DE1193205B - Process and system for melting and casting of materials with the highest melting point and / or highly reactive materials in the melting furnace - Google Patents

Description

FEDERAL REPUBLIC OF GERMANY

GERMAN

PATENT OFFICE

EDITORIAL

Int. Cl .:

B22d

German class: 31 c -12/02

Number: 1193 205

File number: E 24318 VI a / 31 c

Filing date: February 19, 1963

Open date: May 20, 1965

In the metallurgy of high-temperature materials as well as in the manufacture of ultra-high melting point materials Nuclear fuel, such as B. uranium carbide, the so-called skull melting process has recently become special Gained importance. It is a melting process in the electric arc furnace, in which a solid Shell of the material to be melted forms the crucible. In contrast to the industrially applied Vacuum arc melting is here the casting process separately by tilting or rotating (Centrifugal casting) of the water-cooled copper crucible carrying the so-called skull. Ever Depending on the melting conditions, this process achieves homogenization or refining and degassing, regardless of the melting speed, which is otherwise only adjustable within small limits.

In the case of combined melting and casting processes, both processes must be used in terms of equipment and operation run under the best possible conditions. In terms of equipment, optimal should essentially mean that the structural design of the furnace is not determined by the casting process, but entirely on the requirements the melting is stopped. Operationally optimal should essentially mean that Art the execution of both processes even under extreme conditions in terms of material and temperature Methods is superior.

In the skull melting process mentioned at the outset, the melting process is easy to handle, but the casting process cannot be regarded as being optimally resolved in the sense of the above definition if it involves casting thin rods, tubes and other thin shaped bodies. Special and complicated furnace designs are required; the yield is low and the possibility of varying the casting parameters, such as casting and solidification speed and filling direction, is limited. The invention relates to a method and a system for the production of thin moldings from extremely melting and / or highly reactive materials that allow melting and casting separately under optimal conditions in terms of apparatus and operation, and in which the transition from melting to casting also takes place without any inconvenience . According to the invention, the method is characterized in that the materials are melted in a known manner in a water-cooled crucible with or without a skull in a vacuum or under a gas atmosphere, but at the end of the melting process the melt, likewise in a manner known per se, is poured into a then processes and equipment for smelting and
Casting of materials with the highest melting point and / or highly reactive materials in the melting furnace

Applicant:

European Atomic Energy Community (EURATOM),

Brussels

Representative:

Dipl.-Ing. R. Müller-Borner

and Dipl.-Ing. H.-H. Wey, patent attorneys,

Berlin 33, Podbielskiallee 68

Named as inventor:

Dr.-Ing. Ernst-Günter Hess, Berlin-Lankwitz;

Marcel Louis Portal, Brebbia, Varese (Italy) - -

With the opening immersed in the bath, the mold is poured, the mold advantageously from the electrode will be carried.

Compared to the previous skull melting process and suction casting in the induction furnace The advantages achieved are as follows:

Utilization of the proven industrial vacuum arc furnace with a fixed, water-cooled Crucible made of copper for the melting and casting process. Thus: elimination of the contaminating reaction between the weld pool and crucible material, reaching the highest melting temperatures.

Utilization of the casting method through pressure difference (suction casting), but without the melting technology Limitations due to the type of heating. Thus: simple pouring device (no crucible movement), large output capacity, easy variability of the casting speed (controllability of the cast structure within wide limits), good temperature conditions during casting.

509 570/308

Combination effort for fused and cast part, electrode and mold is small. This means: Simply connecting the apparatus for the suction casting to the furnace chamber of the vacuum arc, Arc electrode in the case of a permanent electrode at the same time mold support (thus effective Preheating of the mold by means of electrical heat and radiation).

The complete system for carrying out the process accordingly consists of a vacuum arc furnace with a fixed, water-cooled crucible, one that supports the mold axially symmetrically longitudinally adjustable arc electrode, a pressurized gas container connected to the furnace vessel and - in the case of melting under vacuum or negative pressure - a pump set.

The drawing illustrates schematically an embodiment of the system with three molds; it shows

F i g. 1 the melting ^ casting plant according to the invention in longitudinal section,

F i g. 2 an arc electrode with exchangeable mold insert in longitudinal section,

3 shows an arc electrode with a shell mold in longitudinal section and

F i g. 4 shows a horizontal section through the mold according to FIG. 3 along the line IV-IV.

