JPH04356331A - Casting flask for mold making - Google Patents

Abstract

PURPOSE:To calcine a ceramic mold by detaching a flask with bars before sintering the ceramic mold in a heating furnace. CONSTITUTION:The molding flask for preparing the mold is constituted of the combination of an attachable/detachable flask piece and a bar and the flask is detached before a ceramic mold is sintered in a heating surface of 800-1000 deg.C. Therefore, even if the ceramic mold is sintered, the crack of the mold caused by the difference of thermal expansion of the ceramic mold and the flask is not generated.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to high-temperature firing of ceramic molds for medium-sized and large-sized precision castings, and more particularly to a mold-making flask from which the flask is removed before high-temperature firing of the mold.

0002

BACKGROUND OF THE INVENTION There are two main methods for making ceramic molds: a single ceramic mold method and a composite mold method, depending on the size and shape of the casting to be cast.

[0003] Single ceramic molding is a method used when casting relatively small castings. The manufacturing process is as follows: (1) First, a model and a flask with an appropriate mold thickness are set on a surface plate. (2) After setting, make a slurry containing the required amount of ceramic, binder, and gelling promoter, and pour this into the mold. (3) Once the gelation of the slurry is complete, cut out the model and remove the flask. (4) Next, the combustible material in the mold is burned by ignition. (5) After that, the ceramic mold is fired.

[0004] The composite molding method is used when casting relatively large castings, and is aimed at reducing costs and reinforcing mold strength by reducing the amount of ceramic material used. The manufacturing process is as follows: (1) A backup model and casting flask are set on a surface plate. (2) Fill with CO2 sand and create a backup mold. (3) Cut out the backup model. (4) Set the model on the surface plate, (5) Cover the product model with the backup mold, and pour ceramic slurry into the gap from the ceramic slurry inlet. (6) Once the injected ceramic slurry gels and solidifies, the model is cut out and the flammable substances contained in the ceramic layer are burned (primary combustion), and the ceramic mold is then fired (primary combustion).
(secondary firing).

[0006]

[Problems to be Solved by the Invention] However, in the case of the former ceramic mold single type of the above-mentioned conventional ceramic mold manufacturing methods, gelation occurs in products with complex shapes and large irregularities, even for small castings. Cracks occur in the ceramic layer due to uneven heat distribution and uneven temperature distribution within the ceramic layer during combustion and firing, and these cracks become burrs on the surface of the casting, making it difficult to obtain a casting with an excellent casting surface. There may be no.

[0007] As one method for preventing cracks in the ceramic layer, in the case of the composite molding method that makes the thickness of the ceramic layer uniform, medium-sized and large-sized molds are used, and the process of transporting the mold and removing the model from the mold is difficult. However, the mold must be inverted, and a flask with hanging handles is required. However, the mold is fired at a high temperature in a heating furnace (80
In the step of heating (0 to 1000°C), cracks occur in the ceramic layer due to tensile stress due to the difference in thermal expansion between the mold and the flask.

[0008] As a measure to prevent cracking of this ceramic layer,
Conventionally, the following two methods have been used. (1) Low temperature firing (2) Casting flask without bars

However, in the case of (1) low-temperature firing, if molten Al alloy is poured into a ceramic mold when the ceramic layer is insufficiently fired, moisture, gas, etc. generated from the ceramic layer and the pack-up mold will be released. There is a problem in that the gas enters the molten Al alloy and causes gas defects in the product. Furthermore, in the case of (2), a casting flask without bars, there are no protrusions such as bars inside the flask, so when transporting using a crane, etc., or inverting the mold, the mold does not move away from the flask. There are problems such as slipping and falling.

[0010] Therefore, in order to solve these two problems, the present invention provides a method in which the casting flask with the crosspiece is removed before firing the ceramic mold in the heating furnace, and the ceramic mold and the crosspiece are fired in the heating furnace. purpose.

[0011]

[Means for Solving the Problems] The present invention has been made in view of the above-mentioned problems, and a mold-making flask is constructed by a combination of removable flask pieces and crosspieces.

0012

[Operation] In the present invention, a ceramic mold is formed by integrally constructing a flask by combining a plurality of removable flask pieces and crosspieces, and only the flask is formed before the ceramic mold is fired in a heating furnace. Remove from the ceramic mold.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be explained below with reference to the drawings. Figure 1
~ Figure 3 shows one embodiment of the flask of the present invention, Figure 1 is a perspective view of the flask disassembled into four flask pieces, Figure 2 is a perspective view of the flask and crosspiece combined, FIG. 3 shows a vertical cross-sectional view taken from III-III when molding is performed using the flask shown in FIG.

