Heavy-load locomotive wheel steel capable of resisting surface contact fatigue and wheel production method
阅读说明：本技术 一种抗表面接触疲劳的重载机车车轮钢及车轮生产方法 (Heavy-load locomotive wheel steel capable of resisting surface contact fatigue and wheel production method ) 是由 江波 姚三成 邹强 刘学华 赵海 万志健 杜松林 陈刚 丛韬 张关震 于 2021-07-19 设计创作，主要内容包括：本发明提供了一种抗表面接触疲劳的重载机车车轮钢及车轮生产方法,车轮钢成分：C 0.60～0.67％、Si 0.15～1.00％、Mn 0.60～0.90％、V 0.04～0.15％、Cr 0.10～0.25％、Al≤0.040％、Als≤0.015％、N(70～100)×10～(-4)％、Ti≤0.003％、P≤0.020％、S≤0.015％,其余为Fe及不可避免的杂质元素。车轮生产中,奥氏体化均热温度较常规加热温度高30～50℃,均温段保持时间不低于1.5h。与现有技术相比,本发明提供的车轮抗表面接触疲劳性能明显优于传统机车车轮,减少车轮非计划镟修频次,延长车轮使用寿命。(The inventionThe heavy-load locomotive wheel steel capable of resisting surface contact fatigue and the wheel production method are provided, and the wheel steel comprises the following components: 0.60 to 0.67% of C, 0.15 to 1.00% of Si, 0.60 to 0.90% of Mn, 0.04 to 0.15% of V, 0.10 to 0.25% of Cr, less than or equal to 0.040% of Al, less than or equal to 0.015% of Als, and N (70 to 100). times.10% ‑4 Less than or equal to 0.003 percent of Ti, less than or equal to 0.020 percent of P, less than or equal to 0.015 percent of S and the balance of Fe and inevitable impurity elements. In the production of the wheel, the austenitizing soaking temperature is 30-50 ℃ higher than the conventional heating temperature, and the holding time of the temperature equalizing section is not less than 1.5 h. Compared with the prior art, the surface contact fatigue resistance of the wheel provided by the invention is obviously superior to that of the traditional locomotive wheel, the frequency of non-planned turning repair of the wheel is reduced, and the service life of the wheel is prolonged.)
1. The heavy-duty locomotive wheel steel capable of resisting surface contact fatigue is characterized by comprising the following components in percentage by mass:
C 0.60～0.67％、Si 0.15～1.00％、Mn 0.60～0.90％、V 0.04～0.15％、Cr 0.10～0.25％、Al≤0.040％、Als≤0.015％、N(70～100)×10-4less than or equal to 0.003 percent of Ti, less than or equal to 0.020 percent of P, less than or equal to 0.015 percent of S and the balance of Fe and inevitable impurity elements.
2. The surface contact fatigue resistant heavy-duty locomotive wheel steel according to claim 1, wherein the surface contact fatigue resistant heavy-duty locomotive wheel steel composition is Ni less than or equal to 0.25%, Mo less than or equal to 0.08%, Cu less than or equal to 0.30%, and Cr + Mo + Ni less than or equal to 0.50%.
3. The surface contact fatigue resistant heavy-duty locomotive wheel steel according to claim 1, wherein in said surface contact fatigue resistant heavy-duty locomotive wheel steel composition, Ti + Als is less than or equal to 0.016%.
4. A method for producing a wheel using the heavy-duty locomotive wheel steel resistant to surface contact fatigue of any one of claims 1 to 3, comprising the steps of: and (4) charging the blank wheel formed by rolling into a furnace, and heating to fully austenitize.
5. The method of claim 4, wherein heating to achieve sufficient austenitization is at a soaking temperature of 860 ℃ and 930 ℃ for a soaking time of at least 1.5 hours.
6. The method of claim 4 or 5, wherein the heating is performed for a total heating time of 3.5 to 4 hours for sufficient austenitization.
7. The production method according to claim 4 or 5, characterized in that the wheel heated to be fully austenitized is taken out of the furnace and transferred to a quenching platform, and the heat treatment cooling is completed by adopting large-flow water spraying on the tread.
