Laser filler wire welding method for ultrahigh-strength stainless steel, filler wire and ultrahigh-strength stainless steel welding part

Abstract

The invention discloses a laser filler wire welding method for ultrahigh-strength stainless steel, a welding flux and a welding part, and particularly provides two stainless steel blank workpieces to form an assembly, and filler wires are used for melting the blank assembly and the welding flux to form a welding joint under the action of a laser heat source; the filler welding wire comprises elements such as C, Mn and Si, and the filler welding wire comprises, by weight, 0.01% < = C < = 0.45%, 0.5% < = Mn < = 3.0%, 0.1% < = Si < = 2.0%, 25% < = Cr, 15% < = Ni, 5% < = Mo and the balance Fe and inevitable impurities. The components of the filler wire and the specific proportion of the filler wire added into the welding pool enable the welded joint to meet the conditions that the austenite content in the welded joint is not lower than 70%, and the average microhardness of a melting zone of the welded joint does not exceed 350 HV. The welding joint has ultrahigh strength, and the strength of the welding joint can reach 90% or above of the strength of a base material in a typical low-temperature (-196 DEG C) environment; and the application in environments with different assembly gaps can be met.

Description

Technical Field

[0001] This invention relates to the field of metal material welding technology, specifically to a laser filler wire welding method for ultra-high strength stainless steel, filler wire, and ultra-high strength stainless steel welded components. Background Technology

[0002] Stainless steel, with its excellent corrosion resistance and comprehensive mechanical properties, is widely used in critical fields such as energy, chemical industry, medical, and aerospace. Especially in low-temperature environments, austenitic stainless steel, due to its stable face-centered cubic structure, exhibits excellent toughness and resistance to low-temperature brittleness, making it the preferred material for the storage and transportation of cryogenic media such as liquid oxygen and liquid nitrogen. However, conventional austenitic stainless steel has relatively low strength, often requiring cold work hardening to improve its mechanical properties; for example, cold rolling can significantly improve the material's yield strength and tensile strength. In the aerospace field, rocket propellant tanks, as key components for propellant storage, have extremely high requirements for the comprehensive performance of materials. Cold-rolled austenitic stainless steel, due to its high strength and good low-temperature toughness, is gradually replacing traditional materials in the construction of next-generation lightweight, high-reliability propellant tank structures.

[0003] However, while cold-rolled stainless steel achieves high strength, it also presents new challenges—weld softening. Due to the high dislocation density and lattice distortion introduced by cold work hardening, dynamic recovery, recrystallization, and grain growth occur under the high-temperature thermal cycling of laser welding, leading to a significant decrease in the strength and hardness of the heat-affected zone and weld area. This softening effect makes the welded joint a weak point in the structure, especially in components such as rocket propellant tanks that bear complex loads and extreme temperature conditions. Rocket propellant tanks experience ultra-low temperature (-196°C) service during operation, and the mechanical properties, fatigue resistance, and low-temperature toughness of the welded joints directly determine the structural integrity and service safety of the tank. In particular, the weld structure needs to have high yield strength and tensile strength. Moreover, in actual manufacturing, it is difficult to ensure gapless assembly during workpiece assembly, necessitating high-quality welding of ultra-high-strength stainless steel that can meet the requirements of large assembly gaps.

[0004] The invention patent application No. 201410806107.5 discloses a method for improving the mechanical properties and corrosion resistance of weld zones using ultrasonic and electrical pulse coupling. This method involves introducing pulsed current to the weld surface and the surface of the heat-affected zone of the metal part for electroplastic treatment, while simultaneously using an ultrasonic impact device to sequentially ultrasonically impact the surface of the working area through its high-hardness impact indenter. This method requires very complex equipment and processes, resulting in high costs and low efficiency.

[0005] CN117548807B discloses a method that uses ultrasonic impact equipment during welding to strengthen the welded joint by applying ultrasonic impact immediately after welding. However, this method uses complex ultrasonic equipment, which is inefficient and costly.

