DE1202918B - Electron beam furnace - Google Patents

Description

FEDERAL REPUBLIC OF GERMANY

GERMAN

PATENT OFFICE

EDITORIAL

Int. α .:

H05b

German class: 21h -16/60

Number: 1202 918

File number: St 17796 VIII d / 21 h

Filing date: May 8, 1961

Opening day: October 14, 1965

Electron beam furnace

Applicant:

Stauffer Chemical Company, New York, N.Y.

(V. St. A.) Representative:

Dipl.-Ing. Dr. jur. V. Busse, patent attorney,

Osnabrück, Möserstr. 20/24

Named as inventor:

Hugh Roscoe Smith Jr., Piedmont, Calif.

(V. St. A.)

Claimed priority:

V. St. ν. America May 27, 1960 (32,215) - -

The invention relates to cathode ray tubes for heating materials by electron bombardment in a high vacuum and in particular for melting materials and casting ingots from them, with a cleaning 5 effect, an exceptionally high degree of degassing effect and other advantages.

It is known that materials in a
Electron beam furnaces have been processed, extraordinary and mostly highly advantageous properties
ten because in these ovens a cleaning effect and an exceptionally high degree of degassing effect is achieved. With the ovens known so far, the most varied
Materials satisfactory from a technical point of view 15
processed, and in terms of relative
expensive materials which are difficult in other ways
are to be processed, reasonable costs can be expected, but the economic expansion of the process for other 20
Purposes continued to require ever larger ovens and
an ever longer uninterrupted operating time _

the ovens. These goals are not easy to achieve. ■ *

In particular, cause increases in the furnace gressiv betref- through the lower end of the mold in Geabmessungen growing problems 25 _s Told an ingot of ever increasing fend focusing and control of the length to be deducted. An electron gun with a stronger electron beam current, in particular, sends an electron beam downwards into the upper end of the casting mold, which is open when larger quantities develop, and bombs the gaseous substance from the melting material in the material, so that there is constant rial. The length of the uninterrupted upper end of the solidifying ingot, the material operating time, can be maintained by the instability of the molten elec- tronic fluid in the form of a small sump and in particular by changes. Preferably, the material to be melted in the electrode configuration, emission-specific material, is supplied progressively, that is to say limited on one side of the shaft and the like. Such changes in the electron beam, so that the marions to be melted are melted by the accumulation of deposited material supply to the extent that it is advanced in the electrode material on the electrode as a result of the condenser beam. The absation of the evolved gaseous substances, molten material falls into the open upper end which consists of both volatile impurities and the casting mold and continuously supplements the steaming of the processed material as well as molten material from the molten material located there, and 40 in the sump .

caused by other causes. It is already known to use electron-optical systems, equivalent to a light-optical prism, for deflecting and guiding electron beams. If it is the figure 45 of approximately point-shaped sources, z. B. in electron microscopes, image scanning tubes, electron multipliers, mass spectrographs and the like, magnets are used for this purpose perpendicular to the direction of propagation of the electron beam in the form of a tubular, water-cooled pouring fields,
has shape and at its upper and lower According to the present invention is for additional

The end is open. The solidified material can prelent bundling and guidance of the electron

509 717/338

The present invention provides an improved electron beam furnace that is suitable for larger scale processes and is suitable for longer uninterrupted periods of operation.

Electron beam melting and casting furnaces essentially consist of a continuously evacuated one Tank in which there is a container for the molten metal, generally

3 4

radiate into the upper opening of the container protected in an outer, metal shell 8, known way a magnet in the immediate vicinity The wire lines 9 and 10 connect the coil with

this opening is arranged so that lines of force of its the direct current source 11 in series with a rheo-

Converge magnetic field in this upper opening. stat 12, so that the coil with exciting DC

The magnet is preferably a ring-shaped electric current of adjustable strength can be supplied, tromagnetic coil, which is coaxial around the The magnet created in this way generates a magnetic field

Extends container around. The electron gun, of adjustable strength with a vertical axis of symmetry

preferably also has an annular shape, and with magnetic lines of force extending into the upper

compared to the diameter of the casting mold, in the opening of the casting mold 1, as indicated by the dash-dot

relatively wide distance above the upper opening of the io-oriented lines 13 of FIG. 2 shown, in-

Casting mold arranged, and the electrodes of the converge.

