Sintered flux for improving strip electrode submerged arc surfacing crack resistance of Inconel 690 alloy and preparation method and application of sintered flux

Abstract

The invention discloses a sintered flux for improving strip electrode submerged arc surfacing crack resistance of an Inconel 690 alloy and a preparation method of the sintered flux, and belongs to the technical field of flux preparation. The problem that the Inconel 690 alloy strip electrode submerged arc surfacing layer is high in hot crack sensitivity is solved. The flux comprises the following components: 5%-20% of CaF2, 20%-50% of Al2O3, 1%-10% of CaO, 3%-9% of manganese metal, 2%-5% of niobium metal, 2%-10% of micron-sized chromium oxide, 0.5%-2% of ferrosilicon alloy, and 5%-15% of K2O and Na2O. The melting point of the flux is 1100-1300 DEG C, the strip electrode submerged arc surfacing welding manufacturability is improved, the slag fluidity and the slag detachability are improved, the mechanical property of obtained deposited metal at the room temperature and the high temperature is excellent, and the requirement for the performance of an Inconel 690 alloy corrosion-resistant layer of nuclear power facility construction is met.

Description

Technical Field

[0001] This invention belongs to the field of flux preparation technology, specifically relating to a sintered flux that improves the crack resistance of Inconel 690 alloy strip submerged arc welding, its preparation method, and its application. Background Technology

[0002] As a crucial component of clean energy, the nuclear power industry, with its efficient and stable power generation and abundant resources, has become an important part of the energy structure. The safety and reliability of nuclear power plants are of paramount importance, which depends on the performance of key materials used in the main equipment of the nuclear island. Inconel 690 alloy possesses excellent resistance to corrosion from various aqueous media and high-temperature atmospheres, making it a key material for constructing the primary loop steam generator of the main equipment in the nuclear island.

[0003] Based on the widespread application of Inconel 690 alloy in nuclear power equipment, Inconel 690 alloy welding materials are widely used in the welding of in-core components and the welding of corrosion-resistant layers on tube sheets. Among them, submerged arc welding with strip electrode is the main welding method for corrosion-resistant layer welding. This welding method has the advantages of large welding area and high efficiency, but the welding process has a large heat input, which amplifies the disadvantage of high hot cracking sensitivity of Inconel 690 alloy welding.

[0004] The nuclear power industry is a crucial component of the new energy system. With energy structure reforms, the demand for Inconel 690 series welding consumables is increasing. While the demand for Inconel 690 series welding consumables, primarily those using welding strip flux, is growing, the high susceptibility to hot cracking in Inconel 690 alloy welding remains unresolved. Therefore, there is an urgent need to develop welding consumables suitable for Inconel 690 alloy and to address the hot cracking susceptibility issue in Inconel 690 alloy strip submerged arc welding. Summary of the Invention

[0005] To overcome the problem of high hot cracking sensitivity of current Inconel 690 alloy strip electrode submerged arc weld overlay, this invention provides a sintered flux, its preparation method, and its application to improve the crack resistance of Inconel 690 alloy strip electrode submerged arc weld overlay. It is mainly used for corrosion-resistant layer overlay welding of steam generator tube sheets.

[0006] The technical solution of the present invention is as follows: One of the objectives of this invention is to provide a sintered flux that improves the crack resistance of Inconel 690 alloy strip submerged arc welding. The chemical composition of the flux, by weight percentage, includes: CaF2: 5~20%, Al2O3: 20~50%, CaO: 1~10%, metallic manganese: 3~9%, metallic niobium: 2~5%, micron-sized chromium oxide 2~10%, ferrosilicon alloy 0.5~2%, K2O and Na2O (K2O+Na2O): 5~15%.

[0007] Further specifying, the mass ratio of K2O to Na2O is 3:1.

[0008] The second objective of this invention is to provide a method for preparing a sintered flux that improves the crack resistance of Inconel 690 alloy strip submerged arc welding, the method comprising: (1) The chromium green raw material was successively calcined at high temperature, ball-milled and screened twice to obtain micron-sized chromium oxide; (2) Weigh out each component powder except K2O and Na2O according to the sintering flux ratio, put each component powder into the mixing container in sequence, mix each component powder evenly before adding another component powder, and ensure that each component powder is mixed evenly. After all the component powders have been added, stir and dry mix. (3) After dry mixing, potassium sodium water glass binder is added for wet mixing. The wet mixed material is then granulated, dried at low temperature, screened at low temperature, sintered at high temperature, screened at high temperature and cooled, and then packaged to obtain sintered flux.

