Preparation method of ERNiCrMo-4 welding wire with low inclusion and high welding performance

Abstract

The invention discloses a preparation method of a low-inclusion and high-welding-performance ERNiCrMo-4 welding wire. The preparation method comprises the steps that raw materials and a smelting additive are mixed according to the weight ratio; the raw materials and the smelting additive are subjected to vacuum induction smelting and gas shielded electroslag remelting, and an ERNiCrMo-4 cast ingot is obtained; the ERNiCrMo-4 cast ingot is forged, and an ERNiCrMo-4 bar billet is obtained; the ERNiCrMo-4 bar billet is subjected to hot continuous rolling, then annealing and acid pickling are conducted, and an ERNiCrMo-4 coiled wire is obtained; and the coiled wire is subjected to solution treatment, and the ERNiCrMo-4 welding wire is obtained. The performance of the Hastelloy C-276 welded by using the ERNiCrMo-4 welding wire is superior to the welding effect of an imported welding wire.

Description

Technical Field

[0001] This invention belongs to the field of metal material smelting and processing technology, specifically relating to a method for preparing ERNiCrMo-4 welding wire with low inclusions and high welding performance. Background Technology

[0002] Hastelloy C-27 (N10276) is a tungsten-containing nickel-chromium-molybdenum superalloy. Due to its unique composition and microstructure, it exhibits exceptional corrosion resistance in extreme environments such as high temperatures, strong acids, and strong alkalis, earning it the reputation of "super stainless steel" among corrosion-resistant materials. This alloy possesses excellent resistance to pitting corrosion and stress corrosion cracking, while maintaining good mechanical properties and weldability. Hastelloy C-276 alloy is widely used in various fields. In the chemical industry, Hastelloy C-276 is used to manufacture core equipment such as reactors, towers, heat exchangers, pumps, and valves for highly corrosive media environments, particularly in the production systems of strong acids such as sulfuric acid, hydrochloric acid, and phosphoric acid. In marine engineering, Hastelloy C-276 can be used to manufacture seawater corrosion-resistant components in desalination plants, offshore platform equipment, and ship propulsion systems, where high seawater corrosion resistance is required. In the pharmaceutical and food industries, this alloy is also used to manufacture reaction vessels and pipelines requiring high purity. In conclusion, the localization of this material is of great strategic significance for improving my country's high-end equipment manufacturing level and ensuring the security of the industrial chain.

[0003] ERNiCrMo-4 is a welding wire material specifically designed for Hastelloy C-276 alloy, with the chemical composition code NiCr15Mo16Fe6W4. It possesses excellent welding process performance, producing aesthetically pleasing welds. It also exhibits excellent mechanical properties and resistance to pitting corrosion, stress corrosion, and high-temperature oxidation. It is primarily used for welding Hastelloy C-276 plates, pipes, and parts. However, domestically produced ERNiCrMo-4 welding wire currently has a high content of inclusions and carbides, leading to hot cracking during welding and resulting in weldability that falls short of expectations. Therefore, China currently relies heavily on imports for ERNiCrMo-4 welding wire. Summary of the Invention

[0004] To address the aforementioned problems in the prior art, this invention provides a method for preparing ERNiCrMo-4 welding wire with low inclusions and high weldability. The technical problem to be solved by this invention is achieved through the following technical solution: A method for preparing a low-inclusion, high-weldability ERNiCrMo-4 welding wire, comprising: Step 1: Mix the raw materials according to the following weight ratios: metallic chromium 14.5~16.5%; pure iron 4.0~7.0%; nickel-molybdenum alloy 33.3~37.8%; nickel-tungsten alloy 7.5~10.5%; metallic manganese ≤1.0%; electrolytic nickel 28.0~39.0%; Based on the total weight of the raw materials, smelting additives are added in the following weight ratios: deoxidizer ≤0.02%; nickel-magnesium alloy 0.2~1.0%; composite rare earth ≤0.02%; pure titanium 0.1~0.25%; pure aluminum 0.05~0.2%. Step 2: Add the raw materials and smelting additives described in Step 1 into a vacuum induction furnace for vacuum induction smelting to obtain the first semi-finished product ERNiCrMo-4 ingot. Step 3: After sawing off the upper riser of the first semi-finished ERNiCrMo-4 ingot, bake it to obtain the second semi-finished ERNiCrMo-4 ingot; wherein, the baking temperature is 400~500℃ and the baking time is 6.5~7.5h; Step 4: The second semi-finished ERNiCrMo-4 ingot is subjected to gas-supported electroslag remelting, and after cooling, the riser and bottom pad are cut off to obtain the finished ERNiCrMo-4 ingot. Step 5: Load the finished ERNiCrMo-4 ingot into the furnace, heat it to 950~980℃ and hold it for 200~300min, then heat it to 1200~1250℃ and hold it for 280~340min, and finally forge it to obtain ERNiCrMo-4 billet. The final forging temperature is 900~950℃. Step 6: Heat the ERNiCrMo-4 billet to 1150~1250℃ and hold for 100~140 min, then perform hot continuous rolling to obtain ERNiCrMo-4 wire rod; Step 7: After annealing and pickling the ERNiCrMo-4 wire rod, the ERNiCrMo-4 wire rod is drawn into ERNiCrMo-4 wire. Step 8: Perform online solution treatment on the ERNiCrMo-4 wire coil. The heating temperature is 1100~1150℃, and the temperature is held for 60~80 minutes before cooling to obtain ERNiCrMo-4 welding wire.

[0005] Furthermore, the deoxidizer is calcium silicon.

[0006] Furthermore, the composite rare earth is composed of 43-47% lanthanum, 27-33% cerium, and 23-27% yttrium by weight.

[0007] Further, step 2 includes: Step 2.1: The electrolytic nickel, metallic chromium, nickel-molybdenum alloy, nickel-tungsten alloy, deoxidizer, pure titanium, and pure aluminum are loaded into a vacuum induction furnace for melting. After all the materials are melted, the first liquid metal is obtained. Step 2.2: Refine the first liquid metal to obtain the second liquid metal. The refining time is 80-90 minutes. During the refining process, the metal is stirred once every 15-25 minutes for 3-5 minutes each time. After the refining is completed, the vacuum degree in the vacuum induction furnace is ≤0.1 Pa. Step 2.3: After refining, add composite rare earth to the second liquid metal, then apply electricity to melt it and stir for 5-10 minutes. Finally, add nickel-magnesium alloy and apply electricity to melt it to obtain the third liquid metal. Step 2.4: When the temperature of the third liquid metal reaches 1430~1450℃, pouring is carried out for 5~8 minutes to obtain the first semi-finished product ERNiCrMo-4 ingot.

[0008] Furthermore, step 4 includes: Step 4.1: Select a crystallizer with a specification of Φ530 / 570×2300mm and hoist it onto the steel ring. Then, hoist the second semi-finished product ERNiCrMo-4 ingot into the crystallizer to complete the furnace loading. Step 4.2: Then immediately fill the furnace with argon gas. When the O content is 100ppm, start the arc and quickly add slag. The slag adding process must be completed within 50 minutes, and the slag formation is completed in 50~70 minutes. Step 4.3: After slag formation is completed, the second semi-finished product ERNiCrMo-4 ingot is remelted. When the ingot is reduced to 180~220kg, feeding is started. After feeding is completed, the power is cut off and the ingot is cooled in the crystallizer for 2 hours before being taken out of the furnace and air-cooled. After the riser and bottom pad are cut off, the finished ERNiCrMo-4 ingot is obtained.

[0009] Further, in step 4.2, the slag material includes: calcium fluoride, alumina, calcium oxide, and magnesium oxide; the weight ratio of the slag material is: calcium fluoride 62-67%; alumina 18%-20%; calcium oxide 14-18%; magnesium oxide 1-6%.

