JPS58179536A - Oxidative casting mold - Google Patents

Abstract

PURPOSE:To prevent deposition of carbon and generation of reducing gas in the case of mixing a binder in sand and producing a molding sand by compounding a specific amt. of an oxidizing agent with the sand and the binder. CONSTITUTION:>=0.3 part oxidizing agent is compounded with 100 parts sand (based on weight) in casting mold which is produced by mixing a binder with the sand. The compounding ratio of the binder and the oxidizing agent is usually preferably >=0.3 part oxidizing agent with 1 part binder. The representative oxidizing agent is nitrate, chlorate and peroxide, among which nitrate is more preferable. The binder may be org. or inorg. A phenolic resin is more preferable.

Description

[Detailed description of the invention] The present invention relates to oxidizable templates.

Traditionally, most castings have been manufactured using sand molds3, and binders for sand molds include organic binders and inorganic binders.

@ Radioactive binders include phenolic resins and furan resins. Inorganic binders include water glass and pimento.

However, organic binders generate a large amount of reducing gas when heated. Alternatively, carbon is deposited on the surface of the casting. It also mixes carbon into the sand. Reducing gases and carbon reduce the hot casting. Sand mixed with carbon has an even stronger reducing effect.

Reduction action (or carburization action) is preferred for pig iron castings. However, it is not preferable for ordinary electroformed large objects.

Large electroformed objects are mainly used in glass tank kilns. Therefore, electroformed large objects must have sufficient corrosion resistance against molten glass.

And it has to be precise.

However, when a large electroformed material is reduced, it foams and becomes locally porous. Large porous electroformed materials have poor corrosion resistance against molten glass.

Therefore, when it comes into contact with molten glass, it causes the molten glass to foam or generate stones (gravel).

Conventionally, when manufacturing large electroformed objects, Naruhe<ih
I made it so that I don't receive the n version. The raw materials for electroformed large objects were melted in an oxidizing atmosphere. .

Then, it was cast in a mold with an inorganic binder. However, large porous electroformed objects still occasionally occurred.

The present invention has been made in view of the above-mentioned circumstances, and its object is to provide an oxidizing mold that does not generate carbon or reducing gas.

The oxidizing mold of the present invention is manufactured by adding an oxidizing agent to sand and a binder. The oxidizing agent prevents reduction of the casting. When manufacturing large electroformed objects, it is preferable to use 11 sand as the sand.

Typical oxidizing agents used in the present invention are nitrates, chlorine I
! salts and peroxides. Among these, nitrates are preferred.

The reason is that nitrates are difficult to warp when mixed with binders and their hardeners. Another reason is that nitrates are difficult to dissolve in water and have a high thermal decomposition temperature. Nitrates include sodium nitrate, barium nitrate, and calcium nitrate. Among these, barium nitrate is preferred. This is because barium nitrate, in particular, is difficult to react with when mixed with a binder and its curing agent. In addition, barium nitrate is difficult to dissolve in water;
This is because the thermal decomposition temperature is high. Chlorates include potassium chlorate and sodium chlorate. Among these, potassium chlorate is preferred. The reason is that potassium chlorate has excellent moisture (water) resistance. This is also because potassium chlorate is difficult to dissolve in water. Among peroxides, barium peroxide is difficult to dissolve in water (@small aqueous property), has a high thermal decomposition temperature, and is the most stable among peroxides, thus meeting the purpose of the present invention.

Table 2 (see below) shows nitrate #I salt, chlorine S! List the melting points, decomposition temperatures, and water solubility of salts and peroxides.

In addition to the above-mentioned oxidizing agents, there is gold a oxide.

However, metal oxides are not suitable because they contaminate the sand and castings.

The blending amount of the oxidizing agent varies depending on the type of oxidizing agent and the amount and type of binder. However, it is preferable that the oxidizing agent be 0.361 r or more per 100 parts of normal sand (heavy steam ratio, hereinafter the same).

This will be explained in more detail. 11 to 100 parts of sand! Carbon precipitation can be prevented by using 0.3 parts or more of the curing agent. Oxidizing agent 0.5
% or more, the reducing gas can be almost completely oxidized. When the oxidizing agent O. is 75 parts or more, the following results are obtained.

Materials melted in an oxidizing atmosphere are dense.

C. It becomes a high quality casting. A porous cast product is obtained by melting raw materials in a reducing atmosphere.

Large porous electroformed materials have poor corrosion resistance against molten glass. However, refractories of the same shape manufactured using the mold of the present invention always have approximately the same porosity. In other words,
Foaming is reproducible. The pores are uniform throughout the refractory.
− Dispersed in In this respect, it differs from conventional porous electrocast refractories. Conventional porous electroformed refractories have inconsistent porosity. Porous electrocast refractories produced using water valve and Ming molds have excellent spalling resistance. Therefore, they can be used, for example, as bricks for the upper structure of glass kilns and ceilings.

