A flux-cored material and flux-cored welding wire for 9% Ni steel welding and a preparation method thereof

Abstract

The present invention provides a flux-cored material and flux-cored welding wire for welding 9% Ni steel, and a preparation method thereof, relating to the technical field of welding materials. The flux-cored material comprises the following raw materials in parts by weight: 18-28 parts rutile, 1-3 parts ferrotitanium, 5-10 parts potassium-sodium feldspar, 1-3 parts zirconium dioxide, 3.5-6.5 parts quartz, 3.5-6.5 parts manganese monoxide, 1-3 parts magnesia, 1.5-2.5 parts ferroaluminum, 0.2-0.5 parts fluoride, 15-20 parts metallic chromium, 25-30 parts nickel powder, 6-9 parts molybdenum powder, and 1.5-2.5 parts ferrotungsten. The flux-cored welding wire made with the flux-cored material is suitable for all-position welding of 9% Ni steel, and features stable arc stability, minimal spatter, beautiful weld formation, easy slag removal, excellent mechanical properties, and good anti-porosity properties.

Description

Technical Field

[0001] The invention relates to the technical field of welding materials, and in particular to a flux-cored material and flux-cored welding wire for welding 9% Ni steel and a preparation method thereof. Background Art

[0002] Although my country's LNG (liquefied natural gas) industry started relatively late, it has developed rapidly. 9% Ni steel is generally used in LNG storage and transportation. 9% Ni steel plates have been fully domestically produced by Nanjing Iron and Steel, Anshan Iron and Steel, etc. When welding 9% Ni steel, there are problems such as poor molten pool fluidity and shallow penetration. Low-melting-point impurities during weld crystallization are segregated and distributed on the grain boundaries, which are prone to problems such as porosity, incomplete penetration, thermal cracks and poor impact toughness. These problems seriously restrict the widespread application of 9% Ni steel in the field of LNG storage and transportation. Flux-cored arc welding (FCAW) is highly favored in industrial production due to its advantages such as high deposition efficiency, applicability to a variety of welding positions and ease of automated welding. Although some domestic welding material manufacturers have conducted research, the flux-cored wire used for 9% Ni steel still has a large gap in all-position weldability and porosity resistance, and has not yet been applied in large quantities. Summary of the Invention

[0003] In view of the above problems existing in the prior art, the present invention provides a flux-cored material and flux-cored welding wire for 9% Ni steel welding and a preparation method thereof, so as to improve the problems of poor all-position processability and poor anti-porosity ability of the flux-cored welding wire for 9% Ni steel welding in the prior art.

[0004] To achieve the above-mentioned and other related purposes, the present invention provides a flux core material for welding 9% Ni steel in a first aspect, the flux core material comprising the following raw materials in parts by weight: 18 to 28 parts of rutile, 1 to 3 parts of ferroilan, 5 to 10 parts of potassium-sodium feldspar, 1 to 3 parts of zirconium dioxide, 3.5 to 6.5 parts of quartz, 3.5 to 6.5 parts of manganese monoxide, 1 to 3 parts of magnesia, 1.5 to 2.5 parts of ferroaluminum, 0.2 to 0.5 parts of fluoride, 15 to 20 parts of metallic chromium, 25 to 30 parts of nickel powder, 6 to 9 parts of molybdenum powder, and 1.5 to 2.5 parts of ferrotungsten.

[0005] In one embodiment of the present invention, the fluoride includes any one or more of rare earth fluoride, fluorosilicate, sodium fluoride and potassium fluoride.

[0006] In one embodiment of the present invention, the rutile, the potassium-sodium feldspar and the quartz are respectively sieved through an 80-mesh sieve.

[0007] In one embodiment of the present invention, the metallic chromium, the nickel powder, the molybdenum powder and the ferrotungsten are respectively sieved through a 120-mesh sieve.

[0008] In one embodiment of the present invention, the S content in all raw materials of the core material is ≤0.02%, and the P content is ≤0.02%.

