Stainless steel welding base material and preparation method and application thereof

Abstract

The invention relates to a stainless steel welding base material and a preparation method and application thereof, belongs to the technical field of welding structure materials, and solves the problems that the post-welding strength of an existing stainless steel welding base material is remarkably reduced, the welding joint coefficient is low, and subsequent heat treatment is needed. The stainless steel welding base material comprises the following chemical components in percentage by mass: 0.02%-0.08% of C, 12.0%-16.0% of Cr, 4.5%-6.5% of Ni and the balance of Fe and inevitable impurities, the microstructure of the base material is a martensite matrix, and the base material contains austenite with the volume fraction being 1%-5.5%. According to a structural part formed by welding the base metal, the welding joint coefficient is not lower than 0.92, the room-temperature yield strength is not lower than 770 MPa, and the ductility in the wide temperature range from-196 DEG C to 400 DEG C is not lower than 14% without any overall heat treatment in the welding state. Through collaborative design of components and structures, the base metal has high strength, high plasticity and excellent welding performance in a welding state, and is suitable for direct welding manufacturing of force bearing components in the fields of aerospace, ocean engineering, energy, chemical industry and the like.

Description

Technical Field

[0001] This invention relates to the field of welded structural materials technology, and in particular to a stainless steel welding base material, its preparation method, and its application. Background Technology

[0002] Welding is the primary connection method for manufacturing large and complex metal structural components. The strength of the welded joint directly determines the load-bearing capacity and safety of the entire structure. In harsh environments such as aerospace and offshore platforms, structural components are required to have high reliability and long service life over a wide temperature range.

[0003] Currently, the manufacture of welded structural components using high-strength stainless steel faces a core challenge: when using metastable austenitic stainless steel (such as 304L), although the base metal strength is still acceptable, the welding thermal cycle causes the weld and heat-affected zone to transform into a low-dislocation austenitic structure, leading to a sharp decrease in the strength of this area, a low weld joint coefficient, and becoming a weak point in the structure. If traditional martensitic stainless steel is used, although post-weld softening is not obvious, the low-temperature brittleness of its base metal and its high sensitivity to post-weld cracking limit its application under wide temperature range conditions. To restore the performance of the weld zone, post-weld overall heat treatment is usually required, but this is complex, costly, and prone to inducing new deformations for large or complex components.

[0004] In the existing technology, there are few stainless steel base materials that can achieve a high weld joint coefficient without any subsequent heat treatment in the welded state, while ensuring that the welded structural parts made from it have good strength-plasticity matching in a wide temperature range of -196℃ to 400℃. Summary of the Invention

[0005] In view of the above analysis, the present invention aims to provide a stainless steel welding base material, its preparation method and application, so as to at least solve one of the following prior art problems: 1) The strength of the weld and heat-affected zone of metastable austenitic stainless steel base material (such as 304L) drops sharply after welding, and the welded joint becomes a weak point in the structure. 2) Welded structural components made from traditional martensitic stainless steel base material have poor low-temperature toughness and high sensitivity to post-weld cracking, which limits their use in a wide temperature range. 3) To restore the performance of the welded area, post-weld heat treatment of the entire welded structure is usually required, which is a complex and costly process that can easily lead to component deformation. 4) Traditional cold-rolled austenitic stainless steel base materials (such as 301 and 304 series) exhibit significant anisotropy in properties after cold rolling, which affects structural safety.

[0006] On one hand, embodiments of the present invention provide a stainless steel welding base material, wherein the chemical composition of the base material comprises, by mass percentage: C: 0.02%~0.08%, Cr: 12.0%~16.0%, Ni: 4.5%~6.5%, with the balance being Fe and unavoidable impurities; and the microstructure of the base material is a martensitic matrix containing austenite with a volume fraction of 1%~5.5%.

[0007] Furthermore, when the base material is used for welding to form a welded structure, the weld joint coefficient of the welded structure is not less than 0.92 under the condition that it is in the welded state and does not undergo any overall heat treatment after welding.

[0008] Furthermore, the room temperature yield strength of the welded structural component in the welded state is not less than 770 MPa.

[0009] Furthermore, the elongation of the welded structural component is not less than 14% in the temperature range of -196°C to 400°C.

[0010] Furthermore, in the microstructure of the base material, the austenite is distributed in a thin film form between the martensite laths, and / or, nanoscale MC-type carbide or carbonitride precipitates are also dispersed in the martensite matrix, wherein M is at least one of Nb and V.

[0011] Furthermore, the chemical composition of the base material, by mass percentage, also includes: Mo: 0.5%~1.5% and / or W: 0.5%~1.5%.

[0012] Furthermore, the chemical composition of the base material, by mass percentage, is as follows: C 0.05~0.08%, Cr 13.5~15.0%, Ni 5.2~5.7%, Mn≤0.6%, Si≤0.6%, Mo 0.8~1.0%, W 0.7~1.0%, V 0.15~0.25%, Nb 0.08~0.13%, Cu≤0.25%, N 0.03~0.1%, with the balance being Fe and unavoidable impurities.

[0013] On the other hand, the present invention proposes a method for manufacturing welded structural components, the method using the stainless steel welding base material described above, comprising the following steps: The base material is welded, and the welded structure is not subjected to overall solution treatment or aging treatment after welding. The weld joint coefficient of the obtained welded structure is not less than 0.92.

[0014] Furthermore, the welding is performed using laser welding or argon arc welding; The laser welding process parameters are as follows: laser power 1.5~4.0 kW, welding speed 0.8~2.5 m / min, shielding gas is argon or helium, and gas flow rate 15~25 L / min; And / or, the process parameters for the argon arc welding are: welding current 180-300 A, welding speed 200-400 mm / min, shielding gas is argon, and gas flow rate is 8-15 L / min.

[0015] In addition, this invention proposes the application of the stainless steel welding base material as described above in the preparation of load-bearing components in the fields of aerospace, marine engineering, or energy and chemical engineering.

[0016] Compared with the prior art, the present invention can achieve at least one of the following beneficial effects: 1) This invention, through precise component ratios (C, Cr, Ni, etc.) and microstructure control, forms an ideal multiphase microstructure with martensite as the matrix and containing 1%~5.5% stable austenite and nano-precipitates. During welding, the weld and heat-affected zone undergo a thermal cycle similar to "secondary quenching," enabling the reformation of a strong and tough martensite microstructure. This allows the welded material to achieve a room temperature yield strength of not less than 770 MPa without any overall heat treatment, and an elongation of not less than 14% over a wide temperature range of -196℃ to 400℃, with a weld joint coefficient of not less than 0.92. This completely solves the technical problems of severe post-weld softening of traditional austenitic stainless steel (such as 304 series) and the easy embrittlement of traditional martensitic stainless steel after welding.

