JPS60196247A - Production of casting mold - Google Patents

Abstract

PURPOSE:To prevent the cracking to be generated in the part of a casting corresponding to connecting parts in the stage of producing a casting mold having the plural connecting parts between an outside peripheral part and an inside part spaced from each other by introducing gas from the outside peripheral part into the mold and curing the casting mold. CONSTITUTION:A casting mold of the shape having >=2 connecting parts 3 between an outside peripheral part 1 continuous into one body and an inside part 2 provided apart therefrom on the inside of said part is produced by a gas curing method. A prescribed gas such as CO2 or the like is introduced from a gas cylinder 4 to the part 1 of the casting mold through a blow-port 9 toward the molding sand 1, 2, 3 contained in wooden patterns 5, 6, 7 to cure the sand 1-3 and thereafter the gas is discharged through a gas vent 8. Such casting mold is set in a prescribed molding flask and casting is executed. The product having no defects such as cracks in the parts of the casting corresponding to the connecting parts is thus obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing @-types. More specifically, the present invention relates to a method of manufacturing a mold having a specific shape that is different from a gas hardening process using a foundry dust containing a gas hardening binder.

A method of manufacturing molds by curing molding sand containing a gas-curing binder such as furan resin, water glass, or urethane resin using gas such as carbon dioxide gas, amine gas, or sulfur dioxide gas (gas curing method) Since the molding sand does not harden at all until gas is blown into it, it is useful for manufacturing molds that have complex shapes and require a long time to be molded. It is particularly advantageous for the mass production of relatively small molds, since the desired mold can be obtained in a short time by curing.

Conventionally, molds of various shapes have been manufactured by a gas curing method. When manufacturing a mold having a shape having an inner part 2 installed at a certain distance, and a connecting part 6 that connects the outer peripheral part 1 and the inner part 2, the upper part of the inner part 2 is When manufacturing on a mold by hardening the molding sand by blowing gas into it, I have often experienced that the connecting portion 5 cracks and the mold becomes defective. Therefore, the present inventor compared and investigated various gas curing methods that do not cause cracks in the connecting portion 3. The present invention has been made based on the extensive knowledge obtained through this comparative study.

That is, as shown in FIG. 1, the present invention includes an outer peripheral part 1 forming a continuous integral part, an inner part 2 provided inside the outer peripheral part 1 with a space therebetween, and these outer peripheral parts. A complete method for manufacturing a mold, which includes introducing gas from the outer peripheral part 1 when manufacturing the mold by the full gas hardening method It is something to do.

Therefore, the method of the present invention is shown in FIG. 2, and a companion embodiment will be explained. In FIG. The gas vent hole provided at the bottom, 9 is a gas inlet, and these 5, 6.7
Molding sand containing a gas-curing binder is housed in a wooden mold formed by 1. As shown in FIG. This is the connecting part. Gas is introduced only from the gas inlet 9 provided above the outer periphery, and flows from the outer periphery 1 through the connecting portion 3 to the inner portion 2.
Once reached, the molding sand is hardened and released from the gas vent 68.

As a result, a mold having the shape shown in FIG. 1 can be obtained, and the connecting portion 5 will not be cracked.

In the present invention, the gas may be introduced from above the outer circumferential portion 1 as shown in FIG. 2, or from the side or below. A preferred method for introducing gas is to feed the gas as uniformly as possible to the outer circumferential portion 1 and to uniformly harden the entire mold from the outside to the inside. For this purpose, for example, the entire outer periphery may be covered and the gas may be introduced from above or from the side of the entire outer periphery.

It has been found that the method of the present invention is particularly effective in producing molds whose outer periphery has a circular or oval planar shape. In particular, the outer edge 1a and inner R1b of the outer circumferential portion 1 in FIG. 1 are both circular or oval (that is, the whole is circular or oval).
The effect is strong. In addition, after considering it in more detail,
Vertical cross-sectional area of any part of the outer periphery 1 (A in Fig. 1)
- Means the cross-sectional area when cut along the line A') is the vertical cross-sectional area of any part of the connecting part 5 (B - in FIG. 1)
It was also found that this method is particularly effective in manufacturing molds that are thicker than the total cross-sectional area when cut along line B'.

