Third friction stir welding machine for China for PTG Heavy Industries

The 'Powerstir' FSW machines are being used to weld aluminium panels for railway car bodies similar to those used in the 'Harmony' high speed train, otherwise known as CRH 380A, which recently achieved a record speed for an unmodified passenger train of 486.1 km/hr or 303 mph. The record-breaking test run took place along China's new high speed rail link between the capital, Beijing, and the country's financial epicentre, Shanghai. The third order comes after the second machine had already produced the longest-ever single FSW railway panel in China, coming in at over 15 m in length. The latest machine's superiority derives from its advanced technology. It comes complete with a UK designed and built, medium duty 3,000 RPM 15kW water cooled spindle, 60 kN Z-axis welding force, and 30 kN X and Y-axis welding force. The machine specification includes a Siemens 840 D solution line with 5-axis control and Crawford Swift Powerstir optimised front end, which has been developed by PTG specifically for FSW applications, and employs force control, in which the operator sets a welding force and the machine adapts welding parameters through closed-loop control to maintain a pre-set welding tonnage ensuring that welding parameters are optimised. The machine also features state-of-the-art seam tracking and height sensing laser equipment enabling weld height and seam in the 'X, Y' plane to be tracked along the curves of an aluminium panel or extrusion - an essential requirement in the welding of high speed train carriage panels and roof sections. FSW is a 'solid state' welding process that joins materials by plasticising and consolidating the material around the joint line. A rotating pin generates heat, which creates a tubular shaft of plasticised material around the pin. 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. FSW represents a leap forward from previous MIG welding methods - with speeds of up to 2,000 mm/min, FSW is more than five times faster than conventional welding techniques, which also suffer from a number of other disadvantages, with the conventionally welded material being weakened 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 - excellent mechanical properties, established by rigorous fatigue, tensile and bend testing, with no fumes, porosity or spatter. The tool is non-consumable, can operate in all positions and is energy-efficient requiring no filler wire or gas shielding with some tolerance to imperfect weld preparation. While, most importantly of all, it produces vastly superior joint strength and weld appearance with no post-weld grinding.