High-strength wear-resistant corrosion-resistant steel easy to form for railway vehicle and manufacturing method thereof

Abstract

The easy-to-form high-strength wear-resistant corrosion-resistant steel comprises the following chemical components: 0.058 to 0.076 percent of C, 0.81 to 0.97 percent of Si, 1.26 to 1.46 percent of Mn, less than or equal to 0.015 percent of P, less than or equal to 0.006 percent of S, 0.82 to 1.03 percent of Cr, 0.13 to 0.28 percent of Cu, 0.051 to 0.071 percent of Mo, 0.078 to 0.098 percent of Al, 0.0122 to 0.0138 percent of RE, 0.018 to 0.028 percent of V, 0.031 to 0.046 percent of Ti, 0.059 to 0.079 percent of W, 0.036 to 0.054 percent of Sn, more than or equal to 0.90 percent and less than 1.1 percent of Si + Al + RE, and more than 9.5 percent and less than 11.2 percent of Si / Al. The manufacturing method comprises the steps of pre-desulfurization, converter steelmaking, external refining, slab continuous casting heating, hot continuous rolling, laminar cooling and coiling. The thickness of the steel plate is 6.5-13.5 mm, ReL is larger than 550 MPa, Rm is larger than 730 MPa, A is larger than 32%, the yield ratio is smaller than 0.80, KV2 at-40 DEG C is larger than or equal to 107 J, and the acid environment corrosion rate is smaller than 0.68 g / m < 2 >. H. The high-strength steel has corrosion resistance, wear resistance and excellent formability, and has obvious competitive advantages in the field of high-strength steel for railway vehicles.

Description

Technical Field

[0001] The present invention belongs to the field of corrosion-resistant steel for railway vehicles, and relates to a high-strength, wear-resistant and corrosion-resistant steel for easily formed railway vehicles and a manufacturing method thereof. Background Art

[0002] With the rapid development of China's railway transportation industry, heavy haul has become an important direction for the development of China's railway vehicles. In order to meet the development needs of heavy haul and lightweight of railway freight cars, higher requirements are put forward for the strength and plasticity indexes of the steel used for railway freight cars. At present, the products used for manufacturing steel for railway freight cars are mainly weathering steels of 345MPa and 450MPa grades. In order to meet the development needs of steel for China's railway vehicles, it is urgent to develop a weathering steel for railway freight cars with higher strength and excellent forming performance. In addition, especially for railway coal transport freight cars, the coal water formed inside contains SO4 2- , Cl - acidic ions, which are easy to cause acidic corrosion to the inside of the car body. And during the coal loading and unloading process, the coal continuously causes wear and corrosion to the car body. Therefore, to solve the above problems, the developed weathering steel for railway freight cars not only needs to have high strength and excellent forming performance, but also needs to have excellent acid medium corrosion resistance (the corrosion rate of the steel plate is required to be ≤0.8g / m 2 ·h) and wear resistance under the condition of 24h uniform corrosion in the medium of 10% H2SO4 + 3.5% NaCl solution.

[0003] Before the present invention, the patents related to the present invention mainly include the following several items:

[0004] (1) The invention patent of "A weathering steel for railway vehicles with high corrosion resistance and low yield ratio and its preparation method" with the publication number of CN 112760572A, the component composition is C: 0.01 - 0.06%, Si: 0.20 - 0.50%, Mn: 0.40 - 0.80%, Ni: 0.5 - 1.0%, Cr: 1.0 - 2.0%, Cu: 0.10 - 0.50%, Al: 0.01 - 0.04%, P≤0.030%, S≤0.010%, one or more of Nb, Ti, V 0.010 - 0.050%, and the balance is Fe and impurity elements. This patent is mainly designed for weathering steel in industrial atmospheric environment. This invention mainly improves the corrosion resistance of the invented steel through high contents of Cr, Ni, and Cu, which will inevitably increase the cost, and the high content of Cr therein increases the smelting difficulty; in addition, this invention heats and rolls the steel billet after forging it into a square billet, and this process flow is long, costly, and this patent does not elaborate on the wear resistance of the invented steel.

