A kind of weathering steel for railway bogie containing vanadium and its preparation method

Abstract

The invention discloses a vanadium-containing weathering steel for railway bogies and a preparation method thereof. The weathering steel has the following chemical compositions: C: ≤0.10%, Si: ≤0.40%, Mn: ≤2.10%, S: ≤0.010%, P: ≤0.015%, Al: 0.015-0.050%, V: 0.05-0.15%, N: 0.008-0.020%, Cr: 0.30-0.70%, Ni: 0.20-0.60%, Cu: 0.10-0.50%, Mo: 0.10-0.50%, Ti: 0.006-0.02%, and the remainder is Fe and impurities; and the structural composition of the weathering steel is fine-grained polygonal ferrite, acicular ferrite and granular bainite or fine-grained polygonal ferrite, acicular ferrite, granular bainite and lath bainite. This weathering steel is resistant to atmospheric corrosion and has good comprehensive strength and toughness properties. It does not require preheating before welding and does not require heat treatment after welding.

Description

Technical Field

[0001] The invention relates to the technical field of microalloy steel, in particular to a vanadium-containing weathering steel for railway bogies and a preparation method thereof. Background Art

[0002] Rail transit is the lifeline of new urbanization and high-quality urban development, and is the key to realizing the modernization of transportation. In the competition with highways and aviation, high-speed rail has outstanding advantages in terms of high safety, high punctuality, good comfort, high utilization rate of mobile equipment, long mileage, and good comprehensive technical and economic indicators. The rapid development of rail transit has put forward requirements for rail vehicles to be heavy-loaded, light-weight, high-speed and long-life. In rail vehicle manufacturing, the car body is supported by the bogie, which is made of weathering steel. The bogie needs to have the functions of simultaneous steering and braking to ensure that the train remains stable during high-speed operation. Therefore, as the most critical component of the running performance of rail trains, the product quality of the steel used in the bogie is of great significance to the driving safety of the entire locomotive.

[0003] During the operation of the train, the bogie is often in close contact with humid air and excrement in the train toilet and other media, which is very prone to corrosion. The bogie frame of rail vehicles is made of steel welded structure, which can greatly reduce the dead weight of the vehicle structure. However, with the increase of train speed, load, frequency range, and especially the complex welding joint form, the actual load-bearing condition of the bogie welded frame in operation becomes very bad, causing the welding joint to become the main area of ​​structural failure. The welding performance directly determines the service life of the bogie and even affects the manufacturing level of railway vehicles. In summary, high requirements are placed on the steel plate for the bogie. It must not only meet the characteristics of light weight, high strength and corrosion resistance, but also ensure that the weld area and heat-affected zone of the welded frame have high fatigue resistance, impact resistance and resistance to microcrack propagation.

[0004] At present, the steel used in ordinary rail vehicle bogies is still mostly Q345 series and S355 grade steels, which have low strength, poor low temperature impact toughness and weak atmospheric corrosion resistance, and are difficult to meet the performance requirements of bogies after the train speed is increased. Therefore, with the rapid development of the machinery manufacturing industry in recent years, the market demand for high-strength and high-toughness structural steel is large, and it is developing towards stronger, higher level and better comprehensive performance. It is urgent to develop a new generation of high-speed rail key basic parts, that is, high-strength, easy-to-weld and corrosion-resistant weathering steel for railway bogies, to meet the demand for bogie steel, a key material for the rapidly developing rail transportation. Summary of the invention

