RU2728977C1 - Method of recovery and reinforcement of elements of railroad switches - Google Patents

Abstract

FIELD: technological processes.

SUBSTANCE: invention can be used for recovery of worn-out elements of railway switch units and hardening of new, namely frame rails and tongue rails. Machining is performed with uniform removal of metal layer from side working surface of frame rail and tongue rail at depth not less than thickness of hardened layer. Heating of the processed section of the side working surface is performed, and multilayer surfacing is performed with a wear-resistant material. Performing forging of each deposited layer and performing rough machining. Tongue rail surfacing is carried out after the corresponding frame rail surfacing. Re-heating of each deposited sector is performed to tempering temperature and holding at this temperature during the time required for removal of internal thermal stresses. Deposited section is cooled slowly under cover of heat-insulating material. Finishing mechanical finishing is followed by flaw detection of surfaced surface of switch assembly.

EFFECT: method increases wear resistance and increases durability of treated surface of worn or hardened surface of new elements of railroad switch, eliminates internal thermal stresses and improves structure of deposited layer.

3 cl

Description

The invention relates to the technology of processing by the method of electric arc surfacing of the elements of railway switches worn out during operation, in particular, frame rails and wits and strengthening of new ones.

There is a known method for restoring a turnout switch (patent of the Russian Federation No. 2382695, IPC В23Р 6/00, В23К 9/04, Е01 В 31/18), according to which the worn surface is cleaned to a pure metal, its heating and surfacing by the electric arc method layer by layer to full depth worn surface with excess of the nominal size of the rolling surface of the rails by the amount of allowance for machining. With a decrease in the operating temperature, additional heating of the surface area of the worn rail surface is carried out. Then, natural cooling and mechanical treatment of the restored rail surface is carried out.

The disadvantage of this method is that the deposited layer has an unequal thickness, proportional to wear, and during operation, areas with a smaller thickness of the deposited layer fail faster. In addition, additional heating leads to unnecessary waste of energy and increases the cost of the process.

There is a known method (patent UA 92114, IPC В23Р 6/00, В23К 9/04) of restoration of worn surfaces of switches, in which the worn surface is cleaned, heated, fused by the electric arc method, after which it is cooled and machined on the restored surface. In the area where the worn surface is located, the magnetic capture is fixed. Surfacing is carried out by periodic transverse reciprocal movement of the welding trolley. The process is controlled by a modular microprocessor control unit with digital signal processing, which maintains the specified mode.

This method makes it possible to increase the quality and safety of the restoration of worn surfaces of the switches, as well as to increase their service life by increasing the wear resistance of the restored surface.

However, the disadvantages of the known method should be noted the insufficient reliability of the restored elements due to significant internal stresses arising after surfacing, which cause deformation, cold cracks and, as a result, the elements of the turnouts may break.

The closest to the claimed method is a method (patent of the Russian Federation No. 2675306, IPC В23Р 6/00, Е01В 7/28, В23К 9/04, В23К 101/26) restoration from worn surfaces of turnouts, including heating, surfacing with an electric arc method of worn surfaces wit and frame rail of the turnout switch, subsequent cooling and machining of the restored surfaces, while the worn out surfaces of the wit and frame rail are heated to the design temperature, which is maintained throughout the surfacing time, I perform! multilayer surfacing by imposing a buffer layer of a material with a damping property and wear-resistant layers with forging each layer and its rough machining, and after surfacing, the entire deposited section of the switch is covered with a heat-insulating material for slow cooling, while the cooling rate is controlled using an electric heater and controlled throughout the entire cooling time, and then perform finishing machining and carry out flaw detection of the restored surfaces of the turnout.

The disadvantage of this method is that the buffer layer reduces the thickness of the deposited wear-resistant layer, the material of the buffer layer has low wear resistance, and in the process of operation wears out faster than the base material of the rail. In addition, the wear of the frame rail and the edge is uneven in thickness and, in preparation for surfacing, a thin surface layer of metal is cleaned, repeating the nature of wear, as a result of which the thickness of the deposited layer is also unequal along the length of the restored section. During subsequent operation in places with a smaller thickness of the deposited metal, after its abrasion, rapid wear of the base metal occurs, which softens during surfacing and loses its wear resistance, which leads to a decrease in the service life of the turnout.

The basis of the invention is the task of improving the quality, increasing the reliability and increasing the service life of the elements of the turnouts.

This problem is solved due to the technical result, which consists in surfacing a uniform and maximum possible thickness hardened layer, which provides an increase in the wear resistance of the side working surfaces of the switch elements, as well as a decrease in internal stresses by heat treatment, without surfacing a buffer layer with low wear resistance.

To achieve the above result in the method of processing the worn surfaces of the switch elements, including the preparation of the worn out surfaces of the switch point and the frame rail of the switch, their heating, multilayer surfacing by the electric arc method of wear-resistant metal with the forging of each layer and its rough machining, subsequent cooling under a heat-insulating cover material and machining of the deposited surfaces to size, before surfacing, machining of the surfaces to be deposited is performed to uniformly remove the metal layer from the side working surfaces of the frame rail and the edge to a depth not less than the thickness of the hardened layer, and after surfacing and machining, the deposited sector to the tempering temperature and holding at this temperature for the time necessary to remove internal thermal stresses.

