JPH0360846A - Lost foaming pattern casting method - Google Patents

Abstract

PURPOSE:To improve coating toughness on surface of a lost foam pattern and also to improve accuracy in a casting product by further applying sand having the same grain diameter as that of molding sand after applying facing material on wall surface of the lost foam pattern composed of foam resin. CONSTITUTION:The lost foam pattern 1 is formed with foam styrene and foam styrene-made sprue 2 is fitted through a runner 3. This lost foam pattern 1 is dipped into a primary facing material 7 and coating layer of the primary facing material 7 is formed on the whole surface thereof and dried. Successively, a secondary facing material 8 mainly containing the sand having almost the same grain diameter as that of the molding sand 5 and alcohol solution of vinyl acetate the separately sprayed on the wall surface and dried to form the coating layer of the secondary facing material 8. This lost foam pattern 1 is embedded into the molding sand 5 packed in an iron flask 4, and molten metal 6 is poured from the sprue 2 to form the desired casting product. By this method, the lost foam pattern 1 having high coating toughness on the surface is obtd. and the accuracy in the casting product is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Field of Application) The present invention relates to a lr1 lost model casting method for producing a cast product having a shape corresponding to a lost model made of foamed resin.

(Prior art) Generally, in the vanishing #N type casting method, a vanishing model made of expanded polystyrene having the same shape as the cast product to be obtained is formed, and this vanishing model is placed inside a casting flask. After burying this vanishing model in the foundry sand filled in the vanishing model, molten metal, that is, molten metal, is injected into the vanishing model from a sprue connected to the vanishing model to replace the vanishing model with molten metal. It forms a cast product. In this case, when molten metal is injected from the sprue, the sprue and the vanishing model are sequentially thermally decomposed within the casting sand, and this portion is replaced by the molten metal, producing a cast product having the same shape as the vanishing model.

By the way, in the above-mentioned vanishing model casting method, the wall surface of the vanishing film mold is traditionally coated with a coating agent mainly composed of refractory particles, powder, or flakes, and after drying, the vanishing model is cast. The casting surface of a cast product is kept smooth by embedding it in sand and then casting a cast object in a shape corresponding to the disappearing model in a subsequent casting process. The coating used in this conventional investment casting method was a mixture of refractory particles or powder or flakes, water, a binder, a surfactant, and an antifoaming agent. In this case, in order to improve the precision of the cast product, especially the surface precision, it is necessary to increase the rigidity of the coating mold.

Therefore, in order to increase the rigidity of the coating, it may be possible to apply a coating agent to the wall surface of the vanishing model more thickly than before. However, when a conventional mold coating agent is applied thicker than before on the wall surface of a vanishing model, the rigidity of the coating mold can be increased, but on the other hand, there is a problem that air permeability is deteriorated. Therefore, when molten metal is injected into the inside of the vanishing model from a sprue connected to the vanishing model to replace the vanishing model with molten metal, some of the gas released from the vanishing model to the molding sand side remains, causing casting defects. There was a problem that occurred.

(Problem to be solved by the invention) In order to improve the accuracy of casting products, especially the placement accuracy, when a conventional mold coating agent is applied thicker than before on the wall surface of a vanishing model, the rigidity of the coating mold is increased. However, on the other hand, the permeability will be poor, so when injecting molten metal into the inside of the vanishing model from a sprue connected to the vanishing model and replacing the vanishing model with molten metal, there will be a risk of leakage from the vanishing model to the casting sand side. There was a problem in that some of the emitted gas remained and caused casting defects.

This invention has been made in view of the above-mentioned circumstances, and it is possible to improve the coating rigidity of the surface of the vanishing model, improve the accuracy of cast products, and prevent the occurrence of casting defects. The purpose is to provide a model casting method.

[Structure of the Invention] (Means for Solving the Problems) This invention applies a coating agent mainly composed of refractory particles, powder, or flakes to the wall surface of a disappearing model made of foamed resin,
After drying this, this disappearing model is buried in molding sand filled in a casting flask, and in the subsequent casting process, a cast object having a shape corresponding to the above-mentioned disappearing model is cast. After completing the primary coating agent application process of applying the coating agent to the wall surface of the vanishing model and the drying process of this primary coating agent, a secondary coating mainly consisting of sand with approximately the same particle size as the foundry sand is applied. Applying a secondary molding agent by spraying a molding agent and an alcoholic solution of vinyl acetate onto the wall surface of the disappearing model from separate spray nozzles, and applying the secondary molding agent to the surface of the coated layer of the modified molding agent. This method includes a VHi step and a step of drying the secondary coating agent.

