A high-strength single-phase ferrite weathering steel, its preparation method and applications

Abstract

The present invention relates to the field of metallurgy, and discloses a high-strength single-phase ferritic weathering steel, a preparation method thereof and an application thereof. The weathering steel comprises the following chemical components: C: 0.01-0.07%, Ti: 0.05-0.15%, Nb: 0.01-0.08, Mo: 0.05-0.25%, Cu: 0.3-0.7%, Cr: 1.2-1.8%, Ni: 0.3-1.1%, Si: 0.1-0.5%, Mn: 0.5-1.0%, Al: 0.01-0.05%, Re: 0.01-0.12%, P: ≤0.02%, S: ≤0.01%; the balance is Fe and inevitable impurities. Based on the synergistic effect of rare earth-microalloying and the design idea of medium and high temperature rolling in the austenite recrystallization zone, the present invention prepares a single-phase ferritic weathering steel with high strength, high corrosion resistance, good weldability and excellent comprehensive application performance.

Description

Technical Field

[0001] The present invention relates to the field of metallurgy, and particularly to a high-strength single-phase ferritic weathering steel, a preparation method thereof, and an application thereof. Background Art

[0002] Weathering steel is a low-alloy high-strength steel with good corrosion resistance in the atmospheric environment. The addition of appropriate amounts of weathering metal elements (such as Cu, Cr, etc.) endows it with good atmospheric corrosion resistance, and its corrosion resistance is 2-8 times that of ordinary steel grades. Moreover, the longer the service time, the more prominent the corrosion resistance. Therefore, weathering steel is mainly used for steel structural parts such as railway rails and rail vehicles that are prone to atmospheric corrosion when exposed to the natural environment for a long time.

[0003] New requirements are put forward for the use of basic materials for key components such as the steel for railway freight car bodies, requiring railway freight transportation to be lighter, longer-lived, and more efficient. Up to now, the 450MPa grade general weathering steel in service is difficult to meet the requirements of the times. Especially in harsh medium environments such as transporting raw coal and coastal atmospheric transportation, the service life of railway freight car bodies is severely shortened and cannot meet the 25-year service life requirement. New materials such as aluminum alloy and stainless steel can meet the high weathering resistance requirements of railway vehicles, but there are many problems such as the high price of aluminum alloy and the welding manufacturing technology and high production cost of stainless steel. High-strength low-alloy weathering steel carriages have low cost and excellent weldability, accounting for a large proportion in railway transportation, but their weathering resistance needs to be improved.

[0004] The steel materials for the currently serving car bodies are all "ferrite + pearlite" dual-phase weathering steels. The uneven structure will cause potential differences between different phases to trigger galvanic corrosion, and the high-carbon phase is prone to preferential corrosion, leading to local corrosion behavior, seriously shortening the service life of weathering steel structural parts. In addition, the inevitable impurity element S in the steel is easy to form inclusions such as MnS or CaS with elements such as Mn and Ca in the steel. These inclusions preferentially dissolve during the service process of the material, reducing the pitting corrosion resistance of the steel. The alloy element C in the steel is easy to react with Cr, Fe, etc. in the steel at the medium temperature range of about 680°C to precipitate M 23 C 6 type carbides, such as (Fe, Cr) 23 C 6 , and the precipitation of such carbides will reduce the corrosion resistance of Cr.

[0005] In summary, it is necessary to upgrade and replace the currently serving weathering steel for railway freight car bodies to meet the requirements of the times for high strength and high corrosion resistance. Summary of the Invention

[0006] To solve the above technical problems, the present invention provides a high-strength single-phase ferritic weathering steel, a preparation method thereof, and an application thereof. Based on the synergistic effect of rare earth-microalloying and the design concept of medium-high temperature rolling in the austenite recrystallization zone, the present invention prepares a single-phase ferritic weathering steel with high strength, high corrosion resistance, good weldability, and excellent comprehensive application performance.

[0007] The specific technical solution of the present invention is as follows:

[0008] In the first aspect, the present invention provides a high-strength single-phase ferritic weathering steel, comprising the following chemical components in mass percentages: C: 0.01-0.07%, Ti: 0.05-0.15%, Nb: 0.01-0.08, Mo: 0.05-0.25%, Cu: 0.3-0.7%, Cr: 1.2-1.8%, Ni: 0.3-1.1%, Si: 0.1-0.5%, Mn: 0.5-1.0%, Al: 0.01-0.05%, Re: 0.01-0.12%, P: ≤0.02%, S: ≤0.01%; the balance is Fe and inevitable impurities.

[0009] Among them, Re is one or more of Ce, La, Nd, and Y.

