High-toughness gas-shielded welding wire and preparation method thereof
By constructing a multi-layered composite shell and a fine composite inclusion design, the problem of boron being easily oxidized in high-temperature environments was solved, which improved the tensile strength and low-temperature toughness of the weld metal of the high-strength and tough gas-shielded welding wire, achieving a balance between high strength and low-temperature toughness.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- SICHUAN XIYE NEW MATERIAL
- Filing Date
- 2026-05-12
- Publication Date
- 2026-06-09
AI Technical Summary
In existing high-strength and high-toughness gas-shielded welding wires, boron is easily oxidized and nitrided in high-temperature, high-oxygen, and high-nitrogen environments, resulting in coarse borides that affect the strength and low-temperature toughness of the weld. Furthermore, traditional inclusion control methods are insufficient to effectively improve the weld's resistance to cold cracking.
Using calcium-enriched low-polymer borosilicate as the core, a multi-layered composite shell is constructed through a time-sequence modification method of first hydrolyzing and sealing with a reactive aluminum source and then embedding framework-type alumina nanoparticles. Combined with the preferential distribution of cerium element at defect oxygen and residual hydroxyl sites in the outer layer, fine composite inclusions are formed, which improves the low-temperature toughness and cold crack resistance of the weld.
The synergistic design of stable boron release and fine inclusions improves the tensile strength, low-temperature impact toughness and cold crack resistance of the weld metal, ensuring a balance between high strength and low-temperature toughness in the weld.
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Abstract
Description
Technical Field
[0001] This invention relates to the field of solder technology, specifically to a high-strength and tough gas-shielded welding wire and its preparation method. Background Technology
[0002] High-strength and high-toughness gas-shielded welding wire is in urgent demand in fields such as engineering machinery, marine engineering, and bridge construction. It is especially suitable for multi-layer and multi-pass welding of 960MPa grade low-alloy high-strength steel plates with a thickness of 20mm or more. Such welds not only require a tensile strength of 980MPa or more, but also need to take into account the impact toughness at -40℃ and the stability against cold cracking. Flux-cored welding wire has become an important direction for high-strength steel welding due to its flexible composition control, strong process adaptability, and high deposition efficiency. However, the stable introduction and effective utilization of boron in boron-containing high-strength gas-shielded welding wire remains a key challenge.
[0003] Boron can improve weld strength by inhibiting the formation of proeutectoid ferrite and promoting the transformation of bainite and martensite, and improve low-temperature toughness within a suitable range. However, its effective window is extremely narrow, usually needing to be controlled at 10-30 ppm. Too low a concentration makes it difficult to exert its strengthening and refining effects, while too high a concentration can easily lead to grain boundary embrittlement, microstructure hardening, and decreased resistance to cold cracking. Currently, existing technologies mostly introduce boron by directly adding ferroboron powder, boron alloy powder, or boron-containing mineral powder to the flux core powder. In this method, boron is easily oxidized, nitrided, or forms coarse borates in the high-temperature, high-oxygen, and high-nitrogen environment of the electric arc, resulting in severe burn-off, low utilization rate, and large batch fluctuations. It is difficult for boron to stably enter the austenite grain boundary and agglomerate to exert its effect. Although simply increasing the amount of boron added can compensate for the loss, it can easily lead to an excess of effective boron. Using ordinary borates or simple coating methods also makes it difficult to achieve true delayed release and precise control due to excessively rapid decomposition or insufficient shielding.
[0004] On the other hand, high-strength and high-toughness welds also rely on fine, dispersed inclusions to induce the formation of intragranular needle-like ferrite in order to improve low-temperature toughness. However, the size and distribution of traditional titanium and aluminum oxide inclusions are not easy to control, and coarse inclusions can become crack sources. Therefore, how to achieve delayed release of boron and design it in synergy with the formation of fine composite inclusions is still the core problem that needs to be solved in existing boron-containing high-strength gas-shielded welding wires. Summary of the Invention
[0005] In view of this, the purpose of this invention is to provide a high-strength and tough gas-shielded welding wire and its preparation method, so as to provide a high-strength and tough gas-shielded welding wire that can combine good tensile strength, low-temperature impact toughness and cold crack resistance of weld metal.
[0006] To achieve the above objectives, the present invention provides a high-strength and high-toughness gas-shielded welding wire, comprising a low-carbon steel strip outer sheath and a flux-cored powder filling the outer sheath; the flux-cored powder is prepared from the following raw materials by mass: 613-660 parts of reduced iron powder, 112-122 parts of manganese powder, 152-165 parts of carbonyl nickel powder, 24-28 parts of molybdenum powder, 2-4 parts of titanium powder, 12-16 parts of silicon powder, 3-5 parts of graphite powder, 20-24 parts of rutile titanium dioxide, 12-16 parts of calcium fluoride, 2-4 parts of potassium fluorotitanate, and 1-3 parts of cerium-aluminum co-doped microparticle powder; The preparation steps of the cerium-aluminum co-doped microparticle powder are as follows: (1) After mixing boric acid, fumed silica, calcium carbonate, anhydrous sodium carbonate and magnesium oxide, the mixture is melted at high temperature, cooled rapidly and pulverized to obtain core powder; (2) The kernel powder is subjected to hydroxylation treatment in an acidic water-alcohol mixture to obtain surface-activated kernel powder; (3) The surface-activated core powder is dispersed in isopropanol, and aluminum isopropoxide is added for hydrolysis and polycondensation to obtain a primary aluminum-doped core powder slurry; the pH of the primary aluminum-doped core powder slurry system is adjusted to 6-7, a second aluminum source is added and dispersed evenly, and then aluminum nitrate-colloidal silica dispersion is added to obtain a secondary aluminum-doped core powder slurry; after filtration and calcination, aluminum-doped microparticle powder is obtained. (4) The aluminum-doped microparticle powder is immersed in cerium nitrate solution, filtered and thermally decomposed to obtain cerium-aluminum co-doped microparticle powder.
