Posted to News on 25th Mar 2013, 00:00
The fastest welding for the fastest trains
The installation and commissioning of a 30x4m gantry 'Powerstir' Friction Stir Welder (FSW) by UK-based PTG Heavy Industries - in a joint project with the China Friction Stir Welding Centre - didn't just represent a first for China and for PTG. The Powerstir machine also played its part in a world first, being used in the manufacture of railway car bodies similar to those used in China's record-breaking 'Harmony' high-speed train. In producing the railway car bodies, another record was also broken, with the PTG Powerstir machine producing the longest-ever single FSW railway panel weld in China, at over 15m in length.
>In simple terms, Friction Stir Welding is a 'solid state' welding process that joins materials by plasticising and consolidating the material around the joint line. A rotating pin generates heat that creates a tubular shaft of plasticised material around the pin. Then pressure, provided by forward motion and the downward force of the tool shoulder, forces the plasticised material to the back of the pin, cooling and consolidating the material. No melting takes place and the final result is a fine-grained, hot-worked weld with no entrapped oxides or porosity.
>With speeds of up to 2000mm/min, FSW is more than five times faster than conventional welding methods. It is also not affected by the disadvantages of conventional welding. Namely, weakening in the heat affected zone, high-energy consumption, distortion requiring secondary operations, the requirement for two operators per weld head, no record of weld data, fume extraction and environmental hazards. The FSW process, by comparison, gives low distortion even in long welds and excellent mechanical properties. Most importantly, FSW produces vastly superior joint strength and weld appearance with no post-weld grinding.
>Incorporating the brands of Binns and Berry, Crawford Swift, Holroyd and Precision Components, PTG has established itself at the forefront of high precision machine tool design, build and supply. Industrial sectors served range from aerospace, medical and mould tool and die to marine, power generation, mining, oil and gas, steel, high end and heavy automotive. The friction stir welding process is patented by TWI (The Welding Institute).
