JPH0665788A - Highly airtight al structure and its production - Google Patents

Abstract

PURPOSE:To fill the defective parts such as micropores and cavities, to improve the strength of the filled part and further to increase the pressure tightness and strength of an aluminum structure main body. CONSTITUTION:An aluminum die casting is placed in a treating tank and impregnated with a concd. mixed soln. of chromic acid and phosphoric acid. The treated aluminum casting is taken out, washed with water, dried and heat- treated. The process is repeated at least once. The obtained product is excellent in pressure tightness and strength, and the pressure tightness and strength are improved even with few times of treatments.

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 is capable of improving pressure resistance and strength by filling ceramics with micropores existing in an aluminum structure, particularly cavities and micropores existing in an aluminum casting. The present invention relates to a structure and a manufacturing method thereof.

[0002]

2. Description of the Related Art Aluminum is used for various casting products, sintered products,
It is used as a structure for welded products and thermal spray products. However, in these structures, there are defects such as micropores as well as porosity of the cast product, and when the amount of these is large, the product strength may be reduced and the product cannot be regarded as a defective product. It is a cause of worsening clubbing. That is, 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 cavities. It is said that there are cavities and cast cavities due to insufficient filling.

Therefore, various means have been proposed for sealing these defective portions. 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, etc., and improves mechanical strength. There is. As the impregnating liquid used, for example, iron-based metallic acids such as Plenco (trade name), Mogal (trade name), and Global Seal (trade name), sodium silicate, other oxidation catalysts, rust inhibitors, etc. ThreeBond 3932, an inorganic impregnation liquid such as a suspension containing
Organic brand impregnating liquids such as (trade name), Prase (trade name, cross-linking type methacrylic acid ester), and Superseal P-601 (trade name, methacrylic acid ester) are known.

In order to process using such an impregnating liquid, first, a washed and dried aluminum casting is put in a processing tank and sealed, and then the air inside the processing tank is removed so that the pressure becomes 5 mmHg or less. And make a vacuum. Then, the impregnating liquid heated to a predetermined temperature is injected, and after the impregnating liquid completely covers the cast product, a pressure of 5 to 10 Kg / cm ² is applied and held for 10 to 15 minutes, and the pressure is stopped. The impregnating liquid in the treatment tank is returned to the storage tank and the cast product to be treated is taken out. Next, the impregnated cast product is washed and dried or heated for a specified time to solidify the impregnating liquid in the micropores and porosity of the cast product. Repeats the above process until it passes.

[0005]

However, according to the conventional method, in the case of the inorganic impregnating liquid, the target pore diameter of the defect portion of the die casting is 100 μm at the maximum, and when the impregnated product is heated up to around 100 ° C. The organic impregnating liquid maintains high strength at low temperatures, but when exposed to a high temperature of 200 ° C. or higher, the strength decreases and carbonization occurs. There is a problem that it is only filled.

The present invention not only excels in pressure resistance, but also improves the strength of the filling part and the strength of the aluminum main body as well as the filling of defective parts such as fine holes and porosity. It is an object of the present invention to provide an airtight aluminum structure and a method for manufacturing the same.

[0007]

In order to solve the above problems and achieve the above object, the present inventor has conducted extensive research on means for using ceramics as an impregnating liquid, and chromium oxide and phosphorus oxide are mixed. The present invention has been completed by finding that the object can be achieved by forming a ceramic layer having the above-mentioned structure or a ceramic layer in which ceramic particles are dispersed in the matrix. That is, the first embodiment of the present invention is a ceramic filler in which a chromium oxide and a phosphorus oxide are mixed in a defect such as a micropore or a porosity of an aluminum structure, or a chromium oxide and a phosphorus. A highly airtight aluminum structure is obtained by filling a matrix mixed with an oxide with a ceramic filler in which ceramic or metal particles or fibers are dispersed. A second embodiment is a fine airtight or cast aluminum structure. A method for producing a highly airtight aluminum structure, wherein a process of impregnating a defect such as a nest with an impregnating liquid consisting of a concentrated concentrated liquid of chromic acid and phosphoric acid and heating and firing is repeated at least once. embodiments, the defect such as fine holes or blowholes aluminum structure, mixed with concentrated solution of chromic acid and phosphoric _{acid, Cr 2 O 3, ZrO 2} , Al 2 O 3, TiO ₂ ,
Among metal oxides such as SiO ₂ , metal nitrides such as Si ₃ N ₄ and ZrN, metal carbides such as SiC and Cr ₃ C ₂ , and powders and fibers of Co, Cr, Mo and metals. The slurry consisting of at least one of the above is subjected to pressure or reduced pressure impregnation to fill a defect such as a micropore or a porosity,
This is a method for producing a highly airtight aluminum structure, in which the heating and firing treatment is repeatedly performed at least once.

