CN111996444B

CN111996444B - Medium-carbon and medium-silicon niobium microalloyed high-speed wheel steel and wheel preparation method

Info

Publication number: CN111996444B
Application number: CN202010735003.5A
Authority: CN
Inventors: 赵海; 丁毅; 江波; 刘学华; 张明如
Original assignee: Maanshan Iron and Steel Co Ltd
Current assignee: Maanshan Iron and Steel Co Ltd
Priority date: 2020-07-28
Filing date: 2020-07-28
Publication date: 2021-12-14
Anticipated expiration: 2040-07-28
Also published as: CN111996444A

Abstract

The invention discloses niobium microalloyed high-speed wheel steel containing medium carbon and medium silicon and a wheel preparation method, belonging to the field of railway wheel preparation. Aiming at the problems of poor adaptability and lower strength and hardness of high-speed wheel steel in the prior art, the invention provides medium-carbon medium-silicon niobium microalloyed high-speed wheel steel, which comprises the following components in percentage by weight: c: 0.50-0.58%, Si: 0.50-0.80%, Mn: 0.50-0.90%, Nb: 0.02-0.04%, P less than or equal to 0.015%, S less than or equal to 0.015%, and the balance of Fe and inevitable impurity elements. According to the invention, niobium is added into the wheel steel, niobium and carbon are combined to form niobium carbide, so that the effect of refining pearlite colony is achieved during steel rolling and heat treatment, a certain amount of ferrite precipitation is ensured, the strength and hardness matching of the wheel steel is improved, the strength and hardness level is improved by more than 5% compared with that of an ER8 wheel, and the contact fatigue resistance and the wear resistance are also improved. The preparation method provided by the invention optimizes the heat treatment process, further improves the adaptability of the wheel and enables the wheel to have higher strength and hardness.

Description

Medium-carbon and medium-silicon niobium microalloyed high-speed wheel steel and wheel preparation method

Technical Field

The invention belongs to the technical field of railway wheel preparation, and particularly relates to medium-carbon and medium-silicon niobium microalloyed high-speed wheel steel and a wheel preparation method.

Background

China has attracted attention for the development of high-speed railways, and key parts of high-speed trains are independently innovated. At present, the high-speed wheel in China is mainly an ER8 wheel in European standard EN13262, the wheel made of medium carbon steel has high fracture toughness (more than or equal to 70 MPa-m)^1/2) And the service safety is ensured. The structure of the ER8 wheel is a small amount of discontinuous reticular ferrite and lamellar pearlite, wherein the ferrite is a soft phase, the toughness is good, the yield strength is low, the pearlite strength is high, but the toughness is poor, and the matching relationship of the contents of the two is determinedThe final properties of the material are fixed. The rim yield strength of ER8 wheel is generally not more than 600MPa, the rolling contact stress between wheel rails is large and alternate when the wheel runs at high speed, so that the secondary surface of the wheel rim tread generates plastic deformation in the running process, and because the steel contains inclusions, cementite and other brittle phases, the rim is easy to generate micro cracks, and the micro cracks generate damages such as peeling and the like under the action of the rolling contact fatigue of the wheel during running. The hardness of the ER8 wheel is generally not more than 265HB, and is relatively low, so that regular vibration is generated in the high-speed movement process of the train, and the polygonal shape of the wheel is generated along with the abrasion of the wheel. From the probability of polygon generation of the high-speed wheel and the statistical result of wheel hardness, the hardness improvement can reduce the polygon generation, and therefore, the service performance of the wheel can be improved by improving the hardness level. In addition, from the relationship of rail hardness matching, the wheel hardness cannot be higher than the rail hardness. In general, the yield strength and tensile strength of the material are correspondingly improved after the hardness is improved, and the effect of plastic deformation of the surface layer of the wheel under the contact stress of the wheel and the rail can be reduced, so that the initiation source of the micro-cracks is reduced. However, the improvement of the strength and the hardness inevitably brings about a reduction in the toughness index, and affects the running risk of the vehicle. Meanwhile, the European high-speed railway has relatively single line, relatively short continuous high-speed running time and no obvious change in climatic conditions, and the ER8 wheel shows better service performance. The service of ER8 wheels has obvious inadaptability due to long-term high-speed railway lines, long trains running at high speed for a long time, large temperature difference between south and north, and large change of east-west service conditions in China, and particularly, the damage problems of wheel tread stripping, multiple changes and the like are more in high-speed trains with the speed of 300 kilometers per hour, so that the maintenance frequency of the wheels is greatly increased, the service life of the wheels is shortened, and the comprehensive cost is improved.

