Thermodynamics of molten calcium aluminate slag

近十年来，为了生产高纯净钢和减少精炼过程中的渣量，人们开发了各种钢水脱磷和脱硫剂。实际使用的铁水处理和二次精炼熔剂有Na_2CO_3基熔剂和CaO-CaO-CaN-Fe_xO_y熔剂，但这些熔剂存在以下问题。A)油烟和恶臭气体的巨大排放。B)Na_2CO_3、CaF_2成本高；c)耐火材料腐蚀。D)形成的炉渣处理等。本文研究了CaO-Al_2O_3-Fe_xO_y熔剂对钢铁铁水的脱磷和脱硫，以寻求解决上述问题的方法。采用Al_2O_3作为助熔剂的原因是：(1)CaO-Al_2O_3系中CaO的熔点降低程度与CaO-CaF_2和CaO-Fe_2O_3系的相似。2)铝土矿、一水硬铝石等自然资源丰富，是Al_2O_3的来源；c)Al_2O_3对CaO的脱磷效果不如SiO_2；d)形成的渣处理不麻烦，可用于土地改良。鉴于此，采用CaO-Al_2O_3-Fe_xO_y熔剂处理钢铁铁水。结果表明，CaO-Al_2O_3-Fe_xO_y熔剂的脱磷能力与铁水处理和二次精炼中实际使用的熔剂相近。但该助熔剂对铁水和钢水的脱硫效果不佳。

Various kinds of fluxes for dephosphorization and desulphurization of hot metal and steel have been developed at past decade to producehigh purity steel and to reduce the slag amount formed during refining. Practically used fluxes in hot metal treatment And secondary refining processes are Na_2CO_3 based and CaO-calcium halides-Fe_xO_y fluxes, but the following problems are realized in these fluxes. a)Huge evolution of fume and stinking gas. b) High cost of Na_2CO_3, CaF_2 c)Corrosion of refractories. d)Disposal of the formed slag, and so on. In the present work, dephosphorization and desulphurization of hot metal and steel with CaO-Al_2O_3-Fe_xO_y flux was studied to seek a solution of above-mentioed problems. The reason why Al_2O_3 is used as the flux are as follows: a) The degree of melting point depression of CaO in CaO-Al_2O_3 system is similar to those in CaO-CaF_2 and CaO-Fe_tO systems. b) There is a large amount of natural resources such as bauxite and diaspore as the source of Al_2O_3. c)aL_2O_3 has no so bad effect on the dephosphorization with CaO in comparison with SiO_2. d)There is no trouble in disposal of the formed slag, and it might be useful for land improvement.In view of the above-mentioned, hot metal and steel were treated by the use of CaO-Al_2O_3-Fe_xO_y flux. As the results, it was confirmed that dephosphorization power of CaO-Al_2O_3-Fe_xO_y flux was similar to the practically used fluxes in hot metal treatment and secondary refining processes. But this flux was not so effective for desulphurization of hot metal and steel.