US3429564A - Melting furnace - Google Patents

Melting furnace Download PDF

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Publication number
US3429564A
US3429564A US476474A US3429564DA US3429564A US 3429564 A US3429564 A US 3429564A US 476474 A US476474 A US 476474A US 3429564D A US3429564D A US 3429564DA US 3429564 A US3429564 A US 3429564A
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United States
Prior art keywords
furnace
torch
shell
hearth
metal
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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
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US476474A
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English (en)
Inventor
Karl S Snow
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Titanium Metals Corp
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Titanium Metals Corp
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Publication date
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    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05H—PLASMA TECHNIQUE; PRODUCTION OF ACCELERATED ELECTRICALLY-CHARGED PARTICLES OR OF NEUTRONS; PRODUCTION OR ACCELERATION OF NEUTRAL MOLECULAR OR ATOMIC BEAMS
    • H05H1/00—Generating plasma; Handling plasma
    • H05H1/24—Generating plasma
    • H05H1/26—Plasma torches
    • H05H1/32—Plasma torches using an arc
    • 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
    • C22B9/00—General processes of refining or remelting of metals; Apparatus for electroslag or arc remelting of metals
    • C22B9/16—Remelting metals
    • C22B9/22—Remelting metals with heating by wave energy or particle radiation
    • C22B9/226—Remelting metals with heating by wave energy or particle radiation by electric discharge, e.g. plasma
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10S266/00—Metallurgical apparatus
    • Y10S266/90—Metal melting furnaces, e.g. cupola type

