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Weld-bonding:

Two Processes in One.

SOLUTIONS with Effective, Practical Advice

Weld Bonding: The Best of Two Processes

Weld-bonding, written also as a single word, is a hybrid process combining adhesive bonding and resistance spot welding. It was invented and developed by the Welding Institute (TWI) in the UK.

The joint configuration, normally of overlapping sheet metals, is suitable for both processes either singly or when combined. The advantages are also cumulative, providing a sealed joint with higher strength than that of each process alone.

Before assembling, a paste adhesive is applied to one of the sheets in the area to be joined by Weld-bonding. After assembling the two elements, spot welds are performed through the adhesive. The paste is displaced by the electrode force and electrical contact is established permitting spot welding.

The local heating generated during spot welding causes only a limited damage around the weld. Then, to complete the assembly, the adhesive is cured as required in an oven at up to 180 ⁰C for 30 minutes.

The Weld-bonding method was successfully used for automotive applications to improve important characteristics of the joints like strength, sealing, load distribution and fatigue resistance. For steel materials no special difficulties were encountered.

However for aluminum alloys where much development work was required, it was found that in order to achieve consistent quality, tight controls must be applied.

It has been recognized that there is not yet sufficient information on the long time durability of the adhesive especially in difficult service conditions.

The surface condition or treatment of aluminum alloys has to be selected accurately, not to interfere with the spot welding process.

In selected applications Weld-bonding can provide important benefits both as design advantage and for production economy. However severe controls must be implemented to meet quality requirements and suitable provisions must be in place to protect the workers from hazardous fumes.

In conclusion Weld-bonding can be an advantageous method to consider in certain mass production assembly operations when the benefits of the combined processes are superior to the results obtained from any of the two alone.

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