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FERROUS ALLOYS
The FERROUS group of alloys embraces a large number of materials offering quite diverse characteristics – ranging from the brittle GREY CAST IRONS through to highly MALLEABLE MILD STEELS. An alloying element of central importance to ferrous metals is CARBON, be it in quantity, form or distribution within the alloy. Carbon has a significant influence on both the strength and quality of cast irons, it also affects the mechanical properties of wrought iron as well as both carbon and STAINLESS steels. In these last three materials, a lower carbon content improves their working characteristic (DUCTILITY and MALLEABILTIY), allowing a straightforward HOT WORKING of the alloy (by FORGING for instance).
Whilst the ferrous group of alloys are most often today associated with fabricated metalworks; carbon steels, stainless steels and irons are all castable materials which can be poured into either sand or investment refractory moulds. All these alloys are melted in the furnace at appreciably higher temperatures than copper alloys (the melting point of pure iron is 1536°C, copper 1085°C). This feature can make use of ferrous materials somewhat problematic in the art foundry environment as the common gas fired furnace is less well suited for use at such elevated temperatures. Despite the drawbacks, iron is one of the most requested materials for casting artworks after copper and aluminium alloys, as such a minority of art founders will offer iron casting as a facility to their clients.
One point of particular note, is that workshops that cast or fabricate both ferrous and non-ferrous metals can be prone to problems arising from CROSS CONTAMINATION. Cross contamination occurs when ferrous dusts settle on non-ferrous metal works (and to some extent vice-versa). Contamination can also occur through a common use of machine tools and other equipment (including crucibles, twist drills, bending rolls, abrasive discs, shot blasters etc). The end result of cross contamination by ferrous grinding dusts is the development of an unsightly red oxide ‘bloom’ on copper alloys and a transferred surface rusting of stainless steels. Ideally, ferrous and non-ferrous (including stainless steel), workings should be carried out in separate workshops using dedicated machinery. In practice, religiously dividing work spaces and tooling is very expensive and therefore not always realistic. At the very least great care should be taken when working ferrous metals in proximity to copper and other non-ferrous metals, to control the direction and settling of grinding exhaust.
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