High-activity soldering paste for stainless steel welding and preparation method thereof

Abstract

This invention relates to a flux for welding stainless steel, comprising 73.32% flux base and 26.68% activator. The flux base includes: 23.04% rosin component, 26.4% diethylene glycol monohexyl ether, 2.4% white petrolatum, 2.4% ethylene bis-stearyl ammonium, 3% fluorinated surfactant FS-3100, 2.4% hexanediol, 7.2% diphenylguanidine hydrochloride, 6% 6500 thixotropic agent, and 0.48% hydroquinone. This invention, by using a ratio of 5.33% ammonium ethanol, 10.5% thiophosphoric acid, 9.86% ammonium fluoroborate, and 0.99% ammonium bifluoride, forms a three-stage gradient activation effect: low-temperature start-up, medium-temperature enhancement, and high-temperature sustained activation. This effectively breaks down the dense chromium-rich oxide film on the surface of stainless steel, significantly improves solder wettability, and effectively avoids the activity gap or instantaneous overreaction caused by a single activator due to its narrow temperature window. It is suitable for various heating methods, including manual flame brazing and automated induction brazing.

Description

Technical Field

[0001] This invention belongs to the field of stainless steel welding technology, specifically relating to a high-activity flux for stainless steel welding and its preparation method. Background Technology

[0002] Stainless steel is commonly used in petrochemical, marine engineering, automobile manufacturing, medical equipment and food processing. In the production and repair of stainless steel products, soldering is often used for installation and connection. However, due to the presence of a dense and chemically stable chromium-rich oxide film (Cr2O3) on the surface of stainless steel, conventional soldering fluxes are difficult to effectively remove this oxide film, resulting in extremely poor wettability and spreadability of the solder on the stainless steel surface, making it difficult to guarantee the welding quality.

[0003] Existing technologies often use flux to increase the solderability of stainless steel, while adding chloride-containing or strongly acidic active ingredients to enhance film removal capabilities. Specifically, using flux containing a small amount of chloride can temporarily improve activity, but the residual chloride ions can easily trigger electrochemical corrosion in humid environments, leading to pitting corrosion and even stress corrosion cracking in stainless steel joints, severely compromising long-term reliability. Another type of existing technology uses an organic acid-based active system, with flux containing 20%–35% orthophosphoric acid, 20%–35% ammonium dihydrogen phosphate, and 20%–75% solvents. However, the rosin content is only 2%–5%, which is relatively low, resulting in insufficient film formation and protection of the welded surface during the preheating stage of the flux.

[0004] In addition, in terms of rosin component selection, most solutions use ordinary rosin or single modified rosin, which has limited ability to control the viscosity and high-temperature oxidation resistance of the flux. In terms of the ratio of activator to rosin matrix, there is a common problem of insufficient activator addition, which leads to the contradiction of difficulty in breaking through oxide film or strong corrosiveness of residues and decrease in insulation resistance. Summary of the Invention

[0005] To achieve the above objectives, the first aspect of the present invention provides a flux for stainless steel welding, comprising 73.32% flux base and 26.68% activator, wherein the flux base comprises: 23.04% rosin component, 26.4% diethylene glycol monohexyl ether, 2.4% white petrolatum, 2.4% ethylene bis-stearyl ammonium, 3% fluorinated surfactant FS-3100, 2.4% hexanediol, 7.2% diphenylguanidine hydrochloride, 6% 6500 thixotropic agent and 0.48% hydroquinone;

[0006] The activator comprises: 3-8% ammonium ethanol, 8-15% phosphoric acid thiophosphate, 5-15% ammonium fluoroborate, and 0.5-2% ammonium hydrogen fluoride;

[0007] The flux paste matrix and the activator are mixed and ground to form the flux paste.

[0008] Preferably, the rosin component comprises 14.4% rosin KE-604 and 8.64% 610# rosin.

[0009] Preferably, the activator comprises the following components by mass percentage: 3.5% ammonium ethanol, 9.5% phosphoric acid thiophosphate, 12.5% ​​ammonium fluoroborate and 1.18% ammonium hydrogen fluoride.

