CN112011680A - Intermittent quenching method for railway wheels - Google Patents
Intermittent quenching method for railway wheels Download PDFInfo
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- CN112011680A CN112011680A CN202010735022.8A CN202010735022A CN112011680A CN 112011680 A CN112011680 A CN 112011680A CN 202010735022 A CN202010735022 A CN 202010735022A CN 112011680 A CN112011680 A CN 112011680A
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
- C21D9/34—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for tyres; for rims
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
- C21D1/18—Hardening; Quenching with or without subsequent tempering
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
- C21D1/62—Quenching devices
- C21D1/667—Quenching devices for spray quenching
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D11/00—Process control or regulation for heat treatments
- C21D11/005—Process control or regulation for heat treatments for cooling
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D2211/00—Microstructure comprising significant phases
- C21D2211/005—Ferrite
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D2211/00—Microstructure comprising significant phases
- C21D2211/009—Pearlite
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Abstract
The invention discloses an intermittent quenching method for railway wheels, belonging to the field of heat treatment of railway wheels. The invention is carried out according to the following steps: s1, heating the whole wheel to be completely austenitized; s2, alternately carrying out water cooling and air cooling on the wheel to form a uniform fine pearlite + ferrite structure in the whole rim area; the cooling process comprises a first stage and a second stage, wherein the water quantity V1 of the first stage is less than the water quantity V2 of the second stage, the alternating times of circulating water/air cooling of the first stage are N1, the alternating times of circulating water/air cooling of the second stage are N2, and N1 is more than N2. The invention overcomes the problem of poor wheel performance caused by the conventional quenching method in the prior art, can effectively avoid the abnormal structure caused by the conventional quenching method from being formed on the surface layer close to the tread, and can reduce the depth of the abnormal structure as much as possible, thereby effectively improving the service performance of the wheel in the whole life cycle and prolonging the service life of the wheel.
Description
Technical Field
The invention relates to the technical field of heat treatment of railway wheels, in particular to an intermittent quenching method for railway wheels.
Background
Quenching is a key process in the heat treatment process of the wheel and determines the structure and the performance of the wheel after quenching. The so-called wheel quenching is to heat the whole rolled wheel to a critical point Ac3The wheel is kept warm for a certain time to be completely austenitized, then the tread is subjected to water spray cooling, the rim structure after quenching is fine pearlite and a small amount of ferrite, so that the rim wearing area has certain strong hardness (namely wear resistance), and the spoke plate part is not subjected to water spray cooling in the process, so that the normalizing state is still maintained, and the spoke plate has certain plasticity and toughness, so that the impact, vibration and the like in the running process of a vehicle can be relieved. At present, the quenching method generally adopted is to spray water on the tread surface at a large flow rate, namely a certain water pressure and water spraying time are adopted to control the quenching process, but the method has the defects of large supercooling degree and high cooling speed of the tread surface, bainite abnormal structures are easily formed on the near-surface layer of the tread surface, and the efficiency, the yield and subsequent cutting tools are adversely affected.
The quality of the quenching quality is closely related to the selected cooling medium and the cooling method, so the quenching medium should be reasonably selected and used in the quenching process. The quench medium is typically three types, gas, liquid and solid. The most used of them are liquid media, mainly water and oil. Oil is not used as a quenching medium in the conventional wheel quenching because the oil easily causes environmental pollution and has fire hazard. The water is the quenching medium which is most widely and economically applied at the earliest time, is cheap and easily available, has no toxicity, no combustion, stable physical and chemical properties and large heat capacity, and is usually selected as the wheel quenching medium. According to the cooling characteristic of water, the cooling capacity of water is obviously reduced when the water temperature is increased, so that the water temperature is generally controlled to be 20-40 ℃.
After retrieval, the method comprises the following steps: a high carbon wheel steel, a heat treatment method thereof and a method for manufacturing a wheel using the same are disclosed in the application publication number: CN110616374A, application publication date: 2019-12-27, the application adopts normalizing, quenching and tempering processes for heat treatment, the quenching process is that the wheel is air-cooled for 1 minute after being taken out of the furnace and then the wheel rim is cooled by water spraying, so that the plastic toughness of the wheel is obviously improved, especially the low-temperature toughness is obviously improved under the condition that the strength and the hardness level of the wheel are equivalent to those of the AAR-B, CL60 wheel, and the dispersion difference of the impact toughness value is small. The existing technical defects are as follows: 1) compared with the conventional heat treatment process, the normalizing process is added, so that resource waste, production efficiency and the like are easily caused, and the method is not suitable for large-scale industrial production; 2) the tread temperature is about 700-.
