homepaper 3: iron and steel around campus

Ryan Carmichael 5/19/09 E82

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Homepaper 3: Iron and Steel Around Campus

Fieldhouse Gate / Bell Tower Chandelier

On the path between Fieldhouse Lane and the Mullan Tennis center lies a gate (Figure 1)

that appears to be made of wrought iron. This gate, which seems to be no more than a few

decades old, features the classic

wrought iron characteristic of rough

surface texture, easily imagined to be

from a craftsman’s hammer. The gate

also displays relative stiffness and

strength determined by pulling on the

bars of the gate. Additionally, gates

are a classic application of wrought

iron and the black coat of paint also

alludes to the history of these gates.

Likewise, the chandelier

(Figure 2) hanging on the inside of

Swarthmore College’s Bell Tower, appears to be made of wrought iron from perhaps a century

ago. Similar to the gate, the chandelier has a rough surface, with decorative features that appear

wrought rather than cast. Despite evidence of overall corrosion, the classical layer of black paint

is still visible, and wrought iron has been used for such

applications in the past. To the casual observer, there

would be little question that these objects are made from

wrought iron.

Alternatively, it is possible that these items are

made of mild steel; this type of steel is often fabricated to

look almost identical to wrought iron at a much lower cost.

It is difficult to identify genuine wrought iron from mild

steel without one of the following destructive tests. The

first is the nick bend test. In this test, a sample is sawed to

halve depth, and then bent with the cut surface in tension.

Figure 1: Fieldhouse Gate

Figure 2: Bell Tower Chandelier


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Wrought iron will show “green stick” fracture, exhibiting grains. Steel will have a clean fracture

plane. The second test is to polish the sample bare along the length of the bar and examine for

grain structure. The grain structure of wrought iron will feature linear slag inclusions not found

in steel. A third option is the spark test. Here, the sample is taken to an engineer’s grindstone and

the color of the sparks determines the material. Wrought iron will give off dull red sparks and

steel will give off white sparks.1

These tests are accurate, but not advisable for a Swarthmore student to perform on a

college gate or chandelier. As such, more subtle observations are required to determine if, in fact,

the items are made of wrought iron or the imposter: mild (wrought) steel. In common practice,

mild steel is much more likely to be electrically welded than wrought iron and is also more likely

to have active corrosion run out of the joints, which would stain the paintwork.1

Reexamining the gate looking for these subtle features, both electric welds and corrosion

running out of the joint were found. Additionally, the fence was likely constructed in the recent

past, during a time when wrought iron production had almost entirely been replaced with mild

steel for economic reasons (The only current large-scale use for wrought iron is for historical

restorations). As such, I believe the gate is made of mild steel, not wrought iron as it initially

appeared.

Conversely, a closer examination of the chandelier reveals no evidence of electric

welding (many locations where one would expect welds are held together by metal bands) and

the corrosion present does not run out of joints. Additionally, the chandelier appears to be made a

century or so ago when wrought iron was used more often than today and electric welding was in

its infancy. As a result of these observations, I believe that the chandelier is made of genuine

wrought iron.

Wrought iron and mild steel have comparable

tensile strengths, moduli of elasticity, and densities.

The slag in wrought iron makes it more corrosive

resistant than mild steel; wrought iron rusts more

evenly than mild steel as the steel develops

scattering spotty corrosion. Wrought iron is also

advantageous to mild steel because it does not have

the “snap-off" characteristic of mild steel. Instead it Figure 3: “green stick” fracture


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will exhibit “green stick” fracture (Figure 3). Mild steel is, however, far cheaper to produce than

wrought iron and because of this, the rise of mild steel marked the end for wrought iron’s major

commercial uses.

For the gate, which I’ve never seen locked, its main requirements are to aesthetically

imitate wrought iron, weather reasonably well outside, and be strong enough to seem imposing.

Both wrought iron and mild steel painted like wrought iron meet the requirements of the gate.

They feel sturdy enough to be imposing, have the proper classical gate look, and, given the

proper coating, will weather well enough in the local climate. Mild steel was chosen for the job

based mostly on the significant economic advantage it holds over wrought iron.

The chandelier has similar requirements to the gate with the exception that it need not be

as strong and, to some extent, it can be more susceptible to weathering because it is mostly

removed from the elements. Were this chandelier to be made today, it almost certainly would

have been made out of mild steel painted to look like wrought iron. However, during the time

period it was created, mild steel was in its infancy, and wrought iron was still in production.

Thus, wrought iron was be the material of choice.

Pipe Elbow / Pipefitting

Next, two types of cast pipe pieces found on campus will be

examined. These pieces, shown in Figures 4 and 5 respectively, were

identified as cast pieces because of their rough surface or “casting

skin.” Additionally, the pieces did not have any numbers or markings

clearly defined on

them, a standard

feature for cast

parts. Furthermore, both of these pieces would

be relatively difficult to forge because of their

varying diameters and other non-smooth

features.2

Once the method of formation has been

identified, one must determine whether the

materials used were cast iron or cast steel.

Figure 4: Pipe Elbow

Figure 5: Pipefitting (lower half)


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There are several ways to determine the difference. Like the determination between wrought iron

and wrought steel, a spark test may be used. Cast iron will throw off red sparks, while cast steel

will give off white sparks.

Another slightly destructive test that can be used is a file test. This consists of running a

sharp file over the metal and observing the way in which small metallic pieces are removed. For

standard gray and white cast iron, the filing process will chip off small pieces of iron. For cast

steel, the file will roll up the surface material.

Once again destructive tests shouldn’t be used on college property. Luckily, a

nondestructive (although not quite as accurate) ring test can be used to determine the type of

metal employed. Cast iron has a high level of damping,* and thus, when hit with a hammer, it

will have emit much less of a ring than cast steel.2 From such a ring test the pipe elbow was

determined to be made of cast iron (Figure 4), while the pipefitting (Figure 5) was determined to

be made of cast steel.

Taking into account the service requirements of each metal piece, these material choices

are logical. For basic castings, such as the pipe elbow, where the forces involved are not

particularly large, cast iron is the obvious choice. Cast iron requires far less energy to melt and

cast than steel, as it has a low melting point near the eutectoid temperature. Thus, for basic jobs it

is far more economical to use cast iron. However, for more heavy duty, specialized jobs, like the

pipefitting, cast steel may not meet the service requirements. Cast iron, although strong in

compression, is weak in tension. Moreover, it is brittle. These qualities make cast iron unsuitable

for jobs that require flexibility, strength in tension, or sharp edges. When such occasions occur

and the product is too complicated to be made of wrought steel, the natural choice is cast steel,

despite the very high melting point associated with it.

* The high level of damping in cast iron is part of the reason it is used for engine blocks.


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Works Cited (Metal Identification) 1. "Realwroughtironco : Trading Standards." Realwroughtironco: . 26 Apr. 2009

<http://www.realwroughtiron.com/trading_standards-112.html>. This website is run by

The Real Wrought Iron Company. I used this website to help me distinguish between

mild steel and genuine wrought iron. This source is trustworthy as the company in

charge of the website is a reputable supplier of wrought iron. Site map unavailable.

2. Cook, Tom. "Highway Maintenance Welding." Cornell University. 27 Apr. 2009

<www.clrp.cornell.edu/PDF/welding_manual_1995.pdf>. This website contains a

manual on Highway Maintenance Welding, distributed by Cornell University's local

roads program. I used this source to help identify cast iron and cast steel. This website is

trustworthy, because it managed by a trusted institution in Cornell. Site map unavailable.

homepaper 3: iron and steel around campus

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