[0006] CN 102658416 A discloses a mixed gas shielded welding process for precipitation-strengthened high-strength steel. This process employs mixed gas shielded welding and single / double welding with double-sided forming techniques to weld precipitation-strengthened high-strength steel with a tensile strength of 600 MPa, effectively reducing the softening width of the heat-affected zone. Optimized welding process parameters are used, employing an 80% Ar + 20% CO2 mixed gas, a welding current of 90-140 A, and a heat input of 7-12 kJ / cm. Precipitation strengthening and grain refinement are achieved through Ti(C,N), and the tested weld joint tensile strength reaches 710 MPa. This method primarily reduces the heat-affected zone width through the optimization of various shielding gases and process parameters; however, it is only applicable to 600 MPa grade high-strength steel, limiting its applicability, and the process control is complex.

[0007] CN116529407B discloses a welded joint with excellent performance in low-temperature and room-temperature environments and its preparation method. The weld microstructure is entirely austenitic, but its room-temperature yield strength is only above 400 MPa and its tensile strength is only 660 MPa, indicating relatively low strength. Furthermore, the addition of a large amount of Mn to the weld easily leads to segregation within the weld, resulting in unstable performance.

[0008] CN101495662A discloses an austenitic stainless steel welded joint and material. Addressing the issue of high high-temperature cracking susceptibility in austenitic stainless steel with high phosphorus content, it employs a method of adjusting the elemental ratio in the weld to enhance crack resistance and improve high-temperature strength. The primary focus is on high-temperature creep; however, its mechanical properties at room and low temperatures are not described, and the application is mainly for medium-thick plates.

[0009] CN117583718A discloses a method for obtaining high-strength austenitic stainless steel welded joints using friction stir welding. This method overcomes the problem of softening austenitic stainless steel due to heat by employing friction stir welding, which has a lower heat input. However, friction stir welding requires high assembly quality, has a complex process, and is costly.

[0010] CN118237709A discloses a device and method for overcoming the softening of austenitic stainless steel during welding by utilizing a cooling medium transported during the welding process. However, this method and device are relatively complex and difficult to implement in practical applications.

[0011] CN102728950B discloses a method for improving the performance of laser-welded joints in cryogenic environments by using double-sided laser shock peening in a liquid nitrogen environment. This method involves a complex process, low efficiency, and high cost.

[0012] CN116275690B discloses a method for preparing a welded joint and welding wire for martensitic stainless steel. This method produces a weld structure with austenite + martensite + ferrite, exhibiting comprehensive performance close to the base material and without cracking defects. It is mainly used for repair welding of martensitic stainless steel turbine runners in hydropower stations operating in high-temperature environments. However, the tensile strength of the cladding metal is only 750 MPa, which is relatively low, and it is not suitable for austenitic stainless steel materials.

[0013] As can be seen, current methods for addressing the softening problem of high-strength metal materials during welding mainly involve forced cooling during the welding process, post-weld mechanical treatment, and optimization of process parameters. However, there are currently no welding methods or solders suitable for ultra-high-strength stainless steel that can simultaneously accommodate assembly gaps in ultra-low temperature environments. Furthermore, assembly gaps are unavoidable in actual manufacturing processes, rendering all the above methods inapplicable. Additionally, all the methods mentioned above involve complex processes, high manufacturing costs, and low efficiency. Therefore, there is an urgent need for a simple, low-cost, and highly efficient welding method to overcome the performance degradation of high-strength stainless steel materials under ultra-low temperature service conditions. Summary of the Invention

[0014] The purpose of this invention is to overcome the shortcomings of existing technologies, such as the easy softening of cold-worked ultra-high strength stainless steel welded joints, the weakening of joint mechanical properties under ultra-low temperature service environments, and sensitivity to assembly gaps. This invention provides a laser welding method for manufacturing ultra-high strength stainless steel, a special welding material, and a high-performance welded joint prepared therefrom. This method achieves active design and optimization of the microstructure and mechanical properties of the welded joint by designing and controlling the microstructure ratio of the weld fusion zone. As a result, the welded joint performance strength coefficient remains stable at over 90% at temperatures as low as -196℃, and a reliable connection with good toughness is achieved.

