A method of manufacturing a solid-rolled railway wheels

 

(57) Abstract:

The invention relates to metallurgy, in particular to the technology of solid-rolled railway wheels. The technical result of the invention is to improve the impact strength and fatigue limit of the metal of the wheel when surfacing with the rolling heat. The technical result is achieved due to the one - or bi-cyclic cooling of the disk and parcel of the transition in the rim and the hub when the wheel is in a vertical position in the quenching car, the temperature of the wheel rim before quenching is 940-780°C, and disk - 860-720°C, and the cooling of the disk and parcel of the transition in the rim and the hub produce compressed air at a pressure of 1-3 kgf/cm2and duration of cooling, respectively, is 2.0 to 0.7 of the length of the cooling of the rim. 2 C.p. f-crystals., table 4. 1 Il.

The invention relates to thermo-mechanical processing of rent, in particular to the technology of manufacture of railway wheels with padding from the rolling heat.

A known method of manufacture of railway wheels-hardening rolling heat used for domestic factories and abroad in the period of 30-50-x therefore the deformation of the workpiece by the press wheel and the mill, thermal hardening of the wheel rim on a horizontal table and the subsequent vacation in the pits.

The technology used in connection with the high temperature end of the deformation before hardening rolling heating (1050oC) indication of the low level of toughness of the drive wheel (1.0 to 2.0 kgs m/cm2). However, the levels of values of impact strength and resistance to brittle fracture at low temperatures of the wheel disc are key indicators of the reliability of the wheel in operation.

The method of manufacture of railway wheels with padding from the separate heating of the disk and the wheel rim has allowed to significantly improve the characteristics of the mechanical properties of the wheels, especially the impact strength and resistance to brittle fracture of the wheel at low temperatures, resulting in increased reliability of the wheel in operation [2].

However, the process by hardening with separate heating is a lengthy and time-consuming, which leads to the high cost of the wheel and accordingly reduces its competitiveness.

Closest to the present invention is a method of manufacture of railway wheels in which lnoe the wheel deformation of the workpiece by the press wheel and the mill with the end of the deformation at a temperature 950-850oC, the hardening of the wheel rim by the vertical dashed quenching and tempering, combined with the operation of isothermal aging [3] . In contrast to [1] this method allows you to regulate the structure of the disk and rim before hardening wheels for optimizing end temperature deformation on the aggregates forging-rolling line. This improved toughness values of the drive wheels to 2.0 to 3.0 kgs m/cm2when saving indicatorsin, and HB at a level appropriate to the hardening of the rim with separate heating.

The disadvantage of this method is the relatively low impact strength of the drive for smelting with carbon content at the level of 0.62 is 0.67%.

The task of the invention to provide a method of manufacturing a solid-rolled railway wheels with hardened with heating and rolling high impact strength and resistance to brittle fracture at low temperatures of the wheel.

The technical result to achieve toughness values of the disk at the level of 3.5 to 5.0 kgs m/cm2for the bottoms with the carbon to 0.67%, and increase resistance to brittle fracture at low temperatures of disc material to the second cooling disk and parcel of the transition in the rim and the hub when the wheel is in a vertical position in the quenching car the temperature of the wheel rim before quenching is 940-780oC, and disk - 860-720oC and cyclic cooling of the rim and areas of transition in the rim and the hub produce compressed air at a pressure of 1-3 kgf/cm2and duration, respectively, is 2.0 to 0.7 of the length of the cooling of the rim, and the regulation of the intensity of cooling of the disc and parcel of the transition in the rim and the hub is produced by changing the flow rate of compressed air at its constant pressure, with an increase of the carbon content within the steel grade compressed air consumption is reduced.

The invention consists in that the cyclical cooling of the drive wheel with compressed air causes structural changes in the metal disk, namely grinding grain perlite, uniform and dispersed distribution of ferrite on the diameter of the drive wheel, the reduction of distance between pearlite colonies in perlite, reducing the size of the pearlite colonies.

Increase the length of the boundaries of the actual grain pearlite colonies, and the boundaries between the ferrite and the main structure - perlite causes a sharp increase in toughness of the metal disk, and lowering the temperature of the fight the hardening of the wheel from rolling heat helps prevent the growth of austenite grains, formed during hot plastic deformation, due to the suppression of recrystallization processes hot-deformed austenite.

Limiting temperature interval before quenching rim and cyclic cooling of the disk within 940-780oC and 860-720oC due to the temperature of the end deformation of the rim and the wheel disc and the length of the pause between the end of the deformation and early hardening. The upper limit temperature of the rim and wheel disc before hardening according to the proposed method is 940 and 860oC, respectively, the lower limit temperature, respectively 780 and 720oC. Temperature before hardening 940 and 860oC corresponds to the upper temperature limit is the end of the deformation, equal to 960oC for rim and 880oC for the drive, as well as the minimum duration of the pause between the end of the deformation and hardening of the rim and the disk is equal to 30 seconds (the temperature drop of the rim and disc within 30 seconds is about 20oC).

Temperature before hardening 780 and 720oC corresponds to the lower temperature limit is the end of the deformation, equal to 880oC for rim and 820oC for the disk, and the maximum prodolzhitelnost within 150 seconds is about 100oC).

The feasibility of maintaining the temperature of the end of the deformation within 960-880oC for rim and 880-820oC for the disk considered in the application for invention N 97103043. The proposed temperature before hardening of the rim and disk allows you to form a grain size in the disk and the rim after hardening rolling heat corresponding to the heat with separate heating. The proposed parameters of the compressed air pressure and duration of cooling of the disc is shown on the damn hedgehog.

