JPH02295670A - Precise casting device - Google Patents

Abstract

PURPOSE:To allow casting without entailing a change in material quality under the finest conditions by detecting the temp. of the casting material in a crucible, inclining the crucible in accordance with the detection signal thereof and transferring the casting material into a casting mold. CONSTITUTION:An arc is generated between an arc electrode 1 and the casting material 15 to melt the material 15 in a recess 22 of the crucible. The temp. of the material 15 is detected by a temp. detector 28 and the detection signal thereof is supplied by a preamplifier of a control circuit 29 to a comparing and deciding circuit. The command signal from the comparing and deciding circuit is outputted to an ON-OFF switching circuit and the switching circuit is operated when the material 15 attains the optimum casting temp. The supply of a power source to the arc electrode 1 is stopped in accordance therewith and the crucible 21 is turned around a supporting in an arrow A direction and is thereby inclined. While the molten material 15 in the recess 22 of the crucible 21 forms a flat ellipsoid of revolution and the upper surface of the molten metal forms a nearly level plane in the recess 22 of the crucible 21, a part thereof flows in a pouring groove 23 of the crucible 21 and falls into the casting mold 7. The molten metal is thus injected into a molding cavity 13.

Description

[Detailed Description of the Invention] a. Industrial Application Field The present invention relates to a precision casting apparatus for casting relatively small and precise cast products, and in particular, for producing precision castings for dental and plastic surgery applications made of titanium and titanium alloys, etc., which have extremely high high temperature activity. It is most suitable for use in precision casting equipment. b. Conventional technology Recently, as a material for precision castings for dentistry and plastic surgery,
Titanium and titanium alloys are widely used because they have excellent compatibility with living organisms and corrosion resistance, and are also strong and have low specific gravity. FIG. 6 shows a conventional precision casting apparatus for dental titanium alloy materials. , a reduced pressure casting chamber 5 partitioned by a partition wall 4 below the pressurized melting chamber 3, and a communication hole 6 that communicates these chambers 3.5 with each other;
It consists of a breathable mold 7 placed so as to close the communication hole 6. The above-mentioned crucible 2 is made of copper, and has a mortar-shaped part 8 formed in the center of its upper part, and a circular outlet 9 in the center of its bottom. The crucible 2 is mounted and fixed on a mounting table 10 disposed within the pressurized melting chamber 3.

On the other hand, the above-mentioned mold 7 is formed by forming a sprue 12 and a modeling cavity 13 in an air-permeable embedding material l1, and the sprue 12 is connected to the outlet 9 of the crucible 2 through the through hole 14 of the mounting table lO. are arranged accordingly.

When casting, a casting material 15 made of solid titanium or a titanium alloy is placed in the mortar-shaped part 8 of the crucible 2, and the outlet 9 is closed at the bottom of the casting material 15. Next, by operating a vacuum pump (not shown), air is removed from the pressurized melting chamber 3 and the vacuum casting chamber 5 to create a vacuum state, and then an inert gas such as argon gas is introduced into the pressurized melting chamber 3. A certain pressure difference is applied between the pressurized melting chamber 2 and the reduced pressure casting chamber 3.

Under such conditions, by supplying current to the arc electrode 1, an arc is generated between the arc electrode 1 and the casting material 15, and the casting material 15 is melted. When the casting material 15 is melted, the casting material 15 in a molten state naturally falls from the outlet 9 of the crucible 2 due to the pressure difference between the pressurized melting chamber 3 and the vacuum casting chamber 5 and the weight of the casting material 15. , sprue 1 of mold 7
2 and into the modeling cavity l3.

C. Problems to be Solved by the Invention However, in the conventional precision casting apparatus as described above, when casting the casting material 15, there is a pressure difference between the pressurized melting chamber 3 and the vacuum casting chamber 5, and the pressure difference of the casting material 15. Since it is made to fall naturally due to its own weight, the casting material l5
It is impossible to control the melting temperature of the casting material 1.
Optimum casting temperature according to 50 types (50% lower than melting temperature)
There is a major problem in that it is not possible to cast at a temperature of 0° to 100° higher.