(Function) A secondary molding agent mainly composed of sand with approximately the same particle size as foundry sand and an alcoholic solution of vinyl acetate are applied to the surface of the coating/II layer of the primary molding agent applied to the wall surface of the vanishing model. By spraying from a separate spray nozzle and applying the secondary coating agent to the surface of the coated layer of the modified molding agent, the secondary coating agent is applied to the surface of the coated layer of the primary coating agent in good condition. , - The coating layer of the modified molding agent and the coating Ai layer of the secondary coating agent increase the coating rigidity on the surface of the vanishing model, improving the precision of the cast product, and preventing deterioration of air permeability. This is to prevent the occurrence of casting defects.

(practical) An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 schematically shows the groove bottom of a main part of a vanishing model 1 used when casting a cast product such as an intake manifold by the vanishing model casting method.

This disappearing model 1 is manufactured as follows. First, raw material beads made of expanded polystyrene are prepared. and,
This is filled into a non-illustrated vanishing model forming mold, heated with steam, and then cooled to produce a vanishing model component 1a having the same shape as the cast product.

1b is manufactured. In this case, the vanishing model 1 of this embodiment is made by joining together a first component 1a and a second component 1b, which are divided into two parts as shown in FIG. 2, to form a cast product as shown in FIG. It is formed in the same shape as.

Also, this erasable membrane! As shown in FIG. 4, a sprue 2 made of expanded polystyrene is attached to 21'.

In FIG. 4, numeral 3 indicates a branch portion of the sprue 2 that becomes a runner extending from the sprue 2 toward the disappearing model 1.

Casting is carried out using the vanishing model 1 processed in this way. During the vanishing model casting process, a first step is to apply a coating agent to the surface of the vanishing model 1 and then dry it (Fig. 5). - shown in FIG. 8) and a second step of burying the disappearing model 1 in the molding sand 5 filled in the casting flask (casting container) 4 (
(shown in FIG. 9) and a third step (shown in FIG. 10) of replacing the buried disappearing model 1 with molten metal 6 made of molten metal, for example, an aluminum alloy, are performed sequentially. In this case, the second step is to apply an appropriate amount of molding sand 5 to the inner bottom of the flask 4.
In this state, the vanishing model 1 is set in a predetermined posture, and then molding sand 5 is further supplied to fill the molding flask 4, so that the vanishing model 1 is completely immersed in the molding sand 5. Bury it. Note that this filling of the molding sand 5 is performed while the entire casting flask 4 is vibrated by a vibration device (not shown). Further, when this second step is completed, as shown in FIG. 10, molten metal 6 is injected into the interior of the vanishing model 1 through the sprue 2 to replace the vanishing model 1 with the molten metal 6. In this case, when the molten metal 6 is injected into the vanishing model 1 through the sprue 2, the high-temperature molten metal 6 penetrates the vanishing model 1 while thermally decomposing the sprue 2, gradually heating the vanishing model 1. Let's break it down. Then, the pyrolyzed portion, that is, the space where the sprue 2 and the disappearing model 1 were present, is replaced with the molten metal 6, and a desired cast product is manufactured.

In the embodiment of the present invention, the first step is performed by applying a primary coating agent 7 mainly composed of refractory particles, powder, or flakes, such as mica, to the wall surface of the disappearing model 1. After the coating agent coating process (shown in Figure 5), the drying process of the blow molding agent 7 (shown in Figure 6), and the drying process of the primary coating agent 7, the molding sand 5 and the drying process are completed. Secondary coating agent 8 mainly composed of sand with the same particle size and alcoholic solution of vinyl acetate 9
A secondary coating agent application step (7th 8) and a step of drying the secondary coating agent 8 (shown in FIG. 8).

That is, in the molding agent application process, as shown in FIG.
The vanishing model 1 is immersed in the solution, and a coating layer of the primary coating agent 7 shown in FIG. 1 is formed on the entire surface of the vanishing model 1, including the unbonded portion of the adhesive surface of the vanishing model 1. In this case, - blow molding agent 7
is formed by a mixture of refractory particles or powder or flakes, water, a binder, a surfactant, and an antifoaming agent.
This blow mold agent 7 is applied to each component 1a on the surface of the disappearing model 1.
, lb, or the inside of the bead-patterned recesses formed on the surface of the disappearing model 1,
The surface of the vanishing model 1 is embedded.

- In the step of drying the blowing mold agent 7, the primary molding agent 7 on the surface of the vanishing model 1 is heated in a drying oven 13 as shown in FIG. 6, for example.
Dry.

Furthermore, in the secondary coating agent application step, as shown in Figure S7, a secondary coating agent 8 mainly made of sand with approximately the same particle size as the molding sand 5 is applied from one spray nozzle 10 to the surface of the disappearing model 1. At the same time as spraying, an alcoholic solution 9 of vinyl acetate is sprayed onto the surface of the vanishing model 1 from the other spray nozzle 11, and the secondary coating agent 8 is approximately evenly applied to the surface of the overlapping layer of the blow molding agent 7 (9). +i.

