JPH04103793A - Method for plating steel wire for tire cord with brass - Google Patents

Abstract

PURPOSE:To produce a brass plated steel wire whose plating is not easily exfoliated even by intense drawing with high productivity by forming a Cu plating layer on the surface of a steel wire with a copper pyrophosphate plating soln., further forming a Cu plating layer with a copper sulfate plating soln., then forming a Zn plating layer and converting the metals into brass by thermal diffusion. CONSTITUTION:A steel wire 1 is heat-treated as usual, pretreated and very thinly plated with Cu in Cu plating tanks 7a contg. a copper pyrophosphate plating soln. to form a first layer. The Cu plated wire 1 is passed through a washing tank 5 and further plated with Cu in Cu plating tanks 7b contg. a copper sulfate plating soln. to form a second layer. The wire 1 is then passed through a washing tank 5, plated with Zn in Zn plating tanks 8, washed in a washing tank 5 and heated to about 450 deg.C with a resistance heater 9 to diffuse the metals. The resulting brass plated steel wire is coiled with a coiler 10.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an improvement in a method for plus plating steel wire for tire cords.

(Prior technology) Tire cords are used by being embedded in rubber, and the steel wire surface is coated with positive plating to improve adhesion to the rubber, and the wire is stretched to give it flexibility. Manufactured through wire and stranding processes.

As a general positive plating method, a so-called alloy plating method has been used in which a cyan bath containing copper and zinc is used to simultaneously deposit copper and zinc.

However, cyanide baths are highly toxic and therefore harm the working environment, require measures against pollution such as waste liquid treatment, and require strict management to control the plating composition.

In recent years, in view of the above circumstances, a method has been proposed in which copper and zinc are plated in separate baths and then heated to interdiffuse the copper and zinc to form an alloy, and this method has become common today. Ta.

An overview of this plus plating method is shown in Figure 2.
The steel wire (1) is heat-treated through a heating furnace (2), a lead quenching tank (3), and then transferred to an electrolytic acid cleaning tank (4), a water washing tank (5), an alkali washing tank (6), and a water washing tank ( 5), and then copper plating in the copper plating tank (7), followed by a washing tank (7).
5) and galvanized in a galvanizing tank (8).
After washing with water in the washing tank (5), 45
After being heated to around 0°C and diffused, the winder 011D
It is wound up.

A copper pyrophosphate bath or a copper sulfate bath is generally used in the steel plating tank (7), and a zinc sulfate bath is generally used in the galvanizing tank (8).

(Problems to be Solved by the Invention) The above-mentioned positive plating method for steel wires using heating and diffusion is expected to have excellent effects such as no pollution problem (and easy control of the plating composition). In the above-mentioned positive plating method for steel wire by heating diffusion, a copper pyrophosphate bath is exclusively used when the m-wire is used for tire cords. This is because the adhesion of the surface of the wire to the iron base is poor, and this has the disadvantage of causing the plating to peel off during the wire drawing process, which usually involves a workability of 95 to 98% after the plating process.

However, in the case of copper plating using the copper pyrophosphate bath, the limiting current density is low, and even if electrolysis is performed near the limiting current, the plating will become cloudy, burnt, etc., resulting in poor plating, so it is difficult to improve the plating speed. is difficult. Therefore, the plating processing time could not be shortened, resulting in poor productivity.

The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to efficiently manufacture a plus-plated steel wire that does not easily peel off the plating even during wire drawing under severe working conditions.

(Means for Solving the Problems) In order to achieve the above object, the plus plating method for tire cord conditioning wire of the present invention involves forming a copper plating layer by copper pyrophosphate plating on the surface of the copper wire, and then forming a copper plating layer on the surface of the copper wire. A copper plating layer is formed by copper sulfate plating on the layer, and a zinc plating layer is further formed on the core layer, and then heated and diffused to make it positive.

(Function) A copper plating layer formed by copper pyrophosphate plating is formed on the iron base on the surface of the wire, so it has excellent adhesion and the plating layer does not peel off easily even during wire drawing under severe processing conditions. Furthermore, since the entire copper plating layer is not formed by copper pyrophosphate plating, but only the necessary amount is formed, the plating time during formation of the copper plating layer can be shortened.

