Nickel alloy welding wire for ultra-supercritical boiler and preparation method thereof

Abstract

The present invention belongs to the field of metal material processing, and particularly relates to a nickel alloy welding wire for an ultra-supercritical boiler and a preparation method thereof. The nickel alloy welding wire for an ultra-supercritical boiler comprises the following raw materials in parts by weight: C: 0.01-0.05%, Si: 0.10-0.30%, Cr: 20.0-23.0%, Fe: 17.0-19.0%, Co: 1.0-2.0%, W: 0.50-1.00%, Mo: 3.0-6.0%, B: 0.005-0.010%, total amount of Al+Ti: 3.5-5.5%, Zr The present invention comprises the following steps: nickel alloy: 0.005-0.050%, Nb: 2.0-2.5%, S: <0.005%, P: <0.005%, nano-ceramic material: 4.0-7.0%, and Ni as the balance; the process is smelting-high and low temperature refining-annealing, followed by forging-rolling; multiple drawing-annealing and solution-aging treatment; and finally pickling, coating, and plating to obtain the present invention. The present invention can effectively solve the problem in the prior art that the deposited metal formed after welding with nickel alloy welding wire for ultra-supercritical boilers has unstable grain boundary structure at temperatures of 700°C and above, resulting in poor high-temperature mechanical properties.

Description

Technical Field

[0001] The invention belongs to the field of metal materials, and in particular relates to a nickel alloy welding wire for an ultra-supercritical boiler and a preparation method thereof. Background Art

[0002] With the advancement of thermal power generation technology, the development of ultra-supercritical coal-fired power generation technology at temperatures of 700°C and above is of great significance and practical value for energy conservation, pollutant reduction, and carbon dioxide emissions in my country. A review of 700°C A-USC development plans both domestically and internationally shows that the development of materials for superheaters and reheaters—critical components with the highest operating temperatures—is a primary research focus for A-USC power plants. During long-term operation of 700°C A-USC power plant boilers, the inner walls of superheater and reheater tubes operate in a 700°C high-temperature, 30-40 MPa, steam-pressure environment. The outer tube walls, facing the fire surface, are subject to radiation from the furnace fire at approximately 750-760°C, as well as flue gas and thermal corrosion, creating a harsh operating environment. Under advanced ultra-supercritical conditions, conventional ferritic and austenitic heat-resistant steels and nickel-based alloys are no longer sufficient. Precipitation-strengthened nickel-based superalloys with higher endurance, excellent oxidation resistance, resistance to coal ash corrosion, and enhanced microstructural stability are needed to meet the material requirements for superheaters and reheaters in advanced ultra-supercritical power generation units.

[0003] Because weld joints (welds) are the weak link in critical high-temperature components of power plants, welding filler materials with a higher grade than the parent material are typically selected to ensure weldability. High-temperature alloy welding filler materials, due to their excellent comprehensive high-temperature performance, are widely used in welding (including dissimilar welding) high-temperature components in power plants. Currently, candidate nickel-based or nickel-iron-based high-temperature alloy welding rods (such as AWSENiCrFe 3, ENiCrFe 2, ENiCrCoMo 1(mod.), ENiCrMo 3, etc.) for 700°C ultra-supercritical thermal power units do not yet meet the requirements of 700°C service conditions.

[0004] Because the deposited metal lacks the opportunity for controlled rolling and thermomechanical treatment, traditional weld structures cannot refine the directional columnar (dendritic) crystals. Furthermore, due to the rapid cooling rate of the weld, alloying elements are severely segregated, and Nb, V, and other elements in the deposited metal are difficult to precipitate as fine carbides and nitrides during solidification and cooling. As a result, the weld's comprehensive mechanical properties are far inferior to those of the parent metal and exhibit anisotropy. As the service life of welded joints increases, the weld's mechanical properties (especially toughness) degrade significantly, shortening its service life. Furthermore, due to residual welding stress, stress corrosion (SCC) is prone to occur, becoming a weak link in the entire (welded) component and affecting the safe operation of the power station. Summary of the Invention

[0005] The present invention aims to address the problem in prior art of nickel alloy welding wires for ultra-supercritical boilers, where the deposited metal formed after welding exhibits unstable grain boundary structures at temperatures of 700°C and above, resulting in poor high-temperature mechanical properties. The present invention provides a novel nickel alloy welding wire for ultra-supercritical boilers and a method for preparing the same. This novel material effectively addresses this problem, with the yield strength of the deposited metal exceeding 550 MPa at 700°C. To achieve this objective, the present invention employs the following technical solutions to address the technical problems:

[0006] The present invention provides a nickel alloy welding wire for ultra-supercritical boilers, comprising the following powder raw materials in parts by weight:

[0007] C: 0.01-0.05%, Si: 0.10-0.30%, Cr: 20.0-23.0%, Fe: 17.0-19.0%, Co: 1.0-2.0%, W: 0.50-1.00%, Mo: 3.0-6.0%, B: 0.005-0.010%, total amount of Al+Ti: 3.5-5.5%, Zr: 0.005-0.050%, Nb: 2.0-2.5%, S: <0.005%, P: <0.005%, nano-ceramic materials: 4.0-7.0%, Ni balance.

[0008] Furthermore, the weight ratio of Al to Ti is 1:(0.8-1.5).

[0009] Furthermore, the weight ratio of Al to Ti is 1:(1.0-1.5).

[0010] Furthermore, the nano-ceramic material is carbide, oxide or boride.

[0011] Furthermore, the carbide is titanium carbide or silicon carbide;

[0012] The oxide is zirconium oxide or aluminum oxide; and

[0013] The boride is titanium boride.

