US3551578A - Channel type furnace for vacuum - Google Patents

Description

United States Patent 4 0 0 7 OM23 9 b%2 0 N9 l2 N 00 u 7- m h H c H r a H e n S 1 n m t e h F H m 5 5 n e d e W S m ;& mfm INV r an m m mm 9 am 6 H 9 nmh r 7 EH umww nrBooA B 0 m d w W I AF H N 7 22 [45] Patented Dec.29,1970

[56] References Cited UNITED STATES PATENTS 3,056,847 10/1962 Junker........................,.

[73] Assignee Allmanna Svenska Elektriska Aktiebolaget Vasteras, Sweden 1/1967 Junker............. 1/1968 Beckins et Examiner-.1. V. Truhe a corporation of Sweden [32] Priority Oct. 28, 1966 Sweden Primary No. 678,326, Oct. 26, 1970, now abandoned.

Continuation of application Ser.

Assistant Examiner-L. H. Bender [54] CHANNEL TYPE FURNACE FOR VACUUM 9 Claims, 1 Drawing Fig.

r [III/III IJJII T III PATENTEDnmzsmm INVENTOR. PER ERIK HAMMARWMD QENG'I'" FREVRIRSbD 1 CHANNEL TYPE FURNACE FOR VACUUM This application is a continuation of Ser. No. 678,326, filed Oct. 26, 1967, now abandoned.

BACKGROUND OF THE INVENTION 1. Field of the Invention The invention relates to a channel-type furnace for the vacuum or pressure treatment of a melt with a furnace.

2. The Prior Art U.S. Pat. application Ser. No. 452,699 (US Pat. No. 3,363,044) relates to a channel-type furnace with at least one inductor unit, comprising at least one coil, iron core and at least one loopfor melt running round the coil, which loop has two lateral channels connected to the furnace hearth and a bottom channel connected to the lateral channels. At the external side of the inductor unit is applied at least one electromagnetic stirrer. The stirrer may be applied at the bottom of the inductor unit, outside the bottom channel and/or at the sides of the inductor unit or one of these, outside the lateral channels of the loop. The inductor unit may also contain two coils and channels forming loops, a central channel between the coils, two lateral channels outside these andat least one bottom channel connecting the lateral channels and the central channel and also one or two iron cores running through the coil or coils. In this case at least one stirrer is arranged adjacent the bottom channels and/or at least one stirrer adjacent each of the lateral channels. Such an arrangement produces an effective movement of the melt in one direction and by choice of current direction the direction or pattern of rotation can be suitably varied.

SUMMARY OF THE DISCLOSURE The invention is a development of such a channel-type furnace and is characterized in that the furnace, entirely or partly with inductor units, isprovided with a vacuum and/or pressuretight lining or is placed in a vacuum or pressuretight tank, and the furnace or tank, respectively, is provided with one or more evacuation or pressure medium conduits, respectively, to evacuate the space or provide overpressure above the surface of the melt, respectively. In a preferred embodiment the stirrer, coil and/or iron core are placed under atmospheric pressure (while the other parts are placed under vacuum or pressure, respectively). It has been proved that with such an arrangement a particularly effective degassing is obtained, due to the powerful stirring effect and the fact that nearly all the melt will pass through the melt loops and be brought by the stirring forces up to or in the vicinity of the melt surface where it will be effectively degassed. Since it is possible to alter the stirring direction the vacuum degassing (pressure treatment) can be made even more effective and a particularly high quality is obtained in the treated product.

BRIEF DESCRIPTION OF THE DRAWING The drawing shows in cross section a furnace incorporating an inductor unit according to the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT The invention is exemplified in the accompanying FIG.

I which shows a double-channel-type inductor, removably attached to a furnace body 10, surrounding the melt chamber (hearth) 9. The inductor unit is of double-loop-type and provided with twin coils ll, 12 single or two-phase fed and positioned on one or two iron cores l3, 14. The loops consist of a common, central channel and two lateral channels 16, 17 connected by a bottom channel. In the embodiment shown the loop is shaped with curve channels, but of course it may also be double-rectangular. The central channel with upwardly expanded cross section and all corners in the bottom channel 18 are rounded in order to permit the melt to flow with great speed. The central channel 15 may also have a constant cross section. Below the bottom channel 18 and outside the furnace lining 19 is a stirrer 20, 21 projecting a considerable distance on both sides of the symmetry plane of the inductor unit, possibly even projecting along the sides of the inductor either completely or partly (see dotted lines). The stirrer may be a single stirrer or divided into two, 20, 21, or more parts, divided in the symmetry planeor into several sections with reversible stirring directions independent from each other. Alternatively, the inductor unit may be provided with one, two or more stirrers 22, 23 placed at the sides of the inductor or complemented by stirrers on the other sides of the inductor. The inductor unit is surrounded by a screen 24 consisting of one or more sheets of a nonferromagneticmaterial, at the same time being a good electrical conductor, such as copper or aluminum. Near the stirrer the screen is sealed to a casing 27 in a vacuum or pressuretight manner enclosing the inductor unit and is vacuum/pressuretightly connected to a casing for the furnace 28. As can be seen in the FIG, the stirrer 22, 23 is placed outside the casing so that the corona phenomenon occuring with a vacuum is avoided. The stirrer 20, 21 may either be arranged as shown inside the vacuum/pressuretight casing or be sealed to the rest of the inductor unit by an extension of the casing 27 or a separate casing (not shown).

The complete furnace has a sidewall l, with a cover 2 capa ble of being sealed gastightly to the sidewall, and a pipe 3 through which gas may be furnished to or withdrawn from the furnace. The arrangement may be varied in many ways within the scope of the following claims.

We claim:

1. Induction furnace of submerged resistor-type with a hearth and at least one inductor unit with an electric coil and at least one melt loop around the coil within the hearth casing, said loop having at least two lateral channels running from the hearth and at least one bottom channel connecting said lateral channels, said furnace and said inductor unit being closed by a vacuumtight cover to obtain a closed vacuum space, said space at the hearth being provided with at least one evacuation conduit running from the space in the furnace above the melt surface, electromagnetic stirring means separate from said electric coil outside said vacuum cover adjacent the inductor unit for producing a desired flow direction of the melt in the channels, said stirrers being exposed to the atmosphere.

2. Induction furnace as claimed in claim I in which said hearth has a downward protuberance in which said inductor unit is located.

3. Induction furnace as claimed in claim 2 in which the stirring means is at the sides of the protuberance.

4. Induction furnace as claimed in claim 3 having stirrers beneath the protuberance.

5. Induction furnace as claimed in claim 4 having a screen of nonferromagnetic electrically conductive material surrounding said stirrers.

6. Induction furnace as claimed in claim 5, said inductor unit having a common central channel, two lateral channels and a bottom channel connecting said central and lateral channels, said stirrers extending substantial distances on each side of the central channel.

7. Induction furnace as claimed in claim 4, said inductor unit having a common central channel, two lateral channels and a bottom channel connecting said central and lateral channels, said stirrers extending substantial distances on each side of the central channel.

8. Induction furnace as claimed in claim 2 having stirrers beneath the protuberance.

9. Induction furnace as claimed in claim 8 having a screen of nonferromagnetic electrically conductive material surrounding said stirrers.

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