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Higher-Quality Electric-Arc

teelmakers have traditionally viewed Research Continues to Improve the (EAFs) as unsuitable Quality of Steel for producing steel with the highest- Even with continued improvements to the Squality surface finish because the process design of processes, the steelmaking uses recycled steel instead of fresh . With over research community has focused their attention 100 years of processing improvements, however, on the fundamental materials used in steelmaking EAFs have become an efficient and reliable in order to improve the quality of steel. In my lab steelmaking alternative to integrated steelmaking. In at Carnegie Mellon University, we have several fact, steel produced in a modern-day EAF is often research projects that deal with controlling the DR. P. BILLCHRIS MAYER PISTORIUS indistinguishable from what is produced with the impurity concentration and chemical quality of POSCOManaging Professor Editorof Materials integrated blast-furnace/-steelmaking route. steel produced in EAFs. Science412-306-4350 and [email protected] Mellon University Improvements in design, coupled with research For example, we recently used mathematical developments in , mean high-quality steel modeling to explore ways to control produced quickly and energy-efficiently. . Careful regulation of temperature, and stirring are needed to produce low- Not Your (Great-) Grandparent’s EAF phosphorus steel. We analyzed data from Especially since the mid-1990s, there have been operating furnaces and found that, in many significant improvements in the design of EAFs, cases, the phosphorus removal reaction could which allow for better-functioning burners and a proceed further. This explained why better more energy-efficient process. Now, EAFs often stirring in the furnace helps. On the other utilize as much oxygen per of steel as does hand, lower levels can be obtained by “oxygen steelmaking.” The unique design of the dissolving more into the bath. burners in an EAF increases throughput of the Carbon-rich direct-reduced iron (DRI) is one process, improves heat transfer and protects the good way to deliver carbon to the metal. steel against contamination from elements in These examples show that while phosphorus the air. These burners evenly supply most of the and nitrogen are both detrimental to the energy requirements of down recycled mechanical properties of steel, each is controlled steel by injecting oxygen and to create using different chemical and processing combustion energy. principles. Such increased understanding of Practically speaking, this means that chemical and heat-transfer principles allows steelmakers using EAFs have seen a big shift continued improvement of EAF steelmaking. in productivity. Now, using the same amount Full findings of this research can be found of electrical power, much less time is needed to in “Dephosphorization model for a continuous produce one heat of steel. Processing time has been DRI-EAF process1” and “Carbon transfer cut to around 40 minutes, which is an hour less during melting of .2” For than the same process in the mid-1980s. more information on Pistorius’ research, visit his website or view a short video at www. industrialheating.com/Pistorius.

References: 1. MA Tayeb, R Fruehan, S Sridhar, PC Pistorius; “Dephosphorization model for a continuous DRI- EAF process,” and Conference and Exhibition 2014, v. 1, p. 143-151, By Alfred T. Palmer - Library (2014) of Congress Prints and Photographs Division, Farm 2. Y He, PC Pistorius; “Carbon transfer during melting Security Administration - Office of direct reduced iron,” AISTech 2016–The Iron & of War Information Collection. Steel Technology Conference and Exposition (2016)

18 APRIL 2017 ■ IndustrialHeating.com