Georg Fischer Aktiengesellschaft

Urs Brandenberger

Werner Menk

Ivo Henych

Klaus Hornung

A process for the manufacture of cast iron containing vermicular graphite is described, in which nodular cast iron (GGG) is used as a starting melt. The GGG melt can be produced in a converter in a precise and reproducible way, whereby the sulphur and oxygen contents of the GGG melt are limited within narrow ranges. Additional sulphur is added to the GGG melt in an amount determined by an empirical formula depending on the magnesium and sulphur contents of the GGG melt to produce cast iron containing vermicular graphite (GGV). The GGV is produced by the present process with precision and in a reproducible manner.

Process for manufacturing cast iron containing vermicular graphite

A process for the production of cast iron containing spheroidal graphite is disclosed. In the process, the iron melt, which contains sulphur, is treated with metallic magnesium, forming unstable MgS as a by-product. By the addition of CaSi, the sulphur contained in the MgS present in the slag is converted into stable CaS. As a result, the free sulphur which is released upon decomposition of MgS when the melt is allowed to stand for a fairly long time is prevented from going back again into the melt, reacting there with the dissolved magnesium, and forming MgS once again. Through the stabilization of the sulphur in the form of CaS in the slag itself, resulphurization is effectively prevented. The slag can remain on the melt surface for a longer time than hitherto. The slag provides a heat-insulating effect, so that even longer standing times which are possibly required in certain production processes, can be utilized.

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Dachsen, Switzerland

Urs Brandenberger