Welding powder, flux-cored welding wire and its preparation method

Abstract

This invention discloses a welding material powder for use as an additive in welding operations. The welding material powder includes agglomerated coated micro-powder, which consists of hard particles that have undergone agglomeration and coating treatment. The coating layer formed by the coating treatment is a metal film. This invention also discloses a flux-cored welding wire using this welding material powder and its preparation method. This invention employs agglomeration and coating technology to agglomerate hard particles into micro-powder containing a coating structure. During welding, this reduces changes in the properties of the hard particles, resulting in a more uniform distribution of hard particles in the weld layer and more stable weld layer performance.

Description

Technical Field

[0001] This invention relates to the field of welding technology, and in particular to a welding powder, a flux-cored welding wire, and a method for preparing the same. Background Technology

[0002] In industries such as metallurgy, mining, petrochemicals, cement, and machining, mechanical equipment components frequently experience wear from materials or processed parts. These components require surface wear-resistant reinforcement through welding processes; therefore, the wear resistance of the weld / weld layer is also crucial.

[0003] Using hard phases such as carbides, nitrides, and oxides to improve the strength and hardness of metallic materials is a common and important method. Therefore, to improve the wear resistance of welds, hard phase components such as carbides, nitrides, and oxides can be added to the weld pool.

[0004] For example, Chinese patent application CN116532754A discloses a method for preparing a wear-resistant weld overlay, which uses MAG welding and injects hard particles into the molten pool while the welding torch is performing weld overlay.

[0005] For example, Chinese patent application CN105269183A discloses a nano-modified boron-containing high-chromium cast iron wear-resistant surfacing self-shielded flux-cored wire. This wire uses high-chromium cast iron powder, electrolytic manganese powder, ferrosilicon powder, ferroboron powder, graphite powder, and aluminum-magnesium alloy powder in its flux core. By adjusting the composition of the flux core, ferrochrome carbides are formed to improve the wear resistance of the surfacing layer. Chinese patent application CN103381527A discloses a tungsten carbide-reinforced iron-based wear-resistant surfacing flux-cored wire. This wire incorporates a large amount of cast tungsten carbide into the flux core powder, using it as the main hard phase to act as a wear-resistant skeleton.

[0006] The formation of hard particles such as carbides, nitrides, and oxides in the weld overlay can be achieved through two methods: in-situ precipitation and external addition. However, both methods of forming hard particles in the weld overlay share a common drawback: they cannot efficiently control the morphology and distribution of carbides, nitrides, and oxides in the metal microstructure. For example, when tungsten carbide is used in welding wire to improve the hardness of the weld layer, the precipitation location and size of the tungsten carbide are difficult to control when it precipitates in situ, and the composition of the generated tungsten carbide generally deviates significantly from the design value. When using external additives, although the melting points of hard particles such as carbides, nitrides, and oxides are much higher than those of alloy steels, the temperature of the electric arc during welding can generally reach 1700℃, or even 2900℃, and the instantaneous temperature may be even higher. Therefore, if the added particles are too small, the hard particles will melt or partially melt, forming brittle material in the molten area, reducing the adhesion of the particles and leading to a decline in the performance of the hard particles. If the added particles are too large, they will sink to the bottom, resulting in uneven weld layer hardness. Other metallic compounds that act as hard phases, such as carbides, nitrides, or oxides of tungsten and titanium, also present similar problems of difficulty in controlling the formation and / or distribution of wear-resistant particles due to their respective characteristics.

[0007] Therefore, improving the distribution of hard phases in the weld layer during welding operations to enhance the stability and uniformity of the weld layer, thereby improving its performance, has become a technical problem that needs to be solved. Summary of the Invention

[0008] The main technical problem solved by this invention is to provide a welding powder, a flux-cored welding wire and a method for preparing the same, which can improve the stability and uniformity of the distribution of hard particles in the weld layer during the welding process, thereby improving the performance of the weld layer.