As in chinese patent application No.: 2019103581409, the name of invention creation is: a heat treatment cooling process for railway wheels, which comprises the following steps: firstly, heating the whole wheel to be completely austenitized; then transferring to a quenching platform to enable the wheel to be in a rotating state, and spraying the wheel tread by adopting pressure step incremental type gas mist two-phase flow; putting the whole wheel into a tempering furnace for heat preservation, and finally taking out for air cooling; the pressure step incremental type gas-mist two-phase flow injection wheel tread sequentially comprises three stages, wherein wheel rotating speeds v1, v2, v3 of the three stages are controlled, the water pressure is P1< P2< P3, and the quenching cooling time is T1< T2< T3; the number of the nozzles which are started in three stages and distributed at equal intervals along the circumferential direction of the wheel is M, 2M and 3M in sequence. The cooling capacity to the rim inside can be increased to this application, makes wheel tread to the inside depths of rim obtain balanced unanimous cooling rate, has optimized the organizational structure of rim full section.
As in chinese patent application No.: 2008100204215, the name of invention creation is: the application relates to a heat treatment method and a heat treatment device for the surface of a rim of a high-carbon steel train wheel. By adopting the technical scheme, the anti-contact fatigue performance of the wheel is improved, and the tread stripping of the wheel is reduced.
For example, in a study on a new process for producing a high-performance carbon steel wheel (zhuyun, grandson, Zhao Lin Chun, Zhou Jiu, Li Quan.) [ J ]. Steel, 1991,26(10) ], the whole wheel having a C content of 0.65% is heated to austenitize, and then subjected to powder-spraying intermittent quenching, and a test proves that a fine pearlite structure can be obtained only by using an intermittent ratio of 0.5, and the fatigue strength and the wear resistance are good. The technical defects are as follows: 1) the powder spraying easily causes environmental pollution and is not good for the health of field workers; 2) a special dust collecting device needs to be arranged beside the quenching table, but poor heat dissipation in a sealed space is caused due to large heat of an austenitizing wheel, and the stability of a controller in the quenching table is unfavorable, so that the quenching process is influenced.
The wheels are important bearing moving parts of the railway train, and are complex in stress state and bad in service condition. The structure and the hardness uniformity of the rim abrasion area of the railway wheel are improved, and the method has important significance for improving the service performance of the wheel and improving the whole life cycle of the wheel, and especially preventing or slowing down the early peeling, eccentric wear and the like of the wheel. Therefore, it is necessary to provide an intermittent quenching method for manufacturing a railway wheel with high hardness uniformity, which is environment-friendly and has low labor intensity.
Disclosure of Invention
1. Technical problem to be solved by the invention
The invention aims to solve the problem of poor wheel performance caused by a conventional quenching method in the prior art, and provides an intermittent quenching method for railway wheels, which is a general intermittent quenching method with high hardness uniformity of a rim wearing area, can effectively avoid abnormal structures caused by the conventional quenching method from being formed on the near-surface layer of a tread, and can reduce the depth of the abnormal structures as much as possible, thereby effectively improving the service performance of the wheel in the whole life cycle and prolonging the service life of the wheel.
2. Technical scheme
In order to achieve the purpose, the technical scheme provided by the invention is as follows:
the invention discloses an intermittent quenching method for railway wheels, which comprises the following steps:
s1, heating the whole wheel to be completely austenitized;
s2, alternately carrying out water cooling and air cooling on the wheel to form a uniform fine pearlite + ferrite structure in the whole rim area; the cooling process comprises a first stage and a second stage, wherein the total water quantity V1 of the first stage is less than the total water quantity V2 of the second stage, the alternating times of circulating water/air cooling of the first stage are N1, the alternating times of circulating water/air cooling of the second stage are N2, and N1 is more than N2.
Furthermore, the heating and heat preservation time of the wheel in the step S1 is 2.5-3.5 h.
Further, the cooling time in step S2 amounts to 3-10 min.
Further, the water pressure for water cooling in step S2 is a constant water pressure, and the range of the water pressure is 0.1-0.3 MPa.
Further, the air cooling in step S2 is changed to ordinary air cooling, and the air pressure is 0 MPa.
