JP2002167692A - Coated stainless steel wire and manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a coated stainless steel wire by which design characteristics and surface lubricity can be improved on the basis of the formation of nickel coating having a blackish color on a core material composed of stainless steel, and the identification of final molded articles produced by using the coated stainless steel wire can be facilitated, and also to provide its manufacturing method. SOLUTION: The coated stainless steel wire has a core material composed of stainless steel and a nickel coating layer formed on its surface. Further, the nickel coating layer has substantially blackish color by being composed of a nickel alloy containing nickel and at least sulfur and zinc.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention is based on the formation of a nickel coating having a black color on a stainless steel core material.
The present invention relates to a coated stainless steel wire capable of facilitating identification of a final molded product produced using the same, and a method for producing the same.

[0002]

2. Description of the Related Art In general, stainless steel is a difficult-to-process material. When performing the forming process, it is widely practiced to form a lubricating film on the surface of the wire to be processed in advance so as to withstand such a process.

[0003] In particular, nickel has been found to have high mechanical properties, corrosion resistance and lubricity as well as stainless steel, and also has the function of suppressing temper color during heat treatment after molding. In particular, it has been widely used as a coating material for stainless steel wires for springs.

For example, Japanese Patent Application Laid-Open No. 8-181626 discloses that the thickness of a nickel plating layer on a stainless steel wire for a spring, the hardness ratio with the core stainless steel wire, and the amount of lubricant attached are each within predetermined ranges. This discloses that the coilability in spring molding is improved, and a plating method using nickel sulfamate is proposed.

[0005] By the way, as described in the above proposal, the coil spring is formed by pushing out a supply wire against a guide pin set at a predetermined position in advance, so that the coil spring is excellent in uniformity. In order to obtain a stable spring product, it is necessary to reduce the sliding resistance between the wire and the pin, and the proposal also discloses forming a lubricating film on the surface.

Further, since the spring products obtained from these stainless steel wires are relatively small and cannot be individually displayed on the individual springs, the spring products are often stored in a predetermined container such as a tray, and are often used in lots. Although control is performed on a unit basis, if other types of springs are inadvertently mixed due to carelessness, especially if the spring products are used as important functional parts such as operating parts, fatal defects in the original performance of the equipment Effect.

[0007] Therefore, it is necessary to take measures such as lot out or sorting out all the lots that are likely to be mixed, resulting in a large loss and man-hour loss.

For this reason, Japanese Patent Application Laid-Open Nos. 61-250179 and 60-21370 propose that the surface of the wire be colored in advance. In the former proposal, a color resin is applied to the surface of the wire. In the latter proposal, a predetermined color is given by coloring in a tempering heat treatment after spring forming.

[0009]

The stainless steel wire for a spring disclosed in the above-mentioned proposal (Japanese Patent Application Laid-Open No. 8-181626) has a problem in that the hardness of the plating layer is limited due to the coilability. Nickel sulfamate plating is presented, with the hardness of the stainless steel being 0.2 to 0.83.

However, in such a plating layer, the surface thereof becomes unnecessarily smooth due to slippage with the tool in the subsequent drawing or coiling, and as a result, the surface lubricant has a high carrying capacity on the surface. Has been impaired, making it unsuitable for strong machining and high-speed machining.

That is, although the surface lubricant covers the entire surface of the plating layer at the time of coating, it is well known that the surface lubricant is reduced by subsequent processing. However, the surface lubricant tends to become an ultra-smooth surface such as a mirror surface. In the case of having a lubricant, the lubricant is easily peeled off and removed by contact with a die or a tool, and the portion becomes a state of no film.

Accordingly, in the subsequent processing, poor lubrication occurs, and the separated lubricant scatters to contaminate the surrounding environment, or adheres to coiling nozzles, guide rolls and the like to cause clogging, and the like. Greatly affects workability.

Therefore, it has been found that it is effective to use a minute concave portion formed by making the surface to some extent non-smooth in order to hold a sufficient lubricant during heavy working. The proposed plating method cannot be expected to achieve that.