It is not clear why the mold of the present invention produces porous castings. However, it is thought that this is because the reduced melt reacts with the oxidizing atmosphere and foams. This phenomenon is similar to the foaming phenomenon seen during the manufacture of glass products.

However, if the amount of oxidizing agent exceeds 5 parts per 100 parts of sand, the refractory level of the sand will decrease.

This shortens the life of the sand. Also, if an excessive amount of oxidizing agent is added, the cost will also increase.

Therefore, the amount of the oxidizing agent is preferably 5 parts or less.

The binder used in the oxidizable template of the present invention may be organic or inorganic.

However, those with excellent bonding strength are preferred.

For example, phenolic resin is preferred. A binder with an excellent bonding degree facilitates mold production.

It also facilitates handling of the mold.

The mixing ratio of the binder and the oxidizing agent is usually preferably 0.3 parts or more of the oxidizing agent to 1 part of the binder. Moreover, barium nitrate is preferable for the phenol resin, and barium peroxide is preferable for the water glass.

Next, preferred embodiments of the present invention will be described.

Alumina-zirconia-silica electroformed large objects were manufactured using the oxidizing mold of the present invention.

The raw materials for electroforming large-sized products are 48 parts of Bayer alumina and 1 part of Jill.
250 parts and 2 parts of soda ash. When this mixture is melted in an arc furnace, the melting atmosphere becomes oxidizing according to the method described in Japanese Patent Publication No. 36-5375. In addition, special public service No. 47-5093
According to the method described in the publication, the melting atmosphere becomes reducing.

The raw material melt is placed in the oxidizing mold of the present invention, slowly cooled, and then heated!
Manufactured refractories. The oxidation t used! The basic formulation of the iU type is A-100 parts of Fremantle silica sand from Stralia, 0.8 parts of "Fountrez DA-603" as a binder (Funtrez I) A-603 is a phenol self-hardening resin. commercial product Si), and 0.24 to 0.3 parts of "Fountray C-22-M" as a hardening agent (Fountret C-22-M II is a trademark of phenol self-hardening resin). The chemical composition of the electroformed large product was Zr0□33%, A, +20349
%, 3i0.16%, Na, 01.3% and others. If this electroformed large resistant material is dense, the bulk specific gravity is 3.7~
It becomes 3.8.

The type and amount of oxidizing agent added to the mold was varied.

The results are shown in Table 1 (see below).

In samples A-1 to A-7, the melting atmosphere of the raw materials is oxidizing. Samples B-1 to B-7 have a reducing atmosphere for melting the raw materials.

Sample A-1 was manufactured using a conventional mold. Trial 1
! Carbon was deposited on the outer surface of 4A-1. The tissue also became locally porous. Therefore, the bulk specific gravity is also as small as 3.54. After use, the silica sand was mixed with carbon and turned grayish-black.

Samples 11A-2 to Δ-7 were cast using the mold of the present invention. When an oxidizing agent was added, carbon precipitation was prevented, and the color of the outer surface of the casting changed from white to eyelid white. The organization has also become more elaborate. Therefore, the bulk specific gravity is also 3.7~3
It's as big as ゜E3. No carbon was mixed into the silica sand after use.

Sample B-1 was manufactured using a conventional mold. Carbon was deposited on the outer surface of sample B-1. However, the organization is dense. The bulk specific gravity is also large at 3.77. After use, the silica sand was contaminated with carbon and turned grayish-black.

Sample B-1 is unusual among large electroformed products. In general, when a melt melted in a reducing atmosphere is produced using a conventional mold, a large porous electroformed product is produced. Moreover, its porosity is not constant.

Trial 1.1 r3-2 to B-7 were manufactured using the mold of the present invention. Adding an oxidizing agent prevents carbon precipitation.
It was done. However, the structure became porous as the amount of oxidizing agent increased. Therefore, the specific gravity also became smaller. However, unlike conventional porous electrocast refractories, foaming was reproducible and uniform. No carbon was mixed into the silica sand after use.

The oxidizing mold of the present invention can be used to manufacture not only large electroformed objects. Other castings can of course also be produced.

Since the oxidizing mold of the present invention is configured as described above, it is possible to prevent carbon precipitation and reducing gas. Therefore, the casting is not reduced. In addition, no carbon is mixed into the sand, which is very convenient when reusing it.

Claims (2)

[Claims] (1) In the mold manufactured by mixing sand with a binder, C1 oxidation characterized in that the mold is manufactured by mixing 0.3 parts or more of an oxidizing agent with the sand and the binder per 100 parts of the sand. Gender template. (2) A mold manufactured by mixing a binder with sand, characterized in that the mold is manufactured by mixing 0.3 parts or more of an oxidizing agent with the sand and the binder per 1 part of the binder. Gender template.