Further, in step S2, the total of the water cooling time in the first stage is T1, the total of the air cooling time is T2, the total of the water cooling time in the second stage is T3, and the total of the air cooling time is T4, T1+ T2 is not more than T3+ T4.
Furthermore, in step S2, the number of the first-stage cooling water/air cooling alternation times is N1 times, and the first water cooling time t1 is K × D, where the steel material coefficient K is 0.6-1.0S/mm, and D is the equivalent circle diameter of the rim cross section; the first air cooling time is 1/5-2/3 of the first water cooling time t 1; the second water cooling time t2 is 1/4-4/5 of the first water cooling time t1, and the second air cooling time is 1/6-1/2 of the first water cooling time t 1; the third water cooling time t3 is 1/5-1/3 of the first water cooling time t1, and the air cooling time is 1/10-1/3 of the first water cooling time t 1; and in the alternative stage of the cooling of the residual N1-3 times of circulating water/air after the first three times of cooling, the water cooling time is kept consistent every time, and the air cooling time is also kept consistent every time.
Furthermore, in the process of the rest N1-3 times of alternating cooling of circulating water/air, the water cooling time t is 1/6-1/2 of the first water cooling time t1, the air cooling time is 1/10-1/3 of the first water cooling time t1, and the surface layer of the tread after the first stage of cooling is not heated to 650 ℃.
Furthermore, in the step S2, the number of times of alternation of water/air cooling in the second stage of cooling is N2, the water cooling time is 1-2 times of the first water cooling time t1 in the first stage, the air cooling time is 1/10-1/3 of the first water cooling time t1 in the first stage, and the surface temperature of the tread is not more than 500 ℃ after the second stage of cooling is finished.
Furthermore, in the cooling process of step S2, the wheel is in a horizontal rotation state, the speed of rotation is proportional to the diameter of the wheel, and the speed of rotation is controlled to be 40-120 r/min.
3. Advantageous effects
Compared with the prior art, the technical scheme provided by the invention has the following beneficial effects:
(1) according to the intermittent quenching method for the railway wheel, the cooling speed of the wheel can be accurately controlled by controlling the water cooling time and the air cooling time, the limitation that abnormal structures are formed on the near surface layer of the tread under the condition of large-flow water spraying of the existing tread is overcome, the structure performance of the rim area is basically consistent, and the hardness gradient in the wheel abrasion direction is reduced.
(2) The intermittent quenching method for the railway wheel has the advantages of simple whole process steps, cleanness, environmental protection, no need of additionally arranging equipment, safe and convenient operation, energy conservation, capability of being transformed on the existing quenching platform, capability of large-scale industrial popularization and good application prospect.
Drawings
FIG. 1 is a schematic view of a batch quenching process according to the present invention;
FIG. 2 is a schematic diagram showing a comparison of the depth of an abnormal tissue between an example of the present invention and a comparative example;
FIG. 3 is a graph showing the extreme difference in hardness between 5mm and 35mm (wear limit) under the treads between examples and comparative examples of the present invention.
Detailed Description
For a further understanding of the invention, reference should be made to the following detailed description taken in conjunction with the accompanying drawings.
In the description of the present invention, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc., indicate orientations or positional relationships based on the orientations or positional relationships shown in the drawings, and are only for convenience of description and simplicity of description, but do not indicate or imply that the device or element being referred to must have a particular orientation, be constructed and operated in a particular orientation, and thus, should not be construed as limiting the present invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance.
The present invention will be further described with reference to the following examples.
Example 1
The intermittent quenching method for the railway wheel of the embodiment comprises the following steps:
s1, heating the whole wheel to be completely austenitized; specifically, the wheel in this embodiment is made of conventional ER6 material and has a specification of AG 864. The heating temperature is 840-860 ℃, the temperature is kept for 2.5-3.5h, the whole blank wheel is heated to be completely austenitized, then the wheel is placed on a quenching table through a manipulator, a motor of the quenching table is started, the wheel is in a horizontal rotating state, the rotating speed of the motor is 90r/min, the rotating speed is in direct proportion to the wheel diameter, the cooling speed of the surface of the wheel rim in intermittent quenching is unified as much as possible, and the phenomenon that the local cooling speed is too fast or too slow is avoided.
