JPH0718464Y2 - Differential pressure casting equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to an apparatus for pouring molten metal into a cavity from a lower part of a mold by a pressure difference and casting, a so-called differential pressure casting apparatus.

<Prior Art> Generally, a differential pressure casting method is used in the production of high quality cast products. The differential pressure casting method is represented by a low pressure casting method and a suction casting method, which will be briefly described below.

In the low-pressure casting method, the molten metal surface in a closed heat-retaining furnace or melting furnace is usually applied with a pressure of 1 atm or less, and the molten metal is pushed up through a spout to the mold placed on the furnace and into the cavity. It is a method of casting by pouring molten metal.

On the other hand, the suction casting method is a method in which a mold is placed in a chamber capable of depressurizing the cavity to a negative pressure, and the molten metal in the furnace is sucked from below through a sprue pipe to cast the molten metal into the cavity. is there.

In such a differential pressure casting method, since the molten metal is continuously moved from the bottom to the top and poured into the mold through the spout tube deeply immersed in the molten metal, no air and flux floating on the surface of the molten metal or flux is generated. The entrainment in the mold is almost eliminated, and since it is connected to the lower melt while the melt solidifies in the mold, the melt reinforcement during solidification contraction is smoothly performed, and directional solidification is also performed. As a result, a sound casting with excellent airtightness can be produced. Moreover, since the molten metal can be gently poured by adjusting the pressure, there is an advantage that a sand core such as a shell core can be used and a casting having a complicated shape can be manufactured.

In such a differential pressure casting method, if the sprue pipe is cracked, melted, or the like to lose its airtightness, the molten metal is not retained in the cavity and flows out. If the molten metal has a low melting point such as aluminum or magnesium, it is easy to select the material of the sprue pipe, but if the molten metal has a high melting point such as cast iron or cast steel, sufficient heat resistance (melt loss resistance and It is difficult to obtain a sprue pipe material having thermal shock resistance).

Therefore, when performing differential pressure casting using a molten metal with a high melting point,
Since a certain amount of melting damage of the sprue pipe is unavoidable, conventionally, a sprue pipe made of a metal similar to the molten metal and having a slightly thicker thickness has been used.

On the other hand, as a substitute, a sprue pipe made of ceramics having no fear of melting damage has been proposed in JP-A-63-132762.

<Problems to be Solved by the Invention> However, the sprue tube made of a material similar to the molten metal and made thicker has the following problems. That is, when the sprue pipe is immersed in the molten metal, the melt in the vicinity thereof is temporarily cooled. Therefore, the thicker the thickness of the sprue pipe, the lower the molten metal temperature at the initial stage of casting and the trouble around the molten metal becomes. For this reason, casting is performed by raising the temperature of the molten metal in order to secure the surroundings of the molten metal, but due to the high heat, melting loss is promoted. As a result, melting loss occurs first with respect to the required solidification time. From the above, casting can be performed only under conditions where the thickness of the sprue pipe and the temperature of the molten metal are very limited, and none of the casting defects can be eliminated.

On the other hand, if the ceramic sprue pipe disclosed in the above-mentioned Japanese Patent Laid-Open No. 63-132762 is used, the problem of melting loss can certainly not occur, but the sprue pipe becomes extremely expensive and cannot be repeatedly used. However, the production cost is significantly increased. Moreover, since it is vulnerable to thermal shock, cracking easily occurs and the reliability of ensuring airtightness is poor, so it cannot be used at all.

The present invention has been made for the purpose of solving the above-mentioned problem, and the problem to be solved is to prevent melting of the spout pipe without making the spout pipe made of a material similar to the molten metal thick and thick. An object of the present invention is to provide a differential pressure casting device that can reliably perform casting.

<Means for Solving the Problems> In the differential pressure casting apparatus of the present invention for solving the above problems, a small container is immersed in the molten metal in the large container, and the molten metal in the large container is introduced into the small container. It is characterized in that there is a through hole and that the sprue pipe immersed in the molten metal in the small container is made of the same material as the molten metal.

That is, the differential pressure casting apparatus of the present invention comprises a mold, a molten metal container arranged below the mold, means for depressurizing the mold cavity or pressurizing the molten metal container, and a sprue pipe for guiding the molten metal into the cavity. In the casting apparatus, the molten metal container has a double structure of an outer container and an inner container, and a hole is formed in the inner container to allow the molten metal to move in both the above-mentioned containers, and a material similar to the molten metal. It is characterized in that the sprue pipe made in (4) is immersed in the molten metal in the inner container.

The sizes of the small container (inner container) and the sprue are preferably selected so that when the sprue pipe is immersed, the molten metal in the vicinity of the spout exhibits an appropriate temperature drop and rapid temperature recovery. In addition, it is important to reduce the wall thickness of the sprue pipe as compared with the conventionally used one.

<Operation> With the above configuration, the molten metal in the small container has a small heat capacity. Therefore, when the sprue pipe is immersed, the temperature drop of the molten metal in the vicinity becomes remarkable. Therefore, a solidified layer is formed on the sprue pipe.

When the pouring is started, the high temperature molten metal is replenished from the large container, so the temperature of the molten metal recovers quickly. Keeping the heat capacity of the sprue pipe small without thickening it also helps in temperature recovery.

