JPS5877739A - Molding method for casting mold - Google Patents

Abstract

PURPOSE:To dry and harden molding sand quickly and firmly by improving the packability of the molding sand by blowing potassium silicate as a binder and passing hot air through the packed molding sand. CONSTITUTION:Molding sand contg. potassium silicate as a binder is packed into the cavity parts consisting of a top mold and a bottom mold 17; thereafter the top mold is removed and a cover member 22 is put on so as to cover a casting mold 21 and the mold 17. An upward and downward moving table 2 is moved upward by the extending operation of a cylinder 2 and the supply hole 24 of the member 22 is press stuck airtightly with the vent hole 13 of a clamping head 11 so as to be communicated therewith. Thereafter an electromagnetic stop valve 15 is opened to supply the heated and compressed air in a tank 7 through a hose 14, the hole 13 and the hole 24 into the member 22. The heated and compressed air passes through the inside of the mold 21 from the entire surface of the mold 21 and is discharged through an air release hole 5 after passing through vent holes 20, a recess 18 and a through-hole 4. Thus the moisture in the mold 21 is evaporated quickly and the molding sand is dried and hardened in a short time.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for molding a mold, and more specifically, a mold molded using molding sand containing potassium silicate or a mixture of potassium silicate and sodium silicate as the main binder. The present invention relates to a mold making method for rapidly and strongly drying and hardening.

Conventionally, the method of hardening the mold by passing carbon dioxide gas through it for several tens of seconds to several minutes into a mold made using foundry sand containing sodium silicate as a binder is known as the carbon dioxide gas curing method (C02 process). However, molding sand that uses sodium silicate as a binder has poor filling properties when blowing, so molds with complex shapes are generally tamped by hand. , which was considered a problem from a productivity perspective.

The present invention has been made in view of these problems, and uses potassium silicate as a binder to improve the filling properties of molding sand by blowing, and to mainly blow hot air into the filled molding sand. Accordingly, it is an object of the present invention to provide a mold making method that rapidly and firmly dries and hardens the foundry sand.

The configuration of the present invention will be explained below based on examples. (
1) is a column whose side shape is C-shaped;
) is provided with an upward-facing clamp cylinder (2), and an elevating table (3) is fixed to the tip of the piston rod of the cylinder (2). A through hole (4) is formed in the upper surface of the box body having a hollow interior, communicating with the hollow part, and an exhaust stand (6) having an exhaust hole (5) on one end side is attached. Further, a compressed air storage tank (7) is installed behind the column (1), and the tank (7) is communicated with a pressure 1 air source (not shown) via a pressure reducing valve (8). At the same time, the compressed air in it is heated to 60 to 200°C.
A heating device (not shown) capable of raising the temperature to a certain degree is equipped. Furthermore, at a position directly above the lifting table (3) on the ceiling of the column (1), there is a vertically oriented support rod (9) with a screw threaded on its outer circumferential surface, which is screwed through and can be adjusted up and down. A packing material (12) is adhered to the lower surface of the support rod head (11), and a passage leading to the hollow chamber (10) is formed on the lower wall of the clamp head (11) and the east end of the packing (12). A vent (13) is provided through the hollow chamber (10), and the hollow chamber (10) is communicated with the tank (7) via a flexible hose (14), an electromagnetic on-off valve (i5), and a main pipe (16). There is. (17) is a lower mold, which is placed on the exhaust stand (6) via a packing (19) with the through hole (4) located in the recess (18) formed on the lower surface thereof; A plurality of small exhaust holes (20) communicating with the recess (18) are transparently provided on the upper surface of the lower mold (17). On the upper surface of the lower mold (17) is a mold (before drying and hardening) made of foundry sand whose main binder is potassium silicate.
21) is placed. (22) is a cover member placed on the exhaust stand (6)-1 through the gasket (23) so as to cover the F-type (17) and the mold (21); 22) In the center of the upper plate, a heated compressed air supply hole (24) connects to the ventilation hole (13) of the clamp head (11).
).

