High-toughness manual arc welding electrode for extremely-low-temperature austenite high-manganese steel and preparation method and application of high-toughness manual arc welding electrode

Abstract

The invention provides a high-toughness manual arc welding rod for extremely-low-temperature austenite high-manganese steel. The high-toughness manual arc welding rod is composed of a core wire and a coating wrapping the core wire. The composition of the core wire is optimized and adjusted, on one hand, the content of the N element is optimized, an enough stable austenite structure can be obtained, the tensile strength of a weld joint is ensured, and the adverse effect on toughness caused by the pore defect generated by excessive N element can be avoided; and on the other hand, the content of the impurity element Bi is strictly limited, the adverse effect of low-melting-point eutectic of Bi on the hot crack sensitivity and toughness of the weld joint is avoided, and therefore the impact toughness of the weld joint at the extremely low temperature is improved. The invention further provides a preparation method of the manual arc welding rod. According to the manual electric arc welding rod, the low-temperature toughness is higher in matching degree with the impact toughness of an extremely-low-temperature austenite high manganese steel matrix, the mechanical property of a welding joint also meets related technical requirements, and then the structural safety of LNG storage and transportation equipment is improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of ultra-low temperature high manganese steel welding rods, and specifically relates to a high-toughness manual arc welding rod for ultra-low temperature austenitic high manganese steel and a preparation method thereof, and also relates to the application of the high-toughness manual arc welding rod for ultra-low temperature austenitic high manganese steel in the construction of LNG storage and transportation equipment. Background Art

[0002] In recent years, as the international community has increasingly stringent environmental protection requirements, the market demand for LNG (liquefied natural gas) powered ships has been showing a clear upward trend. It is precisely because of its broad prospects that major shipbuilding countries have launched fierce competition around its materials. Ultra-low temperature austenitic high manganese steel (Mn content is 22%-28%) has the same physical metallurgical characteristics as 9Ni steel, which ensures that this type of steel has good toughness reserves under extremely low temperature conditions below -196℃, and also reaches basic yield and tensile strength at room temperature. In particular, the price of Mn element is low. Therefore, ultra-low temperature austenitic high manganese steel is the preferred material for LNG storage tank steel.

[0003] The production of LNG storage tanks with ultra-low temperature austenitic high manganese steel mainly adopts welding technology, among which manual arc welding electrodes (hereinafter referred to as welding electrodes) have outstanding advantages in the construction process of LNG storage tanks due to their good adaptability to welding operations, accounting for more than 50% of all welding materials. Ultra-low temperature austenitic high manganese steel LNG storage tanks need to be stored and transported in an extremely low temperature environment. Due to the extremely low working environment temperature, the brittleness of the product material will increase during long-term use, and the low-temperature impact toughness will deteriorate, reducing the service life. This puts higher requirements on the impact toughness of the welding rod under extremely low temperature conditions.

[0004] At present, in some existing research and disclosure of welding applications of welding rods suitable for welding LNG storage tanks, there is a common problem of insufficient impact toughness reserve of butt weld metal under extremely low temperature conditions. For example, the patent with publication number CN118180566A provides an arc welding rod suitable for ultra-low temperature high manganese steel storage tanks and a preparation method thereof, and the butt weld metal formed by welding with the welding rod has an impact toughness of 65-88J at -196℃; the patent with publication number CN 109623194 A discloses a low-hydrogen type welding rod for manual arc welding of ultra-low temperature high manganese steel, and the impact toughness at -196℃ is 75-102J; the patent with publication number CN 113458654 B discloses an ultra-low temperature high manganese steel welding wire, welding rod and preparation method thereof, and the impact toughness at -196℃ is 83-98J; the patent with publication number CN 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 electrode prepared by the above technical solution generally has an impact toughness of less than 100J at -196℃, which is not well matched with the toughness of the ultra-low temperature high-toughness austenitic high manganese steel plate substrate (usually 184-195J). Insufficient toughness of the electrode will affect the quality of the weld metal, thereby threatening the safety of the LNG tank structure.

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

[0006] One of the purposes of the present invention is to provide a high-toughness manual arc welding electrode for ultra-low temperature austenitic high manganese steel, which has excellent impact toughness of butt weld metal under low temperature conditions and can match the impact toughness of ultra-low temperature high-toughness austenitic high manganese steel plates, and the mechanical properties of the weld joint meet the technical requirements.