[0005] The purpose of the present invention is to provide a vanadium-containing weathering steel for railway bogies with excellent weather resistance, excellent low-temperature toughness, no preheating and no post-weld heat treatment, uniform organization and mechanical properties in the thickness direction of the steel plate, and a preparation method thereof. The present invention proposes to adopt a low-carbon vanadium nitrogen microalloying component route, and its organization composition is (polygonal ferrite, acicular ferrite and granular bainite) or (polygonal ferrite, acicular ferrite, granular bainite and lath bainite), and utilizes the deformation-induced VN precipitation phase in austenite to promote the intracrystalline nucleation mechanism of acicular ferrite, and improves the strength through acicular ferrite organization strengthening and V (C, N) precipitation strengthening, and acicular ferrite high-angle grain boundary enhancement toughness and plasticity, so as to obtain a high-strength steel that is easy to weld and has matching strength and toughness. The steel grade of the present invention has a simple rolling operation process, does not require quenching and tempering treatment, is resistant to atmospheric corrosion, has good comprehensive strength and toughness, has good low-temperature impact performance and welding performance, is easy to realize industrial production, and is better marketed. It can be used in the railway vehicle manufacturing industry to replace the current bogie steel.

[0006] To achieve the above object, the present invention provides the following solutions:

[0007] One of the technical solutions of the present invention is a vanadium-containing weathering steel for railway bogies, wherein the chemical composition of the vanadium-containing weathering steel for railway bogies is as follows by weight percentage: C: ≤0.10%, and not 0, Si: ≤0.40%, and not 0, Mn: ≤2.10%, and not 0, S: ≤0.010%, P: ≤0.015%, Al: 0.015-0.050%, V: 0.05-0.15%, N: 0.008-0.020%, Cr: 0.30-0.70%, Ni: 0.20-0.60%, Cu: 0.10-0.50%, Mo: 0.10-0.50%, Ti: 0.006-0.02%, and the balance is Fe and other inevitable impurities; the organizational composition of the vanadium-containing weathering steel for railway bogies is one of the following two situations:

[0008] Composition (1): fine-grained polygonal ferrite, acicular ferrite and granular bainite;

[0009] Composition (2): fine-grained polygonal ferrite, acicular ferrite, granular bainite and lath bainite.

[0010] Furthermore, the chemical composition of the vanadium-containing weathering steel for railway bogies is as follows by weight percentage: C: 0.10%, Si: 0.35%, Mn: 1.10%, S: 0.010%, P: 0.015%, Al: 0.015%, V: 0.05%, N: 0.008%, Cr: 0.55%, Ni: 0.30%, Cu: 0.20%, Mo: 0.10%, Ti: 0.006%, and the remainder is Fe and other inevitable impurities; the microstructure of the vanadium-containing weathering steel for railway bogies is fine-grained polygonal ferrite, acicular ferrite, granular bainite and lath bainite.

[0011] Furthermore, the vanadium-containing weathering steel for railway bogies is a steel plate with a thickness of 2.5 to 16.0 mm.

[0012] Furthermore, the steel plate has a yield strength of 550-690 MPa, a tensile strength of 690-810 MPa, an elongation of 18-25%, an impact energy of ≥120 J at -60°C, a welding cold crack sensitivity coefficient of ≤0.28%, and an atmospheric corrosion resistance index of ≥6.0.

[0013] Furthermore, the relative corrosion rate of the atmospheric corrosion resistance of the vanadium-containing weathering steel for railway bogies is less than 50% of that of Q345.

[0014] The second technical solution of the present invention is a method for preparing the above-mentioned vanadium-containing weathering steel for railway bogies, comprising the following steps:

[0015] (1) smelting molten steel according to a set chemical composition, and then casting and forging to a thickness of 60 to 140 mm to obtain a steel billet;

[0016] (2) heating the steel billet to 1100-1200°C and keeping it at this temperature for 2-4 hours (to ensure that the steel billet is fully austenitized and the microalloying elements are fully dissolved);

[0017] (3) The steel billet is subjected to two stages of rough rolling and finish rolling to be rolled into a steel plate with a thickness of 2.5 to 16.0 mm;

[0018] (4) After rough rolling and finish rolling, the obtained steel plate is water-cooled to a surface temperature of 490-550°C by laminar cooling, and then cooled to room temperature using insulation felt to obtain a vanadium-containing weathering steel plate for railway bogies (controlled cooling to ensure uniform structure and performance).

