EA022297B1 - Method and device for heat treating rails - Google Patents

Abstract

The invention relates to the iron and steel industry, more specifically to methods and devices for heat treating railway rails. The technical result is a universal method and device which can be used to heat treat rails made from non-alloyed carbon steels as well as rails made from alloyed steels. The method makes it possible to cool rails at cooling rates within a range of 2-20°C/s, smoothly adjust the cooling rates during the heat treatment process, produce a uniform fine pearlite structure (tempered sorbite) to a depth of more than 22 mm from the surface and produce a running surface hardness of up to HB401. The cooling capacity of a gaseous medium is regulated according to a programmed regime by means of the pulsed, quasi-continuous and/or the continuous injection of water into a stream of air. Depending on the chemical composition of the rail steel and the initial temperature of the rail not lower than the austenitizing temperature, the consumption of gaseous medium is regulated from 20 to 60 m/min per linear metre of rail, while the consumption of injected water is up to 12 l/min per linear metre of rail. Furthermore, the amount of water in the gaseous medium is up to 0.2 litres of water per cubic metre of air. The pressure of the gaseous medium is regulated within a range of 0.005 to 0.1 MPa.

Description

The invention relates to the field of ferrous metallurgy, in particular to methods for heat treatment of rails, including railway rails.

State of the art

A known method of cooling the rail (patent KI 2266966 C 21 Ό9 / 04, C 21 Ό11 / 00, C 21 Ό1 / 02), including passing the heated rail through the cooling section with inlet and outlet regions and cooling to convert the rail microstructure to pearlite or ferrite pearlitic microstructure, characterized in that the rail is passed through a cooling section, consisting of separate, independent, sequentially located along the length of the cooling section cooling modules with independently adjustable cooling parameters and with intermediate regions located between the cooling modules for removing structural stresses, with means for determining the actual temperature of the rail head. Depending on the corresponding value of the actual temperature of the part in the intermediate region, the cooling intensity parameters of at least the next cooling module are adjusted to provide a predetermined temperature of the rail head during the entire passage of the cooling section exceeding the critical temperature of formation of the bainitic structure.

The disadvantage of this method can be attributed to the limited range of adjustment of cooling rates during the cooling mode. In addition, the temperature drop on the surface of the head during the first 4–5 s of the cooling regime reaches 350–450 ° C, which can lead to the formation of bainitic structures in the microstructure of the surface layers of the rail. Thus, the main disadvantage of this method is the high temperature fluctuations on the surface of the rail head (from 350 ° C to 100 ° C), which can lead to heterogeneity of the macrostructure.

Another disadvantage is the heterogeneity of the heat treatment along the length of the rail, since in the continuous heat treatment mode with regulation of the cooling intensity in separate independent modules, different sections of the rail go through different cooling modes.

There is a method and device for differentiated hardening with cooling of the rail head and sole of the rail using compressed air through a collector system with openings (nozzles) (I8 patent 4913747, IPC C 21 Ό 9/04). This patent is selected as a prototype rail heat treatment device.

The device consists of mechanisms for loading, unloading, positioning and fixing the rail in a head-up position (on the sole), a turbocharger, a duct system and manifolds with openings (nozzles) for supplying a cooling medium to the rail, positioning mechanisms of the upper, lower, and side collectors with a part air ducts, air supply control system and temperature control system.

This method and device allows heat treatment of rails only from alloyed and high carbon (hypereutectoid with a carbon content of 0.9-1.2 wt.%) Steels.

The main disadvantage of the method and device is the narrow range of regulation of cooling rates, providing heat treatment of rails with speeds up to 4.5 ° C / s, since the cooling medium is air, which does not allow heat treatment of rails made of carbon unalloyed steel, since this requires speed cooling significantly higher (10 ° C / s or more).

Another disadvantage of the device is the use of powerful drives and complex metal structures, since for the heat treatment of each rail it is necessary to raise and lower the design of the upper and side rail cooling collectors with part of the supply ducts.

