JPH06220688A - Colored spring steel formed article and its production - Google Patents

Abstract

PURPOSE:To produce a colored spring steel formed article which is not deteriorated, having a colored Cu-Sn alloy plating layer on the surface to improve corrosion resistance, with the size and quality being easily discriminated and having an improved beautiful surface appearance. CONSTITUTION:The colored spring steel formed article has a colored Cu-Sn alloy plating layer obtained by high-temp. thermodiffusion after the spring is formed. A two-layer plating (lower Cu layer and upper Sn layer) is applied on the spring steel material while controlling the thickness ratio of the Sn layer to 5-30%, the coated material is worked into a spring material with the final total plating layer thickness controlled to 2-25mum, the material is formed into a spring, which is then heated to 250-400 deg.C and low-temp. annealed, and the plating layer is colored.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a colored spring steel molded product and a method for manufacturing the same, and more particularly to a colored spring steel molded product and a method for manufacturing the colored spring steel molded product in which the dimensions, materials and the like can be properly identified.

[0002]

2. Description of the Related Art Spring steel molded products (that is, springs) such as coil springs and leaf springs are used in various fields such as machine parts, office supplies and daily life. The spring steel material which is a material of such a spring includes a linear material (steel wire for spring) and a plate-shaped material (steel plate for spring). As steel wires for springs, hard steel wires, piano wires, and stainless steel wires for springs, which are specified in JIS, are known.

The surface colors of these spring steel wires are relatively similar to each other, and it is impossible to distinguish between the hard steel wire and the piano wire only by the color tone. Further, in the case of a stainless steel wire, it generally has a luster as compared with a hard steel wire or a piano wire, but in the case of a wire material finished by oil drawing (wet drawing), it is extremely difficult to identify it by color tone. Therefore, a product having a similar size after spring molding has a dimensional error or a material error, and a problem that a non-standard spring product is mistakenly incorporated into a mechanical structure has occurred.

Conventionally, in order to prevent the occurrence of such troubles, the spring steel wire is coated with various resin coatings or baking coating, or ion plating such as PVD or CVD or Ti is used.
The spring steel wire is colored by coating with N or the like, which facilitates the identification of the dimensions and material of the spring steel molded product, and at the same time improves the appearance.

[0005]

However, the spring steel wire is subjected to severe abrasion near the galling with the forming tool during the spring forming process, and at the temperature of 250 to 400 ° C. for improving the spring characteristics after the spring forming process. Since heat treatment (low-temperature annealing treatment) is performed for about 2 to 10 minutes, the conventional resin coating or paint baked may have a scratch on the surface during spring molding and the coating may peel off. There are problems that the coating softens during the low-temperature annealing to form a recess, and the springs are welded to each other. On the other hand, in the case of coating with ion plating or TiN, etc., such a problem does not occur, but there is a drawback that the coating work is difficult and costly, and none of the methods show sufficient function. is the current situation.

The present invention has been made in view of such circumstances, solves the above problems, facilitates identification of dimensions and materials of spring steel molded products, and improves surface aesthetics. The goal is to achieve.

[0007]

[Means for Solving the Problems] In order to achieve the above object, the inventors of the present invention have conducted extensive studies, and as a result, the spring characteristics of the spring steel material are not deteriorated by the plating treatment, and the low temperature heating after the spring forming process is performed. Since the plating layer develops color during annealing, if the color tone is selected appropriately, different dimensions of the spring molded product,
The inventors have found that it is possible to identify different materials, and have completed the present invention.

That is, the present invention is directed to a spring steel molded product having a colored Cu-Sn alloy plating layer alloyed by low-temperature heat diffusion after spring molding on the surface, and also on the surface of the spring steel material. , The lower layer is Cu and the upper layer is Sn so that the thickness ratio of the Sn layer to the total thickness of the plating layer is 5 to 30%, and then the spring material is processed to make the final plating total thickness. Of 2 to 25 μm is formed into a spring, and then the formed product is heated to 250 to 400 ° C. and annealed at a low temperature, and the plated layer of the spring formed product is colored. The gist is the method of manufacturing a molded product.