[0010] As described in the background art part of the present application, the existing steel materials for vehicle bodies are all "ferrite + pearlite" dual-phase weathering steels. The uneven structure will cause potential differences between different phases to trigger galvanic corrosion, and the high-carbon phase is prone to preferential corrosion to cause local corrosion behavior, seriously shortening the service life of weathering steel structural parts. In addition, the inevitable impurity element S in the steel is easy to form inclusions such as MnS or CaS with elements such as Mn and Ca in the steel. These inclusions preferentially dissolve during the use of the material, reducing the pitting corrosion resistance of the steel. The alloying element C in the steel is easy to react with Cr, Fe, etc. in the steel at about 680 °C in the medium-temperature section to precipitate M 23 C 6 type carbides, such as (Fe, Cr) 23 C 6 , and the precipitation of such carbides will reduce the corrosion resistance of Cr.

[0011] Therefore, the present invention adopts a single-phase ferritic weathering steel, wherein:

[0012] (1) The present invention adds appropriate amounts of microalloying elements such as Ti, Nb, and Mo to the steel, which can form fine and dispersed (Ti, Nb, Mo)(C, N) nano-precipitation phases with free C and N in the steel at high temperature; on the one hand, precipitation strengthening improves the strength of the steel, and on the other hand, the precipitation of (Ti, Nb, Mo)(C, N) consumes the C element, thereby reducing the precipitation risk of M23C6 and further improving the corrosion resistance of the steel.

[0013] (2) By adding an appropriate amount of Re (Ce, La, Nd, Y) to the steel, Re 2 O 2 S can be formed in the liquid phase state, avoiding the formation of easily corroded MnS, and improving the corrosion resistance and mechanical properties of the steel. Re 2 O 2 S precipitates first in the liquid state, and the precipitated Re 2 O 2 S can serve as the nucleation sites of (Ti, Nb, Mo)N, forming (Ti, Nb, Mo)N-coated Re 2 O 2 S composite inclusions, modifying the inclusions, and further improving the corrosion resistance and mechanical properties.

[0014] (3) In the steel of the present invention, the precipitation temperature of Re 2 O 2 S is about 1750 °C, the precipitation temperature of (Ti, Nb, Mo)N is about 1560 °C, the precipitation temperature of MnS is about 1320 °C, and the precipitation temperature of M23C6 is about 660 °C. Compared with traditional materials, the precipitation risks of MnS and M23C6 and their harm to the corrosion resistance are greatly reduced. By adding Ti, Nb, Mo, controlling the precipitation of (Ti, Nb, Mo)(C, N) nanophases, pinning the grain boundaries, inhibiting the growth of austenite grains, refining the grains, and enhancing the strength through precipitation strengthening and fine grain strengthening.

[0015] Preferably, Ti: 0.06 - 0.09%, Nb: 0.02 - 0.05%, Mo: 0.08 - 0.18%, Re: 0.04 - 0.1%.

[0016] It is found through experiments in the present invention that by further optimizing the contents of the above four elements within the above ranges, the mechanical properties, corrosion resistance, and welding properties of the finally obtained weathering steel are better.

[0017] Preferably, the mass percentages of the chemical components simultaneously satisfy the following relationship: (Ti + Nb + Mo): Re = (3.5 - 20): 1; Re: S = (2.5 - 60): 1.

[0018] It is summarized through a large number of experiments in the present invention that when the chemical components in the weathering steel simultaneously satisfy the above conditions, the mechanical properties, corrosion resistance, and welding properties of the finally obtained weathering steel are better.

[0019] Preferably, during the melting process of preparation, Si, Mn, and Al are added successively at intervals first, and then Re, Mo, Ni, and Ti are added successively at intervals.

[0020] According to the difference in oxygen potential in the alloy metallurgical physical and chemical characteristics, the present invention first adds Si, Mn and Al in sequence and at intervals for deep deoxidation, thereby ensuring the yield of the subsequent addition of easily oxidizable elements such as rare earth and titanium.

[0021] In a second aspect, the present invention provides a method for preparing a high-strength single-phase ferrite weathering steel, comprising the following steps:

[0022] S1 material selection: select continuous casting billet containing the chemical composition;

[0023] S2 slab heating: heating the continuous casting slab;

[0024] S3 slab rolling: rolling the slab obtained after heating;

[0025] S4 Coiling: The slab obtained after rolling is cooled and coiled.

[0026] Preferably, in S1: the continuously cast billet is a slab with a thickness of 240-260 mm.

[0027] Preferably, in S1: the continuous casting billet is pre-grinded and repaired (especially surface scars, ears, etc. are cleaned) to reduce the problem of subsequent rolling cracking.