[0005] (2) "Wear and corrosion resistant steel plate for railway coal transportation vehicles and its manufacturing method" with the publication number CN 107653423 B, the composition is C: 0.01 - 0.15%, Si: 0.10 - 0.50%, Mn: 0.20 - 1.0%, P ≤ 0.020%, S ≤ 0.010%, Cu: 0.20 - 0.60%, Ni: 0.50 - 1.5%, Cr: 0.20 - 2.0%, Sb: 0.030 - 0.10%, Mo: 0 - 0.25%, Nb: 0 - 0.05%, V: 0 - 0.05%, Ti: 0 - 0.10%, B: 0 - 0.005%, and the rest is Fe and impurities. In this invention, by controlling the contents of C, Cr, and Ni to satisfy 1.6% ≤ 12C + Cr / Ni ≤ 2.8%, the wear and corrosion rate relative to Q450NQR1 is 20% - 30%. In this invention, the content of Ni element is relatively high, resulting in a relatively high production cost, which is not conducive to its popularization and application.

[0006] (3) The invention patent of "A 450MPa grade wear and corrosion resistant steel and its manufacturing method" with the publication number CN 114574782A, the composition is C: 0.061 - 0.082%, Si: 0.51 - 0.79%, Mn: 0.45 - 0.89%, P ≤ 0.018%, S ≤ 0.006%, Cr: 0.81 - 1.31%, Cu: 0.14 - 0.24%, Sb: 0.041 - 0.075%, W: 0.15 - 0.35%, Ti: 0.051 - 0.072%, Als: 0.015 - 0.045%, N ≤ 0.004%, and the balance is Fe and inevitable impurities. In this invention, through the synergistic effect of Si, Mn, Cr, and W elements, and the formation of a certain amount of FeMnCrC, TiC, and WC, the anti-wear performance of the material is improved. However, the wear and corrosion resistance performance it focuses on for containers is different from the service environment of weather resistance, wear, and corrosion resistance of railway freight cars.

[0007] "(4) \"A low-alloy wear-resistant and corrosion-resistant steel and its manufacturing method\" with a publication number of CN 101423916A has a composition of C: 0.10 - 0.16%, Si: 1.0 - 1.6%, Mn: 0.8 - 1.6%, Cr: 1.0 - 1.6%, Mo: 0.3 - 0.4%, Ni: 0.30 - 0.40%, Al: 0.6 - 1.0%, rare earth + Nb ≤ 0.1%, and the balance is Fe and impurities. This patent obtains a low-alloy wear-resistant and corrosion-resistant steel suitable for the marine sediment abrasion and corrosion environment by forming a carbide-free bainitic steel of the Mn-Si-Cr-Mo-Al system. It mainly adopts a composition design with high Si and high Al to inhibit the formation of carbides, and adds elements such as Cr, Ni, and Mo to improve corrosion resistance. However, it pays more attention to wear resistance and atmospheric corrosion resistance, which is different from the service environment of coal-water abrasion and corrosion. Summary of the Invention

[0008] The object of the present invention is to provide a high-strength wear-resistant and corrosion-resistant steel for railway vehicles that is easy to form and its manufacturing method. By strictly controlling the chemical composition in the steel and the rolling production process, the steel produced by this invention is a high-strength steel with both corrosion resistance and wear resistance, especially with excellent formability, which can improve the processing performance of high-strength steel for railway vehicles and has obvious competitive advantages in the application field of high-strength steel for railway vehicles.

[0009] The present invention provides a high-strength wear-resistant and corrosion-resistant steel for railway vehicles that is easy to form. The chemical composition by weight percentage is C: 0.058% - 0.076%, Si: 0.81% - 0.97%, Mn: 1.26% - 1.46%, P ≤ 0.015%, S ≤ 0.006%, Cr: 0.82% - 1.03%, Cu: 0.13% - 0.28%, Mo: 0.051% - 0.071%, Al: 0.078% - 0.098%, RE: 0.0122% - 0.0138%, V: 0.018% - 0.028%, Ti: 0.031% - 0.046%, W: 0.059% - 0.079%, Sn: 0.036% - 0.054%, where 0.90% ≤ Si + Al + RE < 1.1% and 9.5 < Si / Al < 11.2, and the balance is Fe and inevitable impurities.

