RU2610761C1 - Method of rail bar connection with recovery of continuous welded rail operating temperture at low temperatures - Google Patents

Abstract

FIELD: construction.

SUBSTANCE: invention relates to construction of track and may be used in the repair or continuous welded rail laying. For rail bar connection with the recovery of continuous welded rail operating temperature at low temperatures ends of adjacent rail bars are welded with a traction device. Necessary clearance is determined before the calculation of bars tension. After thermite welding the part of the rail bar determined by calculation is detached at both ends of the weld joint. Ram down sleepers and fix rails on them. On both sides of the tensioning device in a calculated rail length before welding detach, heat and bent to the calculated value. After rails cooling and the reaching of the necessary strength by the welded joint the heating is stopped, and the curved areas of the rails are straightened.

EFFECT: possibility of withdrawing the excess longitudinal force in the tensioner is achieved.

Description

When performing aluminothermic welding, it is necessary that between the welded ends of the rails a gap of 25 ± 1 mm is stably maintained and that this position of the rails is maintained until the weld has acquired the necessary tensile strength. This condition can be ensured with the simultaneous entry of the rail lash into the specified temperature operating mode using a hydraulic tensioning device (GNU) [1].

The currently used GNU designs can provide a rail tension of a maximum of 620 and 800 kN, which corresponds to a tensile longitudinal temperature force equivalent to a change in rail temperature of 31 and 40 ° C. Such a tension force for most real conditions can be considered sufficient. Experience has shown that at higher forces than 400 kN, in the known GNU designs, a stable gap during welding is not provided.

In P. 4.6. [2] it is said that "It is allowed to restore the lashes with aluminothermic welding at a temperature of lashes above and below their fastening temperature, followed by re-fastening or discharge of stresses by methods similar to those used for PRSM welding." But the “methods similar to PRSM welding”, given in [2], are not suitable for practical use, since they are laborious and do not provide the required temperature regime of the jointless path.

In [1], it was taken into account that when the two ends of the rail lash are tensioned, their total displacement can be calculated using the well-known formula:

where α is the coefficient of thermal expansion of rail steel, α = 11.8⋅10 ^{-6 1} / ° C;

E is the modulus of elasticity of rail steel, E = 2.1⋅10 ⁵ MPa;

ω is the cross-sectional area of the rail ω _p65 = 80⋅10 ^-4 m ² ;

Δt is the difference between the rail temperature and the fixing temperature of the rail lash;

r is the linear resistance to the longitudinal movements of the rails.

If α, E, ω, and Δt have sufficiently definite numerical values, then r is a random variable with a large dispersion. In this regard, when tensioning the ends of the rail lash using GNU, one should expect that the displacement found using the average values of r according to formula (1) will be either insufficient or excessive. In the first case, the linear resistance should be reduced by unfastening part of the end sections of the lash until the gap becomes equal to the calculated value, in the second case, the ends of the welded rails should be cut.

, которая вычисляется по следующей формуле (одна из рисок ставится сразу за захватами ГНУ):Prior to the tension of the rail lashes, their 50-meter end sections should be in a loose state to be fixed by risks against constant points on the sleepers. This is necessary to control the magnitude of the longitudinal force. The tension of the rails is controlled by measuring the difference in displacements on two adjacent sections

, which is calculated by the following formula (one of the pictures is placed immediately after the GNU captures):

- увеличение длины 50-метрового концевого участка рельсовой плети (достаточна точность определения расстояния в 50 м ± 0,5 м).Where

- increase in the length of the 50-meter end portion of the rail lash (sufficient accuracy in determining the distance of 50 m ± 0.5 m).

Since F = αEωAt, it is easier to use, instead of formula (2), the formula

where Δt is the change in the temperature of fastening at the end sections of the rail lash to enter the place of welding in the required temperature regime of the welded joint.

If the GNU due to its design features or the state of hydraulics cannot ensure stable fixation of the welded ends of the rails for the period of welding, especially with large longitudinal forces of up to 800 kN, then in this case the welded ends of the lashes should be unloaded by unfastening them on both sides of the GNU by heating sections of rail lashes determined by calculation, unfastened and curved in plan with an arrow, at which the longitudinal force at the end of the curved section will be close to zero. This force is determined by the formula given in [3]:

where q is the linear resistance to transverse displacements of the curved part of the rails in plan along the metal side, q = 0.13 kN / m;

- длина изгибаемого участка рельсов (40 м);

- the length of the bent section of the rails (40 m);

I is the moment of inertia of the rail section when it is bent in plan (for a rail of type P65 I = 5.67 510 ^-6 m ⁴ ).

In [3] in fig. 2.9 shows the dependency graphs found by the formula (4)

After the ends are stretched using GNU and the necessary clearance is created, in this position the rails for monitoring are fixed by risks on the sleepers detached from the rails near the GNU grips. After welding, this position of the marks should remain. During heating of the bent sections of the rails, it is ensured that these risks fall into place, which is easy to do by adjusting the boom and using GNU, only then can welding be started. In order to remove the excess longitudinal force in the tensioner, on both sides of the tensioner for a certain calculated length, the rails are unfastened, heated and bent by the calculated value before welding, and after the rails have cooled down and the welded joint has acquired the necessary strength, the heating is stopped and the curved sections of the rails are straightened.

Information sources

1. Patent for invention No. 2291240 “A method for connecting rail lashes of a welded jointless path” (V. I. Novakovich, A. N. Ignatiev, N. I. Zalavsky, A. B. Kireevnin, G. V. Karpachevsky). Publ. 01/10/2007. Bull. No. 1.

2. Instructions for the installation, installation, maintenance and repair of the jointless path CP-2788 dated 12/29/2012.

3. Novakovich V.I. Jointless path with extra-long rail lashes: A manual for universities of railway transport (recommended by the Office of Personnel and Educational Institutions of the Federal Agency for Railway Transport). M .: Route, 2005

Claims (1)

A method of connecting rail lashes with restoring the temperature regime of a weldless path at low temperatures, namely, that a coupling device is mounted at the ends of two adjacent rail lashes, with which the ends of the rail lashes are moved towards each other, the gap is set and the welding is performed before by tensioning the adjacent rail lashes with a clamping device, the calculation approximately determines the longitudinal displacement of the ends of the rail lashes, with a practically larger Compared to the calculation, the premises trim the ends of the rail lashes and, in case of virtually insufficient movement, unfasten the rail lashes and sleepers, starting from the ends of the lashes, until the gap becomes equal to the calculated value after termite welding and cooling of the joint with the acquisition by the welded joint of sufficient strength, the clamping device is removed, the length of the part of the rail whip, determined by calculation, is fixed on both sides of the welded joint, and then until the path for the train rails in the same section knock down the sleepers and fasten the rail lashes, characterized in that in order to remove the excess longitudinal force in the tensioner from both ends from the tensioner at a certain calculated length, the rails are heated and bent by the calculated value, and after cooling rails and acquiring a welded joint of sufficient strength, the heating is stopped and the curved sections of the rails are straightened.