Application of the technique of removing dissolved gas by irradiating of ultrasonic waves on a molten metal system was discussed. In water model experiments, dissolved gas can be removed by "rectified diffusion" and the apparent removal rate constant increases linearly with the input power. The addition of non-wettable particles to the bath enhances the degassing. A mathematical model of rectified diffusion suggests that it would be difficult to apply the technique to the gas removal in practical steelmaking processes, where the gas concentration must be controlled to a ppm level. However, since Al2O3 and SiO2 are non-wettable to molten iron, it is promising that small inclusions can be removed by the bubbles generated by ultrasonic waves in a molten iron system.
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