Through research for decades, the comprehensive performance of carbon steel wheels is basically exerted to a limit level, and the further improvement through the optimization of a heat treatment process is difficult. The addition of other elements and alloying become the most direct and effective method for improving the performance of the wheel. In the North American AAR M107/M208 standard, the upper line of Si content is put to 1.0 percent and is obviously higher than 0.40 percent of carbon steel, which is mainly because the AAR M107/M208 standard is mainly used for wheels of trucks, the wheels are braked by brake shoes, the wheel treads are easy to generate heat cracks, and the addition of Si improves the material phase change point and reduces the production of the heat cracks. The 12 national standards of GOST 10791 such as Russia and the like put the line of V content to 0.15%, play the role of V reinforcement and grain refinement, and improve the comprehensive performance of the wheel. Therefore, the characteristics of the high-speed railway in China are combined, component innovation and performance improvement are realized by adding alloy elements on the basis of ER8 wheel component design and performance indexes, and the method has great significance for realizing high-speed wheel products with independent intellectual property rights.

Corresponding improvement is also carried out aiming at the problems, for example, Chinese patent application No. CN201310736261.5, the publication date is 2014, 4, 23, the patent discloses a medium carbon steel wheel steel for railway locomotives and a wheel preparation method, the medium carbon steel wheel steel for railway locomotives and the wheel preparation method improve the fracture toughness, and the weight percentages of chemical components are as follows: 0.46-0.53% of C, 0.20-0.37% of Si, 0.70-0.85% of Mn, 0.10-0.25% of Ni, 0.24-0.32% of Cr, 0.020-0.040% of Als, less than or equal to 0.008% of P, less than or equal to 0.008% of S, and the balance of Fe and inevitable impurity elements, wherein the heat treatment process comprises the following steps: heating the rolled and roughly processed wheel to 860-880 ℃ along with a furnace, preserving heat for 3-3.5 hours, discharging the wheel out of the furnace, and air cooling the wheel to room temperature; heating the wheels to 840-860 ℃ along with the furnace, preserving heat for 4 hours, and then taking the wheels out of the furnace and spraying water for cooling for 400 s; and then putting the mixture into a furnace at 480-500 ℃, preserving heat for 5 hours, and then discharging the mixture out of the furnace for air cooling. The disadvantages of the patent are that: although the toughness level of the material is improved by adding Ni element, the hardness is not obviously improved, and the problem of polygon generated in service of the wheel cannot be effectively solved.

As another example, chinese patent application No. CN201410247587.6, published as 2014, 9, and 3, discloses a medium-carbon low-alloy wheel steel for subways and a manufacturing method thereof, and the steel comprises the following chemical components in percentage by weight: 0.50-0.60% of C, 0.80-1.20% of Si, 0.90-1.10% of Mn0.15-0.35% of Cr0.15-0.35%, 0.010-0.030% of Als, less than or equal to 0.015% of P, less than or equal to 0.015% of S, and the balance of Fe and inevitable impurity elements. The manufacturing method comprises the following steps: an electric furnace smelting process, an ingot cutting and rolling process and a heat treatment process. The disadvantages of the patent are that: the wheel steel of this patent is a medium to high carbon and high silicon manganese steel with a high level of hardness but relatively low toughness.