[0010] Preferably, the activator comprises the following components by mass percentage: 4.68% ammonium ethanol, 14.5% thiophosphoric acid, 6.5% ammonium fluoroborate, and 1.00% ammonium hydrogen fluoride.

[0011] Preferably, the activator comprises the following components by mass percentage: 5.33% ammonium ethanol, 10.5% phosphoric acid thiophosphate, 9.86% ammonium fluoroborate and 0.99% ammonium hydrogen fluoride.

[0012] Preferably, the activator comprises the following components by mass percentage: 7.5% ammonium ethanol, 8.5% phosphoric acid thiophosphate, 9.68% ammonium fluoroborate and 1.00% ammonium hydrogen fluoride.

[0013] A second aspect of the present invention provides a method for preparing a flux paste for stainless steel welding, comprising the following steps:

[0014] S01 is made by mixing 14.4% rosin KE-604, 8.64% 610# rosin, 26.4% diethylene glycol monohexyl ether, 2.4% white petrolatum, 2.4% ethylene bis-stearyl ammonium, 3% fluorinated surfactant FS-3100 and 2.4% hexanediol, and dissolving them at 150°C.

[0015] SO2 is prepared by mixing 7.2% diphenylguanidine hydrochloride, 6% 6500 thixotropic agent and 0.48% hydroquinone, dissolving at 120°C, and then cooling.

[0016] S03 involves cooling the materials obtained from S01 and S02 and then dispersing them using a disperser to obtain the flux base.

[0017] S04 is prepared by mixing 5.33% ammonium ethanol, 10.5% phosphoric acid, 9.86% ammonium fluoroborate and 0.99% ammonium bifluoride at room temperature and grinding them with a grinder to obtain the activator.

[0018] Finally, in step S05, the flux base obtained in step S03 is added to the activator obtained in step S04, and after mixing, it is stirred and ground to produce stainless steel flux.

[0019] The third aspect of this invention is a flux paste for stainless steel welding, characterized in that the flux paste is used in stainless steel welding, welding materials for steel, special functional brazing filler metals, or brazing flux products.

[0020] Compared with the prior art, the beneficial effects of the present invention are:

[0021] This invention, by using a ratio of 5.33% ammonium ethanol, 10.5% thiophosphoric acid, 9.86% ammonium fluoroborate, and 0.99% ammonium bifluoride, forms a three-stage gradient activation effect: low-temperature start-up, medium-temperature enhancement, and high-temperature sustained activation. This effectively breaks down the dense chromium-rich oxide film on the surface of stainless steel, significantly improves solder wettability, and effectively avoids the activity gap or instantaneous overreaction caused by a single activator due to its narrow temperature window. It is suitable for various heating methods, including manual flame brazing and automated induction brazing.

[0022] While ensuring strong activation ability, this invention controls the acid-base balance of the flux within a suitable range by introducing 7.2% diphenylguanidine hydrochloride and 0.48% hydroquinone, thereby minimizing excessive corrosion of the stainless steel substrate and avoiding pitting and stress corrosion cracking problems that are easily caused by traditional chloride fluxes.

[0023] This invention uses a high softening point modified rosin KE-604 and a high acid value 610# rosin as a film-forming substance, which can form a continuous protective coating during the welding preheating and high temperature stages, effectively isolating air and preventing re-oxidation.

[0024] In this invention, the rosin component forms a thin and brittle film after welding, and the reaction products of each active component are mostly gaseous or soluble substances. Combined with dispersants such as ethylene bis-stearyl ammonium, the peeling performance is improved, making the weld residue easy to clean and remove, thus ensuring the cleanliness and insulation resistance of the weldment surface. Attached Figure Description

[0025] Figure 1 This is a flowchart illustrating the preparation process of the solder paste in this embodiment; Detailed Implementation

[0026] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0027] Example 1

[0028] A flux for welding stainless steel is composed of 73.32% flux base and 26.68% activator.

[0029] The flux base comprises: 23.04% rosin, 26.4% diethylene glycol monohexyl ether, 2.4% white petrolatum, 2.4% ethylene bis-stearyl ammonium, 3% fluorinated surfactant FS-3100, 2.4% hexanediol, 7.2% diphenylguanidine hydrochloride, 6% 6500 thixotropic agent, and 0.48% hydroquinone; the flux base is prepared according to the above proportions.

[0030] Of these, 23.04% rosin component acts as a film-forming substance, providing basic protective coverage during the welding process and preventing the metal surface from oxidizing again at high temperatures;

[0031] 26.4% of diethylene glycol monohexyl ether, as a high-boiling-point solvent, is responsible for dissolving rosin and adjusting the fluidity and application viscosity of the paste. At the same time, due to its slow evaporation rate, it can ensure that the flux paste maintains sufficient wet dwell time during the preheating and soldering heating stages.

[0032] 2.4% white petrolatum acts as a lubricant and adjusts the texture of the paste, making it more delicate and smooth, and easier to apply.

[0033] 2.4% ethylene bis-stearyl ammonium acts as a lubricating dispersant, which helps to uniformly disperse the solid components in the system, avoids agglomeration and precipitation, and improves the peeling performance of post-weld residue at high temperatures.

[0034] The 3% fluorinated surfactant FS-3100, with its extremely low surface tension, can significantly reduce the interfacial tension between the molten brazing filler metal and the stainless steel base material, thereby significantly promoting the spreading and wetting of the liquid brazing filler metal on the welding surface. It is one of the key additives for improving welding quality.

[0035] 2.4% hexanediol is used as an auxiliary solvent, which works synergistically with the main solvent to further optimize the polarity and solubility of the paste;

[0036] 7.2% diphenylguanidine hydrochloride acts as both an activation promoter and a corrosion inhibitor in the system, which can slow down excessive corrosion of the base material during high-temperature activation.

[0037] The 6% 6500 thixotropic agent allows the flux to maintain a high viscosity without dripping when at rest. When subjected to shear force during scraping or dotting, the viscosity drops rapidly to facilitate application. After the external force is removed, the viscosity quickly returns to its original value, thus ensuring the accuracy and stability of the coating shape.

[0038] 0.48% hydroquinone acts as an antioxidant, which can effectively inhibit the oxidation and deterioration of rosin and organic solvents during prolonged heating, prevent the formation of charred or gelatinous residues, and delay the premature failure of active components due to oxidation.

[0039] Thus, by uniformly mixing the above components in the stated proportions and subjecting them to appropriate heating, stirring, and dispersion treatment, a stable flux base can be obtained.

[0040] The activator contains: 3-8% ammonium ethanol, 8-15% thiophosphate, 5-15% ammonium fluoroborate, and 0.5-2% ammonium hydrogen fluoride. The specific proportions refer to the proportions of each activator component to the total mass of the flux, and the proportions of the above components must be precisely adjusted so that their sum is exactly equal to 26.68%.

[0041] Ammonium ethanol, as an organic alkaline activator, can react chemically with the oxide layer on the surface of stainless steel during the welding heating process, playing a role in initially loosening and breaking the oxide film, while also opening a channel for subsequent acidic activator corrosion.

[0042] Thiophosphoric acid is a potent phosphorus-containing active substance. After decomposition in the medium and high temperature range, it generates active phosphides, which can effectively reduce the oxides of metals such as chromium, nickel, and iron, and convert the oxide film into easily volatile or floatable phosphorus oxides, thereby achieving the purpose of deep removal of the oxide layer. At the same time, phosphorus can also promote the micro-area alloying bonding between the brazing filler metal and the base metal at the interface, which is beneficial to improving the joint strength.

[0043] When heated, ammonium fluoroborate decomposes to produce active gaseous species such as boron trifluoride and hydrogen fluoride. These species have extremely strong etching ability and can powerfully attack the dense chromium-rich oxide layer on the surface of stainless steel, achieving efficient removal of the passivation film. Moreover, its decomposition products are mostly gaseous and can escape on their own during the welding process, making it difficult to form stubborn inclusions.

