620mpa grade low alloy steel electrode for super low hydrogen coating for generator set and its preparation method, deposited metal

Abstract

The application relates to a 620MPa-grade ultra-low-hydrogen coating low-alloy steel electrode for a generator set and a preparation method and deposited metal thereof, and belongs to the technical field of welding. The chemical components of the coating include dolomite, lithium carbonate, barium carbonate, magnesite, fluorite, ferrosilicon, nickel powder, ferromolybdenum, metallic chromium, potassium fluoborate, aluminum-magnesium alloy, sodium alginate and soda ash; in terms of mass parts, the dolomite is 100-200 parts, the lithium carbonate is 100-150 parts, the magnesite is 100-200 parts, the fluorite is 300-350 parts, the ferrosilicon is 100-150 parts, the nickel powder is 10-20 parts, the ferromolybdenum is 10-20 parts, the metallic chromium is 5-10 parts and the aluminum-magnesium alloy is 1-3 parts. The electrode has excellent mechanical properties, the arc is stable during welding of the electrode, the appearance is beautiful, the electrode deposited metal has good crack resistance, and the weld metal has chemical components and mechanical properties equivalent to those of steel.

Description

Technical Field

[0001] This application relates to the field of welding technology, and in particular to a 620MPa grade low alloy steel welding electrode with an ultra-low hydrogen coating for generator sets, its preparation method, and the deposited metal. Background Technology

[0002] Welding electrodes are mainly used for welding steel components of conventional island steam and feedwater circuit equipment in nuclear power plants, as well as feedwater pipelines and high-pressure heaters in high-parameter thermal power generation equipment.

[0003] However, the mechanical properties of the weld metal deposited by the current welding electrodes are difficult to meet the construction needs of my country's nuclear power projects, making it difficult to achieve the localization of the welding electrodes. Furthermore, foreign welding electrodes are expensive, communication and supervision during the production process are difficult, the production cycle is long, and the procurement risk is high. Summary of the Invention

[0004] This application provides a 620MPa grade low-alloy steel welding electrode with ultra-low hydrogen coating for generator sets, its preparation method, and the deposited metal, to solve the following technical problem: how to improve the mechanical properties of the weld metal of the welding electrode.

[0005] In a first aspect, embodiments of this application provide a 620MPa grade low-alloy steel welding electrode with an ultra-low hydrogen coating for generator sets. The welding electrode comprises a core and a coating covering at least a portion of the surface of the core. The chemical composition of the coating includes: dolomite, lithium carbonate, barium carbonate, magnesia, fluorite, ferrosilicon, nickel powder, ferromolybdenum, metallic chromium, potassium fluoroborate, aluminum-magnesium alloy, sodium alginate, and soda ash; wherein, by mass,

[0006] The composition is as follows: 100-200 parts dolomite, 100-150 parts lithium carbonate, 100-200 parts magnesite, 300-350 parts fluorite, 100-150 parts ferrosilicon, 10-20 parts nickel powder, 10-20 parts ferromolybdenum, 5-10 parts metallic chromium, and 1-3 parts aluminum-magnesium alloy.

[0007] Optionally, the barium carbonate is 200 to 300 parts, the potassium fluoroborate is 1 to 4 parts, the sodium alginate is 1 to 15 parts, and the soda ash is 5 to 10 parts.

[0008] Optionally, the chemical composition of the welding core includes: carbon, manganese, silicon, nickel, molybdenum, chromium, niobium, copper, sulfur, phosphorus, and the base element Fe; wherein, by mass,

[0009] Carbon is 0.07 to 0.12 parts, manganese is 0.90 to 1.50 parts, silicon is 0.05 to 0.10 parts, nickel is 0.50 to 1.00 parts, molybdenum is 0.01 to 0.10 parts, chromium is 0.01 to 0.10 parts, niobium is 0.01 to 0.10 parts, copper is 0.50 to 0.70 parts, sulfur is 0.001 to 0.005 parts, and phosphorus is 0.001 to 0.007 parts.

[0010] Secondly, embodiments of this application provide a method for preparing the welding electrode according to any one of the embodiments of the first aspect, the method comprising:

[0011] The powdered drug coating is mixed with a binder to obtain a mixture.

[0012] The mixture is subjected to a first baking, a second baking, and cooling in sequence to obtain a welding rod; wherein the temperature of the first baking is 85℃~90℃, and the temperature of the second baking is 380℃~400℃.

[0013] Optionally, the weight of the binder is 20% to 30% of the weight of the drug coating powder.

[0014] Optionally, the final temperature of the cooling is ≤50°C.

[0015] Thirdly, embodiments of this application provide a cladding metal for welding low-alloy steel electrodes with ultra-low hydrogen coatings for generator sets at a pressure of 620 MPa, wherein the cladding metal is obtained from the electrodes described in any one of the first aspects during the welding process.

[0016] Optionally, the chemical composition of the deposited metal includes: carbon, manganese, silicon, nickel, molybdenum, chromium, niobium, copper, boron, aluminum, magnesium, sulfur, phosphorus, and the base element Fe; wherein, by mass parts,

[0017] Carbon: 0.07-0.12 parts; Manganese: 0.90-1.50 parts; Silicon: 0.15-0.30 parts; Nickel: 0.80-1.40 parts; Molybdenum: 0.30-0.60 parts; Chromium: 0.10-0.30 parts; Niobium: 0.01-0.10 parts; Copper: 0.50-0.70 parts; Boron: 0.0001-0.003 parts; Aluminum: 0.0001-0.010 parts; Magnesium: 0.0001-0.010 parts; Sulfur: 0.001-0.005 parts; Phosphorus: 0.001-0.007 parts.

[0018] Optionally, the diffusible hydrogen content of the deposited metal is 0.5 ml / 100g to 4.0 ml / 100g, and the moisture content of the electrode coating is 0.05% to 0.15%.

[0019] Optionally, the deposited metal satisfies the following mechanical properties: room temperature tensile strength of the weld is 620MPa~800MPa, room temperature yield strength is 530MPa~700MPa, room temperature elongation after fracture is 18%~35%, high temperature tensile strength of the weld at 400℃ is ≥500MPa, single impact value at 0℃ is ≥100J, single impact value at -40℃ is ≥60J, and drop hammer test ductile-brittle transition temperature is ≤-10℃.

