JPH06272078A - Electroplating method - Google Patents

Abstract

PURPOSE:To provide the electroplating method capable of suppressing the generation of deformation and residual strains in a metallic material to be plated and forming a plating layer having a good adhesion property through an easy pretreatment. CONSTITUTION:This electroplating method includes a stage for degreasing a metallic surface made of aluminum or aluminum alloy by electrolytic washing, a stage for acidically activating the metallic surface rotating in the state of making friction contact with an anode body by electrolytic washing after the degreasing, a stage for forming an under coating layer by applying nickel plating to the metallic surface rotating in the state of making friction contact with the anode body after the acidic activation and a stage for forming a wear resistant outer layer on the under coating layer of the metallic surface. The metallic surface is clegreased and acidically activated and thereafter, the nickel plating liquid is electrodeposited thereon in the state of bringing the anode body into friction contact with the metallic surface under rotation and, therefore, the activation of the electrodeposited surface is accelerated and the oxide layer of the metallic surface is sufficiently removed. In addition, the nickel is strongly electrodeposited on the metallic surface and the under coating layer having high adhesive force is formed thereon.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plating technique, and more particularly to an electroplating method in which a metal surface of aluminum or an aluminum alloy material is plated.

[0002]

2. Description of the Related Art Ion plating method, plasma CVD method, diffusion permeation method, electroplating method, anodic oxidation method, etc. are known as methods for forming a wear-resistant and seizure-resistant film on the surface of aluminum or aluminum alloy material. Various dry surface treatment methods are known. In electroplating by chrome plating or the like, a metal surface is sufficiently activated by using a mixed acid such as hydrofluoric acid and nitric acid or dichromic acid, and then nickel plating is performed and then chrome plating is performed.

[0003]

By the way, when the piston ring is subjected to the dry plating treatment, a large thermal deformation and residual strain are generated in the piston ring due to the high treatment temperature, and the obtained piston ring is sufficient for the internal combustion engine. I can't secure good airtightness. On the other hand, in electroplating at a low treatment temperature, the dimensional accuracy of the metal surface deteriorates due to the strong activation performed in the pretreatment. Further, when the composition of the specific mixed acid solution used in the pretreatment is unstable, there is a drawback that the adhesion to the metal surface becomes insufficient and the generated reaction gas causes pollution problems, so improvement of the treatment method is required. Has been done.

Therefore, an object of the present invention is to provide an electroplating method capable of suppressing the deformation and residual strain of a metal material to be plated and forming a plating layer having good adhesion through easy pretreatment. Is.

It is another object of the present invention to provide an electroplating method capable of forming a film which provides wear resistance and scuffing resistance on the outer peripheral surface of a piston ring formed of aluminum or aluminum alloy.

[0006]

The electroplating method according to the present invention comprises a step of degreasing a metal surface made of aluminum or an aluminum alloy by electrolytic cleaning, and a step of degreasing the metal surface rotating in a state where the anode body is in frictional contact. A step of acid-activating by electrolytic cleaning, a step of forming a subbing layer by nickel plating on the metal surface that rotates in a state where the anode body is in frictional contact after the acid activation, and a step of forming a subbing layer on the metal surface. Forming a wear resistant outer layer. In the embodiment of the present invention, the outer peripheral surface of the piston ring is plated. The wear-resistant outer layer is formed on the subbing layer while rotating the metal surface while the anode body is in frictional contact or by immersing in a plating solution.

[0007]

[Function] After the metal surface is degreased and acid-activated, the nickel plating solution is electrodeposited while the anode body is in frictional contact with the rotating metal surface, so that activation of the electrodeposition surface is promoted.
The oxide layer on the metal surface is sufficiently removed, and nickel is strongly electrodeposited on the metal surface to form a sublayer having strong adhesion. The subbing layer is formed to a predetermined thickness in a shorter time than the conventional one. Then, an outer layer is formed on the subbing layer.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the electroplating method according to the present invention applied to a piston ring made of an aluminum alloy mounted as a top ring of a four-cycle motorcycle engine will be described below with reference to FIGS.

FIG. 2 shows a piston ring 10 made of 6 silicon / aluminum alloy formed of 6 wt% silicon, 4 wt% copper and the balance aluminum. FIG. 3 shows a nominal diameter of 56 mm, a width of 0.8 mm and a thickness. FIG. 2 shows a cross section of a piston ring 10 having a dimension of 2.4 mm.