[0044] Ammonium bifluoride mainly undertakes the initial activation task in the low temperature range. When the temperature rises above 150°C, it can release active fluorides and form a gradient relay activation effect with ammonium fluoroborate. This ensures that there are always enough active species to participate in the membrane removal reaction throughout the heating process, avoiding insufficient activation or instantaneous overreaction due to a narrow single-point temperature window.

[0045] Thus, by accurately weighing and mixing the above four active components in a predetermined ratio, a composite activator with graded activation capability can be prepared.

[0046] Finally, the prepared flux base is thoroughly mixed with the prepared activator to ensure that the active components are evenly dispersed in the base system. Then, the mixture is stirred and ground to ensure that the paste has the required fineness and good uniformity, thus obtaining the finished stainless steel flux.

[0047] This flux can be widely used in stainless steel welding processes, and can also be used as a matching flux for welding materials of various steels, special functional brazing filler materials, or various flux products. It is suitable for a variety of heating methods and welding conditions, and has good process adaptability and stable performance.

[0048] Example 2

[0049] A flux for stainless steel welding, comprising 14.4% rosin KE-604 and 8.64% 610# rosin; wherein rosin KE-604 is a modified high-activity rosin with a high softening point and good thermal stability, which can maintain a molten protective state for a long time during the welding heating process, and is not prone to premature carbonization or decomposition. At the same time, it has certain active groups, which can assist the activator in participating in the oxide film removal process and improve the overall fluxing effect; 610# rosin is a highly refined ordinary rosin with a high acid value and excellent solubility, which can complement KE-604 rosin, adjusting the softening range and viscosity characteristics of the entire rosin component while ensuring basic film-forming properties.

[0050] When used in a specific ratio, the two components ensure that the flux has good film-forming properties and adhesion at room temperature, allowing it to adhere firmly to the surface of the stainless steel base material without dripping or falling off. They also ensure that the rosin component softens and melts gradually during the welding heating process, forming a continuous protective coating on the molten solder, effectively isolating oxygen in the air and preventing the metal surface from oxidizing again at high temperatures. At the same time, the residual film formed by the rosin during the cooling process after welding is brittle and thin, making it easy to clean and remove, and will not cause serious corrosion residue or insulation pollution to the surface of the welded workpiece.

[0051] Example 3

[0052] like Figure 1 The method for preparing the flux base for stainless steel welding, as shown, includes:

[0053] S01 mixes 14.4% rosin KE-604, 8.64% 610# rosin, 26.4% diethylene glycol monohexyl ether, 2.4% white petrolatum, 2.4% ethylene bis-stearyl ammonium, 3% fluorinated surfactant FS-3100, and 2.4% hexanediol, and dissolves them at 150°C. At this temperature, the rosin components can fully melt, and high-boiling-point solvents such as diethylene glycol monohexyl ether and hexanediol can also exert their optimal dissolving power, completely dissolving the rosin, white petrolatum, ethylene bis-stearyl ammonium, and fluorinated surfactant components into a homogeneous and transparent liquid system. Continuous stirring is required throughout the dissolution process to ensure sufficient contact and mixing between the components and to avoid local overheating or incomplete dissolution.

[0054] S02 mixes 7.2% diphenylguanidine hydrochloride, 6% 6500 thixotropic agent, and 0.48% hydroquinone, dissolves them at 120°C, and then cools. At this temperature, diphenylguanidine hydrochloride melts smoothly and disperses uniformly in the system. The 6500 thixotropic agent is fully activated at 120°C, allowing its polar groups to expand, thus effectively constructing a three-dimensional network structure during subsequent cooling, giving the paste excellent thixotropic properties. Hydroquinone, after dissolving at 120°C, is uniformly distributed in the system, acting as an antioxidant. After dissolution, the mixture is cooled, allowing each component to gradually form a stable physical and chemical state during the cooling process, preparing it for subsequent mixing with the material obtained from S01.

[0055] In step S03, the high-temperature mixture obtained in step S01 and the material obtained in step S02 are dissolved and cooled separately, then combined and placed in a disperser for high-speed dispersion. Under the high-speed shearing action of the disperser, the two components are fully mixed and refined, so that the components that were originally prepared in steps achieve a highly uniform dispersion state at both the macroscopic and microscopic levels, and finally a flux matrix with a delicate and uniform appearance, good thixotropic properties and stable performance is obtained.

