Atmosphere control system for annealing furnaces

This paper will describe an innovative atmosphere control system for annealing processes of carbon steel and other type of metals, monitoring and regulating the N2/H2 atmosphere based on the reducing potential, but also preventing decarburisation. The system itself includes a closed loop control algorithm, but also a cloud communication for data acquisition and further optimisations of the process, like recipe development for different annealing applications. It can be also used for scheduling preventive maintenance and therefore allows the operator to control shutdowns and troubleshooting efforts. It was found in a customer case study, that surface finish of the annealed product has been improved and rework as well as atmosphere costs have been reduced. In cases where a pre-set N2/H2 blend is used, the system can help reducing the overall atmosphere costs by either reducing the amount of used H2 or by reducing the overall atmosphere consumption. In cases where a pure N2 atmosphere is used, the system can help improving the surface quality and keeping the required amount of H2 at a minimum.