(Example) Hereinafter, one embodiment of the present invention will be described based on the drawings.

FIG. 1 is a block diagram showing an outline of an embodiment of the method of the present invention. In the same figure, a steel wire (1) is heat-treated in the same manner as in the conventional positive plating method by heating diffusion (FIG. 2), and then Pre-treated and then copper pyrophosphate plating tank (7a
), the first layer of ultra-thin copper plating is applied, and the washing tank (
5), the second layer of copper plating is applied in the copper sulfate plating tank (7b), then zinc plating is applied in the galvanizing tank (8) after passing through the rinsing tank (5), and then in the rinsing tank (5). After washing with water, it is heated to around 450° C. by an electric heating device (9) and diffused, and then wound up by a winding JIGω.

The plating conditions in the copper pyrophosphate plating tank (7a), copper sulfate plating tank (7b), and zinc plating tank (8) are shown below.

(Copper pyrophosphate plating bath) Copper pyrophosphate 75-105g/j! Potassium pyrophosphate 280-370g#Ammonia water (28%) 2-5 companies/l Potassium nitrate
0-15 glIP ratio
7-9 PH 8,5-9 Current density 3-12 (zinc sulfate plating bath) Copper sulfate sulfate temperature current density (zinc sulfate plating bath) Zinc sulfate 200-400 g/l Ammonium sulfate O-20 g/l.

Temperature: 20~30℃ Current density: 10~30 A/di Wire diameter: 1.2
A 5Wlφ steel wire was subjected to heat treatment and pretreatment in the steps shown above, and then under each of the above plating conditions,
First, a copper plating layer with a thickness of 0.3 μm is formed by copper pyrophosphate plating at a current density of 10 A/dnf, and after washing with water, a copper plating layer with a thickness of 8/daf1 g/1 g/1 °C A/da1 180~ is formed by copper sulfate plating. 240 45-60 20-40 10-40 A 0.7 μm copper plating layer was formed at a current density of 40 A/d, and after washing with water, a 0.6 μm thick galvanized layer was formed by zinc sulfate plating and washed with water. Thereafter, the mixture was heated at 420° C. using an electric heating device to cause diffusion, thereby obtaining a plus plated steel wire.

In the plus plating method shown in the above example, the plating speed of copper plating was approximately three times that of conventional dorophosphate copper plating.

The thickness of the copper plating layer applied in the copper pyrophosphate plating tank is preferably 0.3 to 0.5 μm. This is 0.3μ
If it is thinner than m, the copper plating by copper pyrophosphate plating will not be uniformly adhered to the wire surface, and as shown in Figure 3, the plating will fall off during wire drawing (assuming the degree of processing is 96%). This is because if the ratio is large and the thickness is greater than 0.5 μm, the plating time required will be large.

By the way, the thickness of the plus plating layer of the steel wire for tire cord is, for example, 1.0 to 1.0 in the case of a steel wire with a wire diameter of 1.25 mmφ.
3.0 μm is optimal.

(Effects of the Invention) According to the present invention, a thin copper plating layer made of copper pyrophosphate plating with good adhesion is applied to the iron base on the surface of the wire, and then a copper plating layer made of copper sulfur plating is formed. Therefore, it is possible to efficiently produce a plus-plated A-wire that does not easily peel off the plating even during wire drawing under severe processing conditions.

[Brief explanation of drawings]

Fig. 1 is a schematic process diagram showing a plus plating method according to an embodiment of the present invention, Fig. 2 is a schematic process diagram showing a conventional plus plating method using heat diffusion, and Fig. 3 is a copper plating layer formed by copper pyrophosphate plating. 3 is a graph showing the relationship between the thickness of the wire and the rate of removal of plus plating due to wire drawing.

Claims (1)

[Claims] A copper plating layer is formed on the surface of the steel wire by copper pyrophosphate plating, then a copper plating layer is formed by copper sulfate plating on the surface of the steel wire, and a zinc plating layer is further formed on the layer, followed by heating diffusion. A method for plus plating steel wire for tire cords, which is characterized in that it is coated with plastic.