Method and apparatus for rheocasting
OwnerJames E. Kelly, Kenneth E. Blazek +1inventors
InventorsJames E. Kelly, Kenneth E. Blazek, Kenneth P. Young
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Abstract
A method and apparatus for rheocasting (slurry casting) molten metal employ a stirring chamber located upstream of a casting mold. Electromagnetic stirring is employed in both the stirring chamber and the casting mold. Structure is provided for minimizing secondary recirculating flows in the molten metal as it flows downstream through the apparatus, for preventing hangers and for eliminating the columnar dendritic zone at the periphery of the casting. The efficiency of utilization of the magnetic field is optimized as is the agitation required for producing a desired fine, spheroidal, degenerate dendritic grain structure in the solidified casting.
Claims35
An apparatus for use in the continuous casting of molten metal, said apparatus comprising:
- a casting mold having an inlet and an outlet;
- a chamber located upstream of said mold and having an inlet for receiving molten metal and an outlet vertically aligned with said inlet of the mold;
- magnetic stirring means disposed around said chamber, for inducing, in molten metal contained in said chamber, a primary circulatory flow in a first rotational sense;
- said magnetic stirring means having an upstream end and a downstream end and having a linear dimension between its upstream and downstream ends substantially less than the linear distance between said inlet of the chamber and said outlet of the casting mold;
- and a plurality of means for substantially reducing secondary recirculating flows caused in said molten meal by said electromagnetic stirring means, to conserve the energy available from said primary circulatory flow;
- said plurality of means comprising one such means adjacent said upstream end of said magnetic stirring means and another such means adjacent said downstream end of the magnetic stirring means.
An apparatus for use in the casting of molten metal, said apparatus comprising:
- a casting mold having an upstream end, an inlet at said upstream end and an outlet;
- means enclosing said upstream end of the mold from the atmosphere outside said mold;
- a chamber located upstream of said mold and having an inlet for receiving molten metal and an outlet linearly aligned with said inlet of the mold;
- magnetic stirring means disposed around said chamber;
- a conduit composed of refractory material and extending between said outlet of the chamber and said inlet of the mold, for confining molten metal flowing from said chamber into said mold;
- said mold comprising means for solidifying a solid peripheral skin around the molten metal in said mold;
- and first preventing means for preventing said solid peripheral skin in the mold from extending upstream, in the direction of said enclosed upstream end, beyond a predetermined location.
An apparatus for use in the casting of molten metal, said apparatus comprising:
- means for confining a volume of molten metal flowing downstream;
- said confining means having upstream and downstream ends;
- magnetic stirring means, disposed around said confining means, for inducing, in said downstream-flowing volume of molten metal, primary circulatory flow in a first rotational sense;
- and a plurality of means for substantially reducing secondary recirculating flows caused in said volume of molten metal by said magnetic stirring means, to conserve the stirring energy available from said primary circulatory flow;
- said plurality of means comprising (a) additional magnetic means located upstream of said magnetic stirring means and (b) means, located downstream of said magnetic stirring means, which is at least as close to said stirring means as the downstream end of said confining means.
An apparatus for use in the continuous casting of molten metal, said apparatus comprising:
- a cylindrical casting mold having an inlet and an outlet;
- magnetic stirring means disposed around the outside of said mold;
- said mold having a diameter no more than about 150 mm (6 in.) and a wall thickness between about 1.6 and 4.8 mm (1/16-3/16 in.);
- and said mold being composed of a metallic material having a conductivity no greater than about 0.29.times.10.sup.8 (ohm m).sup.-1.
A method for use in the casting of molten metal, said method comprising the steps of:
- providing a column of molten metal flowing downstream, and confining at least a portion of said column, said confined portion having upstream and downstream ends;
- magnetically stirring said column, at a first location between said ends of said confined column portion, to induce in the molten metal at said first location a primary circulatory flow in a first rotational sense;
- and a plurality of steps for substantially reducing secondary recirculating flow caused by said magnetic stirring;
- said plurality of steps comprising (a) magnetically affecting said column at a location upstream of said first location and (b) reducing said secondary recirculating flow at a location, downstream of said first location, which is at least as close to said first location as the downstream end of said confined column portion.
A method for use in the casting of molten metal, said method comprising the steps of:
- providing a column of molten metal flowing downstream;
- magnetically stirring said column, at a magnetic stirring zone having upstream and downstream ends, to induce in the molten metal in said magnetic stirring zone a primary circulatory flow in a first rotational sense;
- and a plurality of steps for substantially reducing secondary recirculating flow caused by said magnetic stirring;
- said plurality of steps comprising constricting said column at a first constricting location not substantially further upstream than said upstream end of the magnetic stirring zone;
- and constricting said column at a second constricting location not substantially further downstream than said downstream end of the magnetic stirring zone.
A method for rheocasting molten metal to produce a degenerate, dendritic microstructure comprising substantially spheroidal grains, said method comprising:
- providing a column of molten metal flowing downstream;
- confining said column to a substantially circular cross-section;
- subjecting said column of molten metal to electromagnetic agitation in a stirring zone;
- allowing said molten metal to cool as it flows downstream through said stirring zone;
- said method being conducted in accordance with the following equation-- ##EQU5## where:
- B is the magnetic field strength, in Tesla
- R is the radius, in meters, of the molten metal column undergoing stirring in the stirring zone
- .sigma. is the electrical conductivity of the molten metal, in (ohm meters).sup.-1
- .omega. is the angular frequency of the stirring in the stirring zone, in radians/second
- .rho. is the density of the molten metal, in kg/m.sup.3
- L is the latent heat of fusion of the molten metal, in Joules/m.sup.3
- Q is the rate of heat extraction from the molten metal in the stirring zone, in Watts/m.sup.2.
An apparatus for use in the continuous casting of molten metal, said apparatus comprising:
- a casting mold having an inlet and an outlet;
- a chamber located upstream of said mold and having an inlet for receiving molten metal and an outlet vertically aligned with said inlet of the mold;
- said casting mold having a constricted cross-section compared to the cross-section of said chamber;
- first magnetic means, disposed around said chamber in close proximity thereto, for stirring the molten metal in said chamber;
- and second magnetic means, disposed around said casting mold in close proximity thereto;
- said second magnetic means being separate and discrete from said first magnetic means.
Dependencies are inferred from the claim text.