Study On Composition,Structure And Performance Of Stopper For Con-casting System

Some factors affecting properties of stopper for con-casting system are studied in this paper. This paper is divided into two series:Al2O3-C system and MgO-C system. The relationship between amounts of binders, grain granularity distribution, additives and properties of samples are studied respectively. Effect of amounts of different anti-oxidants on properties of samples are studied emphatically.In the view of amounts of binders, amounts of binders are studied, on the basis of work done and combing with the self characteristics of stopper. Through detecting physical properties of samples and studying the carbonization mechanism of resin, the following conclusions can be drawn. For the Al2O3-C system what critical granularity is 1mm, when the amounts of resin are 6%, grain can be surrounded sufficiently by resin and can combine together more compactly with fine powder and the sample has optimal properties. For the MgO-C system what critical granularity is 2mm, the fittest amounts of resin is 4%.In the regard of the experiment of grain granularity distribution, on the basis of the Andreassen formula, through changing the distribution condition of the particle size, it is concluded that grain and matrix combine together more compactly and the sample has higher cold crushing strength, when distribution coefficient equal 0.44 and 0.40 respectively in the Al2O3-C system and in the MgO-C system. Meanwhile, It shows that higher intensity can not be gotten through diminishing critical granularity or adjusting granularity distribution.As for the study on additives, the amounts of zirconia-corundum and SiC added are studied. It indicates that zirconia-corundum added can enhance the intensity of samples in the A12O3-C system. The grain granularity distribution of system is changed when the amounts added is above 10%, this results in the imperfect and noncontinuous structure, meanwhile, new structure has not formed, the porosity of sample increases, intensity decreases. When the amounts of SiC added is below 9%, the original structure is destroyed, result in porosity increases, intensity decreases. Attacking is the most when the amounts of SiC added are 6%.The effects of single additive and multiple additives are studied at the end. Experimental results show that additive of B4C is beneficial for improvement of sample's intensity at room and elevated temperature , oxidation prevention, but the erosion prevention is decreased, so the amount added should be appropriate. Specific experimental results are as follow: for A12O3-C system, samples added 2%Si+2%B4C have higer intensity at room and elevated temperature, better oxidation resistance. Samples added 4%Si have well corrosion resistance by slag and molten steel. For MgO-C system, samples added 3%Al+l%Si+l%B4C have higher intensity at room and elevated temperature, oxidation resistance. The samples added Al and BN at the same time have well corrosion resistance by molten steel. The samples added Al and Si at the same time have well corrosion resistance by slag.