JPS6344838B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for mirror plating aluminum extruded sections. Aluminum extrusion profiles are
Because it is lightweight and easy to process, it is widely used as a building material. Extruded shapes are generally subjected to surface treatments such as painting, alumite treatment, alumite coloring treatment, etc. from the viewpoint of corrosion resistance and aesthetics. However, plating, which is commonly used for other metals, is not generally performed as a surface treatment for extruded sections.

It is known that aluminum can be plated, and by applying gloss plating to a flat aluminum surface, a beautiful mirror surface with high decorative value can be obtained. However, the surface of extruded aluminum shapes has very complex irregularities and undulations, such as dice marks, streaks, and rough skin, so even if you apply gloss plating to the surface, the distortion will be noticeable and a beautiful mirror surface will not be obtained. In order to remove this distortion, it is necessary to polish the extruded shape in advance to make the surface flat, and simply smoothing the surface by buffing or the like will not eliminate the distortion.

The present inventors investigated a method of polishing an extruded shape suitable for forming a mirror surface, and found that polishing using a platen-type belt polisher is suitable (see Japanese Patent Application No. 58-7969).

The present inventors further studied the polishing of extruded shapes and found that the polishing conditions vary greatly depending on the surface shape of the shape, and completed the present invention. That is, the present invention involves polishing the surface of an extruded aluminum material having a flat or slightly convex surface using a platen-type belt polishing machine, and then applying gloss plating to the surface. This paper focuses on the mirror plating method, which is characterized by:

To explain the present invention in more detail, the material for the aluminum extruded shape is mainly 6000 series aluminum alloy, especially 0.20-0.6% silicon and 0.45-0.45% silicon.
A 6063 alloy containing 0.9% magnesium is used, although pure aluminum or other aluminum alloys can be used if desired.

The extruded profile must be manufactured so that the surface to be mirror-plated is flat or slightly convex, that is, the cross section perpendicular to the extrusion direction is slightly hilly. Conventionally, extruded sections have generally been manufactured with slightly concave surfaces.
If the surface becomes flat or convex during extrusion, the surface is even corrected to a concave shape by pressing with a roller. This is because if the surface of the extruded material is flat or convex, it is easily damaged during handling, whereas if the surface is concave, both ends serve as supporting points, so the surface does not come into contact with other objects. This is because there are fewer scratches on the surface, and therefore the surface is less likely to be scratched.

However, when such an extruded profile with a concave surface is polished using a platen-type belt sander, the protruding edges on both sides are easy to polish, but the central part is difficult to polish, and if you try to polish the central part thoroughly, It requires long-time polishing, reduces polishing efficiency, and causes severe wear on the polishing belt. Further, it is preferable that the surface after polishing be flat or slightly convex from the viewpoint of image quality when used as a mirror surface, and if there are depressions on the surface, distortion will occur in the image. By the way, polishing an extruded material with a concave surface to make the surface flat or convex requires a long period of polishing. Being familiar is a disadvantage.

On the other hand, if the surface of the extruded shape is flat or slightly convex, the entire surface including both side edges will be well polished from the beginning of polishing, resulting in good polishing efficiency. Furthermore, even if the surface after polishing is not flat and has a convex shape, the image quality will hardly be affected when it is made into a mirror surface. A polished surface can be obtained. Furthermore, in platen-type belt polishing, the central portion of the surface of the profile generally tends to be depressed due to elastic deformation due to the pressing force of the platen. Therefore, if the surface is flat, both end portions are more likely to be polished to a convex polished surface than the central portion. Further, it is difficult to manufacture an extruded shape with a flat surface, and the surface tends to become concave, so it is preferable to manufacture the extruded shape in a convex shape. However, if the shape is too convex, the amount of polishing required to obtain a polished surface with good image quality will increase.
If it is about mm, the radius of curvature of the surface should be set to 2×
It is appropriate that the thickness be 10 ³ mm or more, preferably 4×10 ³ mm or more. Note that the length of the extruded shape is arbitrary, but it is 1000 mm or more, usually about 4000 mm. Further, the shape of the extruded section is arbitrary, but the surface to be polished must be flat.

