JP2539279Y2 - Pure titanium or titanium alloy precision casting equipment - Google Patents

Description

[Detailed description of the invention]

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for casting small precision castings such as dental prostheses made of pure titanium or titanium alloy.

[0002]

2. Description of the Related Art Titanium material consisting of pure titanium or an alloy containing titanium as a main component is said to be a metal having excellent corrosion resistance and being extremely stable and compatible with living organisms, and having strength, ductility, small thermal expansion and lightness. It is considered optimal for dental metal. However, the melting point of titanium is about 1,70.
0 ° C and in a molten state (standard pouring temperature
At 900 ° C), it has a very high activity and reacts with oxygen and nitrogen in the atmosphere or various elements in the crucible material to embrittle the casting. It is extremely difficult to produce on an industrial basis. However, in the situation where there is a strong demand for the use of precision castings made of metal that is optimal for dental use, research on titanium precision casting technology is being actively conducted. The authors have also been conducting research on the above-mentioned titanium precision casting in the evening following the day, but initially focused on the crucible that melts titanium,
Research has been conducted to prevent oxygen from oxides in the crucible material or to prevent oxidation or nitridation of the molten metal by reacting with air remaining in the pores of the crucible inner wall. However, even if the material of the crucible was made of a refractory material that did not react with the molten metal during melting of titanium, and the air remaining in the pores was completely removed by purging with argon gas, the purpose could not be achieved completely.

[0003] Therefore, the subject of the study was then transferred to the investment material forming the mold cavity. In other words, the main components of the conventional phosphate investment are quartz and cristobalite and a mixture of quartz and cristobalite. The quartz and cristobalite are silica, and the molten titanium reacts with the silica to decompose the silica. It has been found that titanium is oxidized. Therefore, by successfully coating the crucible, runner and mold cavity in contact with the molten titanium with magnesia-based investment material, which has better heat resistance than phosphate-based investment material, titanium precision casting of small dental items was finally achieved. I have an eye for it.

However, as an actual casting operation, a crucible
To coat the runner and mold cavity with magnesium-based investment material and dry and harden,
It takes a long time, it takes about 2 hours to bury it in a phosphate-based investment material, dry and harden it, and furthermore, it takes about 3 hours of heat treatment to burn the pattern wax. As described above, it takes about 6 to 9 hours to complete the mold, and there is a strong demand for more efficient mold production in the practical use of titanium casting.

[0005]

The problem to be solved is that in a pure titanium or titanium alloy precision casting device, a crucible and a runway made of a magnesia-based investment material that does not react with molten high-temperature molten titanium and does not oxidize titanium. And the mold cavity or the runner / mold cavity is encapsulated and formed.
The point is to make the casting of a high quality titanium casting more efficient by making a mold without burying the encased portion with the phosphate investment material.

[0006]

The most important object of the present invention is to cover a mold runner and a mold cavity with a magnesia-based investment material, and to house the cover in a space formed inside the mold. Features. The first configuration of this invention is
In a high-frequency induction heating type pressure casting device using a convex mold, a crucible is molded with magnesia investment, and the runner and mold cavity communicating with it are covered.
The crucible is removably supported on a fire-resistant tubular body, and a separate convex mold is provided in which the envelope is accommodated in the tubular body space. Still another configuration is an arc discharge or high-frequency induction heating type separate plate melting and pressurizing apparatus, in which a runner communicating with a mold gate and a cavity of the mold are covered with a magnesia-based investment material, and the covered section is molded. It is designed to be accommodated in the internal space formed by the outer shell.

[0007]

FIG. 1 shows an embodiment of a pure titanium or titanium alloy precision casting apparatus according to the first structure of the present invention, ie, a casting part (1) of a high frequency induction heating type pressure casting apparatus using a convex mold. It is a longitudinal cross-sectional view. The vacuum evacuation system and the argon gas supply system of this apparatus are described in Japanese Utility Model Application No. 61-8
No. 0492, "Pressure Casting Apparatus" is not described here. The main part of the present invention is a separation type convex mold (2) for casting titanium. Prior to the description of the mold (2), the configuration of the casting part (1) will be schematically described. The heating chamber (4) surrounded by the refractory cylindrical body (3) is sealed at the top with a viewing window (5), and a high-frequency induction coil (6) is wound around the periphery. The lower end of the heating chamber (4) is engaged with a pedestal (7) made of, for example, an asbestos molding material to form a lower opening (8). The above separated mold convex mold (2)
Is mounted on a mold receiving stand (9), and the mold receiving stand (9) is moved up and down by a mold elevating mechanism constituted by a not-shown pneumatic cylinder and its piston (10), and is raised at a set pressure at the time of ascending. The mold (2) is pressed against the pedestal (7) to seal the heating chamber (4). The lower chamber housing (13) for housing the lower mold base (12) is moved up and down by a piston (14) of a housing elevating mechanism (not shown), and a ring-shaped member (7) engaged with the periphery of the pedestal (7) when ascending. 15) O-ring (16)
To seal the lower chamber interior space (17) airtightly to the outside air. Returning to the heating chamber (4), the upper side wall (18) is provided with a vacuum exhaust hole (19) for reducing the pressure of the heating chamber to a predetermined vacuum pressure, and an argon gas replacement and pressurized argon gas inlet / outlet (20). The ring-shaped member (15) for sealing the lower chamber space (17) also has a vacuum exhaust hole (22) and an argon gas inlet / outlet (23).
Is provided. The exhaust port and the conduits for the gas inlet / outlet are not shown. The configuration of the casting part (1) used in the present invention has been described above. The difference from the conventional apparatus is that no gas-tight gasket is provided between the pedestal (7) and the lower base (12). This is because the use of the separation-type convex mold (2) described below does not require airtight shutoff between the heating chamber (4) and the lower chamber (17).

