US2040787A

US2040787A - Melting and holding furnace

Info

Publication number: US2040787A
Application number: US538144A
Authority: US
Inventors: John G G Frost
Original assignee: National Smelting Co Ltd
Current assignee: National Smelting Co Ltd
Priority date: 1931-05-18
Filing date: 1931-05-18
Publication date: 1936-05-12
Anticipated expiration: 1953-05-12

Description

vMay 12, 1936.

J. G. G. FRosT vIVIE]' J'I'ING AND HOiLDING yFURNAUE Filed .May is, 1951 3 Sheets-Sheet 1 INVENTOR John, G'. G'. Frost BY Y L? ATTORNEY J. G. G. FROST MELTING AND HOLDING FURNACE May 12,-/1936.

Filed May 18, 1951 I5 Sheets-Sheet 2 VINVEN'roR John G'. G.Fr 0st f/WA/ ATroRNEYS May 12, 1936. v.1. G. G. FROST MELTING' ANDHOLDING' FURNACE INVENTOR John G. G'. Frost.

ATTORNEYS Patented May 12,1936

'A MELTING AND HOLDING FURNAQE John G. G. Frost, Cleveland, Ohio, assignor to The National Smelting Company, Cleveland, Ohio, a corporation of Ohio Application May 18, 1931, Serial No. 538,144 I 1 Claim. (Cl. 26S-33) 'I'his invention relates to the art of casting metals, and particularly to improvements in melting and holding furnaces for use in connection with the melting of aluminum and alloys, and

other alloys containing small percentages of aluminum, nickel, tin, 'or other non-ferrous metals, in which alow 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 iron pot or transfer the moltenv metal from the large furnace directly to the iron pot for'nishing. 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 gas, `oil or electricity near the casting operation. vIn the die ycasting lof such metals, the iron melting 20 potis 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 conholding pot of iron.

There are many disadvantages that arek -in-v herent with the use of the iroripot. In ordinary practice,firn pots are very short lived, evenwhen particular attention isjpaidto .the various linings that are frequently used and,'as

a result; considerable money is expended in replacing worn out iron pots, and time is ywasted in coating such holding pots. Many alloys, and silicon alloys in particular, have agreat tendency to dissolve iron from the conventional melting and holding pot of iron, and heretofore it has been,` very diicult 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 upor dissolve iron from the pot and thus increase its iron content. In the casting of non-ferrous metal alloys, it is very essential that the iron content be maintained at a, low percentage, since a high percentage iron may have a deleterious effect, s'uch as cracking, on theV castings being produced. This is particularly true in die casting, where thin-sectioned, intricate castings are made of aluminum and alloys thereof.

It is 'one of the objects of the present invention to provide a melting and holding furnace 4of holdingfurnace for-,the casting of aluminum,

aluminum alloys, and other alloys containing small percentages of aluminum, nickel, tin or other non-ferrous metals whichtend 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', and which willy tend toward a more economic production of satisfactory castings.

yAnother object is to provide a melting and holding furnace of such construction that the molten metal availablev foruse in the casting operation `will be maintained at the proper temperature for casting, and. will dross.

' A further object is to provide a melting and holdingfurnace for use ,in connection with the casting of aluminum, valuminum alloys, and other alloys of the character referred to, which may be used adjacent and in connection with a die casting machine, and in which the molten bey free of skimmings or ,l metal available for use is contained within a chamber of refractory material whereby to avoid an increase in the, iron^content of the molten metal.

A-further object is to provide a melting and holding furnace for use in the casting of metals in whichthe surface of the molten `metal available for use is separated from the surface of vthe molten metal that is being subjected tothe melting heat, in order that the 4body of metall available for use will be free of skimmings and other surface impurities, but subjected to the heat of the metal being 4melted.

With the above and other objects in view which will be apparent from the following detailed de- Fig. 2 is a fragmentary view similar to Fig. 1" 1 showing the gooseneck ladle of the die casting molten metal supply chamber;

machine in its 1owerod niiing position within the Fig. 3 is a transverse section taken substantially on the line 3-3 of Fig. 1;

Fig. 4 is a vertical section taken substantially pot-that has heretofore been used in the castingof non-ferrous metal alloys. The furnace proper, as shown in the various views, preferably .comprises a rectangular shaped shell I supported by suitable base members ,2.l The bottom of the shell I is-preferably covered with a relatively thick layer 3 of sand or other suitable material, and the layer of sand, is surrounded with 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 completely covered with a relatively thick `refractory material 6. The sides and ends Ajof the shell adjacentand above the material are also provided with relatively thick refractory material 1.

' The space vWithin the sides and ends of the refractory material, as shown in Figs. 1 and 4, is

divided into-two chambers A and B by a fire wall 8 of refractory material which extends between the sides of the apparatus. This fire wall 8 does not completely v'separate the chambers A and B, but extends downwardly in such a manner that its lower edge will always lie below the level 9 of molten metal contained therein to permit a y ow of the molten metal between the two chambers and to prevent the accumulation of skimmings and dross on the molten metal that vis available for use.

'I'he chamber A, as will be later described and as shown in the drawings, is open at its top and contains the molten metal that is available for immediate use. This chamber in reality forms the holding p'ot for available molten metal.

The chamber B, defined by the transversely extending re wall andthe one end and the sides of the device, is completelyenclosed to form the furnace proper. The enclosure for the chamber B preferably embodies a rectangular shell portion including sides I0 an`d ends I I suitably lined with refractory material I2, anda roof portion .I3 which is also of refractory material I4.

