Low-smoke environment-friendly submerged arc welding flux and preparation method thereof

Abstract

This invention discloses a low-smoke, environmentally friendly submerged arc welding flux and its preparation method, belonging to the field of welding materials technology. The flux is a sintering type, composed of the following components by mass percentage: 28%-38% magnesia, 6%-12% medium-low carbon ferromanganese, 12%-20% high-alumina bauxite, 8%-16% wollastonite, 2%-6% calcium fluoride, 3%-8% ilmenite, 2%-5% potassium feldspar, and 1%-4% calcium carbonate, totaling 100%. During preparation, all raw materials are pulverized to pass through a 200-mesh sieve, dry-mixed, and then granulated with potassium sodium silicate. The mixture is pre-dried at 150-200℃, sintered at 760-880℃, cooled, and sieved to obtain the final product. This flux reduces welding fume generation by limiting calcium fluoride to 2%-6% and calcium carbonate to 1%-4%, and by introducing K2O instead of potassium salt with potassium feldspar. This synergistic reduction comes from three sources: fluoride and carbonate decomposition and alkali metal volatilization. The fume generation is 3.7-5.2 mg / s, which is more than 55% lower than that of conventional fluorine-alkali fluxes. The slag automatically falls off after welding, with a slag removal rate of over 93%. The diffusible hydrogen content of the deposited metal is less than 4.0 mL / 100g, and the mechanical properties meet the requirements of GB / T5293 standard.

Description

Technical Field

[0001] This invention belongs to the field of welding materials technology, specifically relating to a low-smoke, environmentally friendly submerged arc welding flux and its preparation method. Background Technology

[0002] Submerged arc welding (SAW) is widely used in shipbuilding, pressure vessels, pipelines, and steel structures, resulting in high consumption of welding materials. Flux is one of the main consumables in SAW, covering the electric arc and molten pool during welding, serving to slag form, deoxidize, alloy, and isolate air. Based on manufacturing processes, fluxes are classified into smelting-type and sintering-type fluxes. Smelting-type fluxes require melting the raw materials into a liquid state in an electric furnace and then water-quenching and crushing them, while sintering-type fluxes involve mixing and granulating the powder before sintering it into a sintered shape. Sintering-type fluxes are manufactured at lower temperatures, have more flexible formulation adjustments, and their proportion in SAW fluxes is gradually increasing.

[0003] To ensure good slag removal and deoxidation effects in sintered fluxes and to guarantee that the diffusible hydrogen content of the deposited metal meets standards, a significant amount of fluorite is typically added to the formulation. In the market, widely used fluorine-alkali sintered fluxes generally contain 25%-35% fluorite. Fluorite partially decomposes under an electric arc, generating fluorine-containing gases and fluorine-containing fumes. Inhalation of these gases can damage the respiratory tract of operators, and emissions pollute the environment. While submerged arc welding (SAW) produces less smoke per burst than open arc welding (SAW), it often involves high current and prolonged continuous operation, resulting in a significant cumulative amount of fumes and harmful gases. Furthermore, fluorite powder also generates fluorine-containing dust during the batching, mixing, and granulation processes of flux production, which also requires treatment.

[0004] To reduce fluorite usage, some technical solutions have lowered the fluorite content to over 25%, but the effect on reducing fluoride content is limited. Other solutions reduce fluorite to 3%-7%, but require the addition of 17%-22% ZrO2 to replace fluorite and reduce slag viscosity. ZrO2 has a melting point exceeding 2000℃, making it difficult to fully react at sintering temperatures of 760-880℃, resulting in low utilization. Furthermore, ZrO2 is expensive, increasing flux costs. Some solutions completely eliminate fluorite, employing a smelting process. However, smelting flux itself is energy-intensive, still relies on ZrO2, and suffers from poor slag removal, making the weld prone to porosity.

[0005] The inventors discovered that the sources of welding fumes are not limited to fluorides. When carbonates, commonly added to flux formulations, decompose under an electric arc, the released gases easily carry fine slag droplets and metal particles, forming fumes. Furthermore, alkali metal oxides K₂O and Na₂O, used for arc stabilization, have high vapor pressures at high temperatures and also volatilize into the fumes. Currently, the flux industry primarily focuses on reducing fluoride content to control fume emission, paying insufficient attention to the decomposition of carbonates and the volatilization of alkali metals. This results in a situation where reducing fluoride content does not necessarily lead to a corresponding reduction in total fume emission. Therefore, it is necessary to synergistically suppress fume emission from three sources—fluoride, carbonate decomposition, and alkali metal volatilization—while ensuring that slag removal, deoxidation, and weld quality remain at the same level as with conventional fluxes. Summary of the Invention

[0006] The purpose of this invention is to provide a low-smoke, environmentally friendly submerged arc welding flux and its preparation method.

