A method for preparing an inconel 625 nickel-based alloy and x65 pipeline steel clad plate

Abstract

This invention belongs to the field of metal materials technology and provides a method for preparing a composite plate of Inconel 625 nickel-based alloy and X65 pipeline steel, including billet assembly, welding, heating, rolling, and cooling; adopting a multi-pass gradient rolling + staged gradient cooling process, controlling the bainite content in the phase transformation products to reach 60%~70%, so that the composite plate does not delamination failure when the bending radius reaches 2.5 times the plate thickness, the interface diffusion layer thickness is 8~12µm, and the shear strength is increased to over 350MPa.

Description

Technical Field

[0001] This invention belongs to the field of metallic materials, and particularly relates to a method for preparing a composite plate of Inconel 625 nickel-based alloy and X65 pipeline steel. Background Technology

[0002] With the rapid development of offshore oil and gas resource development, deep-earth energy extraction, and chemical equipment manufacturing, the service environment of engineering equipment is becoming increasingly harsh, placing higher demands on the comprehensive performance of structural materials. Traditional single-metal materials are no longer sufficient to meet the multiple requirements of high strength, corrosion resistance, fatigue resistance, and long service life under extreme working conditions. Especially in deep-sea oil and gas pipelines, high-sulfur oil and gas fields, and acidic medium storage and transportation equipment, materials must simultaneously withstand complex effects such as high pressure, alternating loads, Cl⁻ ion corrosion, H₂S / CO₂ acid corrosion, and high-temperature oxidation. Single-metal materials have performance limitations, leading to shortened equipment life, increased maintenance costs, and even safety hazards.

[0003] Inconel 625 nickel-based alloy is a high-performance, corrosion-resistant alloy with excellent corrosion resistance, high-temperature strength, and good machinability, widely used in petrochemical, aerospace, and other fields. However, its high cost limits its large-scale application. X65 pipeline steel, on the other hand, is a high-strength, high-toughness pipeline steel primarily used for transporting media such as oil and natural gas, offering good weldability and cost-effectiveness. As oil and gas field development extends to complex environments such as deep seas and polar regions, and the corrosiveness of the transported media increases, higher demands are placed on the corrosion resistance of pipeline steel. However, X65 pipeline steel has relatively weak corrosion resistance, especially in corrosive environments such as strong acids and alkalis.

[0004] To meet these requirements, a composite plate made of Inconel 625 nickel-based alloy and X65 pipeline steel has been developed. This material fully leverages the advantages of both materials, possessing both high strength and toughness, as well as excellent corrosion resistance. However, the fabrication of this bimetallic composite plate presents several technical challenges. First, the significant differences in high-temperature and room-temperature properties between Inconel 625 nickel-based alloy and X65 pipeline steel necessitate precise control of deformation temperature and rolling processes during composite plate fabrication. Second, the different chemical compositions and microstructures of the two materials make it difficult to guarantee the metallurgical bonding at the composite interface. Furthermore, brittle intermetallic compounds are easily formed during the composite process, affecting the overall performance of the composite plate.

[0005] The patent document, "A Method for Manufacturing a 2205 / X65 Bimetallic Composite Bending Pipe" (Patent No.: CN107755980A), discloses the selection of composite plate materials and the preparation process. The composite material and substrate are 2205 duplex stainless steel and X65 pipeline steel, respectively, and the preparation process is explosive bonding followed by rolling. This patent focuses on the later pipe-making process and does not provide specific parameters for the composite plate preparation.

[0006] The patent document "An 825 / X70 / 825 Double-Sided Composite Plate and Its Production Method" (Patent No.: CN109693072A) discloses the selection of composite plate materials and the preparation process. The patent involves 825 nickel-based alloy and X70 pipeline steel as the composite material and substrate, respectively. Vacuum electron beam welding is used for the composite process, which is superior to welding edge strips and explosive bonding. However, the rolling method in this invention is only applicable to 825 nickel-based alloys with good plastic deformation, and cannot be applied to 625 alloys. 825 alloys, due to their moderate solid solution strengthening, good dynamic recrystallization behavior, and wide hot working window, can adapt to the high reduction rate rolling process specified in the patent. In contrast, 625 alloys, due to their higher solid solution strengthening, greater deformation resistance, and more difficult dynamic recrystallization initiation, are difficult to achieve stable plastic deformation and good interfacial bonding under the same process conditions. Therefore, this rolling composite method cannot be directly applied to 625 alloys.