[0020] The technical solutions provided in this application have the following advantages compared with the prior art:

[0021] The 620MPa grade low-alloy steel welding electrode with ultra-low hydrogen coating for generator sets provided in this application embodiment has a coating chemical composition including: dolomite, lithium carbonate, barium carbonate, magnesia, fluorite, ferrosilicon, nickel powder, ferromolybdenum, metallic chromium, potassium fluoroborate, aluminum-magnesium alloy, sodium alginate, and soda ash. Specifically, by weight, fluorite can reduce the diffusible hydrogen content of the electrode's weld metal. During welding, the GaF2 in fluorite reacts with H2O to produce GaO and HF gases. GaO can increase the basicity of the slag, and H... The release of sulfur (F) gas can reduce the diffusible hydrogen content in the weld metal of the welding electrode; dolomite and magnesia can increase the basicity of the coating while simultaneously building slag and generating gas. The slag can purify impurities such as sulfur (S) and phosphorus (P) in the weld, and the generated CO2 gas can be used to protect the weld. Increasing the basicity of the slag and reducing the diffusible hydrogen content in the weld metal can improve the crack resistance of the weld. Reducing impurities such as sulfur (S) and phosphorus (P) in the weld can improve the weld strength and low-temperature impact toughness, and can further improve the crack resistance of the weld; lithium carbonate can generate protective gas CO2 and a small amount of slag, which can stabilize the arc during welding. Since dolomite and magnesia react violently during electrode welding, the large amount of gas released has caused intense molten pool reaction and poor molten pool formation. Therefore, aluminum-magnesium alloys can lower the molten pool temperature, which is beneficial for weld formation and can achieve the target alloy composition of the weld; ferrosilicon is beneficial for the aesthetic appearance of the weld formation. Ferrosilicon can also deoxidize, reduce the oxygen content of the weld, and improve the mechanical properties of the weld; nickel powder, ferromolybdenum, and metallic chromium can also improve the mechanical properties of the weld; barium carbonate and fluoroboric acid... Potassium, sodium alginate, and soda ash are used as additives to fully exert their role in welding and improve the mechanical properties of the weld. At the same time, the following components are required: dolomite 100-200 parts, lithium carbonate 100-150 parts, magnesite 100-200 parts, fluorite 300-350 parts, ferrosilicon 100-150 parts, nickel powder 10-20 parts, ferromolybdenum 10-20 parts, metallic chromium 5-10 parts, and aluminum-magnesium alloy 1-3 parts, thereby improving the mechanical properties of the weld metal deposited by the electrode. Attached Figure Description

[0022] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application.

[0023] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0024] Figure 1 This is a schematic flowchart illustrating a method for preparing a welding electrode according to an embodiment of this application. Detailed Implementation

[0025] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0026] Various embodiments of this application may exist in the form of a range; it should be understood that the description in the form of a range is merely for convenience and brevity and should not be construed as a hard limitation on the scope of this application; therefore, it should be considered that the range description has specifically disclosed all possible sub-ranges and single numerical values ​​within that range. For example, it should be considered that the range description from 1 to 6 has specifically disclosed sub-ranges such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., and single numbers within the range, such as 1, 2, 3, 4, 5, and 6, regardless of the range. Furthermore, whenever a numerical range is referred to herein, it means including any referenced number (fraction or integer) within the referred range.

[0027] In this application, unless otherwise stated, directional terms such as "upper" and "lower" specifically refer to the orientation shown in the accompanying drawings. Furthermore, in the description of this application, the terms "comprising" and "including" mean "including but not limited to." In this document, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. "Parts" expressions such as parts by weight or parts by mass indicate the proportional relationship between the components. Unless otherwise specified, all raw materials, reagents, instruments, and equipment used in this application are commercially available or can be prepared using existing methods.

[0028] In a first aspect, embodiments of this application provide a 620MPa grade low-alloy steel welding electrode with an ultra-low hydrogen coating for generator sets. The welding electrode comprises a core and a coating covering at least a portion of the surface of the core. The chemical composition of the coating includes: dolomite, lithium carbonate, barium carbonate, magnesia, fluorite, ferrosilicon, nickel powder, ferromolybdenum, metallic chromium, potassium fluoroborate, aluminum-magnesium alloy, sodium alginate, and soda ash; wherein, by mass,

[0029] The composition is as follows: 100-200 parts dolomite, 100-150 parts lithium carbonate, 100-200 parts magnesite, 300-350 parts fluorite, 100-150 parts ferrosilicon, 10-20 parts nickel powder, 10-20 parts ferromolybdenum, 5-10 parts metallic chromium, and 1-3 parts aluminum-magnesium alloy.

[0030] In this embodiment, the dolomite content can be 100 to 200 parts, allowing it to fully exert its slag-forming and alkalinity-regulating functions during welding. Dolomite's main components are calcium carbonate and magnesium carbonate, which decompose at high welding temperatures to produce carbon dioxide gas and alkaline oxides. An appropriate amount of dolomite ensures sufficient gas protection for the weld, while increasing the slag alkalinity, allowing the slag to better cover the molten pool, preventing harmful gases from entering the molten pool, and avoiding defects such as porosity in the weld. For example, the dolomite content can be 100, 120, 140, 160, 180, or 200 parts.

[0031] The lithium carbonate content can range from 100 to 150 parts. A higher lithium carbonate content significantly contributes to reducing the diffusible hydrogen content in the weld metal. This content range ensures effective reaction with hydrogen or alters the metallurgical reaction conditions of the molten pool, reducing hydrogen absorption. Furthermore, lithium carbonate also affects the properties of the slag; an appropriate content helps the slag maintain good fluidity and coverage. For example, the lithium carbonate content can be 100, 110, 120, 130, 140, or 150 parts.

[0032] Magnesia can be present in quantities of 100 to 200 parts. Its main component is magnesium oxide, and this content range helps to further increase the basicity of the slag. High-basicity slag is beneficial for purifying impurities in the weld, such as reacting with sulfur and phosphorus, reducing their content in the weld, thereby improving the weld's strength and low-temperature impact toughness, and enhancing its crack resistance. Simultaneously, magnesia also participates in the slag-forming process, working with other components to form a high-performance slag.

[0033] The fluorite can be 300 to 350 parts, and its main component, calcium fluoride, decomposes and reacts with moisture during welding to generate calcium oxide and hydrogen fluoride gas. A large amount of fluorite can more effectively reduce the diffusible hydrogen content of the deposited metal while increasing the basicity of the slag. Calcium oxide can improve the properties of the slag, while the removal of hydrogen fluoride gas plays a crucial role in reducing the risk of hydrogen-induced cracking in the weld. For example, the fluorite can be 300 parts, 310 parts, 320 parts, 330 parts, 340 parts, 350 parts, etc.

