RagingDragon (a@b.c) on 9/21/09 wrote:
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>Michael S (already5chosen@yahoo.com) on 9/20/09 wrote:
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>>RagingDragon (a@b.c) on 9/20/09 wrote:
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>>>
>>>First pure metals aren't used for anything structural - they all have abysmal physical
>>>properties. Steel is an alloy of iron, carbon, and optionally other metals and non-metals.
>>
>>Coming from the field of metallurgy (in very distant past) I wonder why talking
>>about additional elements in steel common people think first and foremost about
>>carbon when, in fact, your typical mass-market steel contains much higher percentage
>>of manganese and more often than not higher percentage of silicon.
>>May be, it happenss because it is _called_ "carbon steel"?
>
>All steel, by definition contains iron + carbon, and carbon content plus heat treating
>are the primary determinants of crystaline structure and thus hardness for most
>steels (the only exception which comes immediately to mind are 300 series stainless
>and other austenite steels). And as slacker pointed out carbon content is also the
>primary difference between steel and cast iron... Some alloying agents are used
>in high concentrations in some steels, but only iron and carbon are intentionally present in all steels.
>


That's a common misconception.
Manganese in steel is both more ubiquitous than carbon and no less critical to the mechanical properties.
As for silicon, it is less important in final product, but very critical during production phase. Silicon is especially important in Bessemer-Thomas process and its modern derivate where burning silicon produces the heat required to raise the temperature to the levels required for removal of sulfur and carbon.

>Carbon steel is iron + carbon + impurities. Though, I guess low carbon steels could
>easily have higher percentages of impurities than carbon.
>
>

Manganese is not "impurity", it's an essential component of so called "carbon steel". More essential than carbon.