[0007] Preferably, the reduced iron powder has an iron mass fraction of not less than 98% and a particle size of 100 mesh.
[0008] Preferably, the manganese powder has a particle size of not less than 325 mesh and a mass fraction of not less than 99%.
[0009] Preferably, the mass fraction of the carbonyl nickel powder is not less than 999‰.
[0010] Preferably, the molybdenum powder has a particle size of less than 150 μm and a mass fraction of not less than 999‰.
[0011] Preferably, the titanium powder has a particle size of 300 mesh and an oxygen content of no more than 5‰.
[0012] Preferably, the silicon powder has a particle size of 1 μm and a mass fraction of not less than 999‰.
[0013] Preferably, the graphite powder has a particle size of 8000 mesh and a mass fraction of not less than 999‰.
[0014] Preferably, the low-carbon steel strip is one of Baosteel DC01 or SPCC cold-rolled low-carbon steel strip.
[0015] Preferably, in step (1), boric acid, fumed silica, calcium carbonate, anhydrous sodium carbonate and magnesium oxide are mixed and then melted at high temperature, rapidly cooled and pulverized to obtain core powder.
[0016] Preferably, the weight ratio of boric acid, fumed silica, calcium carbonate, anhydrous sodium carbonate and magnesium oxide in step (1) is 900-950:280-300:220-240:62-72:18-22.
[0017] Preferably, the segmented heat preservation temperatures for high-temperature melting in step (1) are 330-370℃, 830-870℃ and 1130-1170℃, and the heat preservation time for each stage is 50-70 min; the median particle size of the core powder is 800-1200 nm.
[0018] Preferably, in step (2), the kernel powder is stirred in an acidic water-alcohol mixture to hydroxylate its surface, thereby obtaining surface-activated kernel powder.
[0019] Preferably, the pH of the acidic water-alcohol mixture in step (2) is controlled to be 4-5.
[0020] Preferably, the hydroxylation temperature in step (2) is 40-50°C and the time is 20-40 min.
[0021] Preferably, the weight ratio of the surface-activated core powder, aluminum isopropoxide, second aluminum source, aluminum nitrate, and colloidal silica dispersion in step (3) is 480-520:60-68:9-13:1-3:26-34.
[0022] Preferably, in step (3), the second aluminum source is an alumina nano-isopropanol dispersion with a solid content of 20%.
[0023] Preferably, the silica solid content of the colloidal silica dispersion in step (3) is 30%.
[0024] Preferably, the aluminum nitrate in step (3) exists in the form of hydrate.
[0025] Preferably, the hydrolysis-condensation reaction temperature in step (3) is 45-55℃.
[0026] Preferably, the hydrolysate in step (3) is composed of deionized water and glacial acetic acid.
[0027] Preferably, the calcination in step (3) is carried out at 500-540℃ for 80-100 minutes in an air atmosphere, and then at 630-670℃ for 35-45 minutes in an argon atmosphere.
[0028] Preferably, the weight ratio of aluminum-doped microparticle powder to cerium nitrate in step (4) is 480-520:15-21.
[0029] Preferably, the cerium nitrate in step (4) exists in the form of hydrate.
[0030] Preferably, the thermal decomposition temperature in step (4) is 440-460℃ and the holding time is 50-70min.
[0031] Furthermore, the present invention also provides a method for preparing a high-strength and tough gas-shielded welding wire, comprising the following steps: Reduced iron powder, manganese powder, carbonyl nickel powder, molybdenum powder, titanium powder, silicon powder, graphite powder, rutile titanium dioxide, calcium fluoride, potassium fluorotitanate, and the cerium-aluminum co-doped microparticle powder are mechanically mixed to obtain a flux core powder. The flux core powder is filled into a U-shaped groove of a low-carbon steel strip, closed into a tube blank, and drawn in multiple passes to obtain a high-strength and tough gas-shielded welding wire.
[0032] Preferably, the low-carbon steel strip has a thickness of 0.33-0.37 mm and a width of 10.3-10.7 mm.
[0033] Preferably, the core filling rate is 15%-17%.
[0034] Preferably, the diameter of the welding wire is 1.15-1.25 mm.
[0035] Preferably, the single-pass surface reduction rate during the drawing process is controlled below 15%; the welding wire is vacuum dried at 200-240℃ for 2-3 hours.
