STEEL – A METAL AFTER THE HEART OF BUILDING CONSTRUCTION

If your trained sensibilities have survived the political crassness in this country, then it’s high time we took a pause to appreciate the beauty of  our land  and in particular the significant contribution  by steel and iron  in  facilitating infrastructure and housing construction  that our society  depends for the kind of life  we  live .  Apart from  being a source of  livelihood  in the  form of welding, metal  fabrication   and steel rolling mills  jobs , steel  one of the most widely used metals  in buildings  construction.  It’s used in column bases,concrete columns, in the foundation concrete slab and in walls in the form of  binding wires   steel bars, wall-pass, door frames and windows ;in roofing it shows up as   corrugated iron sheets,  steel tiles,ordinarily nails  and roofing nails. And that is not all!

So what is  steel like 

It’s strong and tough like nails  and is manufactured from   Iron and carbon combo . Whereas Iron is   hard heavy   metal mined from iron ore or iron stone, Carbon on the other hand is a chemical element found not only in all living things but also in diamond and coal.

As such we are on point, when we say that Steel is a ferrous metal that is relatively cheap, explaining in part why it popular in buildings construction and civil works.It’s cheaper than other metals because of the ingredients –  iron ore is like a low hanging fruit-relatively abundant in supply  on this planet earth  and recyclable.

Up close and personal 

Steel being a ferrous metal, it’s  various manifestation  are  classified based on their  carbon content .

Wrought iron

Wrought iron contains 0.02% carbon. The low carbon content makes it ductile with high melting point making it unsuitable for welding and casting.

Cast iron

Cast iron contain over 2% carbon and with   lower melting point making it suitable for welding. Also  it is good  for casting(i.e. forming  an object by pouring molten iron into a  moulds, allowing  the liquid to become hard and then removing the moulds)   and its  resistant to corrosion .Hence  it is a  good  material for  boiler casting ,street furniture and Manhole covers.

Steel

Steel is an alloy of iron and carbon plus a few other element in minor quantities like Nickel. You might find it interesting to learn that 97% of Nickel produced in the world is used in making Steel.

Steel is as tough as nails and is manufactured by smelting iron from iron ores, followed by carbonizing the metal to increase   carbon content to a desired level. Then Nickel  and  other elements in minor quantities are added  to it  and the molted mix is formed into  strips .Finally  coils  of  steel  strips  are cold  rolled into   thin sections and  profiled  sheets.

The carbon content in steel can range from as low as 0.07 % to   as high as 1.7%. Higher carbon content in steel increases the strength and wear resistance of the metal but makes it   increasingly less elastic or ductile.

Structural steel

Structural steel  can be welded  and  has higher  carbon content of about 0.16 to  0.25%.Its normalized  by natural  cooling  in air  after hot air  rolling.

Hollow section steel

They are made by progressively bending a flat section of steel until it’s almost round. The edges are then fused together at high temperatures. The hollow steel can be circular, oval, square or rectangular.

Profiled steel sheeting

The Pre-coated steel strips are shaped into desired   design by   passing it through a set of rolls .The continuous profiled sheet is then cut and packaged   for hardware store shelves.

  • Profiled steel sheets are used   make   corrugated iron and   wall cladding sheets. Corrugated  sheets  are those  sheets  that have been   moulded  into parallel  folds  or troughs and  more often than not,are used  as  roofing  materials. Curved   profiled  sheets for  eaves and  the roof hip   are manufactured by the  brake  pressing  from the  same  coated  strips.

Steel cables

Steel cable are  made  by  pulling  a thin steel rod  through  a series  of tungsten carbide  dies  which causes the  steel  rod to increase in length. The pulling process increases the strength of the steel while at same time reducing its ductility. It is because of this phenomena that Steel cable require high carbon content steel as raw materials. For suspended structures the set of individual wires are woven around a core wire to produce a rope. A series of this ropes are then joined to make a cable of required design.

Ferrous alloys

  • Weathering steel-This a structural steel alloyed with minor proportions of copper, silicon and manganese. This provide strong resistance to rust and corrosion.
  • Stainless steel-It’s an alloy containing 10.5% chromium. The resulting metal-Stainless steel –is resistant to corrosion because of the passive film of chromium oxide that form immediately over the material in the presence of oxygen. When the surface of stainless steel is scratched, the protective layer naturally reforms or as it were heals the damage.

Coated steel

To prevent corrosion steel may be coated   with metallic or organic materials. Metallic coating include Zinc, and Zinc aluminium alloys. The coat is applied by dipping steel sheets in hot molten metal. The durability of the coat will depend on the thickness of the coat and the quality of the environment in a given location.

Zinc coating   produces galvanized steel sheets and offer protection by acting as a physical barrier   between sheet and environment.  On the other hand steel coated with Aluminium (55%), Zinc (43.5%) and Silicon (1.5%) is more durable than steel coated by pure Zinc.

Organic coating include liquid paint, powder coating   and film.

Steel Tiles

Steel Tiles are lightweight and made from galvanized steel sheets. They are usually coated with acrylic resin and given a finish that look like grains of sand. These Tiles may give an appearance of traditional tiles but are better because they are lighter and easy to refurbish.

©2017 eastafricaminihardware.com

Sources:Materials  for Architects and Builders by Arthur Lyons-PhD.

Advertisements

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out /  Change )

Google+ photo

You are commenting using your Google+ account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s

This site uses Akismet to reduce spam. Learn how your comment data is processed.