Submerged arc welding agent suitable for double-wire indirect electric arc welding and preparation method and application of submerged arc welding agent

Abstract

The invention relates to the technical field of welding, in particular to a submerged arc welding flux suitable for double-wire indirect electric arc welding and a preparation method and application of the submerged arc welding flux. Comprising an arc striking and arc stabilizing component, a rapid slag formation and energy loss control component, a slag stability and collapse resistance component, an arc position control component, a gas escape management component, a self-triggering ignition component and trace elements and impurities. The submerged arc welding flux provided by the invention can meet the special requirements of use of twin-wire indirect electric arc welding, realizes multiple advantages of low heat input, low deformation, high efficiency, excellent protection and metallurgical treatment capacity, and has huge potential in the aspects of improving deposition efficiency, controlling deformation and improving metallurgical quality.

Description

Technical Field

[0001] This invention relates to the field of welding technology, and in particular to a submerged arc welding flux suitable for twin-wire indirect arc welding, its preparation method, and its application. Background Technology

[0002] The information disclosed in the background section of this invention is intended only to enhance the understanding of the overall background of the invention and is not necessarily to be construed as an admission or in any way implying that such information constitutes prior art known to those skilled in the art.

[0003] Twin-wire indirect arc welding (TWIAM) is a welding process characterized by low heat input, low deformation, and high efficiency. Its arc burns between two welding wires, avoiding a direct arc circuit with the workpiece, thus reducing the thermal impact on the workpiece. Traditional submerged arc welding (SAW), with its excellent protective effect, high deposition rate, and good metallurgical processing capabilities, is widely used in metal joining and additive manufacturing.

[0004] Combining twin-wire indirect arc welding (TIA) with submerged arc welding (SAW) protection in additive manufacturing theoretically leverages the advantages of both technologies. It combines the low heat input, low deformation, and high efficiency of TIA with the superior protection and metallurgical processing capabilities of SAW, demonstrating significant potential for improving deposition efficiency, controlling deformation, and enhancing the metallurgical quality of the deposited layer. However, applying TIA to SAW with flux protection in submerged arc additive manufacturing presents a series of technical challenges that cannot be effectively addressed by existing traditional SAW techniques and fluxes. (1) Challenges of Arc Ignition and Stability: In traditional submerged arc welding, the arc burns between the welding wire and the workpiece, resulting in a large contact area and a relatively short arc path that is easy to ignite. However, in twin-wire indirect arc welding, the arc burns between the two welding wires, limiting the space for stable combustion and increasing the difficulty of breaking down the medium (air or gas between flux particles). Achieving and maintaining stable and reliable twin-electrode indirect arc combustion under the flux layer is the primary challenge. Traditional flux formulations typically provide sufficient ionized particles in a narrow and relatively high space between the two welding wires to achieve rapid breakdown and sustained combustion, but this results in poor stability.

[0005] (2) Control of molten pool behavior and gas escape: The combustion of a twin-wire indirect arc produces a large amount of high-temperature gas, and the arc position is relatively high (compared to traditional submerged arc welding, the downward force of the molten droplets generated by the twin-wire indirect arc is relatively weak), making it susceptible to heat loss due to the heat coverage effect of flux particles. In the complex heat transfer and metallurgical environment of additive manufacturing, how to effectively control the behavior of the molten pool, ensure rapid gas escape to avoid bubble accumulation leading to arc instability or extinction, and ensure compositional uniformity are key issues that are difficult to solve with existing technologies.

[0006] (3) Special requirements for flux slag: Due to the high position of the arc, the flux melting point needs to be low enough to quickly form a slag barrier to envelop the arc and reduce energy loss. At the same time, the dual-wire system is more prone to vibration during welding, which places higher demands on the viscosity and rapid solidification ability of the flux slag to prevent flux layer collapse and short circuit of the welding wire. Traditional submerged arc fluxes do not have a combination of melting point, viscosity and solidification speed that meets these requirements.

[0007] (4) Arc position control and re-ignition: During the combustion of the indirect arc in the twin wires, the arc tends to "climb" away from the welding wire, affecting the welding stability. In addition, during the additive manufacturing process, accidental arc extinguishing may lead to production interruption. Traditional submerged arc welding flux does not have a self-triggering ignition mechanism, making it difficult to quickly resume welding after arc extinguishing. Summary of the Invention

[0008] In view of this, the present invention provides a submerged arc welding flux suitable for twin-wire indirect arc welding, its preparation method, and its application. The submerged arc welding flux provided by the present invention, used in twin-wire indirect arc additive manufacturing, can achieve multiple advantages such as low heat input, low deformation, high efficiency, excellent protection, and metallurgical processing capabilities, and has great potential in improving deposition efficiency, controlling deformation, and improving metallurgical quality.

[0009] To achieve the above objectives, the present invention employs the following technical solution: In a first aspect, the present invention provides a submerged arc welding flux suitable for twin-wire indirect arc welding, comprising an arc ignition and stabilization component, a rapid slag formation and energy loss control component, a slag stability and anti-collapse component, an arc position control component, a gas escape management component, a self-ignition component, and trace elements and impurities. The arc-initiating and arc-stabilizing components are selected from at least one of potassium fluoride (KF), sodium fluoride (NaF), or barium oxide (BaO); The rapid slag formation and energy loss control components are selected from calcium fluoride (CaF2) and CaO·MgO·Al2O3 premelt; The slag stability and anti-collapse components are selected from at least one of silicon dioxide (SiO2), manganese oxide (MnO), or titanium dioxide (TiO2); The arc position control component is selected from at least one of fine-grained magnesium oxide (MgO) or fine-grained aluminum oxide (Al2O3); The gas escape management component is selected from calcium carbonate (CaCO3); The self-triggered ignition component is selected from Al-Mg alloy powder or Fe2O3 powder.