[0009] The second aspect of the present invention provides a flux-cored welding wire for welding 9% Ni steel, the flux-cored welding wire comprising an outer sheath and a flux core material coated in the outer sheath, the flux core material comprising the following raw materials in parts by weight: 18 to 28 parts of rutile, 1 to 3 parts of ferroilan, 5 to 10 parts of potassium and sodium feldspar, 1 to 3 parts of zirconium dioxide, 3.5 to 6.5 parts of quartz, 3.5 to 6.5 parts of manganese monoxide, 1 to 3 parts of magnesia, 1.5 to 2.5 parts of ferroaluminum, 0.2 to 0.5 parts of fluoride, 15 to 20 parts of metallic chromium, 25 to 30 parts of nickel powder, 6 to 9 parts of molybdenum powder, 1.5-2.5 parts of tungsten iron; the outer skin is a nickel-based alloy, which, based on the total mass of the nickel-based alloy, includes the following components and the mass percentage of each component: C≤0.02%, Mn≤1.0%, Fe:4.0-7.0%, Si≤0.08%, S≤0.04%, P≤0.02%, Cu≤0.50%, Co≤0.25%, Cr:14.5-16.5%, Mo:15.0-17.0%, W:3.0-4.0%, and the balance is Ni and unavoidable impurities.

[0010] In one embodiment of the present invention, the filling factor of the core material is 20% to 22%.

[0011] In one embodiment of the present invention, the diameter of the flux-cored welding wire is 1.0-1.6 mm.

[0012] A third aspect of the present invention provides a method for preparing a flux-cored wire for welding 9% Ni steel, comprising the following steps:

[0013] After drying the components of the drug core material, add them into a powder mixer and stir and mix them thoroughly to obtain a drug core material mixture;

[0014] Roll the outer skin into a U-shaped groove;

[0015] Filling the drug core material mixture into the U-shaped groove;

[0016] The U-shaped groove containing the core material mixture is closed, rolled into an O-shape, welded, and drawn to a set diameter.

[0017] In one embodiment of the present invention, the drying temperature of rutile, feldspar and zirconium dioxide in the core material is 900-950°C, and the drying time is 6-8 hours, and the drying temperature of the remaining components is 150-200°C, and the drying time is 2-3 hours.

[0018] The flux-cored wire for welding 9% Ni steel provided by the present invention adds manganese monoxide to the flux-cored material, which can further reduce the oxygen content of the weld and reduce the porosity sensitivity on the basis of the combined deoxidation of titanium iron and aluminum iron; the steel strip is a nickel-based alloy steel strip with C ≤ 0.02%, which further reduces the generation of CO gas. Since the amount of CO generated during welding is reduced, the proportion of slag forming agent in the flux-cored material can be appropriately increased to adjust the slag viscosity. The slag forming agent of the present application selects TiO2-SiO2-ZrO2-Al2O3-MgO for combined slag formation to achieve excellent all-position welding operation performance, especially when operating in vertical welding and overhead welding positions, the molten pool is not easy to fall, and the weld formation is more beautiful and the mechanical properties are better. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other embodiments can be obtained based on these drawings without paying any creative work.

[0020] Figure 1 FIG. 1 is a flow chart of the preparation of a flux-cored welding wire for welding 9% Ni steel according to an embodiment of the present invention. DETAILED DESCRIPTION

[0021] The following describes the embodiments of the present invention through specific examples. Those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the following examples and the features in the examples can be combined with each other unless they conflict. It should also be understood that the terms used in the examples of the present invention are for the purpose of describing specific embodiments, not for the purpose of limiting the scope of protection of the present invention. The test methods for which specific conditions are not specified in the following examples are generally carried out under conventional conditions or under the conditions recommended by the manufacturers.

[0022] When numerical ranges are given in the examples, it should be understood that unless otherwise specified herein, both endpoints of each numerical range and any value between the two endpoints may be used. Unless otherwise defined, all technical and scientific terms used herein are consistent with the prior art as understood by those skilled in the art and the description of the present invention. Any prior art methods, devices, and materials similar or equivalent to those in the examples of the present invention may also be used to implement the present invention.

[0023] The temperature at which nickel-based alloy deposited metal begins solidifying is 1300-1400°C. Due to the rapid solidification rate, CO gas generated during welding has a short escape time and is easily trapped in the weld, causing porosity. To reduce porosity, a common approach is to reduce the slag-forming agent in the flux-cored material to improve the permeability of the slag. However, this approach can increase the fluidity of the molten pool and impair controllability in all-position welding. Therefore, the present invention provides a flux-cored material and flux-cored welding wire for welding 9% Ni steel, as well as a method for preparing the same, to address the poor all-position processability and porosity resistance of existing flux-cored welding wires.

