JPH02220730A - Casting method for using organic self-hardening mold - Google Patents

Abstract

PURPOSE:To improve the ratio of metal to sand and to facilitate the recovering of volume increasing material by packing ceramic balls imparting magnetism after forming facing sand layer with the organic self-hardening molding sand and executing casting into a mold. CONSTITUTION:A pattern (does not show in the figure) is set into a flask 6 and on this surface, the facing sand layer is formed with the organic self- hardening molding sand 8 at the prescribed thickness. Successively, as the volume increasing material, the ceramic balls 20 including magnetic material are charged and packed and further, as necessary, the above-mentioned molding sand 8 is charged as back sand. A cope 2 and drag 4 composed of the mold molded by such a manner, are matched and the prescribed molten metal is poured into a formed cavity 10 and as necessary by arranging a core 12, from sprue 14 to execute the casting. After that, the above-mentioned molds 2, 4 are separated out and the casting product is taken out and also casting flask, etc., in the molding sand 8 is separated with magnetism to recover the molding sand 8. Then, the above ceramic balls 20 imparting magnetism are easily recovered together with inclusion with the magnetism.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field) The present invention relates to a casting method using an organic self-hardening mold, and particularly to a molding process for improving the sand-to-metal ratio of organic self-hardening molding sand.

(Background Art) Conventionally, among cast products, so-called medium and large products weighing 50 kg or more, such as machine tool parts, are often manufactured by a casting method using an organic self-hardening mold. This method of using an organic self-hardening mold is also called the no-bake method, and it allows the desired mold to be obtained by curing without applying heat.For this reason, it is often used as an organic binder. Molds are often made using resins such as furan-based resins, but generally a liquid condensate resin with a not very high molecular weight is used, and an acidic curing catalyst is mixed with this to start the condensation reaction. By gradually increasing the activity and finally maximizing the binding strength through three-dimensional crosslinking, the desired template is completed. When casting using such an organic self-hardening mold, after forming such a mold, a predetermined amount of molten metal is poured into the obtained organic self-hardening mold, and then casting is performed. Thereafter, the formed cast product is taken out by demolding the mold, while the foundry sand is subjected to a magnetic separation operation to remove foreign matter (inclusions) such as casting burrs, iron pieces, and iron powder that have been mixed into the foundry sand. It will be collected and reused.

By the way, the casting method using such an organic self-hardening mold has the following advantages: (a) Since it is completely hardened at room temperature, there is no need for the labor and time required for firing, which reduces the number of molding steps; (b) The mold strength is increased. We can produce high-quality castings with high dimensional accuracy.
(c) It can contribute to the resource saving of silica sand, industrial waste, and pollution prevention. (d) The sand has excellent disintegration properties after pouring, and 90 to 95% of the amount used can be recovered, and can be used repeatedly. For these reasons, many foundries are now using it in casting products for general industrial machinery and machine tool parts. be.

However, casting methods using organic self-hardening molds, which have many advantages, have the problem of high casting costs due to the high cost of the resin used as the organic binder and its hardening agent. Therefore, various efforts have been made to reduce the cost. Sometimes, sand metal (S/M) is used for non-mass-produced castings, such as cast parts for machine tools, because a dedicated casting flask is required for each product, which increases the cost of the metal frame and makes storage and management difficult. The ratio (ratio between the weight of sand used; S and the product weight - M) increases, leading to an increase in product cost.

Incidentally, a mold is completed by placing a predetermined model in a casting flask and filling it with molding sand to form a desired product cavity.
As shown in the figure, it generally consists of an upper mold 2 and a lower mold 4. In addition, in these upper mold 2 and lower mold 4, 6
1 is a casting flask, 8 is molding sand, and 10 is a product cavity that provides the shape of the product to be cast by the upper mold 2 and lower mold 4. Further, 12 is a core, 14 is a sprue, and 16 is a top.

In order to improve the sand-to-metal (S/M) ratio in such a mold structure, as shown in FIG. Volume increasing material 1 such as wood pieces, brick pieces, styrofoam pieces, etc. in the middle part excluding the part (sand layer)
It has been considered to reduce the amount of foundry sand 8 used by embedding sand 8, but it is difficult to obtain the material 18 that increases the volume of molding sand 8 in a timely manner, and In reality, this method is not carried out in actual work because it impairs work efficiency and furthermore, it is difficult to collect the additional material 18.