For this reason, only the upper portion of the casting material 15 may suddenly become overheated before the lower portion thereof melts, resulting in material deterioration. In addition, in the case of the casting material 15 made of an alloy with a wide range of melting temperatures, the casting material melts unevenly and only the partially melted material falls, leaving a considerable amount of material inside the crucible 2, which is undesirable. phenomenon occurs, casting material 15
may not be able to be used efficiently. Therefore, especially when using a casting material such as an alloy that has a wide range of melting temperatures, it may be difficult to carry out smooth and precise casting.

The present invention was made in view of the above-mentioned circumstances, and its purpose is to enable the casting material to be poured into the mold when the casting material reaches an appropriate melting temperature (casting temperature) in the crucible. Our objective is to provide such precision casting equipment.

d. Means for Solving the Problems In order to achieve the above-mentioned objects, the present invention includes a pressurized melting chamber in which a heating means and a crucible are disposed, and a vacuum casting chamber partitioned by a partition wall below the pressurized melting chamber. A precision casting apparatus comprising a chamber, a communication hole that communicates the pressurized melting chamber and the vacuum casting chamber with each other, and an air permeable mold disposed so as to close the communication hole. Temperature detection means for detecting the temperature of the casting material is provided in the pressurized melting chamber, and the crucible is configured to be tiltable, and the casting material placed in the crucible is heated by the heating means in the pressurized melting chamber. When the crucible is heated and reaches a predetermined temperature, the melted casting material in the crucible is poured into the mold by tilting the crucible based on a detection signal output from the temperature detection means. .

Hereinafter, one embodiment of the present invention will be explained with reference to FIGS. 1 to 3. In FIG. 1, the same parts as in FIG. 6 are given the same reference numerals.

FIG. 1 shows the configuration of a precision casting apparatus according to the present invention, and the apparatus includes a closed container 18 consisting of an upper container 16 and a lower container 17 that are configured to be detachably attached to each other. The upper container 16 is composed of a dome-shaped part 16a and a flange part 16b integrally molded on the lower end of this dome-shaped part 16a, and the lower container 17 is composed of a cylindrical housing part 17a and an integrally molded upper end of this housing part 17a. flange part 17
It is composed of b. The flange portions 16b and 17b of the upper container l6 and the lower container l7 are tightly coupled in an overlapping state to form one sealed container 18, and the internal space is formed from the upper wall of the lower container 17. It is divided into upper and lower sections by a partition wall 4.

Thus, the upper part of the partition wall 4 is configured as a pressurized melting chamber 3, and the lower part thereof is configured as a reduced pressure casting chamber 5.

Further, an arc electrode 1 is provided on the ceiling portion of the upper container 16 mentioned above.
is attached, and power is supplied to this arc electrode l from an arc power supply circuit not shown. Further, a rotatable crucible 21 is disposed within the pressurized melting chamber 3. This crucible 2l is made of a steel material with high thermal conductivity so as not to react with the casting material 15 having high high temperature activity such as titanium, and has a stepped recess for placing the casting material 15 as shown in FIG. 22 and a pouring groove 23 connected to the recess 22 are formed on the upper surface. The crucible 21 is configured to be rotatable around support bins 25a and 25b that are pivotally supported by a pair of support plates 24 on both sides of the crucible 21. Furthermore, these support pins 25a. A pair of protruding pins 25c and 25d correspond to crucible 21
These protruding pins 25c,
25d is lifted upward by an L-shaped glue lid (not shown) operated by an air cylinder, and the crucible 21 is thereby moved by the support pins 25a. It is designed to be rotated in the direction of arrow A in FIG. 2 about 25b.

Further, as shown in FIGS. 1 and 2, a through hole 21a is formed in the crucible 2l, penetrating into the recess 22 from the side surface thereof, and a viewing window 26 is provided at a corresponding position in the axial direction of the through hole 21a. It is provided. , that is, lower container 1
A cylindrical member 27 is provided that extends into the pressurized melting chamber 3 through the flange portion 17b of the cylindrical member 27.
The distal end surface serves as a viewing window 26. A temperature sensor 28 is housed inside the cylindrical member, and the output signal of the temperature sensor 28 is supplied to a control circuit 29. The temperature sensor 28 is a photosensitive sensor (heat sensor) that detects the temperature based on light emitted from the casting material 15.