[0019] Furthermore, the starting rolling temperature and the final rolling temperature of the rough rolling stage are 1050-1160° C. and 950-1100° C. respectively, and the starting rolling temperature and the final rolling temperature of the finishing rolling stage are 860-960° C. and 800-850° C. respectively.

[0020] Furthermore, the rough rolling stage has 3 to 4 rolling passes, with a reduction rate of 20 to 30% for each pass; the finish rolling stage has 6 to 7 rolling passes, with a reduction rate of 15 to 25% for each pass.

[0021] Furthermore, the cooling rate of the water cooling is 15-40°C / s.

[0022] Furthermore, after the steel plate is cooled to room temperature, the steel plate is coiled and stored.

[0023] The third technical solution of the present invention: Application of the above-mentioned vanadium-containing weathering steel for railway bogies in the preparation of railway vehicle bogies.

[0024] Furthermore, the steel plate is prepared into a railway vehicle bogie by welding, and no pre-welding preheating or post-welding heat treatment measures are required for the steel plate during the welding process.

[0025] The present invention discloses the following technical effects:

[0026] (1) Weathering steel for railway bogies is required to have high strength and atmospheric corrosion resistance, as well as good impact toughness and welding performance. In the present invention, a composite addition of alloy elements is adopted to obtain the best effect of steel. The atmospheric corrosion resistance of steel is significantly improved by adding elements such as Cr and Mo, which hinders the crystallization of corrosion product grains, increases the density of the rust layer, and forms a uniformly distributed and dense rust layer. At the same time, the addition of Ni elements can not only improve the strength of the steel, but also maintain good plasticity and toughness, and also has a certain corrosion resistance to the acidity and alkalinity in the atmosphere.

[0027] (2) The present invention makes full use of vanadium-containing microalloying technology, combines it with cheap nitrogen elements, optimizes the precipitation of V, and makes full use of VN and V (C, N) nano-sized precipitates to promote the nucleation of intragranular ferrite during the hot rolling process of the steel billet, improves the toughness of the core of the steel plate for the bogie, and produces high-strength weathering steel for the bogie through the principle of fine grain effect and precipitation strengthening. The steel adopts the method of composite addition of alloy elements to obtain the best effect of the steel plate. It has a low carbon content of 0.04-0.10% by weight. The low-carbon design reduces the carbon equivalent, which can improve the welding performance and reduce the crack sensitivity of the continuous casting billet. At the same time, it reduces the hardenability of the welding heat-affected zone, avoids the formation of coarse M / A island hard and brittle phases, realizes the welding process without preheating before welding and post-weld heat treatment, and improves the overall formability of the welded joint. And through controlled rolling and controlled cooling, the formation of coarse cementite in the steel plate structure is avoided, and the steel plate has good low-temperature impact toughness. For weathering steel plates of different thicknesses for bogies, the contents of alloys such as Cr, Ni, and Mo have been optimized and adjusted, which significantly improves the steel's resistance to atmospheric corrosion, hinders the crystallization of corrosion product grains, increases the density of the rust layer, forms a uniformly distributed and dense rust layer, and saves costs, which is of great significance for product upgrades, energy conservation and consumption reduction of steel used in railway bogies.

[0028] (3) The rolling operation process of the present invention is simple, and the TMCP two-stage rolling process technology is used to replace the traditional offline reheating quenching + tempering preparation process, which greatly reduces the preparation steps of high-strength steel, improves production efficiency, and directly delivers in a rolled state without quenching and tempering treatment, and does not require harsh equipment and technology. The vanadium-containing weathering steel for railway bogies prepared by the present invention has the advantages of atmospheric corrosion resistance and good comprehensive strength and toughness performance, and also has good low-temperature impact performance, which is easy to realize industrial production and promotion. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0030] Figure 1 This is a schematic flow chart of a method for preparing vanadium-containing weathering steel for railway bogies according to the present invention;

