Foundries (3% of primary nickel use)
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Most foundry melt shops are equipped with induction melting or vacuum furnaces. These usually require that
the raw materials be added in small pieces. Refining in these furnaces is slow and relatively costly and this
means scrap utilization in the foundry sector is less intense than in large stainless steel plants.
Internal scrap is heavily recycled. The casting process is often chosen originally because complex shaped articles can be produced directly from molten metal -- thereby reducing the need for much subsequent machining to shape. But in making quality castings, it is necessary to cast "extra" pieces which act as liquid metal "reservoirs" during the solidification process.
These extra pieces, called runners and risers, are the same alloy as the main casting and are detached from the casting once it has solidified and cooled. Runners and risers can account for as much as 30% of the total metal melted and are usually segregated into alloys and remelted at the earliest opportunity (together with any castings that are subsequently rejected before sale).
Other internal arisings in the foundry itself include products of grinding and shot-blasting where alloy dusts and pieces are mixed with refractory particles. This mix can be remelted and the refractory part separated from the metal as slag. Some foundries will do this in-house and return the alloy back into their furnaces. Others will sell the material as feed for suppliers to the stainless steel industry. Still others will have the material "toll melted" by outside specialist companies who return the alloy in a product form suited to the originating foundry -- sometimes adjusting the composition to an agreed specification by adding small amounts of primary metals (producing what is known as a "master alloy").
Industrial scrap (i.e., that which is returned to the foundry by his direct customer) is usually limited
to castings which have been spoiled or rejected at a later stage of machining or assembly. Fabricator
turnings, dusts and other by-products are only returned directly to the foundry if individual alloy identity
has been maintained throughout. Usually this is not the case and such products are sold either as feed for
stainless steel blended scrap or as feed for remelting into a master alloy.
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