STEEL FINISHES - CLASS 3

 STEEL PROCESSING AND FINISHING


As the title says, today its about steel processing and the finishes.

PROCESS: 

1. Cold hardening : 

              Hammering and compressing

               To increase the strength and hardness  

2. Quenching : 

               Heating the steel and quickly cool it down in water or oil or air.

               Its used to create a thin crystal layer.

               To make the metal strong and brittle.

3. Tempering :

              Heating and controlled cooling process 

              To increase the strength, hardness, and ductility of the metal.

 4. Annealing :

             Cold working, cutting and forming

              Heating and cooling it very slowly to make hard steel soft

  5. Galvanization : 

             Application of zinc coating to prevent rusting.


There are 2 processes involved in galvanization namely HOT DIPPED  and COLD/ELECTRO processes.


Hot dipped galvanization: 

This method is done by immersing the metal in a bath of molten zinc ( thin layer ). For a thick coating, the process has to repeated. 

Corrugation should be formed before dipping. 

This method increases the durability and prevents the oxidation of the metal. 

The zinc forms a self protecting matte gray colour layer above the metal.


Cold - dipped/electro :

The zinc layer is electrically created. 

It gives a shiny surface.

But, using this method may make the metal less durable. 


There are some questions and answers which were discussed during the class. That's a lot of learning though. 


How to prevent corrosion? Painting, Galvanizing and Chemical treatment can be done to prevent corrosion.

Reaction with fire? It is not combustible but will lose strength and become ductile when there is high temperature. 

How to prevent the metal from fire? It can be enclosed with gypsum layers. It can be encased in concrete ( RCC ). It can also be concealed from its view. 


After this, we saw the finishes of stainless steel. 


FINISHES OF STEEL :

Electropolishing : It is an electro chemical process that allows to decrease the surface roughness. 

Electrolytic colouring : The superficial film of thickness ranging from 0.02 micro m to 0.36 micro m is used to get different colors including bronze, gold, red, purple and green. 

Burnishing : The colour black can be obtained by dipping the work piece in a chemical bath of sodium dichromate. 

Acid etching : The surface is coated with resistant substance, then is dipped in acid. When taken out, it creates patterns. 

Painting 

Enameling 

Physical vapor deposition 

Metallic coating 


The session ended with a discussion on how the material reacts to the environmental issues. A detailed blog will be uploaded soon. 

Until then, 

Bye 😁

- Nandhini














               

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