(Solution Section B) The present invention was made against the background of the above, and its purpose is to improve the sand metal ratio in a casting method using an organic self-hardening mold.
In particular, the objective is to dramatically improve the sand-to-metal ratio and to provide a method that makes it possible to easily recover volume increasing material when recovering sand after pouring.

(Solution Means) In order to solve this problem, the present invention uses organic self-hardening molding sand to mold a target mold, and then pours a predetermined molten metal into the obtained organic self-hardening mold. Casting is carried out by pouring molten metal, and then the mold is broken down to take out the formed cast product. At the same time, the foundry sand and inclusions such as casting burrs are separated by magnetism. In the casting method, the mold is formed by forming a surface sand layer of a predetermined thickness with the foundry sand on the surface of the model placed in the casting flask, and then forming a sand layer of a predetermined thickness with the molding sand. Ceramic balls are placed in the flask to fill the flask, and if necessary, the molding sand is added as backing sand. The present invention is characterized in that the inclusions are separated from the foundry sand together with the inclusions.

(Specific configuration) In short, the present invention attempts to use a ceramic pole that is resistant to heat as a volume increasing material in place of self-hardening foundry sand, unlike conventional volume increasing materials. Moreover, such ceramic balls have magnetic material powder or agglomerates thereof in the center or the entirety thereof, and are thus imparted with magnetism so that they can be magnetically attracted to a magnetic separation device using a magnet or the like. It has a major feature in that it is a magnetic material.

As shown in FIG. 3, the magnetic ceramic balls according to the present invention are filled into the same mold region as the conventional volume increasing material (18). That is, ceramic balls 20 are filled behind a skin sand layer (skin sand portion) of a predetermined thickness that is in contact with molten metal such as molten cast iron or molten steel poured into the molds (2, 4), and the use of foundry sand is The aim is to reduce the amount. In addition, this ceramic ball 20
On top of the filled area, molding sand is further filled as backing sand to reinforce the mold.

By the way, when molding such an organic self-hardening mold (2°4), first, a prescribed mold 6 is placed on the bottom plate 22, as shown in FIG. Next, a model 24 giving a desired product cavity shape 10 (partially) is placed in the flask 6, and with the raised forming member 26 and the like set, organic self-hardening molding sand 8 is poured. As a result, a skin sand layer (skin sand) having a predetermined thickness is formed on the surface of the model 24. The organic self-hardening foundry sand 8 used here is the same as the conventional one, and contains resins such as furan resin, phenol resin, and acrylic resin as an organic binder. A hardening agent is added to harden the resin. Next, after this skin sand layer is formed, the ceramic balls 20 having magnetism according to the present invention are placed on top (behind it) and filled, and if necessary, foundry sand 8 is added on top of it. It is thrown in as back sand to reinforce the mold, and then the model 24 is removed, thereby completing the molding. Of course, those skin sands (8)
When introducing the ceramic balls 20 and back sand (8), vibration is applied using a vibration generator or the like in the same manner as in conventional sand filling work, so that the filling properties of the casting sand 8 and ceramic balls 20 can be improved. Become. Further, the lower mold 4 is also molded in the same manner as described above by filling the ceramic balls 20 behind a skin sand layer formed with a predetermined thickness on a predetermined model, and the obtained upper mold 2 and When combined with the lower mold 4, the desired mold structure as shown in FIG. 3 is realized.

In addition, when molding the molds (2, 4) in this way, skin sand (8), ceramic balls (2OL
Although the ratio of back sand (8) is not constant depending on the shape, size, weight of the product, and the structure of the flask 6,
It is possible to replace 30 to 40% of the volume with ceramic balls 20 without reducing the overall strength of the mold. In addition, even if the contact surface between the skin sand or back sand and the ceramic balls is vibrated by a vibration generator or the like during sand filling, a small amount of sand may enter the gap between the ceramic balls, but the sand itself Since it is in a wet state, it does not invade the entire void.

Furthermore, due to the existence of such gaps between the filled ceramic balls, gas can penetrate more easily than conventional methods, and is effective in preventing casting defects. At the same time, it is possible to harden the mold and shorten the molding time. In other words, in the production of self-hardening molds, the curing time has traditionally been prolonged in winter, etc., and countermeasures have been taken to counter this, such as increasing the amount of curing agent added. Instead, in the present invention, by preheating the ceramic ball 20 (about 80 to 100°C), the curing time can be significantly shortened.