FIG. 1 shows a plating apparatus 1 for forming a plating layer on the outer peripheral surface of a ring block 14 in which a large number of piston rings 10 are superposed on the same shaft in a cylindrical shape and rotatably supported.
5 is shown. The anode body 20 arranged adjacent to the ring block 14 includes a case 21 having a curved shape with the same curvature as the outer peripheral surface of the piston ring 10, and a support rod 22 provided in the case 21 and supporting the anode body 20. The case 21 is provided with a porous graphite anode 25 filled therein and a friction material 26 bonded to the concave surface of the graphite anode 25. An injection pipe 23 that supplies the plating solution from the solution cooling tank 24 to the inside of the case 21 is connected to the case 21. The plating solution supplied from the injection pipe 23 passes through the porous graphite anode 25 and reaches the friction material 26. The friction material 26 arranged along the concave surface of the graphite anode 25 is a net-like woven or non-woven fabric formed of chemical fibers such as vinyl fiber or animal and vegetable fibers such as felt material that can penetrate the electrolytic solution and the plating solution. . A friction material 26 is provided on the outer peripheral surface of the rotating ring block 14.
And the electrolytic solution and the plating solution are brought into contact with the ring block 1
4 is applied.

A ring block 14 rotatably supported
A tray 27 for collecting the electrolytic cleaning liquid and the plating liquid dropped from the ring block 14 is disposed below the ring block 14, and the electrolytic cleaning liquid and the plating liquid collected in the tray 27 are reused by a pump 29 through a filter 28 for solution cooling tank. Returned to 24. The cathode terminal 30 arranged in contact with the ring block 14 is a spring 31 and the ring block 1
It is elastically pressed against the outer peripheral surface of 4 and is energized. The tray 27, the pump 29, and the solution cooling tank 24 actually use different devices for different solutions such as an electrolytic cleaning solution and a plating solution in order to prevent mixture of the solutions, but the devices having the same functional structure are used. Therefore, the same reference numeral is used.

Next, an embodiment of a process of plating the outer peripheral surface of the ring block 14 using the plating apparatus 15 shown in FIG. 1 will be described.

Example 1 First, NaOH: 75 g (gram) / l (liter),
A cleaning solution having a composition of Na ₃ PO ₄ : 10 g / l and Na ₂ CO ₃ : 14 g / l and having a bath temperature of 80 ° C. is supplied to the anode body 20,
A voltage was applied to the cathode terminal 30 for 30 seconds at a voltage of 12 V and a current density (anode) of 7.5 A / cm ² , and the ring block 1
The outer peripheral surface of No. 4 was degreased by electrolytic cleaning.

Next, HCl: 20 g / l, H ₂ SO ₄ : 2
The outer peripheral surface of the ring block 14 having the composition of 00 g / l and degreased in a plating bath having a bath temperature of 40 ° C. was subjected to acidic activation electrolysis. At this time, the current to the cathode terminal 30 has a current density of 0.5 A / cm ² , a piston ring speed of 8 m / min, and an electrolysis time of 20 seconds.

As shown in FIG. 1, the friction material 26 of the anode body 20 was brought into contact with the outer peripheral surface of the ring block 14 rotated by an appropriate driving device. At the same time, the elastic force of the spring 31 brought the cathode terminal 30 into contact with the outer peripheral surface of the ring block 14 to energize the anode body 20. The case 21 of the anode body 20 is provided with a solution cooling tank 24 through an injection pipe 23.
The plating solution was injected from.

Subsequently, an undercoat layer was formed on the outer peripheral surface of the ring block 14 by nickel plating as a base layer. The bath composition is NiCl.6H ₂ O: 250 g / l, H ₃ B
O ₃ : 30 g / l, bath temperature 30 ° C., current density 0.1.
5 A / cm ² , the piston ring speed is 5 m / min, and the electrolysis time is 20 seconds. The plating solution supplied to the anode body 20 penetrated from the graphite anode 25 into the friction material 26. The friction material 26 was activated by rubbing it on the outer peripheral surface of the rotating ring block 14, and a fixed amount of nickel plating solution was supplied. An underlayer 11 made of nickel and having a thickness of 8 μm is formed on the outer peripheral surface of each piston ring 10 that constitutes the ring block 14.
Was electrodeposited as a base layer.