S2, alternately carrying out water cooling and air cooling on the wheel to form a uniform fine pearlite + ferrite structure in the whole rim area; the cooling process comprises a first stage and a second stage, wherein the total water quantity V1 of the first stage is less than the total water quantity V2 of the second stage, the alternating times of cooling of circulating water/air of the first stage are N1, the alternating times of cooling of circulating water/air of the second stage are N2, N1 is more than N2, the total time of water cooling of the first stage is T1, the total time of air cooling is T2, the total time of water cooling of the second stage is T3, the total time of air cooling is T4, and T3+ T4 are not more than T1+ T2. Wherein the water cooling adopts constant water pressure cooling, the air cooling adopts common air cooling, and the air pressure is 0 MPa.
In the step S2, the number of the first-stage cooling water/air cooling alternation times is N1 times, wherein the first water cooling time t1 is K D, the coefficient K of the steel material is 0.6-1.0S/mm, and D is the equivalent circular diameter of the rim section; the first air cooling time is 1/5-2/3 of the first water cooling time t 1; the second water cooling time t2 is 1/4-4/5 of the first water cooling time t1, and the second air cooling time is 1/6-1/2 of the first water cooling time t 1; the third water cooling time t3 is 1/5-1/3 of the first water cooling time t1, and the air cooling time is 1/10-1/3 of the first water cooling time t 1; in the alternate stages of the cooling by the circulating water/air for the rest N1-3 times after the first three times, the water cooling time t is 1/6-1/2 of the first water cooling time t1, the air cooling time is 1/10-1/3 of the first water cooling time t1, and the surface layer temperature return of the tread after the cooling in the first stage is finished is not more than 650 ℃. The alternation times of water/air cooling of the second stage cooling is N2, the water cooling time of each time is 1-2 times of the first water cooling time t1 of the first stage, the air cooling time is 1/10-1/3 of the first water cooling time t1 of the first stage, and the temperature of the surface layer of the tread after the second stage cooling is finished is not more than 500 ℃.
Specifically, in this embodiment, the intermittent quenching computer program is turned on, and the water pressure is controlled to be stabilized at 0.10 ± 0.02MPa during the cooling process, and the flow rate of the quenching table is 140m under the water pressure3And h, performing first-stage cooling, wherein the first water spraying cooling time is 15s, the air cooling time is 3s, the second water cooling time is 12s, the air cooling time is 3s, the third water cooling time is 5s, and the air cooling time is 2s, and then, performing cyclic alternate cooling for 15 times and 18 times N1, wherein the water cooling time is 7.5s and the air cooling time is 2 s. Then proceed withIn the second stage of cooling, the cooling was carried out alternately 8 times and 8 times for N2 while maintaining a cycle of 30s water-spraying cooling time and 2s air-cooling time for each time. At the moment, the transitional position of the wheel rim/the spoke plate is darkened, pearlite phase transformation at different depths below the tread is completed, and then the wheel rim/the spoke plate enters a tempering furnace.
According to the CCT curve of the wheel steel material, namely the lower critical cooling speed of the steel and the cooling characteristics of circulating water at different temperatures, the structure transformation of complete fine pearlite and a small amount of ferrite (namely F-P) is generated within the range of the lamellar pearlite forming temperature A1-650 ℃ within 15mm close to the surface layer of the tread by controlling the intermittent water spraying time and the alternation times in the first stage, but the metal temperature in the rim is still above the pearlite transformation temperature at the moment, and the pearlite transformation does not occur. Then, the second stage of intermittent cooling is started immediately until the tread completely completes pearlite transformation (the joint of the rim and the web turns black). In the embodiment, the F-P structure transformation is independently generated in the near surface layer of the tread and the inner part of the rim through the intermittent quenching process, so that the whole section structure of the rim is obviously improved, the depth of a non-pearlite structure (abnormal structure) in the near surface layer of the tread is greatly reduced, and the radial hardness gradient of the rim is obviously reduced.
Comparative example 1
In this comparative example, the wheel is also of conventional ER6 material and has AG 864. And (3) heating the whole blank wheel to be completely austenitized (840-860 ℃ C., preserving heat for 2.5-3.5h), placing the wheel on a quenching table through a manipulator, and starting a motor of the quenching table to enable the wheel to be in a horizontal rotating state, wherein the rotating speed of the motor is 90 r/min. And then directly opening a quenching computer program to spray water for 300s at a large flow rate under 0.10MPa, and directly entering a tempering furnace when the tread temperature is reduced to be below 500 ℃.
