JPS61212441A - Casting method - Google Patents

Abstract

PURPOSE:To prevent the blow of a molten metal by embedding a pattern for a casting consisting of polyolefin resin foam into molding sand and providing a vent port to the upper part of a casting mold. CONSTITUTION:The pattern 5 for a casting consisting of the polyolefin resin foam, as well as a runner 3 and a gate 4 made of the same material are adhered by an adhesive agent, etc. and thereafter the assembly is installed together with a pattern for the vent port placed atop the pattern and a sprue 2 made of a clay pipe in a molding flask. After the molding sand 1 is packed to the periphery and is solidified, the pattern of the vent port is removed from the molding sand 1 to form the vent port 6. The gas is thereby released into the atm. and the blow of the molten metal is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to an improvement in a casting method, and in particular, a model is buried in foundry sand, and the model is molded using the heat of the molten metal cast into the manufactured mold. This relates to the vanishing model casting method in which a cast metal is produced by decomposing and vaporizing the metal, and then filling the cavity thus formed with molten metal.

(Prior Art) As a vanishing model casting method, a full mold casting method using expanded polystyrene is generally well known.

This casting method uses foamed polystyrene that has been integrally processed and molded into the same shape and dimensions as the desired casting product (sometimes using a core made of foundry sand or metal). K
Fill and solidify the foundry sand to form a mold, then pour the molten metal into the mold, melt, decompose, and vaporize the mold, fill the cavity formed there with the molten metal, and take it out after cooling to create a mold identical to the mold. This is a casting method to obtain cast products with the desired shape and dimensions.

However, the use of this casting method is gradually decreasing due to various problems caused by the chemical properties of polystyrene, which is the base resin of the foam used.

That is, due to the heat of the molten metal) 01~C! It decomposes into n hydrocarbons and a part of it gasifies, but the decomposition products containing benzene rings have a large bond energy, so they are not completely decomposed and vaporized by the heat of the molten metal, and instead form an aromatic polycyclic condensed structure. , generates a large amount of soot (black smoke).

In the above-mentioned nine casting method, the mold made of expanded polystyrene is placed inside the casting chamber, and there is no part that comes into direct contact with the atmosphere, so the generated gas flows between the molding sand that makes up the mold.
! If the gas is not released into the atmosphere through the gas, there is a problem in that it will cause gas defects in the cast products. As a countermeasure for this, it is possible to improve the permeability of the caster by increasing the permeability of the caster or by increasing the particle size of the molding sand, but this also serves as a gas passage and also promotes penetration of the molten metal that has been cast. However, due to the occurrence of the adhesion phenomenon, there is a limit.
The current situation is that no effective solution has been found yet.

On the other hand, the decomposition products containing the benzene ring t-, which cannot be decomposed or vaporized, are not released outside the mold and remain on the surface (particularly the upper part) of the casting as an unvaporized residue, damaging the casting surface.

This problem is particularly noticeable in cast iron-based products), and when only one side is used, such as a machine tool bed or mold material, the necessary side is cast with the bottom side due to the casting method.
In the case of general industrial machine castings, from the viewpoint of commercial value of the casting, it is usually removed by machining or the like. In addition, in cast steel products, the entrainment of such unvaporized residues into the molten metal causes an increase in carbon content, which is particularly problematic in the case of stainless steel castings with a low carbon content.

As mentioned above, the full mold casting method using expanded polystyrene has the drawbacks of gas defects caused by the generated gas, damage to the cast surface of the cast product due to soot generation, and a decrease in the quality of the cast product. Many proposals have been made to solve these problems, but as a complete solution has not yet been reached, the expansion of the use of the full mold method has been greatly hindered, and on the contrary, the use of the full mold method has been gradually reduced.

(Problems to be Solved by the Invention) The present invention seeks to provide a full molding method that does not have the above-mentioned drawbacks.

(Means for Solving the Problems) That is, the present invention involves embedding a foundry board made of a polyolein resin foam in foundry sand in a vanishing model casting method in which casting is performed using a foundry model. At the same time, a vent is provided above the mold so that the casting mold is connected to the atmosphere,
This casting method is characterized by subsequently injecting molten metal.

The present invention will be explained below based on the drawings. FIG. 1 shows an embodiment for explaining the present invention in detail.

After gluing the casting model 5, the runner 3 and weir 4 made of the same material with adhesive, etc., the mold is placed inside the casting flask together with the vent model placed on the top of the model and the sprue 2 made of clay pipe. After filling and solidifying the molding sand 1 around the molding sand 1, a model for the vent is removed from the molding sand 1 to form the vent 6.

Casting is accomplished by injecting molten metal into the spatula made in this manner from the sprue 2 at a temperature of, for example, about 1400°C.

The foundry sand 1 in the present invention includes a refractory aggregate (generally silica sand, sometimes special sand such as zircon sand, oripin sand, furomite sand, etc.) and a binder (sometimes hardening of the binder). For example, clay sand, water glass sand, cement/
There are inorganic foundry sands such as sand, and organic foundry sands such as Fran sand and cold box sand (sometimes non-caking sand with only refractory aggregate and no binder added is used in combination with suction equipment, etc.). It is also sometimes used.

Further, the casting model 5 in the present invention is made of polyolefin resin foam. If you use a foam other than polyolefin resin foam, such as polystyrene foam, will there be a large amount of black smoke (soot) from the vents? This is not preferable because it not only contaminates the working environment but also causes casting defects on the top surface of the casting obtained after casting due to unvaporized residue. Only by using polyolefin resin foam can the problems of contamination of the working environment and casting defects be solved at the same time.