[0007] The patent document "Explosive Welding Method for Preparing Ultra-Thick Large-Area Composite Plates Based on Nickel-Based Alloy Plates" (Patent No.: CN119282348A) describes an explosive welding method for preparing ultra-thick large-area composite plates based on nickel-based alloy plates. This method achieves explosive bonding of ultra-thick large-area nickel-based alloy composite plates, and the shear strength and other properties meet the requirements. However, the explosive bonding method is less environmentally friendly, economical, and convenient to operate than rolling bonding, making it unsuitable for mass production.

[0008] Currently, the main methods for preparing bimetallic composite plates include explosive bonding, brazing, pressure welding, casting, and cumulative rolling. However, these methods have certain limitations. For example, brazing, pressure welding, and casting methods require expensive equipment, involve complex processes, and can only produce a limited number of composite layers. While cumulative rolling can produce composite plates with a larger number of layers, it has limited applicability to various metals and a low yield. Therefore, developing a high-efficiency, low-cost method for preparing Inconel 625 nickel-based alloy and X65 pipeline steel composite plates that can effectively control the interfacial bonding strength is of significant practical importance. Summary of the Invention

[0009] The purpose of this invention is to overcome the above-mentioned problems and deficiencies and provide a method for preparing a composite plate of Inconel 625 nickel-based alloy and X65 pipeline steel, wherein the thickness of the composite steel plate is 19~62mm and the minimum shear strength is 356MPa.

[0010] The objective of this invention is achieved as follows:

[0011] A method for preparing a composite plate of Inconel 625 nickel-based alloy and X65 pipeline steel includes billet assembly, welding, heating, rolling, and cooling.

[0012] Billet assembly:

[0013] Select base material and cladding material of appropriate thickness according to the specifications of the finished composite plate. Stack the Inconel 625 nickel-based alloy / X65 pipeline steel slabs sequentially in the rolling direction, ensuring that the diagonal dimensional deviation of each slab is controlled within 2mm and the maximum gap between slabs is no greater than 0.5mm. Preferably, mill the heterogeneous composite base material and cladding to ensure that there are no residual iron oxide scale, oil stains, dust, or other defects on the surfaces of the Inconel 625 nickel-based alloy and X65 pipeline steel. To ensure the bonding strength of the steel plates, the surface roughness of the bonding surface between the Inconel 625 nickel-based alloy and X65 pipeline steel must be 0.3~0.6µm. To prevent magnetic blow during the subsequent welding process, preferably, use a wire to connect the Inconel 625 nickel-based alloy and X65 pipeline steel. Establishing a reliable electrical connection through wires ensures that the two materials form a unified electromagnetic circuit during welding, eliminating magnetic field distortion and potential difference caused by abrupt changes in magnetic permeability. This disrupts the conditions for magnetic blowout, namely the asymmetrical transverse magnetic field, ensuring the stability of the welding arc and the welding strength, thereby guaranteeing the shear strength of the composite plate. Furthermore, it is preferable to set at least two wire connection points at each end or diagonally opposite position of the composite plate. A single connection point may result in "single-point grounding," which cannot completely eliminate the transverse magnetic potential difference in a circular magnetic field. Multiple connections ensure potential balance across the entire composite plate plane. The connection points should be as close as possible to the arc initiation and termination points, and at least 50mm to 100mm from the weld edge to ensure the shortest possible path for magnetic field balance.

[0014] welding:

[0015] The composite slab is placed in a vacuum chamber, and the vacuum level is controlled at 10. -2 For welds with a strength of less than 40 Pa, vacuum electron beam welding is used to weld the four sides of adjacent steel plates. The minimum weld penetration depth is required to be more than 40 mm. The weld should be full, and there should be no pits larger than 10 mm where the weld melt flows. The arc initiation and arc termination areas of the weld must be consistent and continuous, eliminating discontinuous areas in the weld. The weld surface should be well formed, without cracks, inclusions, porosity, or surface depressions.

[0016] heating:

[0017] The composite billet is loaded into the furnace for heating within 48 hours after welding, with the heating temperature controlled at 1120~1150℃, the heating rate ≤3min / mm, and the total time in the furnace ≥ composite billet thickness mm×2.0min / mm.

