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Description
The use of an electric arc furnace (EAF) can significantly lower CO2 emissions during the steelmaking process compared to the conventional blast furnace route. Depending on the quality of the scrap metal, elements such as chromium, molybdenum, and tin can end up in the steel production process.
These tramp elements are difficult or impossible to remove through metallurgical processing. Furthermore, these elements impact the thermomechanical processing and the associated recrystallization behavior of the austenite after hot working. To ensure the right processing parameters, it is important know the effects of these tramp elements and if necessary to adjust the process accordingly. This work investigates the influence of the tramp elements Cr, Mo and Sn on the static recrystallization behavior of the austenitic phase after the deformation step.
The base material was a micro-alloyed steel with 0.08 wt.-% C, 0.9 wt.-% Mn and 0.04 wt.-% Nb and tramp element content of 0.5 wt.-% Cr, 0.15 wt.-% Mo and 0.05 wt.-% Sn were added to the base respectively.
For the experiments, the pocket-jaw unit of the Gleeble 3800-GTC was used to obtain stress-strain curves at different temperatures and interpass times in double-hit-compression-tests. Using the flow stress data, the recrystallized fractions during the interpass times were calculated. Additionally, laser ultrasonic measurements were applied to measure grain growth during heating and the static recrystallization behavior after hot deformation. Furthermore, thermokinetic simulations via MatCalc© were performed to correlate the precipitation kinetics of Niobium carbonitrides with the recrystallization behavior of the austenitic phase.
The results show that at higher temperatures, tramp elements do not affect the recrystallization kinetics. Chromium shows an accelerated recrystallization behavior at lower temperatures, while Tin shows no effect at all investigated temperatures. The results of the double-hit-compression-tests show similar results regarding static recrystallization behavior as the laser ultrasonic measurement.