JPS6347395Y2 - - Google Patents

Description

[Detailed description of the invention] This invention relates to the improvement of casting sand molds.
The present invention relates to a sheet material for protecting and insulating casting sand molds, which provides heat insulation properties to sand molds, has excellent peelability from solidified castings, and has compressibility and heat insulation properties.

Since the characteristics of conventional casting sand molds, that is, foundry sand and core sand, have a significant effect on the yield, quality, etc. of castings, various considerations are taken into the quality of foundry sand and core sand. For example, the basic properties of foundry sand and core sand include appropriate overall strength and appropriate surface strength. If the sand grains on the surface of the mold tend to fall off, it will itself lead to defects in the casting, such as dents and rough casting surfaces, sand scratches, or mechanical seizures. Accompany. Adequate ventilation is required to allow the escape of gases in the molten metal or water vapor and gases generated from the sand mold itself; extremely low ventilation is known to lead to gas pores in the casting. There is.

Furthermore, if the degree of gas generation in the sand mold and core is high, the risk of the appearance of castings with gas holes is increased.

Next, it is necessary to have some compressibility; if the compressibility is low, cracks will occur in the casting.

In order to satisfy the above conditions, resin-based sand molds using quartz sand with phenol resin or furan resin as a binder, and water glass-based sand molds using quartz sand with water glass as a binder have been commonly used. In addition, graphite, chromite, magnesite, chromium magnesite, etc. are applied to the outer surface of the sand mold that comes into contact with the molten iron for the purpose of preventing seizure between the sand mold and the molten metal.

However, even though the conventional sand mold is coated with an anti-seize material, the following problems have occurred.

(1) Insufficient surface precision and surface strength, causing sand grains to fall off the surface of the sand mold, resulting in depressions in the casting, rough casting surface, sand spots, sand scratches, and seizure between the sand mold and the molten metal. do. Therefore, surface cutting of the casting is required after casting.
Generally, cutting surface treatment of approximately 10 to 20% of the weight of the casting is required.

(2) Compressibility is insufficient, and the property of successively reducing the volume in response to the contraction of solidified castings is insufficient, resulting in cracks on the casting surface.

(3) The anti-seize coating effect is insufficient, and the mold material adheres to the surface of the casting, resulting in uneven or rough surfaces. Furthermore, if the sand mold is made of coarse-grained sand, the molten metal will enter the pores of the sand mold, resulting in an even rougher surface.

(4) The generation of steam or gas directly affects the mold surface, and the contact between the generated gas and the molten metal causes the casting surface to become rough.

(5) The insulation of the sand mold is insufficient, and the surface structure of the solidified casting is different from the internal structure of the casting.

There were other problems.

This invention was made to solve the above problem, and consists of ceramic fiber and one or two types of zirconium oxide, chromium oxide, and zircon.
By arranging a sheet material, which is mainly composed of carbon dioxide and has compressibility, heat insulation properties, and non-stick properties with the molten metal, on the outer surface of the conventional sand mold that comes into contact with the molten metal, the outer surface of the casting is free from roughness or roughness. The object of the present invention is to provide a sheet material for protecting and insulating sand molds for casting, which does not generate unevenness and cracks, and further reduces the structural difference between the inside and outside surfaces of castings by imparting heat insulation properties.

Next, this invention will be specifically explained based on drawings showing examples thereof. Figures 1 and 2 show cross sections of the sand mold structure according to the present invention.
The figure shows the case of a sand mold using a core, in which numeral 1 indicates a casting flask 2 of foundry sand, 3 indicates a molten metal, 4 indicates core sand, and 5 indicates a sheet material layer of the present invention.

Figure 2 shows the case of a sand mold that does not use a core.
1 is a casting flask, 2 is foundry sand, 3 is a molten metal, and 5 is a sheet material layer of the present invention.

The casting sand mold protection and insulation sheet material according to this invention has the following effects.

(1) Since the surface accuracy is good and the molten metal and sand mold do not come into direct contact, there is no spillage of sand grains from the sand mold, and no dents, rough casting surfaces, sand traps, sand scratches, etc. occur in the casting. Therefore, precision casting is possible with almost no need for surface cutting of the casting after casting.