[0014] Another object of the present invention is to provide a method for preparing the above-mentioned nickel alloy welding wire for ultra-supercritical boilers, comprising the following steps:

[0015] S11: Raw materials are weighed according to the mass percentage of the formula and processed to obtain a uniform and refined mixed powder;

[0016] S12: placing the mixed powder and nano-ceramic material in S1 into a melting furnace for melting, and performing high-temperature refining, low-temperature refining, and then remelting and refining to cast into alloy ingots;

[0017] S13: After annealing the alloy ingot, forging and rolling are performed to prepare alloy wire rods;

[0018] S14: performing multiple drawing-annealing steps on the alloy wire rod after pretreatment;

[0019] S15: Processing the alloy wire into the required size and performing solution-aging treatment;

[0020] S16: Pickling the alloy wire; coating; and

[0021] S17: Plating is performed on the surface to obtain a target product.

[0022] Furthermore, the solution-aging treatment in S5 is a multi-step graded treatment.

[0023] Another object of the present invention is to provide a method for welding the nickel alloy welding wire for ultra-supercritical boilers, comprising the following steps:

[0024] S21: Preparation before welding, i.e.

[0025] Prepare grooves at the interface of parent material and remove impurities;

[0026] S22: welding, i.e.

[0027] Welding the ultra-supercritical boiler nickel alloy welding wire to the base material by manual TIG welding or semi-automatic tungsten inert gas (TIG) welding with filler wire;

[0028] S23: Post-weld treatment, i.e.

[0029] After welding and when welding is interrupted, heat treatment is immediately carried out at 200-250℃ for 1-2h, and then the weld joint is heat treated at 1100-1150℃ for 0.5-1.0h, and then air-cooled to form weld deposited metal.

[0030] The present invention has the following beneficial effects:

[0031] (1) The present invention provides a nickel alloy welding wire for ultra-supercritical boilers, which uses Ni as the matrix. Cr can improve the alloy's high-temperature oxidation resistance and corrosion resistance; Co can improve carbonization resistance, plasticity, and hot working properties; Mo can refine grains and improve the alloy's thermal stability; and W can improve the alloy's strength. The addition of Cr, Co, Mo, and W achieves a solid solution strengthening effect, enhancing its high-temperature oxidation resistance and thermal strength. At the same time, Cr, Co, Mo, and W can react with C to form carbides, and hard phases such as chromium carbide are dispersed in the solid solution-strengthened matrix, improving high-temperature strength and plasticity. Moreover, the improvement in high-temperature oxidation resistance and high-temperature strength can effectively suppress welding pores caused by oxidation, effectively improving welding strength.

[0032] (2) The present invention provides a nickel alloy welding wire for ultra-supercritical boilers, wherein a certain proportion of Mo, Fe, and B are added to the alloy. During the high-temperature remelting process, a reaction occurs to form Mo2FeB2 and Mo2NiB2 ternary boride hard phases, which have excellent mechanical properties such as corrosion resistance, hardness, and wear resistance. In addition, B also has the function of improving the plasticity of the nickel alloy.

[0033] (3) The present invention provides a nickel alloy welding wire for ultra-supercritical boilers, wherein a certain amount of Fe and Nb is added to the alloy. First, Fe can improve resistance to high-temperature carburizing environments and control thermal expansion; at the same time, it can reduce the fundamental properties of the material; and when combined with Nb, it can improve the plasticity and high-temperature strength of the alloy and reduce stress cracking; second, Nb is a high-temperature strengthening phase-forming element, which can effectively improve the high-temperature strength and high-temperature stability of the alloy. The precipitation of its carbides at the grain boundaries can make the grain boundary morphology more complex and curved, increase the grain boundary sliding resistance, and thus reduce the tendency of strain cracking; in addition, Nb has a good affinity with O and can form a stable oxide Nb2O5, which has the effect of delaying corrosion.

[0034] (4) The present invention provides a nickel alloy welding wire for ultra-supercritical boilers, wherein a certain amount of composite Al and Ti elements are added to the alloy. On the one hand, Al and Ti can improve the weldability of the alloy. They have a strong affinity with oxygen and can act as deoxidizing elements to protect the weld from oxidation, thereby effectively inhibiting the formation of CO and N2 pores, facilitating the formation of the weld, and having a certain strengthening and toughening effect on the alloy, thereby improving the high-temperature mechanical properties of the alloy.

[0035] (5) The present invention provides a nickel alloy welding wire for ultra-supercritical boilers, wherein a certain amount of nano-ceramic material is added to the alloy. Firstly, the high-temperature oxidation resistance and wear resistance of the welding material can be improved; secondly, the micro-cracks generated by stress can be terminated, thereby improving the mechanical properties.

[0036] (6) The present invention provides a method for preparing nickel alloy welding wire for ultra-supercritical boilers, which adopts a multi-step graded solid solution-aging treatment. On the one hand, it improves the interfacial bonding strength between the nano-ceramic material and the nickel alloy matrix, thereby improving the performance; on the other hand, it can refine the grain size and further improve the mechanical properties.

[0037] (7) The present invention provides a welding method for nickel alloy welding wire for ultra-supercritical boilers. After welding, high-temperature heat treatment is used to cause crystal transformation in the solidified state of the weld zone, thereby eliminating weld component segregation and welding residual stress to the greatest extent and maintaining consistency with the parent material structure. DETAILED DESCRIPTION

[0038] The present invention will be described in detail below with reference to the following examples. However, it should be understood that the following examples are merely illustrative of the embodiments of the present invention and are not intended to limit the scope of the present invention.