[0031] Figure 2 This is the OM structure diagram of the 16.0 mm thick vanadium-containing weathering steel for railway bogies prepared in Example 1 of the present invention;

[0032] Figure 3 This is the OM structure diagram of the 2.5 mm thick vanadium-containing weathering steel for railway bogies prepared in Example 3 of the present invention;

[0033] Figure 4 The weld fracture morphology of the vanadium-containing weathering steel for railway bogies prepared in Example 2 of the present invention in a gas shielded welding experiment with a line energy of 10 kJ / cm. DETAILED DESCRIPTION

[0034] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as limiting the present invention, but should be understood as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0035] It should be understood that the terms described in the present invention are only for describing special embodiments and are not intended to limit the present invention. In addition, for the numerical range in the present invention, it should be understood that each intermediate value between the upper and lower limits of the scope is also specifically disclosed. Each smaller range between the intermediate value in any stated value or stated range and any other stated value or intermediate value in the described range is also included in the present invention. The upper and lower limits of these smaller ranges can be independently included or excluded in the scope.

[0036] Unless otherwise indicated, all technical and scientific terms used herein have the same meanings as those generally understood by those skilled in the art. Although the present invention describes only preferred methods and materials, any methods and materials similar or equivalent to those described herein may also be used in the implementation or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials associated with the documents. In the event of a conflict with any incorporated document, the content of this specification shall prevail.

[0037] It will be apparent to those skilled in the art that various modifications and variations may be made to the specific embodiments of the present invention description without departing from the scope or spirit of the present invention. Other embodiments derived from the present invention description will be apparent to those skilled in the art. The present application description and examples are exemplary only.

[0038] The words “include,” “including,” “have,” “contain,” etc. used in this document are open-ended terms, meaning including but not limited to.

[0039] The test methods used in the following examples, comparative examples and effect verifications are conventional methods unless otherwise specified; the reagents and materials used are commercially available unless otherwise specified.

[0040] The hot rolling mill used in the following embodiments is a Φ450mm hot rolling mill.

[0041] The heating furnace used in the following embodiments is a high temperature box-type resistance furnace, model SX2-5-12.

[0042] The steel billets used in the following examples are obtained by smelting molten steel according to a set chemical composition, and then casting and forging to a thickness of 60 to 140 mm.

[0043] The transmission electron microscope used in the following effect verification is FEI Tecnai G 2 F20 field emission transmission electron microscope.

[0044] The scanning electron microscope used in the following effect verification is an Axiovert 200mat optical electron microscope.

[0045] The cyclic immersion corrosion testing machine used in the following effect verification is a ZQFS-1200OZ corrosion testing machine produced by Xi'an Tongsheng Instrument Manufacturing Co., Ltd.

[0046] Example 1

[0047] The process steps for preparing vanadium-containing weathering steel (steel plate) for railway bogies with a thickness of 16.0 mm are as follows (the schematic diagram of the preparation method is shown in FIG. Figure 1 shown):

[0048] The 140 mm thick steel billet is heated to 1200°C and kept warm for 4 hours. Its chemical composition by weight percentage is: C: 0.04%, Si: 0.40%, Mn: 2.10%, S: 0.003%, P: 0.002%, Al: 0.03%, V: 0.15%, N: 0.02%, Cr: 0.70%, Ni: 0.60%, Cu: 0.50%, Mo: 0.50%, Ti: 0.02%, and the balance is Fe and other inevitable impurities; then it is hot rolled 10 times (divided into two stages of hot rolling in the rough rolling stage and the finishing rolling stage) into a 16 mm thick steel billet. The steel plate is subjected to 4 rough rolling passes (reduction rates of each pass are 25%, 24%, 25%, 20% respectively), the start rolling temperature and the final rolling temperature of the rough rolling stage are 1160°C and 1100°C respectively, and the finishing rolling stage is subjected to 6 finish rolling passes (reduction rates of each pass are 19%, 15%, 18%, 15%, 17%, 15% respectively), the start rolling temperature and the final rolling temperature of the finishing rolling stage are 960°C and 890°C respectively; after the hot rolling, the plate is water-cooled to 550°C (red-return temperature) at a cooling rate of 15°C / s by laminar cooling, and then placed in a thermal insulation felt and cooled to room temperature to obtain a final product.

