High-corrosion-resistance flux-cored wire and preparation method thereof

Abstract

The invention relates to the field of welding, in particular to a high-corrosion-resistance flux-cored wire and a preparation method thereof. The flux core comprises the following components in parts by weight: 20-30 parts of ferrochrome powder, 5-10 parts of nickel powder, 3-8 parts of ferromolybdenum powder, 15-25 parts of rutile, 5-10 parts of calcium fluoride, 3-7 parts of forsterite, 0.5-1.5 parts of a microcapsule compound, 0.8-2 parts of a rare earth compound and 35-48 parts of iron powder. According to the high-corrosion-resistance flux-cored wire, through optimization of flux core components, introduction of the microcapsule compound and the synergistic effect of rare earth, the high-corrosion-resistance flux-cored wire has the remarkable advantages in the aspects of corrosion resistance, welding manufacturability and mechanical performance. The preparation method comprises the steps that the flux core raw materials are mixed and then filled into the steel strip, then rolling and wire drawing are conducted, the technological process is relatively simple, and industrial production is easy.

Description

Technical Field

[0001] The present invention relates to the field of welding technology, and particularly relates to a highly corrosion-resistant flux-cored wire and a preparation method thereof. Background Art

[0002] With the development of offshore oil engineering towards deep water areas, large-scale offshore steel structures are increasing day by day, and the welding of thick steel structures has become the focus of research. DH36 steel is a low-alloy high-strength marine steel. This steel type is based on low-carbon steel and is added with various alloying elements such as niobium, manganese, nickel, and titanium that can improve the low-temperature impact toughness and strength of the steel. It has the advantages of high fatigue strength, low carbon equivalent, excellent weldability, and good processing and forming performance, and has become the mainstream material for welding thick steel structures. It is widely used in modern ships and offshore engineering. However, on steel structure ships with DH36 steel as the main body, due to continuous immersion and perfusion of seawater, rust spots often appear at the welds of the hull. Over time, the welds will be continuously corroded, damaging the welded structure. Since the welded structure is usually an important load-bearing structure, the corrosion of the welds will ultimately cause the entire equipment to be unable to be used normally. If the weld corrosion is not discovered in time and no corresponding repair measures are taken, it is easy to lead to structural failure, equipment failure, and even accidents such as explosion and leakage, posing a great hidden danger to people's lives and property safety. It is urgent to solve the problem of weld joint corrosion of marine steel.

[0003] Patent CN108788516A discloses a nickel-chromium-molybdenum-tungsten series nickel-based flux-cored wire, which includes a nickel-based alloy steel strip and flux-cored powder filled in the nickel-based alloy steel strip. The mass percentage composition of the flux-cored powder is as follows: 15-20% of metallic chromium powder, 27-32% of metallic nickel powder, 1.5-3% of metallic manganese powder, 10-15% of rutile, 0.5-1.5% of ferrotitanium, 3-6% of feldspar, 2-4% of quartz, 1-2.5% of rare earth fluoride, 1-3% of cryolite, 4-7% of ferrotungsten, 13-16% of ferromolybdenum, 0.4-0.7% of ferrovanadium, 1-3% of calcium fluoride, and the balance is iron powder.

[0004] Patent CN114083177B discloses a composite carbide-reinforced flux-cored welding wire for nickel-based alloy surfacing, comprising an outer metal skin and an inner flux core, the flux core being composed of the following weight ratios: 25-40% tungsten carbide, 20-35% titanium carbide, 20-30% Ni-Cr-B-Si alloy powder, 1-3% metal manganese, and the balance being nickel powder. Nickel serves as a bonding matrix, and tungsten carbide and titanium carbide serve as composite carbides to strengthen the wear resistance and corrosion resistance of the nickel alloy. The addition of tungsten iron and composite carbide ceramic particles can improve the performance of nickel-based flux-cored welding wire, but the additives cannot effectively change the dislocation of the material, making it difficult to improve the high-temperature strength of the alloy; and the additives are unevenly dispersed in the metal matrix, and are prone to agglomeration, which hinders the further improvement of the performance of the nickel-based flux-cored welding wire.

[0005] As a welding material, flux-cored welding wire has the characteristics of flexible use. By adding different elements to the flux core, there is an urgent need for a solder that improves its corrosion resistance so that it can be used in special fields such as oceans and chemical plants. Summary of the invention

[0006] In order to solve the above problems, the present invention provides a high corrosion resistant flux cored welding wire and a preparation method thereof. The high corrosion resistant flux cored welding wire of the present invention has significant advantages in corrosion resistance, welding processability and mechanical properties by optimizing the flux core components and the introduction of microcapsule composites and the synergistic effect of rare earth. The preparation method of the present invention comprises mixing the flux core raw materials and filling them into a steel strip, and then rolling and drawing. The process flow is relatively simple and easy to industrialize.