There is another method of heat treatment of rails (patent KI 2280700 C 21 V9 / 04), including continuous cooling of the head, followed by controlled cooling of the rail profile elements, characterized in that the rail from rolling heating is cooled to a temperature of 820870 ° C and cooled in two environments: initially compressed air from the surface of the head for 2030 s at an air flow rate of 3000-4000 m ³ / h, at an air temperature of 10-25 ° C and a pressure of 0.55 MPa, then the head is cooled with a water-air mixture at a water flow rate of 25-30 l / min water temperature 10-30 ° C and a pressure of 0.3-0.4 MPa, while cooling the rail head, the sole is cooled with a water-air mixture at a water temperature of 10-30 ° C, a flow rate of 6-7 l / min and a pressure of 0.08-0 , 09 MPa.

This method is applicable for heat treatment of rails from unalloyed carbon (hypereutectoid) steels, but is limited for heat treatment of hypereutectoid and alloy steels, which is its significant drawback.

Other disadvantages of this method include: a sharp change in the cooling rate of the rail after the air-water mixture is supplied with a water flow rate of 25-30 l / min to the rail profile, which violates the principle of uniform cooling, and can lead to the formation of heterogeneity of macro- and microstructure. And also the use of air with a high pressure of 0.55 MPa, at its indicated costs, entails the need for high-power compressors and high-volume receivers, which will lead to the complication of the device and high energy consumption.

The objectives of the proposed method and device are: regulation of cooling ability

- 1 022297 gas cooling medium, both impulse quasi-continuously and continuously, expanding the range and smoothness of regulation of cooling rates, reducing the time of heat treatment of rails, the possibility of heat treatment of rails from unalloyed and alloyed steels, obtaining high hardness along the rolling surface, increasing plastic and strength properties heat-treated steel, simplifying the device and reducing energy costs.

The technical result is the creation of a method and device that allows you to adjust the cooling ability of the gas cooling medium as a pulse quasicontinuously or continuously according to a programmed mode;

carry out heat treatment of rails from carbon unalloyed (hypereutectoid and hypereutectoid) and alloy steels;

produce cooling of rails with cooling rates in the range of 2-20 ° C / s; quasi-continuously smoothly or abruptly change the cooling rate during the heat treatment at various stages of cooling;

reduce the pressure in the gas cooling medium supply system;

to obtain a homogeneous finely dispersed pearlite structure (quenching sorbitol) to a depth of more than 22 mm from the surface, due to the intensification of the cooling ability of the gaseous medium during cooling;

obtain hardness on the rolling surface to HB401, increase the plastic and strength properties of heat-treated steel, by reducing the dispersion of perlite;

reduce the total heat treatment time of the rail, simplify the device and reduce energy consumption.

The technical result is achieved by the method of heat treatment of rails, including continuous cooling of the head, followed by controlled cooling of the rail profile elements, where the rail from the rolling mill is cooled with initially compressed air, then it is cooled with a water-air mixture, while the rail head is cooled, the sole is cooled, according to the invention, the rail is cooled from carbon unalloyed (hypereutectoid, hypereutectoid) or alloy steel, from rolled and / or repeated to heating, start from a temperature not lower than the austenization temperature, with a gaseous medium, which is an air medium with a controlled change in the degree of humidity of the air, as well as a controlled pressure during heat treatment, while the cooling ability of the medium is regulated by pulsed quasi-continuous injection of water into the air stream according to the programmed mode.

In addition, the regulation of the cooling ability of the medium is carried out continuously according to the programmed mode.

In addition, regulate the flow of the gas medium, depending on the chemical composition of the rail steel, with a flow rate of 10-60 m ³ / min per meter of running rail, while the flow of injected water is changed to 12 l / min per meter of running rail.

In addition, the flow of the gas medium is regulated depending on the initial rail temperature, the values of humidity and the temperature of the source air and the temperature of the water.

In addition, the water content in the gas medium is up to 0.2 l of water per cubic meter of air.

In addition, the pressure of the gas medium is regulated in the range of 0.005-0.1 MPa. In addition, the cooling rate is controlled in the range of 2-20 ° C / s.