[0017] 2) The small amount of austenite pre-existing in the base material of this invention and stably distributed in a thin film form can effectively buffer welding stress and suppress solidification cracks during welding, significantly improving crack resistance. Simultaneously, the introduction of elements such as Mo and W into the composition not only enhances the high-temperature performance and corrosion resistance of the matrix, but more importantly, effectively suppresses the sensitization tendency of the heat-affected zone of the weld. These designs enable the welded joint (including the weld and heat-affected zone) to obtain a fine and uniform strengthened microstructure after rapid cooling when using processes such as laser welding and TIG welding, avoiding performance degradation and thus achieving high load-bearing reliability directly in the weld state.

[0018] 3) Since the superior performance of this invention is directly imparted by the base material itself in the weld state, the welded structural components do not require overall solution treatment or aging treatment aimed at restoring performance after welding. This feature avoids a series of problems that are prone to occur during post-weld heat treatment of large or complex structural components, such as deformation, oxidation, surge in energy consumption, and extended production cycle. It simplifies the manufacturing process, reduces manufacturing costs, and is particularly suitable for the manufacturing needs of key load-bearing components in aerospace, marine engineering and other fields.

[0019] 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

[0020] 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.

[0021] Figure 1 This is a transmission electron microscope (TEM) image of a stainless steel sheet provided in one embodiment of the present invention; Figure 2 yes Figure 1 Transmission electron microscopy (TEM) image of the region shown at a higher magnification; Figure 3 This is an electron backscatter diffraction (EBSD) phase diagram of a stainless steel sheet provided in one embodiment of the present invention.

[0022] Figure 4 This is a microstructure diagram of a stainless steel sheet welded joint provided in an embodiment of the present invention.

[0023] Figure label: 1. Martensitic laths; 2. Thin film retained austenite; 3. Nanoprecipitates; 4. Weld metal; 5. Heat-affected zone; 6. Base metal. Detailed Implementation

[0024] Preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings, which form part of this application 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.

[0025] To overcome the shortcomings of existing stainless steel welded structural components, such as severe post-weld strength softening, low weld joint coefficient, and the need for post-weld heat treatment, this invention provides a stainless steel welding base material that can be used to manufacture wide-temperature-range stainless steel structural components with a high weld joint coefficient in the weld state.

[0026] On the one hand, the present invention proposes a stainless steel welding base material, wherein the chemical composition of the base material comprises, by mass percentage: C: 0.02%~0.08%, Cr: 12.0%~16.0%, Ni: 4.5%~6.5%, with the balance being Fe and unavoidable impurities.

[0027] The following provides a detailed explanation of the function of each element and the basis for their proportions: Carbon (C): Carbon is an important interstitial solid solution strengthening element, enabling stainless steel to achieve sufficient strength while controlling the potential negative impact on corrosion resistance within acceptable limits through careful production and processing (such as solution treatment). Furthermore, carbon influences texture evolution through solid solution and subsequent precipitation behavior, helping to reduce the anisotropy of mechanical properties. Therefore, the carbon content is controlled between 0.02% and 0.08% (e.g., 0.02%, 0.03%, 0.05%, 0.07%, 0.08%). Too low a carbon content leads to insufficient matrix strength, while too high a content results in excessive carbide formation, impairing corrosion resistance and low-temperature toughness.

[0028] Chromium (Cr): The core element for stainless steel to achieve its stainless properties. When its content is too high, it can form an extremely thin and dense chromium-rich oxide film (passivation film) on the surface of the steel. After carbon forms partial carbides, the chromium content in the matrix should still be maintained above the critical value for producing the passivation effect, thereby providing reliable basic corrosion resistance. However, excessive chromium content will lead to excessive formation of high-temperature ferrite, affecting the material's strength and low-temperature performance. Therefore, the chromium content in this invention is controlled at 12.0% to 16.0% (e.g., 12.0%, 13.0%, 14.0%, 15.0%, 16.0%). This range can work synergistically with nickel content to control the phase transformation process while ensuring corrosion resistance, obtaining the target martensitic matrix and a small amount of austenite.

[0029] Nickel (Ni): Nickel is a major austenite stabilizing element, endowing stainless steel with excellent toughness, plasticity, and cold working properties. Nickel also improves the stress corrosion resistance of stainless steel in reducing acid and chloride environments. Based on the effective control of the martensitic matrix in this invention, the nickel content needs to be matched with the chromium content, controlled within the range of 4.5% to 6.5% (e.g., 4.5%, 5.0%, 5.5%, 6.0%, 6.5%). This content range is crucial to ensuring that the material, after solution treatment and cooling to room temperature, obtains a predominantly martensitic composition while retaining a small amount (1%-5.5%) of stable austenite. The uniformity of nickel distribution also helps to reduce the direction dependence of properties.

[0030] As a preferred embodiment, in order to further improve the high-temperature performance, corrosion resistance and resistance to sensitization caused by welding thermal cycling of the base material, Mo: 0.5%~1.5% and / or W: 0.5%~1.5% may be added to the chemical composition of the base material.

[0031] Specifically, molybdenum significantly improves the resistance of stainless steel to pitting and crevice corrosion, especially in media containing chloride ions. It makes the passivation film more stable and less susceptible to damage even in harsh environments. Tungsten has a similar effect to molybdenum, further improving the high-temperature strength and tempering stability of the steel. More importantly, the addition of Mo and W significantly increases the recrystallization temperature of the martensitic matrix and inhibits grain growth and softening tendency in the weld heat-affected zone during thermal cycling. These two elements work synergistically to enhance the material's resistance to localized corrosion and its weldability in harsh environments. Excessive addition of Mo and W would greatly increase the cost of stainless steel and also alter the phase equilibrium relationship. Therefore, in this invention, the molybdenum content is controlled at 0.5~1.5% (e.g., 0.5%, 0.8%, 0.9%, 1.0%, 1.2%, 1.5%), and the tungsten content is controlled at 0.5~1.5% (e.g., 0.5%, 0.7%, 0.9%, 1.0%, 1.2%, 1.3%, 1.5%).

