Defects of excessive rail distortion

In simple terms, torsion is the torsional deformation caused by external force. In the rail, the main section of the rail is twisted by different rotation angles around its longitudinal axis. The twist of the end section and the section 1m away from the end is the end twist. The twisting of the two sections is called full-length twisting, which is manifested by placing the rail on a horizontal platform with a gap between the bottom surface of one side of the rail and the platform.

 

End torsion is measured with a torsion gauge, as shown in Figure 3, and full-length torsion is confirmed with a feeler gauge by placing the rail on a horizontal platform.

 

The permissible deviation of distortion is determined according to 6.2 of the standard "Rail Part 1: 43kg/m~75kg/m Rail" (TB/T 2344.1-2020), as shown in Table 1.

Cause

Both rolling and straightening operations can affect rail distortion by the following factors:
1. Improper installation and adjustment of the rolling mill, the center line of the rolls is not on the same vertical or horizontal plane; axial movement of the rolls, dislocation of the rolling groove, improper installation of the guide plate or serious wear; uneven temperature of the rolled piece or uneven reduction, Causes the extension of various parts of the rail to be inconsistent;
2. Improper installation and wear of the straightening rollers of the straightening machine, improper adjustment of straightening process parameters, etc. lead to distortion.

Approach
If the distortion at the end of the rail does not meet the standard requirements, the partial distortion can be cut off, and if the distortion of the entire length is unqualified, it should be rejected.
Precaution

1. Check the installation of rolls and guides to ensure that the distortion of the rail is not affected. Grind or replace them in time when they are worn out. In addition, avoid excessive temperature unevenness of the rolled piece during rolling, and avoid rail extension caused by poor control of rolling parameters. Distortion due to inconsistency.

2. When straightening, strengthen the inspection of the state of the straightening rollers to avoid large distortions in the straightening process.

 

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Alina Shen

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