JP2706925B2 - AL alloy die casting having wear resistance and lubricity and surface treatment method of AL alloy die casting - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to an aluminum alloy die casting having wear resistance and lubricity, and a surface treatment method thereof.

[Conventional technology]

In general, an anodized film formed by anodizing a material has high hardness (Hv 300 to 450) and good wear resistance, but has poor friction with a mating material and a large coefficient of friction. For this reason, there is a problem that scuff resistance is poor, galling and abrasion (attack property) of a mating material are large.

As a solution to these problems, a method of depositing a lubricating substance such as Sn or Ni by using secondary electrolysis technology in the fine pores of the anodized film formed by anodizing Al alloy to reduce the friction coefficient Has been made. [Problems to be Solved by the Invention] However, in the above-mentioned conventional surface treatment method, even in the wrought material that forms a sound film, fine pores in the film are removed by a lubricating substance. However, it is difficult to completely fill the film, and the micropores contained in the film are only a small number, so that a satisfactory result has not been obtained.

In the case of Al alloy die casting, for example, JIS, AC4
As is clear from the component B, components other than Al (Si, Cu, etc.)
, It forms a eutectic phase, which makes it impossible to produce a sound anodic oxide film. Even if this film is subjected to the aforementioned secondary electrolysis, the eutectic There is a problem that the desired effect cannot be obtained because the precipitation of the lubricating substance is hindered by the phase, or even if the precipitation is slight.

The present invention has been made to solve such a problem of the prior art, and utilizes a eutectic phase that inhibits formation of a sound anodic oxide film, and removes the eutectic phase in the anodic oxide film. By forming a composite film consisting of a film deposited and replaced with a large amount of Ni and Sn and an anodic oxide film formed in the α phase, the abrasion resistance of the anodic oxide film and the oil retention (lubrication It is an object of the present invention to provide an Al alloy die-casting having good scuff resistance in addition to the above-mentioned properties and a surface treatment method thereof.

[Means for solving the problem]

In order to achieve the above object, in the Al alloy die-casting having wear resistance and lubricity according to the first invention of the present application, in an Al alloy having an α-phase and a eutectic phase on its surface, an α-phase portion is subjected to an anodizing film treatment And the eutectic phase is N
It has a composite film that has been precipitated and replaced with i and Sn. Further, in the second invention of the present application, in the surface treatment method of an Al alloy having an α phase and a eutectic phase on the surface, a step of dissolving and removing the eutectic phase; A step of forming an anodized film on the surface, a step of immersing the anodized Al alloy die-cast in an electrolytic bath of Ni or Sn and performing an electrolytic treatment at a low current value, and a current higher than the current value of the previous process. And a step of further performing an electrolytic treatment by the value.

[Specific configuration of the invention]

 Hereinafter, the present invention will be described in more detail.

The present invention is a surface treatment having lubricity in addition to abrasion resistance. The target material is an Al alloy having a eutectic phase (particularly, an Al alloy).
Alloy casting).

That is, in the present invention, the eutectic phase is precipitated and replaced by a wear-resistant metal such as Ni or Sn, and an anodic oxide film is formed on the other α phase to form a composite film having wear resistance and lubricity.

That is, when the composite coating is subjected to anodizing coating treatment after dissolving and removing the eutectic phase on the Al alloy die-casting surface,
The hollow formed when the eutectic phase is removed remains in the film. By plating this concave hole with Ni or Sn, the concave hole is filled and generated.

Normally, it has been considered difficult to perform direct plating on an anodized film, but in the case of Al alloy die-casting having a eutectic phase, it has been discovered that plating is generated under certain conditions.

Thereby, plating is generated from the bottom of the concave hole (deeutectic phase) in the film, and the hole can be filled.

The film thus formed has excellent adhesion due to the anchoring effect, and has good scuff resistance in addition to the wear resistance and oil retaining property of the anodic oxide film.

Al alloy die casting having abrasion resistance and lubricity according to the present invention is basically configured as follows,
Hereinafter, the surface treatment method will be described in detail with reference to the accompanying drawings.

As shown in FIG. 1, of the eutectic phase 2 of the material 1, those near the material surface are chemically dissolved and removed to form a large number of concave holes 3 as shown in FIG.

The etchant used at this time is difficult to dissolve the α-phase 1a and must be selectively dissolved with a focus on the eutectic phase 2. Therefore, the type must be selected depending on the material 1. However, nitric acid, hydrofluoric acid, Alternatively, a mixed acid of nitric acid, hydrofluoric acid and acetic acid is effective.

Next, an anodizing treatment is performed to form a uniform film 4. As shown in FIG. 3, although the shape slightly changes with the formation of the film 4, the concave hole 3 in the deeutectic portion remains as it is. The broken line in FIG. 3 shows the shape of the material 1 before the anodic oxidation treatment.

Here, as the anodic oxidation bath, any treatment solution such as a normal sulfuric acid bath, a high-concentration sulfuric acid bath, an oxalic acid bath, and a mixed acid bath can be used. Can be expected. The electrolytic conditions are not particularly limited.

