CA1038132A - Automatic unplugging aluminothermic welding crucible - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE

The present invention relates to an automatic unplugging aluminothermic welding crucible comprising a crucible per se made of refractory material, shaped generally as a truncated cone with a vertical axis, said cone tapering inwardly to the lower base thereof and comprising a vertically oriented conical hole, in said crucible, receiving a crown provided with a conical bore, said conical bore extending vertically through said crown and being inwardly downwardly tapered, said conical bore of said crown and said conical hole receiving a casting socket disposed vertically therein, the lower base of said crucible being sealed by sealing means before filling of said crucible. The sealing means comprise a plug made of an aluminothermic compound consisting of iron oxide and aluminum agglomerated with a suitable binder, said plug resting on a steel washer.

Description

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~ he ~nventioh -elates to an automatic unplugging al~-m~nothermic welding crucible.
Aluminothermic ~elding crucibles, designed, in psrti-cular for welding rails, are generally shaped as a truncated cone ~ith a vertical axis, the larger base, opened, being located in the upper part thereof,and the smaller base, provided with a hole designed to allow the flow of melted metal, being located in the lower part thereof. Said cruci-bles conRist of a highly refractory material and provision is generally made at ssid lo~er base, which supports the greatest therm~l eifects of the aluminothermic reaction, for an e~tremely resistant crown, provided with a hole e~ten-ding vertic~lly therethrough and tapering inwardly in the downward direction, said hole reeeiving a socket through which the casting is madeO Said sockets are rapidl~ destroyed by the melted metal and must be replaced in general, after five or si~ castingsO
In kno~n dovices with manual unplugging, the caeting hole is sealed with a metallic nail, the head thereof being protected by an asbestos washer covered with some magnesia in grain form. When the ~ nother~ic reaction is completed in~ldo the crucible, the operator strikes the tip of the nail which pro~ects outside the crucible to make the nail come up again and the melted metal flows into the mold located below said casting socket the conduit of which was unplugged as a result of lifting of the nail.
Var~ous attempts have been made to replace thi6 manual unplugging by an automatic unplugging opera'ion. Thus, it has been sugge~ted to replace said sealing nail by a metal washer~

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and, recently, by a fusible plug. In the ca~e o~ a metal washer~
the latter may melt very quickly~ a6 ~oon as melted met~l come~
into contact therewith or, on the contrary, not quickly enough, which may cau~e solidification of part oi the metal at the bottom of the crucible and clog it.
The fu~ible plug8 co~morcially available oi late generally give irregular and non reproducible results. Indeed, thelr melting results irom the supply oi a predeter~ined aaount oi h~atO The amount oi heat Yupplied to ~aid ~usible plug depends partly on the way in which the reaction proceed~;
which is not always ldentical and sub~ect to control. In addition, the prod~ct~ resulting iro~ the melting oi said plug mN~t go through the ~teel bath and may dissolve at least partially therein and thereiore conta~inate it.
The ob~ct oi the invention i~ to pro~ide an a~t~natic regular unplu4ging operation, whate~er tho way in which the alnmlnothormic roaction occurs may be, which i8 iree oi any risk of contamination Or the steel bath. ~or this purpose, in Pn aluminothormic w lding crucible oi tho type d00cribed, th- sealing meano con~ist oi a plug ~ormed irom an alu~lnoth-r~ic compound conoioting oi lron o~ide and alu~inu~ gglo~orated Yith a ~ultable bind-r, ior ~sample, aa- oi eilicate. ~hu~, the plug d-otruction time is perfectly det-rmined as a ~unctlon oi it~ length and its deotructlon llb-rates producto whic!h can dlo~ol~e in the ~d ding ~teel ~ithout eserting any har~ful eifect on lto ~uality eince theoe producte are practically the os~e ao tho~e used in th~
cruclbl to iorm the ~ dding ote d .
In a preierred ombo ~ent, the plug reste on a - - .

