Method of making ductile iron treating agents

Abstract

A method of making a more economical and reliable treating agent for use in late metal treatment when pouring metal castings. The treating agent is defined as an essentially homogeneous solid cast block preferably containing alloying ingredients to nodulize or inoculant ferrous metal. Each block is designed to present a generally uniform reaction surface to molten metal to be treated. This is obtained by casting the block to a shape which snugly fits a prepared basin in the mold gating system over which the molten metal to be treated must flow, or to cast the block in an annular configuration through which the molten metal must flow. The latter block has contoured inner surfaces which maintain a generally constant reactive surface as the block is consumed. These blocks are preferably prepared by simultaneously casting a large number in closely nested relation. Each mold for said blocks receives molten material, out of which the agent is formed, from a common sprue; runners interconnect the mold cavities and sprue, for example, in a simulated 'Christmas tree' arrangement. The gating system and mold cavity pattern, for casting the treating agent to a special shape are all comprised of a material that will vaporize upon contact by the molten treating agent, such as polystyrene. The unitary tree structure of foam patterns and gating system is placed in a flask and surrounded by unbonded heat absorbing particles, such as sand or steel shot. Rapid solidification is assured by the selection of heat absorbing particles and by the use of the vaporizable patterns to avoid noticeable segregation in the alloy blocks. The blocks formed for the treating agent are characterized by increased homogeneity, absence of undesirable segregation, absence of internal oxidation, and absence of organic or refractory impurities; the blocks are less costly to make both as to capital requirements and operating expenses.