JPS5935307B2 - Water-soluble mold and its manufacturing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a water-soluble mold suitable for aluminum alloys, copper alloys, cast iron, cast steel, etc., and a method for producing the same.

Conventionally, molds using inorganic binders, such as CO□ molds and inorganic self-hardening molds, have been used as molds for metal casting.

The disadvantages of these molds are that they have poor collapsibility after casting (and that it takes time to remove the mold).

Furthermore, molds using organic binders with good disintegration properties have the disadvantage of insufficient heat resistance and the generation of gas due to decomposition of the binder during casting, which tends to cause casting defects.

An object of the present invention is to provide a water-soluble mold that has high heat resistance, generates little gas during casting, and collapses when water is drained from casting, and a method for manufacturing the same.

This water-soluble mold is made by molding refractory particles such as silica sand, alumina, magnesia, zircon, olivine, and chromite using calcium phosphate or a mixture of calcium phosphate and phosphoric acid as a binder. Can be manufactured cheaply.

As a binder, the molar ratio of CaO/805 is 0.1 to 2.
85 or a mixture of calcium phosphate and phosphoric acid is used.

Tricalcium phosphate is known as a compound with a CaO/P205 molar ratio of 3.0.

However, tricalcium phosphate has low solubility in water (0,
25g/1000g of water or less), and slightly dissolves in water containing CO□, which is also 0.75g/1000g of water.
It is as follows.

However, tricalcium phosphate (Ca3 (P 04 )2
) by adding phosphoric acid (H3PO4) to Ca3 (
It has been found that po4)2 can be dissolved to obtain a highly viscous solution, which can bind refractory particles.

It was also found that a binder made of a mixture of calcium phosphate and phosphoric acid does not react with silica sand even at high temperatures, and that molds made of silica sand bound by this binder disintegrate with water even after being heated at high temperatures.

In the present invention, CaO/B is 0! The molar ratio of i ranges from 0.1 to
The reason for setting it to 2.85 is that if the molar ratio is smaller than 0.1 or larger than 2.85, the caking force will be small and it will not be possible to obtain optical strength when refractory particles are caked. be.

Also, if phosphoric acid is added to calcium oxide or calcium hydroxide, the calcium oxide or calcium hydroxide will dissolve and a highly viscous solution will be obtained, which can be used as a binder for refractory particles, and in this case as well, CaO/P2O5 When the molar ratio is in the range of 0.1 to 2.85, the caking force is large.

When sodium phosphate and potassium phosphate are mixed in a mixture of calcium phosphate and phosphoric acid, the water solubility of the mold is improved because sodium phosphate and potassium phosphate have high solubility in water.

Zinc phosphate and magnesium phosphate have high melting points and improve the heat resistance of the mold.

All of these have low solubility in water, but if phosphoric acid coexists, they will dissolve in water and will not interfere with the water solubility of the template.

Alternatively, a binder consisting of one of the group of calcium phosphate, calcium oxide, or calcium hydroxide and phosphoric acid is mixed with refractory particles, and after the mixture is formed, ammonia gas is passed through it to form ammonium phosphate (NH8)3PO. , is precipitated, and Ca in the viscosity is converted to calcium phosphate (Ca
3 (PO4)2), calcium hydrogen phosphate (Ca
HPO4, etc.) and the mold self-hardens.

〔Example〕

(1) Phosphoric acid (100 parts H3P0
4) 1.5 parts tricalcium phosphate (Cps (P 04
)2) A mold was formed using a mixture of 1-0 parts of water and 6.0 parts of water.

The mold after drying at 200°C had a compressive strength of 30% or more.

Cast iron (Fe12) and aluminum alloy (AC4A) were cast using this mold, and when water was poured into the mold after casting, the mold easily collapsed.

(2) Add 1.3 parts of calcium hydroxide (Ca(OH)2) to 100 parts of alumina (120 mesh) and phosphoric acid (
A mold was formed by adding a solution of 1.5 parts of 100%) 13PO4) as a binder and dried at 200°C.

This mold shows a compressive strength of 40% or more after drying, and has a cast iron,
and could cast aluminum alloys.

Moreover, the mold after casting collapsed due to water.

(3) Phosphoric acid (100 parts H3P0
4) 4.0 parts, tricalcium phosphate (Ca3(PO4)2
) and 4 parts of water (the molar ratio of CaHPO4 in this binder corresponds to 0.1).

) was added to form a mold and dried at 200°C.

The dried molded product showed a compressive strength of 20% or more, and a water-soluble mold that could be used for casting copper alloys, cast iron, and aluminum alloys was obtained.

(4) Phosphoric acid (100 parts H3P0
4) 0.14 parts tricalcium phosphate (Ca5(PO4
)2) a binder consisting of 4.1 parts (CaO in this binder)
/P2O5 has a mo/1/ratio of 2.85.

) was added to form a mold and dried at 200°C.

The dried molded product showed a compressive strength of 20 wonders or more, and a water-soluble mold that could be used for casting copper alloys, cast iron, and aluminum alloys was obtained.

(■ Phosphoric acid (1004H3PO
4) A mixture of 2.5 parts of tricalcium phosphate, 2.0 parts of tricalcium phosphate, and 3 parts of water was molded and cured by passing ammonia gas.

The compact exhibited a compressive strength of 7 degrees or higher, and a water-soluble mold that could be used for casting cast iron, copper alloys, and aluminum alloys was obtained.

As explained above, the water-soluble mold obtained by the present invention has high heat resistance, no gas is generated from the mold during casting, and the cast iron after casting is easily disintegrated by water and can be reused. It has become possible to systemize it, and it has a great effect in terms of effective use of resources.

In addition, the phosphoric acid and calcium phosphate that are the binders of this mold do not harm the human body, and the PO4'' ions in the wastewater are
It is easy to precipitate and recover as calcium, and there is no problem of environmental pollution.

Claims (1)

[Scope of Claims] 1. Refractory particles such as silica sand, alumina, magnesia, zircon, chromite, and olivine are used as a base material, and CaO/
It is characterized in that the molar ratio of P2,05 is 0.1 to 2.85, and a mixture of phosphoric acid and one of the group consisting of calcium alkaliphosphate, lucium oxide, and lucium hydroxide is molded as a binder. water-soluble mold. 2 Using refractory particles such as silica sand, alumina, magnesia, zircon, chromite, and olivine as a base material, cao/P
20. A mixture of calcium phosphate and phosphoric acid having a molar ratio of 0.1 to 2.85, and one or more of the group consisting of sodium phosphate, potassium phosphate, magnesium phosphate, and zinc phosphate. A water-soluble mold characterized by being molded using a binder. 3 Using refractory particles such as silica sand, alumina, magnesia, zircon, chromina, and olivine as a base material, CaO/P
Molding a mixture of phosphoric acid and one of the group of calcium phosphate, calcium oxide, and calcium hydroxide with a molar ratio of 2O5 of 0.1 to 2.85 as a binder, and then curing by passing ammonia gas A method for producing a water-soluble mold characterized by: