US2673229A - Low-frequency induction furnace for melting nonferrous metals - Google Patents

Description

March 23, 1954 M. KHEK Low-FREQUENCY INDUCTION FURNACE FOR MELTING NONFERROUS METALS Filed April 17, 1951 2 Sheets-Sheet l list Ma-rch 23, 1954 KHEK 2,673,229

M. LOW-FREQUENCY INDUCTION FURNACE FOR MELTING NONFERROUS METALS Filed April 17, 1951 2 Sheets-Sheet 2 .fm/wrok Aff/MM /Awa K11/5K Arron/vir Patented Mar. 23, 1954 UNITED STATES PATENT f OFFICE v LOW-FREQUENCY INDUCTION FURNACE FOR MELTIN G NONFERROUS METALS 6 Claims. l

Low frequency induction furnaces for melting non-ferreous metals such as zinc, copper, aluminium, etc. and their alloys, have mostly melting channels formed in to the furnace vessel either laterally or at the bottom in circular shape.

This wide-spread type .of construction offers, as known, the disadvantage of diiiicult access to the melting channels, which can be cleaned only with special tools (chains or other Scrapers).

Another disadvantage resides in the insuflicient mechanical resistance of said channels due either to an electrodynamic phenomenon (Pintsch effect) or to the higher thermal stress as compared with the bath. That is to say, there must exist a temperature gradient between the channel and bath in order that a transfer of heat and energy may take place from the former to the latter (as a rule, about 200 C.).

All the disadvantages of the previous embodiments of low frequency melting furnaces have led to the design and construction of new structures with straight channels. With this construction, the furnace vessel is divided into several parts (working chambers) between which there is provided a space for placing the furnace transformers.

The latter with their yokes and windings form the primary circuit of the plant. There may be provided single-phase, two-phase, three-phase or even combined three-phase and two-phase Scottsystem connections to the existing main network.

Between the windings, there are accommodated the straight melting channels having large dimensions and easily accessible, which contain the liquid metal and transmit thermal energy to the two chambers; one ofl these chambers vis the charging chamber, where the cold charge is introduced, while the other one represents the chamber containing the completely melted bath. It serves also as a storage and supply chamber.

Obviously, the mechanical stress affecting straight channels is smaller than that affecting circular channels and the mechanical strength of the most sensitive part of the low frequency furnaces, namely, of the melting channels, also in consideration of the smaller temperature gradient between channel and bath (about 25- 50 C.) is higher with this construction.

Obstruction of the straight channels by the metal is less likely to occur and accessibility and facility of cleaning are improved. o

The low frequency furnaces heretofore known' with straight channels and two working cham-v bers have the disadvantage of not permitting a correct distribution of power to the said chambers.

Thermal transmission from the channels t0 the two furnace chambers, that is to say to the loading chamber with the cold charge and to the delivery chamber with the liquid bath, is almost equal, whilst it would be more desirable to convey the maximum of heat energy to the cold material so as to supply it with both the energy for heating up and the energy for melting the metal to be melted.

In the delivery chamber it is only necessary to keep the bath at constant temperature or slightly to overheat it.

The present invention relates to an induction melting furnace with straight channels characterized in that it comprises at least three working chambers separated from one another by transformer sets, the total power of which is divided in such a manner that the delivery chambers are defined by transformers of lower power than the charging and melting chambers.

With such an arrangement, it is possible to obtain a distribution of the total power tothe various transformers such as to convey to each chamber the energy that is absorbed by the material contained therein. In particular, the transformers of maximum power are associated with the chamber wherein the cold material is loaded, while smaller energy will be supplied to the delivery chambers.

In the accompanying drawing several embodiments of the invention are shown by way of illustration and not by way of limitation.

In the drawing:

Fig. 1` is a plan view of a furnace according to the invention, partly in section.

Fig. 2 is a sectional View of Fig. l.

Fig. 3 is a plan View of a modification of the furnace.

Fig. 4 is a plan view of another modification of the furnace, and

Fig. 5 is an elevational sectional view of a tiltable furnace according to the invention.

Figures 1 and 2 illustrate respectively in plan and in section a furnace with two melting chambers A and one delivery chamber B; with C are designated two three-phase transformers, which separate said chambers. The melt in these chambers forms the secondary circuit of the transformers. Of said two transformers, the one that denes the delivery chamber B is dimensioned for a power smaller than the power-.of the transformer that separates the two melting chambers A, wherein a higher absorption of energy takes place.

In Figures 1 and 2, with D are marked refractory layers surrounding the transformers while with F are marked eight furnace channels, four for each transformer. The windings of the transformers form the primary circuit.

Fig. 3, where the same reference numerals refer to corresponding parts, shows a furnace with two delivery chambers A and one melting chamber B, separated by two series of two three-phase transformers C each, arranged closely together. Altogether, the furnace comprises four threephase transformers.

Figure 4 shows a furnace with four chambers, the two central chambers A are melting .chambers, while the two chambers B arranged at the end are delivery chambers.

