RU2353672C1 - Method of thermal strengthening of railway wheels - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: invention relates to thermal treatment field. For providing of solidity not less than 300 HB on depth not less than 50 mm from surface of volution wheel tread, exclusions during the process of cooling of formation of hardening structures and providing of maximal drop of residual voltage, solid-rolled wheels made of steel with carbon content no less than 0.60 wt % is heated till the austenitising temperature and intensively cooled, at that during the cooling process from the moment of the beginning for 50-100 seconds it is implemented increasing of cooling intensity of comb roll surface and side surfaces of crown by all height from 0 till value 2-3 W/(cm²·s), then it is cooled during 40-300 sec with constant refrigeration rate of specified wheel face equal to value 2-3 W/(cm²·s) for providing of strengthening in all crown volume.

EFFECT: providing of material strengthening.

2 dwg, 3 tbl

Description

The invention relates to the heat treatment of steel products and can be used in the manufacture of railway solid-rolled wheels of steel with a carbon content of at least 0.60%.

A known method of thermal hardening of railway wheels, see G. Bibik and other production of railway wheels. M .: Metallurgy, 1982, p. The specified technology of thermal hardening of the wheels includes heating them to 840-870 ° C uniformly throughout the volume depending on the content of carbon and manganese in the steel, transferring the heated wheel to the quenching machine with a minimum time interval specified in the regulatory documentation.

The use of such technology provides a low level of strength properties of the metal and wear resistance of the rim during operation.

Of the known technical solutions, the closest in technical essence to the claimed method is a method of heat treatment of railway wheels, see.with. USSR No. 549485, cl. C21D 9/34, 1977, which is selected as a prototype. This method includes heating the railway wheels to a temperature of Ac ₃ + (30-50) ° C, aligning the temperature of the inner and surface zones of the rim by holding it at a temperature of Ac ₃ + (30-50) ° C, thermally hardening the rim by cooling it with water, reducing temperature of the wheels by freezing in the air and their subsequent vacation.

The disadvantage of this method is the fact that at the moment of termination of cooling, quenching structures (up to 100% martensite), plastic deformations, as well as a high level of tensile stresses are formed in the surface zones of the rim, which increases the likelihood of cracking at the end of cooling. It is possible to determine the stress-strain and structural state of the wheel rim at various points during the cooling stage only by computer simulation methods.

The technical result of the invention is to improve the properties of the material of railway seamless wheels - steel with a carbon content of at least 0.60%, namely, providing a hardness of at least 300 HB at a depth of at least 50 mm from the surface of the wheel rim with the exception or maximum reduction during cooling quenching structures and the maximum reduction in residual stresses at the time of quenching.

To achieve a technical result in the cooling process from the moment of its start, in 50-100 seconds there is a gradual increase in the cooling intensity of the skating surface, ridge and side surfaces of the rim over their entire height from 0 to 2-3 W / (cm ² · s), then cooling continues for 40-300 seconds with a constant intensity of cooling of the indicated surfaces of the rim equal to the value of 2-3 W / (cm ² · s) to ensure hardening in the entire volume of the rim.

The invention is illustrated by the accompanying drawings, where:

- figure 1 shows the location of the zones of assessment and comparison of the stress-strain state in the radial section of the railway wheel for various variants of hardening technology;

- figure 2 shows a typical temperature distribution in the radial section of the railway wheel at the time of completion of quenching (see table.).

The wheel rim (see Fig. 1) in radial section is divided into the following zones: 1 - skating surface, 2 - zone under the skating surface at a depth of 10-20 mm, 3 - crest top, 4 - crest base, 5 - middle of the inner side side of the rim, 6 - the rim angle from the inside, 7 - the zone near the transition from the rim to the disk, 8 - the angle from the outside of the rim at the tread surface, 9 - the middle of the outer side of the rim, 10 - the rim angle from the outside.

The material in these zones differs in the structural state, values of temperature, cooling rates, stresses and strains during and after quenching.

In addition, 3 tables are given in the description of the invention. In the tables for the indicated zones after quenching, the following parameters are presented:

B - the content of the hardening structure of bainite,%;

M is the content of the quenching structure of martensite,%;

HB - Brinell hardness, MPa;

σ _r , σ _o and σ _θ are respectively radial, axial and circumferential stresses, MPa;

σ _i - stress intensity, MPa;

ε _i ^PL - the intensity of plastic deformation,%.

The essence of the proposed method is as follows. The wheel is completely heated to the austenization temperature Ac ₃ + (30-50) ° C, and the temperature of the inner and surface zones of the rim is equalized. Further, according to the developed method, thermal hardening of the rim by intensive cooling and wheel tempering are carried out.

