MgO Refractory Attack by Transient Non-saturated EAF Slag
- PDF / 1,328,860 Bytes
- 7 Pages / 593.972 x 792 pts Page_size
- 24 Downloads / 286 Views
C refractory is widely used in the sidewalls of electric arc furnaces (EAF). The MgO refractory is readily attacked by a MgO-undersaturated slag.[1] Therefore, a MgO-saturated slag is usually preferred in EAF practice. A small degree of supersaturation, causing the slag to contain suspended solid magnesiowu¨stite, promotes slag foaming that can reduce energy losses and improve refractory service life.[2] Accordingly, it is essential to know the MgO saturation level in steelmaking slags, and to adjust flux additions accordingly. The MgO saturation concentration depends on the temperature and slag components. The main EAF slag components are CaO, SiO2, FeO, and MgO; others are Al2O3, MnO, P2O5, and TiO2. In EAFs that use a large
SHENGQIANG SONG is with the The State Key Laboratory of Refractories and Metallurgy, Wuhan University of Science and Technology, Wuhan 430081, China and the Center for Iron and Steelmaking Research, Department of Materials Science & Engineering, Carnegie Mellon University, Pittsburgh, PA 15213. JUNXUE ZHAO is with the School of Metallurgical Engineering, Xian University of Architecture and Technology, Xian 710055, China and the Center for Iron and Steelmaking Research, Department of Materials Science & Engineering, Carnegie Mellon University. PETRUS CHRISTIAAN PISTORIUS is with the Center for Iron and Steelmaking Research, Department of Materials Science & Engineering, Carnegie Mellon University. Contact e-mails: [email protected]; [email protected] Manuscript submitted August 16, 2019.
METALLURGICAL AND MATERIALS TRANSACTIONS B
proportion of direct-reduced iron (DRI), several of these oxides, in particular SiO2 and Al2O3, originate from gangue in the DRI pellets. SiO2 and Al2O3 may also originate from dust and coal ash or form by oxidation of Si and Al in the scrap. FeO originates from the oxidation of iron. CaO is charged as burnt lime (CaO) and doloma (calcined dolomite; approximately equimolar CaO-MgO) and is beneficial for dephosphorization. Dephosphorization is the main refining operation in EAF steelmaking; the relatively oxidizing conditions severely limit the extent of desulfurization. The effect of slag components on MgO solubility has been studied extensively; some sources of data are reported below.[3–5] As an example of reported trends, Jung and Min[5] reported that MgO solubility is lower at higher optical basicity, higher FeO concentration and lower Al2O3 concentration in the CaO-SiO2-FeO-Al2O3-MgO slag system at 1823 K. Varying compositions of materials charged to the EAF can lead to significant fluctuations in slag composition. In general, iron ore pellets that are used to produce DRI have lower gangue contents, to limit the amounts of acid components (SiO2 and Al2O3) charged to the EAF.[6] However, cost and availability may lead to the use of pellets with more gangue. The resulting increased SiO2 and Al2O3 concentrations in DRI would tend to lower slag basicity in EAF steelmaking, and pose a risk of MgO-C refractory erosion. The work reported here originated from a report by
Data Loading...
