The application discloses a submerged-arc welding flux suitable for Q550qENH steel and a preparation method and deposited metal thereof.

Abstract

The application provides a submerged-arc welding flux suitable for Q550qENH steel and a preparation method and deposited metal, and belongs to the field of fluxes. The submerged-arc welding flux comprises the following chemical components: 1-5 parts of SiO2, 10-18 parts of MgO, 30-40 parts of Al2O3, 40-45 parts of ΣCaO, 0.5-3 parts of MnO, 0.5-1 part of Na2O, 0.5-1 part of K2O, 0.5-3 parts of TiO2, ≤1.0 part of Fe2O3, ≤0.020 part of S, ≤0.020 part of P and ≤5 parts of LiF. By reasonably designing the chemical components of the submerged-arc welding flux, the chemical components and the structure of the weld metal can be optimized by cooperating with special welding wires, the weld metal has good and reasonable mechanical performance indexes such as tensile strength, impact value, bending property, crack resistance and hardness under the as-welded condition, there are no pores, slag inclusions and cracks in the weld, the low-temperature impact toughness at-40 DEG C is above 100 J, and the standard requirements of the Q550qENH steel are completely met.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of welding flux, in particular to a submerged arc welding flux suitable for Q550qENH steel and a preparation method and deposited metal. BACKGROUND

[0002] Due to the excellent performance of Q550qENH steel, it not only has good strength and toughness, but also has good weather resistance, which can effectively protect the material from corrosion by atmosphere. It is often used to manufacture buildings and bridges, and is used to make riveted and bolted structures of highway bridges and railway bridges (including cross-sea bridges). A small amount of corrosion-resistant elements such as copper and nickel are added to Q550qENH steel, which has excellent strength, toughness, plasticity, elongation, forming, welding, abrasion, high temperature, fatigue resistance and other properties; at the same time, it has rust resistance, which can prolong the service life of the component, reduce the thickness and consumption, save labor and energy, etc. It is also used for steel structures that are exposed to the atmosphere for a long time, such as railways, vehicles, bridges, towers, photovoltaics, high-speed engineering, etc. It is used to manufacture containers, railway vehicles, oil derricks, harbor buildings, oil production platforms and vessels containing sulfur hydrogen corrosion medium in chemical and petroleum equipment.

[0003] However, how to ensure that the welded joint of Q550qENH steel has the same performance as the base material under high temperature, high pressure and various corrosion media after welding is a test of the welding material.

[0004] Embodiments of the application

[0005] The present application provides a submerged arc welding flux suitable for Q550qENH steel and a preparation method and deposited metal, to solve the technical problem of providing a submerged arc welding flux specially used for welding Q550qENH steel.

[0006] In a first aspect, the present application provides a submerged arc welding flux suitable for Q550qENH steel, which comprises the following chemical components in parts by weight: SiO2 1-5 parts, MgO 10-18 parts, Al2O3 30-40 parts, ΣCaO 40-45 parts, MnO 0.5-3 parts, Na2O 0.5-1 part, K2O 0.5-1 part, TiO2 0.5-3 parts, Fe2O3≤1.0 part, S≤0.020 part, P≤0.020 part and LiF≤5 parts.

[0007] Optionally, the submerged arc welding flux comprises the following chemical components in parts by weight: SiO2 4 parts, MgO 18 parts, Al2O3 30 parts, ΣCaO 45 parts, MnO 0.5 parts, Na2O 1 part, K2O 0.5 parts, TiO2 2 parts, Fe2O3 0.2 parts, S 0.012 parts, P 0.012 parts and LiF 2 parts.

[0008] Optionally, the submerged arc welding flux comprises the following chemical components by weight: SiO2 5 parts, MgO 12 parts, Al2O3 40 parts, ΣCaO 40 parts, MnO 0.8 parts, Na2O 0.6 parts, K2O 0.6 parts, TiO2 0.8 parts, Fe2O3 0.6 parts, S 0.010 parts, P 0.010 parts, and LiF 3 parts.

[0009] Optionally, the submerged arc welding flux comprises the following chemical components by weight: SiO2 2 parts, MgO 11 parts, Al2O3 35 parts, ΣCaO 42 parts, MnO 3 parts, Na2O 0.5 parts, K2O 1.0 parts, TiO2 0.5 parts, Fe2O3 0.5 parts, S 0.015 parts, P 0.015 parts, and LiF 4 parts.