[0007] The technical solution adopted by the present invention to achieve the above-mentioned purpose is:

[0008] A highly corrosion-resistant flux-cored welding wire, the flux core comprising the following components by weight: 20-30 parts of ferrochrome powder, 5-10 parts of nickel powder, 3-8 parts of ferromolybdenum powder, 15-25 parts of rutile, 5-10 parts of calcium fluoride, 3-7 parts of forsterite, 0.5-1.5 parts of microcapsule composite, 0.8-2 parts of rare earth composite, and 35-48 parts of iron powder; the preparation method of the microcapsule composite comprises the following steps:

[0009] Step 1, mixing benzotriazole and ammonium molybdate in a mass ratio of 7-8.5:1.5-3, adding into an aqueous solution of ethanol, stirring and dissolving at 40-60° C. to obtain a uniform transparent solution;

[0010] Step 2: Mix tetraethyl orthosilicate with hydrochloric acid solution, adjust the pH to 1.5 - 2.5, react at 35 - 45 °C for 3 - 5 hours to form silica sol; drop the transparent solution obtained in Step 1 into the silica sol, control the dropping rate at 1 - 2 mL / min, continue stirring for 2 - 3 hours to form a suspension, perform centrifugal separation, wash with deionized water 3 times, and dry in vacuum at 50 - 60 °C to obtain the microcapsule precursor;

[0011] Step 3: Mix zirconium oxychloride, tetraethyl orthosilicate and yttrium oxide nanopowder according to the mass ratio of 3 - 5:5 - 7:1 - 3, add deionized water, adjust the pH to 9 - 10 with ammonia water, react at 57 - 63 °C for 5.5 - 6.5 hours to form a composite sol, disperse the microcapsule precursor obtained in Step 2 in the composite sol, and perform ultrasonic treatment for 10 - 20 minutes; slowly heat up to 70 - 80 °C, continuously stir for 4 - 6 hours to deposit zirconia - silica composite on the surface of the microcapsule precursor, perform centrifugal separation, wash with absolute ethanol, and dry in vacuum at 60 - 80 °C to obtain the product.

[0012] Furthermore, in Step 1, the mass ratio of benzotriazole to ammonium molybdate is 7 - 8.5:1.5 - 3, and the weight - volume ratio of benzotriazole to ethanol aqueous solution is 1 g:10 - 15 mL.

[0013] Furthermore, in Step 2, the mass ratio of the transparent solution obtained in Step 1 to the silica sol is 1:2 - 4, the volume ratio of tetraethyl orthosilicate to hydrochloric acid solution is 1:0.5 - 1, and the concentration of the hydrochloric acid solution is 0.1 - 0.2 mol / L.

[0014] Furthermore, in Step 3, the weight - volume ratio of zirconium oxychloride to deionized water is 1 g:5 - 6 mL, the mass ratio of zirconium oxychloride, tetraethyl orthosilicate and yttrium oxide nanopowder is 4 - 6:5 - 7:1 - 3, and the mass - volume ratio of the microcapsule precursor obtained in Step 2 to the sol is 1 g:8 - 12 mL.

[0015] Furthermore, sieve the microcapsule composite after drying in Step 3, take the particles with a particle size of 15 - 25 microns, and perform heat treatment at 500 - 600 °C for 1 - 2 hours in an argon atmosphere.

[0016] The design of the above - mentioned microcapsule composite realizes the intelligent controlled release, high - temperature stability and welding adaptability of the corrosion inhibitor through multi - level coating and the synergy of functional components. Among them, the inner layer SiO 2 coats benzotriazole and ammonium molybdate by the sol - gel method to form a porous network structure, initially isolating the corrosion inhibitor from the external environment. The outer layer forms a dense shell layer by the deposition of the composite sol, further improving the thermal stability and mechanical strength. ZrO in the outer shell 2 and Y 2 O 3, can withstand the instantaneous high temperature of the welding arc (>1000 °C), prevent premature rupture of the microcapsules, Y 2 O 3 The stabilizing effect of can inhibit ZrO 2 high-temperature phase transformation and reduce the risk of thermal stress cracking. In a corrosive environment, SiO in the shell 2 (acid-soluble) and ZrO 2 (Cl⁻ sensitive) selectively dissolve or crack, releasing corrosion inhibitors, among which benzotriazole adsorbs to form a film, and ammonium molybdate generates MoO 4 ²⁻ to repair the passive film. By controlling the shell thickness and porosity, the gradient release of the corrosion inhibitor is achieved, avoiding depletion at one time. Benzotriazole can form stable complexes with ions on the metal surface to form a dense protective film, thereby preventing the contact between the corrosive medium and the metal surface. Benzotriazole also has good antioxidant properties, can scavenge free radicals in chemical reactions, and prevent the oxidation of the metal surface. Ammonium molybdate can form a protective film with the metal surface to prevent metal corrosion, and can act synergistically with benzotriazole to enhance the stability and density of the protective film. Benzotriazole and ammonium molybdate, through their respective action mechanisms and synergistic effects in the microcapsule composite, jointly improve the corrosion resistance and welding performance of the flux-cored wire. The microcapsule structure controls the release rate of benzotriazole and ammonium molybdate, enabling them to continuously play a role during welding and extending the protection time.

