US2472465A - Apparatus for the treatment of molten metals - Google Patents

Description

June 7, 1949. R. c. CORNELL 7 APPARATUS FOR THE TREATIENT OF MOLTEN IETALS 3 Sheets-Sheet 1 Filed July 26, 1945 INVENTOR. l2cu6evvt2 Cluvve/V June 7, 1949. R. c. CORNELL APPARATUS FOR THE TREATMENT OF IOLTEN METALS s Sheds-Sheet z Filed July 26. 1945 INVENTOR. Robert 61 Corne A TTORNEYS June 7, 1949.

Filed July 26, 1.945

R. C. CORNELL APPARATUS FOR THE TREATMENT OF MOLTEN METALS 3 SheetsASheet 3 INVENTOR- Rober/C Corn e// BY ATTORNEYS Fatalities? china 3': i g

QFFEE APPARATUS FOR THE TREATMENT OF,

MOLTEN METALS Application July 26, 1945 Serial No. 607,182-

2 Claims. (or. 266-34) The invention relates to an apparatus for treating magnesium and its alloys inpreparation for casting or the like. It more particularly concernsmelting, refining, and maintaining a body" of the molten magnesium or alloy thereof in I a refined state so'that a succession of clean charges may be ladled from-sit, into a die-casting machine.

magnesiumalloys, the metal to be cast is dipped with av ladle from a casting; pot con tain'ing a quantity of molten metal maintained at casting; I

- temperature andfprotected from oxidation andnitridationby' sulfur dioxideigas. The amount ladled at each dipping-ls"usually :Iust sufilci'ent for one casting and the. transfer from'thepot to :the mold'is, made expeditiously and by hand s using a spoon type of ladle.- c I, Several difllculties,: I have found, inure toisuch practice; For example;- it is difllcult', ii not im-, 4 possible, to keep, the metal in a the casting pot; frombecoming contaminated with products-Jot if not impossible, to perform the .ladling opera-, tion rapidly and accurately, as to volume of metal ladled 1 01' each casting, without introducing some flux into the casting.

It is a des'ideratum in this art to provide a means for maintaininga body of flux-free but refined or contaminant-free metal from which I H V alsu'ccession of ladlings can be made directly In the conventional practice of making a suc-' 1 to a die casting' machine or molds so as to pro-' cession of castings, particularly die castings of,

duce in rapid succession castings sumciently free from oxide and flux contamination to be commercially acceptable. p.

Havingregard to the, accomplishment of the "foregoing and-related ends," the invention then consists of v the means hereinafter fully described and particularll' pointed out? in the claims. -In: accordance with-- the'invention', I establish attack by the ail-Fin, spite-of; the use of. ap'ro-yj tective gas. ."contaminants"comprise prin-h cipally magnesium nitride and oxide. These; in -part, tend to fioat'on the'n'ietah'as a skin entrainment of'wh'ich in the metal vladled from the I casting pot is difiicult, if not-impossible, to avoidk The balance of the nitride and'oxide conte'inii nants become distributed partly in the molten metal and partly at the bottom-oi the pot'to which it settles forming a dry' sludge which.

must be removed from the pot from time to time. This sludge entrains a considerable, pro-;

portion of metal'and its removal, although necessary, produces a waste of metal.

In order to maintain a supply of molten metal sufiiciently free from contaminantsv to. permit dipping a ladle into the melt and withdrawing clean metal for pouring directly into the diecasting machine, it has been necessary hereto-,

fore'to maintain an extra pot in which the metal to be used is first melted and refined. This melting and refining has been accomplished by agitating the molten metal with a refining flux in a refining pot and transferring periodically refined flux-free metal from the refining pot to thecasting pot and from which it is thereafter transferred by ladling to the die-casting machine or molds.

Ladliug the metal directly from the refining pot intothe die-casting machine or molds in an" attempt to eliminate the use of a flux-free cast me not is not satisfactory because it is diificult,

extensive with a. fiuxed body ofjthejme al i-ne melting vessel in which" the metal may be'i fiuxed and refined :wit-hout' introducin fflux-iinto the flux -free dipping zone Molten metal free 'frome contaminants is ladled'wfor 'cast'ing i'rom the flux- .tree dipping zone wlriile the balance of the melt is'subiect' to the purifying action of the fiux, a protective gas such as 'o'nefcontalning sulfur dioxide being maintained .over the fiux-freerzone so as to prevent the. flux-free metal from being irapidlyrattackedwbythe air. fBy-this method not only is it unnecessary to. maintain an extra melting vesselfor the reflning' oper'ation but also only arelatively small area of the'surface of the fluxfree metal need be' exposed during ladling,- thus reducingattack" by. the air and simultaneously maintaining, high purity metal for casting; In addition, the use of the flux eliminates dry sludge formation and thus reduces metal loss. 1

In the annexed drawings, a number of advantageous modifications of the invention are illustrated by way of example.

