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Metal Types

The metals that Builders work with are divided into two general classifications: Ferrous and nonferrous.

Ferrous metals are those composed primarily of iron and iron alloys.
Nonferrous metals are those composed primarily of some element or elements other than iron.

Nonferrous metals or alloys sometimes contain a small amount of iron as an alloying element or as an impurity.

Ferrous Metals

The word is derived from the Latin word ferrum "iron").

Ferrous metals include all forms of iron and steel alloys. A few examples include wrought iron, cast iron, carbon steels, alloy steels, and tool steels. Ferrous metals are iron-base alloys with small percentages of carbon and other elements added to achieve desirable properties. Normally, ferrous metals are magnetic and nonferrous metals are nonmagnetic.

Iron

Pure iron rarely exists outside of the laboratory. Iron is produced by reducing iron ore to pig iron through the use of a blast furnace. From pig iron many other types of iron and steel are produced by the addition or deletion of carbon and alloys.



Iron Ores

Iron ores are rocks and minerals from which metallic iron can be economically extracted.

The ores are usually rich in iron oxides and vary in color from dark grey, bright yellow, deep purple, to rusty red.

The iron itself is usually found in the form of magnetite (Fe3O4), hematite (Fe2O3), goethite (FeO(OH)), limonite (FeO(OH).n(H2O)) or siderite (FeCO3).

Hematite is also known as "natural ore", a name which refers to the early years of mining, when certain hematite ores containing up to 66% iron could be fed directly into iron-making blast furnaces.
Iron ore is the raw material used to make pig iron, which is one of the main raw materials to make steel.

98% of the mined iron ore is used to make steel. Indeed, it has been argued that iron ore is "more integral to the global economy than any other commodity, except perhaps oil.



Pig Iron

Pig iron is composed of about 93% iron, from 3% to 5% carbon, and various amounts of other elements. Pig iron is comparatively weak and brittle; therefore, it has a limited use and approximately 90% produced is refined to produce steel. Cast-iron pipe and some fittings and valves are manu­factured from pig iron.



Wrought Iron

Contains 0.15% carbon

wrought iron to resist corrosion and oxidation.

The chemical analyses of wrought iron and mild steel are just about the same. The difference comes from the properties controlled during the manufacturing process.

Wrought iron can be gas and arc welded, machined, plated, and easily formed; however, it has a low hardness and a low-fatigue strength.

It can be molded easily and has good resistance to corrosion.
Wrought iron is used extensively where corrosion resistance is needed.

It’s ductility is lower than steel.

It’s tensile strength is lower.



Cast Iron

Cast iron is any iron containing greater than 2% carbon alloy.
Manufactured by reheating pig iron (in a cupola) and blending it with other material of known composition.

Alternate layers of pig iron (with or without scrap steel) and coke are charged into furnace.

Limestone is added to flux the ash from the coke.

Heat necessary for the smelting is supplied by the . combustion of coke and air supplied by the blast.

Cupola function to purify iron and produce a more uniform product.
When sufficient metal is accumulated at the bottom of the furnace, it is tapped.

Cast iron has a high-compressive strength and good wear resistance; however, it lacks ductility, malleability, and impact strength. Alloy­ing it with nickel, chromium, molybdenum, silicon, or vanadium improves toughness, tensile strength, and hardness. A malleable cast iron is produced through a prolonged annealing process.



Ingot Iron

Ingot iron is a commercially pure iron (99.85% iron) that is easily formed and possesses good ductility and corrosion resistance. The chemical analysis 'and properties of this iron and the lowest carbon steel are practically the same. The lowest carbon steel, known as dead-soft, has about 0.06% more carbon than ingot iron. In iron the carbon content is considered an impurity and in steel it is considered an alloying ele­ment. The primary use for ingot iron is for galvanized and enameled sheet.