[0017] Further, the rare earth composite is La 2 O 3 : Y 2 O 3 : CeO 2 The weight ratio of the three is 3:2:1.

[0018] The preparation method of the above high-corrosion-resistant flux-cored wire is specifically as follows: After weighing the above flux raw material components in proportion and mixing them evenly, roll the low-carbon steel strip into a U shape, fill the evenly mixed flux raw material into the U-shaped groove, seal it and roll it into an O shape, and then draw it to make a flux-cored wire.

[0019] Further, replace the benzotriazole in the microcapsule composite with a mixture of benzotriazole and modified benzotriazole in a weight ratio of 3-5:1.

[0020] The preparation method of the modified benzotriazole includes the following steps:

[0021] Step a: Add benzotriazole and sodium hydroxide (sodium hydroxide with a concentration of 10%) into ethanol, stir to obtain a mixed solution, then dropwise add chloroacetic acid or bromoacetic acid, reflux and react at 60 - 80 °C for 4 - 8 hours, adjust the pH to 2 - 4 with 0.1 mol / L hydrochloric acid, precipitate, and obtain carboxylated benzotriazole after centrifugation, washing, and drying; wherein, the molar ratio of benzotriazole to chloroacetic acid or bromoacetic acid is 1:1.0 - 1.5, the molar ratio of benzotriazole to sodium hydroxide is 1:2 - 2.5, and the mass - volume ratio of benzotriazole to ethanol is 1 g:15 - 20 mL;

[0022] Step b: Dissolve the carboxylated benzotriazole prepared in step a in water, adjust the pH to 5 - 7, add copper chloride, stir and react at 20 - 40 °C for 1 - 3 hours. After the reaction is completed, concentrate the solution and add an alcohol solvent to precipitate, centrifuge, and vacuum - dry at 40 °C to constant weight to obtain the product; wherein, the molar ratio of carboxylated benzotriazole to copper chloride is (1.8 - 2.2):1, the weight - volume ratio of carboxylated benzotriazole to water is 1 g:10 - 20 mL, the dosage of the alcohol solvent is 1 - 3 times the total volume of the concentrated solution, and the alcohol solvent is ethanol, methanol, or isopropanol; the pH adjustment is carried out using 10% sodium hydroxide solution.

[0023] The above - mentioned modified benzotriazole enhances the binding force with the metal matrix through carboxyl adsorption, forming a denser protective film. Copper promotes the formation of a Cu 2 O / CuO passivation layer on the weld surface, filling the defects of the Cr 2 O 3 film; in an acidic environment (such as a local corrosion area), the carboxyl group of the modified benzotriazole is protonated, accelerating dissociation and releasing active components; while under neutral conditions, it releases slowly. At the same time, the - COO⁻ therein can form weak coordination bonds with Zr 2 ⁺ on the surface of the ZrO 4 shell, enhancing the dispersibility of the corrosion inhibitor in the shell and reducing the volatilization loss of benzotriazole during high - temperature welding. Unmodified benzotriazole rapidly adsorbs and forms a film at the initial stage of welding, while the modified benzotriazole continuously releases active components in the later corrosion environment. The co - adsorption of Cu²⁺ and benzotriazole can dynamically repair local film breakage, and Cu²⁺ reacts with S²⁻ in the weld to form CuS precipitation, inhibiting sulfur - induced cracking.

[0024] The present invention has the following beneficial effects:

[0025] The high - corrosion - resistant flux - cored wire of the present invention has significant advantages in terms of corrosion resistance, welding processability, and mechanical properties through optimizing the flux - cored composition, introducing micro - capsule complexes, and the synergistic effect of rare earths. Among them, chromium forms a dense Cr 2 O 3The passivation film improves the substrate's resistance to pitting and general corrosion (especially in acidic or chloride environments). Nickel stabilizes the austenitic structure, reducing the tendency of intergranular corrosion. Molybdenum enhances resistance to local corrosion (such as crevice corrosion), especially in Cl⁻-containing environments, where it synergistically acts with chromium. Rare earth oxides refine the weld grains, purify the grain boundaries (adsorb impurities), and reduce the formation of electrochemical corrosion microcells; CeO 2 can promote the self-healing ability of the passivation film. Benzotriazole (BTA), as an organic corrosion inhibitor, forms a protective film by adsorbing on the metal surface. After ammonium molybdate decomposes, MoO 4 ²⁻ is generated, forming an insoluble compound with Fe²⁺ to block the corrosion micropores. By wrapping the corrosion inhibitor with a silica / zirconia composite shell, a gradual release at the high temperature of welding is achieved (the shell controllably decomposes at the high temperature of the arc), extending the action time of the corrosion inhibitor. The yttrium oxide (Y 2 O 3 )-doped shell enhances the thermal stability and avoids premature failure of the corrosion inhibitor. Rutile (TiO 2 ) improves the arc stability, reduces spatter, and forms short slag (easy to remove slag); CaF 2 lowers the melting point of the slag, improves fluidity, and simultaneously reacts with SiO 2 to generate low-fluoride gas, inhibiting porosity. Forsterite regulates the viscosity and surface tension of the slag, reducing weld slag inclusion defects. The rare earth complex can also improve the strength and toughness of the weld by inhibiting grain growth and promoting the formation of acicular ferrite. In a corrosive environment, benzotriazole inhibits initial corrosion, and yttrium oxide and cerium oxide stably maintain the passivation film for a long time, forming a dual protection. The two act synergistically to jointly enhance the anti-corrosion performance. The zirconia-silica composite shell matches the thermal expansion coefficient of the substrate during the cooling process, and can also reduce welding residual stress and lower crack sensitivity. When the weld is exposed to a corrosive environment, the shell gradually releases the corrosion inhibitor due to changes in pH or Cl⁻ concentration, achieving long-term protection. Heat treatment in an argon atmosphere (200 - 250 °C) further stabilizes the microcapsule structure and avoids premature decomposition caused by the high temperature of welding. The flux-cored wire of the present invention forms a weld with long-term corrosion resistance, less spatter, low porosity, high strength, good toughness, and excellent comprehensive performance, and is especially suitable for harsh environments such as the ocean and chemical industries.

[0026] The preparation method of the present invention includes mixing the flux core raw materials and then filling them into a steel strip, followed by rolling and drawing. The process flow is relatively simple and is easy for industrial production. Specific embodiments

[0027] Next, in combination with the embodiments of the present application, the technical solutions in the embodiments of the present application will be clearly and completely described. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present application.

[0028] Chromium iron powder, Cr≥60%, Qinghe Xingxin New Material Technology Co., Ltd.; nickel powder, content 99.9%, Tianjin Zhuxin Metal Materials Co., Ltd.; molybdenum iron powder, FeMo60, Sichuan Gerun Forest Technology Co., Ltd.; rutile, TiO 2 ≥90%; calcium fluoride, content 98%, Shijiazhuang Hualang Mineral Products Trading Co., Ltd.; forsterite, MgO content 47.58%, SiO2 content 39%, Xixia Qi'an Forsterite Processing Co., Ltd.; cerium oxide, content ≥99.9%; iron powder, mesh number 300 mesh, content 99.99%, Nangong Xindun Alloy Welding Wire Spraying Co., Ltd.; zirconium oxychloride, content 99%, Shanghai Hongzhuang Chemical Technology Co., Ltd.; the raw materials used in the following examples are all ordinary commercially available products.

[0029] Example 1

[0030] A highly corrosion-resistant flux-cored wire, the flux of which includes the following components by weight: 25 parts of chromium iron powder, 8 parts of nickel powder, 5 parts of molybdenum iron powder, 20 parts of rutile, 7 parts of calcium fluoride, 5 parts of forsterite, 1.2 parts of cerium oxide, 1 part of microcapsule complex, 1.4 parts of rare earth complex, and 40 parts by weight of iron powder; the rare earth complex is La 2 O 3 (50-100nm): Y 2 O 3 (20-50nm): CeO 2 (30-80nm), and the weight ratio of the three is 3:2:1.

[0031] The preparation method of the microcapsule complex includes the following steps:

[0032] Step 1, mix benzotriazole and ammonium molybdate in a mass ratio of 8:2, add it to an aqueous solution of ethanol with a concentration of 60%, and stir and dissolve at 50°C to obtain a homogeneous and transparent solution. Among them, the weight-volume ratio of benzotriazole to the ethanol aqueous solution is 1g:13mL;

[0033] Step 2: Mix tetraethyl orthosilicate with hydrochloric acid solution, adjust the pH to 1.5 - 2.5, react at 40 °C for 4 hours to form silica sol; drop the transparent solution obtained in Step 1 into the silica sol, control the dropping rate at 1.5 mL / min, continue stirring for 2.5 hours to form a suspension, perform centrifugal separation, wash 3 times with deionized water, and vacuum dry at 55 °C to constant weight to obtain the microcapsule precursor. Among them, the mass ratio of the transparent solution obtained in Step 1 to the silica sol is 1:3, the volume ratio of tetraethyl orthosilicate to hydrochloric acid solution is 1:0.7, and the concentration of the hydrochloric acid solution is 0.1 mol / L;