[0032] As the preferred embodiment, to achieve the optimal balance of strength, plasticity, toughness, and weldability, the base material adopts the following precisely controlled chemical composition (by mass percentage): C 0.05~0.08%, Cr 13.5~15.0%, Ni 5.2~5.7%, Mn≤0.6%, Si≤0.6%, Mo 0.8~1.0%, W 0.7~1.0%, V 0.15~0.25%, Nb 0.08~0.13%, Cu≤0.25%, N 0.03~0.1%, with the balance being Fe and unavoidable impurities. The role and proportion of each element within this optimal range are based on the following: Carbon (C): 0.05~0.08%. This range can minimize the total amount of carbide precipitation while ensuring sufficient solid solution strengthening and meeting strength requirements. It provides the optimal space for precise control of carbonitrides in Nb and V microalloying, and fundamentally avoids the risk of corrosion resistance and low-temperature toughness deterioration caused by excessive carbon solid solution.

[0033] Chromium (Cr): 13.5~15.0%. This narrow range is the optimal window for the synergistic effect of chromium-nickel-carbon-molybdenum-nitrogen multi-element combination. It can ensure the density and stability of the passivation film while controlling the volume fraction of high-temperature ferrite within 3%, thus ensuring the continuity of the martensitic matrix and the matching of strength and toughness.

[0034] Nickel (Ni): 5.2~5.7%. This range allows for precise control of the room temperature residual austenite content to the target range of 2%~4%, optimally utilizing the austenite phase transformation-induced plasticity (TRIP effect) to enhance toughness, while avoiding strength loss caused by excessive austenite, and forming an efficient nickel-nitrogen composite austenite stabilization mechanism with the N content.

[0035] Manganese (Mn) and silicon (Si): Manganese has a certain austenite-stabilizing effect, but its ability is about half that of nickel, and its role is more important in nickel-saving stainless steels. It is also a good deoxidizer and desulfurizer, which can improve the hot working properties of steel. Silicon is mainly added as a deoxidizer, which can improve the casting properties of molten steel, and at the same time improve the high-temperature oxidation resistance of steel. Controlling the content of manganese and silicon at a low level ≤0.6% (e.g., 0.6%, 0.5%, 0.4%, 0.3%, 0.2%) is mainly to ensure the material's production processability while preventing excessive addition from adversely affecting the plasticity, toughness, or weldability of the steel, and to avoid exacerbating the anisotropy of mechanical properties due to segregation.

[0036] Molybdenum (Mo): 0.8–1.0% (e.g., 0.8%, 0.85%, 0.9%, 0.95%, 1.0%). This range represents the optimal balance between the synergistic effect of molybdenum-tungsten and cost-effectiveness. When the Mo content is below 0.8%, it is difficult to effectively suppress the softening tendency of the heat-affected zone under welding heat input exceeding 1.5 kJ / mm; while above 1.0%, the alloy cost increases significantly, but the effect of increasing the recrystallization temperature tends to saturate. This precise range can maximize the increase of recrystallization temperature and enhance the stability of the weld heat-affected zone while controlling costs.

[0037] Tungsten (W): 0.7~1.0% (e.g., 0.7%, 0.75%, 0.8%, 0.85%, 0.9%, 0.95%, 1.0%). Tungsten and molybdenum form a complementary synergistic effect, further improving high-temperature strength and tempering stability. Controlling the W content within the range of 0.7~1.0% ensures that the total Mo+W equivalent is within the optimal economic-efficiency range, avoiding the exponential cost increase caused by the total content exceeding 1.5%, while also fully leveraging the synergistic effect of the two elements on the passivation film stability, significantly improving the material's resistance to pitting and crevice corrosion in chloride-containing media.

[0038] Vanadium (V): Its role is to refine the grain structure of stainless steel, thereby improving the steel's strength and ductility. It can also form carbonitrides, producing a certain precipitation hardening effect. These carbonitrides precipitate during low-temperature annealing, contributing to nano-precipitation strengthening along with NbC. The addition of vanadium also helps promote the formation of large-angle grain boundaries, positively impacting the achievement of a large-angle grain boundary ratio exceeding 60%. However, excessive addition may adversely affect the material's processability and toughness; therefore, the vanadium content is controlled between 0.15% and 0.25% (e.g., 0.15%, 0.18%, 0.20%, 0.22%, 0.25%).

[0039] Niobium (Nb): It preferentially combines with carbon to form stable niobium carbide, thereby effectively fixing carbon atoms and preventing carbon from combining with chromium to form chromium carbide. This reduces the risk of chromium-depleted zones at grain boundaries during welding or heat treatment, effectively preventing intergranular corrosion, i.e., suppressing the sensitization effect. Furthermore, undissolved NbC particles pin grain boundaries, inhibiting excessive grain growth in the heat-affected zone; while nano-sized NbC precipitated during subsequent low-temperature annealing contributes significantly to precipitation strengthening. The uniform distribution of nano-sized NbC particles helps weaken the texture and is one of the key factors in achieving a transverse and rolling tensile strength difference of less than 15 MPa in the sheet material. Therefore, this invention controls the Nb content to 0.08~0.13% (e.g., 0.08%, 0.09%, 0.10%, 0.11%, 0.12%, 0.13%). Too low a content has little effect, while too high a content easily forms large inclusions that impair toughness.

[0040] Copper (Cu): Improves the corrosion resistance of stainless steel to certain media, especially its resistance to reducing acids such as sulfuric acid. It also improves the cold workability of stainless steel. Therefore, the copper content should be controlled at ≤0.25% (e.g., 0.25%, 0.20%, 0.15%, 0.10%, 0.05%). Excessive copper content (e.g., >0.5%) may cause hot work brittleness.

[0041] Nitrogen (N): A strong austenite-forming and stabilizing element, its ability far surpasses that of nickel, and therefore it is often used to partially replace expensive nickel to stabilize austenitic structures. It also has a solid solution strengthening effect, significantly improving the strength of steel with minimal negative impact on corrosion resistance. Therefore, controlling nitrogen content within the range of 0.03–0.1% (e.g., 0.03%, 0.05%, 0.08%, 0.1%) is to improve strength and corrosion resistance while avoiding porosity or other defects caused by excessive content. The synergistic effect of nitrogen and nickel, precisely controlling the austenite content and stability, is one of the key elements for achieving a small amount of stable retained austenite. Nitrogen solid solution also helps promote the formation of large-angle grain boundaries during recrystallization.

[0042] Through the synergistic effect of the aforementioned multi-element alloying elements, this composition system achieves optimal overall performance while ensuring excellent weldability.

[0043] Regarding weldability, when this base material is used for welding to form welded structural components, the weld joint coefficient of the welded structural components in the as-welded state, without any overall heat treatment after welding, is not less than 0.92. The room temperature yield strength of the welded structural components in the as-welded state is not less than 770 MPa, and its elongation is not less than 14% over a wide temperature range of -196℃ to 400℃. These superior as-welded properties are entirely dependent on the unique composition and microstructure design of the base material.

