LECTURE 4.2

OUTLINE Steel, Cast Iron and Wrought Iron Steel, Cast Iron and Wrought Iron The Early Iron Age The Early Iron Age Georgius Agricola and the Hoovers Georgius Agricola and the Hoovers The Bessemer Converter The Bessemer Converter Monumental Building Monumental Building

CAST IRON CAST IRON Cast iron usually contains between 2% and 6% carbon. Cast iron usually contains between 2% and 6% carbon. Cast irons are usually used in the “cast” condition. Cast irons are usually used in the “cast” condition. Cast irons consist of virtually pure iron (the light phase), graphite (the black constituent) and “pearlite” (the grey regions), themselves a mixture of an iron carbide (called cementite) and “pure” iron. Cast irons consist of virtually pure iron (the light phase), graphite (the black constituent) and “pearlite” (the grey regions), themselves a mixture of an iron carbide (called cementite) and “pure” iron. Cast irons tend to be brittle!! Cast irons tend to be brittle!! 200µm

WROUGHT IRON Wrought iron is a composite of virtually pure iron, together with slag inclusions Wrought iron is a composite of virtually pure iron, together with slag inclusions Historically, wrought iron was produced without the iron ever being molten. Historically, wrought iron was produced without the iron ever being molten. Wrought irons contain little or no carbon. Wrought irons contain little or no carbon. 200µm

STEEL Steel is an alloy of iron and carbon. Steel is an alloy of iron and carbon. Typically the carbon content is less than1% Typically the carbon content is less than1% The microstructure consists of virtually pure iron (the white regions), and “pearlite”, which is a mixture of virtually pure iron, together with the compound, cementite, Fe3C The microstructure consists of virtually pure iron (the white regions), and “pearlite”, which is a mixture of virtually pure iron, together with the compound, cementite, Fe3C 200µm

THE CATALAN FORGE The Catalan Forge produced a “bloom” or “loupe” of virtually pure iron, intimately mixed with slag particles, This “bloom” would be converted to: The Catalan Forge produced a “bloom” or “loupe” of virtually pure iron, intimately mixed with slag particles, This “bloom” would be converted to: WROUGHT IRON WROUGHT IRON The wrought iron was never molten. The wrought iron was never molten. Excess slag had to be hammered out of the pasty iron at the blacksmith’s forge Excess slag had to be hammered out of the pasty iron at the blacksmith’s forge

SMELTING AND SLAGGING REACTIONS 2Fe 2 O 3 + 3CO  4Fe + 3CO 2  2Fe 2 O 3 + 2SiO 2  2Fe 2 SiO 4 + O 2 

STEELING IRON Sheets of wrought iron would be surface carburized to produce hard, steel, surface regions Sheets of wrought iron would be surface carburized to produce hard, steel, surface regions The interior of the piece would remain as a tough “iron” The interior of the piece would remain as a tough “iron” Strips of the surface carburized material would be hammer-welded to create a strong, yet tough finished product. Strips of the surface carburized material would be hammer-welded to create a strong, yet tough finished product.

STEELING IRON

CHINESE BLAST FURNACE TECHNOLOGY

THE SLAGGING TEMPERATURE OF LIMESTONE-FLUXED FURNACES Limestone is added to iron- smelting furnaces to combine with e.g., the silica to form a siliceous slag. Limestone is added to iron- smelting furnaces to combine with e.g., the silica to form a siliceous slag. As the amount of limestone increases, then so does the slagging temperature. As the amount of limestone increases, then so does the slagging temperature. The limestone is not added to reduce the slagging temperature: rather it prevents much of the iron from ending up in the slag! The limestone is not added to reduce the slagging temperature: rather it prevents much of the iron from ending up in the slag!

DE RE METALLICA

PARTINGTON STEEL AND IRON CO. 1917

THE BESSEMER CONVERTER

MONUMENTAL BUILDING

POST AND BEAM CONSTRUCTION

CONSTRUCTION MATERIALS

SELECTED EXAMPLES

STONEHENGE: POST AND BEAM CONSTRUCTION

THE ZIGGURAT AT UR: SIR LEONARD WOOLEY DRAWING

THE PYRAMIDS AT GIZA

THE PARTHENON: POST AND BEAM CONSTRUCTION

THE PARTHENON AND WROUGHT IRON REINFORCEMENT

THE ARCH, COMPRESSIVE AND “OUTWARD STRESSES”

THE ROMAN AQUEDUCT: I

THE ROMAN AQUEDUCT: II

THE PANTHEON: TEMPLE FOR ALL THE GODS

CONCRETE CONSTRUCTION OF THE PANTHEON The Pantheon is constructed predominantly of concrete! The Pantheon is constructed predominantly of concrete! The walls have a “graded” specific gravity”, being densest at the bottom, and least dense at the top. The walls have a “graded” specific gravity”, being densest at the bottom, and least dense at the top. The dome is lightweight, the aggregate being highly porous tufa, and volcanic pumice. The dome is lightweight, the aggregate being highly porous tufa, and volcanic pumice. The roof panels were “coffered”, which minimized weight, without sacrificing strength. The roof panels were “coffered”, which minimized weight, without sacrificing strength.