[0010] Further, in step 7, the annealing process is as follows: the ERNiCrMo-4 wire rod is heated to 1050~1150℃, held at that temperature for 80~90 minutes, and then rapidly cooled.

[0011] Further, in step 7, the pickling process is as follows: first, the annealed ERNiCrMo-4 wire rod is pre-pickled with hot sulfuric acid with a concentration of 5-20%, rinsed clean, and then immersed in a mixed acid of nitric acid with a concentration of 10-20% and hydrofluoric acid with a concentration of 1-5% for final pickling.

[0012] The beneficial effects of this invention are: 1. This invention significantly reduces the content of O, N, S, and P impurities in ERNiCrMo-4 welding wire by optimizing the smelting process, resulting in a high-purity ingot with a uniform microstructure. Furthermore, subsequent optimization of the annealing process reduces the precipitation of carbides in the wire coil after annealing, lowering the risk of post-weld hot cracking.

[0013] 2. The impurity element content of the ERNiCrMo-4 welding wire prepared by this invention fully meets the requirements of GB / T 15620. The mechanical properties of the ERNiCrMo-4 welding wire itself also fully meet the requirements of ASME SFA-5.14. The Hastelloy C-276 welded by the ERNiCrMo-4 welding wire produced by this process can fully meet the standards of imported welding wires, and even outperform imported welding wires. Attached Figure Description

[0014] Figures 1-2 The inclusion element content of the ERNiCrMo-4 welding wire prepared in Example 1 of this invention; Figure 3 Photograph of the ERNiCrMo-4 welding wire prepared in Example 1 of this invention; Figures 4-5 This is the mechanical property test report of the ERNiCrMo-4 welding wire obtained in Example 1 of the present invention; Figure 6 Metallographic image of inclusions in the longitudinal section of the ERNiCrMo-4 welding wire prepared in Example 1 of this invention; Figure 7 This is a scanning electron microscope image of the transverse cross-section inclusions of the ERNiCrMo-4 welding wire prepared in Example 1 of the present invention; Figure 8 A scanning electron microscope image of the weld seam of Hastelloy C-276 plate welded using the ERNiCrMo-4 welding wire of the present invention; Figure 9 Photographs of the weld-as-cast microstructure of Hastelloy C-276 plate welded using the ERNiCrMo-4 welding wire of the present invention; Figure 10Photograph of a weld seam with a grain size of grade 8 when welded to Hastelloy C-276 plate using the ERNiCrMo-4 welding wire of the present invention; Figure 11 for Figure 10 Grain orientation diagram; Figure 12 Photographs of welds made using the ERNiCrMo-4 welding wire of the present invention on Hastelloy C-276 plates; Figure 13 Photograph of the ERNiCrMo-4 welding wire prepared in Example 2; Figure 14 Photograph of the ERNiCrMo-4 welding wire prepared in Example 3. Detailed Implementation

[0015] The present invention will be further described in detail below with reference to specific embodiments, but the implementation of the present invention is not limited thereto. Example 1

[0016] This invention provides a method for preparing ERNiCrMo-4 welding wire with low inclusions and high welding performance, wherein the diameter of the prepared welding wire is 2.4 mm.

[0017] Specifically, the following steps are included: Step 1: Mix the raw materials and smelting additives according to the following weight ratio, wherein the raw materials include The raw materials used include high-purity metallic chromium, pure iron, nickel-molybdenum alloy, nickel-tungsten alloy, metallic manganese, and electrolytic manganese. The content of each impurity element in the selected raw materials is shown in Table 1. Smelting additives include deoxidizers, nickel-magnesium alloys, composite rare earth elements, pure titanium, and pure aluminum. The proportions of each component are shown in Table 2. The total weight of all components in the raw materials is 100%, and the smelting additives are proportioned based on the total weight ratio of the raw materials. Refractory metallic molybdenum and tungsten are added in the form of intermediate alloys (nickel-molybdenum alloy and nickel-tungsten alloy) to ensure complete melting of the high-melting-point molybdenum and tungsten elements, resulting in a relatively uniform composition of the ingot and preventing segregation during smelting. Adding smelting additives can remove impurity elements O, N, S, and P from the raw materials, refine the grain size, improve the forgeability of the material, reduce the tendency to crack and wrinkle during processing, and allow for greater plastic deformation.

[0018] Table 1 Content of various impurity elements in raw materials

[0019] Specifically, the raw material input is 3400 kg, and the smelting additive input is 31.62 kg.

[0020] Among them, in nickel-molybdenum alloys, the molybdenum content is 40-55%, and the remainder is nickel; in nickel-tungsten alloys, the tungsten content is 35-50%, and the remainder is nickel; in nickel-magnesium alloys, the magnesium content is 15-45%, and the remainder is nickel.

[0021] Specifically, the composite rare earth is composed of 43-47% lanthanum, 27-33% cerium, and 23-27% yttrium by weight.

[0022] The deoxidizer specifically selected is calcium silicon.

[0023] Step 2: Add the raw materials and smelting additives described in Step 1 into a vacuum induction furnace for vacuum induction smelting to obtain the first semi-finished product ERNiCrMo-4 ingot with a diameter of 440mm.

[0024] In this embodiment of the invention, a 4-ton vacuum induction furnace is used, and the casting mold has a specification of Φ440mm. The casting is completed in one batch.

[0025] Step 2 specifically includes the following steps: Step 2.1: The electrolytic nickel, metallic chromium, nickel-molybdenum alloy, nickel-tungsten alloy, deoxidizer, pure titanium, and pure aluminum are loaded into the crucible of the vacuum induction furnace. Pure titanium and pure aluminum are added last. Then, power is supplied to slowly melt the materials and remove impurity elements from the materials. After all the materials have melted, the first liquid metal is obtained.

[0026] Specifically, the electrolytic nickel is added in three stages. First, 400 kg of electrolytic nickel and deoxidizer are added to the crucible. Then, metallic chromium, nickel-molybdenum alloy, and nickel-tungsten alloy are added. Another 400 kg of electrolytic nickel is added until the crucible is full. After the materials in the crucible have melted, the remaining electrolytic nickel, pure titanium, and pure aluminum are added to the crucible through the feeding hopper. When all the materials in the crucible have melted, the first liquid metal is obtained.

[0027] In the initial stage of melting, due to the skin effect of the current, the material is melted layer by layer. This layer-by-layer melting is very beneficial for degassing and removing non-metallic inclusions. Therefore, a high vacuum and a slow melting rate must be maintained during the melting period. Under vacuum conditions, the deoxidizer, namely calcium silicate, reacts rapidly. The calcium oxide and calcium silicate formed with O are easy to float to the surface, and the N content in the liquid will also decrease rapidly.

[0028] Step 2.2: Refine the first liquid metal to obtain the second liquid metal. The refining time is 80 min. During the refining process, the metal is stirred once every 25 min for 5 min each time. After the refining is completed, the vacuum degree in the vacuum induction furnace is ≤0.1 Pa.

[0029] Step 2.3: After refining, disconnect the power and close the vacuum valve. Add composite rare earth elements to the second liquid metal, then apply power to melt it and stir for 10 minutes. Finally, add the nickel-magnesium alloy and apply power to melt it to obtain the third liquid metal. Adding the nickel-magnesium alloy after refining can refine the grains, improve grain boundary fluidity, form uniformly distributed intermetallic compounds, and reduce the segregation of harmful elements such as S and P.

[0030] Step 2.4: After the liquid surface calms down, measure the temperature. When the temperature of the third liquid metal reaches 1430℃, pour it in. The pouring time is 5 minutes and the pouring power is 500KW. The first semi-finished product ERNiCrMo-4 ingot with a diameter of Ф440mm is obtained.