In the present invention, using the self-hardening mold thus formed, a predetermined molten metal,
For example, molten cast iron, molten steel, etc. are poured to cast the desired cast product, and then the mold is dismantled to take out the cast product formed in the mold. Inclusions such as cast burrs, iron pieces, and iron powder are separated using magnetism in the same manner as before, and the foundry sand that formed the mold is recovered.
Although they will be reused, the ceramic balls used in the present invention and filled in the flask that constituted the mold are also given magnetism by containing a magnetic material. During the magnetic separation operation, the ceramic balls can be effectively separated from the foundry sand together with inclusions such as casting burrs, making it possible to use such ceramic balls again.

This magnetic separation of ceramic balls can be carried out using the magnetic separation device used in conventional casting automation lines as is. By using a magnetic separation device such as a magnetic boom, the ceramic balls filled in the flask can be easily separated and recovered from the foundry sand along with iron-based impurities, and can be introduced into an automated line. It becomes. In short, the present invention is characterized in that ceramic balls as a volume increasing material can be easily recovered in an automated line, and also have strength, heat resistance, abrasion resistance, and are magnetic. It has a major feature in that it has the following characteristics.

Of course, if the volume increasing material is simply a magnetic material, a metal material such as iron could be used, but such metal materials do not have good workability during filling, and may be difficult to work with after filling. This has various problems, such as the overall weight of the mold becomes heavier, the workability becomes worse, and it is necessary to make major changes to the incidental equipment.In addition, ceramic balls that do not have magnetic properties , a special breaker screen is required at the time of its recovery, and new equipment investment is required for its recovery, resulting in an increase in casting costs.

By the way, the ceramic balls used in the present invention are
It is given magnetism so that it can be magnetically attached to a magnet by containing a magnetic material, and is used in an appropriate size, but generally a ball diameter of about 10 to 50 mm is used. Furthermore, the shape does not necessarily have to be a perfect circle as long as it is spherical. Furthermore, when an increase in packing density is required, it is also possible to use a combination of ceramic balls of different sizes.

The magnetic materials contained in the ceramic ball include soft magnetic materials and hard magnetic materials, both of which have the function of imparting magnetism to the pole, and should be selected appropriately. However, especially in the present invention,
Soft magnetic materials are advantageously selected due to the ease of maintenance of the ceramic balls. When separating sand and ceramic balls, which are volume increasing materials, using a magnetic separator in an automated line,
The fact that the line remains magnetic even after it is separated from the magnet is because most of the line is soft magnetic, so poles may become magnetically attached to the line, or ceramic balls may become magnetically attached to each other, forming a ball shape. For this reason, there is a possibility that line troubles may occur when a highly magnetic material is used. Moreover, since the soft magnetic material is mainly composed of oxides, its raw materials are inexpensive, it can be easily molded into a desired shape, and its materials are easily available. Soft magnetic materials with such characteristics include Ni-Zn ferrite, Cu-Zn-Mg ferrite, Mn-Zn ferrite, NiCu ferrite, etc., and are used as high-frequency magnetic core materials and magnetic recording materials. The materials used in the above can be used as they are.

Such magnetic materials, along with ceramic materials such as alumina, cordierite, silicon carbide, silicon nitride, and zirconia, are made into balls of a predetermined size, but such magnetic materials are not available in bulk form. or in a uniformly blended form in a ceramic ball. For example, as shown in FIG. 5(a), there is a ceramic ball 20 having a structure in which a magnetic material is wrapped around a central core 28 and a ceramic layer 30 is provided on the outside, or as shown in FIG. 5(b). As shown,
It is used as a ceramic ball 20 having a structure in which magnetic material 32 in the form of powder or small lumps is distributed throughout.

Moreover, the ceramic ball used in the present invention has a hollow part 34 of a predetermined size inside, as shown in FIGS. 5(c) and (d), in addition to the solid spherical body as shown in the upper part. It is also possible to use it in hollow spheres. By using such a hollow spherical body, the weight of the ball can be reduced, which is advantageous for workability and equipment. However, in the case of forming a hollow spherical body, as shown in FIG. 5(c), a ventilation hole 36 or Figure 5(d)
It is desirable to take measures such as making the pole wall part porous. In addition, in the case of such a hollow spherical body structure, the ball wall is made of a ceramic material containing a magnetic material.
It goes without saying.