[0034] Ferrosilicon can be present in quantities ranging from 100 to 150 parts. As a deoxidizer, ferrosilicon within this content range can effectively combine with oxygen in the weld, reducing its oxygen content. Sufficient ferrosilicon can prevent defects such as porosity in the weld, and silicon can improve the mechanical properties of the weld. Simultaneously, ferrosilicon may also have a certain influence on the properties of the slag and weld formation, helping to obtain a weld with a good appearance. For example, the ferrosilicon can be in quantities of 100, 110, 120, 130, 140, and 150 parts.

[0035] The amount of nickel powder, ferromolybdenum, and metallic chromium can be 10 to 20 parts, 10 to 20 parts, and 5 to 10 parts, respectively. These alloying elements are added in relatively small amounts, but their effects are significant. Nickel powder can improve the toughness and crack resistance of weld metal, especially for welded structures requiring good low-temperature toughness. Ferromolybdenum can refine the weld grains, improve the weld strength and resistance to tempering softening, and enhance the weld's performance at high temperatures. Metallic chromium can improve the oxidation resistance and corrosion resistance of weld metal, and, in conjunction with other alloying elements, improve the weld's microstructure and properties, such as increasing hardness and wear resistance. For example, the nickel powder can be 10, 12, 14, 16, 18, or 20 parts; the ferromolybdenum can be 10, 12, 14, 16, 18, or 20 parts; and the metallic chromium can be 5, 6, 7, 8, 9, or 10 parts.

[0036] The aluminum-magnesium alloy can be 1 to 3 parts. Although the content of aluminum-magnesium alloy is small, both aluminum and magnesium can play a role in deoxidation and slag formation during the welding process. Aluminum can also combine with nitrogen to reduce the nitrogen content in the weld, while magnesium can improve the properties of the slag, which helps to improve the weld quality. For example, the aluminum-magnesium alloy can be 1 part, 2 parts, 3 parts, etc.

[0037] Furthermore, the proportions of the aforementioned components ensure that the flux coating exhibits excellent melting characteristics and stability during welding. For example, components such as dolomite, magnesite, and fluorite guarantee slag formation and fluidity, allowing the slag to effectively cover the molten pool during welding. Simultaneously, gas generation remains relatively stable, preventing welding operations from being affected by excessively vigorous or insufficient reactions. Components such as ferrosilicon and aluminum-magnesium alloys help control the degree of reaction in the molten pool, making the pool temperature and fluidity easier to manage, thus ensuring a smooth welding process. Whether welding in flat, vertical, or other positions, good process results can be achieved.

[0038] From the perspective of weld mechanical properties, the deoxidizing effect of ferrosilicon, the improvement of toughness by alloying elements such as nickel powder, and the enhancement of strength and special properties (such as high-temperature resistance and oxidation resistance) by ferromolybdenum and metallic chromium work together to give the weld excellent comprehensive mechanical properties. From the perspective of chemical composition, the proportions of these components can effectively control the content of impurities such as oxygen, hydrogen, sulfur, and phosphorus in the weld, and can precisely add the required alloying elements to the weld, ensuring a good match between the weld chemical composition and the base metal. In terms of appearance quality, the good properties of the slag and appropriate welding process parameters (thanks to the reasonable design of the component proportions) can result in a beautiful weld formation, good slag removal, and reduced workload for subsequent weld cleaning.

[0039] In some embodiments, the barium carbonate is 200 to 300 parts, the potassium fluoroborate is 1 to 4 parts, the sodium alginate is 1 to 15 parts, and the soda ash is 5 to 10 parts.

[0040] In this embodiment, barium carbonate can be 200 to 300 parts, which can improve slag fluidity and slag removal: Barium carbonate can significantly improve slag fluidity during welding. When the content is in the range of 200 to 300 parts, it can make the slag more smoothly cover the surface of the molten pool. Appropriate slag fluidity can ensure the smooth progress of the welding process. For example, when welding complex shapes or different welding positions (such as vertical welding and overhead welding), good slag fluidity can prevent uneven slag flow from affecting the welding quality. At the same time, barium carbonate also helps to improve the slag removal property, making it easier for the slag to fall off the weld surface after welding, reducing the difficulty of cleaning the weld. By improving slag properties, barium carbonate indirectly improves the weld quality. Good slag coverage can effectively isolate air, preventing harmful gases such as oxygen and nitrogen in the air from entering the molten pool, reducing the possibility of defects such as porosity and oxidation in the weld. For example, the barium carbonate can be 200 parts, 220 parts, 240 parts, 260 parts, 280 parts, 300 parts, etc.

[0041] Potassium fluoroborate, ranging from 1 to 4 parts, primarily functions as a flux within this range. It lowers the melting point and viscosity of the slag, making the flux coating melt more easily during welding and forming a high-performance slag. This facilitates slag formation and flow during welding, ensuring the slag effectively covers the weld pool and provides protection. An appropriate amount of potassium fluoroborate can adjust the interfacial properties between the slag and the weld metal, making it easier for the slag to separate from the weld surface after welding, thus contributing to a weld with better appearance quality. For example, the potassium fluoroborate can be in amounts of 1, 2, 3, or 4 parts.

[0042] Sodium alginate can be present in quantities ranging from 1 to 15 parts, acting as a binder. Within this range, it ensures the flux coating adheres well to the core. During electrode manufacturing, sodium alginate ensures the flux components are tightly bonded together and firmly attached to the core surface. This prevents the flux coating from easily detaching during welding, maintaining its integrity and ensuring the proper functioning of its components. Furthermore, sodium alginate guarantees the stability of the flux coating, allowing the electrode to function consistently and reliably during use. For example, the sodium alginate can be present in quantities of 1, 2, 3, 5, 7, 9, 11, 13, or 15 parts.

[0043] Soda ash (sodium carbonate) can be 5 to 10 parts. Its main function is to adjust the pH of the flux coating. A suitable pH has a significant impact on the reactions of various components in the flux coating and the properties of the slag. It participates in slag formation reactions: Soda ash may participate in some slag formation reactions, interacting with other components (such as dolomite, magnesite, etc.) to jointly affect the properties of the slag. In this way, it also indirectly affects the weld quality, such as improving the protective effect of the slag on the molten pool and reducing weld defects. For example, the soda ash can be 5, 6, 7, 8, 9, or 10 parts.

