MES - II, 5.Welding
Transcript of MES - II, 5.Welding
8/4/2019 MES - II, 5.Welding
http://slidepdf.com/reader/full/mes-ii-5welding 1/12
Department of Electronics and Communication Engineering,Manipal Institute of Technology, Manipal, INDIA
MECHANICAL ENGG. SCIENCE
CHAPTER 5
| WELDING }
By, Akshatha C. Kamath
8/4/2019 MES - II, 5.Welding
http://slidepdf.com/reader/full/mes-ii-5welding 2/12
W ELDING
Welding is a process of joining similar metals by the application of heat with or without the
application of pressure & addition of filler materials.
* Welding rods or Filler rods are used for providing the
extra metal to the weld.
* Flux material is applied to the parts being welded to
prevent the formation of oxides.* Parts being welded are called the base metals or the
parent metals.
8/4/2019 MES - II, 5.Welding
http://slidepdf.com/reader/full/mes-ii-5welding 3/12
TYPES OF W ELDING
Plastic ( Pressure ) Welding I n this process, the piecesof metal to be joined are heated to a very high
temperature i.e. plastic state & then forged together
by external pressure.
Fusion ( Non ± pressure ) Welding I n this process, the
pieces to be joined are heated to a molten state & then
allowed to solidify.
8/4/2019 MES - II, 5.Welding
http://slidepdf.com/reader/full/mes-ii-5welding 4/12
CLASSIFICA T ION
Welding
Pressure Process Fusion Process
Forge Resistance Thermit Arc Gas
Welding Welding Welding Welding Welding
* Spot * Metal Arc
* Butt * Atomic Hydrogen
* Seam * Carbon Arc
* Percussion
8/4/2019 MES - II, 5.Welding
http://slidepdf.com/reader/full/mes-ii-5welding 5/12
ELEC TR IC AR C W ELDING
Slag covering Electrode holder Flux coated AC / DC power supply
electrode Core wire
Weld Electric arc
Gaseous Shield
Job
Crater Molten pool
8/4/2019 MES - II, 5.Welding
http://slidepdf.com/reader/full/mes-ii-5welding 6/12
AR C W ELDING OPE R A T IONS
* Arc Welding Power Source ( AC or DC type )
* Welding Cables
* Electrode Holder * Ground Clamp
* Welding Electrodes
* Helmet or Shield
* Protective Clothing
* Chipping Hammer
* Wire brush
8/4/2019 MES - II, 5.Welding
http://slidepdf.com/reader/full/mes-ii-5welding 7/12
DC PO W E R SOUR CE
DCSP ( Direct Current Straight Polarity )
* Job is connected to + ve terminal & Electrode to ± ve terminal
* 66.66 % ( 2/3 rd ) of heat is supplied to the job.
* 33.33 % ( 1/3 rd ) of heat to the electrode.
* Used of deep penetration.
DCR P ( Direct Current Reverse Polarity )
* Job is connected to - ve terminal & Electrode to + ve terminal
* 66.66 % ( 2/3 rd ) of heat is supplied to the electrode.
* 33.33 % ( 1/3 rd ) of heat to the job.
* Used of less penetration.
8/4/2019 MES - II, 5.Welding
http://slidepdf.com/reader/full/mes-ii-5welding 8/12
AC PO W E R SOUR CE
* There is equal heat distribution at the electrode as
well as at the job.
* No polarity is maintained.
* I t is used for normal penetration.
8/4/2019 MES - II, 5.Welding
http://slidepdf.com/reader/full/mes-ii-5welding 9/12
W EL DING ELEC TR ODES
Consumable Electrodes
* They are made up of materials having a low melting
point.* They are made up of different metals & their alloys.
* When the arc is struck, the electrode melts & transfers
to the job in the form of droplets.
8/4/2019 MES - II, 5.Welding
http://slidepdf.com/reader/full/mes-ii-5welding 10/12
W EL DING ELEC TR ODES
Non ± Consumable Electrodes ( Bare Electrodes )
* They are made up of materials having a high melting
point like Carbon, Tungsten, Graphite««.* Copper coated Carbon or Germanium electrodes are
commonly used.
* The electrodes don¶t melt during welding.
* They maintain an arc which melts the base metals.
* Filler metal addition depends on the plate thickness.
8/4/2019 MES - II, 5.Welding
http://slidepdf.com/reader/full/mes-ii-5welding 11/12
FLUX COA T ING INGR E DIEN T S
* Silicates of Sodium, Magnesium, Al, I ron oxide, Mica produce a slag layer on the molten metal & prevent atmospheric contamination.
* Cellulose, wood, Calcium carbonate form a protective gas shield to prevent combination.
* Calcium carbonate, Potassium silicate add stability tothe arc.
* Coating improves arc penetration & surface finish.* Flux provides a quiet arc & an easily removable slag.
* I t saves the welder from radiations emitted from theelectrodes.
* I t improves metal deposition rates.
8/4/2019 MES - II, 5.Welding
http://slidepdf.com/reader/full/mes-ii-5welding 12/12
W EL DING APPLICA T IONS
The applications of Welding are many. Some of themare as follows :
* I n fabrication & repair work.
* I
n welding metals & their alloys.* I n fabrication of air receiver, boiler, tank, joining
pipes, pressure vessels, building & bridge
construction, automobile & aircraft industry, etc..