The technical result of the method of heat treatment of rails is carried out on a device that includes mechanisms for loading, unloading, positioning and fixing the rail, a turbocharger, a system of ducts and manifolds with nozzle openings for supplying a cooling medium to the rail profile elements, positioning mechanisms of ducts and collectors with nozzle openings, cooling medium supply control system, temperature control system, characterized in that the mechanisms of loading, unloading, positioning and fi rail sections, place it in a head down position and additionally introduced a system of pulsed quasi-continuous injection of water into a gas stream containing a water tank, a system of water pipelines, water flow and pressure regulators, controlled valves, controlled control valves, pulse injectors, as well as a system control, which allows for the injection of water in a pulsed quasi-continuous mode according to the programmed mode.

In addition, water injection is carried out continuously according to the programmed mode.

In addition, the flow rate and pressure of the gaseous medium and the injected water are controlled in accordance with a programmed mode.

In addition, the control system determines the temperature of the rail, the temperature and humidity of the source gas medium, the temperature of the water and adjusts the cooling mode based on the data obtained.

In addition, the device is equipped with mechanisms for moving rails and / or collectors relative to the vertical and / or horizontal axis.

In addition, the cooling of rails of various profiles is carried out by changing the distance from the surface of the rail profile elements to the nozzle openings.

In addition, the control system controls the pressure and flow rate of the gas medium and sets the operation mode of the turbocharger.

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Brief Description of the Drawings

The implementation of the claimed invention is explained in the following figures.

FIG. 1 is an example of an injector control diagram; FIG. 2 is a schematic diagram of a heat treatment device;

FIG. 3 is a schematic diagram of a heat treatment device indicating controlled process parameters;

FIG. 4 is an example of a device for heat treatment of rails, a General view.

The implementation of the invention

During the heat treatment of the rail, in the initial cooling period, the surface temperature of the rail head is smoothly reduced to the temperature of minimum austenite stability during pearlite transformation for 1-90 s, not exceeding the incubation period. Then, at the second stage, the cooling rate necessary for the formation of the finely dispersed pearlite structure in the surface layer is set, then the cooling rate is set to ensure the formation of the finely dispersed pearlite structure as the pearlite transformation moves deeper into the head.

Cooling is carried out with a gaseous medium with adjustable cooling ability in the heat treatment process. By injecting water into the air stream and changing the pressure of the gaseous medium, the cooling ability of the gaseous medium is controlled, thereby obtaining a predetermined rail cooling rate. Water injection is carried out in a pulsed, quasi-continuous mode with a change in the pulse duration from 20 to 10,000 ms or more, as well as a duty cycle of pulses from 1 to 10,000.

Reliability is the ratio of the sum of the duration of the pause between pulses and the duration of the pulse to the pulse duration.

O = (Thpause + Timp) / Timp, where

Tpause - pause between pulses;

Timp is the pulse duration.

An example injector control diagram is shown in FIG. one.

The pulsed water supply and the rapid outflow of air in the device create a homogeneous cooling gas medium with adjustable cooling ability, allowing you to change the cooling rate of the rail within 2-20 ° C / s. The temperature of the injected water can vary between 10-45 ° C.

The temperature of the source air can vary from minus 30 ° C to plus 50 ° C and humidity in the range of 40-100%. With a minimum moisture content of 10 g / m ³ per 1 pulse of 50 ms, 0.008 g / m ^{3 of} water will be added, i.e. less than 0.1%. At a maximum moisture content of 200 g / m per 1 pulse of 1000 ms, 3.33 g of water will be added, i.e. less than 1.7%. For one pulse of water injection, 0.008-3.33 g / m ³ is supplied into the air stream, which leads to a smooth, quasi-continuous change in the moisture content in the air (less than 1.7%), i.e. achieve a smooth change in cooling rate.

In the table. 1 shows the experimentally obtained data on the dependence of the cooling rate of the rail head on the pressure of the gas medium.

