JPH07110407B2 - Method for manufacturing sliding member made of composite of ceramics and metal - Google Patents

Description

The present invention relates to a method for manufacturing a sliding member made of a composite of ceramics and metal.

(Prior Art) Recently, a sliding member has been developed in which the abrasion resistance and seizure resistance of ceramics, the strength reliability of metal, and the heat dissipation property of metal are combined (for example, JP-A-59). -196240 publication).

In this method, rod-shaped or plate-shaped small ceramic pieces are dispersedly arranged in a portion of a mold forming a sliding surface of a sliding member, and the small ceramic pieces are surrounded by molten metal.

(Problems to be Solved by the Invention) By the way, in the above invention, when a ceramic piece is cast with a molten metal, microcracks are apt to occur in the ceramic piece due to thermal shock of the metal, which means that the sliding surface is broken. May develop into In order to prevent such troubles, the mold containing the ceramic pieces is usually preheated in, for example, a high-frequency electric furnace prior to the injection of the molten metal, but the work process becomes complicated and the manufacturing cost is increased. Noticeably higher. Further, in the sliding member of the above invention, since the ceramic pieces are rod-shaped or plate-shaped, the compressive stress when the molten metal solidifies and shrinks does not act evenly on the entire surface of the ceramic pieces during casting. That is, the holding force of the cast-in metal for the small piece becomes weaker, and the local concentration of the compressive stress easily causes cracks in the small piece. Further, during sliding, the load applied to the sliding surface and the heat generated by sliding are not evenly dissipated in each ceramic piece, and the life of the sliding member is shortened accordingly.

The present invention has been made in view of the above circumstances, and a first object of the present invention is to produce a cast metal for a ceramic piece in the process of manufacturing a sliding member made of a composite of a ceramic piece and a metal. The purpose is to mitigate thermal shock by a simple and inexpensive method. A second object is to evenly disperse the load and sliding heat applied to the ceramic pieces in the process of using the sliding member, so that the sliding member lasts longer.

(Means for Solving the Problems) In order to achieve the above object, the present invention disperses spherical ceramic pieces at predetermined positions in a mold through an adhesive or a mold coating agent having a heat insulating property. Is.

That is, according to the present invention, on the cavity surface of a mold having air permeability, a large number of ceramic balls coated with a heat-insulating adhesive or a mold coating agent are attached in layers at predetermined intervals. A cast body is formed, the cast body is incorporated into a mold, and a molten metal is poured into the casting cavity to form a ceramic cast body, and after that,
It is characterized in that a part of the surface of the ceramic ball in the cast body and the cast metal are ground and polished on the same plane.

Hereinafter, the present invention will be described in detail based on examples.

(First Embodiment) FIGS. 1 to 7 show a manufacturing process in an embodiment of the present invention. FIG. 1 is a vertical sectional view of a cast-in body, FIG. 2 is a horizontal sectional view thereof, and FIG. Is a vertical cross-sectional view showing a state in which the body to be cast is set in the mold, FIG. 4 is a vertical cross-sectional view of the cast ceramic body, FIG. 5 is the same horizontal cross-sectional view, and FIG. FIG. 7 and FIG. 7 are transverse cross-sectional views of the relevant part.

In the figure, a shell mold (1) consisting of a cylinder with a height of 70 mm, an outer diameter of 40 mm, and a wall thickness of 3 mm, and having a breathable shell mold (1) has a diameter of 4 mm and a heat-resistant inorganic adhesive (Nissan Chemical Silicon carbide ceramic balls (3) thinly coated with Bond X 81) (2) are attached in layers (single layer) via the adhesive (2). The spacing between the ceramic balls (3) is 0.4 ± 0.2 mm or more. The outer peripheral surfaces of both ends of the shell mold (1) are left without the ceramic balls (3) attached. Next, a cylindrical polystyrene foam (4) having an outer diameter of 80 mm, an inner diameter of 50 mm and a height of 70 mm is wound around the outer peripheral portion of the ceramic ball (3) layer, and a coating mold ( 5) is applied to form a cast body (6) (first
See figure).

In addition, expanded polystyrene (4 ') having a thickness of 5 mm is wound around the outer peripheral surfaces of both ends of the shell mold (1) in advance.

Thereafter, the cast-in body (6) is set in the casting frame (8) after the runner (7) made of expanded polystyrene is attached to the cast-in body (6).

The casting frame (8) has a ventilation structure and an inner box (9) having an open upper end, and a decompression chamber between the inner box (9) surrounding the side and bottom portions of the inner box (9). Outer box (1)
The outer box (12) is provided with a conduit (13) having one end communicating with the decompression chamber (11) and the other end connected to a vacuum pump (not shown).