(2) Since the sheet material 5 has a compressibility of about 50%, it has sufficient physical properties to reduce the volume in response to the contraction of the solidified casting, and no cracks will occur on the surface of the casting.

(3) Due to the difficulty of wetting the molten metal with zirconia, chromium oxide, zircon, etc. contained in the sheet material 5, there is no burning phenomenon between the sheet material 5 and the molten metal, and the sheet material 5 is not easily wetted between the molten metal and the sand mold. Naturally, there is no seizure between the sand mold and the molten metal. Further, since the pore diameter of the sheet material 5 is small, no intrusion of molten metal into the pores of the sheet material 5 is observed.

(4) Since contact between the water vapor or gas generated from the sand mold and the molten metal is blocked by the sheet material 5, roughening of the surface of the casting caused by the generated gas can be sufficiently prevented.

(5) By arranging the sheet material 5, the heat insulation properties of the sand mold are greatly improved, and the difference in structure between the inside and outside surface of the solidified casting is extremely reduced.

It shows the effects of

The sheet material 5 of the present invention is made of ceramic fiber and one or more of zirconium oxide, chromium oxide, and zircon as main raw materials, and alumina sol,
It is possible to use a sheet material that is formed by adding one or more of silica sol, synthetic resin emulsion, and rubber latex, and forming and drying the sheet into a sheet by a papermaking method. In addition, a ceramic fiber sheet obtained by forming and drying a ceramic fiber into a sheet using a sheet-forming method, and a main raw material consisting of one or more of zirconium oxide, chromium oxide, and zircon, as well as alumina sol, silica sol, synthetic resin emulsion, and rubber latex. It can also be obtained by impregnating a slurry containing one or more of the following and then drying it.

Preferable conditions for the sheet material 5 of the present invention are as follows.

(1) The thickness of the sheet material is preferably between 1 mm and 30 mm. If the thickness is less than 1 mm, the insulation effect of the sheet will be insufficient, and the compressibility will be insufficient, causing fine particles to form on the surface of the casting. Easy to cause cracks. If it is larger than 30 mm, it will be difficult to adjust the overall shape of the target casting, making shape control difficult.

(2) The compressibility of the sheet material 5 is the amount (%) of possible dimensional change in the thickness direction, and the value is preferably 80 to 50%, and if it is less than 50%, it is compressible. It becomes insufficient and cracks are likely to occur in the casting. If it exceeds 80%, the insulation properties will be insufficient and there will be a tendency for a difference in structure between the inside and outside surface of the casting.

EXAMPLE Casting was carried out using a sand mold for rolling roll casting having the structure of the present invention (the cross section of which is shown in FIG. 2). At that time, the sheet material is ceramic fiber.
30 parts by weight of zirconium oxide, 70 parts by weight of zirconium oxide, 5 parts by weight of alumina sol, and 5 parts by weight of vinyl acetate resin emulsion were suspended in 200 parts by weight of water, formed by a papermaking method, and dried at 100°C to obtain a 7 mm thick product. A zirconia sheet material with a degree of compression of 60% was used. There is no seizure phenomenon between the casting and the sheet material 5 after casting condensation, there are no cracks on the surface of the casting, there are of course no sand spots or sandy surfaces, and there are extremely few structural differences between the inside and outside surface of the casting. It was possible to cast metals.
In addition, compared to the conventional sand mold structure, which requires a weight ratio of 10 to 20% for surface cutting of castings,
The castings cast according to the structure of the present invention require almost no cutting work, and the amount of cutting work required for applications requiring extreme casting surface precision is only about 1 to 2% by weight.

[Brief explanation of the drawing]

Figures 1 and 2 show cross-sections of the sand mold structure according to the present invention, in which 1 is a casting flask, 2 is a molding sand, and 3 is a sand mold structure according to the present invention.
4 indicates the molten metal, 4 indicates the core sand, and 5 indicates the sheet material layer of the present invention.

Claims (1)

[Scope of utility model registration request] In resin-based sand molds or water glass-based sand molds,
Compressibility of 80-50% and consisting mainly of ceramic fiber and one or more of zirconium oxide, chromium oxide, and zircon, attached to the outer surface of the foundry sand 2 and core sand 4 in contact with the molten iron 3; A sheet material for protecting and insulating casting sand molds with heat insulating properties.