Nickel-based alloy flux-cored wire for 9Ni steel welding and preparation method of nickel-based alloy flux-cored wire

Abstract

The invention relates to the technical field of welding wire preparation, in particular to a nickel-based alloy flux-cored wire for 9Ni steel welding and a preparation method of the nickel-based alloy flux-cored wire. A nickel-based alloy flux-cored wire for 9Ni steel welding comprises a flux core, and the flux core comprises, by weight, 26%-34% of titanium dioxide, 3%-5% of ferrozirconium, 8%-12% of ferrotitanium, 1%-3% of rare earth ferrosilicon, 15%-20% of tungsten powder, 1%-2% of polytetrafluoroethylene and the balance pretreated mixed powder. The nickel-based alloy flux-cored wire for 9Ni steel welding has the advantages that low-melting-point eutectic is not prone to being formed, the hot crack sensitivity is reduced, the nickel-based alloy flux-cored wire is suitable for welding of restrained large structures, the deoxidation and denitrification capacity is enhanced, and the pore sensitivity is reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of wire preparation, and particularly relates to a nickel-based alloy flux-cored wire for welding 9Ni steel and a preparation method thereof. Background Art

[0002] 9Ni steel is an alloy steel containing about 9% Ni. Compared with austenitic stainless steel and aluminum alloy, it has high strength and excellent low-temperature toughness at -196°C, and is widely used in the manufacture of natural gas (LNG) storage and transportation equipment. However, for equipment storing and transporting natural gas, in order to prevent leakage and disasters, the welding requirements for the equipment are very high. To ensure the low-temperature toughness of the welded joint in the as-welded state and the matching of the linear expansion coefficient with the steel plate, 9Ni steel is mainly welded with nickel-based welding materials, and the commonly used alloy systems are Ni-Cr-Mo, Ni-Mo, Ni-Cr-Fe, etc. At present, when welding with electrodes, the electrodes need to be frequently replaced. Porosities are likely to occur at the starting and ending positions of the arc, and grinding is required, resulting in low welding efficiency. At the same time, the clamping end of the electrode is prone to turn red and crack during welding, resulting in about 10% - 30% of the remaining electrode being unable to continue welding, causing a large amount of material waste.

[0003] Flux-cored wire is an efficient welding material with good welding process and can be automatically welded, especially suitable for welding 9Ni steel. Therefore, a large amount of research has been carried out by relevant technical personnel on the technology of flux-cored wire. For example, the Chinese invention patent with the publication number CN105643141A relates to a flux-cored wire for nickel-based alloy, which includes a nickel-based alloy steel strip and a flux powder wrapped and filled in the nickel-based alloy steel strip at a filling rate of 18 - 22%; the mass percentage composition of the flux powder is as follows: 9 - 13% of metal chromium powder, 33 - 36% of metal nickel powder, 1 - 2.5% of metal manganese powder, 16 - 20% of rutile, 1 - 3% of ferrosilicon, 0.5 - 2% of ferrotitanium, 3 - 6% of feldspar, 3 - 5% of quartz, 1 - 2.5% of rare earth fluoride, 1 - 3% of cryolite, 5 - 7% of ferroniobium, 6 - 8% of ferromolybdenum, 1 - 3% of calcium fluoride, and the rest is iron powder. As the component ratios of the flux powder disclosed in the technical solution of this patent, there are problems such as easy formation of low-melting eutectic, high sensitivity to hot cracks, inapplicability to welding of structures with large restraint, weak deoxidation and denitrification capabilities, and high porosity sensitivity. Summary of the Invention

[0004] In view of this, the present invention aims to provide a nickel-based alloy flux-cored wire for welding 9Ni steel. The wire includes a flux core and a nickel-based outer skin steel strip. By weight percentage, the weight fractions of each component in the flux core are as follows: titanium dioxide: 26% - 34%, ferrozirconium: 3% - 5%, ferrotitanium: 8% - 12%, rare earth ferrosilicon: 1% - 3%, tungsten powder: 15% - 20%, polytetrafluoroethylene: 1% - 2%, and the rest is pre-treated mixed powder. The composition of the nickel-based outer skin steel strip is: C ≤ 0.01%, Si ≤ 0.12%, Mn: 0.4% - 0.9%, Mo: 14.2% - 14.8%, Cr: 15.6% - 16.8%, Al + 2Mg: 0.06% - 0.12%, S + P ≤ 0.007%, and the rest is Ni and inevitable impurities. It solves the problems such as easy formation of low-melting eutectic, high sensitivity to hot cracks, inapplicability to welding of structures with large restraint, weak deoxidation and denitrification ability, and large porosity sensitivity.

