Highland environment bridge interface shear strength 400mpa grade stainless steel composite plate and preparation method thereof

Abstract

The present application relates to a kind of highland environment bridge interface shear strength 400MPa grade stainless steel composite plate and its preparation method, belong to composite plate technical field.The composite plate includes austenitic stainless steel and low carbon bainite type weathering steel, wherein the austenitic stainless steel is complex layer, and the low carbon bainite type weathering steel is base layer, and interface shear strength is greater than or equal to 400MPa.With low carbon bainite type weathering steel as base layer, its weathering index is greater than 6.2, can adapt to highland atmospheric corrosion environment.Austenitic stainless steel is used as complex layer, which prevents the erosion of water or corrosion solution at the connection between ballast and bridge deck to the bridge deck structure, and makes up for the deficiency of corrosion resistance of weathering steel;Compared with all stainless steel, the cost is reduced.

Description

Technical Field

[0001] This invention relates to the field of composite plate technology, and in particular to a stainless steel composite plate with an interfacial shear strength of 400 MPa for bridges in high-altitude environments and its preparation method. Background Technology

[0002] The use of weathering steel-stainless steel composite plates in railway steel bridges can effectively inhibit corrosion damage to the bridge deck structure caused by the intrusion of chloride ions and other contaminants. This extends the service life of the steel bridge and avoids the environmental pollution problems associated with applying protective coatings to the bridge deck. Therefore, stainless steel composite plates have broad application prospects in weathering steel bridges. To improve the safety and durability of railway steel bridges in complex high-altitude environments such as extreme cold, large temperature differences, and high radiation, stainless steel composite plates are required to possess excellent corrosion resistance, weather resistance, and high interfacial shear strength.

[0003] In existing research, there are two main types of stainless steel composite plates for bridges: one is made by combining non-weathering carbon steel with stainless steel, but the use of non-weathering steel cannot guarantee the atmospheric corrosion resistance of bridge steel, affecting the long service life of bridges; the other is made by combining weathering steel with stainless steel, which improves corrosion resistance and weather resistance, but the resulting composite plate has low interfacial shear strength. Summary of the Invention

[0004] Based on the above analysis, the present invention aims to provide a stainless steel composite plate with an interfacial shear strength of 400MPa for bridges in high-altitude environments and its preparation method, in order to solve the problem of low interfacial shear strength of existing composite plates.

[0005] On one hand, the present invention provides a stainless steel composite plate with an interfacial shear strength of 400MPa for bridges in high-altitude environments, comprising austenitic stainless steel and low-carbon bainitic weathering steel, wherein the austenitic stainless steel is the cladding layer and the low-carbon bainitic weathering steel is the base layer, and the interfacial shear strength is ≥400MPa.

[0006] Furthermore, the composite plate has a yield strength of 500MPa-550MPa, a V-shaped impact energy of -40℃ ≥240J, and a tensile strength of ≥630MPa.

[0007] Furthermore, the weathering index of the low-carbon bainitic weathering steel is I = 26.01Cu + 3.88Ni + 1.20Cr + 1.49Si + 17.28P - 7.29Cu×Ni - 9.10Ni×P - 33.39Cu 2 Between 6.2 and 6.8, the welding crack susceptibility index Pcm (%) = C + Si / 30 + (Mn + Cu + Cr) / 20 + Mo / 15 + Ni / 60 + V / 10 + 5B ≤ 0.22.

[0008] Furthermore, the alloy composition of the low-carbon bainitic weathering steel base layer, by mass percentage, includes C: 0.045-0.065%, Cr: 0.35-0.55%, Ni: 0.3-0.5%, Si: 0.2-0.35%, Mn: 1.2-1.5%, Al: 0.015-0.035%, Ti: 0.010-0.020%, V: 0.025-0.045%, Cu: 0.25-0.45%, Nb: 0.02-0.03%, Mo: 0.05-0.10%, P: 0.008-0.012%; the balance being Fe and unavoidable impurities.

[0009] Furthermore, the microstructure of the low-carbon bainitic weathering steel base layer is bainitic, including granular bainite and lath bainite.

[0010] Preferably, the yield strength of the low-carbon bainitic weathering steel base layer is between 420MPa and 500MPa, and the V-shaped impact energy at -40℃ is 250-300J.