Further, in the case of a color resin disclosed in the above-mentioned Japanese Patent Application Laid-Open No. 61-250179, not only the lubricity of nickel plating cannot be utilized, but also the resin However, it has not been practiced at present because heat treatment or the like has a greater or less adverse effect on the stainless steel base material, and peeling or cracking is likely to occur due to strong friction during wire drawing or coiling.

The color obtained by the temper color disclosed in Japanese Patent Laid-Open No. 21370/1985 is generally determined by heat treatment conditions (temperature).
And the spring characteristics are also affected accordingly.On the other hand, from the viewpoint of discrimination, if the spring product is made of a relatively thin wire, it will be difficult to distinguish it unless a dark color is added. However, it is difficult to obtain an identifiable color depending on the heat treatment conditions, which lacks versatility.

That is, in the case of the color resin disclosed in the official gazette, not only the lubricity of the nickel plating can not be utilized, but also the resin is more or less likely to be adversely affected by heat treatment or the like on the stainless steel base material. At the present time, it is not practiced because it is easy to cause problems such as peeling and cracking due to strong friction during wire drawing and coiling.

Further, the color obtained by the temper color is generally influenced by the heat treatment conditions (temperature), and accordingly, the spring characteristics are also affected. In the case of thin wires, it is difficult to distinguish them unless a dark color is applied.Therefore, it is difficult to adjust between the desired color and the heat treatment conditions for that purpose, and it lacks versatility. It is.

[0018] Such a problem is the same in other processed molded products such as screws, but an urgent solution is required especially for the use as the spring product.

Accordingly, the present invention provides a coated stainless steel which can easily identify and solve the above-mentioned problems by forming a coating layer of a nickel alloy having a black color itself while utilizing lubricity by nickel plating. The purpose is to provide steel wire.

[0020]

The invention according to claim 1 has a stainless steel core material and a nickel coating layer formed on the surface thereof, and the nickel coating layer is made of nickel and at least sulfur and zinc. The coated stainless steel wire is characterized by having a coloring layer having a substantially blackish color by being formed of a nickel alloy containing the same.

According to a second aspect of the present invention, the nickel coating layer is a laminate comprising the coloring layer and a nickel base layer between the coloring layer and the core material and having a composition different from that of the coloring layer. It is characterized by being a structure.

According to a third aspect of the present invention, the tensile strength is 1500
Not less than MPa and an average surface roughness of 0.1 to
It is characterized in that it is 1.0 μm (Ra) and is used particularly as a spring.

According to a fourth aspect of the present invention, the surface of the core material of stainless steel or the surface of the nickel-coated wire formed by forming a nickel underlayer on the surface is nickel-plated and nickel alloy-plated containing at least sulfur and zinc. The coated stainless steel wire is characterized by having been immersed in a solution and continuously forming a colored layer exhibiting a black color on its surface by electroplating, and then subjected to at least one or more cold workings. It is a manufacturing method.

According to a fifth aspect of the present invention, the cold working is cold drawing or cold rolling performed at a working ratio of 60% or more.

[0025]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In FIG. 1, a coated stainless steel wire 1 of the present invention has a stainless steel core material 2 and a nickel coating layer 3 formed on the surface thereof, and the nickel coating layer 3 is made of nickel. And a coloring layer 4 having a substantially blackish color by being formed of a nickel alloy containing at least sulfur and zinc, and in the present embodiment, the nickel coating layer 3 It is formed of a layered structure of a layer 4 and a nickel base layer 5 which is under the layer 4 and has a composition different from that of the coloring layer 4.

The material and characteristics of the core material 2 can be appropriately selected depending on the application. For example, when the material is for a spring, JIS-G
SUS302, SUS304,
In addition to SUS304N, SUS316, SUS631J1, and the like, austenitic stainless steel such as SUS201, SUS301, and SUS310, or stainless steel such as martensite or ferrite can also be used. It is adjusted to.

The core material 2 may be formed in any shape other than a round wire, for example, a band wire, a deformed wire having a non-circular cross section, or the like. Is a black-based color, a more remarkable discriminating function can be exerted when a thin line having a line diameter of about 0.5 mm or less is used. In addition, it can be set to about 4 mm or less and 0.05 mm or more.

The coloring layer 4 is made of a nickel alloy having a basic composition of nickel and at least sulfur and zinc added thereto, thereby giving a black-based color substantially based on black. I have.