[0015] A laser filler wire welding method for ultra-high strength stainless steel, characterized by comprising the following steps: Provide ultra-high strength stainless steel base material to be welded, wherein the base material is austenitic stainless steel strengthened by cold rolling plastic deformation; The base material is assembled to form an assembly with an assembly gap of no more than 0.5 mm; Laser filler wire welding is used to weld the joint of the assembly to form a welded joint. During the welding process, filler wire with a specific composition is used, and the welding heat input and wire feed speed are controlled so that the portion formed by the melting of the filler wire in the molten pool accounts for 30% to 100% of the total volume of the molten pool. This controls the dilution of the base material and ensures that the fusion zone of the final welded joint meets the following requirements: the average austenite volume content is not less than 70%, and the average microhardness does not exceed 350 HV. The chemical composition of the filler wire, by weight percentage, is: 0.01%≤C≤0.45%, 0.5%≤Mn≤3.0%, 0.1%≤Si≤2.0%, Cr≤25%, Ni≤15%, Mo≤5%, with the balance being Fe and unavoidable impurities.

[0016] Furthermore, the portion of the molten pool formed by the melting of the filler wire accounts for 50% to 80% of the total volume of the molten pool.

[0017] Furthermore, the chemical composition of the filler wire, by weight percentage, satisfies the following: 0.01%≤C≤0.2%, 10%≤Cr≤20%, 2%≤Ni≤10%, Mo≤3%, with the balance being Fe and unavoidable impurities.

[0018] Furthermore, the chemical composition of the fusion zone of the welded joint, by weight percentage, satisfies the following relationship: 0≤500-400×C-30×Mn-18×Cr-12×Ni-7.5×Mo≤100 Where C, Mn, Cr, Ni, and Mo are the weight percentage values ​​of each element.

[0019] Furthermore, the austenite volume content in the mixed microstructure of the molten zone in the welded joint is not less than 80%, and the average hardness HV of the molten zone does not exceed 320HV.

[0020] Furthermore, the chemical composition of the base material, by weight percentage, comprises: 0.05%≤C≤0.3%, 0.5%≤Mn≤3.0%, 0.1%≤Si≤2.0%, 12%≤Cr≤25%, 3%≤Ni≤12%, N≤0.6%, with the balance being iron and unavoidable impurities.

[0021] The present invention also provides a filler wire for implementing the above method, characterized in that its chemical composition by weight percentage is: 0.01%≤C≤0.45%, 0.5%≤Mn≤3.0%, 0.1%≤Si≤2.0%, Cr≤25%, Ni≤15%, Mo≤5%, with the balance being Fe and unavoidable impurities; and the wire is suitable for laser filler wire welding, and by adjusting its addition ratio in the molten pool, the fusion zone of the resulting weld joint can meet the requirements of an austenite content of not less than 70% and a hardness of not more than 350 HV.

[0022] Further, preferably, its composition by weight percentage is: 0.01%≤C≤0.45%, 0.5%≤Mn≤3.0%, 0.1%≤Si≤2.0%, Cr≤25%, Ni≤15%, Mo≤5%, with the balance being Fe and unavoidable impurities.

[0023] Third, the present invention also provides an ultra-high strength stainless steel welded component, characterized in that it is welded by the above-mentioned laser filler wire welding method, and the tensile strength of the welded joint of the welded component at -196°C is not less than 90% of the tensile strength of its base material.

[0024] Furthermore, the average volume content of austenite in the fusion zone of the welded joint is not less than 70%, and the average microhardness does not exceed 350 HV.

[0025] Compared with the prior art, the beneficial effects of the present invention are as follows: By combining solder composition design with molten pool dilution rate control, the microstructure of laser-welded joints of cold-rolled high-strength austenitic stainless steel was designed. This ensures that the weld fusion zone forms a microstructure dominated by stable austenite (≥70%), while controlling the hardness within a reasonable range (≤350HV). This avoids embrittlement caused by excessive martensite transformation, as well as severe softening caused by coarse grains or recrystallization.

[0026] By adjusting the wire feed speed and welding parameters to control the proportion of welding wire in the molten pool (30%-100%), the welding process can flexibly adapt to assembly gap variations of 0 to 0.5 mm. When the gap is large, the amount of welding wire deposited is increased to fill and maintain the weld composition, ensuring the stability and consistency of joint performance under different assembly conditions.