[0039] The purpose of the present invention is to develop a nickel alloy welding wire for ultra-supercritical boilers to solve the problems existing in the existing nickel alloy welding wire for ultra-supercritical boilers. The idea of ​​implementation is: with Ni as the main component, the addition of high-temperature resistant elements such as Cr, Co, Mo, and W is added through formula design to achieve solid solution strengthening, improve oxidation resistance and thermal corrosion resistance; add elements such as B and Fe to improve hardness and plasticity; add Nb to improve the alloy's resistance to stress cracking and high-temperature plasticity; at the same time, add precipitation strengthening elements such as Al and Ti to improve high-temperature strength, purify grain boundaries, and improve alloy structure stability; finally, compound nano-ceramic materials to improve mechanical properties. The above components are subjected to a grain refinement process to improve interphase compatibility and further improve performance; finally, through a post-weld heat treatment process, the crystal transformation is promoted and welding stress is eliminated, so that high-performance weld deposited metal can be obtained. The embodiments of the present invention are as follows:

[0040] An embodiment of the present invention provides a nickel alloy welding wire for an ultra-supercritical boiler, comprising the following powder raw materials in parts by weight:

[0041] C: 0.01-0.05%, Si: 0.10-0.30%, Cr: 20.0-23.0%, Fe: 17.0-19.0%, Co: 1.0-2.0%, W: 0.50-1.00%, Mo: 3.0-6.0%, B: 0.005-0.010%, total amount of Al+Ti: 3.5-5.5%, Zr: 0.005-0.050%, Nb: 2.0-2.5%, S: <0.005%, P: <0.005%, nano-ceramic materials: 4.0-7.0%, Ni balance.

[0042] The weight ratio of Al to Ti is 1:(0.8-1.5).

[0043] And further preferably, the weight ratio of the above-mentioned Al to Ti is 1:(1.0-1.5).

[0044] Al and Ti improve the alloy's weldability, acting as deoxidizing elements, facilitating weld formation, and providing a certain degree of toughening. Al is the primary element in the formation of the γ'(Ni3Al) phase. 80% of the Al added to the alloy reacts with Ni to form Ni3Al, which acts as precipitation strengthening. 90% of the Ti enters the γ' phase, replacing Al in the γ'(Ni3Al) phase to form Ni3(Al, Ti). Under certain Al content conditions, increasing the Ti content and the Ti / Al ratio increases the transformation from the γ' phase to the η phase and the amount of η phase precipitation. Furthermore, excessively high Ti / Al ratios can easily lead to the growth of the γ' phase. Therefore, while ensuring a sufficient amount of γ' phase precipitation, the Ti / Al ratio should be appropriately controlled to significantly improve the alloy's microstructure stability. Taking all factors into consideration, the recommended Al / Ti ratio is 3.5-5.5% combined, with a weight ratio of Al to Ti of 1:(0.8-1.5), preferably 1:(1.0-1.5).

[0045] The nano ceramic material is carbide, oxide or boride.

[0046] The carbide is titanium carbide or silicon carbide;

[0047] The above oxide is zirconium oxide or aluminum oxide; and

[0048] The boride is titanium boride.

[0049] The above-mentioned nano-ceramic materials can form a dispersion-strengthened phase, hinder dislocation movement or refine grains to improve the high-temperature yield strength, toughness, crack resistance and other mechanical properties of nickel alloy materials.

[0050] In addition, other important components and functions in the embodiments of the present invention are as follows:

[0051] Cr is the primary element that ensures the high-temperature oxidation resistance of the alloy of the present invention and is the most important element for stabilizing the alloy surface. It forms a dense, oxidation- and corrosion-resistant Cr2O3 protective layer on the surface of the base material, preventing high-temperature oxidation and hot corrosion. Generally, a Cr content exceeding 12% provides good high-temperature oxidation resistance. Above 33%, the increased Cr content has little effect on improving high-temperature oxidation resistance and can lead to the precipitation of an α-Cr phase, which is detrimental to mechanical properties. Therefore, the present invention controls the Cr content to 20.0-23.0%.

[0052] The addition of Co achieves solid solution strengthening, improving its high-temperature oxidation resistance and thermal strength. A slightly excessive amount of Co can react with C to form carbides, which disperse within the solid solution-strengthened matrix, enhancing high-temperature strength and plasticity. Therefore, the Co content in this invention is controlled within a range of 1.0-2.0%.

[0053] Mo increases high-temperature strength and improves the alloy's corrosion resistance, particularly when combined with chromium, resulting in superior pitting corrosion resistance. Mo also enhances the alloy's creep resistance through solid solution strengthening and reduces radiation-induced grain boundary weakening. The addition of Mo significantly improves the welding wire's corrosion resistance and high-temperature strength. Therefore, the present invention limits the Mo content to 3.0-6.0%.

[0054] Fe is a matrix element in NiCrFe alloys and can improve weld strength through solid solution strengthening. Therefore, the present invention controls the Fe content to 17.0-19.0%. Furthermore, while controlling performance, adding more Fe can help reduce the cost of the welding wire.

[0055] Niobium (Nb) is a strengthening element in high-temperature environments. It increases solid solution lattice distortion and lattice atomic bond attraction, strengthening the matrix and achieving a significant solid solution strengthening effect. It is also a strong carbide former, forming MC, M6C, or M2C carbides, which significantly strengthen the weld metal as a second phase, improving the high-temperature strength-ductility balance and enhancing the high-temperature durability of the nickel alloy of the present invention. Furthermore, it reduces alloying element segregation and improves weld metal plasticity. Therefore, the present invention controls the Nb content to 2.0-2.5%.

[0056] Adding trace amounts of Zr and B elements strengthens the grain boundaries and improves the long-term strength of the weld deposited metal, and trace additions will not increase the sensitivity of welding hot cracks.

[0057] The embodiment of the present invention further provides a method for preparing the nickel alloy welding wire for ultra-supercritical boilers, comprising the following steps:

[0058] S11: Raw materials are weighed according to the mass percentage of the formula and processed to obtain a uniform and refined mixed powder.