Definitions

  • This invention relates to a furnace for melting buttons or small ingots of metals. It is particularly adapted for melting refractory metals whichlrequire metling at are temperatures and which are also reactive at elevated temperature requiring melting in a protective or inert atmosphere.
  • Small button furnaces are most often used to melt small circular discs' or buttons of experimental alloys or for melting samples of metals for analytical purposes.
  • pillow-shaped small ing'ots, as well as bars may be produced.
  • An arc furnace has most often heretofore been employed using a non-consumable tungsten electrode to melt a small amount of metal in a cavity in a water-cooled hearth.
  • the furnace may be maintained under vacuum or filled with inert gas to prevent contamination of the melted metal by atmospheric gases, particularly oxygen and nitrogen.
  • the furnace of this invention operates with a heat source providing a steady and controllable stream of arc plasma.
  • a heat source providing a steady and controllable stream of arc plasma.
  • This avoids problems associated with a melting arc as heretofore known and used. It avoids possible contamination by tungsten from the electrode and enables a plurality of cavities to be arranged in close proximity in a hearth without danger from contaminating spatter.
  • Use of a plasma jet torch provides a stable eflluent that can readily be directed onto a sample or mass of metal to be melted.
  • the torch operates with a tungsten electrode, but this is placed up inside a barrel and protected by the nozzle as well as the high speed plasma efiiuent. Under these conditions, spatter onto the tungsten electrode is eliminated as is tungsten contamination in the melt from this source.
  • the steady and readily controlled plasma efliuent also eliminates or reduces spattering from the molten pool of metal being melted. Therefore, closely spaced cavities in a multiple cavity hearth may be employed; and only minimum, if any, shielding between cavities is required.
  • FIG. 1 shows a side view, partly broken out, of a furnace embodying features of this invention
  • FIG. 2 shows a horizontal cross section of the furnace of FIG. 1 taken along the line 2-2;
  • FIG. 3 shows in detail the furnace view-port and its protective screen
  • FIG. 4 shows in detail the furnace hand-hole and cover
  • FIG. 5 shows a cross section of the hand-hole of FIG. 4 taken along the line 5-5;
  • FIG. 6 shows details of the plasma jet torch.
  • the furnace comprises a supporting base composed of uprights 10, lower horizontal bars 12 and upper horizontal bars 14. On the top-of upper horizontal bars 14 is attached furnace lower plate 16 to which the furnace shell 18 is attached and sealed thereto by O. ring 20.
  • Furnace shell 18 is generally hemispherical at its top and encloses the furnace working parts, as will be hereinafter described in detail. It is constructed so as to be gas-tight or sealed to prevent entry thereinto of atmospheric gases.
  • Drive shaft 22 passes through furnace bottom plate 16, its passages being sealed by rotatable seal and thrust bearing 24.
  • Drive shaft 22 is hollow, carrying a central water inlet tube 26 to which is connected at its bottom cooling water supply line 28.
  • the annular space between bottom pipe 26 and the interior surface of shaft 22 provides a channel for outflow of cooling water, which may be discarded to a suitable drain through drain pipe 30.
  • Vertical shaft 22 is is rotated by means of encircling gear 32, fixedly attached to the exterior surface of vertical shaft 22, which meshes with worm 34, which is rotated at desirable speed by speed reducer 36 connected to the output shaft of motor 38.
  • Support bracket 40 supports motor 38 in proper position for connection of the drive train described, and is itself supported on horizontal bars 12.
  • Rotation when desired of shaft 22 is controlled by pedal switch 42 connected through lead 44 to a suitable source of electric power indicated as power cabinet 45, in turn connected to motor 38 throiigh lead 46.
  • Rotatable hearth 48 Fixedly attached to thev'top of vertical shaft 22 is rotatable hearth indicated at 48 having base 50.
  • Rotatable hearth 48 is provided with an upper heavy circular plate 52, preferably fabricated of copper to take advantage of this metals heat transfer characteristics.
  • Upper plate 52 is attached to base 50 by edge plate 54 maintained in tight contact top and bottom by peripheral bolts 56.
  • the top and bottom elements of hearth 48 are arranged so that there is spaced for circulation of cooling water therebetween, such cooling Water being introduced through pipe 26 and distributed to the edges of hearth 48 by subsidiary pipes 57, the return water flowing through the open space back down through hollow vertical shaft 22 and out drain pipe 30.
  • Upper plate 52 of hearth 48 is provided with a plurality of indentations or open-top cavities as at 58 into which metal may be melted into ingots or buttons.
  • Cavities 58 may be of various shapes to provide the desired button or small ingot shape, as will be seen more clearly in FIG. 2. These, for example, may be designed as pillow block cavities 58a, circular cavities for producing metal buttons, as at 58b, .or bar cavities for producing elongated metal shapes, as at 580.
  • loading port 60 In the top of furnace shell 18 is arranged loading port 60 which is closed by provision of cover plate 62. Clamps 64 maintain cover plate 62 firmly attached to rim 66 of port 60, the connection being sealed by O ring 68.
  • Light bulb 70 is located in a receptacle 72 in cover plate 62 to provide illumination for the interior of the furnace during loading, unloading and other periods when illumination is not provided by discharge from the torch.
  • viewport 74 Whose extending tube 76 is spanned by protective screen 78 and closed at its outer end by window 80. The details of this construction are shown more clearly in FIG. 3.
