JPS62101351A - Mold shaping method - Google Patents

Abstract

PURPOSE:To shape a casting mold suitable for production of cast steel products of a high Mn steel in particular by packing a molding sand mixture composed of basic sand such as olivin sand, acid curing resin and peroxide in a molding flask, then supplying gaseous SO2 into the molding sand to cure the sand. CONSTITUTION:The molding sand prepd. by kneading the basic sand such as olivin sand consisting of, for example, olivin as raw stone, acid curing resin (e.g.; furan resin) as a binder and peroxide is packed under adequate oscillation into a casting mold. The gaseous SO2 is supplied into the molding sand, then the gaseous SO2 reacts with the active oxygen possessed by the peroxide to apply the strong acid to the acid curing resin in the molding sand, thereby quickly polymerizing and curing the acid curing resin so as to act as a binder for the basic sand. The resulted molding sand has an excellent collapsing property and reconditioning characteristic. The casting workability is thereby improved and the cost of casting is reduced.

Description

[Detailed Description of the Invention] [Objective of the Invention] (Industrial Application Field) The present invention relates to a molding method used for manufacturing a mold used for manufacturing a cast product, and particularly relates to a molding method used for manufacturing a mold used for manufacturing a cast product.
For example, J I S S CM n H1-3.11.
The present invention relates to a molding method used to manufacture a mold suitable for manufacturing cast steel products in item 21).

(Prior Art) Conventionally, when manufacturing molds used for manufacturing cast products, for example, silica sand (S i 02
) and mountain sand, which is a natural mixture of silica sand and clay minerals, were often used. Then, a binder is mixed with the foundry sand, which is mainly composed of silica sand, and molded into a predetermined shape by a manual molding method, a mechanical molding method, or the like.

As this binder, clay binders, inorganic binders, organic binders, etc. are used. Among these, organic binders include thermosetting resins such as phenolic resins, furan resins, and urethane-based binders. Resin etc. are used.

On the other hand, in the production of high manganese steel SM products, when a mold using foundry sand mainly composed of silica sand is used, the 5i02 forming the mold reacts with MnO in the molten steel, resulting in low Melting point metal oxide (MnO* S i 02 .
2Mn0*S i02 ) is produced, and this low melting point total bending oxide reacts with carbon to generate CO gas, which causes local blowing and causes casting defects. Therefore, in order to prevent such casting defects, basic olibic acid (o
livine 5and) was also used.

This olivine acid is made from peridotite rock, which is crushed and sieved, and is generally made from (Mg
, Fe)2 Si04, and as a binder for this olibic acid, water glass (sodium silicate (Na2 Si0
3) aqueous solution) was often used.

(Problems to be Solved by the Invention) As described above, if an olivine sand mold is used to manufacture high manganese steel castings, it is possible to prevent casting defects caused by chemical baking. When water glass is used as a binder to harden the mold, there are problems in that the hardening speed of the mold sand is slow and the disintegration properties of the mold sand are not very good. If furan resin is used as a binder to ensure the disintegrability of mold sand and enable recycling, the amount of acid consumed will be considerably large, so olivine sand with furan resin is used as a binder. There was a problem in that it was virtually impossible to harden the mold.This invention was made by focusing on the above-mentioned conventional problem. It is possible to use acid-curing resins such as resins, and in particular, it is possible to manufacture high manganese steel #PI steel products without causing casting defects due to chemical burning, which is the case when acid sand is used. The purpose of this invention is to provide a method for molding a mold.

[Structure of the Invention] (Means for Solving the Problems) The molding method according to the present invention includes filling a molding flask with molding sand that is a mixture of basic sand, acid-curing resin, and peroxide, and then It is characterized by supplying sulfur dioxide gas into the mold sand to harden it.

The basic sand used in this invention is, for example, olivine acid (2MgO.
2 S i 04; also called “dried sand”),
A basic material such as magnesia sand (MgO) is used. In addition, among peridotites, those rich in Mg are also called magnesia peridotite (forsterei), and those rich in Fe are also called iron peridotites (fayarite).