[0011] Furthermore, the alloy composition of the austenitic stainless steel cladding, by mass percentage, includes C: 0.015-0.030%, Cr: 16.5-18.0%, Ni: 10-14%, Si: 0.35-0.60%, Mn: 1.0-1.5%, Mo: 2.0-3.5%, with the balance being Fe and unavoidable impurities.

[0012] Furthermore, the microstructure of the austenitic stainless steel cladding is austenitic.

[0013] Furthermore, the thickness of the austenitic stainless steel cladding layer is 2.5mm-3.5mm; the thickness of the low-carbon bainitic weathering steel base layer is 14mm-19mm.

[0014] On the other hand, the present invention provides a method for preparing a stainless steel composite plate with an interfacial shear strength of 400 MPa for bridges in high-altitude environments, comprising the following steps:

[0015] S1: Base layer / multilayer preparation: Base layer and multilayer billets are obtained by smelting and continuous casting according to chemical composition requirements. The base layer and multilayer billets are heated to 1150-1230℃ and held for 2-4 hours. The billets are then cut to the required size and the surfaces of the base layer and multilayer are polished.

[0016] S2: Asymmetric billet assembly: The cladding layer is placed on top of the base layer, and the thickness of the cladding layer is less than that of the base layer. Then, the cladding layer and the base layer are sealed around the perimeter using gas shielded welding. Vacuum is then drawn using the φ5-30mm holes reserved at the weld seal. After vacuuming, the seal is performed to obtain the composite billet.

[0017] S3: Two-stage hot rolling: The composite billet is heated to 1150-1230℃ and held for 1-2 hours. After removing the oxide scale from the furnace, it is rolled. The total compression ratio is 6-8. The rolling process adopts two-stage rolling: roughing and finishing. The temperature of the roughing is controlled at 1050-1100℃ and the reduction rate of the roughing is 60% of the total deformation. The temperature of the finishing is controlled at 840℃-900℃ and the reduction rate of the finishing is 40% of the total deformation.

[0018] S4: Controlled cooling: After the finishing rolling stage ends, wait for the temperature to drop to 740-810℃, and then carry out two-stage cooling: fast cooling and slow cooling. The fast cooling stage is laminar flow cooling with water sprayed from the top and bottom surfaces, with a cooling rate of 1-15℃ / s and the reddening temperature controlled at 500-650℃. The slow cooling stage is natural cooling in the air until the temperature reaches room temperature.

[0019] S5: Tempering treatment: The hot-rolled composite plate is reheated to 450-550℃, held for 30-40 minutes, and then air-cooled to room temperature to obtain a stainless steel composite plate.

[0020] Furthermore, in step S1, the surface roughness of the base layer and the overlay is controlled within Ra0.4-Ra0.8 after surface polishing.

[0021] Compared with the prior art, the present invention can achieve at least one of the following beneficial effects:

[0022] 1. The stainless steel composite plate for bridges in high-altitude environments of this invention, with an interfacial shear strength of 400MPa, uses low-carbon bainitic weathering steel as the base layer, which has a weathering resistance index >6.2 and can adapt to the atmospheric corrosion environment of high-altitude areas. The austenitic stainless steel cladding layer prevents water accumulation or corrosive solutions at the connection between the ballast and the bridge deck from eroding the bridge deck structure, compensating for the insufficient corrosion resistance of weathering steel; at the same time, it reduces costs compared to all-stainless steel.

[0023] 2. The bainitic weathering steel and stainless steel composite interface of the present invention have good bonding, and the carbon content of the base layer and the cladding layer is low and similar, which has good matching and avoids uneven carbon distribution at the interface.

[0024] 3. Before the billet assembly, the surface roughness of the base layer and the cladding layer is controlled at Ra0.4-Ra0.8, and an asymmetric billet assembly method is adopted to ensure that the base layer and the cladding layer deform together, promote the interface bonding, and is not easily restricted by the mill opening degree when preparing thick plates.

[0025] 4. The composite plate of the present invention has an interfacial shear strength ≥400MPa, a yield strength level between 500MPa and 550MPa, a tensile strength ≥630MPa, and a V-shaped impact energy at -40℃ ≥240J, which meets the requirements for tensile strength and impact energy of steel with a yield strength of 500MPa in GB / T 714-2015 "Structural Steel for Bridges".

