JPS58107250A - Production of core for mold to be hardened by microwave heating - Google Patents

Abstract

PURPOSE:To obtain a core having sufficient surface hardness with a small amt. of a binder by hardening molding sand added with an inorg. binder by irradiation of microwaves in a pattern for microwave heating. CONSTITUTION:Water is added at 0-2% to molding sand and water glass at 1.0-3% as an inorg. binder thereto under thorough mixing. The mixture is packed in a pattern 1 for molding by microwave heating. Here the pattern 1 and the sand are of room temp. and the pattern 1 provided with a reinforcing layer 1b in the outside circumferential part of a reinforcing layer 1a consisting of a non-polar epoxy resin or the like is used. A steam vent hole 1d having an opened top end is provided in the sand packing hole 1c in the upper part of the pattern 1. The pattern 1 packed with the molding sand is charged into a microwave oven where microwaves are irradiated onto the pattern 1 from above to harden the molding sand. The layer 1a does not evolve heat and only the molding sand is heated. Upon completion of the hardening, the core for casting is removed from the inside of the pattern 1.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a core for a mold that is hardened by microwave heating in which the surface stability is improved by adding an inorganic binder to the brocade.

Conventionally, in mold making methods such as CO2 process, it is known to add water glass as an inorganic binder, but in the above conventional method, 4 to 6 glasses of water glass are added to increase the strength of the mold. As a result, the surface stability of the mold was poor, and during casting, the mold sintered due to starvation, resulting in poor collapsibility, making it difficult to remove sand from the casting after casting, and causing brocade on the surface of the casting. There were some problems such as some parts burning. Furthermore, there were also problems such as secondary pollution caused when the brocade was recycled after being cast.

This invention is a method for manufacturing a mold core that improves this problem, and allows sufficient surface stability to be obtained even when the amount of inorganic binder is reduced to 1.0 to 3. It is.

This invention will be described in detail below with reference to the drawings. The tinsel used in the method of this invention may be crushed sand, zircon sand, alumina sand, mullite, recycled sand or recovered sand, and the recycled sand and recovered sand do not contain a dielectric substance. You can also use it.

Add 0 to 2 g of water and 1.0 to 3% of water glass as an inorganic binder to the brocade, mix well, and pour this into the microwave heating model 1 by hand or blowing. Fill by means. At this time, both the model I and the sand were at room temperature, and as the microwave heating model 1, a model as shown in FIG. A water vapor vent hole 1d whose upper end is open is provided in the sand filling hole 1c.

Next, the model 1 filled with brocade is placed in a microwave opener (not shown), and microwaves are irradiated from above the model 1.
Harden the casting sand in model 1.

At this time, the model 1 including the reinforcing layer la made of non-polar epoxy resin or the like does not generate heat, and only the brocade inside the model is heated and hardened. When the hardening of the brocade in the model 1 is completed, it is taken out from the model 1 and used as a casting core, and the resulting core is strong enough to be cast immediately even after microwave curing 1a. there were.

Next, in order to test the resistance pressure of the core obtained by the above method, a test piece of 50φ x 50H was prepared by changing the mixing ratio of silica sand, water glass, and water as shown in Table 1 below, and this was subjected to microwave treatment. Figure 2 shows the strength results of the irradiated and cured material.

For comparison, the strength of a test piece molded using the conventional method (CO process) is also shown as sample C.

Table 1: Surface stability of the same test piece as above (molding 24
Figure 3 shows the residual strength results (measured after 30 minutes), and Figure 4 shows the residual strength results.

As is clear from these diagrams, the core obtained by the method of this invention has higher values of strength and surface stability than conventional product C, and has a lower residual strength. Since it can be used for casting as a core, molding and casting operations can be made more efficient, and since there is no need to mold and stock cores in advance, no space is required for stocking. Further, the reduced residual strength improves the disintegration of the mold after casting, making it easier to take out the casting and remove sand, and the brocade can be recovered without secondary pollution.

Moreover, since an inexpensive inorganic binder is used, costs can be reduced.

Example 0.5 parts of water and 2 parts of water glass as an inorganic binder were added to 100 parts of water-washed recycled sand, and the mixture was thoroughly kneaded.The mixture was filled into model 1 by blowing, and then placed in a microwave oven. The brocade inside the model was heated and hardened by irradiating it with microwaves of 2450 MHz x 6 KW for about 1 minute and 30 seconds. Thereafter, when the core was taken out from the model, there was no missing brocade as shown in FIG. 5, and a core with extremely good surface stability was obtained. For reference, a photograph of the above-mentioned mother cloud ikon core is shown in reference photograph (a).

Comparative Example For comparison, a model was blown with brocade made by adding 0.5 parts of water and 5.5 parts of water glass to 1001 parts of washed recycled sand.
As shown in the figure, the brocade was not packed deep enough into the model, and a high-quality core like the one in the above example could not be obtained. A photograph of the above-mentioned core is shown in the reference photograph ←).

[Brief explanation of drawings]

The drawings show one embodiment of the present invention, and FIG. 1 is a cross-sectional view of the model, FIG. 2 is a diagram showing the strength of the obtained core, FIG. 3 is a diagram showing the surface stability, and FIG. Figure 4 is a diagram showing the residual strength, Figure 5 is an explanatory diagram of the core obtained in the example, and Figure 6 is a diagram showing the residual strength.
The figure is an explanatory diagram of a core obtained in a comparative example. Applicant: Komatsu Ltd. Representative Patent Attorney Masaaki Yonehara Patent Attorney Tadashi Hamamoto i Figure 1d Figure 2 Figure 3 Figure 4 Figure 5 (a) Procedural amendment (method) Patent dated May 18, 1930 Agency Director Haruki Shimada 1, Indication of the incident, Patent Application No. 56-205151 3,
Relationship with the person making the amendment Patent applicant address 2-3-6 Akasaka, Minato-ku, Tokyo Name (+23
) Komatsu Manufacturing Co., Ltd. Representative Ryo Kawai - 5. Date of amendment order: April 9, 1980 (Shipping date: April 27, 1980)
6. Subject of amendment Il+1B11' and drawing l Contents of amendment (1) From "Incidentally, the above..." in lines 7 to 8 from the bottom of page 5 of the specification attached to the application, the same page Delete the fifth line from the bottom up to "Shown in reference photo (a)." (2) In the second line of page 6 of the same specification, “In addition...
"..." to the third line [...]. ] Delete up to . (3) Attachment 1 to the drawing center frame Figures 5 and 6 attached to the application.
, delete the photo (a) ←).

Claims (1)

[Claims] Add 0~2 g of water and 1.0~3% of inorganic binder to the brocade and knead it. After filling the brocade into a model for microwave heating and hardening, irradiate microwaves from above the model to mold the brocade into the model. A method for producing a core for a microwave heat-cured mold, the method comprising curing the brocade and removing it from a horizontal mold after hardening.