[0010] In a second aspect, the present application provides a preparation method of the submerged arc welding flux according to any one of the first aspect or the embodiments thereof, and the method comprises:

[0011] mixing the component powders of the submerged arc welding flux to obtain a first mixed powder;

[0012] mixing and granulating the first mixed powder with a binder, and then pre-drying to obtain a second mixed powder;

[0013] first high-temperature baking part of the second mixed powder to obtain a first welding flux;

[0014] second high-temperature baking the remaining part of the second mixed powder to obtain a second welding flux;

[0015] mixing the first welding flux and the second welding flux to obtain the submerged arc welding flux.

[0016] Optionally, the mass of the binder is 10% to 14% of the total mass of the first mixed powder.

[0017] Optionally, the binder comprises lithium water glass.

[0018] Optionally, the first high-temperature baking is performed at a temperature of 400°C to 500°C for 2 hours.

[0019] Optionally, the second high-temperature baking is performed at a temperature of 600°C to 700°C for 0.5 hours.

[0020] Thirdly, this application provides a weld metal, which is prepared by welding Q550qENH steel with the submerged arc welding flux and the suitable welding wire CHW-S65NHQ3 described in any embodiment of the first aspect. The weld metal satisfies at least one of the following properties: tensile strength of 700 MPa to 760 MPa, reduction of area of ​​55% to 62%, and impact energy KV2 at -40℃ ≥ 100 J.

[0021] The technical solutions provided in this application have the following advantages compared with the prior art:

[0022] This application provides a submerged arc welding flux suitable for Q550qENH steel. By weight, the flux comprises the following chemical components: SiO2 1-5 parts, MgO 10-18 parts, Al2O3 30-40 parts, ΣCaO 40-45 parts, MnO 0.5-3 parts, Na2O 0.5-1 part, K2O 0.5-1 part, TiO2 0.5-3 parts, Fe2O3 ≤1.0 part, S ≤0.020 parts, P ≤0.020 parts, and LiF ≤5 parts. Through the rational design of the chemical composition of the submerged arc welding flux, each component plays its unique role in the flux and works synergistically to improve the weld's formability, mechanical properties, and process performance. When used with specialized welding wire, the chemical composition and microstructure of the weld metal are optimized. Under as-welded conditions, it exhibits good and reasonable mechanical properties such as tensile strength, impact value, bending performance, crack resistance, and hardness. Furthermore, the weld is free of porosity, slag inclusions, and cracks, and its low-temperature impact toughness at -40℃ is above 100J, fully meeting the standard requirements of Q550qENH steel. Attached Figure Description

[0023] 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.

[0024] 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.

[0025] Figure 1 This is a schematic flowchart illustrating the preparation method of submerged arc welding flux provided in the embodiments of this application. Detailed Implementation

[0026] 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.

[0027] 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.

[0028] Furthermore, in the description of this application, the terms "comprising," "including," etc., 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 entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. In this document, "and / or" describes the relationship between related objects, indicating that three relationships can exist; for example, A and / or B can represent: A alone, A and B simultaneously, or B alone. A and B can be singular or plural. In this document, "at least one" means one or more, and "more than" means two or more. "At least one," "at least one of the following," or similar expressions refer to any combination of these items, including any combination of single or plural items. For example, "at least one of a, b, or c" or "at least one of a, b, and c" can both represent: a, b, c, ab (i.e., a and b), ac, bc, or abc, where a, b, and c can be single or multiple. "Parts representation," such as parts by weight or parts by mass, indicates the proportional relationship between components. In the proportional relationships discussed in this article, parameters described by proportion should be understood as the first term of the proportion in the order of description, while the proportion figure should be understood as the second term. For example, if the mass ratio of substance A, substance B, and substance C is 1:2:3, then substances A, B, and C should correspond one-to-one with the proportion figure in the proportion in the order of description, i.e., the mass of substance A : the mass of substance B : the mass of substance C = 1:2:3.

[0029] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this application can be purchased from the market or prepared by existing methods.

