High-hardness and high-strength flux-cored wire and preparation method thereof

Abstract

The invention relates to the technical field of flux-cored wires, particularly discloses a high-hardness and high-strength flux-cored wire and a preparation method thereof, and provides the high-hardness and high-strength flux-cored wire and the preparation method thereof. Iron powder, nickel powder, a boron nitride composite material, manganese powder, chromium powder, molybdenum powder, titanium powder, silica powder, a stabilizer and calcium fluoride are evenly mixed and then dried, and a flux core is obtained; the welding skin is rolled into a U shape, the flux core is added, then sealing and rolling are conducted to form an O shape, and the flux-cored wire is obtained through drawing and diameter reducing; according to the preparation method provided by the invention, the iron powder, the nickel powder, the boron nitride composite material, the manganese powder, the chromium powder, the molybdenum powder, the titanium powder, the silica powder, the stabilizer and the calcium fluoride are reasonably compounded to form the flux-cored powder with high hardness and high strength, so that the prepared flux-cored wire has excellent hardness and excellent mechanical properties after being welded.

Description

Technical Field

[0001] The present invention relates to the technical field of flux-cored wires, and particularly to a flux-cored wire with high hardness and high strength and a preparation method thereof. Background Art

[0002] In the technical field of welding materials, traditional welding processes mainly use electrodes and solid wires as filler materials, but they have significant limitations in terms of welding efficiency, metallurgical properties, and process adaptability. Electrodes achieve molten pool protection and alloy transition through an external coating, but their intermittent welding characteristics result in low production efficiency, poor operation flexibility, and the coating is prone to moisture absorption and insufficient composition stability, making it difficult to meet the requirements of automated production. Although solid wires are suitable for continuous welding, their alloying elements can only be provided by the wire substrate, with limited composition design and unable to achieve complex metallurgical reaction control. Especially when dealing with high-strength steels, weathering steels, or special working conditions (such as low temperature, corrosive environments), the mechanical properties and crack resistance of the welds are difficult to meet the requirements.

[0003] Flux-cored wires (also known as metal-cored wires), as a new generation of welding materials, combine the metallurgical functions of the electrode coating and the continuous wire feeding advantage of solid wires through a composite structure of a steel strip wrapped around a powder core. The composition of its powder core can be flexibly adjusted with alloying elements (such as Mn, Si, Ni, Mo, etc.), deoxidizers (such as ferrosilicon, ferromanganese), slag formers (such as fluorite, titanium dioxide), and arc stabilizers (such as potassium and sodium compounds), forming a combined gas-slag protection during welding, effectively isolating the oxidation and nitridation of the molten pool by air, and at the same time achieving desulfurization, dephosphorization, and purification of the weld through the floating of the slag. In addition, the continuous wire feeding characteristic of the flux-cored wire supports fully automatic or semi-automatic welding processes, significantly improving the deposition efficiency (up to 85%-90%), reducing the groove machining amount by increasing the weld cross-section, reducing the consumption of deposited metal, and showing significant economy in the welding of large structural parts.

[0004] However, the welds welded by current flux-cored wires have problems of low hardness and poor mechanical strength, thus greatly limiting the application of welded structural parts. Summary of the Invention

[0005] Aiming at the deficiencies of the prior art, the purpose of the present invention is to provide a flux-cored wire with high hardness and high strength and a preparation method thereof.

[0006] To achieve the above purpose, the present invention adopts the following technical solutions: A flux-cored wire with high hardness and high strength, the flux-cored wire includes a welding skin and a powder core, and the powder core is composed of the following raw materials in parts by weight: 15-25 parts of iron powder, 8-12 parts of nickel powder, 5-10 parts of boron nitride composite material, 2-5 parts of manganese powder, 2-5 parts of chromium powder, 2-4 parts of molybdenum powder, 0.5-1 part of titanium powder, 0.5-1 part of silica powder, 1-2 parts of stabilizer, and 2-3 parts of calcium fluoride.

[0007] In the technical solution disclosed by the present invention, the number of parts of iron powder can be selected from 15 parts, 16 parts, 17 parts, 18 parts, 19 parts, 20 parts, 21 parts, 22 parts, 23 parts, 24 parts, 25 parts, but is not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0008] The iron powder provided by the present invention will melt and fill into the weld during the welding process, so the metal filling amount of the weld can be increased, thereby improving the welding speed and deposition rate.

