Argon Gas Consumption and Breakup Dynamics in Tool Steel Atomization
Specific gas consumption and nozzle tip pressure determine liquid breakup efficiency and final yield in tool steel atomization.
Melt Tube Freezing
Meaning
Solidification of molten alloy within the nozzle of a gas atomizer terminates the atomization process prematurely. This operational interruption is referred to as melt tube freezing, and it causes expensive downtime and material loss in powder manufacturing. It occurs when the local temperature of the melt delivery tube drops below the liquidus temperature of the alloy being processed.
Thermal Failure
High heat loss from the tube to the high velocity cold atomizing gas causes the alloy to solidify and block the passage. During melt tube freezing, the sudden cessation of metal flow can cause the remaining metal in the tundish to overflow or solidify. This event results in the loss of the entire batch and can damage the ceramic components of the atomizer.
Quality Control
Production records must document every instance of this blockage because it can indicate a malfunction in the heating system. Recurrent melt tube freezing points to inadequate preheating of the delivery system or inconsistent melt temperatures. Operators check these logs to adjust the preheating duration and the starting temperature of the molten metal before the next run.
Preventive Strategy
Inductive heating elements are often positioned around the delivery nozzle to maintain the temperature above the freezing limit. Additionally, optimizing the gas flow angle and using low conductivity ceramics for the nozzle assembly reduces the heat transfer from the melt to the gas stream. Implementing these design modifications ensures a continuous and stable metal feed, which protects the equipment and stabilizes the chemical composition of the final powder.
This thermal stabilization also minimizes the chance of nozzle wear during the atomization cycle.