A high-toughness manual electric arc welding electrode for cryogenic austenitic high manganese steel and a preparation method and application thereof

Abstract

The application provides a high-toughness manual electric arc welding electrode for an austenitic high manganese steel at an extremely low temperature, which is composed of a welding core and a coating wrapped outside the welding core. By optimizing the composition of the welding core, on one hand, the content of N element is optimized, so that a stable austenitic structure can be obtained to ensure the tensile strength of the weld, and the excessive N element can be avoided to produce pore defects and adversely affect the toughness; on the other hand, the content of impurity element Bi is strictly limited to avoid the adverse effects of the low-melting-point eutectic of Bi on the hot crack sensitivity and toughness of the weld, so as to improve the impact toughness of the weld at an extremely low temperature. The application also provides a preparation method of the manual electric arc welding electrode. The manual electric arc welding electrode provided by the application not only has a higher matching degree of low-temperature toughness and the impact toughness of the austenitic high manganese steel base body, but also has mechanical properties of the welded joint meeting the relevant technical requirements, thereby improving the structural safety of liquefied natural gas (LNG) storage and transportation equipment.

Description

Technical Field

[0001] This invention belongs to the technical field of ultra-low temperature high-manganese steel welding electrodes, specifically relating to a high-toughness manual arc welding electrode for ultra-low temperature austenitic high-manganese steel and its preparation method, and also relating to the application of the above-mentioned high-toughness manual arc welding electrode for ultra-low temperature austenitic high-manganese steel in the construction of LNG storage and transportation equipment. Background Technology

[0002] In recent years, with increasingly stringent international environmental protection requirements, the market demand for LNG (liquefied natural gas) powered ships has been steadily rising. Due to its promising prospects, major shipbuilding nations are fiercely competing for its materials. Ultra-low temperature austenitic high-manganese steel (Mn content 22%-28%) shares similar physical and metallurgical characteristics with 9Ni steel, ensuring good toughness reserves even at extremely low temperatures below -196℃, while also achieving basic yield strength and tensile strength at room temperature. Furthermore, the low price of Mn makes ultra-low temperature austenitic high-manganese steel the preferred material for LNG storage tanks.

[0003] The fabrication of LNG storage tanks using ultra-low temperature austenitic high-manganese steel primarily employs welding processes. Among these, manual arc welding electrodes (hereinafter referred to as welding electrodes) offer significant advantages in LNG storage tank construction due to their superior welding operation adaptability, accounting for over 50% of all welding materials used. Ultra-low temperature austenitic high-manganese steel LNG storage tanks require storage and transportation in extremely low-temperature environments. Due to the extremely low operating temperatures, the material's brittleness increases over long-term use, and its low-temperature impact toughness deteriorates, reducing its service life. This places higher demands on the impact toughness of welding electrodes under extremely low-temperature conditions.

[0004] Currently, in some existing research on welding electrodes suitable for welding LNG storage tanks, there is a common problem of insufficient impact toughness reserve in butt weld metals under extremely low temperatures. For example, patent CN118180566A provides an arc welding electrode and its preparation method suitable for ultra-low temperature high-manganese steel storage tanks, with the butt weld metal formed by the electrode having an impact toughness of 65-88J at -196℃; patent CN109623194A discloses a low-hydrogen electrode for manual arc welding of ultra-low temperature high-manganese steel, with an impact toughness of 75-102J at -196℃; patent CN113458654B discloses an ultra-low temperature high-manganese steel welding wire, electrode, and its preparation method, with an impact toughness of 83-98J at -196℃; and patent CN113458654B discloses an ultra-low temperature high-manganese steel welding wire, electrode, and its preparation method, with an impact toughness of 83-98J at -196℃. Patent 112894197A discloses a manual arc welding electrode for ultra-low temperature high-manganese steel, with an impact toughness of 80-115J at -196℃. The welding electrodes prepared using the aforementioned technical solution generally have an impact toughness below 100J at -196℃. This value does not match well with the toughness of the ultra-low temperature high-toughness austenitic high-manganese steel substrate (typically 184-195J). Insufficient electrode toughness will affect the quality of the weld metal, thereby threatening the structural safety of LNG tanks.

