A 1000mpa grade low-temperature high-toughness all-position welding electrode for marine engineering and a preparation method thereof

Abstract

This invention relates to a 1000MPa-grade low-temperature, high-toughness all-position welding electrode for marine engineering and its preparation method, belonging to the field of welding electrode technology. It addresses at least one of the problems of existing methods in preparing welding electrodes, such as poor strength-toughness matching, high cost, and inability to meet the requirements of 1000MPa-grade marine engineering steel. The welding electrode of this invention, through the synergistic effect of the core and coating, and the optimization of the alloying elements in the weld metal, ensures good matching between the welding material performance and the 1000MPa-grade marine engineering steel base material, meeting the construction requirements for all-position welding of steel structures. It exhibits good processability, excellent mechanical properties of the deposited metal, and good all-position welding performance. Specifically, the tensile strength of the deposited metal is >1000MPa, the yield strength is ≥980MPa, the KV2 at -50℃ is ≥50J, the tensile strength of the weld joint is ≥1000MPa, the KV2 of the weld metal at -50℃ is ≥32J, and the KV2 of the heat-affected zone at -50℃ is ≥61J. It has good adaptability to all-position welding, meeting the requirements for horizontal, vertical, and flat welding positions.

Description

Technical Field

[0001] This invention relates to the field of welding electrode technology, and in particular to a 1000MPa grade low-temperature high-toughness all-position welding electrode for marine engineering and its preparation method. Background Technology

[0002] In recent years, the demand for marine engineering steel has continued to increase, and the future development prospects for marine engineering steel are broad. Welding is an important means of connecting steel structures, among which shielded metal arc welding (SMAW) has a wide range of applications due to its advantages such as low cost and strong all-position welding adaptability. However, domestic research on 1000MPa grade welding electrodes for marine engineering steel is limited and faces several problems, such as an unreasonable match between weld metal strength and toughness, making it difficult to maintain good low-temperature toughness while achieving high strength; high-strength steel has high crack sensitivity and poor weldability, making welded joints prone to becoming weak points; and poor adaptability to all-position welding. The quality of the welded joint directly determines the quality of the welded structure. Therefore, it is essential to develop a high-strength, high-toughness 1000MPa grade low-temperature, high-toughness welding electrode for marine engineering that meets all-position welding adaptability.

[0003] Currently, domestic welding material manufacturers produce high-strength steel manual welding electrodes for marine engineering. The electrode coating composition and core alloy element design both adhere to a low-hydrogen design, aiming to effectively control the diffusible hydrogen content in the weld metal, achieving ultra-low hydrogen levels and reducing its susceptibility to cold cracking. The core alloy element content is also designed to be low-alloy, reducing hardenability. However, while low-alloy design improves weldability, the strength and toughness of the weld material do not meet application requirements. Therefore, matching the performance of low-alloy welding materials with high-strength and high-toughness welding materials is difficult, resulting in a poor strength-toughness ratio in the weld metal.

[0004] CN 116586816 A discloses an arc welding electrode for preheating-free welding of 1000MPa high-strength steel and its preparation method. This electrode exhibits advantages such as crack-free room-temperature welding and a good balance of strength and toughness in the weld metal. Its average tensile strength reaches 1125MPa, average yield strength reaches 1040MPa, and KV2 ≥ 94J at -40℃. Although the electrode described in the patent exhibits a good balance of strength and toughness, the Ni content in the core exceeds 4.5%, resulting in high cost. Summary of the Invention

[0005] Based on the above analysis, the present invention aims to provide a 1000MPa grade low-temperature high-toughness all-position welding electrode for marine engineering and its preparation method, in order to solve at least one of the problems of poor strength and toughness matching, high cost, and inability to meet the requirements of 1000MPa grade marine engineering steel in welding electrodes prepared by existing methods.