[0026] In this invention, the above-described technical solutions can be combined with each other to achieve more preferred combinations. Other features and advantages of this invention will be set forth in the following description, and some advantages may become apparent from the description or be learned by practicing the invention. The objects and other advantages of this invention can be realized and obtained from what is particularly pointed out in the description and drawings. Attached Figure Description

[0027] The accompanying drawings are for illustrative purposes only and are not intended to limit the invention. Throughout the drawings, the same reference numerals denote the same parts.

[0028] Figure 1 This refers to the tissue morphology near the interface in Example 2;

[0029] Figure 2 This refers to the tissue morphology near the interface in Example 4;

[0030] Figure 3 The tissue morphology near the interface in Example 5;

[0031] Figure 4 The stretching curve for Example 5;

[0032] Figure 5 The tensile fracture morphology of Example 5;

[0033] Figure 6 This is a comparison of the tissue morphology near the interface in Example 1.

[0034] Figure 7 The tissue morphology near the interface is shown in Comparative Example 4. Detailed Implementation

[0035] The preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings, which constitute a part of the present invention and are used together with the embodiments of the present invention to illustrate the principles of the present invention, but are not intended to limit the scope of the present invention.

[0036] This invention provides a stainless steel composite plate for bridges in high-altitude environments with an interfacial shear strength of 400MPa, comprising austenitic stainless steel and low-carbon bainitic weathering steel, wherein the austenitic stainless steel is the cladding layer and the low-carbon bainitic weathering steel is the base layer, the composite plate has a yield strength of 500MPa-550MPa, and an interfacial shear strength ≥400MPa.

[0037] Compared with the prior art, the composite plate provided by the present invention is composed of an austenitic stainless steel cladding layer and a low-carbon bainitic weathering steel base layer. The low-carbon bainitic weathering steel base layer can adapt to the atmospheric corrosion environment of high altitude, while the austenitic stainless steel cladding layer prevents corrosion damage caused by the intrusion of chloride ions and other substances.

[0038] From a microscopic perspective, the composite plate's microstructure consists of an austenitic cladding layer, an interface, and a bainitic base layer. Near the cladding layer, the interface microstructure is austenitic, while near the base layer, it is bainitic or a combination of bainitic and ferrite. The composite interface exhibits good bonding. The carbon content in both the base layer and the cladding layer is low and similar, demonstrating good matching and avoiding uneven carbon distribution at the interface. Testing revealed that the resulting composite plate possesses high comprehensive mechanical properties: an interface shear strength ≥400MPa, a yield strength between 500MPa and 550MPa, a tensile strength ≥630MPa, and a V-notch impact energy at -40℃ ≥240J, meeting the tensile strength and impact energy requirements for 500MPa grade steel in GB / T 714-2015 "Structural Steel for Bridges".

[0039] Specifically, the weathering index I of the low-carbon bainitic weathering steel is I = 26.01Cu + 3.88Ni + 1.20Cr + 1.49Si + 17.28P - 7.29Cu×Ni - 9.10Ni×P - 33.39Cu 2 Between 6.2 and 6.8, the welding crack susceptibility index Pcm (%) = C + Si / 30 + (Mn + Cu + Cr) / 20 + Mo / 15 + Ni / 60 + V / 10 + 5B ≤ 0.22.

[0040] Specifically, the alloy composition of the low-carbon bainitic weathering steel base layer, by mass percentage, includes C: 0.045-0.065%, Cr: 0.35-0.55%, Ni: 0.3-0.5%, Si: 0.2-0.35%, Mn: 1.2-1.5%, Al: 0.015-0.035%, Ti: 0.010-0.020%, V: 0.025-0.045%, Cu: 0.25-0.45%, Nb: 0.02-0.03%, Mo: 0.05-0.10%, P: 0.008-0.012%; the balance being Fe and unavoidable impurities.

[0041] Specifically, the microstructure of the low-carbon bainitic weathering steel base layer is bainitic, including granular bainite and lath bainite.

[0042] Preferably, the proportion of granular bainite is 80-90%; the proportion of lath bainite is 10-20%.

[0043] Preferably, the yield strength of the low-carbon bainitic weathering steel base layer is between 420MPa and 500MPa, and the V-shaped impact energy at -40℃ is 250-300J.

