plating film. However, if the sulfuric acid concentration exceeds 100 g/l, the solubility of sulfuric acid steel decreases and precipitation of sulfuric acid steel may occur during plating operations, so the upper limit should be 100 g/l. Also, as shown in the vg1 table, the sulfuric acid concentration is 100
If Hgfi exceeds g//, Hgfi in the plating increases and is incorporated into the plating metal, which is unfavorable for welding.

@1 Regarding the temperature of the plating bath, as the bath temperature increases, the movement of ions becomes easier and the bath resistance R decreases. This contributes to an increase in throwing power. By the way, 81℃8Figure 1A) k'i bath temperature 80℃, g
Figure g @ is a microscopic photograph showing the structure of plated steel when bath tjA is 55°C.

In the latter, coarse columnar crystals are electrodeposited smooth and uniformly. Bath group FllFi in Ryoji 8 figure metsuki
, CuSO4・5HgO: 800g//, H2SO4
: Ton at 60g/l, wear speed: 250m/min.

The hardness of the coating obtained by f#'lV unbath plating is generally 160 to 180H, but the hardness of the coating obtained by sulfuric acid steel bath plating is The hardness is 100-186H at a bath temperature of 8G℃, and 86-90H at a bath temperature of 55℃.
It was H-ma. In other words, in sulfur IIIM bath plating, a soft plated layer is generally obtained, and the workability of the plated film is good (although it is even better if the bath temperature is set to 56°C or higher; As shown in Figure 5, CuSO4・5H20
When the concentration of H2SO4 and H2SO4 satisfies the conditions of the present invention and the bath temperature was 40 DEG C., even if the current density was increased, neither the uniformity of electric current distribution nor the adhesion was improved. On the other hand, when the bath temperature was 55 to 80°C, the uniformity of electrodeposition was good in all cases, and the adhesion was good.

Good results were obtained at 150 A/dm2 or higher. The adhesion was determined by wrapping a plated wire around the outer periphery of a wire of the same diameter and observing its surface.

Since the sulfur #copper bath electroplating of the present invention is carried out under the above-mentioned conditions, it is as uniform as cyan bath plating. It became possible to obtain good adhesion and adhesion.

[Brief explanation of the drawing]

Figure 1 is a graph showing the effect of HgSO4 concentration on electrolytic voltage, Figure 2 is a graph showing the effect of bath temperature on cathode polarization, and Figure 8 (2) @ shows the structure of the cross section of the plated layer. Gu Huikey photo (500x), Figure @4 is a graph showing the influence of current density on the amount of displacement plating. 'iTi, flow tight J series ld (A/dm'')゛ 1
1 Koi et E (VvsSe!')
“I.

Claims (1)

[Claims] (t) Copper sulfate mff: 10-800 g/1. sulfur
a concentration: 10-100 g/1. Bath I: A wire for welding steel is immersed in a copper sulfate bath at 65 to 80°C, and the current density is 15.
A method for electroplating a steel wire for welding in a sulfuric acid steel bath, the method comprising electroplating at OA/- or more.