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Can I use cold wire feed in combination with laser welding and why?


Frequently asked questions

Cold wire feeding techniques for laser welding are available and well established. In particular instances, the addition of filler wire might be necessary 

  • Improve the joint fit-up tolerance of autogenous laser 
  • Avoid solidification cracking of the weld 
  • Modify the chemical composition or the microstructure of the weld metal to obtain suitable mechanical 
  • Achieve multi-pass welds or fill a grooved joint preparation

  The use of cold filler wire generally results in a 10% to 20% decrease in welding speed, for a given laser power, to compensate for the laser energy that has to be used to melt the wire. This speed reduction can be counteracted by an increase in laser power (if available), the use of a hot (resistively heated) wire feed or the hybrid laser-arc process.

When welding thicker section materials (> 6~10mm), uneven mixing of the filler wire can be observed through the depth of the weld. This requires additional consideration, particularly if the filler is being used to control the composition, the microstructure and/or the mechanical properties of the weld.

The filler wire nozzle is generally mounted onto the laser welding head so that the wire is aligned with the centre of the joint. In most cases, the wire should intersect the laser beam on the upper surface of the workpiece and feed in to the leading edge of the weld pool. As this leading edge can be very small, accurate positioning of the filler wire is essential to the success of the welding operation.

A first estimate of wire feed rate for a given plate thickness can be gained from a consideration of the cross-sectional area of joint gap to be filled, the welding speed being used and the cross-section of the filler wire, as follows:

Wire feed rate, (m/min) = (Welding speed x cross-sectional area of gap) / (cross-section of filler wire)

If the gap width is variable along the joint length, the wire feed rate may need to be changed accordingly if uniform gap filling is to be maintained. Consequently, some form of gap sensing system is required to detect the gap width and automatically adjust the wire feed rate to suit. Laser vision camera joint tracking systems can be useful in this respect.

Filler wires can also be added using a hybrid laser-arc welding technique. Hybrid laser-arc welding processes are now being used in industry, due to their combined advantages of both laser welding (deep penetration) and arc welding (wire addition to tolerate joint fit-up better).

For further information see Joining Technologies.

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