In carrying out the present invention, there are no particular limitations on the shapes of the inner portion 2 and the connecting portion 3 (and the connecting portion 3 may have two or more
-Can be provided.

Gases that can be used in the method of the present invention include GO□
+ 802I SO5+ HC1+ 012t BCl
3+ BF3 etc. can be given. Further, in the method of the present invention, any known gas-curable binder such as furan resin, water glass, urethane resin, etc. may be selected and used.

The present invention will be explained below with reference to Examples and Comparative Examples, but the present invention is limited to these Examples. A wooden mold whose vertical cross-section is shown in FIG. A mold was manufactured by blowing gas. FIG. 5 is a plan view of the mold, in which 1 is the outer circumferential part, 2 is the inner part, 3 is the connecting part, and 9 is a hole provided above the outer circumferential part 1 for introducing gas. The gas introduction holes 9 had a diameter of 5 mm and were installed at equal intervals of 8 g in total. The outer periphery 1 is circular and its outer diameter is 545 cm, and the outer periphery 10
The width is 2211. The thickness is 42 mm, the cross-sectional area is 924 mm, the diameter of the inner portion 2 is 190 mm, and the thickness is 46 mm.There are a total of 36 connecting portions 5 provided at equal intervals, and the connection end with the outer peripheral portion 1 is The width was 20mm, the width at the end connected to the inner part 2 was 10mm, and the cross-sectional shape was oval, with a minimum cross-sectional area of about 100III+2 and a maximum of about 2003oI2.

A mold was manufactured under the following conditions.

(1) Type of tofu sand used: Enshu borax (2) Binder resin used: Furan-based resin (trade name Kaolite Toner KX-205) The amount of binder is 2 w to sand
t% (3) Peroxide used: one whose main component is methyl ethyl ketone peroxide (part name: p-70) Amount used is 0.6 wt% of sand +4) Amount of So□ gas supplied: 0.8 To! I/I2O3
Force gas is sent for 5 seconds.9. (equivalent to 1,7 & So2 gas/sec) In the obtained mold, all of the connecting parts 3 (56 pieces in total)
There were no cracks (the mold was defect-free).

Comparative Example When building the same mold as in Figure 5, the hole for introducing gas (
Diameter 5M) t - A total of 8 pieces, one centered above the inner part 2 as shown in Fig. 4 (plan view), and the remaining 7 pieces were provided at equal intervals in the y direction. The vertical cross-sectional view of the wooden mold is the second one except that the installation location of the gas introduction hole 9 from the gas cylinder 4 is different.
Same as the figure. The mold was otherwise manufactured under the same conditions as in the example. In the mold obtained by the conventional method of hardening by introducing gas into the inner part, cracks occurred in 19 out of 36 parts of the connecting part 5, resulting in a defective mold.

[Brief explanation of drawings]

Fig. 1 is a perspective view showing an example of the shape of a mold manufactured by the present invention, Fig. 2 is a schematic vertical cross-sectional view showing the state of the mold during manufacture, and Fig. 6 is a plan view showing the mold according to the method of the present invention. , 4th
The figure is a plan view showing a mold made by a conventional method. 1... Outer circumferential part 2... Inner part 3... Connecting part? ...Gas inlet applicant representative
Kaoru Furuya Figure 1 Figure 2

Claims (1)

[Scope of Claims] 1. A continuous outer peripheral part, an inner part provided inside the outer peripheral part at intervals, and two or more connecting parts that fully connect the outer peripheral part and the inner part. 1. A method for manufacturing a mold, which is characterized by introducing gas from the outer periphery when manufacturing the mold by a gas curing method. 2. The method for manufacturing a mold according to item 1, wherein the planar shape of the outer periphery of the mold is circular or oval. 3. The method for manufacturing a mold according to claim 1 or 2, wherein the vertical cross-sectional area of any part of the outer periphery of the mold is larger than the vertical cross-sectional area of any part of the connecting part.