[0027] The welded joint prepared by the method of the present invention has a tensile strength of over 2000 MPa at liquid nitrogen temperature (-196℃), and the strength coefficient (joint strength / base material strength) is stably maintained above 90%. At the same time, it has good elongation at break, achieving a good match between high strength and high toughness, which fully meets the application requirements of extreme environments such as rocket tanks.

[0028] It can be achieved using only conventional laser filler wire welding equipment, along with specific welding wire and an optimized process window, without the need for complex post-weld strengthening equipment (such as ultrasonic or laser shock welding), additional cooling systems, or stringent assembly requirements (such as friction stir welding). This significantly reduces equipment investment, process complexity, and production costs, while improving manufacturing efficiency and facilitating industrial-scale deployment.

[0029] By designing filler solder (welding wire) with specific composition, the element ratio is designed to suppress the formation of excessive hard and brittle martensite in the weld. At the same time, through the precise ratio of austenite stabilizing elements (such as Ni, C, Mn), it is ensured that after the molten pool is mixed with the base material, the final composition can still drive the solidification structure and cooling phase transformation to a high proportion of metastable austenite.

[0030] During the welding process, the ratio (i.e., dilution rate) of the base metal melting amount to the welding wire melting amount is actively adjusted by controlling the matching of laser heat input and wire feed speed. This achieves the desired microstructure (austenite ≥ 70%, hardness ≤ 350 HV) within the "composition window". Attached Figure Description

[0031] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0032] Figure 1 The diagram shown is a schematic of laser welding according to the present invention.

[0033] Figure 2 The image shown is a top view of the weld formed during the welding process of this invention.

[0034] Figure 3 The figure shown is a schematic diagram of the cross-section of the welded joint obtained by the present invention.

[0035] Figure 4 The diagram shown is another schematic diagram of the cross-section of the welded joint obtained by the present invention.

[0036] Figure 5 The image shows the metallographic structure of the welded joint section obtained in Embodiment 1 of the present invention.

[0037] Figure 6 The figure shows the low-temperature tensile failure curve of the welded joint obtained in Example 1 of the present invention.

[0038] Figure 7 The figure shows the low-temperature tensile failure curve of the welded joint obtained in the comparative example.

[0039] Table 1 shows the substrate performance data involved in the embodiments of the present invention.

[0040] Table 2 shows the chemical composition data of the substrates involved in the embodiments of the present invention.

[0041] Table 3 shows the typical chemical composition ratio, austenite content, and average microhardness of the welded joint fusion zone obtained in the embodiments of the present invention.

[0042] Table 4 shows the low-temperature tensile properties of welded joints obtained from other embodiments and comparative examples of the present invention.

[0043] In the attached figures, 111-first high-strength workpiece, 112-second high-strength workpiece, 110-laser beam, 3-welding wire, B-assembly gap, 5-molten pool, 6-weld, B10-width of the first surface side of the molten solidification zone, B11-width of the second surface of the molten solidification zone, t-workpiece thickness, and B2-width of the heat-affected zone. Detailed Implementation

[0044] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the present invention is further described below in conjunction with specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, the accompanying drawings are schematic diagrams; therefore, the apparatus and device of the present invention are not limited by the size or scale of the schematic diagrams.

[0045] It should be noted that in the claims and specification of this patent, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one" does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0046] This invention provides a laser filler wire welding method for manufacturing ultra-high strength stainless steel, comprising the following steps: Base material preparation: A set of ultra-high strength stainless steel billets for welding are provided and assembled into an assembly, wherein the base material of any one of the billets comprises, by weight: 0.05%≤C≤0.3%, 0.5%≤Mn≤3.0%, 0.1%≤Si≤2.0%, 12%≤Cr≤25%, 3%≤Ni≤12%, N≤0.6%, with the balance being iron and impurities generated during manufacturing; The base material is assembled to form a welding assembly, and the assembly gap is allowed to be no more than 0.5 mm; Laser filler wire welding: Laser filler wire welding is used to weld the joints of the components to be welded, forming a welded joint. During the welding process, the melting ratio of the base metal and filler metal in the weld pool is controlled by adjusting the feed rate of the filler metal and the laser welding parameters. A filler metal with a carbon content of 0.01 wt.% to 0.6 wt.% is selected, and its addition ratio in the weld pool is adjusted so that the fusion zone of the final welded joint meets the following conditions: The average austenite content in the molten zone of the resulting welded joint is not less than 70%, and the average microhardness of the molten solidification zone does not exceed 350 HV.

