05Cr17Ni4Cu4Nb steel and HR-2 steel dissimilar material electron beam welding and post-welding synergistic strengthening method

Abstract

This invention provides a method for electron beam welding and post-weld synergistic strengthening of dissimilar materials 05Cr17Ni4Cu4Nb steel and HR-2 steel. The method includes the following steps: Step 1: Mechanically grinding and cleaning the welding area of ​​the plates to be welded with anhydrous ethanol to expose the metallic luster; Step 2: Precision assembling of the two plates; Step 3: Welding a laser locating weld on each side of the plates; Step 4: Single-pass deep-penetration electron beam welding of the plate joint area under vacuum conditions, selecting appropriate welding parameters; Step 5: Post-weld cooling in a vacuum chamber; Step 6: Vacuum aging heat treatment of the weldment, followed by furnace cooling to room temperature. This invention employs a combined process of laser locating welding, vacuum electron beam welding, and post-weld heat treatment. Through joint design and welding parameter control, it solves the problems of cold cracking and uneven mechanical properties in thick dissimilar steel welding. The weld and heat-affected zone exhibit uniform microstructure, refined grains, and excellent mechanical properties, making it suitable for critical components of thick dissimilar steel plates used in nuclear power pressure vessels, hydrogen storage tank heads, and aerospace applications.

Description

Technical Field

[0001] This invention relates to the field of dissimilar stainless steel welding technology, specifically to a method for electron beam welding of dissimilar materials 05Cr17Ni4Cu4Nb steel and HR-2 steel and post-weld synergistic strengthening. Background Technology

[0002] 05Cr17Ni4Cu4Nb is a precipitation-hardening martensitic stainless steel, also known as 17-PH stainless steel, renowned for its excellent mechanical properties, good weldability, and outstanding corrosion resistance. It has important applications in many high-demand fields, including aerospace, chemical, petroleum, food processing, healthcare, and nuclear industries. HR-2 is a special hydrogen-resistant austenitic stainless steel, known for its excellent stability, corrosion resistance, higher yield strength, and better resistance to hydrogen embrittlement. It is widely used in marine components, as well as in the chemical, petrochemical, nuclear, and aerospace industries, especially in equipment exposed to harsh environmental conditions. This study aims to overcome the bottlenecks in high-quality welding technology for 05Cr17Ni4Cu4Nb / HR-2 dissimilar steels. By clarifying the welding formation mechanism, welding process parameters can be precisely optimized, effectively suppressing defects such as component segregation, brittle phase precipitation, and cracks in the fusion zone, achieving a synergistic improvement in the joint's mechanical properties and corrosion resistance, and providing a reliable process solution and quality control basis for the engineering application of this dissimilar steel combination. At the same time, it can provide technical support for the independent application of materials in my country's high-end equipment manufacturing field, help break through the technical barriers in related fields, and promote the development of strategic emerging industries such as hydrogen energy and advanced nuclear power technology.

