Submerged arc sintered flux for welding SA-508Gr. 3C1.1 steel in third-generation nuclear power equipment and preparation method of submerged arc sintered flux

Abstract

The invention provides submerged arc sintered flux for welding SA-508Gr. 3C1.1 steel in third-generation nuclear power equipment and a preparation method of the submerged arc sintered flux. The submerged arc sintered flux comprises, by weight, 20-40 parts of fluorite, 35-50 parts of magnesia, 15-30 parts of aluminum oxide, 10-20 parts of wollastonite, 1-5 parts of silica powder, 0.5-2 parts of silicon iron, 2-5 parts of manganese ore, 1-5 parts of calcium titanate and 1-5 parts of rare earth materials. And the water glass accounts for 25-30% of the sum of the flux powder. The flux provided by the invention has good welding manufacturability, excellent slag removal, beautiful formation and more excellent mechanical properties.

Description

Technical Field

[0001] This invention belongs to the field of welding materials technology, and in particular relates to a submerged arc sintering flux for welding SA-508Gr.3C1.1 steel in third-generation nuclear power equipment and its preparation method. Background Technology

[0002] Welding is a critical process in the manufacturing of nuclear pressure equipment, and welded joints are often the weakest points in such equipment. Therefore, welding materials and processes used in nuclear reactor pressure equipment play a vital role in the design, construction, and safety assessment of nuclear power plants, directly affecting the feasibility and safety of nuclear power plant construction.

[0003] In recent years, with the continuous increase in nuclear reactor power and the further improvement of nuclear power safety levels, higher requirements have been placed on the comprehensive performance of nuclear-grade equipment such as reactor pressure vessels. SA508Gr.3C1.1 steel has excellent weldability, high high-temperature strength and fatigue strength, good low-temperature impact toughness, and excellent resistance to neutron radiation. As a major pressure-bearing material, it is widely used in key parts of reactor pressure vessels such as the core and shell of third-generation and third-generation plus nuclear power plants.

[0004] Currently, key welding materials used in the manufacturing and installation of nuclear-grade equipment are still mainly supplied by foreign manufacturers. Domestically produced nuclear-grade welding materials still lag behind in terms of product performance and stability, primarily manifested in a narrow welding range, large fluctuations in mechanical property data, and insufficient quality stability across multiple batches. Furthermore, the use of imported welding materials suffers from drawbacks such as long delivery cycles, difficulties in communication and supervision during production, and high prices, becoming one of the bottlenecks restricting the development of nuclear power in my country. Domestic welding materials have consistently been excluded from the market, and domestic welding materials cannot yet provide strong support for the manufacturing of nuclear-grade equipment in my country. Therefore, there is an urgent need for domestic welding material manufacturers to conduct research and development on relevant welding materials to meet the current needs of related manufacturing enterprises. Summary of the Invention

[0005] In view of this, the present invention aims to provide a submerged arc sintering flux for welding SA-508Gr.3C1.1 steel in third-generation nuclear power equipment, which has good welding processability, excellent slag removal, beautiful forming, and superior mechanical properties.

[0006] To achieve the above objectives, the technical solution of the present invention is implemented as follows:

[0007] A submerged arc sintering flux for welding SA-508Gr.3C1.1 steel in third-generation nuclear power equipment, wherein the flux comprises, by weight, the following components:

[0008] 20-40 parts fluorite;

[0009] 35-50 parts magnesia;

[0010] 15-30 parts of alumina;

[0011] 10-20 parts of wollastonite;

[0012] 1-5 parts of silica powder;

[0013] Ferrosilicon 0.5-2 parts;

[0014] 2-5 parts of manganese ore;

[0015] 1-5 parts calcium titanate;

[0016] 1-5 parts of rare earth materials;

[0017] The water glass comprises 25%-30% of the sum of the above flux powders.

[0018] Furthermore, the rare earth material is a mixture of aluminum cerium and aluminum yttrium, with a mass ratio of aluminum cerium to aluminum yttrium of (0.5-1):(1-2).