[0059] The above-mentioned treatment process and the treatment process described in the following embodiments of the present invention are as follows: adding the raw material powder except the nanoceramic material to ethanol, magnetically stirring at 1000 r / min for 3 hours, and then subjecting it to 50KHz ultrasonic treatment for 2 hours to obtain an ethanol suspension; filtering, taking out the insoluble matter, placing it in an 80°C drying oven for drying for 2 hours, placing the insoluble matter in a ball mill, and then adding long-chain fatty acids. The ball mill is placed on a high-energy ball mill for ball milling to obtain a uniformly refined mixed powder; wherein the grinding ball material is corundum ball, the ball-to-material mass ratio is 6:1, the ball milling process is 7 hours, and the ball mill speed is 150-200 r / min;

[0060] The ratio of the above-mentioned long-chain fatty acid to the total mass of the raw material powder is 2g:100g;

[0061] The above-mentioned long-chain fatty acid is myristic acid.

[0062] S12: The mixed powder and nano-ceramic material in S11 are placed in a smelting furnace for smelting, and after high-temperature refining and low-temperature refining, remelting and refining are performed, and then cast into alloy ingots.

[0063] The above-mentioned high temperature refining is smelting at 1750-1850℃ for 30-45min;

[0064] The above-mentioned low-temperature refining is smelting at 1650-1700°C for 15-25 minutes;

[0065] The above remelting is electroslag remelting, and the furnace temperature is 1750-1850℃.

[0066] S13: After annealing, the alloy ingot is forged and rolled to prepare an alloy wire rod.

[0067] The above annealing process is heating to 1000-1050℃ and keeping it for 20-35h;

[0068] The forging process is as follows: at 950°C, the blank is forged into alloy blank I with a forging ratio of 3-4; after tempering at 950-1000°C for 1-2 hours, the blank is forged into alloy blank II at 1050°C with a forging ratio of 6-7; and then the blank is forged into alloy blank III at the same temperature with a forging ratio of 3-4;

[0069] The above rolling process is to keep the temperature at 1000-1050°C for 0.5-1.5h and hot-roll the steel into Φ4.05.0mm alloy wire rod at 950-1100°C.

[0070] S14: After pre-treatment, the alloy wire rod is subjected to multiple drawing-annealing passes.

[0071] The pretreatment is to heat the alloy wire rod to 950°C for 1.5 hours, oil cool it for softening, boil it in alkali, then wash it with high pressure water, then pickle it with water, and then ultrasonically clean it.

[0072] The above-mentioned drawing process includes adding a lubricant before drawing and performing multiple drawing processes to obtain the alloy wire;

[0073] The above annealing is vacuum annealing after 6-10 drawing passes, and the annealing temperature is 640-800°C.

[0074] S15: Processing into alloy wire of required size and performing solution-aging treatment.

[0075] The solid solution-aging treatment in S5 is a multi-step graded treatment; specifically, in a nitrogen environment, heating to 950-1050°C, holding for 2-3 hours, continuing to heat to 1050-1100°C, holding for 2-3 hours, continuing to heat to 1100-1150°C, holding for 1-2 hours, continuing to heat to 1150-1170°C, holding for 1-2 hours, and rapid water quenching to obtain a solid solution alloy; the above-mentioned aging is heating to 800-850°C, holding for 3-8 hours, air cooling, then heating to 750-770°C, holding for 10-15 hours, and air cooling.

[0076] S16: Pickling the alloy wire; coating; and

[0077] The pickling described above and in the following embodiments of the present invention are all carried out by pickling the alloy wire after solution heat treatment, firstly pickling it with a mixed pickling solution containing 100 g / L nitric acid and 20 g / L hydrofluoric acid, controlling the temperature to be ≤50°C and the pickling time to be 10 min; finally, cleaning the residual acid on the surface;

[0078] The above coating and the coating described in the following embodiments of the present invention are all obtained by coating a layer of water-soluble coating agent on the surface of the pickled alloy wire, and the coated alloy wire is naturally air-dried.

[0079] S17: Plating is performed on the surface to obtain a target product.

[0080] The above surface coating process and the surface coating process described in the following embodiments of the present invention are all performed as follows:

[0081] Pretreatment: The surface of the high-temperature nickel-based alloy welding wire was cleaned, sanded with sandpaper, and then polished. It was then rinsed in a mixed solution of sodium hydroxide (20 g / L), trisodium phosphate (30 g / L), and sodium silicate (30 g / L) at 50°C for 10 minutes. Finally, it was electropolished in a mixed acid solution of 80% acetic acid and 20% perchloric acid at an electrolysis voltage of 27 V for 7 seconds to produce welding wire I.

[0082] Nickel plating: Prepare a Watt-type electrolyte, which includes nickel sulfate hexahydrate, nickel chloride hexahydrate, and boric acid. Electroplate a nickel layer on the surface of welding wire I to obtain welding wire II. The electroplating process parameters are a current density of 3A / dm 2 , electroplating time 10min, electroplating temperature 45℃, stirring speed 300r / min;

[0083] TiC plating: Prepare a TiC electroplating solution, which includes the following by mass volume ratio: TiC 30g / L, NiSO4 400g / L, NiCl2 45g / L, H3BO 350g / L, and the balance is water; the TiC particle size is 3-10μm, and a TiC coating is electroplated on the nickel layer of welding wire II to produce welding wire III. The electroplating process parameters are a current density of 3A / dm 2 , electroplating time 0.5h, electroplating temperature 45℃, stirring speed 300r / min;

[0084] Nickel plating: Prepare a Watt-type electrolyte containing 400g / L NiSO4, 45g / L NiCl2, 50g / L H3BO3, and the balance being water. Electroplate a nickel layer on the TiC coating of welding wire III to produce a nuclear power high-temperature nickel-based alloy composite welding wire. The electroplating process parameters are a current density of 3A / dm 2 , electroplating time 10min, electroplating temperature 45℃, stirring speed 300r / min.

[0085] The embodiment of the present invention further provides a welding method for the above-mentioned nickel alloy welding wire for ultra-supercritical boiler, comprising the following steps:

[0086] S21: Preparation before welding, i.e.