[0009]

[Operation] When Cu-Sn two-layer plating is heated and alloyed, the plating layer becomes a Cu-Sn alloy plating layer. At this time, the alloy plating layer obtained by the above heating conditions exhibits various surface color tones, for example, low temperature heat annealing after spring forming exhibits a yellowish color, and the color tone is annealing conditions or Sn.
It was found that it varies depending on%. Therefore, the spring steel material should be Cu
-Two-layer plating of Sn, processed into a spring material, formed into a spring, and then annealed at low temperature to obtain a colored spring steel molded product having a colored plating layer with different color tones on the surface depending on the annealing conditions. As a result, the spring molded product can be identified. The present invention aims at preventing different sizes of spring molded products and mixing of different materials by utilizing the difference in color tone of the colored plating layers. It is not practical if the properties of the spring molded product are greatly deteriorated due to the presence of the layer, and therefore the optimum condition is naturally defined even for the colored plating layer. The present invention has been completed based on the findings obtained by thoroughly researching the optimum conditions from the viewpoints of distinguishability and spring characteristics. These will be specifically described below with reference to the drawings.

FIG. 1 shows that a hard steel wire is subjected to two-layer plating (lower layer Cu, upper layer Sn) so that the upper layer has a thickness of 30% of the total plating thickness, wire drawing, coil spring forming, and various other processes. It is an example of the result of examining the change in color tone of the plating surface during heating at temperature and time. The change in color tone has a close relationship with the heating temperature and the heating time, and if the conditions are satisfied, the change from white to a visually recognizable yellowish color occurs almost instantly, and the practical low temperature annealing temperature of the spring Is 250 ~
It can be seen that at 400 ° C, the color tone changes at 250 ° C for 3 minutes or longer, and at 400 ° C for 1 minute or longer. When various experiments were conducted, it was found that the heating and holding time required to cause the above-mentioned color tone change at a temperature T (° C) of 250 to 400 ° C is a time t (min.) That satisfies the following formula. became.

Logt ≧ 0.1789-3.181 × 10 ⁻³ T ---- formula

FIG. 2 shows that after various plating thicknesses are changed and the same plating as described above is performed, wire drawing and spring molding are performed in the same manner,
FIG. 3 shows the relationship between the tin content (%) in the alloy and the color tone by forming a spring having a Cu—Sn alloy plating layer by heating at 00 ° C. for 3 minutes. In the range of 5 to 30% Sn, a beautiful golden color tone is obtained, which is suitable for distinguishing springs of different dimensions and different materials from being mixed, and the aesthetic appearance is significantly improved.

By the way, it is one of the important properties that a spring molded product has excellent corrosion resistance. Therefore, for the same spring as in Fig. 2, Sn (%) in the Cu-Sn alloy plating layer
And the time required for red rust to be generated by spraying with 3% salt water (time for corrosion to reach the material), and the results are shown in FIG. When the plating layer thickness is 2 μm or more, the corrosion resistance improves with the increase of Sn%, and the one with 5-30% Sn has a longer red rust occurrence time than the untreated (unplated) hard steel wire. Without deteriorating the characteristics of the
On the contrary, it turns out that it can be improved. When the thickness of the plating layer is 1 μm, it is affected by the unevenness of the surface of the spring base material, and the effect of improving corrosion resistance is not achieved. The rusting time when using SUS304 stainless steel wire instead of hard steel wire as the spring wire is the rusting time of the SUS304 stainless steel wire spring itself (185hr).
3 is added to the value in FIG.

FIG. 4 shows a Cu-based wire on a 3.5 mmΦ hard piano wire.
Relationship between Sn% and hunter type rotary bending fatigue strength of the wire when Sn is plated in 2 layers and 91.7% wire drawing is performed until it reaches 1mmΦ, and then alloyed by heating at 400 ° C for 5 minutes. ,
Similarly, the results of alloying the plated layer by heating a wire rod having a thickness of 1 mmΦ by performing a double-layer plating on a 2.5 mmΦ stainless steel wire and then performing 84% wire drawing are also shown.
Both the piano wire and the stainless steel wire have a small decrease in fatigue strength up to a plating layer thickness of 25 μm, which is not a problem for practical use, whereas a clear decrease in fatigue strength is observed at 30 μm. Therefore, it is practically desirable to perform plating with a layer thickness of 25 μm or less. This also applies to coil springs (spring steel molded products).

The above data is for the case where the spring steel material is a wire material and the spring steel molded product is a coil spring. In other cases, for example, the spring steel material is a plate material and the spring steel molded product is a plate spring. Also in the case of, the result shows the same tendency as above.