[0031] Step 3: After sawing off the upper riser of the first semi-finished ERNiCrMo-4 ingot, bake it to obtain the second semi-finished ERNiCrMo-4 ingot; wherein, the baking temperature is 400℃ and the baking time is 7.5h.

[0032] After the first semi-finished ERNiCrMo-4 ingot is cooled and demolded, the riser with a relatively high impurity content at the top of the ingot is sawn off. Because the riser area is rich in impurities, porosity and shrinkage cavities, its strength is low and its brittleness is high. Under the stress of hot working (such as rolling and forging), these defects are very likely to become the starting point for crack initiation and propagation. Removing the low-quality riser part ensures that the performance of the entire batch of products is more uniform and predictable. Then, the adhering material on the surface of the ingot is polished clean and baked to obtain the second semi-finished ERNiCrMo-4 ingot, which is used as a consumable electrode for electroslag remelting.

[0033] Step 4: Perform gas-supported electroslag remelting on the second semi-finished ERNiCrMo-4 ingot, and after cooling, cut off the riser and bottom to obtain the finished ERNiCrMo-4 ingot.

[0034] Specifically, step 4 includes: Step 4.1: Select a crystallizer with a specification of Φ530 / 570×2300mm and hoist it onto the steel ring. Then, hoist the second semi-finished product ERNiCrMo-4 ingot into the crystallizer to complete the furnace loading.

[0035] Specifically, the total amount of slag used in this electroslag remelting process is 100 kg, comprising calcium fluoride, alumina, calcium oxide, and magnesium oxide. The weight ratio of the slag is: calcium fluoride 62%; alumina 19%; calcium oxide 16%; and magnesium oxide 3%. This slag composition and proportion ensures that the smelted ingots have good density and few inclusions. The slag must be baked before use. The baking process involves heating the slag to 650°C in a box-type resistance furnace and holding it at that temperature for 7 hours before removing it from the furnace for immediate use.

[0036] The arc-starting plate used in this electroslag remelting process is made of N10276 material and has a specification of Φ1000×12mm.

[0037] Before loading the consumable electrode, also known as the second semi-finished product ERNiCrMo-4 ingot, into the furnace, the welding quality and concentricity between the consumable electrode and the auxiliary electrode need to be checked. When loading the furnace, the surface of the bottom water tank and the surface of the crystallizer steel ring should be cleaned first, and then the arc-starting plate should be installed. An arc-starting agent should be placed in the center of the arc-starting plate. When the crystallizer is hoisted onto the steel ring, the misalignment between the crystallizer and the steel ring should be less than 2mm. Then the electrode is hoisted into the crystallizer, and the distance between the electrode and the crystallizer must be kept consistent.

[0038] 4.2: Then immediately fill the furnace with argon gas. When the O content is 100ppm, start the arc and quickly add slag. The slag adding process should be completed within 50 minutes, and the slag formation should be completed within 50~70 minutes.

[0039] After the electrodes are loaded into the furnace, argon gas is immediately introduced into the electroslag remelting furnace. When the instrument shows that the O content is 100 ppm, the arc is started. After the arc is started, slag is added quickly, and the current and voltage are kept stable by manual control. The slag addition process must be completed within 50 minutes, and slag formation is completed in 50 to 70 minutes.

[0040] 4.3: After slag formation is completed, the second semi-finished product ERNiCrMo-4 ingot is remelted. When the ingot is reduced to 200kg, feeding is started. After feeding is completed, the power is cut off and the ingot is cooled in the crystallizer for 2 hours before being taken out of the furnace and air-cooled. After the riser and the bottom pad are cut off, the finished ERNiCrMo-4 ingot is obtained. The upper diameter of the finished ERNiCrMo-4 ingot is 530mm and the lower diameter is 570mm.

[0041] The entire electroslag remelting process is automated, but it is necessary to pay attention to the water temperature, argon flow rate, and melting rate. During the remelting process, as the molten metal flows from the slag pool to the molten metal pool, impurity elements such as S and P in the molten metal droplets can be removed.

[0042] Electroslag remelting of ERNiCrMo-4 ingots under argon protection can remove O+N to ≤30ppm; the molten slag droplets passing through the slag pool can effectively reduce the content of S and P elements, with S+P reduced to ≤10ppm. The resulting electroslag ingot has uniform composition, fine grains, and good density.

[0043] Samples were taken from the cut-off riser and bottom of the finished ERNiCrMo-4 ingot and sent for testing. The content of impurity elements in the ingot is shown in Table 3. Figures 1-2 : Table 3. Impurity element content (%) of risers and bottom pads of finished ingots

[0044] The test data shows that the impurity element content of the ERNiCrMo-4 ingot obtained after vacuum induction melting and gas-supported electroslag remelting is significantly reduced. In the vacuum induction melting process, the impurity elements O and N are removed by high vacuum and melting additives. In the gas-supported electroslag remelting process, the protective gas argon is continuously introduced to prevent the electrode from being oxidized during the melting process. During the remelting process, the metal droplets pass through the slag pool and undergo a series of reactions to remove impurity elements such as S and P.

[0045] Step 5: Load the finished ERNiCrMo-4 ingot into the furnace. The furnace temperature should be ≤700℃ during loading. Heat the finished ERNiCrMo-4 ingot to 950℃ and hold for 300 minutes. Then heat it to 1200℃ and hold for 340 minutes. Finally, forge it to obtain ERNiCrMo-4 billet with specifications of Ф120×2000~2500mm. The final forging temperature is controlled at 920℃.

[0046] The forging process requires 4 to 5 forging cycles, with each tempering temperature at 1220℃, and the final forging temperature is controlled to reduce the occurrence of cracks in the forgings during the forging process.

[0047] Step 6: Heat the ERNiCrMo-4 billet to 1220℃ and hold for 120 minutes, then perform hot continuous rolling to obtain ERNiCrMo-4 wire rod with a specification of Ф5.5mm.

[0048] The ERNiCrMo-4 billet is cut off at the head and tail and ground to ensure that the surface of the billet is flat and free of defects such as oxide scale, cracks, and folds. Then, after the ERNiCrMo-4 billet is heated and held at a certain temperature, it is subjected to rough rolling, intermediate rolling, pre-finish rolling and finish rolling on a hot continuous rolling mill to obtain ERNiCrMo-4 wire rod with a diameter of Ф5.5mm.

[0049] Step 7: After annealing and pickling the ERNiCrMo-4 wire rod, the ERNiCrMo-4 wire rod is drawn into ERNiCrMo-4 wire with a specification of Ф2.4mm.

[0050] Specifically, the annealing process includes heating the ERNiCrMo-4 wire rod to 1100°C in an annealing furnace, holding it at that temperature for 85 minutes, and then rapidly cooling it to completely eliminate work hardening, obtain a fully softened, equiaxed fine-grained structure, and almost no carbide precipitation, thereby restoring the plasticity of the wire rod and allowing it to continue the subsequent drawing process. After annealing, pickling is usually required.

[0051] Specifically, the pickling process includes: first, using hot sulfuric acid with a concentration of 5-20% to pre-pickle and remove the thick oxide scale on the surface of the ERNiCrMo-4 wire rod; after pre-pickling, rinsing the loose oxide scale and residual acid with clean water; then immersing it in a mixture of nitric acid with a concentration of 10-20% and hydrofluoric acid with a concentration of 1-5% for final rinsing until a uniform, bright silver-white surface is obtained; and finally rinsing with water to remove residual acid to complete the entire pickling process.

[0052] The purpose of pickling is to remove oxides and impurities from the surface of ERNiCrMo-4 wire rod, thereby reducing die wear during subsequent welding wire preparation, improving material flowability, and enhancing the processing accuracy and surface finish of the final welding wire.