[0056] Example 4

[0057] A flux for welding stainless steel, wherein the activator comprises: 3-8% ammonium ethanol, 8-15% thiophosphoric acid, 5-15% ammonium fluoroborate, and 0.5-2% ammonium bifluoride; the above proportions are calculated and weighed based on the proportion of the activator to the total mass of the flux.

[0058] In specific formulation, the amount of ammonium ethanol can be optimized and adjusted according to the actual welding process requirements and the degree of oxidation of the base material surface, specifically within the range of 3% to 8%. It mainly acts as an organic alkaline activator, which can exert a mild chemical erosion effect in the initial stage of welding heating. Through the alkaline environment, it loosens and destroys the oxide layer on the stainless steel surface, creating favorable conditions for the subsequent deep removal of the film by the strong acidic activator. At the same time, its organic amine structure also has a certain coordination complexing ability, which can form soluble complexes with metal ions, promoting the migration and removal of reaction products.

[0059] The dosage of thiophosphoric acid is controlled between 8% and 15%. It is mainly used to decompose and generate active phosphides in the medium temperature zone of welding, which can reduce the dense chromium oxides and nickel oxides on the surface of stainless steel into volatile phosphorus oxides or easily floating phosphates.

[0060] The dosage of ammonium fluoroborate ranges from 5% to 15%. As an ammonium-fluorine composite activator, it gradually decomposes during the welding heating process and releases active fluorine species such as boron trifluoride and hydrogen fluoride. This effectively attacks the chromium-oxygen bonds in the chromium-rich oxide film on the surface of stainless steel, converting chromium oxide into easily volatile fluorides or fluorine oxides, thereby achieving a strong removal of the passivation film.

[0061] Furthermore, the decomposition temperature range of ammonium fluoroborate and the action temperature range of thiophosphoric acid are highly complementary. When used together, they can maintain continuous and stable activation output over a wide temperature range, avoiding the activity gap problem that occurs when using a single activator due to its narrow temperature window.

[0062] The amount of ammonium bifluoride used is between 0.5% and 2%. In this activator system, it mainly undertakes the task of initial activation at low temperature. When the temperature rises above 150°C, it can decompose first and release active hydrogen fluoride to perform preliminary etching and damage on the oxide film on the stainless steel surface.

[0063] Example 5

[0064] A flux for welding stainless steel, wherein the activator comprises the following components by mass percentage:

[0065] 3.5% ammonium ethanol, 9.5% phosphoric acid thiophosphate, 12.5% ​​ammonium fluoroborate and 1.18% ammonium hydrogen fluoride.

[0066] The above formulation has the lowest ammonium ethanol content, the highest ammonium fluoroborate content, and a relatively high ammonium hydrogen fluoride content. The resulting flux has extremely strong fluoride activation ability in the medium and high temperature range, making it particularly suitable for welding stainless steel base materials with extremely dense or thick oxide layers on the surface, such as weldments or cast stainless steel surfaces that have been severely oxidized after long-term high-temperature service.

[0067] However, the lowest ammonium ethanol content results in a weaker alkaline activation effect, and the overall system tends to be acidic with a strong activation route. This makes it more suitable for non-precision structural parts with larger welding gaps and a certain amount of corrosion allowance. It also requires timely and thorough cleaning after welding.

[0068] Example 6

[0069] A flux for welding stainless steel, wherein the activator comprises the following components by mass percentage:

[0070] 4.68% ammonium ethanol, 14.5% phosphoric acid, 6.5% ammonium fluoroborate and 1.00% ammonium hydrogen fluoride.

[0071] The above formulation has an extremely high content of thiophosphate and a low content of ammonium fluoroborate, resulting in a flux with outstanding phosphide activation ability in the medium temperature range. It is particularly suitable for welding stainless steel workpieces that are sensitive to fluoride corrosion or require low fluoride residue, such as food-grade stainless steel containers and medical device components, which are subject to strict restrictions on halogen residue. At the same time, the high content of thiophosphate is beneficial to promoting interfacial alloying between the solder and the base metal, making it suitable for structural load-bearing components that require high weld joint strength.