[0049] Example 2

[0050] The process steps for preparing vanadium-containing railway bogie steel (steel plate) with a thickness of 10.0 mm are as follows (the schematic diagram of the preparation method is shown in FIG. Figure 1 shown):

[0051] The steel billet with a thickness of 80 mm is heated to 1150°C and kept warm for 3 hours. Its chemical composition by weight percentage is: C: 0.08%, Si: 0.20%, Mn: 1.50%, S: 0.005%, P: 0.015%, Al: 0.05%, V: 0.12%, N: 0.015%, Cr: 0.30%, Ni: 0.30%, Cu: 0.29%, Mo: 0.30%, Ti: 0.011%, and the balance is Fe and other inevitable impurities; then it is hot-rolled in 9 passes (divided into two stages of hot rolling in the rough rolling stage and the finishing rolling stage) into 10.0 mm The invention discloses a hot-rolled steel plate with a thickness of m, wherein the rough rolling stage undergoes 3 passes (the reduction rate of each pass is 25%, 22%, and 23% respectively), the starting rolling temperature and the final rolling temperature of the rough rolling stage are 1100° C. and 1050° C. respectively, the finishing rolling stage undergoes 6 passes (the reduction rate of each pass is 19%, 17%, 20%, 20%, 20%, and 16% respectively), the starting rolling temperature and the final rolling temperature of the finishing rolling stage are 920° C. and 865° C. respectively; after the hot rolling, the plate is water-cooled to 520° C. (red-return temperature) by laminar cooling at a cooling rate of 32° C. / s, and then cooled to room temperature by using insulation felt to obtain the final product.

[0052] Example 3

[0053] The process steps for preparing vanadium-containing weathering steel (steel plate) for railway bogies with a thickness of 2.5 mm are as follows (the schematic diagram of the preparation method is as follows Figure 1 shown):

[0054] The 60 mm thick steel billet is heated to 1100°C and kept warm for 2 hours. Its chemical composition by weight is: C: 0.10%, Si: 0.35%, Mn: 1.10%, S: 0.010%, P: 0.015%, Al: 0.015%, V: 0.05%, N: 0.008%, Cr: 0.55%, Ni: 0.30%, Cu: 0.20%, Mo: 0.10%, Ti: 0.006%, and the balance is Fe and other inevitable impurities; then it is hot rolled 11 times (divided into two stages of hot rolling in the rough rolling stage and the finishing rolling stage) into a 2.5 mm thick steel billet. The steel plate is subjected to 4 rough rolling passes (reduction rates of each pass are 25%, 30%, 29%, and 27% respectively), the start rolling temperature and the final rolling temperature of the rough rolling stage are 1050°C and 950°C respectively, the finish rolling stage is subjected to 7 finish rolling passes (reduction rates of each pass are 25%, 25%, 22%, 17%, 20%, 25%, and 24% respectively), the start rolling temperature and the final rolling temperature of the finish rolling stage are 860°C and 800°C respectively; after the hot rolling, the plate is water-cooled to 490°C (red-return temperature) by laminar cooling at a cooling rate of 40°C / s, and then cooled to room temperature by using thermal insulation felt to obtain the final product.

[0055] Effect verification

[0056] 1. Morphological and structural characterization

[0057] The OM microstructure of the vanadium-containing weathering steel (steel plate) for railway bogies with a thickness of 16.0 mm prepared in Example 1 is as follows: Figure 2 As shown by Figure 2 It can be seen that the microstructure of the steel plate is composed of fine-grained polygonal ferrite, granular bainite and acicular ferrite.