[0010] The reason for the selection of the above alloying element types and their contents in the present invention is as follows:

[0011] C: One of the effective elements for increasing the strength in steel. It increases the strength of the material through solid solution strengthening and precipitation strengthening. In addition, an appropriate proportion of element C helps to stabilize the existence of the austenite phase, providing a necessary condition for a certain amount of stable retained austenite to exist at room temperature in the material. However, a higher C content will not only deteriorate the plasticity of the material but also reduce the corrosion resistance of the material due to the formation of more pearlite structures. In the present invention, the content of C is limited to 0.058% - 0.076%.

[0012] Si: It can interact with C in the steel to form a kind of hard SiC particles, which can increase the wear resistance of the material. When added in combination with Cr, it can promote the formation of stable hydroxyl oxide α-FeOOH in the inner rust layer and the enrichment of corrosion-resistant elements, thus improving the corrosion resistance of the material. In addition, element Si has a certain solid solution strengthening effect in ferrite, ensuring that the steel has sufficient strength and a low yield ratio. At the same time, in the present invention, the synergistic effect with Al and RE elements can expand the austenite phase transformation temperature range, improve the coordinated deformation ability of the product by accelerating the bainite transformation, and can significantly inhibit the decomposition of retained austenite and the precipitation of carbides, thereby significantly improving the forming performance of the steel plate. In the present invention, the content of Si is limited to 0.81% - 0.97%, 0.90% ≤ Si + Al + RE < 1.1%; the synergistic effect with Al can avoid the generation of "red scale" Fe2SiO4 on the steel plate surface that is difficult to remove, improving the surface quality of the steel plate, and 9.5 < Si / Al < 11.2 is defined.

[0013] Mn: One of the main strengthening elements in steel. It can increase the strength of the steel plate through solid solution strengthening. At the same time, Mn in the present invention, as an important austenitizing stabilizing element, can expand the austenite phase region, has the effect of improving the stability of retained austenite in steel, and can improve the forming performance of the steel plate. Therefore, in order to ensure the strength of the material and improve its forming performance, the content of Mn in the present invention is set to 1.26% - 1.46%.

[0014] P: When the content of this element is relatively high, it is likely to have an adverse effect on the mechanical properties of the steel plate, especially the impact toughness and formability of the steel plate. In theory, the lower the better, but considering the steelmaking operability and steelmaking cost, P in the steel of the present invention is controlled below 0.015%.

[0015] S: A harmful impurity element, which is prone to form defects such as segregation and inclusions, and when the content is too high, it will cause cracking of the steel during hot processing. Therefore, in the present invention, the content of S should be controlled below 0.006%.

[0016] Cr: As an active cathode in steel, it promotes the passivation of steel as an anode and facilitates the formation of an oxide rust layer with high density and strong adhesion on the steel surface. When combined with Si and Cu elements, it can refine the stable phase α-FeOOH in the rust layer, effectively improving the cation selective permeability of the rust layer to corrosive media. In addition, the addition of Cr easily combines with Fe in steel to form compounds such as CrFe3C and CrFe7C3. When these compounds are distributed at grain boundaries, they can strengthen the grain boundaries, thus significantly reducing the low-temperature ductile-brittle transition temperature of the material and improving the low-temperature impact toughness of the material. Therefore, the Cr content in this invention should be controlled within 0.82% - 1.03%.

[0017] Cu: As an effective element to improve the strength and corrosion resistance of materials. Cu can play a role in solid solution strengthening in steel. And when co-added with rare earth element Ce, by controlling the rolling temperature, Cu4Ce precipitation phases can be formed, achieving the effect of secondary precipitation strengthening. The addition of Cu can promote the formation and enrichment of protective CuO in the inner rust layer, improving the corrosion resistance of the material. However, when the Cu content is too high, it will not only increase the alloy cost but also increase the generation of "copper brittleness" defects. Therefore, the Cu content in this invention should be controlled within 0.13% - 0.28%.

[0018] Mo: Adding Mo can generate a hard Mo2O3 oxide film on the matrix surface, increasing the wear resistance of the matrix surface. At the same time, it can form stable and insoluble alloy cementite (Fe,MO)3C and carbide MoC with C in steel, significantly improving the wear resistance of the material; Mo can partially replace Fe to form molybdenum iron hydroxy oxide, and finally a dense and stable protective phase α-(Fe,Mo)OOH can be formed in the atmosphere and enriched in the inner rust layer, thereby improving the atmospheric corrosion resistance of the material. In addition, when Mo is co-added with Ti, through the control of the rolling process, it is easy to precipitate nano-sized (Ti,Mo)C at the phase interface. The size of this carbide is finer than that of TiC formed by adding Ti alone, and the precipitation strengthening effect is more obvious. However, a high content of Mo will increase production costs. Therefore, the Mo content in this invention should be controlled within 0.051% - 0.071%.