[0019] Furthermore, the flux comprises, by weight, the following components:

[0020] 37 portions of fluorite;

[0021] 35 parts of magnesia;

[0022] 17 parts of aluminum oxide;

[0023] 17 parts of wollastonite;

[0024] 2 parts silica powder;

[0025] Two parts of ferrosilicon;

[0026] 4 portions of manganese ore;

[0027] 4 parts calcium titanate;

[0028] The rare earth material consists of 1 part aluminum cerium and 2 parts aluminum yttrium; the water glass comprises 25% of the sum of the above flux powders. Further, the flux, by weight, comprises:

[0029] 30 portions of fluorite;

[0030] 42 parts of magnesia;

[0031] 22 parts of aluminum oxide;

[0032] 15 parts of wollastonite;

[0033] 3 parts silica powder;

[0034] 1 part ferrosilicon;

[0035] 3 portions of manganese ore;

[0036] 3 parts calcium titanate;

[0037] The rare earth material consists of 1 part aluminum cerium and 1 part aluminum yttrium; the water glass comprises 26% of the sum of the above flux powders. Further, the flux, by weight, comprises:

[0038] 25 parts fluorite;

[0039] 46 parts of magnesia;

[0040] 28 parts of aluminum oxide;

[0041] 12 parts of wollastonite;

[0042] 3 parts silica powder;

[0043] 1 part ferrosilicon;

[0044] Two portions of manganese ore;

[0045] 2 parts calcium titanate;

[0046] The rare earth material consists of 0.5 parts aluminum cerium and 1.5 parts aluminum yttrium;

[0047] The water glass comprises 27% of the sum of the above flux powders.

[0048] Furthermore, the water glass is potassium sodium water glass.

[0049] Furthermore, the basicity of the flux is 2.5-2.8.

[0050] Furthermore, the flux-specific welding wire is THM-10Mn2NiMoA.

[0051] This invention also provides a method for preparing submerged arc sintering flux for SA-508Gr.3C1.1 steel used in welding third-generation nuclear power equipment as described above, the method comprising the following steps:

[0052] (1) Sieve the rare earth material through a 40-mesh sieve;

[0053] (2) Place fluorite, magnesia, alumina, wollastonite, silica powder, ferrosilicon, manganese ore, calcium titanate and sieved rare earth materials in a vibrating screen, vibrate and sieve through a 30-mesh screen, then place them in a mixer and stir to mix evenly for 15-20 minutes.

[0054] (3) Add water glass, stir and mix evenly, granulate, then bake at a low temperature of 300°C by natural gas heating, sinter at a high temperature of 820°C by electric heating, and obtain the flux after sieving.

[0055] In the flux of this invention:

[0056] Fluorite's main component is CaF2, a multi-origin mineral belonging to the alkaline fluoride family. In submerged arc welding flux, it acts as a slag-forming agent, diluent, and dehydrogenator. Under the influence of the welding arc, CaF2 ionizes to release fluorine (F), reducing the partial pressure of hydrogen in the arc atmosphere, similar to the effect of carbonates. The decomposition of CaF2 reduces the oxygen content in the weld metal, which is beneficial for improving the low-temperature impact toughness of the weld metal. CaF2's low melting point effectively reduces the high-temperature viscosity of the slag, improves slag fluidity, enhances conductivity, and improves weld formation. It plays a significant role in improving welding processes and enhancing the mechanical properties of the weld metal. A reasonable CaF2 content can stabilize the arc; however, excessive CaF2 content leads to poor arc stability, harder slag, and reduced AC weldability.

[0057] Magnesia slag, primarily composed of MgO, is a strongly alkaline substance and an excellent slag-forming material, crucial for controlling weld shape. For alkaline slag systems, MgO improves the impact toughness of the weld metal and reduces diffusible hydrogen. Magnesia oxide has a high melting point, increasing slag viscosity and hindering slag flowability. This makes slag removal difficult and results in poor weld formation.

[0058] Aluminum oxide is an amphoteric oxide that increases the surface tension of molten slag and acts as a viscosity modifier. Through extensive comparative experiments, it has been found that increasing a certain amount of Al2O3 can reduce pitting and its tendency. However, excessively high Al2O3 content will make the weld bead more pointed and uneven, easily producing porosity and pitting, and hardening the slag shell. Conversely, too low Al2O3 content will make the weld surface uneven, affecting the weld formation.

