JP5814564B2 - Pressure casting method and apparatus - Google Patents

Description

  The present invention relates to a pressure casting apparatus and a pressure method used in a manufacturing process of a bare metal in lost wax casting.

  A lost wax method is known as a method for accurately and integrally producing a cast product having a complicated shape such as a metal accessory. Mainly, in the lost wax method, i) a wax model production process using a rubber mold, ii) a mold production process using a wax model, and iii) a final casting product casting process using a mold. And iv) It is roughly divided into each stage of the finishing process of the cast product. In the “final casting process using the completed mold”, a vacuum pressure casting apparatus is used. Here, “vacuum” means a pressure casting apparatus having a vacuum process in which the internal pressure is once evacuated and replaced with a rare gas such as argon. This means having a step of pressurizing gold, and in the present specification, these are collectively referred to as a pressure casting apparatus. Here, with reference to FIG. 1 and FIG. 2 about the pressure casting apparatus of this invention, the outline of the conventional typical pressure casting apparatus is demonstrated.

  The pressure casting apparatus 1 has a melting chamber 20 for melting a bare metal and a mold chamber 30 for placing a molten casting mold. In the melting chamber 20, a melting crucible 4 for placing and melting the bare metal after blowing is disposed. The metal melted in the melting chamber 20 is poured into the mold 2 disposed in the mold chamber 30. However, in lost wax casting for jewelry, the runner inside the mold 2 is thin and complicated, and the viscosity of the molten metal is very high, so it is difficult for the metal to flow deep into the runway. Therefore, it is necessary to make it easy to pour the molten metal into the runner inside the mold 2, and it is necessary to pressurize the melting chamber 20.

In the lost wax casting for jewelry, the mold 2 is formed of a gypsum-based material in which cristobalite, silica and gypsum are mixed, for example. When the molten ingot flows into the mold 2, the gypsum-based material constituting the mold and the molten ingot react to generate gas (hereinafter referred to as “mold-derived gas”). Since the mold-derived gas is an oxidizing gas, there is a problem that the metal is damaged if it remains inside the metal.
However, in a state in which the molten metal is pressurized in the melting chamber 20 in order to make it easier to pour the molten metal into the runner inside the mold 2, the mold-derived gas remains in the molten metal. Are not discharged to the outside. Therefore, if the metal is cooled and solidified in this state, a defective product in which a nest is formed inside the finished product occurs, and it causes corrosion. On the other hand, if pressure is not applied, the melted metal having high viscosity does not sufficiently reach the runner inside the mold 2 and is liable to cause defective products.

  Therefore, the present invention has a mold chamber having a mold made of gypsum material inside, and a melting crucible for melting the metal, and is disposed so as to be hermetically connected to the mold chamber and melted. A melting chamber having a communication port for introducing gold from the melting crucible into the mold at the bottom; a pressurizing means connected to the melting chamber for introducing a rare gas; and a pressure in the melting chamber. A pressure sensor to be detected, and the pressurizing means is controlled to pressurize the molten metal surface injected into the mold by introducing a rare gas into the melting chamber in accordance with the pressure detected by the pressure sensor. This is solved by a pressure casting apparatus including a control device.

  Further, the present invention has a mold chamber having a mold made of a gypsum material inside, and a melting crucible for melting the metal, and is disposed so as to be hermetically connected to the mold chamber and melted. A melting chamber having a communication port for introducing a metal from the melting crucible into the mold at the bottom, and exhaust means connected to the mold chamber, each exhaust gas capable of exhausting the internal gas; A pressure sensor for detecting the pressure in the mold chamber, and exhausting the gas in the mold chamber according to the pressure detected by the pressure sensor to pressurize the molten metal surface injected into the mold. It solves by the pressure casting apparatus provided with the control apparatus which controls a means.

  Further, the present invention is a pressurizing method for pressurizing a molten metal surface in a mold by a pressure casting apparatus, and a rare gas is introduced into the mold by the pressurizing means when pouring molten metal into the mold. Pressurizing the melting chamber, maintaining the pressure in the melting chamber at a constant pressure for a predetermined time when the detected pressure of the pressure sensor reaches a predetermined pressure, and And a step of executing control for further pressurization from the constant pressure.

  The present invention also relates to a pressurizing method of pressurizing a molten metal surface in a mold by a pressure casting apparatus, wherein the mold chamber is evacuated when molten metal is poured into the mold, and a pressure sensor is detected. A step of stopping the evacuation means for a predetermined time when the pressure reaches a predetermined pressure, and maintaining the inside of the melting chamber at a constant pressure; And a step of further reducing the internal pressure from the constant pressure.