[0053] Finally, a multi-hole wire drawing machine is used to cold draw the acid-washed ERNiCrMo-4 wire rod to the final product specification of Ф2.4mm wire.

[0054] Step 8: Perform online solution treatment on the ERNiCrMo-4 wire coil. The heating temperature is 1120℃, and after holding at this temperature for 70 minutes, the wire is cooled to obtain ERNiCrMo-4 welding wire with a specification of Ф2.4mm. Figure 3 As shown, its surface is smooth and flat, with no obvious appearance defects.

[0055] Before online solution treatment, multiple processes including solvent cleaning, alkaline cleaning, and ultrasonic cleaning are used to remove all drawing oil and lubricant residue from the ERNiCrMo-4 wire. Electrolytic polishing is then employed to obtain an ultra-clean, ultra-smooth surface free of stress concentration and micro-defects. Polishing removes an extremely thin surface layer but significantly improves the welding performance and corrosion resistance of the resulting welding wire. The core objective of this degreasing and oil removal process is to eliminate the interference of contaminants generated during drawing on the welding process, ensuring the purity of the molten pool and thus obtaining a defect-free, high-strength weld.

[0056] 2.4mm ERNiCrMo-4 wire was subjected to online solution treatment in a multi-tube continuous heat treatment furnace, followed by air cooling and water cooling to obtain ERNiCrMo-4 welding wire. Water cooling prevents oxidation of the metal surface during the cooling process.

[0057] Solution treatment can ultimately obtain a microstructure with uniform composition and optimal corrosion resistance, ensuring that the weld metal has excellent resistance to pitting corrosion, crevice corrosion and stress corrosion cracking in various harsh corrosive environments (such as acidic media containing halide ions), greatly improving the weld metal's resistance to hot cracking, reducing the risk of post-weld cracking, and improving the welding performance of the welding wire.

[0058] The prepared ERNiCrMo-4 welding wire was sampled and tested. Its comprehensive properties, including mechanical properties, corrosion rate, inclusion evaluation, and grain size level, were evaluated. The test results are shown in Table 4. Figures 4-5 As shown: Table 4 Mechanical properties of ERNiCrMo-4 welding wire and comparison with imported welding wire

[0059] From Table 4 and Figures 4-5 It can be seen that the mechanical properties of the ERNiCrMo-4 welding wire prepared by this invention are superior to those of imported welding wires, and the performance of the ERNiCrMo-4 welding wire itself fully meets the requirements of ASME SFA-5.14.

[0060] The inclusions in the ERNiCrMo-4 welding wire prepared by this invention are shown in the following photograph. Figures 6-7 As shown, the welding wire exhibits a distinct twinned structure within its grains, resulting in excellent resistance to cold cracking and basic toughness. Furthermore, it contains relatively few inclusions, fully meeting the requirements of GB / T 15620.

[0061] After welding using the ERNiCrMo-4 welding wire of the present invention, Figure 8 It can be seen that after the weld near the inner wall is leveled, recrystallization is induced in the weld area near the inner wall, which refines the grains and improves the strength of the weld.

[0062] After solution treatment of ERNiCrMo-4 wire, the resulting welding wire was used to weld Hastelloy C-276 sheet metal. Figures 9-11 It can be seen that the weld microstructure is significantly refined, and the grain structure is more uniform; and from Figure 12 It can be seen that after welding Hastelloy C-276 plates with this welding wire, the weld seam is dense and there are no obvious defects in appearance. Example 2

[0063] This invention provides a method for preparing ERNiCrMo-4 welding wire with low inclusions and high welding performance, wherein the diameter of the prepared welding wire is 2 mm.

[0064] Specifically, the following steps are included: Step 1: Mix the raw materials and smelting additives according to the following weight ratio, wherein the raw materials include The raw materials used include high-purity metallic chromium, pure iron, nickel-molybdenum alloy, nickel-tungsten alloy, metallic manganese, and electrolytic manganese. The content of each impurity element in the selected raw materials is the same as in Table 1. Smelting additives include deoxidizers, nickel-magnesium alloys, composite rare earth elements, pure titanium, and pure aluminum. The proportions of each component are shown in Table 5. The total weight of all components in the raw materials is 100%, and the smelting additives are proportioned based on the total weight ratio of the raw materials. Refractory metallic molybdenum and tungsten are added in the form of intermediate alloys (nickel-molybdenum alloy and nickel-tungsten alloy) to ensure complete melting of the high-melting-point molybdenum and tungsten elements, resulting in a relatively uniform composition of the ingot and preventing segregation during smelting. Adding smelting additives can remove impurity elements O, N, S, and P from the raw materials, refine the grain size, improve the forgeability of the material, reduce the tendency to crack and wrinkle during processing, and allow for greater plastic deformation.

[0065] Table 5. Proportions of raw materials and smelting additives

[0066] Specifically, the amount of raw materials fed is 3450 kg, and the amount of smelting additives fed is 31.743 kg.

[0067] Among them, in nickel-molybdenum alloys, the molybdenum content is 40-55%, and the remainder is nickel; in nickel-tungsten alloys, the tungsten content is 35-50%, and the remainder is nickel; in nickel-magnesium alloys, the magnesium content is 15-45%, and the remainder is nickel.

[0068] Specifically, the composite rare earth is composed of 43-47% lanthanum, 27-33% cerium, and 23-27% yttrium by weight.

[0069] The deoxidizer specifically selected is calcium silicon.

[0070] Step 2: Add the raw materials and smelting additives described in Step 1 into a vacuum induction furnace for vacuum induction smelting to obtain the first semi-finished product ERNiCrMo-4 ingot with a diameter of 440mm.

[0071] In this embodiment of the invention, a 4-ton vacuum induction furnace is used, and the casting mold has a specification of Φ440mm. The casting is completed in one batch.

[0072] Step 2 specifically includes the following steps: Step 2.1: The electrolytic nickel, metallic chromium, nickel-molybdenum alloy, nickel-tungsten alloy, deoxidizer, pure titanium, and pure aluminum are loaded into the crucible of the vacuum induction furnace. Pure titanium and pure aluminum are added last. Then, power is supplied to slowly melt the materials and remove impurity elements from the materials. After all the materials have melted, the first liquid metal is obtained.

[0073] Specifically, the electrolytic nickel is added in three stages. First, 400 kg of electrolytic nickel and deoxidizer are added to the crucible. Then, metallic chromium, nickel-molybdenum alloy, and nickel-tungsten alloy are added. Another 400 kg of electrolytic nickel is added until the crucible is full. After the materials in the crucible have melted, the remaining electrolytic nickel, pure titanium, and pure aluminum are added to the crucible through the feeding hopper. When all the materials in the crucible have melted, the first liquid metal is obtained.

[0074] In the initial stage of melting, due to the skin effect of the current, the material is melted layer by layer. This layer-by-layer melting is very beneficial for degassing and removing non-metallic inclusions. Therefore, a high vacuum and a slow melting rate must be maintained during the melting period. Under vacuum conditions, the deoxidizer, namely calcium silicate, reacts rapidly. The calcium oxide and calcium silicate formed with O are easy to float to the surface, and the N content in the liquid will also decrease rapidly.

[0075] Step 2.2: Refine the first liquid metal to obtain the second liquid metal. The refining time is 85 min. During the refining process, the metal is stirred once every 20 min for 4 min each time. After the refining is completed, the vacuum degree in the vacuum induction furnace is ≤0.1 Pa.