[0005] Based on this, a high-toughness manual arc welding electrode for ultra-low temperature austenitic high-manganese steel and its preparation method are provided. The butt weld metal formed after welding by the electrode has excellent impact toughness under ultra-low temperature conditions, which can match the impact toughness of ultra-low temperature high-toughness austenitic high-manganese steel plate. Moreover, the mechanical properties of the butt weld metal meet the technical requirements. This is of great significance for ensuring the structural safety of LNG tanks and is also a technical problem that urgently needs to be solved. Summary of the Invention

[0006] One of the objectives of this invention is to provide a high-toughness manual arc welding electrode for ultra-low temperature austenitic high-manganese steel that exhibits excellent impact toughness of butt weld metal under low temperature conditions, matches the impact toughness of ultra-low temperature high-toughness austenitic high-manganese steel plates, and whose weld joint mechanical properties meet technical requirements.

[0007] The second objective of this invention is to provide a method for preparing a high-toughness manual arc welding electrode for ultra-low temperature austenitic high-manganese steel, which exhibits excellent impact toughness of butt weld metal under low temperature conditions, matches the impact toughness of ultra-low temperature high-toughness austenitic high-manganese steel plates, and whose weld joint mechanical properties meet technical requirements.

[0008] The third objective of this invention is to provide an application of a high-toughness manual arc welding electrode for ultra-low temperature austenitic high-manganese steel.

[0009] One of the technical solutions adopted to achieve the objective of this invention is to provide a high-toughness manual arc welding electrode for ultra-low temperature austenitic high-manganese steel, which consists of a core and a coating wrapped around it. The composition of the welding core, by weight percentage, is: C 0.31%-0.46%, Si 0.02%-0.07%, Mn 26.30%-33.31%, Ni 2.75%-3.85%, Cr 3.32%-4.46%, Mo 1.03%-2.04%, N 0.40%-0.60%, S≤0.001%, P≤0.002%, Bi≤0.0003%, with the balance being Fe and unavoidable impurities.

[0010] The overall concept and inventive principle of this invention are as follows: To effectively improve the impact toughness of butt weld metal formed by manual arc welding electrodes under extremely low temperature conditions and enhance its toughness matching with the ultra-low temperature high-toughness austenitic high-manganese steel plate matrix, this invention, through extensive research and experimentation, identified the main influencing factors of impact toughness and, in conjunction with these factors, optimized the core composition of the welding electrode. Specifically: On the one hand, a stable austenitic structure is a necessary condition for ensuring excellent impact toughness of welds at extremely low temperatures. On the other hand, alloying elements determine the microstructure. To obtain a stable austenitic structure, sufficient austenitizing alloying elements (C, N, Ni, Mn, Cu, etc.) need to be added. The austenite-forming ability can be calculated using the Ni equivalent formula: Ni equivalent = Ni% + 30C% + 30N% + 0.5Mn% + 0.25Cu%. From the above Ni equivalent calculation formula, it can be seen that C and N are strong austenite-forming elements, with an austenite-forming ability 30 times that of Ni. This invention, while maintaining a C content in the weld core close to existing solutions, addresses the issue of existing solutions not adding N or adding very little N. This invention obtains a sufficiently stable austenitic structure by adding enough N, thereby improving the impact toughness of the weld metal at extremely low temperatures. The present invention sets the N content in the welding core to 0.40wt.%-0.60wt.%, which can obtain a sufficiently stable austenitic structure to ensure the tensile strength of the weld, while avoiding the adverse effect of excessive N on toughness due to porosity defects.

[0011] On the other hand, harmful elements in the core material not only affect purity but also severely impact the toughness of the weld metal at extremely low temperatures. In the core material composition of this invention, in addition to controlling the content of harmful elements S and P, the content of harmful element Bi is strictly controlled, ensuring it is far below the requirement of ≤0.002 for Bi in austenitic stainless steel welding materials as specified in API 582 Welding Guidelines for the Chemical, Petroleum and Gas Industries. Harmful element Bi is one of the main causes of hot cracking and severely affects the impact toughness of welds at low temperatures. In the weld, it usually exists as a low-melting-point eutectic Bi₂O₃ (melting point 824℃). During welding, when the molten pool heats up or cools down to the aforementioned temperature, the weld will crack at the low-melting-point eutectic containing Bi due to melting. This exacerbates the hot cracking sensitivity of the weld, thus severely affecting toughness. Therefore, the Bi content in the weld must be strictly controlled. In this invention, the Bi content in the welding core is controlled at 0.0003 wt.% or less, which significantly reduces the weld crack sensitivity and thus improves the weld impact toughness at extremely low temperatures.