8. The production method according to claim 7, wherein the wheel is taken out of the furnace and transported to a quenching platform, after the distance between the wheel tread and the water outlet panel of the nozzle is adjusted to be consistent, the driving motor is started to rotate the wheel, the rotating speed of the driving motor is controlled to be 50-75 r/min, continuous large-water-volume spray quenching of the wheel tread is adopted to finish heat treatment cooling, specifically, 6 nozzles are adopted and uniformly distributed around the quenching platform, the included angle between the water outlet angle of each nozzle and the rotating direction of the wheel is 40-55 degrees, and the water outlet flow of each nozzle is 19-22 m3And/h, the duration is 440-480 s.
9. The production method according to claim 7 or 8, wherein the wheel after quenching treatment is tempered and then subjected to machining and tread profiling procedures to obtain a finished wheel.
10. The production method according to any one of claims 4 to 9, wherein the wheel texture produced is fine pearlite and ferrite with a volume fraction of 4 to 5.5%, the grain size is greater than 8.0 grade, and the pearlite sheet spacing is 130 to 150 nm.
Technical Field
The invention belongs to the technical field of railway wheel preparation, and particularly relates to surface contact fatigue resistant heavy-load locomotive wheel steel and a wheel production method.
Background
The locomotive wheel is one of the key parts of the locomotive, has great difference with the service conditions of other wheels, and is the main transmission of traction power and braking force. For a locomotive towing a heavy-duty freight train, the maximum shear stress borne by the wheels is on the surface of the tread and is higher in level due to high traction coefficient and large traction moment. Therefore, the surface contact fatigue damage of heavy-duty locomotive wheels is significantly more sensitive than other wheels, and the tread stripping caused by the surface initiated contact fatigue cracks is a common and frequent failure mode of the locomotive wheels.
The tread is stripped to generate impact load on the contact surface of the wheel rail, the caused vibration can cause early failure of other parts of the locomotive, the locomotive and the locomotive can be continuously put into operation after the tread stripping defect is turned and repaired, and the operation safety and the reliability of the train are directly influenced. The contact fatigue performance of the wheel determines the tread stripping generation period, and is directly related to the turning frequency and the service life of the wheel, thereby having important influence on the railway transportation efficiency and the economy.
Crack initiation from contact fatigue damage of the tread surface occurs under high traction coefficient conditions. In the contact process of the wheel rails, longitudinal and transverse sliding and relative rotation exist on the contact surfaces at the same time, the traction coefficient caused by the sliding between the wheel rails is increased, the position of the maximum shear stress on the wheel moves to the contact surfaces, and when the traction coefficient exceeds 0.25, the maximum shear stress is positioned on the surface of the wheel, which is the mechanical condition that rolling contact fatigue cracks are generated on the surface. At high traction coefficient (>0.25), the surface of the wheel rail undergoes non-proportional tension, shear and compression load paths, causing the surface material to ratchet, and when the accumulated plastic strain reaches the critical value of the material, the surface is initiated to crack. The mechanical nature of rolling contact fatigue is plastic deformation of the material, and thus crack initiation resistance can be improved by increasing the shear yield strength of the wheel material. Depending on the size of the surface crack and the subsequent environmental conditions, if the crack is deep and meets the weather of rain and snow, the liquid entering the crack can affect the distribution of the contact pressure acting on the crack to prevent the crack from closing, and the liquid closed in the crack can obviously increase the type I stress intensity factor, namely the so-called 'oil wedge effect', so that the crack is promoted to expand and branch inwards to cause the tread to peel. Therefore, in order to improve the surface contact fatigue resistance of the wheel, the crack initiation resistance of the material needs to be improved, and the size of the crack needs to be reduced.
In order to solve the problem of high wheel tread stripping rate of the existing heavy-duty locomotive, the wheel with high surface contact fatigue damage resistance and good economical efficiency and the preparation method thereof are particularly necessary.