[0044] The low-carbon bainitic weathering steel base layer has a yield strength between 420MPa and 500MPa, a weathering index I between 6.2 and 6.8, and a weld crack sensitivity index Pcm (%) ≤ 0.22, ensuring strength, weather resistance, and weldability, meeting the requirements for steel bridge construction in high-altitude environments. Simultaneously, the low-carbon bainitic weathering steel contains microalloying elements such as Ti, V, and Nb, which easily form dispersed carbides, inhibiting the degradation of interfacial corrosion resistance caused by the combination of carbon and chromium at the interface and the consumption of chromium.

[0045] Specifically, the alloy composition of the austenitic stainless steel cladding, by mass percentage, includes C: 0.015-0.030%, Cr: 16.5-18.0%, Ni: 10-14%, Si: 0.35-0.60%, Mn: 1.0-1.5%, Mo: 2.0-3.5%, with the balance being Fe and unavoidable impurities.

[0046] Specifically, the microstructure of the austenitic stainless steel cladding is austenitic.

[0047] This invention provides a method for preparing a stainless steel composite plate with an interfacial shear strength of 400 MPa for bridges in high-altitude environments, comprising the following steps:

[0048] S1: Base layer / multilayer preparation: Base layer and multilayer billets are obtained by smelting and continuous casting according to chemical composition requirements. The base layer and multilayer billets are heated to 1150-1230℃ and held for 2-4 hours. The billets are then cut to the required size and the surfaces of the base layer and multilayer are polished.

[0049] S2: Asymmetric billet assembly: The cladding layer is placed on top of the base layer, and the thickness of the cladding layer is less than that of the base layer. Then, the cladding layer and the base layer are sealed around the perimeter using gas shielded welding. Vacuum is then drawn using the φ5-30mm holes reserved at the weld seal. After vacuuming, the seal is performed to obtain the composite billet.

[0050] S3: Two-stage hot rolling: The composite billet is heated to 1150-1230℃ and held for 1-2 hours. After removing the oxide scale from the furnace, it is rolled. The total compression ratio is 6-8. The rolling process adopts two-stage rolling: roughing and finishing. The temperature of the roughing is controlled at 1050-1100℃ and the reduction rate of the roughing is 60% of the total deformation. The temperature of the finishing is controlled at 840℃-900℃ and the reduction rate of the finishing is 40% of the total deformation.

[0051] S4: Controlled cooling: After the finishing rolling stage ends, wait for the temperature to drop to 740-810℃, and then carry out two-stage cooling: fast cooling and slow cooling. The fast cooling stage is laminar flow cooling with water sprayed from the top and bottom surfaces, with a cooling rate of 1-15℃ / s and the reddening temperature controlled at 500-650℃. The slow cooling stage is natural cooling in the air until the temperature reaches room temperature.

[0052] S5: Tempering treatment: The hot-rolled composite plate is reheated to 450-550℃, held for 30-40 minutes, and then air-cooled to room temperature to obtain a stainless steel composite plate.

[0053] Compared with existing technologies, this application employs asymmetric billet assembly and two-stage hot rolling, followed by precise control of cooling rate and tempering temperature. The resulting stainless steel composite plate exhibits high interfacial bonding strength and excellent interfacial bonding. During the hot rolling process, the base layer and cladding layer deform collaboratively without any breakage or cracking.

[0054] Specifically, the thickness of the austenitic stainless steel cladding layer is 2.5mm-3.5mm; the thickness of the low-carbon bainitic weathering steel base layer is 14mm-19mm.

[0055] It should be noted that the present invention adopts an asymmetric billet assembly method, that is, using base layers and cladding layers of different thicknesses for composite assembly. On the one hand, this ensures that the base layers and cladding layers deform together during the rolling process, promoting the bonding of the interface. On the other hand, it is less restricted by the mill opening when preparing thicker composite plates.

[0056] Specifically, in step S1, the surface roughness of the base layer and the overlay is controlled within Ra0.4-Ra0.8 after surface polishing.

[0057] It should be noted that the bainitic weathering steel and stainless steel composite interface in this invention exhibits good bonding, with both the base layer and the cladding layer having low and similar carbon contents, resulting in good compatibility and preventing uneven carbon distribution at the interface. Before billet assembly, the surface roughness of the base layer and cladding layer is controlled within Ra0.4-Ra0.8. If the roughness value is too high, more impurities are easily trapped during the meshing process of the two plates; if the roughness value is too low, it will reduce the meshing performance of the two plates and increase production costs.

