US2232886A

US2232886A - Melting and casting of metals

Info

Publication number: US2232886A
Application number: US299014A
Authority: US
Inventors: Robertson Neil Douglas Gordon; Lewis Eric Crisp
Original assignee: Magnesium Elektron Ltd
Current assignee: Magnesium Elektron Ltd
Priority date: 1938-10-20
Filing date: 1939-10-11
Publication date: 1941-02-25
Anticipated expiration: 1958-02-25

Description

N. D. s. ROBERTSON Er Ar. 86

MELTING AND CASTING OF METALS Feb. 25, "1941.

2 Sheets-Sheet 1 Filed Oct. 11, 1939 Lewis P M v A ter-neg:

By E. W,

F 1941. N. D. G. ROBERTSON EIAL 2,232,886

MELTING AND CASTING OF METALS Filed Oct... 11., 1959' Y z sheets-sh et '2 IV. D. 6'. Robe/tun and By 8 7* Q Aflqhneys v Patented Feb. 25,1941

netmcmn meme mun i [Nell DouIEiGorJonBobeI-tson, Bushey Heath,

' and Eric Crisp lcwis l'ntnemllondomlilnzlsnd, i

llfltn rlloMalnesiumllektron HmiteilmadolilEllzlend a-Brltlshcompgny' 2 1 v i iilicwefi amum;ims;seaum. 299,014 1 In Gre otBrlt ginoctober zo,1938 g y l y b v 22141914 This invention relates to the f neltingilendj tie-:1

ing otmetals.

According to the inyentlon theiibbaratusfcom,

prises a. crucible adapted tocontain molten metal 5 and gas under pressure, and having adelivery,

pipe adapted to extendjb elow. I the level of {the molten metal, its upper end beirigl outside the crucible for dellyery ot molten metal; 12, device containing gas, preferably inert to "the r'noltenfl meteland connected by a. pipette tliejinterion of the crucible andl aylng relatively movable walls and means for "moving said walls towards each other tog'eneratethe .required gas pressure (without other means for supplying ges Iunder gmay'fbe" dlsben'sed wlth altogether. The rvessel .rnaybe af crucible for normal @Ioundry. work or jrnay 'of tlie large tyr suitable wfor magnesium production or alloying purposes. The expelled metalf inay be received directly into a; ladle for v casting or into a mould-tor. sand or permanent lfmould casting-tr may enter epressure chamber Q for injection into 'a 'mould ot'a. pressure die-cest-;;10,, fing machine or directly "into the mould ot suchbut I not ncesserily for t the" 6: sbrotecting the magnesium from oxidatlonyaand a machine. i

v The deliveryplpe is preferably constentlyopen to the molten metafbeneath theupper surfacexi pressure) which is transmitted to the crucible. thereofand is of such increaslngdlameterwith-9 therebyyexpelling molten metal through the de vin tliecrucible from ltsupper end downwards livery pipe and forfmoving saigl walls apart to as tofpreve nt jafiiming should metalsbecorne so; :4 reduce said pressure, thereby 'jstoppingtl out;" lidifledfthereln; andtOr'ender-removal o solidiflow offmetel; through thedelivery pipeandrel fied'metaran easy 'matterpf" 11m 1, y

turning the metal inthe delivery pipe to e, re; 1 In order thjt tlie dboveoescrlbed iand otherx quiredwlevel there being noqoutlet, in the ga features of the inyention may' be more easilyle system during use through whlch any appre i understood afconstruotionaliorm of the invent-t able lossof the gas couldmormelly occur llfh tion will now befdescribed- -by wayof examplew.