Further, the outer layer 12 was formed on the sublayer 11 by the chromium oxide composite dispersion plating of the Co--Ni--P alloy by the friction method of the friction abrasive and the usual immersion plating method. The bath composition used to form the outer layer is NiSO ₄ 6
H ₂ O: 100 g / l, NiCl ₂ 6H ₂ O: 80 g /
1, CoSO ₄ 7H ₂ O: 100 g / l, H ₃ PO ₃ : 25
g / l, NaH ₂ PO ₂ H ₂ O: 2 g / l. The hydrogen ion concentration is pH = 2.0, and the bath temperature is 50 ° C. In the friction plating method using a friction abrasive, the current density: 300 A / d
m ² , current flow time: 30 minutes, chromium oxide suspension amount (average particle size: 1.5 μm): 20 g / l. In the composition of the electrodeposited alloy, cobalt (Co): 65% by weight, phosphorus (P): 3.
0% by weight, chromium oxide dispersity 20% by volume, film hardness Hmv
= 830 micro Vickers.

In the dipping method using the same bath composition and bath temperature, current density: 5 A / dm ² , energizing time: 120 minutes, chromium oxide suspension amount (average particle size 1.5 μm): 100 g /
1, electrodeposited alloy composition: Co: 60% by weight, P: 2.8
% By weight, chromium oxide dispersity: 10% by volume, film hardness Hmv
= 810 micro Vickers. In this embodiment, the outer layer 12 is made of composite dispersion plating and hard chrome.
Was formed. The coating hardness indicates the hardness of the coating when the outer layer 12 electrodeposited with a plating thickness of 100 μm is subjected to a thermosetting treatment at a temperature of 400 ° C. for 1 hour.

Example 2 Next, the same material as the piston ring 10 used in Example 1,
Using the same size piston ring, the same treatment as in Example 1 was performed until electrolytic cleaning, acidic activation electrolysis, and formation of the nickel plating layer 11. The bath composition used in the hard chrome plating treatment was CrO ₃ : 250 g / l, H ₂ SO ₄ : 2.5 g / l.
1, bath temperature: 55 ° C. Current density: 55 A / d
m ² , electrolysis time: 5 hours. The hard chrome plating layer obtained has a thickness of 100 μm. Furthermore, at 200 ℃ 1
As a result of performing a baking treatment for a period of time and inspecting the hardness, the micro Vickers hardness (HMV) of the hard chromium plating layer was 970. In order to confirm the effect of the plating method according to the present invention, Comparative Example 1 and Comparative Example 2
It was created.

Comparative Example 1 A piston ring having the same material and shape as the piston ring 10 used in Examples 1 and 2 was prepared, and the activation treatment after alkaline electrolytic cleaning was based on the ASTM (American Society for Testing and Materials) standards. 20 in mixed acid solution by dipping method
Soaked for 2 seconds. The mixed acid solution had a hydrofluoric acid / nitric acid ratio of 1: 3 and a bath temperature of 30 ° C. After washing with water, the activated etching solution of sodium dichromate 250 g / l and hydrofluoric acid 48 mg (milligram) / l was added again at a temperature of 80 ° C. for 20 times.
Soaked for a minute. After washing again with water, the same nickel plating bath as that of the above-described example in which the sublayer 11 was immediately formed was used, and a nickel plating layer was formed at a current density of 7 A / dm ² for 5 minutes by a usual dipping method. After that, composite plating is performed under the same conditions by the friction method and the dipping method of the same chromium plating bath (Co-Ni-P alloy chromium oxide composite dispersion plating) as in the above-described embodiment for forming the outer layer 12, and at 400 ° C for 1 hour. Heat-treated.

Comparative Example 2 In addition, a piston ring made of the same material and shape as the piston ring 10 used in Examples 1 and 2 was prepared, and alkaline electrolytic cleaning and hydrofluoric acid / nitric acid activity were performed in the same method and conditions as in Comparative Example 1. After activation, sodium dichromate, activation of hydrofluoric acid, and formation of a nickel plating layer, hard chrome plating was performed under the same conditions as in Example 2, and roasting treatment was performed at 200 ° C. for 1 hour.

From the above example, the following sample numbers 6 to 6 are shown.
A kind of piston ring was obtained. Friction Plating with Friction Abrasives-Friction Method (Example 1) Each Complex Plating Treatment by Immersion Method-Dip Method (Example 1) Hard Chromium Plating Treatment-Hard Chrome Plating (Example 2) Friction Plating Method with Friction Abrasive Materials-Friction Method ( Comparative Example 1) Composite plating treatment by dipping method-Dip method (Comparative Example 1) Film forming ring by hard chrome plating-Hard chrome plating (Comparative Example 2) 4-cylinder 4-cycle water-cooled aluminum alloy cast iron sleeve casting engine The above 4 types of piston rings are mounted as the top ring of the engine, and after running-in, the rotation speed is 1400 at full load.
A durability test for 200 hours was performed at 0 rpm. The table below shows the results of measuring the amount of wear by observing the sliding surface of the cylinder facing each piston ring. Sample number Surface condition after test Abrasion amount after test (μm) Piston ring Cylinder No peeling 8 4 Peeling at 2 places from sublayer 13 5 No peeling 30 3 Peeling at 6 places from outer layer 10 8 Peeling at 7 places from outer layer, As shown in the above table, in Examples 1 and 2 according to the present invention, the adhesion of the plating layer was good and the peeling from the outer layer 12 was observed. The piston ring and cylinder wear less, and the surface condition is good. Further, the piston ring made of aluminum or aluminum alloy plated according to the present invention forms a wear-resistant heat dissipation path for smoothly transmitting the heat of the piston heated during the operation of the engine to the cylinder, so that the scuffing resistance is improved. It will be understood that it is excellent.