[0058] Specifically, in step S2, the composite blank is evacuated to below 30 Pa.

[0059] Specifically, in step S3, the total compression ratio is 6-8.

[0060] It should be noted that this invention adopts an asymmetric billet assembly method, that is, using base layers and cladding layers of different thicknesses for composite assembly. On the one hand, this ensures that the base layer and cladding layers deform together during rolling, promoting interfacial bonding. On the other hand, it is less affected by the mill opening degree when preparing thicker composite plates. After billet assembly, the vacuum degree is controlled below 30 Pa and the total compression ratio during the rolling stage is 6-8, ensuring the dispersed distribution of fine oxides in the composite plate. When the compression ratio is too high, the required base layer billet is too thick, which cannot guarantee the quality of the billet core and is not conducive to mass production. When the compression ratio is too low, the interfacial oxides are continuously distributed, reducing the interfacial performance.

[0061] Specifically, the cooling process employs a combination of rapid and slow cooling.

[0062] It should be noted that during the rapid cooling stage, the hot-rolled slab is cooled by spraying water, mainly on both the top and bottom surfaces, with a cooling rate controlled at 1-15℃ / s. During the slow cooling stage, air cooling is used.

[0063] Specifically, the tempering temperature is 500-550℃, and the holding time is 30-40 minutes.

[0064] It should be noted that the tempering temperature of 500-550℃ was selected during the heat treatment process to ensure the matching of strength, toughness and low yield strength ratio of the composite plate. When the tempering temperature is too low, the low-temperature impact energy of the bainitic weathering steel and stainless steel composite plate is low; when the tempering temperature is too high, the content and size of the second phase precipitation in the bainitic weathering steel base layer increase, which greatly increases its yield strength ratio and affects the safe service of the bainitic weathering steel and stainless steel composite plate.

[0065] To more clearly describe the present invention, the following embodiments and comparative examples are provided for further illustration.

[0066] The chemical compositions of the selected base layer and cladding layer are shown in Tables 1 and 2. 1# and 2# are both base layers. The weathering index I of base layer 1# is 6.24, and the weld crack sensitivity index Pcm (%) is 0.18; the weathering index I of base layer 2# is 6.75, and the weld crack sensitivity index Pcm (%) is 0.20. 3# and 4# are both cladding layers.

[0067] Table 1 Chemical composition of the base layer (wt%)

[0068] Group C Al Si P S Ti V 1# 0.055 0.026 0.22 0.008 0.005 0.014 0.031 2# 0.058 0.032 0.34 0.011 0.0011 0.012 0.039 Group Cr Mn Ni Cu Nb Mo 1# 0.45 1.31 0.32 0.28 0.029 0.058 2# 0.49 1.38 0.39 0.32 0.021 0.10

[0069] Table 2 Chemical composition (wt%) of the multilayer

[0070] Multilayer C Si P S Cr Mn Ni Mo 3# 0.027 0.53 0.038 0.006 16.78 1.19 10.39 1.99 4# 0.016 0.44 0.032 0.006 17.90 1.29 13.81 3.17

[0071] The mechanical properties of the selected low-carbon bainitic weathering steel base layer are shown in Table 3.

[0072] Table 3 Mechanical Properties of Weathering Steel Plates

[0073]

[0074]

[0075] Example 1

[0076] The preparation of the composite board includes the following steps:

[0077] S1: Base layer / multilayer preparation: Base layer and multilayer billets are obtained by smelting and continuous casting according to the chemical composition requirements of base layer #1 and multilayer #3. The base layer and multilayer billets are heated to 1200℃ and held for 2 hours. The billets are then cut to the required size. The surface of the base layer and multilayer is then polished. The surface roughness of the base layer and multilayer is controlled to Ra0.8 after surface polishing.

[0078] S2: Asymmetric billet assembly: The cladding layer is placed on top of the base layer, and the cladding layer and the base layer are sealed together around the perimeter using gas shielded welding. Vacuum is then drawn through the φ15mm hole reserved at the weld seal to a vacuum level below 30Pa. After vacuuming, the seal is performed to obtain the composite billet.