[0044] In addition, the particle size requirements for dolomite are as follows: CaCO3 ≥ 50%, MgCO3 ≥ 40%, S ≤ 0.03%, P ≤ 0.03%, with a particle size requirement of -40 mesh: ≥ 100%, -150 mesh: ≤ 60%; for lithium carbonate: Li2CO3 ≥ 99.5%, with a particle size requirement of -40 mesh: ≥ 100%; for barium carbonate: BaCO3 ≥ 99.5%, with a particle size requirement of -40 mesh: ≥ 100%; for magnesite: MgCO3 ≥ 95%, S ≤ 0.01%, P ≤ 0.02%, with a particle size requirement of -40 mesh: ≥ 100%, -150 mesh: ≤ 60%; and for fluorite: CaF2 ≥ 98%, SiO2 ≤ 1.0%, C ≤ 0.05%, S ≤ 0.01%, P ≤ 0.02%, with a particle size requirement of... The particle size requirements are as follows: -40 mesh: ≥100%, -150 mesh: ≤60%; Ferrosilicon: Si: 42%-47%, S≤0.02%, P≤0.03%, particle size requirement -40 mesh: ≥100%; Nickel powder: Ni≥99.8%, particle size requirement -60 mesh: 100%; Ferromolybdenum: Mo: 55%-60%, S≤0.02%, P≤0.03%, particle size requirement -60 mesh: ≥100%; Metallic chromium: Cr≥99.9%, particle size requirement -60 mesh: 100%; Potassium fluoroborate: KBF4≥99.9%, particle size requirement -40 mesh: ≥100%; Aluminum-magnesium alloy: Al+Mg≥97.5%, Al: 47%-53%, particle size requirement -80 mesh: ≥95%.

[0045] In some embodiments, the chemical composition of the welding core includes: carbon, manganese, silicon, nickel, molybdenum, chromium, niobium, copper, sulfur, phosphorus, and the base element Fe; wherein, by mass parts,

[0046] Carbon is 0.07 to 0.12 parts, manganese is 0.90 to 1.50 parts, silicon is 0.05 to 0.10 parts, nickel is 0.50 to 1.00 parts, molybdenum is 0.01 to 0.10 parts, chromium is 0.01 to 0.10 parts, niobium is 0.01 to 0.10 parts, copper is 0.50 to 0.70 parts, sulfur is 0.001 to 0.005 parts, and phosphorus is 0.001 to 0.007 parts.

[0047] In this embodiment, the core electrode provides a basic metal framework and some alloying elements, while the flux coating further supplements and regulates the alloy composition. For example, the nickel powder, ferromolybdenum, and metallic chromium in the flux coating, combined with the existing nickel, molybdenum, and chromium in the core electrode, work synergistically to achieve a more precise degree of alloying in the weld, meeting complex and diverse performance requirements. The flux coating protects the molten pool through a series of metallurgical reactions such as slag formation, deoxidation, and desulfurization, reducing impurities in the weld. Furthermore, the core electrode's low sulfur and phosphorus content design, combined with the flux coating's purification function, significantly enhances the purity of the weld, ensuring higher strength, toughness, and crack resistance.

[0048] Carbon can range from 0.07 parts to 0.12 parts. Carbon is a key element affecting the strength and toughness of steel. Within this content range, it can provide a certain strength to the weld core. For example, the carbon content can be 0.07 parts, 0.08 parts, 0.09 parts, 0.10 parts, 0.11 parts, 0.12 parts, etc.

[0049] Manganese can be 0.90 parts to 1.50 parts. Manganese is an effective deoxidizer that can combine with oxygen in the weld, reducing oxygen content and preventing defects such as porosity. Simultaneously, manganese can strengthen ferrite, improving the strength and toughness of the weld core, making it less prone to deformation and fracture under external forces, thus helping the weld maintain good mechanical properties. For example, the manganese content can be 0.90 parts, 1.0 parts, 1.10 parts, 1.20 parts, 1.30 parts, 1.40 parts, 1.50 parts, etc.

[0050] Silicon can be present in amounts ranging from 0.05 to 0.10 parts. Silicon also possesses deoxidizing capabilities; it reacts with oxygen to form silicon dioxide, purifying the weld. An appropriate amount of silicon can also improve the fluidity of the weld core, allowing the molten metal to fill the gaps in the base material more smoothly during welding, facilitating weld formation and contributing to the optimization of the final mechanical properties of the weld core. For example, the silicon content can be 0.05 parts, 0.06 parts, 0.07 parts, 0.08 parts, 0.09 parts, or 0.10 parts.

[0051] The nickel content can range from 0.50 parts to 1.00 parts. After being incorporated into the weld core, nickel significantly improves its toughness, especially its low-temperature toughness. For some welded structures that may operate in low-temperature environments, the presence of nickel can lower the brittle transition temperature of the weld core, allowing the weld to maintain good impact resistance even at low temperatures and preventing brittle fracture. For example, the nickel content can be 0.50 parts, 0.60 parts, 0.70 parts, 0.80 parts, 0.90 parts, 1.00 parts, etc.

[0052] The molybdenum content can range from 0.01 to 0.10 parts. Molybdenum refines the grain structure, which simultaneously improves the strength and toughness of the weld core. Furthermore, molybdenum imparts resistance to tempering softening to the weld core, maintaining good mechanical properties during subsequent heat treatment processes and ensuring stable weld quality. For example, the molybdenum content can be 0.01, 0.02, 0.04, 0.06, 0.08, or 0.10 parts.

[0053] Chromium can be present in amounts ranging from 0.01 to 0.10 parts, providing the weld core with oxidation and corrosion resistance. When the welded components are exposed to a corrosive environment, the dense oxide film formed by chromium can prevent external corrosive media from eroding, extending the service life of the weld and the overall weldment. For example, the chromium content can be 0.01, 0.02, 0.04, 0.06, 0.08, or 0.10 parts.

[0054] Niobium can be 0.01 to 0.10 parts. Niobium is a strong carbide-forming element. It combines with carbon to form stable carbides, which can refine grains, achieve dispersion strengthening, enhance the strength of the welding core, inhibit grain growth, maintain the stability of the welding core's microstructure, and improve overall performance. For example, the niobium can be 0.01, 0.02, 0.04, 0.06, 0.08, or 0.10 parts.

[0055] The copper content can range from 0.50 to 0.70 parts. Copper helps improve the corrosion resistance of the welding core, especially in weakly acidic or weakly alkaline corrosive environments. Copper can also strengthen the welding core to some extent; however, excessive addition may cause hot brittleness, so limiting the content to this range is more appropriate. For example, the copper content can be 0.50 parts, 0.55 parts, 0.60 parts, 0.65 parts, 0.70 parts, etc.

