JP2802371B2 - Precision casting method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION a. Industrial Field of the Invention The present invention relates to a precision casting method for casting a relatively small and precise cast product, and particularly to a dental or titanium alloy having extremely high temperature activity such as titanium and titanium alloy. It is optimally applied to a precision casting method for producing a precision casting for plastic surgery or the like.

b. Conventional technology Recently, titanium and titanium alloys which are excellent in affinity with a living body and corrosion resistance, and have high strength and low specific gravity are widely used as materials for precision castings for dental and plastic surgery.

FIG. 4 shows an apparatus for precision casting of a dental titanium alloy material. This apparatus comprises a pressure melting chamber 3 in which an arc electrode (non-consumable electrode) 1 and a crucible 2 are arranged, and A vacuum casting chamber 5 partitioned by a partition 4 below the pressure melting chamber 3
And a communication hole 6 communicating the chambers 3 and 5 with each other, and a gas-permeable mold 7 arranged to close the communication hole 6. The above-mentioned crucible 2 is made of copper, and a mortar-shaped portion 8 is formed in the upper central portion thereof.
Further, a circular outlet 9 is formed at the center of the bottom. The crucible 2 is mounted and fixed on a mounting table 10 arranged in the pressure melting chamber 3.

On the other hand, the above-mentioned mold 7 is formed by forming a gate 12 and a molding cavity 13 in a gas-permeable buried material 11, and the outlet 7 of the crucible 2 passes through the through hole 14 of the mounting table 10 of the gate 12. Corresponding arrangement.

In performing the casting, a casting material 15 made of solid titanium or a titanium alloy is placed on the mortar-shaped portion 8 of the crucible 2, and the outlet 9 is closed at the bottom surface of the casting material 15. Next, by operating a vacuum pump (not shown), air is evacuated from the pressure melting chamber 3 and the vacuum casting chamber 5 to evacuate the inside thereof, and then an inert gas such as argon gas is injected into the pressure melting chamber 3. To give a constant pressure difference between the pressure melting chamber 2 and the vacuum casting chamber 3.

Under such a state, an electric current is supplied from the power supply circuit to the arc electrode 1 to generate an arc with the casting material 15 to melt the casting material 15. Then, the molten casting material 15 is discharged from the outlet 9 of the crucible 2 by the pressure difference between the pressure melting chamber 3 and the reduced pressure casting chamber 5 and the weight of the casting material 15.
From the mold 7 and cast into the molding cavity 13 through the gate 12 of the mold 7.

c. Problems to be solved by the invention However, in the case of the precision casting method as described above,
Since the casting 15 is heated from the upper surface side and the lower surface of the casting material 15 is in contact with the copper crucible 2 having good thermal conductivity, the upper and lower portions of the casting material 15 are uniformly formed. Not heated. That is, the upper part of the casting material 15 is first heated to a high temperature first, and then the lower part is gradually heated to a high temperature, which causes a difference between the temperature of the upper part and the temperature of the lower part. Then, this temperature difference increases depending on the magnitude of the electric power supplied to the arc electrode 1 and thus on the strength of the heating.

Specifically, if the electric power supplied to the arc electrode 1 is too large, only the upper part of the casting material 15 may be overheated in the early stage of heating, and the material may be deteriorated. Further, if such a state continues, only the central shaft portion of the casting material 15 is partially melted and falls first, and the outer peripheral portion of the equivalent material is not melted and remains in the crucible 2 which remains solid. In some cases, such an undesirable phenomenon occurs that the casting material 15 cannot be used efficiently.

The present invention has been made in view of such circumstances, and an object of the present invention is to be able to heat a casting material as uniformly as possible without a partial temperature difference, and to set an appropriate casting temperature (50 ° C. or higher than the melting temperature). It is an object of the present invention to provide a precision casting method capable of performing a casting operation in a mold by setting the temperature to a temperature higher by 100 ° C.).

c. Means for Solving the Problems In order to achieve the above-mentioned object, according to the present invention, the casting material is melted by heating the upper surface of the casting material placed in the crucible and cast into a mold. In the precision casting method described above, the temperatures of the upper surface and the lower surface of the casting material are detected when the casting material is heated, and the strength of the heating is adjusted based on the difference between these temperatures.

Hereinafter, an embodiment of the present invention will be described with reference to FIGS. In FIG. 1, the same parts as those in FIG. 4 are denoted by the same reference numerals.

FIG. 1 shows an apparatus for carrying out a precision casting method according to the present invention. The apparatus comprises a closed container comprising an upper container 16 and a lower container 17 which are detachably attached to each other.
Eighteen. The upper container 16 is composed of a dome-shaped portion 16a and a flange portion 16b formed integrally with the lower end of the dome-shaped portion 16a. The lower container 17 is formed integrally with a cylindrical housing portion 17a and the upper end of the housing portion 17a. And the formed flange portion 17b. Then, the flange portions 16b and 17b of the upper container 16 and the lower container 17 are tightly joined in a superposed state so that one closed container 18 is formed, and the internal space is formed from the upper wall of the lower container 17 The partition wall 4 is vertically divided. Thus, the upper part of the partition wall 4 is the pressure melting chamber 3,
The lower part is configured as a reduced pressure casting chamber 5.

An arc electrode 1 is provided on the ceiling of the upper container 16 described above.
The arc electrode 1 is supplied with power from an arc power supply circuit (not shown). In addition, a crucible 21 that is configured to be rotatable is disposed in the pressure melting chamber 3. The crucible 21 is made of a copper material having a high thermal conductivity so as not to react with a casting material 15 having a high temperature activity such as titanium, and as shown in FIG.
The mounting stepped concave portion 22 and the pouring groove 23 connected to the concave portion 22 are formed on the upper surface. The crucible 21 is configured to be rotatable around support pins 25a and 25b that are supported by a pair of support plates 24 on both sides of the crucible 21. Further, a pair of protruding pins 25c, 25d are attached to the side of the crucible 21 corresponding to the support pins 25a, 25b, and these protruding pins 25c,
25d is lifted upward by an L-shaped lifter (not shown) operated by an air cylinder, and the crucible 21d
Is rotated in the direction of arrow A in FIGS. 1 and 2 around the support pins 25a and 25b.

As shown in FIGS. 1 and 2, the crucible 21 is formed with a through hole 21a penetrating from the side surface thereof into the concave portion 22, and a viewing window 26a is formed at a position corresponding to the through hole 21a in the axial direction. Is provided. That is, a cylindrical member 27a that penetrates through the flange portion 17b of the lower container 17 and extends into the pressure melting chamber 3 is provided, and a distal end surface of the cylindrical member 27a serves as a viewing window 26a. . A heat sensor (photosensitive temperature detector) 28a for measuring the temperature of the lower surface of the casting material 15 is housed inside the cylindrical member 27a, and an output signal of the heat sensor 28a is supplied to the control circuit 29. It is configured as follows. Further, in the dome portion 16a of the upper container 16,
A cylindrical member 27b extending into the pressure melting chamber 3 is provided, and a distal end surface of the cylindrical member 27b serves as a viewing window 26b. A heat sensor 28b for measuring the temperature of the upper surface of the casting material 15 is housed inside the cylindrical member 27b, and an output signal of the heat sensor 28b is supplied to the control circuit 29.

On the other hand, the control circuit 29 includes preamplifiers 31a and 31b that amplify output signals from the heat sensors 28a and 28b, respectively.
A comparator 32 that compares the outputs of these preamplifiers 31a and 31b
And a power adjuster 33 that outputs a control signal for power adjustment to an arc power supply circuit 34 based on the output of the comparator 32. Note that the emissivity of infrared rays differs depending on the type of the casting material 15.
Can be corrected.

Further, a cylindrical mold receiver 35 having a bottom and protruding into the vacuum casting chamber 5 is integrally formed with a partition wall 4 that partitions the pressure melting chamber 3 and the vacuum casting chamber 5. A communication hole 6 that connects these chambers 3 and 5 to each other is formed. A gas permeable mold 7 having a gate 12 and a molding cavity 13 is disposed in the mold receiver 33, and the communication hole 6 is closed by the mold 7. The gate 12 of the mold 7 is open upward, and is arranged corresponding to the opening 37 formed in the mounting table 36 of the support plate 24.

Although not shown, the pressure melting chamber 3 contains a casting material.
An inert gas such as an argon gas is supplied so as to prevent oxidation of the chamber 15. A vacuum pump for evacuating the closed vessel 18 is provided in the vacuum casting chamber 5.

Next, an operation and an operation when precision casting is performed using the precision casting apparatus having the above configuration will be described.

First, the upper container 2 is closed, a predetermined mold 7 is stored in the mold receiver 33, and the solid casting material 15 is placed in the concave portion 22 of the crucible 21 held horizontally. Thereafter, as shown in FIG. 1, the container 2 is closed to bring the flange portions 16b and 17b into a tightly connected state, and the air in the closed container 18 is evacuated by a vacuum pump (not shown) to make a vacuum state. Next, the pressure dissolution chamber 3
An inert gas such as an argon gas is injected thereinto and pressurized to a predetermined pressure, and a predetermined pressure difference is applied between the pressurized melting chamber 3 and the reduced pressure casting chamber 5.

After setting to such a state, by supplying power to the arc electrode 1 to generate an arc between the arc electrode 1 and the casting material 15, the casting material 15 is transferred to the concave portion 22 of the crucible 21.
Allow to dissolve in. At this time, the temperatures of the upper and lower surfaces of the casting material 15 are detected (measured) by the heat sensors 28a and 28b, and the detection signals are supplied to the comparator 31 by the preamplifiers 30a and 30b of the control circuit 29.