To summarize the above points, regarding the colored Cu-Sn alloy plating layer on the surface of the spring steel molded product, the Cu-Sn alloy composition is in the range of 5 to 30% Sn from the viewpoint of the color tone effect, and the plating thickness is the corrosion resistance. 2 μm or more from the viewpoint of
The thickness is preferably 25 μm or less, while the low temperature annealing condition for color development is preferably 250 ° C. · 3 minutes or more to 400 ° C. · 1 minute or more.

The colored spring steel molded product and the method for manufacturing the same according to the present invention are constructed in consideration of the above points (conditions), and therefore, the colored Cu-Sn alloy does not deteriorate in the characteristics of the spring molded product. The color tone effect of the alloy plating layer can be exerted to facilitate the identification of the spring steel molded product and improve the surface aesthetics.

In the manufacturing method according to the present invention, the spring steel material is subjected to a two-layer plating (lower layer: Cu, upper layer: Sn) and processed into a spring material so as to satisfy the above points (conditions). It is a method of forming a colored spring steel molded product according to the present invention by a method of forming a colored spring steel by heating at a temperature of 250 to 400 ° C., annealing at a low temperature and developing a color of the plating layer. However, the colored spring steel molded product according to the present invention can be manufactured by a method other than this method, such as 250
It can also be manufactured by a method of heating to a temperature of 400 ° C. to color the plated layer, then spring forming and low temperature annealing. However, in such a method, the heating step is increased by one step and the manufacturing process is complicated. On the other hand, the method of the present invention causes the plating layer to color by the low temperature annealing which is indispensable after the spring forming process, and therefore the manufacturing process is simple. It can be said that the economy is excellent.

[0019]

【Example】

(Example 1) C: 0.82% of hard steel wire was lead-patented, pickled, and descaled.
Two-layer plating of u and the upper layer Sn was performed using a two-cell continuous electroplating tank. At this time, for Cu plating, the bath composition was CuSO ₄ : 130 g /
l, 62% H ₂ SO ₄ : 33 cc / l aqueous solution, pH was 1.5, temperature was 30 ° C., plating current density was 5 A / dm ² , and a Cu plate was used as the anode. Sn plating bath composition _{SnSO 4: 50g / l, H} 2 SO 4: 50g
/ l, gelatin: 2g / l, naphthol: 2g / l aqueous solution, p
H: 1.0, current density 3 A / dm ² , temperature 20 ° C., Sn plate used as anode. The plating time was changed to four types in order to change the Sn thickness ratio and the like as described below. That is,
The Sn thickness ratio to the total thickness of the two-layer plating was changed to four types of 0, 5, 30, 40%. At the same time, the total plating thickness was adjusted so that the total plating thickness after drawing was 2, 25 and 30 μm.

After the above-mentioned two-layer plating, JIS G3521 hard steel wire is drawn by ordinary wire drawing 8 times up to 1 mmΦ by 91.7% wire drawing.
A wire equivalent to 1 mmΦ at the SWC strength level was obtained. After forming this 1mm Φ wire into a contact spring with an outer diameter of 10mm, a length of 20mm and a winding number of 20, it is heated at 150 ℃ for 7 minutes, 200 ℃ for 5 minutes, 250 ℃ for 3 minutes, and 400 ℃ for 1 minute. , The color development state was examined.

[0021]

[Table 1]

[0022]

[Table 2]

[0023]

[Table 3]

After heating and cooling, the corrosion resistance was examined by a salt spray test. In addition, the tensile strength, twist value, and
The fatigue strength was measured. The results are shown in Table 1.

As a comparative example, a bare wire obtained by drawing the same 3.5 mmΦ raw wire as described above to 1 mmΦ,
Also, after drawing the original wire of 3.5 mmΦ to 1 mmΦ, the polyester paint is dissolved in thinner and immersed in a diluted solution, and baking is performed by 2 baking and 2 coating methods.
The same test as above was performed on the obtained polyester-coated wire (color tone: red). The results are shown in Table 1.

(Example 2) 1150 stainless steel wire for spring
Using a 2.5 mm Φ original wire made by softening by bright annealing at ℃,
Two-layer plating and wire drawing similar to those in Example 1 were performed to JIS G
4314 Stainless steel wire for spring WPB After obtaining a wire having a strength level equivalent to 1 mmΦ, it was formed into a coil spring similar to that of Example 1,
A heat treatment was performed and a similar test was performed. As a comparative example, a bare wire obtained by wire drawing from the same 2.5 mmΦ original wire to 1 mmΦ was tested. The results are shown in Table 2.

