Abstract：In the latest years, as steel industry becomes more demanding and competitive, steel shop process has an increasing need to control the production specifications on time with reliable results. In this context, accurate nitrogen results are essential to control process sealing and to guarantee desired product characteristics (especially tenacity and machinability).Clearly, classical combustion techniques (CC) have been widely used in past years for determining carbon, sulfur and nitrogen in steel. However, spark emission has also been used and has been gaining popularity as a result of improved performances, reduction in consumables costs (associated with CC) and time gains.This work aimed to optimize nitrogen analysis by optical emission spectrometry (OES) in the Steel Chemical Analysis Laboratory of ArcelorMittal Tubaro located in Serra, Brazil and was performed according to DMAIC methodology (specific tool to improve the quality of processes)［1］. The potential influence variables were analyzed (shift, sample and period), the basic causes related to nitrogen precision were identified and prioritized. After that the action plan was implemented and the results were evaluated focusing in precision (evaluated based on an internal reference material standard deviation) and accuracy (evaluated comparing with OE certified reference material and LECO cross checks).Before this project development, nitrogen standard deviation by optical emission reached 0.004 0%. The trials made after the implementation of all planned actions in one of ArcelorMittal Tubaro’s spectrometers showed the potential of this technique, since a standard deviation of 0.000 5% was achieved. This result was monitored weekly during 3 months, floating from 0.000 3 to 0.000 5% what demonstrate its stability. Therefore，optical emission technique appears as a promising method to perform nitrogen analysis.
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