  According to the present invention, the metal poured into the mold reacts with the gypsum-based material mold, and the mold-derived gas generated in the metal can be discharged, thereby reducing the occurrence of nests in the finished cast product. It becomes possible.

It is an external view of a pressure casting apparatus. It is the figure which showed the inside of the melting chamber 20 and the mold chamber 30 of the pressure casting apparatus of this invention. It is the figure which showed the piping structure of the pressurization system of a pressure casting apparatus, and a pressure reduction system. It is the figure which showed the pressurization profile of the melting chamber 20 and the mold chamber 30 of a pressure casting apparatus.

  Hereinafter, the pressure casting apparatus 1 of the present invention will be described with reference to FIGS. 1 to 4. FIG. 1 is an external view of a pressure casting apparatus 1. FIG. 2 is a schematic view showing the internal structure of the pressure casting apparatus 1 of the present invention. FIG. 3 is a view showing a pressurization system (air supply system) and a decompression system (exhaust system) of the pressure casting apparatus 1 of the present invention. FIG. 4 shows a pressure profile in the pressure casting apparatus 1 of the present invention.

  The pressure casting apparatus 1 has a melting chamber 20 for melting a bare metal and a mold chamber 30 for placing a melted casting mold 2. The bullion is gold, silver, brass or the like. The mold 2 is generally made of a gypsum material. Specifically, it is a material containing cristobalite 30% to 40%, silica 30% to 40%, gypsum 20% to 30%). These molten metals are likely to react with the gypsum-based material and generate gas. The melting chamber 20 is provided with a melting crucible 4 for melting the molten metal after blowing and a protective crucible 5 for holding it. The melting chamber 20 is located above the mold chamber 30 and is fixed to the pressure casting apparatus 1. A lid 22 of the melting chamber 20 is disposed above the melting chamber 20. A lock cylinder 40 is disposed below the mold chamber 30. The mold chamber 30 is attached so as to be movable up and down in the vertical direction along the support rod 23a and the support rod 23b. Furthermore, the mold chamber 30 can be rotated around one support rod 23b, and can be disposed at a position directly below the melting chamber 20, or can be disposed at a position that is horizontally drawn from directly below the melting chamber 20. It is also possible.

  A hollow cylindrical protective crucible 5 is arranged inside the melting chamber 20. The upper surface of the protective crucible 5 has an opening 5 a larger than the outer shape of the melting crucible 4, and the opening 5 b is disposed at the bottom of the protective crucible 5. A stage is arranged inside the protective crucible 5 so that the melting crucible 4 can be supported. A hollow space for holding the metal is arranged inside the melting crucible 4, and its outer shape is a cylindrical shape that can be inserted into the space inside the protective crucible 5. The melting crucible 4 has a wide-mouth opening 4a on the upper side and a nozzle-like discharge port 4b on the bottom side. The melting crucible 4 is inserted into the protective crucible 5 through the opening 5 a of the protective crucible 5. The melting crucible 4 inserted from the opening 5 a of the protective crucible 5 is placed on the stepped surface inside the protective crucible 5 and fixed.

  The melting chamber 20 has an opening 20a on the upper side and a communication port 20b facing the opening 30a of the mold chamber 30 on the bottom side. A seal packing 20c is attached around the opening 20a. An opening 30 a is also provided on the upper side of the mold chamber 30. A seal packing 30b is also attached around the opening 30a. The opening 20 a is an opening for supplying metal to the melting crucible 4 through the opening 5 a on the upper surface of the protective crucible 5. The communication port 20 b is an opening for discharging the molten metal from the melting crucible 4 in the melting chamber 20 toward the mold chamber 30. The discharge port 4b at the end on the bottom side of the melting crucible 4 corresponds to the position of the opening 5b on the bottom side of the protective crucible 5, and the metal melted in the melting crucible 4 passes through the opening 5b of the protective crucible 5 through the mold chamber 30. It can flow toward the upper opening 30a.

  A mold raising / lowering cylinder 31 is disposed below the interior of the mold chamber 30. Inside the mold raising / lowering cylinder 31, a piston 32 is arranged inside the mold chamber 30 so as to be vertically movable. A mold base 33 having a flat surface is arranged on the upper surface of the piston 32. The mold 2 is placed on the mold base 33. As the piston 32 moves up and down, the mold 2 moves up and down together with the mold base 33.

