Low-temperature steel electrode for SA-350 Gr. LF3 base material of high burn-up spent fuel storage and transportation container and preparation method thereof

Abstract

The present invention discloses a low-temperature steel electrode for the base material SA-350Gr.LF3 of a high-burnup spent fuel storage and transportation container and a preparation method thereof. The electrode is obtained by wrapping a welding core with a powder. The composition of the powder is as follows in parts by weight: 4.5-10 parts of electrolytic manganese, 1-5 parts of titanium-boron alloy, 3-12 parts of sodium fluoride, 6-12 parts of nickel powder, 15-30 parts of calcium fluoride, 4-10 parts of silica fume, 10-15 parts of iron powder, 1-2.5 parts of silicon-zirconium alloy, and 15-35 parts of marble. The composition of the welding core is as follows in weight percentage: 0.02%-0.2% of carbon, 0.1%-0.4% of manganese, 0.01%-0.03% of silicon, 99.5%-99.9% of iron, and the balance is inevitable impurities. The electrode of the present invention has good welding process, and the mechanical properties, impact properties and crack resistance of the weld are good.

Description

Technical Field

[0001] The present invention relates to the field of welding technology, and particularly to a low-temperature steel electrode for the base material SA-350Gr.LF3 of a high-burnup spent fuel storage and transportation container and a preparation method thereof. Background Art

[0002] In recent years, the nuclear power industry in our country has developed rapidly, and the localization of welding materials required for nuclear power projects has become a trend. In the past, many welding materials for nuclear power projects in our country mainly relied on imports. However, imported welding materials have a high cost, a long production and transportation cycle, which affects the production of nuclear power equipment manufacturing enterprises in our country and further affects the development of the nuclear power industry and the national economy in our country. Therefore, it is necessary to develop low-alloy steel welding materials for high-burnup spent fuel storage and transportation containers and realize the localization development of such welding materials.

[0003] SA-350Gr.LF3 Cl.2 belongs to a new type of steel for containers for storing and transporting highly radioactive spent fuel and is a low-temperature steel used under more severe conditions. Due to the particularity of the service environment of SA-350Gr.LF3 Cl.2, the mechanical properties requirements for the welded joints formed by welding SA-350Gr.LF3 Cl.2 steel under ultra-low temperature conditions (-101 °C) are more stringent. Therefore, it is necessary to develop welding electrodes that meet the stringent requirements.

[0004] There is a 3.5Ni steel similar to SA-350Gr.LF3 Cl.2. It is required that the tensile strength of the welded joints formed by welding 3.5Ni steel with electrodes is ≥490 Mpa under the heat treatment conditions of 620 °C / 1 h, the impact test temperature is required to be between -60 °C and -80 °C, and the impact energy Akv is required to be ≥27 J; there is no relevant requirement for the fracture toughness TNDT temperature. Such electrodes cannot meet the welding requirements of SA-350Gr.LF3 Cl.2 low-temperature steel. Summary of the Invention

[0005] The technical problem to be solved by the present invention is that the current electrodes for welding low-temperature steel cannot meet the welding requirements of SA-350Gr.LF3 Cl.2. The purpose is to provide a low-temperature steel electrode for the base material SA-350Gr.LF3 of a high-burnup spent fuel storage and transportation container, and also provide a preparation method thereof to solve the above problems.

[0006] The first purpose of the present invention is to provide a low-temperature steel electrode for the base material SA-350Gr.LF3 of a high-burnup spent fuel storage and transportation container, which is manufactured by wrapping a welding core with a powder. The composition components of the powder are as follows in parts by weight: 4.5 parts - 10 parts of electrolytic manganese, 1 part - 5 parts of titanium-boron alloy, 3 parts - 12 parts of sodium fluoride, 6 parts - 12 parts of nickel powder, 15 parts - 30 parts of calcium fluoride, 4 parts - 10 parts of silica powder, 10 parts - 15 parts of iron powder, 1 part - 2.5 parts of silicon-zirconium alloy, 15 parts - 35 parts of marble;

[0007] The composition components of the welding core are as follows by weight percentage: carbon 0.02% - 0.2%, manganese 0.1% - 0.4%, silicon 0.01% - 0.03%, iron 99.5% - 99.9%, and the balance is inevitable impurities.