Now, description will be given of the separation type convex mold (2) which is a main part of the first structure of the present invention. Lower base (12)
Is molded from, for example, a gypsum material (11), and the upper end of, for example, a hollow alumina cylinder is protruded from the upper surface of the base (12) by a predetermined height (H) as a refractory tubular body (24) at the center thereof. The cylinder is standing upright with its lower surface flat. Thus, the lumen (25) of the cylinder (24) is a space. An envelope-shaped mold part (26) removably mounted on the upper end of the cylinder (24) is made of a magnesia-based investment material such as a refractory material generally called magnesia cement and a hardening accelerator or zirconia metal powder. It was coated or encapsulated by the added investment material. The encased mold part (26) forms a crucible (27) on the upper part, and integrally encloses a runner (28) communicating with the crucible (27) and a mold cavity (29). The protruding height (H) of the above-mentioned cylinder (24) is for positioning the metal material in the crucible (27) at the position with the highest thermal efficiency in the heating chamber (4). When the crucible (27) is placed on the cylinder (24) in this manner, the encased portion (30) is stably accommodated in the space of the cylindrical lumen (25).

Next, an example of a casting process in the above configuration will be outlined. Although the details of the vacuum evacuation system and the argon gas supply system are omitted, it should be noted that the capacity of the accumulator chamber of the argon gas supply system is several times larger than that of the heating chamber (4). After both the heating chamber (4) and the lower chamber (17) are air-tight, the pressure is reduced to about 10 ⁻³ Torr, and then the atmosphere is replaced with 0.1 kg / cm ² G of argon gas. The titanium material is melted in the gas-replaced crucible (27), and at the timing of pouring, the argon gas stored at a pressure of about 2 kg / cm ² G is injected into the heating chamber (4) at a stroke to remove the molten metal (M). It is pressurized, gas-replaced, and poured into a mold cavity (29) having no residual air or the like.
The pressurized gas pressurizes the cylindrical bore (25) through the contact portion (32) between the crucible (27) and the cylinder (24), but immediately before pouring it into the mold cavity (29). Has been completed. The above-mentioned encased mold part (26) is generally made of a magnesia-based investment material, but in some cases, only the crucible (27) is molded from an alumina refractory material having a water absorption of 0% and communicates therewith. The runner (28) and the mold cavity (29) may be covered with a magnesia-based investment material.

FIG. 2 is a longitudinal sectional view of a casting section (33) of an arc discharge type pressure casting apparatus which is one embodiment of the pure titanium or titanium alloy precision casting apparatus according to the second embodiment. The heating chamber (34) is formed in a closed state by a case (35),
The operation port (36) provided on the lateral side is closed by a viewing window (38) of the lid (37). A casting chamber (40) is provided below the heating chamber (34) via a base plate (39).
The casting chamber (40) is a casting case (42) having an upper opening.
The case (42) is pressed into contact with the base plate (39) by columns (43), locking members (44) and the like, and is hermetically sealed by an O-ring (45). A ring-shaped crucible (27) made of copper or a copper alloy is placed at the center on the base plate (39), and a mold (47) is hermetically pressed to the lower surface of the base plate (39) by a ring-shaped gasket (46). You. The mold (47) is supported on the casting case (42) by the pedestal (48) and the adjustment bolt (49). A container (50) is formed in the center of the crucible (27) in a mortar shape, a through hole (52) is formed in the bottom thereof, and a material receiving surface (53) is formed flat so as to surround the periphery. You. Mold outer part (5
Reference numeral 4) denotes an iron casting ring, and a gate (55) mounted on the upper part thereof has a center located at the center of the molten metal through hole (5) of the crucible.
Fix to the center vertical line of 2). The gate (55) is formed of, for example, a magnesia-based or alumina-based refractory material. The essential part of this invention is that the runner (28) communicating with the gate (55) and the mold cavity (29) are covered to a suitable thickness by the magnesia-based investment material obtained by adding a slight additive to the magnesia cement described above. The point is that the encapsulated mold cavity (56) is accommodated in the internal space (25) of the mold outer shell (54). When the gate (55) is made of magnesia-based investment material, the gate (55) is molded and at the same time, the runner (28) and the mold cavity (29) are covered. Returning to the heating chamber (34), an argon gas injection port (57) is provided in a part of the upper surface, and a vacuum exhaust hole (58) is provided in a part of the lower surface. Further, a vacuum exhaust hole (59) and an argon gas injection port (60) are provided in a part of the casting chamber (40). In the above configuration, the columnar material (62) is placed upright on the material receiving surface (53) of the crucible (27), and the arc discharge electrodes (63) are provided at a predetermined interval from a power supply (not shown) to a required DC. A voltage is applied to melt the material (62), but the detailed description is omitted.

