Wrought Iron

In the eighteenth and early nineteenth centuries, blacksmiths had a very narrow range of materials to work with under the hammer. There was wrought iron, wonderfully malleable, and three types of high carbon steel.

Wrought iron isn’t available to smiths today. What we have instead is a variety of mild steel alloys. These are tougher than wrought iron, suitable to more applications in this power-tool age. What the mild steels have lost is wrought iron’s malleability under the hammer and its resistance to corrosion.

This is an old hardy tool that Molly uses. The maker forge welded a piece of steel to the wrought iron body. The seam is visible in the photograph. Early trades’ tools were often made of wrought iron with pieces of high carbon steel forge welded onto it for cutting or other purposes. Today, we’d tend to make the whole tool out of high carbon steel. In the past the body of an anvil was wrought iron with a relatively thin piece of tool steel plate forge welded to it for the working surface. Woodworkers’ tools like chisels, axes, hammers, plane irons, and so forth were made this way with just a small piece of tool steel for the working surface or cutting edge.

Smiths 200 years ago had three types of tool steel available. Blister steel, the least expensive, was made by placing large bars of wrought iron surrounded by leather scraps in huge kilns where they were heated to high temperatures. The bars were crudely case hardened and had a blistered appearance but still retained a wrought iron core. Shear steel was made by reforging the blister steel bars into a more homogenous product. Cast steel was the most expensive steel of its time. It was made by cutting bars of shear steel into small pieces and melting them in a crucible. This was a truly homogenous material with wonderful edge-holding properties for tradespersons’ tools. Often quality tools of the period are marked “Cast Steel.” Here are a couple of nineteenth century center bits for woodworkers. One is marked and still has its temper color.

High carbon steels are much more varied today and have a range of properties unknown to earlier smiths. For tool making we use W1 or O1 tool steels – water or oil hardening. These steels we have to anneal (or normalize) after forging to return the steel to a soft state. This relaxes the tensions in the steel caused by forging and prevents breaking when it is hardened. We harden the steel tool in the fire by heating it to the temperature at which steel loses its magnetic properties. Then the tool is plunged into its proper quench – brine for W1, oil for O1. The tool in this state is too hard and we temper it by reheating it to a much lower temperature, either in the fire or in the kitchen oven. About 450 degrees is the proper temperature to temper a woodworking chisel. For a tool like a cold chisel used to cut steel, the tool is heated to a higher temperature, one at which the polished metal turns blue, about 550 degrees.

Wrought iron, unlike modern steels, has a grain, much like wood. This large forged nut shows the grain. In forging wrought iron, operations would have to be done in consideration of this. Holes punched near the end of a bar would be liable to break out. If the bar is spread first, forming a cusp, a hole punched on the cusp would be less likely to exceed its boundaries. Many decorative elements in traditional ironwork also serve a functional purpose.

Because of the weakness of wrought iron and its easy workability, a smith formed this washer by wrapping a piece of iron in a circle and forge welding the ends. The overlap is clearly visible. Ram’s horn nuts are useful, beautiful, and necessary adaptations for wrought iron’s weakness.

As blacksmiths today we are having to deal with materials changing. Mild steel, low carbon and low alloy, is difficult to find. Instead, steel dealers in our area have products like A36 which are versatile but tough to hand forge and which have a tendency to form stress cracks when shaped hot. This means that a sizeable portion of our raw stock has to be purchased from out-of-state suppliers.

Even though our craft is an ancient one, it is not static, but continues to evolve in accord with the world’s changing circumstances.

Go to the next post, Blacksmith Finish.

The Wrought Iron post originally appeared here.

 

Blacksmith's Blog Posts

The Shop
A Shop Shaded by Trees
The Blacksmith's Fire
Wrought Iron
Blacksmith Finish

The Library
The Blacksmith's Library -- Objects
The Blacksmith's Library -- Books

Tools
The Blacksmith's Hands -- the Hammer
The Blacksmith's Hands -- Tongs
What's It?
Using a Power Hammer

Processes
Cutting Steel Cold
Cutting Steel Hot
Blacksmith's Riveting, Brazing and Welding, part 1
Blacksmith's Riveting, Brazing and Welding, part 2
Shaping a Grip
Shaping the Braced Driven Catch
Making a Suffolk Latch -- The Thumber's Slot
Forging a Suffolk Latch Bar

Making a Latch
is a description, with photos, of the steps we go through to make a Suffolk Latch.

Making a Hinge
is a description, like Making a Latch, that shows the steps we go through to make a Butterfly Hinge.

Making a Grip
shows the process for making a Cabinet Grip.

Tools of the Trade
shows some of the tools in Molly’s blacksmith shop.

Making a Living
describes how we became blacksmiths.

Glossary of Blacksmithing Terms
is linked to various words that are not commonly known by non-smiths throughout this section of the site.