Railroad wheel heat treatment method

FIELD: metallurgy.

SUBSTANCE: cooling of working layer of rim during the first 180 sec is performed at discrete increase in flow rate of cooler of 0.0005 to 0.02 l/(cm2/s) by 0.0001 l(cm2/s) every 15-30 sec and the next 120 sec at constant flow rate of cooler to 0.5 l/(cm2/s), and cooling of end surface of rim on the ridge side is performed with air with flow rate of 0.5 m3/(cm2/s); then, wheel is cooled in the air and tempering is performed.

EFFECT: high application properties of railroad wheels owing to improving wear resistance of working layer of wheel rim and mechanical properties of wheel disc; heating to austenisation temperature and differentiated cooling of working layer of rim and its face on the ridge side is performed during 300 s.

1 ex, 2 tbl

 

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 wheel rim throughout its depth and mechanical properties of the wheel.

A known method of thermal processing of solid-rolled railway wheels [1], lies in their heated to the temperature of austenization are determined, intermittent cooling cooler surface of the rim when the wheel spins, and the subsequent exposure of the wheels in the air. Consumption in the process of cooling time remains unchanged. With this method it is impossible to obtain high wear resistance of the rim simultaneously throughout its depth, because 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 metal structure in the form of fine plastic perlite to ensure high wear resistance, it is necessary to cool the surface layer of the rim with a speed higher than the optimal offered [1], and this will lead 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 [2], which includes heating to a temperature austenite the AI, 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. In the future, the supply of coolant to the surface of the wheel is produced at a constant flow rate.

When using this method partially aligned properties of the metal wheel rim at its depth. The disadvantage of this method is that during the first and subsequent pulses in the superficial layers of metal in the carbon content of more than 0,65-0,67% time to cool down before the end of martensite transformation.

Closest to the technical nature of the claimed (prototype) is a method of heat treatment of railway wheels [3], which 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 throughout the depth of cooling is carried out with a specific consumption of the chiller first 0,009-0,01 l/(cm2/C) for 80-30, then 0,015-0,018 l/(cm2/C) for C and 50-70 next 0,009-0,01 l/(cm2/s). With this method it is impossible to ensure close the cooling rate of the outer layer and the inner the indoor layers of 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.

The technical result of the invention is to improve the wear resistance of the working layer of the rim through the creation of a homogeneous structure oncoplastic perlite directly on the surface and at the depth of the rim and an increase in mechanical properties of the disk due to differential cooling 3 elements of the rim (2 end rim and the circle of Catania) independently from each other.

The technical result is achieved by the fact that the claimed method of heat treatment of railway wheels includes heating to a temperature of austenization are determined, differential cooling of the working layer of the rim and its end side of the ridge within 300 C, while the cooling of the working layer of the rim in the first 180 is carried out at discrete increase the flow of coolant from 0.0005 to 0.02 l/(cm2/s) of 0.0001 l/(cm2/with) every 15-30 s and in the next 120 seconds at a constant flow rate of coolant to 0.5 l/(cm2/C)and the cooling end surface of the rim from the side of the ridge carry out air with a flow rate of 0.5 m3/(cm2/s), then the wheel is cooled in the air and spend the holiday.

Distinctive features of Appl is imago method is:

- a smooth increase of consumption in the first 180 seconds;

is equal to the speed of the cooling zones of the rim due to the fine adjustment of the nozzle location relative to the surface of the rim and programmable flow cooler on each element of the rim.

Due to the inventive solution it is possible to provide the same 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. This is due to the following. The outer layer is cooled with a low consumption, however, sufficient to obtain the optimal structure of the metal in the form of fine lamellar pearlite without martensite vacation. Layers at a depth of 30-50 mm also cooled with a speed close to the optimum, due to the increase of the coolant on the outer layer.

Optimal consumption for all elements of the rim and the time is determined beforehand by experiment as consumption required to obtain the necessary properties at a depth of 30-50 mm

An example of executing.

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

After heating to a temperature of austenization are determined wheels farmstead, which was regalis hardening. Hardening of the wheels were made when the rotation speed of 30 rpm Total time surface cooling of the rim - 300, discrete cooling of the rim - the first 180 s, the initial specific discharge cooler - 0,0005 l/(cm2and /or its discrete increase to the optimum specific consumption of the chiller is 0.019 l/(cm2/C) with an increase of 0.0001 l/(cm2/s), and then in the subsequent 120 s after reaching the specific consumption of the chiller 0,0185-0,019 l/(cm2/s) at constant consumption 0,033 l/(cm2/s), together with the cooling of the end surface of the rim from the side of the ridge the air specific flow rate of 0.5 m3/(cm2/s). The hardening parameters wheels by the present method are shown in table 2, the results of testing the mechanical properties, hardness and microstructure are shown in table 3.

Cooler for quenching rim was supplied through the valve block, accessed by a given program cooling on three water-cooling loop and one loop air cooling, which was programmed time intervals, the degree of opening of the water and air valves. This ensured a smooth growth of consumption from the initial value to the optimum. After quenching wheel was subjected to cooling during transportation to the vacation furnaces and leave at the optimum temperature.

For comparison of the proposed and known way of quenching [2] table 2 shows the cost parameters are cooler and table 3 - results of mechanical testing, hardness, microstructure of the hardened layer by the present method and the method prototype.

Wheels, hardened by the present method, all of the bottoms at depths of up to 30 mm have a structure fine lamellar pearlite, evenly rolling at a depth of 50 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.

Sources of information

1. A.S. 724583. A method of manufacturing a solid-rolled railway wheels. Applicants: ISI, NTRP, NTMK. Publ. 30.03.1980, bull. No. 12.

2. A.S. 1425229. A method of manufacturing a solid-rolled railway wheels. Applicant: NTRP. Publ. 23.09.1988,, bull. No. 35.

3. Patent 2140997. Method of heat treatment of railway wheels. Applicant: JSC "Vyksa steel works". Publ. 10.11.1999,

The method of thermal ababadeclaration wheels includes heating to a temperature of austenization are determined, differential cooling of the working layer of the rim and its end side of the ridge within 300 C, while the cooling of the working layer of the rim in the first 180 is carried out at discrete increase the flow of coolant from 0.0005 to 0.02 l/(cm2/s) of 0.0001 l/(cm2/with) every 15-30 s and in the next 120 seconds at a constant flow rate of coolant to 0.5 l/(cm2/C)and the cooling end surface of the rim from the side of the ridge carry out air with a flow rate of 0.5 m3/(cm2/s), then the wheel is cooled in the air and spend the holiday.



 

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