研究A286和V57合金电渣重熔过程中钛烧损时,发现渣中TiO_2浓度较高时,TiO_2是钛烧损的主要氧化剂。与合金中的钛相平衡的渣中低价钛氧化物主要是Ti_3O_5.决定钛烧损速率的主要因素是Ti~(4+)在钢/渣界面层的传质速度。传质速度随渣中TiO_2浓度的增加而增大。降低Ti~(3+)向渣/气界面的扩散速度是减少合金中钛烧损的关键。研究了CaF_2-Al_2O_3-TiO_2渣系中Ti~(4+)在电极/熔渣和金属熔池/熔渣界面在1700±10℃的传质系数与渣中TiO_2含量的关系,测定了Ti~(3+)向渣/气界面的传质系数为2.2×10~(-1)cm/s(1500℃)。
The titanium loss during electroslag remelting superalloys A286 and V57 has been studied. It was shown that TiO_2 becomes the predominant oxidant causing the titanium loss of the superalloys when the concentration of TiO_2 in slag used is higher enough, and that the oxide of lower valence titanium which may be kept in eqilibrium with titanium in molten superalloy seems mainly to be Ti_3O_5. The controlling factor for the rate of titanium loss may be the speed of mass transfer of Ti~(4+) across metal/slag interface which increases with the increase of concentration of TiO_2 in the slag. Thus, the remedy for its titanium loss will be dependent upon reducing Ti~(3+) diffusion rate toward slag/atmosphere interface. Attempt has also been made on the correlation between TiO_2 concentration in the slag and the mass transfer coefficient of Ti~(4+) in CaF_2-Al_2O_3-TiO_2 slag system across either electrode/slag or metal pool/slag interfaces at 17004±10℃. The mass transfer coefficient of Ti~(4+) may be expressed as:k_(e/s)=6.59exp(-0.078TiO_2), 10~(-2)cm/sk_(p/s)=2.84exp(-0.079TiO_2), 10~(-2)cm/s The mass transfer coefficient of Ti~(3+) toward slag/atmosphere interface was measured, i.e. 2.2×10~(-1) cm/s at 1500℃.
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