[0059] The main component of silica powder is SiO2. At high temperatures, it combines with free oxygen in the molten pool to form a silicate slag layer (such as FeO-SiO2), which effectively reduces the oxygen content of the weld. It also forms low-melting-point eutectics with metal oxides (such as CaO-SiO2 slag), with a melting point of about 1200-1300℃, which reduces the viscosity of the slag by 30%-40%, thereby enhancing the spreadability of the molten pool. Through silicon element transition (Si content is usually controlled at 0.2%-0.8%), it can refine ferrite grains and improve toughness.

[0060] Wollastonite's main component is Ca3Si3O9. The wollastonite group of minerals includes two polymorphs of CaSiO3: the high-temperature polymorph, β-CaSiO3, belongs to the triclinic system (pseudo-orthorhombic system) and is called pseudowollastonite. The low-temperature polymorph, α-CaSiO3, has two polymorphs: one is triclinic, i.e., wollastonite-Tc; the other is monoclinic, i.e., wollastonite-2M. The most common wollastonite is wollastonite-Tc. In welding materials, it is mainly used in low-hydrogen electrodes and basic fluxes, where its function is slag formation. Because wollastonite contains CaO, it increases the alkaline oxides in the welding slag, but because it contains SiO2, the amount added is limited. Due to its crystal structure, wollastonite often exists as fibrous, radial aggregates, or fibrous structures, which is beneficial for improving the strength of the electrode coating and preventing cracking. In sintered fluxes, it is beneficial for improving the particle strength of the flux.

[0061] Ferrosilicon and manganese ore: Commonly used deoxidizers in welding flux. When ferrosilicon and manganese ore are used together for deoxidation in an appropriate ratio, the deoxidation products can form silicates MnO.SiO2. These silicates have low density and low melting point. They are liquid in molten steel and easily aggregate into particles with large radii, which float to the slag, reducing inclusions in the weld and thus reducing the oxygen content in the weld.

[0062] Manganese ore is an important material for smelting and sintering welding fluxes. In welding fluxes, manganese mainly exists in the form of MnO, with a small amount of Mn3O4 (or Mn2O3). The melting point of pure MnO is 1650℃. MnO reduces slag viscosity and improves slag flowability; it also has good electrical conductivity and stabilizes the electric arc. MnO has oxidizing properties, which can reduce the ability to generate hydrogen porosity. Whether in welding electrodes or welding fluxes, when the amount of manganese ore added exceeds a certain level, some of the MnO2 can be reduced to elemental Mn under the action of the electric arc, participating in deoxidation. At the same time, it reacts with sulfur in the coating or welding flux material, reducing the sulfur content in the weld metal.

[0063] Calcium titanate can be used as a slag-forming agent to improve slag coverage during welding by adjusting slag fluidity, thus ensuring weld quality; it can also improve arc stability, reduce spatter during welding, and increase arc efficiency; it helps reduce weld oxidation, further optimizes weld formation, and ensures the mechanical properties of the welded joint.

[0064] Rare earth materials, which use aluminum cerium and aluminum yttrium, have a purifying effect on weld metal, improving weld structure and refining grains, changing the morphology, size and distribution of inclusions, and have deoxidizing, dehydrogenating and desulfurizing effects. They can reduce the content of harmful elements in weld metal and improve the low-temperature impact toughness of weld metal. There is an optimal value for the amount of rare earth added; if the amount added is too small or too large, the effective effect will be reduced.

[0065] Compared with existing technologies, the submerged arc sintering flux and its preparation method for welding SA-508Gr.3C1.1 steel in third-generation nuclear power equipment described in this invention have the following advantages:

[0066] The submerged arc sintering flux for welding SA-508Gr.3C1.1 steel in third-generation nuclear power equipment described in this invention optimizes the proportions of each element, resulting in excellent welding processability. In particular, during the welding process, the weld formation is aesthetically pleasing, the slag shell can automatically lift and fall off, and the weld transition is smooth. It is suitable for welding under different conditions, and the process and performance are stable under different heat input conditions, resulting in excellent weld mechanical properties. By adding rare earth materials, the low-temperature impact toughness of the weld metal can be guaranteed to meet the design requirements for SA-508Gr.3C1.1 steel used in third-generation nuclear power equipment. Detailed Implementation

[0067] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other.

