JPH05123852A - Composite parts cast-in with ceramics and metal - Google Patents

Abstract

PURPOSE:To decrease the stresses in the composite parts by specifying the shape of a ceramic member and casting-in a low thermal expansion alloy of an iron system. CONSTITUTION:The outside shape in the axial section of the ceramic member 1 is formed to a tapered shape 3 of the size increasing gradually from the side of the ceramic member not clad with a metal toward the side of the ceramic member coated with the metal. A stepped shape 4 is provided in at least a part of the ceramic member in contact with the metal and is cast-in with the low thermal expansion alloy 2 of the iron system. The adhesion of the ceramic member and the metal is enhanced in this way and the generation of the high stresses in the composite parts is obviated even if a difference of thermal expansions arises between both. The destruction of the ceramic member does not arise.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ceramic-metal cast stuff composite part in which a ceramic member is cast by a metal.

[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 insulating properties and the like of ceramics have been actively conducted. Since many ceramic materials are more brittle than metals, it is often difficult to use ceramic materials alone as mechanical structural parts, and therefore it is generally known to be used in the form of a composite with a metal. .. As a method for compounding such ceramics and metals, cast dolls are an inexpensive and effective method.

[0003]

However, when casting is performed using a ceramic member having a straight shape in which the axial cross-sectional outer shape is not tapered, the force for pressing the ceramic member of the direction vector due to metal shrinkage is weak. Therefore, there is a problem that a gap is generated at the boundary between the ceramic member and the metal. In addition, since many ceramic materials have a smaller coefficient of thermal expansion than ordinary metal materials for mechanical structures, parts whose operating temperature changes, particularly parts used at high temperatures, have a metal and a ceramic member at high temperatures. A gap is likely to be formed at the boundary portion, which reduces the holding force of the ceramic member and may cause the ceramic member to slip out. The present invention has been made in view of the above problems of the prior art, and an object thereof is to have high adhesion between a ceramic member and a metal, and to have a high holding force even when used in a high temperature range. It is an object of the present invention to provide a highly reliable ceramic-metal cast-gurg composite component which can be maintained and in which the ceramic member does not come out even when metal fatigue due to repeated stress occurs or when an excessive force is applied.

[0004]

According to the present invention, there is provided a composite component in which a ceramic member is cast around a metal, and the axial cross-sectional outer shape of the ceramic member is from the ceramic member side not covered with the metal. A ceramic-metal cast gurney composite part characterized by having a taper shape that gradually becomes thicker toward the ceramic member side coated with metal, and having a stepped shape in at least a part of the ceramic member that contacts the metal. Provided. Further, in the present invention, it is preferable that the contact surface between the ceramic member and the metal is in a slidable contact state. Further, in the present invention,
The taper angle is preferably 10 ° to 45 °.

[0005]

According to the present invention, as described above, the axial cross-sectional outer shape of the ceramic member is tapered so as to gradually increase from the ceramic member side not covered with metal to the ceramic member side covered with metal. As a result, the direction vector of metal shrinkage works in a direction that strongly presses the ceramic member, so that high adhesion can be obtained without creating a gap at the boundary portion, and high holding force is maintained even when used in a high temperature range. .. Furthermore, since at least a part of the ceramic member has a stepped shape, the ceramic member does not come out even when metal fatigue due to repeated stress occurs or when excessive force is applied.

If the contact surface between the ceramic member and the metal is not in a bonded state by a chemical reaction but in a slidable contact state, even if a difference in thermal expansion occurs between the ceramic and the metal, high stress is not generated in the composite part. It does not occur and the ceramic member is not destroyed.

In the present invention, the taper angle of the ceramic member is preferably 10 ° to 45 °. If the taper angle is less than 10 °, the direction vector of the metal shrinkage exerts a weak force on the ceramic member, a gap 15 is formed at the boundary between the ceramic member 1 and the cast metal 2, as shown in FIG. When used, ceramic member 1
Due to the difference in the coefficient of thermal expansion between the cast metal 2 and the cast metal 2, a gap is likely to occur at the boundary portion, not only the holding force of the ceramic member 1 is lowered, but also the ceramic member 1 may come out. On the other hand, when the taper angle exceeds 45 °, as shown in FIG.
As shown in 0, a sharp portion 16 is formed in the shape of the metal portion, and there is a risk of cracking the metal portion.