[0030] This application provides a submerged arc welding flux suitable for Q550qENH steel. By weight, the submerged arc welding flux comprises the following chemical composition: SiO2 1-5 parts, MgO 10-18 parts, Al2O3 30-40 parts, ΣCaO 40-45 parts, MnO 0.5-3 parts, Na2O 0.5-1 part, K2O 0.5-1 part, TiO2 0.5-3 parts, Fe2O3 ≤1.0 part, S ≤0.020 parts, P ≤0.020 parts, and LiF ≤5 parts.

[0031] The functions of each component in the submerged arc welding flux suitable for Q550qENH steel are as follows:

[0032] Besides acting as an acid to reduce flux alkalinity, SiO2 also participates in the slag-forming process, helping to adjust the slag's solidification point, surface tension, and viscosity at high temperatures. Simultaneously, an appropriate amount of SiO2 is crucial for controlling weld formation, as it can balance the alkaline components in the flux, thereby optimizing weld quality and appearance. For example, the weight percentage of SiO2 can be 1 part, 2 parts, 3 parts, 4 parts, 5 parts, etc.

[0033] MgO: As a strong alkaline substance and an excellent slag-forming material, MgO not only controls the weld shape but also improves the impact toughness of the weld metal and effectively reduces the content of diffusible hydrogen. Although MgO has a high melting point, which may increase the viscosity and solidification temperature of the slag, by precisely controlling its addition amount (10 to 18 parts), good weld formation can be achieved while ensuring weld process performance. For example, the weight parts of MgO can be 10, 12, 14, 16, or 18 parts, etc.

[0034] Al2O3: As an amphoteric oxide, Al2O3 adjusts the viscosity of molten slag by increasing its surface tension. Adding a certain amount of Al2O3 can reduce indentation and its tendency in welds, thereby improving the appearance and mechanical properties of the weld. For example, the weight parts of Al2O3 can be 30 parts, 32 parts, 34 parts, 36 parts, 38 parts, 40 parts, etc.

[0035] ΣCaO (Total Calcium Oxide): ΣCaO plays a role in slag formation and increasing the basicity of welding flux. It mainly originates from CaO-containing compounds or other complexes synthesized through decomposition. It not only improves the flux's resistance to high currents but also enhances the mechanical properties of the weld. Simultaneously, ΣCaO has the effect of removing impurities such as sulfur (S) and phosphorus (P), contributing to improved weld purity and quality. For example, the weight percentage of ΣCaO can be 40 parts, 41 parts, 42 parts, 43 parts, 44 parts, 45 parts, etc.

[0036] MnO: MnO can reduce the tendency of welds to develop hot cracks, thereby improving weld reliability. However, excessive MnO content can lead to poor weld formation, so its addition amount must be strictly controlled (0.5 parts to 3 parts). For example, the weight parts of MnO can be 0.5 parts, 1 part, 1.5 parts, 2 parts, 2.5 parts, 3 parts, etc.

[0037] Na₂O and K₂O: As low-ionization oxides, Na₂O and K₂O can increase the basicity of the flux and enhance the stability of the arc. Appropriate amounts of Na₂O and K₂O help improve weld formation and slag removal, thereby improving welding efficiency and quality. For example, the weight parts of Na₂O can be 0.5 parts to 1 part, etc. For example, the weight parts of K₂O can be 0.5 parts, 0.6 parts, 0.7 parts, 0.8 parts, 0.9 parts, 1 part, etc.

[0038] TiO2: TiO2 is an acidic oxide that can improve the physical properties of slag, such as transforming long slag into short slag and allowing the molten slag to change more rapidly with temperature. This contributes to rapid weld formation and good slag removal, thereby optimizing the welding process and improving weld quality. For example, the weight parts of TiO2 can be 0.5 parts, 1 part, 1.5 parts, 2 parts, 2.5 parts, 3 parts, etc.

[0039] LiF: LiF can lower the molten pool temperature and improve the impact and wear resistance of the weld. As an important inorganic fluorine material, LiF can also enhance the acid corrosion resistance of the weld metal, thereby broadening the application range of the weld. For example, the weight parts of LiF can be 5 parts, 4.5 parts, 4 parts, 3.5 parts, 3 parts, 2.5 parts, etc.

[0040] In summary, the components in the submerged arc welding flux for Q550qENH steel work synergistically to achieve excellent weld formation, mechanical properties, and process performance.