[0058] The microstructure of the vanadium-containing weathering steel (steel plate) for railway bogies with a thickness of 10.0 mm prepared in Example 2 is polygonal ferrite, acicular ferrite and a small amount of granular bainite.

[0059] The OM microstructure of the 2.5 mm thick vanadium-containing weathering steel (steel plate) for railway bogies prepared in Example 3 is as follows: Figure 3 As shown by Figure 3 It can be seen that the microstructure of the steel plate is polygonal ferrite, granular bainite, acicular ferrite and a small amount of lath bainite. As the final cooling temperature of water cooling gradually decreases, the proportion of acicular ferrite and granular bainite increases, with good strength and toughness matching, and lath bainite appears accordingly, which makes the yield strength and tensile strength of the experimental steel increase accordingly.

[0060] 2. Physical performance test

[0061] The yield strength, tensile strength, elongation and -60°C impact energy of the vanadium-containing weathering steel (steel plate) for railway bogies prepared in Examples 1-3 were tested respectively, and the results are shown in Table 1:

[0062] Table 1

[0063] Yield strength / MPa Tensile strength / MPa Elongation / % -60℃ impact energy / J Example 1 550 690 25.1 169 Example 2 603 725 21.1 141 Example 3 690 810 18.8 120

[0064] It can be seen from the results in Table 1 that the vanadium-containing weathering steel (steel plate) for railway bogies prepared in Examples 1-3 has good physical properties.

[0065] 3. Welding performance test

[0066] The present invention carries out a gas shielded welding experiment with a line energy (Q) of 10 kJ / cm on the experimental steel on the basis of good strength and toughness matching.

[0067] Before the experiment, the welding crack sensitivity index (P cm ), welding crack sensitivity index refers to standard GB / T 1591-2008 according to formula P cm=C+Si / 30+(Mn+Cu+Cr) / 20+Mo / 15+Ni / 60+V / 10+5B calculation, the results are shown in Table 2:

[0068] Table 2

[0069] <![CDATA[P cm / %]]> Example 1 0.28 Example 2 0.22 Example 3 0.20

[0070] From the results in Table 2, it can be seen that the vanadium-containing weathering steel (steel plate) for railway bogies prepared in Examples 1-3 has a lower welding crack sensitivity index. It is preliminarily judged that the experimental steel with this composition has good weldability and is easy to weld, and does not require measures such as preheating before welding and heat treatment after welding.

[0071] The experimental steel was processed into a rectangular welded steel plate with a size of 260 mm (rolling direction) × 180 mm (width direction) × 12 mm (thickness) by a sawing machine, of which the 260 mm direction is the weld direction. According to the requirements of JB / T 9186-1999 and GB / T 985-2008 "Recommended grooves for gas welding, arc welding, gas shielded welding and high-energy beam welding", a single V-groove butt welding was adopted, the V-groove angle was 60°, and the butt welding assembly gap was controlled between 2 and 3 mm.

[0072] In the gas shielded welding experiment with a line energy of 10 kJ / cm, the specific data of the tensile properties of the welded joint are shown in Table 3. It can be seen from the data in the table that the yield strength and tensile strength of the welded joint are lower than the strength of the parent material, the elongation is about 17-18%, the fracture position is the heat affected zone, and the weld fracture morphology is composed of large dimples and small dimples, such as Figure 4 As shown ( Figure 4 The fracture morphology of the weld in Example 2 is similar to that in Example 1. This indicates that the welding performance of the vanadium-containing weathering steel for railway bogies of the present invention can meet certain strength requirements.