In the said drawings 1 Fig. 1 is aside elevation in section of a melting pot having a flux-free molten metal dipping zone separated from the balance of, the metal by abaflled shield covered with a hood supplied with protective gas:

Fig. 2 is a plan view of the same;

Fig. '3 is a front elevation ofQthe bafiled shield and hood. alone; v

Fig; 4 is a side elevation in section of a modification-of the apparatus of Fig. 1 showing the flux-free metal dipping zone and protectivegas melting pot.

Fig. 5 is a fragmentary view in plan of the flux-free metal dipping zone of Fig. 4;

Fig. 6 is a rear sectional View on the line 6-6' of Fig. 4 showing the batiied entrance to the fluxfree metal dipping zone from the melting pot;

Fig. 7 is a cross-section on the line 1--1' of F18. 4;

Fig. 8 is a plan view showing another modification of the apparatus of Fig. 1 while empty;

Fig. 9 is a side elevation of the same in section filled with molten metal covered with flux;

Fig. 10 is a sectional view on the line Ill-l0 of Fig. 9;

Fig. 11 is a spoon type of ladle suitable for use with the apparatus.

Referring to Figs. 1, 2, and 3, there is shown a melting pot I having a generally hemispherical bottom and cylindrical side wall terminating in a circular rim 2 resting on a furnace setting 3 provided with a heating burner 4 and flue 5. Shown within the pot is a. hooded baffled shield indicated generally by numeral 6, the interior forming a flux-free dipping well for the molten metal. It comprises a cylindrical dam or flux shield portion I and a bafile 8 in the form of a plate of greater diameter than the shield attached to the bottom by spacers 9. Attached to the top of the shield is a hood l0 having a ladling opening II and pipe connection l2. A set of arms l3 are provided by which the hooded baflied shield is supported on the rim of the pot so that the space H between-the bottom of'the shield and the baille is well submerged in the molten metal body l5. As shown, the molten metal is covered outside the shield with flux l6.

In the modification shown in Figs. 4, 5, 6, and 7, the melting pot ll of generally hemispherical bottom and cylindrical side wall is supported by its rim iii in a. furnace setting l9 provided with a heating burner and flue 2|. The melting pot is provided with a metal dipping well 22 for flux-free metal as an extension of one side of the pot between the rim l8 and center of the side wall. The well is provided with an opening 23 in the side wall of the pot for the passage of flux-free molten metal between the pot and the well, the side wall of the pot above the opening serving as a flux shield. A bafile 24 is attached to the inside of the pot wall just below the opening 23 so as to deflect sludge, which may accumulate in the pot, away from the opening. The well 22 is covered with the hood 25 having a ladling opening 26 and a pipe connection 21 for admitting protective gas, such as sulfur dioxide, to the hood.

In the modification shown in Figs. 8, 9, and 10, the melting pct 28, which may be of similar form to that shown in Fig. 1, is supported by its circular rim 29 on the furnace setting 30 in the same manner as in the modification shown in Fig. 1 and the burner and flue arrangement, not shown, are also similar. The pot is provided with a hooded baflled shield indicated generally by numeral 3|. It comprises a dam or fiux shield 32 having vertical walls extending into the pot to below the working level for the molten metal. A baille 33 in the form of a plate is attached to the bottom of the shield by spacers 34. Attached to the top of the flux shield is a hood 35 provided with a ladle opening 36, the bottom edge 31 of which extends onto the rim 29 of the pot forming a support for itself on that side. An arm "is attached to the hood at the opposite side from the opening and extends across the pot to rest upon the rim 29 and serves as a-further support for the hooded shield. The hood contains a sulfur dioxide generating compartment 58, bounded-by the upper side wall 35 of the hood. the Hip 39, and the plate 40. As shown, a filling opening 4| having a removable cap 42 is provided in the top 39 through which sulfur may be introduced into the compartment. A vent 43 in the top 39 allows air to enter the compartment for burning the sulfur introduced therein. A tube 44 welded in the plate provides a passage leading from inside the top of the compartment to the inside of the hood 35 for conveying the sulfur dioxide mixture from the generating compartment to a point near the ladling opening 36 of the hood.

The operation of each of the modifications of the apparatus is similar being based upon the principle of establishing and maintaining a fluxfree metal dipping zone contiguous to and co-extensive with a body of flux-refined metal. the dipping zone being protected from air attack by a protective gas while the melt is at operating temperature. usually from about 1180 F. to

1400 F. for die casting.

As to the operation of the apparatus of Figs. 1, 2, and 3, the molten metal level 45 in the potis maintained well above the bottom 46 of the flux shield I. The molten metal outside the dipping zone 47 is covered with a suitable flux for refining and protecting the metal, such fluxes being well known in the art. A slightly thickened flux is used preferably, the thickening agents tending to reduce creep of flux. For example, a flux made by mixing equal amounts of a conventional fluid flux and a conventional thickened flux may be used. A typical composition of such mixture is 50 parts by weight potassium chloride, 27 parts of anhydrous magnesium chloride, 7.8 parts of magnesium oxide, 5 parts of barium chloride, and 9 parts of calcium fluoride. The molten metal may be agitated from time to time with the flux so as to purify the metal.