[0010] Furthermore, the amount of arc-initiating and arc-stabilizing components added is 1% to 3% of the total mass of the submerged arc welding flux.

[0011] The arc-initiating and arc-stabilizing components contain at least one low-ionization-energy material, which can be rapidly ionized under the high temperature of the arc, generating a large amount of K. + Na + Ba 2+ Charged particles significantly reduce the arc breakdown voltage, ensuring that the arc ignites rapidly and burns stably in the narrow region between the two wires.

[0012] Furthermore, in the rapid slag formation and energy loss control component, the amount of CaF2 added is 20% to 40% of the total mass of the submerged arc welding flux; the amount of CaO·MgO·Al2O3 premelted body added is 15% to 30% of the total mass of the submerged arc welding flux, and the mass ratio of CaO, MgO and Al2O3 in the CaO·MgO·Al2O3 premelted body is 1.8~2.8:0.8~1.2:0.8~1.2; preferably, the mass ratio is 2.0~2.5:1:1.

[0013] The rapid slag formation and energy loss control component comprises at least one low-melting-point material and a rapid slag-forming material. CaF2 is used to lower the melting point of the submerged arc welding flux (below 1200 °C), and the CaO·MgO·Al2O3 premelt is used to rapidly form a stable slag. CaO primarily serves as an alkaline oxide component in the low-melting-point slag system to lower the melting point and promote rapid slag formation. The premelted CaO·MgO·Al2O3 serves as an alkaline slag matrix. Through the premelting process, CaO, MgO, and Al2O3 fully react and uniformly distribute at high temperatures. This reduces the hygroscopicity and chemical activity of the raw materials, improving the storage stability and moisture resistance of the submerged arc welding flux. Furthermore, it provides a uniformly composed and stable slag skeleton during welding. Based on this, a small amount of finely powdered MgO and Al2O3 is further added, allowing them to preferentially melt and participate in the reaction in the arc zone. This is used to finely adjust the slag softening temperature, high-temperature viscosity, arc shrinkage, and weld pool wettability. By combining "pre-melted matrix + fine powder fine-tuning", the process adaptability to different welding currents, welding speeds and welding positions is enhanced while maintaining the overall slag basicity and macroscopic stability. This expands the process window of submerged arc flux and improves the consistency of weld formation and the stability of welding quality.

[0014] Furthermore, in the slag stability and anti-collapse components, the amount of SiO2 added is 10% to 20% of the total mass of the submerged arc welding flux; the amount of MnO added is 2% to 10% of the total mass of the submerged arc welding flux; and the amount of TiO2 added is 1% to 5% of the total mass of the submerged arc welding flux.

[0015] The slag stability and anti-collapse components include at least one material that enhances slag viscosity and rapid solidification. SiO2 is used to strengthen the slag skeleton and increase slag viscosity; MnO is used to increase the surface tension of the slag and prevent slag flow; TiO2 is used to stabilize the arc column, reduce arc oscillation, enhance arc contraction and guidance, and concentrate the arc in the center of the molten pool, which is beneficial for obtaining a weld surface with regular weld formation and smooth weld toe transition. These components work together to give the slag higher viscosity and rapid solidification ability, preventing the flux layer from collapsing due to vibration of the dual-wire system and causing short circuits in the welding wires.

[0016] Furthermore, in the arc position control component, the amount of fine-grained MgO added is 4% to 10% of the total mass of the submerged arc welding flux; the amount of fine-grained Al2O3 added is 4% to 10% of the total mass of the submerged arc welding flux; and the particle size of fine-grained MgO and fine-grained Al2O3 is less than 0.1 mm.

[0017] The preferred component for arc position control is a fine-grained high-melting-point oxide, such as MgO and Al2O3 with a particle size of less than 0.1 mm. Finer particles have a larger specific surface area, allowing them to heat up rapidly under the high temperature of the arc and soften or partially melt, forming a continuous high-melting-point skeleton structure around the arc together with the surrounding slag. On one hand, this high-melting-point skeleton provides stable support on the surface of the molten pool and in the arc root region, inhibiting the arc from climbing upwards along the welding wire and stabilizing the arc's combustion position. On the other hand, the fine particles can fuse with the slag quickly, forming a dense slag barrier layer, which is beneficial for enveloping the arc, reducing heat loss, and improving arc thermal efficiency. If larger-grained MgO or Al2O3 particles are used, their heating and softening rates are slower, making it difficult to form a continuous skeleton and dense slag layer around the arc in a timely manner. This can lead to the high-melting-point particles settling or becoming unevenly distributed, thus weakening the constraint on the arc position and hindering stable arc combustion and good weld formation.

[0018] Furthermore, the amount of CaCO3 added is 3% to 10% of the total mass of the submerged arc welding flux. CaCO3 decomposes at high temperatures to produce carbon dioxide (CO2), and the release of CO2 helps the gas in the molten pool to escape, thus preventing the accumulation of bubbles.

[0019] Furthermore, the self-ignition component is incorporated in proportions of 3% to 6% of the total mass of the submerged arc welding flux. The Al-Mg alloy powder is incorporated in proportions of 0.5% to 1% of the total mass of the flux; the Fe2O3 powder is incorporated in proportions of 2.5% to 5% of the total mass of the submerged arc welding flux.

