Let’s start with the absolute basics: what is steel? Fundamentally, steel is an alloy of iron and carbon. We can, for the most part, dispense with many modern varieties of steel that involve more complex alloys; things like stainless steel (which add chromium to the mix) were unknown to pre-modern smiths and produced only by accident. Natural alloys of this sort (particularly with manganese) might have been produced by accident where local ores had trace amounts of other metals. This may have led to the common belief among ancient and medieval writers that iron from certain areas was superior to others (steel from Noricum in the Roman period, for instance, had this reputation, note Buchwald, op. cit. for the evidence of this), though I have not seen this proved with chemical studies.
So we are going to limit ourselves here to just carbon and iron. Now in video-game logic, that means you take one “unit” of carbon and one “unit” of iron and bash them together in a fire to make steel. As we’ll see, the process is at least moderately more complicated than that. But more to the point: those proportions are totally wrong. Steel is a combination of iron and carbon, but not equal parts or anything close to it. Instead, the general division goes this way (there are several classification systems but they all have the same general grades):
Below 0.05% carbon or so, we just refer to that as iron. There is going to be some small amount of carbon in most iron objects, picked up in the smelting or forging process.
From 0.05% carbon to 0.25% carbon is mild or low carbon steel.
From about 0.3% to about 0.6%, we might call medium carbon steel, although I see this classification only infrequently.
From 0.6% to around 1.25% carbon is high-carbon steel, also known as spring steel. For most armor, weapons and tools, this is the “good stuff” (but see below on pattern welding).
From 1.25% to 2% are “ultra-high-carbon steels” which, as far as I can tell didn’t see much use in the ancient or medieval world.
Above 2%, you have cast iron or pig iron; excessive carbon makes the steel much too hard and brittle, making it unsuitable for most purposes.Bret Devereaux, “Collections: Iron, How Did They Make It, Part IVa: Steel Yourself”, A Collection of Unmitigated Pedantry, 2020-10-09.
October 26, 2023
QotD: Making steel
Filed under: History, Quotations, Science, Technology — Tags: BretDevereaux, Materials, Metalworking — Nicholas @ 01:00
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