JPH101380A - High-strength vibration damping material and method of manufacturing the same - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To provide a high-damping material having high strength and a manufacturing method thereof. SOLUTION: An aluminum-zinc-based damping alloy is injected into a porous silicon nitride sintered body made of a silicon nitride columnar crystal having an average minor axis of 1 μm or less and an aspect ratio of 5 or more. This vibration damping material is formed by adding 5 to 15% by weight of a sintering aid to a silicon nitride powder having an average particle size of 1 μm or less and molding the molded product into a predetermined shape.
Heat at a temperature of 1800 ° C, open porosity is 30-70% by volume
Forming a silicon nitride porous sintered body in which the minor axis of the columnar silicon nitride particles is 1 μm or less and the aspect ratio is 5 or more, and in the open pores of the sintered body, the aluminum-zinc-based damping alloy It is produced by injecting a melt.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high-strength vibration damping material and a method for manufacturing the same. More specifically, the present invention relates to a high-strength vibration damping material using silicon nitride ceramics as a reinforcing material, and a method for manufacturing the same.

[0002]

2. Description of the Related Art A vibration damping material (also referred to as an anti-vibration material) is a material that absorbs the energy of mechanical vibration and does not transmit it to others, that is, a material that has a large internal friction or a large damping capacity that converts vibration energy into heat. . Among metal materials, it is known that a soft material such as lead has a large damping capacity, while a hard material such as carbon steel has a small damping capacity. In general, in applications where vibration or noise is a problem, a high-strength material is often used.Therefore, a material having a somewhat high strength and a large damping capacity that can be used as a structural material is required. As one of such damping material metals, an aluminum-zinc alloy is known (for example, a precision vibration isolation handbook,
(See, NTS, 1987).

[0003]

However, although this aluminum-zinc alloy is lightweight and has a certain degree of strength, it has a tensile strength of 350 MPa or less. The strength is not enough to use as a piston, piston pin, cylinder liner, etc.
There is a problem that it cannot be used for such an application.

[0004]

According to a first aspect of the present invention, there is provided a porous silicon nitride sintered body, comprising:
In a vibration damping material comprising an aluminum-zinc damping alloy present in 70% by volume and the remainder of the open pores of the sintered body,
The porous silicon nitride sintered body is made of silicon nitride columnar crystals having an average minor axis of 1 μm or less and an aspect ratio of 5 or more.

According to a second aspect of the present invention, in the method for producing a vibration damping material, a sintering aid is added to silicon nitride powder having an average particle size of 1 μm or less by 5 to 15% by weight, Forming a powder, shaping the mixed powder into a predetermined shape, 1550-1800 in an inert atmosphere
To form a silicon nitride porous sintered body having an open porosity of 30 to 70% by volume, a minor axis of columnar silicon nitride particles of 1 μm or less, and an aspect ratio of 5 or more; After the porous sintered body is preheated, a step of injecting a molten aluminum-zinc damping alloy into the open pores of the sintered body is performed.

The vibration damping material of the present invention has a structure in which an aluminum-zinc damping alloy having vibration damping properties is occupied in voids of a porous sintered body in which β-type silicon nitride columnar crystals are three-dimensionally bonded. Therefore, the strength can be increased without impairing the vibration damping characteristics due to the presence of the porous sintered body.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION The vibration damping material of the present invention is obtained by increasing the strength of an aluminum-zinc damping alloy by forming a composite material using a porous silicon nitride sintered body as a reinforcing material. This porous silicon nitride sintered body has an average minor axis of 1 μm.
It is necessary to be a silicon nitride columnar crystal having an aspect ratio of 5 or less. This average minor axis is 1μ
If it exceeds m, the strength of the obtained composite material will decrease.
If the aspect ratio (ratio of major axis / minor axis) is less than 5, the obtained vibration damping material will have reduced strength.

It is necessary that the porous silicon nitride sintered body composed of the columnar crystals occupies 30 to 70% by volume of the vibration damping material.
If the sintered body is less than 30% by volume, the strength of the obtained vibration damping material is not sufficient. On the other hand, if it exceeds 70% by volume, metal cannot be sufficiently introduced, and as a result, sufficient vibration damping property cannot be obtained. .