[0076] Step 2.3: After refining, disconnect the power and close the vacuum valve. Add composite rare earth elements to the second liquid metal, then apply power to melt it and stir for 7 minutes. Finally, add the nickel-magnesium alloy and apply power to melt it to obtain the third liquid metal. Adding the nickel-magnesium alloy after refining can refine the grains, improve grain boundary fluidity, form uniformly distributed intermetallic compounds, and reduce the segregation of harmful elements such as S and P.

[0077] Step 2.4: After the liquid surface calms down, measure the temperature. When the temperature of the third liquid metal reaches 1440℃, pour it in. The pouring time is 7 minutes and the pouring power is 500KW. The first semi-finished product ERNiCrMo-4 ingot with a diameter of Ф440mm is obtained.

[0078] Step 3: After sawing off the upper riser of the first semi-finished ERNiCrMo-4 ingot, bake it to obtain the second semi-finished ERNiCrMo-4 ingot; wherein, the baking temperature is 450℃ and the baking time is 7h.

[0079] After the first semi-finished ERNiCrMo-4 ingot is cooled and demolded, the riser with a relatively high impurity content at the top of the ingot is sawn off. Because the riser area is rich in impurities, porosity and shrinkage cavities, its strength is low and its brittleness is high. Under the stress of hot working (such as rolling and forging), these defects are very likely to become the starting point for crack initiation and propagation. Removing the low-quality riser part ensures that the performance of the entire batch of products is more uniform and predictable. Then, the adhering material on the surface of the ingot is polished clean and baked to obtain the second semi-finished ERNiCrMo-4 ingot, which is used as a consumable electrode for electroslag remelting.

[0080] Step 4: Perform gas-supported electroslag remelting on the second semi-finished ERNiCrMo-4 ingot, and after cooling, cut off the riser and bottom to obtain the finished ERNiCrMo-4 ingot.

[0081] Specifically, step 4 includes: Step 4.1: Select a crystallizer with a specification of Φ530 / 570×2300mm and hoist it onto the steel ring. Then, hoist the second semi-finished product ERNiCrMo-4 ingot into the crystallizer to complete the furnace loading.

[0082] Specifically, the total amount of slag used in this electroslag remelting process is 100 kg, and the slag includes: calcium fluoride, alumina, calcium oxide, and magnesium oxide; the weight ratio of the slag is: calcium fluoride 64%; alumina 18%; calcium oxide 15%; and magnesium oxide 3%. This slag composition and proportion ensures that the smelted ingots have good density and few inclusions. The slag must be baked before use. The baking process involves heating the slag to 700℃ in a box-type resistance furnace and holding it at that temperature for 6 hours before removing it from the furnace for immediate use.

[0083] The arc-starting plate used in this electroslag remelting process is made of N10276 material and has a specification of Φ1000×12mm.

[0084] Before loading the consumable electrode, also known as the second semi-finished product ERNiCrMo-4 ingot, into the furnace, the welding quality and concentricity between the consumable electrode and the auxiliary electrode need to be checked. When loading the furnace, the surface of the bottom water tank and the surface of the crystallizer steel ring should be cleaned first, and then the arc-starting plate should be installed. An arc-starting agent should be placed in the center of the arc-starting plate. When the crystallizer is hoisted onto the steel ring, the misalignment between the crystallizer and the steel ring should be less than 2mm. Then the electrode is hoisted into the crystallizer, and the distance between the electrode and the crystallizer must be kept consistent.

[0085] 4.2: Then immediately fill the furnace with argon gas. When the O content is 100ppm, start the arc and quickly add slag. The slag adding process should be completed within 50 minutes, and the slag formation should be completed within 50~70 minutes.

[0086] After the electrodes are loaded into the furnace, argon gas is immediately introduced into the electroslag remelting furnace. When the instrument shows that the O content is 100 ppm, the arc is started. After the arc is started, slag is added quickly, and the current and voltage are kept stable by manual control. The slag addition process must be completed within 50 minutes, and slag formation is completed in 50 to 70 minutes.

[0087] 4.3: After slag formation is completed, the second semi-finished product ERNiCrMo-4 ingot is remelted. When the ingot is reduced to 220kg, feeding is started. After feeding is completed, the power is cut off and the ingot is cooled in the crystallizer for 2 hours before being taken out of the furnace and air-cooled. After the riser and the bottom pad are cut off, the finished ERNiCrMo-4 ingot is obtained. The upper diameter of the finished ERNiCrMo-4 ingot is 530mm and the lower diameter is 570mm.

[0088] The entire electroslag remelting process is automated, but it is necessary to pay attention to the water temperature, argon flow rate, and melting rate. During the remelting process, as the molten metal flows from the slag pool to the molten metal pool, impurity elements such as S and P in the molten metal droplets can be removed.

[0089] Electroslag remelting of ERNiCrMo-4 ingots under argon protection can remove O+N to ≤30ppm; the molten slag droplets passing through the slag pool can effectively reduce the content of S and P elements, with S+P reduced to ≤10ppm. The resulting electroslag ingot has uniform composition, fine grains, and good density.

[0090] Samples were taken from the cut-off riser and bottom of the finished ERNiCrMo-4 ingot and sent for testing. The content of impurity elements in the ingot is shown in Table 6. Table 6. Impurity element content (%) of risers and bottom pads of finished ingots

[0091] The test data shows that the impurity element content of the ERNiCrMo-4 ingot obtained after vacuum induction melting and gas-supported electroslag remelting is significantly reduced. In the vacuum induction melting process, the impurity elements O and N are removed by high vacuum and melting additives. In the gas-supported electroslag remelting process, the protective gas argon is continuously introduced to prevent the electrode from being oxidized during the melting process. During the remelting process, the metal droplets pass through the slag pool and undergo a series of reactions to remove impurity elements such as S and P.

[0092] Step 5: Load the finished ERNiCrMo-4 ingot into the furnace. The furnace temperature should be ≤700℃ during loading. Heat the finished ERNiCrMo-4 ingot to 970℃ and hold for 260 minutes. Then heat it to 1230℃ and hold for 310 minutes. Finally, forge it to obtain ERNiCrMo-4 billet with specifications of Ф120×2000~2500mm. The final forging temperature is controlled at 930℃.

[0093] The forging process requires 4 to 5 forging cycles, with each tempering temperature at 1230℃, and the final forging temperature is controlled to reduce the occurrence of cracks in the forgings during the forging process.

[0094] Step 6: Heat the ERNiCrMo-4 billet to 1160℃ and hold for 140 minutes, then perform hot continuous rolling to obtain ERNiCrMo-4 wire rod with a specification of Ф5.5mm.

[0095] The ERNiCrMo-4 billet is cut off at the head and tail and ground to ensure that the surface of the billet is flat and free of defects such as oxide scale, cracks, and folds. Then, after the ERNiCrMo-4 billet is heated and held at a certain temperature, it is subjected to rough rolling, intermediate rolling, pre-finish rolling and finish rolling on a hot continuous rolling mill to obtain ERNiCrMo-4 wire rod with a diameter of Ф5.5mm.

[0096] Step 7: After annealing and pickling the ERNiCrMo-4 wire rod, the ERNiCrMo-4 wire rod is drawn into ERNiCrMo-4 wire with a specification of Ф2.0mm.

[0097] Specifically, the annealing process includes heating the ERNiCrMo-4 wire rod to 1050°C in an annealing furnace, holding it at that temperature for 90 minutes, and then rapidly cooling it to completely eliminate work hardening, obtain a fully softened, equiaxed fine-grained structure, and almost no carbide precipitation, thereby restoring the plasticity of the wire rod and allowing it to continue the subsequent drawing process. After annealing, pickling is usually required.