In the present invention, first, as described above, the extruded shape having a flat or slightly convex surface is polished using a platen-type belt polishing machine. This removes surface roughness, undulations, etc. that occur during extrusion, and provides a flat or slightly convex surface with good planarity. As is well known, there are two types of belt sanders: contact wheel type and platen type. Generally, the former is used for polishing large items such as long steel materials, and the latter is used for polishing small items such as camera parts. ing. However, according to the inventors' study,
In the case of polishing an extruded aluminum profile, the contact wheel method removes unevenness and undulations on the surface of the extruded profile and makes the surface smooth, but on the other hand, new scratch-like scratches and feed marks are created on the surface of the extruded profile. Even if the surface is smoothed by buffing and plated, it is difficult to obtain a beautiful mirror surface without distortion. This method also has the disadvantage that the polishing belt is easily clogged and the belt has a short service life. On the other hand, in the case of the platen method, scratches and feed marks do not occur, and the belt has a long service life. Furthermore, since a polished surface with low surface roughness is obtained, a beautiful mirror surface without distortion can be obtained even when the next puff polishing is simply performed. The reason why there is such a large difference in the life of the abrasive surface and abrasive belt between the contact wheel method and the platen method is unknown, but the contact condition between the extruded profile and the abrasive belt is line contact in the contact wheel method. On the other hand, in the platen method, surface contact is used, which is thought to have a large influence.

In the present invention, the abrasive belt used is what is usually called a polishing belt, that is, an abrasive belt having a structure in which a soft carrier such as cork carries abrasive grains and is fixed to a belt base material with an adhesive. It is preferable to use Polishing belts are usually used for ejecting steel products, but since extruded aluminum shapes are soft, this belt can provide sufficient grinding power, and is flat and can be used for polishing with small surface roughness. surface is easily obtained.

Incidentally, in the present invention, it is of course possible to use an ordinary abrasive belt having a structure in which abrasive grains are directly bonded to a belt base material with an adhesive. In this case, it is preferable to use a soft platen whose surface that comes into contact with the belt is made of an elastic material such as rubber or a rubber material with a sponge bonded to its back surface. Since such a soft platen is prone to wear due to friction with the abrasive belt, it is preferable to attach a scrap abrasive belt to its surface to prevent wear of the platen itself. When a soft platen is used, the pressure of the abrasive grains protruding on the surface of the abrasive belt trying to cut into the extruded shape is moderately alleviated by the elasticity of the platen, resulting in a flat surface without scratches or feed marks. A good polished surface can be obtained. If the platen is too soft, this pressure will be relaxed too much, and the flatness of the polished surface will worsen. In addition, when using the above-mentioned polishing belt, the cutting pressure of the abrasive grains is alleviated by cork, which is the carrier of the abrasive grains, so the platen should be made of metal or a hard platen with a wear-resistant material coated on its surface. It is preferable to use
The abrasive grain size of the abrasive belt is generally selected from the range of #180 to #600. Usually, it is preferable to sequentially polish the grains from coarse grains to fine grains using two to four types of polishing belts.

The pressing force of the platen is usually 0.2 to 10 kg/cm ² G per unit contact area of the workpiece, preferably 0.4 to 4 kg/cm ²
selected from the range of G. If the pressing force is small, the grinding force of the polishing belt will be small, and many polishing steps will have to be performed to obtain the desired polished surface. Furthermore, as the pressing force increases, heat generation increases and cooling by the polishing liquid cannot keep up. The optimal range of platen pressing force is 0.4 to 2.5 kg/cm ² G, especially 0.4 to 2.5 kg/cm 2 G.
It is 1Kg/cm ² G. The feed rate of extruded sections is usually 1
~10 m/min, preferably 2-4 m/min. Increasing the feed rate increases the number of times of polishing to obtain the desired polished surface.