[0047] The stainless steel billet is austenitic stainless steel that has undergone cold rolling and plastic deformation. This type of material, after solution annealing, is strengthened by cold rolling deformation ranging from 10% to 90%. Its microstructure is typical deformed austenite, containing high-density dislocation entanglements, deformation twins, or deformed martensite. Through this work hardening mechanism, its room temperature tensile strength can be significantly increased to over 800 MPa, and even to over 1200 MPa, thus meeting the high strength requirements of structures such as rocket propellant tanks. Commonly used grades include austenitic stainless steels such as 301, 304, 304L, 316, 316L, 321, and 347 series. The mass percentage of elements contained in the billet matrix is: 0.05%≤C≤0.3%, 0.5%≤Mn≤3.0%, 0.1%≤Si≤2.0%, 12%≤Cr≤25%, 3%≤Ni≤12%, N≤0.6%; the balance is iron and impurities generated during manufacturing. Preferably, the C content is 0.05% ≤ C ≤ 0.2%. These stainless steel grades achieve the aforementioned high strength levels in the cold-rolled state, and their inherent austenitic structure ensures excellent toughness even at extremely low temperatures. A typical base material grade is 301, whose elemental composition is mainly as follows: 0.1% ≤ C ≤ 0.2%; 1% ≤ Mn ≤ 2.5%; 0.5% ≤ Si ≤ 1.5%; 16% ≤ Cr ≤ 18%; 6% ≤ Ni ≤ 8%; N ≤ 0.15%; the remainder being Fe and unavoidable impurities. Its thickness is generally between 0.5 and 5.0 mm.

[0048] Figure 1The image shows a weldable assembly formed by butt-jointing the stainless steel blanks 111 and 112. The two blanks are of the same thickness and have an assembly gap B, typically 0 to 0.5 mm. A solder 3 and a laser beam 110 are provided to melt the blanks and solder in a controlled ratio, allowing them to enter the weld pool. After cooling and solidification, a welded joint is formed. Figure 2 The diagram shown is a top view of the weld formed during the welding process, where 5 is the weld pool and 6 is the weld formed after solidification.

[0049] During the welding process, the carbon content in the added filler solder is from 0.01% to 0.6% by weight. The composition and addition ratio of the filler solder are selected into the weld pool so that the fusion zone of the obtained weld joint meets the following conditions: The average austenite content in the molten zone 6 of the obtained welded joint is not less than 70%, and the average microhardness of the molten solidification zone does not exceed 350 HV.

[0050] Generally, the elements in the welded joint 6, by weight percentage, satisfy the following: 0.05%≤C≤0.2%, 0.5%≤Mn≤2.5%, 0.1%≤Si≤2.0%, 5%≤Cr≤25%, 3%≤Ni≤15%. More preferably, 10%≤Cr≤25%, 3%≤Ni≤10%. Generally, the element weight percentages in the welded joint satisfy the following: 0≤500-400*C-30*Mn-18*Cr-12*Ni-7.5*Mo≤100. Preferably, 20≤500-400*C-30*Mn-18*Cr-12*Ni-7.5*Mo≤70.

[0051] The solder addition method can take various forms, including powder or wire feeding. When fed with wire, it is laser wire-filled welding, which is well known in the art. The wire feeding device can be, for example, MAG (metal active gas), MIG (metal inert gas), or TIG (tungsten inert gas). The welding wire can be solid or flux-cored. Adding in the form of flux-cored wire or powder makes it easier to control the composition ratio, which is also well known in the art. The solder addition method can also be a combination of two different devices, for example, using two filler devices to feed different solders, one feeding a solder with a certain composition and the other feeding a solder with a different composition. The combination of the two solders achieves the desired proportion of solder composition in the final molten pool. Alternatively, solder 3 can be synthesized and added through multiple steps or components; for example, solder 3 consists of three independent welding wires, and the average mass composition ratio of the final three solder combinations satisfies the requirements of this invention. In addition, the addition of solder can be done in a multi-step manner, such as by adding it one step at a time, to ensure that the fusion zone of the final weld joint meets the requirements. When it is in the form of welding wire, its diameter is generally between 0.8-1.6 mm, and the wire feed speed is generally between 0.5-4.0 m / min.

