Measuring lance for the measurement of a position and a thickness of a slag layer on top of a molten metal

A method for determining in a metallurgic container a position (has) of an air-slag interface (2as) between an atmosphere (4) and a slag layer (2) sitting on top of a molten metal (3), and a position (hsm) of a slag-metal interface (2sm) between the slag layer (2) and the molten metal (3), comprising:

• position a measuring lance (1) according to anyone of the preceding claims above the air-slag interface (2as) with the second end of the first conducting element (11) positioned closest to the air-slag interface (2as),
• start measuring a vertical position of the measuring lance (1) along a vertical axis (Z) substantially normal to the air-slag interface (2as),
• start measuring values of the first material property with the slag-metal interface detection unit (8),
• start measuring an electrical property of the first conducting element (11),
• translate the measuring lance along at least a vertical component parallel to the vertical axis (Z), downwards, towards the air-slag interface (2as),
• upon detection of a gradient in the electrical property of the first conducting element (11) indicative that the second end of the first conducting element (11) has contacted the air-slag interface (2as), recording the vertical position of the measuring lance (1) as the position (has) of the air-slag interface (2as),
• keep translating downwards the measuring lance (1) along the vertical component sufficiently far to ensure that the measuring unit (6) is in the molten metal (3), beyond the slag-metal interface (2sm),
• allow the thermal fuse (13) to blow and thus conductively separating the first end from the second end of the first conducting element (11),
• measure the values of the first material property with the slag-metal interface detection unit (8) and maintain the measuring unit (6) in the molten metal (3) until the measured values of the first material property become substantially constant,
• translating the slag-metal interface detection unit (8) along the vertical component upwards, towards the slag-metal interface (2sm),
• upon detection of a sharp gradient in the values of the first material property measured with the slag-metal interface detection unit (8), recording the vertical position of the measuring lance (1) as the position (hsm) of the slag-metal interface (2sm), and keep translating upwards the measuring lance (1) along the vertical component until it is totally in the atmosphere (4).