JP2920004B2 - Cast-in composite of ceramics and metal - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cast-in composite of a ceramic and a metal, and more particularly, to a ceramic-metal joint having a high strength even at a high temperature and a stress generated in the ceramic at a low temperature. The present invention relates to a cast-in composite of a ceramic and a metal which has a low strength, a high strength reliability, a simple manufacturing process and a low cost.

[0002]

2. Description of the Related Art In recent years, research and development of mechanical structural parts utilizing the excellent heat resistance, wear resistance, light weight, heat insulation properties, etc. of ceramics have been actively conducted. Many ceramic materials are brittle compared to metals, so it is often difficult to use ceramic materials alone as mechanical structural parts.
Therefore, it is generally known to use it in the form of a composite with a metal. However, many of the ceramic materials having the above-mentioned excellent properties have a small coefficient of thermal expansion as compared with ordinary metal materials for mechanical structures. Sometimes, there is a problem that the holding force between the metal and the ceramic is reduced or a gap is generated. Conversely, if a sufficient holding force at a high temperature is to be obtained, there is a problem that excessive stress is generated in the ceramic at normal temperature and the ceramic is broken.

As a countermeasure, a method has been proposed in which a low thermal expansion metal such as titanium or kovar having a thermal expansion coefficient close to that of ceramics is provided as an intermediate layer between a cast-in metal such as cast iron or an aluminum alloy and ceramics.
These intermediate layer members need to be fitted to the ceramics by means of shrink fitting, press-fitting, brazing, and the like, and there has been a problem that the machining and brazing of the ceramics require many steps and are expensive. In addition, although a method using a ceramic wool, a low-density ceramic calcined layer, or a low-rigidity material such as copper as the intermediate layer has been proposed, there was a problem that sufficient strength could not be obtained. Particularly in the case of moving parts requiring weight reduction, it is advantageous to use an aluminum alloy as a metal material from the viewpoint of weight reduction.However, since the aluminum alloy has a higher thermal expansion coefficient than an iron-based material, The problem due to the difference in thermal expansion coefficient from ceramics was even more serious than when an iron-based material was used.

[0004]

SUMMARY OF THE INVENTION Accordingly, the present invention solves the above-mentioned conventional problems and has a low stress of ceramics at room temperature and does not perform machining of a joint portion of ceramics with metal. It is an object of the present invention to provide an as-cast composite of a ceramic and a metal, which can be manufactured at a low cost with a small number of manufacturing steps and has a sufficient strength.

[0005]

And its object Means for Solving the Problems], according to the present invention, a ceramic, a weight ratio, C 0.3
~ 2.0%, Ni 25-32%, Co 12-20
%, Si 0.3 to 2.0%, Nb 0.2 to 0.8
%, Mg or Ca 0.01 to 0.2%, Mn 1.0%
Hereinafter, the remainder has a composition of Fe containing impurities, and is from room temperature to 4
The thermal expansion coefficient at 00 ° C. is 3.5 × 10 ⁻⁶ / ° C. to 9.0 × 1
Low expansion cast iron is 0 ^-6 / ° C. or, in a weight ratio, C
0.8-3.0%, Ni 30-34%, Co 4.0
~ 6.0%, Si 1.0 ~ 3.0%, Mn 2.0%
Below, sulfur 1.0% or less, phosphorus 1.5% or less, Mg
1.0% or less, the balance has a composition of Fe containing impurities,
Thermal expansion coefficient from room temperature to 400 ° C is less than 9 × 10 ^-6 / ° C.
Thermal expansion coefficient from temperature to 200 ° C is 2 × 10 ⁻⁶ / ° C to 3 × 10
^This can be achieved by an insert-molded composite of a ceramic and a metal, which is made of low-expansion cast iron at ^-6 / ° C.
Further, in the present invention, there is provided a cast-in composite of a ceramic and a metal, in which the above-mentioned low expansion cast iron side is further cast with an aluminum alloy. In addition, the cast-in composite of the present invention, ceramics at a severe heat load site, for example,
It is preferable to use only the lip portion of the combustion chamber opening, the central portion of the combustion chamber, etc., and to apply the ceramic as a ceramic insert piston made of low expansion cast iron.