[0007] To achieve the above objectives, the present invention provides the following technical solution: A low-smoke, environmentally friendly submerged arc welding flux, wherein the flux is a sintered flux, and is composed of the following components by mass percentage: magnesia 28%-38%, medium-low carbon ferromanganese 6%-12%, high-alumina bauxite 12%-20%, wollastonite 8%-16%, calcium fluoride 2%-6%, ilmenite 3%-8%, potassium feldspar 2%-5%, and calcium carbonate 1%-4%, wherein the sum of the mass percentages of each component is 100%.

[0008] Furthermore, the basicity of the flux is calculated to be 2.0-2.8 according to the International Institute of Welding (BIIW) formula.

[0009] Furthermore, the flux has a particle size of 10-60 mesh and a loose packing density of 1.15-1.40 g / cm³. 3 .

[0010] Furthermore, it is composed of the following components by mass percentage: 30%-36% magnesia, 7%-11% medium-low carbon ferromanganese, 14%-20% high-alumina bauxite, 10%-15% wollastonite, 3%-5% calcium fluoride, 4%-8% ilmenite, 2%-4% potassium feldspar, and 1%-4% calcium carbonate, with the sum of the mass percentages of each component being 100%.

[0011] Furthermore, the magnesia contains MgO with a mass fraction of not less than 95%, the high-alumina bauxite contains Al2O3 with a mass fraction of not less than 80%, the medium-low carbon ferromanganese contains Mn with a mass fraction of 75%-85%, the calcium fluoride contains CaF2 with a mass fraction of not less than 95%, the ilmenite contains TiO2 with a mass fraction of not less than 48%, and the calcium carbonate contains CaCO3 with a mass fraction of not less than 98%.

[0012] A method for preparing a low-smoke, environmentally friendly submerged arc welding flux includes the following steps: (1) Ingredients and dry mixing: Weigh out magnesia, medium and low carbon manganese iron, high alumina bauxite, wollastonite, calcium fluoride, ilmenite, potassium feldspar and calcium carbonate according to the proportion, crush them to pass through a 200-mesh sieve, put them into a mixer and dry mix for 15-25 minutes to obtain dry mixture. (2) Wet mixing and granulation: Add potassium sodium water glass as a binder to the dry mixture. The amount added is 18%-25% of the total mass of the dry mixture. After mixing, granulate to obtain wet granules. (3) Low-temperature pre-drying: Dry the wet granules at 150-200℃ for 30-60 min; (4) High-temperature sintering: The pre-dried particles are sintered at 760-880℃ in air atmosphere for 1.5-2.5h; (5) Cooling and sieving: After sintering, the particles are naturally cooled to room temperature, and 10-60 mesh particles are sieved out, which are the low-smoke environmentally friendly submerged arc welding flux.

[0013] Furthermore, the potassium-sodium water glass mentioned in step (2) has a modulus of 2.8-3.2, a Baume degree of 38-42°Bé, and a potassium-sodium molar ratio of 1:1.

[0014] Furthermore, in step (2), the amount of binder added is 20%-23% of the total mass of the dry mix, and the modulus of potassium sodium water glass is 2.9-3.1.

[0015] Furthermore, the heating method in step (4) is as follows: heat up to 550-600℃ at 5-8℃ / min, keep warm for 15-20min, and then heat up to 760-880℃ at 3-5℃ / min.

[0016] Furthermore, the sintering temperature in step (4) is 800-840℃ and the sintering time is 2.0-2.5h; the dry mixing in step (1) is carried out in a V-type mixer or a double cone mixer, and the granulation in step (2) is carried out in a rotary granulator or a disc granulator.

[0017] The beneficial effects of this invention are as follows: 1. Fluorite content is limited to 2%-6%, calcium carbonate to 1%-4%, and potassium is introduced not in the form of water glass or potassium salts, but as potassium feldspar. Potassium feldspar is a silicate mineral, with potassium fixed in the silicate framework. Its volatilization rate under arc is relatively slow, and its contribution to smoke emission is less than that of potassium salts at the same potassium content. Actual measurements using 4.0mm diameter H10Mn2 welding wire, a welding current of 650A, and an arc voltage of 32V showed smoke emission of 3.7-5.2 mg / s, compared to 12.8 mg / s for fluorine-alkali flux under the same conditions, representing a reduction of over 55%.