[0041] In some embodiments, the submerged arc welding flux comprises the following chemical components by weight: 4 parts SiO2, 18 parts MgO, 30 parts Al2O3, 45 parts ΣCaO, 0.5 parts MnO, 1 part Na2O, 0.5 parts K2O, 2 parts TiO2, 0.2 parts Fe2O3, 0.012 parts S, 0.012 parts P, and 2 parts LiF.

[0042] In some embodiments, the submerged arc welding flux comprises the following chemical components by weight: 5 parts SiO2, 12 parts MgO, 40 parts Al2O3, 40 parts ΣCaO, 0.8 parts MnO, 0.6 parts Na2O, 0.6 parts K2O, 0.8 parts TiO2, 0.6 parts Fe2O3, 0.010 parts S, 0.010 parts P, and 3 parts LiF.

[0043] In some embodiments, the submerged arc welding flux comprises the following chemical components by weight: 2 parts SiO2, 11 parts MgO, 35 parts Al2O3, 42 parts ΣCaO, 3 parts MnO, 0.5 parts Na2O, 1.0 part K2O, 0.5 parts TiO2, 0.5 parts Fe2O3, 0.015 parts S, 0.015 parts P, and 4 parts LiF.

[0044] Figure 1 This is a schematic flowchart illustrating the preparation method of submerged arc welding flux provided in the embodiments of this application.

[0045] like Figure 1 As shown, this application provides a method for preparing submerged arc welding flux according to any of the above embodiments, the method comprising:

[0046] S1. Mix the component powders of the submerged arc welding flux to obtain a first mixed powder;

[0047] The powdered components of submerged arc welding flux are mixed to ensure uniform distribution of each component within the flux. This is a fundamental step in preparing high-quality flux and directly affects its chemical composition and physical properties.

[0048] S2. The first mixture is mixed with the binder and granulated, then pre-dried to obtain the second mixed powder.

[0049] The granulation process forms the mixed powder into granules, facilitating subsequent processing and use. The pre-drying step removes excess moisture and volatiles from the granules, preventing cracks or bubbles from forming during baking and ensuring the stability and quality of the flux.

[0050] In some embodiments, the mass of the binder is 10% to 14% of the total mass of the first mixed powder.

[0051] The binder mass is limited to 10% to 14% of the total mass of the first mixed powder. The amount of binder (such as lithium-ion glass) added directly affects the granulation effect and the strength of the flux. An appropriate amount of binder can ensure good adhesion between powder particles, forming a stable particle structure. Too much binder may cause the flux to be too viscous, making it difficult to disperse and coat; while too little binder may make the particle structure loose, affecting the stability and strength of the flux. For example, the binder mass can be 10%, 11%, 12%, 13%, 14%, etc., of the total mass of the first mixed powder.

[0052] In some embodiments, the binder includes lithium water glass.

[0053] S3. A portion of the second mixed powder is subjected to a first high-temperature baking to obtain a first flux;

[0054] In some embodiments, the temperature of the first high-temperature baking is 400℃~500℃, and the baking time is 2 hours.

[0055] The first high-temperature baking is designed to further solidify the particles, improving the strength and stability of the flux. A temperature range of 400℃ to 500℃ ensures that the components in the flux undergo appropriate chemical reactions, forming more stable compounds. Simultaneously, a baking time of 2 hours ensures that the reaction proceeds fully, achieving the desired curing effect. For example, the temperature for the first high-temperature baking can be 400℃, 420℃, 440℃, 460℃, 480℃, 500℃, etc.

[0056] S4. The remaining portion of the second mixed powder is subjected to a second high-temperature baking to obtain the second flux;

[0057] In some embodiments, the temperature of the second high-temperature baking is 600℃~700℃, and the baking time is 0.5h.

[0058] Compared to the first high-temperature baking, the second high-temperature baking involves a higher temperature and a shorter time. These baking conditions are designed to further refine the flux's structure and properties, making it more suitable for specific soldering needs. High-temperature baking removes residual moisture and volatiles from the flux while promoting further reaction and curing of its components. The shorter baking time helps prevent over-sintering or burning of the flux, maintaining its good physical properties and chemical stability. For example, the second high-temperature baking temperature can be 600°C, 620°C, 640°C, 660°C, 680°C, 700°C, etc.

[0059] S5. Mix the first flux and the second flux to obtain the submerged arc welding flux.

[0060] Mixing the first flux and the second flux yields a submerged arc welding flux with comprehensive performance. This mixing method fully utilizes the performance characteristics of fluxes under different baking conditions, resulting in a flux that possesses both high strength and stability, as well as good welding performance and slag removal properties.