[0009] Further restrictions are imposed: (1) the calcination temperature is 950℃ and the secondary sieving mesh size is 200 mesh; the ball milling and secondary sieving processes are both completed at dry room temperature.

[0010] Further specify that, in (2), the micron-sized chromium oxide is added in three equal portions according to the flux formula during the addition and mixing of each component powder, and dry stirring is carried out at the same time to ensure that the micron-sized chromium oxide is mixed evenly with other component powders.

[0011] Furthermore, the dry mixing time is specified as 5 minutes, and the speed is specified as 150 rpm.

[0012] Further specified, (2) the dry stirring time is 5 min and the speed is 150 rpm.

[0013] Further specified, the amount of potassium sodium water glass binder in (3) is 5~20wt% of the powder of each component except K2O and Na2O. Further specified, the composition of potassium sodium water glass binder in (3) by mass percentage is: K2O: 11~15%, Na2O: 3~5%, SiO2: 30~40%.

[0014] Further specified, (3) the medium and low temperature drying temperature is 250-450℃, the low temperature sieve mesh is 10~60 mesh, the high temperature sintering temperature is 550-650℃, and the high temperature sieve mesh is 10~60 mesh.

[0015] Further specified, the sintering flux has a mesh size of 10~60 mesh and a melting point of 1100℃~1300℃.

[0016] The third objective of this invention is to provide an application of the above-mentioned sintered flux that improves the crack resistance of Inconel 690 alloy strip submerged arc welding. Specifically, the sintered flux uses EQNiCrFe-7A welding strip as the welding material and is used for the surfacing of Inconel 690 alloy corrosion-resistant layers in nuclear power equipment, especially for the surfacing of Inconel 690 alloy corrosion-resistant layers in nuclear power steam generator tube sheets.

[0017] The fourth objective of this invention is to provide a weld metal obtained from the above-mentioned application, wherein the weld metal has a room temperature tensile strength ≥580MPa, a room temperature yield strength ≥310MPa, a 350℃ tensile strength ≥470MPa, and a 350℃ yield strength ≥270MPa.

[0018] The beneficial effects of this invention are as follows: (1) This invention regulates the flux composition by adding metallic manganese and metallic niobium to the flux to increase the content of manganese and niobium elements in the deposited metal. The manganese and niobium elements form intragranular compounds such as MC carbides and Ni3Nb to prevent grain slippage and thus reduce the sensitivity of the weld overlay to hot cracking, while improving the mechanical properties of the deposited metal. The sintered flux of this invention has good weld bead formation and slag removal properties during the strip electrode submerged arc welding process, with smooth overlap between weld beads and strong resistance to hot cracking. The resulting deposited metal has a room temperature tensile strength ≥550MPa, a yield strength ≥310MPa, a 350℃ tensile strength ≥450MPa, and a 350℃ yield strength ≥224MPa. It has excellent mechanical properties at high temperatures, meeting the performance requirements of the Inconel 690 alloy corrosion-resistant layer for nuclear power facility construction.

[0019] (2) By adjusting the flux composition, the flux melting point is controlled at 1100℃~1300℃, which improves the welding processability of strip electrode submerged arc welding and enhances the fluidity and deslag removal properties of the slag.

[0020] (3) The addition of micron-sized chromium oxide to the flux of the present invention effectively increases the surface area of ​​the added chromium oxide, thereby improving its uniformity in the flux and facilitating the transition of chromium into the deposited metal, thereby improving the resistance of the deposited metal to stress corrosion cracking. At the same time, the micron-sized chromium oxide interacts with metal Mn and metal Nb, and through chemical reaction, helps to adjust the melting point and fluidity of the flux, which helps the transition of Mn and Nb into the deposited metal, thereby steadily improving the resistance of the deposited metal to hot cracking.

[0021] (4) After using the flux provided by the present invention to perform submerged arc welding of Inconel 690 alloy strip electrode, the properties of the deposited metal meet the actual construction requirements of nuclear power equipment, and solve the problem of high crack sensitivity of Inconel 690 alloy weld layer. Attached Figure Description

[0022] Figure 1The TG-DTA curve of the sintered flux prepared in Example 1; Figure 2 The image shows the metallographic microstructure of the deposited metal obtained in Example 1. Figure 3 This is a diagram showing the weld bead formation and slag shedding after welding in Example 1. Detailed Implementation

[0023] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the examples in the specification.

