Characteristics and Terminology of Wrought Iron
– Very low carbon content (less than 0.05%)
– Semi-fused mass of iron with fibrous slag inclusions
– Tough, malleable, ductile, corrosion resistant
– Easily forge welded, but more difficult to weld electrically
– Highly refined, with around 99.4% iron by mass
– Wrought iron means ‘worked iron’
– Distinguished from cast iron, which is brittle and cannot be worked
– Different terms used for wrought iron in the past based on form, origin, or quality
– Cast and pig iron have higher carbon content and excess slag compared to wrought iron
– Fusion and heat treating are key differences between iron and steel
Historical Uses and Decline of Wrought Iron
– Most common form of malleable iron before steelmaking methods improved
– Used for swords, cutlery, tools, springs, files, ironclad warships, railways
– Declined in use as properties of mild steel improved and became cheaper
– Used for rivets, nails, wire, chains, rails, water and steam pipes, horseshoes
– Also used for handrails, wagon tires, straps for timber roof trusses, ornamental ironwork
Types, Shapes, and Origin of Wrought Iron
– Bar iron is a generic term for ingots of cast metal
– Rod iron is cut from flat bar iron and used for spikes and nails
– Hoop iron is used for barrel hoops, made by passing rod iron through rolling dies
– Plate iron is suitable for use as boiler plate
– Blackplate is thinner than plate iron, from the black rolling stage of tinplate production
– Charcoal iron, puddled iron, oregrounds iron, Danks iron, and forest iron are different types of wrought iron based on their origin
Ironmaking Processes for Wrought Iron
– Bloomery process: used to produce wrought iron, involving removing slag and carbon monoxide during smelting and mechanically shaping the bloom
– Potting and stamping: processes developed to make bar iron without charcoal
– Puddling process: most successful process for making wrought iron without charcoal, involving the use of a puddling furnace to remove impurities and carbon from pig iron
– Shingling: process to remove remaining slag and cinder from the puddle balls
– Rolling: passing the bloom through rollers to produce bars, improving their quality through reheating, forge welding, and rolling multiple times
Corrosion Resistance, Welding, and Applications of Wrought Iron
– Slag inclusions disperse corrosion, but can also be pathways to corrosion
– Sulfur decreases corrosion resistance, while phosphorus increases it
– Welding wrought iron is similar to mild steel, but oxide or inclusions can lead to defective results
– Wrought iron’s rough surface allows it to hold platings and coatings better than steel
– Wrought iron has a long history in furniture and is used for various home decor applicationsSources: https://en.wikipedia.org/wiki/Wrought_iron