As can be seen from the results of Tables 1 and 2, when the plating thickness is 2 to 25 μm, the tensile strength, the twist value characteristic,
Both the fatigue strength and the corrosion resistance are good as a spring wire. On the other hand, when the thickness of the plating layer is 30 μm, the fatigue strength is markedly reduced, which is not practical. It can be said that the polyester coated wire is excellent in terms of corrosion resistance.

(Embodiment 3) In the 1 mmΦ element wire of the embodiment 1, a total thickness of the plated wire after drawing is changed to 2 μm and 5 μm is formed, and this is formed into a coil spring and heat-treated to examine the color development state. It was In addition, Sn in the alloy plating layer is 0, 5, 3
It was changed to 4 types of 0 and 40%. As can be seen from Table 3, if the plating thickness ratio of the Sn layer in the two-layer plating is adjusted so that the amount of Sn in the alloy plating layer is 5 to 30%, the color tone changes remarkably due to the heat treatment. By doing so, it is possible to surely identify the spring steel molded product.
In addition, the present invention is advantageous because the resin coating causes surface deterioration such as galling during molding, discoloration, and welding.
In the case of the coil spring (strand wire: stainless steel wire) of Example 2, the plating thickness ratio of the Sn layer of the two-layer plating is adjusted so that the Sn content in the alloy plating layer is 5 to 30%. Changed the color tone in the same manner as above.

[0029]

Since the present invention is configured as described above, it is possible to easily identify the material or size of the raw material of the spring steel molded product by coloring the plating layer during the spring manufacturing process. At the same time, it is possible to exert a remarkable effect that the spring steel molded product or the surface of the product is exhibited a color tone that gives an aesthetic appearance, and the characteristics of the spring steel molded product such as the spring characteristics are not deteriorated and the corrosion resistance can be improved. , Very useful in industry.

Needless to say, the present invention is applicable not only to coil springs, but also to spring materials (forming materials, torsion springs, leaf springs, etc.) or similar materials that are subjected to low temperature annealing after forming.

Furthermore, since a colored Cu-Sn alloy plating layer alloyed by low-temperature heating diffusion is provided on the surface, a golden color tone can be exhibited. Therefore, aesthetics other than the spring steel molded product are important in this respect. It has an advantage when applied to products such as eyeglass frames, ornaments such as bracelets, and office supplies.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing a relationship between a heating time and a heating temperature of a Cu—Sn plating layer on the surface of a spring molded product and a color tone change.

FIG. 2 is an explanatory diagram showing a relationship between Sn content in a Cu—Sn plating layer on the surface of a spring molded product and a color tone.

FIG. 3 is an explanatory diagram showing the relationship between the Sn content in the Cu—Sn plating layer on the surface of the spring molded product, the plating layer thickness, and the red rust occurrence time.

FIG. 4 is an explanatory diagram showing a relationship between a Sn content and a plating layer thickness in a Cu—Sn plating layer on a surface of a wire for spring and a hunter type rotary bending fatigue strength.

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Claims (6)

[Claims] 1. A colored spring steel molded product having a colored Cu—Sn alloy plating layer alloyed by low temperature heating diffusion after spring molding on the surface. 2. The colored spring steel molded product according to claim 1, wherein the plated layer is an alloy of Cu-5 to 30% Sn. 3. The plating layer has a thickness of 2 to 25 μm.
Alternatively, the colored spring steel molded product described in 2. 4. The lower layer is Cu and the upper layer is Cu on the surface of the spring steel material.
Two-layer plating made of Sn is applied so that the thickness ratio of the Sn layer to the total thickness of the plated layer is 5 to 30%, and then processed into a spring material so that the final plated total thickness is 2 to 25 μm. Formed into a spring and then
A method for producing a colored spring steel molded product, which comprises heating to a temperature of up to 400 ° C, annealing at a low temperature, and coloring the plated layer of the spring molded product. 5. The method for manufacturing a colored spring steel molded product according to claim 4, wherein the heating and holding time in the low temperature annealing is set to a time t that satisfies the following formula. logt ≧ 0.1789 −3.181 × 10 ⁻³ T ---- Formula However, in the above formula, T represents the heating temperature (° C.) in low temperature annealing, and t represents the heating holding time (min.). 6. The method for producing a colored spring steel molded product according to claim 4, wherein any one of a hard steel wire, a piano wire and a stainless steel wire for spring is used as the spring steel material.