JPS59197370A - Pressure casting device by high frequency melting - Google Patents

Abstract

PURPOSE:To enable easy pressure molding of various embedding materials by constituting a projecting mold for casting of a mold base part having a crucible bottom, and placing and engaging freely separably a short pipe-shaped body forming a crucible side wall on the crucible bottom. CONSTITUTION:A projecting mold 30 for casting is constituted of a mold base part 31 including a precision mold part 3 formed of an embedding material 6 and a sprue 4, and the height h1 in the upper projecting part 32 is made to about 1/2 of the overall length of a high-frequency heating induction coil 23. A funnel-shaped crucible bottom 33 is formed at the top end thereof. A refractory cylindrical short pipe-shaped body 35 having the fire resistance equivalent to or higher than the fire resistance of the part 31 is freely attachably and detachably fitted to the concentrical fitting part 34 provided at the circumferential edge of the bottom 33. Various embedding materials 6 are thus easily molded and the casting amt. thereof can be increased as desired. The body 35 after completion of casting is thoroughly strippable of a molten metal 36 on account of a difference in the coefft. of expansion.

Description

DETAILED DESCRIPTION OF THE INVENTION This invention involves casting metal melted by high-frequency induction heating in a vacuum atmosphere, inert gas atmosphere, or atmospheric pressure into a mold placed in the same atmosphere, This invention relates to a high-frequency melting and pressure casting apparatus for manufacturing small precision castings for dental or industrial use.

Among the high-frequency casting equipment conventionally used for casting high-melting point alloys such as gold or silver alloys, nickel-chromium alloys, and cobalt-chromium alloys that have excellent properties as dental prosthetic materials, equipment that uses a continuous pressure casting method is centrifugal. Separate volume containing casting ``Compared to melting casting equipment, the crystal grains of the cast product are finer, the shape of the dendrites is irregular, the growth direction is irregular, there is no directionality, and the casting surface is rough. It is smooth and widely used as a dental dipping device. Fig. 1 is a longitudinal cross-sectional view showing the main parts of an example of the conventional continuous pressure casting apparatus mentioned above. -(3) The gates (4) and 4 are molded into one piece using phosphate-based investment material (6), and the upper protrusion, that is, the crucible part (2), is made of quartz glass. accommodated inside the cylindrical body (7), that is, in the heating chamber (7R),
In addition, the lower base of the convex mold, that is, the part (8) including the above (3) and (4), is covered with asbestos ring 0 on the mold holder (9).
It is supported through 0. This mold pedestal (9) is pushed up from below with a preset pressure ωU) by, for example, a compression spring (2) or a pneumatic cylinder piston (not shown), and the mold lower base (8) is pushed up into the asbestos backing. Upper cover α made of asbestos molding material
4). The top lid 04) is airtightly connected to an annular lid OQ made of metal that engages with the device base OQ, so the heating chamber (7R) is an air-opening part where the mold holder (9) is located. However, the surroundings of the mold base (8) are separated, for example, from 10' to 1['Torr].
The dotted line indicates the case where the efficiency of enema is improved by reducing the pressure to 1Kg/CM-2G and replacing with an inert gas such as argon. The inside of the lower chamber (A) is separated from the heating chamber (7R) by the exhaust pipe/gas inlet/output pipe I: IfJ) 01), which is in pressure contact with the annular lid Qf9 and indicated by the arrow, and is independently pressurized. and gas replacement.

A high frequency induction heating coil (
C) is wound around the heating chamber (7R), and a viewing window (2) is provided to seal the upper end of the heating chamber (7R). c) and a gas conduit (to) for introducing and discharging a pressure source such as pressurizing argon gas having a pressure of about 5 kg/lyi G.The above describes the casting part of the conventional high-frequency melting and pressure casting equipment. Since the mold pressure welding mechanism is not directly related to the present invention, illustrations and explanations are omitted.7 By the way, the above convex mold (
As mentioned above, 1) is usually integrally molded with an investment material (6) such as phosphate or stone bone, and like the former investment material, the compressive strength when hardened is approximately i.
In the case of large materials such as 4oxg/i, molding is easy, and the crucible part (2) of the convex mold is made large.
Although molding is possible even if the upper protrusion is made higher, this phosphate investment material has the disadvantage that the metal to be melted is almost limited to nickel-chromium alloys or cobalt-chromium alloys. The latter gypsum investment material is pressed as described above. In addition, there are cristobalite-based investment materials, which are metastable crystal forms of silicic acid suitable for melting and casting gold and silver alloys, and high-melting-point investment materials mainly composed of magnesia or zircon, which are essential for melting titanium and titanium alloys. The former hardens at a low firing temperature but has extremely low compressive strength during hardening, while the latter requires a high firing temperature and has high hardness after hardening, but both crumble easily, as shown in Figure 1. There is a drawback that a convex mold having a complicated shape having a thin wall portion such as a crucible peripheral wall cannot be easily formed.

This invention was made in view of the above-mentioned current situation, and is applicable to a wide range of molten materials from precious metals to non-metals used in dental prosthetic materials. Alternatively, the bottom of the crucible is formed only on the upper protrusion of the mold base, which has a simple shape that can be easily fired and molded using any type of zircon-based investment material, and has a fire resistance equal to or higher than that of the mold investment material. A high-frequency melting and pressure casting apparatus characterized in that the mold is a composite convex mold in which a crucible part is formed by placing a cylindrical member, such as quartz or borosilicate glass, on the bottom of the crucible. This configuration facilitates the firing and molding of various types of investment material molds that can accommodate a wide range of molten metals, and improves casting capacity by increasing the capacity of the crucible. The purpose is to provide a convenient device that can be used repeatedly and reduce casting costs.

