JPH02254132A - Manufacture of iron porous body used for reinforcing metallic parts for pressure casting of aluminum or the like - Google Patents

Abstract

PURPOSE:To manufacture the iron porous body used for reinforcing metallic parts for pressure casting at low cost by packing iron powder into a heat- resistant vessel at specified bulk density and sintering the powder together with the vessel at a high temp. in a low oxygen atmosphere. CONSTITUTION:Reduced iron powder 1 (having about 1 to 1000mu grain size and about 45mu average grain size) is packed into a vessel 2 made of stainless steel into a cone shape by free-falling. The vessel 2 is vibrated and leveled into a planar shape to regulate the bulk density of the packed iron powder 1 to about 1.5 to 4.3g/cm<2>, which is sintered at about 1100 to 1150 deg.C in a mixed atmosphere of H2 and N2 while it is still in the vessel 2 to form a plate-shaped iron porous body 1a. The iron porous body 1a is preliminarily heated to about 100 to 300 deg.C and is charged to a mold 3 for casting, to which Al molten metal is poured from a sprue 3a, then, pressure of about 400 to 1000kg/cm<2> is applied and solidifying is thereafter executed, so that the composite material 4 infiltrated with an aluminum material 5 perfectly into the core part of the iron porous body 1a can be formed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to press-casting gold of aluminum, magnesium or zinc used for parts such as screws in internal combustion engines. The present invention relates to a method for producing a porous iron body used to enhance the wear resistance, rigidity, and various physical performances of metal parts for die casting.

[Conventional technology]

Recently, in pressure casting metal parts such as aluminum used for screws in internal combustion engines, in order to amplify the various mechanical strengths of the pressure casting metal parts, Embedding a porous metal body inside a metal part for pressure casting, that is, placing the porous metal body in a casting mold for casting the metal part for pressure casting such as aluminum. After this, a molten metal for pressure casting such as aluminum is placed in a pressurized state (approximately 400 kg) in the casting mold.
The metal parts for pressure casting are made into a composite material of the metal for pressure casting and a porous metal body by injecting the pressure casting metal parts at a pressure of more than /cra.

In this case, JP-A-51-21 as the prior art
No. 2159 and Japanese Unexamined Patent Publication No. 118367/1988 propose the use of a porous nickel material such as nickel foam as a porous metal material for reinforcing the aluminum cast parts.

[Problem to be solved by the invention]

In this prior art, a Nikenol porous body is used as a porous metal body by electroplating nickel inside a foamed synthetic resin, and then burning out the synthetic resin by heating. However, nickel itself is quite expensive and has a high specific gravity, which increases the manufacturing cost and weight.Moreover, the coefficient of thermal expansion of nickel is Because of its large size, the effectiveness of suppressing the thermal expansion of the aluminum material by the porous nickel material was low. Furthermore, sufficient reinforcement cannot be achieved in terms of wear resistance, rigidity, and other physical performance.

Therefore, H
First, it is thought that it would be better to use a porous body of iron, which is inexpensive and has a small coefficient of thermal expansion.

However, when manufacturing porous iron bodies, it is not possible to foam by direct foaming using a foaming agent, and nickel is not added inside the foamed synthetic resin, such as Nikesol described in the above-mentioned publication. It is not possible to adopt a method of electroplating and then burning out the synthetic resin by heating.

Therefore, when manufacturing porous iron bodies, as is well known, iron powder of an appropriate particle size is pressed under high pressure in a mold to solidify it into a predetermined shape, and then molded into a metal mold. It must be taken out of the mold and sintered at high temperature, but according to this sintering method, the compressive fracture strength of the porous iron material is quite high, so when molten aluminum material is injected into the casting mold at high pressure, Although this iron porous body has the advantage that crushing failure does not occur, the iron porous body has a high bulk density and a low porosity, so the permeability of molten aluminum material into the porous structure of the iron porous body is low. If the penetration is extremely poor and only a very shallow portion of the surface is penetrated, the weight of the composite member will increase significantly.