[0009] To address the aforementioned technical problems, this invention provides a welding powder for use as an additive in welding operations. The welding powder comprises agglomerated coated micro-powder; the agglomerated coated micro-powder consists of hard particles that have undergone agglomeration and coating treatment; wherein the coating layer formed by the coating treatment is a metal film; wherein the agglomeration treatment forms agglomerated particles, increasing the size of the small particles in the welding powder and thus enhancing its fluidity. Under the high temperature during welding, the agglomerated hard particles return to a loose state and are evenly distributed in the weld metal layer; the coating treatment causes the metal film to melt and absorb heat when the agglomerated particles pass through a high-temperature welding heat source, thereby reducing the heat received by the hard particles and preventing melting or performance degradation of the hard particles.

[0010] The present invention also provides a method for preparing welding powder, wherein the welding powder is used as an additive in welding operations, and the preparation method includes:

[0011] Hard particles are agglomerated and coated to form agglomerated coated fine powder; wherein the coating layer formed by the coating process is a metal film;

[0012] The agglomerated coated fine powder is used to prepare welding material powder. The agglomeration treatment forms hard particles into agglomerated particles, making the small particles of the welding material powder larger and thus enhancing its fluidity. Under the high temperature of the welding process, the agglomerated hard particles return to a loose state and are evenly distributed in the weld metal. The coating treatment causes the metal film to melt and absorb heat when the agglomerated particles pass through the high temperature of the welding heat source, thereby reducing the heat received by the hard particles and preventing the hard particles from melting or degrading in performance.

[0013] This invention also provides a flux-cored welding wire, comprising an outer sheath and a flux core, wherein the outer sheath is a metal strip, and the flux core comprises agglomerated coated fine powder, which is a fine powder of hard particles that has undergone agglomeration and coating treatment, and the coating layer formed by the coating treatment is a metal film; wherein, the agglomeration treatment forms hard particles into agglomerated particles, making the small particles of the welding material powder larger, thereby enhancing the fluidity, and under the high temperature of the welding process, the agglomerated hard particles return to a loose state and are evenly distributed in the welding layer metal; the coating treatment causes the metal film to melt and absorb heat when the agglomerated particles pass through the high temperature of the welding heat source, thereby reducing the heat received by the hard particles and preventing the hard particles from melting or degrading in performance.

[0014] The present invention also provides a method for preparing flux-cored welding wire, the method comprising:

[0015] The preparation of agglomerated coated fine powder includes: agglomerating and coating hard particles to form agglomerated coated fine powder; wherein the coating layer formed by the coating process is a metal film.

[0016] Prepare a drug core containing the agglomerated coated micropowder;

[0017] Fill the core material into the U-shaped metal strip;

[0018] The U-shaped metal strip filled with flux is rolled and then drawn to form the flux-cored welding wire of the required specifications. The agglomeration treatment forms hard particles into agglomerated particles, which increases the size of the small particles of the welding powder and enhances its fluidity. Under the high temperature of the welding process, the agglomerated hard particles return to a loose state and are evenly distributed in the weld metal. The coating treatment causes the metal film to melt and absorb heat when the agglomerated particles pass through the high temperature of the welding heat source, thereby reducing the heat received by the hard particles and preventing them from melting or degrading in performance.

[0019] The beneficial effects of the present invention are: the embodiments of the present invention use agglomeration and coating technology to agglomerate hard particles into fine powder containing a coating structure, which can make the distribution of hard particles in the weld layer more uniform and the performance more stable during welding. Detailed Implementation

[0020] The preferred embodiments of the present invention will be described in detail below so that the advantages and features of the present invention can be more easily understood by those skilled in the art, thereby making a clearer and more explicit definition of the scope of protection of the present invention.

[0021] The welding material powder of this invention includes agglomerated coated micropowder. The agglomerated coated micropowder consists of hard particles processed using agglomeration and coating techniques. The particle size of the agglomerated coated micropowder is 100 nm to 100 μm.