[0005] To solve the above problems, the present invention provides a nickel-based alloy flux-cored wire for welding 9Ni steel. The wire includes a flux core. By weight percentage, the weight fractions of each component in the flux core are as follows: titanium dioxide: 26% - 34%, ferrozirconium: 3% - 5%, ferrotitanium: 8% - 12%, rare earth ferrosilicon: 1% - 3%, tungsten powder: 15% - 20%, polytetrafluoroethylene: 1% - 2%, and the rest is pre-treated mixed powder.

[0006] Further, by weight percentage, the weight fractions of each component in the pre-treated mixed powder are as follows: barium fluoride + magnesium fluoride: 12% - 18%, quartz: 16% - 24%, manganese monoxide: 6% - 12%, potassium silicotitanate: 27% - 45%, spodumene: 14% - 22%, lithium fluoride: 1% - 3%.

[0007] Further, the wire also includes a nickel-based outer skin steel strip. By weight percentage, the composition of the nickel-based outer skin steel strip is: C ≤ 0.01%, Si ≤ 0.12%, Mn: 0.4% - 0.9%, Mo: 14.2% - 14.8%, Cr: 15.6% - 16.8%, Al + 2Mg: 0.06% - 0.12%, S + P ≤ 0.007%, and the rest is Ni and inevitable impurities.

[0008] A preparation method for a nickel-based alloy flux-cored wire for welding 9Ni steel as described in any one of the above, includes:

[0009] S100. Prepare the flux core powder;

[0010] S200. Prepare the nickel-based outer skin steel strip;

[0011] S300. Prepare the wire rod;

[0012] S400. Final processing, including: cleaning, electrostatic oiling, coiling and packaging.

[0013] Further, in step S100, the steps of preparing the flux cored powder include:

[0014] S110. Powder pretreatment;

[0015] S120. Preparing the flux cored powder.

[0016] Further, in step S110, the method of powder pretreatment includes:

[0017] S111. Configuring the powder in proportion;

[0018] S112. Placing the powder in an electric arc furnace, melting the powder using an iron electrode, and stirring during the melting process;

[0019] S113. Cooling the molten powder in a water-cooled crystallizer;

[0020] S114. Crushing the cooled powder to form particles.

[0021] Further, in step S120, the method of preparing the flux cored powder includes:

[0022] The flux cored powder configured in proportion is mixed evenly in a mixer, baked at 150 - 200 °C for 2 h and then kept warm at 100 °C.

[0023] Further, in step S200, the method of preparing the nickel-based outer skin steel strip includes:

[0024] S210. Making an electroslag ingot by vacuum + electroslag remelting;

[0025] S220. Forging and hot rolling to make a steel strip with a preset thickness;

[0026] S230. Performing solution treatment on the steel strip, with the solution treatment temperature being 1130 °C - 1200 °C and the time being 2 h;

[0027] S240. Performing alkali washing and acid washing on the steel strip;

[0028] S250. Gradually reducing the thickness of the steel strip by cold rolling according to the process requirements to form a finished steel strip;

[0029] S260. Dividing the steel strip according to the process requirement length using a steel strip coiling machine.

[0030] Further, in step S300, the method of preparing the wire rod coil includes:

[0031] S310. Adding the flux cored powder to the steel strip and rolling it into a wire rod coil;

[0032] S320. Perform wire drawing and diameter reduction operations on the manufactured wire rods.

[0033] Further, in step S400, intermediate frequency induction heating is used to remove the wire drawing powder and oil stains on the surface of the welding wire.