Hereinafter, the present invention will be described in detail. The cast-in composite of ceramics and metal in the present invention has a composite structure in which C 0.3-2.0% by weight and N
i 25-32%, Co 12-20%, Si 0.3
~ 2.0%, Nb 0.2 ~ 0.8%, Mg or Ca
0.01-0.2%, Mn 1.0% or less, balance is impure
Having a composition of Fe containing material, and having a thermal expansion coefficient of from room temperature to 400 ° C.
Low number is 3.5 × 10 ^-6 /℃~9.0×10 ^-6 / ℃
Expanded cast iron, or C 0.8-3.0 by weight ratio
%, Ni 30-34%, Co 4.0-6.0%, S
i 1.0-3.0%, Mn 2.0% or less, sulfur 1.
0% or less, phosphorus 1.5% or less, Mg 1.0% or less,
The balance has a composition of Fe containing impurities, and is between room temperature and 400 ° C.
Has a coefficient of thermal expansion of 9 × 10 ⁻⁶ / ° C. or less, from room temperature to 200 ° C.
Thermal expansion coefficient and having a low expansion Guru I I part cast ceramic by cast iron which is ^{2 × 10 -6 / ℃ ~3 ×} 10 -6 / ℃.

The reason why it is desirable to use cast iron having the above composition is as follows.
These cast iron graphite during solidification (density of about 2 g / cm ³⁾ is reduced precipitated solidification shrinkage from a liquid metal (density: about 8g / cm ^3), the total shrinkage of up to ambient temperature by the temperature drop Ya Invar alloy It is smaller than low thermal expansion alloys such as Kovar, and in metals other than the low expansion cast iron having the above composition, the thermal expansion coefficient is closer to that of ceramics than ordinary iron-based materials, and the low expansion of the above composition is possible. This is because they do not have suitable characteristics such as cast iron. The term “ceramics” as used herein means silicon nitride (silicon nitride), sialon, which is superior to metal in heat resistance, thermal shock resistance, abrasion resistance, light weight, heat insulation, etc., and has the necessary strength as a mechanical structural member. , Silicon carbide, alumina, aluminum titanate and the like.

In the present invention, as for the relationship between the thickness of the ceramic member and the thickness of the cast-in low-expansion cast iron around it, it is desirable that the average thickness of the cast-in cast iron be smaller than the average thickness of the ceramic member. The reason why such a thickness relationship is desirable is that even in low-expansion cast iron, the average value of the thermal expansion coefficient over a wide temperature range is still larger than the thermal expansion coefficient of ceramics, so that the average This is because a stress is generated due to a difference in the coefficient of thermal expansion between the ceramic and the metal. If the ceramic is too thin, the stress becomes too large and the ceramic is broken. For the same reason, it is more preferable that the stress generated in the ceramic member and the cast iron member is grasped by FEM analysis or the like, and the stress is designed to be sufficiently small. In the present invention, as the outer shape of the ceramic member, it is desirable that the diameter of the opening be smaller than the diameter of the other part. The reason why such an outer shape is desirable is that even at the time of high temperature, the low expansion cast iron has a larger coefficient of thermal expansion than the ceramic member, so that the bonding force between the ceramic member and the low expansion cast iron is reduced. This is to prevent the ceramic member from easily coming out of the low expansion cast iron even at such a high temperature.

When casting ceramics with low-expansion cast iron, the ceramic member is preheated in consideration of the thermal shock temperature of the ceramic member so that the ceramic is not destroyed by thermal shock during pouring. It is preferable to reduce the temperature difference between the two. For this reason, it is desirable to preheat the ceramic member to about 600 ° C. or more, and more preferably to about 800 ° C. or more. When preheating a ceramic member, it is preferable to preheat the ceramic member together with the mold in a state where the ceramic is set in the mold from the viewpoint of work efficiency and further from preventing the ceramic from cooling down. Preferably, a template is used.

