Metallurgy and Materials Engineering Department, University of Punjab Lahore

1. Asif Hussain M14-351
Iraq Khan M14-348
Shujahat M14-350
Mubashir M14-345
Metallurgy and Materials Engineering
College of Engineering and Emerging
Technologies University of the Punjab Lahore

2. Introduction
Spot welding is the process in which adjoining
metal surfaces are joint together by the heat obtained
from resistance to current flow, thus forming a
welding Nugget between them.

3. Working Principle:
 At Low voltage, the current flowing through the joint generates
large amount of heat due to High Contact Resistance, which
causes Melting of Joint and further Fusion of Metals.
 Mathematically, the heat generated is given by the formula:
H = I2Rt

4. How Does it Work?
 Let us consider two plates and try to join them

5. Five basic steps:
 Squeeze
 Weld
 Hold
 Forge
 Pressure off

6. 1. Squeeze:
1. Lap Joint 1. Clamping Electrodes
1. Connect the electrodes with the step
down transformer.

7. 2. Weld:
1. Switch on the AC Source 2. Heat generation

8. 3. Hold:
4. Forge

9. 5. Pressure Off step
 Removal of the electrodes from the join area and further the joint is allowed to
cool.
So the technique in which metals are joint with each
other by resistance heating at a single point is called
Resistance spot welding

10. Equipment:
 Electrodes
(Low resistance alloy)
 Water Supply
 Heat regulator
 Pressure Gauge
 Foot switch
 Hydraulic or Air Cylinder
 Knee

11.  Advantages:
Limitations:
 Quick and Easy
 No need of Flux and Filler metals
 Multiple sheets joined together at the same time
 No dangerous open flames
 Saves production cost
 Difficulty for maintenance or repair
 Generally have higher cost than most arc welding equipment
 Internal and surface cracking
 The full strength of the sheet cannot prevail across a spot welded joint

12.  Applications:
Automobile Industries Handle of cooking utensils
Dental Prosthesis Batteries