[0006] In a first aspect, the present invention provides a 1000MPa-grade low-temperature, high-toughness, all-position welding electrode for marine engineering, the welding electrode comprising a core and a coating, in the following mass percentages:

[0007] The welding core comprises: C: 0.03-0.08%, Si: 0.2-0.5%, Mn: 1.0-2.4%, Ni: 2.0-3.5%, Cr: 0.4-0.9%, Mo: 0.7-1.1%, S < 0.005%, P < 0.005%, with the balance being Fe and unavoidable impurities;

[0008] The coating comprises: marble: 40-48%, fluorite: 18-25%, quartz: 5-10%, rutile: 3-8%, titanium dioxide: 0.5-1.5%, soda ash: 0-1%, deoxidized iron alloy: 12-23%, and alloyed iron alloy: 5-18%.

[0009] Furthermore, the deoxidized iron alloy comprises ferromanganese: 2-5%, ferrosilicon: 3-6%, and ferrotitanium: 7-11%.

[0010] The alloyed iron alloy comprises ferromolybdenum: 0-5%, metallic manganese: 4-8%, and nickel powder: 1-5%.

[0011] Furthermore, after welding with the aforementioned welding rods, the tensile strength of the deposited metal is >1000MPa, the yield strength is ≥980MPa, the KV2 at -50℃ is ≥50J, the tensile strength of the welded joint is ≥1000MPa, the KV2 of the weld metal at -50℃ is ≥32J, and the KV2 of the heat-affected zone at -50℃ is ≥61J.

[0012] Secondly, the present invention provides a method for preparing the above-mentioned welding electrode, comprising the following steps:

[0013] (1) The welding core material is smelted and refined three times in sequence, cast into a continuous casting billet, rolled into wire rod, and drawn to obtain welding core steel;

[0014] (2) Weigh the raw material of the medicine according to the mass percentage, and then dry mix and wet mix in sequence, and extrude to obtain powder;

[0015] (3) The welding core steel and the powder are coated and baked using a hydraulic welding electrode coating machine to obtain the welding electrode.

[0016] Furthermore, in step (1), desulfurized molten iron is used as raw material and smelted in a vacuum induction furnace, with a vacuum degree of less than 1 Pa during smelting.

[0017] Furthermore, during the smelting process, the impurity elements are guaranteed to be S≤0.005%, P≤0.005%, O≤0.003%, N≤0.003%, and H≤0.0003%.

[0018] Furthermore, in step (1), the temperature of the three refining processes is 1580±20℃, and the refining times for the three processes are 30~50min, 20~40min, and 20~30min, respectively.

[0019] Furthermore, in step (2), the dry mixing time is ≥10 min and the wet mixing time is ≥7 min.

[0020] Furthermore, in step (3), the mass ratio of the core steel to the powder is 0.4:1 to 0.6:1, and the eccentricity of the welding rod is less than 7%.

[0021] Thirdly, the present invention provides a welding method for the above-mentioned welding rod, comprising: drying at 400°C for 1 hour and then placing it in a heat preservation container for later use; welding current of 160-170A; welding voltage of 25-32V; welding speed of 140-200mm / min; preheating temperature of 80-120°C; interpass temperature of 100-120°C; and post-heating temperature of 200-250°C for 2 hours.

[0022] Compared with the prior art, the present invention can achieve at least one of the following beneficial effects:

[0023] (1) The welding electrode described in this invention, through the synergistic effect of the core and the coating, and the optimization of the alloying elements of the weld metal, ensures that the performance of the welding material is well matched with the 1000MPa grade marine engineering steel base material, meets the construction requirements of all-position welding of steel structures, has good processability, excellent mechanical properties of the deposited metal, and good all-position welding performance. Among them, the tensile strength of the deposited metal is >1000MPa, the yield strength is ≥980MPa, the KV2 at -50℃ is ≥50J, the tensile strength of the welded joint is ≥1000MPa, the KV2 of the weld metal at -50℃ is ≥32J, the KV2 of the heat-affected zone at -50℃ is ≥61J, and the adaptability of all-position welding is good, meeting the requirements of horizontal, vertical and flat welding positions;

[0024] (2) The electrode deposited metal and butt joint prepared by the method of the present invention have good performance. The weld joint strength in horizontal, vertical and flat welding positions is ≥1000MPa, and the low-temperature impact absorption energy at -50℃ is >32J. The strength and low-temperature toughness of the deposited metal are well matched, while taking into account the low-temperature toughness of the weld zone in the weld joint, ensuring the service capability in low-temperature environment, and matching well with the steel plate base material;

[0025] (3) Compared with other welding methods, the electrode welding method of the present invention has lower manufacturing and usage costs, lower requirements for welding environment and assembly precision, flexible welding operation, and can achieve all-position welding by adjusting the flux ratio.

