JPH0775758B2 - Mold making method using microwave heating - Google Patents

Description

[Detailed Description of the Invention] (Industrial field of application) The present invention relates to a mold making method, in particular, by forming a fine mold layer on the mold surface by microwave heating, it is possible to improve casting surface roughness and dimensional accuracy. The present invention relates to a mold making method using microwave heating.

(Prior art) Precision casting methods such as the lost wax method and the ceramic molding method have been applied to cast products that have conventionally required excellent casting surface roughness and good dimensional accuracy. Because of its high productivity and poor productivity, microwave heating is used to form a dense coating film layer on the mold surface by microwave heating, which can achieve a casting surface and dimensional accuracy similar to precision casting products at low cost. The mold making method is used. As shown in FIG. 4, in the mold making method using microwave heating, a slurry type coating agent 101 is poured into a model 102 to adhere the coating agent to the entire surface of the model, and then the coating agent 101 is reversed and discharged. Let Next, after filling the inside with a core sand 104 coated with a binder, the coating agent 101 and the core sand 104 are simultaneously cured by microwave heating, so that the core 1 after curing is
07 is a hard coating layer on which the properties of the inner surface of the model are accurately transferred.
105 is formed. As the binder for the coating type and the core sand, an inorganic binder or an organic binder is used.

(Problems to be solved by the invention) When a core is formed by using an inorganic binder in a coating mold and foundry sand (core sand), damage to the model surface in the process of heating and curing by microwaves However, when this core is used to make castings that are injected at high temperatures like cast steel,
Since the core reaches a temperature (800 ° C or higher), the binder adhering to the surface of the core used during molding is sintered and sand cannot be removed. On the other hand, in the core using the organic binder in the coating mold and foundry sand, sand can be satisfactorily removed without the concern that the binder is sintered to the casting injected at high temperature. In the process of heating and curing the mold coating agent and foundry sand with microwaves, the curing temperature rises (250-300 ° C), which has a drawback that the surface of the model for making the core is deteriorated and damaged more quickly. Focusing on the above problems, the present invention uses an inorganic binding agent as a mold coating agent and an organic binding agent for foundry sand, and an inorganic binding agent is used between the two in claim (1). With the dry molding sand used, in claim (2), by applying the liquid organic resin, a heat insulating layer is formed between the two so that the ammonia gas generated from the organic binder does not hit the model. The object of the present invention is to provide a mold making method using the microwave heating described above.

(Means for Solving the Problem) In order to achieve the above-mentioned object, claim (1) In a mold making method in which a core to which a mold coating agent is previously attached is cured by microwave heating in a model, the entire surface of the model is After applying a coating agent using an inorganic binder, insert dry intermediate sand using an inorganic binder, turn over the model, and discharge the excess dry intermediate sand from the model, then Filling core sand using a systemic binder, microwave heating in this state,
A mold molding method using microwave heating, characterized in that dry intermediate sand and core sand are simultaneously cured. Claim (2): A core pre-coated with a mold coating agent is microwave heated in a model. In the mold molding method of curing with, after applying a coating agent using an inorganic binder to the entire surface of the model, after drying the surface with a liquid organic resin, using an organic binder A mold molding method using microwave heating was characterized in that core mold was filled with core sand, and the coating agent and core sand were simultaneously cured by microwave heating in this state.

(Operation) According to the above configuration, the dry sand or the liquid organic resin using the coating agent and the intermediate inorganic binder forms the heat-insulating layer at the time of microwave heating to form the organic binder. It exerts the function of the film so that the ammonia gas generated from the core sand containing the agent does not hit the model surface. It also serves as a heat-insulating layer for heat-curing core sand using an organic binder to improve the durability of the model during molding. Further, since the organic binder is used in the mold, the sand removal property after casting is improved.

(Example) An example of a mold making method using microwave heating according to the present invention will be described with reference to the drawings. FIG. 1 is a schematic explanatory view of a core molding process based on an embodiment of the present invention. The inorganic coating agent 1 is poured into the inside of the model 2, the coating agent is attached to the entire surface of the model, and then the model 2 is inverted to discharge the coating agent. The dry intermediate sand 3 using the inorganic binder is put in the model 2 and attached to the inorganic coating material, and then the remaining intermediate sand is discharged. Next, the core sand 4 using an organic binder is modeled 2
It is filled inside (blow filling or vibration filling). In this state, the mold coating agent and core sand are simultaneously cured by microwave heating. A hard coating layer 5 on which the properties of the inner surface of the model are accurately transferred is formed on the core after curing. In claim (2), the core is molded in the same steps as in claim (1) except that the liquid organic resin 3a is used instead of the intermediate sand 3. Table 1 shows molding conditions of various test pieces prepared according to the above process. * NO.3 is a model in which HR400M, instead of intermediate sand, is applied after drying the mold coating agent, and core sand is filled. In addition, after applying the inorganic coating agent to the model, directly filling the shell sand and performing microwave heating, the water in the coating agent does not penetrate into the core sand, so the coating layer surface becomes avatar. , NO.1 or NO.2, in order to make a path for water vapor during heating to pass, after applying a coating agent, insert inorganic intermediate sand and invert and discharge it, then use an organic binder It was filled with sand and molded. These core test pieces were melted into cast steel by the casting method shown in FIG. 2, and FIG. 3 shows the measurement results of the respective casting surface roughness at that time. In the test peat NO.1 NO.2 according to the embodiment of the present invention, sand removal is easily performed by sand blasting and casting surface roughness is
With NO.1 and NO.2, about 25-30S was obtained. No. 4 indicates a conventional technique that does not use a coating agent.

(Effects of the Invention) As described above, according to the present invention, deterioration and damage of a model are prevented, and durability of the model is improved, so that the cost of the model can be reduced. Further, since the sand-removing property of the core is good, it is possible to reduce the man-hours required for sand-removing the core, which conventionally required a large number of man-hours.

[Brief description of drawings]

FIG. 1 is a schematic explanatory view of a core molding process based on an embodiment of the present invention. FIG. 2 is a casting plan diagram of a core test piece manufactured according to the embodiment of the present invention. FIG. 3 is a comparison diagram of casting surface roughness and measurement results of core test pieces manufactured according to the examples of the present invention. FIG. 4 is a schematic explanatory view of a mold making method utilizing microwave heating based on the conventional technique. 1 …… Inorganic coating agent 2 …… Model 3 …… Intermediate sand using inorganic binder 3a …… Liquid organic resin 4 …… Core sand 5 using organic binder 5 …… Coating Membrane layer

Claims (2)

[Claims] 1. A mold molding method in which a core preliminarily coated with a mold coating agent is cured by microwave heating in a model,
After applying a coating agent using an inorganic binder to the entire surface of the model, insert dry intermediate sand using an inorganic binder, invert the model, and discharge excess dry intermediate sand from the model. After that, the core sand using an organic binder is filled, and in this state, the coating agent, the dry intermediate sand, and the core sand are simultaneously cured by the microwave. Mold making method using heating. 2. A mold molding method in which a core to which a mold coating agent is previously attached is cured by microwave heating in a model,
After applying a coating agent using an inorganic binder on the entire surface of the model, after drying and applying the surface with a liquid organic resin,
A mold molding method using microwave heating, characterized in that core sand using an organic binder is filled, and in this state, the mold coating agent and core sand are simultaneously cured by microwave heating.