Patent application of the new-day iron company in China, application publication number: CN 103221561 a, application publication date: 2013.07.24, discloses a steel for wheel with excellent balance of wear resistance, contact fatigue resistance and thermal damage resistance, and long service life, which comprises C0.65-0.84 by weight percentage; 0.02-1.00% of Si; 0.50-1.90% of Mn; 0.02-0.50% of Cr; v is 0.02-0.20; s is less than or equal to 0.04; p is less than or equal to 0.05; cu is less than or equal to 0.20; ni is 0.20 or less, satisfies [34 or less and 2.7+29.5 XC +2.9 XSI +6.9 XMN +10.8 XCr +30.3 XMO +44.3 XV or less and 43, and [0.76 XSexp (0.05 XC). times.exp (1.35 XSI). times.exp (0.38 XMN). times.exp (0.77 XCr). times.exp (3.0 XMO). times.exp (4.6 XV) or less ]. However, the invention focuses on the optimal design and adjustment of the components of the wheel steel, so that the key factors influencing the comprehensive performance of the wheel steel cannot be rapidly identified, and the conventional tread forced cooling process is adopted, and some parts of the wheel have undesirable non-pearlite structures.
Disclosure of Invention
The invention aims to provide a heavy-duty locomotive wheel steel with surface contact fatigue resistance, which is based on the optimization of the competitive relationship between contact fatigue and abrasion, has high yield ratio and high ferrite content, has obviously improved surface contact fatigue resistance, and is suitable for heavy-duty locomotive wheels with the axle weight of more than 27 tons and the traction weight of more than 5000 tons.
The invention also aims to provide a method for producing a wheel by using the heavy-duty locomotive wheel steel with the surface contact fatigue resistance, the surface contact fatigue stripping resistance of the wheel is obviously superior to that of the traditional locomotive wheel, the problem of high stripping incidence of the wheel tread of the traditional locomotive is solved, the surface contact fatigue resistance of the heavy-duty locomotive wheel is improved, the unintended turning frequency of the wheel is reduced, and the service life of the wheel is prolonged.
The specific technical scheme of the invention is as follows:
the heavy-duty locomotive wheel steel capable of resisting surface contact fatigue comprises the following components in percentage by mass:
C 0.60～0.67％、Si 0.15～1.00％、Mn 0.60～0.90％、V 0.04～0.15％、Cr 0.10～0.25％、Al≤0.040％、Als≤0.015％、N(70～100)×10-4less than or equal to 0.003 percent of Ti, less than or equal to 0.020 percent of P, less than or equal to 0.015 percent of S and the balance of Fe and inevitable impurity elements.
Furthermore, in the components of the heavy-load locomotive wheel steel for resisting surface contact fatigue, Ni is less than or equal to 0.25 percent, Mo is less than or equal to 0.08 percent, Cu is less than or equal to 0.30 percent, and Cr + Mo + Ni is less than or equal to 0.50 percent;
in the components of the heavy-duty locomotive wheel steel for resisting surface contact fatigue, Ti + Als is less than or equal to 0.016 percent.
Carbon is one of the most important strengthening alloy elements in steel, the carbon content is set to be 0.60-0.67%, and the vanadium microalloying is adopted in the range, so that the yield ratio of the wheel is obviously improved, the performance characteristics of obviously improved yield strength and small hardness increment are generated, and the aims of coordinating the competitive relationship between contact fatigue and abrasion and improving the surface contact fatigue resistance of the wheel are fulfilled.
Vanadium is an important strong carbonitride forming element in the wheel steel, and clearance type VC and V can be formed in the steel through heating dissolution and cooling precipitation4C3And nitrogen-rich V (C, N) second phase particles, and strong precipitation strengthening and fine grain strengthening are generated, so that the effect of obviously improving the yield strength is achieved. In addition, the formation of the vanadium-containing second phase particles promotes the formation of proeutectoid ferrite due to poor carbon and smaller lattice mismatch degree with the ferrite in the micro-area around the particles, so that the normal wear rate is moderately increased, and the aims of coordinating the competitive relationship between contact fatigue and wear and improving the surface contact fatigue resistance of the wheel are fulfilled. The invention sets the vanadium content range to be 0.04-0.15%, the reason is that: on one hand, if the vanadium content exceeds the value, a higher heating temperature is needed to generate a remarkable strengthening effect, otherwise, the effect of improving the strength of V microalloying can be greatly limited and even a negative effect can be generated under the influence of double factors of low solid solution V content and low matrix carbon content; on the other hand, too low a vanadium content does not exert a significant precipitation strengthening effect, and even if the heat treatment system is improper, vanadium causes a decrease in strength due to the abstraction of carbon in the matrix. The design of V content is one of the important innovation points of the invention. The similar traditional wheel steel material contains no V or low V, and the content is more than 0.09%. The invention is set to be 0.04-0.15%, and the dissolving proportion of V can be controlled according to actual needs, such as a wider heating temperature range. Wherein the solutionThe subsequent cooling precipitation of V in the matrix produces precipitation strengthening effect, and undissolved V pins grain boundary with V (C, N) particles with stable thermodynamics to produce fine-grain strengthening effect, and the weight of two mechanisms of precipitation strengthening and fine-grain strengthening is adjusted to further realize high yield strength, fine-grain granularity and high ferrite content.
