New System to Control Magnetic Arc Blow in Welding
NEWPORT NEWS SHIPBUILDING VA
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Welding of magnetized steels has long been a problem in the welding industry. When welding is attempted in the presence of a magnetic field the welding arc becomes deflected. This phenomena is known as arc blow. Arc blow can cause significant weld defects it can reduce productivity and it is frustrating to the welder. Sometimes weld joint magnetism is so great that control methods must be used to produce a satisfactory weld. In 1991 Newport News Shipbuilding developed and built six Magnetic Field Negators patent applied for for their welding department. Each unit consists of a small hand-carried electromagnet and power supply that operates off any standard 110120 volt AC power source. The lightweight system is designed to counteract magnetic fields up to 200 milli-tesla mT 2000 gauss across a 13 mm .5 in weld joint in 25 mm 1 in thick steel. Through laboratory and production testing the magnetic field negator has demonstrated the ability to neutralize local areas of high residual magnetism resulting in a considerable reduction of magnetism-related weld quality problems.
- Marine Engineering
- Couplers, Fasteners and Joints