[0026] In this invention, the above-described technical solutions can be combined with each other to achieve more preferred combinations. Other features and advantages of this invention will be set forth in the following description, and some advantages may become apparent from the description or be learned by practicing the invention. The objects and other advantages of this invention can be realized and obtained from what is particularly pointed out in the description and drawings. Attached Figure Description

[0027] The accompanying drawings are for illustrative purposes only and are not intended to limit the invention. Throughout the drawings, the same reference numerals denote the same parts.

[0028] Figure 1 This is a photograph of the welding electrode before slag removal in Embodiment 1 of the present invention;

[0029] Figure 2 This is a photograph of the welding electrode after slag removal in Embodiment 1 of the present invention. Detailed Implementation

[0030] The preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings, which constitute a part of the present invention and are used together with the embodiments of the present invention to illustrate the principles of the present invention, but are not intended to limit the scope of the present invention.

[0031] A specific embodiment of the present invention discloses a 1000MPa-grade low-temperature high-toughness all-position welding electrode for marine engineering. The welding electrode comprises a core and a coating, in the following mass percentages:

[0032] The welding core comprises: C: 0.03-0.08%, Si: 0.2-0.5%, Mn: 1.0-2.4%, Ni: 2.0-3.5%, Cr: 0.4-0.9%, Mo: 0.7-1.1%, S < 0.005%, P < 0.005%, with the balance being Fe and unavoidable impurities;

[0033] The coating comprises: marble: 40-48%, fluorite: 18-25%, quartz: 5-10%, rutile: 3-8%, titanium dioxide: 0.5-1.5%, soda ash: 0-1%, deoxidized iron alloy: 12-23%, and alloyed iron alloy: 5-18%.

[0034] Preferably, the deoxidized iron alloy comprises, by mass fraction, 2-5% ferromanganese, 3-6% ferrosilicon, and 7-11% ferrotitanium.

[0035] The alloyed iron alloy comprises ferromolybdenum: 0-5%, metallic manganese: 4-8%, and nickel powder: 1-5%.

[0036] Preferably, the ratio of marble to fluorite is 1.6–2.5, and the total addition of rutile and titanium dioxide is less than or equal to 8%. In this invention, to ensure the performance of the weld metal, an alkaline slag-based electrode coating is selected to guarantee a high alloy element transition coefficient, fewer weld impurities, lower impurity gas content, and better crack resistance. The electrode coating composition is based on marble, fluorite, silicates (quartz), and titanates (rutile and titanium dioxide), and employs a combined deoxidation process using ferrotitanium, ferrosilicon, and ferromanganese to obtain a coating composition that meets the performance requirements of 1000MPa grade electrodes. This alkaline slag coating composition, through gas-slag combined protection, results in low content of impurities such as H, O, N, S, and P in the deposited metal, excellent mechanical properties such as plasticity and toughness, good crack resistance, and allows for all-position welding.

[0037] The welding electrode described in this invention exhibits good processability, excellent mechanical properties of the deposited metal, and good all-position welding performance. Specifically, the tensile strength of the deposited metal is >1000 MPa, preferably 1002–1049 MPa; the yield strength is ≥980 MPa, preferably 980–1003 MPa; the KV2 at -50℃ is ≥50 J; the tensile strength of the welded joint is ≥1000 MPa, preferably 1090–1105 MPa; the elongation is 16.0–17.0%; and the diffusible hydrogen content is 1.94–2.40 mL / 100 g.

[0038] The weld metal exhibits a KV2 ≥ 32 J at -50℃ and a KV2 ≥ 61 J in the heat-affected zone at -50℃, demonstrating excellent adaptability to all-position welding and meeting the requirements for horizontal, vertical, and flat welding positions. Optimization of the weld metal alloy elements ensures good matching between the welding material performance and the 1000MPa grade marine engineering steel base material, meeting the construction requirements for all-position welding of steel structures.