[0028] Preferably, in S2: the heating is divided into a preheating section, a heating section and a soaking section; the temperature of the preheating section is ≤1000°C, and the residence time is 30-40min; the temperature of the heating section is 1240-1270°C, and the residence time is 80-115min; the temperature of the soaking section is 1200-1240°C, and the residence time is 35-55min; the total heating time is 2.5h≤T≤3.5h.

[0029] The present invention has found that by limiting the process parameters in S2 within the above range, the product yield rate is higher and the various properties of the obtained weathering steel are better.

[0030] Preferably, in S2: during the heating process, the volume ratio of air to fuel in the heating device is 0.5-0.7:1, and the atmosphere is low in oxidation.

[0031] Preferably, in S3: two-stage controlled rolling is adopted; the first stage is rough rolling, the first stage starting rolling temperature is 1180-1220℃, the final rolling temperature is 1060-1080℃, and the first stage final rolling thickness is 38-42mm; the second stage is finish rolling, the second stage starting rolling temperature is 1020-1060℃, the second stage final rolling temperature is 850-880℃, and the second stage final rolling thickness is 3-5mm.

[0032] The present invention has found that by limiting the process parameters in S3 within the above range, the product yield rate is higher and the various properties of the obtained weathering steel are better.

[0033] Preferably, in S3: in the first-stage rough rolling, the rolling mill is a reciprocating triple rolling mill, and descaling is carried out before rolling; in the second stage, it is finish rolling, and the rolling mill adopts a seven-stand tandem rolling mill in one pass.

[0034] Preferably, in S3: in the finish rolling of the second stage, the reduction ratio of the last pass is 8-11%, and the reduction ratios of the other passes can be analogized accordingly.

[0035] Preferably, in S4: the cooling adopts spray laminar cooling, the cooling rate is 15-40 °C / s, coiling is carried out after cooling to 640-680 °C, and slow cooling is carried out after coiling.

[0036] In a third aspect, the present invention provides an application of the above high-strength single-phase ferritic weathering steel as a steel for vehicle bodies.

[0037] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0038] (1) Through the synergistic effect of rare earth-microalloying, the present invention utilizes the strong binding ability of rare earth with O and S in steel to modify sulfides and oxides in steel, thereby improving the corrosion resistance of the material.

[0039] (2) Through the single-phase ferrite design, the present invention solves the problem of bimetallic galvanic corrosion of the existing ferritic + pearlitic dual-phase weathering steel.

[0040] (3) Through microalloy precipitation strengthening and controlled rolling and cooling, the present invention can obtain a weathering steel with high tensile strength.

[0041] (4) The rolling process system proposed by the present invention is reasonably designed, the process system operation is loose, and it can be stably produced on a wide and thick plate industrial production line. Specific embodiments

[0042] The present invention will be further described below in conjunction with embodiments.

[0043] General embodiment

[0044] A high-strength single-phase ferritic weathering steel contains the following chemical components in mass percentages: C: 0.01-0.07%, Ti: 0.05-0.15%, Nb: 0.01-0.08, Mo: 0.05-0.25%, Cu: 0.3-0.7%, Cr: 1.2-1.8%, Ni: 0.3-1.1%, Si: 0.1-0.5%, Mn: 0.5-1.0%, Al: 0.01-0.05%, Re: 0.01-0.12%, P: ≤0.02%, S: ≤0.01%; the balance is Fe and unavoidable impurities. Among them, Re is one or more of Ce, La, Nd, and Y.

[0045] Preferably, Ti: 0.06 - 0.09%, Nb: 0.02 - 0.05%, Mo: 0.08 - 0.18%, RE: 0.04 - 0.1%, and the mass percentages of the chemical components simultaneously satisfy the following relationships: (Ti + Nb + Mo):Re = (3.5 - 20):1; Re:S = (2.5 - 60):1.

[0046] Preferably, during the smelting process of preparation, Si, Mn, and Al alloys are added successively at intervals first, and then Re, Mo, Ni, and Ti alloys are added successively at intervals.

[0047] A preparation method of a high-strength single-phase ferritic weathering steel, comprising the following steps:

[0048] S1 Material selection: The raw materials of the chemical components in the above formula are processed into continuous casting billets by conventional methods;

[0049] S2 Billet heating: Heat the continuous casting billet;

[0050] S3 Billet rolling: Roll the billet obtained after heating;

[0051] S4 Coiling: Cool the slab obtained after rolling and coil it.

[0052] In some specific embodiments, in S1: During the smelting process of preparation, Si, Mn, and Al are added successively at intervals first, and then Re, Mo, Ni, and Ti are added successively at intervals.

