Rail Straightness –An Important Rail Indicator

Rail straightness refers to an index that reflects the undulations of the rail along the longitudinal direction of the rail, including vertical straightness and horizontal straightness.

What are the effects of poor flatness?

The flatness state of the rail not only affects the wheel-rail relationship, but also has an impact on the wheels, the ballast, etc., which will cause vehicle vibration, noise, comfort, etc., and will directly affect the smoothness of the track operation and threaten driving safety.

How to control flatness in production

In the process of rail from continuous casting billet to rail finished product, there are more than ten processes, among which rolling, pre-bending and straightening are closely related to the control of rail flatness.

1. Precise rolling control

From continuous casting billet to rail, not only the length of rail increases by about 13 times, but also the shape changes from a regular cuboid to a small I-shape with a small head and bottom. Complex deformation requires the exquisite design and accurate control of process parameters such as pass shape and rolling force to keep the rolled long rail basically straight.

2. To be Straight, pre-bending first

Due to the unique shape characteristics of the rail, coupled with the influence of thermal expansion and contraction of the rail, it is necessary to avoid the situation that the rail head will eventually warp to the rail head due to the large heat dissipation of the rail head during cooling, and it is necessary to skillfully use the rail pre-bending technology to make the rail more “flat” after natural cooling and create favorable conditions for subsequent straightening.

3. The track is not “broken” not straight

To “break” the rail straight, it is necessary to straighten the rail. The first is the flat composite roller bridge, through which the full length of the rail is straightened, and then the flatness of the blind area of the end roller is locally fine-adjusted by the two-way pressure correction.

How to check the flatness of the rail?

A good rail must stand up to inspection. Therefore, the flatness of the rail before the final storage needs to pass a comprehensive inspection. First, the high-tech online flatness laser detector is used to detect the length of the rail, which can determine the flatness within the range of the rail length to check and prevent “fish in the net”; The third is the quality supervision of the plant to conduct a scientific batch sampling inspection to comprehensively determine the quality of the rail.

What is a good level of flatness?

China’s railway industry standards for the flatness of the rail requirements are almost harsh, every place of the rail body flatness to meet the standard, can be regarded as a qualified rail. China’s standard has been at the leading level in the world, the most stringent requirements for high-speed rail rail body parts vertical direction flatness requirements of no more than 0.3㎜ per 3m, which is equivalent to 3 pages of A4 paper thickness.

How to protect the rail?

The rail seems to be “rigid”, but it is actually “weak”. Qualified rail in the process of lifting, storage, etc., will also cause bending defects due to improper operation, so after the qualified rail leaves the factory, in the process of transportation, unloading should also do the corresponding protection, to avoid the rail from falling from the height, the lifting is not synchronized, but also to avoid the rail directly from the transport car pushed off the “barbaric” operation.