US2040788A - Melting and holding furnace - Google Patents

Description

J. G. G. FROST 2,040,788

'AMEL'YTING AND HOLDING FURNACE Filed June e, 1932 4 sheets-sheet 1 INVENTOR John G. G. Frost BY rv-M4 g-yf/CC ATTORNEYS May l2, 1936.

May 12, 1936. j, G, Q FRQST 2,040,788

MELTING AND HOLDING FURNACE Filed June e, '1952 4 sheets-sheet 2 F1- 3. l'NvENToR 5 John G. G. Frost vATTORNEYS 4 Sheets-Sheet 4 J. G. G. FROST MELTING AND HOLDING FURNACE Filed June 6,- 1952 May' 12, 1936.

aJ-m YM f* ATTORNEYS Patented May 12, k1936 UNITED STATES MELTING AND HOLDING FuItNfAjoE y John G. G. Frost', cleveland, ohio, asignan` The National Smelting Company, Clevelaml,v

Ohio, a corporation of Ohio Applicationoune s, i932, serial No. clases. f

of my copending application Serial No. 538,144,

filed May 18, 1931, relates to the art of casting metals, and particularly to improvements inr melting and holding furnaces for use in connection with the meltin'g of aluminum and its alloys, and other alloys containing small percentages of aluminum, nickel, tin, or other non-ferrous metals, in which a low iron content is desired.

In the casting of metals of this character it is usually the practice to melt the metal in a large furnace and to either cast into ingots and remelt in an Viron pot or transfer the molten metal from l the large furnace directly to the iron pot for Ifin- 19 ishing. This practice is usually carried out in all types'of casting, whether it be sand casting, permanent mold casting, or die casting.

In each case it is the practice to provide a melting pot that is suitably heated externally by 20 gas, oil or electricity near the casting operation.

In the die casting of such metals, the iron melting pot is positioned adjacent the casting machine so that the gooseneck ladle that'is generally used can -be conveniently operated between the molten metal and the casting machine. This arrangement, and the open pot usually employed in connection with sand and permanent mold casting, makes it practically'impossible'l to use anything other than an externally heated melting and holding pot of iron. f

There are many disadvantages that areinherent with the use of the iron pot. In ordinary practice, iron pots are very short lived, even when particular attention is paid to the various linings that arefrequently used and,` as aresult, considerable money is expended in replacing worn out iron pots, and time is wasted in coating such holding pots. Many alloys, and silicon alloys in particular, have a great tendency to dissolve'iron from the conventional melting and holding pot of iron, and heretofore it'has been very diiiicult to control the iron content of such alloys because of this disadvantage.

The greatest disadvantage in using the conventional iron melting and holding pot is the tendency of the molten metal to pick up ordissolve iron from thepot and thus increase its iron content. In the casting of non-ferrous metal alloys, it is very essential that the iron content be maintained It is one `of the objects'k ofthe lpresent invention to provide a melting and holding furnace of improved construction which may be conveniently located at the place of casting the metal', and which will overcome the many disadvantages 5 that are inherent with the use of the so-called melting and holdingopots of iron.

Another object is to provide a melting and hold. ing furnace for the casting of aluminum, aluminuml alloys, and other alloys containing small 10 percentages of aluminum, nickel, tin or other non-ferrous metals which tend `to pick up iron when melted, of such construction that considerable time and expense can be'saved as compared with the use of conventional holding pots,l and 15 which will tend toward a more economic production of satisfactory castings.

Another object is to provide a meltingy and holding furnace of such construction that the molten vmetal available for use in they casting 20 operation will be maintained at the proper temperature for casting, and will be free of skimmings or dross.

A further object is to provide a melting and vholding furnace for use in connection with the 25 casting of aluminum, aluminum alloys, and other alloys of the character referred to, which may be used adjacent to and in connection with a die casting machine, and in which the molten metal available for use is contained within a chamber 30 of refractory material whereby to avoid anA increase in the iron content of the molten metal.

A further object is to provide a melting and holding furnace of vpreferred form for use in the casting of metals 4iri which the surface of the 35 molten metal available for use is separated from the surface of the molten metal that is being subjected to the melting heat, in order that the body lof metal available-for use 4will be free of skimmings and other surface impurities,'but sub- 4o jected to the heat of the metal being melted.

With the above and other objects in view which will be apparent from the following detailed description, the present invention consists in certain features of construction or combina- 45 tions of parts which `will be readily apparent to those skilled in the art to which the invention appertains.

In the drawings, which illustrate a suitable embodiment of the invention, v 5o Figure 1 isfa side elevation of a melting and holding furnace, portions of the same being broken away and shown in section, and shown in cooperative relation with one type of die cast-` ing machine;

on the line 4 4 of Fig. 1, showing the position of the charging opening for the furnace;

Fig. 5 is a section taken substantially on the.

line 5 5 of Fig. 3 showing the position of the flue for the furnace;

Fig. 6 is a fragmentary section similar to Fig. 2 showing a means of allowing a portion of-.the heat inl the heating chamber to be directed against the ladle; l

Fig. 7 is a view similar to Fig. 1 of a slightly modified construction, the casting machine being removed;

Fig. 8 is a section taken approximately on the line 8 8 of Fig. 7;

Fig; 9 is a fragmentary section showing a modied arrangement of the end portion which spans the furnace walls.

