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10/20/2014 : 6:20 am : +0200

Common welding defects and how to avoid them

Defect Main reasons Prevention and counter measurements
Porosity Contaminated filler wire. Humidity on the surface of the filler wire. Improve the cleanliness of the filler wire and the environment. Welding above dew-point.
  Improve the cleanliness of the filler wire and the environment. Welding above dew-point. Cleaning and drying of the welding area, ie. Preheating. Make sure that the base material is at room temperature before welding.
  Unsuitable welding positions. Use welding positions PA, PB, PF if possible.
  Degassing time too short. Increase heat-input and/or preheating. Modify joint preparation.
  Contaminated shielding gas, due to leaking cooling water or gas supply systems. Remove leaks.
  Contaminated shielding gas due to diffusion of humidity. Unsuitable hose material. Use gases complying to EN 439. Use suitable hose materials, replace old and porous hoses and keep hose length as short as possible.
  Non-laminar gas flow due to too high or too low gas flow or air draft. Optimize shielding gas quantity. Prevent air drafts.
  Arc voltage too high. Optimize arc voltage.
  Torch angle too small. Use proper torch angle.
Oxide inclusions Formation of oxides in the arc or in the weld pool by intake of Oxygen due to insufficient gas flow. See porosity. Optimize gas flow quantity. Prevent air drafts.
  Insufficient cleaning of the welding area and/or the preceding layers. Make sure that the welding area and preceding layers are cleaned.
  Excess of oxygen in the preheating flame. Optimize flame.
  Unsuitable treatment of the rods with TIG-welding. Do not retract the rod end from the shielding gas.
Cracking Solidification characteristic of the weld pool. Select the filler wire for optimized weldability. Make endcrater on run-out plates or use a crater fill program.
  Inner tensions. Use welding sequences which reduce tension and distortion.
  Remelting of components with a low melting range, which precipitate at grain boundaries in the heat affected zone. Reduce heat input and inter-pass temperature. Reduce susceptibility of cracks by using a single-pass technique. Reduce inner tensions. Select suitable ? ller wires (ie. 4xxx-series).
Tungsten inclusions Tungsten inclusions from excessive current or from touching the weld pool. Reduce current or select a larger diameter. Do not touch the weld pool with the electrode tip.
Copper inclusions Copper inclusions with MIG-welding due to overheating. Select a torch and a tip suitable for the amperage.
  Uptake of Copper from the backup plate. Replace the Copper backing plate. If necessary use backup made from stainless steel, Aluminium or ceramics.