[0036] The beneficial effects of this invention are: This invention uses calcium-enriched low-polymer borosilicate as the core and constructs a multilayer composite shell with high high-temperature stability through a time-sequential modification method of first hydrolyzing and sealing with a reactive aluminum source and then embedding framework-type alumina nanoparticles. This shell can effectively shield the boron source in the early stage of arc droplet formation, reducing the oxidation, nitridation, and formation of coarse borosilicates of boron in high-temperature, high-oxygen, and nitrogen-containing environments, ensuring high strength while also taking into account low-temperature toughness.
[0037] Before introducing colloidal silica into the main system, this invention first forms a pre-bridging structure with aluminum nitrate nonahydrate that has an aluminum-silicon bridging tendency, and then combines it with framework-type alumina nanoparticles to improve the continuity and integrity of the shell. Furthermore, cerium is preferentially distributed at the defect oxygen and residual hydroxyl sites in the outer layer to form a cerium end-capping layer. During the welding process, this structure is conducive to the generation of fine and dispersed cerium-aluminum-silicon-titanium-oxygen composite inclusions, thereby improving the impact toughness of the weld metal at -40°C.
[0038] In this invention, after the aluminum isopropoxide is hydrolyzed, an aluminum oxide boron and aluminum oxide silicon chemical sealing layer is preferentially formed on the core surface. The subsequently introduced alumina nanoparticles then form a physical reinforcing framework, creating a layered synergistic structure. This structure not only improves the integrity and erosion resistance of the shell during the high-temperature droplet stage, but also reduces the problem of easy cracking and peeling of a single sealing layer. Therefore, it can more effectively improve the boron retention rate and release stability. Detailed Implementation
[0039] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments.
[0040] Raw material source, model and parameters: Boric acid: Aladdin, B431198 boric acid, mass fraction not less than 995‰; Fumed silica: Aladdin, S104587 hydrophilic fumed silica, particle size 7-40nm, specific surface area 200m² 2 / g; Calcium carbonate: Aladdin, C111986 calcium carbonate, mass fraction not less than 995‰; Anhydrous sodium carbonate: Aladdin, S432764 anhydrous sodium carbonate; Magnesium oxide: Aladdin, M489765 magnesium oxide, particle size 100-300nm, mass fraction not less than 999‰; Aluminum isopropoxide: Maclean, A800380 aluminum isopropoxide, mass fraction not less than 998‰; Aluminum oxide nano-isopropanol dispersion: Maclean, A801482 aluminum oxide nano-isopropanol dispersion, alumina particle size 30nm, solid content 20%; Aluminum nitrate nonahydrate: Maclean, A800886 aluminum nitrate nonahydrate, reagent grade, mass fraction not less than 990‰; Colloidal silica aqueous dispersion: Sigma-Aldrich, 420824, LUDOXHS-30 colloidal silica aqueous dispersion, silica solid content 30%, specific surface area 220m² 2 / g; Cerium nitrate hexahydrate: Maclean, C804686 Cerium nitrate hexahydrate, mass fraction not less than 995‰; Reduced iron powder: Maclean, R812026 Reduced iron powder, iron mass fraction not less than 98%, particle size 100 mesh; Manganese powder: Sigma-Aldrich, 266132 Manganese powder, particle size not less than 325 mesh, mass fraction not less than 99%; Carbonyl nickel powder: Maclean, C913585 Carbonyl nickel powder, mass fraction not less than 999‰; Molybdenum powder: Sigma-Aldrich 266892 molybdenum powder, particle size less than 150μm, mass fraction not less than 999‰; Titanium powder: Maclean, T675401 titanium powder, particle size 300 mesh, oxygen content not more than 5‰; Silicon powder: Aladdin, S130845 silicon powder, particle size 1μm, mass fraction not less than 999‰; Graphite powder: Maclean, G810365 graphite powder, particle size 8000 mesh, mass fraction not less than 999‰; Low carbon steel strip: Baosteel DC01.
