CN112126750A - Alloy steel high-speed railway axle with long fatigue life and speed per hour of more than or equal to 400 kilometers and modification method - Google Patents
Alloy steel high-speed railway axle with long fatigue life and speed per hour of more than or equal to 400 kilometers and modification method Download PDFInfo
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Abstract
The invention provides an alloy steel high-speed railway axle with long fatigue life and a speed per hour of more than or equal to 400 kilometers and a modification method, and the alloy steel high-speed railway axle comprises the following components: 0.23 to 0.28 percent of C, 0.20 to 0.35 percent of Si, 0.62 to 0.75 percent of Mn, 0.012 percent of P trace, 0.008 percent of S trace, 1.00 to 1.18 percent of Cr, 0.22 to 0.28 percent of Mo, 0.18 to 0.28 percent of Ni, 0.03 to 0.05 percent of V, 0.015 to 0.050 percent of Al, less than or equal to 0.20 percent of Cu, and the balance of Fe and other inevitable impurities. Compared with the prior art, the invention designs the alloy steel axle components, carries out heat treatment on the axle, carries out surface induction quenching on the whole length of the axle, and carries out low-temperature tempering treatment, the surface hardness is more than or equal to 550HV, the surface residual compressive stress exceeds-800 MPa, and the fatigue strength exceeds 707 MPa.
Description
Technical Field
The invention belongs to the technical field of high-speed rail axles, and particularly relates to an alloy steel high-speed rail axle with a long fatigue life and a speed per hour of more than or equal to 400 kilometers and a modification method.
Background
The axle is an ultra-large step-shaped axisymmetric part, the maximum diameter of the axle exceeds 200mm, the length of the axle can reach 2320mm, the axle and wheels are connected in an interference manner to form a wheel pair, and the axle bears the whole weight of a rolling stock, so that the axle is one of three key parts of a railway rolling stock. The heavy loading and high speed are the key development directions of high-speed trains, axles are the heaviest key moving parts of single bodies, and the improvement of fatigue performance is the constant theme of axle steel research and development.
Due to different national conditions and different technical viewpoints of various countries, the axle materials selected are different. From the practice of foreign high-speed railway transportation, the application of carbon steel and low-carbon alloy steel axles is feasible, but has various advantages and disadvantages.
Chinese patent CN101857914A published in 10/13/2010 discloses a heat treatment method of a 25CrMo alloy steel hollow axle material for a high-speed railway passenger car, and the axle performance can meet the requirement of a train with the speed of 200-350 km/h through pretreatment, quenching and tempering. However, the materials and the process adopted by the patent can not meet the requirement of the train with the speed per hour being more than 350 kilometers.
Chinese patent CN101649387A published in 2/17/2010 discloses a heat treatment method for an axle, which adopts a mixed liquid quenching and tempering process to enable a 42CrMo axle to meet the requirements of a railway locomotive axle. This patent is applicable to the train that the speed of a motor vehicle is lower, and the tensile strength of axletree can not satisfy high-speed train's needs.
Chinese patent CN107988563A published in 2018, 5, month and 4 discloses a fine-grain ultrahigh-toughness axle steel and a heat treatment method thereof, which indicates that the tensile strength of the axle can be kept about 1000MPa and the grain size is about 11 μm by the process of quenching and tempering twice. The patent adopts twice quenching to increase energy consumption, has no economy, and although the obdurability of the material is improved, the material lacks fatigue performance and can not be directly applied to high-speed railway axles with the speed of 400 kilometers per hour. The domestic research on the heat treatment process of the axle steel is only a conventional heat treatment process and lacks a novel heat treatment process.
The European high-speed rail axle adopts alloy steel integral tempering to ensure the axle fatigue performance, while the Japanese high-speed rail axle adopts a carbon steel surface induction quenching treatment mode to ensure the axle fatigue performance. The surface induction quenching is carried out on the Japan new mainline S38C, the depth of a hardening layer is 4mm, the surface hardness is more than or equal to 500HV, the fatigue strength is improved by more than 30 percent, and the highest speed per hour can reach 320 kilometers at present. Carbon steel has low obdurability, larger axle body size, alloy steel has better obdurability matching, and the axle size is relatively smaller, but if the fatigue performance is further improved, the axle size needs to be increased or the alloy content needs to be increased. Increasing the alloy content increases the material cost and is not economical.