  A lock cylinder 40 is disposed below the mold chamber 30. The lock cylinder 40 has a lock cylinder raising / lowering piston 41 that can be raised and lowered. When the lock cylinder elevating piston 41 is raised, the mold chamber 30 is pushed up. The pushed-up mold chamber 30 eventually comes into contact with the lower part of the melting chamber 20 and closes the opening 30a of the mold chamber 30 with the seal packing 30b. On the other hand, when the cylinder housing of the lock cylinder 40 is lowered and the support rod 23a and the support rod 23b are lowered, the upper portions of the support rod 23a and the support rod 23b are lowered so as to push down the lid 22. The lowered lid 22 closes the opening 20 a of the melting chamber 20. A seal packing 20c is provided between the lid 22 and the opening 20a, and a seal packing 30b is provided between the melting chamber 20 and the mold chamber 30 to seal each other.

  The bare metal is set in the melting crucible 4 with the melting chamber 20 and the mold chamber 30 being opened. Then, the opening 20a of the melting chamber 20 is closed with the lid 22, and the mold chamber 30 is closed. An induction coil 21 for heating the protective crucible 5 is attached to the outer surface of the protective crucible 5 so as to surround the protective crucible 5, and the melting crucible 4 and the metal in the melting crucible 4 are generated by energizing the induction coil 21. By the applied magnetic force, it is directly heated and melted by the principle of high frequency induction heating.

  In the melting chamber 20, a stopper rod 24 extending in the vertical direction is attached substantially at the center. The stopper rod 24 can be moved up and down in the vertical direction by a stopper driving mechanism, and has a role as a plug for the discharge port 4 b of the melting crucible 4. The tip of the stopper rod 24 closes the nozzle-like discharge port 4b of the melting crucible 4 while descending in the vertical direction, while the nozzle-like discharge port 4b of the melting crucible 4 opens when it rises upward. Is done. When the stopper rod 24 rises and the discharge port 4b is opened, the melted metal flows from the discharge port 4b through the opening 30a of the mold chamber 30 into the mold 2.

  A pressure port 46 is disposed in the melting chamber 20, and is fluidly connected to a pressure pump 41 and a rare gas source 42 as pressure means. The pressurizing means may be only the pressurized rare gas source 42 without the pressurizing pump 41, or may be a pressurized tank whose inside is pressurized with the rare gas. The rare gas is, for example, argon. As long as it has a pressure sufficient to control the melting chamber so that it can be pressurized to a predetermined pressure, it can be a pressurizing means. A pressure sensor 43 is attached to the lysis chamber 20 so that the internal pressure can be measured. The pressure sensor 43 can be attached to the pressurization port 46, for example, but may be attached at any location as long as the pressure inside the melting chamber 20 can be detected.

  The pressure casting apparatus 1 has an exhaust pump 51 as exhaust means. As the exhaust pump 51, various types of vacuum pumps can be typically used. The exhaust pump 51 is fluidly connected to the melting chamber 20 and an exhaust port 56 disposed in the mold chamber 30. A valve 54 is connected between the melting chamber 20 and the exhaust pump 51, and a valve 55 is connected between the mold chamber 30 and the exhaust pump 51. Thereby, the inside of the melting chamber 20 and the mold chamber 30 can be exhausted separately. A pressure sensor 53 is attached to the mold chamber 30 so that the internal pressure can be measured. The pressure sensor 53 can be attached to the exhaust port 56, for example, but may be attached at any location as long as the pressure inside the mold chamber 30 can be detected.

  The pressure casting apparatus 1 has a control device 52. The control device 52 is electrically connected to the pressurizing means pump 41 and the vacuum pump 51, respectively. The control device 52 can pressurize the interior of the melting chamber 20 by introducing a rare gas into the melting chamber 20 in accordance with the pressure detected by the pressure sensor 43, and the surface of the molten metal 7 injected into the mold 2. It is possible to control the pressure for pressurizing 7a. The control device 52 controls the exhaust pump 51 so as to pressurize the molten metal surface 7 a of the metal 7 injected into the mold 2 by exhausting the gas in the mold chamber 30 according to the pressure detected by the pressure sensor 53. Is possible.

  Next, a method of casting and pressurizing the metal injected into the mold using the pressure casting apparatus 1 of the present invention will be described. As described above, first, the metal before melting is set in the melting crucible 4 with the melting chamber 20 and the mold chamber 30 being opened. Then, the opening 20a of the melting chamber 20 is closed with a lid 22, the mold chamber 30 is closed, and the lid 22, the opening 20a, the melting chamber 20 and the mold chamber 30 are sealed. And the valve | bulb 54 and the valve | bulb 55 are opened, the exhaust pump 51 is driven, and the inside of the melting chamber 20 and the mold chamber 30 is evacuated. Thereafter, a rare gas is introduced into the melting chamber 20 and the mold chamber 30 that are evacuated. The timing of introduction and the timing of melting can be freely determined by the casting process.

