JP6435183B2 - Spring member - Google Patents

Description

  The present invention relates to a spring member having a corrosion-resistant coating film formed on the surface.

  The spring member made of a metal material is corroded depending on the use environment, and changes in characteristics and deterioration of strength occur. In order to prevent such corrosion, a protective film such as a coating film by plating or a coating film by paint is provided on the surface of the metal member.

  Corrosion occurs when metal atoms on the surface of the metal member are ionized and desorbed from the surface of the member. If there is a metal (base metal) that has a higher ionization tendency than the metal constituting the member on the surface of the metal member, the base ion has a higher ionization tendency than the metal (precious metal) that constitutes the metal part in a corrosive environment. The metal of this can be ionized to prevent corrosion of the metal member. Such anticorrosion is called sacrificial anticorrosion. In the case of an iron member, zinc is mainly used as a sacrificial material.

  As a protective film using sacrificial anticorrosion by zinc, there is a coating film obtained by applying a powder paint containing a relatively high concentration of zinc powder and curing it by baking.

  A coating film made of a paint containing such zinc powder at a high concentration may cause cracks due to pores generated during coating, and corrosive substances may enter the cracks, resulting in a decrease in the protective function of the coating film. .

  In particular, since the spring member repeatedly undergoes elastic deformation, cracks generated in the coating film with the passage of time of use tend to extend. In addition, when used as a suspension spring for a vehicle or the like, pebbles and gravel jumped up by a wheel collide with the surface of the suspension spring, and a crack generated in the coating film easily extends.

  When the crack generated in the coating film extends, the corrosive substance easily enters and the anticorrosion property is greatly reduced.

  In Patent Document 1, a high-concentration zinc powder coating material using an epoxy-based synthetic resin as a binder is applied to the surface of the spring plate on the tensile force acting side to form a first coating film, and the same series of epoxy is coated on the first coating film. A rust prevention method is described in which a synthetic resin coating is applied to form a second coating film. Patent Document 2 describes a powder coating containing an epoxy resin, a curing agent, two types of zinc powders having different particle sizes, and a rust preventive pigment.

Japanese Patent Laid-Open No. 11-188309 JP2013-119582A

  The rust prevention method described in Patent Document 1 forms a second coating film on a first coating film coated with a high-concentration zinc powder paint, thereby preventing the invasion of corrosive substances and providing a protective function by the coating film. Trying to improve. However, there is a problem caused by providing the second coating film.

  As described in Patent Document 1, the spring member is often used by being fixed to a frame or the like by a fastening member such as a bolt. The resin coating film such as an epoxy-based synthetic resin paint used as the second coating film described in Patent Document 1 has a variation in thickness over time at the part where the fastening member is in contact, and the phenomenon that the thickness is often reduced over time. Arise. This is a phenomenon called so-called sag of the coating film. When the coating film on the bearing surface portion of the bolt becomes thin, the fastening axial force of the bolt decreases and the bolt loosens. Patent Document 1 describes that the second coating film is not formed on the portion of the fastening tool in order to prevent the fastening tool from becoming loose easily due to the sag of the second coating film (paragraph [0006]. ]).

  Since the coating film by the powder coating described in Patent Document 2 is a single-layer coating film containing zinc powder, there is almost no sag of the coating film, but the protective function by corrosive substances entering the cracks Can not be sufficiently prevented, and the corrosion resistance is poor.

  An object of the present invention is to provide a spring member that maintains high anticorrosion properties and also has improved sag resistance.

The present invention includes a spring body,
It is a coating film formed by coating the surface of the spring body with a powder coating composition containing an epoxy resin, an acid-terminated polyester resin and zinc powder so that the uncured thickness becomes 60 to 100 μm. A zinc-containing layer containing more zinc powder than the epoxy resin and the acid-terminated polyester resin on the surface side of the spring body, and the epoxy resin and the acid rather than the zinc powder on the zinc-containing layer. a coating film having a resin-containing layer having a lot of terminal polyester resin, only including,
The powder coating composition is
When the sum of the content of the epoxy resin and the content of the acid-terminated polyester resin is 100 parts by mass, the content of the epoxy resin is 10 to 80 parts by mass, and the content of the acid-terminated polyester resin is 20 to 90 parts by mass,
The spring member is characterized in that the content of the zinc powder is 55 to 80 mass% with respect to the whole powder coating composition .

Moreover, this invention is a manufacturing method of the spring member which manufactures the spring member of Claim 1, Comprising:
One of the powder coating composition by coating once, the the spring body surface characteristics and to Luba ne member to form the coating film so as to have the zinc-containing layer and the resin-containing layer It is a manufacturing method .