[0034] Step 3: Add zirconium oxychloride to preheated deionized water and mix, stir at 50 °C until completely dissolved, sequentially add tetraethyl orthosilicate and yttrium oxide nanopowder (20 - 50 nm), stir for 10 minutes, dropwise add 10% ammonia water, adjust to pH = 9 - 10, react at 57 °C for 6.5 hours to form a composite sol. Add the microcapsule precursor obtained in Step 2 to the sol, with a power of 250 W and a frequency of 40 kHz, perform ultrasonic treatment for 15 minutes (ice bath temperature control < 30 °C), heat up to 75 °C and keep warm for 6 hours, perform centrifugal washing: centrifuge at 8000 rpm for 10 minutes, wash sequentially with deionized water, absolute ethanol, and acetone, vacuum dry at 60 °C to constant weight, sieve, collect particles of 15 - 25 μm, and perform heat treatment in a tubular furnace under an argon atmosphere at 550 °C for 1.5 hours to obtain the product; among them, the weight - volume ratio of zirconium oxychloride to deionized water is 1 g:5.5 mL, the mass ratio of zirconium oxychloride, tetraethyl orthosilicate to yttrium oxide nanopowder is 5:6:2, and the mass - volume ratio of the microcapsule precursor obtained in Step 2 to the sol is 1 g:10 mL.

[0035] The preparation method of the above - mentioned highly corrosion - resistant flux - cored wire is as follows:

[0036] Weigh the above - mentioned flux raw material components according to the ratio, place them in a three - dimensional mixer or V - type mixer and mix for 1.5 hours to ensure uniform dispersion. Then roll the low - carbon steel strip into a U - shape, fill the uniformly mixed flux raw materials into the U - shaped groove, seal and roll it into an O - shape, and then perform wire drawing to make the flux - cored wire.

[0037] Example 2

[0038] A highly corrosion - resistant flux - cored wire, the flux of which includes the following components by weight: 20 parts of chromium iron powder, 10 parts of nickel powder, 8 parts of molybdenum iron powder, 15 parts of rutile, 5 parts of calcium fluoride, 7 parts of forsterite, 2 parts of cerium oxide, 1.5 parts of microcapsule complex, 0.8 part of rare - earth complex, and 48 parts of iron powder; the rare - earth complex is La 2 O 3 : Y 2 O 3 : CeO 2 The weight ratio of the three is 2.8:2.2:1.

[0039] The preparation method of the microcapsule complex comprises the following steps:

[0040] Step 1: Mix benzotriazole and ammonium molybdate at a mass ratio of 7:1.5, add them into an aqueous solution of ethanol with a concentration of 60%, and stir to dissolve at 55°C to obtain a homogeneous and transparent solution. Among them, the weight-to-volume ratio of benzotriazole to the ethanol aqueous solution is 1 g:12 mL;

[0041] Step 2: Mix tetraethyl orthosilicate and hydrochloric acid solution, adjust the pH to 1.5 - 2.5, and react at 45°C for 3 hours to form silica sol; drop the transparent solution obtained in Step 1 into the silica sol, control the dropping rate at 1 mL / minute, continue to stir for 3 hours to form a suspension, perform centrifugal separation, wash 3 times with deionized water, and vacuum dry at 50°C to constant weight to obtain the microcapsule precursor. Among them, the mass ratio of the transparent solution obtained in Step 1 to the silica sol is 1:2, the volume ratio of tetraethyl orthosilicate to the hydrochloric acid solution is 1:0.5, and the concentration of the hydrochloric acid solution is 0.2 mol / L;

[0042] Step 3: Add zirconium oxychloride to preheated deionized water and mix, stir at 50°C until completely dissolved, successively add tetraethyl orthosilicate and yttrium oxide nanopowder, stir for 10 minutes, drop 10% ammonia water, adjust the pH to 9 - 10, react at 60°C for 6 hours to form a composite sol. Add the microcapsule precursor obtained in Step 2 to the sol, with a power of 250 W, a frequency of 40 kHz, and an ultrasonic treatment time of 15 minutes (ice bath temperature control < 30°C), heat up to 75°C and keep warm for 6 hours, perform centrifugal washing: centrifuge at 8000 rpm for 10 minutes, wash successively with deionized water, absolute ethanol, and acetone, vacuum dry at 60°C to constant weight, sieve, collect particles of 15 - 25 μm, and perform heat treatment in a tubular furnace at 600°C for 1 hour in an argon atmosphere to obtain the product; among them, the weight-to-volume ratio of zirconium oxychloride to deionized water is 1 g:6 ml, the mass ratio of zirconium oxychloride, tetraethyl orthosilicate, and yttrium oxide nanopowder is 5:7:3, and the mass-to-volume ratio of the microcapsule precursor obtained in Step 2 to the sol is 1 g:8 ml.