[0012] Furthermore, in manual arc welding electrodes, the weight percentage of the core is 70%-80%, and the weight percentage of the coating is 20%-30%.

[0013] Furthermore, the composition of the coating, by weight percentage, is 40%-45% dolomite, 40%-45% fluorite, 3%-5% lithium fluoride, 1%-1.5% soda ash, with the balance being Fe and unavoidable impurities.

[0014] The flux coating of this invention uses an alkaline slag system, which is beneficial for removing harmful impurities such as sulfur (S) and phosphorus (P), and results in a low diffusible hydrogen content in the deposited metal. Dolomite primarily functions as a gas generator and slag former. Its main components are calcium carbonate (CaCO3) and magnesium carbonate (MgCO3). Its decomposition produces carbon dioxide and carbon monoxide gases, which protect the molten pool, increase the degree of reaction, and allow gases inside the molten pool to escape. The decomposed CaO and MgO can also act as slag-forming agents. However, excessive dolomite should be avoided, as it can lead to excessive blowing force and poor weld formation. Therefore, this invention adds 40 wt.%-45 wt.% dolomite to the flux coating to further improve electrode blowing force and slag coverage. Fluorite effectively removes hydrogen porosity, and its decomposition of CaO also acts as a slag-forming agent. Therefore, controlling the fluorite content in the flux coating to 40 wt.%-45 wt.% ensures a certain amount of slag formation and reduces hydrogen porosity.

[0015] Lithium is a strong arc-stabilizing element, resulting in low spatter and a gentle arc. When less lithium fluoride is added, arc stability decreases and spatter increases; while adding more lithium fluoride lowers the melting point of the slag, altering the overall physical properties of the slag. Therefore, the lithium fluoride content in the coating of this invention is controlled at 3wt.%-5wt.% to ensure excellent arc stability. Furthermore, 1wt.%-1.5wt.% of soda ash is added to the coating of this invention to ensure smooth electrode coating.

[0016] Furthermore, the coating also contains a binder, the amount of which is 8%-13% of the total weight of all components of the coating.

[0017] Furthermore, the binder is composed of K2O·SiO2 and Na2O·SiO2 mixed in a mass ratio of 3:1, and the modulus of the binder is 2.5-3.1.

[0018] Furthermore, the purity of the dolomite is ≥99.9%, and the particle size of the dolomite is 0.2-0.3 mm; the purity of the fluorite is ≥99.9%, and the particle size of the fluorite is 0.2-0.3 mm; the purity of the lithium fluoride is ≥99.9%, and the particle size of the lithium fluoride is 0.1-0.2 mm; the purity of the soda ash is ≥99.9%, and the particle size of the soda ash is ≤0.1 mm.

[0019] The second objective of this invention is achieved by providing a method for preparing a high-toughness manual arc welding electrode for ultra-low temperature austenitic high-manganese steel, as described in one objective of this invention, comprising the following steps: First, prepare each raw material according to the composition of the coating and mix them thoroughly. Then, add the binder and stir evenly to obtain the coating mixture. Press the coating mixture onto the surface of the welding core to obtain the welding rod.

[0020] The third objective of this invention is to provide an application of a high-toughness manual arc welding electrode for ultra-low temperature austenitic high-manganese steel as described in the first objective of this invention, or a high-toughness manual arc welding electrode for ultra-low temperature austenitic high-manganese steel prepared by the preparation method described in the second objective of this invention.

[0021] Furthermore, the high-toughness manual arc welding electrode for ultra-low temperature austenitic high-manganese steel is applied to the construction of liquefied natural gas (LNG) storage and transportation equipment. Preferably, the LNG storage and transportation equipment is an LNG-powered vessel.

[0022] Furthermore, the ultra-low temperature austenitic high-manganese steel is used with high-toughness manual arc welding electrodes for welding the substrate of liquefied natural gas (LNG) storage and transportation equipment, wherein the substrate of the LNG storage and transportation equipment is ultra-low temperature austenitic high-manganese steel.