The present invention, in the spring body that is heated pre Me, by heating before the deposition of the powder coating composition, or forming the coating film so as to have the zinc-containing layer and the resin-containing layer, or the powder coating composition after depositing on the spring body, by heating after heating the spring body, and forming the coating film so as to have the zinc-containing layer and the resin-containing layer .

According to the present invention, the spring member includes a spring body and a coating film formed on the surface of the spring body. The coating film is formed by coating a powder coating composition containing an epoxy resin, an acid-terminated polyester resin and zinc powder so that the uncured thickness becomes 60 to 100 μm, and contains zinc containing a large amount of zinc powder. It has a two-layer structure of a layer and a resin-containing layer containing a large amount of resin. A zinc-containing layer is on the surface side of the spring body, and a resin-containing layer is on it.

  Since zinc is unevenly distributed on the surface side of the spring main body in the coating film, even if the zinc content is small compared to the conventional case, the spring main body and zinc are sufficiently in contact with each other, and higher corrosion resistance is exhibited. Since the resin component is unevenly distributed on the surface side of the coating film in the coating film, the impact from the outside is alleviated and cracks occurring in the coating film are prevented. Since the resin-containing layer is formed with a relatively thin layer thickness, the variation in the layer thickness is small and the sag resistance is improved without causing sag. And even if the layer thickness is thin, it is formed integrally with the zinc-containing layer, so there is no clear interface between layers, and no delamination occurs.

  Thus, the coating film of this invention can implement | achieve the spring member which improved high sag-proof property while maintaining high corrosion resistance with a zinc content layer and a resin content layer.

According to the invention, the powder coating composition has a content of the epoxy resin of 10 to 80 when the sum of the content of the epoxy resin and the content of the acid-terminated polyester resin is 100 parts by mass. In one coat, the content of the acid-terminated polyester resin is 20 to 90 parts by mass, and the content of the zinc powder is 55 to 80% by mass with respect to the entire powder coating composition. A coating film containing a zinc-containing layer and a resin-containing layer can be formed , and the corrosion resistance can be further improved.

  Further, according to the present invention, the two layers, the zinc-containing layer and the resin-containing layer, can be formed on the surface of the spring main body by simply applying one kind of powder coating composition once. There is no need for painting, and the number of steps can be reduced while the coating film is highly functional, and the spring member can be easily manufactured.

  In addition, according to the present invention, either the pre-heating in which the spring body is heated in advance before the powder coating composition is attached, or the post-heating in which the spring body is heated after the powder coating composition is attached is contained in zinc. A highly functional coating film having a layer and a resin-containing layer can be formed.

It is a figure which shows the spring board 1 which is 1st Embodiment of this invention. It is a figure which shows the overlap spring board 2 which is 2nd Embodiment of this invention. It is a schematic diagram for demonstrating the measuring method for measuring sag resistance.

  The kind of the spring member of the present invention is not particularly limited. For example, a coil spring, a leaf spring, a torsion bar, a stabilizer and the like can be mentioned. The spring member of this invention has a spring main body and the coating film formed on the surface of a spring main body using the powder coating composition containing an epoxy resin, an acid terminal polyester resin, and zinc powder.

<Spring body>
The material of the spring body is not particularly limited as long as it is a metal that exhibits an anticorrosive effect by zinc. The anticorrosive effect by the coating film of the present invention is due to so-called sacrificial anticorrosion, and the base metal is prevented from being corroded using a base metal having a higher ionization tendency than the base metal. Since the coating film of the present invention contains zinc powder, the spring body may be made of a noble metal having a smaller ionization tendency than zinc, and for example, iron, nickel, copper and the like can be used.

  Specifically, JIS-regulated spring steel that is generally used as a material for the spring body is suitable. For the spring main body, for example, after hot or cold forming of spring steel or the like, surface hardening treatment may be performed by shot peening or the like, or the surface roughness may be adjusted. Moreover, it is desirable that a coating of a phosphate salt such as zinc phosphate or iron phosphate is formed on the surface of the spring body. By forming the phosphate film, the corrosion resistance of the spring member and the adhesion of the coating film are improved. In this case, it is effective that the phosphate coating covers 80% or more of the area of the painted surface of the spring body. In particular, when the phosphate is zinc phosphate, the corrosion resistance is further improved. For forming the phosphate film, a known forming method can be used. For example, a dipping method in which the spring body is immersed in a phosphate solution tank, or a spray method in which a phosphate solution is sprayed onto the spring body with a spray gun or the like is used.

