JPH0484661A - Casting apparatus for directional solidification - Google Patents

Abstract

PURPOSE:To prevent the dissipation of heat of a heater and a mold body downward through the gap between these, to facilitate temp. control of a molten metal and to execute stable directional solidification by plugging the gap between the lower end of the heater and the lower end of the mold body with a shield body. CONSTITUTION:In a casting apparatus for directional solidification, the gap between the lower end of the heater 12 and the lower end of the mold body 1, is plugged with the shield body 10. The dissipation of heat of the heater 12 and the mold body 1 downward through the gap between these, is prevented and calorific power of the heater 12 is effectively transmitted to the molten metal Y in the mold body 1. Therefore, the temp. control of molten metal Y is facilitated and the uniform directional solidification is executed. Further, as the heater 12 is bisected and has constitution of separately flowing the electric current to each heater 12A, 12B, heating quantity to each part of the upper and the lower parts in the mold body 1 can be varied and further, fine temp. control is executed by the above constitution and the ideal molten metal temp. gradient can be obtd. Further, as a flange part 3 is pushed down with the shield body 10 and brought into pressed contact with the cooling body 4, such trouble that the mold body 1 is shifted or dropped from the cooling body 4 during cooling, is prevented.

Description

Detailed Description of the Invention The present invention relates to a casting device for directional solidification for producing castings such as turbine blades by a directional solidification method, and in particular, to Concerning improvements to facilitate management.

``Conventional technology'' The directional solidification method is a technology that creates a temperature gradient in the molten rh metal poured into a mold and causes solidification to proceed in one direction, thereby eliminating grain boundaries in that direction and increasing fracture strength. It is applied to turbine blades that require heat resistance and high strength.

For example, in the manufacture of this type of turbine blade, there has traditionally been a seventh
A casting apparatus for directional solidification as shown in the figure is used.

The reference numeral 1 in the figure is a mold body, in which a cavity IA having the shape of a turbine blade is formed, a sprue 2 is formed at the upper end, and the bottom surface is open.

The mold body 1 is a shell mold obtained, for example, by wax molding, and is formed by covering a wax model with a refractory binder, refractory particles, etc., solidifying it, and then melting and removing the wax model.

A flange portion 3 having an enlarged diameter is integrally formed at the lower end of the mold body 1, and this flange portion 3 is removably placed on a cooling body 4. The cooling body 4 is made of metal such as copper and has a built-in cooling channel.

Further, an elevating shaft 5 is connected to the lower surface of the cooling body 4, and the entire cooling body is elevated and lowered by an elevating mechanism (not shown).

On the other hand, a cylindrical high-frequency heater 6 having almost the same height as the mold body 1 is arranged around the mold body 1, and the molten metal Y in the mold body 1 is uniformly heated by electricity supply. There is.

According to the above device, a molten metal Y such as a heat-resistant alloy is injected from the sprue 2 of the mold 1, and while controlling the temperature of the molten metal Y by energizing the heater 6, cooling water is supplied to the cooling body 4 (jt). This makes it possible to gradually solidify the molten metal Y in one direction from the bottom end, making the entire casting a columnar crystal structure, which increases the fracture strength in the longitudinal direction compared to normal equiaxed castings. Two I can do it.

``Problems to be Solved by the Invention'' However, when examining the longitudinal section of a casting obtained using the above-mentioned directional solidification casting apparatus, a non-uniform structure was found, which was thought to be caused by insufficient control of the temperature gradient during cooling. There is a possibility that the strength may be reduced accordingly.
This was discovered through investigation by the inventors.

Therefore, in order to more strictly control the temperature of the molten metal Y, the present inventors conducted a detailed study on the factors that inhibit the temperature control of the molten metal Y in the above-mentioned apparatus. As a result, in the above device, the heater 6 is
It was also found that the heat of the mold body L escapes downward, which disturbs the heat and makes the temperature gradient of the molten metal Y unstable.

[Means for Solving the Problems] The present invention has been made to solve the above-mentioned problems. The present invention is characterized in that a shield is provided to seal the gap between the two.

A flange portion with an enlarged diameter is formed at the lower end of the mold body, and the lower surface of this flange portion contacts the upper surface of the cooling body that closes the lower end of the mold body, and the shield is annular. The inner peripheral portion may be pressed against the upper surface of the flange portion.

Further, the heater may include a plurality of independent cylindrical heaters.
They may be configured by arranging them below.