[0023] The ultra-low temperature austenitic high-manganese steel matrix used in this invention exhibits an impact toughness of 184-195 J at -196℃. The weld metal formed using high-toughness manual arc welding electrodes on ultra-low temperature austenitic high-manganese steel provided by this invention has an impact toughness of 150-159 J at -196℃, demonstrating a higher degree of matching with the impact toughness of the ultra-low temperature austenitic high-manganese steel matrix. Furthermore, the butt weld metal formed by electrode welding has a yield strength of 433-497 MPa, a tensile strength of 672-790 MPa, and an elongation (A) of 35%-40%, meeting relevant technical requirements and improving the structural safety of liquefied natural gas (LNG) storage and transportation equipment.

[0024] Furthermore, in the welding process, a V-shaped welding groove is used, with a single-sided angle of 30°-35°, a welding current of 120-130A, a welding speed of 10-12cm / min, and an interpass temperature of 100-120℃.

[0025] Compared with the prior art, the beneficial effects of the present invention are as follows: (1) The present invention provides a high-toughness manual arc welding electrode for ultra-low temperature austenitic high-manganese steel and its preparation method. By optimizing and adjusting the composition of the welding core, on the one hand, the nitrogen content is set to 0.40 wt.%-0.60 wt.%, which can obtain a sufficiently stable austenitic structure to ensure the tensile strength of the weld, and avoid the adverse effect of excessive nitrogen on toughness due to porosity defects. On the other hand, the content of harmful element Bi is strictly controlled to effectively avoid the adverse effects of Bi's low melting point eutectic on the hot cracking sensitivity and toughness of the weld. It is controlled at 0.0003 wt.% or below to reduce the weld cracking sensitivity, thereby improving the impact toughness of the weld at ultra-low temperatures.

[0026] (2) The high-toughness manual arc welding electrode for ultra-low temperature austenitic high-manganese steel provided by this invention is applied to the welding of ultra-low temperature austenitic high-manganese steel in liquefied natural gas (LNG) storage and transportation equipment. It forms a weld metal with a sufficiently stable austenitic structure, ensuring excellent ultra-low temperature toughness. The mechanical properties of the welded joint meet the technical requirements. The impact toughness at -196℃ is 150-159J; the yield strength is 433-497MPa; the tensile strength is 672-790MPa; and the elongation A is 35%-40%. Not only is the low-temperature toughness better matched with the impact toughness of the ultra-low temperature austenitic high-manganese steel matrix, but the mechanical properties of the welded joint also meet the relevant technical requirements, improving the structural safety of LNG storage and transportation equipment. Attached Figure Description

[0027] Figure 1 This is a microstructure diagram of the butt weld metal formed by welding in Embodiment 1 of the present invention. Detailed Implementation

[0028] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments. 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.

[0029] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other.

[0030] The present invention will be further described below with reference to specific embodiments, but these are not intended to limit the scope of the invention.

[0031] The core composition of the manual arc welding electrodes provided in Embodiments 1-3 of this invention, by weight percentage, is shown in Table 1; the coating composition, by weight percentage, is shown in Table 2.

[0032] Table 1

[0033] In Table 1 above, to ensure that the Bi content in the welding core meets the expected requirements (Bi≤0.0003wt.%), this invention controls the Bi content in each ferroalloy raw material (C, Si, Mn, Ni, Cr, Mo, etc.) during the smelting process of the welding core, so that Bi≤0.0001wt.%; furthermore, through multiple smelting and purification processes, the addition of smelting additives, and control of cooling rate, the precipitation and aggregation of Bi are promoted, which facilitates subsequent removal processes, thereby gradually reducing the Bi content in the steel. After each smelting, the molten steel is tested to ensure that the Bi content meets the expected requirements.

[0034] Table 2

[0035] In Table 2 above, the purity of dolomite is ≥99.9%, and the particle size of dolomite is 0.2-0.3 mm; the purity of fluorite is ≥99.9%, and the particle size of fluorite is 0.2-0.3 mm; the purity of lithium fluoride is ≥99.9%, and the particle size of lithium fluoride is 0.1-0.2 mm; and the purity of soda ash is ≥99.9%, and the particle size of soda ash is ≤0.1 mm.

[0036] In the preparation of the drug coating, a binder is added to each raw material of the drug coating at a dosage of 8 wt.%-13 wt.%. The binder is composed of K2O·SiO2 and Na2O·SiO2 mixed in a mass ratio of 3:1, and the modulus of the binder is 2.5-3.1.