After this secondary coating agent application step is completed, the secondary coating agent 8 on the surface of the vanishing model 1 is dried in a drying oven 14 as shown in FIG. Note that this drying oven 14 may also be used as the drying oven 13 used in the drying process of the primary mold coating agent 7.

Therefore, according to the above method, the surface of the coating layer of the primary mold coating agent 7 applied to the wall surface of the vanishing model 1 is coated with a secondary mold coating agent 8 mainly composed of sand having approximately the same particle size as the foundry sand 5, and vinyl acetate. The alcohol solution 9 of It is possible to reliably prevent the primary coating agent 7 from peeling off during the work of coating the surface of the coating layer of the primary coating agent 7, and to apply the secondary coating agent 8 to the surface of the coating layer of the primary coating agent 7. can be applied in good condition.

Furthermore, since the secondary coating agent 8 is applied to the surface of the coated layer of the modified molding agent 7, the coating rigidity of the surface of the vanishing model 1 can be increased compared to the conventional method, and the molding of the vanishing model 1 can be improved. It is possible to improve the precision of cast products by preventing casting defects from occurring due to deformation during molding or pouring.

Further, since the secondary mold coating agent 8 is mainly formed of sand having approximately the same particle size as the foundry sand 5, a decrease in air permeability can be prevented. Therefore, entrainment and retention of gas from expanded polystyrene generated by thermal decomposition of the vanishing model 1 when pouring the molten metal 6 can be prevented, and the occurrence of casting defects in cast products can be effectively prevented.

It should be noted that the present invention is not limited to the above-mentioned embodiments, and it goes without saying that various modifications can be made without departing from the gist of the present invention.

[Effects of the Invention] According to the present invention, a primary coating agent application step of applying a primary coating agent mainly composed of refractory particles, powder, or flakes to the wall surface of the disappearing tfi 'Jl, and a drying step of this primary coating agent. After the process is completed, a secondary molding agent mainly consisting of sand with approximately the same particle size as foundry sand and an alcoholic solution of vinyl acetate are sprayed onto the walls of the vanishing model from separate spray nozzles to form a coated layer of modified molding agent. A secondary coating agent application process for applying a secondary coating agent to the surface of the vanishing model and a drying process for this secondary coating agent are provided, thereby increasing the coating rigidity on the surface of the vanishing model and improving the precision of cast products. In addition, it is possible to prevent casting defects from occurring.

[Brief explanation of drawings]

The drawings show one embodiment of the present invention; FIG. 1 is a vertical cross-sectional view showing a schematic configuration of the main parts of the vanishing model, FIG. 2 is a perspective view showing the components of the vanishing model, and FIG. 3 is a vanishing model. Figure 4 is a perspective view showing how the model is assembled, Figure 4 is a front view showing how the vanishing model is attached to the sprue, and Figure 5 is the vanishing model immersed in the primary coating agent in the primary coating agent storage container. Fig. 6 is a longitudinal cross-sectional view showing the drying process of the primary coating agent, Fig. 7 is a longitudinal cross-sectional view showing the secondary coating agent application process, and Fig. 8 is the secondary coating agent. Figure 9 is a vertical cross-sectional view showing the process of burying the lost model in the molding sand filled in the flask, and Figure 10 is a vertical cross-sectional view showing the process of burying the lost model in the molding sand filled in the flask. FIG. 3 is a longitudinal cross-sectional view showing a casting process for injecting molten metal. 1... Vanishing model, 5... Foundry sand, 7... - Modified molding agent, 8... Secondary coating agent, 9... Alcohol solution of vinyl acetate, 10.11... Spraying nozzle.

Claims (1)

[Claims] A coating agent mainly consisting of refractory particles, powder, or flakes is applied to the wall of the vanishing model made of foamed resin, and after this is dried, the vanishing model is buried in foundry sand filled in a casting flask. In the vanishing model casting method, in which a cast object having a shape corresponding to the vanishing model is cast in a subsequent casting process, a primary coating agent application step of applying the coating agent to the wall surface of the vanishing model and this primary coating are performed. After the drying process of the molding agent is completed, a secondary molding agent mainly composed of sand with approximately the same particle size as the foundry sand and an alcoholic solution of vinyl acetate are sprayed onto the wall surface of the disappearing model from separate spray nozzles.
A vanishing model casting method comprising: a secondary coating agent coating step of applying the secondary coating agent to the surface of the coating layer of the primary coating agent; and a drying step of the secondary coating agent.