Active agent for welding, process for its preparation, use thereof and electron beam active welding method

Abstract

This invention belongs to the field of welding technology, specifically relating to a welding activator, its preparation method, its application, and an electron beam active welding method. The welding activator comprises an active component; the active component comprises the following components by mass percentage: CaF2 30%-45%, NaAlF2... 6 The active agent comprises 10%-20% CaF2, 20%-35% NaAlF6, 10%-20% MoO3, and 1-10% nanomaterials; the particle sizes of CaF2, NaAlF6, Cr2O3, and MoO3 are 1-1000 μm, respectively; the nanomaterials are selected from at least one of nano-TiB2, nano-Y2O3, and nano-TiO2. When used in electron beam active welding of high-carbon, high-chromium stainless steel, the activator in this invention can significantly increase the weld penetration, reduce the weld width, refine the grain size, and improve the joint's resistance to hot cracking, thereby improving the joint's mechanical properties.

Description

Technical Field

[0001] This invention belongs to the field of welding technology, specifically relating to a welding activator, its preparation method and application, and an electron beam active welding method. Background Technology

[0002] High-carbon, high-chromium stainless steel, due to its high carbon content (≥1%) and the addition of various alloying elements such as Cr and Mo, possesses high hardness, high wear resistance, and corrosion resistance. Therefore, it outperforms ordinary stainless steel and is widely used in the manufacture of key components such as high-end bearings and premium knives and scissors. The widespread application of metallic materials relies heavily on welding technology. Compared to ordinary stainless steel, high-carbon, high-chromium stainless steel, with its higher carbon and alloying element content and larger carbon equivalent, exhibits a greater tendency to harden, resulting in poor weldability. Traditional welding methods suitable for ordinary stainless steel involve high heat input, making joints prone to cracking and hindering effective bonding.

[0003] Electron beam welding technology boasts advantages such as high welding speed, high energy density, and precise parameter control. Equipped with high-speed scanning capabilities, it can thoroughly stir the molten pool, resulting in high-quality weld joints, making it an ideal method for joining high-carbon, high-chromium stainless steel. However, electron beam welding of high-carbon, high-chromium stainless steel still faces the following challenges: First, the increasingly sophisticated structural design of key components such as high-end bearings leads to narrower welding areas. Simultaneously, to ensure joint strength, the weld needs to meet the characteristics of narrow weld width and deep penetration. Electron beam welding typically achieves deep penetration by increasing power, but this not only increases equipment costs and energy consumption but also leads to a wider heat-affected zone and coarser grains in high-carbon, high-chromium stainless steel joints, resulting in poor joint performance. Second, the high carbon and chromium content results in a wide solidification range and poor fluidity, easily forming a brittle eutectic structure in the weld center and increasing susceptibility to hot cracking. Rapid cooling also easily induces brittle martensite, increasing the risk of cold cracking. Third, some high vapor pressure elements (such as Cr and Mo) may burn off, affecting the compositional uniformity, corrosion resistance, and wear resistance of the weld metal. In actual production, in order to save costs and improve efficiency, it is necessary to use low power (less than 1000W) to achieve a certain depth of weld while ensuring that the joint meets the requirements of use. However, low power electron beam welding has low production efficiency and cannot meet this requirement.

[0004] Electron beam active welding technology involves applying a layer of activator composed of special chemical substances to the area to be welded before electron beam welding. This significantly alters the surface tension gradient and flow behavior of the molten pool, thereby increasing penetration and improving weld formation without increasing heat input. The challenge of electron beam active welding lies in developing suitable activators for specific materials. Currently, most publicly available activator formulations are for low-carbon steel and austenitic stainless steel; no activators specifically designed for high-carbon, high-chromium martensitic stainless steel and its electron beam welding process window have been reported. General-purpose activators may encounter problems such as incompatibility with the base material composition and exacerbated joint embrittlement when applied to these materials. Furthermore, in the preparation process of the activator, existing technologies mostly employ conventional mechanical mixing methods, such as ball milling. This mixing method easily leads to the agglomeration of nano-functional phases, lattice distortion of low-melting-point components, and the introduction of impurities due to wear, making it difficult to reliably reproduce the designed effects of the activator in actual production.

[0005] CN1442264A discloses an active electron beam welding method and provides an activator for stainless steel welding. The activator consists of SiO2, Cr2O3, NaCl, B2O3, TiO2, and MnO. When using the activator, this literature uses a medium power of 1350W and a low speed of 360mm / min as welding parameters. The weld penetration increases after welding, but the mechanical properties of the joint remain unchanged.

[0006] Therefore, developing an activator specifically for electron beam welding of high-carbon and high-chromium stainless steel that can significantly increase penetration depth and improve joint performance has important application value. Summary of the Invention

[0007] In order to overcome at least one of the technical problems existing in the prior art, one of the objectives of the present invention is to provide a welding activator.

[0008] The second objective of this invention is to provide a method for preparing a welding activator.

[0009] The third objective of this invention is to provide an electron beam active welding method.

[0010] The fourth objective of this invention is to provide the application of the above-mentioned welding activator in the field of steel welding. To achieve the above objectives, the technical solution adopted by the present invention is as follows: The first aspect of the present invention provides a welding activator comprising an active component; said active component comprising the following components in mass percentage: CaF2 30%-45%, NaAlF6 10%-20%, Cr2O3 20%-35%, MoO3 10%-20%, and nanomaterials 1-10%; The particle sizes of CaF2, NaAlF6, Cr2O3, and MoO3 are 1-1000 μm, respectively. The nanomaterial is selected from at least one of nano TiB2, nano Y2O3, and nano TiO2.

[0011] In some embodiments of the present invention, the mass percentage of CaF2 is any value or a range formed by any two of the following: 30%, 32%, 34%, 35%, 36%, 38%, 40%, 42%, 44%, 45%, 46%, 48%, 50%.

