Method of heat treatment of the wheel

 

(57) Abstract:

The invention relates to heat treatment of steel and can be used in the manufacture of solid-rolled railway wheels. The technical result is more effective removal of hydrogen from the metal wheels and improvement of technical and economic indicators of their production. It is solved by a method of heat treatment of the wheel in the process of their production, including the heating of the billets under deformation, rolling wheels in a hot state, isothermal exposure, termouprochnenija, vacation, hypothermia wheels, exposure to air and cooling to ambient temperature, according to the invention of the original piece and wheels, from heating under deformation to leave heat-treated wheels are subjected to continuous heat treatment with dual hypothermia and exposure to the air, after rolling and the first cooling and exposure to air wheels heated to a temperature of austenitization, and after heat strengthening, and the second hypothermia and exposure to air carry out combined operations leave and isothermal aging, and in the process of hypothermia wheels teneale lead temperature 350oWith combined operations leave and isothermal aging is carried out for 3.0 to 3.5 h, and the shutter speed of the wheels in the air after hypothermia produced within 0,5 - 0,8 h 1 C.p. f-crystals, 1 Il., table 1.

The invention relates to heat treatment of steel and can be used in the manufacture of wheels for railway transport.

Known production technology of solid-rolled wheels [1] include the operation protivogololednoy processing (isothermal aging) after rolling. She is aging at a temperature of approximately 600oC in a heated furnaces within 2-3 hours. It is assumed that at moderate (2-3 cm3/100 g) content of hydrogen in steel flakey in metal finished products should not be produced. After isothermal exposure wheel is cooled to ambient temperature over several days are cold processing (inspection, repair, machining) and then again subjected to heat treatment (heating for quenching and tempering).

The process of removing hydrogen from laminated metal consists of two stages [2]:

1) Distinguishing it from the solution, which is the more intense, the lower tall.

In this regard, it is rather useful hypothermia wheels after rolling up to 300-350oC, thereby accelerating the release of hydrogen from a solution of its in-gland, and then heated and kept at the maximum possible temperature when the rate of diffusion from a metal will be the greatest.

As a prototype adopted a known method of thermal processing of the wheels in the process of their production, which includes heating of the billets under deformation, rolling wheels in a hot state, isothermal exposure, termouprochnenija, vacation, hypothermia wheels, exposure to air and the cooling wheel to the ambient temperature [3]. In heat treatment of the wheel is formed of a technological break - cooling wheel to the ambient temperature after isothermal aging. Adopted the term "hypothermia" wheels means reducing the temperature to a value no lower than 300-350oC, below which, under appropriate conditions, the formation of platanov very likely.

The process sequence of the prototype the following (table 1, drawing). The original piece is heated in the annular furnace to a temperature of 1280oC, rebuff and molded, the wheel podslushivaet on the conveyor and in the feet maintained at a temperature of 350-450oC, then placed in heated wells for protivolavinnoj processing - isothermal aging in air for 2.5 hours at a temperature of 600oC. Upon completion of this operation the wheel is put into the warehouse, where cool down to the ambient temperature of the shop (20oC). This ends the main heat treatment of the wheel, which helps to remove hydrogen from the metal. With increased content of hydrogen in steel wheel (more than 3 cm3100 g of metal) plopeni are formed during the cooling of the wheels below 300oC, i.e., after isothermal aging. Stock finding wheels in the cold time is not regulated (almost 2 to 5 days) and during this time are subject to inspection, repair, machining. Then the wheel is heated in the annular furnace to a temperature of austenitization (900oC), cooled in a quenching machines to a temperature of 500oC and subjected to vacation in heated wells at a temperature of 550oC for 2.5 hours. After the holidays wheels put feet to the warehouse, where they are cooled to ambient temperature (20oC). During thermal hardening is observed distortion of the profile of the rim to the fir wheels about 10%.

The main disadvantages of the technologies under consideration: increased energy consumption during heating "cold" wheels under termouprochnenija 20oC; the need for additional warehouse space for storage of wheels after isothermal exposure, after inspection, after repair after mechanical treatment; the need for re-inspection, measurement and repair after the heat treatment for distortion of the profile of the rim; the formation of placenow in the metal rim when the cooling wheels after isothermal aging.

The objective of the proposed method is more effective removal of hydrogen from the metal wheels and improvement of technical and economic indicators of their production.

This problem is solved due to the fact that in the method of heat treatment of the wheel in the process of their production, including the heating of the billets under deformation, rolling wheels in a hot state, isothermal exposure, termouprochnenija, vacation, hypothermia wheels, exposure to air and cooling to ambient temperature, the original piece and wheels, from heating under deformation to leave heat-treated wheels are subjected to continuous heat treatment with double PE wheel is heated to a temperature of austenitization, and after heat strengthening, and the second hypothermia and exposure to air carry out combined operations leave and isothermal aging, and in the process of hypothermia heated wheels after rolling to a temperature of austenitization carried out from a temperature of 350-450oC, combined operations leave and isothermal aging is carried out for 3.0 to 3.5 hours, and the shutter speed of the wheels in the air after hypothermia produced within 0.5 to 0.8 hours.