[0003] A literature search of existing technologies revealed that numerous researchers have conducted studies on dissimilar steel welding and post-weld heat treatment. For example, Yu Dongxin et al. published an article in the *Journal of Mechanical Engineering* on the microstructure and properties of PCrNi3MoVA / 40Cr steel rotating arc TIG welded joints. They used E307T0-1 stainless steel flux-cored welding wire to prepare dissimilar steel joints via rotating arc TIG welding, followed by stress-relieving heat treatment. The results showed good weld formation with no obvious surface defects. After heat treatment, the weld grain size decreased from 74.57 μm to 55.71 μm, the proportion of high-angle grain boundaries increased, and the microstructure uniformity improved. The tensile strength of the joint significantly increased from 587.2 MPa to 829.6 MPa. Both tensile and impact specimens fractured in the weld zone, exhibiting numerous dimples on the fracture surface, characteristic of a typical ductile fracture mode. Simultaneously, the impact toughness and corrosion resistance of the joint were significantly improved. Sirohi et al. reported in *Fusion Engineering and Design* a study on the microstructure and property control of multi-layer, multi-pass welded joints of dissimilar P22 and F69 steels using GMAW (Glass Metal Arc Welding). The study investigated the control of the joint's microstructure and properties through post-weld heat treatment. Results showed that the transition zone of the welded joint in the as-welded state exhibited typical beach and island microstructures; Cr and Mo enrichment was observed near the interface, forming M6C and M... 23 C6 carbides are distributed along the dendrites. After heat treatment, Mo-Ti carbides with higher density and more uniform distribution are formed in the weld metal. This change not only significantly increases the hardness of the weld metal, but also causes the fracture location of the weld joint to shift from the weld to the heat-affected zone. This study shows that post-weld heat treatment can effectively optimize the joint microstructure and properties, but the heat treatment process parameters have a significant impact on carbide precipitation and fracture location, requiring precise control. In his dissertation at Southwest Petroleum University, Yin Wenfeng conducted a study on the performance of 316L / Q235 dissimilar steel welded joints and numerical simulation of the welding process. Post-weld aging heat treatment experiments were carried out on dissimilar steel welded joints, with holding at 300℃, 500℃, and 700℃ for 2 hours respectively. The results show that low-temperature aging treatment at 300℃ is beneficial to the decomposition of martensite and retained austenite, and cementite precipitates in the weld. At the same time, the weld grains are significantly refined, and the microstructure uniformity is greatly improved. Rajesh et al. reported a study on the post-weld heat treatment of friction-welded dissimilar joints of AISI 1010 / D3 tool steel in the *J. Manuf. Mater. Process.*. The results showed that a distinct ultrafine grain region was formed at the joint interface, which promoted the redistribution of carbides and alloying elements, optimized the joint microstructure, eliminated coarse grains, and thus reduced galvanic corrosion at the weld interface, decreasing the joint corrosion rate and weight loss by approximately 54.8% and 60%, respectively.

[0004] In summary, existing methods for welding dissimilar steels primarily involve optimizing traditional welding processes, selecting appropriate filler materials, and post-weld heat treatment to improve joint microstructure and performance. However, these traditional welding methods generally suffer from problems such as high heat input, significant welding deformation, complex interface microstructure, and difficulty in effectively controlling elemental segregation. This is particularly true for thick plate structures where process efficiency is low, and even with post-weld heat treatment, it is difficult to fully compensate for the inherent defects of traditional welding. In contrast, electron beam welding offers unique advantages such as high energy density, narrow heat-affected zone, minimal welding deformation, and the ability to achieve single-pass deep penetration welding without beveling. It is the preferred process for high-quality connections in thick plate dissimilar steel structures. Post-weld heat treatment is a key means to further optimize the performance of electron beam welded dissimilar steel joints—through appropriate post-weld heat treatment, the grain size of the electron beam welded joint can be refined, carbide distribution optimized, and interface elemental segregation alleviated, thereby significantly improving the mechanical properties and corrosion resistance of the joint and effectively solving problems such as uneven microstructure and performance fluctuations that may exist in electron beam welded dissimilar steel joints.

[0005] Therefore, optimizing the post-weld heat treatment process for electron beam welding of dissimilar steels and exploring the evolution law of joint microstructure and performance regulation mechanism during heat treatment are of great significance for giving full play to the advantages of electron beam welding and achieving efficient and high-quality connection of dissimilar steels. It also provides technical support for the engineering application of electron beam welding of dissimilar steel structures in complex service environments. Summary of the Invention

