JPS6054244A - Improvement of molding surface of casting mold - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] The present invention relates to a method for improving the mold surface of a casting mold.

Note that the mold here includes a core.

When producing a cast product by molding a casting mold (hereinafter simply referred to as the mold) using refractory particles such as silica sand, and pouring molten metal (hereinafter referred to as molten metal) into the product cavity formed by this mold, The molten metal may enter the gaps between the refractory particles forming the mold, which may deteriorate the casting surface of the cast product, or even cause the refractory particles to be baked onto the surface of the cast product.

In order to solve this problem, a coating agent using water or alcohol as a solvent and using fine powder such as lime powder or zircon flour as aggregate is applied or sprinkled on the surface of the mold that comes into contact with the molten metal. However, it has been difficult to completely solve the above-mentioned problem since the mold coating agent cannot sufficiently fill the voids in the surface layer of the mold by simply applying or spraying the mold coating agent.

Therefore, in order to compensate for the insufficiency of this mold coating agent, various improvements have been made in terms of both the mold coating agent and the mold. However, methods such as applying a thick coat of mold coating agent or using a penetrating mold coating agent that utilizes capillary action are used to coat the surface of the mold coating agent, and from the mold surface, methods such as coating the mold coating agent thickly or using a penetrating mold coating agent that utilizes capillary action are used. Conventionally, only the parts that come into contact with the molten metal are molded using refractory particles with a smaller particle size, or expensive refractory particles such as high-performance zircon sand are used.

However, none of the above methods can be said to have sufficiently solved the above-mentioned problems.

The present invention was made in order to solve the above-mentioned problems of the prior art, and its object is to obtain a mold that can prevent the penetration (insertion) of molten metal.

According to the mold skin improvement method of the present invention, a mold made by an appropriate method is placed in a fluidized bed containing refractory fine powder, and the mold is suctioned to define a product cavity. This can be achieved by filling the voids on the surface of the mold with refractory fine powder.

According to the present invention, refractory fine powder smaller than the gap is sucked into the gap between the refractory particles on the mold surface defining the product cavity, which is in direct contact with the molten metal, and fills the gap. Therefore, the density of the surface of the mold increases, and the mold surface becomes fine.

Therefore, when a mold improved by the mold skin improvement method of the present invention is used for casting as it is or after being coated with a mold coating agent by a conventional method, the following effects are achieved.

(a) Since the voids on the mold surface are greatly reduced and become dense, there is no intrusion of molten metal into the mold.

In addition, as a result, there is no burning of the cast product and the refractory particles.

(b) The casting surface of the cast product is improved, the dimensional accuracy is also improved, and post-processing is not required.

(c) The mold surface can be improved with a simple method, compared to conventional methods that use large amounts of expensive refractory particles such as zircon sand.
Cost reduction can be achieved.

Next, the mold skin improving method according to the present invention will be explained with reference to the drawings.

In the present invention, first, a mold made of refractory fine particles, such as a green mold, a CO2 sand mold, or a shell mold, is prepared. The present invention can be applied to all molds other than metal molds.

The pressure reduction means inside the mold can be accessed from this mold.

At this time, the pressure reducing means is provided in a direction opposite to the mold surface defining the product cavity. In other words, if the mold is an integrated mold with a product cavity inside, it is provided on the outer peripheral surface of the mold,
In the case of a split mold, it is installed on the back side of the mold surface that defines the product cavity. As the pressure reduction means, for example, a cover that seals and covers a part of the mold, and a vacuum pump connected to this cover can be used.

The mold, equipped with a pressure reduction means, is then placed in a fluidized bed containing fluidized refractory fine powder. Then, the pressure inside the mold is reduced by operating the pressure reduction means. As a result, the refractory fine powder is attracted and enters the gaps between the refractory particles forming the mold, resulting in the state shown in FIG. 1. In FIG. 1, 1 is a refractory particle, and 2 is a refractory fine powder.

The refractory fine powder used in the present invention needs to be smaller than the refractory particles forming the mold, and preferably has a average particle size of 1/10 or less of the refractory particles. As this refractory fine powder, for example, silica flour or the like can be used.

In the present invention, the suction force should be appropriately determined depending on the condition of the mold, particularly the size of the voids in the mold. The smaller the void in the mold, the greater the suction force required.

In this way, a mold is obtained which has a fine texture, ie a high density of surfaces defining the product cavity of the mold.

When pouring the metal into such a mold and performing casting, a more desirable result can be obtained by performing the casting after applying or spraying the mold coating agent 3, which is commonly done, as shown in FIG. That is,
As shown in Figure 3, in the case of a conventional casting mold coated with mold coating agent 3, the gaps between the refractory particles 1 are large, causing unevenness in some parts of the coating mold surface, allowing molten metal to enter. In contrast, the mold with improved mold surface according to the present invention has a smooth coating surface.

Next, the present invention will be explained in detail.

Example A CO2 sand mold was made using silica sand with an average particle size of 0.2 mm. Find a means of depressurizing this sand mold, 1. Nrn
While suctioning at '/ct/min, silica flour with an average particle size of 10 μm was immersed in a fluidized bed for 1 minute.
Fine silica flour powder was embedded in the surface layer of the mold that defined the product cavity. Next, a commercially available molding material for general casting steel containing zircon flour as a paste was sprayed onto the surface of the mold.

After that, apply JIS 5C318 1600 to this mold.
The hot water was poured at a temperature of ℃. After cooling, the mold was milled, and the casting was taken out and inspected for 8 rounds to check the casting surface, sintering condition, etc.

Comparative Example Except for embedding silica flower in the mold, everything else was
A mold made the same as in the example is prepared, and the mold is poured under the same conditions as in the example to produce a casting.
We investigated the burning situation.

The investigation results of the above examples and comparative examples are shown in FIG.

Table 1 As is clear from Table 1, the casting mold using the mold with improved spinning surface according to the present invention not only has a much better casting surface than the conventional mold, but also There was no insertion of molten metal, and no burning caused by insertion was observed.

In other words, by using a mold with an improved mold surface according to the present invention, casting defects are significantly reduced compared to the conventional method, and a casting with a good casting surface and high dimensional accuracy can be obtained.

[Brief explanation of drawings]

Fig. 1 is a schematic diagram showing a state in which refractory fine powder is buried in a mold according to the present invention, Fig. 2 is a schematic diagram showing a state in which a mold coating agent is applied to the mold of Fig. 1, and Fig. 3 is a schematic diagram showing a state in which a coating agent is applied to the mold of Fig. FIG. 3 is a schematic diagram showing a state in which a mold coating agent is applied to a mold. 1 - - - - Fire-resistant particles 2 - - - Fire-resistant fine powder 3 - = - 1-coat molding agent Applicant: Toyota Motor Body Engineering Co., Ltd.)

Claims (1)

[Claims] (1) A mold formed by an appropriate method is placed in a fluidized bed containing refractory fine powder, and the mold is suctioned to fill the voids on the mold surface defining the product cavity with refractory fine powder. A method for improving the mold surface of a casting mold.