Nitrogen is an alloy element which acts with vanadium element in the wheel steel and is beneficial and cheap. Theoretically, the higher the nitrogen content is, the higher the precipitation driving force of the nitrogen-rich V (C, N) second phase particles is, the higher the strengthening effect is, but considering the nitrogen process stability during steel making, the nitrogen content in the present invention is defined as (70 to 100). times.10-4％。
Titanium and aluminium are also strong carbonitride forming elements and form compounds which are thermodynamically more stable than the vanadium-containing precipitates, even larger-scale harmful inclusions, that is to say form a strong competitive relationship with vanadium, so that the invention provides a strict control of the titanium and aluminium contents.
Aluminum is the most important deoxidizer in steel, and according to the form existing in steel, Al dissolves aluminum Als which corresponds to an alloy element in steel and insoluble aluminum forms inclusions, the present invention simultaneously defines Al and Als, and defines the whole and part for the purpose of ensuring the alloying degree, while controlling the cleanliness of steel. Ti, Als and their combination are limited in the present application because Ti, Als interact with N to form a relatively stable compound, thereby affecting V, N binding.
The invention provides a production method of a wheel, which is produced by using the heavy-load locomotive wheel steel with the surface contact fatigue resistance, and the production method of the wheel comprises the following steps: charging the rolled blank wheel into a furnace, and heating for full austenitizing;
the heating for full austenitizing refers to soaking temperature of 860-930 ℃, total heating time of 3.5-4 h, specific time is determined according to factors such as charging amount, material distribution mode, actual condition of a heating furnace and the like, but the holding time of the uniform temperature section is not less than 1.5 h.
Generally, the conventional heating temperature is 830-880 ℃ for soaking and heat preservation. The austenitizing heating temperature is 30-50 ℃ higher than the conventional heating temperature, and full austenitizing is carried out.
Discharging the wheel heated to be fully austenitized out of the furnace and transferring the wheel to a quenching platform, and finishing heat treatment cooling by adopting large-flow water spraying on a tread; the method specifically comprises the following steps: and discharging the wheel from the furnace and transferring the wheel to a quenching platform, adjusting the distance between the tread of the wheel and the water outlet panel of the nozzle to be consistent, starting a driving motor to enable the wheel to rotate, controlling the rotating speed of the driving motor to be 50-75 r/min, and finishing heat treatment cooling by adopting continuous large-water-volume spray quenching of the tread. Specifically, 6 nozzles are uniformly distributed around the quenching platform, the included angle between the water outlet angle of each nozzle and the rotation direction of the wheel is 40-55 degrees, and the water outlet flow of each nozzle is 19-22 m3And/h, the duration is 440-480 s.
And (3) tempering the wheel after quenching treatment, and then performing machining, tread profiling and other procedures to obtain a finished product wheel.
The produced wheel tissue is fine pearlite and ferrite with the volume fraction of 4-5.5%, the grain size is larger than 8.0 grade, and the content of the ferrite is increased from the surface to the inside; the pearlite sheet interval is 130-150 nm, and the pearlite sheet interval is increased from the surface to the inside.