[0006] This invention aims to regulate the microstructure and property matching relationship during electron beam welding of dissimilar steels 05Cr17Ni4Cu4Nb martensitic precipitation-hardening stainless steel and HR-2 austenitic stainless steel, solving problems such as uneven weld microstructure, grain coarsening, and property fluctuations caused by differences in microstructure, thermophysical properties, and alloying elements between the two steels. By optimizing beam intensity and welding speed, and rationally controlling heat input and melting ratio, a stable weld penetration depth and suitable weld width are achieved, resulting in microstructure homogenization and grain refinement. Based on optimized welding parameters, a staged post-weld heat treatment process is further introduced, combining medium-temperature stress relief treatment with aging strengthening treatment to reduce residual welding stress, promote precipitation of precipitation-strengthening phases, and stabilize the microstructure, thereby mitigating the property gradient between the weld and the base metal. After synergistic regulation of welding and heat treatment, the weld microstructure is dominated by austenite with significant grain refinement, improved joint tensile strength, and a fracture surface exhibiting typical ductile fracture characteristics; simultaneously, the fusion zone width is reduced, and the joint strength and toughness are coordinated and improved. This method features a simple process flow and highly controllable parameters. While ensuring the stable formation of welds with a high aspect ratio, it also achieves uniform microstructure and optimized overall performance, providing a reliable and widely applicable technical solution for high-quality connection of dissimilar steel structural components.

[0007] The specific technical solution of the present invention is as follows: A method for electron beam welding of dissimilar materials 05Cr17Ni4Cu4Nb steel and HR-2 steel and subsequent synergistic strengthening after welding, characterized by comprising the following steps: S1. Surface pretreatment: Select 05Cr17Ni4Cu4Nb stainless steel plates and HR-2 stainless steel plates with a thickness of 20mm. Remove the oxide film on the surface of the plate to be welded area by mechanical grinding, and then clean the oil stains on the surface of the plate to be welded area with anhydrous ethanol and let it dry for later use. S2. Precision assembly: The two pre-treated plates are joined together and fixed with a workbench fixture to ensure that the welding area is tightly connected and the gap tolerance is ≤0.1mm and the misalignment is ≤0.05mm. S3. Laser tack welding: A 5mm long tack weld is welded on each side of the butt plate using laser welding. The tack welding process parameters are welding power 2kW and welding speed 2mm / s. S4. Vacuum Electron Beam Welding: Place the assembled plate in the vacuum chamber, adjust the working height to 150mm, close the vacuum chamber and evacuate to a vacuum level below 5×10⁻² Pa; adopt the vacuum electron beam welding method of no beveling, no filler wire, and single-pass deep penetration, with an electron beam of 0.2mm in diameter moving directly to the center of the gap between the areas to be welded. The welding process parameters are: accelerating voltage 120kV, beam current 35~55mA, focusing current 500mA, welding speed 400~600mm / min, and surface focusing is used in the welding process; S5. Cooling and Removing the Part: After welding, the weldment is left to cool in the vacuum chamber for 10 minutes, and then the weldment is removed. S6. Post-weld heat treatment: Vacuum aging heat treatment is performed on the cooled weldment. The heat treatment process is to heat up to 400℃, hold for 2 hours, and then cool to room temperature in the furnace. In the above technical solution, as a preferred technical solution of the present invention: the mechanical grinding described in S1 uses 180# sandpaper for grinding, and the grinding range is 20mm on both sides of the area to be welded, grinding until the surface of the base material reveals a metallic luster.

[0008] In the above technical solution, as a preferred technical solution of the present invention: the welding process parameters in S4 are: accelerating voltage 120kV, beam current 35mA, focusing current 500mA, welding speed 500mm / min, and surface focusing.

[0009] In the above technical solutions, the preferred technical solution of the present invention is as follows: after welding with the process parameters, the weld penetration depth is 20.06mm, realizing the one-time full penetration forming of a 20mm thick plate.

[0010] In the above technical solutions, as a preferred technical solution of the present invention: after the post-weld heat treatment described in S6, the weld grains are refined, no secondary brittle phases precipitate, and the overall mechanical properties of the welded joint are improved.

[0011] In the above technical solutions, the preferred technical solution of the present invention is that the welded joint prepared by the method has high tensile strength and the fracture surface of the joint exhibits typical ductile fracture characteristics.

[0012] In the above technical solution, as a preferred technical solution of the present invention: the two positioning welds in S3 are each 5mm away from the edge of the area to be welded.

[0013] In the above technical solutions, the preferred technical solution of the present invention is as follows: the weld of the welded joint is a uniform δ-ferrite and austenite composite structure, without compositional segregation, brittle phase precipitation and crack defects, the heat-affected zone is narrow and the structure is uniform, and there is no obvious welding deformation.