[0008] In an optional embodiment, the composition components of the powder are as follows by weight parts: electrolytic manganese 8 - 9.5 parts, titanium boride alloy 2.4 - 3.4 parts, sodium fluoride 4.2 - 4.6 parts, nickel powder 7.5 parts, calcium fluoride 23.8 - 26 parts, silica powder 6 - 8 parts, iron powder 12 - 13 parts, silicon zirconium alloy 1.3 - 1.5 parts, marble 29.8 - 31.6 parts;

[0009] The composition components of the welding core are as follows by weight percentage: carbon 0.05% - 0.1%, manganese 0.3% - 0.35%, silicon 0.03%, iron 99.555% - 99.559%, and the balance is inevitable impurities.

[0010] In an optional embodiment, the composition components of the powder are as follows by weight parts: electrolytic manganese 9.5 parts, titanium boride alloy 3.0 parts, sodium fluoride 4.6 parts, nickel powder 7.5 parts, calcium fluoride 23.8 parts, silica powder 7.8 parts, iron powder 12.5 parts, silicon zirconium alloy 1.5 parts, marble 29.8 parts;

[0011] The composition components of the welding core are as follows by weight percentage: carbon 0.05%, manganese 0.35%, silicon 0.03%, iron 99.555%, and the balance is inevitable impurities;

[0012] Or

[0013] The composition components of the powder are as follows by weight parts: electrolytic manganese 8 parts, titanium boride alloy 2.4 parts, sodium fluoride 4.2 parts, nickel powder 7.5 parts, calcium fluoride 26 parts, silica powder 6 parts, iron powder 13 parts, silicon zirconium alloy 1.3 parts, marble 31.6 parts;

[0014] The composition components of the welding core are as follows by weight percentage: carbon 0.1%, manganese 0.3%, silicon 0.03%, iron 99.559%, and the balance is inevitable impurities;

[0015] Or

[0016] The composition components of the powder are as follows by weight parts: electrolytic manganese 9 parts, titanium boride alloy 3.4 parts, sodium fluoride 4.2 parts, nickel powder 7.5 parts, calcium fluoride 24 parts, silica powder 8 parts, iron powder 12 parts, silicon zirconium alloy 1.5 parts, marble 30.4 parts;

[0017] The composition of the welding core is as follows by weight percentage: carbon 0.1%, manganese 0.3%, silicon 0.03%, iron 99.556%, and the balance is inevitable impurities.

[0018] In an optional embodiment, the weight ratio of Mn to Si in the chemical composition of the deposited metal after welding of the welding electrode is 8:3 to 8:4.

[0019] In the present invention:

[0020] Electrolytic manganese: Mn is an important deoxidizer and also an important alloying agent for weld metal. It has an important influence on the strength and toughness of weld metal. Mn can lower the transformation temperature from austenite to ferrite and promote the formation of AF (acicular ferrite), thereby improving the low-temperature impact toughness of the weld. However, when the addition amount is too high, the impact toughness will decrease due to the increase in tensile strength. In the present invention, through the combined action of the powder with a reasonable composition and ratio design and the welding core, the ratio of Mn to Si in the deposited metal formed by welding reaches 8:3 to 8:4. In this way, Si has a stronger deoxidizing ability before the welding molten pool solidifies, and Mn has a stronger deoxidizing ability in the later stage of the welding molten pool solidification. Moreover, it can also form MnS with the impurity element S, reducing the impurities in the weld and purifying the weld metal.