[0053] In some specific embodiments, in S1: The continuous casting billet is a slab with a thickness of 240 - 260 mm.

[0054] In some specific embodiments, in S1: The continuous casting billet is pre-ground and repaired (especially cleaning surface scabs, ears, etc. clean) to reduce subsequent rolling cracking problems.

[0055] In some specific embodiments, in S2: The heating is divided into a preheating section, a heating section, and a soaking section; the temperature of the preheating section is ≤ 1000 °C, and the residence time is 30 - 40 min; the temperature of the heating section is 1240 - 1270 °C, and the residence time is 80 - 115 min; the temperature of the soaking section is 1200 - 1240 °C, and the residence time is 35 - 55 min; the total heating time is 2.5 h ≤ T ≤ 3.5 h.

[0056] In some specific embodiments, in S2: During the heating process, the air-fuel ratio in the heating device is 0.5 - 0.7:1, with a low oxidation atmosphere.

[0057] In some specific embodiments, in S3: Two-stage controlled rolling is adopted; in the first stage of rough rolling, the starting rolling temperature is 1180 - 1220 °C, the finishing rolling temperature is 1060 - 1080 °C, and the finishing thickness in the first stage is 38 - 42 mm; in the second stage of finishing rolling, the starting rolling temperature is 1020 - 1060 °C, the finishing rolling temperature is 850 - 880 °C, and the finishing thickness in the second stage is 3 - 5 mm.

[0058] In some specific embodiments, in S3: In the first stage of rough rolling, the rolling mill is a reciprocating triple-stand rolling mill, and descaling is carried out before rolling; in the second stage of finishing rolling, a one-pass seven-stand rolling mill is used.

[0059] In some specific embodiments, in S3: In the second stage of finishing rolling, the reduction ratio in the last pass is 8 - 11%, and the reduction ratios of the remaining passes can be analogized accordingly.

[0060] In some specific embodiments, in S4: The cooling adopts spray laminar cooling, the cooling rate is 15 - 40 °C / s, coiling is carried out after cooling to 640 - 680 °C, and slow cooling is carried out after coiling.

[0061] Specific embodiments and comparative examples

[0062] Example 1

[0063] First, a 230-mm-thick continuous casting slab is prepared, and the chemical composition (mass percentage) is shown in Table 1. During the melting process of the preparation, ensure that the addition order of Si, Mn, and Al takes precedence over Re, Mo, Ni, and Ti. The obtained continuous casting slab is ground to remove burrs and scars, and then continuously heated in a heating furnace. The volume ratio of air to fuel in the heating furnace is 0.6:1. The temperature in the preheating section is lower than 800 °C, and the time is 35 min. The temperature in the heating section is 1260 °C, and the residence time is 90 min. The temperature in the soaking section is 1220 °C, and the residence time is 45 min. After leaving the heating furnace, surface descaling is carried out. The starting rolling temperature of rough rolling is 1185 °C, and it is rolled to 40 mm thick by a reciprocating triple-stand rolling mill. The finishing rolling temperature of rough rolling is 1080 °C. After being transported by a track, it enters a one-pass seven-stand rolling mill for finishing rolling. The single-pass reduction amounts in sequence are 8.6%, 12.5%, 16.3%, 15.9%, 14.2%, 10.8%, and 9.2%. The starting rolling temperature of finishing rolling is 1055 °C, and the finishing rolling temperature of finishing rolling is 865 °C. After the steel plate is rolled, spray laminar cooling is carried out, the cooling rate is 35 °C / s, then coiling is carried out, the coiling temperature is 650 °C, and after coiling, it is transferred to a slow cooling pit for cooling.

[0064] Example 2

[0065] The preparation process of this example is the same as that of Example 1, except that the chemical composition of the continuous casting slab is different from that of Example 1 (S = 0.0226 wt%, Re(Ce) = 0.05 wt%). The specific chemical composition of the continuous casting slab in this example is shown in Table 1.

[0066] Example 3

[0067] The preparation process of this example is the same as that of Example 1, except that the chemical composition of the continuous casting slab is different from that of Example 1 (S = 0.0226 wt%, Re(Ce) = 0.12 wt%). The specific chemical composition of the continuous casting slab in this example is shown in Table 1.

[0068] Comparative Example 1

[0069] The preparation process of this comparative example is the same as that of Example 1, except that the chemical composition of the continuous casting slab is different from that of Example 1 (without Ti, Nb and Mo). The specific chemical composition of the continuous casting slab in this comparative example is shown in Table 1.