[0061] Based on a general inventive concept, this application provides a weld metal, which is prepared by welding Q550qENH steel with the submerged arc welding flux and the suitable welding wire CHW-S65NHQ3 described in any of the above embodiments. The weld metal satisfies at least one of the following properties: tensile strength of 700 MPa to 760 MPa, reduction of area of ​​55% to 62%, and impact energy KV2 ≥ 100 J at -40℃.

[0062] This application rationally adopts the proportion of each element content, so that the flux of the present invention has good welding processability, beautiful weld formation, and the slag shell can automatically lift and fall off. It is especially suitable for high strength and high toughness welding, resulting in excellent weld mechanical properties and ensuring the low-temperature impact toughness of the weld metal (-40℃).

[0063] The advantages of the submerged arc welding flux and its preparation method provided in this application are summarized as follows:

[0064] (1) Composition optimization and synergistic effect: By precisely controlling the content of each component (such as SiO2, MgO, Al2O3, ΣCaO, MnO, etc.), the composition of the flux was optimized. These components play their unique roles in the flux and work synergistically to improve the weld's formability, mechanical properties and process performance.

[0065] (2) Good weldability: The prepared flux has good weldability, which can ensure the stability and reliability of the welding process. The weld is aesthetically pleasing, and the slag shell can automatically lift and fall off, reducing the cleaning work after welding and improving welding efficiency.

[0066] (3) High strength and high toughness: It is particularly suitable for welding requirements with high strength and high toughness, such as welding Q550qENH steel. The components in the flux help to improve the mechanical properties of the weld, including tensile strength, reduction of area and low temperature impact toughness.

[0067] (4) Excellent comprehensive performance: By mixing fluxes obtained under different baking conditions, a submerged arc welding flux with comprehensive performance was obtained. This flux has both high strength and stability, as well as good welding performance and slag removal properties.

[0068] (5) Precise control of baking conditions: Precise control of baking conditions (such as temperature and time) helps ensure that the components in the flux undergo proper chemical reactions to form more stable compounds. At the same time, it avoids excessive sintering or burning of the flux, maintaining its good physical properties and chemical stability.

[0069] (6) Wide range of applications: The addition of inorganic fluorine materials such as LiF to the flux enhances the acid corrosion resistance of the weld metal, thereby broadening the application range of the weld. This makes the flux suitable not only for welding Q550qENH steel, but also for other occasions with special requirements for weld performance.

[0070] (7) Environmental protection and sustainability: Although this point is not explicitly mentioned in the original description, reasonable component selection and preparation process help reduce the emission of harmful substances during the welding process, which meets the requirements of environmental protection and sustainable development.

[0071] In summary, this method for preparing submerged arc welding flux improves the overall performance of the flux by optimizing its composition, precisely controlling baking conditions, and mixing fluxes under different baking conditions. It is particularly suitable for welding requirements requiring high strength and high toughness, and has broad application prospects and environmental advantages.

[0072] The product prepared by the method of preparing submerged arc welding flux is the aforementioned submerged arc welding flux. The chemical composition and microstructure of the submerged arc welding flux prepared by the method of preparing submerged arc welding flux can be referred to the above embodiments. Since the method of preparing submerged arc welding flux adopts some or all of the technical solutions of the submerged arc welding flux embodiments, it has at least all the beneficial effects brought about by the technical solutions of the submerged arc welding flux embodiments, which will not be elaborated here.

[0073] 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 industry standards. If there is no corresponding industry standard, then common international standards, conventional conditions, or conditions recommended by the manufacturer are followed.

[0074] Example 1

[0075] The components are as follows: SiO2 4kg, MgO 18kg, Al2O3 30kg, ΣCaO 45kg, MnO 0.5kg, Na2O 1kg, K2O 0.5kg, TiO2 2kg, Fe2O3 0.2kg, S 0.012kg, P 0.012kg, LiF 2 kg of powder was placed in a mixer and stirred until uniform. Then, 12 kg of lithium water glass was added and granulated. After pre-drying, part of the flux was baked at 450℃ for 2 hours, and part of the flux was baked at 650℃ for 0.5 hours. The fluxes after the two bakings were mixed evenly to obtain a product with an alkalinity of 3.2. This flux product, when used with special welding wire and 50 mm thick matching base material for submerged arc welding, exhibits excellent process performance. The weld performance was tested and found to be: tensile strength of welded joint 740 MPa, reduction of area 60%, and impact energy of weld metal at -40℃ KV2 = 145 / 156 / 162 J. The bending test was also qualified (bending angle 180°, bending diameter four times the wall thickness).