[0024] The flux-cored welding wire provided in the present application includes the following raw materials in parts by weight: 18 to 28 parts of rutile, 1 to 3 parts of ferroilan, 5 to 10 parts of potassium-sodium feldspar, 1 to 3 parts of zirconium dioxide, 3.5 to 6.5 parts of quartz, 3.5 to 6.5 parts of manganese monoxide, 1 to 3 parts of magnesia, 1.5 to 2.5 parts of ferroaluminum, 0.2 to 0.5 parts of fluoride, 15 to 20 parts of metallic chromium, 25 to 30 parts of nickel powder, 6 to 9 parts of molybdenum powder, and 1.5 to 2.5 parts of ferrotungsten.

[0025] In one embodiment, the fluoride includes any one or more of rare earth fluoride, fluorosilicate, sodium fluoride, and potassium fluoride. For example, rare earth fluoride, fluorosilicate, sodium fluoride, or potassium fluoride, or any combination of the above fluorides, such as a combination of rare earth fluoride and fluorosilicate, or a combination of sodium fluoride and potassium fluoride, which are not listed here one by one.

[0026] In one embodiment, rutile, potassium-sodium feldspar and quartz are respectively passed through an 80-mesh sieve, and metallic chromium, nickel powder, molybdenum powder and tungsten iron are respectively passed through a 120-mesh sieve.

[0027] In one embodiment, the S content in all raw materials of the core material is ≤0.02%, and the P content in all raw materials is ≤0.02%.

[0028] The flux-cored welding wire for 9% Ni steel welding provided by the present application comprises an outer sheath and a flux core material coated in the outer sheath, wherein the flux core material comprises the following raw materials in parts by weight: 18 to 28 parts of rutile, 1 to 3 parts of ferroilan, 5 to 10 parts of potassium-sodium feldspar, 1 to 3 parts of zirconium dioxide, 3.5 to 6.5 parts of quartz, 3.5 to 6.5 parts of manganese monoxide, 1 to 3 parts of magnesia, 1.5 to 2.5 parts of ferroaluminum, 0.2 to 0.5 parts of fluoride, 15 to 20 parts of metallic chromium, 25 to 30 parts of nickel powder, 6 to 9 parts of molybdenum powder, and 1.5 to 10 parts of ferrotungsten. The outer skin is a nickel-based alloy, which, based on the total mass of the nickel-based alloy, includes the following components and the mass percentage of each component: C≤0.02%, Mn≤1.0%, Fe:4.0~7.0%, Si≤0.08%, S≤0.04%, P≤0.02%, Cu≤0.50%, Co≤0.25%, Cr:14.5~16.5%, Mo:15.0~17.0%, W:3.0~4.0%, and the balance is Ni and unavoidable impurities.

[0029] The functions of the components in the drug core material of the present invention are as follows:

[0030] Rutile: The main component is TiO2. It forms uniform slag during welding, improves arc stability, and is the main powder material for the welding wire to achieve good all-position welding operation. If the amount added is too little, the slag coverage is incomplete, and the vertical welding and overhead welding performance deteriorate. If the amount added is too much, slag inclusions are easily generated in the weld, which increases the oxygen content of the weld and deteriorates the mechanical properties of the deposited metal.

[0031] Quartz: The main component is SiO2, which increases the viscosity of the slag and makes the weld shape more beautiful; if the amount added is too small, the above effect cannot be achieved; if the amount added is too much, the slag removal of the weld will deteriorate, and the Si content in the weld will increase, resulting in a decrease in the weld's resistance to thermal cracking.

[0032] Manganese monoxide: An important additive in the flux-cored welding wire of this application. Below 2400°C, it can transfer the Mn element to the weld, while also combining with ferrotitanium and ferroaluminum for deoxidation, reducing weld inclusions and improving low-temperature impact toughness and fracture toughness of the weld.

[0033] Ferro-titanium and ferro-aluminum: added as deoxidizers to reduce the oxygen content of the weld and improve the impact toughness of the weld. Ferro-aluminum can reduce the surface tension of the molten pool and improve wettability.

[0034] Potassium-sodium feldspar: Added as an arc stabilizer and slag-forming agent, its main components are Al2O3, K2O, Na2O, and SiO2. Adding an appropriate amount can stabilize the arc, adjust the slag viscosity, and improve weld formation. Adding too much will increase the oxygen content in the weld and reduce low-temperature impact toughness.

[0035] Zirconium dioxide and magnesia: These powders have high melting points and accelerate the solidification of the welding slag, facilitating both vertical and overhead welding operations and improving weld formation. They also enhance arc force, enabling stable low-current welding. However, if too much is added, the slag solidifies too quickly, preventing pores from escaping and resulting in porosity defects.