[0070] Comparative Example 2

[0071] The preparation process of this comparative example is the same as that of Example 1, except that the chemical composition of the continuous casting slab is different from that of Example 1 (without Re). The specific chemical composition of the continuous casting slab in this comparative example is shown in Table 1.

[0072] Example 4

[0073] First, prepare a continuous casting slab with a thickness of 230 mm. The chemical composition (mass percentage) is shown in Table 1. During the melting process of the preparation, ensure that the addition order of Si, Mn, and Al takes precedence over Re, Mo, Ni, and Ti. Grind the obtained continuous casting slab to remove burrs and scabs, and then put it into a heating furnace for continuous heating. The volume ratio of air to fuel in the heating furnace is 0.6:1. The temperature in the preheating section is lower than 800 °C, and the time is 32 min. The temperature in the heating section is 1260 °C, and the residence time is 95 min. The temperature in the soaking section is 1220 °C, and the residence time is 45 min. After leaving the heating furnace, perform surface dephosphorization. The starting rolling temperature for rough rolling is 1193 °C, and it is rolled to a thickness of 40 mm through a reciprocating triple-stand rolling mill. The final rolling temperature for rough rolling is 1077 °C. After being conveyed by the track, it enters a seven-stand tandem rolling mill for finish rolling. The single-pass reduction ratios in sequence are 8.5%, 12.5%, 16.5%, 15.8%, 14.3%, 10.9%, and 9.3%. The starting rolling temperature for finish rolling is 1052 °C, and the final rolling temperature for finish rolling is 872 °C. After rolling, the steel plate is cooled by spray laminar cooling with a cooling rate of 35 °C / s, and then coiled. The coiling temperature is 654 °C, and after coiling, it is transferred to a slow-cooling pit for cooling.

[0074] Example 5

[0075] First, prepare a continuous casting slab with a thickness of 230 mm, and the chemical composition (mass percentage) is shown in Table 1. During the melting process of the preparation, ensure that the addition order of Si, Mn, and Al takes precedence over Re, Mo, Ni, and Ti. Grind the obtained continuous casting slab to remove burrs and scabs, and place it in a heating furnace for continuous heating. The volume ratio of air to fuel in the heating furnace is 0.6:1. The temperature in the preheating section is lower than 800 °C, and the time is 35 min. The temperature in the heating section is 1260 °C, and the residence time is 90 min. The temperature in the soaking section is 1220 °C, and the residence time is 40 min. After leaving the heating furnace, perform surface dephosphorization. The starting rolling temperature of rough rolling is 1184 °C, and it is reciprocally rolled to a thickness of 40 mm by a reciprocating triple-stand rolling mill. The final rolling temperature of rough rolling is 1080 °C. After being conveyed by a track, it enters a seven-stand tandem rolling mill for finish rolling. The single-pass reduction ratios in sequence are 8.6%, 12.6%, 16.5%, 15.9%, 14.3%, 10.8%, and 9.4%. The starting rolling temperature of finish rolling is 1046 °C, and the final rolling temperature of finish rolling is 853 °C. After the steel plate is rolled, it is cooled by spray laminar cooling with a cooling rate of 35 °C / s, and then coiled. The coiling temperature is 671 °C, and after coiling, it is transferred to a slow-cooling pit for cooling.

[0076] Example 6

[0077] First, prepare a continuous casting slab with a thickness of 230 mm, and the chemical composition (mass percentage) is shown in Table 1. During the melting process of the preparation, ensure that the addition order of Si, Mn, and Al takes precedence over Re, Mo, Ni, and Ti. Grind the obtained continuous casting slab to remove burrs and scabs, and place it in a heating furnace for continuous heating. The volume ratio of air to fuel in the heating furnace is 0.6:1. The temperature in the preheating section is lower than 800 °C, and the time is 35 min. The temperature in the heating section is 1260 °C, and the residence time is 93 min. The temperature in the soaking section is 1220 °C, and the residence time is 55 min. After leaving the heating furnace, perform surface dephosphorization. The starting rolling temperature of rough rolling is 1181 °C, and it is reciprocally rolled to a thickness of 40 mm by a reciprocating triple-stand rolling mill. The final rolling temperature of rough rolling is 1074 °C. After being conveyed by a track, it enters a seven-stand tandem rolling mill for finish rolling. The single-pass reduction ratios in sequence are 8.5%, 12.7%, 16.4%, 15.8%, 14.3%, 10.9%, and 9.2%. The starting rolling temperature of finish rolling is 1047 °C, and the final rolling temperature of finish rolling is 858 °C. After the steel plate is rolled, it is cooled by spray laminar cooling with a cooling rate of 35 °C / s, and then coiled. The coiling temperature is 646 °C, and after coiling, it is transferred to a slow-cooling pit for cooling.