The four chambers are separated by -i'fl'n'eev three-phase transformers C the central one of which is the most powerful as it separates vthe two chambers wherein the highest absorption of energy takes place.

The other reference numerals marked in this figure refer to the same .components as the corresponding reference numerals of Figures l to 3.

Fig. 5 shows a tiltable low frequency furnace with two melting chambers A and one delivery chamber B separated lby two transformers C of which the most powerful `one is the one interposed between the two chambers A.

In said gure are indicated with G the conduits `for the cooling air, with H the pouring spout, with I and L respectively the winch and chain for tilting the furnace.

From the examples 'illustrated it can be seen how the arrangement of the chambers and the proportioning of the transformers according to the invention permits to supply directly the `cold charge introduced into the melting chambers with the maximum quantity of energy and to the liquid bath contained in the delivery chamber just the quantity of energy needed for maintaining the required operational temperature and for slightly overheating, if needed, said` i bath.

`Of course, furnaces according to the invention may have more than four chambers, with delivery chambers at one or at both ends. In case the furnaces are provided with only one delivery chamber, the power ratings of the transformers will be increasing from the one that defines said chamber, toward the opposite end of the furnace. In case of two delivery chambers are provided at the two ends of the furnace, the power ratings of the transformers will be increasing from the two ends towards the .cem tral part of the furnace.

Having now particularly described and ascertained the nature of lmy said invention and in what manner the same is to be performed, I de` clare that what I claim is:

1. In a low frequency induction furnace lfor melting metals, at least three separate working chambers disposed in alignment `and having their bottoms at substantially the same level, two adjacent ones of said chambers constituting melting chambers and the third one a storage and `discharge chamber for the melt, first primary transformer means disposed between said two melting chambers, and 4second primary transformer means disposed between the discharge chamber and the adjacent melting chamber, the said first transformer means being dimensioned for a higher power output than vthe said second transformer means, melt in the primary of said transformer means being in form of substantially rectangularly shaped coils, the said coils being spatially disposed so as to define with adjacent wall portions of the furnace straight melting channels interconnecting adjacent chambers Abelow thenormal operating level of the metal andending within the foutlines of the respective transformer means, the said channels extending generally vertical tot the axes of said coils, said melting channels forming the secondary loops 'for the transformer means.

2. Ina low frequency induction furnace for melting metals, two primary transformer means in form of substantially rectangularly shaped coils .disposed in a spaced-apart relationship so Vas to `form three` separate working chambers within the furnace interconnected `by straight melting channels below the normal operating level of the metal, the jsaid channels extending generally vertical tothe axes of said coils, two of said chambers constituting melting chambers and the third a storage and discharge chamber for the melt, the bottoms of said chambers being at .substantially the same level, the transformer means between the two melting chambers being dimensioned for a higher power output than the transformer means separating the discharge chamber from the respective melting chamber, the melt in said melting channels forming the secondary loops for the transformer means.

3. In a low frequency induction furnace for melting metals a plurality of primary transformer means having substantially rectangularly shaped `coils disposed in a spaced-apart aligned relationship so as to form at least three separate adjacent working chambers, adjacent chambers being interconnected by straight melting channels disposed below the normal operating level of the metal substantially vertical to the `axes of said coils and ending within the configuration of the respective transformer means, the chamber at one end of the furnace constituting a storage and discharge chamber for the melt, the other chambers constituting melting chambers, the bottoms of said chambers being at substantially the same level, the said primary transformer means being dimensioned for a power output increasing from the transformer means separating the said discharge chamber from the adjacent melting chamber toward the other end of the furnace. the melt in said melting channels forming the secondary loops for the transformer means.

4. In a low frequency induction furnace yfor melting metals, a plurality of primary transformer means having substantially rectangularly shaped coils disposed in' a spatial relationship so as to form a plurality of aligned and juxtaposed separate working chambers interconnected by straight melting channels below the normal operating level of the metal and extending substantially vertically to the axes of said coils, the said channels ending within the configuration of the respective transformer means, one chamber at each end of the furnace constituting a storage and discharge chamber for the melt, the intermediate chambers constituting melting chambers, the bottoms of said chambers being substantially at the same level, the said transformer means being dimensioned for a power output increasing from the transformer means separating a kdischarge chamber from the respective adjacent melting chamber to- Ward the central `part of the furnace, the melt 5 in said straight melting channels forming the secondary loops for the transformer means.

5. An induction furnace according to claim 1, wherein each of the said transformer means between two adjacent chambers comprises several transformer units disposed in alignment spaced apart so as to form a plurality of melting channels therebetween.

6. An induction furnace according to claim 1, wherein the axes of the said melting channels are substantially parallel to the planes of the coil windings of the transformer means whereby the flux lines traverse the said channels substantially at an angle of 90.

MASSIMILIANO KHEK.

6 References Cited in the ille of this patent UNITED STATES PATENTS Number

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