BLOG ENTRY 5

 

Hello guys!


Today we had our 3rd class, in Steel and Architecture, regarding its finishes and processes.

After the manufacture of steel through its various stages, we learnt the different ways in which steel can be shaped.

Steel is hot rolled, which is the process of rolling it out of the casting area to attain the desired thickeness. Cold rolled steel is a product of hot rolled steel. 

The different processes are:

  • Galvanization
  • Quenching 
  • Cold Hardening 
  • Tempering 
  • Annealing 

COLD HARDENING

Steel is hammered and compressed numerous amounts of times to gain strength and hardness 

QUENCHING 

Heats and cools the steel quickly with water,oil or air to form a thin crystal layer which protects the underlying steel from corrosion becoming brittle and strong.

TEMPERING

Heating and controlled cooling processes which increases the strength and hardness of the steel and makes it ductile. 

ANNEALING 

Heating and cooling it very slowly to make it hard soft steel. Cold working, cutting and forming it.

This process is mostly used to produce arts and crafts out of steel. 

GALVANIZATION

The basic process of coating steel with a Zinc layer to protect and prevent steel from rusting.

There are two ways through which this can be achieved, which are

  1. Hot- dipped - Immersing the metal in a bath of molten Zinc- thin layer ( Matte Grey colour) which coats the metal, and by repeating this process, it can be coated heavily (Thick coating), it now becomes durable to prevent oxidation.
  2. Cold- dipped - The zinc layer here is electrically created, the metal now achieves a shiny surface after coating, but this is less durable compared to hot- dipping. 

CORROSION AFFECTS THE APPEARANCE OF THE MATERIAL

How can we prevent this?

  • Through painting 
  • Galvanization
  • Chemical treatments
  • Powder coating 
  • Copper alloy

Stainless steel is highly resistant to atmospheric corrosion.Why?

Stainless steel is an alloy, which according to its composition reacts oxygen from air and water to form a thin layer with corrosion resistant properties which protects the material.

TREATMENTS AND FINISHES - 

Basic methods:

  • Polishing
  • Brushing 
  • Textured
  • Electro- chemical method 

Other methods: 

  • Burnishing - Colours the material black, by dipping the material in a chemical bath of sodium dichromate. From a opaque texture to glossy by application through oils and waxes.
  • Acid Etching - Creating an uneven surface, by removing certain parts. It is dipped in acid which coats the exposed areas. 
  • Enamelling - Material coated with a mix of ceramic powder and is baked in high temperature.
  • Physical vapour desposition- increases the mechanical properties and induces more variety in colours.
  • Metallic coating - Corrosion resistance of stainless steel + the aesthetics of another metal 
  • Painting - Aesthetic purpose. Pre-painted sheets/coils. 


HOW DO YOU THINK STEEL REACTS WITH FIRE?

Steel is a metal, metals are not combustible in general. During a fire, when the temperature raises to alarming high rates, this metal melts and loses its strength which in turn is very harmful.

So how can we prevent this?

  • Enclosing with gypsum layers
  • Encasing in concrete 
  • fire-proof spray
  • By not leaving it exposed 



Signing off
Tejashri Kumaresan 


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