[0020] By incorporating a small amount of Al-Mg alloy powder or Fe2O3 powder, when an accidental arc extinction causes the submerged arc welding flux cavity to cool rapidly, these high oxidation state components can quickly release energy under the action of welding current, forming a local hot zone. Combined with the current, the medium is broken down again, achieving self-triggered ignition of the arc.

[0021] Furthermore, the trace elements and impurities are components that are unavoidably introduced during the raw material preparation and melting process, as well as trace element additives intentionally added to improve the properties of the weld metal. Components that are unavoidably introduced during the raw material preparation and melting process include, but are not limited to, Fe, Na, K, S, P, etc., and their total amount usually does not exceed 1.5 wt% of the total flux mass, preferably not exceeding 1 wt%. These components have no substantial adverse effect on the overall performance of the flux of the present invention. The trace elements are at least one of Ce, La, and B, with Ce content of 0.05~0.3 wt% of the total flux mass, La content of 0.05~0.3 wt% of the total flux mass, and B content of 0.01~0.05 wt% of the total flux mass, and the total content of Ce, La, and B is 0.3~0.8 wt% of the total flux mass.

[0022] Furthermore, Ce and La are added in the form of oxides; B is added in the form of boron oxide or metal borides, wherein the metal borides are FeB, Fe2B or TiB2.

[0023] Furthermore, the particle size of the submerged arc welding flux is 0.8 mm to 1.4 mm. Under this particle size condition, the submerged arc welding flux layer has a certain porosity, allowing gas to escape smoothly.

[0024] In a second aspect, the present invention provides a method for preparing the submerged arc welding flux described in the first aspect, comprising the following steps: (1) The raw materials CaO, MgO and Al2O3 are melted at 1550~1700 °C in a mass ratio of 1.8~2.8:0.8~1.2:0.8~1.2. The melted product is then rapidly cooled, crushed and sieved to obtain CaO·MgO·Al2O3 pre-melted material for later use.

[0025] (2) Weigh each component raw material according to the predetermined ratio and mix them thoroughly; (3) The mixture is granulated to form particles with a diameter in the range of 0.8 mm to 1.4 mm; (4) The granulated particles are sintered; (5) The sintered particles are sieved to obtain the final product.

[0026] Furthermore, in step (1), the particle size of the CaO·MgO·Al2O3 premelt is controlled between 0.5 and 2.0 mm.

[0027] Furthermore, in step (2), the mixing is either dry mixing or wet mixing; the mixing time is 10~40 min.

[0028] Furthermore, in step (3), the granulation method is ball pressing, extrusion or disc granulation; 4%~6% water glass solution is also added as a binder during the granulation process.

[0029] Furthermore, in step (4), the sintering temperature is 700~900 ℃; the time is 1~3 h.

[0030] Thirdly, the present invention provides the application of the submerged arc welding flux described in the first aspect in twin-wire indirect arc welding additive manufacturing.

[0031] Compared with the prior art, the present invention has achieved the following beneficial effects: (1) The submerged arc welding flux provided by the present invention significantly improves the ionization efficiency of the flux by adding arc ignition and arc stabilization components, ensuring that the arc in the narrow area between the two welding wires can be quickly ignited and continuously and stably burned, overcoming the shortcomings of traditional submerged arc welding flux under this working condition; the flux's rapid slag formation ability and gas escape mechanism effectively control the shape and stability of the molten pool, avoid bubble defects, and ensure the density and uniformity of the deposited layer; the components used in the submerged arc welding flux formulation to enhance the viscosity of the slag and the ability to solidify quickly mainly include Al2O3 and MgO, preferably a part of the matrix component existing in the form of pre-melted CaO·MgO·Al2O3 and a part of MgO and Al2O3 added separately in the form of fine particles. The aforementioned high-melting-point oxides, combined with slag-forming components such as CaO, SiO2, and TiO2, collectively improve the viscosity of the slag at high temperatures and shorten the time for the transition from the molten state to the semi-solid state. This endows the slag with strong anti-flow and rapid crusting capabilities, enabling it to remain stable even under vibration of the dual-wire system. This effectively prevents the collapse of the submerged arc flux layer and short circuits, ensuring the continuity of the welding process. The arc position control components effectively suppress the tendency of the arc to "climb" upwards towards the welding wire, ensuring the stability of the arc combustion position and facilitating precise control of the molten pool and deposition shape.

[0032] (2) The submerged arc welding flux provided by this invention optimizes the particle size and gas-generating component design of the submerged arc welding flux, enabling the high-temperature gas generated by the arc combustion to be discharged quickly, preventing the gas from lingering in the molten pool, and effectively avoiding defects such as porosity. The introduction of high oxidation state metal powder endows the submerged arc welding flux with the ability to self-ignite after accidental arc extinction, which greatly improves the reliability and automation of the additive manufacturing process and reduces downtime.

[0033] (3) This invention combines the advantages of low heat input, low deformation and high efficiency of twin-wire indirect arc welding with the excellent protection and metallurgical processing capabilities of submerged arc welding, which significantly improves the deposition efficiency of additive manufacturing, controls deformation, and improves the metallurgical quality and mechanical properties of the deposited layer. Attached Figure Description

[0034] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0035] Figure 1 This is a photograph of the welded object from Example 1; Figure 2 This is a microstructure diagram of the welded structure in Example 1.

[0036] Figure 3 This is a photograph of the welded object from Example 2; Figure 4 This is a photograph of the actual welded object for Comparative Example 1; Figure 5 This is a photograph of the actual welded object in Comparative Example 2; Figure 6 This is a photograph of the actual welded object for Comparative Example 3. Detailed Implementation

[0037] It should be noted that the following detailed descriptions are exemplary and intended to provide further illustration of the invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0038] The technical solution of the present invention will be further described below with reference to specific embodiments.