[0044] In terms of microstructure, the microstructure of the base material is a martensitic matrix containing 1% to 5.5% austenite by volume.

[0045] Preferably, the austenite is distributed in a thin film form between the martensite laths. This form of austenite has higher mechanical stability and phase transformation stability, and can more effectively buffer welding stress by coordinating deformation during the rapid thermal cycling of the welding process, thereby significantly suppressing the generation of solidification cracks and cold cracks.

[0046] Furthermore, nanoscale MC-type carbide or carbonitride precipitates may be dispersed in the martensitic matrix, wherein M is at least one of Nb and V. These nanoscale precipitates formed during low-temperature annealing can effectively pin dislocations and produce a significant precipitation strengthening effect, which is crucial for maintaining the strength of the matrix, especially in the weld heat-affected zone where the peak high temperature region has not been experienced.

[0047] It is worth noting that the martensitic matrix has special grain boundary characteristics, with large-angle grain boundaries greater than 15° accounting for no less than 60%. This high proportion of large-angle grain boundary structure not only helps to hinder crack propagation and improve the fracture toughness of the material, but also effectively promotes the uniformity and coordination of plastic deformation, which is one of the key microstructural factors to ensure the low level of anisotropy of the material.

[0048] This microstructure, through multiphase synergy, enables the sheet metal to achieve excellent comprehensive properties: the martensitic matrix provides the foundation for high strength; the nanoprecipitates effectively pin dislocations, producing a significant precipitation strengthening effect, which is crucial for maintaining the material's strength at high temperatures; a small amount of stable austenite can coordinate local stresses under external forces through the transformation-induced plasticity (TRIP) effect, inhibiting crack initiation and propagation, thereby significantly improving the material's plasticity, especially its toughness at low temperatures. Furthermore, this austenitic phase can effectively coordinate internal stresses during the preparation process, playing a positive role in controlling the shape of the sheet roll.

[0049] Furthermore, the present invention provides a method for preparing the aforementioned base material, which is used to prepare the stainless steel welding base material described above.

[0050] Its core lies in achieving precise control of microstructure during continuous industrial production through a combined process of "flat cold rolling (S5) + low-temperature annealing (S6)," while simultaneously ensuring sheet shape and surface quality. The method includes the following steps: S1. Smelting and casting: Smelting and casting are carried out to obtain slabs; S2. Hot rolling: The slab is hot rolled; S3. Cold rolling: The hot-rolled plate is cold rolled once or multiple times, during which intermediate annealing may be performed between two cold rolling processes, and the plate is cold rolled to the target thickness. S4. Solution treatment: The cold-rolled sheet is subjected to solution treatment at a temperature of 1050℃-1180℃ (e.g., 1050℃, 1100℃, 1150℃, 1180℃). S5. Cold rolling: Cold rolling is performed on the solution-treated sheet to flatten it, with a reduction of 0.1%-2% (e.g., reduction of 2%, 1.5%, 1%, 0.5%, 0.2%). S6. Low-temperature annealing: The flattened cold-rolled sheet is subjected to low-temperature annealing treatment at a temperature of 150℃-400℃ (e.g., 150℃, 200℃, 250℃, 300℃, 350℃, 400℃) and a holding time of 8-20h (e.g., 8h, 10h, 12h, 15h, 18h, 20h).

[0051] Furthermore, in step S1, the chemical composition of the slab, by mass percentage, is: C: 0.02%~0.08%, Cr: 12.0%~16.0%, Ni: 4.5%~6.5%, with the balance being Fe and unavoidable impurities.

[0052] Specifically, in step S1, conventional stainless steel smelting methods can be employed, such as electric arc furnace (EAF) combined with ladle refining (e.g., AOD, VOD), and slabs are obtained through continuous casting or ingot casting. This step aims to obtain an initial billet with precise and uniform composition, laying the foundation for achieving stable target properties. It is essential to ensure that the chemical composition of the final billet falls entirely within the range required by this invention; this is a prerequisite for the effectiveness of all subsequent heat treatment processes.

[0053] Furthermore, in step S2, the purpose of hot rolling is to break down the as-cast structure and achieve homogenization of composition and structure. To ensure the smooth progress of the hot rolling process and avoid cracking, the initial rolling temperature must be ≥1150℃ (e.g., 1150℃, 1200℃, 1250℃, 1300℃, 1350℃), and the final rolling temperature must be controlled at ≥900℃ (e.g., 900℃, 950℃, 1000℃, 1050℃, 1100℃).

[0054] Compared to existing technologies where ordinary stainless steel can be hot-rolled at relatively low temperatures, the alloy of this invention contains a higher content of strong carbide-forming elements such as W and Nb. At lower heat deformation temperatures (e.g., <1150℃), these elements readily precipitate coarse carbides at the austenite grain boundaries, weakening the grain boundary bonding strength and leading to cracks during hot working. This invention employs a higher initial rolling temperature and maintains a sufficiently high final rolling temperature, ensuring that elements such as W and Nb are fully dissolved in the austenite matrix, avoiding or reducing the formation of these harmful precipitates during hot working, thereby ensuring the integrity of the hot-rolled slab and improving the yield.

[0055] Furthermore, in step S3, the material is gradually rolled to the target thickness through cold rolling and intermediate annealing. The intermediate annealing aims to eliminate the work hardening caused by cold rolling and restore the plasticity of the material. The temperature is set at 1000℃-1200℃ (e.g., 1000℃, 1050℃, 1100℃, 1150℃, 1200℃). At this high temperature, the material can fully recrystallize and dissolve the second phases such as carbides produced during the preceding hot and cold rolling processes, thereby providing a softened and uniform microstructure for subsequent rolling.

[0056] Compared to conventional cold rolling intermediate annealing, this invention employs a higher intermediate annealing temperature. This is because if the intermediate annealing temperature is insufficient, the carbonitrides of elements such as Nb and V cannot be completely dissolved, leading to difficulties in subsequent cold rolling, uneven microstructure, and ultimately affecting the stability of the finished product's performance. Therefore, both the intermediate annealing and subsequent solution treatment in this invention require a higher temperature range to ensure that the precipitates formed in the preceding processes are effectively dissolved, laying the microstructural foundation for obtaining a uniform, high-performance product.

