| The amount of retained oxygen and it`s relation with the formation of graphite in the gray cast iron melted with the medium frequency induction furnace were investigated. And also the effect of retained oxygen on the inoculation by adding mill scale as the oxidizing agent at 1,450℃, 1,500℃, and 1,550℃ respectively were studied. The results were as follows: (1) The amount of retained oxygen was approximately 80-100 ppm (2) The number of graphite nucleus was decreased as carbon equivalent decreases. The number of nucleated graphite was decreased and the hardness was increased, as increasing the amount retained oxygen. (3) when 3% aad 6% mill scale, respectively, were added into the molten gray cast iron, the activation energy for the graphite nucleation was 15,000 ㎈/㏖ and 21,000 ㎈/㏖, respectively. (4) The shape of graphite, as the amount of retained oxygen increases, was changed from coarse flake, rossete to eutectic gradually. |
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