The Research On Processability And Anti-oxidation Of Natural Graphite Electrode

The major uses of graphite electrode were electric steelmaking,orefurnace phosphorus making,fused magnesite,fused refractory,electrolytic aluminium and industrial manufacture phosphorus,silicon,carbide etc.. Graphite electrode was classified into natural graphite electrode and artificial graphite electrode. Natural graphite electrode did not need graphitizing, so the production period was greatly decreased, energy consume and pollution were also greatly decreased, cost was obviously reduced, price dominance and economic performance is invisible. This was one of the prime reasons to develop natural graphite electrode. Additionally, natural graphite electrode was natural graphite deep treatment production with a high added value. Natural graphite electrode had great development and application values, but its mold performance, anti-oxidation and mechanical properties were worse than artificial graphite electrode. This was the main barrier to develop it. Therefore, to overcome these barriers was the key to develop natural graphite electrode.The samples were prepared by natural flakes graphite powder without binding by cold pressing. The effect of density,pore degree and bending strength of samples were studied by the variation of shaped press and pressing time. A qualitative analysis was proposed to account for the relation between bending strength and microstructure of the samples. Boric acid - urea system and ethylorthosilicate - acetone - hydrochloric system were selected to study the anti-oxidation performance and mechanism of natural flakes graphite powders and natural flake graphite electrodes that with and without treatment.The main study contents and results were as followed.Mold performance of natural graphite is researched. It was showed that, with shaped press of samples increasing, the density and bending strength of samples increased, but pore degree of samples reduced. The press-maintained-time had little influence on density of samples. Good shaped properties were obtained when the press-maintained-time was more than 5 minutes. Bending strength had apparent anisotropic property, average bending strength in different orientation is 5.95MPa,9.68MPa,12.70MPa. Anisotropic property of bending strength is related with microstructure of shaped samples.Oxidation resistance of natural flakes graphite powers with and without silica sol and B-N coating were researched. It is showed that, with dipping frequency increasing, Silica sol and B-N system coating quantity on natural flake graphite powers increased, and Oxidation resistance was much better. The starting oxidation temperature of natural flake graphite powers is about 883K and the weight-loss rate is about 407.6 mg/g/h at 923K. The oxidation weight-loss rate of powers at 923K static atmosphere, which had been dipped into B -N system or Silica sol system for 9 times and then been heat-treated for 1h in N2 atmosphere at 1273K, depressed to 47.9 mg/g/h and 206.1mg/g/h. The oxidation weight-loss rate respectively reduced to 3.0 mg/g/h and 42.0 mg/g/h after being heat-treated for 1h at 1973K and 1723 in N2 atmosphere. The oxidation weight-loss rate of powers was reduced by using two systems. The anti-oxidation effect of B-N system was overmatched to Si-O system.Oxidation resistance of natural flakes graphite blocks with and without silica sol and B-N coating were researched. It is showed that, with dipping frequency increasing, Silica sol and B-N system coating quantity on natural flake graphite blocks increased, and Oxidation resistance was much better. The weight-loss rate of natural flake graphite blocks is about 122.432mg/g/h and 122.432mg/g/h at 923K and 1273K, respectively. The oxidation weight-loss rate of blocks at 923K static atmosphere, which had been dipped into B -N system or Silica sol system for 9 times and then been heat-treated for 1h in N2 atmosphere at 1273K, depressed to 20.477mg/g/h and 28.753mg/g/h. The oxidation weight-loss rate of blocks with same treatment at 1273K static atmosphere depressed to 37.064mg/g/h and 54.398mg/g/h. The oxidation weight-loss rate respectively reduced to 8.182 mg/g/h and 31.347 mg/g/h after being heat-treated for 1h at 1973K and 1723 in N2 atmosphere. The oxidation weight-loss rate of powers was reduced by using two systems. The anti-oxidation effect of B-N system was overmatched to Si-O system.