[0018] Rolling:

[0019] The total reduction rate for the first three roughing passes is 50%~60%, the final roughing temperature is ≥1050℃, the total reduction rate is 60%~70%, and the rolling speed is 3.0~4.0m / s. After that, the intermediate billet is cooled by laminar flow at a cooling rate of 15~35℃ / s, and the surface temperature at the water outlet is 810~880℃. The initial rolling temperature is 780~860℃, the final rolling temperature is 730~820℃, and the reduction rate is implemented in a progressively decreasing pattern. The rolling speed is 3.0~4.0m / s, and the total reduction rate for the penultimate to penultimate passes is 12%~30%.

[0020] cool down:

[0021] The composite plate is cooled using laminar flow cooling, with an initial cooling temperature of 600~650℃ and a final cooling temperature of 360~430℃. Preferably, a staged gradient cooling process is adopted to achieve a cooling rate deviation of ≤5℃ / s in the thickness direction. The first stage of cooling rapidly cools the plate to 810~880℃ at 15~35℃ / s to suppress carbide precipitation along grain boundaries; the second stage of cooling rapidly cools the steel plate from 600~650℃ to 360~430℃ at 15~40℃ / s, controlling the bainite content in the phase transformation products to 60%~70%, so that delamination failure does not occur when the bending radius of the composite plate reaches 2.5 times the plate thickness.

[0022] Furthermore, the Inconel 625 nickel-based alloy and X65 pipeline steel composite plate includes a base steel plate and a composite material; the elemental composition of the base steel plate, by mass percentage, is as follows: C: 0.055%~0.075%; Si: 0.15%~0.25%; Mn: 1.50%~1.60%; P≤0.015%; S≤0.002%; Cr: 0.09%~0.15%; Mo: 0.10%~0.14%; N ≤0.007%, balance being Fe and unavoidable impurities; the composite material is Inconel 625 nickel-based alloy, and the elemental composition by mass percentage is as follows: Ni: ≥58%; Mo: 8%~10%; Cr: 20%~23%; C: ≤0.1%; Si: ≤0.5%; Mn: ≤0.5%; Ti: ≤0.4%; P≤0.015%; S≤0.015%; Co≤1.0%, balance being Fe and unavoidable impurities.

[0023] Furthermore, the microstructure of the composite plate substrate includes bainite, polygonal ferrite and trace M / A islands, and by volume percentage, bainite: 60%~70%, polygonal ferrite: 30%~40%, M / A islands <5%; the composite plate is 100% austenitic.

[0024] Furthermore, the composite plate structure includes a steel base layer, an interface diffusion layer, and a nickel-based alloy layer, wherein the thickness of the interface diffusion layer is 8~12µm.

[0025] The microstructure composition of each phase in the composite plate exhibits a significant synergistic optimization effect. Bainite, as a non-equilibrium structure, provides numerous rapid diffusion channels for alloying elements such as Ni and Cr through its high-density dislocations and fine lath interfaces. This effectively promotes interdiffusion of elements at the interface, accelerates the formation of the diffusion layer, and ensures its thickness uniformity. Meanwhile, polygonal ferrite, as an equilibrium structure, has a uniform composition and relatively straight grain boundaries. During high-temperature composite processes, it can suppress excessive diffusion or local component segregation at the interface, preventing the diffusion layer thickness from exceeding 12µm and thus avoiding the formation of brittle intermetallic compounds. At the same time, the extremely low M / A island content avoids the formation of microcracks or stress concentrations in the hard and brittle phases near the interface due to diffusion differences. This ensures that the diffusion layer achieves an ideal metallurgical bonding state with a smooth compositional transition, high interfacial bonding strength, and no brittle phase precipitation within a thin layer range of 8~12µm.

[0026] Furthermore, the shear strength of the composite plate is ≥350MPa; according to GB / T 8165-2008 "Stainless Steel Composite Plates and Strips" and GB / T 6396-2008 "Test Methods for Mechanical and Technological Properties of Composite Steel Plates", the qualified standard for the shear strength of composite plates is 210MPa. During the shear strength test, it is required that no delamination failure occurs when the radius of curvature reaches 2.5 times the plate thickness; this is far higher than the standard requirements.