As described above, a nickel alloy containing at least sulfur and zinc can be given a color different from a normal metal color depending on the mixing ratio of each element, for example, 3 to 6 wt% of sulfur and 10 to 20 wt% of zinc. % Of the nickel alloy has a gray color, and a nickel alloy containing 1 to 3 wt% of sulfur and 7 to 10 wt% of zinc can have black or dark black.

Further, when the coloring layer 4 on the surface is formed by plating a nickel alloy containing such an additive element, the hardness of the layer is higher than that of pure nickel alone.
In addition, since the texture is also columnar and rich in undulation, the surface of the coloring layer 4 can be made non-smooth with microscopic fine irregularities. More lubricant can be retained.

The non-smooth surface state after the plating does not change so much by the subsequent wire drawing, and FIG. 2 shows the surface state of the wire drawn at 60% processing rate after the plating, for example. As described above, it can be understood that the non-smooth surface state has few flat portions.

By providing a surface state having minute irregularities in this manner, for example, in the case of a multi-step process such as spring processing, the function of supporting the lubricant on the wire surface is enhanced by increasing the function. Accordingly, it is possible to solve problems such as nozzle clogging due to lubricant peeling caused by excess lubricant, and it can be said that it is preferable in reducing frictional resistance with a tool interface during molding.

When the coated stainless steel wire 1 is used for a spring, the required strength is to have a tensile strength of, for example, 1500 MPa or more. The JIS average surface roughness (Ra) is preferably 0.1 to 1 μm (Ra) (more preferably 0.5 μm (Ra) or less. If necessary, various additives that have been frequently used in the past may be used. It can be added as needed.

Typical composition of the plating solution for the plating is, for example, nickel sulfate 60 to 80 g / L, nickel ammonium sulfate 35 to 50 g / L, zinc sulfate 2
0 to 35 g / L, sodium thiocyanate 15 to 25 g
/ L can be easily formed by adding the necessary additive to the nickel sulfate-based liquid composition containing / L.

As described above, the nickel alloy plating layer is inferior in toughness as compared with general nickel (eg, nickel sulfamate) plating, and tends to be somewhat inferior in flexibility because it has a columnar structure. Therefore, when the plating layer is formed to be extremely thick, problems such as cracking and peeling of the plating layer are likely to occur.

In order to prevent this, it is preferable that the plating thickness of the coloring layer is, for example, 0.8 μm or less. However, if it is too thin, the absolute amount of nickel itself is insufficient and lubrication is not performed. For example, the thickness is preferably about 0.05 to 0.5 [mu] m, since the original property is impaired and the color, which is the original purpose, becomes faint and the discrimination function is reduced.

In the present invention, such a plating layer may be formed directly on the surface of the core material 2, but as shown in FIG. 5 to ensure the absolute amount of nickel required as a coated stainless steel wire, as well as enhance the identification function,
At the same time, it is possible to improve the bonding adhesion between the adjacent coloring layer 4 and the nickel base layer 5.

In this case, as the nickel underlayer 5, for example, a plating method using a Watt bath or the above-mentioned nickel sulfamate, which has been carried out so far, can be adopted. It has a different composition that does not contain high sulfur or zinc. Therefore, in this case, the nickel underlayer 5 has a strong adhesion to the stainless steel core material and can be formed to be relatively thick, and even in the adhesion to the coloring layer 4, both of them contain a large amount of nickel. Because they are things,
Problems such as delamination can be prevented and the whole can be firmly integrated.

Although the thickness of each coating layer in such a laminated structure is not particularly limited, in the case of a wire used for heavy working, the total thickness is, for example, about 0.2 to 2 μm, and Is preferably about 2 to 6 times the thickness of the coloring layer.

Therefore, such a nickel underlayer 5
By adjusting the nickel underlayer 5, it is possible to provide both the coloring function and the lubrication function of the entire steel wire by making the plating thickness necessary for strong processing such as wire drawing and coiling. Since the coloring layer 4 on the surface is directly colored on the nickel plating itself, defects such as peeling and uneven coloring can be improved.