One end II of the enclosed heating portion of the furnace is provided with one or more suitable openings I5, which, in conjunction with suitable burners I6, are arranged to project a heating iiamefsubstantially horizontally above the surface of the metal in the enclosed heating chamber; As showninfFig. 4, the lining I4 of the roof is arched in order to radiate the heat downwardly onto the metal in the chamber B.

. The products of combustion are discharged i from the enclosed chamber B through-a suitable v'flue `I'I arranged in the wall containing the heater openings I5, but at a point remote from the heater openingsl5. The ue I1 opens into thev closed chamber near the normal vlevel of the metal.4 i

One side I0 ofthe enclosure is vformed with a relatively large charging opening I8 which is arranged toy be closed by a suitable refractory llined door I8. The furnace is provided vwith a tap hole opening 20 disposed adjacent the bottom and extending through one of the sides.

In the use of the melting and holding'furnace of the present invention, the transversely extending fire wall 8 separates the molten metall that is available for immediate use from the metal that isbeing melted Within the chamber B, but does not retard the motion of the molten metal from the chamber B into the chamber A.

The primary function, however, of the transversely extending fire wall 8 is to separate the surfaces of the molten material in the chambers A and B so that the skimmings and dross will rise to the surface within the chamber B and will be -prevented from oating to the availablev metal in the chamber A. It will be readily apparent that the metal that is available for use in' the chamber A will be free of skimmings or dross.

One of the advantageous features of the furnace construction is that the skimmings and other objectionable material remain in the furnace proper and can be easily removed without contaminating the metal in the holding'chamber A. Furthermore, the motion of the molten metal Y in the chamber B underneath the firev wall 8 and into the chamber A, serves to keep the molten metal in the chamber A at the proper temperature for casting.

Another advantageous featurebf the furnace- `iron holding pots are-used. 'This thus tends toward the economic production of castings having the desired minimum iron content.

A further 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 ofv the molten metal.` Heretofore this has not been possible when conventional holding potsformed of iron, graphite crucibles of the like were used, since the'ux when used in connection with alloys would attack the iron pot or crucible and greatly increase the iron content of the lmetal being melted and held by these containers.

In order to show the advantageous features of the furnace ofthe' present invention, the same is sho'wn in cooperative relation with one type of die casting machine that is frequently used. In this machine a pair of moldmembers`2| and 22 are used -and the mold member 22 lis rigidly secured to a vertically extending member 23 and the mold member 2I is mounted onk a reciprocating he'ad 24 that is `slidably mounted on a pair of 'spaced guiderods25. The rods 25 at one end are-secured to the vertically extending member 23. and atfthey other end to a support 26. The support 26 carries a rotatable shaft 21 having afcrankvarm 28 at one end thereof. 'I'his crank arm isf connected by means of a pitman rod 29 to the reciprocating head 24. [.10:

'I'his device is arrangedjadjacent the'open holding chamber A of the furnace, as shown'in Fig. l.

and the Ivertically.extending member 23 is provided with a sprue opening. 3U which is positioned slightly above the end 'I of the open chamber A.

, The molten metal is forced under pressure 'by compressed air into the sprue opening 33 by means of a gooseneckladle 3| that is arranged directly'over the open chamber A. This ladle 3| is formed with an upward extension 32 and is supported by upper and lower pairs of links 33 and 34, respectively. The lower links 34 are pivoted to the ends of crank arms 35 that are rigidly secured to a shaft 36 which is rotatably mounted within a bracket 31 secured to the upwardlyextending member 23. The upper links 33 likewise are pivoted to the member 32 and are rigidly secured at their other ends to a shaft 38 that is also mounted in the bracket 31. 'I'he shaft 38 is provided'with a gear segment 39 which is in mesh with a reciprocable rack 40 and the shaft 36 is provided with a gear segment 4| which is also in mesh with a reciprocable rack 42. When the racks 4|) and 42 are reciprocated, the ladle, through the connecting mechanism, is moved into and out of the metal in the chamber A.A In its lowermost position, as shown in Fig. 2, the gooseneck ladle 3| is filled with the molten metal in the supply chamber A, and upon reciprocation of the racks A4l) and 42 the ladle 3| is moved upwardly to the positiony shown in Fig. 1, in which position the open end of the ladle is brought into engagement with the upwardly extending member 32 with its opening in alignment with the sprue opening 30. Pressure is then exerted within the 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 moldmembers 2| and 22. The pressure within the 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 lowermost position within the supply chamber A below the surface of the molten metal, where it is again filled with the molten metal and ready for the casting of the next article that is to be formed in the die casting machine.

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. 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 supply of molten meta-l will always be clean and be at the right temperature, thus eliminating the disadvantages that are 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 efficient 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 explanationand 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 desired, comprising a refractory lined bottom, end, and side walls, one 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 defined by the upwardly extending wall portions, and a wall formed of refractory material extending downwardly from the freeend of said cover to a point below the.

normal operating level of the molten metal in the furnace, thereby dividing the furnace into a closed heating portion andan open holding portion, said refractory wall being spaced from the bottom of the furnace to permit molten metal to flow freely from the heating portion into the open portion, means for projecting a flame substantially horizontally through one of the walls of the closed heating portion of the furnace into the interior of said heating portion above the metal, a charging opening in said closed heating portion, a door for closing said opening, and a flue passageway opening into said closed heating portion for carrying off the products of combustion, said flue passageway being positioned in the same Wall of the closed heating portion as the means for projecting a flame, and having its opening into said closed heating portion adjacent the normal level of the molten metal, for carrying off the products of combustion, said flue opening being also positioned with respect to said return substantially horizontally over the metal to escape through the flue opening.

JOHN G. G. FROST.