[0012] In some embodiments of the present invention, the particle size of CaF2 is any value or a range formed by any two of the following: 1 μm, 10 μm, 20 μm, 40 μm, 50 μm, 60 μm, 80 μm, 100 μm, 110 μm, 120 μm, 140 μm, 150 μm, 160 μm, 180 μm, 200 μm, 210 μm, 220 μm, 240 μm, 250 μm, 260 μm, 280 μm, 300 μm, 500 μm, 700 μm, 800 μm, 900 μm, and 1000 μm; in some embodiments of the present invention, the particle size of CaF2 is 1-300 μm; in some embodiments of the present invention, the particle size of CaF2 is 1-100 μm; in some embodiments of the present invention, the particle size of CaF2 is 50-80 μm.

[0013] In this invention, CaF2 can reduce the surface tension of the molten pool during welding, change the surface tension temperature coefficient to a negative value, promote molten pool convection, and increase the penetration depth. The F ions generated by the decomposition of CaF2 at high temperature have extremely strong deoxygenation and dehydrogenation capabilities, and can combine with [H] and [O] to form HF, CaO, etc., which escape from the molten pool, significantly reducing the hydrogen and oxygen content in the weld. This is crucial for preventing hydrogen-induced delayed cracking and oxide inclusions in high-carbon martensitic steel.

[0014] In some embodiments of the present invention, the mass percentage of NaAlF6 is any value of 10%, 12%, 14%, 15%, 16%, 18%, 20%, or a range formed by any two of these values.

[0015] In some embodiments of the present invention, the particle size of NaAlF6 is any value or a range formed by any two of the following: 1 μm, 10 μm, 20 μm, 40 μm, 50 μm, 60 μm, 80 μm, 100 μm, 110 μm, 120 μm, 140 μm, 150 μm, 160 μm, 180 μm, 200 μm, 210 μm, 220 μm, 240 μm, 250 μm, 260 μm, 280 μm, 300 μm, 500 μm, 700 μm, 800 μm, 900 μm, and 1000 μm; in some embodiments of the present invention, the particle size of NaAlF6 is 1-300 μm; in some embodiments of the present invention, the particle size of NaAlF6 is 1-100 μm; in some embodiments of the present invention, the particle size of NaAlF6 is 40-60 μm.

[0016] In this invention, NaAlF6 can lower the melting point of the activator, promote the flow of the molten pool, and provide sodium ions to increase plasma conductivity.

[0017] In some embodiments of the present invention, the mass percentage of Cr2O3 is any value or a range formed by any two of 20%, 22%, 24%, 25%, 26%, 28%, 30%, 32%, 34%, and 35%.

[0018] In some embodiments of the present invention, the particle size of Cr2O3 is any value or a range formed by any two of the following: 1 μm, 10 μm, 20 μm, 40 μm, 50 μm, 60 μm, 80 μm, 100 μm, 110 μm, 120 μm, 140 μm, 150 μm, 160 μm, 180 μm, 200 μm, 210 μm, 220 μm, 240 μm, 250 μm, 260 μm, 280 μm, 300 μm, 500 μm, 700 μm, 800 μm, 900 μm, and 1000 μm; in some embodiments of the present invention, the particle size of Cr2O3 is 1-300 μm; in some embodiments of the present invention, the particle size of Cr2O3 is 1-100 μm; in some embodiments of the present invention, the particle size of Cr2O3 is 80-100 μm.

[0019] In this invention, Cr2O3 partially decomposes under electron beam bombardment. The surface of the Cr2O3 powder particles undergoes intense thermal decomposition and reduction reactions, providing active Cr atoms to instantly compensate for chromium burn-off during welding, stabilize the chromium equivalent of the weld metal, and prevent a decrease in corrosion resistance due to Cr loss. Cr is a surface-active element that effectively reduces the surface tension of the molten pool, alters the temperature gradient, thermal conductivity, and fluidity within the molten pool, and promotes convection from the edge to the center, i.e., drives centripetal Marangoni convection. This is the core hydrodynamic mechanism for increasing weld penetration.

[0020] In some embodiments of the present invention, the mass percentage of MoO3 is any value or a range formed by any two of 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, and 20%.

[0021] In some embodiments of the present invention, the particle size of MoO3 is any value or a range formed by any two of the following: 1 μm, 10 μm, 20 μm, 40 μm, 50 μm, 60 μm, 80 μm, 100 μm, 110 μm, 120 μm, 140 μm, 150 μm, 160 μm, 180 μm, 200 μm, 210 μm, 220 μm, 240 μm, 250 μm, 260 μm, 280 μm, 300 μm, 500 μm, 700 μm, 800 μm, 900 μm, and 1000 μm; in some embodiments of the present invention, the particle size of MoO3 is 1-300 μm; in some embodiments of the present invention, the particle size of MoO3 is 1-100 μm; in some embodiments of the present invention, the particle size of MoO3 is 80-100 μm.

[0022] In this invention, Mo in MoO3 has a strong affinity for C and is a strong carbide-forming element. When a small amount is incorporated into the weld, it combines with carbon to form fine carbide particles, thus providing dispersion strengthening. Simultaneously, Mo can improve the tempering stability and high-temperature strength of steel, which is beneficial for improving the overall mechanical properties of the joint.

[0023] In some embodiments of the present invention, the mass percentage of the nanomaterial is any value or a range formed by any two of 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%.

[0024] In some embodiments of the present invention, the particle size of the nanomaterial is any value or a range formed by any two of the following: 1 nm, 10 nm, 20 nm, 40 nm, 50 nm, 60 nm, 80 nm, 100 nm, 110 nm, 120 nm, 140 nm, 150 nm, 160 nm, 180 nm, 200 nm, 210 nm, 220 nm, 240 nm, 250 nm, 260 nm, 280 nm, and 300 nm; in some embodiments of the present invention, the particle size of the nanomaterial is 1-100 nm.

