In this article we will discuss about the design of core and coreless induction furnace. An improved form of core type furnace is Ajax-Wyatt vertical core type . ea1 ring induction type. CONSTRUCTION. OF FURNACE. The vertical-ring ioduction furnace makes use of the pat- sented Ajax-Wyatt heating element. VERTICAL CORE TYPE INDUCTION FURNACE Also known as AJAX-WYATT FURNACE. Vertical crucible is used for the charge. Bottom is usually V-shaped or .
A purpose of my invention is to improve the stirring in a submerged channel electric inductlon furnace. To overcome this difficulty, core type induction furnace is operated at a very low frequency say 10 Hz.
The “kicking” is due to vaporization of zinc, which breaks the electrical circuit through the submerged channel and causes momentary cessation of heating. Standard sizes of these furnaces are 60 — KW, single phase 50 Hz working at volts.
The Ajax‐Wyatt or Vertical Ring Induction Furnace
It will be evident that the temperature differential between the pool and the channel will be maintained whatever the temperature of the pool and cannot be equalized by merely operating the furnace longer to increase the pool temperature since molten metal flowing down from the pool at the higher temperature will again be increased in temperature by reason of the unnecessarily reduced flow of metal in the channel.
Pinch effect flow, due to the tendency of current in different parts of the same molten conductor to constrict the conductor and to cause ‘5 molten metal to flow upwardly along the middle of the channel has been considered in the above discussion, but has not been discussed before nor further than is herein explained for the reason that the elimination of counter-pressures along the outer walls of the channel, provided by my invention herein, is highly beneficial whether pinch effect be weak or strong.
The angle 44 of the V, which is the angle between the adjacent straight portions of the branches of the channel, may vary from the angle shown in Figure 2. In the present invention, primary-on-secondary stirring still tends to send the charge in both directions along the channel from the point of concentration of flux, but this point is now the point 39 at which the branches of the channel meet, the same point at which the secondary-onsecondary forces are concentrated and from which they spring, and both stirring effects combine to send charge up the outside of each branch, no longer bucking one another.
In the drawings, like numerals refer to like parts.
The use of core-type transformers about the points of angles in submerged channels has been attempted in which the point of the angle of the channel is directed toward the pool. It will be understood that these are examples merely, and that considerable variation can be made in the type of contour used.
Aside from the theory, I find that the practical results obtained by my invention are highly desirable, in quicker and more efficient heating, better stirring and much longer life of the-refractory in the submerged channel. Circulation is of great importance in submerged channel electric induction furnaces, not only because it is relied upon to convey heated 43 charge to the pool of molten charge, but because, without adequate and properly controlled circulation, the charge in the molten conductor will reach an abnormally high temperature at which attack upon the refractory lining of the channel will be more rapid, at which vaporization of charge in the channel may occur and at which other undesirable effects of overheating may be observed.
Induction Heating | Ajax Wyatt Furnace – your electrical guide
At most it will make circulation a little easier by clearing metal out of the way along the outer wall of the channel from a point at which circulation has already begun to be easier to effect by reason of the flaring of the channel.
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Figure 7b is a view corresponding to Figure 7, and illustrating another variation in channel cross section. Alert me to new issues of J. Likewise, the transformer core 47 is protected by the refractory material, and may indudtion artificially cooled if this be deemed necessary. In the prior art, the general practice has been to construct a submerged channel electric induction furnace as illustrated rurnace Figure 8, furmace the coil between wyaatt branches of the channel surrounding the middle leg of a shell-type transformer core, whose outer legs are each jaax the channel.
The submerged channel is heated by electric current induced in it from the primary coil The results of the tests made upon my invention are remarkable and convince me of the commercial feasibility of the furnace of my invention; not only for alloys of lower melting point, including brass relatively high in zinc, such as red brass, copper, but also for iron and steel.
Ajax Wyatt Vertical Core Furnace is used for melting and refining of non-ferrous metal like brass, copper and zinc.
The attempt to use the core-type transformer about re-entrant angles amax above has not produced the advantage nor the flow relations of my ajwx invention. This is not wholly 6o true as the ultimate circulation in the lower part of the channel may be so nearly stagnated before the molten metal gets up to wyat medial line of the transformer that the chief effect of the primary-on-secondary pressure above the medial line will be to cause local circulation from this medial line up to the pool and back again.