[0009] In the technical solution disclosed by the present invention, the number of parts of nickel powder can be selected from 8 parts, 9 parts, 10 parts, 11 parts, 12 parts, but is not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0010] The nickel powder provided by the present invention can moderately improve the strength of the welded joint through the ferrite solid solution strengthening effect. Nickel is an element that forms and stabilizes austenite and can exist in the form of mutual solubility with iron in the weld in ferrite and austenite, thereby strengthening the weld metal.

[0011] In the technical solution disclosed by the present invention, the number of parts of the boron nitride composite material can be selected from 5 parts, 6 parts, 7 parts, 8 parts, 9 parts, 10 parts, but is not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0012] Specifically, the preparation method of the boron nitride composite material is as follows: S1. Add boron nitride whiskers to nitric acid solution, carry out impregnation treatment, and then filter, wash, and dry to obtain pretreated boron nitride whiskers; S2. Dissolve soluble magnesium salt, soluble aluminum salt, and urea in water, then add pretreated boron nitride whiskers, stir and disperse evenly, carry out hydrothermal reaction, after the reaction is completed, cool to room temperature, filter, wash, dry, and grind to obtain the boron nitride composite material.

[0013] More specifically, in step S1, the impregnation treatment is carried out at room temperature, and the impregnation treatment time is 1 - 3h.

[0014] More specifically, in step S2, the mass ratio of the soluble magnesium salt, soluble aluminum salt, urea, and pretreated boron nitride whiskers is 5 - 6:3 - 4:2.5 - 3.5:5 - 10.

[0015] Among them, the soluble magnesium salt is selected from magnesium sulfate, magnesium chloride, or magnesium nitrate.

[0016] Among them, the soluble aluminum salt is selected from aluminum chloride, aluminum nitrate, or aluminum sulfate.

[0017] More specifically, in step S2, the temperature of the hydrothermal reaction is 100-120 °C, for example, 100 °C, 105 °C, 110 °C, 115 °C, 120 °C can be selected; the time of the hydrothermal reaction is 12-24 h, for example, 12 h, 14 h, 16 h, 18 h, 20 h, 22 h, 24 h can be selected, but not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0018] In the present invention, boron nitride whiskers are first added to a nitric acid solution for pretreatment, which can increase the number of hydroxyl active groups on the surface of boron nitride whiskers and facilitate the subsequent loading of hydrotalcite; then, by hydrothermal method, magnesium-aluminum hydrotalcite is in-situ grown on the surface of boron nitride whiskers. The Mohs hardness of boron nitride whiskers reaches 9, while the Al2O3 (Mohs hardness 9.0) and MgO (Mohs hardness 5.5) particles decomposed from magnesium-aluminum hydrotalcite during the high-temperature welding process fill the grain boundary voids, forming a "whisker-oxide" composite hard phase, which has a better effect of improving the hardness of the material compared with single boron nitride whiskers or magnesium-aluminum hydrotalcite; at the same time, the generated Al2O3 and MgO particles serve as heterogeneous nucleation cores, promoting the rapid nucleation of the molten pool metal and significantly refining the weld grains, thereby improving the mechanical properties of the flux-cored wire; in addition, by in-situ growing magnesium-aluminum hydrotalcite on the surface of boron nitride whiskers in the present invention, compared with directly blending the two, a more uniform composite structure can be formed, and problems such as powder stratification or agglomeration caused by performance differences during blending can be avoided.

[0019] In the technical solution disclosed in the present invention, the number of parts of manganese powder can be selected as 2 parts, 3 parts, 4 parts, 5 parts, but not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0020] The addition of manganese powder can improve the welding process performance, such as stabilizing the arc and reducing spatter, making the welding process more stable, improving the strength and toughness of the weld metal, and at the same time, manganese powder can effectively remove oxygen and sulfur in the weld during the welding process, reduce the oxide inclusions in the weld and the content of sulfur in the weld, and reduce the risk of hot cracks.

[0021] In the technical solution disclosed in the present invention, the number of parts of chromium powder can be selected as 2 parts, 3 parts, 4 parts, 5 parts, but not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0022] The addition of chromium powder can significantly improve the corrosion resistance of the deposited metal, especially the pitting resistance; chromium forms a stable passive film in the deposited metal, thereby improving the corrosion resistance of the weld.

