JPS61103644A - Production of casting mold - Google Patents

Abstract

PURPOSE:To decrease considerably the staining of a pattern and to improve the productivity of a casting mold by coating zinc powder to a pattern for producing the casting mold in the stage of molding granular refractories with an org. binder. CONSTITUTION:The zinc powder having <=5mm average grain size is coated on the pattern for producing the casting mold and molding is executed in a process for producing the casting mold in which the granular refractories are molded with an acid curable org. binder. The staining of the pattern is thus considerably decreased and the productivity of the casting mold by a furan cold box process is much improved.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method for manufacturing a mold, and in particular, when manufacturing a mold using an organic binder such as an acid-curable resin, molds such as resin and sand adhesion are removed. This invention relates to a method for manufacturing molds with improved staining.

[Conventional technology] Conventionally, in order to manufacture molds in medium to large quantities, a shell molding method has been used in which a refractory granular material is coated with phenolic resin, and this is filled into a mold using air, pressure, etc., and thermoset molded. It has been.

However, in order to save energy during mold manufacturing, improve mold production speed, and improve the quality of molds and castings, the cold box mold manufacturing method, which hardens at room temperature using gaseous or aerosol materials, has become an alternative mold manufacturing method to the shell molding method. Serious attempts are being made to introduce it in the foundry industry.

The cold box method involves curing acid-curing resins, typically furan-based resins, with sulfur dioxide using peroxide as an oxidizing agent, and curing polyols and polyisocyanates using an aerosol-like tertiary amine as a catalyst. There is a urethane cold box that hardens.

Molds using urethane cold boxes have drawbacks such as poor disintegration of casting sand during casting production, and the tendency to cause casting defects such as sand trapping, scooping, pinholes, and soot defects.

On the other hand, the Francold box has been rapidly attracting attention in recent years as a method for solving the above-mentioned difficulties.

The present invention relates to a method for manufacturing a mold suitable for the Franco cold box method, and is intended to improve model staining, which is a factor that causes a decrease in productivity in cold boxes that harden instantly by gas injection at room temperature.

Conventionally, automatic molding machines have been used to manufacture medium-sized molds, in which acid-curing resin and peroxide are added and kneaded to fire-resistant granular material to coat the surface of the fire-resistant granular material, and air pressure, etc. Filling, molding, curing, and removal are automatically performed continuously in a cycle of less than one minute.

[Problems to be Solved by the Invention] However, in the cold box method, the binder coated on the surface of the refractory granular material is transferred to the model surface due to the pressure of the curing gas and air and uneven gas flow. It has the disadvantage that it tends to cause model stains such as resin adhesion caused by resin adhesion and sandy layers due to uneven hardening of the mold surface.

Due to mold stains adhering to the resin and sand, the molding machine must be stopped several times per day to remove the mold stains during continuous production, reducing mold productivity.

Therefore, in order to further improve mold productivity in the cold box method, there is a need for a mold release agent that improves resin adhesion and sand buildup.

[Means for Solving the Problems] The present inventors have arrived at the present invention as a result of intensive research into a mold manufacturing method for significantly improving model staining and further improving mold productivity.

That is, the present invention relates to a method for manufacturing a mold, which is characterized in that when a mold is manufactured using a granular refractory using an organic binder, zinc powder is applied to a mold manufacturing model.

The present invention is characterized in that zinc powder is used, and conventionally used inorganic powders such as talc, mica, graphite, aluminum, etc. cannot provide sufficient effects.

In the present invention, methods for applying zinc powder to a model for mold production include (a) spraying it with air, (b) spraying it in the form of an aerosol, (e) scattering it on the model surface with a brush or puff, etc. d) It is appropriate to put the powder in a cloth bag or the like and sprinkle it on the surface of the model. The zinc powder may be applied as is, but it is also possible to spray the zinc powder together with a volatile solvent or apply it with a brush.

It is also possible to mix the zinc powder with conventionally used inorganic or organic powders.

The average particle size of zinc powder is 51 in terms of adhesion to models and applicability! It is preferable that it is below m.

[Examples] Hereinafter, the present invention will be explained in more detail with reference to Examples, but the present invention is not limited to the following Examples.

Examples 1 to 3 and Comparative Examples 1 to 3 Mold molding methods include water glass self-hardening using a calcium silicate as a hardening agent, furan self-hardening using an organic sulfonic acid as a hardening agent, and phenol using a pyridine-based tertiary amine as a catalyst. When manufacturing molds using self-hardening urethane, zinc powder according to the present invention and talc powder, which is conventionally used publicly in foundries, are added to wooden molds, aluminum molds, and epoxy resin molds as mold manufacturing models, respectively. 1 for every 5 molds
The coating was applied several times and molds were repeatedly molded to evaluate the critical number of molds at which the surface stability of the mold deteriorated due to the adhesion of river sand to each mold and required cleaning of the mold. The results are shown in Table 1.

Table 1 Examples 4 to 6 and Comparative Examples 4 to 6 The mold manufacturing method is the so-called furan cold box method in which a mold is formed by blowing sulfur dioxide gas into furan resin in the presence of an organic peroxide, and cast iron is used as a mold manufacturing model. Using a mold, apply the zinc powder according to the present invention as a powder or in a suspended state in a dispersion medium once every 10 molds, and continuously
The amount of contaminants adhering to the model during 0-time molding and the number of times the model was cleaned to maintain the surface condition of the mold were evaluated. The results are shown in Table 2.

Table 2

Claims (1)

[Claims] 1. When manufacturing a mold using a granular refractory using an organic binder,
A mold manufacturing method characterized by applying zinc powder to a mold manufacturing model. 2. The manufacturing method according to claim 1, wherein the organic binder is an acid-curable organic binder. 3. The manufacturing method according to claim 1, wherein the average particle size of the zinc powder is 5 μm or less.