[0039] The welding electrode of the present invention is applicable to the following composition of 1000MPa grade marine engineering steel base material, according to the following mass percentage: C: 0.05-0.10%, Si: 0.2-0.4%, Mn: 0.5-1.0%, P≤0.01%, S≤0.01%, Cr: 0.5-0.7%, Ni: 5-9%, Mo: 0.5-0.9%, with the balance being Fe.

[0040] The alloy composition of the welding core is a decisive factor in determining the properties of the weld metal. To ensure that the welding electrode has good strength and toughness, a welding core design approach combining micro-alloying and multi-element alloy composite reinforcement is adopted. The specific roles and ranges of alloying elements in the welding core are as follows:

[0041] C: C is a strengthening element that can improve the hardenability of weld metal, increase the tendency of martensitic transformation and the sensitivity to cold cracking in welding, and thus worsen the low-temperature impact toughness. Therefore, under the premise of meeting the strength requirements, the C content should be reduced as much as possible. In this invention, the C content is 0.03-0.08%.

[0042] Si: Si has the function of deoxidation and strengthening of the weld matrix. However, excessive Si content will increase the hardenability of the weld metal, resulting in a decrease in the ductility and toughness of the weld metal. In this invention, the Si content is 0.2-0.5%.

[0043] Mn: Like Si, Mn has the function of deoxidation and strengthening the weld matrix, and it is also beneficial to weld desulfurization and prevents the formation of iron sulfides that cause hot cracking. However, excessive Mn content will significantly reduce the low-temperature impact toughness of weld metal. In this invention, the Mn content is 1.0-2.4%.

[0044] Ni: Ni is an austenite-forming element that can exist in a miscible form with Fe in austenite and ferrite structures, playing a role in solid solution strengthening and improving strength. It also enhances low-temperature impact toughness and lowers the ductile-brittle transition temperature. Therefore, Ni is an ideal alloying element for welding materials of 1000MPa grade high-strength steel. Thus, the Ni content in this invention is 2.0-3.5%.

[0045] Cr: Cr is a ferrite-forming element and a medium-strong carbide-forming element. Its carbides increase the strength and hardness of the weld metal, and Cr can improve the hardenability of the weld structure, increasing the amount of martensite and bainite, but decreasing the plasticity and toughness. Therefore, the Cr content in this invention is 0.4-0.9%.

[0046] Mo: Mo is the main element for obtaining high-strength weld metal; as a high-melting-point substance, it has a good grain-refining effect and does not significantly damage ductility and toughness while improving strength. It can significantly improve the hardenability of steel and prevent temper brittleness. Therefore, the Mo content in this invention is 0.7-1.1%.

[0047] S and P: S and P are harmful elements. Controlling their content is crucial to improving weld purity and weldability. S and P are highly prone to segregation and easily form non-metallic inclusions and second-phase particles between grains. They can significantly reduce the plasticity and toughness of steel. Therefore, the content of S and P in welding wire must be strictly controlled. Thus, in this invention, S is less than 0.005% and P is less than 0.005%.

[0048] The welding electrode described in this invention has a core alloy system of C-Si-Mn-Ni-Cr-Mo, with Ni being the highest alloying element at 2.0-3.5%, and the total content of alloying elements not exceeding 8%. The welding material composition is designed using micro-alloying technology and multi-component composite strengthening, and the content of impurity elements such as P and S in the core is effectively controlled by ultra-pure smelting technology, as well as the content of diffusible hydrogen.

[0049] The composition and formulation design principle of the medicated coating of this invention are as follows:

[0050] Marble: Decomposition produces CO2 and CaO, acting as both a gasifier and a slag-forming agent. When marble decomposes and releases gas, it increases the blowing force on the molten droplets, reducing spatter. The decomposed CaO stabilizes the electric arc and increases the basicity of the slag, resulting in effective desulfurization and dephosphorization, which is beneficial for improving the low-temperature toughness of the weld metal. Therefore, the marble content should be controlled between 40% and 48%.