[0018] 2. After welding, the slag can automatically lift and fall off in whole pieces, achieving a slag removal rate of over 93%. The flux has a high magnesia content, which reacts with high-alumina bauxite during welding to form magnesium olivine and magnesium aluminum spinel. These two mineral phases have significantly different coefficients of thermal expansion from steel. As the weld cools and shrinks, the slag-steel interface cracks spontaneously. Furthermore, a small amount of fluorite accumulates at the interface, further improving slag removal. Although the flux has a low fluorite content, its slag removal performance is unaffected.

[0019] 3. The arc burns stably in both DC reverse polarity and AC modes, the arc ignition is normal, the weld surface has uniform ripples, and there is no undercut or surface porosity. Arc stabilization is achieved by the K2O introduced by potassium feldspar. In the early stage of arc ignition, a small amount of gas produced by the decomposition of calcium carbonate forms an air cushion on the slag surface, which is beneficial for arc building and initial slag coverage.

[0020] 4. When used with H10Mn2 welding wire on Q345B steel plate, the tensile strength, yield strength, elongation, and impact absorption energy at -20℃ all meet the requirements of GB / T5293, and the diffusible hydrogen content is below 4.0mL / 100g. The flux basicity, calculated according to the BIIW formula, is 2.0-2.8, indicating sufficient deoxidation and desulfurization capabilities. The TiO2 produced by the decomposition of ilmenite under the electric arc reacts with CaO and MgO in the slag to form CaTiO3 and MgTiO3, making the slag cover layer dense and preventing air intrusion during welding, thus helping to maintain the purity of the weld metal.

[0021] 5. All raw materials are commercially available industrial minerals, and no high-cost components such as ZrO2 are used. The sintering temperature is 760-880℃. A two-stage heating method is adopted, first removing the moisture from the binder, and then raising it to the target temperature for sintering. The process is easy to control and suitable for mass production. Attached Figure Description

[0022] Figure 1 This is a process flow diagram for the preparation of a low-smoke, environmentally friendly submerged arc welding flux. Detailed Implementation

[0023] The present invention will be further described below with reference to embodiments and comparative examples, but the scope of protection of the present invention is not limited to these embodiments.

[0024] The raw materials used in the examples and comparative examples are as follows: magnesia (MgO mass fraction 96.2%), medium-low carbon ferromanganese (Mn mass fraction 80.5%), high-alumina bauxite (Al2O3 mass fraction 83.5%), wollastonite (CaSiO3 mass fraction 93.0%), calcium fluoride (CaF2 mass fraction 96.8%), ilmenite (TiO2 mass fraction 50.2%), potassium feldspar (K2O mass fraction 13.5%, Al2O3 mass fraction 18.8%, SiO2 mass fraction 64.5%), and calcium carbonate (CaCO3 mass fraction 98.5%). The binder is potassium-sodium silicate with a modulus of 3.0, a Baume degree of 40°Bé, and a potassium-sodium molar ratio of 1:1.

[0025] BIIW alkalinity is calculated using the following formula: BIIW=[CaO+MgO+BaO+SrO+Na2O+K2O+Li2O+0.5(MnO+FeO)] / [SiO2+0.5(Al2O3+TiO2+ZrO2)] The basicity of the flux is converted into oxides by the distribution ratio of each group and then substituted into the above formula for calculation. Example

[0026] Formula: 36% magnesia, 8% medium-low carbon ferromanganese, 18% high-alumina bauxite, 16% wollastonite, 6% calcium fluoride, 8% ilmenite, 4% potassium feldspar, 4% calcium carbonate, with the sum of all components being 100%. After conversion to oxides, the BIIW alkalinity is approximately 2.4.

[0027] Preparation steps: (1) Ingredients and dry mixing: Weigh each raw material according to the proportion, crush them separately to pass through a 200-mesh sieve, put them into a V-type mixer and dry mix for 20 minutes to obtain dry mixture.

[0028] (2) Wet mixing and granulation: Add potassium sodium water glass to the dry mixture, the amount of which is 22% of the total mass of the dry mixture. After mixing, granulate in a rotary granulator to obtain wet granules.

[0029] (3) Low temperature pre-drying: wet granules are dried at 180℃ for 45 min.