In an electric induction furnace, a crucible, walls forming a single-conduit submerged chan- 3s nel extending laterally from the crucible, communicating at its ends with the crucible and having an angle whose point is directed away from the crucible and transformer means for concentrating flux at the angle including a core linking the channel with one leg adjacent the angle and a transformer coil within the angle which coil affords the sole energization for the transformer.
It is by virtue of the V or the angle having its point directed away from the pool that secondary-on-secondary furnaxe is so greatly accentuated. The walls of the channel curve at 54 preferably around the same axis of curvature as that of the coil, and the straight portions inducion and 58 of the branches 37 and 38 of the submerged channel are preferably tangential at 57 to wyaatt curved portion The present invention applies to submerged channel furnaces having angles in the firnace whose points are directed away from the pool, whatever the cross sectional contour of the submerged channel and the contour is therefore not specifically claimed in this application.
In addition to secondary-on-secondary stirring, there is primary-on-secondary stirring in an electric induction furnace of the type under discussion. Without repeating, in the description of the aiax of Figures 5 to 7b, inclusive, the parts already described in relation to Figures 1 to 4b, inclusive, it will be evident that the channel 38′ as seen in Figure 6 need not be of exactly the same contour as the channel 36 of Figure 2. For example, in Figure 2a the angle 44′ of the V is an obtuse angle rather than an acute angle as shown in Figure 2, and any type of angle between an extremely obtuse angle and a very acute angle may be used, provided the angle point faces away from or is directed away from the pool, and does not reach or greater for reasons later explained.
Another disadvantage of this furnace is that a crucible is of inconvenient shape from the metallurgical point of view. Due to the secondary-on-secondary stirring, there is a tendency to cause molten metal to flow upwardly from the whatt 39 along the outside of the channel in each branch toward the pool as indicated by the arrows 64, and to permit molten metal to flow by gravity down the inside of the channel from the pool as indicated by the arrows 66, to replace the upwardly flowing molten metal.
The charge is given from above and the molten metal is taken out through the spout. My electric wywtt furnaces are- ordinarily used to melt metals and alloys and. The induction heating may be low frequency as in the case of core type wyat furnace or high frequency as the case with coreless induction furnaces. In an electric induction furnace, a crucible adapted to hold a charge, inducyion forming a submerged channel depending from the crucible, communicating at its upper ends with the crucible and having a V-bend whose angle point is directed away from the crucible, a closed rectangular transformer core surrounding the Vbend, having a first side extending transversely of the plane of the channel above the V-bend, a second side parallel to the first below the Vbend, and third and fourth sides joining the ends of the first two sides, there being but one channel conduit within the transformer core, and electrically energized means including a coil furance said first side and comprising the sole energization of the core to set up lines of magnetic force in the magnetic circuit having a maximum at the angle.
The essential features of Figures 5 to 7b, inclusive, are, however, the same as those of Ayatt 1 to 4b, inclusive.
No attempt has been made to indicate where individual laminated plates end and others begin in making up the core. In an electric induction furnace, a crucible, walls forming a V-shaped single-conduit channel nearer to one side of the crucible pool than to the other side, communicating at its ends with the lower part of the crucible and having the point of the angle extending away from the crucible and a transformer having a rectangular core surrounding the bend of the V and having its sole excitation from a coil surrounding one leg of the core and inside the V.
The force indicated by the arrow 69 directly helps to move molten metal toward the pool, but the force represented by the arrow 68 tends to move molten metal toward the point 39 where the branches of the channel meet.
In both forms, likewise the coil surrounds the core and is located between the branches. This causes secondary-on-secondary flow along the inner 3o channel walls at the angle directly opposing gravity return flow from the primary-on-secondary circulation. Yet another disadvantage is that it requires low frequency 10 Hz supply which requires frequency changer, which involves extra cost.
The charge is heated by a submerged channel 36 having branches 37 and 38 meeting at 39 in an angle whose point is directed away from the pool This results in a tendency of the molten charge to flow in both directions in and out through the channel away from the ‘points 66 of high leakage field intensity. While the theory above cannot be verified practically in its entirety it seems to me to be well founded and is confirmed in part, at least by the fact that excessive lateral erosion takes place in the channel at about the place where the eddy flow arrows 73 and 74 appear.
In view of my invention and disclosure variations and modifications to meet individual whim or particular need will doubtless become evident to others skilled in the art, to obtain all or part of the benefits of my invention without copying the structure shown, and I, therefore, claim all such in so far as they fall within the reasonable spirit and scope of my invention.
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