[0027] The technical advantages of this invention are as follows:

[0028] (1) This invention precisely controls the heating temperature within the range of 1180~1250℃, which is based on the coupled design of the matrix phase dissolution temperature (1100℃~1150℃) of Inconel 625 nickel-based alloy and the austenitizing temperature (AC3+30~50℃) of X65 pipeline steel. A multi-pass gradient rolling process is adopted. In the roughing stage, a large reduction is applied to achieve interfacial metallurgical bonding through dislocation multiplication and dynamic recrystallization mechanisms. In the finishing stage, a small reduction is applied to improve the strength of the composite plate through work hardening. This process results in an interfacial diffusion layer thickness of 8~12µm and a shear strength exceeding 350MPa.

[0029] (2) By connecting the wires, the magnetic field distribution between the composite material and the substrate is improved, thereby reducing the magnetic deflection effect in the vacuum electron beam welding process, so that the electron beam is always at the joint surface during the welding process, ensuring the welding depth at the joint surface.

[0030] (3) A staged gradient cooling process is adopted to achieve a thickness direction cooling rate deviation of ≤5℃ / s. By setting a two-stage cooling curve: the first stage is laminar flow cooling after rough rolling, which is rapidly cooled to 810~880℃ at 15~35℃ / s to suppress the precipitation of carbides along the grain boundaries; the second stage is cooling after rolling, which rapidly cools the steel plate from 600~650℃ to 360~430℃ at 15~40℃ / s to control the bainite content in the phase transformation products to reach 60%~70%, so that the composite plate does not delamination failure when the bending radius reaches 2.5 times the plate thickness. Attached Figure Description

[0031] Figure 1 This is a metallographic image of the microstructure at the bonding surface of the composite plate in Embodiment 1 of the present invention.

[0032] Figure 2 This is a metallographic image of the microstructure at the bonding surface of the composite plate in Embodiment 2 of the present invention.

[0033] Figure 3 This is a metallographic image of the microstructure at the bonding surface of the composite plate in Embodiment 3 of the present invention. Detailed Implementation

[0034] The present invention will be further illustrated below through examples.

[0035] According to the component ratio of the technical solution, the present invention performs billet assembly, welding, heating, rolling and cooling.

[0036] Billet assembly:

[0037] Inconel 625 nickel-based alloy / X65 pipeline steel are sequentially stacked in the rolling reduction direction to form billets, with the diagonal dimension deviation of each billet ≤2mm and the gap between billets ≤0.5mm;

[0038] welding:

[0039] The composite slab is placed in a vacuum chamber, and the vacuum level is controlled at 10. -2 For welds with a strength of less than 40 Pa, vacuum electron beam welding is used to weld the four sides of adjacent steel plates; the minimum weld penetration depth is ≥40 mm, and no pits larger than 10 mm should appear where the weld melt flows.

[0040] heating:

[0041] The composite billet is heated in the furnace within 48 hours after welding. The heating temperature is 1120~1150℃, the heating rate is ≤3min / mm, and the total time in the furnace is ≥2.0min / mm (composite billet thickness mm).

[0042] Rolling:

[0043] The total reduction rate for the first three passes of rough rolling is 50%~60%, the final rolling temperature of rough rolling is ≥1050℃, the total reduction rate is 60%~70%, and the rolling speed is 3.0~4.0m / s; after rough rolling, the intermediate billet undergoes laminar flow cooling at a cooling rate of 15~35℃ / s, and the surface temperature at the water outlet is 810~880℃; the initial rolling temperature of finish rolling is 780~860℃, the final rolling temperature is 730~820℃, the reduction rate per pass adopts a progressively decreasing pattern, the rolling speed is 3.0~4.0m / s, and the total reduction rate for the last three passes is 12%~30%.

[0044] cool down:

[0045] The initial cooling temperature is 600~650℃, the final cooling temperature is 360~430℃, and the cooling rate is 15~40℃ / s.

[0046] Furthermore, the heterogeneous composite substrate and cladding were milled, and the Inconel 625 nickel-based alloy and X65 pipeline steel surfaces were free of residual iron oxide scale, oil stains, dust and other defects, with a roughness of 0.3~0.6µm at the bonding surface.