On the basis of a conventional heating system, according to the solid solubility product relation of carbon-nitrogen-vanadium, the method comprises the following steps: lg ([ V ]]·[C])γ＝6.72-9500/T；lg([V]·[N])γWhen the austenitizing temperature is increased to 3.63 to 8700/T, vanadium in the steel is dissolved in an appropriate ratio in the austenite matrix, and V existing in the undissolved V (C, N) second phase particles does not participate in the subsequent precipitation strengthening but can become a nucleation core of the proeutectoid ferrite. In the subsequent quenching and cooling process, V (C, N) second phase particles which are coherent or semi-coherent with the matrix are separated out from the V precipitates dissolved in the matrix, and a strong precipitation strengthening effect is generated, so that the yield strength is obviously improved. The non-eutectic V (C, N) second phase particle near the substrate becomes catalyst for ferrite heterogeneous nucleation due to the lack of micro-region C, V and small lattice mismatch degree with ferrite, so as to improve the interface energy and driving force of ferrite nucleation, improve the content of pro-eutectoid ferrite in the quenching and cooling process, and inhibit the increment of tensile strength and hardness.
While increasing the material shear yield strength increases the surface RCF crack initiation life, if excessive, the rate of wear is low making it difficult to remove or reduce the surface cracks that have formed, but instead increases the probability of contact fatigue failure. Therefore, the high-yield-strength wear-resistant wheel rail material has high yield strength and moderate wear rate, and is a characteristic required to be possessed by the wheel rail material. The relationship of coordinating and balancing the shear yield strength and the wear performance from the material characteristics is the key for effectively improving the contact fatigue performance of the wheel surface.
The invention can obviously improve the yield strength of the wheel, thereby obviously improving the capability of resisting the contact fatigue crack initiation; on the other hand, the wear resistance is in a positive correlation with the tensile strength and the hardness and in a negative correlation with the ferrite content, so that the increase of the tensile strength and the hardness is small, the ferrite content is increased, and the wear rate can be improved. Therefore, the invention can improve the competitive relationship of contact fatigue and abrasion, thereby improving the surface contact fatigue resistance of the wheel material.
Compared with the prior art, the surface contact fatigue resistance of the wheel provided by the invention is obviously superior to that of the traditional locomotive wheel, the yield strength is more than 700MPa, the yield ratio is more than 0.67, the yield ratio is high, the ferrite content is high, the normal wear rate is slightly higher than that of the conventional similar wheel product, the service effect of balancing and coordinating the 'competition relationship between wear and contact fatigue' is achieved, the yield strength level is improved by nearly 20 percent to the maximum extent, and the yield ratio is improved by 12 to 16 percent. The problem of high incidence of tread stripping of the traditional locomotive wheel can be solved, the surface contact fatigue resistance of the heavy-duty locomotive wheel is improved, the unintended turning frequency of the wheel is reduced, and the service life of the wheel is prolonged. Moreover, the process is simple and feasible, and is convenient for industrial production.
Drawings
FIG. 1 is a microstructure of 15mm under the tread of the wheel of example 1, fine pearlite (134 nm interplate distance) + 4.4% ferrite, grain size grade 9.0;
FIG. 2 is a microstructure of fine pearlite (149 nm chip spacing) + 2.1% ferrite at 15mm under the tread of the wheel of comparative example 1, grade 8.5 grain size;
FIG. 3 shows the evolution of the ratchet behavior of the wheel materials of example 1 and comparative example 1;
FIG. 4 is a graph of the wear rates of the wheel materials of example 1 and comparative example 1;
FIG. 5 is a surface contact fatigue crack morphology after the wheel material dry grinding experiment of example 1;
FIG. 6 is a surface contact fatigue crack morphology after a dry grinding experiment for the wheel material of comparative example 1;
FIG. 7 is a profile of a longitudinal section of a wheel material of example 1 after a dry grinding experiment;
FIG. 8 is a profile of a longitudinal section of a wheel material of comparative example 1 after a dry milling experiment;
FIG. 9 is a graph of the profile of a longitudinal section of a wheel material of example 1 after a dry grinding + wet-sliding contact fatigue test, with a plastic deformation layer depth of about 110 μm;
FIG. 10 is a graph of the profile of a longitudinal section of a wheel material of comparative example 1 after a dry grinding + wet-sliding contact fatigue test, with a plastic deformation layer depth of about 167 μm;
FIG. 11 is a microstructure 17.5mm below the tread of the wheel of example 2, fine pearlite (138 nm interplate) + 4.9% ferrite, grade 9 grain size;
FIG. 12 shows the microstructure 17.5mm below the tread of the wheel of example 3, fine pearlite (135 nm interplate) + 5.1% ferrite, grade 9 grain size.