[0068] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0069] Example 1

[0070] A submerged arc sintering flux for welding SA-508Gr.3C1.1 steel in third-generation nuclear power equipment, comprising, by weight parts:

[0071] 37 portions of fluorite;

[0072] 35 parts of magnesia;

[0073] 17 parts of aluminum oxide;

[0074] 17 parts of wollastonite;

[0075] 2 parts silica powder;

[0076] Two parts of ferrosilicon;

[0077] 4 portions of manganese ore;

[0078] 4 parts calcium titanate;

[0079] The rare earth material consists of 1 part aluminum cerium and 2 parts aluminum yttrium;

[0080] The water glass is 25% of the sum of the above flux powders.

[0081] The preparation method of the above flux includes the following steps:

[0082] (1) Sieve the rare earth material through a 40-mesh sieve;

[0083] (2) Place fluorite, magnesia, alumina, wollastonite, silica powder, ferrosilicon, manganese ore, calcium titanate and sieved rare earth materials in a vibrating screen, vibrate and sieve through a 30-mesh screen, then place them in a mixer and stir to mix evenly for 15 minutes.

[0084] (3) Add potassium sodium water glass, stir and mix evenly, granulate, then bake at a low temperature of 300°C by natural gas heating, sinter at a high temperature of 820°C by electric heating, and obtain the flux after sieving.

[0085] The flux basicity is 2.7.

[0086] Example 2

[0087] A submerged arc sintering flux for welding SA-508Gr.3C1.1 steel in third-generation nuclear power equipment, comprising, by weight parts:

[0088] 30 portions of fluorite;

[0089] 42 parts of magnesia;

[0090] 22 parts of aluminum oxide;

[0091] 15 parts of wollastonite;

[0092] 3 parts silica powder;

[0093] 1 part ferrosilicon;

[0094] 3 portions of manganese ore;

[0095] 3 parts calcium titanate;

[0096] The rare earth material consists of 1 part aluminum cerium and 1 part aluminum yttrium;

[0097] The water glass comprises 26% of the sum of the above flux powders.

[0098] The flux preparation method is the same as in Example 1.

[0099] The flux basicity is 2.6.

[0100] Example 3

[0101] A submerged arc sintering flux for welding SA-508Gr.3C1.1 steel in third-generation nuclear power equipment, comprising, by weight parts:

[0102] 25 parts fluorite;

[0103] 46 parts of magnesia;

[0104] 28 parts of aluminum oxide;

[0105] 12 parts of wollastonite;

[0106] 3 parts silica powder;

[0107] 1 part ferrosilicon;

[0108] Two portions of manganese ore;

[0109] 2 parts calcium titanate;

[0110] The rare earth material consists of 0.5 parts aluminum cerium and 1.5 parts aluminum yttrium;

[0111] The water glass comprises 27% of the sum of the above flux powders.

[0112] The flux basicity is 2.5.

[0113] Comparative Example 1

[0114] The difference from Example 1 is that no rare earth materials are added; otherwise, it is the same as Example 1.

[0115] Comparative Example 2

[0116] The difference from Example 1 is that only aluminum and cerium are used as rare earth materials, while the rest is the same as in Example 1.

[0117] Comparative Example 3

[0118] The difference from Example 1 is that only aluminum yttrium is used as the rare earth material, while the rest is the same as in Example 1.

[0119] Comparative Example 4

[0120] The difference from Example 1 is that the rare earth material contains 2.5 parts aluminum cerium and 0.5 parts aluminum yttrium, while the rest is the same as in Example 1.

[0121] The flux obtained in the above embodiments and comparative examples is used in conjunction with the welding wire THM-10Mn2NiMoA. Welding tests were conducted on the deposited metal. The welding process specifications are shown in Table 1, and the mechanical properties of the deposited metal are shown in Table 2.

[0122] In addition, the flux obtained in Example 1 was used in conjunction with the welding wire CHW-S55HRF to conduct a weld metal deposition test, which is recorded in Table 2 as Comparative Example 5.

[0123] Table 1 Welding Procedure Specifications

[0124]

[0125] Table 2 Mechanical properties of deposited metal

[0126]

[0127] As shown in the table above, the flux prepared in the examples exhibits better welding processability, superior slag removal, aesthetically pleasing formation, and superior mechanical properties compared to the comparative examples. Comparative Examples 1-4 demonstrate that rare earth materials have a significant impact on flux performance, and only when aluminum, cerium, and yttrium are added in the proportions specified in this invention can a flux with superior performance be obtained. Comparative Example 5 shows that the flux of this invention needs to be used in conjunction with the welding wire THM-10Mn2NiMoA to achieve better results; replacing it with other welding wires will reduce the mechanical properties of the deposited metal.