[0034] Compared with the prior art, the nickel-based alloy flux-cored wire for welding 9Ni steel of the present invention has the following advantages:

[0035] The advantages of this technical solution are that the welding wire includes a flux core and a nickel-based outer steel strip. By weight percentage, the weight fractions of each component in the flux core are: titanium dioxide: 26% - 34%, zirconium iron: 3% - 5%, ferrotitanium: 8% - 12%, rare earth ferrosilicon: 1% - 3%, tungsten powder: 15% - 20%, polytetrafluoroethylene: 1% - 2%, and the rest is pre-treated mixed powder. The composition of the nickel-based outer steel strip is: C ≤ 0.01%, Si ≤ 0.12%, Mn: 0.4% - 0.9%, Mo: 14.2% - 14.8%, Cr: 15.6% - 16.8%, Al + 2Mg: 0.06% - 0.12%, S + P ≤ 0.007%, and the rest is Ni and unavoidable impurities. It is not easy to form low-melting eutectics, reduces the sensitivity to hot cracks, is suitable for welding structures with large constraints, enhances the deoxidation and denitrification capabilities, and reduces the porosity sensitivity. Detailed implementation manners

[0037] In the present invention, the descriptions involving "first", "second", "upper", "lower", etc. are only for descriptive purposes and should not be construed as indicating or implying their relative importance or implicitly indicating the quantity of the indicated technical features. Thus, the features defined with "first", "second", "upper", "lower" may explicitly or implicitly include at least one of such features. Additionally, the technical solutions between various embodiments can be combined with each other, but it must be based on the ability of those of ordinary skill in the art to implement. When the technical solutions between embodiments can be implemented in combination, they are all within the protection scope required by the present invention.

[0038] The present invention will be described in detail below with reference to embodiments.

[0039] A nickel-based alloy flux-cored wire for welding 9Ni steel, the welding wire includes a flux core. By weight percentage, the weight fractions of each component in the flux core are: titanium dioxide: 26% - 34%, zirconium iron: 3% - 5%, ferrotitanium: 8% - 12%, rare earth ferrosilicon: 1% - 3%, tungsten powder: 15% - 20%, polytetrafluoroethylene: 1% - 2%, and the rest is pre-treated mixed powder.

[0040] Further, by weight percentage, the weight fractions of the components of the pre-treated mixed powder are as follows: barium fluoride + magnesium fluoride: 12% - 18%, quartz: 16% - 24%, manganese monoxide: 6% - 12%, potassium silicotitanate: 27% - 45%, spodumene: 14% - 22%, lithium fluoride 1% - 3%.

[0041] Further, the welding wire further includes a nickel-based outer skin steel strip. By weight percentage, the composition of the nickel-based outer skin steel strip is: C ≤ 0.01%, Si ≤ 0.12%, Mn: 0.4% - 0.9%, Mo: 14.2% - 14.8%, Cr: 15.6% - 16.8%, Al + 2Mg: 0.06% - 0.12%, S + P ≤ 0.007%, and the balance is Ni and unavoidable impurities.

[0042] The above components constitute the welding wire of the present application. Among them, the composition of the flux-cored powder accounts for 22% - 24% of the total weight of the entire welding wire. As a preferred embodiment, the thickness of the made steel strip is 0.3 mm and the width is 12 mm. Compared with the prior art, the welding wire of this embodiment reduces the content of Nb, is not easy to form eutectics with low melting points, reduces the sensitivity to hot cracks and pores, improves the deoxidation and denitrification capabilities of the welding wire, is applicable to the welding of structures with large restraint, and meets the requirements of high-efficiency and low-defect welding of 9Ni steel.

[0043] A method for preparing a nickel-based alloy flux-cored welding wire for welding 9Ni steel as described in any one of the above, comprising:

[0044] S100. Prepare the flux-cored powder;

[0045] S110. Pretreat the powder;

[0046] S111. Configure the powder in proportion;

[0047] S112. Place the powder in an electric arc furnace, use an iron electrode to melt the powder, and stir the powder with a large circuit during the melting process to avoid stratification caused by too large a difference in specific gravity between different powders;

[0048] S113. Cool the molten powder in a water-cooled crystallizer;

[0049] S114. Crush the cooled powder to form particles, preferably with a particle diameter of 75 μm - 180 μm;

[0050] The purpose of powder pretreatment: (1) Remove the moisture in the powder and reduce the sensitivity to hydrogen pores; (2) Lower the melting point of the flux-cored powder, improve the spreading and wettability of the weld, and reduce defects such as slag inclusions and lack of fusion; (3) Improve the fluidity and uniformity of the powder and stabilize the mechanical properties of the weld metal.