<Coating film>
The coating film is obtained by applying a powder coating composition containing an epoxy resin, an acid-terminated polyester resin and zinc powder on the surface of the spring body and curing it by baking. This coating film has a zinc-containing layer containing more zinc powder than the epoxy resin and acid-terminated polyester resin, and a resin-containing layer containing more epoxy resin and acid-terminated polyester resin than the zinc powder. The zinc-containing layer is formed on the surface side of the spring body, and the resin-containing layer is formed on the zinc-containing layer. The coating film may be formed on the entire surface of the spring body, or may be formed only on a part thereof.

Below, the powder coating composition for forming the coating film of this invention is demonstrated.
-Powder coating composition The powder coating composition for forming the coating film of this invention contains an epoxy resin, an acid terminal polyester resin, and zinc powder as mentioned above.

  Regarding the content of each component in the powder coating composition, when the sum of the content of the epoxy resin and the content of the acid-terminated polyester resin is 100 parts by mass, the content of the epoxy resin is 10 to 80 parts by mass. The content of the acid-terminated polyester resin is preferably 20 to 90 parts by mass, and the content of the zinc powder is preferably 30 to 80% by mass with respect to the entire powder coating composition.

  In the state of the coating composition before being applied to the surface of the spring body, the powder coating composition is uniformly distributed without any bias between the resin component and the zinc powder. It can be handled in the same manner as the body coating composition. Moreover, the electrostatic coating method can be used similarly to the conventional coating method, and the same handling as the conventional method is possible. That is, the powder coating composition can be handled in the same manner as before without any change from the conventional one.

  On the other hand, when a powder coating composition is applied to the surface of the spring body to which corrosion protection is to be imparted and a coating film is formed on the surface of the spring body, zinc powder is formed on the surface side of the spring body. Bias, the resin component is biased on the surface layer side, and two layers having different characteristics are formed.

  The zinc-containing layer containing a relatively large amount of zinc powder covers the surface of the spring body with zinc powder, and exhibits the sacrificial anticorrosive effect of zinc on the iron material. Since the zinc powder is concentrated in the zinc-containing layer, even if the content of the zinc powder with respect to the whole powder coating composition is relatively small, the anticorrosion property is sufficiently exhibited. Since the content of zinc powder can be reduced, handling is easier and coating workability is better than conventional powder coating compositions containing an excessive amount of zinc. Since the resin component is unevenly distributed on the surface side of the coating film and no zinc powder is present, surface smoothness can be easily obtained. In addition, when the powder coating composition contains a colorant such as a pigment, a large amount of pigment is also contained on the resin-containing layer side, and since there is almost no zinc powder in the resin-containing layer, Color development is improved. The zinc-containing layer and the resin-containing layer are integrally formed with one coat, and a clear interface is not formed between the zinc-containing layer and the resin-containing layer, so that there is no separation between these layers.

(Epoxy resin)
Examples of the epoxy resin contained in the coating composition include bisphenol A type epoxy resin, bisphenol F type epoxy resin, novolac type epoxy resin, biphenyl type epoxy resin, polymer type epoxy resin (phenoxy resin), which are solid at room temperature, and these A hydrogenated epoxy resin obtained by hydrogenating a resin can be exemplified. It is preferable that the softening point is 60 to 120 ° C, preferably 60 to 100 ° C. When the softening point is less than 60 ° C., blocking of the powder coating composition occurs, which is not preferable. When the softening point exceeds 120 ° C., when the melt kneading is performed, the viscosity is too high and the dispersion is not sufficiently performed. Film performance is not demonstrated. The equivalent of the epoxy resin is 400 to 3000 g / equivalent, preferably 600 to 2500 g / equivalent. Specific examples of bisphenol A type epoxy resin and bisphenol F type epoxy resin include jER-1001, 1002, 1003, 1004, 1055, 1007, 1003F, 1004F, 1005F, 1009F, 1004FS, 1006FS, 1007FS, manufactured by Mitsubishi Chemical Corporation. 4005P, 4007P, Nippon Steel Chemical Co., Ltd. Epototo YD-011, 012, 013, 014, 017, 902, 903N, 904, 907, 2004, 2005RL, Dow Chemical Co., Ltd. DER-662E, 663U, 664U, 666E, 667E etc. are mentioned.

  Specific examples of novolak type epoxy resins include EPICLON N-660, N-665, N-670, N-673, N-680, N-695, N-770, N-775 manufactured by DIC Corporation, Nippon Steel Examples include Epototo YDCN-700-5, 700-7, and 700-10 manufactured by Chemical Co., Ltd. Specific examples of biphenyl type epoxy resin and polymer type epoxy resin (phenoxy resin) include JER-YX4000, YX4000H, YL612H, YX7399, 1256, 4250, 4275, etc. manufactured by Mitsubishi Chemical Corporation.