[0007] The second purpose of the present invention is to provide a method for preparing a high-toughness manual arc welding electrode for ultra-low temperature austenitic high manganese steel, which has excellent impact toughness of butt weld metal under low temperature conditions, can match the impact toughness of ultra-low temperature high-toughness austenitic high manganese steel plate, and the mechanical properties of the weld joint meet the technical requirements.

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

[0009] The technical solution adopted by the present invention to achieve one of the purposes is: to provide a high-toughness manual arc welding electrode for extremely low-temperature austenitic high-manganese steel, which is composed of a welding core and a coating wrapped on the outside; The composition of the welding core is calculated by weight percentage, C is 0.31%-0.46%, Si is 0.02%-0.07%, Mn is 26.30%-33.31%, Ni is 2.75%-3.85%, Cr is 3.32%-4.46%, Mo is 1.03%-2.04%, N is 0.40%-0.60%, S≤0.001%, P≤0.002%, Bi≤0.0003%, and the balance is Fe and unavoidable impurities.

[0010] The overall idea and inventive principle of the present invention are as follows: In order to effectively improve the impact toughness of the butt weld metal formed by the manual arc welding electrode under extremely low temperature conditions, and improve its matching degree with the extremely low temperature high toughness austenitic high manganese steel plate matrix in terms of toughness, the present invention has determined the main influencing factors of impact toughness through a large number of research experiments, and combined with the relevant influencing factors, optimized the design of the welding core component of the welding rod, specifically: On the one hand, stable austenite structure is a necessary condition to ensure that the weld has excellent impact toughness at extremely low temperatures. At the same time, alloy elements determine the structure. In order to obtain a stable austenite structure, it is necessary to add enough alloy elements (C, N, Ni, Mn, Cu, etc.) to strengthen austenitization. The austenite forming ability can refer to the Ni equivalent calculation formula: Ni equivalent = Ni% + 30C% + 30N% + 0.5Mn% + 0.25Cu%. It can be seen from the above Ni equivalent calculation formula that C and N are strong austenite forming elements, and their austenite forming ability is 30 times that of Ni. Under the premise of keeping the C content in the welding core close to that of the existing solution, the present invention obtains sufficient stable austenite structure by adding enough N elements, aiming at the situation that the existing solution does not add N elements or the amount of N elements added is very small, 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 not only obtain a sufficiently stable austenite structure to ensure the tensile strength of the weld, but also avoid excessive N element from generating pore defects and bringing adverse effects on toughness.

[0011] On the other hand, harmful elements in the welding core composition will not only affect the purity, but also seriously affect the toughness of the weld metal at extremely low temperatures. In the welding core composition of the present invention, in addition to controlling the content of harmful elements S and P, the content of harmful element Bi is strictly controlled to make it far lower than the requirement of Bi≤0.002 in austenitic stainless steel welding materials stipulated in the "API582 Welding Guidelines for Chemical, Petroleum and Natural Gas Industries". Harmful element Bi is one of the main reasons for causing hot cracks and seriously affecting the impact toughness of welds at low temperatures. It usually exists in the form of low-melting eutectic Bi2O3 (with a melting point of 824°C) in the weld. During the welding process, when the molten pool is heated or cooled through the above temperature, the weld will crack at the low-melting eutectic containing Bi due to its melting, which will aggravate the thermal crack sensitivity of the weld, thereby seriously affecting the toughness, so the Bi content in the weld should be more strictly controlled. In the present invention, the Bi content in the welding core is controlled at 0.0003wt.% or less, which significantly reduces the crack sensitivity of the weld, thereby improving the impact toughness of the weld at extremely low temperatures.

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

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

[0014] The coating of the present invention adopts an alkaline slag system, which is conducive to removing harmful impurities such as S and P, and the content of diffusible hydrogen in the deposited metal is low. Among them, dolomite mainly acts as gasification and slag making. The main components of dolomite are calcium carbonate (CaCO3) and magnesium carbonate (MgCO3). Its decomposition produces carbon dioxide and carbon monoxide gas, which can protect the molten pool, increase the degree of reaction, and discharge the gas inside the molten pool. The decomposed CaO and MgO can also be used as slag making agents. However, dolomite is not easy to be excessive, otherwise it will cause excessive blowing force and poor weld formation. Therefore, the present invention adds 40 wt.%-45wt.% of dolomite to the coating to further improve the blowing force of the electrode and the coverage of the slag. Fluorite can effectively remove hydrogen pores, and fluorite decomposition of CaO is also a slag making agent. Therefore, the fluorite content in the coating is controlled to be 40 wt.%-45wt.%, to ensure a certain slag making amount and reduce the hydrogen porosity.

