Nitrogen desorption in molten stainless steel during immersion argon blowing

The behavior of nitrogen desorption reaction in molten stainless steel for AISI 304 and 316 during immersion argon blowing through an immersed alumina nozzle with 3 mm in I. D. has been investigated by sampling method. Some kinetic parameters such as reaction order, rate constant and apparent activation energy of nitrogen desorption reaction for AISI 304 and 316 have been obtained. Results show that nitrogen desorption reaction from molten stainless steel for AISI 304 and 316 is the second order reaction. The rate constant at 1550 °C and 1580 °C for AISI 316 is 0.08407%−2 • min−1 and 0.82370%−1 • min−1, respectively. The rate constant at 1550 °C for AISI 304 is 0.4166%−1 • min−1. The apparent activation energy E, of nitrogen desorption reaction for AISI 316 is 2136.47 kJ/mol. This huge value of apparent activation energy verifies that the nitrogen desorption reaction has a complex and multistep reaction mechanism. The rate of nitrogen desorption reaction from molten stainless steel is mixed controlled by the desorption reaction of diatomic molecule nitrogen or of monatomic nitrogen from molten metal at the gas-metal interface and the mass transfer of nitrogen in molten metal. The rate equation of process for nitrogen desorption has been deduced.