[0079] S3: Two-stage hot rolling: The composite billet is heated to 1200℃ and held for 1 hour. After removing the oxide scale from the furnace, it is rolled. The rolling process adopts two-stage rolling: roughing and finishing. The temperature of the roughing is controlled at 1050-1100℃ and the reduction rate of the roughing is 60% of the total deformation. The temperature of the finishing is controlled at 840℃-900℃ and the reduction rate of the finishing is 40% of the total deformation.

[0080] The overall compression ratio is 7;

[0081] S4: Controlled cooling: After the finishing rolling stage ends, wait for the temperature to drop to 740-810℃, and then carry out two-stage cooling: fast cooling and slow cooling. The fast cooling stage is laminar flow cooling with water sprayed from the top and bottom surfaces, with a cooling rate of 6-9℃ / s and the reddening temperature controlled at 500-650℃. The slow cooling stage is natural cooling in the air until the temperature reaches room temperature.

[0082] S5: Tempering treatment: The hot-rolled composite plate is reheated to 500℃, held for 30-40 minutes, and then air-cooled to room temperature to obtain a stainless steel composite plate.

[0083] Example 2

[0084] The preparation process of Example 2 is largely the same as that of Example 1, except that in Example 2, the base layer is #2 and the cladding layer is #3, and the tempering temperature is 550℃.

[0085] Example 3

[0086] The preparation process of Example 3 is largely the same as that of Example 1, except that the tempering temperature of the No. 2 base layer and the No. 4 cladding layer in Example 3 is 550℃.

[0087] Example 4

[0088] The preparation process of Example 4 is largely the same as that of Example 1. The difference is that in Example 4, the No. 2 base layer and the No. 3 composite layer are cooled by laminar water spraying from the top and bottom surfaces during the rapid cooling stage. The cooling rate is 1-5℃ / s, and the tempering temperature is 550℃.

[0089] Example 5

[0090] The preparation process of Example 5 is largely the same as that of Example 1. The difference is that in Example 5, the No. 1 base layer and the No. 3 composite layer are cooled by laminar water spraying from the top and bottom surfaces during the rapid cooling stage. The cooling rate is 10-15℃ / s, and the tempering temperature is 550℃.

[0091] Comparative Example 1

[0092] The preparation process of Comparative Example 1 is largely the same as that of Example 1, except that the total compression ratio in Comparative Example 1 is 4.

[0093] Comparative Example 2

[0094] The preparation process of Comparative Example 2 is largely the same as that of Example 2, except that the tempering temperature in Comparative Example 2 is 650°C.

[0095] Comparative Example 3

[0096] The preparation process of Comparative Example 3 is largely the same as that of Example 3, except that the surface roughness of the base layer and the overlay layer in Comparative Example 3 is controlled to Ra1.6 after surface polishing.

[0097] Comparative Example 4

[0098] The preparation process of Comparative Example 4 is largely the same as that of Example 5, except that the cooling rate in Comparative Example 4 is 1-5℃ / s and the vacuum degree is above 1000Pa.

[0099] Performance testing

[0100] The above embodiments and comparative examples were subjected to performance tests, mainly including interfacial shear strength, yield strength, yield ratio and -40℃ V-type impact energy. The test results are shown in Tables 4 and 5.

[0101] Table 4. Detection Results of Examples

[0102]

[0103] Table 5 Comparative test results

[0104]

[0105]

[0106] Reference Figure 1-7 In conjunction with Examples 1-5 and Comparative Examples 1-4, the interfacial shear strength and yield strength were tested using a shear testing machine and a tensile testing machine. In Example 1, a composite of base layer #1 and cladding layer #3 was selected, with an interfacial shear strength and yield strength of 403 MPa and 516 MPa, respectively. In Example 2, a composite of base layer #2 and cladding layer #3 was selected. Compared with base layer #1, base layer #2 could obtain more lath bainite structure under the same cooling rate. The morphology of the structure near the interface is as follows. Figure 1 As shown, the interfacial shear strength and yield strength increased to 443 MPa and 554 MPa, respectively. In Example 3, a composite of base layer #2 and cladding layer #4 was selected. Compared with cladding layer #3, cladding layer #4 had higher Cr, Ni, and Mo contents, a wider interfacial width, and more ferrite. The interfacial shear strength and yield strength were 405 MPa and 552 MPa, respectively. Compared with Example 2, Example 4 selected a composite of base layer #2 and cladding layer #3. The cooling rate in the first stage after rolling was slower, resulting in more ferrite. The microstructure near the interface was as shown. Figure 2 As shown, the interfacial shear strength and yield strength decreased to 413 MPa and 532 MPa, respectively. Compared with Example 1, Example 5 selected a composite of base layer #1 and cladding layer #3, which resulted in the fastest cooling rate in the first stage after rolling. The microstructure near the interface is shown in the figure. Figure 3 As shown, the interfacial shear strength remained consistent, more fine lath bainite was obtained in the matrix, and the yield strength increased to 567 MPa. The tensile curves and tensile fracture morphology are shown in the figures below. Figure 4 and Figure 5 As shown.

