Principle: At Low Voltage, high Current flowing through the joint generated large amount of heat due to High contact resistance which couses melting of joint and further fusion of metals.this includes five steps
1.squeezeeing
2.weld
3.hold
4.forge
5.Pressure off
Resistance Spot welding is the process in which the Adjoining metal surface are joined togrther by the heat obtained from Resistance to current flow , thus forming a weld nugget between them.
Mathamatically:
Heat Generated in the resistance spot welding is H=KIsquere Rt
Where I is Electric Current R Resistance of the joint
t= Time for which Electic current is paassed through thr joint
K= Constant accounting for Heat leoasse from the welded joint
Application:
Welding handles of Cooking Utensils
Welding in Automobile
Advantages of Resistance Spot Welding
No Filler Metal or Flux is required
High Production Rate occurs
Process can be easily automated
Dissimilar metal with Different Thicknesses can be welded together
Disadvantage of Resiistance Spot Welding
Leads to High Initial Costs
Warping and Loss of fatigue Strenght occur aroung the weld point
Appearance become very ugly
Cracks are formed aroung the weld point and on the weld surfaces