[0056] The sulfur content can range from 0.001 to 0.005 parts. Sulfur is a harmful impurity, and even a small amount can lead to hot brittleness of the weld core. Strict control of the sulfur content is to prevent sulfur from forming low-melting-point eutectics with iron during welding heat treatment, which would reduce the toughness and heat treatment performance of the weld core. For example, the sulfur content can be 0.001, 0.002, 0.003, 0.004, or 0.005 parts.

[0057] Phosphorus can range from 0.001 to 0.007 parts. Phosphorus is also a harmful impurity, as it can cause cold brittleness in the weld core, significantly reducing its toughness at low temperatures. Controlling the phosphorus content to a low level ensures the weld core and subsequent welds function properly under low-temperature conditions. For example, the phosphorus content can be 0.001, 0.002, 0.003, 0.004, 0.005, 0.006, or 0.007 parts.

[0058] Secondly, embodiments of this application provide a method for preparing the welding electrode as described in any one of the embodiments of the first aspect. Figure 1 A schematic flowchart illustrating a method for preparing a welding electrode according to an embodiment of this application; please refer to [link / reference]. Figure 1 The preparation method includes:

[0059] S1. Mix the drug coating powder with the binder to obtain a mixture;

[0060] S2. The mixture is subjected to a first baking, a second baking, and cooling in sequence to obtain a welding rod; wherein the temperature of the first baking is 85℃~90℃, and the temperature of the second baking is 380℃~400℃.

[0061] In some embodiments, the binder accounts for 20% to 30% of the weight of the drug coating powder.

[0062] In some embodiments, the final temperature of the cooling is ≤50°C.

[0063] In this embodiment, the binder binds these loose powders together to form a relatively stable whole. First baking (85℃~90℃): This stage is low-temperature baking, the purpose of which is to initially remove moisture from the flux coating mixture. Second baking (380℃~400℃): This is a high-temperature baking stage, with two main key functions. First, it further dries the flux coating, thoroughly removing residual moisture. This is particularly important for ultra-low hydrogen flux coating electrodes, as moisture is a significant source of hydrogen in the weld. Strict moisture control can greatly reduce the hydrogen content of the weld, reducing the risk of hydrogen-induced cracking. Second, the high temperature promotes some pre-reactions between the flux coating powders, optimizing the fusion and interaction between the components, allowing the slag formation characteristics, alloy element transition ability, and other properties to reach their optimal state during subsequent welding. Cooling (final temperature below 50℃): The cooling process is indispensable. It allows the high-temperature baked flux coating to cool down rapidly, stabilizing the internal structure and composition, avoiding excessive oxidation and deterioration of components due to prolonged high temperatures, ultimately obtaining a high-performance, stable welding electrode. For example, the temperature of the first baking can be 85℃, 86℃, 87℃, 88℃, 89℃, 90℃, etc.; the temperature of the second baking can be 380℃, 390℃, 400℃, etc.; and the final cooling temperature can be 50℃, 49℃, 48℃, 47℃, etc.

[0064] The binder weight can be 20% to 30% of the coating powder weight. This ensures the coating powder is fully bonded, preventing the coating from easily loosening or peeling off during electrode manufacturing. It also avoids the possibility of incomplete decomposition of excessive binder during baking, which could leave residual binder components that affect the metallurgical properties of the coating, interfering with normal slag formation and alloy element transitions, ultimately damaging the electrode and weld quality. For example, the binder weight can be 20%, 22%, 24%, 26%, 28%, or 30% of the coating powder weight.

[0065] The preparation method of this welding electrode is based on the above-mentioned welding electrode. The specific chemical composition of the welding electrode can be referred to the above embodiments. Since the preparation method of this welding electrode adopts some or all of the technical solutions of the above embodiments, it has at least all the beneficial effects brought about by the technical solutions of the above embodiments, which will not be elaborated here.

[0066] Thirdly, embodiments of this application provide a cladding metal for welding low-alloy steel electrodes with ultra-low hydrogen coatings for generator sets at a pressure of 620 MPa, wherein the cladding metal is obtained from the electrodes described in any one of the first aspects during the welding process.

[0067] In this embodiment, if the diameter of the welding core is 3.2 mm, the welding current is 90A–120A, the welding voltage is 20V–25V, the welding speed is 150 mm / min, and the interpass temperature during welding is 90℃–110℃; if the diameter of the welding core is 4.0 mm, the welding current is 160A–180A, the welding voltage is 22V–30V, the welding speed is 150 mm / min, and the interpass temperature during welding is 90℃–110℃. Because a low-alloy steel electrode with an ultra-low hydrogen coating is used, its coating composition is special, requiring strict welding process control. Precise control of current, voltage, and speed, combined with a specific interpass temperature, allows the coating to fully function. A stable arc ensures smooth melting of the coating, releasing alloying elements that precisely transition to the deposited metal. The slag-forming components form high-quality slag to protect the molten pool; a suitable interpass temperature helps the slag continuously cover and purify the molten pool, synergistically reducing the hydrogen content of the weld, improving crack resistance, and comprehensively ensuring the high quality of the welded plate. For example, if the diameter of the welding core is 3.2 mm, the welding current can be 90A, 100, 110, 120A, etc., the welding voltage can be 20V, 21V, 22V, 23V, 24V, 25V, etc., the welding speed can be 150mm / min, and the interpass temperature during welding can be 90℃, 100℃, 110℃, etc. If the diameter of the welding core is 4.0 mm, the welding current can be 160A, 170, 180A, etc., the welding voltage can be 22V, 23V, 24V, 25V, 26V, 27V, 28V, 29V, 30V, etc., the welding speed can be 150mm / min, and the interpass temperature during welding can be 90℃, 100℃, 110℃, etc.

[0068] In some embodiments, the chemical composition of the deposited metal includes: carbon, manganese, silicon, nickel, molybdenum, chromium, niobium, copper, boron, aluminum, magnesium, sulfur, phosphorus, and the base element Fe; wherein, by mass parts,

[0069] Carbon: 0.07-0.12 parts; Manganese: 0.90-1.50 parts; Silicon: 0.15-0.30 parts; Nickel: 0.80-1.40 parts; Molybdenum: 0.30-0.60 parts; Chromium: 0.10-0.30 parts; Niobium: 0.01-0.10 parts; Copper: 0.50-0.70 parts; Boron: 0.0001-0.003 parts; Aluminum: 0.0001-0.010 parts; Magnesium: 0.0001-0.010 parts; Sulfur: 0.001-0.005 parts; Phosphorus: 0.001-0.007 parts.