[0047] Furthermore, during the billet assembly process, in order to prevent magnetic blow during the later welding process, Inconel 625 nickel-based alloy is connected to X65 pipeline steel using wires.

[0048] Furthermore, at least two wire connection points are set at each end or diagonal position of the composite plate, and the distance from the weld edge is at least 50mm to 100mm.

[0049] Furthermore, the Inconel 625 nickel-based alloy and X65 pipeline steel composite plate includes a base steel plate and a composite material; the elemental composition of the base steel plate, by mass percentage, is as follows: C: 0.055%~0.075%; Si: 0.15%~0.25%; Mn: 1.50%~1.60%; P≤0.015%; S≤0.002%; Cr: 0.09%~0.15%; Mo: 0.10%~0.14%; N ≤0.007%, balance being Fe and unavoidable impurities; the composite material is Inconel 625 nickel-based alloy, and the elemental composition by mass percentage is as follows: Ni: ≥58%; Mo: 8%~10%; Cr: 20%~23%; C: ≤0.1%; Si: ≤0.5%; Mn: ≤0.5%; Ti: ≤0.4%; P≤0.015%; S≤0.015%; Co≤1.0%, balance being Fe and unavoidable impurities.

[0050] Furthermore, the microstructure of the composite plate substrate includes bainite, polygonal ferrite, and trace M / A islands. The volume percentages of each microstructure are as follows: bainite: 60%~70%, polygonal ferrite: 30%~40%, M / A islands <5%; the composite plate cladding is 100% austenitic.

[0051] Furthermore, the composite plate structure includes a steel base layer, an interface diffusion layer, and a nickel-based alloy layer, wherein the thickness of the interface diffusion layer is 8~12µm.

[0052] Furthermore, the composite board has a shear strength ≥350MPa.

[0053] The composition (wt%) of the steel substrate of this invention is shown in Table 1. The composition (wt%) of the nickel-based alloy of the steel composite of this invention is shown in Table 2. The main process parameters for steel plate assembly and welding of this invention are shown in Table 3. The main process parameters for steel heating and first rolling of this invention are shown in Table 4. The main process parameters for steel second rolling and cooling of this invention are shown in Table 5. The properties of the steel of this invention are shown in Table 6. The microstructure of the steel of this invention is shown in Table 7. The composition and microstructure characteristics of the weld interface of steel in Example 1 of this invention are shown in Table 8.

[0054] Table 1. Composition (wt%) of the steel substrate in the embodiments of the present invention

[0055] Example C Si Mn Cr Mo N P S 1 0.064 0.23 1.54 0.11 0.12 0.004 0.012 0.0010 2 0.067 0.23 1.54 0.11 0.11 0.004 0.011 0.0008 3 0.065 0.24 1.52 0.12 0.11 0.003 0.012 0.0008 4 0.059 0.25 1.60 0.14 0.12 0.005 0.010 0.0009 5 0.072 0.16 1.50 0.09 0.10 0.004 0.013 0.0011 6 0.056 0.23 1.59 0.15 0.14 0.004 0.012 0.0010 7 0.064 0.24 1.55 0.12 0.12 0.005 0.011 0.0008 8 0.064 0.23 1.55 0.12 0.13 0.004 0.011 0.0009 9 0.069 0.18 1.54 0.11 0.11 0.004 0.012 0.0009 10 0.063 0.23 1.54 0.12 0.12 0.003 0.011 0.0009

[0056] Table 2. Composition (wt%) of nickel-based alloy in steel composite materials according to embodiments of the present invention.

[0057] Example Ni Mo Cr C Si Mn Ti Co 1 61.45 9.21 22.32 0.032 0.24 0.32 0.31 0.04 2 61.34 9.34 22.10 0.041 0.31 0.25 0.15 0.03 3 61.33 9.23 21.54 0.033 0.24 0.24 0.18 0.02 4 61.58 9.55 21.36 0.021 0.23 0.30 0.24 0.03 5 60.03 8.65 22.67 0.043 0.27 0.25 0.15 0.04 6 59.98 9.11 21.77 0.031 0.25 0.25 0.17 0.02 7 61.33 9.32 21.95 0.034 0.26 0.23 0.16 0.02 8 60.78 8.78 22.89 0.031 0.26 0.30 0.23 0.05 9 61.78 8.79 21.33 0.043 0.24 0.42 0.41 0.04 10 61.65 9.01 20.89 0.032 0.25 0.34 0.32 0.02

[0058] Table 3 Main process parameters for steel plate assembly and welding in embodiments of the present invention.