[0041] Example 1: A method for preparing a high-strength and tough gas-shielded welding wire, the specific steps of which are as follows: S1: Weigh 924g boric acid, 290g fumed silica, 232g calcium carbonate, 68g anhydrous sodium carbonate, and 20g magnesium oxide. Place the above raw materials in a mixing container and dry mix for 30min. Then, load the mixture into an alumina crucible, heat it to 350℃ at 5℃ / min and hold for 60min. Continue to heat it to 850℃ at 5℃ / min and hold for 60min, then heat it to 1150℃ and hold for 60min to obtain a homogeneous glass melt. Pour the glass melt onto a pre-cooled copper plate and quickly press it into a sheet using another pre-cooled copper plate to obtain a borosilicate glass sheet. Dry the borosilicate glass sheet at 120℃ for 2h, then pulverize and air classify it to obtain a core powder with a median particle size of 800-1200nm and 90% of the particles having a particle size less than 1800nm. S2: Weigh 800g of kernel powder and add it to a mixture of 3200g of anhydrous ethanol and 800g of deionized water. The stirring speed is controlled at 300r / min. Add glacial acetic acid to control the pH of the system to 4-5 and stir at 45℃ for 30min. Then filter and dry at 120℃ for 2h to obtain surface-activated kernel powder. S3: Weigh 500g of surface-activated core powder and add it to 3000g of isopropanol. Stir for 20min under dry nitrogen protection to obtain an isopropanol dispersion of core powder. Separately, add 64g of aluminum isopropoxide to 640g of isopropanol and stir until an aluminum isopropoxide solution is formed. Add the aluminum isopropoxide solution dropwise to the isopropanol dispersion of core powder at 50℃ for 60min. After the dropwise addition is complete, add the hydrolysate consisting of 72g of deionized water and 10g of glacial acetic acid dropwise to the reaction system within 60min. Continue to keep warm and stir for 40min to obtain a primary aluminum-doped core powder slurry. S4: Add ammonia to the primary aluminum-doped core powder slurry obtained in S3 to adjust the pH of the system to 6-7; then add 11g of alumina nano-isopropanol dispersion and continue stirring for 15min; separately take 30g of colloidal silica aqueous dispersion, 2g of aluminum nitrate nonahydrate and 20g of deionized water, stir at 25℃ for 10min, then add ammonia to adjust the pH of the premix to 5-6, and continue stirring for 15min to obtain aluminum nitrate-colloidal silica dispersion; add the aluminum nitrate-colloidal silica dispersion dropwise to the above system within 20min, and control the pH of the system to 6-7 during the dropwise addition. After the dropwise addition is completed, continue stirring for 30min to obtain secondary aluminum-doped core powder slurry; S5: The secondary aluminum-doped core powder slurry obtained in S4 was filtered and quickly washed once with a mixture of 500g anhydrous ethanol and 125g deionized water; then dried at 90℃ for 6h; the dried powder was heated to 520℃ at 3℃ / min and held for 90min under air atmosphere and ventilation exhaust conditions; then heated to 650℃ at 3℃ / min and held for 40min under argon atmosphere; after cooling, it was lightly ground and passed through an 800-mesh sieve to obtain aluminum-doped microparticle powder; S6: Weigh 500g of aluminum-doped microparticle powder and add it to a mixture of 3500g of anhydrous ethanol and 900g of deionized water. Stir at 300r / min for 20min. Add 18g of cerium nitrate hexahydrate and continue stirring for 10min. Slowly add ammonia water to control the pH of the system to 5-6 and stir at 35℃ for 30min. Then filter, dry at 90℃ for 4h, and then keep warm at 450℃ for 60min to obtain cerium-aluminum co-doped microparticle powder. S7: Weigh 638g of reduced iron powder, 116g of manganese powder, 158g of carbonyl nickel powder, 26g of molybdenum powder, 3g of titanium powder, 14g of silicon powder, 4g of graphite powder, 22g of rutile titanium dioxide, 14g of calcium fluoride, 3g of potassium fluorotitanate, and 2g of cerium-aluminum co-doped microparticle powder; premix the reduced iron powder and cerium-aluminum co-doped microparticle powder for 3 minutes, then mix the remaining reduced iron powder, manganese powder, carbonyl nickel powder, molybdenum powder, titanium powder, silicon powder, graphite powder, rutile titanium dioxide, calcium fluoride, and potassium fluorotitanate for 20 minutes to obtain the core powder; S8: A low-carbon steel strip with a thickness of 0.35 mm and a width of 10.5 mm is used as the outer skin. The low-carbon steel strip is rolled into a U-shaped groove after conventional alkaline washing, water washing and drying at 120℃. The core powder is continuously filled into the U-shaped groove, and the filling rate is controlled at 16%. Then it is closed into a tube blank and drawn in multiple passes to obtain a high-strength and tough gas-shielded welding wire with a diameter of 1200 μm. During the drawing process, the single-pass surface reduction rate is controlled below 15%. After the drawing is completed, the high-strength and tough gas-shielded welding wire is vacuum dried at 220℃ for 2 hours and then wound up and sealed.
