The method of thermal treatment of steel wheels

 

(57) Abstract:

The invention relates to metallurgy and mechanical engineering, in particular to methods of heat treatment of steel stamped-rolled railway and crane wheels. Applying the method of heat treatment comprising heating to a temperature of austenization are determined, the shutter speed differential cooling of the rim with water to a temperature of Mn+(30-50o(C) with speeds close to the critical speed quenching to martensite, next to the temperature 240-300oWith speeds of 1-2oC/C and tempering at a temperature 30050°C. Implementation of this method of treatment allows wheels with high abrasion and heat resistance due to the layered design of the structural state of the metal of the wheel rim with the desired properties. 4 Il., table 1.

The invention relates to metallurgy and mechanical engineering, in particular to methods of heat treatment of steel rail and crane wheels.

The known method of heat treatment of railway wheels, comprising heating to a temperature of austenization are determined, intermittent quenching rim, podstugivaniya on the air for 35-45 min, and tempering at a temperature of 450-500oC /1/. Wheels treated by this silent hill 2">

There is a method of heat treatment of steel wheels, comprising heating to a temperature of AC3+(30-50oC), the shutter speed, the cooling water to a temperature of Mn+(300-350oC) at a speed of not less than 0.03oC/s, vacation /2/. Differential cooling of the wheel rim contributes to the improvement of the strength properties of the metal of the wheel rim, but the level does not provide a high service life of the wheel due to the low abrasion and heat resistance.

The closest to the technical essence of the proposed solution is the method of thermal treatment of steel wheels, comprising heating to a temperature of AC3+(30-50oC), the shutter speed differential cooling of the rim with water to a temperature of Mn+(300-350oC) at a rate of 10-15oC/sec, then cooling to a temperature of 320-420oC at the rate of 1-2oC/s and vacation /3/. The implementation of this method allows to increase the hardness of the strip skating wheels due to the formation sites with the structure of martensite tempering at the plastic characteristics. The disadvantages of this method are that the wheels, heat treated by the method prototype have:

- low wear resistance, requiring regrinding up to 50% ekspluatiruemykh layers wheel rim), the degree of dynamic effects and the resulting contact stresses, especially at higher speeds composition and axle load;

- low temperature resistance, expressed in cracking and spalling of the surface layer due to heating of the strip Catania due to plastic deformation of the near-surface layer under the influence of frictional forces during braking and movement locked wheel skidding.

The purpose of the proposed solutions is to develop a method of heat treatment of steel wheels with high wear and heat resistance, high operational durability of the wheels, especially in terms of increasing the speed of the motion and axle load.

This goal is achieved by applying the method of thermal treatment of steel wheels, comprising heating to a temperature ANDC3+(30-50oC), the shutter speed differential cooling of the wheel rim with water and leave. Features of the proposed method lies in the fact that differential cooling of the wheel rim water are at the first stage to a temperature of Mn+(30-50oC) at a speed close to the critical one for quenching to martensite, then, in the second stage, to a temperature of 240-300o

Change cooling parameters affect the process of decomposition of austenite grains in the surface and deep layers of the metal wheel rim. So in the surface layers, cooled more intensively, the formation of the structure of martensite hardening and deep layers of the structures of the intermediate decomposition of austenite with a high degree of dispersion. Regulated slow cooling when the temperature of the wheel rim Mn+(30-50oC) contributes to the alignment of thermal gradient, prevents warping, cracking and smoothmuscle reinforced rim.

In the process of tempering at a temperature 30050oC the conditions of fixation martensitic structures in the surface layers of the metal wheel rim.

Thus f is however associated with a layer, educated superfine intermediate products of the decomposition of austenite (Fig. 2 and 3), smoothly transitioning into the layer of perlite with minor areas of free ferrite (Fig. 4). This achieves a uniform high hardness throughout the cross section of the wheel rim while maintaining the level of plastic characteristics. With increasing hardness increases abrasion resistance, and the zone of plastic deformations in the surface layers of the rim is reduced, shifting in the depth of the rim. As a result, when braking and movement locked wheel skidding heat and, as a result, recrystallization of the surface due to plastic deformation of the near-surface layer, which causes the resolution of the surface, does not occur, thus ensuring high wear and temperature resistance of the wheel rim in terms of increasing the speed of the motion and axle load.

The inventive method was tested in OJSC VMZ in the manufacture of a pilot batch (700 PCs) rail wheels.

Source material served laminated wheels of steel grade 2 (GOST 10791-89). Wheels of steel-one of melting thermoablative by means of analogue /1/, prototype /3/ and claimed. Temped to a temperature of Mn+(30-50oC), i.e., 310-330oC, was performed at a speed of 100oC/s, and temperatures of 240-300oC at the rate of 1-2oC/S. the Vacation was carried out at a temperature 30050oC for 2.5 hours.

During hardening of the wheels by the present method the moments of change of the quenching rates were determined from the readings, recording the temperature of the surface of the wheel rim. The intensity of cooling was achieved by changing the pressure of the quenching water. Testing of mechanical properties of the samples was carried out according to GOST 10791, testing thermal stability of the samples was carried out according to the method of transport. The results are given in the table and allow us to draw the following conclusions.

The inventive method of heat treatment of steel wheels, modifying parameters quenching and tempering in comparison with analogues allows you to produce railway wheels with high abrasion and heat resistance by creating layers of a given structural composition of the metal wheel rim: the surface - layer tempered martensite with maximum hardness and the depth of the rim transition structures with high hardness while maintaining the level of plastic characteristics, which is confirmed by the old N 1237716, C 21 D 9/34. BI N 22, 1986.

3. A. S. USSR N 575374, C 21 D 9/34. BI N 37, 1977.

4. Bibik, A., Joffe, A. M., Holidays A. C., Staroseletskaya M. I. Production of railway wheels. M.: Metallurgy, 1982.

The method of thermal treatment of steel wheels, comprising heating to a temperature of austenization are determined, the shutter speed differential cooling of the rim with water and leave, characterized in that the cooling from the temperature of austenization are determined lead to Mn + (30 - 50)oWith speeds close to the critical speed quenching to martensite, and then to 240 - 300oWith speeds of 1 to 2oWith a/C and tempering is carried out at a temperature of 300 50oC.

 

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