[0025] In some embodiments of the present invention, the nanomaterial comprises the following components by mass percentage based on the total mass of the active components: 1%-3% nano TiB2, 1%-3% nano Y2O3, and 1%-4% nano TiO2. (1) The present invention uses nano TiB2, nano TiO2 and nano Y2O3 to form a composite nano system, wherein nano TiB2 and TiO2 refine the grains together, and nano Y2O3 strengthens the grain boundaries. The three nano powders work together to improve the joint's resistance to thermal cracking and toughness, thereby enhancing the joint's performance.

[0026] In some embodiments of the present invention, the particle size of nano-TiB2 is 1~300nm; in some embodiments of the present invention, the particle size of nano-TiB2 is any value or a range formed by any two of the following: 1nm, 10nm, 20nm, 40nm, 50nm, 60nm, 80nm, 100nm, 110nm, 120nm, 140nm, 150nm, 160nm, 180nm, 200nm, 210nm, 220nm, 240nm, 250nm, 260nm, 280nm, 300nm; in some embodiments of the present invention, the particle size of nano-TiB2 is 1-100nm; in some embodiments of the present invention, the particle size of nano-TiB2 is 50-100nm.

[0027] In this invention, the main functions of nano-TiB2 are as a grain refiner and carbide regulator: TiB2 has good lattice matching with ferrite, and acts as a heterogeneous nucleation site in the early stage of weld pool solidification, promoting weld metal nucleation and refining the solidification structure; Ti in TiB2 combines with C to form TiC, reducing the chance of Cr combining with C, thereby inhibiting harmful Cr carbides at grain boundaries. 23 C6 precipitation.

[0028] In some embodiments of the present invention, the particle size of nano-Y2O3 is 1~300nm; in some embodiments of the present invention, the particle size of nano-Y2O3 is any value or a range formed by any two of the following: 1nm, 10nm, 20nm, 40nm, 50nm, 60nm, 80nm, 100nm, 110nm, 120nm, 140nm, 150nm, 160nm, 180nm, 200nm, 210nm, 220nm, 240nm, 250nm, 260nm, 280nm, 300nm; in some embodiments of the present invention, the particle size of nano-Y2O3 is 1-100nm; in some embodiments of the present invention, the particle size of nano-Y2O3 is 30-80nm.

[0029] In some embodiments of this invention, nano-Y₂O₃ serves as a grain boundary strengthening agent. Nano-Y₂O₃ possesses an extremely large specific surface area, and its surface Y atoms exhibit high activity at high temperatures, demonstrating a strong affinity for impurity elements such as O and S. Through solid-state diffusion and chemical reactions, it captures harmful elements dissolved in the metal, forming stable, high-melting-point rare earth oxides (such as Y₂O₂S). During the solidification process in the molten pool, the nanoparticles and rare earth oxides are "pushed" to the grain boundaries. This process not only pins the grain boundaries but also continuously purifies them, reducing the risk of low-melting-point eutectic films caused by impurity elements and improving grain boundary bonding strength, thereby significantly enhancing the joint's resistance to hot cracking.

[0030] In some embodiments of the present invention, the particle size of nano-TiO2 is 1~300nm; in some embodiments of the present invention, the particle size of nano-TiO2 is any value or a range formed by any two of the following: 1nm, 10nm, 20nm, 40nm, 50nm, 60nm, 80nm, 100nm, 110nm, 120nm, 140nm, 150nm, 160nm, 180nm, 200nm, 210nm, 220nm, 240nm, 250nm, 260nm, 280nm, 300nm; in some embodiments of the present invention, the particle size of nano-TiO2 is 1-100nm; in some embodiments of the present invention, the particle size of nano-TiO2 is 50-100nm.

[0031] In this invention, nano-TiO2 has a large specific surface area and extremely high activity. Its efficiency in changing surface tension and increasing melting depth far exceeds that of micron-sized TiO2. Nano-TiO2 can serve as an additional heterogeneous nucleation site, working together with TiB2 to further refine the grains.

[0032] In some embodiments of the present invention, the welding activator further includes a binder component; the mass ratio of the binder component to the active component is 1:(2~5); in some embodiments of the present invention, the mass ratio of the binder component to the active component is any value of 1:2, 1:3, 1:4, 1:5 or a range formed by any two of them.

[0033] In some embodiments of the present invention, the bonding component includes an adhesive and a solvent; the mass of the adhesive is 1 to 10% of the total mass of the bonding component.

[0034] In some embodiments of the present invention, the adhesive component includes at least one of polyvinyl alcohol and sodium silicate.

[0035] In some embodiments of the present invention, the solvent includes at least one selected from water, ethanol, propanol, glycerol, and butanol.

[0036] In some embodiments of the present invention, the mass of the adhesive is any one of 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10% of the total mass of the adhesive components, or a range formed by any two of these values.

[0037] In some embodiments of the present invention, the welding activator is used for welding martensitic stainless steel.

[0038] In some embodiments of the present invention, the martensitic stainless steel contains ≥0.95% carbon by mass and ≥16% chromium by mass.

[0039] In some embodiments of the present invention, the mass percentage of carbon in the martensitic stainless steel is 0.95-1.2%; in some embodiments of the present invention, the mass percentage of carbon in the martensitic stainless steel is any value or a range formed by any two of the following: 0.95%, 0.98%, 1%, 1.01%, 1.02%, 1.03%, 1.04%, 1.05%, 1.06%, 1.07%, 1.08%, 1.09%, 1.1%, 1.11%, 1.12%, 1.13%, 1.14%, 1.15%, 1.16%, 1.17%, 1.18%, 1.19%, 1.2%.