  The content of the epoxy resin in the powder coating composition is preferably 10 to 80 parts by mass when the sum of the content of the epoxy resin and the content of the acid-terminated polyester resin is 100 parts by mass.

(Acid-terminated polyester resin)
The acid-terminated polyester resin contained in the coating composition is not particularly limited as long as it is used in an ordinary epoxy resin-containing powder coating composition. Examples of the acid-terminated polyester resin include those having a functional group such as a carboxyl group at the end of the polyester resin, and those having a phosphate compound ester-bonded to the end of the polyester resin. Specific examples of the carboxyl group-terminated polyester resin include CRYLCOAT (CC) 1683-0, 2621-1, and 2670 manufactured by Daicel Ornex Co., Ltd.

  The content of the acid-terminated polyester resin in the powder coating composition is preferably 20 to 90 parts by mass when the sum of the content of the epoxy resin and the content of the acid-terminated polyester resin is 100 parts by mass. .

(Zinc powder)
The zinc powder contained in the coating composition is not particularly limited as long as it is used in an ordinary powder coating composition. For example, a zinc powder having a median particle size of 1 to 30 μm, preferably 4 to 15 μm can be used. As such zinc powder, zinc powder F-500 (medium particle size 7.5 μm), F-1000 (medium particle size 4.9 μm), F-3000 (medium particle size 3.7 μm) manufactured by Honjo Chemical Co., Ltd. Sakai Chemical Industry Co., Ltd. zinc powder # 1 (median particle size 5. 0 .mu.m), # 3 (median particle size 4.0 .mu.m), # 40 (median particle size of about 50.0 micrometers), Ekaruto Co. Zink Flake GTT ( Medium particle size 13 μm), AT (medium particle size 20 μm), and the like. A plurality of zinc powders having different median particle sizes may be mixed and used. The medium particle size of the zinc powder means a particle size at an integrated value of 50% in a particle size distribution measured using a laser particle size distribution measuring instrument such as Microtrack manufactured by Nikkiso Co., Ltd.

  The content of zinc powder in the powder coating composition is 30 to 80% by mass, preferably 55 to 80% by mass, and most preferably 60 to 70% by mass with respect to the entire powder coating composition. . When zinc powders having different particle sizes are mixed and used as the zinc powder as described above, the total amount may be within the above range.

  When the content of the zinc powder in the powder coating composition is 30 to 80% by mass with respect to the whole powder coating composition, layers are separated so that the coating film has a zinc-containing layer and a resin-containing layer. Furthermore, if content is 55-80 mass%, even if it does not contain a rust preventive pigment, a powder coating composition will exhibit sufficient corrosion resistance.

(Anti-rust pigment)
The powder coating composition can obtain a desired coating film as long as it contains the above-described components as essential components, but may further contain a rust preventive pigment. Antirust pigments include phosphate derivatives such as aluminum phosphate, molybdate derivatives such as zinc molybdate and aluminum phosphomolybdate, borate derivatives such as cyanamide calcium zinc and barium borate, and vanadates such as strontium vanadate. Derivatives, bismuth hydroxide and the like can be mentioned, and preferably aluminum phosphate, zinc phosphate, zinc molybdate, aluminum phosphomolybdate, zinc cyanamide calcium, barium borate, strontium vanadate. As such rust preventive pigments, PM-300 (aluminum phosphomolybdate, manufactured by Kikuchi Color Co., Ltd.), LF Bowsei CP-Z (zinc phosphate, manufactured by Kikuchi Color Co., Ltd.), K-WHITE (aluminum tripolyphosphate, Manufactured by Teika Corporation), View Sun 11M-1 (barium borate, Sakai Chemical Industry Co., Ltd.), and the like.

  Content of the antirust pigment in a powder coating composition is 0-70 mass% with respect to the whole powder coating composition, Preferably it is 10-50 mass%.

(Other additives)
In addition to the above-mentioned components, the powder coating composition further includes a coloring pigment, an extender pigment, a fluidity adjusting agent, an antiblocking agent, a surface adjusting agent, an anti-waxing agent, and a charge control agent that are used in ordinary powder coating compositions. In addition, other additives such as a curing accelerator may be contained.

(Method for producing powder coating composition)
As a method for producing the powder coating composition, for example, a known production method such as a pulverization method can be used. In the pulverization method, a mixture of an epoxy resin, an acid-terminated polyester resin, zinc powder and, if necessary, a rust preventive pigment and other additives is dry-mixed with a mixer such as a tumbler mixer or a Henschel mixer, and melt-kneaded with a kneader. As a kneading machine, for example, a general kneading machine such as a monoaxial or biaxial extruder, a triple roll, a laboratory blast mill can be used.

