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

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