After the heat treatment of the wheel is finished, the hardness of the abrasion limit of the rim and the depth of the abnormal structure on the surface layer of the rim of the wheel of the example 1 and the comparative example 1 are checked, the rim hardness is shown in the table 1 and the figure 2, and the depth of the abnormal structure is compared with the table 3.
As can be seen from table 1 and fig. 2 to 3, the hardness at the abrasion limit of the wheel rim of example 1 slightly improved the hardness at the abrasion limit, but the hardness uniformity was greatly improved, the hardness range at the abrasion limit was reduced from 8HB to 2HB, and the hardness range at the 5mm tread was reduced from 12HB to 5HB, which is a major breakthrough. Further, the depth of the abnormal structure of the wheel of example 1 was reduced from about 7mm to 2.3mm in the wheel of comparative example 1, indicating that the intermittent quenching method is effective for controlling the cooling rate of the rim skin.
Example 2
The intermittent quenching method for railway wheels of the embodiment is basically the same as the embodiment 1, except that:
s1: in this embodiment, the wheel is made of conventional ER7 material and has specification AT 850. The blank wheel is integrally heated to be completely austenitized, then the wheel is placed on a quenching table through a manipulator, and a motor of the quenching table is started to enable the wheel to be in a horizontal rotating state, wherein the rotating speed of the motor is 40 r/min.
S2: in the embodiment, the cooling water pressure is controlled to be stabilized at 0.3 +/-0.02 MPa, the first-stage cooling is carried out, the first water cooling time is 12s, and the air cooling time is 8 s; the second water cooling time is 8s, and the air cooling time is 5 s; the third water cooling time is 4s, and the air cooling time is 4 s; thereafter, the water cooling time was kept 6s and the air cooling time was kept 4s, and the operation was performed 12 times and N1 was 15 times alternately. And then, carrying out second-stage cooling, keeping the water cooling time at 12s and the air cooling time at 4s for 12 times alternately, wherein N2 is 12 times, at the time, the transitional position of the rim/spoke plate is darkened, pearlite phase transformation at different depths under the tread is completed, and then, the tread enters a tempering furnace.
Comparative example 2
The wheels of this comparative example were also of conventional ER7 material and were of AT850 gauge. The blank wheel is integrally heated to be completely austenitized, then the wheel is placed on a quenching table through a manipulator, and a motor of the quenching table is started to enable the wheel to be in a horizontal rotating state, wherein the rotating speed of the motor is 50 r/min. Then directly opening a quenching computer program to spray water for 280s with large flow under 0.3MPa, and directly entering a tempering furnace when the temperature of the tread is reduced to be below 500 ℃.
After the heat treatment of the wheel is finished, the hardness of the abrasion limit of the rim and the depth of the abnormal structure on the surface layer of the rim of the wheel of example 2 and comparative example 2 are checked, the rim hardness is shown in table 1 and fig. 2, and the depth of the abnormal structure is compared with table 3.
As can be seen from table 1 and fig. 2 to 3, the hardness at the wear limit of the wheel rim of example 2 slightly improved the hardness at the wear limit, but the hardness uniformity was greatly improved, the extreme difference in wear limit was reduced from 5HB to 3HB, and the extreme difference in hardness at 5mm on the tread was reduced from 8HB to 4HB, which indicates that the intermittent quenching method controls the rim cooling rate and thus plays a role in improving the hardness uniformity. Further, the depth of the abnormal structure of the wheel of example 2 was reduced from about 7.3mm to 2.5mm in the wheel of comparative example 2, indicating that the intermittent quenching method is effective for controlling the cooling rate of the rim skin.
Example 3
The intermittent quenching method for railway wheels of the embodiment is basically the same as the embodiment 1, except that:
s1: in the embodiment, the wheel is made of conventional ER8 material and has the specification of HG 860E. The blank wheel is integrally heated to be completely austenitized, then the wheel is placed on a quenching table through a manipulator, and a motor of the quenching table is started to enable the wheel to be in a horizontal rotating state, wherein the rotating speed of the motor is 120 r/min.