atm D B eoIZ-QEELS withinmthe vessel wlllbe sewith referenceito the accompanying diegramlected according to the requlrements -of ;the mati c dra wings,- wherein. w H

metalconcerned. Ifmagnesiurn or amegnesium Figure '1, is *efvertialsectional e :of an base alloy; or analuminium base alloy contain appa ratus irlgde' n accordance withth invertingt a. proportiorrof magnesium isbeing treatedr tion; d f i i o theetm'osphere in,thepvessel may besulplourqdl- Figur e j2 illustretesfa modlflcation to be de- L oxideor hydrogen" or hydrogen,;.su1ph1de;orother rscribedf li w gases .inertdr' comparatively inert to magnesium; 5x A crucible 3rnount ediira idrnag'ce 4 is formed or mixturesmof suchgrgases or air -an d;sulf)hur from iron, steel, or other suitable. matermr or p w y rbeivusedr rf p rcor th ixm e oy, of ve ted; dome-shape and withofit open xalsrthe*atmosphererwill be-suitably chosen andvings therein except of coursl its open up e will ;.usually:=be-;inert' to the metal under treatt end. The crucible is provided with an outwardly mentm ItT -is .yerywdesireble however;that; gases directed file get rounditsupperjend'or mouth which are appreciably soluble iinthe melt shouldq 1d Win a; s-tight not bewemployed. or (porosity 01313118 final castings 1 40 Xmay resu1t.+ The: ;gas employed, furthermor e, v may-bet chosen with xa view towefiecting a.Jciev oxidationrof; themolten metahge. g. hydrogen or 11 carbon-monoxide: v i ,1; 11

Whenqtreating magnesium or alloys scontain ting i magnesium; the; metal may bevflrst purified bywusuals fluxmethods or may beipu lsfledbyefluxintroduced Jintoi, thet-g cruciblegit self, ,{If large I scrap :x(suclr as :foundry; runners p,nd;;-; T sers ,;;o1 ingot istoibe introduoed lntosthe crucible it m ay 1 .1 first treated: to 1 remove surfacer vimpuritiesr;

e. ig; 1 by n sendiablasting'; If rflux; is i to ghei introduced into the crucible this maybe 'ofthe very,

fluidr'nature 'orl 10f :hormelly torvmore @than norf1; mallyv-irispissatedanature; ore awfiuidi-flux may 551F136 -used vflrst andithen insplssated later; but the The -inside p V a t y lie ee m diam ter!" freeziee 6 m l here n rnet 1 if it snomas'ou an inch in diameter at its upper end, according I bottom of the crucible or may be higher to avoid picking up any sediment, and may conveniently be six inches in diameter at its lower end, and say to requirements. The lower end of the pipe is constantly open to receive molten metal. The inner surface of the-delivery pipe is unbroken by any valve device and presents a continuous surface from its lower inlet end to its outlet or delivery end. The openings I are large enough to permit withdrawal of the delivery pipes therethrough.

Passing through the cover 6 is a gas tube IS. The gas in the crucible tends to escape when themetal charging opening is opened and thus substantially prevents ingress of air. The gas tube is connected to a chamber it having relatively movable walls, e. g. a bellows (as shown) or pistonand cylinder, which walls can be moved towards or away from each other by hand or power to produce negative, zero, or positive pressure within the crucible, variable at will. This chamber will not necessarily require to be in communication with a supply of gas under pressure, and as shown receives gas through a pipe I! and nonreturn valve It. In the example illustrated the bellows is contained in a metal jacket I! and the top plate 2! of the bellows carries an up wardly extending toothed rack 2| with which a splined shaft 12 gears, this shaft having a handle 23 whereby the operator can move the walls of the bellows towards each -other or apart for increasing or decreasing the pressure of gas in the crucible 'without loss of gas. The operator will apply a slight positive pressure to elect metal and will reduce the pressure to stop the flow and enable the level of metal to fall in the delivery pipe. when the pressure in the bellows is below atmospheric pressure, the non-return valve situated in the bellows inlet pipe opens and inert gas or a mixture of sulphur dust and air. etc.. is drawn into the bellows. Immediately the pressure rises above atmospheric the non-return valve closes and pressure is built up in the crucible. The pressure used for ejecting the metal preferably is less than say 5 lbs. per square inch and; may be only about lb. with very fiuid metal. No valve or other means for permitting escape of the gas from the crucible to the atmosphere is required since the gas in the chamber can be' used continuously. A cock or blow off valve may be provided in the gas pipe it. This chamber may be connected to two or more such crucibles through the medium of a distributing cock if desired.