[0098] Specifically, the pickling process includes: first, using hot sulfuric acid with a concentration of 5-20% to pre-pickle and remove the thick oxide scale on the surface of the ERNiCrMo-4 wire rod; after pre-pickling, rinsing the loose oxide scale and residual acid with clean water; then immersing it in a mixture of nitric acid with a concentration of 10-20% and hydrofluoric acid with a concentration of 1-5% for final rinsing until a uniform, bright silver-white surface is obtained; and finally rinsing with water to remove residual acid to complete the entire pickling process.

[0099] The purpose of pickling is to remove oxides and impurities from the surface of ERNiCrMo-4 wire rod, thereby reducing die wear during subsequent welding wire preparation, improving material flowability, and enhancing the processing accuracy and surface finish of the final welding wire.

[0100] Finally, a multi-hole wire drawing machine is used to cold draw the acid-washed ERNiCrMo-4 wire rod to the final product specification of Ф2.0mm wire.

[0101] Step 8: Perform online solution treatment on the ERNiCrMo-4 wire coil. The heating temperature is 1100℃, and after holding at that temperature for 80 minutes, it is cooled to obtain ERNiCrMo-4 welding wire with a specification of Ф2.0mm. Figure 3 As shown.

[0102] Before online solution treatment, multiple processes including solvent cleaning, alkaline cleaning, and ultrasonic cleaning are used to remove all drawing oil and lubricant residue from the ERNiCrMo-4 wire. Electrolytic polishing is then employed to obtain an ultra-clean, ultra-smooth surface free of stress concentration and micro-defects. Polishing removes an extremely thin surface layer but significantly improves the welding performance and corrosion resistance of the resulting welding wire. The core objective of this degreasing and oil removal process is to eliminate the interference of contaminants generated during drawing on the welding process, ensuring the purity of the molten pool and thus obtaining a defect-free, high-strength weld.

[0103] 2.0mm ERNiCrMo-4 wire was subjected to online solution treatment in a multi-tube continuous heat treatment furnace, followed by air cooling and water cooling to obtain ERNiCrMo-4 welding wire. Water cooling prevents oxidation of the metal surface during the cooling process.

[0104] Solution treatment can ultimately obtain a microstructure with uniform composition and optimal corrosion resistance, ensuring that the weld metal has excellent resistance to pitting corrosion, crevice corrosion and stress corrosion cracking in various harsh corrosive environments (such as acidic media containing halide ions), greatly improving the weld metal's resistance to hot cracking, reducing the risk of post-weld cracking, and improving the welding performance of the welding wire.

[0105] The prepared ERNiCrMo-4 welding wire is as follows Figure 13 As shown, its surface is smooth and flat, with no obvious appearance defects. Example 3

[0106] This invention provides a method for preparing ERNiCrMo-4 welding wire with low inclusions and high welding performance, wherein the diameter of the prepared welding wire is 1.2 mm.

[0107] Specifically, the following steps are included: Step 1: Mix the raw materials and smelting additives according to the following weight ratio, wherein the raw materials include The raw materials used include high-purity metallic chromium, pure iron, nickel-molybdenum alloy, nickel-tungsten alloy, metallic manganese, and electrolytic manganese. The content of each impurity element in the selected raw materials is the same as in Table 1. Smelting additives include deoxidizers, nickel-magnesium alloys, composite rare earth elements, pure titanium, and pure aluminum. The proportions of each component are shown in Table 5. The total weight of all components in the raw materials is 100%, and the smelting additives are proportioned based on the total weight ratio of the raw materials. Refractory metallic molybdenum and tungsten are added in the form of intermediate alloys (nickel-molybdenum alloy and nickel-tungsten alloy) to ensure complete melting of the high-melting-point molybdenum and tungsten elements, resulting in a relatively uniform composition of the ingot and preventing segregation during smelting. Adding smelting additives can remove impurity elements O, N, S, and P from the raw materials, refine the grain size, improve the forgeability of the material, reduce the tendency to crack and wrinkle during processing, and allow for greater plastic deformation.

[0108] Table 7. Proportions of Raw Materials and Smelting Additives

[0109] Specifically, the raw material input is 3350 kg, and the smelting additive input is 31.155 kg.

[0110] Among them, in nickel-molybdenum alloys, the molybdenum content is 40-55%, and the remainder is nickel; in nickel-tungsten alloys, the tungsten content is 35-50%, and the remainder is nickel; in nickel-magnesium alloys, the magnesium content is 15-45%, and the remainder is nickel.

[0111] Specifically, the composite rare earth is composed of 43-47% lanthanum, 27-33% cerium, and 23-27% yttrium by weight.

[0112] The deoxidizer specifically selected is calcium silicon.

[0113] Step 2: Add the raw materials and smelting additives described in Step 1 into a vacuum induction furnace for vacuum induction smelting to obtain the first semi-finished product ERNiCrMo-4 ingot with a diameter of 440mm.

[0114] In this embodiment of the invention, a 4-ton vacuum induction furnace is used, and the casting mold has a specification of Φ440mm. The casting is completed in one batch.

[0115] Step 2 specifically includes the following steps: Step 2.1: The electrolytic nickel, metallic chromium, nickel-molybdenum alloy, nickel-tungsten alloy, deoxidizer, pure titanium, and pure aluminum are loaded into the crucible of the vacuum induction furnace. Pure titanium and pure aluminum are added last. Then, power is supplied to slowly melt the materials and remove impurity elements from the materials. After all the materials have melted, the first liquid metal is obtained.

[0116] Specifically, the electrolytic nickel is added in three stages. First, 400 kg of electrolytic nickel and deoxidizer are added to the crucible. Then, metallic chromium, nickel-molybdenum alloy, and nickel-tungsten alloy are added. Another 400 kg of electrolytic nickel is added until the crucible is full. After the materials in the crucible have melted, the remaining electrolytic nickel, pure titanium, and pure aluminum are added to the crucible through the feeding hopper. When all the materials in the crucible have melted, the first liquid metal is obtained.

[0117] In the initial stage of melting, due to the skin effect of the current, the material is melted layer by layer. This layer-by-layer melting is very beneficial for degassing and removing non-metallic inclusions. Therefore, a high vacuum and a slow melting rate must be maintained during the melting period. Under vacuum conditions, the deoxidizer, namely calcium silicate, reacts rapidly. The calcium oxide and calcium silicate formed with O are easy to float to the surface, and the N content in the liquid will also decrease rapidly.

[0118] Step 2.2: Refine the first liquid metal to obtain the second liquid metal. The refining time is 90 min. During the refining process, the metal is stirred once every 15 min for 3 min each time. After the refining is completed, the vacuum degree in the vacuum induction furnace is ≤0.1 Pa.

[0119] Step 2.3: After refining, disconnect the power and close the vacuum valve. Add composite rare earth elements to the second liquid metal, then apply power to melt it and stir for 5 minutes. Finally, add the nickel-magnesium alloy and apply power to melt it to obtain the third liquid metal. Adding the nickel-magnesium alloy after refining can refine the grains, improve grain boundary fluidity, form uniformly distributed intermetallic compounds, and reduce the segregation of harmful elements such as S and P.

[0120] Step 2.4: After the liquid surface calms down, measure the temperature. When the temperature of the third liquid metal reaches 1450℃, pour it in. The pouring time is 8 minutes and the pouring power is 500KW. The first semi-finished product ERNiCrMo-4 ingot with a diameter of Ф440mm is obtained.

[0121] Step 3: After sawing off the upper riser of the first semi-finished ERNiCrMo-4 ingot, bake it to obtain the second semi-finished ERNiCrMo-4 ingot; wherein, the baking temperature is 500℃ and the baking time is 6.5h.