  Subsequently, the metal in the melting crucible 4 is heated and melted by the magnetic force generated by energizing the induction coil 21 according to the principle of high-frequency induction heating. The timing of melting the metal can be freely determined according to the casting process. After completely melting, the stopper rod 24 is raised. When the stopper rod 24 is raised and the discharge port 4b is opened, the molten metal 7 flows from the discharge port 4b into the mold 2 through the opening 30a of the mold chamber 30. Let The hot water surface 7a of the ingot 7 that has flowed in is pressurized.

  There are two methods for pressurizing the molten metal surface 7a of the metal 7 that has flowed in. One is a method of increasing the pressure inside the melting chamber 20 with respect to the pressure of the mold chamber 30, and the other is a method of decreasing the pressure inside the melting chamber 30 with respect to the pressure of the melting chamber 20. The pressure casting apparatus 1 may have both of these functions, or may have only one of the functions. As long as the molten metal surface 7a of the metal 7 that has flowed in due to the pressure difference can be pressurized, the pressure casting apparatus 1 has a function.

  First, the former method, that is, a method of increasing the pressure inside the melting chamber 20 relative to the pressure of the mold chamber 30 will be described. A rare gas is introduced into the melting chamber 20 by the pressurizing pump 41 to pressurize the interior of the melting chamber 20 (first pressurizing step in FIG. 4). Since the pressure in the mold chamber 30 is reduced, the pressure difference in the mold chamber 30 becomes higher than the pressure inside the melting chamber 20, and the molten metal surface 7 a of the metal 7 flowing into the mold 2 is pressurized. At this time, at least the pressure in the melting chamber 20 is detected by the pressure sensor 43. When the pressure sensor 43 detects that the pressure in the melting chamber 20 has reached a predetermined pressure, the control device 52 stops supplying the rare gas to the melting chamber 20 by the pressurizing pump 41 and pressurizes for a predetermined time. Is stopped (pressure holding step in FIG. 4). During this time, the control device 52 controls the pressurizing pump 51 so as to maintain this constant pressure for a predetermined time. After the predetermined time has elapsed, the control device 52 restarts the supply of the rare gas again and starts pressurization from the pressure (second pressurization step in FIG. 4).

  Subsequently, the latter method, that is, a method of reducing the pressure in the mold chamber 30 with respect to the pressure in the melting chamber 20 will be described. A rare gas is introduced into the melting chamber 20 by the pressurizing pump 41 to pressurize and hold the interior of the melting chamber 20 to a certain degree (for example, about atmospheric pressure). In the latter method, the pressure is not changed by the pressurizing pump 41. Here, that is, the gas inside the mold chamber 30 is exhausted by the exhaust pump 51, and the pressure inside the mold chamber 30 is gradually reduced (first pressurizing step in FIG. 4). The pressure difference in the mold chamber 30 becomes higher than the pressure inside the melting chamber 20, and the molten metal surface 7a of the metal 7 flowing into the mold is pressurized. At this time, at least the pressure in the mold chamber 30 is detected by the pressure sensor 53. When the pressure sensor 53 detects that the pressure in the mold chamber 30 has become a predetermined pressure, the control device 52 stops the exhaust from the mold chamber 30 by the exhaust pump 51 and stops the pressurization for a predetermined time ( Pressure holding step in FIG. 4). During this time, the control device 52 controls the exhaust pump 51 so as to maintain this constant pressure for a predetermined time. After the predetermined time has elapsed, the control device 52 resumes the exhaust of the rare gas again and starts depressurization from the pressure (second pressurization step in FIG. 4).

  In both the former method and the latter method, the “predetermined pressure” and “predetermined time” are determined as follows. It is set so that it can be sufficiently discharged from the molten metal surface of the mold 2. In particular, the predetermined pressure is set lower than the partial pressure of the mold-derived gas. When the pressurization pressure exceeds the partial pressure of the mold-derived gas, the effect of discharging the mold-derived gas from the metal is lost even if the pressure is kept constant for a predetermined time. By setting in this way, it is possible to prevent the mold-derived gas from remaining and pressurize the molten metal surface appropriately. Note that the pressurization speed in the second pressurization process in which the supply of the rare gas is resumed is preferably the same as the pressurization speed in the first pressurization process.