[0051] S120. Prepare the flux-cored powder. The flux-cored powder prepared according to the proportion is mixed evenly in a mixer, baked at 150 - 200 °C for 2 h and then kept at 100 °C for heat preservation;

[0052] S200. Prepare the nickel-based outer skin steel strip;

[0053] S210. Use vacuum + electroslag remelting to make an electroslag ingot;

[0054] S220. Forge and hot-roll the steel strip into a steel strip with a preset thickness. As a preferred embodiment, the steel strip is made into a 0.35 mm thick steel strip after forging and hot-rolling;

[0055] S230. Perform solution treatment on the steel strip. The solution treatment temperature is 1130 °C - 1200 °C, preferably 1160 °C ± 30 °C, and the time is 2 h;

[0056] S240. Perform alkali washing and pickling on the steel strip;

[0057] S250. Gradually reduce the thickness of the steel strip through cold rolling according to process requirements. The preferred thickness is 0.3 mm to form a finished steel strip;

[0058] S260. Use a steel strip slitting machine to cut the steel strip according to the process requirements for length. As a preferred embodiment, the width of the steel strip is 12 mm;

[0059] S300. Prepare the wire rod;

[0060] S310. On the flux-cored wire rolling equipment, add the flux-cored powder to the steel strip online synchronously and roll it into a wire rod. The preferred diameter of the wire rod is Φ3.6 mm;

[0061] S320. Perform wire drawing and diameter reduction operations on the formed wire rod. The preferred final diameter is Φ1.0 mm, Φ1.2 mm or other required specifications.

[0062] S400. Final treatment, including: cleaning, electrostatic oiling, coiling and packaging.

[0063] Among them, the cleaning method uses intermediate frequency induction heating to remove the drawing powder and oil stains on the surface of the wire;

[0064] Through electrostatic oiling, the wire feeding resistance is reduced, the arc stability is improved, and the weld formation is improved.

[0065] The present invention mainly reduces the porosity sensitivity through the following means: (1) Adding a certain amount of Mg and Al to the steel strip. Both can deoxidize, protect carbon from oxidation, and reduce the sensitivity to CO porosity; Al can fix nitrogen and reduce the sensitivity to N2 porosity. (2) Remelting mineral powder to form a dense and non-hygroscopic vitreous melt while removing moisture, which can effectively remove moisture and reduce the sensitivity to hydrogen porosity. (3) Using Si, Zr, and Ti for combined deoxidation to protect C from oxidation and reduce the sensitivity to CO porosity. (4) Using Ti for deoxidation and nitrogen fixation to reduce the sensitivity to CO and N2 porosity. (5) Adding polytetrafluoroethylene, barium fluoride, magnesium fluoride, and lithium fluoride. The four types of fluorides are used together to remove hydrogen. Without deteriorating the arc, it can reduce the sensitivity to hydrogen porosity, and the effect is significantly better than using only one or two of them for dehydrogenation. (6) Adding a certain amount of rare earth ferrosilicon, which can deoxidize and remove hydrogen at the same time, reducing the porosity sensitivity. (7) Adding slag modifiers such as MnO, spodumene, and lithium fluoride to increase the gas permeability of the slag, promote the rapid escape of gas, and reduce the porosity sensitivity. Through the synergistic effect of the above seven means, the gas content in the weld metal can be significantly reduced, and the porosity sensitivity is extremely low.

[0066] The present invention mainly reduces the sensitivity to hot cracks through the following means: (1) Adding a certain amount of MnO to increase the basicity of the slag, which can effectively fix S, deoxidize, purify the weld metal, and reduce the sensitivity to hot cracks. (2) Controlling the content of low-melting-point impurities such as S and P in the steel strip, reducing the formation of low-melting-point phases, and reducing the sensitivity to hot cracks. (3) Instead of using Nb strengthening that is prone to segregation and can increase the sensitivity to hot cracks, W, Mo, Cr, and Fe are used for combined strengthening to reduce the segregation of low-melting-point phases and reduce the sensitivity to hot cracks. Through the synergistic control of the slag, impurity elements, and alloy composition, the sensitivity to hot cracks can be significantly reduced.

[0067] The main functions of the alloying elements in the steel strip in the present invention are as follows:

[0068] C: An inevitable impurity. Excessive C is likely to form carbides, reducing the low-temperature thermal toughness of the weld metal. C should be controlled below 0.01%.

[0069] Si: An inevitable impurity. Excessive Si will increase the sensitivity of the weld metal to hot cracks and should be controlled below 0.12%.

[0070] Mn: Its main functions are deoxidation and solid solution strengthening. Combining with low-melting-point substances such as S can reduce the sensitivity to hot cracks. When the content is less than 0.4%, the beneficial effect is insufficient. When it is greater than 0.9%, it deteriorates the low-temperature thermal toughness.

