Patent ID: 6375701
Filing Date: 2002-04-23
Classification: C21C,F27B,F27D,Y02P

Abstract:
A method for controlling the amount of nitrogen in a steel during manufacture in an electric arc furnace comprising the successive stages of:melting iron scrap; refining the melted iron scrap to produce a melted steel under a foaming slag; and heating the melted steel under the foaming slag; measuring the amount of NOx in exhaust gas throughout refining and heating stages; and controlling the state of the foaming slag depending on the measured amount of NOx to control the amount of nitrogen in the steel to produce a low nitrogen steel containing less than 70 ppm of nitrogen; wherein the refining stage and the measuring stage are initiated when melting of the iron scrap is finished and the melted steel surface becomes flat or when the melted steel temperature becomes higher than 1550Â° C.