The chromic acid used in the present invention is used as a concentrated aqueous solution in which chromium trioxide is dissolved in water to have 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.

A concentrated liquid mixture of chromic acid and phosphoric acid has a concentration of 0.
48 to 2.7 molecular weight ratio, preferably 0.96 to
It is preferable to use a mixture of 1.36. This is because when the ratio of the molecular weight of chromic acid is less than 0.48, the viscosity becomes high and the impregnation into the fine pores is not performed smoothly. Therefore, the gap is completely filled even if the treatment is repeated. When the ratio of the molecular weight of chromic acid exceeds 2.7, the effectiveness of phosphoric acid as a reducing agent decreases, and it is difficult to obtain the desired properties unless the firing temperature is raised.

The raw materials are ZrO ₂ and Al.
Metal oxides such as ₂ O ₃ , Cr ₂ O ₃ , TiO ₂ and SiO ₂ , metal nitrides such as Si ₃ N ₄ and ZrN, Si
C, metal carbides such as Cr ₃ C ₂ , and Co, C
At least one selected from powders of ceramics and metals such as r or Mo, and fibers of the ceramics such as whiskers and metal amorphous is used, and in each case, the maximum particle size is about 5 μm. Is preferable and the average particle size is 1 μm or less.

As the ceramic slurry, 1.5 to 2.5 kg of at least one of the ceramic raw materials is added to the concentrated concentrated liquid of chromic acid and phosphoric acid prepared as described above.
It is added at a ratio of 1 / l and sufficiently stirred and adjusted, but the order of mixing is not limited.

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 mm.
Hold for minutes, release pressure, wash, then 200-300 ℃
It is preferable to form a ceramic coating by heating and baking for 30 to 120 minutes. After the impregnation-heating / baking treatment, if the impregnation-heating / baking treatment is further performed once or twice, it is possible to more effectively fill the defective portions such as the micropores and the porosity.

[0013]

In this way, a ceramic layer in which chromium oxide and phosphorus oxide are mixed in a defect such as a fine hole or a porosity of an aluminum structure or a ceramic layer in which ceramic particles are dispersed in the ceramic is formed. It is formed, and it is possible to bring about an effect that a low temperature treatment such as a heating and firing temperature of 200 to 300 ° C. is possible and the number of treatments is sufficient once. This forms a polymer structure from dehydration condensation of phosphoric acid itself or addition to metal ions, or has a reducing effect of chromic acid, and has a polymer bonding structure via chromium and oxygen, resulting in a stronger structure. The effect of phosphoric acid as a reducing agent for the low-temperature reduction of chromic acid by forming an oxide film on the surface, and when CrO ₃ is converted to Cr ₂ O ₃ , there is a chemical change with phosphoric acid and an organic oxidative bond. It is considered that this is because it remains as a film and is an effective means for obtaining the hardening and filling effect of the ceramic layer.

As a result of investigating the ratio of the molecular weights of phosphorus oxide and chromium oxide in 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 recognized.

Further, the present invention is a cast product produced by various methods,
It can be applied to sintered products and thermal spray products.

[0016]

EXAMPLES Next, examples of the present invention will be described. Example 1 1) Preparation of Mixing Concentrated Liquid 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 commercially available 85% phosphoric acid were mixed sufficiently. It was prepared by stirring.

