The Introduction of Track Welding
In the immediate post-war years, certain wartime teething troubles with metal arc welding were eventually ironed out and were better understood, as wider experience was gained. In particular, failure of welds or the parent metal in the heat affected zone of welds by metal fatigue took some time to be clearly understood and to be able to be correctly predicted. These fatigue failures were particularly troublesome in some of the early welded ships and to a lesser extent in some welded bridge members.
Metal arc welding was used extensively on steel structures in shop fabrication. By the late fifties, shop welding of this type had completely replaced the earlier shop riveting of structures, site joints generally being site bolted or very infrequently, site welded.
Although some metal arc welding and electro-slag welding is used for the fabrication and repair of point and crossing work, the welding of rails end to end to form continuous welded rail (CWR) is carried out in the shops by a process known as Flash Butt Welding (FBW).
Flash butt welding of rails commenced in the UK on a large scale in the late 1950's and since that time the process but still remains basically the same. In the mid-1950's London Underground introduced flash butt long welded rails using the standard bullhead section.
The FBW rails were produced by welding five standard sixty foot lengths into a long rail of 300 feet (about 90 metres). These rails were joined using ?tight' bolted -plates joints were clamped where to the rail using the high fis strength friction grip bolts, tightened to a predetermined torque. London
Underground are now in the process of changing over to flat bottom rail. Main line railways in the UK use flat bottom section rail for CWR which is flash butt welded in the shops in lengths up to 240 metres. In recent years in the UK British Steel PLC have been able to supply long lengths of rail already flash butt welded into long lengths.