Referring specifically to the accompanying drawings, in which like numerals refer to like parts throughout the several views, the melting and holding furnace of the present invention is arranged to replace the conventional iron holding pot that has heretofore been used in the casting of non-ferrous metal alloys. The furnace proper, as shown in the various views, preferably comprises a rectangularshaped shell I supported by suitable base members 2. The bottom of the shell is preferably covered with a. relatively thick layer 3 of sand or other suitable material, and the layer of sand is surroundedwith a liner 4 which may be of common fire brick.

A layer of suitable insulation 5 is arranged over the bottom liner 4 and this layer of insulation is in turn completelyy covered with a relatively thick refractory material 8. The sides and ends of the shell adjacent and above the material are also provided with relatively thick refractory material 'I.

'I'he melting and holding furnace, asshown in the drawings, is substantially closed over one portion to provide a heating chamber A and is open over the other portion to provide a. space B of 'suillcient size for the ladle of a casting machine to be disposed within the holding furnace and remove molten metal therefrom.

The heating chamber A preferably embodies' and end portions is also preferably of refractory material. In. the preferred. form of the present invention, the lining I2 of the end portion II which spans the furnace walls is preferably provided with a portion 8 depending belowthev operating level of the molten metal in the furnace but Ispaced from the bottom 8 to permit the free iiow of molten metal from the furnace portion below the heating chamber to the holding portion which sulting from the melting operation large, it is preferred to employ the downwardly extending portion 8 in order to retain the dross and skim however, as shown in Fig. 9, the bottom of this end II shouldbe sufficiently close to the level of the metal as not to permit too great a loss of f heat underneath the same.

One end IVI of the enclosure, is provided with one'or`more suitable openings I5 which, in conjunction with suitable burners I6, are arranged to discharge heat into the interior of the enclosure. These burners and openings may also be arranged in the side portions I0 and may be of the gas or oil fired type. Also electrical means may be employed-for supplying heat to the heating chamber. As shown in Fig. 4, the lining of the roof B is arched in order to deflect the flame and hot gases downwardly toward the metal in the heating chamber A. f

The products of combustion are preferably discharged` from'the enclosed chamber Athrough a suitable ue I1 which may be arranged near the level of the metal and in the end containing the heater openings I5, but at a point remote from the openings I5.

One side I0 of the enclosure is formed with a relatively large charging opening I8 which is arranged to be\closed by a suitable refractory lined door I9. The furnace is provided with a tap hole opening 20 disposed adjacent the bottom and extending through one of the sides.

In the use of the preferred form of the melting and holding furnace of the present invention, the transversely extending wall portion 8 separates the molten metal that is available for immediate use from the metal that is being melted within the chamber A, but does not retard the motion of the molten metal within the furnace, and it is readily apparent that in the preferred form described, the metal that. is available for use will be free of skimmings or dross.

The greatest advantage of the furnace construction described is that the 'entire melting and holding operation can be carried on right at the casting machine without liability of having the iron content of the molten metal increased through an attack of the molten metal on the holding furnace, which has been the case in the conventional iron holding pots. u Another advantageous feature of the furnace construction is that the motion of the molten metal in the chamber A underneath the wall 8 and into the open portion Bi serves to keep the molten metal at the proper temperature for casting.

Another advantageous feature of the furnace construction -described is that larger ingots can be melted than is possible in the conventional melting and holding pots, thus reducing the initial cost of the metal and saving considerable time in charging the furnace. Furthermore, ingots having a higher content of iron may beused forchargingf since there will be no chance of iron pick-up, which occurs when conventional iron holding pots are used. This thus tends in Fig; 1, and the vertically extending member toward the economic production of castings having minimum or low iron content.

Aifurther advantage derived from the use of a melting and holding furnace of the character just described -is that suitable and desirable fluxes may be used during the melting and holding of the molten metal. Heretofore this has not been possible when conventional holding pots formed of iron, graphite crucibles or the like were used, since the flux-when used in connection with alloys would attack the pot and greatly increase the iron content' of the metal beingk secured to a vertically extending member 23, and

the mold member 2l is mounted on a reciprocating head, 24 that is slidably mounted on a pair *of spaced guide rods 25.

