SU1433992A1 - Method of heat treatment of railway vehicle wheels - Google Patents

Abstract

The invention relates to the field of metallurgy, specifically to methods of heat treatment of railway wheels. The aim of the invention is to increase the fatigue strength of the disc and compressive residual stresses in the rim. The method includes austenitization, hardening of the rim, tempering, cooling of the middle part of the disk from tempering temperature to 200-300 ° C and final cooling. The method allows to increase the operational durability of the wheels and the fatigue strength of the disk. 1 tab.

Description

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with

The invention relates to metallurgy, specifically to the heat treatment of solid-rolled railway wheels, with

The purpose of the invention is to increase the intrinsic strength of the disk and compressive residual stresses in the rim. The method includes stripping} the hardening of the rim and tempering, cooling the) of the middle part of the disk from the tempering temperature to the temperature by 200-300 ° C below the rim temperature and final cooling.

Primer p. The wheels were machined with a diameter of 950 mm, manufactured in a wheel-rolling shop made of steel with a% content; C, 0.58; Mp 0.78; Si 0.39,

The wheels were heated in electric furnaces up to 20 ° C at 850 ° C for 1.5 hours, and the rim was cooled in a hardening machine from Spayron for 130 seconds at a water pressure of 5 atm.

Some of the wheels were subjected to tempering at a temperature of 500 ° C for 1.0 h. Immediately after the tempering, the wheel disks were cooled with compressed air at a specific flow rate of 0.1 (under normal conditions) in several versions. The middle part of the disk 120 mm wide was cooled to reach temperatures of 300, 250, 200, 150, respectively, for 200, 350, 470, 630 and 740 s, respectively (options 1-5, respectively). For two wheels, the entire surface was cooled by compressed air. disc for 10 minutes until temperature Q is reached (option 6). The average temperature of the rim for all variants at the end of the disk cooling with air was 450 ° C. Then the wheels were cooled in the air in calm air to normal temperature.

In addition to toga 5, heat treatment is performed using the known method (option 7). For this, part of the wheels after thermo strengthening of the rims was cooled in the workshop in calm air to a temperature of ambient air (for 4.5 hours), then the rims of the wheels were heated in a stepwise manner on a thermal induction stand. Each step was heated for 10 seconds before and made for 50 s. Over the 7th hub, the rim was heated to 490 ° С (at a depth of 5 mm from above

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About Q

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post Katani), and in places where the rim goes to the disk - up to 280-290 C.

Determination of residual stresses in the wheel disk was carried out in a destructive way using cutting templates with strain gauges (type 2KB with a base of 10 mm) using the digital strain-gauge bridge CTM-5. The residual stresses in the rim were estimated using the method of the international standard UIC812-3 by radially cutting the wheel and measuring the initial distance (1,100 mm) between fixed points on the rim on both sides of the cut. The standard requires that the distance be reduced to at least 1 mm. The measurement results are shown in the table.

The proposed method of heat treatment of wheels (options 2, 3, and 4) enhances the fatigue strength of a disk by creating compressive residual stresses in the side of the disk. The output of the heat treatment parameter over the specified interval — cooling the middle part of the disk until the temperature difference between the rim and the middle part is reached — does not ensure the formation of compressive stresses in the auxiliary part of the disk (option I),

Cooling the middle part to achieve a temperature difference between the rim and the middle part of the disk at 350 ° C (option 5) provides for the formation in the side of the disk from the inner side of the reducing residual stresses, but leads to a decrease in the value and proportion of compressive stresses in the rim below the allowable limits as evidenced by the estimation of residual stresses in the rim Oil (0.9). Cooling the entire disk (option 6) to achieve a temperature difference between the rim

Q

And a disk already at 200 ° C leads to favorable stresses in the disk, but stresses in the rim become unacceptable - d1-0.7 mm. Additional heat treatment by a known method (variant 7) ensures the formation of residual stresses in the S disk, which increase its mouth strength. At the same time, compressive residual stresses in the rim are reduced in magnitude, but remain within acceptable limits. To reduce the duration of additional processing by the proposed method by 3-4 times, it is possible to use the air / air mixture when cooling the middle part of the disk.

Thus, the proposed method of heat treatment of railway wheels simplifies the process of creating residual stresses in a disk, increasing its fatigue strength and eliminates the need to use additional sophisticated equipment, the use of which is proposed by a known method.

Claims (1)

Invention Formula The method of heat treatment of railway wheels, including heating to austenitizing temperature, intermittent hardening of the rim and tempering, characterized in that, in order to increase the fatigue strength of the disk and compressive residual stresses in the rim, after tempering, the middle part of the disk is heated to 200 - lower rim temperature and final wheel cooling.