On the other hand, as shown in FIG. 3, the control circuit 29 includes a preamplifier 30 that amplifies the output signal from the temperature sensor 28, a comparison judgment circuit 31 that compares the output of the preamplifier 30 with a reference voltage, and ON-O for turning on and off the arc power supply circuit (not shown) based on the output of the comparison/judgment circuit 31
It is composed of an FF switching circuit 32. In addition, since the infrared emissivity of the casting material 15 differs depending on the type of the casting material 15, the above-mentioned comparison judgment circuit 31 selects the arc electrode 1 according to the type of the casting material 15.
It is equipped with a function that allows the reference voltage to be arbitrarily corrected in order to change the threshold value when turning ON and OFF the energization. Also, a partition wall 4 that partitions the pressurized melting chamber 3 and the reduced pressure casting chamber 5 is provided.
A cylindrical mold receiver 33 with a bottom that projects into the vacuum casting chamber 5 is integrally molded in the mold receiver 33, and a communication hole 6 is formed at the bottom of the mold receiver 33 to communicate the chambers 3 and 5 with each other. There is. A breathable mold 7 having a sprue l2 and a modeling cavity 13 is disposed in the mold receiver 33, and the communication hole 6 is closed in this mold 7.

Incidentally, the sprue 12 of the mold 7 is opened upward and is arranged corresponding to the opening 35 formed in the mounting table 34 of the support plate 24.

Although not shown, the pressurized melting chamber 3 also includes a casting material 1.
The vacuum casting chamber 5 is configured to be supplied with an inert gas such as argon gas to prevent oxidation of the casting chamber 5, and a vacuum pump is provided in the vacuum casting chamber 5 to bring the inside of the closed container 18 into a vacuum state.

Next, operations and effects when performing precision casting using the precision casting apparatus configured as described above will be described.

First, the upper container 2 is opened, a predetermined mold 7 is stored in the mold receiver 33, and the solid casting material 15 is placed in the recess 22 of the roof 21 held horizontally. After that, as shown in FIG. 1, the upper container 2 is closed and the flange portion 16 is closed.
b. 17b is brought into a tightly coupled state, and the air inside the closed container 18 is removed using a vacuum pump (not shown) to create a vacuum state. Next, an inert gas such as argon gas is injected into the pressurized melting chamber 3 to increase the pressure to a predetermined pressure, thereby creating a predetermined pressure difference between the pressurized melting chamber 3 and the vacuum casting chamber 5.

After setting such a state, by supplying power to the arc electrode 1 and generating an arc between the arc electrode 1 and the casting material 15, the casting material 15 is transferred to the recess 2 of the crucible.
Dissolve within 2 hours. At this time, the temperature of the casting material is detected by the temperature detector 28, and the detection signal is supplied to the comparison judgment circuit 31 by the preamplifier 30 of the control circuit 29. When the casting material 15 reaches the optimum casting temperature, a predetermined command signal (comparison output) is turned on from the comparison judgment circuit 31.
The signal is output to the OFF switching circuit 32, and the ON-OFF switching circuit 32 is activated. Based on this, the supply of power to the arc electrode 1 is stopped, and an air cylinder (not shown) is activated to activate the protruding pin 25c. As the crucible 25d is lifted upward, the crucible 21 is moved to the support pins 25a and 25b.
It is rotated and tilted in the direction of arrow A in FIGS. 1 and 2 about the center. At this time, the molten casting material 15 in the recess 22 of the crucible 21 becomes a flat spheroid due to its surface tension, and while the upper surface of the molten metal forms a substantially horizontal surface within the recess 22, The molten metal flows through the pouring groove 23 of the crucible 21 and gradually falls toward the mold 7 below, and is poured into the modeling cavity 13 through the sprue 12 of the mold 7.

In this case, the molten casting material l5 in the recess 22 of the crucible 21 falls from the upper layer where the temperature is higher into the mold 7, and the lower temperature portions that are in contact with the crucible 2 fall last. (or a portion of the molten metal solidifies and remains in the recess 22 of the crucible 21), but since the crucible 21 is tilted as described above, a large amount of molten metal remains in the recess 22 of the crucible 2l. Never. In other words, even if the casting material l5 remains, the amount is extremely small;
Most materials can be cast effectively. Therefore, there is no risk that the casting material will be unevenly melted and only the partially melted casting material 15 will be cast, and a considerable amount of the remaining casting material 15 will fall from the crucible 21 while remaining solid.