[0024] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and those skilled in the art can make similar extensions without departing from the spirit of the invention. Therefore, the invention is not limited to the specific embodiments disclosed below.

[0025] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The phrase "in one embodiment" appearing in different places in this specification does not necessarily refer to the same embodiment, nor is it a single or selective embodiment that is mutually exclusive with other embodiments.

[0026] Unless otherwise specified, the experimental methods used in the following examples are conventional methods. Unless otherwise specified, the materials, reagents, methods, and instruments used are all conventional materials, reagents, methods, and instruments in the art, and can be obtained commercially by those skilled in the art.

[0027] This invention uses a matching EQNiCrFe-7A welding ribbon and sintering fluxes of CaF2, Al2O3, CaO, metallic manganese, metallic niobium, MnO, micron-sized chromium oxide, ferrosilicon alloy, K2O, and Na2O. Therefore, the resulting weld metal also contains Mn, Cr, Al, Ti, and Nb. The roles of the main elements in diluting the weld metal are as follows: Mn: A MO-type oxide and MC-type carbide forming element that prevents grain slippage by pinning, reducing the susceptibility to high-temperature low-plasticity cracks.

[0028] Cr:γ ’ Solid solution strengthening and carbide forming elements effectively improve the resistance of deposited metal to stress corrosion cracking.

[0029] Al:γ ’ -Ni3(Al,Ti) phase and surface Al2O3 forming elements promote deoxidation of the molten pool and improve the strength of the deposited metal.

[0030] Ti: a solid solution strengthening element, forms γ-Ni3(Al,Ti) phase and MC, M(C,N) type carbides, improves the strength of the weld metal, and reduces the sensitivity of the weld metal to high-temperature low-plasticity cracking.

[0031] Nb: solid solution strengthening element, γ ’’ -Ni3Nb phase, MC, M(C,N) type carbides, and Laves phase forming elements improve the strength of the weld metal and reduce the sensitivity of the weld metal to high-temperature low-plasticity cracking.

[0032] Example 1 The flux chemical composition provided in this example, by weight percentage, includes: CaF2: 15%, Al2O3: 45%, CaO: 3%, metallic manganese: 4%, metallic niobium: 3%, micron-sized chromium oxide: 3%, 75# ferrosilicon alloy: 1%, K2O+Na2O: 8%, with the mass ratio of K2O to Na2O in K2O+Na2O being 3:1. The specific composition of the flux is shown in Table 2.

[0033] In this invention, CaF2 is added in the form of fluorite, Al2O3 is added in the form of α-alumina, CaO is added in the form of calcite, and other metal components are added in the form of metal powder with a purity of ≥99.9%.

[0034] The preparation method of the sintering flux in this example is as follows: (1) Preparation of micron-sized chromium oxide: Chromium green raw material (i.e. chromium oxide powder) was placed in a beaker, and sufficient distilled water was added for ultrasonic washing for 10 min. After washing, the solid was filtered and dried at 200℃ for 1 h. After drying, it was calcined at 950℃ for 2 h. After cooling to room temperature, it was crushed and ground by a small cone crusher and then sieved through an ultrasonic vibrating sieve machine at 150 mesh. After sieving, it was ball-milled for 5 min and then sieved through a 200 mesh sieve again to obtain micron-sized chromium oxide. (2) Powder preparation: Weigh out the powders of each component except K2O and Na2O according to the proportion of sintering flux, including mineral powder: fluorite powder, α-alumina powder, calcite powder, metal powder: manganese powder, niobium powder and 75# ferrosilicon alloy powder. Put each component powder into the mixing container in sequence. Dry mix each powder evenly (5 min, 150 rpm) before adding the next one to ensure that each powder is evenly mixed. After all the component powders are added, stir and dry mix for 5 min (150 rpm). Among them, micron-sized chromium oxide is added in three equal portions according to the flux formula. Dry mixing is carried out at the same time as adding (time is 5 min, speed is 150 rpm) to ensure that the micron-sized chromium oxide is evenly mixed with the other component powders. (3) Stirring: Add potassium sodium water glass binder to the dry-mixed powder in (2) so that the K2O+Na2O content is 8%, and the mass ratio of K2O to Na2O is 3:1. Perform wet mixing to obtain wet flux. (4) Granulation: The wet mixed material is fed into a disc-type rotary granulator for granulation and then sieved through a 10-60 mesh screen to obtain a wet semi-finished product; (5) Low temperature drying: The wet semi-finished product is transferred to a rotary continuous low temperature drying oven and the drying temperature is 250℃; (6) Low-temperature screening: The low-temperature dried material is fed into a vibrating screen for screening, and the screening particle size range is 10~60 mesh; (7) High-temperature sintering: The low-temperature screened material is fed into a rotary continuous high-temperature drying furnace for sintering at a temperature of 650℃. (8) High-temperature screening: The material after high-temperature sintering is transferred to a vibrating screen for further screening. The screening particle size range is 10~60 mesh. (9) Cooling: The high-temperature screened material is transferred to a continuous cooling furnace for cooling; (10) Packaging: The cooled material is packaged to obtain sintered flux with a mesh size of 10~60 mesh and a melting point of 1100℃~1300℃.