With the rapid development of rail transit industry, particularly coastal high-speed rail construction, higher requirements are put forward on the performance of high-speed rail axles, although the research on the high-speed rail axles in China has a certain accumulation, the current requirements of trains with the speed per hour being less than or equal to 350 kilometers are only met, the research on the heat treatment process of the high-speed rail axles with the high fatigue life and the speed per hour being more than or equal to 400 kilometers is almost blank, and the development of the heat treatment process of the high-speed rail axles with the speed per hour being more than or equal to 400 kilometers and higher fatigue strength is urgently needed.
Disclosure of Invention
The invention aims to provide an alloy steel high-speed railway axle with long fatigue life and speed per hour of more than or equal to 400 kilometers, the fatigue strength of the axle exceeds 707MPa, the surface hardness of the axle is more than or equal to 550HV, the surface residual compressive stress exceeds-800 MPa, and the fatigue strength of the axle is improved by more than 94 percent.
The invention also aims to provide a method for modifying an alloy steel high-speed railway axle with long fatigue life and speed per hour of more than or equal to 400 kilometers, which improves the fatigue strength of the axle by normalizing, quenching and tempering and then carrying out induction quenching treatment, and is suitable for high-speed railway operation with speed per hour of more than or equal to 400 kilometers.
The specific technical scheme of the invention is as follows:
an alloy steel high-speed railway axle with long fatigue life and a speed per hour of more than or equal to 400 kilometers comprises the following components in percentage by mass: 0.23 to 0.28 percent of C, 0.20 to 0.35 percent of Si, 0.62 to 0.75 percent of Mn, 0.012 percent of P trace, 0.008 percent of S trace, 1.00 to 1.18 percent of Cr, 0.22 to 0.28 percent of Mo, 0.18 to 0.28 percent of Ni, 0.03 to 0.05 percent of V, 0.015 to 0.050 percent of Al, less than or equal to 0.20 percent of Cu, and the balance of Fe and other inevitable impurities.
The invention provides a method for modifying an alloy steel high-speed railway axle with long fatigue life and speed per hour of more than or equal to 400 kilometers, which comprises heat treatment, surface induction quenching and low-temperature tempering treatment.
Because the axle belongs to an ultra-large step-shaped axisymmetric part and has larger size, the fatigue property of the axle is ensured by adopting a mode of integrally tempering alloy steel with better obdurability matching and higher hardenability for both the European high-speed railway axle and the domestic high-speed railway axle at present, but the alloy steel high-speed railway axle at home and abroad is only suitable for high-speed rails with the speed per hour being less than or equal to 350km at present. The alloy steel has stronger hardenability, can obtain a more uniform tempered sorbite structure after integral normalizing, quenching and high-temperature tempering heat treatment, easily obtain austenite with uniform components in the induction quenching heating process, and is converted into a uniform martensite structure after surface induction quenching, so that a high-hardness hardening layer is formed on the surface layer of the axle, the fatigue property of the axle is greatly improved, and the alloy steel is suitable for high-speed rails with the speed per hour being more than or equal to 400 kilometers.
The heat treatment includes normalizing, quenching and tempering.
The normalizing specifically comprises the following steps: heating the axle to 890-940 ℃, preserving heat for 4-6h, and then air-cooling to below 300 ℃;
the quenching specifically comprises the following steps: heating the normalized axle to 870-910 ℃, preserving heat for 4-6h, and cooling with water to below 100 ℃;
the tempering specifically comprises the following steps: heating the quenched axle to 580-680 ℃, preserving heat for 5-8h, and then air cooling to below 100 ℃.
The surface induction hardening specifically comprises the following steps:
1) when the surface induction quenching is carried out, the quenching machine tool is vertical, and the axle is vertically arranged; bending deformation caused by self weight in the axle quenching process is reduced to the maximum extent;
2) the heating inductor and the water spraying coil move axially at a constant speed along the longitudinal direction of the axle;
3) when the surface is quenched by induction, the quenching machine tool needs to drive the axle to rotate;
4) the water spraying coil is provided with a plurality of rows of different angles;
5) quenching and water spraying are carried out from bottom to top;
6) the current frequency of the induction hardening equipment is selected according to the following formula: 15000/H2<f<250000/H2Wherein f is the current frequency (unit: Hz), and H is the depth of the hardening layer (unit: mm).