Furthermore, according to the precision casting apparatus of this embodiment, the casting material 1
By correcting the reference voltage of the comparison judgment circuit 31 according to the type of material in step 5, the optimum casting temperature (50' to 100' below the melting temperature) can be achieved even for alloy materials with a wide range of melting temperatures.
℃ higher temperature).

Although one embodiment of the present invention has been described above, the present invention is not limited to the embodiment described above, and various modifications and changes can be made based on the technical idea of the present invention.

For example, in the embodiment described above, the arc electrode 1 is made of a cast material 15.
However, instead of the arc electrode 1, a high frequency induction heating coil, a laser heating device, or the like may be used as the heating means.

Further, in the embodiments described above, the temperature of the lower surface of the casting material 15 placed in the recess 22 of the crucible 2l is detected, but the temperature is not limited to this, and as shown in FIG. The temperature of the upper surface of the casting material 15 may be detected from the outside with the temperature detector 28 through the viewing window 36 provided on the upper side of the casting material 16. Further, as shown in FIG. 5, a cylindrical member 37 having a viewing window 37 at the tip is attached to the upper container
The temperature sensor 28 may be attached to the dome-shaped portion 16a of the casting member 6 and housed within the cylindrical member 38 to detect the temperature of the upper surface of the casting material 15.

e. Effects of the Invention As described above, the present invention provides temperature detection means for detecting the temperature of the casting material in the crucible, tilts the crucible based on a detection signal from the temperature detection means, and heats the material to an appropriate casting temperature. Since the molten casting material is poured into the mold, the casting operation can be started when the optimum casting temperature for the type of casting material is reached. Therefore, even if the casting material has a wide range of melting temperatures, it can be cast under the best conditions without causing material changes. Moreover, according to the present invention, since the crucible is tilted to allow the casting material to flow down at the optimum casting temperature, only the casting material that is partially melted unevenly in the crucible is cast. The remaining portion will not remain solid in the crucible, making it possible to efficiently cast most of the casting material.

[Brief Description of the Drawings] Figures 1 to 3 show an embodiment of the present invention, in which Figure 1 is a cross-sectional view of a precision casting device, Figure 2 is a perspective view of a crucible, and Figure 3 is a perspective view of a crucible. The figure is a block diagram showing the configuration of the control circuit.
5 and 5 are sectional views similar to FIG. 1 showing modified examples of the present invention, and FIG. 6 is a sectional view of a conventional precision casting apparatus. DESCRIPTION OF SYMBOLS 1... Arc electrode as a heating means, 3... Pressurized melting chamber, 4... Partition wall, 5... Reduced pressure casting chamber, 6... Communication hole, 7... Mold,
15... Casting material, 16... Upper container, 17... Lower container, 18... Sealed container, 21... Crucible, 21a...
・Through hole, 23...Pouring groove, 25a,
25b-Support pin, 26, 36, 37...
Peep window, 28...Temperature detector (heat sensor), 29
...control circuit, 30...briamplifier, 31...comparison judgment circuit with correction function, 32...
・ON-OFF switching circuit. Patent applicant Denki Kogyo Co., Ltd. (2 idiots) Figure 4 Figure 5

Claims (1)

[Claims] A pressurized melting chamber in which a heating means and a crucible are arranged, a reduced pressure casting chamber partitioned by a partition below the pressurized melting chamber, and a communication hole that communicates the pressurized melting chamber and the reduced pressure casting chamber with each other;
In a precision casting apparatus each comprising a breathable mold disposed so as to close the communication hole, a temperature detection means for detecting the temperature of the casting material in the crucible is provided in the pressurized melting chamber; The crucible is configured to be tiltable, and when the casting material placed in the crucible is heated by the heating means in the pressurized melting chamber and reaches a predetermined temperature, a detection signal is output from the temperature detection means. A precision casting apparatus characterized in that the melted casting material in the crucible is poured into the mold by tilting the crucible based on.