Metals

Metals have been used by humans for over 6000 years. For building purposes most metals are alloys The major base of metals used are : • Iron • Copper • Lead • Zinc • Aluminium

Metals

Metals that contain Iron as there base are called ‘ Ferrous’ Other metals are called ‘Non Ferrous’ Metals can also be joined together to form ‘ALLOYS’ A commonly used alloy is Brass, made by combination of copper and zinc

Forging Metals

Metals are formed into shape by: • Casting : molten metal is poured into moulds and allowed to cool and harden

• Forging : Hot metal is squeezed into shape

• Extrusion : Heated metal is forced through a suitable shaped hole

• Drawing Wire : Metal is pulled through tapered dies to reduce thickness

Joining Metals

Metals can be joined by: • Mechanical joints : Bolts, nuts, screws and rivets • Soldering : Metals are joined using an alloy that’s melts at a lower temp

than metal being joined usually tin-lead or lead-silver alloys • Brazing : Similar to soldering but at much higher temperatures (over

600ºc) • Welding : By applying heat and pressure with or without filler material to produce a union through fusion

Heat Treating Metals

Annealing : heating and cooling of the metal in the solid state. The cooling is done slowly and will reduce hardness and give more machinability.

Tempering : Metal is heated to a desired temperature and the cooled

suddenly in water or oil bath, this will harden metal to a desired level

Surface Finishing Metals

To change the finish appearance of the metals surface we can use: Blasting : Obtains a mottled or pebbled finish Cleaning : by blasting surface with sand, grit, or steel via air pressure Brushing : Gives a smooth, satin, bright or buffed finish Polishing : Belts on sanding wheels or disks on hand buffers/ grinders Etching : A process of chemically etching the surface with acid or alkali solutions Grinding : A surface texture obtained by using a grit wheel or disk Hammering : Surfaces a struck with rounded hammer to obtain a mottled or dented finish

Ferrous Metals

Are metals formed or an Iron Base and include: • Cast iron • Wrought Iron • Steels

Iron ore is melted an furnessed to reduce its carbon content to less than 1% and the metal can then be treated by adding other elements Carbon : this controls the workability and finish strength, high carbon means less workability but great strength Magnesium : Similar to carbon but to a lesser degree. Improves toughness and abrasion resistance of steel Chromium : Increases hardening ability and tensile strength along with corrosion and abrasion resistance. It is associated with nickel in the forming of stainless steel

Types of Steel

Cast Iron: Produces by remelting pig iron and mixing with steel, it has a high carbon content and is excellent for moulding

intricate shapes. Often gets called wrought iron but is used more extensively Wrought Iron: Is a low carbon steel, excellent when used for forging but cannot be welded, cast or tempered. Once used extensively for decorative balustrades. Carbon Steel: The most commonly used has high tensile strengths but low performance in fires and corrosion resistance. Made by reducing the amount of carbon in the pig steel Stainless Steel: Made by adding Chromium and Nickel to carbon steel giving a much higher tensile strength and corrosion resistance with a silvery white appearance. Used extensively in the building industry from kitchen sinks to handrails and structural components

Non Ferrous Metals

Copper: A pinkish metal is easily hammered, but more expensive than alternatives. It has excellent corrosion resistance forming a protective green copper oxide layer. It is also an excellent conductor of electricity

Brass : An alloy of copper and zinc used for fittings in plumbers hardware along with screws, hinges, locks,

latches and chains. Aluminium : A light weight white silver metal, with excellent corrosion resistance. It will form its own protective

white coating but should be treated for long term appearance. It is effected by other materials and care should be taken what materials are in contact with aluminium.

Non Ferrous Metals

Zinc : A soft grey metal that can be easily hammered or rolled into shape. Zinc is often used as a protective coating over other metals like steel.

Lead : An easily workable metal with great density and excellent corrosion

resistance make it suitable for flashing and DPC. However its toxicity prevents its use anymore in water supply pipes Nickel : is a hard malleable metal very resistant to corrosion and is used as a

base for chromium plating and is part of the alloy mixture for stainless steel

Non Ferrous Metals

Tin : Is an expensive, soft, weak metal with a low melting point but is resistant to corrosion. Its main use is as a protective coating for steel sheets and as a solder.

Cadmium : used for electroplating steel components like screws, latches, handles, As a plating on brass plumbing fittings Chromium : has a high corrosion resistance and is used extensively as a

plating and is part of alloys like stainless steel. It is extremely hard and scratch resistant.

Non Ferrous Metals

Stainless Steel : Much harder than mild steel and silvery in appearance. It has a high corrosive resistants and is used for many finished products like kitchen sinks, handrail and balustrades, nails, bolts and screws along with structural beams

Dissimilar Metals

Metals with a dissimilar nature will corrode the weaker metal through a process called galvanic reaction via electrolysis.

The less noble metal, called the anode,

is eaten away. The other metal, the more noble metal, is called the cathode and is protected. Thus the cathode is protected by the anode

Anodic index[9][page needed]

Metal Index (V)

Most Cathodic

Gold, solid and plated, Gold-platinum alloy -0.00

Rhodium plated on silver-plated copper -0.05

Silver, solid or plated; monel metal. High nickel-copper alloys -0.15

Nickel, solid or plated, titanium an s alloys, Monel -0.30

Copper, solid or plated; low brasses or bronzes; silver solder; German silvery high

copper-nickel alloys; nickel-chromium alloys

-0.35

Brass and bronzes -0.40

High brasses and bronzes -0.45

18% chromium type corrosion-resistant steels -0.50

Chromium plated; tin plated; 12% chromium type corrosion-resistant steels -0.60

Tin-plate; tin-lead solder -0.65

Lead, solid or plated; high lead alloys -0.70

2000 series wrought aluminum -0.75

Iron, wrought, gray or malleable, plain carbon and low alloy steels -0.85

Aluminum, wrought alloys other than 2000 series aluminum, cast alloys of the silicon

type -0.90

Aluminum, cast alloys other than silicon type, cadmium, plated and chromate -0.95

Hot-dip-zinc plate; galvanized steel -1.20

Zinc, wrought; zinc-base die-casting alloys; zinc plated -1.25

Magnesium & magnesium-base alloys, cast or wrought -1.75

Beryllium -1.85

Most Anodic

More Information

Lets go to the web and find out more about steel sheets We will start with colourbond http://steel.com.au/library