JPS61204302A - Porous al sintered material - Google Patents

Abstract

PURPOSE:To obtain a porous Al sintered material having an excellent sound absorbing characteristic and corrosion resistance by sintering a mixture contg. Al, Mg, Mn, Ni, Cu, Si, etc. in a non-pressure and non-oxidative atmosphere and forming further a chromic acid film contg. no crystal water thereon. CONSTITUTION:The powder mixture consisting essentially of Al and contg. 1 or 2 kinds of Mg, Mn, Ni, Cu and Si as the additive components is sprayed in a vessel consisting of graphite or the like which does not react with Al and is sintered under no pressure in the non-oxidative atmosphere of the decomposed gas of NH3, gaseous N2, etc. The preferable sintering temp. is the temp. at which the liquid phase of the additive components is generated or above or the temp. below the m.p. of Al. The porous Al sintered body having 30-60% porosity is thus obtd. The sintered body is then immersed in a chromic acid soln. and after the excess treating liquid is removed by a centrifugal separator, the sintered body is calcined at about 300 deg.C by which the chromic acid film contg. no crystal water is formed on the sintered body. The porous Al sintered material having the excellent sound absorbing characteristic, corrosion resistance and heat resistance is thus obtd.

Description

[Detailed Description of the Invention] <Object of the Invention> Industrial Application Field The present invention relates to a porous AI-based sintered material, and more specifically, it is a porous AI-based sintered material that has excellent sound absorption characteristics such as noise and noise, and excellent corrosion resistance. It concerns a porous Al-based sintered material.

Conventional Technology Porous AI-based sintered materials have (1) a lower specific gravity than Cu- or Fe-based porous sintered materials;

(2) Since it has good malleability, bending is relatively easy.

(3) The sintering temperature is low and it can be manufactured at relatively low cost.

Since it has the following advantages, its development has been actively promoted.

However, in the early days, Tokuko No. 43-20884, 4
No. 5-2420G, No. 45-24007, 47-321
As shown in each publication of No. 63, since the development was mainly aimed at oil-impregnated bearings for mechanical parts, the strength of porous sintered materials was required, and sinterability was inevitably required as a sintered component. Many sintered materials contain Cu, which is easy to obtain good strength, and technically speaking, the common method was to press the surface oxide film that inhibits sintering to break it and allow sintering to proceed. The porosity of the resulting sintered material is at most 10
It was ~20%.

Later, in Japanese Patent Publication No. 5G-11373, a method was developed to obtain a porous A/type sintered material by sintering in a non-pressure, non-oxidizing atmosphere, and it was widely applied to sound absorbing materials, ura, overlay materials, etc. It started to be done.

However, the use of porous AI-based sintered materials is limited to applications and locations that require corrosion resistance, and because of the large surface area that porous materials have, the surface treatment is superior to conventional rust prevention treatments. was requested.

Problems to be Solved by the Invention The present invention aims to solve these problems, and specifically, it aims to provide a porous Al-based sintered material that is rich in sound absorption properties and corrosion resistance without blocking the pores of the porous body. The purpose is to provide materials.

<Structure of the Invention> Means for Solving the Problems and Their Effects The present invention contains AI as a main component and additional components such as shun, persimmon,
A mixed powder containing one or two selected from Ni%CU and Si is heated without pressure in a container that does not react with AI.
It is characterized in that it is made by chemically surface-treating a porous Al-based sintered body with a porosity of 30 to 60%, which is sintered in a non-oxidizing atmosphere.

The present invention will be explained below with reference to the drawings.

FIG. 1 is an explanatory diagram of an example of a manufacturing process for manufacturing a porous AI-based sintered material according to the present invention.

In Figure 1, AI is the main component and MQ is the added component.
A raw material powder 1 containing one or two selected from , Mn%Ni%Cu, and Si is uniformly scattered to a predetermined thickness from a hopper 2 into a container 3 (for example, a graphite container) that does not react with AI.

The thickness of the spray at this time is adjusted depending on the depth of the container. Containers 3 naturally filled with raw material powder are stacked and sintered in a sintering furnace 4 maintained in an atmosphere of NH3 decomposed gas or N2 gas, cooled in a cooling zone 6, and removed from the containers 3. A porous Al-based sintered material 7 is obtained.