[0040] In some embodiments of the present invention, the mass percentage of chromium in the martensitic stainless steel is 16-18%; in some embodiments of the present invention, the mass percentage of chromium in the martensitic stainless steel is any value or a range formed by any two of the following: 16%, 16.1%, 16.2%, 16.3%, 16.4%, 16.5%, 16.6%, 16.7%, 16.8%, 16.9%, 17%, 17.1%, 17.2%, 17.3%, 17.4%, 17.5%, 17.6%, 17.7%, 17.8%, 17.9%, 18%.

[0041] In some embodiments of the present invention, the viscosity of the welding activator measured at 25°C is 5000-8000 cP; in some embodiments of the present invention, the viscosity of the welding activator measured at 25°C is any value of 5000 cP, 6000 cP, 7000 cP, 8000 cP, or a range formed by any two of these values.

[0042] In some embodiments of the present invention, the welding activator is used for welding using an electron beam active welding method.

[0043] The second aspect of the present invention provides a method for preparing the welding activator described in the first aspect of the present invention, comprising the following steps: CaF2, NaAlF6, Cr2O3, and MoO3 are mixed to obtain micron-sized mixed powder; The nanomaterial is mixed with a portion of the micron-sized mixed powder, and then mixed with the remaining micron-sized mixed powder to obtain an active component. Optionally, the active component is mixed with a binder component to obtain the final product.

[0044] In some embodiments of the present invention, CaF2, NaAlF6, Cr2O3, and MoO3 are all dried before use to remove adsorbed moisture.

[0045] In some embodiments of the present invention, the CaF2 is dried at 130-170°C for 2-6 hours before use to remove adsorbed moisture.

[0046] In some embodiments of the present invention, the NaAlF6 is dried at 130-170°C for 2-6 hours before use to remove adsorbed moisture.

[0047] In some embodiments of the present invention, the Cr2O3 is dried at 130-170°C for 2-6 hours before use to remove adsorbed moisture.

[0048] In some embodiments of the present invention, the MoO3 is dried at 130-170°C for 2-6 hours before use to remove adsorbed moisture.

[0049] In some embodiments of the present invention, the nanomaterial is dried before use to remove surface-adsorbed moisture.

[0050] In some embodiments of the present invention, the drying temperature is 60-100°C.

[0051] In some embodiments of the present invention, the drying process is carried out for 4-10 hours to prevent the agglomeration of nanomaterials.

[0052] In some embodiments of the present invention, the mixing of nanomaterials with a portion of the micron-sized mixed powder is performed using a three-dimensional motion mixer.

[0053] In some embodiments of the present invention, the mixing in the remaining micron-scale mixed powder mixing step is performed using a three-dimensional motion mixer.

[0054] In some embodiments of the present invention, the rotational speed during mixing is 10-100 rpm; in some embodiments of the present invention, the rotational speed during mixing is 20-40 rpm.

[0055] In some embodiments of the present invention, the mixing time is 1-5 hours.

[0056] In some embodiments of the present invention, the mass ratio of a portion of the micron-sized mixed powder to the remaining micron-sized mixed powder is 1:(2~3).

[0057] In some embodiments of the present invention, the step of mixing the active component and the binder component is performed using a planetary mixer.

[0058] In some embodiments of the present invention, the planetary mixer has a revolution speed of 10-100 rpm.

[0059] In some embodiments of the present invention, the planetary mixer has a rotation speed of 800-3000 rpm; in some embodiments of the present invention, the planetary mixer has a rotation speed of 800-1500 rpm.

[0060] In the preparation of the activator, this invention fully considers the special characteristics of multi-component, multi-scale composite powder systems. First, a three-dimensional motion mixer is used to premix the micron-sized powders (i.e., CaF2, NaAlF6, Cr2O3, MoO3) to achieve macroscopic uniformity. Then, the nanomaterials and part of the premixed micron-sized powders are premixed. Finally, the pre-dispersed nanocomposite powders are added to the remaining micron-sized powders and placed back into the three-dimensional motion mixer at a lower speed so that the dispersed nanomaterials can be uniformly adsorbed on the surface and gaps of the micron-sized particles through diffusion, forming a stable multi-scale composite structure.

[0061] A third aspect of the present invention provides an electron beam active welding method, comprising the following steps: The welding activator described in the first aspect of the present invention is applied to the joint of two martensitic stainless steel workpieces, and then the workpieces are welded using an electron beam welding method.

[0062] In some embodiments of the present invention, the welding method includes the following steps: applying the welding activator described in the first aspect of the present invention to the connection position of two martensitic stainless steel workpieces, and then welding them using an electron beam welding method after drying.

[0063] In some embodiments of the present invention, the two martensitic stainless steel workpieces need to be demagnetized before use to ensure that the residual magnetic induction intensity is ≤2Gs. The purpose of the demagnetization treatment is to eliminate the interference of the magnetic field carried by the martensitic stainless steel workpieces on the electron gun emitted by the electron beam welding equipment, and to avoid magnetic deflection. The residual magnetic induction intensity is measured using a digital gaussmeter.

[0064] In some embodiments of the present invention, the two martensitic stainless steel workpieces need to be cleaned after demagnetization.

[0065] In some embodiments of the present invention, the cleaning is performed by using a wire brush to polish away surface impurities and wiping with alcohol to remove surface oil.

[0066] In some embodiments of the present invention, the coating thickness of the welding activator is 0.1-0.15 mm.

[0067] In some embodiments of the present invention, the coating width of the welding activator is 7-10 mm.

[0068] In some embodiments of the present invention, the two martensitic stainless steel workpieces are fixed by a clamp during welding.

[0069] In some embodiments of the present invention, the electron beam welding method has at least one of the following parameters: (a1) The accelerating voltage is 60-70kV; (a2) The intensity of the electron beam current is 8-15 mA; (a3) The welding speed is 1000-1500 mm / min; (a4) Vacuum degree during welding ≤7×10 -5 mbar; (a5) Circular wave scanning is used during welding; (a6) Welding power ≤1000W.