2) Preparation of Aluminum Structure Using an aluminum material (ADC-12) by a die casting method, the inner diameter is 32 mm, the outer diameter is 36 mm, and the length is 70 m.
An aluminum casting of size m was produced, washed with trichlene, and thoroughly dried to prepare.

3) Formation of ceramic layer The cast aluminum product prepared in 2) is put in a treatment tank and 5 m in length.
After being kept under reduced pressure of mHg for 20 minutes, the impregnating solution, which is stored in the storage tank and is composed of the concentrated concentrated solution of chromic acid and phosphoric acid, is introduced until the aluminum casting in the processing tank is sufficiently covered. . Then, pressurize to 4 Kg / cm ² and
After holding for a minute, pressurization is stopped and the impregnating liquid is returned to the storage tank,
The aluminum casting is taken out, washed with water and dried. Then, it is heated and baked at 250 ° C. for 1 hour to complete one impregnation treatment.

4) Test pressure resistance: A submersion type pressure resistance test was conducted for 10 minutes at an air pressure of 6.5 kg / cm ² , but no defect such as bubble generation was observed in all 10 samples. Example 2 1) Preparation of Ceramic Slurry Cr ₂ O _{3 having} a particle diameter of 5 μm or less, stabilized Zr
O ₂ and α-Al ₂ O ₃ are used, Cr ₂ O ₃ 90 parts by weight,
Stabilized ZrO _{2 (} 10 parts by weight) and α-Al ₂ O _{3 (} 10 parts by weight) were added to 15 parts by weight of the concentrated concentrated solution of chromic acid and phosphoric acid prepared in Example 1-1), and an alumina ball mill was used. And pulverized and mixed for 40 hours to prepare a slurry.

2) Formation of Ceramic Layer Using the aluminum cast body prepared in the same manner as in Example 1-2) and the ceramic slurry prepared in 1), the same treatment as in Example 1-3) was performed.

3) Test As a result of testing in the same manner as in Example 1-4), the pressure resistance of 10 samples was normal. Comparative Example A commercially available inorganic impregnating agent Mogar (trade name) was used, treated in the same manner as in Example 1-3), and tested in the same manner as in Example 1-4). As a result, it was found that in three out of ten samples, defects of bubble generation were observed, and there was a problem in pressure resistance.

[0022]

INDUSTRIAL APPLICABILITY The present invention disperses ceramic particles in a ceramic layer in which chromium oxides and phosphorus oxides are mixed, or in a matrix thereof, in a defect portion such as a micropore or a porosity existing in an aluminum structure. Since the formed ceramic layer is formed, the filling portion is dense and has excellent pressure resistance, heat resistance and corrosion resistance, and high hardness.
This makes it possible to achieve lighter weight and smaller size than before in the design stage, a ceramic film mainly containing Cr ₂ O ₃ is obtained on the surface, and it is possible to add extremely good slidability. It is a thing.

Claims (3)

[Claims] 1. A ceramic filler containing a mixture of chromium oxides and phosphorus oxides or a matrix containing a mixture of chromium oxides and phosphorus oxides in a defect such as a fine hole or a porosity of an aluminum structure. A highly airtight aluminum structure characterized in that it is filled with a ceramic filler in which ceramic or metal particles or fibers are dispersed. 2. A process of impregnating a defective portion such as a fine hole or a porosity of an aluminum structure with an impregnating liquid composed of a concentrated concentrated liquid of chromic acid and phosphoric acid and heating and repeating the treatment at least once. A method for manufacturing a highly airtight aluminum structure, comprising: 3. A concentrated liquid mixture of chromic acid and phosphoric acid is added to a defective portion such as a fine hole or a porosity of an aluminum structure, and C
r ₂ O ₃ , ZrO ₂ , Al ₂ O ₃ , TiO ₂ , SiO ₂
At least among metal oxides such as, metal nitrides such as Si ₃ N ₄ and ZrN, metal carbides such as SiC and Cr ₃ C ₂ , and powders and fibers of Co, Cr, Mo and metals. A highly airtight aluminum structure, characterized in that a slurry consisting of one kind is impregnated under pressure or under reduced pressure to fill a defect such as a micropore or a porosity, and heat firing is repeated at least once. Manufacturing method.