[0059] Example Roughness / µm X65 Specifications / mm Inconel 625 Specifications / mm Diagonal dimension deviation / mm Billet gap / mm <![CDATA[Vacuum degree / 10 -2 Pa]]> Minimum weld penetration depth / mm Indentation depth / mm 1 0.33 500×450×147 500×450×15.5 0.44 0.22 0.6 42 0 2 0.34 500×450×147 500×450×15.5 0.32 0.23 0.7 43 0 3 0.36 500×450×147 500×450×15.5 0.67 0.18 0.6 43 0 4 0.35 500×450×228 500×450×24 0.54 0.32 0.8 42 0 5 0.41 500×450×228 500×450×24 0.53 0.44 0.3 42 0 6 0.39 500×450×295 500×450×31 0.87 0.19 0.5 46 0 7 0.35 500×450×295 500×450×31 0.45 0.32 0.6 45 0 8 0.48 500×450×441 500×450×46 0.61 0.43 0.6 42 0 9 0.49 500×450×441 500×450×46 0.79 0.23 0.8 46 0 10 0.34 500×450×441 500×450×46 0.32 0.34 0.5 43 0

[0060] Table 4 Main process parameters for steel heating and first rolling in the embodiments of the present invention.

[0061] Example Heating temperature / ℃ Heating rate / min / mm Total time in the furnace / min Total reduction rate of the first three passes / % Roughing finishing temperature / ℃ First stage total reduction rate / % Rolling speed / m / s Cooling rate / ℃ / s Water outlet surface temperature / ℃ 1 1137 2.77 354 57.4 1057 65.8 4.0 33 817 2 1129 2.73 369 57.4 1063 65.8 4.0 31 815 3 1127 2.89 361 57.4 1069 65.8 4.0 29 824 4 1141 2.90 554 57.2 1071 60.1 3.6 30 828 5 1139 2.85 578 57.2 1069 60.1 3.6 28 844 6 1127 2.81 678 57.9 1075 66.3 3.2 19 857 7 1132 2.91 669 57.9 1072 66.3 3.2 24 872 8 1144 2.79 1004 52.4 1066 60.6 3 17 869 9 1140 2.82 985 52.4 1077 60.6 3 19 878 10 1134 2.93 997 52.4 1070 60.6 3 16 873

[0062] Table 5. Main process parameters for the second rolling and cooling of steel in the embodiments of the present invention.

[0063] Example The initial rolling temperature (°C) for the second stage of rolling Final rolling temperature / ℃ pass reduction rate % Rolling speed / m / s Total reduction rate (%) of the last three passes Cooling temperature / ℃ Final cooling temperature / ℃ 1 784 739 17.4，16.9，12.7，12.6，12.2，10.1，7.0 4.0 14.4 615 364 2 789 744 17.5，16.8，12.5，12.5，12.0，10.3，7.3 4.0 14.3 607 378 3 793 751 17.4，16.9，12.6，12.4，12.4，10.9，7.1 4.0 14.0 622 382 4 788 753 20.0，19.3，18.3，13.8，12.0，9.1 4.0 15.6 633 387 5 779 755 20.0，19.3，18.3，13.3，12.6，9.3 4.0 15.3 633 394 6 788 767 20.5，19.5，18.4，13.5，12.2，9.5 4.0 16.4 647 392 7 793 765 20.5，19.5，18.5，13.1，12.6，9.1 4.0 16.6 638 405 8 851 797 22.5，20.8，20.6，18.5，13.6 3.0 27.3 623 407 9 837 811 22.5，20.8，20.6，18.3，13.3 3.0 27.7 629 423 10 832 817 22.5，20.8，20.5，18.0，13.5 3.0 27.3 628 417