[0087] Prepare grooves at the interface of the parent material, and clean the grooves and both the inner and outer walls to remove water, oil and impurities;

[0088] The above-mentioned parent materials and the parent materials in the following embodiments of the present invention are all GH2984 nickel-iron based alloy.

[0089] S22: welding, i.e.

[0090] Welding the ultra-supercritical boiler nickel alloy welding wire to the base material by manual TIG welding or semi-automatic tungsten inert gas (TIG) welding with filler wire;

[0091] Welding current intensity: 105-170A; welding arc voltage: 11-15V; welding speed: 100-140mm / min; current type / polarity: DC / positive connection SP; interpass temperature not higher than 100℃; shielding gas: Ar, gas flow rate 12-16L / min.

[0092] S23: Post-weld treatment, i.e.

[0093] After welding and when welding is interrupted, heat treatment is immediately carried out at 200-250℃ for 1-2h, and then the weld joint is heat treated at 1100-1150℃ for 0.5-1.0h, and then air-cooled to form weld deposited metal.

[0094] In order to further understand the present invention, the nickel alloy welding wire for ultra-supercritical boiler provided by the present invention is described in detail below with reference to specific embodiments. The protection scope of the present invention is not limited by the following embodiments.

[0095] Example 1

[0096] This embodiment provides a nickel alloy welding wire for an ultra-supercritical boiler, comprising the following powder raw materials in parts by weight:

[0097] C: 0.03%, Si: 0.20%, Cr: 21.5%, Fe: 18.0%, Co: 1.5%, W: 0.70%, Mo: 4.5%, B: 0.008%, total amount of Al+Ti: 4.5%, Zr: 0.030%, Nb: 2.35%, S: 0.002%, P: 0.002%, nano-ceramic material: 5.5%, Ni balance.

[0098] The weight ratio of Al to Ti is 1:1.2.

[0099] The above-mentioned nano ceramic material is carbide.

[0100] The carbide is titanium carbide.

[0101] This embodiment also provides a method for preparing the nickel alloy welding wire for ultra-supercritical boilers, comprising the following steps:

[0102] S1: The raw materials are weighed according to the mass percentage of the formula and processed to obtain a uniform and refined mixed powder.

[0103] S2: The mixed powder and nano-ceramic material in S1 are placed in a smelting furnace for smelting, and after high-temperature refining and low-temperature refining, they are remelted and cast into alloy ingots.

[0104] The above high temperature refining is smelting at 1800°C for 35 minutes;

[0105] The above-mentioned low-temperature refining is smelting at 1680°C for 20 minutes;

[0106] The above remelting is electroslag remelting, and the furnace temperature is 1780°C.

[0107] S3: After annealing, the alloy ingot is forged and rolled to prepare alloy wire rod.

[0108] The above annealing process is heating to 1020°C and keeping it warm for 25h;

[0109] The forging process is as follows: at 950°C, the billet is forged into alloy billet I with a forging ratio of 3.5; after tempering at 970°C for 1.4 hours, the billet is forged into alloy billet II at 1050°C with a forging ratio of 6.5; and then forged into alloy billet III at the same temperature with a forging ratio of 3.5.

[0110] The above rolling process is to keep the temperature at 1020°C for 1 hour and hot-roll the alloy wire rod at 1000°C into Φ4.5mm.

[0111] S4: After pre-treatment, the alloy wire rod is subjected to multiple drawing-annealing passes.

[0112] The pretreatment is to heat the alloy wire rod to 950°C for 1.5 hours, oil cool it for softening, boil it in alkali, then wash it with high pressure water, then pickle it with water, and then ultrasonically clean it.

[0113] The above-mentioned drawing process includes adding a lubricant before drawing and performing multiple drawing processes to obtain the alloy wire;

[0114] The above annealing is vacuum annealing after 8 drawing passes, and the annealing temperature is 720°C.

[0115] S5: Processing into alloy wire of required size and performing solution-aging treatment.

[0116] The solid solution-aging treatment in the above S5 is a multi-step graded treatment; specifically, in a nitrogen environment, heating to 1000°C, holding for 2.3 hours, continuing to heat to 1080°C, holding for 2.5 hours, continuing to heat to 1120°C, holding for 1.5 hours, continuing to heat to 1155°C, holding for 1.5 hours, and rapid water quenching to obtain a solid solution alloy; the above aging is heating to 820°C, holding for 5 hours, air cooling, then heating to 760°C, holding for 12 hours, and air cooling.

[0117] S6: pickling the alloy wire; coating; and

[0118] S7: Plating is performed on the surface to obtain the target product.

[0119] This embodiment further provides a welding method for the above-mentioned nickel alloy welding wire for ultra-supercritical boilers, comprising the following steps:

[0120] S21: Preparation before welding, i.e.

[0121] Prepare a groove at the interface of the parent material, and clean the groove and both the inner and outer walls to remove water, oil and impurities.

[0122] S22: welding, i.e.

[0123] Manually TIG welding the nickel alloy welding wire for ultra-supercritical boiler onto the base metal;

[0124] Welding current intensity: 140A; welding arc voltage: 13V; welding speed: 120mm / min; current type / polarity: DC / positive connection SP; interlayer temperature not higher than 100℃; shielding gas: Ar, gas flow rate 13L / min.

[0125] S23: Post-weld treatment, i.e.

[0126] After welding and when welding is interrupted, heat treatment is immediately performed at 220°C for 1.5 hours. The weld joint is then heat treated at 1100°C for 1.0 hour and air-cooled to form weld deposited metal.

[0127] Example 2

[0128] This embodiment provides a nickel alloy welding wire for an ultra-supercritical boiler, comprising the following powder raw materials in parts by weight:

[0129] C: 0.01%, Si: 0.30%, Cr: 20.0%, Fe: 17.0%, Co: 2.0%, W: 0.50%, Mo: 6.0%, B: 0.01%, total amount of Al+Ti: 5.5%, Zr: 0.005%, Nb: 2.0%, S: 0.002%, P: 0.002%, nano-ceramic material: 7.0%, Ni balance.