[0076] Example 2

[0077] The components are as follows: SiO2 5kg, MgO 12kg, Al2O3 40kg, ΣCaO 40kg, MnO 0.8kg, Na2O 0.6kg, K2O 0.6kg, TiO2 0.8kg, Fe2O3 0.6kg, S 0.010kg, P 0.010kg, LiF 3 kg of powder was placed in a mixer and stirred until uniform. Then, 14 kg of lithium water glass was added and granulated. After pre-drying, part of the flux was baked at 450℃ for 2 hours, and part of the flux was baked at 650℃ for 0.5 hours. The fluxes after the two bakings were mixed evenly to obtain a flux with an alkalinity of 2.1. This flux product, when used with special welding wire and 50 mm thick matching base material for submerged arc welding, exhibits excellent process performance. The weld performance was tested as follows: tensile strength of welded joint 755 MPa, reduction of area 58%, impact energy of weld metal at -40℃ KV2 = 163 / 147 / 150 J, and bending tests were also qualified (bending angle 180°, bending diameter four times the wall thickness).

[0078] Example 3

[0079] The components are as follows: SiO2 2kg, MgO 11kg, Al2O3 35kg, ΣCaO 42kg, MnO 3kg, Na2O 0.5kg, K2O 1.0kg, TiO2 0.5kg, Fe2O3 0.5kg, S 0.015kg, P 0.015kg, LiF 4 kg of powder was placed in a mixer and stirred until uniform. Then, 14 kg of lithium water glass was added and granulated. After pre-drying, part of the flux was baked at 450℃ for 2 hours, and part of the flux was baked at 650℃ for 0.5 hours. The fluxes after the two bakings were mixed evenly to obtain a flux with an alkalinity of 2.8. This flux product, when used with special welding wire and 50 mm thick matching base material for submerged arc welding, exhibits excellent process performance. The weld performance was tested as follows: tensile strength of welded joint 733 MPa, reduction of area 60%, impact energy of weld metal at -40℃ KV2 = 155 / 168 / 166 J, and bending tests were also qualified (bending angle 180°, bending diameter four times the wall thickness).

[0080] The experimental performance of Examples 1 to 3 all meet the technical requirements of Q550qENH for high strength and high toughness welds, especially the requirement for low-temperature impact toughness at -40℃.

[0081] Comparative Example 1

[0082] Based on Example 1, the following modifications are made:

[0083] Without adding lithium fluoride to the chemical composition of the flux, the impact energy of the weld metal at -40℃ is 102 / 88 / 110J;

[0084] Furthermore, one or more technical solutions in the embodiments of this application have at least the following technical effects or advantages:

[0085] In the embodiments of this application, the proportions of each element are reasonably adopted, so that the flux of the present invention has good welding processability, beautiful weld formation, and the slag shell can automatically lift and fall off. It is particularly suitable for high-strength and high-toughness welding, resulting in excellent weld mechanical properties and ensuring the low-temperature impact toughness of the weld metal (-40℃).

[0086] In this embodiment, the flux uses an alkaline slag system and is used with a special welding wire CHW-S65NHQ3, which has excellent weld performance. The tensile strength of the welded joint is 700-760 MPa, and the impact energy of the weld metal at -40℃ is KV2≥100J.

[0087] In the embodiments of this application, the addition of LiF to the flux slag system significantly improves the impact toughness and ensures its stability. When the lithium fluoride content is 2%, the impact energy of the weld metal at -40°C is 145 / 156 / 162 J; when the lithium fluoride content is 3%, the impact energy of the weld metal at -40°C is 163 / 147 / 150 J; when the lithium fluoride content is 4%, the impact energy of the weld metal at -40°C is 155 / 168 / 166 J; and when no lithium fluoride is added to the product, the impact energy of the weld metal at -40°C is 102 / 88 / 110 J.

[0088] In this embodiment, the flux can be matched with other carbon steel and low alloy steel welding wires. When welding carbon steel and low alloy steel, it has good welding processability, excellent slag removal, beautiful shape, and good mechanical properties.