The step 1) is specifically as follows: carrying out full-length surface induction quenching on high-speed rail axle steel with the maximum diameter of 226mm and the length of 2320mm, wherein a quenching machine tool is vertical, and an axle is vertically placed to reduce deformation in the axle quenching process;
in the step 2), the heating inductor and the water spray coil axially move at a constant speed along the longitudinal direction of the axle, and the quenching moving speed of the wheel seat is 100-240 mm/min.
Further, 2) fine adjustment is carried out on the heating inductor and the water spraying ring along the horizontal direction, so that the axle is ensured to be positioned in the middle of the coil; because the axle is in a stepped structure, the diameter difference between the wheel seat and the axle body is large, the heating temperature is difficult to ensure uniform and consistent by the heating sensor in the continuous heating process, in order to heat all parts of the axle uniformly as much as possible, the moving speed of the heating sensor needs to be controlled in a segmented manner, the axle body part, the transition part and the wheel seat part adopt different quenching moving speeds, the axle body part and the transition part with small diameters need to be correspondingly slowed down to ensure the heating effect because the axle body part and the transition part are far away from the heating sensor, the heating temperature is low, the quenching moving speed needs to be correspondingly slowed down to ensure the heating effect, according to the diameter difference between the wheel seat and the axle body and the actual quenching condition, the quenching moving speed of the axle body position is slowed down to 80-180mm/min, and;
step 4), arranging a plurality of rows of water spraying coils at different angles, wherein the included angle between a nozzle and the lower end of the axle ranges from 90 degrees to 150 degrees, so that the R-angle transition part of the axle is well and uniformly cooled; preferably, the water spray coils are arranged in 3-5 rows.
Step 5), quenching and water spraying are carried out from bottom to top, the water pressure is 0.20-0.30MPa, the water spraying time is suitable for ensuring full cooling, and the temperature after cooling is less than 100 ℃;
and 6) the current penetration depth and the current frequency are in inverse proportion in the induction heating process, and in order to ensure the surface induction quenching effect, the selection of the current frequency needs to be matched with the depth requirement of a hardening layer. The current frequency of the induction quenching equipment needs to be selected according to the following formula: 15000/H2<f<250000/H2Wherein f is the current frequency (unit: Hz), and H is the depth of the hardening layer (unit: mm). In addition, the selection of the current frequency has a certain relation with the diameter of the part, the axle is a large-size part, the middle and lower limit frequency is preferably selected when the current frequency is selected, the current frequency is selected to be 1000-3000Hz, and the depth of the hardening layer is 4-10 mm. Because the hardening layer depth of the axle needs to be determined by an axle-breaking tester, the target hardening layer depth of the axle in the actual production process needs to be determined by a large number of testers, and in order to reduce the test times and the test cost, the hardening layer depth H (unit: mm) of the axle can be estimated by the following formula: h ═ kPTt/v, where k is a constant related to the steel grade, the quenching frequency, the part diameter and the heat treatment state, and ranges from 4 × 10-4-6×10-4(unit: mm)2V (kW. DEG. C. s. min)), the specific value is adjusted accordingly according to the actual test result, and T is the heating temperature (unit: c), t is heating time (unit: s), P is heating power (unit: kW), v is the quenching speed (in mm/min) of the wheel seat portion of the axle.
The low-temperature tempering means that the surface of the axle is heated to 150-250 ℃ after induction quenching, is kept warm for 2-4h, and is cooled in air to below 80 ℃ to eliminate internal stress.
And (5) finely grinding the surface of the axle after tempering is finished.
And (3) carrying out surface hardness test and residual stress test on the finished axle after fine grinding, sampling a position close to the surface, carrying out a rotary bending fatigue test, and after surface induction quenching, wherein the surface hardness is not less than 550HV, the surface residual compressive stress exceeds-800 MPa, the fatigue strength exceeds 707MPa, and the fatigue strength is improved by more than 95% compared with that (362MPa) of an axle sample without surface induction quenching.