[0130] The weight ratio of Al to Ti is 1:1.2.

[0131] The above-mentioned nano ceramic material is carbide.

[0132] The carbide is titanium carbide.

[0133] This embodiment also provides a method for preparing the nickel alloy welding wire for ultra-supercritical boilers, comprising the following steps:

[0134] S1: The raw materials are weighed according to the mass percentage of the formula and processed to obtain a uniform and refined mixed powder.

[0135] S2: The mixed powder and nano-ceramic material in S1 are placed in a smelting furnace for smelting, and after high-temperature refining and low-temperature refining, they are remelted and cast into alloy ingots.

[0136] The above high temperature refining is smelting at 1750℃ for 45min;

[0137] The above-mentioned low-temperature refining is smelting at 1650°C for 25 minutes;

[0138] The above remelting is electroslag remelting, and the furnace temperature is 1750°C.

[0139] S3: After annealing, the alloy ingot is forged and rolled to prepare alloy wire rod.

[0140] The above annealing process is heating to 1000°C and keeping it at this temperature for 35h;

[0141] The forging process is as follows: at 950°C, the billet is forged into alloy billet I with a forging ratio of 3; after tempering at 950°C for 2 hours, it is forged into alloy billet II at 1050°C with a forging ratio of 7; and then forged into alloy billet III at the same temperature with a forging ratio of 4.

[0142] The above rolling process is to keep the temperature at 1000°C for 1.5 hours and then hot-roll the alloy wire rod at 950°C into Φ4.0mm.

[0143] S4: After pre-treatment, the alloy wire rod is subjected to multiple drawing-annealing passes.

[0144] The pretreatment is to heat the alloy wire rod to 950°C for 1.5 hours, oil cool it for softening, boil it in alkali, then wash it with high pressure water, then pickle it with water, and then ultrasonically clean it.

[0145] The above-mentioned drawing process includes adding a lubricant before drawing and performing multiple drawing processes to obtain the alloy wire;

[0146] The above annealing is vacuum annealing after 10 drawing passes, and the annealing temperature is 640°C.

[0147] S5: Processing into alloy wire of required size and performing solution-aging treatment.

[0148] The solid solution-aging treatment in the above S5 is a multi-step graded treatment; specifically, in a nitrogen environment, heating to 1050°C, holding for 2 hours, continuing to heat to 1100°C, holding for 2 hours, continuing to heat to 1150°C, holding for 1 hour, continuing to heat to 1170°C, holding for 1 hour, and rapid water quenching to obtain a solid solution alloy; the above aging is heating to 850°C, holding for 3 hours, air cooling, then heating to 770°C, holding for 10 hours, and air cooling.

[0149] S6: pickling the alloy wire; coating; and

[0150] S7: Plating is performed on the surface to obtain the target product.

[0151] This embodiment further provides a welding method for the above-mentioned nickel alloy welding wire for ultra-supercritical boilers, comprising the following steps:

[0152] S21: Preparation before welding, i.e.

[0153] Prepare a groove at the interface of the parent material, and clean the groove and both the inner and outer walls to remove water, oil and impurities.

[0154] S22: welding, i.e.

[0155] Manually TIG welding the nickel alloy welding wire for ultra-supercritical boiler onto the base metal;

[0156] Welding current intensity: 170A; welding arc voltage: 15V; welding speed: 140mm / min; current type / polarity: DC / positive connection SP; interlayer temperature not higher than 100℃; shielding gas: Ar, gas flow rate 16L / min.

[0157] S23: Post-weld treatment, i.e.

[0158] Immediately after welding and when welding is interrupted, a post-heat treatment at 250°C for 1.0h is performed, and then the weld joint is heat treated at 1150°C for 0.5h and air-cooled to form weld deposited metal.

[0159] Example 3

[0160] This embodiment provides a nickel alloy welding wire for an ultra-supercritical boiler, comprising the following powder raw materials in parts by weight:

[0161] C: 0.05%, Si: 0.10%, Cr: 23.0%, Fe: 19.0%, Co: 1.0%, W: 1.0%, Mo: 3.0%, B: 0.005%, total amount of Al+Ti: 3.5%, Zr: 0.05%, Nb: 2.5%, S: 0.002%, P: 0.002%, nano-ceramic material: 4.0%, Ni balance.

[0162] The weight ratio of Al to Ti is 1:1.2.

[0163] The above-mentioned nano ceramic material is carbide.

[0164] The carbide is titanium carbide.

[0165] This embodiment also provides a method for preparing the nickel alloy welding wire for ultra-supercritical boilers, comprising the following steps:

[0166] S1: The raw materials are weighed according to the mass percentage of the formula and processed to obtain a uniform and refined mixed powder.

[0167] S2: The mixed powder and nano-ceramic material in S1 are placed in a smelting furnace for smelting, and after high-temperature refining and low-temperature refining, they are remelted and cast into alloy ingots.

[0168] The above high temperature refining is smelting at 1850°C for 30 minutes;

[0169] The above low temperature refining is smelting at 1700°C for 15 minutes;

[0170] The above remelting is electroslag remelting, and the furnace temperature is 1850°C.

[0171] S3: After annealing, the alloy ingot is forged and rolled to prepare alloy wire rod.

[0172] The above annealing process is heating to 1050°C and keeping it at this temperature for 20 hours;

[0173] The forging process is as follows: at 950°C, the billet is forged into alloy billet I with a forging ratio of 4; after tempering at 1000°C for 1 hour, it is forged into alloy billet II at 1050°C with a forging ratio of 6; and then forged into alloy billet III at the same temperature with a forging ratio of 3;

[0174] The above rolling process is to keep the temperature at 1050°C for 0.5h and hot-roll the alloy wire rod at 1100°C into Φ5.0mm.

