JP2002143982A - Coating agent for producing cast iron - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a coating agent for producing cast iron by which the intrustion of molten metal into the space between mold sand grains is securely prevented so as to prevent the burning of the mold. SOLUTION: Zircon powder of 85 to 95 wt.% and graphite powder of 5 to 15 wt.% are used as aggregates, further, a small amount of caking agent essentially consisting of bentonite and a small amount of surfactant are contained, and they are dissolved into a solvent, so that the penetration depth of the coating agent to a mold is controlled to about >=2 mm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a casting mold for producing cast iron, and more particularly, it is useful as a coating mold attached to the surface of a mold for the purpose of preventing seizure of the mold when producing cast iron.

[0002]

2. Description of the Related Art Silica sand is used as a mold when flake graphite cast iron, spheroidal graphite cast iron and the like are manufactured by sand casting. The particle size of the silica sand is 0.3 to 0.5 mm, and the filling rate of the sand is generally 55 to 70%. For this reason, when a molten metal having good fluidity, such as cast iron, is cast into a sand mold, the molten metal penetrates between the sand particles, that is, so-called seizure occurs, which is a problem.

[0003] As a measure for preventing the seizure as described above,
It is common practice to apply a coating material (brush coating method, spray method, dipping method) to a mold, and various types of coating materials are used. That is, as shown in FIG. 7, a molten metal (casting) between sand particles of a mold formed of sand 1
In order to prevent infiltration of the mold 3, a coating mold 2 using fine ceramic particles as an aggregate is permeated between particles of the sand 1 to make the mold dense.

[0004]

When the coating material is applied to the mold to form the coating mold 2, cracks may occur in portions where the thickness of the coating mold 2 is thin or in the layers of the coating mold 2. In the portion where the crack has occurred, the molten metal 3 penetrates between the particles of the sand 1 forming the mold and seizure occurs. In other words, the prior art has not yet completely prevented the seizure of the mold,
The appearance of the coating mold 2 that more reliably prevents seizure is desired.

SUMMARY OF THE INVENTION In view of the above prior art, an object of the present invention is to provide a coating mold for producing cast iron, which reliably prevents infiltration of molten metal between sand particles of a mold so as to prevent seizure of the mold.

[0006]

The structure of the present invention that achieves the above object has the following features.

1) 95 to 85% by weight of zircon powder and 5 to 15% by weight of graphite powder as an aggregate, and a small amount of a binder mainly composed of bentonite and a small amount of a surfactant. Dissolved in the solvent.

[0008] 2) The average particle size is 20 μm or less,
And 95 to 85% by weight of zircon powder;
A mixed powder with graphite powder of weight% was used as an aggregate, and a small amount of a binder mainly composed of bentonite and a small amount of a surfactant were contained and dissolved in a solvent.

3) The average particle size is 20 μm or less,
And 95 to 85% by weight of zircon powder;
In a mold using 5% by weight of graphite powder as an aggregate, the mixing ratio of the solvent is adjusted so that the density of the mold becomes 40 to 65 Baume.

[0010]

Embodiments of the present invention will be described below in detail with reference to the drawings.

[First Embodiment] It is considered that the penetration depth of the mold into the mold is an important factor in preventing the mold from cracking. Therefore, a spheroidal graphite cast iron is cast in a measuring device as shown in FIG.
FCD450, casting temperature: 1390 ° C.), and the amount of baked sand in the core-shaped test piece was measured. More specifically, FIG.
A number of core test pieces 4 as shown in FIG.
Each core test piece 4 is coated with a coating mold having different conditions,
Then, as shown in FIG. 1B, which is a view along the line A in FIG. 1A, the core test pieces 4 coated with the coating mold are arranged in a ring shape, and the molten graphite graphite cast iron is cast in a mold 5. Was injected, and the amount of baked-in sand of the core test piece 4 in the resulting casting was examined.

FIG. 2 shows the relationship between the amount of baked sand and the penetration depth of the coating mold in this case. Referring to the figure, it can be seen that the greater the penetration depth of the coating mold, the less the seizure. In order to prevent the baking of the mold, that is, the intrusion of the molten metal between the sand particles of the mold, the penetration depth of the mold may be increased.
In particular, if the penetration depth exceeds 2 mm, good seizure prevention can be achieved.

As a measure for increasing the penetration depth of the coating mold,
There are two main types. One is to adjust the composition and particle size of the aggregate, and the other is to reduce the viscosity of the mold (the proportion of the aggregate, that is, the density).