[0078] Comparative Example 3

[0079] First, prepare a continuous casting slab with a thickness of 230 mm. The chemical composition (mass percentage) is shown in Table 1. During the melting process of preparation, ensure that the addition order of Si, Mn, and Al takes precedence over Re, Mo, Ni, and Ti. Grind the obtained continuous casting slab to remove burrs and scars, and then place it in a heating furnace for continuous heating. The volume ratio of air to fuel in the heating furnace is 0.6:1. The temperature in the preheating section is below 800 °C for 40 min, the temperature in the heating section is 1260 °C with a residence time of 100 min, the temperature in the soaking section is 1220 °C with a residence time of 90 min. After leaving the heating furnace, perform surface dephosphorization. The starting rolling temperature of rough rolling is 1172 °C, and it is rolled to a thickness of 40 mm through a reciprocating triple-stand rolling mill. The final rolling temperature of rough rolling is 1079 °C. After being transported by track, it enters a seven-stand tandem rolling mill for finish rolling. The reduction per pass in sequence is 8.5%, 12.5%, 16.6%, 15.8%, 14.2%, 10.7%, 9.4% respectively. The starting rolling temperature of finish rolling is 1047 °C, and the final rolling temperature of finish rolling is 858 °C. After rolling, the steel plate is cooled by spray laminar cooling with a cooling rate of 35 °C / s, and then coiled. The coiling temperature is 646 °C, and after coiling, it is transferred to a slow cooling pit for cooling.

[0080] Comparative Example 4

[0081] First, prepare a continuous casting slab with a thickness of 230 mm. The chemical composition (mass percentage) is shown in Table 1. During the melting process of preparation, ensure that the addition order of Si, Mn, and Al takes precedence over Re, Mo, Ni, and Ti. Grind the obtained continuous casting slab to remove burrs and scars, and then place it in a heating furnace for continuous heating. The volume ratio of air to fuel in the heating furnace is 0.6:1. The temperature in the preheating section is below 800 °C for 46 min, the temperature in the heating section is 1260 °C with a residence time of 110 min, the temperature in the soaking section is 1220 °C with a residence time of 150 min. After leaving the heating furnace, perform surface dephosphorization. The starting rolling temperature of rough rolling is 1182 °C, and it is rolled to a thickness of 40 mm through a reciprocating triple-stand rolling mill. The final rolling temperature of rough rolling is 1064 °C. After being transported by track, it enters a seven-stand tandem rolling mill for finish rolling. The reduction per pass in sequence is 8.7%, 12.5%, 16.3%, 15.7%, 14.3%, 10.6%, 9.3% respectively. The starting rolling temperature of finish rolling is 1026 °C, and the final rolling temperature of finish rolling is 842 °C. After rolling, the steel plate is cooled by spray laminar cooling with a cooling rate of 35 °C / s, and then coiled. The coiling temperature is 642 °C, and after coiling, it is transferred to a slow cooling pit for cooling.

[0082] The chemical compositions, heating furnace heat preservation processes, and rolling temperature controlled rolling differences of weathering steels in each example and comparative example are shown in Table 1, Table 2, and Table 3 respectively.

[0083] Table 1: Chemical compositions (wt%) of weathering steels in each example and each comparative example

[0084]

[0085] Table 2: Insulation process of continuous casting billets in various embodiments and comparative examples

[0086]

[0087]

[0088] Table 3: Rolling process and product yield of each embodiment and each comparative example

[0089]

[0090] As shown in Table 3, the product yield of Comparative Examples 3 and 4 is significantly lower than that of other embodiments and comparative examples, and obviously does not have a market competitive advantage. The main reason is that the soaking treatment time of Comparative Examples 3 and 4 is significantly longer than that of other cases (Comparative Example 3 is 90 minutes, and Comparative Example 4 is 150 minutes).

[0091] The remaining embodiments and comparative examples were tested for performance, and the statistical results are shown in Tables 4 and 5. The mechanical properties test was carried out in accordance with GB / T228.1-2010 "Metallic Material Tensile Test Part 1: Room Temperature Test Method" standard; standard specimens were processed according to "TB 2375-1993 Railway Weathering Steel Cyclic Immersion Corrosion Test Method", and weathering steel was selected with 0.01 mol / L NaHSO 3 (sodium bisulfite) is the corrosive solution, the test water bath temperature is 45±1℃, the corrosion time is 72h, and the sample is weighed before the test and after cleaning and drying. The weight loss rate is calculated according to formula ①:

[0092]

[0093] Where: W-weight loss rate, g / (m 2 h);