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thin lro~ or steel wa~herJ ior e~a~ple9 appro~imately 1 ~hick, ~o that the eiiectlYe unplugging o~ the ~ocket hole tak~8 place only ~ter the destruction oi the plug , i.e.
~ithout the possib~lity o~ the ~elding steel to drive a~ay, under tha e~rect o~ lts ~eight, only part oi the disintegra-ted plug~
Dhc iDvention will be more clearly understood ~pOR read~ng the iollowing description with reierence to the appended drawing in which the sin~le iigure i8 an a ial sec-tion schematic view oi part Or a crucible according to thein~ention berore i~ ng, ln a partioular embodiment.
~he crucible 1, per ~e9 made oi a reiractory ; ~ateri~l, such as magnesia, mag~esia pise or corindon, i9 generally shaped as a truncated cone with 8 ~artic~l ~Y18~ -~hich tapers into a ~m~ller downwardly facing base provided ! with a conical hole 2 which pro~ides ior communication bet~een the inside Or crucible l and the welding mold ( not sho~n). ~he base ot cr~cible l, can recei~e a crown 3 , made oi highly resistant material comprising a truncated bore 4 ~hich e2tends hole 2. Receivable with~n hole 2, and parti~lly bore 4, there ~8 pro~ided a socket 5, made oi refractory material, such as magnesia or compressed sand. Socket 5 is provided with a bore 6 comprising a sho-~der 7.
~ steel ~asher 8 engages the shoulder 7 whereby sealing bore 6 and 18 stopped by a plug 9 formed irom an alumi~othermic compound consisting o~ iron 02ide and aluminum glomerated vith a silicate based binder.
~ he destruction time for plug 9, as a result oi the alnm~nothermic resctlon inside crucible l, ~ith the pro-Vi80 0~ a con~tant particle size o~ th~ products ueed, a very intimate mixture oi the~e product~ ~nd strictly constant manu~ac~uring conditions, depend~ solely on the length bhereof ~rom the moment at which melted metDl comes in~o contsct with the upper part oP plug 9. After destruction o~ plug 9, the steel ~asher 8 ~elts itsel~ in a set time which adds to the time required ior the dl~inte~ration o~ plug 9. The destruction oi plug 9, which is no lon4er a ~unction o~ an amount oi heat supplied, starts a~ ~oon a~ th~ iirst drop~
o~ melted metal come into contact th~rewith and the plug dlsintegratee by it~eli at a per~ectly well determined rate.
The tlme requlred ~or melting the stcel washer bel1g ~l~o per~ectly w~ll deter~inea and ¢o~stant, sinc~ the heat r quired ior melting result~ from the reaction oi plug 9 and irom the steel inside the crucible which comes into contact therewith, as a mass, a~ a reffult oi the iact th~t the reaction oi the welding mixture i8 substantially co~pleted, sinca it has occurred during the aestruction Or the plug, the total time roquirod ior unplugglng oi the casting holo i8 constant.
In aadition, the product~ resulting ir~m the molting Or plu 9 and washer 8 are the same as those u~ed in ~h0 produ¢tion o~ the welding steel, whereby this ~olding ~t0el i~ not contaminated by the molt products. The corindon resulting irom the sluminothe~mic reaction is eliminated in a con~entional ma~ner, through gra~ity as it iB producedO

Claims

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. An automatic unplugging aluminothermic welding crucible comprising a crucible per se made of refractory material, shaped generally as a truncated cone with a vertical axis, said cone tapering inwardly to the lower base thereof and comprising a vertically oriented conical hole, in said crucible, receiving a crown provided with a conical bore, said conical bore extending vertically through said crown and being inwardly downwardly tapered, said conical bore of said crown and said conical hole receiving a casting socket disposed vertically therein, the lower base of said crucible being sealed by sealing means before filling of said crucible, said sealing means comprising a plug made of an aluminothermic compound consisting of iron oxide and aluminum agglomerated with a suitable binder, said plug resting on a steel washer.