[0070] In this embodiment, the chemical composition of the weld metal is determined by both the core and the flux coating. Alloying elements in the core directly enter the weld metal during melting, while alloying elements in the flux coating are transferred to the weld metal through metallurgical reactions. The nickel powder, ferromolybdenum, and metallic chromium in the flux coating can replenish these elements in the weld metal, ensuring their content meets the required range. Simultaneously, deoxidizers (such as ferrosilicon or aluminum-magnesium alloys) in the flux coating can control the oxygen content in the weld metal, and desulfurizers can reduce the sulfur content, thereby guaranteeing the quality of the weld metal.

[0071] In some embodiments, the diffusible hydrogen content of the deposited metal is 0.5 ml / 100g to 4.0 ml / 100g, and the moisture content of the electrode coating is 0.05% to 0.15%.

[0072] In some embodiments, the deposited metal satisfies the following mechanical properties: room temperature tensile strength of the weld is 620MPa to 800MPa, room temperature yield strength is 530MPa to 700MPa, room temperature elongation after fracture is 18% to 35%, high temperature tensile strength of the weld at 400℃ is ≥500MPa, single impact value at 0℃ is ≥100J, single impact value at -40℃ is ≥60J, and drop hammer test ductile-brittle transition temperature is ≤-10℃.

[0073] In this embodiment, the preheating and interpass temperature of the electrode weld is 90℃-110℃, and the heat treatment after the weld is completed is as follows: maximum heat treatment 620℃×9h, minimum heat treatment 620℃×1h, the heating and cooling rates above 300℃ are 40℃ / h-100℃ / h, and the heating and cooling rates are not controlled below 300℃.

[0074] For example, this welding electrode is mainly used for welding 15NiCuMoNb5-6-4 steel in the steam and feedwater loop equipment of nuclear power conventional island and WB36 steel in high-parameter thermal power generation equipment. Please refer to Table 1 for the main chemical composition of 15NiCuMoNb5-6-4 steel and the weld metal deposited by the welding electrode, and please refer to Table 2 for the main mechanical properties of 15NiCuMoNb5-6-4 steel and the weld metal deposited by the welding electrode.

[0075] Table 1. Main chemical composition of 15NiCuMoNb5-6-4 steel and weld metal.

[0076]

[0077] Table 2 Main Mechanical Properties of 15NiCuMoNb5-6-4 Steel and Welding Electrode Deposited Metal

[0078]

[0079] Chemically, the electrode deposited metal involved in this application is similar in main components to the matching base material. The carbon content in the electrode deposited metal is appropriately reduced to improve its weldability, and appropriate trace amounts of alloying elements such as Cr and Mo are added to refine the grain size and improve the mechanical properties of the weld. Regarding tensile strength, the electrode deposited metal involved in this application is comparable to that of steel. Regarding impact performance, the electrode deposited metal involved in this application is designed to be slightly superior to steel, resulting in better impact toughness in the weld metal.

[0080] This welding method is based on the above-mentioned welding rod. The specific chemical composition of the welding rod can be referred to in the above embodiments. Since this welding method adopts some or all of the technical solutions of the above embodiments, it has at least all the beneficial effects brought about by the technical solutions of the above embodiments, which will not be elaborated here.

[0081] The present application is further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the application. Experimental methods in the following embodiments that do not specify specific conditions are generally determined according to national standards. If there is no corresponding national standard, then generally accepted international standards, conventional conditions, or conditions recommended by the manufacturer are followed.

[0082] Example 1

[0083] A low-alloy steel welding electrode with an ultra-low hydrogen coating, rated for 620 MPa, is disclosed for use in generator sets. The electrode comprises a core and a coating covering the core surface. The coating composition and content are as follows: 130 parts by weight of dolomite, 140 parts by weight of lithium carbonate, 280 parts by weight of barium carbonate, 150 parts by weight of magnesia, 310 parts by weight of fluorite, 120 parts by weight of ferrosilicon, 15 parts by weight of nickel powder, 15 parts by weight of ferromolybdenum, 6 parts by weight of metallic chromium, 2 parts by weight of potassium fluoroborate, 1 part by weight of aluminum-magnesium alloy, 5 parts by weight of sodium alginate, and 8 parts by weight of soda ash. The core diameter is 4.0 mm, and the length is machined to 400 mm. The core material is composed of 0.10% carbon, 1.40% manganese, 0.08% silicon, 0.85% nickel, 0.05% molybdenum, 0.02% chromium, 0.02% niobium, 0.65% copper, 0.003% sulfur, and 0.005% phosphorus, with the remainder being iron and impurities.

[0084] A method for preparing a welding electrode includes: mixing flux powder for 18 minutes, adding a binder (43° potassium sodium water glass) equal to 25% of the total flux powder volume, and mixing for 8 minutes. The mixed flux powder is then fed into an oil pump to coat the welding core. The electrode is baked at a low temperature of 88°C for 2.5 hours, followed by a high temperature of 390°C for 1.5 hours to obtain the welding electrode. After the high-temperature baking, the electrode is cooled to 48°C to obtain the finished welding electrode. The finished welding electrode with a welding core diameter of 3.2 mm has a diameter of 5.20 mm, and the welding electrode with a welding core diameter of 4.0 mm has a diameter of 6.60 mm. The welding electrode is then packaged. Storage and handling require attention to temperature and humidity. The indoor temperature should be above 5°C, the relative humidity should not exceed 60%, and the electrode should be kept a certain distance from the ground and walls. The storage environment should be kept dry and clean, with clear labeling, and hazardous media should not be stored there.

[0085] A welding method includes the following welding conditions: The welding test plate is prepared according to standard GB / T25774.1-2010 "Inspection of Welding Materials - Part 1: Preparation and Inspection of Mechanical Properties of Deposited Metals of Steel, Nickel and Nickel Alloys". The test plate thickness is 20 mm, the width is 150 mm, and the length is 400 mm. The preheating temperature of the test plate before welding is 90℃, and the welding power source is DC reverse polarity. For 3.2 mm diameter plates, 1 to 3 layers are welded at a welding current of 100 A, a welding voltage of 23 V, a welding speed of 150 mm / min, and an interpass temperature of 100℃ during welding. For 4.0 mm diameter plates, 4 to 8 layers are welded at a welding current of 170 A, a welding voltage of 26 V, a welding speed of 150 mm / min, and an interpass temperature of 100℃ during welding. The total number of welded layers on the test plate is 8. After welding, the test plate is cooled to room temperature and then surface-polished. After the surface is smoothed, a test plate backing is processed and then subjected to flaw detection.

