US3881709A - Diffuser castings - Google Patents

Diffuser castings Download PDF

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Publication number
US3881709A
US3881709A US340199A US34019973A US3881709A US 3881709 A US3881709 A US 3881709A US 340199 A US340199 A US 340199A US 34019973 A US34019973 A US 34019973A US 3881709 A US3881709 A US 3881709A
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US
United States
Prior art keywords
diffuser
cast
refractory
stem
core
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
Application number
US340199A
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English (en)
Inventor
William John Steen
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Morgan Refractories Ltd
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Morgan Refractories Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Morgan Refractories Ltd filed Critical Morgan Refractories Ltd
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
    • B22D1/00—Treatment of fused masses in the ladle or the supply runners before casting
    • B22D1/002—Treatment with gases
    • B22D1/005—Injection assemblies therefor
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B28—WORKING CEMENT, CLAY, OR STONE
    • B28B—SHAPING CLAY OR OTHER CERAMIC COMPOSITIONS; SHAPING SLAG; SHAPING MIXTURES CONTAINING CEMENTITIOUS MATERIAL, e.g. PLASTER
    • B28B7/00—Moulds; Cores; Mandrels
    • B28B7/34—Moulds, cores, or mandrels of special material, e.g. destructible materials
    • B28B7/342—Moulds, cores, or mandrels of special material, e.g. destructible materials which are at least partially destroyed, e.g. broken, molten, before demoulding; Moulding surfaces or spaces shaped by, or in, the ground, or sand or soil, whether bound or not; Cores consisting at least mainly of sand or soil, whether bound or not
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
    • C22B21/00—Obtaining aluminium
    • C22B21/06—Obtaining aluminium refining
    • C22B21/064—Obtaining aluminium refining using inert or reactive gases

