Classifications

• • 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
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
  • B22D11/00—Continuous casting of metals, i.e. casting in indefinite lengths
  • B22D11/10—Supplying or treating molten metal
  • B22D11/11—Treating the molten metal
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
  • B22D41/00—Casting melt-holding vessels, e.g. ladles, tundishes, cups or the like
  • B22D41/005—Casting melt-holding vessels, e.g. ladles, tundishes, cups or the like with heating or cooling means
  • B22D41/01—Heating means
  • B22D41/015—Heating means with external heating, i.e. the heat source not being a part of the ladle
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F27—FURNACES; KILNS; OVENS; RETORTS
  • F27D—DETAILS OR ACCESSORIES OF FURNACES, KILNS, OVENS OR RETORTS, IN SO FAR AS THEY ARE OF KINDS OCCURRING IN MORE THAN ONE KIND OF FURNACE
  • F27D11/00—Arrangement of elements for electric heating in or on furnaces
  • F27D11/02—Ohmic resistance heating
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F27—FURNACES; KILNS; OVENS; RETORTS
  • F27D—DETAILS OR ACCESSORIES OF FURNACES, KILNS, OVENS OR RETORTS, IN SO FAR AS THEY ARE OF KINDS OCCURRING IN MORE THAN ONE KIND OF FURNACE
  • F27D99/00—Subject matter not provided for in other groups of this subclass
  • F27D99/0001—Heating elements or systems
  • F27D99/0006—Electric heating elements or system
• • H—ELECTRICITY
  • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
  • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
  • H05B3/00—Ohmic-resistance heating
  • H05B3/78—Heating arrangements specially adapted for immersion heating
  • H05B3/82—Fixedly-mounted immersion heaters
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F27—FURNACES; KILNS; OVENS; RETORTS
  • F27D—DETAILS OR ACCESSORIES OF FURNACES, KILNS, OVENS OR RETORTS, IN SO FAR AS THEY ARE OF KINDS OCCURRING IN MORE THAN ONE KIND OF FURNACE
  • F27D99/00—Subject matter not provided for in other groups of this subclass
  • F27D99/0001—Heating elements or systems
  • F27D99/0006—Electric heating elements or system
  • F27D2099/0008—Resistor heating
  • F27D2099/0011—The resistor heats a radiant tube or surface
  • F27D2099/0013—The resistor heats a radiant tube or surface immersed in the charge