[0107] Compared to Example 1, in Comparative Example 1, the overall compression ratio decreased from 7 to 4, such as Figure 6 As shown, the interface oxides are continuously distributed without significant breakage. The interfacial shear strength and yield strength decreased from 403 MPa and 516 MPa to 370 MPa and 480 MPa, respectively. Compared with Example 2, in Comparative Example 2, the tempering temperature increased from 550℃ to 650℃, and the yield strength ratio increased from 0.85 to 0.91, affecting the safe service of the stainless steel composite plate. Compared with Example 3, in Comparative Example 3, after surface grinding of the base layer and cladding, the surface roughness control changed from Ra0.8 to Ra1.6, i.e., the surface became rougher. The interfacial shear strength and yield strength decreased from 405 MPa and 552 MPa to 381 MPa and 545 MPa, respectively. Compared with Example 5, in Comparative Example 4, the vacuum degree was above 1000 Pa, and the microstructure near the interface was as shown. Figure 7As shown, a large amount of oxides are distributed at the interface, and the interfacial shear strength and yield strength decrease from 402 MPa and 567 MPa to 358 MPa and 520 MPa, respectively.

[0108] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. A stainless steel composite plate with an interfacial shear strength of 400 MPa for bridges in high-altitude environments, characterized in that, It includes austenitic stainless steel and low-carbon bainitic weathering steel, wherein the austenitic stainless steel is the cladding layer and the low-carbon bainitic weathering steel is the base layer, and the interfacial shear strength is ≥400MPa. The stainless steel composite plate is obtained through the following steps; S1: Base layer / multilayer preparation: Base layer and multilayer billets are obtained by smelting and continuous casting according to chemical composition requirements, and then the billets are cut to the required size. The surface of the base layer and multilayer is then polished. The surface roughness after polishing is controlled at Ra0.4-Ra0.

8. S2: Asymmetric assembly: The cladding layer is placed on top of the base layer, and the thickness of the cladding layer is less than the thickness of the base layer. Then, the cladding layer is sealed to the base layer around the perimeter using gas shielded welding. S3: Two-stage hot rolling: The rolling process adopts two stages of roughing and finishing rolling, with a total compression ratio of 6-8; S4: Controlled cooling: After the finishing rolling stage is completed, after the temperature drops to 740-810℃, a two-stage cooling process of fast cooling and slow cooling is carried out. The cooling rate is 1-15℃ / s, and the reddening temperature is controlled at 500-650℃. The slow cooling stage is natural cooling in the air until the temperature reaches room temperature. S5: Tempering treatment: The hot-rolled composite plate is reheated to 450-550℃, held for 30-40 minutes, and then air-cooled to room temperature to obtain a stainless steel composite plate.

2. The stainless steel composite plate with an interfacial shear strength of 400 MPa for bridges in high-altitude environments according to claim 1, characterized in that, The composite plate has a yield strength of 500MPa-550MPa, a V-shaped impact energy of ≥240J at -40℃, and a tensile strength of ≥630MPa.

3. The stainless steel composite plate with an interfacial shear strength of 400 MPa for bridges in high-altitude environments according to claim 1, characterized in that, The weathering index I of the low-carbon bainitic weathering steel is I = 26.01Cu + 3.88Ni + 1.20Cr + 1.49Si + 17.28P - 7.29Cu×Ni - 9.10Ni×P - 33.39Cu 2 Between 6.2 and 6.8, the welding crack susceptibility index Pcm (%) = C+Si / 30+(Mn+Cu+Cr) / 20+Mo / 15+Ni / 60+V / 10+5B ≤ 0.