Table 1. Data on the dependence of the cooling rate of the rail head on the pressure of the gas medium Cooling medium / pressure in collectors Gas medium Pressure 0.005 MPa Pressure 0.015 MPa Pressure 0,025, MPa Pressure 0.04 MPa Pressure 0.05 MPa Pressure 0.1 MPa Initial speed cooling ° C / s 2.0 4.34 4,55 4.82 4.91 4.99

The pressure of the gas cooling medium is determined in accordance with the chemical composition of the rail steel in the range of 0.005-0.1 MPa.

With an increase in air pressure above 0.1 MPa, the cooling rate does not increase significantly, a further increase is not economically feasible.

The lower cooling rate range of 2 ° C / s is achieved by supplying a gaseous medium at a pressure of 0.005 MPa without water injection.

In the table. 2 shows the experimentally obtained data of the dependence of the cooling speed of the rail head on the air flow and the amount of injected water.

- 3 022297

Table 2. Dependences of the cooling rate on the pressure of the gaseous medium and the amount of injected water Gas pressure, MPa 0.005 0.015 0,025 0.04 0.05 0.1 Gas flow rate, m ³ / min per 1 m.p. rail 8 20,0 35.0 45.0 50,0 60.0 Water consumption, l / min on 1 mp rail ... 0.2-4.0 0.35 - 7.0 0.45-9.0 0.5 - 10.0 0.6-12.0 Cooling rates, C / s 2 4,5-10,0 4.7-15.0 4.9-17.0 5.6-18.0 6.0-20.0

Rails from rolling and / or reheating to austenitization temperature are cooled by differentially supplying a gaseous medium to various elements of the rail profile: to the head rolling surface, side surfaces of the head and the bottom of the rail.

Heat treatment modes are set programmatically based on experimental data in accordance with the chemical composition of rail steel, the required physical and mechanical properties, the initial temperature of the rail before cooling, and the temperature and humidity of the initial gas medium and water temperature.

To ensure minimal curvature of the rail, the necessary cooling mode of the sole is selected depending on the mode of cooling of the head.

Cooling is carried out to a temperature of 150-500 ° C depending on the chemical composition of rail steel.

This method of heat treatment of rails is carried out on a device, a schematic diagram of which is shown in FIG. 2, where are shown:

- rail;

- the lower manifold, which is a container with nozzle holes for cooling the surface of the head;

- side collectors, which are a container with nozzle holes for cooling the side surfaces of the rail head;

- the upper collector, which is a container with nozzle holes for cooling the bottom of the rail;

- turbocharger;

- pressure reducing valve to maintain a given pressure of the gas medium or water;

- Pressure Sensors;

- control valves for regulating the flow of water or the gas environment;

- injector;

- water supply device;

- a container of water;

- control system;

- positioning and fixing mechanism;

- air preparation system;

- filter system;

- water pipeline;

- gas pipeline;

I - cooling zone of the rolling surface of the rail head (PCG);

II - cooling zone of the side surfaces of the rail head;

III - cooling zone of the surface of the bottom of the rail.

In FIG. 3 is a schematic diagram of a heat treatment device indicating controlled process parameters, where:

- pressure of the gaseous medium;

- water pressure;

- gas flow rate;

- water consumption;

- temperature of the gaseous medium;

- water temperature;

- rail temperature;

- humidity of the gas environment.

In FIG. 4 shows an example of a device for heat treatment of rails - a General view, where:

- tilter;

- loading mechanism;

- 4 022297

- unloading mechanism;

- rail positioning and fixing mechanism;

- positioning mechanism of the upper collector;

- positioning mechanism of the lower and side collectors;

- roller conveyor receiving rail;

- roller conveyor issuing rail.

This method is carried out in the described device as follows.

Received in a position on the side of the rolling or reheating of the rail, tilter 1 (Fig. 4) turns over onto the receiving roller 7 (Fig. 4). The loading mechanism 2 transfers the rail to the positioning and fixing mechanism 4, while the positioning mechanism of the upper collector 5 raises the upper collector. After fixing the rail head down, the upper collector is lowered and the rail is cooled.

