Engineering experts from the University of Western Australia have discovered a method for strengthening infrastructure repair work via the application of a "buffer" of soft metal prior to welding.
The team of scientists discovered that the application of a “buffering” layer of soft metal can dramatically increase the fatigue life of metallic infrastructure when performing repairs using welding.
According to Xiaozhi Hu, Winthrop Professor with UWA’s School of Mechanical and Chemical Engineering, although weld repair is often the most economical means of dealing with the damage incurred by infrastructure, it can also cause significant weakening of the surrounding material.
Massive residual stress is produced along the welded interface when hard weld metals are applied directly to a hard metal base, as a result of the cooling down of the heat-affected zone.
As a result, welding can leave a material brittle and severely compromised if poorly performed, diminishing its resilience by as much as 50 per cent.
The UWA scientists stumbled upon a method for resolving this dilemma while conducting research into the impact of tensile over-load (OL) on high-strength low-alloy steels, which are frequently used as the material for mining equipment.
Their solution is the welding of a soft metal layer first, which involves a more rapid process and results in a more modest heat-affected zone.
Hu compares this soft metal layer to the undercoat that is applied to the exterior of a home during painting, which serves as a transitional, buffering layer for the external application.
The use of a soft metal as a buffering layer means that the hard metal weld is not applied directly to the hard metal base, resulting in far less stress for the underlying material.
The method also has the added advantage of neutralizing carbon content, which means there is less of high carbon concentration area which would leave the base material more brittle.
Hu’s team tested their method via the flux cored arc welding of soft metal layers of varying widths, and discovered that under overloading conditions the fatigue life of weld-repaired steel can be increased as much as six fold by the addition of a 10mm buffer.