In addition, in order to improve the adhesion between the ceramics and the cast iron, it is preferable to pressurize the molten metal immediately after pouring the molten metal into the mold, or to suction and reduce the pressure inside the mold. After the casting, it is gradually cooled in an annealing furnace, and especially at 400 ° C. to 600 ° C., it is effective to increase the holding time to remove the stress of the casting. If the cooling is too fast, the ceramic may be damaged or peeled off due to the stress due to the difference in thermal expansion. From the viewpoint of weight reduction of parts, ceramics
Since it is desirable that as much of the metal part of the metal composite as possible be made of a material having a high (strength / weight) ratio, such as an aluminum alloy, the outside of the ceramic is cast with low expansion cast iron, and the outside is further made of an aluminum alloy or the like. It is desirable to have a structure that can be cast in.

When the outside of the low-expansion cast iron is cast with an aluminum alloy, if the surface of the low-expansion cast iron is subjected to an alfin treatment or an alumet treatment, the cast iron and the aluminum alloy are chemically bonded to each other, and a gap is formed at the interface. It is effective for realizing no strong connection. When casting the ceramics-low expansion cast iron composite with an aluminum alloy, it is desirable to perform pressure casting at a pressure of ^{2 to} 50 kg / cm ² by gas pressure or oil pressure so as not to cause a cast or the like.

[0012]

Hereinafter, the present invention will be described in more detail with reference to the illustrated embodiments, but the present invention is not limited to these embodiments. (Example 1) FIG. 1 shows an example in which the cast-in composite of a ceramic and a metal of the present invention is applied to a crown portion of a two-part piston of a direct injection diesel engine. As shown in FIG. 1, the cavity 1 of the piston combustion chamber has a large heat transfer resistance per weight and has an outer shape that is a thick member made of silicon nitride having an opening having a diameter smaller than that of other portions. By casting this with the low expansion cast iron 3 constituting the piston body, it is possible to reduce the heat transfer loss from the combustion gas in the combustion chamber to the combustion chamber wall surface, and to reduce the heat resistance of the opening of the combustion chamber. This is an example of use for the purpose of improving the problem and preventing problems such as burning and cracking of the opening, which are problems with metal pistons. By adopting such a configuration, a component having a low stress of the ceramics over the entire operating temperature range and a high strength-to-metal-ceramic bonding strength and high reliability can be obtained.

FIG. 2 shows an example of the method of casting in the embodiment shown in FIG. After setting the piston cavity member 1 made of silicon nitride which has not been machined with the outer peripheral surface being a fired surface in a ceramic mold 2, the ceramic mold 2 is heated together and heated to about 900 ° C. in advance. , C 1.2% by weight, Si 1.2
%, Mn 0.3% or less, Ni 28%, Co 14
%, Mg 0.03%, and Nb 0.3% of a low expansion cast iron 3 having a chemical composition of 1400 ° C. were poured into a mold. At this time, in order to improve the adhesion between the silicon nitride piston cavity member 1 and the low expansion cast iron 3, the inside of the mold 2 was suctioned and depressurized through the lower chamber 4. When the temperature of the molten metal has dropped to about 800 ° C., the entire mold 2 is transferred to an electric furnace, cooled down to room temperature, released from the mold 2 to obtain a ceramic-low expansion cast iron composite, and the outer periphery of the low expansion cast iron 3 Was machined.

(Embodiment 2) FIG. 3 shows an example in which the cast-in composite of ceramics and metal of the present invention is applied to a cylinder liner of a diesel engine. That is, the inner surface of the cylinder liner 5 is made of silicon nitride 6 having excellent wear resistance and a small coefficient of friction between the cylinder liner 5 and the metal piston ring, and the outer surface of the cylinder liner 5 is made of low-expansion cast iron 3. This is an application example for the purpose of reducing wear and reducing engine friction loss. FIG. 4 shows a method of manufacturing the component of the embodiment shown in FIG. An insert mold (core) in which a cylindrical silicon nitride member 6 that has not been machined but has been machined on the inner and outer surfaces is set in a mold 7 and the surface is coated with carbon, zircon, or the like. 8 and then preheated to about 400 ° C., C 2.0% by weight, Si
2.3%, Mn 0.3% or less, Ni 32.5%, C
Immediately after pouring a melt of low-expansion cast iron 3 having a chemical composition of 5.4% and Mg 0.03% at a temperature of about 1300 ° C., a pressure of about 40 kg / cm ² was applied to the piston 9 from above with a hydraulic pressure of about 40 kg / cm ² . .
Thereafter, the mold 7 was gradually cooled in an electric furnace to room temperature and then released from the mold 7 to obtain a cast-in composite of ceramic and metal. The outer periphery and upper and lower surfaces of the cast iron of the composite were machined, and the inner surface of the ceramic was ground to obtain a cylinder liner 5.