[0064] Table 6 Properties of steel in embodiments of the present invention

[0065] Example <![CDATA[R t0.5 / MPa]]> <![CDATA[R m / MPa]]> <![CDATA[A 50 mm / %]]> <![CDATA[-20℃ KV2 / J]]> Bending (forward, reverse) 1-Substrate 534 629 28 263、261、265 —— 1-Full Thickness 542 667 42 —— qualified 2-Substrate 523 627 31 277、283、265 —— 2-Full Thickness 530 656 41 —— qualified 3-Substrate 526 643 30 267、261、276 —— 3-Full Thickness 543 687 42 —— qualified 4-Substrate 521 646 31 276、269、275 —— 4-Full Thickness 555 679 43 —— qualified 5-Substrate 532 650 32 277、280、261 —— 5-Full Thickness 548 677 43 —— qualified 6-Substrate 508 620 31 271、272、275 —— 6-Full Thickness 522 642 44 —— qualified 7-Substrate 510 638 33 298、278、278 —— 7-Full Thickness 531 655 46 —— qualified 8-Substrate 543 654 28 271、256、275 —— 8-Full Thickness 565 677 43 —— qualified 9-Substrate 533 641 31 275、268、275 —— 9-Full Thickness 572 689 43 —— qualified 10-Substrate 521 629 31 288、268、264 —— 10-Full Thickness 567 676 42 —— qualified

[0066] Table 7. Microstructure of steel in embodiments of the present invention.

[0067] Example Steel plate thickness / mm Multilayer thickness / mm Diffusion layer thickness / µm Shear strength τ / MPa Bainite volume fraction / % Volume fraction of bulk ferrite / % 1 19 2 5 397 64 32 2 19 2 4 404 61 34 3 19 2 5 372 65 32 4 30.5 3 5 377 63 33 5 30.5 3 6 360 64 31 6 40 4 5 378 64 32 7 40 4 8 357 63 34 8 64 6 10 366 65 33 9 64 6 9 358 63 32 10 64 6 9 367 62 34

[0068] Table 8. Composition and microstructure characteristics of the steel weld interface in the embodiments of the present invention.

[0069] Location diffusion layer location C / % Ni / % Cr / % Mo / % Mn / % Fe / % Organizational characteristics X65 substrate -∞~-2.5 0.06 ~0 0.1 0.12 1.55 ~97.5 Bainite + Ferrite X65 side interface area -2.5~-1.5 <0.03 0→5 0.1→1 0.12→0.5 1.55→1.0 97.5→90 Carbon-depleted region + austenite zone diffusion layer center -1.5+1.5 Carbide enrichment 5→30 1→15 0.5→6 1.0→0.7 90→50 Mixed tissue + carbides Inconel 625 side interface area +1.5~+2.5 Carbide precipitation 30→58 15→22 6→9 0.7→0.5 50→12 austenite + dispersed carbides Inconel 625 matrix +2.5~+∞ ≤0.1% ≥58% 20~23% 8~10% ≤0.5% 10~15% austenite

[0070] The microstructure of the composite plate substrate produced using this invention includes bainite, polygonal ferrite, and trace amounts of M / A islands. The volume percentages of each microstructure are: bainite: 60%~70%, polygonal ferrite: 30%~40%, M / A islands <5%; the composite plate cladding is 100% austenitic. The composite plate structure includes a steel base layer, an interface diffusion layer, and a nickel-based alloy layer, wherein the thickness of the interface diffusion layer is 8~12µm; the composite plate shear strength is ≥350MPa; according to GB / T 8165-2008 "Stainless Steel Composite Plates and Strips" and GB / T 6396-2008 "Test Methods for Mechanical and Technological Properties of Composite Steel Plates", the qualified standard for the composite plate shear strength is 210MPa, and during the shear strength test, no delamination failure is required when the radius of curvature reaches 2.5 times the plate thickness; this is far higher than the standard requirements.

[0071] To illustrate the present invention, the present invention has been appropriately and sufficiently described above through embodiments. The above embodiments are only for illustrating the present invention and are not intended to limit the present invention. Those skilled in the art can make various changes and modifications without departing from the spirit and scope of the present invention. Any modifications, equivalent substitutions, improvements, etc., should be included within the protection scope of the present invention. The patent protection scope of the present invention should be defined by the claims.