In employing the apparatus a charge of metal or alloy, such for example as magnesium, magnesium alloy, aluminium alloy or copper alloy, is placed within the crucible through the charging door melted, cleaned and if necessary refined, and the door is closed. The dies or moulds may be arranged upon a platform or secured in position in any convenient manner with their "feeders or runners" adjacent to the delivery pipe. Pressure may then be increased in the chamber to raise the internal pressure to a convenient amount to expel the metal into the dies or moulds.

In the modification shown in Figure 2 the outlet end 26 of the delivery pipe is shaped to receive a nozzle 26 on the bottom of a ladle 28 so that no metal will be left to solidify in this open ing. For this purpose the ladle may have such a nozzle at the lower part thereof corresponding in shape to the shape of the outlet opening. The interior of'this nozzle may also be of frustoaasasee conical shape to receive a ball on the lower end of a vertical rod. The ball serves as a valve to prevent-egress of metal but will be pushed upwardly by the metal received from the crucible. The rod may carry a circular or dished plate to prevent the incoming metal from spurting too far upwardly. The ladle may be lagged and provided with a cover plate. The ladle may be placed in a supporting frame when not in use. These details of the ladle are not illustrated as they are well known in the foundry industry.

The crucible may be maintained in the furnace for long periods, thus reducing heat losses, and may be fitted with a pyrometer, safety valve, and other desired parts. Two or more crucibles may be used so that a supply of metal can be arranged always to be available in at least one of them.

We claim:

1. An apparatus comprising a crucible adapted to contain molten metal and gas-under pressure, a delivery conduit adapted to extend below the level of the molten metal and having its upper end outside the crucible for the delivery of molten metal, a device containing gas and having relatively movable walls, a pipe connecting such device to the interior of the crucible and constructed to enable the flow of gas between the device and the crucible to occur in either direc-- tion along the pipe at any moment, the said device, pipe and crucible forming a gas system, means for moving such walls towards each other to generate the required gas pressure which is transmitted along said pipe to the crucible thereby expelling the molten metal through the delivery conduit and for moving said walls apart whereby said pressure is reduced thereby stopping the outflow of metal through the delivery conduit and returning the metal in the delivery conduit to a required level, there being no outlet in the gas .systeni during use through which any appreciable loss of the gas could normally occur, an inlet for gas to the said system, and an automatically operating return valve controlling said inlet and permitting gas to enter said system if the gas pressure in said system falls below a predetermined degree.

2. An apparatus comprising a crucible adapted to contain molten metal and gas under pressure, a delivery conduit comprising a pipe adapted to extend below the level of the molten metal and having its upper end outside of the crucible for delivery of moltenmetal, the conduit being constantly open to the molten metal beneath the upper surface thereof and of such increasing diameter within the crucible from its upper end downwards as to enable solidification of the metal therein to be avoided, means whereby said pipe i'snormally held in position in relation to the crucible and whereby the delivery pipe can be readilyremoved from the crucible for cleaning, a device containing gas and having relatively movable walls, a pipe connecting such device to the interior of the crucible and constructed to enable the fiow of gas between the device and the crucible to occur in either direction along the pipe at any moment, the said device, pipe and crucible forming a gas system, hand operable means for moving such walls by mechanical connections towards each other to'generate the required gas pressure whichis transmitted along said pipe to the crucible thereby expelling the molten metal through the delivery conduit and for moving said walls apart whereby said pressure is reduced thereby' stopping the outflow of metal through the delivery conduit and retumaasaaso ,3

ing the metal in the delivery conduit to a required mitting gas to enter said. system it the gas pres level, there being no outlet in the gas system .sure in said system falls below a predetermined during use through which any appreciable loss degree. of the gas could normally occur, an inlet for gas 5 tothe said system, and an automatically operat- NEIL DOUGLAS GORDON ROBERTSON. 5

flng return valve controlling said inlet and per-; ERIC CRISP LEWIS.