Seamless rail is not afraid of expansion and contraction?
The rail welding seamless rail is 25 meters long up into several hundred meters or even thousands of meters long, and then put on the roadbed, seamless rail gap of 11 mm between each segment. Seamless rail is seamed, will also be affected.
Seamless rail is also afraid of thermal expansion, cold contraction, but better than ordinary steel pipe. Thermal expansion and contraction are the laws of physics. When heated, the distance between molecules increases, and the rails extend. Similarly, cold contracts.
Seamless rail not thousands of kilometers without gaps, but the 25 meter long rail welding up into hundreds of metres long or even thousands of meters long, and then in the shop on the embankment, or the gap between 11 mm and a section of a seamless rail, now Shanghai Nanjing line is 303 km long ultra long seamless rail, seamless rail in order to solve the thermal expansion and contraction by slot number is not enough, now solve the thermal expansion and contraction in two ways, one is the long rail itself under all temperature stress, will be locked in the long rail sleepers, which is due to temperature change and contraction, this method is suitable for a year four small temperature difference areas, for example in the south of China. In some temperature difference regions should take another approach, namely the long rail itself does not bear the temperature stress, and stress or regular bleeding stress to automatic bleeding Method, make the long rail with temperature rise and free shrinkage, at the time of laying also try to choose the optimum temperature of the rail laying, the expansion value in the minimum range, so that regardless of the temperature rising or falling, the rail expansion always control at a minimum.
