Kinetics of evaporation removal of Cu and Sn from carbon tool steel under reduced pressure

Abstract

The removal of residual Cu and Sn from steel is crucial for advancing the recycling of steel scrap and promoting the development and production of clean steel. In this study, the kinetics of evaporative removal of Cu and Sn from carbon tool steel under reduced pressure were investigated. The results show that increasing the smelting temperature and lowering the gas phase pressure significantly enhance the removal efficiency of Cu and Sn from molten steel. The evaporation of Cu and Sn follows first-order reaction kinetics, with both elements evaporating as monatomic molecules. The observed evaporation rate constants for Cu and Sn range from 2.3×10⁻⁶ m·s⁻¹∼10.5×10⁻⁶ m·s⁻¹ and 1.6×10⁻⁶ m·s⁻¹∼8.5×10⁻⁶ m·s⁻¹, respectively. At a gas phase pressure of 60 Pa and a smelting temperature of 1550 °C∼1650 °C, the apparent evaporation activation energies for Cu and Sn are 192.52 kJ·mol⁻¹ and 181.84 kJ·mol⁻¹, individually. Cu evaporation is restricted by the rate of reaction at the gas-liquid interface. Moreover, within the experimental parameters of this investigation, mass transfer in the liquid phase has negligible influence on Cu and Sn evaporation.