Meaning
Unintended solidification of molten metal at the exit of a delivery tube stops the flow of liquid during atomization. Sourcing teams in the metal powder industry dread melt freeze off because it terminates production and requires a full teardown of the nozzle assembly. This event occurs when the temperature of the liquid metal falls below its liquidus point before it is disintegrated by the gas jets.
Thermal Loss
Heat transfer from the hot liquid metal to the colder gas stream can lower the temperature at the nozzle tip too quickly. When melt freeze off is triggered by this thermal deficit, the metal solidifies inside the narrowest part of the ceramic pathway.
Mechanical Design
Nozzle positioning and the thickness of the insulation around the delivery tube determine how well heat is retained at the point of exit. If the tube is placed too close to the expanding gas stream, the localized cooling effect becomes too intense and promotes melt freeze off. Refractory sleeves and heating elements are often installed around the nozzle to maintain the required temperature.
These design features protect the liquid stream from being chilled by the high-velocity gas.
Control Strategy
Automated monitoring of flow rate and temperature allows systems to detect blockages early. Prompt intervention minimizes the risk of melt freeze off and avoids costly production delays.