[0019] Al: An important deoxidizing element that can avoid the generation of excessive rare earth oxides and at the same time improve the surface quality problem of "red scale" caused by Si element; Al can shift the corrosion potential of steel to the positive, and mainly exists as Al2FeO4 in spinel-type oxides, promoting the transformation of spinel to a finer and denser structure, refining the grains of the inner rust layer and increasing the density of the inner rust layer; accelerating the formation of the protective phase α-FeOOH in the inner rust layer. In addition, Al significantly inhibits the decomposition of retained austenite and the precipitation of carbides to improve the formability of the material. However, excessive Al is not only unfavorable for casting the billet during continuous casting but also increases the number of inclusions in the steel. Therefore, the scope of this invention is limited to 0.078% - 0.098%.

[0020] RE: The main functions in the steel of this invention are as follows: (1) Modifying inclusions, reducing the number of inclusions and decreasing the tendency of pitting corrosion. The rare earth ions (La 3+ 、Ce 3+ ) dissolved in the steel, as a kind of cathodic corrosion inhibitor, often precipitate in the cathodic area, which can inhibit the electrochemical reaction occurring at the cathode and effectively slow down the further progress of corrosion; (2) In this invention, due to the presence of the easily segregating element Sn, the addition of rare earth elements can effectively improve the segregation problem caused by Sn, and then significantly improve the plasticity and toughness of the material; (3) When co-added with Cu, it can not only make the Cu in the steel disperse and inhibit the generation of "copper brittleness", but also act synergistically with Cu. By controlling the rolling temperature, nano-scale Cu4Ce precipitation phases can be formed, and the strength of the material can be further improved through precipitation strengthening; (4) The addition of rare earth elements helps to inhibit the decomposition of retained austenite and the precipitation of carbides, and can significantly improve the plasticity of the steel plate. The scope of this invention is limited to 0.0122% - 0.0138%.

[0021] V: This element reacts with C and N in the steel to form insoluble V(C,N). These compounds precipitate during and after the γ / α phase transformation. By controlling the rolling and coiling temperatures, the purpose of refining the precipitation phases can be achieved, playing a precipitation strengthening effect to improve the strength of the steel plate, especially significantly increasing the tensile strength of the material and reducing the yield ratio of the material, and then improving the formability of the product. In addition, V combines with N in the steel, fixing the dissolved N in the steel, which helps to improve the low-temperature impact toughness of the steel plate. However, too much V also increases the manufacturing cost and reduces the welding performance of the steel plate. Therefore, the scope of V in this invention is limited to 0.018% - 0.028%.

[0022] Ti: One of the alloying elements that plays a strengthening role. Ti in steel mainly exists in the forms of TiC and Ti(C, N). Ti(C, N) formed during the heating of the continuous casting billet can effectively inhibit the growth of austenite grains, playing a role in fine grain strengthening. During the rolling and cooling processes, nano-sized (Ti, Mo)C precipitates between the phases to play a role in precipitation strengthening. It is particularly significant in improving the tensile strength, and thus can reduce the yield ratio of the material and improve the forming performance of the product. However, when the Ti content is too high, it will deteriorate the plasticity and toughness of the material. The scope of this invention is limited to 0.031% - 0.046%.

[0023] W: Due to its strong binding force with C in steel, W dissolved in steel can form the hard phase (Fe, W)7C3 through substitution, which can improve the wear resistance of the steel plate. Especially when added together with Mo, the dissolved W can form a stable and hardly soluble nano-scale hard phase (Fe, W, Mo)7C3 with Mo in the steel, and the wear resistance effect produced by this hard phase on the steel plate is more significant. However, when the W content is too high, it will not only increase the cost but also deteriorate the impact performance of the steel plate. Therefore, the scope of this invention is limited to 0.059% - 0.079%.