The cast metal used in the present invention is preferably a cast iron alloy having a small shrinkage during casting and a low melting point. Above all, an alloy having a thermal expansion coefficient of 6 × 10 ^-6 / ° C. or less is used in consideration of high temperature use. desirable. Examples of such cast iron alloys include Japanese Patent Application No. 01-119952 or Japanese Patent Publication No. 60.
The alloys shown in No. 51547 can be mentioned.
Specifically, in weight ratio, (a) C 0.8 to 3.0% (more preferably 1.5 to
2.5%), Si 0.8 to 3.0% (more preferably 1.5 to 2.5%), Mn 2% or less, Ni 30 to 3
4% (more preferably 31 to 32%), Co 4 to 6
%, Mg or Ca 0.02 to 0.08%, the balance Fe (b) C containing impurities 0.3 to 2.0% (more preferably 0.8 to
1.2%), Si 0.3 to 2.0% (more preferably 1.0 to 1.2%), Mn 1% or less, Ni 26 to 3
0% (more preferably 28 to 29%), Co 12 to 1
6%, Mg or Ca 0.02-0.08%, Nb
It is preferable to have a composition of Fe of 0.2 to 0.8% and the balance being Fe containing impurities.

The ceramic member used in the present invention is not particularly limited. For example, silicon nitride, silicon carbide,
Examples include zirconia, but when used at high temperatures,
Either silicon nitride or silicon carbide is preferable. Further, it is preferable that the outer ceramic shape of the portion that is cast around the metal has an R shape with rounded edges for stress relaxation. In the present invention, the stepped shape also includes a concave shape and a convex shape.

[0010]

EXAMPLES Next, the present invention will be described in more detail based on examples, but the present invention is not limited to these examples.

1 to 6 are longitudinal sectional explanatory views showing an embodiment of the present invention. FIG. 1 is an example in which a ceramic member 1 having a small deep recess 5 in the upper portion and a taper portion 3 and a stepped portion 4 continuously provided is cast with metal 2 except for the upper surface thereof. .. FIG. 2 shows an example in which a ceramic member 1 having a large deep recess 5 in the upper portion and a tapered portion 3 and a stepped portion 4 sandwiching a cylindrical body portion 6 is cast around. Figure 3
Is a cast member of a ceramic member 1 having a large shallow depression 5 in the upper portion, a tapered portion 3 and a stepped portion 4 are continuously provided, and a tapered barrel portion 3'is continuously provided below the tapered portion 3 and the stepped portion 4. An example is shown. Further, FIG. 4 shows an example of a cast member of a ceramic member 1 having a projecting portion 7 that is not cast in the upper portion, and a tapered portion 3 and a stepped portion 4 provided below the projecting portion 7 with a cylindrical body portion 6 sandwiched therebetween. is there. In FIG. 5, instead of providing the stepped portion, the concave portion 8 is provided.
6 is an example of a cast member of the ceramic member 1 provided with FIG.
Shows an example of a cast member of the ceramic member 1 in which the convex portion 9 is provided instead of the stepped portion. 1 to 6 of the present embodiment, for convenience of explanation, the side of the ceramic member not covered with metal is set to the upper side. However, when the ceramic-metal cast gurney composite component of the present invention is actually used, it is optional. Of course, it can be oriented.

(Examples and Comparative Examples) The ceramic members 1 having the taper angle θ and the stepped portion dimension l shown in Table 1 were respectively C 1.2%, Si 1.2% and Mn in weight ratio.
0.3% or less, Ni 28%, Co 14%, Mg
0.03%, Nb 0.3%, the balance is casted with a metal melt of an iron-based low thermal expansion alloy having a composition of Fe containing impurities,
After cooling, the obtained ceramic-metal composite component was examined for the presence of a crack at the boundary between the ceramic member and the metal and for the presence of a metal crack. Further, as shown in FIG. 7, a hole 12 is made in the bottom metal portion of the ceramic-metal composite part, the hole 12 is fixed upward and fixed to the holding jig 11, and a load F is applied to the ceramic member 1 through the hole. And the punching load was measured. The results are shown in Table 1.