The metal to be injected into the porous silicon nitride sintered body is an aluminum-zinc-based damping alloy which has sufficient damping characteristics and is lightweight and can be cast. This aluminum
Zinc-based damping alloys include silicon, copper, etc. in addition to aluminum and zinc, such as Cosmal-ZM-11, Cosmal-ZM-3, Supe
r Cosmal and Super Cosmal II are well known. The chemical composition of these Cosmal-Z is shown in Table 1 below.

[0010]

[Table 1]

This metal is used to form voids in the porous silicon nitride sintered body.
Preferably, it occupies 98% or more. If the proportion occupied by the metal is low, vacancy defects occur in the composite material, the strength is reduced, and sufficient damping properties may not be obtained.

The vibration damping material of the present invention is manufactured by sintering silicon nitride powder and injecting a metal into the obtained porous sintered body. The raw material silicon nitride powder needs to have an average particle size of 1 μm or less. If the average particle size of the powder exceeds 1 μm, the short diameter of the columnar silicon nitride crystal obtained by sintering cannot be reduced to 1 μm or less.

A sintering aid is used when sintering the silicon nitride powder. This sintering aid promotes columnarization of the silicon nitride particles, and an oxide of a rare earth metal, for example, yttria (Y ₂ O ₃ ), scandia (Sc ₂ O ₃ ), or the like can be used. The amount of the sintering aid used is preferably 5 to 15% by weight of the silicon nitride powder. If it is less than 5% by weight, columnar crystals of silicon nitride do not grow, and if it exceeds 15% by weight, the solidified liquid phase produced by the sintering aid during sintering increases, resulting in deterioration of the properties. Because there is.

The total amount of metal impurities (metal oxides) in the mixture of the silicon nitride powder and the sintering aid used for sintering is 0.
It is preferably at most 01%. These impurities include not only silicon nitride powder as a raw material and a sintering aid, but also impurities mixed from a container or the like during mixing. Examples of the impurities include CaO, MgO, Al ₂ O ₃ , and SiO _{2. If} these impurities exceed 0.01%, the melting point of the liquid phase decreases due to the presence of the impurities, and sintering proceeds. Therefore, a desired open porosity may not be obtained in the porous silicon nitride sintered body. Therefore, the purity of the silicon nitride powder and the sintering aid is preferably at least 99.9% or more. The above metal impurities are usually used as sintering aids, but the present invention is characterized in that the progress of sintering is controlled and reduced as much as possible in order to obtain a desired open porosity. is there. That is, 0.01% of metal impurities
If added in excess of sintering, sintering will proceed and the open porosity will be less than 10%.

The heating temperature during this sintering is 1550-1800
° C. If the temperature is lower than 1550 ° C., the columnar crystals of silicon nitride do not grow. If the temperature exceeds 1800 ° C., the columnar crystals of silicon nitride become thicker than 1 μm, and the strength of the obtained vibration damping material decreases. Further, a desired open porosity cannot be obtained in the porous silicon nitride sintered body.

By this sintering, a porous sintered body having a closed porosity of 2% by volume or less, an open porosity of 10 to 65% by volume, a β silicon nitride columnar crystal having a minor axis of 1 μm or less, and an aspect ratio of 5 or more. Is obtained. Since metal cannot be injected into the closed pores and causes pore defects in the composite material, the closed porosity is preferably 2% or less to obtain a desired strength. Satisfactory strength can be obtained by setting the open porosity to 30 to 70% by volume. In particular, the open porosity is preferably set to 50% by volume or more. This is because a highly reliable material having a large Weibull coefficient, that is, a small variation in strength, can be obtained.

A metal is injected into the thus obtained porous silicon nitride sintered body by a conventional method, so that the metal is occupied in the open pores. As a method of injecting the metal, it is preferable to perform the injection at a pressure of about 1 ton by a high pressure casting (squeeze casting) method. It is also possible to use the capsule HIP method. In this case, the capsule uses a metal foil having a higher melting point than the metal to be injected, for example, a SUS foil.

As a composite material of a metal and a ceramic such as the vibration damping material of the present invention, a metal-based composite material (MMC) has been conventionally known. Although this conventional composite material uses ceramic whiskers as a reinforcing material, the whisker content in the production of ceramic fiber preforms
30% was marginal. The vibration damping material of the present invention uses a columnar crystal of silicon nitride as a material corresponding to the whisker, and the content of the columnar crystal can be increased to about 30 to 70%. A material having high strength can be provided.