[0015] Lithium is a strong arc-stabilizing element, which reduces spatter and makes the arc soft. When less lithium fluoride is added, the arc stability decreases and the spatter increases; when more lithium fluoride is added, lithium will cause the melting point of the slag to decrease, causing the overall physical properties of the slag to change. Therefore, the lithium fluoride content in the coating of the present invention is controlled at 3wt.%-5wt.%, ensuring excellent arc stability. In addition, 1wt.%-1.5wt.% of soda ash is also added to the coating of the present invention to ensure the smooth pressure coating of the electrode.

[0016] Furthermore, a binder is added to the drug coating, and the amount of the binder is 8%-13% of the total weight of the components of the drug coating.

[0017] Furthermore, the binder is formed by mixing K2O·SiO2 and Na2O·SiO2 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 0.2-0.3mm; the purity of the fluorite is ≥99.9%, and the particle size of the fluorite is 0.2-0.3mm; the purity of the lithium fluoride is ≥99.9%, and the particle size of the lithium fluoride is 0.1-0.2mm; the purity of the soda ash is ≥99.9%, and the particle size of the soda ash is ≤0.1mm.

[0019] The technical solution adopted by the present invention to achieve the second purpose is: to provide a method for preparing a high-toughness manual arc welding electrode for ultra-low temperature austenitic high-manganese steel according to one of the purposes of the present invention, comprising the following steps: Firstly, various raw materials are prepared according to the composition of the coating and fully mixed, then a binder is added and stirred evenly to obtain a coating mixture; the coating mixture is pressed onto the surface of the welding core to obtain a welding rod.

[0020] The technical solution adopted by the present invention to achieve the third purpose is: to provide an application of a high-toughness manual arc welding electrode for ultra-low temperature austenitic high manganese steel according to one of the purposes of the present 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 purpose of the present invention.

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

[0022] Furthermore, 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, and the substrate of the liquefied natural gas (LNG) storage and transportation equipment is ultra-low temperature austenitic high manganese steel.

[0023] The impact toughness of the ultra-low temperature austenitic high manganese steel matrix used in the welding of the present invention is 184-195J at -196°C, and the impact toughness of the weld metal formed by the ultra-low temperature austenitic high manganese steel high toughness manual arc welding electrode provided by the present invention is 150-159J at -196°C, which is more matched with the impact toughness of the ultra-low temperature austenitic high manganese steel matrix. In addition, the yield strength of the butt weld metal formed by electrode welding is 433-497MPa, the tensile strength is 672-790MPa, the elongation A is 35%-40%, and the mechanical properties also meet the relevant technical requirements, which can improve the structural safety of liquefied natural gas LNG storage and transportation equipment.

[0024] Furthermore, in the welding, a V-shaped welding groove is used, the single-side angle is 30°-35°, the welding current is 120-130A, the welding speed is controlled at 10-12cm / min, and the interpass temperature is 100-120°C.

[0025] Compared with the prior art, the present invention has the following beneficial effects: (1) The present invention provides a high-toughness manual arc welding electrode for ultra-low temperature austenitic high-manganese steel and a preparation method thereof. By optimizing and adjusting the composition of the welding core, on the one hand, the N element content is set to 0.40 wt.%-0.60wt.%, which can not only obtain a sufficiently stable austenite structure to ensure the tensile strength of the weld, but also avoid excessive N elements from generating pore defects and bringing adverse effects on toughness. On the other hand, the content of the harmful element Bi is strictly controlled to effectively avoid the adverse effects of Bi's low melting point eutectic on the hot crack sensitivity and toughness of the weld, and control it to 0.0003wt.% or less, reduce the crack sensitivity of the weld, and thus improve 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 the present invention is applied to the welding of ultra-low temperature austenitic high manganese steel in liquefied natural gas (LNG) storage and transportation equipment, and the weld metal has a sufficiently stable austenitic structure, ensuring excellent ultra-low temperature toughness, and the mechanical properties of the welded joint meet the technical requirements, with an impact toughness of 150-159J at -196°C, a yield strength of 433-497MPa, a tensile strength of 672-790MPa, and an elongation A of 35%-40%. Not only is the low-temperature toughness more compatible 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, thereby improving the structural safety of liquefied natural gas (LNG) storage and transportation equipment. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 This is a microstructure diagram of the butt weld metal formed by welding in Example 1 of the present invention. DETAILED DESCRIPTION

[0028] The technical solution of the present invention will be clearly and completely described below in conjunction with the embodiments. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0029] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments may be combined with each other.

