JPS599254B2 - How to make a hollow core - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for making cores used in casting processes.

Since furan resin sand has good sand disintegrability, it has recently come to be used in place of water glass-based CO2 type, Dical type, etc., and it tends to be widely used especially as core sand.

Furan resin sand is hardened by the condensation reaction of furan/phenol resin or furan urea resin, which is a caking agent, under the action of an acid catalyst.

That is, the hardening speed of this furan resin sand is significantly influenced by the pH value of the sand.

As can be seen from FIG. 1, the higher the pH value of the furan resin sand, the longer it takes to harden.

Furan resin sand has such properties, but in conventional cores, the good disintegration properties only appear on the surface area, which is heated to above the carbonization temperature of the resin (approximately 500°C) by the heat of the molten metal. The core was hardened significantly, making it difficult to remove the core.

The present invention aims to eliminate the above-mentioned drawbacks, and involves filling a model with molding sand mixed with a furan resin and a catalyst, infiltrating the core of the molding sand with an alkaline solution that increases the pH value of the sand, and contacting the model with the molding sand. This is a hollow core manufacturing method characterized by manufacturing a core having a hollow portion by removing unhardened sand in the core after the molding sand in the hardened portion has hardened.

Embodiments of the present invention will be described above based on the drawings.

In FIGS. 2 and 3, 1 is a model having a cavity in the shape of a core to be manufactured, and this model 1C is provided with a vent hole 2 and has a ventilation hole 3 communicating with the outside air.

4 is furan resin molding sand; 5 is the furan resin molding sand 4;
This is a pipe for permeating an alkaline solution into the inside of the pipe 4, and a large number of holes 6 are perforated around the outer circumference of the pipe 4.

7 shows the range of the alkaline solution permeated into the furan resin molding sand 4.

Note that as the alkaline solution, solutions such as ammonia water diluted with water and water glass are suitable.

Next, the manufacturing order of the hollow core is shown.

a) Weight ratio: sand 100, furan resin 1.0, catalyst (85
Furan resin foundry sand mixed at a ratio of 0.2% lJ acid) 4
Fill the inside of the model 1.

b) Inside the furan resin molding sand 4 (when a pipe 5 is inserted and the alkaline solution is poured into the pipe 5, it permeates through the hole 6).

The optimum permeation amount and permeation range of the alkaline solution are determined by the position and number of holes 6, the permeation time, etc. which are predetermined depending on the shape of the core.

C) After about 2 hours, the model 1 is demolded and the uncured part (alkaline solution permeated part) 7 of the furan resin molding sand 4 is removed to form a hollow core.

As is clear from the above explanation (according to the present invention, the conventional core is made hollow), a) improvement in collapsibility b) weight reduction c) reduction in the amount of sand used) improvement in air permeability It brings about such effects.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the curing situation depending on the difference in pH value of the furan resin, and FIGS. 2 and 3 are cross-sectional views showing examples of the present invention. 1... Model, 4... Furan resin casting sand, 5... Pipe.

Claims (1)

[Claims] 1 Fill a model with molding sand mixed with a 7-run resin and a catalyst, infiltrate the core of the molding sand with an alkaline solution that increases the pH value of the sand, and after the molding sand in contact with the model hardens, A method for manufacturing a hollow core, which is characterized by manufacturing a core having a hollow portion by removing unhardened sand from the core.