[0030] (4) High-temperature sintering: The pre-dried particles are sintered in an air atmosphere. The heating method is to raise the temperature from room temperature to 580℃ at 6℃ / min, hold for 18min, and then raise it to 820℃ at 4℃ / min and hold for 2.0h.

[0031] (5) Cooling and sieving: After sintering, the particles are naturally cooled to room temperature in the furnace, and sieved to obtain 10-60 mesh particles to obtain the flux. Loose packing density: 1.28 g / cm³ 3 .

[0032] Welding process performance test: Using 4.0mm diameter H10Mn2 welding wire, surfacing was performed on a 20mm thick Q345B steel plate. The welding conditions were: DC reverse polarity, welding current 650A, arc voltage 32V, welding speed 35cm / min, and wire extension length 25mm. The flux was baked at 350℃ for 1 hour before use. The arc burned stably without interruption, and the weld surface had uniform ripples, no undercut, and no surface porosity. After welding, the slag automatically lifted and fell off in whole pieces during cooling, with a slag removal rate of 97%. X-ray inspection of the weld showed no porosity, cracks, or slag inclusions.

[0033] The dust emission was determined according to the method specified in GB / T25776-2010. Under the above welding conditions, the dust emission was 4.1 mg / s. Under the same conditions, the measured dust emission of commercially available SJ103 fluorine-alkali sintering flux (CaF2 content 25%~35%) was 12.8 mg / s.

[0034] The mechanical properties of the deposited metal were tested using test plates prepared according to GB / T5293-2018: tensile strength R m =565MPa, yield strength R eI =438MPa, elongation A =27.5%, Charpy V-notch impact absorption energy at -20℃ KV2 =72J (average of three samples). The diffusible hydrogen content was determined by the mercury method according to GB / T3965, and the result was 3.2mL / 100g. Example

[0035] Formula: 34% magnesia, 10% medium-low carbon ferromanganese, 20% high-alumina bauxite, 16% wollastonite, 5% calcium fluoride, 6% ilmenite, 5% potassium feldspar, 4% calcium carbonate, totaling 100%. BIIW alkalinity is approximately 2.2.

[0036] The differences between the preparation steps and those in Example 1 are as follows: Step (4) sintering temperature 840℃, holding time 2.5h; Step (1) dry mixing 15min; Step (3) pre-drying temperature 200℃, time 30min. The rest are the same as in Example 1.

[0037] Loose packing density: 1.25 g / cm³ 3 Tested under the conditions of Example 1, the arc was stable, the weld formation was good, the slag removal rate was 95%, and the X-ray flaw detection was qualified. Dust emission was 5.0 mg / s. Mechanical properties of the deposited metal: R m =545MPa, R eI =412MPa, A=26.0%, KV2 (-20℃)=65J, diffusible hydrogen content 3.8mL / 100g. Example

[0038] Formula: 37% magnesia, 9% medium-low carbon ferromanganese, 20% high-alumina bauxite, 16% wollastonite, 2% calcium fluoride, 7% ilmenite, 5% potassium feldspar, 4% calcium carbonate, totaling 100%. BIIW alkalinity is approximately 2.7.

[0039] The differences between the preparation steps and those in Example 1 are as follows: Step (4) sintering temperature 780℃, holding time 1.5h; Step (1) dry mixing 25min; Step (3) pre-drying temperature 150℃, time 60min. The rest are the same as in Example 1.

[0040] Loose packing density: 1.32 g / cm³ 3Tested under the conditions of Example 1, the arc was stable, the weld formation was good, the slag removal rate was 93%, and the X-ray flaw detection was qualified. Dust emission was 3.7 mg / s. Mechanical properties of the deposited metal: R m =585MPa, R eI =460MPa, A=25.0%, KV2 (-20℃)=68J, diffusible hydrogen content 2.8mL / 100g. Example

[0041] Formula: 33% magnesia, 12% medium-low carbon ferromanganese, 19% high-alumina bauxite, 16% wollastonite, 3% calcium fluoride, 8% ilmenite, 5% potassium feldspar, 4% calcium carbonate, with the sum of all components being 100%. BIIW alkalinity is approximately 2.3. Preparation steps are the same as in Example 1.

[0042] Loose packing density: 1.26 g / cm³ 3 Slag removal rate: 96%; Dust generation: 4.6 mg / s. Mechanical properties of deposited metal: R m =558MPa, R eI =425MPa, A=26.8%, KV2 (-20℃)=70J, diffusible hydrogen content 3.5mL / 100g. Example

[0043] Formula: 35% magnesia, 10% medium-low carbon ferromanganese, 18% high-alumina bauxite, 16% wollastonite, 6% calcium fluoride, 6% ilmenite, 5% potassium feldspar, 4% calcium carbonate, with the sum of all components being 100%. BIIW alkalinity is approximately 2.5. Preparation steps are the same as in Example 1.