[0089] In this embodiment, the flux, combined with a special welding wire, produces welded joints with excellent low-temperature impact toughness (-40℃) under low-temperature conditions, and the welding quality meets the high strength and high toughness technical requirements for Q550qENH steel. It also meets the technical requirements for steel structures used in bridges, railways, vehicles, towers, photovoltaic projects, and highway engineering that are exposed to the atmosphere for extended periods, as well as structural components such as oil derricks, harbor buildings, oil platforms, and containers containing hydrogen sulfide corrosive media in chemical and petroleum equipment.

[0090] In this embodiment, the flux combined with the special welding wire can optimize the chemical composition and microstructure of the weld metal, resulting in good and reasonable mechanical properties such as tensile strength, impact value, bending performance, crack resistance, and hardness under weld conditions. Furthermore, the weld is free of porosity, slag inclusions, and cracks, and its low-temperature impact toughness at -40℃ is above 100J, fully meeting the standard requirements of Q550qENH steel.

[0091] 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 submerged arc welding flux suitable for Q550qENH steel, wherein the submerged arc welding flux comprises the following chemical composition by weight: SiO2 1-5 parts, MgO 10-18 parts, Al2O3 30-40 parts, ΣCaO 40-45 parts, MnO 0.5-3 parts, Na2O 0.5-1 part, K2O 0.5-1 part, TiO2 0.5-3 parts, Fe2O3 ≤1.0 part, S ≤0.020 parts, P ≤0.020 parts, and LiF 2-5 parts.

2. The submerged arc welding flux according to claim 1, characterized in that, The submerged arc welding flux comprises the following chemical components by weight: 4 parts SiO2, 18 parts MgO, 30 parts Al2O3, 45 parts ΣCaO, 0.5 parts MnO, 1 part Na2O, 0.5 parts K2O, 2 parts TiO2, 0.2 parts Fe2O3, 0.012 parts S, 0.012 parts P, and 2 parts LiF.

3. The submerged arc welding flux according to claim 1, characterized in that, The submerged arc welding flux comprises the following chemical components by weight: 5 parts SiO2, 12 parts MgO, 40 parts Al2O3, 40 parts ΣCaO, 0.8 parts MnO, 0.6 parts Na2O, 0.6 parts K2O, 0.8 parts TiO2, 0.6 parts Fe2O3, 0.010 parts S, 0.010 parts P, and 3 parts LiF.

4. The submerged arc welding flux according to claim 1, characterized in that, By weight, the submerged arc welding flux comprises the following chemical components: 2 parts SiO2, 11 parts MgO, 35 parts Al2O3, 42 parts ΣCaO, 3 parts MnO, 0.5 parts Na2O, 1.0 part K2O, 0.5 parts TiO2, 0.5 parts Fe2O3, 0.015 parts S, 0.015 parts P, and 4 parts LiF.

5. A method for preparing submerged arc welding flux according to any one of claims 1 to 4, the method comprising: The components of the submerged arc welding flux are mixed to obtain a first mixed powder. The first mixed powder is mixed with the binder and granulated, and then pre-dried to obtain the second mixed powder; A portion of the second mixed powder is subjected to a first high-temperature baking process to obtain a first flux; The remaining portion of the second mixed powder is subjected to a second high-temperature baking to obtain a second flux; The first flux and the second flux are mixed to obtain the submerged arc welding flux.

6. The method according to claim 5, characterized in that, The mass of the binder is 10% to 14% of the total mass of the first mixed powder.

7. The method according to claim 6, characterized in that, The adhesive includes lithium water glass.

8. The method according to claim 5, characterized in that, The temperature of the first high-temperature baking is 400℃~500℃, and the baking time is 2 hours.

9. The method according to claim 5, characterized in that, The second high-temperature baking temperature is 600℃~700℃, and the second high-temperature baking time is 0.5h.

10. A weld metal, wherein the weld metal is prepared by welding Q550qENH steel with the submerged arc welding flux as described in any one of claims 1 to 4 and a suitable welding wire CHW-S65NHQ3, and the weld metal satisfies at least one of the following properties: tensile strength of 700 MPa to 760 MPa, reduction of area of ​​55% to 62%, and impact energy KV2 ≥ 100 J at -40℃.

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