[0042] Example 2: A method for preparing a high-strength and tough gas-shielded welding wire, the specific steps of which are as follows: S1: Weigh 900g boric acid, 280g fumed silica, 220g calcium carbonate, 62g anhydrous sodium carbonate, and 18g magnesium oxide. Place the above raw materials in a conventional mixing container and dry mix for 25min. Then, load the mixture into an alumina crucible, heat it to 330℃ at 4℃ / min and hold for 50min. Continue to heat it to 830℃ at 4℃ / min and hold for 50min. Then heat it to 1130℃ and hold for 50min to obtain a homogeneous glass melt. Pour the glass melt onto a pre-cooled copper plate and quickly press it into a sheet using another pre-cooled copper plate to obtain a borosilicate glass sheet. Dry the borosilicate glass sheet at 110℃ for 2h, then pulverize and air classify it to obtain a core powder with a median particle size of 800-1200nm and 90% of the particles having a particle size less than 1800nm. S2: Weigh 780g of kernel powder and add it to a mixture of 3000g of anhydrous ethanol and 750g of deionized water. The stirring speed is controlled at 250r / min. Add glacial acetic acid to control the pH of the system to 4-5 and stir at 40℃ for 20min. Then filter and dry at 110℃ for 2h to obtain surface-activated kernel powder. S3: Weigh 480g of surface-activated core powder and add it to 2800g of isopropanol. Stir for 15min under dry nitrogen protection to obtain an isopropanol dispersion of core powder. Separately, add 60g of aluminum isopropoxide to 600g of isopropanol and stir until an aluminum isopropoxide solution is formed. Add the aluminum isopropoxide solution dropwise to the isopropanol dispersion of core powder at 45℃ for 50min. After the dropwise addition is complete, add the hydrolysate consisting of 65g of deionized water and 8g of glacial acetic acid dropwise to the reaction system within 50min. Continue to keep warm and stir for 35min to obtain a primary aluminum-doped core powder slurry. S4: Add ammonia to the primary aluminum-doped core powder slurry obtained in S3 to adjust the pH of the system to 6-7; then add 9g of alumina nano-isopropanol dispersion and continue stirring for 10min; separately take 26g of colloidal silica aqueous dispersion, 1g of aluminum nitrate nonahydrate and 18g of deionized water, stir at 20℃ for 8min, then add ammonia to adjust the pH of the premix to 5-6, and continue stirring for 10min to obtain aluminum nitrate-colloidal silica dispersion; add the aluminum nitrate-colloidal silica dispersion dropwise to the above system within 15min, and control the pH of the system to 6-7 during the dropwise addition. After the dropwise addition is completed, continue stirring for 25min to obtain secondary aluminum-doped core powder slurry; S5: The secondary aluminum-doped core powder slurry obtained in S4 was filtered and quickly washed once with a mixture of 450g anhydrous ethanol and 110g deionized water; then dried at 85℃ for 5h; the dried powder was heated to 500℃ at 2℃ / min and held for 80min under air atmosphere and ventilation exhaust conditions; then heated to 630℃ at 2℃ / min and held for 35min under argon atmosphere; after cooling, it was lightly ground and passed through an 800-mesh sieve to obtain aluminum-doped microparticle powder. S6: Weigh 480g of aluminum-doped microparticle powder and add it to a mixture of 3400g of anhydrous ethanol and 850g of deionized water. Stir at 250r / min for 15min. Add 15g of cerium nitrate hexahydrate and continue stirring for 8min. Slowly add ammonia water to control the pH of the system to 5-6 and stir at 30℃ for 25min. Then filter, dry at 85℃ for 3h, and then keep warm at 440℃ for 50min to obtain cerium-aluminum co-doped microparticle powder. S7: Weigh 613g of reduced iron powder, 112g of manganese powder, 152g of carbonyl nickel powder, 24g of molybdenum powder, 2g of titanium powder, 12g of silicon powder, 3g of graphite powder, 20g of rutile titanium dioxide, 12g of calcium fluoride, 2g of potassium fluorotitanate and 1g of cerium-aluminum co-doped microparticle powder. Premix the reduced iron powder and cerium-aluminum co-doped microparticle powder for 2 minutes, and then mix the remaining reduced iron powder, manganese powder, carbonyl nickel powder, molybdenum powder, titanium powder, silicon powder, graphite powder, rutile titanium dioxide, calcium fluoride and potassium fluorotitanate for 18 minutes to obtain the core powder. S8: A low-carbon steel strip with a thickness of 0.33 mm and a width of 10.3 mm is used as the outer skin. The low-carbon steel strip is rolled into a U-shaped groove after conventional alkaline washing, water washing and drying at 110℃. The core powder is continuously filled into the U-shaped groove, and the filling rate is controlled at 15%. Then it is closed into a tube blank and drawn in multiple passes to obtain a high-strength and tough gas-shielded welding wire with a diameter of 1.15 mm. During the drawing process, the single-pass surface reduction rate is controlled below 15%. After the drawing is completed, the high-strength and tough gas-shielded welding wire is vacuum dried at 200℃ for 2 hours and then wound up and sealed.