When changing to different types of rails, the positioning mechanism of the lower and side collectors 6 controls the distance from the surface of the rail head to the collectors.

The air entering the injection system of the gas medium passes through a filter system 15 (Fig. 2), an air preparation system 14 to prevent the influence of seasonal fluctuations in the temperature of the source air.

Further, air from the turbocharger 5 (Fig. 2) is supplied through the pressure reducing valve 6 and control valves 8 to the manifolds 2, 3, 4. Moreover, the control system 12 controls the pressure and flow rate of the gas medium using valves 6 and 8.

Water from the tank 11 or any other source by the water supply device 10, through the control valves 8, is supplied to the injectors 9. Due to the injection of water by the injectors 9 into the gas flow, the cooling ability of the gas medium is changed.

Then the gas medium is fed into the collectors 2, 3, 4 and sent to the cooling zone of the rail surface I, II, III. Moreover, the control system 12 automatically sets the operation mode of the valves 8 so that the injectors 9 operate in a quasi-continuous and / or continuous pulse mode, due to which the cooling ability of the gas medium changes smoothly.

The control system 12 (Fig. 2) according to the programmed mode controls the heat treatment of the rail with the correction of the mode according to the controlled parameters 1-8 (Fig. 3).

At the end of the cooling mode, the positioning mechanism of the upper collectors 5 (Fig. 4) raises to the upper position, the unloading mechanism 3 moves the rail to the roller conveyor issuing 8.

The experiments were carried out on the cooling device shown in FIG. 2, FIG. 3 and FIG. 4 on full-profile samples of the P65 rail 1200 mm long. Samples taken from steels with chemical compositions; given in table. 3.

Table 3. steel alloy Chemically? sample composition Ke p. FROM Mp δί R 8 A1 V SG Νί Si Τί Mo N one 0.78 0.97 0.37 0.010 0.009 0.004 0.056 0.277 0.115 0.009 less 0.0050 2 0.76 0.95 0.37 0.012 0.005 0.005 0,052 0,037 0.107 0.013 0.0034 less 0.0050 0.0086

According to the results of the experiments, each hardened sample was subjected to laboratory tests. The hardness, microstructure, and physicomechanical properties of the rail were investigated.

In the table. Figure 1 shows the experimental data of the dependence of the rail cooling rate on the pressure of the gas medium.

In the table. Figure 2 shows the experimental data of the dependence of the rail cooling rate on the pressure of the gas medium and the amount of injected water.

From the table. 1 and table 2, technological parameters and cooling rate ranges were selected for rails made of chromium alloyed steel of chemical composition No. 1 and carbon steel No. 2 from table. 3.

Data on the technological parameters of heat treatment of samples of rails P65 from steel of chemical composition No. 1 and No. 2 from table. 3 and the results of physical and mechanical tests and studies of the microstructure are given in table. 4 and tab. 5.

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Table 4. Technological ι composition No. 1 of the mik research office heat treatment parameters for samples of R65 rails from steel of chemical grade 3 and the results of physical and mechanical tests and growth structure No. p.p Pressure gas environment MPa Gas flow rate, m ³ / min per 1 m.p. rail Water consumption, l / min per 1 m.p. ‘Rail Soon st cooling Senia S / s Vre me ooh awaited oia, with Microstr uktura hardened th rail head The hardness of the rail, HB N / mm 2 PC g 10 mm 22 mm one 0,025 thirty 0.35 4.7 150 Sorbitol hardening 363 351 331 1210 2 0,025 thirty 0.45 4.8 140 Sorbitol hardening 375 363 341 1280 3 0,025 thirty 0.55 5,0 120 Sorbitol hardening 388 375 363 1320 4 0,025 35 0.65 5.1 110 Sorbitol hardening 401 388 378 1350 prototype way It does not allow heat treatment of rails of this chemical composition

Table 5

Technological parameters of heat treatment of samples of R65 rails from steel of chemical composition No. 2 from Table 3 and the results of physical and mechanical tests and studies of the microstructure .........