[0072] However, the low ammonium fluoroborate content weakens the fluorine activation ability in the high-temperature range, making it more suitable for welding processes with relatively low welding temperatures or short holding times, or for stainless steel with relatively thin oxide films.

[0073] Example 7

[0074] A flux for welding stainless steel, wherein the activator comprises the following components by mass percentage:

[0075] 5.33% ammonium ethanol, 10.5% phosphoric acid thiophosphate, 9.86% ammonium fluoroborate and 0.99% ammonium hydrogen fluoride.

[0076] In the above formulation, the contents of ammonium ethanol, thiophosphate, and ammonium fluoroborate are moderate and coordinated, while the content of ammonium bifluoride is controlled at a low level. The resulting flux has a moderate and consistent activation capacity output in the three temperature ranges of low temperature, medium temperature, and high temperature. It will not cause a sudden increase in activity or reaction instability due to excessively high levels of a single component, nor will it cause activation interruptions or incomplete film removal due to excessively low levels of a single component.

[0077] Specifically, 5.33% ammonium ethoxide ensures a mild alkaline pre-activation effect in the low-temperature range, providing a good transitional basis for subsequent acidic activation, while avoiding the adverse effects of excessive alkalinity on the stability of the rosin system; 10.5% thiophosphoric acid ensures sufficient phosphide reduction and film removal capacity in the mid-temperature range, without causing excessive phosphorus residue or excessive corrosion after soldering due to excessive addition; the moderate content of ammonium fluoroborate at close to 10% ensures sufficient but not excessive fluoride etching capacity in the high-temperature range, forming a good activity complement to thiophosphoric acid; ammonium bifluoride is controlled at a low level of close to 1%, providing just the right low-temperature start-up activation capacity, but without causing the reaction in the low-temperature range to be too violent.

[0078] Example 8

[0079] A flux for welding stainless steel, wherein the activator comprises the following components by mass percentage:

[0080] 7.5% ammonium ethanol, 8.5% phosphoric acid thiophosphate, 9.68% ammonium fluoroborate and 1.00% ammonium hydrogen fluoride.

[0081] The above formulation has the highest content of ammonium ethanol and the lowest content of thiophosphate, resulting in a flux paste with a significant tendency to be activated by alkaline conditions. The alkaline environment is conducive to the formation of a corrosion-inhibiting protective layer on the stainless steel surface, and has the lowest corrosiveness to the base material. It is particularly suitable for welding applications such as thin-walled stainless steel parts, precision small parts, or applications with extremely high dimensional accuracy requirements, such as stainless steel capillaries, precision instrument parts, and electronic packaging shells.

[0082] However, a high content of ammonium ethanol can lead to excessive alkalinity, which may affect the stability of rosin components or cause a slow acid-base reaction in the paste during storage.

[0083] Example 9

[0084] According to the components and proportions in the foregoing embodiments, rosin, solvent, activator and 6500 thixotropic agent are added to the reaction vessel in sequence, heated and stirred at 80-100°C until completely dissolved, and after cooling, solder alloy powder is added and stirred and mixed evenly to obtain the flux paste of each embodiment.

[0085] To examine the printing performance and welding effect of the flux obtained in the above embodiments, performance tests such as printing release properties and post-soldering residue corrosivity were conducted.

[0086] Comparison Projects Example 5 Example 6 Example 7 Example 8 Acid-base tendency strong acid Slightly acidic Near-neutral equilibrium Weakly alkaline Main activation temperature range Medium and high temperature zone medium temperature zone Low temperature-medium temperature-high temperature full gradient Low temperature to medium temperature range Activate output coherence Weakness in medium and low temperatures, and a sudden increase in high temperatures. Sudden increase in medium temperature, insufficient high temperature Smooth and consistent throughout The temperature is slightly stronger at low temperatures and decreases towards medium and high temperatures. Corrosiveness to the base material Larger Medium to large Mild and controllable smaller Post-weld cleaning difficulty Difficult medium easy relatively easy

[0087] In summary, the third ratio (5.33% ammonium ethanol, 10.5% phosphoric acid, 9.86% ammonium fluoroborate, and 0.99% ammonium bifluoride) was determined to be the optimal ratio in this embodiment, which is applicable to a variety of base material types, workpiece specifications, and heating methods, from ordinary austenitic stainless steel to molybdenum-containing high-grade stainless steel, from thin plates to thick plates, and from manual flame brazing to automated induction brazing.