Definitions

• the invention relates to an electric immersion heater for maintaining a previously melted metal bath in the liquid state or for melting a batch of solid metal, in particular alloys or non-alloyed metals of aluminum, magnesium or zinc.
• an electric immersion heater is an electrical device which comprises a heating zone intended to be placed in contact with a bath of liquid metal to be heated, and a non-heating zone making it possible to make the connection between the heating zone and an electrical power supply unit.
• an immersion heater In a foundry workshop, the most common use of an immersion heater is to maintain the temperature of a molten metal, previously melted using a gas furnace for example. For example, this temperature maintenance can be done in a liquid metal treatment ladle, during degassing or filtration of the liquid metal. According to a more recent application, designed by the applicant company, an immersion heater can be used to melt metal in the solid state and possibly to maintain the temperature of the molten metal thus obtained.
• Immersion heaters for heating a bath of liquid metal have been known for decades, for example from GB 1 027 163, FR 2 720 888, they generally comprise one or more heating elements placed in a cylindrical sheath which separates them from the bath which they are to heat.
• the sheath can be made of inert ceramic material, for example silicon nitride, boron nitride, SiAlON, silicon carbide.
• the heating element can be made in the form of a heating ceramic, for example SiC, as is known from WO 2005/060314, or graphite, as described in FR 2 559 886 and FR 2 622 382.
• Immersion heaters are also known for heating a bath of liquid metal, the tubular sheath of which comprises a plurality of metal heating elements which are embedded in an electrofused magnesia powder, which is an electrical insulator and has suitable thermal conductivity.
• the immersion heaters which are currently on the market use this principle.
• an immersion heater usually comprises an inert tubular sheath which surrounds a core comprising electrically insulating ceramic powder, for example electrofused magnesia, in which the heating elements of the immersion heater and the electrical supply lines necessary for the operation of these heating elements.
• Electrically insulating ceramic powder has a very high production cost. Consequently, increasing the volume of the immersion heater in order to position more heating elements or heating elements of larger size and power in said immersion heater induces a cost, associated with the necessary electrically insulating ceramic powder, which is too high. We are therefore looking for an alternative way to reduce the cost of immersion heaters, without reducing their quality and longevity.
• the present invention aims to remedy the limitations described above and in particular to provide an immersion heater offering increased heating capacity, while limiting the cost associated with this increase in power.
• the invention aims at an immersion heater configured to be placed in contact with a material to be heated, in particular a molten non-ferrous metal, which comprises:
• sheath delimiting a first compartment at least partly filled with electrically insulating ceramic powder, said sheath being configured to be placed in contact with the material to be heated,
• the second compartment is filled at least in part with an inert material.
• an immersion heater comprising a second solidly empty compartment
• This thermal draft phenomenon occurs because the temperature difference between the bottom of the immersion heater with its resistors between 800°C and 1100°C and the top of the immersion heater which causes an air flow.
• the hot air whose density and pressure are lower than those of cold air, rises in the tube.
• the addition in the second compartment of an inert material, and in particular of a refractory ceramic insulator makes it possible to limit this thermal draft effect.
• the inert material at least partially filling the second compartment delimited by the wall is a refractory ceramic insulating material. Said material may be of the flexible type, in a machined block or vacuum-molded.
• the second compartment delimited by the wall is partly filled with an inert material and remains partly empty of solid material.
• the second compartment delimited by the wall is filled at least partly with an inert gas which may be argon or another noble gas.
• the second compartment is at least 30% by volume filled with an inert material, the remaining volume of the second compartment being left empty of solid material. In other embodiments, the second compartment is at least 40%, 60%, 80% or 90% filled with an inert material.
• An electric immersion heater comprises a heating zone, and a non-heating zone for connecting the heating zone to a support of the immersion heater connected by means of an electrical supply.
• the heating zone of the immersion heater is located on the lower part of the immersion heater, it comprises a plurality of heating elements, usually electrical resistors, brought to a high temperature by the passage of an electric current.
• the part of the second compartment corresponding in height to the heating zone of the immersion heater is filled with inert material and the part of the second compartment corresponding in height to the non-heating zone of the immersion heater is left empty of solid material.
• the immersion heater comprises at least one thermocouple type temperature sensor.
• the at least one thermocouple is positioned in the first compartment of the immersion heater and more preferably in the heating zone of the immersion heater.
• the at least one thermocouple is arranged in the electrically insulating ceramic powder.
• the temperature sensor is protected by a glove finger.
• the electrically insulating ceramic powder is selected from zinc oxide powder, alumina powder, magnesium oxide [magnesia] powder or boron nitride powder. It advantageously has good thermal conductivity.
• the wall disposed inside the sheath and delimiting a compartment filled at least in part with an insulating material is formed at least in part from a ceramic material.
• the wall can be formed from a material of comparatively low cost compared to the cost of electrically insulating ceramic powder, while exhibiting sufficient mechanical strength and thermal resistance characteristics.
• the wall is formed from a high performance alloy, preferably a nickel-based alloy exhibiting low expansion at 1100°C.
• the wall is formed from an alloy selected from Inconel alloys or CMSX single-crystal alloys.
• a high-performance alloy or superalloy is a metal alloy having excellent mechanical strength and good creep resistance at high temperature, good surface stability and good resistance to corrosion and oxidation.
• the sheath has a circular section.
• the sheath has an external diameter greater than or equal to 50 millimeters, preferably greater than 75 mm, more preferably greater than 95 mm, and even more preferably greater than 115 mm.
• the immersion heater has sufficient dimensions to include more heating elements or larger heating elements.
• the wall is a tube of circular section.
• the center of the circular section sheath and the center of the circular section wall are substantially identical, so that the first compartment, formed between the sheath and the wall, and intended to be filled at least in part with electrically insulating ceramic powder, has an annular section.
• the heating elements can be arranged in said first compartment of annular section. The heating elements thus positioned are close to the sheath, thus allowing better diffusion of heat towards the sheath and indirectly towards the material to be heated.
• the heating elements are arranged in substantially straight turns arranged substantially parallel to an axis running through the center of the sheath and in which the immersion heater comprises at least 15 turns, preferably at least 20 turns, preferably at least 20 turns, preferably at least 25 turns, preferably at least 30 turns.
• the immersion heater comprises 36 turns.
• a coil is a plurality of heating resistors supplied by the same current supplies and forming a substantially linear assembly arranged longitudinally in the immersion heater, preferably close to the sheath.
• the immersion heater object of the invention is particularly distinguished from known immersion heaters in that the diameter of the first compartment delimited by the sheath can be increased in order to accommodate more heating elements or larger heating elements.
• the immersion heater comprises 16, 24, 32 or 36 turns.
• the heating elements are arranged in substantially straight turns arranged substantially parallel to an axis running through the center of the sheath and in which said turns are positioned close to the inner periphery of the sheath.
• the turns thus positioned are close to the sheath, thus allowing better diffusion of heat towards the sheath and indirectly towards the material to be heated.
• the heating elements comprise electrical resistors comprising molybdenum or an alloy selected from an iron-chromium-aluminum alloy [FeCrAl], a nickel alloy and a chromium alloy.
• the device according to the invention advantageously has a cylindrical shape and a coaxial and symmetrical structure with respect to the central axis.
• the device has a different shape and/or structure, for example an orthogonal section or a section of variable diameter.
• FIG. 1 represents, schematically and in axial section view, a first embodiment of an immersion heater according to the invention
• Fig 2 represents, schematically and in cross-sectional view, the immersion heater object of the first embodiment
• the immersion heater 100 is an electric immersion heater comprising a heating zone 101, and a non-heating zone 102 making it possible to make the connection between the heating zone and a support of the immersion heater 100 connected to an electrical power supply means 110.
• the immersion heater 100 is intended to be positioned in a tank [not shown] containing metal to be heated.
• the heating zone 102 of the immersion heater 100 is intended to be placed in contact with the metal, whether it is a molten metal to be maintained at temperature in order to keep it in the liquid state or a solid metal to be heated.

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• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• General Engineering & Computer Science (AREA)
• Resistance Heating (AREA)

Applications Claiming Priority (2)

Publications (1)

Family

ID=87974736

Family Applications (1)

Country Status (4)

Family Cites Families (12)

• 2023
  • 2023-06-12 FR FR2305907A patent/FR3149746A1/fr active Pending
• 2024
  • 2024-06-10 EP EP24735311.3A patent/EP4724221A1/de active Pending
  • 2024-06-10 CN CN202480038555.7A patent/CN121285437A/zh active Pending
  • 2024-06-10 WO PCT/IB2024/055653 patent/WO2024256949A1/fr not_active Ceased

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