"Function" According to this casting device for directional solidification, by closing the gap between the lower end of the heater and the lower end of the mold body with the shield, the heat of the heater and the mold body can escape downward through this gap. It can be prevented. Therefore, the amount of heat generated by the heater is effectively supplied to the molten metal in the mold, so that the temperature of the molten metal can be efficiently controlled and stable directional solidification can be performed.

"Embodiment" Fig. 1 is a longitudinal cross-sectional view showing an embodiment of the directional solidification casting apparatus according to the present invention, and the same parts as in Fig. 7 are given the same reference numerals and explanations are omitted. do.

This device has the following two main features.

An annular plate-shaped shield 10 is fixed horizontally and coaxially to the lower end of the heater 12 arranged around the mold body 1.
The point where the gap between the lower end of the heater 12 and the lower end of the heater 12 is closed.

, the heater 12 is constituted by two cylindrical heaters I2A and 12B divided into upper and lower parts.

The heaters 12A and 12B have a cylindrical inner wall made of a heat-resistant material such as graphite, and have built-in coils (
(not shown) are connected to separate high-frequency power sources, and the molten metal Y is heated by induction by applying high-frequency current.

These coils 12A and 12B may be fixed to each other, or may be supported separately via a support, and if they are supported separately, a slight gap may be formed between them. You can.

Further, the axial lengths of the heaters I 2A, 12B do not necessarily have to be the same, and the ratio may be changed as necessary.

It is desirable that the shielding body 10 is made of a material having a coefficient of thermal expansion comparable to that of the material forming the lower ends of the heaters I 2A and 12B and having excellent heat insulation properties. Preferred materials include:
Examples include graphite, molybdenum, and tungsten, which are the same materials used for the inner wall of the heater.

The inner diameter of the shield IO is set to be larger than the outer diameter of the mold body l excluding the flange part 3 and smaller than the outer diameter of the flange part 3, and the inner circumference of the shield IO is set to the lower end of the mold body 1. is in contact with the top surface of the flange. Note that in the illustrated example, the outer diameter of the shield 10 is equal to the outer diameter of the heater 12B, but the present invention is not limited to this, and the outer diameter of the shield 10 is equal to the outer diameter of the heater 12B.
The outer diameter of the heater 12 may be expanded or contracted.
The shield 10 may be fitted into the inner circumferential surface of the lower end of I3.

Note that the thickness of the shield 10 should be considered so that sufficient strength can be obtained even at high temperatures. Further, the shield IO may be directly fixed to the lower end surface of the heater 12B with bolts or the like, or may be fixed via other fixing means.

In addition, in this example, the lifting shaft 5 is forced upward by a constant force by the lifting mechanism during casting, and the flange portion 3 is pressed against the shield 10, and the reaction force is used to push the flange portion 3 upward. is pressed against the cooling body 4.

According to the casting apparatus for directional solidification having the above configuration, the gap between the lower end of the heater 12 and the lower end of the mold body l is
By closing the gap, the heat of the heater 12 and the mold body 1 can be prevented from escaping downward through this gap, and the calorific value of the heater 12 can be effectively transmitted to the molten metal Y in the mold body 1. Therefore, temperature control of the molten metal Y becomes easier,
Uniform directional coagulation can be performed.

Further, the heater 12 is divided into two, each heater 12A.

12B is configured to energize separately, the amount of heating for the upper and lower parts of the mold body l can be changed, and in combination with the above configuration, more detailed temperature control can be performed, making it possible to obtain an ideal molten metal temperature gradient. be.

Furthermore, the cooling body 4 is pressed by pressing the flange part 3 with the shielding body IO.
By bringing the mold body 1 into pressure contact with the cooling body 4, problems such as the mold body 1 being displaced from the cooling body 4 or falling during cooling can be prevented.

In addition, it is also possible to install a temperature sensor such as a thermocouple in each of the second part and the lower part of the mold body 1, and to control the amount of current to each heater I2A, 12B by computer while checking each temperature. The temperature control of the molten metal Y can be automated.

Further, in the above embodiment, the heater 12 was divided into two parts, but
If necessary, the heater may be divided into three or more parts, or the effects of the present invention can be obtained even with a single heater as in the past.

Next, FIGS. 2 and 3 show a second embodiment of the present invention, in which the mold body! It is characterized in that the flantz portion 3 and the cooling body 4 are fixed in advance by a fixing means.

The outer peripheral edge of the flange portion 3 (this is where cutouts 3A are formed at multiple locations equally spaced in the circumferential direction, and female screw holes 4A are formed at positions facing each cutout 3A of the cooling body 4). The holding plate 16 is larger than the notch 3A.
The bolt 14 that has passed therethrough is tightened into the female threaded hole 4A through the notch 3A.