[0094] G0-original weight of sample, g;

[0095] G1-weight of the sample after testing, g;

[0096] a-specimen length, mm;

[0097] b- sample width, mm;

[0098] c-specimen thickness, mm;

[0099] t-test time, h;

[0100] Table 4: Mechanical properties test results of weathering steel obtained in each embodiment and each comparative example

[0101] Case Tensile strength Rm Yield strength Rel Elongation A Example 1 761 ± 5 Mpa 633 ± 2 Mpa 24.8±1.4％ Example 2 793 ± 5 Mpa 673 ± 3 Mpa 20.8±1.7％ Example 3 759 ± 4 Mpa 642 ± 3 Mpa 25.4±1.6％ Comparative Example 1 673 ± 5 Mpa 543 ± 4 Mpa 29.8±0.8％ Comparative Example 2 693 ± 3 Mpa 563 ± 2 Mpa 27.1±1.1％ Example 4 796 ± 3 Mpa 676 ± 5 Mpa 21.1±2.2％ Example 5 783 ± 4 Mpa 657 ± 2 Mpa 21.3±1.2％ Example 6 787 ± 2 Mpa 661 ± 4 Mpa 22.7±2.2％

[0102] It can be seen from the data in Table 4 that:

[0103] (1) The difference between Comparative Example 1 and Examples 1-3 is that Ti, Nb, and Mo are not added to the weathering steel; the difference between Comparative Example 2 and Examples 1-3 is that Re (Ce) is not added to the weathering steel. Through the comparison of various mechanical property data, the above differences all result in significantly lower indicators of Comparative Example 1 and Comparative Example 2 than those of the examples.

[0104] (2) In Examples 1-3, the preparation processes are basically the same, and the main difference lies in the chemical composition of the weathering steel; (the contents of S and RE are different). Specifically: in Example 1, Example 2, and Example 3, the content of Re (Ce) increases in turn (Example 1 = 0.02 wt%, Example 2 = 0.05 wt%, Example 3 = 0.12 wt%); and, in Example 1, (Ti + Nb + Mo):Re ≈ 11.5:1; Re:S ≈ 2:1; in Example 2, (Ti + Nb + Mo):Re ≈ 4.5:1; Re:S ≈ 19:1; in Example 3, (Ti + Nb + Mo):Re ≈ 1.9:1; Re:S ≈ 46:1. From the mechanical properties of the finally obtained weathering steel, Example 2 is the best in terms of tensile strength, yield strength, and elongation at break. In Example 1, due to the low content of Re and the low Re:S, and in Example 3, due to the high content of Re and the low (Ti + Nb + Mo):RE, the properties are all inferior to those of Example 2. Combining other test data of the present invention (not given in the specification), it is summarized that: in the weathering steel, the weathering steel that meets the conditions of "Ti: 0.06 - 0.09%, Nb: 0.02 - 0.05%, Mo: 0.08 - 0.18%, Re: 0.04 - 0.1%" and "(Ti + Nb + Mo):Re = (3.5 - 20):1; Re:S = (2.5 - 60):1" has the best mechanical properties.

[0105] (3) In Examples 4-6, other types of Re elements are added to the weathering steel (Example 4 is La, Example 5 is Nd, and Example 6 is Y), and they also meet the two major conditions of "Ti: 0.06 - 0.09%, Nb: 0.02 - 0.05%, Mo: 0.08 - 0.18%, Re: 0.04 - 0.1%" and "(Ti + Nb + Mo):Re = (3.5 - 20):1; Re:S = (2.5 - 60):1". The final data shows that the comprehensive mechanical properties of the obtained weathering steel are better.

[0106] Table 5: Welding crack sensitivity coefficient Pcm, corrosion resistance index I, and periodic immersion test detection results of the weathering steel obtained in each example

[0107] Case Pcm (%) I Microstructure <![CDATA[Weight loss rate (g / m 2 .h)]]> Example 1 0.1873 6.040 Ferrite 0.952 Example 2 0.1664 8.167 Ferrite 0.733 Example 3 0.184l 6.132 Ferrite 0.945 Comparative Example 1 0.1962 4.63l Ferrite 1.156 Comparative Example 2 0.1903 5.032 Ferrite 1.024 Example 4 0.1770 8.09l Ferrite 0.884 Example 5 0.1740 7.985 Ferrite 0.765 Example 6 0.1727 8.002 Ferrite 0.828

[0108] Note: When the welding crack sensitivity coefficient Pcm ≤ 0.2, it indicates good welding performance of the steel. When the corrosion resistance index I ≥ 6.0, it indicates good corrosion resistance of the steel.

