SMS Concast Italia S.p.A. (Tarcento, Italy)

Fabrizioli M., e-mail: mauro.fabrizioli@sms-concast.it

Michelon G.

University of Padova (Padova, Italy):
Dal Corso F.

Borsato E., Dept of Physics and Astronomy

Saarstahl AG. (Völklingen, Germany):
Fries S.

Ney G.

Lech-Stahlwerke GmbH (Meitingen. Germany):

Nagy R.

This paper presents a new advanced radiometric sensor for mould level measurement, which can overcome the well-known drawback of this technology in closed casting, i. e. the incapacity to determine the real position of the steel meniscus due to the bias of the undetermined thickness of the lubricating powder lying at its top. This measurement takes a few seconds for statistical reasons and requires processing by a specially developed algorithm. The plant test results from both small bloom and billet sections are reported. By processing the information from the multi-crystals using a maximum likelihood algorithm, it is possible to discriminate the meniscus position and the thickness of the powder layer on top of it with a good level of precision on a time scale of a few seconds. At the same time, simply summing the counts of all the crystals, the usual level control signal is established and used for the fast mould level control system (the improved dynamics of the signal on a wider level range makes it appealing also for safety reasons). Steel level is a parameter of major importance for the control of process quality: measuring it also gives the possibility to avoid well-known drawbacks of conventional radiometric sensors estimating only a single level parameter which is a combination of steel and powder level, such as the steel level depression caused by an increase of casting powder. Furthermore, the new radiometric sensor can measure steel level and powder thickness using only one measuring device and at the same time allows the implementation of a closed control loop for an automatic mould powder feeding system.

1. EP2492650 A1, European Patent applied.
2. http://physics.nist.gov/PhysRefData/XrayMassCoef/ComTab/cesium.html