Gas atomization melt tube assembly

In a confined gas atomization apparatus for producing fine metal powder from a high temperature melt, and having a melt reservoir having a downwardly opening outlet, an annular gas nozzle to deliver high pressure gas to an atomizing zone below the melt reservoir, the gas nozzle having a longitudinal bore therethrough, and a melt delivery tube projecting from the reservoir outlet, through the gas nozzle bore to near the atomizing zone, the improvement wherein the melt delivery tube comprises a melt delivery tube assembly comprising:

• a refractory melt delivery tube having a longitudinal bore therethrough and comprising an upper portion seatable at the reservoir outlet for melt flow from the reservoir generally vertically downward through the reservoir outlet and melt tube bore, and a lower portion;
• a refractory melt tube tip not unitary with the melt tube, having a longitudinal bore therethrough, and comprising an upper portion coaxially and removeably positionable at the melt tube lower portion for melt flow from the melt tube bore through the melt tube tip bore, and a lower portion;
• and
• a supporting and thermally insulating shield having a longitudinal bore therethrough and coaxially and removeably mountable surrounding the longitudinal outer surfaces of the entire melt tube tip and at least the lower portion of the melt tube to provide a thermal barrier against impinging atomizing gas, wherein the shield bore is shaped complementarily to the surrounded outer surfaces for close and slideable fit thereover, and the outer surface of the support shield is of a diameter permitting close and slideable fit of the support shield within the annular gas nozzle bore, the support shield includes means for removably retaining the melt tube tip in position within the assembly and means adapted for support of the shield by the annular gas nozzle, and the support shield and melt tube tip are easily disassemblable from and reassemblable with each other and with the melt tube without removing the melt tube from the reservoir outlet by lowering or raising the annular gas nozzle relative to the reservoir.

In a confined gas atomization apparatus for producing fine metal powder from a high temperature melt, and having a melt reservoir having a downwardly opening outlet, an annular gas nozzle to deliver high pressure gas to an atomizing zone below the melt reservoir, the gas nozzle having a longitudinal bore therethrough, and a melt delivery tube projecting from the reservoir outlet, through the gas nozzle bore to near the atomizing zone, the improvement wherein the melt delivery tube comprises a melt delivery tube assembly comprising:

• a refractory melt delivery tube having a longitudinal bore therethrough and comprising an upper portion seatable at the reservoir outlet for melt flow from the reservoir generally vertically downward through the reservoir outlet and melt tube bore, and a lower portion;
• a refractory melt tube tip not unitary with the melt tube, having a longitudinal bore therethrough, and comprising an upper portion coaxially and removeably positionable at the melt tube lower portion for melt flow from the melt tube bore through the melt tube tip bore, and a lower portion;
• and
• a supporting and thermally insulating shield having a longitudinal bore therethrough and coaxially and removeably mountable surrounding the longitudinal outer surfaces of the entire melt tube tip and at least the lower portion of the melt tube to provide a thermal barrier against impinging atomizing gas, wherein the shield bore is shaped complementarily to the surrounded outer surfaces for close and slideable fit thereover, and the outer surface of the support shield is of a diameter permitting close and slideable fit of the support shield within the annular gas nozzle bore, the support shield includes means for removably retaining the melt tube tip in position within the assembly and means adapted for support of the shield by the annular gas nozzle, and the support shield and melt tube tip are easily disassemblable from and reassemblable with each other and with the melt tube without removing the melt tube from the reservoir outlet by lowering or raising the annular gas nozzle relative to the reservoir;
• wherein the melt tube bore provides a metering orifice for the melt flow through the assembly;
• and the melt tube tip comprises one of a plurality of interchangeable tips of differing metering orifice diameters, the one tip being selected to provide the desired metering orifice diameter.

In a confined gas atomization apparatus for producing fine metal powder from a high temperature melt, and having a melt reservoir having a downwardly opening outlet, an annular gas nozzle to deliver high pressure gas to an atomizing zone below the melt reservoir, the gas nozzle having a longitudinal bore therethrough, and a melt delivery tube projecting from the reservoir outlet, through the gas nozzle bore to near the atomizing zone, the improvement wherein the melt delivery tube comprises a melt delivery tube assembly comprising:

• a refractory melt delivery tube having a longitudinal bore therethrough, upper surfaces of a configuration for seating of the melt tube at the reservoir outlet for melt flow from the reservoir generally vertically downward through the reservoir outlet and melt tube bore, and a downwardly facing countered socket coaxial with the melt tube bore;
• a refractory melt tube tip not unitary with the melt tube, having a longitudinal bore therethrough, and comprising an upper portion coaxially and removeably positionable within the melt tube socket for melt flow from the melt tube bore through the melt tube tip bore, and a lower portion;
• and
• a supporting and thermally insulating shield having a longitudinal bore therethrough and coaxially and removeably mountable surrounding the longitudinal outer surfaces of the entire melt tube tip and at least the lower portion of the melt tube containing the socket to provide a thermal barrier against impinging atomizing gas, wherein the shield bore is shaped complementarily to the surrounded outer surfaces for close and slideable fit thereover, and the outer surface of the support shield is of a diameter permitting close and slideable fit of the support shield within the annular gas nozzle bore, the support shield includes means for removeably retaining the melt tube tip in position within the assembly and means adapted for support of the shield by the annular gas nozzle, and the support shield and melt tube tip are easily disassemblable from and reassemblable with each other and with the melt tube without removing the melt tube from the reservoir outlet by lowering or raising the annular gas nozzle relative to the reservoir.