As a coating material for cast iron, a coating material using zircon and graphite as aggregates is generally used, has excellent seizure resistance, and is inexpensive. Therefore, in the present invention, the coating aggregate was a two-component system of zircon and graphite. Therefore, the core test piece 4 in the measuring apparatus of FIG. 1 as described above was applied with variously changed components of a two-component coating mold of zircon and graphite, and was subjected to a predetermined measurement. FIG. 3 shows a typical example. In the figure, commercially available coating molds A and B are coating molds according to the prior art.

The penetration depth of the mold between the sand particles of the mold varies depending on the ratio of the zircon powder and the graphite powder. FIG. 4 is a characteristic diagram for examining the effect of the blending ratio of graphite on the penetration depth of the coating mold when the test is conducted with a constant viscosity as much as possible. As shown in the figure, when the blending ratio of graphite increases, the penetration depth of the mold decreases, and the blending of graphite is not preferable from the viewpoint of the penetration depth. However, if a small amount of graphite is added, FIG.
As shown in the figure, the seizure of the mold tends to decrease.
This is because the wettability between graphite and the molten metal is poor, and the presence of graphite in the mold has the effect of preventing the infiltration of the molten metal.

Therefore, the penetration depth of the mold required to reduce the seizure of the mold is required to be about 2.0 mm or more as shown in FIG. 2, and therefore the upper limit of the amount of the graphite powder added is about 15 from FIG.
% By weight. Further, from the viewpoint of seizure resistance, the lower limit of the compounding ratio of graphite is preferably set to 5% by weight. Therefore, the coating mold according to this embodiment uses 95 to 85% by weight of zircon powder and 5 to 15% by weight of graphite powder as aggregates,
In addition, a small amount of a binder mainly composed of bentonite and a small amount of a surfactant were contained and dissolved in a solvent.

[Second Embodiment] As described above, the point of preventing the seizure of the mold is to increase the permeation thickness of the mold to prevent the molten metal from entering between the mold sand particles. It is. As a measure to increase the penetration depth of the coating mold, it is considered effective to reduce the particle size of the aggregate of the coating mold. Therefore, the effect of the particle size of the zircon powder on the penetration depth of the coating mold was examined.

FIG. 5 is a characteristic diagram showing the effect of the particle size of the zircon powder on the penetration depth of the coating mold. As shown in the figure, the smaller the particle size of the zircon powder, the better the permeability. Incidentally, zircon powder having an average particle diameter of 30 to 40 μm is generally used in a coating mold using zircon powder according to the prior art as an aggregate. Therefore, by employing finer zircon powder as the aggregate, it is possible to increase the penetration depth of the mold.

The penetration depth of the mold differs depending on the density (viscosity) of the mold or the filling rate of the mold as described later.
Therefore, it is difficult to strictly determine an appropriate zircon powder particle size. However, from the viewpoint of the baking property shown in FIG. 2, the penetration depth of the coating mold needs to be about 2 mm or more, while the penetration depth of the coating mold and the particle size of the zircon aggregate shown in FIG. In order to ensure a penetration depth of about 2 mm or more, the particle size of the zircon aggregate needs to be 20 μm or less. Therefore, the coating die according to the present embodiment is obtained by adding a restriction that the average particle diameter is 20 μm or less to the zircon powder of the coating die according to the first embodiment.

[Third Embodiment] In the first embodiment, it has been described that the penetration of the molten metal into the mold, that is, the seizure can be reduced by increasing the penetration depth of the coating mold. Here, as a measure for increasing the penetration depth of the coating mold, in addition to the means for optimizing the composition and particle size of the aggregate described in the first embodiment and the second embodiment, There is also a method for reducing the viscosity (the ratio of the aggregate, that is, the density).

FIG. 6 is a characteristic diagram showing the effect of the density (viscosity) of the coating mold on the penetration depth of the coating mold. As shown in the figure, the permeability of the coating mold depends on the composition of the coating mold, the viscosity of the coating mold (the ratio of the aggregate in the same type of coating,
That is, the density greatly varies depending on the density (Bome).
Incidentally, the lower the density of the coating mold (the lower the viscosity), the deeper the penetration depth. On the other hand, if the density of the mold is too low (the content of the aggregate is too small), the thickness of the mold that should be present on the surface of the mold becomes thin, and the irregularities of the mold sand are transferred to the surface of the mold, and There is a problem that the surface roughness is hindered. This means that the density (viscosity) of the coating mold has an appropriate range.