[0021] Titanium boride alloy: Currently, titanium boride alloy is not added to conventional low-temperature steel welding electrodes because its addition will have a certain impact on the welding process performance of the welding electrode. Especially if the addition amount is not well controlled and excessive titanium oxide is formed during the welding process, it will lead to insufficient hydrogen dehydrogenation ability of the weld, and instead deteriorate the low-temperature impact toughness. However, in the present invention, the inventor verified through a large number of experiments that by controlling the addition amount of the titanium boride alloy at 1% - 5% by percentage and appropriately increasing the alkalinity (raising it to 3.7 - 4.0), the inclusions generated will play an important role in the nucleation of acicular ferrite and can prevent the crystal grain size from being too large. The principle is that in the weld metal with Ti-B microalloying, the inclusions that can promote the formation of acicular ferrite are mainly the composite oxides of Ti, Si, Mn, and Al. Acicular ferrite is centered around these inclusions, and a plastic distortion zone can be formed around the inclusions. The appearance of this distortion zone reduces the total nucleation strain energy. Therefore, it can reduce the ferrite nucleation work and promote the formation of acicular ferrite, so as to meet the design requirements for the mechanical properties of the weld at the macroscopic level.

[0022] Sodium fluoride, calcium fluoride: NaF and CaF are important components in almost all basic electrodes. It can reduce the viscosity of the slag, maintain appropriate fluidity, and is beneficial to the metallurgical reaction in the molten pool and the formation of the weld. The melting point of CaF is relatively low. Under the action of high temperature, fluorine gas is generated, which can combine with H atoms to form HF and discharge from the molten pool, reducing the H content in the molten pool, being beneficial to improving the low-temperature impact toughness of the weld metal and reducing the probability of generating H pores. At the same time, in this invention, NaF which is not added to ordinary low-temperature steel electrodes is added and its addition amount is controlled. Its main function is to adsorb HF generated in the welding molten pool. The two will react to form NaHF2 and enter the slag to prevent excessive HF gas from forming pores in the weld, making the pore sensitivity and diffusible hydrogen content lower. However, too much NaF should not be added, which will deteriorate the welding process performance (such as spatter, slag detachment, etc.) of the electrode, and generate fluoride ions in the slag, breaking the Si-O bond and decreasing the viscosity of the slag, which is not conducive to the formation of short slag. In all-position welding, it is mainly reflected in the worse process stability at the end of the electrode during vertical up welding.

[0023] Nickel powder: The grain size of the deposited metal is related to the growth process of its austenite grains. The growth of austenite grains is restricted by two forces. One is the driving force for grain boundary migration, which depends on the initial grain size and its uniformity of the welding metal. The other is the resistance to grain boundary migration, which mainly comes from some dispersed trace metal alloying elements such as Ni, Mo, rare earth elements, etc. The greater the density of the dispersed particles, the greater the effect of hindering grain growth. In the electrode of this invention, since Mo has a greater influence on the tensile strength of the weld and will form MoC with C, the grain size grows rapidly after heat treatment, affecting the low-temperature impact toughness after long-term heat treatment. Therefore, compared with ordinary low-temperature steel electrodes, the addition of Mo is removed and the addition amount of Ni is increased to increase the density of dispersed particles. At the same time, as an inoculant, Ni can also refine grains, reduce segregation, promote the formation of acicular ferrite, and improve the toughness of ferrite. Nickel also increases the dislocation energy, promotes the cross-slip of screw dislocations at low temperatures, increases the work consumed by crack propagation, and controls the grain size of the deposited metal within a certain range, making the weld have reasonable tensile strength, high plasticity and toughness.

[0024] Silica fume: The main component of silica fume is SiO2, its bond energy is relatively small, and its surface tension is also relatively small. When it exists in the slag, due to its low bond energy, it is repelled to the surface layer of the slag, reducing the surface tension of the slag. For welding slag, SiO2 belongs to a surface-active substance. Whether in basic coatings or in rutile electrodes, as the proportion of silica fume in the coating increases, the droplet particle size becomes finer, and the electrode can achieve slag-wall transfer. However, when the content of SiO2 in the powder is too high, the solidification speed of the electrode slag becomes slow, and the slag belongs to long slag. During vertical and overhead welding, the molten iron and slag are easy to flow down. Therefore, the ratio of silicate in the powder is very important.