As described above, in the present invention, the raw material powder 1 containing AI as a main component in the container 3 is in a naturally packed state, and the surface oxide film that inhibits sintering in a normal sintering method is destroyed by pressing. On the other hand, during sintering, the Aj powder particles are destroyed due to the difference in thermal expansion coefficient between the inside of the particles and the oxide film, and sintering progresses through this destroyed portion. At this time, the destroyed and exposed metallic parts and the generated liquid phase parts are easily oxidized, so the atmosphere in the sintering furnace must be controlled to have a low partial pressure of oxygen, and the sintering furnace must be sintered in an atmosphere with a dew point of 130°C or less. tied. Further, the sintering temperature is higher than the liquid phase generation temperature of the additive component powder and lower than the melting point of AZ.

The resulting porous Al-based sintered material can have a porosity of 60% or more by using fine-grained powder and controlling the liquid phase layer of the additive components to a small level. The material is not practical because it has low strength and tends to become unsintered.

In addition, by controlling the sintering temperature and the amount of added ingredients, the porosity can be reduced to 30.
It is possible to obtain a sintered material with a porosity of 30% or less, but when the porosity is 30% or less, independent pores increase locally and the temperature control limit is exceeded, which tends to result in metallic sintering. Therefore,
The porosity is preferably 30 to 60%.

In general, alloys consisting of two or more different phases are more susceptible to corrosion than single-phase alloys due to the electrochemical action between the different phases. Since the surface area is much larger and the strength is lower, the influence of corrosion is extremely large (improving corrosion resistance is an important issue).

As a method to improve the corrosion resistance of porous AI-based sintered materials, we have already proposed a method for improving the corrosion resistance of porous AI-based sintered materials by selecting, as the additive component of Aj, a metal in which the electrolytic potential of a solid solution with Aj or an intermetallic compound is close to that of pure AI. Knowing that it is possible to improve the corrosion resistance of quality sintered materials, I decided to use additives to improve the corrosion resistance.
Mn.

A system containing one or two selected from Cu and Si, that is, Aj-MQ system, Al-Mn system, AI-Cu
system, kl-Si system, Aj-Mg-Si system%Aj-Mn
We proposed a porous AI-based sintered material with excellent sound absorption properties and corrosion resistance based on the -8i system.

However, as a method for improving the corrosion resistance of porous Al-based sintered materials, in addition to the method by selecting alloying elements as described above, there are also methods by painting and chemical surface treatment.

The present invention proposes a method for improving the corrosion resistance of a porous AJ-based sintered body by chemical surface treatment.
The surface treatment methods commonly used for surface treatment of Aj, ie, methods using anodizing treatment, phosphate treatment, and chromic acid treatment, are not sufficient in terms of corrosion resistance, workability, and sound absorption. An essential condition for surface treatment of porous materials is that uniform surface treatment can be performed to the inside of the porous material, and it is desirable to use a treatment liquid with low surface tension.
Thereby, chemical treatment can be carried out to the inside of the pores due to capillary action of the porous material. In addition, it is difficult to remove the treatment liquid that has entered the pores of a porous material even by washing with water, so surface treatment methods that include a step of washing the chemical solution with water will conversely corrode Aj with the remaining chemical solution, so the washing step is difficult. Processing methods involving this should be avoided.

As a surface treatment method similar to the present invention, JIS-563
3, Cry, , ZnO1
There are rust-preventing effects obtained by coating the metal surface with H3po, butyral resin as a complex salt, and rust-preventing treatment with a chromic acid rust-preventing film using a basic treatment solution of CrO3-H2304 called chromate treatment. The chromic acid film structure is -Cr203・CrO3
- It has a composition like nl+20-, and the reason for its corrosion resistance is that the hexavalent chromium in the film dissolves in water and acts as an inhibitor.

The film structure obtained by the surface treatment of the present invention is -Cr2O3・Cr0
3. It is an amorphous polymer that does not contain water of crystallization, and the reasons for its corrosion resistance are: (1) The film is insoluble in water, so it can be used for a long time without a resin coating to protect the film. maintains its rust-proofing properties.

(2) Since the chromic acid film does not contain water of crystallization, the film is dense and difficult to crack on the surface, making it difficult for corrosion to occur.

