Effect of Slag on Inclusions During Electroslag Remelting Process of Die Steel
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a critical problem to control non-metallic inclusions in steel in the steelmaking process, which has a direct relationship to the performance of production. Inclusions will easily initiate micro-voids and cracks at interface between inclusions and steel, which might be the origins of fatigue fractures or other defects,[1] and it is not the exception for electroslag remelting steel. Besides controlling homogeneous composition and compact solidification structure, removal of non-metallic inclusions is an important characteristic for electroslag remelting.[2] However, cleanliness of conventional electroslag steel cannot meet the requirements of customers with the increasing demand for more excellent performance of steel. Many measures have been investigated for improvement of the cleanliness of electroslag steel. As a matter of fact, the control of oxygen and non-metallic inclusions is coherent due to lower level of dissolved oxygen in steel. Control of oxygen content has been studied by many investigaYAN-WU DONG, Associate Professor, ZHOU-HUA JIANG, Professor, YU-LONG CAO and DONG HOU, Ph.D. Candidates, and ANG YU, Graduate Student, are with the School of Materials and Metallurgy, Northeastern University (NEU), Shenyang 110819, Liaoning, P.R. China. Contact e-mails: [email protected] and [email protected] Manuscript submitted September 12, 2013. METALLURGICAL AND MATERIALS TRANSACTIONS B
tors.[3–6] They found that oxygen pickup would happen when a low oxygen content electrode was employed during electroslag remelting,[3–5] while oxygen content would decrease in the case of using a high oxygen content electrode.[6] Deoxidization during casting of the consumable electrode[7] and deoxidization of slag during electroslag remelting[8] have proved to have an important influence on the non-metallic inclusions in electroslag steel. Different deoxidizers including Al, SiCa, and so on have been adopted for manufacture of consumable electrodes, and subsequent deoxidization during electroslag remelting with different deoxidizers has been investigated. Calcium treatment has been studied on the oxide inclusions’ modification during protective gas electroslag remelting.[9] Results indicate that deoxidization affects the characteristics of non-metallic inclusions in electroslag steel. Generally, MgOÆAl2O3 spinel inclusions will arise with Al deoxidization during ESR, which is hard and brittle, and commonly very harmful to the final products. The removal of non-metallic inclusions during electroslag remelting is mainly at the tip of the electrode and it is mainly absorption and dissolution of the inclusions in the slag.[10,11] A lot of factors influence the cleanliness of electroslag steel including slag, melting rate, input power, steel grade, and so on, in which the slag plays an important role for controlling inclusions during electroslag remelting.[12] The current work focused on the impact of fluoride containing slag on the inclusions in steel. The behavior of non-metallic
inclusions through interactions at the slag-metal inter
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