[0057] Optionally, after step S2 and before step S3, a softening annealing step is included, wherein the softening annealing temperature is 600℃-650℃ (e.g., 600℃, 610℃, 620℃, 630℃, 640℃, 650℃), preferably 620℃. It should be noted that this step is not mandatory, but for hot-rolled materials with alloy compositions at the upper limit or high hardness after hot rolling, this medium-temperature softening annealing can significantly reduce their yield strength, making the subsequent cold rolling process easier. It can effectively reduce the number of rolling passes or the rolling load, which is beneficial for improving production efficiency and sheet shape, making it a practical and adaptable process.

[0058] Specifically, in step S4, the core purpose of solution treatment is to dissolve all the carbides, nitrides, and other second phases precipitated during hot and cold working into the austenitic matrix to the maximum extent possible, thereby obtaining a homogeneous supersaturated solid solution. Subsequently, rapid cooling (such as water quenching) fixes this high-temperature state to room temperature, primarily obtaining a microstructure dominated by martensite with a certain amount of metastable austenite. This step provides an ideal initial state with homogeneous composition and low internal stress for the subsequent crucial microstructure control steps (S5 and S6). Rapid cooling after solution treatment is essential to prevent premature precipitation of elements during cooling and ensure that alloying elements are fixed in the matrix to form a supersaturated solid solution.

[0059] The core of this invention lies in the combination of step S5 (leveling cold rolling) and step S6 (low-temperature annealing). This combined process constitutes a unique "deformation-precipitation" synergistic control mechanism, which is key to obtaining ideal microstructure and realizing industrial production.

[0060] In step S5, the effect of leveling cold rolling goes far beyond its conventional use in improving sheet shape. This invention employs a "rolling instead of cold rolling" process approach: In traditional high-strength stainless steel production, for sheet and coil products, it is difficult to control the volume fraction of austenite using the thermal stability of austenite through mass cryogenic treatment (usually holding at -73℃ or even lower), due to the high equipment investment, high energy consumption, and low efficiency. This invention, however, utilizes the mechanical stability principle of austenite, applying a small but precisely controllable reduction (0.1%-2%) through leveling cold rolling, achieving multiple objectives: (1) It effectively eliminates the yield plateau of the plate after solution treatment and improves the plate shape.

[0061] (2) The small deformation is sufficient to induce some unstable residual austenite to undergo martensitic phase transformation, thereby precisely controlling the volume fraction of austenite in the final structure from the higher level after solution treatment to the ideal range of 1%-5.5%.

[0062] (3) The plastic deformation process introduces crystal defects such as dislocations with controllable density into the martensitic matrix. These defects can serve as "catalyst" sites for preferential nucleation of nano-precipitates during the subsequent low-temperature annealing process, promoting the diffuse distribution of precipitates.

[0063] It should be noted that the reduction amount needs to be strictly controlled. Exceeding 2% will cause too much austenite to transform into martensite and introduce an excessively high dislocation density, which will impair plasticity. On the other hand, if the reduction amount is too low (<0.1%), it will not have a sufficient effect on the regulation of microstructure and plate shape.

[0064] Preferably, the reduction of the flat cold rolling is 0.5%-1.5% (e.g., 1.5%, 1%, 0.5%), within which the best balance can be achieved between shape control, microstructure regulation and plasticity retention.

[0065] Specifically, in step S6, low-temperature annealing involves holding the material at a relatively low temperature (150℃-400℃) for an extended period (8-20h). Its main functions are twofold: first, to eliminate internal stress; and second, to promote the dispersion and precipitation of nanoscale carbides (such as carbides rich in Mo, W, Nb, and V) from the supersaturated martensite matrix, thereby achieving significant precipitation strengthening while stabilizing the remaining austenite.

[0066] Processing within this relatively low temperature range allows the nano-precipitates to precipitate at a high density, providing the desired strengthening effect while effectively avoiding the severe oxidation, adhesion, and roll collapse issues on the surface of traditional martensitic aging stainless steel caused by higher aging temperatures (typically ≥450℃), thus ensuring the surface quality and shape of the product.

[0067] Choosing a holding time of 8-20 hours is to strike a balance between ensuring sufficient nucleation and growth of the precipitated phase to achieve the best strengthening effect and avoiding excessively low production efficiency due to excessive holding time.

[0068] Preferably, in step S6, the low-temperature annealing temperature is 180℃-250℃ (e.g., 180℃, 190℃, 200℃, 220℃, 230℃, 250℃). Within this temperature range, the precipitation strengthening effect is most significant, while the adverse effects on the surface quality of the sheet / coil are minimal.

[0069] Furthermore, the plate after solution treatment in step S4 and the plate after low-temperature annealing in step S6 have a microstructure with martensite as the matrix.

[0070] The base material of this invention, through the synergistic regulation of the above-mentioned chemical composition and preparation process, possesses excellent welding thermal cycle structure stability and anti-sensitization ability. The joint area after welding can achieve the same strength, toughness and corrosion resistance as the base material without solution treatment or aging treatment.

[0071] Based on this characteristic, the present invention further provides a method for manufacturing welded structural components: welding is performed using the stainless steel welding base material, and no solution treatment or aging treatment is applied to the overall structural component after welding.

[0072] The manufacturing method specifically includes the following steps: Step 1: Preparation of base material and beveling At least two stainless steel base materials to be welded are provided, with a thickness between 1 mm and 5 mm, to meet the specifications of most load-bearing structures. The edges of the areas to be welded are then precision machined, for example, using milling or precision cutting processes, to obtain a smooth, clean weld bevel.

[0073] Step 2: Cleaning before welding Use solvents such as acetone or alcohol to thoroughly clean the beveled areas to be welded, completely removing oil and oxides to ensure a clean welding area.

[0074] Step 3: Assembly and Fixing The cleaned base material is assembled and fixed on the welding fixture in the form of a butt joint. During assembly, it is necessary to ensure that the butt gap is less than 0.15mm to guarantee the quality of the subsequent weld formation.

[0075] Step 4: Select welding process and perform welding. The assembled joints are welded using laser welding or TIG welding processes that utilize concentrated heat input and rapid cooling. The welding process must be carried out under controlled environmental conditions to avoid interference from wind or other factors that could affect the protective gas field.

[0076] For example, when laser welding is used, the specific process is as follows: a focused laser beam with a spot diameter of 0.2~0.6mm is used as the heat source to perform non-contact deep penetration welding on the butt joint of the workpiece. The key process parameters are controlled as follows: laser power 1.5~4.0 kW, welding speed 0.8~2.5 m / min, defocusing amount -2~+2 mm (negative defocusing is used to increase penetration depth, positive defocusing is used to increase weld width), and high-purity argon or helium gas with a purity ≥99.99% is used as the shielding gas, with a gas flow rate controlled at 15~25 L / min, and the nozzle distance from the workpiece is approximately 8~12 mm. This process has extremely concentrated heat input and extremely fast heating and cooling rates (cooling rate can reach 10). 3 ~10 6 (℃ / s), which can form a narrow heat-affected zone with a width of only 0.5~1.5mm, thereby minimizing microstructure coarsening and alloy element burn-off.

