SU1433985A1 - Method of thermal treatment of railway axles - Google Patents

Abstract

The invention relates to the heat treatment of steel and can be used in the manufacture of railway axles. The purpose of the invention is to increase the service life by eliminating the formation of tensile axial residual stresses in sub-axle parts. The essence of the invention is that after heating the entire axis to the austentiation temperature, the cooling of the neck, the pre-shaped front-seat and central parts of the axis are carried out separately, starting with the front-seat part, and when the surface reaches 400-450 ° C, the other parts are cooled. axis. 1 tab. with (L

Description

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The invention relates to the heat treatment of steel and can be used in the steel industry in the manufacture of railway axles.

The purpose of the invention is to increase the service life by eliminating the formation of tensile axial residual stresses in the wheelrests of the axle.

The essence of the invention is that after heating the axis to the austenization temperature, cooling under the hub and other parts is carried out separately, with cooling of the cervical, pre-stage and central parts begin upon reaching the surface of the front-seat parts with a temperature of 400-450 ° C.

Cooling in the first stage of processing only the wheelrests of the axle eliminates the disadvantage of the known method, since the thermal field arising during such cooling eliminates the possibility of the formation of tensile residual axial stresses in the front risers and ensures the formation of compressive axial residual stresses, the magnitude of which depends on the intensity filing chiller.

The cooling of the front-facing parts before cooling the remaining parts of the axis upon reaching a surface temperature of 450 ° C ensures that a temperature gradient occurs in the axis sufficient to eliminate the possibility of the formation of unfavorable axially axial residual stresses in the front-facing parts.

Cooling the surface of the front-seat parts below is impractical, since it does not lead to an increase in the positive effect, but it lengthens the rest before cooling the other parts of the axis. In addition, when cooling the wheelrests below 400 ° C, the risk of quenching cracks in their fillets increases.

Example. Used billet axles made at the Dnieper metallurgical plant (Dneprodzerzhinsk) of steel containing elements,%: C 0.46; Mp 0.83 Si 0.29; P 0.034; S 0.035.

All axes are heated in an electric furnace: to temperature. Part of the axes is sprayed cooled over the entire surface with a water supply rate of 0.2 m / m C. At that,

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cooling with water begins with the front-facing parts and leads in five variants until their surface layer reaches a temperature of 350,400,420,450 and for 26, 23, 10, 18 and 15 seconds, respectively. Temperature control is carried out using a thermocouple set at a depth of 3 mm from the surface. Then the whole axis is cooled with the same intensity of water supply for 100 seconds until the average temperature reaches 400 ° C. In addition, the axes are heat treated by a known method. To do this, the axis heated to 850 ° C is cooled in a water bath by dipping it at 0.25 diameter with rotation relative to the axis of rotation, which is parallel to the surface of the water for 210 seconds until the axis reaches average temperature. The axes formed by these two methods are released at a temperature of 500 s for 1.5 hours.

5 Residual stresses on the surface of the axis are determined in a destructive way by cutting templates with rosettes of strain gauges of type 2KB with a base of 10 mm with strain measurement using

0 digital tensometric bridge DTM-5.

The results of the experiments are presented in the table.

The obtained results show that during the heat treatment of the axles according to the proposed method with the beginning of cooling of the cheek, the central and pre-stage parts, when the surface of the front-seat parts reaches a temperature within 400-450 C (options 2, 3 and 4 in the table), a positive effect is achieved due to the formation of compressive axial residual stresses in the surface layers of the wheelrests.

Going beyond the proposed TeNfflepaTyp interval does not achieve a positive effect. Upon precooling of the wheelrests to 350 ° C (option 1), compressive axial residual stresses (-120 MPa) are formed in their surface layers, however, unfavorable tensile axial residual stresses of +50 and +60 are formed in the frontal and central parts. - Sha, respectively, reducing the operational reliability of the axis.

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Pre-cooling of the sub-portion to (option 5) is not enough to form compressive axial residual stresses in its surface layers.

During heat treatment according to a known method, tensile axial residual stresses (+80 MPa) are formed in the wheel seat, reducing the ability of steel to resist the nucleation and growth of fatigue cracks.

Thus, the proposed method of heat treatment of railway axles increases their operational reliability by increasing the strength characteristics and eliminating the formation of tensile axial residual stresses in the axle section of the axle, reducing the ability of the material to resist the nucleation and growth of fatigue cracks.

Claims (1)

Invention Formula The method of heat treatment of railway axles, including heating the neck, having a pre-wheelchair, front-wheel seat and central parts, to the austenitization temperature, water cooling, tempering, characterized in that, in order to increase the service life by the formation of tensile axial residual stresses in the front wheel axle parts, cooling of the cheek, pre-stage, front-wheel seat and central parts are carried out separately, starting with the front end, and upon reaching its surface temperature of 400-450 C, cool the remaining parts of the axis. 0.65 0.70 0.65 0.70 . 0.65 0.60 0.65 0.60 0.70 0.70 0.70 0.70 0.65 0.65 0.65 0.65 -110 -90 -90 -95 -too -85 -85 -85 -100 -85 -90 -90 -90 -80 -80 -80 -120 -5 +50 -60 +5 + to + 15 -50 + 15 -45 +5 + 15 + t5 famous Prvdpodstupa tsa775 Central 770 Approach tsa660 Sheika660 Pre-suit Tsentrvl d 660 510 510 390 385 24,051.0 23,552.0 28.05t, 0 26,053.0 385 27.0 52.0 385 27.5 52.5 51.0 52.0 5t, 0 53.0 52.0 52.5 205,200 184,184 184 184 0.70 0.65 0.60 0.70 about 60 0.60 -85 -80 -90 -80 -75 -85 -five 4-10 1-80 -10 -5 +5