Annealing is essential to forming quality steel products, especially for high-performance applications like sheet, plate, rod, wire, and tubular goods. Careful and effective heating makes the material more formable by relieving internal stresses, refining the metallurgical structure, and improving its cold-working potential. In the same way, the gas atmosphere is essential to successful annealing

Linde Group (www.linde.com) has updated its CarboJet nozzles, saying high-speed gas injection alters furnace atmospheres and improves gas circulation, which enhances convection and increases heat and carbon transfer rates.

Other advantages are more homogenous product quality; better utilization of carburizing gases and reduced soot formation; optimized physical and thermodynamic heat-treatment processes; and better overall process control.

With current conditions, however, gas consumption is an equally critical concern. Capable of treating 30 m3 of furnace atmosphere by delivering just 1 m3 of gas, Linde points to a German heat-treating specialist that is posting considerable cost savings thanks to its adoption of CarboJet nozzles.

Sennestahl GmbH installed for Carbo- Jet nozzles for two pit furnaces, one in August 2006 and another January 2007. Linde’s CarboThan control system had been installed previously, but adopting CarboJet allowed Sennestahl to operate the furnaces without fans. This led to significant savings on maintenance costs.

Linde says CarboJet nozzles eliminate a significant drawback of standard gas furnaces, because they stabilize atmospheres without ventilators. This is done by installing one or more nozzles with piping and flow train: The number of nozzles corresponds to the furnace size and its normal gas consumption. Gas flows can be controlled manually, or with an atmosphere control system. As a result, tailor-made solutions provide better quality products and increase productivity through faster carburization.

In addition to annealing, CarboJet technology can be used in carburizing, carbonitriding, and other furnaces, like roller hearth, belt, and rotary retort furnaces.