Method of heat treatment of railway wheels

 

(57) Abstract:

The invention relates to metallurgy, namely thermal processing of solid-rolled railway wheels. The technical result of the invention is to improve the wear resistance of the working layer of the rim of the wheel throughout its depth. This is ensured by the fact that during heat treatment of railway wheels, comprising heating to a temperature of austenization are determined, intermittent cooling of the surface layer of the rim, the subsequent exposure of the wheels in the air and release, flow of coolant in the first 20 - 40 increase linearly from 0,001 - 0,003 l/(cm2(C) to the optimal values determined by the content of (C + 1/4Mn), where C and Mn - interest content in the steel, respectively, carbon and manganese. 4 tab., 4 Il.

The invention relates to the field of metallurgy, namely thermal processing of solid-rolled railway wheels.

A known method of thermal processing of solid-rolled railway spike lies in their heated to the temperature of austenization are determined, intermittent cooling surface of the rim when the wheel spins, the cooler, the consumption of which is in the process of cooling time remains unchanged (see Fig.1A), the subsequent kind is vremenno throughout its depth, since the cooling rate of the inner layers of the metal rim is always lower than the cooling rate of the outer layer. To get into the inner layers of the structure of the fine lamellar pearlite, ensuring their high durability, it is necessary to cool the surface layer of the rim with a speed higher than optimal, leading to the formation of the structures of type martensite tempering, prone to chipping with low wear resistance.

In the method of heat treatment of railway wheels, comprising heating to a temperature of austenization are determined, intermittent quenching rim by submitting to it cooler under pressure when the wheel spins, the subsequent exposure of the wheels in the air and leave, at the beginning of interrupted quenching exercise 3-4 times a pulsed flow of coolant within 4-5 with each pulse with an interval of 2-3 seconds between pulses /2/. In the future, the supply of coolant to the surface of the wheel is produced at a constant flow rate (Fig.1B). When using this method partially aligned properties of the metal of the wheel rim of his depth. The disadvantage of this method is that during the first and subsequent pulses of the surface layers of the metal content ogle technical nature of the claimed (prototype) is a method of heat treatment of railway wheels, includes heating to a temperature of austenization are determined, the shutter speed and intermittent cooling of the surface layer for 110-220, characterized in that to increase the wear resistance of the working layer over the entire depth, the cooling is carried out with a specific consumption of the chiller first 0,009-0,01 l/(cm2(C) within 80-30, then 0,015-0,018 l/(cm2C) for 50-70 with further 0,009-0,01 l/(cm2C) (Fig. 1B).

With this method it is impossible to ensure close the cooling rate of the outer layer and the inner layers of the metal of the rim and, as a consequence, it is impossible to avoid significant differences in the structure and durability of metal directly on the surface and in depth, it is impossible to ensure optimum metal structure throughout the depth of the rim especially when heat-treated wheels with high carbon content, for example the wheels of a class "With" standard of the Association of American railroads AAR M-107 with a carbon content of 0.64 to 0.80%.

The aim of the proposed solutions is to increase the wear resistance of the working layer of the rim through the creation of the lamellar structure of pearlite directly on the surface and at depth.

This goal is achieved by the fact that in the present method heat the surface layer of the rim, subsequent exposure of the wheels in the air and release, flow of coolant in the first 20-40 with increases linearly from 0,001-0,003 l/(cm2(C) to the optimal values determined by the content of (C + 1/4 Mn), where C and Mn - interest content in the steel, respectively, of carbon and manganese, and then remains constant (Fig.1G).

Distinctive features of the proposed method is:

- linear increase of consumption in the first 20-40 seconds;

- increase the flow of coolant is done from 0,001-0,003 l/(cm2(C) to the optimal values determined by the value (C + 1/4 Mn), where C and Mn - interest content in the steel, respectively, carbon and manganese.

Due to the inventive solution it is possible to provide approximate cooling rate of the outer layer and the inner layers of the metal rim, the maximum level the structure of the metal on the surface and in depth, having an optimal structure throughout the thickness of the working layer of the rim, including wheel of high carbon content, for example the wheels of a class "C" standard of the Association of American railroads AAR M-107 with a carbon content of 0.64 to 0.80%. This is due to the following. The outer layer is cooled with a low consumption, sufficient however the vacation. Layers at a depth of 20-30 mm are also cooled with a speed close to the optimum, due to the increase of the coolant on the outer layer.

Optimal consumption is determined beforehand on the basis of thermokinetic diagrams or empirically as consumption required to obtain the necessary properties at a depth of 30-50 mm

For wheels with low carbon content while increasing the flow of coolant is selected the minimum and initial maximum flow. For wheels with high carbon content time linear increase of consumption is chosen as the initial expense is minimal.

The example run.

Heat treatment by the proposed method were subjected wheels of steel three heats, whose chemical composition is given in table 1.

After heating to a temperature of austenization are determined wheels were subjected to tempering. Hardening of the wheels were made during their rotation with a speed of 100 Rev/min hardening Parameters wheels by the present method are shown in table 2.

Cooler for quenching rim was supplied through the valve is opened by the motor for 320-40 with from the start of cooling. It provided a linear p is the air and leave at the optimum temperature.

To obtain comparative data were carried out in parallel heat treatment of railway wheels the same heats the method prototype. In table 3 and 4 shows the mechanical properties of the wheels after heat treatment.

The wheels, hardened by a known method, the structure at the depth of 5 mm from the tread surface to the bottoms 2 and 3 consisted of martensite tempering, and in the transition zone sorbitol with grid sections ferrite, and for melting 1 at a depth of 20 mm - fine lamellar pearlite.

The wheels, hardened by the present method, all of the bottoms at depths of up to 5 mm fine lamellar pearlite, evenly rolling at a depth of 20-30 mm in lamellar pearlite with minimal parts of ferrite.

Thus, compared with the prototype of the proposed method allows to obtain the structure of the fine lamellar pearlite with high wear resistance on the surface and at a depth of wheels with different carbon content, for example the wheels of a class "C" standard Association of American railroads AAR M-107 with a carbon content of 0.64 to 0.80%.

Method of heat treatment of railway wheels, comprising heating to a temperature of AWSC, characterized in that the flow rate of the refrigerant in the first 20 - 40 increases linearly from 0,001 - 0,003 l/(cm2c) to the optimal values determined by the content of (C + 1/4Mn), where C and Mn-interest content in the steel, respectively, carbon and manganese.

 

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