JPS6354466B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a casting method and a ceramic shell mold, and more particularly to a casting method and a ceramic shell mold that can produce high-quality, high-yield castings.

Ceramic shell molds are manufactured using a method called the lost wax method or the investment method, and are heated to a high temperature of approximately 900°C before pouring, but the feeder solidifies slower than the casting to prevent solidification defects in the casting. It is necessary. For this reason, various studies have been made on the size, shape, position, number, etc. of the feeder. FIG. 1 is a cross-sectional view showing an example of a conventional ceramic shell mold made from this viewpoint. According to this, riser parts 2 are provided at the top and bottom, and a thick runner is provided in the center of the mold 1. A riser portion 2a that also serves as a feeder is provided.

In order to solidify the feeder slower than the casting, various methods have been adopted to keep the feeder warm and to promote cooling of the casting, thereby improving the quality and yield of castings. For sand molds that are not heated during pouring, a general method is to cool the molten metal by forming a cold metal into the shape of the inner surface of the mold and embedding it in the mold wall near the inner surface. However, in ceramic shell molds that are usually heated and poured, if the chiller is integrated with the mold, the chiller will be heated together with the mold, creating a heat retention effect, which will have the opposite effect. Furthermore, because the ceramic shell mold has a very rough outer surface due to its manufacturing method, even when a molded chiller is applied to the outer surface, the adhesion is poor and the cooling effect is small. For this reason, ceramic shell molds were not cooled with a chiller. Conventionally, in order to keep the feeder part warm, methods such as wrapping a heat insulating material 6 made of fire-resistant fiber around the outside of the mold of the feeder part 2, or making the mold wall of the feeder part 2 thicker than other parts, as shown in Fig. 1, were used. This method has been adopted and has been somewhat effective in removing defects caused by solidification shrinkage, but problems such as coarsening of crystal grains and weakening of grain boundaries arise. Therefore, it is preferable to accelerate the cooling of the casting part after pouring molten metal into the mold. For this purpose, a gas such as air or nitrogen is blown onto the bottom of the mold, or a cooling metal plate (a water-cooled copper plate is usually used) is used to cool the mold. .) Methods such as placing it on top of the
However, the method of blowing gas has the disadvantage that the effect of cooling the metal is small because it cools through the outer wall of the mold. In fact, after pouring molten metal into the mold shown in Figure 1, the inventors conducted casting while strongly blowing nitrogen gas at the bottom of the mold, but found that shrinkage cavities were formed in the casting. . Furthermore, the method of placing the mold on a metal plate for cooling has the disadvantage that it is difficult to bring the mold into close contact with the metal plate, and the portion of the mold that comes into contact with the metal plate is likely to break.

Furthermore, although ceramic shell molds have high strength at high temperatures, the strength of the cooled portions decreases. Furthermore, the thickness of the mold must be such that it can withstand the pressure of the molten metal, but if the mold is thick enough to withstand the pressure of the molten metal, even if a coolant is brought into contact with the outer surface of the mold, the cooling effect will be small.
Therefore, in the case of bringing the coolant into contact, which has not been known in the past, it is necessary to reduce the thickness of the mold as much as possible and at the same time reinforce the mold to the extent that the thickness has been reduced. An object of the present invention is to provide a casting method equipped with a cooling method for cooling molten metal without impairing the strength of the ceramic shell mold, and a ceramic shell mold suitable for applying the cooling method.

One of the above-mentioned problems is that in the method of injecting molten metal into a heated ceramic shell mold and solidifying it in the ceramic shell mold to obtain a casting, at least a part of the periphery of the mold is mixed with powder and liquid. This is achieved by a casting method characterized by cooling the cast part of the mold by bringing it into contact with a coolant consisting of one or more of the following.

Another one of the above-mentioned problems is a ceramic shell mold having a riser part and a casting part, which is characterized in that a container for charging a coolant is provided around the casting part. This is achieved by

In the present invention, any solid or liquid fluid object can be used as the coolant, such as various metal or non-metal powders,
Examples include molten salts, low melting point metals, and molten metals such as light metals.

