JPH0452048A - Mold and molding method thereof - Google Patents

Abstract

PURPOSE:To prevent leakage of molten metal from a mold having high strength and excellent dimensional accuracy and buffering property without using sealing material by nicely utilizing synthetic sand and self-curing sand. CONSTITUTION:The self-curing sand 3 is charged on a pattern 2 put on a table 1. In this case suitable distance 6 remains at between inner peripheral part in a flask 5 and the self-curing sand 3 in mating face 4 in the mold. By blowing gas for accelerating curing in the self-curing sand 3, while accelerating the curing of self-curing sand 3, the molding in the flask 5 is executed with the synthetic sand 7. After completing the curing of self-curing sand 3, the pattern 2 is taken out. At this time, even in the case the parts of self-curing sands 3, 3 in the mating faces 4 in the mold do not closely contact, the synthetic sands 7, 7 in the mating faces 4 in the mold closely contact with cushion action of the synthetic sands 7, 7 at peripheral part of the mold 9, 10 to prevent the leakage of molten metal. After cooling the molten metal, shake-out of the mold 9, 10 is executed. At this time, as the peripheral part in the mold 9, 10 is formed with synthetic sand 7, 7, this is comparatively easily collapsed and released. Then, the obtd. casting having good accuracy is manufactured with the self- curing sand 3, 3 having good accuracy.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a mold used in casting a casting and a method for making the same.

[Prior art] There are many types of molds, including green sand molds made of clay caking material (hereinafter referred to as synthetic sand molds), and various inorganic and organic molds including water glass and carbon dioxide molds. The main type is a special mold using a caking material (hereinafter referred to as a self-hardening sand mold).

The above synthetic sand mold uses clay as the caking material, so its strength is 0.5 to 2 kg/cm' (compressive strength).
There are various degrees, and the mold hardness is 60 to 95 on the mold hardness scale.
It is of a certain degree. On the other hand, the current mainstream of self-hardening sand molds is organic self-hardening sand molds, and their strength is determined by the relationship between the amount of organic matter as a binder and the curing time depending on the amount of hardening agent. /crn', which is more than 10 times stronger than synthetic sand molds. -For boat fishing, self-hardening sand molds can be demolded using anti-pressure cuffs that increase the strength during demolding time.kg/c
m' or more. For this reason, the mold hardness of self-hardening sand molds is so high that it cannot be measured with a normal mold hardness meter.

[Problem to be solved by the invention] However, in casting, the pressure of the molten metal during pouring acts as a buoyant force that lifts up the upper mold of the mold, and due to this tension, the dimensional accuracy of the mold decreases, and furthermore, the upper mold and lower mold A weight or a clamp is used to prevent this, which can lead to the phenomenon of molten metal leaking from the mold mating surface between the molds. In this case, if the buoyancy that lifts the upper mold is F from the hydrostatic pressure equation when pouring molten metal, then F = rSH (r: specific gravity of the molten metal, S: area occupied by the molten metal on the mold mating surface, H: molten metal head) This buoyant force F is considered to be applied as static pressure of the molten metal, and a holding weight corresponding to this is applied, for example, a holding weight of about three times the buoyant force F, the weight of a weight, or a clamping force.

At this time, the synthetic sand mold is in a state where the counter pressure is often less than 2 kg/crrf, and the surface of the casting mold space is about to be crushed by the weight of the presser foot (however, the surface of the mold space for casting is about to be crushed). If it is, the function as a mold cannot be maintained, so the upper and lower molds should be in close contact with each other around the entire mold mating surface to maintain cushioning.
), and although this state prevents molten metal from leaking from the mold mating surfaces, there is a problem in that it is difficult to achieve dimensional accuracy of the mold.

On the other hand, self-hardening sand molds have higher strength than synthetic sand molds, so even if you apply weight like synthetic sand molds, the precision of the mold mating surfaces may not be achieved.

The mating surfaces of the molds do not come into close contact, leaving a slight gap. For this reason, as shown in Section 5, the sealing material 21 such as starch-based glue or mold seal is applied to the mating surfaces 2 of the upper and lower molds 22 and 23.
4 is sealed to prevent water leakage, and sealing material 21
The mold 22.2
However, if there is a problem in dimensional accuracy, or if there is too much mold space 25 for casting on the upper mold 22, there is still a large possibility of molten metal leaking, resulting in poor casting workability. In addition, in the same figure, 26 is self-hardening sand, 27.
28 are the upper and lower frames.