[0077] For example, when using argon arc welding, the specific process is as follows: a cerium-tungsten electrode with a diameter of approximately 2.4 mm is used as the non-consumable electrode, and welding is performed by the arc generated between the electrode and the workpiece. The arc burns stably in an inert argon atmosphere with a purity of ≥99.99%. The standard welding process requires control of the following parameters: welding current 180~300 A (selected according to plate thickness, using the lower limit for thin plates and the upper limit for thick plates, and using DC positive polarity to maximize penetration and weld cleanliness), arc voltage 10~16 V, and welding speed 200~400 mm / min. Simultaneously, a nozzle diameter of 8~12 mm, a shielding gas flow rate of 8~15 L / min, and a tungsten electrode extension length of 5~8 mm are used to ensure good and stable gas protection for the molten pool and prevent metal oxidation during welding.

[0078] After welding is completed, the welded structural component is kept in the welded state without the need for overall heat treatment aimed at restoring performance. The welded structural component manufactured by the above method has excellent performance: its weld joint coefficient is not less than 0.92, its room temperature yield strength in the welded state is not less than 770 MPa, and its elongation is not less than 14% in a wide temperature range from -196℃ to 400℃.

[0079] The realization of these superior properties depends entirely on the composition and microstructure of the base material itself. The martensitic matrix of the base material ensures that the weld heat-affected zone can recover to a strengthened martensitic structure after rapid cooling ("secondary quenching"), which is the cornerstone of high weld strength. The small amount of austenite that is pre-existing and stably distributed in a thin film form plays a key role in buffering stress and inhibiting the formation of solidification cracks and cold cracks by coordinating deformation under welding thermal cycles and stress. The dispersed nanoscale MC-type carbonitride precipitates, although they may dissolve in the high-temperature zone near the weld, are retained in the lower peak temperature region of the heat-affected zone or recrystallize during subsequent cooling, and can still contribute significantly to precipitation strengthening, ensuring the uniformity of joint strength.

[0080] Compared with existing technologies, this method eliminates the complex and energy-consuming post-weld heat treatment process because the base material itself imparts high performance in the weld state. This not only simplifies the manufacturing process, improves production speed and reliability, and avoids problems such as component deformation, oxidation, and increased energy consumption that may be caused by post-weld heat treatment, but also significantly reduces the total life cycle manufacturing cost. It is particularly suitable for manufacturing large or structurally complex components such as aerospace vehicle frames, deep-sea probe pressure shells, and energy and chemical pressure vessels.

[0081] Furthermore, the present invention clarifies the application directions of the stainless steel welding base material and its welded structural components, specifically involving the preparation of key load-bearing components in the fields of aerospace, marine engineering, or energy and chemical engineering.

[0082] This application's advantages stem directly from the combined strengths of the base material and its as-welded manufacturing method: welded components made from it exhibit a good balance of high strength and high ductility across a wide temperature range (-196℃ to 400℃), and achieve a stable weld joint coefficient of at least 0.92 in the as-welded state, while systematically eliminating the need for post-weld overall heat treatment. These superior properties, resulting from the inherent characteristics of the base material and the specific welding process, precisely meet the core requirements of aerospace (with stringent requirements for material weight reduction, high structural reliability, and weld integrity of complex geometries), marine engineering (constantly facing challenges such as deep-sea low temperatures, chloride ion corrosion, and the manufacture of large welded structures), and energy and chemical engineering (involving high-temperature and high-pressure conditions, hydrogen-containing environments, and corrosion resistance to harsh media) for critical load-bearing components, providing a highly reliable and efficient material solution.

[0083] The present invention will be described in more detail below through specific embodiments. These embodiments are merely descriptions of the best implementation of the invention and do not limit the scope of the invention in any way.

[0084] The detailed chemical composition (wt. %) of the stainless steel welding base materials involved in the following embodiments is shown in Table 1. Among them, components 1-3 and components 6 are within the core component range of the present invention, while components 4-5 deviate from the scope of the present invention.

[0085] Table 1: Alloy chemical composition (wt.%, balance Fe and unavoidable impurities)

[0086] Example 1 This embodiment provides a stainless steel welding base material, its preparation method, and its welding application, using an alloy with composition 1 in Table 1.

[0087] S1. Smelting and Casting: Stainless steel is smelted in an electric furnace and then cast in molds to obtain billets. The billets are heated and held in a soaking furnace, and then forged after being taken out of the furnace. The initial forging temperature is 1230℃ and the final forging temperature is 950℃. Finally, the billets are air-cooled to room temperature.

[0088] S2. Hot rolling: The hot-rolled raw material after billeting is heated and kept at a certain temperature. After exiting the furnace, it is hot-rolled at an initial rolling temperature of 1200℃ and a final rolling temperature of 920℃. The thickness of the hot-rolled plate is 6mm. Then it is placed in the hot coiling zone, air-cooled to room temperature, and then pickled to form cold-rolled white material.

[0089] S3. Cold Rolling: Hot-rolled stainless steel undergoes multi-pass cold rolling. The first pass reduces the thickness by 1.2 mm, resulting in a sheet thickness of 4.8 mm. A softening treatment is then performed, heating the cold-rolled sheet to 1180℃ followed by cooling and pickling. The second pass reduces the thickness by 1 mm, resulting in a sheet thickness of 3.8 mm, and the same softening process is repeated. The third pass reduces the thickness by 0.8 mm, resulting in a sheet thickness of 3 mm.

[0090] S4. Solution treatment: The cold-rolled coil is subjected to solution pickling at a temperature of 1150℃, and then pickled after cooling to room temperature.

[0091] S5. Leveling cold rolling: The solution-treated cold-rolled coil is leveled, with a cold rolling reduction of 1%.

[0092] S6. Low-temperature annealing: The cold-rolled coil is subjected to low-temperature heat treatment in a bell-type furnace at a temperature of 200℃ for 20 hours, and then air-cooled to room temperature after being removed from the furnace.

[0093] Application Example 1 Using the base material obtained in Example 1, welded structural components were manufactured according to the following steps: Step 1, Base Material Preparation and Beveling: Process the base material into a 3mm thick plate and perform precision milling on the edges to obtain a smooth bevel.