(Embodiment 3) FIG. 5 shows an example in which a cast-in composite of ceramics and metal of the present invention is applied to a piston of a small direct injection diesel engine. By using silicon nitride having excellent heat resistance for the lip portion 11 provided at the opening of the piston combustion chamber, burning and cracking of the lip portion 11 which are problems with a metal piston can be avoided. This is an application example of the present invention for the purpose of taking local countermeasures against heat load and suppressing an increase in the weight of the entire part by being made of a lightweight aluminum alloy. After obtaining a composite ring-shaped member of the silicon nitride ring (lip portion) 11 and the low-expansion cast iron ring 3 by the same method as in Example 1 or 2, the surface of the low-expansion cast iron 3 is subjected to alumet treatment, After setting this composite ring-shaped member in a metal mold and preheating,
The molten aluminum alloy at ~ 700 ° C was poured. At this time, pressure casting of about 5 kg / cm ² was performed to prevent the occurrence of castes. Then, after cooling to room temperature, the mold was released from the mold, and an outer peripheral portion, a piston ring groove, and a piston pin hole were processed to obtain a piston.

Embodiment 4 FIG. 6 shows an example in which a cast-in-mold composite of ceramics and metal of the present invention comprising silicon nitride, low-expansion cast iron, and aluminum alloy is manufactured in the same process as in Embodiment 3. In other words, using the heat resistance and heat insulation properties of silicon nitride to improve the heat resistance of the upper part of the piston,
Aluminum alloy piston 1 to reduce heat loss
2 is an example in which the upper part of the cylinder 2 is covered with a silicon nitride 18 and is applied to a piston of a small direct injection diesel engine.

(Embodiments 5 to 7) FIGS. 7 to 9 show examples in which ceramics are used only in portions where the thermal load is severe, and show examples in which the ceramics are applied to a two-part piston of a direct injection diesel engine. FIG. 7 shows an example in which silicon nitride having excellent heat resistance is used for the lip portion 11 provided at the opening of the piston combustion chamber, and the silicon nitride is cast with low expansion cast iron 3. Reference numeral 21 denotes an aluminum skirt. FIG. 8 shows a relatively large portion 20 of the entire lower part, including the center of the piston combustion chamber.
An example using silicon nitride having excellent heat resistance and heat insulation is shown below. With this configuration, it is possible to improve the heat insulation of the combustion chamber, increase the gas temperature in the combustion chamber, improve fuel efficiency, and purify exhaust gas while taking measures against erosion and cracks due to heat load. FIG. 9 shows an example in which measures against heat load and the degree of heat insulation of the combustion chamber are further improved by combining the examples of FIG. 7 and FIG. In addition, as in the embodiment of FIG. 9, composing the combustion chamber with a plurality of ceramic members is
Although it was difficult with the conventional shrink-fitting method or the like, the cast-in body of the present invention can be easily implemented. As described above, since the ceramics are divided and used, breakage of each ceramic member can be avoided.

(Embodiment 8) FIG. 10 shows that an inner surface 14 of an exhaust port provided in a cylinder head body 13 of a diesel engine is formed of a tubular aluminum titanate member, and a valve guide 15 is formed of a silicon nitride member. In addition, the valve seat 16 is made of silicon nitride, and the cylinder head plate 17, which is the ignition surface, is made of a silicon nitride disk-shaped member. This is an application example of the ceramic-metal cast-in composite member of the present invention, which aims to reduce the wear of the valve seat 15 and the valve seat 16 and reduce the heat loss to the ignition surface.

