The temperature dependence of surface tension and density for Fe-Cr-Mo (AISI 4142), Fe-Cr-Ni (AISI 304), and Fe-Cr-Mn-Ni TRIP/TWIP high-manganese (16 wt% Cr, 7 wt% Mn, and 3-9 wt% Ni) liquid alloys are investigated using the conventional maximum bubble pressure (MBP) and sessile drop (SD) methods. In addition, the surface tension of liquid steel is measured using the oscillating droplet method on electromagnetically levitated (EML) liquid droplets at the German Aerospace Centre (DLR, Cologne). The data of thermophysical properties for Fe-Cr-Mn-Ni is of major importance for modeling of infiltration and gas atomization processes in the prototyping of a ''TRIP-Matrix-Composite.'' The surface tension of TRIP/TWIP steel increased with an increase in temperature in MBP as well as in SD measurement. The manganese evaporation with the conventional measurement methods is not significantly high within the experiments (D Mn \ 0.5 %). The temperature coefficient of surface tension (dr/dT) is positive for liquid steel samples, which can be explained by the concentration of surface active elements. A slight influence of nickel on the surface tension of Fe-Cr-Mn-Ni steel was experimentally observed where r is decreased with increasing nickel content. EML measurement of high-manganese steel, however, is limited to the undercooling state of the liquid steel. The manganese evaporation strongly increased in excess of the liquidus temperature in levitation measurements and a mass loss of droplet of 5 % was observed.
The aim of the current research is the experimental investigation of the mass median particle size d 50 as a function of surface tension for liquid Cr-Mn-Ni steel alloy with 16% Cr, 7% Mn, and 9% Ni. To modify the liquid steel design sulfur was add to the Cr-Mn-Ni steel in five steps up to a 1000 mass ppm. The surface tension of the liquid steel alloy was measured using maximum bubble pressure method and yttria stabilized capillary in a temperature range from 1701 to 1881 K. In addition, the same steel charges were sprayed to steel powder using a vacuum inert gas atomization using pure argon gas. The increase of sulfur in Cr-Mn-Ni steel will decrease the surface tension to 0.91 N m À1 . The temperature coefficient of surface tension is positive for all investigated Cr-Mn-Ni alloys due to a sulfur content !100 mass ppm. The final mass median particle size d 50 decreases from 54.3 mm for AISI 304 reference steel alloy to 17.1 mm for Cr-Mn-Ni steel alloy (16-7-9 S10) with the highest sulfur content and the lowest surface tension of all investigated liquid steels. It is concluded from the present work that surface tension is the decisive factor in adjusting d 50 at a constant spraying parameters.
The thermophysical properties of liquid Cr‐Mn‐Ni steel alloys (16 wt% Cr, 7 wt% Mn, and 3–9 wt% Ni) are investigated using the maximum bubble pressure method in which the manganese evaporation and change in chemical composition is very low after experimental trial. The surface tension of copper was measured as reference and experimental σ is in the range of literature values. It is shown that for AISI 304 austenitic steel the surface tension decreased by an increase of oxygen concentration in steel composition. For Cr‐Ni and Cr‐Mn‐Ni steels, the temperature coefficient dσtrue/dT is positive which is explained by sulfur steel concentrations larger 50 mass ppm. A slight influence of nickel to the surface tension of Cr‐Mn‐Ni steels was experimentally observed where σ was lowered by rising weight percentage of nickel.
For the investigation of rheological features like dynamic viscosity, a high temperature rheometer was able to be successfully established at the Institute of Iron and Steel Technology of the TU Bergakademie Freiberg. Based on known calibration problems with high-level pyrometries, the viscosity was calculated directly without calibration. This is possible with an air-bearing rheometer and exact absolute torque measurement via the electrical parameters of the drive and via movement parameters and geometry of the measuring pairing. This technique meets the desired requirements in view of measuring accuracy and reproducibility of the measured results. The measurements were carried out on silicone oils in the low temperature range under dynamic conditions. It was demonstrated that the silicone oils are suited for comparative measurements under different rheological conditions. The results from the comparison of the two measuring systems (CPM and CCM in high temperature configuration) have shown that, in the high-level temperature range, a measurement error <1% is to be expected.
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