[0073] Table 3 Tensile properties of welded joints

[0074] Examples <![CDATA[R eL / MPa]]> <![CDATA[R m / MPa]]> A / ％ Fracture location 1 500 578 18.8 HAZ 2 555 630 18.0 HAZ 3 585 668 17.4 HAZ

[0075] 4. Corrosion resistance test

[0076] The corrosion resistance of weathering steel for bogies was evaluated in accordance with the railway industry standard "TB / T 2375-93 Test Method for Periodic Infiltration Corrosion of Weathering Steel for Railways". The dry / wet alternating periodic infiltration corrosion test was used to simulate the corrosion process of the experimental steel in the industrial atmosphere. The ZQFS-1200OZ periodic infiltration corrosion test machine produced by Xi'an Tongsheng Instrument Manufacturing Co., Ltd. was used. The box is equipped with heating, cooling, baking, air circulation systems, rotatable pendant discs and corrosion solution tanks. The temperature in the box should reach 45±2℃ and the humidity should be 70±5%RH to prevent condensation droplets from falling on the sample.

[0077] Ordinary carbon steel Q345B and vanadium-containing weathering steel for railway bogies prepared in Examples 1-3 of the present invention were used as comparative samples, and a 72-hour periodic immersion corrosion test was carried out. The experimental steel was cut into 60mm×40mm×3mm (length×width×thickness) by an electric spark wire cutting machine. There were no less than 3 parallel samples in each group under the same corrosion cycle. The average corrosion rate was obtained by calculating the corrosion weight loss per unit area per unit time of each sample. All samples that need to be corroded need to drill a Φ3mm small hole in the middle of one side of the edge for hanging on the corrosion pendant disc. The surface of the sample must be cleaned before the experiment. The burrs on the surface of the corrosion sample and the debris in the hole were polished and removed using 240#, 400#, 600#, 800#, 1000# and 1200# sandpaper. Gasoline was used first, then anhydrous ethanol, and finally propanol was used for cleaning. The original weight of the sample was measured and recorded to an accuracy of 1mg, and the external dimensions of the sample were measured to an accuracy of 0.1mm.

[0078] The solution used in the corrosion experiment of the present invention is NaHSO3 (sodium bisulfite) solution with an initial concentration of (1.0±0.05)×10 - 2 mol / L, pH should be in the range of 4.4 to 4.8, using 2.0×10 -2 mol / L NaHSO3 solution is used as compensation liquid. In the process of adding replenishing liquid, analytical pure NaOH needs to be used to regulate the pH value of the corrosive liquid in real time. Each cycle period: 60±3min, wherein the immersion time: 12±1.5min. After the corrosion experiment is completed, the sample is cleaned with 500ml hydrochloric acid + 500ml deionized water + 5g hexamethylenetetramine to remove the surface corrosion products, and rust is removed at room temperature. After pickling, it is rinsed with clean water until the rust layer attached to the surface is completely removed, and then soaked with anhydrous ethanol and propanol, taken out and blown dry with cold wind, placed in a dryer and stored for 24h, and then the sample is weighed (accurate to 1mg). By recording the original mass of the sample and the mass after removing the corrosion products, the weight loss method is used to calculate the corrosion rate and relative corrosion rate of the vanadium-containing railway bogie weathering steel and Q345B plain carbon steel prepared in Examples 1-3 of the present invention in a simulated industrial atmosphere environment.

[0079] In addition, the atmospheric corrosion resistance index (I) of the vanadium-containing railway bogie weathering steel prepared in Examples 1-3 was calculated according to the atmospheric corrosion resistance index formula, and the formula is as follows:

[0080] I=26.01(%Cu)+3.88(%Ni)+1.20(%Cr)+1.49(%Si)+17.28(%P)-7.29(%Cu)(%Ni)-9.10(%Ni)(%P)-33.39(%Cu) 2

[0081] The average corrosion weight loss rate is calculated by the corrosion weight loss rate formula, which is as follows:

[0082]

[0083] Where W is the corrosion weight loss rate, g / (h﹒cm 2 ); G0 is the original weight of the sample, g; G1 is the weight of the sample after removing the corrosion products, g; t is the corrosion time, h; a, b and c are the length, width and height of the sample, cm, respectively.