[0014] In the above technical solutions, as a preferred technical solution of the present invention: the welded joint is suitable for the connection of dissimilar steel plates in nuclear power pressure vessels, hydrogen storage tank heads, and aerospace precision structural components.

[0015] Compared with existing welding technologies for 05Cr17Ni4Cu4Nb and HR-2 dissimilar steels, this invention has the following significant advantages: (1) Achieve full penetration welding of thick plates in one operation High-energy-density vacuum electron beam single-pass deep penetration welding is adopted, which can achieve full penetration of 20 mm thick plates in one pass without beveling or filler wire. This avoids the risk of interlayer defects caused by multi-layer and multi-pass welding, significantly simplifies the process, and improves welding efficiency and forming consistency.

[0016] (2) Synergistic regulation of microstructure by welding and heat treatment Based on the optimization of beam intensity and welding speed, a vacuum aging heat treatment process of 400 ℃×2 h is introduced to effectively reduce welding residual stress, promote the dispersion precipitation of strengthening phase and microstructure stabilization, alleviate the performance gradient between the weld and the base material, and achieve microstructure homogenization and grain refinement.

[0017] (3) Concentrated heat input and narrow heat-affected zone Electron beam welding features high energy density and strong penetration. The heat input is concentrated and controllable, and the heat-affected zone is significantly reduced. It can effectively suppress the risk of coarsening of the base material and deterioration of its properties, while ensuring stable weld penetration and uniform weld formation.

[0018] (4) The organization is stable and the overall performance is significantly improved. After post-weld heat treatment, the joint grains are further refined, the tensile strength is improved, and the fracture surface exhibits typical ductile fracture characteristics, achieving a coordinated improvement in strength and toughness.

[0019] (5) Strong applicability to engineering The process parameters of this invention are clear and highly controllable, and it is applicable to the connection of thick plate dissimilar steel structures in the fields of nuclear power, hydrogen energy and high-end equipment. It has good repeatability and prospects for widespread application.

[0020] In summary, this invention is superior to existing dissimilar steel welding methods in terms of process simplification, microstructure control, residual stress control, and overall performance stability, demonstrating significant technological advancement and practical value. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of vacuum electron beam welding of dissimilar steels; where 1. filament; 2. negative electrode; 3. anode; 4. focusing coil; 5. electron gun; 6. electron beam; 7. workpiece; 8. worktable; 9. vacuum chamber; 10. 05Cr17Ni4Cu4Nb stainless steel; 11. HR-2 stainless steel.

[0022] Figure 2 Microstructure diagram of electron beam weld between dissimilar steels; Figure 3 This is a microstructure diagram of the weld after heat treatment; Figure 4 Here are the microstructure diagrams of the heat-affected zones on both sides of the weld after heat treatment: (a) OM diagram of the fusion zone on the HR-2 side; (b) OM diagram of the fusion zone on the 05Cr17Ni4Cu4Nb side; Figure 5 A comparison diagram of the mechanical properties of the welded joint before and after heat treatment; Figure 6 Here is a comparison chart of the hardness of the welded joint before and after heat treatment: (a) Distance from the center of the weld; (b) Distance from the weld surface. Detailed Implementation

[0023] The following will refer to the appendices in the embodiments of the present invention. Figure 1-6 The technical solutions in the embodiments of the present invention are clearly and completely described herein. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0024] The main challenge in electron beam welding of 05Cr17Ni4Cu4Nb and HR-2 steels stems from the significant differences in their microstructure and thermophysical properties. The former is a martensitic precipitation-hardening stainless steel, while the latter is a stable austenitic stainless steel. Their different crystal structures and phase transformation mechanisms lead to complex phase composition in the weld zone under the rapid melting and solidification conditions of a high-energy-density electron beam, making microstructure matching and performance coordination difficult. Furthermore, the significant differences in thermal conductivity and coefficient of linear expansion between the two materials can easily cause imbalances in the melting ratio and uneven elemental distribution, increasing the risk of microstructure segregation. The extremely rapid cooling rate of electron beam welding narrows the microstructure control window and creates a complex residual stress field in the joint area, potentially causing performance fluctuations. Achieving deep penetration in a single pass under 20 mm thick plates also places high demands on the matching of energy input and welding speed; even slight deviations can affect weld formation stability. Therefore, ensuring stable weld formation while achieving microstructure homogenization and performance matching is the core technical challenge of electron beam welding these dissimilar steels.