[0043] Example 3: A method for preparing a high-strength and tough gas-shielded welding wire, the specific steps of which are as follows: S1: Weigh 950g boric acid, 300g fumed silica, 240g calcium carbonate, 72g anhydrous sodium carbonate, and 22g magnesium oxide. Place the above raw materials in a conventional mixing container and dry mix for 35min. Then, load the mixture into an alumina crucible and heat it to 370℃ at 6℃ / min and hold for 70min. Continue to heat it to 870℃ at 6℃ / min and hold for 70min. Then heat it to 1170℃ and hold for 70min to obtain a homogeneous glass melt. Pour the glass melt onto a pre-cooled copper plate and quickly press it into a sheet using another pre-cooled copper plate to obtain a borosilicate glass sheet. Dry the borosilicate glass sheet at 130℃ for 3h, then pulverize and air classify it to obtain a core powder with a median particle size of 800-1200nm and 90% of the particles having a particle size less than 1800nm. S2: Weigh 820g of kernel powder and add it to a mixture of 3400g of anhydrous ethanol and 850g of deionized water. The stirring speed is controlled at 350r / min. Add glacial acetic acid to control the pH of the system to 4-5 and stir at 50℃ for 40min. Then filter and dry at 130℃ for 3h to obtain surface-activated kernel powder. S3: Weigh 520g of surface-activated core powder and add it to 3200g of isopropanol. Stir for 25min under dry nitrogen protection to obtain an isopropanol dispersion of core powder. Separately, add 68g of aluminum isopropoxide to 680g of isopropanol and stir until an aluminum isopropoxide solution is formed. Add the aluminum isopropoxide solution dropwise to the isopropanol dispersion of core powder at 55℃ for 70min. After the dropwise addition is complete, add the hydrolysate consisting of 80g of deionized water and 12g of glacial acetic acid dropwise to the reaction system within 70min. Continue to keep warm and stir for 50min to obtain a primary aluminum-doped core powder slurry. S4: Add ammonia to the primary aluminum-doped core powder slurry obtained in S3 to adjust the pH of the system to 6-7; then add 13g of alumina nano-isopropanol dispersion and continue stirring for 20min; separately take 34g of colloidal silica aqueous dispersion, 3g of aluminum nitrate nonahydrate and 24g of deionized water, stir at 30℃ for 15min, then add ammonia to adjust the pH of the premix to 5-6, and continue stirring for 20min to obtain aluminum nitrate-colloidal silica dispersion; add the aluminum nitrate-colloidal silica dispersion dropwise to the above system within 25min, and control the pH of the system to 6-7 during the dropwise addition. After the dropwise addition is completed, continue stirring for 40min to obtain secondary aluminum-doped core powder slurry; S5: The secondary aluminum-doped core powder slurry obtained in S4 was filtered and quickly washed once with a mixture of 550g anhydrous ethanol and 140g deionized water; then dried at 95℃ for 7h; the dried powder was heated to 540℃ at 4℃ / min and held for 100min under air atmosphere and ventilation exhaust conditions; then heated to 670℃ at 4℃ / min and held for 45min under argon atmosphere; after cooling, it was lightly ground and passed through an 800-mesh sieve to obtain aluminum-doped microparticle powder. S6: Weigh 520g of aluminum-doped microparticle powder and add it to a mixture of 3700g of anhydrous ethanol and 950g of deionized water. Stir at 350r / min for 25min. Add 21g of cerium nitrate hexahydrate and continue stirring for 15min. Slowly add ammonia water to control the pH of the system to 5-6 and stir at 40℃ for 40min. Then filter, dry at 95℃ for 5h, and then keep warm at 460℃ for 70min to obtain cerium-aluminum co-doped microparticle powder. S7: Weigh 660g reduced iron powder, 122g manganese powder, 165g nickel carbonyl powder, 28g molybdenum powder, 4g titanium powder, 16g silicon powder, 5g graphite powder, 24g rutile titanium dioxide, 16g calcium fluoride, 4g potassium fluorotitanate and 3g cerium-aluminum co-doped microparticle powder; premix the reduced iron powder and cerium-aluminum co-doped microparticle powder for 4min, then mix the remaining reduced iron powder, manganese powder, nickel carbonyl powder, molybdenum powder, titanium powder, silicon powder, graphite powder, rutile titanium dioxide, calcium fluoride and potassium fluorotitanate for 25min to obtain the core powder; S8: A low-carbon steel strip with a thickness of 0.37 mm and a width of 10.7 mm is used as the outer skin. The low-carbon steel strip is rolled into a U-shaped groove after conventional alkaline washing, water washing and drying at 130℃. The core powder is continuously filled into the U-shaped groove, and the filling rate is controlled at 17%. Then it is closed into a tube blank and drawn in multiple passes to obtain a high-strength and tough gas-shielded welding wire with a diameter of 1.25 mm. The single-pass surface reduction rate is controlled below 15% during the drawing process. After the drawing is completed, the high-strength and tough gas-shielded welding wire is vacuum dried at 240℃ for 3 hours and then wound up and sealed.
[0044] Comparative Example 1: The difference from Example 1 is that in the preparation step of the core powder, the cerium-aluminum co-doped microparticle powder is replaced by an equal amount of the core powder obtained in S1; the other conditions are the same as in Example 1.
[0045] Comparative Example 2: The difference from Example 1 is that aluminum isopropoxide solution is not added in S3, but instead an equal amount of aluminum oxide nano-isopropoxide dispersion is added. The other conditions are the same as in Example 1.
[0046] Comparative Example 3: The difference from Example 1 is that in S3, alumina nano-isopropanol dispersion was first added to the surface-activated core powder isopropanol dispersion and stirred, and then an aluminum isopropoxide solution formed by aluminum isopropoxide and isopropanol was added dropwise. The other conditions were the same as in Example 1.
[0047] Comparative Example 4: The difference from Example 1 is that in S3, the alumina nano-isopropanol dispersion and the aluminum isopropoxide solution were mixed together and added, while the other conditions were the same as in Example 1.
[0048] Comparative Example 5: The difference from Example 1 is that in S4, aluminum nitrate nonahydrate is not added to the colloidal silica aqueous dispersion. Instead, aluminum nitrate nonahydrate and alumina nano isopropanol dispersion are mixed and used. The other conditions are the same as in Example 1.
