JPS6171153A - Molding method of casting mold - Google Patents

Abstract

PURPOSE:To improve the strength of a casting mold by coating a solidifying liquid on the surface of the casting mold then penetrating the liquid into the mold by a ventilation effect and curing the green sand mold. CONSTITUTION:A master mold 3 having a cavity surface 2 is molded in a molding flask 1 by squeezing green sand. The flask 1 contg. the mold 3 is then placed on a suction board 6 and the solidifying liquid consisting of a liquid mixture composed of a binder and hardener is uniformly coated by spraying, etc. on the cavity surface. A vacuum pump is drieven to such and evacuate the inside of the hollow chamber 4 of the suction board 6 and the solidifying liquid is penetrated from the cavity surface 2 to the inside of the mold 3 through vent holes 5. The mold 3 is rested thereafter to form a cured layer 7 on the surface 2. The surface strength of the mold 3 is improved by the above- mentioned method.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method of molding a main mold and a core using green sand.

(Prior art) Molding the main mold by squeezing green sand has been practiced for a long time, and in recent years, molding the core by squeezing green sand has also been practiced. These green sand molds have low surface strength, and the core itself has low strength, so it can break or deform, causing various casting defects and impairing the dimensional accuracy of the casting. There was a problem.

(Purpose of the invention) The present invention has been made in view of the above circumstances.

(Configuration of the Invention) Hereinafter, the configuration of the present invention will be described in detail based on drawings of embodiments. First, to explain the case of the main mold based on Fig. 1, green sand is squeezed by an appropriate conventional means to form a main mold (3) having a cavity surface (2) in the casting flask (1). . Next, the main mold (3) and the built-in casting flask (1)
into a hollow chamber (4) connected to a vacuum pump (not shown).
), and its upper surface has a plurality of vent holes (5
) It is placed on a rectangular plate-shaped suction disc (6) that communicates with the hollow chamber (4) through (5), and then a binder and a hardening agent are applied to the cavity surface (2) of the main mold (3). Apply a solidifying solution consisting of a mixture of the above evenly with a spray or brush. Next, the vacuum pump is driven to reduce the pressure inside the hollow chamber (4) of the suction plate (6), thereby causing the air to flow through the vent hole (5) to the cavity surface (2) of the main mold (3). Suction is applied to infiltrate the solidification liquid from the cavity surface (2) into the main mold (3), and after the solidification liquid has penetrated, the vacuum pump is stopped and the main mold (3) is left alone. The cured liquid reacts and hardens to form a hard hardened layer (7) on the cavity surface (2). Thus, a hard hardened layer (7) is formed on the cavity surface (2).
) can be obtained.

Next, to explain the case of the core based on Figure 2, green sand is filled into the cavity of the mold, and a piercing rod is inserted into the cavity to squeeze out the sand, as shown in Figure 2. A hollow and stepped core (21) is molded as shown in FIG. Next, the core (21) is placed upright on the suction disc (6) in the same manner as the main mold (3), and then the solidifying liquid is applied to the outer surface of the core (21). Place the meng (22) on the upper end surface of the core (21) and close the upper end opening. Next, the vacuum pump is driven to reduce the pressure in the hollow chamber (4) of the suction plate (6), thereby creating a suction aeration effect on the surface of the core (21) and displacing the solidified liquid into the core (21). ), and after the solidification liquid has penetrated, the vacuum pump is stopped and the core (21) is left alone.The solidification liquid reacts and hardens, forming a hard hardened layer (23) on the outer surface. Ru. Thus, a core (21) with a hard hardened layer (23) formed on the outer surface can be obtained.

Example 1 A solidified liquid obtained by suitably mixing a furan resin binder and an organic sulfonic acid curing agent is applied to the surface of a mold made by squeezing green sand, and then sucked onto the surface of the mold. When the solidifying liquid was permeated into the mold by aeration and the mold was then left to stand, the area near the surface of the mold reacted and was completely hardened within 30 minutes.

Then, the surface hardness of the hardened casting became comparable to the hardness of the self-hardening mold, and the mold as a whole came to have sufficient strength.

Example 2 A solidified liquid obtained by suitably mixing a phenol resin and polyisocyanate as a binder with an organic basic compound as a curing agent was applied to the surface of a mold made by squeezing raw sand, and then When the solidifying liquid was permeated into the mold by suction aeration on the surface of the mold, and the mold was then left to stand, the area around the surface of the mold reacted and was completely hardened within 30 minutes. The surface hardness of the hardened mold was comparable to the hardness of the self-hardening mold, and the mold had sufficient strength as a whole.

Note that the solidifying liquid is not limited to those mentioned above, and any liquid may be used as long as it is liquid, has adhesive properties, and has high strength after curing. Further, the amount of curing agent added is changed depending on the ambient temperature, and is increased when the temperature is low and decreased when the temperature is high. Further, the curing time of the mold surface can be adjusted by increasing or decreasing the amount of curing agent added.

In addition, in the example, the penetration of the solidified liquid is promoted by suction action, but a cover is placed over the top of the flask (1) in Fig. 1, and compressed air is supplied from the cover side (pressurized ventilation action). The same effect can be obtained even if the same effect is obtained. In this case, the molding time of the cured layer can be further shortened by ventilating heated compressed air. Further, in the embodiment, the solidifying liquid is applied before suction and ventilation, but it may also be applied while suction and ventilation.

(Effects of the Invention) As is clear from the above description, the present invention applies a solidifying liquid to the surface of a green sand mold, allows the solidifying liquid to permeate through aeration, and then leaves the surface of the green sand mold. By forming a hard hardened layer on the green sand mold, the surface strength of the green sand mold becomes as strong as that of a self-hardening mold, and as a result, the strength of the green sand mold itself is greatly improved. The core has excellent effects such as being completely free from damage or deformation even when handled.

[Brief explanation of the drawing]

The drawings show an embodiment of the present invention; FIG. 1 is a vertical cross-sectional view of a green sand main mold, and FIG. 2 is a vertical cross-sectional view of a green sand core. (2): Cavity surface (3): Main mold (7): Hardened layer (21): Core (23): Hardened layer NXI Bee 2 prisoners

Claims (1)

[Claims] A solidifying liquid is applied to the cavity surface or the surface of the green sand mold, and the solidifying liquid is allowed to permeate into the mold by aeration, and the green sand mold soaked with the solidifying liquid is left to react and harden. A mold making method characterized by forming a hard hardened layer on the chipping surface or surface of a sand mold.