[0039] Example 1 The submerged arc welding flux, by total mass, comprises the following components: CaF2: 30.0 wt%, CaO·MgO·Al2O3 premelt: 24.0 wt%, SiO2: 15.0 wt%, MnO: 6.0 wt%, TiO2: 4.0 wt%, CaCO3: 6.0 wt%, Fe2O3: 3.0 wt%, Al-Mg alloy powder: 0.5 wt%, KF: 1.0 wt%, BaO: 1.0 wt%. Fine-grained MgO: 4.0 wt%, Fine-grained Al2O3: 5.5 wt%.

[0040] The total amount of trace elements shall not exceed 1 wt%. The trace elements include two parts: (1) unavoidable impurity elements (Fe, S, P, etc.), with a total mass fraction not exceeding 0.18 wt%; (2) rare earth elements Ce, La and B used to improve performance, which are added in the form of corresponding oxides, wherein the content of CeO2 is 0.10 wt%, the content of La2O3 is 0.20 wt%, and the content of B2O3 is 0.02 wt%.

[0041] In this embodiment, the CaO·MgO·Al2O3 premelt is prepared by a high-temperature melting-rapid cooling process: industrial pure CaO, MgO, and Al2O3 raw materials weighed in a mass ratio of CaO:MgO:Al2O3 = 2.3:1.0:1.0 are added sequentially into a melting furnace and heated to 1600 °C until completely melted, and held at that temperature for 1 h to allow CaO, MgO, and Al2O3 to react fully and become homogeneous; then the melt is poured into water or rapidly cooled by water-cooled copper rollers to obtain a block or sheet-like premelt; after crushing and sieving, the particle size of the premelt is controlled between 0.5 and 2.0 mm.

[0042] Preparation of submerged arc welding flux: The above-mentioned CaO·MgO·Al2O3 premelt is weighed and mixed with CaF2, SiO2, MnO, TiO2, CaCO3, Fe2O3, Al-Mg alloy powder, KF, BaO, fine MgO, fine Al2O3, rare earth oxides and B2O3 according to the formula ratio. The mixture is first dry mixed for 30 min, and then 4% of water glass solution by mass of the mixture is added as a binder. The mixture is then granulated on a disc granulator to control the particle size to 0.8~1.4 mm. After granulation, the mixture is sintered at 800 ℃ for 2 h, cooled and sieved to remove excessively fine and coarse particles, and a submerged arc welding flux product with a median particle size of about 1.0 mm is obtained.

[0043] Additive manufacturing experiments were conducted using the submerged arc welding flux prepared in Example 1. The experimental results showed that the arc ignition was rapid, combustion was stable, and there was no obvious arc extinction phenomenon. A photograph of the welded product from Example 1 is shown below. Figure 1 As shown, the microstructure after welding is as follows: Figure 2 As shown.

[0044] The welding qualification results show that, under typical submerged arc welding current, voltage, and welding speed parameters (typical process parameters are: single-wire welding current of about 220 A, arc voltage of about 28 V, and welding speed of 0.5 m / min), the submerged arc welding flux prepared in this embodiment has stable arc initiation and re-arc initiation performance, good slag fluidity and coverage, easy slag removal, uniform and full weld formation, fine grains in the welded joint, and the tensile strength and low-temperature impact toughness of the welded joint can meet the requirements of the corresponding standards.

[0045] Example 2 The submerged arc welding flux, by total mass, comprises: CaF2: 40.0 wt%, CaO·MgO·Al2O3 premelt: 30.0 wt%, SiO2: 10.0 wt%, MnO: 4.0 wt%, TiO2: 2.0 wt%, CaCO3: 5.0 wt%, Fe2O3: 3.0 wt%, Al-Mg alloy powder: 0.8 wt%, NaF: 1.0 wt%, fine MgO: 2.0 wt%, and fine Al2O3: 2.2 wt%.

[0046] The total amount of trace elements does not exceed 1 wt%, including unavoidable impurity elements (Fe, S, P, etc.), with a total mass fraction not exceeding 0.18 wt%; and rare earth elements Ce, La, and B that can improve performance. Ce, La, and B are added in the form of oxides, with CeO2 content of 0.2 wt%, La2O3 content of 0.3 wt%, and B2O3 content of 0.02 wt%.

[0047] The preparation method of CaO·MgO·Al2O3 premelt is the same as that in Example 1, that is, a high-temperature melting-rapid cooling process is used to obtain a premelt with uniform composition and stable structure.

[0048] Preparation of submerged arc welding flux: CaO·MgO·Al2O3 premelt, CaF2, SiO2, MnO, TiO2, CaCO3, Fe2O3, Al-Mg alloy powder, NaF, fine MgO, fine Al2O3, rare earth oxides, and B2O3 are weighed according to the above mass percentages. After dry mixing in a mixer for 20 min, 6% water glass is added as a binder. Wet particles with a particle size of 0.8~1.4 mm are obtained by disc granulation. After sintering at 820 ℃ for 1.5 h, the particles are cooled and sieved to obtain the finished submerged arc welding flux.

[0049] The submerged arc welding flux prepared in Example 2 was used to conduct additive manufacturing experiments using dual-wire indirect arc welding. The experimental results showed that the arc ignition was rapid, the combustion was stable, and there was no obvious arc extinction phenomenon.