The inner box (9) of such a flask (8) is filled with silica sand for foundry sand (equivalent to AFS grain size -100) (14), and fluidity is imparted to the silica sand (14) by vibrating means (not shown). Meanwhile, the upper end of the sprue (7) of the cast body (6) is an inner box (9).
It is set in the inner box (9) so that it appears on the upper surface of the.

Next, cover the upper surface of the flask (8) excluding the upper end of the sprue (7) with an airtight sheet (1) of vinyl acetate copolymer, polyethylene or the like.
Seal with 5).

Then, activate the vacuum pump (not shown) to
3) and the decompression chamber (11) are used to eliminate the air in the inner box (9), so that the pressure in the inner box (9) is 200 to 500 mm above atmospheric pressure.
Make it as low as Hg. As a result, the silica sand (14) is solidified in the inner box (9) while the cast-in body (6) is contained therein to form a mold (see FIG. 3).

When molten metal of 1,380 ° C cast iron (16) is poured from the upper end of the sprue (7) in this state, the expanded polystyrene (4) (4 ') and the adhesive (2) in the cast body (6) are combusted and vaporized. The cavities and gaps generated thereby are filled with the molten metal in a substitutional manner, and the cast ceramic body (17) is formed. Since the gas generated by the combustion of the adhesive (2) passes through the breathable shell mold (1) and diffuses into the silica sand (14), the surface in contact with the shell mold (1), that is, the sliding surface, No gas holes are formed, and the ceramic balls (3) are reliably surrounded by the molten metal. When the operation of the vacuum pump is stopped and the depressurized state in the inner box (9) is released after a lapse of a predetermined time, each particle of the silica sand (14) becomes free to move and the mold collapses. The product can be removed. At this time, the shell mold (1) was burned by the heat of the molten metal and lost its shape retention property, and was easily separated from the product.

The inner peripheral surface of the cylindrical cast ceramic body (17) thus obtained was ground by 2 mm and further polished to reveal a sliding surface made of ceramics and cast iron.
8) In such a sliding member (18), the ceramic balls (3) are firmly fixed in the cast iron (16), and the ceramic balls (3) are fixed.
No cracks were generated on the sliding surface.

In addition, when a ceramic ball whose surface is not coated with an adhesive is mounted on the outer peripheral surface of the shell mold and cast around, a part of the ball is washed with molten metal, and as a result, the sliding surface of the sliding member is Misalignment occurred in the ceramic balls. Also, cracks occurred on the sliding surface of some ceramic balls.

(Second Embodiment) FIG. 8 is a vertical sectional view of an object to be cast in another embodiment of the present invention, and FIG. 9 is a vertical sectional view of a cast ceramic body. In the figure, an alumina-based ceramics ball (2) with a diameter of 2 mm and a thin graphite coating agent (19) using methanol as a solvent on the inner surface of a shell mold (1) having a bottomed cylinder and having air permeability ( 3) is mounted in layers (single layer) via the mold wash (19). The spacing between the ceramic balls (3) is also 0.4 ± 0.2 mm or more. Next, a cylindrical portion that can be loosely fitted in the cavity of the shell mold (1), and a flange portion that is formed at the upper end of the cylindrical portion and has an outer diameter that is approximately the same as the inner diameter of the shell mold (1). The expanded polystyrene (4) consisting of is inserted into the cavity of the shell mold (1), and the upper end opening of the shell mold (1) is closed by the flange of the expanded polystyrene (4).
Then, a coating mold (not shown) is applied to the exposed surface of the expanded polystyrene (4) to form a cast body (6) (see FIG. 8). Thereafter, the cast-in body (6) was attached to the runner (7) made of expanded polystyrene, set in a flask similar to that in the first example, and the same procedure was performed at 750 ° C. A molten aluminum alloy (21) was poured to obtain a cast ceramic body (17) as shown in FIG.

The outer peripheral portion and the bottom portion of such a cast ceramic body (17) are ground to a predetermined size and further polished to expose a sliding surface made of ceramics and an aluminum alloy, and a sliding member (not shown) is thus formed. ).

In such a sliding member, the ceramic balls (3) were firmly fixed by casting with the aluminum alloy (21), and no cracks were generated in the ceramic balls (3).