[0051] Fluorite: Fluorite acts as a slag-forming agent, lowering the melting point and viscosity of the slag, making the molten pool more reactive, and improving slag removal. During welding, fluorite has a strong dehydrogenation effect, reducing the hydrogen content in the weld metal and significantly reducing hydrogen porosity in the weld. Therefore, the fluorite content is typically between 18% and 25%. The ratio of marble to fluorite in the electrode coating has a significant impact on process performance; a ratio of 1.6 to 2.5 is generally preferred, with the total amount of marble and fluorite controlled between 58% and 73%.

[0052] Quartz: Quartz is a slag-forming agent that can adjust the viscosity of molten slag and improve its fluidity. It has a certain diluting effect in alkaline slag systems and can also improve the coating performance of alkaline welding electrodes. Therefore, the amount of quartz added is 5% to 10%.

[0053] Rutile: Rutile has arc-stabilizing and slag-forming properties, and can adjust the melting point, viscosity, surface tension, and fluidity of molten slag, which is beneficial for all-position welding and improving weld formation. Appropriate addition of rutile can improve the processing performance of welding electrodes. Therefore, the amount of rutile added should be controlled at 3-8%.

[0054] Titanium dioxide: A small amount of titanium dioxide is added to basic welding electrodes to act as a slag-forming and plasticizer, giving the coating good plasticity and improving the electrode's coating performance and welding process performance. The total amount of rutile and titanium dioxide added is less than 8%, and it is used in combination with quartz.

[0055] Soda ash (Na2CO3): The main function of soda ash is to improve the coating performance of welding electrodes. Adding too little will not improve the coating performance; adding too much will cause the electrode coating to become damp, leading to an increase in the hydrogen content of the weld metal and causing cracks. Therefore, the amount of soda ash added should be 0-1%.

[0056] Deoxidized ferroalloys: Deoxidation is achieved through a combination of ferromanganese, ferrosilicon, and ferrotitanium, with the total ferroalloy content around 12-23%. Ferrotitanium primarily acts as a deoxidizer, protecting Mn and Si from oxidation and allowing them to transition into the weld metal. Ferromanganese and ferrosilicon are mainly alloying agents, also contributing to deoxidation. Sufficient Mn and Si must be present in the weld metal composition to ensure mechanical properties. Ferromanganese also has a certain desulfurization effect. Ferrosilicon's main functions are deoxidation and desulfurization, modifying inclusions in the weld metal to improve its low-temperature toughness. Ferromanganese: 2-5%, Ferrosilicon: 3-6%, Ferrotitanium: 7-11%.

[0057] Alloyed ferroalloys: Ferromolybdenum, metallic manganese, and nickel powder are used to alloy the weld metal. Nickel powder's main function is alloying, simultaneously improving the weld metal's strength and low-temperature toughness while lowering the ductile-brittle transition temperature. Ferromolybdenum and metallic manganese primarily function as alloyers; small amounts result in minimal alloying effects and insufficient strength increase in the weld metal, while excessive amounts lead to a significant strength increase but may cause a substantial decrease in toughness. Ferromolybdenum: 0-5%, metallic manganese: 4-8%, nickel powder: 1-5%.

[0058] Specifically, the diameter of the welding electrode of the present invention is 4.0±0.1mm.

[0059] The flux coating of this invention uses a low-hydrogen alkaline slag-based flux coating. The flux coating not only protects the weld metal, but also introduces alloying elements into the weld metal by adding alloy powder and other materials. The welding electrode is designed and prepared using a low-hydrogen flux coating and a low-alloy welding core, resulting in less welding spatter and better weld formation.

[0060] The electrode deposited metal and butt joint prepared using this invention exhibit excellent performance. The weld joint strength in horizontal, vertical, and planar welding positions is ≥1000MPa, the low-temperature impact absorption energy at -50℃ is >32J, and the low-temperature impact absorption energy at -50℃ in the heat-affected zone is ≥61J. The strength and low-temperature toughness of the deposited metal are well-matched, while also considering the low-temperature toughness of the weld zone in the weld joint, ensuring service capability in low-temperature environments and good compatibility with the base steel plate.