The invention is illustrated in the drawing, which shows the graphs discontinuous (1) and continuous (2) heat treatment of the wheel.

The distinguishing features of the claimed method are:

Continuous thermal processing of the wheels, without intermediate cooling, heating of the billets to leave the wheels.

Double hypothermia metal wheels 350oC aged in air at this temperature.

Heated wheels after rolling, hypothermia and exposure to the temperature of austenitization.

The implementation of combined operations leave and isothermal aging after heat strengthening.

Limiting the temperature of the cooling wheel size 350oC.

On vacation and isothermal exposure for 3.0 to 3.5 hours.

The implementation of the extracts of the wheels in the air after cooling for 0.5 to 0.8 hours.

The method consists in the following (table 1; the drawing). After rolling wheels and lowering the temperature of the metal from 1280 to 900oC carry out the first hypothermia and exposure in air at a temperature of 350oC for 0.5 to 0.8 hours. Then the wheel is heated to a temperature of 900oC, again cooled (termouprochnenija) to a temperature of 350oC, kept in air for 0.5 to 0.8 hours (second subcooling) and again heated to a temperature of 550oC (vacation+isothermal exposure). The high content in steel hydrogen (>2 cm3per 100 g) such deep hypothermia metal wheels (350oC) with high temperature and subsequent rise, and double this process has a positive effect on the allocation to a safe level (less than 2 cm3100 g) of hydrogen. This is due to the necessity of guaranteed transformations of iron , as the preservation of individual sections of the austenite is not possible during isothermal aging in old technology to evacuate the hydrogen from metal and evenly distribute its residual content of the rim. The proposed Yunosti hydrogen from solution at low temperatures and in the process of diffusion at high temperatures.

Passed by the lower level of hypothermia 350oC is explained by the fact that flakey in the metal begin to form at temperatures slightly below 300oC. to ensure That you eliminate the formation of cracks in the metal, adopted a somewhat higher temperature hypothermia.

Conducting combined technological operations leave and isothermal exposure for 3.0 to 3.5 hours, i.e., adopted a slightly increased duration is due to the fact that the temperature of these combined operations 550oC (temperature, providing the required level of properties of the metal below the optimal temperature protivolavinnoj processing wheeled metal (600oC).

Exposure to air cooled wheels for 0.5 to 0.8 hours determined experimentally and corresponds to: 0.5 hours for steel with a maximum carbon content of 0.65%, 0.8 hour with a minimum carbon content of 0.55%.

The new technology of continuous thermal processing of wheels provides: guaranteed removal of hydrogen from the metal to the level of not more than 1 cm3100 g due to continuous, for 9-10 hours, the heat treatment of workpieces and wheels with two hypothermia (instead of 4.5-6.0 hours stremah selling of wells and reduction of intermediate warehouses, the complete elimination of repair wheels before their acceptance, since machining is carried out after thermal and dimensional variances are.

Example. In the manufacture of solid-rolled railway wheels 9577 mm initial workpiece weight 475 kg was heated in a rotary furnace to a temperature of 1280oC for 5 hours. They were two systems at the press of 3000 t, was formed on the press 7000 cu, rolled on the mill and grooved on the press 3000 TC. The temperature of the wheels was reduced to 900oC. for 20 min wheel was cooled on a belt conveyor to a temperature of 350oC, collected in the foot by 6 pieces and at this temperature was kept for 30 minutes Then the wheels were placed in a rotary furnace and heated to a temperature of 900oC for 2 hours, after which the hardening tables Thermopanel rim cooled water within 150 C) lowering the temperature of the rim 500oC. On the belt and the metal temperature was lowered to 350oC, collected in the foot by 6 pieces and held at this temperature for 30 minutes After the wheel stops were placed in heated wells, warmed up to 550oC and kept at this temperature for 3.5 hours (combined tempering and ISAT the water. In this condition, the wheels were inspected were subjected to repair and mechanically processed. Quality control flakey was absent.

Literature

1. Nodes And., and other Wheeled steel. Kiev, Tekhnika, 1985, S. 95-96.

2. Bibik, A. and others, the Production of railway wheels. M, metallurgy, 1982, S. 157-162.

3. Auth. mon. N 245826. The method of thermal processing W.D. wheels and discs. Bull. N 20, 1969 (prototype).

1. Method of heat treatment of the wheel in the process of their production, including the heating of the billets under deformation, rolling wheels in a hot state, isothermal exposure, termouprochnenija, vacation, hypothermia wheels, exposure to air and cooling to ambient temperature, characterized in that the source of the workpiece and the wheel, heated for deformation to leave heat-treated wheels are subjected to continuous heat treatment with dual hypothermia and exposure to the air, after rolling and the first hypothermia and exposure to air wheels heated to a temperature of austenitization, and after heat strengthening, and the second hypothermia and exposure to air carry out combined operations leave and isothermal aging, and about the decomposing those that heated wheels after rolling to a temperature of austenitization lead temperature 350oC, combined operations leave and isothermal aging is carried out for 3.0 to 3.5 h, and the shutter speed of the wheels in the air after hypothermia produced within 0,5 - 0,8 PM

 

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