Disclosure of Invention

1. Problems to be solved

Aiming at the problems of poor adaptability and lower strength and hardness of high-speed wheel steel in the prior art, the invention provides medium-carbon medium-silicon niobium microalloyed high-speed wheel steel and a wheel preparation method. According to the invention, niobium is added into the wheel steel, niobium and carbon are combined to form niobium carbide, so that the effect of refining pearlite colony is achieved during steel rolling and heat treatment, a certain amount of ferrite precipitation is ensured, the strength and hardness matching of the wheel steel is improved, the strength and hardness level is improved by more than 5% compared with that of an ER8 wheel, and the contact fatigue resistance and the wear resistance are also improved. The preparation method provided by the invention optimizes the heat treatment process, further improves the adaptability of the wheel and ensures that the wheel has higher strength and hardness.

2. Technical scheme

In order to solve the above problems, the present invention adopts the following technical solutions.

The medium-carbon medium-silicon niobium microalloyed high-speed wheel steel is characterized by comprising the following components in percentage by weight: comprises the following components in percentage by weight: c: 0.50-0.58%, Si: 0.50-0.80%, Mn: 0.50-0.90%, Nb: 0.02-0.04%, P less than or equal to 0.015%, S less than or equal to 0.015%, and the balance of Fe and inevitable impurity elements.

Furthermore, the paint comprises the following components in percentage by weight: c: 0.53%, Si: 0.55%, Mn: 0.70%, Nb: 0.02%, P:0.005 percent of S, 0.007 percent of S and the balance of Fe and inevitable impurity elements.

A method for preparing a medium-carbon silicon-in-niobium microalloyed high-speed wheel by using the medium-carbon silicon-in-niobium microalloyed high-speed wheel steel, which comprises a heat treatment process, wherein the heat treatment process comprises the following steps:

s1: the wheel is kept warm for 2.0 to 3.5 hours at the temperature of 860 ℃ and 890 ℃;

s2: spraying water to cool the heat-insulated wheel;

s3: and tempering the cooled wheel.

Further, the wheel is cooled to below 550 ℃ in S2 and then the next step is carried out.

Further, in the step S2, the wheel is horizontally placed on the wheel cooling platform, and the wheel is self-transmitted on the wheel cooling platform in the clockwise direction at a speed of 20r/min to 30r/min, and the wheel is subjected to water spray cooling treatment by using a nozzle on the wheel cooling platform.

Furthermore, a plurality of nozzles are uniformly distributed on the wheel cooling platform at intervals around the circumference of the wheel tread.

Further, the wheel in S3 is tempered at 500-550 ℃ for 4.5-6.0 hours.

Furthermore, before the heat treatment process, the method also sequentially comprises an electric furnace steelmaking process, an LF furnace refining process, an RH vacuum treatment process, a round billet continuous casting process and an ingot cutting and rolling process; the heat treatment process also comprises a processing process and a finished product detection process.

3. Advantageous effects

Compared with the prior art, the invention has the beneficial effects that:

(1) according to the invention, niobium is added into the components of the high-speed wheel steel, the niobium is taken as an important added alloy element, the niobium can be combined with carbon to form niobium carbide, the effect of refining pearlite groups is achieved during steel rolling and heat treatment, a certain amount of ferrite precipitation is ensured, the obdurability matching of the wheel steel is improved, the strength and hardness levels are improved by more than 5% compared with those of ER8 wheels on the premise that the toughness index of the high-speed wheel steel is not reduced, and the contact fatigue resistance and the wear resistance are also improved;

(2) according to the invention, the wheel is subjected to heat preservation at the temperature of 860-890 ℃ in the heat treatment process, because the niobium element is added into the components of the wheel steel, the effect of the niobium element is fully exerted, and second phase particles formed by the niobium element are dissolved in austenite, if the temperature exceeds 890 ℃, the austenite grains can obviously grow up, and the influence on the toughness index is large; meanwhile, the cooling speed of the wheel is selected within 2 ℃/s-5 ℃/s, the rim structure of the wheel is ensured to be a pearlite + ferrite structure at the cooling speed, a bainite structure can be generated due to overhigh cooling speed, the cooling speed is overlow, the spacing between generated pearlite pieces is overlarge, the content of precipitated ferrite is high, and the comprehensive performance of the wheel is reduced;