(Examples) In order to clarify the present invention more specifically, typical examples of the present invention will be shown below, but the present invention should not be construed in any way limited by the description of such examples. It goes without saying that it is nothing.

In order to cast a gear material with an outer diameter of 1200 mmφ, a thickness of 50 mm to 120 mm, a weight of 550 kg, and a material made of Fe20 as the target casting product, the metal frame dimensions are 1600 mm x 1800 mm x 300 mm (upper mold) or 250 mm (lower mold). In addition to using a casting flask, the molding sand was 0.8% by weight of AFS40 strangely furan resin.
A conventional mold as shown in FIG. 1 and a mold according to the present invention as shown in FIG. I did it.

In addition, when molding the mold according to the present invention, a fifth ceramic ball having a size (outer diameter) of 30 mm is used as the ceramic ball.
A structure as shown in Figure (a) was used. In addition, as a material of ceramics, cordierite (2Mg
O・2 A 1 t O3・5SiO
It was formed with a size of mmφ.

The sand metal ratio of the mold thus obtained is the first
In the conventional mold shown in the figure, S/M = 4.1, and the third
In the mold of the present invention shown in the figure, it is 37M-1,63,
This was a remarkable improvement of 1/2.5 compared to the conventional one.

Furthermore, regarding the curing time of the mold, the conventional mold shown in Fig. 1 takes 10 to 15 minutes (in summer), whereas the mold of the present invention shown in Fig. 3 takes 8 to 15 minutes. It only takes 11 minutes,
It has become clear that the time can be reduced by as much as 20% compared to the conventional method.

Further, using the mold of the present invention thus obtained, FS30 molten metal is poured into it according to a conventional method to cast the desired gear material, and then the mold is disassembled to cast the desired gear material. While taking out the gear material (casting product) formed in the mold, in the automated line,
As a result of using a magnetic separation device to separate the foundry sand from contaminants such as foundry burrs, it was possible to separate the ceramic balls from the foundry sand at the same time as the contaminants.

It should be noted that the present invention is by no means limited to the above specific explanations and preferred embodiments, and various changes, modifications, improvements, etc. can be made based on the knowledge of those skilled in the art without departing from the spirit of the present invention. It should be understood that the present invention also includes such embodiments.

(Effects of the Invention) As is clear from the above explanation, in the present invention, by using ceramic balls as the volume increasing material, it was possible to dramatically improve the sand metal ratio, and such By imparting magnetism to the ceramic balls, it has become possible to easily recover the ceramic balls as a volume increasing material when collecting sand after pouring, and this is where the present invention will be applied to large industries. There is a certain significance.

[Brief explanation of the drawing]

1 and 2 are vertical cross-sectional views of a mold for explaining a conventional mold structure, and FIG. 3 is a vertical cross-sectional view showing an example of a mold structure used in the present invention, Fourth
The figure is a cross-sectional explanatory view showing the molding process of the mold according to the present invention, and FIGS. 5(a) to 5(d) are, respectively,
FIG. 3 is an explanatory cross-sectional view showing different examples of ceramic balls used in the present invention. 2: Upper mold 4: Lower mold 6: Casting flask 8: Molding sand 10: Product cavity 12: Core 18: Conventional volume increasing material 20: Ceramic ball 22: Bottom plate 24: Model 28; Core body, 30: Ceramic layer 32:
Magnetic material 34: Hollow part 36: Ventilation hole

Claims (1)

[Claims] After molding a target mold using organic self-hardening foundry sand, pouring a prescribed molten metal into the obtained organic self-hardening mold to perform casting, and then In the casting method, the casting method comprises taking out the formed casting product by demolding the mold, and recovering the casting sand by magnetically separating the casting sand from inclusions such as casting burrs mixed therein. After forming a sand layer of a predetermined thickness with the molding sand on the surface of the model placed in a casting flask, the mold is filled with ceramic balls that have been given magnetism due to the presence of a magnetic material, and then The above-mentioned foundry sand is added as backing sand to the top of the casting flask as needed, and the ceramic balls filled in the flask are separated from the foundry sand along with the inclusions by the magnetic separation operation. A casting method using an organic self-hardening mold characterized by: