JPH0716708A - Method and device for casting small size metallic ingot - Google Patents

Abstract

PURPOSE:To provide a method and a device for casting a small size metallic ingot having simple constitution, in which the process of melting and casting can be automated with a robot. CONSTITUTION:In this device, a melting furnace composed of plural high frequency induction coils 2, a thermometer arranged at the upper part of the center line of the high frequency induction coils and a means for charging and discharging a crucible into the inner part of the high frequency induction coil, a first heating device for preheating a mold, a casting table 7 for laying the mold in the condition of casting and a second heating device set near the casting table and slowly cooling a base metal in the mold, are arranged. Further, a crucible supplying device 12 laying the crucible to charge the crucible into the melting furnace, a releasing agent coating device 10, a turn-over table 8 for separating the mold and laying by turning over the cast small size metallic ingot, a stock table 13 for incorporating the ingot, a multi-joint robot 9 for shifting the crucible, mold and the ingot between each device and a control unit for sequence-controlling the robot, are arranged.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a casting method and casting apparatus for a small metal ingot, and particularly to a casting step and other steps when a precious metal such as gold is precisely melted and cast to produce a gold ingot or the like. The present invention relates to a casting method and a casting apparatus suitable for automating a casting.

[0002]

2. Description of the Related Art Small metal ingots, especially 100 g
Small gold ingots such as bars, 500g bars, 1000g bars etc. do not have the exact weight imprinted on the surface,
High precision is required. For example, in the case of 1000 g bar of gold, it is simply stamped as 1 kg, but if the minimum scale of the weighing machine (currently 0.01 g) is insufficient, the commercial value will be lost, so melting and casting again Try again or weigh a large amount in advance so that there is no shortage. In the latter case, the excessive addition causes economic loss for the manufacturer. Further, in the case of a gold ingot, strict conditions are imposed such that the casting surface has a low glossiness, marking cannot be performed if shrinkage cavities or wrinkles are remarkable, and the commercial value is lost.

For this reason, workers have carefully and manually performed melting and casting. There is a problem in that the manual work of the operator is inefficient and varies depending on the operator.
As measures against this, as described in JP-A-1-239384, an articulated robot in which the crucible is held by a robot hand, a melting device for melting while moving the crucible table on which the crucible is mounted, and a mold are mounted. Using a table that is placed and rotated, spray the mold release material on the mold, dry it, melt the gold in the crucible in the melting device, and inject the melted gold into the mold coated with the mold release material to cast gold. After casting, there has been proposed a method of automatically manufacturing a gold ingot by tilting the mold and putting the gold ingot in water to cool it.

Further, as described in Japanese Patent Laid-Open No. 4-305359, gold is melted by using a high frequency coil arranged in a C shape, and a mold made of graphite or ceramic is used to preheat before casting. A method has been proposed in which a mold is preheated by a mold preheater with a door, and a robot is used while exchanging the robot hand for supporting the crucible at three points and the robot hand for the mold to cast gold.

[0005]

However, in the former invention described in Japanese Patent Application Laid-Open No. 1-239384, since a melting furnace having a complicated structure is used, the temperature control is good, but the equipment is complicated, and therefore the equipment is complicated. Is difficult to maintain and there are limits to increasing the dissolution rate. In addition, it takes time to work on the table, which imposes a time constraint on the entire melting / casting process. Also, since the gold ingot is put in water, the surface of the gold ingot may be deteriorated.

On the other hand, in the latter invention disclosed in Japanese Patent Laid-Open No. 4-305359, when the crucible comes out of the cutout portion of the high frequency coil, the robot holds the crucible and injects the metal in the crucible into the mold, Return the empty crucible to the cutout of the same coil, load a predetermined amount of metal into the crucible, rotate the base again and melt the crucible with the high frequency coil, so it is time limited, melting / casting However, there is a problem that the entire process is subject to time constraints due to the time required for the above process. Furthermore, since we are using a mold preheater with a door,
There is also a problem that it takes time to move the mold to the pouring table, and also it takes time to replace the robot hand, which makes control of the robot more complicated.

Therefore, an object of the present invention is to precisely melt and cast a small metal ingot, particularly an ingot of a noble metal such as gold, and perform melting and casting by one robot without damaging the casting surface of the obtained ingot. It is an object of the present invention to provide a casting method and casting apparatus for a small metal ingot, which casts a small metal ingot with a simple structure that can efficiently automate a large number of work processes.

[0008]

In order to achieve the above-mentioned object, according to the present invention, crucibles containing metal ingots are successively charged into a plurality of high frequency coils to melt and melt the metal ingots. When the temperature of the radiation thermometer for detecting the temperature of the molten metal reaches a preset temperature, the crucible is sequentially taken out from the high frequency coil, a release material is attached in advance, and then the mold is preheated to a predetermined temperature. This is a method for casting a small gold ingot, which is characterized in that the metal in the crucible is sequentially cast.

The present invention also includes a plurality of high frequency coils,
A melting thermometer comprising a radiation thermometer provided above the center line of the high frequency coil, and means for charging and discharging the crucible inside the high frequency coil, and first heating for preheating the mold. A device, a pouring table for placing the mold in a state where the metal ingot from the crucible is cast into the mold, and a metal placed in the vicinity of the pouring table to gently cool the metal ingot in the mold. A second heating device for heating the metal, a crucible supply device for mounting the crucible for supplying the crucible to the high-frequency coil, a mold release material deposition layer for depositing the mold release material on the mold, and casting For reversing and releasing the small metal ingot and placing it on it, an ingot stock table for accommodating the small metal ingot, and for transferring the crucible, the mold and the small metal ingot between the respective devices. Articulated robot It is intended to employ casting apparatus of small metal ingot and having a control device for sequence control of the multi-joint robot.

[0010]

Embodiments of the present invention will now be described with reference to the drawings. FIG. 1 is a side view schematically showing a melting furnace used in the casting apparatus of the present invention, and FIG. 2 is a schematic layout diagram showing the arrangement of individual apparatuses constituting the casting apparatus.

In FIG. 1, a plurality of high-frequency coils 2 for heating a crucible 1 containing a metal ingot are connected in series and connected to a power source 3 (see FIG. 2). Crucible 1
Is configured to be moved up and down by the push-up cylinder 5 while being placed on the cylindrical refractory 4 and inserted into the high frequency coil or discharged from the coil. A radiation thermometer 6 is installed above the center line of the high frequency coil 2 in the vertical direction, and the radiation temperature (melting state) of the metal ingot in the crucible 1 can be monitored by these radiation thermometers 6.

In FIG. 2, a casting table (not shown) on which the casting mold is placed, and a casting burner device (not shown) provided near the casting table so that a flame is ejected to the casting mold.
The casting device 7 consisting of is installed at the position closest to the high frequency coil. A reversing table 8 which is reversed by a mold containing the solidified metal ingot and is received by the mounting table is placed in the vicinity of the pouring device 7. A mold release material attaching device 10 is arranged with a dead angle (a region that cannot be moved by simply turning the robot arm, 60 ° in this embodiment) from the high-frequency coil 2 around the robot 9, and the release material attaching device 10 is disposed. The release material is automatically attached to the mold by 10. Further, in order to preheat the mold to which the mold release material is attached, the upper open type hot plate 11 having a structure in which the mold is placed on a flat plate and the lower surface of the flat plate is heated is provided near the pouring device 7 and above the reversing table 8. It is provided in. A crucible supply device 12 for mounting a plurality of crucibles is arranged next to the reversing table 8 so that the crucible 1 containing metal ingots can be sequentially supplied to the high frequency coil 2. A stock base 13 for sequentially mounting metal ingots, that is, metal ingots, is arranged between the crucible supply device 12 and the release material deposition device 10 described above.

In summary, as shown in FIG. 2, the high frequency coil 2, the casting device 7, the reversing table 8, the upper open type hot plate 11, the crucible supplying device 12, the ingot stock table 13 and the mold release material attaching device 10 are The articulated robot 9 is disposed on the same circumference as the center, and the operations of these devices and the articulated robot 9 are sequence-controlled by the controller 14.

The detailed description of the above-mentioned reversing table, pouring machine, crucible feeding apparatus, ingot stock table, release material adhering apparatus, and robot hand of the articulated robot (related to these) is the present application by the applicant. Patent application filed on the same day as ((1) Reference number: 05-0030P, title of invention:
Gold ingot positioning device and gold ingot processing method, (2) reference number: 05-0031P, title of invention:
A robot hand for gold ingot casting, and a mold suitable for being held by the robot hand, (3) Reference number: 05
-0032P, title of invention: method and device for attaching release material to mold, (4) reference number: 05-0033P, title of invention: stock base of small gold ingot and method of placing gold ingot on the stock base, (5) Reference number: 05
-0034P, title of invention: crucible supply device, and (6) reference number: 05-0035P, title of invention: burner device and casting method for gold ingot casting).

Next, the operation (casting method) of the casting apparatus of the present invention will be described. First, the crucible 1 containing the prepared metal ingot in the crucible supply device 12 is heated by being sandwiched by a hand (not shown) at the tip of an arm (not shown) of the articulated robot 9. The high-frequency coil 2 is moved to a position above the high-frequency coil 2 and placed on the upper surface of the cylindrical refractory 4 which has been raised in advance by the operation of the push-up cylinder 5. Next, the push-up cylinder 5 is operated to lower the crucible 1 and set it in the high temperature range. On the other hand, the mold is applied with a mold release material on its surface by the mold release material attaching device 10, and then the articulated robot 9
Is placed on the upper open type hot plate 11 by the hand and is preheated while controlling the temperature so that the metal mold becomes a predetermined temperature (T ₂ ) when the metal ingot is cast into the metal mold. . When the metal ingot in the crucible 1 set in the high temperature region of the high frequency coil is melted and the radiation thermometer 6 indicates the predetermined temperature (T ₁ ), the preheated mold is poured into the casting device 7 It is carried by the hand of the articulated robot 9 on the pouring table.

Next, a radiation thermometer 6 for indicating the temperature of the metal
When the temperature reaches a predetermined temperature (T ₃ ), the push-up cylinder 5 is operated to raise the crucible 1 and raise the high-frequency coil 1.
Put out from. The hand of the multi-joint robot 9 which is moved to a position above the high frequency coil 2 in advance and holds the crucible 2 is moved to a position above the metal mold already mounted on the pouring table of the pouring device. Then, the crucible 1 is inclined and the metal ingot melted in the crucible is cast.

After the casting, the hand of the articulated robot 9 is withdrawn, and at the same time, the casting burner device of the casting device 7 is operated to gradually cool and solidify the metal ingot. When the solidification is completed and the operation of the casting burner device is stopped, the hand of the multi-joint robot 9 holds the metallic mold and moves it to the reversing table 8 to reverse the metallic mold and remove it from the metal ingot. The produced ingot is released from the mold, and the ingot is cooled on this inversion table.

Thereafter, the metallic mold from which the ingot has been released is transferred to the release material attaching device 10 while being held by the hand of the articulated robot 9, and the release material is attached again, and then the upper open hot plate 11 is placed. To be preheated. On the other hand, the ingot sufficiently cooled on the inversion table 8
The ingot stock base 1 is nipped by the hand of the articulated robot 9 and transferred to the ingot stock base 13.
3 is dropped and stored.

The above is a series of operations. Next, the crucible containing the metal ingot is charged in the high frequency coil 2 with a substantially constant time interval so as not to hinder the previous series of operations. However, the sequence is controlled so that they are sequentially charged.

In this case, since the melting furnace is always controlled to the same heating state, it is presumed that the time from charging the crucible 1 containing the metal metal to the high frequency coil 2 to discharging it is substantially the same. Then, it is possible to control only by the time sequence, but in reality, even if the weight of the metal ingot is the same, the melting time differs depending on the shape of the metal ingot, and the size of the crucible 1 is slightly different. And high frequency coil 2
Since the melting time varies considerably even with a slight difference in the position of the crucible in the inner part, it is not sufficient to simply control the sequence in time, and it is preferable to use the temperature control together. However, in the heating by the high frequency coil 2 whose upper part is open, the temperature uniformity in the vertical and horizontal directions of the high frequency coil is very poor and the temperature fluctuation is large. It does not indicate the substantial temperature of the entire metal ingot, but merely indicates a rough temperature reading. However, it has been found that even if the temperature indication of the radiation thermometer having such a problem is used as in the present invention, there is almost no problem.

When manufacturing a 1 kg bar ingot (a rough size of 116 × 50 × 8 mm) in which the metal ingot is a gold ingot, the temperature of the radiation thermometer 6 discharged from the high frequency coil 2 by raising the crucible 1 is indicated. Preferred temperature (T ₃ ) of
Is 1250 to 1300 ° C., and when the instruction to place the metallic mold from the upper open hot plate 11 on the pouring table of the pouring device 7 is given, the predetermined temperature (T ₁ ) is 1170 to 1200 ° C. If the temperature (T ₃ ) is less than 1250 ° C, the wrinkles on the casting surface of the gold ingot surface after casting become deep and the commercial value decreases, and if the temperature (T ₃ ) exceeds 1300 ° C, the gold volatilizes. Or, when cast, the fine particles of gold scatter and the weight of the gold ingot falls below the specified value, and it becomes a product, or the solidification time becomes longer, and as a result, the specific gravity (19.2 g). / Cm ³ ) It becomes lower than commercial products.

Further, the temperature of the metal mold when the metal ingot is cast into the metal mold has a great influence on the quality of the obtained ingot. Therefore, the temperature should be adjusted to a predetermined temperature (T ₂ ). Is desirable, and the metal bullion is gold bullion 1
When manufacturing a kg bar ingot, a desirable predetermined temperature (T ₂ ) is 220 to 270 ° C.
_{If 2} ) is less than 220 ° C, the solidification time will be shortened, and the wrinkles on the cast surface of the gold ingot surface after casting will become deep,
The product value is reduced and the temperature (T ₂ ) is 270 ° C.
If the temperature exceeds the range, the surface of the ingot that was in contact with the mold will be discolored, many small dents will occur, and fine particles of gold will scatter during casting, and the weight of the ingot will drop below the specified value, or solidification will occur. As the time becomes longer, the specific gravity of the product becomes lower than the specified value, and the product becomes unusable. The temperatures (T ₃ ) and (T ₂ ) differ depending on the type of metal ingot and the weight and size of the ingot, so they must be set appropriately.

In the present invention, since the metallic mold having good heat conductivity is used, the metallic mold can be sufficiently preheated by the upper open type hot plate, and the ceramic mold as described in JP-A-4-305359. Compared with the method of preheating in a mold preheating furnace with a door, it is easier for the robot to hold the mold, and a time margin can be given for control. Although it is also possible to use a metal mold having a normal shape, a mold having a specially shaped handle that is easy to be clamped by a robot hand as described in the above-mentioned applicant's patent application is preferable, and at the time of casting. A heat-resistant cast iron mold that is resistant to heat shock is preferable.

A metallic mold is placed on the open top hot plate 11 on the pouring table of the pouring device 7, and the high frequency coil 2 is placed.
In a series of work in which the crucible 1 discharged by the push-up cylinder 5 is clamped by and the metal crucible is cast on the pouring table of the pouring device 7, the robot hand clamps the crucible and the mold. In this case, JP-A-4-305359
It is also possible to carry out while exchanging the hands of the robot as described in Japanese Patent Publication, but since these steps are related to each other, it is preferable to carry out smoothly in a short time,
As described in the above-mentioned applicant's patent application, a robot hand having a crucible holding portion, a mold holding portion, and an ingot holding portion is used at the tip of the robot arm, and these portions are switched and used. It is preferable.

Further, as shown in FIG. 2, it is preferable to place the casting device 7 at the center and dispose the high-frequency coil 2 and the upper open type hot plate 11 on both sides since the work flow can be made smooth.

It should be noted that the articulated robot has a blind spot portion that cannot be reached only by simply turning the arm, and the complicated arm movement can move the arm to this blind spot area. It is preferable to avoid such arm movements, as it involves danger when dealing with hot objects that the present invention is directed to.

The reversing table 8, the mold release material attaching device 10, the crucible supplying device 12, and the ingot stock table device 13 may have any structure as long as they can be easily automated.

Next, specific examples and comparative examples of the present invention will be described.

Example 1 A crucible (6.2 cmφ × 7.1 cmH) in which 1000.07 to 1000,09 g of gold having a seriousness of 99.99% by weight was weighed, and an inner diameter of 9.5 cmφ was used.
4 high-frequency coils of 5 cmH were connected in series, and were sequentially charged into the high-frequency coil of a high-frequency furnace heated at a frequency of 9 kHz, a voltage of 400 V and a current of 35 A, and the radiation thermometer indicated (T ₁ ) was 1170 ° C. At this time, the mold release material is attached in advance, and the heat-resistant cast iron mold that has been preheated on the upper open type hot plate is placed on the pouring table. The radiation thermometer indicates 12
When the temperature reaches 50 ° C, a signal is sent to move the robot hand from the fixed position to the furnace, and after a few seconds, the robot hand detects the robot on the furnace and activates the push-up cylinder to activate the crucible. Is discharged from the high-frequency coil (at this time, the radiation thermometer indicates, T ₃ is 1270 ° C), the temperature (T ₂ ) is 220 ° C and the heat-resistant cast iron mold is cast with gold from the crucible and cast by the casting device. The gold is solidified while operating the burner device. After solidification, the mold was inverted over the inversion table to release the ingot, and after cooling was completed, the ingot was placed on the ingot stock table.

In these steps, a crucible, a mold, and an ingot were moved by using a multi-joint robot having one robot hand having a crucible holding portion, a mold holding portion, and an ingot holding portion. It was 45 seconds until the heat-resistant cast iron mold was lifted from the upper open hot plate according to the instruction of the radiation thermometer (T ₁ ) and then the metal ingot was cast into the heat-resistant cast iron mold.

Gold ingots were manufactured at intervals of 6 minutes, and the weight of the obtained gold ingots was 1000.02-1000.
It has a specific gravity of 19.22 to 19.30 g / cm ³ , has no large shrinkage cavities, strong wrinkles, and is glossy.
It was of high commercial value.

(Embodiment 2) T _{3 is set} to 1250 ° C.
Example 1 was repeated except that ₂ was 270 ° C. The variations in weight and specific gravity of the obtained gold ingot were the same as in Example 1, and there were no problems. The surface of the ingot was slightly wrinkled as compared with Example 1, but there was no problem in commercial value.

(Embodiment 3) T _{3 is set} to 1300 ° C.
_{The same} procedure as in Example 1 was performed except that ₂ was 220 ° C. The variations in weight and specific gravity of the obtained gold ingot were the same as in Example 1, and there was no problem. The surface of the ingot had a slightly deeper shrinkage cavity than that in Example 1, but there was no problem in commercial value.

COMPARATIVE EXAMPLE 1 T _{3 is set} to 1230 ° C.
_{The same} procedure as in Example 1 was performed except that ₂ was 210 ° C. The variations in weight and specific gravity of the obtained gold ingot were the same as in Example 1 and there was no problem, but the surface of the ingot was too deeply wrinkled, and the commercial value was poor.

(Comparative Example 2) T ₃ was set to 1320 ° C.
_{The same} procedure as in Example 1 was performed except that ₂ was 210 ° C. When the crucible was ejected from the high frequency coil, it was observed that fine particles of gold were scattered, and the same phenomenon was observed when the gold was cast into the mold. The weight of the obtained gold ingot is 999.08 to 1000.05 g, and the specific gravity is 19.18 to 19.25 g / cm ³ ,
Product standard (1000g or more, 19.2g / cm ³ or more)
It was observed that the surface of the gold ingot had large shrinkage cavities, and the surface in contact with the mold, especially the cast metal part, turned a little reddish. In this way, many products with no commercial value were manufactured.

[0036]

As described above, according to the present invention,
We have obtained a casting machine that has good weight accuracy for precious metals such as metal, especially gold, can produce clean ingots without shrinkage cavities and strong wrinkles, and can be automated with a simple structure.

[Brief description of drawings]

FIG. 1 is a side view schematically showing a melting furnace used in a casting apparatus of the present invention.

FIG. 2 is a schematic layout diagram showing the layout of the individual devices that make up the casting device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 crucible 2 high frequency coil 7 pouring device 8 reversing table 11 open top hot plate 12 crucible supply device 13 ingot stock table 10 release material attaching device 9 articulated robot

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[Procedure amendment]

[Submission date] August 9, 1993

[Procedure Amendment 1]

[Document name to be corrected] Drawing

[Correction target item name] All drawings

[Correction method] Change

[Correction content]

[Figure 1]

[Fig. 2]

Claims (2)

[Claims] 1. A temperature preset by an instruction of a radiation thermometer for detecting the temperature of a molten metal surface by sequentially loading crucibles containing metal ingots in a plurality of high-frequency coils to melt the metal ingots. When, the crucible is sequentially taken out of the high-frequency coil, a mold release material is attached in advance, and then the metal in the crucible is sequentially cast into a mold preheated to a predetermined temperature. Casting method. 2. A plurality of high-frequency coils, a radiation thermometer provided above the center line of the high-frequency coils, and means for loading and unloading the crucible inside the high-frequency coil. A melting furnace, a first heating device for preheating the mold, a pouring table for placing the mold in a state in which the metal ingot from the crucible is cast into the mold, and a pouring table arranged in the vicinity of the pouring table in the mold. A second heating device that heats the metal ingot to gently cool the metal ingot, a crucible supply device that mounts the crucible to supply the crucible to the high-frequency coil, and a mold release material attached to the mold. A mold release material adhering device, a reversing stand for reversing and releasing the cast small metal ingot, and an ingot stock stand for accommodating the small metal ingot, a crucible, a mold and a small metal ingot. The above each device A casting machine for a small metal ingot, comprising: an articulated robot for transferring between the robots and a control device for sequence-controlling the articulated robot.