The thickness of the film 4 is desirably about 5 to 25 μm, and the film thickness is preferably as uniform as possible.

Next, the metal 5 is deposited from the bottom of the concave hole 3 by electrolytic technique (plating) into the deeutectic phase concave hole 3 in the anodic oxide film 4 and filled as shown in FIG.

The treatment liquid may be an ordinary plating bath, but considering the dissolution of the anodic oxide film 4, a neutral bath having a higher electrodeposition rate is advantageous.

Electrolysis conditions are important, and the way in which current flows in particular has the greatest effect on electrodeposition. After being immersed in the treatment bath and being blended for a while, low current electrolysis is performed for 1 to 5 minutes.

Next, it must be gradually increased to a predetermined current value. Here, if the current value rises sharply, a spalling phenomenon occurs and plating cannot be performed.

The treatment time may be such that the de-eutectic phase concave hole 3 is filled and slightly protruded, and may be short.

This step may be divided into two steps, one for low-current electrolysis and the other for electrodeposition filling. In that case, even if the deposited metal is different,
It may be the same.

Next, since the metal 5 filling the concave hole 3 in the film 4 partially protrudes from the surface, the surface roughness is adjusted by machining or polishing (barrel, honing, buff, etc.) It is completed as shown in FIG. In the machining or polishing, only the metal protruding from the anodic oxide film may be removed, or it may be processed together with the anodic oxide film to such an extent that the anodic oxide film is not completely removed.

FIG. 9 shows a microscopic state of the film surface after processing.

In case of light honing finish or buffing finish, as shown in Fig. 9 (a), friction surface (metal surface)
There are many very small steps A between the surface and the anodic oxide film surface.

When the amount of metal to be electrodeposited is reduced by adjusting the electrolysis conditions, many fine cavities as shown in FIG. 9 (b) exist on the surface of the processed film. . Further, by selecting an appropriate electrolysis condition and finishing the process, it is possible to mix the step A and the fine cavities in the film.

These steps A and minute cavities serve as oil sumps at the time of friction and release wear powder.

〔Example〕

 Hereinafter, embodiments of the present invention will be specifically described.

Example 1 The surface of ADC10 was finished to about 2S with a polishing buff, immersed in a mixed acid of nitric acid: hydrofluoric acid: acetic acid (= 4: 1: 1) for 30 seconds to perform a deeutectic phase treatment.

Subsequently, a uniform anodic oxide film of about 16 μm was formed in a mixed acid (sulfuric acid 400 g /, oxalic acid 5 g /) under the conditions of a current density of 2.5 A / dm ² , an electrolysis time of 30 minutes, a bath temperature of 10 ° C and a counter electrode pb plate did.

Immediately after washing with water, Ni plating bath (280g nickel sulfate /
, Nickel chloride 50g /, boric acid 45g /, brightener appropriate amount,
After immersion in a bath temperature of 45 ° C for 1 minute, low current electrolysis (0.05 A /
dm ² ) for 2 minutes.

Furthermore, the current value was gradually increased, and after 1 minute, 1.5 A / dm ²
For 5 minutes to complete the plating. (It was confirmed by microscopic observation that Ni plating protruded from the concave hole on the surface.) Finally, the surface was adjusted to 1S by buff polishing.

FIGS. 6 (a) and 6 (b) show a cross section and a micrograph of the surface of the film formed in Example 1 described above.

In the photographs shown in FIGS. 6A and 6B, the black portion is an oxide film, and the white portion in the film is metal (Ni).

Based on Example 1 described above, the effect was confirmed by the following method.

(1) While adding the engine oil in the form of a mist, the flat plate of Example 1 and the FC25 pin (R sphere 42.5 mm) were rubbed under a load of 10 kgf for 30 minutes at a speed of 600 cpm (stroke 5 mm).

The coefficient of friction at that time was 0.08, which was the same as that of the hard chrome plating tested under the same conditions.

The anodic oxide film had a coefficient of friction of 0.12.
The effect of was confirmed.

In addition, when the worn portion was observed, almost no wear was observed, and it was found that the wear resistance was good.

(2) The flat plate of Example 1 and a pin of AC8A (φ ball 42.5m
m) Add 1μ of engine oil to the contact area and load 10k
Friction was performed under the conditions of gf, speed of 100 cpm, and stroke of 50 mm, and a test for running out of oil was performed.

While the ordinary anodic oxide film was scuffed in 7 minutes, in Example 1, no scuff occurred for 23 minutes or more.
(Hard chromium generates scuff in 13 minutes.) As a result, the scuffing performance of Example 1 was 3 times and 2 times that of the anodic oxide film and the hard chromium plating, respectively.

(3) A steel ball for bearing (JIS B1501 product) and the flat plate of Example 1 were loaded at a load of 0.2 kgf, a speed of 10 cpm, and a stroke of 15 mm.
A friction test was performed under the following conditions. (No lubricating oil) FIG. 7 shows the change in the coefficient of friction at that time.