To strengthen the elements of the new turnouts, the working surfaces of the new, worn frame rail and the wit are welded and processed using the specified method

As a result of a comparative analysis of the proposed method for processing worn surfaces of turnouts with a prototype, it was found that they have the following common features:

- surface preparation;

- heating before surfacing;

послойную наплавку электродуговым методом с проковкой и механической

layer-by-layer electric arc surfacing with forging and mechanical

processing layers;

охлаждение под слоем теплоизоляционного материала;

cooling under a layer of thermal insulation material;

- machining of weld coated surfaces to size, as well as distinctive features:

перед наплавкой изношенные боковые рабочие поверхности остряка и рамного рельса обрабатывают для равномерного снятия слоя металла на глубину не менее толщины закаленного слоя;

before surfacing, the worn out side working surfaces of the wit and frame rail are processed to uniformly remove the metal layer to a depth not less than the thickness of the hardened layer;

многослойную наплавку выполняют без наложения демпфирующею буферного слоя;

multilayer surfacing is performed without imposing a damping buffer layer;

после наплавки и механической обработки выполняют повторный жирев наплавленного сектора до температуры отпуска с последующей выдержкой при данной температуре, достаточной для снятия внутренних термических напряжений;

after surfacing and machining, the welded sector is reheated to the tempering temperature, followed by holding at a given temperature sufficient to relieve internal thermal stresses;

- the same sequence of operations is used to strengthen and increase the wear resistance of new frame rails and wits.

Thus, the proposed method of processing the worn surfaces of the turnouts has new operations, a new sequence of operations and new conditions.

Due to the fact that a uniform metal layer is removed from the machined surfaces before surfacing to a depth of at least the thickness of the hardened layer and a layer of buffer material is not used, as a result of surfacing, a uniform thickened layer of hardened material is obtained with a wear resistance 2.3 times greater than that of the hardened layer a new frame rail and 1.3 times a new wit. Due to the uniform thickness of the deposited layer, the wear during the operation of the elements of the turnouts does not reach the base metal weakened during surfacing and proceeds much more slowly, which contributes to an increase in the wear resistance and durability of the turnouts.

Due to the fact that the deposited sector of the point and frame rail after surfacing and roughing is reheated and held for a specified time before cooling, internal thermal stresses are removed and the elements of the turnouts can be restored without using a buffer layer with low wear resistance, since minimizing internal thermal stresses prevents the formation of cracks in remanufactured products.

Taking into account the fact that the wear resistance of the deposited surfaces exceeds the characteristics of new products, the method is proposed to be used to improve the performance of new elements of turnouts.

The exclusion of a distinctive feature from the specified set of features does not provide the delivered technical result.

The technical solution has an inventive step because the proposed technology for a specialist does not explicitly follow from the prior art.

The claimed technical solution is not known from the prior art, therefore it is new.

The claimed technical solution is industrially applicable, since its implementation is not difficult.

Thus, the claimed solution can be provided with legal protection because it is new, has an inventive step and is industrially applicable.

The essence of the proposed method is as follows.

First, a visual inspection and measurement of the worn out sections of the switch elements are carried out. Then flaw detection is performed for the presence of internal defects and elements of the switches suitable for surfacing are selected. After that, the worn surfaces of the elements are prepared for surfacing. The worn sections of the side working surfaces of the frame rail and the wit are machined with uniform removal of the metal layer to a depth not less than the thickness of the hardened layer.

Further, the surfaces to be welded are divided into sectors and heated! to the design temperature. This temperature is maintained pa throughout the entire subsequent surfacing process. Surfacing of the ground areas is performed by the electric arc method and is carried out in a multilayer manner. Surfacing of a frame rail and a point is carried out sequentially in sectors and is performed with the main self-shielded flux-cored wire for repair and surfacing of defective sections of rail tracks or with special surfacing electrodes with the imposition of horizontal rollers in a reciprocating step method. It should also be noted that the cladding of the edge is performed after the surfacing of the corresponding frame rail, and the place of its surfacing is first bent and fixed according to a special scheme to prevent its deformation after the end of the surfacing process.

Before surfacing of each next bead, the previously deposited metal is cleaned of slags and forged, which strengthens the deposited layer and partially relieves internal stresses arising during surfacing. After surfacing of each sector, preliminary rough machining (hot grinding) is performed.

After machining, the welded sector is reheated to the tempering temperature and kept at this temperature for a time that allows the removal of internal thermal stresses. Then slow cooling of the overlaid sectors of the wit and frame rail is performed under a layer of thermal fiber. In this case, surfacing and heat treatment of the following sectors are sequentially performed. After cooling and processing the elements, their final finishing machining (grinding) is performed to size.

At the final stage of processing the elements of the turnouts, control of their geometric dimensions is carried out in accordance with the technical conditions, which regulate their parameters, using special measuring instruments. The welded elements should be checked for defects in the weld overlay zone by flaw detection.

From the foregoing, it follows that the implementation of the method of processing worn out and hardening of new surfaces of switch elements in accordance with the claims increases the thickness of the hardened layer with characteristics that, according to laboratory studies, are 2.3 times higher than the wear resistance of a new frame rail and 1.3 times - new wit, and also eliminates the formation of brittle structures and minimizes internal stresses after surfacing, which improves the quality, reliability and service life of the switch elements.

Claims (3)

1. A method of processing the elements of turnouts for the restoration and strengthening of their surfaces, including preliminary machining of the surfaces of the point and the frame rail of the turnout, breakdown of the processed surfaces into sectors, heating of each sector and multilayer surfacing of wear-resistant metal by the electric arc method with forging of each layer, then carry out rough machining of the deposited sector and subsequent slow cooling, and after the completion of surfacing, the final machining of the deposited surfaces is carried out, characterized in that the preliminary machining is performed by completely uniform removal of the metal layer from the side working surfaces of the wit and the frame rail of the turnout switch to a depth of at least thickness the hardened layer, and after surfacing and rough machining of each deposited sector, the deposited metal is reheated to the tempering temperature and Holding at this temperature for the time required to relieve internal thermal stresses. 2. A method according to claim 1, characterized in that worn frame rails and points of turnouts are processed. 3. The method according to claim 1, characterized in that new frame rails and switch points are processed.