S2: in the embodiment, the cooling water pressure is controlled to be stabilized at 0.2 +/-0.02 MPa, the first-stage cooling is carried out, the first water cooling time is 30s, and the air cooling time is 8 s; the second water cooling time is 15s, and the air cooling time is 5 s; the third water cooling time is 6s, and the air cooling time is 3 s; thereafter, the water cooling time was kept 5s and the air cooling time was kept 3s, and the operation was alternately performed 20 times and N1 was 23 times. And then, carrying out second-stage cooling, keeping the water cooling time at 30s and the air cooling time at 3s for 7 times alternately, wherein N2 is 7 times, and then, turning the transitional part of the rim/spoke plate dark to finish pearlite phase change at different depths under the tread, and then, entering a tempering furnace.
Comparative example 3
The wheels in the comparative example are also made of conventional ER8 material and have the specification of HG 860E. The blank wheel is integrally heated to be completely austenitized, then the wheel is placed on a quenching table through a manipulator, and a motor of the quenching table is started to enable the wheel to be in a horizontal rotating state, wherein the rotating speed of the motor is 120 r/min. Then directly opening a quenching computer program to spray water for 260s under 0.2MPa at a large flow rate, and directly entering a tempering furnace when the temperature of the tread is reduced to be below 500 ℃.
After the heat treatment of the wheel is finished, the hardness of the abrasion limit of the rim and the depth of the abnormal structure on the surface layer of the rim of the wheel of the example 3 and the comparative example 3 are checked, the rim hardness is shown in the table 1 and the figure 2, and the depth of the abnormal structure is compared with the table 3.
As can be seen from table 1 and fig. 2 to 3, the hardness at the abrasion limit of the wheel rim of example 3 slightly improved the hardness at the abrasion limit compared with the wheel of comparative example 3, but the hardness uniformity was greatly improved, the hardness range 9HB at the abrasion limit was reduced to the range 2HB, and the hardness range 5mm on the tread was reduced from 13HB to 6HB, which indicates that the intermittent quenching method controls the rim cooling rate and thus plays a role in improving the hardness uniformity. Further, the depth of the abnormal structure of the wheel of example 3 was reduced from about 7.6mm to 2.8mm in the wheel of comparative example 3, indicating that the intermittent quenching method is effective for controlling the cooling rate of the rim skin.
Example 4
The intermittent quenching method for railway wheels of the embodiment is basically the same as the embodiment 1, except that:
s1: in this embodiment, the wheel is made of conventional ER9 material and has specification ZZ 840B. The blank wheel is integrally heated to be completely austenitized, then the wheel is placed on a quenching table through a manipulator, and a motor of the quenching table is started to enable the wheel to be in a horizontal rotating state, wherein the rotating speed of the motor is 80 r/min.
S2: in the embodiment, the cooling water pressure is controlled to be stabilized at 0.1 +/-0.02 MPa, the first-stage cooling is carried out, the first water cooling time is 24s, and the air cooling time is 10 s; the second water cooling time is 6s, and the air cooling time is 4 s; the third water cooling time is 8s, and the air cooling time is 6 s; thereafter, the water cooling time was kept 6s and the air cooling time was kept 3s, and the operation was alternately performed 20 times and N1 was 23 times. And then, carrying out second-stage cooling, keeping the water cooling time at 45s and the air cooling time at 4s for 5 times alternately, wherein N2 is 5 times, and then, turning the transitional part of the rim/spoke plate dark to finish pearlite phase change at different depths under the tread, and then, entering a tempering furnace.
Comparative example 4
The wheel in this comparative example is also of conventional ER9 material and has ZZ840B specification. The blank wheel is integrally heated to be completely austenitized, then the wheel is placed on a quenching table through a manipulator, and a motor of the quenching table is started to enable the wheel to be in a horizontal rotating state, wherein the rotating speed of the motor is 80 r/min. Then directly opening a quenching computer program to spray water for 240s under 0.1MPa with large flow, and directly entering a tempering furnace when the temperature of the tread is reduced to be below 500 ℃.
After the heat treatment of the wheel is finished, the hardness of the abrasion limit of the rim and the depth of the abnormal structure on the surface layer of the rim of the wheel of example 4 and comparative example 4 are checked, the rim hardness is shown in table 1 and fig. 2, and the depth of the abnormal structure is compared with table 3.
As can be seen from table 1 and fig. 2 to 3, the hardness at the abrasion limit of the wheel rim of example 4 slightly improved the hardness at the abrasion limit compared with the wheel of comparative example 4, but the hardness uniformity was greatly improved, the extreme difference 8HB in the abrasion limit was reduced to the extreme difference 1HB, and the extreme difference in the hardness at the 5mm portion of the tread was reduced from 11HB to 4HB, which indicates that the intermittent quenching method controls the rim cooling rate and thus plays a role in improving the hardness uniformity. Further, the depth of the abnormal structure of the wheel of example 4 was reduced from about 7.8mm to 3.1mm in the wheel of comparative example 4, indicating that the intermittent quenching method is effective for controlling the cooling rate of the rim skin.