[0025] Silicon zirconium alloy: Appropriately adding silicon zirconium alloy in this invention can prevent the stress generated during the solidification of the weld seam from cracking the weld seam, increasing its crack resistance. At the same time, Zr is easy to absorb H, N, and O, especially with a strong affinity for O and H. Si also has a strong deoxidation ability in the early and middle stages of welding. As a deoxidizer, silicon zirconium alloy can also purify the impurity elements in the weld seam, playing a good role in improving the crack resistance and low-temperature toughness of the weld seam.

[0026] Marble: The main role of adding marble to the powder is to form slag, generate gas, stabilize the arc, increase the basicity of the slag, and have good desulfurization ability and indirect dephosphorization effect. The CO2 decomposed during the welding process can reduce the oxidation and nitridation of the weld seam and lower the diffusible hydrogen content. At the same time, when used in combination with other carbonates with different decomposition temperatures, it enters the molten pool before it has time to decompose completely during welding, absorbs the heat energy of the molten pool, rapidly reduces the temperature of the slag, increases the viscosity of the slag, and accelerates the solidification speed of the slag, which is beneficial for all-position welding.

[0027] Iron powder: It can improve the welding efficiency and stabilize the arc, ensuring the welding process and a high deposition efficiency.

[0028] The second object of this invention is to provide a preparation method for the above-mentioned welding rod, including the following steps:

[0029] (1) According to the proportion, add the powder of each component in the powder to the mixer. After stirring and mixing evenly, add potassium-sodium water glass with a modulus of 3.1, a viscosity of 42Be’, and a weight percentage of 20.0% - 23.0% for mixing and powder adjustment to obtain a mixed powder.

[0030] (2) Place the powder of each component of the welding core and the mixed powder obtained in step (1) in a welding rod hydraulic press. After coating and pressing, it becomes a welding rod with the powder wrapping the welding core.

[0031] (3) Bake at a low temperature of 80°C - 120°C, bake at a high temperature of 350°C - 380°C, print the characters, and package.

[0032] In an optional embodiment, in the above step (2), the percentage of the mixed powder in the total weight of the welding rod is 24% - 30%, the percentage of the welding core in the total weight of the welding rod is 70% - 76%, and the coating and pressing pressure is 45MPa - 55MPa.

[0033] In the above preparation method, by controlling means such as the addition amount of water glass, the coating pressure of the powder, the baking temperature, and the weight ratios of the mixed powder and the welding core, the arc blow force of the manufactured welding rod is concentrated, it has good stiffness during vertical and overhead welding, and has excellent all-position operation performance.

[0034] The third object of this invention is to provide a welding method, using the above-mentioned welding rod to weld the base material SA-350Gr.LF3 of a high burn-up spent fuel storage and transportation container with low-temperature steel.

[0035] In an optional embodiment, in the welding method, the welding pass temperature ≤ 250°C; the welding current is 140A - 210A; the arc voltage is 20V - 30V; the heat input is 1.8 KJ / mm - 2.8 KJ / mm.

[0036] In the above welding method, by controlling reasonable welding parameters, weld bead temperature, welding heat treatment and other means, mechanical properties with good impact toughness and stability under ultra-low temperature conditions (-101°C) are obtained.

[0037] The fourth object of the present invention is to provide a low-temperature steel welded joint for the base material SA-350Gr.LF3 of a high burn-up spent fuel storage and transportation container. The chemical composition of the weld metal of the welded joint in the as-welded state is: C 0.036% - 0.038%, Mn 0.75% - 0.83%, Si 0.38% - 0.45%, S 0.004% - 0.006%, P 0.005% - 0.006%, Ni 3.34% - 3.51%, and the balance is Fe and unavoidable impurities;

[0038] Or the chemical composition under the heat treatment condition of 620°C / 16h is: C 0.035% - 0.040%, Mn 0.77% - 0.82%, Si 0.37% - 0.42%, S 0.004% - 0.006%, P 0.004% - 0.005%, Ni 3.28% - 3.5%, and the balance is Fe and unavoidable impurities.