[0086] The welding control technology test plate heat treatment and testing items involved in this application include: a maximum heat treatment of 620℃×9h, a minimum heat treatment of 620℃×1h, a heating and cooling rate of 40℃ / h-100℃ / h for temperatures above 300℃, and no control over the heating and cooling rate for temperatures below 300℃. The testing items include chemical composition analysis, tensile testing, impact testing, drop hammer testing, hydrogen diffusion testing, and electrode coating moisture content.

[0087] After welding: The chemical composition of the electrode deposited metal is as follows: carbon 0.09%, manganese 1.25%, silicon 0.20%, nickel 1.25%, molybdenum 0.33%, chromium 0.15%, niobium 0.015%, copper 0.60%, boron 0.0004%, aluminum 0.005%, magnesium 0.0005%, sulfur 0.004%, phosphorus 0.006%, and the remaining elements are iron and impurities.

[0088] The mechanical properties of the weld (deposited metal) after heat treatment at 620℃ for 9 hours are as follows: room temperature tensile strength 671 MPa, room temperature yield strength 549 MPa, room temperature elongation after fracture 20%, high temperature tensile strength at 400℃ 544 MPa, impact strength at 0℃ 200 J, 211 J, 202 J, impact strength at -40℃ 120 J, 131 J, 132 J, and drop hammer test ductile-brittle transition temperature -25℃. The mechanical properties of the weld after heat treatment at 620℃ for 1 hour are as follows: room temperature tensile strength 695 MPa, room temperature yield strength 579 MPa, room temperature elongation after fracture 20%, high temperature tensile strength at 400℃ 577 MPa, impact strength at 0℃ 190 J, 200 J, 192 J, impact strength at -40℃ 100 J, 101 J, 112 J, and drop hammer test ductile-brittle transition temperature -20℃. The electrode deposited metal contains 3.6 ml / 100 g of diffusing hydrogen, and the electrode coating contains 0.12% moisture.

[0089] Example 2

[0090] A low-alloy steel welding electrode with an ultra-low hydrogen coating, rated for 620 MPa, is disclosed for use in generator sets. The electrode comprises a core and a coating covering the core surface. The coating composition and content are as follows: 180 parts by weight of dolomite, 130 parts by weight of lithium carbonate, 250 parts by weight of barium carbonate, 140 parts by weight of magnesia, 310 parts by weight of fluorite, 120 parts by weight of ferrosilicon, 15 parts by weight of nickel powder, 15 parts by weight of ferromolybdenum, 6 parts by weight of metallic chromium, 2 parts by weight of potassium fluoroborate, 1 part by weight of aluminum-magnesium alloy, 5 parts by weight of sodium alginate, and 8 parts by weight of soda ash. The core diameter is 4.0 mm, and the length is machined to 400 mm. The core material is composed of 0.10% carbon, 1.40% manganese, 0.08% silicon, 0.85% nickel, 0.05% molybdenum, 0.02% chromium, 0.02% niobium, 0.65% copper, 0.003% sulfur, and 0.005% phosphorus, with the remainder being iron and impurities.

[0091] A method for preparing welding electrodes includes: mixing flux powder for 18 minutes, adding 25% (or 43° potassium sodium water glass) of binder based on the total flux amount, and mixing for 8 minutes. The mixed flux powder is then fed into an oil pump to coat the welding core. The electrode is baked at a low temperature of 88°C for 2.5 hours, followed by a high temperature of 390°C for 1.5 hours to obtain the welding electrode. After the high-temperature baking, the electrode is cooled to 48°C to obtain the finished welding electrode. The finished welding electrode with a welding core diameter of 3.2 mm has a diameter of 5.20 mm, and the welding electrode with a welding core diameter of 4.0 mm has a diameter of 6.60 mm. The welding electrodes are then packaged. Storage and handling require attention to temperature and humidity. The indoor temperature should be above 5°C, the relative humidity should not exceed 60%, and the electrode should be kept a certain distance from the ground and walls. The storage environment should be kept dry and clean, with proper categorization and clear labeling. Hazardous media should not be stored in the electrode.

[0092] A welding method includes the following welding conditions: the welding test plate is prepared according to the standard GB / T25774.1-2010 "Inspection of Welding Materials - Part 1: Preparation and Inspection of Mechanical Properties of Deposited Metals of Steel, Nickel and Nickel Alloys", the thickness of the welding test plate is 20 mm, the width of the test plate is 150 mm, and the length of the test plate is 400 mm. Please refer to welding scheme 1 and welding scheme 2 below.

[0093] Welding Scheme 1

[0094] The preheating temperature of the test plate before welding was 90℃. The welding power source was DC reverse polarity, with a 3.2 mm weldment diameter, a welding current of 100A, a welding voltage of 23V, and a welding speed of 150 mm / min. The interpass temperature during welding was 100℃, and the total number of welded layers on the test plate was 9. After welding, the test plate was cooled to room temperature for surface grinding to achieve a smooth surface. The test plate backing was then processed for flaw detection.

[0095] The welding control technology test plate heat treatment and testing items involved in this application include: a maximum heat treatment of 620℃×9h, a minimum heat treatment of 620℃×1h, a heating and cooling rate of 40℃ / h-100℃ / h for temperatures above 300℃, and no control over the heating and cooling rate for temperatures below 300℃. The testing items include chemical composition analysis, tensile testing, impact testing, drop hammer testing, hydrogen diffusion testing, and electrode coating moisture content.

[0096] The chemical composition of the weld metal deposited by the welding rod is as follows: 0.087% carbon, 1.15% manganese, 0.19% silicon, 1.27% nickel, 0.34% molybdenum, 0.16% chromium, 0.017% niobium, 0.61% copper, 0.0004% boron, 0.005% aluminum, 0.0005% magnesium, 0.003% sulfur, 0.006% phosphorus, and the remaining elements are iron and impurities.

