Metals

Metals

In the Construction Industry we use metals in the many areas such as;• Structural• Claddings• Architectural Systems• Building Service

Metals

Metals that are commonly used in the Construction Industry are;• Steel• Stainless• Aluminium• Lead• Copper• Zinc• Metals that make fusible links etc.

Metals

Metals are Divided into 2 Groups

• Ferrous • Non - Ferrous

Ferrous Metals

Metals that contain Iron

• Produced From Iron Ore

• Softer Than Aluminium

• Carbon make harder

• Iron + Carbon = Steel

Iron

Ferrous Metals

• Steel

• Stainless Steel

Steel

• The term Steels covers a range of metals

• Type of Steel Depends on amount of Carbon

Structural Steel

• Steel with higher carbon content will be harder and less ductile

Definitions

Structural Steel

Tradionally Steel Known as

Structural Steel Grades

Structural Steel Grades

Hot Rolled Formed Sections

• Structural sections are formed by rolling of the flat plate steel to the required section shape while the steel is above its crystallisation temperature (semi-molten). Virtually any thickness of steel may be formed in this process

Hot Rolled Formed Sections

• As the steel recrystallises on cooling the crystalline structure is distributed more evenly around the axis and will retain its ductility

Welded Structural Steel Sections

• These Structural sections are comprised of flat plate steel that is welded into the shape required. Typically “ I ” beams are fabricated in this manner

Welded Structural Steel Sections

• The structural suitability of the member is dependent on the quality of the weld and the effect of the Heat Affected Zone (HAZ)

Welded Structural Steel Sections

• The heat-affected zone (HAZ) is the area of metal which has had its microstructure and properties altered by the welding operations. The heat from the welding process and subsequent re-cooling causes this change in the area surrounding the weld. The extent and magnitude of property change depends primarily on the base material, the weld filler metal, and the amount and concentration of heat input by the welding process.

Cold Formed Sections

• These are manufactured in a similar manner but the process occurs below the crystallisation temperature. A consequence of this is the steel is “Work Hardened” during the process which leads to an increase in the yield strength of the steel due to dislocation of the crystalline structure

Oxidisation

• Steel will oxidise when a electrolyte is present

• Oxidised material will expand and flake off

• Process Repeats

Stainless Steel

• Stainless steel is a generic term for a family of corrosion resistant alloy steels containing 10.5% or more chromium.

• All stainless steels have a high resistance to corrosion. This resistance to attack is due to the naturally occurring chromium-rich oxide film formed on the surface of the steel. Although extremely thin, this invisible, inert film is tightly adherent to the metal and extremely protective in a wide range of corrosive media. The film is rapidly self-repairing in the presence of oxygen, and damage by abrasion, cutting or machining is quickly repaired

Stainless Steel

Stainless Steel Corrosion Resistance

• All stainless steels have a high resistance to corrosion. Low alloyed grades resist corrosion in atmospheric conditions; highly alloyed grades can resist corrosion in most acids, alkaline solutions, and chloride bearing environments, even at elevated temperatures and pressures.

• PASSIVASION

Non-Ferrous Metals

• Do not contain Iron

Aluminium

• Worlds most abundant metal

• Makes up 8% of Earths Crust

• Very hard to Extract

• 15Kwh per kg of Aluminium produced

Aluminium

• Relatively soft

• Ductile

• High Strength to Weight Ratio

• Cannot Tolerate Mechanical – Thermal Damage

Aluminium

• Relatively soft

• Ductile

• High Strength to Weight Ratio

• Cannot Tolerate Mechanical – Thermal Damage

Aluminium

• Steel becomes Brittle at low Temperatures

• Aluminium does not

Aluminium

• When exposed to air Aluminium will oxidise

• Oxidised material will bond & form a protective coating

• Oxidisation virtually stops

Aluminium

• Particularly susceptible to Alkalines

• Cement based products are Alkalines

• Will cause severe damage which is virtually irrepairable

Thermal Conductivity of Aluminium

• High and not a good Thermal insulator.

• Insulation is reflective of Light frequency