(3) according to the invention, chromium element capable of improving the hardenability of the wheel and further improving the hardness is not added in the design components of the wheel steel, and the hardenability of the chromium element is further improved at high temperature, so that a deeper abnormal structure, namely a non-pearlite structure, can be generated on the surface layer of the rim tread of the wheel during heat treatment, and certain influence can be caused on the performance of the wheel; according to the invention, the hardness of the wheel is enhanced by increasing the content of the silicon element, the problem of hardness reduction caused by lack of the chromium element is solved, and meanwhile, the toughness of the wheel is improved by the niobium element, so that the prepared wheel has higher service performance;

(4) the preparation method is simple and convenient to operate, and the parameters of the heat treatment process are optimized, so that the toughness of the prepared wheel is basically not reduced compared with that of an ER8 wheel, but the strength and the hardness are improved, and better comprehensive mechanical properties are obtained; meanwhile, under the condition of a laboratory, the wear resistance and the contact fatigue resistance of the material are better than those of an ER8 wheel material, the wheel prepared by the method can keep the ferrite-pearlite structure state of the original wheel without increasing the difficulty of wheel preparation, and in addition, the hardness of the wheel prepared by the method is still in the wheel rail hardness matching range, so that the use of the steel rail is not influenced.

Drawings

FIG. 1 is a microstructure of a wheel rim according to example 1 of the present invention;

FIG. 2 is a microstructure of a wheel rim according to example 2 of the present invention;

FIG. 3 is a microstructure of a wheel rim according to example 3 of the present invention;

fig. 4 is a microstructure diagram of ER8 wheel rim.

Detailed Description

The invention is further described with reference to specific embodiments and the accompanying drawings.

The steel for train wheels at home and abroad is medium and high carbon steel with a ferrite-pearlite structure, and compared with other structures, the steel has the best wear resistance at a certain hardness level, so the steel for train wheels of the invention has a ferrite-pearlite structure state. The currently commonly used ER8 wheel steel comprises the following components in percentage by weight: less than or equal to 0.56 percent of C, less than or equal to 0.40 percent of Si, less than or equal to 0.80 percent of Mn, less than or equal to 0.015 percent of P, less than or equal to 0.025 percent of S, less than or equal to 0.08 percent of Mo, less than or equal to 0.06 percent of V, less than or equal to 0.30 percent of Cr, less than or equal to 0.30 percent of Ni, less than or equal to 0.30 percent of Cu, and the balance of Fe and inevitable impurity elements. According to the invention, Si and Nb elements are added to form a brand-new wheel steel component design system, and corresponding heat treatment processes are matched, so that the strength and hardness of the wheel are improved by more than 5% compared with those of an ER8 wheel on the premise of not reducing the toughness index, the contact fatigue resistance and the wear resistance are also improved, the wheel is suitable for high-speed motor train units, and the wheel can stably run under the conditions of high running speed, long mileage and large temperature change of service environment. The specific scheme of the invention is as follows:

the medium-carbon medium-silicon niobium microalloyed high-speed wheel steel comprises the following components in percentage by weight: c: 0.50-0.58%, Si: 0.50-0.80%, Mn: 0.50-0.90%, Nb: 0.02-0.04%, P is less than or equal to 0.015%, S is less than or equal to 0.015%, and the balance is Fe and inevitable impurity elements, wherein the detailed description is given for each component:

c element: in the aspect of improving the hardness of the wheel, C contributes most to the strength and the hardness, the strength and hardness index of the wheel can be obviously improved along with the increase of the carbon content, the wear resistance of the wheel is improved, but the toughness of the wheel is reduced due to the excessively high content of C, so that the content of C is properly adjusted to be between 0.50 and 0.58 percent in order to ensure that the toughness of the wheel is not reduced compared with ER 8;