[0052] Generally, the laser beam used in laser welding has a wavelength of 0.3-10 μm, especially 0.5-3 μm infrared lasers, and more commonly 900-1100 nm wavelengths, which are common in laser processing. The laser beam is generally emitted by a laser, which can be of various types, such as solid-state lasers or gas lasers. Specifically, it can include fiber lasers, disk lasers, semiconductor diode lasers, and Nd:YAG type solid-state lasers, or CO2 gas lasers. Other types are also possible, as long as they can generate a laser beam and melt the solder and workpiece to form a weld pool. During the welding process, the laser beam can travel along the welding direction in a fixed or synchronous high-speed motion, such as oscillation. The oscillation shape can include circular, zigzag, figure-eight, and infinity shapes, with an oscillation frequency generally between 50-500 Hz and an oscillation amplitude between 0.1-1.5 mm. During the welding process, various single or mixed shielding gases can be added, such as Ar, N2, He, etc., or the welding can be performed without a shielding gas. The power of the laser beam is generally 500W-10KW, preferably 1000W-6KW; and the travel speed of the laser beam relative to the workpiece assembly is generally 1-10m / min, preferably 1.5-8m / min.

[0053] It is worth mentioning that the equivalent circular diameter of the area irradiated by the laser beam on the surface of the assembly is generally 0.2-1.2 mm, preferably 0.3-0.8 mm. To achieve efficient melting, the laser heat source has a high power density, which can be achieved using a single-mode laser with a good beam quality factor or a high-power multimode laser. The energy distribution of the laser beam can be uniform, Gaussian, or other configurations. The shape of the irradiated area on the surface of the assembly by each laser beam can be circular, rectangular, annular, or a combination of straight lines and curves.

[0054] In this invention, the amount of melting can be controlled by adjusting the matching of laser welding speed and welding wire feed speed, as well as controlling the composition of the welding material, ultimately ensuring that the fusion zone of the weld joint meets the requirements. The average hardness H of the fusion zone 6 of the final weld joint is obtained. fz The voltage is not more than 350 HV, preferably not more than 320 HV; and its internal structure includes austenite and martensite, with the austenite ratio not less than 70%, preferably not less than 80%.

[0055] refer to Figure 3 The average width B1 of the upper and lower surfaces of the weld melting zone 6 is generally between 0.5 mm and 4.0 mm, preferably 0.7 ≤ B1 ≤ 3.0 mm; B10 is the width of the initial upper surface of the weld, and B11 is the width of the initial lower surface of the weld. The cross-sectional morphology of the formed initial weld can include various types, including Y-shaped and U-shaped morphologies, and its specific morphology can be adjusted by matching the process parameters of the laser welding process.

[0056] In the solder, 0.01% ≤ C ≤ 0.45%, 0.5% ≤ Mn ≤ 3.0%, 0.1% ≤ Si ≤ 2.0%, Cr ≤ 25%, Ni ≤ 15%, Mo ≤ 5%, with the balance being Fe and unavoidable impurities. Preferably, the solder composition, by weight percentage, is as follows: 0.01%≤C≤0.2%, 0.5%≤Mn≤3.0%, 0.1%≤Si≤2.0%, 10≤Cr≤20%, 2≤Ni≤10%, Mo≤3%, balance is Fe and unavoidable impurities.

[0057] In the welded joint obtained by this invention, there are welding heat-affected zones on both sides of the molten zone 6, such as... Figure 3 In the cross-section of the joint shown, 7 represents the heat-affected zone, with a width of B2. The average width of B2 typically does not exceed 1.5 mm. The elemental content in the solder or joint described in this invention can be obtained by methods well-known in fields such as energy dispersive spectroscopy and optical spectroscopy.

[0058] It is also worth noting that after the weld joint is formed by laser welding, the surface can be smoothed through methods such as thermomechanical processes, including grinding, rolling, polishing, and remelting. Figure 4 The diagram shows a cross-section of the welded joint after the surface has been ground smooth.

