Oxide Scale Formation of Stainless Steels with Different Heating Methods – Effect of Hydrogen as Fuel

Abstract

The evolution from natural gas usage to new technologies, such as the use of hydrogen as fuel or electricity-based heating, strongly influences the oxidation of the stainless steel surface in the reheating furnace. Thermogravimetric tests using different simulated combustion and induction reheating conditions are performed for austenitic AISI 301, AISI 304, and ferritic AISI 444 steel grades. Simulated furnace atmospheres in combustion methods are based on methane–air, methane–oxygen, hydrogen–oxygen, and methane–hydrogen–oxygen combinations. For induction simulations, air and nitrogen are used as furnace atmospheres. The results indicate that changes in heating conditions to H2-fueled combustion or induction only have a minor influence on the oxidation of the ferritic grade; whereas, their effects on the austenitic grades are more pronounced. The transition from a methane–air to H2–oxyfuel combustion increases the total oxidation by 1.7 and 4 times for steel grades 304 and 301, respectively; therefore, grade 304 can be considered better suited for transition for H2–oxyfuel use. The shorter induction heating considerably decreases the amount of oxide scale for austenitic grades, but the nitrogen atmosphere produces a subscale inside the steel matrix, which can hinder the descaling process.