Further, as the acid-curable resin, a resin 1 that hardens upon contact with an acid, such as furan resin, phenol-formalin resin, urea-formalin resin, etc., is used. In this case, since pure furan resin (C4H40) is expensive, it is preferable to use a furan resin obtained by polycondensing furfuryl alcohol with formaldehyde, urea, phenol, etc. as the furan resin used as the binder. In the usual case, it is preferable to use a liquid condensate having a not very large molecular weight, add an acidic curing catalyst to this, and finally form a three-dimensional crosslink.

Further, as the peroxide, an organic peroxide, for example, if methyl ethyl ketone peroxide type peroxide is used. Normally, this peroxide gradually decomposes during kneading and loses its oxidizing power, so if it cannot be treated within the pot life, new peroxide can be added to extend the pot life. is necessary. Therefore, in order to reduce the amount of peroxide consumed, it is desirable to process the product within its pot life as much as possible.

Then, molding sand made by adding peroxide to a mixture of basic sand and acid-curing resin and kneading is packed into the molding flask under appropriate vibration, and then the molding sand is filled with sulfur dioxide gas (S02 gas). ), the So2 gas in the mold sand reacts with the active oxygen of the peroxide and provides a strong acid to the acid-curing resin, causing the acid-curing resin to rapidly polymerize and harden.
It becomes possible to act as a binder for M-based sand.

In addition, when packing mold sand into the M frame, for example,
Place mold sand into the casting flask where the model is set.

A manual molding method performed manually using a stamp or an air rammer, or a mechanical molding method using one of squeeze, jolt, blowing, pie plate, slinking, etc. or a combination of these methods may be employed.

It is also desirable, if necessary, to apply a coating to the inside of the mold prior to casting.

It is best to select a material by taking into account adhesion with the mold, reactivity with the cast metal, etc.

(Example) Oridon sand (2MgO-Si02) was used as the 1M basic sand, and furan resin (Ca H40) was used as the acid-curable resin.
), and methyl ethyl ketone peroxide (CH3COOC2Hs) was used as the peroxide. Then, 1.5 parts of furan resin was added to the olivine sand and mixed, and then 50% by weight of methyl ethyl ketone peroxide was added and kneaded to make mold sand, which was then stamped into a mold with an inner diameter of 250 mm. 0 filled with sand
Next, before the decomposition of methyl ethyl ketone peroxide progressed, S02 gas was supplied into the mold sand for about 2 seconds, and then discharged for about 5 seconds to harden the furan resin, thereby producing a mold.

Next, high manganese steel (JISS CM
A bar-shaped cast high manganese steel product was produced by casting the molten metal of nH).

Therefore, when we examined the cast steel products obtained in this way, we found that the incidence of chemical burnt stone was 0, and it was confirmed that there was almost no reaction between the mold and the molten metal. We were able to obtain steel M copper W.

On the other hand, for comparison, a mold was made in almost the same manner as described above except that recycled silica sand was used instead of olivine sand, and a molten 7" high manganese steel (SCMnH) was placed in the mold.
,', When rod-shaped high manganese steel castings were manufactured by cold casting, low melting point MnO・5in2 and 2Mn
0*5i02 Metal oxide produces chemical burnt stone,
The burn rate in this case was about 30%, which was an unfavorable result.

[Effects of the Invention] As explained above, in the molding method according to the present invention, after filling the molding flask with molding sand that is a mixture of basic sand, acid-curing resin, and peroxide, the molding sand is filled with By supplying sulfur dioxide gas for hardening, it is possible to manufacture high-manganese steel castings in particular without the occurrence of casting defects due to chemical burning stones, and the mold sand has excellent disintegration and recyclability. As a result, the extremely excellent effects of improving casting workability and reducing casting costs are brought about.

Claims (3)

[Claims] (1) A molding method characterized by filling a molding flask with molding sand that is a mixture of basic sand, acid-curing resin, and peroxide, and then supplying sulfur dioxide gas into the molding sand to harden it. (2) Claim No. 1 in which the basic sand is olivine sand (
1) The molding method described in section 1). (3) The molding method according to claim (1) or (2), wherein the acid-curable resin is a furan resin.