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
give some best names

Q. Corrosion - Erosion Allowance? The required design life shall be based on written agreement between the user and the Engineering Contractor. Allowance specified shall be ba

minimum mass of air required for complete combustion of the HFO

what is plc and how does it works

A cantilever beam of 4 metre length is loaded with uniformly distributed load of 20 KN/m throughout the whole beam. It is also loaded with 30 KN operating at 3m from the fixed end

Q. Source of Materials? The user may restrict sources of fabrication materials. If there is a restriction, the prospective manufacturers must be informed at the time of biddin

(a) What is the importance of safety at workshop? (b) What problems may arise, if we do not take safety precautions in the workshop?

what is the formula of sensitivity of governor?

A single jet pelton wheel runs at 300 rpm under a head of 510 m. the jet diameter is 200m, its deflection inside the bucket is 165 o and its relative velocity is reduced by 15% be

Velocity acquired by block - system released from rest: T wo blocks shown in the figure given below, have masses A = 20N and B = 10N and the coefficient of friction between