TY - JOUR
T1 - Controlled undercooling of liquid iron in contact with ZrO2 and MgO substrates under varying oxygen partial pressures
AU - Valdez, Martin E.
AU - Shibata, H.
AU - Cramb, Alan W.
N1 - Funding Information:
The authors thank the member companies of the Center for Iron and Steelmaking Research, Carnegie Mellon University (Pittsburgh, PA), and the AISI DOE Project 0101 ‘‘Inclusion Optimization for New Generation Steel Products’’ for the financial support.
PY - 2006/12
Y1 - 2006/12
N2 - The objective of this study is to determine the conditions under which the inclusions present in liquid steel can act as heterogeneous nucleants for solidification. In order to study the factors that define the undercooling of a given metal/oxide couple, the undercooling of a pure iron sessile droplet in contact with Al2O3, ZrO2, and MgO substrates was measured under controlled oxygen partial pressures by observing droplet recalescence. The results showed that the undercooling of iron, in contact with a particular substrate, did not have a unique value, but was significantly affected by the oxygen content on the gas phase. For oxygen partial pressures between 10-21 and 10-19, the undercooling of iron on ZrO2 substrates was stable and around 290 °C. In the same range of oxygen partial pressure, the undercooling of iron on MgO substrates remained below 100 °C due to the low stability of this oxide. At lower oxygen contents, substrate decomposition might be the cause for the observed drop in the undercooling of iron on ZrO2 substrates to below 100 °C. The undercooling also decreased for increasing oxygen content as verified when the gas was changed from gettered Ar/Ar-H2 to CO/CO2 mixtures. The variation in undercooling was related to the wetting of the substrate by the liquid metal, where the deep undercooling observed in the ZrO2 experiments occurred when the highest contact angle between the liquid metal and the substrate was achieved.
AB - The objective of this study is to determine the conditions under which the inclusions present in liquid steel can act as heterogeneous nucleants for solidification. In order to study the factors that define the undercooling of a given metal/oxide couple, the undercooling of a pure iron sessile droplet in contact with Al2O3, ZrO2, and MgO substrates was measured under controlled oxygen partial pressures by observing droplet recalescence. The results showed that the undercooling of iron, in contact with a particular substrate, did not have a unique value, but was significantly affected by the oxygen content on the gas phase. For oxygen partial pressures between 10-21 and 10-19, the undercooling of iron on ZrO2 substrates was stable and around 290 °C. In the same range of oxygen partial pressure, the undercooling of iron on MgO substrates remained below 100 °C due to the low stability of this oxide. At lower oxygen contents, substrate decomposition might be the cause for the observed drop in the undercooling of iron on ZrO2 substrates to below 100 °C. The undercooling also decreased for increasing oxygen content as verified when the gas was changed from gettered Ar/Ar-H2 to CO/CO2 mixtures. The variation in undercooling was related to the wetting of the substrate by the liquid metal, where the deep undercooling observed in the ZrO2 experiments occurred when the highest contact angle between the liquid metal and the substrate was achieved.
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U2 - 10.1007/BF02735018
DO - 10.1007/BF02735018
M3 - Article
AN - SCOPUS:33846199898
SN - 1073-5615
VL - 37
SP - 959
EP - 965
JO - Metallurgical and Materials Transactions B: Process Metallurgy and Materials Processing Science
JF - Metallurgical and Materials Transactions B: Process Metallurgy and Materials Processing Science
IS - 6
ER -