[0175] S4: After pre-treatment, the alloy wire rod is subjected to multiple drawing-annealing passes.

[0176] The pretreatment is to heat the alloy wire rod to 950°C for 1.5 hours, oil cool it for softening, boil it in alkali, then wash it with high pressure water, then pickle it with water, and then ultrasonically clean it.

[0177] The above-mentioned drawing process includes adding a lubricant before drawing and performing multiple drawing processes to obtain the alloy wire;

[0178] The above annealing is vacuum annealing after 6 drawing passes, and the annealing temperature is 800°C.

[0179] S5: Processing into alloy wire of required size and performing solution-aging treatment.

[0180] The solid solution-aging treatment in the above S5 is a multi-step graded treatment; specifically, in a nitrogen environment, heating to 950°C, holding for 3 hours, continuing to heat to 1050°C, holding for 3 hours, continuing to heat to 1100°C, holding for 2 hours, continuing to heat to 1150°C, holding for 2 hours, and rapid water quenching to obtain a solid solution alloy; the above aging is heating to 800°C, holding for 8 hours, air cooling, then heating to 750°C, holding for 15 hours, and air cooling.

[0181] S6: pickling the alloy wire; coating; and

[0182] S7: Plating is performed on the surface to obtain the target product.

[0183] This embodiment further provides a welding method for the above-mentioned nickel alloy welding wire for ultra-supercritical boilers, comprising the following steps:

[0184] S21: Preparation before welding, i.e.

[0185] Prepare a groove at the interface of the parent material, and clean the groove and both the inner and outer walls to remove water, oil and impurities.

[0186] S22: welding, i.e.

[0187] Welding the nickel alloy welding wire for ultra-supercritical boiler onto the base material using semi-automatic tungsten inert gas (TIG) welding;

[0188] Welding current intensity: 105A; welding arc voltage: 11V; welding speed: 100mm / min; current type / polarity: DC / positive connection SP; interlayer temperature not higher than 100℃; shielding gas: Ar, gas flow rate 12L / min.

[0189] S23: Post-weld treatment, i.e.

[0190] Immediately after welding and when welding is interrupted, a post-heat treatment at 200°C for 2.0h is performed, and then the weld joint is heat treated at 1100°C for 1.0h and air-cooled to form weld deposited metal.

[0191] Example 4

[0192] The rest is the same as in Example 1, except that:

[0193] In a nickel alloy welding wire formula for ultra-supercritical boilers,

[0194] The preferred weight ratio of Al to Ti is 1:1.0.

[0195] Example 5

[0196] The rest is the same as in Example 1, except that:

[0197] In a nickel alloy welding wire formula for ultra-supercritical boilers,

[0198] The preferred weight ratio of Al to Ti is 1:1.5.

[0199] Example 6

[0200] The rest is the same as in Example 1, except that:

[0201] In a nickel alloy welding wire formula for ultra-supercritical boilers,

[0202] The preferred weight ratio of Al to Ti is 1:0.8.

[0203] Example 7

[0204] The rest is the same as in Example 1, except that:

[0205] In a nickel alloy welding wire formula for ultra-supercritical boilers,

[0206] Preferably the nano-ceramic material is an oxide.

[0207] The above oxide is zirconium oxide.

[0208] Example 8

[0209] The rest is the same as in Example 1, except that:

[0210] In a nickel alloy welding wire formula for ultra-supercritical boilers,

[0211] Preferably the nano-ceramic material is an oxide.

[0212] The above oxide is aluminum oxide.

[0213] Example 9

[0214] The rest is the same as in Example 1, except that:

[0215] In a nickel alloy welding wire formula for ultra-supercritical boilers,

[0216] Preferably the nano-ceramic material is carbide.

[0217] The carbide mentioned above is silicon carbide.

[0218] Example 10

[0219] The rest is the same as in Example 1, except that:

[0220] In a nickel alloy welding wire formula for ultra-supercritical boilers,

[0221] Preferably the nano-ceramic material is a boride.

[0222] The boride is titanium boride.

[0223] The following comparative examples are compared with Example 1:

[0224] Comparative Example 1

[0225] The rest is the same as in Example 1, except that:

[0226] In a nickel alloy welding wire formula for ultra-supercritical boilers,

[0227] The weight ratio of Al to Ti is 1:0.5.

[0228] Comparative Example 2

[0229] The rest is the same as in Example 1, except that:

[0230] In a nickel alloy welding wire formula for ultra-supercritical boilers,

[0231] The weight ratio of Al to Ti is 1:2.0.

[0232] Comparative Example 3

[0233] The rest is the same as in Example 1, except that:

[0234] In a nickel alloy welding wire formula for ultra-supercritical boilers,

[0235] The weight fraction of Nb is 0; that is, no Nb is added.

[0236] Comparative Example 4

[0237] The rest is the same as in Example 1, except that:

[0238] In a nickel alloy welding wire formula for ultra-supercritical boilers,

[0239] The weight fraction of the nano-ceramic material is 0; that is, no nano-ceramic material is added.

[0240] Comparative Example 5

[0241] The rest is the same as in Example 1, except that:

[0242] In a method for preparing nickel alloy welding wire for ultra-supercritical boiler,

[0243] No S15 process was performed, that is, no solution-aging treatment was performed.

[0244] Comparative Example 6

[0245] The rest is the same as in Example 1, except that:

[0246] In a method for preparing nickel alloy welding wire for ultra-supercritical boiler, in S15,

[0247] The solid solution is carried out in a nitrogen environment, heating to 1000℃, keeping warm for 2.3h, continuing to heat to 1155℃, keeping warm for 1.5h, and quickly quenching with water to obtain a solid solution alloy; the aging is carried out by heating to 760℃, keeping warm for 12h, and air cooling.

