JPH06126377A - Method for manufacturing resin coated sand - Google Patents

Abstract

(57) [Abstract] [Purpose] To provide a method for producing a resin coated sand having a high flame retardant effect. [Structure] When a resin coated sand is manufactured, a flame retardant is formed on the surface of a substrate by adding a flame retardant to sand before the binder, and the binder is formed on the surface of the flame retardant.
Therefore, since the flame retardant remains around the base material during molding, the desired flame retardant effect can be expected during casting, and there is no concern that the surface of the product will become rough due to oxidation.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a resin coated sand, and more particularly to a method for producing a resin coated sand suitable for forming a sand mold used for casting a highly reactive metal such as a magnesium alloy. It is a thing.

[0002]

2. Description of the Related Art Conventionally, metal casting by a shell mold method has been widely performed. In particular, when casting a light alloy, it is common to use a shell type. Resin coated sand is one of the sands used for molding such shell molds. In this resin coated sand, a base material made of silica sand or the like coated with, for example, a phenol resin as a binder is used.

Further, in particular, in the case of casting which requires a core of a metal having a high reactivity of a molten metal such as a magnesium alloy, the resin coated sand is used for molding.
Since this core has air permeability so as to ensure the escape of gas in the mold, the surface of the product in contact with the core is likely to be oxidized, which may increase the surface roughness. In order to prevent this, the resin coated sand for molding the core is made of, for example, potassium borofluoride (KB).
A flame retardant consisting of F ₄ ) is added.

However, in practice, even if a flameproofing agent is added to the resin coated sand, the surface roughness of the product during magnesium alloy casting may not always be appropriately prevented. This is because when a flame retardant is laminated on the surface of the resin as a binder during the molding of the shell mold, the resin coated sand is blown into the mold during the molding, and heating
Although it is hardened to mold the mold, most or all of the flame retardant lightly attached to the surface layer of the resin scatters when performing this blowing, and since it is molded as it is, the effect of the flame retardant is extremely small. Is. Another reason is that the flame-retardant effect of the flame-retardant agent remaining on the surface of the binder cannot be expected because the resin as the binder is thermally decomposed and volatilized during the pouring of the molten metal. .

Therefore, the present inventor has found that the timing of addition of the resin material as a binder and the flame retardant is an important factor for leaving the flame retardant on the surface of the substrate during the production of the resin coated sand. I thought up.

[0006]

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems of the prior art, and its main object is to provide a method for producing a resin coated sand having a high flameproof effect. It is in.

[0007]

According to the present invention, the above object is a method for producing a resin coated sand used in a casting shell mold, in which a flame retardant is added to cover the base sand. It is achieved by providing a method for producing a resin coated sand characterized by having a step and a step of adding a resin material as a binder in order to cover the flameproofing agent coated on the sand. It

[0008]

In this way, by adding the flameproofing agent before the binder, the flameproofing agent forms a film on the surface of the substrate, and the binding agent forms a film on the surface of the flameproofing agent.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment of the present invention will now be described in detail with reference to the accompanying drawings.

FIG. 1 shows a procedure for manufacturing a resin coated sand according to the present invention. In this embodiment, the resin coated sand is manufactured by the known hot method.

First, high silica sand (silica sand) as a base material heated to 120 ° C. to 140 ° C. is charged into a mixer, and at the same time, potassium borofluoride as a flame retardant has a diameter of 0.2 mm.
Coarsely pulverize to some extent and add. Then, the mixture is kneaded for 10 seconds to 15 seconds to form a uniform flame retardant layer on the sand surface. next,
A predetermined amount of a resol-type phenol resin as a binder is added (point A), kneading is performed for 30 seconds to 40 seconds, and cooling water is added (point B). Then, after kneading for 45 to 60 seconds to confirm disintegration, after 30 seconds have passed, calcium stearate (WAX) is added and left for 20 to 30 seconds, and then sand is removed and cooled to protect the silica sand surface. A resin coated sand in which a flame retardant and a binder are laminated in this order is obtained.

Table 1 shows the type and particle size of sand as a base material of resin coated sand for main port casting and water jacket casting of an intake manifold of an automobile engine, the type of resin as a binder, the amount added, and a flame retardant. The amount of potassium borofluoride added and the basic physical properties of the resin coated sand produced are shown.