It can be seen from the drawing that the initial conformability of the first embodiment is good and the friction coefficient is small. FIG. 8 shows the magnitude of wear of the bearing steel balls. It can be seen from the figure that the attack on the partner material is small.

[Examples 2 to 6] ADC10 was subjected to the same pretreatment as in Example 1 and the same anodic oxidation treatment.

Then, it was immersed in a copper plating bath (copper sulfate 180 g / sulfuric acid 50 g / bath temperature 25 ° C.) to perform plating at a current density of 0.2 A / dm ² for 1 minute.

Next, plating was performed under each of the following conditions, and a metal was filled in the deeutectic phase concave hole in the anodic oxide film.

Example 2 Ni plating (same bath as in Example 1) Current density 2 A / dm ² hours 3 minutes Example 3 Sn plating [Commercial neutral Sn plating bath (Dipsole Sn-232) PH6, bath temperature 25 ° C] Current density 1A / dm ² hours 10 minutes Example 4 Sn-Ni alloy plating [commercially available (Harshaw Murata Co., Ltd. = Stalloy) PH8, bath temperature 55 ° C] Current density 1A / dm ² hours 7 minutes Example 5 Ni -P plating (Ni 200g / sulfuric acid, nickel chloride 1
00g /, phosphorous acid 20g /, phosphoric acid 70g /) PH1, bath temperature 55
℃ Current density 5A / dm ² hours 5 minutes Example 6 Pb-Sn alloy plating [commercial product (TL-280 manufactured by Dipsol) PH7, bath temperature 25 ° C Current density 1A / dm ² hours 10 minutes After plating, surface Was polished and adjusted to about 1S.

Observation from the surface confirmed that the plating metal was filled in the eutectic phase between the α phase and the α phase as in Example 1.

[Example 7] ADC6 was finished to about 2S with a polishing buff, and nitric acid: hydrofluoric acid (=
It was immersed in warm acid of 4: 1) for 30 seconds to perform a deeutectic phase treatment.

Next, in a sulfuric acid bath (H ₂ SO ₄ 150g /, 15 ° C), current density 3A
An anodic oxide film of about 20 μm was formed under the conditions of / dm ² , electrolysis time of 20 minutes, and a counter electrode Pb plate.

Then, the deeutectic phase concave holes in the anodized film were immediately filled with Ni in the same manner as in the plating conditions (Ni plating) of Example 1.

Finally, the surface roughness was adjusted to about 1S by buff polishing.

Example 8 AC4B was processed in the same manner as the ADC 10 of Example 1 and Example 6.

Observation of the film surface and cross section shows that the plating metal is filled in the deeutectic phase concave hole in the same manner as in Example 1.

〔The invention's effect〕

As described above, according to the Al alloy die-casting having wear resistance and lubricity according to the present invention, the eutectic phase is Ni, Sn
Excellent effect of improving lubrication and scuffing resistance due to abrasion resistance and oil retention because it has a composite coating in which an anodic oxide coating is formed on the other α phase by precipitation substitution with a metal having abrasion resistance There is.

According to the surface treatment method of the present invention, an anodic oxide film is formed by dissolving and removing a eutectic phase present on the surface of a material, and a lubricating metal is electrolytically formed in a myriad of deeutectic concave holes present in the film. It is possible to generate a large amount of Ni and Sn in the film by precipitation-filling, so that there is an advantage that it is easy to obtain an Al alloy die-casting with good lubrication and scuff resistance due to wear resistance and oil retention. is there.

[Brief description of the drawings]

FIGS. 1 to 5 are cross-sectional views of materials sequentially showing specific steps of Al or an Al alloy having a lubricating film according to the present invention and a surface treatment method thereof, and FIGS. FIG. 7 is a photograph showing the surface metallographic structure of the film formed in Example 1 of the surface treatment method of the present invention, and FIG. A graph showing the change in the coefficient of friction in the confirmation test of the effect of the material,
It is a table | surface which shows the magnitude | size (diameter) of the wear mark of the bearing measured after the end of a friction test. FIG. 9 is a cross-sectional view showing a microscopic state after finishing the film surface of the present invention. DESCRIPTION OF SYMBOLS 1 ... Material having eutectic phase 2 ... Eutectic phase 3 ... De-eutectic phase concave hole 4 ... Anodized film 5 ... Metal having high lubricity or wear resistance

Claims (2)

(57) [Claims] 1. An aluminum alloy die-casting having an α phase and a eutectic phase on its surface, wherein an α phase part is anodized and a eutectic phase part is electrolytically precipitated and replaced by Ni and Sn. An aluminum alloy die casting having wear resistance and lubricity, characterized by having: 2. A method for surface-treating an Al alloy die-cast having an α-phase and a eutectic phase on a surface thereof, the method comprising: dissolving and removing the eutectic phase; A step of forming an oxide film, a step of immersing the anodized Al alloy die-cast in an Ni or Sn electrolytic bath and performing an electrolytic treatment at a low current value, and at a current value higher than the current value of the previous step. A surface treatment method for an Al alloy die-cast, further comprising a step of performing an electrolytic treatment.