[0059] Example 1 Table 1 shows the substrate composition and mechanical properties at different temperatures of the two main materials used in the embodiments of this invention. Table 2 shows the chemical composition of the substrates. The 301-3 / 4H substrate has a room temperature tensile strength exceeding 1200 MPa and a yield strength exceeding 900 MPa, while its low-temperature tensile strength exceeds 2000 MPa and its yield strength exceeds 1000 MPa. Its high-temperature tensile strength exceeds 1000 MPa and its yield strength exceeds 850 MPa. The 304-1 / 4H substrate has a room temperature tensile strength of 890 MPa and a yield strength of 620 MPa.

[0060] Table 1 Table 2 The laser welding equipment used in this embodiment has a focused laser beam spot diameter of 0.62 mm, a power of approximately 2500 W, a welding speed of 3.0 m / min, and an assembly gap of approximately 0.2 mm. It employs a butt welding method using 1.5 mm 301-3 / 4H and 1.5 mm 301-3 / 4H weld joints. N2 is used as the shielding gas during welding. When using N2, the front shielding gas pressure is 0.4-0.7 MPa, and the back shielding gas flow rate is 15-25 L / min. The main components of the welding material are: C: 0.01-0.05%, Si: 0.5-1.0%, Mn: 1.5-2.0%, 17≤Cr≤21%, 7≤Ni≤11%, Mo≤2%, with the balance being Fe and unavoidable impurities. The welding wire diameter is 1.0 mm. The average hardness of the molten zone is approximately 256 HV, and the austenite content in the joint is approximately 95%. Figure 5 Metallographic features of a welded joint section obtained as an example of the invention. Figure 6 The figure shows the stress-displacement curve of the welded joint obtained by the present invention under tensile testing at -196℃. Its tensile strength exceeds 2000 MPa and the fracture displacement value reaches more than 15 mm. It has a very good elongation and a yield strength exceeding 1200 MPa.

[0061] Examples 2-5 In other embodiments of the present invention, the laser welding equipment used has a focused laser beam spot diameter between 0.3-0.98 mm, a power range of 1800-6000 W, a welding speed between 1.2-5.4 m / min, an assembly gap of 0-0.5 mm, and adopts a butt welding method. During welding, no shielding gas or N2 is used. When N2 is used, the front shielding gas pressure is 0.4-0.7 MPa, and the back shielding gas flow rate is 15-25 L / min. The main components of the welding material used are: C: 0.01-0.05, Si: 0.5-1.0, Mn: 1.5-2.0, 10≤Cr≤21, 3≤Ni≤12, Mo≤2, with the balance being Fe and unavoidable impurities. Table 3 shows the weight percentage of characteristic elements, the proportion of austenite, and the average microhardness value in the welded joints obtained in different embodiments of the present invention.

[0062] The average hardness of the molten zone of the joint obtained in all embodiments was less than 350 HV, and the austenite content in the joint was not less than 80%. Table 4 shows the typical mechanical properties of the welded joints obtained in different embodiments of the present invention at low temperature (-196℃). In all embodiments of the present invention, the strength at -196℃ exceeded 90% of the base material.

[0063] Table 3 Table 4 Comparative Example Comparative Examples 1, 2, and 3 represent direct laser welding without filler wire. Table 4 shows the joint performance data for these comparative examples. The results indicate that the tensile strength and elongation of the welded joints are relatively low under different temperature conditions. Figure 7 The figure shows the tensile failure curve of the comparative example at low temperature. It can also be seen from the figure that the comparative example is prone to brittle fracture and has low strength at low temperatures.

[0064] This embodiment provides an advanced welding method for ultra-high strength deformed austenitic stainless steel for low-temperature applications. By precisely designing and selecting a specific composition of weld metal and strictly controlling its melting range with the base metal, a welded joint with excellent comprehensive performance in a service environment of -196°C is successfully achieved. The strength coefficient of the prepared joint remains consistently above 90%, effectively overcoming the industry challenge of softening during welding of cold-worked stainless steel. Furthermore, this method exhibits good process adaptability to assembly gaps, significantly improving its feasibility and reliability in actual manufacturing. Simultaneously, the welded component demonstrates excellent corrosion resistance matching that of the base metal, ensuring the long-term service safety and service life of the structure in harsh environments.