mn element: the strength and hardness of the wheel can be effectively improved, the content of Mn element in the ER8 carbon steel wheel is generally 0.50-0.80%, the Mn content can be properly improved for further playing the role of Mn element, but the excessive Mn content, namely the Mn content is more than 0.90%, has adverse effect on the comprehensive mechanical property and the processing property of the wheel, so the Mn content is controlled to be 0.50-0.90%;

si element: increasing the content of Si element not only can increase the phase transformation point of the material, but also can improve the strength and the hardness, but too high Si can increase the thermal sensitivity and the brittleness of the material. The upper limit of the Si content of the carbon steel wheel in ER8 is 0.40 percent, and the Si content of the invention is controlled between 0.50 and 0.80 percent;

nb element: the niobium can be combined with carbon to form niobium carbide, and plays a role in refining pearlite colonies during steel rolling and heat treatment. However, higher Nb content, combined with higher C content, tends to result in a reduction in cementite and a reduction in the level of strength. The Nb content in the invention is controlled to be 0.02-0.04%, a small amount of niobium carbide can be formed to play a role in refining grains and pearlite colonies, on the other hand, the content of cementite in pearlite cannot be greatly reduced due to the combination of C and Nb, and a certain amount of ferrite is precipitated, so that the toughness matching is improved.

P and S are impurity elements, so that the content thereof should be controlled to not more than 0.015%.

According to the invention, the hardness of the wheel is enhanced by increasing the content of the silicon element, and chromium element capable of improving the hardenability of the wheel so as to improve the hardness is not required to be added, and the hardenability of the chromium element at high temperature is further improved, so that a deeper abnormal structure, namely a non-pearlite structure, can be generated on the surface layer of the rim tread of the wheel during heat treatment, and certain influence can be caused on the performance of the wheel; meanwhile, the toughness of the wheel is improved by the niobium element. As the foreign railways are developed earlier than China, the technology and the system are complete, and the traditional carbon steel wheel can meet the use requirements. The railway in China starts late, but the development is rapidly advanced in nearly 20 years, and the overall level is beyond foreign countries. As the service conditions of railways in China are obviously different from those in China, the temperature difference between the south and the north is large, and the east-west landforms, the moisture, the wind sand and the like also have differences, and high-speed railways in China have the highest operation speed, the factors cause new problems in the service process of wheel products imported from the abroad, so that new design is required on materials. In the last decade, the inventor has carried out a great deal of research on wheel materials, and researches on the interaction of different elements on the organization and performance of the wheel materials. Taking Nb as an example, conventional wheel steel is added with Nb to form Nb carbides and carbonitrides, which promote ferrite precipitation and improve toughness, but cause a decrease in hardness. Through a large number of experiments and researches on interaction among C, Si and Nb, the inventor finds that the toughness of the material can be improved and the hardness of the material can be improved through reasonable component matching.

The preparation method of the medium-carbon and medium-silicon niobium microalloyed high-speed wheel steel comprises a heat treatment process, wherein the heat treatment process comprises the following steps of:

s1: the wheel is heated at the temperature of 860-890 ℃, and the temperature is kept for 2.0 to 3.5 hours after the heating; if the heating temperature exceeds 890 ℃, austenite grains can obviously grow up, and the influence on the toughness index of the wheel is large;

s2: spraying water to cool the heat-insulated wheel; specifically, the wheel kept warm in the step S1 is horizontally placed on a wheel cooling table, the wheel is automatically transmitted on the wheel cooling table in the clockwise direction at the speed of 20 r/min-30 r/min, and a nozzle on the wheel cooling table is used for carrying out water spraying cooling treatment on the wheel, so that metal in the wheel is accelerated and cooled to below 550 ℃ at the cooling speed of 2 ℃/S-5 ℃/S; in the cooling process, martensite and bainite structures are not generated, and the section of the wheel is ensured to be a pearlite + ferrite structure; furthermore, in the step, a plurality of nozzles are uniformly distributed on the wheel cooling table at intervals around the circumferential direction of the wheel tread, the nozzles are inclined nozzles, the inclined nozzles are arranged above the wheel, and the inclined nozzles are inclined downwards to spray water for cooling the wheel, so that the wheel can be uniformly cooled in all directions in multiple directions, and the uniform performance of the circumferential organization of the wheel is better;

s3: and tempering the cooled wheel at 500-550 ℃ for 4.5-6.0 hours.