[0023] In the technical solution disclosed in the present invention, the number of parts of molybdenum powder can be selected as 2 parts, 2.5 parts, 3 parts, 3.5 parts, 4 parts, but not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0024] The addition of molybdenum powder can not only improve the strength of the welded joint through solid solution strengthening, but also improve the toughness. The molybdenum element has the effect of delaying the precipitation and growth of proeutectoid ferrite, which is beneficial to the formation of acicular ferrite tissue with high density dislocations in the weld.

[0025] In the technical solution disclosed in the present invention, the amount of titanium powder can be selected as 0.5 part, 0.6 part, 0.7 part, 0.8 part, 0.9 part, 1 part, but is not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0026] The addition of titanium powder can form more inclusions in the crystal grains, thus becoming nucleation cores, promoting the formation of acicular ferrite tissue in the weld, refining the grains. In addition, during the formation of the deposited metal, it also has the effect of capturing hydrogen, effectively reducing the content of diffusible hydrogen in the deposited metal, and improving the mechanical properties of the welded joint.

[0027] In the technical solution disclosed in the present invention, the amount of silica fume can be selected as 0.5 part, 0.6 part, 0.7 part, 0.8 part, 0.9 part, 1 part, but is not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0028] The addition of silica fume can improve the fluidity and wettability of the welding material, promote the reaction between the welding material and the base material, thereby enhancing the welding strength. At the same time, silica fume can form a slag with other components during the welding process, covering the surface of the molten pool to prevent oxygen and nitrogen in the air from entering the molten pool, thus reducing the generation of pores and oxides.

[0029] In the technical solution disclosed in the present invention, the amount of stabilizer can be selected as 1 part, 1.2 parts, 1.4 parts, 1.5 parts, 1.6 parts, 1.8 parts, 2 parts, but is not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0030] Specifically, the stabilizer is selected from at least one of potassium titanate, yttrium oxide, and lanthanum oxide.

[0031] The addition of the stabilizer can significantly improve the stability of the welding arc, make the arc softer and smoother, reduce spatter, and thus improve the welding process performance.

[0032] In the technical solution disclosed in the present invention, the amount of calcium fluoride can be selected as 2 parts, 2.2 parts, 2.4 parts, 2.5 parts, 2.6 parts, 2.8 parts, 3 parts, but is not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0033] Calcium fluoride is a commonly used slag former, which can form slag during welding, covering the surface of the molten pool and playing a role in isolating air and protecting the molten pool from oxidation and contamination.

[0034] In the technical solution disclosed in the present invention, the flux-cored wire accounts for 15-25% of the mass of the flux-cored wire. In the technical solution disclosed in the present invention, for example, 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24%, 25% can be selected, but it is not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0035] The present invention also provides a method for preparing the above-mentioned flux-cored wire, which includes the following steps: (1) Mix iron powder, nickel powder, boron nitride composite material, manganese powder, chromium powder, molybdenum powder, titanium powder, silica powder, stabilizer and calcium fluoride by weight, and dry them evenly to obtain the flux-cored wire; (2) Roll the welding skin into a U shape, add the flux-cored wire, then seal it and roll it into an O shape, and obtain the flux-cored wire through drawing and reducing the diameter.

[0036] In the technical solution disclosed in the present invention, in step (1), the drying temperature is 100-120°C, for example, 100°C, 105°C, 110°C, 115°C, 120°C can be selected; the drying time is 1-3h, for example, 1h, 1.5h, 2h, 2.5h, 3h can be selected, but it is not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0037] In the technical solution disclosed in the present invention, in step (2), the diameter of the flux-cored wire is 1.2-1.8mm, for example, 1.2mm, 1.3mm, 1.4mm, 1.5mm, 1.6mm, 1.7mm, 1.8mm can be selected, but it is not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0038] Compared with the prior art, the present invention has the following beneficial effects: (1) The present invention provides a flux-cored wire with high hardness and high strength and a preparation method thereof. By mixing iron powder, nickel powder, boron nitride composite material, manganese powder, chromium powder, molybdenum powder, titanium powder, silica powder, stabilizer and calcium fluoride evenly and then drying, the flux-cored wire is obtained; the welding skin is rolled into a U shape, the flux-cored wire is added, then sealed and rolled into an O shape, and the flux-cored wire is obtained through drawing and reducing the diameter; the preparation method provided by the present invention forms a flux-cored powder body with high hardness and high strength through reasonable compounding of iron powder, nickel powder, boron nitride composite material, manganese powder, chromium powder, molybdenum powder, titanium powder, silica powder, stabilizer and calcium fluoride, so that the prepared flux-cored wire has excellent hardness and mechanical properties after welding.