[0036] Fluoride: Its main function is to remove hydrogen from the weld. If too little is added, the effect is not obvious; if too much is added, it will affect the arc stability.

[0037] Metal chromium, nickel powder, molybdenum powder, and tungsten iron: added as alloying agents to transition alloy elements to the deposited metal to ensure that the weld has good mechanical properties.

[0038] In one embodiment, the fill factor of the flux core material is 20% to 22%, such as any value between 20%, 21% or 22%. In this application, the fill factor of the flux core material is the percentage of the weight of the flux core material to the total weight of the flux cored welding wire.

[0039] In one embodiment, the diameter of the flux-cored welding wire is 1.0-1.6 mm.

[0040] See also Figure 1 The method for preparing the core welding wire in this application includes the following steps:

[0041] S1. After drying the components of the core material, add them into a powder mixer and stir and mix them thoroughly to obtain a core material mixture;

[0042] S2, rolling the outer skin into a U-shaped groove;

[0043] S3, filling the core material mixture into the U-shaped groove;

[0044] S4. The U-shaped groove containing the core material mixture is closed, rolled into an O-shape, welded, and drawn to a set diameter.

[0045] In step S1, the core material includes the following raw materials in parts by weight: 18 to 28 parts of rutile, 1 to 3 parts of ferroilan, 5 to 10 parts of potassium and sodium feldspar, 1 to 3 parts of zirconium dioxide, 3.5 to 6.5 parts of quartz, 3.5 to 6.5 parts of manganese monoxide, 1 to 3 parts of magnesia, 1.5 to 2.5 parts of ferroaluminum, 0.2 to 0.5 parts of fluoride, 15 to 20 parts of metallic chromium, 25 to 30 parts of nickel powder, 6 to 9 parts of molybdenum powder, and 1.5 to 2.5 parts of ferrotungsten. The drying temperature of rutile, feldspar, and zirconium dioxide in the core material is 900-950°C, for example, any value within the range of 900-950°C, such as 900°C, 920°C, or 950°C, and the drying time is 6-8 hours, for example, any value within the range of 6 hours, 7 hours, or 8 hours. The drying temperature of the remaining components is 150-200°C, for example, any value within the range of 150-200°C, such as 150°C, 180°C, or 200°C, and the drying time is 2-3 hours, for example, any value within the range of 2 hours, 2.5 hours, or 3 hours. The powder mixer can be any commonly used powder mixer in the field.

[0046] In step S2, the outer sheath of the flux-cored welding wire is a nickel-based alloy. Based on the total mass of the nickel-based alloy, the nickel-based alloy includes the following components and the mass percentage of each component: C≤0.02%, Mn≤1.0%, Fe:4.0-7.0%, Si≤0.08%, S≤0.04%, P≤0.02%, Cu≤0.50%, Co≤0.25%, Cr:14.5-16.5%, Mo:15.0-17.0%, W:3.0-4.0%, and the balance is Ni and unavoidable impurities.

[0047] In step S3 , the filling factor of the core material is 20% to 22%, for example, any value within the range of 20% to 22%, such as 20%, 21% or 22%.

[0048] In step S4, the diameter of the flux-cored welding wire is 1.0-1.6 mm.

[0049] The technical solutions of the present invention are described in detail below through several specific examples. Unless otherwise specified, the raw materials and reagents used in the following examples are commercially available or can be prepared by conventional methods in the art, and the instruments used in the examples are all commercially available.

[0050] Example 1

[0051] In this embodiment, a flux-cored wire for welding 9% Ni steel comprises an outer sheath and a flux core material encased within the outer sheath. The flux core material comprises the following raw materials in parts by weight: 20 parts rutile, 2.5 parts ferroilan, 7 parts potassium-sodium feldspar, 2.5 parts zirconium dioxide, 5.5 parts quartz, 3.5 parts manganese monoxide, 2 parts magnesia, 2.2 parts ferroaluminum, 0.3 parts fluoride, 17.8 parts metallic chromium, 26.5 parts nickel powder, 8 parts molybdenum powder, and 2.2 parts ferrotungsten. The outer sheath is made of a nickel-based alloy. Based on the total weight of the nickel-based alloy, the nickel-based alloy comprises the following components, in percentage by weight: 0.02% C, 0.8% Mn, 5.0% Fe, 0.08% Si, 0.04% S, 0.02% P, 0.50% Cu, 0.25% Co, 16.5% Cr, 16.0% Mo, 3.0% W, with the remainder being Ni and unavoidable impurities.