(3) Since a chromic acid film is formed by firing, unlike conventional films containing crystal water, it does not deteriorate or crack due to heat, so it can exhibit rust prevention effects even in applications that require heat resistance.

This is the reason for the corrosion resistance of the rust preventive film according to the present invention.

The surface treatment agent used in the present invention is manufactured by DIAMO of America.
NOS) was developed by IAMROK and is commercially available in Japan under the trade name Dacromet #100.

To explain the liquid composition and film formation of Dacromet #100, the liquid composition consists of a 20% aqueous solution of chromic anhydride, a reducing agent, a reducing catalyst, and an additive, and the pH of the liquid is approximately 4 and the specific gravity contains almost no free acid. Target 1.1 is a chromic acid solution. In order to obtain a rust-preventing film of -Cr203, Cr03- crystalline polymer that does not contain crystal water, after forming the film, 3 steps are required.
It is obtained by firing for about 15 minutes at 00°C or about 60 minutes at 250°C, and hexavalent chromium does not dissolve from the film.

Coating Dacromet #100 onto porous metal can be carried out by conventional methods such as dipping, spraying, and roll coating, but in any method, it is necessary to avoid excessive impregnation. ) In the case of the immersion method, remove the excessively impregnated processing liquid using a centrifuge.

(2) In the case of the spray method, determine the discharge amount and determine the operating conditions of the spray gun according to the thickness of the porous body, etc.

(3) In the case of the roll coating method, the amount of feed of the processing liquid and the roll speed may be adjusted.

Any of the above-mentioned known methods can form a rust-preventing film on the metal surface inside the porous body without blocking the pores of the porous body.

Next, examples will be further explained.

Example: A porous sintered aluminum plate with a thickness of 3 mm is coated with Dacromet #
The porous plate was immersed in a solution of 100 RP, and kept for about 2 minutes while moving gently to expel the air in the porous plate. After that, the remaining drops were removed using a centrifuge at a rotation speed of about 1100 RP, and the plate was heated in a firing furnace at 30 RP.
A rust preventive film was obtained by firing at 0°C for 15 minutes.

The ventilation resistance after the treatment was 1.2 times that of the untreated case, and no clogging of the pores that would affect the sound absorption performance was observed.

In order to compare the anti-corrosion ability, a corrosion resistance test was conducted using the salt spray test method described in Monthly SZ 2371 with untreated material and conventional chromate treated material. The results are shown in Table 1, and it can be seen that the products treated according to the present invention have extremely excellent corrosion resistance.

Table 1 <Effects of the Invention> As explained in detail above, the present invention has a porosity of 30 to 60.
% porous Al-based sintered body with a chromic acid coating that does not contain water of crystallization. Porous A has excellent sound absorption properties and corrosion resistance.
By further applying chemical surface treatment to the AI-based sintered body, which is an I-based sintered material and has excellent corrosion resistance, the following effects are produced, and it can be used in locations and applications where there have been problems in the past. The scope of use has further improved.

(The corrosion resistance, which was a disadvantage of 1y porous, is the same as that of the anodic oxide film of ordinary aluminum alloys,
Since it has corrosion resistance over time, it can be used in the same environment as ordinary aluminum alloys.

(2) Since it is heat resistant, it can be used as a soundproofing material in corrosive and hot environments such as exhaust and intake sections.

(3) The anti-corrosion film is almost colorless, so it does not damage the color of the material.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram of an example of a manufacturing process for manufacturing a porous AI-based sintered material according to the present invention. Code 1... Raw material powder 2... Hopper 3... Container 4... Sintering furnace 5... Sintering zone 6... ...Cooling zone 7... Porous AI-based sintered material patent applicant KonuDC Co., Ltd. Agent Patent attorney Yoshikatsu Matsushita Attorney Deputy Fumiyu Shima

Claims (1)

[Claims] The main component is Al, and the additional components are Mg, Mn, Ni,
A porous Al-based sintered material with a porosity of 30 to 60% is produced by sintering a mixed powder containing one or two of Cu and Si in a container that does not react with Al under no pressure and in a non-oxidizing atmosphere. A porous Al-based sintered material characterized in that the body is coated with a chromic acid film that does not contain water of crystallization.