[0088] Its active components have the most coordinated and balanced proportions, enabling a three-stage gradient activation effect of low-temperature start-up, medium-temperature enhancement, and high-temperature sustained activation throughout the entire welding heating process. There are no performance shortcomings caused by the excess or deficiency of any single component.

[0089] Furthermore, the moderate acid-base balance ensures that the flux's corrosivity to the base material is controlled at an optimal level, guaranteeing sufficient film removal and activation capabilities while minimizing excessive corrosion of the stainless steel substrate. Post-weld residue is also easier to clean and remove due to the full reaction.

[0090] Example 10

[0091] like Figure 1 The method for preparing a flux for stainless steel welding, as shown, includes the following steps:

[0092] S01 is made by mixing 14.4% rosin KE-604, 8.64% 610# rosin, 26.4% diethylene glycol monohexyl ether, 2.4% white petrolatum, 2.4% ethylene bis-stearyl ammonium, 3% fluorinated surfactant FS-3100 and 2.4% hexanediol, and dissolving them at 150°C.

[0093] SO2 is prepared by mixing 7.2% diphenylguanidine hydrochloride, 6% 6500 thixotropic agent and 0.48% hydroquinone, dissolving at 120°C, and then cooling.

[0094] S03 involves cooling the materials obtained from S01 and S02 and then dispersing them using a disperser to obtain the flux base.

[0095] S04 is prepared by mixing 5.33% ammonium ethanol, 10.5% phosphoric acid, 9.86% ammonium fluoroborate and 0.99% ammonium bifluoride at room temperature and grinding them with a grinder to obtain the activator.

[0096] Finally, in step S05, the flux base obtained in step S03 is added to the activator obtained in step S04, and after mixing, it is stirred and ground to produce stainless steel flux.

[0097] Specifically, 14.4% rosin KE-604, 8.64% 610# rosin, 26.4% diethylene glycol monohexyl ether, 2.4% white petrolatum, 2.4% ethylene bis-stearic acid ammonium, 3% fluorinated surfactant FS-3100 and 2.4% hexanediol were accurately weighed and added to a reaction vessel. The mixture was heated to 150°C to dissolve the components, with continuous stirring during the dissolution process, until all components were completely melted and formed a uniform and transparent liquid system.

[0098] Then, weigh 7.2% diphenylguanidine hydrochloride, 6% 6500 thixotropic agent and 0.48% hydroquinone according to the proportion and place them in another reaction vessel. Heat at 120°C to dissolve, so that diphenylguanidine hydrochloride is fully melted, 6500 thixotropic agent is fully activated, and hydroquinone is completely dissolved and uniformly dispersed. After dissolution, allow the resulting mixture to cool naturally to room temperature.

[0099] After the high-temperature mixture obtained in S01 is cooled to room temperature, it is combined with the cooled material in step S02 and fed into a disperser. Under high-speed shearing, it is fully dispersed. During the dispersion process, the 6500 thixotropic agent forms a complete and uniform thixotropic network structure, and finally a flux matrix with a delicate and uniform appearance and excellent thixotropic properties is obtained.

[0100] Then, 5.33% ammonium ethanol, 10.5% phosphoric acid, 9.86% ammonium fluoroborate, and 0.99% ammonium bifluoride were accurately weighed according to the proportions and added to a stirring container at room temperature for mixing. This allowed the four active components to be initially and evenly mixed. Subsequently, the resulting mixture was transferred to a grinder for fine grinding. Grinding further reduced the particle size of each active component and improved the contact and distribution between the components, ultimately yielding a composite activator with highly uniform dispersion and good reaction consistency.