The polyolefin resin foam in the present invention includes:
Both an extruded foam and an in-mold foamed product can be used, but an in-mold foamed product is preferred. In addition, the density of the foam is reduced to 0.1 α due to the relationship with mechanical strength and gas generation amount.
0197cm”%K,a 025~[101597cm
” is preferred.

Furthermore, the resins that make up the entire foam include low density polyethylene, linear low density polyethylene, medium density polyethylene, high density polyethylene, ethylene-propylene random copolymer, ethylene-propylene-block copolymer,
Copolymers of propylene and other olefins, homocopolymers of propylene, and mixtures thereof may be mentioned. It is also possible to mix resins other than polyolefins within a range that does not impair the intended purpose of the present invention.

In the present invention, it is necessary to provide a vent above the mold so that the casting model is connected to the atmosphere. In order to embed a foundry model in foundry sand, it is necessary to have a compressive hardness that allows it to fit into the foundry model. In order to improve compression hardness, it is possible to use a foam with a high density, but this results in an increase in the amount of decomposed gas.In particular, polyolefin resin foam generates a large amount of decomposed gas, and is not provided with ventilation holes. If casting is carried out using conventional casting temperatures, the gas pressure will easily cause the molten metal to blow out, making the work extremely dangerous. However, according to the present invention, since the vent is provided, the gas is released into the atmosphere, thereby preventing the molten metal from blowing away.

The vent in the present invention is a discharge port for the decomposed gas of the casting model, and also functions as a feeder for molten cast steel, and its position, size, and number are determined from within the casting model "Ik mold". This is based on the same concept as the gas vent and riser in the general casting method for cutting out molds, but in addition, in the present invention, it is particularly designed to serve as a pocket where gas and unvaporized residues become concentrated. It is necessary to install gas vents in easily accessible areas.

As described above, since the present invention uses a polyolefin resin foam as a casting material for casting, it is possible to solve the problem of casting defects caused by unvaporized residue that occurs when conventional polystyrene foam is used. At the same time,
Because it is equipped with ventilation holes, it is possible to prevent the molten metal from blowing away, which occurs when polyolefin resin foam is used, and it overcomes all the drawbacks of conventional casting methods, making it extremely useful in industry. It can be called an invention.

The following is a description based on the entire implementation of the present invention.

Example 1 Bead method in-mold foam molded product of ethylene-propylene random copolymer (ethylene content: i2.8 wt%) (density α0
2297cm”), 200X2 as shown in Figure 1.
After making a 00x200 casting model and gluing the runners and weirs made of the same material with an acetic acid vinyl resin adhesive, the entire surface was coated with a graphite-based coating material with poor air permeability, and the sprues ( A clay pipe was used] and a vent model with an outer diameter of 50φ placed on the center of the top of the model was placed in a casting flask, and furan sand (Ar 145 to 50) was filled around it and solidified. The model was cut out from the sand and used as a ventilation hole.

Molten cast iron (carbon & 6%, silicon 2.7%, manganese (L4%, Mg [LO459k)) was poured into the mold at 1390°C. At that time, colorless gas was released, but no soot was generated. Also, no blowing phenomenon was observed.No casting defects were observed on the top surface of the obtained casting.

Example 2 High-density polyethylene foam molded product by bead method Density (
A mold was prepared in the same manner as in Example 1, and the same molten metal was poured as in Example 1.The casting conditions and the appearance of the cast iron casting were as in Example 1. As in the previous case, there were no problems with the factory environment, and sound castings with no casting defects were obtained.

Example 3 A cast IJ similar to that in Example 1 was created, and ordinary cast steel (carbon 11
6%, silicon a, 51chi, manganese 165%)'i1,5
It was cast at 50°C. Carburizing situation 1: In order to open I11, holes were drilled on the top side of the casting at the corner of the top side, and the carbon content was analyzed.

As a result, the carbon content was 116%, and almost no carburization phenomenon was observed.

Comparative Example 1 Foamed polystyrene (density 102617
The same procedure as in Example 1 was carried out except that 2 cm") was used.

As a result, a large amount of black smoke (soot) 1 was emitted from the vent, and a casting defect (wavy roughness λ) due to unvaporized residue was observed in a fairly wide area around the top of the casting.

Comparative Example 2 The same procedure as in Example 1 was carried out except that no vent hole was provided. As a result, molten metal was blown during the pouring process, and the pouring operation was interrupted.

Comparative Example 5 The same procedure as in Example 3 was carried out except that expanded polystyrene having a density of α01817 cm was used as the casting model.

As a result, the analytical value of the carbon content was 125%, which was an increase of 109% compared to Example S.

[Brief explanation of the drawing]

FIG. 1 is a diagram for explaining the present invention in detail. 1. Foundry sand, 2. Sprue, 5. Runway, 4. Weir, 5
・・Casting model, 6.・Vent sub-agent 1)
Meifuku agent Ryo Hagiwara −

Claims (1)

[Claims] In the vanishing model casting method in which casting is performed using a foundry model, a foundry model made of polyolefin resin foam is buried in foundry sand, and a vent is provided above the mold so that the casting model is connected to the atmosphere. A casting method characterized by providing a molten metal and then injecting molten metal.