JPH0952149A - Method for drying mold - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the gas defect in a product of a casting, etc., to improve the yield of the product, to reduce of a production cost and to improve the quality and reliability, in a method for drying a mold by utilizing the high gas permeability in a short time while preventing the development of defective drying part. SOLUTION: Ceramic grains having large grain diameter and high gas permeability are used, and in order to dry a mold 6 using organic resin as binder, at first, the opening hole parts of a sprue 3 and a riser 4, etc., of the mold are plugged with a seal material 5 to close a space for filling the molten metal. Successively, the air dried in high temp. is blown into the mold 6 from the opening hole part of the riser through a warm blast drier 1 and a blasting hose 2 to make the pressurized condition. By this method, the mold is dried so that the air dried in the high temp. is passed through the inside the mold formed of ceramic grains having the high gas permeability from the molten metal contact surface of the mold and flowed to the outer part of the mold.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for drying an artificial ceramic mold used for producing a casting, especially a cast steel, in which pressurized warm air is ventilated.

[0002]

2. Description of the Related Art Conventionally, except for precision casting and the like, cast steel molds having a weight of several tens of kilograms to several tens of tons are generally manufactured as sand molds.

The materials of sand are mainly silica sand, chromite,
Zircon is used, and the average particle size of sand is about 0.3 m for silica sand.
m, chromite about 0.2 mm, zircon about 0.1 m
m.

As the binder for forming a mold with these sands, many binders such as inorganic binders such as water glass and cement, organic binders such as furan, phenol and urethane are used. Is used.

Further, it is necessary to dry the moisture absorbed by the sand and the moisture contained in the binder. As a drying method, air dried at a high temperature using a conventional hot air dryer is used as a mold. Drying is generally carried out by feeding a molten metal into a space filled with molten metal from a sprue or the like and allowing the molten metal to be naturally exhausted.

[0006]

In the mold, a binder is used for the purpose of binding and hardening the sand grains.

This binder contains a large amount of water,
When water is present in the mold, the water in the mold vaporizes as the temperature of the mold rises during pouring, and the water penetrates into the melt, causing gas defects (blowholes).

Therefore, in order to evaporate a large amount of water contained in the binder together with the water absorbed by the sand, it is necessary to dry the mold after molding.

FIG. 6 shows a conventional mold drying method. In the conventional drying method, air dried at a high temperature by using a warm air dryer 1 or the like is sent from a pusher 4 or the like to a space 8 in which a molten metal of a mold 6 is filled by a blower hose 2 and is naturally exhausted to a spout 3 or the like. Is going by.

However, in the above-mentioned conventional method, the air dried at high temperature only comes into contact with the molten metal contact surface of the mold 6,
In order to dry the inside of the mold, it is necessary to use the temperature rise of the mold 6 due to heat conduction to vaporize the water inside the mold and move it to the molten metal contact surface of the mold 6, which causes a problem that it takes a very long time to dry. is there.

Further, since the air dried at a high temperature by the warm air dryer 1 and the like during the drying is mixed with the moist air which absorbs the moisture of the mold 6, the drying efficiency is lowered and the space position 14 in FIG. In the portion shown by, there is also a problem that insufficient drying is likely to occur due to insufficient air circulation.

The present invention solves each of the above problems, provides a new method for drying a mold by preventing the occurrence of defective drying and making it possible to dry the mold in a short time by utilizing high air permeability. It is an object.

[0013]

[Means for Solving the Problems] As a structure for achieving the above object, a method of drying a mold according to the present invention uses an organic resin as a binder and ceramic particles having a large particle size and high air permeability as a mold material. Then, in the method of drying the molded mold,
At the time of drying, first, the mouth of the mold, the opening of the riser, etc. is closed with a sealant etc., the space filled with the molten metal is sealed, and then the air dried at high temperature is sent from the opening of the riser to bring it into a pressurized state. This is a method of drying the mold by allowing the air dried at a high temperature to flow from the molten metal contact surface of the mold to the outside of the mold through the inside of the mold.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment of the present invention will be described below with reference to FIGS. FIG. 1 shows a mold drying method of the present invention, and FIG. 2 shows an example of a schematic shape of a casting to be manufactured.

As shown in FIG. 1, a casting mold 7 was molded into a casting mold 6 using a water-soluble phenol resin as a binder and an organic ester as a curing catalyst. This mold 6 has a particle size of 0.4 to 1.0 m
1.2 parts of a phenol binder and 0.25 part of an organic ester were mixed with 100 parts of a mullite ceramic having a range of m.

Further, a gas vent was appropriately installed in the mold 6, and a thermometer 10 and a hygrometer 11 were arranged in the mold 6 at a position 100 mm from the molten metal contact surface indicated by a measurement position 12.

Subsequently, the openings of the sprue 3 shown in FIG. 1 and the risers 4, 13 shown in FIG. 2 are closed with a sealing material 5, and the risen 4 is dried with warm air dryer 1 at about 180 ° C. Was blown through the blower hose 2 and dried by the drying method of the present invention in which the space 8 filled with the molten metal during pouring was pressurized. At this time, the obtained pressure was 0.1 atm.