[0050] Welding test results show that under high welding current and high welding speed conditions (specific welding process parameters: welding current 200A, welding voltage 33.5V, positive electrode wire feed speed 6.5m / min, negative electrode wire feed speed 8.0m / min, welding speed 60cm / min), the flux in this embodiment provides excellent arc rigidity and stability, strong slag fluidity and rapid spreading, sufficient gas escape, good weld formation, and significantly fewer defects such as weld porosity and slag inclusions compared to conventional fluxes. It is especially suitable for high-efficiency automatic or semi-automatic welding conditions. A welding sample image is shown below. Figure 3 As shown.

[0051] Example 3 The submerged arc welding flux, by total mass, consists of the following components: CaF2: 20.0 wt%, CaO·MgO·Al2O3 premelt: 15.0 wt%, SiO2: 18.0 wt%, MnO: 8.0 wt%, TiO2: 5.0 wt%, CaCO3: 8.0 wt%, Fe2O3: 5.0 wt%, Al-Mg alloy powder: 1.0 wt%, NaF: 1.0 wt%, fine MgO: 9.0 wt%, and fine Al2O3: 10.0 wt%.

[0052] The total amount of trace elements does not exceed 1 wt%, including unavoidable impurity elements (Fe, S, P, etc.), with a total mass fraction not exceeding 0.36 wt%; and rare earth elements Ce, La and B that can improve performance are added in the form of oxides, with CeO2 content of 0.3 wt%, La2O3 content of 0.3 wt%, and B2O3 content of 0.02 wt%.

[0053] The preparation method of CaO·MgO·Al2O3 premelt is the same as in Example 1, and a premelt with uniform composition is obtained by high-temperature melting-rapid cooling process.

[0054] Preparation of submerged arc welding flux: CaO·MgO·Al2O3 premelt, CaF2, SiO2, MnO, TiO2, CaCO3, Fe2O3, Al-Mg alloy powder, NaF, fine MgO, fine Al2O3, rare earth oxides and B2O3 are weighed in proportion, dry mixed in a mixer for 30 min, and then 5% water glass is added as a binder. Wet particles with a particle size of 0.8~1.4 mm are obtained by disc granulation. After sintering at 780 ℃ for 2.5 h, the particles are cooled and sieved to obtain the finished submerged arc welding flux.

[0055] The submerged arc welding flux prepared in Example 3 was used to conduct additive manufacturing experiments using dual-wire indirect arc welding. The experimental results showed that the arc ignition was rapid, the combustion was stable, and there was no obvious arc extinction phenomenon.

[0056] Welding qualification results show that the flux in this embodiment, even with the CaF2 and CaO·MgO·Al2O3 premelt contents both at the low end of the formulation range of this invention, still achieves good arc initiation and re-arc initiation performance. The flux in this embodiment exhibits sensitive arc initiation and good re-arc initiation performance during welding, is insensitive to welding current fluctuations and arc length changes, and the slag fluidity and coverage still meet the process requirements for multi-position welding such as flat welding and fillet welding. The weld formation is full with few internal defects, fully demonstrating that the formulation of this invention still has good process adaptability and robustness in the low CaF2 and low premelt content range.

[0057] Comparative Example 1 Submerged arc welding flux by total mass: CaF2: 30.0 wt%, CaO: 13.4 wt%, MgO: 5.8 wt%, Al2O3: 5.8 wt% (the sum of the three is equivalent to the equivalent amount of the CaO·MgO·Al2O3 premelt in Example 1, but added separately in non-premelt form), SiO2: 15.0 wt%, MnO: 6.0 wt%, TiO2: 4.0 wt%, CaCO3: 6.0 wt%, Fe2O3: 3.0 wt%, Al-Mg alloy powder: 0.5 wt%, KF: 1.0 wt%, BaO: 1.0 wt%, fine MgO: 4.0 wt%, fine Al2O3: 5.5 wt%.

[0058] The total amount of trace elements does not exceed 1 wt%, including unavoidable impurity elements (Fe, S, P, etc.), with a total mass fraction not exceeding 0.18 wt%; and rare earth elements Ce, La, and B that can improve performance. Ce, La, and B are added in the form of oxides, with CeO2 content of 0.1 wt%, La2O3 content of 0.20 wt%, and B2O3 content of 0.02 wt%.

[0059] In Comparative Example 1, the total amount and mass ratio of CaO, MgO and Al2O3 are consistent with the converted values ​​in Example 1 (approximately 2.3:1.0:1.0). CaF2 and the other components are also the same as in Example 1. The only difference is that in this comparative example, CaO, MgO and Al2O3 were not subjected to high-temperature melting and pre-melting treatment, but were directly involved in flux granulation and sintering in ordinary powder form.

[0060] Preparation of submerged arc welding flux: After accurately weighing the above components according to the proportion, dry mix for 30 min, then add 4%~6% water glass solution as a binder, and granulate on a disc granulator to control the particle size to 0.8~1.4 mm; after granulation, sinter at 800 ℃ for 2 h, cool, and sieve to remove excessively fine and coarse particles to obtain a submerged arc welding flux product with a median particle size of about 1.0 mm.