Therefore, the present invention skillfully utilizes synthetic sand and self-hardening sand to provide strength and excellent dimensional accuracy, as well as cushioning properties to prevent water leakage without using a sealing material. This is an attempt to solve the problems of the prior art.

[Means for Solving the Problems] In other words, the invention of 1s1 uses self-hardening sand to form the surrounding part of the casting mold space in the frame, and the remaining part in the frame, including the mold mating surface, to be made of synthetic sand. The gist is a mold that is characterized by the fact that it has been molded.

In the second invention, self-hardening sand is poured onto the model leaving the inner peripheral part of the frame, and then the inside of the frame is molded with synthetic sand while promoting the hardening of the self-hardening sand, and the self-hardening sand is hardened. The gist of this invention is a method for making a mold, which is characterized by removing the model after completion.

[Function] During casting, when pouring into this mold, the upper and lower frames are placed together and a weight is applied by weights or clamps, and the cushioning action of the synthetic sand causes the molten metal to flow from the mating surfaces of the mold. High-precision castings can be obtained using self-hardening sand that prevents leakage and has excellent strength and dimensional accuracy.

Further, as a molding method, when molding the inside of the frame using synthetic sand, self-hardening sand is also molded by the molding pressure of the synthetic sand.

[Example] Next, an example of the present invention will be described with reference to FIGS. 1 to 4.

In this example, first, as shown in FIG. 1, self-hardening sand 3 is poured onto a model 2 placed on a chiffle 1. In this case, an appropriate distance 6 is left between the inner peripheral portion of the frame 5 and the self-hardening sand 3 on the mold mating surface 4.

Next, as shown in FIG. 2, the inside of the frame 5 is molded with synthetic sand 7 while a hardening accelerating gas is blown into the self-hardening sand 3 to promote hardening of the self-hardening sand 3. As a result, the self-hardening sand 3 is also shaped by the shaping pressure of the synthetic sand 7.

Next, as shown in FIG. 3, after the hardening of the self-hardening sand 3 is completed,
Demold model 2. As a result, a mold 9 is obtained in which the surrounding portion of the casting mold space 8 within the frame 5 is molded using the self-hardening sand 3, and the remaining portion within the frame 5 is molded using the synthetic sand 7.

When casting the mold 9, as shown in FIG. 4, the mold 9 is fitted with a mating mold 10 of a mating mold formed in the same manner as the mold 9 without using glue or a mold seal. Apply pressure with a clamp and pour the molten metal.

At this time, even if the self-hardening sand 3.3 is not in close contact with the mold mating surface 4, the synthetic sand 7 around the mold 9.10
．． Due to the cushioning action of 7, the synthetic sand 7.7 comes into close contact with the mold mating surface 4 to prevent molten metal from leaking.

After cooling the molten metal, mill the mold 9.10.

At this time, since the molds 9 and 10 are made of synthetic sand 7 and 7 in their peripheral portions, they are relatively easily disintegrated and separated. The obtained casting has good precision due to the self-hardening sand 3.3 having good precision.

[Effects of the Invention] As described above, in the present invention, since the self-hardening sand has strength and excellent dimensional accuracy, castings with high precision can be obtained by casting, and the cushioning effect of the synthetic sand makes it possible to easily hold the mold during casting. It is possible to prevent molten metal from leaking from the mating surfaces, eliminating the need for sealing materials, and the synthetic sand improves the collapsibility of the mold after casting.

Furthermore, as a molding method, by molding the inside of the frame with synthetic sand while promoting the hardening of the self-hardening sand, the self-hardening sand is also molded by the molding pressure of the synthetic sand, which speeds up the molding work.

[Brief explanation of the drawing]

1, 2, and 3 are longitudinal cross-sectional views for explaining the process of one embodiment of the present invention, FIG. 4 is a vertical cross-sectional view of the frame assembled state, and FIG.
The figure is a vertical cross-sectional view of a conventional frame assembly state. 3... Self-hardening sand, 5... Frame, 7... Synthetic sand, 8...
... Mold space for casting, 9... Mold, 10... Mold 1
Figure 2

Claims (1)

[Scope of Claims] 1. A mold characterized in that the surrounding portion of the mold space for casting within the frame is molded with self-hardening sand, and the remaining portion within the frame, including the mold mating surface, is molded with synthetic sand. 2. Put self-hardening sand on top of the model, leaving the inner circumference of the frame, then mold the inside of the frame with synthetic sand while promoting the hardening of the self-hardening sand, and after the hardening of the self-hardening sand is completed, remove the model. A mold making method characterized by molding.