[0044] Loose packing density: 1.30 g / cm³ 3 Slag removal rate: 96%; Dust generation: 4.3 mg / s. Mechanical properties of deposited metal: R m =572MPa, R eI =440MPa, A=27.0%, KV2 (-20℃)=74J, diffusible hydrogen content 3.1mL / 100g.

[0045] Comparative Example 1 Formula: 36% magnesia, 8% medium-low carbon ferromanganese, 18% high-alumina bauxite, 12% wollastonite, 12% calcium fluoride, 6% ilmenite, 4% potassium feldspar, and 4% calcium carbonate. The rest is the same as in Example 1.

[0046] The arc was stable during welding, with a slag removal rate of 98%, but the dust generation increased to 9.8 mg / s. The diffusible hydrogen content was 4.5 mL / 100 g. KV2 (-20℃) = 63 J.

[0047] Comparative Example 2 The formula does not contain calcium fluoride: 38% magnesia, 12% medium-low carbon ferromanganese, 20% high-alumina bauxite, 16% wollastonite, 8% ilmenite, 5% potassium feldspar, and 1% calcium carbonate. The rest is the same as in Example 1.

[0048] Dust emission was 3.2 mg / s, but the slag removal rate was only 72%. Slag adhered locally to the weld surface, requiring manual tapping, and sporadic surface porosity appeared in the weld. KV2 (-20℃) = 58 J.

[0049] Comparative Example 3 Magnesia 36%, medium-low carbon ferromanganese 8%, high-alumina bauxite 18%, wollastonite 14%, calcium fluoride 4%, ilmenite 6%, potassium feldspar 4%, calcium carbonate 10%. The rest is the same as in Example 1.

[0050] Dust emission was 7.6 mg / s, with a significant increase in gas escape during welding and increased spatter. Diffusible hydrogen content was 4.8 mL / 100g.

[0051] Comparative Example 4 The formula is the same as in Example 1, and the sintering temperature is 680℃. Everything else is the same as in Example 1.

[0052] The flux particles have low strength, a slag removal rate of 80%, and the particles break during feeding. The arc occasionally breaks. Dust generation is 5.1 mg / s. KV2 (-20℃) = 68 J, and diffusible hydrogen content is 4.0 mL / 100g.

[0053] Comparative Example 5 The formula is the same as in Example 1, but the sintering temperature is changed to 950℃. Everything else is the same as in Example 1.

[0054] The flux particles exhibit surface vitrification, with a slag removal rate of 85% and a dust generation rate of 5.3 mg / s. KV2 (-20℃) = 66 J.

[0055] Table 1: Key Data Tables for Examples and Comparative Examples

[0056] As can be seen from Table 1: In Examples 1 to 5, the calcium fluoride content was within the range of 2%-6%, the dust generation was 3.7-5.2 mg / s, the slag removal rate reached 93%-97%, and the diffusible hydrogen content was 2.8-3.8 mL / 100g. All mechanical properties met the requirements of GB / T5293 standard. In Comparative Example 1, the calcium fluoride content was increased to 12%, resulting in a dust generation of 9.8 mg / s and a diffusible hydrogen content of 4.5 mL / 100g, indicating that both dust generation and diffusible hydrogen content significantly deteriorated after the calcium fluoride content exceeded 6%. Comparative Example 2 contained no calcium fluoride. Although the dust generation decreased to 3.2 mg / s, the slag removal rate was only 72%, surface porosity appeared in the weld, and the impact energy at -20℃ decreased to 58 J. This demonstrates that an appropriate amount of calcium fluoride is necessary to ensure slag removal and weld quality, and 2%-6% is a reasonable range balancing dust reduction and process performance. Comparative Example 3, with calcium carbonate increased to 10%, resulted in approximately 85% higher dust generation compared to Example 1, reaching 7.6 mg / s, and diffusible hydrogen increased to 4.8 mL / 100g. Increased gas escape and spatter during welding confirmed that controlling calcium carbonate content between 1% and 4% is crucial for suppressing dust generation and ensuring weld quality. Comparative Example 4, with a sintering temperature of 680℃, below the lower limit of 760℃, exhibited insufficient particle strength, a slag removal rate reduced to 80%, particle fragmentation during feeding, and occasional arc interruptions. Comparative Example 5, with a sintering temperature of 950℃, above the upper limit of 880℃, resulted in vitrification of the particle surface and a slag removal rate reduced to 85%. Examples 1 to 5, with sintering temperatures all within the range of 760-880℃, all achieved slag removal rates exceeding 93%, indicating that this temperature range ensures sufficient mineral phase formation without vitrification and stable process performance.