[0014] The flask 1 has a rectangular shape and is composed of two sets of flat flask pieces 1a and 1b, front, rear, left and right.
Both ends of the flask pieces 1a and 1b are joined with bolts 10. In addition, three holes 3a for wood screws are bored in each of the opposing flask pieces 1a and 1b at the same pitch, and wooden nail-shaped crosspieces 4 having an appropriate length are formed here. is designed to be fixed with two wood screws 3 at the top and bottom for each one. Claw-shaped crosspieces 4 fixed to the flask pieces 1a and 1b are also mounted in sets of three so as to face each other.

[0015] In the rectangular casting flask 1, in the longitudinal direction,
In the square-shaped flask 1, holes are made in the opposing flask pieces 1a and 1b to insert reinforcing bars that will serve as hangers for transporting the mold after firing. , insertion hole 5a of cylindrical foamed polystyrene 5
are bored in the flask 1 at two spaced apart locations. In addition, in order to further securely hold both ends of the cylindrical polystyrene foam 5 in the flask 1, a protruding tube 2 for fixing the polystyrene foam is fixedly protruding from the outside of the flask 1. There is.

The sequence of steps for molding and firing a ceramic mold 11 using the flask 1 of the present invention constructed as described above will now be described. (1) First, two sets of flat flask pieces 1a, 1a, 1a, 1a, 1a, 1a, 1a, 1a,
Both ends of b are joined with bolts 10. (2) Next, fix the 12 claw-shaped crosspieces 4 with wood screws 3. (3) After this, two cylindrical foamed polystyrene 5
are respectively loaded through the protruding tube 2 for fixing foamed polystyrene. (4) Next, a model larger than the product model and the flask of the present invention are set on a surface plate (not shown). (5) A backup mold 6 is formed by filling with CO2 sand. (6) Turn the mold over and cut out the backup model. (7) Next, a product model (not shown) is set on a surface plate, (8) the backup mold 6 is placed over the product model, and ceramic slurry is poured into the gap from the ceramic slurry inlet 12 to form the ceramic layer 7. do. (9) After the ceramic mold 11 has been molded, and before firing the ceramic layer using a burner, the bolts 10 that join the flask 1 and the wood screws 3 that secure the claw-shaped crosspiece 4 to the flask 1 are removed. are removed, respectively, and the ceramic mold 11 and the flask 1 are separated. (10) Next, only the ceramic mold 11 is placed in a heating furnace maintained at 800 to 1000° C. and fired. During this time, the polystyrene foam 5 and the wooden claw-shaped crosspieces 4 are burnt down. (11) After cooling the mold 11 that has been fired while being placed on the surface plate described above, molten metal is poured to produce a casting.

In the present invention, a case has been described in which the claw-shaped crosspieces 4 are attached to the flask 1, but the present invention is not limited to this, and a grid-like crosspiece 13 as shown in FIG. 4 is attached to the flask 1. It may also be configured such that it is attached to the Furthermore, although the claw-shaped crosspiece 4 is made of wood in the present invention, it may be made of any material that is combustible, has a certain degree of strength, and does not undergo thermal expansion; for example, bamboo may be used.

[0018]

[Effects of the Invention] As is clear from the above explanation, in the present invention, the flask for mold making is constructed of a combination of removable flask pieces and crosspieces, thereby increasing the strength of the ceramic mold. Even when firing in a heating furnace at 800 to 1000°C, since there is no flask, the mold does not crack due to the difference in thermal expansion between the mold and the flask. In addition, the mold can be easily transported by inserting reinforcing bars into the space left by the burning of the foamed polystyrene after firing.

[Brief explanation of the drawing]

FIG. 1 is a perspective view showing an embodiment of the present invention when a flask is disassembled into four flask pieces.

FIG. 2 is a perspective view showing an embodiment of the present invention in which a flask and a crosspiece are combined.

[Fig. 3] When molded using the flask shown in Fig. 2, III-I
It is a longitudinal cross-sectional view seen from II.

FIG. 4 is a perspective view showing another embodiment of the present invention in which a flask and a lattice-shaped crosspiece are combined.

[Explanation of symbols]

1 Casting flask 1a, 1b Cast flask pieces 2. Polystyrene foam fixed protrusion tube 3 Wood screws 4 Claw-shaped crosspiece 5 Polystyrene foam 6 Backup mold 7 Ceramic layer 8 Product cavity part 11 Ceramic mold 12. Lattice-like crosspiece

Claims (1)

[Claims] 1. A flask for mold making, characterized in that the flask is constituted by a combination of removable flask pieces and crosspieces.