非接触レーザー周期加熱カロリメトリー法による溶融Feの熱物性計測法の開発

概要

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Newly developed noncontact modulation laser calorimetry has enabled us to measure accurate thermophysical properties such as thermal conductivity and heat capacity of high temperature liquid metals with suppressing chemical reactions and convections. However, in spite of the demand for accurate thermophysical properties as input parameters in precise numerical simulation for casting and welding processes, it is still difficult to measure those of liquid iron (Fe). The difficulty is caused by the high density and electrical resistivity of liquid Fe. In this study we designed a new levitation coil having high lifting force with moderate heating for liquid Fe. Furthermore, a superconducting magnet, which has a maximum dc magnetic field of 10 T, was equipped to the measurement system to suppress the convection in the liquid Fe. The isobaric molar heat capacity of liquid Fe was successfully measured at lower dc magnetic field (3 and 4 T). This can be explained by the accomplishment of the semi-adiabatic condition caused by the higher thermal conductance of the convection. The isobaric molar heat capacity of liquid Fe was determined as follows; cp=45.5±4.1 J·mol−1·K−1 [1816–1992K]. On the other hand, the apparent thermal conductivity of liquid Fe decreased with increasing dc magnetic field, and then finally converged to be 38.7±2.5 W·m−1·K−1 [1794–2050 K] above 9 T due to the suppression of convection.