Guns are shaped and aligned so that the ring-shaped electrode gun is vertical Electrons are ejected on paths that are aligned over the upper opening of the casting mold 1 are parallel to the magnetic lines of force. In and preferably from this in a relative to As a result of their distance, the electron gun has a large distance from the casting mold relatively little among the harmful influences of the gas- purposes of reducing the harmful influence Shaped substances suffer from the melting of the evolving gaseous substances developing and molten material. That arranged the cannon. The electrode gun around the magnetic field bundles and directs the cannon grabs in its preferred embodiment electrons coming into the upper opening of the 30 ring-shaped, thermionic cathode 14, mostly Casting mold into it, although the gaseous substance consists of a horizontal loop of tungsten wire arising from the melting and molten and through lines 15 and 16 and a TransMaterial has developed a dense ion cloud in formatorl7 with an alternating current source 18 verdem Space which is traversed by the electron beam, the alternating current through the wire 14 is crossed, generated. In addition, the electro- 35 to heat it to the thermionic emismagnetic stir Forces the molten material delivers in sion temperature. The acceleration elecdem The sump in the upper part of the mold vigorously trode 19 is arranged just below the cathode 14, through, causing the delivery of the volatile connection and a focusing electrode 20 is just over impurities is supported and other advantages of the cathode 14 arranged as from the drawing can be achieved. 30 can be seen. Electrical connections are the foregoing aspects of the invention and are still provided to ensure that the accelerator are essentially on the same spelling as the following explanatory leveling electrode 19 In connection with the drawings, there is still an electrical potential like the casting mold 1, more clearly understandable. preferably at ground potential. This is Fig. Figure 1 of the drawing illustrates a schematic 35 in the drawing schematically through the ground connection view a vertical section of an improved training symbols at 21 and 22 indicated. the Electron beam furnace; Cathode 14 and focusing electrode 20 wer-F i g. 2 is a partial view of the vertical section held at much more negative potentials; of the same furnace, which usually draws 5000 to 15,000 volts on a somewhat larger scale than the Schleu It shows the typical 40 magnetic tilt electrode. This can be achieved e.g. B. Lines of force and the trajectories of electrons. by means of the connection 23 between electrode 20 In the drawings is a tubular copper and pipe 16 and connection 24 between pipe shape with a vertical axis denoted by 1. They be 16 and the negative pole of the high tension sits open top and bottom and is connected to DC power source 25.

a water jacket 2 through which 45 The overall design of the electron gun can be water or some other coolant by itself similar to that which is continuously described in the German known means (not shown) by patent application St 16459. When the flow can be allowed to flow, so that the casting mold lying furnace, in which a magnetic field is cooled and the molten Ma- steering of the electron beam located therein is used, are materially solidified. Other parts of the 50, the cathode, the accelerating electrode and the furnace, can, if so desired, be water-cooled with the water-focusing electrode so shaped and aligned. Since this can be done by self-evident that the electrons parallel to the converging lent means, magnetic lines of force are directed downwards and inwards a referring precise description, so that a hollow, cone-like exercise. The solidified material can be formed by the open 55 converging jet. The magnet lower end of the casting mold 1 progressively in the form field plays in the sequence when focusing and a cast ingot 3 of continuously increasing length directing the electron beam into the upper opening. This ingot can play a significant role from time to the mold 1,
to be cut off at will. The A horizontal feed trough 26 extends progressively withdrawing the ingot can, for. B. 60 inside over the mold 1, which an outlet end by the rollers 4, which are driven by the electric motor 5 26 'in the vicinity of the upper opening of the mold, are made. having. This feed trough (and also its in-As can be seen from the illustration, extends stop) is electrically grounded, as is indicated by the usual ring-shaped electromagnetic coil 6 ko symbol at 27. That which is to be melted axially around the casting mold 1. Your vertical 65 material 28 can be in any suitable shape, ie in axis concentric with the upper open form of bars, billets, blocks of the pressed end of the mold. This coil is preferably powder, etc. through the trough 26 on one side of the by means of an inner insulating layer 7 and an electron beam that penetrates into the mold 1,

are fed. The feed mechanism is difficult to work with, and a lower bar symbolic through the rollers 29, which is the result of the electrical quality.