[0071] Mo: Its main function is solution strengthening. When the Mo content is less than 14.2%, the strengthening effect is insufficient, and a certain amount of Mo needs to be added to the flux-cored powder, resulting in an excessive filling rate and easy wire breakage. When the Mo content is greater than 14.8%, the processing of the welding strip is difficult, and at the same time, brittle second phases / intermetallic compounds are likely to form in the weld metal, significantly reducing the low-temperature toughness of the weld metal.

[0072] Cr: Its main function is solution strengthening, and its effect is similar to that of Mo. When the Cr content is less than 15.6%, the strengthening effect is insufficient, and a certain amount of Cr needs to be added to the flux-cored powder, resulting in an excessive filling rate and easy wire breakage. When the Cr content is greater than 16.8%, the processing of the welding strip is difficult, and at the same time, it is prone to significant interaction with Mo, forming brittle second phases / intermetallic compounds, significantly reducing the low-temperature toughness of the weld metal.

[0073] Al, Mg: They can reduce the porosity sensitivity and improve the plasticity and low-temperature toughness of the weld metal. Al and Mg are strong deoxidizers, which can reduce the C + O2 = 2CO reaction and the tendency of CO pores, and at the same time can improve the low-temperature toughness of the weld metal. Al is an important denitrifier, reducing the tendency of N2 pores. When it is less than 0.06%, the deoxidation and denitrification effects are insufficient, and the porosity sensitivity of the weld metal is relatively large. When Al + 2Mg is greater than 0.12%, the beneficial effects are weakened, and second phases are easily formed, making the processing of the steel strip difficult.

[0074] S, P: They are inevitable impurity elements, which are likely to form low-melting-point second phases. When the content exceeds 0.007%, the hot crack sensitivity of the weld metal increases.

[0075] The functions of the main components of the flux-cored powder in the present invention are as follows:

[0076] Titanium dioxide: It is the main slag former, mainly used to adjust the viscosity and surface tension of the molten slag and improve the weld formation. When the content is less than 26%, the melting point and viscosity of the molten slag are relatively high, the weld formation is poor, and the porosity sensitivity is large. When the content is greater than 34%, the viscosity of the molten slag is too low, the molten slag coverage is incomplete, the protection effect decreases, and at the same time, the Ti content in the weld metal is too high, resulting in a decrease in low-temperature toughness.

[0077] Ferro-zirconium: Its main function is deoxidation. Its deoxidation product ZrO2 is an important slag former, which can reduce the tendency of the molten slag to sag during vertical welding and improve the weld formation. When the content is less than 3%, the deoxidation effect is insufficient, the low-temperature toughness of the weld metal is relatively poor, and at the same time, the content of ZrO2 in the molten slag is relatively low, and the vertical welding process is relatively poor. When it is greater than 5%, the melting point of the molten slag is too high, the weld formation becomes worse, and defects such as slag inclusion and lack of fusion are likely to occur.

[0078] Ferrotitanium: Its main functions are deoxidation and denitrification. When the content is less than 8%, the deoxidation and denitrification effects are insufficient, the porosity sensitivity of the weld metal is high, and the low-temperature toughness is poor; when it is greater than 12%, the arc blowing force is small, the penetration is shallow, incomplete fusion is likely to occur, and the low-temperature toughness of the weld metal also decreases significantly.

[0079] Rare earth ferrosilicon: Its main function is to purify the weld metal, reduce the content of impurities such as S, P, and O, and improve the low-temperature toughness of the weld metal. When the content is less than 1%, the effect of improving low-temperature toughness is insufficient; when it is greater than 3%, high-melting-point inclusions are easily formed, deteriorating the welding processability and low-temperature toughness.

[0080] Tungsten powder: Its main function is to alloy transition and play a role in solution strengthening in the weld metal. When the content is less than 15%, the strengthening effect is insufficient; when the content is greater than 20%, the beneficial effect does not increase significantly further, while the cost of the welding consumables increases significantly.

[0081] Polytetrafluoroethylene: On the one hand, it can reduce the hydrogen in the weld metal and lower the hydrogen porosity sensitivity; on the other hand, it has good lubricity and reduces the wire breakage frequency during the wire drawing process. When the content is less than 1%, the beneficial effect is insufficient; when it is greater than 2%, the spatter increases.