[0043] The preparation method of the above high-corrosion-resistant flux-cored wire is the same as that in Example 1.

[0044] Example 3

[0045] A high-corrosion-resistant flux-cored wire, the flux of which comprises the following components by weight: 30 parts of chromium iron powder, 5 parts of nickel powder, 3 parts of molybdenum iron powder, 25 parts of rutile, 10 parts of calcium fluoride, 3 parts of forsterite, 0.5 part of cerium oxide, 0.5 part of microcapsule complex, 2 parts of rare earth complex, and 35 parts of iron powder; the rare earth complex is La 2 O 3 :Y 2 O3 : CeO 2 The weight ratio of the three is 3.2:1.8:1.

[0046] The preparation method of the microcapsule composite includes the following steps:

[0047] Step 1: Mix benzotriazole and ammonium molybdate at a mass ratio of 8.5:2.5, add them to an aqueous solution of ethanol with a concentration of 60%, and stir to dissolve at 60°C to obtain a homogeneous transparent solution. Among them, the weight-to-volume ratio of benzotriazole to the ethanol aqueous solution is 1 g:10 mL;

[0048] Step 2: Mix tetraethyl orthosilicate and hydrochloric acid solution, adjust the pH to 1.5 - 2.5, and react at 35°C for 5 hours to form silica sol; drop the transparent solution obtained in Step 1 into the silica sol, control the dropping speed at 2 mL / min, continue to stir for 3 hours to form a suspension, centrifuge and separate, wash 3 times with deionized water, and vacuum dry at 60°C to constant weight to obtain the microcapsule precursor. Among them, the mass ratio of the transparent solution obtained in Step 1 to the silica sol is 1:4, the volume ratio of tetraethyl orthosilicate to the hydrochloric acid solution is 1:1, and the concentration of the hydrochloric acid solution is 0.2 mol / L;

[0049] Step 3: Add zirconium oxychloride to preheated deionized water and mix, stir at 50°C until completely dissolved, add tetraethyl orthosilicate and yttrium oxide nanopowder in sequence, stir for 10 minutes, drop 10% ammonia water, adjust the pH to 9 - 10, react at 63°C for 5.5 hours to form a composite sol, add the microcapsule precursor obtained in Step 2 to the sol, with a power of 250 W and a frequency of 40 kHz, ultrasonic treatment for 15 minutes (ice bath temperature control < 30°C), heat up to 80°C and keep warm for 5.5 hours, centrifuge and wash: centrifuge at 8000 rpm for 10 minutes, wash with deionized water, anhydrous ethanol, and acetone in sequence, vacuum dry at 60°C to constant weight, sieve, collect particles of 15 - 25 μm, and heat-treat in a tubular furnace under an argon atmosphere at 500°C for 2 hours to obtain; among them, the weight-to-volume ratio of zirconium oxychloride to deionized water is 1 g:5 ml, the mass ratio of zirconium oxychloride, tetraethyl orthosilicate and yttrium oxide nanopowder is 4:5:3, and the mass-to-volume ratio of the microcapsule precursor obtained in Step 2 to the sol is 1 g:12 ml.

[0050] The preparation method of the above highly corrosion-resistant flux-cored wire is the same as that in Example 1.

[0051] Example 4

[0052] In the preparation of the microcapsule composite, benzotriazole in Step 1 is replaced with a mixture of benzotriazole and modified benzotriazole with a weight ratio of 4:1. The preparation method of the modified benzotriazole includes the following steps:

[0053] Step a: Add benzotriazole and 10% sodium hydroxide into ethanol, stir to obtain a mixed solution, then dropwise add chloroacetic acid, reflux and react at 70 °C for 6 hours, adjust the pH to 2 - 4 with 0.1 mol / L hydrochloric acid, precipitate, and obtain carboxylated benzotriazole after centrifugation, washing, and drying; wherein, the molar ratio of benzotriazole to chloroacetic acid is 1:1.2, the molar ratio of benzotriazole to sodium hydroxide is 1:2.2, and the mass - volume ratio of benzotriazole to ethanol is 1 g:18 mL;

[0054] Step b: Dissolve the carboxylated benzotriazole prepared in step a in water, adjust the pH to 5 - 7, add copper chloride, stir and react at 30 °C for 2 hours. After the reaction is completed, concentrate the solution and add an alcohol solvent to precipitate, centrifuge, and vacuum - dry at 40 °C to constant weight to obtain the product; wherein, the molar ratio of carboxylated benzotriazole to copper chloride is 2:1, the weight - volume ratio of carboxylated benzotriazole to water is 1 g:15 mL, the dosage of the alcohol solvent is 1 - 3 times the total volume of the concentrated solution, and the alcohol solvent is ethanol, methanol, or isopropanol; the pH is adjusted using a 10% sodium hydroxide solution.

