JPS61249643A - Composition for casting mold having good collapsing property - Google Patents

Abstract

PURPOSE:To obtain a compsn. for a casting mold having a good collapsing property after pouring by consisting essentially of a base material for the mold in which at least prescribed weight % of molding sand is replaced with a refractory high specific gravity granular material having a specific value or above of the true specific gravity and a curable org. binder. CONSTITUTION:At least 10wt% of the molding sand constituting the compd. for the casting mold consisting essentially of the molding sand and curable org. binder is replaced with the refractory high specific gravity granular material having >=3.4 true specific gravity. Such refractory high specific gravity granular material is selected from zircon sand, chromite sand, converter air granulated slag and granular iron. A thermosetting resin, air permeable curable resin or cold self-curing resin is used for the curable org. binder. The compsn. for the casting mold having the good collapsing property after pouring is thus obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a molding composition that has good disintegration properties after pouring, particularly for molding that is suitably used in the preparation of light alloy castings such as aluminum alloys. The present invention relates to a composition.

BACKGROUND OF THE INVENTION Usually, molds used for casting are made from a molding composition consisting of foundry sand and an organic binder, but this molding composition is required to easily disintegrate after pouring. A lot of research has been carried out for this purpose.

In particular, when casting light alloys such as aluminum alloys, unlike iron, the mold does not have enough heat history to decompose the binder in the mold, so the mold tends to collapse after pouring. <<, it is necessary to remove the sand by applying a large impact to the casting with an air hammer, etc., or heat it at a high temperature of about 500°C for 4 to 8 hours and sand-burn it, which consumes a lot of labor and energy. was needed. By the way, recent automobile-related cast parts have tended to use light alloys such as aluminum alloys instead of conventional iron in order to reduce weight, and the problem of improving the collapsibility of molds has become increasingly urgent. It is becoming.

One way to improve the disintegration of molds after pouring is to break down the binding force of the binder by adding a substance that thermally decomposes at a relatively low temperature. As the substance, halogen-containing organic compounds, peroxides, phosphoric acid esters, inorganic chlorides, etc. have been proposed (Japanese Patent Laid-Open No. 57
-139442, JP 57-149043, JP 57-156858, JP 58-3
745, JP-A-58-205641).

However, since these substances destroy the binding force of the binder, the strength of the resulting mold inevitably decreases, and therefore there is a natural limit to the amount of these substances that can be added, and it is difficult to achieve sufficient disintegrability. There is no hope for improvement.

Problems to be Solved by the Invention An object of the present invention is to easily provide a mold composition that exhibits good disintegration properties after pouring, even in the casting of light alloys such as aluminum alloys whose pouring temperature is low. That is.

Means to Solve the Problem The inventors of the present invention have conducted intensive research on a means to quickly propagate the vibration to the entire mold and promote its collapse when removing sand while applying vibration to the casting. As a result, it was discovered that the above object could be achieved by replacing at least a portion of the foundry sand with a true specific gravity of 2.6 with refractory granules of high specific gravity, and based on this knowledge, the present invention was completed. reached.

That is, the present invention provides a molding composition containing foundry sand and a curable organic binder as main components, and in which at least 10% of the foundry sand is mixed with refractory high specific gravity granules having a true specific gravity of 3.4 or more. The object of the present invention is to provide a molding composition with good disintegrability, characterized in that the composition is substituted with

In the composition of the present invention, all of the foundry sand has a true specific gravity of 3
．． It may be replaced with a refractory high specific gravity granule of 4 or more,
Also, a part of it may be replaced with a fire-resistant high-density granular material, but when replacing a part, it is necessary to replace a part with a weight factor of at least 10. If this amount is less than 10% by weight, the vibration propagation effect will not be sufficiently promoted.

Furthermore, there is no particular restriction on the particle size distribution of the granules.

It is preferable to use a granular material in which the amount that does not pass through a 20-mesh sieve is 20 weight i-4 or less, and the amount that does not pass through a 270-mesh sieve is 10 weight i-4 or less.

Furthermore, if the refractory high specific gravity granules have a true specific gravity of less than 3.4, they will not have a sufficient effect of transmitting vibrations. The higher the true specific gravity, the better; however, substances higher than 8.0 are generally impractical because they become expensive and valuable metals. Specific examples of the refractory high specific gravity granules used in the composition of the present invention include zircon sand, chromite sand, pulverized converter slag, and granular iron, each of which may be used alone, or Two or more strains may be used in combination. The true specific gravity shown here is J
This is a value measured in accordance with Engineering 5-R-2205.