Compared with the prior art, the axle is pretreated by normalizing, quenching and high-temperature tempering to obtain a uniform tempered sorbite structure, austenite with uniform components is easily obtained in the subsequent induction quenching and heating process, and the austenite is transformed into a uniform martensite structure after surface induction quenching, so that a high-hardness hardened layer (the surface hardness is more than or equal to 550HV) is formed on the surface layer of the axle, the hardness and the strength of the surface layer are greatly improved, the surface plastic distortion resistance of a sample is improved, meanwhile, residual compressive stress is formed on the surface of the axle, the near-surface residual compressive stress exceeds-800 MPa, the effective tensile stress born by the surface layer of the sample is greatly reduced, and the endurance limit stress of the surface layer is obviously improved; in addition, when the laser quenching is heated, the phase transition temperature is high, the austenite nucleation rate is high, and sufficient time is not available for growth, so that the actual grain size of the austenite of the quenched layer is far smaller than the grain size of a matrix part, the grain size of a surface layer is obviously refined, the grain size of a matrix structure is 8.0-8.5 grade, and the grain size of the surface layer is 12.0-12.5 grade after surface strengthening; the fatigue property (the fatigue strength is more than or equal to 707MPa) is improved, and the fatigue strength is improved by more than 95 percent compared with that of the axle without surface induction quenching.
Drawings
FIG. 1 is a surface microstructure (500X) of the axle produced in example 1;
FIG. 2 is a surface microstructure (500X) of the axle produced in comparative example 1.
Detailed Description
The following examples are intended to illustrate the invention, but the scope of protection of the invention is not limited to the following examples.
Example 1
An alloy steel high-speed railway axle with long fatigue life and a speed per hour of more than or equal to 400 kilometers comprises the following components in percentage by mass: see table 1.
The balance not shown in table 1 is Fe and inevitable impurities.
TABLE 1 EXAMPLES AND COMPARATIVE EXAMPLES chemical composition (unit: wt%)
The axle is produced by the following process flow: axle blank forging → rough turning of blank axle → processing of axle flush end face → heat treatment → fine turning processing of axle excircle → boring processing of axle inner hole → excircle grinding → fault detection → surface induction quenching → low temperature tempering → excircle grinding.
The modification method related in the production process flow comprises heat treatment, surface induction quenching and low-temperature tempering treatment.
The heat treatment includes normalizing, quenching and tempering.
The normalizing specifically comprises the following steps: heating the axle to 910 ℃, preserving heat for 5 hours, and then air-cooling to below 300 ℃;
the quenching specifically comprises the following steps: heating the normalized axle to 890 ℃, preserving heat for 6 hours, and then cooling with water (the water temperature is 25 ℃) to below 100 ℃;
the tempering specifically comprises the following steps: and heating the quenched axle to 630 ℃, preserving the heat for 7 hours, and then cooling the axle to below 100 ℃.
Specific process parameters of the heat treatment of the high-speed rail axle in the embodiment 1 are shown in a table 2;
TABLE 2 Heat treatment Process for examples and comparative examples
The mechanical property test results of the axle steel after heat treatment are shown in Table 3.
TABLE 3 mechanical Properties of the examples and comparative examples
| Categories | Rm/MPa | ReL/MPa | A/％ |
| Examples 1 to 3, comparative example 1 | 716 | 548 | 23 |
| Example 4 | 721 | 543 | 24 |
| Comparative example 2 | 723 | 461 | 23 |
The axle subjected to the heat treatment is subjected to axle outer circle finish turning → axle inner hole boring → outer circle grinding → flaw detection → surface induction quenching → low-temperature tempering → outer circle grinding. The surface induction hardening specifically comprises the following steps:
1) carrying out full-length surface induction quenching on high-speed rail axle steel with the maximum diameter of 226mm and the length of 2320mm, wherein a quenching machine tool is vertical, and an axle is vertically placed to reduce deformation in the axle quenching process;