  • Handhole tube 82 is provided with gauntlet 84, having a comparatively long sleeve 86 whose free end is fixedly attached to the rim on tube 82 and in sealing engagement therewith.
  • Gauntlet 84 may be fabricated of any suitable flexible and gas impermeable material, such as nibber or plastic and its sleeve end may be attached to the rim of tube 82 by a suitable adhesive and sealant.
  • cover 88 which is hingedly arranged to close the end of tube 82, as by articulated bolts 90.
  • Gauntlet 84 and its sleeve '86 are prevented from ballooning into the interior of the furnace under the effect of vacuum therein by provision of plate 92 which abuts against a ledge formed of spaced segments 94 fixedly attached to the tube wall.
  • plate 92 When it is desired to work with gauntlet 84 inside the furnace, plate 92 is pivoted to a position parallel with the axis of tube 82 so that it may he slipped edgewise through the spaces between ledge segments 94 and placed temporarily inside the furnace proper, manipulation being accomplished through gauntlet 84.
  • Plate 96 is normally maintained across tube 82 by action of spring clips 98 to act as an additional radiation shield to protect gauntlet 84 and sleeve '86 from heat in the furnace. Plate 96 can be removed from its position as shown, conveniently when plate 92 is edgewise in the tube between ledge segments 94, and both plates may be placed in the furnace temporarily and Without breaking the furnace seal by manipulation through gauntlet 84.
  • a plasma jet torch mounteded through the Wall of furnace shell 18 and sealed as it passes therethrough is a plasma jet torch, indioated generally at 100, whose construction is shown in more detail in FIG. 6.
  • Torch barrel 102 slidably engages ball 104 being sealed as it passes therethrough by flexible bushing 106.
  • Ball 104 is mounted in flexible cupped sealing ring 108, which is in turn fixedly attached to mount tube assembly 110, as by screws 111, which act to tighten clamp ring 112.
  • Torch 100 can therefore be slidably moved up and down through seal bushing 106 and in a variety of pivotal movements through the action of ball 104 in its sealing ring 108.
  • Material which is slightly flexible and which can be compressed to form a tight seal will be suitable for fabrication of bushing 106 and ring 108.
  • these elements are fabricated from a plastic fluorinated hydrocarbon, such as manufactured and sold under the trade name Teflon. Such material has self-lubricating properties, as well as functioning adequately as
  • Handle bar 113 is suitably curved and bent so that it may be readily grasped by an operator conveniently seated so that he can view the operation inside the furnace through window 80 and also be in a position to perate the control foot pedals mounted on horizontal bars 12.
  • One pole of a DC. electric power source is connected to the electrode of plasma jet torch 100 (as will be seen more clearly in FIG. 6) by means of power lead 116.
  • Cooling water is supplied to the torch through cooling pipe 118 connected to a suitable source of cooling fluid, such as water, such fluid being withdrawn from torch 100 through drain line 120 connected to a suitable sewer or sump, also not shown.
  • Inert gas fitting 121 is connected to torch 100 to supply this gas for its operation.
  • the weight of plasma jet torch 100 is suitably counterbalanced so that the operator may readily actuate it up and down and rotatably to put the end of barrel 102 in proper position for melting metal in cavities 58 in hearth plate 52.
  • Counter-balancing is arranged by provision of clamp 122, which is fixedly attached to an upper part of plasma torch body 110, conveniently supporting also Water pipes 118 and 120, as shown, the clamp being connected to cable 124, which passes over elevated pulleys 126 and Whose free end is attached to counterweight 128.
  • a suitable lead 130 is shown attached to shell cover 18 and to plate 16 from which connection will be made through shaft 22 and to hearth 48 and its upper plate 52 and so to metal in a cavity 58.
  • Various power levels are advantageous for best operation of the device, and these may be arranged by inclusion of suitable and conventional equipment in the power cabinet 45 and controlled through lead 132 by pedal switch 134.
  • the furnace shell 18 will comprise a sealed, gas-tight shell in which metals may be melted without contact with atmospheric gases.
  • Pipe 136 fitted with valve 138 communicates with the furnace interior, as shown, and for initial evacuation may be connected to a suitable pump (not shown).
  • a suitable pump not shown
  • This atmosphere will in most cases be maintained by additional inert gas introduced into the furnace shell through plasma jet torch 100.
  • Excess gas may be vented from the furnace interior through bleed pipe 140, whose outlet is submerged in oil bubbler 142, which prevents any back-flow or entry of outside atmosphere gases into the furnace.
  • bleed pipe 140 whose outlet is submerged in oil bubbler 142, which prevents any back-flow or entry of outside atmosphere gases into the furnace.
  • Plasma jet torch is of conventional design and is shown in FIG. 6 in suflicient detail for appreciation of its construction and operation in the furnace of this invention.
  • Cooling Water introduced in pipe 118 circulates inside the body tube and also barrel 102 with baflie 144 arranged spaced apart from inner wall 146 to provide a return for cooling water circulated back up to the top of the torch to be discharged through pipe 120.
  • the torch central electrode is formed with a tip 148 of heat an corrosion resistant metal such as tungsten, the electrode proper being formed of an outer tube 150 and an inner tube 152. Cooling water from pipe 118 is circulated down the electrode between tubes 150 and 152, being returned through inner tube 152 and discharged through pipe 120.
  • Inert gas is supplied to the torch through fitting 121 from a convenient source (not shown) and provides a flow of inert gas through the annular space 154 between the center electrode and the inner barrel wall 146.