[0094] Step 2, Pre-welding cleaning: Thoroughly clean the bevel and adjacent areas with acetone.

[0095] Step 3, Assembly and Fixing: Assemble the base material on the tooling using a butt joint, ensuring a butt gap of 0.10-0.15mm.

[0096] Step 4, Welding: Laser welding is selected. Specific parameters are: laser power 3.0 kW, welding speed 1.5 m / min, defocusing amount -1 mm, shielding gas is high-purity argon (purity ≥99.99%), flow rate 20 L / min.

[0097] After welding, the structural components remain in the welded state without undergoing any overall heat treatment.

[0098] Example 2 This embodiment uses the same component 1 and preliminary preparation process as Embodiment 1, the only difference being that the process parameters in step S6 are different: S6. Low-temperature annealing: Annealing temperature 400℃, holding time 8 hours.

[0099] Example 3 This embodiment provides a stainless steel welding base material and its preparation method, using an alloy with component 2 in Table 1.

[0100] S1. Smelting and Casting: Stainless steel was smelted in an electric furnace to obtain alloy composition 2 in Table 1, and then continuously cast to obtain 3 billets. One of the billets was heated and held in a soaking furnace, and after exiting the furnace, it was rolled into a roughing sheet with an initial rolling temperature of 1220℃ and a final rolling temperature of 920℃, and then air-cooled to room temperature.

[0101] S2. Hot Rolling: The hot-rolled raw material after billet preparation is heated and held at a certain temperature. After exiting the furnace, it undergoes initial hot rolling at 1250℃ and final rolling at 910℃, with a hot-rolled plate thickness of 4mm. It is then placed in a hot-rolling zone and air-cooled to room temperature. The hot-rolled coil undergoes softening annealing at 620℃ for 15 hours. After exiting the furnace, it is air-cooled to room temperature and then pickled to form cold-rolled white sheet.

[0102] S3. Cold Rolling: Hot-rolled stainless steel is cold-rolled. The first rolling pass reduces the thickness by 1.2 mm, resulting in a sheet thickness of 2.8 mm. A softening treatment is then performed by heating the cold-rolled sheet to 1150℃, followed by cooling and pickling. The second rolling pass reduces the thickness by 0.75 mm, resulting in a material thickness of 2.05 mm.

[0103] S4. Solution treatment: The cold-rolled coil is subjected to solution pickling at a temperature of 1080℃, and then pickled after cooling to room temperature.

[0104] S5. Leveling cold rolling: The cold-rolled coil is leveled, and the cold rolling reduction is 2%.

[0105] S6. Low-temperature annealing: The cold-rolled coil is subjected to low-temperature heat treatment in a bell-type furnace at a temperature of 150°C for 20 hours, and then air-cooled to room temperature after being removed from the furnace.

[0106] Example 4 This embodiment uses the same component 2 and the same preliminary preparation process as Embodiment 3. The only difference is the amount of cold rolling reduction in step S5. S5. Leveling cold rolling: Reduction is 1%.

[0107] Example 5 This embodiment provides a stainless steel welding base material and its preparation method, using an alloy with component 3 in Table 1.

[0108] S1-S4. The process flow is similar to that of Example 1, with slight adjustments to the specific parameters.

[0109] S5. Leveling Cold Rolling: The cold-rolled coil is leveled and then cold-rolled down by about 1%.

[0110] S6. Low-temperature annealing: The cold-rolled coil is subjected to low-temperature heat treatment in a bell-type furnace at a temperature of 250°C for 20 hours, and then air-cooled to room temperature after being removed from the furnace.

[0111] Example 6 This embodiment provides a stainless steel welding base material and its preparation method, using an alloy with component 3 in Table 1.

[0112] S1-S4. The process flow is similar to that of Example 1, and the final cold rolling is to 1.02mm.

[0113] S5. Leveling Cold Rolling: The cold-rolled coil is leveled, and the cold rolling reduction is 2%.

[0114] S6. Low-temperature annealing: The cold-rolled coil is subjected to low-temperature heat treatment in a bell-type furnace at a temperature of 200℃ for 18 hours, and then air-cooled to room temperature after being removed from the furnace.

[0115] Comparative Example 1 This comparative example uses the same alloy composition (composition 1) and preliminary preparation process as Example 1. The difference is that the leveling cold rolling in step S5 is not performed, and the low-temperature annealing in step S6 is performed directly after the solution treatment.

[0116] Comparative Example 2 This comparative example uses the same alloy composition (composition 1) as Example 1. The difference is that in step S2, the final rolling temperature of hot rolling is reduced to 850°C, which causes a large number of macroscopic cracks to appear in the billet, making it impossible to carry out subsequent processing and performance testing.

[0117] Comparative Example 3 This comparative example uses the same alloy composition (composition 2) and preliminary preparation process as Example 3, except that the amount of cold rolling reduction in step S5 is increased from 2% to 10%.

[0118] Comparative Example 4 This comparative example uses the exact same preparation process as Example 2, but the alloy composition used is component 4 in Table 1.

[0119] Comparative Example 5 This comparative example uses the exact same preparation process as Example 5, but the alloy composition used is composition 5 in Table 1.

[0120] Performance Testing and Results Analysis Performance tests were conducted on the base materials and welded joints obtained from the above embodiments and comparative examples, and the results are summarized in Table 2. Meanwhile, to visually demonstrate the advantages of this invention in terms of isotropic microstructure, the electron backscattering diffraction (EBSD) phase diagram of Example 1 is provided (…). Figure 3 ) and the EBSD phase diagram of traditional 304 stainless steel in the cold-rolled state ( Figure 4 (For comparison)

[0121]

[0122]

[0123] Performance test data (Table 2) confirms that Examples 1-6 of this invention fully achieved the preset goals. The austenite volume fraction in its microstructure was precisely controlled within the ideal range of 1%-5.5%, forming the microscopic basis for achieving high performance over a wide temperature range. Specifically, the material exhibits high strength and toughness at room temperature (tensile strength ≥1150MPa, yield strength ≥943MPa, elongation ≥17%); it displays ultra-high strength and good plasticity at a low temperature of -196℃ (tensile strength ≥1653MPa, yield strength ≥1348MPa, elongation ≥20%); and it maintains excellent thermal strength at a high temperature of 400℃ (tensile strength ≥1114MPa, yield strength ≥811MPa, elongation ≥14%).

[0124] In key engineering applications, the material of this invention also demonstrates superior performance. The weld joints of all embodiments, in the as-welded state without heat treatment, exhibit a room temperature weld joint coefficient of not less than 0.92. Furthermore, the material exhibits significantly superior isotropic mechanical properties compared to traditional stainless steel, with the difference between its transverse and rolling strength being less than 15 MPa (measured at 8-14 MPa).