Examples of the organic binder used in the composition of the present invention include heat-curing resins (shell mold method), air-curing resins (cold box method), and room-temperature self-curing resins that are commonly used in the production of molds. For example, in the shell mold method, novolac type or resol type phenolic resins, urea resins, etc. are used.In the cold box method, phenol incyanate fruit trees, furan resins, etc. are used at room temperature. In the curing method, phenolic resin @17 run resin, phenol incyanate resin, etc. are used.

Furthermore, modified resins prepared by reacting or mixing various additives such as bromine-containing organic compounds and chlorine compounds with these resins for the purpose of improving disintegration properties can also be used.

In the composition of the present invention, these organic binders are contained in an amount of 0.1 to 0.1 to
It is preferable to mix in a range of 10% by weight or less.

The method for producing the molding composition of the present invention includes, for example, using a room-temperature or heated base material in which part or all of the foundry sand has been replaced with the refractory high-density granules, and the organic binder;
A method of mixing using an appropriate mixer, or mixing the foundry sand at room temperature or heated and the organic binder or the refractory high specific gravity granules and the organic binder separately using a mixer. , and then blending these in a desired ratio.

By the way, molds are usually manufactured and controlled using a mold composition so as to have a certain strength depending on the shape and target casting in order to prevent destruction during molding, transportation, casting, etc. In this case, the mold strength differs depending on the type and particle size distribution of the refractory granules used even with the same organic binder, so it is generally adjusted by the amount of the organic binder added. The easily disintegrating molding composition of the invention uses refractory high specific gravity granules having a true specific gravity of 3.4 or more alone or a mixture thereof with foundry sand as a molding base material, and The mold has significantly improved disintegration properties after pouring aluminum light alloy, etc., compared to conventional molds, and the time required for its disintegration can be significantly shortened. Therefore, by using the composition of the present invention, production efficiency can be significantly improved, and since sand can be easily removed with low knockout pressure, there is less destruction of castings. Product yield is improved, and it is also possible to save energy by shortening heat treatment time and save labor by reducing manual work during knockout.

Example Next, the present invention will be explained in more detail with reference to Examples.

The mold bending strength was measured according to JIS K6910, and the collapsibility was examined as follows.

That is, a dog-bone type core (
40 m'l in width, 751 m in length, and 25 m in thickness.
On the other hand, separately mold an outer mold having slightly larger dimensions than the core, set the core therein, and then
Pour molten aluminum alloy at ±5°C. After cooling, vibration was applied to one part of the casting using an air blower with an air pressure of 0.4 KP/cII, and the time (disintegration time) until the core completely came out from the exit of diameter 10j11 of the casting was measured. , the collapsibility was investigated.0 Examples 1 to 4 5000 parts by weight of the fire-resistant high specific gravity granules as shown in Table 1 were used as the base material for the mold, and
Heat to 150℃ and use a speed mixer (manufactured by Enshu Tekko Co., Ltd.)
Immediately, a predetermined amount of novolac type phenolic resin (manufactured by Asahi Yokuzai Kogyo ■, SP 69) as shown in Table 2 is added as a binder to obtain a constant mold strength.
0 ] and kneaded for 50 seconds in a mixer to coat the granules with the resin, then add 1.5% by weight of cooling water to the mold base material and 15% by weight of hexamethylenetetramite to the resin. % as an aqueous solution, and after about 40 to 60 seconds, when the contents became free-flowing, 0.1% by weight of calcium stearate was added as a lubricant to the mold base material, and an additional 15% by weight was added as a lubricant. After kneading for seconds, the mixture was taken out from the mixer to obtain a thermosetting molding composition with high fluidity. O shown in Table 2 Examples 5 and 6 Instead of using the refractory high specific gravity granules alone as the base material for the mold, a mixture of foundry sand and refractory high specific gravity granules as shown in Table 1 was used. A thermosetting mold composition was prepared in the same manner as in Examples 1 to 4, except that the composition was used, and the bending strength and collapsibility of molds made from this composition were determined.The results are shown in Table 2. 0 Example 7 Resin-coated molding sand (using 1.2% by weight of 7-Pollack type phenolic resin) was prepared in the same manner as in Examples 1 to 4, except that foundry sand was used instead of the refractory high specific gravity granules. A) was obtained. On the other hand, in the same manner as above, the fire-resistant high specific gravity granules and 1.
Resin-coated fire-resistant high-density granules using 2% by weight novolac type phenolic resin (obtained odor).

Next, (A) and (B) thus obtained were mixed at a weight ratio of 50:50 to produce a thermosetting mold composition, and a mold made with this composition was bent. Strength and collapsibility were determined. The results are shown in Table 2.

Comparative Example 1.2 A thermosetting mold composition was produced in the same manner as in Examples 1 to 4, except that foundry sand was used as a substitute for the refractory high-density granular material as a base material for the mold. The mold bending strength and collapsibility of the material were determined. The results are shown in Table 2.