With increasing pressure from 1 to 3 kgf/cm2the ratio of the length of the cooling disk is changed from 2 to 0.7 of the length of the cooling of the rim. The proposed interval of air pressure allows to vary the cooling rate of the disk within the steel grade from 1 to 3oC/sec (constant flow rate of refrigerant per unit time).

For minimum carbon content within the steel grade (0,53-0,57%), appropriate use of limit values of the air pressure of 3 kgf/cm2and duration of cooling of 0.7 on the duration of the cooling of the rim, because with increasing supercooling in steel suppressed the release of excess ferrite, reduced especial cooling rate of about 3oC/sec. From the data of [4] implies that in a given range of cooling rates observed decreases ductility and toughness of the metal disk, and the lower critical temperature of brittleness.

For the bottoms with the average carbon content of 0.58-0.62 percent) within the steel grade, it is advisable to use more gentle cooling mode of the disk, namely: air pressure 2.0 kgf/cm2and duration of cooling of 1.0 on the duration of the cooling of the rim. The cooling rate is about 2oC/sec.

Accordingly, for the bottoms with a maximum carbon content (0,62-0,67%) recommended air pressure of 1 kgf/cm2and the duration of the cool disk 2.0 on the duration of the cooling of the rim. The cooling rate of the disk is about 1oC/sec.

Milder cooling disk for the bottoms with the average and maximum carbon content due to the need to exclude surface cracking of the disk due to the higher gradient of residual stresses. Upon cooling of the disk with a constant air pressure in all groups on the carbon duration of cooling of the disc is produce. The cooling rate of the disk is about 2oC/sec.

According to the proposed method for regulating the intensity of cooling of the disc and parcel of the transition in the rim and the hub are also produced due to the change of consumption of compressed air, with an increase of the carbon content within the grade of steel consumption is reduced. This mode of cooling of the disc is useful when cooling with a constant air pressure. Consumption adjust so that the cooling speed of the disk was within 1-3oC/sec. And for the bottoms with the maximum (0,63-0,67%), average (0,58-0,62%) and minimum (0,53-0,57%) carbon content within the grade of steel consumption vary so that the cooling speed of the disk on the listed groups of the chemical composition were respectively 1,0; 2,0 and 3,0oC/sec.

The proposed cooling mode disk provides for the formation of grains of perlite 7-8 points, it suppressed the secretion of a massive grid of excess ferrite by increasing the cooling rate of the disk. This causes the growth of the plastic characteristics, impact strength and fatigue limit of the drive wheel.

For implementing is-neigh carbon respectively 0,57, of 0.62 and 0.67% (the maximum value in each of the groups on carbon). Heating under deformation produced in a rotary furnace to a temperature of 1200oC. the Temperature of the end of deformation in accordance with the proposed method and the prototype, as well as the cooling of the disk and parcel of the transition in the rim and the hub with compressed air are given in table 1 (table. 1-4, see the end of the description). The length after deformation pause before hardening for all wheels produced in accordance with the current technological instruction. The mechanical properties of the rim and disc in accordance with the proposed technology and the prototype are shown in table 2. As shown, the mechanical properties of the wheels, made by the proposed method is higher than on the technology of the prototype. Temporary resistance metal disk above 5.8 kgf/mm2, rim - 3.3 kgf/mm2. The impact strength of the metal disk on the proposed method for all temperatures tested higher than on the technology of the prototype, so, at the test temperature +20oC - 1.9 times (average of 3 values), at 0oC - 1.8 times, -20oC - more than three times.

The regulation of the intensity of cooling of the disc and areas of transition in which ladenia drive when changing the flow rate of compressed air are given in table 3. The pressure of compressed air for all modes of treatment was 2 kgf/cm2the duration of the cooling disk and parcel of the transition to the rim and the hub was 220, 160 and 100 seconds, respectively, for blanks with carbon or 0.57, 0.62 to 0.67%. The specified duration of the cooling disk corresponded to the duration of the cooling of the rim. Air consumption with increasing carbon content from 0.57% to 0.67% reduced from 32 m3per hour up to 16 m3/hour. The mechanical properties of the wheels, prepared according to the modes of table 3, are shown in table 4.

As shown, the increase in the consumption of compressed air by decreasing the carbon content increases the strength characteristics with satisfactory values of plastic characteristics and toughness. When the carbon content of 0.57%, there is a slight temporary increase of the resistance of the rim and disk with satisfactory values of plastic characteristics, toughness and ductile-brittle transition temperature.

Sources of information

1. K. F. Starodubov, Heat treatment of railway wheels. M Metallurgizdat, 1948.

2. Instruction manual for the production of the purpose of the B 21 H 1/04 (Patent RU 2123405 C1, 20.12.98-prototype).

4. I. Year Of Nodes, N.And.Danchenko, A. G. Serdyuk, I. A. Borisov, "investigation of the influence of structural factors on properties of medium-carbon structural steel. The book "the production and operation of railway wheels and axles". , Dnepropetrovsk, 1971.

1. A method of manufacturing a solid-rolled railway wheels, comprising heating under deformation to 1200-1240oWith consistent deformation on presses and wheel mill, hardening of the wheel rim by the vertical dashed hardening, characterized in that the hardening process of the wheel rim to produce single or double circular cooling disk and parcel of the transition in the rim and the hub when the wheel is in a vertical position in the quenching car, the temperature of the wheel rim before quenching is 940-780oWith and drive 860-720oC.

2. The method according to p. 1, characterized in that the cyclic cooling of the disk and parcel of the transition in the rim and the hub produce compressed air at a pressure of 1-3 kgf/cm, and the duration of cooling, respectively, is 2.0 to 0.7 of the length of the cooling of the rim. 1

3. The method according to p. 1, characterized in that the regulation intensity of halogen with exceptiona at its constant pressure, with the increase of carbon content within the steel grade compressed air consumption is reduced.

 

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