[0128] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A submerged arc sintering flux for welding SA-508Gr.3C1.1 steel in third-generation nuclear power equipment, characterized in that: The flux comprises, by weight, the following: 20-40 parts fluorite; 35-50 parts magnesia; 15-30 parts of alumina; 10-20 parts of wollastonite; 1-5 parts of silica powder; Ferrosilicon 0.5-2 parts; 2-5 parts of manganese ore; 1-5 parts calcium titanate; 1-5 parts of rare earth materials; The water glass comprises 25%-30% of the sum of the above flux powders.

2. The submerged arc sintering flux for welding SA-508Gr.3C1.1 steel in third-generation nuclear power equipment according to claim 1, characterized in that: The rare earth material is a mixture of aluminum cerium and aluminum yttrium, with a mass ratio of aluminum cerium to aluminum yttrium of (0.5-1):(1-2).

3. The submerged arc sintering flux for welding SA-508Gr.3C1.1 steel in third-generation nuclear power equipment according to claim 2, characterized in that: The flux comprises, by weight, the following: 37 portions of fluorite; 35 parts of magnesia; 17 parts of aluminum oxide; 17 parts of wollastonite; 2 parts silica powder; 2 parts ferrosilicon; 4 portions of manganese ore; 4 parts calcium titanate; The rare earth material consists of 1 part aluminum cerium and 2 parts aluminum yttrium; The water glass is 25% of the sum of the above flux powders.

4. The submerged arc sintering flux for welding SA-508Gr.3C1.1 steel in third-generation nuclear power equipment according to claim 2, characterized in that: The flux comprises, by weight, the following: 30 portions of fluorite; 42 parts of magnesia; 22 parts of aluminum oxide; 15 parts of wollastonite; 3 parts silica powder; 1 part ferrosilicon; 3 portions of manganese ore; 3 parts calcium titanate; The rare earth material consists of 1 part aluminum cerium and 1 part aluminum yttrium; The water glass comprises 26% of the sum of the above flux powders.

5. The submerged arc sintering flux for welding SA-508Gr.3C1.1 steel in third-generation nuclear power equipment according to claim 2, characterized in that: The flux comprises, by weight, the following: 25 parts fluorite; 46 parts of magnesia; 28 parts of aluminum oxide; 12 parts of wollastonite; 3 parts silica powder; 1 part ferrosilicon; Two portions of manganese ore; 2 parts calcium titanate; The rare earth material consists of 0.5 parts aluminum cerium and 1.5 parts aluminum yttrium; The water glass comprises 27% of the sum of the above flux powders.

6. The submerged arc sintering flux for welding SA-508Gr.3C1.1 steel in third-generation nuclear power equipment according to any one of claims 1-5, characterized in that: The water glass is potassium sodium water glass.

7. The submerged arc sintering flux for welding SA-508Gr.3C1.1 steel in third-generation nuclear power equipment according to any one of claims 1-5, characterized in that: The basicity of the flux is 2.5-2.

8.

8. The submerged arc sintering flux for welding SA-508Gr.3C1.1 steel in third-generation nuclear power equipment according to any one of claims 1-5, characterized in that: The flux-specific welding wire is THM-10Mn2NiMoA.

9. A method for preparing submerged arc sintering flux for welding SA-508Gr.3C1.1 steel in third-generation nuclear power equipment as described in any one of claims 1-8, characterized in that: The method includes the following steps: (1) Sieve the rare earth material through a 40-mesh sieve; (2) Place fluorite, magnesia, alumina, wollastonite, silica powder, ferrosilicon, manganese ore, calcium titanate and sieved rare earth materials in a vibrating screen, vibrate and sieve through a 30-mesh screen, then place them in a mixer and stir to mix evenly for 15-20 minutes. (3) Add water glass, stir and mix evenly, granulate, then bake at a low temperature of 300°C by natural gas heating, sinter at a high temperature of 820°C by electric heating, and obtain the flux after sieving.

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