[0061] Welding qualification results showed that, compared with Example 1 which used CaO·MgO·Al2O3 premelted material, the flux in Comparative Example 1 exhibited uneven dispersion of CaO, MgO, and Al2O3 and insufficient local solid-phase reaction during sintering. This resulted in certain segregation and inhomogeneity of the slag composition at the microscale. Specifically, this manifested as larger fluctuations in slag viscosity during welding, greater sensitivity to changes in welding current and welding speed, and a tendency for insufficient slag coverage or localized over-thickness in certain areas of the weld. Furthermore, due to the lack of a pre-melting-rapid cooling homogenization process, some CaO and Al2O3 formed high-melting-point multi-component compounds at high temperatures, resulting in a higher overall liquidus level in the slag and slightly poorer high-temperature fluidity compared to Example 1. This was particularly evident in multi-layer, multi-pass welding, manifesting as difficulty in slag removal from some weld passes and the tendency for small slag inclusions to remain near the weld toe, which was detrimental to ensuring a long service life of the welded joint. Comprehensive comparison shows that, under the premise that the total amount of CaF2 and the total amount and mass ratio of CaO / MgO / Al2O3 are basically the same, there are significant differences between Comparative Example 1 (without CaO·MgO·Al2O3 premelted body) and Example 1 (with premelted matrix) in terms of slag uniformity, arc stability, and weld formation quality. Welding images are shown below. Figure 4 As shown, the uneven presence of slag inclusions on both sides of the weld indicates that the present invention has outstanding technical effects in constructing a stable slag matrix through the CaO·MgO·Al2O3 premelt method.

[0062] Comparative Example 2 The submerged arc welding flux prepared in this comparative example does not use CaO·MgO·Al2O3 premelt in its formulation; instead, CaO, MgO, and Al2O3 are directly added in ordinary powder form. By total mass, the flux comprises: CaF2: 30.0 wt%, CaO: 17.0 wt%, MgO: 3.2 wt%, Al2O3: 3.2 wt%, SiO2: 24.8 wt%, MnO: 6.0 wt%, TiO2: 4.0 wt%, CaCO3: 6.0 wt%, Fe2O3: 3.0 wt%, Al-Mg alloy powder: 0.5 wt%, KF: 1.0 wt%, BaO: 1.0 wt%. The total amount of trace elements does not exceed 1 wt%, including unavoidable impurity elements (Fe, S, P, etc.), whose total mass fraction does not exceed 0.18 wt%; and rare earth elements Ce, La and B used to improve performance, which are added in the form of corresponding oxides, wherein the content of CeO2 is 0.10 wt%, the content of La2O3 is 0.20 wt%, and the content of B2O3 is 0.02 wt%.

[0063] The total addition of CaO, MgO, and Al2O3 was approximately 23.4 wt%, still within the 15%~30% range required by this invention. However, its internal mass ratio was approximately 17.0:3.2:3.2≈5.34:1.00:1.00, with CaO being significantly higher and MgO and Al2O3 significantly lower, deviating severely from the CaO:MgO:Al2O3 range of 1.8~2.8:0.8~1.2:0.8~1.2 specified in this invention. Furthermore, this comparative example did not employ a pre-melting process; CaO, MgO, and Al2O3 were all added directly in ordinary powder form.

[0064] Under the same welding process parameters as in Example 1, welding tests using this comparative flux revealed the following: Slight lag was observed in both arc ignition and reignition processes; the arc position shifted slightly; and brief arc extinction and re-ignition occurred locally. Arc stability was significantly worse than in Example 1. During welding, the slag viscosity was low and its fluidity was high. Under the vibration of the two wires, the slag layer was prone to local collapse and deviation. The slag shell edging on both sides of some welds was discontinuous, and slag shell cracking and slag entrapment occurred in some locations. Post-weld slag removal was difficult, requiring considerable mechanical force to completely remove the slag. A small amount of unremoved residue was visible on the weld surface. (See the weld image below.) Figure 5 As shown. Macroscopic observation revealed that the weld formation in this comparative example was not as smooth and full as in Example 1, and there were slight undercuts and uneven reinforcement at the weld toe transition.

[0065] The above results show that, under the condition that the total amounts of CaO, MgO and Al2O3 are basically equal, adding the three directly in the form of ordinary powder without using a pre-melted body will result in uneven distribution of slag composition and difficulty in fully melting local raw material particles in a short time. This weakens the slag's coating and support effect on the molten pool, which is not conducive to stable arc combustion and molten pool shape control. The weld formation and overall performance of the welded joint are significantly worse than those of the embodiments of the present invention, thus verifying the necessity and effectiveness of the CaO·MgO·Al2O3 pre-melted body design in the present invention.

[0066] When the total addition of CaO, MgO, and Al2O3 is within the range of 15% to 30%, but its internal mass ratio deviates significantly from the preferred ratio of this invention, even if other components such as CaF2 are kept at a reasonable level, the flux is unlikely to achieve ideal slag performance and weld metal performance. Furthermore, compared with Example 1, which uses a CaO·MgO·Al2O3 premelted body, the significant advantages of the combined effect of the premelted matrix and a reasonable CaO / MgO / Al2O3 ratio are clearly evident. Therefore, the experimental results of Comparative Examples 1 and 2 strongly support the necessity and significant technical effects of the technical solution of this invention regarding "using a CaO·MgO·Al2O3 premelted body and controlling the internal mass ratio of CaO, MgO, and Al2O3 within the range of 1.8~2.8:0.8~1.2:0.8~1.2 respectively".

[0067] Comparative Example 3 Using the same flux chemical composition and group distribution ratio as in Example 1, only the flux particle size distribution was adjusted so that the particle size was mainly concentrated in 0.3~0.6 mm, and all less than 0.8 mm.

[0068] Submerged arc welding tests were conducted under the same welding conditions as in Example 1. The results showed that: the slag cover was too dense during the welding process, the molten pool metal was not stirred enough, and the arc was prone to local blow-off; the weld formation was not full enough, the weld toe transition was poor, the weld surface ripples were finer, and spatter increased slightly; the impact toughness of the weld at -20 ℃ was significantly lower than that in Example 1, with an average decrease of about 15~30%.

