Q1: Required properties

Strength

Correct, for these structural applications strength is a very important property as a bridge deck, for example, must support a given load without yielding. Stiffness can be seen to be an important property here too - however we cannot change the stiffness of steel (its Youngs modulus), it is always about 210 GPa regardless of the processing history or chemistry. We can control the stiffness of a structure though through design (for example using I beams for improved bending resistance)

Toughness

Correct, toughness is one of the top three properties to consider because we must guarantee structural components against sudden catastrophic failure. In order to control toughness we need to understand how a steel microstructure, processing history and chemistry affects toughness.

Corrosion Resistance

Corrosion resistance is very important but is relatively simply dealt with by painting. Also these components can generally be checked visually for signs of corrosion and repairs made where appropriate. This means that corrosion, whilst important is not critical. Try another property.

Magnetic properties

Magnetic properties are not really important for this application. Try another property.

Aesthetics

The appearance of the bridge deck is less important than many other properties as it is more important that the bridge does not collapse. Aesthetics are taken into account by designers who may require thinner sections with the same properties etc. Try another property for one of the three most important.

Cost

Cost is always an issue with design and materials selection. In this case cost will need to be considered but is only my fourth choice as there are other properties that are more critical. Try another property.

Steel cleanliness

This is important as customers want increased consistency in their products and consistency is at least partially controlled by cleanness. However modern steel making procedures give relatively clean steels and this is an ongoing concern rather than an over riding one for this application. Try another property.

Fatigue resistance

Fatigue resistance is important as these applications are expected to experience varying load cycles (for example waves crashing against a ship, cars and lorries crossing a bridge). Steel shows good fatigue resistance which is sufficient for these applications. Try another property. Fatigue resistance is important as these applications are expected to experience varying load cycles (for example waves crashing against a ship, cars and lorries crossing a bridge). Steel shows good fatigue resistance which is sufficient for these applications. Try another property.

Formability

It is important that the steel can be rolled to give plates however little subsequent forming is required meaning that extremely good formability is not required. Try another property.

Machinability

This is not a very important property in this case because the steels are rolled to plate , flame cut and dressed to final size then welded together. Try another property.

Weldability

Correct, this is an extremely important property as ships, oil rigs, bridge decks are constructed from a number of steel plates that are welded together to form the final product.

Electrical properties

Electrical properties are not really important for this application. Try another property.

Wear resistance

Not really important for this application as the steel is usually structural. In the case of ship plate there are limited wear problems and with bridge plate there is often a surface coating (such as a concrete layer) which can be replaced if excessive wear occurs. Try another property.

Creep

Not really important for this application as creep in steels is only an issue at elevated temperatures and long exposure times, for example power plants where components may experience temperatures of 400�C+ for 20+ years. Try another property.

Recyclability

This is less important for these applications as they are designed to have a long life time, however steel is an easily recycled material in all its forms. Try another property.

When you have correctly identified all three, they will be displayed in a 'Notepad', from where you can link to pages giving more detail.