(Note) A collapse time of 0 seconds indicates that the mold collapsed only due to vibrations when the outer mold was disassembled.

As is clear from Table 2, the disintegration time of the composition of the present invention is significantly shortened and the disintegration property is significantly improved compared to the conventional composition.Example 8 As a base material for the mold, 2500 parts by weight of zircon sand as shown in Table 1 above was charged into a tabletop mixer (manufactured by Hinayo Kogyo Co., Ltd.), and then immediately caking was carried out to obtain approximately constant mold strength. A predetermined amount of phenol resin (manufactured by Asahi Yukizai Kogyo ■, AP-P200) and a curing accelerator (manufactured by Asahi Yukizai Kogyo ■, UA) as shown in Table 3 were added as agents, and mixed for 30 seconds in a mixer. After that, add polyisocyanate [AP-M750, manufactured by Asahi Yukizai Kogyo ■], and add 30
After kneading for seconds, the mixture was taken out from the mixer to obtain a self-hardening molding composition at room temperature.

The collapsibility and compressive strength of the molds made from the mold compositions thus obtained are determined, and the results are shown in Table 3. The compressive strength of the mold composition is 50Bφ×
It was hand molded into a 50♂ wooden mold and measured after being left for 24 hours.

Example 9 A self-hardening mold composition at room temperature was produced in the same manner as in Example 8, except that a mixture of zircon sand and foundry sand was used instead of zircon sand as the base material for the mold. The collapsibility and compressive strength of
Shown in the table.

Comparative Example 3% 4 A self-hardening mold composition at room temperature was produced in the same manner as in Example 8, except that foundry sand was used in place of zircon sand as the base material for the mold, and the disintegrability and Compressive strength was determined. The results are shown in Table 3.

Example 11 2,500 parts by weight of zircon sand as shown in Table 1 above was used as a base material for the mold, put into a tabletop mixer (manufactured by Shinyo Kogyo Co., Ltd.), and then immediately mixed to obtain a constant mold strength. As a binder, a predetermined amount of phenol resin (manufactured by Asahi Yikizai Kogyo ■, 0B-P) as shown in Table 4 and polyincyanate (manufactured by Asahi Yikizai Kogyo ■% aB-yt) is used as a binder.
After mixing for 60 seconds, the mixture was taken out from the mixer to obtain an aeration-curing mold composition. Triethylamine gas was aerated to create a mold, and the collapsibility and compressive strength were determined. The results are shown in Table 4.

Comparative Example 5 An air-curable molding composition was produced in the same manner as in Example 11, except that freemantle sand was used instead of zircon sand as the molding substrate.

The collapsibility and compressive strength of this material were determined. The result is the fourth
Shown in the table.

Table 4 Procedural Amendments July 29, 1985 Commissioner of the Patent Office Black 1) Akio Tono 1, Indication of the case Ninth Ward 1988
Patent Application No. 92529 2, Title of the invention: Molding composition with good disintegration properties 3, Person making the amendment, Relationship to the case Patent applicant: 2-5955 Nakanose-cho, Nobeoka City, Miyazaki Prefecture Asahi Yokuzai Kogyo Co., Ltd. Representative Isao Kawanami 4, Agent.

5. Date of amendment order Initiated 6. Number of inventions increased by amendment 0 7. Subject of amendment Detailed explanation of the invention in the specification column 8
゜Amendment details (1) Table 2 on page 13 of the specification, "8" in the comparative example column
" will be corrected to "2".

(2) Add the following sentence next to Table 4 on page 18.

"Comparative Example 6 Examples 1 to 6 except that fire-resistant high specific gravity granules (7Erochrome slag) with a true specific gravity of 3.06 were used as the base material for the mold, and the amount of binder was 1.5% by weight. A thermosetting mold composition was produced in the same manner as in 4, and the mold bending strength and collapsibility of this material were determined. As a result, the bending strength was 34.2 kg/cx.
2. The disintegration time was 14 seconds. ”

Claims (1)

[Scope of Claims] 1. In a molding composition containing foundry sand and a curable organic binder as main components, at least 10% by weight of the foundry sand is composed of refractory high specific gravity granules having a true specific gravity of 3.4 or more. A molding composition with good disintegrability, characterized in that it contains a substituted metal. 2. The molding composition according to claim 1, wherein the refractory high specific gravity granules are at least one selected from zircon sand, chromite sand, blasted converter slag, and granular iron. 3. The mold composition according to claim 1 or 2, wherein the curable organic binder is a thermosetting resin, an air-curing resin, or a room-temperature self-hardening resin.