Claims

1. A laser filler wire welding method for ultra-high strength stainless steel, characterized in that, Includes the following steps: Provide ultra-high strength stainless steel base material to be welded, wherein the base material is austenitic stainless steel strengthened by cold rolling plastic deformation; The base material is assembled to form an assembly with an assembly gap of no more than 0.5 mm; Laser filler wire welding is used to weld the joint of the components to form a welded joint. During the welding process, filler wire with a specific composition is used, and the welding heat input and wire feed speed are controlled so that the portion formed by the melting of the filler wire in the molten pool accounts for 30% to 100% of the total volume of the molten pool. This controls the dilution of the base material and ensures that the fusion zone of the final welded joint meets the following requirements: the average austenite volume content is not less than 70%, and the average microhardness does not exceed 350 HV. The chemical composition of the filler wire, by weight percentage, is: 0.01%≤C≤0.45%, 0.5%≤Mn≤3.0%, 0.1%≤Si≤2.0%, Cr≤25%, Ni≤15%, Mo≤5%, with the balance being Fe and unavoidable impurities.

2. The laser filler wire welding method for ultra-high strength stainless steel according to claim 1, characterized in that, The portion of the molten pool formed by the melting of the filler wire accounts for 50% to 80% of the total volume of the molten pool.

3. The laser filler wire welding method for ultra-high strength stainless steel according to claim 1, characterized in that, The chemical composition of the filler wire, by weight percentage, satisfies the following: 0.01%≤C≤0.2%, 10%≤Cr≤20%, 2%≤Ni≤10%, Mo≤3%, with the balance being Fe and unavoidable impurities.

4. The laser filler wire welding method for ultra-high strength stainless steel according to claim 1, characterized in that, The chemical composition of the fusion zone of the welded joint, expressed as a weight percentage, satisfies the following relationship: 0≤500-400×C-30×Mn-18×Cr-12×Ni-7.5×Mo≤100 Where C, Mn, Cr, Ni, and Mo are the weight percentage values ​​of each element.

5. The laser filler wire welding method for ultra-high strength stainless steel according to claim 1, characterized in that, The austenite volume content in the mixed microstructure of the molten zone of the welded joint is not less than 80%, and the average hardness HV of the molten zone does not exceed 320HV.

6. The laser filler wire welding method for ultra-high strength stainless steel according to claim 1, characterized in that, The chemical composition of the base material, by weight percentage, includes: 0.05%≤C≤0.3%, 0.5%≤Mn≤3.0%, 0.1%≤Si≤2.0%, 12%≤Cr≤25%, 3%≤Ni≤12%, N≤0.6%, with the balance being iron and unavoidable impurities.

7. A filler wire for implementing the method according to any one of claims 1-6, characterized in that, Its chemical composition by weight percentage is: 0.01%≤C≤0.45%, 0.5%≤Mn≤3.0%, 0.1%≤Si≤2.0%, Cr≤25%, Ni≤15%, Mo≤5%, with the balance being Fe and unavoidable impurities; and the welding wire is suitable for laser filler wire welding. By adjusting its addition ratio in the molten pool, the fusion zone of the resulting weld joint can meet the requirements of austenite content not less than 70% and hardness not exceeding 350HV.

8. The filler wire according to claim 7, characterized in that, Its composition by weight percentage is: 0.01%≤C≤0.45%, 0.5%≤Mn≤3.0%, 0.1%≤Si≤2.0%, Cr≤25%, Ni≤15%, Mo≤5%, with the balance being Fe and unavoidable impurities.

9. A welded component made of ultra-high strength stainless steel, characterized in that, The welded component is formed by laser wire filler welding method according to any one of claims 1-6, wherein the tensile strength of the welded joint at -196°C is not less than 90% of the tensile strength of its base material.

10. The ultra-high strength stainless steel welded component according to claim 9, characterized in that, The average volume content of austenite in the fusion zone of the welded joint is not less than 70%, and the average microhardness does not exceed 350 HV.

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