Definitions

  • ABSTRACT A method of making a cast refractory diffuser for feeding gas into molten aluminium or other fluid material at high temperatures, said diffuser having a tubular inlet stem integral with a hollow, gas-permeable outlet head which extends laterally from the stem and has an unbroken wall around a cavity extending from the bore of an inlet stem, in which method there is used at least for the outlet head a compressible, fugitive casting core that maintains its shape during casting of the refractory from an aqueous mix but yields to shrinkage of the cast during drying and commencement of firing and, before completion of firing, is lost to leave at most only an insignificant ash or other residue in the hollow head.
  • such a unit is suitable for feeding nitrogen into molten aluminium in a crucible, or other molten-metal holding furnace vessel, during treatment of the aluminium to remove gas and impurities.
  • Such treatment is carried out in a crucible divided into an inlet and an outlet side by a vertical partition extending nearby to the bottom.
  • Molten aluminium flows in through a layer of flux, down to a layer of fluxcoated alumina balls, across the bottom of the crucible through a layer of uncoated balls and up the outlet side through more uncoated balls.
  • the nitrogen is introduced above the balls on the inlet side of the crucible and bubbles up the inlet side to escape through the layer of flux.
  • the two essential structural features of the refractory unit that introduces the nitrogen are a tubular inlet stem, made gas-tight such as by a liner, and a hollow, gas-permeable, outlet head which branches from the stem to extend across the stream of molten metal and diffuse the gas into it.
  • the stem and head together may have, for example, an L-shaped, an inverted T-shape or mushroom shape or the head may be a spider.
  • the junction between the stem and the head of a cast unit involves a change in direction of the gas passage, between the bore of the tubular stern and the interior of the hollow head, through which a casting core cannot be withdrawn.
  • the obvious solution is to use two withdrawable cores, meeting at the junction, and to plug the hole through which the head core is withdrawn.
  • Such a plug however entails a refractory joint and this, like the junction between a separate stem and head, has proved liable to early failure when immersed in molten metal.
  • the present invention solves the problem by casting, as an integral branch from a refractory tubular stem, a laterally extending hollow head with an unbroken wall.
  • Use is made, at least and preferably only for the head, of a fugitive or expendable casting core, in particular of combustible material, that retains its shape for easting of the refractory material from an aqueous mix, yields to shrinkage of the cast material during drying and commencement of firing so that the casts do not crack and, before completion of firing, becomes consumed or reduced to an insignificant ash or other residue in the hollow head.
  • a particularly useful combustible core material is a plastics foam or cellular material of the rigid or semirigid type, such as a polyurethane, which can be cast to foamed or cellular form by known simple mixing and pouring techniques. Such materials can be made finepored with good self-sustaining strength characteristics but yieldable to cast refractory shrinkage and combustible at a suitable temperature, such as 750C, with a small residue.
  • a fugitive core for the head is preferably used in conjunction with a withdrawable core, such as a metal tube, for the stem and this can serve to locate the fugitive core by engagement therewith at the junction of the gas passage between the stem and the head, or a short distance up the stem.
  • a withdrawable core such as a metal tube
  • the or each terminal end of the fugitive core is temporarily supported, until shortly before casting is completed, by a supporting pin withdrawable through the wall of the plaster or other outer former for the casting. Possible location difficulties with for example the slightly flexible polyurethane cores that allow for casting shrinkage are thus avoided. After withdrawal of the pin, the fugitive core being by then well located and supported by cast material, the small hole left by the pin is filled by flow of the cast material.
  • the present invention includes the casting method described above, using a fugitive core preferably in combination with a withdrawable core, as well as the particular cast product.
  • the product can be defined as a diffuser, for feeding gas into fluid material at high temperature, especially molten aluminium, comprising a cast integral unit of refractory material having a tubular inlet stem and a hollow, gas-permeable, outlet head which branches laterally from the stem and has an unbroken wall around a cavity which extends laterally from the bore of the stem.
  • Suitable materials for such a diffuser are silicon carbide bonded with carbon, alumina or clay and especially a zirconia-mullite bonded silicon carbide such as is described in our U.K. Pat. Application No. 35977/71 (Steen US. application Ser. No. 274,656 filed July 24, 1972).
  • These materials are made from a particular mix comprising zircon, alumina and silicon carbide and optionally a clay or other inorganic or organic plasticiser, the proportions and particle sizes of the zircon and alumina being such that they react on firing to give a bonding and protective matrix for silicon carbide.
  • FIGS. 1 and 2 are axial sections respectively of an inverted T-shaped diffuser and an L-shaped diffuser
  • FIG. 3 is an exploded perspective view of a split plaster mould and the cores for casting of refractory material to form a diffuser as shown by FIG. 1.
  • the diffuser shown by FIG. 1 comprises a tubular stem 1, open at its upper end for supply of gas, and an inverted T-shaped hollow head 2 branching from the lower end of the stem.
  • the stem 1 Before use, the stem 1 is lined with a metal tube (not shown) so that its bore 3 forms a gas-tight passage to lead gas to the interior 4 of the head 2 through the wall of which gas can permeate to diffuse into the molten metal under treatment.
  • a metal tube not shown
  • the diffuser shown by HO. 2 has a stem 5 and a head 6 forming an L-shape but is otherwise similar to that of FIG. 1.
  • Each diffuser is cast integrally from a pourable composition of a refractory material, preferably a silicon carbide composition as mentioned above, which after drying and firing has the required refractory and porous characteristics, as known in the arts of refractory production and metal treatment.
  • a refractory material preferably a silicon carbide composition as mentioned above, which after drying and firing has the required refractory and porous characteristics, as known in the arts of refractory production and metal treatment.
  • a mould for casting, head uppermost, a diffuser of inverted T-shape comprises a plaster case in two parts 7 and 8 which each have a longitudinal half-cavity, 9 and 10 respectively, which conjointly define the external shape of the diffuser when the two case parts are closed.
  • a mould base 11 has a socket for the root of a withdrawable metal core 12, to form the bore 3 of the stem 1 of the diffuser, and at the top of the core 12 a dowel 13 is provided to locate, as a spigot in a socket 14, a combustible core 15 to form the interior 4 of the diffuser head 2.
  • each end thereof is bored to receive a withdrawable pin 16 withdrawable through a respective hole 17 in the mould case.
  • a diffuser may be carried out as follows:
  • a diffuser for feeding gas into molten aluminum or other fluid material at high temperatures comprising a cast refractory having a tubular inlet stem integral with a hollow, gas-permeable outlet head which extends sharply laterally from the stem and has an unbroken wall around a cavity extending from the bore of the inlet stem, said gas-permeable outlet head being an integrally cast branch of said tubular inlet stem, and said unbroken wall being constituted by as-cast refractory surfaces devoid of joints or joined refractory components or like discontinuities.
  • a cast refractory diffuser as claimed in claim 1 made by casting pourable refractory material for the entire diffuser about suitably shaped core members, the core member for the cavity in the outlet head comprising a compressible fugitive casting core that maintains its shape during casting of the pourable refractory mix but yields to shrinkage of the casting during drying and commencement of firing and, before completion of firing, is lost to leave at most only an insignificant residue in the hollow head, and drying and firing the casting.
  • a cast refractory diffuser as claimed in claim 3 in which said fugitive core is located by a withdrawable stem core removed after the cast has become selfsupporting.
  • a cast refractory diffuser as claimed in claim 3 in which the or each end of the fugitive core away from the stem of the diffuser is temporarily supporting during casting by a pin which is withdrawn through the wall of the casting mold once the wet cast is firm enough to support the core, the hole in the cast left by withdrawal of the pin being filled by flow of the cast material.