Thus, when the difference between the temperature of the upper surface and the temperature of the lower surface of the casting material 15 is equal to or greater than a predetermined value,
When the heating of 15 is rapid, the output of the comparator 31 increases, and based on this, a control signal corresponding to the temperature difference is output from the power regulator 33 and the arc power supply circuit 34 supplies the control signal to the arc electrode 1. The supplied power is gradually reduced. As a result, the heating of the casting material 15 by the arc discharge becomes relatively weak, and the temperature difference between the upper surface and the lower surface of the casting material 15 decreases. Then, when the temperature difference reaches a predetermined value, the reduction of the electric power is stopped, and thereafter, the casting material 15 is heated with the electric power at that time. Conversely, when the temperature difference is equal to or less than a preset value, that is, when the heating of the casting material 15 is slow, the comparator
The output of 31 is reduced, and based on this, the power
Output a control signal corresponding to the temperature difference, and the electric power supplied from the arc power supply circuit 34 to the arc electrode 1 is gradually increased. As a result, the heating of the casting material 15 by the arc discharge becomes relatively strong, and the temperature difference between the upper surface and the lower surface of the casting material 15 increases. Then, when the temperature difference reaches a predetermined value, the increase in power is stopped, and thereafter, the casting material 15 is heated with the power at that time. Thus, the casting material 15 is melted under an ideal condition without being partially melted.

Thus, when the casting material 15 reaches the optimum casting temperature, an unillustrated crucible-rotating air cylinder is operated based on the output signal of the preamplifier 31a or 31b. Along with this,
Since the protruding pins 25c and 25d are lifted upward, the crucible 2
In FIGS. 1 and 2, the support pins 25a and 25b are pivoted in the direction of the arrow A in FIGS. At this time, the molten casting material 15 in the concave portion 22 of the crucible 21 becomes a flat spheroid due to its surface tension, and the upper surface of the molten metal becomes the concave portion 22.
While forming a substantially horizontal surface within the crucible 21
, Gradually falls toward the lower mold 7, and is poured into the molding cavity 13 through the gate 12 of the mold 7.

In this case, the molten casting material 15 in the concave portion 22 of the crucible 21 falls from the upper layer having a higher temperature toward the inside of the mold 7, and the lower temperature portion in contact with the crucible 2 drops last. (Or a part thereof solidifies and remains in the concave portion 22 of the crucible 21.) However, since the crucible 21 is inclined as described above, a large amount of molten metal remains in the concave portion 22 of the crucible 21. Never. That is, even if the casting material 15 remains, the amount is extremely small, and most of the material can be effectively cast. Therefore, only the casting material 15 in which the casting material is unbalancedly melted and partially melted is cast, and there is no danger that a considerable amount of the remaining casting material 15 is dropped from the crucible 21 which remains solid. .

As described above, one embodiment of the present invention has been described. However, the present invention is not limited to the described embodiment, 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
However, instead of the arc electrode 1, a high-frequency induction heating coil or a laser-type heating device may be used as the heating means.

Further, the method according to the present invention is not limited to the case of using the rotating crucible 21 as shown in FIGS. 1 and 2, but the naturally falling type as shown in FIG. It goes without saying that the present invention is applicable to the case where the crucible 2 is used.

e. Effects of the Invention As described above, the present invention detects the temperatures of the upper surface and the lower surface of a casting material placed in a crucible and adjusts the intensity of heating of the casting material based on a difference between these temperatures. Therefore, it is possible to perform as uniform heating as possible by minimizing the temperature difference between the upper layer and the lower layer of the casting material, and only the upper layer or the central shaft portion is partially biased and melted. The occurrence of such a situation can be prevented. In addition, the inconvenience that the casting material is deteriorated due to rapid heating can be solved.

Further, according to the precision casting method according to the present invention, since means for detecting the temperature of the upper surface and the lower surface of the casting material is used, based on the temperature detection signal from one or both temperature detecting means. The casting material can be set to an appropriate casting temperature to perform the casting operation into the mold.

[Brief description of the drawings]

1 to 3 are views for explaining one embodiment of the present invention. FIG. 1 is a sectional view of a precision casting apparatus, FIG. 2 is a perspective view of a crucible, and FIG. 3 is a control circuit. FIG. 4 is a sectional view of a precision casting apparatus used for carrying out a conventional precision casting method. DESCRIPTION OF SYMBOLS 1 ... Arc electrode as a heating means 3 ... Pressure melting chamber 4 ... Partition wall 5 ... Decompression casting chamber 7 ... Mold 15 ... Casting material 18 ... Closed container 21 ... Crucible, 21a ... through hole, 23 ... pouring groove, 26a, 26b ... sight glass, 28a, 28b ... heat sensor, 29 ... control circuit.

Continuation of the front page (56) References JP-A-60-244458 (JP, A) JP-A-60-257962 (JP, A) JP-A-1-91953 (JP, A) JP-B-62-34453 (JP, A) , B2) (58) Field surveyed (Int. Cl. ⁶ , DB name) B22D 23/00 A61C 5/10 A61C 13/20

Claims (2)

(57) [Claims] In a precision casting method wherein an upper surface of a casting material placed in a crucible is heated to melt the casting material and cast it into a mold, the casting material is heated when the casting material is heated. A precision casting method comprising detecting temperatures of an upper surface and a lower surface, and adjusting heating intensity based on a difference between these temperatures. 2. The method according to claim 1, wherein when the temperature difference is large, the heating state is adjusted to a weak heating state, and when the temperature difference is small, the heating state is adjusted to a strong heating state. The precision casting method according to the item 1).