Side-Trak Model 830/840 Automates Gas Delivery in Metal Processing Applications

Many aluminum and steel manufacturers use Sierra's Side-Trak® Model 830/840 mass_flow controllers (MFCs) to inject purification, stirring and shielding gases into their melting, casting and annealing processes. Precise, automated gas flow control reduces toxic emissions and material costs. It also ensures higher product quality and uninterrupted processing. Final purification of aluminum is accomplished by bubbling a mixture of argon and chlorine gases through the molten metal. This process separates sodium and calcium salts, which are skimmed off in the filter box. The ratios of bi-gas and tri-gas mixtures are critical in molten metal treatment, particularly with the use of such gases as SF6.

Excess gas delivery can cause inclusions in the finished product and result in higher emissions of costly and toxic gases. Insufficient gas delivery can result in clogging of the refractory components. A fully automated mixing station with manual overrides allows the operator to simply push a button to flux the molten metal. A trickle flow of gas can also be set to ensure that sludge does not build up in the bubbling mechanism. Mass flow controlled mixing equipment provides accurate and repeatable delivery of these treatment gases, even with pressure fluctuations in the carrier gas.

In stirring applications, precise gas mass flow delivery ensures continuous and uninterrupted production of a high-quality product. Excess gas usage is known to cause plugging of the nozzles and/or plugs, caused by low temperature gases chilling the molten metal to a solidifying temperature. In the steel pouring system, injection of argon or nitrogen during the casting process prevents re-oxidation and clogging of refractory components with aluminum oxide.

Generally, gas is injected at several points in the slide gate: through the upper nozzle, upper plate brick and submerged entry nozzle. Gas sealing can also be used around the plate brick mating surfaces and the lower nozzle/SEN joint to assure that there is no air aspiration during casting. In the annealing process, MFCs are used to control the flow of nitrogen from on-site gas plants, to allocate costs and identify "wasters", such as leaks in the line or a purge left on to a non-operating annealing oven.