[0013]

[Table 1]

The structure of the resin coated sand produced as described above is schematically shown in FIG. In the resin coated sand produced by the method according to the present invention,
The surface of silica sand 1 as a substrate is coated with potassium borofluoride 2 as a flame retardant, and the surface of this potassium borofluoride 2 is coated with a phenol resin 3 as a binder. Therefore, even if most of the phenolic resin 3 is volatilized by thermal decomposition during the molding described later, potassium borofluoride 2 remains, so that a flameproof effect in actual casting can be expected.

3 (a) to 3 (f) are schematic cross-sectional views showing a procedure for molding a shell mold using the resin coated sand described above.

First, in FIG. 3 (a), the mold 10 formed by combining the cracking molds 11 and 12 is heated, and in FIG. 3 (b), air blow is carried out to put the resin coated sand into the mold 10.
Then, it is baked for about 40 seconds in FIG.
The mold 10 is turned over to remove unnecessary sand. Here, when molding a solid core or the like, the step of sand removal by this inversion can be omitted. Subsequently, the mold 10 is opened in FIG. 3 (e), and the shell core 13 completed in FIG. 3 (f).
Take out. Table 2 shows the mold temperature, firing time and the like during molding of the main core shell core for the intake manifold of the automobile engine and the shell core for the water jacket at this time.

[0017]

[Table 2] The graph of FIG. 4 shows the relationship between the amount of potassium borofluoride added to the resin coated sand for main port casting and water jacket casting, and the rate of oxidation on the product surface during casting by a shell mold using this resin coated sand. Indicates. As you can see from this graph,
In the manufacturing method according to the present invention, addition of 0.4% or more of potassium borofluoride for main port casting and 0.1% or more of water jacket casting surely prevents oxidation of the product surface. I know that I can do it.

[0018]

As is apparent from the above description, according to the method for producing a resin coated sand according to the present invention, the flame retardant remains around the base material during molding, so that a desired flame retardant effect is expected during casting. Therefore, there is no fear that the surface of the product will be increased in roughness due to oxidation. From the above, the effect of the present invention is great.

[Brief description of drawings]

FIG. 1 is a time schedule showing a procedure for manufacturing a resin coated sand according to the present invention.

FIG. 2 is a cross-sectional view schematically showing the structure of a resin coated sand manufactured by the manufacturing method according to the present invention.

FIGS. 3 (a) to 3 (F) are explanatory views showing a process of molding a core for casting an intake manifold of an automobile engine by using a resin coated sand manufactured by a manufacturing method according to the present invention. It is a figure.

FIG. 4 is a diagram showing an amount of potassium borofluoride added to resin coated sand for main port casting and water jacket casting of an intake manifold of an automobile engine manufactured by the manufacturing method according to the present invention, and shell molding using the resin coated sand. It is a graph which shows the relationship with the oxidation generation rate of the product surface at the time.

[Explanation of symbols]

 1 Quartz sand 2 Potassium borofluoride 3 Phenolic resin 10-12 type 13 Shell core

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[Procedure amendment]

[Submission date] November 9, 1993

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] Brief description of the drawing

[Correction method] Change

[Correction content]

[Brief description of drawings]

FIG. 1 is a time schedule showing a procedure for manufacturing a resin coated sand according to the present invention.

FIG. 2 is a cross-sectional view schematically showing the structure of a resin coated sand manufactured by the manufacturing method according to the present invention.

FIGS. 3 (a) to 3 ( f ) are explanatory views showing a step of molding a core for casting an intake manifold of an automobile engine by using a resin coated sand manufactured by a manufacturing method according to the present invention. It is a figure.

FIG. 4 is a diagram showing an amount of potassium borofluoride added to resin coated sand for main port casting and water jacket casting of an intake manifold of an automobile engine manufactured by the manufacturing method according to the present invention, and shell molding using the resin coated sand. It is a graph which shows the relationship with the oxidation generation rate of the product surface at the time.

[Explanation of Codes] 1 Quartz sand 2 Potassium borofluoride 3 Phenolic resin 10-12 type 13 Shell core

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Tetsuro Goto 341-5 Nishino, Sakai City, Osaka Prefecture (72) Inventor Isamu Ide 1648-15, Kanaoka-cho, Sakai City, Osaka Prefecture Kazuhiko Takada, Aoi Hamamatsu City, Shizuoka Prefecture 318, Machi Enkei Stock Company

Claims (1)

[Claims] 1. A method for producing a resin coated sand used in a shell mold for casting, comprising a step of adding a flame retardant to cover the base sand, and a step of covering the flame retardant coated on the sand. A method for producing a resin coated sand, which comprises the steps of adding a resin material as a binder in this order.