[0039] (2) In the present invention, boron nitride whiskers are first added to a nitric acid solution for pretreatment, which can increase the number of hydroxyl active groups on the surface of boron nitride whiskers and facilitate the subsequent loading of hydrotalcite. Then, by means of hydrothermal method, magnesium-aluminum hydrotalcite is in-situ grown on the surface of boron nitride whiskers. The Mohs hardness of boron nitride whiskers reaches grade 9, while the Al2O3 and MgO particles generated by the decomposition of magnesium-aluminum hydrotalcite during high-temperature welding fill the grain boundary voids, forming a "whisker-oxide" composite hard phase. Compared with single boron nitride whiskers or magnesium-aluminum hydrotalcite, it has a better effect of improving the hardness of the material. At the same time, the generated Al2O3 and MgO particles serve as heterogeneous nucleation cores, promoting the rapid nucleation of the molten pool metal and significantly refining the weld grains, thereby improving the mechanical properties of the flux-cored wire. In addition, by in-situ growing magnesium-aluminum hydrotalcite on the surface of boron nitride whiskers in the present invention, compared with directly blending the two, a more uniform composite structure can be formed, and problems such as powder stratification or agglomeration caused by performance differences during blending can be avoided. Specific Embodiments

[0040] The present invention will be further described in detail below through specific preferred embodiments, but the present invention is not limited to the following embodiments.

[0041] It should be noted that unless otherwise specified, the chemical reagents involved in the present invention are purchased through commercial channels.

[0042] In the embodiments of the present invention, the purity of iron powder, manganese powder, chromium powder, molybdenum powder, titanium powder, and calcium fluoride used is ≥99.9%, and the particle size is 200-300 mesh; The purity of nickel powder is ≥99.8%, and the particle size is 150 mesh; The purity of silica powder is ≥99.9%, and the particle size is 800 mesh; The diameter of boron nitride whiskers is 1μm, and the length is 10-20μm; The welding skin is H08A alloy steel strip, with a width of 10mm and a thickness of 0.3mm.

[0043] Example 1 A preparation method of a flux-cored wire includes the following steps: (1) 20 parts of iron powder, 10 parts of nickel powder, 8 parts of boron nitride composite material, 3 parts of manganese powder, 3 parts of chromium powder, 3 parts of molybdenum powder, 0.8 part of titanium powder, 0.8 part of silica powder, 1 part of potassium titanate as a stabilizer, and 2 parts of calcium fluoride are mixed evenly and then dried. The drying temperature is 120°C, and the drying time is 1h to obtain the flux core; Among them, the preparation method of the boron nitride composite material is as follows: S1. 10g of boron nitride whiskers are added to 100mL of 30wt% nitric acid solution, impregnated at room temperature for 2h, and then filtered, washed, and dried to obtain pretreated boron nitride whiskers; S2. Dissolve 5 g of magnesium nitrate, 3 g of aluminum nitrate and 3 g of urea in 100 mL of water. Then add 8 g of pretreated boron nitride whiskers, stir and disperse evenly, and carry out hydrothermal reaction at 120 °C for 12 h. After the reaction is completed, cool to room temperature, and obtain boron nitride composite material through filtration, washing, drying and grinding.

[0044] (2) Roll the welding skin into a U shape, add the flux-cored wire, then seal it and roll it into an O shape, and obtain the flux-cored wire through drawing and reducing the diameter. The flux-cored wire accounts for 20% of the mass of the flux-cored wire, and the diameter of the flux-cored wire is 1.5 mm.

