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Emulsification of Top Slags during Argon Stirring through a Porous Plug in the Ladle of Si Deoxidised Carbon Steels
Author(s) -
Valentin P.,
Bruch C.,
Gaule J.
Publication year - 2009
Publication title -
steel research international
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.603
H-Index - 49
eISSN - 1869-344X
pISSN - 1611-3683
DOI - 10.2374/sri09sp056
Subject(s) - ladle , slag (welding) , materials science , metallurgy , eutectic system , spark plug , carbon fibers , porosity , viscosity , plug flow , composite material , microstructure , thermodynamics , physics , composite number
Intensive experiments with 170‐t heats of carbon steels in the LD steel plant of Saarstahl AG were performed to study the emulsification of an acid top slag during different stirring conditions in this research project. During ladle treatment samples were taken from steel for the analysis of the composition of the inclusions together with the top slag. Within these investigations gas flow rates and stirring times were systematically varied in order to study their influence on the entrapment of top slag in the steel melt. At the same time a model was developed for the evaluation of the performance of the porous plug with regard to gas flow rate and gas pressure or finally for blockades and leakages. According to the experiments of this project the following results were established. Small top slag particles are discovered nearly in all steel samples together with endogenous SiO 2 ‐Al 2 O 3 deoxidation products. But emulsified phases or parts of the top slag generating larger inclusions with a size of 30 – 60 μm show the low melting eutectic composition. On the other hand, this emulsification process leads simultaneously to CaO depletion and SiO 2 accumulation of the top slag particularly when a longer stirring period is applied as shown during these experimental trials. The whole process requires low melting top slags and low melting emulsified inclusions in combination with a low viscosity level. To meet the emulsification requirements the gas flow is characterised by high gas flow rates in the order of 30 – 40 STP m 3 /h and high pressures with 8 – 12 bar indicating a blockade of the porous plug and the existence of a gas jet.