[0013]

[Table 1]

From the above examples and comparative examples, the following can be seen. Test No. In the composite component of 7, since neither the tapered shape nor the stepped portion is provided, a gap is generated at the boundary portion,
The pushing load is also very small. Test No. In the composite component of No. 8, since the taper angle is too small, a slight gap is generated at the boundary portion, and since the stepped portion is not provided, the punching load is very small. Test No. 9-14 composite parts
Since a proper taper angle is provided, no gap is generated at the boundary portion, but since there is no stepped portion, the punching load is small. Test No. The composite parts of 15 and 16 are
Since the taper angle is too large, cracks occur in the metal part, and since there are no stepped parts, the punching load is a little small. Test No. The composite parts of 17 and 18 are
Since the stepped part is provided, the pushing load is large, but
Since no tapered shape was provided, a gap was generated at the boundary. Test No. In the composite parts of 19 and 20, the stepped part was provided, so the pushing load was large, but the taper angle was too large, so cracks occurred in the metal part. In contrast to these comparative examples, the test No. which is an example of the present invention. 1 to
In the composite component of No. 6, cracks in the boundary portion and the metal portion do not occur, and the punching load is large.

(Application Example) FIG. 8 is a vertical cross-sectional explanatory view showing an example in which the ceramics-metal cast gurney composite part of the present invention is applied to a piston of a diesel engine. A cavity 13 made of Si ₃ N ₄ having a taper angle of 15 ° and a stepped portion size of 5 mm was set in the mold, and a metal melt of an iron-based low thermal expansion alloy having the same composition as that used in Examples and Comparative Examples was poured. Then, after cooling, it was taken out from the mold to obtain a ceramics-metal cast stuffed body composite. After that, the metal outer periphery, the piston pin hole 14, the piston upper surface and the like were machined to obtain a diesel engine piston. As a result of incorporating this diesel engine piston into an actual engine and performing a durability test, sufficient durability could be confirmed.

[0016]

As described above, according to the present invention,
The following effects are exhibited. (A) Since the direction vector of metal shrinkage works in a direction that strongly presses the ceramic member, there is no gap at the boundary between the ceramic member and the metal, and high adhesion is obtained. Maintained. (B) Since it has a stepped shape, the ceramic member does not come out even when metal fatigue due to repeated stress occurs or when excessive force is applied. (C) By making the contact surface of the ceramic member and the metal in a slippery contact state, even if a difference in thermal expansion between the ceramic and the metal occurs, high stress does not occur in the composite part, and the ceramic member is destroyed. Not even.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional explanatory view showing an embodiment of the present invention.

FIG. 2 is a vertical cross-sectional explanatory view showing an embodiment of the present invention.

FIG. 3 is a vertical cross-sectional explanatory view showing an embodiment of the present invention.

FIG. 4 is a vertical cross-sectional explanatory view showing an embodiment of the present invention.

FIG. 5 is an explanatory longitudinal sectional view showing an embodiment of the present invention.

FIG. 6 is a vertical cross-sectional explanatory view showing an embodiment of the present invention.

FIG. 7 is a vertical cross-sectional explanatory view showing a method for testing a pushing load.

FIG. 8 is an explanatory longitudinal sectional view showing an example in which the ceramics-metal cast stuffed composite part of the present invention is applied to a piston of a diesel engine.

FIG. 9 is a vertical cross-sectional explanatory view showing a ceramic-metal composite component when the taper angle is less than 10 °.

FIG. 10 is a vertical cross-sectional explanatory view showing a ceramics-metal composite component when the taper angle exceeds 45 °.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Ceramic member 2 Casting metal 3 Tapered part 3'Tapered body 4 Stepped part 5 Depression 6 Cylindrical body 7 Projection 8 Recess 9 Projection 10 Boundary gap and metal part crack observation site 11 Holding jig 13 Si ₃ N ₄ cavity 14 Piston pin hole 15 Gap 16 Sharp part F Push-out load θ Tapered angle l Stepped part dimensions

Claims (3)

[Claims] 1. A composite component in which a ceramic member is cast around a metal, and the outer shape of the axial cross section of the ceramic member extends from the ceramic member side not covered with the metal to the ceramic member side covered with the metal. A ceramic-metal cast stuff composite part having a tapered shape that gradually becomes thicker, and at least a part of a ceramic member that comes into contact with a metal has a stepped shape. 2. The ceramic-metal cast gurney composite component according to claim 1, wherein the contact surface between the ceramic member and the metal is in a slidable contact state. 3. The ceramic-metal cast stuffed composite component according to claim 1, wherein the taper angle is 10 ° to 45 °.