[0035] Using the welding strip with the composition shown in Table 1, and the sintered flux obtained in this embodiment, the strip electrode submerged arc welding was performed on the surface of SA5083 steel according to the welding process parameters in Table 4. The test plate size was 300mm×300mm×50mm.

[0036] The mechanical property test results of the weld metal obtained by strip electrode submerged arc welding of flux and welding strip in this example are shown in Table 5.

[0037] The flux obtained in this example, analyzed by a synchronous thermal analyzer, yielded the following TG-DTA curve: Figure 1 As shown, the metallographic microstructure of the weld metal obtained by submerged arc welding of flux and solder strip in this example is as follows. Figure 2 As shown, the weld bead formation and slag shell after welding are as follows: Figure 3 As shown.

[0038] Example 2 The difference between this embodiment and Embodiment 1 is that the chemical composition of the flux contains 4% niobium. The specific composition of the flux is shown in Table 2. The remaining operation steps and parameter settings are the same as in Embodiment 1, and a sintered flux is obtained.

[0039] In this example, the welding strip with the composition shown in Table 1 is used in conjunction with the sintered flux obtained in this embodiment. The strip electrode submerged arc welding is performed on the surface of SA5083 steel according to the welding process parameters in Table 4. The test plate size is 300mm×300mm×50mm.

[0040] The mechanical property test results of the weld metal obtained by strip electrode submerged arc welding of flux and welding strip in this example are shown in Table 5.

[0041] Example 3 The difference between this embodiment and Embodiment 1 is that the flux contains 4% niobium and 6% manganese. The specific composition of the flux is shown in Table 2. The remaining operation steps and parameter settings are the same as in Embodiment 1, and a sintered flux is obtained.

[0042] In this example, the welding strip with the composition shown in Table 1 is used in conjunction with the sintered flux obtained in this embodiment. The strip electrode submerged arc welding is performed on the surface of SA5083 steel according to the welding process parameters in Table 4. The test plate size is 300mm×300mm×50mm.

[0043] The mechanical property test results of the weld metal obtained by strip electrode submerged arc welding of flux and welding strip in this example are shown in Table 5.

[0044] Example 4 The difference between this embodiment and Embodiment 1 is that the flux chemical composition contains 3% niobium and 5% manganese. The specific composition of the flux is shown in Table 2. The remaining operation steps and parameter settings are the same as in Embodiment 1, and a sintered flux is obtained.

[0045] In this example, the welding strip with the composition shown in Table 1 is used in conjunction with the sintered flux obtained in this embodiment. The strip electrode submerged arc welding is performed on the surface of SA5083 steel according to the welding process parameters in Table 4. The test plate size is 300mm×300mm×50mm.

[0046] Comparative Example 1 The difference between this comparative example and Example 1 is that the flux chemical composition contains 1% niobium and 2% manganese. The specific composition of the flux is shown in Table 2. The remaining operation steps and parameter settings are the same as in Example 1, and a sintered flux is obtained.

[0047] This comparative example uses welding strips with the composition shown in Table 1, along with the sintered flux obtained in this comparative example. The strip electrode submerged arc welding is performed on the surface of SA5083 steel according to the welding process parameters in Table 4. The test plate size is 300mm×300mm×50mm.

[0048] The mechanical property test results of the weld metal obtained by submerged arc welding of flux and weld strip in this comparative example are shown in Table 5.