[0248] Comparative Example 7

[0249] The rest is the same as in Example 1, except that:

[0250] A welding method for nickel alloy welding wire for ultra-supercritical boiler, in S23,

[0251] The post-weld heat treatment parameters are heat treatment at 750°C for 8.0 hours, followed by air cooling to form weld deposited metal.

[0252] The physical properties of the nickel alloy welding wires for ultra-supercritical boilers prepared in the embodiments of the present invention and the comparative examples were measured, and the results are shown in Table 1.

[0253] Table 1 Physical test performance of each embodiment

[0254]

[0255] It can be observed from Examples 1-10 that the nickel alloy welding wire for ultra-supercritical boilers of the present invention has excellent mechanical properties, corrosion resistance, hardness, and also has excellent surface properties.

[0256] From Example 1 and Comparative Examples 1-4, it can be observed that the nickel alloy welding wire for ultra-supercritical boilers of the present invention contains appropriate amounts of Al and Ti in a suitable ratio, which has a certain strengthening and toughening effect on the alloy; Nb has the ability to reduce the tendency of strain cracking and can improve the high-temperature strength, creep resistance, corrosion resistance and other properties of the alloy; the nano-ceramic material has good mechanical strength, etc.

[0257] It can be observed from Example 1 and Comparative Examples 5-6 that the solution-aging process and the multi-step solution-aging process are beneficial to grain refinement and enhance the interphase compatibility of materials such as ceramic materials, thereby further improving performance; that is, a suitable preparation process has a positive effect on the performance of nickel-based alloy welding materials;

[0258] It can be observed from Example 1 and Comparative Example 7 that a suitable post-weld heat treatment process is beneficial to the transformation of solidified columnar crystals and dendrites in the weld zone into equiaxed crystals, thereby eliminating weld component segregation and welding residual stress to the greatest extent possible; and can positively improve mechanical properties.

[0259] In summary, the nickel alloy welding wire for ultra-supercritical boilers of the present invention has excellent mechanical properties, corrosion resistance, etc., and can meet the use requirements of 700°C ultra-supercritical boilers.

[0260] The test method is as follows:

[0261] (1) Crack resistance: Observe whether there are visible cracks on the weld strip, and if the specimen is intact after bending or the length of a single crack is ≤1.5mm, it is recorded as "OK"; otherwise, if there are visible cracks and the length of a single crack after bending is greater than 1.5mm, it is recorded as "NG".

[0262] (2) Hardness. Measured using a microhardness tester (HXS 1000A) with a load of 30 kgf and a loading time of 15 s. Each specimen was tested at five points, and the arithmetic mean was taken to obtain the hardness value (HV30).

[0263] (3) Mechanical property test: The room temperature mechanical property test and high temperature mechanical property test of the welded joint were carried out at room temperature and 700℃ respectively according to GB / T2651 2008 “Tensile test method for welded joints”.

[0264] (4) Corrosion rate: The corrosion resistance test was carried out using the ASTM G28 A method, and the test time was 120 h.

[0265] With the above-described preferred embodiments of the present invention as a guide, and with reference to the above description, relevant personnel are fully capable of making various changes and modifications without departing from the technical scope of this invention. The technical scope of this invention is not limited to the contents of the specification and must be determined according to the scope of the claims.

Claims

1. A nickel alloy welding wire for ultra-supercritical boilers, characterized by: The powder raw materials include the following parts by weight: C: 0.01-0.05%, Si: 0.10-0.30%, Cr: 20.0-23.0%, Fe: 17.0-19.0%, Co: 1.0-2.0%, W: 0.50-1.00%, Mo: 3.0-6.0%, B: 0.005-0.010%, total Al+Ti: 3.5-5.5%, Zr: 0.005-0.050%, Nb: 2.0-2.5%, S: <0.005%, P: <0.005%, nano-ceramic material: 4.0-7.0%, Ni balance; The nano ceramic material is carbide, oxide or boride; The carbide is titanium carbide or silicon carbide; The oxide is zirconium oxide or aluminum oxide; and The boride is titanium boride.

2. The nickel alloy welding wire for ultra-supercritical boiler according to claim 1, characterized in that: The weight ratio of Al to Ti is 1:(0.8-1.5).

3. The nickel alloy welding wire for ultra-supercritical boiler according to claim 1 or 2, characterized in that: The weight ratio of Al to Ti is 1:(1.0-1.5).

4. A method for preparing a nickel alloy welding wire for an ultra-supercritical boiler according to claim 1, characterized in that: include Follow these steps: S11: Raw materials are weighed according to the mass percentage of the formula and processed to obtain a uniform and refined mixed powder; S12: Put the mixed powder and nano-ceramic materials in S11 into the melting furnace for melting, and then refine them at high temperature and low temperature. After smelting, it is refined by remelting and cast into alloy ingots; S13: After annealing the alloy ingot, forging and rolling are performed to prepare alloy wire rods; S14: performing multiple drawing-annealing steps on the alloy wire rod after pretreatment; S15: Processing the alloy wire into the required size and performing solution-aging treatment; S16: Pickling the alloy wire; coating; and S17: Plating is performed on the surface to obtain a target product.

5. The method for preparing a nickel alloy welding wire for an ultra-supercritical boiler according to claim 4, wherein: The solution-aging treatment in S15 is a multi-step graded treatment.

6. A method for welding a nickel alloy welding wire for an ultra-supercritical boiler according to claim 1, characterized in that: include Follow these steps: S21: Preparation before welding, i.e. Prepare grooves at the interface of parent material and remove impurities; S22: welding, i.e. Welding the ultra-supercritical boiler nickel alloy welding wire to the base material by manual TIG welding or semi-automatic tungsten inert gas (TIG) welding with filler wire; S23: Post-weld treatment, i.e. After welding and when welding is interrupted, heat treatment is immediately carried out at 200-250℃ for 1-2h, and then the weld joint is heat treated at 1100-1150℃ for 0.5-1.0h, and then air-cooled to form weld deposited metal.

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