[0024] Sn: The addition of Sn is beneficial to form a dense and well-adhered amorphous oxide (hydroxy oxide) protective layer on the surface of the steel, which can prevent the infiltration of SO4 2- , Cl - in acidic media, and the acid corrosion resistance is obvious. However, Sn belongs to the elements prone to segregation. When the Sn content is on the high side, it is easy to segregate at the grain boundaries, which will not only reduce the plasticity and toughness of the material but also deteriorate the corrosion resistance of the material. Therefore, the Sn content in this invention should be controlled within 0.036% - 0.054%.

[0025] The structure of the steel in this invention consists of ferrite + bainite + pearlite. Among them, the proportion of the ferrite phase is 34.7% - 37.9%, and the proportion of the bainite phase is 49.7% - 52.6%. Fine strengthening phases (Ti, Mo)C and hard phases (Fe, W, Mo)7C3 are precipitated in the structure. Among them, the area proportion of (Ti, Mo)C with a size range of 10 - 40 nm reaches 62.6% - 65.3%, and the area proportion of (Fe, W, Mo)7C3 with a size range of 30 - 60 nm reaches 55.7% - 58.6%. This level of precipitated phases is beneficial to improving the strength and wear resistance of the steel in this invention.

[0026] This invention also provides a manufacturing method for a high-strength, wear-resistant and corrosion-resistant steel for easily formed railway vehicles. This method manufactures a highly corrosion-resistant and wear-resistant steel containing the above chemical components through hot metal pre-desulfurization, converter steelmaking, secondary refining (LF furnace + RH furnace refining), slab continuous casting, continuous casting billet heating, hot strip rolling, laminar flow cooling and coiling. Among them:

[0027] Slab heating: To ensure the full solution of alloying elements such as Si, P, Sn, and W, and considering the relatively high content of Si added to the steel, to avoid the formation of hard-to-remove Fe2SiO4 / FeO "red scale" during slab heating, in this invention, the slab discharging temperature is controlled at 1191 - 1224 °C, the heating furnace atmosphere is a reducing atmosphere, and the air-fuel ratio is controlled at 1.3 - 1.5, which helps to reduce the liquefaction of Fe2SiO4, make the scale thinner, and facilitate descaling; when the heating temperature is below 1151 °C, slow heating is required, and the heating rate is controlled at 6.9 - 8.9 °C / min to ensure uniform temperature inside and outside the billet and full solution of the alloy; when above 1151 °C, rapid heating is required, and the heating rate is controlled at 18.9 - 20.3 °C / min, and the slab residence time in the furnace is 156 - 176 min to reduce the adhesion of liquid Fe2SiO4 to the steel plate and achieve an easy descaling effect.

[0028] Hot tandem rolling: Two-stage controlled rolling is adopted in rough rolling and finish rolling. In rough rolling, a high-temperature and large reduction method is used. The rough rolling exit temperature is 1138 - 1158 °C, and the cumulative reduction rate in the rough rolling stage is 74.1 - 77.1%. In this stage, by increasing the reduction amount, the purpose of refining grains and crushing the oxide scale on the steel plate surface is achieved. The finish rolling starting temperature is 1054 - 1078 °C. To reduce the formation of viscous scale Fe2SiO4, and at the same time ensure the full precipitation of Cu4Ce and (Ti, Mo)C strengthening phases without excessive growth of the precipitation phases, the finish rolling ending temperature is controlled at 906 - 926 °C.

[0029] Laminar cooling and coiling: After finish rolling, two-stage cooling is used for laminar cooling. In the first stage, it is cooled at a cooling rate of 5 - 12 °C / s to 729 - 749 °C (this temperature range belongs to the ferrite transformation region), and air-cooled for 19 - 23 s (to ensure the full formation of ferrite and hard phases). In this stage, soft-phase ferrite tissue can be formed and the precipitation of hard phases (Fe, W)7C3, (Fe, W, Mo)7C3, and Cu3(PO4)2 can be ensured, thereby obtaining the required plasticity and wear resistance of the steel plate; then, it is cooled in the second stage at a cooling rate of 29 - 34 °C / s and coiled when cooled to 581 - 599 °C. In this stage, by rapid cooling, a sufficient amount of hard-phase bainite can be formed, the formation of pearlite in the matrix can be reduced to ensure the strength of the steel plate, and the corrosion resistance of the steel can be improved. In addition, this coiling temperature has a good control effect on refining grains and inhibiting the coarsening of precipitation phase (Ti, Mo)C.

