INTERFACIAL-TENSION EFFECTS ON SLAG-METAL REACTIONS

Dynamic X-ray imaging of a metal droplet in a slag phase is an elegant way to monitor the rate of the interfacial reactions. In an attempt t o follow the kinetics of dephosphorization, the changes in the shape o f the sessile drop of molten iron with 0.1 wt% P immersed in a slag ke pt in MgO crucibles were recorded as a function of time. The slag had all initial composition 40 wt% CaO, 30 wt% SiO2 and 30 wt% Fe2O3. Whil e in a set of runs, solid iron was added to the molten slag, the seque nce was reversed in others, where a pellet of the slag was added to th e molten iron. In the former case; it was found that after 10 s, the d rop flattened and the contact angle, theta was well below 90 degrees, indicating a significant increase in the contact area. Beyond 250 s, t he contact angle showed a gradual increase. In the second series, wher e the slag was added to the metal, the contact angle remained high thr oughout the dephosphorization reaction; indicating a rapid mass transf er of phosphorus. Similar application in the field of copper metallurg y, where the transfer of arsenic and antimony from copper metal to mol ten Na2CO3 was studied, confirm that this technique is very useful in understanding the mechanisms of the slag-metal reactions.