抄録
With the view of elminating the various defects in white iron casting containing high manganese as 0.85 to 1.10%, the compelled oxidation and reduction refining of molten iron from cupola were carried out in Heroult electric arc furnace with acid lining. As the results of using this type of melting operation, the as-cast fracture of white iron castings showed neither mottling tendency nor pinholing defects which were often found in the castings melted by ordinary duplex melting process. In this case, however, post aluminum deoxidising treatment has no effect on the mottling occurence in white iron castings.
Trial production melting and annealing have shown that high manganese content in white iron made it possible to obtain pearlitic malleable iron having laminar pearlitic matrix along with standard black heart malleable iron by continuous furnace annealing.
On the other hand, granular pearlitic malleable iron were also manufactured with ease by heat treatment consisting of first stage graphitisation followed by rapid cooling and short time tempering.
It is also clarified that pinholing defects occurring when the molten iron treated with manganese in ladle was poured into green sand mold, were reduced comparatively by adding special reagent as borasic acid into facing sand of the mold.
