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In the era of high-speed rail, passengers can no longer hear the sound of the track ''clanging", which thanks to China's high-speed rail core technology -- seamless lines.

In 2015, a foreigner posted a video in which he put a coin on the windows ill of a train speeding at 300km/h and the coin held for nine minutes.

Welding track base staff explained "One of the biggest reasons for keeping coin standing for nine minutes is the long rail. The long rail is used to improve the stability of the train". "long rail" is the welding of five 100m steel rails into a 500m long rails. There are 14 procedures in the welding process, such as rail inspection(before welding), rail derusting, flash wielding, welding rough grinding, rail normalizing, rail cooling, welding straightening, welding accurate grinding, rail flaw detection and etc. Rails can only leave the factory after passing the inspection.

Under the fine operation of rail welders, a "strong rail" has been continuously produced to laying the foundation of high-speed railway, which making China's high-speed railway faster and more stable.