[0097] The mechanical properties of the weld (deposited metal) after heat treatment at 620℃ for 9 hours are as follows: room temperature tensile strength 669 MPa, room temperature yield strength 570 MPa, room temperature elongation after fracture 22%; high temperature tensile strength at 400℃ 540 MPa; impact strength at 0℃ 220 J, 221 J, 209 J; impact strength at -40℃ 140 J, 137 J, 133 J; and drop hammer test ductile-brittle transition temperature -25℃. The mechanical properties of the weld after heat treatment at 620℃ for 1 hour are as follows: room temperature tensile strength 690 MPa, room temperature yield strength 575 MPa, room temperature elongation after fracture 21%; high temperature tensile strength at 400℃ 575 MPa; impact strength at 0℃ 195 J, 185 J, 190 J; impact strength at -40℃ 110 J, 121 J, 116 J; and drop hammer test ductile-brittle transition temperature -20℃.

[0098] Welding Scheme 2

[0099] The preheating temperature of the test plate before welding was 90℃. The welding power source was DC reverse polarity, with a 4.0 mm weldment diameter, a welding current of 170A, a welding voltage of 26V, and a welding speed of 150mm / min. The interpass temperature during welding was 100℃. The total number of welded layers on the test plate was 7. After welding, the test plate was cooled to room temperature for surface grinding to achieve a smooth surface. The test plate backing was then processed for flaw detection.

[0100] The welding control technology test plate heat treatment and testing items involved in this application include: a maximum heat treatment of 620℃×9h, a minimum heat treatment of 620℃×1h, a heating and cooling rate of 40℃ / h-100℃ / h for temperatures above 300℃, and no control over the heating and cooling rate for temperatures below 300℃. The testing items include chemical composition analysis, tensile testing, impact testing, drop hammer testing, hydrogen diffusion testing, and electrode coating moisture content.

[0101] The chemical composition of the weld metal deposited by the welding rod is as follows: 0.10% carbon, 1.30% manganese, 0.23% silicon, 1.31% nickel, 0.36% molybdenum, 0.17% chromium, 0.016% niobium, 0.62% copper, 0.0004% boron, 0.004% aluminum, 0.0004% magnesium, 0.005% sulfur, 0.005% phosphorus, and the remaining elements are iron and impurities.

[0102] The mechanical properties of the weld (deposited metal) after heat treatment at 620℃ for 9 hours are as follows: room temperature tensile strength 680 MPa, room temperature yield strength 579 MPa, room temperature elongation after fracture 20%; high temperature tensile strength at 400℃ 589 MPa; impact strength at 0℃ 200 J, 191 J, 189 J; impact strength at -40℃ 90 J, 97 J, 93 J; and drop hammer test ductile-brittle transition temperature -20℃. The mechanical properties of the weld after heat treatment at 620℃ for 1 hour are as follows: room temperature tensile strength 700 MPa, room temperature yield strength 605 MPa, room temperature elongation after fracture 19%; high temperature tensile strength at 400℃ 601 MPa; impact strength at 0℃ 175 J, 165 J, 170 J; impact strength at -40℃ 80 J, 81 J, 86 J; and drop hammer test ductile-brittle transition temperature -15℃. The electrode deposited metal contains 3.4 ml / 100 g of diffusing hydrogen, and the electrode coating contains 0.11% moisture.

[0103] One or more technical solutions in the embodiments of this application have at least the following technical effects or advantages:

[0104] (1) The welding electrode provided in this application provides a stable arc and aesthetically pleasing weld formation during welding. The weld metal exhibits good crack resistance, and the weld metal possesses chemical composition and mechanical properties comparable to steel. It can replace foreign welding electrodes for welding 15NiCuMoNb5-6-4 steel in conventional island steam and feedwater circuit equipment of nuclear power plants, as well as WB36 steel in high-parameter thermal power generation equipment. Achieving domestic production of this welding electrode can also reduce manufacturing costs and shorten procurement cycles, thus contributing to cost savings.

[0105] The above description is merely a specific embodiment of this application, enabling those skilled in the art to understand or implement this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features claimed herein.

Claims

1. A 620MPa grade low-alloy steel welding electrode with an ultra-low hydrogen coating for generator sets, the electrode comprising a core and a coating covering at least a portion of the surface of the core, the chemical composition of the coating being: dolomite, lithium carbonate, barium carbonate, magnesia, fluorite, ferrosilicon, nickel powder, ferromolybdenum, metallic chromium, potassium fluoroborate, aluminum-magnesium alloy, sodium alginate, and soda ash; wherein, By weight, the composition is as follows: dolomite 100-200 parts, lithium carbonate 100-150 parts, magnesite 100-200 parts, fluorite 300-350 parts, ferrosilicon 100-150 parts, nickel powder 10-20 parts, ferromolybdenum 10-20 parts, metallic chromium 5-10 parts, aluminum-magnesium alloy 1-3 parts, barium carbonate 200-300 parts, potassium fluoroborate 1-4 parts, sodium alginate 1-15 parts, and soda ash 5-10 parts. The chemical composition of the welding core, by mass percentage, consists of the following: 0.10% carbon, 1.40% manganese, 0.08% silicon, 0.85% nickel, 0.05% molybdenum, 0.02% chromium, 0.02% niobium, 0.65% copper, 0.003% sulfur, 0.005% phosphorus, with the remainder being iron and impurity elements.

2. A method for preparing the welding electrode according to claim 1, the method comprising: The powdered drug coating is mixed with a binder to obtain a mixture. The mixture is subjected to a first baking, a second baking, and cooling in sequence to obtain a welding rod; wherein the temperature of the first baking is 85℃~90℃, and the temperature of the second baking is 380℃~400℃.

3. The preparation method according to claim 2, characterized in that, The weight of the binder is 20% to 30% of the weight of the drug coating powder.

4. The preparation method according to claim 2, characterized in that, The final temperature of the cooling process is ≤50℃.

5. A weld metal obtained by welding a low-alloy steel electrode with an ultra-low hydrogen coating of 620MPa grade for generator sets, wherein the weld metal is obtained by welding the electrode of claim 1 during the welding process.

6. The weld metal according to claim 5, characterized in that, The diffusible hydrogen of the welded metal is The flux content of the welding electrode is 0.5ml / 100g to 4.0ml / 100g, and the moisture content of the electrode coating is 0.05% to 0.15%.

7. The weld metal according to claim 5, characterized in that, The deposited metal meets the following mechanical properties: the room temperature tensile strength of the weld is 620MPa~800MPa, the room temperature yield strength is 530MPa~700MPa, the room temperature elongation after fracture is 18%~35%, the high temperature tensile strength of the weld at 400℃ is ≥ 500MPa, the single impact value at 0℃ is ≥ 100J, the single impact value at -40℃ is ≥ 60J, and the drop hammer test ductile-brittle transition temperature is ≤-10℃.

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