[0125] The tissue characterization of the sample from Example 1 was performed: Microstructural characteristics: Transmission electron microscopy (TEM) analysis results ( Figure 1 and Figure 2 It clearly demonstrates its typical "martensitic lath 1 + thin film-like retained austenite 2 + nano-precipitated phase 3" multiphase synergistic structure. The thin film-like austenite is uniformly distributed between the martensitic laths, effectively coordinating stress and toughening; while at high magnification ( Figure 2 It can be seen that a large number of nanoscale precipitates with sizes in the range of 5-50 nanometers are dispersed in the matrix, which is the key source of the material’s high strength.

[0126] Isotropic structure: Electron backscattering diffraction (EBSD) phase diagram ( Figure 3 The results show that the martensitic matrix of Example 1 has no significant preferred orientation, exhibiting a random grain orientation. This contrasts sharply with the strong texture exhibited by conventional 304 stainless steel in the cold-rolled state. This uniform, textureless microstructure is a technological advantage of the present invention and the fundamental reason for its achievement of low mechanical anisotropy (the difference between transverse and rolling strength is only 12 MPa).

[0127] Macroscopic morphology and weld structure: The plate prepared in Example 1 has a smooth macroscopic morphology and excellent plate shape. The microstructure of its laser-welded joint shows that the weld metal 4, heat-affected zone 5 and base metal 6 are well bonded, the heat-affected zone is narrow, and no obvious grain coarsening or softening phenomenon is observed. This provides a direct microstructural basis for obtaining a weld joint coefficient as high as 0.93.

[0128] In contrast, each of the comparative examples has obvious defects in different aspects due to its deviation from the technical solution of the present invention.

[0129] Comparative Example 1, lacking a leveling cold rolling step, resulted in a high austenite volume fraction (6.5%). Although its plasticity was acceptable, its yield strength at room temperature, 400℃, and -196℃ failed to meet standards, and the difference between transverse and rolling strength (25MPa) increased, indicating poor isotropy. Comparative Example 2 cracked during processing due to an excessively low hot rolling finishing temperature (850℃). Comparative Example 3, with an excessively large leveling cold rolling reduction (10%), resulted in an excessively low austenite volume fraction (0.3%). Although its strength was high, its elongation at room temperature, 400℃, and -196℃ deteriorated sharply to 8.5%, 5.0%, and 6.5%, respectively, exhibiting brittle characteristics. Furthermore, the difference between transverse and rolling strength reached as high as 45MPa, indicating severe anisotropy. Comparative Example 4, due to its excessively high content of elements such as Cr and Ni, deviated from the design of this invention, resulting in an excessive amount of austenite (volume fraction 21.5%) in its microstructure, leading to severely insufficient room temperature and 400℃ strength, as well as a room temperature weld joint coefficient (0.82). Comparative Example 5, due to insufficient content of microalloying elements such as W, Nb, and V, resulted in a significant decrease in both its low-temperature elongation (9.5%) and high-temperature strength, and poor wide-temperature range strength-plasticity matching.

[0130] In summary, this invention successfully prepared a stainless steel weldable base material with a microstructure of "martensitic matrix + a small amount of austenite + nano-precipitates". This base material exhibits an excellent balance of high strength and high ductility across a temperature range of -196℃ to 400℃, while simultaneously possessing a high weld joint coefficient and low mechanical anisotropy. The preparation method is stable, reliable, and easily implemented industrially. Welded structural components based on this base material possess a high weld joint coefficient. This invention effectively solves the industry challenge of simultaneously achieving wide-temperature performance, excellent weldability, and low anisotropy in existing technologies, and has broad application prospects in high-end fields such as aerospace and deep-sea equipment.

[0131] 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 welding base material, characterized in that, The chemical composition of the base material, by mass percentage, includes: C: 0.02% to 0.08%, Cr: 12.0% to 16.0%, Ni: 4.5% to 6.5%, with the balance being Fe and unavoidable impurities; and the microstructure of the base material is a martensitic matrix containing 1% to 5.5% austenite by volume.

2. The stainless steel welding base material according to claim 1, characterized in that, When the base material is used for welding to form a welded structure, the weld joint coefficient of the welded structure is not less than 0.92 under the condition that it is in the welded state and does not undergo any overall heat treatment after welding.

3. The stainless steel welding base material according to claim 2, characterized in that, The room temperature yield strength of the welded structural component in the welded state is not less than 770 MPa.

4. The stainless steel welding base material according to claim 2, characterized in that, The welded structural component has an elongation of not less than 14% in a temperature range of -196℃ to 400℃.

5. The stainless steel welding base material according to claim 1, characterized in that, In the microstructure of the base material, the austenite is distributed in a thin film form between the martensite laths, and / or, nanoscale MC-type carbide or carbonitride precipitates are also dispersed in the martensite matrix, wherein M is at least one of Nb and V.

6. The stainless steel welding base material according to any one of claims 1-5, characterized in that, The chemical composition of the base material further includes, by mass percentage: Mo: 0.5% to 1.5% and / or W: 0.5% to 1.5%.

7. The stainless steel welding base material according to claim 6, characterized in that, The chemical composition of the base material, by mass percentage, is as follows: C 0.05–0.08%, Cr 13.5–15.0%, Ni 5.2–5.7%, Mn ≤0.6%, Si ≤0.6%, Mo 0.8–1.0%, W 0.7–1.0%, V 0.15–0.25%, Nb 0.08–0.13%, Cu ≤0.25%, N 0.03–0.1%, with the balance being Fe and unavoidable impurities.

8. A method for manufacturing a welded structural component, characterized in that, The method uses stainless steel welding base material as described in any one of claims 1-7 and includes the following steps: The base material is welded, and the welded structure is not subjected to overall solution treatment or aging treatment after welding. The weld joint coefficient of the obtained welded structure is not less than 0.

92.

9. The manufacturing method according to claim 8, characterized in that, The welding is performed using laser welding or argon arc welding; The laser welding process parameters are as follows: laser power 1.5-4.0kW, welding speed 0.8-2.5m / min, shielding gas is argon or helium, and gas flow rate 15-25L / min; And / or, the process parameters for the argon arc welding are: welding current 180-300A, welding speed 200-400mm / min, shielding gas is argon, and gas flow rate is 8-15L / min.

10. The application of a stainless steel weld base material as described in any one of claims 1-7 in the manufacture of load-bearing components in the fields of aerospace, marine engineering, or energy and chemical engineering.

Images