[0045] Example 2 A method for preparing a flux-cored wire includes the following steps: (1) Mix 15 parts of iron powder, 8 parts of nickel powder, 5 parts of boron nitride composite material, 4 parts of manganese powder, 4 parts of chromium powder, 2 parts of molybdenum powder, 0.5 part of titanium powder, 0.5 part of silica powder, 1 part of potassium titanate stabilizer and 2 parts of calcium fluoride evenly and then dry. The drying temperature is 120 °C and the drying time is 1 h to obtain the flux-cored wire. Among them, the preparation method of the boron nitride composite material is as follows: S1. Add 10 g of boron nitride whiskers to 100 mL of 30 wt% nitric acid solution, immerse at room temperature for 2 h, then filter, wash and dry to obtain pretreated boron nitride whiskers. S2. Dissolve 6 g of magnesium nitrate, 4 g of aluminum nitrate and 3.5 g of urea in 100 mL of water. Then add 10 g of pretreated boron nitride whiskers, stir and disperse evenly, and carry out hydrothermal reaction at 120 °C for 12 h. After the reaction is completed, cool to room temperature, and obtain boron nitride composite material through filtration, washing, drying and grinding.

[0046] (2) Roll the welding skin into a U shape, add the flux-cored wire, then seal it and roll it into an O shape, and obtain the flux-cored wire through drawing and reducing the diameter. The flux-cored wire accounts for 20% of the mass of the flux-cored wire, and the diameter of the flux-cored wire is 1.5 mm.

[0047] Example 3 A method for preparing a flux-cored wire includes the following steps: (1) Mix 25 parts of iron powder, 12 parts of nickel powder, 10 parts of boron nitride composite material, 5 parts of manganese powder, 5 parts of chromium powder, 4 parts of molybdenum powder, 1 part of titanium powder, 1 part of silica powder, 2 parts of potassium titanate stabilizer and 3 parts of calcium fluoride evenly and then dry. The drying temperature is 120 °C and the drying time is 1 h to obtain the flux-cored wire. Among them, the preparation method of the boron nitride composite material is as follows: S1. Add 10 g of boron nitride whiskers to 100 mL of 30 wt% nitric acid solution, immerse at room temperature for 2 h, then filter, wash and dry to obtain pretreated boron nitride whiskers. S2. Dissolve 5.5 g of magnesium nitrate, 3.5 g of aluminum nitrate and 3 g of urea in 100 mL of water. Then add 6 g of pretreated boron nitride whiskers, stir and disperse evenly, and carry out hydrothermal reaction at 120 °C for 12 h. After the reaction is completed, cool to room temperature, filter, wash, dry and grind to obtain boron nitride composite material.

[0048] (2) Roll the welding skin into a U shape, add the flux-cored wire, then seal it and roll it into an O shape, and carry out drawing and reducing to obtain the flux-cored wire. The flux-cored wire accounts for 20% of the mass of the flux-cored wire, and the diameter of the flux-cored wire is 1.5 mm.

[0049] Example 4 A preparation method of a flux-cored wire includes the following steps: (1) Mix 18 parts of iron powder, 12 parts of nickel powder, 6 parts of boron nitride composite material, 2 parts of manganese powder, 2 parts of chromium powder, 3 parts of molybdenum powder, 1 part of titanium powder, 0.5 part of silica powder, 1.5 parts of potassium titanate stabilizer and 3 parts of calcium fluoride evenly and then dry at a drying temperature of 120 °C for 1 h to obtain the flux-cored wire. Among them, the preparation method of the boron nitride composite material is as follows: S1. Add 10 g of boron nitride whiskers to 100 mL of 30 wt% nitric acid solution, impregnate at room temperature for 2 h, then filter, wash and dry to obtain pretreated boron nitride whiskers. S2. Dissolve 5 g of magnesium nitrate, 4 g of aluminum nitrate and 3 g of urea in 100 mL of water. Then add 8 g of pretreated boron nitride whiskers, stir and disperse evenly, and carry out hydrothermal reaction at 100 °C for 24 h. After the reaction is completed, cool to room temperature, filter, wash, dry and grind to obtain boron nitride composite material.

[0050] (2) Roll the welding skin into a U shape, add the flux-cored wire, then seal it and roll it into an O shape, and carry out drawing and reducing to obtain the flux-cored wire. The flux-cored wire accounts for 15% of the mass of the flux-cored wire, and the diameter of the flux-cored wire is 1.5 mm.