[0055] The rest is the same as in Example 1.

[0056] Example 5

[0057] In the preparation of the microcapsule composite, in step 1, benzotriazole is replaced with a mixture of benzotriazole and modified benzotriazole with a weight ratio of 3:1. The preparation method of the modified benzotriazole includes the following steps:

[0058] Step a: Add benzotriazole and 10% sodium hydroxide into ethanol, stir to obtain a mixed solution, then dropwise add chloroacetic acid, reflux and react at 80 °C for 4 hours, adjust the pH to 2 - 4 with 0.1 mol / L hydrochloric acid, precipitate, and obtain carboxylated benzotriazole after centrifugation, washing, and drying; wherein, the molar ratio of benzotriazole to chloroacetic acid is 1:1.0, the molar ratio of benzotriazole to sodium hydroxide is 1:2.5, and the mass - volume ratio of benzotriazole to ethanol is 1 g:15 mL;

[0059] Step b: Dissolve the carboxylated benzotriazole prepared in step a in water, adjust the pH to 5 - 7, add copper chloride, stir and react at 20 °C for 3 hours. After the reaction is completed, concentrate the solution and add an alcohol solvent to precipitate, centrifuge, and vacuum - dry at 40 °C to constant weight to obtain the product; wherein, the molar ratio of carboxylated benzotriazole to copper chloride is 2.2:1, the weight - volume ratio of carboxylated benzotriazole to water is 1 g:20 mL, the dosage of the alcohol solvent is 1 - 3 times the total volume of the concentrated solution, and the alcohol solvent is ethanol, methanol, or isopropanol; the pH is adjusted using a 10% sodium hydroxide solution.

[0060] The rest is the same as in Example 1.

[0061] Example 6

[0062] In the preparation of the microcapsule complex, in step 1, benzotriazole is replaced with a mixture of benzotriazole and modified benzotriazole with a weight ratio of 5:1. The preparation method of the modified benzotriazole includes the following steps:

[0063] Step a: Add benzotriazole and 10% sodium hydroxide to ethanol, stir to obtain a mixed solution, then dropwise add chloroacetic acid, reflux and react at 60 °C for 8 hours, adjust the pH to 2-4 with 0.1 mol / L hydrochloric acid, precipitate, and obtain carboxylated benzotriazole after centrifugation, washing, and drying; among them, the molar ratio of benzotriazole to chloroacetic acid is 1:1.5, the molar ratio of benzotriazole to sodium hydroxide is 1:2, and the mass-volume ratio of benzotriazole to ethanol is 1 g:20 mL;

[0064] Step b: Dissolve the carboxylated benzotriazole prepared in step a in water, adjust the pH to 5-7, add copper chloride, stir and react at 40 °C for 1 hour. After the reaction is completed, concentrate the solution and add an alcohol solvent to precipitate, centrifuge, and vacuum dry at 40 °C to constant weight to obtain it; among them, the molar ratio of carboxylated benzotriazole to copper chloride is 1.8:1, the weight-volume ratio of carboxylated benzotriazole to water is 1 g:10 mL, the dosage of the alcohol solvent is 1-3 times the total volume of the concentrated solution, and the alcohol solvent is ethanol, methanol, or isopropanol; the pH adjustment is carried out using a 10% sodium hydroxide solution.

[0065] The rest is the same as in Example 1.

[0066] Comparative Example 1

[0067] A highly corrosion-resistant flux-cored wire, the flux of which does not contain a microcapsule complex, and the rest is the same as in Example 1.

[0068] Comparative Example 2

[0069] A highly corrosion-resistant flux-cored wire, in the microcapsule complex, only contains benzotriazole and does not contain ammonium molybdate, and the rest is the same as in Example 1.

[0070] Comparative Example 3

[0071] A highly corrosion-resistant flux-cored wire, in the microcapsule complex, only contains ammonium molybdate and does not contain benzotriazole, and the rest is the same as in Example 1.

[0072] Performance test

[0073] Weld the flux-cored wires of Examples 1-6 and Comparative Examples 1-3 with a stainless steel plate as the base material, and then perform performance tests on the welds.

[0074] Corrosion resistance test: The corrosion rate of the welded part obtained after welding the welding wires of the examples and comparative examples was determined according to the standard of JB / T 7901. The corrosion source was: cooling water containing 5 wt% sulfuric acid and 5 wt% hydrofluoric acid, fully immersed for 24 h.

[0075] The tensile strength and shear strength of the welded joints were detected according to GB / T228.1-2010 and GB / T 11363-2008. The results are shown in Table 1.