[0030] Furthermore, the addition amount of the hot metal pre-desulfurization desulfurizer is ≥4.0 kg / t to ensure that the S after desulfurization is ≤0.015%; the converter adopts a top-bottom combined blowing process, the converter tapping temperature is ≥1656 °C, and ferro-aluminum alloy is added during tapping to deoxidize the molten steel.

[0031] Furthermore, secondary steelmaking includes LF refining and RH refining. LF refining mainly focuses on deoxidation and desulfurization, and temperature increase and minor composition adjustment are carried out at this stage. All compositions are preferably controlled within the target range before the LF refining ladle is tapped, and the S content in the molten steel is controlled to be ≤0.006%. During the RH refining process of the molten steel, the vacuum degree in the vacuum chamber is maintained at less than 3.2 kPa, and rare earth alloy is added to the molten steel in the RH refining furnace. After adding the rare earth alloy, the molten steel is subjected to 2.6 - 4.6 minutes of pure RH circulation. After the RH refining furnace breaks the vacuum, the molten steel is gently blown for 30 - 33 minutes to ensure that inclusions float up sufficiently.

[0032] Furthermore, the rare earth alloy is La, Ce alloy.

[0033] Preferably, the flow rate of the gentle argon blowing is 74 - 86 NL / min, and the pressure is 0.25 - 0.36 MPa.

[0034] Furthermore, during continuous slab casting, mold powder is used throughout the process to protect the molten steel and prevent it from being exposed to the air. The thickness specification of the continuous casting slab is 210 - 230 mm. Since the rare earth elements (La, Ce) in the inventive steel have a strong affinity and are likely to form a large amount of rare earth inclusions with O and S elements in the steel, which affects the fluidity of the molten steel, the casting speed is controlled at 1.48 - 1.63 m / min during casting. To reduce the "segregation" problem of the continuous casting slab caused by P and Sn in the steel, the superheat is controlled between 20 - 27 °C during casting, and electromagnetic stirring technology is adopted, with the electromagnetic stirring current being 348 - 354 A and the frequency being 4.2 - 6.2 HZ.

[0035] Applying the above chemical compositions and processes to produce steel for railway freight cars with a thickness of 6.5 - 13.5 mm has high strength, excellent formability, wear resistance, and corrosion resistance. Through precise control of the composition and tissue ratio, the yield strength ReL of the inventive steel is >550 MPa, the tensile strength Rm is >730 MPa, the elongation after fracture A is >32%, the yield ratio is <0.80, the cold bending performance is qualified, and KV2 at -40 °C ≥107 J (tested with the minimum impact standard specimen); through the selection and reasonable combination of wear-resistant and corrosion-resistant elements, the corrosion rate of the steel plate in the acidic medium corrosion environment simulating coal-carrying freight cars is <0.68 g / m 2 ·h, and the corrosion rate in the industrial atmospheric environment relative to Q345B is <47.8%. The wear rate relative to the currently mainstream used steel Q450NQR1 is 45.4% - 47.7%. While having high strength, corrosion resistance, and wear resistance, the inventive steel also has excellent formability. Compared with steel of the same strength level, it can not only extend the service life of steel for railway vehicles, but also improve the formability of high-strength steel for railway vehicles during the processing process. Detailed implementation mode

[0036] In order to make the objectives, technical solutions and advantages of the embodiments of the present invention clearer, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments.

[0037] The following embodiments are only some of the optimal implementation solutions of the present invention, and do not impose any limitations on the scope of the foregoing invention and technical means. Among them, the composition of the steel in the embodiments of the present invention is shown in Table 1, the main process parameters of the steel smelting and continuous casting in the embodiments of the present invention are shown in Table 2, the heating process parameters of the steel in the embodiments of the present invention are shown in Table 3, the rolling and coiling process parameters of the steel in the embodiments of the present invention are shown in Table 4, the various properties of the steel in the embodiments of the present invention are shown in Table 5, the microstructures of the steel in the embodiments of the present invention are shown in Table 6, and the results of the cyclic immersion corrosion test of the steel in the embodiments of the present invention are shown in Table 7.