[0052] First, the rutile, feldspar and zirconium dioxide in the above-mentioned core material are dried at 900°C for 8 hours, and the remaining components are dried at 200°C for 2 hours. Then, the components of the core material are added into a powder mixer and stirred and mixed thoroughly to obtain a core material mixture. The outer skin is rolled into a U-shaped groove, and the core material mixture is filled into the U-shaped groove. The U-shaped groove containing the core material mixture is closed, rolled into an O-shape, welded, and drawn to a set diameter.

[0053] In this embodiment, the fluoride is rare earth fluoride, and the filling rate of the core material is 20.8%.

[0054] Example 2

[0055] In this embodiment, a flux-cored wire for welding 9% Ni steel comprises an outer sheath and a flux core material encased within the outer sheath. The flux core material comprises the following raw materials in parts by weight: 25.5 parts rutile, 2 parts ferrotitanium, 5.6 parts potassium-sodium feldspar, 1.5 parts zirconium dioxide, 4.5 parts quartz, 6 parts manganese monoxide, 1.5 parts magnesia, 1.8 parts ferroaluminum, 0.5 parts fluoride, 16 parts metallic chromium, 27 parts nickel powder, 6.5 parts molybdenum powder, and 1.6 parts ferrotungsten. The outer sheath is made of a nickel-based alloy. Based on the total weight of the nickel-based alloy, the nickel-based alloy comprises the following components, in percentage by weight: 0.01% C, 1% Mn, 4.0% Fe, 0.05% Si, 0.01% S, 0.015% P, 0.40% Cu, 0.20% Co, 15.0% Cr, 15.0% Mo, 4.0% W, with the remainder being Ni and unavoidable impurities.

[0056] First, the rutile, feldspar and zirconium dioxide in the above-mentioned core material are dried at 920°C for 7 hours, and the remaining components are dried at 180°C for 2.5 hours. Then, the components of the core material are added into a powder mixer and stirred and mixed thoroughly to obtain a core material mixture. The outer skin is rolled into a U-shaped groove, and the core material mixture is filled into the U-shaped groove. The U-shaped groove containing the core material mixture is closed, rolled into an O-shape, welded, and drawn to a set diameter.

[0057] In this embodiment, the fluoride selected is fluorosilicate, and the filling rate of the core material is 20.6%.

[0058] Example 3

[0059] In this embodiment, the flux-cored welding wire for welding 9% Ni steel includes an outer sheath and a flux core material wrapped in the outer sheath. The flux core material includes the following raw materials in parts by weight: 26.8 parts of rutile, 1.5 parts of ferrotitanium, 8 parts of potassium-sodium feldspar, 1.2 parts of zirconium dioxide, 3.5 parts of quartz, 4.5 parts of manganese monoxide, 2.5 parts of magnesia, 1.6 parts of ferroaluminum, 0.4 parts of fluoride, 15.5 parts of metallic chromium, 25.5 parts of nickel powder, 7 parts of molybdenum powder, and 2 parts of ferrotungsten. The outer skin is made of nickel-based alloy. Based on the total mass of the nickel-based alloy, the nickel-based alloy includes the following components and the mass percentage of each component is: C content 0.015%, Mn content 0.9%, Fe content 7.0%, Si content 0.07%, S content 0.03%, P content 0.02%, Cu content 0.35%, Co content 0.23%, Cr content 14.5%, Mo content 17.0%, W content 3.8%, and the balance is Ni and unavoidable impurities.

[0060] First, the rutile, feldspar and zirconium dioxide in the above-mentioned core material are dried at 900°C for 8 hours, and the remaining components are dried at 150°C for 3 hours. Then, the components of the core material are added into a powder mixer and thoroughly stirred and mixed to obtain a core material mixture. The outer skin is rolled into a U-shaped groove, and the core material mixture is filled into the U-shaped groove. The U-shaped groove containing the core material mixture is closed, rolled into an O-shape, welded, and drawn to a set diameter.

[0061] In this embodiment, sodium fluoride is selected as the fluoride, and the filling rate of the core material is 21.2%.