[0069] Compared with Example 1, Comparative Example 3 shows that when the flux particle size is too small, significantly deviating from the range of 0.8~1.4 mm, the uniformity of flux powder delivery and slag formation behavior change adversely, and the welding formation and mechanical properties deteriorate significantly.

[0070] Comparative Example 4 Using the same flux chemical composition and group distribution ratio as in Example 1, only the particle size distribution of the flux was adjusted so that the particle size was mainly concentrated in 1.6~2.5 mm, and all were greater than 1.4 mm.

[0071] Submerged arc welding tests were conducted under the same welding conditions as in Example 1. The results showed that: the arc was difficult to stabilize in the initial welding stage, the arc ignition time was prolonged, and occasional arc extinction occurred; slag protection was discontinuous, with a tendency for localized porosity, and slag inclusions were present on the weld surface; the tensile strength and impact toughness of the weld metal were significantly lower than in Example 1, with the impact toughness decreasing by more than 20%. The above comparison indicates that when the flux particle size is significantly larger than 1.4 mm, the flux spreading and melting are insufficient, leading to delayed slag formation, ineffective arc protection and stabilization, and a significant decrease in weld joint performance.

[0072] Based on the results of Example 1 and Comparative Examples 3 and 4, it can be seen that controlling the flux particle size within the range of 0.8~1.4 mm can ensure arc stability while obtaining good slag coverage and weld formation, which is one of the necessary conditions for obtaining excellent welding performance.

[0073] Comparative Example 5 Based on the composition of Example 3, the arc-initiating and arc-stabilizing components were removed, while the remaining components and their amounts remained unchanged.

[0074] Submerged arc welding tests were conducted under the same welding specifications as in Example 1. The actual welded product is shown in the image below. Figure 6 As shown, the results revealed that: arc ignition was difficult, the arc ignition time was significantly prolonged, and the arc ignition failure rate was significantly increased; the arc oscillated significantly in the initial stage of welding, the arc combustion was unstable, and obvious arc jumping phenomenon occurred; local incomplete penetration and uneven weld formation were observed on the weld surface, and even humps of weld beads appeared. This indicates that the lack of arc ignition and arc stabilization components will seriously affect the ignition and stability of the arc, and the expected welding effect of this invention cannot be obtained.

[0075] Comparative Example 6 This comparative example was used to investigate the effects of rapid slag formation and energy loss control components (CaF2 and CaO·MgO·Al2O3 premelt) on the welding process and weld quality. Based on Example 3, the rapid slag formation and energy loss control components were removed, i.e., CaF2 and CaO·MgO·Al2O3 premelt were not added, while the remaining components and their amounts remained unchanged.

[0076] Submerged arc welding tests were conducted under the same conditions. The results showed that slag formation was significantly delayed, the arc was exposed to air for an extended period during welding, the arc column diverged, and spatter increased significantly. The oxygen and nitrogen content in the weld metal increased, and the impact toughness and plasticity of the weld metal decreased significantly. Poor weld formation was observed, with a marked tendency for surface depressions, undercut, and porosity. This indicates that components controlling rapid slag formation and energy loss are key to ensuring effective arc wrapping, reducing ineffective energy loss, and improving the mechanical properties of the welded joint.

[0077] Comparative Example 7 Based on Example 1, the content of the arc position control component was changed, specifically by halving the content of fine-grained MgO and fine-grained Al2O3 high-melting-point refractory oxides, and normalizing the formulation, while keeping the types and relative proportions of the remaining components unchanged. Specifically, the submerged arc welding flux, by total mass, includes the following components: CaF2: 31.5 wt%, CaO·MgO·Al2O3 premelt: 25.2 wt%, SiO2: 15.8 wt%, MnO: 6.3 wt%, TiO2: 4.2 wt%, CaCO3: 6.3 wt%, Fe2O3: 3.2 wt%, Al-Mg alloy powder: 0.5 wt%, KF: 1.0 wt%, BaO: 1.0 wt%, fine-grained MgO: 2.1 wt%, and fine-grained Al2O3: 2.9 wt%. The total mass fraction of the above components is 100 wt%.

[0078] The total amount of trace elements does not exceed 1 wt%. The trace elements include two parts: (1) unavoidable impurity elements (Fe, S, P, etc.), with a total mass fraction not exceeding 0.18 wt%; (2) rare earth elements Ce, La and B used to improve performance, which are added in the form of corresponding oxides, wherein the content of CeO2 is 0.10 wt%, the content of La2O3 is 0.20 wt%, and the content of B2O3 is 0.02 wt%.

[0079] The experimental results show that during welding, the electric arc tends to climb upwards along the welding wire, making it difficult to control the arc length and resulting in phenomena such as weld metal deviation and weld bead misalignment; the slag partially collapses at the top of the weld, leading to poor weld toe formation; the weld metal properties fluctuate significantly, and undercut defects are prone to appear on the weld surface. Therefore, the arc position control component plays a crucial and indispensable role in suppressing arc climbing and ensuring weld formation.

[0080] Comparative Example 8 Based on Example 1, CaF2 was replaced with an equal mass of NaF, while the rest of the formulation and process conditions remained unchanged.

[0081] Welding test results showed that the viscosity of the slag decreased significantly during the welding process, the slag flow was severe, and it was difficult to form a stable slag layer on the upper surface of the weld; the electric arc was prone to deflection and arc length fluctuation, and the weld formation was irregular; the Na content in the weld metal increased, resulting in a significant decrease in the impact toughness of the weld.