[0070] In some embodiments of the present invention, the electron beam welding method uses surface focusing and a focusing current of 1600-1700mA.

[0071] In some embodiments of the present invention, the accelerating voltage is any value of 60kV, 62kV, 64kV, 65kV, 66kV, 68kV, 70kV, or a range formed by any two of them.

[0072] In some embodiments of the present invention, the intensity of the electron beam current is any value of 8mA, 9mA, 10mA, 11mA, 12mA, 13mA, 14mA, 15mA, or a range formed by any two of these values.

[0073] In some embodiments of the present invention, the welding speed is any value of 1000 mm / min, 1100 mm / min, 1200 mm / min, 1300 mm / min, 1400 mm / min, 1500 mm / min, or a range formed by any two of them.

[0074] In some embodiments of the present invention, the welding power is 800-1000W; in some embodiments of the present invention, the welding power is 900-1000W.

[0075] This invention uses circular waves for scanning to stir the molten pool and promote composition homogenization.

[0076] In some embodiments of the present invention, the focusing current employs surface focusing, and the electron beam spot diameter is 0.18-0.22 mm.

[0077] Using the activator in this invention for electron beam active welding can increase the penetration depth of low-power electron beam welding, achieving a 2-3 times increase in penetration depth at low power levels below 1000kW, thus broadening the application range of low-power electron beam welding.

[0078] The third aspect of the present invention provides the application of the welding activator described in the first aspect of the present invention in the field of steel welding.

[0079] The beneficial effects of this invention are as follows: When the activator in this invention is used for electron beam active welding of high carbon and high chromium stainless steel (i.e., martensitic stainless steel), it can significantly increase the material penetration during low-power electron beam welding, significantly increase the weld depth, and reduce the weld width. It can not only meet the designed weld depth requirements and avoid the generation of defects such as welding cracks, but also inhibit the precipitation of harmful carbides, refine the grains, and improve the joint's resistance to hot cracking, thereby improving the mechanical properties of the joint, improving welding quality and welding efficiency, and reducing welding costs.

[0080] The activator in this invention is specifically designed for high-carbon, high-chromium stainless steel. The activator components are highly compatible with the elements of the high-carbon, high-chromium stainless steel base material, thus avoiding the introduction of foreign elements that could lead to embrittlement.

[0081] The method for preparing the activator in this invention involves premixing micron-sized powders and then mixing them with nanomaterials in batches to achieve physical uniform mixing of multi-scale components, while strictly protecting the original physicochemical characteristics of each component, especially the nano-reinforcing phase and the low-melting-point component. Attached Figure Description

[0082] Figure 1 This is a schematic diagram of high-carbon, high-chromium stainless steel being subjected to electron beam active welding in an embodiment of the present invention, wherein 1 and 2 are the high-carbon, high-chromium stainless steel base material, 3 is the activator, 4 is the electron beam current, and 5 is the welding direction.

[0083] Figure 2 This is a diagram showing the dimensions of the tensile strength test specimen in an embodiment of the present invention.

[0084] Figure 3 This is a diagram showing the dimensions of the flexural strength test specimen in an embodiment of the present invention. Detailed Implementation

[0085] The specific implementation of the present invention will be further described in detail below with reference to the accompanying drawings and examples, but the implementation and protection of the present invention are not limited thereto. It should be noted that any processes not specifically described in detail below are those that can be implemented or understood by those skilled in the art by referring to the prior art. Reagents or instruments used without specified manufacturers are all conventional products that can be purchased commercially.

[0086] The raw material information used in the following examples and comparative examples is as follows: CaF2: Purity ≥99%, particle size 50-80μm; NaAlF6: Purity ≥98%, particle size 40-60μm; Cr2O3: purity ≥99%, particle size 80-100μm; MoO3: Purity ≥99%, particle size 80-100μm; Nano TiB2: purity ≥99%, particle size 50-100nm; Nano Y2O3: purity ≥99%, particle size 30-80nm; Nano TiO2: purity ≥99%, particle size 50-100nm.

[0087] Example 1 This example provides an activator for electron beam welding of high-carbon, high-chromium stainless steel, which is composed of activator powder and polyvinyl alcohol aqueous solution (as binder) in a mass ratio of 3:1.

[0088] The composition and mass percentage of the activator powder are as follows: CaF2 38%, NaAlF6 12%, Cr2O3 28%, MoO3 15%, nano TiB2 2%, nano Y2O3 2%, and nano TiO2 3%. The polyvinyl alcohol aqueous solution is a propylene solution of polyvinyl alcohol (PVA) with a mass percentage of 5%.

[0089] The surfactant in this example was prepared using the following method, with the specific steps as follows: Step 1: Prepare the powder. Based on a total powder mass of 100g, mix the powder according to the following mass ratio: CaF2:NaAlF6:Cr2O3:MoO3:Nano TiB2:Nano Y2O3:Nano TiO2 = 38:12:28:15:2:2:3. Weigh the powder using a high-precision electronic balance as follows: CaF2 38g, NaAlF6 12g, Cr2O3 28g, MoO3 15g, Nano TiB2 2g, Nano Y2O3 2g, Nano TiO2 3g.

[0090] Step 2: Powder pretreatment. Micron-sized CaF2, NaAlF6:Cr2O3:MoO3 powders were vacuum dried at 150℃ for 4 hours to remove adsorbed moisture; nano-TiB2, nano-Y2O3 and nano-TiO2 powders were vacuum dried at 80℃ for 6 hours to prevent nanoparticle agglomeration.

[0091] Step 3: Place the micron-sized CaF2, NaAlF6:Cr2O3:MoO3 powders into a three-dimensional motion mixer and mix at 30 rpm for 2 hours to obtain micron-sized mixed powder.