[0062] Example 4

[0063] In this embodiment, a flux-cored wire for welding 9% Ni steel comprises an outer sheath and a flux core material encased within the outer sheath. The flux core material comprises the following raw materials in parts by weight: 18 parts rutile, 3.0 parts ferroilan, 8.3 parts potassium-sodium feldspar, 1 part zirconium dioxide, 6.5 parts quartz, 5 parts manganese monoxide, 3 parts magnesia, 1.5 parts ferroaluminum, 0.2 parts fluoride, 20 parts metallic chromium, 25 parts nickel powder, 6 parts molybdenum powder, and 2.5 parts ferrotungsten. The outer sheath is made of a nickel-based alloy. Based on the total weight of the nickel-based alloy, the nickel-based alloy comprises the following components, in percentage by weight: C 0.02%, Mn 0.7%, Fe 6.1%, Si 0.078%, S 0.034%, P 0.018%, Cu 0.45%, Co 0.24%, Cr 15.6%, Mo 16.7%, W 3.4%, with the remainder being Ni and unavoidable impurities.

[0064] First, the rutile, feldspar and zirconium dioxide in the above-mentioned core material are dried at 950°C for 6 hours, and the remaining components are dried at 170°C for 1.8 hours. Then, the components of the core material are added into a powder mixer and thoroughly stirred and mixed to obtain a core material mixture. The outer skin is rolled into a U-shaped groove, and the core material mixture is filled into the U-shaped groove. The U-shaped groove containing the core material mixture is closed, rolled into an O-shape, welded, and drawn to a set diameter.

[0065] In this embodiment, potassium fluoride is selected as the fluoride, and the filling rate of the core material is 20%.

[0066] Example 5

[0067] In this embodiment, a flux-cored wire for welding 9% Ni steel comprises an outer sheath and a flux core material encased within the outer sheath. The flux core material comprises the following raw materials in parts by weight: 28 parts rutile, 1 part ferrotitanium, 5 parts potassium-sodium feldspar, 1.8 parts zirconium dioxide, 5 parts quartz, 6.5 parts manganese monoxide, 1 part magnesia, 2 parts ferroaluminum, 0.2 parts fluoride, 15 parts metallic chromium, 25 parts nickel powder, 8 parts molybdenum powder, and 1.5 parts ferrotungsten. The outer sheath is made of a nickel-based alloy. Based on the total weight of the nickel-based alloy, the nickel-based alloy comprises the following components, in percentage by weight: C 0.018%, Mn 0.93%, Fe 6.5%, Si 0.069%, S 0.033%, P 0.017%, Cu 0.39%, Co 0.21%, Cr 14.9%, Mo 16.5%, W 3.2%, with the remainder being Ni and unavoidable impurities.

[0068] First, the rutile, feldspar and zirconium dioxide in the above-mentioned core material are dried at 930°C for 6.5 hours, and the remaining components are dried at 180°C for 2.5 hours. Then, the components of the core material are added into a powder mixer and stirred and mixed thoroughly to obtain a core material mixture. The outer skin is rolled into a U-shaped groove, and the core material mixture is filled into the U-shaped groove. The U-shaped groove containing the core material mixture is closed, rolled into an O-shape, welded, and drawn to a set diameter.

[0069] In this embodiment, the fluoride is a mixture of sodium fluoride and potassium fluoride, the mass ratio of sodium fluoride to potassium fluoride is 1:1, and the filling rate of the core material is 20%.

[0070] Example 6

[0071] In this embodiment, a flux-cored wire for welding 9% Ni steel comprises an outer sheath and a flux core material encased within the outer sheath. The flux core material comprises the following raw materials in parts by weight: 18.4 parts rutile, 1.2 parts ferroilan, 10 parts potassium-sodium feldspar, 3 parts zirconium dioxide, 3.5 parts quartz, 3.5 parts manganese monoxide, 1 part magnesia, 2.5 parts ferroaluminum, 0.4 part fluoride, 16 parts metallic chromium, 30 parts nickel powder, 9 parts molybdenum powder, and 1.5 parts ferrotungsten. The outer sheath is made of a nickel-based alloy. Based on the total weight of the nickel-based alloy, the nickel-based alloy comprises the following components, in percentage by weight: C 0.018%, Mn 0.95%, Fe 5.8%, Si 0.075%, S 0.04%, P 0.016%, Cu 0.44%, Co 0.23%, Cr 15.1%, Mo 16.3%, W 3.6%, with the remainder being Ni and unavoidable impurities.

[0072] First, the rutile, feldspar and zirconium dioxide in the above-mentioned core material are dried at 900°C for 8 hours, and the remaining components are dried at 170°C for 1.8 hours. Then, the components of the core material are added into a powder mixer and stirred and mixed thoroughly to obtain a core material mixture. The outer skin is rolled into a U-shaped groove, and the core material mixture is filled into the U-shaped groove. The U-shaped groove containing the core material mixture is closed, rolled into an O-shape, welded, and drawn to a set diameter.