[0023]

As described above, according to the electroplating method of the present invention, a wear resistant film can be formed on the surface of lightweight aluminum or aluminum alloy with a strong peel strength. Therefore, it is possible to form a wear-resistant and scuffing-resistant film on the outer peripheral surface of the lightweight piston ring that is used under the severe conditions of high speed and high load, improving the engine performance and extending the life. It becomes possible.

[Brief description of drawings]

FIG. 1 is a block diagram of a plating apparatus used in the electroplating method according to the present invention.

FIG. 2 is a plan view of a piston ring plated by the electroplating method according to the present invention.

3 is a sectional view of the piston ring taken along the line AA in FIG.

[Explanation of symbols]

10. ． Piston ring, 11. ． Sublayer, 12. ． Outer layer, 14. ． Ring block, 15. ． Plating equipment,
20. ． Anode body, 21. ． Case, 25. ． Graphite anode,
26. ． Friction material, 30. ． Cathode terminal, 31. ． Spring, 24. ． Solution cooling tank, 27. ． tray

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[Procedure amendment]

[Submission date] April 16, 1993

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] 0022

[Correction method] Change

[Correction content]

From the above example, the following sample numbers 6 to 6 are shown.
A kind of piston ring was obtained. Friction Plating with Friction Abrasives-Friction Method (Example 1) Each Complex Plating Treatment by Immersion Method-Dip Method (Example 1) Hard Chromium Plating Treatment-Hard Chrome Plating (Example 2) Friction Plating Method with Friction Abrasive Materials-Friction Method ( Comparative Example 1) Composite plating treatment by dipping method-Dip method (Comparative Example 1) Film forming ring by hard chrome plating-Hard chrome plating (Comparative Example 2) 4-cylinder 4-cycle water-cooled aluminum alloy cast iron sleeve casting engine The above 4 types of piston rings are mounted as the top ring of the engine, and after running-in, the rotation speed is 1400 at full load.
A durability test for 200 hours was performed at 0 rpm. The table below shows the results of measuring the amount of wear by observing the sliding surface of the cylinder facing each piston ring. Sample No. Surface condition after test Abrasion amount after test (μm) Piston ring Cylinder No peeling 7 3 Peeling at 2 places from sublayer 1 5 No peeling 28 3 6 places peeling from outer layer 10 7 7 places peeling from outer layer, As shown in the above table, in Examples 1 and 2 according to the present invention, the adhesion of the plating layer was good and the peeling from the outer layer 12 was observed. The piston ring and cylinder wear less, and the surface condition is good. Further, the piston ring made of aluminum or aluminum alloy plated according to the present invention forms a wear-resistant heat dissipation path for smoothly transmitting the heat of the piston heated during the operation of the engine to the cylinder, so that the scuffing resistance is improved. It will be understood that it is excellent.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display location F16J 9/26 C 7366-3J

Claims (4)

[Claims] 1. A step of degreasing a metal surface made of aluminum or an aluminum alloy by electrolytic cleaning, a step of acidifying the metal surface rotating in a state where the anode body is in frictional contact with electrolytic cleaning by electrolytic cleaning after the degreasing, and an acidic activity. After that, the steps of forming a subbing layer by nickel plating on the metal surface that rotates in a state where the anode body is in frictional contact and forming a wear-resistant outer layer on the subbing layer of the metal surface are performed. An electroplating method comprising: 2. The electroplating method according to claim 1, wherein the metal surface is an outer peripheral surface of the piston ring. 3. The electroplating method according to claim 1, wherein a wear-resistant outer layer is formed on a subbing layer of a metal surface that rotates while the anode body is in frictional contact. 4. The electroplating method according to claim 1, wherein the metal surface is immersed in a plating solution to form a wear-resistant outer layer on the metal surface subbing layer.