Method and apparatus for making alloy powder

Claim 2

In a method for making a metal powder, the steps of: disposing in a fluid-cooled hearth having delivery means a metallic material defining an alloy composition; melting the material in the hearth using a plasma heat source to provide a molten metallic alloy while providing a skull of resolidified material substantially completely between the molten alloy and the hearth and said delivery means; and delivering the molten metallic alloy from the fluid-cooled hearth into a powder metal producer, wherein, in said method, the molten alloy substantially contacts only said skull.

Claim 3

An improved method for making a metal powder comprising the steps of: providing a hearth having delivery means, said hearth and delivery means having fluid-cooled walls; disposing in the hearth a metallic material defining an alloy composition; directing a plasma heat source at the metallic material in the hearth to melt the metallic material; providing cooling fluid in the walls sufficient to resolidify melted metallic material adjacent to the cooled walls to form a skull of a portion of the metallic material substantially completely on the cooled walls, while maintaining molten alloy in the hearth, and separated therefrom by the skull, as a molten alloy reservoir; and delivering a stream of the molten alloy from the hearth into a powder metal producer, wherein, in said improved method, said molten alloy substantially contacts only said skull.

Claim 4

An improved method for making a metal powder comprising the steps of: providing a hearth having delivery means, said hearth and delivery means having fluid-cooled walls; disposing in the hearth a metallic material defining an alloy composition; directing a plasma heat source at the metallic material in the hearth to melt the metallic material; providing cooling fluid in the walls sufficient to resolidify melted metallic material adjacent to the cooled walls to form a skull of a portion of the metallic material substantially completely on the cooled walls, while maintaining molten alloy in the hearth, and separated therefrom by the skull, as a molten alloy reservoir; and delivering a stream of the molten alloy from the hearth into a powder metal producer, wherein, in said improved method, said molten alloy substantially contacts only said skull.

Claim 5

The method of claim 2 in which the plasma heat source is swept over a surface of the metallic material to provide substantially uniform heat to the metallic material.

Claim 6

The method of claim 2 further including delivering the molten alloy into the powder metal producer through a stream control device, said device having a second delivery means and having a skull formed therein substantially completely between said stream control device and said second delivery means and the molten alloy wherein said molten alloy substantially only contacts said skull.

Claim 7

The method of claim 4 wherein: a pouring trough having fluid-cooled walls is the stream control device.

Claim 8

The method of claim 5 including directing a secondary plasma heat source at the molten alloy in the trough.

Claim 9

The method of claim 6 including sweeping the secondary plasma heat source over the surface of the molten alloy in the trough to provide substantially uniform heat to the molten alloy.

Claim 10

The method of claim 2 including delivering the molten alloy into the powder metal producer by tipping the hearth.

Claim 11

The method of claim 2 including injecting an atomizing gas into the stream of molten alloy delivered to the powder metal producer to solidify the alloy in powder form.

Claim 12

The method of claim 9 including collecting the powder metal alloy.

Claim 13

An improved method for making a metal alloy powder comprising the steps of: providing a hearth having delivery means, said hearth and delivery means having fluid-cooled walls; disposing in the hearth a metallic material defining an alloy composition; directing a plasma heat source at the metallic material in the hearth to melt the metallic material; providing cooling fluid in the walls sufficient to resolidify melted metallic material adjacent to the cooled walls to form a skull of a portion of the metallic material substantially completely within the hearth and the delivery means at the cooled walls, while maintaining molten alloy in the hearth, and separated therefrom by the skull, as a molten alloy reservoir; delivering the molten alloy from the hearth into a stream control device, said stream control device comprising a pouring trough having a second delivery means, the walls of which trough are fluid-cooled, said trough having a skull formed therein substantially completely between the molten alloy and said fluid-cooled walls; sweeping a secondary plasma heat source over the surface of the molten alloy in said trough to maintain the alloy molten in the trough; delivering a stream of molten alloy from the trough to a powder metal producer; injecting an atomizing gas into the molten alloy stream; converting the molten alloy to powder alloy; and collecting the powder metal alloy, wherein, in said improved method, said molten alloy substantially contacts only said skull.