The polished surface obtained in this way has excellent flatness and smoothness, and can be used as a base for mirror plating even as it is, and when anodized in an electrolyte, a beautiful alumite surface is formed. Ru.
When used for these purposes, it is preferable to use an abrasive belt with small grain size to keep the abrasive surface as flat and smooth as possible. In addition, when using the base for mirror plating, it is preferable to apply copper plating in advance to smooth the base, or to apply a thick layer of semi-gloss plating or gloss plating.This will further buff the polished surface of the belt. A beautiful plating mirror surface can be obtained without polishing.

However, the most advantageous method is to further buff the polished surface of the belt before plating. In this way, the polishing marks caused by belt polishing can be easily removed by buffing, producing an extremely smooth polished surface.

Buffing is usually carried out using a lime-based abrasive according to a conventional method. In the present invention, since a polished surface with low surface roughness can be obtained by belt polishing, a mirror surface can be easily obtained by simple buff polishing.

The extruded shape that has been smoothed by buffing is then subjected to gloss plating to form a mirror surface. There are several known bright plating methods for aluminum, and any of these known methods can be used in the present invention. Usually, the pressed shaped material that has been polished is degreased with a solution containing a surfactant, then immersed in an alkaline aqueous solution, and further treated with a nitric acid aqueous solution to clean the surface. Next, the extruded shape is immersed in an aqueous solution containing zincate or an aqueous solution further containing salts such as copper, nickel, iron, etc., and a displacement treatment is performed once or several times to precipitate these metals on the surface of the extruded shape. . Finally, the extruded shape is immersed in a plating bath to serve as a cathode, and a direct current is applied between it and a suitable anode to perform plating. Although bright plating can be performed directly on the extruded section, it is preferable to first perform semi-gloss plating and then bright plating, as this provides a plated surface with good corrosion resistance. Although any plating bath can be used, it is usually a nickel salt aqueous solution containing nickel sulfate as a main ingredient and various auxiliaries added thereto. Further, it is preferable to perform microporous chrome nickel plating to increase corrosion resistance and chrome plating to increase hardness and corrosion resistance by a conventional method on the glossy plating layer.

According to the present invention, it is possible to easily form a beautiful mirror surface without distortion on an extruded shape.

EXAMPLES The present invention will be explained in more detail with reference to Examples below, but the present invention is not limited to the following Examples unless it exceeds the gist thereof.

Example 1 Prism-shaped extruded aluminum sections (6063 material, aged T ₅ ) having a width of 80 mm, a height of 40 mm, a thickness of 2.0 mm, and a length of 1200 mm A and B were polished using a platen-type belt polisher. As a platen, width 150mm,
A hard platen made of a steel plate with a length of 180 mm and whose surface was lined with cemented carbide was used. As polishing belts, polishing cork belt number BCZ180 manufactured by Koyosha Co., Ltd. and polishing belt with cork as a carrier manufactured by Sankyo Rikagaku Co., Ltd. (product code: RBXB,
Particle size 240 and 400. In both cases, C abrasive grains were used. The polishing conditions are: platen pressing force of 0.6 kg/cm ² G per unit contact area of workpiece, polishing belt speed
750 m/min, the feed speed of the extruded section is 2 m/min,
Under these conditions, polishing was performed once each with belts of No. 180, No. 240, and No. 400. Diacut 21T manufactured by Mitsubishi Oil Co., Ltd. was used as the grinding oil. With this polishing,
The surface shape of the extruded section A changed as shown from A to B in FIG. 1, while the surface shape of the extruded section B changed as shown from A to B in FIG.

This extruded shape was buffed twice using a cotton bias buff and a lime-based abrasive (Koyosha product, Prince Lime No. 100) at a pressing load of 10 kg, a polishing speed of approximately 2500 m/min, and a feed rate of the extruded shape of 4 m/min. did.

