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Blacksmithing and metalworking questions answered.

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Wrought Iron :

Wrought iron is pure iron crystals with thin layers of silicous slag resulting in grainyness simliar to wood. Lack of carbon makes wrought iron unhardenable but very ductile. The grainyness requires special handling in forging, cutting and punching. Wrought was the product of early bloomeries and was the primary ductile form of iron for several millennia. It was last manufactured as "charcoal iron" in Sweden in 1968. It was last manufactured by the Beyer process in the U.S ending in the 1950's.

Wrought iron is also the description of decorative ironwork that is made of any metal including wrought iron, steel, cast iron and aluminium. Wrought iron is also used to describe low carbon steel pipe.
See glossary entry on iron

What is the most reliable test for identifying wrought iron? and any tips on good places to find some?

- Loren - Sunday, 03/30/03 21:58:12 GMT

Identifying Wrought Loren, sometimes it is easy and sometimes not. Wrought comes in various non-standardized grades that range from very nearly pure iron to coarse "muck-bar". There are several tests.

1) Spark Test. When ground the carbon free wrought will throw long sparks with heavy heads and few branches. It helps to have a sample to compare to mild steel on the same grinder because spark tests vary quite a bit in apearance depending on the speed, coarseness and press applied to the grinding wheel. Note that pure iron or very low carbon iron will spark the same as wrought.

2) Breaking Test. Take a small bar up to 1/2" square and saw about half way through or a little more. Then bend the bar to break it. The break with show the fibrous grains similar to wood. The better the wrought the finer the grains and in triple refined wrought it may be difficult to distinguish. Compare test to mild steel.

3) Etching or rust. Old rusted wrought clearly shows the grains and looks a lot like rotten wood. A heavy etch will do the same. Again, coarse wrought will be easier to distinguish than fine.

4) Hardenability Test. Wrought does not harden when quenched. Even mild steel will quench hard enough to blunt a good center punch. NOTE that low carbon steels require higher temperatures than the non-magnetic point to harden. +300°F or an orange heat.

5) Forgeability Test. This requires experiance but is almost as reliable as the other tests. Experts can tell very low carbon steel from wrought and pure iron by feel under the hammer.

Depending on where you live wrought may or may not be plentiful. Old buildings contain a lot of wrought. I have several lintle bars from old stone fireplaces that are wrought. Some smiths search for old fencing, much of which was all wrought up into the 1950's. Early truss bridges are often entirely wrought. Those with tension bars with forge welded loops in the ends are all wrought. Ocassionaly old wagon tires are wrought. A few folks have old wrought for sale.

- guru - Sunday, 03/30/03 22:46:54 GMT
On more method of testing for WI: (for amusement only)

From "Formulas for Profit", Bennett, copyright 1939, 4th printing

"To identify iron from steel"
"Mix 5 drops nitric acid with 10 drops H2O", (remember acid into water *NEVER* water into acid),"File a clean spot and place a drop on it.

If it is steel it will turn black immediatly. If it is wrought iron or malleable iron it will stay bright for a considerable length of time."

Use at your own risk!

- Thomas Powers - Tuesday, 04/01/03 16:14:44 GMT

The Beyer Process

The last big industrial made wrought was made by the Beyer process where they started with cast iron. This produced what I would term a "faux" wrought iron. Instead of the slag being part of the smelting process it was added later.

The Beyers process started with "pure" iron made from raw smelted iron or cast iron by the blast furnace process, but the oxygen was blown through until ALL the carbon was burned out rather than leaving some in. Then a special molten slag mixture was poured into a bull crucible holding the molten iron. It was said to react violently with the iron thus self mixing and creating a bloom like consistency. The iron was then pressed similar to consolidating a bloom to make an ingot and then it was processed like mild steel (rolling, slitting. . ).

Then there was puddled wrought iron. This had only had a small amount of slag from the surface of the puddle. This process creates pure decarbonized iron from a pool of cast iron. The pure iron has a higher melting point and forms a skin on the CI. Although there are fine layers of oxide there is not much slag.

SO. . there is wrought and there is wrought.
Wrought Iron with heavy corrosion
Wrought iron showing grain

Wrought Iron and Rust Resistance

IF one is going to write authoritatively on these subjects they should have some experience in the field. Much of the literature on this subject is sales hype and old wives tales. Stating that wrought iron does not rust of corrode is just plain wrong. While wrought has characteristics that slow its rusting (lack of sulfur and carbon) it does rust and often rusts to destruction. If it did not we would have many 1,000 to 2,000 year old iron artifacts like we do bronze. But we do not. The mechanism of rust varies with the local surface environment and the mass of the part. Temperature swings are a significant factor. Condensation is the chief source of water (the electrolyte) in rusting. Metal (iron) objects cool at night and are slow to warm in the day. As noted elsewhere large parts MAY be heated by the sun and thus not attract condensation. But indoors the greater the mass the longer a part remains at night time 1) Wrought and pure iron rusts, just a little slower than mild steel. 2) The general literature on this subject cannot be trusted. 3) The local climate and immediate environment has more to do with corrosion in this case than other variables.

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