[0039] In an optional embodiment, welding is carried out using the above-mentioned electrode. The tensile strength of the weld metal is 485 Mpa - 655 Mpa, the diffusible hydrogen content of the weld metal is less than 4 mg / 100g, the impact energy Akv of the weld metal at -101°C under the as-welded condition is 100J - 130J, and the fracture toughness T NDT temperature ≤ -106°C, and the impact energy Akv of the weld metal at -101°C under the heat treatment condition of 620°C / 16h is 130J - 160J, and the fracture toughness T NDT temperature ≤ -106°C.

[0040] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0041] (1) By reasonably controlling the composition and proportion of the powder, when welding the base metal SA-350Gr.LF3 low-temperature steel of the high burn-up spent fuel storage and transportation container, the present invention has good welding processability, with beautiful weld formation, the slag shell can automatically tilt and fall off, and excellent operability in all-position welding; at the same time, the mechanical properties of the weld are excellent, with good impact performance and crack resistance. When adding titanium-boron alloy, silicon-zirconium alloy, and nickel powder, it can ensure that the weld formation and the impact toughness of the weld metal at ultra-low temperature conditions (-101°C) are above 100 J in both the as-welded state and the heat-treated state.

[0042] (2) When the electrode obtained by the present invention is used to weld the base metal SA-350Gr.LF3 low-temperature steel of the high burn-up spent fuel storage and transportation container, it has excellent weld properties. The diffusible hydrogen content in the deposited metal is less than 4 mg / 100 g, the tensile strength of the welded joint is 485 - 655 Mpa, the diffusible hydrogen content in the deposited metal is less than 4 mg / 100 g, the impact energy Akv of the weld metal at -101°C under as-welded conditions is 100 - 130 J, and the fracture toughness T NDT temperature ≤ -106°C, and the impact energy Akv of the weld metal at -101°C under the heat treatment conditions of 620°C / 16 h is 130 - 160 J, meeting the requirements for welding the base metal of the ultra-low temperature burn-up spent fuel storage and transportation container. Specific embodiments

[0043] To make the purpose, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the embodiments. The illustrative embodiments of the present invention and their descriptions are only used to explain the present invention and are not intended to limit the present invention.

[0044] In the following embodiments, the performance parameters of the raw materials used:

[0045] Overall requirements: particle size 30 mesh - 200 mesh, water content ≤ 5%, S ≤ 0.02%, P ≤ 0.02%;

[0046] Individual requirements: electrolytic manganese (Mn ≥ 99.5%), titanium-boron alloy (Ti ≥ 92%, B2O3 ≥ 6%), sodium fluoride (NaF ≥ 99.5%), nickel powder (Ni ≥ 99.5%), calcium fluoride (CaF ≥ 96.0%), silica powder (SiO2 ≥ 98.0%), iron powder (Fe ≥ 98.0%), silicon-zirconium alloy (Si ≥ 47%, Zr ≥ 47%), marble (CaCO3 ≥ 98%), carbon (C ≥ 99.0%), manganese (Mn ≥ 97.0%), silicon (Si ≥ 98.0%), iron (Fe ≥ 98.0%)

[0047] Example 1:

[0048] The composition components of the powder are as follows by weight: 9.5 kg of electrolytic manganese, 3.0 kg of titanium-boron alloy, 4.6 kg of sodium fluoride, 7.5 kg of nickel powder, 23.8 kg of calcium fluoride, 7.8 kg of silica powder, 12.5 kg of iron powder, 1.5 kg of silicon-zirconium alloy, and 29.8 kg of marble. The mixed powder is obtained.

[0049] The composition components of the welding core are as follows by weight: 0.05 kg of carbon, 0.35 kg of manganese, 0.03 kg of silicon, 99.50 kg of iron, and inevitable impurities brought in by the materials.

[0050] Step 1: Add the component powders of the powder into a mixer. After stirring and mixing evenly, add potassium-sodium water glass with a modulus of 3.1, a viscosity of 42 Be’, and a weight percentage of 23.0% for mixing the powder.