Of course, the heat treatment is only a part of the wheel prepared by using the medium-carbon aluminum-controlled nitrogen-controlled vanadium microalloyed high-speed wheel steel, and the finished process steps are as follows: an electric furnace steelmaking process → an LF furnace refining process → an RH vacuum treatment process → a round billet continuous casting process → an ingot cutting and rolling process → a heat treatment process → a processing process → a finished product detection process. Since other processes are conventional in the art, the steps will not be described in detail in the present invention. The preparation method is simple and convenient to operate, and parameters of the heat treatment process are optimized, so that the toughness of the prepared wheel is basically not reduced compared with that of the ER8 wheel, but the strength and the hardness are improved, and better comprehensive mechanical properties are obtained.

Example 1

The medium-carbon medium-silicon niobium microalloyed high-speed wheel steel comprises the following components in percentage by weight: c: 0.53%, Si: 0.55%, Mn: 0.70%, Nb: 0.02%, P0.005%, S0.007%, and the balance of Fe and inevitable impurity elements; the preparation method of the wheel comprises the following steps: the molten steel containing the components is subjected to an electric furnace steelmaking process, an LF furnace refining process, an RH vacuum treatment process, a round billet continuous casting process, an ingot cutting and rolling process, a heat treatment process, a processing process and a finished product detection process to form the medium-carbon medium-silicon niobium microalloyed high-speed wheel, wherein the heat treatment process comprises the following steps: firstly heating at 870 ℃, keeping the temperature for 2.5 hours after heating, spraying water to cool the wheel, accelerating to cool the metal in the wheel to below 550 ℃ at the cooling speed of 2-5 ℃/s, and finally tempering at 520 ℃ for 5.0 hours. As a comparative example of the invention, in the implementation, the composition of the ER8 wheel steel comprises the following components in percentage by weight: c: 0.56%, Si: 0.40%, Mn: 0.80%, P: 0.015%, S: 0.025%, Mo: 0.08%, V: 0.06%, Cr: 0.30%, Ni: 0.30%, Cu: 0.30 percent, and the balance of Fe and inevitable impurity elements.

As shown in fig. 1 and 4, the metallographic structure of the wheel rim prepared in this example and the ER8 wheel were both pearlite + reticulated ferrite, but the content of ferrite in this example was about 17%, the content of ferrite in ER8 was about 6%, and the content of ferrite in this example was about 11% more than that of the ER8 wheel. The mechanical properties of the wheel in this example are shown in Table 1, with toughness levels substantially the same as those of the ER8 wheel, while strength and hardness are significantly improved over those of the ER8 wheel. The abrasion performance and the contact fatigue performance are compared and tested on an MMS-2A type microcomputer control testing machine, under the same test conditions: in the test process, the main test sample is the wheel test sample prepared in the embodiment and the ER8 wheel test sample, the auxiliary test samples are U71Mn steel rail test samples with the same hardness, and the diameters of the main test sample and the auxiliary test samples are both 60 mm. And (3) wear test: the rotation speed of a main sample is 360rpm, the rotation speed of a matched sample is 400rpm, the corresponding rotation slip rate is 0.75%, the contact stress is 1100MPa, and the cycle frequency is 50 ten thousand times. Contact fatigue test: the rotating speed of a group of 6 samples is 2000rpm, the corresponding rotating slip ratio is 0.3 percent, the contact stress is 1100-. Meanwhile, the cycle frequency of the contact fatigue of the wheel is obviously higher than that of the ER8 wheel, which shows that the rolling contact fatigue resistance of the wheel material in the embodiment is better than that of the ER8 wheel.