(Operation) In the present invention as described above, the molten metal of the cast iron (16) or the aluminum alloy (21) injected into the mold is first the outer shell portion of the cast body (6) (in the case of the first embodiment). Alternatively, the expanded polystyrene (4) that constitutes the content portion (in the case of the second embodiment) is combusted and vaporized, and the space portion generated thereby is substituted and filled with the cast iron (16) layer or the alumina alloy (21).
A heat-resistant inorganic adhesive (2) which forms a layer and is then coated on the surface of the ceramic balls (3) and filled in the spaces between the balls (3) (in the case of the first embodiment). Alternatively, the graphite coating agent (19) (in the case of the second embodiment) is combusted and vaporized to fill the gap between the balls (3) in a substitutional manner, whereby the ceramic balls (3) and the cast iron (16) or A composite layer with an aluminum alloy (21) is formed. At this time, an adiabatic gas film is instantaneously generated by the combustion gas of the adhesive (2) or the coating agent (19), and this film is a ceramic ball of molten metal. The thermal shock to (3) is mitigated and the generation of microrack on the ball (3) is prevented. The melt then cools and solidifies and shrinks,
At this time, the ceramic balls (3) are strongly tightened. This tightening force remains even after the cast iron (16) or aluminum alloy (21) is completely solidified and cooled, so that the ceramic balls (3) and the cast metal (16) (21) are firmly bonded to each other. become.

Ceramic balls (3) and cast metal (16) in the cast ceramic body (17) thus obtained
The surface of the composite layer with (21) is 1 / the diameter of the ball (3).
The sliding surface is exposed by grinding / polishing at a depth of less than 2, but at this time, the ball (3) is still cast metal (1
6) The wedge effect of (21) firmly engages with the metal (16) (21), so that the ball (3) does not rattle on the sliding surface or peel off from it.

(Effects of the Invention) As is apparent from the above description, in the present invention, when a ceramic ball is cast with molten metal, the thermal shock of the metal is mitigated by the heat insulating agent / adhesive agent coated on the surface of the ceramic ball. Therefore, it is not necessary to preheat the mold containing the balls, and the working process is not complicated and the manufacturing cost is not increased.
Further, in the sliding member manufactured according to the present invention, since the ceramic small pieces are spherical, the compressive stress when the molten metal solidifies and shrinks acts evenly on the entire surface of the ceramic ball during casting. The holding force of the stuffed metal on the ball becomes strong, and cracks due to local concentration of compressive stress are eliminated.

Further, during sliding, the load applied to the sliding surface and the heat generated by sliding are evenly dissipated in each ceramic ball, and the life of the sliding member is extended.

In the examples, silicon carbide and alumina ceramics were used as the spherical ceramics, but partially stabilized zirconia, silicon nitride, sialon, carbon, etc., which have high strength and high hardness, are excellent in adhesion wear resistance and have a friction coefficient Any material may be used as long as it is small, and further, not only a sintered body but also an abrasive grain raw material or the like may be used.

Further, in the embodiment, the case of casting with an aluminum alloy or cast iron is shown, but the casting metal may be any metal having good sliding characteristics (for example, copper alloy).

Further, the adhesive or the mold coating agent coated on the surface of the ceramic ball is not limited to that of the embodiment, and any material having a heat insulating property may be used.

Although the cast ceramic body was manufactured by the reduced pressure full molding method in the examples, it can be manufactured by various casting methods such as a low pressure casting method and a casting method using an organic self-hardening mold.

[Brief description of drawings]

FIG. 1 is a longitudinal sectional view of an object to be cast in one embodiment of the present invention, FIG. 2 is a lateral sectional view of the same, and FIG. 3 is a longitudinal sectional view showing a state in which the object to be cast is set in a mold. Is a longitudinal sectional view of the cast ceramic body, FIG. 5 is a lateral sectional view of the same, FIG. 6 is a longitudinal sectional view of an essential part of the sliding member, FIG. 7 is a lateral sectional view of the essential part, and FIG. FIG. 9 is a vertical sectional view of a cast body in another embodiment, and FIG. 9 is a vertical sectional view of a cast ceramic body. (1): Shell mold, (2): Adhesive (3): Ceramic ball, (4): Expanded polystyrene (6): Cast object, (8): Cast frame (16) (21): Cast metal (17): Ceramic cast body (18): Sliding member, (19): Coating agent

Continuation of front page Examiner Takashi Nakagawa (56) References JP-A-59-196240 (JP, A)

Claims (1)

[Claims] 1. A large number of ceramic balls (3) having a cavity surface of a mold (1) having air permeability coated with a heat insulating adhesive (2) or a mold coating agent (19).
Are placed in layers at predetermined intervals to form a cast body (6), the cast body (6) is assembled in a mold, and molten metal (16) (21) is poured into the casting cavity. To form a cast ceramic body (17), and then grind a part of the surface of the ceramic ball (3) and the cast metal (16) (21) on the same plane in the cast ceramic body (17). A method of manufacturing a sliding member comprising a composite of ceramics and metal, which comprises polishing.