Effect of Direct Reduced Iron (DRI) on Dephosphorization of Molten Steel by Electric Arc Furnace Slag
- PDF / 3,039,376 Bytes
- 9 Pages / 593.972 x 792 pts Page_size
- 27 Downloads / 205 Views
INTRODUCTION
THE use of direct reduced iron (DRI) as a substitute for premium scraps in electric arc furnace (EAF) steelmaking has increased in popularity because DRI does not have tramp elements, has a uniform density and shape, as well as higher yield and purity of carbon, affords convenience of charging, and has lower cost of raw materials.[1–7] Unfortunately, however, commercially available DRI contains a relatively high level of phosphorus, which adversely affects the properties of steels.[8,9] The increased use of DRI to produce high-quality steels in an EAF also increases the likelihood of phosphorus contamination of the steel. Thus, phosphorus should be fully controlled in the EAF process. However, because there are various types of oxides (e.g., FetO, SiO2, Al2O3, CaO) as well as carbon present in DRI, a comprehensive understanding of the effect of DRI on slag formation behavior, and thus dephosphorization efficiency in the EAF process, is required. The thermodynamic behavior of phosphorus in CaO-based slags containing various oxides and fluoride has been widely investigated. CaO-based slag is traditionally used in the steelmaking process because of its
JUNG HO HEO and JOO HYUN PARK are with the Department of Materials Engineering, Hanyang University, Ansan, 426-791, Korea. Contact e-mail: [email protected] Manuscript submitted May 29, 2018.
METALLURGICAL AND MATERIALS TRANSACTIONS B
high refining ability and low cost.[10–22] Previous studies generally reported that phosphate capacity and the distribution ratio of phosphorus increased with the increasing CaO content, thereby increasing the stability of P2O5 by decreasing the activity coefficient of P2O5 in the slags. In other words, dephosphorization ability is strongly affected by CaO activity in CaO-based slags, and thus the phosphorus equilibria in CaO-saturated highly basic slags have been reported.[12,18,23,24] Dephosphorization ability also depends on FetO content in CaO-based slags because FetO behaves as an acidic or basic oxide depending on the slag composition at a given oxygen potential. Lee and Fruehan[17] reported that the distribution ratio of phosphorus between carbon-saturated liquid iron and CaO-SiO2MgO-FeO slag increased with the increasing FeO content (3 to 10 mass pct) at 1823 K to 1853 K (1550 C to 1580 C) under an Ar atmosphere. In contrast, Hamano and Tsukihashi[16] reported that the distribution ratio of phosphorus between molten Fe-0.005 mass pct P and CaO-SiO2-FetO-MgOsat (-B2O3) slags had a maximum point at approximate 45 mass pct FetO content in a wide range of FetO (FeO + Fe2O3 = 20 to 70 mass pct) at 1873 K (1600 C) under a CO-CO2 and Ar atmosphere. Similar results were also confirmed by the same research group[18]; the phosphate capacity of the CaO-SiO2-FetO-MgOsat (-Al2O3, Na2O) slags under a CO-CO2 atmosphere for a range of FetO contents (FeO + Fe2O3 = 40 to 70 mass pct) at 1823 K and 1873 K (1550 C and 1600 C) increased with the increasing FeO content up to 40 mass pct and decreased when FeO content exceeded 40 mass pct
Data Loading...