[0030] The present invention will be further described below in conjunction with specific embodiments, but the present invention is not limited thereto.

[0031] The welding core components of the manual arc welding electrodes provided in Examples 1-3 of the present invention are calculated by weight percentage, as shown in Table 1; the coating components are calculated by weight percentage, as shown in Table 2.

[0032] Table 1

[0033] In Table 1 above, in order to ensure that the Bi content in the welding core reaches the expected requirement (Bi≤0.0003wt.%), the present 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 to make Bi≤0.0001 wt.%; further, through multiple smelting and purification treatments, adding smelting additives, controlling the cooling rate, etc., the precipitation and aggregation of the Bi element are promoted, which is convenient for subsequent removal treatment, and then the Bi content in the steel is gradually reduced. After each smelting, the molten steel is tested to ensure that the Bi content reaches the expected requirement.

[0034] Table 2

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

[0036] During the preparation of the drug coating, a binder is added to the raw materials of the drug coating in an amount of 8wt.%-13 wt.%. The binder is a mixture of K2O·SiO2 and Na2O·SiO2 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 is composed of 70wt% of a welding core and 30wt% of a coating, and the coating is wrapped around the welding core; The components of the welding core are, by weight percentage, 0.31 wt.% of C, 0.02 wt.% of Si, 26.30 wt.% of Mn, 2.75 wt.% of Ni, 3.32 wt.% of Cr, 1.03 wt.% of Mo, 0.40 wt.% of N, 0.001 wt.% of S, 0.002 wt.% of P, 0.0003 wt.% of Bi, and the balance is Fe and unavoidable impurities.

[0038] The components of the coating are calculated by weight percentage: 40 wt.% of dolomite, 40 wt.% of fluorite, 3 wt.% of lithium fluoride, 1 wt.% of soda ash, and the remainder is Fe and unavoidable impurities.

[0039] The preparation method of a manual arc welding electrode comprises: firstly preparing materials according to the components of the coating, mixing, then adding a binder accounting for 9wt% of the chemical components of the coating, stirring evenly, and then pressing and coating it on the surface of the welding core to obtain a welding rod with a diameter of Φ4.0mm.

[0040] Figure 1 The microstructure of the butt weld metal obtained by welding in this embodiment is shown in FIG. Figure 1 It can be seen that the microstructure of the butt weld metal obtained after welding in this embodiment is 100% full austenite structure.

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

[0042] The components of the coating are calculated by weight percentage: 42 wt.% of dolomite, 43 wt.% of fluorite, 4 wt.% of lithium fluoride, 1.2 wt.% of soda ash, and the remainder is Fe and unavoidable impurities.

[0043] The preparation method of the manual arc welding electrode comprises: firstly preparing materials according to the composition of the coating, mixing, then adding a binder accounting for 10wt% of the chemical components of the coating, stirring evenly, and then pressing and coating the surface of the welding core to obtain a welding rod with a diameter of Φ4.0mm. The microstructure of the butt weld metal obtained after welding in this embodiment is 100% full austenite structure.

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

[0045] The components of the coating are calculated by weight percentage: 45 wt.% of dolomite, 45 wt.% of fluorite, 5 wt.% of lithium fluoride, 1.5 wt.% of soda ash, and the remainder is Fe and unavoidable impurities.

[0046] The preparation method of the manual arc welding electrode comprises: firstly preparing materials according to the composition of the coating, mixing, then adding a binder accounting for 12wt% of the chemical components of the coating, stirring evenly, and then pressing and coating the surface of the welding core to obtain a welding rod with a diameter of Φ4.0mm. The microstructure of the butt weld metal obtained after welding in this embodiment is 100% full austenite structure.