As shown in the figure, in this structure, the level of the clamp head (11) is adjusted to an appropriate height, and the pressure in the tank (7) is reduced to a predetermined pressure by the pressure reducing valve (8).
) is heated to the required temperature, and under this condition, a mold consisting of an upper mold and a mold (17) having a plurality of ventilation holes (20) communicating from the surface of the mold to the back surface of the mold is heated. After filling the molding sand into the cavity of the combined model, the upper mold was removed and the remaining mold (21) was placed in the lower mold (17).
), and place the cover member (22) on the upper surface of the exhaust stand (6) so that the recess (18) is located in the through hole (4). 17
), and then the cylinder (2) is extended to raise the elevating table (2) and place the cover member (22) on the lower surface of the clamp head (11) via the packing (12). The supply hole (24) of the cover member (22) is crimped in an airtight manner and communicated with the W element L (13). Thereafter, the electromagnetic on-off valve (15) is opened and the compressed air heated to a predetermined temperature in the tank (7) is pumped through the main pipe (16), the electromagnetic on-off valve (15), the flexible hose (14), and the hollow chamber ( 10), when supplied into the cover member (22) through the ventilation hole (13) and the supply hole (24), this heated compressed air enters from the entire surface of the open mold (21) and flows through the mold (21). ), passes through the ventilation hole (20), the fourth part (18), the through hole (4), and is discharged from the exhaust hole (5). The mold (21) is exposed to compressed air heated to a predetermined temperature in this way.
The mold ( 2
1) The moisture inside is quickly evaporated, resulting in lower mold (
17) The upper mold (21) is to be dried and hardened in a short time.

Note that when carbon dioxide gas is supplied at the same time as this heated compressed air, the mold (21) undergoes a reversible dehydration action, and potassium silicate reacts with carbon dioxide gas to produce irreversible silica gel, creating a mold with less hygroscopic deterioration. Obtainable. After the required time has passed, close the electromagnetic on-off valve (15) and remove the cover member (22).
), the cylinder (2) is retracted, the lifting table (3) is lowered, the cover member (22) is unclamped, and the cover member (22) is unclamped. The member (22) is removed and the hardened mold on the upper surface of the lower mold (17) is taken out to complete the molding operation. In the above embodiment, the exhaust table (6) was provided on the upper surface of the elevating table (3), but an exhaust hole communicating with the outside was provided on the upper end surface of the elevating table (3). (3) The lower mold (17) etc. may be placed directly on the upper surface. In addition, in the above embodiment, the lower mold (
17), the ventilation hole (20) is provided in the upper mold, but the upper mold may be provided with a ventilation hole, and after filling with molding sand, the upper mold is placed downward and the lower mold is removed. Furthermore, it is of course possible to fill the molding sand in the vertically divided state of the mating model. In addition, in the above embodiment, after filling the molding sand, the upper mold was removed and the remaining mold was placed on the lower mold (17) and placed on the upper surface of the exhaust stand (6). After filling, the combined model may be placed on the upper surface of the exhaust stand (6), and then the upper mold may be removed.

Further, in the above embodiments, potassium silicate is used as the binder, but sodium silicate may be mixed with potassium silicate to the extent that it does not impair the filling properties of the foundry sand by blowing.

Furthermore, a mold disintegrant made of an organic substance may be added to the foundry sand as required.

In addition, if the shape of the model is complex and there is a risk of breaking the mold when removing the upper mold, you can pre-cure it by blowing carbon dioxide gas for a short time before removing the mold, then remove the upper mold and heat it. Compressed air or a mixture of heated compressed air and carbon dioxide gas may be vented.

In this method of pre-caking and pre-curing the mold by passing carbon dioxide gas through it, potassium silicate reacts quickly with the carbon dioxide gas, and the mold is hardened in a short time.

Next, an experimental example of the present invention will be explained.

(Experiment Example 1) Foundry sand prepared by adding and mixing potassium silicate or a mixture of potassium silicate and sodium silicate as a binder to flattery sand was molded into a cylindrical shape with a diameter of 50 mm and a length of 200 mm as shown in Fig. 3. After filling the cavity of the combined model, the upper mold was removed and a pressure 1. The viscosity of Table 1 shows the results when the blending ratio of the binder and the ventilation time of heated compressed air were varied.