[0073] In this embodiment, the fluoride is a mixture of fluorosilicate, sodium fluoride and potassium fluoride, the mass ratio of fluorosilicate, sodium fluoride and potassium fluoride is 1:1:1, and the filling rate of the core material is 22%.

[0074] Comparative Example 1

[0075] In this embodiment, a flux-cored wire for welding 9% Ni steel comprises an outer sheath and a flux core material encased within the outer sheath. The flux core material comprises the following raw materials in parts by weight: 28 parts rutile, 2 parts ferroilan, 6 parts potassium-sodium feldspar, 1.8 parts zirconium dioxide, 3.8 parts quartz, 1 part manganese monoxide, 2 parts magnesia, 1.8 parts ferroaluminum, 0.4 parts fluoride, 16.8 parts metallic chromium, 28 parts nickel powder, 6.8 parts molybdenum powder, and 1.6 parts ferrotungsten. The outer sheath is made of a nickel-based alloy. Based on the total weight of the nickel-based alloy, the nickel-based alloy comprises the following components, in percentage by weight: C 0.016%, Mn 0.7%, Fe 6.1%, Si 0.077%, S 0.034%, P 0.018%, Cu 0.45%, Co 0.24%, Cr 15.6%, Mo 16.7%, W 3.4%, with the remainder being Ni and unavoidable impurities.

[0076] First, the rutile, feldspar and zirconium dioxide in the above-mentioned core material are dried at 900°C for 8 hours, and the remaining components are dried at 150°C for 3 hours. Then, the components of the core material are added into a powder mixer and thoroughly stirred and mixed to obtain a core material mixture. The outer skin is rolled into a U-shaped groove, and the core material mixture is filled into the U-shaped groove. The U-shaped groove containing the core material mixture is closed, rolled into an O-shape, welded, and drawn to a set diameter.

[0077] In this comparative example, sodium fluoride is selected as the fluoride, and the filling rate of the core material is 21.1%.

[0078] Comparative Example 2

[0079] In this embodiment, the flux-cored welding wire for 9% Ni steel welding includes an outer sheath and a flux core material wrapped in the outer sheath. The flux core material includes the following raw materials in parts by weight: 15 parts of rutile, 2.8 parts of ferrotitanium, 8.5 parts of potassium-sodium feldspar, 2 parts of zirconium dioxide, 6 parts of quartz, 5.5 parts of manganese monoxide, 2.8 parts of magnesia, 2.2 parts of ferroaluminum, 0.5 part of fluoride, 19.2 parts of metallic chromium, 27.5 parts of nickel powder, 6 parts of molybdenum powder, and 2 parts of ferrotungsten. The outer skin is made of nickel-based alloy. Based on the total mass of the nickel-based alloy, the nickel-based alloy includes the following components and the mass percentage of each component is: C content 0.019%, Mn content 0.93%, Fe content 6.5%, Si content 0.069%, S content 0.033%, P content 0.017%, Cu content 0.39%, Co content 0.21%, Cr content 14.9%, Mo content 16.5%, W content 3.2%, and the balance is Ni and unavoidable impurities.

[0080] First, the rutile, feldspar and zirconium dioxide in the above-mentioned core material are dried at 950°C for 6 hours, and the remaining components are dried at 170°C for 1.8 hours. Then, the components of the core material are added into a powder mixer and thoroughly stirred and mixed to obtain a core material mixture. The outer skin is rolled into a U-shaped groove, and the core material mixture is filled into the U-shaped groove. The U-shaped groove containing the core material mixture is closed, rolled into an O-shape, welded, and drawn to a set diameter.

[0081] In this embodiment, potassium fluoride is selected as the fluoride, and the filling rate of the core material is 20.8%.

[0082] The core material components of the flux-cored welding wires prepared in Examples 1 to 6 and Comparative Examples 1 and 2 in the present application are shown in the table. The flux-cored welding wires prepared in Examples 1 to 6 and Comparative Examples 1 and 2 are used for test plate welding. The welding current is 180A, the welding voltage is 25V, the shielding gas is 80% Ar + 20% CO2, and the process performance and mechanical properties of vertical welding position welding are shown in Table 2.

[0083] Table 1: Core material components of flux-cored welding wires prepared in Examples 1 to 6 and Comparative Examples 1 and 2

[0084]

[0085]

[0086] Table 2: Processing performance and mechanical properties of flux-cored welding wires prepared in Examples 1 to 6 and Comparative Examples 1 and 2 in vertical position welding

[0087]

[0088] It can be seen from the data in Table 2 that the flux-cored welding wires prepared in Examples 1 to 6 have good welding processability and mechanical properties, and are suitable for welding 9% Ni steel.