Detailed Description
For a further understanding of the present invention, reference will now be made in detail to the embodiments illustrated in the drawings.
Example 1 to example 3
A heavy-duty locomotive wheel steel resistant to surface contact fatigue comprises the following components in percentage by mass, as shown in Table 1, and the balance not shown in Table 1 is Fe and inevitable impurities.
Comparative examples 1 to 3
A wheel steel comprising the following components in percentage by mass, as shown in Table 1, with the balance Fe and unavoidable impurities not shown in Table 1.
TABLE 1 main chemical composition of wheel (wt%)
Element(s)
C
Si
Mn
V
N
Ti
Al
Example 1
0.64
0.56
0.75
0.13
84×10-4
2.4×10-3
0.013
Comparative example 1
0.65
0.88
0.83
＜0.01
56×10-4
0.021
0.028
Example 2
0.60
0.16
0.75
0.08
80×10-4
2.3×10-3
0.015
Comparative example 2
0.62
0.85
0.84
＜0.01
52×10-4
0.022
0.027
Example 3
0.66
0.94
0.74
0.05
84×10-4
2.5×10-3
0.014
Comparative example 3
0.67
0.88
0.83
＜0.01
55×10-4
0.021
0.028
Element(s)
Cr
Als
Ni
Mo
Cu
P
S
Example 1
0.22
0.011
0.07
0.01
0.08
0.011
0.010
Comparative example 1
0.14
0.019
0.09
0.04
0.10
0.014
0.012
Example 2
0.12
0.009
0.12
0.05
0.08
0.012
0.008
Comparative example 2
0.15
0.022
0.20
0.02
0.13
0.012
0.010
Example 3
0.24
0.012
0.11
0.04
0.06
0.009
0.009
Comparative example 3
0.15
0.023
0.17
0.04
0.09
0.010
0.013
The method for producing the wheel by using the heavy-load locomotive wheel steel resisting the surface contact fatigue, which is disclosed in the embodiment 1, comprises the following steps of:
and (3) charging the rolled blank wheel into a furnace, heating the blank wheel to 890 +/-10 ℃ (the soaking target temperature is 890 ℃) after 2 hours, soaking and preserving heat for 1 hour and 45 minutes, discharging the blank wheel out of the furnace and transferring the blank wheel to a quenching platform, adjusting the distance between the wheel tread and the water outlet panel of the nozzle to be consistent, starting a driving motor to rotate the wheel, controlling the rotating speed of the driving motor to be 60r/min, and finishing heat treatment and cooling by adopting the existing large-water-volume spray quenching of the wheel tread. Specifically adopts 6 nozzles which are uniformly distributedThe included angle between the water outlet angle of the nozzles and the rotation direction of the wheels is 45 degrees around the quenching platform, and the water outlet flow of a single nozzle is 20m3H, duration 450 s. And then the finished product of the wheel is obtained through the working procedures of machining, tread profiling and the like after tempering.
On the basis of a conventional heating system, according to the solid solubility product relation of carbon-nitrogen-vanadium, the invention enables vanadium in steel to be dissolved into an austenite matrix in a proper proportion by properly increasing the austenitizing temperature, and V existing in undissolved V (C, N) second phase particles does not participate in subsequent precipitation strengthening but can become a nucleation core of proeutectoid ferrite. In the subsequent quenching and cooling process, V (C, N) second phase particles which are coherent or semi-coherent with the matrix are separated out from the V precipitates dissolved in the matrix, and a strong precipitation strengthening effect is generated, so that the yield strength is obviously improved. The un-dissolved V (C, N) second phase particle which is not coherent with the matrix becomes a catalyst for ferrite heterogeneous nucleation due to the lack of micro-region C, V and smaller lattice mismatch degree with ferrite, so that the content of pro-eutectoid ferrite is increased in the quenching and cooling process, and the increment of tensile strength and hardness is restrained. By adopting the technical measures of the invention, the yield strength of the wheel can be obviously improved, thereby obviously improving the capability of resisting contact fatigue crack initiation; on the other hand, the wear resistance is in a positive correlation with the tensile strength and the hardness and in a negative correlation with the ferrite content, so that the increase of the tensile strength and the hardness is small, the ferrite content is increased, and the wear rate can be improved. Therefore, the invention can improve the competitive relationship of contact fatigue and abrasion, thereby improving the surface contact fatigue resistance of the wheel material.