[0051] Example 5 A preparation method of a flux-cored wire includes the following steps: (1) Mix 16 parts of iron powder, 8 parts of nickel powder, 6 parts of boron nitride composite material, 4 parts of manganese powder, 2 parts of chromium powder, 2 parts of molybdenum powder, 0.6 part of titanium powder, 0.6 part of silica powder, 1.5 parts of potassium titanate stabilizer and 2.5 parts of calcium fluoride evenly and then dry at a drying temperature of 120 °C for 1 h to obtain the flux-cored wire. Among them, the preparation method of the boron nitride composite material is as follows: S1. Add 10 g of boron nitride whiskers to 100 mL of 30 wt% nitric acid solution, impregnate at room temperature for 2 h, then filter, wash and dry to obtain pretreated boron nitride whiskers. S2. Dissolve 6 g of magnesium nitrate, 3 g of aluminum nitrate, and 3.5 g of urea in 100 mL of water. Then add 8 g of pretreated boron nitride whiskers, stir to disperse evenly, and carry out a hydrothermal reaction at 100 °C for 24 h. After the reaction is completed, cool to room temperature, and then filter, wash, dry, and grind to obtain the boron nitride composite material.

[0052] (2) Roll the welding skin into a U shape, add the flux-cored wire, then seal it and roll it into an O shape, and then carry out drawing and reducing diameter to obtain the flux-cored wire. The flux-cored wire accounts for 25% of the mass of the flux-cored wire, and the diameter of the flux-cored wire is 1.5 mm.

[0053] Comparative Example 1 A method for preparing a flux-cored wire includes the following steps: (1) Mix 20 parts of iron powder, 10 parts of nickel powder, 8 parts of boron nitride whiskers, 3 parts of manganese powder, 3 parts of chromium powder, 3 parts of molybdenum powder, 0.8 part of titanium powder, 0.8 part of silica powder, 1 part of potassium titanate as a stabilizer, and 2 parts of calcium fluoride evenly and then dry. The drying temperature is 120 °C, and the drying time is 1 h to obtain the flux-cored wire. (2) Roll the welding skin into a U shape, add the flux-cored wire, then seal it and roll it into an O shape, and then carry out drawing and reducing diameter to obtain the flux-cored wire. The flux-cored wire accounts for 20% of the mass of the flux-cored wire, and the diameter of the flux-cored wire is 1.5 mm.

[0054] Compared with Example 1, in Comparative Example 1, boron nitride whiskers are used to replace the boron nitride composite material.

[0055] Comparative Example 2 A method for preparing a flux-cored wire includes the following steps: (1) Mix 20 parts of iron powder, 10 parts of nickel powder, 8 parts of magnesium-aluminum hydrotalcite, 3 parts of manganese powder, 3 parts of chromium powder, 3 parts of molybdenum powder, 0.8 part of titanium powder, 0.8 part of silica powder, 1 part of potassium titanate as a stabilizer, and 2 parts of calcium fluoride evenly and then dry. The drying temperature is 120 °C, and the drying time is 1 h to obtain the flux-cored wire. Among them, the preparation method of magnesium-aluminum hydrotalcite is as follows: Dissolve 5 g of magnesium nitrate, 3 g of aluminum nitrate, and 3 g of urea in 100 mL of water, stir evenly, and carry out a hydrothermal reaction at 120 °C for 12 h. After the reaction is completed, cool to room temperature, and then filter, wash, dry, and grind to obtain magnesium-aluminum hydrotalcite.

[0056] (2) Roll the welding skin into a U shape, add the flux-cored wire, then seal it and roll it into an O shape, and then carry out drawing and reducing diameter to obtain the flux-cored wire. The flux-cored wire accounts for 20% of the mass of the flux-cored wire, and the diameter of the flux-cored wire is 1.5 mm.

[0057] Compared with Example 1, in Comparative Example 2, magnesium-aluminum hydrotalcite is used to replace the boron nitride composite material.

[0058] Comparative Example 3 A method for preparing a flux-cored wire, comprising the following steps: (1) Mix 20 parts of iron powder, 10 parts of nickel powder, 4 parts of boron nitride whiskers, 4 parts of magnesium-aluminum hydrotalcite, 3 parts of manganese powder, 3 parts of chromium powder, 3 parts of molybdenum powder, 0.8 part of titanium powder, 0.8 part of silica powder, 1 part of potassium titanate as a stabilizer and 2 parts of calcium fluoride evenly, and then dry. The drying temperature is 120°C and the drying time is 1 h to obtain a flux core; Among them, the preparation method of magnesium-aluminum hydrotalcite is as follows: Dissolve 5 g of magnesium nitrate, 3 g of aluminum nitrate and 3 g of urea in 100 mL of water, stir evenly, carry out hydrothermal reaction at 120°C for 12 h. After the reaction is completed, cool to room temperature, and then filter, wash, dry and grind to obtain magnesium-aluminum hydrotalcite.

