What is projection welding?
Projection welding is a form of resistance welding which uses pressure and electrical current to join two or more metal parts that have been designed to meet at one or more specific points with the maximum amount of contact. This allows for more efficient welding with less energy and greater weld strength.
What are the 12 weld defects?
What are common weld defects?
- Lack Of Penetration or Incomplete Penetration.
- Lack Of Fusion or Incomplete Fusion.
- Undercut.
- Spatter.
- Slag Inclusions.
- Cracks.
- Porosity.
- Overlap.
What are the characteristics of projection welding?
PROJECTION WELDING is a variation of resistance welding in which current flow is concentrated at the point of contact with a local geometric extension of one (or both) of the parts being welded. These extensions, or projections, are used to concentrate heat generation.
What type of machine is used for projection welding?
Projection welding traditionally has been performed using AC controls and power supplies. The welders frequently have been traditional press welders and recently fixed station weld guns.
What are the types of weld defects?
We can break down weld defects into the following main categories;
- Inclusions.
- Lack of fusion.
- Porosity.
- Undercut.
- Under-fill.
- Cracks.
- Excess reinforcement and excess penetration.
- Over-roll/Overlap.
What weld discontinuity is most severe?
Cracks
Cracks – Cracks are the most detrimental discontinuity for the integrity of a welded connection. Cracks, in any amount, will constitute a defect with very few exceptions. Cracks due to stress relieving of hardfacing welds is one of these exceptions.
What is a projection weld?
Projection welds developed via the resistance welding (RW) process use the design or shape of the part to make discreet individual-point contacts to concentrate the current during welding.
What are welding defects?
These defects differ from the desired weld bead size, shape, and quality. Welding defects could occur either from the outside or inside the weld metal.
What factors should be considered when welding with multiple projections?
Projection size or shape: When welding using multiple projections, ensure that the projections are of the same size and shape. Projections of different sizes that make simultaneous contact will heat at different rates, leading to overheating and expulsion.
What are the main causes of poor welding penetration?
Improper joint preparation and insufficient heat input are the two primary causes of lack of penetration. Improper shielding gas mixture and welding wire diameter can also be a factor.