A method for manufacturing a wheel using the wheel steel of comparative example 1, comprising the steps of:
the method adopts the following general heat treatment process: heating the blank wheel to 860 +/-10 ℃ (the soaking target temperature is 860 ℃) for 1h and 30min, preserving heat for 2h, and transporting the blank wheel to a quenching platform after the blank wheel is in a complete austenitizing state. The thermal treatment cooling is completed by adopting large-water-volume spraying quenching of the tread, and the specific quenching system is the same as that of the example 1. And after tempering, performing preprocessing, finish machining and other processes to obtain the finished wheel.
The yield strength and the average hardness at wear of the wheels of example 1 and comparative example 1 were obtained by room temperature tensile mechanical property test and brinell hardness test, see table 2. It can be seen that the yield strength of the wheels of example 1 is significantly higher than that of the wheels of comparative example 1, but the hardness level is slightly lower than that of the wheels of comparative example 1. When the microstructure of the wheel materials of example 1 and comparative example 1 was observed by an optical microscope, as shown in fig. 1 and 2, the ferrite content in the wheel structure of example 1 was significantly higher than that in the wheel of comparative example 1. The static strength and the microstructure characteristics are in accordance with the invention design of balancing and coordinating the competitive relationship between wear and contact fatigue.
The nature of surface contact fatigue crack initiation is ratchet effect, therefore, the service life of the ratchet can be used as a parameter for representing the contact fatigue damage resistance of the material. Ratchet evolution behavior of the wheel was obtained by an asymmetric cyclic tension-compression plasticity experiment, and the ratchet failure life of the wheel samples of example 1 and comparative example 1 is shown in table 3. It can be seen that the ratchet life of the wheel material of example 1 is higher than that of the comparative example under the same stress conditions, and the lower the stress, the more pronounced the difference. The evolution of ratchet strain versus cycle time is shown in fig. 3. The slope at any point on the curve is the ratchet rate, and it can be seen that the ratchet rate is lower for the example 1 wheel material than for the comparative example 1 wheel material, and the lower the stress, the more pronounced the difference. It is shown that the wheel of example 1 is more resistant to fatigue crack initiation than the wheel of comparative example 1 under the same stress conditions.
In order to compare the wear performance of the wheel sample, dry-state wear experiments of different cycle times are carried out, the ground sample is a U75 steel rail sample, the initial point contact stress is 2200MPa, the rotating speed is 800 r/min, the slip ratio is 0.75%, the experiment frequency is 50 ten thousand r, and the sample is air-cooled.
In order to compare the surface crack initiation resistance and the surface crack propagation resistance of the wheel sample, a dry grinding and water lubrication combined contact experiment is carried out. The dry grinding experiment simulates the surface contact fatigue crack initiation process, the grinding sample is a U75 steel rail sample, the contact stress is 1200MPa, the rotating speed is 500 r/min, the slip ratio is 0.75%, the experiment frequency is 15000 r, and the sample is air-cooled; and (3) carrying out a wet-sliding contact experiment immediately after the dry-grinding experiment, simulating the surface contact fatigue crack propagation process, wherein the contact stress and the rotating speed are the same as those of the dry-grinding experiment, the slip ratio is 0.3%, the experiment frequency is 20000 revolutions, and the lubricating medium is 10% glycol aqueous solution.
The wear of the wheel samples of example 1 and comparative example 1 over different cycles is shown in fig. 4. It can be seen that under the same experimental conditions, the wear rate of the wheel sample of example 1 is slightly higher than that of comparative example 1, and the invention design of balancing and coordinating the competition relationship between wear and contact fatigue is met. The weight loss, the contact fatigue crack density and the crack depth of the wheel sample of the embodiment 1 and the wheel sample of the comparative example 1 after the dry grinding and water lubrication combined contact experiment are shown in table 3, and the surface contact fatigue crack and the longitudinal section crack morphology, the tissue morphology and the longitudinal section morphology of the plastic deformation layer are shown in fig. 5-10. It can be seen that the example 1 wheel material has greater resistance to contact fatigue crack initiation and propagation than the comparative example 1 wheel material.
