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ELECTRODES IN RESISTANCE
WELDING
| Electrodes used in
resistance welding are considered a consumable tool and
come in various shapes, depending upon the application.
Welding electrodes are designed to perform one or more
of the following functions: |
 |
- Apply
force to the weld materials.
- Conduct
welding current to the weld materials.
- Clamp
parts in the proper alignment or orientation.
- Draw heat
away from the weld and adjacent material.
In order
to meet the above requirements, materials selected for electrodes
usually possess one or more of the following characteristics:
- High electrical
conductivity*
- High resistance
to mechanical wear and heat stresses.
- High thermal
conductivity*
- Low tendency
to form alloys with weld materials.
* There are
exceptions where the weld materials require special electrode
materials in order to achieve heat balance. An example is the
use of tungsten in the welding of copper or brass materials.
SHAPE OF ELECTRODES:
The larger the mass of the electrode tip, the less the wear.
The use of F and R type (for projection welding) is recommended.
| Name |
Shape |
Description |
| P-type |
 |
Point tip |
| R-type |
 |
Spherical Tip
(radius type) |
| C-type |
 |
Cone Tip |
| E-type |
 |
Offset tip
(eccentric) |
| F-type |
 |
Flat tip |
The table below lists some of the more common materials used
for electrodes in resistance welding and their qualities and
general applications.
| Material |
RWMA |
Qualities |
Application |
Cu-Cr
Cu-Cr-Zr
Chromium,Copper,Zirconium |
Class 2 |
High thermal and electrical
conductivity |
Mild and low alloy steels,
stainless steels, low conductivity copper-base alloys, nickel
alloys |
| Cu-Cr-Ni-Si-Be |
Class 3 |
Higher mechanical and lower
electrical conductivity than Class 2 |
Low alloy steels, stainless
steels, nickel-chromium-iron alloys |
Cu-Be
Copper,Beryllium |
Class 4 |
Higher mechanical and lower
electrical conductivity than Class 3 |
Flash and projection welding
electrodes |
Cu-W
Copper,Tungsten |
Class 10-12 |
Very high mechanical strength,
easily machined, must be ground, very low electrical and
thermal conductivity |
Some stainless steels, copper,
and brass |
W
Tungsten |
Class 13 |
Very high mechanical strength,
must be ground, very low electrical and thermal conductivity |
Copper and brass |
Mo
Molybdenum |
Class 14 |
High mechanical strength, machinable,
very low electrical and thermal conductivity |
Welding or brazing solid or
braided copper to ferrous or non-ferrous lugs |
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