[0022] The hard particles can be at least one of tungsten carbide, chromium carbide, titanium carbide, niobium carbide, chromium oxide, aluminum oxide, rare earth metal oxides, silicon nitride, and gallium nitride, or a combination of several of them. The hard particles are micro-nano-sized particles with a particle size of 20 nm to 20 μm.

[0023] The agglomeration technology of this invention includes techniques for bonding powders together using adhesives, such as rotary spray granulation.

[0024] The coating technology of this invention includes uniformly depositing a metal film on the particle surface through physical or chemical reactions, such as magnetron sputtering or chemical deposition. The coating material includes at least one of nickel, chromium, molybdenum, and copper.

[0025] Agglomerated coated fine powder can be obtained by forming a metal film on the surface of hard particles after they have agglomerated, and then by coating technology.

[0026] Agglomerated coated fine powder can also be obtained by first coating hard particles to form a metal film on the surface of the hard particles, and then agglomerating them to form agglomerated particles.

[0027] The welding material powder of this invention can be prepared by drying the agglomerated coated fine powder.

[0028] The welding powder of this invention can be used as an additive in welding operations, directly during the welding process. During welding, the welding powder is added to the weld pool to form a weld layer.

[0029] Hard particles with a diameter distribution of 20 nm to 20 μm, after being agglomerated into large powder particles, have a particle size several to hundreds of times larger than the original powder, but the shape and properties of the agglomerated hard particles remain unchanged. Micro- and nano-sized powders, with their fine dimensions, exhibit stronger bonding forces between these carbides, nitrides, and oxides and the metal lattice. Under conditions of unchanged physical properties and uniform distribution, the strength and hardness of metallic materials can be significantly improved. However, the small size of micro- and nano-sized powders leads to significant van der Waals forces between the powder particles, resulting in poor flowability and making them unsuitable for subsequent transport in pipelines or conveyor belts. Furthermore, micro- and nano-sized powders are easily melted after being heated by a welding heat source, thus altering their properties and losing their original strengthening effect.

[0030] In the preparation of the welding powder in this embodiment of the invention, agglomeration and coating technologies are used to form agglomerated coated micro-powder from hard particles, increasing the size of the small particles and enhancing their flowability. When the agglomerated particles pass through a high-temperature welding heat source, the metal film melts and absorbs heat, reducing the heat received by the hard particles inside the agglomerated particles, thus preventing the hard particles from melting or degrading in performance and preserving their original properties to the greatest extent. Furthermore, the binder in the agglomerated particles decomposes and volatilizes into the environment under high temperature, causing the hard particles to return to a loose state and distribute uniformly in the weld metal in a state close to their original shape and performance.

[0031] The welding powder of this invention improves the flowability of hard particles through agglomeration and coating processes, making it suitable for industrial production. At the same time, it reduces the damage to the performance of hard particles caused by welding heat and enhances the strengthening effect of hard particles in the weld layer.

[0032] The flux-cored welding wire of this invention includes an outer sheath and a flux core. The outer sheath is a metal strip.

[0033] The core contains agglomerated coated microparticles. Agglomerated coated microparticles are microparticles formed by agglomeration and metal coating processes of hard particles, containing hard particles with both agglomerated and metal film structures.

[0034] In addition, the flux core may also contain conventional fluxes such as scavengers, slag-forming agents, and alloying components. For example, scavengers may be manganese, ferrosilicon, etc., alloying components may include graphite, high-carbon ferrochrome, metallic chromium, metallic nickel, etc., and slag-forming agents may include rutile, calcium fluoride, marble, etc.

[0035] Among them, the agglomerated coating micro powder accounts for 30% to 60% of the weight of the core, and its particle size is 100nm to 100μm.

