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Red hot iron: Materials in a modern blacksmith's shop

Iron, Steel, Copper and Bronze - All will be revealed!

By Magnus BudgePublished 3 years ago 6 min read
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Picture credit to Peat Oberon

A modern blacksmith's workshop is complicated - both technically and actually. Most of the work a blacksmith does is actually in his head, not his hand (though, that does make a difference). Knowing where to strike and on what materials is a very important tool in your repertoire. In order to work with multiple materials, you must first understand how they move, anneal and harden. This is what I wish to explain in this article today!

List of materials to be discussed;

- Mild Steel - Carbon steel -Wrought Iron - Pure Iron - Copper - Bronze - Cast iron

Mild Steel

Mild steel is the main material many blacksmiths use. It's ductility (how well it forms to small material, or just how well it moves when struck) and cost balance well. It's toughness is enough to keep a gate from sagging and it's hardness is soft enough it can be filed easily once annealed. Mild steel is generally used for gates, railings and hand forged items of all sorts! It has replaced wrought iron for almost all uses except restoration of antique listed ironwork.

Mild steel is easy to work and should be done between a snowball (slippery outside, where the outside has started to gently melt) heat and a bright red (or orange, for the rest of us!). It should be planished (Hammer polished) at a cherry red. To anneal mild steel, It must be heated to a cherry red and then left to air cool naturally. It will harden if it's quenched from cherry red and you may not always be able to drill or file it afterward.

Carbon Steel

Carbon steels come in many varieties, so this will be a generalisation focusing on tool steels. Carbon steel is what most people use to make tools from such as cold chisels, centre-punches, hammers and blades. It is still a very ductile material but it is a lot tougher than mild so noticeably harder to forge even at hotter temperatures. If you're making a tool to last (aside from tongs which need to be quenched to keep cool) carbon steel is what you should make them from.

A good forging temperature for carbon steel is between a bright red (orange) and a cherry red. Any hotter and you will decarburise it (Meaning it loses carbon and becomes useless as a tool steel over time). To anneal carbon steel, you heat it to a cherry red and then leave to air cool. Like mild also, you heat it and quench it in it's correct fluid. Some steels like W2 and O2 tool steels have the letter beside them, denoting in what to quench them. W2 is a water quenching steel and O2 is an oil quenching steel. Simple!

Wrought Iron

Wrought iron - the traditional blacksmith's material! Used for well over a millennia, it's use was phased out recently in favour of mild steel. This decision was primarily made for engineering. Wrought has layers of slag (glass from flux in the smelting process) and multiple types of iron in it. It can have mild steel, high carbon, pure iron, mid-carbon steel and slag glass within an inch (25.4mm) of each other. It is much softer than mild steel and bends more readily but due to it's content being a mix of all it's component parts, when forged too cold it can split apart along the grain, where the iron joins together. Unfortunately, no company commercially makes wrought iron new anymore. Topp & Co. re-roll old wrought to make it anew into bars of stock, but it's a finite resource for blacksmiths.

You don't need to anneal wrought iron. It won't harden when you quench it so there's no difference made from air cooling and quenching. this is great if you're rushing a job out the door and forgot one finial or scroll - no waiting for it to cool off! Wrought iron can be worked much hotter than mild steel due to it's glass / slag content which forms a protective barrier on the outside of the iron when nearing melting temperature. It's recommended to work wrought at a bright white to a bright red, otherwise you risk it splitting.

Pure Iron

Pure iron is a material I have worked with very little. It is about six-times more expensive than mild steel. It also the best modern replacement for wrought iron. It's butter soft compared to mild steel when hot and can sometimes bend strangely because it's so very soft. It also has a fast transfer of heat speed so it becomes very hot very quickly! It is the most wonderful thing to work with! The company I work for will be making a few projects out of it soon, so stay posted for some more fun iron facts!

Annealing is possible but unnecessary as quenching doesn't harden it, but hammering cold will though it will naturally relax and anneal over time. It's working temperature is between white and a black heat - It's very soft and very easily worked with little penalty for working cold.

Copper

Copper is very similar to pure iron in it's ductility cold. It melts at a lower temperature and is softer, colder though. It's ideal for decorative elements that will be left "unfinished" and provides nice contrast to the colour of forged iron or steel.

To anneal copper, You heat it up to a cherry red and quench it - the opposite of what you do with steel. You also work with copper cold, not hot. Copper melts at a bright red heat so you must only work it at a cold or cherry (dark) red heat.

Bronze

There are many alloys of bronze, so be careful with what you choose to do with each one. I will be talking about tin bronze here (80% Cu, 20% Sn). With bronze, You must work it like copper and is useful for similar purposes. The common use of bronze is handrails. A lot of Victorian, Regency, Edwardian and Georgian handrails are either bronze or forged iron.

You must work with bronze at a dark red heat (like copper) and you must anneal regularly as bronze has a tendency to crumble if overheated, underheated and sometimes even at the perfect temperature.

Cast Iron

Cast iron is used primarily for decorative castings. There are a few variants of cast iron. Some like welding, some don't. Some can be forged, some can't. Some are ductile, others not so much!

You should never strike cast iron 'lest it crack or shatter. It can be welded if it's the correct grade and it can also be drilled once annealed. It should never need to be annealed by you, always by the foundry.

Thank you for reading. I plan on publishing an article next weekend also. Should you have any questions, feel free to drop me a line at: [email protected]

Stay well in these times,

Magnus

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Magnus Budge

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