'I'he rods 25 atone end are secured to the vertically extending member 23 and at the otherv end to a support 26. The support 26 carries a rotatable shaft 2'I having a crank arm 28 yat one.

end thereof.` This crank arm is connected by means of, a pitman rod V29 to the reciprocatingy head 24. This device is arrangedadjacent the open holding portion of the furnace, as shown I secured'to a shaft 36 which is rotatably mounted withina bracket 31 secured to the upwardly extending member 23. 'I'he upper links 33 likewise are pivoted to the member 32 and are rigidly secured at their other ends to a shaft 33 that is also mounted in the bracket 31. `The shaft 38 is providedwith a gear segment 39 which is in mesh with a reciprocable rack 40 and the shaft 36 is provided with a gear segment 4I which is also in mesh with a reciprocable rack 42. When the racks 40 and 42 are reciprocated, the ladle,

through the connecting mechanism, is moved into and out of the metal at the open portion of the molten metal and upon reciprocation of the with its opening in alignment with the sprue pening 30. Pressure is then exerted withinthe ladle through a compressed air `conduit 43 that is in communication with the @interior of `the ladle, which forces the molten metal within the ladle through the sprue opening 30 and into the chamber 44 formed by the -mold members 2| and 22. 'I he pressure within thev ladle 3| is maintained until the metal within the mold chamber 44 has set, and then the pressure within the ladle is released and the ladle moved again to its lowi 3 ermost position within the furnace A below the surface of the molten metal, where 'it is again lled with'the molten metal and ready for the casting of the next article that is to be formed in the die casting machine.

In certain types of casting machines it is desirable to heat the gooseneck ladle and this can be accomplished, as shown` in Fig.. 6, by providing an opening I4 in the spanning end portion II to direct heat from within the heating chamber A against the ladle 3| In the case where the depending portion 8 is employed and the wall II and its lining I2 terminates slightly above the operating level of the metal, as shown in Fig. 9, sufficient heat may escape underneath the same. to provide sucient heating fory the ladle.

In Figs. 7 and 8 I have shown a modified form of furnace, which, lalthough not the preferred form, may be utilized to accomplish the new results of my invention. In this construction, the

bottom which is of refractory, slopes gradually upwardly into the heating chamber which makes the furnace relatively shallow underneath the heating" chamber but of suiiicient area which will provide for more rapid melting on account of the decreased volume of metal without affect- "ing the area exposed to the heat. I have also shownin this construction a charging door 5I in the upper end portion Il. Firing in this case isv of the cross,.or side type, as indicated by the opening 52 which corresponds to the opening I5 in the construction previously described.

In this construction I have eliminated the flue I 1 of the construction in Fig. 1, and have provided for the escape of the products of combustion by having the spanning'end II and its lining I2 terminate slightly above the operating level of the molten metal. In order to deflect the heat away from the'casting machine, I have provided a baiile 53, preferably of refractory, spaced slightly in front of the last mentioned end I I, but which is preferably arched a short distance beneath' the operating level of the molten metal to permit-free flow of metal in the furnace andat the same time prevent the flow of dross,'other accumulated impurities and the like, over onto the surface of the metal which is available for use in the holding portion of the furnace. In this construction, however, the edge y of the end portion II and itslining I2 should not b e spaced too great a distance above the operating level of the molten metal, so as notto permit too great a waste of heat from the heating chamber.

The advantages of the furnace of the present invention can be readily appreciated when the melting and holding furnace is used in connection with a die casting machine such as the type shown in the drawings.V This arrangement provides a source of clean molten metal that is maintained at the proper temperature for casting.

When the furnace construction is used in connection with permanent mold or sand casting, the molten metal may be removed by a ladle of any conventional construction, and the supplyl of molten metal will always be clean and be at the .right temperature, thus eliminating the disadvantages that arel inherent with the conventional iron holding pots that have been used heretofore.

It is obvious from the drawings and foregoing description that the present invention provides means whereby non-ferrous metals such as aluminum and alloys thereof, may be economically cast without danger of increase in the iron content thereof from the holding pot or furnace,

thus tending toward the eicient production of satisfactory castings.

Furthermore, it is to be understood that the particular forms of apparatus shown and described, and the particular procedure set forth, are presented for purposes of explanation and illustration and that various modifications of said ,apparatus and procedure can be made without departing from my invention as defined in the appended claim.

What I claim is:

A furnace for melting and holding non-ferrous metals in which a low iron content is ldesired, comprising a refractory lined bottom, end, and sidewalls, 4one of said end walls and a portion of each of the side walls extending a. substantial distance above the remaining end wall, a cover of refractory material extending over that portion of the furnace dened by the upwardly extending wall portions, and a curtain wall formed of refractory material extending vdownwardly w to ilow freely from the heating portion into the open portion, `means for projecting a flame into the interior of the enclosed heating portion above the level of the lmetal, a charging opening in said closed portion, a door for closing said opening. and a flue' passageway formed in one of the walls of the heating portion to permit the escape of products of combustiomsai'd curtain wall having a relatively small heat directing opening therein relativelynear i* e -normal level of molten metal in the furnace and'well below said cover for positively directing a portion only of the heat within said heating portion in apredetermined localized path above the metal in said holding portion.

` JOHN G. G. FROST.

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