Table 1 (Experimental Example 2) Foundry sand prepared by adding potassium silicate or a mixture of potassium silicate and sodium silicate as a binder to flattery sand was mixed into a cylindrical shape with a diameter of 50 M11 as shown in Fig. 3.
1 Fill the cavity of a composite model with a length of 200 ff#l, and ventilate 10 tons of carbon dioxide gas at a pressure of 1.0'g4 into the molding sand filled in the cavity to prepare the filled molding sand. After curing, remove the second mold and lower mold (17)
120°C on the upper pre-hardened mold (21) surface.
Heated compressed air with a pressure of 1.0-350. !
Table 2 shows the results obtained by varying the blending ratio of the binder, the aeration time, etc.

Table 2 Note that the potassium silicate used in Experimental Examples 1 and 2 is Si
02/K20 molar ratio -25, concentration -40%, and sodium silicate 5i02/Na'20 molar ratio -2.5
, concentration=40%.

From the results in Table 1, we found that molds made of molding sand containing 5% by weight of potassium silicate in flattery sand, or molding sand containing 2.5% by weight of potassium silicate and sodium silicate, were heated and compressed. When only air or a mixture of heated compressed air and carbon dioxide is applied for 30 seconds, the counter pressure immediately after ventilation is 6C or more,
A strong mold can be obtained in a short time. Furthermore, it can be seen that moisture absorption deterioration is less in cases where a mixture of heated compressed air and carbon dioxide gas is applied (compared to only heated compressed air).

In addition, since the shape of the model is complex and it is difficult to remove the upper mold, carbon dioxide gas is aerated into the molding sand filled in the cavity to pre-harden the molding sand before the upper mold is removed. In this case, from the results in Table 2, a mold containing 5% by weight of potassium silicate becomes strong enough to be removed from the upper mold by aeration of carbon dioxide gas for 3 seconds, and a strength of 6 oz or more is obtained by further applying heated compressed air for 30 seconds. It becomes counter pressure.

As is clear from the above description, the present invention has good filling properties with molding sand by blowing even for complex-shaped models, and can quickly obtain strong molds, greatly improving productivity and quality. The effect of contributing to this type of industry is extremely significant.

[Brief explanation of the drawing]

FIG. 1 is a partially cutaway front view showing six embodiments of the present invention, and FIG.
The figure is a side view of FIG. 1, and FIG. 3 is an explanatory diagram showing an experimental example of the present invention. (20) : Ventilation hole (21) : Mold (2
2): 1 cover, 1 dice■ ? Figure 2 to Figure 3

Claims (1)

[Claims] 1. Potassium silicate or a mixture of potassium silicate and sodium silicate is used as the main binder in the cavity part of the combined model, which has a small number of ventilation holes communicating from the surface to the back side of the mold. - After filling with molding sand, place the mold with one vent hole downward, remove the other mold above, and place the remaining mold on the surface of the lower mold, The ventilation hole is placed on a table top surface provided with an exhaust hole that communicates with the outside from the upper end surface, with the ventilation hole positioned at the exhaust hole, and a cover member is placed over the mold to cover the inside of the cover member. The mold is heated by supplying heated compressed air or a mixture of heated compressed air and carbon dioxide to the mold, passing it through the mold from the open surface of the pre-air mold, passing through the ventilation hole, and exhausting it from the exhaust hole. A mold making method characterized by curing. 2. A small amount of potassium silicate (potassium silicate,
Alternatively, after filling molding sand whose main binder is a mixture of potassium silicate and sodium silicate and pre-curing the molding sand by passing carbon dioxide gas into the molding sand in the cavity, the one vent hole is opened. With the prepared mold facing downward, the other upper mold is removed, and the remaining mold is placed on the upper surface of the lower mold, and the above-mentioned A ventilation hole is placed on the exhaust hole, a cover member is placed over the mold, and heated compressed air or a mixture of heated compressed air and carbon dioxide is supplied into the cover member. do,
passing through the mold from an open surface of the mold,
A method for making a mold, characterized in that the mold is hardened by discharging it from the exhaust hole via the ventilation hole.