In the present invention, the color of the coloring layer 4 basically has a color based on black. However, the color is not particularly limited. That is, such concentration adjustment can be changed by various factors such as the plating composition and the thickness of the formed film, the degree of wire drawing, for example, when the amount of thiosulfate is increased, the color becomes dark brown, and the amount of zinc increases. And become gray. If necessary,
In the final heat treatment, a temper color can be simultaneously formed, and a new color can be obtained by a synergistic effect thereof.

Further, according to the present invention, as a conventional pre-drawing film mainly composed of a resin or various water-soluble inorganic salts, or as an auxiliary lubricant, the surface of a coated stainless steel wire having such a structure is conventionally used. It is also possible to form a lubricating layer using Kosin (trade name) or metal soap (calcium stearate).

As the pre-drawing film, for example, an aqueous solution containing sodium as a main component such as sodium sulfate or sodium sulfite, a water-soluble solution containing a potassium salt such as potassium sulfate as a main component, or a mixed water-soluble solution thereof is used. On the other hand, the formation of a large amount of these coatings not only increases the cost but also causes clogging of the peeling, etc., so that it is preferably 0.1 to 1.5 g / m ² .

Such a coated stainless steel wire 1 can be used in various applications. For example, in addition to the above-mentioned springs, it can also be used for ropes and other forming, or for cold forging such as screws. It can be applied.

Next, a method of manufacturing the coated stainless steel wire 1 in which the nickel coating layer 3 is formed on the stainless steel core material 2 will be described.

As the core material 2, as described above, a stainless steel wire capable of finally achieving predetermined characteristics is selected, and after its surface is cleaned and activated, the nickel underlayer 5 is underplated.

As described above, the nickel underlayer 5 can be formed by a conventional method such as nickel sulfamate, and nickel plating having a predetermined thickness is formed.

Next, a coloring layer 4 having a black color is formed on the surface of the plated wire by using nickel and a nickel alloy containing at least sulfur and zinc, and further processed by cold working. Shall do.

The coloring layer 4 is immersed in a plating solution capable of forming the nickel alloy layer and electroplated. Preferred plating conditions are, for example, 0.5
It is preferable to perform the process at a low current density of about 5 A / dm ² . If the treatment is performed with a high current exceeding 5 A / dm ² , the resulting plating crystal becomes coarse and problems such as peeling are likely to occur. In addition, if it is less than 0.5 A / dm ² ,
Inefficient and poor workability.

In the present invention, the cold working is performed at least once or more, but the purpose is to provide the steel wire with a predetermined property,
This is performed in order to increase the adhesion and toughness of the plating coating layer 3 itself to prevent peeling. For example, when achieving a tensile strength of 1500 Mpa such as for the spring,
Cold working such as wire drawing or rolling at a working ratio of 60% or more is performed, while in the case of cold heading, light skin pass processing is performed to enhance adhesion.

In this case, the plating and the cold working may be performed by plating the nickel base layer 5 and the coloring layer 4 on individual lines, or may be performed simultaneously on a continuous strand line. Alternatively, the coloring layer may be formed after the underlayer plating is performed to perform light processing such as a skin pass to improve the adhesion.

[0052]

EXAMPLE As a core material, a 2.4 mm SUS304 stainless steel wire was prepared, and a soft wire which was once subjected to a bright heat treatment at 1080 ° C. was used.

The soft wire was immersed in a plating solution (solution temperature: room temperature) having the following composition as a base plating, and electroplating was performed at a current density of 12 A / dm ² to obtain a thickness of 2.2 μm. The underlayer nickel plating layer was formed.

[0054]

[Table 1]

Next, black nickel plating was performed on the surface of the plated wire as a raw material, and the plating composition was as shown in Table 2 below.

[0056]

[Table 2]

(Drawing) With respect to the composite coated wire thus obtained, an aqueous solution of sodium sulfate (Na 2 SO 4) containing a water-soluble inorganic salt as a main component (concentration: 0.5%,
After immersion in a liquid temperature of 70 ° C.) to form a lubricating film, the film was dried and set in a continuous wire drawing machine.

The drawing was performed by continuous cold drawing, using a die 8
Calcium stearate metal soap was blended in each die as an auxiliary lubricant as an auxiliary lubricant.

