Resistance welding electrodes and holders, Mechanical Engineering

Resistance welding electrodes and holders

Requisites For Electrodes: The resistance welding electrodes are meant for the following functions:

  • Conducting electricity
  • Conducting (away) the heat
  • Locating
  • Forming
  • Heat balancing functions

 

From the above, the requirements for the electrodes can be derived as:

a. Mechanical strength - This is measured by the hardness.
b. Adequate current carrying capacity This is given by the electrical conductivity.
c. Provisions for cooling.
d. Resistance to deformation and wear under heat and pressure.


Electrode Materials: Resistance Welder Manufacturers Association (RWMA) has categorised the materials used for resistance welding electrodes.

Group A - Copper base D alloys

  • Class 1 Cu - Cd (1 % Cd) - high conductivity
  • Class 2 Cu - Cr (0.8 % Cr) - high mechanical properties.
  • Class 3 Cu - Be (0.5 % Be, 1 % Ni, 1 % Ca) - high conductivity and mechanical properties.
  • Class 4 Cu - Be (1.8 % Be, 0.3 % Cu - do -)
  • Class 5 Al - Bronze (12 % Al) Flash or butt dies, Cu - Zr - Plated materials (galvanised iron or steels).

 


Group B - Refractory

  • Class 10, 11, 12 - Cu & W
  • Class 13 - W
  • Class 14 - Mo - For welding of Cu or brass.

 


Spot and Projection Welding Electrodes: Four main parts of the electrodes are:

  • Face
  • Shank or body
  • Means of attachment to the electrode holder
  • Provision for cooling

 

Spot welding electrodes can have pointed, dome, flat, eccentric, truncated or radius face. The shank may be tapered or it may be straight having threads for attachment. Internal cooling may be provided or immersion cooling, flooding or a wrap around copper tube cooling may be adopted. The holders may be of ejector or non ejector type and straight, universal or offset models. The electrodes should be used with the prescribed holders and adopters in order that a good weld is obtained. Electrode material dressing, cooling, cleanliness of the engagement section, proper alignment and proper machine settings are also important. Projection welding electrodes usually make contact with the work on flat surfaces that must always be larger than the base diameter of the projection. Generally, flat face spot welding electrodes are used. In cross wire welding, rectangular bar stock is used. The projection welding electrodes have internal water cooling and replaceable inserts is used.

Seam Welding Electrodes: These are shaped like wheels or discs. The basic considerations of these electrodes are

  • Face contour
  • Width
  • Diameter
  • Cooling and
  • Attachment

 


The above factors depend on the thickness, size and shape of the work, current density, pressure requirements and the type of drive mechanism. Floor cooling of top and bottom electrodes are employed. Care should be taken to preserve the shape and cleanliness of the electrodes. Special types of elect rodes are also manufactured depending on the requirements.

Posted Date: 9/17/2012 6:03:36 AM | Location : United States







Related Discussions:- Resistance welding electrodes and holders, Assignment Help, Ask Question on Resistance welding electrodes and holders, Get Answer, Expert's Help, Resistance welding electrodes and holders Discussions

Write discussion on Resistance welding electrodes and holders
Your posts are moderated
Related Questions
Describe Nusselt Number, Reynolds Number and Prandtl Number. Get the relation between these three for a circular cylinder losing heat in forced convection to the air flowing around

Newer Approaches To On-Line Scheduling  The on-line scheduling has established to be superior option than off-line scheduling upon the shop floor. The on-line scheduling looks

MATERIALS WELDABILITY Electron beam welding has the ability to weld a variety of materials including dissimilar combinations. These can be split into general categories as to t

Can you explain the principal of resistance welding? Classify various Resistance welding processes and Illustrate in detail two of them. With the help of neat and clean graph ex

The  impeller driveshaft  can either be top driven or bottom driven. Again there are advantages of each and the choice often varies with scale of operation: (a) Top driven (labo

what is blow hole defect ?

ppt of appling queuing model in railwy reservation

Laws of solid friction: Sol.: The friction which exists between two surfaces that are not lubricated is called as solid friction. The two Surfaces can be at rest or one of t

what is the affect of ambient temperature on the performance of GAS turbine

Heat Treating Equipment: The major equipment for heat treatment is furnace. There are two main categories of furnaces - batch and continuous. The furnace selection needs cons