[0025] To address this issue, this invention proposes a method for electron beam welding of dissimilar materials 05Cr17Ni4Cu4Nb steel and HR-2 steel, and post-weld synergistic strengthening, comprising the following steps: S1. Surface pretreatment: Select 05Cr17Ni4Cu4Nb stainless steel plates and HR-2 stainless steel plates with a thickness of 20mm. Remove the oxide film on the surface of the plate to be welded area by mechanical grinding, and then clean the oil stains on the surface of the plate to be welded area with anhydrous ethanol and let it dry for later use. S2. Precision assembly: The two pre-treated plates are joined together and fixed with a workbench fixture to ensure that the welding area is tightly connected and the gap tolerance is ≤0.1mm and the misalignment is ≤0.05mm. S3. Laser tack welding: A 5mm long tack weld is welded on each side of the butt plate using laser welding. The tack welding process parameters are welding power 2kW and welding speed 2mm / s. S4. Vacuum Electron Beam Welding: Place the assembled plate in the vacuum chamber, adjust the working height to 150mm, close the vacuum chamber and evacuate to a vacuum level below 5×10⁻² Pa; adopt the vacuum electron beam welding method of no beveling, no filler wire, and single-pass deep penetration, with an electron beam of 0.2mm in diameter moving directly to the center of the gap between the areas to be welded. The welding process parameters are: accelerating voltage 120kV, beam current 35~55mA, focusing current 500mA, welding speed 400~600mm / min, and surface focusing is used in the welding process; S5. Cooling and Removing the Part: After welding, the weldment is left to cool in the vacuum chamber for 10 minutes, and then the weldment is removed. S6. Post-weld heat treatment: Vacuum aging heat treatment is performed on the cooled weldment. The heat treatment process is to heat up to 400℃, hold for 2 hours, and then cool to room temperature in the furnace. It should be noted that this invention employs an optimal combination of vacuum electron beam welding and post-weld heat treatment. Through precise control of the joint type, welding parameters, preheating, and heat treatment process, high-quality welding of dissimilar high-strength steel plates (05Cr17Ni4Cu4Nb steel and HR-2 steel) is achieved. This method ensures one-time penetration, uniform weld formation, stable and reliable weld quality, and good mechanical properties of the weld and heat-affected zone. It also balances welding efficiency and process controllability, fully meeting the application requirements of dissimilar steel plates in critical structures.

[0026] Specifically, in step S1 of this invention, the preheating of the weld joint is precisely controlled to effectively suppress the sensitivity of the weld to cold cracking. For the combined welding of 20mm thick 05Cr17Ni4Cu4Nb steel and HR-2 steel, the surface of the plate is preheated to 75-200℃ before vacuum electron beam welding. By adjusting the welding beam current, acceleration voltage, and welding speed, the cooling rate of the weld and heat-affected zone is made appropriate. Since both 05Cr17Ni4Cu4Nb steel (yield strength ≥890MPa) and HR-2 steel (yield strength ≥420MPa) are high-strength steels, they are prone to cracking during welding due to hardening tendency. The above-mentioned preheating strategy can effectively alleviate this problem.

[0027] In steps S2 to S5, the present invention optimizes welding efficiency and welding quality through multi-process synergy: First, full penetration of the root weld is achieved through laser tack welding and single-pass electron beam welding, ensuring the continuity of the fusion line and avoiding porosity or incomplete fusion defects. Subsequently, combined with post-weld heat treatment, a uniform microstructure is formed in the weld and heat-affected zone, and the weld penetration depth is matched with the base metal thickness by controlling welding parameters (such as beam current, focusing current, and welding speed), ensuring one-time penetration and reducing the number of thermal cycles and residual stress concentration.

