General Electric Company

Robert T Frost

Hugh R Lowry

Jeffrey N Peterson

Dense, homogeneous tubular metal products such as pipe is cast in long lengths continuously by introducing liquid metal into the lower portion of an annular-shaped casting vessel. The liquid metal is withdrawn in the presence of an outer elongated upwardly travelling alternating electromagnetic levitation field and a second inner electromagnetic levitation field for maintaining the tubular liquid metal column in a substantially weightless and pressureless contact condition while solidifying. The resulting solidified tubular metal product is withdrawn from the upper portion of the field, cooled and further processed to result in a desired and product/and has a homogeneous, fully dense, fine grain structure due to continuous eddy current stirring by the levitating electromagnetic fields and a ripply, shiny exterior surface.

Continuous metal tube casting method and apparatus

The products of this invention are produced in an elongated casting vessel disposed in upright position to receive liquid metal for solidification within an electromagnetic field generating means disposed around the vessel along a portion of its length. The electromagnetic field generating means produces an upward lifting effect on liquid metal in the vessel together with a containment effect wherein the liquid metal is continuously urged upwardly into contact with the lower end of the solidifying product and maintained in a pressureless contact condition with respect to the walls of the casting vessel. In this way, voids and flaws are avoided and fully dense homogeneous products of uniform, small grain cross section result without wear on the casting vessel. The novel products of the invention are long metal bodies which are fully dense and of substantially uniform, fine grain cross section and constant composition throughout in each instance. In their as-cast condition, these bars, rods and other products have smooth, slightly wavy surfaces attributable to the fact that before, during and just after solidification, the metal of which they are formed is electromagnetically maintained out of contact with lateral support structure (such as the surface of a mold) and also due to the fact that the liquid metal at the solidification front is constantly stirred by induced eddy currents. The product may suitably be of multi-element composition which tends strongly to phase separation, however, because of the continuous stirring by induced eddy currents, the resulting products have a high degree of homogeneity.

Continuous metal casting method and apparatus and products

The method of this invention is practiced within an elongated casting vessel disposed in upright position to receive liquid metal for solidification together with means for delivering liquid metal into the lower portion of the vessel. Heat exchange means are associated with the vessel for cooling and solidifying the liquid metal therein and means are provided for removing solidified metal from the upper portion of the vessel. Electromagnetic field generating means are disposed around the vessel along a portion of its length which includes a plurality of electromagnetic coils for connection to successive phases of a polyphase electric current source to produce both an upward lifting effect on liquid metal in the vessel and a containment field effect. By 'lifting effect' is meant that liquid metal is continuously urged upwardly into contact with the lower end of the solidifying product. In this way, voids and flaws are avoided and fully dense homogeneous products of uniform, small grain cross section result. The containment field effect produces a slight gap between the sidewalls of the casting vessel and the liquid metal. This maintains the liquid in a pressureless contact condition that allows for good heat transfer and provides solidification of the metal. The casting apparatus further includes a crucible to contain a bath of molten metal communicating with the lower end of the casting vessel and also includes means associated with the crucible to move liquid metal upwardly into the casting vessel to a level above the lower end of the electromagnetic field generating means. Such may take the form of a hydrostatic pressure source which operates to displace liquid metal upwardly into the casting vessel.

Continuous metal casting method

The new apparatus of this invention comprises an elongated casting vessel disposed in upright position to receive liquid metal for solidification, means for delivering liquid metal into the lower portion of that vessel, heat exchange means associated with the vessel for cooling and solidifying the liquid metal therein, means for removing solidified metal from the upper portion of the vessel, and electromagnetic field generating means disposed around the vessel along a portion of its length. The field generating means includes a plurality of electromagnetic coils for connection to successive phases of a polyphase electric current source to produce a combined electromagnetic upward levitating field effect and a containment field effect on liquid and metal in the vessel. By 'levitating effect' is meant that liquid metal is continuously suspended in space and urged upwardly into contact with the lower end of the solidifying product. In this way, voids and flaws are avoided. The containment field effect produces a slight gap between the walls of the casting vessel and the liquid metal so as to induce a pressureless contact condition in the solidification region. The casting apparatus includes a crucible to contain a bath of molten metal communicating with the lower end of the casting vessel and also includes means associated with the crucible to move liquid metal upwardly into the casting vessel to a level above the lower end of the electromagnetic field generating means. Such may take the form of a hydrostatic pressure source which operates to displace liquid metal upwardly into the casting vessel.

Continuous metal casting apparatus

Apparatus for producing dense homogeneous metal cast in long lengths by introducing liquid metal into the lower portion of a casting vessel in the presence of an elongated upwardly-traveling alternating electromagnetic levitation field that provides a levitation ratio of from 75% to 200% of the weight per unit length of the liquid metal. The apparatus provides cooling for solidifying the metal while moving upwardly through the field, and a withdrawal mechanism for removing solidified metal product from the upper portion of the field. The electromagnetic field producing means is designed to establish an alternating electromagnetic field having a frequency at or near a value F=36.rho./D.sup.2 where F is the frequency in kilohertz, .rho. is the resistivity of the liquid metal column in micro-ohm-centimeters and D is the average diameter of the solidified metal rod product in millimeters.

Dense homogeneous metal is cast in long lengths by introducing liquid metal into the lower portion of a casting vessel in the presence of an elongated upwardly-traveling alternating electromagnetic levitation field that provides a levitation ratio of from 75% to 200% of the weight per unit length of the liquid metal, solidifying the metal while moving upwardly through the field, and removing solidified metal product from the upper portion of the field. The frequency of the alternating electromagnetic field is established at or near a value F=(36.rho./D.sup.2) where F is the frequency in kilohertz, .rho. is the resistivity of the liquid metal column in micro-ohm-centimeters and D is the diameter of the solidified metal rod product in millimeters.

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Berwyn, PA, United States of America

Robert T Frost