JPH0379790A - Corrosion resisting high tensile steel wire and corrosion resisting coil spring using same - Google Patents

Abstract

PURPOSE:To obtain a plated high tensile steel wire for coil spring excellent in corrosion resistance by plating the surface of a high tensile steel wire with Cu alloy and further forming a plating layer of Ni or Ni alloy on the above. CONSTITUTION:In order to make a coil spring of a high tensile steel wire and improve the corrosion resistance of the spring, a plating layer 2 of Cu alloy, such as Cu-Zn alloy and Cu-Sn alloy, is formed on the surface of a steel wire 1 as a stock to 0.04-1.5mu thickness. Successively, a plating layer 3 of Ni or Ni alloy is formed on the above. Even if a pinhole (a) and a pinhole (b) are formed in the Cu alloy plating layer 2 and the Ni or Ni alloy plating layer 3, respectively, the Ni plating layer 3 is not subjected to cathodic protection because it is kept in noncontact with the steel wire 1 as a substrate, though it has a cathodic protection effect to the Cu alloy plating layer 2. As a result, the corrosion resistance of the steel wire can be remarkably improved synthetically by means of double layer coating, and this steel wire can be used in the form of a plated steel wire of >150kgf/mm<2> tensile strength as a superior stock for spring coil composed of corrosion resisting high tensile steel wire.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a corrosion-resistant high tensile strength steel wire whose surface is plated with a double layer of copper alloy and nickel or a nickel alloy, and a corrosion-resistant coil spring using the same.

<Conventional technology and its problems> Conventionally, wire drawing materials that require high corrosion resistance and strength for springs and the like have been coated with Zn, Cu, Ni, etc. as described in Japanese Patent Publication No. 14572/1982 and Japanese Patent Publication No. 35276/1983. Steel wire or stainless steel wire is used.

However, stainless steel wire is expensive, and steel wire plated with copper, nickel, or an alloy thereof has insufficient corrosion resistance due to defects such as pinholes.

In addition, although galvanized steel wire does not easily develop red rust while the surface galvanized film remains, if the zinc plating easily oxidizes or hydroxylates, white rust will occur and the wire will not be suitable for practical use. I cried.

From the above point of view, the surface of the steel wire was plated with a metal that had better corrosion resistance than steel, but due to plating defects such as pinholes, the opposite phenomenon to cathodic protection occurred.

In other words, in areas where the base steel is exposed, such as in pinholes, Fe, which is baser than the base steel, acts as a sacrificial anode and suppresses corrosion of plated metals such as Ni and Cu, which are more noble than the base steel, resulting in red rust. was occurring.

<Means for Solving the Problems> The present invention was discovered as a result of studies to eliminate the above-mentioned disadvantage of red rust, and it is a glazed steel wire whose surface is coated with copper alloy. Furthermore, it is an object of the present invention to provide a corrosion-resistant high tensile strength steel wire whose surface is plated with nickel or a nickel alloy, and a corrosion-resistant coil spring obtained by processing the steel wire into a coil spring.

Namely, in this invention, the surface of a steel wire is first plated with a copper alloy that is more electrochemically effective than steel, and then nickel or a nickel alloy that is less base than the copper alloy but more effective than steel is plated on top. It is plated with

In this case, in the two-layer plating layer applied to the surface of the steel wire 1 as shown in Figure 1, it is rare that pinhole a in the copper alloy plating layer 2 and pinhole b in the nickel plating layer 3 coincidentally overlap. In many cases, the positions of the pinholes a and b are different, as shown in FIG.

Therefore, in the case of Fig. 2, the nickel plating layer 3 has a cathodic protection effect on the copper alloy plating layer 2, but it does not come into contact with the underlying steel wire 1 and is not cathodic protected against the steel wire 1. .

Of course, if the pinhole part a of the copper alloy plating layer 2 is exposed to a corrosive environment, the copper alloy plating layer and the underlying steel wire will be cathodic-protected and the steel wire will rust, but the copper alloy plating layer is nickel-plated. Because it is covered with a layer, it is not exposed to corrosive environments and therefore will not rust.

In this invention, there is basically no limit to the thickness of the plating layer applied to the surface of the steel wire, but if it is too thin, there may be areas where the plating does not adhere or where the plating peels off due to unevenness of the underlying steel wire. 0.0.
It is desirable to have a thickness of 0.04μ or more.

<Example> Hereinafter, this invention will be explained in detail with reference to Examples.

A patented piano wire with a wire diameter of 5.0 mmφ having the chemical components shown in Table 1 is cut into a wire diameter of 2 Ommφ using a hole die.
The wire was drawn to

Further, test materials were prepared by electrolytically cleaning with hydrochloric acid and sulfuric acid, and applying predetermined plating as shown in Table 2.

Also, wire diameter 5. Table 2 also shows the test materials that were plated at Ommφ and then drawn to 2.0mmφ using a die.

Among the test materials in Table 1 and Table 2, N[L5.6.9 and 11
The plating thickness was measured after wire drawing.

The results are shown in Table 3.

Table 3 Next, the tensile strength of the test materials shown in Table 2 was measured, and the results shown in Table 4 were obtained.

Table 1 also shows the corrosion resistance of the obtained test materials in a constant temperature and humidity chamber (8
A continuous salt water spray test was conducted at 0° C. x 95% humidity), and evaluation was made based on the time when red rust begins to occur and the rust area ratio after 50 days of testing. The results are shown in Table 5.

From the results shown in the table above, it was found that all of the present examples (sample materials Na 1 to 6) had better corrosion resistance than the conventional examples (sample materials Na 7 to 12). In particular, for sample material 3, the total plating thickness was 0.3.
It was observed that the corrosion resistance was significantly improved compared to the conventional example, even though it was only μ.

Furthermore, although the plating thicknesses of test materials 3 and 6 of this example were almost the same, it was found that 6, which was subjected to wire drawing after plating, had better corrosion resistance. This is thought to be due to the effect of the plating pinholes being crushed by the wire drawing process.

<Effects of the Invention> As explained above, this invention significantly improves corrosion resistance compared to single plating by applying steel alloy plating to the surface of the steel wire and further applying composite plating of nickel or nickel alloy plating thereon. It was shown to be effective.

It was also found that wire drawing after composite plating was effective in further improving corrosion resistance.

As a result, the steel wire of the present invention is particularly effective as a steel wire for products requiring corrosion resistance, such as springs, lobes, and wire meshes.

[Brief explanation of drawings]

FIGS. 1 and 2 are cross-sectional views of a steel wire whose surface is coated with a copper alloy and nickel plating layer. 1... Steel wire 2... Copper alloy plating layer 3
...Nickel plating layer a...Pinhole in copper plating layer

Claims (1)

[Claims] (1) A corrosion-resistant high-strength steel wire formed by plating a plated steel wire with copper alloy plating on the surface and further plating nickel or nickel alloy on the surface. (2) The corrosion-resistant high tensile strength steel wire according to claim 1, wherein the copper alloy plating thickness is 0.04 to 1.5 μm. (3) Claim (1) wherein the tensile strength of the plated steel wire is 150 kgf/mm^2 or more
) or the corrosion-resistant high-tensile steel wire described in (2). (4) Corrosion-resistant coil spring made by processing a corrosion-resistant high-tensile steel wire made of a plated steel wire whose surface is plated with copper alloy and further plated with nickel or nickel alloy into a coil spring.