In this drawing step, the drawing speed is set to 100
~ 400 m / min. The test was carried out by changing the wire to any of the above. However, it was confirmed that all the wires had good drawability, no troubles such as image sticking and dice mark occurred, and were not much different from conventional nickel plating.

The amount of residual lubricant and the surface roughness of the obtained wire were measured, and the results shown in Table 3 were obtained. FIG. 3 shows the results of the surface analysis of the coated wire, and from the results, a large amount of Ni, sulfur and zinc were detected together with the components of the stainless steel wire as the core material. From this, it can be seen that the surface layer is a nickel alloy containing at least Ni, sulfur and zinc.

[0061]

[Table 3]

(Test of Adhesion) Next, in order to confirm the adhesion of the surface plating layer of the obtained wire, the test specimen was set in a repeated bending fatigue test, and the presence or absence of peeling of the plating layer due to the repeated bending was confirmed. did. The test was conducted by bending at 180 ° using a bending tester manufactured by Tokyo Koki Co., Ltd., and the appearance of the line was observed with a magnifying glass at each bending angle of 90 °. 5 for all products
It has been confirmed that the film has withstood the number of bending times and adhered well.

(Coilability) Next, in order to evaluate the spring formability, the outer diameter of the spring was 10 mm, the total number of turns was 8.5, and the free length was 4
The coil was coiled on a 0 mm coil spring, and the variation in free length was measured. In this test, a conventional nickel sulfamate single layer (plating thickness 0.9 mm) was used as a comparative material.
3 μm).

In the coiling test, 200 springs were manufactured for each wire under the condition of 40 pieces / min, and the average and standard deviation of their free lengths were determined. The results are shown below.

[0065]

[Table 4]

From the results in the above table, it was confirmed that the spring wire according to the present invention had characteristics with little variation, and that all of the practical products had a blackish color obtained in the raw material state.

[0067]

As described above, the coated stainless steel wire of the present invention is formed by forming black nickel plating having a black color on the surface of the stainless steel core wire, and the excellent lubricity of the nickel plating. In addition, by adding a color to itself, peeling and missing are prevented, and at the same time, an identification function is provided, which is excellent in convenience.

In this case, a predetermined plating thickness necessary for the subsequent processing is obtained by interposing a plating layer mainly composed of nickel as the base plating, and the core material and the surface black plating layer are similarly formed. To solve the problems such as peeling of the plating layer.

On the other hand, the manufacturing method does not require a separate line like the conventional resin coating, and can be processed in the same manner as ordinary nickel plating, so that the process can be shortened.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating one embodiment of a coated stainless steel wire of the present invention.

FIG. 2 is a diagram showing a surface state of a coated stainless steel wire.

FIG. 3 is a diagram illustrating an example of a surface analysis result of a coated stainless steel wire.

[Explanation of symbols]

 Reference Signs List 1 coated stainless steel 2 core material 3 nickel coating layer 4 coloring layer 5 nickel base layer

Claims (5)

[Claims] The present invention has a core material made of stainless steel and a nickel coating layer formed on the surface thereof, and the nickel coating layer is substantially made of nickel and a nickel alloy containing at least sulfur and zinc. What is claimed is: 1. A coated stainless steel wire having a colored layer that exhibits a blackish color. 2. The color filter according to claim 1, wherein the nickel coating layer is a laminated structure including the coloring layer, and a nickel base layer between the coloring layer and the core material and having a composition different from that of the coloring layer. The coated stainless steel wire according to claim 1, wherein: 3. The method according to claim 1, wherein the tensile strength is 1500 MPa or more, the average surface roughness is 0.1 to 1.0 μm (Ra), and the material is used as a spring. Of coated stainless steel wire. 4. The surface of a stainless steel core material or a nickel-coated wire formed by forming a nickel base layer on the surface thereof,
Nickel, and immersion in a solution that will become a nickel alloy plating containing at least sulfur and zinc, and after forming a colored layer that exhibits a blackish color on the surface by electroplating, at least once, A method for producing a coated stainless steel wire, characterized in that interworking is provided. 5. The method for producing a coated stainless steel wire according to claim 4, wherein said cold working is cold drawing or cold rolling performed at a working ratio of 60% or more.