[0089] The flux-cored wire for welding 9% Ni steel provided by the present invention adds manganese monoxide to the flux-cored material, which can further reduce the oxygen content of the weld and reduce the porosity sensitivity on the basis of the combined deoxidation of titanium iron and aluminum iron; the steel strip is a nickel-based alloy steel strip with C ≤ 0.02%, which further reduces the generation of CO gas. Since the amount of CO generated during the welding process is reduced, the proportion of slag forming agent in the flux-cored material can be appropriately increased to adjust the slag viscosity. The slag forming agent of the present application selects TiO2-SiO2-ZrO2-Al2O3-MgO for combined slag formation, which achieves excellent all-position welding operation performance, especially when operating in the vertical welding and overhead welding positions, the molten pool is not easy to fall, and the weld formation is more beautiful and the mechanical properties are better. Therefore, the present invention effectively overcomes some practical problems in the prior art and thus has high utilization value and use significance.

[0090] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the present invention. Anyone skilled in the art may modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by one of ordinary skill in the art without departing from the spirit and technical principles disclosed herein are intended to be covered by the claims of the present invention.

Claims

1. A flux-cored welding wire for 9% Ni steel welding, characterized in that: The invention comprises an outer skin and a core material coated in the outer skin, wherein the core material is composed of the following raw materials in parts by weight: 18 to 18.4 parts of rutile, 1 to 3 parts of ferroilan, 5 to 10 parts of potassium-sodium feldspar, 1 to 3 parts of zirconium dioxide, 3.5 to 6.5 parts of quartz, 3.5 to 6.5 parts of manganese monoxide, 1 to 3 parts of magnesia, 1.5 to 2.5 parts of aluminum iron, 0.2 to 0.5 parts of fluoride, 15 to 20 parts of metallic chromium, 25 to 25.5 parts of nickel powder, 6 to 9 parts of molybdenum powder, and 1.5 to 2.5 parts of ferrotungsten; The outer skin is a nickel-based alloy. Based on the total mass of the nickel-based alloy, the nickel-based alloy is composed of the following components, and the mass percentage of each component is: C≤0.02%, Mn≤1.0%, Fe:4.0~7.0%, Si≤0.08%, S≤0.04%, P≤0.02%, Cu≤0.50%, Co≤0.25%, Cr:14.5~16.5%, Mo:15.0~17.0%, W:3.0~4.0%, and the balance is Ni and unavoidable impurities.

2. The flux-cored wire for welding 9% Ni steel according to claim 1, characterized in that: The fluoride includes any one or more of rare earth fluoride, fluorosilicate, sodium fluoride and potassium fluoride.

3. The flux-cored welding wire for 9% Ni steel welding according to claim 1, characterized in that: The rutile, the potassium-sodium feldspar and the quartz are respectively sieved through an 80-mesh sieve.

4. The flux-cored welding wire for 9% Ni steel welding according to claim 1, characterized in that: The metallic chromium, the nickel powder, the molybdenum powder and the ferrotungsten are respectively sieved through a 120-mesh sieve.

5. The flux-cored welding wire for welding 9% Ni steel according to claim 1, characterized in that: The S content in all raw materials of the drug core material is ≤0.02%, and the P content is ≤0.02%.

6. The flux-cored welding wire for 9% Ni steel welding according to claim 1, characterized in that: The filling factor of the core material is 20% to 22%.

7. The flux-cored welding wire for 9% Ni steel welding according to claim 1, characterized in that: The diameter of the flux-cored welding wire is 1.0-1.6 mm.

8. A method for preparing a flux-cored welding wire for welding 9% Ni steel according to any one of claims 1 to 7, characterized in that: The steps include: After drying the components of the drug core material, add them into a powder mixer and stir and mix them thoroughly to obtain a drug core material mixture; Roll the outer skin into a U-shaped groove; Filling the drug core material mixture into the U-shaped groove; The U-shaped groove containing the core material mixture is closed, rolled into an O-shape, welded, and drawn to a set diameter.

9. The method for preparing a flux-cored welding wire according to claim 8, wherein: The drying temperature of rutile, feldspar and zirconium dioxide in the core material is 900-950° C. and the drying time is 6-8 hours, and the drying temperature of the remaining components is 150-200° C. and the drying time is 2-3 hours.

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