[0059] (2) Roll the welding skin into a U shape, add the flux core, then seal it and roll it into an O shape, and then obtain the flux-cored wire through drawing and reducing the diameter. The flux core accounts for 20% of the mass of the flux-cored wire, and the diameter of the flux-cored wire is 1.5 mm.

[0060] Weld the flux-cored wires prepared in Examples 1-2 and Comparative Examples 1-3. The welding steel plate is a Q235B type steel plate (350 mm×150 mm×20 mm), the shielding gas is argon, the welding voltage is 18-20 V, the welding current is 130-150 A, the welding speed is 25 cm / min, and the wire feeding speed is 150 cm / min. Measure various properties of the deposited metal of the welded parts. Among them, the hardness (HRC) is measured according to the national standard GB / T 230.1-2018 "Metallic materials - Rockwell hardness test - Part 1: Test method", and the mechanical properties are tested according to the national standard GB / T 2652-2022. The test results are shown in Table 1.

[0061] Table 1 Performance test results of different groups As can be seen from Table 1, compared with Comparative Examples 1-3, the flux-cored wires prepared in the examples of the present invention have higher hardness and excellent mechanical properties.

[0062] Finally, it should be noted that the above embodiments do not limit the present invention in any form. For those skilled in the art, on the basis of the present invention, some modifications and improvements can be made. Therefore, any modification or improvement made without departing from the spirit of the present invention falls within the scope of protection required by the present invention.

Claims

1. A flux-cored wire with high hardness and high strength, characterized in that, The flux-cored wire includes a welding coating and a flux core, and the flux core is composed of raw materials in the following parts by weight: 15-25 parts of iron powder, 8-12 parts of nickel powder, 5-10 parts of boron nitride composite material, 2-5 parts of manganese powder, 2-5 parts of chromium powder, 2-4 parts of molybdenum powder, 0.5-1 part of titanium powder, 0.5-1 part of silica powder, 1-2 parts of stabilizer, and 2-3 parts of calcium fluoride.

2. The flux-cored wire according to claim 1, wherein The preparation method of the boron nitride composite material is as follows: S1. Add boron nitride whiskers into a nitric acid solution for impregnation treatment, and then filter, wash, and dry to obtain pretreated boron nitride whiskers; S2. Dissolve soluble magnesium salt, soluble aluminum salt, and urea in water, then add the pretreated boron nitride whiskers, stir and disperse evenly, carry out hydrothermal reaction. After the reaction is completed, cool to room temperature, filter, wash, dry, and grind to obtain the boron nitride composite material.

3. The flux cored wire according to claim 2, characterized in that, In step S2, the mass ratio of the soluble magnesium salt, soluble aluminum salt, urea, and pretreated boron nitride whiskers is 5-6:3-4:2.5-3.5:5-10.

4. The flux-cored wire according to claim 2, characterized in that, In step S2, the soluble magnesium salt is selected from magnesium sulfate, magnesium chloride, or magnesium nitrate.

5. The flux-cored wire according to claim 2, characterized in that, In step S2, the soluble aluminum salt is selected from aluminum chloride, aluminum nitrate, or aluminum sulfate.

6. The flux-cored wire according to claim 2, characterized in that, In step S2, the temperature of the hydrothermal reaction is 100-120 °C, and the time of the hydrothermal reaction is 12-24 h.

7. The flux-cored wire according to claim 1, characterized in that, The stabilizer is selected from at least one of potassium titanate, yttrium oxide, and lanthanum oxide.

8. The flux-cored wire according to claim 1, wherein The flux core accounts for 15-25% of the mass of the flux-cored wire.

9. The preparation method of the flux-cored wire according to any one of claims 1-8, characterized in that, It includes the following steps: (1) Mix iron powder, nickel powder, boron nitride composite material, manganese powder, chromium powder, molybdenum powder, titanium powder, silica powder, stabilizer, and calcium fluoride evenly by weight and then dry to obtain the flux core; (2) Roll the welding coating into a U shape, add the flux core, then seal and roll it into an O shape, and through drawing and reducing the diameter, the flux-cored wire is obtained.

10. The preparation method according to claim 9, characterized in that, In step (2), the diameter of the flux-cored wire is 1.2-1.8 mm.

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