Since the solidified layer delays the melting loss of the sprue pipe and gives a sufficient pouring-solidifying time, good casting can be performed.

<Example> Hereinafter, the differential pressure casting apparatus of the present invention will be described with reference to the suction casting apparatus of one example, but the present invention is not limited thereto.

In this apparatus, as shown in FIG. 1, an air-permeable casting 3 composed of an upper mold 1 and a lower mold 2 is installed on a surface plate 4 and covered with an airtight chamber 5. The chamber 5 is provided with an exhaust pipe 6 connected to a depressurizing means (not shown), so that the cavity 7 can be depressurized. The pouring into the cavity 7 is performed by sucking the molten metal 15 in the molten metal container 9 arranged below through the stalk 8 penetrating the surface plate 4.

The molten metal container includes a large container (large crucible) 11 surrounded by a coil 10 and a high-frequency furnace 9 with a capacity of 300 kg, and a small container (a small crucible containing magnesia as a main component with a capacity of 30 kg) 12 attached inside thereof. It is composed of and. The small container 12 is submerged in the molten metal 14 in the large container 11 by a supporting member (not shown) so as to be submerged by about 90%.
A φ70 passage hole is provided so that the molten metal 14 inside can flow in. The tip of the stalk 8 is immersed in the molten metal 15 in the small container 12, and when the molten metal 15 in the small container 12 is sucked, the molten metal 14 is replenished from the large container 11 through the passage port.

Molten metal 14 and 15 are heat-resistant cast steel SCH21 (0.3% C-20% Ni-25% Cr
-Remaining Fe) is melted, and the stalk 8 has an inner diameter of 60 mm made of a similar material (0.08% C-remaining Fe) as the above molten material.
A general commercial iron pipe with a wall thickness of 2.3 mm and a length of 400 mm. When casting a product with a minimum wall thickness of 3 mm and a weight of 20 kg using the above equipment and molten metal under the conditions of a decompression rate of 100 mmHg / sec and a final pressure of -600 mmHg, secure the hot water around the 2.3 mm thick pipe. The minimum casting temperature is 1500 ° C,
On the other hand, the required coagulation time is 50 seconds.

From Fig. 3 which shows the relationship between the stalk wall thickness and the erosion time when the small container 12 is not used, from the conventional equipment, that is, 2.3 mm iron pipe alone
It can be seen that the stalk thickness must be 4 mm or more because it will be melted in 0 seconds. However, in the case of casting with a 4 mm thick pipe, the heat capacity of the pipe becomes large and the initial casting temperature lowers, resulting in defective molten metal flow. Therefore, it is necessary to raise the temperature of the molten metal somewhat. This will melt the stalk by the time pouring-solidification is complete.

In this embodiment, the thickness of the stalk 8 is set to 2.3 mm in order to prevent the decrease of the molten metal temperature of the inflowing molten metal in the early stage of casting. Since the molten metal 15 in the small container 12 is thermally separated from the large amount of molten metal 14 in the small container 12 and has a small heat capacity, when the stalk 8 is immersed in the molten metal 15 in the small container 12 during casting, A solidified layer 16 having a thickness of about 5 mm is formed on the immersed portion. FIG. 2 shows the temperature change of the molten metal in the portion A in the small container 12. When the depressurizing means is operated in this state to perform casting under the above conditions, the molten metal to be cast into the cavity 7 is replenished with the molten metal flowing in from the passage port, so that the temperature drop shown in FIG. Is a large container that has been recovered by the inflow of molten metal
It is the same as the molten metal 14 in 11. Therefore, the molten metal having a substantially desired temperature can be cast, and the solidification layer 16 is formed, so that the casting time is secured.

<Effect of the Invention> As described above, in the casting apparatus of the present invention, the small container having the through hole is immersed in the molten metal, and the gate pipe is immersed in the molten metal in the small container. Produce an effect.

First, melting of the sprue pipe is less likely to occur, and a sufficient pouring-solidifying time can be secured. Therefore, defective casting can be prevented and the yield is improved.

Also, an inexpensive pipe can be used as the sprue pipe.

Moreover, it is not necessary to strictly control the thickness of the sprue pipe and the molten metal temperature.

Moreover, the slag on the surface of the molten metal can be removed only at the small container, and it becomes easier by making the small container detachable.

That is, the device of the present invention can contribute to the improvement of workability and the reduction of production cost.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a low pressure casting apparatus according to an embodiment of the present invention, FIG. 2 is a graph showing changes in molten metal temperature near the sprue pipe according to the apparatus, and FIG. 3 is a sprue made of the same material as the molten metal. It is a graph which shows the relationship between the wall thickness of a pipe and melting time. In the figure, 3 ... Mold, 8 ... Stoke 11 ... Large container, 12 ... Small container 13 ... Melting hole, 14 ... Molten metal in large container 15 ... Molten metal in small container, 16 ... Solidification layer

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Yuuki Yuki 1 Toyota Town, Toyota City, Aichi Prefecture Toyota Automobile Co., Ltd. (56) Reference JP-A-1-104457 (JP, A)

Claims (1)

[Scope of utility model registration request] 1. A small container is immersed in the molten metal in the large container, and the small container is provided with a through hole for introducing the molten metal in the large container.
Further, the differential pressure casting apparatus is characterized in that the sprue pipe immersed in the molten metal in the small container is made of the same material as the molten metal.