[0028] In the post-weld heat treatment stage of step S6, the welded parts are subjected to aging treatment under vacuum conditions: the temperature is raised to 400°C and held for 2 hours, then cooled to room temperature in the furnace. This process can promote the refinement of grain structure and suppress the precipitation of secondary brittle phases, thereby significantly improving the comprehensive mechanical properties and impact toughness of the welded joint.

[0029] See appendix Figure 4By microscopically characterizing the fusion zone of electron beam welded joints after heat treatment, the solidification behavior and microstructure of dissimilar steel welds were revealed. Narrow unfused zones were observed at the interfaces of the 05Cr17Ni4Cu4Nb / weld and the HR-2 / weld, a typical phenomenon resulting from component dilution during weld resolidification after the base metal melts. The weld in the fusion zone on the HR-2 side exhibited austenitic columnar dendrites, with slight grain growth in the heat-affected zone and a stable microstructure. A peninsula structure was present in the weld, originating from changes in solidification mode and micro-segregation of elements. High-magnification SEM observation revealed columnar dendrite branches and intergranular solute segregation. Through the microstructural characteristics of the fusion zone of the electron beam welded joint after heat treatment, this invention achieved a dense, fully penetrated weld with ordered growth of columnar austenitic dendrites, stable grains in the heat-affected zone, and a mixed ferrite and martensite microstructure on the 05Cr17Ni4Cu4Nb side, achieving both high strength and good plasticity. The uniform microstructure and reasonable distribution of peninsula and island structures effectively suppress cracks and brittle phase precipitation, significantly improve low-temperature impact toughness, fatigue resistance and joint service reliability, and meet the engineering application requirements of high-strength dissimilar steel thick plate structures.

[0030] See appendix Figure 6 Heat treatment refines the grains and reduces columnar dendrites in the 05Cr17Ni4Cu4Nb / HR-2 electron beam welded joint, improves the hardness of both the weld and the base metal, and makes the hardness distribution of the welded joint more uniform, thus significantly enhancing the overall mechanical properties of the joint.

[0031] In summary, the electron beam welding and post-weld synergistic strengthening method for dissimilar materials 05Cr17Ni4Cu4Nb steel and HR-2 steel proposed in this invention achieves high-quality control in the welding of thick-plate dissimilar high-strength steels through the organic combination of key steps such as surface pretreatment, precision assembly, laser positioning welding, vacuum electron beam single-pass welding, and post-weld vacuum heat treatment. Before welding, this method effectively reduces the cold cracking sensitivity of the weld seam through a differentiated preheating strategy. During welding, laser positioning and single-pass deep penetration electron beam welding ensure root penetration and uniform weld formation, avoiding defects such as porosity, lack of fusion, and localized embrittlement. Post-weld, precisely controlled vacuum aging heat treatment promotes the homogenization of the weld seam and heat-affected zone microstructure and grain refinement, effectively improving the comprehensive mechanical properties, impact toughness, and ductility of the welded joint, while reducing residual stress and the risk of low-temperature brittleness.

[0032] The method of this invention takes into account the welding efficiency, process controllability, and practical needs of thick plate dissimilar steel structures. It achieves welding results with one-time weld penetration, good weld formation, balanced mechanical properties, and high reliability, providing a reliable and efficient welding technology solution for the engineering application of thick plate dissimilar materials for high-strength bridge steel and other key structures.

[0033] The above description is merely a preferred embodiment of the present invention, but the present invention should not be limited to the content disclosed in this embodiment. Therefore, any equivalent or modified versions made without departing from the spirit of the present invention fall within the scope of protection of the present invention.