[0092] Step 4: Graded mixing of micron-sized and nano-sized powders. First, nano-TiB2, nano-Y2O3, and nano-TiO2 are premixed with a portion of the micron-sized mixed powder (30% of the total mass of the micron-sized mixed powder) using ultrasonic-assisted stirring. The ultrasonic power is 300W, and the time is 30 minutes, resulting in a nano premix.

[0093] Step 5: Add the nano premix to the remaining micron-sized mixed powder (accounting for 70% of the total mass of the micron-sized mixed powder), and mix at a low speed of 15 rpm for 4 hours in a three-dimensional motion mixer to ensure uniform dispersion of nanoparticles and obtain activator powder for electron beam welding of high carbon and high chromium stainless steel.

[0094] Step 6: Mix the activator powder with the polyvinyl alcohol aqueous solution (5wt%) binder at a mass ratio of 3:1.

[0095] Step 7: Use a planetary mixer (30 rpm revolution, 1000 rpm rotation) to mix for 30 minutes to obtain a uniform surfactant paste. The paste viscosity should be controlled at 7000 cP (25℃) for easy application.

[0096] Example 2 This example provides an activator for electron beam welding of high-carbon, high-chromium stainless steel, which is composed of activator powder and polyvinyl alcohol aqueous solution (as binder) in a mass ratio of 3:1.

[0097] The composition and mass percentage of the activator powder are as follows: CaF2 45%, NaAlF6 20%, Cr2O3 20%, MoO3 10%, nano TiB2 1%, nano Y2O3 1%, and nano TiO2 3%. The polyvinyl alcohol aqueous solution is an aqueous solution of polyvinyl alcohol (PVA) with a mass percentage of 5%.

[0098] The surfactant in this example was prepared using the following method, with the specific steps as follows: Step 1: Prepare the powder. Based on a total powder mass of 100g, mix the powder according to the following mass ratio: CaF2:NaAlF6:Cr2O3:MoO3:Nano TiB2:Nano Y2O3:Nano TiO2 = 45:20:20:10:1:1:3. Weigh the powder using a high-precision electronic balance as follows: CaF2 45g, NaAlF6 20g, Cr2O3 20g, MoO3 10g, Nano TiB2 1g, Nano Y2O3 1g, Nano TiO2 3g.

[0099] Step 2: Powder pretreatment. Micron-sized CaF2, NaAlF6, Cr2O3, and MoO3 powders were vacuum dried at 150℃ for 4 hours to remove adsorbed moisture; nano-sized TiB2, Y2O3, and TiO2 powders were vacuum dried at 80℃ for 6 hours to prevent nanoparticle agglomeration.

[0100] Step 3: Place the micron-sized CaF2, NaAlF6, Cr2O3, and MoO3 powders into a three-dimensional motion mixer and mix at 30 rpm for 2 hours to obtain micron-sized mixed powder.

[0101] Step 4: Graded mixing of micron-sized and nano-sized powders. First, nano-TiB2, Y2O3, and TiO2 are premixed with a portion of the micron-sized powder (30% of the total mass of the micron-sized powder) using ultrasonic-assisted stirring. The ultrasonic power is 300W, and the time is 30 minutes, resulting in a nano-premix.

[0102] Step 5: Add the nano premix to the remaining micron-sized mixed powder (accounting for 70% of the total mass of the micron-sized mixed powder), and mix at a low speed of 15 rpm for 4 hours in a three-dimensional motion mixer to ensure uniform dispersion of nanoparticles and obtain activator powder for electron beam welding of high carbon and high chromium stainless steel.

[0103] Step 6: Mix the activator powder with the polyvinyl alcohol aqueous solution (5wt%) binder at a mass ratio of 3:1.

[0104] Step 7: Use a planetary mixer (30 rpm revolution, 1000 rpm rotation) to mix for 30 minutes to obtain a uniformly mixed surfactant paste. The paste viscosity should be controlled at 7000 cP (25℃) for easy application.

[0105] Example 3 This example provides an activator for electron beam welding of high-carbon, high-chromium stainless steel, which is composed of activator powder and polyvinyl alcohol aqueous solution (as binder) in a mass ratio of 3:1.

[0106] The composition and mass percentage of the activator powder are as follows: CaF2 30%, NaAlF6 10%, Cr2O3 35%, MoO3 20%, nano TiB2 2%, nano Y2O3 2%, and nano TiO2 1%.

[0107] The polyvinyl alcohol aqueous solution is an aqueous solution of polyvinyl alcohol (PVA) with a mass percentage of 5%.

[0108] The surfactant in this example was prepared using the following method, with the specific steps as follows: Step 1: Prepare the powder. Based on a total powder mass of 100g, mix the powder according to the following mass ratio: CaF2:NaAlF6:Cr2O3:MoO3:Nano TiB2:Nano Y2O3:Nano TiO2 = 30:10:35:20:2:2:1. Weigh the powder using a high-precision electronic balance as follows: CaF2 30g, NaAlF6 10g, Cr2O3 35g, MoO3 20g, Nano TiB2 2g, Nano Y2O3 2g, Nano TiO2 1g.

[0109] Step 2: Powder pretreatment. Micron-sized CaF2:NaAlF6:Cr2O3:MoO3 powders were vacuum dried at 150℃ for 4 hours to remove adsorbed moisture; nano-sized TiB2, Y2O3 and TiO2 powders were vacuum dried at 80℃ for 6 hours to prevent nanoparticle agglomeration.

[0110] Step 3: Place the micron-sized CaF2:NaAlF6:Cr2O3:MoO3 powder into a three-dimensional motion mixer and mix at 30 rpm for 2 hours to obtain micron-sized mixed powder.

[0111] Step 4: Graded mixing of micron-sized and nano-sized powders. First, nano-TiB2, Y2O3, and TiO2 are premixed with a portion of the micron-sized powder (30% of the total mass of the micron-sized powder) using ultrasonic-assisted stirring. The ultrasonic power is 300W, and the time is 30 minutes, resulting in a nano-premix.