Claim 14

An improved method for making a metal alloy powder comprising the steps of: providing a hearth having delivery means, said hearth and delivery means having fluid-cooled walls; disposing in the hearth a metallic material defining an alloy composition; directing a plasma heat source at the metallic material in the hearth to melt the metallic material; providing cooling fluid in the walls sufficient to resolidify melted metallic material adjacent to the cooled walls to form a skull of a portion of the metallic material substantially completely within the hearth and the delivery means at the cooled walls, while maintaining molten alloy in the hearth, and separated therefrom by the skull, as a molten alloy reservoir; delivering the molten alloy from the hearth into a stream control device, said stream control device comprising a pouring trough having a second delivery means, the walls of which trough are fluid-cooled, said trough having a skull formed therein substantially completely between the molten alloy and said fluid-cooled walls; sweeping a secondary plasma heat source over the surface of the molten alloy in said trough to maintain the alloy molten in the trough; delivering a stream of molten alloy from the trough to a powder metal producer; injecting an atomizing gas into the molten alloy stream; converting the molten alloy to powder alloy; and collecting the powder metal alloy, wherein, in said improved method, said molten alloy substantially contacts only said skull.

Claim 15

An improved method for making a metal powder from a metallic material defining an alloy composition comprising the steps of melting the metallic material in a fluid-cooled hearth having delivery means and delivering the molten metallic material into a powder metal producer, the improvement comprising: forming a skull of resolidified metallic material substantially completely between said molten metallic material and said hearth and delivery means; and contacting said molten metallic material substantially only with said skull.

Claim 16

An improved method for making a metal powder from a metallic material defining an alloy composition comprising the steps of melting the metallic material in a fluid-cooled hearth having delivery means and delivering the molten metallic material into a powder metal producer, the improvement comprising: forming a skull of resolidified metallic material substantially completely between said molten metallic material and said hearth and delivery means; and contacting said molten metallic material substantially only with said skull.

Claim 17

In an apparatus for producing a powder metal alloy from a molten metallic alloy, the improvement comprising: a metal powder producer; a fluid-cooled hearth having fluid cooled walls for melting the metallic alloy, said hearth further having a lip for delivering a stream of the molten alloy substantially out of contact with ceramic members to the metal powder producer; a skull of resolidified alloy having substantially the same composition as the molten metallic alloy, formed on the hearth and lip by removal of heat through said fluid-cooled walls so that molten alloy is substantially out of contact with said hearth and lip; a plasma heat source; means for directing the heat source toward the hearth for melting the metallic alloy and maintaining said stream of molten metallic alloy; a melt chamber enclosing at least the hearth, the heat source and the alloy stream to maintain an inert gas atmosphere over the molten alloy; and means in said metal powder producer for converting the molten alloy stream to a powder alloy metal.

Claim 18

In an apparatus for producing a powder metal alloy from a molten metallic alloy, the improvement comprising: a metal powder producer; a fluid-cooled hearth having fluid cooled walls for melting the metallic alloy, said hearth further having a lip for delivering a stream of the molten alloy substantially out of contact with ceramic members to the metal powder producer; a skull of resolidified alloy having substantially the same composition as the molten metallic alloy, formed on the hearth and lip by removal of heat through said fluid-cooled walls so that molten alloy is substantially out of contact with said hearth and lip; a plasma heat source; means for directing the heat source toward the hearth for melting the metallic alloy and maintaining said stream of molten metallic alloy; a melt chamber enclosing at least the hearth, the heat source and the alloy stream to maintain an inert gas atmosphere over the molten alloy; and means in said metal powder producer for converting the molten alloy stream to a powder alloy metal.

Claim 19

The apparatus of claim 13 further comprising means for directing the heat source to sweep the surface of the metallic alloy in the hearth to provide substantially uniform heat to the metallic alloy.

Claim 20

The apparatus of claim 13 further comprising: a fluid-cooled pouring trough disposed within the melt chamber to receive molten metallic alloy melted in the hearth and to deliver at least a portion of such molten metallic alloy substantially out of contact with ceramic members into the means for converting the molten alloy to a powder metal, said trough having fluid-cooled walls; and a skull of resolidified alloy, having substantially the same composition as the alloy melted, substantially completely between the molten alloy and the fluid-cooled walls so as to prevent contact between the molten alloy and trough walls.

Claim 21

The apparatus of claim 15 further comprising a secondary plasma heat source directed toward the trough to maintain at least a portion of the metallic alloy molten in the trough.

