FR2480419A1 - INSTALLATION AND METHOD FOR MELTING OR MAINTAINING A METAL MATERIAL BY IMMERSION RESISTANT ELEMENT IN METAL - Google Patents

Abstract

1. Installation for melting aluminium or aluminium alloys or for keeping them in a molten state, comprising a container for molten aluminium and an electric circuit with an element immersed in the aluminium, this element consisting of a material with a higher melting point than aluminium, characterised in that the element consists of silicon carbide or graphite and the circuit is operated at a low voltage of about 5 to 15 volts.

Description

The present invention relates to installations for

  melt a metal material or to maintain a melting

  and processes for heating a raw material

  due or melt-conductive electricity.

  To retain a molten metal alloy, that is to say to prevent it from spreading by retaining it, for example in an oven or crucible, it is known to heat the container that constitutes the crucible or the furnace, so that it transmits the

  heat it receives to the melt it contains.

  Fusion or maintenance of normal

  room temperature, which are electrically conductive

  Here, such as metals, can be carried out in various installations.

  The crucible furnace, heated by flames or by resistance

  electricity, radiating energy from the crucible, flaming

  abrade me and use the refractory materials of the furnace.

  Electric resistors do not withstand high temperatures. A crucible induction furnace is expensive to install and maintain especially because of its inductors. Troubleshooting

  can only be performed by specialized electronics specialists.

  For a channel induction furnace, where the metal contained in the channel heats up under the effect of the induced currents created by an induction coil and by a magnetic core enclosing the channel, it is necessary, under penalty of abridging a lot longevity, always leave liquid metal in the channel, which imposes uninterrupted operation. The installed capacity is limited by

  so that the melting speed is small. The refurbishment of

fractaries is expensive.

  In addition, the performance of these known facilities is poor. The invention overcomes these drawbacks by an inexpensive installation to install and maintain, in particular by the fact that its electrical equipment is simple, quick to start, can operate with interruptions without inconvenience, giving more

  because it operates at very low voltage (particularly

  between 5 and 15 volts) improving working conditions, because it does not pollute the atmosphere and does not create noise

  and to achieve a better return than the

previous sections.

248041-9

  The invention therefore relates to an installation for melting metal or for maintaining it in fusion, comprising a

  molten metal container and an electrical circuit with an im-

  merged into the metal, characterized in that the element is made of a material with higher electrical resistivity and melting point

to those of the metal.

  Since this or these immersed elements are made of

  non-metallic material, such as graphite or silicon carbide, or a metallic material whose electrical resistivity is greater than that of the metal in which they are immersed, it is the resistant element or elements which preferentially undergo

  heating by direct passage of the current.

  In the case of a single element looping an electrical circuit, it is applied to it an electrical potential at its two

Y5 ends.

  In the case of several elements, preferably in a number which is a multiple of 2 or 3, it is applied to each of them an electric potential, the circuit being looped by the metal itself in which they are immersed, this in order to achieve a

classical electrical coupling.

  The metal in which the heating elements are immersed may be in the liquid, pasty or solid state, the only condition being that there is an intimate contact between the metal and the immersed resistant element: the melting point of the element is greater than that of the metal of at least 1000 C preferably and better still at least 2000 C. The bath heating by plunging electrodes is a known method in which the weak electrodes have the purpose of

  only purpose to bring the current to the bath which itself is resistant.

  According to the invention, the system is reversed by the fact that the submerged element or elements are much more resistant than the metal in which they dive, the latter having the role of

close the electrical circuit.

  The invention applies with a particular advantage to the

fusion of aluminum.

  In the accompanying drawings, given solely by way of example

  FIG. 1 is a diagram seen in section of an oven according to

  vention with heating by an element

  FIG. 2 is a diagram seen in section of a furnace according to

  f vention with heating by 3 elements.

  In FIG. I., the vessel 1 or vessel of the oven is in

  thermally insulating refractory material.

  A resistive element 2 is immersed in the metal 3 The current leads 4 and 5 are connected to the

  upper faces of element 2 out of bath.

  The feeds 4 and 5 are respectively connected to the terminals of the single-phase secondary of a voltage-controlled step-down transformer 6 by a regulation 7 suitable for thyristors, self-variable or other controlled by sensors such as a cane

  -YY'pyrometric 8 or a telescope 9.

  In FIG. 2., the heating is carried out by 3 elements 10,

He and 12.

  The current leads 13, 14 and 15 are connected respectively

  at the terminals of the three-phase secondary of a voltage-reducing transformer 16 2 controlled by a regulation 17 appropriate to thyristors, self variable or other controlled by sensors

  such as pyrometric cane 18 or bezel 19.

  The following tests were carried out in a 400 mm diameter, 470 mm deep furnace and aluminum capacity

  g 100 kg, illustrate the invention.

First try

  100 kg of aluminum are cast in ingots using a bromine

  their gas. A silicon carbide heating element is immersed

  having a resistivity of 0.005 ohms / cm / cm 2 in light aluminum

  2w quide (cold aluminum resistivity: 2.82 microhms / cm2 / cm).

  - voltage on the element: 10 Volts - Primary voltage of the transformer: 390 V. - Intensity: 110 A. - Power required: 42,900 KVA Second test

  100 kg of aluminum are cast into ingots using a burner

  their gas, Two silicon carbide heating elements are immersed

  cium. - Applied voltage: 10 Volts - Transformer primary voltage: 390 V. - Intensity: 110 V.

- Called power = 42.9 KVA.

  Third test -lo Following the previous test, both elements are

  de-energized to allow solidification of the aluminum

  minium. The solidification being carried out:

  The elements under 10 volts are energized.

  - Transformer Primary Voltage: 390 Volts - Current: 90 A.

- Called power = 35.1 KVA.

  The metal melts by the effect of the submerged elements:

  The values found during the second test are found.

R E Y E N D I C A T IO N S

  1. Installation for melting metal or for keeping it molten, comprising a molten metal container and an electrical circuit having an element immersed in the metal, characterized in that the element is made of a material of electrical resistivity and

    melting point higher than those of the metal.

  2. Installation according to claim 1, characterized by a number of elements immersed in the metal which is a

multiple of 2 or 3.

  3. Installation according to claim 1 or 2,

  characterized in that the element is made of non-metallic material.

  4. Installation according to claim 3, characterized

  in that the element is made of silicon carbide or graphite.

  5. Installation according to claim 1 or 2, characterized in that the element is made of a metallic material of which

  f the electrical resistivity is greater than that of the metal.

  6. Installation according to one of claims I to 5,

  characterized in that the electrical circuit comprises a trans-

  step-down trainer whose secondary is closed by

  one or more elements and by the metal.

  7. Process for retaining a melt or

  melt conductive of electricity, characterized in that it

  to put it in the container of an installation following one

  Claims I to 6 and powering up the circuit.

  8. Method according to claim 7, characterized in that the secondary circuit is under a voltage of 5 to

Volts approx.