The present invention will be explained in detail below with reference to the drawings. FIG. 2 is a partial side sectional view of the fishing mold part of the inverted frequency melting and pressure casting apparatus according to the present invention, and parts with the same symbols as those in FIG. 1 will not be described in detail. Unlike the conventional mold ((1) in Fig. 1), the convex mold (2) has a mold base (31) that includes a '#tve mold part (3) formed of investment material (6) and a sprue (4). is its upper protrusion (
The height (h) from the top surface of the base OD of (to) is the total length of the high-frequency heating induction coil (c), which is wound, for example, 7 to 10 turns around the outer periphery of the heating chamber. The bottom of the crucible (T) is formed in the shape of a shape.This is because the center part of the full length of the High Frequency Heating Induction Coil (O) has the best heating efficiency, reaches a high temperature, and melting occurs from that part. Next, the concentric fitting part (b) provided on the periphery of each of the funnel-shaped bottom parts 1, that is, the part consisting of an annular plane and a barrier surrounding the plane, is placed from above on the short tubular body ( C) is made of a refractory material with a wall thickness of about 1.5 mm, for example.

This refractory material is a refractory cylindrical material such as borosilicate glass or refractory ceramics that has excellent heat resistance and can withstand sudden changes in temperature. As mentioned above, the mold base 61) and the short tubular body ζ4 are simply placed in a predetermined position and no special joining means or molten metal leakage sealing means are required, and this is the combined method of the present invention. This is a major feature of the mold. This is the pressure casting method, for example, 5kg
When argon gas with a pressure (Pd) of /iG pressurizes the molten metal (T), the gas at the same pressure (p, lL3) also acts on the outer wall of the short tubular body, so no leakage occurs. Moreover, after the completion of casting, the short tubular body (to) completely peels off the molten metal cJ4 due to the difference in its expansion coefficient, so it can be reused repeatedly.In the figure, it engages with the mold holder (9). (2) is a universal joint on the upper part of the piston rod (G) of an air cylinder as a lower drive mechanism of the mold pedestal (not shown).The push-up pressure (Pu) of the air cylinder is The structure of press-fitting the heat-resistant banking 03 to the top cover 04) and maintaining airtightness against the casting pressure (Pd) is the same as that of the conventional device.

Next, another embodiment of the convex mold used in the apparatus according to the embodiment of the present invention will be explained with reference to FIG. In the figures, those with the same symbols as in Figures 1 and 2 will not be described in detail. It is known to use a metal ring on the outer diameter of the mold in conventional casting equipment, but as in this example, gold NIJ ring is used on the outer periphery of the mold base of the convex mold (7). This is a new attempt, and in contrast to the conventional problem of placing such a metal ring relatively close to the high-frequency coil, we have experimentally confirmed that there is no electrical loss. Mold base (31) after molding and baking hardening
Not only does it easily prevent brittle fracture and chipping, but it also allows investment materials containing magnesia or zircon to be used as molds without having to be fired to a fully hardened temperature of 1350°C, and the product can be removed after casting. becomes significantly easier.

Although the embodiments of the present invention have been described above, it goes without saying that the present invention is not limited to the illustrations and descriptions. For example, the materials of the mold investment material and the short tubular body may be other than those described above, and the structure of the casting section of the casting apparatus is not limited to that shown in the drawings, but may be of any type as long as it is a continuous pressure casting method. Of course, the mold pressing mechanism is not limited to a fixed heating chamber type, but may be a movable type in which the heating chamber descends from above together with its partition wall, and the pressing force source is not limited to air pressure or a spring.

This invention is constructed as described above, and it improves the drawbacks of the conventional high-frequency melting and pressure casting equipment, particularly the difficulty in creating a mold. The new concept of forming a mold base and crucible separately, which are easy to mold, and forming a convex mold by fully connecting them, allows various investment materials to be molded easily and the amount of casting to be increased freely. 7. It has been possible to provide a convenient device that improves casting efficiency and can reduce mold production costs because the refractory short tubular body of the crucible portion can be reused.

[Brief explanation of the drawing]

FIG. 1 is a partial cross-sectional view showing the configuration of the casting section of a conventional high-frequency melting and pressure casting apparatus, and FIG. 2 is a portion showing a convex mold of a high-frequency melting and pressure casting apparatus according to an embodiment of the present invention. FIG. 6 is a partial sectional view for explaining a convex mold of another embodiment of the present invention. 7...Cylindrical body 7R...Heating ¥9, 12, 37
・38... Mold pressure welding mechanism 14... Partition wall 23.
... High frequency induction heating coil 25 ... Vacuum suction tube 26
... Inert pressurized gas conduit filter 6 ... Crucible bottom 34
...Engaging part 35 at the bottom of the crucible...Short tubular body;', ), (11) Fig. 1 F''''P+, t

Claims (1)

[Claims] It has a convex mold having a crucible part in the upper protrusion part and a mold part in the lower base part, and a cylindrical body that accommodates the protrusion part therein, and a high frequency induction heating coil is wound around the outer periphery of this cylindrical body. , and a heating chamber to which a vacuum suction pipe for decompressing the internal space of the cylindrical body and a conduit for introducing and discharging a pressure source such as an inert pressurized gas are connected to the convex mold base and the heating upper opening hole is connected to the heating chamber. In the high-frequency melting and pressure casting apparatus, the high-frequency melting and pressure casting apparatus is equipped with a mold press-contacting mechanism that hermetically press-fits the lower surface of the partition wall, comprising: a short tubular body forming a crucible side wall capable of separating the convex mold from each other; and a mold base having a crucible bottom. The short tubular body is made of a material having a fire resistance equal to or higher than that of the mold base material, and the short tubular body is placed and engaged with the crucible bottom of the mold base. High frequency melting and pressure casting equipment.