Claim 22

The apparatus of claim 13 further including means for tipping the hearth to deliver a molten alloy stream.

Claim 23

The apparatus of claim 13 wherein the means for converting the molten metal alloy stream to a metal powder comprises: an inlet for receiving the molten alloy stream; a source of atomizing gas selected from the group consisting of helium, argon and nitrogen; atomizing gas spray means for injecting the atomizing gas into the stream of molten alloy after entry into the inlet.

Claim 24

The apparatus of claim 18 wherein the means for converting the molten alloy stream to a powder metal further comprises: a cooling tower through which the powder metal passes; and a collector for the powder metal that has passed through the cooling tower.

Claim 25

In an apparatus for producing a substantially ceramic-free metal powder from a molten metallic alloy stream, the improvement comprising: a hearth for receiving the metallic alloy, said hearth including a lip for delivering the molten alloy stream, said hearth and lip having fluid-cooled walls; a plasma heat source which is adapted, during operation, to sweep a surface of metallic alloy in the hearth to provide substantially uniform heat to melt the metallic alloy and partially maintain it in the molten state; a skull of resolidified alloy having substantially the same composition as the molten metallic alloy, formed on the hearth and lip by removal of heat through said fluid-cooled walls so that molten alloy is substantially out of contact with said hearth and lip; a stream control device, said stream control device comprising a pouring trough disposed to receive molten alloy melted is the hearth, and said trough having means for pouring a stream of molten alloy from the trough into a metal powder producer, said trough and pouring means further having fluid cooled walls for establishing a skull of solidified alloy between the molten alloy and said walls to prevent contact of the walls and the molten metal stream; a means for tipping the hearth for delivering molten alloy to the stream control device; a secondary plasma heat source which is adapted, during operation, to maintain at least a portion of the alloy molten in the trough; a melt chamber enclosing at least the hearth, the heat sources, the stream control device and the alloy stream to maintain an inert gas atmosphere over the molten alloy; and a source of atomizing gas; an atomizing gas spray means for injecting the atomizing gas into the stream of molten alloy poured from the trough to convert the molten alloy to substantially ceramic-free powder alloy; a cooling tower through which the substantially ceramic-free powder alloy passes; and a powder collector for collecting the powder alloy that has passed through the cooling tower, wherein, in said apparatus, said molten alloy substantially contacts only said skull said that contact between said molten alloy and walls, from the hearth to the powder collector, is essentially prevented and contamination of the powder is substantially eliminated.

Claim 26

In an apparatus for producing a substantially ceramic-free metal powder from a molten metallic alloy stream, the improvement comprising: a hearth for receiving the metallic alloy, said hearth including a lip for delivering the molten alloy stream, said hearth and lip having fluid-cooled walls; a plasma heat source which is adapted, during operation, to sweep a surface of metallic alloy in the hearth to provide substantially uniform heat to melt the metallic alloy and partially maintain it in the molten state; a skull of resolidified alloy having substantially the same composition as the molten metallic alloy, formed on the hearth and lip by removal of heat through said fluid-cooled walls so that molten alloy is substantially out of contact with said hearth and lip; a stream control device, said stream control device comprising a pouring trough disposed to receive molten alloy melted is the hearth, and said trough having means for pouring a stream of molten alloy from the trough into a metal powder producer, said trough and pouring means further having fluid cooled walls for establishing a skull of solidified alloy between the molten alloy and said walls to prevent contact of the walls and the molten metal stream; a means for tipping the hearth for delivering molten alloy to the stream control device; a secondary plasma heat source which is adapted, during operation, to maintain at least a portion of the alloy molten in the trough; a melt chamber enclosing at least the hearth, the heat sources, the stream control device and the alloy stream to maintain an inert gas atmosphere over the molten alloy; and a source of atomizing gas; an atomizing gas spray means for injecting the atomizing gas into the stream of molten alloy poured from the trough to convert the molten alloy to substantially ceramic-free powder alloy; a cooling tower through which the substantially ceramic-free powder alloy passes; and a powder collector for collecting the powder alloy that has passed through the cooling tower, wherein, in said apparatus, said molten alloy substantially contacts only said skull said that contact between said molten alloy and walls, from the hearth to the powder collector, is essentially prevented and contamination of the powder is substantially eliminated.