Thermodynamics of molten calcium aluminate slag

为了生产高纯度钢和减少精炼过程中的渣量，近十年来开发了各种铁水和钢的脱磷、脱硫熔剂。铁水处理和炉外精炼工艺中常用的熔剂是Na_2CO_3基和CaO-卤化钙-Fe_xO_y熔剂，但这些熔剂存在以下问题。a）烟气和恶臭气体大量逸出。B）Na_2CO_3、CaF_2成本高;本工作研究了CaO-Al_2 O_3-Fe_xO_y系熔剂对铁水和钢液的脱磷脱硫，以解决上述问题。用Al_2O_3作熔剂的原因是：（1）CaO在CaO-Al_2 O_3系中的熔点降低程度与CaO-CaF_2系和CaO-Fe_tO系相似; B）有大量的自然资源如铝土矿和一水硬铝石作为Al_2O_3的来源。aL_2O_3对CaO脱磷的影响比SiO_2小。（4）渣料处理方便，可用于土地改良，为此，采用CaO-Al_2 O_3-Fe_xO_y熔剂处理铁水和钢。结果表明，CaO-Al_2 O_3-Fe_xO_y系熔剂的脱磷能力与铁水处理和炉外精炼过程中实际使用的熔剂相当。但对铁水和钢液的脱硫效果不佳。

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.