[0084] The results are shown in Table 4:

[0085] Table 4

[0086]

[0087] From the test results in Table 4, it can be seen that the average corrosion weight loss rate of Q345 plain carbon steel is 6.410g / (m 2 ·h), the average corrosion weight loss rate of the vanadium-containing railway bogie weathering steel prepared in Example 1 was 2.101g / (m 2 ·h), and its relative corrosion rate is 32.8%; the average corrosion weight loss rate of the vanadium-containing railway bogie weathering steel prepared in Example 2 is 2.395g / (m 2 ·h), and its relative corrosion rate is 37.4%; the average corrosion weight loss rate of the vanadium-containing railway bogie weathering steel prepared in Example 3 is 2.924g / (m 2 ·h), and its relative corrosion rate is 45.6%; it can be seen that the corrosion rate of the vanadium-containing weathering steel for railway bogies prepared in Examples 1-3 is much lower than that of Q345 ordinary carbon steel, and the corrosion resistance of the three is more than twice that of Q345 ordinary carbon steel, indicating that the corrosion resistance of the vanadium-containing weathering steel for railway bogies prepared in Examples 1-3 meets the requirements.

[0088] The embodiments described above are only descriptions of the preferred modes of the present invention, and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should all fall within the protection scope determined by the claims of the present invention.

Claims

1. A vanadium-containing weathering steel for railway bogies, characterized in that: The chemical composition of the vanadium-containing weathering steel for railway bogies is as follows by weight percentage: C: 0.10%, Si: 0.35%, Mn: 1.10%, S: 0.010%, P: 0.015%, Al: 0.015%, V: 0.05%, N: 0.008%, Cr: 0.55%, Ni: 0.30%, Cu: 0.20%, Mo: 0.10%, Ti: 0.006%, and the balance is Fe and other inevitable impurities; the microstructure of the vanadium-containing weathering steel for railway bogies is fine-grained polygonal ferrite, acicular ferrite, granular bainite and lath bainite; The method for preparing the vanadium-containing weathering steel for railway bogies comprises the following steps: (1) smelting molten steel according to a set chemical composition, and then casting and forging to a thickness of 60 mm to obtain a steel billet; (2) heating the steel billet to 1100°C and keeping it at that temperature for 2 hours; (3) The steel billet is rolled into a 2.5 mm thick steel plate through two stages of rough rolling and finish rolling; (4) After the rough rolling and the finish rolling, the obtained steel plate is water-cooled to the red-return temperature of the steel plate surface layer of 490° C. by laminar cooling, and then cooled to room temperature by using a thermal insulation felt to obtain a vanadium-containing weathering steel for railway bogies; The starting rolling temperature and the final rolling temperature of the rough rolling stage are 1050° C. and 950° C. respectively, and the starting rolling temperature and the final rolling temperature of the finishing rolling stage are 860° C. and 800° C. respectively; The rough rolling stage has four rolling passes, and the reduction rates of each pass are 25%, 30%, 29%, and 27% respectively; the finishing rolling stage has seven rolling passes, and the reduction rates of each pass are 25%, 25%, 22%, 17%, 20%, 25%, and 24% respectively; The cooling rate of the water cooling is 40°C / s; The steel plate has a yield strength of 690 MPa, a tensile strength of 810 MPa, an elongation of 18.8%, an impact energy of 120 J at -60°C, a welding cold crack sensitivity coefficient of 0.20%, and an atmospheric corrosion resistance index of 6.

01.

2. Use of the vanadium-containing weathering steel for railway bogies as claimed in claim 1 in the preparation of railway vehicle bogies.

3. The use according to claim 2, characterized in that The steel plate is prepared into a railway vehicle bogie by welding, and no pre-welding preheating or post-welding heat treatment measures are required during the welding process of the steel plate.

Images