An example of the casting process in the above configuration will be outlined. First, the pressure in the heating chamber (34) and the casting lid (40) is reduced, and then the atmosphere is replaced with argon gas. In this step, the inside of the mold cavity (29) is maintained in an argon gas atmosphere.
Next, the inside of the heating chamber (34) is 5 kg / cm ² G, and the casting chamber (40) is 3 kg / cm ² G, that is, the differential pressure is 2 kg / cm.
Keep to the ² G. Next is the step of dissolving the material (62).
This description is omitted, and the next casting step will be described. While the molten material in the crucible (27) is kept in an appropriate temperature range, all of them are formed as a group, pass through the molten metal through hole (52), and enter the mold through the gate (55) and the runner (28). Cast into the cavity (29). At this time, the molten material is kept pressurized by the above pressure, and its boiling is suppressed. Also, the molten material is poured at a proper speed by the pressure of 3 kg / cm ² G in the casting chamber, the casting speed is moderated, and the differential pressure of 2 kg / cm ² G and its own weight are used.

The above is an example of the embodiment according to claim 2, but the separate plate type pressure casting apparatus is not limited to the arc discharge type, but may be a high frequency induction heating type.
The heating chamber and the casting chamber described in (1) are not limited to ones forming separate chambers, but there are also apparatuses that perform heating and casting in the same chamber.
However, in each of these devices, the main part of the present invention is a configuration in which the runner communicating with the gate and the mold cavity are covered with magnesia investment material and housed in the mold interior space.

[0013]

[Effects of the Invention] Since the invention is constructed as described above, it solves the problem that the conventional phosphate-based investment material, silica, is reacted with titanium and hardens the titanium. A small titanium casting can be cast completely and with good quality by a simple encapsulant that encloses the runner and mold cavity with a magnesia-based investment material that does not react with titanium. Therefore, the step of burying the above-mentioned envelope in the phosphate-based investment material can be omitted, the material cost can be saved, the production of the mold can be speeded up, and the titanium casting efficiency can be improved.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of a casting section of an embodiment of a pure titanium or titanium alloy precision casting apparatus according to a first configuration of the present invention.

FIG. 2 is a longitudinal sectional view of a casting section of an embodiment of a pure titanium or titanium alloy precision casting apparatus according to another configuration of the present invention.

[Explanation of symbols]

 2 Separable convex mold 4 Cylindrical heating chamber 11 Sealing material 12 Lower base 17 Lower interior space 24 Fireproof cylindrical body 25 Lumen space of above 24 26 Enclosed mold part 27 Crucible 28 Runner 29 Mold Cavity part 30 Encapsulation part 34 Heating part 40 Casting part 47 Mold 54 Mold outer part 55 Gate 56 Encapsulation mold cavity part

Claims (2)

(57) [Scope of request for utility model registration] 1. A crucible (27) having an upper projecting portion for accommodating a small amount of metal material and a convex mold comprising a mold portion of a lower base (12). A cylindrical heating chamber (4) for heating and a lower chamber (17) for accommodating the mold section are provided below the cylindrical heating chamber, and the respective internal spaces are formed in a convex shape similar to the shape of the convex mold. In a device in which the heating chamber and the lower chamber are independently depressurized or pressurized to pour the molten metal in the crucible into the mold cavity (29), the crucible is formed by magnesia-based investment material, and the crucible is formed. (2)
8) and an encapsulated mold part (2) enclosing the mold cavity.
6), the above-mentioned encased mold part is removably supported, the crucible is positioned in the heating chamber at a predetermined position, and a lumen space (25) sufficient to accommodate the encased part (30) is formed. Pure titanium or titanium alloy precision characterized by providing a separate convex mold (2) comprising a lower base formed by standing a refractory tubular body (24) with a sealing material (11). Casting equipment. 2. A heating section (34) for melting a small amount of metal material contained in a crucible by a heating means, and a casting section (40) at a predetermined interval below the heating section (34). A mold (47) having a sprue (55) is provided vertically below and the heating section and the casting section are independently or simultaneously decompressed or pressurized,
In a device in which molten metal in a crucible is poured into a mold cavity, a runner communicating with a gate of the mold and a mold cavity formed by covering a mold cavity with a magnesia-based investment material. 56) and a precision titanium or titanium alloy precision casting apparatus comprising: a mold outer shell (54) for mounting the gate and forming an internal space sufficient to accommodate the envelope.