Stringers are filaments of
slag
The general term slag may be a by-product or co-product of smelting (pyrometallurgical) ores and recycled metals depending on the type of material being produced. Slag is mainly a mixture of metal oxides and silicon dioxide. Broadly, it can be c ...
left in
wrought iron
Wrought iron is an iron alloy with a very low carbon content (less than 0.05%) in contrast to that of cast iron (2.1% to 4.5%), or 0.25 for low carbon "mild" steel. Wrought iron is manufactured by heating and melting high carbon cast iron in an ...
after the production process. In their correct proportions their presence is beneficial, as they help to control the
ductility
Ductility refers to the ability of a material to sustain significant plastic Deformation (engineering), deformation before fracture. Plastic deformation is the permanent distortion of a material under applied stress, as opposed to elastic def ...
of the finished product, but when the proportion of slag is too high, or when the filaments run at right angles to the direction of
tension, they can cause weakness.
Manufacture
Wrought iron is no longer made.
The particles of slag present in the iron after preparation by
puddling were drawn into long fibres during the forging or rolling process. The proportion of slag was intended to be about 3%, but the process was difficult to control and examples with up to 10% slag were produced.
Applications
Stays made from puddled iron bar were used as a cheaper alternative to
copper
Copper is a chemical element; it has symbol Cu (from Latin ) and atomic number 29. It is a soft, malleable, and ductile metal with very high thermal and electrical conductivity. A freshly exposed surface of pure copper has a pinkish-orang ...
for joining the inner and outer firebox plates of steam locomotives. The incorporated stringers gave flexibility akin to stranded wire rope and stays made of the material were therefore resistant to snapping in service.
Wrought iron
rivet
A rivet is a permanent mechanical fastener. Before being installed, a rivet consists of a smooth cylinder (geometry), cylindrical shaft with a head on one end. The end opposite the head is called the ''tail''. On installation, the deformed e ...
s made from iron bar typically contained stringer filaments running the length of the rivet, but filaments at right angles to the tension, particularly beneath the head, caused weakness.
See also
Anisotropy
Anisotropy () is the structural property of non-uniformity in different directions, as opposed to isotropy. An anisotropic object or pattern has properties that differ according to direction of measurement. For example, many materials exhibit ve ...
References
{{DEFAULTSORT:Stringer (Slag)
Metallurgy
Iron