[0051] Step 2: Place the welding core and the mixed powder obtained in Step 1 in a welding rod hydraulic press. The weight percentage of the mixed powder in the total mass of the welding rod is 26.5%, and the weight percentage of the welding core in the total mass of the welding rod is 73.5%. The coating pressure is 48 MPa - 51 MPa. After coating and forming, a welding rod with the powder wrapping the welding core is obtained.

[0052] Step 3: Bake at a low temperature of 80 - 120 °C, bake at a high temperature of 350 - 380 °C, print the characters, and package.

[0053] Welding parameters: I = 150 - 170 A, U = 25 - 30 V, heat input = 2.2 - 2.5 (KJ / mm), interpass temperature ≤ 250 (°C), heat treatment: as-welded \ 620 * 16 h.

[0054] According to the standard requirements of ANSI / AWS B4.0M-2000(R2010) "Standard Test Methods for Mechanical Properties of Welds", the properties of the weld are detected as follows:

[0055] Chemical composition of deposited metal: (%)

[0056]

[0057] Mechanical properties of deposited metal:

[0058]

[0059] Diffusion hydrogen content: 3.9 mg / 100 g; According to the standard requirements of ASTM E208-2019 "Drop-Weight Test Method for Determining Nil-Ductility Transition Temperature of Ferritic Steels", after detection, the fracture toughness TNDT temperature of the weld deposited metal ≤ -106 °C.

[0060] Example 2:

[0061] The composition components of the powder are as follows by weight: 8 kg of electrolytic manganese, 2.4 kg of titanium-boron alloy, 4.2 kg of sodium fluoride, 7.5 kg of nickel powder, 26 kg of calcium fluoride, 6 kg of silica powder, 13 kg of iron powder, 1.3 kg of silicon-zirconium alloy, and 31.6 kg of marble. The mixed powder is obtained.

[0062] The composition components of the welding core are as follows by weight: 0.1 kg of carbon, 0.3 kg of manganese, 0.03 kg of silicon, 99.55 kg of iron, and inevitable impurities brought in by the materials.

[0063] Step 1: Add the component powders of the powder into a mixer. After stirring and mixing evenly, add potassium-sodium water glass with a modulus of 3.1, a viscosity of 42 Be', and a weight percentage of 22% for mixing the powder.

[0064] Step 2: Place the welding core and the mixed powder obtained in Step 1 in a welding rod hydraulic press. The weight percentage of the powder in the total weight of the welding rod is 25.5%, and the weight percentage of the welding core in the total weight of the welding rod is 74.5%. The coating pressure is 49 - 52 MPa. After coating and forming, a welding rod with the powder wrapping the welding core is obtained.

[0065] Step 3: Bake at a low temperature of 80°C - 120°C, bake at a high temperature of 350°C - 380°C, print the characters, and package.

[0066] Welding parameters: I = 140 A - 160 A, U = 25 V - 30 V, heat input = 1.8 - 2.2 (KJ / mm), interpass temperature ≤ 250 (°C), heat treatment: as-welded \ 620 * 16 h.

[0067] After testing, the properties of the weld are as follows:

[0068] Chemical composition of the deposited metal (%)

[0069]

[0070] Mechanical properties of the deposited metal

[0071]

[0072] Diffusion hydrogen content: 3.7 mg / 100 g; fracture toughness T NDT Temperature ≤ -106°C.

[0073] Example 3:

[0074] The composition components of the powder are as follows by weight: 9 kg of electrolytic manganese, 3.4 kg of titanium-boron alloy, 4.2 kg of sodium fluoride, 7.5 kg of nickel powder, 24 kg of calcium fluoride, 8 kg of silica powder, 12 kg of iron powder, 1.5 kg of silicon-zirconium alloy, and 30.4 kg of marble.

[0075] The composition of the welding core is as follows by weight: 0.1 kg of carbon, 0.3 kg of manganese, 0.03 kg of silicon, 99.35 kg of iron, and inevitable impurities introduced by the materials.