[0112] Step 5: Add the nano premix to the remaining micron-sized mixed powder (accounting for 70% of the total mass of the micron-sized mixed powder), and mix at a low speed of 15 rpm for 4 hours in a three-dimensional motion mixer to ensure uniform dispersion of nanoparticles and obtain activator powder for electron beam welding of high carbon and high chromium stainless steel.

[0113] Step 6: Mix the activator powder with the polyvinyl alcohol aqueous solution (5wt%) binder at a mass ratio of 3:1.

[0114] Step 7: Use a planetary mixer (30 rpm revolution, 1000 rpm rotation) to mix for 30 minutes to obtain a uniform surfactant paste. The paste viscosity should be controlled at 7000 cP (25℃) for easy application.

[0115] Comparative Example 1 This example provides an activator for electron beam welding of high-carbon, high-chromium stainless steel, without the addition of CaF2. The activator is composed of activator powder and polyvinyl alcohol aqueous solution (as binder) in a mass ratio of 3:1.

[0116] The composition and mass percentage of the activator powder are as follows: NaAlF 650%, Cr2O3 28%, MoO3 15%, nano TiB 22%, nano Y2O3 2%, and nano TiO 23%.

[0117] The polyvinyl alcohol aqueous solution is an aqueous solution of polyvinyl alcohol (PVA) with a mass percentage of 5%.

[0118] The active agent in this example can be prepared by referring to the preparation method in Example 1.

[0119] Comparative Example 2 This example provides an activator for electron beam welding of high-carbon, high-chromium stainless steel, without the addition of Cr2O3. The activator is composed of activator powder and polyvinyl alcohol aqueous solution (as binder) in a mass ratio of 3:1.

[0120] The composition and mass percentage of the active agent powder are as follows: CaF2 66%, NaAlF6 12%, MoO3 15%, nano TiB2 2%, nano Y2O3 2%, and nano TiO2 3%.

[0121] The polyvinyl alcohol aqueous solution is an aqueous solution of polyvinyl alcohol (PVA) with a mass percentage of 5%.

[0122] The active agent in this example can be prepared by referring to the preparation method in Example 1.

[0123] Comparative Example 3 This example provides an activator for electron beam welding of high-carbon, high-chromium stainless steel, without the addition of MoO3. The activator is composed of activator powder and polyvinyl alcohol aqueous solution (as binder) in a mass ratio of 3:1.

[0124] The composition and mass percentage of the activator powder are as follows: CaF2 53%, NaAlF6 12%, Cr2O3 28%, nano TiB 22%, nano Y2O3 2%, and nano TiO2 3%.

[0125] The polyvinyl alcohol aqueous solution is an aqueous solution of polyvinyl alcohol (PVA) with a mass percentage of 5%.

[0126] The active agent in this example can be prepared by referring to the preparation method in Example 1.

[0127] Application Examples 1-6 The experimental material used in this invention is high-carbon, high-chromium stainless steel, specifically 9Cr18Mo, with dimensions of 100mm × 100mm × 2.5mm. Its chemical composition is shown in Table 1.

[0128] Table 1. Composition of 9Cr18Mo high-carbon, high-chromium stainless steel (unit: wt.%)

[0129] This example provides an electron beam active welding method for high-carbon, high-chromium stainless steel, which uses the activators for high-carbon, high-chromium stainless steel prepared in Examples 1-3 and Comparative Examples 1-3, respectively. The workpiece to be welded is 9Cr18Mo high-carbon, high-chromium stainless steel. The specific welding method is as follows: Step 1: Demagnetization. The 9Cr18Mo high-carbon, high-chromium stainless steel workpiece to be welded is demagnetized in a demagnetizing device until the residual magnetic induction intensity is ≤2Gs. The purpose of this is to eliminate the interference of the magnetic field carried by the stainless steel on the electron gun emitted by the electron beam welding equipment, and to avoid magnetic deflection.

[0130] Step 2: Inspection. Measure the residual magnetic induction intensity of the 9Cr18Mo high-carbon high-chromium stainless steel prepared in Step 1 using a digital gaussmeter. If the residual magnetic induction intensity is ≤2Gs, proceed to the next step; otherwise, continue with Step 1.

[0131] Step 3: Cleaning. Sand the stainless steel surface until you see a metallic sheen, then clean it with acetone to remove surface oil and impurities.

[0132] Step 4: Applying the activator. The activators for high-carbon, high-chromium stainless steel prepared in Examples 1-3 and Comparative Examples 1-3 are applied to the weld bead using a scraper. The coating thickness is controlled to be 0.10 mm, the coating length to be 100 mm, and the coating width to be 8 mm. For details, please refer to... Figure 1 The diagram shows how the agent is coated and then dried to remove water from the surfactant.

[0133] Step 5: Assembly. After waiting 10 minutes for the activator to dry, fix and clamp the high-carbon, high-chromium stainless steel prepared in Step 4 onto a special fixture.

[0134] Step 6: Evacuate the vacuum chamber. Secure the assembled stainless steel assembly from Step 5 onto the vacuum chamber turntable, close the vacuum chamber door, and evacuate the vacuum chamber. Wait until the vacuum level reaches 7 × 10⁻⁶. -5 mbar can be used for electron beam welding.

[0135] Step 7: Welding. After vacuuming as described in Step 6, start the pre-set program for automatic welding. The process parameters are: accelerating voltage 70kV, beam current intensity 12mA, surface focusing, focusing current 1638mA, welding speed 1200mm / min, with circular wave scanning added. The welding process parameters are shown in Process 1 of Table 2.

[0136] Table 2 Welding process parameters

[0137] Application Example 7 The only difference between the electron beam welding method in this example and Application Example 1 is that no active agent is applied in this example, the welding process adopts Process 1 in Table 2, and the remaining steps are the same as in Application Example 1.

