Abstract:  During the process of non-protective atmosphere electroslag remelting of 9CrMoCoB steel， Iron oxide scale generated from the oxidation of the electrode surface are introduced into the slag pool ， as a result the oxygen potential of the slag pool increases and easily oxidized elements in the metal melt pool burns seriously. In order to reduce the oxygen potential of the slag pool and improve the yield rate of easily oxidized elements， appropriate deoxygenation agent should be added to the steel during the smelting process. Firstly， the high-temperature oxidation behavior of 9CrMoCoB steel at different temperatures was studied by using a thermogravimetric analyzer， and corresponding oxidation kinetics were established； Secondly， XRD and SEM-EDS analyses were conducted on the oxide scale of the sample； Finally， based on the above experiments and the temperature distribution on the electrode surface in the process of ESR in non protective atmosphere， a better deoxidation system was proposed. The results indicate that the weight gain at low-temperature oxidation （500-700 ℃） can be ignored； The weight gain at medium temperature oxidation （900-1 000 ℃） consists of two stages： the linear law stage of rapid oxidation period and the parabolic law stage of diffusion control； The weight gain during oxidation at high temperatures （1 100-1 200 ℃） follows a parabolic pattern. At different temperatures， the high-temperature oxidation rate of 9CrMoCoB steel is k=exp(44.1317-\frac{40163.707}{{46}^{(h+0.33)}+723.15}. The oxide skin has a layered structure， with an outer layer of iron oxide and an inner layer of iron chromium composite oxide phase. During the smelting process， the 9CrMoCoB electrode （diameter 75 mm） is introduced into the slag pool with a FeO content of 9.02 g every 5 minutes. To completely reduce the introduced FeO ， the addition of pure Si is 1.75 g， which can avoid readily oxidizing elements burning and obtain qualified chemical composition of the electric slag ingots.

Key words: Non Protective Atmosphere Electroslag Remelting, Electrode Oxidation, Oxide Scale, Deoxidation Process, 9CrMoCoB Steel

摘要： 非保护气氛电渣重熔9CrMoCoB钢过程中，电极表面氧化生成的氧化铁皮进入渣池，导致渣池氧势升高，造成金属熔池中易氧化元素发生严重烧损。为降低渣池氧势以提高易氧化元素收得率，冶炼过程中需向钢中加入适量脱氧剂。首先利用热重分析仪研究了不同温度下9CrMoCoB钢高温氧化行为，建立相应氧化动力学；其次对试样氧化皮进行XRD和SEM-EDS分析；最后基于上述实验和非保护气氛电渣重熔过程中电极表面温度分布，提出较优脱氧制度。结果表明，低温（500～700 ℃） 9CrMoCoB钢氧化增重量可忽略；中温（900～1 000 ℃）氧化增重由快速氧化期的直线规律阶段和扩散控制的抛物线规律阶段两段组成；高温（1 100～1 200 ℃）氧化增重呈抛物线规律。不同温度下，9CrMoCoB钢高温氧化速率k=exp(44.1317-\frac{40163.707}{{46}^{(h+0.33)}+723.15}；氧化皮呈复层结构，外层为铁的氧化物和内层为铁铬复合氧化物相；冶炼过程中，9CrMoCoB电极（直径75 mm）每5 min带入渣池FeO为9.02 g，为完全还原带入的FeO，加入纯Si为1.75 g，可避免易氧化元素烧损，可得到化学成分合格的电渣锭。

关键词: 非保护气氛电渣重熔, 电极氧化, 氧化皮, 脱氧工艺, 9CrMoCoB钢