tromotor30 are driven, shown. As soon as the evolving gases, which ionized subsich the material to be melted from the outlet punch and even plasma advances when using the opening of the feed trough, it is only bombarded by the electron beam and has a small effect on the magnetic guide described above Electron trajectories, melted. The material liquefied in this way The electron beam remains well formed and material falls into the upper end of the casting mold 1 and fills sharply into the upper open end of the casting mold 1 continuously a sump 3 'of focused molten material. The material supply to be melted is material which is located at the upper end of the casting i ₀ at a precisely defined and well barred 3 and which is from a depression or agreed level at the edge of the electron beam, which is automatically cut into the solidifying, and it can therefore be worn as the ablative material forms. Share exactly by simply checking the

The magnetic guide that this invention feeds the supply of material to be melted into provides, requires several significant advantages, 15 direction to the electron beam can be mastered, which crucially affects the operation of the furnace Apart from the considerations above and the implementation of the process in were carried out, enables the magnetic guidance, larger and more economical scale during operations as described here in longer periods of time without interruption allowed. larger scale with larger ovens, those with height-at Large scale operations can operate on larger electron beam currents, and also can operate in bulk evolved from a gaseous substance, it enables the elecvass to be more distant usually in irregular proportions of a barrel cannon, which means a longer service life he follows. The gas evolution occurs in particular from and longer periods of an uninterrupted product Melting material at the inner end of the process is allowed because the action of the dispersing melting material supply and, to a certain extent, effects of the electrical space charges by the also measured from the pond with molten Ma- Effect of the magnetic field largely austerial 3 'at the top of the ingot. The largest is switched. The electron gun is a preferred part This gaseous material condenses in such a way that the electrons that are somehow condensed on the first relatively cool surface, with part of the cannon left, in exactly parallel which it comes into contact, and in some cases 30 orbits are steered. The electrons collide However, even the hot cathode 14 can cool one another sufficiently, and it therefore has every part of the Surface represent that condensation is occurring. conical beam striving to be in his Any greater accumulation of deposited ma thickness with increasing distance from the cannon materials on the electrodes of the cannon but leads to expand, as shown in FIG. 2 is shown in soon to faulty work of the cannon, hence which the hatched areas between the lengthens the more distant placement of the cannon, lines 31 and 32 and between lines 33 and what, through the magnetic guidance, actually represents the space made possible by the beam is, to a very high degree, the lifespan is filled.

of the cannon when it is removed from the regions The spreading of the beam segments, however, requires

where the gaseous substance is most likely to cause certain electrons to move in directions

is centered. which are not exactly parallel to the magnetic field, and

In addition, the evolved gaseous form ionizes the resulting electromagnetic

Substance and can form plasma, which is responsible for the forces bend the electron orbits in such a way that the

Focusing necessary electrical potential electrons like a corkscrew around the magnetic ones

fields seriously disturbs. Using the oven at hand, circle 45 lines of force. The electron orbits

the electrons within a short distance are therefore everywhere really parallel to the ma-

from the cathode, d. H. kept approximately at the same distance from the magnetic field and must match the field

the cathode 14 to the electrode 19, substantially converge. This limits the spread of the

accelerated to full speed, and forth- beam, and the stronger the magnetic field, the more

After the trajectories are mainly through 50 the spirals become more dense and the more the

dominated the magnetic field, even if the path of propagation was restricted. By adjustment

Electrons through highly conductive plasma regions through the rheostat 12 and through the resulting

performs which the electrons from their desired adjustment of the magnetic field strength can

Otherwise deflect trajectories. Without the total cross-sectional area of the beam entering the

In particular, the gases entering the upper opening of the casting mold 1 tend to be regulated in this way

are developed from the melting material, that the beam is straight on the melting

to do this, the electrons from the molten sump 3 'liquid sump 3' falls, so that the heat supply too

to the material supply 28 to be melted takes place in an almost ideal way. Even

steer so that the melt plane and the crowd- a weak magnetic field can create a much stronger one

proportion of the melting material supply 60 electron flow into the upper opening of the casting mold

it is not easy to control what is the reason to steer, as this is otherwise because of the beam spread,

faulty way of working. In addition, one of the inevitable consequences of electrical space

Such distraction the development of a cool charge would be possible.