[0049] Comparative Example 6: The difference from Example 1 is that in S4, the amounts of colloidal silica aqueous dispersion, aluminum nitrate nonahydrate, and deionized water are kept unchanged, but the pre-bridged colloidal silica with hydrolyzed aluminum is not prepared in advance. Instead, aluminum nitrate nonahydrate and deionized water are added directly to the core powder slurry that already contains alumina nanoparticles, and then the colloidal silica aqueous dispersion is added directly. The other conditions are the same as in Example 1.
[0050] Comparative Example 7: The difference from Example 1 is that the addition of cerium nitrate hexahydrate was omitted in S6, while the other conditions were the same as in Example 1.
[0051] Performance testing The high-strength and high-toughness gas-shielded welding wires prepared in Examples 1-3 and Comparative Examples 1-7 were numbered E1, E2, E3, D1, D2, D3, D4, D5, D6, and D7, respectively. Each sample was prepared using a 20mm thick 960MPa low-alloy high-strength steel plate to create a weld metal test plate. The mechanical properties of the weld metal were prepared according to GB / T 25774.1-2023. The welding shielding gas was a mixture of 80% argon and 20% carbon dioxide, with a gas flow rate of 18L / min. The welding current was 270A, the arc voltage was 29V, the welding speed was 32cm / min, and the interpass temperature was controlled at 140℃. After welding, the test plates were allowed to cool naturally at room temperature for 24 hours. Particle size distribution: Take 0.20 g of the microparticle powder obtained from each example and comparative example, add it to 100 mL of anhydrous ethanol, disperse it by ultrasonication for 5 min, and then test the particle size distribution by laser diffraction method as specified in GB / T 19077-2024; each sample is tested in parallel 3 times, and the median particle size is recorded; High-temperature thermal shock boron retention rate test: 10g of the particulate powder obtained from each example and comparative example was placed in an argon-protected high-temperature furnace for three sets of thermal shock treatments: the first set was held at 1600℃ for 5s, the second set was held at 1450℃ for 20s, and the third set was held at 1350℃ for 60s. After alkaline fusion digestion, the boron content was determined by inductively coupled plasma atomic emission spectrometry according to GB / T 23942-2009, and the boron retention rate was calculated as (mass of boron in the particulates after thermal shock / mass of boron in the particulates before thermal shock) × 100%. Tensile properties test of weld metal: Prepare tensile specimens of weld metal according to GB / T 25774.1-2023, and perform longitudinal tensile tests on weld metal according to GB / T 2652-2022. The tensile tests are carried out at room temperature, and the loading rate is performed according to the standard. Three specimens are tested for each sample, and the tensile strength, yield strength and elongation after fracture are recorded. The average value of the results is taken. Low-temperature impact performance test: The fused metal impact specimens were prepared according to GB / T 25774.1-2023 and the impact test was carried out according to GB / T2650-2022. The specimens were made with a V-shaped notch, and the notch was located in the center of the fused metal. The test temperature was -40℃. Three specimens were tested for each sample. The Charpy impact absorption energy was recorded and the average value was taken. Composite inclusion testing: The morphology of inclusions was analyzed by scanning electron microscopy and energy dispersive spectroscopy. Quantitative analysis of inclusions was performed according to GB / T 17359-2023. At least 100 inclusions were counted for each sample, and the average particle size of the inclusions was recorded. The test results are shown in Table 1.
[0052] Table 1 Performance Test Results
[0053] Data analysis: As can be seen from the data in Table 1, the high-strength and tough gas-shielded welding wire prepared by the present invention maintains high weld metal strength while exhibiting superior low-temperature impact performance and fineness of composite inclusions.
[0054] As can be seen from the data in Table 1 for Example 1 and Comparative Example 1, when only the core powder is used, the effective boron retention capacity and low-temperature toughness of the deposited metal are significantly reduced. This is because the core lacks the subsequent aluminum isopropoxide sealing layer, alumina nanoparticle reinforcement structure, and cerium outer layer end-capping effect, causing boron to be easily consumed by oxygen and nitrogen in the early stage of arc droplet formation, making it difficult for it to play a stable role in the subsequent microstructure transformation process.
[0055] As can be seen from the data in Table 1 for Example 1 and Comparative Examples 2, 3, and 4, when the addition methods of reactive aluminum source and framework alumina nanoparticles are changed, the low-temperature impact performance of the weld metal and the refinement effect of composite inclusions are both lower than those in Example 1. This is because the two aluminum sources are not simply superimposed; a synergistic effect must be achieved by first sealing and then enhancing them.
[0056] As can be seen from the data in Table 1 for Example 1 and Comparative Examples 5 and 6, when colloidal silica does not form a pre-bridged structure with aluminum nitrate nonahydrate, or when the pre-bridged droplet process is omitted, although the microparticle shell still has a certain shielding effect, the shell continuity, the uniformity of cerium outer layer deposition, and the low-temperature impact resistance are all lower than in Example 1. The main reason is that the pre-bridged structure allows it to have an aluminum-silicon bridging tendency before entering the main system, thereby providing more uniform anchoring points for subsequent cerium deposition, demonstrating the synergistic advantage between the bridging structure and cerium end capping.
