A comparative experimental analysis of the scale formation of various steel grades during reheating under hydrogen and natural gas air-fuel and oxy-fuel combustion conditions

The presented paper, deals with the influence of natural gas and hydrogen air-fuel and oxy-fuel combustion on scale formation. A semi-industrial scale furnace with a multi-fuel, multi-oxidizer burner was used to generate diverse combustion atmospheres, which were utilized to heat steel samples of twelve distinct steel grades to 1250 degrees C. This simulates industrial steel reheating. The weight gains due to oxidation during the reheating was measured. Subsequently, the samples were metallurgically analyzed to identify potential discrepancies in the quality of the reheated steel. Via light microscopy, scanning electron microscopy and electron probe micro-analysis, the structure and composition of the formed scale layer was scrutinized. The results showed, that weight gains were more dependent on the oxidizer, than on the fuel, resulting in a maximum increase of 63 % for H2-O2 combustion. Overall, the metallurgic results, showed no significant changes other than the thickness and the porosity of the scale layers.