Conventionally, when sintering a porous iron body, graphite powder was used to increase the strength of the iron porous body, and
It is common practice to mix copper powder into each material for the purpose of reducing shrinkage during sintering.

[Means to solve the problem]

In order to achieve this objective, the present invention uses iron powder of appropriate particle size,
After filling a heat-resistant container by free-falling, the bulk density of the iron powder filled in the container is reduced to approximately 1.5 to 1.5 by applying vibration for an appropriate period of time without pressurizing.
4.3 g/crA, and then the iron powder was
It was decided to sinter the material in a heat-resistant container at a high temperature in a low oxygen atmosphere or a reducing atmosphere.

[For production]

When iron powder of an appropriate particle size is filled into a container by free fall, a cavity is formed due to the bridging phenomenon of the iron powder, but
After the iron powder is filled into the container by free fall, the bridging phenomenon can be broken by applying vibration for an appropriate period of time, so that a porous body with a uniform structure is created without the generation of uneven and huge cavities. can be obtained.

In addition, iron powder can be filled into a container by free-falling and then vibrated for an appropriate period of time without being pressurized, so that it does not become densely packed. By sintering the iron powder at high temperature in a heat-resistant container, the porosity can be increased. It can be solidified into the shape of the container.

In other words, since a porous iron body with a low bulk density and high porosity can be manufactured in a predetermined shape, this porous iron body can be used as a casting metal for pressure casting metal parts such as aluminum. When the molten metal for pressure casting is filled into the casting mold under high pressure after being placed in the mold, the molten metal for pressure casting will enter the porous structure of the porous iron body. It will penetrate deep.

In this case, the depth at which the molten metal for pressure casting penetrates into the porous structure of the porous iron body is inversely proportional to the bulk density when the iron powder is filled into the container;
If the bulk density exceeds 4.3 g/cl, the penetration depth of the molten aluminum alloy into the iron porous body will decrease rapidly, so the lower limit of the bulk density when filling the iron powder into a container is The value should be 4.3g/C.

On the other hand, the high density when filling the container with the iron powder is 1.5 g/cn! If the pressure is lower than Since cracks will occur, the lower limit of the bulk density when filling the container with the iron powder should be set to 1.5 g/ent.

〔Effect of the invention〕

Therefore, according to the present invention, a porous iron body for reinforcing pressure casting metal parts such as aluminum can be used without causing a significant increase in weight of the pressure casting metal parts, and without causing a significant increase in the weight of the pressure casting metal parts. It can be manufactured under conditions that reliably improve the wear resistance, rigidity, and various physical properties of metal parts for pressure casting, and the raw material cost is lower than that of porous nickel bodies. °゛In addition to being cheap, there is no need to press the iron powder into a predetermined shape in a mold as in the conventional manufacturing method of iron porous bodies, which greatly reduces the cost required to manufacture the iron porous bodies. It has an effect that can be reduced to

〔Example〕

Hereinafter, an example of the present invention will be described in which aluminum material is used as the metal for pressure casting.

First, as iron powder, the brand name KIP2 is available from Kawasaki Steel Corporation.
Using reduced iron powder (particle size 1 to 1000 microns, average particle size 45 microns) sold as 55M, this reduced iron powder 1 was prepared with width dimension W and depth dimension as shown in Fig. 1. The mixture is filled into stainless steel containers 2 each having a depth of 5 Qim and a depth H of 15 mm in a chevron shape as shown in FIG. 2 by free falling.

Next, the container 2 was subjected to vibrations with an amplitude of 0.2 to 511 and a frequency of 10 Hz for about 2 minutes (4 minutes), and the iron powder 1 was leveled into a flat shape as shown in FIG. At the same time, the bulk density of the iron powder filled in the container 2 is 2.2 g/c
It became Po.