[0036] The hard particles can be at least one of tungsten carbide, chromium carbide, titanium carbide, niobium carbide, chromium oxide, aluminum oxide, rare earth metal oxides, silicon nitride, and gallium nitride, or a combination of several of them. The hard particles are micro-nano-scale microparticles with a particle size of 20 nm to 20 μm.

[0037] The agglomeration technology of this invention includes techniques for bonding powders together using adhesives, such as rotary spray granulation.

[0038] The coating technology of this invention includes uniformly depositing a metal film on the particle surface through physical or chemical reactions, such as magnetron sputtering or chemical deposition. The coating material includes at least one of nickel, chromium, molybdenum, and copper.

[0039] Agglomerated coated fine powder can be obtained by forming a metal film on the surface of hard particles after they have agglomerated, and then by coating technology.

[0040] Agglomerated coated fine powder can also be obtained by first coating hard particles to form a metal film layer on the surface of the hard particles, and then agglomerating them to form agglomerated particles.

[0041] In the preparation of flux-cored welding wire, steel strip is rolled into a U-shaped cross section, and then flux containing agglomerated coated fine powder is filled into the U-shaped steel strip; the U-shaped steel strip filled with flux is rolled tightly with a rolling mill and then drawn to form the desired flux-cored welding wire.

[0042] Hard particles with a diameter distribution of 20 nm to 20 μm, after being agglomerated into large powder particles, have a particle size several to hundreds of times larger than the original powder, but the shape and properties of the agglomerated hard particles remain unchanged. Micro- and nano-sized powders, with their fine dimensions, exhibit stronger bonding forces between these carbides, nitrides, and oxides and the metal lattice. Under conditions of unchanged physical properties and uniform distribution, the strength and hardness of metallic materials can be significantly improved. However, the small size of micro- and nano-sized powders leads to significant van der Waals forces between the powder particles, resulting in poor flowability and making them unsuitable for subsequent transport in pipelines or conveyor belts. Furthermore, micro- and nano-sized powders are easily melted after being heated by a welding heat source, thus altering their properties and losing their original strengthening effect.

[0043] In the preparation of the flux-cored welding wire in this embodiment of the invention, agglomeration and coating technologies are used to form agglomerated coated micropowder from hard particles, increasing the size of the particles and enhancing their flowability. When the agglomerated coated micropowder passes through a high-temperature welding heat source, the metal film on the surface of the hard particles melts, absorbing heat and reducing the heat absorbed by the hard particles inside the agglomerated particles, thus reducing the risk of melting or performance degradation of the hard particles. Furthermore, the binder in the agglomerated particles decomposes and volatilizes into the environment under high temperature, causing the hard particles to return to a loose state and be uniformly distributed in the weld metal in a state close to their original shape and performance.

[0044] The agglomerated coated micro-powder of this invention improves the flowability of hard particles through agglomeration and coating processes, making it suitable for industrial production. At the same time, it reduces the damage to the properties of hard particles caused by welding heat and enhances the strengthening effect of hard particles in the weld layer. When using flux-cored welding wire containing agglomerated coated micro-powder during welding, a weld layer with better wear resistance can be obtained.

[0045] In a specific embodiment of the flux-cored welding wire, the outer sheath is made of low-carbon steel strip, with the following composition: C < 0.1%; Si, Mn, Cr, Ni < 1%; balance Fe. The flux core in this embodiment may include: metallic manganese, 4%~8%; 75# ferrosilicon, 3%~6%; metallic chromium, 6%~10%; graphite, 1%~4%; high-carbon ferrochrome (of which the composition is: C, 7.5%~8.0%; Cr, 70%~75%; balance Fe), 30%~50%; metallic nickel, 5%~9%; agglomerated coated fine powder, 30%~60%; rutile, 3%~7%; calcium fluoride, 2%~4%; marble, 3%~7%; balance iron. All percentages are by weight. The weight coefficient of the flux core, i.e., the weight percentage of the flux core in the flux-cored welding wire, is 25%~30%.

