Identifying appearance of slag when tapping metal melt - by measured transition in sound pressure level pref. in given frequency band

摘要

The arrangement is for identifying the moment when, during tapping of liquid metal, e.g. steel from a converter, tapping should be stopped to avoid pouring an underisable amount of slag floating on the melt. During tapping, the sound emitted by the flow is measured and the difference in sound pressure level from metal and from slag is used to produce a signal at the moment of transition. This signal indicates that tapping should be stopped. The measurement may be carried out using a band-pass filter with a frequency range of 250 to 2000 Hz, preferably 500 to 1000 Hz, and a microphone placed as near as possible to the metal flow. Minimises amount of slag poured when tapping a metal melt. The arrangement provides a reliable objective criterion which enables immediate response even before the appearance of slag can be visually identified.