DESCRIPTION OF SYMBOLS 1 Pressure casting machine 2 Mold 4 Melting crucible 5 Protective crucible 20 Melting chamber 30 Mold chamber 41 Pressure pump 51 Exhaust pump 52 Control means

Claims (4)

A mold chamber having a mold made of gypsum material therein;
A melting crucible for melting the metal is disposed inside, and is arranged to be hermetically connected to the mold chamber, and a communication port for introducing the molten metal from the melting crucible to the mold is provided at the bottom. A melting chamber,
A pressurizing means connected to the melting chamber and introducing a rare gas therein;
A pressure sensor for detecting the pressure in the melting chamber;
A controller for controlling the pressurizing means to pressurize the molten metal surface injected into the mold by introducing a rare gas into the melting chamber in accordance with the pressure detected by the pressure sensor. A pressure casting device,
The controller pressurizes the melting chamber when pouring the molten metal into the mold, and keeps the melting chamber constant for a predetermined time when the pressure detected by the pressure sensor reaches a predetermined pressure. The pressure is maintained at a predetermined pressure, and after the predetermined time has elapsed, the melting chamber is further pressurized from the constant pressure .
The predetermined pressure is set so that the mold-derived gas generated in the metal can react with the base metal and the mold and can be discharged from the molten metal surface of the mold. A pressure casting apparatus characterized by being lower than partial pressure . A mold chamber having a mold made of gypsum material therein;
A melting crucible for melting the metal is disposed inside, and is arranged to be hermetically connected to the mold chamber, and a communication port for introducing the molten metal from the melting crucible to the mold is provided at the bottom. A melting chamber,
An exhaust means connected to the mold chamber, the exhaust means capable of exhausting each internal gas;
A pressure sensor for detecting the pressure in the mold chamber;
Pressure casting comprising: a control device that controls the exhaust means so as to pressurize the molten metal surface injected into the mold by exhausting the gas in the mold chamber in accordance with the pressure detected by the pressure sensor. A device,
The control device exhausts the mold chamber when pouring the molten metal into the mold, and stops the exhaust means for a predetermined time when the pressure detected by the pressure sensor reaches a predetermined pressure. Holding the inside of the melting chamber at a constant pressure, and executing the control to further reduce the pressure in the mold chamber from the constant pressure by re-driving the exhaust means after the predetermined time has elapsed ,
The predetermined pressure is set so that the mold-derived gas generated in the metal can react with the base metal and the mold and can be discharged from the molten metal surface of the mold. A pressure casting apparatus characterized by being lower than partial pressure . A pressurizing method of pressurizing a molten metal surface in a mold by a pressure casting apparatus,
The pressure casting apparatus comprises:
A mold chamber having a mold made of gypsum material therein;
A melting crucible for melting the metal is disposed inside, and is arranged to be hermetically connected to the mold chamber, and a communication port for introducing the molten metal from the melting crucible to the mold is provided at the bottom. A melting chamber,
A pressurizing means connected to the melting chamber and introducing a rare gas therein;
A pressure sensor for detecting the pressure in the melting chamber;
The pressurizing method is:
A step of introducing a rare gas into the inside by the pressurizing means when the molten metal is poured into the mold and pressurizing the melting chamber;
Holding the inside of the melting chamber at a constant pressure for a predetermined time when the detected pressure of the pressure sensor reaches a predetermined pressure;
E Bei and performing a further pressurizing control該熔solution chamber after elapse of the predetermined time from the constant pressure,
The predetermined pressure is set so that the mold-derived gas generated in the metal can react with the base metal and the mold and can be discharged from the molten metal surface of the mold. A pressurizing method characterized by being lower than partial pressure. A pressurizing method of pressurizing a molten metal surface in a mold by a pressure casting apparatus,
The pressure casting apparatus comprises:
A mold chamber having a mold made of gypsum material therein;
A melting crucible for melting the metal is disposed inside, and is arranged to be hermetically connected to the mold chamber, and a communication port for introducing the molten metal from the melting crucible into the mold A melting chamber,
An exhaust means connected to the mold chamber, the exhaust means capable of exhausting each internal gas;
A pressure sensor for detecting the pressure in the mold chamber,
The pressurizing method is:
Evacuating the mold chamber when pouring the molten metal into the mold; and
When the detected pressure of the pressure sensor reaches a predetermined pressure, stopping the exhaust means for a predetermined time and maintaining the inside of the melting chamber at a constant pressure;
E Bei a step of re-driving the exhaust means after a lapse of the predetermined time further reducing the pressure within the mold chamber from said constant pressure,
The predetermined pressure is set so that the mold-derived gas generated in the metal can react with the base metal and the mold and can be discharged from the molten metal surface of the mold. A pressurizing method characterized by being lower than partial pressure.

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