Resistance welding

Resistance welding

1. MANUFACTURING TECHNOLOGY – I CRAFTED BY: RAMESH KUMAR A Assistant Professor Sona College of Technology Salem 16-02-2018 10:00 1

2. RESISTANCE WELDING 16-02-2018 10:00 2

3. RESISTANCE WELDING 16-02-2018 10:00 3 The metal parts to be joined are heated by their resistance to the flow of an electrical current No fluxes are employed The amount of heat generated in the work piece depends on the following factors: Magnitude of current Resistance of current conducting path Mathematically, H = I V t = I (IR) t = I^2 R t Where, H – Heat generated in joules I - Current in Amp R – Resistance in ohms t – time of current flow in seconds

4. TYPES OF RESISTANCE WELDING 16-02-2018 10:00 4 Spot welding Seam welding Projection welding Butt welding Upset welding Flash butt welding Percussion welding

5. RESISTANCE WELDING SPOT WELDING 16-02-2018 10:00 5

6. SPOT WELDING 16-02-2018 10:00 6

7. SPOT WELDING… 16-02-2018 10:00 7 Carried out by overlapping the edges of two sheets of metal and fusing them together between copper electrode tips at suitably spaced intervals Resistance offered to current as it passes through the metal raises the temperature of the metal between the electrodes to welding heat The current is cut-off and mechanical pressure is then applied by the electrodes to forge the welds Advantages High production rate Very economical process High skill not required Most suitable for welding sheet metals Dissimilar metals can be welded Small heat affected area Limitations Suitable for thin sheets only High equipment cost

8. SPOT WELDING 16-02-2018 10:00 8

9. RESISTANCE WELDING SEAM WELDING 16-02-2018 10:00 9

10. SEAM WELDING 16-02-2018 10:00 10

11. SEAM WELDING… 16-02-2018 10:00 11 It is analogous to spot welding with the difference the electrodes are in the form of rollers; and the work moves in direction perpendicular to roller axis The welding is usually done under water to keep the heating of the welding rollers and the work to minimum, and thus to give lower roller maintenance and less distortion of the work 2000 A to 5000 A 5 kN to 6 kN 1.5 m/min for thin sheet Applications Pressure tanks (light or leak proof) Oil switches Transformers Refrigerators Evaporators and condensers aircraft tanks etc.,

12. SPOT WELDING 16-02-2018 10:00 12

13. RESISTANCE WELDING UPSET BUTT WELDING 16-02-2018 10:00 13

14. UPSET BUTT WELDING 16-02-2018 10:00 14

15. UPSET BUTT WELDING… 16-02-2018 10:00 15 To join bars and plates together end to end One bar is held in a fixed clamp in the butt welding machine and other in the movable clamp The clamp being electrically insulated, the one from the other, and being connected to a source of current Current is ON, the resistance in the joint causes the ends to heat up to welding temperature Then current is switched OFF, the movable clamp forced up, so that the pressure applied upsets the parts together Applications Non-ferrous of bars, rods, wire Steel rails

16. UPSET BUTT WELDING 16-02-2018 10:00 16

17. RESISTANCE WELDING FLASH BUTT WELDING 16-02-2018 10:00 17

18. FLASH BUTT WELDING 16-02-2018 10:00 18

19. FLASH BUTT WELDING… 16-02-2018 10:00 19 The parts to welded are clamped to the electrode fixtures, as in butt welding but the voltage is applied before the parts butted together As the parts touch each other, an arc is established which continues as long as the parts advance at the correct speed This arc bursts away a portion of the material from each piece When the welding temperature is reached, the speed of travel is increased, the power switched off and the weld is upset Applications Automobile – body, axles, wheels, frames and other parts Welding motor frames, transformer tanks, and many type of sheet steel containers such as barrels and floats

20. FLASH BUTT WELDING 16-02-2018 10:00 20