Cold tundish, and apparatus and method for producing spheroidal micropowders

Abstract

A cold tundish which has a surface made from a thermally conductive metal, and which is cooled by a cooling fluid, is disposed so as to receive a molten material from a cold crucible; high-speed jets of an inert gas are produced from a nozzle at a narrow portion of an orifice that is open at the exit side of the cold tundish, producing a low-pressure region on the exit side of the orifice that draws the molten material and a plasma through the orifice; the high-speed jets of inert gas impinge on the molten material to achieve atomization thereof, using an apparatus that is compatible with atomization of even reactive and refractory metals.

Among my claims are: 
     
         1 . An apparatus for producing spheroidal powders, comprising:
 a molten material supplying apparatus;   a cold tundish configured to receive a molten material from the molten material supplying apparatus, having an orifice at the exit thereof configured to discharge the received molten material, said orifice passing through the cold tundish, with a relatively wide opening diameter at an entrance portion, with a relatively narrow opening diameter in a portion thereafter; and   a jet opening configured to produce a high velocity fluid flow that impinges on, and atomizes, the discharged molten material, wherein:   the cold tundish is configured comprising an entrance-side portion that is made from a high thermal conductivity material and a cooling duct configured to carry a coolant fluid for cooling the thermally conductive entrance-side portion;   a second heating device is provided, configured so as to heat molten material that is in or on the cold tundish; and   the jet opening is provided in the cold tundish, opening at an exit-side portion of the orifice.   
     
     
         2 . The apparatus for producing spheroidal powders of  claim 1  wherein:
 the molten material supplying apparatus comprises a continuous feed source material delivery device configured to deliver a source material into a melting device that comprises a first heating device that is configured to heat and melt the source material into a molten material. 
 
     
     
         3 . The apparatus for producing spheroidal powders of  claim 2  wherein:
 the first heating device is configured as a plasma source configured to cause a plasma to impinge upon the source material that is in or on the melting device, an inductive heating source configured to cause inductive heating of the source material that is in or on the melting device, or a resistive heating source configured to heat the source material that is in or on the melting device. 
 
     
     
         4 . The apparatus for producing spheroidal powders of  claim 1  wherein:
 the jet opening is configured in a ring shape surrounding a center axis of the orifice. 
 
     
     
         5 . The apparatus for producing spheroidal powders of  claim 1  wherein:
 the jet opening is configured from a plurality of jet openings, disposed equally spaced around the vertical axis of the orifice. 
 
     
     
         6 . The apparatus for producing spheroidal powders of  claim 1  wherein:
 the second heating device is configured as a plasma source for causing a plasma to impinge upon the molten material that is in or on the cold tundish. 
 
     
     
         7 . The apparatus for producing spheroidal powders of  claim 1  wherein:
 an inert gas is discharged at a high velocity from the jet opening. 
 
     
     
         8 . The apparatus for producing spheroidal powders of  claim 7  wherein:
 the inert gas is argon. 
 
     
     
         9 . The apparatus for producing spheroidal powders of  claim 1  wherein:
 the jet opening is configured such that a low-pressure region is formed on the exit side of the orifice when a fluid is discharged at a high velocity from the jet opening. 
 
     
     
         10 . The apparatus for producing spheroidal powders of claim wherein:
 the jet opening is configured so that, when a fluid is discharged at a high velocity from the jet opening, a plasma, produced by the second heating device, will be drawn into the orifice.   
     
     
         11 . The apparatus for producing spheroidal powders of  claim 1  wherein:
 the second heating device is configured as a pancake-type inductive heating device configured to heat the molten material that is in or on the cold tundish. 
 
     
     
         12 . The apparatus for producing spheroidal powders of  claim 1  wherein:
 the cold tundish comprises an annular lip. 
 
     
     
         13 . The apparatus for producing spheroidal powders of  claim 1  configured such that:
 the molten material is drawn through the orifice in the form of a sheath. 
 
     
     
         14 . The apparatus for producing spheroidal powders of  claim 1 , further comprising:
 an entrance-side housing on the entrance side of the orifice and an exit-side housing on the exit side of the orifice, wherein:   the entrance-side housing and the exit-side housing are maintained at different static pressures.   
     
     
         15 . The apparatus for producing spheroidal powders of  claim 1 , further comprising:
 an entrance-side housing on the entrance side of the orifice and an exit-side housing on the exit side of the orifice, wherein:   the interior of the entrance-side housing and the interior of the exit-side housing are maintained at different temperatures.   
     
     
         16 . The apparatus for producing spheroidal powders of  claim 1 , further comprising:
 a fluid flow temperature controlling device configured to control a temperature of the high velocity fluid flow.   
     
     
         17 . The apparatus for producing spheroidal powders of  claim 1 , wherein:
 the high velocity fluid flow flows at a supersonic velocity.   
     
     
         18 . The apparatus for producing spheroidal powders of  claim 1 , wherein:
 the orifice passes substantially vertically through the cold tundish.   
     
     
         19 . A method for producing spheroidal powders, including:
 delivering a source material to a melting device;   producing heat in the melting device to melt the source material to produce a molten material;   causing the molten material to run into a cold tundish;   heating the molten material in the cold tundish;   cooling the cold tundish from the interior of the structure of the cold tundish through a cooling fluid;   discharging a jet of a gas from a jet opening on an exit-side portion of the cold tundish to create a low-pressure region on the exit side of an orifice of the cold tundish so as to draw the molten material through the orifice in the cold tundish; and   causing a jet of gas to strike the molten material that has been drawn through the cold tundish; wherein:   all of the aforementioned steps are performed concurrently in a continuous process.