[0082] Barium fluoride and magnesium fluoride: Their main functions are hydrogen removal, reducing porosity sensitivity, and at the same time can improve the slag removal effect. When the content in the mixed powder is less than 12%, the porosity sensitivity is high and slag removal is difficult; when the content in the mixed powder is greater than 18%, the arc stability becomes poor, the spatter increases, and the porosity sensitivity increases.

[0083] Quartz: Its main function is slag formation, adjusting the viscosity of the slag, improving the weld formation, and at the same time having a certain effect of refining the molten droplets. When the content in the mixed powder is less than 16%, the weld formation is poor; when the content is greater than 24%, the silicon content of the weld metal increases, and the hot crack sensitivity of the weld increases.

[0084] Manganese monoxide: On the one hand, it has a relatively low melting point, can increase the gas permeability, accelerate the escape of gas in the weld metal, and reduce the porosity sensitivity; on the other hand, it can be used as a high-temperature deoxidizer to purify the weld metal, improve the low-temperature toughness, and reduce the hot crack temperature sensitivity. When the content in the mixed powder is less than 6%, the porosity and hot crack sensitivities are high, and the low-temperature toughness is poor; when the content in the mixed powder is greater than 12%, the viscosity of the slag is too low, the slag coverage is incomplete, and local slag spattering and slag sticking are likely to occur.

[0085] Potassium silicotitanate: Its main function is arc stabilization. When the content in the mixed powder is less than 27%, the arc stability is poor; when the content in the mixed powder is greater than 45%, it is easy to absorb moisture and the porosity sensitivity increases.

[0086] Spodumene: Its main functions are to lower the melting point of the slag and remove hydrogen, which can significantly reduce the porosity sensitivity. When the content is less than 14%, the melting point of the slag is high, the gas permeability is poor, and the porosity sensitivity is large; when the content is greater than 22%, the melting point of the slag is too low, and vertical welding is difficult.

[0087] Lithium fluoride: Its functions are similar to those of spodumene. It can remove hydrogen, increase the gas permeability of the slag, and reduce the porosity sensitivity. Using it in combination with spodumene has a better effect. When the content is less than 1%, the porosity sensitivity is relatively large; when the content is greater than 3%, the arc is unstable and the spatter increases.

[0088] The following uses specific embodiments to illustrate the welding wire of the present application.

[0089] Three ingots with the compositions of the embodiments are prepared by vacuum melting + electroslag remelting, and then forged, hot-rolled, solution-treated, cold-rolled, and divided into steel strips of 0.3mm * 15mm. The specific compositions are shown in Table 1. The steel strips shown in Table 1 and the flux-cored powder shown in Tables 2 and 3 are rolled into Φ3.6mm wire rods on a flux-cored wire tying machine, and then drawn down to Φ1.2mm in 8 passes on a straight-line drawing machine. Finally, the welding wires of the embodiments are obtained after alkali washing, high-pressure water cleaning, and drying. The filling rates of the welding wires of Embodiment 1, Embodiment 2, and Embodiment 3 are 22.2%, 22.9%, and 23.8% respectively.

[0090] The deposited bead numbers of the welding wires of the embodiments and the butt test plates of the matching 9Ni steel in vertical welding are welded. The welding parameters used are shown in Table 4, the mechanical properties of the deposited metal are shown in Table 5, and the mechanical properties of the joints are shown in Table 6. The results show that the welding arc is stable in the vertical welding position of the welding wires of the embodiments, the weld formation is good, the strength of the deposited metal is moderate, the -196°C low-temperature toughness of the deposited metal and the joints is excellent, and there are no cracks in the forward, reverse, and side bends of 180° of the joints. According to the crack test method of the T-joint weld in GB / T 41107.2, no cracks are generated. The welding joints of the welding wires of the embodiments in the vertical welding position are analyzed for defects according to GB / T 13298 and radiographed according to GB / T 3323. The results are shown in Table 7, and the results show that there are no defects such as porosity, slag inclusion, lack of fusion, and cracks in the joints, and the flaw detection is all Grade I.

[0091] Table 1

[0092]

[0093] Table 2

[0094]

[0095] Table 3

[0096]

[0097] Table 4

[0098]

[0099] Table 5

[0100]

[0101] Table 6

[0102]

[0103] Table 7

[0104]

[0105] The wire welding process proposed by the present invention has good processability. When welding joints of 9Ni steel plates, there are no welding defects such as porosity, lack of fusion and cracks. The welding efficiency is much higher than that of electrodes. The deposited metal and the welded joints have appropriate strength and excellent low-temperature toughness, which can meet the requirements of high-efficiency and high-quality welding of large 9Ni steel storage tanks.