[0019]

EXAMPLES Examples 1 to 7 and Comparative Examples 1 to 5 silicon nitride powder (average particle size 0.2 μm, pregelatinization rate almost 100%,
Yttria (Y ₂ O)
₃ ) Powder (average particle size 0.3 μm, purity 99.9%) was mixed in ethanol with the addition amount shown in Table 2 below. This mixing was performed using a silicon nitride ball mill and a ball manufactured by sintering using a very small amount of Y ₂ O ₃ and Al ₂ O ₃ as a silicon nitride powder used in this example and a sintering aid. . After drying this mixture, it was pressure-molded under the conditions shown in Table 2, and the obtained molded product was packed in a thin rubber bag, vacuum-sealed, and
It was molded by IP to obtain a molded body of 50 × 300 × 10 mm.

The compact was heated in a furnace in a nitrogen atmosphere at atmospheric pressure under the conditions shown in Table 2. The heating rate was 5 ° C./min, and the holding time at the maximum temperature was 4 hours. The porosity of the porous silicon nitride based sintered body thus obtained and the average minor axis and aspect ratio of β silicon nitride columnar crystals were determined. The porosity is n
The relative density obtained by dividing the bulk density of the porous silicon nitride sintered body obtained by the Archimedes method using -butyl alcohol by the theoretical density was subtracted from 100%. The average minor axis and aspect ratio were determined by separating columnar crystals in the porous silicon nitride sintered body one by one in heated hydrogen fluoride and observing them with a microscope. Table 2 shows the results.

The above porous silicon nitride sintered body is put in a mold, and an aluminum-zinc alloy (60% by weight Al-6% by weight Si-34% by weight zinc) melted at 700 ° C. in an inert atmosphere. It was pressurized to 1000 kgf / cm ² and injected into the porous silicon nitride sintered body. A test piece was cut out from the vibration damping material obtained in this manner, and after processing the test piece in accordance with JIS Z 2201,
The tensile strength was measured according to 2241. The damping characteristics were measured in accordance with JIS G 0602 "Testing method for vibration damping characteristics of damping steel sheet". The loss coefficient η was determined from the curve by the half width method. Table 2 shows the results. Here, Comparative Example 1 is a molded body formed only of an aluminum-zinc alloy without using a porous silicon nitride sintered body.

[0022]

[Table 2]

Examples 8 to 9 and Comparative Example 6 A porous silicon nitride sintered body was produced under the conditions shown in Table 2 in the same manner as in the above example, and the composition of the aluminum-zinc alloy was changed. % Al-6% by weight Si-
54% by weight zinc (Example 8), 20% by weight Al-6% by weight S
I-74 wt% zinc (Example 9), 94 wt% Al-6 wt% Si (Comparative Example 6), melted at 700 ° C., 1000 kg
pressurized to f / cm ² and injected into the porous silicon nitride sintered body,
The tensile strength and the loss factor were determined in the same manner as above. Table 2 shows the results.

[0024]

According to the present invention, by forming a composite of a high-strength porous silicon nitride sintered body as a reinforcing material, the damping characteristics of an aluminum-zinc-based damping alloy can be reduced.
The strength can be greatly improved, and the range of application to structural members such as structural members for automobile engines can be expanded.

Continued on the front page (51) Int.Cl. ⁶ Identification number Agency reference number FI Technical display location F16J 1/16 F16J 1/16 10/04 10/04

Claims (2)

[Claims] 1. A porous silicon nitride sintered body comprising 30 to 70% by volume of a porous silicon nitride sintered body and a balance of aluminum-zinc-based damping alloy present in open pores of the sintered body. A high-strength vibration-damping material comprising a silicon nitride-based columnar crystal having an average minor axis of 1 μm or less and an aspect ratio of 5 or more. 2. The following steps: adding 5 to 15% by weight of a sintering aid to a silicon nitride powder having an average particle diameter of 1 μm or less to form a uniform mixed powder, and forming the mixed powder into a predetermined shape; The compact is heated in an inert atmosphere at a temperature of 1550 to 1800 ° C., the open porosity is 30 to 70% by volume, the minor axis of the columnar silicon nitride particles is 1 μm or less, and the aspect ratio is 5 Forming a silicon nitride porous sintered body as described above, after preheating the porous sintered body, injecting a molten aluminum-zinc damping alloy into the open pores of the sintered body. The method for producing a high-strength vibration damping material according to claim 1.