抄録
At our company, molten metal melted with cupola sometimes contains around 5 to 25 ppm boron. For this reason, in the production of FCD700 as-cast, the amount of ferrite structure with boron contamination in creases, and as a result, the required standard for ferritic area ratio at our company, which should be less than 15%, is not met. As a countermeasure, addition of tin promoting pearlitic structure to the spheroidal graphite cast iron was attempted, however, inevitable disadvantages due to the alloy addition occurred.
In order to improve these various problems, the decrease of boron in molten metal of cupola was reviewed. First, it was clarified how much boron should be reduced to satisfy the standard. Secondly, the boron content contained in our charging materials for cupola melting was investigated, then the main materials increasing the boron content in molten metal were specified, and the boron content in molten was considerably reduced by not using these materials. Boron reduction in the melting process was also investigated. Finally, it was newly confirmed that additional boron reduction occurs in desulphurization process.