Examples of metal powders include iron particles and steel particles such as shots used in foundries to remove sand, nonmetallic particles include alumina particles and silica sand particles, and low-melting metals include lead and tin. However, aluminum is preferred as the light metal, and a mixture of fluorite, alumina, and silica is preferred as the molten salt.

According to a particularly preferred embodiment of the mold according to the invention, the container for charging the coolant is preferably of integral construction with the mold.

Embodiments of the present invention will be described in detail below based on the accompanying drawings.

In FIG. 2, a container 5 is provided below the casting part 3 of the ceramic shell mold 1 heated to 900°C, iron particles are filled as a coolant 4 into the container 5, and the coolant 4 is applied to the casting part 3. I made contact with. Immediately after that, molten SUS304 was poured into mold 1. A ceramic fiber sheet is wrapped around the feeder portion 2 as a heat insulating material 6 for heat retention. Casting part 3
The molten metal was solidified while being cooled with coolant 4, and the casting was taken out from mold 1 and inspected. It was confirmed that there were no shrinkage cavities and that the crystal grains were relatively fine.

FIG. 3 shows an example in which a container 5 for charging a coolant is manufactured integrally with a mold 1 by the investment method.

In the investment method, ceramic shells are formed by stacking many layers of refractory material. In this case, 10 layers of coating were applied, but after 6 layers of coating were completed, the space for coolant 4 was filled. The container 5 is formed by depositing the wax and then applying four layers of coating, and the thickness of the container 5 and the thickness of the part of the mold 1 in contact with the coolant 4 are thin. Further, the heat insulating material 6 immediately above the lower feeder portion 2b was inserted after the six layers of coating were completed.

After heating the mold 1 to 900° C., a coolant 4 (iron particles) was charged into a container 5 formed integrally with the mold 1, and molten SUS304 was poured into the mold 1. When the casting was manufactured while cooling the casting part 3 with the coolant 4 in this manner, the lower feeder was required to be extremely small, and a sound casting without any nest-like defects was obtained.

In addition, since the thinner part of the ceramic shell mold for cooling is in contact with a coolant made of one or more of powder and liquid, the pressure of the coolant is applied to the walls of the mold from the surrounding area. This has the effect of reducing the molten metal pressure applied as internal pressure and substantially reinforcing the ceramic shell.

As detailed above, according to the present invention, the casting part of the ceramic shell mold is cooled by bringing a coolant made of one or more of powder or liquid into contact with the periphery of the ceramic shell mold. The method and the ceramic shell mold having a container for holding the coolant around the mold make it possible to cool the molten metal from around the ceramic shell mold, and also make it possible to cool the molten metal from around the ceramic shell mold. It is possible to strengthen molds whose strength has been reduced by the pressure of a coolant made of one or more of powder and liquid, improving the quality of castings made with ceramic shell molds and increasing yields. There is.

[Brief explanation of drawings]

Figure 1 is a sectional view showing an example of a conventional mold, Figure 2 is a sectional view showing an example of a conventional mold.
3 and 3 are cross-sectional views showing specific examples of the mold of the present invention. 1...Ceramic shell mold, 2, 2a, 2b
... riser part, 3 ... casting part, 4 ... coolant,
5... Container, 6... Insulating material.

Claims (1)

[Scope of Claims] 1. A method of injecting molten metal into a heated ceramic shell mold and solidifying it in the ceramic shell mold to obtain a casting, in which at least a part of the periphery of the mold contains particulate matter and a liquid. A casting method characterized in that the cast part of the ceramic shell mold is cooled by contacting with a coolant consisting of one or more of the following. 2. A coolant consisting of one or more of powder and granules and liquid is one of metal powder, non-metal powder, molten low melting point metal, molten light metal, and molten salt. A casting method according to claim 1, characterized in that the method comprises: 3. A ceramic shell mold having a riser part and a casting part, characterized in that a container for charging a coolant is provided around the casting part. 4. The ceramic shell mold according to claim 3, wherein the container for charging the coolant has an integral structure with the ceramic shell mold.