JPS6142449A - Molding method of sand mold - Google Patents

Abstract

PURPOSE:To cure system sand with a stable long pot life and to obtain a sand mold by packing the system sand consisting of sand, self-curable resin and a specific mixing ratio of a curing catalyst such as the Cr salt of paratoluene sulfonic acid into a pattern and subjecting the same to induction heating. CONSTITUTION:The system sand is constituted of the sand, the self-curing resin and the aq. soln., alcohol soln. or water/alcohol soln. (10-50% concn.) of 20- 70wt%, by the weight of the self-curing resin, the metallic salt of transition metal such as Cr, Mn, Fe, Co, Ni, Cu or Zn of the paratoluene sulfonic acid or xylene sulfonic acid. A furan resin, phenolic resin, phenol modified furan resin, etc. having self-curability are used as the above-mentioned self-curing resin. The above-mentioned components may be compounded in any order. The above- mentioned system and is packed into the pattern and is subjected together with the pattern to the induction heating by high-frequency energy to cure, by which the sand mold is obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method of forming a sand mold used when casting a casting.

[Conventional technology]

When making sand molds using self-hardening sand, a part of the hardening reaction has already started in the mixed sand used when it is kneaded, so sand molds using sand that has exceeded the specified time (pot life) It no longer exhibits its original characteristics. In this case, in order to extend the pot life, weakening the strength of the catalyst will extend the pot life to some extent and improve it, but this will have the negative effect of deteriorating the properties of the sand mold.

In order to improve these shortcomings, we created a blended sand containing a weak curing catalyst that does not exhibit much of a catalytic effect in warm and humid conditions. After molding with this sand, we heated it dielectrically using high-frequency energy to form a binder. A method has been adopted in which the temperature of the curing catalyst is increased to accelerate curing.

[Problem that the invention seeks to solve]

In the conventional technology, a curing agent that has a weak catalytic effect at room temperature is used, and after molding, the temperature of the sand mold part is raised by high-frequency energy to increase the catalytic effect. This also improves workability compared to self-hardening mixed sand, but if rollability is possible, it is desirable to provide a more stable pot life. The present invention further provides a method for forming a sand mold which has a long pot life and is excellent in workability.

[Means for solving problems]

In the present invention, in order to obtain mixed sand with a stable pot life, the catalyst has no effect at room temperature (it is only activated when the temperature rises, and curing (polymerization) of the binder begins. A curing catalyst is used.Such curing catalysts include Cr of para-toluenesulfonic acid or xylenesulfonic acid,
Mn.

Metal salts of transition metals selected from Fe, Co, Nl, Cu and Zn are used. 20 to 70 wt % of these metals are blended.

Here, the above transition metal salt can be obtained, for example, as follows.

PTS-Cu (p-toluenesulfonic acid) copper salt) Copper acetate is added to an aqueous solution of para-toluenesulfonic acid and dissolved by heating. The mixture is further heated and evaporated to dryness, water is added to dissolve it, and the mixture is cooled to obtain crystals of PTS-Cu.

As the self-hardening resin, a self-hardening furan resin, a self-hardening phenol resin, a self-hardening phenol-modified furan resin, etc. are used.

The above-mentioned self-hardening resin and the above-mentioned curing catalyst solution are blended with sand to obtain blended sand, and the blending ratio is the same as in the case of making a normal self-hardening mold.

The compounded sand of the present invention has a long pot life, so sand, self-hardening resin,
The curing catalyst solution may be blended in any order.

After this mixed sand is filled into a model, it is hardened together with the model by dielectric heating using high frequency energy.

The present invention will be explained in detail below based on examples.

〔Example〕

Example 1. Comparative Example A self-hardening furan resin was prepared as a binder, and copper 4 (pTs-Cu) of para-toluenesulfonic acid was prepared as a curing catalyst, and a 358% aqueous solution was prepared. (2) As the curing agent for comparison, an aqueous solution of oxalic acid added to para-toluenesulfonic acid (the concentration is 15% wt and 10% wt, respectively) was used. In order to test the effectiveness of this catalyst, the following mixed sand was prepared.

Sand 100 River curing catalyst 60w [% BOR: pT5 copper lump aqueous solution 50 wt% BOR: PTS + oxalic acid aqueous solution binder
1.2wt% BO8: Self-hardening furan resin After kneading this mixed sand, immediately after mixing and after waiting for a predetermined time,
The model was filled with sand and heated with high frequency (13ifilz) energy. The heating time was 7 minutes in each case, and the electrode spacing was 14 cm. After each test piece was cured, it was removed from the mold and the compressive strength was measured 1 hour later. For those using conventional catalysts, when the temperature is 0 to 5℃ and 20 to 2℃,
Measurements were taken during the 5°C season. The results are shown in Figure 1.

FIG. 1 is a graph showing the relationship between waiting time and compressive strength.

1 is catalyst PTS + L oxalic acid, 5℃ 2 is catalyst PTS-1-L oxalic acid, 20℃ 3 is catalyst PTS
-Cu, at 20°C.

Example 2 When PTS-Ni is used as a curing catalyst PTS-Ni
The concentration of B is 11w%, and the proportion of B to sand is 60wt%.
It is OR. The addition rate of furan resin is 1.5wt%BO
It was set as 8. The results of measuring the compressive strength in the same manner as in Example 1 are shown in FIG. 2.

FIG. 2 is a graph showing the relationship between waiting time and compressive strength, and 4 is for the catalyst PTS-Nl at 120°C.

Looking at the results in Figure 1, it can be seen that with the conventional technology, there is no change in strength even after a waiting time of 3 hours at room temperature or 0 to 5 degrees Celsius;
At ~25°C, a change in strength appears after 2 hours, indicating that the sand has deteriorated.

On the other hand, when the curing catalyst of the present invention was used, no change in strength appeared even after a waiting time of 6 hours. This indicates that the catalyst of the present invention does not exhibit any catalytic effect at room temperature. In addition, the strength of the test piece was not much different from that used conventionally, and the catalyst exhibited sufficient effectiveness after heating.

〔Effect of the invention〕

The mold making method of the present invention provides a mold with a long pot life and excellent strength.

[Brief explanation of the drawing]

Figure 1 shows PTS-1-L walic acid and PTS-C as catalysts.
FIG. 2 is a diagram showing the pot life when PTS-N I is used as a catalyst. =7- Figure 1 Figure 2 Waiting time hr

Claims (1)

[Claims] 1. 20 to 7 for sand, self-hardening resin, and self-hardening resin
0 wt% aqueous solution, alcohol solution, or water/alcohol solution (concentration 10 to 50 wt%) of a metal salt of a transition metal selected from Cr, Mn, Fe, Co, Ni, Cu, and Zn of paratoluenesulfonic acid or xylene sulfonic acid A sand mold making method characterized by filling a model with mixed sand consisting of the following: and then dielectrically heating the model together with the model to harden it.