[0106] Although the present invention is disclosed as above, the present invention is not limited thereto. Any person skilled in the art can make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, the protection scope of the present invention should be subject to the scope defined by the claims.

Claims

1. A nickel-based alloy flux-cored wire for welding 9Ni steel, characterized in that the wire includes a flux core. By weight percentage, the weight fractions of each component in the flux core are: titanium dioxide: 26% - 34%, ferrozirconium: 3% - 5%, ferrotitanium: 8% - 12%, rare earth ferrosilicon: 1% - 3%, tungsten powder: 15% - 20%, polytetrafluoroethylene: 1% - 2%, and the rest is pretreated mixed powder.

2. The nickel-based alloy flux-cored wire for welding 9Ni steel according to claim 1, characterized in that by weight percentage, the weight fractions of each component of the pretreated mixed powder are: barium fluoride + magnesium fluoride: 12% - 18%, quartz: 16% - 24%, manganese monoxide: 6% - 12%, potassium silicotitanate: 27% - 45%, spodumene: 14% - 22%, lithium fluoride 1% - 3%.

3. The nickel-based alloy flux-cored wire for welding 9Ni steel according to claim 1, characterized in that the wire further includes a nickel-based outer skin steel strip. By weight percentage, the composition of the nickel-based outer skin steel strip is: C ≤ 0.01%, Si ≤ 0.12%, Mn: 0.4% - 0.9%, Mo: 14.2% - 14.8%, Cr: 15.6% - 16.8%, Al + 2Mg: 0.06% - 0.12%, S + P ≤ 0.007%, and the rest is Ni and unavoidable impurities.

4. A preparation method of a nickel-based alloy flux-cored wire for welding 9Ni steel according to any one of claims 1-3, characterized in that, Including: S100. Prepare the flux core powder; S200. Prepare the nickel-based outer skin steel strip; S300. Prepare the wire rod; S400. Final treatment, including: cleaning, electrostatic oiling, coiling and packaging.

5. The preparation method of the nickel-based alloy flux-cored wire for welding 9Ni steel according to claim 4, characterized in that in step S100, the steps of preparing the flux core powder include: S110. Pretreat the powder materials; S120. Prepare the flux core powder.

6. The preparation method of the nickel-based alloy flux-cored wire for welding 9Ni steel according to claim 5, characterized in that in step S110, the method of pretreating the powder materials includes: S111. Configure the powder materials in proportion; S112. Place the powder materials in an electric arc furnace, use an iron electrode to melt the powder materials, and stir during the melting process; S113. Place the molten powder materials in a water-cooled crystallizer for cooling; S114. Crush the cooled powder materials to form particles.

7. The preparation method of the nickel-based alloy flux-cored wire for welding 9Ni steel according to claim 5, characterized in that in step S120, the method of preparing the flux core powder includes: The flux core powder configured in proportion is mixed evenly in a mixer, baked at 150 - 200 °C for 2 h and then kept warm at 100 °C.

8. The preparation method of the nickel-based alloy flux-cored wire for welding 9Ni steel according to claim 4, characterized in that in step S200, the method of preparing the nickel-based outer skin steel strip includes: S210. Use vacuum + electroslag remelting to make an electroslag ingot; S220. Forge and hot-roll to make a steel strip with a preset thickness; S230. Perform a solution treatment on the steel strip, the solution treatment temperature is 1130 °C - 1200 °C, and the time is 2 h; S240. Alkaline wash and pickling of the steel strip; S250. Gradually reduce the thickness of the steel strip by cold rolling according to process requirements to form the finished steel strip; S260. Use a steel strip slitter to cut the steel strip according to the required length of the process.

9. The method for preparing a nickel-based alloy flux-cored wire for 9Ni steel welding according to claim 4, characterized in that In step S300, the method for preparing the wire rod includes: S310. Add flux powder to the steel strip and roll it into a wire rod; S320. Perform a wire drawing and diameter reduction operation on the formed wire rod.

10. The method for preparing a nickel-based alloy flux-cored wire for 9Ni steel welding according to claim 4, characterized in that In step S400, use medium-frequency induction heating to remove the drawing powder and oil stain on the surface of the wire.

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