  The kneaded product is cooled and solidified, and the solidified product is coarsely and finely pulverized to obtain a pulverized product. As the pulverizer, for example, a jet type pulverizer that pulverizes using a supersonic jet stream, and a solidified material in a space formed between a rotor (rotor) and a stator (liner) that rotate at high speed. An impact pulverizer that introduces and pulverizes can be used. If necessary, a post additive (external additive) may be added to the pulverized product.

  The pulverized product is classified to adjust the powder to a desired particle size and a desired particle size distribution to obtain a powder coating composition. For classification, a known classifier capable of removing excessively pulverized toner base particles by classification with centrifugal force and wind force can be used. For example, a swirl type wind classifier (rotary wind classifier) can be used.

  In addition, the manufacturing method of a powder coating composition is not restricted to said grinding | pulverization method, What is necessary is just a manufacturing method which can obtain the powder coating composition in which each component was disperse | distributed uniformly.

<Method of coating powder coating composition>
A coating film is formed on the surface of the spring body using the powder coating composition obtained as described above. The coating method for applying the powder coating composition includes at least a coating process for applying the powder coating composition to the coating film forming surface of the spring body surface, and a baking process for baking and curing the applied powder coating composition. Including.

[Preheating]
As a first coating method, an embodiment in which a powder coating composition is attached to a preheated spring body will be described. The first coating method is a heating step for heating the spring body, and the surface temperature T (° C.) of the spring body is Tf−20 ≦ T <Tf + 20 (Tf: the temperature at which the powder coating composition is cured (° C.)) ), A coating process for attaching the powder coating composition to the surface of the spring body, and a curing process for curing the attached powder coating composition.

  In the heating step, the method for heating the spring body is not particularly limited. For example, the spring body may be housed in a hot air furnace, a far infrared furnace, or the like and heated. Further, the spring body may be energized or induction heated. Among these, current heating is preferable because it has high thermal efficiency and can be heated regardless of the shape of the spring body. In addition, what is necessary is just to measure the surface temperature of a spring main body using non-contact-type thermometers, such as a thermograph, in a heating process, a painting process, and a hardening process.

  In the heating process, when the surface temperature T (° C.) of the spring body reaches Tf−20 ≦ T <Tf + 20, the heating is stopped. In the subsequent coating process, the powder coating composition is adhered to the surface of the spring body. Note that the curing start point temperature (Ts) and the curing completion point temperature (Tf) of the powder coating composition are determined in advance from the start point and end point of the exothermic peak of the powder coating composition.

  In the application step, the powder coating composition is applied to the surface of the spring body that has been heated in advance in the heating step. As a method for applying the powder coating composition to the spring body, a known electrostatic powder coating method can be used. For example, a corona charging method, a friction charging method, or the like can be used.

  Both the corona charging method and the friction charging method are used for coating using a gun unit with a cylindrical tip. In the case of the corona charging method, a high voltage is applied to the corona electrode arranged at the tip of the gun unit to cause corona discharge, and the generated powder charges the paint powder near the corona electrode. An electric field is formed between the corona electrode and the spring body with the spring body as a ground potential, and the charged paint powder is adhered to the spring body by the electric field.

  In the case of the friction charging method, the coating powder moving inside the gun unit is charged by being rubbed on the inner surface of the gun unit. By setting the spring body to the ground potential, the charged paint powder is injected from the gun unit and attached to the spring body.

  What is necessary is just to set suitably the charge amount by the discharge by a corona charge system, and the injection amount of a friction charge system according to the spring main body which is going to apply | coat a powder coating composition, respectively.

  In the curing step, the powder coating composition is cured in a cooled state, that is, by the residual heat of the spring body. Here, in order to perform sufficient curing, the surface temperature T (° C.) of the spring body at the completion of curing is Ts + 30 ≦ T (Ts: the temperature at which the powder coating composition is cured (° C.)). Is desirable. This is because when the surface temperature of the spring main body is less than Ts + 30 ° C., curing is difficult to proceed. Therefore, when the surface temperature of the spring body becomes less than Ts + 30 ° C. before the curing is completed, it is desirable to heat again to increase the surface temperature of the spring body. That is, it is desirable to cure the powder coating composition by further heating in the curing step.

  As described above, in the first coating method, the spring body is heated, and the powder coating composition is adhered while the surface temperature T (° C.) of the spring body is in the range of Tf−20 ≦ T <Tf + 20. . Thereafter, the surface temperature of the spring body decreases with time due to cooling. Curing is desirably completed while the surface temperature of the spring body is Ts + 30 ° C. or higher. Although it depends on the surface temperature of the spring body at the start of the coating process, the thickness of the coating film, etc., for example, if the surface temperature of the spring body 180 seconds after the start of the coating process is Ts + 0 ° C. or more, it is sufficiently cured. be able to.

