Type of pig iron which must meet particular requirements in terms of quality and purity for the production of particularly pure types of castings.
Pearlitespecial pig iron is available with silicon contents categorized into three varieties and the descriptions gray, mottled and white. The gray sort is mainly used for pearlitic cast iron which is subject to high mechanical loads, while the mottled and white sorts are mainly used for malleable cast iron, white cast iron and roller casting.
Special pig iron for the production of nodular graphite cast iron is particularly pure. The contents of harmful accompanying elements which disrupt the formation of nodular graphite or promote carbidic solidification (e.g. sulfur, phosphorus, chromium, molybdenum, vanadium, lead, etc.) are very low in these sorts of pig iron. Depending on the requirements, the elements which influence the pearlite must be set within specific limits (special pig irons with particularly low manganese, sulfur and phosphorous contents).
Alloyed special pig irons are special pig irons which are alloyed in order to set specific structures, e.g. with titanium or copper.
Low-carbon special pig irons have carbon contents of around 2.4 to 3.4% which is lower than other pig iron varieties. Otherwise, they have the usual Si, Mn, P and S contents as for hematite pig irons. They are used in malleable cast iron foundries, for example.
Manganese iron additives have high manganese contents of 1 to 5 % (in stages) and low phosphorus contents. The are mainly used as iron additives to set a specific manganese content in cast iron and malleable cast iron.
Leading providers of special pig iron varieties are Rio Tinto Iron & Titanium GmbH, DK Recycling und Roheisen GmbH, Richard Anton KG and ASK Chemicals Metallurgy GmbH.