Claims

1. A method for preparing a composite plate of Inconel 625 nickel-based alloy and X65 pipeline steel, characterized in that, This includes billet assembly, welding, heating, rolling, and cooling; Billet assembly: Inconel 625 nickel-based alloy / X65 pipeline steel are sequentially stacked in the rolling reduction direction to form billets, with the diagonal dimension deviation of each billet ≤2mm and the gap between billets ≤0.5mm; welding: The composite slab is placed in a vacuum chamber, and the vacuum level is controlled at 10. -2 For welds with a strength of less than 40 Pa, vacuum electron beam welding is used to weld the four sides of adjacent steel plates; the minimum weld penetration depth is ≥40 mm, and no pits larger than 10 mm should appear where the weld melt flows. heating: The composite billet is heated in the furnace within 48 hours after welding. The heating temperature is 1120~1150℃, the heating rate is ≤3min / mm, and the total time in the furnace is ≥2.0min / mm (composite billet thickness mm). Rolling: The total reduction rate for the first three passes of rough rolling is 50%~60%, the final rolling temperature of rough rolling is ≥1050℃, the total reduction rate is 60%~70%, and the rolling speed is 3.0~4.0m / s; after rough rolling, the intermediate billet undergoes laminar flow cooling at a cooling rate of 15~35℃ / s, and the surface temperature at the water outlet is 810~880℃; the initial rolling temperature of finish rolling is 780~860℃, the final rolling temperature is 730~820℃, the reduction rate per pass adopts a progressively decreasing pattern, the rolling speed is 3.0~4.0m / s, and the total reduction rate for the last three passes is 12%~30%. cool down: The initial cooling temperature is 600~650℃, the final cooling temperature is 360~430℃, and the cooling rate is 15~40℃ / s.

2. The method for preparing the Inconel 625 nickel-based alloy and X65 pipeline steel composite plate according to claim 1, characterized in that, The heterogeneous composite substrate and cladding were milled, and the Inconel 625 nickel-based alloy and X65 pipeline steel were free of residual iron oxide scale, oil stains, dust and other defects. The roughness of the bonding surface was 0.3~0.6µm.

3. The method for preparing the Inconel 625 nickel-based alloy and X65 pipeline steel composite plate according to claim 1, characterized in that, During the billet assembly process, in order to prevent magnetic blow during the later welding process, wires are used to connect the Inconel 625 nickel-based alloy to the X65 pipeline steel.

4. The method for preparing the Inconel 625 nickel-based alloy and X65 pipeline steel composite plate according to claim 3, characterized in that, At least two wire connection points are set at each end or diagonal position of the composite plate, and the distance from the weld edge is at least 50mm to 100mm.

5. The method for preparing the Inconel 625 nickel-based alloy and X65 pipeline steel composite plate according to claim 1, characterized in that, The Inconel 625 nickel-based alloy and X65 pipeline steel composite plate includes a base steel plate and a composite material. The elemental composition of the base steel plate, by mass percentage, is as follows: C: 0.055%~0.075%; Si: 0.15%~0.25%; Mn: 1.50%~1.60%; P≤0.015%; S≤0.002%; Cr: 0.09%~0.15%; Mo: 0.10%~0.14%; N≤0.007%, with the balance being Fe and unavoidable impurities. The composite material is Inconel 625 nickel-based alloy, with the elemental composition by mass percentage as follows: Ni: ≥58%; Mo: 8%~10%; Cr: 20%~23%; C: ≤0.1%; Si: ≤0.5%; Mn: ≤0.5%; Ti: ≤0.4%; P≤0.015%; S≤0.015%; Co≤1.0%, with the balance being Fe and unavoidable impurities.

6. The method for preparing the Inconel 625 nickel-based alloy and X65 pipeline steel composite plate according to claim 1, characterized in that, The microstructure of the composite plate substrate includes bainite, polygonal ferrite and trace M / A islands. The volume percentages of each microstructure are as follows: bainite: 60%~70%, polygonal ferrite: 30%~40%, M / A islands <5%; the composite plate cladding is 100% austenitic.

7. The method for preparing the Inconel 625 nickel-based alloy and X65 pipeline steel composite plate according to claim 1, characterized in that, The composite plate structure includes a steel base layer, an interface diffusion layer, and a nickel-based alloy layer, wherein the thickness of the interface diffusion layer is 8~12µm.

8. The method for preparing the Inconel 625 nickel-based alloy and X65 pipeline steel composite plate according to claim 1, characterized in that, The shear strength of the composite board is ≥350MPa.

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