No. P.P Pressure gas environment MPa Consumption gas environment kg / min on 1 mp rail Consumption water, d / min on 1 mp rail Speed b cooling Senia ‘S / s Time cooling teniya from Mikrostru ktura hardened heads rail The hardness of the rail, HB σ ", N / mm ³ δ % V % pkg 10 mm 22 mm one 0.04 45 2,5 8.3 90 Sorbitol hardening 363 351 330 1250 12 43 2 0.04 45 5 10,4 80 Sorbitol hardening 375 363 345 1290 12 40 3 0.04 45 7 13.1 70 Sorbitol hardening 390 383 375 1350 thirteen 38 4 0.04 45 12 14.9 60 Sorbitol hardening 401 395 388 1380 14 37 5 0.04 45 thirteen 15.3 60 Sorbitol hardening + bainite 415 400 388 1410 10 32 proto type of way ba 0.55 44.5 twenty 140 Sorbitol hardening 388 388 375 1340 12 34

Thus, the proposed method allows the heat treatment of rails of both alloyed and unalloyed (carbon hypereutectoid and hypereutectoid) steels with various preset cooling modes.

The method and device for heat treatment of rails allows to obtain a structure of fine-grained hardening sorbitol at a great depth, to increase the physical and mechanical properties of steel, and thereby increase the operational stability of rails.

Claims (12)

CLAIM 1. A method of heat treatment of rails, including continuous cooling of simultaneously the rail head and sole from rolling and / or reheating from a temperature not lower than the austenization temperature, characterized in that the rail is cooled by air with regulation of changes in the degree of air humidity and its pressure during heat treatment by pulsed quasi-continuous and / or continuous injection of water into the air flow with the provision of changing the cooling ability of the medium. 2. The method according to claim 1, characterized in that the air flow is regulated depending on the chemical composition of the rail steel with a flow rate of 10-60 m ³ / min per meter of running rail, while the flow rate of injected water is changed to 12 l / min per one meter running rail. 3. The method according to claim 1, characterized in that the air flow is regulated depending on the initial rail temperature, humidity values and the temperature of the source air and water temperature. 4. The method according to claim 1, characterized in that the water content in the air is maintained within 0.2 l of water per cubic meter of air. 5. The method according to claim 1, characterized in that the air pressure is regulated within 0.0050.1 MPa. 6. The method according to claim 1 or 2, characterized in that the rail cooling rate is controlled in the range 6 022297 not 2-20 ° C / s. 7. The device for implementing the method according to claim 1, containing mechanisms for loading, unloading, positioning and fixing the rail, a turbocharger, a duct system and manifolds with nozzle openings for supplying a cooling medium to the rail head and sole at the same time, positioning mechanisms for ducts and manifolds with nozzle openings , a control system for supplying a cooling medium, a temperature control system, characterized in that it has a system of pulsed quasi-continuous and / or continuous injection of water into the air th stream containing a water tank, a system of water pipelines, water flow and pressure regulators in the form of controlled valves and controlled control valves, pulse injectors with a control system for injecting water in a pulsed quasi-continuous and / or continuous mode into the air flow with a controlled change in degree humidity and its pressure to ensure changes in the cooling ability of the medium, while the mechanisms of loading, unloading, positioning and fixing the rail are made with the possibility of p the position of the rail during processing with the head down. 8. The device according to claim 7, characterized in that it has an air flow and pressure regulator in the form of controlled valves and controlled control valves in accordance with a programmed mode. 9. The device according to claim 7, characterized in that the control system is configured to determine the temperature and humidity of the source air environment, water temperature and based on the obtained correction data of the cooling mode. 10. The device according to claim 7, characterized in that it is equipped with mechanisms for moving rails and / or collectors relative to the vertical and / or horizontal axis. 11. The device according to claim 7, characterized in that it is configured to change the distance of nozzle openings to the surface of rail profile elements when cooling rails of various profiles. 12. The device according to claim 7, characterized in that the control system has the ability to control the pressure and flow rate of the air and set the mode of operation of the turbocharger. Timp = 200 ms