[0109] It can be seen from the data in Table 5 that:

[0110] (1) The weathering steels obtained in Examples 1 - 6 all have good welding performance and corrosion resistance. Among them, the chemical compositions of the weathering steels in Examples 1 and 3 are different from those in Example 2 (the contents of S and Re are different). Specifically, the Re content in Example 1 is low and Re:S is low, and the Re content in Example 3 is high and (Ti + Nb + Mo):Re is low, both of which result in significantly worse welding performance and corrosion resistance than Example 2.

[0111] (2) The difference between Comparative Example 1 and Examples 1 - 3 is that Ti, Nb, and Mo are not added to the weathering steel; the difference between Comparative Example 2 and Examples 1 - 3 is that Re(Ce) is not added to the weathering steel. Although their welding performance is relatively good, their corrosion resistance is poor.

[0112] The raw materials and equipment used in the present invention are all common raw materials and equipment in the art without special instructions; the methods used in the present invention are all conventional methods in the art without special instructions.

[0113] The above are only the preferred embodiments of the present invention, and do not impose any limitations on the present invention. Any simple modifications, changes, and equivalent transformations made to the above embodiments according to the technical essence of the present invention still fall within the protection scope of the technical solution of the present invention.

Claims

1. A high-strength single-phase ferrite weathering steel, characterized in that: Contains the following chemical components in mass percentage: C: 0.01-0.07%, Ti: 0.06-0.09%, Nb: 0.02-0.05%, Mo: 0.08-0.18%, Cu: 0.3-0.7%, Cr: 1.2-1.8%, Ni: 0.3-1.1%, Si: 0.1-0.5%, Mn: 0.5-1.0%, Al: 0.01-0.05%, modifying elements: 0.04-0.1%, P: ≤ 0.02%, S: ≤ 0.01%; the balance is Fe and unavoidable impurities; Wherein, the modifying element is one or more of Ce, La, Nd, and Y; The mass ratio of (Ti+Nb+Mo):modifying elements is (3.5-20):1; the mass ratio of modifying elements:S is (2.5-60):

1.

2. The high-strength single-phase ferrite weathering steel according to claim 1, characterized in that: The steel comprises the following chemical components in mass percentage: C: 0.03%, Ti: 0.072%, Nb: 0.035%, Mo: 0.12%, Cu: 0.32%, Cr: 1.37%, Ni: 0.42%, Si: 0.43%, Mn: 0.67%, Al: 0.023%, Ce: 0.05%, P: 0.015%, S: 0.0026%; the balance is Fe.

3. The high-strength single-phase ferrite weathering steel according to claim 1, characterized in that: In the smelting process of preparation, Si, Mn, and Al are first added in sequence and intervals, and then the modifying elements, Mo, Ni, and Ti are added in sequence and intervals.

4. A method for preparing the high-strength single-phase ferrite weathering steel according to any one of claims 1 to 3, characterized in that The steps include: S1 material selection: select continuous casting billet containing the chemical composition; S2 slab heating: heating the continuous casting slab; S3 slab rolling: rolling the slab obtained after heating; S4 Coiling: The slab obtained after rolling is cooled and coiled.

5. The preparation method according to claim 4, characterized in that: In S2: the heating is divided into a preheating section, a heating section and a soaking section; the temperature of the preheating section is ≤1000°C, and the residence time is 30-40min; the temperature of the heating section is 1240-1270°C, and the residence time is 80-115min; the temperature of the soaking section is 1200-1240°C, and the residence time is 35-55min; the total heating time is 2.5h≤T≤3.5h.

6. The preparation method according to claim 4 or 5, characterized in that: In S2: during the heating process, the volume ratio of air to fuel in the heating device is 0.5-0.7:

1.

7. The preparation method according to claim 4, characterized in that: In S3: two-stage controlled rolling is adopted; the first stage is rough rolling, the first stage starting rolling temperature is 1180-1220℃, the final rolling temperature is 1060-1080℃, and the first stage final rolling thickness is 38-42mm; the second stage is finish rolling, the second stage starting rolling temperature is 1020-1060℃, the second stage final rolling temperature is 850-880℃, and the second stage final rolling thickness is 3-5mm.

8. The preparation method according to claim 4, characterized in that: In S4: the cooling adopts water spray laminar flow cooling, the cooling rate is 15-40°C / s, and coiling is performed after the temperature drops to 640-680°C, and then slow cooling is performed after coiling.

9. Use of the high-strength single-phase ferrite weathering steel according to any one of claims 1 to 3 or the high-strength single-phase ferrite weathering steel obtained by the preparation method according to any one of claims 4 to 8 as vehicle body steel.

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