MUREX HELPS BRITAIN'S
BIGGEST SCULPTURE
TAKE SHAPE

Corofil R60Ni2 flux cored wire from Murex Welding Products is being used by AK Heavy Engineering of Sheffield in the fabrication of Britain's tallest sculpture. 'B of the Bang', designed by Thomas Heatherwick, has been commissioned to mark the success of the Manchester Commonwealth Games and is named after the famous quote by Linford Christie on winning the Olympic 100 metre race. The whole structure will be tilted at an angle of 30 degrees on the approach to the stadium, symbolising the burst of speed and energy of an athlete launching out of the blocks.

AK Heavy Engineering, sub-contracted by the main steelwork contractor Westbury Structures, has exceptional welding, fabrication and machining resources. The core of the sculpture weighs around 80 tonnes and will occupy a space envelope of 10m long x 5m wide x 4m high once in place. The starburst design of the sculpture features 180 tapered steel spikes that meet and intersect at a central point, 22 metres above the ground.

After consultations with Murex Welding Products, AK Heavy Engineering established that a welding consumable containing an additional 2% nickel was needed to avoid possible micro-cracking, without impairing the distinctive patina of weathering steel - Corofil R60Ni2 proved the answer. It is a rutile flux cored wire designed to provide all positional welding and as a nominal 2.5% nickel weld metal has excellent toughness properties down to -60oC. "Corofil R60Ni2 flux cored wire is being used to weld the complex and highly stressed core together. This consumable was selected as it had been used on the famous Angel of the North sculpture. There it had been used to avoid any potential cracking problems," says Paul Madin, Fabrication Technical Manager at AK Heavy Engineering.

The grade of steel for the construction of 'B of the Bang' is Cor-Ten or weathering steel, a high tensile, low alloy steel that yields exceptional corrosion resistance whilst at the same time producing an attractive purple-orange surface patina.

Westbury Structures supplied the spikes for the core structure as half steel pressings, which were welded together to form complete tapering tubes, no two of which were alike in shape or size. Once the prefabricated spikes, ranging in length up to 9m, had been thoroughly tested by ultrasonic and magnetic methods, they were individually cut to shape to fit the central core. The computer model produced paper templates, which were actually wrapped around the spikes so as to transfer the exact pattern by punch-marking, and the profiles were cut using conventional oxy-propane cutting torches, then hand ground for an exact fit.

AK Heavy Engineering fabricated the core structure on a custom-made jig, and welding was carried out using three main processes including the flux cored wire welding for joining the spikes to the core. Specially adapted welding torches were needed for the more difficult joints and, since some parts were particularly inaccessible, left-handed welders were at a premium. "After more than 6000 hours welding using Corofil R60Ni2 consumable we have not found any case of cracking. R60 is also a very good positional wire, which is vital on very awkward welds and joints," says Paul Madin.