Effect of Oxygen on the Evaporation Rate of Lead from Liquid Copper under Reduced Pressure.

Abstract

Previously, the present authors have investigated the effects of temperature and pressure on the evaporation rates of Pb and Zn from liquid copper under reduced pressure. Oxygen does easily contaminate molten metal during high temperature processing and is known as a strong surface active element. In this study, the effect of oxygen on the evaporation rate of Pb from liquid copper was discussed at 1 473 K and 1.3 kPa. The rate constant was supposed to be slower with oxygen content due to lowering the interfacial chemical reaction rate. However, the rate constant increased with oxygen content in the present experiment. Assuming that the acceleration of vaporization is due to the volatile lead oxide, the rate equation was derived for the evaporation of lead oxide together with that of metallic Pb. As a result of the analysis for the present experiment, it was found that Pb evaporated from copper melt containing higher oxygen in the form of PbO. The presence of PbO in the vapor phase was confirmed by the mass spectroscopy. The rate mechanism of vaporization of Sn and Cu from liquid steel containing oxygen have also been discussed.

Base Metal Co-Fired Multilayer Piezoelectrics

“…The generation of oxygen vacancies was a bulk diffusion rate-dominated process. The dominating path of Pb volatilization was a result of Pb coupling with the oxygen adsorbed on the surface of the materials [28]. This reaction rate-limited process kinetically controlled the Pb-losing rate of the material.…”

“…Figure 2 shows the ionic conductivity change over time; the gentle slope in the N 2 zone means that the Pb-losing rate is low. This evidence suggested that when air was switched to N 2 with pO 2 < 10´5 atm, the decreased low pO 2 atmosphere suppressed the volatility of Pb through reducing the contacting chance between environmental O 2 and the materials [28,31], with the losing rate kinetics being controlled from the surface interaction of lead with oxygen at the intermediate temperature ranges of 700˝C to 1000˝C [27].…”

Verification of Possibility of Molten Steels Decopperization with ZnAl2O4

“…Furthermore, a few ppm of oxygen can significantly reduce the surface tension value [31]. Thereby, its effect on the free evaporation rate constant of copper from liquid iron can be expressed by assuming Langmuir's ideal adsorption isotherm [32,33].…”

Sustainable Ironmaking Toward a Future Circular Steel Economy: Exploiting a Critical Oxygen Concentration for Metallurgical Cu Removal from Scrap‐Based Melts

“…[8] The difficulty to remove Cu from the molten scrap is due to its high solubility and thermodynamic stability in liquid Fe, which requires strategies based on low pressure atmospheres to induce its preferable evaporation, as its vapor pressure is higher than that of iron. [18,19] Also, Cu is more noble than Fe, which impedes its conversion into more easily removable compounds such as slag-forming oxides. [15] The increasing amounts of Cu in steels start to cause serious and highly detrimental effects on steel manufacturing, application and product safety, with the so-called hot shortness-i.e., a dramatically reduced ductility at elevated temperature (>1000 °C)-as the most significant problem (an example of a steel plate compromised by hot shortness is shown in Figure 1c).…”

“…[ 8 ] The difficulty to remove Cu from the molten scrap is due to its high solubility and thermodynamic stability in liquid Fe, which requires strategies based on low pressure atmospheres to induce its preferable evaporation, as its vapor pressure is higher than that of iron. [ 18,19 ] Also, Cu is more noble than Fe, which impedes its conversion into more easily removable compounds such as slag‐forming oxides. [ 15 ]…”