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Chemical & Material Sciences (AREA)
  • Manufacturing & Machinery (AREA)
  • Metallurgy (AREA)
  • Materials Engineering (AREA)
  • Ceramic Engineering (AREA)
  • Organic Chemistry (AREA)
  • Molds, Cores, And Manufacturing Methods Thereof (AREA)
  • Manufacturing Of Tubular Articles Or Embedded Moulded Articles (AREA)
  • Filtering Materials (AREA)
  • Furnace Housings, Linings, Walls, And Ceilings (AREA)
  • Casting Support Devices, Ladles, And Melt Control Thereby (AREA)
US340199A 1972-03-13 1973-03-12 Diffuser castings Expired - Lifetime US3881709A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
GB1159072A GB1425034A (en) 1972-03-13 1972-03-13 Diffuser casting

Publications (1)

Publication Number Publication Date
US3881709A true US3881709A (en) 1975-05-06

Family

ID=9989037

Family Applications (1)

Application Number Title Priority Date Filing Date
US340199A Expired - Lifetime US3881709A (en) 1972-03-13 1973-03-12 Diffuser castings

Country Status (5)

Country Link
US (1) US3881709A (de)
DE (1) DE2333029C3 (de)
FR (1) FR2176007B1 (de)
GB (1) GB1425034A (de)
NO (1) NO133039C (de)

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5804135A (en) * 1995-10-16 1998-09-08 Bayer Aktiengesellschaft Gassing agitator for light metal melts
EP1004682A1 (de) * 1998-11-24 2000-05-31 Blasch Precision Ceramics, Inc. Gasspüleinrichtung aus monolithischer Keramik zum Einleiten von Gasen in eine Metallschmelze
WO2004111281A3 (en) * 2003-06-11 2005-03-24 Porvair Plc Compact micro-porous media device degassing molten metal
US20080245188A1 (en) * 2005-12-06 2008-10-09 Leonard S Aubrey Compact micro-porous media degasser
US20140210144A1 (en) * 2013-01-31 2014-07-31 Pyrotek Composite degassing tube

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2594735A (en) * 1949-04-12 1952-04-29 Ernest W Crumley Angle head abrasive blast nozzle
US2724160A (en) * 1951-06-08 1955-11-22 Int Alloys Ltd Method of reducing shrinkage defects in metal castings
US3053525A (en) * 1957-09-30 1962-09-11 Siderurgie Fse Inst Rech Porous refractory concrete element
US3503597A (en) * 1967-02-20 1970-03-31 Kessler Harry Harvey Metal treating device
US3799522A (en) * 1971-10-08 1974-03-26 British Aluminium Co Ltd Apparatus for introducing gas into liquid metal

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2594735A (en) * 1949-04-12 1952-04-29 Ernest W Crumley Angle head abrasive blast nozzle
US2724160A (en) * 1951-06-08 1955-11-22 Int Alloys Ltd Method of reducing shrinkage defects in metal castings
US3053525A (en) * 1957-09-30 1962-09-11 Siderurgie Fse Inst Rech Porous refractory concrete element
US3503597A (en) * 1967-02-20 1970-03-31 Kessler Harry Harvey Metal treating device
US3799522A (en) * 1971-10-08 1974-03-26 British Aluminium Co Ltd Apparatus for introducing gas into liquid metal

Cited By (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5804135A (en) * 1995-10-16 1998-09-08 Bayer Aktiengesellschaft Gassing agitator for light metal melts
EP1004682A1 (de) * 1998-11-24 2000-05-31 Blasch Precision Ceramics, Inc. Gasspüleinrichtung aus monolithischer Keramik zum Einleiten von Gasen in eine Metallschmelze
US6199836B1 (en) 1998-11-24 2001-03-13 Blasch Precision Ceramics, Inc. Monolithic ceramic gas diffuser for injecting gas into a molten metal bath
US6322729B2 (en) 1998-11-24 2001-11-27 Blasch Precision Ceramics, Inc. Method of forming monolithic ceramic gas diffuser
US6378847B2 (en) 1998-11-24 2002-04-30 Donald G. Rexford Monolithic ceramic gas diffuser for injecting gas into a molten metal bath
WO2004111281A3 (en) * 2003-06-11 2005-03-24 Porvair Plc Compact micro-porous media device degassing molten metal
US7547409B2 (en) 2003-06-11 2009-06-16 Poevair Plc Compact micro-porous media degasser
US20080245188A1 (en) * 2005-12-06 2008-10-09 Leonard S Aubrey Compact micro-porous media degasser
US7585455B2 (en) 2005-12-06 2009-09-08 Porvair Plc Compact micro-porous media degasser
US20140210144A1 (en) * 2013-01-31 2014-07-31 Pyrotek Composite degassing tube

Also Published As

Publication number Publication date
DE2333029A1 (de) 1973-12-06
DE2333029C3 (de) 1975-11-13
NO133039B (de) 1975-11-17
DE2333029B2 (de) 1975-04-03
FR2176007B1 (de) 1978-08-04
GB1425034A (en) 1976-02-18
FR2176007A1 (de) 1973-10-26
NO133039C (de) 1976-02-25

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