[0057] As can be seen from the data of Example 1 and Comparative Example 7 in Table 1, after removing the cerium end cap formed by cerium nitrate hexahydrate, the boron release sequence of the microparticles is still basically reasonable, and the strength of the deposited metal does not change much, but the low-temperature impact performance and the optimization effect of composite inclusions are significantly weakened.
[0058] Those skilled in the art should understand that the discussion of any of the above embodiments is merely exemplary and is not intended to imply that the scope of the invention is limited to these examples; within the framework of the invention, the technical features of the above embodiments or different embodiments can also be combined, the steps can be implemented in any order, and there are many other variations of the different aspects of the invention as described above, which are not provided in detail for the sake of brevity.
Claims
1. A high-strength and high-toughness gas-shielded welding wire, characterized in that, The product includes a low-carbon steel strip outer sheath and a core powder filling the outer sheath; the core powder is prepared from the following raw materials by mass: 613-660 parts of reduced iron powder, 112-122 parts of manganese powder, 152-165 parts of carbonyl nickel powder, 24-28 parts of molybdenum powder, 2-4 parts of titanium powder, 12-16 parts of silicon powder, 3-5 parts of graphite powder, 20-24 parts of rutile titanium dioxide, 12-16 parts of calcium fluoride, 2-4 parts of potassium fluorotitanate, and 1-3 parts of cerium-aluminum co-doped microparticle powder; The preparation steps of the cerium-aluminum co-doped microparticle powder are as follows: (1) After mixing boric acid, fumed silica, calcium carbonate, anhydrous sodium carbonate and magnesium oxide, the mixture is melted at high temperature, cooled rapidly and pulverized to obtain core powder; (2) The kernel powder is hydroxylated to obtain surface-activated kernel powder; (3) The surface-activated core powder is dispersed in isopropanol, and aluminum isopropoxide is added and hydrolyzed and polycondensed to obtain a primary aluminum-doped core powder slurry; a second aluminum source is added to the primary aluminum-doped core powder slurry and dispersed evenly, and then aluminum nitrate-colloidal silica dispersion is added to obtain a secondary aluminum-doped core powder slurry; aluminum-doped microparticle powder is obtained by filtration and calcination. (4) The aluminum-doped microparticle powder was immersed in cerium nitrate solution, filtered and thermally decomposed to obtain cerium-aluminum co-doped microparticle powder; The weight ratio of the surface-activated core powder, aluminum isopropoxide, second aluminum source, aluminum nitrate, and colloidal silica dispersion is 480-520:60-68:9-13:1-3:26-34.
2. The high-strength and high-toughness gas-shielded welding wire according to claim 1, characterized in that, The weight ratio of boric acid, fumed silica, calcium carbonate, anhydrous sodium carbonate, and magnesium oxide in step (1) is 900-950:280-300:220-240:62-72:18-22.
3. The high-strength and high-toughness gas-shielded welding wire according to claim 1, characterized in that, The segmented heat preservation temperatures for high-temperature melting in step (1) are 330-370℃, 830-870℃ and 1130-1170℃, and the heat preservation time for each stage is 50-70min; the median particle size of the core powder is 800-1200nm.
4. The high-strength and high-toughness gas-shielded welding wire according to claim 1, characterized in that, The hydroxylation treatment in step (2) is performed at a temperature of 40-50℃ for 20-40 minutes.
5. The high-strength and high-toughness gas-shielded welding wire according to claim 1, characterized in that, Step (3) The second aluminum source is an alumina nano-isopropanol dispersion with a solid content of 20%; the colloidal silica dispersion has a silica solid content of 30%.
6. The high-strength and high-toughness gas-shielded welding wire according to claim 1, characterized in that, The hydrolysis-condensation reaction temperature in step (3) is 45-55℃.
7. The high-strength and high-toughness gas-shielded welding wire according to claim 1, characterized in that, The calcination in step (3) is carried out at 500-540℃ for 80-100 minutes in an air atmosphere, and then at 630-670℃ for 35-45 minutes in an argon atmosphere.
8. The high-strength and high-toughness gas-shielded welding wire according to claim 1, characterized in that, In step (4), the weight ratio of aluminum-doped microparticle powder to cerium nitrate is 480-520:15-21.
9. The high-strength and high-toughness gas-shielded welding wire according to claim 1, characterized in that, The thermal decomposition temperature in step (4) is 440-460℃, and the holding time is 50-70min.
10. A method for preparing a high-strength, high-toughness gas-shielded welding wire according to any one of claims 1-9, characterized in that, Includes the following steps: Reduced iron powder, manganese powder, carbonyl nickel powder, molybdenum powder, titanium powder, silicon powder, graphite powder, rutile titanium dioxide, calcium fluoride, potassium fluorotitanate, and the cerium-aluminum co-doped microparticle powder are mechanically mixed to obtain a flux core powder. The flux core powder is filled into a U-shaped groove of a low-carbon steel strip, closed into a tube blank, and drawn in multiple passes to obtain a high-strength and tough gas-shielded welding wire.