After buffing, the extruded shape was subjected to the following treatments in the usual manner: degreasing, washing with water, immersion in an alkaline aqueous solution, washing with water, treatment with an aqueous nitric acid solution, and washing with water to clean its surface. Next, this extruded shape was immersed in Bondal Dip solution (manufactured by Canning, UK), washed with water, treated with nitric acid, washed with water, immersed again in Bondal Dip solution, and washed with water to deposit a zinc alloy on the surface of the extruded shape. This was immersed in an electrolytic bath to serve as a cathode, and plating was performed in the following order at a bath temperature of 55°C.

(a) Semi-gloss plating Electrolytic bath Nickel sulfate (NiSO ₄ 6H ₂ O)
300g/nickel chloride (NiCl ₂ 6H ₂ O)
38g/ Boric acid 40g/ (Addition of commercially available non-coumarin semi-gloss plating brightener) Current density 2A/dm ² plating time 40 minutes (b) Bright plating Electrolytic bath Nickel sulfate (NiSO ₄ 6H ₂ O)
260g/nickel chloride (NiCl ₂ 6H ₂ O)
60g/ Boric acid 40g/ (Addition of commercially available brightener for full gloss plating) Current density 2A/dm ² plating time 40 minutes (c) Nickel plating for microporous chrome Electrolytic bath Nickel sulfate (NiSO ₄ 6H ₂ O)
240g/nickel chloride (NiCl ₂ 6H ₂ O)
50g/ Boric acid 30g/ (Commercially available microporous chromium powder added) Current density 1A/dm ² plating time 1 minute (d) Chrome plating Electrolytic bath Chromic anhydride (CrO ₃ ) 250g/ Sulfuric acid 2g/ (Commercially available fluoride Addition of system additives) Current density: 10 A/dm ² Plating time: 3 minutes Both extruded shapes A and B were given a beautiful mirror surface by the above plating treatment. However, its visual quality is
Extruded profile A gave an image with almost no distortion, whereas extruded profile B gave an image with some distortion.

Example 2 Example 1 was carried out using a prismatic extruded aluminum section with a width of 60 mm, a height of 30 mm, a thickness of 2.5 mm, and a length of 1200 mm.
When the material was polished using a platen-type belt sander in exactly the same manner as above, the surface shape of the extruded material changed as shown in A to B in FIG. 3.

When this extruded shape was buffed and plated in exactly the same manner as in Example 1, a mirror surface was obtained that gave a beautiful and distortion-free image.

[Brief explanation of drawings]

Figures 1 to 3 all show the surface shape of the extruded shape, with A being before belt polishing and B being after belt polishing. In these figures, the vertical axis indicates the height μ from an arbitrary reference plane, and the horizontal axis indicates the width direction.

Claims (1)

[Claims] 1. After polishing the surface of an extruded aluminum material having a flat or slightly convex surface with a platen-type belt polishing machine, a gloss plating is applied to the surface. A mirror plating method characterized by applying 2. The mirror plating method according to claim 1, wherein after polishing with a belt polisher, buff polishing is further performed to apply gloss plating. 3. A belt having a structure in which a soft carrier is fixed to a belt base material and abrasive grains are supported on the carrier is used as the abrasive belt, and polishing is carried out using a belt sander equipped with a hard platen. A mirror plating method according to claim 1 or 2. 4. A belt having a structure in which abrasive grains are directly bonded to the belt base material is used as the polishing belt, and polishing is performed using a belt polishing machine equipped with a soft platen whose surface is made of an elastic material. A mirror plating method according to claim 1 or 2. 5. The mirror plating method according to any one of claims 1 to 4, characterized in that the plating is applied in the order of semi-bright nickel plating and bright nickel plating. 6. The mirror plating method according to any one of claims 1 to 5, characterized in that nickel plating for microporous chrome and chrome plating are further applied on the glossy plating layer.