2) the heating inductor and the water spraying ring are finely adjusted along the horizontal direction to ensure that the axle is positioned in the middle of the coil; the heating inductor and the water spraying ring move axially at a constant speed along the longitudinal direction of the axle, the quenching moving speed of the wheel seat position is 100-240mm/min, because the axle is of a stepped structure, the diameter difference between the wheel seat and the axle body is large, the heating inductor is difficult to ensure the uniform heating temperature in the continuous heating process, in order to heat all parts of the axle uniformly as far as possible, the moving speed of the heating inductor needs to be controlled in sections, the axle body part, the transition part and the wheel seat part adopt different quenching moving speeds, the axle body part and the transition part with small diameters need to be far away from the heating inductor, the heating temperature is low, the quenching moving speed needs to be correspondingly slowed down to ensure the heating effect, according to the diameter difference between the wheel seat and the shaft body and the actual quenching condition, the quenching moving speed of the shaft body is slowed down to 80-180mm/min, and the quenching moving speed of the transition position is slowed down to 90-210 mm/min;
3) when the surface is quenched by induction, the quenching machine tool drives the axle to rotate at 0-60r/min so as to ensure that the axle is heated and cooled uniformly;
4) the water spraying coils are arranged in three rows of different angles (the included angle between the nozzle and the lower end of the axle ranges from 90 degrees to 150 degrees), so that the R-angle transition part of the axle is well and uniformly cooled;
5) quenching and water spraying are carried out from bottom to top, the water pressure is 0.20-0.30MPa, the water spraying time is proper to ensure full cooling, and the temperature after cooling is less than 100 ℃;
6) the current frequency of the induction quenching equipment needs to be selected according to the following formula: 15000/H2<f<250000/H2Wherein f is the current frequency (unit: Hz), and H is the depth of the hardening layer (unit: mm). In addition, the selection of the current frequency has a certain relation with the diameter of the part, the axle is a large-size part, the middle and lower limit frequency is preferably selected when the current frequency is selected, the current frequency is selected to be 1000-3000Hz, and the depth of a hardening layer is 4-10 mm.
7) After the surface induction quenching, heating to 150-250 ℃, preserving heat for 2-4h, then cooling in air to below 80 ℃ to eliminate internal stress, and after the tempering is finished, finely grinding the surface of the axle.
The specific process parameters of induction hardening of the surface of example 1 are shown in Table 4.
Table 4 example and comparative example surface induction quenching process
Examples 2-3 and comparative example 1 the same ingredients and production method as in example 1 were used, except that
Example 2-example 3 the surface induction quenching process differs from example 1 in that example 4 employs the same quenching process parameters as example 1, except that the composition and heat treatment process of example 4 differs from example 1; comparative example 1 no laser quenching was used and comparative example 2 used the same quenching process parameters as in example 1, except that the comparative example 2 was different in composition and heat treatment process from example 1. The laser quenching processes of the examples and comparative examples are shown in table 4.
The fatigue strength (test standard: GB/T4337), the surface hardness (test standard: GB/T4340) and the maximum compressive stress (test standard: GB/T7704) of examples 1 to 4 (case hardening) are compared with those of comparative example 1 (case hardening was not performed), comparative example 2 (after laser hardening) in Table 5, the microstructure of the axle surface of examples (case hardening) and comparative example (case hardening was not performed) is shown in FIGS. 1 to 2, and the grain size before and after hardening is shown in Table 6.
TABLE 5 comparison of fatigue strength, surface hardness and surface maximum compressive residual stress for examples and comparative examples
TABLE 6 grain size of examples and comparative examples
As can be seen, the cycle number of fatigue cycles of each example after the induction hardening was 1X 108The fatigue strength is more than or equal to 707MPa,the surface hardness is more than or equal to 550HV, the surface residual compressive stress exceeds-800 MPa, the fatigue strength of the axle sample is respectively improved by 95 percent, 99 percent, 105 percent and 96 percent compared with the fatigue strength (362MPa) of the axle sample without surface induction quenching, and the fatigue strength is improved by 194MPa compared with a comparative example 2 adopting the same surface induction quenching process.
Claims (10)
1. A modification method for an alloy steel high-speed railway axle with long fatigue life and a speed per hour of more than or equal to 400 kilometers is characterized by comprising the following steps: heat treatment, surface induction quenching and low-temperature tempering treatment;
the alloy steel high-speed railway axle with long fatigue life and speed per hour more than or equal to 400 kilometers comprises the following components in percentage by mass: 0.23 to 0.28 percent of C, 0.20 to 0.35 percent of Si, 0.62 to 0.75 percent of Mn, 0.012 percent of P trace, 0.008 percent of S trace, 1.00 to 1.18 percent of Cr1, 0.22 to 0.28 percent of Mo, 0.18 to 0.28 percent of Ni, 0.03 to 0.05 percent of V, 0.015 to 0.050 percent of Al, less than or equal to 0.20 percent of Cu, and the balance of Fe and other inevitable impurities.