[0061] Another specific embodiment of the present invention discloses a method for preparing the above-mentioned 1000MPa-grade low-temperature high-toughness all-position welding electrode for marine engineering, comprising the following steps:

[0062] (1) The welding core material is smelted and refined three times in sequence, cast into a continuous casting billet, rolled into wire rod, and drawn to obtain welding core steel;

[0063] (2) Weigh the raw material of the medicine according to the mass percentage, and then dry mix and wet mix in sequence, and extrude to obtain powder;

[0064] (3) The welding core steel and the powder are coated and baked using a hydraulic welding electrode coating machine to obtain the welding electrode.

[0065] Specifically, in step (1), desulfurized molten iron is used as raw material and smelted in a vacuum induction furnace, with a vacuum degree of less than 1 Pa during smelting.

[0066] Preferably, during the smelting process, the impurity elements are guaranteed to be S≤0.005%, P≤0.005%, O≤0.003%, N≤0.003%, and H≤0.0003%.

[0067] Specifically, the temperature for the three refining processes is 1580±20℃, and the refining times for the three processes are 30~50min, 20~40min, and 20~30min, respectively.

[0068] Preferably, in step (1), the diameter of the wire rod is 5.5 mm.

[0069] Specifically, in step (2), the dry mixing time is ≥10 min.

[0070] Specifically, in step (2), the wet mixing involves adding water glass for wet mixing, and the wet mixing time is not less than 7 minutes.

[0071] Specifically, in step (3), the mass ratio of the welding core steel to the powder is 0.4:1 to 0.6:1.

[0072] Specifically, in step (3), the eccentricity of the welding electrode is less than 7%.

[0073] Another specific embodiment of the present invention discloses a welding method for the above-mentioned welding rod, comprising: drying at 400°C for 1 hour and then placing it in a heat preservation container for later use; welding current of 160-170A; welding voltage of 25-32V; welding speed of 140-200mm / min; preheating temperature of 80-120°C; interpass temperature of 100-120°C; and post-heating temperature of 200-250°C for 2 hours.

[0074] Compared with other welding methods, the electrode welding method of the present invention has lower manufacturing and usage costs, lower requirements for welding environment and assembly precision, more flexible welding operation, and can achieve all-position welding by adjusting the flux coating ratio.

[0075] The technical solution of the present invention will be further explained below with reference to specific embodiments.

[0076] The composition of the core of Examples 1-4 and Comparative Examples 1-3 is shown in Table 1, and the composition of the coating is shown in Table 2.

[0077] Table 1

[0078]

[0079]

[0080] Table 2

[0081]

[0082] Example 1

[0083] A method for preparing the above-mentioned 1000MPa-grade low-temperature high-toughness all-position welding electrode for marine engineering includes the following steps:

[0084] (1) Desulfurized molten iron is used as raw material and smelted in a vacuum induction furnace. The vacuum degree during smelting is less than 1 Pa. The elements are controlled within the design range during the smelting process, as shown in Table 1. During the smelting process, the impurity elements S≤0.005%, P≤0.005%, O≤0.003%, N≤0.003%, and H≤0.0003% are guaranteed. The steel is refined three times in sequence. The temperature of the three refining processes is 1580±20℃, and the refining time is 30~50min, 20~40min, and 20~30min respectively. After refining, the molten steel is cast into a continuous casting billet, which is then rolled into a wire rod with a diameter of 5.5mm by a rolling mill. After mechanical peeling, the wire rod is ground by a sand belt and then drawn into a roller die. After multiple drawing processes, the core steel is obtained.

[0085] (2) Weigh the raw material of the medicine according to the mass percentage, and put it into the mixer in sequence for dry mixing and wet mixing. The dry mixing time is ≥10min, and the wet mixing is carried out by entering water glass for wet mixing. The wet mixing time is not less than 7min. The wet-mixed powder is squeezed into a ball. The ball should not be stored for too long to avoid hardening, and the powder is obtained.

