Blog 7 STEEL - METAL JOINING & MORE



In the construction industry, steel is coupled and alloyed with various other metals to perform well in different environments and contexts. To get an understanding of this, one has to be aware of the working mechanism of steel in comparison to the metals it is alloyed with.

Galvanic Reaction

  • When two metals are in contact, the one that is higher in the Galvanic series will become the anode and will corrode.
  • According to the galvanic series, the current flows from the metal in the higher end of the table to the metal in the lower end of the table.
  • It acts as a guide to decide the metals to be joined, to result in minimal galvanic tendency and reaction. This helps to decide the amount of protection needed to lessen the galvanic reaction.  
Coefficient of Thermal Expansion

Metals expand and contract due to temperature changes. The amount of change in per length of metal per degree of change in temperature is the Coefficient of Thermal Expansion of the metal.

Tensile/ yield strength

It is the stress a metal can withstand before necking and permanent deformation.

Reflectivity

When a light beam encounters a material, radiation is absorbed or reflected by the surface of the material. It is the ratio of reflected radiation to the incident radiation.

Oil Canning

Deformation in a steel panel or sheet, which is seen as waves, commonly found in cold-rolled flat steel products.

JOINING    

                                


Mechanically joined

Rivet

  • Permanent joining of parts by employing a rivet pin.
  • Used mainly for fastening sheet and shaped rolled metal.
  • Riveting maybe used in lap, abutment and double cover plate joints.

Welding

Metals are joined together using high heat and let to cool down. Smaller sections of steel can be welded with an electric arc and MIG (mild inert gas) using a semiautomatic tool and argon gas.

Mechanically fastened

  • A device used to join two or more metal pieces mechanically.
  • Fasteners are used to create temporary joints.
  • They can be removed, dismantled, without damaging the joining components 

Pin

  • A pin connection is similar to a lap joint.
  • It transfers the vertical and horizontal shear loads and cannot resist any bending or moment forces.
  • Pin connections often look like a point of rotation for the structures, which it is not.

Bolt

  • The metal parts are joined together by using bolt or screw
  • Bolting two steel plates can prevent the slippage of the two materials as opposed to how tight they are turned by maintaining a shear resistance.

      

  

Stainless steel

An alloy of steel

Contains chromium (min 10.5%), Nickel, Molybdenum, Carbon, Silicon, Manganese

Ferritic Stainless Steel

  • Iron-chromium alloys with the body-centered cubic crystal structure (BCC)
  • Magnetic in nature
  • Cannot be hardened by heat treatment, but can be strengthened by cold-working

Austenitic Stainless Steel

  • Most corrosion resistant
  • Non-magnetic
  • Non-heat treatable highly weldable.

Martensitic Stainless Steel

  • Extremely strong and tough but not as corrosion resistant as the other two classes.
  • These steels are highly machinable, magnetic and heat-treatable.

Duplex Stainless Steel

  • Two-phase microstructure consisting of grains of ferritic and austenitic stainless steel.
  • Twice as strong as austenitic and ferritic stainless steels.

Precipitation- Hardening (PH) Stainless Steel

Possesses ultra-high strength due to precipitation hardening

Tools Steel

  • High carbon content (0.5% - 1.5%)
  • Contains various amounts of tungsten, cobalt, molybdenum, vanadium to increase the heat and wear resistance and durability of the metal.
  • Ideal for using as cutting and drilling tools.
  • Higher carbon content provides higher hardness and strength
  • Used to make tools and dies.


- Janani Venkateswaran

No.of words -  575

REFERENCES

 

 

 

 

 

 

 

 

 

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