National Standard Rail Straightness Control and Testing Standards
- What indicators are included in the straightness of national standard steel rails?
The straightness indicators of national standard steel rails mainly include longitudinal bending, transverse bending and torsion. Longitudinal bending refers to the bending degree of the rail in the length direction, usually measured by the bending amount per meter; transverse bending is the bending of the rail in the width direction of the section; torsion is the deformation of the rail in both length and width directions. These indicators collectively reflect the overall straightness of the rail, and any over - standard item will affect the quality of track laying.
- What are the differences in the requirements for straightness deviation of national standard steel rails for different purposes?
Steel rails for high - speed passenger dedicated lines have the strictest requirements on straightness. The longitudinal bending shall not exceed 0.3mm per meter, the transverse bending shall not exceed 0.5mm per meter, and torsion is not allowed. For steel rails used in ordinary trunk railways, the longitudinal bending is allowed to be ≤0.5mm per meter, and the transverse bending is ≤1.0mm per meter. The straightness requirements for steel rails used in branch railways and industrial and mining railways are relatively loose. The longitudinal bending can be relaxed to 1.0mm per meter, and the transverse bending is ≤1.5mm per meter.
- How to control the straightness of national standard steel rails during production?
During production, the cooling of the cooling bed after rolling is controlled, and a slow cooling process is adopted to reduce the deformation of the rail caused by uneven temperature. A special straightening unit is set up to adjust the straightening pressure and times according to the rail specifications, and accurately straighten the deformed parts. After straightening, natural aging treatment is carried out to release internal stress and avoid secondary deformation in subsequent use. At the same time, the straightening equipment is calibrated regularly to ensure its accuracy meets the production requirements.
- What are the testing methods for the straightness of national standard steel rails?
A straightness detector is used to record the bending data of the full length of the rail in real time through laser scanning or contact measurement, and generate a straightness curve. For small deviations, a 1 - meter straightedge with a feeler gauge can be used for measurement, and the maximum gap into which the feeler gauge is inserted is the bending amount of that section. Torsion detection requires placing the rail on a platform, measuring the horizontal deviation of different sections with a level, and calculating the torsion angle. The detection frequency is 10% sampling of each batch of rails, and no less than 5 rails.
- What impact does excessive straightness have on rail laying and use?
Excessive straightness will make it difficult for the rail to fit closely with the sleeper during laying, resulting in local suspension. When the train passes, additional impact will be generated, aggravating the wear of the rail and sleeper. Long - term use will cause unevenness of the track, affecting the running speed and comfort of the train, and may even cause wheel - rail resonance, threatening driving safety. In addition, rails with poor straightness are prone to welding stress concentration during welding, reducing the strength of the welded joint.