Meanwhile, under the same test conditions, the abrasion weight loss of the U71Mn steel rail sample ground by the wheel sample prepared in the embodiment is obviously lower than that of the U71Mn steel rail sample ground by the ER8 wheel sample, which is more beneficial to prolonging the service life of the steel rail.

Example 2

The medium-carbon medium-silicon niobium microalloyed high-speed wheel steel comprises the following components in percentage by weight: c: 0.54%, Si: 0.60%, Mn: 0.65%, Nb: 0.03 percent of P, 0.005 percent of S, 0.006 percent of S and the balance of Fe and inevitable impurity elements; the preparation method of the wheel comprises the following steps: the molten steel containing the components is subjected to an electric furnace steelmaking process, an LF furnace refining process, an RH vacuum treatment process, a round billet continuous casting process, an ingot cutting and rolling process, a heat treatment process, a processing process and a finished product detection process to form the medium-carbon medium-silicon niobium microalloyed high-speed wheel, wherein the heat treatment process comprises the following steps: heating at 880 ℃, keeping the temperature for 3 hours after heating, spraying water to cool the wheel, accelerating the cooling of the metal in the wheel to below 550 ℃ at the cooling speed of 2-5 ℃/s, and finally tempering at 540 ℃ for 5.5 hours. The composition of the ER8 wheel steel in this example was identical to that of example 1.

As shown in fig. 2 and 4, the metallographic structure of the wheel rim prepared in this example and the ER8 wheel were both pearlite + reticulated ferrite, but the ferrite content of the wheel in this example was about 14%, which was about 8% more than that of the ER8 wheel. The mechanical properties of the wheel in this example are shown in Table 1, with toughness levels substantially the same as those of the ER8 wheel, while strength and hardness are significantly improved over those of the ER8 wheel. A wear performance and contact fatigue performance comparison test is carried out on an MMS-2A type microcomputer control testing machine, under the same test conditions, main samples in the test process are the wheel sample prepared in the embodiment and an ER8 wheel sample, all the matched samples are U71Mn steel rail samples with the same hardness, and the diameters of the main samples and the matched samples are both 60 mm. And (3) wear test: the rotation speed of a main sample is 360rpm, the rotation speed of a matched sample is 400rpm, the corresponding rotation slip rate is 0.75%, the contact stress is 1100MPa, and the cycle frequency is 50 ten thousand times. Contact fatigue test: the rotating speed of a group of 6 samples is 2000rpm, the corresponding rotating slip ratio is 0.3 percent, the contact stress is 1100-. Meanwhile, the cycle frequency of the contact fatigue of the wheel is obviously higher than that of the ER8 wheel, which shows that the rolling contact fatigue resistance of the wheel material in the embodiment is better than that of the ER8 wheel.

Example 3

The medium-carbon medium-silicon niobium microalloyed high-speed wheel steel comprises the following components in percentage by weight: c: 0.57%, Si: 0.75%, Mn: 0.85%, Nb: 0.04%, P: 0.004%, S: 0.006% of Fe and inevitable impurity elements as the rest; the preparation method of the wheel comprises the following steps: the molten steel containing the components is subjected to an electric furnace steelmaking process, an LF furnace refining process, an RH vacuum treatment process, a round billet continuous casting process, an ingot cutting and rolling process, a heat treatment process, a processing process and a finished product detection process to form the medium-carbon medium-silicon niobium microalloyed high-speed wheel, wherein the heat treatment process comprises the following steps: firstly heating at 870 ℃, keeping the temperature for 3.5 hours after heating, spraying water to cool the wheel, accelerating to cool the metal in the wheel to below 550 ℃ at the cooling speed of 2 ℃/s-5 ℃/s, and finally tempering at 520 ℃ for 5.5 hours. The composition of the ER8 wheel steel in this example was identical to that of example 1.