[0076] Step 1: Add the powder components of the flux to a mixer. After stirring and mixing evenly, add potassium-sodium water glass with a modulus of 3.1 and a viscosity of 42 Be' and a weight percentage of 26% for mixing and powder adjustment. Obtain the mixed flux powder.

[0077] Step 2: Place the welding core and the mixed flux powder obtained in Step 1 in a welding rod hydraulic press. The weight percentage of the flux powder in the total weight of the welding rod is 27.5%, and the weight percentage of the welding core in the total weight of the welding rod is 72.5%. The coating pressure is 47 - 50 MPa. After coating and forming, it is a welding rod with the flux powder wrapping the welding core.

[0078] Step 3: Bake at a low temperature of 80°C - 120°C, bake at a high temperature of 350°C - 380°C, print the characters, and package.

[0079] Welding parameters: I = 145 A - 165 A, U = 25 V - 30 V, heat input = 1.8 - 2.2 (KJ / mm), interpass temperature ≤ 250 (°C), heat treatment: as-welded \ 620 * 16 h.

[0080] After testing, the properties of the weld are as follows:

[0081] Chemical composition of the deposited metal (%)

[0082]

[0083] Mechanical properties of the deposited metal

[0084]

[0085] Diffusion hydrogen content: 3.5 mg / 100 g; fracture toughness T NDT Temperature ≤ -106°C.

[0086] In the flux powder of the welding rods in Examples 1 - 3, add titanium-boron alloy, silicon-zirconium alloy, and nickel powder alloy materials. At the same time, strictly control the contents of impurity elements S and P in the welding core that affect the brittleness of the weld and the tendency to generate cracks at a low level, so that its properties meet the technical requirements of the weld for the base metal SA-350Gr.LF3 low-temperature steel of the high-burnup spent fuel storage and transportation container, especially the ultra-low temperature impact toughness and fracture toughness T NDT Temperature ≤ -106°C requirements.

[0087] The welding electrode of the present invention has good welding processability, with beautiful weld formation and slag shells that can automatically tilt and fall off, and excellent operability in all-position welding. At the same time, it has excellent mechanical properties and can meet the requirements of nuclear power equipment manufacturing enterprises in China for welding materials of SA-350 Gr. LF3 low-temperature steel for high-burnup spent nuclear fuel storage and transportation containers.

[0088] The above specific implementation manners have further elaborated in detail the purpose, technical solutions and beneficial effects of the present invention. It should be understood that the above are only specific implementation manners of the present invention and are not used to limit the protection scope of the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A low-temperature steel electrode for the base metal SA-350 Gr.LF3 of a high burn-up spent fuel storage and transportation container, which is manufactured by wrapping a welding core with a powder, and is characterized in that, The composition components of the powder are as follows by weight: 4.5 parts - 10 parts of electrolytic manganese, 1 part - 5 parts of titanium-boron alloy, 3 parts - 12 parts of sodium fluoride, 6 parts - 12 parts of nickel powder, 15 parts - 30 parts of calcium fluoride, 4 parts - 10 parts of silica powder, 10 parts - 15 parts of iron powder, 1 part - 2.5 parts of silicon-zirconium alloy, 15 parts - 35 parts of marble; The composition components of the welding core are as follows by weight percentage: 0.02% - 0.2% of carbon, 0.1% - 0.4% of manganese, 0.01% - 0.03% of silicon, 99.5% - 99.9% of iron, and the balance is inevitable impurities.

2. The low-temperature steel electrode for the base material SA-350 Gr.LF3 of a high burnup spent fuel storage and transportation container according to claim 1, characterized in that, The composition components of the powder are as follows by weight: 8 parts - 9.5 parts of electrolytic manganese, 2.4 parts - 3.4 parts of titanium-boron alloy, 4.2 parts - 4.6 parts of sodium fluoride, 7.5 parts of nickel powder, 23.8 parts - 26 parts of calcium fluoride, 6 parts - 8 parts of silica powder, 12 parts - 13 parts of iron powder, 1.3 parts - 1.5 parts of silicon-zirconium alloy, 29.8 parts - 31.6 parts of marble; The composition components of the welding core are as follows by weight percentage: 0.05% - 0.1% of carbon, 0.3% - 0.35% of manganese, 0.03% of silicon, 99.555% - 99.559% of iron, and the balance is inevitable impurities.