Spot in this part of the molten pond. The magnetic field has another advantage

below and in close proximity to the outlet end of the 65 with it; the electromagnetic forces,

Feed troughs cause what is sometimes called by the electrical currents in the

stand can lead to the fact that these parts of the sump 3 ', which move non-parallel to the field,

To freeze over the pond. This results in further ar- produce namely a powerful stirring effect in the

melted swamp. This agitation is of exceptional benefit because it attracts impurities brings the surface of the swamp, from which they can evaporate unhindered.

It is important that there is space between the electron gun and the upper opening of the mold 1 is kept under a high vacuum, preferably 1 micron mercury absolute pressure or less, and that requires continuous evacuation with heavy duty pumps to get the gaseous To remove substances that are plentiful and disruptive during a large-scale process to be developed. For this purpose, the mold, the electron gun and the associated Parts enclosed in a vacuum tank 35, through a large cross-sectional line 36 is connected to high-performance vacuum pumps 37. Suitable air locks (not shown) can if so desired, for the introduction of the material supply to be melted, for the removal of the Cast ingots for the replacement and manipulation of the electron gun and the like are provided. the Evacuation is also aided by the condensation of the vapors on the walls of the vacuum tank and other cool surfaces.

It is emphasized that the present invention relates only to electron beam furnaces and that the particular embodiment described is merely an example of how the present one Invention can be carried out in such ovens.

Claims (4)

Patent claims: 1. Electron beam furnace with a container for molten material with an open top End, with an electron gun located above, remotely from the container, which has a converging Electron beam into this upper opening of the container for bombardment and heating of the molten material located therein, and with a continuously evacuated tank, at least the space between the electron gun and the container encloses in which an absolute pressure of about 1 micron Hg or less is maintained is, characterized in that for additional focusing and guiding the electron beams into the upper opening of the container in a manner known per se, a magnet (6, 11, 12) in the immediate vicinity of this opening so is arranged that the lines of force of its magnetic field converge in this upper opening. 2. Electron beam furnace according to claim 1, characterized in that said magnet consists of an electromagnetic coil (6) which extends around the container (1), and its vertical axis substantially concentric with the upper opening of the Container is that the coil (6) is connected to a direct current source (11) for the purpose of power supply is and that means (12) are provided to regulate the strength of this current and serve to focus the electrons to a beam of controllable cross-sectional area, so that the electron beam enters the top opening of the container. 3. Electron beam furnace according to claim 1 or 2, characterized in that the used Electron gun consisting of an annular thermionic cathode (14) that extends vertically across the open end of said container is arranged, an accelerating electrode (19), which is arranged just below this cathode, a focusing electrode (20) which is just above this cathode is arranged, means (21, 22) that this accelerating electrode and the container maintained at substantially the same electrical potential and means (25) that said The cathode and the focusing electrode are at a substantially negative electrical potential with respect to the acceleration electrode hold, and that the focusing electrode and the cathode as well as the accelerating electrode are so shaped and aligned that a downwardly directed, hollow, inwardly converging cone-shaped Electron beam (31, 32, 33, 34) is formed, which is essentially parallel everywhere to the mentioned converging magnetic field. 4. Electron beam furnace according to one or more of claims 1 to 3, characterized in that that the known feed trough (26) has an outlet end (26 ') in the vicinity of the has upper opening of the container (1) and that feed means (29) are provided which the material to be melted through this trough into the electron beam that enters the container, feed on one side of the electron beam. Considered publications:
U.S. Patent Nos. 2,727,936, 2,880,483;
Engineering, 1960, pp. 556/557. 1 sheet of drawings 509 717/338 10.65 © Bundesdruckerei Berlin