As shown in fig. 3 and 4, the metallographic structure of the wheel rim prepared in this example and the ER8 wheel were both pearlite + discontinuous network ferrite, but the ferrite content of the wheel in this example was about 9%, which was about 3% more than that of the ER8 wheel. The mechanical properties of the wheel in this example are shown in Table 1, with toughness levels substantially the same as those of the ER8 wheel, while strength and hardness are significantly improved over those of the ER8 wheel. A wear performance and contact fatigue performance comparison test is carried out on an MMS-2A type microcomputer control testing machine, under the same test conditions, main samples in the test process are the wheel sample prepared in the embodiment and an ER8 wheel sample, all the matched samples are U71Mn steel rail samples with the same hardness, and the diameters of the main samples and the matched samples are both 60 mm. And (3) wear test: the rotation speed of a main sample is 360rpm, the rotation speed of a matched sample is 400rpm, the corresponding rotation slip rate is 0.75%, the contact stress is 1100MPa, and the cycle frequency is 50 ten thousand times. Contact fatigue test: the rotating speed of a group of 6 samples is 2000rpm, the corresponding rotating slip ratio is 0.3 percent, the contact stress is 1100-. Meanwhile, the cycle frequency of the contact fatigue of the wheel is obviously higher than that of the ER8 wheel, which shows that the rolling contact fatigue resistance of the wheel material in the embodiment is better than that of the ER8 wheel.

Table 1 examples 1-3 and ER8 wheel rim performance

TABLE 2 comparison of wear Performance of examples 1-3 and ER8 wheels

TABLE 3 comparison of contact fatigue Performance of examples 1-3 and ER8 wheels

It is clear from tables 2 and 3 that under the laboratory conditions, the wear resistance and the contact fatigue resistance of the medium-carbon and medium-silicon niobium microalloyed high-speed wheel steel are better than those of ER8 wheels, the wheel prepared by the invention can keep the ferrite-pearlite structure state of the original wheel without increasing the difficulty of wheel preparation, and in addition, the hardness of the wheel prepared by the invention is still in the hardness matching range of a wheel rail and does not influence the use of a steel rail.

The examples described herein are merely illustrative of the preferred embodiments of the present invention and do not limit the spirit and scope of the present invention, and various modifications and improvements made to the technical solutions of the present invention by those skilled in the art without departing from the design concept of the present invention shall fall within the protection scope of the present invention.

Claims

1. The preparation method of the medium-carbon medium-silicon niobium microalloyed high-speed wheel comprises a heat treatment process and is characterized in that: the medium-carbon medium-silicon niobium microalloyed high-speed wheel steel comprises the following components in percentage by weight: c: 0.53%, Si: 0.55%, Mn: 0.70%, Nb: 0.02%, P0.005%, S0.007%, and the balance Fe and inevitable impurity elements, the heat treatment process comprising the steps of:

s1: the wheel is heated at the temperature of 860-890 ℃, and the temperature is kept for 2.0 to 3.5 hours after the heating;

s2: spraying water to cool the heat-insulated wheel; horizontally placing the wheel on a wheel cooling table, automatically transmitting the wheel on the wheel cooling table in a clockwise direction at a speed of 20 r/min-30 r/min, spraying water to cool the wheel by using a nozzle on the wheel cooling table, and cooling to below 550 ℃ before entering the next step;

s3: the cooled wheel was tempered to a ferrite content of 17%.

2. The method for preparing the medium-carbon silicon-in-niobium microalloyed high-speed wheel according to claim 1, wherein: and a plurality of nozzles are uniformly distributed on the wheel cooling table at intervals around the circumferential direction of the wheel tread.

3. The method for preparing the medium-carbon silicon-in-niobium microalloyed high-speed wheel according to claim 2, wherein: in S3, the wheel is tempered at 550 ℃ of 500 ℃ and 550 ℃ for 4.5-6.0 hours.

4. The method for preparing the medium-carbon silicon-in-niobium microalloyed high-speed wheel according to claim 3, wherein: before the heat treatment process, the method also sequentially comprises an electric furnace steelmaking process, an LF furnace refining process, an RH vacuum treatment process, a round billet continuous casting process and an ingot cutting and rolling process; the heat treatment process also comprises a processing process and a finished product detection process.