metals and their properties

Metals and their Properties

Ferrous and Non Ferrous Metals

All metals can be categorized as either Ferrous or Non Ferrous

Ferrous Metals contain ironNon Ferrous Metals do not contain

iron

Examples of Ferrous Metals

Cast IronMild Steel (BDMS)Stainless SteelWrought IronTool Steel High Speed Steel (HSS)

Examples of Non Ferrous Metals

CopperBrassLeadZincAluminiumPewterGold

Pure Metals and Alloys

All metals can be categorized as either a pure metal or an alloy

A pure metal is made of only one type of metal and appears in the Periodic Table of Elements

An alloy is a mixture of metals

Examples of Pure Metals

GoldCopperLeadAluminiumPlatinumZinc

Examples of Alloys

Brass (copper/zinc) Bronze (copper/tin) Stainless Steel

(iron/carbon/nickel/chromium/magnesium Duraluminium (aluminium/copper/manganese) Phosphor Bronze (copper/tin/phosphorous) Bell Metal (80% copper/20% tin) Soft Solder (tin/lead) Pewter (traditionally 80% tin/20% lead) Nickel Silver (copper/zinc/nickel) Naval Brass (63% copper 37% zinc)

Properties of Metals

Tensile Strength Compressive Strength Bending Strength Shear Strength Torsional Strength Elasticity Plasticity Malleability Ductility Hardness Toughness/Brittleness Fatigue Durability

Tensile Strength

Is the ability to resist stretching or pull forces. It is an essential property of all cables chains and ropes

Compressive Strength

Is the ability to withstand a pushing force which tries to crush or shorten

Bending Strength

Is the ability to withstand the forces that attempt to bend a piece of material

Shear Strength

Is the ability to resist strong sliding forces acting opposite to each other

Torsional Strength

Is the ability to withstand twisting forces under torsion or torque

Elasticity

Is the ability to flex and bend when subject to loads and forces, and regain normal shape and size when these are removed (like an elastic band).

Most structures need to possess some degree of elasticity

Plasticity

Is the ability of a material to be changed permanently in shape, by external blows or pressure, without cracking or breaking (e.g. plasticine)

Some materials are more ‘plastic’ when heated

Malleability

Is the extent to which a material can be changed by hammering, pressing or rolling.

Ductility

The ability to undergo deformation by bending, twisting but most usually by stretching into wire

Hardness

Is the ability to resist abrasive wear and indentation

It is an important property of cutting tools like files

Toughness/Brittleness

Is the ability to withstand sudden shock, and the resistance to cracking when subjected to bending and shear forces.

Fatigue

Is caused by repeated stress cycles, bending or tension.

It is found in structures such as aircraft wings

Fatigue is also affected by corrosion

Durability

Is the ability to withstand wear and tear, weathering and corrosion