Therefore, while the iron powder 1 was kept in the container 2, the temperature was set to about 1100'C to 1150'C and R.
x gas (tlz: Nx: Co =30.8
By sintering for about 1 hour in an atmosphere of +45.0:21.7>, as shown in FIG.
A plate-like porous iron body 1a having a diameter of 15n+ was obtained.

As shown in FIG.
JIS standard AC
8A molten aluminum alloy is brought to a molten state at 780°C and poured into the casting mold 3 through the sprue 3a.
After applying a pressure of 00 to 1000 kg/Cta, it solidified.

Then, the composite material 4 obtained by this casting was taken out from the casting mold 3, and its cross-sectional structure was observed under a microscope. As shown in FIG. 6, the aluminum material 5 was
It was observed that the solution had completely penetrated into the core of the porous iron body 1a.

In addition, the wear resistance of the composite material 1b obtained here can be improved by 100% at room temperature and by 800% at 400°C, compared to the aluminum material of JIS standard AC8A. The tensile strength of material 1b was improved by about 20% at room temperature and by 100% at 400° C. compared to the JIS AC8A aluminum material.

Next, the present inventors have determined that the bulk density when the iron powder 1 is filled into the container 2 is related to the permeability of the molten aluminum into the porous structure of the iron porous body 1a obtained by the manufacturing method. In order to find out the effect of iron powder 1 in the container 2, we investigated the effect of the iron powder 1 on the iron porous bodies manufactured by varying the bulk density (however, it is not possible to increase the bulk density by just applying vibration to the container 2). Since it was not possible to make the density larger than 4.5g/cA, the bulk density was set to 4.5g/cn.
1 or higher, we decided to apply pressure and press after applying vibration), and inject molten aluminum under pressure under the same conditions as described above, allowing the molten aluminum to penetrate into the porous structure of each porous iron body. The depth measurement results are as shown by curve A in Figure 7, and the penetration depth of molten aluminum is determined by the bulk density of 4.3.
g/Cn! There was a sharp change after 4.3g/
When it exceeds cJ, it is extremely small, but the bulk density is 4.3g/a+! Below that, the size increases rapidly.

From this result, the upper limit of the bulk density when filling the container 2 with the iron powder 1 is 4. ．． It should be 3g/cl. However, even if the bulk density when filling the iron powder 1 into the container 2 is 4.3 g/cJ, it is still 1.5 g/CI.
When filling the container 2 with iron powder 1, it was found that cracks were generated in the iron porous body 1a due to pressurized injection of molten aluminum alloy into the casting mold when the value was less than +. It was found that the lower limit of the bulk density should be 1.5 g/cd.

[Brief explanation of drawings]

The drawings show embodiments of the present invention; Fig. 1 is a perspective view of a heat-resistant container, Fig. 2 is a cross-sectional view when iron powder is filled into the container in free fall, and Fig. 3 is a diagram showing a case in which the container is subjected to vibrations. 4 is a perspective view of the iron porous body, FIG. 5 is a sectional view showing the state of casting, and FIG. 6 is a sectional view of the composite material. FIG. 7 is a diagram showing the relationship between the bulk density in a porous iron body and the penetration depth of an aluminum alloy. 1... Iron powder, 1a... Iron porous body, 2... Heat resistant container, 3... Casting mold, 4... Composite material,
5...Aluminum material. Patent applicant Daihatsu Motor Co., Ltd.

Claims (1)

[Claims] (1) After filling iron powder with an appropriate particle size into a heat-resistant container by free-falling, vibration is applied for an appropriate period of time without pressurizing the iron powder. The bulk density is approximately 1.5 to 4.3 g/cm^3,
Next, the iron powder is placed in a heat-resistant container and sintered at high temperature in a low oxygen atmosphere or a reducing atmosphere, which is used to strengthen metal parts for pressure casting such as aluminum. A method for manufacturing a porous iron body.