[0037] Example 1 This embodiment provides a high-toughness manual arc welding electrode for ultra-low temperature austenitic high-manganese steel. The electrode consists of a 70wt% core and a 30wt% flux coating, with the flux coating covering the core. The composition of the welding core, by weight percentage, is: C 0.31 wt.%, Si 0.02 wt.%, Mn 26.30 wt.%, Ni 2.75 wt.%, Cr 3.32 wt.%, Mo 1.03 wt.%, N 0.40 wt.%, S 0.001 wt.%, P 0.002 wt.%, Bi 0.0003 wt.%, with the balance being Fe and unavoidable impurities.

[0038] The composition of the coating, by weight percentage, is 40 wt.% dolomite, 40 wt.% fluorite, 3 wt.% lithium fluoride, 1 wt.% soda ash, with the balance being Fe and unavoidable impurities.

[0039] The preparation method of manual arc welding electrode includes: first, dispensing and mixing the components according to the composition of the coating, then adding a binder accounting for 9wt% of the chemical composition of the coating, stirring evenly, and then pressing it onto the surface of the welding core to obtain a welding electrode with a diameter of Φ4.0mm.

[0040] Figure 1 This is a microstructure image of the butt weld metal obtained in this embodiment. Figure 1 It can be seen that the microstructure of the butt weld metal obtained after welding in this embodiment is 100% austenitic.

[0041] Example 2 This embodiment provides a high-toughness manual arc welding electrode for ultra-low temperature austenitic high-manganese steel. The electrode consists of a 75wt% core and a 25wt% flux coating, with the flux coating covering the core. The composition of the welding core, by weight percentage, is: C 0.4 wt.%, Si 0.06 wt.%, Mn 29.23 wt.%, Ni 3.05 wt.%, Cr 4.01 wt.%, Mo 1.56 wt.%, N 0.50 wt.%, S 0.0008 wt.%, P 0.001 wt.%, Bi 0.0002 wt.%, with the balance being Fe and unavoidable impurities.

[0042] The composition of the coating, by weight percentage, is 42 wt.% dolomite, 43 wt.% fluorite, 4 wt.% lithium fluoride, 1.2 wt.% soda ash, with the balance being Fe and unavoidable impurities.

[0043] The preparation method of the manual arc welding electrode includes: first, mixing the components according to the composition of the coating, then adding a binder accounting for 10wt% of the chemical composition of the coating, stirring evenly, and then pressing it onto the surface of the core to obtain a welding electrode with a diameter of Φ4.0mm. In this embodiment, the microstructure of the butt weld metal obtained after welding is 100% austenitic.

[0044] Example 3 This embodiment provides a high-toughness manual arc welding electrode for ultra-low temperature austenitic high-manganese steel. The electrode consists of an 80wt% core and a 20wt% flux coating, with the flux coating covering the core. The composition of the welding core, by weight percentage, is: C 0.46 wt.%, Si 0.07 wt.%, Mn 33.31 wt.%, Ni 3.85 wt.%, Cr 4.46 wt.%, Mo 2.04 wt.%, N 0.60 wt.%, S 0.0009 wt.%, P 0.0015 wt.%, Bi 0.0003 wt.%, with the balance being Fe and unavoidable impurities.

[0045] The composition of the coating, by weight percentage, is 45 wt.% dolomite, 45 wt.% fluorite, 5 wt.% lithium fluoride, 1.5 wt.% soda ash, with the balance being Fe and unavoidable impurities.

[0046] The preparation method of the manual arc welding electrode includes: first, mixing the components according to the composition of the coating, then adding a binder accounting for 12wt% of the chemical composition of the coating, stirring evenly, and then pressing it onto the surface of the core to obtain a welding electrode with a diameter of Φ4.0mm. In this embodiment, the microstructure of the butt weld metal obtained after welding is 100% austenitic.

[0047] Application performance testing The manual arc welding electrodes prepared in Examples 1-3 were used for welding ultra-low temperature austenitic high-manganese steel plates. The mechanical properties of the ultra-low temperature austenitic high-manganese steel plates are as follows: tensile strength of 485 MPa, yield strength of 788 MPa, elongation A=44%; and the average impact energy Akv at -196℃ is 184 J.

[0048] The ultra-low temperature austenitic high-manganese steel plate is 20mm thick and 500mm long; the welding bevel is V-shaped with a single-sided angle of 30°. The welding process parameters are as follows: welding current is 120-130A, welding speed is 10-12 cm / min, and interpass temperature is 100-120℃.