[0038] Table 1 Composition of the steel in the embodiments of the present invention (wt%)

[0039]

[0040]

[0041] Table 2 Main process parameters of the steel smelting and continuous casting in the embodiments of the present invention

[0042]

[0043] Table 3 Heating process of the steel in the embodiments of the present invention

[0044]

[0045] Table 4 Main process parameters of the steel rolling and cooling in the embodiments of the present invention

[0046]

[0047] It can be seen from Table 5 that the yield strength of the steel in the embodiments of the present invention is between 571 and 592 MPa, all reaching above the designed strength of 550 MPa, the tensile strength is between 731 and 768 MPa, the elongation rate is greater than 32%, the yield ratio is between 0.77 and 0.79, the cold bending performance is qualified, and the average value of the impact energy at -40°C is 107 to 123 J (tested with the minimum impact standard specimen), indicating that the strength of the steel in each embodiment not only meets the design requirements, but also has excellent plasticity, ductility and high low-temperature impact toughness.

[0048] The abrasion resistance test in Table 5 was carried out on a wet rubber wheel abrasive wear testing machine. A sample piece with a processed size of 57.0 mm × 25.0 mm × 6.0 mm was used for the abrasive wear test, and the wear test was carried out in accordance with "JB / T7705-1995 Loose Abrasive Wear Test Method - Rubber Wheel Method". The result of the abrasion resistance test was that the wear rate of the steel in the example relative to Q450NQR1 steel was 45.4% - 47.7%, which indicated that the steel in the example had excellent abrasion resistance performance.

[0049] Inspection Results of Performance Indicators of Each Example in Table 5

[0050]

[0051] Microstructure of the Steel in the Example of the Present Invention in Table 6

[0052]

[0053] To simulate the corrosion situation in an industrial atmospheric environment, in accordance with the test method specified in TB / T 2375-1993, a 72-hour cycle immersion rapid corrosion evaluation test was carried out on the steel of the invention; at the same time, to simulate the corrosion situation of the steel of the invention in an acid corrosion environment, a full immersion corrosion experiment was carried out in accordance with the implementation method of JB / T 7901 (temperature was 23 ± 2 °C, immersed in a 10% H2SO4 + 3.5% NaCl solution medium for 24 h). Table 7 shows the comparison results of the corrosion resistance performance between the steel in the example of the present invention and the comparative steel. It can be seen from Table 7 that the steel in the example of the present invention has high atmospheric corrosion resistance and acid corrosion resistance, and its corrosion resistance indicators all meet the requirements of the technical objectives.

[0054] Comparison Results of the Cycle Immersion Corrosion Test between the Steel in the Example of the Present Invention and the Comparative Steel in Table 7

[0055]

[0056] It is hereby specified that the above examples are only for illustrating the technical concept and characteristics of the present invention, and are not a limitation to the present invention. Any equivalent replacement or modification improvement that does not depart from the essence of the present invention's creation falls within the protection scope of the present invention.

Claims

1. A high-strength, wear-resistant and corrosion-resistant steel for railway vehicles that is easy to form, characterized in that, The chemical composition of the steel plate by weight percentage is as follows: C: 0.058% - 0.076%, Si: 0.81% - 0.97%, Mn: 1.26% - 1.46%, P ≤ 0.015%, S ≤ 0.006%, Cr: 0.82% - 1.03%, Cu: 0.13% - 0.28%, Mo: 0.051% - 0.071%, Al: 0.078% - 0.098%, RE: 0.0122% - 0.0138%, V: 0.018% - 0.028%, Ti: 0.031% - 0.046%, W: 0.059% - 0.079%, Sn: 0.036% - 0.054%, where 0.90% ≤ Si + Al + RE < 1.1%, 9.5 < Si / Al < 11.2, and the balance is Fe and inevitable impurities.

2. The high-strength wear-resistant and corrosion-resistant steel for easily formable railway vehicles according to claim 1, characterized in that, The thickness of the produced steel plate is 6.5 - 13.5 mm.

