JP2851955B2 - Molding method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a molding method for performing molding using a back metal.

[0002]

2. Description of the Related Art When molding a hard mold on a back metal, a shell mold method is generally used. The shell molding method is a molding method in which a phenol resin mixed in a molding sand is heated and melted, and then thermally cured at a high temperature.

[0003]

In this shell mold method, since the mold is formed by firing, the thickness of the sand mold must be made as uniform as possible in order to prevent over-burning and insufficient baking. Therefore, there is a problem that a sufficient mold thickness cannot be ensured even at a necessary portion. For example,
Since the thickness of the sand mold is uniform throughout, the amount of heat radiated through this sand mold is also equal in most parts of the casting product. However, there is a disadvantage that the cooling rate is slower than that of the conventional method, which leads to a decrease in quality such as generation of sink marks. In addition, it is difficult to secure a sufficient thickness at a mold portion to be protruded by the push bar when removing the sand mold from the back metal, and sometimes the push bar only penetrates through the sand mold without good die removal. Further, in this shell molding method, since it is necessary to heat to 250 ° C. or more, there is a problem that the back metal is easily distorted or deformed.

[0004] The present invention has been made in view of the above points, and an object of the present invention is to provide a molding method capable of exhibiting an excellent effect not achieved by the conventional shell molding method by combining with a back metal. is there.

[0005]

SUMMARY OF THE INVENTION The present invention provides a back metal
In the molding method of performing molding using 11 and 12, a molding method of molding sand molds 13 and 14 on the back metals 11 and 12 by a cold box method.

[0006]

According to the present invention, since the mold is formed by the cold box method, it is easy to make a difference between the thin portion a and the thick portion b in the sand molds 13, 14. Therefore, by changing the thickness of the sand mold according to the heat capacity that differs depending on the location of the casting product W, the sand molds 13 and 14 and the back metal 11,
The amount of heat radiated through 12 is controlled by the thickness of the sand mold,
The cooling rate of the casting W is made uniform. At this time, the thickness of the sand mold is made thinner in the mold part with respect to the casting part having a large heat capacity to promote heat radiation from the back metals 11 and 12.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to embodiments shown in the drawings.

As shown in FIG. 1, a sand mold (lower mold) 13 and a sand mold (upper mold) 14 are respectively formed in a lower frame back metal 11 and an upper frame back metal 12 formed of ductile cast iron by a cold box method. Molded, the core 15 is placed in the sand mold, the lower frame back metal 11 and the upper frame back metal 12 are framed, and the integrated sand mold 1 is formed.
The molten metal is poured into 3,14.

[0009] The pouring is performed by a resilient dam 21 having a refractory structure for temporarily receiving and storing molten metal supplied from a ladle (not shown).
And a graphite stopper 22. The upper sand-type nozzle 24 is in close contact with the molten metal drop nozzle 23 of the hanging dam 21.

The stopper 22 is raised and lowered by a vertically moving cylinder (not shown) via a coil spring or the like, and penetrates through the molten metal dropping nozzle 23 of the hanging dam 21 by lowering. Engages with the seat 26,
The seat 26 is closed.

The cold box method is a low-temperature molding method in which a phenol resin mixed in molding sand is hardened by a chemical reaction using an amine gas at room temperature, and it is not necessary to heat the back metals 11, 12 and the sand molds 13, 14. Back metal
There is no deformation of 11 and 12, and even if the sand molds 13 and 14 have thick parts, they can be molded uniformly, so it is easy to make a difference between thin and thick parts in the sand mold, and sand for cold box There are also advantages such as easy regeneration and resource saving.
Since the thin portions of the sand molds 13 and 14 are reinforced by the back metals 11 and 12, they can be made extremely thin.

The back metal 11, 12 is provided with an insertion hole 27 for inserting a push rod when removing a sand mold from the back metal.

Next, the pouring operation will be described. When the casting flask is carried into the pouring position, the casting flask is resiliently pushed up by an elevating mechanism including a spring (not shown). The upper sand mold nozzle 24 is brought into close contact with the upper mold. Further, the stopper 22 is inserted through the molten metal drop nozzle 23 of the hanging weir 21 into the sand mold nozzle 24, and is elastically pressed against the seat 26 of the gate 25 to close the gate 25. When the molten metal is supplied from the ladle (not shown) to the hanging dam 21 in the closed state, the stopper 22 is raised, and the gate 25 in the sand nozzle 24 is opened. Is poured into the sand molds 13 and 14 through the gate 25.

When the pouring of one casting product is completed in this way, the casting flask is lowered onto a conveyor (not shown), taken out of the pouring position, and transported to the frame separating device. The casting product W is cooled.

In the molding by the cold box method,
Since it is easy to make a difference between the thin portions a and the thick portions b in the sand molds 13 and 14, the thickness of the sand molds 13 and 14 is changed according to the heat capacity that differs depending on the location of the casting product W. This allows
From casting product W after pouring, sand molds 13, 14 and back metal
The amount of heat radiated through 11 and 12 is controlled by the thickness of the sand molds 13 and 14, so that the cooling rate (the temperature falling per unit time) of the casting W is made uniform. For example, the mold part a with respect to a casting part (thick part Wa) having a large heat capacity is made thinner,
Increase the amount of heat radiation from the back metal 11, 12. On the other hand, the thickness of the mold portion b with respect to the casting portion (thin portion Wb) having a small heat capacity is made thicker to reduce the amount of heat radiated from the back metals 11, 12.

In the cold box method, a sand mold 1 is used.
Since uniform molding is performed irrespective of the thickness of 3, 14 as shown in FIG.
If a sufficient thickness is secured in the mold portion c which is pierced by the piercing rod 28 when the 14 is pulled out, it is possible to prevent the piercing rod 28 from penetrating through the sand mold and forming a hole 29 in the sand mold to prevent a defective removal.

[0017]

According to the present invention, it is easy to make a difference between a thin part and a thick part in the sand mold by the cold box method, so that the thickness of the sand mold can be changed according to the heat capacity that differs depending on the location of the casting product. By combining the cold box method with the back metal, the amount of heat radiated from the casting product after pouring through the sand mold and the back metal can be controlled by the thickness of the sand mold, making it possible to make the cooling rate of the casting product uniform. It can prevent the occurrence of sinkholes. Also, when removing the sand mold from the back metal, it is possible to secure a sufficient thickness at the mold part that is protruded by the push rod, and it is possible to perform good removal, and further, since there is no need to heat, there is no distortion in the back metal. There is also an advantage that no deformation occurs.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a pouring state by a sand mold molded by a molding method of the present invention.

FIG. 2 is a cross-sectional view showing a part into which a push rod is inserted when the sand mold is removed.

[Explanation of symbols]

 11,12 Back metal 13,14 Sand mold

Claims (1)

(57) [Claims] 1. A molding method for performing molding using a back metal, wherein a sand mold is molded on the back metal by a cold box method.