3. The low-temperature steel electrode for the base material SA-350 Gr.LF3 of a high burn-up spent fuel storage and transportation container according to claim 1, characterized in that, The composition components of the powder are as follows by weight: 9.5 parts of electrolytic manganese, 3.0 parts of titanium-boron alloy, 4.6 parts of sodium fluoride, 7.5 parts of nickel powder, 23.8 parts of calcium fluoride, 7.8 parts of silica powder, 12.5 parts of iron powder, 1.5 parts of silicon-zirconium alloy, 29.8 parts of marble; The composition components of the welding core are as follows by weight percentage: 0.05% of carbon, 0.35% of manganese, 0.03% of silicon, 99.555% of iron, and the balance is inevitable impurities; Or the composition components of the powder are as follows by weight: 8 parts of electrolytic manganese, 2.4 parts of titanium-boron alloy, 4.2 parts of sodium fluoride, 7.5 parts of nickel powder, 26 parts of calcium fluoride, 6 parts of silica powder, 13 parts of iron powder, 1.3 parts of silicon-zirconium alloy, 31.6 parts of marble; The composition components of the welding core are as follows by weight percentage: 0.1% of carbon, 0.3% of manganese, 0.03% of silicon, 99.559% of iron, and the balance is inevitable impurities; Or the composition components of the powder are as follows by weight: 9 parts of electrolytic manganese, 3.4 parts of titanium-boron alloy, 4.2 parts of sodium fluoride, 7.5 parts of nickel powder, 24 parts of calcium fluoride, 8 parts of silica powder, 12 parts of iron powder, 1.5 parts of silicon-zirconium alloy, 30.4 parts of marble; The composition components of the welding core are as follows by weight percentage: 0.1% of carbon, 0.3% of manganese, 0.03% of silicon, 99.556% of iron, and the balance is inevitable impurities.

4. The low-temperature steel electrode for the base material SA-350 Gr.LF3 of a high-burnup spent fuel storage and transportation container according to claim 1, characterized in that, After welding with the welding rod, the weight ratio of Mn to Si in the deposited metal chemical composition is 8:3 - 8:

4.

5. A method for preparing a low-temperature steel electrode for the base material SA-350 Gr.LF3 of a high burn-up spent fuel storage and transportation container according to any one of claims 1 to 4, characterized in that, It includes the following steps: (1) According to the proportion, add the powder materials of each component in the powder into a mixer. After stirring and mixing evenly, add potassium-sodium water glass with a modulus of 3.1, a Baume degree of 42°Bé, and a weight percentage of 20.0% - 23.0% for mixing the powder to obtain a mixed powder; (2) Place the powder materials of each component of the welding core and the mixed powder obtained in step (1) in a welding rod hydraulic press. After coating and pressing, it forms a welding rod with the powder coating the welding core. (3) Bake at a low temperature of 80°C - 120°C, bake at a high temperature of 350°C - 380°C, print characters, and package.

6. The preparation method according to claim 5, wherein In the said step (2), the percentage of the mixed powder in the total weight of the welding rod is 24% - 30%, the percentage of the welding core in the total weight of the welding rod is 70% - 76%, and the coating and pressing pressure is 45 MPa - 55 MPa.

7. A welding method, characterized in that, Use the welding rod described in any one of claims 1 to 4 to weld the low-temperature steel of the base material SA-350 Gr.LF3 of the high-burnup spent fuel storage and transportation container.

8. The welding method according to claim 7, wherein In the said welding method, the welding pass temperature ≤ 250°C; the welding current is 140 A - 210 A; the arc voltage is 20 V - 30 V; the heat input is 1.8 KJ / mm - 2.8 KJ / mm.

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