[0122] After the first semi-finished ERNiCrMo-4 ingot is cooled and demolded, the riser with a relatively high impurity content at the top of the ingot is sawn off. Because the riser area is rich in impurities, porosity and shrinkage cavities, its strength is low and its brittleness is high. Under the stress of hot working (such as rolling and forging), these defects are very likely to become the starting point for crack initiation and propagation. Removing the low-quality riser part ensures that the performance of the entire batch of products is more uniform and predictable. Then, the adhering material on the surface of the ingot is polished clean and baked to obtain the second semi-finished ERNiCrMo-4 ingot, which is used as a consumable electrode for electroslag remelting.

[0123] Step 4: Perform gas-supported electroslag remelting on the second semi-finished ERNiCrMo-4 ingot, and after cooling, cut off the riser and bottom to obtain the finished ERNiCrMo-4 ingot.

[0124] Specifically, step 4 includes: Step 4.1: Select a crystallizer with a specification of Φ530 / 570×2300mm and hoist it onto the steel ring. Then, hoist the second semi-finished product ERNiCrMo-4 ingot into the crystallizer to complete the furnace loading.

[0125] Specifically, the total amount of slag used in this electroslag remelting process is 100 kg, comprising calcium fluoride, alumina, calcium oxide, and magnesium oxide. The weight ratio of the slag is: calcium fluoride 62%; alumina 20%; calcium oxide 14%; and magnesium oxide 4%. This slag composition and proportion ensure that the smelted ingots have good density and few inclusions. The slag must be baked before use. The baking process involves heating the slag to 670°C in a box-type resistance furnace and holding it at that temperature for 6.5 hours before removing it from the furnace for immediate use.

[0126] The arc-starting plate used in this electroslag remelting process is made of N10276 material and has a specification of Φ1000×12mm.

[0127] Before loading the consumable electrode, also known as the second semi-finished product ERNiCrMo-4 ingot, into the furnace, the welding quality and concentricity between the consumable electrode and the auxiliary electrode need to be checked. When loading the furnace, the surface of the bottom water tank and the surface of the crystallizer steel ring should be cleaned first, and then the arc-starting plate should be installed. An arc-starting agent should be placed in the center of the arc-starting plate. When the crystallizer is hoisted onto the steel ring, the misalignment between the crystallizer and the steel ring should be less than 2mm. Then the electrode is hoisted into the crystallizer, and the distance between the electrode and the crystallizer must be kept consistent.

[0128] 4.2: Then immediately fill the furnace with argon gas. When the O content is 100ppm, start the arc and quickly add slag. The slag adding process should be completed within 50 minutes, and the slag formation should be completed within 50~70 minutes.

[0129] After the electrodes are loaded into the furnace, argon gas is immediately introduced into the electroslag remelting furnace. When the instrument shows that the O content is 100 ppm, the arc is started. After the arc is started, slag is added quickly, and the current and voltage are kept stable by manual control. The slag addition process must be completed within 50 minutes, and slag formation is completed in 50 to 70 minutes.

[0130] 4.3: After slag formation is completed, the second semi-finished product ERNiCrMo-4 ingot is remelted. When the ingot is reduced to 180kg, feeding is started. After feeding is completed, the power is cut off and the ingot is cooled in the crystallizer for 2 hours before being taken out of the furnace and air-cooled. After the riser and the bottom pad are cut off, the finished ERNiCrMo-4 ingot is obtained. The upper diameter of the finished ERNiCrMo-4 ingot is 530mm and the lower diameter is 570mm.

[0131] The entire electroslag remelting process is automated, but it is necessary to pay attention to the water temperature, argon flow rate, and melting rate. During the remelting process, as the molten metal flows from the slag pool to the molten metal pool, impurity elements such as S and P in the molten metal droplets can be removed.

[0132] Electroslag remelting of ERNiCrMo-4 ingots under argon protection can remove O+N to ≤30ppm; the molten slag droplets passing through the slag pool can effectively reduce the content of S and P elements, with S+P reduced to ≤10ppm. The resulting electroslag ingot has uniform composition, fine grains, and good density.

[0133] Samples were taken from the cut-off riser and bottom of the finished ERNiCrMo-4 ingot and sent for testing. The content of impurity elements in the ingot is shown in Table 8. Table 8. Impurity element content (%) of risers and bottom pads of finished ingots

[0134] The test data shows that the impurity element content of the ERNiCrMo-4 ingot obtained after vacuum induction melting and gas-supported electroslag remelting is significantly reduced. In the vacuum induction melting process, the impurity elements O and N are removed by high vacuum and melting additives. In the gas-supported electroslag remelting process, the protective gas argon is continuously introduced to prevent the electrode from being oxidized during the melting process. During the remelting process, the metal droplets pass through the slag pool and undergo a series of reactions to remove impurity elements such as S and P.

[0135] Step 5: Load the finished ERNiCrMo-4 ingot into the furnace. The furnace temperature should be ≤700℃ during loading. Heat the finished ERNiCrMo-4 ingot to 980℃ and hold for 200 minutes. Then heat it to 1250℃ and hold for 280 minutes. Finally, forge it to obtain ERNiCrMo-4 billet with specifications of Ф120×2000~2500mm. The final forging temperature is controlled at 950℃.

[0136] The forging process requires 4 to 5 forging cycles, with each tempering temperature at 1240℃, and the final forging temperature is controlled to reduce the occurrence of cracks in the forgings during the forging process.

[0137] Step 6: Heat the ERNiCrMo-4 billet to 1250℃ and hold for 100 minutes, then perform hot continuous rolling to obtain ERNiCrMo-4 wire rod with a specification of Ф5.5mm.

[0138] The ERNiCrMo-4 billet is cut off at the head and tail and ground to ensure that the surface of the billet is flat and free of defects such as oxide scale, cracks, and folds. Then, after the ERNiCrMo-4 billet is heated and held at a certain temperature, it is subjected to rough rolling, intermediate rolling, pre-finish rolling and finish rolling on a hot continuous rolling mill to obtain ERNiCrMo-4 wire rod with a diameter of Ф5.5mm.

[0139] Step 7: After annealing and pickling the ERNiCrMo-4 wire rod, the ERNiCrMo-4 wire rod is drawn into ERNiCrMo-4 wire with a specification of Ф1.2mm.

[0140] Specifically, the annealing process includes heating the ERNiCrMo-4 wire rod to 1150°C in an annealing furnace, holding it at that temperature for 80 minutes, and then rapidly cooling it to completely eliminate work hardening, obtain a fully softened, equiaxed fine-grained structure, and almost no carbide precipitation, thereby restoring the plasticity of the wire rod and allowing it to continue the subsequent drawing process. After annealing, pickling is usually required.

[0141] Specifically, the pickling process includes: first, using hot sulfuric acid with a concentration of 5-20% to pre-pickle and remove the thick oxide scale on the surface of the ERNiCrMo-4 wire rod; after pre-pickling, rinsing the loose oxide scale and residual acid with clean water; then immersing it in a mixture of nitric acid with a concentration of 10-20% and hydrofluoric acid with a concentration of 1-5% for final rinsing until a uniform, bright silver-white surface is obtained; and finally rinsing with water to remove residual acid to complete the entire pickling process.

[0142] The purpose of pickling is to remove oxides and impurities from the surface of ERNiCrMo-4 wire rod, thereby reducing die wear during subsequent welding wire preparation, improving material flowability, and enhancing the processing accuracy and surface finish of the final welding wire.

[0143] Finally, a multi-hole wire drawing machine is used to cold draw the acid-washed ERNiCrMo-4 wire rod to the final product specification of Ф1.2mm wire.

[0144] Step 8: Perform online solution treatment on the ERNiCrMo-4 wire coil. The heating temperature is 1150℃, and after holding at that temperature for 60 minutes, it is cooled to obtain ERNiCrMo-4 welding wire with a specification of Ф1.2mm. Figure 3 As shown.