The following table 1 shows the wear limit hardness of the wheels obtained in each of the above examples and comparative examples in HB.
TABLE 1 hardness information at wear limit for each of the examples and comparative examples wheels
The present invention and its embodiments have been described above schematically, without limitation, and what is shown in the drawings is only one of the embodiments of the present invention, and the actual structure is not limited thereto. Therefore, if the person skilled in the art receives the teaching, without departing from the spirit of the invention, the person skilled in the art shall not inventively design the similar structural modes and embodiments to the technical solution, but shall fall within the scope of the invention.
Claims (10)
1. A method for intermittent quenching of railway wheels, characterized in that it is carried out according to the following steps:
s1, heating the whole wheel to be completely austenitized;
s2, alternately carrying out water cooling and air cooling on the wheel to form a uniform fine pearlite + ferrite structure in the whole rim area; the cooling process comprises a first stage and a second stage, wherein the total water quantity V1 of the first stage is less than the total water quantity V2 of the second stage, the alternating times of circulating water/air cooling of the first stage are N1, the alternating times of circulating water/air cooling of the second stage are N2, and N1 is more than N2.
2. A method of intermittent quenching for railway wheels according to claim 1, characterized in that: in the step S1, the heating and heat preservation time of the wheel is 2.5-3.5 h.
3. A method of intermittent quenching for railway wheels according to claim 1, characterized in that: the cooling time in step S2 is 3-10min in total.
4. A method of intermittent quenching for railway wheels according to claim 1, characterized in that: the water pressure of the water cooling in the step S2 is a constant water pressure, and the adopted water pressure range is 0.1-0.3 MPa.
5. A method of intermittent quenching for railway wheels according to claim 1, characterized in that: in step S2, the air is cooled to be common air cooling, and the air pressure is 0 MPa.
6. A method of intermittent quenching for railway wheels according to claim 1, characterized in that: in the step S2, the total of the water cooling time in the first stage is T1, the total of the air cooling time is T2, the total of the water cooling time in the second stage is T3, and the total of the air cooling time is T4, wherein T1+ T2 is not more than T3+ T4.
7. A method of intermittent quenching for railway wheels according to claim 1, characterized in that: in the step S2, the number of the first-stage cooling water/air cooling alternation times is N1 times, wherein the first water cooling time t1 is K D, the coefficient K of the steel material is 0.6-1.0S/mm, and D is the equivalent circular diameter of the rim section; the first air cooling time is 1/5-2/3 of the first water cooling time t 1; the second water cooling time t2 is 1/4-4/5 of the first water cooling time t1, and the second air cooling time is 1/6-1/2 of the first water cooling time t 1; the third water cooling time t3 is 1/5-1/3 of the first water cooling time t1, and the air cooling time is 1/10-1/3 of the first water cooling time t 1; and in the alternative stage of the cooling of the residual N1-3 times of circulating water/air after the first three times of cooling, the water cooling time is kept consistent every time, and the air cooling time is also kept consistent every time.
8. A method of intermittent quenching for railway wheels according to claim 7, characterized in that: in the alternate process of the residual N1-3 times of circulating water/air cooling, the water cooling time t is 1/6-1/2 of the first water cooling time t1, the air cooling time is 1/10-1/3 of the first water cooling time t1, and the surface layer temperature return of the tread after the first stage of cooling is finished is no more than 650 ℃.
9. A method of intermittent quenching for railway wheels according to claim 1, characterized in that: in the step S2, the number of the second stage cooling water/air cooling alternation is N2, the water cooling time is 1-2 times of the first stage water cooling time t1, the air cooling time is 1/10-1/3 of the first stage water cooling time t1, and the temperature of the surface layer of the tread does not exceed 500 ℃ after the second stage cooling is finished.
10. A method of intermittent quenching for railway wheels according to claim 1, characterized in that: and step S2, the wheel is in a horizontal rotation state in the cooling process, the speed of the rotation speed is in direct proportion to the diameter of the wheel, and the rotation speed is controlled to be 40-120 r/min.
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