[0046] In another specific embodiment of the flux-cored wire, the outer sheath is a nickel-chromium alloy strip, comprising: Cr, 19%~21%; the balance being Ni. The flux core composition in a specific embodiment of the flux-cored wire may include: metallic manganese, 2%~7%; 75# ferrosilicon, 1%~3%; metallic chromium, 15%~30%; high-carbon ferrochrome (of which the composition is: C, 7.5%~8.0%; Cr, 70%~75%; the balance being Fe), 30%~50%; ferromolybdenum (of which Mo accounts for 60%, the balance being Fe), 6%~10%; agglomerated coated micro / nano powder, 30%~60%; calcium fluoride, 2%~4%; marble, 3%~7%; the balance being metallic nickel. All percentages are by weight. The weight coefficient of the flux core, i.e., the weight percentage of the flux core in the flux-cored wire, is 25%~30%.

[0047] The above description is merely an embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural or procedural transformations made based on the content of the present invention specification, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of the present invention.

Claims

1. A welding powder, used as an additive in welding operations, characterized in that: The welding material powder includes agglomerated coated fine powder; the agglomerated coated fine powder is a fine particle of hard particles that has undergone agglomeration and coating treatment; wherein, the coating layer formed by the coating treatment is a metal film; wherein, the agglomeration treatment forms hard particles into agglomerated particles, making the small particles of the welding material powder larger, thereby enhancing the fluidity, and under the high temperature of the welding process, the agglomerated hard particles return to a loose state and are evenly distributed in the welding layer metal; the coating treatment causes the metal film to melt and absorb heat when the agglomerated particles pass through the high temperature of the welding heat source, thereby reducing the heat received by the hard particles and preventing the hard particles from melting or degrading in performance.

2. The welding powder according to claim 1, characterized in that: The particle size of the agglomerated coating micro powder is 100nm~100μm.

3. The welding powder according to claim 1, characterized in that: Hard particles include at least one of tungsten carbide, chromium carbide, titanium carbide, niobium carbide, chromium oxide, aluminum oxide, rare earth metal oxides, silicon nitride, and gallium nitride.

4. The welding powder according to claim 1, characterized in that: The particle size of the hard particles is 20 nm to 20 μm.

5. The welding powder according to claim 1, characterized in that: Agglomeration treatment includes rotary spray granulation.

6. The welding powder according to claim 1, characterized in that: The materials for the metal film include at least one of nickel, chromium, molybdenum, and copper.

7. A method for preparing welding powder, wherein the welding powder is used as an additive in welding operations, characterized in that, The preparation method includes: Hard particles are agglomerated and coated to form agglomerated coated fine powder; wherein the coating layer formed by the coating process is a metal film. Welding powder is prepared using the aforementioned agglomerated coated fine powder; The agglomeration treatment forms hard particles into agglomerated particles, making the small particles of the welding material powder larger and thus enhancing its fluidity. Under the high temperature of the welding process, the agglomerated hard particles return to a loose state and are evenly distributed in the weld metal. The coating treatment causes the metal film to melt and absorb heat when the agglomerated particles pass through the high temperature of the welding heat source, thereby reducing the heat received by the hard particles and preventing the hard particles from melting or degrading in performance.

8. The method for preparing welding powder according to claim 7, characterized in that: The steps of agglomerating and coating hard particles include: after forming agglomerated hard particles, a metal film is formed on the surface of the agglomerated particles using a coating technology.

9. The method for preparing welding powder according to claim 7, characterized in that: The steps of agglomerating and coating hard particles include: coating the hard particles to form a metal film on the surface of the hard particles, and then agglomerating the coated hard particles to form agglomerated particles.

10. The method for preparing welding powder according to claim 7, characterized in that: The particle size of the agglomerated coating micro powder is 100nm~100μm.