For comparison, a conventional mold 6 (the shape of which is the same as that of FIGS. 1 and 2) in which chromite is used as skin sand and silica sand is used as back sand under the same conditions, is molded. After arranging the thermometer 10 and the hygrometer 11 at a position 100 mm from the molten metal contact surface indicated by the measurement position 12 of the above, the hot air dryer 1 feeds dry air of about 180 ° C. from the hot water 4 to the hot water 13. Dried by conventional method with natural exhaust.

FIG. 3 shows the time change of the temperature of the mold at the measuring position 12 during drying. It can be seen that the temperature of the mold rises faster in the drying method of the present invention than in the conventional method.

FIG. 4 shows the change over time in the relative humidity of the air in the mold at the measuring position 12 during drying.

In comparison with the conventional method, in the drying method of the present invention, the relative humidity is high in the initial stage where water is considered to exist in the mold.

However, in the drying method of the present invention, the measurement position 1
2) The relative humidity rapidly decreases at the stage where it is considered that all the water in the mold has evaporated, and the time to reach the same relative humidity as the dry air sent by the hot air dryer 1 is earlier than the conventional method. I understand.

FIG. 5 shows how the absolute water content in the air in the mold changes with time at the measurement position 12 during drying, which is obtained from FIGS. 3 and 4.

As compared with the conventional method, the absolute water content in the drying method of the present invention is high in the initial stage where water is considered to be present in the mold.

However, in the drying method of the present invention, the absolute water content rapidly decreases at the stage where it is considered that all the water in the mold at the measurement position 12 has evaporated, and the absolute water content is the same as the dry air sent by the warm air dryer 1. The time required to reach an absolute water content to some extent is faster than that in the conventional method, indicating that the mold 6 is sufficiently dried at this point.

A mold dried for 30 hours by the method of the present invention,
A casting test was carried out on each of the molds dried for 48 hours by the conventional drying method. The material of the casting is carbon steel (SC4
9), and the pouring temperature was 1,580 ° C.

When the casting was subjected to defect inspection after demolding, it was dried in a conventional casting mold, and some cast gas defects were found in the casting, whereas casting was performed in the casting mold dried by the method of the present invention. The cast product had almost no gas defects, and a good cast product could be produced.

Although one embodiment of the present invention has been briefly described above, the present invention is not limited to this, and various modifications can be made within the scope of the technical idea of the present invention. Belong to the technical scope.

[0029]

According to the method of drying a mold of the present invention, since the air dried at a high temperature directly passes through the mold, the temperature of the mold rapidly rises as compared with the conventional method, and the mold is also inside the mold. Evaporation of water inside the mold is promoted because the dry air at high temperature comes into direct contact with the water inside.

Further, in the conventional sand mold, since the air permeability is not sufficient, the air permeation amount in the mold is small, and the time required for drying the mold does not change so much, but the ceramic having a large particle size and high air permeability is used. By drying the ceramic mold using the particles by the method of the present invention, the drying time can be greatly shortened, and the mold can be dried without causing defective drying.

As a result, defects (gas defects) in products such as castings are reduced, and it is possible to improve product yield, reduce manufacturing cost, and improve quality and reliability.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of a mold drying method showing an example of a preferred embodiment of the present invention.

FIG. 2 is a perspective view showing a schematic formation of a cast product manufactured by the mold.

FIG. 3 is a graph showing the relationship between mold drying time and mold temperature according to the present invention.

FIG. 4 is a diagram showing the relationship between the mold drying time and the relative humidity of air in the mold according to the present invention.

FIG. 5 is a diagram showing the relationship between the mold drying time and the absolute moisture content of the air in the mold according to the present invention.

FIG. 6 is a schematic explanatory view showing a conventional method of drying a mold and the structure of the mold.

[Explanation of symbols]

 1 Hot Air Dryer 2 Blower Hose 3 Gate 4 Pushing Water 5 Sealing Material 6 Mold 7 Forming Frame 8 Space Filled with Molten Metal 9 Closing Pushing Water 10 Thermometer 11 Hygrometer 12 Measuring Position 13 Hot Water

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Shinji Matsuyama 1-1-1, Wadasaki-cho, Hyogo-ku, Kobe Sanbishi Heavy Industries Ltd. Kobe Shipyard (72) Kenichi Kubo, Wadazaki-cho, Hyogo-ku, Kobe 1-1-1 Sanryo Heavy Industries Co., Ltd. Kobe Shipyard

Claims (1)

[Claims] 1. A method for drying a mold produced by using an organic resin as a binder and using ceramic particles having a large particle size and high air permeability as a mold material. By closing the opening with a sealing material, sealing the space filled with the molten metal, and then feeding hot and dry air through the opening for pushing the molten metal into a pressurized state,
A method of drying a mold, characterized in that air dried at a high temperature is passed from the molten metal contact surface of the mold through the inside of the mold to the outside of the mold.