TABLE 2 static Strength and hardness of wheels
TABLE 3 ratchet wheel durability and contact fatigue Performance for wheels
One of the effects of the invention is to increase the ferrite content and simultaneously make the tensile strength increase smaller than the yield strength increase so as to coordinate and balance the relationship between abrasion and fatigue performance. Fig. 4 is a normal wear rate without fatigue peeling, the example is expected to have a greater effect than the comparative example, and the weight loss in table 2 refers to the weight loss in the case of peeling, and the weight loss in peeling is greater than in the example because of metal loss due to peeling.
The method for producing the wheel by using the heavy-load locomotive wheel steel resisting the surface contact fatigue, which is disclosed in the embodiment 2, comprises the following steps of:
and (3) charging the blank wheel formed by rolling into a furnace, heating to 870 +/-10 ℃ after 1h and 45min (the soaking target temperature is 870 ℃), soaking and preserving heat for 2h, taking out the blank wheel and transferring the blank wheel to a quenching platform, wherein the adopted quenching cooling system is the same as that of the example 1. And then the finished product of the wheel is obtained through the working procedures of machining, tread profiling and the like after tempering.
A method of producing a wheel from the steel of comparative example 2, comprising the steps of:
the method adopts the following general heat treatment process: heating the blank wheel to 840 +/-10 ℃ (soaking target temperature 840 ℃) for 1h and 30min, preserving heat for 2h, conveying the blank wheel to a quenching platform after the blank wheel is in a complete austenitizing state, wherein the adopted quenching system is the same as that of the comparative example 1. And after tempering, performing preprocessing, finish machining and other processes to obtain the finished wheel.
Static load mechanical property test, microstructure analysis, cyclic plasticity experiment, opposite grinding contact experiment and the like are carried out according to the embodiment 1 and the comparative example 1, and the related experiment results are shown in tables 2 and 3. It can be seen that the static strength, the microstructure characteristics, the wear rate and the contact fatigue crack initiation and propagation resistance of the wheel material in the example 2 all accord with the invention design of balancing and coordinating the competition relationship between wear and contact fatigue, and the surface contact fatigue resistance of the wheel in the example 2 is higher than that of the wheel in the comparative example 2.
The method for producing the wheel by using the heavy-load locomotive wheel steel resisting the surface contact fatigue, which is disclosed in the embodiment 3, comprises the following steps of:
and (3) charging the blank wheel formed by rolling into a furnace, heating to 920 +/-10 ℃ after 2 hours (the soaking target temperature is 920 ℃), soaking and preserving heat for 2 hours, taking out the blank wheel and transferring the blank wheel to a quenching platform, wherein the adopted quenching cooling system is the same as that in example 1. And then the finished product of the wheel is obtained through the working procedures of machining, tread profiling and the like after tempering.
A method of producing a wheel from a comparative example 3 round of steel comprising the steps of:
the method adopts the following general heat treatment process: heating the blank wheel to 870 +/-10 ℃ for 1h and 45min (the soaking target temperature is 870 ℃), preserving heat for 2h, conveying the blank wheel to a quenching platform after the blank wheel is in a complete austenitizing state, wherein the adopted quenching system is the same as that of the comparative example 1. And after tempering, performing preprocessing, finish machining and other processes to obtain the finished wheel.
Static load mechanical property test, microstructure analysis, cyclic plasticity experiment, opposite grinding contact experiment and the like are carried out according to the embodiment 1 and the comparative example 1, and the related experiment results are shown in tables 2 and 3. It can be seen that the static strength, the microstructure characteristics, the wear rate and the contact fatigue crack initiation and propagation resistance of the wheel material in the example 3 all accord with the invention design of balancing and coordinating the competition relationship between wear and contact fatigue, and the surface contact fatigue resistance of the wheel in the example 3 is higher than that of the wheel in the comparative example 3.
The above detailed description of a heavy duty locomotive wheel resistant to surface contact fatigue and the method of making the same have been described in detail with reference to the embodiments and the accompanying drawings, which are merely illustrative and not restrictive, and several embodiments may be enumerated within the scope of the limitations, thus changes and modifications may be made without departing from the general concept of the present invention.