[0049] The solder ribbon composition of Examples 1-4 and Comparative Example 1 is shown in Table 1, and the flux composition of Examples 1-4 and Comparative Example 1 is shown in Table 2.

[0050] Table 1 Chemical composition of solder strip (by weight percentage, %)

[0051] Table 2 Chemical composition of flux (by weight percentage, %)

[0052] Table 3 Welding process parameters

[0053] Table 4 Mechanical properties of the deposited metal

[0054] As shown in Table 4, the room temperature tensile strength of the weld metal obtained using the flux of this invention is consistently above 580 MPa, and the yield strength is consistently above 310 MPa, indicating good strength matching and good plasticity reserve. At 350℃, the high-temperature strength of the weld metal is consistently above 470 MPa, and the yield strength is consistently above 270 MPa, demonstrating reliable high-temperature load-bearing capacity. Bending test results show that the weld metal exhibits good plasticity at room temperature, with no obvious tendency to embrittlement, and improved crack resistance. In contrast, Comparative Example 1, due to its low Mn and Nb content in the flux, showed a decrease in the mechanical properties of the weld metal and exhibited bending cracking, proving that Mn and Nb elements can improve the mechanical properties and crack resistance of the weld metal.

[0055] The above results demonstrate that the weld metal obtained by this invention has stable mechanical properties at both room temperature and high temperature, and exhibits no cracks in the bending test, thus meeting the performance requirements of the nuclear power industry for this type of welding material weld metal.

[0056] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A sintered flux for improving the crack resistance of Inconel 690 alloy strip submerged arc welding, characterized in that, The chemical composition of the flux, by weight percentage, includes: CaF2: 5~20%, Al2O3: 20~50%, CaO: 1~10%, metallic manganese: 3~9%, metallic niobium: 2~5%, micron-sized chromium oxide: 2~10%, ferrosilicon alloy: 0.5~2%, K2O and Na2O: 5~15%.

2. The sintering flux according to claim 1, characterized in that, The mass ratio of K2O to Na2O is 3:

1.

3. A method for preparing a sintered flux as described in claim 1 or 2 to improve the crack resistance of submerged arc welding of Inconel 690 alloy strip electrode, characterized in that, The preparation method includes the following steps: (1) The chromium green raw material was successively calcined at high temperature, ball-milled and screened twice to obtain micron-sized chromium oxide; (2) Weigh out each component powder except K2O and Na2O according to the proportion of sintering flux. Put each component powder into the mixing container in sequence. After each component powder is mixed evenly, add another component powder. After all the component powders have been added, stir and dry mix. (3) After dry mixing, potassium sodium water glass binder is added for wet mixing. The wet mixed material is then granulated, dried at low temperature, screened at low temperature, sintered at high temperature, screened at high temperature and cooled, and then packaged to obtain sintered flux.

4. The preparation method according to claim 3, characterized in that, (1) The medium-high temperature calcination temperature is 950℃, and the secondary sieving mesh is 200 mesh; the ball milling and secondary sieving processes are completed at dry room temperature.

5. The preparation method according to claim 3, characterized in that, (2) The mixing time is 5 min and the speed is 150 rpm.

6. The preparation method according to claim 3, characterized in that, (3) The amount of potassium sodium water glass binder is 5~20wt% of each component powder except K2O and Na2O; the components of potassium sodium water glass binder include by mass percentage: K2O: 11~15%, Na2O: 3~5%, SiO2: 30~40%.

7. The preparation method according to claim 3, characterized in that, (3) The medium and low temperature drying temperature is 250-450℃, and the low temperature sieve mesh is 10~60 mesh; the high temperature sintering temperature is 550-650℃, and the high temperature sieve mesh is 10~60 mesh.

8. The preparation method according to claim 3, characterized in that, The sintering flux has a mesh size of 10~60 mesh and a melting point of 1100℃~1300℃.

9. An application of the sintering flux according to claim 1 or 2, characterized in that, This sintering flux uses EQNiCrFe-7A welding strip as the welding material and is used for the surfacing of Inconel 690 alloy corrosion-resistant layers in nuclear power equipment.

10. A weld metal obtained by the application of claim 9, characterized in that, The room temperature tensile strength of the deposited metal is ≥580MPa, the room temperature yield strength is ≥310MPa, the 350℃ tensile strength is ≥470MPa, and the 350℃ yield strength is ≥270MPa.

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