In Fig. 1 denotes 1 the tank of the vacuum arc furnace, 2 a possible crucible insert made of graphite, 3 the melting pot made of copper, 4 the molten bath and 5 the water cooling jacket with inlet and outlet 5 a, Sb. The arc electrode - a permanent electrode - is denoted by 6 and contains a mold-like casting space 7 of about 200 mm in height and 12 mm in diameter, it is attached in the furnace space to the electrode rod 8, which has cooling water inlet and outlet lines 8a, 8b .

The pressure vessel 9 (for example inert gas), with supply line 9α and inlet valve 9b, is connected from the outside to the furnace, furthermore the suction nozzle 10 with safety valve and separator. A vacuum pumping station (not shown) follows the separator.

According to the invention, the melting and casting process goes on so that the melt, z. B. uranium carbide, is melted by an electric arc in the water-cooled crucible, at the end of the melting process but the melt is not tipped or thrown off as usual, but by suction casting, thus creating a positive pressure difference between the melting and Kpkillenraum, driven into the mold will. For this purpose, the mold - in this case the electrode - with the opening is immersed in the bath a.

The mold is shown in FIG. 1 carved out of the electrode. This consists of electrode material, z. B. graphite, and forms a single component with the mold (mold electrode). That means, that for casting the electrode 6 with ever shorter burning arc up to the short circuit is lowered into the molten bath 4. At the same time, the pressure is increased by opening valve 9 & increased in the melting pot. Due to the pressure gradient between the melting and mold space increases then the melt in the mold and fills it out. . .

Depending on the level of the adjustable pressure difference and the likewise controllable pressure equalization speed the casting speed and even the form of solidification can be varied within wide limits. So it is possible to use thin-walled Pouring pipes in a coreless mold.

Successfully carried out tests have shown that rods and tubes made of uranium harbide fine-grained and dense cast structure with a very good

ίο carbon distribution (± 0.05% C) is achieved.

F i g. 2 shows a solution for the mold in which this is made as a separate, exchangeable insert Graphite is formed in a permanent electrode. It denotes 11 the arc electrode, 12 the Mold, 13 the melt and 14 the crucible In the lower part 12 a, the mold is closed, but it has inlet holes 12 on the side & for the melt. With the part 12 a, the mold can when Pour can be lowered to the bottom of the crucible.

While the molds shown so far only allow single casting, the mold according to FIG. 3 the multiple casting and, with appropriate changes, the casting of hollow bodies. The mold 15 is designed as a thick-walled graphite cylinder with casting spaces 15 a introduced into the wall. It is mounted concentrically and displaceably around the electrode relative to the electrode 16, ie both the electrode and the mold can be longitudinally adjusted independently of one another. The thrust member of the electrode is designated by 17, that of the mold is designated by 18. The mold is attached to the lower end of the sleeve 19 made of insulating material. The sleeve has a pressure compensation hole 19 a, which prevents melt from entering the annular space between the electrode and the mold during casting. The molten bath is denoted by 20 and the crucible by 21. The relative displaceability between the electrode and the mold also makes it possible to keep the mold sufficiently far away from the bath surface, particularly when working with a consumable electrode, so that splashes cannot get into the mold's casting spaces. You can also let the arc burn until the mold is immersed in the melt, which prevents premature cooling.

Hollow bodies can be connected to the shell mold according to FIG. 3 pour if you look at Fig. 4 all cast holes thinks supplemented to a (correspondingly narrowed) annular space. Then a mold is created with which pipes can be poured.

Claims (5)

Patent claims: 1. Process for melting and pouring also very high melting point and / or highly reactive Materials in the same furnace, characterized in that the materials in an in a known manner in a water-cooled crucible with or without a skull by means of an electric arc be melted in a vacuum or under a gas atmosphere and at the end of the melting process the melt, likewise in a manner known per se, by suction casting into a then with The mold immersed in the bath of the opening is poured, the mold being advantageous from the electrode is worn. 2. Plant for performing the method according to claim 1, characterized by a Vacuum arc furnace with fixed, what- water-cooled crucible, one that is longitudinally adjustable and carries the mold axially symmetrically Arc electrode, a pressurized gas container connected to the furnace vessel and if necessary a pump set. 3. Plant according to claim 2, characterized in that the mold made of electrode material (Electrode mold) is made and represents a recess in the electrode tip. 4. Plant according to claim 2, characterized in that the mold is replaceable Insert is formed in the electrode tip. 5. Plant according to claim 2, characterized in that the mold is a thick-walled cylinder (Shell mold) is formed with casting spaces incorporated into the wall and is concentric is mounted on the electrode rod, with mutual relative displaceability. 1 sheet of drawings