[0101] Finally, the flux base prepared by SO3 and the composite activator prepared by SO4 are mixed in a ratio of 73.32% and 26.68%, respectively. The activator is slowly added to the base while stirring to ensure that the two are fully contacted and integrated, so that the active components are evenly dispersed in the base system. Then, the paste is stirred and ground to ensure that the fineness of the paste meets the process requirements and that the uniformity is good, and finally, the stainless steel flux paste product is obtained.

[0102] It should be noted that, in this document, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes the element.

[0103] The above is only used to illustrate the technical solution of the present invention and is not intended to limit it. Any other modifications or equivalent substitutions made by those skilled in the art to the technical solution of the present invention, as long as they do not depart from the spirit and scope of the technical solution of the present invention, should be covered within the scope of the claims of the present invention.

Claims

1. A soldering flux for stainless steel welding, consisting of 73.32% of a flux base and 26.68% of an active agent, characterized in that, The flux base comprises: 23.04% rosin, 26.4% diethylene glycol monohexyl ether, 2.4% white petrolatum, 2.4% ethylene bis-stearyl ammonium, 3% fluorinated surfactant FS-3100, 2.4% hexanediol, 7.2% diphenylguanidine hydrochloride, 6% 6500 thixotropic agent, and 0.48% hydroquinone; The activator comprises: 3-8% ammonium ethanol, 8-15% phosphoric acid thiophosphate, 5-15% ammonium fluoroborate, and 0.5-2% ammonium hydrogen fluoride; The flux paste matrix and the activator are mixed and ground to form the flux paste.

2. The flux for stainless steel welding according to claim 1, characterized in that, The rosin component comprises 14.4% rosin KE-604 and 8.64% 610# rosin.

3. The flux for stainless steel welding according to claim 1, characterized in that, The active agent comprises the following components by mass percentage: 3.5% ammonium ethanol, 9.5% phosphoric acid thiophosphate, 12.5% ​​ammonium fluoroborate and 1.18% ammonium hydrogen fluoride.

4. The flux for stainless steel welding according to claim 1, characterized in that, The active agent comprises the following components by mass percentage: 4.68% ammonium ethanol, 14.5% phosphoric acid thiophosphate, 6.5% ammonium fluoroborate and 1.00% ammonium hydrogen fluoride.

5. The flux for stainless steel welding according to claim 1, characterized in that, The active agent comprises, by mass percentage, the following components: 5.33% ammonium ethanol, 10.5% phosphoric acid thiophosphate, 9.86% ammonium fluoroborate, and 0.99% ammonium hydrogen fluoride.

6. The flux for stainless steel welding according to claim 1, characterized in that, The active agent comprises the following components by mass percentage: 7.5% ammonium ethanol, 8.5% phosphoric acid thiophosphate, 9.68% ammonium fluoroborate and 1.00% ammonium hydrogen fluoride.

7. The method for preparing stainless steel welding flux according to any one of claims 1 to 6, characterized in that, Includes the following steps: S01 is made by mixing 14.4% rosin KE-604, 8.64% 610# rosin, 26.4% diethylene glycol monohexyl ether, 2.4% white petrolatum, 2.4% ethylene bis-stearyl ammonium, 3% fluorinated surfactant FS-3100 and 2.4% hexanediol, and dissolving them at 150°C. SO2 is prepared by mixing 7.2% diphenylguanidine hydrochloride, 6% 6500 thixotropic agent and 0.48% hydroquinone, dissolving at 120°C, and then cooling. S03 involves cooling the materials obtained from S01 and S02 and then dispersing them using a disperser to obtain the flux base. S04 is prepared by mixing 5.33% ammonium ethanol, 10.5% phosphoric acid, 9.86% ammonium fluoroborate and 0.99% ammonium bifluoride at room temperature and grinding them with a grinder to obtain the activator. Finally, in step S05, the flux base obtained in step S03 is added to the activator obtained in step S04, and after mixing, it is stirred and ground to produce stainless steel flux.

8. The flux for stainless steel welding according to any one of claims 1 to 6, characterized in that, The flux is used in stainless steel welding, welding materials for steel, special functional brazing materials, or brazing flux products.

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