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

[0048] The thickness of the ultra-low temperature austenitic high manganese steel plate is 20mm and the length is 500mm; the welding groove is V-shaped and the single-sided angle is 30°. The process parameters of the welding process 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 metal formed by welding in various embodiments 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 the present invention is applied to the welding of an extremely low temperature austenitic high manganese steel substrate, and the formed weld metal has a sufficiently stable austenitic structure, ensuring excellent extremely low temperature toughness, and the mechanical properties of the welded joint meet the technical requirements, with an impact toughness of 150-159J at -196°C, a yield strength of 433-497MPa, a tensile strength of 672-790MPa, and an elongation A of 35%-40%. The manual arc welding electrode provided by the present invention not only has a higher matching degree of low temperature toughness with the impact toughness of the extremely low temperature austenitic high manganese steel substrate, but also the mechanical properties of the butt weld metal formed by welding also meet the relevant technical requirements, and can effectively improve the structural safety of liquefied natural gas LNG storage and transportation equipment.

[0052] The above are only 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 be aware that all solutions obtained by equivalent substitutions and obvious changes made using the contents of the specification of the present invention should be included in the protection scope of the present invention.

Claims

1. A high-toughness manual arc welding electrode for extremely low temperature austenitic high manganese steel, characterized in that: It consists of a welding core and a coating wrapped around it. The composition of the welding core is calculated by weight percentage, C is 0.31%-0.46%, Si is 0.02%-0.07%, Mn is 26.30%-33.31%, Ni is 2.75%-3.85%, Cr is 3.32%-4.46%, Mo is 1.03%-2.04%, N is 0.40%-0.60%, S≤0.001%, P≤0.002%, Bi≤0.0003%, and the balance is Fe and unavoidable impurities.

2. The high-toughness manual arc welding electrode for ultra-low temperature austenitic high manganese steel according to claim 1, characterized in that: In manual arc welding electrodes, the weight percentage of the welding core is 70%-80%, and the weight percentage of the coating is 20%-30%.

3. The high-toughness manual arc welding electrode for ultra-low temperature austenitic high manganese steel according to claim 1, characterized in that: The components of the coating are calculated by weight percentage as follows: 40%-45% dolomite, 40%-45% fluorite, 3%-5% lithium fluoride, 1%-1.5% soda ash, and the remainder is Fe and unavoidable impurities.

4. The high-toughness manual arc welding electrode for ultra-low temperature austenitic high manganese steel according to claim 3, characterized in that: The medicine coating is further added with a binder, and the amount of the binder is 8%-13% of the total weight of the components of the medicine coating.

5. The high-toughness manual arc welding electrode for ultra-low temperature austenitic high manganese steel according to claim 4, characterized in that: The binder is prepared by mixing K2O·SiO2 and Na2O·SiO2 in a mass ratio of 3:1, and the modulus of the binder is 2.5-3.

1.

6. The high-toughness manual arc welding electrode for ultra-low temperature austenitic high manganese steel according to claim 3, characterized in that: The purity of the dolomite is ≥99.9%, and the particle size of the dolomite is 0.2-0.3mm; the purity of the fluorite is ≥99.9%, and the particle size of the fluorite is 0.2-0.3mm; the purity of the lithium fluoride is ≥99.9%, and the particle size of the lithium fluoride is 0.1-0.2mm; the purity of the soda ash is ≥99.9%, and the particle size of the soda ash is ≤0.1mm.

7. The method for preparing a high-toughness manual arc welding electrode for ultra-low temperature austenitic high manganese steel according to any one of claims 1 to 6, characterized in that: The following steps are involved: Firstly, various raw materials are prepared according to the composition of the coating and fully mixed, then a binder is added and stirred evenly to obtain a coating mixture; the coating mixture is pressed onto the surface of the welding core to obtain a welding rod.

8. Use of the high-toughness manual arc welding electrode for extremely low temperature austenitic high manganese steel according to any one of claims 1 to 6 or the high-toughness manual arc welding electrode for extremely low temperature austenitic high manganese steel prepared by the preparation method according to claim 7, characterized in that: 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.

9. The use according to claim 8, characterized in that: The high-toughness manual arc welding electrode for extremely low-temperature austenitic high-manganese steel is used for welding the substrate of liquefied natural gas (LNG) storage and transportation equipment, and the substrate of the liquefied natural gas (LNG) storage and transportation equipment is extremely low-temperature austenitic high-manganese steel.

10. The use according to claim 9, characterized in that: In the welding, a V-shaped welding groove is adopted, the single-side angle is 30°-35°, the welding current is 120-130A, the welding speed is controlled at 10-12cm / min, and the interpass temperature is 100-120°C.

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