JP3230697B2 - Method for manufacturing highly airtight aluminum structure - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a highly airtight aluminum which has been improved in pressure resistance and strength by filling micropores present in an aluminum structure, particularly, cavities and micropores present in an aluminum casting with ceramics. The present invention relates to a method for manufacturing a structure.

[0002]

2. Description of the Related Art Aluminum is used in various cast products, sintered products,
It is used as a structure for welded products and thermal spray products. However, these structures have defects such as fine holes, as well as casting cavities in the cast product. When the amount of these is large, the product strength is reduced and the product cannot be regarded as a defective product. It is a factor that worsens the stay. In other words, hereinafter, an aluminum die-cast product will be described as an example, but a major cause of defective aluminum die-cast products is the occurrence of voids. It is said that there are cavities and cast cavities due to insufficient filling.

Therefore, various means for sealing these defective portions have been proposed. That is, in the case of the aluminum die-cast product, a method of impregnating an impregnating liquid by a vacuum-pressure impregnation method is known, which improves pressure resistance, airtightness, corrosion resistance, and the like, and can improve mechanical strength. I have. Examples of the impregnating liquid to be used include iron-based metal acids and sodium silicates such as Plenco (trade name), mogal (trade name), and global seal (trade name), and other oxidation catalysts and rust inhibitors. Inorganic impregnation liquid, consisting of a suspension containing, three bond 3932
Organic impregnating liquids such as (trade name), Placem (trade name, crosslinked methacrylate), and Super Seal P-601 (trade name, methacrylic ester) are known.

In order to perform treatment using such an impregnating liquid, first, a washed and dried aluminum casting is put into a treatment tank, which is then sealed, and then the air inside the treatment tank is removed to a pressure of 5 mmHg or less. And vacuum. After that, the impregnating liquid heated to a predetermined temperature is injected, and after the impregnating liquid completely covers the casting to be processed, a pressure of 5 to 10 kg / cm ² is applied, the pressure is maintained for 10 to 15 minutes, and the pressurization is stopped. The impregnating liquid in the processing tank is returned to the storage tank to take out the casting to be processed. Next, the impregnated casting is washed, dried or heated for a predetermined period of time to solidify the impregnating liquid in the micropores and cavities of the casting, and subjected to a pressure resistance test to obtain a passing product as an incompatible product. Are repeated until the above process is passed again.

[0005]

However, in the conventional method, in the case of the inorganic impregnating liquid, the target pore diameter of the defective portion of the die casting is 100 μm at the maximum, and when the impregnated product is heated to around 100 ° C. In the case of the organic impregnating liquid, the strength is maintained at a low temperature, but the strength is reduced when exposed to a high temperature of 200 ° C. or more, and furthermore, there is a problem that the carbonized material is voided. However, there is a problem that only the filling is performed.

The present invention not only excels in pressure resistance, but also enhances not only the filling of defective portions such as micropores and cavities, but also the strength of the filled portion and the strength of the aluminum body. it is an object to provide a method for manufacturing the airtight aluminum structure.

[0007]

Means for Solving the Problems To solve the above problems and achieve the above object, the present inventor has repeatedly studied on means using ceramics as an impregnating liquid, and mixed chromium oxide and phosphorus oxide. It has been found that the object can be achieved by forming a ceramic layer having a ceramic layer or a ceramic layer in which ceramic particles are dispersed in a matrix thereof, thereby completing the present invention. That is, the present onset Ming,
The defect such as fine holes or blowholes of A aluminum structure,
A concentrated mixture of chromic acid and phosphoric acid, Cr ₂ O ₃ , Zr
Metal oxides such as O ₂ , Al ₂ O ₃ , TiO ₂ , SiO ₂ , metal nitrides such as Si ₃ N ₄ , ZrN, Si
C, metal carbides such as Cr ₃ C ₂ and Co, C
At least once, a slurry comprising at least one of r, Mo, metal powder, and fiber is impregnated with pressure or reduced pressure, and filled into a defective portion such as a fine hole or a casting cavity and heated and fired at least once. The gist of the present invention is a method of manufacturing a highly airtight aluminum structure that is repeatedly performed .

In the present invention, chromic acid is used as a concentrated aqueous solution prepared by dissolving chromium trioxide in water to a specific gravity of 1.5 to 1.65, and phosphoric acid is a commercially available product having a concentration of 75 to 88%. can do.

The concentrated concentrated solution of chromic acid and phosphoric acid is prepared by adding the concentrated aqueous solution of chromic acid to 0.1 molecular weight of the phosphoric acid in an amount of 0.1%.
48 to 2.7 molecular weight ratio, preferably 0.96 to
It is preferable to use one mixed at a ratio of 1.36. This is because if the ratio of the molecular weight of chromic acid is less than 0.48, the viscosity becomes high and the impregnation into the micropores is not carried out smoothly. This is because when the ratio of the molecular weight of chromic acid exceeds 2.7, the effect of the phosphoric acid as a reducing agent decreases, and it is difficult to obtain the desired properties unless the firing temperature is increased.

As raw materials, ZrO ₂ , Al
Metal oxides such as ₂ O ₃ , Cr ₂ O ₃ , TiO ₂ , SiO ₂ , metal nitrides such as Si ₃ N ₄ , ZrN, Si
C, metal carbides such as Cr ₃ C ₂ and Co, C
r, or at least one selected from ceramic or metal powder such as Mo, and fibers such as whisker or metal amorphous of the ceramic, each having a particle diameter of at most about 5 μm. Preferably those having an average particle size of 1 μm or less are used.

As the ceramic slurry, 1.5 to 2.5 kg of at least one of the ceramic raw materials is added to the mixed concentrated liquid of chromic acid and phosphoric acid adjusted as described above.
The mixture is added at a ratio of / l and stirred well to adjust, but the order of mixing is not restricted.