According to the chart shown in FIG. 3, if the density of the coating mold is large, sufficient penetration depth cannot be obtained and seizure occurs. On the other hand, if the density of the coating mold is too low, the permeability and the seizure resistance are good, but there is a problem that the surface roughness of the casting deteriorates as described above. The appropriate density of the mold depends on the proportion of graphite, but even if the proportion of graphite is 5% by weight, the density of the mold is 65 Baume or less in order to ensure a penetration depth of about 3 mm. In addition, when the density of the coating die is 40 or less, the surface roughness of the casting deteriorates. Accordingly, the density of the mold is preferably 40 to 65 Baume (this range is indicated by hatching in FIG. 6). Therefore, the mold according to this embodiment is:
In the mold according to the second embodiment, the density of the mold is 4
The mixing ratio of the solvent was adjusted so as to be 0 to 65 Baume.

[0023]

As described above in detail with the embodiments, the invention described in [Claim 1] is applicable to 95 to 85.
A weight percent zircon powder and a content of 5 to 15 weight percent graphite powder are used as an aggregate, and a small amount of a binder mainly composed of bentonite and a small amount of a surfactant are dissolved in a solvent. Therefore, the following effects are obtained.

In the present invention, the penetration depth of the coating mold is increased by optimizing the mixing ratio of the zircon powder and the graphite powder in the coating aggregate, and the graphite powder in the proper ratio is mixed as the aggregate. Thereby, the wettability with the molten metal is reduced, and the infiltration of the molten metal into the mold, that is, the seizure of the mold can be prevented.

According to a second aspect of the present invention, a mixed powder of zircon powder having an average particle diameter of 20 μm or less and 95 to 85% by weight and graphite powder of 5 to 15% by weight is used as an aggregate. In addition, a small amount of a binder mainly composed of bentonite and a small amount of a surfactant are contained and dissolved in a solvent, so that the following effects are obtained.

According to the present invention, by using a finer zircon powder as compared with a conventional coating die, it is possible to secure a more sufficient penetration depth than the invention described in [Claim 1]. The penetration depth of the coating mold between the sand particles is increased, so that the infiltration of the molten metal can be prevented, and the burning of the mold can be more reliably prevented.

[0027] The invention described in claim 3 is a coating material having an average particle diameter of 20 µm or less, and 95 to 85 wt% of zircon powder and 5 to 15 wt% of graphite powder as aggregates. In the mold, the mixing ratio of the solvent is adjusted so that the density of the coating mold is 40 to 65 Baume, and the following effects are obtained.

According to the present invention, by reducing the density (viscosity) of the mold, the penetration depth of the mold can be increased to prevent the infiltration of the molten metal, that is, the seizure of sand. However, regarding the density (viscosity) of the coating mold, it is not preferable that the density is too small from the viewpoint of maintaining the surface roughness of the cast product in a good condition, and there is an appropriate range. According to the present invention, since the density (viscosity) can be set to the proper range, the surface roughness of the casting can be ensured well, and the burning of sand can be prevented most reliably.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing a measuring device used for obtaining data of the present invention.

FIG. 2 is a characteristic diagram showing a relationship between a penetration depth of a coating mold and baking.

FIG. 3 is a table showing measurement results using the measurement device shown in FIG. 1;

FIG. 4 is a characteristic diagram in which the effect of the mixing ratio of graphite on the penetration depth of a coating mold was examined.

FIG. 5 is a characteristic diagram showing the effect of the particle size of zircon powder on the penetration depth of a coating die.

FIG. 6 is a characteristic diagram showing the influence of the density (viscosity) of the coating mold on the penetration depth of the coating mold.

FIG. 7 is a schematic diagram for explaining an operation of a mold for preventing infiltration of a molten metal between sand particles of a mold, that is, seizure.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Sand (mold) 2 Coating type (aggregate) 3 Molten metal (casting) 4 Test piece (core shape) 5 Mold (main type)

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Masumi Kodama 5007 Itozakicho, Mihara City, Hiroshima Prefecture Mitsubishi Heavy Industries, Ltd. Paper and Printing Machinery Division F-term (reference) 4E092 AA03 AA06 AA36 DA02 EA02 GA02

Claims (3)

[Claims] 1. A zircon powder of 95 to 85% by weight,
5 to 15% by weight of graphite powder as an aggregate, a small amount of a binder mainly composed of bentonite and a small amount of a surfactant, and dissolved in a solvent. . 2. An aggregate having an average particle size of not more than 20 μm and a mixed powder of 95 to 85% by weight of zircon powder and 5 to 15% by weight of graphite powder, and mainly a small amount of bentonite. A casting mold for producing cast iron, characterized by containing a binder and a small amount of a surfactant and dissolved in a solvent. 3. A coating composition having an average particle size of 20 μm or less, and using 95 to 85% by weight of zircon powder and 5 to 15% by weight of graphite powder as aggregates, wherein the density of the coating composition is 40%. A coating mold for producing cast iron, wherein the mixing ratio of the solvent is adjusted so as to be from 65 to 65 Baume.