[0019]

As described above, according to the cast-in-ceramic composite of the present invention, the stress generated in the ceramic at room temperature is low, and the machining of the joint between the ceramic and the metal can be performed without performing machining. Since it can be manufactured, it is possible to obtain a ceramic-metal composite which has a small number of work steps, is low in cost, and has sufficient ceramic-metal bond strength even at high temperatures. Further, in the present invention, it is easy to use ceramics having low reliability because of brittleness alone as a member for a mechanical structure in a composite structure with a metal, heat resistance, abrasion resistance,
In order to make it practical as a component for machine structure utilizing lightness, heat insulation, etc., especially a ceramic cast-in piston,
Very useful in industry.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view showing one embodiment of a composite of a cast-in ceramic and a metal according to the present invention.

FIG. 2 is a schematic cross-sectional view showing an example of the method of casting in the embodiment shown in FIG.

FIG. 3 is a schematic sectional view showing another embodiment of the insert-molded composite of the present invention.

FIG. 4 is a schematic cross-sectional view illustrating a method of manufacturing the component of the embodiment of FIG.

FIG. 5 is a schematic sectional view showing another embodiment of the insert-molded composite of the present invention.

FIG. 6 is a schematic sectional view showing another embodiment of the insert-molded composite of the present invention.

FIG. 7 is a schematic cross-sectional view showing an embodiment in which ceramics is applied only to a portion where a thermal load is severe.

FIG. 8 is a schematic cross-sectional view showing another embodiment in which ceramic is applied only to a portion where a thermal load is severe.

FIG. 9 is a schematic cross-sectional view showing another embodiment in which ceramic is applied only to a portion where a thermal load is severe.

FIG. 10 is a schematic sectional view showing another embodiment of the insert-molded composite of the present invention.

[Description of Signs] 1 piston cavity, 2 ceramic mold, 3
Low expansion cast iron, 4 lower chamber, 5 cylinder liner, 6 silicon nitride, 7 mold, 8 insert mold, 9 piston, 11 lip, 12 piston body, 13 cylinder head body, 14 exhaust port inner surface, 15 valve guide , 16 Valve seat, 1
7 cylinder head plate, 18 silicon nitride, 20 lower part of combustion chamber, 21 aluminum skirt

 ──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-53-79112 (JP, A) JP-A-60-216966 (JP, A) JP-A-58-210149 (JP, A) JP-A-2- 298236 (JP, A) JP-A-1-306540 (JP, A) JP-A-1-80650 (JP, U)

Claims (3)

(57) [Claims] 1. The method according to claim 1, wherein the ceramics is C 0.3 by weight.
~ 2.0%, Ni 25 ~ 32%, Co 12 ~ 20%,
Si 0.3-2.0%, Nb 0.2-0.8%, M
g or Ca 0.01 to 0.2%, Mn 1.0% or less
The lower part has a composition of Fe containing impurities, and is room temperature to 40%.
The coefficient of thermal expansion at 0 ° C. is 3.5 × 10 ⁻⁶ / ° C. to 9.0 × 10
A cast-in composite of metal and ceramics, which is cast in low-expansion cast iron at ^-6 / ° C. 2. A ceramic material, wherein C 0.8
-3.0%, Ni 30-34%, Co 4.0-6.0
%, Si 1.0 to 3.0%, Mn 2.0% or less, sulfur
Yellow 1.0% or less, phosphorus 1.5% or less, Mg 1.0%
Hereinafter, the remainder has a composition of Fe containing impurities, and is from room temperature to 4
Coefficient of thermal expansion at 00 ° C. is 9 × 10 ⁻⁶ / ° C. or less, room temperature to 20
When the coefficient of thermal expansion at 0 ° C. is 2 × 10 ⁻⁶ / ° C. to 3 × 10 ⁻⁶ / ° C.
A composite body of ceramic and metal, which is made of low expansion cast iron . 3. A low-expansion cast iron side further characterized in that they insert casting of an aluminum alloy according to claim 1 or 2 ceramics and insert casting complex metal according.