11. The method for preparing welding powder according to claim 7, characterized in that: Hard particles include at least one of tungsten carbide, chromium carbide, titanium carbide, niobium carbide, chromium oxide, aluminum oxide, rare earth metal oxides, silicon nitride, and gallium nitride.

12. The method for preparing welding powder according to claim 7, characterized in that: The particle size of the hard particles is 20 nm to 20 μm.

13. The method for preparing welding powder according to claim 7, characterized in that: Agglomeration treatment includes rotary spray granulation.

14. The method for preparing welding powder according to claim 7, characterized in that: The materials for the metal film include at least one of nickel, chromium, molybdenum, and copper.

15. A flux-cored welding wire, comprising an outer sheath and a flux core, wherein the outer sheath is a metal strip, characterized in that: The flux core comprises agglomerated coated microparticles, which are fine particles of hard material that have undergone agglomeration and coating treatment. The coating layer formed by the coating treatment is a metal film. The agglomeration treatment forms agglomerated particles of hard material, making the small particles of the welding powder larger, thereby enhancing its fluidity. Under the high temperature of the welding process, the agglomerated hard particles return to a loose state and are evenly distributed in the welding metal layer. The coating treatment causes the metal film to melt and absorb heat when the agglomerated particles pass through the high temperature of the welding heat source, thereby reducing the heat received by the hard particles and preventing the hard particles from melting or degrading in performance.

16. The flux-cored welding wire according to claim 15, characterized in that: The particle size of the agglomerated coating micro powder is 100nm~100μm.

17. The flux-cored welding wire according to claim 15, characterized in that: Hard particles include at least one of tungsten carbide, chromium carbide, titanium carbide, niobium carbide, chromium oxide, aluminum oxide, rare earth metal oxides, silicon nitride, and gallium nitride.

18. The flux-cored welding wire according to claim 15, characterized in that: The particle size of the hard particles is 20 nm to 20 μm.

19. The flux-cored welding wire according to claim 15, characterized in that: Agglomeration treatment includes rotary spray granulation.

20. The flux-cored welding wire according to claim 15, characterized in that: The materials for the metal film include at least one of nickel, chromium, molybdenum, and copper.

21. The flux-cored welding wire according to claim 15, characterized in that: The flux core also includes powders such as deoxidizers, slag-forming agents, and alloy components.

22. The flux-cored welding wire according to claim 21, characterized in that: The metal strip is a low-carbon steel strip, and the weight percentage content of each component in the low-carbon steel strip is as follows: C, 0~0.1%; Si, Mn, Cr, Ni, 0~1%; balance Fe.

23. The flux-cored welding wire according to claim 22, characterized in that, The core composition includes: manganese metal, 4%~8%; 75# ferrosilicon, 3%~6%; chromium metal, 6%~10%; graphite, 1%~4%; high-carbon ferrochrome, 30%~50%; nickel metal, 5%~9%; agglomerated coated fine powder, 30%~60%; rutile, 3%~7%; calcium fluoride, 2%~4%; marble, 3%~7%; and the balance is iron.

24. The flux-cored welding wire according to claim 21, characterized in that: The metal strip is a nickel-chromium alloy strip, and its composition includes: Cr, 19%~21%; the balance is Ni.

25. The flux-cored welding wire according to claim 24, characterized in that: The core composition includes: manganese metal, 2%~7%; 75# ferrosilicon, 1%~3%; chromium metal, 15%~30%; high-carbon ferrochrome, 30%~50%; ferromolybdenum, 6%~10%; agglomerated coated micro / nano powder, 30%~60%; calcium fluoride, 2%~4%; marble, 3%~7%; and the balance is nickel metal.

26. The flux-cored welding wire according to claim 15, characterized in that: The weight coefficient of the core is 25%~30%.