[0082] CaF2 provides a stable slag structure and arc environment, existing stably in the high-temperature arc zone. It can regulate the melting point and viscosity of the slag system, stabilize the arc, and ensure good deep fusion and forming. Small amounts of arc-initiating and arc-stabilizing components (NaF, KF, BaO) can enhance the ionization and arc-initiating sensitivity of the arc, and have a positive effect on the arc's "ignition" and a certain degree of "arc stability". The combined effect is that CaF2 dominates the slag system and the overall arc "skeleton". Small amounts of arc-initiating and arc-stabilizing components improve "arc sensitivity and arc column conductivity" in the initial stage or under low current conditions. However, when the content of arc-initiating and arc-stabilizing components is too high (or completely replaces CaF2), the slag viscosity will be too low, the slag will flow excessively, and the slag layer will be unstable, resulting in weld formation defects; excessive arc diffusion and reduced rigidity will lead to shallower weld penetration, increased arc vibration, and decreased weld toughness.

[0083] The above comparative examples demonstrate that controlling the particle size to 0.8~1.4 mm and coordinating it with the various functional components are key to achieving "stable arc, good slag formation, and excellent weld mechanical properties." If any condition is disrupted (excessive particle size, lack of components, or improper substitution of components, etc.), the welding effect will significantly deteriorate. The above descriptions are merely further embodiments of the present invention and are not intended to limit the invention. For those skilled in the art, the present invention can have various modifications and variations. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A submerged arc welding flux suitable for twin-wire indirect arc welding, characterized in that, It includes components for arc initiation and stabilization, rapid slag formation and energy loss control, slag stability and anti-collapse, arc position control, gas escape management, self-ignition, as well as trace elements and impurities. The arc-initiating and arc-stabilizing components are selected from at least one of KF, NaF, or BaO. The rapid slag formation and energy loss control components are selected from CaF2 and CaO·MgO·Al2O3 premelts; The slag stability and anti-collapse component is selected from at least one of SiO2, MnO or TiO2; The arc position control component is selected from at least one of fine-grained MgO or fine-grained Al2O3; The gas escape management component is selected from calcium carbonate; The self-triggered ignition component is selected from Al-Mg alloy powder or Fe2O3 powder; The flux particles have a particle size of 0.8 mm to 1.4 mm.

2. The submerged arc welding flux as described in claim 1, characterized in that, The amount of arc ignition and arc stabilization components added is 1% to 3% of the total mass of the submerged arc welding flux; or, the amount of CaF2 added is 20% to 40% of the total mass of the submerged arc welding flux; the amount of CaO·MgO·Al2O3 premelt added is 15% to 30% of the total mass of the submerged arc welding flux.

3. The submerged arc welding flux as described in claim 2, characterized in that, The mass ratio of CaO, MgO and Al2O3 in the CaO·MgO·Al2O3 premelt is 1.8~2.8:0.8~1.2:0.8~1.

2.

4. The submerged arc welding flux as described in claim 1, characterized in that, The amount of SiO2 added is 10% to 20% of the total mass of the submerged arc welding flux; or, the amount of MnO added is 2% to 10% of the total mass of the submerged arc welding flux; or, the amount of TiO2 added is 1% to 5% of the total mass of the submerged arc welding flux.

5. The submerged arc welding flux as described in claim 1, characterized in that, The amount of fine MgO added is 4% to 10% of the total mass of the submerged arc welding flux; the amount of fine Al2O3 added is 4% to 10% of the total mass of the submerged arc welding flux; the particle size of fine MgO and fine Al2O3 is less than 0.1 mm.

6. The submerged arc welding flux as described in claim 1, characterized in that, The amount of CaCO3 added is 3% to 10% of the total mass of the submerged arc welding flux.

7. The submerged arc welding flux as described in claim 1, characterized in that, The self-ignition component is incorporated in proportions of 3% to 6% of the total mass of the submerged arc welding flux; or, the Al-Mg alloy powder is incorporated in proportions of 0.5% to 1% of the total mass of the submerged arc welding flux; and the Fe2O3 powder is incorporated in proportions of 2.5% to 5% of the total mass of the submerged arc welding flux.

8. The method for preparing submerged arc welding flux according to any one of claims 1-7, characterized in that, Includes the following steps: (1) The raw materials CaO, MgO and Al2O3 are melted at 1550~1700℃ in a mass ratio of 1.8~2.8:0.8~1.2:0.8~1.

2. The melted product is then rapidly cooled, crushed and sieved to obtain CaO·MgO·Al2O3 premelted material for later use. (2) Weigh each component raw material according to the predetermined ratio and mix them thoroughly; (3) The mixture is granulated to form particles with a diameter in the range of 0.8 mm to 1.4 mm; (4) The granulated particles are sintered; (5) The sintered particles are sieved to obtain the final product.

9. The preparation method according to claim 8, characterized in that, In step (1), the particle size of the CaO·MgO·Al2O3 premelt is controlled between 0.5 and 2.0 mm; Alternatively, in step (2), the mixing can be dry or wet; the mixing time is 10~40 min. Alternatively, in step (3), the granulation method is pelletizing, extrusion, or disc granulation; 4%~6% water glass solution is also added as a binder during the granulation process; Alternatively, in step (4), the sintering temperature is 700~900 ℃; the time is 1~3 h.

10. The application of the submerged arc welding flux as described in any one of claims 1-7 in twin-wire indirect arc welding additive manufacturing.

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