The degree of curing in the curing step can be confirmed by measuring the gelation rate of the coating film. The gelation rate is a mass fraction of insoluble matter in a solvent such as acetone or xylene. For example, after immersing a part (sample) of the coating film in a solvent for a predetermined time, it is dried and the mass is measured. Then, the gelation rate is calculated by the following formula (I).
Gelation rate (%) = (dry mass of sample after solvent immersion / mass of sample before solvent immersion)
× 100 ... (I)
As the curing proceeds, the gelation rate increases. For example, if the gelation rate is 90% or more, it can be determined that curing is sufficiently advanced.

  After the powder coating composition is cured, it is desirable to rapidly cool the coating temperature below the melting temperature of the powder coating composition in order to facilitate handling while maintaining the quality of the coating surface. . The coating film may be rapidly cooled by blast, mist, shower, dipping, or the like.

[Post-heating]
As a second coating method, an embodiment will be described in which a powder coating composition is attached to a spring body and then the spring body is heated. In the second coating method, a powder coating composition is applied to the surface of the spring body, and in the spring body, a coating portion having an uncured coating film and an uncured coating disposed between the coating portions are arranged. An application process for forming two non-coating parts having no film, an electrode connection process for connecting electrodes to each of the two non-coating parts, and applying a voltage between the electrodes to energize and heat the spring body And a curing step of curing the uncured coating film of the painted part disposed between the two non-painted parts.

  In addition to the above steps, a pretreatment step of forming the above-described phosphate film on the surface of the spring body may be performed.

  A spring member having a coating film formed on the surface of the spring main body is obtained through the application process and the baking process. The coating film formed on the surface of the spring body has a zinc-containing layer containing a relatively large amount of zinc powder formed on the surface side of the spring body, and the resin components of the epoxy resin and acid-terminated polyester resin are relatively A resin-containing layer containing a large amount is formed on the zinc-containing layer.

  In the coating film, zinc powder is unevenly distributed on the surface side of the spring body, so even if the zinc content is small compared to the conventional coating film, the spring body and zinc are fully in contact with each other, resulting in higher anticorrosion properties. Demonstrate. Further, since the resin component is unevenly distributed on the surface layer side of the coating film, the impact from the outside is alleviated and the extension of cracks generated in the coating film is prevented. Since the resin-containing layer is formed with a relatively thin layer thickness, the variation in the layer thickness is small and the sag resistance is improved without causing sag. And even if the layer thickness of the resin-containing layer is thin, it is formed integrally with the zinc-containing layer, so there is no clear interface between layers, and no delamination occurs.

  Thus, the coating film of this invention can implement | achieve the spring member which improved high sag-proof property while maintaining high corrosion resistance with a zinc content layer and a resin content layer. Further, these two layers do not need to be individually applied to each layer, and can be formed on the surface of the spring body by applying only one powder coating composition once.

  Therefore, since it is a highly functional coating film, only one coat is required, so the number of manufacturing steps of the spring member can be reduced, and the spring member can be easily manufactured.

  FIG. 1 is a view showing a spring plate 1 according to the first embodiment of the present invention. In the present embodiment, a leaf spring including one spring plate 1 is shown as an example of a spring member, but the present invention is not limited to this.

  The spring plate 1 includes a spring body 10 and a coating film 11. The spring body 10 is made of an iron-based material such as spring steel, and has a shape with a curved central portion as shown in FIG. A coating film 11 is formed on the upper side surface 10 a on which the tensile force of the spring body 10 acts. The coating film 11 is formed from a powder coating composition containing an epoxy resin, an acid-terminated polyester resin, and zinc powder. As described above, the zinc-containing layer containing a relatively large amount of zinc powder is formed on the surface side of the spring body 10, and the resin-containing layer containing a relatively large amount of the resin component is formed on the zinc-containing layer.

FIG. 2 is a view showing a lap spring plate 2 according to the second embodiment of the present invention. The lap spring plate 2 is used, for example, in a leaf type suspension that connects a chassis and an axle. The lap spring plate 2 includes a parent plate 3, a child plate 4, an interleaf 6, and a U bolt 7. A laminated leaf spring 2 in which a child plate 4 is overlapped on the lower surface of the parent plate 3 and fastened to a mating member 5 by two U bolts 7, and the tension of the spring body 13 of the parent plate 3 and the spring body 14 of the child plate 4 A coating film 8 and a coating film 9 are formed on the force acting surfaces 13a and 14a, respectively. Both the coating film 8 and the coating film 9 are formed with the zinc-containing layer and the resin-containing layer as described above, the zinc-containing layer is located on the spring body 13, 14 side, and the resin- containing layer is located on the surface layer side. . An interleaf 6 made of a zinc plate or a synthetic resin plate is extended between the parent plate 3 and the child plate 4 so as to prevent wear due to tightening of the U bolt 7. ing.