27. A method for preparing a flux-cored welding wire, characterized in that, The preparation method includes: The preparation of agglomerated coated fine powder includes: agglomerating and coating hard particles to form agglomerated coated fine powder; wherein the coating layer formed by the coating process is a metal film. Prepare a drug core containing the agglomerated coated micropowder; Fill the core material into the U-shaped metal strip; After the U-shaped metal strip filled with flux is rolled tightly, it is then drawn to form the flux-cored welding wire of the required specifications. The agglomeration treatment forms hard particles into agglomerated particles, making the small particles of the welding material powder larger and thus enhancing its fluidity. Under the high temperature of the welding process, the agglomerated hard particles return to a loose state and are evenly distributed in the weld metal. The coating treatment causes the metal film to melt and absorb heat when the agglomerated particles pass through the high temperature of the welding heat source, thereby reducing the heat received by the hard particles and preventing the hard particles from melting or degrading in performance.

28. The method for preparing the flux-cored welding wire according to claim 27, characterized in that: The steps of agglomerating and coating hard particles include: after agglomerating the hard particles, forming a metal film on the surface of the agglomerated particles using a coating technology.

29. The method for preparing flux-cored welding wire according to claim 27, characterized in that: The steps of agglomerating and coating hard particles include: coating hard particles to form a metal film on the surface of hard particles, and then agglomerating the coated hard particles to form agglomerated particles.

30. The method for preparing the flux-cored welding wire according to claim 27, characterized in that: The particle size distribution of the agglomerated coating micro powder is 100nm~100μm.

31. The method for preparing flux-cored welding wire according to claim 27, characterized in that: Hard particles include at least one of tungsten carbide, chromium carbide, titanium carbide, niobium carbide, chromium oxide, aluminum oxide, rare earth metal oxides, silicon nitride, and gallium nitride.

32. The method for preparing flux-cored welding wire according to claim 27, characterized in that: The particle size distribution of the hard particles is 20 nm to 20 μm.

33. The method for preparing flux-cored welding wire according to claim 27, characterized in that: Agglomeration treatment includes rotary spray granulation.

34. The method for preparing flux-cored welding wire according to claim 27, characterized in that: The materials for the metal film include at least one of nickel, chromium, molybdenum, and copper.

35. The method for preparing flux-cored welding wire according to claim 27, characterized in that: The core also includes powders such as oxygen scavengers, slag-forming agents, and alloy components; the step of preparing a core containing the agglomerated coating micro powder includes mixing the agglomerated coating micro powder with powders such as oxygen scavengers, slag-forming agents, and alloy components.

36. The method for preparing flux-cored welding wire according to claim 35, characterized in that: The U-shaped metal strip is a low-carbon steel strip, and the weight percentage content of each component in the low-carbon steel strip is as follows: C, 0~0.1%; Si, Mn, Cr, Ni, 0~1%; balance Fe.

37. The method for preparing flux-cored welding wire according to claim 35, characterized in that: The core composition includes: manganese metal, 4%~8%; 75# ferrosilicon, 3%~6%; chromium metal, 6%~10%; graphite, 1%~4%; high-carbon ferrochrome, 30%~50%; nickel metal, 5%~9%; agglomerated coated fine powder, 30%~60%; rutile, 3%~7%; calcium fluoride, 2%~4%; marble, 3%~7%; and the balance is iron.

38. The method for preparing flux-cored welding wire according to claim 35, characterized in that: The U-shaped metal strip is a nickel-chromium alloy strip, whose composition includes: Cr, 19%~21%; the balance is Ni.

39. The method for preparing flux-cored welding wire according to claim 38, characterized in that: The core composition includes: manganese metal, 2%~7%; 75# ferrosilicon, 1%~3%; chromium metal, 15%~30%; high-carbon ferrochrome, 30%~50%; ferromolybdenum, 6%~10%; agglomerated coated micro / nano powder, 30%~60%; calcium fluoride, 2%~4%; marble, 3%~7%; and the balance is nickel metal.

40. The method for preparing flux-cored welding wire according to claim 27, characterized in that: The weight coefficient of the core is 25%~30%.