22.

4. The stainless steel composite plate with an interfacial shear strength of 400 MPa for bridges in high-altitude environments according to claim 1, characterized in that, The alloy composition of the low-carbon bainitic weathering steel base layer, by mass percentage, includes C: 0.045-0.065%, Cr: 0.35-0.55%, Ni: 0.3-0.5%, Si: 0.2-0.35%, Mn: 1.2-1.5%, Al: 0.015-0.035%, Ti: 0.010-0.020%, V: 0.025-0.045%, Cu: 0.25-0.45%, Nb: 0.02-0.03%, Mo: 0.05-0.10%, P: 0.008-0.012%; the balance being Fe and unavoidable impurities.

5. The stainless steel composite plate with an interfacial shear strength of 400 MPa for bridges in high-altitude environments according to claim 1, characterized in that, The microstructure of the low-carbon bainitic weathering steel base layer is bainitic, including granular bainite and lath bainite.

6. The stainless steel composite plate with an interfacial shear strength of 400 MPa for bridges in high-altitude environments according to claim 1, characterized in that, The yield strength of the low-carbon bainitic weathering steel base layer is between 420MPa and 500MPa, and the V-type impact energy at -40℃ is 250-300J.

7. The stainless steel composite plate with an interfacial shear strength of 400 MPa for bridges in high-altitude environments according to claim 1, characterized in that, The alloy composition of the austenitic stainless steel cladding, by mass percentage, includes C: 0.015-0.030%, Cr: 16.5-18.0%, Ni: 10-14%, Si: 0.35-0.60%, Mn: 1.0-1.5%, Mo: 2.0-3.5%, with the balance being Fe and unavoidable impurities.

8. The stainless steel composite plate with an interfacial shear strength of 400 MPa for bridges in high-altitude environments according to claim 7, characterized in that, The microstructure of the austenitic stainless steel cladding is austenitic.

9. The stainless steel composite plate with an interfacial shear strength of 400 MPa for bridges in high-altitude environments according to claim 1, characterized in that, The thickness of the austenitic stainless steel cladding is 2.5mm-3.5mm; the thickness of the low-carbon bainitic weathering steel base layer is 14mm-19mm.

10. A method for preparing a stainless steel composite plate with an interfacial shear strength of 400 MPa for bridges in high-altitude environments, as described in any one of claims 1-9, characterized in that... Includes the following steps: S1: Base layer / multilayer preparation: Base layer and multilayer billets are obtained by smelting and continuous casting according to chemical composition requirements. The base layer and multilayer billets are heated to 1150-1230℃ and held for 2-4 hours. The billets are then cut to the required size and the surfaces of the base layer and multilayer are polished. S2: Asymmetric billet assembly: The cladding layer is placed on top of the base layer, and the thickness of the cladding layer is less than that of the base layer. Then, the cladding layer and the base layer are sealed around the perimeter using gas shielded welding. Vacuum is then drawn using the φ5-30mm holes reserved at the weld seal. After vacuuming, the seal is performed to obtain the composite billet. S3: Two-stage hot rolling: The composite billet is heated to 1150-1230℃ and held for 1-2 hours. After removing the oxide scale from the furnace, it is rolled. The total compression ratio is 6-8. The rolling process adopts two-stage rolling: roughing and finishing. The temperature of the roughing is controlled at 1050-1100℃, and the reduction rate of the roughing is 60% of the total deformation. The temperature of the finishing is controlled at 840℃-900℃, and the reduction rate of the finishing is 40% of the total deformation. S4: Controlled cooling: After the finishing rolling stage ends, wait for the temperature to drop to 740-810℃, and then carry out two-stage cooling: fast cooling and slow cooling. The fast cooling stage is laminar flow cooling with water sprayed from the top and bottom surfaces, with a cooling rate of 1-15℃ / s and the reddening temperature controlled at 500-650℃. The slow cooling stage is natural cooling in the air until the temperature reaches room temperature. S5: Tempering treatment: The hot-rolled composite plate is reheated to 450-550℃, held for 30-40 minutes, and then air-cooled to room temperature to obtain a stainless steel composite plate.

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