  Next, the coating method of the spring plate 1 of this embodiment is demonstrated. The method for painting the spring plate 1 of the present embodiment includes a painting process, an electrode connection process, a curing process, and a partial painting process.

  In the painting process, the powder coating composition is coated on the surface of the spring body 10 to form a painted portion and two unpainted portions at both ends in the spring body 10. On the surface of the spring body 10, a zinc phosphate film is formed after a shot peening treatment is performed in advance.

  Next, the powder coating composition is adhered to the entire surface of the spring body 10 using a corona charging coating gun, and an uncured coating film made of the powder coating composition is formed. The thickness of the uncured coating film is 60 to 100 μm. Then, the uncured coating film formed on the left and right ends of the spring body 10 is removed by blowing air with an air gun. Thereby, the spring body 10 is exposed at both left and right ends of the spring body 10. In this way, the spring main body 10 and a painted part made of an uncured coating film and two non-coating parts made only of the exposed spring main body 10 are formed.

  In the electrode connection step, electrodes are connected to the two non-painted portions formed on the spring body 10 respectively. The electrode is connected to a power source by wiring. A controller provided in the power supply controls voltage on / off, voltage value to be applied, and the like.

  In the curing process, the power source is operated to apply a voltage between the electrodes, and the spring body 10 is energized and heated to cure the uncured coating on the painted portion. First, when the power supply is turned on and a voltage is applied, a current flows through the spring body 10 of the painted portion, and Joule heat is generated. Thereby, the spring main body 10 is heated and the uncured coating film on the surface of the spring main body 10 is heated. And when the temperature of a coating part reaches predetermined | prescribed temperature, an uncured coating film is hardened by stopping energization heating and standing to cool. In addition, when the temperature of a coating part falls too much at the time of standing_to_cool, and hardening of a coating film does not fully advance, it is desirable to carry out an electrical heating again and to raise the temperature of a coating part to predetermined temperature. What is necessary is just to measure the temperature of a coating part using non-contact-type thermometers, such as a thermograph, for example. After the coating film 11 is formed by curing, the electrode is removed from the two non-painted parts.

  In the partial painting process, two non-painted parts are painted. First, the same powder coating composition used in the coating process is attached to two non-coating portions using a corona charging coating gun to form an uncured coating film composed of the powder coating composition. . Next, the coating film 11 is formed by heating and curing the uncured coating film using an induction heating device. In this way, the coating film 11 is formed on the entire surface of the spring body 10 to manufacture the spring plate 1.

  Next, although an Example and a comparative example are given and this invention is demonstrated further in detail, this invention is not limited to these. In addition, the compounding quantity about the powder coating composition in a table | surface represents a mass part unless there is special description.

  A powder coating composition having the composition shown in Table 1 was manufactured by the above-described manufacturing method, and washer (outer diameter 40 mm, inner diameter 21 mm, thickness 2.9 mm, made of carbon steel (S45C)) was used as an object to be coated. The test piece of Examples 1 and 2 was produced by electrostatic coating on one side of the washer so that the film thickness was 50 μm, and baking (post-heating) at 170 ° C. for 20 minutes. Furthermore, a test piece of Example 3 was produced in the same manner as Example 1 except that the heating condition was preheating. In the preheating, the test piece was heated in advance so that the surface temperature of the test piece immediately before the powder coating composition was applied to the test piece was 180 ° C.

  As Comparative Example 1, according to the description in Patent Document 1 (Japanese Patent Laid-Open No. 11-188309), a coating film composed of a first coating film and a second coating film is provided on one side of a washer in the same manner as in the example, and compared. Example test specimens were prepared. The first coating film was used for baking a leaf spring ZE primer manufactured by Shinto Paint Co., Ltd., and the tough coating chassis black manufactured by Rock Paint Co., Ltd. was used for the second coating film.

  As Comparative Example 2, a powder coating composition was produced according to the description in Example 3 of Patent Document 2 (Japanese Patent Laid-Open No. 2013-119582), and electrostatic coating was performed on one side of the washer in the same manner as in Example. The coating film was provided and the test piece for a comparative example was produced.