2. The modification method according to claim 1, wherein the heat treatment comprises normalizing, quenching and tempering.
3. The modification method according to claim 1, wherein the normalizing is specifically: heating the axle to 890-940 ℃, preserving heat for 4-6h, and then air cooling to below 300 ℃.
4. The modification method according to claim 1, wherein the normalized axle is heated to 870 to 910 ℃, kept warm for 4 to 6 hours and then cooled to 100 ℃ or lower with water.
5. The modification method according to claim 1, wherein the tempering is in particular: heating the quenched axle to 580-680 ℃, preserving heat for 5-8h, and then air cooling to below 100 ℃.
6. The modification method according to claim 1, wherein the surface induction hardening is specifically:
1) when the surface induction quenching is carried out, the quenching machine tool is vertical, and the axle is vertically arranged;
2) the heating inductor and the water spraying coil move axially at a constant speed along the longitudinal direction of the axle;
3) when the surface is quenched by induction, the quenching machine tool needs to drive the axle to rotate;
4) the water spraying coil is provided with a plurality of rows of different angles;
5) quenching and water spraying are carried out from bottom to top;
6) the current frequency f of the induction hardening equipment and the depth H of the hardening layer have the relationship: 15000/H2<f<250000/H2Wherein the current frequency f unit: hz, depth of quench hardening layer H, unit: mm.
7. The modification method according to claim 6, wherein in the step 2), the heating inductor and the water spray coil axially move at a constant speed along the longitudinal direction of the axle, the quenching moving speed of the wheel seat position is 100-240mm/min, the quenching moving speed of the axle body position is reduced to 80-180mm/min, and the quenching moving speed of the transition position is reduced to 90-210 mm/min.
8. The modification method as claimed in claim 7, wherein in the step 3), the quenching machine tool drives the axle to rotate at 0-60 r/min.
9. The modification method according to claim 1, wherein the low-temperature tempering is heating to 150-250 ℃ after the surface of the axle is subjected to induction quenching, keeping the temperature for 2-4h, and then cooling to 80 ℃ or below in air.
10. An alloy steel high-speed railway axle with long fatigue life and speed per hour more than or equal to 400 km produced by the modification method of any one of claims 1 to 9, characterized in that the surface hardness of the produced axle is more than or equal to 550HV, the surface residual compressive stress exceeds-800 MPa, and the fatigue strength exceeds 707 MPa.
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| CN202011023317.9A CN112126750A (en) | 2020-09-25 | 2020-09-25 | Alloy steel high-speed railway axle with long fatigue life and speed per hour of more than or equal to 400 kilometers and modification method |
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| CN202011023317.9A CN112126750A (en) | 2020-09-25 | 2020-09-25 | Alloy steel high-speed railway axle with long fatigue life and speed per hour of more than or equal to 400 kilometers and modification method |
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Citations (4)
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|---|---|---|---|---|
| CN102758147A (en) * | 2012-08-01 | 2012-10-31 | 清华大学 | Axle material and application thereof in high-speed railway carriage |
| CN105886904A (en) * | 2016-06-07 | 2016-08-24 | 马鞍山钢铁股份有限公司 | Vanadium-containing steel for motor train unit axle and production method and heat treatment process thereof |
| CN109022744A (en) * | 2018-08-03 | 2018-12-18 | 中国科学院金属研究所 | A kind of high-speed train axle surface modifying method |
| WO2019194274A1 (en) * | 2018-04-04 | 2019-10-10 | 日本製鉄株式会社 | Railroad axle |
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2020
- 2020-09-25 CN CN202011023317.9A patent/CN112126750A/en active Pending
Patent Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102758147A (en) * | 2012-08-01 | 2012-10-31 | 清华大学 | Axle material and application thereof in high-speed railway carriage |
| CN105886904A (en) * | 2016-06-07 | 2016-08-24 | 马鞍山钢铁股份有限公司 | Vanadium-containing steel for motor train unit axle and production method and heat treatment process thereof |
| WO2019194274A1 (en) * | 2018-04-04 | 2019-10-10 | 日本製鉄株式会社 | Railroad axle |
| CN109022744A (en) * | 2018-08-03 | 2018-12-18 | 中国科学院金属研究所 | A kind of high-speed train axle surface modifying method |
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| 王树青等: "车轴感应淬火技术研究", 《金属热处理》 * |
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