3. The high-strength wear-resistant and corrosion-resistant steel for easily formable railway vehicles according to claim 1, characterized in that, The microstructure of the steel consists of ferrite + bainite + pearlite. Among them, the proportion of the ferrite phase is 34.7% - 37.9%, and the proportion of the bainite phase is 49.7% - 52.6%. Fine strengthening phases TiC / MoC and hard phases Fe7C3 / W7C3 / Mo7C3 are precipitated in the microstructure. Among them, the area proportion of TiC / MoC with a size range of 10 - 40 nm reaches 62.6% - 65.3%, and the area proportion of Fe7C3 / W7C3 / Mo7C3 with a size range of 30 - 60 nm reaches 55.7% - 58.6%.

4. The high-strength wear-resistant and corrosion-resistant steel for easily formable railway vehicles according to claim 1, characterized in that, The yield strength ReL of the steel > 550 MPa, the tensile strength Rm > 730 MPa, the elongation after fracture A > 32%, the yield ratio < 0.80, the cold bending performance is qualified, and KV2 at -40°C ≥ 107 J.

5. The high-strength wear-resistant and corrosion-resistant steel for easily formable railway vehicles according to claim 1, wherein The corrosion rate of the steel plate under the acidic medium corrosion environment of the simulated coal transport truck is < 0.68 g / m 2 ·h. Under the industrial atmospheric environment, the corrosion rate relative to Q345B is < 47.8%, and the wear rate relative to the currently mainstream used steel Q450NQR1 is 45.4% - 47.7%.

6. A manufacturing method of the high-strength wear-resistant and corrosion-resistant steel for easily formable railway vehicles according to any one of claims 1 to 5, comprising hot metal pretreatment desulfurization, converter steelmaking, secondary refining, slab continuous casting, slab heating, hot continuous rolling, laminar flow cooling and coiling, characterized in that, The tapping temperature of the continuous casting billet is 1191 - 1224°C, the air-fuel ratio is 1.3 - 1.

5. When the heating temperature is below 1151°C, slow heating is required, and the heating rate is 6.9 - 8.9°C / min. When the temperature is above 1151°C, rapid heating is required, and the heating rate is controlled at 18.9 - 20.3°C / min. The residence time of the continuous casting billet in the furnace is 156 - 176 min; in the hot continuous rolling process, temperature-controlled rolling is carried out in two stages: rough rolling and finish rolling. The outlet temperature is 1138 - 1158°C, and the cumulative reduction ratio is 74.1 - 77.1%; the start rolling temperature of the finish rolling is 1054 - 1078°C, and the finish rolling temperature is controlled at 906 - 926°C; after finish rolling, laminar cooling is carried out in a two-stage cooling method. In the first stage, it is cooled at a cooling rate of 5 - 12°C / s to 729 - 749°C and air-cooled for 19 - 23 s; then, it is cooled in the second stage at a cooling rate of 29 - 34°C / s and coiled at 581 - 599°C.

7. The manufacturing method of the high-strength wear-resistant and corrosion-resistant steel for easily formable railway vehicles according to claim 6, characterized in that, When pre-desulfurizing hot metal and converting steel, the addition amount of the desulfurizer ≥ 4.0 kg / t, and the tapping temperature of the converter ≥ 1656°C.

8. The manufacturing method of the high-strength wear-resistant and corrosion-resistant steel for easily formable railway vehicles according to claim 6, characterized in that, During LF refining, the temperature is raised and the composition is slightly adjusted. During RH refining, the vacuum degree in the vacuum chamber is maintained less than 3.2 kPa. After adding rare earth alloys, the molten steel is subjected to 2.6 - 4.6 min of RH pure circulation, and after breaking the vacuum, the molten steel is weakly blown for 30 - 33 min.

9. The manufacturing method of the high-strength wear-resistant and corrosion-resistant steel for easily formable railway vehicles according to claim 8, characterized in that The rare earth alloy is a La, Ce alloy; the weak argon blowing flow rate is 74 - 86 NL / min, and the pressure is 0.25 - 0.36 MPa.

10. The manufacturing method of the high-strength wear-resistant and corrosion-resistant steel for easily formed railway vehicles according to claim 6, characterized in that, The continuous casting slab thickness is 210 - 230 mm. During casting, the casting speed is controlled at 1.48 - 1.63 m / min, the casting superheat is 20 - 27 °C. At the same time, electromagnetic stirring technology is adopted, the electromagnetic stirring current is 348 - 354 A, and the frequency is 4.2 - 6.2 HZ.

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