The solubility of nitrogen in the Fe-C-V-N system was measured at 1 708 K and the model of calculating activity （action concentration） of nitrogen （N） and vanadium （V） was derived according to the phase diagram and the coexistence theory of the metal melt structure. The solubility expression of nitrogen in the Fe-C-V-N system at 1 708 K was ωN =0. 058 194-0. 010 367ωc＋0. 005 543 4ωv. Comparing the computing results with the experimental resuits, a satisfactory conclusion could be obtained. The analysis of the Fe-C-V-N system using this model showed that VN was present in a high temperature metal melt, which would reduce the action concentration of nitrogen obviously. It was consequently disadvantageous to the removal of nitrogen from hot metal.
The purpose of the study is to decrease content of CaF2 in dephosphorization slag. The dephosphorization effects of CaF2 replaced by B2O3 were investigated. The dephosphorization experiments were carried out at 1 450 ℃ in air atmosphere. The results show that the melting points and dephosphorization ratios change little when CaF2 was replaced by B2O3. The dephosphorization ratios are all greater than 80% and melting points can meet the requirement of hot metal pretreatment. Because of the change of alkalinity caused by B2 03, the oxidation of slag increases with increasing of B2 Oa contents. It is beneficial to pre-dephosphorization. As a result, for decreasing its pollution, CaF2 can be replaced by B2Oa to dispose fluoride-free pre-dephosphorization slag.
The solubility of nitrogen in Fe-C-B-N system was measured at 1 758 K,and the computational model on activity （action concentration） of nitrogen and boron was established based on phase diagram and the coexistence theory about metal melt structure model. Comparing the computed results with the experimental results,satisfactory conclusion can be obtained. The result shows that BN and B4C can exist in Fe-C-B-N molten metal at high temperature,which consequently restrains the nitrogen removal from the melt. However,B4C content is extremely low. Before graphite is precipitated,the influence of carbon on activity of nitrogen in melt is higher in ternary system than in binary system; however,this effect is contrary to that after graphite is precipitated.
WANG Shi-junPENG JunDONG Yuan-chiLIU Li-xiaZHOU YunCHEN Er-bao