Claims

1. A method for electron beam welding of dissimilar materials 05Cr17Ni4Cu4Nb steel and HR-2 steel and post-weld synergistic strengthening, characterized in that, Includes the following steps: S1. Surface pretreatment: Select 05Cr17Ni4Cu4Nb stainless steel plates and HR-2 stainless steel plates with a thickness of 20mm. Remove the oxide film on the surface of the plate to be welded area by mechanical grinding, and then clean the oil stains on the surface of the plate to be welded area with anhydrous ethanol and let it dry for later use. S2. Precision assembly: The two pre-treated plates are joined together and fixed with a workbench fixture to ensure that the welding area is tightly connected and the gap tolerance is ≤0.1mm and the misalignment is ≤0.05mm. S3. Laser tack welding: A 5mm long tack weld is welded on each side of the butt plate using laser welding. The tack welding process parameters are welding power 2kW and welding speed 2mm / s. S4. Vacuum Electron Beam Welding: Place the assembled plate in the vacuum chamber, adjust the working height to 150mm, close the vacuum chamber and evacuate to a vacuum level below 5×10⁻² Pa; adopt the vacuum electron beam welding method of no beveling, no filler wire, and single-pass deep penetration, with an electron beam of 0.2mm in diameter moving directly to the center of the gap between the areas to be welded. The welding process parameters are: accelerating voltage 120kV, beam current 35~55mA, focusing current 500mA, welding speed 400~600mm / min, and surface focusing is used in the welding process; S5. Cooling and Removing the Part: After welding, the weldment is left to cool in the vacuum chamber for 10 minutes, and then the weldment is removed. S6. Post-weld heat treatment: The cooled weldment is subjected to vacuum aging heat treatment. The heat treatment process is to heat up to 400℃, hold for 2 hours, and then cool to room temperature in the furnace.

2. The method for electron beam welding and post-weld synergistic strengthening of dissimilar materials 05Cr17Ni4Cu4Nb steel and HR-2 steel according to claim 1, characterized in that, The mechanical grinding described in S1 uses 180# sandpaper and the grinding range is 20mm on both sides of the area to be welded, grinding until the surface of the base material shows a metallic luster.

3. The method for electron beam welding and post-weld synergistic strengthening of dissimilar materials 05Cr17Ni4Cu4Nb steel and HR-2 steel according to claim 1, characterized in that, The welding process parameters described in S4 are: accelerating voltage 120kV, beam current 35mA, focusing current 500mA, welding speed 500mm / min, and surface focusing.

4. The method for electron beam welding and post-weld synergistic strengthening of dissimilar materials 05Cr17Ni4Cu4Nb steel and HR-2 steel according to claim 3, characterized in that, After welding using the aforementioned process parameters, the weld penetration depth is 20.06 mm, achieving full penetration welding of a 20 mm thick plate in one pass.

5. The method for electron beam welding and post-weld synergistic strengthening of dissimilar materials 05Cr17Ni4Cu4Nb steel and HR-2 steel according to claim 1, characterized in that, After the post-weld heat treatment described in S6, the weld microstructure has refined grains, with no secondary brittle phase precipitation, and the overall mechanical properties of the welded joint are improved.

6. The method for electron beam welding and post-weld synergistic strengthening of dissimilar materials 05Cr17Ni4Cu4Nb steel and HR-2 steel according to claim 1, characterized in that, The welded joint prepared by the method exhibits high tensile strength, and the fracture surface shows typical ductile fracture characteristics.

7. The method for electron beam welding and post-weld synergistic strengthening of dissimilar materials 05Cr17Ni4Cu4Nb steel and HR-2 steel according to claim 1, characterized in that, The two locating welds described in S3 are each 5mm from the edge of the area to be welded.

8. A method for electron beam welding of dissimilar materials 05Cr17Ni4Cu4Nb steel and HR-2 steel and post-weld synergistic strengthening, characterized in that, The weld of the welded joint has a uniform composite structure of δ-ferrite and austenite, with no component segregation, brittle phase precipitation and crack defects, a narrow heat-affected zone and uniform structure, and no obvious welding deformation.

9. The 05Cr17Ni4Cu4Nb / HR-2 dissimilar steel welded joint according to claim 8, characterized in that, The welded joint is suitable for connecting dissimilar steel plates in nuclear power pressure vessels, hydrogen storage tank heads, and precision aerospace structural components.

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