JPS6015120Y2 - Inner crucible in electric furnace - Google Patents

Description

[Detailed description of the invention] This invention is a metal denture such as a gold crown used for dental treatment.
When casting and molding metal materials, in the electric furnace used to melt the metal materials, the metal materials to be melted are placed inside a crucible made of alumina porcelain with heating wire wrapped around the outer periphery. This invention relates to improvements to the inner crucible provided.

Electric furnace crucibles used for dentistry have a carbon crucible made of carbon (graphite) inside the crucible with heating wire wrapped around the outer periphery to prevent the metal material from oxidizing when it is melted. The metal material is dropped into the bottom of this carbon crucible and melted, and when it is heated during melting, the carbon dioxide gas generated from the red-hot carbon crucible surrounds the metal material, and the molten metal material is melted. This is to prevent oxidation caused by contact with oxygen.

By the way, such an electric furnace is effective when melting precious metals that are difficult to carbonize, but due to the sudden rise in the price of precious metals, nickel chrome, cobalt chrome, etc. have recently been used as denture materials instead of precious metals. When the alloy is melted, it is easy to carbonize, and the carbonization increases the hardness as if it were burnt using a charcoal burner. It is not suitable for use in electric furnaces for melting such alloys because it causes problems such as cracking, cracking, and difficulty in processing.Instead of the carbon crucible mentioned above, a ceramic crucible can be used inside the electric furnace for melting such alloys. I am trying to use it as a crucible.

However, in an electric furnace that uses a ceramic crucible instead of a carbon crucible as the inner crucible, the carbon crucible naturally has the effect of enveloping the melted metal material with the carbon dioxide gas generated when it becomes red-hot. In order to prevent this oxidation, electric furnace There are restrictions such as creating a vacuum inside the body and replacing the air in the furnace with inert gas such as argon or nitrogen.

Therefore, the present invention solves these problems and allows the use of titanium alloys, nickel alloys, cobalt chromium alloys, etc. without filling the inner cavity of the electric furnace with zero ambient gas or evacuating the inner cavity of the electric furnace to a vacuum. The inner crucible of the electric furnace is divided into an upper half and a lower half, and the upper half is made of carbon (graphite). The lower half is made of ceramic, and the upper half made of carbon and the lower half made of ceramic are joined and bonded to form an integrated inner crucible. When melting an alloy, the alloy dropped into the inner crucible to be melted is
At the bottom of the lower half of the crucible, which is made of ceramic, melting does not take place, and at that time, the carbon forming the upper half of the crucible becomes red-hot in the upper half of the crucible inner cavity. The present invention proposes a means to prevent the oxidation of the molten alloy by filling the resulting carbon dioxide gas and carbon oxide gas.

Next, an example of implementation will be explained in detail according to the drawings.
In the figure, reference numeral 1 denotes an electric furnace, which is mounted on a body 3 of a casting machine A via a support shaft 2 whose one end is fixedly connected to an outer casing 10 of the electric furnace, and a handle 4 provided at the other end of the support shaft 2. It is supported by the body 3 so as to be freely rotated around the support shaft 2 by operation.

As shown in FIG. 2, the electric furnace 1 is equipped with a lid 12 on the top side that can be opened and closed by a hinge 11, and inside is an outer crucible 6 with a heating wire 5 wound around the outer periphery. The inner crucible a, which is covered with a heat insulating material 7 and fixedly installed, has the metal M to be melted inserted into the inner cavity of the outer crucible 6, and is inserted into the above-mentioned heating wire 5 and connected to the support shaft. This is the same as the conventionally known method in that electricity is applied from the body 3 side through the inner cavity 2 to melt the metal M dropped into the inner crucible a.

As shown in FIG. 3, the inner crucible a is divided from the upper and lower intermediate positions into an upper half 8 and a lower half 9, and the upper half 8 of the crucible is made of carbon fibers. (graphite), and the lower half 9 of the crucible is made of ceramic.

A fitting portion 8 is formed at the lower end of the upper half side 8 with the upper half side 8 made of carbon and the lower half side 9 made of ceramic.
0 and a fitting part 90 formed at the upper end of the lower half 9 and join them as shown in FIG. It is designed to constitute an inner crucible a into which it is inserted.

In addition, the inner crucible a configured in this way is used at the joint (
The fitting parts 80 and 90) may be fixed together with alumina cement, etc., but the lower half 9 made of ceramic
Because the crucible may crack if heated rapidly, it is desirable to insert the outer crucible 6 into the crucible 6 before heating it. To avoid wear and tear, it is desirable to insert the outer crucible 6 into the crucible 6 after it has been sufficiently heated. The lower half 9 is fitted into the outer crucible 6, and when the temperature of the outer crucible 6 has been raised to a sufficient temperature by heating with the heating wire 5, the upper half 8 made of carbon is inserted into the lower half 9. In some cases, it can be spliced together.

Further, the length ratio of the upper half side 8 made of carbon and the lower half side 9 made of ceramic, which constitute the inner crucible a, is
In the illustrated example, the ratio is approximately 1:1, but many types with different ratios are made.For example, when melting a small amount of metal, the lower half made of ceramic 9
When melting a large amount of metal, the lower half 9 made of ceramic is long and the upper half 8 made of carbon is long. It is desirable to use one that is distributed and formed so that it is short, and to use it properly depending on the amount of metal to be melted.

Next, to explain the function and effect, the inner crucible a of the electric furnace according to the present invention, which is configured as described above, has a metal M to be melted dropped into the bottom of its inner cavity, as shown in FIG. When the metal M is inserted into the inner cavity of the outer crucible 6 of the electric furnace 1 and the heating wire 5 is energized to melt the metal M, the metal M is located at the bottom of the lower half 9 of the crucible made of ceramic. Therefore, the melting occurs with almost no solubility, and the upper half of the inner cavity of the inner crucible a is made of carbon (graphite). Since it is sealed with carbon and carbon oxide gas G, it melts while oxidation is prevented.

Therefore, the inner cavity of the electric furnace 1 may be degassed to a vacuum, or
This makes it possible to melt titanium alloys and nickel-chrome alloys for denture casting without oxidizing or increasing their solubility, without enclosing an inert gas such as argon or nitrogen inside.

[Brief explanation of the drawing]

Figure 1 is a general perspective view of the casting machine, Figure 2 is a partially cutaway front view of the electric furnace, Figure 3 is a longitudinal sectional front view of the inner lugs before they are joined together, and Figure 4 is the joined state. The vertical sectional front view, FIG. 5, is an explanatory diagram of the operation. Explanation of drawing numbers, A...Casting machine, 1...
・Electric furnace, 10...outer casing, 11...hinge, 12...lid, 2...support shaft, 3
...Airframe, 4...Handle, 5...
...Heating wire, 6...Outer crucible, 7...
...Insulation material, M...Metal, G...Gas, a...Inner crucible, 8...Upper half side,
80...Mating part, 9...Lower half side, 90
······Fitting portion.

Claims (1)

[Scope of utility model registration request] An inner crucible in an electric furnace that is made by joining an upper half made of carbon and a lower half made of ceramic.