On the other hand, in the inner peripheral part of the shielding body IO, a notch 1OA larger than the pressing plate 16 is provided at a location corresponding to the pressing plate 16.
is formed, and the shield 10 is brought into contact with the flange portion 3 with the presser plate 16 disposed within the notch portion 1OA.

According to this embodiment, the mold body l is
Since the mold body 1 and the cooling body 4 are securely fixed even when the mold body 1 is exposed, there is no fear that they will shift or that the mold body 1 will fall.

Next, FIG. 4 shows a third embodiment of the present invention. In this example, notches 3A and 4B are formed on the outer peripheries of the flange portion 3 and the cooling body 4 to match each other. , 4B, a U-shaped stopper 20 is elastically and removably attached to each locking end 2 of the stopper 20.
It is characterized in that the flange portion 3 and the cooling body 4 are fixed by OA, 20r3.

As the material of the fastener 20, a high melting point metal such as Mo, W, etc. is suitable. In addition, the locking end 20 of the stopper 20
A protrusion 22 is formed on B, while a recess 24 into which the protrusion 22 fits is formed on the lower surface of the cooling body 4. This prevents the stopper 20 from falling off and increases the reliability of locking by the stopper 20.

Next, FIGS. 5 and 6 show fourth and fifth embodiments of the present invention. In the first embodiment described above, the shielding body 10 was in the shape of an annular plate, but in these examples, by forming a tapered part at the center in the width direction of the shielding body 10, the inner circumference relative to the outer circumference is Section 26A.

It is characterized by changing the height of 28B.

According to these examples, the relative position between the mold body I and the heater 12 can be arbitrarily set while the flange portion 3 is pressed by the inner peripheral portion of the shield IO.

Note that the present invention is not only applicable to turbine blades as shown in the figure, but can also be applied to other articles, and the shape of the shield IO and other parts can be changed as appropriate depending on the shape of the mold body 1. May be changed.

``Effects of the Invention'' As explained hereinafter, according to the directional solidification casting apparatus according to the present invention, by closing the gap between the lower end of the heater and the lower end of the mold body with a shield, Heat can be prevented from escaping downward through this gap.

As a result, the amount of heat from the heater is effectively supplied to the molten metal in the mold, so the temperature of the molten metal can be easily controlled and uniform directional solidification can be performed.

In addition, if the flange is pressed against the cooling body with a shield, the mold body may shift from the cooling body during cooling.
Inconveniences such as falling can be prevented.

Furthermore, by dividing the heater into upper and lower parts and energizing each heater separately, it is possible to change the heating amount for each of the two parts and the lower part of the mold body. More detailed temperature control is possible.

[Brief explanation of drawings]

FIG. 1 is a longitudinal cross-sectional view showing a first embodiment of a casting apparatus for directional solidification according to the present invention, and FIGS. 2 and 3 are longitudinal cross-sectional views and plan views showing main parts of a second embodiment of the present invention. 4 to 6 are longitudinal sectional views showing main parts of the third to fifth embodiments. On the other hand, FIG. 7 is a longitudinal sectional view showing a conventional directional solidification casting apparatus. L. Mold body, 2. Sprue, 3. Flange portion, 4. Cooling body, 5. Lifting shaft, 10.. Shielding body, 12.. Composite heater, I 2A, 12B.. Heater, 14.. Pol)・
, 20. Stopper, 22. Protrusion, 24. Groove, 26.
28・Shielding body, 26A, 28A... Inner peripheral part of shielding body.

Claims (3)

[Claims] (1) A mold body with a sprue at the top end and an open bottom;
A casting apparatus for directional solidification comprising a cooling body removably attached to cover the bottom of the mold body, and a cylindrical heater disposed around the mold body, at a lower end of the heater, A casting apparatus for directional solidification, characterized in that a shield is provided for sealing a gap between the lower end and the lower end of the mold body. (2) A flange portion with an enlarged diameter is formed at the lower end of the mold body, the lower surface of this flange portion abuts the upper surface of the cooling body, and the shielding body is annular, and the inner circumference of the shielding body 2. The casting apparatus for directional solidification according to claim 1, wherein the flange portion is pressed against the upper surface of the flange portion. (3) The casting apparatus for directional solidification according to claim 1 or 2, wherein the heater is configured by arranging a plurality of independent cylindrical heaters vertically.