[0145] Before online solution treatment, multiple processes including solvent cleaning, alkaline cleaning, and ultrasonic cleaning are used to remove all drawing oil and lubricant residue from the ERNiCrMo-4 wire. Electrolytic polishing is then employed to obtain an ultra-clean, ultra-smooth surface free of stress concentration and micro-defects. Polishing removes an extremely thin surface layer but significantly improves the welding performance and corrosion resistance of the resulting welding wire. The core objective of this degreasing and oil removal process is to eliminate the interference of contaminants generated during drawing on the welding process, ensuring the purity of the molten pool and thus obtaining a defect-free, high-strength weld.

[0146] 1.2mm ERNiCrMo-4 wire was subjected to online solution treatment in a multi-tube continuous heat treatment furnace, followed by air cooling and water cooling to obtain ERNiCrMo-4 welding wire. Water cooling can prevent the metal surface from being oxidized during the cooling process of the welding wire.

[0147] Solution treatment can ultimately obtain a microstructure with uniform composition and optimal corrosion resistance, ensuring that the weld metal has excellent resistance to pitting corrosion, crevice corrosion and stress corrosion cracking in various harsh corrosive environments (such as acidic media containing halide ions), greatly improving the weld metal's resistance to hot cracking, reducing the risk of post-weld cracking, and improving the welding performance of the welding wire.

[0148] The prepared ERNiCrMo-4 welding wire is as follows Figure 14 As shown, its surface is smooth and flat, with no obvious appearance defects.

[0149] In the description of this invention, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined with "first" and "second" may explicitly or implicitly include one or more of that feature.

[0150] The above description, in conjunction with specific preferred embodiments, provides a further detailed explanation of the present invention. It should not be construed that the specific implementation of the present invention is limited to these descriptions. For those skilled in the art, various simple deductions or substitutions can be made without departing from the concept of the present invention, and all such modifications and substitutions should be considered within the scope of protection of the present invention.

Claims

1. A method for preparing a low-inclusion, high-weldability ERNiCrMo-4 welding wire, characterized in that, include: Step 1: Mix the raw materials according to the following weight ratio: metallic chromium 14.5~16.5%; pure iron 4.0~7.0%; Nickel-molybdenum alloy: 33.3%~37.8%; Nickel-tungsten alloy: 7.5%~10.5%; Metallic manganese: ≤1.0%; Electrolytic nickel: 28.0%~39.0%; Based on the total weight of the raw materials, smelting additives are added in the following weight ratios: deoxidizer ≤0.02%; nickel-magnesium alloy 0.2~1.0%; composite rare earth ≤0.02%; pure titanium 0.1~0.25%; pure aluminum 0.05~0.2%. Step 2: Add the raw materials and smelting additives described in Step 1 into a vacuum induction furnace for vacuum induction smelting to obtain the first semi-finished product ERNiCrMo-4 ingot. Step 3: After sawing off the upper riser of the first semi-finished ERNiCrMo-4 ingot, bake it to obtain the second semi-finished ERNiCrMo-4 ingot; wherein, the baking temperature is 400~500℃ and the baking time is 6.5~7.5h; Step 4: The second semi-finished ERNiCrMo-4 ingot is subjected to gas-supported electroslag remelting, and after cooling, the riser and bottom pad are cut off to obtain the finished ERNiCrMo-4 ingot. Step 5: Load the finished ERNiCrMo-4 ingot into the furnace, heat it to 950~980℃ and hold it for 200~300min, then heat it to 1200~1250℃ and hold it for 280~340min, and finally forge it to obtain ERNiCrMo-4 billet. The final forging temperature is 900~950℃. Step 6: Heat the ERNiCrMo-4 billet to 1150~1250℃ and hold for 100~140 min, then perform hot continuous rolling to obtain ERNiCrMo-4 wire rod; Step 7: After annealing and pickling the ERNiCrMo-4 wire rod, the ERNiCrMo-4 wire rod is drawn into ERNiCrMo-4 wire. Step 8: Perform online solution treatment on the ERNiCrMo-4 wire coil. The heating temperature is 1100~1150℃, and the temperature is held for 60~80 minutes before cooling to obtain ERNiCrMo-4 welding wire.

2. The method for preparing the low-inclusion, high-weldability ERNiCrMo-4 welding wire according to claim 1, characterized in that, The deoxidizer is calcium silicon.

3. The method for preparing the low-inclusion, high-weldability ERNiCrMo-4 welding wire according to claim 1, characterized in that, The composite rare earth is composed of 43-47% lanthanum, 27-33% cerium, and 23-27% yttrium by weight.

4. The method for preparing the low-inclusion, high-weldability ERNiCrMo-4 welding wire according to claim 1, characterized in that, Step 2 includes: Step 2.1: The electrolytic nickel, metallic chromium, nickel-molybdenum alloy, nickel-tungsten alloy, deoxidizer, pure titanium, and pure aluminum are loaded into a vacuum induction furnace for melting. After all the materials are melted, the first liquid metal is obtained. Step 2.2: Refine the first liquid metal to obtain the second liquid metal. The refining time is 80-90 minutes. During the refining process, the metal is stirred once every 15-25 minutes for 3-5 minutes each time. After the refining is completed, the vacuum degree in the vacuum induction furnace is ≤0.1 Pa. Step 2.3: After refining, add composite rare earth to the second liquid metal, then apply electricity to melt it and stir for 5-10 minutes. Finally, add nickel-magnesium alloy and apply electricity to melt it to obtain the third liquid metal. Step 2.4: When the temperature of the third liquid metal reaches 1430~1450℃, pouring is carried out for 5~8 minutes to obtain the first semi-finished product ERNiCrMo-4 ingot.

5. The method for preparing the low-inclusion, high-weldability ERNiCrMo-4 welding wire according to claim 1, characterized in that, Step 4 includes: Step 4.1: Select a crystallizer with a specification of Φ530 / 570×2300mm and hoist it onto the steel ring. Then, hoist the second semi-finished product ERNiCrMo-4 ingot into the crystallizer to complete the furnace loading. Step 4.2: Then immediately fill the furnace with argon gas. When the O content is 100ppm, start the arc and quickly add slag. The slag adding process must be completed within 50 minutes, and the slag formation is completed in 50~70 minutes. Step 4.3: After slag formation is completed, the second semi-finished product ERNiCrMo-4 ingot is remelted. When the ingot is reduced to 180~220kg, feeding is started. After feeding is completed, the power is cut off and the ingot is cooled in the crystallizer for 2 hours before being taken out of the furnace and air-cooled. After the riser and bottom pad are cut off, the finished ERNiCrMo-4 ingot is obtained.

6. The method for preparing the low-inclusion, high-weldability ERNiCrMo-4 welding wire according to claim 5, characterized in that, In step 4.2, the slag material includes: calcium fluoride, alumina, calcium oxide and magnesium oxide; the weight ratio of the slag material is: calcium fluoride 62~67%; alumina 18%~20%; calcium oxide 14~18%; magnesium oxide 1~6%.

7. The method for preparing the low-inclusion, high-weldability ERNiCrMo-4 welding wire according to claim 1, characterized in that, In step 7, the annealing process is as follows: the ERNiCrMo-4 wire rod is heated to 1050~1150℃, held at that temperature for 80~90 minutes, and then rapidly cooled.

8. The method for preparing the low-inclusion, high-weldability ERNiCrMo-4 welding wire according to claim 7, characterized in that, In step 7, the pickling process is as follows: First, the annealed ERNiCrMo-4 wire rod is pre-pickled with hot sulfuric acid with a concentration of 5-20%. After rinsing it clean, it is then immersed in a mixed acid of nitric acid with a concentration of 10-20% and hydrofluoric acid with a concentration of 1-5% for final pickling.

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