The fiuxed metal is allowed to settle so that heavy impurities entrained by the flux will settle out as a wet sludge, as indicated at 48. The balance of the flux then forms a floating layer IS on the purified metal body l5. The dam or shield 1 and bafile 8 prevent flux from entering the body of metal in the dipping zone 41 while allowing ready flow of refined metal into the zone through the passage between the bottom 46 of the dam and the baffie plate 8. During the operations of refining and maintenance of the molten metal in the pot a protective gas, such as sulfur dioxide, is led into the space in the hood 10 so that the bare metal surface 49 does not become unduly attacked.

Clean flux-free metal is dipped from the dipping well or zone 4'! by means of a suitable ladle, such as that illustrated in Fig. 1, inserted through the opening II in the hood. As metal is thus removed. additional metal may be added to the pot outside the dipping well for melting and fluxing as needed, the accumulated sludge 48 being removed from the bottom of the pot periodically as in conventional melting practice. If desired, the hooded shield 6 may be lifted out of the melting pot after long periods of use to facilitate cleaning both the pot and the hooded shield.

The apparatus shown in Figs. 4, 5, and 6 is operated in similar manner, metal being introduced into the melting zone 50 and covered with flux 5| as needed. Refined flux-free metal enters the dipping zone 52 through the opening 23 as metal is ladled therefrom, the ladling being accomplished through the opening 25. For protection of the flux-free metal in the dipping zone 52 a protective gas is introduced into the hood 25 as through the pipe connection 21.

The apparatus of Figs. 8, 9, and is used similarly to that of the previous figures and has the added feature of providing its own protective atmosphere in the hood during use. In operating this modification, the cap 42 is removed, a quantity of elementary sulfur 53 placed in the compartment 58 through the filling opening M, and the cap is replaced. The pot 28 is maintained at suitable melting temperature and sufficient metal is added to maintain the molten metallevel-54 well above the bottom 55 of the flux shield or dam 32, thereby excluding the flux 56 from the dipping zone 51.

By virtue of maintaining the metal in the melting pot in the molten state, the sulfur in compartment 58 becomes heated sufilciently to melt and burn, the air necessary to maintain combustion entering by the vent 43. The resulting sulfur dioxide gas mixture passes through the pipe 44 and is discharged near the ladle opening 36 and carried by connection currents into the space under the hood, thereby protecting the flux-free metal from attack by the atmosphere. As metal is dipped from the dippin zone 57, flux-free metal enters to replace it by way of the space between the bottom 55 of the flux shield and the baffle 33, the flux being retained outside the dipping zone by the flux shield 32.

Among the advantages of the invention are that a continuous supply of clean metal at castin temperature is provided which is readily accessible for ladling a rapid succession of casting charges without flux contamination. There is less sludge formation in the melting pot than in conventional practice because only a relatively small area of metal need be exposed for ladling. Because the sludge produced is a "wet type, it more readily separates from the metal than the dry type of sludge or dross produced in conventional gas protected melts, and the metal loss due to entrainment in the sludge is, therefore, substantially obviated.

What is claimed is:

1. An apparatus for preparing magnesium and 6 its alloys for casting comprising an open top melt ing vessel in a furnace setting adapted to hold a body of the molten metal at casting temperature, with a flux on the surface of the molten metal, said vessel having a rim resting on a furnace setting, a flux shield supported on the rim and arranged-to isolate a portion of the surface of the molten metal so as to exclude flux therefrom, a baffle attached to and disposed across the bottom of the shield, a hood over the shield for maintaining a protective atmosphere over the molten metal under the hood, said hood having an opening for the admission of a ladle.

2. An apparatus for maintaining a supply of a molten magnesium alloy in condition for ladling therefrom asuccession of clean casting charges for die casting which comprises an open top melting vessel, means to supply heat to the vessel adapted to maintain a body of the molten magnesium alloy therein at casting temperature with a flux on the surface of said molten metal, a cylindrical shield depending in the vessel and arranged to isolate a portion of the surface of the molten metal so as to exclude flux therefrom. a baflie attachedto and disposed across .the bottom of and spaced from the shield, a hood over the shield for maintaining a protective atmosphere over the molten metal under the hood, said shield having an opening for the admission of a ladle.

ROBERT C. CORNELL.

REFERENCES CITED The following references are of record in the file of this patent:

, UNITED STATES PATENTS Number

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