Hardening is carried out with a gradual increase in the cooling intensity from the surface of the wheel rim from zero to a maximum value that corresponds to 2-3 W / (cm ² · s), according to a linear or nonlinear law, for 50-100 seconds, followed by cooling of the rim at the maximum cooling intensity for 40-300 seconds. The time of change in the cooling intensity determines the magnitude and nature of the stress distribution in the entire volume of the wheel at the time of hardening.

Comparative calculations of the above parameters at the end of hardening for the method chosen as a prototype (see table 1) and the inventive method for different time of rise of the cooling intensity (see tables) were carried out by simulation and computer simulation methods that passed the necessary certification and verification. 2 and 3).

Table 1
Hardening time 160 s, the cooling rate is constant and corresponds to the maximum value of 2-3 W / (cm ² · s) Zone number M% HB, MPa σ _r , MPa σ ₀ , MPa σ _θ , MPa σ _i , MPa ε _i ^pl ,% one up to 97 6070 ~ 0 -1700 -1800 1750 1,6 2 - 3550 ~ 0 429 483 400 ~ 0 3 up to 97 6200 179 -850 -1300 1300 0.7 four - 3920 617 -179 711 850 ~ 0 5 up to 97 6070 -570 ~ 0 483 1450 0.7 6 up to 97 6070 -900 ~ 0 254 900 0.5 7 - 3200 -40 -179 254 41 ~ 0 8 - 6070 -0 214 480 1450 0.8 9 up to 97 6070 400 ~ 0 480 1450 1,6 10 up to 97 6070 ~ 0 ~ 0 480 1100 1,0

table 2
Hardening time 160 s, cooling rate increases from 0 to a maximum value of 2-3 W / (cm ² · s) for 40 s Zone number M% HB, MPa σ _r , MPa σ _about , MPa σ _θ , MPa σ _i , MPa ε _i ^pl ,% one up to 35 5100 ~ 0 -700 -550 630 0.008 2 0 3300 ~ 0 470 315 450 ~ 0 3 up to 49 5500 ~ 0 ~ 0 -340 350 0.08 four 0 3600 280 ~ 0 650 540 ~ 0 5 up to 21 4800 -620 ~ 0 -200 540 ~ 0 6 until 11 4800 -210 ~ 0 -200 270 ~ 0 7 0 3300 ~ 0 ~ 0 -120 170 0.02 8 up to 55 5500 120 80 -300 360 0.008 9 up to 25 5100 -700 ~ 0 -120 540 0.008 10 up to 25 4800 ~ 0 ~ 0 -120 200 ~ 0

Table 3
Hardening time 160 s, cooling rate increases from 0 to a maximum value of 2-3 W / (cm ² · s) for 60 s Zone number M% HB, MPa σ _r , MPa σ _about , MPa σ _θ , MPa σ _i , MPa ε _i ^PL ,% one before 18 4900 ~ 0 -430 -240 280 0.02 2 ~ 0 3500 ~ 0 390 300 390 ~ 0 3 up to 30 4900 ~ 0 -one hundred -80 119 0.02 four ~ 0 3500 320 ~ 0 600 550 ~ 0 5 ~ 0 4300 ~ 517 0 -one hundred 500 ~ 0 6 ~ 0 4300 ~ 150 0 -one hundred 220 ~ 0 7 ~ 0 3200 ~ 0 ~ 0 -one hundred 120 0.02 8 up to 36 5300 ~ 0 -200 -one hundred 120 0.02 9 ~ 0 4600 -500 ~ 0 -one hundred 550 0.02 10 ~ 0 4600 -160 ~ 0 140 280 ~ 0

Comparing the values of the parameters given in tables 1-3, we can conclude that in all working (contacting with the rail) zones of the wheel rim with an increase in the rise time of the cooling intensity:

- tensile stresses at the end of cooling are reduced several times;

- the amount of martensite in the crest of the rim, subject to the most intense wear, decreases from 97% to values in individual zones from 0% to 30%;

- the intensity of plastic deformations decreases from 1.6% to almost 0.

As calculations showed, in the inventive method, in order to achieve the greatest efficiency, it is recommended to choose the value of the rise time of the cooling intensity in the range from 50 to 100 seconds. A further increase in the rise time of the cooling intensity is impractical due to a decrease in the hardness and mechanical characteristics of the metal of the wheel rim.

Claims (1)

The method of thermal hardening of railway wheels made of steel with a carbon content of at least 0.60 wt.%, Including heating the wheel to austenization temperature Ac ₃ + (30-50) ° C, aligning the temperature of the inner and surface zones of the rim, hardening the rim by intensive cooling and wheel tempering, characterized in that from the moment the cooling starts for 50-100 s, a gradual increase in the cooling intensity of the skating surface, ridge and side surfaces of the rim along their entire height from 0 to 2-3 W / (cm ² · s), and then cooling pro should be kept for 40-300 s with a constant cooling rate of the indicated rim surfaces equal to 2-3 W / (cm ² · s), to ensure hardening in the entire volume of the wheel rim.

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