[0138] Application Example 8 The only difference between the electron beam welding method in this example and Application Example 7 is that the welding process uses process two in Table 2; all other steps are the same as in Application Example 7. Neither this example nor Application Example 7 involves the application of any activator.

[0139] Performance testing: The high-carbon, high-chromium stainless steel electron beam welding heads obtained in Application Examples 1-8 were wire-cut after welding. The cut samples were then inlaid, sanded, and polished. The polished metallographic samples were then etched with freshly prepared aqua regia for 20 seconds. The weld penetration, weld width, average grain size, and defect conditions were then tested using optical microscopy and scanning electron microscopy, as shown in Table 3 below.

[0140] Table 3. Test results of macroscopic and microscopic dimensions of weld cross-section

[0141] As shown in Table 3, compared with Application Example 7, Application Examples 1-3 of the present invention, by coating with an activator, achieved a weld penetration depth approximately three times greater and a weld width slightly reduced after electron beam welding at 980W power. Compared with Application Example 8, which did not apply an activator and used a higher power (2100W) for welding, Application Examples 1-3 essentially achieved the same weld penetration depth, with a significantly reduced average grain size and no porosity or crack defects at the weld joint. Compared with Application Examples 3-6, Application Examples 1-3 of the present invention, by adjusting the composition of the micron-sized powder, can further improve the weld penetration depth and reduce the weld width.

[0142] The mechanical properties and corrosion resistance of the welded joints obtained in Application Examples 1-8 were tested respectively, and the specific test methods are as follows: Tensile strength: The room temperature tensile properties of the welded joint were tested using a GP-TS2000 M / 300 KN testing machine. The tensile specimen dimensions are as follows: Figure 2 As shown.

[0143] Bending strength: The bending performance of the joint was tested using a Shimadzu AG-IC 100 kN bending tester. The dimensions of the bending specimen are as follows: Figure 3 As shown.

[0144] Weld hardness: Hardness was tested using a Wilson VH1202 Vickers microhardness tester from Buehler, USA, with a 500 g load for 10 seconds.

[0145] Pitting potential: The test was conducted in accordance with GB / T 17899-2023 Corrosion of metals and alloys - Potentiodynamic measurement method for pitting potential of stainless steel in sodium chloride solution.

[0146] The mechanical properties and corrosion resistance of application examples 1-8, measured according to the above testing methods, are shown in Table 4 below.

[0147] Table 4. Test results of mechanical properties and corrosion resistance of welded joints

[0148] As shown in Table 4, compared with Application Examples 4-8, Application Examples 1-3 of the present invention have higher tensile strength, elongation and flexural strength, wherein the tensile strength is 911-1052 MPa, the elongation is 8.5-10%, the flexural strength is 1310-1622 MPa, and the pitting potential is +0.25-0.35 V.

[0149] The embodiments of the present invention have been described in detail above. However, the present invention is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of the present invention. Furthermore, the embodiments of the present invention and the features thereof can be combined with each other unless otherwise specified.

Claims

1. A welding activator, characterized in that: It includes an active component; the active component comprises the following components by mass percentage: CaF2 30%-45%, NaAlF6 10%-20%, Cr2O3 20%-35%, MoO3 10%-20%, and nanomaterials 1-10%; The particle sizes of CaF2, NaAlF6, Cr2O3, and MoO3 are 1-1000 μm, respectively. The nanomaterial is selected from at least one of nano TiB2, nano Y2O3, and nano TiO2.

2. The welding activator according to claim 1, characterized in that: Based on the total mass of the active components, the nanomaterial comprises the following components by mass percentage: nano-TiB2 1%-3%, nano-Y2O3 1%-3%, and nano-TiO2 1%-4%; And / or, the particle sizes of the nano-TiB2, nano-Y2O3, and nano-TiO2 are 10~300nm respectively.

3. The welding activator according to claim 1, characterized in that: The welding activator also includes a binder component; the mass ratio of the binder component to the activator component is 1:(2~5).

4. The welding activator according to claim 1, characterized in that: The bonding component includes an adhesive and a solvent; the mass of the adhesive is 1 to 10% of the total mass of the bonding component.

5. The welding activator according to any one of claims 1-4, characterized in that: The welding activator is used for welding martensitic stainless steel.

6. The welding activator according to claim 5, characterized in that: In the martensitic stainless steel, the mass percentage of carbon is ≥0.95% and the mass percentage of chromium is ≥16%.

7. The welding activator according to claim 5, characterized in that: In the martensitic stainless steel, the mass percentage of carbon is 0.95-1.2%, and the mass percentage of chromium is 16-18%.

8. The welding activator according to any one of claims 1-4, characterized in that: The viscosity of the welding activator measured at 25°C is 5000-8000 cP.

9. The method for preparing the welding activator according to any one of claims 1-8, characterized in that: Includes the following steps: CaF2, NaAlF6, Cr2O3, and MoO3 are mixed to obtain micron-sized mixed powder; The nanomaterial is mixed with a portion of the micron-sized mixed powder, and then mixed with the remaining micron-sized mixed powder to obtain an active component. Optionally, the active component is mixed with a binder component to obtain the final product.

10. An electron beam active welding method, characterized in that: Includes the following steps: The welding activator according to any one of claims 1 to 8 is applied to the connection point of two martensitic stainless steel workpieces, and then the workpieces are welded using an electron beam welding method.

11. The electron beam active welding method according to claim 10, characterized in that: The electron beam welding method has at least one of the following parameters: (a1) The accelerating voltage is 60-70kV; (a2) The intensity of the electron beam current is 8-15 mA; (a3) The welding speed is 1000-1500 mm / min; (a4) Vacuum degree during welding ≤7×10 -5 mbar.

12. The application of the welding activator according to any one of claims 1-8 in the field of steel welding.

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