[0086] (3) Weigh the powder and the core steel at a mass ratio of 0.5:1, apply the core steel and the powder to the core steel using a hydraulic electrode coating machine, and bake them to obtain the electrode. The eccentricity of the electrode is less than 7%.

[0087] Example 2

[0088] The preparation method of the above-mentioned 1000MPa grade marine engineering low temperature high toughness all-position welding electrode is the same as that in Example 1, except that in step (3), the mass ratio of powder to core steel is 0.4:1, and the eccentricity of the electrode is less than 7%.

[0089] Example 3

[0090] The preparation method of the above-mentioned 1000MPa grade marine engineering low temperature high toughness all-position welding electrode is the same as that in Example 1, except that in step (3), the mass ratio of powder to core steel is 0.6:1, and the eccentricity of the electrode is less than 7%.

[0091] Example 4

[0092] The preparation method of the above-mentioned 1000MPa grade low temperature high toughness all-position welding electrode for marine engineering is the same as that in Example 1, wherein the eccentricity of the electrode is less than 7%.

[0093] Comparative Example 1

[0094] The preparation method of the above-mentioned low-temperature high-toughness all-position welding electrode for marine engineering in this comparative example is the same as that in Example 1.

[0095] Comparative Example 2

[0096] The preparation method of the above-mentioned low-temperature high-toughness all-position welding electrode for marine engineering in this comparative example is the same as that in Example 1.

[0097] Comparative Example 3

[0098] The preparation method of the above-mentioned low-temperature high-toughness all-position welding electrode for marine engineering in this comparative example is the same as that in Example 1.

[0099] Comparative Example 4

[0100] The preparation method of the above-mentioned low-temperature high-toughness all-position welding electrode for marine engineering in this comparative example is the same as that in Example 1.

[0101] Comparative Example 5

[0102] The preparation method of the above-mentioned low-temperature high-toughness all-position welding electrode for marine engineering in this comparative example is the same as that in Example 1.

[0103] Comparative Example 6

[0104] The composition and preparation method of the low-temperature high-toughness all-position welding electrode for marine engineering described in this comparative example are the same as those in Example 1, except that in step (3), the mass ratio of powder to core steel is 0.3:1.

[0105] In the following test examples, the base material components meet the following mass percentage requirements: C: 0.05–0.10%, Si: 0.2–0.4%, Mn: 0.5–1.0%, P≤0.01%, S≤0.01%, Cr: 0.5–0.7%, Ni: 5–9%, Mo: 0.5–0.9%, with the balance being Fe.

[0106] Experimental Example 1

[0107] The welding electrodes prepared in Examples 1-4 and Comparative Examples 1-6 were subjected to cladding metal welding tests. They were first dried at 400℃ for 1 hour before use. The cladding metal welding process parameters were as follows: welding current 160-170A, welding voltage 25-32V, welding speed 140-200mm / min, preheating temperature 80-120℃, interpass temperature 100-120℃, and post-heating temperature 200-250℃ × 2h.

[0108] The welded plates were cut and subjected to mechanical property tests. The test results are shown in Table 3.

[0109] Table 3

[0110]

[0111]

[0112] As shown in Table 3, the tensile strength of the welded plate can reach over 1000MPa, while the yield strength exceeds 980MPa, the impact energy at -50℃ is higher than 50J, and the diffusible hydrogen content in the welding electrode is less than 2.5ml / 100g. This indicates that the welding electrode developed in this invention has a good strength and toughness match, low diffusible hydrogen content, and excellent performance, which can meet the welding requirements of 1000MPa grade marine engineering steel and other high-strength materials.

[0113] Experimental Example 2

[0114] Welding electrodes prepared in Examples 1-4 and Comparative Examples 1-6 were tested using manual arc welding. The welding process was observed, and the welding parameters are shown in Table 4. The results are shown in Table 5.

[0115] Table 4

[0116]

[0117] Table 5

[0118]

[0119]

[0120] As shown in Table 5, the welding electrodes of Examples 1-4 are superior to those of Comparative Examples 1-6 in terms of arc stability, slag removal, weld bead formation, and welding defects, exhibiting good welding processability. Example 1 welding electrode before slag removal... Figure 1 As shown, after slag removal, as Figure 2 As shown.