Claims

1. A low-smoke environment-friendly submerged arc flux, the flux being a sintered flux, characterized by, Composed of the following components by mass percentage Composition: 28%-38% magnesia, 6%-12% medium-low carbon ferromanganese, 12%-20% high-alumina bauxite, 8%-16% wollastonite, 2%-6% calcium fluoride, 3%-8% ilmenite, 2%-5% potassium feldspar, 1%-4% calcium carbonate, with the sum of the mass percentages of each component being 100%.

2. The low-smoke environmentally friendly submerged arc flux according to claim 1, characterized in that, The basicity of the flux is calculated to be 2.0-2.8 according to the International Institute of Welding (BIIW) formula.

3. The low-smoke environmentally friendly submerged arc welding flux according to claim 1, characterized in that, The flux has a particle size of 10-60 mesh and a loose bulk density of 1.15-1.40 g / cm 3 .

4. The low-smoke environmentally friendly submerged arc welding flux according to claim 1, characterized in that, It is composed of the following components by mass percentage: magnesia 30%-36%, medium and low carbon manganese iron 7%-11%, high alumina bauxite 14%-20%, wollastonite 10%-15%, calcium fluoride 3%-5%, ilmenite 4%-8%, potassium feldspar 2%-4%, and calcium carbonate 1%-4%, with the sum of the mass percentages of each component being 100%.

5. The low-smoke environmentally friendly submerged arc welding flux according to claim 4, characterized in that, The magnesia contains MgO with a mass fraction of not less than 95%, the high-alumina bauxite contains Al2O3 with a mass fraction of not less than 80%, the medium-low carbon ferromanganese contains Mn with a mass fraction of 75%-85%, the calcium fluoride contains CaF2 with a mass fraction of not less than 95%, the ilmenite contains TiO2 with a mass fraction of not less than 48%, and the calcium carbonate contains CaCO3 with a mass fraction of not less than 98%.

6. A method for preparing a low-smoke, environmentally friendly submerged arc welding flux as described in any one of claims 1 to 5, characterized in that, Includes the following steps: (1) Ingredients and dry mixing: Weigh out magnesia, medium and low carbon manganese iron, high alumina bauxite, wollastonite, calcium fluoride, ilmenite, potassium feldspar and calcium carbonate according to the proportion, crush them to pass through a 200-mesh sieve, put them into a mixer and dry mix for 15-25 minutes to obtain dry mixture. (2) Wet mixing and granulation: Add potassium sodium water glass as a binder to the dry mixture. The amount added is 18%-25% of the total mass of the dry mixture. After mixing, granulate to obtain wet granules. (3) Low-temperature pre-drying: Dry the wet granules at 150-200℃ for 30-60 min; (4) High-temperature sintering: The pre-dried particles are sintered at 760-880℃ in air atmosphere for 1.5-2.5h; (5) Cooling and sieving: After sintering, the particles are naturally cooled to room temperature, and 10-60 mesh particles are sieved out, which are the low-smoke environmentally friendly submerged arc welding flux.

7. The preparation method according to claim 6, characterized in that, The potassium-sodium water glass mentioned in step (2) has a modulus of 2.8-3.2, a Baume degree of 38-42°Bé, and a potassium-sodium molar ratio of 1:

1.

8. The preparation method according to claim 7, characterized in that, In step (2), the amount of binder added is 20%-23% of the total mass of the dry mix, and the modulus of potassium sodium water glass is 2.9-3.

1.

9. The preparation method according to claim 6, characterized in that, The heating method in step (4) is as follows: heat up to 550-600℃ at 5-8℃ / min, keep warm for 15-20min, and then heat up to 760-880℃ at 3-5℃ / min.

10. The preparation method according to claim 6, characterized in that, The sintering temperature of step (4) is 800-840℃ and the sintering time is 2.0-2.5h; the dry mixing of step (1) is carried out in a V-type mixer or a double cone mixer, and the granulation of step (2) is carried out in a rotary granulator or a disc granulator.

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