The formation of the ceramic layer is performed under a reduced pressure of 1 to 3 mmHg or a pressure of ^{2 to 4} kg / cm ² for 5 to 10 mmHg.
Hold for 200 minutes, remove pressure and wash, then 200 ~ 300 ° C
For 30 to 120 minutes to form a ceramic film. When the impregnation-heating and sintering treatment is performed once or twice after the impregnation-heating and sintering treatment, defective portions such as micropores and voids can be more effectively filled.

[0013]

In this manner, a ceramic layer in which chromium oxide and phosphorous oxide are mixed in a defective portion such as a fine hole or a void in an aluminum structure, or a ceramic layer in which ceramic particles are dispersed in the ceramics is formed. The heat treatment and firing temperature can be as low as 200 to 300 ° C., and the number of times of the treatment is sufficient. This is because the polymer structure is formed by dehydration condensation of phosphoric acid itself or blending with metal ions, or it has the effect of reducing chromic acid and has a polymer bonded structure via chromium and oxygen, which makes it more robust. The effect of phosphoric acid as a reducing agent on the low-temperature reduction action of chromic acid, which forms an oxide film on the surface, and further, when CrO ₃ is converted to Cr ₂ O ₃ , a chemical change occurs due to organic oxidative bonding with phosphoric acid. This is considered to be an effective means for obtaining a hardening and filling effect of the ceramic layer because the remaining layer remains as a film.

As a result of examining the ratio of the molecular weights of phosphorus oxide and chromium oxide to the obtained ceramic layer, it was found that the ratio of the molecular weight of chromic acid to phosphoric acid in the mixed concentrated liquid remained almost unchanged. Was observed.

Further, the present invention relates to a cast product by various methods,
Applicable to sintered products, thermal spray products, etc.

[0016]

Next, an embodiment of the present invention will be described. Example 1 1) Preparation of a mixed concentrated solution of chromic acid and phosphoric acid 100 ml of chromic acid having a specific gravity of 1.65 prepared by dissolving CrO ₃ in water and 100 ml of a commercially available 85% phosphoric acid were sufficiently mixed. It was prepared by stirring.

2) Preparation of Aluminum Structure An inner diameter of 32 mm, an outer diameter of 36 mm and a length of 70 m were obtained by die casting using an aluminum material (ADC-12).
m-sized aluminum castings were prepared, washed with trichlene and dried thoroughly.

3) Formation of ceramic layer The cast aluminum product prepared in 2) is placed in a treatment tank,
After holding at a reduced pressure of mHg for 20 minutes, the impregnating solution containing the mixed concentrated solution of chromic acid and phosphoric acid prepared in 1) stored in the storage tank is introduced until the aluminum casting in the processing tank is sufficiently covered. . Then, pressurized to 4 kg / cm ² to 10
After holding for 1 minute, stop applying pressure and return the impregnating liquid to the storage tank,
Take out the aluminum casting, wash with water and dry. After that, it is heated and baked at 250 ° C. for 1 hour to complete one impregnation treatment.

4) Test Pressure resistance: A water immersion type pressure test was performed at 6.5 kg / cm ² for 10 minutes, but no defects such as generation of bubbles were observed in all ten samples. Example 2 1) Preparation of ceramic slurry Cr ₂ O _{3 having} a particle size of 5 μm or less, stabilized Zr
Using O ₂ and α-Al ₂ O ₃ , 90 parts by weight of Cr ₂ O ₃ ,
10 parts by weight of stabilized ZrO _{2 and} 10 parts by weight of α-Al ₂ O ₃ were blended with 15 parts by weight of a mixed concentrated solution of chromic acid and phosphoric acid prepared in Example 1-1), and the mixture was mixed with an alumina ball mill. For 40 hours to prepare a slurry.

2) Formation of Ceramic Layer The same procedure as in Example 1-3) was performed using the aluminum casting prepared in the same manner as in Example 1-2) and the ceramic slurry prepared in 1).

3) Test As a result of the test in the same manner as in Example 1-4), the pressure resistance of all ten samples was normal. Comparative Example A commercially available inorganic impregnant Mogar (trade name) was used in the same manner as in Example 1-3), and a test was performed in the same manner as in Example 1-4). As a result, three out of the ten samples were found to have a problem of bubble generation, indicating that there was a problem with the pressure resistance.

[0022]

As described above, according to the present invention,
The defect such as fine holes or blow hole present in the aluminum structure, the ceramic layer of chromium oxide and a phosphorus oxide are mixed, or to form a ceramic layer obtained by dispersing ceramic particles into the matrix Rukoto So you can
The filling portion is dense, extremely excellent in pressure resistance, heat resistance and corrosion resistance, and has high hardness, so that it is lighter and smaller than before in the design stage, and the surface is made of Cr ₂ O ₃
It is possible to manufacture a highly airtight aluminum structure that can obtain a ceramic coating mainly and can add slidability.
The effect is excellent.

Claims (1)

(57) [Claims] 1. A mixed concentrated liquid of chromic acid and phosphoric acid is added to a defective portion such as a fine hole or a void in an aluminum structure,
r ₂ O ₃ , ZrO ₂ , Al ₂ O ₃ , TiO ₂ , SiO ₂
Metal oxides such as Si ₃ N ₄ , metal nitrides such as ZrN, metal carbides such as SiC, Cr ₃ C ₂ , and at least one of Co, Cr, Mo, metal powders and fibers, etc. A highly airtight aluminum structure, characterized in that one or more kinds of slurries are impregnated or depressurized, filled in a defective portion such as a fine hole or a void, and heated and fired repeatedly at least once. Manufacturing method.