  • a convenient source not shown
  • the flow of inert gas is converted to a very hot plasma eflluent directed out of the nozzle 156 of torch 100 and which is caused to impinge on the metal to be melted.
  • clamps 64 are first loosened and then cover plate 62 is removed to open the furnace.
  • Various charges of metals to be melted are then placed in cavities 58 in the upper plate 52 of hearth 48.
  • Particular cavities 58a, 58b, or 580 will be selected, depending on the desired shape of the metal button, pillow block, or bar.
  • Vacuum line 136 will have been previously connected to a suitable vacuum pump, which is now started, and valve 138 is opened so that the interior of furnace shell 18 may be evacuated. Care will be taken that the valves in bleed line 139 and oil bubbler line -140 are closed and that all other seals and fittings in and on the furnace are in proper gas-tight engagement.
  • Thegfurnace should be pumped down to a low pressure indicating proper vacuum-tightness of the systemf-With anlormal-sized button furnace of the type described, evacuation to 20 microns pressure will indicate that the furnace is in proper condition for inert gas melting. After a vacuum-tightness check, a leak check should show no more than 5 microns per minute increase in pressure for a 5-minute period; preferably the leak check should show no more than 2 microns per minute for a 5-minute period.
  • valve 138 is closed and a suitable inert gas, such as argon, is admitted into the furnace coriveniently through valve pipeline 139.
  • a suitable inert gas such as argon
  • valve 139 is cloed and cooling water supply to plasma jet torch 100 is'turned on through inlet pipe 118, and argon gas supply is turned on through inlet pipe 121. Cooling water is" caused to be circulated through hearth 48 by inflow of water through pipe 28.
  • Operation of pedal switch 134 now turns on power between the electrode in plasma, jet torchv 100 and the metal charge iii a cavity 58 substantially jaligned underneath it.
  • the procedure may be repeated until the charges in the cavities 58 in hearth 48 have been initially melted.
  • the argon atmosphere inside furnace shell 1'8 is maintained by argon introduced into' plasma torch 94 as plasma-forming gas. Excess argon islvented from the furnace interior through oil bubbler 142.
  • buttons and small ingots After initial melting, and to insure homogenity in the buttons and small ingots, they are best remelted after turning over so that the bottom portions may be exposed to the torch melting heat.
  • power to plasma jet torch 100 is shut off and cover 88 of hand-hole tube 82 is removed by loosening bolts 90, and the operator then inserts his hand in gauntlet 84 and first places plate 92 edgewise aril'tl then places it and plate 96 temporarily inside the furnace shell 18. Then with his gauntlet hand he reaches inside the furnace shell 18 and turns over the initially melted buttons or ingots. This turning is, as will be appreciated, accomplished Without admitting air into the interior of the furnace.
  • buttons are turned, the operator, still with his hand working in gauntlet 84, replaces plate 96 and 92. He then places the gauntlet 84 and sleeve 86 in tube 82 extension and replaces cover 88 and tightens this in place by means of bolts 90. Electric power is then applied between the electrode in plasma jet torch 100 and one of the initially melted buttons or ingots in a cavity 58, and thismetal button or ingot is then remelted to form a final ingot. After remelting one such button or ingot, the hearth is rotated to align another underneath plasma jet torch 100, and the r'emelting operation is repeated as before. After.
  • buttons and small ingots have been remelted (and if desired remelting may be repeated several 6 times), plasma jet torch power is shut down by operation of pedal switch .134, and cover plate 62 is removed after first loosening clamps 64. The finished buttons or ingots may then be removed 'from the furnace.
  • the meltingfurnace of this invention is convenient and efiicient in operation.
  • the plasma effluent from the torch is more stable than an arc discharge heretofore employed for heating in such furnaces. Since the effluent is directed from the end of the torch barrel as a stream of plasma and gas, it can be pointed and accurately controlled to impilfi'ge on the surface of metal in one of the hearth moldcavities.
  • the means for directing this efiiuent that is the slidable and pivotable mounting for the torch barrelfcnables the operator to accurately control the torch effluent for best melting effect.
  • the plasma jet torch therefore provides a readily and accurately controllable source; of intense heat for efficient melting of metal bodies successively in a plurality of mold cavities.
  • Another unique advantage of the furnace of this invention is the additional feature of maintenance of an inert melting atmbsphere inside a sealed furnace shell using the inert gas supplied for operation of the plasma jet torch.
  • the inert gas supplied to the torch serves a dual purposeit provides gas for" plasma generation, and also gas for maintenance of j a protective atmosphere inside the furnace.
  • a furnace for melting metals comprising:
  • a plasma jet torch having a tip and a nozzle located within said shell, and means to supply inert gas past said tip through said nozzle into said shell;
  • a furnace for melting metals comprising:
  • a plasma jet torch having a tip and a nozzle located within said shell, and means to supply inert gas past said tip ;;.t hrough said nozzle into said shell;
  • a furnace for melting metals comprising:
  • a plasma jet torch having a tip and a nozzle located within said shell, and means for supplying inert gas past said tip through said nozzle into said shell;
  • a furnace for melting metals comprising:
  • a plasma jet torch having a tip and a nozzle located within said shell, and meansfor supplying inert gas past said tip through said nozzle into said shell;
  • a furnace as set forth in claim 4 including:

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  • Engineering & Computer Science (AREA)
  • Plasma & Fusion (AREA)
  • Physics & Mathematics (AREA)
  • Chemical & Material Sciences (AREA)
  • Mechanical Engineering (AREA)
  • Materials Engineering (AREA)
  • Manufacturing & Machinery (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Spectroscopy & Molecular Physics (AREA)
  • Vertical, Hearth, Or Arc Furnaces (AREA)
  • Manufacture And Refinement Of Metals (AREA)
  • Furnace Details (AREA)
US476474A 1965-08-02 1965-08-02 Melting furnace Expired - Lifetime US3429564A (en)

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DE (1) DE1508562A1 (nl)
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SE (1) SE317776B (nl)

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4018973A (en) * 1974-08-20 1977-04-19 Paton Boris E Furnace construction for plasma arc remelting of metal
US4651326A (en) * 1985-06-17 1987-03-17 Voest-Alpine Aktiengesellschaft Electric furnace arrangement
US4718477A (en) * 1986-07-30 1988-01-12 Plasma Energy Corporation Apparatus and method for processing reactive metals
US4982410A (en) * 1989-04-19 1991-01-01 Mustoe Trevor N Plasma arc furnace with variable path transferred arc

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS5036407B1 (nl) * 1970-05-19 1975-11-25
EP0289116A1 (en) * 1987-03-04 1988-11-02 Westinghouse Electric Corporation Method and device for casting powdered materials

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4018973A (en) * 1974-08-20 1977-04-19 Paton Boris E Furnace construction for plasma arc remelting of metal
US4651326A (en) * 1985-06-17 1987-03-17 Voest-Alpine Aktiengesellschaft Electric furnace arrangement
US4718477A (en) * 1986-07-30 1988-01-12 Plasma Energy Corporation Apparatus and method for processing reactive metals
DE3723418A1 (de) * 1986-07-30 1988-02-11 Plasma Energy Corp Schmelzvorrichtung fuer reaktive metalle und aehnliche materialien
US4982410A (en) * 1989-04-19 1991-01-01 Mustoe Trevor N Plasma arc furnace with variable path transferred arc

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Publication number Publication date
GB1106393A (en) 1968-03-13
SE317776B (nl) 1969-11-24
DE1508562A1 (de) 1969-10-30

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