[0121] Welding tests of butt joints were conducted using the welding electrodes of Example 1 and Comparative Example 1 of this invention, employing the shielded metal arc welding method. The mechanical properties of the butt joints were tested, and the results are shown in Table 6.

[0122] Table 6

[0123]

[0124] As can be seen from the data in Tables 5 and 6 of the embodiments and comparative examples, the welding electrode of the present invention has good processability and can realize welding in different positions such as flat welding, horizontal welding and vertical welding. The tensile strength of the butt joint exceeds 1090MPa, the weld metal KV2 at -50℃ is ≥32J, the heat-affected zone KV2 at -50℃ is ≥61J, and the weld metal properties are well matched with the 1000MPa grade marine engineering steel base material. The welding electrode of the present invention meets the welding and construction requirements of this grade of steel structure.

[0125] The same experiments were also conducted on other embodiments and comparative examples, and the results were basically the same. Due to space limitations, they will not be listed one by one.

[0126] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. A welding method for a 1000MPa-grade low-temperature, high-toughness, all-position welding electrode for marine engineering, characterized in that, include: The welding current is 160~170A, the welding voltage is 25~32V, the welding speed is 140~200mm / min, the preheating temperature is 80~120℃, the interpass temperature is 100~120℃, and the post-heating temperature is 200~250℃×2h. The welding electrode comprises a core and a coating, in the following mass percentages: The welding core comprises: C: 0.03~0.08%, Si: 0.21~0.31%, Mn: 2.02~2.4%, Ni: 2.96~3.12%, Cr: 0.54~0.9%, Mo: 0.98~1.1%, S < 0.005%, P < 0.005%, with the balance being Fe and unavoidable impurities; The coating comprises: marble: 43-48%, fluorite: 18-20%, quartz: 8-10%, rutile: 3-8%, titanium dioxide: 0.5-1.5%, soda ash: 0-1%, deoxidized iron alloy: 12-23%, and alloyed iron alloy: 5-18%. The deoxidized iron alloy comprises ferromanganese: 2-5%, ferrosilicon: 3-6%, and ferrotitanium: 7-11%. The alloyed iron alloy comprises ferromolybdenum: 0-5%, metallic manganese: 4-8%, and nickel powder: 1-5%; After welding, the electrode exhibits the following properties: tensile strength of deposited metal > 1000 MPa, yield strength ≥ 980 MPa, KV2 ≥ 50 J at -50℃, tensile strength of welded joint ≥ 1000 MPa, KV2 ≥ 32 J at -50℃ for weld metal, KV2 ≥ 61 J at -50℃ for heat-affected zone, good adaptability to all-position welding, meeting the requirements for horizontal, vertical, and flat welding positions, and diffusible hydrogen content < 2.5 ml / 100 g. The welding electrode is prepared by the following method: (1) The welding core material is smelted and refined three times in sequence, cast into a continuous casting billet, rolled into wire rod, and drawn to obtain welding core steel; The temperature for the three refining processes is 1580±20℃, and the refining times for the three processes are 30~50min, 20~40min, and 20~30min, respectively. (2) Weigh the raw material of the medicine peel according to the mass percentage, and then dry mix and wet mix in sequence, and extrude to obtain powder; (3) The welding core steel and the powder are coated and baked to obtain the welding rod.

2. The welding method according to claim 1, characterized in that, In step (1), desulfurized molten iron is used as raw material and smelted in a vacuum induction furnace. The vacuum degree during smelting is less than 1 Pa.

3. The welding method according to claim 2, characterized in that, During the smelting process, the impurity elements must be guaranteed to be S≤0.005%, P≤0.005%, O≤0.003%, N≤0.003%, and H≤0.0003%.

4. The welding method according to claim 2, characterized in that, In step (2), the dry mixing time is ≥10 min and the wet mixing time is ≥7 min.

5. The welding method according to claim 2, characterized in that, In step (3), the mass ratio of the core steel to the powder is 0.4:1 to 0.6:1, and the eccentricity of the welding rod is less than 7%.

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