[0049] The mechanical property test results of the butt weld metals formed by welding in each embodiment are shown in Table 3 below.

[0050] Table 3

[0051] It can be seen from Table 3 above that The manual arc welding electrode provided by this invention is applied to the welding of ultra-low temperature austenitic high-manganese steel matrix. It forms a weld metal with a sufficiently stable austenitic structure, ensuring excellent ultra-low temperature toughness. Furthermore, the mechanical properties of the weld joint meet technical requirements: impact toughness of 150-159 J, yield strength of 433-497 MPa, tensile strength of 672-790 MPa, and elongation (A) of 35%-40% at -196℃. The manual arc welding electrode provided by this invention not only has a higher degree of matching between low-temperature toughness and impact toughness of ultra-low temperature austenitic high-manganese steel matrix, but also the mechanical properties of the butt weld metal formed meet relevant technical requirements, effectively improving the structural safety of liquefied natural gas (LNG) storage and transportation equipment.

[0052] The above are merely preferred embodiments of the present invention and are not intended to limit the implementation methods and protection scope of the present invention. Those skilled in the art should recognize that any equivalent substitutions and obvious changes made based on the content of this specification should be included within the protection scope of the present invention.

Claims

1. An application of a high-toughness manual arc welding electrode for ultra-low temperature austenitic high-manganese steel, characterized in that... The high-toughness manual arc welding electrode for ultra-low temperature austenitic high-manganese steel is used for welding the substrate of liquefied natural gas (LNG) storage and transportation equipment. The substrate of the LNG storage and transportation equipment is ultra-low temperature austenitic high-manganese steel, and the impact toughness of the ultra-low temperature austenitic high-manganese steel substrate is 184-195J at -196℃. The high-toughness manual arc welding electrode consists of a core and a coating. The core accounts for 70%-80% of the weight, and the coating accounts for 20%-30% of the weight. The composition of the welding core, by weight percentage, is: C 0.31%-0.46%, Si 0.02%-0.07%, Mn 26.30%-33.31%, Ni 2.75%-3.85%, Cr 3.32%-4.46%, Mo 1.03%-2.04%, N 0.60%, S≤0.001%, P≤0.002%, Bi≤0.0003%, with the balance being Fe and unavoidable impurities; The Bi content in the welding core is ≤0.0003 wt.% is achieved by the following method: during the smelting process of the welding core, the Bi content in each ferroalloy raw material is controlled to be ≤0.0001 wt.%, and the Bi content in the steel is gradually reduced through multiple smelting and purification treatments. The Bi content is ensured to meet the expected requirements through repeated testing. The composition of the coating, by weight percentage, is: 40%-45% dolomite, 40%-45% fluorite, 3%-5% lithium fluoride, 1%-1.5% soda ash, with the balance being Fe and unavoidable impurities. In the welding process, a V-shaped welding groove is used, with a single-sided angle of 30°-35°, a welding current of 120-130A, a welding speed of 10-12cm / min, and an interpass temperature of 100-120℃. The weld metal formed by high-toughness manual arc welding electrodes has an impact toughness of 150-159J at -196℃.

2. The application according to claim 1, characterized in that, The coating also contains a binder, which is used at a rate of 8%-13% of the total weight of all components of the coating.

3. The application according to claim 2, characterized in that, The binder is composed of K2O·SiO2 and Na2O·SiO2 mixed in a mass ratio of 3:1, and the modulus of the binder is 2.5-3.

1.

4. The application according to claim 3, characterized in that, The dolomite has a purity ≥99.9% and a particle size of 0.2-0.3 mm; the fluorite has a purity ≥99.9% and a particle size of 0.2-0.3 mm; the lithium fluoride has a purity ≥99.9% and a particle size of 0.1-0.2 mm; and the soda ash has a purity ≥99.9% and a particle size of ≤0.1 mm.

5. A method for preparing a high-toughness manual arc welding electrode for ultra-low temperature austenitic high-manganese steel, wherein the high-toughness manual arc welding electrode is the high-toughness manual arc welding electrode used in any one of claims 1-4, characterized in that... The preparation method includes the following steps: First, prepare each raw material according to the composition of the coating and mix them thoroughly. Then, add the binder and stir evenly to obtain the coating mixture. Press the coating mixture onto the surface of the welding core to obtain the welding rod.

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