Next, performance evaluation was performed using the test piece for an Example and the test piece for a comparative example.
<Evaluation method>
-Formation of resin-containing layer It was evaluated whether or not layer separation occurred in the coating film. The coating film is cut and the cut surface is confirmed with an optical microscope and an electron microscope (SEM), and the density of zinc is visually observed with EPMA (Zn mapping). If formed, the evaluation was “Yes”, and if the resin-containing layer was not formed, the evaluation was “None”.

-Sag resistance FIG. 3: is a schematic diagram for demonstrating the measuring method for measuring sag resistance. For sag resistance, four washers 100 are prepared for each of the examples and comparative examples, the surfaces on which the coating films are formed are overlapped, and the four washers 100 are sandwiched from above and below by a pair of pressing jigs 102, and thrust is applied. A pair of pressing jigs 102 and four washers 100 are fixed to the base 101 with fastening bolts 104 via the bearings 103. A strain gauge (Kyowa Dengyo Co., Ltd., bolt axial force measurement gauge KFG-3-120-C20-11) is embedded in the top of the tightening bolt 104 so that the axial force can be measured.

  As shown in FIG. 3, the washer 100 was fixed to the pedestal 101 with the fastening bolts 104, and was then placed in a thermostatic bath and allowed to stand at 60 ° C. for 48 hours. The axial force before charging into the thermostat and the axial force after 48 hours were measured, and the sag rate (%) = (axial force decreased before and after the test / axial force before the test) × 100 was calculated. It can be evaluated that the smaller the sag rate, the better the sag resistance. Specifically, the evaluation is based on the sag rate per unit film thickness. If the sag rate is less than 1% when the film thickness is 10 μm, the evaluation is good. Is judged to be defective. In this example, since the film thickness of the coating film is 50 μm, if the sag rate is less than 5%, the evaluation is “good”, and if the sag rate is 5% or more, the evaluation is “bad”. It was.

-Corrosion-proof property About anti-corrosion property, the neutral salt-water spray property was evaluated by the test method (spraying 5% sodium chloride aqueous solution of 35 degreeC of liquid temperature for 840 hours) based on JISK5600-7-1. It was visually confirmed whether or not the sprayed coating film had an abnormality such as peeling or swelling. If there was no abnormality in the coating film, the evaluation was “good”, and if there was an abnormality in the coating film, the evaluation was “x”.

  In Examples 1 to 3, a zinc-containing layer and a resin-containing layer were formed on the coating film, and the evaluation results were all good. In Comparative Example 1, since the second coating film is a resin coating film, it is inferior in sag resistance, and is often used by being fixed to a frame or the like by a fastening member such as a bolt. Is not applicable. Since the comparative example 2 is a coating film composed of one layer containing zinc powder, the sag resistance is good, but the corrosion resistance is inferior and cannot be applied as a coating film for a spring member.

DESCRIPTION OF SYMBOLS 1 Spring board 2 Lap spring board 3 Parent plate 4 Sub board 5 Opposing member 6 Interleaf 7 U bolt 8 Paint film 9 Paint film 10 Spring main body 10a Upper side surface 11 Paint film 13 Spring main body 13a Working surface 14 Spring main body 100 Washer 101 Base 102 Jig 103 Thrust bearing 104 Bolt

Claims (3)

A spring body;
It is a coating film formed by coating the surface of the spring body with a powder coating composition containing an epoxy resin, an acid-terminated polyester resin and zinc powder so that the uncured thickness becomes 60 to 100 μm. A zinc-containing layer containing more zinc powder than the epoxy resin and the acid-terminated polyester resin on the surface side of the spring body, and the epoxy resin and the acid rather than the zinc powder on the zinc-containing layer. a coating film having a resin-containing layer having a lot of terminal polyester resin, only including,
The powder coating composition is
When the sum of the content of the epoxy resin and the content of the acid-terminated polyester resin is 100 parts by mass, the content of the epoxy resin is 10 to 80 parts by mass, and the content of the acid-terminated polyester resin is 20 to 90 parts by mass,
The spring member, wherein the content of the zinc powder is 55 to 80% by mass with respect to the whole powder coating composition . A spring member manufacturing method for manufacturing the spring member according to claim 1,
One of the powder coating composition by coating once, the the spring body surface characteristics and to Luba ne member to form the coating film so as to have the zinc-containing layer and the resin-containing layer Manufacturing method . The spring body that is heated Me pre, by heating before the deposition of the powder coating composition, or forming the coating film so as to have the zinc-containing layer and the resin-containing layer, or the powder coating composition after depositing the objects on the spring body, according to claim 2, by heating, and forming the coating film so as to have the zinc-containing layer and the resin-containing layer after heating the spring body Of manufacturing the spring member.

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