[0076] Table 1. Performance test results Project Corrosion rate mg / cm²·h Tensile strength / MPa Shear strength / MPa Example 1 1.04 675 285 Example 2 1.08 684 294 Example 3 1.15 689 287 Example 4 0.95 708 343 Example 5 0.94 715 338 Example 6 0.91 720 334 Comparative Example 1 6.14 638 264 Comparative Example 2 4.25 664 298 Comparative Example 3 3.48 682 314

[0077] As can be seen from the above table, for the microcapsule composite of the present invention, benzotriazole and ammonium molybdate are compounded. Through their respective action mechanisms and synergistic effects, the corrosion resistance and welding performance of the flux-cored wire are jointly improved. At the same time, unmodified benzotriazole adsorbs and forms a film rapidly in the initial stage of welding, and the modified benzotriazole continuously releases active components in the later corrosion environment. The compounding of the two further improves the corrosion resistance and other comprehensive performances.

[0078] It should be noted that in this article, relational terms such as first and second are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variant thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements not only includes those elements, but also includes other elements not expressly listed, or also includes elements inherent to such process, method, article or device.

[0079] Although the embodiments of the present application have been shown and described, for those of ordinary skill in the art, it can be understood that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principle and spirit of the present application. The scope of the present application is defined by the appended claims and their equivalents.

Claims

1. A highly corrosion-resistant flux-cored welding wire, characterized in that: The core comprises the following components by weight: 20-30 parts of ferrochrome powder, 5-10 parts of nickel powder, 3-8 parts of ferromolybdenum powder, 15-25 parts of rutile, 5-10 parts of calcium fluoride, 3-7 parts of forsterite, 0.5-1.5 parts of microcapsule compound, 0.8-2 parts of rare earth compound, and 35-48 parts of iron powder; the preparation method of the microcapsule compound comprises the following steps: Step 1, mixing benzotriazole and ammonium molybdate in a mass ratio of 7-8.5:1.5-3, adding into an aqueous solution of ethanol, stirring and dissolving at 40-60° C. to obtain a uniform transparent solution; Step 2, mixing ethyl orthosilicate with hydrochloric acid solution, adjusting the pH to 1.5-2.5, reacting at 35-45° C. for 3-5 hours to form a silica sol; adding the transparent solution obtained in step 1 to the silica sol, continuing to stir for 2-3 hours to form a suspension, centrifuging, washing, and drying to obtain a microcapsule precursor; Step 3, zirconium oxychloride, ethyl orthosilicate and yttrium oxide nanopowder are mixed in a mass ratio of 3-5:5-7:1-3, deionized water is added, ammonia water is used to adjust the pH value to 9-10, and the mixture is reacted at 57-63° C. for 5.5-6.5 hours to form a composite sol, and the microcapsule precursor obtained in step 2 is dispersed in the composite sol, and ultrasonic treatment is performed for 10-20 minutes; the temperature is raised to 70-80° C., and stirring is continued for 4-6 hours to obtain the product.

2. The high corrosion resistant flux-cored welding wire according to claim 1, characterized in that: In step 1, the mass ratio of benzotriazole to ammonium molybdate is 7-8.5:1.5-3, and the weight volume ratio of benzotriazole to ethanol aqueous solution is 1 g:10-15 mL.

3. The high corrosion resistant flux-cored welding wire according to claim 1, characterized in that: In step 2, the mass ratio of the transparent solution obtained in step 1 to the silica sol is 1:2-4, the volume ratio of ethyl orthosilicate to the hydrochloric acid solution is 1:0.5-1, and the concentration of the hydrochloric acid solution is 0.1-0.2 mol / L.

4. The high corrosion resistant flux-cored welding wire according to claim 1, characterized in that: In step 3, the weight volume ratio of zirconium oxychloride to deionized water is 1g:5-6ml, the mass ratio of zirconium oxychloride, tetraethyl orthosilicate and yttrium oxide nanopowder is 4-6:5-7:1-3, and the mass volume of the microcapsule precursor and sol obtained in step 2 is 1g:8-12ml.

5. The high corrosion resistant flux-cored welding wire according to claim 1, characterized in that: The microcapsule composite dried in step 3 is sieved to obtain particles with a particle size of 15 to 25 microns, and heat-treated at 500 to 600° C. for 1 to 2 hours in an argon atmosphere.

6. The high corrosion resistant flux-cored welding wire according to claim 1, characterized in that: The rare earth composite material is La2O3:Y2O3:CeO2 with a weight ratio of 2.8-3.2:1.8-2.2:

1.

7. The method for preparing a highly corrosion-resistant flux-cored welding wire according to any one of claims 1 to 6, characterized in that: Specifically, the above-mentioned flux core raw material components are weighed in proportion and mixed evenly, and then the low carbon steel strip is rolled into a U shape, and the evenly mixed flux core raw material is filled into the U-shaped groove, which is sealed and rolled into an O shape, and then drawn to make the flux cored welding wire.

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